VERBAL" NOTES ANo SKETCHES FOR Marine Engineers J.W. M. SOTHERN M.l.E.S. EIGHTH EDITION 41? ISSUE THE LIBRARY OF THE UNIVERSITY OF CALIFORNIA LOS ANGELES %■■ VERBAL" Notes and Sketches FOR Marine Engineers PRINTED IN^ GREAT BRITAIN liV THE DARIEN PRESS, EDINBURGH Quadruple Expansion Engines of SS. "Vasari." Constructed by Messrs Richardsons, Westgarth & Co, Ltd.. Middlesbrough, for Messrs Lamport & Holt Ltd.. Liverpool. Gross tonnage. — loooo tons. Dimensions of vessel. — 486 feet by 59 feet 3 inches by 27 feet 4 inches. Boilers.— Three double-ended boilers, each 15 feet 3 inches diameter and iS feet 6 inches long, having six furnaces, each 3 feet loj inches outside diameter. Draught. — Natural draught. Total heating surface. — 14010 square feet. Total grate surface. — 363 square feet. Ratio of heating surface to grate. — 38-5 to i. Working pressure. — 220 lbs. per sf|uare inch. Cylinders. — 26i, 37}, 53, and 77 inches diameter. Stroke. — 57 inches. Cut-oir.— H.P. = 63, first I.P. = -62, second I.r. = -6o, I,.1'. = -5S. Type of valve gear. — Ordinary link motion. Valve travel.— H.P. gj inches, others 9 inches. Type! r H.P. inside steam piston valve. . ntt,.H ' '''''^' "-P- inside steam piston valve. - ""'-°- "I Second l.P. nat valve. I L.P. flat valve. H.P. rods crossed. First LP. rods crossed. Second l.P. rods open. L.P. rods open. Distribution ofLH.P. in cylinders. H.P. cylinder First LP. cylinde Second LP. „ L.P. Tutal LH.P.— 4i5gat 75 i per Propeller. — Diaineter ig feet; pitch rg feet; expanded blade square feet ; four loose blades. Speed. — 13 knots. p Cj^ cJ^. / /, '' > ' / "VERBAL" NOTES AND SKETCHES FOR MARINE ENGINEERS A MANUAL OF MARINE ENGINEERING PRACTICE CONTAINS NOTES AND SKETCHES OF VERBAL AND ELEMENTARY QUESTIONS GIVEN AT THE BOARD OF TRADE EXAMINATIONS TO ENGINEERS COMPETING FOR FIRST-CLASS AND SECOND CLASS CERTIFICATES OF COMPETENCY AND IS INTENDED FOR THE USE OF NAVAL AND MERCANTILE MARINE ENGINEERS OF ALL GRADES, STU- DENTS, FOREMEN ENGINEERS, ETC., AND IS SPECIALLY COMPILED FOR THE USE OF ENGINEERS PREPARING FOR EXAMINATIONS OF COMPETENCY AT HOME OR ABROAD J. W. M. SOTHERN Member, Institute of Eng-ineers and Shipbuilders in Scotland; Hon. Member, Glasgow and West of Scotland Association of Foremen Engineers and Draughtsmen. Author of "Marine Indicator Cards," "The Marine Steam Turbine," "Simple Problems in Marine Engineering Design," "Elementary Mathematics for Marine Engineers," etc. Principal, Sothern's Marine Engineering College, Glasgow. 600 ILLUSTRATIONS EIGHTH EDITION ENLARGED, RE-WRITTEN, RE-ILLU.STRATED, AND WITH NEW APPENDLX Fourth Re-issue, with further additions GLASGOW: JAMES MUNRO & CO. LIMITED NEW YORK : D. VAN NOSTRAND COMPANY 25 PARK PLACE 1916 [All Rights Reserved] Seventh Edition published September 1911 Eighth Edition (with new appendix) pub- lished September 1913 Re-issue (with numerous additions) pub- lished January 1915 Re-issue (with further additions) published October 1915 Fourth Re-issue (with additions) published September 1916 Engineering Library (oOO AT 37/ PREFACE TO SEVENTH EDITION- The author would draw special attention to the fact that the work has been practically re-written and re-illustrated, some hundreds of new and original sketches appearing in the volume. The Boiler section has received particular attention, practical examples of the application of the rules of design, &c., being shown and worked out. As in previous editions the practical side of marine engineering science has received chief attention, and in connection with this a new section treating of " Workshop Practice " has been added, which the author trusts will be found of interest as being somewhat in the form of a novelty. As a subject usually neglected in ordinary text-books, a special section on " Valve Settings " has been included, which the author hopes will be found of use to junior engineers, among whom the subject is, speaking generally, very imperfectly understood or appreciated. The writer also wishes to mention that, owing to the great increase in size of the present edition over the last one, it has been found necessary to issue the " Indicator Diagram " section as a separate publication under the title of " Marine Indicator Cards," particulars of which will be found elsewhere. Attention should be drawn to the fact that the illustrations are numbered independently for each section, also that, for greater con- venience, the Index is placed at the front instead of at the end of the work. In conclusion, the author's thanks are due to the following firms, &c., for kind permission to reproduce illustrations, and for subject matter supplied : — Messrs Richardson, Westgarth & Co., Ltd., for Frontis- piece ; Messrs Cochran & Co., Annan, Ltd., for sketch of Boiler ; Messrs Denny & Co., for drawing of Brock Valve Gear ; Messrs The Simms Magneto Co., Ltd., for illustration of Magneto ; Messrs The Technical Publishing Co., Ltd., for numerous illustrations which V i^~f f^ f^ r^ ^ F\ Li o vi Preface to Seventh Edition. appeared in the Practical Engineer under the title of " Leaves from an Engineer's Note Book " ; Messrs The D. Van Nostrand Co., New York, for the illustrations, marked with an asterisk, which appeared in the pages of International Marine Engineering, entitled " Marine Engine Design," by Professor Edward M. Bragg ; the Pro- prietors of International Marine Engineering, for numerous illustra- tions which appeared originally in that journal ; the Proprietors of Engineering, for half-tone illustrations of Boilers ; the Editor of the Scottish Bankers Magazine, for the article on " The Manufacture of Metals " ; the Editor of the Steamship, for illustration and description of the Pulsometer Pump ; the Editor of the Mechanical World, for sketch and data of Belliss and Morcom Engine ; and to other numerous friends and former students of the author who have kindly supplied practical data and sketches for use in the volume. Marine Engineerjng College, 59 Bridge Street, Glasgow, September 191 1. PREFACE TO EIGHTH EDITION. In the New Appendix which is included in this Edition the author has introduced a number of new drawings, notes, and calculations, referring chiefly to Diesel Oil Engines, Boilers, and Marine Turbines, the latter including exhaust turbines and geared down turbines, thus bringing the work right up to date. The author's thanks are due to A. P. Chalkley, Esq., for kind per- mission to reproduce detail drawings of the Diesel type oil engine from "Diesel Engines," by A. P. Chalkley, B.Sc, A.M.I.C.E. ; to the Council of the Institution of Naval Architects for permission to repro- duce the illustration of the "Vespasian" gear wheels from a Paper read before that Institution by Sir Charles Parsons, and entitled "The Application of the Marine Steam Turbine and Mechanical Gearing to Merchant Ships"; to the editors oi Engineering {ox illus- trations of the turbine machinery of Q.SS. " Reina Victoria Eugenia," and SS. " King Orry," and for permission to reprint the descriptions of the machinery which appeared originally in Engineering ; also for permission to reproduce the illustrations showing the Diesel four-cycle and two-cycle action, from a Paper entitled " The Diesel Oil Engine," by Dr Rodolph Diesel of Munich, and read before the Institution of Mechanical Engineers. The author has also to thank Messrs G. & J. Weir for the illustration of their patent " Dual " type Air Pumps, etc. Marine Engineering College, 59 Bridge Street, Glasgow, September 191 3, CONTENTS. SECTION I. Workshop Practice, PAGES Types of Engines — Paddle Engines — Screw Engines — Steam Flow — Balanced Engines — Valves — Pistons — Connecting Rods — Valve Gear — Eccentrics — Main Bearings — Crank-shafts — Columns — Soleplate — Crank-shafts and Columns — Cutting of Eccentric Keyseats — Erect- ing of Columns — Cylinders and Valve Chests — Training Connecting Rods and Running Gear — Training Valve Gear — Cylinder Clearance and Valve Setting — Cylinder and Pump Connections, &c. — Propeller Shaft Liners — Marking off Ship for Boring Out — Thrust Block — Erecting Machinery in Ship — Pipe Connections — Auxiliary Machinery — Trial Trips — Care and Upkeep — How to Keep a Watch — Economical Working- ........ 1.70 SECTION 11, Boilers. Strength of Plates — Elastic Limit and Factor of Safety— Stresses on Shell Seams — Strength of Shell — Shell Pressure, &c. — Strength of Joints — Riveting — Types of Joints — To Prove Joint Strength — Examples of Joints — Circumferential Seam Riveting — Combined Strength of Seam and Rivets — Steam Space Stays — Flat Surfaces and Stays — End Plates and Stays — Water Space Stays — Pitch of Stays Combustion Chambers — Combustion Chamber Stays and Girders — Tubes — Stay Tubes — "Adamson" Rings — "Bowling" Hoops — Corrugated Fur- naces — Furnace Riveting — Strengthening a Furnace— Furnace Manu- facture — Collapse of Furnaces — Furnace Temperatures — Fire-bars and Bearers — Manholes — Natural Draught — Forced Draught — Pitting and Corrosion — Boiler Repairs — Examples of Plate Corrosion, &c. — Tube Stoppers — Leaky Tubes — Safety Valves — Superheated Steam — Steam Pipes — Water Hammer — Circulation and Priming — Doubling Plates — Scarfed Joints — Zinc Plates — Water Gauge — Boiling Points — Salinometer, Density — Ash Ejector — Tube Expander— Cutting out of Tubes — Reducing Valves — Autogenous Welding Process — Hand Sketches of Boilers — Efficiency of Boiler — " Equivalent Evaporation " — Weight of Gases — Shortness of Water — Velocity of Gases — Boiler Dimensions — Vertical Donkey Boiler — Cochran Patent Boiler — Hay- stack Boiler— Yarrow Boiler— Babcock Boiler— Bellville Boiler - 71-177 vU viii Cgntents SECTION III. Notes and Sketches of Various Details. PAGES Crank-pin Lubrication— Reversing Gear — Turning Engine— H. P. Steam Connections— Stern Tube— Condenser Tubes— Thrust Block— Start- ing Valve— L.P. Piston— Air Pump— Edwards Air Pump Bucket- Valve Spindle Eye Bush— Double Beat Valve and Expansion Joint- Testing Fairness of Cylinders and Shaft— Air Pump Valves— "A" Brackets — Connecting Rod Bolts and Nuts — Edwards Pump — Engine- Room Gauges— Air Pump Connections — Piston Rod and Shoes — Balance Weights — Circulating Water Connections — Connecting Rod — Piston Rod — Oil Feed Boxes — Reversing Bell Crank — Pumping Diagram— Feed Pump Connections ----- 178-198 SECTION IV. Slide Valves, Piston Valves, Valve Data, &c. Duties of Valve— Valve Travel— Steam Lap and Exhaust Lap— Lead— Double-Ported Valves — Piston Valves— Trick Valve — Andrews- Martin Valve — Piston Valve Rings — Joy's Assistant Cylinder — Open and Crossed Eccentric Rods — Reversing Gear — Measurement of Lead — Lead Adjustments — Valve Settings— Connecting Rod Angle — Patent Valve Gears— Link Motion— Linking Up— Eccentric Keyseat Templates— Valve Setting Tables— Zeuner Valve Diagrams — Cranks and Eccentric Rods— " Linked Up" Valve Diagram— Bellis and Morcom Engine— Effects of Link Adjustments - - - 199-263 SECTION V. General Notes and Descriptions. Manufacture of Iron and Steel— Alloys— Properties of Metals and Alloys — Composition of Steel, &c.— Tempering Steel — Annealing — Case- Hardening — Brazing— Welding — Strength of Materials— Stresses on Working Parts— Built Shafting— Strength of Shafting— Torsion and Bending Moments — Torsional Stress and Constant 5-1 — Twisting Stress and Shaft Diameter — Mean Twisting Moment, &c. — Board of Trade Constants— Lloyds' Rules for Shafting— Crank Angles- Flaws on Shafts— Shaft Repairs — Thomson Patent Coupling — Stop- ping of Engines — Engine Breakdowns — Pumps — Breakdown of Pumps — Loss of Vacuum — Pet Valves — Air Vessels — Condenser and Air Pump — Oscillating Engine — Diagonal Engines — Paddle Engine Shafts — Paddle Wheels — Weir Feed Heater — Weir Evaporator — Weir Feed Pump — Weir Pump Steam Valves — Feed Water Filter — Aspinall Governor — Worthington Feed Pump — Lamont Pump — Engine and Boiler Data — Pressure Gauge Indications — The Baro- meter — The Thermometer — Tail Shaft Corrosion — Propeller Pitch — Contents ix To Find Cut-off — Crank on Centre — Cutting of Keyseats — Valve in Mid Travel — Shaft Sighting — Lining up Shafting — Flaws on Shafts — Various Engine Adjustments — Pressure Gauge Tube — Main and Bilge Injection — Thrust Block — Crankpin and Piston Travel — Broken L.P. Cylinder Cover — Sight Feed Lubricator — Hydraulic Accumulator-T-Brown's Steam and Reversing Gear — Steering Gears — Brown's Steam Tiller — Metallic Packings— Stern Tube and Shaft — Drawing the Propeller Shaft — Pulsometer — Hot-well Temperature — General Definitions — Density of Steam — Brake Horse-Power — Dryness of Steam — ^Total Heat and Latent Heat — Potential and Kinetic Energy — Adiabatic Expansion — Hyperbolic Expansion — Heat and British Thermal Unit — Saturated Steam, Wet Steam, and Superheated Steam — Boyle's Law of Expansion — Charles' Law — Steam Expansions by Pressures and Volumes — Heat Efficiency — Initial Condensation — Advantage of Multi - Cylinder Engines — Cylinder Ratios and Expansions — Cut-off and Pressures — Suction Lift of Pumps — Stresses on Shafting — To Line up Crank-shaft — Pistons — Stresses on Beams — Consumption and Speed — I.H.P. and Consumption — Coal, I.H.P. and Distance — H.P. Cut-off and Con- sumption — Efficiency of Boilers and Engines, &c. — Squared Paper Diagrams — Curves of Speed, Consumption, Power, and Slip - - 264-407 SECTION VI. Marine Engineering Chemistry Notes. Composition of Coal — Heat Values — Chemistry of Gases — Atmospheric Air — Water — Carbonic Acid Gas and Carbonic Oxide Gas — Free Nitrogen — Marsh Gas — Petroleum Vapour— Ammonia — Iron Oxide — Hydrochloric Acid — Sodium Chloride — Calcium Chloride — Acids — Alkalies — Spontaneous Combustion— Treatment of Fires — Sealing-off — Air Required for Combustion — Carbon — Nitrogen — Hydrogen — Combustion — Coal Gases — General Notes on Combustion — Complete and Incomplete Combustion — Burning of CO — Scale, Density, and Corrosion — Composition of Fresh and Sea Water — Incrustation — Composition of Boiler Scale — Scale and Oil Deposit — Temporary and Permanent Hardness — Corrosion of Boilers — Causes of Corrosion — Prevention of Corrosion — Hydrochloric Acid — Scale and Plate Temperature — Magnesium Chloride — Corrosion of Tubes — Test for CO^ — Evaporator Scale — Boiler Deposits — Leaky Tubes — Density and Scale — General Notes on Scale and Density — Solids in Sea Water — Calcium Carbonate — Calcium Sulphate — Soda — Lime — Rusting — Grooving — Paraffin Oil — Carbonate of Soda — Nitrate of Silver Test — Caustic Soda — Test for Acid — Hydrometer — Oils — Viscosity — Gumminess of Oil — Classes of Oils — Oil Emulsion — Saponification — Acid Test — Viscosity Test— Other Tests — Alkala Boiler Composition — Remedies for Pitting — Galvanic Action — Rusting — Condenser Tube Corrosion ----- 408-431 X Contents SECTION VII. Marine Electric Lighting. PAGES Galvanic Cells or Batteries — Daniell Cell — Electro-Magnets — Field Magnets — Armature — Commutato-r — Brushes— Action of Dynamo — Switchboard — Volt Meter — Ampere Meter — Main Switches — Fuses — Wiring — Three-Wire System — Distribution Boxes — Lamp Switches — Incandescent Lamps — Types of Lamps — Arc Lamps — Projector — Resistance Coils — Testing for Faults — Hints on Running — Jointing of Wires — Electric Motors — Motor Starters — Types of Motors — Electric Notes -------- 432-493 SECTION VIII. Propellers. General Remarks — Thrust — Pitch — Right and Left Hand Screws — Cir- cumference and Thread — Pitch Variation — Pitch Ratio — Diameter and Length of Propeller — Length of Blade — Moulding of Blades — Slip and Wake Speed — Disc Area and Developed Area — Area Ratio — Projected Area — Thrust and Drag Surface of Blades — Cavitation — Apparent Negative Slip — Racing — Designing of Propellers with Examples — To Fit on a New Propeller — Motor Launch Propellers — Blade Interference — Twin Screws— Surface of Blades — Bronze Pro- pellers — Propulsive Efficiency — Resistance — Power Losses — Utilisa- tion of Power — Slip -.-...- 494-5: SECTION IX. Refrigeration. The Ammonia System — Pressures — Evaporator Pressures — Compressor Gland — Oil Extraction — Charging with Ammonia — Overhauling Com- pressor — Making up of Brine — Density of Brine— Circulation of Brine — Chamber Temperatures — Air in System — Carbonic Anhydride System — Properties of CO^ — Compressor — Gland— Separator— Con- denser — Evaporator — Safety Valve — Joints — Testing Parts — Instruc- tions for Charging and Working — Charging with Gas — Latent Heat of Ammonia (NH3) and COo — Critical Temperature of CO^and NH3 — The Compressed Air System — Compressor and Expander Diagrams — General Notes on Refrigeration — Pressures and Temperatures — Temperature Difference — Leaky Compressor Piston and Valves — Testing of Brine — Air Extraction — Overhauling Compressor — Brine Temperature Difference — Joint Testing . , - . 529-56' Contents xi SECTION X. Internal Combustion Engines. PAGES Producer Gas — "Cooler" and Scrubber — Steam Generator — Action — Efficiency — Consumption — Heat Value— Test Burner — Explosion Systems — Paraffin and Petroleum — Petrol — Two-Cycle — Four-Cycle — Comparison of Steam-Engine and Oil-Engine — Pistons — Revolu- tions — Water Jacket — Pressures and Temperatures — Carburetter — Valves — Sleeve Valve — Flywheel— Firing Plug — Cranking — Ignition — Jump Spark — Make-and-Break — Magneto — Setting Magneto — Motor Troubles — Loss of Power in Engine — Leaky Pistons — Exhaust Gases — Reversing — Crank Arrangements — Starting — Speed Regula- tion — Engine Troubles, Causes and Remedies — Tests — Diagrams from Oil Motors — Mean Pressure — Indicated Horse-Power — Brake Horse- Power — Types of Motors — Oil Fuel — Oil and Coal Compared — Com- position of Oil — Methods of Working — Oil Spray — Burners — Kermode Burner — Control — Starting Up — Leakage Test— Colour of Gases — Flash Point and Firing Point — Sand — Black Smoke — White Smoke — Ventilation Pipes — Air Vessel— Settling Tanks — Air Cone — Evaporation of Oil — Water in Oil — White Vapour — Diesel Engine 564-625 APPENDIX. Marine Steam Turbines — De-Laval Turbine — Parson's Turbine — Flow of Steam — Turbine Arrangements — Dummies — Blading List — Tip Clearance — Combination Arrangement — Geared-Down Turbines — SS. "Vespasian"— StS. "King Orry" — Turbines of Liner " Britannic" — Weir "Dual" Air Pumps — Three-Wire System of Lighting — Knocking in Engines — Engine Data — Vertical Donkey Boiler — Riveted Joints, &c. — Various Drawings, with Data - - - 626-664 Table of the Properties of Saturated Steam — Hyperbolic Logarithms ■ 665-676 INDEX. PAGES "A" brackets 189 Absolute pressure, definition of ... 369 Accumulator (electrical) described 492 „ (hydraulic) 335 Acidity of oils, how tested ... ... 429 Acids, properties of ... ... ... 412 Action of dynamo ... ... ... 44.5 „ lime in boilers ... ... 427 „ pressure-gauge tube ... 329 „ steam in cylinder ... 238 „ steering gear valves ... 343 Adamson ring furnace 110 Adiabatic expansion curve 368 Adjusting stroke of Weir pump ... 312 Adjustment of lead 216-19 ., „ examples of 217-18 Advantages of corrugated furnaces 116 „ feed heating . . . 306 „ high-pressure steam 384 „ hydraulic system ... 335 „ multi cylinders ... 384 „ patent valve gears... 222 „ superheated steam... 137 Ahead and astern positions of gear 212 Air extraction (ammonia) ... ... 563 Air pump 185 „ and condenser 296 „ clearance ... ... ... 327 „ connections ... to face 19^3 „ Edwards type ... 186,292 „ valves and vacuum 188, 365 Air required per pound coal ... 410 „ vessels ... ... ... ... 295 Alignment of cylinders and shafting to face 35 "Alkala" boiler composition ... 429 Alkalies, properties of ... ... 412 Alkaline test 429 Alley & iM'Lellan tvpe steering gear ' .348 Alloys, Babbit's white metal ... 274 „ Brass 274 „ strength and composition of 274 Ammonia 412 Pages Ammonia air in system 534 „ brine circulation ... 534 „ „ density 533 „ „ making 533 „ chamber temperatures ... 534 „ charging of machine ... 5.33 ,, compressor ... ... 529 gland ... 532 „ condenser ... ... 529 „ description of plant ... 531 ,, evaporator ... ... 529 „ „ pressures ... 532 „ oil extraction ... ... 533 „ overhauling compressor 533 „ system ... ... ... 529 Ammonia and COo systems to face 530 Ampere, definition of ... ... 491 „ meter ... ... ... 449 Amperes, B. of T. allowance ... 491 Andrews- Martin balanced valve 20.5, 207 Aneroid barometer 320 Angle of connecting rod 221 Angold arc lamps ... ... ... 460 Animal oils 428 Annealing 276 Arc lamps 461 „ G.E.C. type 462 „ in series ... ... ... 466 „ resistance 466 Area (projected) of propeller blades 499 „ ratio of propellers 499 Armature, description of ... ... 438 „ shaft 445 „ testing 469 „ winding ... ... ... 443 Arrangement of cranks in oil motors 581 Ash ejector (See's) 149 Aspinall governor ... ... ... 314 Assistant cylinder (Joy's) 209 „ „ diagrams from ... 210 Atmospheric air, composition of ... 409 „ pressure ... ... 369 Auld's reducing valve ... .•• 155 Autogenous welding ... 157-162 Auxiliary machinery ... .•• 62 XIV Ind ex B PAGES Balance piston 202 „ weight for crank 194 Balanced engines 4 „ ,, Yarrow-Schlick- , Tweedy system 8 Balanced valve, Andrews-Martin 205, 207 " Bandy " punkah 488 Barometer (aneroid) ... ... 320 „ (mercurial) 319 Basic process of steel manufacture 272 Batteries, galvanic ... ... ... 432 Bayonet joints ... ... ... 459 Beam calculations ... * 390-4 Beams 389 Bearing, main 19 Bearings, main ... ... ... 16 Bed-plate chocks ... ... ... 60 Bell crank for reversing ... ... 198 „ reversing 43 Bellis and Morcom engine... ... 260 Bending stress ... ... ... 279 Bessemer process of steel manufac- ture 271 Bilge and main injection ... ... 329 Blade interference (propeller) ... 521 Block for crosshead ... ... 198 Blow-off and circulating connec- tions 151 Board of Trade allowance of amperes ... 491 „ „ rules for shafting ... 282 „ „ test for steel ... 275 Boiler and engine data 318 „ Babcock type 171 „ Bellville „ 173 „ bottom blow-off 163 „ Cochran type 168 „ corrosion, causes of 421 „ „ examples of 129-31 „ „ parts affected ... 421 „ „ prevention of ... 422 „ deposits 423 „ dimensions of 165 „ efficiency 398 » » of 163 „ end plate joints ... to face 1A „ „ riveting 89 „ Haystack type 169 „ how secured ... ... ... 156 „ joints, strength of 75 „ mountings to face 163 „ repairs 127 „ riveting 75 „ scale, composition of ... 420 „ shell pressure 74 „ „ strength of ... ... 74 ,, „ stresses ... ... 74 „ tube, to cut out 152 PAGES Boiler tubes 106 „ Vertical donkey type ... 167 „ Water tube ... ' 170 „ „ Yarrow type ... 170 Boilers 71 „ hand sketches of ... to face 163 Boiling points and steam tempera- tures 147 Bolt for main bearing ... ... 18 Bolts (connecting rod), proportions of 190 Boring out main bearings ... ... 21 „ of stern post, &c. ... 56 Bottle type salinometer 148 Bottom end "leads" 37 Bottoms of cylinders 33 Bowling hoop furnace ... ... Ill Bow-M'Lachlan type steering gear 345 Boxes (distribution) ... ... ... 455 Boyle's Law of Expansion ... ... 376 Bracket (guide) for valve spindle ... 40 Brackets of twin screw steamers ... 189 Brake (friction) 589 „ horse-power, definition of ... 372 Branch wires, jointing of 480 Brazing 277 „ spelter for ... ... ... 274 Break in main wires ... ... 467 Breakdown of engines ... ... 290 ,, of pumps 294 Bremme's valve gear 223 Brine temperature difference (re- frigeration) 563 Brine test for corrosion ... ... 562 British Thermal Unit ... ... 375 Brock's valve gear ... ... ... 227 Broken armature coil test 473 „ L.P. cover 333 „ wire test by detector ... 468 , „ lamp ... ... 468 Brown's reversing gear ... ... 214 „ steam tiller 351 „ Telemotor ... ... ... 353 „ „ instructions for working 356 Brush holders, test for short circuit 470 Brushes (dynamo) described ... 444 Bryce-Douglas valve gear ... ... 227 Buckley type piston rings ... ... 54 Built shafting 278 Bush of main bearing 23 „ valve spindle eye ... ... 186 Butt (double) strap joint, with dimen- sions ... ... ... to face ^^ Butt (double) strap joint, with dimen- sions ... ... ... ... 85 Butt (double) strap joint, with dimen- sions ... ... ... to face SQ Butt straps, thickness of 87 Index XV PAGES Cabin fan and motor 486 Calcium carbonate ... ... ... 425 „ chloride ... ... ... 412 „ sulphate ... ... ... 425 Calculations for beams ... ... 393 „ on Boyle's Law ... 378 Caldwell type steering gear ... 344 Capillary attraction ... ... ... 370 Capstan and motor 487 Carbon 415 „ dioxide 410 „ heat in 418 Carbonate anhydride system of refrigeration 537-54 Carbonate of soda 426 Carbonated hydrogen gas 411 Carburetter (Thornycroft type) ... 591 „ (Wolseley type) ... 590 Care of machinery ... ... ... 67 Case-hardening ... ... ... 276 Casings for piston valves ... ... 29 Cast ieon 274 ,, pistons 10 Castings 267 Cast-steel pistons 53 Caulking tool 91 Caustic soda 427 Cavitation of propellers 500 Cell (Daniell) 433 Cementation process of steel manu- facture 269 Centrifugal force, definition of ... 367 ,, pump ■. 293 "Chain" patch 127 Charging machine with CO.^ ... 554 Charles' Law of Expansion ... 380 Check valve defective 328 Chemistry of gases 409 Chloride of magnesium 423 „ of sodium 412 Chlorine gas and corrosion of stays 93 Chocks for bed-plate 60 Circulating connections 151 „ pump 293 Circulation and priming 140 Circumference of propeller 496 Circumferential shell riveting ... 85 Clearanceof air pump 327 „ of piston 328 „ of pumps... ... ... 52 CO, burning of ... ... ... 417 CO2 (carbonic anhydride) pressures and temperatures 555 Coal, composition of 407 „ evaporation per pound ... 164 „ gases 416 Cock (water gauge) /o /ace 163 Coil (resistance) 465 Cold-air system of refrigeration 555-61 Collapse of furnaces, causes of ... 117 Collapsed furnace, how to strengthen 116 Colour of exhaust gases (oil motors) 580 Columns 16 „ how erected 26 „ how lined off 28 „ types of to face \6 Combined efficiency of plant ... 399 „ steam and hydraulic re- versing engine 337 " Combined " strength of steam and rivets 86 Combined twisting and bending ... 282 Combustion, air supply required ... 415 „ chamber, bottoms ... 101 „ „ girders ...101-6 „ „ method of support ... ■ 99 Combustion chamber stays ... 101 „ „ top riveting... 88 „ chambers ... ... 100 Combustion, definition of .369 „ general notes on ... 417 „ (spontaneous) in bunkers 4U Composition and strength of steel 274 „ of fresh and sea water 418 „ of exhaust gases (oil motors) 580 Compression of safety-valve springs 1.35 „ systems of refrigeration to face 530 Compressor (ammonia), overhaulingof 563 Compressor diagrams (cold air) ... 560 Condensation of water in cylinders 383 Condenser and air pump ... ... 296 ,, „ connec- tions to face 193 Condenser and circulation connec- tions to face 194 Condenser back pressure ... ... 366 Condenser tube corrosion, causes of 431 „ tubes 181 Cone for propellers 502 Connecting rod angle, effect of ... 221 „ „ length, how measured 327 Connecting rod proportions ... 195 „ rods ... ... ... 12 „ rods, training of ... 36 Connections for main steam to face 180 ,, for motor starters ... 484 „ of feed pumps to face 198 „ of pipes 60-1 „ of pumps ... to face 198 Conservation of energy ... ... 370 Constant, 5 1, for torsion ... ... 279 Construction of engines ... ... 16 Consumption and H.P. cut-off ... 398 „ LH.P 395 XVI Index Consumption and speed ... ... 394 „ I. H. P., speed, and dis- tance ... ... ... ... 396 Control valve of steering gear ... 342 Corrosion and bronze propeller blades ... ... ... ... r)23 Corrosion and pitting ... ..: 126 „ density and scale ... 418 „ of boilers, causes of ... 421 „ „ parts affected 129-31, 420 „ „ prevention of 422 „ of tail-end shaft 321 „ oftubes 423 Corrugated furnaces, advantages of 116 „ „ manufacture of 116 Coupling (flexible) for paddle shaft 301 Coupling (Thomson's patent) ... 289 Cover of L.P. cylinder broken ... 333 Crank arrangements in oil motors 581 „ balance weight 194 „ balanced ... ... ... 23 „ on centre ... ... ... 323 Cranking of oil motors ... ... 575 Crank-pin and piston travel ... 331 ,, „ flaws ... ... ... 332 „ „ lubricator 178 Cranks of paddle engines 299 Crank-shaft, how lined up ... ... 388 „ material for 16 Crank-shafts and columns ... ... 23 "Crossed" and "open" eccentric rods 211, 256 Crosshead and shoe ("single" type) 193-4 ,, block 198 Crucibles for above ... ... ... 270 Crushing strength of materials ... 277 Current strength, how calculated ... 493 Curve of adiabatic expansion ... 368 „ hyperbolic expansion ... 368 Curves, combined 405 „ data for 407 „ of consumption and speed 400 „ of I. H. P. and speed ... 401 „ of speed and revolutions ... 403 „ „ slip 404 Cut-off and pressures 385 „ how affected by connecting rod angle 231 Cut-off, how measured ... 49, 323 „ sooner with main valve ... 200 Cut-outs 450 Cutting by oxygen jet 162 „ of eccentric keyseats 25, 326 „ out boiler tubes ... ... 154 Cylinder clearances 44 „ connections ... ... 50 „ covers and bottoms ... 32-3 „ false face, how secured ... 34 PAGES Cylinder (I. P.) starting valve ... 183 „ joy's assistant type ... 209 „ liner ... ... ... 31-2 „ ratios and steam expan- sions ... ... ... ... .385 Cylinder ridge, how prevented ... 328 Cylinders and shaft, testing fairness of 187 Cylinders and shafting, alignment of... ... ... ... to face 35 Cylinders and valve chests 30 D Daniell cell ... Data for curves Davis type steering gear Defective check valve Density and salinometer „ and scale ... 433 407 346 328 147 424 ,, „ general notes on 424 „ of steam ju 371 „ scale, and corrosion ... 418 Deposit of oil ... ... ... 420 „ scale and plate temperature 422 Deposits of boilers 423 Depth of slide-valve face, to find ... 220 Design of propellers ... 502-19 Detector (electrical tests) 467 Developed area of propeller blades 499 Diagonal engine ... ... ... 298 „ pitch of rivets ... ... 91 ,, type engines ... ... 3 Diagram of pump connections to face 198 Diagrams for linked-up gear ... 258 „ from cold-air compressor 560 „ „ „ expander 561 „ „ Joy's cylinder ... 210 „ „ oil motors ... ...583-8 „ of ship performance ... 400 „ of valve motion 248 Diameter and pitch of rivets ... 79 „ of safety valves 136 „ of shafting, how calcu- lated 281 Diameter of propeller ... ... 498 Diesel type oil-engine ... 616-21 Dimensions and types of riveted joints ... ... ... ... 79-1 Dimensions of boilers ... ... 165 „ of connecting rod ... 195 Disadvantage of patent valve gears 222 Disadvantages of superheated steam 137 Disc area (propellers) 499 Dismantling engines ... ... 50 Displacement type air pump ... 186 Distance run, Speed, Consumption, andl.H.P 396 Index xvii Distribution boxes ... ... ... 455 Donkey boiler, Cochran type ... 168 „ Vertical „ ... 167 Double-acting circulating pump ... 293 Double-beat valve to face 186 Double-drum steering gear ... .341 Double-ported valve 201 ,, valves 203 "Doubling plate" 141 " Drag " surface of propeller blades 500 Draught, forced 122 „ natural 121 Drawing out propeller shaft ... 363 Dry-air machines (pressures and temperatures) ... ... ... 560 Dryness fraction of steam ... ... 372 Dynamo, action of, described ... 445 Dynamos, four-pole ... ... 437 „ hints on running ... 474 „ test for polarity of ... 473 Earth lamp test 472 Earth leakage test 473 Eccentric and rods 41 ,, gear in ahead and astern positions ... ... ... 212 Eccentric keyseat templates ... 231 „ keyseats, cutting off ... 323 „ keyseats, how cut ... 25 „ pulley 14 „ pulleys, how locked ... 26 „ rod length 328 „ rods"crossed"and"open" 256 „ rods, open and crossed... 211 „ (single type) 332 „ strap 15 Eccentrics 15 Economical speed 401 „ working 70 i Edwards air pump 293 „ type air pump ... 186,191 , Effect on steering due to propellers 523 Effects of connecting rod angle on cut-off 2.30 ! Effects of link adjustment on I. H. P. 263 ; „ linking up ... ... 230 | Effective pressure, definition of ... 369 ; „ „ (mean), definition of .369 Efficiency 368 , „ (combined) 399 „ (mechanical) .399 „ of boiler 163, 399 ' „ of propulsion ... ... 524 „ (propeller) 399 ' „ (thermal) 381 Ejector (See's) for ashes 149, "Elastic limit " of plates, &c. Electric glow radiator „ punkah (G.E.C. type' Electrical H.P. and I. H. P. compared „ motors „ notes Electricity, definition of Electro-magnets Elevator heating system End-plate seams „ stays Energy, conservation of „ definition of „ kinetic „ potential Engine-room appliances Engine and boiler data „ Bellis and Morcom type „ for turning ... Engines, balanced ... ,, breakdown of „ diagonal „ dismantling of „ oscillating type „ paddle „ paddle cranks „ quadruple „ screw „ stopping „ trunk type Entropy, definition of "Equivalent evaporation" ... I-H.P.. Erecting machinery in ship „ ofcolumns Evaporation per pound coal Evaporator scale „ Weir type Examples of boiler corrosion „ of lead adjustment Excessive piston clearance... Exhaust lap gauges Expanded diagrams (cold air) Expander for tubes ... Expansion, Boyle's Law of „ curve (Adiabatic) » » (Hyperbolic) „ curves of steam „ joint „ joint of steam pipe „ of steam and heat „ of water by heat „ slot of reversing gear Expansions by pressures an volumes ... External heat of steam " Extra " link gear ... PAGES 71 489 488 491 421 490 492 431 490 89 91-8 370 367 373 373 303 192 318 260 180 4 290 2 50 296 /o/ace 298 1 299 7 1 290 299 369 163 372 59 26 164 423 305 129-31 217-8 ... ,328 /o/ace 200 561 150 376 368 368 375 /o/ace 186 140 386 386 213 380 373 242 XVIU Index Fairness of paddle cranks ... „ of shaft and cylinders False face of cylinder, how fixed Fan and motor Feathering paddle wheel Feed heater, Weir's... „ heating, advantages of ,, pump connections „ Weir type „ „ Worthington type „ water filter Ferric oxide ... Ferrules of condenser tubes Field magnets, description of Fire-bars, dimensions of ... Fitting of running gear Flat surfaces ... Flaws in shafts „ L.P. crank-pins „ on shafting, how repaired Following edge of propeller blade Foot-pound, definition of Force, centrifugal, „ PAGE 300 187 34 486 301 303 306 to face 198 , 308 314 313 . 412 , 181 . 436 .118-9 3G . 95 . 326 . 332 .285-9 500 , 366 , 367 , 367 .122-6 . 569 , 437 . 411 , 418 . 589 , 367 , 164 , 110 , 111 , 117 Forced draught Four-cycle oil motors Four-pole dynamos ... Free nitrogen Fresh water, composition of Friction brake „ laws of Funnel gases, weight of Furnace, Adamson ring type „ bowling-hoop „ „ corrugations, types of „ Fox type ... ... tofaceWZ „ front riveting ... ... 114 „ Gourley-Stephen type ... 106 „ manufacture 116 „ method of strengthening 115 „ suspension bulb type ... 112 „ temperatures, &c. ... 118 Furnaces, causes of collapse ... 117 Fuses ... ... ... ... ... 450 Galvanic action, definition of ... 430 „ cells 432 Gases, retention of ... ... ... 127 „ velocity of ... ... ... 164 Gauge for water level ... ... 145 „ for wear-down tests 62-3 „ indications 318 „ pressure, definition of ... 369 Gauges for pressures ... ... 192 Gear, Bremme's patent 223 PAGES Gear, Brock's 227 „ Bryce-Douglas 227 „ for reversing ... ... 179,213 „ Hackworth's ... .!. ... 226 „ in " ahead " and " astern " positions 212 Gear, Joy's 225 „ -Marshall's patent 223 „ Morton's 225 General definitions 366 ,, notes and descriptions ... 264 Gourley-Stephen furnace ... to face 106 (iovernor, Aspinall's ... ... 314 Graphic method of proving boiler shell stresses ... ... ... 72-3 Grate surface and heating surface 127 Gravity, definition of ... ... 369 Grooving in boilers ... ... ... 426 Gross or absolute pressure, defini- tion of .369 Guide bracket, for valve spindle ... 40 Guides, single type ... ... ... 15 Gumminess of oils ... ... ... 428 Gun-metal ... ... ... ... 274 G.E.C. type arc lamps 462 „ projector 463 H Hackworth's valve gear Hall system of COo refrigeration Hand-riveting Hard steel Hardness (permanent) of water „ (temporary) Haslam system of ammonia frigeration Haslam system of CO., refrigeration 550-2 „ „ of cold air refrigera- tion 555-61 . 226 537-50 . 90 . 274 . 420 . 420 534, Hastie type steering gear ... .. 349 Haystack boiler .. 169 Heat absorbed in natural draught 121 „ and expansion of steam .. 386 „ definition of .. 366 „ efficiency .. 381 „ in carbon .. 418 „ in one pound coal .. 409 „ latent, definition of ... .. 367 „ sensible, ,, .. 367 „ total, „ .. 367 „ unit, „ .. 366 Heater for feed water (Weir's) .. 303 Heating, effect of scale .. 427 „ surface and grate surface 127 High -pressure steam, advantage c f 384 Hints on running dynamos... .. 474 Horse-power (brake or shaft) .. 372 Index XIX Horse-power, definition of 366 „ equivalent 372 Hot-well temperature and condenser pressure ... ... ... ... 366 Howden's forced draught ... 122-26 H.P. cut-ofif and consumption ... 398 Hydraulic accumulator 335 „ „ advantages of 335 „ and steam reversing gear 214, 337 „ crane ... ... ... 337 „ piston packing 215 Hydrochloric acid ... ... 412, 422 Hydrogen ... ... ... ... 415 Hydrokineter (Weir's) 141 Hydrometer described ... ... 427 Hyperbolic expansion curve ... 368 I I. H.P. and consumption 395 „ and E.H.P. (electrical) com- pared 491 I. H.P. and link adjustment 263 „ „ speed curve 401 „ (equivalent) 372 Improvement in propeller, effect of 523 Incandescent lamps 457 Increasing pitch (propeller) ... 497 Incrustation, composition of ... 419 Indications of gauges 318 Induction, definition of 492 Inertia, definition of. ,367 Initial condensation ... ... 383 „ pressure, definition of ... 369 Injection, main and bilge 329 Instructions for working Brown's Telemotor ... ... ... 356 Instructions for working CO2 machine 543 .479 . 521 Insulating of joints Interference (propeller blade) Internal combustion engines — Advantages of 564 and steam engine 570 B.H.P. of 589 Carburetter 574 Colour of exhaust gases 580 Crank arrangements ... ... 581 Cranking 575 Diagrams from 585-8 Diesel type 616-21 Disadvantages of ... ... ... 564 Explosion systems 567 Firing plug 574 Four-cycle 569 Ignition 576 I. H.P. of 588 Magneto 576 Internal Combustion Engines Magneto, setting of Mean pressure Number of cylinders Paraffin and petroleum Petrol Pistons Pressures and temperatures Reversing Revolutions Speed control Starting of ... Troubles classified „ of Two-cycle ... Types of Valves Water jacket Internal heat of steam Iron and steel manufacture „ malleable „ oxide „ tubes and stays PAGES -contd. .. 579 .. 588 .. 573 .. .568 .. 568 .. 573 .. 574 .. 581 .. 573 .. 582 .. 582 ..582-4 579-80 .. 569 589-609 574 573 373 264 267 423 313 Joint, insulating of 479 „ (scarfed) 479 Joints and riveting 78 Joints, bayonet pattern 459 „ (scarfed) 142 „ (types of), with dimensions 78-91 Jointing of branch wires 480 „ main cables 479 „ wires 478 Joy's assistant cylinder 209 „ „ „ diagrams ... 210 „ valve gear 225 Jump-spark 576 K Keeping a watch 68 Keyseats for eccentrics, cutting of 323 „ „ how cut ... 25 „ „ position of 231 Kilowatt 492 Kinetic energy 373 Klinger type water gauge 153 Lap, exhaust joint, double riveting „ single „ „ treble „ minus exhaust ... steam 200 78 78 78 200 200 XX Index Lament pump Lamp (pilot) „ switches Lampholders Lamps, incandescent type ... „ Osram type... Latent heat, definition of ... ofNHsandCOo „ of steam Law of Expansion (Boyle's) „ calculations (Charles') Lead PAGES ... 316 ... 477 ... 456 ... 459 ... 457 ... 458 ... 367 ... 554 ... 373 ... 376 ... 378 ... 380 ... 200 „ adjustments 216-9 „ of piston valve, how measured 215 Leading edge of propeller blade ... 500 " Leads " of bottom end 37 „ of main bearings, how taken 24 Leakage in magnet coils 468 Leaky pistons (oil motors) 580 „ tubes 133 „ „ causes of 424 Leather packing of hydraulic piston 215 Length of connecting rod, how found 327 ,, eccentric „ „ 328 „ propeller 498 „ blade 498 „ valve spindle, how found 327 Lift of pumps 387 Lignum vitse strips 181 Lime ... ... 426 „ in boilers, action of 427 Limit of elasticity 71 Liners for cylinders 31-2 „ for piston valves 29 „ of tale-end shafts 55 Lining-off of columns ... ... 28 „ the soleplate 20 Lining up crank-shaft 388 „ of shafting 325 Link adjustment and I. H. P. ... 263 „ brasses and pump clearance... 327 „ motion 229 Linking up, effects of 230 „ gear diagrams 258 Litmus paper tests ... ... ... 429 Liverpool Refrigeration Co., am- monia system 552-34 Liverpool Refrigeration Co., CO2 system ... ... ... ...552-4 Loose eccentric ... ... ... 332 Loss of power in oil motor ... ... 579 „ of vacuum, causes of 294 Losses of power ... ... ... 525 L.P. crank-pin flaws 332 „ cylinder cover, broken ... 333 L.P. piston (naval type) Lubricating oils Lubrication of crank-pin Lubricator M PAGES 184 428 178 334 Machine riveting 88-90 Machinery, erection in ship ... .59 „ upkeep 67 Magnesium chloride ... ... 423 Magneto 577 „ setting of 579 Main and bilge injection ... ... 329 „ bearing bolt ... ... ... 18 „ „ bush 22 „ „ bushes, boring out ... 21 „ „ complete 19 „ bearings ... ... ... 16 „ cables, jointing of ... ... 479 „ switches 449 „ wires, short circuit in ... 473 Make-and-break spark 576 Malleable iron 267 Manholes 119 Manufacture of furnaces 116 „ of iron and steel ... 264 Marine electric lighting 432 „ engineering chemistry ... 408 Marking off ship for boring out ... 56 Marsh gas (Methane) ... 411,413 Marshall's valve gear 223 Martin-Andrews balanced valve ... 205 Material for shafting 387 Materials, crushing strength of ... 277 „ tensile strength of ... 277 Mean effective pressure, definition of 369 Measurement of piston clearance... 328 „ „ valve head 215 Measuring pitch of propeller ... 322 „ the cut-off 49 Mechanical efficiency 399 „ equivalent of heat ... 366 Megohm, value of 493 Mercurial barometer ... ... 320 Metallic packing 11 ,; (U.S.) 359 Methodof chargingmachine with COo 553 „ locking eccentric pulleys 26 „ patching boiler plates ... 128 „ securing false face of cylinder ... ... ... ... 34 Method of setting valves ... ... 47 „ supporting combustion chambers ... ... ... 99 Mild steel 274 Milton, J T., Esq., description of Diesel engine 616 Inde: XXI Mineral oils ... Minus exhaust lap ... Moment of bending „ twist Momentum, definition of . Morcom and Belliss engine Morton's valve gear ... Motor and cabin fan „ and capstan ... „ and centrifugal pumps „ launch propellers „ starter connections „ troubles Motors, electrical „ starting switches „ types of Mountings of boilers Muntz metal ... N Natural draught „ „ heat absorbed in ... Naval brass „ type L.P. piston „ „ piston rod Negative slip (propellers) „ wires, how marked Neutral axis of beam NH;, (ammonia) pressures and tem- peratures Nickel steel Nitrate of silver test for density ... Nitrogen ... 411, Non-freezing fluid for telemotors ... Notes (electrical) „ on density and scale Number of cylinders in oil motors Nuts, proportions of PAGES 428 Oil fue I, flash point, &c. PAGES ... 614 200 leakage test ... 613 281 methods of working ... 611 281 oil spray ... 611 369 sand ... 614 260 settling tanks ... 614 225 shale oil ... 612 486 starting up ... 613 487 ventilation pipes ... ... 614 486 water in oil ... ... 615 521 white smoke ... 614 484 „ vapour ... 615 579 working ... 613 481 Oil motor and steam-engine compared 572 483 Oi motors ... 572 589-609 9> carburetter of ... ... 574 . to file s 163 51 diagrams from... ...585-8 . ,. 274 5J fly-wheel of ... 574 121 121 274 184 196 501 492 390 555 274 426 415 359 490 424 573 190 o Ohm, definition of .. 491 Oil deposit .. 420 „ engine, Diesel type 616-21 Oil-feed box ... .. 197 Oil fuel .. 609 n advantages of .. 610 )? air cone .. 614 >> „ vessel .. 614 5> and coal compared .. 610 ?> black smoke .. 614 1) burners .. 611 >5 colour of gases .. 613 » composition of oil ... .. 611 J> control .. 613 >J disadvantages of ... .. 610 »> evaporation of oil ... .. 615 number of cylinders employed pressures and tempera- tures ... "sleeve" valve sparking plug of speed regulation of ... starting of troubles of ... ... ; valves of Oils 573 574 574 574 582 582 82-4 574 428 428 428 428 428 429 428 „ classes of „ emulsion of ., gumminess of ... „ saponification of „ to test acidity of „ viscosity of "Open" and "crossed" eccentric rods 211, 256 Oscillating cylinder and trunnions 297 „ engines ... ... ... 296 Osram lamps 458 Overhauling ammonia compressor 563 Oxide of iron 423 Oxygen jet (cutting by) 162 Packing, metallic 11 „ of hydraulic piston ... 215 „ rings ("restricted" type)... 204 „ U.S. metallic 359 Paddle engine cranks ... ... 299 „ „ to test fairness of 300 Paddle engines 1 „ shaft flexible coupling ... 301 „ wheel (feathering) 301 Paraffin and petroleum 568 oil, use in boilers 426 XXll Index PAGES Parson's white metal ... ... 274 Patch, chain type ... ... ... 127 Patent shaft coupling (Thomson's) 289 i Patent valve gears ... ... ... 222 „ „ advantage of ... 222 „ „ disadvantage of 222 „ „ Marshall's ... 223 „ „ Bremme's ... 22.3 „ „ Morton's ... 225 „ Joy's 225 „ „ Hackworth's ... 226 Permanent hardness of water ... 420 Pet valves 295 Petrol 568 Petroleum vapour ... ... ... 411 Phosphor bronze 274 Pig-iron 266 Pilot lamp 477 Pipe connections ... ... ... 60-1 Pipes, steam 139 Piston and crank-pin travel ... 331 „ cast-iron type ... ... 10 „ clearance ... ... ... 328 „ „ excessive ... ... 328 „ „ how measured ... 328 „ (L.P.), naval type 184 „ pumps 293 „ rings, Buckley type ... ... 54 „ rod and crosshead ... 193, 194 „ „ naval type 196 „ „ to test fairness of ... 327 Piston valve (Admiralty type) ... 202 „ and piston positions ... 237 „ lead, how measured ... 215 „ liner ports and bars ... 29 „ liners ... ... ... 29 ring 201 Piston valves 206 „ with restrained rings 208 Pistons 9, 388 „ cast steel 53 „ leaky (oil motors) 589 „ of oil motors ... ... 573 Pitch and diameter of rivets ... 79 „ (diagonal) of rivets 91 Pitting and corrosion 126 „ remedies for 430 Plates flanged out 142 „ tensile strength of 71 „ zinc 143 Plugs (wall) 459 „ watertight 460 Position of eccentric keyseats ... 231 Positions of piston and valve ... 236 „ of valve and piston iofciceiZ8 Positive wires, how marked ... 492 Potential (electrical), definition of 490 ,, energy 373 Power and revolutions ... ... 279 Power and speed curve P.\GES 402 )> definition of 366 „ (horse), definition of 366 )) loss in oil motor 579 1? losses... 525 )) utilisation of 525 Pressure, atmospheric 369 ?j effective 369 II gauge ... 369 >» „ indications... 318 5> gauges 192 )) gross or absolute 369 )) initial 369 )? mean effective 369 )? terminal 369 Pressures and cut-off 385 » and temperatures of NH., and COg .555 Pressures and volumes 382 Prevention of ridge in cylinder 328 Priming of boilers and circulation 140 Producer system action 566 9) „ consumption of ... 567 5) „ cooler and scrubber 566 J) „ efficiency of 567 » (gas) 566 )> „ heat value of 567 5> „ steam generator... 566 9) „ test burner 567 Projector arch lamp 463 Propeller blade interference 521 j9 „ to fit on 519 )) blades (bronze) ... 523 5> design 502-19 )) efficiency 399 » (Gaine's reversible) 581 )1 improved, effect of 523 » pitch, how measured 322 5) „ to find 521 J» „ with shaft inclined 519 » shaft, drawing out of 363 J) „ liners, how secured 55 « turbine type ... to face b'i^ Propellers 494 )> area, ratio of 499 )j cavitation 500 )> circumference of 496 » cone 502 » developed area of 499 J5 diameter of 498 )J disc, area of 499 5> drag surface 500 )» following edge 500 » for motor launches 521 55 increasing pitch... 497 >5 leading edge 500 )) length of... 498 » blade 498 J) moulding of blades 498 Index XXlll Propellors, negative slip PAGES 501 „ pitch 495 „ „ ratio 498 „ projected area 499 „ racing .502 „ right and left hand 496 „ set back 502 „ slip 499 „ thread 499 „ thrust 495 „ „ surface 500 „ true screw surface 498 „ wake speed 499 Proportions of connecting rod 195 bohs, &c 190 Propulsive efficiency 524 Puddling furnace 268 Pulley and strap 14 Pulleys, how locked ... 26 Pulsometer type pump 364 Pump (air), naval type 185 „ centrifugal type 293 „ clearance and link brasses ... 327 „ clearances 52 „ connection diagram io face 198 „ (feed), connections of „ 198 „ lifts 387 „ links, how trammelled 51 Pumps 291 „ breakdown of 294 „ Edwards' patent 292 „ Lament's 316 ,. Weir's 308 „ Worthington's 314 Punkah (electric). G.E.C. type 488 Q Quadrant and block 229 Quadruple engines 7 R Racing of propeller 502 Radiators (electrical) 489 Ramsbottom rings ... ... ... 53 Ratio of cylinders and expansions 385 „ pitch to diameter 498 Reduced pressure steam, superheat ing of 157 Reducing valve (Auld's) ... ... 155 Refrigeration... ... ... ... 529 „ ammonia system 529-37 „ CO.j 537-54 „ cold air ... 555-61 „ general notes on ... 561 „ compression systems to face 530 PAGES Refrigeration, joint testing 5G3 „ leaky compressor ... 552 „ pressures and tem- peratures employed 5G2 Relief ring 203 „ frame 204 Remedies for pitting ... ... 430 Repair of shafting 285-289 Repairs for boilers ... ... ... 127 Resistance and arc lamp 466 „ coil ... 465 „ (hull) 525 ,, regulator 485 Restricted type packing ring 204, 208 Retention of gases and furnace collapse ... ... ... ... 127 Reversing bell crank ... 43,198 » gear 179 „ "gear "and "expansion" slot 213 Reversing gear (Brooke) 607 „ „ (Fairbanks) ... 609 „ „ (Hesse and Savory) 608 „ „ steam and hydraulic 214 „ (Stirling) 602 „ of oil motors ... ... 581 „ quadrant and block ... 229 „ shaft 42 Revolution and speed curve ... 403 Revolutions and power ... ... 279 Revolutions of oil motors ... ... 573 Ridge in cylinder, prevention of ... 328 Right and left hand propellers ... 496 Rings, Buckley type 54 Rivet and seam, combined strength 86 „ section 77 Rivets, diagonal pitch of 91 Riveting hand 90 „ machine ... ... ...88-90 „ of combustion chamber top 88 „ of furnace front ... ... 114 „ single 79 Rocking shaft, how tested ... ... 326 Running gear, fitting of ... - ... 36 „ hints (dynamos) ... ... 474 Rusting 426,430 Safety valves Salinometer and density „ (bottle type) ... Saponification of oils Saturation-point of water ... Scale, composition of „ density and corrosion „ from evaporators Scarfed joint 133-6 . 147 . 148 . 428 . 424 . 419 , 418 , 423 , 479 XXIV Index Scarfed joints 142 Screw engines 1 „ (twin or triple) stern brackets 189 Screws (twin) ... ... ... 523 Seam section... ... ... ... 77 Sea water, composition of ... ... 419 Securing of boilers in position ... 156 See's ash ejector ... ... ... 149 Sensible heat, definition of... ... .367 Series arrangement of arc lamps ... 466 Serve type of tube 108 Set back of propeller blades ... 502 Setting of valves ... ... 47,219 „ of valve, tables of ... 2.39-48 „ valve to mid travel 323 Shaft and cylinder alignment to face 35 „ andcylinders,totest fairness of 187 „ corrosion of ... ... ... 321 „ diameter, how calculated ... 281 „ flaws 326 „ horse-power, definition of ... 372 Shafting, B. of T. rules for 282 „ built 278 „ flaws on 284 ,, how repaired 285-9 „ lining up of ... .. 324 „ Lloyd's rules for ... ... 282 „ material 387 „ strength of 278 Short circuit tests 467 .Shortness of water in boiler ... 164 Shrinking-on of shaft liners ... 55 Sight-feed lubricator 334 Sighting of shaft 325 Simm's magneto ... ... ... 577 Single eccentric 332 „ riveting 79 Single-type guide 15 Single-wire system ... ... ... 451 Siphon, action of ... ... ... 370 Siphon-feed oil box 197 Sketches of boilers to face \%^ Slide valve and piston positions ... 236 „ to find depth of ... 220 Slip, description of, by T. Sidney Cockrill, Esq 526 Slip (negative) 501 „ (propeller) 499 Soda, use of ... ... ... ... 425 Sodium chloride ... ... ... 412 Soleplate 16 „ lining off 20 Solids in sea water ... ... 425 Sparking plug 574 Speed and consumption ... ... 395 „ „ curve ... 400 „ and power „ ... 402 „ and slip „ ... 404 „ of wake 499 PAGES Speed, regulation of oil motors ... 582 Specific gravity, definition of ... 368 „ heat, „ „ ... 368 Spelter for brazing ... ... ... 274 Spontaneous combustion ... ... 413 „ „ causes of 414 „ „ prevention of 414 Spontaneous combustion, treatment of 414 Spindle eye bush of valve ... ... 186 Spindles of valves ... ... ... 13 .Squared paper diagrams ... ... 400 Starters for motors ... ... ... 483 „ „ connections of 484 Starting of oil motors ... ... 582 „ valve (LP. cylinder) ... 183 Stay tubes and ordinary tubes ... 107 Stays for end plates ... ... ... 91-8 „ for tube plates ... to face 115 Steam and hydraulic reversmg engine ... ... ... ... 337 .Steam consumption per revolution 383 „ definition of 367 „ density 371 „ dryness, fraction of ... ... 372 „ expansionsandcylinderratios 385 „ „ by pressures and volumes 380 Steam external heat of 373 „ in cylinder, action of ... 238 „ internal „ 373 „ lap 200 „ latent „ 373 „ (main) connections ... to face 180 „ pipe expansion joint ... 140 „ pipes 139 „ „ water hammer in ... 139 „ pressures and volumes ... 382 „ saturated definition of ... 375 „ space stays 91-4 „ superheated by reducing valve ... ... ... 157 „ superheated, definition of ... 376 „ tiller (Brown's) 351 „ total heat of 373 „ wet, definition of ... ... 376 Steel, B. of T. test for 275 „ manufacture, Bessemerprocess 271 „ „ basic „ 272 „ „ cementation pro- cess 269 Steel manufacture, Siemens-Martin process ... ... ... ... 272 Steel, production of 269 „ strength and composition of 274 „ tempered ... 271 „ tempering of ... ... ... 276 Steering gear action of valves ... 343 Index XXV 348 345 345 346 Steering gear, by Messrs Alley &; M'Leilan Steering gear by Messrs Bow, M'Lachlan & Co. Steering gear by Messrs Caldwell & Co Steering gear by Messrs Davis tS: Co. ,, „ by Messrs Hastie& Co. 349 „ ,, control valve... ... 342 „ „ transmission system to face 341 ,, gears 340 Steering, how affected by propellers 523 Stern post, boring out ... ... 56 „ tube after bearing bush „ tube and shaft „ „ Cedervall's Patent Stopper for boiler tubes (Bagguley Patent) toface\^Z Stopping of engines 290 Straightening action of gauge tube 329 Strain, definition of 368 Strength and composition of alloys „ (tensile) of steel ... Strengthening of weak furnace Stress, bending „ circumferential „ definition of ... „ longitudinal ... „ of thrust block „ torsion Stresses on boiler shell seams „ on shafting „ on various parts ... Suction lift of pumps Superheated steam ... Suspension bulb furnace corrugation Switchboard, description of Switches for lamps system » (main) 181 361 362 274 71 116 279 72 367 72 182 279 71 388 278 387 137-9 112 446 456 449 Table of valve setting 219 Tables „ „ ... 239-48 Taking " leads " off bottom ends ... 37 Telemotor, Brown's 353 „ fluid for 359 „ instructions for work- ing, &c 356 Temperature difference (refrigeration) 562 „ of furnaces 118 „ of hot-well and con- denser pressure ... ... 366 Temperatures and pressures of NH3 and COo systems ... ... 555 Temperatures (critical) of NH3 and CO2 systems 555 Tempered steel ... ... ... 271 Tempering steel ... ... ... 276 Temporary hardness of water ... 420 Tensile strength of materials ... 277 Terminal pressure, definition of ... 309 Test for acid in water ... ... 427 „ alkali 429 „ animal or vegetable oils ... 429 ,, break in mains ... ... 467 „ broken armature coils ... 473 „ broken wire... ... ... 470 „ carbonic acid ... ... 423 ,, earth leakage 471 „ polarity 473 ,, short circuit between mag- net and coils 469 Test for short circuit between arma- ture coils 469 Test for short circuit between arma- ture coils and drum ... ... 469 Test for short circuit in brush holders 470 „ „ „ magnet coils 468 „ „ „ mains ... 473 „ „ circuits, &c 467 „ steel 275 ,, viscosity of oils 429 Test with "earth" lamp 472 Testing fairness of paddle cranks ... 300 „ „ piston rod ... 327 „ „ rocking shaft ... 326 ,, „ shaft cylinders 187 „ „ shafting ... 326 „ joints in ammonia system ... 563 Thermal efficiency ... ... ... 381 Thermometer ... ... ... 320 Thickness of butt-straps 87 Thomson patent coupling 289 Thornycroft type carburetter ... 591 " Thread " of propeller blade ... 496 Three-wire system ... ... ... 454 Thrust 330 „ block (part section) 182 „ „ stress 182 „ of propeller 495 „ surface of propeller blades ... 500 Tiller (steam), Brown's 351 "T"joints 481 To adjust stroke of Weir pump ... 312 ,, valves of Worthington pump 316 To find cut-off 323 To set valve in mid-travel 323 Torque 374 Torsion stress ... ... ... 279 Total heat, definition of ... ... 367 „ of steam... ... ... 373 Training of connecting rods ... 36 „ valve gear 39 Trammelling pump links 51 XXVI Inde: IMAGES Transformers, function of ... ... 492 Transmission gear of steering engine /o/rrce Z-il Travel of crank-pin and piston ... 331 „ valve, how found... Trial trips "Trick" type of slide valve... Troubles of oil motors True screw surface (propellers) Trunk types of engines Trunnions of oscillating engines Tube corrosion „ expander „ plate stays „ stopper 260 65 ^o/ace 200 582-84 . 498 . 299 . 297 . 423 . 150 to face 115 ... 132 Bagguley Patent type to face 133 Tubes (condenser) and packing ... 181 „ of condenser corroding ... 431 Tunnel shafting 282 Turbine propeller to face h^O Turning engine and gear 180 Tweedy system of balanced engines 8 Twin screws ... ... ... ... 523 Twine-wire system ... ... ... 451 Twisting moments ... ... ... 281 Two-cycle oil motors ... ... 569 Types of columns ... ... to face 16 „ furnace corrugations (dimen- sioned) ... ... ... ... 117 Types of joints, with dimensions ... 78-91 motors 589-609 u Unit of heat, definition of 366 United States packing ... ... 359 Upkeep of machinery ... ,.. 67 Utilisation of power 525 V Vacuum, and air pump valves ... 365 „ loss of 294 Valve and piston positions 236 „ and piston positions to face 238 „ Andrews-Martin type 205, 207 „ diagrams 248 „ „ linked-up 258 „ double-beat type ... to face 186 „ double-ported type 201 „ exhaust lap 200 „ face, to find depth of ... 220 „ gear, Bremme's 223 „ „ Brock's 227 • „ „ Bryce-Douglas ... 227 „ „ details of ... ... 14 „ Hackworth's 226 PAGES Valve gear, Joy's 225 „ „ Marshall's 223 „ „ Morton's *225 „ ,, training of 39 „ gears, patent types 222 „ lead of 200 „ minus exhaust lap ... ... 200 „ placed in mid-travel... ... 323 „ setting 47 „ „ of Worthington pump 316 „ „ table 219 „ „ tables ... 239-48 „ (slide), duties of 199 „ ,, travel of 199 „ spindle eye bush 186 „ spindle-length 327 „ spindles, type of 13 „ steam lap 200 „ sticks for lead measurement 215 „ throttle to face 186 „ travel, how determined ... 260 „ trick type to face 200 Valves, double-ported type ... 203 „ of air pump ... ... ... 188 „ of Weir pump 309 » (pet) 295 „ piston type 206 „ piston type with restrained rings 208 Valves (safety) 133 „ „ lever type 134 „ „ spring „ ... ... 135 „ „ „ compression... 135 „ „ to find diameter of 136 „ types of ... ... ... 9 Vapour of petroleum 411 Vegetable oils 428 Velocity of gases ... ... ... 164 Vertical type donkey boiler ... 167 Viscosity of oils ... ... ... 428 „ test for oils 429 Volt, definition of 490 Volt-meter 448 Voltage, calculations for 493 w Wake speed 499 Wall plugs 459 Watch, keeping ... ... ... 68 Water, chemical composition of ... 410 „ e.xpansion by heat 386 „ formed by initial condensa- tion 383 „ gauge 145 „ „ Klinger type 153 „ shortness of, in boiler ... 164 Water-gauge cock 163 Index xxvii "Water hammer" Watertight wall plugs Water tube boilers „ „ „ Babcock type „ „ „ Belville type „ „ „ Yarrow type " Wear-down " gauge Wear-down of pump links ... Weight of funnel gases Weir hydrokineter ... „ pump stroke, how adjusted „ type evaporator „ „ feed heater „ „ feed pump valves Welding „ (autogenous process) "Wet" steam, definition of Winding of armature Wing furnace flanging Wires, jointing of ... Wiring „ single system „ twin-wire system "Witness" marks ... FACES 139 460 170 171 173 1 70 62-3 51 164 141 312 305 303 309 277 157-62 376 443 115 478 450 451 451 28 PAGES Wolseley type carburetter 590 Work done during adiabatic expan- sion 383 Working of Hall's COo machine, instructions ... ... 543-50 Working economically ... ... 70 Workshop practice ... ... ... 1 Worthington type feed pump ... 314 „ pump valves, how set 316 Wrought iron ... ... ... 274 "Wyper" shaft 42 Yarrow-Schlick-Tweedy system ... 8 „ type water tube boiler ... 170 Zeuner valve diagrams 248 Zinc block and stud 144 „ plate in box 144 „ plates 143 DESIGN DRAWINGS AND CALCULATIONS. Sheets i and 2 show proportions of Nuts, Bolts, and Screws. Boilers— 1. Single-Ended Combustion Chamber. 2. Double-Ended Combustion Chamber. 3. Furnace and Fire Bars. 4. Water Gauge Column. 5. Vertical Donkey Boiler. 6. Fire Bars and Bearers for Vertical Boiler. Valves — 7. Dead Weight Safety Valve. 8. Spring- Loaded Safely V^lve. 9. Boiler Stop Valve. 10. Engine Room Stop Valve. 11. Feed Check Valve. 12. Bilge Suction Valve Chest. r2A. Bilge Injection Valve. 13. Side Discharge Valve. 14. Cylinder Relief Valve. 15. Slide Valve and Spindle. 16. Inside Steam Piston \'alve. 17. Double Ported Slide Valve. Pumps — 18. Air Pump. 19. Feed Pump Complete. 19a. Feed Relief Air Vessel and Valves. Pump Pistons — 20. H. P. Piston and Rod. 21. L.P. Piston and Rod. 22. L. P. Cylinder Cover. 23. Donkey Pump Cylinder and Valve. Eccentric, etc. — 24. Eccentric and Rod Complete. 25. Quadrant Bars, etc. 26. Reversing Bell Crank. Shafting— 27. Crank Shafting. 28. Thrust Shaft and Shoe. 29. Thrust Block. 30. Stern Tube and Shaft. 31. Propeller Boss. Various — 32. Bottom Blow-Off Cock. 33. Three-Way Change Cock. 34. Main Bearing. 34a. Tunnel Bearing Block. 35. Steam Pipe Expansion Joint. 36. Pump Levers. 37. Connecting Rod. 38. Pump Crosshcad and Links. INDEX TO APPENDIX: Action of sleam in turbine Ahead dummy Air pump (Weir " Dual" type) ... Arrangement of combined turbines and reciprocating engines ... Arrangement of geared-down turbines... ,, of turbines... Benefits of combination arrangement ... Blade tip clearance Blading list Boiler data (vertical type) Channel steamer turbine blades ... Circumferential shell riveting ... ,, ,, seam stress ,, ,, seams Clearance of blades Combined reciprocating engines and turbines... Compensating ring for manhole ... Data of main engines De -Laval turbine .. . Description of geared-down turbines of SS. "Vespasian" Description of propelling machinery of SS. "KingOrry" Description of propelling machinery Q.SS. " Reina Victoria Eugenia " ... Donkey boiler (vertical type) Door (manhole) ... Dummies ... Dummy (ahead type) ,, clearance Engine data ,, knocking... Facial rings Flow of steam in turbine ,, ,, through blades ... Geared-down turbines SS. " Vespasian Height of turbine blades H. P. turbine data " King Orry," machinery of Knocking in engines Length of turbine blades... Longitudinal seams TAGES 628 638 647 639 643 631 639 636 635 653 635 655 656 654 636 639 656 651 626 643 644 640 653 656 634 638 636 651 650 634 628 630 642 643 636 636 644 650 I'AGES Low pressure turbine ... ... ... 640 L. P. turbine data 637 Machinery of Q.SS. "Reina Victoria Eugenia" ... ... ... ... 640 Machinery of SS. " King Orry " ... 644 ,, of SS. "Vespasian" ... 643 Manhole compensation ring ... ... 656 Marine turbines ... ... ... ... 626 Number of l)lade rows ... ... ... 635 ,, of turbines fitted ... ... 631 " Orry, SS. King," turbines of ... ... 644 Parallel flow 628 Parson's turbine .„ ... ... ... 628 Path traced by steam ... ... ... 629 Plan of turbine rooirt ... ... ... 637 Pressure on bearing surfaces ... ... 652 Principle of turbine ... ... ... 626 " Reina Victoria Eugenia," SS. ... 640 Results of trials, " Reina Victoria Eugenia" ... ... 642 Results of trials, " Vespasian " ... ... 644 Ring (compensating) ... ... ... 656 Riveting of vertical donkey Ijoiler ... 653 Rotor drum dimensions ... ... ... 636 Rows of blades, number of ... ... 635 Standard arrangement of turbines ... 631 Steam, action of ... ... ... ... 628 ,, flow 629 ,, speed data ... ... .. 652 ,, turbines ... ... ... ... 626 ,, volumes ... ... ... ... 633 Steamer (twin screw) data ... ... 651 Stop valve data ... ... ... .-. 652 Stresses on seams... ... ... ... 656 Thickness of boiler shell... ... ... 653 Three- wire system of lighting .., ... 649 Turbine arrangements ... ... ... 630 ,, combination arrangements ... 639 ,, (De-Laval) 626 ,, (geared-down) ... ... ... 642 ,, (Parson's) ... ... ... 628 Twin screw steamer data ... ... 651 Vertical donkey boiler data ... ... 653 "Vespasian" ... ... ... ... 643 Volume of steam ... ... ... .. 633 647 649 635 Weir " Dual " air pumps 653 Wire (three) system u VERBAL" NOTES AND SKETCHES SECTION I. WORKSHOP PRACTICE. The reciprocating engine as at present constructed and perfected by tiie numerous auxiliary specialities now in general use un- doubtedly represents vast improvement on the engine of ten or fifteen years ago, and part of this improvement is certainly due to the superior class and make of the machine tools now in general use, and to the ever increasing use of cast steel and mild steel which materials serve to combine strength with lightness of parts. A brief description of the various types of reciprocating engines found in ordinary marine practice will now be given. Types of Engines. Paddle Engines. — For steamers of the paddle type the general practice is to fit an engine of the diagonal pattern (the oscillating type being now nearly obsolete) arranged either single, compound, triple, or quadruple expansion, and generally with two cranks, although three cranks are occasionally arranged for. The Sketches Nos. I, 2, 3, 4 illustrate the various cylinder and crank arrange- ments referred to. Piston valves are often fitted to the H.P. and I. P. of triple expansion paddle engines, and flat double-ported slide valves to the L.P. cylinders. Screw Engines. — In screw steamers the engines arc of the inverted type, being either compound, triple, or quadruple expansion, but in Naval practice the turbine has now completely superseded the reciprocating engine for all classes of vessels, and the success of this type of engine, where high power and speeds are required, is beyond dispute. Many cross-channel steamers and deep sea passenger steamers are also fitted with turbine machinery of the Parsons design, I ** Verbal " Notes and Sketches No. I. — Compound Type Paddle Engines. No. 2. — Triple Expansion Type Paddle Engines. n I , , J LP. E 1 I. P. 3 E 3 E LP. 3 I , , ' HP. No. 3.— Triple Expansion Type Paddle Engines (Two L.P. Cylinders). No. 4. — Quadruple Type Paddle Engines. i Workshop Practice 3 and the combination arrangement, in which reciprocating engines and turbines are arranged to work conjointly in the same engine- room, is rapidly coming forward into more general practice. (For further information on this subject see author's " Marine Steam Turbine.") The Sketches numbered 6, 7, 8, 9 illustrate the various cylinder No. 5.— Diagonal Type Paddle Engine, and crank arrangements mentioned above, and the flow of the steam through each is as follows : — Compound. — Steam flows from boilers through H.P. then L.P. to condenser. Triple. — Steam flows from boilers through H.P., I. P., and L.P. to condenser. 4 "Verbal" Notes and Sketches Triple (with 2 L.P. cylinders and four cranks). — Steam flows from the boilers through H.P., I. P., and then divides into two steam pipes, one led to each L.P. cylinder. Quadruple. — Steam flows from the boilers through H.P., ist I.P., 2nd I. P., and L.P. to condenser. In many designs of large power engines the steam is conveyed from one cylinder to another by means of large pipes, known as "receiver pipes," but in ordinary engines of moderate power the steam flows from one receiver to another through large ports cast in the cylinders themselves. In Sketch No. 9 the cylinders are shown arranged, from forward aft, as PI. P., ist I. P., L.P., and 2nd I. P., which allows of better balancing of the working parts, the crank angles being a few degrees less or more than 90° to each other. L.R HP No. 6. — Triple Expansion Engine (Three Cylinders). Cranks at 120°. Balanced Engines. — The constantly varying pressures on the crank- pin result in corresponding variations in the twisting stresses exerted by the engine, the range of torsional stresses varying with the type of engine, number and position of cylinders, and the steam distribution in each cylinder. These unequal stresses continued for long periods often result in the development of flaws on the shaft, and may finally lead to total breakage. It is therefore desirable to so balance up the moving parts that an even turning movement on the shafting may be obtained, and vibra- tion damped down to a minimum. Workshop Ppactice ALP FLP M.P H. P 1 1 ' 1 ,1 1 . 1 ^ 1 FLP No. 7. — Crank and Cylinder Arrangement, Four-Cylinder Triple Engine. " Verbal ' Notes and Sketches A.LP MP FL.P Al.P FLP No. 8.— Crank and Cylinder Arrangement (Yarrow, Schlick, & Tweedy Balanced System). Workshop Practice 7 Regarding this subject Professor W. E. Dalby, M.A., B.Sc, in a paper read at the forty-second meeting of the Institution of Naval Architects, says : — "The only way of balancing a three-crank marine engine of the usual type is by the addition of balance weights, or bob weights, to the moving parts. In this case, therefore, balancing necessarily means the actual addition of considerable masses of material to the machinery which have no other duty but that of producing forces equal and opposite to the unbalanced forces caused by the motion of the moving parts which are concerned in doing the proper work of the engine. It is well known that Messrs Yarrow, 2"-^ I.R ~J U L.R 1'-^ I.R H R J L J L No. 9.— Quadruple Expansion Type Engine (Large Power;. 1, H.P. piston valve. 2, H.P. cylinder. 3, First IP. piston valve. 4, First I. P. cylinder. 5, Second I. P. slide valve. 6, Second I. P. cylinder. 7, L.P. D.P. slide valve. 8, L.P. cylinder. E, E, E, Exhaust pipes. Schlick, & Tweedy made a departure from existing practice when they began to build engines in which the moving parts concerned in doing the proper work of the engine were so arranged that they were in balance amongst themselves. In engines of this kind no part of the machinery merely turns round or reciprocates for the sake of the forces its motion causes on the frame. No such arrangement is possible, however, unless the engine has, at least, four cranks. This condition and the progressive increase m the power of marine engines have together determined the gradual introduction 8 " Verbal " Notes and Sketches during the last ten years of the four-crank engine into the Navy and the Mercantile Marine. Yet that the possibilities of balancing the four crank engine have not been generally recognised is shown by the fact that many engines of that type have been and are still being built with their cranks at right angles, even when absence of vibration is imperative. Four cranks at right angles is just the one particular arrangement of a four-crank engine which makes it impossible to effect balance without the addition of balance weights. A change in the crank angles, however, and a small change in the mass of the moving parts is all that is necessary to obtain an engine in which the moving parts are balanced amongst themselves; to change, in fact, a four-crank unbalanced engine into a four-crank balanced engine of the Yarrow, Schlick, & Tweedy type. These changes cannot be made in any arbitrary manner. The masses, crank angles, and centres of cylinders must be mutually adjusted to satisfy certain conditions." The necessary calculations required in accurately determining the r.bove arrangement of cranks, balance weights, &c., are worked out from the indicator diagrams, crank effort diagrams, and the carefully calculated weights of the various moving parts, and involve a considerable amount of labour. Balance weights are sometimes fitted to the crank webs of the H.P. and I. P. engines, which are lighter, while the crank-pins of the two L.P. or heavy engines are bored out hollow, so that the weights of the parts may be correctly adjusted. In the Yarrow-Schlick-T weedy system of engine balancing, the calculations are usually so carefully determined that the addition of balance weights is not always required, the necessary balance being found by the relative crank angles and crank sequence, or order of rotation. In an ordinary three-cylinder triple-expansion engine the sequence is either H.P.. LP., and L.P., or L.P., I. P., and H.P., but when four cylinders are fitted (two L.P.) the sequence is usually as shown in the sketches on page 5. Observe that the H.P, and I. P. cranks are directly opposite, also that the F.L.P. and A. L.P. are opposite each other, but at right angles to the other two. It will be thus seen that the crank angles and crank sequence are quite different when the Yarrow-Schlick-l'weedy system is adopted as in the example illustrated on page 6, the H.P. and LP. cylinders being inside, and the two L.P. placed one forward and one aft. Observe that the heavy engines are placed at the ends to balance up the weight of the moving parts. The crank sequence is then (i) H.P., (2) F.L.P., (3) LP., and (4) A. L.P. This arrangement has the effect of reducing the vibration, and also allows of quick and easy handling of the engines. It should be understood that the relative crank angles vary with the size of engine, power, and weight of moving parts. Workshop Practice 9 Valves- — The cylinder valves are either piston valves, single-ported valves, or double-ported valves, a common arrangement being as follows . — H.P. cylinder LP. cylinder L.P. cylinder Piston valve (inside steam). j Piston valve, single-ported or ( double-ported slide valve. Double-ported slide valve. Certain builders fit piston valves to all the cylinders of large engines, and in many cases patent valves of the " Trick " double-ported type (see page 200) or of the " Andrews-Martin " type (see page 205) are fitted, the latter giving particularly satisfactory results owing to the good balance obtained. Pistons. — Pistons are now being constructed in many cases of cast steel, and are fitted with patent rings and springs of approved make, * No. 10.— Cast-Steel Piston (with Dimensions). The dotted lines show the LP. and L.P. pistons equal in depth to the L.P. piston. NOTE. — The radius of each piston is given. which, together with the improved design and construction of piston rod metallic packings at present on the market, have assisted to * Reprinted by permission from " Marine Engine Design." Prof. Edward M. Bragg. D. Van NostrandCc, New York, 1910. lO Verbal " Notes and Sketches bring up the efficiency of the marine engine to its present high standard. The introduction of the metallic packings referred to (notably that known as the U.S. packing) (see page 360) has met with * No. II. — Cast-iron Piston. NOTE. — Depth of packing ring g—3xt. the hearty approval of the marine engineering profession as a body, and the form of combination packing supplied by engineering firms in general, if, perhaps, not so effective as the patent types, is yet a great advance on the asbestos and similar packings formerly used for piston rods. * Reprinted by permission from "Marine Engine Design." Prof. Edward M. F)ragg, D. Van Nostrand Co., New York, 1910. Workshop Practice ii No. 12.— Patent Metallic Packing. (The Combination Metallic Packing Co., Ltd.) N, White metal bearing rings. L, Springs. E, Extension piece for secondary packing. U, White metal bearing blocks C, Gun-metal case. T, Springholder. H, Floatmg rings. 12 " Verbal " Notes and Sketches Connecting Rods. — The two types of connecting rod in common use are known as the single and double top end patterns. The single top end rod is more compact, but the double top end is simpler to manufacture, and is also much easier to overhaul when of large size. In the double type the crosshead is secured to the piston rod by means of a taper and nut, and in the single type the crosshead pin is No. 13.— Double Top End Type Connecting Rod. d= Piston rod diameter. D-d X 1-2. L = Length of crank-pin. * No. 14.— Single Top End Type Connecting Rod. shrunk into the connecting rod jaws, and sometimes further secured by small locking pins as shown. This pattern of rod costs more to produce than the other type, and is also more difficult to take adrift when overhauling. The bearing parts of the double top end rod are sometimes made of cast steel with white metal bearing surfaces, but often brass is em- * Reprinted by permission from "Marine Engine Design.' D. Van Nostrand Co., New York, 1910. Prof. Edward M. Bragg. Workshop Practice i^, ai PI WASHER U SQUARE. No. 15.— Types of Valve Spindles. In the square section type shown with the taper and cotter the rod may be drawn out by the top, but with the round section (sohd) the rod must be drawn out from below. ployed for the top ends, and cast steel and white metal for the bottom ends only. In the cheaper class of engines, cast-iron bushes lined with white metal are employed, and this is now the greneral practice for merchant steamers. H " Verbal " Notes and Sketches Valve Gear. — Valve gear is generally of the Stephenson link motion type with double bar quadrant ; valve spindles are either solid or made in two parts which are connected by a cotter, the upper part fitting by a taper into the lower part. That part of the spindle passing through the guide bracket is sometimes of round section and sometimes of square section. The rod diameter is reduced at the position of the valve, and the washers or cotter under the valve rest on a tapered portion of the spindle. Above the valve a washer is fitted with double nuts (one lock nut), and to further prevent slackening back of these nuts a large split pin or a cotter is run through the rod. A Q- ^^ 5^ * No. i6.— Link Block Pin and Liners. NOTE.— Thickness b^dx-^. The bushes in the valve spindle end are usually of brass, and of large bearing surface to reduce wear to a minimum. The saddle or quadrant blocks are of steel fitted with brass liners which bear on the quadrant bars. No. 17. — Eccentric Pulley. The pulley is divided into two portions at the shaft centre and these are bolted together as shown, the bolts being ar- ranged with taper heads. * Reprinted by permission from "Marine Engine Design." D, Van Nostrand Co., New York, 1910. * No. 18.— Eccentric Strap. The strap is recessed out to receive the pulley and is lined with white metal, dovetailed in place as shown. Prof. Edward M. Bragg. Workshop Practice 15 Eccentrics, &c. — Eccentric rods are generally made of steel with brass bushes at the top ends, and the eccentric straps are generally constructed of cast steel lined with white metal as bearing surfaces ; the pulleys themselves are of cast iron or cast steel ASTERN GUIDE TTir c 5Z 3 3 3 3 A 11 )( i( K ASTERN GUIDt- B0LT5. PLAN. J No. 19.— "Single" Type Guide showing: Ahead and Astern Surfaces. The plan shows the bolted-on knees, which constitute the astern guides, the bearing surface of which is less than for the ahead guides (about 80 per cent). i6 " Verbal " Notes and Sketches Main Bearings. — -Main bearing bushes are generally of cast iron lined with white metal, and the bottom half is often made round to facilitate withdrawal. Suitable gutters or oil ways are cut in the white metal surfaces to allow of efficient lubrication, and often the sides are cut away clear altogether, leaving only the top and bottom surfaces effective. NOTE. — From the foregoing it will be obvious that the term "brasses'' is now hardly correct, brass for bearings being generally superseded by cast steel lined with white metal. Crank-shafts. — The crank-shafts of mild steel are usually of the built pattern with the pins and shaft lengths shrunk into the webs and secured by dowel pins. Sometimes that part of the shaft fitting int© the webs is about h inch greater in diameter. Columns. — Columns vary in design, but the usual types fitted are that known as the " box " pattern, and that of the Y type, which is fitted for engines of large power. In some engines of the "open- fronted" type round steel columns are fitted at the front, and the back columns are then arranged with astern guides which overlap the guide shoes, and are held in place by large bolts. NOTE. —This arrangement of columns was often fitted in the engines of Government torpedo destroyers before the advent of the marine steam turbine. Description of Construction. In the construction of the reciprocating engine we will now proceed to deal with the various operations which are performed from the time the castings, forgings, &c., are delivered at the works until the engine is completed in the fitting department and ready for erection in the ship. Soleplate. — This is generally of box pattern and is made up of several parts, usually three in number, bolted together, one piece forming the forward part, one the centre (Sketch No 21), and one the after part. In large engines, however, the soleplate sometimes con- sists of four parts, which are, of course, bolted together. After delivery of the castings the first operation is that of gauging to ascertain if the thickness of metal as required by drawing has been maintained. This having been found correct, the soleplate is now marked off preparatory to machining the base for columns connecting flanges, and gaps for main bearing bushes. In good practice the bottom of the soleplate is machined, as this ensures good fitting chocks in the ship, and also facilitates the fitting of same. The soleplate is now taken to slotting machine, and has the base for columns and ^- Jl 11 11 , *• /- 1( ][ 1[ ~ I r-r\'\ // \ ^A D 8»i&i \1 Jl R R V 11 )t 1( A, Double type column B. Double type column. ■ F. Plan of single type column showing ahead and astern guides with shoe in position. D, Single type column with open front. * Reprinted by permission from "Marine Sleam Dciign." Prof. Edwaril M. Braj^g D. Van Nustrand Co.. New York, 19U No. 20.— Types of Columns. ' Vcrtial " Notes and Skelches. Workshop Practice J7 connectint^ flanges machined : this operation is carried out on the other parts which form the complete soleplate, and the main bearing gaps are also machined while the soleplate is in this stage. The soleplate being now finished machining, the holes for main bearing bolts, holding-down bolts, and connecting flanges are bored, also the holes for bolting columns to soleplates. The main bearing bolts are now fitted ; these bolts are, in ordinary merchant work, a large double-ended stud having a nut at the bottom end which draws the bolt tight up on a collar at the top end (Sketch No. 22). The bolt * No. 21.— Part of Soleplate showing Base for Columns. is usually reduced to the diameter at the bottom of the thread in the middle, and is a fit in the parallel parts, where it passes through the hole in the soleplate at cither end. A feather on stop pin is fitted under the collar, and this prevents the bolt from turning round when the bolt is being screwed up or slackened. The bottom nut is locked either by a large split pin through the thimble point at the end of the bolt or by a set pin through the nut, and pointed into the screw of the bolt. The main bearing bolts being now fitted in all parts of the sole- * Reprinted by permission from ''Marine Engine Design." Prof. Edward M. Bragg. D, Van Noslrand Co., New York, igio. i8 ** Verbal " Notes and Sketches No. 22.— Main Bearing Bolt. I, Set pin. 2, Feather. 3, Set pin. 4, Split pin. Workshop Practice 19 plate, the next operation is that of setting up or lining off the soleplate. This operation is usually performed on the blocks on which the engine is to be erected. The foundation for the engine usually consists of long logs laid fore and aft, two on each side of soleplate. The sole- plate is laid on the logs and levelled up, and the intervening space is filled up with wooden wedges (Sketch No. 24), the three parts of the soleplate being laid on the logs and as near in line as possible by the eye : the different sections are next brought into line. Through the two gaps of the centre portion a straight-edge is laid resting upon No. 23. — Main Bearing Complete. wooden centres fitted into the gaps, about 3 inches from the top (Sketch No. 25). The straight-edge is kept bearing hard on the side of the gap ; the end of the straight-edge extends into the inside gap of the forward portion of soleplate ; this part of soleplate is now moved sideways (by means of screw jacks) until side of gap bears on straight- edge. The same operation is performed on aft section, and the edge of the straight-edge is tested by means of feelers until all three parts are close up to straight-edge. The straight-edge is now put through bottom of gap and all three parts brought up to line in a similar manner, 20 "Verbal" Notes and Sketches It will be readily understood that after this operation it is necessary to go over the preceding work, so as to ensure that the sides of gaps are still in line. The soleplate is also levelled fore and aft and b )l 11 )l 11, r , It K © @ 1 0) -? Q, (U O C/5 o o • ii oui 5«* Xi QUJ S3: in o bn c *S d q: uj -5 6 2 athwart-ships by applying the straight-edge on the base for columns. The soleplate being now set up, the holes in adjoining or connecting flanges are widened and bolts fitted. The space between soleplate and logs is also filled up with wooden wedges, care being exercised Workshop Practice 21 while drivine^ up same that tlic level of soleplate is not altered. The main bcarini^ bushes are now fitted into the gaps, the main bearing covers put on and screwed up. The next operation is that of marking No. 25 —Lining- off the Soleplate. LINERS I. No. 26. — Boring out of Main Bearing Bushes. Proof" lines. 2, Boring out line = diameter of shaft. off the main bearing bushes: there are several different methods of doing this work. In some works the bushes are not filled with white metal until after being fitted, and the cast iron or steel is bored out 22 "Verbal Notes and Sketches to the diameter of the shaft phis the rehefs, and the bush is then filled with white metal and reset up on the machine to the previous machined parts, and bored out to the diameter of the shaft. The general practice, however, is to have the white metal in bush when fitted, and with all bushes in place a fine piano wire is stretched through all the bushes, being carried on supports at each end. This wire is set up athwart ships to the centre of the main bearing gap, which is projected on to the end of the bush at the forward and aft No. 27.— Main Bearing Bush. L, Liners. D, Shaft diameter. E, Tapped hole for lifting gear. O, Oil service. end. The height is taken from drawing and is measured from base for columns. The wire now being set to these points four lines or chords are drawn on each side of each bush with a pair of jcnnys (Sketch No. 26). The wire is now withdrawn and in each bush a wooden centre is fitted faced with tin, and the centre is picked up from these four lines or chords and the boring out diameter is drawn in on each side of the bush, also a short proof line at four points. This proof line is usually about f inch to i inch larger in diameter than the boring out size, and is used to test the boring bar when the Workshop Practice 23 bush is about bored out to the final size. The bushes are now bored out, and reHefs or gutters cut. The bushes are now put back in place in the soleplate, and are now ready for the bedding down of the crank-shaft. Crank-shafts and Columns. The majority of engineering firms buy in the crank-shafts required for the various engines which they are constructing. This part of the engine is usually delivered in a finished condition, as it is found the steel works which specialise in this work can turn out the finished article much cheaper than it can be constructed in a general engineering concern. The type of crank-shaft now manu- factured is that of the built-up type, with the crank pins and shafts ..... "<."_'_":: ^ No. 28.— Balanced Crank. shrunk into the webs, and is usually in three parts having two couplings. This arrangement admits of interchangeability and necessitates one part only for spare. The method of constructing the shaft is as follows : — The webs are machined to shape and the holes bored and turned out for the pins and shafts. The web is laid flat down on a table, over a pit which is of sufficient depth to receive the shaft, when the web is turned upside down to receive the pin. The web is then heated up by means of a bunsen burner sufficiently to allow a gauge, ^V inch larger than the diameter of the part which is to be shrunk, to pass through, and this expansion having taken place the pin or shaft is lowered into the web and the whole part cooled out. The web is next turned upside down and the same operation takes place ; that is, the pin being shrunk in first and 24 Verbal " Notes and Sketches then the shaft. The other half of the crank is similarly assembled, and then the part consisting of the shaft and pin is suspended above the other part, and the pin is shrunk into the web, thus forrring the complete crank. During the operation of joining the two webs by means of the pin care is taken to ensure that the centre lines through the webs are exactly in line. The crank pins and shafts, besides being shrunk into web, are also prevented from turning by round dowel pins being fitted half into the shaft and half into the web (Sketch No. 28). After the complete shaft is built the coupling holes are bored, and the three parts brought together, the cranks being set to the sequence required. The coupling bolt holes are widened, and bolts E •2; L^ ^ ^ ■•■ 1 f^ WOOD '^l SLOT (3" BY re") SLOT (3" BY ie") .tSMl|Pff3 - No. 48 —Alignment of Cylinders and Shafting. Method of Lining up Cylinders, &c. To either set up tlie uylindcrs ui to tt.'st if the cylinders and shaft centre lines are at right angles to each uther (engine disnianiled) proceed as follows : — 1. Take a piece of board with a slot cut as shown (about 3 inches by ^g inch will do), and secure this by two studs to the cylinder across the centre to bring the hole in wood bridge fair. 2. Fix another slotted board in the centre of the crank-pit fore and afl with the hole dead centred as shown. 3. Tie a bolt or small bar of any kind (a file will do) to the end of a line passed down through the cylinder bridge slot, and secure the other end of this line 10 the crank-pit bridge slot: the bolts or bars to which the hne is attached laid crosswise on the slot will alluw of adju'^tment at top or bottom. 4. Now caliper the line at the top from the cylinder bore, and adjust it by ■ VetUl ■■ Note* and Sketches. means of the small bar as required until it is brought dead central. Repeat this at the bottom of the line, adjusting at the crank-pit bridge slot. 5. Next caliper round the line from stuliing bo.\ bore and adjust cylinder to suit if necessary ; also test distance between line and crank web at top and bottom centre as shown. 6. \Vith crank on top mark crank-pin where line touches, then turn crank to bottom and again mark pin ; now test, by calipering, if both marks are the same distance from the web. 7. To test the alignment of the guide caliper between the hne and guides at top and bottom as shown in the end view. 8. To test if the guides are in line fore and aft, use a surface gauge and adjust it to touch the line when laid up against the guide forward ; now try it aft and if the again touches the line, the guides are in line, fore and aft, If not, they are out oflir nd require to be canted round to square up. I To fact page 35. Workshop Practice 35 shaft is in place centres are fitted between the webs, with one edge central to the centre of the shaft, and with a Hne on each centre equal distance from each web. The cylinders are moved until the three lines hanging from the piston rod stuffing boxes are exactly in line with the marks on the shaft centre sticks and also in line with the centre of the shaft. The bores of the cylinders are also tested with a plumb rule, and it may be necessary to line up the feet of the cylinders to bring them plumb. If this be the case then it will entail machining or filing the head of the columns which show high, but if care has been exercised in setting up the columns it will only be a small JOINT ® e ® © e G ® e e e ® © © ® Q © ® © ® © O e © © Hi e Q n3i ff GUIDE BRACKET ?r-^ PUMP CROSSHEAD '^ LLJJ ® ® No. 61.— Trammelling Pump Links for Wear Down. 1, Lever pin. 2, Pump crosshead blocked up on cover with glands fair and free. 3, Trammel distance. 4, Guide rod of crosshead. 5, Feed pumps. 6, Circulating pump. 7, Air pump. 52 "Verbal" Notes and Sketches and connections are also led from this valve to the H.P. jacket and to the LP. valve casing through a valve, termed an impulse valve (see page 183). This valve is used while heating up cylinders, and also for assisting in smartly moving the engines while man- oeuvring. The gland on the H.P. engine is usually packed with patent packing or with metallic combination packing, the I. P. gland is sometimes packed in a similar manner, and the L.P. gland with soft asbestos packing. The valve spindle glands, in the case of H.P. and LP., are also fitted with metallic packing and the L.P. with soft packing. In the majority of engines now constructed separate pumps are fitted, but the type of engine for cargo steamers usually has the pumps worked off the main engine. These pumps consist of air pump, circulating pump, two feed pumps, and two bilge pumps. These are operated by means of levers connected to the LP. engine by means of drag links. The levers are supported on a double bear- ing at the back of the LP. column, and are usually of two steel plates with bosses between, and riveted together. The pins to which the drag links are connected are riveted into the boss on the levers. At the other end the drag links which connect to the pump crosshead are fixed. The levers are bedded down in their bearings and the covers leaded in a similar manner to that of the other bearings on the engine. The drag links are trained and bedded on to their respective pins, and the clearance of the air and circulating pumps are taken : to get the clearance, the main engines are turned to position with crank on top centre and mark put on air pump and circulating pump rod, or by applying a gauge between crosshead and pump covers. The engine is again turned to bottom centre, and another mark put on — the distance between represents the travel of the levers ; and by discon- necting the drag links and lowering the pump bucket until it rests on the bottom, and putting a mark on, the difference between the travel mark and this mark will represent the bottom clearance. The pump bucket is then lifted up to the top and pulled by means of tackle until it touches the head valve, and a mark put on, and by comparing the two marks the clearance at top is arrived at. The feed and bilge pumps are tested for clearance when the pumps are at bottom stroke. The nuts on the spindles through the crosshead are slackened and the plunger lowered until it rests on the bottom, a mark put on, or gauged by callipers between the shoulder on spindle and crosshead ; the distance representing the clearance will be found by putting on a mark from the same point as before when the plunger spindle is screwed up in crosshead. The usual clearance for air pumps, feed and bilge pumps is as follows : — Air pump - - - top, | inch, bottom, |- inch. Bilge pump - - - bottom, i to i^ inches. Feed pump - - - bottom, | to i^^ inches. It will be noticed that the air pump clearance is most on top; this is explained by the distance between lever pins and crosshead Workshop Practice 53 being decreased as wear on tiie drag links is taken up. The engines are now ready for dismantling, and the cylinders are taken down, also columns. Crank-shaft is lifted and cleaned and oiled and put bad into place in the soleplatc bearings. All hard bits or heavy bearing: No. 62. — Cast-Steel Piston. With Ramsbottom rings fitted into junk ring to allow of removal. in crank-pin bushes and top end bearings are eased, and all gear prepared for transfer to the ship. The cylinders are thoroughly examined to ensure that there is no sand or dirt in any of the ports, and this being so, they are ready for closing up. The piston rods *No. 63.— Cast Steel Piston. Fitted with Ramsbottom rings. For a cylinder 20 inches diameter the proportions are : b-ij inches. d = i inch. e—ii\ inches. 2 or 3 rings to be fitted. = 1 inch. are put into the pistons and hard hammered up, locking cutters or split pins fitted, and the whole is lifted and lowered into the cylinder. The interior of cylinder has been beforehand rubbed over with cylinder oil to prevent rusting during the time that machinery is stationary. The H.P. piston is usually packed with Ramsbottom * Reprinted bv permission from "Marine Engine Design." Prof. Edw.ird M. Bragg D. Van Noslrand Co., New York, 1910. 54 " Verbal " Notes and Sketches * No. 64. — Buckley Type Piston Ring. For a piston 24 inches diameter the proportions are as follows : — b = 2^ inches. c = f^ inch. d=ifj inches. e---ir'g inches. f=i;| inches. g=2i inches. h = i inch. No. 65.— Cylinder Valve Face. Gutters and holes drilled to reduce wear. NOTE.— The holes, i inch diameter, ^V inch deep, are bored out with a flat nosed drill. * Reprinted hy permission from "Marine Engine Design." Prof. Edward M. Bragg. D. Van Nostrand Co., New York, 1910. fh B w TA3M Y8 CiunMTAJ riit^ij ^ I fKSn TO IJ >ID0J6 y !vr-;5d- cM 'HT fi28A«a a^tHA3e P'^ — — ' • .'.Ki-C-.-V-i-ii LINER EXPANDED BY HEAT_^| Q | m^. No. 66.— Method of Shrinking on Propeller Shaft Liners. FOR aTMICK pQp brass! THICK PUTTY PUMP AIR ESCAPE 1 K BEARING ■ No. 67.— Propeller Shaft Continuous Liner. (With Thickness Variation, ) BRASS 4 THICK 1 1 J 1 i 1 r 1 -la 1 t2 L_l___ ■^ '■ No. 68.— Propeller Shaft Continuous Liner. 'Stepped and forced on by Hydraulic Pressure iiio tons ' Verbal" Notes and Sketches. Workshop Practice 55 rings and segment packing rings (Sketch No. 63), and these are assembled and junk ring put on and nuts screwed up. The nuts on the junk ring are prevented from slackening back by means of either split pin above the nuts if square-necked studs are fitted, or by means of a guard ring which bears against nuts or pins, and is itself kept in place by being fitted on square-necked studs having split pins through the nuts. The other two cylinders are closed up in a similar manner, the LP. piston packing rings being same as H.P., and the L.P. being either one of the patent packing rings or the packing ring with coach springs or spiral springs pressing it out against the cylinder wall. The valves are dealt with in a similar manner, the H.P. being a piston valve, LP. a single-ported slide valve, and L.P. double-ported slide valve. Previous to putting the valves in place, oil gutters are cut on the face (Sketch No. 65) ; this assists to reduce friction, and in the case of the H.P. grooves are turned on the rings which join the valves. The cylinder and casing covers are jointed with asbestos joints, and in some cases asbestos tape, glands are packed, and all openings to interior of C}'linders or casings closed up. The pistons and rods are supported, so that when lifting cylinders the rods will not lower to the bottom of the cylinder; the valve spindles and valves are also supported, and the whole three cylinders are now ready for transport to the ship. Propeller Shaft Liners. Propeller shafts are brass lined from end to end to prevent galvanic action taking place between the brass liner and steel of the shaft. The liners are fitted in two styles — 1. Shrunk on hot. 2. Forced on cold by hydraulic ram pressure. 1. Shrinking on (Sketch No. 66). — The shaft is supported by bolting up to one of the tunnel lengths, which leaves the whole length free to receive the liner. The liner is then heated either by gas burners or by a fire built underneath, and after sufficient expansion has taken place the liner is drawn over the shaft by means of blocks and chain tackle. When the liner cools down the contraction resulting is sufficient to lock the liner to the shaft, screwed pins being seldom used in present practice, as in quite a number of cases the pins have been found to slacken back and come out of place. Before shrinking on, the liner is bored out about 5^0 less in diameter than the shaft, therefore for a 12-inch shaft the inside diameter of the liner will be 12 inches — sV^ inch= 1 1-976 inches, say iifj inches full. NOTE. — If the liner sticks when being drawn on it may be forced on by pressure at the end, or expanded again by building a fire underneath. 2. Forced on Cold (Sketch No. 68).— In this method the liner is stepped to three diameters, the difference at each length being ^ir inch. The forward and after diameters should be a bearing fit, but the centre 56 "Verbal" Notes and Sketches length need not be so ; as in the " shrinking on " method the liner is bored out a trifle less in diameter than the shaft at each "step" and the liner is then forced on over the end of the shaft, by a hydraulic ram exerting a pressure of about i lO tons. Notice that the ram pressure only requires to be exerted for one of the stepped lengths, as the three fit simultaneously. Variation in Liner Thickness (Sketch No. 6"]). Occasionally the liner is cast in three thicknesses as shown in the sketch, being .thickest at the position of the forward bearing, next at the after bearing, and least of all at the centre where the shaft does not bear at all. Two holes are bored in the liner at the centre length and putty is forced in by means of a pump through one of the holes to fill up the clearance space inside, the other allowing for the escape of air : these holes are afterwards filled up by means of screwed pins riveted over. Marking off Ship for Boring out — Propeller Shafting and Thrust Block (Sketch No. 69). The part of the ship's hull through which the stern tube passes is bored out to a size so as to ensure the stern tube being a good fit in same, and absolutely watertight. The method of marking off the stern post and bulkheads for boring out is as follows : — In the centre of the hole which passes through the stern bracket a wooden disc is fitted completely filling the hole. Upon this piece of wood the centre of the shaft from keel as given in drawing is marked, and the centre of the present bore of the stern frame or bracket is taken. A small hole ^V or tV inch in diameter is bored through the wood at these points (Sketch No. 69). In the engine-room at the forward bulkhead, the height of centre of shaft from keel is marked off, and also the centre of the ship athwart-ships is marked. A small hole is also drilled here. At the back of this hole a lighted candle or electric lamp is fixed and the operator if by looking through from the stern to the engine-room through the small hole in the wooden disc can see the light, then that point will give the centre for boring out. If the light is not seen, then it will be necessary to shift centres, and to facilitate this, a sliding or movable centre is used, so that it can be moved about until light is visible, the light now being seen from aft end of tube bearing to engine-room. Another centre is fitted in engine-room bulkhead, and the light picked up. A similar centre is fitted in the after bulkhead in the tunnel, and light sighted. The whole is again sighted from the aft end, and light being seen, a centre is put in holes in discs and circles drawn around equal to the boring out size ; proof marks are also put on so as to test boring bar. The bulkhead in forward end of tunnel is marked off in a .<5imilar manner, and is bored out for a bulkhead gland. At various distances throughout >.oa aA3M>IJUQ MOOS^ JH!DH T1AH2 XMA«D ^O 351TH30 OMIWA^a M05n WOOD BATTEN -36" No. 69.— Method of Sighting for Line of Shafting and Boring Stern Post. 1. At distance up marked on drawing as "shaft centre" and at centre alliwartships, cut (say I inch diameter) in the engine-room forward bulkhead, and to this fix a piece of tin ; punch ^ inch diameter at centre and place a small electric lamp in a box in the position shown. 2. Block up the stern post hole (previously bored out to liss than the required diameter) wooden disc, m which cut but a i-inch hole ; on this pin a sheet of tin with a T!,-inch hole at thi centre isee Sketch), and from the centre scribe in the proof circle for boring out. 3. Prepare two straight-edges, say 36 inches in length by 3 inches in width, and recessed at the middle, say 6 inches by ^ inch, so that when placed together the slot so formed will be 3 indies hole dead by r inch. Have, say, i »-inch hole punclied in after peak bulkhead and place the sticks with slot horizontal across the hole : now move the straight edges up and down until the light is seen when looking through from outside the stern post, then with a suitable radius measure upwards and downwards on the bulkhead, and make centre punch marks. Repeat the foregoing with the sticks and slot In a vertical position, and when the light is again picked up make centre punch marks on the bulkhead port and starboard at same radius. Fill up the hole with wood and from the marks so obtained find the dead centre from which a proof circle c I be set off for boring out. (). Intermediate bulkheads are slieets, with ,'„-inch holes in each, forward, should then be visible thro in stern post. treated in the same manner as just described, and as a final lest tin to all the bulkhead openings, and the light, placed I viewed from the outside of the ship through the hole NOTE.— One man is placed to took through the holes and another i I the sliding sticks to find the tight ■ Notes ami SVet-rhcs. r\ Workshop Practice 57 the shaft tunnel sighting sticks are erected, and from these the height of the various stools for the tunnel bearings are derived The centre on the forward end of the engine-room is used when the holding-down holes are templated and bored previous to the engines being installed. In this operation the template is laid down on the engine-room floor, and the centre line on the template is set in line to a centre line on the forward bulkhead in line with the sighting centre. If the shafting is in place then from the centre of the thrust shaft the template is set, or if shaft is not in place, then the template is set to the centre of the hole in which the bulkhead gland is fitted. The stern frame and bulkheads are bored out usually by power derived from an electric motor, or if no electric power is available then a small donkey boiler and steam-engine are erected connecting with belt to the boring bar. After boring out, the stern tube is put in place from the inside, and drawn hard up into position by means of the nut on the after end. The inner end is bolted to the bulkhead and wood liner fitted at back of same. At the outer end of stern tube a brass bush is fitted, termed the stern bush. This bush is lined with lignum vitae, the bottom layers having the grain end on, so as to reduce the wear as much as possible. The lignum vitae is fitted into channels in the brass bush, and is prevented from working out by a collar at the forward end of the bush, and at the aft end by means of a brass gland bolted to the flange of the bush itself (see illustration facing page 361). The space into which the wood is fitted is tapered in a fore and aft direction, and the wood is driven up into same, thus ensuring a good fit. The tail shaft is shipped into stern tube from the interior of the tunnel, and on the inside flange of the stern tube a gland is fitted, which prevents any leakage taking place into the tunnel. This gland is packed with soft rope-yarn packing soaked in tallow, and a water connection is led from the top of the stern tube to this gland, so that in the event of getting hot the gland and shaft can be cooled out. The propeller is held on shaft by means of a feather and nut. This nut is hard hammered up, and a stopper fitted. In the recess in front of the boss a rubber ring is fitted to prevent water getting in or eating away the part of the shaft which is not covered by the brass liner, and in some cases short glands are fitted on the forward side of the boss, being packed with a rubber ring (Sketch No. 69). The tunnel bearings are of cast iron lined with white metal, and are supported on built-up stool, between which and bearing block teakwood liners are fitted, bringing bearings up to required height (Sketch No. 70). At the forward end of the tunnel the thrust block is situated (see page 182) : this block is made up of a number of shoes, as the design may require. The shoes are of cast iron, lined with white metal, having gutters cut on each side, oil being supplied from an oil box cast on each shoe. Water service connec- tions are also made so that a water circulation takes place throughout the interior of the shoe. The block itself is of cast iron, and is rigidly bolted to the ship's frame, this part of the ship being specially 58 V^erbal " Notes and Sketches strengthened. The interior of the block is used as a lubricating bath, being filled with fresh water and oil, through which the collars of the thrust shaft revolve, thus lubricating each face of the shoes. OQ ho a 'u rt S3 (U c PQ - . "^ U O o o ^ CQ a I J3 o Workshop Practice 59 Erecting" Machinery in Ship. The tail shaft being shipped into place, and stern tube gland fitted and packed, the intermediate lengths of shafting are now put in and No. 71.— Cast-iron Chocks. I, Teakwood wedges. 2, Chock. 3, Joint. NOTE.— The size of chock varies, but average proportions are: «vidth 6 to 8 inches, depth i to i| inches, fitting strips ^ to ^ inch. .set up in line. The shaft is blocked up and tunnel bearing block put on shaft, being bound on same by means of canvas between cover of bearings and shaft. The aft coupling of the shaft is brought fair to the coupling of the propeller shaft by means of feelers, that is, the face of the two couplings are tested to ensure that a feeler of say -010 can be inserted at all four points, and the rim of the flange of the coupling tested also by means of a straight-edge, to ensure that shafts are in line sideways, and also for height. The space between the bottom of the bearing block and the stool is now filled up with teakwood liner. During the filling and on completion the shaft couplings are tested to ensure that they remain fair. The next length of shafting is set up in a similar manner, and so on until the complete length of shafting has been set up. At the forward end of the tunnel where the shaft passes through the bulkhead, another gland is fitted, so that in event of the tunnel being flooded, by shutting the watertight door at the entrance to the tunnel, no water would pass into the 6o "Verbal" Notes and Sketches engine-room. This gland is also packed with soft rope-yarn packing. The thrust shaft is set up to the coupling of the intermediate shaft and set, and the holes for fixing block to seating are bored, a^nd fitted bolts put in. The engine soleplate with crank-shaft in place is brought No. 72.— Types of Cast-iron Chocks. 4, Bolt screwed through tank top. into line with coupling of thrust shaft and set up in a similar manner as that previously described, flange of couplings set fair face to face and on the rim of flanges. To arrive at this result the soleplate is made up at suitable points on iron wedges and plates, and these wedges are driven as required to bring crank-shaft coupling up to height of thrust shaft coupling. The soleplate and crank-shaft are moved bodily as required by means of screw jacks. The couplings being fair the space between the engine-room seating and the sole- plate is made up by means of cast-iron chocks. These chocks are usually fitted at each bolt which binds soleplate to ship, and are chipped and filed until they are a good fit. The holes for bolts or studs are bored through the engine seating, if not previously marked off by template. In the case of there being a tank under the engine- room, screwed studs will be fitted as holding-down bolts having a nut inside the tank, jointed with washer and grummet. The soleplate being now made up and set, the columns and cylinders are lowered into position, and gear erected on engine. The pipes connecting the various parts of the engines and boilers are now fitted and jointed, the main connections on the engine being as follows : — Main Steam Pipe. — From boilers to engine stop valve. Main Injection Pipe. — From valve on ship's side to bottom of circulating pump. Main Discharge Pipe. — From top of condenser to ship's side. Feed Pump Suction. — From hot-well to suction valves on feed pump. Workshop Practice 6i Feed Pump Discharge. — From feed pump discharge vah'es to boiler. Bilge Pump Suction. — Led to distribution box in engine-room, from which various holds and wells are connected. Bilge Pump Discharge. — From bilge pumps to discharge valve on ship's side. The boilers are erected on stools in the boiler hold, chocks being fitted between the boiler shell and the stools (see page 1 56). Chocks are also fitted between the boilers, and stays are also fitted from the ship's side to the boiler, to prevent movement of the boilers in bad weather. Knees are also fitted at both ends of the boiler riveted to the tank top, and being close up to the front of the boiler at the centre; these knees are usually left from yV to -£^ inch clear, to allow for expansion of boiler (see page 156), The usual mountings on the boilers are as follows : — Main stop valve - - ^ Auxiliary stop valve - tt u . r u •• Steam to whistle - - [ ^'^'^^ °" ^«P ^^ ^°^'^''- Safety valves - - J Gauge glass connections Scum cock - Auxiliary feed check Main feed check - Test cocks - Salinometer cock - Blow-down cock - Drain cock - On end of boiler. On bottom of boiler. After boilers have been installed and all connections raised steam is got up and the boiler covering put on. This is usually one or other of the specialities on the market. It is put on in the form of wet pulp and dried by the heat of the boiler. Outside, a sheet-iron casing is fitted extending to the bottom quarter of the boiler, and in some ships asbestos mats are fitted round the bottom of the sheet covered with wire netting. After boilers are covered, steam is raised and safety valves set. This means that the washers between the safety valve nuts and the standards are taken out and the nuts adjusted so that the valves will lift and release the pressure on the boiler when it has reached the designed pressure. In a boiler having forced draught, an accumulation test is necessary. This means that with forced draught being maintained to the pressure required, usually f inch air pressure in the ashpits, the pressure on the boiler must not rise more than 5 lbs, on the figure required, thus showing that the safety valves are of ample area to release any pressure over that which it is designed for the boiler to carry. After val\-es have been set, the space between the nuts and collar is gauged, and the 62 " Verbal " Notes and Sketches washers fitted accurately to same. If the engines are in an advanced state of construction at this time, it is usual to have what is termed a basin trial on the same day as the safety valves are set. During a basin trial the engines are rev^olved at a slow speed, it not being possible to exceed this, owing to the risk of carrying away the mooring ropes. No. 73— Wear Down Gauge. 1, Steel pin touching shaft. 2, Collar touching- gauge when pin is touching shaft. 3, Holes for dowel pins. The gauges shown in Nos. 75 and 76 are employed in testing the wear down of shafting, as when the bearings work down a clearance will be shown at the point of the bolt in No. 75 or between the projection on the gauge plate of No. 76. These clearances should be carefully noted for each bearing, and a record kept for future reference and subsequent wear down. Auxiliary Machinery. In describing the auxiliary machinery it will be understood that we are dealing with an installation suitable for a set of engines the construction of which has been previously described. As before explained, the feed pumps are connected and operated by the main Workshop Practice 63 engines. These pumps discharge the feed water to a feed heater, which is situated on the upper platform of the engine-room. The feed water passes through this heater, and becomes heated by contact with steam which is admitted into the interior. A heater of this type is termed a direct contact heater. The water falls to the bottom of the heater, and falls by gravitation to a feed pump, which is situated on the bottom platform of the engine-room. This pump delivers the water through the filter, which is one or other of the various makes described elsewhere, and then through the feed check or valve into No. 74.— Wear Down Gauge. 1, Gauge. 2, Small part filed on top of housing- to allow gauge to touch shaft. the boiler. This pump is usually controlled by automatic gear in the feed heater, which regulates the speed of the pump to the amount of water passing through the heater. The next auxiliary is that usuall}' termed the " General Service Donkey Pump." This pump has con- nections suitable to draw from the sea, hot-well, tanks, and bilges and can discharge to the boilers (through the auxiliar)' feed checks), tanks, and overboard. The ballast pump is used for pumping the various ballast tanks in the ship, and has connection to all parts of the ship, also sea and bilge 64 "Verbal" Notes and Sketches suction, and can discharge overboard and into the tanks (see illustra- tion facing page 198). An evaporator is fitted, one of the various types described elsewhere, the principles of which are as follows : — Steam is passed through copper pipes of various shapes ; outside of these pipes is sea water, which becomes heated, and gives off a steam vapour ; this vapour is collected and led off either to the condenser or L.P. engine casing, thus adding to the amount of feed water which is pumped into the boilers. A small pump is fitted, usually operated by the main engine pump levers. This pump has a sea suction and discharge into the evaporator, and the amount of water being pumped in is adjusted so as to make up for the amount being evaporated. There are various types of feed water filters on the market, the principle of which is. to extract the grease and impurities from the feed water. The filter medium usually consists of cloths of the nature of towelling held between metal perforated grids, and in some filters furnace slag is used, proving a cheap and efficient filtering material. In large ships a sanitarj^ pump operated by the main engine levers is fitted, but in cargo steamers it is usual to have a tank on the top of the engine-room skylights ; this tank is filled up every morning, supplying the necessary water for the sanitary system throughout the day. In ships having forced draught a fan engine is fitted ; this engine operates the fan which supplies the air to the boiler furnaces. In Howden's system the air is carried through a trunk, and then passes around tubes situated in the boiler uptake. The air is heated by this means before passing into the furnaces. The usual pressure to carry on the air gauge or fan is from i^ to 2 inches ; this gives a pressure in the ashpits of | to f inch. It will be understood that this air pressure may be altered according to conditions, such as nature of coal being used, and also as regards weather conditions. In the stokehold an ash hoist is fitted. This may be one of the specialities, such as Alley & M'Lellan's, Crompton's, or See's ash ejector. But it is more common to have a small steam winch fitted up on the top of the fiddley, with a steel ware rope led through pulleys into the venti- lators, and thence to the stokehold floor. If the ship is fitted with electric light the electric engine is usually in the engine-room, steam being supplied either from the auxiliary steam pipe or direct from the boiler. This engine is generally fitted with a governor so as to ensure steady running. On deck the machinery usuall}^ consists of eight or twelve winches, steam being supplied from the main or donkey boiler, and the exhaust from these winches is led back to an auxiliary condenser situated in the engine-room. The auxiliary condenser is generally arranged so that the condensed steam flows into a tank underneath ; the feed pump is connected to same, and supplies the donkey boiler with feed water from this source. The circulating water for the condenser is usually supplied by a small pump fitted for this purpose, and in up-to-date installations the condenser is supplied with circulating water from an engine which works an air circulating and feed pump together, a very compact Workshop Practice 65 arrangement. A steam windlass is fitted on the forecastle head, and in some cases a warping capstan is fitted on the poop or aft end of the ship. On the top platform of the engine-room the steering engine is situated : this engine has exhaust connections to the main and auxiliary condensers and also to the atmosphere. The control gear for this engine is led from the bridge, and is operated by means of the steering wheel. There are various types of steering engines on the market, but the main principles of each are similar. In some ships the steering engine is housed aft, being directly connected to the rudder head, and the connecting shafts are led along inside a casing or deck to the engine, there operating the valve on the steering engine ; this valve is termed the control valve. A sketch is given showing the arrangement of shafting operating the control valve and a description of the various types of steering gears is given elsewhere. (See page 340.) Trial Trips. On completion of the installation of the machinery on board ship, and previous to handing the ship over to the owner's representatives, a trial trip is run. This usually consists of a series of runs over a measured course, posts or sighting points being erected on the shore, the distance between being exactly one nautical mile. After ship leaves the harbour, the compasses are adjusted, that is, the ship is slowly steamed in a circle, the compass adjusters during this time finding out and adjusting the reading of the compasses supplied to the ship. In the engine-room an engineer is told off to attend to a special part of the machinery, one attending to the boilers, regu- lating the water supply and seeing that the steam pressure is main- tained. One man looks after an individual engine, overlooking the running of the main bearings, eccentric straps, and crank-pins. On the middle platform men are also stationed, who observe the running of the top end bearings, guide shoes and piston rods, and valve gear. The piston rods are swabbed with cylinder oil, and the other bearings on connecting rod and guide shoes are supplied with oil from siphon boxes (see page 197) on the top platform, but it is usual on trial trips to augment this supply by hand feeding. A man attends to the pumps and connections on same, overlooking the pumping of bilges, supply of circulating water, and working of feed pumps. An engineer is also in attendance in the tunnel, whose duty it is to attend to the lubrication of the tunnel bearings and thrust block. On the top platform a man is also stationed attending to the supply of oil in the siphon boxes and the working of the feed heater and steering gear, if same gear is situated in the engine-room. It is usual to proceed slowly to the measured mile so as to gradually work the bearings into good running condition. All being well and ready for the first run, draughtsmen are told off for taking indication cards and counters, and observing pressures on the various gauges connected 5 66 "Verbal" Notes and Sketches with the machinery. It will be understood that all operations have to be smartly carried out as the time which elapses between going on the mile and coming off, even in a slow cargo tramp, is not of long duration. Immediately before coming in line with the post on the shore a warning bell is rung, "get ready," and then when in line the telegraph is rung hard signifying that the ship is " now on the mile." When the mile has been run and the ship in line with the other post or point on shore the telegraph is again rung, and the engines are slowed down, while preparations are made in the stokehold for the next run. The ship is brought round again and all ready for the return run. This is carried out five or six times, and then the course is laid for a run of three to six hours at a steady speed, thus proving that machinery is in good working order. During the running on the mile, coal is measured in the stokehold, and after indicators, cards, and particulars taken have been worked out a statement is prepared showing the result of the various runs on the mile. In large passenger ships and Admiralty ships runs of thirty hours' duration are made, the trial trips in these cases usually extending to four or five days. In Admiralty trials the feed water is measured, and the firing is carried out on a system of time firing, that is, arrangements are made to burn a certain amount of coal per square foot of fire grate per hour. The coal is measured out, and on the ringing of a gong or similar signal the firing in each stokehold takes place. Care and Upkeep of Machinery. In considering the care required to keep a set of triple expansion engines in good condition, we will deal with a set of new engines and consider what means are required to maintain the machinery in an efficient condition. It should be borne in mind that a loose bearing has as much chance of heating up as one that is too finely adjusted, especially when it is a connecting rod bearing that is in a slack condition. The bearing will knock on the centres ; this knock- ing tends to spread the white metal, with the result that ridges are formed on the side of the bearings, and also the knocking has the tendency to press out the oil which is between the bush and the pin. To ensure a bearing being in proper adjustment, after leads have been taken off and found correct, the bearings should be put together and nuts hammered up until they are at the marks which were put on when leads were in bush. By inserting a slice bar or other suitable bar between the web and the bush and testing the bush to see that it moves from side to side, this will prove that bush is not too tight, and should give good running results. The same operaton should be carried out on the top end bearing also. After ship has done outward voyage, the top main bearings should be lifted and wear down gauge applied. There are various forms of wear down gauges supplied by various builders. Sketches, Nos. 73 and 74, are given Workshop Practice 67 showing two forms of this gauge which are generally supplied. If wear has taken place, notes of same should be taken, and after the next run this reading should be again verified, as if the wear continues it is possible that the chocking and lining up of the soleplate has not been properly carried out. 