OF THE 
 
 UNIVERSITY 
 

Boiler Accessories 
 
 A Complete and Authoritative Treatise 
 
 ON THE VARIOUS ACCESSORIES OF THE BOILER ROOM AND ENGINE ROOM 
 
 ESSENTIAL TO ECONOMICAL OPERATION, TOGETHER WITH 
 
 PRACTICAL INSTRUCTION IN THEIR USE 
 
 By WALTER S. LELAND, S. B. 
 
 Assistant Professor of Naval Architecture, Massachusetts Institute 
 
 of Technology; American Society of Naval Archi- 
 . tects and Marine Engineers 
 
 ILLUSTRATED 
 
 CHICAGO 
 
 AMERICAN SCHOOL OF CORRESPONDENCE 
 1909 
 
COPYRIGHT 1908 BY 
 AMERICAN SCHOOL OF CORRESPONDENCE 
 
 Entered at Stationers' Hall, London 
 All Rights Reserved 
 
Foreword 
 
 recent years, such marvelous advances have been 
 made in the engineering and scientific fields, and 
 so rapid has been the evolution of mechanical and 
 constructive processes and methods, that a distinct 
 need has .been created for a series of practical 
 working guides, of convenient size and low cost, embodying the 
 accumulated results of experience and the most approved modern 
 practice along a great variety of lines. To fill this acknowledged 
 need, is the special purpose of the series of handbooks to which 
 this volume belongs. 
 
 C, Iu the preparation of this series, it has been the aim of the pub- 
 lishers to lay special stress on the practical side of each subject, 
 as distinguished from mere theoretical or academic discussion. 
 Each volume is written by a well-known expert of acknowledged 
 authority in his special line, and is based on a most careful study 
 of practical needs and up-to-date methods as developed under the 
 conditions of actual practice in the field, the shop, the mill, the 
 power house, the drafting room, the engine room, etc. 
 
 C, These volumes are especially adapted for purposes of self- 
 instruction and home study. The utmost care has been used to 
 bring the treatment of each subject within the range of the com- 
 
 179743 
 
mon understanding, so that the work will appeal not only to the 
 technically trained expert, but also to the beginner and the self- 
 taught .practical man who wishes to keep abreast of modern 
 progress. The language is simple and clear; heavy technical terms 
 and the formulae of the higher mathematics have been avoided, 
 yet without sacrificing any of the requirements of practical 
 instruction; the arrangement of matter is such as to carry the 
 reader along by easy steps to complete mastery of each subject; 
 frequent examples for practice are given, to enable the reader to 
 test his knowledge and make it a permanent possession; and the 
 illustrations are selected with the greatest care to supplement and 
 make clear the references in the text. 
 
 C. The method adopted in the preparation of these volumes is that 
 which the American School of Correspondence has developed and 
 employed so successfully for many years. It is not an experiment, 
 but has stood the severest of all tests that of practical use which 
 has demonstrated it to be the best method yet devised for the 
 education of the busy working man. 
 
 C, For purposes of ready reference and timely information when 
 needed, it is believed that this series of handbooks will be found to 
 meet every requirement. 
 
Table of Contents 
 
 SPECIAL CONSTRUCTIONS AND MECHANICAL AIDS . . . Page 1 
 
 Boiler Setting Supports Foundation Enclosing Walls Furnaces 
 Doors Grates (Circular, Herring-Bone, Rocking, etc.) Bridge Preven- 
 tion of Smoke Down-Draft Furnaces Hollow Arch Fuel Economizers 
 Mechanical Stokers Fusible Plugs Natural Draft Forced Draft Draft 
 Gauge Closed Stoke-Hold System Closed Ash-Pit System Induced-Draft 
 System Howden System Ellis & Eaves System Steam Jets Tube- 
 Cleaners Tube-Stoppers Manholes and Handholes Mudholes 
 
 CONTROL AND SUPPLY DEVICES .. . . .. . Page 29 
 
 Steam Gauges Vacuum Gauges Water Gauges Try-Cocks Gauge- 
 Glasses Valves (Globe, Angle, Gate) Check-Valves Safety- Valves 
 (Lever, Pop) Pop Regulator Muffler Reducing Valves Blow-Out Ap- 
 paratus Surface and Bottom Blow-Outs Feed Apparatus Feed-Pump 
 Donkey Pump Duplex Pump- Injectors or Inspirators Circulating Ap- 
 paratus Hydro-kineter Evaporators Feed-Water Heaters Steam Sepa- 
 rators Wet Steam Superheated Steam Priming Steam Traps (Float, 
 Bucket, Differential) Return Traps Equalizing Valve Calorimeters 
 (Barrel, Separator, Throttling) Sampling Pipe Piping Pipe Line Sup- 
 ports Expansion Joints Lagging Heat Losses rPipe Coverings Pre- 
 ventives of Radiation (Asbestos, Mineral Wool, Felt, Plaster of Paris, 
 etc.) -Boiler Coverings Horse-Power of Boilers 
 
 BOILER TROUBLES AND TESTS Page 81 
 
 Corrosion and Incrustation Pitting Grooving Scale Sludge Hard and 
 Soft Water Grease Extractor Carbonate of Lime Sulphate of Lime 
 Carbonate of Magnesia Iron Salts Water Purification Boiler Explosions 
 - Boiler Inspection Energy in Hot Water Causes of Explosions (Low 
 Water, Grease, Scale, Defective Design, Deterioration, Defective Workman- 
 ship, Mismanagement) Investigation of Explosions Prevention of Explo- 
 sions Fuel Coal (Anthracite and Bituminous, Lignite) Peat Coke 
 Charcoal Culm Wood Straw Sawdust Bagasse Liquid Fuel (Crude 
 Petroleum) Atomizers Gas (Natural, Coal, Water, Producer) Artificial 
 Fuels Boiler Trials Records of Tests Firing Care of Boilers 
 
 INDEX Page 119 
 
 OF THE 
 
 UNIVERSITY 
 
 OF 
 
MANHATTAN 74TH ST. POWER STATION, NEW YORK. 
 
 ^bowing Carey's Magnesia Pipe and Boiler Covering. 
 
BOILER ACCESSORIES 
 
 PART I 
 
 BOILER SETTING 
 
 The setting for a stationary boiler consists of the foundation and 
 as much of the furnace and flues as is external to the boiler shell. Some 
 internally-fired boilers the "Lancashire," for instance have flues in 
 the brick setting. The whole furnace and sometimes the flues, as is 
 the case with the plain cylindrical boiler, are in the setting. Vertical 
 boilers have simply a foundation; and locomotive boilers have no 
 setting, since they are supported by the frames of the engines. Marine 
 boilers are usually placed on saddles, which are built into the framing 
 of the vessel. 
 
 In setting a boiler, there are three principal requisites that should 
 be kept in mind : 1. A stable support or foundation for the shell, so 
 arranged as to allow for proper expansion of the boiler. 2. Properly 
 arranged spaces for both furnace flues and ash-pit. 3. A covering 
 which will prevent loss of heat by radiation, and which will not allow 
 moisture to accumulate in contact with the plates. 
 
 There are two principal methods for support by brackets 
 riveted to the shell plates, and by suspension from overhead girders 
 by means of .hooks, rings, etc. In any case the supports should be 
 so arranged that each shall bear its proper proportion of the load and 
 at the same time allow for expansion. If the boiler is short, brackets 
 are generally used; while for long, plain cylindrical boilers the girder 
 method is the more common. If a very long, cylindrical boiler is 
 supported only at each end, the great weight between the two sup- 
 ports is likely to cause bending and an excessive strain on the middle 
 plates, tension in the bottom plates, and compression in the top plates. 
 
 The first requisite for a setting is a good foundation. If the 
 ground is firm and favorable to a solid foundation, the excavation 
 need be only three or four feet below the level. If it is soft, the exca- 
 vation should be deeper, and the extra depth filled in with broken 
 stone mixed in with cement, gravel, etc. ; or, for very heavy work, 
 
BOILER ACCESSORIES 
 
 piles may be driven. The first course of the foundation should be 
 large stones laid in cement; upon this stonework the walls may be 
 built, either of stone or brick, to within about six inches of the floor- 
 level; and above this, brick should be used. 
 
 Sometimes the bed is made of concrete about two feet .in thick- 
 ness. If the soil is very firm, a foundation of large stonework about 
 three feet wide may be built under the side, middle, and end walls only. 
 
 In determining the area of the bed, the weight that is to be put 
 on each square foot should be estimated carefully. With ordinary 
 condition of the soil, this should not exceed 2,000 pounds. For 
 greater weights, special construction must be used. 
 
 The supporting and enclosing walls are built upon the foundation, 
 with the outer walls at the sides and rear double, the space between, 
 usually about two inches, being an air-space insulation to prevent 
 loss of heat. Projecting bricks, which extend from the outer until they 
 just touch the inner wall, allow for expansion without decreasing the 
 strength of the inner wall. The side walls are strengthened by buck- 
 stays or binders, which are kept in place by long bolts, secured by 
 nuts on each end. Fig. 1 shows a boiler in the brick setting, sup- 
 ported by brackets, the front brackets resting on iron plates which 
 are built into the walls; the rear brackets, being supported by rollers, 
 are free to move as the shell expands. If designed for anthracite 
 coal, the distance between the shell and the grate-bars is about two 
 feet; for softer coal, this distance is increased a few inches. 
 
 The furnace is lined with firebrick, both front and sides ; and 
 sometimes portions back of the bridge, as well as the bridge itself, 
 may thus be protected. The space between the bridge and the shell 
 is from 6 to 8 inches, which brings the hot gases into close contact 
 with the boiler before they enter the combustion chamber beyond, 
 the rear and side walls being built a little higher than the top row of 
 tubes. The fire-line must not be carried above the water-line; if it 
 is, the intense heat is likely to injure the shell-plates. Never expose 
 any part of the boiler not covered by water to the flames from the 
 furnace. The side walls are built about the same height as the rear 
 walls. The space at the rear is bridged over and stiffened by T-irons. 
 In order to increase the heating surface, the top is arched so that the 
 hot gases will pass over the steam space before they enter the chimney. 
 
BOILER ACCESSORIES 
 
BOILER ACCESSORIES 
 
 The smoke box projects over the front end of the boiler and has 
 a rectangular uptake. 
 
 Fig. 3 shows the top view of the same boiler. 
 
 The front is usually of cast iron, with doors for firing and cleaning 
 and for access to the tubes. Soot, dirt, etc., are removed through the 
 door in the brickwork at the rear. 
 
 The end which contains the handhole should be set about one 
 
 Fig. 2. Front Elevation of Boiler in Setting, Showing Binders Bolted in 
 Place, to Strengthen Side Walls. 
 
 inch lower than the other end, so that the sediment and detached scale 
 will tend to accumulate there. 
 
 Internally-fired boilers may also be enclosed in brickwork. The 
 setting is a support and covering, forming the side flues but not the 
 furnace. Excess of brickwork surface in contact with the shell, 
 should be avoided, as brickwork collects moisture, which causes 
 external corrosion. 
 
BOILER ACCESSORIES 
 
6 
 
 BOILER ACCESSORIES 
 
 Water-Tube Boilers. The settings for water-tube boilers are 
 similar to the settings of cylindrical tubular boilers. Marine water- 
 
 Fig. 4. Fig. 5. 
 
 Types of Brackets for Supporting Boilers. 
 
 In Fig. 4 the rivets are all above the flange; in Fig. 5 they are both above 
 and below the flange. 
 
 tube boilers are enclosed in sheet-iron casing, which is lined with non- 
 conducting material, usually asbestos or m agnesia. 
 
 Supports. There are, as already intimated, two common methods 
 of supporting boilers 1. By means of brackets; 2. By suspending 
 from wroughl-ir&n beams. 
 
 If the boiler is about 15 feet long, it is customary to use two 
 brackets on each side. If more than 15 feet, three on each side are 
 used. The front brackets rest on the brickwork, but the others rest 
 on small iron rollers to allow for expansion. Brackets are so arranged 
 that the plane of support will be a little above the middle. There are 
 several forms of brackets. The form shown in Fig. 4 is usually made 
 of cast iron, and is provided with rivets above the flange of the bracket. 
 
 Fig. 6. Fig. 7. 
 
 Two Methods of Supporting Boilers by Suspending from Overhead Beams. 
 
 It is better to have the rivets both above and below the flange, as shown 
 in Fig. 5. 
 
BOILER ACCESSORIES 
 
 Fig. 6 shows one method of suspending from beams. A lug, 
 made of wrought iron, is riveted to the plates of the boiler. A bolt 
 having one end bent like a hook, holds the lug from the beam. In 
 Fig. 7 the lug is replaced by a loop of wrought iron. Fig. 8 shows 
 another method of suspension, the connection between the rod and 
 the boiler-plates being short pieces of boiler-plate arranged for flexi- 
 bility. 
 
 When the boiler is of small diameter, it may be suspended as 
 shown in Fig. 9. 
 
 * FURNACES 
 
 To get the maximum efficiency from any boiler, it is necessary 
 that the fuel shall be properly consumed, and that the proportions 
 
 o o 
 o o 
 o o 
 
 Fig. 8. Flexible Support for Suspended Boiler. Fig. 9. Illustrating Method of Suspend- 
 Flexibility Secured by means of Two ing Boiler of Small Diameter. 
 
 Pieces of Boiler-Plate Bolted 
 Together. 
 
 of the furnace shall be such as to give the maximum results. No 
 boiler is economical the furnace of which is so small that the fire has 
 to be forced to obtain the desired result. The furnace, of course, will 
 vary in shape, size, and detail with the type of boiler and the kind of 
 fuel; but certain essentials such as doors, grate-bars, bridge, and 
 ash-pit are similar in all furnaces. To obtain the maximum effi- 
 
8 BOILER ACCESSORIES 
 
 ciency of combustion, there should be a uniform and abundant supply 
 of air to the under side of the grate. This is easily obtained when the 
 boilers are externally fired, but may be somewhat restricted when they 
 are internally fired. If smoky fuels are used, a moderate supply of 
 air is necessary on the surface of the coal, to prevent excessive smoke 
 formation; but, as the air thus admitted is usually cold, the quantity 
 should be small, to prevent unnecessary cooling of the furnace. This 
 air is generally supplied through a draft-plate in the fire-door. 
 
 All possible radiation should, of course, be prevented. In the 
 case of internally-fired boilers, this radiation is not likely to be exces- 
 sive, for most of the heat would have to pass through the water in the 
 boiler before radiating, and it is a comparatively easy matter to encase 
 such a boiler in some sort of approved lagging which will prevent 
 most of the heat from escaping. The case is somewhat different with 
 the externally-fired boiler, where the furnace is built in a mass of 
 brickwork below the boiler. In such a furnace a considerable amount 
 of heat may radiate directly from the fire without coming in contact 
 with the boiler or water at all. 
 
 To allow for complete combustion, there should be a sufficient 
 space between the grate and the boiler. In externally-fired boilers, 
 this space may be approximately two feet. If this distance is increased 
 beyond proper limits, some effect of the heat will be lost; and if the 
 distance is small, the plates are likely to be damaged, and complete 
 combustion impaired. In the internally-fired boiler, the combustion 
 space is frequently sacrificed in order to obtain a large grate area. If 
 the space between the grate-bars and the boiler is too small to allow 
 complete combustion, a combustion chamber must be provided 
 immediately back of the bridge, which will permit of the complete 
 combustion of the gases. The ideal place, of course, for the combustion 
 chamber, is immediately over the grate. In locomotive boilers, the 
 crown sheet is usually four to six feet above the grate; but such a 
 height is manifestly impossible in marine or other internally-fired 
 boilers, and the combustion chamber behind the bridge wall, in the 
 Scotch boiler, partially compensates for the loss of space immediately 
 over the grate. 
 
 The incandescent fuel and unconsumed gases should not come 
 in contact with the cold surfaces of the boiler if the most efficient com- 
 
BOILER ACCESSORIES 9 
 
 bustion is desired. This condition is violated in internally-fired 
 boilers, where the fire comes directly against metal having water on one 
 side of it. If the flame is chilled by contact with cold surfaces before 
 the gases are completely burned, a considerable amount of smoke is 
 likely to result. 
 
 The fire-grate should be of such dimensions that the fireman can 
 work efficiently. A grate more than six feet long cannot be properly 
 taken care of at the farther end ; and if the grate is more than four 
 feet wide, two fire-doors should be provided. The height of the grate 
 should be laid out with proper reference to the floor, two feet above 
 the floor being about right. If the grate is high, it is difficult, if not 
 impossible, to tend the fire properly. These conditions are dependent, 
 not so much upon the boiler, as upon the physical limitations of the 
 fireman, and of course are eliminated by using the mechanical stoker. 
 
 To the above conditions may be added a suitable temperature in 
 the fire-room. No man can tend a fire properly in excessive heat. 
 In stationary work it is not difficult to maintain proper conditions in 
 the fire-room; but at sea, where the supply of air is necessarily limited 
 to what can come in through small openings, it is a different problem. 
 The fire space on board ship is small ; and the air coming through the 
 ventilating ducts usually makes an exceedingly cold spot immediately 
 under the duct without producing much effect in other parts of the 
 room. 
 
 Door. The furnace door is usually made of cast iron, and is 
 supplied with a circular or sliding draft-plate or grid, which admits 
 air to the top of the fire as needed. It is usually protected by a per- 
 forated, wrought-iron baffle-plate bolted fa the door casting inside, 
 with an air-space of two or three inches between. This not only 
 protects the cast iron of the door from the direct force of the flame, 
 but it forms a chamber for the proper distribution of the air-supply, 
 and also helps to heat it somewhat before reaching the furnace. 
 
 In many of the French torpedo-boats, a patent swinging door is 
 provided, set on horizontal hinges swinging inwards. The door, 
 of course, must be held open while the stoker is tending the fire; but 
 in case a tube blows out, it prevents the rapid escape of steam into the 
 fire-room. This is a matter of much more importance in the restricted 
 fire-room commonly found on a vessel than it would be on land. 
 
 Grate. The size of grate will depend upon the quantity of coal 
 
10 BOILER ACCESSORIES 
 
 likely to be burned. For ordinary draft, this may be 15 Ibs. or upward 
 per square foot of grate surface per hour; for forced draft, 40 to 60 
 Ibs. ; and in some cases as much as 100 Ibs. per square foot of grate 
 surface has been burned. If the grates are long, they are usually 
 inclined slightly downwards, say f inch to the foot, which is a great 
 assistance in firing and makes it easier to keep fire on the farther end 
 of the grate.* The grate-bars are usually made of cast iron, as this 
 material is cheaper than wrought iron and in most instances lasts as 
 well. The bars are made in various forms, according to the fuel 
 burned and the shape of the firebox. 
 
 For large grates, the bars are made singly or in pairs. For 
 smaller grates, they are made in larger groups. Grate-bars should 
 not be more than three feet in length. The length of grate can easily 
 be a multiple of the length of these bars. The bars have distance 
 ' pieces at the ends, and perhaps in the middle, to prevent distortion. 
 They are usually 3 inches or more in depth at the middle, tapering to 
 perhaps an inch or so at the ends; and the cross-section is slightly 
 tapered from top to bottom, so that the bars can easily be withdrawn 
 from the sand after casting. They are usually made a trifle shorter 
 than the place in which they fit, to allow for expansion, 2 per cent of 
 the length of the bar usually being sufficient for this purpose. The 
 air-spaces between the bars are usually about \ inch in width. For 
 burning pea coal or screenings, a finer grate must be used. For 
 anthracite coal, the space may be a little larger. Bituminous coal, 
 which readily cakes, can have a considerable space between the bars- 
 and this, indeed, is essential for a proper supply of air. 
 
 Fig. 10 shows a circular grate, such as is placed in a vertical 
 boiler. M shows the style of grate-bar used in burning sawdust or 
 shavings; N is what is known as the herring bone grate; and is a 
 group of bars of the ordinary form. In locomotives, and in boilers 
 where the grates are subjected to extra hard usage, wrought-iron bars 
 may be used. The point of fusion of wrought iron being higher than 
 that of cast iron, the former would possess a considerable advantage 
 were it not for the fact that wrought iron will bend and twist more 
 readily than cast iron. Grates have been made of hollow bars, 
 through which water is caused to circulate. By this method their 
 
 * The grates have an. incline of a few inches, so that the bed of coal will be thicker 
 at the rear than at the front; this allows a more even consumption of fuel, as the air 
 passes through the fire at the bridge more freely. 
 
BOILER ACCESSORIES 
 
 11 
 
 durability is increased, and the water-grate forms a fairly good' feed- 
 water heater. This type of grate, however, is expensive. 
 
 Fig. 10. Types of Grates for Boilers. 7 Circular Grate for Vertical Boiler ; M Grate for 
 
 Burning Sawdust or Shavings; ^"Herring-Bone" Grate. Group 
 
 of Grate-Bars of Ordinary Form. 
 
 Rocking Grates. The labor of breaking the clinkers is con- 
 siderable when ordinary fixed grate-bars are used ; and to economize 
 this labor, various forms of rocking-grates have been devised. In 
 
 . -;:; . L 
 
 ,/',,,.':' '/'/' ' ' y ' " ',1. ''' -i ; "') ''}<' ' . t " 1 1 -. \- .'.//f'- \ 
 
 Fig. 11. "Kelley Standard" Rocking Grate. 
 
 locomotives, rocking-grates are essential; and since the rate of com- 
 bustion is high, the fire must always be kept in good condition; and 
 
12 
 
 BOILER ACCESSORIES 
 
 the grate, being below the cab floor, cannot easily be reached by hand. 
 Fig. 11 shows the "Kelley Standard' 5 rocking grate. Each bar is 
 made up of a number of separate leaves, which can be removed and 
 replaced without renewing the whole bar. When the bar is moved 
 back and forth by means of a lever outside the brickwork, the leaves 
 oscillate through a small angle and break up the clinkers. 
 
 Another form of bar, shown in. Fig. 12, has proved v6ry satis- 
 factory. A and B are two bars, the ends of which are of different 
 depths. These rest at each end on a crank-shaft C. As this is 
 oscillated by the lever G, the alternate bars move up and down, and the 
 clinkers are easily shaken out. 
 
 Bridge. The bridge is a large wall or partition at the back of the 
 
 Fig. 12. Rocking Grate Consisting of Alternate Bars with Ends of Different Depths 
 Resting on a Crank-Shaft Oscillated by a .Lever. 
 
 grate, usually built of firebrick or cast iron, or of ordinary brick 
 covered with' firebrick. The bridge separates the grate from the com- 
 bustion chamber, and causes the gases to come in close contact with 
 the boiler in passing into the combustion chamber. The proper 
 height of the bridge will depend upon the draft. ' If the space is nar- 
 row between the bridge wall and the boiler, more draft will be neces- 
 sary to carry the gases through. Two or more bridges may sometimes 
 be built in long boilers to keep the gases in contact with the shell as 
 long as possible. 
 
 Special Furnaces. Almost any furnace is adapted for the use of 
 anthracite or bituminous coal containing less than 20 per cent of 
 volatile matter; but if there is more than this amount of volatile 
 matter, the heat is likely to be so intense that the fire should' not be 
 
BOILER ACCESSORIES 13 
 
 brought in direct contact with the boiler. If the fuel should contain 
 40 per cent of volatile matter, the furnace should be surrounded with 
 firebrick and should have a high combustion chamber. Coal is the 
 most common fuel used ; but wood, sawdust, and straw are not uncom- 
 mon fuels. When these are burned, there should be plenty of room 
 in the furnace, and a sufficient supply of air on top of the fuel. Saw- 
 dust, shavings, and fine, coal may be blown into the furnace by an air- 
 blast. 
 
 In the West, crude petroleum is becoming a common fuel. Ex- 
 periments have shown that one pound of crude oil is equivalent in 
 heat units to something less than two pounds of good coal. Oil has. 
 many advantages as a boiler fuel. It is clean, gives a uniform heat, 
 is economical, and requires much less attention than coal. There are 
 no ashes to handle, and one man can easily tend two or three times 
 the number of furnaces that he could if burning coal. The fire can 
 be start,e/l and stopped instantly; and the supply of -air can be so regu- 
 lated that, unless the boiler fs forced to the limit, there will be prac- 
 tically no production of smoke. Whether or not oil is an economical 
 fuel, will depend upon the local conditions and the market. 
 
 Oil fuel is fed into the furnace through a sprayer formed, in 
 some cases of two concentric conical tubes. Compressed air or 
 steam entering through the one tube draws the oil through the other, 
 on the principle of the atomizer, and throws it into the furnace in a 
 fine spray. For marine work, compressed air should be used, as the 
 loss of steam for this purpose would be a matter of considerable 
 consequence. Steam, however, is sometimes used in marine work, 
 in which case the vessel must be equipped with an evaporator to 
 make up the steam thus lost. On land, where fresh water is plenty, 
 steam is usually preferred, and is less expensive in first cost. 
 
 Prevention of Smoke. In large cities, where the escape of con- 
 siderable quantities of smoke is undesirable, several methods have 
 been devised either to consume the smoke or to prevent its formation. 
 The cause of smoke, as we have seen, is an insufficiency in the supply 
 of air, or perhaps a too abundant supply of cold air above the fire; 
 or, again, smoke may be due to the contact of the flame with cold 
 surfaces. An exceedingly high temperature is necessary to consume 
 the finely divided particles of carbon, and anything that tends to chill 
 the flame will cause smoke. 
 
14 
 
 BOILER ACCESSORIES 
 
 The actual loss caused by the escape of smoke, even when it 
 is dense and black, has been found to be slight, and usually the appli- 
 ance used for prevention costs more than is saved. The alternate 
 firing of two furnaces which open into a common combustion chamber, 
 or the alternate firing of two sides of the same furnace, produces a 
 slight gain if the proper amount of air is admitted. But if, in order 
 to burn the smoke, the bed in one furnace or on one side of a furnace 
 is allowed to become thin, there will be no gain in efficiency. 
 
 The introduction of steam is an efficient method, but it is likely 
 to cause a too rapid rate of combustion. 
 
 Another arrangement to prevent the escape of smoke is that by 
 
 Fig. 13. "Hawley" Down-Draft Furnace Attached to Horizontal Multitubular Boiler. 
 Note Upper Grate Consisting of Water Tubes Connected to Steel Drums. 
 
 which the coal is distilled in a small furnace which is separate from the 
 boiler. The coke and gases thus made are burned in the furnace of 
 the steam boiler. This device is not altogether satisfactory, on account 
 of the loss of heat from the detached furnace. Rather than add any 
 smoke-prevention device, anthracite or coke may be used instead of 
 bituminous coal. 
 
 Many engineers and business men consider a good fireman to be 
 the best smoke preventer. 
 
BOILER ACCESSORIES 15 
 
 Down-Draft Furnaces. In order to increase economy and 
 capacity, or to prevent smoke, a down-draft furnace is sometimes 
 used. In this type of furnace, there are two grates, one a foot or more 
 above the other. Fresh coal is fed to the upper grate, and, as f it 
 becomes partially consumed, falls through to the grate below, where 
 the combustion is completed. The draft is downward through the 
 upper grate, and upward through the lower, because the connection 
 to the chininey is from the space between the grates. The volatile 
 gases are carried down through the bed on the upper grate, and are 
 burned in the 
 space below it, 
 where they meet 
 the hot air drawn 
 upward from the 
 lower grate. A 
 large proportion 
 of the air for com- 
 bustion enters the 
 door at the upper 
 grate. Tests on 
 
 tVm TTnwlov fnr Fi - 14 - Upper Grate of "Hawley" Down-Draft Furnace. The 
 ' 1C J Grate-Bars are Water Tubes Connected to Steel Drums 
 
 nace show that 30 
 
 to 45 pounds of coal per square foot per hour can be burned with good 
 
 results. 
 
 In the furnace made by the Hawley Down-Draft Boiler Com- 
 pany, the grates are formed of a series of water tubes opening at the 
 ends into steel drums, shown in Figs. 13 and 14, which are connected 
 with the boiler. Fig. 13 shows this furnace attached to a horizontal, 
 multitubular boiler. It may be applied to both tubular and water- 
 tube boilers with good results, and is advantageous to boilers of insuf- 
 ficient heating surface, and when inferior fuels are burned. It is 
 claimed that this attachment insures complete combustion, small 
 amount of ashes on account of the second grate, good water circula- 
 tion, and increased economy and capacity. 
 
 The Hollow Arch. Among boiler accessories specially adapted 
 for use on locomotives because of their intense draft, the hollow arch 
 has recently come into prominence. Its principle is simply that of a 
 conduit providing a passage for the admission of heated air to the 
 
16 BOILER ACCESSORIES 
 
 firebox above the fire, in addition to the air that comes up through 
 the grate from below in the ordinary way. Its object is to keep the 
 supply of oxygen at all times sufficient in quantity, and at the proper 
 temperature, to insure a practically perfect combustion of the uncon- 
 sumed carbon and hydrocarbon gases which are ordinarily wasted and 
 lost in the form of black smoke pouring from the stack. It thus 
 insures an economy of fuel and a proportional reduction in operating 
 expense. 
 
 The problem of securing complete combustion of fuel on a loco- 
 motive, is one that presents peculiar difficulties. The quantity of 
 fuel to be burned is so large, and the firing space relatively so small, 
 that the. conditions usually are unfavorable for economical combustion. 
 A ton of average bituminous coal contains about 1,000 pounds of pure 
 carbon, 700 pounds of hydrocarbon gases, and 300 pounds of non- 
 combustible matter or ash. The 1,700 pounds 01 carbon and hydro- 
 carbons require about 300,000 cubic feet of air for their complete 
 combustion. In the ordinary method of burning coal on a loco- 
 motive, fully 90 per cent of this air or 270,000 cubic feet per ton of 
 fuel burned must be drawn up through the grate-bars and firebed. 
 This is practically impossible without forcing the draft to such an 
 extent that the fire will .be pulled off the grates, and more or less of the 
 unburned coal carried away through the flues and stack. The result 
 is that the supply of air actually used is, as a general thing, insufficient 
 for perfect combustion, and the combustible carbon smoke and gases 
 pass out of the stack without giving up all of their heat to the water 
 in the boiler. The energy they contain is simply wasted. 
 
 How, then, can this be prevented? In other words, since the 
 quantity of air that comes through the grates is insufficient, how can 
 we get enough air to the fuel without interfering with the fire? It 
 must be let in above the fire; but it will not do to admit cold air, which, 
 as every fireman knows, would act as a damper on the fire, retarding 
 combustion, and increasing rather than preventing smoke and loss 
 of energy. The air to be admitted to the fire must first be heated to 
 as near the ignition point as possible. 
 
 This is done by means of the hollow arch. One of these arches 
 of the "Wade-Nicholson" type, installed on a locomotive, is illustrated 
 in Fig. 15, the method of operation being clearly indicated. The 
 device may be installed at both back and front ends of the firebox. 
 
BOILER ACCESSORIES 
 
 17 
 
 The hollow passage through the arch leads directly through suitable 
 openings in the firebox sheets, from the outer air to the combustion 
 chamber, being deflected downward toward the fire at the inner end. 
 The walls of the arch, being highly heated, impart their heat to the cur- 
 rent of air, which, as it 
 emerges into the firebox, is 
 practically at the tempera- 
 ture of ignition. There 
 mingling directly with the 
 coinbustible gases, an ap- 
 proximately perfect com- 
 bust ion is established. 
 The resulting economy in 
 fuel is estimated to aver- 
 age a saving of at least 8 
 per cent. 
 
 The Chicago & North- 
 western Railway, has, 
 after severe test, adopted 
 arches of the above type 
 on over 200 of its locomotives ; and its example has been followed on 
 many of the locomotives of the Santa Fe, the Chicago, Milwaukee & 
 St. Paul, the Pere Marquette, the Duluth & Iron Range, and other 
 important railroads in this country. In addition to the saving in 
 fuel, the following advantages are claimed for the hollow arch : 
 
 Being air-cooled, its life is two to three times that of the ordinary solid 
 brick arch. 
 
 It does away with tire smoke nuisance. 
 
 The air, being heated before striking the combustible gases, unites with 
 them instantly, giving a brighter, cleaner, more intense fire, and resulting 
 in a better steaming engine. 
 
 The back arch acts as a baffle-sheet, protecting the crown sheet and 
 upper flues, and gives a more uniform distribution of heat throughout, re- 
 sulting in less leaky flues and a saving in boiler repairs. 
 
 The arch can be used either with or without water-filled circulating 
 arch tubes as supports. 
 
 Arches can readily be removed and reset, in^whole or in part, without 
 damage, to give access to flues when repairs are needed. 
 
 Fuel Economizers. Many devices have been employed whereby 
 a portion of the heat may be extracted from the gases as they pass 
 
 
 Fig. 15. Wade-Nicholson Hollow Arch Installed in 
 
 Locomotive Boiler. The Water-Tube Supports 
 
 Here Shown are Sometimes Omitted. 
 
18 
 
 BOILER ACCESSORIES 
 
BOILER ACCESSORIES 
 
 Id 
 
 from the boiler to the uptake. Most of these consist of a tubular 
 arrangement through which the hot gases pass ; but, as these are soon 
 covered with a thick deposit of soot, they quickly become inoperative. 
 The "Green" economizer (Fig. 16) solves this difficulty by means of 
 small scrapers which work up and down between Jhe tubes. These 
 scrapers are operated by a small engine, and keep the tubes free from 
 soot. The feed-water is pumped through these tubes on its way to 
 the boiler, and is thoroughly heated. An economizer of this sort will 
 extract 40 per cent or more of the heat from the waste gases,; but by 
 reducing the temperature of these gases, the draft is somewhat reduced, 
 and either the chimney must be built higher, or a blower must, be 
 used. 
 
 Mechanical Stokers. The mechanical stoker, which feeds coal 
 and tends fires by machinery, is coming more and more into general use. 
 With a good mechanical stoker, one man can tend several furnaces 
 with little labor. There are several different types, and in most of 
 them the coal is fed into a hopper of such size that it need not be often 
 filled. Some stokers work continuously; others, only when thrown 
 
 into gear by the 
 
 
 
 fireman. In the 
 "Roney" stoker 
 (Fig. 17), the 
 grate-bars ex- 
 tend across the 
 furnace, and 
 form a series of 
 steps down 
 which the fuel 
 moves. Each 
 grate bar is hung 
 on pivots at the 
 
 ends, and is operated by a rocker-bar. This rocker-bar is driven by a 
 small steam engine, with a slow, regular reciprocation which causes 
 the grate-bars .to tip so that the coal of its own weight slides from 
 one grate-bar to the next. Coal from a hopper falls onto a hori- 
 zontal plate, and is fed into the top of the grate by a pusher. The 
 rapidity with which the fuel can be fed, is regulated by changing the' 
 stroke of the pusher and by governing the speed of the engine. Ashes 
 
 Fig. 17. Detail of "Honey" Mechanical Stoker. 
 
20 BOILER ACCESSORIES 
 
 and clinkers collect on the dumping-grate at the end of the grate-bars, 
 whence they can be dumped into the ash-pit. 
 
 This type of grate is well adapted for smoke prevention, for the 
 fresh fuel fed in at the top is rapidly coked, and the volatile gases are 
 easily consumed. The rapidity of feed should be so regulated that 
 no unburned fuel gets past the dump-grate. If the fire becomes too 
 thin, there will be a loss of efficiency due to the excess of air which 
 passes through the burning fuel. It is easy to detect the loss from 
 too much fuel, but not so easy if there is too little fuel. 
 
 All mechanical stokers in which the movable parts are inside the 
 furnaces, are likely to get out of order because of the heat and dirt. 
 
 Fusible Plugs. Fusible plugs are usually inserted in the top 
 sheet or crown sheet of boilers, as a safeguard against collapse of the 
 furnace crown should the water in any way be drawn out of the boiler 
 while the fire is burning. These plugs consist of a core composed of 
 an alloy of tin, lead, and bismuth, with a covering of brass or cast 
 iron. The United States inspection law requires at least one fusible 
 plug to be put in every marine boiler,, with the exception of water- 
 tube boilers, the plug to be made of a bronze casing filled with good- 
 quality "Banca" tin from end to end. While this plug is kept -at a 
 comparatively low temperature by water on one side, the fire on the 
 other side will not melt it; but when the water-level becomes low 
 enough to leave one end of the plug uncovered, the alloy core of the 
 plug, having a comparatively low melting point, will fuse, thus running 
 out of its casing, relieving the pressure in the boiler, and allowing the 
 excess of steam to extinguish the fire, which otherwise would be likely 
 to destroy the crown sheet. 
 
 Fusible plugs are frequently unreliable. Sometimes they will 
 blow out when there is no apparent cause, and sometimes remain 
 intact when the plates have become overheated. If a coating of hard 
 scale is allowed to accumulate over the plug, it may stand consider- 
 able pressure, even after the core has become melted. To provide 
 against this, the plug should be replaced frequently. If allowed to 
 remain in the boiler for any length of time, the composition of the 
 alloy is likely to change, the plug thus becoming more or less unre- 
 liable. 
 
 Figs. 18 and 19 illustrate the ordinary plug. It should be so 
 made that, when screwed into the crown sheet, it will project 1^ or 
 
BOTLER ACCESSORIES 
 
 21 
 
 2 inches above the plates, so that when the alloy melts there will be a 
 sufficient depth of water over the crown sheet to prevent injury from 
 heat. 
 
 Sometimes the core is covered with a thin copper cap, as shown 
 
 Fig. 18. Fusible Plug. At Right is Sectional View of Plug Attached to Crown 
 Sheet of Boiler, to Give Automatic Warning in Case of 
 Overheating of Plates. 
 
 in Fig. 18, which protects the alloy from contact with the water, thus 
 preventing a chemical change and the formation of scale. It does 
 not necessarily follow that a hole i inch or f inch in diameter will 
 
 Fig. 19. Illustrating Action of Fusible Plug Attached to Crown Sheet. 
 
 liberate steam fast enough to prevent excess of pressure. If a small 
 quantity of steam is introduced into the firebox, it may have the 
 
22 60ILER ACCESSORIES 
 
 . . , , -..,^~ 
 
 effect of brightening the fire and increasing the heat of combustion, 
 owing to the formation of water gas as the steam mingles with the 
 burning coal. The steam, moreover, might have the effect of inducing 
 additional draft. If, however, the quantity of escaping steam and 
 water is considerable, combustion will be retarded, and the fire will 
 be partially extinguished. It will operate to warn the fireman of 
 what has happened; and if the escape of steam is not too rapid, he 
 may throw on wet ashes and deaden the fire. 
 
 NATURAL AND FORCED DRAFTS 
 
 The draft in a chimney is caused by the difference in weight 
 between the volume of heated gases inside and^the outside air. This 
 being so, it is apparent that the taller the chimney, the greater this 
 difference will be. The force or intensity of a draft is increased, and 
 additional draft is induced, by the force of the wind as it whistles by 
 
 Fig. 20. "Eames Differential" Draft-Gauge. 
 
 the chimney top. The intensity may at any time be measured by a 
 draft-gauge. The most satisfactory instrument of this sort is the 
 "Eames Differential" draft-gauge, shown in Fig. 20. The tube is 
 filled with a special non-drying, non-evaporating oil of known specific 
 gravity. The incline and diameter of the tube are so proportioned 
 that the readings are equivalent to inches of water, in which terms 
 the draft is invariably measured. 
 
 Other things being equal, the rate of combustion depends upon 
 the height of the chimney. A chimney 20 to 25 feet in height will 
 cause a draft sufficient to burn about 8 Ibs. of coal per square foot of 
 grate area per hour. If the height is increased to about 100 feet, 
 the rate of combustion will be increased to approximately 15 Ibs. per 
 square foot; and to burn 25 Ibs., the chimney should be about 175 
 feet high. This is measured above the grate of the boiler. For good 
 bituminous or anthracite coal, the chimney must be higher than for 
 
BOILER ACCESSORIES 23 
 
 wood, if the same rate of combustion is desired. If the boiler has 
 small or winding passages, the chimney must be higher to produce 
 the same effective draft. High chimneys are costly; and it is fre- 
 quently the practice to build two or three small chimneys in place of 
 the big one, and to supplement them with some form of forced draft. 
 
 By means of forced draft, the rate of fuel combustion can be 
 increased under favorable conditions to 100 Ibs. of coal per square 
 foot of grate surface per hour. This, of course, greatly increases the 
 power of the plant, but is likely to injure the boiler, and is uneconomi- 
 cal under most conditions. There are three systems of forced draft 
 in common use : 
 
 1. The closed stoke-hold, as used in marine work; 
 
 2o The closed ash-pit-, 
 
 3. The induced draft. 
 
 Closed Stoke-Hold. One of the most common forms of forced 
 draft, especially as used on warships, is obtained by closing the stoke- 
 holds and blowing a fresh supply of air into the fire-room. This gives 
 an exceedingly good ventilation and keeps the fire-room in good con- 
 dition; but its chief objection is that when the furnace doors are 
 opened there is a tremendous indraft of cold air, which tends to lower 
 the efficiency of the boiler. If this system is employed, the bulk- 
 heads adjacent to the boiler-room must be provided with double doors, 
 forming an air-lock between. By opening only one door at a time, the 
 pressure in the fire-room is not lost. This system seems to possess 
 but one distinct advantage, and that is coolness and therefore comfort 
 for the firemen; but the disadvantage of the inrush of air to the 
 furnaces when firing, is sufficient, in some cases, to make the system 
 questionable. 
 
 Closed Ash-Pit. The essential features of forced draft by this 
 method consist merely in closing the ash-pit tight, and blowing the air 
 directly under the grate. When the fires are cleaned, the draft, of 
 course, must be shut off; otherwise the flames will be blown out into 
 the fire-room. The fire-room, under this system, is likely to be 
 hotter than by the other method ; but this system would seem to be the 
 better from a mechanical point of view. 
 
 There are several patented devices in connection with the forced 
 draft, of which the "Howden" and the "Ellis and Eaves" systems 
 may be specially mentioned. It may be worth while to note that if fuel- 
 
24 BOILER ACCESSORIES 
 
 oil is burned, any one of these systems of forced draft will work better 
 than with coal, for the fire can be tended without opening the fire- 
 doors. 
 
 Induced Draft. Perhaps the most common example of induced 
 draft is to be found in the locomotive, where the exhaust steam is 
 turned into the smokestack. The rush of this steam up the stack, 
 by carrying a large volume of air with it, induces a tremendous draft. 
 Induced draft may also be obtained in stationary and marine plants 
 by placing a blower in the chimney or stack. In marine work, of 
 course, induced draft by exhaust steam is out of the question. When 
 a blower is placed in the smokestack, an economizer should be used, 
 so that the gases may be cooled before they reach the blower. The 
 draft obtained on locomotives is frequently equivalent to a column 
 of five or six inches of water; while a forced draft of two inches is 
 usually considered large, except for torpedo-boats, which may have 
 as strong a draft as a locomotive has. 
 
 Howden System. The Howden system of forced draft with 
 closed ash-pit has been used to a considerable extent in both mer- 
 cantile and naval service. The air supplied to the ash-pit is first 
 heated by passing through a heater in the uptake. Waste gases pass 
 through tubes; and the air, passing among them before entering the 
 furnace, is heated to a high temperature. A consumption of 60 Ibs. 
 of coal per square foot of grate is easily obtained with this system; 
 and care must be taken that the fire is not forced too hard, as there is 
 more danger of burning^ out the grate than if the air-supply is not 
 heated. 
 
 Ellis and Eaves System. Heating the air does not necessitate its 
 being forced into the closed ash-pit, for it is quite feasible to heat the 
 air in connection with draft induced by an exhaust fan at the base of 
 the funnel. Such is the Ellis and Eaves system. This system was 
 first tried in the boiler shops at the works of the John Brown Company, 
 in Sheffield, England, and was later adopted on many vessels. The 
 Ellis and Eaves heater is fixed on top of the boilers, and is divided 
 into two parts separated at the front by a smoke-box and at the back 
 by a funnel. The hot gases, therefore which pass outside the tubes 
 have to take a somewhat circuitous course; while the passage of the 
 air to be heated, on the contrary, takes a direct course. The dis- 
 tribution of air to the ash-pit is similar to that of the Howden system. 
 
BOILER . ACCESSORIES 25 
 
 The advantages of this system lie in the general convenience of the 
 induced draft and the absence of jets of hot air shooting out into 
 the boiler-room. The draft need not be shut off when stoking the 
 fires, unless it is desired to prevent the inrush of air already referred to 
 under the general discussion of "closed stoke-holds." The air in the 
 fire-room being of a relatively higher temperature than would obtain 
 with closed stoke-holds, and the quantity being much less, this objec- 
 tion has no great weight. With the Howden system it is necessary 
 that the doors should be tight; otherwise hot air will be blown out 
 into the fire-room. With this system a few leaks are of no conse- 
 quence, and the fire-room will be somewhat cooler than with the 
 Howden System. The objections to the Ellis and Eaves system are 
 these inherent in any system of draft induced by a fan that is to say, 
 a poor efficiency of the fan working in heated gases, and lost work in 
 drawing air through tortuous passages. 
 
 Steam Jets. Steam jets may be used for inducing a draft. They 
 may be placed either in the smokestack, or below or above the grate; 
 but in general they are not so economical as a fan used for the same 
 purpose. In locomotives and fire-engines, where the exhaust steam 
 is at high pressure, an intense draft may be induced by exhausting 
 this up the smokestack. In both these cases, the saving of weight 
 due to the use of a small boiler running at high tension, is of greater 
 practical importance than the economy of fuel ; and for such purposes 
 this arrangement is entirely satisfactory. 
 
 A steam jet may be used directly in the furnace, either above or 
 below the grate. The steam enters through a small pipe, and ex- 
 pands through a nozzle surrounded by an annular, funnel-shaped 
 tube. The escape of steam from the inner nozzle draws in a large 
 volume of air through the outer tube, and produces an intense draft. 
 If steam is blown into the ash-pit in this manner, it forms a sort of 
 producer gas by mingling with the incandescent fuel, and materially 
 aids in the combustion of cheap and apparently worthless fuel. Al- 
 most as poor fuel can be successfully used with this arrangement as 
 can be used in the grates of the down-draft furnaces. Such arrange- 
 ments have given excellent satisfaction, and the production of smoke 
 is materially lessened. 
 