'Fhe eccentric straps are also liable to wear, especially when coming to a bearing, and to avoid the trouble of opening up valve casings and testing setting of valves, a simple method of proving same is as follows, when engines are new, and this should be done in the works if possible : — With the valve standing at full travel upwards, a mark is put on valve spindle, and from this mark a small trammel is made, touching a point either on the cylinder or valve spindle guide bracket (Sketch No. 59). By turning engine into similar position and trying trammel, any wear down that has taken place can be seen at once, the wear down having taken place either in saddle block bearings or eccentric straps. Another method is to put valve to top lead and put a trammel mark on with spindle in this position ; this is easier, as it only entails turning crank CO top centre, and having gear full ahead, care being taken that link block is in same position as when trammel marks were applied. Piston rods should be carefully watched to see that engines have been carefully lined off, and that glands are true to bore of cylinder, a defect which will show up very early if such should be the case (Sketch No. 48). The working of the various pumps should be noted, and wear of pump links tested in the usual manner, that is, by disconnecting same and testing distance from pump cross- head to pins on lever by means of gauge, which should be made and kept for this purpose (Sketch No. 61). A hint may not be out of place as regards circulating pump, and that is to use as little circulating water as is necessary to ensure good vacuum. By care- fully observing vacuum gauge and gradually closing down circulating inlet it will be found possible to ease the load on pump to a con- siderable extent. The H.P. piston valve should be kept in as tight a condition as possible, and it is not conducive to a good working piston valve to keep on lining out the rings on same. This lining only tends to wear the valve liners into an oval shape, with the result that reboring out is necessary. If the valve liners are plain, then the turning of two or three small grooves round the circumfer- ence of rings will assist to keep valve tight, as condensed steam gets into grooves and forms a film between liner and ring (see page 207). The H.P. piston, being fitted with Ramsbottom rings, should give good results if the rings have been properly manufactured, but if they show signs of having lost their elasticity, then new ones should be fitted. Another point regarding these rings is to have them as near a fit in the grooves in piston as possible, for if slack, then the constant change from one side to the other will not only wear out the rings but will inflict considerable damage on the bonnet or packing ring. The LP. slide valve usually gives trouble, and the face of valve and valve face on cylinder should be carefully tested by 68 " Verbal " Notes and Sketches means of straight-edge and feelers to ascertain that wear is taking place equally all over. Should the valve show wear round the out- side, that is, the inside ports or bars show high, then it will help to equal the wear if a few short gutters are cut on the part that is wear- ing. Another good plan is to bore a series of holes with a flat-nosed drill (Sketch No. 65). These holes should only be about rh to j\ inch deep. It is the practice now to bore out the cylinders with a bell mouth at either end, the piston travels the extreme length of the bore, with the result that no ridges are formed at top and bottom of cylinders. Condensers in new ships are sometimes a source of trouble, leaking taking place, with the result that boiler density is increased. A good test for feed water is by means of nitrate of silver, and the test consists of drawing off a small quantity of feed water in a tumbler or other transparent vessel and adding a drop of nitrate of silver; should the water become milky then salt is present, and the amount can be gauged by the resultant whiteness of the water. The use of water service on engine bearings has greatly decreased, as engineers find that a bearing will run just as well without water, always allowing that it is in line and properly adjusted. Once water is used it is not possible to run a bearing without it, so that the use of water, even in small quantities, should be avoided. How to keep a Watch. The engineer's life at sea is not exactly a bed of roses and the following description of his duties during the time he is on watch will emphasise this statement. The engineer whose turn it is to relieve will be called at a quarter before the hour on which he takes up duty, and promptness in relieving is most important. On entering the engine-room the first inspection should be the steering gear, bearings examined, and moving parts inspected to ensure all being in good order. The feed heater is next visited and pressure on steam gauge noted. Descending to the middle platform L.P. piston rod is felt by hand, also top end and face of columns and guide shoes. The valve gear or L.P. engine is next looked over, and the LP. and H.P. engines dealt with in the same manner. The rocking shaft bearing is felt by hand, and the crosshead links and top end of the pump links. All being well, the bottom platform is next visited, and the bottom ends and eccentric straps and main bearings felt by hand. During the passage from one bearing to another, the L.P. and I. P. pressure gauges are glanced at, to ensure that pressure is being maintained, also the vacuum gauge. The boilers are next visited, and height of water in gauge glasses and steam pressure noted, also that the firemen are at their duties, preparing to clean fires. The pumps are next ex- amined, care being taken to ascertain that bilge pumps are working, and also the connections examined to see what part of the ship the bilge pumps are drawing from. Port and starboard engine-room bilges are examined to ascertain the depth of water in same. The Workshop Practice 69 thrust block is next felt over by hand, and the interior of block examined to see that collars on shaft are immersed in the oil and water bath. The tunnel is next inspected, and each individual bear- ing felt by hand, also the stern tube gland. The tunnel well is examined to see that water is not excessive ; then back to engine- room, and the word passed, " All right," to engineer who is going off duty. The foregoing inspection is usually carried out in from seven to ten minutes. By this time the firemen will be well on the way cleaning fires, and the engineer will know in which boiler fires are being cleaned ; this being so, the feed checks should be regulated, as the boiler on which fires are being cleaned will be at slightly lower pressure than those which are steaming full. As soon as the fires on this boiler are well away and the next fire started cleaning, it will be necessary to again regulate checks, and by the half hour after going on watch, steam should be at full working pressure and checks can then be set, so that with but little alteration the rest of the watch can be run. Should there be no greasers carried, then it will be part of the engineer's duty to attend to the oiling of the machinery. Oil is usually a precious liquid on board ship, and the engineer will only be allowed a certain amount on which to run his watch. The top cups on the side of the cylinder will first claim his attention, and should be filled up to I or h inch below^ top of tube, siphons taken out and dipped into oil and then put back. At the half hour after going on watch the first oiling round should take place. When filling up top cups on engine, the steering gear should be visited and oiled if it is situated in the engine-room, as many gears are. The main bearing cups will require filling up, and siphons redipped as was done on top, eccentric straps oiled, and it may be mentioned that very little oil, properly applied, is as much good as a canful poured on, which only runs out of the bearings and does not lubricate. It is generally the rule to supplement the siphon feed to connecting rod bearings by hand feed ; usually the rule is to insert oil can into oil cup, and give what can be supplied in two or three revolutions, but this amount varies according to how the machinery runs. The valve gear is usually oiled after being on watch one hour, and then again one hour before being relieved. The pump links and rocking shaft bearings are dealt with along with the connecting rods and eccentric straps, that is every half hour. In some engines siphon fed oil cups are fitted to rocking shaft bearings and pump links, so that in this case it is only necessary to refill cups. The usual rule for evaporators is two hours each watch, so that one hour after coming on it will be requisite to get same under weigh. Steam is turned on, and feed pump set, and vapour valve opened, and height of water maintained in gauge glass on evaporator, and steam gauge set to working pressure. On completion of two hours' evaporating, if the level of the water in the boilers is at the required height, the engineer will blow down evaporator, that is, the vapour 70 " Verbal " Notes and Sketches valve and feed pump will be shut off, and a pressure raised on evaporator, the blow-down cock opened and evaporator blown out. This operation is necessary to reduce the density of the water. After blowing down, the evaporator is refilled to the required height with water, and left ready for the next watch. The thermometer on the feed pump, which is drawing from the feed heater, should be examined to see that temperature is being maintained, and that feed heater is working efficiently. Visits should be made to the stokehold and fires examined, also to the bunkers to see that trimmers are working the bunkers as directed. The tunnel should also be visited at least twice each watch, if not every hour, and the solidified oil in bearings renewed or pressed down on shaft. Attention should be given to the pumping of the bilges in the engine-room and tunnel, and mud box on bilge pump cleaned out during the watch. Tem- peratures of the sea water passing to circulating pump and discharge from condenser overboard should be taken and entered in the log, also temperature of feed water, and engine-room temperature, steam pressure on boilers, H.P. cylinder, LP. cylinder, L.P. cylinder, and vacuum should be entered in log, length of times evaporator was working, and height of water in main boilers. At one bell, that is, quarter iDefore the hour of being relieved, the engineer calls the next watch, and is again below ready to take the counter when his four hours are up. The counter is taken as eight bells strikes, and worked out from the counter of the preceding watch, and average revolutions entered in log book. The relief having gone round and passed the word, " All right," the engineer is free if it be the evening watch, but if the day watch, then, after an hour's rest, his winches or other repairs await him and keep him busily employed until seven bells, that is half an hour before the watch preceding his own goes on. Regarding winch repairs, it should be each engineer's duty to see that his winches are in good order. Every engineer has his own winches, either two or four, and by careful overlooking, and by giving attention to them while working, many a hard hour's work is saved when the ship is in port. Such little attention as black-leading piston rods and moving each winch about an inch each day saves a lot of packing and keeps the rods in good condition for future work. Economical Working. To obtain the best results from the engines and boilers the fol- lowing points should be attended to : — 1. Keep grate surface as short as possible. 2. Work with stop and throttle valves well open, and expand by link gear only. 3. See that the indicator cards show good compression curves. 4. If possible balance up the power in each cylinder (allowing extra power for engine driving pumps) by the link gear adjustment. 5. Keep pistons and valve faces tight. VIEW OF BOILER FRONT PLATE, FURNACE, AND COMBUSTION. (Untkr Construction.) Verbal"' Notes and Sketches. [To face page 71. SECTION II. BOILERS. Tensile Strength of Plates. — The tensile strength of steel shell plates ranges from 25 tons to 32 tons per square inch ; if of higher strength the metal is less ductile, and therefore less suitable for flanging or for expansion under heat. The tensile strength of combustion chamber and furnace plates ranges from 26 tons to 30 tons per square inch ; if over 30 tons the plates are too brittle. The tensile strength is also known as the ultimate strength or breaking stress of the material. Elastic Limit and Safety Factor. — If a tensile stress of so many tons is put on a test strip of steel the strip will become elongated, and if the load is then taken off the metal will return to its original length if the stress has been within the elastic limit ; if, however, the stress has exceeded the elastic limit the metal remains elongated, as " permanent set " or fracture has then taken place. If, therefore, the elastic limit is found by testing a number of strips the safe stress may be taken as equal to about half of this limit, and from this the Factor of Safety may be determined. Steel plates have an elastic limit ranging from 12 tons to about 14 tons per square inch. Example. — If 12% tons per square inch is found to be within the elastic limit of a steel plate, and assuming half of this as the safe working stress, determine the Factor of Safety, the tensile strength being 28 tons per square inch. Then, l2-5-r2=6-25 tons safe stress. And, Factor of Safety = 28 -f 6-25 = 4-4. NOTE.— The Factor of Safety for boiler shells varies from 4-4 to 4-6 according to conditions of construction. Stresses on Shell Seams. In cylindrical boiler shells the stress set up by the pressure on the longitudinal joints is equal to twice the stress on the circum- 72 "Verbal" Notes and Sketches ferential joints : this is due to the difference in the end sectional area and side sectional area of the shell acted on by the pressure. Circumferential Stress. Rule — Boiler end area x Pressure : Stress per square inch. Boiler circumference x Thickness Longitudinal Stress. Rule — Diameter x Pressure c^. , — ^, . , — Stress per square mch. Thickness x 2 Graphic Method of Proof for Shell Stresses. No. I.— Circumferential Shell Stress. The pressure per square inch exerts a force acting from the centre on opposite sides of the diameter, and therefore on two thicknesses of the plate : this produces the stress per square inch longitudinally. The pressure per square inch also exerts a force on the boiler end area, throwing a tensile stress on the shell plate circumferentially, which Boilers n produces the stress in that direction : if, then, the end area is calcu- lated and multiplied by the pressure the result will be the total load blowing out the boiler end, and therefore resisted by the strength of the shell plate thickness circumferentially. Example. — Determine the stress per square inch on the longi- tudinal and circumferential seams of a boiler 1 5 feet diameter, i-i inches thick, pressure 200 lbs. per square inch. Longitudinal stress = Diameter x Pressure 180 x 200 Circumferential ) stress / Thickness x 2 Boiler area x Pressure 1-5x2 180- X -7854 X 200 Boiler circum. x Thickness 180 x 3-1416 x 1-5 = 12000 lbs. per sq. id. -6000 lbs. per sq. in NOTE.-isft. = i8oin. ; also observe that, l8?i>i:7854x 200^ 180^200 ^^^^^ 1^3 180 X 3-1416 X 1-5 4x1-5 So that the circumferential stress may be expressed thus — Diameter x Pressure ,. „ .,...,„ ,„ - = lbs. per sq. m. Circumferential stress — - 4 X Thickness Graphic Method of Proof for Shell Stresses. fr b .\\\\\\\^\\^ '^ ^z^ss^s ^S3^^^ \ NNWWWW ; w No. 2.— Longitudinal Shell Stress. 74 " Verbal " Notes and Sketches It should be carefully noted that the longitudinal pressure exerts a stress on the metal circuinferentiaU}\ also that the radial pressure exerts a stress on the metal longitudinally. Observe that on two thicknesses of the shell metal circumferentially (Sketches Nos. i and 2) (each i inch wide) the pressure acts on the two areas B B to produce stress, whereas on two thicknesses of shell metal longitudinally (each i inch wide) the pressure acts on the two areas C C ; these latter areas are therefore equal to twice B B, so that the stress longitudinally is twice that circumferentially, as pre- viously stated. The dotted lines on C C show areas B B which are exactly half NOTE. — The Board of Trade require the centre circumferential shell seams to be equal to 65 per cent. . and the end circumferential shell seams to be equal to 50 per cent, of the solid plate, which allows of ample strength in this direction where the smaller stress is exerted. Strength of Shell. The strength of a boiler shell depends, therefore, on the Diametev and Thickness, and is independent of the Length. Boiler shells do not require stays, as circles are self-supporting : the reason for this is that the forces set up by the pressure are balanced at all positions of the circumference, or are in equilibrium. Boiler Shell Pressure, &c. — The general equation connecting the Pressure, Diameter, and Thickness, &c., of boiler shells is as follows : — 28 X 2240 X T X 2 X Joint-- Diameter x Factor of Safety x Safe pressure. Where 28 tons =- tensile strength of steel plates. ,, T — shell Thickness. „ Joint = smaller result of rivet and seam section strengths. The Factor of Safety in modern boilers varies from about 4-4 to 4-6, and represents the fraction of safe working stress as compared to breaking stress. The number 2 in the rule stands for two thicknesses of shell in one diameter — one at either side. To apply the above it should be remembered that if all of the terms on one side are multiplied together and divided by all of the terms except one of other side then the unknown term will be brought out. Example i. — Determine the required Thickness of boiler shell plate for a Pressure of 200 lbs., the Diameter being 15 feet, the Factor of safety 4-4, and the Joint strength 86 per cent. Then, 28 x 2240 x T x 2 x -86 = 180 in. x 4.4 x 200. Therefore, T = -„A^— 4:iii^^ =1-46 in., or say \\% in. thick. 28 X 2240 X 2 X -So NOTE.— 1^5 = -86, also 15 ft. ^ 180 in. Diameter. «aj , y^ofcv aijq .ejjeq 3«- 1. cGDiLe ffuq fob .£»n<^U Double strap _doubl< No. 5. A double butt strap joint has the rivets in double shear, which increases the strength of the rivet section 1-875 times (see sketch). To count the Number of rivets in a pitch (N) of a joint, take the greatest pitch and count the complete number of rivets enclosed w'lXhm it. The result is taken as the Number of rivets in a pitch (see sketch). No. 6.— Double Butt Strap Joint Type of Riveting (Five Rivets in a Pitch). Plate 1/5 inches thick; Straps I inch thick; Rivets iJA inches diameter. Joint strength, 84 per cent. Observe that the shaded rivets and parts of rivets give the number enclosed within the greatest pitch. NOTE. — This type of joint and riveting is only employed on longitudinal shell seams. Seam Section Strength. A piece of solid plate represents absolute strength, or 100 per cent. ; if then rivet holes are drilled out, the metal is now less in Boilers n area and the strenglli will be under lOO per cent. To find the stren£,'^th, then, of the plate after the holes are made, and which is called the " plate at seam strength." ^•Z" 1 P ■---■> Solid Plate. ^id-< >*d- ^^^^>^^^^^ w - P-d - > P - ^ Plate cut for Holes. No. 7. Solid Plate Per plate left cent. Then, as P x T : (P - ijOO..(P- tf) x loo^g^^^ ^^^^^^^ Notice that we have now one half rivet hole taken away at either end of the pitch distance, or one rivet diameter in all, so that the solid metal section is reduced by one rivet diameter in each pitch distance Also notice that the plate thickness T cancels out top and bottom. Rivet Section Strength. Rivets are fitted into the holes and closed up tight either by hydraulic or hand riveting (depending on the position of the seam). The rivets thus placed in position are intended to act as a substitute for the metal taken away. To find the strength, then, of the rivet section as compared with the solid plate. Rivet section Then, Solid plate as P X T : d- X -7854 X No. Per cent. f Rivet section strength compared with • ^°° ■ \ solid plate. Or, d--'x.78MxNo.xioo_^R- ^t section strength. PxT ^ Observe that the solid plate section for one pitch is equal to " pitch X thickness," and that the rivet area section for one pitch is equal to " rivet area x number of rivets in one pitch," 78 " Verbal " Notes and Sketches NOTE. — The foregoing assumes that the plate section and rivet section are of equal strength, but in the case of steel plates and steel rivets the shearing strength of the rivet section is to be taken as only 23 tons per square inch, and the tensile strength of the plate 28 tons per square inch. Therefore the formula would then read— d X ■785 4^No. X 100 X 23 ^ R-^et section strength. P X T X 28 Again, if double butt straps are fitted, as in longitudinal shell joints, the rivet section strength is doubled, as the rivets are now in " double shear," but as a margin of safety, 6J per cent, of this is deducted and the increase of strength taken as only 1-875 times that of single shear. Joints and Riveting. Single Riveted lap joints are employed in furnaces and combustion chambers, the strength of joint varying from 50 to 55 per cent, of the solid plate. Double Riveted lap joints are employed in boiler end plates and circumferential shell seams, the strength of joint varying from 50 to '54 per cent, of the solid plate. Treble Riveted lap joints are employed in the centre circumferential shell seams of long boilers (double-ended type), the strength of joint varying from 60 to 65 per cent, of the solid plate. Double Butt strap joints with five rivets in the greatest pitch are only employed on the longitudinal shell seams, the strength of joint varying from 83 to 86 per cent, of the solid plate. NOTE.— The "joint" strength is always taken as the smaller of the "rivet section," and the "plate section at seam" strength results, as the weaker section limits the strength. This is shown in the various worked out examples which follow. Types of Joints with Dimensions (suitable for Patches). No. I (Sketch No. 8). Plate | inch thick, single riveted lap joint to be applied. , Then, Rivet diam. = i-2x VT = I'2x >/'37S--734 in., say -75 in. diam. of rivet. Again, Rivet Pitch = l?^iiB^^?M'^ = '~ ^-75 = 1-66 in., say m in. pitch, loo-jomt 100-55 NOTE. — T = Plate thickness ; joint =55 per cent, for single riveting. The width of lap = '75x 3-2-25 inches. Boilers No. 8— Single Riveting. (Furnace or Combustion Chamber.) 79 Diameter and Pitch of Rivets, &c. Rule — Rivet diameter = 1-2 X VT. Therefore, Rivet diameter = i-2x \/-37S = i-2x •612=734 in., say f in. rivet NOTE.— T=plate thickness. Rule — Rivet Pitch = 100 X Rivet diameter 100 -joint Therefore, Pitch = ^°^^ '^S ^i-es »"-. say lU in. IOO-S4 3 ' > T5 Rule — DLstance from edge of plate to Rivet centre = Rivet diameter X 1-5. Therefore, -75 x 1-5 = 1^ in. The width of lap is in this case equal to 1 1 in. x2=2j in. (single riveting). NOTE.— The joint strength for single riveting with thin plates is taken as about 54 per cent, of the solid plate. To prove joint strength. Seam = (Pll^)^^-??=(^-^75--75)xioo^ ^^„^ P 1-6875 33 a** Rivets = tf' X 7854 ^ No. x 23 X 100 ^ -75- X .7854 x I X 23 X 100 ^ ^y. PxTx28 I -6875 X. 375x28 The joint strength is therefore equal to 55-5 per cent, of tlic solid plate. 8o " Verbal " Notes and Sketches No. 2 (Sketch No. 9). Plate i inch thick, single riveted lap joint. Rivet diameter = 1-2 x\/T = 1-2 X V-5 = -848 in., say J^ in. Diameter of rivet. 2-oS in., say 2^ in. pitch. Rivet Pitch = 100 X Rivet diameter _ 100 x -9375 100 -joint 100-55 Width of Lap = •9375x3 = 2-8125 in.=2ii in. No. 9. — Single Riveting. (Furnace or Combustion Chamber.) Strength of Joint. Seam = J *' ^-^a To prove strength of joint. Plate at Seam = ?l^?5 — l?3Z5xioo = 7o per cent. 3125 Rivet Section = -9375'x -7854X 100x2x23^ ^e„^ 3-125 X -5x28 ^ " No. 10. — Double Riveting (Zig-zag). (Furnace or Combustion Diameter.) Diameter and Pitch of Rivets, &c. "Diameter of Rivets-i-2 x V-5 = i-2x •707 = .848 in., say | in., or fg in. NOTE.— In certain cases it is advisable to make the rivet fully the size found by the rule. In this case J^ in. is fixed on as the diameter. Pitch ^^°°-"^^^ diameter^ ioox 93 75^3.125 in., or 3h in- 100-jomc 100-70 Centre of Rivet to edge of plate = Rivet diameter x 1-5 = -9375 x 1-5 = 1-40625 in., or i/j in- Distance between rivet rows (V) (Zig-zag Riveting). Rule — Y_ \'iiixp + 4xd)x(p-t4xrf) _ v'(iix3.i25 + 4x -9375) x (3-125 + 4 x ■9375U 10 10 i-6i in., say ig in., between rivet rows. NOTE. — The average strength of double riveted joints for thin plates=70 per cent, of solid plate. I To /ace ptii^e 80, Verbal ''' Notes and Skelches. .\a-i>i- i>i Sicmou — .01 " ^3S ?:f3viH to rfDJi*5 bnB laJamfiia sJsmaKI ' ■Bin o3 9id£2ivb£ zi Si b^zeo niajiao nI~.3T0Vl •Kiq /;i-:j loi EJrnoi^ D33^ jnaiJa agBiavfi &riT 3T0i1 Boil ers ^1 The joint strength is therefore equal to 70 per cent, of the solid plate. It should be remembered that the shearing strength of steel rivets is only to be taken as 23 tons per square inch, whereas the tensile strength of the steel plate is taken as 28 tons per square inch. The distance between the rows of rivets can be calculated as follows : — Distance between Rivet Rows (chain riveting) ^ 4 ^ diameter of rivet + i ^ 4x -9375 + 1 - 3-7500 + r 2 2 : 2-375 in- (2iin.). Distance between Rivet Rows (zig-zag riveting) = V(ii X pitch + 4 X Rivet diameter) x (pitch + 4 x Rivet diameter) _ __ _ -_ \/(ii X 3-125 + 4 X -9375) X (3^125 + 4 X •9375) _ 10 ^(34-375 + 37-5) x (3- 125 + 3-75) - 10 V38-125X 6-875 - 10 \/262- 10 9375 _ 10 ^-^=1-619 in., say ig in. 10 No. II. — Double Riveting (Chain). (Furnace or Combustion Chamber.) In all cases the distance from edge of plate to centre of ri\et = Rivet diameter X 1-5. Therefore, \l in. x 1-5= 1-406 in., say ii'g in. 82 " Verbal " Notes and Sketches Joint strength (Sketch No. ii). Seam = l^-l^JA^=^3-i25- -9375)21100^70 per cent P 3125 Rivets^*^' " 7854 X No. X 23 X 100^ 9375"- x -7854 x 2 x 23 x 100^ ^^^^ PxTx28 3-125 X. 5x28 ' ^ '^ Joint strength = 70 per cent, of solid plate. Distance between Rivet Rows (V) (chain riveting). Rule— ^^4 xd+ 1^4 X -9375+1^3.375 in., or 2i in. No. 4 (Sketch No. 12). Plate | inch thick, double riveted lap joint (zig-zag). ^ ^^ Rive diameter = I -ax VT-i-2x v''-62S-«948 in., say i in., diameter. Rivet Pitch := 100 X Rivet diameter 100 x i = 3-03 in., say 3,V in. pitch. 100 -joint 100-67 NOTE.— Take 67 per cent, as average strength of double riveted joints. No. 12, — Double Riveting (Zig-zag). (Furnace or Combustion Chamber.) Joint strength. Seam^(P- *^) ^ 100^(3:062 5-^1) x loo ^^ P 30625 ' •* ^ Rivets=^'^-7g4x2x23xioo^i^x.7854x2x23xioo^ ^^^^ P X T X 28 30625 X -625 28 Joint strength (smaller) -67-3 per cent, of solid plate. NOTE.— As the plate thickness increases the joint strength of single and double riveting decreases. u? u> ix> I— t t/5 i^'-v Sf • ^ yiH' ii'^ll- iiitot qBiiS JiuH i Five Rivets ii Diameter and Pitch of Rivets, &c. Rivet diameter Rivet Pitch = No. 13. — Double Butt Strap Joint. (Longitudinal Shell Seams.) double shear, which increases the rivet section strength 1-8751 r that of single shear 1., say 1} i , say 9i in. NOTE.— Strength ot double butt strap joints averages 85 per cent of soUd plate. Distance between outer rivet rows (V). I^ULE— Distance between inner rivet rows (V,). Rule— y _ Vln«p<-gxil))<(p+»«ifl _ N/(iii.9aS+8«l-3?5)'<(9a5+8 '< ' ao ao Rivet centre to edge of plate=l-5x i-375=a-o635 i ■ 2lV i To prove joint Strength. Se»m = fc^^™=!?L?L:±i?5':i'00^85-. per cent P 9-25 B,^.|,- rf'^-78S4>No. ■:23 >|.»;s,ioo_ |.37S'>-78S 4-5 a3'i S75 ioo _ ^ P ^ T < a8 9-25 > 125 28 '' "^ NOTE— The number of rivets i n a pitch is five, as will be seen from the shaded rivet : sketch ; notice that the half rivet sections enclosed within the pitch Umit require to be count Combined Rivet and Seam Section. RULE- (|.-| Rivet diameter 100x1-375 , . , ■ -.^t. Rivet Pitch = — —. — ^'^ — g-io in., say gl m. pitch. loo-jomt 100-85 To prove strength of joint. Plate at Seam = ^'^^~ ^'^'^^ x 100-85 per cent. 925 Rivet Section =. ^-375'^ " '7854 x 23 ^5 ^ 1-875 >^ ^00 = 976 per cent. 9-25 x 1-25 X 28 Referring to Sketch No. 13, the joint strength or smaller result is therefore equal to 85 per cent, of the solid plate. It will be noticed that in this type of joint the rivets are unequally distributed, the outer row having every second rivet omitted. The 84 " Verbal " Notes and Sketches omission of these rivets has the effect of raising up tiie joint strength, for, were the rivet included, we should then have a very strong rivet section strength, but a very weak plate section strength, and, as the smaller section strength must in all cases be taken as \\\QJoi)it strengtJi, the joint would be weak. By omitting every second rivet in the outer row the rivet section strength is decreased, and the plate section increased ; therefore the smaller result being now higher than before, the joint strength is proportionally greater. There is no benefit to be got by having a high rivet section strength, and a low plate section strength, as the smaller or joint strength governs the safe working pressure to be allowed on the plates. The result on the joint strength by giving equal rivets in each row will now be shown. Observe that the greatest (only) pitch is now 4f inches, and that the number of rivets included in one pitch is tJiree instead of five as previously. Therefore, Plate at seam = ^' ^^~ ^'^^^ x 100 = 70 2 per cent. 4625 Rivet section = L375^^ 7854x23x3x1^875x100^^^8 ^^„^ 4-625 X 1-25 X 28 1. As shown above, the joint strength has dropped from 85 per cent, to 702 per cent., which proves that the omission of every alternate rivet in the outer row as actually carried out in practice has the effect of raising up the joint strength to a maximum. 2. The rivet section strength is increased from 97-6 per cent, to 118 per cent., but, as the smaller result only must always be taken, this simply represents rivet section strength wasted. The re- adjustment of rivet section w^ith every second rivet omitted in the outer row takes away from the rivet section and gives to the plate section, or, what the rivet .section loses the plate section gains, and the joint strength is proportionately increased. Circumferential Riveting (Sketch No. 14). Seam strength ^ ^^"^^^ 100 ^ O'S- 1-37 5) ^ 100 ^60 7 per cent. Rivet strength = ^ ^ -^^g No. -^23 x 100^ i.375'^ -7854 2 > 23 x iQO^gg.y eent. PxTx28 3-5 X 1-25x28 NOTE.— The shell plates are i;^ in. thick. Joint strength = 557 per cent, of solid plate. Boilers 85 This is sufficient for the end seams, which according to Board of Trade requirements must not be less in strength than half that of the longitudinal seams, which in this case is exceeded by a fair margin. Distance between Rivet Rows (V). y_ N/(iixp + 4x • € -101 -. ^ ^5AJ ^ ^°°^'3-^75 - '^^-= 1.625=2-4375 i ^- — ^=58 per cent. Rivet ! • 7854 X No. X 23 < P d •" M 1-4 4_) OJ >. cu , . -C "n rt (/I i U-, -4-> 4J > to m c -M "S C CJ 3 1 "S. r !0 ^ CO jc »^ Q 3 rt X 1 1 a \n vd C 73 0) C X M nJ X a 'a; u. ir> > .-y 1 tA u .ij-c o = u, "0 1^ I (U (-1 " Verbal " Notes and Sketches CAULKED -, L 3"_4 !5"_ . ' i 1 No. 17. — Machine Riveting. (With Dimensions.) The dimensions should be carefully studied and compared. CAULKED No. 18.— Riveting and Caulking of Combustion Chamber Top. (With Dimensions.) Hand riveting is usually as shown, that is, the rivet is counter- sunk on one side, and snap or flat headed on the other side. Compare the plate thickness and rivet diameter, &c> Boilers JOINT r-T'sTRAP 89 rit PLATE No. 19.— Shell Plates and Butt Straps. This view, a fore and aft section, of the sliell shows clearly how the butt straps sit in position. To find Butt Strap Thickness. — Rivets if inches diameter, pitch 9 inches. Rule — Thickness = |ii^^^4^^^ =5,^ ^'^5 x (9- i-375)^ ^ i^ch thick. 8x(p-(dx2)) 8 X (9 -(1.375x2)) PLATE fl" THICK /--0- O Q Q -O'-^-Q' 000 G- o o •■ o ' Q -o=.^-e O RIVETS ' • TUBE PLATE 25" 32 THICK No. 20. — View of Boiler End near Top. (Showing Riveting of Tube Plate and Top End Plate.) Joint strength. Seam Section =^-1—- x ioo = 5^5jl_ x loo — 60-2 per cent. P 3-25 Rivet Section^- ^^^^ ^°°^^3 ^ i-x -7854 >^2>^ 100- zS ^gQ.g per cent. P T 28 325 V 78 28 ^ ^ The joint strength is, therefore. 508 per cent, of the solid plate 7 90 ** Verbal " Notes and Sketches Distance between Rivet Rows. Rule — \^(ii X p + 4 X d) X (p + 4 X d) _ V(ii X 3-2S + 4X I) x (3-25 + 4^)^^.^ ^^ 10 say I J in. Distance between edge of hole and edge of plate. Rule— -J- - No. 24— Diagonal Pitch of Rivets. For the type of joint shown above the diagonal pitch of the rivets should not be less than that found by the following rule. Rule — Diagonal Pitch=.3> Pitch + 4^x diameter • Therefore, Diagonal Pitch = 3^^'^^"'"'^^ ^'^^ = 3-326 in., or say 31^ in. Steam Space Stays. These steel stays range in diameter from 2J to 3I inches diameter, with a normal pitch of 16 inches for pressures of from 160 to 210 lbs. per square inch. The stays are secured to the plates by one of the following methods. 1. Holes cut in both plates and stays held in place by nuts and washers both inside and outside the plate at either end. 2. Stays screwed through both end plates and fitted with single nuts and washers on outside of plates onl)-. 3. Holes cut in both end plates and stays held in place by means of a thin nut inside and a thick nut outside. Occasionally the nuts are bevelled off as shown in the sketch, and 92 " Verbal " Notes and Sketches -X-- ^_, c ►Ok*- (U gjpr---T-- S 0) c CO S O U i^ o -< U, C/l >, (A (Ti >t C« OJ CJ W in O f. X! C3 u -*j m tl, a QJ ►J UJ •d D ^ c Pi; ^ 7854 - 9000 ^ 667. Pressure 200 Therefore, v'66 = 8-i in., say 8 in., pitch. CAULKED No. 29.— Caulking of Stays. When the stays are screwed into the plates the latter are caulked round the stays, to ensure tightness, a touch of mastic cement or red lead putty being placed on the face of the nut before screwing up. • III ill I ,"' No. 30. — Steam Space Stay. (With Double Nuts and Riveted Washers.) The space 4 (about ^^ inch) is filled up with lead putty or mastic cement In this type of stay the outside washers, which are riveted to the end plates, require to be ot the same thickness as the plates, and of a diameter equal to two-thirds of the stay pitch. The Constant allowed in this case is 168 for iron and 210 for steel. Data — Pressure = 215 lbs. (g. Diameter = 16 ft. 6 in. Length = 20 ft. 2j in. "^■ Rates of heating surfa Tensile strength of st Pitch of rivets = 10 inj Strength of plate = 82^"^ Strength of rivets = 9 bers Double riveted. Double riveted. Treble riveted. D. B. strap vyith five rivets in a pitch. Single riveted. Factor of Safety.— Giver^ (^""o"* <^° back) =4 ft. 6 in. tJmg . chambers = 10 ft. 6 in. Tons X 2240 X T Then, So that in. each. 30x2240x1! . . ,. u , • J . stay bolts = each i^ m. diameter. Factor spension stays of any kind are fitted in this D.-E. ered that in many boilers of this type such stays Note. 30 tons is taken, so that the four separate combustion chambers are i6 ft. 6 in. = id^^ supported, by means of angle-plate stools riveted hambers. 828 per cent. = -8 " Verbal " Notes and Sketchc [ To face page 98. Daia— Pres9ure = 2i5 lbs. (gauge). Diameter = i6 ft. 6 in. Length = 20 ft. 24 in. Rates of heating surface to grate surface = 45 : l- Tensile strength of steel = From 30 to 32 tons per square inch, Pitch of rivets = 10 in. Strength of plate = 82-8 per cent (joint strength). Strength of rivets = 90-5 per cent Factor of Safety.— Given the above data the Factor of Safety can 1 thus ;— Tons >. 2240 < T in. >. 2 v Joint = Diameter x Pressure x Factor. Then. 30* 2240 ^ Iji in. >^^ 2 x -828 = 198 in. > 215 >; Factor. No 30 A.— Double-Ended Boiler. Shell plate thickness = So that. Factor = 3ai«40; 30 tons is taken, being the 16 ft 6 in =198 in 828 per cent. = 828 ' Verbal " Notes and Sketches. ' = 4-5(nearly)- tlnimam tensile strength of the plates. ■215 Double riveted. Double riveted. Treble riveted. D, B strap with five rivets in a pitch. Single riveted. :o back) -4 ft, 6 m = 10 ft 6 in. Riveting— End circumferential shell seams End plate seams Centre circumferential shell seams Longitudinal shell seams Furnaces and combustion chambers - Depth of combustion chambers 1 front t Height of centre combustion chambers Depth of girders ^13 in Thickness of girder p!ates = il in. each. Each girder is fitted with six stay bolts = each ij in, diameter. It will be nuciced that no suspension stays of any kind are fitted ii> this D.-E. boiler, but it should be remembered that in many boilers of this type such stays are fitted {see p. 99). Observe also that the four separate combustion chambers are held in place, and at the same time supported, by means of angle-plate stools riveted on to the adjoining combustion chambers. \To f j^ —+6=6(1.5, "nd. V66.5=8.i ia, say 8 in.. Pitch. Notice that the Smfiice- Square of pitch so that to ,v,n„.„ e r „. , ' M u. piicn, so tnai to convert Surface into Pitch, the stjuai No. 35.— Boiler under Construction. ^'ievv showing combustion chamber boxes, girders, stays, and front end plate. The close staying of the combustion chamber back plates should be carefully noted. NOTE.— The girders shown are all of the single plate type, bossed out where the stays pass through. The bevelled joints of the combustion chamber bottom plate and side plates should also be noted. ' ' Verbal " Notes and Sketches. To face page 10 1. Boilers loi Combustion Chamber Stays. It will generally be found that the marginal stays of combustion chambers are first affected by wear, and particularly the top row. Often the stays in this row develop minute cracks which may, however, on testing, be found to extend right into the body of the stay metal. The floating tendency of the combustion chamber (which, it should be observed, is simply a hollow vessel immersed in water) throws severe stresses on the stays, and generally, through time, results in straining the metal of the stays as described, due to the bending stresses set up. The marginal stays having to support more surface than the inner stays are of larger section foften i4 to i| inches diameter). Combustion Chamber Bottoms. — The following rule brings out the safe working pressure for combustion chamber bottom plates, which, it should be observed, form semicircular surfaces of plain section. Rule — 9900 ^•n ■^ 73 w C ^ ^ O „" -s^ > ^ / 53 S > '^ • .23 '^ o 1 Ic t/T -t^. H ■r; OJ '$ •o V O -G c Is 4J G 3 3 O O _ )-i -M ci cn O 00 C "^ CO ill 6 5 "^ e Boilers 105 No. 39.— Combustion Chamber Top and Girder. Some firms arrange the girders cut clear of the top plate as shown. Attention should be given to the dimensions of the plates, rivets, and stays. io6 "Verbal" Notes and Sketches The strength of girders varies (as in the case of a beam) directly as the Depth- and the Thickness, and inversely as the Length. RULE- D-x T Or, Strength varies as, — Working P'-essure = ^-^^^^^^^ = lbs. Where, € = 990 for three stays, and iioo for four stays. d= Depth (inches). T = Combined thickness of girder plates. W = Width of combustion chamber (inches). P= Pitch of stays (inches). D = Distance between girder centres (inches). L= Length of girders (feet). Application. — To apply the rule to the case above (Sketch 36). Then, Working Pressure = — 990x8-5" >"• xi 5 i"- ^207 lbs. per sq. in. (31 in. - 7-5 in. ) X 8 in. x 275 NOTE. — The width of combustion chamber is about 31 inches, and assume the distance between the girders as 8 inches. Again notice that 33 inches = 275 feet. Depth of Girders (Sketch 39). C = 990 for three stays through girders. d= Depth of girder. T«: Thickness of girder plates (combined) = ii inches. W = Combustion chamber width = 31 inches P = Pitch of stays = 8. V inches. D = Distance between girders = 8 inches. L = Length of girders in feet = 275 feet. Pressure = 190 lbs. per square inch. Rule — Cxd xT = (W-P)xDxLx Pressure. Therefore, ^^- (W- P) x D x Lx Pressure . CxT (31 - 8-5) x 8 x 275 x 190 -63.3 990x15 And, ^63-3 = 7-9 in., say 8 in., depth of girders. Tubes. The smoke tubes are generally made 3 or 3I inches outside diameter with natural draught and 2| inches outside diameter with forced draught, the thickness ranging "from |^ or y\ inch in the case of ordinary tubes, to j% or | inch in the case of stay tubes. The |0 ipC bptG 3 7; // \^ TV • .33BmuH (n^riq O O O O O O O'O o o oooooo O O O O^Hr.' ^^B SOLID ^_STAY 2"dia SCARFED JOINT No. 40. — Front View of Goose-Neck Type (Gourley Stephen) Furnace. (Front Tube Plate removed.) This sketch shows clearly the difference in the section of the furnace at back and front, the back being conslricted to an oval section (30 inches diameter). The flange at the back is also much higher in position than the circular portiuQ of the furnace and is riveted all round to the back tube plate. Also observe the scarfed joint of the combustion chamber plating at the sides. The side wrapper plates are g inch thick, but the bottom is heavier, bciny [^ inch thick. Thickness of Combustion Chamber Bottom Plate. Rule — /9(>00 xT\ ^ /'5-^+ "\= Working Pressure. Where T=Thickness= ^ = -8125. „ D=Diaraeter outside-46 inches. „ L=Leag;th (front to back)=33 inches. Then. Safe Pressure = l^99°° ^ 'l'^^)^(s- J^\"-) = Z32-i lbs. V 3<46 J \ 60 X -8125/ ^ This proves that the bottom plate is of ample strength, as less thickness would be suffici to the plate allows a margin for corrosion. nl, but the extra thickness giv< ' Verba! " Notes and Sketches. ooo It, Si eaauT ya72 ^^^ xoIht"' '^ - ^ r^ O O TUM TUO O O w ^ Okj-O. ooo^d O W LV-^ oooo "ioo(9 o o v> 6 o ooo 0©0^! ■ 83aUT YHAMIOfloO^ YAie 8^ y JATOT 8SU^ .^ O O O Q iJ O O O O O O O O G rn^' ^^O^^'^c '•%/ r-> A u ; ATOT esi // I01OI01O oooo THICK 0)0 00 «ITHOUI Nurs OOOO oooooo 10)000000000000 OOOOOOOOOOOO0 [^O O O O O O O o o o o o O O O O(01O($]OlOlO^Ol5) pooo OOOO 01OOO OOOO 0OOO OOOO ^oo OOOO Oooo OOOO OOOO OoOo No. 41. —Tube Boxes, showing dimensions and number of Stay Tubes and Ordinary Tubes. The pitch of the tubes is 3| inches, and thL- inaxiniuin pilch of ihe stay tubes loj inches. Notice that the marginal or bounding stay lubes are the heaviest fitted, and are secured by Sat nuts at front tube plate. Also note the tube plate solid stays 2 inches diameter. The clear space between the lube nests is II or 12 inches, as this is required to allow of access to the lower parts of the boiler. As stays cannot be litted on this plate area, the end plates are strengthened by means of doubliag piates riveted on, which take the place of solid stays {see No. 31). W = Width of combustioa chamber. (D-rf) 'iT.28ooo = W ■ Where D=Pitch of Tubes. Where T = Thickncss of Tube Plates. ,. (f= Inside diameter of tubes. Example. — Determine the required thickness of tube plaits for a pressure ( being jf inches, the inside diameter of tubes 3^ inches, and the width of combust Then, T^WxDxPressure SS^ SfiaS-ao Q ^ ^^ .^ . ^ ~ "(|)"rrfyT2Booo (3-625 - 2-125) . 2S000 NOTE.— The bock tube plate is aeldom nude less than i inch thick, notwithstanding the calculated thickness by role. Boilers 107 front end of all the tubes is slightly larger in diameter than the back end to allow of easy insertion or extraction. In the case of the tubes the ends are expanded out to the holes in the plate by an appliance known as a "tube expander" (see sketch), which operation is considered sufficient to ensure tightness. The stay tubes represent solid bar stays and are required to support the flat surfaces formed by both tube plates. The sectional area of the stay tube metal should therefore be equal to that of a solid stay. The required thickness can be found as follows : — Example. — Determine the required thickness of steel stay tubes 2| inches outside diameter to be equal in strength to a solid stay, the maximum pitch of the stay tubes being io|^ inches and the pressure 180 lbs. per square inch. Then, Diameter of solid stay= /-^75i^ 180=1. 74 say ij in., diameter. ^ V 9000x7854 '^ ^ The cross sectional area of metal of the stay tubes must also be equal to the solid stay area. Therefore, (2-5- - d2) = 1752 = (6-25- rf-') = 3-0625. Therefore, 6-25 - 3-0625 = d-= 3- 1875. Therefore, Inner diameter of tube = \/3- 1875 =1-78 in,, say if, in. And Tube thickness = ?^5j:1^= -375 in. (§ in.). The ends of the tubes are staved up to slightly increase the diameter and so allow for the cutting of the screw, and it should be noted that the external diameter at the front end exceeds that of the back end by about \ inch. The ordinary tubes are subject to a compressive stress and the stay tubes to an additional tensile stress. In general practice about one-third or more of the total tubes are arranged as stay tubes, and these tubes are usually fixed by one of the following methods : — 1. Both plates tapped and tubes screwed in, then expanded into the plates. 2. Both plates tapped and tubes screwed in, expanded into the plates, and a nut | inch thick fitted outside the front tube plate only. The plates are caulked round the tubes and the back end of the tubes are also beaded over as shown in sketch. It is now the common practice to fit nuts only on the marginal or bounding stay tubes, the others being merely screwed into the plates, expanded in the screws, caulked and beaded over. The sketch on page 108 illustrates the foregoing. Often three thicknesses of stay tubes are employed in one boiler to meet the requirements of the differently supported areas of the tube plates, the heaviest type |- inch thick being used for the marginal stay tubes, and the others, varying in thickness from i to /^ inch, are fitted inside the marginal area of the plates. io8 " Verbal " Notes and Sketches 8'0" 10 THREADS PER INCH ?" THICK fe STAY TUBE toioo r I" THICK COMMON TUBE v^^^'.'.v'v'. vv^'^'v'^'.^jfc^.'v^^^'.^vV'.vvv.v'..^^^ X^^^^^^■^^^^.'v^^'v^'v^ ■v'^^^^^^^^^'^^^Vv^'^■^^^^^v -^ No. 42.— Boiler Tubes. The stay tubes are f inch thick, and are screwed into both plates and caulked in place ; in addition, a flat nut is screwed over the front end. This type of stay tube is used round the boundary of a tube nest. Notice the difference in diameter at either end, the front being the larger. About one-third of the total tubes are fitted as stay tubes, the thickness ranging from ^ inch for the inner stay tubes to f inch for the outer or marginal stay tubes, which are nutted. The ordinary tube shown is i\ inch in thickness, and like the stay tube is swelled out at the front end. These tubes are expanded in place by an ordinary three-roller tube expander. Stay Tubes. — The light pattern stay tubes (internal) are expanded into both tube plates, and beaded over ; the heavy pattern of stay tubes (marginal) are caulked in position both inside and outside at the front, and inside at the back end, also beaded over, as is usual "with all tubes. NOTE.— The ratio of tube heating surface to grate surface is as 25 is to i in most cases. "Serve" Tubes. — The ribs inside this type of tube increases the effective area of the tube, and thus extracts more heat from the waste gases as the}' pass through. ^nd economy. extracts more heat from the waste This results in increased evaporation Boilers FRONT TUBE PLATE 109 8 THICK CAULKED No. 43.— Heavy Pattern Stay Tube. (With Flat Nut in Front Tube Plate.) These tubes being too heavy for expanding, the plates are caulked round the tube instead. Tubes of this type are placed on the margins of a tube nest. BEADED OVER BACK TUBE PLATE No. 44.— Back End of Stay Tube. (Showing Screwing in, Caulking, and Beading over.) I lO "Verbal" Notes and Sketches I" SOFT IRON CAULKING RING. ^^^^^ ^ ^^mmv^mm\w-m\ms\m^^^m:^ 27 ->•! ADAMSON RING FURNACE S\\\\\\V\\\\\^ ^ \\\\ \ \\\\' \V^V\V\VVV\\\ \^^V\V<.VV V V VVV^V^^VW^' No. 45.— Adamson Ring Furnace. As with the Bowling Hoop furnace the different lengths are riveted together through the flanges and soft iron caulking rings. The flanges stiffen the furnace and allow for expansion, while tightness of joint is obtained by close caulking up of the soft metal rings. Safe Pressure. — For a plain steel furnace the rule is as follows : — ... , . 99000XT2 Working: pressure^^ ^^^^^ ^ p - Where T = Thickness. ,, L- Length in feet „ D=c Diameter in inches. Boilers 1 1 1 If, however, the furnace is fitted with stiffeiiini; rings as shown above, then Y^ — Loigtli betwcoi the rings subject to a hmit pressure found as follows : — Limit pressure = ^?^^^^ — . So that the actual working pressure is to be the smaller of the two results obtained. Example. — Determine the safe working pressure for the furnace shown in Sketch No. 45, which is f inch thick and 42 inches diameter. Working Pressure _ 99000 x 75" _ .. (If less than limit pressure) (2-25 + i)x42 in. NOTE.— 27 inches := 2-25 feet. Limit Pressure = ^552JL125.= 176 lbs. 42 The safe pressure to be carried is therefore 176 lbs. NOTE. — The strength of a plain furnace depends on the Length, Diameter, and Thickness squared. <-.. IIM;v;w/lw/m^^^M^^;^^ >^ — 27" — 5 ^ - - BOWLING HOOP FURNACE "'-' Y'L ■ -^ '^'/y/yy^/yy/z^y//-'- •-'///// n::! {y//y///i No. 46.— Bowling Hoop Furnace. 112 Verbal " Notes and Sketches The flanged rings shown are known as " Bowling Hoops," and when fitted to a plain furnace increase the strength and at the same time allow for expansion. As will be understood the furnace length is divided up into two or three sections, and these are joined by the hoops. 8" -I* No. 48. — Suspension Bulb Furnace Corrugation. No. 49. — Suspension Bulb Furnace. The lengths marked A B at front and C D at back are required by Board of Trade not to exceed 9 inches. No. 50. — Morison Type Furnace. The lengths marked A B and C D are required by Board of Trade not to exceed 9 inches. *>:5i?:triAi£i»o 409:; i»q r>jriu lukM: tv Ju^'i < ^11 svii's* • 5:•-tv*^t' No. 55.— Section through "Goose-neck" Type Furnace (Showing FUnge at Baclc End and Riveting.) Strength of Joint. Seam^ "*' **' " '°° = '^' '^'' '°° = 50 pel cent PxTx28 2« .625x28 loiot strength = 50 per cent, of solid plate. = 51.5 per cent • ■ Verbal ■ Notts and SWetche: 3DAH These stays ar (Sketch No. 41). No. 56.— Furnace and Tube Plate Solid Plates. : fitted to support the front and hack lube plates on either side of the furnaces " \'crbal " Notes and Skciclicj. [7,> facf page 115. Boilers 115 I'rivets, 2" pitch No. 54.— Wing Furnace Flanging. Notice that the flange is extended out to fit the shape of the combustion chamber. To find Thickness of Furnace (Diameter, D-=44 inches, Pressure = 200 lbs.). Rule— 14000 X T in. = D in. ^ Pressure. Therefore, T in. = P '"• ^ P'- ^gsur^ = 44 ^200^ .^2 ^^ ^ 3^y ,. i„ 14000 14000 ii6 "Verbal" Notes and Sketches Furnaces. Furnaces are usually made from i to f inch in thickness. The strength of a plain furnace depends on the Length, Diameter, and Thickness squared. Method of Strengthening a Weak or Collapsed Furnace (with Dimensions). The Sketch No. 57 illustrates the best method of repair for a weak furnace, or for a collapsed furnace which cannot be set up. Observe that the ^-inch studs are screwed into the furnace metal and riveted over, also that thin thimbles or distance pieces are fitted between the half-round strengthening ring and the furnace, to allow of free circulation of the water. The pitch of the studs varies from 10 to 13 inches. As in a plain furnace the strength depends upon the length, diameter, and thickness squared, if we reduce the length by one-half we double the strength ; therefore the ring round the centre practically shortens the length, and correspondingly increases the strength (always subject to Limit Pressure Rule result). NOTE.— Thimbles must be fitted between the furnace and the ring to allow of •water circulation between. Types of Furnaces. The Sketches No. 58 illustrate the corrugations of the three mosi important types of furnaces in use at the present time. Corrugated Furnace Manufacture. The process of manufacture of furnaces is as follows : — The plate is rolled with one edge thicker than the rest of the plate, so as to allow for the thinning which takes place in flanging. The plate is then sheared to size, and bent to a cylindrical shape in the bending rolls. It is then passed to the electrical welding apparatus, where it is welded up, after which the furnace is taken to the corrugating mill to be corrugated, and to the various hydraulic machines for flanging. The furnace is then machined to correct sizes, and set true to template. Finally, each furnace is carefully annealed before despatch. Advantages of Corrugated Furnaces over Plain Furnaces. 1. Stronger than a plain furnace of the same dimensions. 2. Better expansion allowance by means of the corrugations or ribs. 3. More surface for the same length, and therefore better evapora- tion is obtained. NOTE.— For a plain furnace the limit pressure is equal to 9900 ^T ■1^^, flD"^ ^4 ;* ^* ^4^ No. 57. — Method of Repair for a Weak or Collapsed Furnace. Ai will be seen from the sketch, the repair consists of two an^Ie irons riveted together through thimbles, and forming two half rings which are bolted together as shown. Pins f inch diameter are tapped into the furnace and are riveted over inside, with nuts and washers outside, the pitch of these being about la inches. This arrangement stiffens the furnace, and is "iqually suitable for either plain or corrugated. NOTE.— The ring is kept 3 inches cleat of the furoace aietal I r ot free circulation of the 1 "Vcrlwr- Notes ami .Skclclie {Te/ace f^e llO. ii; MORISON DEIGHTON No. 58. — Types of Furnaces. (With Pitch and Depth of Corrugations. ) A corrugated furnace of the same dimensions is about half as strong again as a plain furnace of average proportions. The strength of a corrugated furnace depends upon the Diameter and Thickness. Collapse of Furnaces. Furnaces may be collapsed by any of the following causes : — I. Excessive scale. The scale keeps the water from being in direct contact with the plate, and overheating takes place (about 600° Fahr.), with the result that as the plate is weakened part of the furnace bulges in. ii8 " Verbal " Notes and Sketches 2. Oil deposits adhering to the furnace. Oil deposited on the furnace top or sides, for a given thickness, is more serious than ordinary scale, as greater overheating of the furnace plates will ensue. 3. Saturation or salt deposits. The boiler density rising above o\r, the surplus salt in the water deposits, and the water not being in contact with the metal, overheating of the plates takes place and collapse follows. Cases have been observed where furnaces have come down when lying under banked fires. One of the most reasonable theories put forward to account for this is the lack of circulation existing (especially with a high density), causing a layer of steam to form between the water and the metal of the furnace, with consequent overheating and collapse ; but opinion is somewhat divided on this point, and the true cause is not definitely known. Furnace Temperatures, &c. (approximate). Furnace temperature - - - - Combustion chamber temperature - Uptake temperature - - - - Funnel temperature - - - - NOTE. — The above temperatures (measured by a pyrometer) vary under different conditions, but these may be taken as average. about 2600° Fahr. „ 1500° 5. 750° » 600° >,\^ No. 59.— Fire Bar. (With Dimensions.) The air spaces are formed by small projections cast on the sides of the bars, which ensures the required air clearance. When the bars are fitted in two lengths, the dimensions are usually as marked. Notice that one end of the bar is bevelled away to allow for expansion under heat, and the other end is "hooked ' to grip the edge of the centre bearer. ,'^^ No. 6i— Boiler Shell Manhole (i6 inches by 12 inches). I, Compensation Ring. 2, Joint of Door. 3, BoUer Shell. NOTE.— The upper view (sectionl is taken in the longitudinal direction, and shows the short diameter of the manhole (12 inches). The compensation ring is of the same thickness as the shell plate. [n/atepaga 119. •Ni-rljal" Nolesand Sketclitrs. Boil ers 3'- I" © © © (h]'f rm — - 3 rm -4" - - rm rm 1 loleo 1 , , , , . . , 1 "ml© 1 II !! 1- ;i «i«J- 1 . ■ 1 I : : ! 1 T 3' 4 BOLTS LLU 1^ ^16 ILU 1 THIMBLES lU) No. 6o. — Centre Bearer for Fire Bars. When the bars are arranged in two lengths, the centre bearer is fitted as shown ; the bearer sits on an angle knee plate at either side of the furnace, the knees being held in position by studs screwed through the furnace, and the bars hook on to the edge of the bearer plates. Manholes. The standard size for manholes is i6 inches by I2 inches, but sometimes those on the end plates between the furnace openings are less, being 15 inches by 11 inches, or thereabout. Shell manholes are cut with the long diameter circumferentially and the short diameter longitudinally, as the strength of the plate is least in this direction. Shell manholes have compensation rings riveted to the shell and of equal thickness, the area of ring to be not less than that of the metal cut out plus the rivet hole areas. The compensation ring also forms the joint for the door (Sketch No. 61). The clearance round the door and opening should be as nearly as possible iV inch a side, as excessive clearance is often the cause of the doors blowing out. After blowing down the boilers, and before taking off the manhole doors, the drain cock of the water gauge should be opened so that air may enter the boiler and destroy the possible vacuum left by blowing down. Neglect of this may lead to an accident, as the doors might be blown in by atmospheric pressure when the nuts are eased back. The manholes in the boiler ends are often arranged with the end plates flanged in to give strength, instead of fitting a compensation plate ; in addition to this three large stays are passed through from end to end of the boiler, and secured to the end plates by nuts, as shown in the sketch. These stays support the plate round the portion weakened by the cutting of the holes. 120 "Verbal" Notes and Sketches No. 62.— Boiler End Plate Manhole (15 inches by 11 inches). 1, Joint of door. 2, Stays. 3, End plate flanged in. Boilers 121 A doublini^ plate is also riveted to the back of the boiler opposite to the manhole in the front (Sketch No. 33), and covering a similar area. Natural Draught. Natural draught is caused by the difference of weight in the heated air of the uptake and the cold air entering the furnace. To obtain a good draught the funnel and uptake temperatures must be between 600" and 700", this temperature being necessary to bring about the required difference of weight. The draught can often be improved by increasing the length of the funnel, as by this means the column of heated, and therefore lighter, air is made less in weight, against the same weight of cold and heavy air. The production of natural draught is an example of heat con- vection, as the cold air at, say; 60^ temperature, passing down the ventilators, enters the furnace and becoming heated expands and therefore rises, passing off by way of the tubes, uptake, and funnel. The weight of the heated air is less than that of the cold air, and the difference in weight can be found by taking the absolute temperature as shown below. Example. — A cubic foot of air at 62° temperature weighs -076 of a lb. ; determine the weight if the air is heated to 600° temperature. Then, 62 + 461 = 523, and 600 + 461-1,061. Therefore, As 1061 : 523 : : -076 --0374 of a pound. The difference of weight as shown produces a current or draught. Heat Absorbed in Creating Natural Draught. — The specific heat of the funnel gases is about -23, which means that to raise i lb. of the gases i^ in temperature -23 of a heat unit is necessary. To show then the loss incurred by the generation of natural draught: — Example. — Cold air temperature 62', uptake temperature 700", and allowing 24 lbs. of air per lb. coal, calculate the heat units per lb. coal used in producing the draught. Then, 700" - 62' — 638' increase of air temperature, and B.T.U. required = 638 x 25 x •23 = 3668-5. NOTE.— 24 lbs. of air + i lb. coal = 2S lbs. gases in all (neglecting ash and clinker). As a Percentage. — Assuming that i lb. coal contains 14,500 Heat Units, Then, As 14500 : 3668-5 : : 100 : 25 per ceni 122 "Verbal" Notes and Sketches So that 25 per cent, of the heat units in each lb. of coal are used up in producing the necessary difference in temperature of the funnel gases required to form a draught by difference of weight. Howden's Forced Draught. In this well-known system of artificial draught, a large fan driven by means of a small engine, usually placed in the engine- room, forces the air along the air trunk into the air heating box Front View. Inside View. No. 64. — Howden's Forced Draught Furnace Mountings. a, Top Valve Handle. b, Back Catch. c, Front Catch. d, Hinge Flat. e, Hinge Centre. fc, Ashpit Door Handle for Centre Front, fs, Ashpit Door Handle for Side Front, g, Catch for Ashpit Door. h, Hanger for Ashpit Door, k, Side Valve Handle. 1, Left-hand Baffle Plate (or Air Box), m, Mica Plate, r, Right-hand Baffle Plate (or Air Box), s, Door Baffle Plate (or Air Box), t, Top Baffle Plate (or Air Box), u, Furnace Door. X, Ashpit Door. situated in the uptake, and consisting of two tube plates with a series of short vertical tubes between. The hot gases from the smoke tubes pass up through the sets of short tubes in the box, and the air, being outside of these, is heated by the otherwise waste gases, and passes by openings in the sides through a casing on the boiler end down to the hot air receiver above the furnaces (see sketch). The fronts of the furnaces are closed, and have three metal valves fitted, by which the air supply can be regulated to the furnaces, both above and below the fire-bars, one valve admitting the air / STAVED UP TO SCREWED 6THREAD3 !3 S'l^tiir;^ r^:^ •tHIA?:.: No. 63.— Sectional View of Boiler with Howden's Forced Draught. The draught 11 genented by the Eia jhown, ud the cold air (say at 60*) ia delivered, by way of the air casing, into the air heating box which is ' *"k*'if "^-^ ** which temperature it enters the fuRuc«s, being adinitted by one valve above the fire-bare, and by two valves (buth operaied by c ow the bars. This pressure can only be measured by a porUble U tube similar to the one shown in the drawing, aught the walet would ri»e highest u Boilers 123 HOT AIR RECEIVE AIR VALVE )UBLE DOOP. -jJ ! No. 65. — Howden's Forced Draught. The air is heated by the otherwise waste gases to about 220° temperature before entering the furnaces. 124 *' Verbal " Notes and Sketches above the bars, and the other two admitting it below. The furnace doors are made double, the outer half being airtight, and the inner half being perforated with small holes for the jets of air to pass through. It should be mentioned that with forced draught the smoke tubes are made smaller than usual, generally from 2^ to 2| inches in diameter outside, and that strips of twisted metal, called " retarders," are often fitted inside of them to increase their heating power by retarding or keeping back the hot gases, so that as much of the heat as possible is given up to the water before the gases leave the tubes. The force or intensity of the draught is measured by a U-shaped glass tube containing water, one end of the tube being connected TO FAN CASING. WATER. No. 66. to the air trunk and the other end left open to the atmosphere. The air pressure in the trunk forces the water higher in the leg of the tube which is open to the atmosphere and lower in the leg open to the air casing, and the difference of the two water levels is called the air pressure, and is expressed in inches of water. In practice from i| to 3 inches of water is the amount carried. If the water gauge shows, say, 3 inches of water, to find the pressure of the draught divide this by 27-66 inches. NOTE.— A column of water 27-66 inches in height weighs 1 lb. per square inch. Thus, — 3^ = .108 lb. per sq. in. 27-66 ^ ^ NOTE.— If the water gauge for the draught indicates about 2 J or 3 inches at the fan, the pressure under the fire-bars will only be equal to about I inch or thereabout. Boilers 125 Gains of Forced Draught. 1. Smaller boilers for the same power, as the consumption is more per square foot of grate. 2. Hot air enters the furnace in place of cold air. 3. Better steaming of power boilers. 4. Better control of fires, as the draught is independent of weather conditions. With forced draught the air is partly heated by the waste gases before entering the furnaces, which means that less heat requires to be taken from the coal to heat it, and, as the consumption per square foot of grate surface is more than with natural draught, more evapora- tion will be the result, and therefore a smaller boiler will supply the same amount of steam : in addition to this the boilers generally steam much easier with forced draught. NOTE. — As part of the heat of the wasLe gases is absorbed by the air in the heating box, the temperature of the funnel gases is less, being somewhat between 450° and 550° in general practice. The safety valves are made larger when forced draught is fitted, to allow for the increased evaporation per square foot of heating surface and resultant increase of steam generation. Notes on Forced Draught. About 20 lbs. of air per pound of coal are required for combustion, instead of 24 lbs. as with natural draught. The air being heated to about 210" by the waste products of combustion, requires less heat from the coal to effect combustion. The consumption of coal may range from 25 to 40 lbs. per square foot of grate per hour according to the force of the draught carried. This results in reduced size of boilers being sufficient for a given power. The air being forced into the furnaces is better distributed and more effective, which results in higher furnace temperatures. With a water pressure of 2h inches at the fan, the pressure under the bars should be equal to about | inch water, and above the bars equal to about ^ inch water. The chief disadvantages of forced draught are : — 1. Greater risk of collapsed furnaces if coated with scale or oil deposit, owing to higher temperature of furnace. 2. Greater tendency to leaky tubes and seams, owing to higher temperature of gases. 3. Trouble with tubes choking up with soot, if not cleaned often and regularly. Heat Saved. The approximate number of heat units saved by forced draught per pound of coal may be calculated as follows : — T26 ♦* Verbal" Notes and Sketches Natural Draught. — Assume 24 lbs. of air per pound coal, cold air temperature 62°, funnel gases temperature 650°, specific heat of gases '23. Then, 650° -62° = 588° rise of air temperature. And, 588 X 25 X •23=3,381 Heat units required per pound of coal. NOTE.— 24 lbs. of air + i lb. of coal = 25 lbs. weight of gases in all. Forced Draught. — Assume 20 lbs, of air per pound coal, heated air temperature 200°, funnel gases temperature 550^ Then, 550° - 200° = 350° rise of air temperature. And, 350x21 X •23 = 1690-5 Heat units required per pound of coal. NOTE. — 20 lbs. of air + i lb. of coal = 21 lbs. of gases in all. So that 3381 - 1690-5- 1690-5 Heat units saved per pound of coal burnt. Howden's Forced Draught. — As a general rule the best results are obtained when the air pressure below the bars is equal to i inch water, and above the bars | inch water, giving a difference of f inch, and to obtain this it may be found necessary to build up the bridge by, say, two brick thickness more than that arranged for originally by the makers. If this alteration is made, the results will, in most cases, be found to be the best possible, both as regards combustion and the life of the boilers. Pitting and Corrosion. — In boilers the general causes of corrosion are : — I. Fatty acids from animal or vegetable oils, which are set free when the oil is decomposed by the heat. 2. Oxygen and CO., from air brought in with the feed water, and set free by the heat. 3. Galvanic action, due to the difference in composition of the metals used in the construction of the boiler, such as iron and steel, and to other similar causes. The best oil for internal lubrication, or for rods, is mineral oil, which is a pure hydrocarbon, and free from acids. Most of the oil used for internal lubrication of the engines finds its way to the boilers, by being brought with the steam into the condenser, and afterwards pumped into the boilers by the feed pumps. Places Pitted. — The parts of a boiler where pitting occurs vary a great deal in different boilers, but the most common places are — (i) About the line of the fire-bars on the water side of the furnaces; (2) at the sides, bottom, and back of the combustion chamber ; (3) at the back ends of the tubes, and at the combustion chamber end of the small stays, which are exposed to the high temperature gases. Boilers 127 Furnace Collapse by Retention of Gases. In some cases the collapse of furnaces may be brought about as follows : — If with forced draught the tubes become badly choked up with soot the outlets for the products of combustion are correspondingly reduced, and the gases being thus retained, may rise in temperature to a serious degree, and overheat the furnace metal; if the tempera- ture of the plates exceeds 600°, collapse of the crown will likel)' take place. Retarders placed in the tubes unfortunately tend to produce the choking up referred to, as also do the " Serve " type of boiler tube. Collapse of Furnaces. — When a furnace crown is brought down by oil deposits, it often happens that after the boiler has been blown down and the furnace examined inside, no trace whatever can be discovered of the cause of collapse. This is accounted for by the fact that when overheating of the plate takes place, and consequent buckling, the intense heat resulting burns completely away the layer of oil, thus leaving no trace. The only clue to the true cause of the collapse lies in the fact that generally the metal is cleaner at the place where the oil had formerly lain than on other parts of the furnace metal. Heating Surface and Grate Surface. In cylindrical marine boilers the ratio of Heating to Grate surface is about 30 or 35 to I, and in water-tube boilers from 40 to i upwards. Boiler Repairs, Parts Corroded, &c. Chain Patch. — Cracks in furnaces and combustion chambers are often repaired by means of a chain patch, consisting of a series of pins tapped into the crack and into each other, the ends being riveted over as shown in the sketch, this method of repair being handy and suitable for small cracks. Patches. — For a badly corroded section of a furnace or combustion chamber a riveted patch may be found necessary and should be arranged as follows : — 1. First cut out the defective piece of plate. 2. Shape the patch to template, and of a thickness about jV i"ch less than the furnace or combustion chamber it is to be fitted on to. 3. Emplc*y rivets of a diameter determined as follows : — Rule— 1-2 X ^'plate Thickness = rivet diameter. 128 *' Verbal " Notes and Sketches 8 RIVETS (countersunk) No. 67. — Method of Repair for a Crack. The repair consists of a series of rivets countersunk on one side, and just touching each other as shown. This method of repair for a longitudinal crack in a furnace or combustion chamber will be found, in most cases, to stand better than the chain patch obtained by screwed pins tapped half into each other and riveted over. And of a pitch found as follows : — Rule — 100 X rivet diameter ^p-t^t^ ^^ ^.j^^ts 100 - joint It must be remembered that the joint strength referred to is equal to about 52 per cent, if single riveting is employed, and 68 to 70 per cent, if double riveting. 4. Rivet the patch on to the fire side of plate so that the effect of the heat will take place on the edges of the patch in place of the Boilers 129 edges of the furnace or combustion chamber metal. This will also be found more convenient for caulking. 5. The patch should form a metal to metal joint without any- other jointing material. 6. The distance from edge of rivet hole to edge of plate must be equal to one rivet diameter, and the width of lap for single riveting will therefore be equal to three rivet diameters. General Repairs. If a combustion chamber shows a buckle between some of the stays, it is probably due to defective circulation, oil or scale deposits adhering to the plate and causing overheating. If the buckle is bad, tap a stay through it and the boiler plate between the other stays. If a furnace or combustion chamber plate develops a blister, it is usually caused by the plate being laminated, which means that some dirt or sand has been rolled up with the metal during manufacture ; the plate, not being solid throughout, blisters when heated. If a piece of a furnace requires to be patched, first cut out the defective piece of the plate and then rivet on the patch (metal to metal) on the fire side of the plate. The thickness of patch should be from f inch to h inch, and the diameter of rivets about | inch. If a combustion chamber stay leaks badly, and cannot be kept tight, take out the stay and tap the holes to a larger diameter, then screw in a new stay. NOTE. — If the plates cannot be tapped, a distance piece or thimble is neces- sary to form a joint, when a bolt is used instead of a screwed stay. Stay Repair. — The following method of repair for a leaky com- bustion chamber riveted stay may be applied when a new stay of a slightly larger size cannot be obtained. Chip off the riveted head flush with the plate, bore a hole in the stay, say f inch diameter, then drift out the hole to tighten up the threads in the plate, next tap the hole f inch diameter and screw in a pin of that size, fitting a f-inch thick washer, with a joint of asbestos and red lead. NOTE.— As the s-inch pin now takes the place of the stay, theoretically, the pressure should be reduced by rule to this size. In the proportion of the respec- tive stay areas assume original stay to be i^ inches diameter and boiler pressure 180 lbs., then, As, 1-25" X 7854 : -875- X .7854 : : 180 lbs. Or, as, 1-25'- : -875- : : 180 lbs. Therefore, ' '5_±^L_?-88 lbs. Safe pressure. 125- This of course neglects the holding power of the stay obtained by the expanding out of the metal, which may more or less make up for the loss of area, and permit of the original pressure being carried. 10 I30 "Verbal" Notes and Sketches O SL'Of^T OlTTlH^ INSlOC o o/o o o to o o o o Pi.AN Showing the Defect _J No. 68.— Pitting of Boiler Shell Plate. The above sketch shcjws the effects produced by pitting on a boiler shell plate i^^ inch thick, and which resulted in an explosion. The pitting appears to have originated in local galvanic action on a small area of the plate, due to impurity in manufacture, and this afterwards extended as shown above and blew out. BACK TUBE PLATE No. 69.— Tube Plate Corrosion. If a boiler tube leaks and the leakage is not checked at once by re-expanding, the tube plate is in danger of corroding as shown in the sketch. This corrosion is caused by small quantities of water leaking through, which, becoming decomposed by the heat, sets free oxygen gas : the oxygen gas combines chemically with the tube metal to form iron oxide, which results in wasting of the metal. I V 2RA8 i^ MIJ riS ,233£muH no noiaonoQ cii&'jqtb laaic basi. .saBsig o: 3tii> uoiSonoO p///////W////^^^^^^^^^^ 1 No. 72— Corrosion on Furnaces, &c- X, Corrosion above line of bars due to high temperature and liberation of free oxygen gas. 2, Corrosion due to moisture, such as from wet ashes. 3, Corrosion due to expansion and leakage, also repeated caulking of the plate edges. 4, Corrosion due to unequal expansion, straining, and leakage. to straining of plates and faulty o straining of plates, intense heat. 5, Corrosion due circulation. 6, Corrosion due and leakage. 7, Corrosion due to grease, and other deposits. " Verlial ' Noics and Sketches. 'To fat* fagt 131. ^j^V B oilers i;;i CO^yiBUSTION CHAMBER BACK No. 70.— Combustion Chamber Plate Corrosion If a stay leaks at the back end, corrosion may follow by the oxygen gas set free by the heat. This is shown at 2 in the sketch, and the repair would be to take out the stay and re-tap the holes to a larger size, screwing in a heavier stay. No. 71.— Furnace Corrosion. 1, Corrosion due to heat setting free oxygen gas. 2, Corrosion due to moisture such as from wet ashes, &c. The heat sets free oxygen and CO as, which in combination are highly corrosive. c ■<-» 4-> C^ a a, 13 .22 ^ *-■ o CO fl I? 2^ S o H d c ^2- r- " •5 -Q L^^^^^^^^^.^.mv<^^^v^.^^^.^^^■.w.^^^^^^ -----^^^^^^^^^^^^^^^^^^^^^----^^--^^^^^^^^^^ No. 74.— The Bagguley Patent "All-Metal" Tube Stopper, When the nut is tightened up the cones press out the ends of the sleeves, thus forming four metal-to-metal joints. The patent stopper shown above makes four metal-to-metal joints in the faulty tube, two at each end, and the whole operation is performed by means of screwing up a single nut at the front end of the tube, the stopper being placed in position from the front end. The patent stopper consists of a long bolt wh.ich passes right through the boiler tube to be stopped ; this bolt has a tapered head on the back end which exactly fits the tube. Three conical sleeves slip on to this bolt, making a tight fit externally on the bolt, and internally on the boiler tube. The front end of the bolt is screwed and fitted with a feather-way, and on this end a hexagon washer or nut is fitted witii a feather to fit the above-mentioned feather-way. A screwed nut is then fitt^ to the bolt, and a raalleable-iron tube is passed over the bolt, which keeps the cone pieces in position, and enables them to be tightened up simultaneously. Two soft metal sleeves, i, i, complete the arrangement. In stopping a faulty tube the whole apparatus is passed through from the smoke-box end as one piece, and by holding the hexagon washer by means of a spanner and screwing up the nut the four taper pieces are screwed up simultaneously, expanding the soft metal sleeves and thus elTeciively stopping up the faulty tube, and cutting it out of action for any length of time. ITo /cue pant \ZI. "Verb.ll" NolcM and Skclchi-' Boilers 133 Iron Tubes and Stays. In steel boilers the tubes and small stays are often made of iron, for the reason that iron corrodes less than steel under corrosive influences. Leaky Tubes. Owing to the tubes and tube plate expanding at different rates, the back ends of the tubes often leak. This is remedied by re- expanding, or by fitting into the tube at the back end a capped ferrule as used in the Navy, to keep the heat off the tube end and the plate (Sketch No. 75). Scale and soot on the tubes and plates tend to increase the leakage, and with forced draught, as the heat is more intense, the leakage is still further increased. No. 75. — Capped Ferrule for Leaky Back Ends. Collapsed Tubes. For a collapsed tube the best repair is a permanent stopper (Sketch No. 73), formed of a long rod screwed at the ends, and cap washers fitting over the ends of the tube and screwed up tight with a joint between the tube and the washers. Patent stoppers are also employed to close up a cracked tube, the " Bagguley " type being shown in Sketch No. 74. Safety Valves. To find the Load on any valve, multipl}^ the valve Area by the Pressure per square inch. To find the Pressure per square inch, divide the Load on the valve by the valve Area. Example. — The Pressure is to be 40 lbs. per square inch and the valve is 5 inches diameter, find the Load. 5' ^ 7854 X 40-785-4 lbs. load. Example. — The Load on a dead-weight valve is 1000 lbs., and the valve is 3 inches diameter ; find the blowing-off Pressure per square inch. 1000 I, ~ — =1414 lbs. pressure per sq. in. 3- X -7854 134 "Verbal" Notes and Sketches Lever Safety Valve. ^ L . ^ PT: ^^t> No. 76. NOTE.— A=valve Area, load - A x boiler pressure. Then, LxW = /xload. Therefore, L X W 1 J J load = load, and, ^-^ = pressure per sq. in. / Again, I X load TTT / X load , 16 >;•-. >^ Example i.- RULE — Then, No. 77. 16 in. X 100 lbs 16 in. X 100 lbs. 4 in. 4 in. X Load. = 400 lbs. Load, and Pressure per sq. in =^ Load -: Valve Area - 400 -MO = 40 lbs. per sq. in. NOTE. — Valve area = 10 square inches. In the foregoing case, the weight of the lever, and of the valve and spindle, are neglected, data must be eiven : — If they are to be allowed for, the following 1. Centre of gravity of the lever. 2. Weight of the lever. 3. Weight of the valve and spindle. Example 2. — In the previous case the lever weighs 7 lbs., its centre of gravity is 12 inches from the fulcrum, and the valve and spindle weigh 5 lbs. ; find the load on the valve, and the pressure per square inch, allowing for the lever and the valve and spindle. 12 in. X 7 lbs. 1. J i. 1 ^' = 21 lbs. more due to lever. 4 in. Then, 400 + 21 + 5 = 426 lbs. load, 426 and 42-6 lbs. pressure per sq. in. NOTE.— The centre of gravity is the point at which the lever balances if placed on a knife edge. As the weight of the valve and spindle is direct weight, it is simply added to the other two loads. Boilers 135 Example 3. — Fulcrum to Weight 30 inches, fulcrum to Valve 5 inches, Load on valve 300 lbs. ; find Weight. Then, Lx W = /xload = 30x W = s x 300. Therefore, W = 1^300 ^ -^ n^g ^ ^ 30 Example 4. — Fulcrum to valve 6 inches, Weight 20 lbs., boiler pressure 30 lbs. per square inch, valve area 4 square inches ; find the Length from fulcrum to W^eight. Then, L x W = /x load- Lx 20 = 6 x 120. NOTE. — 4x30 = 120 lbs. load on valve. Therefore, L = ^i^i??=36 in. 20 Example 5. — Fulcrum to valve 6 inches, fulcrum to Weight 32 inches, Weight 25 lbs. ; find the boiler pressure per square inch if the valve is 3 inches diameter. Then, L x W = /x load = 32x 25 = 6 x load. Therefore, load = 3^^ -133-3 Jhs. Then, Pressure = load -=- valve area = 133-34-3- x ■7854=18-8 lbs. per sq. in. Spring Safety Valves. At 60 lbs. gauge pressure, the Board of Trade allowance of safet}' valve area is h square inch per square foot of fire-grate surface. At higher pressures the valve area required is less, because high- pressure steam has less volume than low-pressure steam, and at lower pressures the valve area required is more. To find the valve area per square foot of grate for, say, 160 lbs. gauge pressure, 60+ 15 =75 lbs. gross, and 160-I- 15 = 175 lbs. gross. Then, as 175 lbs. : 75 lbs. : : -5 in. = -214 of a square inch. NOTE. — In working out valve areas, the gross pressure must be taken. The lip cast round the safety valve face is to give an increase of valve surface when the valve lifts, so that the extra compression of the spring, due to the lift, may be neutrali.sed. Without this fitting, the boiler pressure would increase with the valve lift. To find the Compression. Rule — Load on val ve x Spring mean diameter" x Number of coils _ r-omoression 2000000 < steel 136 "Verbal" Notes and Sketches Example. — Find the compression required for a 4-inch safety valve, pressure 160 lbs., and mean diameter of spring 3I inches : there are thirteen coils of square steel of f inch side. 4l^^54>^ 160x3.5x3.5x3.5x13^^^^ .^ compression. 2000000 X .75 X -75 X .75 X -75 The pressure per square inch varies as the compression of the spring. Example. — The pressure is 160 lbs. per square inch, and the compression is 2 inches ; find the compression and thickness of the washer required to be put in to have the valve blowing off at 150 lbs. per square inch. As 160 : 2 in. : : 150 = 1-875 in. compression. Then, 2 in. -1-875 in. = -125 of an inch thickness of washer to go in under the compression nut. NOTE. — The compression varies directly as the pressure. To find the Diameter of Safety Valve. y Square feet of grate ^375 = diameter of valve, gross pressure x -7854 NOTE. — If for forced draught allow about 25 per cent, more area of valve. The Constant 37-5 is obtained b}' multiplying the valve area allowed at 60 lbs. gauge pressure by the gross pressure corresponding to it. Thus, 60 + 15 = -75, and 75 X .5 := 37.5. Superheated Steam. Of late years a decided reaction has set in among marine engineers in favour of superheated steam, which, as proved conclusively by recent exhaustive experiments, possesses undoubted advantages, and the use of which results in considerable economy. It has been found that w ith superheating to the extent of 50" the gain is about 8 per cent., and if the superheat is increased to 200° above the natural pressure temperature of the steam, then the resulting economy is about 30 per cent. It should be noted that if saturated steam — that is, steam drawn from a boiler — is raised in temperature and Xh^ pressjire kept constant, the volume increases ; this means a larger volume of steam produced for the same amount of water evaporated, and therefore less boiler space required. Again, by superheating steam which originall)' contains water, the water is evaporated, thus giving drier steam, which results in less c\'linder condensation losses, and less transfer of heat Boilers 137 to the cylinder walls. It will thus be seen that the advantages of superheated steam are undoubted. NOTE. — The volume varies with the absolute temperature if the pressure is kept constant. Example. — Boiler steam (saturated) at a pressure of 180 lbs. gauge pressure, temperature of 380, and specific volume 2-31 cubic feet ; find the volume if the steam is superheated 100° Fahr. Then, 380° + 100 = 480" steam temperature when superheated. And, 461= absolute temperature constant. Therefore, as, (380° + 461°) : (480° + 461) : : 2-31 -^2-58 cubic feet volume. So that the volume of the steam per pound is nowr increased by 258 -2-31 = •27 of a cubic foot. In addition to this it must be remembered that the temperature is higher, and the steam of a drier condition. Advantages of Superheated Steam. (i.) Increase of steam volume. (2.) Dry steam enters the cj'linders, and less condensation losses result. (3.) Less leakage of steam past valves and pistons. (4.) Less danger from water hammer in main steam pipes or chests. Against these gains there are, however, certain disadvantages, which also require to be taken into account. Disadvantages of Superheated Steam. (i.) Difficulty of lubrication, (2.) Piston rmgs more easily broken. (3.) Trouble experienced in keeping superheater coils or tubes tisfht and in eood workine order. Methods of Superheating. — In marine practice the ordinary method has been to utilise the funnel gases in superheating the steam, although the independently fired type as devised by Professor Watkinson has also been fitted in some steamers. The Watkinson superheater (Sketch No. 78) consists of a series of U-shaped mild steel tubes, expanded into large headers similar to those employed in water-tube boilers. This nest of tubes is fitted in the uptake, and the steam from the boiler enters one of the headers, and passing through the U-shaped tubes becomes superheated by the furnace gases which are flowing over tiie tubes. The steam then enters the other header and flows along the steam pipe to the engine. I^.cS *' Verbal " Notes and Sketches Suitable drainage arrangements are fitted to keep the drums and tubes clear of water, and by suitable bye-pass valves and pipes the steam may, if required, pass direct from the boilers to the engine, without entering the superheater coils. When it is stated that the average loss due to initial cylinder con- densation is about 15 per cent, with saturated steam, the advantage of superheated or dry steam will be apparent, as less water being present No. 78.— "Watkinson" Type Marine Superheater. m the steam the condensation losses are greatly reduced, and may be practically eliminated. To overcome the lubrication difficult)-, special high temperature mineral oils are now manufactured by the various oil companies, which are said to resist the disintegrating effects of the superheated steam, and allow of suitable lubrication of rods, pistons, and valves. Regarding the resulting increase of volume due to superheating Professor Watkinson says : " During superheating, although the Boilers 139 pressure of the steam remains constant, its volume is j^reatly in- creased. The amount of heat required to superlieat I lb. of steam by 1 50° Fahr. is 72 British heat units, which is only about 6 per cent, of the heat required to generate i lb. of dry saturated steam. The increase in volume due to this additional 6 per cent, of heat averages about 30 per cent." Steam Pipes. Steam pi{)es are made of the following materials : — 1. Copper, seamless or brazed. 2. Wrought iron, generally lap welded. 3. Steel, also lap welded. Sometimes in steel pipes a riveted butt strap is fitted covering the weld, and copper pipes are further strengthened by being covered with wrappings of wire rope, or by iron bands secured at short distances along the pipe. Cast iron also, in a few cases, has been used for steam pipes. The three principal causes of recent accidents to steam pipes were — (i) Insufficient allowance for expansion ; (2) defective drainage arrangements ; and (3) vibration. Before opening the main stop-valves the drains on the pipes or chests should be opened to clear away all water which may have collected in them. When steam pressure strikes a body of water it imparts to the water a velocity nearly equal to its own, and the resulting force acquired is so great that the chest or pipe may be burst : this is known as " water hammer," and accounts for many of the accidents to steam pipes and stop-valve chests ; hence the necessity for drain cocks being fitted and used. Water Hammer in Steam Pipes. — Whenever possible water lodging in steam pipes should be drained out when the steam pressure is off, otherwise the draining out of the water may result in the setting up of water hammer action with danger of bursting the pipe or v^alve chest. According to Mr C. E. Stromeyer of the Manchester Steam Users Association, the conditions favourable to water hammer are as follows : — 1. Water in contact with steam. 2. Rapid condensation in pipes or chests. 3. Agitated water surfaces. 4. Steam pressure at one part of a pipe and vacuum at another part. Under ordinary practical conditions the pressure per square inch on a pipe ])roduced b)' water hammer may range from 250 lbs. to 300 lbs., or e\en more. 140 "Verbal' Notes and Sketches VALVE (?HEST No. 79. — Steam Pipe Expansion Joint NOTE. — When no expansion joints are fitted on steam pipes, bends are formed on the pipes to allow for expansion. Circulation and Priming. Circulation in a boiler is the rising of the heated and expanded water, and tlie sinking of the colder and heavier water to take its place, resulting in a continuous current passing from the bottom upwards, and from the top downwards. When water is heated it becomes lighter, and expanding, rises to the top in the form of small steam bubbles, which, on reaching the surface, burst and give off a small amount of steam, and, if the boiler is properly designed, the colder water being heavy falls, and in its turn becomes heated. Should insufficient allowance be made for the circulation, or anything occur to check it, priming will most likely begin, as priming is caused by bad circulation. Defective circulation may be caused by : — 1. Close arrangement of tube nests. 2. Small steam space. 3. Dirty water. 4. Bad firing. Observe that any of the foregoing causes bring about bad circula- tion, and consequently priming. The bottom seams of the boiler sometimes leak owing to the difference of temperature existing between the top and bottom caused by defective circulation. The top plates being hotter, and expanding more in proportion, tend to drag open tlie bottom seams, and leakage is the result. ( # ./t' ooo ooo ooo ooo ooo ooo ooo oo ooo ooo ooo ooo ooo oool ooo ooo ooo ooo ooo No. 8i. — " Doubling Plate. "VetU.l ■ N.ili-samlSkclclic. No. 82. — End View of Boiler (Half in Section). in/firrfaKr 141. Boilers 141 No. 80. — Weir's Patent Hydrokineter. In getting up steam, circulation is assisted by means of a hydrokineter (Sketch No. 80), or by the donkey connection for pumping the water from one part of the boiler to another (see page 151). Doubling Plates. Doubling plates, as shown in Sketch No. 81, are sometimes fitted to boilers to increase the strength of flat surfaces in places where ordinary stays or stay tubes cannot be fitted. The plate shown is about "^ inch thick, and is riveted to the boiler end plates in the spaces between the tubes. Stays are not admissible at this part of the boiler owing to the necessity for keeping clear the spaces between the tubes to allow of the furnaces being examined, cleaned, or repaired, so that the only alternative method of support is by means of doubling plates. End View (Sketch No. 82). The sketch shows the general construction of a modern high- pressure boiler, as seen half in section from the end. Observe how the combustion chamber tops are supported by the "dogs," or girders, and stays passing through which are tapped into the top plates. 142 " Verbal " Notes and Sketches The following are the principal dimensions to be carefully noted : — Pitch of girders, about 8 inches. Depth „ ,, 9 inches. Distance between combustion chamber plates, about 7 inches. „ „ combustion chamber and boiler shell, about 7 inches. „ „ furnace and bottom of boiler, about 7 inches. „ „ bottom row of tubes and furnace top, about loh inches. „ ,, each nest of tubes, about 1 1 inches. Observe how the plate at the sludge hole openings is strengthened by means of the sta)'s shown, which pass from end to end of the boiler, the top one being heavier than the lower two. These stays are usually about if inches or 2 inches diameter Also note the arrangement of the stay tubes, which are indicated by dark circles. NOTE. — The manhole opening- in the shell (about 16 inches 12 inches) is strengthened by means of a doubling or "compensating" ring riveted to the plate round the hole. The effective surface area of this ring should not be less than the area of the metal cut away to form the opening. Scarfed Joints. — This type of joint is used in boilers where three plates overlap each other, as for example when two end plates and the shell overlap. Two of the plates are scarfed or thinned down, as shown in the sketch, and the third plate covers both ; this reduces the thickness to that of only two plates. Extra heavy caulking is required to keep the joint tight. CAULKED SHELL PLATE END PLATE SCARFED END PLATE No. 83.— Scarfed Joint. SINGLE _ CAULKING SINGLE^ CAULKING No. 84. — Flanged-out Plates. Boilers H3 Flanged-out Plates. — Sometimes one end of the boiler is flanged outwards, as shown, to allow of the convenience of the hydraulic riveting machine. The disadvantage of this arrangement lies in the fact that only single caulking is possible, whereas with the plates flanged inwards double caulking can be employed. Zinc Plates. The sketches show the usual methods of connecting the zinc slabs to the boiler metal, and it is important that the following points be attended to : — (i) Proper metallic contact between the zinc and the boiler, and to ensure this the surfaces in contact should be filed up bright. No. 85. 144 " Verbal " Notes and Sketches HfM _y: — No. 86.- Zinc Block and Stud. The zinc plates fitted into boilers to set up galvanic action and reduce corrosion are usually fixed to the furnaces, com- bustion chambers, and end plates as shown, the stud being screwed in to form effective metallic contact. ZINC 9>rT r77rr77r77ryt No. 87.— Zinc Plate in Box, In water tube boilers the zinc plates are often carried in perforated boxes, the idea being to prevent the oxide of zinc (produced by the galvanic action) from being distributed over the boiler. The oxide drops to the bottom of the box, and is thus kept by itself. Boilers H5 (2) When convenient the removal of scale or oily deposits from the zinc plate connections, as these substances insulate the parts and interrupt the flow of the current. (3) The renewal of the zinc slabs whenever they are found to have become spongy, as the galvanic action is then practically exhausted. When the zinc is suitably connected as above described, the chemical action which occurs results in the formation of Oxide of Zinc and the liberation of bubbles of Hydrogen Gas. At the zinc plate Oxygen is set free and combines with the zinc, and at the boiler metal Hydrogen Gas is set free. NOTE. — As the proportion of zinc used is very small compared with the amount of boiler metal to be protected, the corrosion is merely reduced in extent. and is not prevented altogether. The usual allowance of zinc is about one square foot, inch thick per each 80 I.H.P. Water Gauge. In Fig. I the column shown is hollow cast, so that the water or the steam could pass through it : the test cocks show this. NOTE.— Open the drain and blow through, then close the drain and see if the water rises to the working level ; if so, the connections are all clear ; if, however, no water shows, then either C or D is choked or the water is too low ; if, on the other hand, the glass shows full, then either A or B is choked or the water is too high. To test if the steam connections are clear, shut cocks C and D, and have open cocks A, B, and the drain cock E. If steam blows through the cocks are clear. To test if the water connections are clear, shut cocks A and B, and have open cocks D, C, and the drain cock E. If water blows through, the cocks are clear. If cock A or cock B is choked, the glass will show full up. It will show the same if the pipe between A and B is choked. If cock C or cock D is choked, the glass will continue to show what the water level was at the time the cocks stuck, as the water will be shut off from the boiler altogether. If the drain is opened and shut, the glass will show empty as long as the cocks remain choked. The same thing will happen if the pipe between C and D is choked. If the glass is showing full water, due to the cock A, or the cock B, having got choked, to test if it is A, shut D and B and blow through A, C, and E ; if steam blows out A is clear, if not, A is stuck. To test B, shut A and C and blow through D, B, and E ; if water blows out, B is clear, if not, B is choked. If one of the two cocks C and D is choked, to find which it is, shut A and C and blow through D B and the drain E ; if water blows out, II 146 "Verbal" Notes and Sketches Fig. I. Fig. 2. No. 88. D is clear, if not, D is choked. To test C, shut D and B and blow through A, C, and E ; if steam blows out, C is clear, if not, C is choked. NOTE. — In testing, before closing any of the cocks A, B, C, or D, it is advisable to first open the drain cock E, so that shocks on the pipes and glass may be avoided. If cocks A and B are closed and the others left open and the glass blown through, if water comes, the water connections are clear : if, next, cocks C and D are closed and the glass blown through with cocks A and B open so that steam comes, the steam connections are clear ; but if, on shutting the drain cock, no water shows in the glass, this proves that the water level in the boiler is too low, as it must be lower than the bottom nut of the gauge glass, otherwise the glass would show water. If the gauge column is cast solid as shown in Fig. 2, then the water or steam could not pass through it, and to test the water and the steam, single shutting off on the column is sufficient. To test the steam side, shut cock C, and leave cocks A, B, and the drain cock E open ; if steam blows out, the connection is clear. To test the water side, shut cock B and blow through cocks D, C, and the drain cock E ; if water blows out, the connection is clear. The glass usually shows from ih inches to 2 inches less than the boiler level, the reason for this being that the water in the glass is colder than the water in the boiler, and, as water contracts in cooling, the level is lower in proportion, Boilers 147 60 lbs. gauge 80 100 150 160 180 200 250 Boiling Points and Steam Temperatures. Fresh water boils at a temperature of 212" under the atmospheric pressure. In a good vacuum water will boil at a temperature of 90'', while under a pressure of 160 lbs. gross, the boiling point of fresh water would be 370°. Therefore the boiling point depends on the pressure on the surface of the water and varies accordingly, being high for high pressures, and low for low pressures. At 15 lbs. atmospheric pressure the temperature is 212° Fahr. 307° ,, >» » 5) 324 )) " >' >> 33° >) » » „ 366° „ ') ). ). 370° )> ». >» » 380° M ') >> )) 3^^ » >i >> )) 405 »> NOTE.— The temperature of the water is the same as that of the steam. Salinometer, Density, &c. The salinometer measures the density of the boiler water. The salinometer does not in all cases measure the amount of salt in the water. If we take 32 lbs. of sea water and boil off all the water, about I lb. of solid matter will be left behind, hence the figure .jV. A gallon of water weighs about 10 lbs., and 10 lbs. x 16 oz.= 160 oz., therefore 160^32=5 oz. of solid matter per gallon. Of the 5 oz. of solid matter in i gal. of sea water, fully 4 oz. are salt and the rest lime, &c. The temperature marked on the salinometer is 200° Fahr., and if the water cools down below this, the salinometer will show more density in proportion to the drop of temperature, because water contracts in volume when cooling down to 39" Fahr. For every 10" less temperature, allow the salinometer to be showing f oz. more than the actual density. Thus, suppose the water cools to 160', that is 40° lower than it should be, then the salinometer would indicate about 3 oz. in excess of the real density, which amount would require to be subtracted from that shown by the salinometer to obtain the correct density. Water is at its least volume at 39, and expands if heated above this temperature, or if cooled below it. Ordinary sea water at a temperature of 50 will show on the salinometer as fully 13 oz. density. NOTE.— Salt and sugar will show on the salinometer as density, as these substances enter into solution. To make a rough salinometer, take a long, narrow bottle, weight it and cork it ; take a gallon of fresh water and heat it to 200 ; put in the bottle and mark where it floats O, or fresh water : next take 148 " Verbal " Notes and Sketches a gallon of sea water, heat it to 200^, and mark where the bottle floats aV. boil down the water to half a gallon, and when it cools down to 200° put in the bottle a third time, and mark where it floats /g. or 10 oz. ; other densities may be set off by evaporating the water away to one-third and one-fourth the original quantity. To test the density without a salinometer, draw off some of the boiler water and boil it over a fire ; when boiling, put in the thermo- meter and observe the temperature ; the density may then be roughly found by means of the following table : — Fresh water boils at 5 oz. density 10 „ 15 20 212 213.2° 214-4° 215-6° 217-8° Allow 216° as the limit temperature, corresponding to about 15 oz. density : should the boiling point exceed this, surface the boiler to keep down the density. * NOTE. — The above boiling points correspond to a barometer height of 30 inches. The boiling point varies with the barometer, up and down ; for every inch difference in the barometer, the boiling point varies 1-5' in temperature. If the boiler retains a density of 35 oz. (saturation point) and more feed water containing salt is supplied, then] when the water fed in is evaporated, the salt contained in it deposits. MAIN STAY IRON CLIPS 9" 3" BOLTS jnternal feed pipe (iron) No. 89.— Method of Supporting" Internal Feed Pipes. See's Ash Ejector. See's ash ejector consists of a cast-iron hopper with a grating for limiting the size of the ash or clinker put in, a water nozzle and pipe led up to the shii)'s side abo\e the water le\el, and a cock to regulate the flow. A high-pressure donkey pump connection is also required * NOTE.— For accuracy, it is advisable to first boil fresh water and note the boiling point, then allow i-2 degrees per 5 oz. for the boiler water boiling point excess. Boilers 149 No. 90.— See's Ash Ejector. W, Hopper. P, Combined ejector cock, nozzle, and escape valve. M, Pressure gauge. T, Air inlet valve. S, Removable cover. V, Discharge pipe. Z, Ship's side valve. to obtain the necessary force of water pressure. Before opening the ejection cock it is necessary that the water pressure of the pump be not less than 200 lbs. per .square inch, as shown by the gauge, also that the valve on the ship's side is full open. When the cock is opened the rush of water at high pressure past the grating carries with it the ashes shovelled through, and discharges them overboard. A small air valve is fitted on the pipe, and this must be kept open when working the ejector. Tube Expander (Sketch No. 91). The expander consists of a built-up case containing three rollers which project through corresponding openings cut in the shell of the u a Ui H 6 Boilers 151 case. A taper mandril fits into the centre space of the rollers, and, on being knocked in with a hammer and revolved by a bar at the end, forces out the rollers a^^ainst the tube and tube plate, thus forming a steam and water tight joint. In adjusting the position of the expander care should be taken that the rollers are in line with the tube plate, as otherwise the tube may leak, and, in addition, fracture may result owing to the tube being unduly stressed by the rollers acting at the wrong position. All boiler tubes are expanded as described, with the exception of the heaviest pattern of stay tubes, which are caulked in, the expander beins in this case too licrht for the work. No. 92. — Blow-off and Circulating Connections. 1, Bottom blow-off valve. 3, Bottom blow-off pipe. 2, Ships side blow-off cock (two-way). 4, Surface blow^-off pipe. 5, Donkey suction pipe for circulating. The above is a common arrangement of surface and bottom blow-off combined with the donkey circulating connection. Pipe 5 leads to the donkey pump suction valve, and the colder water lying at the bottom of the boiler can thus be pumped out, and discharged back into the boiler through the check valve. 152 Verbal " Notes and Sketches To Cut out a Boiler Tube. The usual method of removing a defective tube is illustrated in the sketch, and may be described as follows : — The beading at the Boilers 153 back end of the tube is first cut off Hush with the plate, and the tube end cut or ripped in three or four places. The end thus cut up is then hammered inwards, and the bar or rod passed through the tube, with a strong washer fitted in position over the tube end, the washer diameter being of course less than the diameter of the hole. At the front end a dog is fitted as shown and a screwing-up nut ; if the bar is then held by the square on the end, and the nut tightened up, the tube will, in most cases, be started and finally drawn out. No. 94.— Klinger " Reflex " Water Gauge Klinger Patent Water Gauge. In this admirable form of water gauge the chief improvement consists in the water and steam being shown in striking contrast to 154 "Verbal" Notes and Sketches each, the water in the glass appearing dark and the steam Hght ; the water level can thus be read at some distance away from the gauge. In the " Klinger " water gauge a metal casing connects the top and bottom cocks, and a window of thick and strong glass inserted in the casing allows of the reading of the water level. This window takes the place of the fragile glass tube commonly fitted. The observation glass or window being corrugated vertically at the back, reflects the light in that part of the gauge which contains the steam, whereby this part of the glass becomes opaque and of a bright lustre. In that part of the gauge containing the water the light is not reflected, but passes in a slight deflection to the rear of the gauge. The glass being thus transparent in this part of the gauge, the water will appear of the dark colour of the background of the casing, in other words the water appears black, while the steam shines with a silvery lustre. This, it must be admitted, is a vast improvement over the ordinary glass, in which if any distance away it is often very difficult to determine whether full of water or empty altogether. A further advantage of the " Klinger " type of water gauge is the elimination of stuffing boxes at the top and bottom of the glass, which is in itself a consideration of some importance to practical men. Auld's Patent Steam Reducing Valve. The inflowing steam is admitted between the valve and a piston, covered by an elastic disc. The piston and the valve are in equilibrium on the high-pressure side. The reduced pressure on the outlet side is obtained by compressing or relaxing the spring by the adjusting screw until the pointer or spring cap is opposite the figure on index plate representing pressure wanted. The valve being thus opened, the steam flows through valve to low-pressure side of same, until the pressure on reduced side balances the load on the spring by pressing on top side of valve, and so regulating the reduced pressure to the point desired. A column of water of condensation, shown by dotted lines, is interposed between the steam and the elastic disc. Should it be desired to obtain steam (the reverse way through reducing valve) from donkey boiler for deck or engine-room Boil ers 155 machinery, when there is no steam in main boilers, open up the reducing valve by compressing the spring by means of the adjusting JAM NUT- WASHER . INDIA RUB6ER DISC PISTON SEAT- BOSS NUT I -I— j- ADJUSTING SCREW No. 95.— Auld's Patent Steam Reducing Valve. screw till the reducing valve opens ; of course, reset the reducing valve to its usual working pressure on reduced side before getting up steam in the main boilers. NOTE.— A reducing valve will pass steam of lower pressure than it is set for, but will not pass steam of higher pressure. "Verbal" Notes and Sketches o u 'o ho c '>. o 6 2: Boilers 157 Boilers Secured in Position (Sketch No. 96). The boilers rest on stools (which, if required, are wedged as shown at C, C), and are prevented from moving longitudinally by knees K, which are riveted or bolted to the ship's frames, clearance being left (about | inch) between the boiler ends and the knees for fore and aft expansion. Side stays B are fixed by eyes and pins to brackets riveted to the boiler shell, and block stays S are often fitted in between the boilers at the centre. The pins and eyes of the side stays B allow for expansion under heat. Table giving Results of a few Experiments with Auld's Patent Steam Reducing Valve, showing how much the Reduced Pressure Steam is Superheated in passing through the Valve. Gauge Pressure. Temperature. Reduced Pressure. Temperature. Superheat. 160 lbs. 160 „ 200 ,, 200 ,, 200 „ 370° 370° 384° 384° 384° 100 lbs. 40 » 120 ,, 40 „ 10 „ 349° 338° 369° 354° 341° 12° 52° 20° 68° 128° Autogenous Welding. The writer is indebted to the British Autogenous Welding Com- pan)', Ltd., for the following description of their system of welding : — The main application of this new method of repair, known under the name of Autogenous Welding, by means of the oxy-acetylene blowpipe, is in repairing cracks and corrosions in marine boilers, doing away with the old and unsatisfactory patching, and, in a great many cases, saving the whole boiler from being scrapped ; as, if the boilers are systematically kept in repair by this process, they will remain in good condition for a number of years longer than would be the case otherwise : stems, stern posts, rudder posts, and rudders can be repaired by the same method. The plant employed to carry out these repairs, known as a high pressure plant, consists of a cylinder of acetylene and one of oxygen, a regulator and length of tubing for each of the gases, and an oxy- acetylene blowpipe as shown in Sketch No. 97. 158 "Verbal" Notes and Sketches No. 97.— Autog-enous Welding Apparatus. For this class of work this plant has great advantages over any- other plant, which would, of necessity, have to be of the low pressure type in which an acetylene generator is used, when there would be risk of leakage caused through too fast generation or upsetting. The high pressure plant, when work is being done inside a furnace, is taken into that furnace, thus, being out of the way of any one working in the stokehold, this is a decided advantage when a ship is in port for a short time only and a lot of work has to be got through. Besides the above-mentioned advantage over the low pressure system there are several others, such as safet)% high efficiency caused through having both gases under about the same pressure, thus getting Boilers 159 a very intimate mixture and the gas being better purified, easy adjust- ment of the flame, and the simple construction of the blowpipe, there being nothing to go wrong inside it, and the lightness and balance of the same, which is very important when it is considered that a man has frequently to work in a very strained position, the work being done on the horizontal, vertical, or overhead, it being immaterial, provided he can get his blowpipe flame to play on the correct place ; in some cases, in fact, a man cannot see directly what he is doing but has to work more or less by feel, and makes as good a job as if it was perfectly easy to get at. For this process of repair the men employed must, when not actually at work on board ship, be kept practising in the shops on an old boiler, and no new man should be put to work on a ship before he has had some months' tuition and practice in the shops ; practice on lighter work is of no use whatever, in fact, if anything, it is detri- mental to good work on heavy work, and all ship work comes under this class. As mentioned earlier, the main faults in boilers are found in cracks and corrosions : we will discuss the former first, giving a few sketches and showing the method of repair. Cracks are usually found in the furnaces on a belt of from 4 to 8 inches wide, a short distance above the fire-bars, and running the whole length of the furnace. If there are only one or two, each one is cut out, as shown in No. 98, to a V shape, new metal is then added from a rod of Swedish No. 98. iron by the welder, who holds his blowpipe in one hand and this iron in the other, adding it drop by drop to the molten mass at the tip of the flame ; if he does not get the original plate properly molten before adding new metal he will not make a weld, and the crack will open on cooling. Other positions in which cracks are to be frequently found are in the landing edges of the furnaces and combustion chamber plates running inwards from the edge of the plate into the i6o Verbal " Notes and Sketches rivet holes and sometimes beyond ; these cracks are repaired in the same way as furnace cracks, only great care must be taken not to weld the top plate to the one underneath, if this is done endless trouble will be caused. In some cases there are a number of cracks within a small area ; it is then advisable to cut out the whole of the affected part and weld in an entirely new piece of plate. In case of a furnace with thickened ribs it is an easy matter to build up the new plate to the correct shape as shown in No. 99, the new metal being shown bj; No. 99. the dotted lines and shaded portions. Corrosion usually takes place in the same region in a furnace as cracks, that is, in a belt 4 or 8 inches wide, a short distance above the fire-bars, extending the whole length of the furnace ; to repair this all scale and dirt has to be carefully removed from the corrosion which is then built up to the original thickness of the furnace ; the method employed is exactly the same as that for cracks, new metal being added little by little as the plate is brought to a molten state. Corrosions very frequently occur at the landing edges of the furnaces and combustion chamber plates ; when this is so it is usually found that the back plate is also corroded as shown in No. 100. No. 100. Boile rs i6i To repair, the corroded places are first thoroughly cleaned, the corrosion C is then first made good, the landing of the front plate is then built up to the required amount, the same care being taken in this case not to weld the front to the back plate as in the case of landing edge cracks. Besides cracks and corrosions in furnaces and combustion chambers, the same defects sometimes arise in the tube plates : cracks extend from one tube hole to another, and are very difficult to repair ; as this is the least section of the metal (see No. loi), and is subject to great strain, fortunately these cracks do not often occur. To repair, the crack is cut out as previously explained, and welded ; a sheet of iron should be put over the further end of the tubes to prevent a draught being set up. No. loi. Corrosion in the tube plates occurs when there is a leak between a tube and the plate ; this can be easily repaired by cleaning and adding the necessary new metal. Another frequent defect in a boiler is corrosion round the mud hole flanges ; this can be repaired, if not too far gone, b>' building up as previously explained. If, however, a flange is too far gone to be repaired by this means, a new flange can be welded in as shown in No. I02, and the joint of the cover can be made at the surface. wM^m 12 No. IC2. i62 " Verbal " Notes and Sketches With regard to repairs to hulls of vessels these are far more limited than those of boilers ; this is to a great extent due to th'e inferior metal used in their construction as compared to that used in boilers, thus it is impossible to weld a piece into the middle of a ship's side plate. Welding of frames does not always succeed unless they are set free over a great length. No difficulty is met with in repairing stems as they are of com- paratively small thickness. The repair is carried out as follows : — The crack is cut to a V both sides, the bottoms of the two incisions meeting in the centre, the welding is then done from both sides simultaneously. Stern posts and rudder posts are much more difficult to repair owing to their thickness. Before repairing, the work must be brought to a red heat by means of a forge or some other method, the blow- pipes are then brought into use and the work proceeds in the usual way, only, when once started, the job must not be left till finished. Besides the above-mentioned repairs, cutting away of furnaces, ship's plates, rivets, &c., can be done with a specially-constructed blow- pipe in which an oxy-acetylene flame is used to heat the part to be cut, and an oxygen jet is used to do the cutting ;. with this blowpipe a great deal of time can be saved, for example, a stem can be cut in four minutes, and the largest stern post in ten minutes, or a furnace can be cut out in about one and a half hours if it is desired to replace it. Autogenous welding is the uniting of metals by means of heat alone, without the intervention of any different rnetal. The heat is obtained by the combustion of acetylene with pure oxygen, which gives a temperature of about 6500" Fahr. Cutting by Oxygen Jet. — In cutting plates a small surface spot is first heated up by the acetylene flame, and a jet of oxygen is pro- jected on to this hot plate from a separate orifice, the metal being burnt or oxidised away where the jet strikes, with the result that a cut is made similar to that produced by a saw. General. Acetylene (C9H.,) is a gas of nearly the same weight as atmo- spheric air. Each cubic foot of gas generates about 1450 B.T.U. During combustion of C9H2 carbonic acid gas is formed (CO2), also water vapour (H^O). The flame formed by the blowpipe consists for the most part of CO gas, but at the point of CO.^. The welding flame is surrounded by a film of Hydrogen gas which prevents oxidation from taking place, and thus allows of an efficient weld being formed without the use of a flux, 1^ I _ oatn I I i '^ i i /; 1 — "I -^ 1 K^ L V .loIioS no ^DoD s^ubO isIbW -loi 'ili fiJOii gui'; No 103— Water Gauge Cock on Boiler. This type of cock has the plug taper reversed, thus reducing risk of the plug blowing out. In r tlie plug from the shell, it must first be knocked down into the boiler. A small set pin screwed through the shell of the cock prevents the plug from dropping out of plai when in use. The objection to this type of plug is the tendency for the hole in the plug to become choked up wi grease and dirt, and thus reduce the opening of the port. ■ Virbal " Noles :md Sketches. 3VJAV «?C / -i^O-WOje 3DA^RUa ~MAJG SI // a t :3d. F.^ -rzT PAIR OF SAFETY VALVES EACH 5? DIAM^ DONKEY FEED CHECK 2f orAM. No. 104— Boiler Mountings- ire dimensioned for a boiler 16 feet dia . Safety T»lTe3. ~To relieve the pressure when it e: the ufe limit , Mfcb rtop-Talvea. — To admit the »te»t , Donkey Feed c 6. Surface Blow 4, M»in Feed check yalTe. — To gire a —To ftdmit a 1 cootrol the feed 1 the greasy matter off tl working pressure of iSo lbs. per square inch. The _ — To show the < 9. Hydroki NOTE.— Notice that the bottom c I up from the bottom, for should the pipe break off o "^1 I 1 ' aA3flHT in TOa TA MAia ^^ •AT2 J331T I .MAIQ B\ -81 'P Trrr^ .|-w£^i£;;;, L_A .,.. ;5" -J \ i ::i^ -i ^4 1 - 1- Si 5 a? ] < . f U!U Oj vAie No io6— Sketch of Marine Boiler, with Principal Dimensions (half section). Students preparing for the First Class Exaniinaiion should practise drawing the above sketch from memory, notinf^ carefully the dimensions and the flanging of the plate, &c. Safe Pressure-— To find the required Safe Pressure, if the Diameter is 14 feet 6 inches, Factor of Safety 4-6, and the joint strength 84 per cent. Ru LE- TS X 2240 > T y 2 X joints Factor x D in. >c Safe Pressure. Therefore, Pressure, f^i^^'i,? ' ^ ■i""'^^ ^^^^^ySJ-^^^Al = , 8^ lbs., sa, .80 Ib^ Factor :^ Diameter in 4'0 >< i74 "»• NOTE.— 1| inches=i 375; 14 feet 6 iaches=i74 inches; ^ = -84' iTo fact page 163. xy I • • • t 1 M. HDTiq gl MAiCJ ^ > r 3TAJ9 3aiiT Si \ No. 105 - Sketch of Marine Boiler with Principal Dimensions (Longitudinal section). Students preparing for the First Class Examination slioutd practise drawing the above sketch from memory, noting carefully the dimensions, and the Hanging of the plates, &c. Notice that the furnace shown is of the Gourlcy-Stephen withdrawable type, as the slightly elevated position of the flange at the b^ck allows of the furnace being canted up and withdrawn from the front end opening. Shell Thickness. — To find the required shell thickness if the pressure is to be 180 lbs. per square inch, joint 84 per cent., and Factor of Safety 4-6. Rule — 28 X 2340 V T X 2 X joint= Factor • D in. ^ Safe Pressure. , Factor x D in. ■-: Safe Pressure _46 - 174 In. • i8o _ 38 X 2240 X3X joint 38x 2240x2 X '84 Therefore, say i| i [n/oftpagt 163. "Verbal " Nntcs ami SVelchcs. Boilers 163 The pressure of oxygen supply to the blowpipe varies (with different sizes) from 10 lbs. to 25 lbs. In cuttini^ plates by means of an oxygen jet the oxygen ignites the plate, which burns away as oxide of iron (similar to rust). Bottom Blow-off. — In the opinion of the writer the boiler bottom blow-off cock to the ship's side might well be dispensed with alto- gether, as, unless carefully handled, it undoubtedly constitutes a danger, owing to the possibility of lowering the water level below the combustion chamber tops, which may result in : — 1. Collapse of combustion chamber tops. 2. Deposit of greasy scum matter on top of combustion chambers. Many engineers are now in favour of discarding the bottom blow- off as commonly fitted, and connecting the bottom pipe as a donkey pump suction, which arrangement allows of either pumping out the boiler, or of circulating when getting up steam by drawing out the colder water at the bottom and pumping it back into the boiler through the donkey feed check higher up. The surface blow-off (Sketch No. 104), if properly fitted as shown, when opened, only allows the water to be lowered down to the scum pan level, and by its use the oily scum floating on the surface can be blown out, whereas, if the bottom cock is employed, the scum referred to is apt to settle down on the combustion chamber tops, and once deposited will be found extremely difficult to remove except by thorough washing out of the boiler. Efficiency of Boiler. — The average heating value of i lb. of coal is 14500 heat units, and with a feed temperature of, say, 140', and steam temperature of 380'' (180 lbs. gauge pressure), the evaporation would be as follows if no loss of heat occurred : — Heat Units of Evaporation = 11 15 + -3x380°- 140" = 1089 Heat Units. And, 14500 -r 1089 = 13-3 lbs. of water evaporated into steam per pound of coal. If, however, the actual evaporation as measured is only 9^ lbs. of water per pound of coal. Then, Boiler Efficiency =9-5+ 13-3 = -714 or 71-4 per cent. Equivalent Evaporation. — As a standard of comparison the evapo- ration obtained by a fuel " from and at" 212° is usually taken, that is, the feed is assumed as being at 212" temperature, and the steam at 212° temperature. Example. — Feed temperature 140^, steam pressure 180 lbs., and temperature 380' ; if the actual evaporation per pound of coal as tested is 10 lbs. of water, find the equivalent evaporation. Then, Heat Units for evaporation -1115+ -3 x T°- ^° = 1115 + '3x380 - 140 = 1089 Heat Units per pound water. Therefore, ^°^9 10 ^ 11.27 lbs. 966 164 "Verbal" Notes and Sketches One pound of the coal referred to can therefore evaporate 11 '27 lbs. of water into steam " from and at" a temperature of 212°. Weight of Gases passing up Funnel.