 Some tests made in the French Navy some years ago, showed 
 that, with the use of the steam jet above the grate, the coal con- 
 
26 
 
 BOILER ACCESSORIES 
 
 sumption per square foot of grate area could readily be doubled; 
 but this result would be attained at the expense of fuel economy; 
 for, while with natural draft one pound of coal produced approxi- 
 mately eight pounds of steam which could be used by the engine, 
 with a steam jet less than 6f pounds of steam per pound of coal was 
 available for like purposes. The total evaporation per pound of fuel 
 was approximately the same in each case, the difference being the 
 quantity of steam used in the jet. If a steam jet is used on board 
 ship, it consumes a considerable amount of fresh water, which must 
 be replaced by evaporators, or by the use of salt 
 water, which is decidedly objectionable. 
 
 TUBE=CLEANERS 
 
 To secure the best results from a boiler, the 
 tubes should be kept thoroughly clean. The collec- 
 tion of soot on the tubes is .as detrimental to 
 economy as the formation of boiler scale. The soot 
 may be removed by the insertion of brushes when 
 the boiler is 'not under steam, or the tubes may 
 be blown out with a steam jet designed for this 
 purpose. Fig. 21 illustrates forms of tube-cleaners, 
 of which there are numerous types on the market. 
 The type shown at B is de- 
 signed for use with a steam 
 jet. In the case of oil-burn- 
 ing locomotives, the tubes 
 are usually cleaned with the 
 aid of a sand-blast. 
 
 A B . 
 
 Fig. 21. Types of Tube-Cleaners. 
 
 TUBE-STOPPERS 
 
 It frequently happens, 
 when tubular boilers are under pressure, that leaks occur in the 
 tubes through pitting, defective welding, or the development of 
 cracks. Formerly, when this occurred, the fire was drawn, and thu 
 ends of the tube plugged with hardwood bungs driven hard home or 
 with iron plugs calked in. With high pressures, such procedure is 
 impossible. Tube-stoppers used for high pressure are joined to- 
 gether by a tie-bar of some sort. They are usually wedge-shaped ; and 
 
BOILER ACCESSORIES 
 
 27 
 
 the tie-rod, passing through the stopper at one end, with a plug at the 
 other end, can be screwed hard up. 
 
 The simplest form of stopper has to be inserted from the rear, and 
 necessitates drawing the fire ; but Fig. 22 illustrates a stopper which 
 can be inserted without drawing the fire. At the end of the rod is 
 hinged a folding bung, which can be passed through the tube and 
 
 Fig. 22. Tube-Stopper Designed for Insertion without Drawing Fire. 
 
 which opens out in the combustion chamber before being pulled into 
 position. At the smoke-box end of the boiler, an india-rubber 
 washer, pressed between two pieces of metal, affords temporary 
 protection while the plug is being put in position. The stopper can 
 then be screwed up tightly with a handle provided for that purpose. 
 Fig. 23 illustrates another arrangement w r hich can be inserted 
 in the leaky tube without drawing the fire. The ends, being in the 
 
28 
 
 BOILER ACCESSORIES 
 
 form of stuffing glands, press an asbestos packing hard against the 
 side of the tube. 
 
 Another Type of Tube-Stopper Used without Drawing Fire. As the Parts are 
 Screwed Up, the Asbestos Packing is Driven Hard against Side ef Tube. 
 
 MANHOLES AND HAN DHOLES 
 
 A manhole allows access to the boiler for cleaning and repairs, 
 It is usually elliptical in form and large enough to admit a maii. 
 
 About 16 inches for the major axis, and 
 12 for the minor axis, is a good size. 
 The manhole is closed by a plate or 
 cover made of cast or wrought iron. 
 This plate is held to the seat by a yoke 
 or yokes, and bolts. Fig. 24 shows one 
 form, Y being the yoke, L the cover, 
 and'-ZV the bolt. The joint between 
 the cover and the shell is made steam 
 tight by packing. 
 
 The strength of the boiler should 
 always remain unimpaired; so, when- 
 ever a large hole is cut in the plate, 
 the ed g e should be strengthened, for 
 
 Manhole cover. t } ie tension is concentrated there, and 
 
 the plates are, moreover, likely to become weak by corrosion. The 
 strain put upon the plate by screwing up the cover, if no packing 
 is used, is considerable, especially if a piece of scale gets between the 
 faces and the joint is then made tight. 
 
 j 
 
 L 
 
 
 Fig. 
 
It* 
 
 g 
 
 +3 ^ 
 
 ir 
 
 Q s 
 w -3 
 ou. ,3 
 
 Pu 
 
 p 
 or 
 
 w 
 
BOILER ACCESSORIES 
 
 29 
 
 Fig. 25 shows the section of a strong and simple manhole. The 
 edge of the plate is strengthened by a broad ring of steel, which is 
 flanged and riveted to the shell, its edge forming the seat. The cover 
 as shown in the figure is shaped for strength. The edge of the ring 
 which forms the seat, and the cover, are machined to make a tight joint 
 without packing. The strengthening ring should be at least f inch 
 thick and 4 inches wide, that the rivet-holes may not be too near the 
 edge. 
 
 Handholes and mudkoles are more commonly placed in boilers, 
 which are so constructed that a man cannot enter in a vertical boiler, 
 for example. They are used to some extent in other boilers; in 
 horizontal return-tube boilers there is usually a handhole in each end, 
 
 Fig. 25. Section of a Strong but Simple Type of Manhole. 
 
 near the bottom. Handholes are very convenient to admit hose for 
 washing out the boiler, also for removing scale and sediment. Hand- 
 holes are similar to manholes in construction, but require only one 
 yoke and one bolt to keep them in place. Mudholes should be pro- 
 vided in order that the sediment and detached scale can be removed 
 without lifting the accumulated mass to the top manhole. Mudholes 
 and handholes greatly facilitate cleaning the fire-box water-leg of 
 locomotive and small vertical, boilers. 
 
 STEAM AND VACUUM GAUGES 
 
 The steam pressure in the boiler is measured in pounds per 
 square inch. When we say the boiler is working or steaming at 80 
 pounds' pressure, we mean that the gauge pressure is 80 pounds; that 
 is, the pressure in the boiler is 80 pounds above atmospheric pressure. 
 It could be measured by a water or mercury column; but, as these 
 would need to be very high to measure the pressures used at the present 
 day, they are not practicable, and so a spring-pressure gauge is used 
 instead. 
 
 The dial gauge, now used almost universally, was invented by 
 M. Bourdon. It is designed in accordance with the principle that a 
 
30 
 
 BOILER ACCESSORIES 
 
 flattened, curved tube closed at one end tends to become straight 
 when subjected to internal pressure. 
 
 The tube, which is usually oval in section, is bent into the arc 
 of a circle as shown in Fig. 26. One end is fixed, and is in com- 
 munication with the boiler. The other 
 is closed and free to move. By means 
 of levers, a curved rack, and a pinion, 
 the motion of the free end is multiplied 
 and indicated by a needle, which is 
 attached to the pinion. The needle 
 moves over a dial which is graduated 
 to agree with a mercury column, or 
 with a standard gauge. The back-lash 
 of the levers is taken up by a hair 
 spring. Fig. 27 shows the interior and 
 face of a Bourdon steam gauge manu- 
 factured by the American Steam Gauge 
 Company. 
 
 Fig. 28 shows the exterior and interior of a steam gauge with 
 a light tube for low pressures; the face of the dial is graduated corre- 
 sponding to the mercury column. The only difference between this 
 gauge and the vacuum gauge, is that in the latter the curved tube is 
 
 Fig. 26. Steam-Filled Curved Tube 
 Indicating Pressure in Bour- 
 don Steam Gauge. 
 
 Fig. 27. Interior Mechanism, and Dial, of "Lane" Type of Steam Gauge. 
 
 turned in the opposite direction so that the needle will move clockwise 
 with a decrease of pressure. 
 
BOILER ACCESSORIES 
 
 31 
 
 On account of the jarring, the gauge for locomotives must be 
 very strong. To prevent excessive vibration of the needle, two short, 
 stiff er springs are used, as shown in Fig. 29. 
 
 Fig. 28. Interior Mechanism, and Dial, of Low-Pressure Steam Gauge. 
 
 Sometimes two pressure gauges are fitted to a boiler, one indicating 
 the working pressure, and the other graduated to about twice the work- 
 ing pressure. The latter is useful in testing the boiler under water 
 pressure, and also serves as a check on the other. The pipe which con- 
 nects the pressure gauge to the boiler should have bends in it near the 
 gauge. These bends or, better, a coil pipe, as shown in Fig. 30 
 
 Fig. 29. Steam Gauge for Use ou Locomotives. Excessive Vibration of Needle 
 Prevented by Use of Two Short, Stiff Springs. 
 
 are filled with water, which transmits pressure and keeps the spring at 
 a nearly constant low temperature. Gauges should be placed where 
 
32 
 
 BOILER ACCESSORIES 
 
 the water in the coiled pipe will not freeze; also, the gauge should 
 not be exposed to strong heat. In order that the gauge may be 
 
 Fig. 30. Water- Filled Coil Pipe for Connection to Steam Gauge. The Water 
 Transmits Pressure and Regulates Temperature. 
 
 removed from the boiler for examination, repairs, or calibration, 
 when the boiler is under pressure, the connection should be provided 
 with stop-cocks. 
 
 In a battery of boilers, each should have its pressure gauge, which 
 should be connected directly to the boiler, not to the steam pipe. 
 
 WATER GAUGES 
 
 It is of great importance that the level of the water in the boiler 
 can easily be ascertained at all times. Should the level be too low, 
 
 there is danger 
 o f overheating 
 the furnace plates 
 or tubes. If it is 
 too high, there is 
 likely to be an 
 undue amount of 
 The 
 
 prmng. 
 
 water-level is 
 usually indicated 
 by gauge-cocks 
 or try-cocks or 
 watergauge- 
 glasses. Some- 
 times a float is 
 provided, which 
 is connected to a small whistle, and if the water-level falls below a 
 
 Fig. 31. Ordinary Form of Try-Cock for Determining Water- 
 Level in Boiler. 
 
BOILER ACCESSORIES 
 
 33 
 
 Fig. 32. Try-Cock Operated by Means of Lever. 
 
 certain point, an alarm is sounded. Such a device can readily be 
 
 used in conjunction with the ordinary water-gauge. 
 
 Try-Cocks. Try-cocks are very generally used. They are of 
 
 widely different 
 forms, and may 
 be either like the 
 general type 
 shown in Fig. 31, 
 which is the ordi- 
 nary 1 o c o m o- 
 tive form, con- 
 structed in two 
 
 parts so" that they can be separated for the purpose of repacking 
 
 without detachment from the boiler; or 
 
 they may be of the lever type shown in 
 
 Fig. 32. There are usually three cocks, 
 
 one at the highest desired water-level, one 
 
 at the lowest, and one midway. More 
 
 cocks may, of course, be used if desired. 
 
 The water-level can be determined by 
 
 opening the cocks in succession and ob- 
 serving whether dry steam or hot water 
 
 flows out. If the boiler is encased in 
 
 brickwork, as is customary for externally- 
 fired boilers, the gauge-cocks are placed 
 
 outside the brickwork, and are connected 
 
 to the boiler by nipples of the proper 
 
 length. 
 
 Qauge-Glasses. In order that the 
 
 fireman may know the water-level without 
 
 trying the cocks, a water gauge-glass is 
 
 used. It consists of a strong glass tube 
 
 about one foot in length, having the ends 
 
 connected to the boiler by suitable fittings. 
 As both ends of the tube are in com- 
 munication with the boiler, the water-level 
 
 in the glass will be the same as in the 
 
 boiler, and is always in sight. Fig. 33 shows a good form of gauge- 
 
 Fig. 33. A Good Type of Water 
 Gauge-Glass. 
 
34 
 
 BOILER ACCESSORIES 
 
 glass. The glass is protected by rods which are parallel to it. As 
 the glass frequently needs cleaning, repacking, or renewing, cocks 
 are provided for shutting off communication with the boiler. A 
 drain-cock is also placed at the lower end to empty the glass when the 
 attendant wishes to ascertain whether the glass is working properly 
 or not. The drain-cock is often provided with a drain-pipe. The 
 steam and water passages should be at least one half-inch in internal 
 diameter. 
 
 The glass is likely to break because of accident or of changes in 
 temperature. To prevent serious injury to the fireman and loss of 
 
 water as a result of the 
 breaking of the gauge- 
 glass, automatic valves 
 may be placed in the 
 passages. In Fig. 34 
 the ball-valve is shown 
 in detail. If the glass 
 breaks, the pressure of 
 the steam drives the 
 ball outward, filling 
 the conical passage. 
 When a new glass is 
 put in, the balls are 
 forced back by slowly 
 screwing in the stems. 
 This, like other safety 
 devices, is very likely 
 not to work when it 
 should. 
 
 In boilers where the steam space is small, as in locomotives, the 
 allowable variation of water-level is slight; but the greater care with 
 which the glass is watched makes up for the small margin of safety. 
 If dirty water is used, or if the water foams, the level in the glass will 
 be unsteady and unreliable, since dirt clogs the passages, unless they 
 are large, and the foaming causes a fluctuation of the water-level. A 
 small pipe connecting with the steam space where no ebullition occurs, 
 will insure a steadier water-level. If the steam and water connection* 
 are long, the pipes should be made large. 
 
 Fig. 34. Automatically Acting Ball- Valve to Prevent 
 
 Injury to Workmen and Loss of Water on 
 
 Breaking of Gauge-Glass. 
 
BOILER ACCESSORIES 
 
 35 
 
 The chief objection to the gauge-glass namely, its breaking 
 may be to some extent overcome by attaching the gauge-glass to a 
 gauge-column, which is usually made of brass and stands quite clear 
 
 To Bo^er 
 
 -To Boiler 
 
 Pig. 35. Ordinary Water Gauge-Glass Supplemented (at right) by "Klinger 
 Patent" Gauge-Glass. 
 
 of the boiler itself. In such an arrangement as this, the temperature 
 in the gauge-glass cannot vary so widely as if it were attached directly 
 to the boiler. The "Klinger Patent" water gauge-glass is not easily 
 broken, and possesses many advantages over the common glass. 
 Fig. 35 illustrates both these devices. 
 
 The water gauge is not absolutely reliable, for the water in the 
 gauge, being cooler than that in the boiler, may not indicate the true 
 level, and the small passages leading to it may become choked with 
 
36 
 
 BOILER ACCESSORIES 
 
 sediment. If the gauge-glass is frequently blown out by the engineer 
 and kept clean, this difficulty will be reduced to a minimum. 
 
 VALVES 
 
 Of all boiler accessories, perhaps the most important are the 
 cocks and valves by means of which the flow of steam or water may 
 be shut off completely or partially. The valve operates by moving 
 a disc across the pipe in a transverse direction, or by bringing a cap 
 
 Fig. 36. Ordinary "Competition" Type of 
 Globe Valve. 
 
 Fig. 37. Globe Valve with Detachable 
 
 Cap and Removable Interior Disc 
 
 of Comparatively Soft Material 
 
 to Insure Tightness. 
 
 tight upon the seat in a fore-and-aft direction. A cock consists of a 
 block inserted in the passageway, with an opening cut through in one 
 direction. When the handle of the cock is in line of the pipe, the 
 opening allows the steam to pass through; but if turned crosswise, the 
 opening is closed. 
 
 The Globe Valve. The valve shown in Fig. 36 gets its name from 
 the globular shape of the casing which encloses the valve. Extending 
 across this whole casing is a substantial diaphragm, the central portion 
 
BOILER ACCESSORIES 
 
 37 
 
 of which is in a plane parallel with the length of the pipe. The open- 
 ing is cut in this portion, horizontal in the figure, through which steam 
 or other fluid may pass when the valve is opened. When the valve is 
 closed, a cap is forced down to close its opening. The rim around 
 the opening is known as the valve-seat. The valve-cap is operated by 
 a spindle, which passes through the bonnet of the valve and is mounted 
 at the upper end by a small wheel or handle. To prevent the escape 
 of steam around this spindle, a stuffing-box is provided. The valve- 
 cap may or may not rotate as the spindle turns; usually it does not. 
 The valve shown in Fig. 36 is the ordi- 
 nary globe valve known to the trade as 
 the "Competition" valve. It is the 
 cheapest valve of the type, and is not 
 satisfactory where absolutely tight work 
 is required. If the cap becomes scored, 
 the valve will leak and is then worthless. 
 
 A valve shown in Fig. 37 has a 
 detachable valve-cap; and instead of 
 relying for tightness upon the valve 
 and seat coming together, metal to 
 metal, a removable disc is provided, 
 which being softer than the metal valve- 
 seat, easily takes up the wear, and the 
 valve not only can be closed tighter, 
 but if anything happens so that the 
 tightness of the valve is impaired, the 
 valve-cap can be replaced by another 
 at a trifling expense. In the cheaper 
 valve, when the cap is scored, the valve 
 is worthless. The valve-seat sometimes has a slight bevel, the valve- 
 cap being shaped like the frustum of a cone. 
 
 It is impossible to close a valve tightly if the slightest particle 
 of scale or grit gets between the disc and the seat. If this happens, 
 the valve-seat is likely to become scored so that it does not hold tight; 
 but it may be reground, and if the valve disc itself is damaged, it can 
 readily be replaced. 
 
 Angle Valves. An angle valve, shown in Fig. 38, is constructed 
 in a similar manner to the ordinary globe valve, and is sometimes 
 
 Fig. 
 
 Angle Valve of Oi-dinary 
 Globe Pattern. 
 
38 
 
 BOILER ACCESSORIES 
 
 used in place of the straightway valve and an elbow. Both these 
 styles of valve should be so placed in the steam pipe that the entering 
 steam comes beneath the valve-seat. If this is done, the valve-stem 
 may easily be repacked simply by closing the valve. If the steam 
 enters in the opposite direction, a leaky valve-stem cannot be packed, 
 
 as loosening the stuffing-box would per- 
 mit the escape of the steam. 
 
 The Gate Valve. The gate or 
 straightway valve gives a straight pas- 
 sage through the pipe, and, when open, 
 .offers very little resistance to flow. The 
 globe valve, of course, offers much re- 
 sistance, because the fluid has to change 
 its direction of flow completely. 
 
 There are two forms of gate valve 
 one with wedge-shaped sides, and the 
 other having the valve sides parallel. 
 Fig. 39 shows a "Chapman" valve with 
 wedge-shaped sides. A collar holds 
 the valve spindle at a fixed point; and 
 to open or close, the valve is drawn up 
 or lowered by turning the spindle. When 
 the gate reaches the bottom of the pipe, 
 a wedge on the lower end of the spindle 
 causes the sides to move laterally, with 
 sufficient force to bring a strong pres- 
 sure against the valve-seat. For heavy 
 work, these valves are made with a rising spindle instead of a 
 stationary one. This possesses the distinct advantage of indicating 
 at a glance whether they are opened or closed, while one cannot tell 
 by looking at the ordinary gate valve whether it is open or not. 
 
 Check- Valves. When it is necessary that the flow should always 
 take place in the same direction, as in the feed-pipe of a boiler, check- 
 valves are used. There are several forms shown in Fig. 40, one of 
 which has a similar pattern to a globe valve, with a ball or flat valve, 
 the seat being parallel to the direction of flow. The valve is held in 
 place by its own weight, and by the pressure of the fluid in case of a 
 reverse flow. In the swinging check-valve, the seM is at an angle 
 
 Fig. 39. "Chapman" Gate Valve 
 with Wedge-Shaped Sides. 
 
BOILER ACCESSORIES 
 
 39 
 
 of about 45 degrees to the direction of flow. It is fitted somewhat 
 loosely where it is fastened to the swinging arm, so that it may prop- 
 erly seat itself. This form is usually preferred, as it offers less 
 resistance to flow and there is less chance for impurities to lodge on 
 the valve-seat. When a check-valve is used in the boiler-feed pipe, 
 
 ABC 
 Fig. 40. Types of Check-Valves. ^i-Ball- Valve ; .C-Flat Valve; tf-Swinging Check- Valve. 
 
 there should be a stop-valve between it and the boiler, which can be 
 shut in case the check-valve should get out of order. 
 
 Materials. For pressures under 200 Ibs. per square inch, cast 
 iron may be used for the body of the valve; but, for economy, it 
 should be used only when the pressure is over 130 Ibs. For heavy 
 work it is frequently necessary to have a massive valve that cannot 
 easily be broken. In such a case a cast-iron body is the most suit- 
 able thing. The valve-seat, valves, spindles, stuffing-box, glands, 
 and nuts are 
 usually made of 
 gun-metal or 
 brass. For very 
 high pressures, 
 especially o n 
 steam mains, 
 cast steel is 
 generally used, 
 with gun-metal 
 fittings similar to those enumerated for the cast-iron valves. 
 
 Safety- Valves. Safety-valves are used for reducing the pressure 
 in the boiler when it exceeds a certain limit, and to give warning of 
 high pressure. There are several different types, but the essential 
 features are a valve opening upward, held on its seat by a weight or 
 
 Fig. 41. Common Type of Lever Safety- Valve. 
 
40 
 
 BOILER ACCESSORIES 
 
 spring. When the pressure in the boiler exerts a force greater than 
 that holding down the valve, the valve will open automatically. 
 
 The lever safety-valve shown in Fig. 41 is the most common type 
 for stationary work, especially for small boilers. The valve is held 
 in place by a weight at the end of a lever. The force required to lift 
 the valve is governed by the location of the weight on the lever-arm. 
 
 The body of 
 the valve is 
 usually made 
 of cast iron, 
 the seat being 
 of brass. An 
 
 Fig. 42. Diagram for Safety-Valve Calculations. 
 
 opening on 
 the side of the 
 
 valve may be connected with the feed-water heater or drain, if the 
 escape of steam into the air is undesirable. If -the valve becomes 
 leaky, it should be reground; but no attempt should be made to 
 make it tight by increasing or moving the weight on the lever. 
 
 The amount of necessary weight on the lever, and- its distance 
 from the fulcrum, can be determined in the usual manner of com- 
 puting leverage forces and moments, remembering that weight 
 times weight-arm is equal to power times power-arm. In such a 
 valve as this, power is the steam pressure, and the power-arm is the 
 distance of the center of the valve from the fulcrum. There are four 
 weights acting downward -the ball, the lever-arm, the valve, and the 
 spindle and in the process of computation the weight and leverage 
 of each must be taken into account. 
 
 Suppose, for example, that we have a lever safety-valve such as 
 is illustrated in outline in Fig. 42, and that we know the following con- 
 ditions: the ball weighs 125 Ibs., and is suspended at the end of the 
 lever 48 inches from the fulcrum ; the valve and valve spindle together 
 weigh 18 Ibs., and are 4J inches 'from the fulcrum; the lever-arrn 
 itself weighs 50 Ibs. If the valve-seat is 5 inches in diameter, at what 
 pressure will the valve blow off, ignoring the friction of the stuffing- 
 box and fulcrum pivot? 
 
 The center of gravity of the lever-arm must be determined from 
 the drawing (Fig. 42), and this is found to be 20 inches from the 
 
BOILER ACCESSORIES 
 
 41 
 
 fulcrum The leverage of the weights acting downwards is then 
 follows : 
 
 as 
 
 Ball 125 X 48 - 6,000 
 
 Lever 50 X 20 = 1,000 
 
 Valve and Stem 18 X 4 = 81 
 
 Total moment = 7,081 inch-pounds. 
 
 Now, if the valve-seat diameter is 5 inches, the area of the valve 
 
 will be 
 
 TT D 2 3.1416X25 
 
 = 19.63 sq. in. The total moment to 
 
 4 4 
 
 be overcome is 7,081 inch-pounds, and its distance from the fulcrum 
 is 4J inches. Therefore the necessary 
 upward pressure on the valve will be 
 _7,OS1 = 
 
 4* 
 
 the valve is 19.63 sq. in., then the 
 necessary pressure in pounds per 
 ,573.5 
 
 Ibs. If the area of 
 
 square inch would be 
 
 80 Ibs., 
 
 19.63 
 
 approximately. That is, this safety- 
 valve would blow off when the boiler 
 pressure reached 80 Ibs. per square inch. 
 If it is desired to design a valve 
 that will blow off at known pressure, 
 the same principles will apply, but the 
 computations will be figured in the re- 
 verse order. The area of the valve, 
 times the boiler pressure, would give 
 the total lifting force ; and this, multi- 
 plied by its leverage, would give the 
 lifting moment, which would be re- 
 sisted by the downward moment of the 
 combined weights of valve, valve-stem, 
 lever, and ball. If the moments of the lever, valve, and valve-stem 
 were known, the rest, of course, would be made up by the ball. 
 If the length of the lever-arm were known, then the weight of the ball 
 would be varied to correspond; and, conversely, if the weight of the 
 ball were fixed, the length of the lever must be made to correspond. 
 
 Fig. 43. "Crosby" 
 
 for Stationary 
 
 -Valve 
 
42 
 
 BOILER ACCESSORIES 
 
 The lever safety-valve has several defects. It does not close 
 promptly when the pressure is reduced; and it is likely to leak after 
 it is closed, and may readily be overloaded, or even wedged on its 
 seat. It is essential that a safety-valve should be automatic, certain 
 in its action, and prompt in opening and closing at the required 
 pressure. It must be one that can be relied upon under all circum- 
 stances. 
 
 The pop safety-valve fulfils the above requirements better than 
 those of the lever type. Pop valves open when the steam pressure 
 
 is sufficient to overcome 
 the tension of the spring. 
 Fig. 43 shows a "Crosby" 
 pop safety-valve for sta- 
 tionary service. The 
 valve C is connected by 
 the flange B to the cen- 
 tral spindle A, and is held 
 down on its seat by the 
 pressure of the spring S. 
 The valve C is provided 
 with wing guides and an 
 annular lip E. The 
 guides fit smoothly into 
 the seating D, upon 
 which the valve rests. 
 The seats of the valve 
 have an angle of 45 de- 
 grees. The under face of the lip E, together with the seating, 
 forms a small chamber through which all the steam must pass 
 to the open air. A number of small holes drilled vertically through 
 the flange F, connect with the chamber and allow part of the 
 steam to escape. The action of the valve is regulated by the screw 
 ring G, which allows more or less steam to escape through the holes in 
 the flange F, Raising the screw diminishes, and lowering it increases, 
 the area of the holes. If the loss of steam is too great when the 
 valve blows, turn the screw ring down. 
 
 Safety-valves should be connected directly to the boiler without any 
 pipe or elbow. They should be tried every day by means of the lever. 
 
 Fig. 44. "Ashton" Valve with Pop Regulator for 
 Stationary Boilers. 
 
 
BOILER ACCESSORIES 
 
 43 
 
 The valve shown in Fig. 44 for stationary boilers, is made by the 
 Ashton Valve Company. The general principles are those of all pop 
 safety-valves. The valve-seat is made of composition or nickel, and 
 with a bevel of 45 degrees, as is the United States Government stand- 
 ard. The pop chamber is surrounded by a knife-edge lip, which 
 wears down in proportion with the seat, thus keeping the outlet of the 
 same relative proportions, giving a constant amount of pop. 
 
 The amount of pop that is, the difference of pressure between 
 the opening and the closing of the valve is regulated from the out- 
 
 Fig. 45. 
 
 'Star Marine" Pop Safety- Valve, 
 with Cam Lever. 
 
 Pig. 46. "Ashton" Safety- Valve for 
 Locomotive Boilers, with Pop Regula- 
 tors on Each Side, and Top Muffler. 
 
 side by means of the screw-plug pop regulator shown at H in Fig. 44. 
 If more pop is desired, turn the regulator so that S will be more nearly 
 perpendicular. To lessen pop, make more nearly perpendicular. 
 The springs are made of Jessop's best steel. 
 
 The inlet and outlet are both on the same casting, so that the 
 valve may be taken apart to be cleaned or repaired, without disturbing 
 the boiler connection. It has a lock-up attachment, so that the regu- 
 lating parts cannot be tampered with, either by accident or by design, 
 The spring is encasea, thus protecting it from the steam. 
 
44 
 
 BOILER ACCESSORIES 
 
 The "Star Marine" pop safety-valve is shown in Fig. 45. It 
 has a bevel seat, and is provided with a cam lever by which it may be 
 raised from its seat when there is no steam pressure. The outlet of 
 the valve, if desired, may be piped to the supply tank or to any other 
 point. 
 
 Safety-valves for locomotive boilers must be made of heavy material 
 to stand the severe usage. They should be so constructed that they 
 will not cock or tilt. The "Ashton" valve shown in Fig. 46 is con- 
 
 rig. 47. "Holt" Reducing Valve with Diaphragm Regulating Pressure. 
 
 structed so that the amount of pop can be regulated by merely turning 
 the two posts marked 2 and 3 to the right or left. The noise of the 
 steam escaping from the ordinary safety-valve is disagreeable, and in 
 some States the law requires the use of the muffler safety-valve. The 
 Ashton valve shown in Fig. 46 has a top muffler. 
 
 Reducing Valves. Sometimes steam is desired at a lower pres- 
 sure than that of the boiler. For instance, a small low-pressure engine 
 may be run by steam taken from the same boiler that supplies a 
 higher-pressure engine. This reduction is accomplished by throttling 
 the steam by means of reducing valves. These are arranged to be 
 

THE 
 'NIVERSITY 
 
 OF 
 
 UFORNl- 
 
BOILER ACCESSORIES 45 
 
 operated automatically so that the pressure can be reduced and a 
 constant pressure in the steam pipes maintained. There are several 
 forms in general use. 
 
 In the "Holt" valve, Fig. 47, the low-pressure steam acts on the 
 lower side of the diaphragm; and the weight, which may be set so as 
 to cause the desired pressure, acts on the other. The movement of 
 this diaphragm causes a balanced valve to move to or from its seat. 
 The valve opens until the steam pressure equals the weight above. 
 The pressure in the main steam pipe does not affect the movement 
 of the valve. It depends only upon the pressure on the two sides of 
 the diaphragm. 
 
 Another form, the "Mason," is shown in Fig. 48. A spring, which 
 may have its tension altered by a key, takes the place of the lever and 
 weight in the Holt valve. When the pressure in the low-pressure 
 system has risen to the required point, which is determined by the 
 spring, the valve closes, and no more steam is admitted until the 
 pressure falls sufficiently to open the valve again. 
 
 In another form, a piston acted on by the low-pressure steam 
 regulates the opening of a balanced valve, and this maintains a con- 
 stant steam pressure. 
 
 In the "Foster" reducing valve, the valve is held open by the 
 spring and levers, until the steam pressure at exit presses on the dia- 
 phragm sufficiently to close the valve. The valve is held open so as 
 to admit just the proper amount of steam to maintain the required 
 pressure. 
 
 When a reducing valve is used, a stop-valve should be put in to 
 prevent flow when steam is not in use. 
 
 BLOW=OUT APPARATUS 
 
 Boiler feed-water, if taken from rivers or ponds, is likely to 
 contain vegetable matter as well as solid materials. The vegetable 
 matter will usually float to the surface, while the solids will collect at 
 the bottom. To keep the boiler clear of such sediment, it is neces- 
 sary to provide two blow-outs a surface blow-out, to take care of 
 what rises to the top; and a bottom blow-out, to take out the sediment 
 that collects at the bottom of the boiler. The surface blow-out 
 usually consists of a dish or funnel-shaped receptacle set with its face 
 
46 
 
 BOILER ACCESSORIES 
 
 vertical, as shown in Fig. 49. When the water-level is in line with 
 this blow-out opening, the opening of the valve at the bottom will 
 skim the impurities from the surface of the water quite readily. Oil 
 
 may get into the boiler through the feed- 
 water, and a considerable portion of it 
 can be removed in this manner. 
 
 The bottom blow-out consists merely 
 of a pipe leading from the bottom of the 
 boiler outward. Both these blow-outs 
 may be connected into one outlet. 
 
 In water-tube boilers a mud-drum 
 is usually installed, which readily collects 
 the solid matter, and the bottom blow- 
 out is then connected with this mud-drum. 
 Fig. 50 shows an arrangement of surface 
 and bottom blow-outs as usually installed 
 on a Scotch boiler of the marine type. 
 
 If the feed-water contains salt, which 
 may frequently happen in marine prac- 
 tice, it is necessary that the boiler should 
 Fig. 48. "Mason" Reducing vaive. frequently be blown out in order to re- 
 
 Pressure Regulated by Means 
 
 of a spring. move the excess of salt. The density of the 
 
 boiler water, if salt feed is used, should be carefully determined by a 
 salimeter. The loss due to this frequent blowing out is considerable, 
 as a large amount of 
 heat is necessarily wasted ; 
 but it cannot be avoided, 
 except by the use of 
 fresh water, which some- 
 times may be impossible 
 at sea. 
 
 The blow-out pipe 
 leading from the bottom 
 of an externally-fired 
 
 boiler through the brick Fig 49 surface Blow-Out Installed in Boiler. 
 
 setting, if not properly 
 
 protected, may be burned off, owing to the heat of the fire. This 
 
 pipe is frequently covered with asbestos or other fire-resisting material ; 
 
BOILER ACCESSORIES 
 
 47 
 
48 
 
 BOILER ACCESSORIES 
 
 but it can be best protected by the means shown in Fig. 51. A pipe 
 connected to the boiler slightly below the water-level, runs out through 
 the brick setting and connects into the main blow-out pipe. This 
 causes a circulation of water continually to pass through the system, 
 and prevents destruction of the blow-out pipe. When it is necessary 
 to use the bottom blow-out, the valve A is closed, and the blow-off 
 valve B is opened; otherwise, B is closed, and A is open while the 
 water circulates. 
 
 The blow-out pipe is usually shut off by a cock, which, although 
 not so easily operated as a valve, is more trustworthy. Frequently 
 both a cock and a valve are provided. Should a small particle of 
 
 sediment lodge on 
 
 the valve-seat, it 
 \ ^Water Level woukl be impossi _ 
 
 ble to close the 
 valve tightly, and 
 a considerable leak- 
 age would result, 
 while an inspection 
 of the valve would 
 not indicate 
 whether it were 
 completely closed 
 or not. But a 
 glance reveals the fact whether or not a cock is tightly closed. The 
 cock is likely to stick because of corrosion or unequal expansion, 
 but, if frequently opened, this difficulty is not of great weight. 
 The plug and casing of the cock should not be made of the same 
 material, as in that case they will more readily stick if the cock 
 remains closed any length of time. 
 
 Boner 
 
 Fig. 51. Method of Protecting Bottom Blow-Out Pipe by 
 Means of Circulation Pipe Connected to Boiler. 
 
 FEED APPARATUS 
 
 Perhaps the most important of all auxiliaries connected with the 
 boiler is the feed apparatus. This is vital; for, if the feed is inter- 
 rupted and the water runs low in the boiler, not only is there danger 
 of damaging the boiler itself, but a disaster may follow of far greater 
 concern. For marine purposes and the same is true to a consider- 
 
BOILER ACCESSORIES 49 
 
 able extent in stationary work at least two independent feed systems 
 should be provided. In marine work,, the main feed-pump draws 
 water from the filter box or feed-water heater, and pumps it into the 
 boilers under ordinary conditions. There should be a by-pass around 
 this pump, and the feed line should be connected by means of a valve 
 to what is known as the donkey pump, which may be used for auxiliary 
 feed purposes in case the main pump is damaged or needs repairs in 
 any way. 
 
 Both these pumps draw from and discharge into the same feed 
 line; but, to provide against emergencies, there is usually a cross- 
 connection to the sea, so that sea water may be had if necessary. 
 While in port, when the main engines are not running, and conse- 
 quently when the feed-water cannot be heated economically, an in- 
 jector is almost invariably used. On land it is usually considered 
 sufficient to install an injector in addition to the feed pump, although 
 in large plants an auxiliary feed pump should be installed as well. In 
 a small plant the fireman usually attends to the water; but on board 
 ship and in large plants, a water tender is usually provided, whose 
 business it is to keep the water in the boiler at the proper level. His 
 task may be materially lessened by some automatic arrangement, so 
 that if the water discharged into the hot well from the condenser rises 
 above the normal level, a float will open the valve leading to the feed- 
 pump and increase the rapidity of its stroke. This will reduce the 
 level of the hot well or filter box, as the case may be. 
 
 Such an arrangement as this will keep a fairly uniform level of 
 water in the boilers; and if a surface condenser is employed, and all 
 the condensation is pumped back into the boilers, the water-level will 
 remain constant except for slight leakages of steam and for the possi- 
 bility of improper action of the feed-pump. Leakage of steam can 
 be made up from the supply of fresh water. At sea, salt water may have 
 to be used for this purpose although its use is objectionable. 
 
 There is a considerable difference of opinion as to where the feed- 
 water should be introduced into the boiler, although the consensus 
 of opinion seems to be that it should enter not far from the water-line. 
 In stationary practice, the feed-water is introduced at the rear of the 
 boiler near the bottom; but this is open to grave objections, for the 
 feed-water, being comparatively cool and being introduced into the 
 coldest part of the boiler, naturally tends to become dead water and to 
 
50 BOILER ACCESSORIES 
 
 retard proper circulation which is essential to economical steaming 
 and often essential to the safety of the boiler itself. 
 
 The best place for introducing the feed-water will naturally 
 depend upon the type of boiler, and the service for which it is intended. 
 If the entering water is of high temperature, it might enter near the 
 bottom of the boiler. But if the feed -water is comparatively cold - 
 and it is always colder than the water in the boiler and the surround- 
 ing steam if the circulation is good great care must be taken that 
 it does not strike directly against the hot boiler-plates, as it might 
 thereby cause local contraction and possibly a serious leak, and it 
 should be introduced in such a way as to make sure of its aiding the 
 natural circulation of the boiler. 
 
 The higher the steam pressure in the boiler, the more difficult 
 becomes the problem of feed, and the more danger there is of injury 
 to the boiler by the comparatively cold feed-water striking hot plates. 
 It is a universal practice in marine work, and a common practice on 
 land, especially for internally-fired boilers, to cause the feed to enter 
 above the water-level near the center of the boiler; then branching 
 off into two pipes, one leading to each side through the steam space 
 until the side of the boiler is reached; and then running downward 
 toward the bottom. The feed -water, which very likely has been 
 previously heated by a feed-water heater, is still further heated by its 
 passage through this feed-pipe, which is in direct contact with the live 
 steam of the boiler. This internal feed-pipe, turning down at the sides, 
 causes the water to strike the outer shell of the boiler which is the 
 most remote from the fire, and this downward motion materially 
 assists the circulation in the boiler. When this arrangement of feed 
 is adopted (see Fig. 50), care must be taken that the lower end of 
 the feed-pipe is well below the low-water level. If the end of the 
 pipe is alternately immersed in water and then exposed to steam, 
 violent explosions in the pipe are likely to follow, although they are 
 likely to do nothing more serious than break an elbow or frighten 
 the attendants. 
 
 In stationary practice, it is quite common to admit the feed-water 
 into the steam space through a horizontal pipe entering it through the 
 tube-plate a few inches below the low-water level, and terminating in 
 a perforated pipe of large diameter. This method distributes the feed- 
 water admirably, and allows it to become considerably heated before 
 
BOILER ACCESSORIES 
 
 51 
 
 it reaches the bottom of the boiler. If the feed-water contains a con- 
 siderable amount of magnesia or calcium carbonate, holes so arranged 
 in the feed-pipe are likely to become clogged and the feed interrupted. 
 Water of this sort should be fed into a trough, or the feed-pipe be 
 opened at the top by a long slot, so that the feed-water may over- 
 flow. The trough in this case forms an admirable mud-drum or 
 sediment collector. 
 
 In internally-fired boilers of the "Cornish" or "Lancashire" type, 
 
 Fig. 52. Steam-Driven Boiler Feed-Pump. 
 
 
 
 the feed is usually delivered near the bottom through a horizontal 
 pipe either through the front end or by a vertical pipe through the 
 crown. This method is not conducive to the best circulation. 
 
 In addition to these effects on circulation, there are other grave 
 objections to introducing feed -water near the bottom of the boiler; for, 
 should anything happen to the feed-pump, or a piece of scale lodge 
 under the check-valve, the water might be almost entirely blown out 
 of the boiler before the difficulty could be discovered or remedied. 
 
52 
 
 BOILER ACCESSORIES 
 
 If the pipe enters in the vicinity of the low-water level, no water could 
 be drawn out below this point. 
 
 The feed supply should always be regulated so as to keep the 
 water-level as nearly stationary as possible; this is not only much 
 more economical, but also far better for the boiler, than to wait for the 
 water-level to fall and then feed a few inches rapidly. The sudden 
 introduction of a large volume of comparatively cold feed -water, causes 
 local contraction of the plates, and hence tends to cause leakage: 
 
 Fig. 53. Section of "Worthington" Duplex Steam Pump. 
 
 moreover, it necessitates irregular firing if anything like a uniform 
 steam pressure is to be maintained. 
 
 Sometimes the feed-water is forced into the steam space in the 
 form of a fine spray. In this way it not only is thoroughly heated 
 before mingling with the water in the boiler, but the air is got rid of; 
 and salts, such as sulphate of lime, insoluble at high temperatures, 
 are immediately precipitated. But the advantage of introducing the 
 feed-water in a body so as to produce useful circulating currents, 
 should not be overlooked. 
 
BOILER ACCESSORIES ' 53 
 
 If several boilers are attached together in the form of a battery, 
 each should be supplied with an independent connection to feed- 
 pipe. Otherwise a damage to the feed-pipe in one boiler might affect 
 the others. Moreover, if several boilers are fed from one pipe, the 
 pressure in each of them being slightly different, an excess of water 
 will naturally be fed into the boiler having the least pressure, whereas 
 it is usually the case that the most water is needed in the boiler hav- 
 ing the greatest pressure. The automatic float previously referred to, 
 can regulate the amount of water fed into boilers only in a general 
 way, through providing a method by means of which all the con- 
 densation is fed back into some of the boilers; but the quantity of 
 feed which is led into each individual boiler must be watched and 
 regulated by the water tender, who can open or close the individual 
 valves as desired. 
 
 Pumps. Boilers are usually fed by a small, direct-acting 
 steam pump placed near the boiler. Although these pumps require 
 a large steam supply per horse-power per hour, the total amount of 
 steam used is small because the work done is small A more eco- 
 nomical pump is the power pump driven by the large steam engine; 
 but in this case the rate at which water is supplied is not easily regu- 
 lated to the demand of the boiler. Power pumps are usually 
 arranged to pump a larger quantity of water into the boiler than is 
 required, the excess of water being allowed to flow back into the 
 suction pipe through a relief valve.. 
 
 The pump shown in Fig. 52 is well adapted for feeding boilers. 
 In Fig. 53 is shown the section of a duplex "Worthington" steam pump. 
 The action of each of these two types is similar. Steam, controlled 
 by valves, drives the piston in the steam cylinder, which moves the 
 plunger in the water cylinder, since both are fastened to the same rod. 
 The movement of the plunger forces a part of the water in front 
 of it up through the valves into the air-chamber, and through the 
 pipes into the boiler. On account of the partial vacuum caused by the 
 movement of the plunger, water will be drawn from the suction pipe, 
 through the valves, into the pump cylinder, filling the space left by 
 the movement of the plunger. During the return stroke, this water 
 is forced up into the air-chamber, and a like quantity enters the other 
 end of the pump cylinder. The valves are kept on the seats by light 
 
54 
 
 BOILER ACCESSORIES 
 
 STEAM 
 
 springs, until the pressure on the bottom side is sufficient to lift them 
 and allow water to flow through. 
 
 When two pumps are placed side by side, and have a common 
 delivery pipe, the machine is called a duplex pump. It is usual to set 
 
 the steam valves so that 
 when one piston is at the 
 end, the other is at the mid- 
 dle of its stroke. A duplex 
 pump having a large air- 
 chamber and valves set to 
 act in this manner, delivers 
 water with an approxi- 
 mately constant velocity. 
 
 Injectors. Water may be 
 forced into a boiler by an 
 injector or inspirator. By 
 means of this instrument, 
 the energy of a jet of steam 
 is used to force the water 
 into the boiler. That there 
 is sufficient energy to do 
 this work is evident from 
 the fact that each pound of 
 steam, in condensing, gives 
 up about 1,000 B. T. U., 
 and a B. T. U. is equiva- 
 lent to 778 foot-pounds. 
 Not all the energy of the jet 
 of steam is used in forcing 
 water into the boiler; some 
 is wasted, and much is used 
 to heat the feed-water. 
 
 The action of the injector 
 is briefly as follows: The steam escapes from the boiler with 
 great velocity, and, as it passes through the cone-shaped passage, 
 draws air along with it, thus creating a partial vacuum in 
 the suction pipe. Atmospheric pressure forces water up into the 
 suction pipe, and the jet of steam which it meets is partly condensed. 
 
 OVERFLOW 
 
 Fig. 54. Sectional View of "Hancock" Injector. 
 
BOILER ACCESSORIES 
 
 55 
 
 The energy of the jet carries the water along with it into the boiler. 
 
 Experiments show that the injector, if considered as a pump, 
 has a very low efficiency. When used for feeding a boiler, it has a 
 thermal efficiency of nearly 100 per cent, since all the heat of the steam 
 passes to the water except STEAM 
 the slight amount lost in 
 radiation. The pump, 
 however, has one great ad- 
 vantage over the injector; 
 it can force hot water 
 from a heater into the 
 boiler, while an injector 
 can be used only with cold 
 or moderately warm water. 
 
 Figs. 54 and 55 show 
 the interior section and 
 exterior of a "Hancock" 
 inspirator. To inject water 
 to the boiler, first open 
 overflow valves 1 and 3; 
 close valve 2; and open 
 starting valve in the steam 
 pipe. When the water ap- 
 pears at the overflow, 
 open 2 one quarter-turn, 
 close 1, and then close 3. 
 The inspirator will then be 
 in operation. When the 
 inspirator is not working, 
 open both 1 and 3 to allow 
 water to drain from it. 
 
 Both temperature and 
 quantity of delivery water 
 can be varied by increas- 
 ing or decreasing the water supply. When the water in the suction 
 pipe is hot, either cool off both pipe and injector with cold water, 
 or pump out the hot water by opening and closing the starting valve 
 suddenly. 
 
 OVERFLOW 
 
 Fig. 55. Exterior View of "Hancock" Injector. 
 
56 BOILER ACCESSORIES 
 
 Circulating Apparatus. There is always more or less danger in 
 starting a fire under a boiler. If the circulation is poor, the result 
 will be that not only will the water be of an uneven temperature, hot 
 near the .top and cold at the bottom, but the boiler shell is likely to 
 be subjected to severe strain, owing to the difference of temperature 
 arising from the stagnation of the cold water near the bottom. The 
 fire must be started slowly, and a considerable time consumed in 
 getting up steam. To overcome the difficulty of poor circulation, 
 several mechanical devices have been applied. 
 