^The weight of the waste gases which pass up the funnel can be estimated as follows : — Example. — If the consumption is 25 tons of coal per twenty-four hours, determine the total weight of the products of combustion passing up the funnel during that period. NOTE. — Each pound of coal requires about 24 lbs. of air for complete combustion. Therefore, Weight of air required = 25 x 24 = 600 tons. But (neglecting ash and clinker) the 25 tons of coal also pass off in the form of gas. So that, total weight of gases = 600 + 25 = 625 tons per twenty-four hours. The actual weight of the gases would be perhaps about 10 per cent, less than the above, if the residue of ash and clinker were deducted. Shortness of Water. — If a boiler runs short of water through faulty check valve, or other causes, the first thing to do is to pump in more feed water, either hot or cold, preferably hot of course, but even cold water will in most cases result in no serious injury or danger if the water is not actually below the crowns. The seams or tubes may afterwards leak slightly, but nothing more is likely to happen. If, then, one boiler out of, say, a set of four boilers shows a low water level, the engineer on watch should at once open up the check valve of that boiler, and reduce the lift of the check valves on the other three boilers : in addition to this it may become necessary to put on an extra feed pump (if one is available) to the boiler which shows no water in the glass. The point to be remembered is to get water into the boiler as soon as possible, and, as before stated, even cold feed water may be pumped in without risk of accident if the boiler is merely short of water. Velocity of Gases. The mean velocity of the gases passing through the uptake and funnel is about 13 feet per second; the mean velocity of the gases passing over the furnace bridge is about 75 feet per second ; the mean velocity of the gases passing through the tubes is about 60 feet per second. Evaporation per Pound of Coal. One pound of average coal gives out about 9000 units of heat(B.T.U.). ',VV- ■■VvJ > 1 edi 1 •*■ =?>- 1 r — ' mtx). 6\ 'Rate, nsu^ 'idui. *&Katoi ^ U— « J* : -Zr.O-Mic^Xenxiih-^- -^— >) •2V.0' Mea7vI.enjgtK Doubie-Ended Boiler of White Star Liner " Britannic' (Reproduced by permission from "Engineering," Feb. 27. 1914. White Star Liner "Britannic." (By Messrs Harland & Wolff Ltd.) GENERAL DATA- Length over aU Breadth • Depth, moulded Height from keel to bridge Gross toimage Load draught Displacement at load draught Combined 1. H. P. of wing reciprocating engines (ahead i Shaft horse power of centre turbine (ahead only) - Sea speed ... 64 .. 3 " 104 .. 6 , 50000 tons 34 ft- 7 in, 53000 tons 32000 ., 31 knots. BOILER DATA- Nuraber of double-ended boilers ,, single ,, ,, ... Diameter of all boilers ... Length of double ended boilers ,, single .. ., ... Number of furnaces on each double-ended boiler - 6. single- ,. 3 Total heating surface per double-ended boiler ■ 5702 sq. ft ■ • Srrate i30"8 .. .. ., heating „ ,. smgle ended ,, 2823 „ ., ,. grate 65-4 .. .. 1 Ratio of heating surface to grate surface ■ Inside diameter of furnace corrugations 3 ft 9 in. 1 Type of corrugation Total number of furnaces Workmg boiler pressure . . . . . Test pressure ■-..... 215 lbs. Igauge). ■ 430 .. It will be noted tliat eacii crombustiotl cimfnber is suspended from the shell by a large central stay, secured top and bottom by eyes and pins to angle irons above and to the girder below. The large scale drawing on right shows clearly the details and dimensions of the suspension stay. It should also be carefully noted that when suspension suys are fitted the combustion chambers are also anchored to the shell at the bottom, cither by screwed stays (centre furnace) or by plate stays (wing furnaces). ' VerUil ■' Notes and Sket.hev r\ Boilers 165 To find the units of heat required io evaporate i lb. of water into steam, the rule is as follows : — III5 + -3 :T - <^ Units of heat. T ~ Steam temperature, t -- Feed temperature. Example. — The steam pressure is 160 lbs. or 370" temperature, and the feed water temperature is 140° ; find the units of heat required to evaporate i lb. u( water into steam, and the number of pounds of water evaporated by i lb. of coal. Then, 1115 + -3x370°- 140" = 1086 units of heat required per pound of coal. Therefore, ^^ —8-28 lbs. of water evaporated per pound of coal. NOTE. — To evaporate i lb. of water at 212' temperature into a pound of steam at atmospheric pressure requires 966 units of latent heat. Boiler Dimensions. The following data refer to a modern type double-ended boiler carrying a pressure of 170 lbs. per square inch, and the various plate thicknesses and details of riveting should be carefully noted. Boiler Data. Pressure .... 170 lbs. per .square inch. Diameter - - - 13 feet 10 inches. Length (double ended) - - - 20 „ i| ,, Number of furnaces - - - 6. ,, combustion chambers - 6. Grate length - - - - 6 feet 10 inches. „ width - • - - 3 .. 4i „ Total grate area - - - - 138 square feet. Heating surface of tubes - 2840 ,, „ ,, furnaces - - 242 ,, ,, ,, combustion chambers 444 ,, Total heating surface - - - 3664 ,, Heating surface to grate - - 26-5 is to i. Area over bridge - - - 3-11 square feet. Shell consists of three courses of plates, each course having three plates ; the centre course is outside of the end courses. Shell thickness - - - - ij inches. Longitudinal Shell Seams. Double-butt strap thickness - - i inch. Rivet diameter - - . - i^ inches (holes ly^ inches). Maximum Pitch of Rivets (five rivets per pitch) Distance between inner rows - - z^V ,, " )> outer ,, - - 3Yg „ Rivet section strength - - - 93-2 per cent. Plate „ „ - . . 83-7 „ i66 "Verbal" Notes and Sketches I /g- inches (holes i| inches). Centre Circumferential Shell Seams Rivet diameter - „ pitch (three rivets per pitch) ,, section strength - Plate „ „ - End Circumferential Seams. Rivet diameter - „ pitch (two rivets per pitch) „ section strength - Plate 4f? 5> 68-6 per cent. 66-6 ,. I J inches (holes ij^ inches). 70-15 per cent. 62-5 End Plates. Top end plate thickness Centre ,, „ (front tube plate) Bottom ,, ,, (furnace plate) - Furnace length - - - - „ diameter „ thickness Combustion chamber width Back tube plate thickness Thickness of combustion chamber plates Diameter of combustion chamber stays - Pitch „ „ Length of combustion chamber girders - Depth ,, „ „ 7f inches. Thickness ,, „ „ (two plates each) - - - f inch. Each girder fitted with three i i-inch diameter bolts. i^ inches, f inch. i^ inches. 7 feet 8 inches. 3„ 7 ., h inch. 2 feet 6 inches, f inch. 1 H _'» i^ inches (bottom of thread), from 6h to Sh inches. 2 feet 6| inches. Tubes. Diameter of tubes Length „ Pitch of tubes - Number of plain tubes per boiler .. stay „ „ Diameter of main stays (steel) - Manhole Mudholes (five in number) 3 inches outside. 7 feet 4I inches. 4^ inches horizontally. 4 ,, vertically. 324 (No. 8 B.VV.G.). 180 ( „ 6 „ ). 2 1 inches. 16x12 inches. 15x11 » NOTE. — The grate surface for each furnace is equal to the length of bars multiplied by diameter of furnace. 6' 10" 3' 4^" 12 12 Therefore, 405 ^23 sq. ft., and 23 x six furnaces- 138 sq. ft. (total). 144 And, Total Heating Surface ^ Grate Surface = Ratio. Then, 3664^138-265 to i. Boilers 167 Referring to the joint strengths of each seam, it must be remembered that the smaller per cent, of rivet section and plate section at seam is the joint strength, therefore, Joint strength for longitudinal shell seams = 83-7 per cent. ,, ,, centre circumferential shell seams = 66-6 ,, " " ^^<^ >. ,, ,, = 62-5 ,, The screwed portions of the stay tubes and combustion chamber stays have twelve threads per inch. Vertical Donkey Boiler (see also page 653). No. 107.— Vertical Type Donkey Boiler. Pressure, 80 lbs. (gauge). i68 Verbal " Nolcs and Sketches Sketch 107 shows clearly the construction of this kind of boiler. The cross water tubes are for improving the circulation and increasing the heating surface, and it is to be noted that a handhole is fitted opposite each tube for cleaning purposes. There are usually from four to six stays of about 2 inches diameter for supporting the fire-box. This boiler has a wet uptake, and corrosion takes place at the water level ; corrosion also goes on at the bottom, between the shell and the fire-box, and is caused by what is called "grooving," that is, the upper part of fire-box expands by the heat, but the lower part at the bottom being riveted to the shell is kept rigid ; therefore the skin of the metal cracks slightly at the bend, and allows of corrosion taking place. The corrosion is also increased by the want of circulation at this part of the boiler. As the fire-bars are low down, and the ash-pit immediately underneath, the boiler is a dry bottomed one. For ordinary proportions, the shell i: about I inch thick and the fire-box | inch thick. The average dimensions for this type of boiler are as follows : — Pressure Diameter Height Shell plates - Fire-box plates 80 lbs. gauge. 5 feet. 10 „ g to 5 inch thick. A to a Cross tubes Uptake - ■ - Water space round fire-box Vertical stays - 10 inches diameter. IS .. 6 inches to 3 inches. 2 inches diameter (six in number). riREHOLC. OOCE RINO. SPtCIALLY THICK TO 0 \ rrv.'0(l *^- ■■'nigcfd. A I oM Notes and Sketches of Various Details 179 . rr^ . No. 2.— Reversing Gear Complete (Cruiser Type). This gear is known as the " all round " type, as if the gear is " missed," the wheel continues moving round without damage or shock to the link motion. For an engine of 1200 I.H.P. the reversing engine cylinders (two) will be about 4^ inches diameter by 4-inches stroke, and from 20 to 25 revolutions of the reversing engine will be required to reverse the gear. The engine is usually made reversible by means of a hand operated piston valve, similar in design to the control valves of steering gear engines, which admits steam either to the centre or to the ends of the cylinder valves as required. The reversing engine shown on left drives a worm shaft geared into a large worm-wheel, to which is attached the link from the bell crank. Hand-wheel gear is also shown, and a brake strap connection to the worm-wheel, to increase the control. i8o "Verbal" Notes and Sketches No. 3.— Twin Cylinder Turning Engine with Double Worm Gear. The lower end of the main worm can be drawn out of gear by means of the wheel shown on right. The turning engine runs at about 300 revolutions per minute, and travels about 2000 revolutions for one revolution of the main engine, thus requiring 6| minutes to turn the main engines once round, as 2000-^300 = 6-6 minutes. For engines of, say, 1500 I.H.P. the turning engine cylinders will be about 3^ inches diameter and 4 inches stroke. ai'i. fo tp(; CI O V a. J3 .. , c -, > w *> = ,., 3 3 ^ o g o .5 o O U i; C S O M c r^ >- ho •* ttJ '<" "n 5 «, rt !" 6 ^ 0) U Ul' 3 -^ (A ^ igo "Verbal" Notes and Sketches (A -i-> 3 iz: xj c OJ CO -M o CQ 'd 1 o .• p:: en bo _o G £ Q ci 6 ^ N in ^ ■5 V- «5 :2 ^"S d m ^°fc h-i d ►t^ d H-* *"* " d c t:|x p^ d Hm w d m|x c r Cjrf '^ Area of Bolt at Reducec Part. t^ , O *^ 'C i^l-^ _:. to G ""^ i^ X • o ? ^C' _: o ^ JZ 1—1 «-.■ Q^H rO rt O ^^J= 1 ^1.1 -^-»• ro ' ••=^1. 1 c o ^ — <-M .2« *i: fO '^ o Notes and Sketches of Various Details 19T -K—^f No. 21.— Edwards Type Air Pump (with Displacement Bucket). Observe the air inlet ports near the bottom, also that head valves only are fitted. The pump as shown is independent and is driven by a separate engine (Naval practice). 19: " Verbal " Notes and Sketches S c o U) •- c a xn 3 o o >. ES D nJ -^ Ji! 1) C o 3 •S bo v-l V e u u § (U .5 ^ • 3 C o <1) Vh OJ Ui nt PU bo n o •J3 .s o 6 O ^G rt w !3 ^^ 3-£3 • — • i-> V U (U a; c ■S 4> " h donkey is also arranged to draw from tbt bottom of the condenser in case of 1 when Weir pumps are fitted. \Tt>jtutfagt 193. Notes and Sketches of Various Details 193 No. 24.— Piston Rod Crosshead and Shoe ("Single" Guide Type). D = Crank pin diameter x -55. L = Dxi-2. " NOTE. — The astern guide surface = 80 per cent, of ahead guide surface. Jt4 194 *' Verbal " Notes and Sketches r^Oi i^^-JdWffi ^c=px=^ Kn I llij tr 4 * No. 26.— Single Guide T3rpe Solid Crosshead. In this pattern the Crosshead Pin is shrunk into the connecting Rod Jaws. No. 27.— Balance Weight for Crank. B, Riveted bolt. C, Dowel pins fitted half into web and half into weight (a driving fit). * Reprinted by permission from "Marine Engine Design. " Prof. Edward M. Bragg. D. Van Nostrand Co., New York, 1910, / w L o ^ No. 25.— Condenser and Circulating Water Connections. A, Main injection valve. B, Bilge injection valve. C, Bilge stnim. D, Injection pipe leading to purap suction. E, Ballast pump circulating pipe to condenser. F, Centrifugal circulating pump. G, Centrifugal pump delivery to condenser. H, Condenser division plate. J, Circulating discharge pipe. K, Side discharge valve. NOTE. — ^In the condenser about 60 per cent, of the heat in the st ■atent heat units of the steam to the circulating water, which transfer temperature of 65* Fahr., the discharge temperature would be somewhei by absorbing the latent heat (approximately 1000 B.T. U. per poui NOTE. —The evaporator is fed with the condenser discharge L, Exhaust (or eduction) pipe from L.P. cylinder to Condenser, M. Air pump suction pipe from condenser bottom. N, Auxiliary sea water feed. O, Auxiliary fresh water feed from tanks P, Vacuum gauge pipe. R, Soda cock. S, Cock to allow escape of sir. T, Cock to allow esci^ of air. W, Cooling water to guides. V, Evaporator feed. 5 rejected, representing an unavoidable loss : this is due to the transfer of the essary for condensation to take place, If the injection water enters at. say. a about 110° Fahr., so that the discharge water is thus raised in temperature of steam) of the exhaust s rater, at a teniperature of. say i i less heat is then required for evaporatioiL yrojact jsast 194, I Notes and Sketches of Various Details 195 •o o (^ bo '■13 u a> c a o U 00 d 'Z 0) > (A c C o ^ O c CO CO ^ *o II II II II .5 .5 c M N w rjl-* ^ II II II II II v + 0) S u -w fi c «Hi ^ '*> '^^ n ci , M loO vo VO fl) 'O 1 II li II II II •0 «^'S fcOffi-'W i-tN II > C 3 •" CT" «H.JJ s -!-! J5 00 •-< M r^oo II II II II II < M U Q W 196 "Verbal" Notes and Sketches No. 29.— Piston Rod (Naval Type) showing Method of Removing- Piston. F, Dog by means of •which the double clamp E draAws the piston off the rod. NOTE. — When the nuts of the hinged bolts are tightened up the clamp E acts to draw the piston off the rod. Notes and Sketches of Various Details 197 No. 30.— Syphon Feed Oil Box (on Cylinders). 1, To ahead guide. 2, To astern g^ide. 3, To crosshead. 4, To crank pin. 5, To crank pin. * No. 33— Crosshead Block with Dimensions for a 5^-inch Piston Rod. No. 34.— Reversing: Bell Crank with Expansion Slot. F, Ahead position. S, Astern position. Notice that linking up is only possible when in ahead gear, as when in astern gear the expansion slot is in a vertical position, so that any change of position of the block has little or no effect on the drag link. No. 35.— Diagram Sketch of Double-Beat Valve. Steam enters from the boilers by the right hand branch, and is admitted to the engine through both valve openings ; the upper valve having the larger area allows of easy manipulation owing to the equilibrium obtained. * Reprinted by permission from "Marine Engine Design." Prof. Edward M. Bragg. D. Van Nostrand Co., New York, 1910. u * C ^ o lu ly f u, > - 1. < -1 ,1 ^ o o 1 Ul r ( 1 >s 0» ^5 Ho u -i > Ul 3 ,o ! 1 1 i 1 Q i ) _ — ' i ! o i m j 1 — o Q "W^" • C' 1 • 1 • 1 .YJM ^M U*J G flO^- ' 1 c r I 1 m J . , i mfi- !^&i<] I noi ta9 ^h6^»l3 90IK> Jfi ^ nfiD TiiB JKtlJ o? M''^' i;i£T5> ' •! Tlo birl j'f tif > ■ < J 1- 1 ZiO to < .'. i< 5 z z < (0 o p i or 11 L "Z I< 1- lOI < UJ13 5> HZ Pump c _a • o o BallastPump sue o • • • o Feed Pumps OlS • O o • • Service DONKEY sue 015 o • • • o o o o o AUl^lLIARY Feed Pump 015 « o • Fresh Water pump OlS^ • O Hot Water Pump OlS. • O Refrigerotor Pump 5UC OlS o Sanitary Pumps ON M Engines DiS o o o Evaporator Pump sue o • ,N.ECTOP OlS o • BiLGt Pumps ON M Engines OlS •- -FORD PUM PONC f • o o.^. 3 PU MP C NLY Fee.0 Pumps ON M Engines OlS o • O o MAiNC0NDeN5£fl sue • • Air Pumps OlS • o o -H IT WE 1 ov >w NOTE #="SUCTION from" 0^=" DISCHARGE TO" The above table shows how the located by reference. All the suction If the pumping arrangements No. 31.— Pump Connection Diagram, : pump suction and discharge connections can be laid off '. shown as dark circles, and the discharge I any way complicated, a diagram made out similarly ti Referring above to the "General Service Donkey" connections it will be seen that this pump Bilge, or Ballast Tanks, and to discharge to Auxiliary Feed, Overboard, Sanitary Tank, Deck, or tt out in the same way. n diagram form, so that any can be at once clear 15 as open circles, le shown above will be found of great benefit. . arranged to draw from either the Sea. Hot well. Ma the Distiller. The other pump < "Verbal " Note^ and Sketches. /^ n-'i p)i tf sltLsrX o| cojqet tfJiGV j}G naniTJ MSfX- J,pG jJCSfGL pr.GU qiSTMU HOIH* 3^>k' f}JG *| \jrR. bibe t. 'I i Oi.; Hi I it.-i:; fv.ii'fja- jro sfajo«l>jici.c A4.peu arobLmK tPJiCjiw 1, Main Teed pump s 2, Maui feed pump ! 3, Suction valve of i 4, Delivery vaive of 5, Relief valve of mi 6, Pet (air) valve. jctlon from hot-well. ucUon pipe, lain feed pump, main feed pump. in feed pump. No. 32.— Feed Pump Connections. 7, pressure balance connection between feed pump and hot-well. 8, Test cock (for temperature of water). 9, Regrulating valve. 10, Main feed pump discharge to 61ter and heater. 11, Heating steam from I. P. or L.P. receiver. 12, Donkey feed pump suction from heater. 13. Donkey feed pump delivery to boil 14. Boiler feed check valve. 15. Cord fur quick opening of heater t t6. Air pipe connection to coodcnser 17. Steam to donkey feed pumps. 18. Pressure gauge. atmosphere when stopping eni^tcca- .- of. Descriptton. —The main feed pumps deliver the feed water at a tempcrau filter ; after passing throuf^h ihe filtering cloths it enters the feed lieater at the same tcniperatiire, I here heated to a temperature ranging frura 195* to about 220', the temperature depending on the pre carried in the healer. As is well known, the heating is effected by live steam placed in direct contact with the water, this results in the condensation of the iteam, the latent heat of which is thus given up to the feed \ ■'Verbal" Note* and Sketches. the and reenters the boilers. Had the steam gone lo the condenser instead of the heater the latent heat would have been rejected in the form of heated sea water (condenser discharge). This saving of the latent heat units more than counterbalances for the loss of work by the steam having been drawn from, say, the L.P. cbest, and not having expanded and done work in the L.P. cylinder in the usual way. The heater is therefore similar in action to a jet condenser as the steam is condensed direct by a spray of colder water. ITtfOiepa^t 198. SECTION IV. SLIDE VALVES, PISTON VALVES, VALVE DATA, ETC. Duties of Valve. The slide valve (or piston valve) has the following duties to perform : — 1. To admit the steam to the cylinder. 2. To cut off the supply of steam. 3. To open the port to exhaust (Release), 4. To close the port to exhaust (Compression), and so retain some of the steam for cushioning. Valve Travel. The travel of a valve is equal to (Steam Lap + Port Opening) x 2. Suppose lap to be 2 in. and port opening i| in., then 2+ii = 3i in., and 33X2 = 7 in. travel of a valve. The narrow part of the eccentric subtracted from the broad part equals the travel (Sketch No. i). Therefore, 7-2 = 5 in. Travel. Or, take the distance from the centre of shaft to centre of eccentric and multiply by 2 ; this also gives the travel of valve. Thus, 2-5x2 = 5 in. Travel. 199 200 Verbal " Notes and Sketches Steam Lap is the amount the valve face covers the steam port when the valve is at half stroke, and is for cutting off the steam to cause expansion, therefore the more lap the valve has, the sooner on the stroke will the cut-off take place, and vice versa. The bottom steam lap is less than the top. Exhaust Lap (usually at bottom end of valve) is the amount the exhaust edge of the valve covers the bar when the valve is at half stroke, and is for causing compression and cushioning. No. 2.— Slide Valve. S, Steam Lap. E, Exhaust Lap. Minus Exhaust Lap (usually at top end of valve) is the amount the exhaust edge of the valve is short of the bar when the valve is at mid stroke : it causes the exhaust to open early and close late, and thus reduces the cushioning. Lead is the amount the port is open for steam when the crank is on the top or bottom centre, and is for giving the engine a turning movement over the centre. The bottom lead is always more than the top, to allow for the weight of the moving parts to be lifted up against gravity. To cut off sooner with the main valve, steam lap must be put on and the eccentric advanced an equal amount to keep the lead the same. No. 3. — Trick Double Ported Valve. At Position of Mid-Travel. For the valve shown the width of steam port = half travel of valve. The advantages of this type of valve are : — 1. Reduced travel. 2. Reduced face friction. No. 4.— Trick Double Ported Valve. At Position of Maximum Steam Opening at Top. Notice that half the steam supply is admitted over the top edge of the valve, and the other half from the bottom by means of the internal port, as shown clearly by the arrows. Pulley Position for above. Pulley Position for above. Verbal " Note.s and Sketche.s. [ To face page 200. ,3V If. V bvBiT biM lo itoilizol JA xiil)iw -nil nv/oriii avffiv tjdl loM .'.v/Ik/ 'Io iavfiil Uxid - Jioq rriKv>J2 1 : -JIB tjvic, / V/Z \^, \ I' / Slide Valves, Piston Valves, Valve Data, &c. 201 No. 5.— Common Double Ported Valve. No. 6.— "Trick" Double Ported Valve. S, Steam Lap. E, Exhaust Lap. Valve Opening to Steam at Top, /^ ■N ■ / ^ V .^ "^ No. 7.— Piston Valve Ring. Fitted with double tongue piece. 202 " Verbal " Notes and Sketches To cut off later with the main valve, steam lap must be taken off and the eccentric put back an equal amount to keep the lead the same No. 8.— Piston Valve and Balance Piston (Admiralty Type). NOTE.— The packing rings are, in this case, of the solid pattern, the cut ends being bolted together by lugs shown in the upper section view. This valve takes steam from the ends and exhausts to the centre ; the eccentric keyseat position is therefore similar to that of a slide valve : at 90° + mean steam lap and lead in advance of the crank. The balance piston has the chest steam pressure on the under side, and the condenser pressure on the upper side, a pipe connection from the top of the balance cylinder leading to the condenser. Slide Valves, Piston Valves, Valve Data, &c. 203 Double Ported Valves. A double ported slide valve has only half the travel of a single ported valve, and the face friction is less, owing to the steam pressure in the inner ports tending to ease the valve off the cylinder face. In the common valve the inner ports receive steam from the sides, but in the Trick valve the steam passes either from bottom to top or from top to bottom. No. 9.— Double Ported Slide Valve and Relief Ring. T, Steam port width (about -7 of which = steam opening). L, Minus exhaust lap (sometimes called "internal lead"). E, Exhaust port of cylinder. N, Depth of valve inside. F, Packing of ring. C, Connection to condenser (to relieve friction). NOTE. — In the case of L.P. valves it is sometimes found of benefit to bore, say, ten or twelve | inch holes through the back metal of the valve, thus opening up additional connections to the condenser. This alteration has resulted in an improved vacuum on the back of the valve, the usual vacuum carried ranging from 18 in. to 22 in. 204 " Verbal " Notes and Sketches No. 10 —Slide Valve Relief Frame. L, Faced brass ring. T, Springs to keep ring up to back of valve. C, Space in connection with condenser. NOTE.— The studs (six or eight in number) can be screwed up to give additional compression to the springs. The small black sections shown in the brass ring represent soft packing. No. II.- "Restricted" Type Packing Rings. The ring expansion is limited by the small projections formed on them whicli fit into corresponding recesses in the carriers. The tongue piece is shown in the small views on the top. Depth of Rings W = Lineal piston clearance x 2. Slide Valves, Piston Valves, Valve Data, &c. 205 No. 12.— Andrews and Martin Balanced Slide Valve. This valve is of the balanced or equilibrium type, steam being ad- mitted from back and front through the ports shown ; the face friction is thus considerably reduced. No. 13.— Piston Valve fitted with Two Solid Packing Rings. The rings are turned larger than the bore of valve chest liners, cut, bolted together as shown in the plan, and fin- ished to fit liner diameter. A tongue piece of usual construction is also fitted. The Andrews-Martin valve is shown in the position of steam " admission " at top, and exhaust at bottom. This valve is known among engineers as the " Matchbox '' valve. The wear of the valve faces can be taken up by means of liners fitted in behind the spring on the back casing, which is adjustable. 206 Verbal " Notes and Sketches No. 14— Solid Type Piston Valve (Inside Steam). In this type of piston valve (steam inside) the eccentric keyseat position = 90° - mean steam lap and lead, following the crank. No. 15.— Hollow Type Piston Valve with Rings (Outside Steam). In this type of piston valve (steam outside) the keyseats are cut at an angle of 90° + mean steam lap and lead, in advance of the crank. NOTE. -Piston valves are in nearly all cases arranged with steam inside and exhaust over ends, as in No. 14. Slide Valves, Piston Valves, Valve Data, &c. 207 e e 4J > > o -4-> Ui o tM9 I 1 i-g O .>:; ^ '•< O C . "^ ii Ci. )-i Ix C .> '^ I" ^^ >^ ^ o-^ > rt ^ 2 E § £.S ^ t-' JiC *-> 5 ^- 3 OS X b3 « sssssss > •a o u ■4-> OS u •a G < O z 73 OJ C o a; CO o C/5 > OJ -a g (/3 1) . ^ c3 OS W CO OJ ^ > o . DATA. Type of Valve fitted -Double-Pot Position of eccentric rods with Valve Travel (C' Mean steam lap and lead iBi Distance valve travels when gear Astero ' Position (crank going down). will eaiily be seen thai if ihe g. preifure after ttopping, ind valve, but in additi •ie is compMoi, thus revn Action of Reversing Gear- awn in sketch B, the valve ii fuHtd down ig the direcllon of crank and shaft roUlio tarling or impulse valve* (see inge iSjjn corresponding posiuon and in the act of coming up : ihe v be top and simn is ih«n shut off. and the engines stopped ii certain amount and the lop porlt opened, thus admitting SK : the engine it then leversed. The same prindple holds i ; fitted. The starting valves admit Slide Valves, Piston Valves, Valve Data, &c. 2 1 1 No. 22.— "Open and "Crossed" Eccentric Rods (in " Ahead " Gear). With crank on bottom centre, the full lines show the eccentric rods as "open" and the dotted lines as "crossed," the ahead pulley being A. " Open rods " is the usual arrangement as it allows of better link expansion when the gear is shut in (see page 257) and gives full lead in any position of link. 212 *' Verbal " Notes and Sketches No. 23. — Eccentrics in "Ahead" and "Astern" Positions. D = Valve travel x 3. E = Distance between ahead and astern pulley. Full lines show gear "^ ahead." Dotted lines show gear astern. The difference in the hnk position in the two cases shows how the valve operates in reversing the engine, as the top port may be open for steam in one position, and the bottom port open for steam in the other. Slide Valves, Piston Valves, Valve Data, &c. 213 -~I^ No. 24.— Reversing Gear and Link Expansion Slot. In this arrangement the reversing engine is fulcrumed on the bed-plate, the piston rod of the gear then acting direct on a forked arm keyed to the reversing (wyper) shaft. As usually arranged, the hydraulic cylinder is above and the steam cylinder below. 214 "Verbal" Notes and Sketches No. 25.— Combined Steam and Hydraulic Reversing Gear (Brown's Patent). This type of reversing gear consists of a steam cylinder below and a controlling oil cylinder above, the piston rod being common to both. The piston rod connects by a crosshead and pair of links to the reversing shaft bell crank. Action. — The steam cylinder valve has no lap, and a bye- pass valve on the oil cylinder is worked by a continuation of the steam cylinder valve spindle. The two valves mentioned are actuated by a lever (shown in sketch), also by a secondary gear connected with the reverse motion, so that a " hunting " arrangement is obtained which causes the gear when moving to bring the valves back to mid position (shut). For hand reversing a stop-cock is fitted in the bye-pass pipe of the oil cylinder and a small pump connected up to it. The oil cylinder piston is packed by means of two cup leathers (Sketch No. 26). For an engine with cylinders, 35^ inches, 53 inches, and 63 inches (two), stroke 48 inches, the reversing engine dimensions are: — Steam cylinder diameter Oil cylinder diameter - Stroke 16 inches 8^ „ 2o| „ J---«^--" _ ir 1 i! I ,1 I n 1 ; ; I 1 Li, e K ; H H?^ ■^ / a "^ ■5 .-!?• "TS,'^ .;> li. ",iy\ ■^.:^ «rt1 ^ S2 IB I I :-^^L Marking-off of Sticks. Sticks in position for "Top Lead.'' No. 27. Si. Top steam lap. S-, Bottom steam lap. E, Bottom exhaust lap. B, Distance top piston is from top of casing, and sticks have to be placed to same distance. P, Bottom exhaust opening at top lead position. Slide Valves, Piston Valves, Va^lve Data, &c. 215 No. 26. — Leather Packing for Hydraulic Piston of Reversing Gear. Notice the grooves cut in the piston to allow of the fluid pressure finding its way to the back of the cup leathers and thus forcing them out against the cylinder walls. To Measure Lead of Piston Valve (Sketch No. 27). To measure the lead or the lap of a piston valve with steam inside and exhaust at the ends, two long sticks must be cut. Having drawn the piston valve out from the chest, place one of the sticks alongside of it and mark the depth of the pistons, &c., on the stick in the exact positions they are on the valve, as shown in the sketch marked " valve stick." On the other stick, which must be equal in length to the depth of the valve casing, mark the various spaces corresponding to the bars and ports in the cylinder, shown on "casing stick." If the valve is then placed in mid travel, and the sticks put together in the same relative position, the amount of steam lap and exhaust lap will be shown, and can be measured. Tc measure the lead, top or bottom, have the valve chest cover off, and, turning the crank to the top or bottom centre as the case may be, and with the valve gear in the required position, measure how far the top piston is from the top of the casing ; then, placing the two sticks together in a similar position, the amount of the lead will be shown, and can be measured on the sticks. The sketch shows a valve with steam lap top and bottom (S^ and S.,), with exhaust lap on the bottom E, but having no exhaust lap on the top. N.otice that the top piston is larger than the bottom one ; this allows better for 2l6 Verbal " Notes and Sketches the withdrawing or fitting in of the valve, and also gives it a floating tendency, the difference of area and of pressure lifting up the valve and reducing the weight on the pulleys. NOTE. — Sticks for ordinary slide valves (single or double portedj are made and used in the same way as above. Lead. Slide Valves and Piston Valves. — Advancing the eccentric increases the lead top and bottom equall}-. Putting back the eccentric decreases the lead top and bottom equally. No. 28.— Piston Valve. S, Steam Lap. E, Exhaust Lap. Slide Valves or Outside Steam Piston Valves. — Taking out a liner increases the top lead and decreases the bottom lead. Putting in a liner increases the bottom lead and decreases the top lead. To give lead to the top only, advance the eccentric for half the amount and take out a liner for half the amount. To give lead to the bottom only, advance the eccentric for half the amount and put in a liner for half the amount. To reduce the top lead, put back the eccentric for half the amount and line up for half the amount. Slide Valves, Piston Valves, Valve Data, &c. 217 To reduce the bottom lead, put back the eccentric f(jr half the amount and take out a liner for half the amount. NOTE.— With double ported valves advancing the pulley for, say, J in. g^ves J in. lead in all, as the lead is duplicated by the double ports top and bottom. Piston Valves (Inside Steam). — Taking out a liner decreases the top lead and increases the bottom lead. Putting in a liner decreases the bottom lead and increa.ses the top lead. To give lead to the top only, advance the eccentric for half the amount and put in a liner for half the amount. To give lead to the bottom only, advance the eccentric for half the amount and take out a liner for half the amount. To reduce the top lead, put back the eccentric for half the amount and take out a liner for half the amount. To reduce the bottom lead, put back the eccentric for half the amount and put in a liner for half the amount. NOTE. — The upper piston is usually slightly larger in diameter than the lower one, say 14 in. diameter at top and 13 in. diameter at bottom. This is more convenient for entering or drawing the valve, it also allows of balance, the top piston ' ' floating " and relieving the pulleys of the weight. A piston valve (getting steam in the inside) has the following advantages over a common slide valve : — ■ 1. Less friction, and is better balanced. 2. Only e.xhaust steam pressure on the valve spindle gland packing, instead of high pressure steam. 3. Reduced travel, the ports being circular and therefore longer. Examples of Lead Adjustments. Slide Valves. 2l8 "Verbal" Notes and Sketches A. B. C. ends. D. steam E. steam F. G. travel. Answers. 1. Advance pulley yV in. 2. Put back pulley — in. 3. Take out ^5- in. liner. 4. Put in y\ in. liner. J 5. Advance pulley ^^ in. and put in ^V in. liner. I 6. Put back pulley for .j'^ in. and take out ^}.i in. liner. The sum of the steam lap + lead is the same for top and bottom. What is gained in lead at the bottom is lost in lap, or vice-versa. Advancing the pulley increases the sum of the lap + lead at both Lining up increases the top steam lap and decreases the bottom lap. Lining out decreases the top steam lap and increases the bottom lap. Advancing or putting back the pulley does not alter the valve travel. Increasing or decreasing the steam lap does not alter the valve Inside Steam Piston Valves. Present Lead. Required Lead. No. Top. Bottom. Top. Bottom. I \ in. \ in. 0. • fV 'n- tVin. 2 \ i'l- iin. tV '"■ A in. 3 iin. iin. tV i"- A in- 4 \ in. iin. tV in- A in- 5 i in. iin. tV in. f in- 6 \m. iin. tV in- iin. Answers, 1. Advance pulley Jg- in. 2. Put back pulley J^- in. 3. Put in J^ in. liner. 4. Take out j^y in. liner. , ( 5. Advance pulley .A. in. and take out jV in- liner. I 6. Put back pulley for ^'V in. and [nit in .V in. liner. Slide Valves, Piston V' alves, V^alve Data, &c. 2 1 8a Steam Lap and Lead. Rule i. — Top steam lap 4- Lead = Bottom steam lap + Lead. Therefore, Top steam lap + Lead — Bottom lead = Bottom steam lap. Rule 2. — For unequal increase or decrease of lead top and bottom. A. Alter pulley for half si/m of lead increase or decrease. j9. Alter liners for half difference of lead increase or decrease. NOTE.— If bottom lead is to be the greater, line up, but if top is to be the greater, line out. Rule 3. — For unequal lead increase and decrease, top and bottom. A, Alter liners for half sum of lead increase and decrease. B. Alter pulley for half difference of lead increase and decrease. NOTE. — The nature of the question will decide whether lines have to be inserted or taken out, also whether the pulley has to be advanced or put back. Example i. — Top steam lap 2 inches and lead ^ inch ; find bottom steam lap if the lead at that end is to be \ inch. Then, 2 + ^ = Bottom steam lap -r \ inch. Therefore, 2j-J = i| inches steam lap at bottom. Answer. So that, (Top) 2 inches + 1 inch = {Bot.) ig inches + ^ inch=2j inches (in both cases). Example 2. — Present Lead, Top g inch, Bottom \ inch. Required ,, „ ^ „ „ i „ The sum of the lead increase = J + i = §• Then, Pulley advance = 1 4- 2 = ^^ inch. And, Liner to go in = (J inch - ^ inch) -f 2 = yV inch thick. NOTE. — Advancing pulley {■., inch increases lead at both ends by -^z inch, but by lining up for the odd -^z inch, the top is now reduced by i\ and the bottom still further increased by iV, giving finally \ inch at top and \ inch at bottom, as required by the question. Example 3. — Present Lead, Top \ inch. Bottom i inch. Required „ „ ', ,, „ \ „ Sum of Lead difference = ^ + 1 = ; inch. Then, Liner to go in, i; inch -f 2= {^ inch. And, Pulley advance = ^^-^^ - 5 i"ch ^ ,^ ^^j^ NOTE. — The f^-inch liner put in increases bottom lead to i^^ inch, and reduces top lead to i\ inch, but the pulley advanced iV inch again corrects this by giving iV inch more at both ends, thus obtaining ^ inch at top and ^ inch at bottom, as required by the question. 2 1 8^ "Verbal" Notes and Sketches NOTE.— If minus lead is given, treat this as so much additional or plus lead required, then proceed as explained above. Example 4. — The top lead is - i inch and the bottom lead is h inch. The lead required is I inch on top and g inch on bottom. Then, +4: + s = i i"ch more lead required on top. And, J-i = i ,y less ,, ,, ,, bottom. a J- 1 Therefore by Rule 3, " * = :^ inch liner out. 3 _ 1 And, "^ — * = J inch pulley forward. Answer -f ^"^"<^^ ^^"^'' *° ^^ taken out. \ 8 -inch pulley put forward. Example 5. — The original lead was, top \ in., bottom | in., the present lead, on testing, is found to be, top - f in., bottom — i^ in. Find how much the pulley ha^ worked back on shaft, and the thickness of liner which has dropped out from under foot of rod. Then, Total lead decrease = (f + f) + (i^" + ^") = i" + ii" = 2f. 2 5" Pulley has gone back = _!L = i jB^". Answer. 2 t5' _ 1" Liner thickness (out) = -^ =1^". Answer. 2 This question will be much easier understood if the student takes it backwards, that is, assume that the present lead is top — | in., and bottom - li in., and that the lead required is, top | in., and bottom ^ in. Then by rule previously enunciated — Total lead increase = f + ^" +1^" + h" = 2^". 2-" Advance pulley half sum = ^ — i j\ ". Answ^er. Line up rod half difference = ? " "" ^ = 1=5". Answer. These answers reversed give the solution to the question as originally stated. Lead of Double Ported Slide Valves.— For this type of valve the examples given for the single ported valve also hold good, but it must be remembered that the pulley or hner alterations only refer to one of the two top leads or one of the two bottom leads, as advancing the pulley, say, -^V i"-. will give I in. extra lead in all top and bottom. In the same way, lining up for say yV in. gives | in. more lead at bottom and | in. less lead at top, and taking out a j^}n. liner gives i in. more lead at top and ^ in. less lead at bottom. This is owing to the duplicating of the leads at both top and bottom due to the double ports. * NOTE.— In slide valve example No. 5 observe that the pulley requires to be advanced half the sum of the two lead increases top and bottom, which is equal to Slide Valves, Piston Valves, Valve Data, &c. 219 ,V in. + 1 in. or i\ in. in all ; the pulley is therefore advanced half of this, or ,''5 in. and a 3S in. liner put in to make up the difference top and bottom. In example No. 6, as the leads have to be decreased top and bottom, the pulley is put back .;\ in. and a .'. in. liner taken out. ♦ For the inside steam piston valve notice that liners are taken out instead of being put in, and and put in instead of being taken out, to give similar lead results top and bottom. Valve Setting. — The following example of valve setting from an engine of 2500 I.H.P., will give a fair idea a-s to the varying pro- portions of lap, lead, and port opening usually arranged for. Valve Setting. Cylinders, 27 in., 43 in., and 72 in.; stroke, 51 in.; pressure, iSo lbs. H.r. IM.P. 1 L.P. Valve Travel 7 in. Valve Travel 7 in. \'alve Travel 7 in. (Piston Valve). (Slide Valve). (D.P. Slide Valve). Tf.p. Bottom. Top. Bottom. Top. Bottom. Steam lap 2fV in. ilf in. I I ill. if in. iiifin- iliin. Port opening ItV in- ^i\ in. if in. if in. lijin. I If in. Lead iin. F'n- f in. h in- J in. fin. Cut-off - 33l in- 29^ in. 35c in- 34 in- 35f in- 34 in- Per cent, of stroke •62 (mean) •66 (mean) •66 (mean) Exhaust lap iVin- §f in. t in- 4 in. tV i"- 'Ain- Release 4I in- 3f in. 31 in. 2iin. 3t in- 2h in. Compression i 8 in. 81 in. 9h in. 10 in. io| in. 1 1 in. Referring to the above table of valve setting it is important to note the following : — 1. The top steam lap is more than the bottom steam lap. 2. The bottom port opening is more than the top port opening in proportion to the difference of lap and lead. 3. The sum of any lap and port opening top or bottom is just equal to half the valve travel. Referring to the H.P. valve : — Top steam lap = 2y\ in. Bottom steam lap =ijg-in. Top port opening = ly^^ in. Bottom port opening = lyV in. Half travel = 3^ in. The same holds good for each valve. Half travel = 3^ in. 220 " Verbal " Notes and Sketches 4. The cut-off is earlier on the up stroke in all three engines ; this is due to the angularity of the crank and connecting rod when link motion valve gear is fitted. The reverse should be the case, were it possible, as on the up stroke the weight of the working parts have to be raised against the force of gravity. With patent valve gear such as Brock's, Morton's, Joy's, &c., the cut-off can generally be arranged to be later on the up stroke, or equal on both strokes. 5. As less compression is required at top than bottom, it will be seen that the top exhaust lap is always less than the bottom, and is generally " minus " exhaust lap. To Find (approximately) the Depth of a Slide Valve. If the valve is broken up or not to be got, proceed as follows : — Obtain a flat board, and draw out on it, full size, the shaft diameter, the valve travel, and two centre lines. NOTE.— The valve travel can easily be found by taking the difference of the narrow side and the broad side of the eccentric pulley. Next, calliper on the shaft the exact distance between the eccentric keyseat centres, as shown at A, B of the shaft sketch, and transfer this distance to the shaft circle on the flat board, also marked No. 29. A, B. Now, from any one of these two points run in a line to the shaft centre, and where this line cuts the travel circle draw a horizontal line giving the distance C. The distance C is equal to the steam lap and lead added together Slide Valves, Piston Valv^es, Valve Data, 8cc. 221 so that if a certain lead is determined on, say } in., and subtracted from distance C, the amount left will then be the steam lap. Finally, measure the distance from the top of the top steam port to the bottom of the bottom steam port, as shown at D, and add to it tza'ce the steam lap, to allow for the top and bottom ; the result will then be approximately the required depth of valve. Or, D + (C - lead) x 2 = valve depth. NOTE. — The most accurate method is by that of the valve diagram (see page 249), but as the cut-off is not given in the question as stated above, this method cannot be applied. Connecting Rod Angle, &c. When the piston is at half stroke, as at B on the sketch, the crank is lying at the ani^le B above the horizontal. Again, if the crank is placed exactly horizontal, as at C, the piston will be a little /ozver than half stroke, as C on the sketch. The cause, in both cases, is the angle of the connecting rod, and the shorter the rod is made the greater No. 30 222 ''Verbal" Notes and Sketches will be the difference between the piston and crank positions at half stroke. If the slide valve has the same amount of steam lap and lead top and bottom, and the valve gear is of the ordinary link motion type, the effect of the connecting rod angle is to cut off the steam sooner on the up stroke than on the down stroke. In practice this difference of cut-off is partly corrected by lining up the slide valve, so that the top lap is more and the bottom lap less, and the bottom lead more and top lead less. Patent Valve Gears. Patent valve gears are fitted with the object of correcting the defects peculiar to the ordinary Stephenson link motion, and which are as follows : — 1. Wire drawing of steam owing to slow motion of gear at moment of cut-off. 2. Variation in lead and compression when linked up (usually increased). 3. Difference in cut-off on up and down stroke, with equal steam lap top and bottom, due to effect of connecting rod angle with crank, the cut-off being much earlier on the up stroke. 4. Space saved in fore and aft direction, as the valves can (in certain cases) be placed on the sides of the cylinders. 5. Eccentrics are done away altogether in certain gears (Joy, Morton), while in others (Hackworth, Brock, Bryce-Douglas, Bremme- Marshall) one eccentric only is required. Advantages of Patent Gears.— i. Most of the patent gears arrange for a quick travel of valve at the instant of cut-off, and thus reduce the wire drawing losses by giving a much sharper cut-off. 2. In the majority of patent gears the lead remains constant for all positions of the link, whether " full out " or " shut in." 3. Certain gears are arranged with compensating rods or links which give equal cut-off on both strokes, or allow for a later cut-off on the up stroke, which is better still. Disadvantage of Patent Gears. — The chief disadvantage of patent gears lies in the number of joints required, the slight wear of which (in the majority of gears) upsets the valve adjustment to a more or less serious degree, as the wear of, say, -^j in. in a brass may become magnified to three or four times that amount at the valve by means of the lever or link connected to it. In some gears as many as sixteen small pins and brasses are fitted, all of which require to be kept in practically perfect adjustment, if the correct setting of the slide valves or piston valves is to be maintained. 1, Eccentric rod. 2, Swinging link centre on reversing bell crank. 3, Astern position of swinging link centre. 4, Swinging link (Radius Rod). No. 31.— Marshall Valve Gear. 5, Link travel for "ahead," 6, Link travel hr "astern." 7, Reversing engine. 8, Slide valve spindle. [To fact page 23M. " Verbal " Notes and Sketches. rJ .3VJAV T 11 L TJ ilj O 9vIbV Il6rf81£.«"^/^ ,.T>t .jlOAl' ii^ ^ •iJtiao fvoT '>hin'V»33 itaSii alrui -^i-ij^uwe .* Slide Valves, Piston \^alves, Valve Data, Sec. 223 The general experience of engineers is that the disadvantages of patent gear more than balance the advantages, with the result that the ordinary Stephenson link motion will be found fitted in even the most modern and up-to-date marine engines, as being simpler and more reliable than patent \alve gears of any type. Marshall- Bremme Gear (one Eccentric) (Sketch No. 31). Marshall's and Bremme's gear are similar, the chief difference being that the valve link is connected to the efid of the eccentric rod in Bremme's gear, and the swinging link to the middle, whereas in Marshall's the valve link is connected to the eccentric rod about the middle of its length, and the swinging link at the end. Marshall Gear (Sketch No. 31). Type of Valve fitted. — Slide valve or piston valve with steam over ends Position of Eccentric. — Opposite crank (180°). Action. — The eccentric rod i is connected to the swinging link 4, which is hung on a pin 2 from the bell crank. The gear is shown in " ahead " position, and the travel of the link is shown at 5. The No. 32.— Link Travel of Marshall Valve Gear. " astern " position of the gear is shown at 3 and 6, as then the bell crank is moved over to the right by the rod 7 from the reversing engine. When the swing link is at position 3, the free end travels the arc 6, and thus changes the direction of the valve travel. The small Sketch, No. 32, shows the travel of the swinging link produced by the eccentric when in ahead position. Bremme Gear (Sketch No. 33). As before described, in this gear the valve link is placed at the end of the eccentric rod, which thus reverses the motion of the valve, r6 224 "Verbal" Notes and Sketches so that the pulle}- position is now with the crank in place of being- opposite to it as in Marshall's gear, otherwise the gear is similar. No. 33. — Bremme Valve Gear. 1, "Ahead" position of link. 2, ' ' Astern " position of link. 3, Valve rod link. 4, Reversing engine rod. Type of Valve fitted. — SHde valve or piston valve with steam over ends. Position of Eccentric. — With the crank. Action. — The action of the swing link 2 is as before described for Marshall's gear, but it should be noticed that the angle of the link is reversed in this case, position I being for " ahead " and 2 for "astern." The distance between the swinging link pin on the eccentric rod and the valve link allows for the required lead, and it should be noted that the end of the eccentric rod and valve link describe an irregular ellipse when in motion, the long sides of which incline to the vertical and produce the quick travel of valve at the cut-off positions. It may also be stated that with equal steam lap top and bottom the cut-off and release can be arranged to take place earlier on the down stroke than on the up stroke, this result being obtained by the ■ v')- tt. ! V -y ' 6 \\ uhl inBtbBup i{h^ biloa .^Ih.i' P *lt Tr\»\»ni\vV } No. 34 - Morton Valve Gear 1, Link suspended frorr rrosshead. 4. Suspension Imks from guide bracket 2, Lever connecting to quadrant rod 5 through small 5. Quadrant rod lever 3. 6, Crosshead of valve spindle, solid with quadrant. 3, Compensating lever. ?■ Wyper shaft 8, Reversing engine rod. {To/ate page 22%. • VerUI '■ Noles and Sketches. >f,^0 nvIfiV ^( M 4 :i3oid ,&>'. n>r. '•'■I. No. 35 —Joy Valve Gear. 1, Suspended link. 2, Compensating link. 3, Lever connecting compensating link and valve rod through quadrant block 4. 4, Quadrant block (travelling). 5, Angle of quadrant for "ahead." 6, Angle of quadrant for "astern." 7, Slide valve spindle. 8, Reversing engfine rod. ' Verbal "' Notes and Sketches. \To fate page 22g. Slide Valves, Piston Valves, Valve Data, &c. 225 lenf^th o-iven to the swinging link, the oscillations of which produce the^difiference in cut-ofif mentioned. It should also be noted that the lead remains constant for all grades of expansion. Morton Valve Gear (Sketch No. 34). This valve gear consists of a series of levers and links, connected to a vertically moving quadrant which is in one with the valve spindle, no eccentric being required, as the valve motion is obtained from the connecting rod. Type of Valve fitted. — Slide valve or piston valve with steam over ends. Action. — The valve lever 2 is suspended from the crosshead by the link I, from the connecting rod by the pivoted arm 3, and from the guide bracket by the heavy links 4, at a point near the outer end, the end of the lever being connected direct to the valve link 5, which gives vertical motion to the quadrant and thus to the valve: the small compensating arm 3 corrects the unequal effect of the connecting rod. Notice that the centres of the suspension link 4 are not in line with the valve spindle, and when the crank is centred the links 4 are parallel to the centre line of the engine, and in this position the valve link 5 ma)' be moved over the quadrant from one side to the other without moving the valve. When linked up, the lead remains the same as in full gear, and equal steam lap gives equal cut-off top and bottom. Joy Valve Gear (Sketch No. 35). This gear is similar to Morton's in the fact that links and a quadrant take the place of eccentrics, the connecting rod supplying the necessar)' motion to the valve. Type of Valve fitted. — Slide vahe or piston valve with steam over ends. Action. — The suspended link i on the column connects to a vibrating link 2 on the connecting rod, and the \ahe lever 3 is fixed to a pin on this link at an intermediate position. Near the other end of the valve lever is a fulcrum point which slides back and forward on the quadrant bar by means of a block 4, the actual end of the lever being connected direct to the valve link and spindle 7. The angle given to the quadrant hy the reversing engine 8 determines the direction of rotation, 5 being for "ahead" and 6 for "astern," the block 4 sliding back and forward in the dotted arc shown. When the quadrant is in a horizontal position (as shown in Sketch No. 35) the gear is in the neutral position. It should be noted that 226 ''Verbal" Notes and Sketches the quadrant bar is hinged at the centre to a supporting bracket bearing on the left column. The leverage given by the distance from the fulcrum point on the lever to the end allows for the "steam lap + lead" travel of the valve, while the to-and-fro travel of the block 4 on the quadrant bar allows for the additional port opening travel required. Hackworth Gear (Single Eccentric) (Sketch No. 36). This gear works on the same principle as the Bremme-Marshall Gears, but instead of the swinging link an inclined bar is emplo\'ed, on which a bearing block connected to the end of the eccentric rod slides up and down with the motion of the pulley. Type of Valve fitted. — Slide valve or piston vahe with steam over ends. Position of Eccentric. — At 90' leading the crank. Action. — The bracket i supports the pair of slide bars 2 by a pin and brass as shown, and the angle given to the slide bar by the re\ ersing engine rod 9 determines the position of the gear whether " ahead " or " astern." The motion of the eccentric rod is carried to the valve link 7 through the bell crank 6 by means of the double link 5 con- nected to the eccentric rod by a large pin joint ; adjustable slippers 3 are fitted to the end of the eccentric, and the dotted lines show the angle of the bars for ahead or astern running. In the Sketch the gear is shown in mid position, the valve travel being then equal to the steam lap + lead for either end, the side way slide motion of the eccentric rod in the bars allowing for the additional port opening required. The slide bars angle is changed by means of the usual drag link 8 from the reversing engine, and an expansion slot of the usual type is fitted for working " linked-up." No. 37.— Eccentric Rod at Limit of upper travel on Slide Bar, No. 36— Hackworth Valve Gear. 1, Supporting bracket for slide bars. 2, Slide bars for slippers 3. 3, Slippers on end of eccentric rod. 4, Eccentric rod. 5, Links connecting eccatric « od and valve bell cranlr " Verbal " Notes and Sketches. 6, Valve bell crank working on fixed bearing. 7, Valve link. 8, Drag link. 9, Reversing engine rod. \.To face page 226. I, Eccentric rod. 3, Rocking quadrant- 3, Valve link. 4, Lever connected at one end to valve link, and at the other end to crosshead link 7, also connected to the valve spindle near the end. 'Vurhal' Notc?.-.nrI Sketches. No. 38,— Brock Valve Gear. 5, " Ahead " position of valve link. 6, " Astern " position of valve link. 7, Crosshead link 8, Crosshead sliopet- 9, Valve spindle- 10. Drag link. 11. Reversing engine rod. 12. Guide on column. in/iuefagt 227. ^^ " s^^ - »3^v»&\tr i II il i]A3HA ^ .IB^D 5vUiV 3i301 3vLaV ,Q .jlnil ^vi No 39 — Bryce-Douglas Valve Gear. I, Link suspended from crosshead. 4, Quadrant rod. 3, Lever connecting crosstiead with valve rod 5 5, Valve rod. through a fulcrum oil bell crank 3 6. "Ahead" position of quadrant 3, Bell crank working on fixed bearuig. 7. •■ Astern" position of quadrant 8, Reversing engine rocL ' Verbal " Nol I Sketches. Slide Valves, Piston Valves, Valve Data, &c. 227 The small Sketch, No. 37, shows the gear in " ahead " position, with the slipper at the upper limit of its travel on the incHned bars. In this gear the bearing of the bell crank (6) shaft is subject to the most wear, and requires the most frequent overhaul, as the setting of the valve is affected by wear down of this bearing. Brock Gear (Single Eccentric) (Sketch No. 2,8). In this gear a rocking quadrant actuated by the eccentric is employed to convey the motion to the valve. Type of Valve fitted. — Piston valve with steam inside. Position of Eccentric. — Following the crank at an angle of 90' less steam lap and lead. NOTE.— As in the case of other single eccentric gears (such as Hackworth's and Bremme's) the travel of the pulley exceeds the actual travel of the valve, as the motion is reduced down from the extended end of the quadrant in the present case. Action. — The eccentric rod i gives motion to the rocking quadrant 2, which is hinged on a bracket cast on the engine framing, and this is transmitted to the valve by means of the link 3 and travelling lever 4. This lever is held at the other end to a bracket cast on the crosshead, and travels to and fro with the piston rod stroke. The valve spindle is connected to lever 4 at a point near the end, thus giving a small leverage which allows for the " lap + lead " travel of the valve, the remainder of the travel required to give port opening being obtained by the rocking motion of the quadrant produced by the eccentric 5 being the " ahead " position, and 6 the "astern " position of the link, as shown by the dotted lines. The drag link 10, moved by the reversing engine links ii, changes over the link block to the "ahead" or "astern" position as required, and the gear can be linked up by means of the expansion slot shown in the reversing bell crank. In all positions of gear the lead remains constant, and is unaffected by linking up. NOTE.— The Sketch shows the gear as applied to a diagonal type paddle engine, but if the reader turns the page round so that the gear, assumes a vertical position with the shaft below, the position of the gear as applied to an ordinary triple expansion marine engine will be obtained, and can be studied. Bryce-Douglas Gear (Single Eccentric) (Sketch No. 39). In this gear a fixed quadrant and travelling block, actuated by a single pulley, is employed, together with a link, lever, and bell crank. Type of Valve fitted. — Slide valve or piston valve with steam over ends. 228 Verbal " Notes and Sketches Position of Eccentric. advance of the crank. -At an angle of 90" plus lap and lead in Action. — The eccentric rod block travels back and forward in the slot of the quadrant, which is hinged on a bracket bearing as shown, the angle given to the quadrant by the reversing engine 8 determining the direction of rotation whether "ahead" or "astern," 6 being ahead and 7 astern : from the quadrant the motion is carried to a fixed TRAVEL CENTRE No. 40. Slide Valves, Piston Valves, Valve Data, &c. 229 bell crank 3 by a link 4, the otlier arm of the bell crank finally giving the motion to the valve link 5, through the lever 2, suspended from the engine crosshead by the small link i. Observe that the lever 2 is fulcrummed near the end by a pin to the bell crank, and the leverage to the valve spindle obtained in this way allows for the " steam lap + lead " travel of the valve, the additional travel necessary to give the required port opening being obtained by the travel of the block of link 4 in the quadrant ; the lead is therefore constant for all positions of the gear, whether " full out " or " shut In." As before stated, the quadrant is hinged by the centre, and is canted over to the required ahead or astern angle by the drag link of the reversing engine, and remains in that position, the block travelling back and forward by the action of the eccentric. Link Motion. — In the most modern types of reciprocating engines, the " Stephenson " link motion gear is generally fitted, patent valve gears having been not altogether satisfactory in many respects, experience proving the superiority of the old t>pe of gear. Observe that the link radius is equal to the distance from the pin centre B to the pulley centre, and the centre of curvature is found by describing an arc from the pulley centre to the shaft centre line, as shown by the small cross. S = valve travel x 3. T = throw or eccentricity. E = steam lap plus lead. No. 41. — Reversing Quadrant and Block. NOTE.— Distance D should be equal to three times the valve traveL 230 "Verbal" Notes and Sketches Linking Up.— Assuming pin A to be in line for "full gear," in linking up, the pin B is moved over towards the valve spindle block C, so that the effect is to reduce the valve travel. The general results of linking up are as follows : — (i) Travel reduced. (2) Port opening reduced (producing wire-drawing of the steam). (3) Cut-off sooner, (4) Lead increased (with rods " open," crank on bottom). (5) Compression increased. Generally speaking, all points occur earlier. NOTE. — With the gear in mid position as shown, if the engine is turned one revolution with the turning gear, the valve will travel a distance equal to twice the Steam lap and lead. Example. — To prove by a valve diagram that with equal laps on the valve, top and bottom and ordinary link motion valve gear, the steam is cut off sooner on the up stroke. NOTE. — This difference in cut-off is caused by the connecting rod and crank angle. ADMISSION No. 42. Referring to No. 42, set oft" top and bottom of the valve travel circle, small circles equal in radius to the lead ; also from the centre of the travel circle set off" with the compasses the amount of steam lap on the valve ; now draw tangents to both the lead circles and the lap arcs, and the crank angles at " Admission " and " Cut-off" will be obtained. Slide Valves, Piston Valves, Valve Data, &c. 231 Next, take with the compasses the length of the connecting rod as radius, and putting the pencil on the crank position at "Cut-off, " and the needle on the centre line, draw arcs inwards to the centre line to obtain the distance the steam is carried on the down and up strokes respectively. It will then be found, on measuring, that the distance U is less than the distance D, that is, the cut-off occurs earlier on the up stroke than on the down stroke, owing to the angle formed by the connecting rod and the crank. NOTE.— For complete explanation of Valve Diagram, see page 248. Eccentric Keyseat Templates. Without Steam Lap and Lead. — If a valve has no steam lap lead, as, for example, a stearing gear engine valve, the keyseat position is at right angles, or 90" to the crank leading it (Sketch No. 43). In this case the steam is carried the full length of stroke, and, with the crank on the centre, the valve is exactly at mid position, ready to open for steam. The valve travel will then be equal to twice the port opening. With Steam Lap and Lead. — When a slide valve has steam lap and lead the sum of the mean steam lap and lead must be measured down from the centre, and a horizontal line drawn through the travel circle, then lines drawn out to the shaft circle through the points of inter- section from the centre, will give the correct keyway positions ahead and astern (Sketch No. 44). The valve travel circle diameter is equal to tzvice the steam lap anc' steam port opening. The key- seat position is therefore 90", plus lap and lead, in advance of the crank, as when the crank is centred the valve is lower than mid position by a distance equal to the steam lap and lead. Piston Valves. — For a piston valve of the inside steam type as commonly constructed, the valve travel motion is reversed from that of a slide valve, as, instead of moving down to give lead and steam to the top port the valve requires to move up. This necessitates the position of the keyways being changed to scarcely the opposite side of the shaft (Sketch No. 46), the position being therefore 90° behind the crank less mean steam lap and lead. In setting off the keyseat template the mean steam lap and lead have to be measured up from the shaft centre. To sum up, for a common slide valve or a double ported slide valve the keyway is cut at an angle greater than 90' leading the crank, but for a piston valve the keyway is cut at an angle less than 90° following the crank. NOTE. — After the keyways are cut and the pulley secured to the shaft, a liner may require to be fitted under the rod if a slide valve, or a liner taken out if a piston valve, to give more lead at bottom than top. 232 "Verbal" Notes and Sketches Eccentric Keyseats. Crank on Top Centre. LEVELLED No. 43. — Valve without Steam Lap and Lead (Steering Gear Engine Valve). Keyseat at right angles to crank, if a slide valve leading the crank, if a piston valve following the crank. Slide Valves, Piston Valves, Valve Data, &c. 233 Crank on Centre. LEVELLED No. 44.— Slide Valve with Steam Lap and Lead. Shaft, 12 in. diameter. Mean steam lap, 2 in. Mean port opening, ij in. Mean lead, | in. Then, (2+i-5)x2 = 7 in. valve travel. iA.nd, B = steam lap + lead =2 + ^ = 2^ in. 234 "Verbal" Notes and Sketches Crank on Centre. VALVE TRAVEL LEVELLED No. 45.— Double Ported Slide Valve. Shaft, 12 in. diameter. Mean steam lap (each of two, top or bottom), 2 in. Mean port opening „ „ „ i| in. Mean lead, ^ in. Then, (2 + 1-5) x 2 = 7 in. valve travel. And, B = steam lap + lead = 2 + | = 2| in. NOTE.— Only one of the two top or bottom laps and port openings are taken, and not the combined or total lap and port opening at either end. Slide Valves, Piston Valves, Valve Data, &c. 235 Crank on Centre. LEVELLED No. 46.- Inside Steam Piston Valve. Shaft, 12 in. diameter. Mean steam lap, 2 in. Mean port opening, i| in. Mean lead, ^ in. Then, (2+1-5) x 2 = 7 in. valve travel. And, B = steam lap + lead = 2 + | = 2^ in. NOTE. — As the valve motion is reversed from that of a slide valve, the mean steam lap and lead are measured up from the centre with crank on top. 236 "Verbal" Notes and Sketches LEAD CUT-OFF Wv^'yvVv'; '.vs.v ^^^^v^v ^ ^ ^^ '^ ^^^^^\\\\-.x^:s\x\\xV''''^^''^^^Y'-'^'''''^^'^^'-'^^''- EXHAUST OPENING No. 47.— Slide Valve and Piston Positions. Slide Valves, Piston Valves, Valve Data, &c. 237 LEAD CUT-OFF EXHAUST OPENING EXHAUST CLOSING. No. 48— Piston Valve and Piston Positions. 238 "Verbal" Notes and Sketches Action of Steam in a Cylinder. During one revolution the action of the steam on one side of the piston is as follows : — With the crank on the top centre the top steam port is open for the amount of lead ; the valve then moves down and opens the port further, and the piston moves down to, say, half stroke, when the valve moving up again cuts off the supply of steam. The steam in the cylinder expands and forces the piston down towards the end of the stroke, and when near the bottom centre the port opens to the exhaust ; the piston then completes the stroke and travels up again, and when near the top centre the port is closed to exhaust. The steam thus retained in the cylinder is compressed by the return- ino" piston to an increased pressure, and cushioning is effected ; the piston next reaches the top centre, and the port again opening for lead, the same cycle of operations is repeated. Notice that " exhaust opening " occurs when the piston is near the end of one stroke, and " exhaust closing " when the piston is near the end of the other stroke. NOTE. — A piston valve travels in the reverse direction to that of a slide valve in the above cycle of operations, as vdll be seen by comparing the sketches of each. Observe that in " lead " and in " cut-off" the valve is in the same position, but going down for " lead " and going up for " cut-off." Also that for "exhaust opening" and "exhaust closing " the valve is also in the same position, but going up for "exhaust opening" and going down for "exhaust closing." Again notice that the piston is near the bottom for " exhaust opening," and near (not at) the top for " exhaust closing." Observe that as steam is entering from between the pistons, the valve requires to travel in the rev^erse direction to that of a slide valve to give similar results. In "lead" and in "cut-off" the valve is in the same position, but is going z// for "lead" and going down for "cut-off." In "exhaust opening" and in "exhaust closing" the valve is in the same position, but is going doivn for "exhaust opening" and up for "exhaust closing." NOTE. — Between the positions of "Cut-off" and "Exhaust Opening" ("Release") the steam in the cylinder expands in approximate accordance with Boyle's Law of Expansion ; that is, the volume is increasing and the pressure decreasing proportionally: between the positions "Exhaust Closing" ("Com- pression") and " Lead" the steam is also following out this law but reversed in action, as in this case the volume is decreasing and the pressure increasing proportionally. ~'~^~~~ \ae( Cf09iu&; i^FV-. &■ w V X lio \ VALVE DATA. | trovjl -8 Top Bot Liod, \ » £ih«OrT\ \op. 24 2l Ft,h Ootninq li ll £»K lof +t + 1 Lead B. Cut off. No. 48a.— Valve and Piston Positions. For one revolutioo, top side of piston. (Aogle of coonectiag rod and crank neg^Iected.) C. Release (exhaust opening). D. Compression (exhauit closing) The above diagram illustrates the comparative positions of piston and valve referred to the valve diagram, cylinder stroke, afid indicator card : the relative positions of crank and eccentric are also shown throughoul. Observe that the valve data table given corresponds with the keyseat template, but it should be carefully noted, that after cutting the keyseats and bolting on the pulleys a liner is required to go in under the foot of the rod to give the required difference in steam lap and lead lop and baltotn, in this case a iiner A in. thick, or eaual in thickness to half ihp lead Hiflpr*>nr*> ac *— til^' = T equal in ihickni required. By "admission" is mear is to half (he lead difTere the position of the crank when steam I E. Admission. It the port i the cylinder, "■ lead " being the amount the port is actually open when the crank is a. dead centre, in the present case \ in. Notice where this shows on the valve dia^jram. The following points should be carefully noted, 1. Top Steam Lap 4- Lead - Bottom Steam Lap + Lead. 2. .. .. + Port Opening-- .. t Port opening ^ half valve t Therefore Top 2i + i = 2), Also. Top aj ni=4in. (half travcll. Bot. 2j + i^af. ., Bot23*ig-4., NOTE.~The reader is advised to study carefullj the nrious positions of valve and [ NOTE.— For detailed description of valve diagram t Slide Valves, Piston Valves, Valve Data, &c. 239 Valve Setting Tables. The following tables of valve settings, showing lead, steam lap, exhaust lap, cut-off, &c., for both up and down strokes, are from a set of engines of a modern fast passenger steamer, and should be care- fully studied. The differences in lead, steam lap, port opening, cut- off, &c., occurring on the up and down strokes, and chiefly due to the effect of the angle of the connecting rod and crank, when link motion is fitted, are of great importance to the student, and the writer strongly advises special attention to this subject, as being one of particular interest and benefit to the marine engineer. No. I — Type; — Fast Passenger Steamer. — I. H. P., 4500; Speed, 21 knots ; Cylinders, 27, 44, 70 inches ; Stroke, 2 feet 9 inches ; Boiler pressure, 185 lbs.; Revolutions, 180; H.P. cylinder M.E.P. = 65 lbs. ; I. P. cylinder M.E.P. = 32-2 lbs. ; L.P. cylinder M.E.P. = 16 lbs. ; Link motion valve gear. H.P. Piston Valve. 1 Exhaust Exhaust > Lead. Steam Lap. Tort Opening. Exhaust Lap. Cut-off. Opening (from end Closing (from end Expansion H of stroke). of stroke). (jrade. > Top In. Bot. Top. Bot. Top. Hot. Top. Bot. Top. Bot. Top. Bot Top. Hot. In. In. In. In. In. In. In. In. In. In. In. In. In. In. ■75 (full out) 8 3 8 7 17 .1 3 ^16 if 2t% 2h .3 ~ 16 + A 26| 23i 4 4 2rV 2t\ •58 (shut in) 6| 1 1 2 1 Sir ^U If lA •1 3 ~ TIT + -A 2l| i6tV 5tV 6 5i Astern - - 8tV 1 3 .T2 1 1 32 III If 4 III 3 ~T5- + A 27i 22f 4 2f 3 2tV LP. Piston Valve. •70 (full) - 8 8 T8 2 III 2 ^tV 3 ~ 16 + tV 24I 2If 4 2l 3l 3h • 53 (shut in) 6.1 1 I t§ 2 lit ItV ^11 3 <-T6 19I •51 5f 5f 6f 6| Astern - - 8tV 3 8 7 T6 2 III I^ 2| 3 ^ 16 + T1S 24f 23I -i 2^ 3Tff 3t'7l 221 I2| NOTE.— The small letter B signifies "bare" and the letter F "full." Observe that /la// the valve travel is equal to steam lap and port opening, and that if the travel is decreased by shutting in the link the port opening (not the steam lap) is decreased in exact proportion. Also notice that at all grades of expansion the up stroke cut-off is sooner than the down stroke, the cause as previously explained being the angle of the connecting rod and crank when link motion valve gear is fitted. " Linked-up" Effects. 1. Valve travel reduced. 2. Lead increased. 3. Steam lap unaltered. 4. Port opening reduced. 5. Cut-off, exhaust opening, and exhaust closing all occur earlier on the stroke. If H.P. link is the one shut in then less steam is admitted to the engine as a whole, which means less revolutions, LH.P., and speed. If the LP. or L.P. links are shut in, no appreciable difference in total power results, but the pressures in the LP. or L.P. receivers are varied, which produces a change in the distribution of the power developed in 244 "Verbal" Notes and Sketches each cylinder of the engine, the adjustment of which depends greatly on the setting of the links of each valve. No. 3 — Type; — Cargo Steamer. — Cylinders, 27,43, 72 inches; Stroke 51 inches; Boiler pressure, 180 lbs.; I.H.P., 2550; Link motion gear. Valve Settings. H.P. Piston Valve. Expansion Grade (mean of top and bottom). > H >_ > Lead. Steam Lap. Port Opening. Cut-off. Exhaust Lap. Com- pression (from end). Top. Bot. Top. Bot. Top. Bot. Top. In. 33b- Bot. Top. Bot. Top. Bot. •62 In. 7 In. In. 3 s In. 2tc In. In. lye lye In. In. 29I In. 1 T6 In. 25 32 In. 8 In. 8i LP. Double Ported Valve. •66 7 8 1 ^l '1 ll 35i 3ii :5 8 4 10 loi L.P. Double Ported Valve. ■66 7 i 5 8 ill i ill ri3 35l 3'l 7 16 I A loL 1 1 Example i. — Referring to the foregoing : — Half travel^7v2=3-5 = Steam lap-fport opening. H.P. valve, top steam lap =2y\ inches. „ „ port openings I /jj ,, Then, 2y\-Hi^5=3J inches half travel. L.P. valve, bottom steam lap =i\l inches. ,, „ port opening=i}J ,, Then, iTc + irl=3i inches half travel. Example 2. — Rule — Top steam lap + lead = Bottom steam lap -t- lead. H.P. valve, top steam lap = 2iV inches. >j ,, lead = I inch. Then, 2,V. + J -^ 2i\ inches. Again, HP. valve, bottom steam lap = i|^ inches. >. ,, lead = I inch. Then, t.\1-^% = 2^% inches. Slide Valves, Piston Valves, Valve Data, &c. 245 Example 3. — Then, Then, Again, Then, L. P. valve, top steam lap =i}^ inche^. ,, ,, port opening = i[J ,, iic + iiti— si inches half travel. L. P. valve, top steam lap = i}g inches. ,, ,, lead = ^ inch. lie + 2 = 2y'% inches. L. P. valve, bottom steam lap = i j * inches. ,, ,, lead = ^ inch. ixh + ^ = 2i% inches. Again observe that in each cylinder the cut-off takes place earlier on the up stroke. No. 4 — Type; — Fast Cargo Steamer. — I.H.P., 2200; Cylinders, 26, 44, 70 inches ; Stroke, 48 inches. Valve Settings. H.P. Piston Valve. Expansion Grade (mean of top and bottom). > Lead. .Steam Lap. Port Opening. Exhaust Lap. Exhaust Opening. Exhaust Closing. Top Bot. Top Bot. Top. Bot. Top. Bot. Top. Bot. Top. Bot. ■66 In. 6f In. .3 Te In. T6 In. 2 In. In. ^1 In. In. In. 4- « + 10 In. 3l In. 32 In. 6| In. 6 LP. Double Ported Slide Valve. •66 7 1 5 liT 2 41 It«F ,11 .-5 1 + ^^ 4| 4 51 4f L.P. Double Ported Slide Valve. ■66 7 us in 2 lU r i|b ^ 8 3l 3I 6 5? NOTE. — In the above example the sum of the steam lap and port opening shows a slight difference from half the valve travel in the case of the LP. and L.P. valves, this being accounted for by the angle and crossing over action of the eccentric rods. The mean cut-off in each cylinder = 32 inches. Therefore, 32 inches -^ 48 = -66 Expansion Grade, 246 "Verbal" Notes and Sketches No. 5 — Type; — Large Cargo Passenger Steamer. — Speed, 14 knots ; I.H.P., 6000; Quadruple expansion cylinders, 3U, 45, 64, 92 inches; Stroke, 60 inches ; Boiler pressure, 200 lbs. VALVE SETTINGS. H.P. Piston Valve (20 inches diameter). Expansio n Grade (mean of top and bottom). H > Lead. Steam Lap. Port Opening. Cut-off. Exhaust Lap. Release. Com- pression. Piston Clear- ance. Top Bot. Top. Bot. In. Top. Bot. Top. Bot. Top Bot. Top. Bot. In. Top In. Bot. In. Top In. Bot. In. In. In. In. In. In. In. In. In. In. In. In. Full gear 9h 1 8 1 i H\ 2tV 21/2 -I 44i 39h 1 8 1 n 16 4 H 7 7l 3 8 I Shut in - 7M 1 1 ■6'1 T6 ^A 2tV T 5 ^s% 34 25-1 1 • 8 1 ?, T6 8 7 14 14 8 I 1st LP. Martin and Andrews' Patent Valve (seepage 207). Full gear loi ■•5 16 3 8 41 ^A 2f 2tV 43 38I 2 9 64 9 32^ 5f 5i 6 6| I I Shut in - 8A 7' T6- 5 8 2II 2tV I/^ If 24i 26I 29 64 9 32 "1 loi III I2J 5 8 I 2nd LP. Martin and Andrews' Valve. Full gear loi 1 4 h ,13 4 2M 2f 44| 40 2 9 ^4 9 32 5l 5f 5 5i 5 16 2 9 32 Shut in - 81 1 7 Ti2 2 5 32 ,13 2t6 4 iM If 31I 28I 29 6T 9 ^2 nf 14 10 I Of 5 T6 2 9 32 L.P. Double Ported Slide Valve. Full gear 9h 5 T6 1 ,13 4 4 2U 395 35l 5 2 9 32 4I 5l lo-l 9^ 5 T6 1 3 16 Shut in - 1 711 1 7 13 ,13 4 ii.^^ lA 27 24f 5 16 2 9 Si 9 9^ 18 i6| 5 13 IF i NOTE.— By "release" is meant the position of the piston from end of stroke at moment of exhaust opening. By "compression" is meant the position of the piston from end of stroke at moment of exhaust closing. Slide Valves, Piston Valves, Valve Data, &c. 247 Mean Cut-off and Expansion Grade. — These are determined as follows : — H.P. Cylinder, Full Gear — Top cut-off =44 J inches, Bottom cut-off = 39| ,, Then, 44:^ ±39:5 _ 41.875 inches mean cut-off. Expansion Grade = 4i-875 inches -;-6o inches (stroke) =69 of stroke ist LP. Cylinder, Full Gear — Top cut-off -43 inches, Bottom cut-off =393 ,, Then, ^ — ^^'^'^ = 41-18 inches mean cut-off. 2 Expansion Grade = 41 -18 inches -f 60 inches =-68 of stroke. 2nd LP. Cylinder, Full Gear — Top cut-off =44i inches, Bottom cut-off =40 ,, Then, 44i-?_5_M9_, 42-31 inches mean cut-off. Expansion Grade =42-31 inches -f 60 inches = -70 of stroke. L.P. Cylinder, Full Gear — Top cut-off =39^ inches. Bottom cut-off =35 J ,, Then, 5?-5 — 35' 5 -37-37 inches mean cut-off. Expansion Grade = 3737 inches -f 60 inches = -62 of stroke. 248 " Verbal " Notes and Sketches No. 6 — Type; — Cargo Steamer. — I.H.P., 1630; Speed, ii-6 knots; Cylinders, 26, 42, 70 inches ; Stroke, 48 inches ; Boiler pressure, 180 lbs.; H.P. receiver, 175 lbs.; LP., 56 lbs.; L.P., 9 lbs. ; Vacuum, 24 inches ; Revolutions, 60-5. VALVE SETTINGS. H.P. Piston Valve. Expansion Grade (mean). 1) > H > Lead. Steam Lap. Port Opening. Cut-off. Exhaust Lap. Release. Com- pression. Top Bot. Top. Bot. Top. Bot. Top. Bot. Top Bot. Top Bot. Top. Bot. •52 In. 7 In. In. 3 s In. 2tf In. In. In. In. 27| In. 2 2f In. 1 T« In. 1 .", 10 In. 5f In. 5* In. 9l In. 9I LP. D.P. Valve. •62 7 S 1 2 2 I^ 4 l| 3^1 28i T6 li 31 4 lo| lof L.P. D.P. Valve. •56 7 1 11 T6 2tV ill ^16 Ifp 1 ^ 29^ 25-i A li 44 3I 12I I2f NOTE. — The above is a very fair example of valve setting- for a set of engines of the power given, and the results as tabulated represent good practice. It will be noticed that the "compression" or exhaust closing- position occurs earlier in the I. P. than the H.P., and earlier still in the L.P. This is to allow for the heavier weight of the moving parts in these cylinders, the inertia of which has to be overcome at the end of each stroke. Observe, then, that — 1. The amount of lead opening increases with each cylinder. 2. „ „ exhaust lap „ „ „ 3. The moment of compression (exhaust closing) is earlier in each cylinder from H.P. to L.P. Valve Diagrams. By means of the well-known " valve diagrams " devised by Zeuner the eminent Swiss engineer and scientist, the required steam lap, port opening, exhaust lap, &c., may be calculated for a valve, and the following example from actual practice should be carefully studied. Slide Valves, Piston Valves, Valve Data, &c. 249 Example. — Engine stroke, 42 inches ; connecting rod, 7 feet 6 inches in length ; valve travel to be 7^ inches ; top lead, ^ inch ; bottom lead, ^ inch; bottom exhaust lap +^ inch; top exhaust lap —I inch. (A.) Find the required steam lap and port opening for a maximum down stroke cut-ofif of -7. (B.) Also find the cut-off on the up stroke due to the necessary difference in steam lap and lead at the bottom as compared with the top. NOTE.— The sum of the steam lap and lead is the same top and bottom, there- fore what is gained in lead at the bottom end is lost in steam lap ; this also propor- tionally alters the maximum port opening. Application. — Stroke, 42 inches x 7 = 29-4 inches cut-off on down stroke, (A.) First set off to a small scale (say i inch to i foot) the small diagram of crank-pin circle and crosshead or piston travel as shown in No. 49, proceeding as follows : — 1. Set off vertically 42 inches by scale, then measure down from the centre of this, or half stroke the connecting rod length of 7 feet 6 inches which gives the centre of shaft ; next with a radius of 21 inches (half stroke) set off the crank-pin travel circle. Now measure down from the top of stroke 29-4 inches (shown by the inch divisions from the 24-inch distance) and with the connecting rod length of 7 feet 6 inches in the compasses set the needle point on the crosshead centre and make a mark, F, on the crank-pin circle : this mark F is the position of crank-pin centre at cut-off. Connect the shaft centre and F, the crank-pin centre, which gives the crank angle at the "cut-off" position. 2. To a scale of full size, or at least half size, set off the valve travel circle of 7^ inches diameter, and with the lead radius of -^- inch also set off an arc from the top diameter of the circle marked as L ; now transfer the angle of the crank at cut-off from the small diagram to the larger one, by describing a radius as at B, which is again repeated on the large diagram at B, and the length between taken in the compasses from the small diagram and measured off on the large one as shown : this gives the exact angle of the crank at cut-off, which is carried out as shown to point 2 on the valve travel circle. 3. Draw a line from point 2 tangentially to the lead arc L, and where it cuts the valve circle put in by hand a small locating circle, also one at point 2 ; now bisect the line extending between points I and 2, by either describing arcs as shown, or by trial with the dividers, and draw out a line from the centre. We then find the required steam lap and maximum port opening as measured, the steam lap being 2yV inches, and the port opening ifV inches, the sum of the two (2^-V+ii% inches) being, of course, equal to half the valve 2 50 "Verbal" Notes and Sketches travel, or 3I inches; finally describe a circle on the line as shown, called the primary valve circle. I2'' 24" 36" 42' < 294"--- --> ^ UJ -:v .^,' Eri IV V \ \-a_ \cr> r No. 49. 4. Set off a small semicircle, E, \ inch radius on the line last mentioned, which semicircle represents the minus exhaust lap of the No. 50.— Vah L = Lead ^ inch. f, Crank Angle at Lead. 2. ,, „ Cut-off. VerUal"' Notes and Sketches. No. 50-— Valve Diagram for Top. L = Lea >> 2. Crank at cut-off 2B. „ „ 3. Crank at release 3^' >) " 4. Crank at compression 4B. „ n Full gear. Linked up. Full gear. Linked np. Full gear. Linked up. Full gear. Linked up. If the various crank angles are now transferred back to the small scale engine stroke diagram, as described previously, the new positions of release, compression, &c., can be determined. In the example shown the Hnked-up data work out as follows : — Valve Data (Linked up). Valve Travel, 6 in. Lead. Steam Lap. Tort Opening. Cut-off. Exhaust Lap. Release. Com- pression. Top - In. 7 16 In. 2A In. 1 3 1 b In. In. 1 4 In. In. 1 1 NOTE.— It should be carefully noted that the gear is of the open rods type, that is, with the crank on bottom centre the rods are open as showrn in the Sketch No. 22. If with a slide valve the rods are arranged "crossed " the lead would be less, and the expansion range much more limited, as the arc C,E, would then require to be taken from a centre above the shaft in place of below, and this would result in the arc being convex to the shaft centre line instead of concave as at present. To find Valve Travel. (No. 59.) In a case where the steam port opening is decided upon first of all, the required valve travel (and therefore steam laps) may be deter- mined by the following construction. First set off, to a suitable scale, ACB, the crank pin travel circle, OB being the angle of crank at cut-off. Join AB, and bisect it at point C, now join AC, and set off at D, DE, the port opening determined on, less the lead ; next draw a line at E parallel to AD, and where the line so drawn cuts AC at F, draw a short line parallel to OC into the centre line at G ; then EG is equal to half the valve travel, so that twice EG will give full travel of valve required. Bellis and Morcom Engine. This type of engine is compound with the valve chest common to both cylinders placed between them, the valves of the piston type being arranged tandem fashion, and on the same valve spindle. Action.— The engine cranks are opposite each other, or are at an angle of 180°. The H.P. piston valve receives steam in the centre c Of — 4b VALVE TRAVEL 7 2 sro : S V SB' " 5' C^^vp iru&{& IB MO o> \ 4b»' VALVE TRAVEL 7''2" No. 58.— Valve Diagram showing Effects of Linking Up. 1, Crank angle at "'lead," full gear. 3, Crank angle at "release," full gear. IB. ., ,. ., linked up. 3B, ,, linked up. 2, Crank angle at "cut-off," full gear. 4, Crank angle at •■ compression," full gear. 2B. „ » „ linked up. 4B, .. ., „ linked up. Slide Valves, Piston Valves, Valve Data, &c. 261 No. 59.— Construction to find Valve Travel. No. 60. — Bellis and Morcom High Speed Compound Engine. 262 " Verbal " Notes and Sketches or inside edges, and the L.P. valve receives steam at the ends or outside edges, so that the exhaust of the H.P. valve being over the ends serves as the admission steam for the L.P. valve, the exhaust of the L.P. valve opens up to the exhaust casing and exhaust pipe to the condenser. Notice that the valves are hollow cast to allow of steam flow from end to end. The sketch and following data of valve setting for this type of engine are taken from the Mechanical ^Fi!7r/(f/ of September 1910. Data for Bellis and Morcom Engine. Cylinders, 10 inches diameter and 17 inches diameter; stroke, 9 inches; piston valves, 6| inches diameter ; revolutions, 400. Valve Travel, 2% Inches. II. 1'. Cylinder. L.P. Cylinder. Top. Bottom. Top. Bottom. Steam Lap Lead . . . - Cut-off (Mean) - Inch. 2 7 T52 1 a 2 Inch. 1 .'5 T6 1 T6 Inch. f 1 8 Inch. 1 1 T6 t"r ■64 •66 NOTE.— Observe that the sum of the top or bottom steam lap and lead is the same, or, in other words, Twhat is gained in lead at the bottom end is lost in steam lap, the sum of the two remaining the same. Referring to table H.P f Top, I Bottom :j 2 ^ :3 2 ' 16^16 li 1 fi 1 4 inch. LP /ToP' f -*■ i = I Bottom ii + ^'- = lA = As the same pulley drives both valves, the sum of the steam lap and lead requires to be the same for each cylinder, as shown above. Port Opening. Therefore, j^ p fAnd, ' ' iAlso, T p /Again, Half travel = Steam Lap + Port Opening 2f inches ^ 2 = if inches ■= Half travel. 1 1 inches -\\ inch W inch Port opening at top. 1 :i 9 Its jj i(r 3 5 4 )> - 8 1 1 >> _ 1 I -TB" bottom. top. bottom. slide Valves, Piston Valves, Valve Data, Sec. 263 Effects of Link Adjustments on I. H.P. No. Link Alteration. Effect on LILT. I 3 4 5 6 H.P. shut in - H.P. opened out LP. shut in LP. opened out L.P. shut in L.P. opened out ( H.P. power unaltered. LP. and L.P. power decreased. ( Total power reduced. 1 H.P. power unaltered. LP. and L.P. power increased. ( Total power increased. / H.P. power decreased. ) LP. power increased, j L.P. power unaltered. ( Total power unaltered. / H.P. power increased. ) LP. power decreased. J L.P. power unaltered. ' Total power unaltered. { H.P. power unaltered. ) LP. power decreased. j L.P. power increased. ' Total power unaltered. / H.P. power unaltered. LP. power increased. ] L.P. power decreased. ^ Total power unaltered. From the foregoing it will be noticed that the back pressure of one engine varies with the cut-off in the next engine, so that if, say, the LP. link is shut in the H.P. back pressure will rise, but if the LP. link is opened out the H.P. back pressure will fall ; the same holding good for the L.P. cut-off in relation to the LP. back pressure. The back pressure on a piston depends then on the following : — I. On the point of cut-off, which gives a proportional terminal pres- sure and back pressure for a receiver of given capacity. 2. On the cut-off of the next engine, which, if early, increases the back pressure of the preceding engine piston, and which, if late, lowers that back pressure as before described. SECTION V. GENERAL NOTES AND DESCRIPTIONS. The Author is indebted to the Editor of the Scottish Bankers'' Magazine for permission to reproduce the following article on the Manufacture of Metals from the pages of that journal. Manufacture of Iron and Steel. Sources. — Native iron, as it is called, possessing similar properties to that extracted from ores, has been found in Greenland and elsewhere in small quantities, but for practical purposes it is from the ores we derive our iron supply. These are widely distributed throughout the earth, and vary considerably in their characteristics and purity. The chief kinds in use are (i) the Magnetic (loadstone or black oxide), which is the richest of all, containing as much as up to over 70 per cent, of iron, A high class iron is made from this ore in conjunction with charcoal in Sweden. (2) Red Hcsmatite, which contains up to 60 per cent, of iron. This ore is plentiful in the district of West Cumberland and North Lancashire, and also in the north of Spain. (3) Brozvn Hcematite, which is similar to the red, and from which the bulk of the French and German iron is made. And (4) the carbonates of iron, called spathic when comparatively pure, and also blackband and clayband ironstone. This ore contains from 37 to 48 per cent. of iron. It has the advantage of being found usually along with coal measures ; and it has been the staple ore of Scotland. Great deposits also exist in the Cleveland district, but not of equal quality. The Blast Furnace. — The reducing or extraction of the ore is effected by smelting in a blast furnace. In the case of the poorer ores where more impurities are present, calcining or roasting may be a preliminary operation. The effect of this is to get rid of carbonic acid, water, and such other undesirable ingredients which are volatile, and so render the material more suitable for treatment in the blast furnace. Blast furnaces, fairly familiar objects, are large, circular, tower-like 264 General Notes and Descriptions 265 erections. The interior, which is not straight in form but contracts towards top and bottom, is lined with refractory fire-brick and ganister (a very refractory siliceous rock) ; around this is an annular space or ring filled with loose material to allow of expansion, and the outer wall of masonry is enclosed in iron sheathing strongly bound together. The furnaces range from 40 feet or so to 100 feet, and even more, in height, with internal capacity of 500 to 25,000 cubic feet or over. The modern furnaces are the highest, but it has been found that practical difficulties in working counterbalance the advantages of greater height when carried beyond a certain point. One advantage of the higher furnace is to render previous calcining of the ore less necessary, the same effect being accomplished in the upper part of the furnace. At the top of the furnace is a gallery or platform from whence the charge is admitted. The mouth of the furnace is closed by means of a large cone, which can be lowered by a chain when charge is being admitted, and then closed again. The closed top is a modern advance. Formerly the mouth was open and the great, lurid flames belching out made the blast furnace a picturesque feature of the district where it was erected. Many will remember the time when " Dixon's blazes," as they were familiarly called, formed a landmark in Glasgow ; and when shipmasters on the Ayrshire coast could shape their course by the glare of the Ardeer furnaces. But the old order changes, and the picturesque has to give way to the practical. The closed tops came into being when the gases generated in the blast furnace were utilised with resulting efficiency and economy. By-products have also become a feature of present-day practice. With the utilising of the gases and slag, recovery of ammonia, and so on, a combination of iron and chemical work is now common. The Charge. — The charge consists of fuel, ore, and flux. The first is commonly coke, but may also be coal or a combination of both ; and charcoal is mostly used in Sweden, where coal does not abound. The ores, as has been said, vary considerably. The flux is commonly limestone, although other agents are also used. It is introduced in consequence of the impurities remaining in the ore. It combines with the silica and other prejudicial matter, and forms a slag or cinder separated from the iron. A strong blast of air is introduced through piping surrounded by water tuyeres (outer casings). Power- ful blowing engines force the blast into furnace and through the charge therein. The water circulating through the tuyeres serves to cool the inlet where the heat becomes intense, and might cause trouble by fusing the parts. At one time a cold blast was used, and another of the most important modern improvements was the inven- tion and use of the hot blast by Neilson of Dundy van. By heating the air before its admission into the furnace great efficiency and economy of working were attained. Various forms of heating stoves have been devised, and these are now usually fired by the escaping blast furnace gases. 266 "Verbal" Notes and Sketches Pig-iron. The proportions of fuel and flux are so far determined by the nature of the ore used, and there are modifications of appHances and methods according to varying circumstances and requirements. The close tops and greater height of the furnaces have led to thinner walls and iron casings. As the charge becomes affected by the intense heat, chemical and other changes take place, impurities being taken up by the flux, though some others partially remain, as sulphur, phosphorus, and carbon. After these changes fusion speedily ensues, and the molten iron falls to the bottom, the slag floating on the top, while other waste elements escape in the form of gases. Once started, a blast furnace may be kept in operation for years. At the bottom of the furnace is an aperture called a tapping-hole, kept closed until the melting of the iron is completed. A large bed of sand is formed in front of the furnaces in which channels are made with smaller furrows branching off from them. These are called sows and pigs respectively, whence the term pig-iron. The tap-hole being opened, the melted iron runs out like a stream of liquid fire, flows down the large furrows into the smaller ones, where, on cooling, it assumes the familiar form of the oblong bars called pig-iron. The cinder or slag is drawn off over a dam at a higher level, independent of the iron. The pig-iron thus produced is of different grades, the fracture dis- closing divergencies of character and quality. The colour varies, ranging from grey to white, and the degree of hardness varies corre- spondingly. Grey is the softest, running through the mottled to the whitest, which is also the hardest. The quality is distinguished by numbers, beginning with No. i, and these numbers also indicate the suitability of the iron for further uses, all not being alike adapted for the same purposes. The grey iron is most suitable for foundry purposes, the white for forging. Castings. — We now arrive at the parting of the ways, so to speak The pig (or cast) iron may be applied, broadly speaking, in two ways. It may be employed for the producing of castings, or it may be con- verted into malleable iron or steel. Although large and rough castings might be made direct from the blast furnace, and malleable iron direct from the ore, these methods have been discarded, as it is more advantageous to make both indirectly from the pig-iron. The grey or softer pig-iron, as has been said, is most suitable for castings. But as there is great variety in the size, shape, intricacy, and purpose of castings, ranging from, say, a boot protector to a large steam-engine cylinder, mixture and manipulation of the different brands of iron are often required. For example, the bottom of a pan mill ^ subject to constant grinding and heavy pressure, naturally requires to be of very hard metal ; whereas, an ornamental article showing design will require fluid and easily running metal. Again, castings which have to be machined— that is, turned, planed, drilled. General Notes and Descriptions 267 &c., cannot be economically treated if too hard, and yet generally require toughness and strength. The Foundry. — The castings are produced in the foundry, to which the pig-iron is conveyed ; and there it first undergoes a process some- what analogous to that already described. The iron, along with the fuel and flux, is remelted in a furnace called a cupola, and drawn off at a tap-hole, the slag being afterwards thrown down through an aperture at bottom. Frequently scrap iron (old castings broken up) is used along with the pig-iron. Obviously the additional refining gives purer and better metal, but all is regulated very much by the purpose for which the castings are required. The metal runs from the tap-hole into a large iron ladle lined internally with fire-clay, and for pouring the metal into the lesser moulds small hand ladles are used. The castings may be made in sand or loam moulds. Patterns or models of the articles required have, mostly, to be made in the first instance, and may be of stucco, wood, or iron, but generally the last when many articles are required, as it stands tear and wear better, and lasts longer. The sand is enclosed in an iron frame or box, made in halves and hinged ; and the patterns of the article required, which may be simple or complicated and in one or more pieces, are embedded in the sand so as to form an exact mould. The patterns are then withdrawn and the box closed, an aperture being left for pouring in the metal, and small holes pierced to allow the escape of air and gases. When sufficiently cool the castings are removed from the boxes and dressed — that is, cleaned and filed. Loam is a mixture, such as sand, clay, and horse manure, faced with blacking or coal dust, and built in a pit or brick-work. Appliances called loam boards are used in forming the moulds, and the skill of the moulder is called into requisition in building these together. For water and gas pipes, iron moulds coated with plumbago are now sometimes used. More expensive to begin with, they save afterwards, seeing they are not destroyed at each casting like sand or loam moulds. What are called chilled (hardened) castings are made in metal or mixed metal and sand moulds, in which the melted iron cools rapidly and becomes extremely hard. This does for shot, &c. Cast iron is distinguished by its granular formation, which can be seen on fracture, its brittleness, and its hardness. It cannot be welded or riveted, and is not pliable. So-called malleable castings are of the opposite kind from the chilled, and are soft and to a certain extent pliable. For this process the articles are placed in powdered haematite ore or similar preparation, packed in chests, heated in a furnace for several days, and allowed slowly to cool until annealed. Malleable Iron. For the manufacture of malleable or wrought iron a different process is employed. Malleable iron, as the name implies, is ductile 268 "Verbal" Notes and Sketches and fibrous. It is softer than cast iron and can be bent, twisted, welded, and riveted. The difference between it and cast iron is principally due to the larger proportion of carbon in the latter. It has been described as free from carbon, but this is hardly correct, as usually it contains a very small percentage of that element. Puddling Furnace. — The first step is to treat the pig-iron in a puddling furnace. This is of the reverberatory type — that is, one where the fuel and the iron do not come into contact as in the open and closed hearth furnaces. As usual, the inner lining of the furnace is of a refractory material encased in strong iron outer sheathing. The bed or hearth is divided into two parts by a low wall or bridge, the fuel being placed in one and the charge of pig-iron in the other. The flame passes over the bridge against the roof, which is so shaped as to reverberate or throw it down in a fierce heat upon the iron and then pass on to the flue. The furnace may hold a charge of about 4 cwt. of metal, and is worked by two men, a fore and an under hand. When partially heated the furnace is fettled — that is, plastered with composition embodying oxide of iron in the form of haematite made into paste with water, or else of slag from previous meltings, which comes in cheaper. Lumps of metal are thrown in, the fire is then raised, and by means of long iron bars (changed as required) the puddlers, in turn, keep working or stirring and distributing the metal. During melting the iron is decarbonised (divested of the carbon remaining in the pig-iron) and various other impurities removed. Before complete fusion the mass becomes of a pasty consistency, and is well " rabbled " or distributed by the puddlers. When melted it seethes and bubbles, and shortly afterwards begins to thicken, the iron separating from the impurities unites in solid pieces which gradually become welded together, while the waste or slag is run off in liquid form. It will be obvious that the process of puddling is a very exhausting one to the men engaged in it, and means of accomplishing the required work by mechanical action have been devised. These need not be described, as the object is the same whether manual labour or machinery be the method employed. Besides the mechanical contrivances for puddling, experiments have been made in the opposite direction by constructing rotary furnaces actuated by machinery. These have not, however, displaced the stationary furnaces. The mass of iron having combined, is now removed from the furnace, and for convenience of handling is divided into parts or balls, and at once taken to a steam hammer to be beaten. Thereafter the balls can again be united and hammered into shape. During these operations the waste or slag is being further pressed out. The next stage is to convey the iron to the roughing or cogging mills with rolls of large diameter through which it is passed, the openings between the rolls being gradually reduced. The iron is thus con- verted into slabs, while it is also being additionally cleansed. By General Notes and Descriptions 269 reheating and rerolling the quality can be improved up to a certain point, but beyond that harm results from burning, &c. The final step is the passing of the wrought iron through the rolling-mills with rollers having sections of the different forms required. These mills are massive in construction, and driven by powerful steam- engines. The billets are passed backwards and forwards through the rolls — the mills being reversible — and the rollers brought closer until the desired sizes and shapes are obtained. These are principally sheets, plates, round, square, and flat bars, angles, and other sections. The quality of the iron is denoted (after the puddled bars) as common, best, best best, and treble, — the superior quality being the result of the reheating and rolling of the previous grade. The qualities of different works, however, vary. There are some special brands — such as Lowmoor and the products of other Yorkshire works — of a high class, where the results are dependent on special methods and local advantages as regards fuel and ore. Steel. Steel is a material of valuable and unique properties. It may be extremely hard, or soft enough to be bent, twisted, hammered, or drawn out to the thinnest sheet or finest wire. It can be so hard as to cut any other metal or material and to scratch glass, or it may be elastic to a degree. It has been described as a metal intermediate between cast and wrought iron as to the carbon it contains. But this, correct enough as far as it goes, is somewhat misleading, as it does not take all considerations into account. According to the amount of carbon it contains, steel is harder or softer. According, also, to the propor- tion of carbon it contains, the tensile breaking strain and the limit of elongation vary. The tensile breaking strain will range from 20 to as much as 80 tons per square inch, or more if the steel be wire-drawn. Cementation Process. — The highest quality of steel is made by what is termed the cementation process. The best puddled wrought-iron bars, preferably Swedish charcoal iron, are used. The cementing furnace is of fire-brick, circular or rectangular in form, having a wide, conical top and dome-like chimney. The fireplace is in the centre at the bottom, with door at each end for firing. On each side, supported above it, are pots or chests, so arranged that the flames pass underneath and all around, rising against the arched top, which, as it becomes heated, radiates down on the pots. These are perhaps 1 5 feet long or more, and 3 feet deep or thereby, A manhole at each end permits of charging the pots or converters, but these are closed during the working. A layer of charcoal is first deposited on the bottom of the pots, then a layer of bars with spaces between also filled with charcoal, and so on in alternate layers. 270 "Verbal" Notes and Sketches The charcoal is partly fresh and partly previously used. Then a plaster of cement (used charcoal and ground waste) is applied to the top, and the whole is sealed with clay to exclude air. The charge will range from 12 to 18 tons, according to size of furnace, and may even reach 30 tons. One or two of the bars are longer than the others and project outside for testing purposes. The furnace is heated for eight or ten days, when a testing-bar is with- drawn and examined to see if the material has been sufficiently carbonised. Afterwards the furnace is left for a day or two to cool down gradually. It will be found that the carbon is not uniformly distributed through the bars, but is greatest at the surface, decreasing as the centre is reached. The skin is raised in blisters (blister steel). If not intended to go through the further crucible process, the bars are then sheared into short lengths, bound together in bundles, powdered with mixture of clay or sand, heated to welding-point, and then subjected, while in a plastic state, to rapid action of a tilting-hammer or rolling-mill till welded. This gives what is called sijigle shear steel. By repeating the process double shear steel is obtained, and so on. This shear steel is of cheaper description than the crucible steel, and serves for shear blades, certain kinds of knives, &c. Crucibles. — For a finer steel under same process, to attain uni- formity, the bars after being withdrawn from the furnace are remelted and mixed. This is done in crucibles. What is called the melting- house varies somewhat in arrangement, as light or heavy ingots are to be produced. The melting furnaces form a series of rectangular chambers, separated by thin brick partitions, the tops being level with floor of house, while the fireplace and ashpit are at bottom, accessible from underground passages running in front of them. Each hole or chamber is lined with ground ganister (a refractory siliceous rock), leaving an opening sufficient to hold two pots or crucibles resting on stands placed over the fire-bars. Crucibles differ in dimensions, but a common size is 18 inches high by 9 inches diameter. They are made of a mixture principally of fire-clay, with added coke dust, old ground pots, and for some purposes plumbago. They have to be very carefully made, and are dried, annealed, and fitted with lids before use. The first melting will take four or five hours for complete fusion, but subsequent meltings about half that time in consequence of the previous heat being maintained. The molten steel is poured from the crucibles into ladles with tap-holes for discharging into the ingot moulds, or for small moulds with hand ladles. The crucibles in good condition are at once replaced in the furnace for a second heat. Great care has to be exercised throughout in order to secure sound ingots. It will be obvious that the specially high class of iron used and the slow method makes this description of steel costly, but on the other hand there is nothing that can take its place. General Notes and Descriptions 271 Tempered Steel. — From the high class steel are made the various tools for hand and machine use to operate on metal, wood, and stone, also cutlery, surgical instruments, swords, springs of various kinds, saws, &c. To render it suitable for these varied uses it has to be tempered — a distinctive feature of steel. When heated and then suddenly cooled, and afterwards reheated to the given temperature required, it becomes available for the particular service to which it has to be applied. The cooling is usually efifected by plunging in water. But if hardened and tempered in oil a somewhat greater toughness, more elastic limit, and tensile strength are the result. Workmen have a simple means of ascertaining the temperature by the colours which the steel assumes at the different stages of heating. These may be described as follows : pale straw, straw, yellow, brown, purple, bright blue, deep blue, according as the temperature increases. Bessemer Process. — There were many purposes where a class of steel, not necessarily possessing the properties of the crucible product, would be of immense advantage, and this led to research and experi- ment. On the assumption that steel was a material containing a proportion of carbon intermediate between cast and wrought iron, the inference followed that a mixture of these would give steel, and this method was tried but without success. The fact overlooked was that cast iron contained impurities (in particular sulphur and phosphorus) in a degree sufficient to render it useless for steel making. There was also a practical difficulty in regulating the exact proportion of carbon necessary. The Bessemer process, however, accomplished the purpose, supplanting in great measure the use of malleable iron for many purposes, particularly rails and other railway material, forgings, plates, and various sections for structural work. The first step in success was by using selected pig-iron, containing very little of the objectionable elements, and the addition of spiegeleisen also exercised a purifying effect. It was found that by first eliminating all the carbon and then adding the spiegeleisen (a particular pig- iron containing a considerable and known amount of carbon) or ferro-manganese in proper proportion, the difficulties were overcome. Finally, Thomas and Gilchrist devised their method of lining the converter with a refractory basic material containing lime and magnesia. These agents having an affinity for phosphorus absorbed this impurity, and thus the bulk of the impurities being removed, ordinary pig-iron could be utilised. The essential feature of the process is the forcing of a current of air through melted pig-iron in a special vessel named the con- verter. The original Bessemer method is called the acid process, because of the converter being lined with siliceous (ganister) material. The Bessemer converter is an iron vessel, and may contain from 5 to 15 tons, lined as usual with refractory material, the bottom being perforated with holes through which a blast of air is conveyed. It is mounted on axles which allow of its being swivelled round ; one 19 272 "Verbal" Notes and Sketches of these being hollow is utilised to admit the blast. The converter after being heated is brought to a horizontal position, giving access to the mouth. Melted pig-iron is poured in, the blast turned on, and the converter raised to its vertical position. The blast is sufficiently strong to counteract the weight of the charge, so that the metal does not run down through the perforations. The air is forced through the molten metal, burning up the carbon, and a kind of fairy fountain effect is set up by the flames, spray, and colour which ensue, while, to paraphrase Tennyson, " The blast is roaring and blowing." The near exhaustion of the carbon is indicated by the waning of the flames. The converter is once more brought to the horizontal position, while the melted spiegeleisen is added in the proportion required to give the necessary amount of carbon, and then reversed. The mixing of the metals causes at first a violent agitation. Alto- gether about twenty minutes is occupied in converting, say, 10 tons of hsematite pig-iron into steel. The temperature at the close of the blast is said to reach 3250" Fahr. It will be readily understood that the intense heat generated in all these smelting operations, together with the corrosive action of the slags, necessitates the use of materials for lining the different furnaces capable of withstanding as far as possible the destructive effect of these agents — hence the frequent allusions to refractory linings. For the most part special deposits of fire-clay and of siliceous or flinty rock ground to form ganister have been found best adapted for the purpose. Basic Process. — The distinctive feature of what is called the basic process of producing the steel — as distinguished from the original acid Bessemer process — is the substitution of a basic lining of magnesian lime for the coating of the converter instead of the acid ganister. As already noted, the basic material extracts the phosphorus from the iron, which cannot be done by the ordinary process, and so renders it possible to use Cleveland and other lower class iron in the making of steel. With some modifications the processes and appliances are, in general, similar to those already described. The amount of slag produced in the basic process is much larger than in the other, but is of a different character, and as it contains a considerable proportion of calcium phosphates useful for fertilising land, it is employed after suitable treatment for this purpose. Apart from the capability of using the inferior iron by the basic method, the large quantity of material which can be handled at a time, the rapidity of the conversion, and the comparative absence of manual labour combine to render the Bessemer process of steel making one of the most important of the present day, and great quantities of material are turned out for the purposes already named. Siemens- Martin Process. — Another succe.ssful method largely in 'ise is the Siemens-Martin, by which a mild steel with a low percent- General Notes and Descriptions 273 age of carbon, approximating to wrought iron, is obtained. .\ batii of melted pig-iron of high quality is first made, and to this there is gradually added wrought iron and steel scrap in small quantities at a time. Impurities are removed during the melting, and the presence of the scrap already refined by the previous puddling gives very good results. Spiegeleisen is added to supply the desired amount of carbon, as in the Bessemer process. The furnace employed is generally a Siemens Regenerative Gas Furnace. The roof and sides are of refractory silica or brickwork, and the bed (of considerable depth) of sand of a like nature. There are doors for introducing the charge and also for stirring and mixing. Externally it is encased in iron plates. The regenerative chambers are built underneath the furnace, with spaces between. The gas is produced in separate furnaces, of which there are several patterns. The gas and air necessary for combustion, ascending through one set of regenerators, are admitted by separate valves through portholes into the furnace hearth. The furnace having been already heated, an intense heat and volume of flames soon ensue. The hot air and gas enter at one end of furnace, and the flames and waste gas pass out through ports at the other end down to the other set of regenerators, and thence to chimney. There are means for reversing this cycle, so that a constant heat is maintained. Different kinds of gases are used, and in America natural gas is sometimes employed. ' As much as 50 tons of metal can be treated at one operation, or it may be only a few tons, according to the size of furnace. The proportions of pig-iron and scrap vary according to conditions and requirements ; and the melting of a lo-ton charge will occupy three and a half to four hours. A small sample is ladled out to see if the desired degree of decarbonisation (removal of the carbon) is reached, then the spiegeleisen or ferro-manganese is added, and these quickly melting, the tap-hole can be opened, and the steel flows out into a large ladle with a stopper in bottom, and thence is discharged into the moulds. In order to ensure soundness in the ingots several devices are used, principal among these being the addition of some alloy at the end of the melting and the compression of the steel while in the fluid state. Siemens Process. — In the Siemens process, besides the pig-iron and scrap used in the Siemens-Martin method, rich haematite ores are introduced, and somewhat different chemical reactions take place, but the working arrangements do not differ much, though longer time is required for fusion. If pig-iron of a lower class with many impurities be used, then the sand-bed of the furnace must be replaced by a basic material, as in the Bessemer converter. There are also some important alloys used in the manufacture of steel. For instance, nickel alloyed with steel intensifies its hard- ness, while it can be rolled or hammered to advantage. Harveyised nickel steel is much used for armour-plates. Chromium is also used 2/4 '* Verbal " Notes and Sketches as an alloy. It imparts greater strength, toughness, and ductility. It is employed in the production of armour-plates, and also of projectiles, conferring on the latter the property of keeping intact when striking steel plates at the highest velocity. In the making of large and heavy forgings, whether in wrought iron or steel, besides the steam hammers already alluded to, very powerful hydraulic presses have been devised and come into use for shaping and compressing. It may be said that the great development of the machinery and appliances for dealing with iron and steel in recent years, and the developments in the treatment of these materials themselves, together with the reciprocal interaction of these two factors, have made possible advances unthought of even at the beginning of the present generation. It is difficult to forecast what further progress may be in store in the future. Strength and Composition. — The following table gives the average tensile and crushing strengths of Cast Iron, Wrought Iron, Mild Steel, Nickel Steel, and Hard Steel, also the per cent, proportion of Carbon, &c., in each. Metal. Tensile Strength. Cast Iron - Wrought Iron Mild Steel - Nickel Steel Hard Tool Steel Tons per Sq. In. 7 20 28 to 30 I 40 ' 50 Crushing Strength. Carbon. Tons per Sq. In. I'ercent. 45 3-5 16 22 -16 •3 100 I I -I Manganese, Silicon, j^.j^j.^, rhospliorus. Sulphur, &c. Percent. 'Percent. 3-5 Alloys. Alloy, Tensile Strength. Copper. Zinc. Tin. Antimony. Tons per Sq. In. Per cent. Per cent. Per cent. Per cent. Brass 12 66 33 Naval Brass 27 62 36 I Muntz Metal 22 60 40 ... Gun-metal 16 91 9 Phosphor. Phosphor Bronze 16 92 7 Antimonv. Babbit's White Metal 8-3 83-3 8-3 Lead. Parson's White Metal I 30-5 68 •5 Spelter for Brazing 50 50 General Notes and Descriptions 275 Properties Cast Iron Wrought Iron Mild Steel Nickel Steel Hard Steel Brass Naval Brass Muntz Metal Gun-metal Phosphor Bronze Babbit's White Metal Parson's White Metal of Metals and Alloys. - Can be cast. „ forged, welded. ,, forged, welded. ,, forged, tempered, cast. ,, forged, tempered, cast. „ cast. „ cast, rolled, forged (hot). „ cast, rolled, forged (hot). „ cast, rolled. ,, cast, rolled. ,, cast, cast. Composition of Steel. The following extract from Greenwood's work on steel and iron gives the average composition of various steels : — Analyses of Steel. Soft Siemens Crucible Hard In 100 parts of Siemens- Steel Steel for Tool Martin Steel. Plates. Forgings. Steel. Carbon - - - - •167 •21 •36 I144 Manganese - •044 •36 .30 •104 Silicon - - - - •023 ■047 •02 •166 Sulphur •013 •052 •02 Phosphorus - •062 ■035 •03 Copper - - - - ■076 ... trace Mild steel can be forged and welded, but cannot be tempered. Hard steel only can be tempered. Composition of Manganese Bronze. Per cent. Copper . - - . 52 Zinc ----- 46 Tin - I Iron - - - - - - about 0-5 AluminiuiTi - . - . » 0-5 Manganese - - - . trace Test for Steel. The Board of Trade test for a piece of steel plate to be used for a furnace or combustion chamber is as follows : — Strips of the metal 8 by 2 inches are heated to a cherry red, and afterwards plunged into water of 80^ temperature : the strips must then be able to stand being bent over without fracture until the sides are parallel at a distance equal to three thicknesses of the plate. 2/6 "Verbal" Notes and Sketches Tempering Steel. In tempering a piece of steel, as for example, a chisel, the tool is first heated to a cherry red and the point of it dipped into water ; if the metal be then rubbed with a piece of stone, the various colours will appear as the heat travels along to the point. When the required tint shows, the tool must be plunged into cold water and kept there until cold, and the temper will be fixed. The following are the colours and corresponding temperatures required in tempering different articles : — Article. Colour, Temperature. Turning tools Chipping chisels Springs Straw Purple Blue - 450° 530° 570° Annealing. In working or flanging a steel plate the smaller number of heats the plate has to undergo the better, as the effect of repeated heating of part of a plate is to strain the metal ; the necessary flanging should therefore be done in one heat if at all possible. After the flanging is done the plate should be annealed, that is, heated uniformly through- out and allowed to cool down slowly, as this has the effect of taking out the strain and bringing back most of the strength lost previously by local heating. Case-Hardening. Case-hardening consists of putting a thin skin of steel on parts made of iron by the addition of carbon, so that the surface of the metal is hardened. This is usually done by enclosing the iron parts to be case- hardened in an air-tight box together with substances rich in carbon, such as bones and horns of animals, or prussiate of potash, and the box is then left in a furnace for a number of hours. The heat causes carbon to deposit on the surface of the iron, and thus changes it into steel. After being withdrawn from the furnace the articles require to be plunged into water. Gear which only requires to be lightly case-hardened is usually packed in finely ground bone, and heated for a few hours ; if a deeper case-hardening effect is required, then the articles are packed up in the boxes with coarser bone powder, and heated for ten hours or more, but if a greater depth still of hardening is required, it is then necessary to repack and again heat up, finally dipping in the cooling water bath. For certain classes of work, wood charcoal is employed instead of bone. General Notes and Descriptions 2/7 Brazing:. Brazing is hard soldering, and consists of the joining together of parts made of copper or brass, such as, for example, a brass flange to a copper pipe. The pieces to be joined are first carefully cleaned, then fitted in place and clamped together in the required position, and, after they have been covered over with spelter (composed of one part copper and one part zinc), heat is applied by means of a charcoal fire, and the spelter runs into the spaces of the joint. Borax is sprinkled over the parts as a flux to make the spelter run easily. After cooling, the spelter sets hard and the parts are then firmly soldered together. NOTE. — Soft solder is made up of equal parts of tin and lead, resin or spirits of salts being employed as a flux. Welding. In welding, two pieces of metal are joined by being first heated to about 1600° Fahr. (white heat) and then hammered together. The ends to be joined require to be scarfed or tapered away at an angle, and before putting the two surfaces together sand (if iron) or borax (if steel) is sprinkled over them as a flux, and the hammering proceeded with. It is important that the two pieces be heated to as nearly the same temperature as possible before joining. NOTE. — The flux (sand or borax) acts to clean the surfaces of the magnetic oxide which forms on the heated surfaces, and which would otherwise prevent perfect adhesion. Strength of Materials. Tensile strength of nickel steel, 34 tons per square inch. ,, ,, boiler steel, 28 ,, „ ,, ,, wrought iron, 20 ,, „ „ ,, Muntz metal, 20 ,, „ „ ,, brass, 12 „ „ „ „ copper, 12 „ „ cast iron, 7 NOTE. — Nickel steel is mild steel with about 3-2 per cent, of nickel added. Crushing Strengths. Crushing strength of hard steel, 100 tons per square inch. „ „ cast iron, 40 „ ,, „ ,, wrought iron, 16 ,, ,, Alloys. An alloy is a combination of two or more metals. Brass consists of about 2 parts of copper and i part of zinc. Muntz Metal consists of about 3 parts of copper and 2 parts of zinc. White Metal consists of about 84 per cent, of tin, and the remainder of copper and antimony. NOTE.