 The first device tried was a hydro-kineter a sort of injector in 
 which jets of steam driven through a conical nozzle drew in the sur- 
 rounding water. This was so arranged as to induce the cold water 
 to flow from the bottom toward the top, where it was more intensely 
 heated. This arrangement is efficient, but slow of action. In large 
 marine boilers in which the fire is cautiously started, as is proper 
 the temperature at the surface of the water, four hours after lighting 
 up, has been found to be as high as 205, while at the bottom it was. 
 only 73. Several observations with a hydro-kineter ill action have 
 shown the temperatures to be 205 and 144 respectively. It was 
 six hours more before the temperature was equalized throughout. 
 
 In naval vessels, where it is frequently necessary to raise steam 
 rapidly, this device is altogether too slow. It has, moreover, two 
 other drawbacks. There must be an auxiliary boiler under steam 
 pressure, and it will cease to act when the temperature and pressure 
 of steam in the main boiler has reached that in the auxiliary boiler. 
 The steam jet, in the American Navy, has been replaced by a jet of 
 feed -water forced, through a conical nozzle. This arrangement 
 answers very well so long as steam is being drawn from the 
 boiler; but when the boiler is at rest and steam is being raised, it is 
 inoperative. 
 
 The best service can be had by means of small centrifugal pumps 
 fixed beside the boilers, which take water from the bottom of the 
 boilers and discharge it a little below the water-level. The pumps 
 may be turned by hand while raising pressure, and may be worked 
 by steam when sufficient pressure has been attained. A small engine 
 of perhaps 1 J horse-power is sufficient to give a proper circulation to 
 a large boiler. With such a circulating device, steam can be raised 
 with safety, in a comparatively short time. 
 
BOILER ACCESSORIES 
 
 57 
 
 Evaporators. No engine can be run without a certain loss of 
 water, due either to a slight continuous leakage or to blowing off. In 
 stationary practice, this loss can be readily made up by the appli- 
 cation of fresh water; but at sea it is seldom possible to carry a suffi- 
 cient amount of fresh water, and the make-up must be had either 
 from sea water, or from fresh water provided by the use of an evapora- 
 tor. The evaporator is really a small boiler, the water in which is 
 
 OUTLET 
 
 Cold 
 Water 
 
 Fig. 56. Feed-Water Heater, 
 Closed Type. 
 
 Fig. 57. Feed-Water Heater, 
 Open Type. 
 
 heated by a steam coil supplied from the main boiler. The evaporated 
 water called the evaporation passes into the condenser and then 
 becomes a part of the regular feed water. 
 
 In a single evaporator, if the evaporation passes directly to the 
 condenser, its heat is lost to useful work. To provide a more econom- 
 ical arrangement, multiple evaporators are installed, which consist of 
 a series, the evaporation from the first passing into a coil in the bottom 
 of the second; the water in the second condenses the evaporation 
 from the first, while at the same time the evaporation from the first 
 
58 
 
 BOILER ACCESSORIES 
 
 helps to heat the water of the second. The steam and water pass 
 through the series of heaters in opposite directions. 
 
 It is a rule in the French Navy, to provide 380 Ibs. of fresh water 
 
 per hour for each 
 
 -Exhaust Outlet 1,000 indicated 
 
 horse-power; this 
 provides for a loss 
 
 Regulating 
 t Valv< 
 
 Oil Separai 
 
 Ex. Inlet 
 Skimmer 
 
 Perforated 
 Plates 
 
 Cold Water of about 2 P er cent 
 without drawing 
 
 on the reserve sup- 
 ply, which is 4,500 
 Ibs. for the same 
 amount of power. 
 The evaporator 
 may be arranged 
 to communicate 
 with a low-pres- 
 sure valve-chest, 
 in which case the 
 evaporation may 
 be made to do 
 work in a low- 
 pressure cylinder 
 of a triple-expan- 
 sion engine before 
 entering the con- 
 denser, or it may 
 be connected with 
 the feed-water 
 heater if the ex- 
 haust steam is in- 
 adequate. 
 
 FeecUWater 
 Heaters. The in- 
 troduction of feed- 
 water at a high 
 temperature increases the economy and tends to prolong the life of 
 the boiler. The injurious effects from unequal expansion are dimin- 
 
 Oll Separator 
 
 Fig. 58. 
 
 "Cochrane" Combined Feed- Water Heater and 
 Purifier, Open-Heater Type. 
 
u to 
 
 a 
 
 c/3 
 
 11 
 
 S5 ^ 
 
 ? 
 
 -a 
 
 0) 
 
BOILER ACCESSORIES 59 
 
 ished; and when the feed is warmed by exhaust steam or by the waste 
 gases in the uptake, the saving of fuel is considerable. 
 
 If this gain comes from waste gases or exhaust steam, which 
 would otherwise make no return for their heat, the gain is clear; but 
 there is no gain in thermal economy by heating feed-water with live 
 steam directly from the boiler. 
 
 There are several ways of heating the feed-water. In condensing 
 engines, the feed-pump discharges from the condenser into the hot 
 well, and the water is drawn from the hot well at a temperature of 
 100 to 140 F. This, however, if the pressure is over 100 Ibs., is 
 entirely inadequate; and for the best economy, feed -water at this 
 temperature should be passed through some form of feed-water 
 heater. In the non-condensing engines, it is absolutely necessary 
 that in some way the feed-water should be heated by the exhaust 
 steam or by waste gases from the chimney, the apparatus in the first 
 case being called a feed-water heater, and in the second an economizer. 
 
 The feed-water heater may be arranged so that it will not only 
 heat the water, but will at the same time purify it, precipitating the 
 calcium and magnesia salts, which collect on suitably prepared plates, 
 and gathering, at the bottom of the heater, dirt and other sediment 
 that would injure the boiler. 
 
 There are two types of feed-water heater the open, which is 
 frequently used in land work; and the dosed, which may be used 
 either on land or at sea. In the open heater, the steam raises the 
 temperature of the water by mingling with it in direct contact. The 
 closed type of heater resembles in its action a surface condenser; the 
 steam used for heating purposes surrounds tubes which contain the 
 feed-water, or the water circulates about tubes through which the 
 heating steam passes. 
 
 Fig. 56 shows a feed-water heater of the closed type, the exhaust 
 steam heating the feed -water within the tubes. The heater shown in 
 Fig. 57 is of the open type, the feed -water becoming heated and depos- 
 iting sediment while flowing from one tray to another. 
 
 The "Cochrane" heater, Fig. 58, is a combined heater and puri- 
 fier of the open-heater type, the water entering at the top and flowing 
 in a thin sheet over a series of trays. The exhaust steam enters 
 through the oil separator, and rising among the trays, heats the water 
 to about 210 F, the action being similar to that of a jet condenser. 
 
60 BOILER ACCESSORIES 
 
 The gases held in solution in the feed -water are liberated by the heat, 
 and escape into the atmosphere ; while the mineral impurities in solu- 
 tion, which cause scale, are precipitated by the heat, and are deposited 
 on the trays instead of on the plates and tubes of the boiler. The 
 impurities, mud, clay, etc., settle to the bottom, because of the large 
 surface and consequent low velocity of the feed -water through the 
 heater, and are readily removed. Coke, hay, etc., are used for filters, 
 a strainer being constructed so that the hay or coke will not enter 
 the pump. The impurities, having less specific gravity than the 
 water, collect at the surface, and are removed by flushing. 
 
E 
 
 O S5 
 
 < 
 
 S5 ^ 
 
 S o 
 
BOILER ACCESSORIES 
 
 PART II 
 
 STEAM SEPARATORS 
 
 Priming. Steam is said to be wet or to be superheated, according 
 as it has an excess of moisture or an excess of heat. Wet steam not 
 only is uneconomical, because it carries a considerable amount of heat 
 into the engine in the form of water, which cannot do useful work, 
 but, if a considerable amount of water gets into the engine, it is really 
 dangerous, for it may so completely fill the clearances that the piston 
 will strike a blow against the cylinder-head sufficient to break it. The 
 svater in the pipes, moreover, may <^ause a serious hammering, which 
 lot only is exceedingly annoying, but may be actually dangerous, for a 
 severe water-hammer may break the joints of the steam pipes, and a 
 considerable quantity of escaping steam at high pressure would be 
 exceedingly dangerous to the lives of the engine-room attendants. 
 This especially would be true on board ship, where the engine-room is 
 small, the supply of air meager, and the means of escape limited. 
 
 A considerable amount of water may be deposited in a sag in the 
 pipe line, and would undoubtedly remain there for a considerable 
 length of time if the pressure in the boiler did not fluctuate; but a 
 sudden rise of boiler pressure would likely cause this water to pass 
 bodily through the pipe toward the engine. Moisture is carried 
 directly from the boiler as a result of priming. This is caused by 
 steam bubbles which, instead of bursting, become connected on the 
 surface of the water, forming a foam, half-liquid, half-gaseous, which 
 fills the steam space and passes out of the steam pipe. Priming may 
 be due to fluctuations of boiler pressure or to the presence of dirt, oil, 
 or other foreign matter. The smaller the free surface of the water 
 in the boiler, the more likely the water is to prime. Boilers will fre- 
 quently prime badly under forced draft, when otherwise there would 
 be little trouble. 
 
 Priming may be detected from the unusual behavior of the water 
 in the gauge-glass, or from the hammering in the steam pipes or 
 
62 
 
 BOILER ACCESSORIES 
 
 cylinder. To avoid a breakdown under such conditions, the speed of 
 the engine should be reduced, the drain-cocks of the cylinders and 
 pipes opened, and the fires eased down. Sometimes, by suddenly 
 shutting the main stop-valve, the pressure in the boiler can be in- 
 creased sufficiently to overcome the difficulty. 
 
 Almost any boiler is likely to prime to some extent; and to obtain 
 as dry steam as possible, several devices are employed. On the top 
 
 of stationary boilers and locomotives, a 
 steam dome is frequently built, from 
 which the steam is drawn, the idea being 
 that less moisture will be found here than 
 if the steam be drawn directly from the 
 main portion of the boiler. In marine 
 work, and sometimes in stationary plants, 
 a dry-pipe is used (see Fig. 50). This is 
 merely a large pipe inside the boiler, from 
 which the steam is drawn. The pipe is 
 near the top of the boiler, and the upper 
 side of it is perforated with holes through 
 which the steam may pass. A consider- 
 able amount of moisture is in this way 
 prevented from leaving the boiler. 
 
 The moisture in steam can be reduced 
 by the familiar process of superheating; 
 but if this, for any reason, is impractica- 
 ble or undesirable, a steam separator may 
 be used for the purpose of extracting the 
 moisture that comes from the priming of 
 the boiler or from condensation in the 
 steam pipe. 
 
 Separators. There are several forms of separator; but all are 
 designed on the general principle that if the direction of the steam 
 current is suddenly changed, or if it is diverted upward and then down- 
 ward, the water will be separated from the steam and will fall to the 
 bottom of a suitable receptacle. The depth of water collected in the 
 bottom of the separator is readily indicated by a gauge-glass, and it 
 may be drawn off as desired. To prevent the possibility of flooding 
 the separator, it is well to connect it with an automatic trap which 
 
 Fig. 59.. "Stratton" Separator. 
 
BOILER ACCESSORIES 
 
 63 
 
 will empty it without close attention from the engineer. It is needless, 
 of course, to say that the trap from this separator should be con- 
 nected to the hot well, and the drip should be returned to the boiler 
 with the loss of as little heat as possible. 
 
 In the "Stratton" separator, Fig. 59, the steam 
 enters at one side of a cylinder, flows down- 
 ward, and then upward through a pipe in the 
 middle. Dry steam escapes from a pipe near 
 on the opposite side from which it 
 enters. The separated water is drained at the 
 bottom. 
 
 The "Cochrane" steam separator, shown in 
 section in Fig. 60, is of the baffle-plate type. 
 The branches for the entrance and exit of 
 
 the top, 
 
 Fig. 60. Sectional Elevation 
 and Plan of " Coehrane " 
 Steam Separator. 
 
 Fig. 61. Separator Designed for Connection 
 to Main Steam Pipe near Engine. 
 
 the steam project from each side of the spherical head. Another 
 branch from the bottom provides for connection with the well The 
 baffle-plate, which is cast as a part of the head, is ribbed, or corrugated, 
 and has ports at each side for the passage of steam. The area of the 
 ports is large, to prevent loss by friction. A small pipe is inserted 
 in the plate on the outlet side at the bottom of the baffle-plate, to drain 
 
64 
 
 BOILER ACCESSORIES 
 
 any condensation in the outlet chamber. Steam, entering at the left- 
 hand opening, strikes the baffle-plate and passes to the outlet chamber 
 by means of the two side passages, as shown in the plan, Fig. 60. 
 
 A form of separator which is fitted to the main steam pipe near 
 the engine, is shown in Fig 61. Steam enters at A and strikes the 
 dash-plate B-, any water coming with the steam is separated and falls 
 to the bottom. The steam takes the direction indicated by the arrows, 
 and flows out at D. This separator is fitted with a gauge-glass which 
 is similar to a boiler gauge-glass. 
 
 , STEAM TRAPS 
 
 Steam traps are used for collecting the water of condensation 
 from steam pipes. They consist of a receptacle with an inlet and 
 
 outlet valve so arranged 
 that the condensation 
 which collects may flow 
 out, but steam cannot 
 pass. 
 
 In the float trap shown 
 in Fig. 62, the float rises 
 and falls with the change 
 
 Fig. 62. Simple Steam Trap Operated by Float. 
 
 in. water-level. When the water-level rises above a certain point, 
 the float opens the discharge valve. The trap shown in Fig. 63 is 
 similar, the float being 
 replaced by a weight 
 W, which is nearly 
 counterbalanced b y 
 the weight T. The 
 raising of PFby the wa- 
 ter opens the valve V. 
 There are other 
 forms called bucket 
 traps. In the one 
 shown in Fig. 64, the 
 water enters at W. While there is only a little water around 
 the bucket F, it floats, and the valve V is closed ; but when the 
 water rises high enough to flow over the edge, the weight of water in the 
 bucket causes it to sink, and opens the valve V. Water is forced up 
 
 Fig. 63. Steam Trap Operated by Nearly Counter- 
 balanced Weight. * 
 
BOILER ACCESSORIES 
 
 65 
 
 Fig. 64. Bucket Type of Steam Trap. 
 
 the passage M, and out through the pipe N, by the pressure of the 
 
 steam on the sur- 
 face of the water 
 
 surrounding the 
 
 bucket. 
 
 Another form 
 
 of trap, called the 
 
 differential steam 
 
 trap, depends upon 
 
 a head of water 
 
 acting on a flexible 
 
 diaphragm. Water 
 
 enters at either top 
 
 or bottom by the 
 
 pipes E, Fig 65. 
 
 When the water- 
 level rises, it fills 
 
 the chamber G and the pipe N. This causes a pressure on the under 
 
 side of the diaphragm greater than that caused by the spring II, 
 
 which spring acts on the upper 
 side of the diaphragm and tends 
 to keep the valve open. While 
 the pressure below the diaphragm 
 preponderates, the valve P re- 
 mains closed. When the water 
 rises and fills the chamber J so 
 as to flow down the pipe M , the 
 water-pressure on the upper and 
 lower side of the diaphragm will 
 become equal, because the head 
 of water in M is practically 
 the same as that in N. The 
 spring will now open the valve P, 
 and water will be discharged 
 from the pipe 7. When the 
 head in M falls, the pressure on 
 
 Fig. 65. Differential Steam Trap. Operated by . L . 
 
 Water-Pressure on a Flexible Diaphragm. the under Side of the diaphragm 
 
 again becomes greater, and the valve accordingly closes. 
 
66 
 
 BOILER ACCESSORIES 
 
 Return Traps. Traps that are used for returning water of con- 
 densation to the boiler are called return traps. There are a variety 
 of forms, but the principle of action in all is similar, and is shown in 
 Fig. 66. B represents the boiler, and T the trap, which is placed a 
 few feet above the boiler. The trap is supplied with steam from the 
 boiler. It is also connected with the boiler by the pipe P, in which 
 is a check-valve at C. Water of condensation enters the trap through 
 the pipe E, in which is a check-valve H, until it reaches a depth 
 sufficient to raise the float F, which opens the balanced steam valve V, 
 
 H 
 
 Fig. 66. Diagram Illustrating Operation of Return Trap. 
 
 called an equalizing valve. Steam from the boiler then enters the 
 trap and equalizes the pressure. Since the pressures are equal, water 
 in the trap, because of its height above the water-level of the boiler, 
 will flow to the boiler until the level in the pipe P is nearly the same as 
 the water-level in the boiler. As the water-level in the trap falls, the 
 float F drops, and the equalizing valve is closed. 
 
 In some forms of return traps, buckets are used instead of floats. 
 
 CALORIMETERS 
 
 "Steam from a boiler is generally accompanied with more or less 
 moisture. This, being mechanically suspended in the steam, cannot 
 readily be measured without the use of special apparatus. An instru- 
 
BOILER ACCESSORIES 
 
 67 
 
 ment by means of which the percentage of moisture in steam can be 
 determined, is generally called a calorimeter. There are several dif- 
 ferent types of this instrument, only three of which will be described. 
 The Barrel Calorimeter. This was invented by the distinguished 
 engineer, Mr. G. A. Hirn, and is not only one of the earliest of these 
 devices, but is by all means the simplest and most inexpensive form 
 of calorimeter in practical use. It is shown in Fig. 67. The essential 
 apparatus consists of a barrel holding about 400 Ibs. of water, scales 
 for weighing and nothing more. A pipe with suitable connections 
 leading from the boiler or steam main, conveys the sample of steam 
 to be tested. This pipe should be provided with a valve, and on the 
 end should be a piece of rubber hose which can readily be inserted in 
 the barrel or removed. 
 The principle of this calor- 
 imeter is extremely simple. 
 As steam flows through the 
 pipe, it is condensed by the 
 water in the barrel, and the 
 increase in the weight of 
 the barrel after the test in- 
 dicates the total amount of 
 moist steam condensed, 
 while the rise in tempera- 
 ture of the Water in the Fig. 67. Details of Barrel Calorimeter. 
 
 barrel is an exact measure of the quantity of heat obtained from this 
 moist steam. 
 
 The steam tables give the number of B. T. U. in dry steam and 
 hot water at various temperatures and pressures; and with this data 
 and the above-mentioned observations made in the barrel, the per- 
 centage of steam and moisture can readily be determined. 
 
 The sampling pipe usually projects into the steam main a few 
 inches, the end being perforated so that the sample will be drawn from 
 a point near the middle of the pipe. An agitator should be placed 
 in the barrel,- so that the water may be thoroughly stirred and a uni- 
 form temperature maintained during the test. 
 
 To test a sample of steam by this method, fill the barrel about 
 two-thirds full of cold water; place it on platform scales, and carefully 
 note its weight and temperature. The weight of the barrel and 
 
68 BOILER ACCESSORIES 
 
 fittings, when empty, should of course be known, so that the weight 
 of the water alone can be determined. With the hose removed from 
 the barrel, allow steam to blow through the pipe until it has become 
 thoroughly heated If the sampling pipe is long, it should be wrapped 
 with hair felt or some form of lagging, to prevent condensation during 
 the test. As soon as the pipe line has become thoroughly heated, 
 plunge the hose into the barrel and allow the steam to blow through 
 the water until it has become well heated. Shut off the steam, and 
 carefully note the weight and temperature. 
 
 Suppose W = Final weight of water in barrel; 
 
 w = Weight of cold, condensing water before steam is turned on; 
 ti = Temperature of the cold water; 
 /2 = Temperature of the hot water; 
 
 P == Absolute pressure of steam in steam pipe (gauge pressure + 
 atmospheric pressure), 
 
 From the steam tables in the back of the book may be found : 
 
 q, the B. T. U. in one pound of the liquid contents of the moist steam; 
 q iy the B. T. U. in one pound of the cooling water, before the steam was 
 
 added; 
 g 2 , the B. T U. in one pound of this water after the steam has been 
 
 added ; 
 r, the heat of vaporization corresponding to the absolute pressure i e., 
 
 B. T. U. given up by one pound of steam condensed into water. 
 
 If x equals the percentage of dry steam contained in the supply 
 pipe, 1 x will represent the amount of priming. 
 
 x (W w) = the total amount of dry steam condensed ; 
 
 (1 x) (W w) = the total amount of moisture brought into 
 the barrel by the moist steam. 
 
 If q l equals the heat in one pound of cooling water, then q^w will 
 equal the total heat in the barrel at the beginning. 
 
 For the same reason q 2 W will equal the total heat after the steam 
 has been condensed, and q 2 W - q l w will equal the total amount of 
 heat gained by the water in the barrel. 
 
 If r is the heat of vaporization, then r x (W- w) will equal the 
 B. T. U. contained in the dry steam; and if q is the heat of the liquid 
 corresponding to the same pressure, then q (1 - x) (W - w) will equal 
 the B. T. U. contained in the moisture brought over by the steam. 
 It is apparent that the sum of these two quantities will be the total 
 number of B. T. U. brought from the steam main to the water barrel, 
 and must be equal to q' 2 W - q^ w, the heat gained by the water in the 
 
BOILER ACCESSORIES 69 
 
 barrel. The solution of this equation will result in a formula which 
 will save some mathematical computations. 
 
 That the method may be perfectly clear, let us first consider a 
 numerical example in full. 
 
 Suppose w = 455 Ibs. 
 W = 495 Ibs. 
 
 ti = 50 F. 
 
 h = 140 F. 
 P = 75 Ibs. 
 
 q (from steam tables) = 276.9 
 0i '" " " = 18.1 
 
 g 2 " " " = 108.2 
 
 Then the total heat in the barrel after condensation, is equal 
 to (495 X 108.2) = 53,559 B. T. U. 
 
 The total heat before condensation was equal to 455 X 18.1 = 
 8,235 B. T. U. Therefore the heat brought over by the moist steam 
 will be 53,559 - 8,235 = 45,324 B. T. U. 
 Now, from the steam tables 
 
 q = 276.9; and r = 898.8. * 
 
 The heat given up by condensation of the dry steam will then be 
 898.8 X (495- 455)* = 40* X 898.8 = 35,952*; and the heat of the 
 liquid in the moisture" and condensed steam will be 40 X 276 . 9 = 
 11,076, making the total heat in the moist steam = 11,076 + 35,952*. 
 Therefore, 11,076 + 35,952* = 45,324 
 35,952* = 34,248 
 x= 0.952 
 
 That is, every pound of moist steam contains .952 Ib. dry steam and 
 . 048 Ib. moisture ; or we may say there was 4 . 8 per cent of priming. 
 The formula may be derived by the following algebraic work: 
 
 Total heat in bbl. after condensation = W q 2 ; 
 
 Total heat in bbl. before condensation = w q l ; 
 
 Total heat brought over by steam = W </, w q l ; 
 
 Heat of liquid in condensed steam = (W w) </; 
 
 Latent heat in dry steam = x (W w) r; 
 
 Total heat in moist steam = x (W w) r + (W w) q. 
 
 Therefore, 
 
 x (W w) r + (W w ) q = W q 2 w q^ 
 xr (W w) = W q 2 w q L W q + w q; 
 
 or, transposing to a more convenient form, 
 
70 
 
 BOILER ACCESSORIES 
 
 = 
 
 r (W-w) 
 
 The use of this form of apparatus is" not especially to be com- 
 mended, for it is liable to error, and a slight discrepancy in the weights 
 or the temperatures may cause a large error in the result. In the 
 above calculations, no allowance is made for loss of heat through 
 radiation. 
 
 Separator Calorimeter. This instrument shown in Fig. 68, 
 consists of a chamber A, into which is led 
 a steam pipe D, bringing a sample of 
 steam from the boiler k or steam main. 
 This pipe leads into an enlargement per- 
 forated with small holes, or into a cham- 
 ber A as shown in Fig. 68. The calori- 
 meter separates the moisture from the 
 steam just as a steam separator does; 
 and the exhaust, which is dry steam, 
 passes out of the pipe , wherein is in- 
 serted a diaphragm containing small ori- 
 fices, by means of which the quantity of 
 steam flowing out can be calculated by 
 thermodynamic methods. The exhaust 
 steam can, of course, be led to some 
 form of condensing apparatus, and the 
 condensation weighed, if desired. 
 
 As the steam enters the calorimeter, the 
 moisture is drawn toward the bottom of 
 the chamber. The amount of water 
 collected can readily be read from the 
 gauge-glass at the side, to which a gradu- 
 ated scale should be attached. 
 Fig. es. separator calorimeter. The amount of moisture contained in 
 
 the steam can be weighed directly by 
 
 drawing it out of the gauge-cock E. The amount of dry 
 steam is measured by its flow through the orifices, or by conden- 
 sation.* If W = weight of steam discharged -from the calorimeter, 
 
 *NOTE: For principles governing flow of steam through, an. orifice, consult any 
 treatise on Thermodynamics. 
 
BOILER ACCESSORIES 
 
 71 
 
 and w = weight of water collected, then the percentage of priming 
 
 will be fjT 
 
 W + w 
 
 If only a small quantity of steam is used, an allowance must be 
 made for condensation; but if the instrument is well lagged with 
 hair felt or other suitable material, and a sufficient quantity of steam 
 is used, the error from radiation may be neglected. Steam should be 
 allowed to flow p ressureiTlCalort p ressure inStearnR 
 
 through the instru- MainSteamPipe 
 
 ment until it has 
 become thoroughly 
 heated, before be- 
 ginning the test. 
 
 Throttling Cal= 
 o r i m e t e r. This 
 was invented b y 
 Prof. Cecil H. Pea- 
 body, and is made 
 with varying con- 
 structive details. 
 Fig. 69 shows the 
 general arrange- 
 ment. The mix- 
 ture of steam and 
 water from the 
 boiler is taken from 
 the main steam 
 
 ,, , , Fig. 69. General Arrangement of Throttling Calorimeter. 
 
 pipe through what 
 
 is termed a sampling pipe. Various forms of this pipe are made; one 
 arrangement consists of a pipe closed at its inner end, but having 
 numerous holes J inch in diameter drilled staggering around the sides. 
 The calorimeter should be placed as close as possible to the main 
 steam pipe; and the gauge for indicating the pressure in the main 
 steam pipe should be placed on the latter and near the calorimeter. 
 The gauge is sometimes connected to a tee on the pipe leading to the 
 calorimeter; but it is better to have this gauge where the velocity of 
 the flowing steam is less. A valve is placed in the pipe to the calori- 
 meter, below which is inserted a nipple A having a small converging 
 
 Sampling Pipe 
 
 fGas Pipe 
 Globe Valve 
 
72 BOILER ACCESSORIES 
 
 orifice D, about two-tenths of an inch in diameter and very carefully 
 made. The object of such an orifice is to determine the weight of 
 steam flowing through the calorimeter, so that an allowance can be 
 made for the loss when testing an engine or boiler, where the net 
 weight used is required. A cup B is screwed into the top, for holding 
 an accurate thermometer. The cup is made of brass, and is filled with 
 oil; but if mercury is used, the cup must be of iron or steel. A deli- 
 cate gauge C, for determining the pressure in the calorimeter, and a 
 pipe and valves at the bottom, complete the apparatus. The valve N 
 is sometimes omitted, and a simple pipe used, as the throttling is best 
 accomplished by use of the valve E or orifice D. All pipes leading to 
 the calorimeter should be well covered with a good non-conductor. 
 
 To use the instrument, proceed as follows : Open wide valves E 
 and N, to bring the apparatus to a uniform temperature; then gradu- 
 ally close E until the steam in the calorimeter is superheated ; that is, 
 until the temperature as shown by the thermometer is greater than that 
 corresponding to the absolute pressure determined from the reading 
 of the gauge C and barometric pressure. The result may now be 
 calculated as follows : 
 
 x = Weight of steam contained in one pound of the mixture from 
 the main steam pipe or other source; 
 
 \ = Total heat corresponding to the absolute pressure determined 
 from the reading of the gauge (7 and barometric pressure; * 
 
 T = Temperature as shown by the thermometer; 
 
 t c = Temperature of steam corresponding to the absolute pressure 
 as determined by the reading of the gauge C and barometric pressure; 
 
 q s = Heat of the liquid corresponding to the absolute pressure 
 in the steam pipe; 
 
 r s = Heat of evaporation corresponding to the absolute pressure 
 in the steam pipe ; 
 
 . 48 = Heat required to superheat the steam one degree Fahren- 
 heit under constant pressure. 
 
 Total heat in 1 Ib. superheated steam in calorimeter = \ + 
 0.48 (T-OB.T. U. 
 
 Total heat in 1 Ib. moist steam in steam main = xr a -f q a B. T. U. 
 
 These two quantities are equal ; and x, being the only unknown 
 quantity, the equation can easily be solved. 
 
 *NOTB: Some steam tables use //instead of the Greek letter A (lambda). 
 
H 
 
 lib 
 
 s 
 
 IS 
 
 1 
 
BOILER ACCESSORIES 
 
 73 
 
 x , 
 
 n 
 
 Example. Barometric pressure, 14.78 Ibs. , Absolute pressure 
 in main steam pipe, 87.78 Ibs. Absolute pressure in calorimeter, 
 23.03 Ibs. Temperature (T) = 260 F. Then, 
 
 X c = 1,153.68 q a = 288.1 
 
 4 = 235.28 r s = 890.88 
 
 1,153 . 68 + . 48 (260 - 235 . 28) - 288 . 1 
 x = - n - 0-984 pound. 
 
 Or, in other words, 98.4 per cent of the mixture is steam; or the 
 moisture = 1 0.984 = 0.016, or 1.6 per cent. 
 
 This form of calorimeter is suitable only for cases where the 
 moisture does not exceed three per cent of the mixture. Its principle 
 is based upon the assumption that there is no loss of heat, in which 
 case steam mixed with a small amount of water is superheated when 
 the pressure is reduced by throttling. 
 
 PIPING 
 
 Although piping can hardly be considered a boiler accessory, 
 a few general remarks will not be out of place. 
 
 Pipes must not only be of sufficient size and strength, but should 
 be so installed as to make 
 
 ample provision for expansion (Jfy 
 
 due to the high temperature f* 
 when they are filled with A 
 steam. The supports for long 
 pipe lines should be arranged 
 somewhat as shown in Fig. 70, 
 which allows the pipe a con- 
 siderable amount of lateral 
 
 Fig. 70. Side and Transverse Sectional Views 
 
 Showing Methods of Arranging Supports 
 
 for Long Pipe Lines. 
 
 motion. 
 
 If the pipe line is long, 
 an expansion joint must be 
 provided. Sometimes a curved 
 U-bend may be inserted in the pipe line, which of itself will have 
 flexibility enough to provide for reasonable expansion. Or, if the 
 steam main is not all in one line, a similar bend may be pro- 
 vided, with elbows and nipples, as shown in Fig. 71. In this 
 
74 
 
 BOILER ACCESSORIES 
 
 case, any expansion of the steam main will cause the nipples to turn 
 slightly in "the elbows. This motion, of course, is slight, but it is 
 sufficient to prevent rupture. U-bends and swivel-joints are hardly 
 practicable in large pipe ; and in such cases a slip-joint, made tight by 
 a stuffing gland, is usually provided. If this is done, great care must 
 be taken that the steam- main is straight and in perfect alignment, as 
 the pipe may otherwise bind in the expansion joint and cause much 
 damage from leakage. 
 
 In marine work, especial care must be taken that the pipe lines 
 are not so rigidly connected together that they will be injured by the 
 working of the ship. This can readily be provided for by laying 
 the pipe in such a way as to provide a simple form of swivel-joint. 
 
 ,^ The pipe lines should be as 
 
 frj IB 
 
 straight as possible, to prevent 
 unnecessary friction of the 
 steam and unnecessary con- 
 densation; and they should, if 
 possible, be so installed as to 
 leave no pockets wherein con- 
 densation may collect. If such 
 a pocket is unavoidable, a 
 
 drain must be provided, lead- 
 ,, , 
 mg from the pocket to the 
 
 steam trap, whence the con- 
 densation may be discharged into the hot well or filter-box, because 
 the collection of water in steam pipes is a source of inconvenience 
 and danger. 
 
 The pipe lines should be installed with sufficient slope, so that 
 the condensation will readily drain to a convenient point whence it 
 may be drawn off. This slope should be in the direction of the flow 
 of the steam, as the water will not readily flow otherwise. Great 
 care should be taken that the pipe lines nowhere sag, as such a de- 
 pression will collect condensation. This may cause very little dis- 
 turbance unless the pressure of the steam is suddenly raised, in which 
 case the water is liable to flow bodily along the pipe; and if it does 
 not enter the cylinder of the engine and cause damage there, it will 
 cause a serious water-hammer which may rupture the elbows of the 
 pipe and may endanger life. 
 
 ELEVATION 
 
 Fig 71. Method of Forming Swivel-Joint in 
 Steam Piping to Counteract Effects of 
 Expansion and Contraction. 
 
BOILER ACCESSORIES 75 
 
 Formerly, when low pressures were used, cast iron was a common 
 material for a main steam pipe leading from the boiler to the engine, 
 but the higher pressures of to-day require the best wrought iron or 
 steel. In marine work, copper is commonly used; but with the 
 advent of higher and higher pressures, copper fails to give the 
 requisite strength, and it has to be' reinforced with wire or iron 
 bands. At pressures not over 150 Ibs., copper pipes may be used, by 
 the British Board of Trade rules, 15 inches in diameter; but at 200 
 Ibs., copper pipes are not allowed over 10 inches in diameter. For 
 large sizes, riveted iron or steel pipe may be used. For high pres- 
 sures, cast-steel fittings are required by the U. S. Steamboat Inspec- 
 tion rules. There was always danger that the large copper pipe would 
 burst; and it is now the common practice to use steel for such 
 purposes. 
 
 Large steam pipe is made in sections which can be riveted to- 
 gether. The small sizes are fitted with the ordinary type of flange, and 
 the sections may be bolted together, a suitable gasket being used 
 between the two flanges to make a steam-tight joint. The flanges are 
 machined perfectly smooth, and the packing may consist of rubber and 
 fiber reinforced with wire insertion, or of asbestos, or of corrugated 
 copper. 
 
 The true inside diameter of steam, gas, or water pipe is not always 
 the same as the size of the pipe as popularly known. For instance, 
 what is called "3-inch" pipe has an actual inside diameter of 3.067 
 inches, and 3 . 5 inches outside diameter. The actual sizes of pipe, 
 inside and outside, can be found in any handbook or steamfitter's 
 catalogue. 
 
 LAGGING 
 
 When steam pipes are exposed to the air, a considerable amount 
 of condensation will collect in them, depending on the condition of 
 the surface of the pipe, on the difference in temperature between the 
 steam and the surrounding air, and on the velocity of the steam 
 through the pipe. This condensation will cause a large amount of 
 heat to be lost to useful work, and will make the dangers of water- 
 hammer possible unless carefully drained. Tests have shown that 
 about 2 B. T. U. are lost per square foot of pipe per hour per degree 
 
76 BOILER ACCESSORIES 
 
 of difference in temperature. While the loss for a few hours is not 
 likely to be great, yet, if taken for an entire year throughout a con- 
 siderable length of pipe, the sum total will be very large indeed. The 
 following table gives some idea of the loss of heat through bare pipe at 
 200 Ibs. pressure : 
 
 HEAT LOSSES IN BARE PIPES 
 
 B. T. U. Loss 
 . } PER SQ. FT. 
 CONDITION OF PIPE PER MINUTE 
 
 New Pipe .' 11.96 
 
 Painted Glossy Black . 12.10 
 
 Painted Glossy White 12 .02 
 
 Fair Condition 13 .84 
 
 Rusty 14.20 
 
 Coated with Cylinder Oil 13 .90 
 
 Painted Dull Black 14 .40 
 
 VARIATION OF HEAT LOSS WITH PRESSURE 
 
 HEAT Loss 
 B. T. U. PER SQ. 
 PRESSURE FT. PER MINUTE 
 
 340 '. 15 .97 
 
 200 13.84 
 
 100 8 .92 
 
 80 8.04 
 
 60 : 7.00 
 
 40 5.74 
 
 A full account of some interesting tests can be found in a paper 
 entitled Protection of Steam-Heating Surfaces, by C. L. Norton, Vol. XIX, 
 Proceedings of the American Society of Mechanical Engineers, 1898, from 
 which these tables have been taken. 
 
 Pipe Coverings. To make this loss from radiation as small as 
 possible, it is customary to cover the pipe or boiler with some material 
 which will prevent loss of heat and which will not burn. There is 
 considerable difference in the value of various substances as preventa- 
 tives of heat radiation. Their value varies nearly in an inverse ratio 
 to their conducting power; but due allowance must be made for the 
 possible deterioration of the pipe covering. The following table gives 
 the relative value of various substances with reference to their ability 
 to prevent radiation of heat. For purposes of comparison, the value 
 cf wool is taken as the standard : 
 
BOILER ACCESSORIES 77 
 
 RELATIVE VALUES OF VARIOUS PREVENTATIVES OF 
 RADIATION OF HEAT 
 
 Felt, Hair, or Wool 100 
 
 Asbestos Sponge 98 
 
 Air-Cell Asbestos 89 
 
 Mineral Wool 68-83 
 
 Carbonate of Magnesia 67 76 
 
 Charcoal 63 
 
 Sawdust 61 68 
 
 Asbestos Paper 47 
 
 Wood 40-55 
 
 Asbestos, Fibrous 36 
 
 Plaster of Paris 34 
 
 Air Space (Undivided) 22 
 
 There are many patented coverings which are very efficient, but 
 they are too numerous even to mention. The above-mentioned article 
 from the Proceedings of the American Society of Mechanical Engineers 
 gives the results of tests of several of these coverings. A good pro- 
 tection is afforded by air confined in minute cells, such as is to be had 
 in the air-cell asbestos board; this is made by cementing together 
 several layers of asbestos paper which have been corrugated or in- 
 dented by machinery so as to form minute air-cells. The more 
 minute the subdivision of these cells, the better the protection is likely 
 to be. Hair felt is one of the most efficient non-conductors, because it 
 is very porous and contains a large number of air-cells. It is not one 
 of the best coverings, however, because it is liable to deteriorate, and 
 its life on high-pressure pipes is not likely to be more than four or five 
 years. On low-pressure work it may last for a considerably longer 
 time. 
 
 Mineral wool, a fibrous material made from blast-furnace slag, 
 is an efficient and noncombustible covering, but is brittle and liable 
 to fall off. 
 
 The coverings most easily applied to pipes are those applied in 
 sectional form, which clasp around the pipe and are fastened by brass 
 bands at convenient intervals. Such coverings are made both of 
 asbestos and of magnesia, and are usually of about 1 inch in 
 thickness. 
 
 A good, cheap covering can be made by wrapping several layers 
 of asbestos paper around the pipe, and then covering these layers with 
 a layer of hair felt perhaps f inch thick, the whole being wrapped in 
 
78 BOILER ACCESSORIES 
 
 canvas. On low-pressure steam pipes this covering will last ten to 
 fifteen years. 
 
 Cork is perhaps one of the most satisfactory coverings from the 
 point of radiation loss, but is rather more expensive than asbestos or 
 magnesia. 
 
 It has generally been the impression that it is not economical 
 to cover a pipe to more than one inch in thickness. This will depend 
 upon the cost of the covering and the length of time it is likely to last. 
 If it does not last more than five years, one inch is probably the most 
 economical thickness; but if the life of the covering is likely to be 
 ten years or more, a second inch in thickness can be applied to advan- 
 tage. For instance, in the above-mentioned tests, in the case of " Non- 
 pareil cork," increasing the thickness from one to two inches raised the 
 cost from $25 to $30 per 100 square feet, and increased the net saving 
 in five years by $10, and by $30 in ten years. A third inch of covering 
 did not produce saving enough to pay for its cost. In each case with 
 the asbestos fire-board, a second inch in thickness showed a saving 
 of $20 in ten years, while the third inch in thickness showed an 
 actual loss from the dollars-and-cents point of view. It would be 
 well to remark that it is of great importance that the pipe covering 
 should be kept in repair, for a loose-fitting covering is of little value. 
 
 Boiler Coverings. Much the same remarks may be made with 
 regard to boiler covering as have been made with regard to pipe 
 covering, except that the covering put on boilers is usually somewhat 
 less efficient and is applied in greater thickness. Probably one of the 
 best coverings for a marine boiler or, in fact, for any internally- 
 fired boiler is a layer of air-cell asbestos board, covered with a coating 
 perhaps two inches thick of magnesia or asbestos. This comes in 
 powder form, and when mixed with water can be readily applied with 
 a trowel. Coverings on boilers are best placed directly against the 
 shell without an air-space, so that any leak in a joint or rivet will reveal 
 the spot by moistening the covering; otherwise the escaping water may 
 run down through the air-space and appear at some remote point, the 
 leak thus being difficult to locate. 
 
 An efficient covering for boilers is made of either magnesia or 
 asbestos in the form of blocks of the proper curvature, which can lie 
 directly against the boiler; but this form of covering is rather more 
 expensive than the asbestos or magnesia cement. To secure an extra 
 
BOILER ACCESSORIES 79 
 
 hard finish a coating of plaster of Paris may be put on outside the 
 magnesia or asbestos. No boiler or pipe covering should contain 
 sulphate of lime, as this is liable to cause corrosion. 
 
 If an internally-fired boiler is properly lagged, there is little danger 
 that any large amount of heat will be lost, as the heat of the fire must 
 pass through the water before radiating. This is not true with an 
 externally-fired boiler, where a considerable amount of heat may 
 radiate through the brick setting of the boiler without coming in 
 contact with the boiler at all. The setting of such a boiler should 
 be arranged with properly confined air-spaces; a 1 id an efficient pro- 
 tection from the radiation of heat at the top of the boiler may be had 
 by allowing a slight space between the boiler and the top covering 
 for the circulation of the hot gases of combustion. These are on their 
 way to the chimney; and as they are necessarily hotter than the water 
 in the boiler, they prevent radiation at this point. 
 
 HORSE-POWER OF BOILERS 
 
 The unit which we call the horse-power is arbitrary. Assuming 
 that 30 pounds of steam are required per horse-power per hour for 
 an average engine, this unit for boilers has been adopted. 
 
 One (1) horse-power is the evaporation of 30 pounds of water 
 per hour, from a temperature of 100 F. into steam at 70 pounds gauge 
 pressure. This is considered equivalent to the evaporation of 34 \ 
 pounds per hour from and at 212 F. A boiler horse-power is equiv- 
 alent to 33,327 B. T. U. per hour. 
 
 As all boilers do not generate steam at the same pressure and 
 from the same temperature of feed-water, it is necessary to reduce the 
 actual evaporation to an equivalent evaporation. Unless this is done, 
 the relative performances of boilers cannot be compared. 
 
 For this comparison, the actual evaporation is reduced to the 
 equivalent evaporation from and at 212 F. That is, we suppose 
 the water to be fed at 212 and evaporated into steam at 212. 
 Let W Water actually evaporated in pounds; 
 
 H = Total heat of steam above 32 F., at factual absolute pres- 
 sure; 
 
 T = Temperature of feed water; 
 
 w = Equivalent evaporation from and at 212 F. 
 
 Since 966 B. T. U. are necessary to evaporate one pound of water 
 
80 
 
 BOILER ACCESSORIES 
 
 88 S3 8 
 
 izrS 
 
 M IK 
 
 l 
 
 p 
 
 O 
 
 tf ~ 
 
 ails ssssS SSSS3 31111 ! 
 
 SsSJiS SS322 SSSSS 
 
 !H! !!H! !!!! 835^ ^ssss 
 
 isiss giiss 
 
 ffl CO GO C<I t- (Nt^tNt^oq CO i-l CO i-( CO O U5 O lO O T}< O5 rfi O5 <* 00 CO UD CO 00 OJt^cNCOCN CO rH OJ 
 
 3 cs cs rn rH o o oj 05 oo oo i> t~ cc co o ift <* * co c^ IN r< I-H o o 05 os oo oo t- 1 ~ c& co 25 3 9 
 
 ..... ..."^^ r ^ r ^ l ^ 1 "l r ^ r ^'~ tl ^ r ^ 1 ^ iHiHrHrHrH rHrHOOO OOOOO OOO 
 
 SUSS I1SI1 IsSSI SSISS Illll lg|| 
 
 : 
 
 OOOOO OO< 
 
 OOO 
 
 Oi * O5 * oo eo oo co oo r<i t> csi t- <N to 1-4 to r-no owoico Tftoi^oartt oocor-i 
 
 SSSS 53533 inSSJnS SSSSS OOlOSOOOO StcSioS M^^ 
 
 txMt^esn>- H to ^H o r-i 
 
 S S S 
 
 ooicw^OT -^oi-^os-^ oocoooeooo <NI><NI>(N CO,HCO,-I< 
 ^H ^n I-H o as a> oo on t> i> to to 10 10 TJ< ^ji eo co CM CM -H .H o o < 
 
 COCOOO(Nt- (NIXNIXN ^-lOr-l< OlOOiCO * Ol Tf< 
 
 rti-iooa> osoooot-t- cocoioio^ ^COCOCMIN THOO 
 
 (N<N<N(NrH r-( r-l r-l rH rH rl r-j rH ^-1 rH rH -H rH rH r-l rH rH rH 
 
 (N1XNIXN 0r-l< 
 
 coiomrjiTti cocot 
 
 OOOOO OO 
 
 00 Nt>(Nt~(M to -H to i-l CO O 1C O i 
 5 <OlOiOTt<-<* COCOIMIN^I rHOO< 
 
 10 o m Oi * a> * as eo oo eo oo co t-<Nt~e<ii>- 1-1 co 1-1 co I-H icoio< 
 t-t-co ioiO-<HT}teo eofNOJ^r-i ooosoioo oot-t-Sco inire-* 5 
 
 ir-Hr-Jr-H rH rH rH ? * rH rHrHr-trHrH rHrHOOO OOOOO O O O < 
 
 os-^oi-^ oocoooeooo <Nt^c<i^ 
 -^^coco <N<Nrtr-.o 0050500 
 rrrr r " r " r " r " r ' r< * 
 
 lO O5^O3M-O5 COXCOOOOO t^CMt^iMt^ rHCO-iCOT-( ICOlOOiO O5TPCN 
 
 S3 ^^eccctN (Ni-irHoo os a. oo oo i> E * 5 3 x*t-5!cocoN TH.-!;-! 
 
 rH rH rH r-l >- rH rH rH rH rH rH OOOOO OOOOO OOOOO OOO 
 
 (Nt-iNt-(N cO'HcorHco oicoinp -^os-^os-* oo 
 
 '* -^COCOIMCN rHrHOOOS OSOOXt-l^ CDiOlO^Tfl CO 
 
 r-O 
 
 CO t^CNt>C^l> rHCOi ICO^H JOOICOIO'O5"^O5^O5 COOOCOCOCO rHCN 
 '*! COCOcVlCNIrH rH O O O5 O5 00 00 r- (^ CO ggggg g g g "" ^ g; 
 
BOILER ACCESSORIES 81 
 
 from and at 212 R, the equivalent evaporation may be found from 
 the formula, 
 
 W (H + 32 T) = 966^, or w = 
 
 9oo 
 
 Then the horse-power of the boiler is : 
 
 w 
 
 H.P. = 
 
 34.5 
 The above method is considerably shortened by substituting for 
 
 TT , OO _ m 
 
 the quantity - - -- > the number found in the accompanying 
 
 table (page 80) which corresponds to the actual feed-water tempera- 
 ture and steam pressure. 
 