— White metal melts ^t about 600° Fahr, 278 "Verbal" Notes and Sketches Stresses on Various Parts. Boilers. On the stays the stress is tensile. On the shell plates the stress is tensile. On the furnace the stress is compression. On the tubes the stress is compression. On the stay tubes the stress is compression and tensile. On the back tube plates the stress is compression. On the combustion chamber dogs the stress is compression on top edge and tensile on bottom edge. On the rivets the stress is shearing. Engines. On the shafting the stress is torsion, but the tail end shaft has also a bending stress due to the propeller weight outside of the stern tube. On the shafting from the thrust shaft aft there is an end com- pressive stress going ahead, and a tensile stress going astern. On the crank-shaft there are also bending and crushing stresses combined with torsion. For these reasons the tail shaft and shaft crank are usually made a little larger in diameter than the tunnel shafting (about i inch). Coupling bolts have a shearing stress. Crank webs and pump levers have a bending stress. Built Shafting. — Instead of shrinking the webs on to the shaft, some engineering firms force them on by hydraulic pressure, the ram exerting a load of anything from 100 to 125 tons. The holes in the webs are bored out a i&\\ thousandths less in diameter than the pin or shaft, and for a shaft of, say, 14 inches diameter, the difference would amount to y^w iiich, which is just under /^ inch. Strength of Shafting. The strength of a solid shaft varies as the cube of its diameter, therefore, the comparative strength of two shafts of, say, 8 inches diameter and 10 inches diameter will be — Dameterio' _, . , Diameter- "8"^ = Ratio 0/ strengths = as i : 1-95. A hollow shaft is stronger than a solid one of the same sectional area, as, the diameter being greater, the leverage of the power acting to twist it is less in proportion. In addition to this, the removal of the central core of metal reduces the risks of flaws, which often develop at the centre and then extend outwards. Internal inspection for flaws is also to some degree possible. NOTE.— The torsional stress is o at the centre of a shaft, and increases from that point out to the circumference ; the mean stress may therefore be taken as acting at a leveraere of half of the shaft radius, or one-fourth of the shaft diameter. The strength of a hollow shaft varies as D^ - tf ^ D = outer diameter. D Shaft'. Therefore, ^ A- 1 X Load X Crank Lengfth ^. , ^, , . / ~ -■ r"r5T Diameter of Shaft, \' Torsional Stress S-i X Load X Crank Length ^ . . ^ "Shaft Diameter^ " = Torsional Stress. NOTE.— For Torsional Stress the maximum Load may be taken as approrxi- mately equal to that on the piston, or, Piston area ; Pressure -Load. Rule (Bending). — 10-2 X Load X Length = Bending Stress x Shaft^. Twisting Moment (T.M.) = Crank Length x pounds load on pin. Bending Moment ( B. M.) = Length x pounds Load. Example. — Calculate the bending stress per square inch on a tail end shaft 12 inches diameter, distance from stern post to centre of propeller boss 30 inches, weight of propeller 10 tons. Also express the Bending Moment in inch-pounds. Then, io-2x B.M. = or, Load x crank leverage^ Diameter^ x Stress ; 3^1416 16 Load X rranW or, or. Load x crank leverage x 5-1 = Diameter' x Stress ; so that in dividing by ^ — - — , we invert it, and obtain ;;, which •^16 3-1416 gives 5-1 Constant for torsion, and as the resistance to bending stress is only half of this, then 5-1 x 2 = io-2 = Constant for bending stress. Twisting Stresses and Tunnel Shaft Diameter. — The ratio of piston travel to crank-pin travel per revolution is in the ratio of 2:3-1416, as during one revolution the piston travels through two strokes and the crank-pin through a circle equal in diameter to the stroke. The crank-pin has therefore more travel than the piston, and, by the principle of work, what is gained in travel is lost in pressure, so that the average pressure on the crank-pin is less than the average pressure on the piston in the ratio of 3-1416 : 2. General Notes and Descriptions 281 Example. — The stroke is 4 feet and the total mean pressure on the piston 36000 lbs. F'ind the mean pressure on the crank-pin. Then, 4 x 2 x 36000 = 4x3-i4i6xp, and, 4j<2 X 36000^3 g ij,g 4x3.1416 Mean Twisting Moment. The mean twisting moment (T.M.) = Crank Length x Pounds (LxP). Therefore, T. M. - 24 inches ; 22918 - 550072 inch -pounds. For one minute the equation will read as follows : — I. H. P. X 33000 X 12 inches - Crank Length x 2 x 3- 1416 x Pounds x Revs. Therefore, I- H. P. x 33000 x 12 ^ ^^^^^ Length x Pounds (T. M. ). 2 x 3-1416 x Revs. Example. — I.H.P. 1,400, stroke 4 feet, and revolutions 62. Find the mean T.M. Then, 1400 x 33000 x 12 = 24 inches x 2 x 3-1416 x 62 x Pounds. Therefore, T. M. - Moox^ssooox 12 ^ ^^^ jg^ inch-pounds, 2x3-1416x62 ^^ ^ and, Pounds = 1423180 ^24 inches = 59298 lbs. Notice that the Twisting Moment in inch-pounds divided by the crank length in inches brings out the pounds applied at end of crank. Maximum T.M. The foregoing onl)' takes into account the mean or av^erage T.M., and to allow for the usual cut-off and the varying effects of the crank angle a constant of about i-2 is usually employed, so that Maximum T.M. = Mean T.M. x 1-2. Shaft Diameter. From the foregoing principles the required diameter of tunnel shaft for a three-crank engine can be calculated as follows : — C. I.H.P. X 33000 X 12x5-1 X i-2 = No. 2. — Flaws on Crank Shafting. 900 horse-power on the shaft, as all the power effectively developed travels along the shafting aft to the propeller, each engine successively adding its share. If the M.P. shaft shows a flaw at A, link up the M.P. gear, and this will reduce the stress on the weak part, as less horse-power will now be developed in the H.P. engine, and more in proportion in the M.P. ; therefore less will be transmitted through the weak part of the shaft. If a flaw shows at B on the M.P. shaft, if possible turn that shaft end for end, as this will give only half the stress on the weak part. Shutting in the M.P. gear would still further reduce the stress, as more power will now be developed in the M.P. and less in the H.P. For a flaw at C on the L.P. shaft, as before, turn the shaft end for end, and link up the L.P. gear, on the same principle as before. If the H.P. shaft is a duplicate of the other two, in the event of flaws appearing in either the M.P. or L.P. shafts, change the H.P. shaft for either one which has the flaw, instead of doing as above General Notes and Descriptions 285 described, as the further forward the weak shaft is placed, the less stress will there be on it. Crank-Shaft Repairs. The following description of crank-shaft repairs, supplied by John M'Callum, Esq., are reprinted from the pages of hiternatio}uiL Marine Engineering. (i.) Loose Web. — The crank-shaft had been kept under observa- tion, as a certain amount of slackness had been noticed between the shaft and the web. Later on, when at sea, knocking was heard, and it was located in the loose web. The repair was effected by drilling a number of holes round the end of the shaft, as shown in Fig. i, and fitting taper screw pins, if inches diameter, in each hole, and screwing them up as tightly as a key with a good leverage would accomplish. if inches was the size of the largest screw tap on board. Holes were drilled in the end of the shaft for about one-third of its circumference, as shown in the figure ; the line of the holes being arranged to leave h inch of metal between them and the edge of the shaft. The holes were drilled 6 inches deep, and screwed with taper tap only. Each hole and pin was finished, and the pin screwed up as FiC Z ^ ' j- mEm - No. 3.— Repair for Loose Crank Web, &c. far as it would go before commencing the next. The line of screwed pins swelled the shaft in the neighbourhood of the holes, and tightened the shaft in its web sufficiently to carry the ship to her home port without further trouble. When arrived in port a new shaft end was fitted to the existing web. The possibility of this being done, and so avoiding the expense of new shaft and web, had been foreseen when 286 "Verbal" Notes and Sketches the method described above was adopted. If plugs had been fitted interlocking the shaft and web, apart from the fact of their liability to slack back when at work, a new shaft and a new web would have been required on arrival home. (2.) Flaw in Fillet. — When at sea, a flaw was noticed in the fillet of the low-pressure crank-pin, which though slight at first developed very rapidly, necessitating a very careful repair, or stoppage of the ship would have been necessary. The flaw extended over about one- third of the circumference of the after fillet and underneath the pin, "crank on top," as shown at B in F'ig. 3. In the writer's experience, defects in crank-shafts, whether solid or built up, usually occur at this point, and are mainly attributable to the faulty position of the thrust block. Instead of the thrust being taken up by the shaft bearing, the thrust block has to be adjusted, and a nip is thrown on the crank-pin at the point B in Fig. 3, which usually results in a loose pin in a built-U4) crank-shaft, or a flaw, as in this case, in a solid one. As the runs between the ports were not long the engines were kept running, but were well watched, while the engineers thought out the difficult problem of repair and got the necessary appliances ready. The repair was effected by fitting a pin through the crank, as shown at A in Fig. 3, a spare main-bearing bolt with collar and nut, shown in Fig. 2, being employed for the purpose. Drills and ratchets were got all ready before the engine was stopped, and drilling was commenced from each end, a i|-inch hole being drilled through both webs and crank-pin, the holes meeting in the centre. Coloured labour being plentiful on the coast, the holes were got out in good time. After the holes were drilled the complete hole was bored by means of the arrangement shown in Fig. 4. A boring bar E was fitted with a pilot end H screwed into the boring bar, to save forging down and to keep the bar true. The slot for the cutting tool was arranged, as shown in F in Fig. 5, so that the body of the bar E took up the weight of the cutting. Another slot was cut at G in the boring bar, and a larger cutting tool was placed in it, which came into operation after the cutter F. Fig. 4 shows the arrangement of the boring bar. The plates D D were used to support it, with the distance pieces C C, long bolts, as shown, holding the whole thing together, and keeping the bar and the boring central with the pin. The hole was recessed at each end to receive the collar and nut, as shown in Fig. 3, and the nut was cut down for the recess. When the boring was finished the crank was well warmed by means of a wood fire, the bolt tapped in with an anvil slung in ropes for the purpose, the bolt end outside of the collar being left on until the bolt was right in its place. The nut was then put on, hardened up, and the bolt end riveted over it. The ship completed her charter, General Notes and Descriptions 287 and ran home with tlie repaired shaft. A new shaft had been sent out, but it was not necessary to use it. Repairs for Flawed or Broken Shafts. Flaw on Crank Web. — Two iron or steel straps, say about 2 inches thick, heated and shrunk on, then bolted as shown. tr strap No. 4.— Repair for Flaw in Crank Web. The bolts should be as large as possible, for ordinary size of shafting about 2h inches diameter, but larger than this if they can be obtained. Coupling bolts would do very well in most cases. Broken Crank-Pin. — Bore out the crank-pin to about one-third of its diameter, and put in a repair-pin, a driving fit. A small locking- t - . . . 1 _^l- - — - No. 5.— Repair for Broken Crank Pin. pin screwed half into crank-pin and half into repair-pin will keep it in place. Repair for Thrust Shaft— The collars to be bored or slotted out, and bolts with thimbles fitted between the collars where the flaw or 20 i88 Verbal " Notes and Sketches 7 and bolts No. 6.— Repair for Broken Thrust Shaft. break is situated. The thrust block rings next the broken part will have to be removed. Repair for Tunnel Shaft— The shaft to be cut for keys of the shape shown, the number of keys depending on the extent of the <- clavvi^ No. 7.— Repair for Broken Tunnel Shaft. flaw or crack, and the shaft clamped round over the ke}'s and securely bolted. NOTE. — In the foregoing cases the revolutions will require to be reduced. Notable Shaft Repair. — The following is a brief de.scription of the method adopted in repairing the broken tail end shaft of the steamer " Fazilka," of the British India Steam Navigation Company, in the Indian Ocean. The binding of the shaft together by means of a set of bottom end brasses applied as a clamp, and the further locking of the clamp by steel pins driven in through the brass into the shaft, constitute the most noteworthy and original points of this repair. The tail end shaft gave way in the stern tube at two places, so that a piece fully 3 feet 6 inches in length was detached, and in breaking also broke through the stern tube. The engines were promptly stopped and the .stern of the ship afterwards tipped to prevent the entrance of water to the tunnel while the work of repair was being carried on. A number of holes were first bored into the tube and the metal broken awa}', so that a hole was made large enough to allow of General Notes and Descriptions 289 access to the shaft inside. The broken piece was removed and the propeller shaft disconnected from the last tunnel length, and pushed out aft until the broken ends touched. Two sets of bottom end brasses were then taken and used as clamps to bind together the two parts of the shaft, and to obtain one of these sets the H.P. engine had to be disconnected. Plates of h inch thickness were fitted across the two brasses top and bottom, and the bolts passed through to more effectually support the broken parts, and, to allow of going astern, holes, two of 2 inches diameter and two of 2^ inches diameter, were bored into the shaft through the brasses, and steel pins driven in. It will be noticed that a gap was left between the last tunnel length of shafting and the tail end, owing to the bringing together of the broken ends of the latter. To join these the after length of the tunnel shaft (132 inches diameter) was at^ through, by first boring round it twenty-two holes of about i inch diameter and cutting between them. The flange was then brought aft and coupled to the propeller shaft, and the cut parts of the tunnel shaft connected by means of a " Thomson " patent coupling. To complete the job and make the whole, as far as possible, one solid mass, molten metal was run in to fill up the various spaces left by the ragged ends of the broken shaft inside of the clamps, and when the engines were turned round the parts were found to hold together satisfactorily enough to allow of a reduced speed being easily maintained. The work spent on repairing the shaft occupied about three weeks' time, but this was mainly due to temporary failure of one or two of the methods tried, which are not given here in detail. It is sufficient to add that the " Fazilka " steamed safely, and without assistance, into Colombo Harbour by the use of her M.P. and L.P. engines, working at a reduced boiler pressure. "Thomson" Patent Coupling. This coupling is specially designed for clamping up a broken shaft, and forms the best means of repair. It consists of three nmrm lOncD ' i.... : , ! I ■ 1 1 j :.:.}.: : \ i Ll'i .1-. _V _ 1 . . No. 8.— "Thomson" Patent Coupling. 290 "Verbal" Notes and Sketches pieces bolted together, and is so arranged that it may extend between two lengths of shafting if required, an enlarged part of the coupling allowing for the flanges. Stopping of Engines. Sudden stopping of the engines may be caused by the following : — 1. Slide valve loose on spindle, or spindle broken. 2. Stop valve seat lifted with valve. 3. Go-ahead eccentric broken, or loose on shaft. 4. Throttle valve turned round on its spindle. If any steam connection on the H.P. is opened and steam blows out, this proves that the stop valve and throttle valve are clear. If the slide valve is loose on the spindle, the piston of that engine will most likely stop on the top centre, as the valve will stick on the top, and the bottom port remain full open to steam. If the steam be shut off quickly, the noise of the valve dropping down would locate the trouble. In the case of a valve slack on the spindle the following generally holds good : — 1. If H.P. inside steam piston valve is slack on spindle, H.P. engine will stop with piston on bottom centre. 2. If LP. or L.P. slide valve (or outside steam piston valve) is slack on spindle, the corresponding engine will stop with piston on top centre. Failing the foregoing, testing, by means of the indicator cock con- nections top and bottom, will usually locate the valve which has slackened back. Engine Breakdowns. If the H.P. engine breaks down, take out the valve and disconnect the engine, and work with the I. P. and L.P. The pressure should be reduced to about 100 lbs., as the LP. cylinder is of larger diameter the H.P., and therefore weaker. If the LP. engine breaks down, take out the valve and disconnect the engine (if the pumps are not worked off it). The steam will then pass direct from the H.P. exhaust to the L.P. chest. The boiler pressure may require to be reduced in this case, owing to the fact that the steam in expanding down to the L.P. pressure does not drop in temperature, as no work is done during this expansion, and to obtain the same condenser vacuum the boiler pressure may, as stated, require to be reduced. To develop the same I. H.P. the consumption will be more, owing to the great difference of temperature existing between admission and exhaust in the H.P. cylinder, and the con- sequent excessive condensation of steam causing loss of heat. NOTE.- In the foregoing cases it is advisable to leave in the valve spindle to close up the gland. General Notes and Descriptions 291 Pumps. The suction valve of a feed pump should be placed low down on the barrel, and the delivery valve as high up as possible. This arrangement allows of better working when the feed-water tempera- ture increases, as the air or vapour will rise clear of the pump suction, and allow of a better vacuum being formed. Most patent feed donkey pumps are not fitted with relief valves, the reason being that should anything occur to choke the delivery valves, the pump would stop working by over-pressure on the water side. With feed pumps worked off the main engines the case is different for if, say, the delivery valve seat rises up with the valve, the pumps would of course still go on working, and unless a relief valve is fitted, the chest or connections would be damaged. The feed relief valve should be placed on the pump chest between the suction and delivery valves, so that, should the delivery valve seat lift up with the valve, the relief will act and prevent damage to the chest. If the check valve on the boiler stuck or was left shut, the relief vahe would also act and save the feed pipe from bursting. In an ordinar)' feed pump, it should be noted that, with the chest cover off, the top of the suction valve is always open to the pump plunger, and the bottom of the delivery valve is open to the plunger. A Plungfer pump has suction and delivery valves, and is a single- acting force pump. No. 9.— Bucket Air Pump. 292 " Verbal " Notes and Sketches A Bucket pump has foot, bucket and head valves, and is a single- acting lift pump. Broken or leaky foot valves do not, in most cases, affect the vacuum, as the pump is placed much lower down in position than the bottom of the condenser, but the foot valves act to control the action of the pump and induce more regular flow. Broken or leaky bucket valves affect the vacuum most, and broken or leaky head valves next. The Edwards Patent Air Pump. In the Edwards air pump, as will be seen in the sectional illustra- tion, foot and bucket valves are dispensed with ; the water flows continuously by gravity into the base of the pump, and being dealt No. 10.— Edwards Air Pump. with mechanically by the conical bucket working in connection with a base of similar shape, is projected silently and without shock at a high velocity through the ports into the barrel. As soon as the ports open, there are clear inlets for the admission of the air, and the water is immediately afterwards injected, thereby tending to compress the air in the barrel and carry in more air with it. Another important feature of the Edwards pump is that the top clearance is reduced to a minimum. Before any air pump can dis- charge, the pressure in the pump must exceed that of the atmosphere, and thus all air remaining in the pump is compressed. As soon, however, as the bucket descends, and the pressure is reduced, the air in the clearance water is given off, and expanding, occupies space General Notes and Descriptions 293 in the pump which should be available for a fresh supply from the condenser, consequently the smaller the top clearance the more efficient is the pump. The practical advantages of the Edwards pump are numerous ; there being no foot and bucket valves, the risk of breakdown and stoppage through the failure of valves, which cannot be -examined while the pump is at work, is eliminated, and there being only one set of valves instead of three sets, the cost of maintenance and the time necessary for overhauling are reduced to a minimum. By means of the door at the top of the pump the only valves used can be readily examined, and if necessary can, in some cases, be renewed while the engines are running, without loss of water or vacuum. QEUVERY SUCTION DELIVERY SUCTION INTECTlON No. II.— Double-acting Circulating Pump. A Piston pump has suction and delivery valves at either end, and is a double-acting pump. On the up stroke the bottom suction and top delivery valves are open, and on the down stroke the top suction and bottom delivery valves are open. Air-\alves are usually fitted to either end of the pump to admit air to allow of cushioning of the water. A Centrifugal pump, as the name implies, works from the centre, and consists of a cast-iron chamber containing hollow vanes kej'ed to a spindle; a small engine coupled direct to the spindle rotates the vanes, and the water entering, by suitable passages, the pump casing at the centre, where the vacuum is created by the rapid vane rotation, travels through the hollow vanes and is delivered tangentially at the circumference of the vane circle: thus peripheral force is converted into pressure head. This type of pump has no valves. The usual driving speed of the pump is from 180 to 220 rcvolu- 294 ' "Verbal" Notes and Sketches lions per minute. If by mistake the engine is started to run in the wrong direction, the water will merely be churned by the impeller, and no effective discharge will take place. Sometimes a steam pipe and cock is fitted on the pump chamber to assist in starting by blowing through a jet of steam, which, on condensing, produces a partial vacuum. In place of this, the pump may require to be first " primed," that is, filled up with water ; the air escaping meantime by a small air-cock on the top. In ordinary practice, however, neither of the above aids to starting are required, as the position of the pump being lower than the sea level, the water flows by the force of gravity into the pump chamber, the air being allowed to escape by the small cock fitted on top of the pump casing. This type of pump is of low dis- charge pressure and would not be suitable for, say, boiler feeding, unless two or more pumps of the same type were coupled up " in series" (as in coal mine practice), which arrangement would result in increase of water pressure. Breakdown of Pumps. If the air pump breaks down, feed the boilers by " Weir's " pump, which usually has a suction direct from the condenser. If no such connection is fitted, remove the air pump bucket and valves, leave on the cover and rod, close the hot-well overflow pipe, and allow the water in the condenser to drain into the hot-well. Draw the feed from there by the main feed pumps or the donkey pump. The vacuum will of course go back in this case, and most likely disappear altogether. If the circulating pump breaks down, put on the ballast donkey to the condenser for circulating ; if it is not suitable for this, then the engines must be worked jet condensing. To effect this draw' a number of the condenser tubes, aitd open up the air pump discharge valve ; also when under weigh again take the boiler density oftener, as the feed will be chiefly salt water. To find number of tubes to draw :■ — Injection pipe diameter^ ^ ^^^^^^^^ ^^ ^^^^^ Condenser tube diameter^ Loss of Vacuum. Vacuum may be lost through the following causes : — 1. Head or bucket valves of air pump broken. 2. Valves of circulating pump broken, or injection choked. 3. Division plate in condenser door carried away. 4. Leaky L.P. gland. To find the probable cause of the vacuum going back, feel the temperature of both ends of the condenser. If both ends are cold, broken air pump valves are the cause, or leaky L.P. gland. If both No. 12.— Centrifugal Type Circulating Pump- I, Inlet from main injection. 3, Water flow to each side of pump. 3, Water inlet to pump at centre. DATA. • ■ in inches of suction or deliver; pipe:= / l.H.r. V '7* Vacuum position. Delivery at periphery of pump. Driving shaft of engine. (■04S •7854 NOTE.— Allow -045 square inch of pipe area per I.H.P. Diameter of impeller = Diameter of pipe x 2-5. Diameter of inlet opening at centre = Diameter of pipex [•!. Example.— Determine the diameter of circulating pump suction and delivery pipe, the diameter of the impeller, and the diameter of inlet opening at pump centre for an engine of 1800 I.H.P. Then, Diameter of circulating pipe= / i8oox-045 ^ ,„ inches. V 7854 and, Diameter of impeller = 10 x2-5==25 inches, Diameter of inlet at centre^ 10 xx-x=ti inches- [Tr/iu* fit^ 294- ' VerVial " Notes and Sketches. General Notes and Descriptions 295 ends are warm, either broken circulating pump valves or choked injec- tion valve is the cause. If one end is cold and the other end warm, the division plate in the condenser is most likely carried awa}'. NOTE. — 24 inches of vacuum means that the air pump has drawn 12 lbs. of air pressure out of the condenser, leaving 3 lbs. absolute back pressure on the L. P. piston. Pet Valves. On feed or bilge pumps the pet valve is usually placed between the suction and delivery valves. On double-acting circulating pumps a pet valve is placed on the suction side of the pump at both ends. On air pumps the pet valve is placed high up on the pump chamber, just under the head valve, so that the air drawn in for cushioning the water will not affect the vacuum under the bucket. Many air pumps have no pet valves fitted. On horizontal double-acting piston air pumps no pet valves are fitted, as, no matter where they might be placed, the air drawn in would affect the vacuum more or less seriously, since suction valves are fitted at both ends of the pump. Air Vessels. Air vessels are usually fitted on single-acting pumps, to give a continuous flow of water similar to that of a double-acting pump. 'S ^liCt FR3M Pump TO fl>>r>.tRS 15 arc; No. 13. — Closed Type Air Vessel. No. 14.— Open Type Air Vessel. 296 *' Verbal" Notes and Sketches They are made in two ways— (i) A plain dome with the air for compression in the top, the water entering and leavmg by the same branch. (2) A dome open at the top, with a pipe extendmg down about three-quarters of the length of the vessel ; the pipe is to allow of an air space round it, and the water in this case passes up through the pipe and top of vessel into the main feed pipe. On the down stroke of the pump plunger the water pressure compresses the air in the top of the vessel, and on the up stroke, the pressure being released, the air reacts on the water, and forces it out of the chamber and along the feed pipe, thus giving a continu- ous flow, similar to that obtained by a double-acting pump. NOTE.— The Board of Trade appear to object to cocks or connections of any kind being fitted to air vessels. The Condenser and Air Pump. The function of the air pump is to draw out the air and water from the condenser, and, b}' the vacuum formed, to reduce the back pressure on the L.P. piston. As all water contains a certain proportion of air, the feed pumps deliver air into the boilers along with the feed water, and most of the air so brought in is carried back with the steam to the condenser, where it remains in the form of back pressure. Air cannot be con- densed in the same manner as steam, and for this reason the air pump is required to take out the air and reduce the back pressure by the formation of a vacuum in the condenser. The valv^es most necessary in the air pump to maintain the vacuum are the bucket and head valves ; foot valves are not absolutely neces- sary when the pump is placed lower down than the bottom of the condenser, as the water will then flow by gravit}' into the pump chamber. The air pump only delivers about -J inch depth of water over the valves each stroke, the remainder of the pump being filled with air and vapour. On the up stroke of the air pump the foot valves and head valves are open, and on the down stroke the bucket valves onl}- are open. If the vacuum gauge indicates 24 inches, it means that the air pump has taken 12 lbs. of air pressure out of the condenser, which leaves a back pressure of 3 lbs. gross, as 15—12 = 3 lbs. Oscillating Engines. The steam enters the valve chest through one of the trunnions (usually the outer), and after doing its work in the cylinder exhausts through the other trunnion. The trunnions allow the steam to pass to and from the valves, and also allow for the oscillation of the cylinder. fdy-' fsjjC^- -x**^^ No. 15.— Surface Condenser (Two Flow Independent Type). 1, Exhaust or eduction pipe from L.P. cylinder to condenser. 2. Air pump suction. 3, Delivery from circulating pumps to condenser. 4, Circulating discharge from condenser to ship's side. 5. Stays. 6. Division plate. DATA. Cooling Surface. I.H.P. = i8oo. Allow 1.4 square feet cooling surface per I.H.P Tubes, 10 feet by J inch external diameter. 1800 y] Then, number of tubes- -75 7, Hand hole. 8, Bafflff plate for steam. 9, Supplementary feed. 10, Tube plate. 11, Screwed ferrule. 12, Packing space. 3-1416' 1283 tubes. Assume exhaust ste; then. NOTE.-The cooling surface of a tube in square feet = Iength in feet x circumference in feet Circulating Water. I pressure = 5 lbs. absolute and temperature 162°, hot-well temperature 130°, sea 60', and di9v.-harge 102', 1115 h -3 ^ 162^-1163-6 total heat of steam, "d, 1163-6- 130-1033-6 units to be extracted. Again, 102 -60-^42 units absorbed by each pound of cooling water, then, 1033-6^^2-24-6 lbs coolmg vgater required per lb. steam. Assuming 15 lbs. steam per I.H.P. per hour, then, 1800X 15^24-6 = 664200 lbs. of circulating water required per hour. -Air Pump Water. Exclusive altogether of expanded vapour and neglecting losses, the air pump will lift per hour 27000 lbs. of feed water and discharge it into the hot well, as 1800 x 15 = 27000 lbs. \Tc/au page 2961 ' Verbal " Notes ami Sketches. General Notes and Descriptions 297 An expansion joint is formed between that part of the steam pipe which enters the trunnion and the trunnion itself. The flanges of the steam pipe are bolted to a bracket on the engine framing, as will be seen by referring to the sketch, and this does away with the necessity of having a collar on the pipe and long tuds, as are usually fitted to expansion joints of steam pipes. ..r\ No. 16.— Oscillating Cylinder and Trunnions. To test if one or other of the trunnion bearing brasses have worn down, slacken back the piston rod head bolts and measure the clearance between the crank web and piston rod brass at the top centre and the bottom centre ; if the sizes do not agree one of the trunnions has worn down. In oscillating engines the feed and bilge pumps are worked by large eccentrics, fixed either on the shaft or on the trunnions, and the air pump by an extra crank on the main shaft : to allow of this the pumps are usually of the trunk pattern (see sketches). The valve gear of the oscillating engine (see sketch) consists of two vertical pillars, connecting the top and bottom framing, with a slotted quadrant working between them on brass shoes. The reversing link from the eccentrics connects to a block on the quadrant. The radius of the slot in the main quadrant is taken from the centre of the trunnion with the gear at half position, the radius of the reversing link slot is taken from near the shaft centre. Usually two valves are fitted, one on either side, each suppl}'ing steam simultaneously to the cylinder or exhausting simultaneously from the cylinder. The block on which the reversing link slides is a fixture, it should be 298 "Verbal" Notes and Sketches PUMP CRANK TRUNK PUMP ECCENTRIC No. i8. — Method of working Pumps in Oscillating Engines. noted, to the main quadrant, and the drag link changes the position of the link and rods from ahead to astern as required. A rocking lever works on a pin fixed on the side of the cylinder, and one end of the lever moves in the slot of the quadrant as the cylinder oscillates ; the other end is connected to the valve spindle, and so gives the necessary travel to the valve, but in the opposite direction. NOTE.— For a slide valve, the eccentric key centre is placed behind the crank at an angle of 90% minus lap and lead, because the rocking lever reverses the motion, but if a piston valve (inside steam), the key is cut at an angle of 90° plus lap and lead before the crank, as the one position corrects the other. Diagonal Engines. No. 19.— Diagonal Engine and Air Pumps. A-^ TOP CENTRE No. 17.— Oscillating Engine and Valve Gear Complete. . Cylinder bell through which the steam passes ftom ihe admission truiimoiis to the valve chest or thn ' Valve chest. Valve rod. Pin fixed to cylinder side and on Guide bracket for valve rod. Rocking lever, one end of which connected to the valve spindle . Moving blocks of rocking levers. . Fixed block on main quadrant an , Tail guide rod of main quadrant . Reversing link. . Drag link. . Vertical pUlara or columns on which work . Valve travel circle. . Main quadrant . Ahead pulley. B = steam Lap and lead. which the rocking lever moves by a movable joint, thus conveying t d on which the reversing link slides 1 : travel to the valvt i( the drag link. m General Notes and Descriptions 299 In diagonal engines the pumps are often worked by bell crank levers connected to the piston rod crosshead (see sketch), and the pumps are usually made of the trunk type. Trunk Engines. A trunk engine has no piston rod, but simply a connecting rod extending between the crank-pin and the piston. The trunk passes No. 20.— Trunk Engine and Double-Acting Air Pump. through both ends of the cylinder, and is bolted by a flange to the piston. For a right-handed propeller this type of engine is placed on the starboard side of the engine-room, so that when going ahead the stress will be thrown on the top side of the trunk and piston ; for a left-handed propeller the engine would be placed on the port side to obtain the same result. The air pump shown on the sketch is of the double-acting type, and has foot and head valves at either end, and a solid piston ; the condenser suction is below, and the hot-well above. When the engines are of the inverted type, the pump is worked from the main shaft by an eccentric, or by a pin on the crank web. Paddle Engine Cranks. In nearly all paddle engine crank-shafts, the crank-pin is only fixed to one web, and is an easy fit in a brass bush in the other web (see sketch). This is to allow for the extra wear which takes place at the outside bearing due to the weight of the paddle wheels. The crank-pin is fitted into one web by a taper and nut, and in the other web it is simply a loose fit in a brass bush as previously stated. This arrangement allows for the shaft wearing down outside, and prevents undue stresses being thrown on the web and on the pin. In ordinary paddle engines with double cranks the crank-pin is fixed to the inner web and is loose in the outer web, but in discon- necting paddle engines the reverse is the case, that is, the pin is fixed to the outer web, and is loose in the inner one. This is to allow ,300 " Verbal " Notes and Sketches No. 21.— Method of Testing Fairness of Paddle Shaft. of the inside crank being drawn away from the pin when the engines have to be disconnected. From the above it will easily be understood that to test if the outer bearing is wearing down, the cranks must be placed on the top centre, and the distance between the webs at the top taken by a length stick ; then the cranks put on the bottom centre, and the same distance again measured ; if it is found that the top width is greater than the bottom, the outer bearing will be down. To find Thickness of Liner for Outer Bearing. Referring to the sketch, suppose that the distance between the webs is I inch more at the top than at the bottom, and the distance from the top of the web to the centre of the shaft is A, and from the caitre of the outer bearing to the inside of the web is B, then by proportion as follows : — As A : B : : i inch = thickness of liner required. NOTE.— Observe that it is only half the amount that the webs are open at top more than at bottom, which is taken for the third term. General Notes and Descriptions 301 Paddle Shaft Flexible Coupling. If the crank-shaft of a paddle engine is made similarly to that of a screw steamer, that is, with the webs and pins forged solid, or built up, allowance for wear down is arranged for by a flexible coupling fitted between the paddle shaft and the crank-shaft (see' page 325). The coupling consists of a hard rubber ring fitted between the two flanges with the coupling bolts an easy fit in one side, the holes being made larger for that purpose. This allows for the outside bearing wearing down, and prevents the pin and webs from being subjected to heavy stresses in consequence. Feathering Paddle Wheel. In a feathering paddle wheel the floats are hung by pins to brackets on the circumference of the wheel, the brackets being bolted to the rim and forming continuations of the paddle arms. No. 22. — Feathering Paddle Wheel. The floats have small feathering levers (see sketch) fitted on the back, to which the eccentric rods are connected by pins hi brass bushes, the other end of the rods being fitted in a similar manner to the feathering strap. 302 "Verbal" Notes and Sketches The feathering- pin is fixed to a bracket bolted to the outer paddle box, and its centre is placed forward of the shaft centre and higher up so that the pin position is " eccentric " to^ that of the shaft ; the feathering strap revolves round the pin which is stationary. One rod, called the " driver," is made of greater strength than the others, and, No. 23. — Feathering Paddle Wheel. instead of being secured to the strap by an eye and pin, is fitted in to a specially arranged recess and firmly bolted there ; the other end of this rod is connected to the float in the same manner as the other rods : the driving rod gives the motion to the feathering strap, and therefore to the other rods. The feathering pin being eccentric to the shaft, the floats are feathered as the wheel turns round, that is, they alter their angle so as to enter the water in a vertical position, and thus obtain a good thrust, and leave it at an inclined position, which prevents loss of power by water being lifted up. The various pins mentioned are brass bushed, and lubricated with water. General Notes and Descriptions Engine-Room Appliances. 303 rrom Auxil. Feed Pumps 125° To eondenw OOO^gj) to Pupps No. 24— "Weir" Feed Heater In this well-known type of feed-water heater, the heating steam is taken from the low-pressure receiver of the main engines and exhaust of the auxiliary engines, and enters the heater through a non-return valve on the side ; the feed water is forced up into the top of the heater by the main feed pumps on the engine, and, the pressure of the water overcoming the tension of the spring, forces open the internal valve and allows the water to enter the body of the chamber, through a perforated ring in the form of a fine spray, which, 21 ]04 ''Verbal" Notes and Sketches iS*< No. 25.— Weir Vertical Type Evaporator. General Notes and Descriptions 305 No. 26. — ^Weir Vertical Type Evaporator. 3o6 " Verbal " Notes and Sketches meeting the heating steam entering by another set of perforations becomes raised in temperature to that of the steam: the air present in the water is set free by the heat, and rising, escapes from the heater by a cock on the top to either the condenser or the atmosphere. The float shown near the bottom of the heater is connected by a system of levers to the steam stop valve of " Weir's" pumps, which take away the hot feed water and deliver it into the boilers, and as the water level in the chamber falls, the float sinking shuts off the steam supply to the pumps, so that they work slower, and, on the other hand, when the water level is high, the float rising correspondingly opens the steam valve, and the pumps work faster in proportion. Two pressure gauges are fitted on the top of the heater, one to indicate the water pressure entering, and the other to indicate the pressure in the body of the chamber, upon which latter depends the temperature of the hot feed water. NOTE.— With a pressure of 5 lbs. in the L.P. receiver, the feed temperature in the heater will be about 220^ Advantages of Feed Heating. The practical advantages of feed heating are as follows : — 1. Less straining of the plates in high-pressure boilers. 2. Less air enters the boilers, and consequently the corrosion due to oxygen is reduced. 3. The boilers steam better with hot feed water, as circulation is checked when cold water enters a boiler. 4. The heat of condensation of the steam is given up to the feed water instead of being given to the circulating water and lost over the side, as would be the case if the steam condensed in the condenser. "Weir" Evaporator. The Weir Vertical Type Evaporator is a single casting of close- grained cast iron. The heating surface is formed of heavy solid drawn copper tubes attached by hollow conical couplings, at one end to the steam inlet chamber cast on the side of the evaporator, and at the other end to the corresponding outlet chamber cast alongside it. The tube space is separated from the steam space by a deflector. The arrangement of this deflector allows the steam to rise, but throws down the water so that it is returned again to the water space. With this arrangement it is almost impossible to make the evaporator prime under anything like reasonable limits. The usual mountings consist of steam inlet valve, steam outlet valve, feed check valve, brine valve, drain valve and coupling to hot-well, blow-off cock, safety valve, gauge glass fittings, pressure gauge, compound gauge, salinometer valve, also gun-metal feed pump to work off main engines. General Notes and Descriptions 307 1, Steam Slide Valve Chest. 2, Double Joint. 3, Front Stay. 4, Bottom Spindle. 5, Valve Gear Levers. 6, Front Stay Bush. 7, Ball Crosshead. 8, Main Crosshead. 9, Crosshead Pin. 10, Piston Rod. 11, Piston Body. 12, Piston Rings. 13, Cylinder Cover. 14, Discharge Valve Seat. 15, Discharge Valve Seat Ring. 16, Suction Valve Seat. 17, Suction Valve Guard. 18, Discharge Valve Guard. 19, Water Valves. 20, Bucket. 22, Pump Cover. 23, Valve Chest Covers. 24, Steam Stop Valve. 25, Exhaust Stop Valve. No. 27.- Sectional View, Weir Standard Feed Pump. 3oS "Verbal" Notes and Sketches List of Parts of Evaporator. 1. Shell of Evaporator. 2. Main door of Evaporator (i) for withdrawing tube coils (6). 3. Hand cleaning door. 4. Bafifle plate, or deflector. 5. Shelves for supporting tube coils (6). 6. Evaporating tube coils. 7. Inlet steam couplings for coils (6). 8. Drain outlet couplings for coils (6). 9. Coupling nuts for 7 and 8. 10. Inlet steam header. 11. Drain header. 12. Drain collecting pocket. 13. Inlet vaJve for steam coils (6). 14. Valve for drain from coils (6) to hot- well. 15. Feed check valve. 16. Brine valve. 17. Salinometer cock. 18. Cock for blowing off to sea. 19. Top cock for water gauge. 20. Bottom cock for water gauge. 21. Safety valve. 22. Outlet valve for generated steam. 23. Compound gauge for generated steam in shell (i). 24. Cock for compound gauge (23). 25. Pressure gauge for inlet steam to coils (6). 26. Cock for pressure gauge (25). 27. Swing crane bar for door (2). 28. Eye bolt for supporting door (2) on crane bar (27). 29. Connection from top of water gauge. (19) to steam space in Evaporator shell ( I). Weir's Patent Direct-Acting Feed Pumps. (To work in connection with Main Feed Pumps and Heater.) The Weir pump is of the direct-acting type, and has suction and delivery valves for top and bottom independently. The pump is vertical, single cylinder, and is usually supplied in pairs. The steam piston is fitted to the top end of the rod, and the water piston to the bottom end, the latter being smaller in area than the former. Weir's feed pump is a slow-speed, high-pressure, full-stroke pump. Group Valves. — These are milled but of the solid metal, and are arranged to give a large area with a small lift. Each seat contains a number of small valves, and in all cases these are duplicate, with a lift of ^ inch. The delivery valves have light springs fitted. The suction seat contains a /argernumher of small valves than the delivery seat ; it will therefore be noted that the delivery valves have /ess area than the suction valves, and in addition have small springs fitted to keep them down. The screwed pin in the centre of the valve box covers is for keeping the valve guards in position, and is not for regulating the lift of the valves. The Weir Steam Valves. — The steam valves of Weir's pumps are simple in action, and the main valve face (known as the "shuttle" valve) is half round instead of flat, and instead of travelling up and down is moved by steam horizontally from side to side. The ports General Notes and Descriptions 309 End View. Cylinder Face (Half Round). A, Steam Port to Cylinder Bottom. C, Steam Port to Cylinder Top. B, Exhaust Port. No. 28. — Weir Pump Cylinder Ports. are therefore arranged to allow of this, and are cast side by side in place of one above the other. The result is, of course, the same, as the left-hand port leads to the bottom of the cylinder, and the right- hand port to the top (see sketch). Main Valve. — x'\s before stated, this valve is moved by steam hori- zontally in the chest, and in this way opens up the cylinder ports from steam to exhaust at the end of each stroke. It must be remembered, however, that previous to this the steam passing through the main valve into the cylinder ports has already been cut off by the expansion valve at three-quarters stroke. The ends of the main valve are round, and work in extended cylindrical casings at each side of the chest, the valve being moved across by steam alternately admitted and exhausted from the ends which act as pistons. The main valve has two faces. That on the front contains four ports, two steam and two exhaust. The face on the back contains five ports (see sketch). The port E leads from back to front and admits steam to the cylinder bottom by port A. The port D leads from back to front and admits steam to the cylinder top by port C. The port G admits steam to, or allows of exhaust from, the left side of the chest in which the round end of the main valve works steamtight. The port H admits steam to, or allows of exhaust from, the rigJit- hand side of the chest in which the round end of the main valve works steamtight. The centre exhaust port F is common to all the ports. Observe that port G leads to the left-hand end, where a small hole allows the steam to pass out and act on the piston end of the main valve to ,10 " Verbal " Notes and Sketches JUL F F No. 29— Main (Shuttle) Valve Front Face (Half Round). No. 30.— End View (Left). ^ 1 i ^ J SB s No. 31.— Shuttle Valve Back Face (Flat). force it across ; it also allows of exhaust to take place from that end to the exhaust port F by means of the small auxiliary or expansion valve. Auxiliary Valve. — This small valve works vertically on the back of the main valve, and admits steam to the ports E D and G H alternately, or allows of exhaust from H and G to port F. The auxiliary valve is moved up and down by the levers from the General Notes and Descriptions 311 pump rod striking a pair of adjustable nuts fitted in the valve spindle, the distance between the nuts allowing of a certain amount of lost motion. The auxiliary valve has two separate functions : — 1. To work the main slide valve by admitting steam and exhaust- ing it from the valve ends ; and 2. To cut off steam at a definite part of stroke. No. 32.— Expansion (Auxiliary) Valve Face. No. 33.— End View of Main and Auxiliary Valves in Position. Action of Valves (Up Stroke). — When the cylinder piston is on the bottom centre, the main valve is at the right-hand side of the chest, and the auxiliary valve at its lowest position. Steam is then entering through the main valve port E into the bottom port A of the cylinder, and to the left-hand end of the main valve by port G : this continues as the piston moves upward until about half stroke, when the lever strikes the nut on the auxiliary valve spindle, and the valve coming up cuts off the steam entering port E at about three-quarters stroke ; the steam in the main valve and cylinder then expands and completes the stroke. When the piston reaches the end of the stroke the auxiliary valve opens up the exhaust port G from the left-hand end of the main valve, and the steam acting on the other end, forces the valve across, thus opening the bottom cylinder port A to the exhaust 312 " Verbal " Notes and Sketches No, 34. — Plan of Main and Auxiliary Valves in Position for Steam to Bottom of Cylinder. and at the same time opening the top cylinder port C to steam for the down stroke. For the down stroke the same process is gone through with the other ports, the main valve moving in the opposite direction, that is, from left to right. It is important to note that the main valve does not move until one end is opened to exhaust : it is then forced across by the steam pressure on the opposite end. The auxiliary valve after opening the end to exhaust by port G or H, is arranged to close again, so that steam is retained to act as a cushion to the main valve when it flies over, and thus prevent hammering on the chest end covers. It will be seen from the fore- going that the valve gear is positive in action, the main valve being always open to steavi for one end of the cylinder, and to exhaust for the other end, with the piston on the corresponding centre. It is therefore impossible for the pump to stick on the centre points. Bye-Passes. — Small bye-passes are fitted at each end of the cylinder to admit steam full stroke when required. This may be necessary when starting the pumps, as the cylinder may then contain a quantity of water. " Knocking " can also be reduced by suitable adjustment of the bye-passes. The bye-passes are formed either by notches cut in the edges of the cylindrical caps, which may be opened or shut by turning round the caps, or by parallel plug cocks, one at each side, which can be adjusted to admit as much steam as required for the occasion. To Adjust the Length of Stroke of a Weir Feed Pump. This is done by screwing the valve spindle up into the joint until the piston comes to rest against the cylinder cover, without having raised the auxiliary valve sufficient to throw the main valve. By noting the distance of the crosshead from the gland when the piston is against the cylinder cover, the spindle can be brought down until the valve throws and the piston clearance is h inch. The lock nut General Notes and Descriptions o'o should now be carefully fixed to prevent the spindle from shaking loose. The bottom stroke adjustment is done by slacking the nuts on the bottom end of the spindle. These should be screwed down until the piston rests against the bottom of the cylinder, and by again notin"- the distance of the crosshead from the pump gland you can again adjust it for the valve to throw when the pump has ^ inch of clearance. Always run the pump slozvly when adjusting the stroke. It is most important that anyone having the working of a "Weir" Pump should become familiar with the method of adjusting the stroke. Feed- Water Filters. A feed-water filter is employed to prevent oil and grease from entering the boilers with the feed water. It is usually placed between the feed pumps and the feed check valve, and consists of a cast-iron No. 35.— Feed Water Filter. (American Steam Gauge and Valve Manufacturing Co.) chamber containing a series of perforated brass plates with filter cloths fitted between them, or brass grids arranged in a similar manner. The feed water is forced through the perforations and cloths, and leaves behind the greasy matter, which is blown out at intervals. The fittings on the filter are : — Bye-pass valve (used when cleaning out or changing the cloths), safety valve, pressure gange, soda cock, and drain cock. Sometimes, instead of cloths, ashes or charcoal are used as the filtering medium. 314 ^'Verbal" Notes and Sketches Aspinall's Patent Governor. Aspinall's patent governor is usually bolted to the side of the pump levers, and consists of a frame containing a hinged weight W, which operates on two pawls P, P ; the pawls when in action striking a lever connected to the throttle valve and so regulating the steam supply to the engines. No. 36.— Aspinall Governor. When the revolutions increase by about 5 per cent, above the normal speed, the weight W is left behind by the increase of momentum, and this reverses the position of the pawls, causing the bottom one to fall out and strike the lever H, and lift it on the upward stroke ; the throttle valve is by this means closed : on the downward stroke the detent D is lifted, and this again sets free the weight W, and, if the racing is over, the top pawl P strikes the lever H and brings it back again to its original position, which has the effect of reopening the throttle valve. An emergency gear is also fitted, which locks the weight W in the shut-off position, in the event of a serious accident happening, such as, for example, the shaft breaking or the propeller coming off. This type of governor is fitted to the turbine steamer " Carmania." Vorthington Vertical Type Feed Pumps (Sketch No. 37). These pumps are supplied in pairs, the crosshead of one pump actuating the steam valve of the other pump. The steam valve is generally of the piston type and is allowed about \ inch or f inch " lost motion " to allow of full steam admission each stroke ; double ports are arranged for at top and bottom, the outer one being for steam admission only and the inner one for exhaust only, compres- sion and cushioning being provided for by the piston travelling over and closing the inner or exhaust ports, and so retaining the required amount of compression steam. The water valves are spring loaded, and are, of course, four in number, one suction and one delivery for either end of pump. By the momentary pause which occurs at the end of each stroke, the suction valve of one end and the delivery valve of the other end get time to seat themselves quietly and without shock. General Notes and Descriptions 315 No. 37.— Worthington Patent Feed Pump. 3i6 "Verbal" Notes and Sketches To Set the Valves of a Worthington Type Pump. The steam valve of a Worthington pump has no outside lap, consequently, when in its central position, it just covers the steam ports leading to opposite ends of cylinder. By lost motion is meant the distance a valve rod travels before moving the valve ; or, if the steam chest cover is off, the amount of lost motion is shown by the distance the valve can be moved back and forth before coming in contact with the valve rod nut. To set the piston in the middle of its stroke, open the drip cocks and move piston by prying on the crosshead (not on lever), until it comes in contact with the cylinder head ; make a mark on piston rod at face of steam end stuffing box follower ; move piston back to contact stroke at opposite end. Make second mark on piston rod half-way between first mark and the aforesaid follower. Then if piston is again moved until second mark coincides with the face of same follower, it will be exactly at the middle of its stroke. Bear in mind that the piston on one side moves the valve on opposite side. {a) When the steam valve is moved by a single valve rod nut. Place one piston in the middle of its stroke ; disconnect link from head of valve rod on opposite side. Then set the valve in its central position ; place valve nut evenly between jaws on back of valve, screw valve rod in or out until eye on valve rod head comes in line with eye of valve rod link ; then reconnect. Repeat the operation on opposite side and the valves will be properly set. {b) When the valve rod has more than one lock nut. Place one piston in the middle of its stroke and the opposite slide valve in central position ; adjust lock nuts so as to allow about yV inch lost motion on each side of jaw, and valve is set. Do not disconnect the valve motion. Repeat operation on other side. The best way to divide the lost motion equally is to move the valve each way until it strikes the nut or nuts, and see if the port openings are equal. It is advisable to place both pistons at the middle of their strokes before touching either slide valve. Too much lost motion will tend to lengthen the stroke, and may cause the piston to strike the cylinder heads ; vice versa, when there is not enough lost motion the stroke will be perceptibly shortened. Lament Pump (Sketch No. 38). Action. — P is the auxiliary piston, which, with both slide valves S and T, is moved by the main piston B before coming to rest, by means of the links and levers to a little over the central position, and this puts one end of the auxiliary cylinder R in communication with pressure and the other end with the exhaust, whereby the auxiliary piston and valves S and T are moved by the steam pressure on P to the extent necessary to give full port openings to the main General Notes and Descriptions Z^7 cylinder, and at the same time the auxiliary piston P covers the supplementary port V to the end of the main cylinder, which is open to the exhaust and uncovers the one at the end open to steam pressure. The opening and closing of the supplementary ports VS V by the piston 1* takes place simultaneously with the opening of steam or exhaust to the ends of the auxiliary cylinder R, so that as soon as either supplementary port V^ or V is uncovered by P, steam is admitted to that end of the auxiliary cylinder by the slide No. 38.— Lamont's Patent Pump. valve T, and conversely as soon as the slide valve T opens either end of the auxiliary cylinder to exhaust the supplementary port in that end V^ or V is covered b}- P. The drawing shows the piston P and the auxiliary valve T in the central position, but the main valve S is still open, and will cause the main piston B to move in the direction of the arrow until it passes the port \V, which is open to the exhaust, when it will graduall)- be brought to rest by the imprisoned steam forming a cushion between the piston and the end of the cj-linder, as 3i8 "Verbal" Notes and Sketches this space is now completely closed. The stop nuts N N are fixed on the valve spindle M in such a position as just to move P a little over the central position before the main piston B comes to rest. The auxiliary valve T will then admit steam by the auxiliary port Z to the end of the auxiliary cylinder R, and at the same time the other end of the auxiliary cylinder will be opened to the exhaust through the port Z^ The pressure of the steam will thus cause the auxiliary piston, with both slide valves S and T, to move to the other end, and so reverse the steam and exhaust passages to the main cylinder, but as the main piston B still covers the port W in the cylinder, the steam will only be admitted through the supplementary port V until the piston B has moved so as to uncover the port W and allow the full flow of steam. The compression and slow reversal of motion is the same for both ends of the stroke. Engine and Boiler Data. A good idea of the general proportions and dimensions for a steamer of given speed and power will be obtained from the following data taken from a modern fast ocean-going steamer : — Boilers, Number 2 single-end ; 2 double-end Pressure - 185 lbs. Diameter 15 ft. 6 in. Length - 10 ft. 6 in.; 18 ft. Number of furnaces - 18 H.S. total - 14840 sq. ft. G.S. „ - - 465 „ LH.P. on trial - 6500 Speed ,, - 17 knots H.S. -LH.P. - 2-28 LH.P. -^ G.S. - - 13-98 H.S. -r G.S. - 31-91 Length over all - - 434 ft. ,, between perps. - 420 ,, Breadth, moulded - - 50 „ Depth, . ,, - 30 ft. 6 in. Height between decks, 7 „ 1 1 „ Gross tonnage - - 5600 tons Engines - - - single, triple Diameter cylinders 31, 51, and 85 in. Stroke - - - 54 „ Valves, piston on H.P., slide on LP. and L.P. Pressure Gauge Indications. The boiler pressure gauge indicates the pressure in the boiler above the atmosphere, and therefore the initial pressure in the H.P. cylinder (less a few pounds drop of the pressure). The M.P. gauge indicates roughly the back pressure on the H.P. piston, and the initial pressure in the M.P. cylinder. The L.P. gauge indicates roughly the back pressure on the M.P. piston, and the initial pressure in the L.P. cylinder. The vacuum gauge indicates how many pounds of pressure the air pump has taken out of the condenser, and if this be subtracted from the atmospheric pressure of 15 lbs., it will give the pressure still left in the condenser, and therefore acting on the L.P. piston as back pressure (approximately). Example. — The boiler pressure gauge indicates 160 lbs., the M.P. gauge 53 lbs., the L.P. gauge S lbs., and the vacuum gauge General Notes and Descriptions 319 24 inches. Allow a drop of pressure between boilers and engines of, say, 5 lbs. Then, Boiler pressure - - - - 160 lbs. gauge. Initial pressure in H.P. cylinder - 155 lbs. „ Back pressure in H.P. - - - 55 lbs. gauge. Initial pressure in M.P. - - - 53 lbs. „ Back pressure in M.P. - - - 10 lbs. gauge. Initial pressure in L.P. - - - 8 lbs. „ Back pressure in L.P. - - - 4 lbs. gross. Pressure in condenser - - " 3 lbs. „ Notice that the gross back pressure on the L.P. piston is obtained by taking the vacuum in pounds from the atmospheric pressure. Thus : 24 inches -^ 2 =12 lbs., and 15 — 12 = 3 lbs. pressure in the condenser, which is, within a pound or so, the back pressure on the L.P. piston. NOTE. — Allow a difference of about 2 lbs. between the back pressure of the one engine and the initial pressure in the next engine, as naturally a fall of pressure must take place between the two. The Barometer. The barometer is an instrument used in measuring the pressure or weight of the atmosphere. The mercurial type of barometer consists of a glass tube fully 31 inches in length, closed at the top, and open at the bottom to a cup containing mercury. Between the mercury and the top of the tube there is a vacuum practically perfect, and the pressure of the atmosphere acting on the surface of the mercury in the cup forces it up the tube against the vacuum in the top, and so indicates the air pressure. When the weight of the atmosphere is 1 5 lbs. per square inch, the difference in level of the mercury in the cup and tube will be 30 inches, and this is termed the height of the barometer. It will thus be seen that every pound of atmospheric pressure raises the mercury 2 inches up the tube, and the atmosphere being 15 lbs., then 15x2 inches = 30 inches of mercury. If the atmo- spheric pressure fell to 14 lbs. the barometer would show 28 inches, and if the atmosphere increased to 15^- lbs. the barometer would indicate 31 inches, and so on, every pound causing a difference of 2 inches, and every h lb. i inch in the mercury level. High up, as, for example, on a mountain top, the barometer will show less than 30 inches, because the air pressure will be less than 15 lbs. ; and low down, as at the bottom of a mine, the barometer height will be more than 30 inches, as the atmospheric pressure will exceed 15 lbs. If water were used instead of mercur}% then the height of the barometer would be 34I feet, because i 5 lbs. x 2305 = 34-5 feet : this is, at the same time, the theoretical limit that a pump can draw up water. In practice the limit is 26 feet, as it is impossible to obtain a perfect vacuum, even with the best pump fittings, &c. NOTE.— One pound of pressure per square inch is equal to a column of water 2-305 feet in height. 22 320 " Verbal " Notes and Sketches If the pump has to draw water at a high temperature, then the limit of Hft becomes less, as the temperature rises, and at, say, 200° Fahr. the pump would hardly draw up the water any height, owing to the vapour formed destroying the vacuum. This is the reason that "Weir's" feed-heater is placed high up in the engine- room, so that the water may fall by gravity to the pump suction. The barometer can be made to act as a vacuum gauge by opening up the closed end, and connecting it by a pipe to the condenser, the 30 _v_ . ■VACUUM MERCURY OPEN No. 39.— Mercurial Barometer. other end being still left open to the atmosphere. Every pound of pressure taken out of the condenser by the air pump will cause the mercury to rise 2 inches in the tube; therefore if, say, I2i lbs. are drawn out by the air pump, the difference of level in the^cup and the tube will be 25 inches. If there be no vacuum in the condenser, the level of the mercury will be the same in the cup and in the tube, that is, there will be no difference of level. Aneroid Barometer. — The barometer in general use at the present day is of the " aneroid " type, consisting of a vacuum box at the back. General Notes and Descriptions 321 and a set of very sensitive levers connecting to the indicating pointer on the dial face. The variations in the atmospheric pressure act on the back of the vacuum box, and either slightly force it in, or allow it to ease back, and this setting in motion the set of finely adjusted levers and gear, causes the pointer to move round the dial and indicate correspond- ingly the pressure of the atmosphere. The Thermometer. The thermometer is" an instrument used in measuring the temperature of bodies. It consists of a glass tube of fine bore, partly filled with mercury or spirits, and having a bulb at the bottom end, and the top end sealed. In graduating the instrument, the tube is placed in a closed vessel with the steam from boiling water surrounding it, and the heat causes the mercury to expand and rise in the tube ; when the mercury stops rising a mark is made at the level and fixed as 212°, representing the boiling point of fresh water in the atmosphere. The tube is next placed in a dish containing pieces of broken ice, and the cold causes the mercury to contract and fall in the tube, the point when the liquid falls being marked as 32°, which is the melting point of ice, or the freezing point of water. Between the 212' and the 32" marks, the scale is divided into 180 equal parts, each part representing i"" of temperature. NOTE.— Mercury solidifies at -38-5° and boils at 725° Fahr. Tail Shaft Corrosion. On propeller shafts fitted with two separate liners corrosion occurs at the places marked A, that is, at the end of the brass liners. This is caused by galvanic action between the iron or steel of the shaft and the brass of the liners in sea water, and the effect is intensified by the heavy stresses thrown on the shaft when the stern rises and rf~ /\->| fevasj Imtr |<"A A^l ^"'^^^ tiHtT No. 40.— Corrosion on Tail End Shaft. falls in a heavy seaway, and the propeller and shaft strike the water. When a tail shaft breaks it usually gives way at one of the places marked A. The bending stresses are concentrated at the end of the liners, owing to the difference in diameter of the liners and the shaft, and it will be noticed that the wasting away of the latter is due to a combined mechanical and chemical action, one leading up to and assisting the other. 322 "Verbal" Notes and Sketches If the sea water is prevented from coming in contact with the shaft, galvanic action cannot take place, and the shaft is preserved. Therefore all remedies for the preservation of the tail shaft consist of arrangements for keeping the sea water from the shaft. The three most important methods are : — 1. The brass liners carried the whole length of the shaft. 2. A rubber sleeve extending between the two brass liners, and made watertight at the ends. 3. A packed gland at the stern post (outside) between the boss and the stern tube, and oil let into the stern tube for the shaft to run in instead of sea water, the shaft being without brass liners, and running on white metal instead of lignum vitae strips (see Cedarvall's patent stern tube). Iron Shafts. — Many makers prefer good iron for tail end shafts instead of steel, for the reason that under conditions of galvanic action iron does not corrode so fast as steel. Propeller Pitch. The pitch of a propeller means the distance the propeller would travel in one revolution if working in a solid nut. As the propeller works in water, the actual advance is less, owing to slip. The usual amount of slip is from 5 to 15 per cent. The hollowed after surface of the blades is called the "thrust surface," and the rounded forward surface the "drag surface." In running ahead the after surface of the blades thrusts back the water and the resultant reaction thrusts forward the steamer. In running astern, the drag surface thrusts the water forward, and the reaction resulting sends the steamer aft. To Measure the Pitch. — With the ship in dry dock, and the shaft turned round so that one of the blades is horizontal, take a string with a weight tied to each end of it, and hang the string over the blade, about two-thirds out from the boss. Now take a straight-edge and fix it parallel to the shaft, and just touching the bottom end of the blade where the string hangs. The distance between the string is piece of pitch =/, and the length of string from the top of the blade to the straight-edge is piece of circumference = <:. Next measure from the string to the centre of the boss, and multiply by 2 and by 3-1416. This will give the full circumference =:C, at the position of the string and straight- edge ; then by proportion as follows : — As piece of circumference : Full Circumference : : piece of pitch : Full Pitch. Or, as ^ : C : : / : Full Pitch. NOTE.— If the pitch varies radially, take the pitch as described at three different radii, and the mean of the three may then be taken as the average pitch. \ .lelnoshoH ion zi iUriS bodJbOi anil fhriulq idJ ^rbla;!?'. rti ?.& b^nibni No. 41a. -To Measure Pitch when Shaft is not Horizontal. When shall line is not dead horizontal, hut is slightly inclined as in sketch, the plumb lin of pilch measurement does not apply, and steel or wood squares or straight edges should be ar shown to obtain part pitch and part circumference, after which the full pitch can be determined the same manner as shown in No. si- 41 —To Measure Pitch of Propelle (With Shaft Homonlali- / = Piece pitch. .= Piece circumfetcnce C = Full cir umference at position of weights R = Radius, and Radius --2:<3i4i6=C. Then. as C f Full pitch. 1 taken off and put on again reversed (assuniing the shaft parallel at boss), then the propeller will still rentun ew. but the efficiency will be reduced for ahead running, and increased for astern running. [7)3/lUt /^a^e J22. ^w O- J3MMAHT / J3^ ^,11 . H K )1 v-v ji 3f8*:A ii First Mark B Second I 41a.— Crank on Centre. C. Centre Mark. D. Position of Guide and Shoe at each Crank Angle. General Notes and Descriptions 323 To Find the Cut-off. To measure the distance the steam is carried on the down stroke, put the crank on the top centre and mark the crosshead and guide, take off the valve casing cover, and turn the engine round with the turning gear until the valve comes up and closes the port ; when it does so, or cuts off, stop the turning gear, and the distance measured down from the mark on top centre to where the crosshead stops will be the cut-off or distance the steam is carried. NOTE. — ^The exact time of closing the port is best determined by inserting a slip of paper into the steam port, so that the edge of the valve "nips" the paper on the instant of closing the port. Crank on Centre. To put the crank on the top centre, first turn the engine up to near the top, and mark the guide and shoe at D ; then with a trammel fixed on the column, and long enough to reach the crank, mark the top of the crank at A. Now turn the engine over the centre until the marks on the guide and shoe come together again at D, and again mark the crank top with the trammel at B, Find the centre between the two marks on the top of the crank, and make a mark C, and turn the engine until the mark C comes in line with the trammel point. The engine will then be on the top centre. The crank is put on the bottom centre by the same method, the trammel being applied to the bottom end of the crank instead of the top. Cutting of Key Seats (see also page 232). To mark the position of the eccentric key seats on the shaft, first put the crank on the top centre, and with the eccentric gear connected up, turn round the pulley until the valve is open for the required top lead, and mark the shaft. Having fixed the pulley by a set pin, turn the engine to the bottom centre, and easing back the set pin, shift the pulley further round the shaft until the valve is open for the required lead at the bottom, and again mark the shaft. Find the centre between the marks on the shaft, and this will be the position of the key seat. Cut the key seat, bolt on the pulley, and put a liner under the rod to make up the difference of leads top and bottom. NOTE.— If the lead is to be i inch at the top, and i inch at the bottom, the liner v^ill require to be rV inch thick. To Set Valve in Mid Travel. Turn round the engine until the valve comes to its top position, and mark the valve rod at the gland ; then turn the engine until 324 " Verbal " Notes and Sketches the valve comes to its bottom position, and again mark the rod at the gland ; next divide the two marks, and set the valve to the centre mark so found, which will be the exact mid position of the valve. By marking the c)linder face, top or bottom, at the position of the steam edge of the valve, the steam lap can be found by simply taking the distance between the marks and the edge of the steam ports of the cylinder. Shaft Sighting. To test the fairness of a line of shafting by " sighting," obtain three strips of iron all the same length, and with a small hole in two of them, say ^ inch in diameter, cut in each at the same distance up, ilt)HtT\'.? To find the Connecting Rod Length. To find the length of the connecting rod, put the engine at half- stroke, and measure from the centre of the crosshead pin to the centre of the shaft. 328 "Verbal" Notes and Sketches To find the Eccentric Rod Length. To find the length of the eccentric rod (the pulleys being on the shaft), put the crank on the top centre, and set the valve to the required lead, then measure from the centre of the link block to the top of the eccentric strap ; this gives the exact length of the eccentric rod. Another method is as follows : — Place the valve at mid-stroke, and measure the distance between the centre of the link block to the centre of the shaft ; then subtract from this half of the pulley diameter and the thickness of the eccentric strap at the place where the rod joins it : this will leave the length of the rod. Piston Clearance. The piston and cylinder cover clearance at top is usually about f inch, and at bottom about f or f inch. The bottom clearance requires to be more than the top, to allow for the wear down of the top end and bottom end " brasses " or " white metals." To Measure the Piston Clearance. It is measured by turning the crank to the top centre and marking the shoe and guide, then disconnecting the crosshead brasses and lift- ing or wedging up the piston until it touches the cover ; then again mark the guide, and the distance between the marks will be the top clearance. The bottom clearance is measured in a similar manner. Excessive Clearance. Excessive clearance means a distinct loss of heat, because the steam must first fill up the clearance spaces before it can do work on the piston, and, when the exhaust opens, this steam is exhausted out of the cylinder. Prevention of Ridge in Cylinder. Cylinders are usually made bell-mouthed at the bottom to prevent the piston wearing a ridge on the cylinder or liner. Defective Check Valve. With two boilers, if the check valve of one gets so damaged that it cannot be shut and the boiler is getting too much feed, regulate the feeding by the stop valves, partly shutting down the one on the boiler which is getting too much water and opening up the one on the boiler that is not getting enough of feed water. The difference of evaporation will then keep the water from entering the one boiler and allow it to enter the other. The same result can be obtained by firing one boiler more than the other. General Notes and Descriptions 329 U Tube in Pressure and Vacuum Gauges. The gauge tube is of flattened section, as shown in the sketch, and when acted on by increase of pressure, the tube section tends to become more circular, but when acted on by decrease of pressure the tube section tends to become more flattened. This difference in section produces a reaction, the effect of which is to straighten out the tube when the tube becomes more circular in section, and to curl up the tube when the section becomes flatter. For pressure, the tube loses diameter in one direction and gains diameter in the other, being forced more into a circular shape by the action of the steam pressure, whereas in a vacuum gauge, for example, the reverse effect takes place, that is, the tube becomes less circular in section, and takes its length on a more curved line in consequence. It will easily be understood that with the tube quite flat in section the curvature of its length would be at a maximum, and with the tube fully circular in section its line would naturally be straight. Therefore (i) under pressure the long diameter of the tube decreases, and the short diameter increases, and this results in the tube length straightening out and indicating (by means of the small quadrant and toothed gearing) increase of pressure. (2) Under decrease of pressure the long diameter increases and the short diameter decreases, and this results in the tube length forming a smaller curve, and indicating decrease of pressure, or vacuum. o SECTION No. 45. — Pressure Gauge Tube. NOTE. — If the pressures are equal inside and outside of the U tube, the gauge will register o : therefore when the atmospheric pressure increases, the gauge will register less pressure in like proportion, although the actual pressure in the tube is exactly the same as before : similarly, if the atmospheric pressure decreases, the gauge will register more, although the actual pressure in the tube will be the same. Main and Bilge Injection (Sketch No, 46). The illustration shows the usual arrangement of the main and bilge injection connections. Observe that the bilge injection pipe leading from the bilge strum is connected to the main injection pipe by means of a non-return valve, which is peculiar in the fact that the valve and spindle are separate. The valve can be shut down but not lifted up by the screwed spindle, as only the pressure of the water below acts to lift the valve. 330 "Verbal" Notes and Sketches No. 46. — Injection Connections. This type of valve is advisable, as it prevents the return of water back to the bilges. NOTE.— If, when using the bilge injection, the strum becomes choked up, cut the pipe above the strum, and fix a basket over the end of the pipe, or close up the pipe end and pierce a number of holes through the pipe. Thrust. With a right or left hand propeller and the engines going ahead, the thrust is on the after side of the thrust block rings, and on the forzvard side of the shaft collars. With a right or left hand propeller and the engines going astern the thrust is on the forward side of the thrust block rings, and on the after side of the shaft collars. General Notes and Descriptions 33^ The total or combined effective horse-power of the engines come on the thrust block and is transmitted to the ship's hull through the holding down bolts. The following are the points in connection with the thrust block demanding the most careful attention : — • 1. Proper lubrication. 2. Proper adjustment of the rings. 3. Secure bolting down to the ship. No. 47— Thrust Block (Horse-Shoe Type), with bearing at each end No. 48.— End View of Thrust, showing Oil and Water Service, &c. Crank-Pin and Piston Travel. The travel of the crank-pin is about one-half more than that of the piston, for while the piston travels two strokes (up and 332 " Verbal " Notes and Sketches down), the crank-pin travels round a circle, the diameter of which is equal to the stroke. The speed of the crank-pin is about one-half more than that of the piston, or in exact proportion to the extra distance it has to travel. Flaws in L.P. Crank-Pin. The after end of the L.P. crank-pin often develops flaws, usually due to the wearing down of the after lengths of shafting throwing heavy stresses on the L.P. shaft. A built shaft is not so liable to flaws as a solid shaft, owing to the webs and pins being separate pieces ; also with a built shaft, if flaws develop on the pin a new one can be fitted without entailing the condemnation of the whole shaft. Loose Eccentric. This t}'pe of single eccentric is not keyed on the shaft, but is loose circumferentially, and is driven round by a stop on the shaft, striking a corresponding stop on the pulley. Bod ®^^^^ No. 49.— Single Eccentric. The position of the centre of the pulley stop is found by the same method as is used in finding the key seat for ordinary eccentrics (see page 232). General Notes and Descriptions 3'> 3 The balance weight is to counterbalance the weight of the broad side of the pulley, and is fitted on the narrow side. The top of the eccentric rod has a gab or clutch, which, when in gear, fits on a pin in the end of the valve spindle, and gives the motion to the valve. In reversing, this gab is thrown off the pin by a hand lever, and the valve is put in the reverse position by another hand lever, and when the shaft travels round, and the shaft stop strikes the pulley stop on the other side, the gab is again put in gear with the valve spindle, and the engine continues to run in that direction. A spring is often fitted on the rod to force the gab on to the pin. WOOD ZA x WOOD No. 50.— L. P. Cylinder with Top Ports Closed Up. Broken L.P. Cylinder Cover. If the L.P. cover breaks and cannot be repaired, the L.P. engine can be run on the atmospheric principle, that is, with atmospheric pressure on the top side, and steam on the under side. To arrange for this, take off the L.P. valve chest cover, draw the valve, and drive wooden plugs into the two top steam ports, taking care that the plugs are clear of the face : then replace valve and cover and go ahead. The atmospheric pressure will now assist the down stroke of the piston, and the steam pressure, as before, will act on the up stroke. 334 "Verbal" Notes and Sketches As the pressure carried in the L.P. chest is often only a few pounds above the atmosphere, the difference in pressure on each side of the piston will not, in most cases, be excessive. No. 51— LP. Card with Top Ports Closed Up. With the top steam ports closed up the bottom ports will receive steam of a higher pressure than before, as shown by the dotted line, and the back pressure on the M.P. piston will be more in proportion. Observe that the atmospheric line now represents the top diagram. Sight Feed Lubricator. The principle of construction is that of displacement. Oil being lighter than water rises to the surface of the w^ater, and is forced down the internal tube to the sight glass and steam chest. NOTE. — The specific gravity of oil is .9, and of water i. No. 52.— Improved Sight Feed Lubricator. (By Messrs Schaffer & Budenberg Limited.) Action. — Steam from the steam pipe condenses in the small con- denser shown on the left of the sketches, and the water of condensa- tion entering the bottom of oil chamber displaces the oil, which rises and flows down the small internal tube. General Notes and Descriptions jj^ The oil then enters the sight tube by the nozzle shown, and passes up the sight feed tube in drops, from the top of which it is forced into the steam chest. Sometimes the condenser is formed of a copper coil placed a good height above the lubricator. Instructions for Using. — The oil chamber is charged by unscrewing the plug (T. The sight feed glass should then be filled up with water or a solution of salt and water (concentrated). To start the lubricator first open the valve d, then gradually open the valve c, and the drops of oil will be seen ascending through the water in the glass. Valve c regulates the amount of lubrication desired. When the engine is stopped, the two valves d and c must be closed. Hydraulic Accumulator. As will be seen from the sectional drawing, the accumulator piston is steam loaded by a reduced pressure of 80 lbs. per square inch. The pumping engine first of all pumps up the ram against the steam pressure, and when the piston reaches the top the pumps are auto- matically stopped by a rod and lever connected to the ram. The water is then stored up at a pressure of 800 lbs. per square inch and ready for use in the cranes, hoists, &c. The relative area of ram and piston being as i is to 10, a pressure of 80 lbs. per square inch on the one gives a pressure of approximately 800 lbs. per square inch on the other. As the water pressure is used in the cranes the ram and piston descend, until at a certain position the automatic gear in connection acts and starts the pumping engine : the ram is then raised back again to its former position. NOTE.— The ram is packed by a leather ring which constitutes the best hydraulic packing yet discovered. The water pressure inside the ring forces it out against the ram and against the chamber. The crane consists of three rams, one large central lifting ram and two smaller side rams for slewing round the crane post. The water is admitted by a hand valve to each ram as required, and after doing the work of lifting or slewing exhausts by return pipes back to the supply tank of the pumping engine (see sketch of accumulator). When the water is admitted by the hand valve the ram is raised, and when exhausted the ram is lowered, but if the valve is put in mid position the ram is locked and therefore maintains the position it may be in at the time. Advantages. Among other advantages possessed by the hydraulic .system, the following may be specially mentioned : — 23 -Li LUxn r.Di TO CRANES WATER PRESSURE 800 LBS, PER 5Q. INCH. No. 53.— Hydraulic Accumulator. (Brown Bros., Edinburgh.) 336 General Notes and Descriptions ZZ7 (i.) Great smoothness of working. (2.) Quickness of handling. (3.) Absence of noise in working cargo ; a consideration in passenger steamers. ^lM^^■i';^:ji?i■^l"^» "■'■■■> No. 54. — Hydraulic Crane. (Brown Bros., Edinburgh.) Brown's Patent Combined Steam and Hydraulic Reversing Engine. The engine as shown is attached to the bedplate or column of the main engine by the oscillating joint A formed on the end of the 338 "Verbal" Notes and Sketches steam cylinder. In this cylinder is fitted a piston B with rod C, upon which is cottered a block piston D, working- in the hydraulic cylinder E, the fluid beinj^ allowed to pass from one end to the other of the cylinder E by means of a small hole bored in the piston D. The rod C passes through stuffing boxes on the steam and hydraulic cylinders, terminating in a joint F, which lays hold of the weight shaft lever G. The lever is carried out to the joint H, upon which works the rod and rack I geared into the pinion J, both being shrouded to the pitch line. Upon the pinion shaft is keyed a worm-wheel K, which is actuated by the bronze worm L, this being revolved by the hand-wheel M. The worm and hand-wheel shaft are thrown out of gear with the worm-wheel K by the eccentric N, which is turned by the handle O, and held in position by the checkpin shown in dotted lines. When the hand-wheel and worm are disengaged, the rack and worm-wheel are free to revolve on the engine, making a stroke either way. This hand gear, therefore, forms no integral part of the starting engine, and is unaffected by any derangement of either hydraulic or steam cylinder or the steam valve. A locking arrangement on the hand gear is provided, so that the main valve gear can be linked up in any position of the ahead stroke. This consists of a pawl P, which is made to engage the teeth of the rack, and the engine is held up against the pawl by means of the slide valve being left slightly open to steam. The pawl is provided with a balance weight Q, so that, on the engine being reversed for the astern position, immediately pulls the pawl out of gear. The hydraulic cylinder is kept charged by means of the condensed steam in the bottom of the valve casing being driven by the steam through the non-return valve R, and led by a small copper pipe, as shown, into the lower end of the cylinder. The engine is handled by a simple reversing lever S, which is connected by two links to the fulcrum of a lever at T. This lever has its end extended to U, which is connected direct by a link to the valve spindle V. A curved link W is securely attached to the lever T U, and on this there slides a block X, which is carried from the piston rod. The action of this valve gear is as follows : — When the lever S is pulled into the ahead position, the lever T U, which is attached to the curved link W sliding in the block X, is depressed. The valve spindle is also moved down, opening the top end of the cylinder to steam. The piston rod now begins to move down, and carries with it the guide block X, which forces the end of curved link to move into the centre line of the block, thus moving the point U of the lever T U in an upward direction, the fulcrum at T by means of the reversing handle S being held stationary. In this way the valve spindle V is brought back into its original position, thus bringing the engine to rest. The same operation is performed for the astern or any intermediate position. General Notes and Descriptions 339 No. 55— Brown's Patent Combined Steam and Hydraulic Reversing Engine. 340 " Verbal " Notes and Sketches Steering Gears. -i h- * t IS ^ in m mJLn ho i c O bo (U -M 6 2 '=^ a -3 -i^ o, K t/J 05 rf in ^ *} o S 3 -(J u s <" •a a ^ •S ^ -S O O K c « o g W t) ao o « ^ -^ ■^ 2 .S ^ 3 ^ •'^ 0) «ti ^^ "■ e rt « ^ ^ J O I " ^ I « .S ^ w ^ ^^ c O D W •« .^u aoi-^^.^niajfti i .■Jii . - ,g ■s^j.yz s ^d £ b*dw ojoj nasg i: l^£ *^\ »>5J>. '7%. ] No. 58— Steering Engine Transmission Gear. 1, Horizoatal shaft coonectiiig; steering wheel and engine. 2, Vertical shaft connecting [by bevel wheels) to control valve lever. 3, Hunting or return gear from engine womi to control valve. NOTE.— The small spindle connected to the control valve 1 6, Wonn ■< ) wheel 3 by a ' Notes and Sketches General Notes and Descriptions 541 o u 73 "rt *i r; w .ii •- o - o s 3 t: > E U 0, M N fo ^ m^ > W s s 'rt "rt •g ^-g °^ « (/) W • W O 342 " Verbal " Notes and Sketches Steering Gear Engines. The majority of patent steering gear engines are fitted with three valves — a central control valve and two piston valves or slide valves, one for each cylinder of the engine. The control valve distributes the steam to the engine valves so that the gear may run either to port or starboard as required, and this being the case it will be observed that each piston valve or slide valve requires only one eccentric, the control valve acting as the reversing gear. The piston valves or slide valves have little or no steam lap, so that the steam is carried for the full length of the stroke, and to allow of this the eccentric kej'seats are cut at risjht angles to the cranks. Control Valve. — This valve is sometimes a flat valve, but more generally a round or piston valve. It is operated directly (i) by hand from the steering wheel on the bridge, and (2) automatically by a counteracting return gear from the chain drum or crank-shaft of the steerinsT engine. " -v^ '^ -\XU n ^ ~lr—^ — — ^ — J^riVil No. 59.— Steering Gear Engine Valves. When the engine is stationary, if the hand-wheel is turned, the control valve opens and starts the engine ; this again has the effect of brmgmg mto play the return gear in connection with the crank-shaft, so that as the hand gear (if still moving) tends to open the control valve the return gear tends to close it : if both gears, hand and auto- matic, run at the same speed the control valve remains open, but if the hand gear is stopped the automatic gear shortly afterwards brings the engme to a stop by closing the control valve. From this it will be seen that to keep the steering gear running the hand-wheel must be kept m motion, otherwise the automatic gear will bring the control If •V--..— :*.X«,»-U._- 25vl&\ anoi'ii^iib STEAM STEAM SHEWN THUS. ^ EXHAUST - - . > E EXHAUST PORT No 59a.— Steering Gear Valves. Steam is bting admitted to the cylinder from the centre of piston valves, and is exhausting to ends o back to exhaust port E, and the direction of engine rotation is as shown. NOTE. -In this type of gear the steam ia admitted from the ends of the control valve for both dii of running, as clearly shown in the sketches. l7«/<>«/«i-'i4J- XZZiii. w STEAM STEAM SHEWN THUS, EXHAUST •■ E. EXHAUST PORT No 59b.— Steering Gear Valves Steam ta being admitted to the cylinder from the ends of the piston valves, ■ame back to exhaust port E : the direction of engine rotation is as shown, and Direction of Rotatioi) :entTe of General Notes and Descriptions 343 valve back to mid-position and thus stop the gear. As before stated, the control valve does away with the necessity of having two eccentrics for each valve, one only being required, as the reversal of rotation is obtained by the action of the control valve. Engine Valves. — The valves of the engine are generally of the hollow piston type, although in some cases special flat valves are used, as in the gear of Messrs Alley & M'Lellan. The hollow piston valves are arranged so as to receive steam at the ends and exhaust in the centre, or, to receive steam at the centre and exhaust at the ends, the ports being suitably cast to admit of this (see sketch of control valve). Action of Valves. — If the steam is admitted to the ends of the piston valves by the control valve C being moved in the direction of A, the cylinders obtain the steam from the ends and the exhaust takes place in the centre of the piston valves, the engine running so that the rudder is brought over to, say, the port side ; but if the steam is admitted to the centre of the piston valves, by the control valve C being moved in the direction B, then the cylinders receive steam from the centres of the valves and exhaust at the ends : the direction of motion being thus reversed, the rudder is brought over to the centre asrain and so to the starboard side. Types of Gear. — The following five types of steam steering gear engines in general use will give a very good idea of the principle of working and of the mechanism employed by some of the best makers of this important piece of auxiliary machinery. It will be noticed that, with the exception of Messrs Hastie's gear, the control valve is moved laterally to open and close the ports, but in the gear produced by Messrs Hastie & Co. the control valve moves round somewhat after the manner of a Corliss valve ; the spindle therefore of this gear does not move laterally, but simply revolves for part of a ircle, as will be seen by examining the sketch. Steering Gear by Messrs Caldwell & Co. In this gear the control valve is opened or closed b}' a cam in connection with the "sun and planet" motion contained in the brass casing. The toothed wheel A is in connection with the hand-wheel on the bridge, and the toothed planet wheel B is in one with the cam, while the toothed casing C is in connection by bevel wheels with the chain drum. 344 "Verbal" Notes and Sketches FROM STEERING— H WHEEL CONTROL ^ VALVE , f /CAM ^ CAB GUIDE Siin and Planet Motion. No. 60.— Steering Gear by Messrs Caldwell & Co. General Notes and Descriptions 345 Action. — (i.) If wheel A is moved round by the steering wheel with C stationary, B moves round the casing and opens the control valve, thus starting the engine and setting C in motion. (2.) If A is stopped, C moves round in the reverse direction, carry- ing B and the cam back again until the control valve is brought to mid-position and the engine stopped, (3.) If A and C move at the same relative speed the control valve will remain open and the engine keep running, but if the speed of C exceeds that of A the control valve will close and the engine stop. In the same way, to open the control valve further the speed of A must exceed that of C. FROM _ STEERING WHEE SHAFT TRAVELS LATERALLY -H^ B _WORM WHEEL FORMING NUT WORM ON CRANK SHAFT A\\\lll////^i > S ^ FEATHER i;; 4 v^ TO CONTROL VALVE No. 61.— Steering Gear by Messrs Bow, M'Lachlan, & Co. Steering Gear by Messrs Bow, M'Lachlan, & Co. In this gear the control valve is moved horizontally by the spindle B turning in the nut wheel C and so acting on the lever in connection with the control valve spindle to move it from mid-position to the right or to the left as required. The bevel wheel actuated from the steering wheel turns the spindle B, which being screwed into the 346 " Verbal " Notes and Sketches nut C causes a lateral movement. The feather shown on the spindle allows the spindle to move horizontally without turning, if actuated by the nut wheel C travelling round. Action. — (i.) If wheel A is moved round by the steering wheel with C stationary, the spindle B turns and moves either in or out of the nut wheel C and opens the control valve, thus starting the engine and setting wheel C in motion. (2.) If A is stopped, C moves round and causes the spindle to travel (without turning) back again to mid-position of the control valve, thus stopping the engine. The feather and slot referred to allow of this taking place. (3.) If A and C move round at the same relative speed the control valve will remain open and the engine keep running, but if the speed of C exceeds that of A the control valve will close and the engine stop. In the same way, to open the control valve further the speed of A must exceed that of C. Steering Gear by Messrs Davis & Co. In this gear an expansion or regulating steam vah'e is fitted in addition to the control valve. The expansion v^alve is operated by a nut, which travels up or down the vertical shaft connecting the steering wheel and control valve spindle and opens the expansion valve a certain amount on either side, admitting the steam to the control valve in proportion to the amount of work to be done. The spindle B of the control valve works in or out of the nut wheel C as required, and admits the steam to the main valves of the engine. The wheel A is connected to the spindle B by a slot and feather which allows of a lateral movement of the spindle B when it is not turning. Action. — (i.) If wheel A is moved round by the steering wheel the spindle B moves either in or out of the nut wheel C and opens the control valve, thus starting the engine and setting wheel C in motion. (2.) If A is stopped C moves round and causes the spindle B to travel (without turning) back again to mid-position of the control valve, thus stopping the engine. The feather and slot referred to allow of this taking place. (3.) If A and C move round at the same relative speed the control valve will remain open and the engine keep running, but if the speed of C exceeds that of A the control valve will close and the engine stop. In the same way, to open the control valve further the speed of A must exceed that of C. The expansion valve is arranged to open when full steam is required in the engine. General Notes and Descriptions 347 o U > Q (0 V) U at a; O bo o (0 53 6 2 548 " Verbal " Notes and Sketches Steering Gear by Messrs Alley & M'Lellan. In this gear the spindle B moves horizontally for a small distance in or out of the teeth of the bevel wheels, which are cut specially deep to allow of this, a'nd, acting on the lever in connection with the control valve spindle, moves the valve to right or left as required. The small travel of the spindle B is increased at the control valve FROM STEERING^ WHEEL CONTROL VALVE THE SHAFT TRAVELS LATERALLY < DEEP -TEETH PINION WHEEL, FORMING NuT B . FIXED C- TO SHAFT CONNECTS No. 63.— Steering Gear by Messrs Alley & M'Lellan. by the leverage obtained. The pinion wheel C, which gears with the chain drum wheel, forms the nut in which the spindle travels. Action. — (i.) If wheel A is moved round by the steering wheel with C stationary, the spindle B moves horizontally to right or left and opens the control valve, thus starting the engine and setting C in motion. (2.) If A is stopped C moves round, causing B to move back again until the control valve is brought to rnid-position and the engine is stopped. (3) If A and C move round at the same relative speed the control valve will remain open and the engine keep running, but if the speed General Notes and Descriptions 349 of C exceeds that of A the control valve wiil close and the engine stop. In the same way, to open the control valve further the speed of A must exceed that of C. Steering Gear by Messrs Hastie & Co. In this gear the control valve moves round on its axis instead of travelling laterally as in the others, and so opens the ports to the centre or to the ends of the engine valves. The control valve mechanism consists of three bevel wheels, one of which travels round the other two and operates the rolling quadrant connected to the control valve. The left-hand bevel wheel of the three is keyed to the rotating spindle actuated by the steering wheel, and the right-hand bevel wheel is keyed to the worm-wheel, which, observe, is clear of the spindle. The top bevel wheel B is free, and is one with the rolling or "tumbling" quadrant which connects by teeth to the control valve spindle to move it round to right or left as required. It will thus be seen that the top wheel B travels roiuid between the teeth of the other two bevel wheels. With B at top the control valve is in mid-position and therefore closed, but if it travels down on either side the control valve is opened. Action. — (i.) If A is moved round by the steering wheel with C stationary, wheel B travels round and down between the other two bevel wheels and opens the control valve, thus starting the engine and setting C in motion. (2.) If A is stopped C moves round in the reverse direction, causing B to travel back and up again to the top position, so that the control valve is closed and the engine stopped. (3.) If xA and C move round at the same speed one counterbalances the other, and the control valve will remain open and the engine keep running, but if the speed of C exceeds that of A the control valve will close and the engine stop. In the same way, to open the control valve further the speed of A must exceed that of C. NOTE.— In all of the foregoing- types of steering gear engines a limit is fixed to the running of the engine by means of "stop" arrangements, which prevent damage to the steering gear in general. The "stops" check the travel of the rudder chains beyond a fixed point. It .should be noted that when the steamer is going ahead, say at full speed, with the rudder hard over to either port or starboard, the friction of the steering gear prevents the chain barrel from revolving, and so allowing the rudder to slip back again to mid-position. This will perhaps be understood when it is remembered that though the worm may cause the worm-wheel to revolve, it is almost a mechanical 350 "Verbal" Notes and Sketches o u X tn u t/i (/) us u O bo C a; 6 2: u ^1 n \ OJ :^ 'I 'J fjmrn^r'] , ■(J ^^ f No. 65.-Browns Patent Steam Tiller (Direct Geared Type). .i.r'N«.s,ndSk,u.h„. General Notes and Descriptions 351 impossibility for the worm-wheel to cause rotation of the worm, in fact, the teeth would give way first. Supposing, however, that the worm-wheel and barrel did revolve and cause the worm to go round, the effect would be to set in operation the control valve, which, opening, would then start the steering engine to run in the opposite direction, and thus prevent further movement of the chain barrel. NOTE.— By having two cylinders and the valves for each without steam lap, certainty of action is ensured, as one or other of the cylinder ports will always be open to receive steam, and so effect instant starting of the gear. Also, the key seats being at right angles to the crank, this allows the engine to run either way as required. Description of Brown's Patent Steam Tiller. (Direct-Geared Type.) This type of gear, which contains many improvements over the older designs of direct gears, has been introduced specially for ships that require a smaller power of gear than the 1905 design with countershaft. The general arrangement is similar to the old direct gear, except that the worm-wheel has been considerably increased in diameter, and the worm is now double-threaded. The oil pumps are worked direct from the eccentrics, and placed in a well at the bottom of the engine pan. The friction clutch is increased in size, so as to make it more powerful. Brown's patent economic valve, which absolutely shuts off steam every time the engine comes to rest, is also fitted. The great advantage possessed by this valve is that, should dirt or any foreign matter get in so as to obstruct its working, it can only remain in the open position, so that the gear does not become disabled, and would work under the same conditions as an ordinary steering gear without this attachment. The cut-off gear Q embodies the 1907 patents, with which no stops on the valves are ever reached, thus preventing any strain or damage to the gear by forcing over the telemotor when no steam is on the engine. This gear gives a very quick opening at the commencement of the move- ment of the control gear, and the motion of the valve is gradually reduced to practically nil, though the control gear moves uniformly. The same thing occurs in closing — that is, it commences to close very slowly, and just at closing the motion is very quick and decided. This gives a very fine and delicate control of the gear without an}' danger of reaching the stops on the control valve or its gear. With the standard design and a rudder angle of 40°, it is possible, when there is no steam on the gear, for the tiller to be hard over in one direction while the telemotor is pulled hard over to the other ; and a greater angle of rudder can be arranged for, if necessary. This does away with any need for disconnecting the control gear when using the hand or other gear for moving the rudder. 24 352 "Verbal" Notes and Sketches The crank-shaft A is forged from high-tensile steel ; and the worm B is cast on to it from a special hard and tough bronze. The valvelessoil pumps C are placed in a well, and discharge up into the tank D, from whence the oil is carried by small brass pipes to the various bearings, guides, &c. The main pinion E is machine cut from a forging of high-tensile steel, and is solid with its shaft. The rack F, having machine-moulded knuckle teeth of special design, is made in halves, which are interchangeable, bolted together, so that, should the teeth in the middle get worn through long usage, the two ends can be turned in to the centre, the worn portions going of course to the outside. The slipper G slides on the top of the rack, and helps to carry the weight of the tiller, engine, &c. The slipper or friction block H is made of cast steel. The slides on inclined planes for about lo"" each side of midships, being tightest at the centre ; and it has been found to hold the tiller quite steady, and act perfectly. The stops I attached to the ends of the rack fit into the teeth, and are secured by through bolts, so that they can be moved when the rack is changed. The form of control valve J, fitted with this gear, is of the well-known piston type, having one of Brown's patent economic valves K fitted on top. The worm-wheel M forms part of the friction clutch casing, and has its teeth cut in a special machine, so that great accuracy is obtained. The distance piece between the cylinders N has been increased in length, so that no part of the piston rod that goes into the engine pan passes into the steam cylinders or the packing in the stuffing boxes. This prevents oil being taken over from the engine pan into the cylinders, and thus into the feed water. The hand gear has been redesigned and brought up to date. Both the steam and hand gears are connected and disconnected by the large friction bralces L, which give every satisfaction, and quite take the place of the separate brakes frequently fitted. As the "cut-off" is of the floating type, the steam and hand gear can be put in and taken out in any position of the rudder, it not being necessary to connect them in the position in which they were disconnected, or bring the gear to the rudder. The mechanical standard O has also been considerably modified in design and brought up to date. This is, of course, for use in lieu of the telemotor, or when it is desired to control the steering gear aft. When changing from the telemotor to this standard, or vice versa, the connection can be made in a second or two, as all that is necessary is to take out a pin from one hole (marked P) and put it in the other, according to which change is being made. These pins are of brass, and have a large eye at the top, with a tapered point for easy entrance, so that they can be easily unshipped and put in. R is the receiving cylinder of the telemotor installation, and is of the latest design, with patent single spring. This gear can, of course, be arranged To work with control shafting m place of the telemotor, if desired ; but as the type of telemotor is lil » ^ V -^ -^ ^ ••VerU No. 66.— Brown's Patent Hydraulic Steering Telemotor. General Notes and Descriptions 353 thoroughly reliable, its adoption can be recommended in every case where the distance from the steering gear to the steering position is of any considerable length. Description of Brown's Patent Hydraulic Steering Telemotor (Sketch No. 66). When the distance between the steering engine and the position of the steering wheel is considerable, as in most modern ships, and it is desired to have as frictionless as possible a connection between the steering wheel and the steering engine, the telemotor shows to the greatest advantage over shafting and its equivalents. One of the advantages is that the small copper pipes can be led almost anywhere, provided they are protected from heat and damage ; in fact, through places where it would be very undesirable to hav^e shafting, such as saloons, berths, &c., as there is no noise, or oiling required, and no motion, except, of course, the fluid through the pipes, so that there is no danger of anything getting foul of bevel wheels, &c., and dis- abling the gear. The telemotor described and illustrated herein is the outcome of the original inventor's and makers' experience up to this date. Fig. I shows the vertical section of the transmitting cylinder A, fitted with the piston B attached to the rack C, into which gears a pinion D, the shaft E of which is made to revolve by the hand-wheel through pinion and spur wheels F and G, by which a suitable number of turns of the hand-wheel are obtained. Pipes H and I from the top and bottom of the cylinder respectively are led to the gear aft, and are joined up to either end of the cylinder K by means of the pipes L and M, the connection being made accord- ing to which way the after cylinder is required to move in relation to the forward one. (Fig. 3.) This cylinder is fitted with a piston N with the usual piston rod, and connecting links O which are attached by a lever to the conti oiling valve of the steering engine. The piston rod is fitted with two crossheads P P, between which lies a spiral spring Q, under initial compression, and which is compressed further by any motion of the piston, the object being to always cause the piston to return to mid-position — the steering engine control valve, of course, moving with it — when the pressure on both sides is equal, or tending to become so. When the apparatus is fully charged with fluid, any movement of the steering wheel will bring about a corresponding movement of the piston in the receiving cylinder K, and consequently the valve gear of the steering engine. In pulling the wheel round, it will be found to become sensibly stiffer until it is hard over, .so that the steersman feels the amount of helm he is giving the ship, much in the same way as in steering by hand with the antiquated winding drum and chains ; and, on "letting 324 "Verbal" Notes and Sketches go," the steering wheel will run back to midships together with the steering gear aft. The increase of resistance of one large spring is very much less than with the old design with two springs of small diameter, and as the minimum power required here is fixed by the amount required to move the control valve of the steering engine and bring the steering wheel back to its central position, it follows that with the single spring considerably less power is required to put the wheel hard over. Further advantages are that a much better design of spring is possible, with a larger factor of safety, and being co-axial with the cylinder it is more efficient, as, with the two springs, one on each side, there is generally a cross-winding action, or tendency of the cross- heads to bear hard on the guide rods, due to it being practically impossible to get two springs to exert equal resistance, or give out equal power, through equal ranges of motion. The telemotor on the bridge is fitted with an indicator R, as shown in Fig. 2, which, when everything is in order, shows the actual position of the helm. It is possible, however, that the piston packing leathers may in time become worn, so as to admit of considerable leakage, and it may happen that the piston B may be working altogether in the top or bottom of the cylinder A, with the piston aft in the mid- position, and the ship steered on a straight course with the indicator pointing at, say, 20°, and this may go on until the indicator pointer is almost past the degrees marked on the quadrant, still without dis- abling the gear, as the capacity of the cylinder A is considerably more than that of the cylinder K aft. To readjust the indicator and position of the helm, it is only necessary to turn the steering wheel until the indicator is brought to zero, and the piston enters the bye-pass or central position, allowing a free communication of liquid between both sides of the system, when the compressed spring aft will immediately bring everything into correspondence. As, however, the piston B in steering a ship is always more or less passing the centre position in "porting" or "starboarding" even to the smallest extent, the tendency is for the piston N in the cylinder K always to return to the mid-position every time the forward piston B is in that position. The bye-pass is now greatly improved, being formed by drilling two rows of very small holes, which are the correct distance apart longitudinally, so that the two leather packings of the piston B are between them, thus allowing a free passage for the fluid through the holes and so round the piston. This, of course, allows the pressure between the two sides of the system to come into equilibrium should there be any difference, and the spring on the cylinder K then brings the piston N and the control valve of the steering engine to their central position. The small holes are not liable to catch the leathers and turn the edges over, as frequently happened with the old style of bye-pass where the opening extends right round. This is quite obvious when it is explained that the holes are only just over ^V i"ch General Notes and Descriptions ^cc diameter and nearly ] inch apart, the leathers being thus supported by the metal between the holes. Another advantage is that the cylinder is all in one piece and can be bored right through at one operation, which prevents any possibility of getting out of line at this part, such as was always liable to take place with the old arrange- ment, through the joints not being properly nipped up, or any defect in machining, &c. It is sometimes necessary to set the gear so that the central position does not actually represent the rudder as true fore and aft, but a certain amount of permanent helm is required to counteract the action of the propeller, &c., when the ship is under weigh. This is done by making the connecting links longer or shorter, as the case may require, by means of the adjusting nuts provided, thus altering the central or shut position of the steam control valve. In some exceptional cases, where it might be inconvenient to adjust the gear by running the indicator into its midship position, should the two pistons have got out of correspondence, there is provided the hand-wheel S which opens the stop valve T, giving a free communication between the top and bottom parts of the cylinder, taking the place of the automatic adjustment by bye-pass at the central position, and so allowing the indicator to be brought to zero without moving the rudder aft. This valve must be shut and kept so when working. It should only be used in cases where there is very little room to manoeuvre the ship, as in narrow waters. The reason for this precaution is that it may be opened when unnecessary and left open or slightly open. In port it may be left open with advantage, as should any one move the wheel, nothing is moved aft, and so no damage can result. A small tank U is provided with gauge glass, as shown. This is usually charged with a mixture of glycerine and water, one part of the former to two or three of the latter. The cock V is provided for shutting the tank off from the system when charging up, &c., but it must always be kept open when the telemotor is being used for steering. As it is very important that the whole system of pipes and cylinders should be fully charged, and no air should be present, it is necessary to provide for the expansion and contraction of the fluid, due to changes of temperature, &c., and for this purpose a valve box is fitted on the bye-pass, a section of which is shown on Fig. 4. It contains a small inlet and outlet valve, the latter being simply an ordinary safety valve loaded above the working pressure, which is about 200 lbs. per square inch. As the temperature rises, a portion of the fluid passes into the tank U, and as the pressure falls the fluid returns through the inlet valve. The entire telemotor on the bridge is constructed of gun-metal, so as not to affect the compass. The motor cylinder aft is of the same material, and the pipes are of solid drawn copper of diameters varying from § to f inch internal diameter, according to the length 356 "Verbal" Notes and Sketches fitted. These are easily run, and may be bent into any number of corners without adding materially to the friction of the gear. A hand pump Y with tank Z is provided for charging up the system, and suitable pipes for connecting are supplied according to the arrano^ement of the gear on the ship. The cock on the tank is for shutting off the fluid from the pump when not in use. Screw- down valves J^ and J- are provided for shutting off the pump and its connections when the system is charged, the discharge pipe from the pump being connected to J' and the return pipe to J^ Two similar valves, J^ and J*, are provided so that they can be closed when it is desired to open out the cylinder K, and so prevent loss of fluid from the system. When working, these latter valves must be kept open, as also when charging up. A spring-loaded valve ]■' is provided, as shown, so that when charging up a system where the forward cylinder is a great height above the cylinder K, the fluid is retained in the pipes instead of coming down and leaving a vacuum or empty space at the highest point. Instructions for Charging, Adjusting, and Working. It is of the utmost importance that all joints be watertight, as any leakage will empty the small tank. After all the pipes are coupled and the connections made to cylinders and to tank in wheel-house, close the cock underneath the tank and fill to about one-third full with fresh water. For cold climates, add 30 per cent, glycerine, which ke'eps the parts lubricated, and will resist frost to about zero Fahrenheit (see table of freezing temperatures of various mixtures of water and glycerine on page 359 ). Put the hand-wheel in mid gear, which will be seen by the pointer coming between the two zero marks on indicator. This opens the bye-pass between the top and bottom ends of the cylinder, and allows the whole system to be charged by one operation from the after part of the ship. Open the cocks on the side of the cylinder K or motor cylinder, and see the cocks J^ and J* are open. When pumping, great care should be taken that the liquid in tank Z never gets so low as to allow the pump to draw air, as the good working of the gear depends upon the air being expelled. The liquid will shortly be seen to run from the small pipe back into the tank Z, but the pumping must be continued for some time, say three times as long as it took to come back. By this time the air should nearly all have been driven out, and each stroke of the pump should show a corresponding rush, and not a continuous flow back through the return pipe to the tank. Being satisfied as to this, the air cock J^ on the top of the cylinder should be closed, and a slight but continuous strain kept on the pump. Now, go forward to the wheel-house, and on the valve casing cover on the transmitting cylinder A will be seen a brass plug General Notes and Descriptions 357 W^ ; remove it, and press down the spindle of the inlet valve, which is immediately underneath, when the liquid will rush up owing to the pressure being kept on by the pump from aft. When the casing is quite full, and no more air bubbles up, screw in the plug W^ ; also the plug A^ on the top of the transmitting cylinder should be slacked back to allow any air imprisoned in the cylinder to escape, afterwards tighten up the plug, close the cock J" on the under side of the motor cylinder K, when the installation will be fully charged ; open the cock V underneath the tank U, and all is ready for use. The tank U in the wheel-house should be kept half full. The gear may now be tried by putting the wheel over to port and starboard, and noticing aft if a corresponding movement takes place in the piston of the motor cylinder. Should it not respond on one side or the other, then an internal leakage may be suspected ; in which case, examine the leathers in the telemotor and motor cylinder. To take out for examination or renewal the leathers on the piston B (a section of this piston with its leathers, springs, nuts, &c., is shown to a larger scale in Fig. 7), it is only necessary to remove the cylinder cover and turn the wheel so as to bring the piston up. The rack is sufficiently long to enable the piston to be run up right out of the cylinder and so be easily got at. If the bye-pass valve T is opened, and the cover left on until the piston comes against it, this can be done with little, if any, loss of fluid. To get at the leathers in the after cylinder K (Fig. 8 shows the piston with its leathers, springs, nuts, &c., to a larger scale), it is necessary to shut valve J^, remove the cylinder cover, slack off and remove the two large nuts that bear on the top yoke P, when the piston rod, &c., can be drawn sufficiently far out to examine or renew the leathers. As soon as the piston comes out of the cylinder, valve J^ should be shut, so that no more fluid may be lost. It should not be closed before the piston is out, or difficulty may be experienced in getting it so. All the leathers used for the two pistons (four in all) are exactly alike, which is a great advantage, as only one size of leather has to be carried as spare instead of two sizes as in the older designs. Care should be taken that any new leathers obtained are the proper depth, as the action of the automatic bye-pass on the cylinder A may be rendered inoperative, if they are too deep and cover the holes. The leathers in the pistons themselves will not cause any trouble until actually worn out, and even when in a leaky condition will work quite well and keep in correspondence with the gear aft, in virtue of the spring always putting the rudder in a fore and aft central position when the piston enters the bye-pass portion of the cylinder. The inlet and relief valves in the valve box W are not workiiig but automatic valves ; they merely open and shut as occasion requires, to allow for expansion and contraction of the fluid in the pipes due to change of temperature. After having made any repairs that may have been necessary, 35S "Verbal" Notes and Sketches and before recharging, it is advisable to clean out the pocket under- neath these valves, the purpose of which is to collect any dirt or sediment that may have been in the liquid. This is done by removing the brass plug in the bottom, when the small quantity of liquid that flows out of the pocket will carry anything with it. When first charging up after erection, or after any repairs or alterations to pipes, &c., it is advisable to disconnect the pipes from both cylinders and force clean water through them, so as to wash out any dirt or other foreign matter that may be in the pipes, and so prevent it getting into the cylinders and valve boxes. In addition to the stuffing box of the valve T, there are only three more one on the cylinder on the bridge and two aft — and as the water pressure need never exceed 250 lbs. per square inch, there is no reason for any serious loss of the fluid in the tank. Keep the stuffing boxes full of greasy cotton packing, and screw up as lightly as is necessary to secure tightness, but not stiff}icss. It is advisable to occasionally examine the leathers in the telemotor and motor cylinder aft when the ship is in port. The necessity for this can be ascertained by pulling the steering wheel hard over to port and securing it there. The motor cylinder will be found to have responded to same extent. If the gear is now left, say for half an hour, the spring in the motor cylinder will have moved the piston towards midship position if there is any leakage in the port leather. A similar trial may be made to starboard, which will test these leathers. It need not be expected that these leathers should be quite tight, but the motor piston should remain over for say ten minutes without any serious movement towards midship position, that being about the maximum time that, in practice, a helm would be held hard over ; and so any little deviation due to leaky leathers would be at once adjusted when the steering wheel is let go, the motor springs running it back to zero, and the bye-pass allowing the free circulation of the fluid. Fig. S is a section of the telemotor through the centre of the shaft, and shows a screwed plug X. When it is desired to take out the shaft E (the indicator being at zero), this plug is withdrawn and the other end screwed into the cylinder until its point enters a recess in the rack C. The rack is thus kept in its central position until the shaft and the pinion are replaced. Care should be taken to lubricate with good oil the various working parts of the gear. A glycerometer and thermometer are supplied with each installa- tion, so that it is possible to test the actual proportion of glycerine in the fluid at any time when the gear is not in use, by drawing some of the fluid out of the circuit and testing in a similar manner to that adopted for ascertaining the density of the water in boilers, the glycerometer reading right off the percentage of glycerine. General Notes and Descriptions 359 Non-Freezing Fluid for Telemotors. Water conlaining Refined ^^^^ ^^ ^^^,. j^ Kahrenheit. (jlycerine. 