 For example, a boiler is required to furnish 2,100 pounds of 
 steam per hour. If the gauge pressure is 85 pounds, and the feed- 
 water enters at 50 F., what is the equivalent evaporation, and what 
 is the horse-power? 
 
 From the table, the factor for 85 pounds pressure and 50 F. is 
 1.204. Then the equivalent evaporation would be 1.204 X 2,100 = 
 
 2,528.4 pounds; and 2 > 528 ' 4 , = 73 (approx.) = the H. P. 
 o4.5 
 
 CORROSION AND INCRUSTATION 
 
 There are several causes which tend to shorten and destroy the 
 life of every boiler. These may be divided into two general classes, 
 chemical and mechanical, and are usually the result of improper feed- 
 water or of improper care. Pure water, free from air and carbon 
 dioxide, has no evil effect on the iron; but all natural waters, whether 
 from rain, lake, river, or sea, contain air and a little carbon dioxide in 
 solution, and such water will cause iron to corrode, even though no 
 other impurities are present. 
 
 Sea water, heated under a steam pressure of 30 Ibs., even if it 
 contains no air, will liberate a small amount of hydrochloric acid, 
 which instantly attacks the iron of the boiler unless counteracted by 
 some chemical agent. 
 
 External Corrosion. There are two forms of corrosion, external 
 and internal. External may be due to faulty setting, to improper care, 
 or to moisture from external sources or from leakage from joints and 
 
82 BOILER ACCESSORIES 
 
 valves. A large amount of external corrosion is the result of setting 
 boilers in a mass of brickwork, which readily absorbs moisture, and 
 which, when not under fire, is likely to keep the boiler-plates damp. 
 The exterior of a boiler encased in brickwork, moreover, is not so 
 easily accessible, and a considerable amount of deterioration may take 
 place without being readily detected. The leakage from a joint, al- 
 though slight, may, if long continued, badly corrode the boiler. 
 
 Internally-fired boilers are supported on saddles and are easily 
 accessible; and the magnesia or asbestos lagging with which they are 
 usually covered will tend to absorb a certain amount of moisture, which 
 will be given off when hot, thus helping to keep the boiler dry. If a 
 leak occurs of appreciable size, the covering will become softened and 
 its presence will be detected at once, and repairs can be made before 
 any serious damage is done. The exterior of an internally-fired 
 boiler, being at all times accessible, can be properly taken care of, 
 which is not true of a boiler set in brickwork. Rivets and riveted 
 joints should as far as possible be kept out of contact with the fire. 
 
 Internal Corrosion. This is the result of the chemical action of 
 impure feed-water. It may occur in the form of a general corrosion 
 or wasting-away of the boiler-plates, or in the form of pitting or 
 grooving, the effects of which are likely to be local. Pitting and 
 general corrosion are entirely the result of chemical action, while 
 grooving is the result of chemical and mechanical action combined. 
 
 It is not easy to discover general corrosion, because it acts more 
 or less uniformly over a large surface. Sometimes the rivet-heads 
 rust in proportion to the plates, so that the wasting-away of the plates 
 is not easily noticeable. A uniform corrosion is the hardest to detect, 
 and can usually be discovered only by drilling the boiler and gauging 
 the thickness of the plate. If the thickness of the plate is found to be 
 materially reduced, the working pressure of the boiler should be 
 lowered in proportion. 
 
 Sometimes the water will attack the plates only in the vicinity 
 of the water-line, in some instances confining the damage to a belt 
 inches or 8 inches wide. Sometimes a few rivets below water-level 
 will be corroded, the rest remaining in a comparatively good con- 
 dition. Often the stays are weakened more rapidly than the plates, 
 and the screw-threads of a stay may be badly corroded while the 
 shank of the stay remains uninjured. 
 
BOILER ACCESSORIES 83 
 
 Pitting. Fatty acids, which are likely to come over in the feed- 
 water if vegetable oils are used to lubricate the cylinder, are especially 
 active in the production of small pits throughout the interior of the 
 boi ler. Pitting appears in the form of small holes or in patches from 
 J inch to 1 inch in diameter, or even as irregularly shaped depressions. 
 If the holes are small and close together, the plate is said to be honey- 
 combed. It is generally believed that this phenomenon, the result of 
 chemical action, is due to a lack of homogeneity in the material of 
 the boiler, although an entirely satisfactory explanation has not yet 
 been given. Pitting may also be caused by galvanic action, which 
 may take place especially if sea water is used. As pitting occurs 
 when there is no cause whatever for galvanic action, this can be only 
 a secondary cause at best. It is reasonable to suppose that acids will 
 attack the most susceptible portions of the plate; and if there is any 
 lack of homogeneity in the icon, it is probable that the places or spots 
 most favorable to chemical attack will suffer first. 
 
 Grooving. Grooving is probably the result of straining, springing, 
 or buckling of the plates, aided by local corrosion or by the same forces 
 which cause pitting. Straining of the plates may be due to insufficient 
 or improper staying, thus causing the plates to spring back and forth 
 as the steam pressure varies. This phenomenon is most commonly 
 found in stationary boilers of the "Cornish" or "Lancashire" types 
 appearing in the flat end-plates around the edge of the angle iron, or 
 in the root of the angle iron. Too rigid staying of the ends by gussets 
 or diagonal stays, or too great a difference in expansion between dif- 
 ferent parts, is almost sure to produce grooves. 
 
 Internal grooving may be caused as the direct result of excessive 
 calking, which, by injuring the surface of the metal, exposes it to the 
 corrosive action of the feed -water. It is to be expected that if strains 
 which cause the plates to come and go are set up in the boiler 
 especially if the stresses can be concentrated along a definite line a 
 weakness will be developed there, and it will be a susceptible point 
 for chemical attack. Sometimes grooving is so fine as to appear to 
 be a mere crack. But the crack, although perhaps only ^ T inch in 
 width, may extend into the plate for a considerable depth. Grooves 
 are not readily detected, and if allowed to continue for any length of 
 time are likely to produce serious results. 
 
84 BOILER ACCESSORIES 
 
 Prevention. The best way to prevent internal corrosion is to 
 use water that has no corrosive effect on the plates. If internal cor- 
 rosion has begun, a change of feed-water may prolong the life of the 
 boiler, but in many instances it is cheaper to build a new boiler than 
 frequently to change the water supply. Sometimes the introduction 
 of a thicker jSlate at places where the water is found to be most active 
 will be advisable; but, as these plates are stronger than the rest of 
 the boiler, the strains will not be uniformly distributed, and stresses 
 are likely to concentrate along the edge of this heavy plate, which will 
 be a susceptible point for the formation of grooves. 
 
 The acidity of the feed-water may be neutralized by some alka- 
 line substance, such as soda, before it enters the boiler. The amount 
 of soda to be used varies with the acidity of the water; but it should 
 always be used in the smallest possible quantity, as the soda is likely 
 to produce priming in the boiler and will be injurious if there is much 
 salt present. Vegetable oils should not be used for cylinder lubri- 
 cation if the condensation is to be fed back to the boiler, as such oils 
 contain acids which will always produce injurious effects. Mineral 
 oils alone should be used. 
 
 To allow for a general corrosion, T ^ inch to T \ inch extra thick- 
 ness of shell should be provided. All seams of a boiler should be 
 tight, and no w r elded tubes should be used, as pitting and grooving 
 are likely to occur in the vicinity of the weld. When not in use, no 
 moist air should be allowed in the boiler. A boiler can be thoroughly 
 dried out either by the application of heat or by placing in it lime, 
 which will readily absorb the moisture. 
 
 The water fed to the boiler should be thoroughly filtered to re- 
 move as much grease as possible, for, although mineral oil is not likely 
 to cause pitting, it has a serious effect in the formation of boiler scale. 
 
 Incrustation. The incrustation formed by the accumulation of 
 the deposit of sediment in the feed water, is called scale or sludge, 
 The solid matter in the feed-water may be precipitated by the rise 
 in temperature, or left behind as the result of the evaporation of the 
 water. These solids, unless blown out, are liable to become hardened 
 on the inner surface of the boiler. A thin coating of scale in itself 
 is beneficial, for it keeps the water from direct contact with the iron, 
 and prevents corrosion and pitting; but the danger is that if a thin 
 scale forms, a thicker one will form, and this heavy scale, being a poor 
 
BOILER ACCESSORIES 85 
 
 conductor of heat, not only causes considerable waste of fuel, but 
 allows the plates next the furnace to become overheated, with the 
 result that they are likely to give way, and the boiler may collapse. 
 
 The amount of solid matter in solution is measured in grains per 
 U. S. gallon. The quantity varies greatly in waters from different 
 sources, but is seldom over 40 grains per gallon. It is not the quantity 
 of matter in solution, but its nature, that determines the influence of 
 feed -water. With proper attention to the boiler, the presence of a 
 certain amount of carbonate or sulphate of soda would not be injurious ; 
 while the same number of grains per gallon of salts of lime would 
 cause serious trouble. Salts of lime (calcium), together with car- 
 bonate of magnesia, are the solids most frequently found, and are the 
 most troublesome. Hard water contains considerable quantities of 
 lime. So-called soft water has usually but little solid matter in sus- 
 pension, but it may contain vegetable or organic impurities that will 
 cause corrosion or pitting. 
 
 The oil used in the engine is likely to get into the boiler through 
 the feed-water, if it is not carefully filtered or passed through a grease- 
 extractor. The oil is likely to be deposited on the sides and tubes of 
 the boiler, and not only is a poor conductor of heat, but, mingling 
 with the sediment which is precipitated from the hot water, pro- 
 duces a mixture which is readily baked onto the boiler-plates and is 
 especially obstinate and difficult to remove. There are efficient 
 grease-extractors now on the market, which will remove practically 
 every trace of oil. 
 
 Carbonate of Lime, Carbonate of lime is held in solution in water 
 by an excess of carbon dioxide. As the water is heated, the excess of 
 carbon dioxide, or carbonic acid, is driven off, and the carbonates will 
 be precipitated in the form of a whitish or grayish sediment of the 
 consistency of mud. If these precipitates are not mixed with im- 
 purities, they may be washed out of the boiler after it has been allowed 
 to cool; but if there is oil, organic matter, or sulphate of lime, the 
 deposits are likely to become hard. They may readily be drawn off 
 through the bottom blow-out; but if there is much pressure in the 
 boiler, the blow-out valve should be opened only for a very short time. 
 If a considerable amount of water js blown out while the boiler is still 
 very hot, a large part of this precipitation is likely to be baked onto the 
 tubes and interior of the boiler in a manner that defies removal. Short 
 
86 BOILER ACCESSORIES 
 
 and frequent blowings will accomplish the desired result; for while 
 the boiler is in action these precipitates are more or less in motion, and 
 frequent blowing will keep the boiler clear. Oil and various organic 
 matters rising to the surface can easily be removed by frequently 
 opening the surface blow-out. 
 
 Sulphate of Lime. This troublesome salt, like the carbonate of 
 lime, is precipitated with a rise of temperature; and at 280 F., none 
 is left in solution. This sediment is likely to form a hard, adhering 
 scale ; but if a little carbonate of soda, or soda ash, is introduced with 
 the feed water, calcium carbonate .is precipitated in the form of a 
 white powder which can be readily washed out. The carbonate of 
 soda should be introduced at regular intervals, a portion of it being 
 dissolved in water which can be mixed with the feed in the hot well. 
 As little soda as possible should be used, as it is likely to cause priming 
 and foaming. The hardness of the scale formed by the sulphate of 
 lime depends on the other impurities in the water and on the tempera- 
 ture ; and consequently the amount of soda that can safely be used can 
 be determined only by trial. Ammonium chloride, commonly called 
 sal-ammoniac, is sometimes used to break up these lime compounds, 
 but is not always desirable, as it may break up the chlorides if other 
 conditions are right, thus forming free chlorine, which attacks the 
 boiler. 
 
 Carbonate of Magnesia is seldom found in such large quantities 
 as calcium salts. Like the carbonate of lime, it is precipitated in hot 
 water. If there is any oil or organic matter present, it is likely to 
 form an injurious precipitation. 
 
 Iron Salts form a reddish incrustation which is very injurious to 
 boiler-plates. B rakish water containing chloride of magnesium is 
 also injurious; for, when heated, the chloride decomposes, forming 
 magnesia and hydrochloric acid, the latter rapidly corroding iron. 
 
 A piece of thick scale broken from the plates of the boiler, will 
 show a series of layers of various thickness, some of them crystalline 
 and some amorphous. Between these hard layers are frequently 
 found layers of soft or earthy matter. 
 
 Nothing definite is known in regard to the loss of heat caused by 
 scale on heating surfaces, for there are too many circumstances to be 
 considered to admit of exact calculation. It has been stated that a 
 layer T Y inch thick in the tubes of multitubular boilers, is equivalent 
 
BOILER ACCESSORIES 87 
 
 to a loss of from 15 to 20 per cent of fuel. The loss increases rapidly 
 with the thickness of the scale. A uniform coating of scale is not 
 nearly so harmful as irregular deposits, for in the latter case the evil 
 effects of overheating are likely to be produced, and overheating will 
 result where it is least suspected. 
 
 Prevention. Incrustation may be prevented by precipitating the 
 scale-forming substances before the feed -water reaches the boiler, 
 by the introduction of chemical compounds to neutralize the evil 
 effects, or by removing the sediment before it becomes hard. Scale 
 may, of course, be removed by hand from the interior of the boiler ; but 
 this is a slow and tedious process. One of the chief objections to 
 removing scale by hand is that the surfaces of the boiler are likely to 
 become abraded by the chipping tools, and this offers excellent oppor- 
 tunity for pitting and local corrosion to set in. 
 
 Scale has sometimes been removed by blowing the boiler off at 
 comparatively high pressure, and then filling it with cold water. This 
 causes a severe contraction of the plates, and is likely to loosen the 
 scale; but it will at the same time cause serious injury to the boiler, 
 and is a practice that should not be tolerated. 
 
 After the impurities are deposited in the boiler, they may be 
 removed by the blow-out apparatus; and if it is possible to "lay off" 
 the boiler occasionally, it should be allowed to cool down slowly, and 
 then the water may be drawn off and the boiler properly washed out. 
 A considerable amount of heat is abstracted from the boiler by fre- 
 quent blowing-off, and this is a matter of direct loss, but it is nothing 
 like so much as would be caused by the formation of scale. 
 
 Water may be purified to a certain extent by passing it through 
 a purifier before allowing it to enter the boiler. The carbonate and 
 sulphate of lime are precipitated at the same time that the water is 
 heated. The purifier was referred to under the topic of "Feed- 
 \Yater Heaters." The use of soda for the neutralization of sulphate 
 of lime has already been spoken of; but various compounds are on 
 the market for overcoming the evil effects of other solids; and it is 
 possible, by an analysis of the feed water, to prescribe a boiler com- 
 pound that will give satisfactory results. Cheap compounds, sold 
 without reference to the analysis of the feed -water, should be avoided. 
 Caustic soda may be used instead of the carbonate, but should be used 
 in small quantities. A rapid circulation of the water will prevent the 
 
88 BOILER ACCESSORIES 
 
 formation of scale, the sediment being swept from the tubes or shell 
 into the mud-drum, whence it may be blown off. This is one of the 
 chief advantages claimed for water-tube boilers. 
 
 Zinc plates have frequently been used to prevent corrosion and 
 incrustation. The brass fittings are likely to set up a galvanic action 
 with the steel plates; but if the zinc is put in, it will be acted upon 
 instead of the iron, which otherwise might be rapidly wasted. It is 
 claimed that this galvanic action prevents the formation of scale by 
 liberating hydrogen at the exposed surfaces. The zinc neutralizes 
 the free acids by combining with them, and takes the place of iron 
 in causing precipitation of copper salts when present. 
 
 Kerosene oil is used to a considerable extent to prevent the forma- 
 tion of scale and to assist in its removal. It breaks up and loosens 
 hard scale, and prevents its formation. About one quart a day is 
 sufficient for each 100 horse-power of the boiler. 
 
 BOILER EXPLOSIONS 
 
 Safety is one of the first requisites in a steam boiler, and must be 
 assured not only by proper design in the beginning, but by subsequent 
 care and proper maintenance. The evil effects of corrosion and 
 incrustation have been clearly shown; and it is apparent that a boiler 
 which has suffered materially from either cause is not in condition to 
 stand full steam pressure. Since the explosion of a boiler, especially 
 in a city or a factory, is likely to prove fatal to many people and to 
 cause the destruction of considerable property, not only by the ex- 
 plosion itself but also by fire, which almost invariably follows such an 
 occurrence, it is impossible to lay too great emphasis on the necessity 
 of seeing that the boiler is in proper working condition. 
 
 All boilers must be carefully tested land boilers, by the State 
 Inspectors; marine boilers, by the United States Inspectors. The 
 boilers are carefully examined inside and outside, and subjected to a 
 hydraulic pressure test 50 per cent greater than the designed pressure 
 of steam; and if there is the slightest sign of pitting or corrosion, the 
 boiler-plates may be drilled and the thickness calipered, the hole being 
 refilled by a proper plug. If a boiler passes inspection, a subsequent 
 explosion will probably be the result of mismanagement, although 
 inspection is not infallible. 
 
BOILER ACCESSORIES 89 
 
 The owner of the boiler is usually held liable in case of explosion; 
 but may protect himself from financial loss by insurance against 
 accident in any of the boiler insurance companies. If so insured, the 
 Insurance Inspector, as well as the State Inspector, examines the 
 boiler; and there is consequently less likelihood of an explosion, for 
 an insurance inspector will naturally be exceedingly careful in th? 
 interests of his company. 
 
 The damage done by an explosion is due to the energy stored in 
 the hot water, which energy can be calculated by thermodynamic 
 methods. If a boiler contains a large quantity of water at high pres- 
 sure, and that pressure is suddenly relieved, as would happen in case 
 of rupture, a considerable portion of this large volume of water will 
 be turned instantly into steam, and the resulting explosion will ensue. 
 
 When a fracture starts in a boiler-plate, the steam escaping 
 through the rent or opening tends to diminish the pressure rapidly 
 within the boiler; and this causes the rapid formation of a large 
 amount of steam. It must be remembered that the water in the boiler 
 at high pressure is held in the form of water only because of the high 
 pressure exerted on it. If this pressure is relieved, large quantities of 
 water will evaporate into steam at once, without the application of 
 further heat. This almost instantaneous formation of a large quantity 
 of steam prevents the boiler pressure from dropping, and the fracture 
 naturally widens. The larger the body of hot water, the greater the 
 disaster. This accounts for the relative safety of water-tube boilers. 
 The division of the water in such a boiler into small masses in different 
 sections, prevents a violent explosion. Should a water tube burn 
 out, probably nothing more serious would happen than the rapid 
 escape of a considerable quantity of steam, which might fill the boiler- 
 room, drive out the attendants, and ultimately cause the destruction 
 of the boiler because of the absence of water together with a hot fire. 
 It would be necessary for several water tubes to burst at once in order 
 that there should be serious damage from such an accident. 
 
 Energy. The available energy in one pound of hot water at 
 150 Ibs. absolute pressure and 358 R, is about 42,800 foot-pounds; 
 that is, it is sufficient to move one pound nearly eight miles; and if at 
 250 Ibs. pressure, it has sufficient - energy to move it nearly twelve 
 miles. This energy may be determined somewhat as follows: From 
 the table of the properties of saturated steam, given in the back of the 
 
90 BOILER ACCESSORIES 
 
 book, it is seen that at 150 Ibs. absolute pressure (approximately 135 
 gauge), the temperature is 358.26 F. The heat contained in a pound 
 of hot water at this temperature will be 330 B. T. IL, equivalent to 
 330 X 778 = 256,740 foot-pounds. This represents the total heat 
 energy in one pound of hot water at boiler pressure; but since one 
 pound of steam at atmospheric pressure contains very many more 
 heat units than a pound of water at 150 Ibs, -pressure, it is apparent 
 that only a portion of this water can evaporate into steam, the balance 
 remaining as hot water. About 17 per cent of the total energy will be 
 thus available in vaporizing the water into steam; or, approximately, 
 42,800 foot-pounds per pound of water will be developed. The 
 remaining heat is in the form of hot water. 
 
 A cylindrical boiler 5 feet in diameter and 16 feet long is likely to 
 contain about 6,600 pounds of water and 22 pounds of steam. Neg- 
 lecting the energy of the steam, which is relatively small, the energy 
 in the water due to its expansion from water at boiler pressure into 
 steam at atmospheric pressure, will be approximately 6,600 X 42,800 
 = 282,480,000 foot-pounds, or 141,240 foot-tons. 
 
 A marine boiler 13 feet in diameter and 12 feet long ,would develop 
 approximately twice this energy, which would be about equivalent 
 to the energy developed by the explosion of a ton of gunpowder. The 
 explosion of one boiler on a modern battleship would develop sufficient 
 power to lift the ship completely out of the water. Of course it must 
 be realized that a large part of this energy is lost, and considerable is 
 consumed in the destruction of the boiler itself, which leaves but a 
 comparatively small amount to be expended in wrecking the im- 
 mediate surroundings; but it nevertheless is a fact that the energy 
 developed in the explosion of a large boiler is almost beyond the power 
 of comprehension. 
 
 Causes of Explosions. Boiler explosions are usually the 
 result of low water, grease, or scale. The two latter, by preventing 
 the transmission of heat from the water, are likely to cause undue 
 overheating of the furnaces or tubes, which may result in their collapse; 
 these two causes grease and scale have been discussed under the 
 subject of " Incrustation." 
 
 Low water may be caused by failure of the water glass to indicate 
 properly the amount of water in the boiler, or by failure of the feed 
 pump to work properly. 
 
BOILER ACCESSORIES 91 
 
 Safety-valves have been known to be rusted to their seats so 
 tightly that they failed to work at the proper time. 
 
 It is seldom that a boiler can fail as the result of defective design, 
 for the laws in regard to construction, especially of marine boilers, are 
 very definite. Defective workmanship or material, however, cannot 
 be easily discovered; and it is possible that corrosion or incrustation 
 may take place locally, without being readily detected; and, indeed, 
 boiler-plates may even be tapped, and their thickness calipered^ 
 without discovering small local weaknesses which later may cause 
 disaster. Minute fractures which escaped the Inspector's detec- 
 tion have later become serious. The majority of explosions can 
 undoubtedly be traced to mismanagement in either care or operation. 
 