25 per cent. - - +18° 33 ^^ - - ■ +1°°, 50 „ - - - -20 60 „ - - - - 30 > gt-'tliiig lliick 70 „ - - - Too thick to work at - 25. Metallic Packing (Sketches Nos. 67 and 68). The United States type of packing is entirely metallic, and is thus specially suitable for high pressure steam or gas. Consisting as it does of various members or sections carefully fitted into each other, any side play of the rod is compensated for, the accommodating nature of the springs, cones, rings, and blocks forming the packing, and which constitutes perhaps the most valuable point of this well-known system of packing ; the regulation of the packing block pressure is automatic, constant, and reliable, and is regulated to suit equally well the out and in stroke of the rod. To exert a minimum packing pressure against a rod, a packing must be of the floating type, and this important result is attained in the U.S. packing, which is automatic and floating, exerting a minimum but effective pressure against the rod, and thus preventing the escape of steam in the case of high pressures and intermediate cylinder rod glands, and the admission of air in the case of the L.P, cylinder rod gland. The packing is free to " follow the rod," and this being so, the pressure of the packing against the rod is reduced to a minimum. Description. Duplex Packing is designed for use with high pressures. It consists of a block packing as described above used in conjunction with a cone packing which includes a set of white metal rings (ii) placed in a vibrating cup (10), the interior of which is partly conical. The duplex follower ring (12) holds the cone rings in position, and transmits to the latter the pressure from the duplex follower springs, which are held in the ring (14) and protected by the spring cover (13). In this arrangement the inner cone packing checks the steam pressure, and the outer block packing is thus assisted, and the escape of steam absolutely prevented. Atmospheric Duplex Packing. — For use on low-pressure condensing cylinders. It consists, like the Duplex Packing, of two parts, but with this difference : in the Duplex Packing both parts are steam setting, and operate in the same direction to prevent the escape of steam : in the Atmospheric Packing the parts are placed face to face and act in 36o "Verbal" Notes and Sketches United States Marine Type Packings. »o — -^-^ — 1 — ^l„R! fJ^y>-^yZ/A.^M / ^^"t; No. 67.— Duplex Packing. No. 68.— Atmospheric Duplex Packing. t jaAjHMJuas— ^ awm <1U 3>IAM"G00W ;f-4S^^--|^5^-->| /-C QMAJO r--24--t4-' Check Ring and After-Bush. Section through Tube. No. 6g.— Stern Tube and Propeller Shaft. (With dimensions for a i2-iach shaft.) Gland and Flange of Tube. r General Notes and Descripiions 361 opposite directions. The inner packing only is steam setting and prevents the escape of steam. The outer part is open to and set by the atmosphere. When there is a vacuum in the cylinder, the atmosj)heric pressure is actually used to tighten the outer packing and automatically prevent the passage of air, which would impair the vacuum. DESCRIPTION OF COMPONENT PARTS. A, Stuffing Box. 5A Guide Blocks. 10, Duplex Vibrating B, Piston Rod. 6, Horn Rings. Cup. I, Packing- Case. 7. Block Springs. 11, Duplex Cone Rings. 2, Stud Bolts. 8, Spring Cover 12, Duplex Follower. 3. Ball Joints. , Plate. 13. Duplex Spring Cover. 4. Sliding Plates. 9, Follower Bush and 14. Duplex Spring Holder 5, Packing Blocks. Springs. and Springs. Stern Tube and Shaft (Sketch No. 69). Description. — The stern tube is generally constructed of cast iron, the thickness varying from about i| to 2-^ inches. The tube is larger in diameter at the forward end (24 inches) and slightly less (23^- inches) at the stern-post end for convenience in fitting in or in taking out. The forward end is flanged and bolted to the after bulkhead, a " make-up " liner of lead or wood being in.serted between the two as shown. The forward end is supplied with a stuffing box packing and gland to keep water out of the tunnel, and the after end runs on a bearing composed of lignum vit^e (hard wood), the wood strips being fitted dovetail fashion into the after brass bush. Waterways are left at four or more positions to allow access of water to the shaft after bearing. The wood strips are kept in place forward by a collar or lip on the bush, or on the stern tube, and aft by a " check ring," which is secured by means of tap bolts to the flange of the brass bush. The bush itself is pinned in turn to the stern tube by countersunk screws, as shown in the drawing. A rubber " stop " ring is fitted hard up between the end of shaft liner and the propeller boss, which is recessed out to allow the rubber ring to be fitted, the object of the rubber ring being to prevent the access of water to the metal of the shaft, and thus prevent galvanic action taking place between the shaft metal and the brass of the liner, which would result in corrosion of the shaft. "Keeper" plates are pinned on to nut at back of boss to prevent turning, and to the large nut screwed on to the tube aft of the stern post for the same object. The propeller boss is fitted to the shaft on a taper (J inch per foot), a feather or key being also sunk on the shaft, and secured by pins as shown. The boss should have a bearing fit on the feather at the sides, but should be clear at the top of feather. For a right-hand propeller the boss nut should have a left-hand 362 "VerbaP Notes and Sketches screw, so as to be self-locking when revolving. Needless to say the stern tube is put in place from the inside of the ship. Observe that a small check collar is cast on the tube forward of the stern post for tightening up the nut. In the drawing shown the diameter of the shaft liner is 13! inches forward and 13I inches aft : this is for convenience in fitting in or drawing out the shaft. In running, it is better that a small drip of water should show at the gland, as otherwise the gland brass bushes and packing may heat up, and possibly tear up the shaft liner. A water service is fitted, leading from the tube to the bulkhead just over the gland, the temperature of which will indicate if the shaft inside the tube is running cool or otherwise. To allow for partial repacking at sea, the gland is often fitted in halves, with long studs, so that the gland need not be taken off altogether when inserting the turn of packing required. Cedervall's Patent Stern Tube (Sketch No. 70). — The lubrication of propeller shaft bearings within the stern tube has hitherto been chiefly effected by the eakage of a certain amount of water into the bearings, and its combination there with the oily surfaces of lignum-vitae strips ; or by forcing a mixture of oil and tallow between the plain unprotected bearing surfaces. In the one case the shaft, although partially protected by a sleeve of brass, has certain parts constantly exposed to the corrosive action of sea water ; while the other method, under usual conditions, does not afford a satisfactory means of lubrication, as the water w^ashes away the lubricant from the parts where it is most required, and the resultant corrosion and wear of shaft and bearings are most excessive. To overcome imperfections, and to reduce first cost, " Cedervall's Patent Protective Lubricating Box " has been invented. The principal objects of this invention are to absolutely prevent the access of any external water to the stern tube, and to provide a reservoir of oil capable of supplying a steady and continuous lubrication to the whole bearing surface. The invention consists, essentially, of an annular box of brass or gun-metal, containing an inner packing ring, which is pressed outwards by a series of small spiral springs. The box fits over the shaft, and is fixed to the forward face of the propeller boss by means of screws, thus turning with the propeller, and the inner movable ring presses against the prepared face of the stern tube bush. The springs, while of ample strength, are of such elasticity that, irrespective of any play which the shaft may have in revolving or reversing, the ring maintains a watertight joint with the end of the tube. As the ring is faced with antifriction metal and well lubricated by oil from the inside, it revolves with the minimum amount of friction. The method of applying the protective lubricating box, and the arrangement for supplying the lubricant, are shown in the drawing. Three or more grooves are cut in the stern tube bush. .'^o^OHUin -■f' J!^-"-^"^ ^ OvCTflo* Oltk. ^r^ff-'TT^'W^r^, ^DaatNCociv^ No. 70.— Cedervall's Patent Stern Tube. " Verbal " Notes and Sketches. General Notes and Descriptions 363 The top one is for the escape of air, and the others are for leading the oil to the inside of the movable ring of the protective box. From the stern tube three pipes are carried through the aft bulkhead, or to any other convenient place, and fitted with cocks. The oil is forced in by means of a small hand pump, and when all the spaces are filled, the oil shows at the overflow cock. From the foregoing description it will be obvious that the protective lubricating box has several highly important advantages. Its adoption does away with the necessity for expensive liners and metal bearings, the plain cast-iron stern tube bush being all that is required, and as a consequence of the efficient and uniform lubrication, coupled with the exclusion of all dirt and gritty substances from the bearings, the wear and tear on the propeller shaft is reduced to a minimum, and the usual vibration at the after part of most steamers is practically eliminated. Experience with vessels already fitted with the patent lubricating box amply proves its efficiency, as after several years' constant working the shafts on examination exhibit bearing surfaces quite as good as any smoothly working bearing connected with the engine proper. The safeguard which this immunity from corrosion and absolute wear affords against breakdowns of the shafting must be obvious to, and appreciated by, all having experience with the present expensive and not very efficient mode of fitting and lubricating propeller shaft bearings. Although heating of the stern tube bearings is most unlikely to happen with the arrangements shown, should it occur, the oil may be discharged at the drain cock, and water forced through the bearing by means of a hose attached to the filling cock. To obviate the possibility of the box being fouled by ropes, ice, or other floating bodies, a strong guard ring, made in halves, is fitted over the box, as shown. Drawing- the Propeller Shaft. — The usual method of drawing out the tail end shaft for examination or repair is as follows : — With steamer in dry dock, have all necessary working gear at hand, such as : chain and wire rope tackle, strong wooden blocks, screw or hydraulic jacks, light ram for coupling bolts, &c. 1. Fit up suitable staging round propeller. 2. Disconnect tunnel shafting and remove to one side two lengths of same. 3. Place tackle in position for drawing out tail end shaft (usually consisting of rope and chain blocks). 4. Shore off coupling of tail shaft solidly from bulkhead by means of the wooden blocks mentioned before, and remove gland and packing. 5. Remove nut at back of boss, by means of blows from a hammer on the large spanner, having previously secured the propeller from turning. ;64 "Verbal" Notes and Sketches 6. Drive in steel wedges hard up between boss and stern post, and by means of a ram (hydraulic) force boss off the taper. 7. Connect up propeller to tackle, and draw tail shaft gradually into tunnel, supporting it by blocks as it emerges. NOTE.— Very often the boss is found difficult to start, and when this is found to be the case one of the following methods may be tried : — 1. Build a fire below the boss, and when heated up apply blows from a large hammer on the end of the shaft, or the pressure of a ram on the steel wedges. 2. Bore a number of holes into the metal of the boss, then try the heating up, &c., as before. The holes are to allow of easier expansion of the boss when heating up. No. 71. — Pulsometer Pump. Description of the Pulsometer Type Pump. The body casting comprises the two working chambers A A, the air vessel B, and the discharge box, which is shown by the dotted lines in the illu.stration. Valves G G are fitted between the suction branch General Notes and Descriptions 365 C and the working chambers, and a second set of similar valves F F is arranged in the passages connecting the discharge box with the working chambers. Hand-holes L L are provided to give access to the suction valves, whilst the discharge valves are reached by removing the cover of the discharge box. Surmounting the body there is the "neck" casting J, which contains the gun-metal ball I, and is fitted with the steam pipe K. The air vessel B communicates with the suction branch C, by means of a prolongation running down in front of and between the two chambers A A, The action of the pump consists of the alternate filling and empty- ing of each working chamber, as the condensation and pressure of the steam respectively exert an upward and downward force on the surface of the water. The alternation of these operations is effected by means of the ball valve I in the following manner : — Assuming one of the chambers A be open to steam and full of water, the steam entering by the steam pipe K, and past the ball I, passes into the chamber and presses upon the small surface of water exposed. This depresses it and drives it through the discharge valves F F into the rising main D. The moment, however, the water in the chamber falls to the level of the opening in the branch leading to the discharge box, the steam blows through, and the consequent disturbance of the water surface causes the instantaneous condensation of the steam. The vacuum thus formed in the emptied chamber immediately pulls the control ball I over on to the corresponding seat and cuts off further admission of steam, allowing the vacuum to be completed. Water immediately enters through the suction pipe C, and lifting the inlet valve G, rapidly fills the chamber again. A similar operation has been taking place in the opposite chamber, the period occupied by filling one chamber corresponding with that of emptying the other, and these operations continue alternately in the two chambers so long as the pump is supplied with steam and water. The alternations follow so rapidly and with such regularity that the stream of water is practicall\' continuous. A small " snifting" valve is fixed in the upper part of each of the working chambers. Their function is to introduce a small quantity of air at each pulsation for the purpose of cushioning the ball as it changes its position and to separate the steam from the water by a non-conducting film, thus preventing loss of steam by condensation during the forcing part of the stroke. Air Pump Valves and Vacuum. Tlie condenser vacuum is affected most of all by broken or leaky bucket valves, next by broken or leaky head valves, and least of all by defective foot valves, particularly so in the case of the newer t>-pe of independent condenser which is placed much higher than the bottom of the air pump and allows of complete drainage of the water. Foot valves, although not much required for the maintenance of the vacuum, allow the pump to work steadier and more regularly than would be the case if these valves were omitted or were broken.' o 66 " Verbal " Notes and Sketches Hot-well Temperature and Condenser Back Pressure. Neglecting air leakage, the pressure in the condenser can be determined from the hot-well temperature as follows : — Note the hot-well temperature and look up the " Table of Saturated Steam," page 622, for the corresponding pressure. Example. — The temperature of the water in the hot- well is 141 ^ Find the corresponding vapour pressure. Answer. — On looking up the Table, page 622, we find that the vapour pressure for this temperature is 3 lbs. absolute, which is, of course, the back pressure in the condenser. In actual practice air leakage reduces the hot-well temperature for a given degree of vacuum. NOTE.— The actual back pressure on the L.P. piston is usually from i to 2 lbs. in excess of this, as a slight difference of pressure must of necessity exist between the two positions of steam flow. From the foregoing it will be evident that it is impossible to have both a high vacuum and high hot-well temperature as the two vary in inverse ratio. With a high temperature of hot-well water the vapour corresponding to the temperature is also high, with, of course, a proportionally reduced vacuum in the condenser. General Definitions. Heat. — Heat is a form of energy. When the molecules of a body are set in rapid motion or vibration, heat results, and the more rapid the vibration the more intense is the heat generated. The amount of heat given to a body produces a difference in its temperature. Heat may, then, be expressed as molecular energy, and the value of one unit — generally known as one British Thermal Unit, or simply one B.TU. — is equal to 778 foot-pounds of work. It should always be borne in mind that Heat and Work are mutually interchangeable, Heat giving out Work, and Work done producing Heat. Foot-Pound. — I foot-pound of work is equal to a weight of i lb. raised i foot. Power. — Power is the amount of work done in a given time (as, for example, per minute). Horse-Power. — i Horse-Power (Indicated) is equal to a weight of 33000 lbs. raised i foot in one minute or to a weight of i lb. raised 33000 feet in one minute. Unit. of Heat— To raise the temperature of i lb. of water one degree requires the expenditure of 778 foot-pounds of work. This is known as the Mechanical Value of one Heat Unit. (jeneral Notes and Descripiions 367 Sensible Heat. — Sensible Heat raises the temperature of a body, and is measured by the thermometer. Latent Heat. — Latent Heat changes the condition of a body (as, for example, ice to water, or water to steam) without adding to its temperature. To change or evaporate into steam i lb. of water at 212^ temperature requires 966 units of Latent Heat. Total Heat. — Total Heat is the sum of the Sensible and Latent Heats. Energy.— Energy is the capacity to do work. All energy really originates from the heat of the sun. Potential Energy is stored up energy, as, for example, a raised weight, a coiled spring, gunpowder, and steam in a boiler. Kinetic Energy is the energy of motion, as, for example, a moving piston rod, or pump plunger, a revolving shaft, and machines in general. NOTE. — Potential Energy when set free changes to Kinetic Energy. Force. — Force is that which moves or tends to move a body, as, for example, the force of steam, the force of water, the force of gravity, &c. Inertia. — Inertia is the natural property possessed by bodies at rest to remain at rest unless acted on b}- some force, or, if set in motion to continue in motion unless acted on by other forces, such as friction, &c. Centrifugal Force. — Centrifugal Force means a force acting outwards from the centre. An example of this is the centrifugal circulating pump where the water enters at the centre and is forced outwards to the circumference or periphery of the vanes. Friction. — Friction depends on the pressure exerted and nature of the surfaces in contact, and is independent of surface area. For example, if a small guide shoe is changed for a larger one the total friction is still the same, but the pressure per square inch on the shoe is less The coefficient of friction for lubricated metals is -08, which means that -08 of the pressure exerted is absorbed in overcoming friction. Steam. — Steam is an invisible gas obtained by the evaporation of water. It may be expanded to a lower pressure, or compressed to a higher pressure : it can also be condensed back again to water. Stress. — Stress means the forces set up in a material to resist strain or fracture, as, for example, a pressure of, say, 100 lbs. acting on a surface of 10 square inches will produce a tensile stress of lOOO lbs. on a stay of i square inch area. -5 368 " Verbal " Notes and Sketches Strain.— Strain means change of form in a structure due to stress, as for examjilc, when a rod is lengthened by tensile stress, or shortened by compressive stress. Specific Gravity. — Specific Gravity means the weight of a body com- pared with water and of the same volume. The specific gravity of Wrought Iron is 77, of Mercury 13-5, and of Oil -9. NOTE.— Water is taken as representing the figure i. Efficiency. — The efficiency of an engine is lowered by (i) Boiler losses, (2) Engine losses, (3) Mechanical losses, and (4) Propeller losses. The average combined efficiency of a marine boiler, engine, and propeller is only about 6 per cent, of the total, or is represented by the fraction yV Specific Heat (Capacity for Heat). — Is the heat required to raise I lb. of anything i° in temperature compared with the heat required to raise i lb. of water l°. Specific Heats. Water (at 39°) ----- i-oo Steam (at 212°) - - - - - -48 Ice ------ .5 Wrought Iron - - - - -113 Mercury - - - - - .033 From the above it will be seen that the amount of heat required to raise i lb. of water 1° in temperature would be sufficient to raise i lb. of wrought iron nearly 9° in temperature, as i-f-ii3 = 8-8^ Hyperbolic Expansion Curve. — This is known as the " Isothermal " or even temperature curve of a gas, and is obtained from the law of Boyle which states that : Pressure x Volume = Constant. From this it follows that if the volume of a gas be doubled the pressure falls to half, or if, as shown in the diagram, the original volume of the gas is increased three times, the pressure falls to one- third. Observe that the steam is cut off at one-third stroke, and at the end of the stroke the final pressure is only one-third of the initial pressure. Adiabatic Expansion Curve.— If heat is neither given to nor taken away from the gas the curve follows out that shown and is then called the "adiabatic" or varying temperature curve. Notice that during expansion the adiabatic line falls below the " isothermal " and during compression rises above it. General Notes and Descriptions 369 Entropy. — An " Entropy ' diagram represents heat and work, the area representing heat units per pound, and the cle[)th of the diagram the absolute temperature of the gas. The length of the diagram, or parts of the length, represent the "entropy." This diagram is of great value in estimating the expenditure of energy in steam or gas engines. Gravity. — The attraction of the earth, known as gravity, causes an accelerating effect in falling bodies of 32 feet per second. This number is commonly expressed as ^'"=32. Momentum. — Momentum means the force or energy acquired by a moving body, and is equal to the quantity of Matter multiplied by its Velocity; or, Mass x Velocity = Momentum. Atmospheric Pressure. — At the sea level the Atmospheric Pressure varies between 14^ lbs. (average, 147 lbs.) and 15 lbs. per square inch. This pressure is measured by the barometer. Gauge Pressure. — "Gauge" Pressure is pressure above that of the atmosphere. Ordinary steam gauges indicate pressures above the atmosphere only. Gross, or Absolute, Pressure.— The gauge pressure added to the atmospheric pressure is equal to the " Gross " or " Absolute " Pressure. Initial Pressure. — The pressure at the commencement of the stroke is called the " Initial" Pressure. Final, or Terminal, Pressure. — " Terminal " Pressure is the pressure at the end of the stroke. Effective Pressure. — The " Effective " Pressure is the difference between the steam pressure on one side of the piston and the e.xhaust pressure on the other side. If the steam pressure is, say, 80 lbs., and the exhaust pressure 10 lbs., then, 80— 10 = 70 lbs. Effective Pressure (not mean effective). Mean Effective Pressure is the average effective pressure exerted on the piston throughout the stroke, or during one revolution. This is the pressure required in calculating the Indicated Horse-Power of an engine. Combustion is a chemical process, and consists of the combining (chemically) of Carbon of coal with Oxygen of the air, producing COo and heat. Complete combustion produces COg and water. Incomplete „ „ CO and smoke. NOTE. -The small percentage of water formed in combustion is due to the combination of the Hydrogen of the Coal and the Oxygen of the air, giving H^O. Z70 "Verbal" Notes and Sketches Conservation of Energy. By this is meant that energy, like matter, is indestructible, and can only be transformed from one state to another. Energy is said to be wasted or lost in overcoming friction, for example, and this reduces the useful energy of a machine, but the total energy remains the same as originally supplied. A dynamo engine of a certain horse- power transforms mechanical energy into electrical energy, but the amount of electrical energy given out by the dynamo is less than the amount of mechanical energy supplied by the engine, as part of the energy is wasted in overcoming friction, weight, &c. Neverthe- less the sum of the energy wasted and the useful energy given out by the dynamo is equal to the energy originally supplied by the engine, and can be all accounted for Capillary Attraction. The force which causes the oil in an oil cup to creep up the worsted, and so flow down the pipe, is known as " capillary attraction," and is due to the attraction of the molecules of the oil to those of the cotton strands. The absorption of water in a sponge is due to the same force, and the difference in level of a liquid outside and inside of a tube of very fine bore, as shown by the sketches, is another example of the same. If in tube A the liquid moistens the tube, the level rises as shown above the normal and is concave. If in tube C the liquid does not moisten the tube, then the level is below the normal and is convex. ABC No. 72. — Examples of Capillary Attraction. Vessel B shows the normal level of the liquid when free from the influence of capillary attraction. Siphon. By means of a bent pipe with a long and a short leg known as a siphon, water may be caused to flow from one tank to another one lower down in position. For the efficient working of a siphon the following requirements are necessary : — General Notes and Descriptions 37 1 (i.) The height H (sketch) must not exceed 26 feet, which is the practical lift of a pump by the atmospheric pressure effect. (2.) The bent pipe must first be filled with water to start the flow, and this is usually done by drawing- out the air in the pijie and so forming a vacuum. NOTE. —The siphon will work equally well with cold or hot water, in which, it will be noted, it differs from a pump. The weight of the water in the length D of the pipe is the cause of the flow of water from the one tank to the other, and the longer this is made the faster will the upper tank be emptied of its contents. TANK No. 73.— Action of Siphon. Density of Steam. By density of steam is meant the weight per cubic foot volume. The density increa.ses with the pressure, as will be seen on referring to the Steam Table, page 622. If the specific volume of the steam be given, the densit)' can be determined as follows : — 272 "Verbal" Notes and Sketches Rule. — Density = i -^ specific volume in cubic feet. Example. At i8o lbs. pressure absolute, the specific volume of the steam is 2-49 cubic feet per lb. ; express the density. Then density = I -r 2-49 = 40 1 lb. nearly ; therefore the dens-ty or weight of each cubic foot of steam at the pressure given is -401 of a pound. Shaft or Brake Horse Power. It is now well known that so far no method has been devised, or, in fact, is likely to be devised, for the indicating of the horse-power as done in the case of reciprocating engines, but the actual power transmitted along the shafting to the propeller may be determined by means of the "torsion meter," an instrument which measures the twist or torque put on the shaft by a given power. For accuracy of results it is advisable to have the shafting calibrated beforehand, as different builds of shafts and materials give slightly varying results. It should be noted that the shaft horse-power or brake horse-power, as measured by the torsion meter, is the useful horse-power, and that the I.H.P. by comparison is a matter of indifference, the effective horse-power being actually transmitted along the shafting to the propeller being of chief importance. Equivalent I.H.P. Repeated trials have proved that the ratio of shaft horse-power by torsion meter as compared to indicated horse-power is usually in the ratio of 90 to 100, or -9 to I. Therefore, Equivalent LH.P.= Shaft Horse- Power -r -9. Example. — The collective shaft horse-power by torsion meter is found to be 8100; calculate the equivalent I.H.P. Then, Equivalent LH.P. =8100 -^ -9 = 9000. Dryness Fraction (or Factor). — In considering the actual work done by steam, it is important that the dryness fraction be taken into account, as the result greatly depends on this quantity. After work is done by adiabatic expansion, the steam contains a certain amount of water, which proportionally reduces the internal heat still left in the steam. The dryness fraction is the ratio between the weight of dry steam per pound and the weight of the dry steam and water added together ; 0>-. .,. ■ ^Weigh^oXdry steam ^ j^ Fraction. Weight of dry steam + weight of water Suppose the water to be 25 per cent, of each pound v/eight of mixture. Then, 100 25^ 75 ^ 15 ^ 3 __ ^ ^^ Fraction. 100 100 20 General Notes and Descriptions 0/ v) So that after expansion and work done by the steam the actual units or foot-pounds of energy left are, in this case, equal to the internal heat units multiplied by the fraction f. Total Heat of Steam. — By the total heat of saturated, or boiler steam, is meant the number of heat units required to produce i lb. of steam from a temperature of 32° Fahr. to any given temperature and pressure. The total heat includes the latent heat of steam formation and the sensible or thermometer heat. Rule.— 1083 + -3 xT° = Total Heat (above 32" Fahr). Where, T° = Temperature of the steam (Fahr.). Internal Heat* of Steam. — By this is meant the heat or energy required to change i lb. of water into steam at any given pressure. External Heat of Steam. — By this is meant the heat required to produce increase of volume (water to steam) against an external resistance or pressure. Latent Heat of Steam. — The sum of the Internal heat and External heat is equal to the latent heat. The Latent Heat can be calculated as follows : — Rule.— 1114 - 7 xT°- Latent Heat. Where, T' = Temperature of the steam (Fahr.). Example. — Calculate the Total Heat, Latent Heat, and Sensible Heat of I lb. of steam at 160 lbs. pressure by gauge. 160 + 15 = 175 lbs. Absolute pressure and 371° Temperature (from Table, page 622). Then, 1083 + -3 x 371 = 1194-3 Total Heat, and 1114- -7x371= 8543 Latent Heat. Therefore, 371° -32°= 333-9 Sensible Heat. NOTE.— The above are all calculated from a temperature of 32 Fahr. Potential Energy is the energy contained or stored up in steam of a given pressure and temperature, the amount of energy contained increasing with the pressure and the temperature. Kinetic Energy is the result of setting free the potential or stored- up energy of the steam, which then shows as active energy in the performance of work. In a steam-engine the steam acts on the pistons, and by causing motion to take place work is done, and, as a result, the steam falls in pressure and in temperature. In a turbine. the steam at a given pressure and velocity leaves .the first row of guide blades, and striking the first row of moving blades gives up 374 "Verbal" Notes and Sketches part of its kinetic energy, which results in a decrease in pressure and in heat. Adiabatic Expansion. — If steam expands in a cylinder or turbine casing, and neither receives heat from any external source nor gives out any heat externally, then the expansion is said to be "adiabatic," and all work done in the cylinder or turbine is obtained at the expense of the internal heat of the steam, which in falling in pressure and temperature conforms to this condition, and part of which condenses. In the cylinders of a marine engine of the reciprocating type, the expansion is approximately hyperbolic or isothermal, and in a turbine the expansion is approximately " adiabatic." Hyperbolic or Isothermal Expansion. — This is founded on the well-known law of Boyle and Marriot that the pressure of a gas varies inversely as the volume ; or, as it is expressed — Rule. — Pi X Vj = Po X v., = Constant. Where, Pi = Initial pressure. Where, P., = Final pressure. ,, Vi = Initial volume. ,, Vo = Final volume. Therefore, and, or, and, Foot-Pound. — A foot-pound is the work done in raising a weight of I lb. up through a distance of i foot. Torque. — Torque is the turning movement to which a shaft is sub- jected when a force is exerted to rotate the shaft against a resist- ance such as that of the screw propeller in water. In ordinary engines the turning effort or torque is applied by means of the crank, and in turbines by the direct energy of the steam acting on the periphery of the blade circle of the rotor. H^3,t. — Heat is merely a form of energy, and as such exists in two states — (i) in that of Potential or stored-up energy, and (2) in that of Kinetic or active energy. When the molecules of a body or gas are set in rapid motion or vibration, heat is developed atid work done. Con.sequently in the case of a steam-engine, either of the reciprocating type or turbine type, the energy which produces rotation of the shaft is obtained by means of the transformation of heat energy into mechanical work. General Notes and Descriptions 375 150 I hs. (I) Isothermal or Hyperbolic Curve, P V = Constant (Perfect Gas). 11 (2) Saturation Curve, P x V ' ^^ = Constant (Reciprocating Engine, ap- U proximately). • 1\\ (3) Adiabatic Curve, PxV'-'" = Constant (Turbine Engine, approxi- \\\ mately). %- ® \^v^ — ® ^%. (D A.L. ^^^^=;-___ RV.L. ^"^^""^ No. 74.— Expansion Curves of Steam. British Thermal Unit (B.Th.U.).— This is taken as being equal to 778 foot-pounds of work or energy, and signifies that one heat unit, when transformed into mechanical energy, gives out 778 foot-pounds of work. Saturated Steam. — Steam taken direct from the boilers is known as "saturated steam," as the densit)-, or weight of water per cubic foot, is constant for any given pressure, as also is the temperature and volume. The steam supplied to all marine engines (without superheaters) is therefore of this quality, and calculations as to expan- sion, work done, and fall of pressure, are usually made on this assumption. The steam supplied to the H.P. turbine of a turbine 376 "Verbal" Notes and Sketches engine is therefore saturated steam. Sometimes the term "dry saturated steam " is used to distinguish this quality of steam from wet steam, or steam containing water from priming. "Wet" Steam. — If water is carried off with the steam due to priming taking place in the boilers, the steam contains more water per cubic foot than is natural to the " saturation " pressure, volume, and temperature, and it is then known as " wet steam," or " wet saturated steam." Superheated Steam. — If saturated steam from the boilers is passed through the tubes of a superheater, the water contained in the steam is evaporated out of it, with the following results : — 1. Rise of temperature. 2. Increase of volume if pressure is kept constant ; or, 3. Increase of pressure if volume is kept constant. The chief advantage of superheated steam lies in the fact that cylinder condensation is practically eliminated, as the steam does not then readily condense when exposed to cooled surfaces : leakage is also reduced. Another point of importance is that the specific heat of this steam being only -48 (some authorities give -5), one B.T.U. of heat supplied to the steam has the effect of raising its temperature fully two degrees, as i -I- -48 = 2-08. Boyle's Law of Expansion. Boyle's Law of expansion states that "The pressure of a gas varies inversely as the volume if kept at constant temperature." Or, PxV = C; therefore, C^V = P, or, C^P = V, where P = Absolute pressure, ,, V = Volume in cubic feet, ,, C = Constant. This means that the pressure multiplied by the volume is always equal to a constant number, or in other words what is lost in pressure is made up in volume or vice versa, so that the result of the multi- plication is always the same. Example i. — The H.P. initial pressure is 185 lbs. gauge pressure, and the cut-off -6 ; find the pressure at the end of the stroke. Rule — PxV = C ; therefore, (185+ 15) x -6=120 = C. c v., Again, 120^1 = 120 lbs. absolute = P.,, and, 120-15 = 105 lbs. gauge pressure. It should be noted that the initial pressure is 185 + 15, or 200 lbs. absolute, and the volume -6, also that at the end of the stroke the volume will be equal to i. General Notes and Descriptions 377 Example 2. — Initial pressure, 160 lbs. gauge, and volume, 2-56 cubic feet ; find the volume when the pressure drops down to 80 lbs. gauge. Then, i6o( 15=175- P,, 80 + 15 = 95 = ?.,. Pi V, Therefore, 175X 2-56 = 448 = 0, C P, and, 448 r 95 = 4-71 cubic feet = Vo. JJOTE. — On referring to the Steam Table, page 622, it will be seen that the actual volume of saturated steam at 95 lbs. pressure absolute is 4-54 cubic feet in place of 4-71 cubic feet as brought out by Boyle's Law, which difference is prin- cipally due to the fact that, under practical conditions, fall of pressure is accompanied by fall of temperature. Example 3. — The L.P. initial pre.s.sure is 11 lbs. by gauge, and the cut-ofir-5 stroke ; find the pressure at the end of the stroke. Then, 11 + 15 = 26 lbs. =Pi, and -5 = Vj, so that, 26 X '5 = 13 lbs. absolute = C, then, 13 -r I = 13 = P.. absolute. Notice that V.3= i, that is, the whole volume of the cylinder. Cylinder Clearance Allowance. — For even approximate results it is necessary that the clearance volume of the cylinder should be allowed for, so that the rule corrected for this reads thus : — (Cut-off + clearance) x Initial pressure = (Stroke + clearance) x Terminal pressure. Example 4. — H.P. initial pressure, 165 lbs. gauge; cut-off, -6; clearance volume, 10 per cent, that of cylinder ; find gauge pressure at end of stroke. Then, Clearance = ^ ^-° = 'i (assuming cylinder as unit i). 100 Therefor*, (-6 + -i) x i8o = (i + -i) x P, so that, P = '7^^^°= 114-5 lbs. absolute, I.I ^^ and, 114-5- 15 = 99-5 lbs. gauge terminal pressure. NOTE. — If the I. P. receiver is, say, 1-4 times the capacity of the HP. cylinder, then, ii4-5-M-4 = 8i-7 lbs. absolute, and 817 -15 = 667 lbs. on LP. receiver gauge. Example 5. — Apply Boyle's Law and find the H.F., I. P., and L.P. terminal gauge pressures, also the I. P. and L.P. receiver pressures; given H.P. initial, 155 lbs. gauge; H.P. cut-off, -6; LP. cut-off, .5 ; L.P. cut-off, -4 ; clearance volume, 10 per cent, in each case. LP. receiver=i-4 times H.P. cyh'nder vokime, and L.P. receiver= 1-5 times LP. cyHnder volume. 378 "Verbal" Notes and Sketches H.P. Cylinder. 155 + 15 = 170 absolute, ^ ^ ^°=-i clearance. 100 Tnen, (-6 + -i) x i7o = (i 4 -i) x P. Therefore, P = "^-^^°r^io8 lbs. absolute, and 108- iS = 93 Jbs. g-auge terminal pressure. LP. Receiver. H.P. terminal pressure -108 lbs. absolute, Therefore, Receiver ^108^ 1-4^77 lbs. absolute, and, 77- 15=^62 lbs. gauge. I. P. Cylinder. Therefore, p--6x77^^2 lbs. absolute, i-i and, 42-15 = 27 lbs. gauge terminal pressure. L.P. Receiver. I. p. terminal pressure = 42 lbs. absolute. Therefore, Receiver = 42 -M -5 = 28 lbs. absolute, and, 28- 15=13 lbs. gauge. L.P. Cylinder. (■4 + -I) x28 = (i + -i)xP. Therefore, P = '-^^-^ = 12-7 lbs. absolute. Observe that the last pressure found is equal to about 2^ lbs. belozv that of the atmosphere. Boyle's law of expansion may, as before stated, be expressed as follows : — P] X Vi = P., X V.J, or. Pi X Vi = Constant. Therefore, ^i^i = P,, or.^'-^l Y> ^ y. Again, P^..v„or, P^^3=P, "1 * 1 Where Pi = Initial absolute pressure, ,, V, — Initial volume, ,, P.2 = Terminal absolute pressure, ,, Vo = Terminal volume. At constant temperattire the initial pressure absolute multiplied by the volume is equal to the terminal pressure absolute multiplied by the volume, which simply means that as the pressure decreases the volume increases proportionally, or vice versa. What is lost in General Notes and Descri|)tions 379 pressure is gained in volume, or what is gained in pressure is lost in volume. After the cut-off takes place we have an example of decrease in pressure and increase in volume, and when the exhaust closes we have an example of decrease of volume and increase of pressure (compression). Example i. — H.P. initial pressure, 165 lbs. gauge ; cut-off, '6 ; find the pressure at end of stroke. (I. ) Then, P, x Vj = P.^ x V,= i8o x -6-= Po x i. Therefore, ~ — ^i^ = P.,= io8 lbs. absolute, I and, 108-15=93 lbs. by gauge. Answer. Observe that the volume at cut-off is -6 of stroke, and at the end of stroke the volume is i or the full stroke, also 165 -|- 15 = 180 lbs. absolute pressure. At the end of the stroke the pressure is therefore 93 lbs. gauge, but when the steam flows into the M.P. chest the pressure drops still further owing to the receiver capacity being greater than that of the preceding cylinder, assuming that the M.P. receiver is 1-4 times the capacity of the H.P. cylinder. Then, 108^1-4 = 77 lbs. absolute, and, 77 — 15 = 62 lbs. gauge in M.P. chest. NOTE. — It must be remembered that in all steam expansion problems the pressures must be expressed as absolute or gross. Example 2, — H.P, initial pressure, 170 lbs. gauge; cut-off, -6; M.P. receiver capacity, 1-4 times that of H.P. cylinder ; cut-off in M.P cylinder, -5 ; L.P. receiver capacity, 1-5 times that of M.P. cylinder; cut-off in L.P. cylinder, -5. Determine (i) the H.P. terminal gauge pressure, (2) the M.P. receiver gauge pressure, (3) the M.P. terminal gauge pressure, (4) the L.P. receiver gauge pressure, and (5) the L.P. terminal absolute pressure. Then, 170+15=185 lbs. absolute H.P. initial pressure, and, Pi X Vj = P.J X V... = 185 x -6 = P,, x i. Therefore, 185 X -6 ^^^^ ji^g absolute, and 111-15 = 96 lbs. gauge terminal pressure H.P. Again, iii-f i-4=79-2 lbs. absolute, and 792- 15 = 64-2 lbs. gauge M.P. receiver pressure. (2. ) Pj X Vi = P., X V, = 79-2 ;; -5= Po X i. Therefore, ^^-"^^ = 39-6 lbs. absolute, and 396 15 = 24-6 lbs. gauge terminal pressure M.P. Again, 39-6+1-5 = 26-4 lbs. absolute in L.P. receiver, or, 26-4 - 15= ii'4 lbs. gauge in L. P. receiver. 3S0 "Verbal" Notes and Sketches (3. ) Pi X V, - P, X V, = 26-4 X .5 - P, X I. Therefore, ?^'A "^J=i3.2 lbs. absolute terminal L.P. pressure. Observe that the L.P. terminal pressure is below that of the atmosphere. It should be noted that the foregoing rule assumes the steam to act as a perfect gas, whereas in actual practice the conditions are somewhat different as shown below. (i.) Difference due to initial cylinder condensation and re- evaporation. (2.) Difference due to the steam being of the condition known as " saturated " (see page 622). (3.) Difference due to work done by the steam on the piston. These differences produce a drop in the pressure for any given expansion below that as determined by the rule given. The saturated steam expansion curve drawn out on page 375 illustrates clearly the difference referred to and should be compared with the isothermal curve. Steam Expansions by Pressures and by Volumes. — The differences in the action of the steam under practical conditions, as compared with Boyle's Law, naturally results in a difference in the number of expansions obtained throughout the cylinders. Example i. — Find the total number of expansions by pressures if the H.P. initial pressure is 165 lbs. gauge, and the L.P. terminal pressure 12 lbs, absolute; also by volumes if the cylinder ratio is as I : 27 : 7-2 and the H.P. cut-off -6. Rule. — H.P. initial pressure (absolute) -^ L.P. terminal pressure (absolute) = No. of Expansions by Pressures. 165 + 15 -180 lbs. absolute. Therefore, 180-M2— 15 Expansions by pressures. Rule. — L.P. ratio -^ H.P. cut-off= No. of Expansions by Volumes. Therefore, 7-2^ -6= 12 Expansions by volumes. In practice the pressure at the end of L.P. stroke, being less than that found by Boyle's Law, gives a correspondingly increased number of expansions as compared with the number of expansions obtained by the volumes. Charles' Law. A. The pressure of a gas at constant volume varies with its absolute temperature. 11/ 1 ?i3.;;Ct dec No. 74a.— Pressure and I.H.P. for Heat Efficiency Calculation. * \'erbal " Notes and SUetchu: General Notes and Descriptions 381 B. The volume of a gas at constant pressure varies with its absolute temperature. Example i. — A superheater contains 200 cubic feet of steam at a constant pressure of 165 lbs. gauge ; find the volume when the temperature is raised to 450° Fahr. NOTE.— Absolute temperature =^ Fahr. Temp. +461°. Therefore, 165 + 15 ^^^ 180 lbs. Absolute and Temperature of 373° Fahr. and, 373 + 461 - 834 Absolute Temp. , again, 450 + 461 = 911' ,, ,, then. As 834 : 911 :: 200 : 218-4 cubic feet. Answer. Example 2. — If the pressure of a gas is 150 lbs. absolute, and the temperature 366° Fahr., find the pressure if the gas is heated up to 400° Fahr. Then, 366 + 461 -827, and 4004 461 ^86i. Therefore, As 827 : 861 : : 150 : 157-4 ^t)s. Absolute. Answer Heat or Thermal Efficiency. Data — Cylinders — 24, 40, 65 inches. Stroke — 3 feet 6 inches. Revolutions — 72. H.P. steam — 175 lbs. gauge. I.P. steam — 60 ,, L.P. steam — -lo „ Vacuum — -24 inches. I.H.P. of H.P. cylinder - - 472 I.H.P. of I.P. cylinder - - 566 I.H.P. of L.P. cylinder - - 540 I.H.P. collective - - - 1,578 Coal per twenty-four hours — 28 tons. Coal per I.H.P. hour — T-65 lbs. Rule. — Work done + Heat supplied = Efficiency, and, Heat supplied - Work done = Heat rejected. Again, Heat supplied (per pound water or steam) = iii54--3x T°-^°. Where, T' = H.P. Initial steam temperature. / =L.P. Exhaust steam temperature. Work done in heat units per LH.P. =33000 ^ "^ = 2545 Heat Units per hour. NOTE. — 778 foot-poimds of work-i Heat unit value. Heat supplied per LH.P. hour -pounds feed water per LH.P. x Heat per pound. ^82 "Verbal" Notes and Sketches Application. — To apply the above rules to the case shown in the sketch facing page 381 : — Heat supplied=: 1,115 > -3 X 377-5 -i6o=- 1068-25 Heat Units per pound steam. NOTE.— 175 + 15=190 lbs. absolute, and temperature (from Table, page 622) 377-5. Heat given up as work per I.H.P. hour = 2545 units. Pounds water (or steam) per I.H.P. hour \ _. 28 x 2240 x 8-8 ._ ^^ ^^^ ^^^. (Evaporation assumed as 8-8 lbs.) / 1578 24 NOTE. The evaporation of water per pound coal is the most troublesome item to obtain with any degree of accuracy ; it can, of course, be determined by actual evaporative tests, but the most satisfactory method is that adopted in Admiralty trials where measuring tanks are employed which record the actual amount of feed water entering the boilers during a given period. It should be noted that the steam (or water) used per I.H.P. is the true test of economy as the quality of coal varies greatly, and therefore does not constitute a reliable standard of comparison. Then, 14-6 x 1068-25 -15489625 Heat Units supplied per hour Therefore, Efficiency = 2545 ^ 15489-625 = - 164, and •164x100=16-4 per cent. Thermal Efficiency. It will thus be seen that of 15489-625 Heat Units supplied only 2545 Heat Units appear as actual work clone in the engine. Pressures, Volumes (Sketch facing page 381). The following data of pressures, volumes, and temperatures throughout the range of c)'linders and receivers should be carefully studied by the student. [ Pressure = 175 lbs. gauge. H.P. valve chest < Specific Volurae = 2-43 cubic feet per pound. ( Temperature = 377-5° Fahr. [ Pressure = 60 lbs. gauge. LP. valve chest Specific Volume = 5-68 cubic feet per pound. (Temperature = 307-5° Fahr. ( Pressure = 10 lbs. gauge. L.P. valve chest Specific Volume = 15-97 cubic feet per pound. ( Temperature = 240° Fahr. I Pressure = 2-8 lbs. absolute. Condenser - - Specific Volume =117 cubic feet per pound. ( Temperature = 140° Fahr. NOTE. ^The above figfures assume saturated steam at all stages of expansion, but this is not strictly the case in practice, as the steam expands to a certain General Notes and Description.s 3^3 amount adiabatically, which results in reduced steam volume per pound at the latter stag^es of expansion, part of the steam condensing in the performance of work. The "dryness fractions" of the steam produced in this way may therefore show somewhat like the following :— H.P. Valve Chest. II. P. Cylinder. LP. Cylinder, L.P. Cylinder. .78 Dryness Fraction of Steam - I (dry) •9 •8 As a set-back against the above it should, however, be noted that the steam in the receivers is more or less superheated, owing to simple expansion into the receivers from the preceding cylinders, without actual work being done during such expansion. Taking the I.P. chest the pressure is 75 lbs. absolute, and the specific volume 5-68, then 5-68 x •8 = 4-524 cubic feet, as the actual volume when the dryness is -8, the remainder of the steam having condensed in the performance of work. Steam Consumption per Revolution. — For methods of calculating the steam (or feed water) consumption of an engine see author's " Marine Indicator Cards." Water formed by Initial Condensation. — The weight of water produced by cylinder initial condensation may be closely approximated by the following rule, assuming that the H.P. initial steam is of dry saturated quality and free from priming water. Steam condensed - Pounds steam in H.P. per rev. - (pounds steam in L.P. per rev. + steam condensed by work done in engine). Example. — The weight of steam used per revolution in the H.P, cylinder from the H.P. cards is 6-2 lbs., and the steam used in the L.P. cylinder from the L.P. cards is 4-25 lbs. If the weight of steam condensed by work done is 1-3 lbs., find the amount of water formed by initial condensation in the cylinders. Then, weight = 6-2- (4-2S + i-3) = -6s of a lb. per revolution. Work done during Adiabatic Expansion. — To calculate the work done, or, which is the same thing, the units of heat given up or con- verted into work during the adiabatic expansion of steam in a turbine, the following data are required : — The absolute temperature of the steam before and after expansion. The latent heat of the steam before and after expansion. The dryness factor of the steam before and after expansion. 26 384 "Verbal" Notes and Sketches Let, T,° = Absolute temperature before expansion. To° = Absolute temperature after expansion. Hi = Latent heat before expansion. Ho = Latent heat after expansion. /, = Dryness factor before expansion. y;.= Dryness factor after expansion. The heat energy given out in British Thermal Units = /, X Hi -/, X H. + Ti° - To° = B.T. U. Example. — Find the work done per pound of steam in expanding adiabatically from an H.P. initial pressure of 180 lbs. gauge, to a terminal L.P. pressure of 10 lbs. absolute, the dryness fractions being -99 and 76 respectively. Then, 180+15-195 lbs. absolute =3797 temperature from Table, page 622. Latent heat = 846-5 B.T.U. from Table. And, 10 lbs. absolute = 193-3 temperature. Latent heat = 1140-3 B.T.U. Therefore, 379-7 + 461=840-7 absolute temperature, and, 193*3 + 461 =654-3 absolute temperature. /i Hi /, H., Ti T, Then, -99 x 846-5 - -76 x 1 140-3 + 840-7 - 654-3 = 838-035 - 866-628 + 840-7 - 6543 = 1678-735 - 1520-928 = 157-807 B.T.U. Foot-pounds - 157-807 x 778 = 122768-4 foot-pounds. Advantages of High Pressure Steam. To prove the economy of high pressure steam as compared with ow pressure steam. Compound 80 lbs. pressure = 324° temperature. Triple 180 „ „ =380° 1 1 15 +-3 X 324= I2i2'4 units of heat required. 1 115 + -3 X 380= 1229 units „ „ Then 1229—1212-4=16-6 additional units of heat required to give more than double the pressure. High pressure steam is stronger and more expansive than low pressure steam, therefore a lesser quantity of it will do the same work. Advantages of Using a Number of Cylinders. Neglecting the advantage of two or more cranks in regard to the stresses on the crank shafting, the principal gain by jhaving, say, three cylinders is that the pressure is lowered a certain amount in each cylinder, and the drop of temperature does not take place all at once, but is divided into three stages ; the re- evaporation of the H.P. doing work in the M.P. cylinder, and the re-evaporation of the M.P. doing work in the L.P. cylinder, only the L.P. re-evaporation of the L.P. being lost in the condenser ; therefore the condensation losses, due to the cylinder cooling down during exhaust, are very much reduced. General Notes and Descriptions 385 If we were to use steam of 200 lbs. pressure in one cylinder, instead of in three cylinders, the great difference of temperature occurring between admission and exhaust would cause excessive condensation to take place owing to the cooling of the cylinder during exhaust, but, by dividing this drop of temperature into a number of cylinders the condensation losses are proportionally decreased owing to the counterbalance by re-evaporation. Cylinder Ratios and Steam Expansions. In compound engines the ratio of H.P. to L.P. C)'linder is usually about i to 4, and in triple expansion engines about i to 7, or I to 725. To find cylinder ratios — L.P. dia.--rH.P. dia.2= Ratio, or L.P. dia.--^ LP. dia.2= Ratio. If the steam is cut off at half stroke in the H.P. cylinder, this equals two expansions in the H.P. ; then 2x4 = 8 expansions altogether in compound engines. For triple, 2x7=14 expansions, or 7^ | = 14 expansions. Or, L.P. Ratio -f H.P. cut-off = total Expansions. Example. — Cylinder Ratios are as i : 2-7 and 7-2 H.P. cut- off -6 ; find No. of expansions by volumes. Then, 7-2 -^ -6= 12 Expansions (Volumes). NOTE. — To find number of expansions by pressures, divide initial absolute pressure by final absolute pressure. If we take the cut-off at one-third stroke, the 3x4=12 expan- sions in compound engines, and 3x7 = 21 expansions in triple engines. In working out the number of steam expansions the size of the H.P. cylinder and L.P. cylinder only are required, as the I. P. makes no difference in the result, the reason being that the viitia/ and fifial volumes of the steam limit the expansion range. Cut-off and Pressures. The final pressure, or pressure at the end of the stroke, is exactly proportional to the cut-off. If the cut-off is at half stroke, the final pressure will be half of the initial pressure, and so on. Example. — Initial pressure, 100 lbs. gross; cut-off, 15 in.; and stroke, 30 in. ; find the pressure at 20 in. of the stroke, at 25 in., and at the end of the stroke. 386 " Verbal " Notes and Sketches lool bs. xi5in. _^yg lbs. at 20 in. of stroke. 100 lbs. X IS in. ^^ jjjg ^t 25 in. of stroke. 25 in. lOOjbs^x^Sjn: =50 lbs. at end of stroke. 30 in. NOTE.— The above are all gross pressures; therefore if the answer is required to be expressed as gauge pressure, 15 lbs. must be subtracted from the result in each case. Expansion of Steam and Heat. — Steam expanding in a cylinder, and doing work on the piston, falls in pressure and in temperature, the fall in heat ("heat drop") corresponding to i B.T.U. for each 778 foot-pounds of work done. Steam expanding withojit doing work, as for example from the exhausting position of one cylinder to the receiver of the next engine, falls in pressure by expansion, but only slightly in tempera- ture ; in a word, the steam becomes superheated. Steam therefore in the I. P. or L.P. receivers, at a given pressure, is usually at a higher temperature than that corresponding to the pressure shown on the gauge. A similar result is obtained with reduced steam from a reducing valve, as the steam having only to do a small amount of work in compressing the spring, falls in pressure, but not nearly so much, proportionally, in temperature ; the reduced steam is thus, to a certain degree, superheated. Expansion of Water by Heat. The following table shows the relative volume of water at various pressures and temperatures, and the gradual expansion with rise of temperature should be noted. Temperature and Relative Volume of Water. Pressure (Gauge). Temperature. Volume. 212° 1-043 60 307-5° 1-093 160 370-8° I-136 180 379-7° 1-142 200 381-7° I-148 220 389-9° 1-154 From the above it will be seen that for a given weight of water (say I lb.) the level will be higher with a higher temperature. An example of this may be found in the case of the water gauge glass, General Notes and Descriptions 3^7 which in many cases shows a lower level than the actual water level in the boiler, the difference being due to the colder water in the glass occupying a lower level. Suction Lift of Pumps. The suction lift of a pump depends on the vacuum obtained and on the atmospheric pressure, so that when the barometer indicates, say, 28 inches, the pump lift will be less than when the barometer indicates, say, 30 inches, the difference of i lb. accounting for nearly 2 feet of difference in lift. Strictly speaking, no such force as suction exists, only difference in pressure, but the word suction is still in use with reference to valves, &c. At a higher level than the sea the atmospheric pressure is less, therefore a pump will have less lift in due proportion. It should also be remembered that the vacuum will show less when the atmospheric pressure is lessened, as the pressure on the outside of the U tube tending to bend it is reduced with the same pressure inside the tube ; this will naturally give the tube less curvature. Vertical Suction Lift of Pumps at Different Atmospheric Pressures. Barometer Practical \'enical Reading. ' Lift (approx.). 29-4 inches ----- 25 feet. 28 ,, - - - - - 24 „ 266 23 22-6 „ - - - . - 19 „ 19-7 „ - - - - - 17 „ Material or Shafting.— Shafting is now generally constructed of ingot steel, that is, large masses of steel known as ingots, which after casting are afterwards turned down by machine to the required diameter, the ingots being originally much in excess of the size wanted to ensure soundness of material. Good scrap iron forged is also employed for shafting, propeller lengths particularly, many builders preferring this to steel, owing to its less corrosive action in sea water. Stresses on Shafting.— All lengths of shafting are subjected to a torsional stress due to the twisting moment set up by the cranks ; in addition to this the crank shafting has to withstand a bending stress, produced by the bending moment of half the piston load multiplied by the distance from centre of crank-pin to centre of main bearing. The propeller shaft is also subjected to a bending stress, set up by the bending moment of the propeller weight multiplied by the distance from centre of boss to stern post. To allow for these excess stresses it is necessary to increase the diameter of these shafts over that of the tunnel lengths. The general stresses on shafting may therefore be classed as follows : — 388 "Verbal" Notes and Sketches _ , «, e.- f Torsional. Crank Shafting - JBending. i Torsional. End compression (ahead). End tensile (astern). Torsional. Bending. End compression (ahead). End tensile (astern). Propeller Shafting It will be obvious that if the propeller rises out of the water during racing- the bending moment and stress will be much increased. To Line up Crank Shaft. 1. Disconnect bottom ends and hang up connecting rods and eccentric rods. 2. Take out keeps and top half bearings. 3. Jack up the shaft until coupling faces all fair, or test with bridge gauge for level. 4. Take out bottom half bearings, refill with W.M. and bore out true. 5. Replace bearings, lower shaft into place, and test again before finally connecting up the engine. NOTE. — If the wear- down is slight and the engine not of large power, liners may be fitted in below the bottom half bearings instead of rebushing the same. Pistons. — For highest efficiency the piston rings require to join steam-tight joints at three places. 1. Between rings and cylinder walls. 2. Between rings (top edge) and junk ring. 3. Between rings (bottom edge) and piston flange. At the same time the rings require to be a floating fit, otherwise the springs or compression of the rings would be ineffective in pre- venting steam leakage from one side of the piston to the other. All patent types of piston rings aim at forming the threefold joint referred to, which, however, is not easily attained in practice. The Buckley, Lancaster, and other rings fitted with coiled springs are designed so that the spring pressure exerts a force outwardly and at the same time presses the two half rings away from each other, thus forming a steam-tight joint between the upper ring and the junk ring, and between the lower ring and the piston flange, the idea being to prevent steam leakage to the back of the rings, which, if taking place, results in excessive friction and wear of the rings and cylinder barrel. This will perhaps be understood when it is stated that a pressure of General Notes and Descriptions 389 about 4 lbs. per square inch 011 the rings is sufficient to prevent piston leakage in ordinary cases. On the down stroke the friction between the rings and cylinder barrel will naturally produce contact between the upper edge of the top ring and the junk ring and so form a steam-tight joint, but for the same reason the lower ring is apt to come away from the piston flange unless held firmly in position by the piston springs, if not, the exhaust pressure (about 60 lbs. in the case of H.P. cylinders) will be admitted to the back of the rings and results in the sericjus frictional effects referred to. On the up stroke the positions of the rings are reversed, the lower edge of the bottom ring bearing hard against the piston flange and so preventing the admission of steam to the back of the rings, but the upper ring will now be loose, unless kept in place by the springs, and will allow the admission of exhaust pressure steam to the back of the rings. No. 75. — Lancaster Piston Ring and Spring. The rings are made from a special mixture of cast iron, containing principally cold blast iron and hematite, giving a tensile strength of 20 tons per square inch, making them ex- ceedingly strong, close-grained, hard, and capable of taking a high polish. To alter the length and tension of the spring (if necessary) the ends are screwed into each other, and by varying the distance which one end screws into the other, the diameter of the spring can be altered so as to put more or less pressure on the rings, thus furnishing compensation for increased steam pressure or wear. The spring has ample bearing inside the rings so that it cannot wear away. In the case of patent feed pumps the water pistons require even more careful adjustment, as if leakage to the back of the rings occurs the water pressure is much in excess of the steam piston leakage pressure. The side of the water piston where the rings would be loose may have a pressure of 220 lbs, or more in the case of boiler feeding, and if leakage occurred would result in enormous friction between the rings and pump barrel. Beams. Many examples of beam construction occur in marine engineering practice, such as, for example, in main-bearing keeps, escape-valve bridges, pump levers, crank webs, tail-end shafts, &c., and a few 590 '• Verbal " Notes and Sketches simple examples of the general principles involved should be found of service. Neutral Axis. — A beam or lever fixed at one end (cantilever) and loaded at the other end (Sketch No. i) is subjected to a tensile stress NEUTRAL AXIS No. 76. — Neutral Axis of a Beam. at the upper edge and a compressive stress at the lower edge (Sketch No. 2) ; but at the neutral axis, situated midway between the two, there is neither tension nor compression stress. This will perhaps be understood when it is noticed that the upper edge is lengthened (Sketch No. 2) by the effect of the load producing TENSILE r _ I^HT COMPRlssn7F--STREs3- No. 77.— Stresses on Loaded Beam, a bending tendency, and the lower edge proportionally sJun-tened, but at the neutral axis the length remains unchanged, and the beam is therefore subject to neither tension nor compression at this position. From the neutral axis upwards the tensile stress increases from o to a maximum, and from the neutral axis downwards the compressive stress increases from o to a maximum, and allowing for a mean position of stress and for the beam cross-sectional area, the constant number 6 is obtained, which is employed in the equation connecting the bending moment, load, and stress per square inch. i^T-^l No. 78. General Notes and Descriptions No. I (Sketch No. 78). Rule. Therefore, 6xWxL = D'-xTx Stress. Bending Moment = L x W. 6 X W X L D^xT = Stress -v? xWx L x Stress = D, 391 yfj _ D- X T X Stres s 6VL ' T _ D^ X T X Stress 6xW ' ^_ 6 xWxL D'^ X Stress' NOTE.— The strength of a beam varies directly as the Depth- and Thickness and inversely as the Length, or as D-xT No. 79. No. 2 (Sketch No. 79). Rule. — 6 xWxL = = D- xT> Stress X 2. Therefore, S = 6x D2 Wx xT L Bending Momenta _L w " L No. 5 (Sketch No. 82). Rule. — No. 82. ^T-»; Therefore, 6xWxL = D2xTx Stress x 8. (Same as last example. ) Stress^ l^^^^ D^ X T X 8 Q^ / 6 X W X L V T X Stress x 8' B.M. = t2LW. 8 General Notes and Descriptions 393 No. 83. No. 6 (Sketch No. S^). Rule. — Therefore, 6xWxL=D2xTx Stress x 12. 6xWxL Stress = T= D2 X T x 12' 6xWxL T X Stress x 12' '=x/ 6xWxL B.M. T X Stress x 12 LxW 12 x\N -T^, Example No. i. — Find the bending stress per square inch on a beam fixed at one end and loaded at the other end by a weight of 5 tons. The beam is 6 feet long, 10 inches deep, and 3 inches thick. Then, 6 x 72 inches x 5 x 2240= 10^ x 3 x Stress. Therefore, Stress = 6X72X5X 2240 ^^^^^^ ^ j^^ square inch. I0'^x3 EXAiNlPLE No. 2. — Calculate the required depth of lever for a lever safety valve. Length from valve to weight 25 inches, weight 20 lbs., thickness of lever h inch, and the stress on lever metal 3000 lbs. per square inch. 6 X 25 inches x 20 = D- x .5 inch x 3000. Then, Therefore, Depth V^ 6 X 25 X 20 = 1-4 inches (say ih inches). 5 X 3000 Example No. 3. — Piston 24 inches diameter, pressure 120 lbs. per square inch, distance between centres of connecting rod bottom end bolts 18 inches. Find the required thickness of the cap if the width is 9 inches and the stress not to exceed 6000 lbs. per square inch. NOTE.— Assume the construction to be as that of a beam supported at both ends and loaded throughout. (Sketch No. 8i.) Load = 24- X .7854 X 120 = 54360 lbs. Then, 6 x 54360 x i8 inches = D- x 9 inches x 8 x 6000. Therefore, D ^ ^^f^^~6coo=2-7 inches (say 3! inches). ^g^ "Verbal" Notes and Sketches Example No. 4. — A condenser door weighs 1000 lbs., and when taken off is hung on a bar ih inches thick and 18 inches in length. Find the required depth of the bar if the stress on the metal is not to exceed 4000 lbs. per square inch. NOTE.— This case is similar to Sketch No. 78. Then, 6 x 18 inches x 1000= D- x 1-5 inches x 4000. ^ /6 X 18 x 1000 . , ... Therefore, ° = \/ i x 4000 ~ ^^'^ inches (say 4^ inches). Example No. 5. — Find the required depth of the bridge bar of a feed-pump spring-loaded relief valve if the distance between the pillar studs is 5 inches and the width of bridge 3 inches, valve 2i inches diameter, and loaded to 50 lbs. per square inch ; stress 3000 lbs. NOTE. — This case may be assumed as being similar to Sketch No. 82. Load = 2-5- x 7854 X 170 = 833 lbs. Then, 6x5 inches x 833 = D- x 3 inches x 8 x 2250. / 6 X ^ X 8*?^ Therefore, D^^ 3x8x2250 " "^^ ^"*=^ ^^^^ i* ^"*=^)- Consumption and Speed. At ordinary speeds the consumption or I.H.P. varies as the cube of the speed. Example. — The consumption per day is 14 tons and the speed II knots ; find the consumption if the speed is increased to 12 knots. As 11^ : 12^ : : 14 = 18-17 tons per day. From this it will be seen that to increase the speed by i knot per hour the consumption increases 4-17 tons per day. Example. — A twin screw steamer develops 2000 I.H.P. in each set of engines, or 4000 I.H.P. in all, and runs at a speed of 14 knots ; find the speed when running with one set of engines only, and developing 2000 I.H.P. As V4000 : 2000 : : 14^ : : II knots, SO that with 4000 I.H.P. the speed will be 14 knots, and with 2,000 I.H.P. II knots. NOTE.— The cube root requires to be extracted. Speed and Slip. The engine speed in knots per hour is worked out as follows : — PxRx6o — g-g- — =engme speed per hour. P- propeller pitch. 60 = minutes per hour. R = revolutions per minute. 6080=^ feet per knot. General Notes and Descriptions 395 If the ship's speed per hour be subtracted from the engine speed, the difference is the apparent slip. To express the sh'p as a per- centage proceed as follows : — • As Engine knots : Slip knots : : 100 per cent. = per cent, of slip (apparent). Example. — The pitch is 20 feet, the revolutions per minute 70, and the speed of the ship 12 knots ; find the per cent, of slip. 20x70x6o _^ g^ 6080 ^ And. 13-81 - 12^ i-8i knots slip. Then, as 13-81 : 1-81 :: 100 :: 13-1 per cent, of slip. To find the percentage of slip if the distance run by the ship per day is known, and the revolutions for the same time as indicated by the counter. Example. — The distance gone by the ship in twenty-four hours is 360 knots, and the counter indicates 135 112 revolutions for the same period ; find the per cent, of slip if the propeller pitch is 18 feet. I35II2 X 18 1 i u -^^-__j— =400 knots by engine. 400-360 = 40 knots slip. Then, as 400 : 40 : : 100 : : lo per cent. slip. Indicated Horse-Power and Consumption. After finding the mean pressure from a pair of diagrams, the I.H.P. is obtained as follows : — D- X -7854 xSx2xRxM.P. _j pj p 33000 D = diameter of piston in inches. R = revolutions per minute. S = stroke in feet. 2 = two strokes per revolution. M.P. =mean pressure. 33000 = foot-lbs. per LH.P. per minute. The I.H.P. of each cylinder must be worked out separately, and the results added together to obtain the total I.H.P. of the engine. To find the consumption of coal per I.H.P. per hour divide the coal used per day in lbs. by the I.H.P. and twent\'-four hours. Example.— The total I.H.P. of the three cylinders amounts to 1,100, and the consumption per day is 18 tons; find the pounds ot coal burnt per I.H.P. per hour. 18^^2240^ J lbs. of coal per LHP. per hour, iioo X 24 396 " Verbal " Notes and Sketches Example. — The H.P. cylinder of a compound engine develops 420 I.H.P., and the L.P. 460 I. H.P. ; if the consumption is 20 tons per day, find the coal used per I. H.P. per hour. 420 + 460 = 880 total I. H.P. Then, 20x2240^^ ^^ j^g ^f ^.^^1 i.H.P. per hour. 880 X 24 The cylinders of a triple expansion engine are 24, 40, and 65 inches in diameter, stroke 3 feet 6 inches, and revolutions 70 per minute. The mean pressures obtained from the indicator cards are — H.P. 55-6 lbs., M.P. 24-8 lbs., and L.P. 8-9 lbs. The consumption per day is 22-5 tons. Find (i) the I.H.P. of each engine ; (2) the total I.H.P. developed; and (3) the consumption per I.H.P. per hour. 24^x 7854 X3-5X 2x70x556^ 84-1 I.H.P. in H.P. cylinder. 33000 ^ ^ ■' 40' X 7854 X3-5X 2x70x24-8^ , j^ p j„ j^ p ,j„^^^ 33000 65^^ X 7854 X 3-5 X 2^70 X 8-9^ g, I.H.P. in L.P. cylinder. 33000 Then, 384-1 + 4759 + 451 = 1,311 total I.H.P. developed. Tons. *°*^' 225 X 2240 ^^^ ,^g ^f j,^^j J j^ p j^^jyj. 1311x24 NOTE.— For average cases the consumption should be somewhere between 1-3 and i-6 lbs. per hour per I.H.P. Coal Consumption, I.H.P., Speed, and Distance Run. In comparing coal consumption, speed, and distance run, it should be remembered that within moderate speeds the coal consumption (or I.H.P.) varies as the speed"^ x distance, which means that the coal burnt per knot varies as the speed'^. This amounts to the same thing as stating that the consumption varies as the cube of the speed. Therefore we have the following laws which apply to moderate speeds for any given steamer : — 1. The consumption (coal or water) (or I.H.P.) varies as the speeds 2. The consumption per knot varies as the speed-. 3. The consumption over a voyage varies as the speed- x distance. NOTE.— Above a certain speed limit the I.H.P. may vary as the 4th, 5th, or 6th power of the speed. From the foregoing it will be seen that if a steamer runs short of coal, port may be reached if the speed is reduced, for although the time taken is much longer, this is more than balanced by the reduced daily con- sumption which, under the reduced speed conditions, may be found sufficient to last the voyage. General Notes and Descriptions 397 Examples. — (i.) The consumption per day is 14 tons and the speed 11 knots; find the consumption if the speed is increased to 12 knots. As 11' : 12^ : : 14=18-17 tons per day. From this it will be seen that to increase the speed by i knot per hour the consumption increases 4-17 tons per day. (2.) A twin screw steamer develops 2000 I.H.P. in each set of engines, or 4000 I.H.P. in all, and runs at a speed of 14 knots ; find the speed when running with one set of engines only, and developing 2000 I.H.P. As ^'4000 : 2000 : : 14^ : : II knots, SO that with 4000 I.H.P. the speed will be 14 knots, and with 2000 I.H.P. II knots. (3.) The speed is 14 knots and the coal consumption 40 tons per day ; find the reduced consumption if the H.P. is linked in to give a speed of only 1 2 knots. Tons As 14^ : 12^ : : 40 = 25-2 tons (nearly). Therefore the consumption falls from 40 tons to 25-2 tons, a difference of 14-8 tons per day. (4.) A steamer after having run 1000 nautical miles at a speed of 10 knots and consumed 72 tons of coal, has yet to run 1200 miles, but the coal has run short, as the bunkers only contain 65 tons ; find the economical speed required so that port may be made. Then, 65X looox io-=72x 1200X K-. Therefore, 65X looox lo^^^^,^ 72x1200 and, V75-23=8-7 knots (nearly). Therefore by reducing the speed from 10 knots to S-y knots (say 8| knots), the coal will last the voyage, although a longer time is taken to complete the distance. (5.) Distance run, 2880 miles; speed, 12 knots; coal consumed, 300 tons ; time taken, ten days ; find the required speed to make port, and the time taken, distance yet to go 1500 miles, and coal supply only 100 tons. Then 100 x 2880 x 12^=300 x 1500 xK-. Tt. r 100 X 2880 X 12- r^o _ ^ Therefore, ^^^ — ^-^^-^ = K- = 02-i6, 300 X 1500 and, \ 92^ = 9-6 Knots. Time taken = 1500 -=-9-6x24 = 6-5 Days. 9,^8 "VerbaJ'' Motes and Sketclier, Therefore the coal will last 6-5 days at a reduced speed ct" cy6 kiicts, the steamer covering a distance of 1500 miles, as I5cx)-r9-6x 24 = 6-5 days, but would only last 3-33 days at 12 knots, and cover a distance of only 959 miles, as 3-33 x 12 X 24 = 959. The proof can be shown as follows : — 300 Tons ^10 Days = 30 Tons per day at 12 Knots. Then, As 12' -. 9-6'' : : 30 : 15-36 Tons at 9-6 Knots, so that, 30x3.33 = 99-9 Tons, and, 1536 X 6-5 =998 Tons. H.P. Cut-off and Consumption. The consumption (either coal or steam), and therefore the Horse- Power dev^eloped, vary as the cube of the speed (at moderate speeds). As the H.P. valve cut-off is the approximate measure or rate of the steam consumption, and therefore the coal consumption, then the variation in cut-off required for a given speed may be approximated as follows : — Example. — Speed, 12 knots, with H.P. cut-off at -6 ; find the H.P. cut-off required to reduce the speed to 1 1 knots. Then, As 12^ : 11^ :: -6 : 46 cut-off. Answer. Therefore the H.P. link must be run in to cut-off at -46 for 46 per cent.) to reduce the speed from 12 knots to 1 1 knots. NOTE. —In actual practice the consumption is found to vary more often as the 4th power of the speed in place of the cube of the speed. Efficiency. The general average efficiency of the boilers, engines, working parts, and propellers are as follows : — No. I — Boiler Efficiency = — or -66, or 66 per cent. NOTE. — I lb. good coal contains about 14500 heat units, and to change i lb. water into steam, if the steam temperature is 212 , and the feed water temperature 212" (see page 622), requires 966 heat units. Therefore, Theoretical evaporation = 14500^-966 = 15 lbs. water. In practice, however, i lb. evaporates only 9 or 10 lbs. water. Therefore, Boiler efficiency = —. No. 2— Steam Efficiency. — The heat efficiency of the steam acting on the piston to develop horse-power varies from 10 to 15 per cent, in actual practice. NOTE.— Maximum Theoretical Efficiency of an engine = , T''-)-46i' V/here, T = Steam temperature. / = Exhaust ,, 461 = Absolute temperature Constant. General Notes and Descriptions 399 Example. — The initial pressure is 180 lbs., and temperature 380" Fahr., the exhaust temperature is 2QO° Fahr, ; express the maximum heat efficiency of the engine. Then, Efficiency = ^„ ~ ^ -■21, or 21 per cent. •' 380 + 461 ^ In practice only about 56 per cent, of this efficiency can be obtained. Therefore, Actual efficiency = ^ '^ -11-7 per cent, efficiency. 100 Combined Boiler and Engine Efficiency. — Suppose that i-6 lbs. of coal are burnt per I.H.P. per hour. Then, Combined efficiency = — - — 33000 -.116, or 11 -6 per cent. 1-6 X 14500 X778 NOTE I.— Heat Value per lb. coaU 14500 B.T.U. ,, 2. — Mechanical Value of each B.T.U. =778 foot-lbs. of work. ,, 3.— 60 minutes per hour. This result, it should be noted, corresponds with the last. Mechanical Efficiency. — The power lost in driving the air pump, feed and bilge pumps, together with that required to overcome the friction and weight of the moving parts, amounts to about 10 or 1 2 per cent, of the total power. Therefore, Mechanical efficiency = 100-10 = 90 per cent. Combined efficiency of Boilers, Engines, Shafting, &c. = —^ = 10-44 per cent. Propeller Efficiency. — The actual power utilised in driving the ship through the water is only about 60 or 65 per cent, of that delivered to the propeller, as blade friction, slip, useless effort of rotation, &c., waste the remainder of the power. Therefore, Propulsive efficiency = -60, or 60 per cent. Combined Efficiency of Boilers, Engines, Shafting, and Propeller. Total efficiency = — '.^^ — —6-264 per cent. 100 Therefore, of 100 per cent, coal, or power supplied at the boiler end of the plant, only 6-26 per cent, of this is utilised by the propeller to drive the steamer, or the combined total loss is equal to 100 — 6-26 = 93-74 per cent. 27 400 "Verbal" Notes and Sketches Squared Paper Diagrams or Curves. By means of paper ruled off into squares (which can be easily made by ruling off a series of vertical and horizontal lines, say J inch apart), useful diagrams known as " speed power " curves can be con- structed which will be found of immense service to the chief engineer of a steamer. The writer is quite aware that the majority of marine engineers do not trouble themselves much with so-called "theoretical " diagrams, but he would direct the special attention of readers to the use of the curves here referred to, which are of a strictly practical nature, and if once grasped will be found both interesting and instructive. The curves can be applied as a comparison or check on speed, consumption slip, horse-power, revolutions, &c., and a few examples are given by way of application. Speed and Consumption Curve. Example i. — From observation, notes are made of the con- sumption of coal at various ship speeds, which are as follows : — At 2-5 knots the consumption was 6 tons. 4 6-2 7.8 7 10 15 20 10 „ „ „ 34 From the above plot out a curve of " speed and consumption." TOWS 40 35 30 2 O jl 20 2 o / :::-.: '" ._.. .., "■ ... ^'" '" 7 i oi / 14 ^ y^\ :"■''■": - :__: "9^ -r^ .^ -f ^ cy-' ' i 1 1 1 1 ill; i i i 1 ' ' ' ! I'll I'll : : 1 ' 1 • 2 34 5~67& SCALE OF SPEED IN KNOTS. No. 84.— Speed and Consumption Curve. 10 II General Notes and Descriptions 401 Method. — Draw out on a sheet of paper a number of, say, ^-inch squares, and let each horizontal space represent i knot, and each vertical space or division 5 tons. Where required each horizontal division can be divided into five smaller divisions, each representing f-^ or -2 of a knot, and each vertical division into five smaller divisions, each representing I ton. Number the spaces as shown, up to, say, 1 1 knots and 40 tons. Now, at the first noted speed of 2-5 knots erect a vertical line, and draw out a horizontal line from the corresponding consumption of 6 tons to meet it ; at the intersection describe a small circle or large dot. At the next observed speed of 4 knots draw out a horizontal line from the corresponding consumption of 7 tons, and again describe a small ring at the intersection. Repeat this successively for each noted speed and consumption, describing small circles at each point of intersection as shown. Notice that at the speed of 6-2 knots the vertical line is run up at the first subdivision between the spaces of 6 and 7 knots, this representing 6-2 knots ; also that at 78 knots the vertical line is run up at the fourth small division between spaces 7 and 8, this being equal to 7-8 knots, and so on for each decimal of a knot. Last of all, draw either by hand or wooden curves a line running through all the small rings so found, and the result will be a speed consumption curve which shows at a glance the relation existing between speed and coal consumed at various speeds. NOTE. — The value of the spaces may be changed to any convenient measure without in any way affecting the result. That is, each vertical space may be made to represent 2 tons in place of 5 tons, or each horizontal space made to cpresent half a knot, or if found more suitable 2 knots, in place of i knot. Economical Speed. By this is meant the speed which will give the greatest distance run for a given coal bunker supply, or in other words the greatest distance which can be run per ton of coal burnt. This can be closely approximated on the diagram by simply drawing a tangential line from the left-hand bottom corner to the curve as shown, arid the point of contact gives the speed and con- sumption for greatest economy of steaming. If, then, on a voyage the coal supply runs short, this speed would be the best to adopt under the circumstances (see page 400) to make the coal last out the voyage. The economical speed is at position B, which corre- sponds to about 5-5 knots. I.H.P. and Speed Curve. Example 2. — This curve is constructed in a similar manner to the last, and is of very nearly the same value, as generally speaking the consumption and power are practically equivalent terms, and vary in the same relative proportion to the speed. 402 "Verbal" Notes and Sketches Method. — Set off horizontal spaces of I or l inch as found most suitable, repre'senting knots and vertical spaces of similar size, each representing, say, lOO I.H.P. Therefore if each space be divided into five smaller divisions each will be equal to 20 I.H.P. Suppose that the following observations were made of I.H.P. at different speeds during progressive trials : — At knots the I.H.P. was 3 4 4-5 5 6 7 40 At 8 60 9 80 9-4 100 9-8 120 10 180 IO-4 260 IO-8 knots the I.H.P. was 360 520 600 700 760 900 1080 At each speed noted, where required, run up vertical lines, and connect these with horizontal lines run out from the left at the corresponding I.H.P., and at the points of intersection describe little IIVAT ek lOfMV I 900 800 7nn- p ---" - - - - — ■ - - - - - — . _ - --G (; ; fino- 500 V _ " -1 £iW / 300- : - : • ■ - ■ - ■ - ■/ { £00 100 : :: . . - . - - - -- - - y / ZJ.~ — - - • v^ ^ : : :.-. :i^ S:^ H r^ r r I ', , 12 3 4 5 6 7 8 SCALE OF SPEED IN KNOTS No. 85.— Power and Speed Curve. 10 II General Notes and Descriptions 403 circles ; finally, connect these circles by a curve, which is then the "speed and I.H.P." curve required. NOTE.— Observe that each vertical space-ioo I.H.P., therefore each fifth of each space = 20 I.H.P. Also that each horizontal space = 1 knot, therefore the fifth of each division = -2 of a knot. ro SCALE OF SPEED IN KNOTS. ■t* at CP o \ c/> o > r- _ m en Tl O < o 5° o Z «- ut rn 73 Z "• o o U a o o a a 0) 00 6 Speed and Revolution Speed. Example 3. — This curve is useful in showing the relation between the ship speed and engine revolutions. Set off the vertical spaces on the left as knots and the horizontal spaces as revolutions. Then 404 "Verkd" Notes and Sketches at any observed or noted speed and revolutions connect the points and describe small circles as shown ; repeat this for as many speeds and revolutions as may be known or noted, and draw a curve through the points so marked, which gives the speed and revolution curve. Speed and Slip Curve. Example 4. — This curve shows the relation between speed and slip, which, owing to cavitation, generally shows as increase of slip with increase of speed. Method. — Set off as before, horizontal spaces (I inch or | inch) as knots, and vertical divisions as per cent., each space representing, say, 5 per cent, of slip. Now from the log or other data connect «fc »o i" :t/_-: \ \ \ 1 ; 1 1 1 I 1 1 ' 'I ;:! 1 1 i ' 1 ' 1 1 1 1 i 'ii i ' 1" 1 ;' i ; ; : 1 : ■ < 1 1 1 O) CO u> o z CO o ui in LU 0- o < m cins dO 3nVDS General Notes and Descriptions 405 the corresponding positions of speed and per cent, slip (see page 404), and describe little circles as shown. Suppose the data to be as follows : — At 4 knots the slip is 7 per cent. )> o >) )) o )) » 7 5J )) 9 >' » 8 „ ,, 10 ,, „ 10 „ ,, 125 „ „ 12-6 „ „ 16 ,, Observe that 12-6 knots is equal to twelve spaces horizontally and three-fifths of a space or -6, the vertical is then run up to join the horizontal line, projected over at the 16 per cent, level. As before explained, draw a line through all the points of intersection, and the result will be the " speed and slip curve." Points to be Observed. Example i. — As previously explained (page 402) at intermediate speeds the consumption or power varies approximately as the cube of the speed. This can be seen in the "speed consumption curve" which shows the consumption to be 15-5 tons at 8 knots and 34 tons at 10 knots. Be}^ond this speed the consumption may vary as the 4th power in place of the cube, which brings out a still greater consumption ratio, but which nevertheless reduces the consumption per I.H.P. per hour, so that at low speeds the coal per I.H.P. per hour is more than at high speeds. Example 2. — This curve is very similar to the last, and in some cases is practically equivalent, but generally it is found that the power varies as the cube or as the 4th power of the speed. Example 3. — Roughly speaking the revolutions vary directly as the speed, and this is borne out by the curve shown, where it will be seen that at nearly 6 knots the revolutions are twenty-five per minute, and at 12 knots nearly fifty revolutions per minute. Example 4. — An ordinary reciprocating engine propeller de- velops greatest efficiency at low revolution speed, therefore as the revolutions increase the efficiency falls off, and the slip ratio increases ; this is shown by the curve, in which the slip ranges from about 6 per cent, at 6 knots to 16 per cent, at 12-5 knots. Combined Curves. In modern trial trip practice it is usually found more convenient to combine the various curves previously described instead of having them drawn out separately, as the various results can then be com- pared simultaneously, and a more comprehensive idea obtained of the general efficiency. The following is a combined curve diagram of a 4o6 "Verbal" Notes and Sketches modern high speed passenger steamer, and the I.H.P., Speed, Slip, and Revolution curves are all shown together, thus allowing of a general comparison to be made. o > r" m Z o H CO o> SCALE OF INDICATED HORSE POWER. O O — ro rsj fvj tM tx ODroCJ^O.f*00'^>C^> ^OOOCSO C30 ooocscz>ooo «:» j::> -t^ O *» 00 O CD O O O O n — ^^~ "T — r~i — I) ' 1 1 fj— 1 — ' 1 • ' I 1 1 1 1 r r-T -- - -i ^"' 1 \ \ 1 \ A 1 1 \ \ \o. \ 1 ^ 1 • •": \ v.- .\ V- V \ u ^ > i\ 1 \ V i ::: -^ ^. 1 1 k ' 1 \ \ 1 1 N :\ Nj -'" .... .... 1 1 X :\ L — _ - - - . — .L_( K-" . _ -> r - \ ' - - 1 1 1, 1 i' , - L . 1 1 r »o>6 ■ c c r'"i SCALE 5 I OF 3 t 9 < REVS . pef 1' 1- f. Ml N. c c \ c \ \ 9 > Z " c S :ale OF i 5 Z >LIP 5 S PER :ent i r r 3 o > (U c nt .2* m (U (U o. (U o 3 U C a o U oo 00 6 In the above diagram of ship performance the spaces representing knots are divided up into tenths or fifths where required to allow of General Notes and Descriptions 407 projecting the necessary points on to the I.H.P., revolutions, or sh"p curves. In the same way the I.H.P. divisions are divided up into four parts, each being equal to 100 I.H.P. ; the slip spaces are also divided into tenths for decimals of per cent., and the revolution spaces are divided into ten divisions, each being equal to a revolution. Dotted lines are shown to illustrate as clearly as possible how the small rings which form the connecting points of the curves are located. The three curves shown on the diagram were developed from the following trial trip data, and it should be noted that the mean results of a series are taken in each case. Data for Curves. Mean Speed in Knots. Mean I.H.P. Mean Slip per Cent. Mean Revs, per Minute. IO-5 400 17-5 82 14-8 1270 20-6 120 17-2 2000 211 140 20-2 3325 21-2 165 21-2 3790 21 172 21-7 4393 21-2 177 22-1 4650 21-8 182 With reference to the curves, the following points should be carefully studied : — I. Between 11 knots to 21 knots the I.H.P. varies approximately as the knots cubed, which can be proved as follows : At 1 1 knots the I.H.P. is 500 ; to find the I.H.P. at 16 knots, Then, As 11' : 16^ : : 500=1600 I.H.P. (nearly), After which is exactly the figure shown on the curve at this speed, this speed the ratio is still higher. 2. The revolutions vary almost directly as the speed, for at 10-5 knots the revolutions are 82, and at double that speed or 21 knots the revolutions are 170. 3. The propeller slip is high owing to the high engine revolution speed reducing the propeller efficiency, but at 21-2 knots the slip is less than at 19 knots, which is somewhat unusual. From 21-2 knots to the maximum speed of 22-1 knots, the slip increases rapidly, as shown by the upward tendency of the slip curve at this position. SECTION VI. MARINE ENGINEERING CHEMISTRY NOTES. It need hardly be pointed out that a slight knowledge of chemistr>% or at least of chemical processes, is a necessity for the modern engineer, surrounded as he is by numerous active examples of chemical action and reaction, which ha\e, in many cases, to be resisted or neutralised by means of other chemical actions or reactions. Unfortunately, however, man)- of the effects referred to, instead of being eliminated altogether, can onl)' be minimised. Examples. — The following are a few ordinary- examples of chemical action and reaction : — 1. Combustion of coal or oil in a furnace. 2. Rusting (combustion). 3. Explosion of gases (combustion). 4. Corrosion in boilers, Feed Heaters, &c. 5. Corrosion in tank tops, condenser tubes, tail-end shafts, rudder posts, propellers, &:c. 6. Scale deposits in boilers, P3vaporators. &c. 7. Formation of Marsh Gas in bunkers, oil tanks. 8. Formation of COo gas and Free Nitrogen in ballast tanks, &c. From the foregoing it will be admitted that, to cope more or less successfully with the destructive effects produced by the processes referred to, a knowledge of chemistry is really necessary, as b}- it the engineer may know how to obtain good combustion in the furnaces, how to correct the action of acid or oxygen in boiler water, the best methods of preventing explosion of Marsh Gas in bunkers, methods of protecting the boilers against corrosion and pitting, how to keep down scale deposit in boilers, &c. &c., all of which come under the general heading of chemistry. Composition of Coal. Carbon - - 80 per cent. Hydrogen - - 5 Oxygen - - 8 Nitrogen - . jl Sulphur - - li Ash. &c. - - 4 100 per cent. 408 Average Coal Marine Engineering Chemistry Notes 409 Heat Values. Carbon = 14500 Heat Units per lb. Hydrogen = 62000 ,, „ Sulphur = 42 „ „ Heat in i lb. Coal. I lb. good coal contains about 14700 Heat Units, made up as follows : — 1450 X 80 ^ ^^gPQ Heat Units from Carbon. 100 62000 xs_ 3100 Heat Units from Hydrogen. 100 14700 Heat Units, total. NOTE.— The heat of the other elements may be neglected. Chemistry of Gases, &c. In chemical formula; the various elements are represented b}- the following s}-mbols : — C = Carbon. CI = Chlorine. H = Hydrogen. Na = Sodium. N = Nitrogen. Fe = Iron. = Oxygen. Ca = Calcium S = Sulphur. Small numbers affixed to any of the above s}"mbols indicate the atoms or volumes of that element which go to make up the chemical compound expressed. For example, water is compos'ed of two atoms of h)drogen and one atom of ox}'gen ; it is therefore expressed chemicall)' as H.,0. Again, dr)- Ammonia is composed of one atom of nitrogen and three atoms of H}'drogen, and is expressed as NHo. The prefix " Mon " means one atom, and " Di " two atoms. The following are the most important chemical compounds to be studied and committed to memor)- : — Atmospheric Air. Composition, By Volume. By Wei^h . Nitrogen- .... 79-04 77 Oxygen ----- 2096 23 Ordinar}' atmospheric air contains water vapour and a very small percentage of carbonic acid gas — about -04 per cent. It also contains small proportions of Ammonia, Argon, also Aqueous Vapour and Nitric Acid. One pound of air at ordinary atmospheric temperatures occupies about 13 cubic feet, and consists of Oxygen 23 parts, Nitrogen "jy parts by weight. 4IO "Verbal" Notes and Sketches ,. • _ / Oxygen -23 of i lb. I ID. air--^^ jj-^j.jjggjj .^^ Qf J ijj (nearly). NOTE.— Atmospheric air also contains a very small proportion of C0._, gas- about -04 per cent. Air Required per Pound Coal. — (i.) Assuming that each pound of coal requires in forced draught 20 lbs. of air for perfect combustion, Then, 20 x 13 = 260 cubic feet of air per pound coal. (2.) If natural draught, 24 lbs. are required, Then, 24x13=312 cubic feet of air per pound coal. Water = H,0. Carbon Monoxide, or CO = Carbonic Oxide. — This gas is obtained by incomplete combustion, due to an insufficient supply of air or oxygen. CO will change into CO2 if sufficient ox}'gen be supplied to it. An example of this is flame sometimes seen at the funnel top. CO burns with a pale bluish flame. The specific gravity of CO = -96. Carbon Dioxide, or C02 = Carbonic Acid Gas. — This gas is obtained (one wa}-) b}' perfect combustion in the furnace. It supports neither combustion nor animal life. It is used in the form of ^^ carbonic anhydride'^ (that is, "without water") for refrigerating machines, as when reduced to a liquid under pressure and cold, it quickly evaporates again at a low temperature if the pressure is withdrawn, and expansion allowed to take place. It can be prepared in large quantities by the action of Hydrochloric acid on Limestone. CO, (together with Free Nitrogen) is also found in empty ballast tanks and boilers under the name of "foul air," and the CO., gas being fully one and a half times heavier than the atmosphere, accumulates at the lowest parts of the tanks, &c. It has been recently found by careful experimental tests that " foul air" is made up of fully 85 per cent. Free Nitrogen, and onl\' about 15 per cent. CO.,, instead of being, as was at one time supposed, entire!)' made up of CO., gas. The presence of COg and Free Nitrogen can be detected b)' lowering a lighted taper (or open lamp) into the suspected place, which, if extinguished, denotes these gases present in quantit}'. The atmosphere contains about 0-4 per cent, of CO.,, and this is under- stood to be one of the causes of corrosion in boilers, as the air admitted with the feed water contains Oxygen and COg, both of which in combination are conducive to corrosion when set free by heat in a moist atmosphere. In testing for the presence of " foul air," a light, if lowered into the tank or boiler to be tested, will either burn smok\- and black or go Marine Engineering- Chemistry Notes 411 out altogether, according to the percentage of " foul air" present. If the light is extinguished, CO3 is present in dangerous quantity. Free Nitrogen. — When oxidation goes on in a ballast tank or boiler, Free Nitrogen is produced by the rapid combination of the Oxygen, which is therefore used up, and leaves behind the Nitrogen gas. Nitrogen liberated in this manner is similar in its effects on life and combustion to CO.,, in that it neither supports life nor combustion, and thus constitutes " foul air." Light Carburetted Hydrogen, Methane, or CH^ = Marsh Gas. — This gas is usually found in coal bunkers, and is generated by the gradual evaporation of the coal and its absorption of oxygen from the air especially if damp. As the gas slowly forms by chemical action, heat is generated, and the temperature rises, it may be, to the ignition point, thus causing what is known as spontaneous combustion. It should be noted that this gas will explode on the introduction of a naked light into the bunker. Small or wet coal is most liable lo produce spontaneous combustion. Danger of explosion from a light exists when the proportion of CHj to air is in the ratio of i to 10; that is, I cubic foot of CH^ to 10 cubic feet of air. Coal shipped direct from the mine contains more CH^ than coal which has lain for some time previous to shipping, as in the latter case most of the Marsh Gas has passed off. Air containing 5 to 6 per cent. CH^ will explode sharply, and when 10 per cent, is present it explodes with greatest violence, complete combustion taking place. When CH^ is suspected in a coal bunker, the only sure way of detecting it is by means of a miner's Davy lamp, its presence being shown by a pale blue " cap " or halo on the top of the flame. When an explosion of CH^ takes place in a bunker great caution should be exercised in entering it as the resultant gases (CO and COo) are highly poisonous. CH^ itself in a pure state is also poisonous. Marsh Gas (specific gravity = -5 5) is lighter than the atmosphere, and therefore occupies the highest parts of bunkers and tanks. Marsh Gas supports neither life nor combustion. Petroleum Vapour, or Light Carburetted Hydrogen, is also found in empty oil tanks, and is formed by the evaporation of the layer or skin of oil left adhering to the bottom and sides of tanks after they have been pumped out. Oil gas is of nearly the same composition as coal gas, with the difference that it contains less carbon and more hydrogen. This will be understood when it is stated that average mineral oil as used in furnaces for fuel is made up as follows: — Carbon, 84 per cent; Hydrogen, 14-5 per cent.; and Ox}-gen. 1-5 per cent. Carburetted Hydrogen, if mixed with air, is highly explo- sive ; it is also fatal to life. For this reason oil tank steamers are fitted with special fans for exhausting the foul gases from the tanks after the oil is pumped out. Petroleum vapour from heavy mineral 412 "Verbal" Notes and Sketches oils is much heavier than the atmosphere (two and a half times), and occupies the lowest level of a tank. Ammonia = NH.5. — This alkali (the opposite of an acid) is peculiar in the fact of its having what is usually the property of an acid, that is, a corrosive action on brass and copper. Ammonia being an alkaline substance, changes red litmus paper to blue ; whereas an acid changes blue litmus paper to red. Litmus paper is the ordinary chemical test for acid or alkali. NOTE.— Acids and alkalies combine to form salts, and in combining the one counteracts or destroys the effects of the other. Ferric Oxide = Feo03. — This is obtained by the chemical combina- tion of iron and oxygen in a damp atmosphere. When two atoms of iron combine with three of oxygen we obtain five atoms forming FeoOg. Hydrochloric Acid = HCl. — This is composed of hydrogen and chlorine, and is often found in empty boilers. The chlorine is obtained from Magnesium Chloride, a constituent of sea water. Sodium Chloride, or Common Salt = NaCl2. NOTE.— Na is the chemical symbol for Sodium (Natrium). Calcium Chloride = CaCL. — This compound is used as a brine former in refrigerating machines, where the brine pipe system is used for cooling. This salt is very much more intense in its effect, and is better in every way than common salt. In making up the brine with calcium chloride fresh water only should be used, as sea w^ater sets up corrosion in the brine pipes and brine pump. Common salt has the same injurious effect. Acids. — An acid is a chemical compound possessing the following characteristic properties : — (i.) Is sour to the taste. (2.) Changes blue litmus paper to red. (3.) Neutralises alkalies, and with them forms chemical salts. (4.) Contains hydrogen. Alkalies. — An alkali is a chemical compound possessing the following characteristic properties : — (i.) Is soapy to the taste. (2.) Changes red litmus paper to blue. (3.) Absorbs CO., gas. (4.) Easily combines with acids to neutralise them and form chemical salts (is then known as a *' base "). Marine Engineering Chemistry Notes 413 Spontaneous Combustion in Coal Bunkers. This is likely to occur in bunkers exposed to the effects of fairly hiijh temperatures, such as may exist when the bunkers are placed very near the boilers of a steamer. By the oxidation of coal the carbon is set free, and combines with the oxygen of the air and forms CO^ and CO. The gas produced by the gradual oxidation of the coal is CHj or Marsh Gas, and it should be noted that this gas of itself is not explosive, but only when mixed with certain proportions of atmo- spheric air. A lighted taper plunged into a jar of pure Marsh Gas will not produce an explosion, but if the Marsh Gas were mixed with, say, 10 cubic feet of air to i cubic foot of gas, a violent explosion would result. If the air supply is reduced to one-half of the above proportion, the resulting mixture will not produce an explosion, or if the air supply is increased to tzvice the above proportion, the resulting mixture will not be explosive. The most violent explosion occurs when the proportion of air to CH^ is as 10 is to i, a weaker explosion, however, taking place when the proportion is as 8 is to i. Marsh Gas can be detected by means of a safety lamp similar to that used by miners, for if the flame of the lamp is turned down low a blue " cap " or top will form and burn above the flame, thus indicating the presence of Marsh Gas. Marsh Gas can only be got rid of by means of ample ventilation of bunkers or tanks, or, in the case of the latter, by means of special exhausting fans, as employed in oil-carrying steamers. NOTE.— The gases obtained after explosion of Marsh Gas (CH4) and air are:— CO.;, H,0, and N. Or, Carbonic Acid Gas, Steam, and Free Nitrogen. Marsh Gas (CH,). The following points regarding the explosive properties of Marsh Gas when mixed with air are of importance : — 1. Ignition point, 1200" Fahr. 2. If atmosphere contains 5| per cent, of Marsh Gas ignition only will take place if a light such as a match, candle, lamp, or fat electric spark is applied. 3. If atmosphere contains 10 per cent, of Marsh Gas a violent explosion will take place if a light is applied. 4. If atmosphere contains 18 per cent, of Marsh Gas ignition only will take place if a light is applied ; and if the percentage of Marsh Gas is more than this the combustible nature of the mixture decreases. Briefly, if the oxygen (or air) supply is low (5 A per cent.) the mixture is not favourable to combustion, and if the oxygen (or air) supply is high or excessive (20 per cent), the same holds good ; the most suitable mixture for explosion being 10 per cent, of Marsh Gas ^l^ ''Verbal" Notes and Sketches in the atmosphere, as with this proportion the chemical combination is most favourable for instantaneous combustion. Causes of Spontaneous Combustion. — F"ires in coal bunkers or in coal cargoes are due to the rapid absorption of oxygen by the coal, and the most favourable conditions for this occurrence are as follows : — 1. With freshly worked coal. 2. With small coal, slack, or dross. 3. With moist coal. 4. By heat in surrounding atmosphere. The first signs of spontaneous combustion in a coal cargo are a peculiar smell like burning oil, and the appearance of a mist-like vapour in the air currents, also a rise in temperature of the surrounding atmosphere. Inferior coal is more likely to ignite spontaneously than good coal ; and coal of small size than lump or thick coal. With small coal there are more spaces containing air, as for a given cubic mass the weight will be less than for large coal. The oxygen of the contained air is greedily absorbed by the coal under the con- ditions mentioned, and this results in a rise of temperature, as when- ever chemical combination takes place heat is developed. The heat may in time rise to the ignition point of Marsh Gas (CH^), which is 1200" Fahr., and fire will then break out. This firing of coal generally originates in the centre or heart of a pile of coal and well down in the mass, as on the surface the heat generated is carried off by the ventilating atmosphere, and the temperature is thus kept down below ignition point. Prevention. — With coal cargoes, as usually stowed loose in the holds, it is practically impossible to adopt really effective preventive measures against the generation of Marsh Gas and danger of spon- taneous combustion, but the following suggestions may be of use — 1. Liberal ventilation. 2. In handling coal ashore, the coal is divided up into sectional lots, with divisions betw-een. 3. Great care as regards ventilation is necessary with small coal for the reasons given previously. 4. Coal to be kept as cool as possible. Treatment of Fires. — When a coal cargo or bunker takes fire the following methods of dealing with the outbreak may be employed — 1. For small fires the use of sand thrown on the flame will be found sufficient for the purpose. 2. For more serious outbreaks "digging out" may in some cases be successfully resorted to ; that is, the mass of coal which is burning is (if possible, and safe to do so) dug out altogether. Marine Engineering Chemistry Notes 415 "Sealing Off." — In other cases of fire it is advisable to close down or "seal off" the hold altogether, so that the fire may be starved of oxygen. This method is only effective, however, if the closing down is really effective, and all ingress of air actually prevented. If leaks of air, however small, take place, the fire will be intensified instead of diminished. Water. — Water played on the flame may in some cases be effective if the supply is ample and directed on the coal actually burning, but if otherwise, the water applied may generate "water gas" and only make the state of matters worse. COo. — This gas may be effectively employed to put out a fire if applied in the initial stages, but if the coal once becomes incandescent the use of CO.^ as an extinguisher may be totally ineffective. Carbon. — In the solid state carbon exists as charcoal, coke, soot, graphite, and the diamond, the latter being carbon in the hard and purest cr}'stalline form. Solid carbon may be obtained by heating coal without allowing actual combustion to take place ; this expels the volatile gases, and carbon in the form of coke is left as the residue. The average heat value is 14500 B.T, units per pound. Nitrogen. — This gas does not assist combustion, as it is a quite" inert gas, and is termed a "non-supporter" of combustion. It reduces the activity of the oxx'gen, and thus moderates oxidation and com- bustion. During combustion it passes off unchanged in condition, but raised in temperature. Hydrogen. — This gas is the lightest substance known. It exists in water as H.3O. It is also combined with Carbon, Nitrogen, and Oxygen in coal, and other substances. All acids contain Hydrogen. When Hydrogen burns in air or Oxygen, water is produced, the water consisting of two volumes of Hydrogen and one volume of Oxygen, or H.2O. The action takes place in the furnaces, and water vapour or steam is evolved by the liberation of Hydrogen from the coal, and the combination of the same with atmospheric Oxygen. Combustion. — Allowing 24 lbs. of air per pound of coal — Then, •77x24 = 18-48 lbs. Nitrogen, And, '23x24= 552 lbs. Oxygen. 24-00 lbs. Air. From this it will be seen that for each pound of coal 18-48 lbs. of Nitrogen require to be heated up from say 62 degrees to 650 degrees (Funnel Temperature), or 588 degrees. This illustrates the unavoid- able waste of heat due to the heating of the Nitrogen of tlie air. 28 4i6 "Verbal" Notes and Sketches Coal Gases.— Moist or damp coal in the bunkers generates the followintj gases by steady absorption of Oxygen — -- Light Carburetted Hydrogen^ (I.) I Marsh Gas l = CHi. I Methane J The gas CH^ (which, it will be observed, has three different names) is colourless, tasteless, and inodorous. It burns with a yellow coloured flame, and can be detected by the use of a safety Davy type lamp, which burns with a "blue cap" at the top of the flame if this gas is present. (2.) CO gas, or Carbonic Oxide. This gas is also colourless, tasteless, and inodorous. It is poisonous and burns with a bluish coloured flame. The Davy test lamp has the flame surrounded by a mantle of gauze, the cooling effect of which is to reduce the temperature of the flame below the ignition point of Marsh gas. In testing for the presence of explosive gases the lamp requires to be turned down to a mere peep, and if Marsh gas is present the blue cap will then show at the top. CO can only be detected by a flame when 12 per cent, is present, whereas | per cent, is dangerous to life. The only sure test is by means of a small, warm blooded animal, such as a mouse or canary, which are now used in coal mines when this gas is suspected. General Notes. Combustion is the chemical combination of the Carbon and Hydrogen of the coal with the Oxygen gas of the air, producing heat. Weight for weight with Carbon, Hydrogen gives out the most heat, as i lb. of Hydrogen contains about 62,000 units of heat, and 1 lb. of Carbon about 14,500 units of heat, but in actual combustion the amount of Hydrogen in coal is so small (about 5 per cent.) that its heating power may be neglected altogether, and all the effective heat assumed to come from the Carbon, which constitutes four-fifths of the coal. If twelve parts of Carbon (by weight) combine with thirty-two parts of Oxygen (by weight), Carbonic Acid gas, CO.,, is obtained, giving complete combustion. If twelve parts of Carbon combine with less that thirty-two parts of Oxygen, Carbonic Oxide gas, CO, is obtained, giving incomplete ombustion, with a corresponding loss of heat. The funnel gases consist chiefly of Carbonic Acid gas. Carbonic Oxide gas. Oxygen and Nitrogen, or of CO^, CO, O, and Free N. NOTE.— Under conditions of good combustion the funnel gases are made up as follows :— Nitrogen = 80 per cent. CO,, = 10 per cent. (CO, Oxygen, and H.,0) = 10 per cent. Marine Engineering Chemistry Notes 417 If CO is present in waste or funnel gases, combustion of the fuel is incomplete and a loss of heat is taking place. Black smoke is chiefly composed of uncombined particles of Carbon. In combustion the Sulphur of the coal combines with Oxygen and produces SO., (Sulphur Dioxide), or more correctly Sulphurous Anhydride. This is a colourless gas, possessing a strong, pungent smell. Black smoke may be caused by excess of air as well as by want of air, as excess of air lowers the temperature of combustion and prevents the formation of CO^. The surplus air absorbs heat in passing through the furnaces. If coal is placed in a closed chamber, technically known as a retort, and subjected to destructive distillation, gases are given off, leaving behind carbon in the form of coke. Therefore, — 1. In complete combustion the Carbon of the coal combines chemically with Oxygen of the air to produce CO2 gas. 2. In incomplete combustion part of the Carbon of the coal combines chemicall}' w ith the Oxygen of the air to produce CO gas, and part combines mechanically with the air to produce black smoke. 3. In combustion the Hydrogen of the coal combines with Oxygen of the air to produce water vapour, H.,0. 4. In combustion the Nitrogen of the air remains chemically un- combined, but passes up the funnel raised in temperature, thus carrying offbeat and representing the principal loss occurring in combustion. Burning of CO. A light bluish coloured flame noticed burning at the back of the furnace indicates the presence of CO gas (Carbonic Oxide, or Carbon Monoxide). During combustion the Hydrogen in the coal, set free by the heat, combines chemically with Oxygen of the air and produces water vapour, the proportions being Hydrogen two volumes, and Oxygen one volume, or H.^O (water). Carbon particles which have not been supplied with sufficient Oxygen become mixed mechanically with the water vapour and produce black smoke, the intensity of colour depending on the proportion of solid Carbon held in suspension. If CO., gas combines with an additional amount of Carbon the result is the formation of Carbonic Oxide (Carbon Monoxide), Thus, C + CO0-2CO. 4.S "Verbal" Notes and Sketches Heat in Carbon. With perfect combustion each pound of Carbon converted into CO2 gas (Carbon Dioxide) gives out about 14500 Heat Units. With imperfect combustion each pound of Carbon converted into CO gas (Carbon Monoxide) only gives out 4450 Heat Units: the serious loss of heat resulting from incomplete combustion will thus be obvious. Scale, Density, and Corrosion. The generation of steam being a continuous process the supply of feed water must also be continuous, and this natural!)' results in the concentration of the impurities introduced with the feed water ; these impurities develop as scale, increase of densit)', corrosion, or by suspended matter (oil). Scale Deposit is due to the more or less combined effects of heat, pressure, and concentration of impurities. Corrosion is due chiefly to the introduction of gases and acids into the boiler with the feed, but may also be caused by galvanic action. Scale in forming may also indirectly produce corrosion, as, b}' the effects of the heat when the scale matter concentrates and deposits, acids (such as Hydrochloric) are set free which cause corrosion. Composition of Fresh Water and Sea Water. Fresh Water. Name. Grains per Gallon. Effect in Boiler. Calcium Bicarbonate (or Carbonate of Lime) Calcium Sulphate (or Sulphate of Lime) Magnesium Sulphate - Carbonateof Magnesium Chloride of Sodium (common salt) Silica, Iron Oxide, Organic Matter Total Grains per gallon IO-8 •3 0-25 1-25 1.8 1 3-21 ] 7-61 Forms lime carbonate scale at low pres- sure and temperature (200° to 2 12°). Forms hard scale at 40 lbs. pressure or 290° Temperature. Remains soluble in the water. Remains soluble in the water. Begins to deposit at 35 oz. density and water is fully saturated at 60 oz. density. Form muddy deposits. Marine Engineering Chemistry Notes 419 Sea Water. Name. • Grains per Gallon. Effect in Boiler. Calcium Carbonate, or Carbonate of Lime Calcium Sulphate, or Sulphate of Lime Magnesium Sulphate - Magnesium Chloride - Chloride of Sodium (common salt) Silica, &c. - Total Grains per gallon 3-9 93- 1 124-8 220-5 1850- 8-4 2300-7 1 [ Forms scale at low pressures and at temperatures of from 200° to 212°. Forms hard scale at about 40 lbs. pressure and 290° Temperature. Remains soluble in the water. Decomposes at 360° Temperature, and liberates Hydrochloric Acid, the Chlorine gas of which produces severe corrosion. Begins to deposit at 35 oz. density, and water is fully saturated at 60 oz. density. Form muddy deposits. NOTE. — At densities over 15 oz. per gallon the lime sulphate deposits at lower temperatures than 290". 1850 X 100 4 NOTE.— Per cent, of Salt (Sodmm Chloride)- — — -r- — =80 per cent., or _. Incrustation (Scale). A .sample of boiler scale formed from Thames water was com- posed of the following : — Per cent. Sulphate of Lime (CaSO^) - . - . 20-41 Sodium Chloride (NaCl) ... - 68-25 Magnesic Hydrate (MgHoO.,) - - - - 2-81 Magnesic Chloride (MgCU) - - - -3-14 Oxide of Iron (FcgOs) " ■ " - -02 Silica (SiO,) - - - . - -ii Organic Matter - - - - - -lo Moisture (HgO) - - - - - 5-16 Total ----- I GO-GO 420 " Verbal " Notes and Sketches Chemical Composition of Boiler Scale. Sea Water I'resh Water Scale. Scale. Sulphate of Lime (parts in loo) - 85-53 • 3-68 Carbonate of Lime „ ,, •97 75-85 Hydrate of Magnesia ,, „ 3-39 2-56 Chloride of Sodium (salt) „ „ 2-79 ■45 Silica „ „ i-i 7-66 Oxide of Iron ,, „ •32 2-96 Organic Matter „ >»■ - 3-64 Moisture ,, Total _ 5-90 3-20 lOO-OO lOO-OO Scale and Oil Deposit Compared. — An oily deposit, yV inch thick, on the furnaces will result in more overheating of the plates than that produced by h inch thickness of lime scale. Oily matter deposits more readily with a low boiler density, as with a higher density the oily mass tends to float on the surface, whereas if the water is nearly fresh the weight of the mass may cause it to sink down and deposit on the combustion chamber tops, smoke tubes, or furnaces. Temporary Hardness. — When water is boiled at 212° temperature the CO2 gas is driven off, and the carbonate of lime then becoming insoluble is deposited ; thus the " temporary hardness " is got out of the water. Permanent Hardness. — Lime Sulphate, Lime Chloride, and Magnesia Chloride form the permanent hardness of water, as these substances are not deposited until a temperature of 290° is reached, when the Lime Sulphate becomes insoluble and deposits in the form of Gypsum, or hard close-grained scale. The Magnesium Chloride does not deposit until a temperature of 360° is attained. The scale formed from Lime Carbonate is more open in the pore than that from Lime Sulphate, is lighter in colour, does not adhere so closely, and is more easily removed. Lime Sulphate scale is often combined with Lime Carbonate, and thus shows as a series of layers of varying shade. Corrosion of Boilers. Parts Affected. — Damage to boilers is caused by internal or ex- ternal corrosion, wearing away of the rusted edges by repeated caulking of same, and by cracks due to unequal expansion or con- Marine Engineering Chemistry Notes 421 traction, which finally produce " fatigue " of the metal. The latter condition is particularly applicable to the "saddle" of the furnace where the combustion chamber is riveted to the furnace flange, and which in so many boilers gives trouble by cracking or by leakage. Leakage, if not taken up at once, will produce corrosion, as the decomposition of the water or steam passing the leak liberates Oxygen, which combining chemically with the metal produces oxide of iron. On the furnace sides above the fire-bar level the intense heat sets free oxygen bubbles, which adhere to the plate and produce corrosion by chemical action. Again, the tendency to unequal ex- pansion in the upper and lower half of the furnace is apt to strain the metal at this position and slightl}' fracture the surface skin, which is thus placed in a condition most favourable to corrosion. NOTE. — The upper half of the furnace is exposed to a temperature of about 2500", and the lower half to a temperature of about 1000°. This is due to the fact that the upper half receives the heat of convection, whereas the lower half only receives the heat of radiation. To sum up, the following positions are most often affected b\' corrosion, &c. : — 1. On water sides of furnaces above line of fire-bars (see sketch). 2. Bottom of furnace near the back end, and bottom of combustion chamber. 3. Cracks round corrugations of furnaces (expansion and con- traction of metal). 4. Cracks near back ends of furnaces at combustion chamber (more often in plain furnaces). 5. Corrosion at tube plates due to leaky tubes, or at combustion chamber back and side plates due to leaky stays. 6. Corrosion at ends of furnaces due to straining set up b\' expansion and contraction. 7. Corrosion at bottom of boiler and combustion chambers due to deposits and to weak circulation at these parts. 8. External corrosion caused by damp (CO^ gas) from the bilges, from wet ashes, and other similar causes. If manhole or sludge-hole doors are not tight the leakage will in time produce corrosion, as explained previously. Furnace corrosion, cracks, combustion chamber and tube leakage are all intensified in the case of forced draught owing to the higher temperature of combustion obtained. Causes of Corrosion. 1. Oxygen and CO, gas brought in with the air in the feed water and set free by heat. 2. Chlorine gas set free by heat at high pressures from the Magnesium Chloride contained in Sea water feed. 3. Galvanic action due to dissimilar metals, such as brass and 422 "Verbal" Notes and Sketches steel, &c., connected metallically in a solution of sea water or acid water, such as is found in boilers. 4. Fatty acids set free by heat from oil taken into the boilers with the feed water. Stearic and Oleic acids are contained in vegetable and animal oils, but not in mineral oil, which is of so-called pure " Hydrocarbon " composition and free from acid of any kind. Cylinder or valve oil should always be of this class. It should be noted, however, that any class of oil if deposited on the furnace crowns may bring about collapse. Prevention of Corrosion. Taking the case of new boilers, corrosion can be hindered to a great extent by working as follows : — 1. By using some sea water feed and frequent surfacing, or by the direct addition of lime, first obtain a light protective lime scale of ^^2 J"ch thick on the heating surfaces. 2. Use fresh feed water at all times if possible, and avoid alto- gether the use of sea water as feed. For this a large evaporator is necessary. 3. Employ a feed heater wdiich, in addition to heating up the feed water, extracts most of the air and other gases from the water gases, which (in the case of Weir's heater) pass away to the condenser. 4. Employ a feed water filter which, fitted between the hot-well and boiler check valves, traps most of the oil or grease which may be present in the feed water when it leaves the condenser. 5. Fit inside of the boiler and in clean metallic contact with the plates or stays, slabs of zinc to set up galvanic action between the zinc and steel, which action results in the wasting away of the positive element zinc and the proportionate protection of the boiler plates. 6. If necessary, use soda in moderation. Hydrochloric Acid. — This corrosive acid is formed as a result of the decomposition at high temperature of certain chlorides present in sea water and reactions between such substances as Magnesium Sulphate and Sodium Chloride. Hydrochloric Acid giving off Chlorine produces corrosion in the steam space of boilers ; as, however, it is both volatile and soluble, it may produce pitting below the water line as well as above it. Scale Deposit and Plate Temperature. — The overheating effects produced on the furnace metal by various thicknesses of lime scale deposit are shown below : — A scale thickness of j-\- inch requires an expenditure of 15 percent, more fuel. " " i j> )) ), 60 ,, ,, " " 2 >> » „ 150 „ ,, At a scale thickness of \ inch or less the plates may reach the Marine Engineerin<;' Chemistry Notes 423 critical temperature of over 600', and collapse of the furnaces take place. This will easily be understood when it is stated that a temperature of 700° produces a low red heat on the plate. A scale thickness of ^V inch is quite sufficient to protect the plates from corrosion. Magnesium Chloride. — This sea water chemical decomposes at a temperature of 360 , and the Chlorine set free combines with iron to produce corrosion. During decomposition of Magnesium Chloride, Magnesia is produced and deposits as a form of mud or slime. A gallon of ordinary sea water contains about 220 grains of Magnesium Chloride, and under conditions of heat and concentra- tion this substance splits up into Hydrochloric Acid and Magnesia: the acid mentioned combines with the iron of the boiler to form iron salts, and therefore produces corrosion. Corrosion of Tubes in Boilers. — Ma)- be due to (i) fatty acids obtained from the decomposition of animal or vegetable oiJs ; (2) H}'drochloric Acid produced by the decomposition, at a high temperature, of a magnesium and chlorine compound in the sea water ; (3) galvanic action ; (4) the presence of Carbonic Acid and air in the water. Red and Black Iron Oxides. — Red oxide of iron (FcoOg) is formed when excessive air is entering the boilers with the feed water, and Black Oxide of Iron (Fe„OJ when the air admission is not excessive. Air should therefore be kept out of the boilers as much as possible, as the amount of corrosion will then be reduced in proportion. Test for Carbonic Acid. — To test for the presence of CO.^ gas in boiler water : make up equal volumes of boiler water and lime water, and if CO.^ is present, the mixture will turn cloudy or milky in appearance. Evaporator Scale. — The scale in evaporators is chiefly Lime Car- bonate, as the pressure and temperature carried are not high enough to produce deposit of Lime Sulphate. The Lime Sulphate therefore remains in solution in the water, and is blown out by way of the blow-down cock. Boiler Deposits. — The impurities in boiler water are deposited in the following order : — 1. Carbonate of Lime (at low pressures and temperatures). 2. Sulphate of Lime (at 290" temperature, 40 lbs. pressure). 3. Oxide of Iron. 4. Silica, Alumina, Magnesia H\'drate. 5. Common salt (at 35 oz. density deposit begins, and the water is fully saturated at 60 oz. density). 424 " Verbal " Notes and Sketches Leaky Tubes.— If cold air is admitted to the tubes by opening the smoke-box doors the tubes are apt to contract and leak at the ends. Leaky tubes may therefore be caused by (i) unequal expansion, or by (2) unequal contraction of the tubes and plates. Severe vibration, due to blowing down, may also produce leaky tubes. It should also be noted that leakage ultimately sets up corrosion on the plate round the tube necks and on the tubes themselves. Density and Scale. — The following points should be carefully noted : — 1. Scale deposit is due to heat, and is quite independent of evapora- tion, as, even though no evaporation is going on in a boiler (under banked fires), if sea water feed is admitted scale will be deposited shortly afterwards, 2. Increase of density (over 5 oz. per gallon) is entirely due to evaporation, as, if no evaporation takes place, the boiler density cannot rise above that of sea water feed. Therefore, the limit of density (saturation point) being 35 oz., should the boiler reach this density, and still more sea water feed be pumped in, when the water so fed in evaporates, the salt contained in it will be deposited. NOTE.— It must be clearly understood that the salt forming the 35-oz. density does not deposit, but only the salt contained in feed water put in after the 35-oz. density has been reached. General Notes on Scale and Salting. Salting or saturation of the boiler water means that the density has reached ^V, or 35 oz. per gallon. If at this density more sea water feed is admitted the salt in it begins to deposit after the water evaporates. Scale consists chiefly of sulphate of lime and carbonate of Hme. Scale is caused by the action of heat on sea water feed. The heat concentrates the sulphate and carbonate of lime, and as a result these substances deposit on the tubes, furnaces, &c. This occurs when the air and CO^ gases are expelled by heat. To sum up, scale is due to heat, and is quite independent of evaporation, as although no evaporation takes place scale may yet deposit. Increase of density above 5 oz. (sea density) is entirely due to evaporation, and cannot take place unless evaporation goes on. All waters contain lime, so that even with fresh water feed scale will form (chiefly carbonate of lime), but the hardest and most troublesome scale is that deposited by sea water feed, as it is largely composed of sulphate of lime. Sulphate of lime scale forms from a pressure of 40 lbs. and a temperature of 290°. Scale increases with the pressure, because the temperature is higher in proportion. Marine Engineering Chemistry Notes 425 The scale thickness depends upon the amount of sea water put into the boiler as feed, and does not depend upon the density of the boiler. Surfacing a boiler (having no evaporator fitted) reduces the density but increases the amount of scale, because every time the boiler is surfaced extra feed water has to be pumped in, therefore more sulphate of lime will deposit. The scale formed from fresh water feed is composed chiefly of carbonate of lime. 'Yo form a scale on a new boiler, keep the density low by surfacing and feed up with sea water. This will cause rapid deposit of sulphate and carbonate of lime, and the formation of a protective scale on the heating surfaces. As oil in boilers causes pitting, and may also bring down the furnaces by depositing on them, it is best kept out altogether, and this is done by having a feed filter fitted between the feed pump and the boiler check valve. A feed heater is used for raising the temperature of the feed water, and partly clearing it of air before entering the boiler. Solids in Sea Water. — The solid matter in sea water (forming 5. of the weight) is chiefly made up (approximately) as follows : — Sodium Chloride (common salt) - - 80 per cent. Magnesia Chloride - - - - 10 ,, Magnesia Sulphate - - - - 6 ,, Calcium Sulphate (gypsum) - - - 4 „ In addition to the above, Calcium Carbonate exists in combination with COo, forming Calcium Bicarbonate in solution. The heat drives off the CO., and the Calcium Carbonate is left, which, depositing, forms a scale. Calcium Sulphate. — This forms the hardest scale found in boilers, and is deposited largely from sea water feed. It is similar to plaster of Paris and marble (gypsum). Calcium Carbonate. — This composition gives a softer scale than Calcium Sulphate unless combined with the latter, and is similar to common chalk. It is deposited chiefly from fresh water feed when the CO^, previously in combination with it, is set free by heat. NOTE. — The scale found in evaporators is principally made up of Calcium Carbonate. A piece of Calcium Carbonate scale, when broken across, is coarser in the grain than Calcium Sulphate scale. Soda. — The addition of an alkali such as soda into the boiler feed water has the effect of tending to convert the Calcium Sulphate into 426 "Verbal" Notes and Sketches Calcium Carbonate, and thus make the scale less objectionable and less insoluble. Soda being an alkali also tends to combine with acids present in the water, and, forming chemical salts, destroys the corrosive effects of the acids. The addition of soda into a boiler often causes the density to rise shortly afterwards, as the soda softens the hard scale, and, making it soluble, the water becomes denser in proportion. Lime. — When lime is used in boilers, the proportion to allow is about 1 1 lbs. of lime per day per each looo I.H.P., dissolved in i gallon of water, and forming what is known as " milk of lime." This mixture is very useful in forming a scale on a new boiler, and should be used when the boiler water shows of a red (rust) colour. Rusting. — Iron immersed in pure water free from air will not rust, but with air present rusting takes place owing to the fact that air contains a small percentage of carbonic acid, which in contact with iron decomposes the water and sets free Hydrogen, which thus allows the Oxygen to combine chemically with the iron and form oxide of iron, Fe.^Oa (or Ferric Oxide). Grooving. — By this is meant corrosion produced by mechanical causes, such as unequal expansion. An example can be found in the case of vertical donkey boilers, at the bottom of the fire-box, where the expansion at the top end being much more than at the bottom (the latter being rigidly riveted to the shell), the resultant stresses set up crack the skin of the metal circumferentially, and the skin thus broken, allows of corrosion taking place to a serious extent. Paraffin Oil. — Paraffin oil is sometimes used in boilers with the object of softening the scale, which is then found to be easily removable. The heating surfaces are treated by being rubbed over with the oil and allowed to stand for a few hours before filling up. Carbonate of Soda. — The moderate use of soda is to be recom- mended, as the Soda has the effect of converting the Lime Sulphate into Lime Carbonate. Nitrate of Silver Test for Saltness. — As boilers are now often worked at an extremely low density (i oz. or 2 oz.), it becomes necessary to employ a more sensitive method of testing for the density than by the salinometer, and this can be carried out by a Nitrate of Silver test. A supply of this chemical having been obtained a few drops added to a glass of the boiler water will quickly discover the presence of salt by the water instantly becoming cloudy. This method is also the most suitable for testing the tightness of the condenser, as the smallest leakage will be indicated. Marine Engineering Chemistry Notes 427 Caustic Soda. — Caustic soda added to boiler water has the effect of converting the Hydrochloric Acid into common salt, thus destroying the corrosive properties of the acid. When pitting or corrosion is located in patches or small areas, the plates affected should be scraped clean, and washed with soda solution. A final coating of weak solution of Portland cement will reduce the danger of the corrosion spreading. Corrosion in the form of oxide of iron formation is apt to occur in those positions of a boiler where the circulation is weak, such as the lower parts of the furnaces and combustion chambers, and if once started may extend to other parts higher up. Heating Effect of Scale. — A scale of tjV inch is sufficient to protect the plates from corrosion, and any increase over this may lead to serious overheating, especially in the case of forced draught boilers carrying a high water gauge air pressure. New Boilers. — Messrs Babcock & W'ilcox recommend that 10 lbs. of lime per each looo I.H.P. be put into the boiler when new, and from 4 to 6 lbs. per day per 1000 I.H.P. for .six days afterwards ; the object of this is to form a light protective scale on the heating surfaces. In the first case the lime should be dissolved in water, and poured in through the manhole, and in the second case the mixture (made up as milk of lime) should be put into the hot-well. Test for Acid. — Draw off some of the boiler water and put into it a few drops Methyl-Orange (obtainable at the chemist). If the water remains yellow then it indicates an alkaline condition, but if the water turns into a pink colour it indicates the presence of acid. Action of Lime. — Lime added to the boiler water has the effect of converting the Magnesium Chloride into Magnesia and Calcium Chloride, the former being corrosive and the latter non-corrosive. Hydrometer. This instrument, which is simply a t)'pe of salinometer, is employed in Naval practice, and is generall}- graded for use at a temperature of 80° instead of 200°. The divisions or degrees represent half ounces, so that 20 indicates a density of 10 oz., 15, yh oz., and so on. The hydrometer thus allows of finer density readings than those obtained by the ordinary salinometer. 428 "Verbal" Notes and Sketches Oils. Lubricating Oils. For cylinder lubricatiori, mineral oil only should be used, as this class of oil is composed of Hydrogen and Carbon and is free of acids. The flash point should not be less than 400° Fahr. The Viscosity of an oil or cohesive nature of the fluid should be such that the lubricant is not so thick as to produce friction, nor yet so thin as to be squeezed out from between the surfaces in contact. Viscosity ma}' be said to be the consistency of the oil, and should be high for heavy bearings and low for lighter wearing parts. The viscosity of all oils becomes reduced with increase of temperature. Gumminess. — If an oil evaporates easil)' it will naturally become gummy and lose proportionally its lubricating properties. A rough test for gumminess can be made by painting over an earthenware dish with the oil and placing it in a warm position, where it can be tested by hand at intervals for stickiness. Classes of Oil. ( I. Extracted from Shale, and Cannel coal. Mineral Oils. < 2. Found in Russia and America in oil springs. Paraffin ( Petroleum, Kerosene, Benzine, Naphtha, &c. Vpp-ptflhlf* Oil*; i C^^^^' Linseed, Rape, Castor, Olive, Cottonseed, &c, ' vegeiaoie Ulis. j Manufactured from the seeds of the plants named. Animal Oils. — Sperm (whale), Seal, Neatsfoot. At moderate temperatures vegetable oils decompose into Oleic acid, and animal oils into Stearic acid, both of which act corrosively on the c}'Hnders, valve faces, and on the boilers if admitted with the feed water. Oil Emulsion. — Although feed water filters collect most of the grease or oil in the water often a certain amount passes the filter cloths in the condition known as "emulsion," and the small atoms of oil in this state combine easily with the Magnesia present in the boiler water, resulting in the formation of a slimy deposit, which forms a bad non-conductor of heat, and which ma)' bring about buckled plates or collapsed furnaces. "Saponification." — If animal or vegetable oils enter the boilers with the feed water, and soda is present, then the fatty acids of the oil (set free by the heat) combine with the soda to form a soapy substance which is a particularly bad conductor of heat, and which if deposited on the furnace crowns is likely to bring about buckling or collapse of the same. The combination of the acids and soda is called *' saponification " Marine Engineering Chemistry Notes 429 To Test Acidity of Oil. A. Make up a solution of Sodium Chloride with an equal weight of water, take a measured quantity of the solution and an equal quantity of the oil, which place together in a bottle. Shake up the bottle and allow it to stand, after which, if acid is present, it will show by settling to the bottom of the bottle. If no deposit takes place the oil is free from acid. B. Chemically prepared papers of a pale bluish tint and known by the name of " litmus papers," can be obtained in little books at a very small cost from any chemist, and these can be applied to test the acidity of an oil. To make the test, boil some of the oil and dip one of the litmus papers into it, and if, on withdrawing, the colour has become a deeper shade only, the oil is clear of acid ; but if the paper changes to a pink or red colour, it denotes with .certainty the presence of acid in the oil, which should therefore be rejected for purposes of internal lubrication. The redder the paper becomes, the greater is the quantit}' of acid present in the oil. , Boiler water can be tested for acid in the same way. NOTE. — A clean copper wire if immersed in oil for a few hours will show^ discoloration if acid is present. Viscosity Test for Oil. — The viscosit)' of an oil is tested in the following manner. The apparatus consists of a small cup-shaped vessel fitted with an internal pan, in the bottom of which a small round hole is truly bored, and a thermometer dips into the oil ; the oil is then heated up to a fixed temperature, say 180^, and the time taken for a measured quantity of oil to drip out through the small hole in the bottom is noted. Oil of high viscosit}' will take a longer period to escape than oil of low viscosity. To Test for Animal or Vegetable Oils. — To test whether an oil is of vegetable or animal nature add a small portion of chlorine to the oil, and note the change of colour ; if to brown the oil is animal, and if to white the oil is vegetable. Alkali Test. — To test for alkalinity use red-coloured litmus paper, which will change to blue if the water is strongly alkaline. Most of the oil used for internal lubrication of the engines finds its way to the boilers, (unless extracted by means of a filter), b)' being brought with the steam into the condenser, and afterwards pumped into the boilers by the feed pumps. "Alkala" Boiler Composition. Lambie's patent boiler composition, known as " Alkala," has proved, after severe and exhaustive tests, to be most effective in 430 "Verbal" Notes and Sketches the prevention of scale deposit and corrosion; used in conjunction with the usual zinc plates, boilers working under the highest pressures are found to be in excellent condition after months of hard steaming, the scale being of a light, easily removable nature, and the pitting or corrosion checked to a remarkable degree. Alkala is a paint and is applied by brush to the parts requiring protection, such as furnaces, plates, stays, and tubes. The composition referred to is rapidly becoming known as the most efficient boiler preservative in the market. Remedies for Pitting. Zinc plates (see page 143) are used internally to check the wasting of the platesj and are fitted so as to form with the boiler plates a galvanic couple, of which the zinc is the positive element. The zinc plates are connected metallically to the boiler by the following methods : — (i) Studs screwed into the furnace sides ; (2) metal hangers suspended from the stays. Sometimes zinc balls with a copper wire passed through them and connected to the boiler are used instead. These are called " Electrogens." Externally, feed heaters (such as Weir's) assist in keeping out the air, and feed filters assist in keeping out the grease or oil. Galvanic Action. If two dissimilar metals are placed in a bath of sulphuric acid, both will in time show signs of corrosion ; but, if the two metals are connected by a copper wire soldered to each, then only one of them will corrode, as a galvanic couple is then formed, and the corrosive effects take place on the most electro-positive metal only. (See page 432.) By connecting the two metals a weak electrical current is set up between them, through the liquid and wire, resulting in the wasting away of the one element which is electro-positive to the other. Examples of the foregoing are to be found in the boilers by the zinc plates fixed inside, and on the tail end shaft at the end of the brass liners, the brass and iron or steel of the shaft being dissimilar metals and connected in a bath of sea water. Sea water, as it contains salt, acts in a like manner to sulphuric acid, but in a milder form. NOTE. — The current flow is produced by the difference in electrical potential obtained. Rusting. Rusting of a metal is an example of combustion at a low temperature, and is due to the Oxygen of the air combining with iron (or steel) to form Oxide of Iron. Marine Engineering Chemistry Notes 431 The chemical name for red iron rust is P^erric Oxide, or, by symbols (Fe.^Og). Rusting is in reality the burning of the metal, but at a low temperature (the atmospheric temperature). Rusting can only take place when Carbonic Acid gas (CO.,) is present in quantity, as in a damp atmosphere. Rusting cannot occur in a dry atmosphere. A good example of rusting, or the formation of oxide of iron, is to be seen at the water line on the wet uptake of vertical boilers. The action that takes place is as follows : — The intense heat on one side of the plate sets free the Oxygen of the water adhering to the plate on the other side, and the Oxygen being present with Carbonic Acid gas combines with iron to form Oxide of Iron, or rust (Ferric Oxide). If a rivet or stay in the combustion chamber leaks, and the leakage is not at once checked, the plate and stay will soon begin to waste away, owing to the formation of Oxide of Iron. Oxide of Iron formation also accounts for the wasting away of boiler bottoms, just above the bilges, furnaces at the ashpits, and on the tops of tanks. Condenser Tube Corrosion, In most cases the corrosion of condenser tubes is due to one of the following causes : — (i.) Galvanic action produced between the condenser metal and tubes in sea water, resulting in the loss of the zinc, of which the tubes are partly composed. This produces small holes in the tubes at various positions throughout the length, but usually near the ends, and is known as "de-zincification." (2.) Acids from animal or vegetable oils producing corrosion on outer surface of the tubes by chemical action. (3.) General thinning of the tube by wear, and caused by the long- continued mechanical attrition action of the water inside the tubes. In the great majority of cases the corrosion is caused by decom- position of the zinc, as stated in No. i cause. 29 SECTION VII. MARINE ELECTRIC LIGHTING. General Description. The following elementary description of electric lighting is intended by the author for marine engineers who have had no exp-erience with dynamos, and who may have had no opportunity to study electricity — in other words, for beginners. For further information on the subject the writer can recommend " Electrical Engineering," by Messrs Slinger and Brooker. Galvanic Cells or Batteries. — An electric current may be produced either by chemical or mechanical means. If chemically, by a galvanic battery or cell ; and if mechanically, by a dynamo. WIRE ZINC .e:4^. SULPHURIC 7/ ACID Yy SOLUTION No. I.— Simple Cell. The sketch shows a simple cell, or galvanic couple, consisting of two plates, one of Copper and one of Zinc, placed in a bath of sulphuric acid, and connected together at the top by a wire. A current flows from the Copper plate through the wire to the Zinc plate, and back again from the Zinc through the liquid to the Copper. The Copper is called the "positive pole" but the negative element, Marine Electric Lig-hting 433 and the Zinc the nci,^ativc ikjIc and the positive element. The dotted lines in the sketch show how the current may be led to an external circuit so as to do work, such as, for example, to operate an electric bell, instead of passing direct from one plate to the other, as shown by the full lines. It should be noted that the current flowing in the direction described results in the dissolving of the zinc plate, and the formation of sulphate of zinc. NOTE. — The current flow is produced by the difference of electrical potential obtained. Daniell Cell. — One form of this well-known t)-pe of galvanic cell is shown in the sketch, in which the outer vessel is of Copper and constitutes the positive pole. The inner vessel is of porous construc- tion to allow of the liquid to pass through gradually, and the negative pole is formed by a rod of Zinc placed inside. Two liquids are em- POROUS VESSEL I./ 4. SULPHURIC ACID (A SOLUTION No. 2.—" Daniell " Cell. ployed — sulphate of copjDer solution in the outer vessel, and, as in the simple cell, sulphuric acid in the inner vessel. The current flows from the Copper to the Zinc as described previously in the case of the simple cell. The electro-motive force of the Daniell cell is fully one volt. Dotted lines are shown in the sketch to illustrate the manner in which the current may be applied to an external circuit, instead of passing directly from one pole to the other. Electro- Magnets. — If a bar of iron is enclosed within a coiled wire, and a current from either a galvanic battery or a dynamo passed through the wire, the bar becomes magnetised for so long as the current is passing. 434 "Verbal" Notes and Sketches IRON—, WIRE No. 3.— Electro-Magnet. TO SWITCHBOARD TERMINAL- FROM SWITCH BOARD -^ V. 5ASe PLATE No. 4. — Dynamo. Marine Electric Lighting 435 The bar is then known as an electro-magnet. If the bar is bent into a horse-shoe shape so as to form two legs, when a current is passed through the wire both legs of the bar become magnetised, and form a pair of electro-magnets. The space between the legs is called the " magnetic field," and if an armature be made to revolve in 436 Verbal " Notes and Sketches the magnetic field so as to cut the Hnes of force or magnetism passing across, currents are generated in the coils or conductors of the armature. The two legs constitute north and south poles. The field magnets of a dynamo are of the type just described, the poles receiving their magnetism from the dynamo itself, as the winding of the magnets consists of wires led direct from the brushes, the wires obtainingf their current direct from the armature. A dynamo is a machine which, by the application of mechanical power, generates electro-motive force. This electrical force or power can be utilised either for lighting or for the running of motors, or for both purposes combined. The four principal parts of a dynamo are — (i) Field magnets; (2) armature ; (3) commutator ; (4) brushes. Field Magnets. — The field magnets consist (in a two-pole dynamo) of two masses of cast steel connected at the top by a "yoke piece" No. 6.—" Belliss " Engine direct coupled to G.E.C Witton Generator used for lighting and power on board Steam- ships, Shipyards, Dockyards, Factories, &c. which gives to them the well-known horse-shoe shape. Each magnet is wound with coils of insulated copper wire which are in connection with the armature by one of three ways — (i) In series ; (2) in shunt ; or (3) compound, which is a combination or compound of the first two. In series winding the zvhole of the current generated in the armature passes from the brushes round the field magnets, and then to the lamps and back again. Marine Electric Lighting 437 In shunt winding only part of the current passes round the field magnets, as the shunt wire to the magnets is smaller and finer than the series wire, and in this way offers more resistance to the current. In compound winding the field magnets are wound with two sets of wire, and the whole of the current generated in the armature passes round them, but by two distinct and separate paths ; first by the thick or series coils, and next by the thin or finer " shunt " coils. The object of this method of winding may be described as follows : — As lamps are switched on and more current is required, the extra current, on its way to and from the lamps, passes through the series coils of the magnets, and therefore strengthens the magnetic field in pro- portion. Again, if a certain number of lamps are switched off, less current passes through the series coils as less is now passing through the main wires, but more current will pass through the shunt coils, and thus tend to maintain the same strength as before in the magnetic field, and keep the voltage constant. It will thus be seen that a compound wound dynamo is, to a great extent, self-regulating, and retains practically the same voltage, no matter how many lamps are on or off. This is of great importance in ship-lighting, and for this reason nearly all dynamos used for marine purposes are of the compound wound type. It should be noted that the exciting current for the magnets comes from the armature itself, and though small at first, increases as more current is developed, so that the one, in a sense, supplies the other in proportion to the demand. On examining a dynamo of the compound wound type, it will be noticed that the wires from the brushes are connected to terminals or studs fixed on an insulated plate which is placed on the side of the field magnets, and from these terminals the main leads or wires to the lamp circuits are branched off, and the series coils and shunt coils to the magnets. The fine shunt wire will generally be seen to connect across the two magnets and to the main terminals, as shown in the sketch. Four-Pole Dynamos are now being supplied for ship-lighting, and it is evident that this type is rapidly coming to the front and taking the place of the older- fashioned two-pole machine. In some cases six-pole machines are supplied. The four-pole dynamo is supplied with four sets of brushes, each alternate set being in connection, so that there are two sets of positive and two sets of negative brushes in use. The other parts of the machine are similar to those of the ordinary two-pole dynamo, but the four-pole type is of more compact form, and can be made of high magnetic strength. On examining a dynamo of this type, the thick wires of the series and the fine wire of the shunt will be noticed extending from one magnet to the other, and connecting them with the brushes and lamp cables. 43^^ \'erbal " Notes and Sketches Armature.— The two types of armature in general use for ship- lighting dynamos are those known as the " Ring" and " Drum " type, the latter being usually preferred and supplied asbeing the best suited for the work. It will therefore be sufficient to describe this type of armature in detail. The " Drum " pattern of armature is formed of sheets of soft iron or steel discs insulated from each other and clamped together on a sleeve keyed to the spindle or driving shaft. The sleeve is cast with recesses and webs so that air may pass freely from end to end, and by the ventilation so afforded prevent excessive rise of temperature when the armature is revolving at a high speed. The iron or steel discs are slotted longitudinally for the reception of the insulated copper conductors or wires, and each slot is also carefully insulated COPPER STRIP COnnUTATOR DRUh ARMATURE z:::^ COIL No. 7. — Drum Armature, showing one Conductor Connected. and the copper wire embedded in it. The complete armature consists of a number of these conductors wound on the surface of the com- pressed iron sheets or discs, and each conductor passes from the commutator end back to the other end, and then forward again to the commutator end, where the extremities of each conductor are connected (usually soldered) to the copper strips or bars of the commutator. Each conductor has one end connected to one copper bar of the commutator and the other end connected to the adjacent bar, so that when all the conductors are fixed and bound in place they form an enclosed ring right round the armature and commutator, and thus allow of the passage of the currents generated from the one end to the other, and so to and from the brushes and main wires. Calling the commutator end of the armature the front, and the other end the back, it should be noted that when the armature is revolving, currents are passing from the front end to the back in 07ie //' cases where more light is required in a vessel, it can be obtained by taking out the carbon filament lamps and installing Osram metallic filament lamps of a greater candle-power without increasing the size of the plant (which in all probability is fully loaded with carbon filament No. 34— Bayonet Joint. No. 35.— Section through Lamp- holder, showing Spring Contact. lamps), and which would have to be increased if more carbon filament lamps were added. Again, with the Osram metallic filament lamp, it is possible to obtain double the candle-power of the carbon filament lamp and still effect a saving of 50 per cent, in current. There is no doubt whatever that in the near future metallic filament lamps will be universally adopted for ship lighting, which No. 36.— Wall Plug for use in Cabins, &c., for Fans, Cable Lamps, &c. will mean that the installation can be put in at a considerably decreased cost, as the plant would be considerably smaller and the wiring throughout the vessel in proportion would be of a smaller size. We illustrate a Robertson carbon filament and an Osram metallic filament lamp. Lampholder. — The neck of the lamp connects to the lampholdcr by a bayonet joint. Two small brass contacts in the holder press down 460 '* Verbal " Notes and Sketches against the contact strips or plates of the lamp to which the platinum wires from the thread are attached. The lamp wires are connected to the spring contacts of the Contact *- No. 37. — G.E.C. Water-tight No. 38.— Lampholder Terminals Wall Plug, for use with and Spring Contacts. Handlamps, Portables, &c. lampholder by small screw terminals carefully insulated from each other. Sometimes a switch is supplied inside the lampholder. No. 39.— G.E.C. "Angold" Arc Lamp, for Lighting of Decks and Holds. Arc Lamps. — If a single wire carrying a current be cut and two carbon pencils (one to each end of the cut wire) inserted in the gap, the current will pass across from one carbon to the other, provided the space or "arc" between them is not too great In crossing over Marine Electric Lighting 461 the space, light is given out by the particles of carbon which pass from one carbon (the positive) to the other (the negative) becoming heated to a white heat. This is, roughly, the principle of the well- known arc lamp. It is important to note that before light can be obtained the two carbon pencils must first touch, and then be drawn POSITIVE ^ NEGATIVE. REGULATING SERIES AND SHUNT COILS FOR CONTROLING ARC RETURN FIXED r GUIDE B^'^^ No. 40.— Arc Lamp with Case and Globe removed. away to the required distance from each other: this is termed "striking the arc." The space between the carbons is usually from ■g m. to I in., depending on the amount of current supplying the lamp. The upper carbon is the positi\e one, from which the current passes to the lower or negative one. The mechanism of an arc lamp has to perform the following functions : — 462 " Verbal " Notes and Sketches 1. On the current being switched on, to " strike the arc." 2. After the arc is struck, to maintain the carbons at the proper distance apart. 3. If two or more lamps are run in "series" (on the same wire), to allow the current to pass to the other lamps if anything goes wrong. SHUNT COIL SERIES COIL REGULATING GEAR RESISTANCE TOP CARBON BOTTOM CARBON L No. 41.— G.EC. Type Arc Lamp. The gear for regulating the arc varies a great deal in design, different makers having different methods. The general principle, however, is as follows : — Two small bobbins wound with wire, one being of coarser (series) wire than the other (shunt), are arranged so as to form electro- magnets. When a current flows through the shunt wires, the magnetism resulting attracts a piece of metal or lever placed in Marine Electric Lighting 463 connection with the small vvlieel and chain attached to the carbon- holders. The chain and wheel act so that as one carbon is raised the other is lowered, thus keeping the focus or arc always in the same place. When the current is flowing from the positive carbon down to the negative one, and the space between them is properly adjusted, the coarse or scries wire carries the current ; but if the space becomes too great, then as the resistance to the current passing across is now increased, less passes through the series wire and more through the fine or shunt wire, and the magnetism resulting attracts the lever in connection with the chain gear, which being set in motion, draws the carbons together until the balance is restored. When the lamp is first switched on, the current momentarily passes through the shunt wires, and the effect of this is to draw quickly together the two carbons, thus striking the arc. After the connection is made in this way, most of the current then passes through the series coils and the carbons, weakening the shunt in proportion, so that the arc is correctly set. Nearly all patent arc lamps are worked on this system, called the " differential," owing to the difference in the series and shunt bobbins. Put briefly, then, when the carbon pencils are at the proper "arc," most of the current passes through the series coils ; but if the arc lengthens owing to the consumption of the carbons, less current passes through the series coils and more through the shunt coils, and the shunt coils attracting a magnet, set in motion the clockwork gear which draws the carbons together again until the proper arc is established. An automatic cut-out and substitutional resistance is usually provided in case the lamp fails to act. The upper or positive carbon burns away about twice as fast as the negative one, and becomes slightly hollowed at the lower end, whereas the negative carbon assumes in time a pointed or conical shape. The carbon pencils only last from six to ten hours, after which they require to be renewed, unless in the case of enclosed arc lamps, the carbons of which last for a much longer period. Arc lamps are generally run at about 50 volts, and require from 8 to 10 amperes of current per lamp. Projector. — The Suez Canal Regulations require each steamer passing through in the night time to be supplied with a strong projector or searchlight. The projector consists of a cylindrical casing hung on movable trunnions, and containing inside the necessarry mirror, lenses, carbons, and adjusting gear. The regulation of the arc is in most cases obtained by the hand- feed arrangement, the carbon pencils being held in two brackets screwed on to a right and left hand threaded spindle. By means of small handwhcels the arc can be focussed and adjusted as required. As in the case of other single arc lamps, a " resistance " is also employed to reduce the voltage, and obtain a steady light. The 31 464 Verbal " Notes and Sketches amount of current required for the projector is very high, as much as from 100 to 150 amperes being sometimes necessary, although the voltage may only be from 50 to 60. The wire from the dynamo runs to a terminal box near the position required for the projector, and from the box the wire is led direct to the lamp. The positive terminal is marked with a + sign, and the negative with a — sign. No. 42— G.E.C. Projector. A fuse and switch are often fitted in the terminal box for greater safety. Description of G.E.C. Projector. The case and pedestal is made of light sheet steel with copper protection guards and sight holes fitted with blue glass for examining the arc. The side standards, trunnions, lamp box, and back frame door, and frame in front working head, and all exposed parts are made of gun metal highly finished, polished, and lacquered. The vertical and horizontal movements are obtained by gearing worked by hand- wheels, but arranged so that, if desired, the gear can be thrown out and the projector left free to be moved by the handles fitted on the frame at the back. The hand feed lamp is of special construction and fitted Marine Electric Lighting 46; with vertical focusing gear. The feed motion is worked by bevel wheels from the outside of the lamp box, the carbons being moved together by a left and right hand screw. The horizontal focusing gear No. 43— G. E.G. Type Projector. is worked by a screw passing through the lamp box fitted with hand- wheel at side and end of box. The projector can also be fitted with automatic feeding gear if required. A resistance is placed in the circuit to reduce the voltage to suit arc voltage, and this also ensures steadier working. No. 44.— Resistance Coil. Resistance Coils. — Single arc lamps are often fitted forward and aft, and for these the current is led from the switchboard by separate wires 466 Verbal " Notes and Sketches to a " resistance coil," where the voltage is reduced to suit that required by the lamp. After passing through the resistance coil the current enters the carbons of the lamp at the reduced voltage. FKOW DYNAMO 70 VOLTS ~ TO LAMP 55 VOLTS \jC — =" 3 RESISTANCE COILS 51NGLE ARC LAMP No. 45- — Arc Lamp and Resistance. The resistance coil for single arc lamps consists of a metal box or case containing coils of fine platinoid wire, arranged either in vertical rows or wound on a cylinder. If two or more coils are fitted, they are connected "in series," that is, the end of one coil is joined to the end of the next, and so on. The current in passing through the coils is lowered in voltage, as the resistance of the platinoid wire is much more than that of copper wire. NEGATIVE No. 46. — Two Arc Lamps 'in Series." As work is done by the wire resistance referred to, heating up of the coils and box ensues, and to allow for this the case should be made of fireproof material to prevent damage from overheating. As before stated, arc lamps are usually run at about 50 volts, and this being so, if the dynamo runs at 100 volts, as is sometimes the case, then two arc lamps can be run " in series," that is, on the same wire, Marine Electric Lip^hting 467 each one receiving 50 volts. If the dynamo, however, only runs at, say, 70 volts, then the arc lamps must be run singly, and a resistance employed to dissi[)ate about 15 volts, so that the lamps may each receive no more than 55 volts. This tends towards steadiness in the light. Testing for Faults. — Testing can be done by means of a "detector" formed of a magnetic needle and galvanic battery, or by a small portable hand lamp with a length of wire connected to each of its terminals. When using the hand lamp the ends of the copper wires must be carefully stripped of insulation so that the copper is bared. The detector can be used in most cases when the dynamo is stopped, but the lamp can only be used when the dynamo is running. No. 47.— Detector. The detector is supplied with a battery, so that a current will flow through it and deflect the needle whenever the positive and negative poles of the dynamo or wires to be tested are connected up to the terminals of the detector. In the case of the portable lamp, a current must first be sent through the wires, &c., when the ends of the lamp wires are put in contact with the positive and negative connections under test, before the light will show in the lamp. NOTE.— A *' short circuit " is a connection (usually metallic) between any positive and negative part of the dynamo connections, or between any two of the wires. An "earth " is a metallic connection between one of the poles of the dynamo or wires to the metal of the ship's plates. Break in Main Wires. — To discover the position of a break in a pair of wires, begin from the source of the current in question or distribution box from which the wires branch off, and baring the two wires at short distances, touch them both with the free ends of the wires connected to the detector. If the needle deflects, a current is passing at the point tested ; but if after repeating this a few times the 468 " Verbal " Notes and Sketches needle does not deflect at a point further on, it indicates that a break is situated somewhere between this point and the last place where the needle deflected. No. 48.— Broken Wire Test by Detector. The wires will therefore require to be carefully examined between the two places referred to for the location of the break. The portable lamp will do equally well as the detector, only in MAIN WIRE y -L MAIN WIR£ TEST LAMP No. 49.— Broken Wire Test by Lamp. this case the dynamo must be run to obtain a light in the lamp when the bared ends of the lamp wires are put in contact with the wires under test. If at a certain point no light shows in the lamp, it indicates a break in the current or circuit. NOTE.— The switches of the circuit in question must be "on " when testing with the detector. Leak in Magnet Coils. — To test if leakage is occurring between the magnet coils and magnet, connect one of the detector wires to the end of the coil to be tested, and after carefully cleaning and polishing up a small part of the metal work of the magnet, put the end of the other detector wire in close contact with it. If the needle deflects, it Marine Electric Lighting 469 indicates a leak between that particular coil and the core of the magnet : if no deflection of the needle takes place, it proves the insulation to be intact. Each coil will require to be tested in turn. No. 50.— Test for Leakage between Coils and Magnet. Leak between Armature Coils or Commutator and Armature Drum. — Take out the armature and support it on a pair of trestles, place one detector wire on the armature shaft or drum (either will do) f — ^'^ — No. 51 —Test for Leakage between Armature Coils and Drum. and with the other wire touch the commutator bars as the armature is slowly turned round. If the needle deflects it indicates a short circuit between the armature coils or commutator bars and the drum. 470 " Verbal " Notes and Sketches Short Circuit in Brush-holders. — Lift the brushes from the com- mutator and disconnect them from the cables leading to the dynamo terminals, then place one detector wire on one brush-holder, and the No. 52.— Test for Short Circuit between Brush-holders. other detector wire on the other brush-holder. If the needle deflects, a current is passing indicating a short circuit. Each part of the brush connections can be tested in the same manner. No. 53.— Test for Broken Wire {Continuity Test). Marine Electric Lielitine 471 Test for Broken Wire. — Disconnect the wire to be tested so that the ends are free, and place one detector wire to each end. If the needle deflects, a current is passinc]^, and the wire is not broken ; but if the detector needle remains stationary, it indicates that the wire in question is broken, as the circuit is not complete. Test for "Earth" Leakage. — With the main and lamp switches " on," connect one detector wire to the positive and negative wire of the dynamo in turn, and put the other detector wire in contact with the floor plates or ship's skin as the case may be. If a deflection of the needle occurs, it indicates that leakage to "earth " is taking place, that is, at some part of the circuit one of the wires is in b^re contact with the metal of the ship, and the current is returning to the d}'namo by that path. To locate the part of the circuit affected, switch off the main switches one by one till the needle comes back to its zero position, No. 54.— Test for "Earth" Leakage. and the last switch opened will be that of the circuit affected. Now connect one of the detector wires to one of the " bus " bars or terminals of the distribution box of the circuit, and, as before, connect the other detector wire to the ship's metal. If the positive and negative fuse bridges in the box are now pulled out one by one, the needle will only move back to zero when the fuse bridge of the " earthed " wire is disconnected, and in this way the exact "earthed" wire can be located. Another method of carrying out this test, should a galvanometer not be available, is to connect up a lamp, the lamp being of the same voltage as the dynamo. In this case it is necessary to have the dynamo running and to test both negative and positive sides of the leads, as the lamp only lights up when there is a fault on the opposite pole to that to which it is connected. For instance, should there be a fault on the positive lead to a lamp, when the test lamp is con- 472 "Verbal' Notes and Sketches nected to the negative wire it will light up, but if connected to the positive it would remain black. SHIP (EARTH} No. 55.— Earth Lamp Test. " Earth " Lamp Test. — To test for an earth leakage arrange a pair of lamps as shown in the sketch, one connected to the positive lead, No. 56.— Short Circuit Test. the other to the negativ^e lead, and both connected to the ship metal by a cross wire. Marine Electric Lighting 473 With the dynamo running one of the lamps will burn brighter than the other if there is a leakage to earth, and the leak will be on the opposite wire to that of the bright lamp. For example, if lamp A burns brightest the leakage will be on the positive wire, but if lamp B burns brightest then the fault is on the negative or return wire. To Test for Short Circuit in Main Wires, — Disconnect one of the main wires from the dynamo terminal, and insert between the wire and terminal the detector, as shown. Now switch off the lamps (not the main switches), and run the dynamo. If a deflection of the needle takes place it indicates a short circuit between the main wires, as with the lamp switched off no current should then be passing. To Test for Broken Armature Coil. — This can only be accurately determined by the following method : — Disconnect both ends of each ^=u END OF COIL No. 57.— Test for Broken Armature Coil. armature conductor from the commutator bars, and place one wire of the detector to each end ; then if no deflection of the needle takes place it indicates a broken wire : a deflection proves the wire to be continuous or unbroken. Each armature coil must be tested separately. To Test for Polarity of Dynamo. — It is often very convenient to know which is the positive and which the negative connections or wires of a dynamo, and these can be located as follows : — Obtain a piece of "pole-finding" paper (procurable at any Electrical Supply Stores), and after moistening the paper place it on a piece of dry wood ; now lead a suitable length of wire from each dynamo terminal, as shown in the sketch, and with the free ends of the wires touch the wetted " pole-finding " paper. A red coloured blot will then 474 *' Verbal " Notes and Sketches @ TEST^ WIRES -1 POLE FINDING 1 PAPER WOOD No. 58.— Polarity Test appear on the paper at the wire connected to the negative terminal ; the other will of course be the positive connection. Hints on Running. — In the case of a new dynamo it is advisable to run the machine for a couple of hours or so with the brushes lifted from the commutator, as a test of the mechanical balance, lubrication, &c. The armature, commutator, and field magnets should be kept absolutely free of dust, grit, oil, or moisture, as these allow of the formation of short circuits. The commutator should be supplied with the least amount of lubrication possible, and that only of vaseline or mineral oil. A commutator in good working condition presents a surface covered with an even bronze glaze or skin, and this should be main- tainedif at all possible. The brushes should be placed at exactly opposite positions on the commutator circle (mathematically opposite). It is safest to first get the speed up on the dynamo, and the proper voltage showing on the voltmeter, before switching in the lights. Examine the armature conductors to see that the commutator Marine Electric Lighting 475 ends of the wires arc not bent and in contact with each other, as this will produce a short circuit. Keep all small tools away from the dynamo, as the magnetic attraction may draw them into the field space and result in serious damage. Brass or copper oil cans only should be used. To test the armature balance, lift it out and place the shaft on two fine levelled knife edges ; if the armature is then gently rolled from side to side it will come to rest with the heavy side down ; this side should therefore be reduced in weight, or the other side increased in weight. Short circuits in the armature coils show either by burning of the insulating material resulting in a strong smell, or merely by heating up of certain coils when felt by hand immediately after stopping the dynamo. If a commutator develops an untrue surface or "flats," it should be turned up with a diamond-nosed tool, as this type of tool prevents the burring of the copper edges over the insulation. Make sure that the binding terminals are screwed up and in metallic contact. If the dynamo has become demagnetised it will refuse to generate current when the speed is up. To remedy this, either tap the field magnets with a light hammer, or, if this fails, reverse the brushes, that is, turn them round 180 degrees of the commutator circle (if a two-pole machine), so that they change places with each other, and run the machine for a short period with reversed current ; this tends to restore the magnetic conditions : afterwards replace the brushes to their original positions. Excessive rise of temperature in fields or armature indicates a short circuit between some of the wires. A short circuit or earth leak may result in overloading the dynamo and produce sparking at the brushes. In place of the ordinary galvanometer or detector a small bell and dry battery may be used for testing. When the circuit is completed by the wires from the bell terminals the bell will ring. Whenever possible slow down and stop the dynamo before switch- ing off the lights, as this prolongs the life of the incandescent lamps. Before starting up the dynamo be sure that the lubrication is reliable and the oil cups filled up ; also that the armature shaft is clear. 476 " Verbal " Notes &nd Sketches The brushes should not be hfted from the commutator while the dynamo is runnhig, as this produces destructive sparking. Sand-paper only should be used to polish up the commutator surface, and it should be applied by means of a board on which the sand-paper is pasted, the width of the board to be cut to the length of the commutator bars. Hold the sand-paper board against the commutator, and have the armature shaft revolved by hand. This is best done with the armature lifted out and laid on a pair of wood trestles. At intervals feel by hand the temperature of the magnet coils. It is important to see that the engine is not started to run in the wrong direction, that is, against the brushes, as damage would result. The brush position, when the machine is running without load, will not be suitable when the load is on, and the brushes must then be rocked forward to obtain a sparkless contact. NOTE. — " Forward" means in the direction of rotation. In polishing up the commutator in position, take care to lift up the brushes clear of the commutator surface. The voltage of the dynamo varies in proportion to the speed of the machine. If a fuse blows or burns out it should be replaced by one of the same size, and not by a larger one as is sometimes done. Copper gauze brushes should be kept well trimmed up and free of ragged edges. Violent sparking at the commutator may be caused by a broken armature coil, or broken armature and commutator connection. The " pilot " lamp serves as a guide to the voltage of the dynamo, as, being connected direct to the dynamo terminals, it indicates whether the machine is generating the required E.M.F. or not. If therefore a fault appears on a section of the lighting circuit and the pilot lamp of the dynamo is still burning brightly, it proves that the fault is not in the machine, but must be in the wiring or lamps. If the speed is too high this may show in the pilot lamp by possible burning out, and if too low, by the lamp only glowing instead of being at a white heat. Engine-room " waste " should never be used on a dynamo, as the loose fibres are apt to detach and lodge between the commutator bars or armature coils, and ultimately bring about short circuits. A linen cloth is much to be preferred. Marine Electric Liorhtinor 477 No. 59— Pilot Lamp. Become acquainted w ith the usual temperatures of the machine at different parts when running, so that any abnormal rise of temperature may be noticed at once, and the cause located. When lifted out of the bearings the armature should be laid on a pair of wood trestles as mentioned elsewhere, or if laid on the floor should rest on sacking or some such soft material, as, being a delicate piece of work, it easily becomes damaged. By careful adjustment of the brush rocker the best position of the brushes can be found, and this should give a practically sparkless contact. See that the brushes have no side-play in the holders. The point or toe of copper gauze brushes should be cut to an angle of about 4o\ Apply the nece.ssary lubrication to the commutator either by the palm of the hand or by means of a piece of liuoi rag, and remember that a very small amount of mineral oil is sufficient. If the armature is mucli out of balance it will probably injure both the commutator and the brushes. 478 " Verbal " Notes and Sketches The disadvantage of carbon brushes is a tendency to heat up if not accurately adjusted, as, for example, by excessive compression on the holder springs. If the dynamo is situated in a part of the steamer where the tem- perature is high (say iOO°), sparking will ensue at the brushes and commutator, owing to the increased resistance due to heating. If the dynamo is placed near the condenser corrosion of the tubes may result, due, it may be supposed, to galvanic action. This has occurred in several cases which have come under the writer's observation. When the brushes become ragged at the bearing edges, they can be quickly repaired by cutting off the rough parts with a knife run along a straight-edge, a cut also being taken off the corners at an angle. Jointing of Wires. — In joint making the following materials are required, all of which are obtainable at Electrical Supply Stores : — 1. Solder sticks. 2. Resin. 3. Pure rubber strip or tape. 4. Rubber solution (Challerton's compound is one of the best). 5. Prepared tape. 6. Shellac varnish. 7. Emery cloth. 8. Fine copper wire (for binding). The number of separate layers of rubber tape and solution depend on the thickness of the insulation originally on the wire, the heavier the insulation the greater the number of layers, and vice versa. COPPER RUBBER SOLUTION RUBBER SOLUTION OUTER COVERING VARNISH No. 60.— Section through Main Wire- In lapping the rubber tape over the soldered part of the joint, only carry it up to the ends of the rubber on the wires, and not beyond this point. Before applying the first lapping of rubber strip, file up all rough edges of solder or of wire so that a smooth-jointed surface is obtained. Marine Electric Lighting 479 In cutting the ends of wires previous to jointing, it is advisable to take off each layer of insulation in steps, as shown in the sketches. This allows of the covering of the jointed part fitting in better with the original layers of insulation. Before applying the insulation layers, the rubber ends should be cut down to form a taper to the bare wire, as shown in the sketch. The lapping of the rubber strip over this ensures closeness of joint. RUBBER TAPERED No. 6i.— Tapering of Insulation. To cause adhesion the solution must be applied between each layer of rubber strip, and last of all a good coating of shellac varnish. The following instructions as to jointing of wires are issued by Messrs Scott & Mountain, Electrical Engineers, Newcastle-on-Tyne : — Main Cables. Preparing Ends. — Remove the two outside tapes for about 5 in. from each of the ends intended to be jointed. Bare the conductor of its covering of indiarubber and inside lapping of tape for about 1 1 in., and clean the wires with emery cloth. Metal Joint. — Solder together the wires composing the strand for about I in., and scarf two ends with a fine file. Bring the two scarfed ends together and solder them. If this is carefully done, the conductor will be of uniform size. Over the joint bind spirally a fine copper wire, and solder the whole together. Resin, and not acid, must always be used for soldering. BINDING I WIRE No. 62.— Scarfed Joint. Insulating Joint. — Taper each end of insulation with a sharp jointer's knife for li in. from the conductor to the outside of the indiarubber. Cover the metal joint with one lap of i-in. broad indiarubber, coated with cotton tape. Over the cotton tape lap spirally pure indiarubber strip (i in. broad), stretching it at the same time, and building up the joint, by a series of coverings in alternate directions, to the same size as the indiarubber coating of the wire, or slightly larger, to allow for the thickness of binding wire. A very small portion of indiarubber 32 480 " Verbal " Notes and Sketches solution should be applied over each coat, and sufficient time allowed for the spirit to evaporate before putting on another coat ; this will cause the indiarubber strips to unite together. BINDING I WIRE No. 63.— Joints for Heavy Wires. Outer Protection. — Two coverings of prepared tapes (i| in, broad) are to be laid on in opposite directions, with strong shellac varnish between them, and then, outside, another covering of waterproof tape, and finally varnished over all. Branch Wires. Preparing Ends. — Remove the braiding tape and indiarubber for about 4 in. from each end intended to be jointed. Unlap the cotton serving next the conductor for about i| in. (do not cut it off). Metal Joint. — Thoroughly clean the ends of the wire with fine emery cloth, and scarf them with a fine file. Bring the two scarfed ends together and solder them. If this is carefully done the conductor will be of uniform size. Over the joint bind spirally a fine copper wire, and solder the whole together. Resin, and not acid, must always be used for soldering. Insulating Joint. — Cover the metal joint evenly and as thinly as possible with the cotton which had been previously unwound from the ends. Over the cotton covering lap spirally pure indiarubber tape (h in. broad), stretching it at the same time, and building up the joint by a series of coverings in alternate directions, to the same size as the indiarubber covering of the wire, or slightly larger, to allow for the thickness of binding wire. A very small portion of indiarubber 0^=^2^^^^s^^^^=d7 No. 64.— Joint for Small Lamp Wires. solution should be applied over each coat, and sufficient time allowed for the spirit to evaporate before putting on another coat ; this will cause the indiarubber to unite together. Outer Protection. — Two coverings of felt tape (|- in. broad) are to be laid on, in opposite directions, with strong shellac varnish between them, and finally varnished over all. Marine Electric Lighting 481 " T " Joints. Preparing Ends- — Remove the two outside tapes for about 5 in. from the main lead. Bare the conductor of its covering of indiarubber and L^ T No. 65— Small "T" Joint No. 66.— "T" Joint inside lapping of tape li in. Remove the braiding and tape for 6 in. from the end of the wire intended to be jointed to the main lead. The two rubber coverings and cotton serving are then to be unlapped for 3 in. and the rubber cut off. Thoroughly clean the strand, and also the solid wire with fine emery cloth. Metal Joint — Solder the wires composing the strand together, take two or three turns of the solid wire round the main conductor, and back round itself for three or more turns, and solder only at the top of the T. Resin, and not acid, must always be used for soldering. NOTE.— In joint making care must be taken to keep the hands, tools, and materials clean and dry. Electric Motors. The construction of a motor is similar to that of a dynamo — all the various parts, such as armature, magnets, commutator, brushes, &c., corresponding to the latter ; but in the case of shunt motors a difference exists in the wire connections, v/hich will be explained later. As will readily be understood, a motor receives current from a 482 " Verbal " Notes and Sketches dynamo, and the action is reversed, that is, in place of mechanical power generating electro-motive force, electro-motive force generates mechanical power. Put simply, a motor is a dynamo reversed in its action. Sketch No. Gy illustrates the principle of a dynamo with motors in connection. Marine Electric Lighting 483 In numbers of motors in use at present, the various parts are so fitted as to occupy very little space and to allow of the working parts of the motor being covered in or enclosed. This protects the delicate parts of the motor such as commutator, brushes, &c., from dirt and grit, and reduces the chances of breakdown occasioned by short circuits formed possibly by the dirt and grit in question. In this type of enclosed motor, four poles are often used instead of two, as being more suitable, as the four-pole arrangement lends itself better to the circular shape of the motor. As stated before, in shunt motors an extra wire is fitted. The wire referred to is employed in the starting and stopping of the motor, and is connected between the field magnets and the supply wire through a " starting resistance " or switch. On switching on the current at the starter it first enters the field magnet coils, and after freely exciting them, is then admitted gradually to the brushes and armature coils. The object of this is to prevent what may be called "racing" of the motor when the current is first turned on, as by first passing the current into the magnet coils the magnetic field is strengthened, and the tendency of the armature to run off at a high speed is checked by the magnetism developed opposing its too rapid rotation. This prevents mechanical shock, and possible damage to the working parts ; it also checks undue variation in the current passing through the wires and supplying other motors or lamps in connection, and which might otherwise be affected. In a series wound motor the whole of the current entering the armature first passes through the field magnets, and gives the necessary strength to the field. In a shunt wound motor only part of the current passes through the magnet coils by the fine shunt wires which are branched off from the main or supply wire. This being the case, it will be obvious that with a shunt motor the starting resistance must first freely excite the field magnets before the current enters the armature, otherwise by suddenly switching on the current the machine may be seriously damaged. It is also important that the current be only admitted to the armature by small degrees, and this is arranged for by fitting a " starting resistance " between the motor and supply wire. Motor Starters. — A "starting resistance" consists of a box con- taining a number of platinoid wire coils connected together in series and to insulated earthenware bases. Each coil has a brass or copper contact piece, and the hand lever, which is in connection at one end with the supply wire and to the contact stops at the other, can be moved over the coils in succession, so that at first all the coils are in series ; but as the handle moves over each stop in rotation, one less coil is included in the circuit, and the resistance decreased in proportion. When the handle passes the last contact stop, all the resistances are cut out, and the full current 484 *' Verbal " Notes and Sketches FROM ARMATURE AND FIELD MOTOR STARTER ENCLOSED MOTOR No. 68.— Motor Starter Connections ("Series Wound") TWO POLE "SWITCH FROM ARMATURE \lO ARMATURE TO FIELD HAONETS TtO FIELD .n AG NETS MOTOR STARTER ENCLOSED MOTOR No. 69.— Motor Starter Connections ("Shunt Wound"). Marine Electric Lighting 4^5 is then passing direct from the supply wire to the armature. The starting handle should be moved slowly over the contacts, and allowed No. 70. — "Resistance" Regulator. to press on each for a few seconds, as the speed of the motor gradually increases. In stopping a motor the same precautions must be used, that is, the current must be switched off gradually by moving the resistance handle from stop to stop with an mterval for each, so that each coil is inserted in rotation until the lever is in the "off" position. The speed of the motor can also be regulated by the insertion of more or less of the resistance coils into the supply circuit by means of the handle and contact stops. Some motor starters have small electro-magnets or bobbins arranged so that the lever is held in the " on " position so long as the proper amount of current is passing, but should anything happen to destroy the balance by excess or loss of current, the lever automatically flies over to the " off" position and cuts off the current altogether. Small fan motors, as used for state-rooms, &c., are usually of the series wound type ; and larger fans, for ventilation or induced draught purposes, of the shunt wound type. 486 "Verbal" Notes and Sketches No. 71.— Type ofG.E.C "Freezor" Cabin Fan for Table or as Bracket Fan. These Fans are fitted with Three-speed Regulators in Base. G.E.C. "Witton" Motor Driving Capstan. One of the latest electrically driven appliances is the capstan A motor direct coupled gives complete and instantaneous control by No. 72.— "Witton" Motor direct coupled to Centrifugal Pump. Marine Electric Lighting 487 488 "Verbal" Notes and Sketches means of a starting switch placed in a convenient position, and operated by foot only. Pull, 4480 lbs. ; speed, 100 ft. per minute ; motor, series wound. Largely used on board steamships, shipbuilding yards, and dockyards. Circulating water for condensing, or washing down decks, and fire purposes. :i No. 74.— Electric Punkah, G.EC. "Bandy." For Saloons, Cabins, &c. Installed on board many of the large liners on the Eastern Routes. The only electrically operated punkah giving the " flick " — the distinctive feature of punkahs as compared with other cooling devices. The G.E.C. Bandy punkah effects a saving of 50 to 70 per cent, in current, when compared with an ordinary ceiling fan. The con- sumpt per one hour is approximately : — Of the 2 ft. 6 in. size - „ 3 ft. 6 in. „ - „ 4 ft. 6 in. „ - An ordinary ceiling fan 27 watts 34 )j 38 J) 100 Marine Electric Lighting 489 No. 75.— Extension Box. No. 76.— Luminous Electric Glow Radiators. For Heating State Rooms, Music Rooms, &c. This horizontal type of glow lamp Radiator is a great improve- ment over the vertical type, specially for ships' use where vibration and jarring occur. The lamps are made with the poles at opposite ends, and one zig-zag filament runs through the lamp supported in the middle. Each lamp is rated at 250 watts. 490 " Verbal " Notes and Sketches Advantages of Zig-Zig Type Radiators. Lamps firmly held by clip at each end. Opposite poles at opposite ends of lamp. Increased contact surface. Longer life of lamps. The " Zig-Zag " filament increases radiation of heat. Horizontal arrangement of lamps gives more pleasing effect. No. 77.— Elevector. "Archer" System of Heating by Convection, for State Rooms, Dining Saloons, &c. The Elevector is an air warmer. The cases are supplied in various metals and finishes, and all types have interchangeable heaters or elements of 500 watts each, i watt for each cubic foot of space to be heated should be allowed for. Electrical Notes. By "Potential" is meant the difference of electrical tension existing between the positive and negative leads. A Volt is the measure of electrical pressure or E.M.F. (Electro- Motive Force). NOTE.— A Volt is the E.M.F. required to give one Ampere of current ag&inst one Ohm resistance. Marine Electric Liorhtin^ 491 An Ampere is the measure of electrical current, and is taken as the standard flow of clectricit}- in a wire per second. An Ohm is the measure of electrical resistance, and is about equal to that of one mile of copper wire I in. in diameter. Volts X Amperes = Watts. 746 watts are equal to i Electrical Horse- Power. Therefore, VoltsxAmperes^^ ^ p^ 746 E.H.P. compared to I.H.P. It should be noted that the Electrical Horse-Power refers to ofie second of time as the ampere flow is measured for that period, whereas the I.H.P. of steam refers to one minute of time. Therefore, 33000 -=-60=550 foot-pounds per second, and, 746 watts = 550 foot-pounds. So that, 746-^550= 1-35 watts per foot-pound. As work and heat are equivalent, then it can be proved that to produce the same heating effect (energy), 1-35 watts are equal to i foot-pound. E.H.P. per minute = 746x60 =44760 watts per min. The size of a wire depends on the amount of current it has to carry ; in other words, on the number of amperes. The insulation of a wire depends more on the number of volts carried by the wire. The Board of Trade limit is 1000 amperes per square inch of wire section. Fuses or cut-outs are constructed to melt when the current becomes double the working current. Insulating materials are composed of indiarubber, tape, varnish, vulcanised fibre, glass, cotton, earthenware, &c. Arc lamps are usually run at from 45 to 55 volts. Arc lamps require from 8 to 12 amperes of current. Projector arc lamps require from 80 to 150 amperes of current. A 16 candle-power incandescent carbon filament lamp requires about 60 watts. A 16 candle-power incandescent lamp run at 75 volts requires -8 of an ampere, because 60 watts-^^75 volts = -8 of an ampere. An " Osram " 16 candle-power incandescent metallic filament lamp only requires about 20 watts, as the resistance of the filament is higher and requires less current to produce the same heat. 492 "Verbal" Notes and Sketches 1000 watts are equal to i kilowatt. The positive wire or terminal is often marked thus +. and painted red. The negative wire or terminal is often marked thus — , and painted black. Fuses in earthenware cases are placed at different parts of the wire circuits to act, if required, as automatic circuit-breakers. Dynamos for ship-lighting usually develop from 65 volts to 100 volts. " In series " means in continuation. " In shunt " means branched off. Continuous current dynamos are generally employed for lighting purposes, and alternating current dynamos for power stations. Transformers are used in power stations to reduce the current from a high to a low voltage without serious loss. 100 amperes at 2CK)0 volts will give 400 amperes at 500 volts if a transformer is used, because Amperes. Volts. 100x2000 500 volts =400 amperes. NOTE. — This neglects loss of efficiency in transformer. Accumulators are used for the storage of electricity, and consist of a number of galvanic cells joined in series. The cells are charged by the current from a dynamo, which decomposes the acid bath of the cells and reverses the chemical conditions. After charging, the electricity so stored up may be released and employed to act on an external circuit if suitable wiring is arranged, as the chemical relation of the plates causes a return to their original condition. Accumulators are often employed on yachts, where a small number of lamps may be required during the night, and in cases where the dynamo is not kept running constantly. The quantity of current flowing past a one ampere section of wire in one second is called a " coulomb." Electricity is one form of " energy " or " force." Induction is the magnetic or electrical effect produced on surround- ing bodies or substances by an electric current. Marine Electric Lighting 493 The principle of induction is employed in transformers, where a current of high voltage in a set of fine wires is made to induce currents of a lower voltage in a set of coarser wires. One " megohm " is equal to 1,000,000 ohms. All substances offer more or less resistance to the flow of an electric current : those having least resistance are employed as "conductors," and those having most resistance are employed as " insulators." Rules — To find the Current strength in Amperes passing through an electrical circuit. Rule— Volts = Amperes. Ohms Resistance and, Volts ^ohms, Amperes or, Amperes x Ohms = Volts. Example i. — The voltage is 100, and the resistance of a 16 candle- power lamp 220 ohms. Find the required current in amperes. Then, Amperes = X°— = -°° = -45 Ampere ^ Ohms 220 ^^ ^ Example 2. — Find the resistance in ohms if the voltage is 100 and the amperes 300. Then, Ohms = -M*i- = ^°° = .33 Ohm. Amperes 300 Example 3. — The output in amperes is 250, and the resistance •4 ohm. Find the required voltage. Then, Volts - Amperes x Ohms = 250 x ^4 = 100 Volts. Example 4. — Find the number of watts required for a lamp taking -6 of an ampere at 100 volts. Then, Watts = Volts \ Amperes = loo x -6 = 60 Watts. SECTION VIII. PROPELLERS. As the majority of marine engineers are unfamiliar with the various definitions connected with the screw propeller, the author has deemed it advisable to endeavour to give clear and, if possible concise explanations of each, accompanied by suitable illustrations. General. — The marine propeller, simply considered, is merely a common screw working in a nut. If a screwed bolt be turned one complete revolution in a corre- sponding nut, the bolt will advance or travel along the nut a distance equal to that between two adjacent threads, or, as it is usually expressed, equal to one pitch, P (see sketch), so that if a bolt has, sa}% eight threads to the inch, in one turn of the bolt or nut the advance will be 1 inch. No. I.— Common Screw. P = Pitch. The diameter of the propeller boss represents the bolt at the bottom of the thread, and the propeller blades the actual threads, or, more correctly, /)/eces of thread (see sketch). Propellers 495 No. 2.— Actual Propeller compared with Actual Screw. A three-bladed propeller consists of three pieces of thread set oti the boss, and a four-bladed propeller consists of four pieces of thread set on the boss. The water in which the propeller is immersed, and in which it works, represents the nut, so that when the boft or propeller shaft is revolved the screw or propeller advances in the nut, which, as before stated, is represented by the water in which the propeller works. As, however, the water constitutes a yielding nut and gives way a certain amount to the blades, the actual advance of the propeller and ship is less than one pitch of the screw for one complete revolu- tion of the shaft ; this difference of advance is known as the slip. Thrust. — The effect of the propeller thrust is, generally speaking, twofold — (i) to drive the water aft, (2) to drive the ship forward. The reaction of driving the water aft results in the steamer being driven or propelled forward. Pitch. — As stated above, the pitch is the longitudinal advance of a screw during one revolution, if working in a solid nut. A screw or helix, if unrolled, forms with the pitch and circumference a triangle, of which the thread represents the h\'pothenuse or diagonal. If, therefore, a sheet of paper is taken, and a line A B drawn from corner to corner, and the sheet rolled up into a cylinder, the ruled line A B will represent the edge of a screw or thread, and the length of the roll the pitch (Sketches Nos. 3 and 4). 35 496 "Verbal" Notes and Sketche 3 \ V"^ X''- \-0 \o \-^ X'i- V \^ lU V o \^^ z 111 a. A UJ V II. \'*» S \^ 3 V ""a .'"Sv Of Vo \ t / \«« \ < ; \ a / V \ B-. --A r / \ <-- ---PITCH > ^ PITCH — ^ B No. 3.— Flat Sheet of Paper. No. 4.— Paper rolled up. Triangle described by Screw. It will thus be seen that the pitch is the length between the two ends of the thread taken for one complete turn of the screw, or the advance made by any point or piece of the thread during one revolution. In an actual propeller the breadth of blade represents the piece of thread or the hypothenuse of the triangle, the distance between the leading and after edges the piece of pitch, and the distance, measured vertically, between the lower and upper edges the piece of circum- ference : these all correspond, it will be noted, with the screw representation on the sheet of paper as shown above. Right- and Left-hand Screw. — The blades of a right-handed propeller revolve from port to starboard (upper half of blade circle), and the blades of a left-handed propeller revolve from starboard to port. Circumference. — As will readily be understood from the foregoing, the circumference is the distance round the cylinder forming the screw surface at right angle to the shaft, which, when unrolled, forms one of the shorter sides of the triangle. The diameter of the propeller multiplied by 3-1416 is equal to the complete circumference. Thread. — As before stated, the thread is the complete length of the Propellers 497 unrolled helix, and each propeller blade is equal in width to a piece y- No. 5. — Right-hand Propeller Blade. T, Piece of Thread, or Hypothenuse. P, Piece of Pitch. C, Piece of Circumference. of the thread onl\-. The thread forms the diagonal or h\-pothenuse of the pitch triangle, and therefore its longest side. Increasing Pitch. — Propellers are sometimes designed with a varying pitch — (ij the pitch increasing radially, that is, the pitch at or near the tip of the blades is more than the pitch near the boss ; or (2) the pitch may increase axiallx', or from forward aft, that is, the pitch near the after edge of the blade may be slightly more than the pitch near the forward edge. In the sketch shown below the pitch at B is more than the pitch at A. THRUS ■ SURFACI (FACE) LEADING EDGE No. 6. — Thrust and Drag Surfaces. 498 " Verbal " Notes and Sketches True Screw. — When the blades have no variation in pitch, either radially or axially, the blade surface is said to be that of a " true screw." Some of the most efficient propellers of present day practice, including those of turbine steamers, are of this type. Pitch Ratio. — The propeller pitch, divided by the propeller diameter, is equal to the " pitch ratio." The pitch ratio may vary from about •9 in small propellers to 1-4 in large propellers, in steamers with reciprocating engines. Diameter of Propeller. — The diameter of a propeller is the diameter of the circle described by the tips of the blades. Length of Propeller. — The length of a propeller is measured longi- tudinally on the shaft, and is usually about equal to the length of the boss. Length of Blade. — The length of a blade is measured from the root at the boss to the tip of the blade. Moulding of Blades. — In moulding the propeller blades a horizontal arm is rotated round a vertical spindle, and at the same time moved up or down the spindle, thus generating the screw surface or helix. To guide the travel of the moving arm one or more curved vertical guide templates are placed in position, and the moving arm travelling over the upper edges of the templates shapes out the blade surface for the required pitch, &c. The vertical templates referred to are triangular in shape, and are cut to the correct pitch angle for various points of radius on the blade. PITCH TEMPLATE No. 7.— Method of producing the Screw Surface. Propellers 499 Slip. — Slip is of three kinds — (i) apparent slip, (2) real or actual slip and (3) negative slip. The "log" slip found by taking the difference of the propeller speed and the ship speed is only apparent slip, the real slip being (in nearly every case) in excess of this. The real slip is found by adding together the apparent slip and the "wake speed" (if known). Wake Speed. — Wake speed is the name given to the velocity of the stream or column of water \wh\c\\ follows at the stern of a vessel. The wake speed will be more with a bluff-lined steamer than one with fine lines, as the more square shape of the stern tends to pull the water along with the vessel, and thus give a higher wake speed. From the foregoing it will perhaps be seen that the speed of the vessel is less relatively to the wake speed than to still water. This, therefore, has the effect of taking away, as it were, part of the actual slip. As before stated, to calculate the real slip the wake speed must be added to the apparent slip. Disc Area. — By disc area is meant the area of the circle described and enclosed by the tips of the propeller blades. Developed Area. — By developed or expanded blade area is meant the full area of all the blades if flattened out and taken as approxi- mate plane surfaces. No. 8.— Expanded Blade Area. Area Ratio. — B)- area ratio is meant the relative total expanded area of the blades compared with the " disc area." The area ratio varies from -3 to -6 of the disc area. Projected Area. — This means the actual area of blades as projected at right angles to the line of shafting, and constitutes the effective thrusting area of the blades. NOTE.— The blade area as seen when looking forward from behind the propeller is the 'projected area." 500 "Verbal" Notes and Sketches No. 9. — Projected, or Effective Thrusting Area of Blades. Thrust Surface or Driving Face. — The after surface of the blades is the thrusting surface, which acts on the water to drive forward the vessel. Drag Surface or Back of Blade. — The forward (usually the rounded) surface of the blades is known as the drag surface. Leading Edge. — With the blade in a horizontal position (see sketch), the "leading edge" is that edge lowest down, and which for a right- hand propeller lies on the starboard side ; for a left-hand screw the leading edge will be on the port side. Following Edge. — With the blade in a horizontal position, the after edge and that highest up is called the " following edge." Cavitation. — By cavitation is meant the failure of water supply or " feed " to the propeller, due generally to excessive blade velocity ; in other words, the blade speed exceeds the water flow speed to the blades, therefore the effective thrust falls off in proportion, as cavities form at the forward side of the blades. Cavitation is therefore caused by the ineffectiveness of the atmospheric pressure to press up the water at the back of the blades (forward side) fast enough to allow of effective thrust ; this usually occurs at high revolution speeds and high blade pressures per square inch. The phenomenon of cavitation has been very exhaustively investi- gated in a series of elaborate experiments carried out by the Hon. Propellers 5^^ C. A. Parsons, in connection with trials of turbine-engine propellers (see " The Marine Steam Turbine," by J. W. Sothern). It should be noted that slip is an absolute necessity for the effective effort of a screw propeller, and if a propeller shows a very low slip percentage it indicates that the propeller fitted is evident!)' unsuitable for the steamer in question, as it is not delivering an effective thrust on the water. In most cases the slip should average from 5 to 1 5 per cent., and in some cases even more. Apparent Negative Slip. — If without strong current speed a pro- peller shows negative slip, it may be taken for granted that (as in the case of low positive slip) the propeller is not suited for the work it has to do, and indicates the necessity for another propeller of different design being substituted, probably one of greater pitch and diameter. Negative slip is most likely to show in steamers having very bluff stern lines, and therefore giving a resultant high wake speed. NOTE. —Apparent negative slip may occur with a strong current going with the steamer. It is generally admitted now by authorities on the propeller that negative slip can only be apparent, and an example may be given as follows : — Example. — Pitch 15 feet, Revolutions 62, ship's speed 14 Knots, speed o{ following cm-rent 4 Knots, find slip. Then, Engine Knots = ^8 x 62 x 60 ^ ^ ^ j^^^^^ ^ 6080 and, 14 - II = 3 Knots apparent negative sUp. But, Actual Propeller advance through water = 14-4 = 10 Knots. Therefore, Real Slip = 11- 10=1 Knot. So that instead of an apparent negative slip of 3 Knots we have a positive and real slip of i Knot. No. 10.— Blade "Set Back." 502 " Verbal " Notes and Sketches Set Back. — Sometimes the blades of a propeller are set with an inclination aft instead of being arranged at right angles to the shaft : this is known as " set back " or " skew." Racing. — Racing is produced by the blades or parts of the blades rising out of the water when the stern lifts in pitching. The effect of this is to carry down into the water a quantity of air, and as the resulting mixture of air and water is less .solid or dense than water alone, the blades meet with less resistance, and the engines "race" in consequence. It will be noted that the whole propeller does not require to come out of the water to produce racing, as part only of a blade coming above the surface may be sufficient to produce it. Less racing will occur when small propellers are fitted low down, as in the case of turbine steamers. Cone.--In well-finished propellers the nut aft of the boss is covered with a thin metal cover, conical in shape, which continues aft the round of the boss, and prevents interruption of the " flow " or " run " of the water past the blades. CONE No. II. — Nut and Cone. Propeller Design. The majority of the following rules for propeller design are taken from Seaton's " Manual of Marine Engineering," also Seaton and Rounthwaite's " Pocket-Book of Marine Engineering Rules and Tables," and the author would take this opportunity of recommending a copy of either of these standard works to all readers anxious to investigate more fully into the various problems of marine engineering design. The following descriptions are therefore intended to be applied in conjunction with the above-named books, a copy of which, as before stated, should be obtained for reference. NOTE.— It must be clearly understood that no absolutely correct hard and fast rules suitable for the successful designing of propellers can be laid down on paper, as in actual drawing-office practice comparative records of previous performances, tables of "slip" factors, "area factors," Admiralty coefficients, results of tank Propellers 503 experiments, and other data, are largely employed in arriving at the best pattern of propeller suitable for a steamer of given type, dimensions, and speed. A vast amount of investigation is yet open to experimenters in propeller efficiency and design, as at present, in a number of cases, the most suitable propeller is often only found after repeated trials of other propellers of different pitch, diameter, and area. In support of this the writer remembers once seeing nineteen propellers which had all been tried successively on a torpedo destroyer before the one giving the best results was discovered. I. To Design and Draw a Propeller for the following: — Given - /I.H.P. - - 600. Knots - - 10. Revolutions - 76. Tail shaft - - 11 inches diameter. Type of steamer Cargo boat. Propeller to l)e of the four-bladed, cast-iron, solid type. NOTE.— It should be stated that it is not usual in drawing-office practice to show as many different views of the blades, &c., as here drawn in the examples given, but as this description is specially written for the use of marine engineers with little or no experience of geometrical projection drawing, it has been considered advisable, for the sake of clearness, to show each separate stage of the construction, hence the necessity for repeating some of the views which might otherwise, as will easily be seen, have been combined in one. To find Propeller Pitch. — Allow 10 per cent, for apparent slip, and proceed as follows : — Rule. — Knots X 60 8 X 1 00 -pt h Rev. X 60 X effective per cent. Therefore, 10x6080x100 ^ ^^^^ p.^^j^ 76 X 60 X 90 NOTE.— 6080 feet= 1 knot. 60 min. = I hour. 100 - 10 = 90 per cent, effective advance Rule. — To find Propeller Diameter. Constant K x V /pj^lftTev. y = Diameter. V 100 / Therefore, K i8 x ^ 7iS~>^6 V"^ "'4^ ^^^*' °'' ^^^ "^ ^^^^ Diameter. V lOO NOTE.— K = Constant i8 in present case (see Seaton and Rounthwaite's " Pocket Book" for table of Constants). 6oo = I.H.P. 15 = pitch. 76 = revolutions. 504 " Verbal " Notes and Sketches To find Total Expanded Blade Area. — The total expanded blade area is found as follows : — Rule.— Sj rev. C X / ii^- P- = total Surface. Therefore, Constant 16 x /"°°=44.9, or say 45 square feet. V 76 NOTE. — C = Constant 16 in present case (see Seaton and Rounthwaite's " Pocket- Book" for table of Constants). 600- 1. H. P. 76 = revolutions. To find Diameter and Length of Boss. — For a cast-iron propeller with blades and boss solid, the diameter and length of the boss are found as follows : — Rule. — Constant 27 x shaft diameter = boss diameter and boss length, therefore 2-7x11 =29-7 inches, or say 30 inches diameter and length of boss. NOTE. — II inches = tail shaft diameter. The boss diameter varies from \ to \ of propeller diameter. The curve of boss radius is taken w^ith a radius equal to boss diameter x -8, therefore 30 inches x -8 = 24 inches radius for curve. To find Blade Thickness. — The blade thickness, if continued to the shaft centre line or axis, is found as follows : — Rule, — J 1VT K ^Yt y^"^y ^^ ~. X Constant 4 + "5 = Thickness. Number of blades x boss length Therefore, / ^-. x4 + -5 = 6-S inches thickness at shaft axis. \/ 4 X 30 mches NOTE. — II inches = shaft diameter. 4 ,, = number of blades. 30 ,, = breadth of blade at boss (roughly). The blade thickness near the tip is found as follows : — Rule. — Constant -04 x propeller diameter in feet + -4 = thickness. Therefore, •04X ii-5 + -4 = -86 inch, or say | inch thick near tip. NOTE.— ii-5 = propeller diameter in feet. To find Boss Thickness. — The boss thickness at position of the blades is found as follows : — Rule. — Constant -65 x blade thickness at shaft axis - thickness. Therefore, •65x6-5 = 4-22 inches, or say 4^ inches thirk. NOTE.— 6-5 inches = blade thickness at shaft axis. T331 5«Aw}.; 3CAJ8 LA - ^- ^- - '^■^ J- n f- ■-^. SOLID BLADED CAST IRON PROPELLER SCALE i" PER FOOT PITCH 15-0 DIAMETER ll'-6" EXPANDED BLADE AREA 45 SQUARE FEET PITCH RATIO = /5 -h//-S = /-J AREA RATIO = ^5 -h //S^ X -7654 =43 6 SLADE PROJEC • Verbal " Nole> and Sktlches. {Ts /arr fagr ip^. Propellers 505 To find Taper in Boss. — Allow the taper of shaft hole in boss to be not less than \ inch per foot of length. Therefore, 25 feet x 75 inch = 1875 inches taper, and II inches - 1-875 inches = 9-i25 inches diameter at small end, or say 9 inches. NOTE.— 30 inches = 2-5 feet = length of boss. To find Dimensions of Key. — The width and thickness of the key which secures the boss to the shaft are found as follows : — j^^^LE.— Shaft diameter ^.g^^-^^^^ ^^ ^^^ Therefore, ?^ + -6=2-4 inches, or say 2i inches in width. 6 Rule. — Width of key X '5 = thickness of key. Therefore, 2-5 x -5 = 1-2 inches, or say i| inches in thickness. To find Dimensions of Nut. — The diameter and thickness of the nut at back of boss are found as follows : — Rule. — Shaft diameter at screw x 1-5 = diameter of nut, therefore 8-5xi-5 = i2j in. diam. Shaft diameter at screw x 75 = thickness of nut, therefore 8-5x-75 = 6i in. thick. NOTE. — 8-5 inches = shaft diameter at screw. To find Single Blade Expanded Area. — As there are four blades, the area of one blade is found as follows : — Total blade area -f 4 = one blade area. Therefore, 454-4=11-25 square feet surface for one blade. NOTE. — 45 square feet = total blade area. To find Blade Length. — Half of the boss diameter subtracted from half of the propeller diameter will give the blade length : — Therefore, 11-5-^2 = 5-75 feet, and 2-5 -=-2 = 1-25 ; then 575- 1-25 = 4'5 feet length of blade. NOTE. — 1 1-5 feet = propeller diameter. 2-5 ,, =boss diameter. To find Width of Blade Area Rectangle. — The single blade area divided by the blade length will give the mean width of the blade area rectangle. Therefore, 11-25-^4-5 = 2-5 feet width. NOTE. — 11-25 square feet = single blade area. 4-5 feet = blade length. Shape of Blade. — The standard shape of blade takes the form of an ellipse, but in practice various modifications of this are adopted, with more or less satisfactory results. Experience proves that difference in blade contour affects the efficiency but slightly, provided that the area of blade is kept constant. 5o6 " Verbal " Notes and Sketches Set Back. — Allow a " set back " of blade equal to about i inch per foot of propeller diameter, or say 12 inches in all, at tip. Radial Pitch Angles and Thickness Templates. — In a working drawing the pitch angles and thickness templates at various radial distances on the blade require to be shown for the fitting up of the shop moulding templates, and as the length of blade from centre of boss to tip is equal to the radius of the circumference circle, the corresponding reduced pitch distance will be equal to the full pitch divided b}- 2x3-1416; hence, 15^ 2 X 3- 1416 = 2-38 feet, or 2 feet 4i inches. NOTE. — This distance of 2 feet 4^ inches requires to be measured horizontally from the boss centre, and all lines from radial points on the blade drawn to it. Summary of Results, The principal dimensions as found by the foregoing rules are then as follows : — Propeller pitch ... - „ diameter - - - - Expanded blade area Single blade area - - - - Boss diameter . . . . „ length - . - . „ taper ----- Breadth of key - - . - Thickness of key - - - . Nut diameter - . . - „ thickness . . . - Pitch angle distance Length of blade area rectangle Width of „ „ " Set back of blade - - - - Blade thickness at shaft axis - - „ _ „ near tip - - - - . |. ,, Boss thickness - - - - - 4^ „ To Draw the Propeller (Sketch No. 12). The following method, it should be noted, is not mathematically correct (particularly in the case of the " projected area " view), but is quite near enough for practical purposes as required in a working drawing. For the shop moulding of a propeller the projected area view is not required. I. Blade Area Rectangle. — Set off the horizontal shaft centre line and the vertical centre line of the boss, then from the centre of boss, with a 15-inch radius, describe the circle of the boss diameter, 30 inches; also measure up from the shaft centre line half of the propeller - 15 ft. II ft, 6 in. - 45 sq. ft. II- 25 „ 2 : ft. 6 in. 2 >, 6 1 1 in . to g - 4 i^ - I2f - ^i 2 it4h 4 „ 6 2 „ 6 - 12 - 6J Propellers 507 diameter, or 5 feet 9 inches. Next measure on each side of the boss centre line half of the blade rectangle width, i foot 3 inches, and complete the rectangle as shown. Now proceed to sketch in by hand the approximate shape of the blade, taking care that the actual surface of blade when drawn in is at least equal to the original rectangular area. A good plan is to dixide off the blade area rectangle into a number of divisions, horizontally and vertically, counting up the total number, and after the blade is shaped out as desired, arrange that the actual area of blade contains the same number of division*:. 2. Blade and Boss Thickness. — Set off the length of the boss, 30 inches, and the diameter of the boss, also 30 inches, then complete the boss outside curve with a 24-inch radius. Next draw in the taper of the hole in the boss 1 1 inches to 9 inches. Then set off aft at the propeller tip the "set back" of 12 inches, and draw a line for the face of the blade through the boss curve at the vertical centre line, and from where this inclined line cuts the shaft centre line measure forward the thickness of blade at shaft axis (6| inches). At the blade tip also measure forward the thickness at that position, that is | inch, and draw a line parallel to the face of blade line. To complete the blade section, draw another line from the thickness at shaft axis (6| inches) to the tip of propeller, then run the two thickness lines into each other by a suitable curve as shown in the drawing, and join the blade at the root to the boss at the forward side by a large fillet of, sa)-, 6 inches radius. The hollow cast part of the boss is shown as 14 inches in length, as this leaves sufficient strength of metal fore and aft. 3. Pitch Angles and Thickness Templates. — Begin this view by again drawing in the complete boss and blade as in view i, and set off any convenient number of di\isions from the beginning of the blade radius at root. The first is at 18 inches from the centre, and the others, Nos. 2, 3, 4, 5, are at equal distances of 12 inches. Draw horizontal lines, and where these lines cut through view 2, the thick- ness of blade at each division will be found. Transfer the various thicknesses to view 3, and complete the thickness sections by drawing in radial curves for the back of the blade or forward surface. Observe that near the root the after edges are slightly rounded away to allow a free flow of water past the blade. Next measure to the right the pitch angle distance of 2 feet 4^ inches, and from each radial point draw lines to it as shown ; this gives the required pitch angles at the differentradial positions marked. 4. Boss, Key, and Nut. — This view will be easily drawn, as the dimensions are simply taken from the " Summary of Results," and measured off. Observe that the screw for the nut is left-handed for a right-hand propeller, to keep the propeller hard up when the shaft is revolving. 5oS *' Verbal " Notes and Sketches 5. Nut. — The nut shown has four small projections 3 inches wide, to allow of the nut being screwed on or off. 6. Blade Projection. — As usual, set off the propeller radius of 5 feet 9 inches, and the various divisions, i, 2, 3, 4, 5, from view 3, and draw long horizontal lines. Now complete the external view of the boss and the blade angle centre line at the set back of 12 inches from tip. At each of the divisions marked, Nos. i, 2, 3, 4, 5, drop down vertical lines from each intersection of the blade angle line with the horizontal division lines, and where these vertical lines cut the shaft centre, set off the corresponding blade angle at that position, w^hich requires to be transferred from view 3, so that at position i on shaft centre the angle is that marked i on view 3 ; at position 2 the angle is that marked 2 on view 3, and so on for each of the five radial points, which gives the projected lines of the horizontal blade as seen looking from the starboard side. On each of these angle lines set off the half width of blade, measured from view 3, and, taking No. 2 as an example, note that the width across B in view 3 is the same as B in view 6. Repeat this blade width measurement at each of the radial positions i, 2, 3, 4, 5, and then through the points so found draw in, first by hand and afterwards with a " French Curve," the blade contour. NOTE. — " French curves " are wooden shapes used in drawing- when the contour required does not readily allow of the use of radial curves, and are very convenient for use in propeller design. " French curves "' are obtainable st shops where drawing instruments are sold, and the purchase of one or two is recommended. 7. Blade Projection. — In this view transfer the previous view of the boss and blade complete, and run up lines from the various blade widths at the radial points i, 2, 3, 4, 5, and observe where the vertical lines so drawn cut the corresponding radial horizontal lines ; mark these points with a dot or a small cross, and if this is done for each of the var)-ing widths of blade, the curve can then be drawn in by hand, and afterwards (as before) completed more carefully with the " French curves." Notice that the width of blade at B (No. 5 radial line) in the vertical view of the blade is run up from the horizontal view of the blade also marked B, and each width is similarly treated. 8. Projected Blade Area. — This view is fairly simple in construction and requires very little explanation. Set off the various circles of the tip of blade, radial points of blade and boss, then project over, by lines from view 7, the various widths of the blade at the same radial points I, 2, 3, 4, 5, and where these lines cut the radial curves of view 8, mark small dots or small crosses ; if these points be then connected by hand curves, the approximate shape and width of the blade, looking from aft forward, will be shown. After completing the horizontal blade, merely transfer the widths, &c., to the vertical blade and complete it also. As before mentioned, in speaking of Propellers 509 other views, the blade contour can be better finished by the use of " French curves." Observe that width B on radial line 5 of view 7 corresponds to width B on radial curve 5 of view 8. II. To Design and Draw a Propeller for the following:— I.H.P. - - 2350 (twin screw). Knots - - 12-5. p. / Revolutions - - 100. '^^^^^ ) Tail shaft - - 1 1-5 inches diameter. Type of steamer - Passenger cargo boat. Propeller to be of the four-bladed, cast-iron, solid type. To find Propeller Pitch. — Allow 10 per cent, for apparent slip, and proceed as follows : — Rule. — Knots X 6080 X 100 Pitch Rev. X 60 X effective per cent. Therefore, . J ^^Sji 6080x^0^ f^^t Pi^^h. 100 X 60 X 90 NOTE. -6080 feet = I knot. 60 min. = I hour. 100-10 — 90 per cent, effective advance. To find Propeller Diameter. Rule. — \ / pitch X rev. X" Constant K x ^ / _:^lu"' fey. ^ - '^ Diameter. 100 Therefore, K ip x a/ T^Yi^ " ^^ ^^^^ Diameter. V 100 / NOTE.— K = Constant 19 in present case (see Seaton and Rounthwaite"s " Pocket Book' for table of Constants). 2350 ^2= 1175 = LH. P. for one engine. 14 = pitch. 100 = revolutions. NOTE.— Being a twin screw steamer each engine will require to develop one- half of the total LH.P. To find Total Expanded Blade Area. — The fotirl expanded blade area is found as follows : — Rule. — C X / ii^^ ^ total Surface. /rw \/ re'v Therefore, Constant 16 x / 1175 ^24-4, or say 54', square feet. ■\ 100 5IO "Verbal" Notes and Sketches NOTE. -C = Constant i6 in present case (see Seaton and Rounthwaite's " Pocket- Book" for table of Constants). ii7S=I.H.P. 100 = revolutions. To find Blade Thickness. — The blade thickness, if continued to the snaft centre Hne or axis, is found as follows : — Rule. — / Shaftdiam^er^^ ^, x Constant 4 + .5 == thickness. V Number of blades x boss length Therefore, / ^^'5 — xa 1-5 = 7-5 inches thickness at shaft axis. \/ 4 X 31 mches NOTE.— II-5 inches — shaft diameter. 4 ,, = number of blades. 31 ,, = breadth of blade at boss (roughly). The blade thickness near the tip is found as follows : — Rule. — Constant -04 x propeller diameter in feet + -4 = thickness, therefore -04 X 12 + -4 = -88 inch, or say ^ inch thick near tip. NOTE.— 12 = propeller diameter in feet. To find Diameter and Length of Boss. — For a cast-iron propeller with blades and boss solid, the diameter and length of the boss is found as follows : — Rule. — Constant 27 x shaft diameter = boss diameter and boss length, therefore 27 x 1 1-5 = 3105 inches, or say 31 inches diameter and length of boss. NOTE.— ii-s inches == tail shaft diameter. The boss diameter varies from ^ to i of propeller diameter. The curve of boss radius is taken with a radius equal to boss diameter x -8, therefore 31 inches x -8 = 24 inches radius for curve. To find Boss Thickness.— The boss thickness at position of the blades is found as follows : — Rule. — Constant -65 x blade thickness at shaft axis = thickness therefore -65 x 7-5 =4-875 inches, or say 4I inches thick. NOTE.— 7-5 inches = blade thickness at shaft axis. To find T aper in Boss.— Allow the taper of shaft hole in boss to be not less than \ inch per foot of length. Therefore, 2-6 feet x 75 inch= 1-95 inches taper, and 1 1-5 inches- 1-95 inches = 9-55 inches diameter at small end, or say 95 inches. NOTE.— 31 inches ^2-6 feet = length of boss. /L^.: ^ T^ — ■■=r ^f X run &,nn,zzm V y'i^^. nu nu/, Hitftj / /i I BLADE AREA RECTANGLE ? BLADE & BOSS THICKNESS 3 PITCH ANGLES & THICKNESS TEMPLATES 4. B05S,KEY. * NUT 5. BLADE PROJECTION 6. PROJECTED BLADE AREA SOLID BLADED CAST IRON PROPELLER. SCALE ilNCH PER FOOT PITCH 14-0" DIAMETER 12-0* EXPANDED BLADE AREA 54 5 SQUARE FEET. PITCH RATIO H7. AREA RATIO -46. No. 13. Propellers 511 To find Dimensions of Key. — -The width and thickness of the key which secures the boss to the shaft are found as follows : — Rule. — Shaftdiameter ^ .g ^ ^-^^^ ^^ ^^^ 6 Therefore, -> +'6=2-5 inches, or say2i inches in breadth. Rule. — Width of key x -5= thickness of key, therefore 2-5 x -5 = 1-25 inches, or say i\ inches in thickness. To find Dimensions of Nut. — The diameter and thickness of the nut at back of boss are found as follows :— Rule. — Shaft diameter at screw X i-5=diameter of nut, therefore 9-25 X 1-5 = 1 3I inches diameter. Shaft diameter at screw x -75 = thickness of nut, therefore 925 x .75 =6j^ inches thick. NOTE. — 9-25 inches = shaft diameter at screw. To find Single Blade Expanded Area. — As there are four blades the area of one blade is found as follows : — Total blade area^4 = one blade area, therefore 54-5-^4 = 13-625 square feet surface for one blade. NOTE.— 54-5 square feet = total blade area. To find Blade Length. — Half of the boss diameter subtracted from half of the propeller diameter will give the blade length : — Then 12-^2 = 6 feet, and 2-6-^2= 1-3; therefore 6— i-3 = 47 feet length of blade, say 4 feet 8^ inches. NOTE. — 12 feet = propeller diameter. 2-6 feet — boss diameter. To find Width of Blade Area Rectangle. — The single blade area divided by the blade length will give the mean width of the blade area rectangle. Therefore, 13-625 -^4-7 = 2-89 feet wadth, or say 2 feet ii inches. NOTE. — 13-625 square feet -single blade area. 4-7 feet = blade length. Set Back. — Allow a " set back " of blade equal to about i inch per foot of propeller diameter, or say 12 inches in all, at tip. Radial Pitch Angles and Thickness Templates. — In a working drawing the pitch angles and thickness templates at various radial 34 512 "Verbal" Notes and Sketches distances on the blade require to be shown for the fitting up of the shop moulding templates, and as the length of blade from centre of boss to tip is equal to the radius of the circumference circle, the corresponding reduced pitch distance will be equal to the full pitch divided by 2x3-1416; hence, 14-^2x3-1416 = 2 feet 2f inches. NOTE.— This distance of 2 feet 2 J inches requires to be measured horizontally from the boss centre, and all lines from radial points on the blade drawn to it. Summary of Results. The principal dimensions as found by the foregoing rules are as follows : — Propeller pitch . . . . - „ diameter ----- Expanded blade area - - Single blade area ----- Boss diameter . . - . . „ length- . - . . . „ taper ------ Breadth of key . . . - . Thickness of key ----- Nut diameter ----- „ thickness ----- Pitch angle distance . - . - Length of blade area rectangle Width of „ ,, ... Set back of blade ----- Blade thickness at shaft axis „ „ near tip - - - - - i „ Boss thickness - - - - - - 4^ „ To Draw the Propeller (Sketch No. 13). — The various views and pro- jections are found in the same manner as those in the previous, design, as will be seen by reference to the drawing, and as the descriptions apply equally in both cases no difficulty should be experienced by the beginner in setting off the views required for a shop working drawing. NOTE.— The projected area view in this case is correctly set off, and it will be noted that vertical lines are set off at each radial position of the horizontal blade and the corresponding blade width projected over to each line. An arc is then taken from the centre line and half width radius to the radial arcs, and the points so found are then connected by hand as before. III. To Design and Draw a Propeller for the following :— - 14 ft. - 12 91 54-S sq. ft. 13-6 25 „ 2 ft. 7 in. 2 „ 7 in. to '9h - 2^ - li - 13I - 1 HI 2 ft. 2f 4 „ H 2 „ I of - 12 - 7i (I.H. Kno ) Rev( .P. - - 1200. Knots - . II. i-.: / Revolutions - 77. I Tail shaft - - 13 inches diameter. Type of steamer - Cargo boat. Propeller to be of the loose, cast-iron, four-bladed type. Propellers 513 To find Propeller Pitch. — Allow 10 per cent, for apparent slip, and proceed as follows : — Rule. — Knots x6o8ox 100 _ p:i~v. Rev. X 60 X effective per cent. Therefore, n x6oto>ooo^^6 feet Pitch. 77 X 00 X 90 NOTE— 6080 feet = I knot. 60 min. = I hour. 100-10^90 per cent, effective. To find Propeller Diameter. Rule. — Constant K x ^ . pjtch x rev, y " P'^'"^^^'"- V 100 / yI200 ^^^„. 3 =14-4 feet, or say 14-5 feet Diameter. \ 100 y NOTE.— K = Constant 18 in present case (see Seaton and Rounthwaite's " Pocket- Book" for table of Constants). i200 = LH.P. 16 = pitch. 77 = revolutions. To find Total Expanded Blade Area. Rule.— ^ Constant C x /UL^ = blade area (total). \/ rev. Therefore, Constant 16 x / =63 square feet area. V 77 NOTE.— C = Constant 16 in present case (see Seaton and Rounthwaite's " Pocket- Book "' for table of Constants). 1200 = LH. P. 77 = revolutions. To find Diameter of Boss. Rule. — •9 X VPropeller diameter in feet = boss diameter. Therefore, -g x 's/i4-S = 3-4 feet, or sa}- 40 inches diameter. NOTE.— Propeller diameter = 14-5 feet 514 "Verbal" Notes and Sketches To find Length of Boss. Rule. — 26 x tail shaft diameter = boss length. Therefore, 2-6 x 13 = 33-8 inches, or say 34 inches in length. NOTE.— 13 inches = tail shaft diameter. To find Diameter of Blade Flange. Rule. — 22 x tail shaft diameter = flange diameter. Therefore, 22 x 13 inches = 28 inches diameter. NOTE.— 13 inches = tail shaft diameter. To find Taper in Boss. Allow the taper of shaft hole to be not less than | inch per foot of length. Therefore, 2-833 feet x -75 inch = 2-124 inches taper, and 13 inches — 2-124= 10-876, or say lof inches diameter at small end. NOTE. — 34 inches = 2-833 feet = length of boss. To find Thickness of Blade at Boss. Rule. — ^LRRx3 300o ^thrust lbs., and Pitch X rev. x No. of blades y Thrust lbs. X blade length from flancre X -8 , ^ . , . .,. , a :j-. — ^\ ^ + "25 -blade thickness. flange diameter x 320 Therefore, ^o^^SOOo^g g ^^ ^^^ 16 X 77 X 4 y 8036x77 inchesx^8^. 68 inches, or say 73 inches thick. 28 inches x 320 ' NOTE.— i6 = pitch. 77 inches = blade length from flange. 320 = constant for cast iron. To find Thickness of Blade near Tip. Rule. — 04 x propeller diameter /«/^^/+ -4 = thickness. Therefore, -04 x 14-5 + -4 = -98 inch, or say i inch thick. NOTE.— 14-5= Propeller diameter in feet. To find Diameter of Flange Studs. Rule. — V I.H.P.x 33000 it. i.iu J P-. . ,T fui J = thrust lbs., and Pitch X rev. x No. of blades Thrust lbs. x blade length from flange x -8 .• , r i. j 7854 X No. of st^idi^ stud radTus^iTSo" ^^^^^n^^^r of studs, Propellers 515 Therefore, , 1^ x 33000 ^ ^^ ^^^ ^^^ ' 16 X 77 X 4 / 8o36j< 77jnchesxJ ^ ^^^.j^^^ ^^^ ^i inches diameter of stud. V 7854 X 7 X 10 inches x 1700 NOTE.— 16 = pitch. 77 = revolutions. 4 = No. of blades. 10 inches = radius (allowed) of studs. 77 ,, = blade length from flange. 1 700 = constant for steel studs. 7 = No. of studs allowed. To find Dimensions of Nut. Rule. — Tail shaft diameter rt/ screzu x 1-5 = diameter of nut. Therefore, 10-5 X i'5 = I575 inches, or 16 inches diameter. Rule. — Tail shaft diameter at screw x -75 = thickness of nut. Therefore, 10-5 x 75 =7-875 inches, or say 8 inches thick. NOTE. — The shaft diameter at screw may be taken as 10^ inches. To find Dimensions of Key. Rule. — Tail shaft diameter^.^^^^^t^ ^^ ^^^ 6 Therefore, 13 "^c ^^ + .5=2-76 inches, or say 2| inches in width. o Rule. — Width of key x -5 = thickness of key. Therefore, 2-75 inches x -5 = if inches thick. NOTE. — 13 inches = tail shaft diameter. Blade Area Rectangle. — Total blade area = 63 square feet. Therefore, 63 -=-4= 15-75 square feet for one blade, and 1 5*75 -r 5-83 = 27 feet in width, or say 33 inches. NOTE.— Propeller radius -boss radius^blade length. Therefore, 7 feet 3 inches - i foot 8 inches - 5 feet 7 inches, length of blade. S feet 7 inches = 5-583 feet. Radial Pitch Angles and Thickness Templates. — In a working drawing the pitch angles and thickness templates at various radial points of the blade require to be shown for the fitting up of the shop moulding templates, and as the length of blade from centre of boss to tip is equal to the radius of the circumference circle, the corresponding reduced pitch distance will be equal to the full pitch divided by 2X 3-1416. 5i6 "Verbal" Notes and Sketches Therefore, 16-^(2 x 3-1416) = 2-54 feet, or say 2 feet 6i- inches pitch angle distance. NOTE.— This distance of 2 feet 6^ inches requires to be measured horizontally from the boss centre, and all lines from radial points on the blade drawn to it. Summary of Results. The principal dimensions, as found by the foregoing rules, are then as follows : — Propeller pitch . . - . „ diameter Expanded blade area Single blade area - - - - Width of area rectangle Length of blade area rectangle Boss diameter . . . . Boss length .... Blade length from flange - Diameter of steel studs - - Flange thickness - ^ - . Blade thickness at boss „ „ near tip - Flange diameter - - - . Pitch angle distance Width of key - Thickness of key .... Diameter of nut - . . . Thickness of nut - - - . Boss taper - . . . To Draw the Propeller (Sketch No. 14).— The following method, it should be noted, is not mathematically correct (particularly in the case of the projected area view), but is quite near enough for practical pur- poses as required in a working drawing. For the shop moulding of a propeller the projected area view is not required. I. Blade Area Rectangle.— Set off the horizontal shaft centre line and the vertical centre line of the boss, and from the boss centre measure off on each side half the boss length, i foot 5 inches, and vertically half the boss diameter, i foot 8 inches, and half propeller diameter, 7 feet 3 inches, then complete the boss by drawing in the curves at a radius of 20 inches. Next, measure on each side of the boss centre line half of the blade rectangle width, i foot 4^ inches, and complete the rectangle as shown. Proceed next to sketch in by hand the approximate shape of blade, taking care that the actual area of blade when drawn in is at least equal to the original rectangular area. A good plan is to divide off the blade area rectangle into a number of divisions horizontally and vertically, counting up the total - 16 ft. 14 ft. 6 in, - 63 sq. ft, 15-75 >. - 2 ft. 9 in. -5 „ 7 „ - 3 )) 4 )> - 2 „ 10 „ -6 j> 5 >> - 4., - 3i » - 7f » - I ,. - 2 ft. 4 „ - 2 „ 6| „ - 2|„ - i|„ - I ft. 4 „ - 8 „ 13 in. to lof „ 6 SLSDE PROJECTION LOOSE BLADED CAST IRON PROPELLER SCALE i" PEB FOOT PITCH le'-o' DIAMETER /4'-s" - EXPANDED BLADE AREA 6i SqUARE FEET PITCH RM\0 = /S-h/4-5 = /-/ AREA RATIO = 53 ^/' the following method : — With the steamer in dry dock turn the engines until one of the remaining blades is in an upright or vertical position. Then with a straight-edge placed 520 "Verbal" Notes and Sketches against the stern post, and at a convenient radius, R, mark the blade at the leading edge A ; shift the straight-edge to the other side of the blade, and mark the following edge B. Now turn the shaft round until the surface of the boss to receive the spare blade is in position, and when the new blade is placed on the boss turn round the flange until the leading and following edges coincide with the marks on the No. 17.— Fitting on a New Blade. straight-edge, which in the meantime must be held or fixed up against the stern post at the same radius R. The new blade will then have the correct pitch angle, and the studs may be screwed up. NOTE.— The foregoing method is necessary when the stud holes in the flange are cut oval to allow of pitch variation. To find the Pitch when the Propeller is in the position shown (on the surface table or shop floor).— Fit up two set-squares and r 1..-.L.. --T^- / TURBINE TYPE PROPELLER SCALE i" PER FOOT PITCH 5-0" DIAMETER 5-7" • EXPANDED BLADE AREA.. JI-8 SQUARE FEET PITCH RATIO --■89 AREA RATIO -48 * Verbal '" Notes and Sketches. No. 19. G Propell ers 521 a horizontal piece of wood as shown, at a suitable radius R (say- about two-thirds out from boss to give average pitch) ; then the piece No. 18.— Pitch with Propeller Horizontal. of pitch P will be obtained by the vertical measurement, and the piece of circumference C by the horizontal or floor measurement. And R X 2 X 3-1416 = full circumference at radius R. To find corresponding pitch — As C : full circumference : : P : full pitch. NOTE.— If the blades have a varying pitch, repeat the above at two or three radial positions, and take the mean of the two or three pitches so found as the average pitch. Motor Launch Propellers. — In oil motor launches the two-bladed propellers usually fitted are often of the reversible kind, that is, the blades are so arranged that their angles can be changed as desired, to "stop" or "astern" or "ahead." In the "stop" position the blades lie at right angles to the centre line of the ship, and for "ahead " the blades are moved round with the leading edge forward, while for " astern " the blades are turned round with the leading edge aft. These changes in blade position are obtained by means of a rod passing through the hollow tail-end shaft, the rod being operated by a suitable handle. It will thus be seen that the engines always run in the same direction. Blade Interference.— By this is meant the effect produced by one blade on another blade acting on the water in such a manner as to break up the surface, and thus cut out or rob the next blade of its 0^ o d 2 uj 7 2 ^ CO cn ID UJ LU < 2 ° O DD vO in < H QC O < I*. o: ili X o z UJ o^ O < Or: X u I- •.•-.'••'"-'I >.«^ffi« 31jq fl'^tfCj-k .'>"•■■'■-*: '^• h ' '}) ^':rr||A pe c!66JJ ifUl I" fi'- ■;..,' , • f^l^PO '( :■ now r|" : b02ItIC;iJ K' yVi- MjlJJ JMO of' Pitch of Propeller. To measure the pitch of a propeller lying on the floor as shown, proceed . folio 4. Shift the long straightedge through om division of the boss marks (or ^), as shown at position c, and again measure down to the blade surface. 5. Subtract the two measurements in inches, and the difference is the mean pitch infect. 1. Mark off the face of the boss into twelve equal divisions, 2. Take a long straightedge, and place it in line wirti two oppositely placed divisions, as at position B. 3. Take another straightedge (or plumb line) and measure the distance down from tlie lon^- straightedge to the blade surface at a radius k, taken at, say, | out from the boss centre. In the sketch shown the first measurement is 4 in. and the second measurement 18 in. Therefore. 18 inches -4 inches -14 feet pitch. It will easily be seen that the difference of the measurements is equal to -j^ of the pitch only. Therefore, 14 inches x 12 inches=i68 inches pitch, and — inches=i4 feet The bove the line and the 12 below the line cancel out in all cases, thus leaving the difference tly equal to the pitch in feet. in inches NOTE.— The above method 1 also be apphed with the propeller in the usual position on the shaft. [To fan past 522. " Verbal "' Notes and Sketches Propellers 523 effective thrust. For this reason an improvement is sometimes effected by chanjj^in_L,r a four-bladed propeller for one of three blades, and, it may be noted, that this change has been made in the case of the turbine steamer " Victorian." Blade interference has not, as yet, been fully investigated by experiment, and is therefore at present largely a matter of speculation. Twin Screws. — In twin-screw steamers it has been observed that in most cases the starboard engine runs at a higher revolution speed than the port engine, and this may be due to some effect of blade inter- ference reducing the efficiency of one of the propellers. Effect on Steering". — The steering is found to be improved if in twin-screw steamers the propellers revolve outwards from each other, instead of inwards, that is, the port engine propeller to be a left-hand screw, and the starboard engine a right-hand screw. The propellers also develop a more effective thrust, as the blades work in unbroken water. Surface of Blade. — It has recently been proved beyond doubt that a polished blade surface increases the efficiency of the propeller. This is fully recognised in turbine propulsion, as nearl}' all propellers fitted to turbine steamers have highly polished surfaces. In a case which came under the writer's notice, an increase of one knot was obtained, for the same power and consumption, b\- changing a cast-iron propeller for one of polished bronze. NOTE. — If the propeller pitch is increased by, say, i or 2 feet, the mean pressure of the indicator diagrams will be more if the engine develops the same power with reduced revolutions, and the ship runs at the same speed. Bronze Propeller Blades and Corrosion. With bronze propeller blades the chemical conditions are much like those of an electric battery, the steel stern posts and hull forming one electrode, the bronze propeller blades the other, and the salt water the solution of the battery. As the propeller is the positive terminal and the ship the negative terminal, the current flows from the ship to the propeller, causing pitting of the steel hull. In order to overcome this galvanic action, zinc plates are fitted, in single-screw ships to the after face of the stern posts, and in twin- screw ships fitted round the after propeller bracket. This arrange- ment does not prevent galvanic action, but such action takes place between the propeller blades and the zinc plates instead of between the propeller blades and the steel plates of the steamer. Improved Propeller. — A case which came under the writer's notice gave the following data, and clearly indicates the fact that propeller design, in many cases, is more or less a matter of " trial and error," 524 "Verbal" Notes and Sketches as notice the great improvement effected by the increase of blade area and of pitch, and the alteration in blade m.aterial, shown as follows : — With Original Propeller. Diameter, i8 feet 6 inches. Pitch, 1 8 feet 6 inches. Expanded blade area, 98 square feet. Revolutions, 72 to 75. Cast steel blades. Consumption, 52 to 55 tons per day. Speed, about 11-5 to 11-75 knots. Slip per cent, 15 to 30 per cent. I.H.P., about 3300. With New Propeller. Diameter, 18 feet 6 inches. Pitch, 20 feet. Expanded blade area, 104 square feet. Revolutions, 64 to 66. Bronze blades (polished). Consumption, about 40 to 45 tons per day. Speed, 12 knots. Slip per cent., 5 to 10 per cent. I.H.P., about 2800. From the foregoing it is evident that the original propeller was not absorbing the full power of the engines, and the alteration made in increased pitch and surface utilised more effectively in propulsive effort the I.H.P. developed. Notice that the consumption, and there- fore the I.H.P., developed is less in the second case, and the speed rather more. The above rather striking results were therefore obtained by — (i.) Increasing the pitch, with slight pitch variation. (2.) Increasing the expanded blade area. (3.) Changing the material of the blades from steel to that of polished bronze, which allows of thinner blades. The polishing of the blade surface and thinning down of the thickness both contribute to increased propeller efficiency. It is, of course, difficult to accurately estimate how much each of the foregoing alterations contributed individually to the resulting general improvement in propulsive efficiency. Propulsive Efficiency. Of the total I.H.P. developed by the engines only about 50 per cent, or thereabout is applied in the effective advance of the steamer Propellers 525 when the various losses are eh'miiiated — that is, the actual hull resistance in lbs. at any given speed, multiplied by the advance of the hull per minute and divided by the constant 33,000 foot-pounds, will give the effective horse-power, or, as usually expressed, the E.H.P. Therefore, E.H.P. -^ I.H.P. = Propulsive efficiency. This efficienc}' can only be accurately determined by model tank experiments of re- sistance, after which the data so obtained is converted into terms of the actual hull by a series of calculations known as the "law of comparison," and devised by the late Dr Froude. The tank experi- ments with the reduced scale hull models obtain progressive " tow rope " resistances which are the actual resistances at various speeds of the model hull (the propeller being omitted). These are made up as follows : — Resistance. — i. Skin frictional resistance of the hull surface. 2. Wave making resistance of the hull body. 3. Eddy making resistance of the hull bod)'. The foregoing constitute what ma}- perhaps be termed the true resistances, and to overcome these the effective horse - power is required. Power Losses. — The losses of engine power are made up as follows : — 1. Friction (initial and load). 2. Propeller inefficiency. 3. Hull inefficiency. The frictional losses are those occasioned b}' the working parts and the power absorbed by the thrust block. The propeller losses are due to excessive slip, blades friction, and other causes, and the hull efficiency is a result which may either be under or above unit}', according to the difference between what is called " augmentation of resistance," due to the propeller blades at the stern, and " wake speed gain." Generall}', however, the " wake speed gain " balances the augment of resistance to within a very few per cent., although an allowance of about 95 per cent, is often taken as the " hull efficiency." The " wake speed " is produced by the water closing in on the stern as the hull advances, and this body of water acquires a forward motion or speed varying in degree with the lines of the hull bod}'. Utilisation of Power. — The total I.H.P. developed by the engines is therefore used up somewhat as follows, although it must be understood that the values given var}' in different cases and under different conditions in the same case : — Taking the total I.H.P. as 100 per cent. 526 "Verbal" Notes and Sketches Reciprocating Engines. Indicated horse-power - - - - 100 per cent. Engine friction loss - - - - 10 ,, Horse-power at propeller - - - - 90 ,, - Propeller efficiency, 62 per cent. Then, 90 x ■62 = 55-8 „ Horse-power by propeller - - - - 55-8 „ Hull efficiency, 95 per cent. Then, 55-8 x -95 = 53 n Effective horse-power - - - - 53 >. Therefore, propulsive efficiency = -53_, or -53. 100 Turbine Engines. Shaft horse-power - - - - - 100 per cent. Propeller efficiency, 60 per cent. Then, 100x60 = 60 ,, Horse-power by propeller - - - - 60 ,, Hull efficiency, 95 per cent. Then, 60 X 95 = 57 „ Effective horse-power - - - - 57 n Therefore, propulsive efficiency = " , or -57. The following explanations of propeller slip are taken from a paper on " Screw Propellers," read by T. Sidney Cockrill, Esq. M.l.Mech.E., before the Liverpool Engineering Society in April 1907 and are well worthy the attention of students. " Slip. — The slip is the difference between the speed of advance of the propeller (supposing it to be working in an unyielding substance) and the actual speed of the ship. In other words, it is equal to the pitch multiplied by the revolutions, less the distance traversed by the ship. If the water did not yield to the propeller and flow sternward, the speed of the ship would be the same as the speed of the propeller, and there would be no such thing as slip ; but water, being a fluid, is driven astern by the action of the propeller as the ship moves ahead. The rate at which the water is driven astern relatively to the surrounding water is usually said to be equal to the slip ; but this is only true provided the pitch multiplied by the revolutions is equal to the speed of the race relatively to the ship, or, in other words, provided the propeller itself does not slip in the race. As far as the author can see, we have no means of ascertaining the truth of this. " The above, however, only relates to apparent slip, for it does not take account of the fact that the propeller is not working in still water, but in water in motion in a forward direction owing to the influence of the ship in passing through it ; and, as it is the propeller that is und> - I knot. 12 knots. -9 " SECTION IX. REFRIGERATION. The Ammonia Compression System. Anhydrous ammonia has found great favour as a refrigerating medium on account of its high latent heat of vaporisation and the comparatively low pressure at which it can be liquefied. The idea involved in an ammonia refrigerating plant may be explained as follows : the same, however, holds good for machines using carbonic acid, sulphurous acid, ether, &c. : — Anhydrous ammonia, i.e., ammonia free from all water or moisture, is naturally a gas. Under pressure and cooling by water it may easily be condensed to liquid form. It is almost colourless, and in appearance just like water, and weighs at ordinary temperatures about 37 lbs. per cubic foot. In this form it may be purchased in steel cylinders or drums containing from 50 to 100 lbs. in weight. If the pressure be relieved from the liquid ammonia it will quickly revaporise, producing as it does so intense cold. An ammonia refrigerating machine consists of the following principal parts : — {a?j A vaporiser, evaporator, or refrigerator — a vessel in w hich the ammonia is allowed to vaporise, producing a low temperature and surrounded either by the air or brine to be cooled. {b?) A gas pump or ammonia compressor which draws the ammonia gas from the refrigerator and compresses it into the condenser. (r.) The ammonia condenser in which the gas discharged ncm the compressor is condensed to liquid form read}' for vaporisation .n the refrigerator. The diagram (No. i) will further explain this paragraph. It should here be explained that the ammonia in vaporising under low pressure in the refrigerator, changing its form from liquid to gas, must absorb into itself the latent heat of vaporisation. This is taken from the brine surrounding the coils — or in the case of direct expansion, from the air itself — and in condensing to liquid form again this heat is given up to the condensing water. The pressure necessary to 530 " Verbal " Notes and Sketches condensation is automatically regulated by the temperature of the. condensing water, and will vary from lOO to 200 lbs. pressure per square inch. The pressure in the refrigerator is controlled by the I i I I I C5 o iz; regulating valve, which is adjusted according to the temperature required, and varying from 70 lbs. absolute per square inch for a vaporising temperature of 40' Fahr. to 20 lbs. absolute per square inch -I! AlMOMM q ti J oeo> r r~ .-3 ..^if'^' f •v- ..•"' TSL, -^. No. I A- —Compression Systems of Refrigeration. (Aminonia uid CO..) CO, System. Carbonic anhydride (t;0~), naturally a gas. and obtained from the following 1, Natural springs. 3. Combustion of carbon. y Action of sulphuric acid on calcium carbonate. 4. Fermentilion of wort in brewing processes. The gas collected from these sources is firsi purified and dried, then com- pressed in stages, next cooled to ihc liquid slate, and finally forced into steel bottles for supply purposes. As the COj is under pressure in the bottles, it remains in the liquid condili'm until the pressure is reduced. When charging up ihc machine it evaporates back into gas by expansion, LAlent heal value per lb lat average evaporator pressures) == 13$ B T U off 1 CO., Ammonia iNH,i System. Ammonia, nn alk.-ilt, und naturally 3 ga^, is obtained by the healing of vil^immoniac and quicklime mixtures, or by the forced decomposition of animal iiubslances. The gas is collected and treated similarly to CO, gas as regards com- preffiion, cooling, and storing m steel bottles. Ammonia changtrs red litmus |»ipcr blue, and being alkaline in nature destroys copper, brass, and' leather. Ammonia is soluble in wuler, one part of the latter absorbing about 800 parts of ammonia. erage e = 580 BTL er«ture = 2s6' F. re up.) lighter than air. Average Pressures and Temperatures. The following represent average marine refrigerating practic temperature of 70* and brine outlet of 4* F. By- the combined effects of compression and cooling, ammor COj gas can be reduced to the liquid condition. ' Al».i.„ Temperilure Pleuure. '*''""'""■ Ammonia (NH,|- Brtne cooler - -6- isvs Condenser Brine out Brine returns ^K Sea - m Discharge - ?8" co,- Bnne cooler ■ 180 -6* |r-? Condenser ■ 1050 8S" Brine out Brine returns • .„ l2-o« Sea - ■=■" ?B Discharge - ;8' Brine pressure about 10 01 15 )bs. by gauge- ,, density about 40 01. per gallon. „ composed of fresh water and calcium chloride (calcium salt). Tests, Etc. I To Test Compressor or Regulator.— Stop machine and shut regulator . if presiure rises in evaporator gauge und falls in condetiser gauge, the compressor rings are leaky, or regulator is passing gas. 2- To Test for Shortage of Gas. — Close down regulator, and run machine for, say, 15 revs.; if, during this period, the evaporator gauge pointer falls back it indicates insufficient gas, as the machine should hold up to the pressure if the supply is sufficient. Insufficient gas also shows by jumping of the gauge pointers, and by rise of brine temperature, loss of temperature difTerence, etc. If delivery pipe from compressor heats up, and still remains heated after further opening of the regulator valve, it indicates shortage of gas ; the condenser gauge falling in pressure is also an indication of insufficient charging. Temperature Differences. — The following examples of difference in temperatures represent good refrigeraung practice, and should be kept to as nearly as possible. To Clear System of Air when Machine is Charged. Ammonia Machine. — After running for some time when charged, stop machme. hui keep circulating, then connect a rubber tube either to condenser gauge 1 ock fitting, previously mentioned, or to the air escape cock sometimes placed on rondenset delivery valve chest, and immerse lower end , gently open the cock, and close same when leedc iiing li I good for the CO, 1 Evapc ,.,.,. TempCTBiore. Gu 6* 4; -4' -(>■ -8- About 10' difference, i c.„ etiMr. SnWuo , 0" 60; 75; !5' 90" 95' ss' About ts difference. pre; ■ syst 1 show by a r To Work Rectifier System.— At intervals of. say, 30 minutes or. more, open cock D, and blow out separator into rectifier chamber, then shut cock D, and open cock E, which allows the machine to draw off any ammonia which has passed into rectifier: next shut cock E, and drain olToil from rectifier into a bucket by the cock fitted for that purpose. Air in Brine System- — Air in the brine system can be got rid of by opening the air escape cock fitted on tup of the evaporator chamber (shown in the sketch), the sea water temperature nd temperature of the refrigerant the same temperature difference evaporator gauge NOTE, -The ;ame n tube connectioQ to the 1 safely discharged to the atmosphere Orercharging. — If ili- ma. hm.- of Ih.- condL-n^.:. ^jug. pn-^uri- .\: the wme result. Rise of Sea Temperature. - 1 machine requires more gas, as the pre? must be proportionally increased to o and cooling effect as previously. Oil in System. —This shows by pointer, and variation in temperature of delivery pipe. Air in System. — The presence of air is indicated by the machine falling oJTin efficiency, and by jumping o( condenser gauge pomier To Clear System of Air before Charging Machine. CO, Machine.— Break joint between condenser liquid pipe and regulator and discharge air, etc., into atmosphere. Ammonia Machine.— ("lose stop cock B and disconnect gauge from delivery pipe fitting, then run machine slowly, and air will be discha^ed through this opening. The evaporator and condenser gauges will indicate a vacuum when the air is exhausted out of the symem. Testing of Gauges.— -After stopping machine, leave regulator full open and the two gauges should show identical readings, with the temperature shown corresponding (o that of the liquid brinc- ir»/a,ifaf S3©. J. Refrigeration 531 for a vaporisinc^ temperature of minus 15" Fahr., or higher or lower as required. Passing on now to a description of typical plants. The one described below is manufactured by the Liverpool Refrigeration Company Limited, Liverpool, and is largely used in the North Atlantic chilled beef trade. It is also equally applicable to the carriage of frozen goods, mutton, &c. As a rule, plants are fitted in duplicate. The diagram (No. 2) shows the essential parts and arrangement of this plant. We may here mention that, with few exceptions, the cold chambers on shipboard are entirely chilled by means of wrought-iron jjifiing arranged on the ceilings, sides and ends, and through which the brine cooled in the refrigerator is circulated. The plant before us is one of this type. Description of Plant. The ammonia compressor (No. 2) arranged in single, and in the duplex form, is direct steam driven, and is of the horizontal double- acting type. For convenience and for saving of space, the box bed on which the engine and compressors are mounted, contains the ammonia condenser, which consists of a series of coils of wrought-iron tubing in which the ammonia is condensed, the water circulating round the outside of the tubes. After passing the condenser, the liquefied ammonia collects in the reservoir AR from whence it passes through the regulating valve RV into the refrigerator, which is of the vertical type, and contains several circular concentric coils of pipe placed in a steel shell with covers top and bottom. The ammonia vaporises inside the coils, the brine circulating round the outside. After passing through the refrigerator, the ammonia is drawn back to the pump as shown, to be compressed and discharged at the higher pressure into the ammonia condenser for recondensation. The reader will please note that the ammonia circuit is complete, and there is no loss whatever of ammonia, which goes through the cycle of vaporisation, of compression, and condensation time after time indefinitely. The condensing water is supplied either by a separate pump, or from one of the ship's donke)'s, is drawn from the sea, pumped through the condenser, and overboard. The cold brine is drawn from the refrigerator by the brine pump, which is preferably one of the " Worthington " duplex or similar type, and is discharged to the distributing headers from whence, in several independent circuits, it passes through the pipes in the cold chambers, returning again to the return headers. Both distributing and return headers are fitted with controlling valves so that each brine circuit may be regulated as desired ; each circuit controlling a separate portion of the cold chamber. The temperatures may thus be regulated by allowing more or less brine to pass through any particular section of piping. The thermometers index the return temperature and are useful adjuncts in the regulating of the brine. After passing through 532 *' Verbal" Notes and Sketches the return header it goes backr to the refrigerator for recooHng, after- wards to go through the same cycle again and again continuousl}^ Pressure gauges are fitted recording the ammonia pressures both on condenser and refrigerator— high and low pressure— side, and also the brine pressure. A small brine tank is fitted for mixing brine, and is connected as shown, so that fresh brine may be introduced into the system to make up any loss from leakage, &c. The following extracts from the Liverpool Refrigefation Com- pan)''s Book of Instructions may be of use : — Pressures. — All ammonia pressures are absolute. The pressure on the ammonia condenser gauge will vary with the temperature and quantity of water passing through the condenser, and should generally vary from 120 to 180 lbs. per square inch. The warmer the con- densing water, the higher the pressure. The pressure on the refrigerator gauge may be regulated as desired b}' means of the regulating valve RV (see diagram), which should be adjusted to the brine temperature ; the higher the temperature, the higher the pressure. Evaporator Pressures. — The following table gives the approximate evaporator pressures and temperatures which should be kept to secure the best effects : — For brine temperatures of zero Fahr. - - - 24 lbs. 5° » - - - 28 10° „ - - - 32 15° M - - - 36 V „ 20° „ - - 40 >» » ^5° » - - - 45 " )> 35 )) " " " 55 » ). 50° » - - 70 The refrigerator pressure should, while approximating to these figures, be such that the discharge pipe from the ammonia compres- sion pump should not be warmer than can be easily borne by the hand, say roughly at a temperature not higher than 1 20^ Fahr. ; if warmer than this, open the regulating valve slightl)' ; if colder, close same slightly. The discharge pipe of the compression pump should never be allowed to get cold or ver}' hot, but should alwa}'s be kept as stated above. Compressor Gland. — Sufficient oil should alwa}'s be kept in this for the lubrication of the cylinder, and to keep the gland ammonia tight. The packing in the gland should alwa}'s be very carefull}^ fitted ; if slack and badly fitted, the oil will leak past the packing into the compressor in considerable quantities, which is undesirable. The least possible quantity of oil to keep the rods Kf:-.V\S*K mAGRAM OF MABIJVB 7TPB MACHIN£ S/fFW/MG C OJVM£Cr/OJiS. The Liverpool ^^efpjceration 6° L'^". O.C . D/scAarge CoeA on Compressor. S.C. Soe//on Coc/r o/> Compressor. O. T. Oir/ Trip on Sucrion Branei. AC A ir Coc* on Compressor />/seAfr fe S.G Ammonia Sue// on or ffefri fjrsfor Gaufe O.6 . Ammon/a Oisefiarge or Condenser Oau ^e . L_C. Ammonia Lifuic/ CoeA O.C OiV CooA for Drauiinf o/POi/ ^y. Ammonia P efu/e/inf l^a/ye C C C^d r^ing CoeJt SG Brine leisure Geu fe 6 fi S/an. u c E o bo U c bji '-t-> C3 rt *J^ Ui a C bo 'u c UJ Cki •o c rt rt 'c >. o •o B c 3 6 o < E 1 iS CO cit 6 E 2 V in case of leakage. The method of cooling the meat chambers is either b)' brine pipes, as has alread\' been described, or by blowing air by means of fans over nests of coils in which the liquefied 53^ Verbal " Notes and Sketches u O B V) J a> >« i-i c o. rt 6 a. F o o U U bo G o Si fi C 6 bo a < M «4-l o c r? o •o -4-> o o (l4 g 1 nt "=+ U) (It o E y, lU J3 H s Refrig^eration 537 ammonia is evaporated ; the cooled and dried air is then distributed throui^hout the meat chambers through wooden ducts or trunks. Haslam's machinery, working on the brine pipe system, is at the present time bringing chilled beef from the River Plate, a voyage lasting thirty days, with a variation of temperature of within half a degree on each side of a fixed point, the cargo being invariably landed in perfect condition. Haslam's double-acting ammonia compressor, of which we show a section, is fitted with suction and delivery valves in the end covers, which are made concave to give room for the valves ; the piston is turned an accurate fit for the covers so that the clearance is reduced to a minimum, being in fact considerabU' less than if the valves were placed in the c}'linder body, as is sometimes done. The special form of gland with two separate packings allows of either packing being adjusted independently of the other. The annular space between the packings is kept full of oil, and there is also a lubricator on the outer gland. The method of working these machines is generally as has been before described. The Carbonic Anhydride System. The general principle of this system is similar to that of the ammonia compression machine, in regard to the c\xle through which the refrigerating agent passes. This is made clear b)- the diagram given below, which consists of the following parts : — 1. The compressor (the only moving part), in which the gas draw n from the evaporator is compressed. 2. The condenser, consisting of coils, in which the compressed warm gas is cooled and liquefied b)' the action of cooling water. 3. The evaporator, consisting of coils, in which the liquid carbonic anh}'dride evaporates, producing an}' degree of temperature that ma\- be required, down to 80' below freezing point. We are indebted to Messrs J. & E. Hall Limited, Dartford, for the following description of their refrigerating machinery : — The difference between the Hall carbonic anhj'dride machine and the ammonia machines lies chief!)- in the employment of another refrigerating agent. Carbonic acid is gas which liquefies under a pressure of about 50 atmospheres under temperate conditions and about 75 atmospheres in the tropics, and the parts of the machine are constructed of sufficient strength to stand these pressures, and moreover are tested to 3-4 times the working pressure, as will be mentioned below. The efficiency of the refrigerating agent is found in these machines to be ver)' high, and the reduction of cooling effect due to higher temperatures of condensing water is found to be, in practice, about the same as that which occurs with other t\pes of refrigerating machines. 538 "Verbal" Notes and Sketches The charge of carbonic anhydride originally put into the machine is used over and over again, going progressively through the processes of compression, condensation, and evaporation, passing through a closed cycle. Thus a small quantity only is required to be added from time to time to replace any small losses, and for this purpose carbonic acid is sent in steel cylinders to any part of the world. The cost of Ink' ^«- No. 5.— Diagram of Messrs J. & E. Hall's Carbonic Refrigerating Machine. the material is only a few pence per pound. The quantity required for a complete charge is very small, the cost of a charge for a 24-ton ice plant being only about £y. Properties of CO.,. — Carbonic anhydride is a non-poisonous gas, and a constituent of atmospheric air. To give an idea of the freedom from danger of J. & E. Hall's patent refrigerating machines, it may be stated that the entire contents of the maciiine might be allowed to escape into an ordinary engine-room without any disastrous results or, in most cases, even inconvenience. Though it is not contended that an atmosphere containing only carbonic acid will support life, on the other hand, it has been found by careful experiments made by well-known scientists, that men can breathe fairly comfortably in air containing as much as 15 per cent, of carbonic acid, in which atmosphere one of the investigators remained for three quarters of an hour. Now the entire charge in the machines usually fitted on board ship by Messrs J. & E. Hall Limited is such that the atmosphere would not contain so large a proportion of Refrieeration 539 carbonic acid even if the whole charge escaped instantaneously from the machine into the main engine-rooin. The details of the machines are as follows : — Description of Hall Plant Compressor. — -The compressors for the large machines are bored out of solid steel forgings, partly to secure strength, but principally on Condenscf Co/ 1 Brine rcfurn Jhzrnjometer Paf^nf Safety Volve in here >.. / Cylinder^ Compressor.^ ^(jTc; Separator ^ PQ^e^f hollow I— fifV^" Oil Gland "^ Conmdmq Rod ^ Pbt cakhmcj Oil from Gland Condenser Gua^z Evaporator VGuage Regulator -Evaporator Xoil -Insulation round fuaporatof Water Circulahna Pump "" Condenser Cas/no No. 6. — Section of Hall Vertical Marine Type Machine. account of greater certainty of soundness of the matenal, and to provide a perfect bore in which may work the cup leathers with which the pistons are provided. Compressors of smaller machines are cast in a special bronze, which secures the two essentials of soundness and hardness. The suction and delivery valves are identical for facilities of interchange. Gland. — The gland is made gas-tight by mean:; of two cupped leathers on the compressor rod. A special lubricating oil is forced into the space between these leathers at a pressure superior to the 540 " Verbal " Notes and Sketches greatest pressure in the compressor, so that whatever leakage takes place at the gland is a leakage of the oil either into the compressor or out into the atmosphere, and not a leakage of gas. What little leakage of the oil takes place into the compressor is advantageous, inasmuch as it in the first place lubricates the compressor, and in the second place it fills up all clearances, thereby increasing the efficiency of the compressor. In order to replace the special oil which leaks out of the pressure lubricator, there is a small hand hydraulic pump, a few strokes of which are required to be made every two or three hours, as may be indicated by the position of the pressure lubricator piston rod. This form of gland is now in constant use on nearly 2000 machines supplied by J, & E. Hall Limited. Separator. — Any oil which passes into the compressor, beyond what is necessary to fill the clearance spaces, is discharged with the gas through the delivery valves. In order to prevent this passing into the condenser coils, all the gas is delivered into a patent separator. The oil drains to the bottom of this vessel, whence it is drawn off from time to time ; meanwhile the compressed gas passes off by an opening at the top on its way to the condenser. It may here be remarked that the oil has no affinity for carbonic anhydride, hence it undergoes no change in the machine, and there is, therefore, no fear of the coils becoming clogged by any small amount of oil which might be carried over in spite of the separator. Condenser. — This consists of coils of copper tube, which are placed in a tank and surrounded by water, similar to the condenser of a steam-engine, with, however, the gas inside the tubes and the cooling water outside. These coils are welded together into such length as to avoid altogether any joints inside the tank, where they would be inaccessible. The welding of these pipes is all done at J. & E. Hall's works by the electrical method, which gives very good and reliable results. In connection with the condenser, one very important advs.ntage of carbonic acid machines is apparent, for as carbonic acid has no chemical action on copper, in the numerous cases where sea water only is available for condensing purposes, that metal is used in the construction of the coils. Evaporator. — This also consists of nests of wrought-iron hydraulic pipes electrically welded up into long lengths, inside of which the carbonic anhydride evaporates. The heat required for evaporation is usually obtained either from brine surrounding the pipes, as in cases where brine is used as the cooling medium, or else from air surrounding the pipes, as in cases where air is required to be cooled direct. Between the condenser and evaporator there is a regulating valve VERTICAL MARINE TYPE CO^ MACHINE. By Messrs J. & E. Hai.l, Limited. Verbal " Notes and Sketches. [ To face /<7. Y 540. Refrigeration 541 for adjusting the quantity of the liquid carbonic anhydride passing from the condenser. J. & E. Hall's Patent Safety Valve. — In order to enable the compressor to be opened up for examination of valves and piston without loss of carbonic anhydride, it is necessary to fit a stop-valve on the suction and delivery sides, so as to confine the carbonic anhydride to the condenser and evaporator. It is, of course, possible for a careless attendant to start the machine again without opening the delivery valve, and in such case an excessive pressure would be created in the delivery pipe, from which there would be no outlet. To provide against this danger a patented safety device is adopted, consisting of an ordinary spring safety valve, at the base of which is a thin copper disc, which is designed to burst at a pressure consider- ably below that to which the machines are tested. This disc is made perfectly gas-tight, an object which could not be attained by the spring safety valve alone, and the latter only comes into play when the disc is ruptured. Great care is necessarily exercised in making the discs to provide against variation in strength, due to any variation either in the thickness or hardness of the copper sheets out of which the discs are made. Joints. — With regard to the joints to withstand the pressures, those which are not subject to a high temperature can be made absolutely tight with any suitable material, such as leather, but for the hot joints, special rings are supplied which withstand the heat and still have the necessary elasticity to ensure the joint being perfectly tight when either hot or cold. The absolute tightness of all joints is effectually tested by brushing them over with soap and water, the slightest leak being thereby detected. Testing Parts. — Very careful tests are carried out in J. & E. Hall's works to ensure perfect soundness of all parts subject to the gas pressure. The working pressure varies from about 750 lbs, per square inch in temperate climates, with water at 50' Fahr., to about 1 1 25 lbs, with water at 84"^ to 9o\ as is usual in the tropics. Owing to the very small diameter of all parts, even in large machines, there is no difficulty in securing a very ample margin of strength. All parts of machines subject to the pressure of the carbonic anhydride are, in the first place, tested for strength by hydraulic pressure to 3000 lbs. per square inch, and they are then again tested while immersed in warm water by air to 1350 lbs, per square inch, whereby the slightest porosity which might exist in any of the materials is at once detected bv air bubbles ascendinsT throuorh the water, * Extract from Paper read before the British Association by Mr E. Ilesketh, M.Inst.C.E., M.I.iMech.E., Managing Director of J. & E. Hall Limited. 14th September 1895. ^42 " Verbal " Notes and Sketches Refrigeration. — As a refrigerating agent, liquefied carbonic acid is second to none. Under atmosplieric pressure it evaporates from the liquid state at the particularly low temperature of 120° f"ahr. below zero, or 152° below the freezing point of water. In J. & E. Hall's refrigerating machine, however, it is caused to evaporate at only a few degrees below the temperature of the material which it is desired to cool, the principle of the machine being exactly the same as that of machines using anhydrous ammonia on the com- pression system — viz., as water boils at 212° Fahr. under atmospheric pressure, and about 250° Fahr. at 15 lbs. pressure, fire being usually the source of heat, so liquid carbonic acid boils or vaporises at 30° Fahr. at 35 atmospheres' pressure, and thus permits cold water or colder brine to be the source from which the necessary heat to boil it is absorbed, exactly in the same manner as the heat of the fire is absorbed in boiling water. The compressor draws the gas or vapour from the evaporator and compresses it to the liquefying pressure, which is controlled within certain limits by the temperature of the cooling water. The heat due to compression is absorbed by the cooling water in the condenser, the gas circulating within the condenser coils and becoming liquefied by the time it reaches the lower extremity of these coils. We are able, by regulating the pressure in the evaporator, to cause the liquid to boil throughout the coils of the evaporator, which act in the same manner as the heating surface in a steam boiler, and the temperature or boiling point of the liquid carbonic acid adjusts itself to that of the source of heat which is causing it to boil, whether it be water at 70" to be reduced to 40 , or brine to be maintained at + 10' Fahr. or — 10° Fahr. The surfaces of the evaporator coils are so proportioned that all the liquid which enters at the lower end of the coil is evaporated by the time it reaches the top end, and thus the maximum efficiency is obtained. The compressor then draws in only gas, and compresses it up again to the pressure necessary to liquefy it, and delivers it warm to the condensing coils to continue the cycle of operation.* The vertical marine type machine, illustrated on the preceding pages, consists of a single vertical steam cylinder, with the compressor arranged alongside of it, both secured to a casting containing the condenser coils, which are made of copper, and behind this casting is another secured to it containing the evaporator coils, the whole making a very compact and accessible design. These small machines are perfectly simple, work quite noiselessly, and can easily be worked by a person of ordinary intelligence from the printed instructions supplied with each machine. They need very little attention, and the wear and tear and consequent need of repairs is almost nil. No increase in the staff of engineers is necessitated, as * ?:xtract from Paper read before the Institute of Brewing, by Mr Alex. Marcet, A.M.Inst.C.E., Managing Director, J. & E. Hall Limited. May 1894. < Q O £ U :: W ""- Oh :: J w H . ^ "-> O ^ s: ^ 5 2 Refrigeration ^42 they can be placed in any available corner of the engine-room, where they come under the e)e of the engineer on watch. The complete charge of carbonic anhydride in the machine is so small that it may be allowed to escape into the engine-room without the slightest inconvenience. A patent safety valve is fitted so that no No. 7.— Patent Safety Valve, Hall Machine. mistake or neglect on the part of the attendant can cause an}'thing like an accident. Instructions for Charging and Working. Before Charging. Pressure Lubricator. — Fill receptacle above hand pump with Vacuum Dartford Refrigerating Oil, and pump this into the pressure lubricator by means of hand pump till piston is at inner end of stroke. Compressor. — In a vertical machine put piston at bottom end of stroke, take off cover and about one-fourth fill compressor with Vacuum Dartford Refrigerating Oil. Replace cover. In a horizontal machine, take out one of the delivery valves and put piston at the other end of the compressor. Then about one-fourth fill compressor with Vacuum Dartford Refrigerating Oil. Replace the valve. Pull machine round twice, then run machine for a quarter of an hour, all screw-down valves being open. After this commence charging. Charging. — The CO2 is supplied in steel flasks of various sizes containing from 22 lbs. to 40 lbs. each, as stamped on flask. About * lbs. constitutes a charge. Suspend the flask, valve upwards, on the spring balance, and connect by copper pipe provided to small screw-down valve at end of evaporator coil. Note the weight. Open valve on flask and on 36 * Varies according to size of machine. 544 "Verbal" Notes and Sketches machine. See that the connecting joints, which are made with leather washers, are tight. After the CO^ has passed into the system, note weight again, and the difference is the weight of COg passed into the machine. When flasks have had lo lbs. taken out (not before) they may be warmed by pouring on hot water to assist in driving out further gas. While this proceeds the lower end of flask will remain cold so long as liquid CO., remains, but when the whole flask has become heated, no more liquid CO., remains, and valve should be closed while flask is still warm. To get the utmost out of the flask before closing its valve the evaporator should be pumped down to say 1 5 atmospheres (on outer circle of gauge) by running the compressor for a few minutes with closed regulator. When first charging, blow the air out of the system by breaking the joint between the regulator and pipe leading to it from condenser, the regulator being closed, and all other valves open, and blow some CO., to waste according to size of machine, thus : — Up to No. 9 Machine - - - - 2 lbs. >> )) '3 )5 " " " " 5 " ,) „ 16 „ - - - - 10 „ » » 20 „ - - - - 20 „ As the pressure, while charging, rises, carefully examine all joints. The slightest leaks become visible when painted with soap and water lather. Gauges. — The COg gauges on condenser and evaporator show on outer circle the pressure in atmospheres, and on inner circle the corresponding temperature of CO.,. (When logging, the inner circle only should be recorded, figures in red on the gauge being entered in log with a minus sign thus : -15" denoting 15° below zero.) Working Conditions. — Having fully charged, start the machine, and adjust the regulator {i.e., inlet valve of evaporator coil) so that the evaporator gauge indicates on inner circle 10° to 15" Fahr. (6° to 9" Cent.) below the temperature of the brine leaving the evaporator. If the machine be sufficiently charged, the condenser gauge will indicate usually some 15" Fahr. (8° Cent.)* above the temperature of the water entering the condenser. (Note. — This varies with the quantity of water passing condenser, and is correct if the water outlet is 10° fahr. higher than the inlet. If the rise in temperature of water is only 5° Fahr. the gauge should stand about 12° above water inlet. If the rise in temperature of water is 20" Fahr., the gauge should stand about 20" above water inlet.) Refrigeration 545 An excessive charge is indicated by the gauge standing higher, and a very excessive charge by a considerable fluctuation of the pointer. Under ordinary working conditions, the compressor should be cold or partly covered with snow, and the delivery pipe from it should be rather warmer than the hand can comfortably bear. If the delivery pipe is not hot enough, slightl)' close the regulator, when the temperature will quickly rise. If compressor becomes warm, it points to regulator being insufficiently open. If unable to obtain the indications given above on condenser gauge, then the s}'stem is short of gas.* As a further test of this close the regulator : if sufficient gas is present, the evaporator gauge should hardly fall for some fifteen or more revolutions of machine. If the gauge falls immediately, without any pause, it indicates shortness of CO.,. If in doubt as to sufficiency of charge add more ; some extra gas in the system, up to one-fourth of a charge, will be far more beneficial than a slight undercharge. If machine is short of gas, the refrigerat- ing work done will be but a fraction of its proper duty. A rise of several degrees of temperature of inlet cooling water will necessitate the addition of CO.^ in order to keep machine fully charged, and similarl}' a fall in temperature may cause indications of overcharge. Brine. — The density should be regulated by the addition of calcium chloride till the densimeter supplied floats at central mark, which is 40° on Twaddell's Densimeter, or till one gallon weighs about 1 2 J- lbs., that is, a specific gravity of about 1-25. The brine should be made in a separate vessel, and lumps of calcium should not be thrown into the evaporator tank for fear of choking the pipes. It is important that sea water should not be used. Common salt (sodium chloride) may be used instead of calcium chloride, but to prevent corrosion, for every 100 lbs. of salt used i lb. of caustic soda is to be added. In machines fitted with open evaporators there should be sufficient brine in the s}'stem to ensure the evaporator coils being entirely covered by about 6 inches when machine is running. In machines fitted with closed evaporators the cock on air pipe must be kept slightly open to prevent air collecting in evaporator. Compressor Piston and Rod. — The machine is fitted with a double or single acting compressor. Whenever replacing piston observe the following instructions : — * (Note. — In above instructions as to working conditions it is assumed that the valves and piston leathers are in good order. If doubt exists as to this, proceed as explained under heading " Test.") 546 "Verbal" Notes and Sketches For Double- Acting Compressor. — As the clearances between the piston and the ends of compressor are very small they must be maintained , equal at both ends. Always bar round before starting after replacing piston. The piston is packed with hydraulic leathers which will require examination and renewal occasionally. The compressor rod must be kept in a highly polished state and free from any marks, and if machine is lying idle, the rod should be removed and kept well greased in a dry place. It is very necessary that the nut securing the piston leathers should be well screwed up and locked ; when new leathers are put in, it is advisable, a icw hours after starting, to tighten the nut up again. (See instructions under " To Examine COMPRESSOR.") Compressor Valves. — The suction and delivery valves will require occasional examination and cleaning. A set of spare ones should be kept ready for use. * The valve seats are separate from the compressor and make double joints : see that both copper rings are equally crushed by the valve casing. Leakage at the outside joi?tt will indicate itself outside, but at the inner Joint will not be perceptible except in reducing the work done by the machine. Test. — To test the working of the compressor, close the regulator, when evaporator gauge should be pumped down from say 25 atmo- spheres to 5 atmospheres in about 200 revolutions. If slower, either the valves or the piston leathers are faulty, or the regulator may be leaking. Compressor Gland. — This is packed with two hydraulic leathers and compressible rings, between which a pressure of Vacuum Dart- ford Refrigerating Oil is maintained by the patent automatic pressure lubricator provided. The gland should be screwed up hard enough to compress the rings, and will require tightening up occasionally, but this should not be done while running. The pressure lubricator will require pumping back when its piston has moved 4 inches, but this should not occur at least under three hours if the gland leathers and compressor rod are in good order. The pressure lubricator valves must be full open, otherwise, though not easily observable, the gland cannot be gas-tight. The oil which leaks from the gland should be caught, and after filtering and separating any water from it, used over again. Separator. — Any oil passing into the compressor will be caught in the separator and must be drawn off every second time of pumping * For steel block compressors only. Refrigeration 547 up pressure lubricator, or oftener if much oil is passing in, by slackening drain plug, and after filtering it may be used over again. COg. — This must be pure and free from water and air. If the gas cannot be obtained dry, a CO., dryer should be fitted to the machine. As a precaution against moisture each flask should be suspended valve down for some twenty-four hours before using, and then by very slightly opening valve any water present will escape. Gland Oil. — As an improper oil may cause trouble, it is strongly recommended that only Vacuum Dartford Refrigerating Oil should be used. This is obtainable from the Vacuum Oil Co., York House, Norfolk Street, London, W.C., and its branches. Strainer. — On suction side of compressor is a strainer, which should, with a new machine, be taken out and cleaned after the second day's working, and afterwards occasionally if required. Stopping and Starting. — When stopped for some days, the screw- down valves on suction and delivery of compressor should be closed, but no other valves. For shorter stoppages, no valves need be closed. The gauges will then equalise, standing at temperature of brine in evaporator. Before starting, care should be taken that any valves closed are reopened, but should this be neglected a safety valve is provided to relieve the pressure. If machine is run at constant speed the regulator should require very little alteration after being once adjusted. Speed. — The machine should run* revolutions per minute. Leakages. — It is very necessary that all pipe joints and glands of valve spindles should be carefully examined with soap lather and kept tight. For the first few days especially they should be examined daily and all bolts and gland nuts screwed hard up. The most minute leak must instantly be stopped. To Examine Compressor. — Close the suction and delivery screw- down valves, also the valve between pressure lubricator and gland, and slack off a joint to let the gas escape. Make sure all pressure is gone before opening up. * According to size and type of machine. 548 "Verbal" Notes and Sketches Stores and Spares. — It is recommended that a supply of the following be kept on hand : — Flasks of CO2. Vacuum Dartford Refrigerating Oil. Calcium Chloride. Compressor Piston Leathers. Compressor Gland Leathers. Pressure Lubricator Leathers (two sizes). Compressible Rings for Gland. Set of Delivery Valves. Set of Suction Valves. Set of Bronze Joint Rings for Compressor. Compressor Piston Rod, highly polished. Safety Valve Discs. Possible Causes of Trouble. 1. Owing to leakage, or to a rise in temperature of condensing water, the machine may become insufficiently charged. Remedy : — Add more gas until COg gauges show indications under heading " Working Conditions." 2. Gland leathers may be worn out. This will be indicated by pressure lubricator piston working out to its full stroke in one hour or less. Remedy : — Renew gland leathers, carefully examining piston rod for roughness ; if necessary use spare rod, and repolish rod taken out. NOTE. — This may also rarely be caused by a defective piston leather in the pressure lubricator itself. 3. Piston leathers may be slack at nut or worn out. This will be indicated by compressor failing to pump out evaporator as indicated under heading " Test." Remedy : — Tighten piston nut, or, if necessary, change piston leathers. NOTE. — The same indications may be caused by the valves being worn or stuck up, in which case they must be examined, cleaned, and, if necessary, repaired. 4. Irregular action of evaporator gauge and also the delivery pipe from compressor changing from hot to cold frequently without apparent reason, indicates that there is some foreign liquid present in the system, probably oil from pressure lubricator which has not been drained from separator. Remedy : — Slack joint between liquid pipe and condenser outlet coil box, and allow foreign matter to escape. Also open the valve on evaporator coil used for charging machine and blow out any oil, &c., present. Also drain separator frequently till trouble ceases, and then drain it according to the instructions. As an alternative remedy when brine is not at a low temperature, run the machine with regulator full open for ten minutes, then close Refrio'eration v> 549 regulator to working position, and, as soon as compressor delivery is warm, drain separator, 5. Evaporator gauge may register a much lower temperature than stated under " Working Conditions" in spite of further opening of regulator. This may be due either to the evaporator casing being partly empty or to the formation of ice on the outside of the coils owing to the brine density being insufficient. 6. Gauges sometimes give false indications — To test this, both gauges should indicate alike when the machine is stopped, regulator remaining open. They should then both indicate the temperature of the brine surrounding the evaporator coils. 7. Condensing water pump may be out of order, or the supply of water may be insufficient. This will be indicated by unusually high condenser pressure, and high temperature of overflow water. Remedy: — Examine water pump or increase water supply. 8. Do not run machine faster than these instructions state. If not effecting usual refrigerating work, ascertain fault and apply remedy. 9. Hand pump on pressure lubricator may refuse to work. Remedy: — Examine and clean the valves of hand pump and small strainer covering suction. In case CO.2 has got in between the gland leathers, slack joint of guard round pressure lubricator piston rod, allowing gas to escape, 10. When cooling chambers, loss of efficiency is sometimes due to the chamber doors (i) being open too often, or (2) being left open, or (3) shrinking and becoming a bad fit. The cold air will then flow out and necessitate machine running many more hours than necessary. Doors can be tested for tightness by closing them on slips of paper which will then be nipped if door fits tightly. Log. — It is advisable to keep a log, recording especially speed, indication of gauges, temperature of condensing water, in and out, and brine, in and out Compare present log with past logs, and if any falling off is indicated, ascertain the cause and apply remedy. As a guide, a form of log is appended. Assistance. — J. & E. Hall Ltd. gladly give advice to users of their machines, but letters explaining any difficulty experienced should always be accompanied by a log of actual working in the form appended. Important. — WJienever consulting makers as to any point in ivorking of machine, send them a log giving the follozving particulars so far as they apply ^ and always give number cast on machine. 550 "Verbal" Notes and Sketches Time. Hours run per Day. Revolu- tions. Steam. Vacuum Brine. Gauges Inner Circle Cooling Water. Return to Evap. Outlet from Evap. Evap- orator. Con- denser. Inlet. Outlet. Readi ngof G auges f if teen r ninutes after st opping Haslam CO2 Machines. The Haslam Foundry Company Ltd., of Derby, are also large makers of COg machines, so that the following description of this firm's machines will be of interest : — The arrangement and general construction is practically similar to that already described, the smaller machines being made vertical and self-contained, and either steam or belt driven. The condenser for use on land is a coil of heavy wrought-iron pipe, but on board ship, copper pipe is used. The larger machines are made horizontal, and the marine type duplex, as shown by illustration on page 551. The condenser is here contained in the bed, but in the large machines it is in a separate casing ; the evaporator is also in a separate casing. Messrs Haslam fit a safety valve to all their machines. These machines work either with the brine pipe or air circulation system. NpTE.— See page 554 for notes on COo and Ammonia, and method of charging machme with gas. Arrangement of "Haslam" Plant on the CO2 System. The plate opposite represents a cross section through a ship, showing the arrangement of a Haslam refrigerating plant on the CO^ system. The ships are so arranged that they are capable of COo SYSTEM ON SHIPBOARD. By Messrs The Haslam Foundry and Engineering Co., Limited, Derby. " Verbal " Notes and Sketches. [ To Jace page 550. Refrigeration 551 carrying a mixed cargo, such as frozen meat in the holds and fruit in the 'tween decks, or a general cargo, such as butter, eggs, cheese, poultry, fish, &c. The holds are fitted with brine pipes, under the W^^*fi .r: ni u E nl o 2 ■- ho > It W CTUU-V- r »,, ^ II. Colo Chamber OR Refrigerator Srlr H^ Cooling Water Inlet Press 50 Lbs, No. II. — Diagram of Compressed Air System. VERTICAL ELKCTRICALLY-DRIVKX CARBONIC ANHYDRIDE REFRIGERATING MACHINE. ADMIRALTY TYPE. Verbal "' Notes and Sketches. [To face fa^e 556- Refrigeration 557 lated by a separate pump. Here the air is cooled down to a few degrees above the circulating water temperature and delivered to the No. 12.— Vertical Type Haslam Dry Air Machine. air expander, where it is allowed to expand behind the piston, doing mechanical work by assisting to drive the air compressor. The expanding air thus gives up heat in the form of work, and is thereby 558 "Verbal" Notes and Sketches reduced in temperature to about —90° Fahr. The air is then dehvered into the cold chamber at one side near the top, and, circulating through the room to the return trunk, is drawn again to the com- pressor, the cycle thus being complete. In most cases patent drying pipes are fitted in connection with the above apparatus, their function being to dry the compressed air before it is expanded. This is done by passing it through tubes round which is circulated the returning air from the cold rooms. By this method the compressed air is cooled, and any moisture is deposited in the " dryer " and discharged through cocks or valves at the bottom. Sir A. Scale Haslam has developed the compressed air machine from its experimental stage, and machines built by his firm were the first to carry successfully large cargoes of frozen meat from the colonies. We now give illustrations and descriptions of machines as built by the Haslam Foundry and Engineering Company Ltd., of Derby. The machine here illustrated is of the vertical type, and is capable of circulating 8ocxd cubic feet of air per hour. It is driven by a com- pound steam-engine, the steam cylinders being arranged tandem ; the steam supply is controlled by a piston valve in each cylinder, actuated by a single eccentric. The compressor, arranged alongside the steam cylinders, is double acting and water jacketed, and has hollow covers of brass in which are the suction and delivery valves of phosphor bronze. The air expander, placed alongside the compressor, is also double acting and has main and cut-off valves, the latter being adjustable. The ports of this cylinder are made as short and direct as possible to avoid choking with snow, which in small machines not fitted with drying pipes would otherwise give trouble. Across the back of the machine is arranged the air cooler, similar in construction to an ordinary steam surface condenser, in which the compressed air on its way to the expansion cylinder is cooled by the sea water surrounding the tubes, A water-circulating pump is fixed to bed and driven from crank-shaft. The next illustration shows Haslam's duplex compressed air refrigerator, capable of circulating 180,000 cubic feet of air per hour at 90' below zero (Fahr.). It is specially arranged to work in the 'tween decks of a ship, and is duplicated so that either side of the machine, consisting of one steam cylinder, one compressor, and one expansion cylinder, can be worked separately in case of accident to the other side, thus giving greater security to the cargo. The machine is fitted with steam surface condenser, air, circulating, and feed pumps, contained within the soleplate, the pumps being driven by a rocking shaft worked from either crosshead pin. When worked as one machine the steam cylinders work compound. The drying pipes are separate nests of tubes, and are not shown in the illustration. The plate illustration opposite shows the usual arrangement of the refrigerating machine, drying pipes, and air trunks as fitted on board a steamer, and is a good type of a large cargo installation. The holds ^ Refrigeration 559 G u Q a CO Q O. 5 o U byo a a ■& B w •a c ex, 3 4) o --' 37 56o "Verbal" Notes and Sketches and upper and lower 'tween decks are insulated. The air trunks ar6 made collapsible when not in use, and are arranged on both sides of the ship so that a perfect circulation is obtained, and by an arrangement of doors the direction of the air current may be reversed at will. The 'tween decks may be used for carrying cheese or other produce not requiring so low a temperature as the meat, and are then cooled by the air returning from the holds to the machine. The vertical trunks on each side of bulkhead connect to the longitudinal trunks at sides of ship ; the connection is made separately on each side of bulkheads to obviate the necessity of cutting the bulkhead and fitting watertight doors. Two duplex machines are fitted side by side, and on the upper deck, so as to be directly above their work. Haslam Dry Air Machines. Pressures and Temperatures. Air entering Compressor „ leaving „ ,, entering Cooler „ leaving „ - - . ,, entering Dryers „ leaving „ . - - 5, entering Expander - ,, leaving „ _^ - Cut-off in Expander, | stroke. Sea water, 64" Fahr. Air leaving chamber at 20" is raised to 32" to 36° on entering compressor usually, but if the return pipe in engine-room is not sufficiently lagged, the temperature rises, as shown in the above log, to 40' or 45'. Compressor and Expander Cylinder Diagrams. — Observe that the pressure entering the compressor is rather less than that of the atmosphere, as the initial pressure line is just below the atmospheric TEMR 280° Gauge Pressure- in lbs. Temperature. Degrees Fahr. 50 40° to 45° 280° 50 280° - 50 - 50 49 49 67° 67° 32° to 36° 32° to 36° - I to 2 -90° to - 100 TEMR 40° No. 14.— Diagram from Compressor. Refrioferation 561 line ; also that the pressure rises to 50 lbs. (gauge) and the tempera- ture to 280 Fahr. The air at 50 lbs. pressure and 280^ temperature is discharged into the cooler, where most of the heat (work) is carried off by the circu- lating water passing through the cooler overboard, so that the air, still at 50 lbs. pressure, is now reduced to a temperature of 6"]" Fahr. TEMP 36° AT.yNE -90" No. 15. — Diagram from Expander. This necessary loss of heat in the cooler accounts for the difference in area in the compressor and expander diagrams, and means that work at least equal to the loss must be given out by the steam cylinders of the machine. In the expander diagram, which is of less area than the com- pressor diagram, notice that the compressed air enters the expansion cylinder at a pressure of 49 lbs. and a temperature of only 36' Fahr., so that when the air is cut off at three-eighths stroke it expands and falls in pressure to about i or 2 lbs. above the atmosphere ; but the fall in temperature is very much more in proportion, as work is being done by the air in assisting to drive the expander piston. Briefly, b)' the combined effects of low initial temperature, expansion, and work done, the exhaust temperature is reduced to —90'' Fahr. or to — 100^ Fahr, NOTE. — If the air merely expanded without doing work the pressure would drop, but the temperature would remain constant ; as, however, work is done on the expander piston by the air, heat is lost and the temperature lowered. One B.T.U. disappears for every 778 foot-pounds of work done. General Notes on Refrigeration. Pressures and Temperatures. For a sea temperature of about 70° the following are the average pressures and temperatures required for the three systems of refrigera- tion obtaining in ordinary marine practice — cold air, ammonia, and CO.,:— 56: Verbal " Notes and Sketches Medium Employed. Cold Air - - • Ammonia (NH^) Carbonic Anhydride (COo Absolute Pressure. Temperature Fahr. 1 7 lbs. (Expander exhaust) 65 „ (Compressor) 25 ,, (Evaporator) 170 ,, (Compressor) 280 ,, (Evaporator) 1050 ,, (Compressor) -90 . 280°. - 6° (Brine - 4°). 85° (Sea 70^). ^ - 6" (Brine - 4°). 85° (Sea 70°). NOTE.— In the Ammonia and CO., systems with brine circulation the brine temperature would be somewhere about - 4' Fahr. for the pressure and temperature of the gas as given in the Table. Notice that the brine temperature is above that of the Ammonia or CO.2 in the evaporator coils, and that the sea water tempera- ture is below that of the Ammonia or COo in the condenser coils (from 12' to 18'' difference in each). Temperature Difference. — For the cooling effect required, it is necessary that a difference of temperature should exist between the gas in the condenser coils and the circulating sea water, the latter being the lower temperature of the two, so that the excess heat picked up by the refrigerant from the brine in the evaporator may be trans- ferred to the circulating water and so carried over the side. It will thus be obvious that if the sea water rises to a temperature of, say, 80'' Fahr., then the temperature of the Ammonia or CO^ must be in excess of this by 8^ or 10'' to allow of heat transfer, and to obtain this difference of temperature the pressure of the gas must be increased in due proportion. For a gas temperature of 90" the ammonia pressure would require to be 180 lbs., and the CO2 pressure 1 140 lbs., and if the sea tempera- ture rose to 85" and the gas temperature is to be, say, 93°, the ammonia pressure would require to be 200 lbs., and the CO., pressure 1180 lbs. per square inch ; so that the higher the sea temperature the higher the pressure required in the compressor to still maintain the necessary temperature difference. Ammonia (NH3) evaporates at a temperature of —37° when the pressure is 14-7 lbs. (atmospheric) and has a latent heat of evaporation of555B.T.U. Leaky Compressor Piston and Valves. — i. Leaky suction valves show by a rise on the evaporator gauge. 2. Leaky delivery valves show by a rise on the evaporator gauge, and a variation in pressure on the condenser gauge. 3. Leaky compressor pistons show by a rise on the evaporator gauge and a fall on the condenser gauge. To Test if Brine is Corrosive. — Immerse a piece of bright iron in Refrigeration 563 the brine for a period of, say, two clays, and the iron will remain unchanged if the brine is non-corrosive. Air Extraction (Ammonia System). — In extracting air from the system by means of the air cock on top of condenser coils, for safety it is adv^isable to connect up a flexible length of tubing from the cock, the other end of the tube being immersed in a bucket of water. When the air has all passed out any ammonia which follows will be absorbed by the water, and the smell of which will indicate when to shut off the cock. Previous to repacking the gland or piston the ammonia contained in the compressor can be got rid of by the same method, first closing the hand suction and delivery valves. Overhauling- Compressor (Ammonia System). — In opening up the compressor or any other working part of an ammonia machine the gas should first be got rid of by thorough ventilation, otherwise a light brought near may produce an explosion. Brine Temperature Difference. — The difference in temperature between the outgoing and return brine should be from 3" to 5" Fahr. CO., evaporates at a temperature of — 120" at an atmospheric pressure of 14-7 lbs., and has a latent heat of evaporation of 130 B.T.U. Cold Air System. — For good efficiency the following points require attention : — 1. Tightness of pistons, valves, of compressor and expander, also Cooler and Dryer tubes. 2. When starting up machine after standing idle for some time, all relief cocks should be kept open, and the machine run for some time before drawing the air direct from the cold chambers. 3. The following temperatures should be regularly taken : — A. Air temperature before entering compressor. B. ,, ,, after leaving compressor. C. ,, ,, before entering expander. D. ,, ,, after leaving expander. E. Cooling water temperature. 4. Drains on Cooler and Dr}-er to be opened at regular intervals. Joint Testing. — To test for gas leakage at joints or connection soap lather is employed, and bubbles form if leakage exists. Brine Temperature. — The brine temperature kept is about 8' or 10° lower than the temperature of the cold chamber, so that if, say, fruit is to be maintained at a temperature of 16 Fahr., then the brine temperature should be 8 Fahr. SECTION X INTERNAL COMBUSTION ENGINES. General. The gas engine is now rapidly coming to the front in marine practice, and (on the Continent particularly) is being effectively developed for use at high powers. The chief difficulty, so far, is that of reversing, but this has been overcome to some extent by the use of compressed air, which, forced into the cylinder, changes the direction of piston travel and thus reverses the engine. The four- stroke engine is still more in evidence than the two- stroke type, but the latter system has been much improved and perfected of recent years. Some foreign makers build gas engines of the double-acting type, but the reliability and efficiency of this s}^stem has yet to be proved. Advantages. 1. Boilers deleted. 2. Smaller bunker space (petrol or petroleum tank) required. 3. Instant starting (with petrol). 4. Ease of manipulation. 5. Cleanliness. 6. Economy. 7. Reduced staff. Disadvantages. I. Ignition and other troubles. 3. Danger from petrol and petroleum vapour. 6. Difficulty of reversing^ 7. Complication of machinery with engines of large power. 8. Deposits of carbon in cylinder heads. 9. Difficulty of revolution speed control. Producer Gas. In land installations, gas obtained by the "Producer" system is used, and this has also been experimented with in marine practice. It is the opinion of many eminent engineers that this is the best method of running internal combustion engines. In the producer sj-stem the 564 Internal Combustion Engines 565 gas instead of being obtained from oil, is produced direct from coal by heating, the appliance being known as a "producer." This, of course, necessitates the carrying of coal and the use of furnaces, &c., whereas in the case of oil, the oil only is carried in the tanks, and is No. I.— Dowson Suction Gas Producer. 1, Coal hopper. 2, Incandescent coal. 3, Coke scrubber. 4, Water supply to scrubber. 5, " Water seal." 6, Gas outlet to engine. 7, Funnel, 8, Water inlet to boiler. 9, Boiler (low pressure). 10, Ashpit. 11, Hand fan for starting- up. 12, Funnel shut-off valve. 13, Water overflow pit. 566 "Verbal" Notes and Sketches supplied direct to the cylinders, after heating by means of a heating lamp to produce vaporisation. Producer System. The gas is obtained b}' passing a jet of low pressure steam and air through a mass of incandescent fuel. The orincipal parts of the appliance are : — 1. Producer. 2. Cooler and scrubber. 3. Small steam generator. 4. Hand-driven fan for starting up fire. Producer. — This is a vertical cylinder chamber with a coal feed hopper at the top, into which the coal (usually Anthracite) is tipped : at the bottom is a fire-box with the ordinar\' fire-bars and furnace door. Cooler and Scrubber. — The scrubber is filled up with water (" water seal ") for a short distance from the bottom, and the gas entering from the producer enters below the water level, thus forcing the gas through the liquid for cleaning purposes ; the upper part of this chamber contains lump coke, and has a water drip from the top ; the gas passing up and through the coke is purified or scrubbed of the tarry substances which ^^•ould otherwise cause trouble in the engine by depositing in the valves, c}dinders, &c. Steam Generator. — This is a smaller boiler fitted on the producer to obtain steam for admission to the incandescent fuel, so that the gas may be produced b)- the chemical action resulting. Action. — The general action of the producer is as follows : — After lighting the fires and using the hand fan to create a draught, when the heat is sufficiently strong, the funnel outlet valve is closed and the coal gases pass into the water of the cooler, thence to the scrubber, and from there by suction to the oil engine cylinders, to be com- pressed and fired in the usual way. The steam generated in the small boiler together with air passes down a pipe and enters the producer among the fuel ; in doing so the steam (H.3O) is decomposed by the heat of the coal, and H)-drogen and Oxygen are set free. These gases combine with the carbon of the coal to give CO or Carbonic Oxide, and this, together with the H3'drogen, passes to the top of the producer chamber, then to the cooler and scrubber as previously described. Therefore, producer gas is obtained by passing air and steam through the heated fuel, and the chemical reactions which take place are as follows : — 2C + 0. = 2CO. C + H,o'^CO + H,. In other words. Oxygen of the air combines chemically with Carbon Internal Combustion Engines 567 of the fuel to produce CO (Carbonic Oxide), and the water (steam) is decomposed and forms more CO, also free Hydrogen. CH^ (Marsh Gas) and CO., are also formed during the heating process, so that we have as a result — Combustible gases = CO, H.>, CH^. Incombustible ,, =CO.j, N.j. The average chemical composition of producer gas is as follows : — CO (Carbon Monoxide) .... about 30 per cent. H (Hydrogen) - - - ,, 15 " CH^ (Marsh Gas) - - - ,, i „ C0.> (Carbonic Acid) - - - - „ 6 ,, N (Nitrogen) - - - - - - ,, 48 ,, Efficiency. — The efficiency of producer j^lant is about 80 per cent. Consumption. — The coal consumption per I.H.P. per hour varies from about -9 lb. coal at low powers to about i| lbs. coal at high powers. Heat Value. — The heat value of producer gas varies from 140 to 180 B.T.U. per cubic foot of ga.s. Test Burner. — A testing burner is fitted on the pipe leading from the producer to the cooler, and this when lighted indicates the quality of the gas which, if satisfactor\', is allowed to enter the cooler, but which, if not satisfactor}-, is allowed to pass up the waste gas funnel. NOTE. --It should be observed that when the engine is running, the regular suction of the cylinders acts like a draught to keep the producer working, so that the supply is equal to the demand, and this being so, the hand fan is stopped as soon as the engine is started running. It should also be noted that the producer is worked at a pressure slightl)' under that of the atmosphere, owing to the suctional action of the engine in drawing off the gas generated. This also explains how the atmospheric air pressure enters the producer. After the gas passes from the producer to the engine it*is mixed with the required amount of air in the carburetter or vaporiser to form a more highl}' explosive mixture for rapid combustion (explosion) in the cylinders. Explosion Systems. — The oil motor is an explosive engine, the cylinder head constituting the explosion or combustion chamber, and to allow of this the clearance space is equal to about 30 per cent. of the cylinder volume. When the explosion is produced b\' a spark, or, as in the case of paraffin motors, by a hot tube or lamp, the engine is then really of the " e.xplosive " tj-pe ; but if, as in some cases, the explosion is produced by the gases being compressed sufficient!)- to ignite spontaneous!)- b)' the heat left in the cylinder head, t!ie motor 568 "Verbal" Notes and Sketches is then of the " internal combustion " type, although the term internal combustion is generally applied in both cases. In the typical modern motor boat using petrol, the energy is stored in the petrol ; this is transformed into gas and mixed with air in the carburetter, while the energy is liberated as heat in the engine cylinder, and then directly transformed into mechanical work by the piston, and into propulsive work by the propeller. The oil or explosive engine is of course a heat engine, and as such develops concentrated energy at the moment of ignition of the gases, whereas with steam the energy is distributed more over a longer period. The gas entering the cylinder represents potential energy, which on ignition changes almost instantly into kinetic or active energy, the fly-wheel receiving and storing up some of this power or energy, which is afterwards employed in completing the three other powerless strokes. In one of these, the compression stroke, a large proportion of the power previously developed is absorbed or used up in compressing the gases to the necessary pressure required for effective ignition and explosion. This work, then, is done by the piston on the gas, and may be called negativ^e work. As heat and work are equivalent, the intense heat obtained by the explosion of the charge produces work, each unit of heat being equal to, or giving out, 778 foot-pounds of work. Paraffin and Petroleum. — The paraffin or petroleum motor is certainly the most convenient in many ways, as being usually ignited by a heating lamp less trouble is experienced than with electrical connections, magneto, &c., all of which require careful attention and regular overhaul. Paraffin can always be obtained, and is fairly cheap ; it is also safe, as vaporisation docs not readily take place, hence the necessity for the heating lamp previously referred to. This at the same time, however, constitutes a disadvantage, as time is required to heat up the vaporiser before the engine can be started. After once starting, however, the heating lamp is usually turned off, as the carburetter is then kept hot by the exhaust gases. The flash point of paraffin, which is known as a " heavy " oil, is about 84^ Fahr. Petrol or Gasoline.— Petrol is the spirit obtained from the crude petroleum, and is chiefly composed of carbon and hydrogen, about 85 per cent, carbon and 14 per cent, hydrogen. The flash point is low, about 35° Fahr., so that evaporation takes place very easily under atmospheric pressure, which is an advantage in the matter of instant starting, but which at the same time constitutes a danger, as if leakage of petrol takes place explosion readily occurs when the vapour formed becomes mixed with atmospheric air. The heat units in I lb. of oil fuel are usually about 20,000 units, or roughly about one-half more than that in \ lb. of ordinary coal, so that for the Internal Combustion Enoines 569 same power about two-thirds the amount of petrol or paraffin is sufficient. As the fuel is in liquid form it also occupies less bunker space, and, as before stated, for the same weight contains half as much again power or energy, which still further reduces the fuel space required for a given distance to be run. Two-Cycle. — In small single-cylinder motor sets up to about 7 Brake Horse-Power, and two-c}-linder 10 B.H.P., the two-cycle s}'stem is usually adopted, and is carried out as follows : — The crank case is air-tight, and is fitted with a small port, which is opened and closed by the piston as it travels up and down. Through the opening or port referred to, the charge of oil vapour and air is drawn in from the carburetter on the up-stroke, and compressed on the down-stroke, until released by the piston uncovering a con- nection between the crank case and the top of the cylinder : the charge then rushes into the cylinder, and at the same time drives out the exhaust or burnt gases through the exhaust port which has just opened : when the piston comes up to the top the spark occurs and ignites the compressed mixture of oil vapour and air, and explosion follows, driving the piston down, and, as before stated, when near the bottom the exhaust port is uncovered, and shortl)' afterwards the connection between the crank case and c}-linder. Observe that the exhaust port is opened just previous to the inrush of the fresh charge, which being at a slight pressure assists in forcing out the burnt gases left from the previous stroke. The two-cycle motor, it will be noticed, gives one impulse or power stroke to each revolution. A disadvantage exists in the confusion of the intake gases with those of the exhaust, which to a certain extent reduces the effective energy developed, and which increases with the number of revolutions per minute. This type of motor, however, requires no valves or cams of any kind, as ports only are required to admit and exhaust the gas and air. If two C)-linders are employed, the cranks are placed opposite to give good balance and an even turning moment on the shaft. Both two-c)xle and four-cycle motors are single acting — that is, the power stroke only occurs on one side (top) of the piston. Four or "Otto" Cycle. — The action of a "four-cycle" oil motor is as follows: — (i) On the down-stroke of the piston the air and oil vapour are drawn into the c}'linder through the inlet valves ; and (2) on the following up-stroke the gas is compressed ; then (3) fired by an electric spark, or a hot tube, set to act when the piston is near or at the top centre ; the explosion which follows drives the piston down, and. on the next up-stroke (4) the burnt gases are expelled through the exhaust valves, and out into the atmosphere by way of the " silencer." The inlet valves are sometimes worked by the piston suction and springs, and sometimes mechanically b\' a cam fixed on a special shaft. The exhaust valves are opened by cams 570 " Verbal " Notes and Sketches « 5 S g b e w .get/) lU -c c b ^ u o "i '"T 0) rt U) ^ J? 2 o ° " li c S c c ^5 S o c5^ « Oh 00 C "'it! « !2 rt « _ ^ ^ ^ -t; o C s o n u r, '^ O O o y; Cl > 1) S-O ° " 3 rt o c p-t; (jj > ° D rt u c! M .-I .5 u >» U 6 o u < d 2: Internal Combustion Engines 571 t/5 1- U 1) . I" ij > j= c; 5^!" JS u U O CO d 2 57^ " Verbal " Notes and Sketches on the shaft referred to, and arc kept shut by strong springs as shown in the sketches. Steam-Engine and Oil Motor compared. Steam-Engine. — Coal stored in bunkers and containing heat energy is supplied to the furnaces, and, combustion more or less complete being effected, the heat obtained is transmitted through the furnace metal, and evaporation of the water in the boiler results. The imperfect steam gas thus produced passes along the steam pipe and enters the cylinder, where the heat energy is employed to drive the pistons up and down, and so produce rotation of the shaft. After doing work in the various cylinders, the steam finally exhausts to the condenser, where condensation takes place, and the water thus ob- tained is put back into the boilers as feed. During the process of condensation most of the heat in the steam is absorbed by the circulating water, and is thus lost overboard. Oil Motor. — In the oil motor the boilers are deleted and the fuel contained in the oil tank or bunker is supplied direct to the cylinder head, which also forms the combustion chamber. Combustion is effected by a spark, and the energy thus developed is applied direct to the piston, and acts on the down-stroke only. The waste gases produced by the rapid combustion are then exhausted out to the atmosphere, and the whole of the heat contained is thus rejected. Notice that a condenser cannot be fitted, so that no return of heat is possible. Again, it will be seen that to obtain the same impulse effect on the crank-shaft four cylinders are required if the motor is of the " four-cycle " type, and two cylinders if of the " two-cycle " type, to be equal in effect to one double-acting steam cylinder. The chief difference then exists in the fact that with steam as the motive power ordinary combustion takes place in the furnaces of the boilers, whereas with oil rapid combustion takes place direct in the cylinders, and the heat energy developed during explosion does the work of turning the shaft and propelling the boat. In the steam-engine steam gas generated in the boilers is admitted to the H.P. cylinder, and is cut off at say one-third stroke. This gas expands, and after doing work in the H.P. is admitted to the larger M.P. cylinder, where more work is done and further expansion takes place ; the gas then expands into the still larger L.P. cylinder, where the last stage of work and expansion is completed, the gas then passing into the condenser where condensation is effected. The steam gas charge, be it noted, is only supplied to the H.P. cylinder, and by exjDanding about twenty-two times or so altogether in the other two larger cylinders, most of the effective energy is extracted and useful work done. The oil-gas engine, on the other hand, is a single-acting, and, of Internal Combustion Kn^lnes 5)73 Course, non-condensing engine, each cylinder requiring its own inde- pendent charge of gas, and, as before stated, combustion is effected in the cyHnder head. The cyHnders are therefore all of equal diameter, and the gas only expands in one cylinder. No condfcnser is possible, so that after driving the piston down the expanded gases at a high temperature are exhausted direct into the atmosphere through the "silencer." The back pressure is therefore somewhere about 18 lbs. per square inch absolute, whereas in the steam-engine the back pressure is usually only about 2h lbs. absolute, owing to the condenser vacuum. Number of Cylinders, &c. — Any number of cylinders may be employed in an oil motor, but for small launches two or four is the usual number. The number of cylinders, in fact, depends on the power required, and as many as six, eight, twelve, and eighteen cylinders are occasionally fitted, according to the H.P. to be developed by the motor. The cylinders are of cast iron, and are occasionally fitted with liners, which allow better for the expansion of the upper end of the cylinder due to the intense heat of explosion. One or two casCs have come under the writer's notice of cylinder heads cracking, due to the unequal expansion of the upper and lower portions. Pistons.— The pistons, of cast iron, are kept tight by means of four or six light Ramsbottom cast-iron rings, which are cut as usual. The pistons are of the trunk type, being very deep in section, and open at the bottom to the crank case, which is often arranged to form an oil bath, thus supplying lubrication to the working parts by the " splash " system. Revolutions. — Developing full power, the revolutions vary in oil motors from 700 to looo per minute, and therefore, tieglecting miss- fires and premature explosions, the average number of power strokes in a "four-cycle"' motor will be equal to one-half of the revolutions. Water- Jacket. — Steam cylinders are sometimes fitted with steam- jackets to keep up the temperature, whereas in oil motor c)'linders cooling water-jackets are required to extract the intense heat pro- duced by explosion, and thus keep down the temperature. The water- jacket is a very important detail, and is indispensable. The tempera- ture of the waste gases may be anything from looo'' to 1500" Fahr., which fact in itself indicates the great waste of energy which goes on, and which is evidently unavoidable. Sometimes the valve pockets are also water-jacketed, and occasionally the exhaust gases are arranged to pass round the carburetter to raise the temperature and allow of quick vaporisation of the oil inside. 274 "Verbal" Notes and Sketches Pressures and Temperatures. — The pressure of compression just previous to explosion varies from 50 lbs. to 70 lbs. or 80 lbs. per square inch, and the pressure of explosion from 150 lbs. to 300 lbs. per square inch. The temperature of the gases at explosion is estimated as being somewhere about 1 500' Fahr. and upwards. Carburetter. — The carburetter is a small chamber employed to vaporise the petrol and at the same time mix with it the proper proportion of air. The openings are arranged to give from five to ten parts of air to one of petrol vapour, but of course this varies greatly with running conditions. Throttle valves are also fitted on the carburetter to regulate both the amount of air supplied and the amount of vapour admitted. A float and needle valve regulates the oil supply to the mixing chamber of the carburetter. A single carburetter is sufficient for any number of cylinders, as by suitable pipe connections the vapour can flow into each as required. Valves. — The valves are usually of the cam and poppet type, and are opened and shut by means of a "half-time" shaft. This shaft is connected up by gear wheels with the engine shaft so as to only give one revolution for every two revolutions of the engine. It will be noticed that the valves employed are similar to those of the historic Smeaton and Watt engine, and were in use before the slide valve was introduced. Recently, however, the " sleeve " type of valve has come into more general use. "Sleeve" Valve. — The "sleeve" valve consists of two cylindrical casings fitted round the cylinder with ports cut in each ; the outer sleeve is actuated by a link from the connecting rod, and when the ports coincide the gas is admitted to, or exhausted from, the cylinder. This type of valve is particularly silent in running, and gives very little wear. Fly- Wheel. — A fairly heavy fly-wheel is fitted to motors of both the two-cycle and four-cycle types, the latter requiring the heavier wheel. The fly-wheel makes for steady running balance, and also stores up energy, which is released when the power strokes become irregular or intermittent. The wheel is also convenient for use in starting up by hand. Firing or Sparking Plug.— This appliance is screwed into the cylinder head, and, when possible, is placed direct in the path of the incoming charge of vapour. One wire from the contact maker, induction coil, and battery (or from \:he magneto contact brush of this system) passes through the centre, and forms a point from which Internal Combustion Engines 575 the spark passes to the other point, which makes metalHc contact with the body of the plug, and so to the cyhndcr, engine frame, and battery, &c. The current, therefore, is "earthed," and after sparking returns to the battery, &c., or magneto, by means of the engine metal (Single Wire System). Half Compression. — This is fitted in the larger engines for con- venience in starting, and consists of a lip on exhaust cam extending half its width. The whole cam is capable of sliding on its axis when the half-compression lever is moved. Thereby, in one extreme position the lip lifts the exhaust valve during the compression stroke and releases the compressed air, making it much easier to pull the engine over the centre ; in the other extreme position it clears the valve tappet rod, and the exhaust valve is only opened on the exhaust stroke. " Cranking." — A petrol motor is started by having the engine dis- connected from the propeller, and the handle connected to the shaft or fly-wheel turned smartly round, with the half-compression valve open to reduce the opposing back pressure. After a few revolutions the spark acting at the right time catches up the running, and the motor runs up to the ordinary revolution speed. The spark gear is also " retarded," that is, set to fire when the piston has just passed over the centre. The half-compression valves are, of course, shut down once the motor takes up the speed, and the spark " advanced " or set so as to fire just before the piston reaches the top centre. In starting, care has to be taken in "cranking up" not to set the motor running in the wrong direction, as this is very easily done, and in some cases may be, to put it mildly, awkward. In one motor boat in which the writer had an experimental run, the engine unfortunately went off in the reverse direction, and as a counterbalance, rather than stop (the motor being of the paraffin type and slow to heat up), the angles of the propeller blades were simply reversed to suit the direc- tion of rotation of the engine, and the run completed under these conditions, which were certainly not the best. During another run the motor stopped dead owing to wrong adjustment of the oil or choking up of the supply pipe, and as before, being a paraffin motor, the boat had to be allowed to drift about or the oars emplo)'ed for about ten minutes, until the pressure heating lamp was set away and the carburetter heated up sufficiently to allow of the motor starting again. This little experience indicates very clearly one of the drawbacks to paraffin, as, being what is known as a "heavy" oil, it requires some considerable heating up before vaporisa- tion takes place. At the same time, it should be stated that quite recently a patent paraffin carburetter has been devised which is said to "start from cold." Given a reliable ignition gear, the petrol motor of the four-c\xle t)'pe is certainly the sweetest-running motor of any; this, at least, is the writer's experience after many trials of other 3S 2^6 "Verbal" Notes and Sketches types. At the same time, it is only right to state that paraffin-type motor launches give every possible satisfaction, being steady and cool in running, also easily and quietly stopped and reversed. Ignition. In petrol motors the greatest difficulty is experienced in obtaining a reliable ignition gear, and the most frequent cause of stopi)age is undoubtedly that due to defective ignition. The best method of firing is at present a matter of much discussion and difference of opinion. Some makers prefer the battery and "jump spark" system, others the magneto or " make-and-break " method of producing the firing spark. The "jump spark" system offers the greatest complication of parts with correspondingly increased risks of breakdown ; it also necessitates the charging of chemical batteries, and some knowledge of electrical science, while the magneto, on the " low tension " system, has fewer working parts, and being a mechanical device, driven by the shaft, presents less danger of breakdown. Jump Spark. — In this ignition system the sparking points are both fixed, and a current of high intensity being produced in the circuit, a spark is generated between the two points referred to, and is therefore called a "jump spark." The ignition gear is made up of four separate and independent parts. 1. Chemical cells or battery. 2. Induction coil or " intensifier." 3. Contact maker. 4. Firing plug. All of the foregoing parts are, of course, liable to derangement and breakdown, as they are affected seriously by damp and sea water. Make-and-Break. — In the " make-and-break " system a small lever rests against a pin and at the required time is drawn away from the pin, thus leaving a small gap of about yV inch. The current endeavours to follow up the moving lever, and as before, a spark results. In both systems, then, the explosion is produced by means of an electric spark arranged to flash out at the correct instant, so that in the case of a four-cycle motor running at 800 R.P.M., about 400 sparks are pro- duced per minute in each cylinder head. This means, then, a constant shower of sparks require to be produced when the motor is running. Magneto and Spark Plug Ignition. This system of firing is the best, being, as a rule, more reliable than the " make-and-break " or coil and battery, and lasting longer without ^1 i Xi 13b r: :o>»i*iiJ ,rf .;»9 iuo6» 016 iLudw \o No. 4.^Simms Magneto (four-cylinder type). 2, Slip Ringf. 6, Distributer. 7, Collector Carbon Holder. 8, Distributer Carbon Holder. ID, Half-Speed Wheel and Spindle, (I, Timing Lever. : NOTE.— The dimensions on the diagrj 50 millimetres =2 inches (approx.). 'Verbal " Nules and Sketches. 13, Segment. 15, Milled Nut. 17, Ball Bearing. 18, Dust Cap. 21, Long Contact Breaker Sci 22, Terminal. 25, Collector Brush and Spring. 26, Distributer Brush and Springy. 27, Central Connection. 30, Contact Breaker Lerer. 31, Contact Piece. jtpresscd in millimetres, 25 of which axe about equal to i inch, therefor* [ To face t^ge 577- J Internal Combustion Engines 577 requiring attention or repair. The magneto wiring is connected direct to the sparking plug, and the spark passes across the platinum points of the latter as in the coil and battery system. While the engine is running the magneto is generating the current for the spark, and, of course, when the engine is stopped the current ceases to flow, no loss of current taking place. The magneto is usually driven by gear wheels off the main shaft, and the current is taken from the small carbon brushes of the commutator by the positive wire direct to the plug, the return or negative being made by means of the engine metal back to the magneto, on the "single wire" system. The magneto spark is much stronger than that of the coil and battery system, and produces a much more powerful explosion of gas in the cylinder, giving greater power. The Simms Magneto (Four-Cylinder Type). General Description. The armature carries two windings, viz., the low-tension winding (formed of a comparatively small number of turns of thick wire) and the high-tension winding (composed of a very large number of turns of a very fine wire). This arrangement entirely dispenses with the necessity for the ordinary high-tension coil, such as is used in connection with accumulators, owing to the fact that both the high and low tension windings form an integral part of the magneto itself The low-tension circuit is interrupted by the contact breaker twice per revolution, thus giving two sparks per revolution, and the high- tension current is led from the carbon holders or the distributer to ordinary high-tension sparking plugs on the engine b}' means of the usual insulated cable. The diagram shows the connections of the "four-cylinder" type. One end of the low-tension armature winding is connected to the armature core, and thus to the frame of the magneto, and the other end is led through the hollow spindle of the armature to the contact breaker, the fixed portion of which, 31, is insulated, and carries a platinum pointed screw, and the bell crank lever, which carries a second platinum pointed screw, is connected to the frame of the magneto. Both the bell crank lever 30 and the contact piece 31, together with the contact breaker disc, revolve solid with the armature, and as the fibre heel of the bell crank lever comes into contact with the segments 13 the two platinum points are caused to break, owing to the bell crank lever rocking about its pivot. This sudden inter- ruption of the piimary or low-tension circuit induces a current of very high potential in the secondary or high-tension circuit, and gives a flaming spark of great heat at the points of each of the sparking plugs in turn. On the timing lever 1 1 is a milled nut and terminal for making connection to the insulated terminal of a single pole switch. One terminal of the switch should be connected to the frame of the car. Connected to the terminal is a spring 12, which makes contact 578 '•Verbal" Notes and Sketches with screw 21. It will thus be seen that for one position of the switch the terminal (which represents one end of the primary winding, the other being permanently connected to the frame of the magneto) is still insulated, but in the other position is joined to the frame of the car, thus earthing both ends of the primary armature winding, and causing the magneto to become inoperative, and consequently stopping the engine. The hio-h-tension winding of the armature has one end connected with the primary, or low-tension winding, and through this winding to earth, the other end of the secondary, or high-tension winding, being connected to the slip ring 2, from which the current is collected by the carbon brush 25. In the "four-cylinder" type, as shown, the No. 5. current leaves the carbon holder and passes along the central con- nection 27 to the distributer. A safety spark gap is formed between the hollow spindle surrounding it, the central rod passing through a glass disc 40. The central connection is held in contact with the central disc of the distributer by a spring. Connection is made between the central disc and the distributer segments by a carbon brush, which rotates with, and is insulated from, the half-speed wheel. The safety gap is made sufficiently long to prevent the spark passing here in preference to jumping the plug gap inside a high compression cylinder. To ensure satisfactory working, care must be taken that clean contact is made between the slip ring 2 and the carbon brush, and also between the distributer carbon 26 and the central contact piece and segments in the distributer. Internal Combustion Engines 579 Setting the Magneto. — The four segments of the distributer 6 are connected to the four terminals on the front of the distributer. The terminals are numbered i, 2, 3, 4, in the order in which they fire. The distributer carbon holder runs in the opposite direction to that of the armature. When viewed from the distributer end, the distributer carbon holder rotates clockwise in a right-hand machine, and anti-clockwise in a left-hand machine. 1. Set the piston of No. i cylinder of the motor exactly at the top of the firing stroke. 2. Fully retard timing lever, which is done by moving the lever as far as possible in the same direction as the armature rotates. 3. Rotate the armature in its proper direction until the distributer carbon rests on No i. segment, and continue rotating slowly until the distance A (see diagram on page 578) measures 7 millimetres, then tighten all up. 4. Connect the magneto to the motor when both are in the above- described positions, taking care there is no movement. It will be found that the motor can be started more easily if the timing lever is advanced as far as possible (usually about two-thirds) without causing back-firing. Motor Troubles. — Overfeeding with oil or petrol is a common source of trouble, as this produces a mixture too heavy for the digestion of the motor, resulting in miss-fires, premature explosions, and slowing down or actual stoppage of the engine. The majority of the owners of private motor launches have the fixed idea that if the machine is not running satisfactorily it needs more fuel, with the result above mentioned. It should also be noted that when the charge is too hea\y some of the oil or petrol is not vaporised at all, and remains in the cylinder to perhaps form sooty deposits which, remaining red-hot, may afterwards produce premature explosions, or may form a carbon bridge across the points of the sparking plug and thus do awa}- with the spark altogether. The same remark holds good if oil from the crank-case or " splash " lubrication system is carried up into the cylinder head, as similar troubles may result. Loss of Power in Engine. — Should there be a loss of power in the engine, the following points should be examined for the cause : — Leakage at either the exhaust or inlet valve, sparking plug, or piston rings. Weak accumulators. Dirty sparking plugs (or contact breakers with low tension). Im[)erfect contact at the contact breaker, caused b}' weak spring at contact hammer, or imperfect connection of high-tension wire to plug screw, due to screw being slack. Carbonised oil on the fibre disc and contact pieces. ^So "Verbal" Notes and Sketches Fusino- or burning of the platinum on the trembler of the induction coil. The formula very commonly quoted with reference to the economy of internal combustion motors using gasoline is, " one pint per horse- power hour." This is better than two-cycle engmes can be depended on to give, and small four-cycle engines will not give any such figures except with care and under the best conditions. One pint per horse-power hour means good conditions with the four-cycle engine of moderate large size. Economy with an internal combustion engine depends chiefly on the following conditions : — (i.) Correct proportion of air to petrol vapour. (2.) Correct degree of compression. (3.) Prompt ignition and complete combustion. The first step is combustion, or union with oxygen, and as the gas itself will not burn, it must therefore first be mixed with a suitable amount of oxygen. This is accomplished most cheaply and con- veniently by using air, but even then such gases, when mixed with a suitable amount of air, will not burn readily at ordinary pressures, and it is not until they are compressed to a high degree that com- bustion once started will act with sufficient vigour and rapidity to produce the action desired. Leaky Pistons. — It is of the utmost importance that the piston is kept absolutely gas-tight, as should leakage occur, as will easily be seen, the motor will not develop the full power. With a leaky piston, compression will be less on the up-stroke, and the resultant explosion on the down-stroke weakened in due proportion. Colour of Exhaust Gases. — The colour of the exhaust gases leaving the silencer affords a fair indication of the completeness of combustion in the cylinders, as if the colour is strong it indicates incomplete combustion. The more colourless, therefore, the waste gases appear, the more complete is the combustion, and only a very faint tinge of grey colour should be visible if the motor is working satisfactorily. If any of the lubricating oil passes into the cylinder it becomes burnt and gives out a disagreeable smell, and also colours the waste gases ; a similar result may be produced by overfeeding with petrol or paraffin, as incomplete combustion of the gas may take place in the cylinder head. Composition of Exhaust Gases. — The following analysis of the exhaust gases of an oil engine, using Russian Petroleum, is of interest : — / COo = 92 per cent. Composition of Exhaust Gases < -'P ^ 55 » IN, &c. = 84 Internal Combustion Engines 581 Reversing. — Reversing is usually effected by one of two methods. (i.) Reversible propeller, the blades of which can be rotated to any angle by means of suitable gear contained in the hollow boss, and actuated by a lever and rod, the rod passing through the hollow tail shaft. This method is very much in favour at present, although it is not the best as regards propeller efficiency. (2.) By a reversing clutch, which is commonly arranged to give a direct drive from engine shaft to propeller when in the " ahead " position, but which, by means of a gear box, reverses the propeller shaft rotation when in the " astern " position, the gear box in that case also revolving. It should be noted that in this case the propeller speed for astern is only about half that for ahead. When in the No. 6.— Gaines' Reversible Type Propeller. intermediate position, both engine and propeller shafts are dis- connected, and the engine thus running free, and with the load off, requires a governor to check the speed. There are many t\-pes of patent reversing gear now in the market, all claiming, of course, certain advantages over the others. In cases where the engine is connected to the propeller shaft through a reversing clutch, and where in consequence the engine may be running without load, the throttle, in the best designs, is placed under the control of an automatic governor of the centrifugal type, thus placing the speed under limitation with any and all conditions. Crank Arrangements. — It should be noted that to obtain the same power, other conditions being the same, a foitr-cylznder " four-c>'cle ' motor would be necessary to give the same power per revolution as that of a single double-acting steam-engine C}'linder. NOTE.— When four cylinders are employed in the four-cycle system, the cranks are generally arranged as follows, to produce two impulses per revolution : — No. I cylinder, crank on top explosion taking place. No. 2 cylinder, crank on bottom compression taking place. No. 3 cylinder, crank on top admission taking place. No. 4 cylinder, crank on bottom exhaust taking place. 582 "Verbal" Notes and Sketches Starting-, &C. — Before starting a paraffin or petroleum motor, the lamp burner is set away to heat up the oil vapour, and the oil supply seen to be free to flow to the carburetter from the tank. The exhaust valves are also eased back, and the engine turned round by hand to force out any gas left behind in the cylinders. After the vaporiser is sufficiently heated up, the supply cock to carburetter is opened and the engine turned quickly by hand to start. If starting prove difficult, it might be caused b)' insufficient heating up of the vaporiser or by dirty or defective sparking gear. The oil suppl}' should also be examined in case the petrol is not flowing into the carburetter. Piston speed is varied by means of the governor, which regulates the petrol supply and sometimes the time of ignition. The fewer the number of ignitions per minute, the slower the piston speed, and vice versa, the speed of the vessel varying in proportion. A petrol motor can be started at once by merely "cranking" and adjusting the spark, as the petrol spirit vaporises instantl}- on passing the spra}' nozzle of the carburetter. Speed Regulation. — The speed of the engine is varied by one of the following methods : — (i.) Advancing or retarding the period of sparking, as advancing the spark increases the speed, and retarding the spark decreases the speed. (2.) Shutting down the petrol supply to the carburetter. (3.) Throttling the amount of the charge passing into the c}'linder. (4.) Increasing the"* proportion of air to oil vapour, and thus weakening the charge. (5.) Easing the compression, and thus reducing the force of the explosion. Sometimes a combination of two of the above systems is employed, and the governor is often arranged to both reduce the petrol supply and retard the spark simultaneously. Internal Combustion Engine Troubles. Symptom. Cause. Remedy. Engine refuses to start. I. Faulty ignition. 2. Weak compression. 3. Want of petrol or water in petrol. 4. Spark plug broken. 5. Weak mixture. 6. Spark plugs screwed into wrong cylinders. Examine wiring, test plugs, test for compression, put petrol into cylinder through compression cock, take out plugs and test for spark in each cylinder. Internal Combustion Engines Internal Combustion Engine Troubles— conh'nued. 583 Symptom. Cause. Remedy. Engine stops suddenly. I. No spark. 2. No petrol. 3. Chokedcarburetter jet. 4. Fault in coil or in magneto. 5. ^^'lri^gshort circuited to metal of engine. Test spark plugs, test for petrol supply, clear car- Imretter jet, examine and test battery, coil, and wiring for short circuit or l)roken wire, &c. Engine stops gradually and miss- fires. 1. Weak spark. 2. Want of petrol. 3. Carburetter partly choked. 4. Spark plugs fouled up with oil. 5. Wrong mixture. Test spark plugs and ex- amine coil contacts, examine carburetter, ex- amine petrol tank to see if air-bound, &c. Overheating. I. Faulty circulation. 2. Pump broken down. 3. Steam lock in pipes. 4. Mix- ture too rich in petrol. 5. Spark retarded. 6. Exhaust throttled. 7. Valve timing wrong. 8. Silencer choked up with carbon. Test pumps and pipes for water circulation, in- crease air supply to carburetter, test timing of valves, examine silencer. Engine knock- ing. I. Faulty lubrication. 2. Igni- tion advanced too far. 3. Premature ignition. 4. Worn bottom, end,orniain bearings. 5. Cylinders loose on bed plate. Examine and test lubrication system, put back igni- tion lever, overhaul engine for worn bearings, &c. Hissing noise from engine. I. Spark plug broken, joint blown out between engine and exhaust or between engine and carburetter. 2. Compression cock partly open. Test spark plugs, examine joints mentioned, &c. Loss of engine power. I. Loss of compression due to leaky piston rings. 2. Too much petrol. 3. Want of lubrication. 4. Throttled exhaust. 5. Wrong ad- justment of valves. 6. Faulty wiring, coil, bat- tery or magneto. Test pistons for compres- sion, reduce petrol flow, examine lubricator, test timing of valves, examine and test battery, coil, wiring, and magneto. ^84 "Verbal" Notes and Sketches Internal Combustion Engine Troubles — continued. Symptom. Cause. Remedy. Hot crank-case. I. Leaky pistons allowing gas to enter crank-case. 2. Cracks in cylinder. Test for compression, ex- amine for cracks. Explosions in silencer. Mixture too weak to fill in cylinder, one cylinder miss- ing and charge afterwards exploding in silencer. Increase petrol supply, test plugs for spark and for timing of spark. Red-hot • silencer. I. Using excessive gas. 2. Spark too far retarded. 3. Exhaust throttled. 4, Faulty adjustment of valves. 5. Choked up silencer. Give more air, advance spark, test for timing of valves, examine silencer. Engine refuses to stop. I. Short circuit of wiring. 2. Carbon deposit in cylinder head or on plug spark points (red hot). Test wiring, examine plugs and cylinder heads for carbon deposits. Engine refuses to start. Cylinders full of water owing to leaky silencer or cracked cylinder. Examine silencer and c)lin- iler heads, &c. Blue smoke from silencer. Overheating due to faulty lubri- cation or defective water circulation. Examine and test lubrication system, and water cir- culation. Engine stops when re- versed. Clutch jammed owing to dirt, grinding of metal, or want of lubrication. Clean clutch and lubricate. Engine refuses to take up drive. Clutch slipping. Examine clutch for wear, clean clutch if over lubri- cated, fit new collar if required. I Internal Combustion Enirines 585 Carburetter. — The carburetter needle valve should be ground in regularly, as if not the mixture will become too rich, and in some cases the carburetter may become flooded, resulting in loss of power and probable stoppage of the engines. Tests. Spark Plugs. — Screw out the plug to be tested, and lay it on the cylinder top with the wire connected up ; now turn engine round by hand with switch on, and if there is no fault a spark will show across the points. NOTE.— With the spark retarded the spark should show just as the piston is passing the top centre, but if the spark appears when the piston is at half stroke or thereabout, it indicates that the plugs have not been put into the right cylinders, or that the timing of the spark is wrong. This fault shows when starting up by back firing out of the air inlet. Valves. — To test the timing of the valves, open compression cock on cylinder top, and fit in a straight copper wire, now move engine by hand and see if the inlet valve lifts just as the piston comes to the top, and if the exhaust valve lifts just before the piston comes to the bottom (every second stroke for a four-c}'cle motor) ; if not, alter the washers on ends of valve lifting rods to either increase or decrease the clearance as required. The exhaust valves should be set to close down just before the piston commences the down (inlet) stroke. Battery. — For battery testing a small pocket voltmeter is required, and when connected up with the positive and negative terminals of the cell, the voltage indicated should not be less than 4-2. The cells should be recharged ever)- four or six weeks. Diagrams from Oil Motors. Diagrams Nos. 7 and 8 show clearl}- what goes on above and below the piston in this type of motor, as on the down-stroke simultaneous expansion of gas after explosion above the piston and compression of the next charge below the piston is taking place, and on the up-stroke simultaneous admission of oil vapour below the piston and compression of the previous charge above the piston. Observe that line i in A and line i in B are described at the same time, also line 2 in A and line 2 in B at the same time. As the bottom card represents work done on the air and oil vapour by the piston, the actual work done is equal to the difference in area of the two diagrams, A and B, and the mean effective pressure is found by making this allowance. 586 " Verbal " Notes and Sketches Diagram No. 9, taken with a light spring, shows clearly the four operations which constitute the "Otto" cycle, so named from Dr Otto, who first apphed this principle to gas engines, (i.) The lowest line shows the admission of air and oil vapour at a pressure rather TOP CENTRE A.L. No. 7. — Diagram from Cylinder of Two-Cycle Motor. below that of the atmosphere, the indicator pencil travelling from left to right. (2.) The line rising and going from right to left shows the compression of the gas on the up-stroke, the pressure increasing to about 80 lbs. per square inch or so. (3.) At, or just before, the top TOP CENTRE A.L < — t RELEASE No. 8.— Diagram from Crank-Case of Two-Cycle Motor. centre, the charge of air and oil vapour is fired and explosion follows, as shown by the sudden rise of pressure to about 240 lbs. or more ; the effect of the explosion is to drive the piston down, the pressure falling at the same time by expansion and loss of heat. (4.) On the next up-stroke the exhaust valves open and the burnt gases are expelled at a pressure ju.st above that of the atmosphere, which is seen j^y the sloping line crossing that of the compression curve. After this the C3'cle begins again and repeats itself. The arrows show the direction of indicator pencil travel. Internal Combustion Engines 5^7 The small numbers shown in the sketch indicate the successive stroke in the same rotation as follows : — TOP CENTRE No. p.— Diagram from Cylinder of Four-Cycle Motor. I, Admission. 2, Compression. 3, Explosion and Expansion. 4, Exhaust (i.) Down-stroke, air and oil vapour admission to c\'linder. (2.) Up-stroke, air and oil vapour compression in cylinder. (3.) Down-stroke, air and oil vapour explosion in c}'linder. (4.) Up-stroke, burnt gases (CO^ and X) expelled from cylinder. No. 10.— Typical Four-Cycle Diagram. No. 3 stroke is the only working stroke of the four, and is known as the "impulse" stroke, so that there is only one /xrwer stroke in ever}' four strokes, or in two revolutions. So that 800 revolutions per minute require 400 sparks in each cylinder of the motor. 588 "Verbal" Notes and Sketches Diagram No. lo shows the average pressures obtained in ordinary petrol motors, and the dotted hnes show the effect of retard- ing the spark or ignition, which, it should be noted, has the effect of slowing down the engine. The loop shown in both the foregoing diagrams, and caused by the crossing of the admission and compression lines, represents negative work, and must be deducted from the diagram area to obtain the effective work done, and to measure the mean effective pressure in calculating the I.H.P. No. II.— Heavy Spring Diagram. NOTE. — The scale of the diagram being small, the difference between the admission line, atmospheric line, and esshaust line is imperceptible, as the three lines merge more or less into one. Mean Pressure. — As an oil engine is single acting, the mean effective pressure is calculated from a single diagram, the method adopted being similar to that for a steam-engine. The card is divided into, say, ten divisions, or nine whole divisions and two half divisions, and the pressures measured by the scale of the diagram on each line. The ten pressures are then added together, and the result divided by ten gives the mean effective pressure. Indicated Horse-Power.— The I.H.P. is found by the following formula, viz. : — AxS'xNxP _j pj p 33000 Where A = piston area in square inches. S' = stroke in feet. • N = number of explosion strokes per minute. P = mean effective pressure (from card). 33000 = foot-pounds per minute per I.H.P. Brake Horse-Power.— In high-speed engines the I.H.P. as found by calculation cannot always be relied upon ; it is therefore more satis- factory to state the B.H.P., or actual power transmitted to the propeller. The friction brake required to obtain this consists of a double rope passed once round the fly-wheel, one end being secured to Internal Combustion Knsfines 589 a sprinj:^ balance hung overhead, and the other end supporting the required amount of weights to balance the spring, when the engine is running the average number of revolutions. fLY WHEEL No. 12. — Friction Brake. S, Spring Balance. W, Weights. R, Rope Radius in feet. NOTE. — The shaft is revolving from left to right. The B.H.P. is found as follows : — (W - S) X R X 2 X 3-1416 X Revolutions 33000 = B.H.P. NOTE. — The difference in pounds of the weights and spring is the actual pull. W— Pounds weight on rope. S = Pounds shown by spring balance. R = Radius of rope from shaft centre. 2 = Twice radius for diameter. Types of Motors, &c. The following descriptions of modern marine motors and motor details are reprinted from various issues of " The Motor Boat," to the proprietors of which journal the author's thanks are due for permis- sion to reproduce both text and illustrations. The Wolseley Carburetter. This carburetter is of the float feed automatic type, fitted with an auxiliary hand-controlled extra air inlet; the float chamber and float (A) are of the usual construction, and serve the customar)- purpose of 590 "Verbal" Notes and Sketches maintaining' a constant level of the petrol, which is supplied through the pipe (B) in the spraying nozzle (C). Surrounding this nozzle is a choke tube (D), supported by arms (E) fixed to a disc, the section of which may be seen in the illustration, the whole being capable of a vertical movement against the action of the helical spring (F). The passage of the air when the engine is running is clearly shown by the arrows, entering through the pipe (I), which leads from the neighbour- hood of the exhaust system in order that warm air may be obtained ; it passes up through the choke tube, and drawing the petrol from the nozzle (C) in the form of a spray forms the explosive mixture which "^'-■EXTFCR flIR INLET No. 13.— Wolseley Petrol Carburetter. issues from the top of the tube and reaches the motor through the throttle (H) and the induction pipe. When the speed, and thus the suction of the engine, increases, the disc attached to E is raised from its seating, lifting with it the choke tube to the position shown by the dotted lines, and air is allowed to travel through the ports normally covered by it to the chamber (G) without passing over the spraying jet, thus automatically adjusting the proportion of vapour and air which is supplied to the motor. The pressure of the spring (F) tending to keep the disc on its seating may readily be varied by altering the position of the .screw cap v^hich may be seen in the Internal Combustion Engines 591 J IS illustration, thus enabling very accurate adjustment to be made an extra air inlet which may be moved by hand when desired. This carburetter has proved itself to be thoroughly satisfactory in use, the moving parts are very accessible, and, as has been mentioned above, accurate adjustment can be made without dismantling any part of the apparatus. Thornycroft Type Carburetter. It will be seen upon reference to the figure that the carbuietter consists of a float chamber and a vaporising chamber located in very close proximity to one another. When the float (A) sinks, the needle valve (B) is lifted by the balance levers (C), and petrol is allowed to enter the chamber through the inlet (D). The top of the spindle (B) is protected by a cap (E), which may be removed and the valve (B) No. 14.— Thornycroft Carburetter. lifted when it is desired to flood the carburetter. Leaving the float chamber by the port (F), the petrol gains access to the spray nozzle (G) through the ducts (H and J). K is an adjustable spindle, enabling the spray at L to be regulated by the movement of the screw (M), a lock nut (N) maintaining the correct position of this screw when the adjustment has been made. Should the duct (J) become obstructed it may be readily cleared upon removing the screw (O), whilst the duct (H) is continued to the top of the float chamber for the same purpose. The vaporising chamber is warmed by a hot-water jacket (P), which is connected with the engine-cooling system. This carburetter is of the hand-controlled t)'pe, no auto- matic air valve of any kind being relied upon. The main air supply 39 592 " Verbal " Notes and Sketches is drawn in through the pipe (Q), which has its intake in proximity to the exhaust piping in order that warm air may be obtained, and, passing over the jet (L), forms the explosive mixture which is carried to the engine through the induction pipe (R). The throttle valve (S) is of the ordinary disc type, pivoted in the induction pipe at T. The auxiliary air supply is controlled by a revolving collar (U), having four holes bored in it, which may be made to coincide with four holes — three of which may be seen at W, bored in the pipe Q ; thus, by moving the collar, the amount of air drawn in through the ports (W) may be regulated. The chief feature of this carburetter is its simplicity, whilst its substantial construction should enable it to withstand a considerable amount of roueh usage. The Tylor 30 H.P. Motor. (Fitted to Lifeboat.) The engine has four c}'linders (5-inch bore by 5|^-inch stroke, separately cast) and develops its rated power at 900 revolutions per No. 15.— The Tylor 30 H.P. Four-Cylinder Motor Engine: Exhaust Side View. minute. The valve pockets are on opposite sides of the cylinders, the inlet being to starboard and exhaust to port, and the pockets being cast in one piece with the c)'linders. A very neat arrangement has been adopted for holding down the valve caps ; a dog, held by Internal Combustion Engines 593 two nuts, on the " swing-gate " principle, has a central set-screw (see illustration), which keeps the cap in position, so that by slacking the set-screw the gate can be swung clear of the dog. The tappet guides are extra long and screw direct into the crank-case with key-way guides to prevent the tappets turning. It may be mentioned that a spring is provided inside the guide to keep the tappet roller always in contact with its cam. The length of the tappet can be adjusted by a screw and lock nut. The cam-shafts are stepped, so that the cams can be threaded on in order, the bearing brasses being threaded in a similar way and secured in webs in the crank-case casting by small set-screws ; in addition, the inlet cam-shaft carries the magneto trip gear, of which more anon. All gear wheels are enclosed in a separate cover at the forward end of the crank-case. The crank-case, which is of cast iron, is divided into two portions, the lower part, however, merely forming an oil tray ; all the main bearings (one between each pair of cylinders) are carried by the upper portion of the case, the bottom caps being held by nuts and studs, which are fitted with an ingenious double locking arrangement. A sectional plan of the crank- case shows the cam-shaft construction referred to above and also the general arrangement of the crank-shaft, from which it will be seen that the two middle cranks are set at 360", the order of firing of the c}'linders being i, 3, 4, 2. This system is the one generally adopted, and, being symmetrical on each side of the centre transverse section of the motor, gives much better balance than would be obtained where all cranks are set at 180° in rotation. The bottom part of the crank- case calls for no remark, save that webs to keep the oil evenly dis- tributed are provided between each pair of cylinders, as for lifeboat work the engine will have to be installed at a very considerable angle. Further reference to the sectional plan will show that all crank-shaft and crank-pin bearings are exceptionally large, a remark which applies equally to the small end bearings. In connection with the latter, it should be noted that the gudgeon pin set-screws have capstan heads and are locked in position by a steel wire passing through both. The explosive mixture is supplied by an improved Cremorne carburetter, this type being unaffected by the pitching of the boat. Ignition is normally by low-tension magneto, the drive being taken from the inlet cam-shaft and thence to the magneto. The action of the tapper inside the cylinder is self-evident, as also is the method by which it is worked by the vertical tappet rod. This latter is actuated by a small cam on the inlet cam-shaft, but the tappet roller is not rigidly attached to the tappet rod. The roller is carried by the horizontal arm, and the bottom of the vertical tappet slides in a groove in the end of the horizontkl rod. Referring again to the figure, if the cam- shaft is rotated clockwise and the horizontal rod is pulled to the left, the ignition is advanced by bringing the roller earlier into contact with the cam, and, conversely, if the horizontal rod is pushed to the right ignition is retarded. As a stand-by, and in case of any difficult)- in starting, high- 594 " Verbal " Notes and Sketches Internal Combustion F.nglnes 595 tension magneto with single coil and high-tension distributer is fitted. The distributer is mounted on the starboard bearer arm at the forward end of the engine, and is driven by bevel gearing. It co*\sists simply of a four-point low-tension wipe contact with a high-tension jump spark contact to each cylinder, all rotating parts being enclosed in an ebonite case with a watertight glass top, through which it can be seen if the high-tension circuit is in order. A centrifugal shaft governor acting on the throttle is mounted inside the spar wheel of the two-to-one gear of the inlet cam-shaft (see sectional plan) and is completely enclosed. The levers connecting it to the throttle may be clearly seen in the illustration of the inlet ^_^ .^^ M H ■n W^ » H /•^1S^*M m M HwSn^Sv- c 1 ^^ MB HH ^^S^g ^^ p^*" ■ I^^K^^^H fe, , ~-'ii» -'■ Q SB WL lii m flHI ■Hn igjg^K ^ *^__ -' (n a (d ci o -M u 0} a o M 6 Internal Combustion Engines 6oi Hot circulating water is passed through the carburetter jacket. It will be noticed that there is a row of small holes round the circum- ference of the throttle chamber ; these holes are just open to the induction pipe when the throttle is completely closed, and thus admit pure air to the cylinders to assist in cooling. The governor is contained inside the spur wheel of the inlet cam- shaft and consists of two spring-controlled balls, which fly out by centrifugal force as the speed rises and so actuate the throttle through intermediate bell cranks and distance rods. On the end of the other cam-shaft is the low-tension wipe contact communicating with four separate trembler coils, and also under control of the governor, besides the ordinary hand advance and retard. By this means abuse of the advance spark lever by unskilful driving is rendered impossible, since, so soon as the engine slows up, the ignition is always automatically retarded, though, on the other hand, it can be retarded to any extent by hand, whatever the engine speed, which can do no harm, but cannot be advanced too much. Water circulation is maintained by a rotary pump mounted on one of the cam-shafts, the water passing first to a special form of silencer very much on the principle of a water-tube boiler and then to the jackets, whereby the very common fault of marine engines of keeping the cylinders too cold is avoided ; the water outlet is from the top of the cylinders, but the pipes are kept as low as possible to avoid any needless top hamper. Large jacket covers are provided on the tops of the jackets and also on each side, making cleaning a very simple matter. A similar type of pump, intended as a bilge pump, is mounted on a swivel table for driving off the propeller shaft when required, but able to be readily swung out of engagement when not in use. The lubrication system is very complete. A lubricating box is situated right forward at the highest point of the engine and supplies oil through separate pipes to each main bearing and each piston and small end bearing, only the big ends being dependent on splash. The arrangement of the bottom piston ring has already been described, and this ring acts as an oil scoop on the up-stroke, taking oil from the piston walls and allowing it to drain into the hollow gudgeon pin, whence it reaches the small end bearing. The lubricating box is sight fed from a c\'lindrical oil tank, with glass ends, through which the amount of oil available can be instantly seen. The reverse gear is of the differential type, and encased in a hollow cast-iron drum. The whole rotates as one when going ahead by means of a wedge and internal expanding brake when the lever is in the forward position. For the reverse, the action of throwing the lever back releases the internal brake and applies an external band brake, which, gripping the cast-iron drum, allows the differential to act, and consequently rotates the propeller shaft in the opposite direction to that of the engine. A neutral or free clutch position is obtained by putting the lever in the middle switch ; both brakes are 6o2 Verbal " Notes and Sketches t-4 O V CO u ho C W o u in o ^*— ' Internal Combustion Engines 60 J then free, and the propeller shaft being stationary, by reason of its resistance, the reversing gear rotates at half the speed of the engine. This gear is mounted on the same frame as the engine, together with the control levers, which are arranged very simply and as much like an ordinary steam-engine as possible. 18 H.P. Brooke Motor. The 45 H.P. four-cylinder engine has all cylinders separately cast, and in one piece with their combustion heads, the bore being 5i inches and the stroke 6 inches, with a normal running speed of 900 revolu- tions per minute. Water-jacketing of the valve pockets has been very well carried out, as may be seen from the cross section, and they are provided with extra large screw-in valve caps to simplify the operation of removing the valve stem guides should this be necessary. Except that the ends of the valve springs are hooked through the valve stems instead of the more complicated collar and cotter arrange- ment, there are no special points in the valve and tappet gear, the tappets being of the ordinary roller type. Both cam-shafts are carried by ordinary end bearings bolted to the ends of the crank-case, and by split intermediate bearings sup- ported by the cross-webs and held in position by set-screws. For lightness the crank-shaft is hollow, as also are the crank-pins, one end of the shaft carrying the pinion of the two-to-one gear, the pinion and both spur wheels being of phosphor-bronze, as the firm find that quieter running is possible than with steel, while the bad wearing qualities of fibre wheels are avoided. On the other end of the crank- shaft is the combined fly-wheel and clutch, which is of a special type, very ingeniously arranged, so that the thrust due to the clutch is entirely self-contained. The entering member of the clutch is free to slide on the squared end of the tail shaft, and is normally kept in engagement by a spiral spring bearing at its after end on a collar of the tail shaft. The extreme forward end of the tail shaft is enlarged to form a flange (or there may be a disc bolted to the end face of the shaft), and this flange is inside a flanged ring bolted to the after face of the engine fly-wheel. Between these two flanges is a row of ball bearings, and from the illustration it will be evident that these balls take the whole thrust due to the clutch spring, which is tending to pull the tail shaft aft, and also tending, with an equal force, to push the entering member of the clutch forward. This thrust is transmitted to the other clutch member, and then falls on the ball bearing between the two flanges already described, so that the two stresses exactly neutralise each other. Returning to the crank-shaft. There is a main bearing between each pair of cylinders, and these bearings, together with the big end and cam-shaft bearings, are white metal lined, it being considered that a really badly-heated bearing causes less damage by running out 6o4 "Verbal" Notes and Sketches Internal Combustion Engines 605 the metal and starting a knock that makes it instantly necessary to stop the engine, than would be done by the constant scoring that is liable to occur with phosphor bronze, which will continue to run until it seizes up. With a view to reducing vibration as far as possible, the pistons are made very light, with thin strengthening webs ; they each have only two grooves for piston rings, but there are two rings in each groove, the idea being, of course, that gas getting through the slot in one ring does not have an annular space (caused by the comparatively loose fit of the piston in the cylinder) by which to reach the slot in "* -I- -lii^ gji nr^,,, ri. ^ jyr- il A i^^ ^fik |H[HI ■1 S! ^M MbI - i • QH^V wlHL ^^^^^^^ ~ '^/^^ySm^r bI nsa ' A'^mivT liiM m s 1 ^KPif flU Tl t *-<-. H B^ "^"^ ^ |§9L No. 23.— Brooke Engine with Control Board. the next ring, but is stopped at once by the second ring in the slot ; it is for this reason that only two grooves are necessar}'. W^ith mention of the fact that the connecting rods are of H sectioned steel stampings, the description of the engine proper is concluded. Water circulation is maintained by a rotary pump of the eccentric type driven off the cam-shaft, and the direction of the flow of water in the jackets is, to a certain extent, guided by a web inside the jackets, serving the double purpose of a baffle plate and of giving extra strength to the c\linders. Splash lubrication is relied upon entirely, oil being fed in at the 6o6 "Verbal" Notes and Sketches forward end of the crank-case from a sight-feed lubricator. There is no separate feed to the pistons, as Messrs Brooke & Co. consider that this system leads to sooting-up of the cylinder and a dirty exhaust ; the piston truck, however, gets a good dose of oil at the bottom of the stroke, since it projects a little below the cylinder, and there is a point on the bottom of the internal web of the pistons which catches oil and allows it to drip in a little pocket on the top of the connecting rod to feed the gudgeon-pin bearing. Little need be said about the Brooke carburetter, as it was recently described in this journal, but it may be repeated that the throttle governor attached to the carburetter is one of the special features No. 24.-18 H.P. Brooke Engine. with which the Brooke engine is fitted. As regards ignition, there is a tendency to abandon the low-tension magneto, which was at one time much favoured by this firm, in favour of the latest Simms high-tension pattern, which gives an extremely hot spark of very high frequency, and is not therefore nearly so much affected by wet as the ordinary high-tension electric circuit. Another point in favour of this magneto is that starting is as easy as with coil and battery, so low is the speed at which a spark is obtained. The Meissner reversible propeller is supplied with a considerable number of Brooke engines, but to those who prefer reversing gear a very neat type has been evolved from the Adrian works. It is of the sliding gear type, giving a direct drive ahead through a dog clutch internal Combustion Eno^ines 607 no wheels being in motion except those which are out of mesh. On the reverse the drive is, of course, through two countershafts. The gear is very compact and efficient, in addition to which it can be No. 25.— Brooke Reverse Gear. got very close to the bottom of the boat, is perfectl\- silent goint ahead, and far quieter astern than is usually the case. Hesse and Savory Reverse Gear. The Hesse and Savory combined clutch and reverse gear is a very neatly-designed piece of mechanism, an elevation and sectional half-plan of which appear herewith. A dish-shaped member is bolted to the after face of the engine fly-wheel, the inner face of the flange of the dish forming the female portion of a cone clutch, of which the male member is keyed direct to the tail shaft, giving a direct drive ahead when engaged, the thrust of the propeller sufficing to keep 40 Oo8 "Verbal" Notes and Sketcnes the clutch in engagement. The reversing gear is of the ordinary differential type, but differs from the usual practice in that the bevcl wheels and case do not revolve bodily when the boat is going ahead. The large bevel wheels are free to revolve on the tail shaft, the forward one being mounted on the back of the female member of a clutch, which, for going astern, engages with the outer face of the flange of the member attached to the fly-wheel. The after bevel wheel has Elevation. Sectional Half-Plan. No. 26.— Hesse and Savory Reverse Gear. one member of a dog clutch on its back face, the other member of the clutch being keyed to the tail shaft. For going astern the bevel wheels are brought bodily aft, so that this dog clutch is let in at the same time as the last-mentioned cone clutch engages. The drive from the cone clutch to the dog clutch is, of course, transmitted by the bevel pinions, which are carried by the case of the gear; this ca.se, as already mentioned, being mounted on the engine bearers, Internal Combustion Engines 609 cannot revolve. This gear, the makers claim, is strong and efficient ; it certainly has few parts to get out of order, and possesses the additional merit of cheapness. It will be noticed that the complete control is effected by one lever, the only function of which is to bring the clutches in and out of engagement, and which requires little or no skill to manipulate ; indeed, the gear possesses all the handiness of a reversible propeller without any of its disadvantages. A remarkable feature is the entire absence of springs of any kind. Fairbanks' Reverse Gear. This reversing gear is of the ordinary differential type, the ahead drive being direct through a cone clutch, which carries the bevel wheels round as a solid body, while for going astern, the reversing o o No. 27.— Fairbanks' Reverse Gear lever is simply pulled aft, taking the ahead clutch out of gear and engaging another cone clutch on the gear-case with a stationary member, thus holding the star pinions of the gear in a fixed position and giving a drive astern. OIL FUEL. This method of firing has recently come very much to the front, particularly in naval practice, and a brief description of the system will not be out of place. The chief drawbacks to the use of oil fuel at present are those of suppl\' and of cost ; oil supply ports being few in 6io "Verbal" Notes and Sketches number, although in time this matter will be remedied. The cost is also a 'consideration, but this will also be adjusted to meet the requirements of the demand. It may safely be stated that as fuel, oil has a great future before it in marine practice. Advantages of Oil Fuel over Coal. 1. Less bunker space required (about 36 cubic feet against 44 cubic feet per ton). 2. Greater heat per pound (20,000 B.T.U. for oil agamst 14,500 B.T.U. for coal). 3. Cleanliness both in working and bunkering. 4. Reduced stoke-hole staff. 5. Greater control of fires. 6. More complete combustion obtained. Disadvantages. 1. Difficulty of obtaining oil supplies, 2. Cost. 3. Danger from inflammable vapour caused by leakage into bilges, &c. 4. Danger of oil leaking into steam side of heater and finally entering boilers. Oil and Coal Compared. -.. , Heat units Puel. 1 , 1 per pound. J 1 Bunker space per ton. Coal - - - Oil - - - 14,500 19,000 44 cub. ft. 36 „ „ NOTE.— Taking into account both heating value and bunker space, one ton of oil is equivalent to i-6 tons of coal. The U.S. Naval Department Committee report on the advantages of oil fuel as follows : — 1. A greater evaporative efficiency in ratio of about 14 to 9. 2. A reduction in the fire-room force. 3. Elimination of ashes and dirty fires. 4. Convenience of storage. Oil tanks may be located in double bottoms, in spaces now useless. 5. Rapidity and ease of taking aboard and handling. The manual labour in this connection is eliminated. 6. Easy control of fires, permitting sudden variations in power developed by boilers. Internal Combustion Engines 6ii 7. Facility of controlling proportions of the air and fuel, thus ensuring good combustion. There is no opening or shutting of furnace doors of varying thicknesses as is the case with coal. 8. Elimination of cinders and of smoke, except at full power. 9. The reduction of fire room, there being no space required to permit working of the fires. 10. As there is still a much better distribution of coal among the seaports of the world than oil, this is said to be one of the principal disadvantages of oil. Composition of Oil. — The average composition, &c., of the oils used as fuel are as follows : — Class. Flash Point. Specific Gravity. Carbon (C). Hydrogen Oxygen (O). Heat Units per Lb. Burmah Shale - Russian Petroleum '200° 125° 120° •92 •81 •822 Per Cent. 86 86 86 Per Cent. 12 14 '•5 I 18,800 19,000 20,000 Methods of Working. — Oil is pumped into the tanks which act as bunkers, and is afterwards pumped into direct supply tanks known as " settling tanks." These tanks are generally placed at some height above the floor plates, and are intended to allow any water which may have become mixed with the oil to settle to the bottom, leaving the pure oil on top. This oil, after being heated and filtered, is then pumped under pressure direct to the burners which are fitted on the front of the furnaces. Oil Spray. — The oil, under pressure, is sprayed into the furnace through the nozzle and needle valve of the former, and this results in atomising of the oil which flashes up just after leaving the nozzle point, the effect produced being that of a mass of gas at white heat filling up the entire space of the furnace or combustion chamber. Burners. — In one system the oil jet is mixed with steam as it enters the burner, and in another system air only is mixed with the oil jet and forced through the burner. In the Navy, however, the oil, at a pressure of about 100 lbs. and temperature of 200" Fahr., is forced through the burner, and the air (of usual forced draught pressure) enters the slots of a specially designed cone, and .so mixes with the rotary spray. The burner itself sits inside the air cone at a slight upward angle, and the air enters first by air doors on the boiler front, and from these into the slots of the cone previously mentioned. Each 6l2 "Verbal" Notes and Sketches cone is boxed in by division plates so that the air supply is localised to the corresponding burner. No. 28.—" Kermode " Type Oil Burner. The Admiralty type burner is similar in principle to the above, but is of much improved design, giving higher efficiency. A, Oil feed to burner. B, Nozzle. C, Regulating spindle. D, Burner body. E, Cap nut. F, Graduated wheel. G, Pointer. H, Grooves in nozzle end. Shale Oil.— With Scotch shale oil a heating temperature of about 125 Fahr. is generally sufficient. Specific gravity of CO = -96. No. 29.— Oil Fuel System. 1, Fuel pumps. 2, Suction from supply tanks. 3, Air vessel. 4, Discharge from pump to cold filter, "Verbal" Notes and Sketches. 5, Cold filter or strainer. 6, Heater. 7, Hot filter or strainer. S» Distribution chest or header. 9, Oil fuel to burner. 10, Oil burner. 11, Air-tight box. 12, Air cone The above is the system in use in the Navy. 13, Air doors, 14, Steam to heater. 15, Drain from heater to feed tank. 26, Thennometer for oil temperature \_To ja^e po£e t\l Internal Combustion Engines 6i o Working Oil Fuel. — The oil fuel is pumped from the supply tanks by the oil pumps, and forced through a cold filter, then through a steam heater where the temperature is raised, next through a second or hot filter, and from there to the distribution header on the boiler front, from which valves and pipes connect to the several burners fitted. In Yarrow type boilers from eight to eleven burners are supplied, but of course all of these may not be required except when steaming under full power conditions. The pressure of the oil is about loo lbs., and the temperature 200 , with "shale" or "Texas" oil as fuel. Control. — The regulation of the fires is controlled by the needle valve of the burner, which can be altered to increase or decrease the angle of discharge, and therefore the output or consumption ; one small wheel on the burner constituting the entire control gear. The combustion of the oil is therefore regulated by the oil needle valve and the air supply doors. The oil fuel is pulverised by being forced, under pressure, through the restricted opening of the burner end, which, by means of the grooves, imparts a rotary motion to the jet, the latter being dis- tributed in a cone-like spray or cloud of pulverised oil particles. In the Navy the closed stoke-hole forced draught system is employed, which means a constant and steady air pressure on the oil fuel. , Starting Up. — In starting up the fires, a hand pressure pump is employed, which forces a small quantity of oil through a (J -shaped and flexible tube which is placed inside the air cone ; and, having previously set fire to a quantity of oily waste, the heat so produced raises the temperature of the oil flowing through the U tube on its way to the starting burner. After the starting burner has been the means of raising sufficient steam to set away the oil pumps, the starting device described is withdrawn, and the other burners are set away. About three hours is allowed to get up steam in water tube boilers. Leakage Test. — Before the fires are started a leakage test of the oil system is generally made by raising a pressure of 50 lbs. or more with the hand pump, and examining for leaks at the tanks, pipes, joints, bilges, &c. Colour of Gases. — The colour of the gases in the combustion chamber space indicates the efficiency of the combustion taking place inside, and the pressure and temperature of the oil, in addition to the output required, is regulated accordingly. A very small tail of smoke at the funnel top indicates that combustion is practically complete. The colour of the gases can be observed by means of sighting holes in the boiler casings. 6i4 "Verbal" Notes and Sketches Flash Point and Firing Point. — It should be noticed that the spray of atomised oil at a flash point of 200° is below the " firing point," but on striking the cone ring, the temperature of which exceeds the flash point, ignition instantaneously takes place. Firing" Point. — The firing point of oil is above the flash point, and means that the oil itself (instead of the vapour) ignites. Flash Point. — By this is meant the temperature at which the vapour formed from heated oil flashes into flame when brought in contact with a light. The flash point varies from. 70° in light petrol spirit to about 240" in heavy burning oils. The Board of Trade require a flash point of not less than 185" Fahr, Sand. — As a safeguard against fire, boxes of sand are placed ready for use in the stoke-holes, as the sand thrown on oil flame quickly extinguishes the same. Black Smoke. — This is caused by the temperature or pressure of the oil fuel being too low for complete combustion. White Smoke. — This may be caused by excessive air suppl}' or by faulty oil feed through the burner. Ventilation Pipes. — To allow for the escape of oil vapour " swan- neck " pipes should be led from the top of the oil tanks to the deck, the ends of the pipes being open, but covered with gauze wire to reduce risk of explosion by a naked light. When the tanks are empty, however, the vapour formed by slow evaporation is much heavier than the atmosphere, and will therefore occupy the lowest positions in the tanks, and the gases thus formed are best removed by means of exhausting fans. Air Vessel. — To maintain a steady oil pressure in the sprayers an air vessel is fitted on the discharge side of the oil supply pump. Settling Tanks. — Sometimes these tanks are fitted with a steam coil to heat up the oil, the effect of which is to separate more quickly the water ; the heating up causing a greater difference in the respective densities of the two liquids. The heating is done by exhaust steam of low pressure and temperature, so that there will be no danger of the oil vaporising. A gauge glass is fitted on the tanks, and the water shown can be drained off by suitable drain pipes. A temperature of 180° is required to produce separation of the water from the oil in the settling tanks. Air Cone.— The air cone (Sketch No. 29) is fitted with small air openings round the shell, these being formed by three-sided cyts, the No 30— Sulzer Marine Diesel Engine, 200 I. HP. (Speed Revolutions per minute ^.m iVUU \ I.H.P. hour ^ i.n.r. I Fuel per I.H.P. per h y Cost of fuel per mile IO-6 knots. 300. 174. •40 of a pound. 15 pence. 'Verbal " Notes and .Sketches. LTo /(ut fage 615. Internal Combustion Engines 615 fourth side being bent outwards to form the air opening. This arrangement gives a centrifugal motion to the entering air and to the oil spray, which effect chiefly accounts for the efficiency of this system. Evaporation of Oil. — i lb. of oil fuel evaporates about 15 lbs. of water into steam (from and at a temperature of 212°). Water in Oil. — In burning oil fuel, water shows by the oil forming a brown coloured foam near the burner nozzle. Sputtering also occurs at the burner, and if the water present is excessive, the burner flame may go out altogether. White Vapour. — In burning oil fuel white vapour at the funnel top indicates that the oil vapour is passing off unconsumed owing to excessive air supply, which lowers the temperature of combustion, with the result stated. Diesel Oil Engine. Regarding the development and application of the Reversing Internal Combustion Engine on a large scale, it is the opinion of most experts that a great future exists for this type of engine, and it would appear that this future is by no means far distant, since all the more important yards are preparing to supply Diesel Marine Engines, and, in many instances, the construction has already been begun. It was apparent, however, that not being direct reversing, its application to large steamers was impossible, inasmuch as the systems employed for reversing the screw by means of revolving blades or reversing the propeller shaft by special gear, could never offer the same amount of safety in a large ship, and for this reason underwriters considered it a greater risk than the steam marine engine. These difficulties were overcome, however, in the year 1906 by the invention and introduction by Messrs Sulzer Brothers of VVinterthur and Ludwigshafen-on-the-Rhine of the direct reversing engine which transformed the Diesel engine into an actual marine engine suitable for the very largest vessels in which the shafts remain coupled direct to the engine, as is invariably necessary in large boats. After an experience extending over three years with marine engines of the above mentioned firm, which had been supplied for a number of boats still in service, and in view of the fact that substantial improvements have been introduced into the details of construction, the advantages possessed by this engine are now easy to prove. Compared with a boat driven by steam, a saving of about one-third in the length of engine-room is effected, while the weight of the entire plant is about one-fourth that of a steam-engine plant of equal power, so that considerably more cargo can be carried with a corresponding 6i6- "Verbal" Notes and Sketches increase in freight receipts. A further increase in freights is obt€.ined by the reduced weight of liquid fuel as compared with coal. This amounts to 20-25 per cent, less than would be required for the coal of a steam-engine of similar power. There is a further saving in working expenses, as no stoker is required, no repairs to boiler are ever necessary and fewer hands are required to attend to the machinery. In the Diesel engine all physical processes for converting the fuel into energy take place inside the working cylinder. Combustion of the liquid fuel, which is introduced by means of compressed air, takes place automatically in the hot air obtained by compression in the working cylinder. The combustion is gradual, there is no increase of pressure and, consequently, no explosions. The motor is started by means of compressed air, which is stored at a pressure of about 800 lbs., and the supply is sufficient for twenty starts without replenishing. Compressed air is admitted to the cylinders by simply turning a wheel, a further turn puts the starting valve out of gear, and operates the fuel valve, and the engine then begins to work upon the introduction of the fuel. In the same way the engine is brought to a standstill, restarted, and reversed. These engines require much less attention than a steam-engine, the supply of liquid fuel to the cylinders is automatic, and, therefore, one engineer is sufficient to look after the engine. One great advantage in favour of the Diesel motor as a marine engine and deserving of special mention is the fact that it is always ready for use, and being on the two-stroke pgnciple, only the starting and fuel valves on each cylinder require reversing. The following descriptions of the action of the Diesel type marine engine are taken from a paper by J. T. Milton, Esq. (Vice- President), read before the Institution of Naval Architects, 6th April 191 1 : — " It may be well to state here what is claimed for the Diesel engine in the way of consumption. In an ordinary steam-engine the power is generally reckoned as indicated horse-power. This is the work performed by the steam on the piston, and is the gross power obtained. It has to overcome the friction of the mechanism, work the slide-valves and the pumps, and only about 85 per cent, in round numbers is transmitted to the shaft. " In the Diesel engine the indicated horse-power has similarly to overcome the friction of the mechanism, it has to work the fuel-pump, the mechanism for actuating the valves, and to supply the com- pressed air necessary for injecting the fuel. In the two-stroke cycle also it has to work the scavenging pump. These take up more of the gross power than do the accessories in a steam-engine, and hence a less proportion of the gross, or indicated power, is transmitted to the shaft than in a steam-engine. For this reason the power of a Diesel engine is more usually expressed as its brake horse-power— that is, the power usefully exerted outside itself. Internal Combustion Engines 617 " It is usually claimed that the oil consumption per brake horse- power per hour is 04 lb. when the engine is working at full power, and when working at somewhat lower powers the rate of consumption is not much increased. " If one assumes that in a modern steam-engine the consumption of coal is 1-25 lbs. per indicated horse-power per hour this corresponds to about 1-47 lbs. per brake horse-power, so that the weight of fuel to be carried for the same voyage in a vessel fitted with Diesel engines would be only 28 per cent, of that of the coal necessary with ordinary steam-engines. "We will now turn to the engine itself. Its principle of working is generally known. It is made in three forms for marine purposes — viz., as a four-stroke cycle single-acting engine, a two-stroke cycle single-acting engine, and a two-stroke cycle double-acting engine. An essential feature of these engines is that they require, besides their own cylinders and pistons, an auxiliary air-compressor capable of producing a pressure of about 700 lbs. per square inch. "In the four-stroke cycle-engine the cylinder-cover contains a fuel-valve, a compressed-air admission-valve, one or more ordinary air-admission valves, and one or more exhaust-valves. All these valves are actuated — that is, opened — by means of cams fixed to a cam-shaft, and are kept closed by powerful springs when the cams are out of action. The cam-shaft is driven by a two-to-one gear — that is, it makes only one revolution for two revolutions of the engine crank-shaft. Broadly speaking, the cams are so arranged that the air-admission valves are open during one whole down-stroke, and the exhaust-valves during one whole up-stroke, but actually a little ' lead ' is necessary. The cams for the fuel-valve and the compressed-air valve are so arranged that only one of these can be in operation at a time, so that when either is in use the other is entirely inoperative. In ordinary running, the fuel-valve is opened at the proper time when the piston is at the top of its travel, and is closed again when about one-tenth of the downward stroke has been made. The compressed- air valve is only used for starting purposes, and it is kept open for a longer period — say, for half or even more of the stroke — its range of opening being made to depend upon the number of cylinders used, so that when these valves are in gear there is no position of the engine in which there is not at least one of them open. " In starting the engines these valves are put into gear, and the fuel-valves are consequently put out of action. When the engine has made one or more complete cycles, the compressed-air valves are put out of gear, the fuel-valves commence their work, and the engine then continues its motion, working under ' fuel ' conditions. As the air- admission valve-gear is in full operation during the starting opera- tions, the full compression would have to be overcome in each cylinder in turn, if it were not for a special arrangement made to relieve part of the pressure in order to facilitate starting. This is put out of action when the fuel admission is put into gear. 6t8 "Verbal" Notes and Sketches " Commencing with a piston at the top of the cylinder, the four- stroke cycle is as follows : — " First Down-Stroke. — The ordinary air-admission valve is opened during the whole stroke, and the cylinder becomes filled with atmo- spheric air at the ordinary atmospheric pressure. " Second Stroke. — The air-valve is closed, and the piston returns to the top of the cylinder, compressing the air which has been drawn in during the previous stroke. The clearance is so proportioned that in ordinary working at full speed the pressure becomes about 500 lbs. per square inch, and the temperature is, at the same time, very much raised. The compression is not quite adiabatic, as the cold cylinder walls must abstract a little of the heat from the air. If it were truly adiabatic the temperature of the air would be raised from, say, 60" Fahr. to 1000° Fahr. " During this stroke a quantity of fuel has been pumped by the fuel-pump into an annular space round the fuel-valve. When the piston is at the top of the stroke,, the fuel-valve is raised, and, at the same time, cold air from the air-compressor reservoir at a pressure of 700 lbs. per square inch blows the fuel into the cylinder, which con- tains hot air, at a pressure of 500 lbs. per square inch. The construc- tion of the fuel-valve is such that the oil is pulverised or atomised — that is, it is divided up into a spray of very fine particles. These, upon coming into the very hot air in the cylinder, ignite, and the heat produced by the combustion increases the volume or the pressure of the air. When the adjustment of the valve is correct, the admission of the fuel and the combustion proceed at such a rate that they are almost completed during the time taken for the piston to travel one- tenth of its stroke, and during this period the pressure of 500 lbs. per square inch is maintained. " TJiird Stroke. — The third stroke of the cycle commences with the combustion of the fuel as mentioned above, after which, during the remainder of the stroke, the hot gases in the cylinder expand until the end of the stroke is reached. " Fourth Stroke. — The return of the piston constitutes the fourth stroke, and during this time the exhaust-valves are open, and the burnt gases are expelled from the cylinder. After this the cycle commences afresh. " In the two-stroke cycle single-acting engine, the cylinder covers are similarly fitted with fuel valves and compressed-air valves for starting purposes, but the ordinary air-inlet valves and exhaust valves are replaced by scavenge air-valves. All these valves are actuated by cams ; the cam-shaft, however, in these engines rotates at the same speed as the main engine shaft. " The pistons are made somewhat deeper than the total length of stroke. At the lower end of the part of the cylinder barrel uncovered by the movement of the piston, there are numerous ports leading into the exhaust passage. These ports have a vertical dimension of about one-seventh of the stroke. f^Qrcle. Intake. C i (em.q '■ Verbal " Notes an< WORKING DIAGRAMS OF SINGLE-ACTING DIESEL ENGINES. JntaJoe. FOUR-STKOHE CYCLE. Z'^fyde. S'^Q.'df. 4'^Qfcle. CompressioTv. Wcrkin f»i#»»#»»»^ ^\i 1 1 ^^ _i-^[ ^■^ 1 _,^^^ , ^. ^^ y ./ ' A v^ -^ -/ ■ it: _r o- _u t "it T ^ .. t "it '" -t ^ • •VorlMl -Notes and Skelcl.c No. 4.— Sectional View of H.P. Turbine. (Also Blade Angles and S'.eam Velocities I Messrs A. i: J. Inglis Lid. " Vutbal ■• Nolcs mid Skctclie No. 5. ^L.P. Ahead and Reverse Turbines. I The H.P. Turbine shown in background. Khedive's Yacht "Mahroussa.' Appendix Increase of Steam Volume. — To allfjw of the steam incrcasinj^ in V')lLime, as fall of pressure takes place, the various sets of blades increase in length from the forward to the after end, the clearance spaces between the blades also increasing- in proportion, which necessitates packing pieces of a larger size being employed. The blades also vary in shape or curvature, being flatter in section aft COPPER WIRE BRASS WIRE PACKING PIECES COPPER WIRE PLAN No. 6 — Elevation and Plan of Rotor Blades in Position, showing how secured (full size). than forward Each set of blades for each expansion requires its own allowance for expansion of metals by heat, so that the working clearance between the blades and casings or drums increases slightly throughout the turbine from forward aft. One of the practical diffi- culties met with in turbine construction at present is the correct adjustment for this expansion, as slight mishaps have occurred in 634 Verbal" Notes and Sketches one or two instances ovvin^^ to fouling of the parts when heated up, the clearance allowance being insufficient. Strictly, each successive ring of blades should be either of a wider pitch or greater height than the preceding one, as the steam is con- tinuously falling in pressure and expanding in volume. Dummies. — The dummies are placed at the steam admission end of each turbine, and two kinds of dummies, known respectively as radial and facialj are employed: the facial dummy is usually fitted in the ahead turbine, and the radial dummy in the astern turbine. The principle of the dummy is to prevent the steam from escaping through the interior of the rotor to the exhaust end of the casing instead of doing its legitimate work in passing through the blades of the turbine. Another reason is that if no dummies were fitted, the full initial pressure would be on the glands instead of exhaust or terminal pressure. A facial No. 8. — Ahead H.P. Dummy Facial Rings. (With average dimensions.) dummy consists of two parts called the casing dummy and the rotor dummy. The casing dummy is a cast-iron cylinder, which is in two halves, bolted together at the horizontal joint. This cylinder is bored out and grooved, the grooves being usually i in. wide and yV in. deep, and into these grooves are driven brass strips. The brass strips are bent to the radius of the cylinder, and a serration made in them, so that the serration is just flush when the strip is driven into groove. After the blades are in place, the metal of the cylinder is caulked into the serration, thus binding the strips. The strips are cut in lengths of about 6 in. No. 7.— Turbine Thrust Block. Lower Half for Ahead Thrust ; Upper Half for Astern Thrust. (1) Ahead thrust. ' (5) Oil inlet. (2) Astern thrust. (6) Counter gear worm. (3) Taper key for adjustment of lower half. (7) Inspection door. (4) Taper key for adjustment of upper half. (8) White metal of mean bearing. (9) "Reliefs" for wear down. \_To face page 634 " Verbal '' Notes and Sketches. rit- VA "Qzzz /////// ,y^ .rmow ifi5^ .loofa no Msi}\ laqqU ; JeinriT besriA lo^ llsH »woJ (2) •vob -ifi9W lol ' elsibS ifl:)i9}<8 bnfi »loid Appendix 635 "BLADING LIST." The following example of a " blading list " from actual practice will afford the student a fair idea as to the blade heights, &c., generally fitted :— Type— Fast Channel Steamer. Speed, 22 knots. Equivalent I.H.P., 8.500 (approximate). Turbine Data. H.r. Turbine. (Drum, 2 ft. 6 in. Diam.) Expansion. Number of Blade Rows. Blade Heights. I 2 3 4 13 13 14 14 \\ in. 2in 3 ,. 4^- „ L.P. Turbines ( two). (Drums, 3 ft. 9 in. Diam.) Number of Blade Expansion. Rows. B ade Heights. I I .^- in. 2 ^i>. 3 3 „ 4 4i„ 5 6 „ 6 8 n 7 8 „ 8 8 „ Astern Turbines. (2 ft. 6 in. Diam.) Expansion. Number of Blade Rows. Blade Heights. I 2 3 4 5 00000 ii in 2^ „ 2^ „ 2| . 636 " Verbal " Notes and Sketches the casing in one row a 9-in. piece is put in, and in the succeeding row a 4i-in. piece is put in, so that the joints in each row are not in line. The strips are left "-012" clear of each other at the ends so as to allow for expansion. After the blades are all in place and caulked, the dummy is put into lathe, and the blades turned up. The blades have a face bearing of "-015 " so as to ensure that if the rotor dummy should touch, the friction caused thereby would be reduced to a minimum. The rotor dummy is of steel, and usually cylindrical, and is sometimes made in two halves. The dummy is rigidly bolted to the rotor, and turned up in place. A series of grooves corresponding to the brass strips in the casing dummy are turned out, having a fillet in both sides of groove, the grooves being fV '"• deep. The brass strips in the casing dummy project into the groove in the rotor dummy ^ in. When the rotors are set to position in the casing, the factor which determines this position is the dummy clearance, this varying according to the size of turbines. For average sizes the clearance is usually as follows : — •025 to -040 in the high-pressure turbine, and -025 to -060 in the low-pressure turbine. The working clearance allowed between the tips of the rotor blades and casing, also between the casing blades and rotor, are given in the following" table taken from an actual case : — BLADE TIP CLEARANCES. Taken -when cold. H.P. Turbine. Rotor Drum, 48 in. Diameter. Expan- Radial Clearance (Port). Radial Clearance (Starboard). Longitudinal Clearance. sion. Rotor Casing Rotor Casing Port Port Starboard .Starboard Blade Blade Blade Blade Forward Aft Forward Aft Tips. Tips. Tips. Tips. Side. Side. Side. Side. Inch. Inch. Inch. Inch. . No. I •041 ■041 •052 •043 i 3 T6 1 5 32" ,, 2 •051 •055 •059 •049 9 3T 1 4 1 4 i » 3 •063 •055 •070 •061 9 ■■J 2" 1 4 '.!_ i „ 4 .049 •055 •054 •051 •2 li 04 5 T6 1 1 ■S-2 11 3 5 .2 "a !- V rt - O := > ■£ — O ■? y vj O u C S e; -13 O = > 3 __ u a? ^ '^ U «5 ^ Z 2S Appendix Starboard L.P. Turbine. Rotor Drum, 68 in. Diameter. ^2>1 Radial Clearance 1 Radial Clearance Expan- (Port). 1 (Starboard). Longitudina 1 Clearance. 1 ■ sion. Rotor Casing Rotor Casing Port ! Port Starboard' SUr board Blade Blade 1 Blade Blade Forward Aft Forward Aft 1 Tips. Tips. Tips. Tips. Side. Side. Side. Side. Inch. ^ Inch. Inch. Inch. No. I •070 •080 •068 -070 7 TTir 1 .-J 64 1 7 6T » 2 •072 •085 •070 •085 T?r 7 ¥5" \ tV . n 3 •078 •090 •082 •092 11 9 ay i 1 7 6T » 4 •082 •092 •082 •085 5 11 32 5 T6" 3 8 » 5 ■085 •093 •085 •088 7 11 ■3 2 1 1 11 T2 „ 6 •095 •123 •098 •115 7 i 13 iV M 7 •102 •125 •105 •112 tV i TT 15 32 » 8 •102 •115 •105 -3 iV k tV \ NOTE.- •050 inch = -^ — inch, 1000 •092 inch = -2^ inch, &c., &a 1000 No. 9. — Plan of Turbine Room. 638 "Verbal" Notes and Sketches Oli 4) M V ^ 4-> -c: X ^ c a. p M 3 3 a ,,,^^ c r^ rt f^ u 6 Q u p c U a; c C 6 f) '4- •a a, :3 i) r Q •a t/; a, U4 cj OJ (/) ^- •^ a t>0 c 5 C h (A X) rt C ^ TJ 2 c^ nS m >, < 3 u u. 4) i c 1 h 3 '. 3 U c M U hfl D rt u n u. u lO >-, Kl ^) ^Z oiu -G 4} a '•a H 3MIOM. = os. 3e L \^ No. II.— Plan of Combined Reciprocating and Turbine Arrangement. With Theoretical Horse Powers. (1) Change valve, giving steam either to turbine or condenser direct. (2) Reciprocating engine thrust block. (3) Turbine thrust block. 'Verbal" Notes and Sketches. (41 E.ihaust from reciprocating engine to turbine or to condenser. (5) Branch to turbine. (6) Branch to condejiser. Appendix 639 Combined Reciprocating Engines and Turbines.— The most recent practice in mercantile steamers is the combination of reciprocating engines and turbines for vessels of moderate or low speeds. Several steamers of this class are at present under construction, and the arrangement consists of two wing triple or quadruple expansion engines exhausting into a central low-pressure ahead turbine, driving a third shaft and propeller, the revolution speed of the centre turbine shaft being much higher than that of the wing shafts. An alternative design is that of two wing low-pressure turbines and one centre re- ciprocating engine. The engines are arranged to be run as follows : — (i) Boiler steam to both H.P. cylinders, and exhaust from these to turbine, the exhaust from the turbine being divided and led into two separate condensers. (2) Boiler steam to both H.P. cylinders, and exhaust from these to condensers direct, the turbine being then cut off. This is required when running astern as the turbine is for ahead running only, and may be used for ahead running with two propellers only. (3) Boiler steam to either H.P, cylinder, and exhaust from L.P. to centre turbine, then into one condenser only. These combinations are obtained by the use of " change valves " fitted on the L.P. exhaust pipes, and by large butterfly valves fitted in the turbine exhaust branches. The change valves admit the reciprocating exhaust steam of either side to the turbine, or to the condenser as required, and the large valves in the turbine exhaust pipe shut off the condenser on either side as may become necessary should one reciprocating engine require to be disconnected through breakdown. Benefits of the System. — As, broadly speaking, the economy of the reciprocating engine depends chiefly on high-pressure steam, and the turbine on low-pressure steam, the judicious combination of the two ought to result in higher efficiency results. The turbine is therefore most effective in dealing with steam of a pressure which cannot be utilised with benefit in a triple or quadruple expansion engine, owing more particularly to the huge volumes involved, and requiring increase of weight, space, and frictional losses. The L.P. exhaust pressure to the centre turbine is usually 7 or 13 lbs. absolute. This will produce a difference in the usual L.P. cylinder diagram cards, bringing up the exhaust line to a position much nearer the atmospheric line than usual. The loss of work energy so represented by the reduced indicator card area in the L.P. engine will be more than balanced by the in- crease of power developed in the turbine. The economical result of the combination arrangement is, to all appearance, beyond question, and may in time, with suitable improve- ments which experience suggests, prove adaptable for the usual tramp steamer speed of from 8 to 10 or 11 knots. An innovation has been made in the case of the turbine glands, 42 640 "Verbal" Notes and Sketches which, instead of the frictionless steam packing hitherto adopted, have in one case been changed for the usual marine type of piston-rod gland, consisting of rack and pinion screwing-up gear with soft packing inside, this type of gland being fitted at both ends of the turbine. Description of the Propelling Machinery of the Q.SS. " Reina Victoria-Eugenia." Constructed by Messrs Swan, Hunter, & V/igham Richardson Ltd., Newcastle-on-Tyne. "The propelling machinery consists of two complete units of reciprocating engines and turbines, driving four screws in all. " The reciprocating engines are of the well-known four-crank triple- expansion type, balanced on the Yarrow-Schlick-T weedy prmciple, with cylinders 29 in., 43 in., 45 in., and 47 in. in diameter, and a stroke of 42 in. The low-pressure cylinders at each end of the engines are designed to develop less power than the other two cylinders, so that a very uniform turning moment is obtained, in addition to good balancing. " Each engine exhausts into a steam turbine through special mancEuvring-valves mounted at the back of each low-pressure cylinder, and operated by levers on the reversing-shaft. These valves are so arranged that the exhaust steam is passed direct to the con- denser when the reversing-gear is in the astern position. Thus all manceuvring is done by the reciprocating engines on the inboard shafts. Provision is made, by means of screw and hand-wheel, whereby the turbines can be cut out entirely by passing the steam directly into the condenser under all conditions. " The turbine installation comprises two low-pressure Parsons turbines driving the wing-shafts, and designed for working ahead only. Steam enters each turbine at the forward end through two iSi-in. diameter pipes — i.e., one from each low-pressure cylinder — with a suitable strainer in each branch, the admission pressure being about 10 lbs. per square in. absolute, with a maximum steam con- sumption of 135,000 lbs. per hour. The exhaust branch, having a cross-sectional area of 30 sq. ft., is designed for a condenser pressure of I lb. absolute. The rotor drum is parallel, 68 in. in diameter, and carries thirty rows of blades. The dummy at the forward or steam end is fitted with labyrinth-packing strips of the radial type — ten strips in the rotor and ten in the casing. The diameter of the dummy is such that the total axial steam thrust on the rotor substantially balances the propeller thrust. The rotor shaft glands are of Parsons combined labyrinth and ring type, each being fitted at the inner end with ten rows of moving, and ten rows of fixed, rings, and with four Ramsbottom rings at the outer end. The glands are so designed as to be easily overhauled without lifting the turbine-cover. The rotor journals at each end are 12 in. in diameter, working in white-metal bearings, each 23 J, in. long. A rotor adjusting-block is fitted at the 18 Cl Overall SET N°IZ PORT ENGINE Revs.pe-r Mirt. jl't-l (lS.S.REINAVICTORm-EUCENI/\. SET Nrl2 a HOURS STEAM TRIAL STARBOARD ENGINE. FEB. iai3. Jj^sperUutHS-S ToUUl^f^Mm ' WfOTotai/.fLP Total JJfJ^ Both Engine 74SO No. 12— Parson's Exhaust Turbine for the QSS. " Reina Victoria Eugenia ' (and Set of Diagram Cards). Appendix 641 forward end for the purpose of adjustini,^ the axial position of the rot(jr, and contains ten rini^s, which bear upon the faces of correspond- in^^ collars on the rotor shaft. Lubricating oil is supplied under pressure to the bearings and adjusting-blocks b\- a duplex oil-pump. The oil draining from the bearings, &c., is collected in a tank and cooled before being discharged again to the bearings. One of the turbines is illustrated on opposite page. "The condensers are of the 'Uniflux' type, and have each a cooling surface of 5100 sq. ft., designed for a vacuum of 28 in. with an average sea temperature of 75". The ig-'m. circulating-pumps supplied by Messrs H. Watson & Co. have proved capable of dis- charging 8500 gallons per minute against 23-ft head. "The air-pumps are of Weir's latest 'Dual' type, of 13 in. by 24 in. by 17 in. each. There are further installed two pairs of Weir's feed-pumps, with cylinders 13I in. by 10 in. by 24 in., two 35-ton evaporators, two 90-in. Howden fans, three 60-kw. dynamos, a 12-ton distiller, a ballast donkey, two general service donkeys, various smaller pumps, a refrigerating plant, and a Clayton fire-extinguish- ing machine, which has already been illustrated and described in Engi}iccring. The exhaust steam from all au.xiliaries is utilised for heating up the feed-water, a ' Neptune ' surface-heater being in- stalled for this purpose. "There are seven single-ended boilers of 16 ft. 3 in. outside diameter and 1 1 ft. 6 in. in length, working on Howden's system of forced draught. Each boiler has three large furnaces, yielding a total grate surface of 480 sq. ft. : the total heating surface is 20,965 sq. ft., and the working pressure 180 lbs. per sq. in. "On trial the ship half laden was required to steam 17-5 knots for eight consecutive hours, and when fully laden at a speed of 16 knots for twenty-four consecutive hours. The actual results obtained are given in the table on \^. 642, and show that on the eight hours' trial a speed of 181 2 knots was obtained in adverse weather, while on the twenty-four hours' trial the speed obtained was i6-iO knots. In good weather conditions and in deep sea, it is certain that higher speeds would have been secured, and we are informed that off Cadiz, in a deep sea and fine weather, the speed obtained has been greatly in excess of that realised at the trials carried out off Newcastle. " The steam consumption was measured by means of standard nozzles regularly employed by the builders for this purpose ; the figures given in the table include make-up feed (about 1-5 per cent.). Progressive runs over the measured mile at St Mary's, on the North- East Coast, were made during each trial in order to determine the speeds obtained on the respective trials. The maximum speed recorded on a double run was i8-6 knots in shallow water (about 75 ft. deep), as, owing to the foggy weather, the mile-posts could only be seen a small distance from the shore. "A set of indicator-cards taken during the eight hours' trial is shown, and the results are of special interest in view of the high pro- 642 Verbal " Notes and Sketches pulsive efficiency indicated by the low consumption of power. It should be mentioned in connection herewith that the experiments made by the builders some years a ») I per cent, slip - 4 per cent, slip Turbines .... 481 r.p.m. - 395 r-P-m. j ,, 20 per cent, slip - I 3 per cent, slip Indicated horse-pouer 7340 5760 Shaft horse-power - 3500 2157 Total horse-power - 10,840 7910 s'd* H.P. 257 • 294 Pressure, H.P. chest 170 lbs. per sq. in. 170-5 lbs. per sq. in. ,, turbine 7'8 lbs. per sq. in. absolute 5'4lbs. per sq. in. absolute ,, condenser 0'5 lbs. per stj. in. absolute 0-56 lt)s. persq. in. absolute Temperature, sea - 43 deg. Fahr. . 45 deg. Fahr. ,, discharge - 70 . 64 ,, hot- well 70 62 ,, feed - 183 Feed-water consumption for main engines 1 14,000 lbs. per hour 85,000 lbs. per hour Feed-water consumption for auxiliaries - - . . 14,000 ., ,, Air pressure in ash-pits - 0'4 in. water - 0-35 in. water Coal heating value by calori- meter - - - . . 14,200 B.Th.U.- 14,400 B.Th. U. Ashes by calorimeter 3 per cent. GEARED DOWN TURBINES. To allow of combined high turbine speeds and low propeller shaft speeds geared down turbines have recently been introduced. This arrangement admits of economy at low ship speeds, owing to the fact that turbines are most efficient at high revolution speeds, and propellers most efficient at low revolution speeds. —i M ^ / / I I I I I I i^ — K-f.-ii PtAN OfMTOR SHEWING LEFT HAND BLAOINC. 20.2^' Over Gland, MouUbS ■ W. ;;V Over Expansions I Reproduced by permission from • Engfineering." Feb. 27, 1914. White Star Liner " Britannic." (By Messrs Harland & Wolff Ltd.) RECIPROCATING ENGINE DATA - The two wing reciprocating engines with two L.P. cylinders placed 01 Schlick Tweedy system. Diameter of cylinders Stroke Type of valves fitted Type of valve gear 97 1 97 1 Type of piston rings fitted Piston valves in all cylinders. Stephenson link motion- wood and Carlisle rings on all cylinder pistons. ept H.P., and on all piston valves. The H,P of the Ramsbottom type. Diameter of HP and IP. piston rods (high tension steel) 14 in. Diameter of LP piston rods ilj in. H.P. and IP. connecting rods From I3J in. to 15 in. L.P. connecting rods - From II) in. to 13 in. Diameter and length of top ends (HP. and I.P.I 16J in. by 171 in. iL.P.l ■ 13J in. by 14I in. Diameter of crank pins 27J in. with 9 in. hole. Length of crank pins (HP and I PI 35 in- (L.P.) 24 in Diameter of crank shaft thrust shaft Number of collars Total thrust surface per block 68«o sq. ft. Diameter of line shafting 2«l in. with 12 in. hole. propeller shaft 28S in. with 13 in. hole, reduced to 6 in. bole at after end ^ Reciprocating Engine X>a.iA--icntinu^a''eb\(i. Appendix 647 The Weir "Dual" Air Pump. The duty of an air pump is to take from the condenser a mixture of air, water, and vapour ; and to obtain economical working, this should be done at the highest possible temperature. If a single pump is used to handle this mixture, the hotwell temperature for a given vacuum is dependent on the amount of air leakage and the air l^ump capacity. Consequently, with a single air pump the tempera- ture of the mixture must be a considerable degree colder than the theoretical temperature due to the vacuum. B)' the use of separate pumps handling the air and water, the dry pump having a cold injection non-returnable to the feed, the above conditions are changed, and higher thermal efficiency is rendered possible. This method enables the wet (or water) pump to handle water at approximately the steam temperature, while at the same time the dr)- pump will deal with the air and vapour at the volume and temperature conditions imposed by the temperature of the injection water. With the " Dual " pump the above advantages are obtained, together with increased efficiency of the dr}' pump, due to its contents being densified or decreased in volume through cooling by the injection water, which circulates continuously, never leaves the system, and is never subjected to atmospheric pressure with con- sequent aeration. The dr)' air pump further works only at less than half the pressure range, as it discharges below the head valves of the wet pump. The apparatus, moreover, is compact, self-contained, and of good mechanical design. Description. — No. i shows in a diagrammatic form the arrange- ment of Surface Condenser, " Dual " air pump, and injection water cooler. In all cases the pump A or wet pump is situated below the steam cylinder, as this pump is the only one which works under any considerable load ; the dry pump B is driven by the beam and links in the usual manner. One connection C is made to the condenser, but a branch pii^e is led to the dry pump, the connection being made in such a manner that the water will all pass by C to the wet pump. Both pumps are generall}' of the three-valve marine type, but in certain cases the dry pump may be of the suction valveless type. The first and most important difference from an ordinary twin pump consists in the dry pump discharging through the return pipe E, through a spring-loaded valve F, into the wet pump at a point below its head valves. The next point concerns the suppl)' of water to the dr\' pump for water scaling, clearance filling, cooling, and vapour condensing. When starting the pump the filling valve G must be opened for a minute or so to enable the vacuum to draw in 648 " Ve^rhal " Notes and Sketches a supply from the hotwell of the wet pump. The valve is then closed, and the water passes from the hotwell of the dry pump by the pipe H to the annular cooler, and after being cooled passes into the suction of the dry pump, then, passing through the pump, it becomes heated and again passes to the cooler, and so on in a continuous closed circuit, any excess passing over the pipe E to the wet pump. The spring-loaded valve F is adjusted to maintain about 20 in. vacuum in the dry pump hotwell when the condenser is working at 28 in, vacuum, and this 8 in. difference of pressure is sufficient to cause the water to overcome the cooler friction and pass into the THE WEIR "DUAL" AIR PUMP. [ To face page 648. Appendix 649 suction, and at the same time never allow any direct air connection between the dry suction and discharge. Operation of Three- Wire System. The generators of this system consist of an ordinary direct current machine with two or more slip rings on the armature shaft extending as shown in the sketch. These slip rings are connected to the arma- ture winding in such a manner as to give single phase in the case of two slip rings, three phase in the case of three slip rings, and two phase in the case of four slip rings. BalancoColls -% CoUector JOL T Comma tatoT* Armature No. 3.— Three-Wire System. (With Single Dynamo.) The slip rings are also connected through the brushes to one or more auto-transformers or balance coils, the middle or neutral point of the balance coils constituting the mid point of the direct current circuit. The sketch shows diagrammatically a two-pole direct current armature. The direct brushes are shown as bearing on the com- mutator, and the four slip rings are connected to points on the armature diametrically opposite. An alternating voltage appears at 650 " Verbal " Notes and Sketches the slip rings, having a frequency equal to the number of poles multiplied by the speed. Thus a four- pole generator running at 3000 revolutions per minute would have 12,000 alternations per minute = 100 periods per second. The balance coil is simply an alternating current transformer with a single winding, and a tap from the middle point, and since it is connected to an alternating current circuit, an alternating magnetising current will flow through its windings ; but as this magnetising current is ordinarily very small, it may be neglected when considering the flow of the direct current from the neutral wire to the armature windings. Thus, under ordinary conditions, the onl}' current in the coil which need be considered is direct current. The object of the balance coil is to give a point midway between the direct current brushes to which the neutral wire of the system may be connected, and to afford a path by which the current flowing in the neutral wire may pass through the armature to one of the main brushes. It will be seen from the diagram that this system is very valuable where it becomes necessary to have electric lighting on a low voltage, and heavy driving power from the outers or high voltage. An out of balance load up to 15 per cent, may safel}' be carried between one outer wire and the neutral wire. Knocking in Engines. Knocking ma}^ be caused as follows : — 1. Want of clearance in cylinder, top or bottom ; if on bottom, due perhaps to wear down. 2. Slack guide shoes. 3. High compression forcing slide valve off face at end of stroke. 4. Loose piston rod nut. 5. Loose crosshead nut. 6. Worn top end brass or bottom end brass. 7. Water in cylinder due to priming. 8. Want of compression (remedy — shut in link). 9. Junk ring pins slackening back, or working out altogether. 10. Worn valve gear brasses, &c. Diagram cards, if taken off at the time, would indicate causes i, 3, 7, and 8 ; for the others endeavour to locate position of knock, whether internal or external. If the knocking is due to priming, this will further show by slowing down of the engines as the steam suppl}- is reduced by the water passing over with it from the boilers. Appendix 651 Engine Data. — The following data referring to the machinery of a modern twin screw meat-carrying steamer may be studied with advantage by the student, as a good idea of the relative proportions of the various working parts can be obtained by reference to the data supplied. Twin Screw Steamer, I.H.P. (Combined) 5000. Cylinders 25, 42, 69 in. (2 off). Stroke - 4 ft. Crank shaft 13I in. diameter. „ pin - 13I Length of crank pin 14 in. Condensing surface 6000 sq. ft. (?). Thrust surface 1324(2). Piston rods 6| in. diameter. Connecting rod - 6| and 7} in. diameter. „ ,, centres - - 8 ft. 6 in. Valve rod, diameter in gland - 3t i'l- Main steam pipe 8 in. diameter. Propellers (2) j x6 ft. 7i in. diameter. \ 20 ft. pitch. Expanded area 68-8 sq. ft. Projected „ - 53-5 sq. ft. Blades - - 4- ,, thickness at root - 6|in. . » top 2 '"• Boss Blades Studs Nuts Shaft nut - Boilers Pressure - Tube surface Heating surface - Grate area Tubes „ diameter - Length of fire bars Furnaces - Cast iron. Manganese bronze. Mild steel. Gun metal. Mild steel. 5 single-ended, 15 ft. 6 in. by 1 1 ft. 6 in. 180 lbs. 11,508 sq. ft. i3>56o „ 295 8 ft. 2 in. and 8 ft. i{\- in. 2| in. 5 ft. 6 in. 3 ft. 7 in. diameter. 652 " Verbal " Notes and Sketches Stop Valves. Boiler Stop Valve, 5^ /;/. Diameter. Inches Open. Number of Turns of Hand Wheel. Steam Speed. (Feet per Second.) f in. 1 » 3 2 231 Engine-room V/6'/ /'rt/7'^ {balanced), 8 ///. Diameter. 2\ in. iSh 90-6 2 „ i6i 95-2 a ,, 14 IOO-2 I5 „ 14 I 17-2 li » io| 140-5 Pressures on Bearing Surfaces. M. Bearings. Crank Pin. C. Rod. Top Ends. Slipper Guide. Thrust Surface. Stern Bearing. 13^ X 14 in. 234 lbs. per sq. in. I3ix I3ff in- 472 lbs. per sq. in. 7^ X 8 in. 737 lbs. per sq. in. 26 X 21 in. 38-1 lbs. per sq. in. 44--^ lbs. I per sq. in. 28-8 lbs. per sq. in. Steam Speeds. Cylinders. Revolu- tions. Piston Speed. Port Area. Port Op ning. Exhaust Speed. .Steam Speed. Valve Travel. Cut- off. Speed in Pipes. Exhaust to Condenser. H.P. Sq. In. 67 Sq. In. 53-8 71-4 88-8 In. 5^ •'] 8 in. dia., 95F.P.S. I.P. 73 5S4 I 12 93-8 I20-5 143-8 5i •7 L.P. ... 246^ 229 147-3 159 5i •7 ( I 10 "(F.P.S. %. Ai ^P + 4^ ) >^ ( P+j^ ). 10 NOTE.— p = rivet pitch, d^ rivet diameter. Then, ^_ T^. , . , \ (II X 2-75 + 4 X -8125) A (2-75 + 4 X -8125) Distance between rows = — ! 12_5 si — 5^ — i^ i 10 41 inches, say i^ inches. -i-5> 21 inc Width of lap-14 + ii + ii inches --4 inches. Distance between edge of plate and centre of rivets 1-5 x c/= 1-5 x -8125 = 1-21 inches, say i^ inches 654 "Verbal" Notes and Sketches Circumferential Shell Seams (Single riveting). — Rivet diameter same as before = J ;j --8125. Rivet pitch — ^°^^ '" '-5^ 1-7 inches, say ij inches. 100-54 Width of lap (3 rivet diameters) = ^J + J§ + ic inch = 2i'5 inches. Fire Box (Welded).— Rule. — 90000 xT-= (Height in feet + 1) x Diameter in inches x Pressure. ^. - ^_ /(Height in feet + 1) x Diam. in inches x Pressure ' ~\/ ~90000 T /(S*75 + i)xSi inch X 80 „„ ■ . • u „ T- / ^j3_l2 '. — 3 = .55 inch, say , • inch. Allow, say, six sta}-s round uptake, each with a working stress of 9000 lbs. per square inch. Then, Area of surface to be supported = (54-- 30-) x •7854 = 1583-3 square inches. NOTE.-— As the fillets of the shell and fire box act to stay the top end of the boiler, the unstayed area may be taken to be equal to the difference between a 54-inch circle and a 30-inch circle, which will sufficiently allow for the strengthen- ing effect of the uptake ring. Diameter of stays- /, — ^ j^^ — 1-7 inches, say i? inches diameter. V 6x7854x9000 ' ' J i Fire Box Riveting. — Plate -^^ inch thick. Rivets i inch diameter. Jomt strength = 53 per cent. pj^^j^^ioo^^^jnch^2.i2 inches, say 2i inches. 100-53 Seam strength =— — ^~- x 100 = 53 per cent, of solid plate (nearly). Rivet strength = ^ ' 54 - ^ -• 23 ^ 1 00 __ cent, of solid plate (nearly). ^ 2- 125 X. 5625x28 ^^ ^ f ^ J As the smaller result = joint, then 53 per cent, is the joint strength. This riveting also holds good for the crown plate of the shell, the cross water-tube flanges, and the solid ring joining the uptake and the crown plate. To Verify Joint Strength, Vertical Shell Seams. — Rule. — Seam section strength = ^^^^^ p-gg*"^^^ -^ x 100. Rivet = ^^y^t ar ea x No. in a pitch x 23 x l oo Pitch X Thickness X 28 NOTE. — Shear strength of steel rivets = 23 tons per square inch. Tensile ,, ,f plates = 28 ,, ., „ .4-^ No. 2.— Sectional Plan showing Fire Bars an< Verbal '' Notes and Sketches. a^e 654. No. 2— Sectional Plan showing Fire Bars and Bearer Ring. No. 3.— Plan of Boiler. Appendix 655 No. 4. — Circumferential Shell Riveting. Plates I inch thick. 41 DIA, No. 5.— Longitudinal (Vertical) Shell Riveting. Plates i: inch thick. 43 656 "Verbal" Notes and Sketches Then, Seam strength= ^'^^ ~ ' ^^^ x 100=70-4 per cent, of solid plate. and, Rivet strength ^ 'l^J S- x 7854 ^ 2 x y jiigo^g^.g ^^^ ^^^^^ ^^ ^^jj^ pj^^^^ 2'75 X '375 X 20 Circumferential Shell Seams. — Seam strength = ^1^2^^^-—^ x loo = 56 per cent, of solid plate. Rivet strength = '^"5' x -7854 x i x 23 x ^oo ^60-5 per cent, of solid plate. ^ 1.875 X. 375x28 Stresses on Shell Seams. Vertical (longitudinal) Seams. — Rule. — Diameter in inches x Pressure = T" x 2 x Stress per square inch. ~, re. ■ u Diameter" x Pressure Therefore, Stress square mch = =y-, — . ,, „ ,, _ X o _g.QQ iY)s. square inch. .375x2 Circumferential Seams. — Rule. — Diameter x Diameter x -7854 x Pressure = D" x 3-1416 x T" x Stress per sq. in. or. Diameter" X Pressure = T" X 4 X Stress per square inch. NOTE.- B"xD"x.y854 _D" &" x3*+J^ 4 _. Diameter" x Pressure T"x 4 _6o" X 80 „^ 00 : lbs. so Therefore, Stress square inch •375x4 As will be seen from the foregoing, the stress longitudinally is exactly equal to twice the stress circumferentially in all cases, hence the necessity for the stronger type of joints required for the longi- tudinal shell seams. Manhole Door Compensating Ring. — Rule. — Breadth of ring (if same thickness as shell) = Small diameter of door x '5. Then, Breadth of ring = 12 inches x -5 = 6 inches. Therefore, Outside sizes of compensating plate ring=: 6 inches + 16 inches + 6 inches -28 inches! o • u u «- ;.,-u«» 6 inches + 12 inches + 6 inches .^24 inches T'' ^^ "^^^^^ ^^ ^4 'nches. DESIGN DRAWINGS AND CALCULATIONS. The following Set of Drawings and Design Calculations include, among others, those given at the Board of Trade Examinations to First-Class Engineer Candi- dates, and for practice these should be drawn out to the scales marked on each. Note. — The calculations shcnvn for the various proportions of parts repre- sent average practice, but it should be noted that these vary to some extent in the designs of different engine builders. Sheets i and 2 show proportions of Nuts, Bolts, and Screws. Boilers— 1. Single-Ended Combustion Chamber. 2. Double-Ended Combustion Chamber. 3. Furnace and Fire Bars. 4. Water Gauge Column. 5. Vertical Donkey Boiler. 6. Fire Bars and Bearers for Vertical Boiler. Valves— 7. Dead Weight Safety Valve. 8. Spring-Loaded Safety Valve. 9. Boiler Stop Valve. 10. Engine Room Stop Valve. 11. Feed Check Valve. 12. Bilge Suction Valve Chest.. I2A. Bilge Injection Valve. 13. Side Discharge Valve. 14. Cylinder Relief Valve. 15. Slide Valve and Spindle. 16. Inside Steam Piston Valve. 17. Double Ported Slide Valve. Pumps — 18. Air Pump. 19. Feed Pump Complete. 19A. Feed Relief Air Vessel and Pump Valves. Pistons, etc — 20. H.P. piston and Rod. 21. L.P. Piston and Rod. 22. L.P. Cylinder Cover. 23. Donkey Pump Cylinder and Valve. Eccentric, etc. — 24. Eccentric and Rod Complete. 25. Quadrant Bars, etc. 26. Reversing Bell Crank. Shafting, etc. — 27. Crank Shafting. 28. Thrust Shaft and Shoe. 29. Thrust Block. 30. Stern Tube and Shaft. ^ 31. Propeller Boss. (Various— 32. Bottom Blow-Off Cock. 33. Three- Way Change Cock. f 34. Main Bearing. V 34A. Tunnel Bearing Block. £ 35. Steam Pipe Expansion Joint. ^k 36. Pump Levers. ^^B 37. Connecting Rod. ^H 38. Pump Crosshead and Links. uy^ -^ -< \ III I MII H ■ ii^ ill a-sA- i]:^ m- <|r*'i.;*fi;i* K ni' li tu- tu- 3 JO ■•■-■ ■ - ft walL. if HI* 3 m- i ISj? «|- VI :il!s2 lU- r~3^ 111- po;f pctft; (ot V poif :s lU- ()ivfu»r«;t' m "^ pi'fcK X 3 Bolt and Nut Complete. Notice thai the radius of curvature is taken as equal to the depth of the nut (equal to d) : this is not strictly correct, but is quite near enough for practical purposes. Observe the positions of radius for the nut curvature in the side view, which is about two-thirds distant from the top edge. In the plan the construction circle (equal in diameter to the distance over angles) is divided up into six by the circle radius distance in the compasses. Nuts, Bolts, and Screws. Let d = diameter of bolt. (Whitworth Standard.) Width across angles of out Width across flats of out Depth of nut Diameter of round bolt head Depth of round bolt head Diameter of point of bolt Depth of point of bolt Depth of top lock nut Depth of bottom lock nul Diameter of washer Thickness of washer i-75Xrf+« = diameter at bottom of thread = pitch of thread x 3. Bolt and Lock Nuts. The hexagon sides of the nut shown in the plan may be drawn in by applying the 60 degree square langentially to the circle over flats. This circle = 1-5 X **.'+ i i" The nuts are chamfered off to an angle of 45°- EXAMPLE.— Calculate the required dim«nsioos of nut and bolt head for a bolt 2 in. diameter, with 4i threads per inch, LDglei - flats Then, Diameter Diameter Depth of nut =:rf Depth of lock nut (if fitted) = 7 X Diameter of bolt head = 1-5 X Depth of bolt head = -75 X = 1-75 X a 4- -125 >«■ = 3-fa5 «■ = 3fi = 1-5 xa+iaS In =3"5 in=3i Diameter at bottom of thread Pitch of thread = 1-7-45 "Verh.!" Not«anc 9000= Surface X Pressure As the pitch is unequal, being 7} in., by 8 in. the Surface =7:25^+^ =58.28 sq. in. Then, Diameter of stays = / 58;28Xi8o _ ^ ^j V -7854x9000 say ij in. diameter. y.s other than the B. of T. the slays arc, in the present .0 ,s9duT 9>Joa- ■ ;tai in. diameter; Pitch 2i in. Internal riveting (single): Rivets, U in. ; Pitch, if in. NOTR— For, say, a pressure of 100 Iba. and boiler diameter of 6 ft. in., it would be advisable to give the firebox a thickness of J in., and the boUer shell 4 in., and to i the height by. say, i ft. l»yA /' /..I). No. 6 —Donkey Boiler Fire Bars. (Draw to a scale of lA in. = I ft.) 'Votbal" Nolcs and Sketches. 0A t I bant o{ .. i«IX OU 0-- i:ii '1 No. 7— Dead Weight Safety Valve [Scale, i( In. = i ft.) (Draw to a scale of 3 m. = I ft.) Oata — Boiler grate surface consists of 2 furnaces, each 5 ft. by 3 ft. Then. Rule. Therefore, Total grate surfBce = 2XSX3.33 = 33.3. say 34 gq ft 375 -^ Absolute pressure = Valve area in sq in. per sq ft grate. 37-S-M30+i5l=S33 sq. in.. Total valve area = 34X.833= 28-3 sq. in. '^'^ Diameter of valve = / *J = 6 in. diameter V -7854 "''• Load on valve = 6x.7854X 30= 848-2 lbs. Assuming that weight of valve and spindle amount to, say, 20 lbs , '^*"' Actual load required = 8482 — 20 = 828-2. ^eiua. Fix on diameter of weights aj. say. 16 io. Then, Depth of werghts = .5^ J^.^ = .5-8, say ,5) in- AUowmg 7 separate weights. ^*'*"' *^^ -- =2-2«; in. =2* in. thickness of each weight single valve. (5 in. = 2i m fitted, each 1 pair of valves Diameter of each valve e only requires to be half the ■ N.iles and Skelchej. ; ifncp «v^ ' y..'i 3;' J!!. r';M ■ (f.j I- juii; o^ fpf. """" YI|OM' Esl' 3ooo ipa- bci ad- id- . 1,1,- .. r\,n ,(.,.-. ri_.t.- S JO ar.f ci' V"';" K''l*^ tiooo = < luoc V- - posrq 0. <-,(&, 01 cot] LOf»| &9lAe »16'J MO g -b^^t 01 gbuus: j[-03qt Washer No. 8. -Pair of Spring-Loaded Safety Valves. \Sc3lf. i^ In =: I II. \ (Draw to a scale of 3 in - i ftt !i per sq. ft. of grate at 20 lbs. c< !i4X3X5-5X3-5X^=l8-53 sq, in. , say 3i i Rule, Where, ■ of each valve = . / -^- - V 2x7854 Xd'= Load on valve x Mean diameter of coil. Then. And. 11000 = Constant for square steel. d = Side of coil in inches. iioooXd" = 3-5^X78S4Xi6oX3 in. rf ^3/3^78 54x1^X3 ^ .75 in. Notice ihat the a/fif rooi requires to be extracted after division. Diameter of boiler branch bore = s'3-5-X2 = 4-9 in., say 5 in. diameter. Flange Studs. Allow, say. 3000 lbs. per sq. in- stress on studs, and assume pressure to act out as far as the pitch centre Une of the studs ; also take pitch circle diameter oa 10 in. or 10} in. and fix on number of studs as 6. Then, Diameter of stud5 = . / l°*5:^^i^ =.0, sav i in, diameter. V 3000X 7854 *' ' Noi K. -Only oae valve of the pair is drawn out. "■0 + qruiijsi&i fclGSSniG IQO |p3 1 /^, /V^l/ /^sjv '\IrA '\ '-,-, 1 No. 9— Boiler Stop Valve. (Draw to a scale of 2 in. = i ft i Oars. — Pressure i6o I Forced draught. augei. Heating surface (double ended boiler), 3200 sq. ft. Rule, Diameter of vaUe = . 6 ^ / Hc»U„g 'surface^ V Absolute pressure Then, Dia r or 1 Rule, Diameter of spindle Valve diameter 1., say, 7 m. diameter. s Pressure -|--l Then, Diameter of spindle = ^X \^i6b4--i2 = i78 in., say i Cover Studs. Assume that i in. diameter studs are decided on for the cover, not to exceed, say, zooo lbs. per sq. m Then, Number of studs = ,3TT;n„„ = 96 studs. -Inside diameter of chest = " Verl-al " Nuies and Skcithes. .'IT-C. JtTG Dj}: m -^-\r K I'gcUgTn.. No. 10— Engine-Room Stop Valve. Scale. 2 in. = i ft (Draw to a scale of 3 in. = 1 ft) MoTC— The calculations are similar to those of the boiler stop valve, No. 9. /«P»I., V.' (jiTcjruc?e linrLfcq v ■J |«l&6l &V}AG 9||OM ' n jJGCfC A'JAt' i h -l^'-h,^.-^;S^ No. II —Feed Check Valve. (Scale, 3 in. =; i ft) Data. — Pressure, Valve. 3 io diameter. Allow diameter of chest, inside, to be not less than li t Then, 3 io x 1-5 = 45 in ; say 5 in. diameter. Diameter of 3pindle=diaraeter of valve -~ 3 — 3 in i of 3000 sq. in. on studs, am Then, Then, Then, V* Allow a tensile Diameter of studs Diameter of studs = ^ / ^^ ^ ^ -57 in, To allow of a good safety margin fix on, say. i i Allow width of flange for studs = stud diameter > ■625 y 3= 1-875 "> . say 2 in. on each side. Diameter of coverts in. 4-2 in. +3 in. =9 in. Allow full lift clearance of valve equal to t diame 3 in. -> 4 = 75 in. lift clearance. i diameter of valve. diameter studs. The thickness of the chest is taken 1 NoTR, — Tht wearing parts i or a larger valve allow if in. always be in excess of the chest \ — ■*■ \i~^>^-W \ol xoa ^'erlial " Noi o 4^ o ^ o o No. 12— Bilge Suction Box. (Draw to a scale of 3 in. = i ft.) I«-- 10- .-i- \ itfH W;. MOJ«« ""'I h"\\ nil ticsi. \ - b;i?:=- =^ ID > ilod8 yf c ""^?ff InjecHor, c\^it No. 12a.— Bilge Injection Valve. (Draw to a scale of 4 in. = i ft.) No special calculabons are required for this drawing as the stresses 00 the working parts Full Uft clearance of valve = diameter ^ 4 = 6 in, -1-4=14 Jd. ' Verbal " Notes and Skelches. :L^N^ 3f6« vvq 8|^C(' ITX -M-.i VAGI XV f^" [til 'JO ' °//^4 a ti ^ C.5.K Bol ts V No- 13— Side Discharge Valve. {Scale, ih in. = i ft.) (Draw to a scale of 2 in. = i ft ) As the pressure on this type of valve is low, it is sufficient if the various parts are of light construction as shown above. The inside diameter»of the chest is equal to about 13 times the diameter of the valve. Then, Width of flange = stud diameter X 3 = -75 X 3 = Diameter of cover = 2-25 in. + 16 in. + 2-25 in. = wjj i Allow full lift equal to ^ diameter of valve, or 3 in. The studs in the flange on ship's side are screwed through the plate, countersunk, and rivetted over on the outside, with clearing holes in the chest flange inside. irbal ■' Notes and Sketches r IJ'-" ■■■»■ .LP«^" XP<^a M ' 3^iu '1 qitrawf. qf9m«(Si 1 «» »9}At: 1.'. h^M I Then, Rule, Then. No. 14— Cylinder Relief Valve. {Scale, 3 /n. = I ft.) (Draw to a scale of 4 io. = i f t ) Data.—V»\vc, 4 in. diameter. Pressure, zo lbs. ameter of spring as being about equal to diameter of valve 1000 X T' = Mean diameter of coil x Load on valve. 1000 X T' = 3-5 X 4- X -7854 X »■ -p = 3j,Xf X-:^Sj_X 20 ^ .^^ 1^= V-0799 = -43 in-, or. say, ^ in. coU. Observe that cude root extraction is required. Allow 6 studs of ample strength, say \ in. or \ in. diameter. Diameter of spmdle = Valve diameter -r- 3. = 4 in -^S^ *■"■ say li in. diameter. .; f Xpcu reucfu IV- B f>Oli 'al DvicT t tl^ OjiM. — Cylinder ports = 2j in s Centre bars=tj in. Valve travel = 7 in. Top lead =: ^ in. Bottom lead = i in Top exhaust lap ^ o in. Bottom exhaust lap — +i in. Pressure = 56 lbs Cylinder diameter = 24 in Stroke = 36 in. Assume that, Top steam por Then, Bottom steam por No- 15.— Slide Valve and Spindle. (Scale. 2 in. = i ft.). (Draw to a scale of 3 in. = i Tt). 6 in exhaust As the bottom lead i port opening is also J iiorethan top lead, the bottom ; than top port opening. Rule. ) travel = Steam lap + Lead (either top or bottom). Then. (Top), 7 in.-i-2=3.s m.. and 35 in, — 1-25 = 2-25 steam lap. And, (Bottom), 7 in.-r2=3-5 in., and 3-5— 1-375 = 2125 steam lap. Length of ports = Diameter of cylinder X 75. = 24 I 75 = >8 i Allow bearing^ width at sides as. say, 2 id. Then. liepth ol valve face = 21 -(- li + lA + 6 -f li + 2i + 2J = Width of valve face Diameter + 18 + 2 = 22 in. Face are a X Pres sure x 3500 X 785; Allow 2 for Erictioa. and 3500 lbs. tensile stress per sq. Then, ^ /22X^9X56X V 3500 X -7854 Bottom exhaust opening with crank on steam lap + Lead — Bottom exhaust lap. , of p,st iy ih in- diam w screw =1-5 in. X 1-33 = 1-99 in-, gland = 1-5 in. X 1-6 = 2-4 "> 1 say in front of spindle and J to. clear at bottom). Then, Area of pistoi (crank on top). — 25 — 2-125 opening 1 nd steam port openi exhaust. J. compared (for 24' X 7854 - iB or ' »8 X 1-375 and exhaust port opening j:f^t Valve (rAvel-7' 'TiT/s PT r.,. Bte if^i /& •H' «i-«»\^ a.A' 2" 1?,^ ./....=. \'l< I'/t' U..-> I.I- 0" /<■ ''■■'' -'r- No i6— Inside Steam Piston Valve. (Draw to a scale of 3 in. = i ft, | Rule. Diameter of valve rod at body = VaIve diameterx-is. ■^"i- -. .. .. =i5in.xi5 = 2-2Sin.. sayzii Half valve travel = Steam lap + Port opening. Then, = (Top)2lm,-|-iiin.=3iin.i _ l7 in- travel. = tBot)2m.+iJin.=3jin.r Observe that the difference in lead top and bottom is also equal to the difference a steam lap and port opening top and bottom (that is, \ in. difference). Again, lotice that the sum of "steam lap + lead" is the same for top and bottom. Thus, Top, ai in. + fc in. = 28 i and Bottom, 2 in. + J! in. = 21 ?q) N.)H; The valve face measures' rourhly 50 in. by 52 in AIIovj diamclcr of rod at gland = db Thcre'orc, 2-75>;i-4 = 385, say 3; in. diameter. The rod is swelled out at top and bottom to 3 in. diameter, which forms the outside diameter of the screw Allow spindle i in. clear at front and \ in ^kar at back for Data.~L.P. cylinder, 74 diameter of pump. No. i8.— Air Pump Complete (Draw to a scale of 2 in. = 1 ft ) in. diameter. Stroke, 42 in. Air pump stroke. say 25 I Rule. Air pump capacity = ^ ^- '^y'*"'*" capaci^ Then, Air pump diameter = /74*'142_ >" =24, Note. — 7854 cancels out top and bottom Rule. Diameter 'of pump rod - ^-}^^^^?LA.£^P + .6. 9 Then. ^^S^.6^3-3;7 in., say 3* i Rule. Thickness of barrel - °'*"«'SiL?f-P'™P-|-.3. Then, -^ ^^+3 =[7^6 in., say I ia. 60^ Length of barrel 1 - Stroke + Bucket -!-Vatve depth + CIear; - 20 + 5 in. + 3i + 2 in Note.— Allow, say, t in. clearance top and bottom. i'cibai ■ Noleb ami Jjkcichts. J ;J6u' A- XP«o' c^'^'^l'f^ <*l ^!' '^^^''^l I _i : A i^i jpt bti 2d w\ . 1 ynje 1 1000 ■" «^v = r^pq '>« ' i^HH A'l^^ 2^M"^ hi2:~9^^ fsR te -- i—y. ■r-^ Mep^t No 19.— Feed Pump Complete with Air Vessel. \ Draw to a scale of 3 in = : ft, ) Dafa. 1 HP. 1500 Engine revolutioos or pump strokes, 65 per min. Stroke of pump. 24 b. Steam ( water consunipuon taken as 15 lbs per I. HP hour. Assume pump effidfncv as equal to 50 ptf cent Then to find diameter of each feed pump of a pair. h ^ y f Pump Plunger Rule. l.H P xlbs, waterx2766= Diameter'x7854XStroke in X Strokes per I Therefore. 1500x15x27.66= Diameter-x7854X24 in. x65x6ox-50, so that Diameter^ = - iSWXi5X27'66 _ _. . ■7854X24X6sx6ox-50~ ^' and Diameter xVi6^ = 4 ic. diameter of each feed pump plunger. Note. -27-66 cub. in. of fresh water=i lb. Relief Valve Spring. Rule. iiooox«/'=Load 1 Bay, 125 lbs. per sq. in. Then 10 that t valve X Mean diameter of spring. Assume 1 iioooxrf= = 3^X7854Xi25X3. rfs = 3^7854Jl_i35X3 _ . j. x6o> Effideccy. I loading pressure of, t for square steel. d=5ide of square of steel spring. Mean diameter of coil =r 3 in. Air Vessel- Allow capacity of air vessel to be equal to 17 t say. 6i in, Then, Capacity of air vessel (exclusi NrvTF.,— 5 in, = inside diameter of pump barrel 24 in. = working stroke of pump. , say. I in. square steel ;s capacity of the pump chamber, and fix diameter 1 top and bottom) = 5-x7854X24 in. xi7 = 8oo cub, 1 Then. Height of air vessel = j\^c£Gi' suq t>nmb /^ai -*i1. -3rg M4t No. I9a.-Feed Relief, Air Vessel, and Pump Valves. I Draw to a scale of 3 in, = i ft.) See Drawing No. 19 for calculations and data. J .li«| J»f«iC)J« q hio/iq i^oi q>G "Jnuf. uo6 iK*" VUOM- O' 1^3 W oi' sal' q lu oujl _ / 3oco o^ a SLooq wsl^L _ _,^ - pof (oui 0{ cpLCsrq > JISlUCfGL O^ ?CLeM iooo ipa 2d- iu lO;. i?ooo IP? sd IU ^ol qrauj»u.i DitsUTGfSi. 01 :.?q »f pr^qi ■J«.(.uii- j;. I,I.698nLC- IgO IpS No. 20— HP Piston and Rod (Cast Steel;. (Scale. 2 in. = i ft. ). (Draw to a scale of zin = i ft.). r of rod at screw Ibottom of thread Diameter of rod at body Piston area X Pressure 5000 x~7854 Piston area K Pressure 3000 X 7854 for tensile stress limit, for compressive stress limit. / 5000 Oiometer of rod : V i6r X 180 _ 39 in . or, say, 4i in., which allows 3000 of a good margin of safety. Allow. Depth of piston at boss = Rod diameter ■ 1-5. Then, Depth = 4-25 x 15 = 6-3 in., or, say. 6 in only. Allow i of this as taper, and make the remamder parallel. Allow a taper of 6 in, for 4 in. of length as shown. The nuiiiljcr and size ol studs allowed provide ample strenglh for the junk ring. A I in. shoulder is allowed for the fitting of the piston on the rod. / V ■ / / 1 /^ j,}nc|cn6a2 c ^, _.. ... , , < bd3 Di.Of]! -.000 yi|Oiw n . say jj in. 'diameter of one strap bolt " Depth of eccentric key = "-'^^ Diameter of bolts in top end brass = . / =v/V=-- Thickness of cap and butt = diameter of bolts x 1-3 ' 3^7 <'5 in, diameter. = *S in- Xi.33=»-99i •Verbal" Note* and Skcichc: 'ilr ft ■It (U K* V ^.' ;i::..p k" fin m ■:5S rr 3_, 'UJ K' .,1 I t>^ } V i. 1 iS'i ; y ,. 1 .^Jiui^l '^BiQ bi VIJOM fp.(| .r.i ;> v£« No. 25.— Quadrant Bars, Valve Eye Block, and Drag Links. ( Draw to a scale of 2 in. = i ft ) travel, 7 in. Diameter of valve spindle at body. 3^ 10. — rf. Distance between bars = dx 1-75 + -25. ■■ =3-5Xi75 + -25 = 6'37. say 6i in. Diameter of valve rod eye (steeli = ixdepth of bars. Allow eye block brass to be. say, j in. thijk. Length of slipper = dX3-6. Then, .. ,. =3.5x3-6- Allow thickness of slipper to be about i in. at centre. Allow eye block thickness at sides to be about ;; in. Allow eye block thickness at top and bottom to be about i^ in. Diameter of bolts in eye bIock = dX*5-|-'2. = 3-5 X -5 + -2 =1-95. say : Diameter of drag links f2l=dx-7Z. = 3-5X72-2'52. say 21 m. NoTK.~For other proportions of quadrant bars and eccentric rods. pins. : drawing No. 24. 'Verbal" Notes and Sketches. • C 5- y^^ H2^ — f zi: A&tern -'(U Y No. 26. — Reversing Gear Bell-Crank and Expansion Slot. (Draw to a Scale of 3 in. = 1 ft.) The expansion block has a range of 4 inches in the slot. N0TE.-Depth of key = ^M^-^iin^?t?^+.i2S=5inches^.^ . ^^ ^, .^^^^^^ 4 4 Thickness „ = Depth X-5 = -687S, or f^ inch. Observe that "linked up" ahead becomes "full gear" astern, owing to the change from the horizontal position to the vertical position of the expansion slot. "Verbal" Notes and Sketches. 1 _! 1 i o ')." JBttJ svnaadO 30' •><< ^ 'f' Rule Where Then, (.11 X.- •'U^•^ = £x^I = .s- X llfirfa = zu'tban i9^lJ^ ;gfltb "• - -s- Xji — ; isxie = islsmsib ahiio dbi» .11.' i> .y_t>v. .1,1 ^-5.: -^t;-. .< £1 — ziioi So tsdraun X 3uib4i r d X 2-11 .bsvtroUf tt99d svitd oilod xi8 .g-ii =s-^ .nx £S =8aibai Jiofl •X- X ilarie -- e Data. —CyVmdtts 30 in., 52 in., 8( Stroke, 48 in. Boiler steam, 185 lbs. Rule C X P X D^ = S^ X Constant Where C = Length of crank. ,, P = Absolute boiler pressure. „ D= L.P. cylinder. d=H.P. ,, S = Shaft diameter. Constant = mo for propeller shafts and crank shafting. ,, =1295 ,, tunnel shafting. Constant X (2 + °=j- 3 24in. XaooX Sg^ S (shaft diameter) = ^'3041-2= ^4*5 ^ . say, IS in. diameter. Note.— Observe that cube root extraction is required. Note.— Stroke = 48 in. therefore crank (C) = 24 in. 185 +15 = 200 = P. Diameter of couplings = Shaft diameter X 2 [at least). = 15 X 2 = 30. say 3* in- diametef. Thickness of couplings = shaft X -3. = 15x3= 4-5 in. Coupling fillet radius = shaft X -2. = 15 X -2 = 3 in. Bolt pitch circle diameter = shaft X 1-5. = i5X 1-5 = 2 Shaft diameter" X half shaft radius Bolt pitch radius X number of bolts = 3-S (nearly) say, 3-5 i ig- X 17- 5 ' 1-5X6 Six bolts have been allowed. Bolt radius = 23 in. ^-2=11-5. Thickness of crank webs = shalt X -7- = i5X ■7=10-5. or, aay. II in Diameter of web bosses = shaft X 2. =15x2=30 in. Allow length of crank pin = Diameter of crank pin = Diamelc Therefore. Crank pin= 15 in. x 15 in. Length from centre of coupling length of pin + web thickness 4- cleai bearing 4- clearance and coupling rad Allowing pulley thickness as 4) Then, 7-5 + " + I in- + 9 in- + 15 in- + I in- + 3 in- + 4-.S in. = 52 ii centre of crank pin is equal to half e 4- twice pulley thickness + length of 4- coupling thickness. h) and bearing 15 in. length. "\erbat" Notes and Sketches. 2 Rod ^ ■3i' \ 3 diai O ^!=. ■* I— i^ -^ -^ - - K 1- I-SOI >ria pdi ' Verbal " Note No. 28.— Thrust Shaft and Shoe. {Scale, -i in. = i ft.) (Draw to a scale of lA in. = i ft) For (ompUU design cakiilalions jcc Drawing No, 29. D«(a.-1.H.P. 1500. Speed, 10 knots. Pressure on shoes Ahead surface Astern 60 lbs. per sq. 567 sq. in. 486 sq. in. ring surface is equal to about | only of the total surface of the Shaft -f clearance = iz in. + 4 in- + J in. = 13 in. Annulus area of collar = 1 18- — 13'-) X •78s4=i2i'7 sq. in. Actual bearing surface = 121-7 X i)=8i-i. As there are 7 shoes for ahead, then, 8ir X 7 = 567-7 sq, in. 6 astern, ,, 8ii X 6 = 486-6 sq. in. Total pressure on block = 15?? .>133^^ = 33218 tbs. 6o~ Pressure per square inch on each shoe = 5^= = 58 lbs., or, say. 60 lbs. -Allow -68 of total I.H.P. as effective power on block. ■'Verbal" Nolcs and Sketches. ^ L H'l 15 J. \s' I ' I .k- ii» ^. m U-— ^ ti _. e "l.i , OO »rj€ »f»lL pWT?' rpSL'' e .;tr S r t: , ^5 -.- ,^j .„ fCoiFTt QftcjcoCiW ^ 2) -I- .03- 5 ;axs = 4 ru- le oif"^ fpKjr0622X3 - s. absolute. "Verbal" Notes and Sketches. JT- (D 1 W- — .t^ — M Data.—{ I I 1 < ] Len£ Dian Thic A^erbal" N No. 31.— Propeller Boss- (4 Bladed Propeller.) {Scale. I ln. = i {{. ) [Draw to a scale of ij in. = i Data. —Cylinders I.H.P. - Pitch of propeller Diameter of propeller - Circumference of propellei Tunnel shaft Propeller ,. - Length of boss = Tail shaft diametej X 2-6 ft = 12 io. X 26 = 3i-2 in., or. say, 32 i Diameter of boss = Shaft diameter X 2'S = 30 in. of blade flange = Shaft diameter x 2-i. = 12 in. X 2-1 =252, or, say. 254 in. Thickness of blade flange = Shaft diameter X -25. t. .. =: 12 in. X -25 = 3 in. (bronze). Combined for each blade Combined area of studs for each blade of studs) ^Shafts Then, So that, Diameter of studs = Thickness of key The boss is recessed 1 60 degrees. Note.— Blades of bron V -7854 ' _Sha ft diamet er , ^ = Breadth of key x -5. = 2.625 in. X 5 = i-3«S. to fit the blade flanges ; Boss of cast steel. Verbal " Notes and Sketches r I joint: JOLTS SCREWED-" \^ PLATE AND RIVETTED L|J«J ? rarHf-3-2 in jKsa qnrmcfct oi by ■jiua' .^LCiiUi^'&i.cucfe o^ b|r' gfoqa 01 ' lo qrsrnicru. A&ortjq pc 3n|}ic:«ur pn( ;o ay, '* idviSjii 01 svifif^ esl Vn^^ 9 efi^ . I oa (;;c \pm. 9(aqr ;^C9U >viiq^^ o^ bu. i C98| VL69 O^ bott- yt63 '^^ ' '^^ tvbbi.oxmKr(v]l> * BOLTS SCREWED-^ ^ INTO PLAT£ AND RrVETTED No. 32.— Bottom Blow-Down Cock. (Ship's Side.) ( Draw to a scale of 6 in. = i ft ) Boiler pressure. 180 lbs. gauge per sq. in. ast area of port = Area of pipe. Taper of plug — 3 in. per Mean width of port= ^5t:_ =2.25. Area of port = 4 X 2'25 ~ 9 sq. in. (approximately). ., pipe = 3- X 7854 = 7 sq. in. Allow a stress of 3000 lbs. per sq. in. on the four studs. Diameter of studs : - /s" X 7 854 X 1 80 _ V 4x7854 , say i in diameter. < 7854x3000 NoTR.— Studs of g in. diameter would be sufGcient, but to allojff for a margin of safety say in. diameter. Rule, Cover < /"Mean circumference of plug\ Then, lap when closed = ( - —' = 4-25 in. mean diameter of plug. (Mean width of port). VerUr' Nous and Skelches. oiE 1 "« p^n*^' i 10 tiuc l^'-'K- IJjaBUf £;lL-a=Gi&'i- '■; Ci'^L"-* 2^'^'- JCJir nb : ni cc AA «f1k r"n«fii¥?f. No> 33-— Tbree-'Way Change Cock. To Find Cover or Lap when Cock is Closed. Cover = ""° circumference of plug_ j^^ ^J^, ^j ^^ .{^^^^^U^^^^^)= It should be observed thai the pi]>e branches of the plug are not rcukr in section, but are flattened to correspond to the taper lape of (he port, so that in elevation th: port and branches are ich 4 in. in depth inside, but in plan the port and branches only lOw as a in. in width (mean). This accounts for the sectional No 33a.— Sketch Showing Tank>filUag Arrangements. ^ ,^^- .^.nfa f^oJtf Tg^- -/'«> gnnBsH xiieM ii^ locf .adi 00(:{; lo lioui eanJa ^iis ibit^idl 1 No. 34.— Main Bearing. (Scale. i\ ln:= 1 ft)', (Draw to a scale of 2 in. = i ft 1 sq. Rule. Holding down bolt diameter = /ilP: area x Pressure. V 4>'-3JOox-78s4 Then. Holdiner down bolt diameter — , /=^ — =2-fi. say 2; in diameter (bottom of thread) V 4x3300 Note. — Allow a tensile stress of 3300 lbs. per sq. in. NOTB — 7854 cancels out top and bollom. Note. —TTie total load on each crank is taken up by a pair of main bearings, hence 4 bolts. Thickness of white metal = -04 x Diameter of shaft -f-i in. = 04Xi3-375-h-r = -63Sin., say g in. Thickness of metal (W.M. included! = Diameter of shaft X -144 + -s. = 13-375 X ■14'i + -3 = 2-22. say zi in. Thickness of caps= Bolt diameter X -7+ Bolt pitch x i. = 275 X -7 + 24-5 X -I = 4-37 in., say 4^ in. -^ \ ^ & d Jl A \. yj.. ...■h d.r liSl / \ -J ^ ■^ ^ ji TW? "•f- - 13"- --V--^ 'lO ' ' : !r^ [I'll I, 15"- ^ 1 K_ ,3- , l::. liU: ... 15" ^_-> - 13" - ■ ->l ' ^ <^ 9 9 i, 1 1 No. 34a — Tunnel Bearing Block Scale = lA id. per ft. I Draw to a scale of 2 in. = i ft.) The size of the holding- down bolts depends on the shearing stresses set up by the rolling or pitching of the vessel. Wliite metal at thickest part = shaft diameter X -05 = 14 X ■05 = 7 in., say ^ in. '• Verbal ' Notes and Sketches. iWHi 1 ■p u €) li \ «Ulii ^flKl ''I Irt Iftffi '>■ /, q t»n*t ■St'^A No 35— Steam Pipe Expansion Joint (Draw to a scale of 3 in. = i ft) iPresstire. 180 lbs. per sq. in.) Diameter of Tie Bolts. Allow a tensile stress ot 3700 lbs. per sq. in. on the bolts. Then, Diameter of each tie bolt= /?_?1™= 1.24 in,, say li in. diameter. V 2x3700 NoiB.— The pressure is taken as acting on an 8 in. diameter circle, in place of that of the pipe bore. ' Notes and Sketches. "w t (8 — > — rrf D«/a I Engine stroke - I Pump stroke u No. 36.— Pump Levers. {Seah, 8 //i. = i /(.) (Draw to a scale of ij in. =: i ft 7 ft., and set ofiT the respective strokes stroke to the opposite end of the engine gudgeon. After finding the rocking shaft t. Pump stroke Assume a distance between centre of cylinder and o at either end. If now a line is drawn diagonally from one stroke, it will cut the horizontal centre line at the required ( centre in this way, arrange (by trial) that the centre of the pin in pump end of lever is exactly as far short of the pump centre line when on top or bottom position as it is beyond the pump centre line when at half stroke. Repeat this for the engine end and it will be found on scaling that the distance from pin centre at pump end to rocking shaft centre is exactly 2 ft. 5^ in., and from pin centre at engine end to rocking shaft centre is exactly 5 ft. loj in. The correct position of these centres is all-important. We have then the following dimensions determined as described: — Centre of pump to ceattc of ^dgeon Length of pump end of lever, centre t< „ cylinder ,, 4 ft 8 in. 2 ft Si in. 4 ft loi in As the strokes. Square inches of effective bearing surface of studs (pins) per^ _ 4-5 X 4-5 X_2 square inch of bucket area ■ . J "~ 24* x -7854 ' Square inches of stud (pin) area per square inch of bucket - = ^^i.^ci ='°7 ^ *"■ Note.— The bearing surface of a pin, stud, or journal is equal to Length x Diameter (not circumference). In the foregoing calculations the two pins of the pump end are taken. "Verbal" Noies and Sketches. S/ggI pir\ —r- -IW rjisu'bjfc) ■ ^un poj;: a Sfeol pin I No. 37.— Connecting Rod. {Scale I ln. = i ft.) (Draw to a Scale of i^ in. =1 ft.) -Cylinders. 24 in.. 40 in., 66 in. Stroke, 42 in. Boiler steam, 170 lbs. Crank pin, 12^ in. diameter by 14A in. Crosshead pin, 6h in. diameter by 63 i Piston rod, 6} in. diameter. Then, Diameter = V 2x4000 <40oo t tensile stress of 4000 lbs. per sq. . diameter. . X 2-3 = 96-6, or, say, 9S i Make diameter of rod : piston rod, and allow i 6j^ in. and 7J in. as the t\\ small end equal to diameter of n. taper in length, ' which gives I diameters. Make thickness of jaw = rod diameter at top X ' Then. 6-5 in. x -55 = 3-57 ">.. or. aay, 3§ in. Inner radius of jaw, 5 in., and outer radius=5 in. -(-3^ ii After striking off the jaw < the line of jaw into rod w shown. at 8^ in. radius, contin 60° angk- set square, Width of jaw = diameter of rod (small end) x 1 Then. 6-5 in. x M =7'i in., say 7 in. width. BOLTS, Diameter of bottom end bolts = /-■ (2 bolts) \' 2 Load ( Then, Diameter = /?4ix_L7? V 4x^)00 2.47, . Thickness of connecting rod butt = bolt diameter x t- Then. 3-5 in. X 1-32 = 4-62 in., qf. say. 4^ in. thick. Thickness of butt at jaws =: bolt diameter X 1*2. Then, 25 x 1-2 = 3 i" thick. Total thickness of metal round crank pin and crosshead pin — pin diameter x -16. Then, 12-5 X -16= 2 in. (bottom end), and. 6-5 X -16= 1-04 in. (top end). Allow thickness of white mi-tal ^ in. to ^ in. reduced to I in. between recessed dovetails. Depth of nuts + collars = diameter of bolts (at least). Width of bottom end but Then, 35 Width of top end butt i and cap = in. X 2-6 - bolt diameter > 9-10 in., or, say, gi in, length of crosshead pin. less clearance at sides. 3'liut ^_ For " Verbal " Not ?ia. J No. 38— Pump Crosshead and Links. {Scale, i in =1 ft) (Draw to a scale of i^ in = 1 ft ) For pumps of the size^; given, the above are the average diniensipns and proportions adopted in practice. " Verbal " Notes and Skclches, baturated Steam Tabks 665 Properties of Saturated Steam Of from 0-5 lb. to 250 lbs. Absolute Pressure per Square Inch. Absolute Total Heat of I lb. of Sleam Total Latent ^/" sity or Weight Volume of i lb. of Pressure per Square Inch. 'leniperatureb. from Water sup- plied at 32° Fahr. Heat of Steam. ° ' Cubic Yoox. of Steam. Steam. Lbs. Deg. Fahr. Units. Units. Lbs. 001376 Cubic Feet. 0-5 80 2 1105-5 1058 4 726-608 l' 102 I III2-5 1042 9 003027 330-360 1-5 115 9 in6-7 ^^Zl 2 004433 225-580 3 125 3 1119-9 1025 8 OO5811 172-080 2-5 134 6 II22-5 IOI9 9 007 169 139-488 3 T4I 6 1 1246 IOI5 00851 I 117-500 3-5 147 7 1126-4 lOIO 6 009839 101-632 4 153 I 1128-1 1006 8 OII16 89-632 4'5 157 9 1129-6 1003 4 01246 80-231 5 162 3 1130-9 1000 3 01370 72-991 5-5 166 4 1132-1 997 4 01505 66-428 6 170 2 ^^ll-l 994 7 01634 61-201 6-5 173 6 1134-3 992 3 01762 56-761 7 176 9 1135-3 990 01889 52-936 7-5 180 1136-3 987 8 02016 49-610 8 182 9 1137-2 985 7 02142 46-686 8-5 185 7 1 138-0 983 8 02268 44-097 9 188 3 1138-8 981 9 02394 41-777 9-5 190 8 1139-5 980 r 02547 39-261 10 193 3 1 140-3 978 4 02642 37-845 IO-5 195 6 1141-0 976 7 02767 36-145 1 1 197 8 1141-7 975 2 02890 34-599 II-5 200 I 1 142-4 973 6 03026 33-043 1 2 202 1143-0 972 2 03137 31-879 12-5 204 1143-6 970 8 03260 30-678 13 205 9 1 144-2 969 4 03382 29-573 13-5 207 8 1 144-8 968 I 03504 28-536 14 209 6 1 145-3 966 8 03627 27-573 M-7 212 1146-1 965 2 03797 26-360 15 213 I 1 146-4 964 3 03870 25-843 16 216 3 II47-4 962 I 041 12 24-320 17 219 6 1148-3 959 8 04253 23-513 18 222 4 1 149-2 957 7 04594 21-766 19 225 3 1 1 50- 1 955 7 04834 20-687 20 228 1 150-9 953 8 05074 19-710 21 230 6 1151-7 951 9 053II 18-828 22 233 I 1152-5 950 2 05549 18-022 23 235 5 1153-2 948 5 05786 17-282 24 237 8 II53-9 946 9 06023 16-603 25 240 I 1154-6 945 3 06259 15-977 26 242-3 1155-3 943-7 06495 15-401 666 Absolute Pressure per Square Inch. ** Verbal" Notes and Sketches Properties of Saturated Steam — continued. Temperatures. Lbs. 27 28 29 30 31 32 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 64 65 66 67 68 69 Deg. Fahr. Total Heat of I lb. of Steam from Water sup- plied at 32° Fahr. Units. 244 246 2 250 252 254 255 257 259 260 262 264 265 267 268 270 271 273 274 275 277 278 279 281 282 283 284 285 287 288 289 290 291 292 293 294 295 296 298 299 300 300 301 •4 1155 •4 1156- •4 1157 •4 1157- • 2 1158. •I 1158- ■9 1159- •6 I i6o- •3 1 160 •9 ii6i- •6 ii6i- •2 1 162- •8 1162- •3 1162- ■7 1163- •2 1163- •6 1164- ■0 1 164- ■4 1165- •8 1165. •I 1165- •4 ii66- ■7 ii66- •0 1167- •3 1167- •5 1167. •7 ii68- ■9 ii68- •1 1 169- •2 1 169- •3 1169- •4 1170- ■6 1170- •7 1170- ■8 1171- •8 1171- •9 1171- 9 1172- 1172- •0 1172- 1172- 9 II73- 9 1173- Total Latent Heat of Steam. Units Density or Weight of I Cubic Foot of Steam. 942 2 940 8 939 4 937 9 936 7 935 3 934 932 8 931 6 930 5 929 3 928 2 927 1 926 924 9 923 9 922 9 921 9 920 9 919 9 919 918 I 917 2 916 3 915 4 914 5 913 6 912 8 912 911 2 910 4 909 6 908 8 908 907 2 906 4 905 6 904 9 904 2 903 5 902 8 902 I 901 4 Lbs. •06728 •05971 •07196 •07430 •07663 •07894 •08128 •08358 •08590 •08821 •09050 •09282 •09510 •09740 •09946 •1020 •1042 ■1065 •1088 •III I •II34 •II56 •ri79 •1202 •1224 •1247 •1269 •1292 •^314 •1337 •1357 •1382 •1404 •1426 •1449 ■1471 •1493 •1516 •1538 •1560 •1583 •1604 •1627 Saturated Steam Tables Properties of Saturated Stta.m— continued. 66^ Absolute Pressure per Square Inch. Temperatures. Total lieat of I lb. of Steam from Water sup- plied at 32° Fahr. Total Latent Heat of Steam. Density or Weight of I Cubic Foot of Steam. Volume of 1 lb. of Steam. Lbs. Deg. Fahr. Units. Units. Lbs. Cubic Feet. 70 302 •9 II73-8 900-8 -1650 6-059 1 71 303 •9 II74-I 900-3 -1671 5-984 72 304 ■8 1 174-3 899-6 •1693 5-905 73 305 ■7 1174-6 898-9 -1716 5-829 74 306 6 1174-9 898-2 -1738 5-764 75 307 5 II75-2 897-5 •1760 5-683 76 308 4 II75-4 896-8 -1782 5-610 77 309 3 1175-7 896-1 -1803 5-544 78 310 2 1176-0 895-5 -1826 5-476 79 311 I 1176-3 894-9 -1848 5-41 1 80 312 1176-5 894-3 -1870 5-348 81 312 8 1176-8 8937 -1892 5-286 82 313 6 1177-1 893-1 -1912 5-230 83 314 5 1177-4 892-5 -1936 5-167 84 315 3 1177-6 892-0 ■1957 5-109 85 316 I 1177-9 89T-4 -1980 5-052 86 316 9 1178-1 890-8 -2001 4-996 87 317 8 1178-4 890-2 -2023 4-942 88 318 6 1178-6 889-6 -2046 4-889 89 319 4 1178-9 889-0 -2067 4-837 90 320 2 1179-1 888-5 -2088 4-790 91 321 II79-3 887-9 •21 II 4-737 92 321 7 II79-5 887-3 -2133 4-688 93 322 5 1179-8 886-8 -2154 4-642 94 323 3 1 180-0 886-3 -2176 4-595 95 324 I 1 180-3 885-8 -2198 4-549 96 324 8 1 180-5 885-2 -2220 4-505 97 325 6 1 180-8 884-6 -2241 4-462 98 326 3 1181-0 884-1 ■2263 4-419 99 327 I 1181-2 883-6 -2286 4-375 100 327 9 1181-4 883-1 •2307 4-335 lOI 328 5 1181-6 882-6 •2329 4-305 102 329 I 1181-8 882-1 •2350 4-256 103 329 9 11820 881-6 -2372 4-216 104 330 6 1182-2 881-1 •2393 417S 105 331 3 1 182-4 880-7 -2415 4-140 106 331 9 1182-6 880-2 -2437 4-104 107 332 6 1182-8 879-7 -2458 4-068 108 333 3 11830 879-2 -2480 4-033 109 334 1183-3 878-7 -2502 3-998 1 10 ,, 334 6 1183-5 878-3 -2523 3963 1 1 1 335 3 1.83-7 877-8 -2545 3930 1 12 336-0 1183-9 877-3 -2566 3-897 668 "Verbal" Notes and Sketches Properties of Saturated Steam — continued. Absolute Total Heat of I lb. of Steam Total Latent '^^'^\ ity or Weight Volume of I lb. of Pressure per Square Inch. Temperatures. from Water sup- plied at 32° Fahr. Heat of Steam. ^UDic root or Steam. Steam. Lbs. Deg. Fahr. Units. Units. Lbs. Cubic Feet. 113 336 7 1184-1 876-8 2588 3-865 114 337 4 I 184 3 876 3 2610 3 832 115 338 I184 5 875 9 2631 3 801 116 338 6 1184 7 875 5 2653 3 770 117 339 3 1184 9 875 2674 3 740 118 339 9 1185 I 874 5 2696 3 710 119 340 5 I185 3 874 1 2717 3 681 120 341 I 1185 4 873 7 2738 3 652 121 341 8 1185 6 873 2 2760 3 623 122 342 4 1185 8 872 8 2781 3 595 123 343 1186 872 3 2803 3 567 124 343 6 1186 2 871 9 2824 3 541 125 344 2 I 186 4 871 5 2846 3 514 126 344 8 1186 6 871 1 2867 3 488 127 345 4 1186 8 870 7 2889 3 462 128 346 1186 9 870 2 2910 3 436 129 346 6 I187 1 869 8 2931 3 411 130 347 2 1187 3 869 4 2951 3 388 131 347 8 1187 5 869 2974 3 362 132 348 3 1187 6 868 6 2996 3 338 133 348 9 I187 8 868 2 3017 3 315 134 349 5 I188 867 8 3038 3 291 135 350 I 1188 2 867 4 3060 3 268 136 350 6 1188 3 867 3080 3 246 137 351 2 II88 5 866 6 3102 3 224 138 351 8 I188 7 866 2 3123 3 201 139 352 4 1188 9 865 8 3145 3 180 140 352 9 11 89 865 4 3166 3 159 141 353 5 1189 2 865 3187 3 138 142 354 I189 4 864 6 3209 3 117 143 354 5 1189 6 864 2 3230 3 096 144 355 1189 7 863 9 3251 3 076 M5 355 6 1189 9 863 5 3272 3 056 146 356 I 1 190 863 1 3293 3 037 147 356 7 I 190 2 862 7 3315 3 017 148 357 2 1 190 3 862 3 3336 2 998 149 357 8 1 190 5 861 9 3357 2 979 ^5° 358 3 1 190 7 861 5 3378 2 960 151 359 I 190 9 861 I 3400 2 941 '52 359 5 1191 860 7 3421 2 923 '53 360 II9I 2 860 4 3442 2 905 154 360 5 II9I 4 860 3463 2 887 155 361-1 1191-5 859-6 3484 2 870 i Saturated Steam Tables 669 Properties of Saturated Steam — continued. Absolute Total Heat of I lb. of Steam Total Latent D«"'A'^- °'' "^''^''- Volume of i lb. of Pressure per Square nch. Lbs. Teniperatures. from Water sup- plied at 32° Fahr. Heat of Steam. °' ' S UDlC 1-OOt Ot 3team. Steam. Deg. Fahr. Units Units. Lbs. Cubic Feet. 156 361-6 II9I-7 859-2 3505 2-853 157 3621 I I9I-8 858 9 3527 2 836 158 3626 I 1920 858 5 3548 2 818 159 3631 I 192-1 858 I 3569 2 802 160 363-6 1192-3 857 8 3590 2 785 165 366-0 I 192-9 856 2 3696 2 706 170 368-2 II93-7 854 5 1 380I 2 631 175 370.8 1194-4 852 9 3905 2 559 180 372-9 II95-I 851 3 40 1 1 2 493 185 375-3 1195-8 849 6 4115 2 430 190 377-5 1196-5 848 4220 2 370 195 379-7 II97-2 846 5 4324 2 313 200 381-7 II97-8 845 4419 2 263 210 386-0 I199-I 841 9 463 2 157 220 389-9 1200-3 839 2 484 2 065 230 394-0 I20I-0 836 505 , I 98 240 397-0 I202-0 S33 525 I 90 250 401-0 1203-0 831-0 i 546 1-83 670 "Verbal" Notes and Sketches Table of Circumferences and Areas of Circles. Diam. Circum. Area. Diam. Circum. Area. Diam. Circum. Area. Inches. Inches, Sq. In. Inches. Inches. Sq. In. Inches. Indies. Sq. In. •03125 •0981 -00077 6 18-8496 28-274 12 37-6991 113-10 •0625 ■1963 -00307 6-125 19-2423 29-465 12125 38-0918 115-47 •125 •3926 •01227 6-25 19-6350 30-680 12-25 38-4845 117-86 •25 •7853 •04909 6-375 20-0277 31-919 12-375 38-8772 120-28 •375 1-1781 •11045 6-5 20-4204 33183 12-5 39-2699 122-72 •5 1.5708 •19635 6-625 20-8131 34-472 12-625 39-6620 125-19 •625 r9635 •30680 6-75 21-2058 35-785 12-75 40 0553 127-68 •75 2^3561 •4417 6-875 21-5984 37-122 12-875 40-4480 13019 •875 2^748 •601 7 21-9911 38-485 13 40-8407 132 73 1 3^1416 •7854 7-125 22-3838 39-871 13-125 41-2334 135-30 M25 3-5342 0-9940 7-25 22-7765 41-282 13-25 41-6261 137-89 1-25 3-9269 1-2272 7-375 23-1692 42-718 13-375 42-0188 140-50 r375 4-3196 1-4849 7-5 23-5619 44-179 13-5 42-4115 143-14 15 4-7129 1-7671 7-625 23-9546 45-664 13-625 42-8042 145-80 r625 5-1050 2-0739 7-75 24-3473 47-173 13-75 43-1969 148-49 175 5-4977 2-4053 7-875 24-7400 48-707 13-875 43-5896 151-20 r875 5-8904 2-7612 8 25-1327 50-265 14 43-9823 153-94 2 6-2831 3-1416 8-125 -25-5224 51-849 14-125 44-3750 156-70 2125 6-6758 3-5466 8-25 25-9181 53-456 14-25 44-7677 159-48 225 7-0865 3-9761 8-375 26-3108 55-088 14-375 45-1604 162-30 2-375 7-4612 4-4301 8-5 26-7035 56-745 14-5 45-5531 165-13 2-5 7-8539 4-9087 8-625 27-0962 58-426 14-625 45-9458 167-99 2625 8-2466 5-4119 8-75 27-4889 60-132 14-75 46-3385 170-87 275 8^6393 5-9396 8-875 27-8816 61-862 14-875 46-7312 173-78 2^875 90320 6-4918 9 28-2743 63-617 15 47-1239 176-71 3 9^4247 7-0686 9-125 28-6670 65-397 15-125 47-5166 179-67 3125 9^8174 7-6699 9-25 29-0597 67-201 15-25 47-9093 182-65 3-25 10-2102 8-2958 9-375 29-4524 69 029 15-375 48-3020 185-66 3-375 10-6029 8-9462 9-5 29-8451 70-882 15-5 48-6947 188-69 3-5 10-9956 9-6211 9-625 30-2378 72-760 15-625 49 0874 191-75 3-625 11-3883 10-321 9-75 30-6305 74-662 15-75 49-4801 194-83 3-75 11-7810 11045 9-875 31 0232 76-589 15-875 49-8728 197-93 3 875 121737 11-793 10 31-4159 78-540 16 50-2655 20106 4 12^5664 12-566 10-125 31-8086 80-516 16-125 50-6582 204-22 4125 12-9591 13-364 10-25 32-2013 82-516 16-25 510509 207-39 4-25 13-3518 14-186 10-375 32-5940 84-541 16-375 51^4436 210-60 4-375 13-7445 15-033 10-5 32-9867 86-590 16-5 5P8363 213-82 4-5 14-1372 15-904 10-625 33-3794 88-664 16-625 52-2290 217-08 4-625 14-5299 16-800 10-75 33-7721 90-763 16-75 52^6217 220-35 4-75 14-9226 17-721 10-875 34-1648 92 •886 16-875 53-0144 223-65 4-875 15-3153 18-665 11 34-5575 95-033 17 53-4071 226-98 5 15-7080 19-635 11-125 34-9502 97-205 17-125 53-7998 230-33 5-125 16-1007 20-629 11-25 35-3429 99-402 17-25 54-1925 233-71 5-25 16^4934 21-648 11-375 .35-7356 101-62 17-375 54-5852 237-10 5-375 16^8861 22-691 11-5 36-1283 103-87 17-5 54-9779 240-53 5-5 17-2788 23-758 11-625 36-5210 106-14 17-625 55-3706 243-98 5 625 17-6715 24-850 11-75 33-9137 108-43 17-75 55-7633 247-45 5 75 18 0642 25-967 11-875 37-3064 110-75 17-875 56-1560 250-95 5 875 18-4569 27-109 Areas and Circumferences 67 l Table of Circumferences and Areas of C'wqXqs— continued. Diam. Circum. Area, Diam. Circum. Area. Diam. Circum. Area. Inches. Inches. Sq. In. Inches. Inches. Sq. In. I nches. Inches. .Sq. In. 18 56-5487 254-47 24 75-3982 452-39 30 94-2478 706-86 18 125 56-9414 258-02 24-125 75-7909 457-11 30-125 94-6405 712-76 18-25 57-3341 261-59 24-25 76-1836 461 -86 30-25 95-0332 718-69 18-375 57-7268 265-18 24-375 76-5763 466-64 30-375 95-4259 724-64 18-5 58-1195 268-80 24-5 76-9690 471-44 30-5 95-8186 730-62 18-625 58-51-22 272 -4iS 24-625 77-3617 476-26 30-6-25 96-2113 736-62 18-75 58-9049 276-12 24-75 77-7544 481-11 30-75 96-0(t40 742-64 18-875 59-2976 279-81 24-875 78-1471 485-98 30-875 96-9967 748-69 19 59-6903 283-53 25 78-5398 490-87 31 97-3894 754-77 19-125 60-0830 287-27 25-125 78-93-25 495-79 31-125 97-7821 760-87 19-25 60-4757 291-04 25-25 79-3252 5(XI-74 31-25 98-1748 766-99 19-375 60-8684 294-83 25-375 79-7179 505-71 31-375 98-5675 773-14 19-5 61-2611 298-65 25-5 80-1106 510-71 31-5 98-9602 779-31 19-625 61-6538 302-49 25-6-25 80-5033 515-72 31 -620 99-35-29 785-51 19-75 62-0465 306-35 25-75 80-8960 520-77 31-75 99-7456 791-73 19-875 62-4392 310-24 25-875 81-2887 525-84 31-875 100-138 797-98 20 62-8319 314-16 26 81-6814 530-93 32 100-531 804-25 20-125 63-2246 318-10 26125 82-0741 536-05 32-1-25 100-9-24 810-54 20-25 63-6173 3-22-06 26-25 82-4668 541-19 32-25 101-316 816-86 20-375 64-0100 3-26-05 26-375 82-8595 546-35 32-375 101 -709 823-21 20-5 64-4026 330-06 26-5 83-2522 551-55 32-5 102-102 829-58 20-625 64-7953 334-10 26-625 83-6449 556-76 32-625 102-494 835-97 20-75 65-1880 338-16 26-75 84-0376 562-00 32-75 102-887 842-39 20-875 65-5807 342-25 26-875 84-4303 567-27 32-875 103-280 848-83 21 65-9734 346-36 27 84-8230 572-56 33 103-673 855-30 21 125 66-3661 350-50 27-125 85-2157 577-87 33-125 104-065 861-79 21-25 66-7588 354-66 27-25 85-6084 583-21 33-25 104-458 868-31 21-375 67-1515 358-84 27-375 86-0011 588-57 33-375 104-851 874-85 21-5 67-5442 363-00 27-5 86-3938 593-96 33-5 105-243 881-41 21-625 67-9369 367-28 27-6-25 86-7865 599-37 33-625 105-636 888-00 21-75 68-3296 371-54 27-75 87-1792 604-81 33-75 106-029 894-62 21-875 68-7223 375-83 27-875 87-5719 610-27 33-875 106-421 901-26 22 69-1150 380-13 28 87-9646 615-75 34 106-814 907-92 22-125 69-5077 384-46 28-125 88-3573 621-26 34-125 107-207 914-61 22-25 69-9004 388-82 28-25 88-7500 626-80 34-25 107-600 921-32 22-375 70-2931 393-20 28-375 89-1427 632-36 34-375 107-992 9-28-06 22-5 70-6858 397-61 28-5 89-5354 637-94 34-5 108-385 934-82 22-625 71-0785 402-04 28-625 89-9-281 643-55 34-625 108-788 941-61 22-75 71-4712 406-49 28-75 90-3208 649-18 34-75 109170 948-42 22-875 71-8639 410-97 28-875 90-7135 654-84 34-875 109-563 955-25 23 72-2566 415-18 29 91-1062 660-52 35 109-956 96211 23-125 72 0493 4-20-00 29-125 91-4989 666-23 35-1-25 110-348 969-00 23-25 73-0420 424-56 29-25 91-8916 671-96 35-25 110-741 975-91 23-375 73-4347 4-29-13 29-375 92-2843 677-71 35-375 111-134 982-84 23-5 73-8274 433-74 29-5 92-6770 683-49 35-5 111-527 9S9-80 23-625 74-2201 438-36 29-6-25 93-0697 689-30 35-6-25 111-919 996-78 23-75 74-61-28 443-01 29-75 93-4624 695-13 35-75 112-312 1003-8 23-875 75-0055 447-69 29-875 93-8551 700-98 35-870 112-705 1010-8 672 "Verbal" Notes and Sketches Table of Circumferences and Areas of Circles— conftnued. Diam. Circum. Area. D-|am. Circum. Area. Diam. Circum. Area. Inches. Inches. Sq. In. Inches. Inches. Sq. In. Inches. Inches. Sq. In. 36 113 097 1017-9 42 131-947 1385-4 48 1.50-796 1809-6 36 125 113-490 10-25 42125 132-340 1393-7 48-125 151-189 1819-0 36-25 113-883 10321 42-25 132-732 1402-0 48-25 151-582 1828-5 36-375 114-275 1039-2 42-375 133-125 1410-3 48-375 151-975 1837-9 36-5 114-668 1040-3 42-5 133-518 1418-6 48-5 152-367 1847-5 36-625 115061 1053-5 42-625 133-910 1427-0 48-625 152-760 1857-0 36-75 115-454 1060-7 42-75 134-303 1435-4 48-75 153-153 1866-5 36-875 115-846 1068 42-875 134-696 1443-8 48-875 153-544 1876-1 37 116-239 1075-2 43 135-088 1452-2 49 153-938 1885-7 37-125 116-632 1082-5 431-25 135-481 1460-7 49 125 154-331 1895-4 37-25 117 024 1089-8 43-25 135-874 1469-1 49-25 154-723 1905 37-375 117-417 1097-1 43-375 136-267 1477-6 49-375 155-116 1914-7 37-5 117-810 1104-5 43-5 136-659 1486-2 49-5 155-509 1924-2 37.625 118-202 1111-8 43-625 137 052 1494-7 40-625 155-904 1934-2 37-75 118-596 1119-2 43-75 137-445 1503-3 49-75 156-294 1943-9 37-875 118-988 1126-7 43-875 137-837 1511-9 49-875 156-687 1953-7 38 119-381 1134-1 44 138-230 1520-5 50 157-080 1963-5 38-125 119-773 1141-6 44-125 138-623 1529-2 50-125 157-472 1973-3 38-25 120-166 1149-1 44-25 139015 1537-9 50-25 157-865 1983-2 38-375 120-559 1156-6 44-375 139-408 1546-6 50-375 158-258 19931 38-5 120-951 1164-2 44-5 139-801 1555-3 50-5 158-650 2003-0 38-625 121-344 1171-7 44-625 140-194 1564 50-625 159 043 2012-9 38-75 121-737 1179-3 44-75 140-586 1572-8 50-75 159-436 2022-8 38-875 122-129 1186-9 44-875 140-979 1581-6 50-875 159-829 2032-8 39 122-522 1194-6 45 141-372 1590-4 51 160-221 2042-8 39 125 122-915 1202-3 45-125 141-764 1599-3 51-125 160-614 2052-8 39-25 123-308 12100 45-25 142-157 1608-2 51-25 161-007 2062-9 39-375 123-700 1217-7 45-375 142-550 1617-0 51-375 161-399 2073-0 39-5 124-093 1225-4 45-5 142-942 1626-0 51-5 161-792 2083-1 39-6-25 124-486 1233-2 45-625 143-335 1634-9 51-625 162-185 2093-2 39-75 124-878 1241-0 45-75 143-728 1643-9 51-75 162-577 2103-3 39-875 125-271 1248-8 45-875 144-121 1652-9 51-875 162-970 2113-5 40 125-664 1256-6 46 144-513 1661-9 52 163-363 2123-7 40-125 126-056 1264-5 46 125 144-906 1670-9 52-125 163-756 2133-9 40-25 126-449 1272-4 46-25 145-299 1680-0 52-25 164-148 2144-2 40-375 126-842 1280-3 46-375 145-691 1689-1 52-375 164-541 2154-5 40-5 127-235 1288-2 46-5 146-084 1698-2 52-5 164-934 2164-8 40-625 127-627 1296-2 46-625 146-477 1707-4 52-625 165-326 2175-1 40-75 128 020 1304-2 46-75 146-869 1716-5 52-75 165-719 2185-4 40-876 128-413 1312-2 46-875 147-262 1725-7 52-875 166-112 2195-8 41 128-805 1320-3 47 147-655 1734-9 53 166-504 2206-2 41-125 129198 1328-3 47-125 148-048 1744-2 53125 166-897 2216-6 41-25 129-591 1336-4 47-25 148-440 1753-5 53-25 167-290 2227 41-375 129-993 1344-5 47-375 148-833 1762-7 53-375 167-683 2-237-5 41-5 130-376 1352-7 47-5 149-226 1772-1 53-5 168-075 2248 41-625 130-769 1360-8 47-625 149-618 1781-4 53-625 168-468 2258-5 41-75 131-161 1369-0 47-75 150011 1790-8 53-75 168-861 2269 1 41-875 131-554 1377-2 47-875 150-404 1800-1 53-875 169-253 2279-6 Areas and Circumferences 673 Table of Circumferences and Areas of Circles— tron/i/iued. Diam. Circum. Area. DUm. Circum. Area. Diam. Circum. Area. Inches. Inches. Sq. In. Inches. Inches. Sq. In. Inches. Inches. Sq. In. 54 169-646 2290-2 60 188-496 2827-4 66 -207-345 3421-2 54125 170-039 •2300-8 60-r25 188-888 2839-2 66-125 •207-738 3434-3 54 25 170-431 •2311-5 60-25 189-281 2851-0 66-25 •208-131 3447-2 54-375 170-824 2322-1 60-375 189-674 2862-9 66-375 208-523 3460-2 54-5 171-217 •23.32-8 60-5 190 066 2874-8 66-5 208-916 3473-2 54-625 171-609 2343-5 60-625 190-459 2886-6 66-625 209-309 3486-3 54-75 172-002 -2354-3 60-75 190-852 2898-6 66-75 209-701 3499-4 54-875 172-395 2365-0 00-875 191-244 2910-5 66-875 210 094 3512-5 55 172-788 2375-8 61 191-637 2922-5 67 210-487 3525-7 55-125 173-180 2386-6 61-125 192-030 2934-5 67-125 210-879 3538-8 65-25 173-573 2397-5 61-25 192-423 2946-5 67-25 211-272 3552-0 55-375 173-966 •2408-3 61-375 192-815 2958-5 67-375 211-665 3565-2 55-5 174-358 '2419-2 61-5 193-208 2970-6 67-5 212-068 3578-5 55-625 174-751 2430-1 61-625 193-601 2982-7 67-625 212-450 3591-7 55-75 175-144 2441-1 61-75 193-993 2994-8 67-75 212-843 3605-0 55-875 175-536 2452 61-875 194-386 3006-9 67-875 213-236 3618-3 56 175-929 2463-0 62 194-779 3019-1 68 213-628 3631-7 56-125 176-322 2474-0 62-125 195171 3031-3 68-125 214-021 3645 56-25 176-715 2485-0 62-25 195-564 3043-5 68-25 214-414 3658-4 56-375 177-107 2496-1 62-375 195-957 3055-7 68-375 214-806 3671-8 56-5 177-500 2507-2 62-5 196-350 3068-0 68-5 215-199 3685-3 56-6-25 177-893 2518-3 62-625 196-742 3080-3 68-6-25 215-592 3698-7 56-75 178-285 2529-4 62-75 197-135 3092-6 68-75 215-984 3712-2 56-875 178-678 2540-6 62-875 197-528 3104-9 68-875 216-337 3725-7 57 179-071 2551-8 63 197-920 3117-2 69 216-770 3739-3 57-125 179-463 2563 63-125 198-313 3129-6 69125 217-163 3752-8 57-25 179-856 2574-2 63-25 198-706 3142-0 69-25 217-555 3766-4 57-375 180-249 •2585-4 63 375 199-098 3154-5 69-375 217-948 3780 57-5 180-642 -2596-7 63-5 199-491 3166-9 69-5 218-341 3793-7 57 •6-25 181-034 2608-0 63-6-25 199-884 3179-4 69-625 218-733 3807-3 57-75 181-427 2619-4 63-75 200-277 3191-9 69-75 219-126 3821-0 57-875 181-820 2630-7 63-875 200-669 3-204-4 69-875 219-519 3834-7 58 182-212 2642-1 64 201-062 3217 70 219-911 3848-5 58-125 182-605 2653-5 64 125 201-455 3-229-6 70-125 2-20 -3U4 3862-2 58-25 182-998 2664-9 64-25 201-847 3242-2 70-25 2-20-697 3876-0 58-375 183-390 2676-4 64-375 202-240 3254-8 70-375 221-090 3889-8 58-5 183-783 2687-8 64-5 202-6.33 3267-5 70-5 221-482 3903-6 58-625 184-176 2699-3 64-625 203-0-25 3280-1 70-625 221-875 3917-5 58-75 184-569 2710-9 64-75 203-418 3292-8 70-75 2-22-268 3931-4 58-875 184-961 27^22 •* 64-875 203-811 3305-6 70-875 2-22-660 3945-3 59 185-354 27340 65 204-204 33 IS -3 71 2-23-053 3959-2 59-125 185-747 2745-6 65-125 204-596 3331 1 71 •125 223-446 3973-1 59-25 186-139 2757-2 65-25 204-989 3343-9 7125 •223-838 3987-1 59-375 186-532 2768-8 65-375 205-382 3356-7 i 71375 2-24231 4001-1 69-5 186-9-25 2780-5 65-5 205-774 3369-6 715 •224-6-24 4015-2 59 -6-25 187-317 2792-2 65-625 206-167 3382 -4 71-625 2-25-017 40-29-2 59-75 187-710 •2803-9 65-75 -206-560 3395-3 71-75 2-25-409 4043-3 59-875 188-103 2815-7 65-875 -206-952 3408-2 71-875 •2^25-802 4057-4 ($74 "Verbal" Notes and Sketches Table of Circumferences and Areas of CircXts— continued. Diam. Circum. Area. Diam. Circum, Area. Diam. Circum. Area. Inches. Inches. Sq. In. Inches. Inches. Sq. In. Inches. Inches. Sq. In. 72 226-195 4071-5 78 245-044 4778-4 84 263-894 5541-8 72-125 2-26-587 4085-7 78-125 245-437 4793-7 84-125 264-286 5558-3 72-25 226-980 4099-8 78-25 245-830 4809-0 84-25 264-679 5574-8 72-375 227-373 4114-0 78-375 246-2-22 48-24-4 84-375 265-072 5591-4 72-5 227-765 4128-2 78-5 246-615 4839-8 84-5 265-465 5607-9 72-625 228-158 4142-5 78-625 247-008 4855-2 84-625 265-857 5624-5 72-75 228-551 4156-8 78-75 247-400 4870-7 84-75 266-250 5641-2 72-875 228-944 4171-1 78-875 247-793 4886-2 84-875 266-643 5657-8 73 229-336 4185-4 79 248-186 4901-7 85 267-035 5674-5 73-125 229-729 4199-7 79-125 248-579 4917-2 85-125 267-428 5691-2 73-25 230-122 4214-1 79-25 248-971 4932-7 85-25 267-821 5707-9 73-375 230-514 4228-5 79-375 249-364 4948-3 85-375 268-213 5724-7 73-5 230-907 4242-9 79-5 249-757 4963-9 85-5 268-606 5741-5 73-625 231-300 4257-4 79-625 250-149 4979-5 85-625 268-999 5758-3 73-75 231-692 4271-8 79-75 250-542 4995-2 85-75 269-392 5775-1 73-875 232-085 4286-3 79-875 250-935 5010-9 85-875 269-784 5791-9 74 232-478 4300-8 80 251-327 5026-5 86 270-177 5808-8 74-125 232-871 4315-4 80-125 251-720 5042-3 86-125 270-570 5825-7 74-25 233-263 4329-9 80-25 252-113 5058-0 86-25 270-962 5842-6 74-375 233-656 4344-5 80-375 252-506 5073-8 86-375 271-355 5859-6 74-5 234-049 4359-2 80-5 252-898 5089-6 86-5 271-748 5876-5 74-625 234-441 4373-8 80-625 253-291 5105-4 86-625 272-140 5893-5 74-75 234-834 4388-5 80-75 •253-684 5121-2 86-75 272-533 5910-6 74-875 235-227 4403-1 80-875 254-076 5137-1 86-875 272-926 5927-6 75 235-619 4417-9 81 254-469 5153-0 87 273-319 5944-7 75-125 236-012 4432-6 81-125 254-862 5168-9 87-125 273-711 5961 -8 75-25 236-405 4447-4 81-25 255-254 5184-9 87-25 274-104 5978-9 75-375 236-798 4462-2 81-375 255-647 5200-8 87-375 •274-497 5996-0 75-5 237-190 4477-0 81-5 256-040 5216-8 87-5 274-889 6013-2 75-625 237-583 4491-8 81-6-25 256-433 5232-8 87-6-25 275-282 6030-4 75-75 237-976 4506-7 81-75 256-825 5248-9 87-75 275-695 6047-6 75-875 238-368 4521-5 81-875 257-218 5-264-9 87-875 276-067 6064-9 76 238-761 4536-5 82 257-611 5281-0 88 276-460 6082-1 76-125 239-154 4551-4 82-125 258-003 5-297-1 88-125 276-853 6099-4 76-25 239-546 4566-4 82-25 258-396 5313-3 88-25 277-246 6256-7 76-375 239-939 4581-3 82-375 258-789 5329-4 88-375 277-638 6134-1 76-5 240-332 4596-3 82-5 259-181 5345-6 88-5 278-031 6151-4 76-625 240-725 4611-4 82-625 259-574 5361-8 88-625 278-424 6168-8 76-75 241-117 4626-4 82-75 259-967 5378-1 88-75 278-816 6186-2 76-875 241-510 4641-5 82-875 260-359 5394-3 88-875 279-209 6203-7 77 241-903 4656-6 83 260-752 5410-6 89 279-602 6-221-1 77-125 242-295 4671-8 83-125 261-145 5426-9 89-126 279-994 6-238-6 77-25 242-688 4686-9 83-25 261-538 5443-3 89-25 280-387 6'256-l 77-375 243-081 4702-1 83-375 261-930 5459-6 89-375 280-780 6273-7 77-5 243-473 4717-3 83-5 262-323 5476-0 89-5 281-173 6291-2 77-625 243-866 4732-5 83-625 262-716 5492-4 89-025 281-565 6308-8 77-75 244-259 4747-8 83-75 263-108 5508-8 89-75 281-958 63-26-4 77-875 244-652 4763-1 83-875 263-601 5525-3 89-875 282-351 6344 1 Areas and Circumferences 675 Table of Circumferences and Areas of Circles -continued. Diam. Circum. Area. Diam. Circum. Area. Diam. Circum. Area. Inches. Inches. Sq. In. Inches. Inches. Sq. In. Inches. Inches. .Sq. In. 90 282-743 6361-7 94 295-310 6939-8 98 307-876 7543 90 125 283-136 6379-4 94-125 295-702 6958-2 98-125 308-269 7562-2 90-25 283-529 6397 1 94-25 296-095 6976-7 98-25 308-661 7581-5 90-375 283-921 6414-9 94-375 296-488 6995-3 98-375 309-054 7600-8 90-5 284-314 6432-6 94-5 296-881 7013-8 98-5 309-447 76-20-1 90-6-25 284-707 6450-4 94-625 •297-273 7032-4 98-625 309-840 76.39-5 90-75 -285-100 6468-2 94-75 297-666 7051-0 98-75 310-2.32 7658-9 90-875 285-492 6486-0 94-875 298-059 7069-6 98-875 310-625 7678-3 91 285-885 6503-9 95 298-451 7088-2 99 311-018 7697-7 91125 286-278 6521-8 95-125 298-844 7106-9 99-125 311-410 7717-1 91-25 286-670 6539-7 95-25 299-237 7125-6 99-25 311-803 7736-6 91 -375 287-063 6557-6 95-375 •299 -6-29 7144-3 99-375 312-196 7756-1 91-5 287-456 6575-5 95.5 3(X)-a22 71630 99-5 312-588 7775-6 91-625 287-848 6593-5 95.625 300-415 7181-8 99-625 312-981 7795-2 91-75 -288-241 6611-5 95-75 300-807 7200-6 99-75 313-374 7814-8 91-875 288-634 6629-6 95-875 301-200 7219-4 99-875 313-767 7834-4 92 289-027 6647-6 96 301 -593 7238-2 100 314159 7854-0 92125 289-419 6665-7 96-125 .301-986 7257-1 92-25 289-812 6683-8 96-2.5 .302-378 7276-0 92-375 290-205 6701-9 96-375 302-771 7-294-9 92-5 290-597 67-20-1 96-5 303-164 7313-8 92-625 290-990 6738-2 96-625 303-556 7332-8 92-75 291-383 6756-4 96-75 303-949 7351 -8 92-875 291-775 6774-7 96 875 304-342 7370-8 93 292-168 6792-9 97 304-734 7389-8 93-1-25 -292-561 6811-2 97-1-25 305 127 7408-9 93-25 292-954 6829-5 97-25 .305-5-20 74-28-0 93-375 293-346 6847-8 97-375 305-913 7447-1 93-5 293-739 6866 1 97-5 306-305 7466-2 93-6-25 •294-132 6884-5 97-625 306-698 7485-3 93-75 294-5-24 6902-9 97-75 307-091 7504-5 93-875 294-917 6921-3 97-875 307-483 75-23-7 6/6 Verbal " Notes and Sketches Hyperbolic Logarithms. No. of No. of No. of No. of 1 Expansions Hyp. log. Expansions Hyp. log. Expansions Hyp. log. Expansions Hyp. log. R. R. R. R. 11 0-0953 3-6 1 -2809 6-1 1 -8083 8-6 2-1518 1-2 01823 3-7 1-3083 6-2 1 -8245 8-7 2-1633 1-3 0-2624 3-8 1 -3350 6-3 1 -8405 8-8 2-1748 1-4 0-3365 3-9 1-3610 6-4 1 -8563 8-9 2-1861 1-5 0-4055 4-0 1 -3863 6-5 1-8718 9-0 2-1972 1-6 0-4700 4-1 1-4110 6-6 1-8871 91 2-2083 1-7 0-5306 4-2 1-4351 6-7 1 -9021 9-2 2-2192 1-8 0-5878 4-3 1-4586 6-8 1-9169 9-3 2-2300 1-9 0-6419 4-4 1-4816 6-9 1-9315 9-4 2-2407 2-0 0-6931 4-5 1-5041 7-0 1 -9459 9-5 2-2513 21 0-7419 4-6 1-5261 7-1 1 -9601 9-6 2-2618 2-2 0-7885 4-7 1-5476 7-2 1-9741 9-7 2-2721 2-3 0-8329 4-8 1-5686 7-3 1 -9879 9-8 2-2824 2-4 0-8755 4-9 1 -5896 7-4 2-0015 9-9 2-2925 2-5 0-9163 5-0 1-6094 7-5 20149 10-0 2-3026 2-6 0-9555 51 1-6292 7-6 2-0281 10-5 2-3513 2-7 0-9933 5-2 1 -6487 7-7 20412 11-0 2-3979 2-8 1-0296 5-3 1-6677 7-8 2-0541 11-5 2-4430 2-9 1-0647 5-4 1 -6864 7-9 2 -0669 12-0 2-4849 3 1-0986 5-5 1-7047 8-0 2-0794 12-5 2-5262 31 1-1314 5-6 1 -7228 8-1 2-0919 13-0 2-5649 3-2 1-1632 5-7 1-7405 8-2 2-1041 13-5 2-6027 3-3 1-1939 5-8 1-7579 8-3 2-1163 14-0 2-6391 3-4 1 -2238 5-9 1-7750 8-4 2-1282 15-0 2-7081 3-5 1-2528 6-0 1-7918 8-5 2-1401 16-0 2-7726 Printed at The Darien Pkess Edinburgh. -CEB UNIVERSITY OF CALIFORNIA LIBRARY Los Angeles •T^rhis book is DUE on the last date stamped below. DEC 1 1954 MAR 1 2 1962 0.33H ^ ^^J^W MAY 2 519^|||| i^OV d RQTD AUG 2 6 1966 mz hui Fcrm L9-10Cm-9,'52(A3105)444 ■'■'"I "-"'-'^ r}h\M ':.";:i$.:.:iailli >^.b;;-:>, ^^^^|