 Defective Design. If a boiler is improperly set; if the stays are 
 too small, too few, or cut or bent to clear floats, pipes, etc., danger is 
 likely to result therefrom. All manholes, targe handholes, or domes 
 should be strengthened with a reinforcing plate to make up for the 
 material cut out. If the boiler is set too rigidly on its seating, without 
 proper provision for its expansion, trouble is likely to follow. A 
 defective water circulation is likely to cause excessive incrustation and 
 unequal expansion of the plating, which is liable to open seams and 
 produce fractures in the plates. 
 
 Deterioration. The strength of a boiler is likely to be impaired 
 by fractures, general corrosion, pitting, or grooving. But external 
 corrosion is the cause of many disasters. It proceeds unnoticed iix 
 many -eases, and rupture may occur when least expected. In the dis- 
 cussion of "Corrosion," it was shown that improper setting of the 
 boiler would cause or at least aggravate external corrosion; and that, 
 on account of the close setting of the boiler, it was not easy to get at 
 the plates to examine them. The strength of a boiler originally suf- 
 ficient to sustain high pressure may become suddenly reduced by over- 
 heating or over-straining, either of which weakens the plates. Over- 
 heating may be caused by poor circulation, lack of water, or the accum- 
 ulation of sediment or scale. Over-straining is caused by sudden 
 cooling and contraction, or equally by sudden expansion. In starting 
 the fire in a Scotch boiler or, in fact, in any boiler with a large quan- 
 tity of water care must be taken that the fire is started slowly, or the 
 boiler, becoming overheated locally, will develop excessive strains. 
 
92 BOILER ACCESSORIES 
 
 Dejects of Workmanship. Defective workmanship is not of so 
 frequent occurrence under present conditions as formerly, when many 
 defects used to be produced by careless punching of plates; but for 
 most boilers, and for all marine boilers at present, punching is pro- 
 hibited; the holes must be drilled, and the plate edges planed and 
 carefully calked. A rigid inspection of material is required, and there 
 seems little danger of unsatisfactory work. Cheap boilers may of 
 course be subject to various defects, but a good boiler should be free 
 from such troubles. Material may be defective and may not be 
 readily detected; but the careful tests now required, especially in 
 marine work, reduce these possibilities to a minimum. 
 
 Mismanagement. The pressure in a steam boiler may rise 
 above that at which the safety-valve has been set to operate, because of 
 corrosion or overloading of the valve. Stop-valves are sometimes 
 placed between the boiler and the safety-valve; but this practice 
 should be condemned, as it is possible that the stop-valve may be 
 closed when the fireman thinks the safety-valve is open to the boiler 
 pressure. If the size or lift of the safety-valve is too small, steam may 
 be generated faster than it can escape, in which case the pressure will 
 rise in spite of the safety-valve. It has been claimed that the blowing- 
 off of the safety-valve when the boiler is under excessive pressure may 
 be the cause of starting an explosion; but the reason why this should 
 be so does not seem to be especially clear, and it seems to be improb- 
 able if the opening of the safety-valve is sufficient to cause a reduction 
 in pressure. Safety-valves have sometimes been loaded down tem- 
 porarily to prevent leakage at working pressure; but such a practice 
 is little short of criminal. If a safety-valve leaks, it should be re- 
 ground, but under no circumstances should the weight on the lever be 
 altered. 
 
 It is a common idea that when the furnace plates become very 
 hot, perhaps heated to redness, due to a lack of water, and the feed is 
 turned on, a violent explosion is sure to follow. Experiments show 
 that when a piece of wrought iron is heated to redness and plunged 
 into a weight of water three or four times greater than that of the iron, 
 a comparatively small quantity of steam is disengaged. There is no 
 reason to believe that this quantity would be greater if the iron were 
 in the form of a boiler than in the form of a plate. If a small quantity 
 of water were admitted to hot plates, the danger would 
 
BOILER ACCESSORIES 93 
 
 be greater; and while a boiler under this condition might explode, 
 the comparatively small quantity of water in it would make the re- 
 sulting danger much less than if the boiler were under working con- 
 ditions. 
 
 The following experiments illustrate the action of cold water on 
 hot plates. A boiler 25 feet long and 6 feet in diameter was heated 
 red hot and the feed turned on. No explosion occurred ; but the sud- 
 den contraction of the overheated plates caused the water to pour out 
 in streams at every seam and rivet-hole as far as the fire-mark extended. 
 In another instance, the water was almost entirely drawn off while the 
 fires were burning briskly. When the remaining water had been con- 
 verted into steam and all the fusible plugs melted out, water at the rate 
 of 28 gallons per minute in a series of fine jets was played on the hot 
 plates. Such treatment may ruin a boiler for further service, though 
 the boiler may not explode. 
 
 That a tough paper or cloth is easily torn when once a tear is 
 started, is a well-known fact. Similarly a boiler-plate may be rup- 
 tured at slight pressure if a fracture has been started. 
 
 The position of the fracture or hole has a great influence on the 
 results. In case a large rent occurs at the top of a cylindrical boiler, 
 the steam and hot water may blow out of the hole ; and the boiler, if 
 strongly enough seated to stand the reaction, will remain on its seat. 
 The damage to the boiler would be slight. But suppose the same rent 
 were situated on the under side of the boiler near the ground or floor; 
 the effect would be very different, the reaction of the escaping steam 
 would probably blow the whole boiler through the roof. 
 
 Investigation. When an explosion occurs, it should be investi- 
 gated, not only to fix the responsibility where it belongs, but also to 
 provide for and take means to prevent future disasters. It has been 
 customary to attribute all explosions to low water, since it is an easy 
 way to throw the responsibility from the makers or owners upon the 
 fireman, who, even if living, cannot defend himself. In the investi- 
 gation of an explosion, the weights, shapes, positions, and directions 
 of the scattered pieces should be noted, so that their original places 
 may be known. The original size and shape of the boiler and of the 
 fittings should be known as accurately as possible. The primary rent 
 may be discovered from comparison and from deductions of the 
 directions taken by the heavier pieces. Light pieces will generally 
 
94 BOILER ACCESSORIES 
 
 take the direction of the escaping steam, while the heavy parts take an 
 opposite direction, that of the reaction. A careful examination of the 
 pieces, noting the age of fractures, thickness of plates, amount of 
 corrosion, condition of plates, etc., will generally show the cause. A 
 test of the plates will in many cases show any softening or yielding to 
 the pressure and excessive thinness caused by bulging. 
 
 Prevention. The means taken to prevent boiler explosions 
 from most of the above-mentioned causes, have already been given. 
 It is of primary importance that at the start only a well-designed and 
 well-made boiler should be used. The matter of type is not of so 
 much importance; but it is well to use a sectional boiler in large cities 
 or in buildings where many people are employed. There are many 
 methods, some of which have been discussed, that are taken to pre- 
 vent deterioration by corrosion, fracture, etc. Proper setting is of 
 great importance in this matter. Mishaps from mismanagement 
 may be greatly lessened by the employment of licensed attendants. . 
 A boiler should never be in the hands of a man who is not thoroughly 
 competent to run it. The most effective method to prevent explosions 
 is the law of the State, compelling regular, thorough inspection and 
 licensed firemen. The inspection by the Boiler Insurance companies 
 is also an efficient method. 
 
 During a period of eleven and one-half years, 70,000 boilers were 
 inspected by Boiler Insurance companies. It was estimated that there 
 were 140,000 in use during that time. Of the inspected boilers, there 
 were 23 explosions and 50 collapses, resulting in 27 deaths from ex- 
 plosions, and 28 deaths from collapses. The explosion rate was 1 in 
 11,000; and the death rate, 1 in 14,600. The uninsured boilers did 
 not make so good a showing, the death rate being 1 in 5,000 boilers, 
 or about 3 times as high as among the insured boilers, 
 
 FUEL 
 
 There are various kinds of fuel used in steam production, loca- 
 tion, cost, and the exigencies of the case being the deciding factors. 
 Usually the kind of fuel is determined upon, and the boiler designed 
 with that end in view. Sometimes, however, the fuel must be adapted 
 to the boiler. 
 
 Coal. Coal is not only the most important fuel, but in many 
 localities the only one available. It is of vegetable origin, being the 
 
BOILER ACCESSORIES 
 
 95 
 
 long-decayed product of ancient forests. Frequently it occurs so 
 mixed with earthy matter as to be of little value; but the supply of 
 good coal is still abundant, and likely to be so for some time to come. 
 
 The most important elements in coal are hydrogen, producing 
 62,000 B. T. U. per pound, and carbon, producing 14,500 B. T. U. 
 per pound. Although several coals may have the same total per- 
 centage of combustible material and ash, the heat values may not be 
 the same, because heat value depends upon the amounts of hydrogen 
 and carbon they contain. The heat value of fuels is determined by 
 chemical analysis, or by calorimetric test, and varies for coal from 
 different localities. The following table is compiled from several 
 sources : 
 
 ANALYSIS AND HEAT VALUE OF VARIOUS COALS 
 
 
 
 
 POUNDS OF 
 
 KIND OF COAL 
 
 PER CENT 
 OP ASH 
 
 THEORETICAL 
 B. T. U. 
 
 WATER 
 EVAPORATED 
 PER POUND 
 
 
 
 PER POUND 
 
 (THEORETI- 
 
 
 
 
 CAL) 
 
 Penn. Anthracite 
 
 3.49 
 
 14,199 
 
 14.70 
 
 Penn. Anthracite 
 
 2.90 
 
 14,221 
 
 14.72 
 
 Peun. Cannel 
 
 15.02 
 
 13,143 
 
 13.60 
 
 Penu. Connellsville 
 
 6.50 
 
 13,368 
 
 13.84 
 
 Penn. Semi-bituminous 
 
 10.70 
 
 13,155 
 
 13.62 
 
 Penn. Brown 
 
 9.50 
 
 12,324 
 
 12.75 
 
 Kentucky Caking 
 Kentucky Canuel 
 Kentucky Lignite 
 
 2.75 
 2.00 
 7.00 
 
 14,391 
 15,198 
 9,326 
 
 14.89 
 16.76 
 9.65 
 
 Indiana Caking 
 
 5.66 
 
 14,146 
 
 14.64 
 
 Indiana Cannel 
 
 6.00 
 
 13,097 
 
 13.56 
 
 Maryland Cumberland 
 
 13.88 
 
 12,226 
 
 12.65 
 
 Arkansas Lignite 
 
 5.00 
 
 9,215 
 
 9.54 
 
 Colorado Lignite 
 
 9.25 
 
 13,562 
 
 14.04 
 
 Texas Lignite 
 
 , 4.50 
 
 12,962 
 
 13.41 
 
 Washington Lignite 
 
 3.40 
 
 11,551 
 
 11.96 
 
 In practice, no fuel gives its theoretical evaporation value. On 
 account of several losses that are inevitably incurred, heat is radiated 
 from, and conducted away by, the boiler setting. The admission of 
 too much air into the furnace, either through the doors or through 
 cracks in the setting, reduces the theoretical evaporation value. Im- 
 proper firing causes considerable loss; and errors in design, con- 
 struction, or setting reduce the efficiency. 
 
 The different kinds of coal are too numerous to be easily named, 
 but in general they may be classified as anthracite or bituminous, com- 
 
96 BOILER ACCESSORIES 
 
 monly called hard or soft respectively, of which there are various sub- 
 divisions. 
 
 Anthracite. Anthracite coal consists almost entirely of carbon, 
 but has a small amount of hydrocarbon. Good anthracite is lustrous, 
 hard, flinty, but breaks up easily under high temperature. It burns 
 with very little flame and smoke, and gives an intense heat. It does 
 not ignite so readily as the softer varieties of coal; but once started, 
 the fire requires less attention. It is an excellent fuel where the pro- 
 duction of smoke is a decided objection. 
 
 Semi=Anthracite. This is a coal between pure anthracite and 
 semi-bituminous. It is not so hard as anthracite, and burns more 
 freely. It is not so compact as anthracite, and burns with a short 
 flame, the anthracite having practically no flame. 
 
 Semi=Bituminous. This is the next softer grade of coal. It 
 burns more freely than either anthracite or semi-anthracite, contains 
 more volatile hydrocarbon, and is a valuable coal for steaming pur- 
 poses. 
 
 Bituminous. Bituminous coal forms by far the larger portion of 
 steam coal. It contains a large but varying amount of hyrocarbon or 
 bituminous matter. Unless fired with care, it will produce a consider- 
 able amount of smoke and clinkers. 
 
 Dry Bituminous. This is a black coal with a resinous luster. 
 It burns freely, and kindles with much less difficulty than the anthra- 
 cites. It is hard, but is easily splintered. When burning, it gives a 
 moderate amount of flame, with but little smoke, and does not cake. 
 It is found chiefly in Maryland and Virginia. 
 
 Caking Bituminous. This contains less carbon and more hydro- 
 carbon than the former class. It is not so black; is more resinous; 
 and, under intense heat, readily forms into a solid, pasty mass. Un- 
 less frequently broken up, this pasty mass forms a blanket over the 
 grate, and checks the draft. Caking bituminous is a valuable coal 
 for the manufacture of gas. It is mined chiefly in the Mississippi 
 valley. 
 
 Cannel. Cannel or long-flame bituminous coal produces a con- 
 siderable quantity of smoke. It is mined chiefly in Pennsylvania, 
 Indiana, and Missouri; and is a free-burning coal, with a strong 
 tendency to cake. It is largely used for open-grate purposes. 
 
 Lignite. Lignite, or brown coal is intermediate between coal and 
 
BOILER ACCESSORIES 97 
 
 peat. It is made up mostly of carbon, with some moisture and 
 mineral matter. Poor varieties are of little value. Good lignite 
 kindles with ease, and burns freely, but is likely to contain a con-- 
 siderable amount of water, and unless kept in a dry place will absorb 
 moisture. It is not a -very good fuel, but is used in some localities 
 where other varieties are more expensive. It comes largely from 
 Colorado, Texas, and Washington. 
 
 Peat. This is a form of fuel consisting of decayed roots, tree- 
 trunks, etc., and earthy matter. It is found in swamps and bogs, and 
 has been in process of decomposition a much shorter time than any 
 of the coals. It is cut out in blocks and dried. Peat has a specific 
 gravity of .4 to .5, but it can be compressed to a much greater density. 
 It is necessary that peat should be kept in a dry place, for it will readily 
 absorb moisture. 
 
 Coke. This is made by driving off by heat the hydrocarbon of 
 bituminous or semi-bituminous coals. It may be made in gas retorts, 
 as a by-product of gas production ; or it may be made in coking ovens, 
 the gas being the by-product. The latter form of coke is more valu- 
 able as a fuel. If the coal is very moist, or if steam is used in the coking 
 process, as in the manufacture of water gas, the sulphur is burned out. 
 Coke burns without flame; and, with a free supply of air, will make 
 an intensely hot fire. 
 
 Charcoal. Charcoal is practically never used for steam fuel, its 
 chief use being for household or manufacturing purposes. It is made 
 by evaporating the volatile matter from wood, either by partial com- 
 bustion or by heating in retorts. About 50 bushels of charcoal can be 
 obtained from a cord of wood. 
 
 Culm. This is a name given to refuse dust at the coal mines, 
 sometimes called slack. It can be bought at the mines at a very low 
 rate; but the cost of transportation prohibits its use except in the 
 immediate vicinity of the mines. On account of its fineness, it cannot 
 be burned in an ordinary grate, and is usually blown into the boiler 
 with a sufficient quantity of air, where it burns somewhat like a gas. 
 A grate beneath usually contains a moderate fire, which keeps the 
 culm well ignited and prevents the loss of any particles that might 
 otherwise drop out of the furnace. 
 
 Wood. There are two principal divisions of wood hardwood, 
 which is compact and comparatively heavy, such as oak, ash, and 
 
98 BOILER ACCESSORIES 
 
 hickory; and soft wood, which is of soft and porous texture and of less 
 specific gravity, such as pine, birch, and poplar. Wood contains 
 , considerable moisture, even if left to season in a dry place; and after 
 being thoroughly dried, it will absorb and retain from 10 to 20 per cent 
 of moisture. Kiln-dried wood contains nearly 8,000 B. T. U. per 
 pound, while the average wood, containing about 25 per cent of 
 moisture, has a heating value of about 6,000 B. T. U. 
 
 The chemical composition of different woods is nearly the same, 
 and pound for pound one class of wood contains about the same 
 heating value as another. Pine weighs about half as much as oak 
 per cubic foot, and a cord of such wood contains about half the heating 
 value that a cord of oak would contain. 
 
 Sawdust and shavings are frequently used as fuel in sawmills 
 and planing mills. This kind of fuel is blown into the furnace with 
 air from a fan, and makes an intense heat. A fine grate at the bottom 
 collects the burning embers, which might otherwise drop into the ash- 
 pan. In mills where sawdust and shavings are used, they are a by- 
 product. 
 
 Straw. Threshing machines through the West use straw almost 
 entirely for fuel. It gives an intense heat, furnishing 5,000 to 6,000 
 heat units per pound ; and this is a quick and easy way to get rid of it. 
 
 Bagasse is the fibrous portion of the sugar-cane left after the juice 
 has been extracted. In the modern process of sugar manufacture, 
 the cane is pressed so tightly that it is ready for fuel without further 
 treating. Under favorable conditions it forms an excellent fuel. The 
 pressed cane is a by-product which must in some way be got rid of. 
 It is usually fed into the furnace through an automatic hopper; or it 
 may be dumped in the fire-room and fed into the furnace by hand. 
 The furnace is constructed of brick, independent of the boilers; and 
 when bagasse is consumed at a high temperature, the oxygen contained 
 in it is nearly sufficient to satisfy the carbon and hydrogen, so that 
 little air from the outside is required. Such material, of course, 
 cannot be fed into an ordinary furnace. 
 
 Liquid Fuels. These consist of petroleum and its products, and 
 their use has become quite extensive in the last few years. The field 
 would undoubtedly be wider were there less difficulty in obtaining a 
 regular and constant supply. The greatest quantities of petroleum 
 oil are produced in the United States and Russia. Large quantities 
 
BOILER ACCESSORIES 
 
 99 
 
 are found on the Pacific Coast, especially in Southern California; and 
 in that section of the country, oil is used as fuel to a greater extent 
 than in the East, being largely used on tugboats, ferryboats, and loco- 
 motives. 
 
 The following, approximately, is the composition of petroleum: 
 Carbon 82 to 87 per cent. 
 
 Hydrogen 1 1 to 15 per cent. 
 
 Oxygen . r 5 to 6 per cent. 
 
 The theoretical heating power of petroleum is approximately 
 20,000 B. T. U. per pound/which is nearly half as. much again as 
 that of good coal. Oil has a further advantage over coal, in that no 
 unburned fuel necessarily passes through the furnace, and there is no 
 ash an important item in marine work. 
 
 The composition and specific gravity of petroleums vary con- 
 siderably, many of the lower grades being unsafe on account of their 
 low flash-point. 
 
 The fuel is fed into the furnace through an atomizer operated 
 either by steam or by compressed air. Several types of such de- 
 vices are shown 
 in Fig. 72. The 
 use of the oil as a 
 fuel can be readily 
 controlled by the 
 simple manipula- 
 tion of a valve; and 
 if the fire is once 
 regulated to pro- 
 duce the required 
 heat, it can be kept 
 at that point with 
 very little care. 
 The fire can be 
 started with slight 
 trouble, and can be extinguished instantly. The vaporizing efficiency 
 of oil is much greater than that of coal; and on the Pacific Coast, 
 where oil can be readily obtained, it is a much more economical fuel. 
 If burned properly, without too heavy an air-blast, there should be no 
 production of smoke. A considerable saving may be effected in the 
 
 
 C.Cha.mber Burner 
 Fig. 72. Types of Atomizers for Liquid Fuel. 
 
100 BOILER ACCESSORIES 
 
 fire-room force, one man being able to operate several burners. There 
 is, of course, danger from explosion, on account of vapor which 
 rises from the fuel; but if the fuel tank is thoroughly ventilated, there 
 is little danger from this source. 
 
 Oil fuel may be used to advantage in what is called mixed firing ; 
 that is, the oil may be sprayed onto the bed of burning coal. This 
 has been condemned by many engineers, but it has nevertheless gained 
 considerable headway, and, under proper conditions, has given satis- 
 factory results. It is beyond the scope of this work to go minutely 
 into the subject of oil fuel; but for further information the student is 
 referred to the reports of the Oil Fuel Boards of the U. S. Navy and of 
 the British Admiralty. 
 
 Gas. Gas has many advantages over any other kind of fuel. 
 There are four different varieties natural gas, coal gas, water gas, 
 and producer gas. Natural gas is used largely in the vicinity of Pitts- 
 burg, Buffalo, and some parts of Indiana, both for illuminating and 
 for steam purposes. Where natural gas is plentiful, it is by far the 
 cheapest fuel that can be used. 
 
 Coal gas, made by the distillation of coal, and water gas, obtained 
 by the decomposition of steam by incandescent carbon, have been 
 used both for lighting and for fuel ; but in most cases these gases may 
 be used to greater economy directly in the cylinder of a gas engine 
 than as fuel under a steam boiler. The same may be said of pro- 
 ducer gas, which is made by blowing steam and air through incandes- 
 cent coal. 
 
 The relative values of these gases for evaporation, are shown in 
 the following table: 
 
 EVAPORATIVE POWER OF GASES 
 
 NATURAL GAS COAL GAS WATER GAS PRODUCER GAS 
 Cubic feet of gas 1,000 1,000 1,000 1,000 
 
 Pounds of water evap- 
 orated 893 591 262 115 
 
 Experiments in Pittsburg have shown that 1,000 cubic feet of 
 natural gas equals 80 to 133 pounds of coal. The coal used in the com- 
 parison varied from 12,000 to 13,000 B. T. U. per pound. 
 
 The Western Society of Engineers has stated that one pound of 
 good coal is equivalent in heating value to 1\ cu. ft. of natural gas. 
 
BOILER ACCESSORIES 101 
 
 As in the case x>f petroleum, the economy of burning gaseous fuels 
 depends upon the locality. 
 
 Artificial Fuels. The waste of charcoal, coal, sawdust, etc., is 
 often pressed into cakes or briquettes, by means of some adhesive 
 mixture, with compression. Wood tar, coal tar, and clay are used, ac- 
 cording to convenience. These cakes are compact, can be stored in 
 small space, and are used where good fuels are difficult to obtain. 
 
 STEAM BOILER TRIALS 
 
 The object of a boiler trial is to determine the quantity and 
 quality of steam that the boiler will supply under given conditions, 
 the horse-power of the boiler, the amount of fuel it takes to make the 
 required steam, and its efficiency. 
 
 The quantity of steam is taken as the amount of water evaporated, 
 which j of course, is the total amount fed into the boiler during the test 
 the water-level being the same at the beginning and the end. 
 
 The quality of the steam can be determined by some form of 
 calorimeter already described; and the efficiency is the ratio of the 
 heat units utilized in evaporating the water to the total heat supplied to 
 the boiler. The heat utilized in evaporation can be found by multi- 
 plying the number of pounds of feed-water by the number of heat 
 units required to change the water at the temperature of the feed into 
 steam at gauge pressure. The heat units supplied can be determined 
 by carefully weighing the fuel used during the test, and deducting the 
 amount of ash and unburned fuel going through the grates, with 
 proper allowance for moisture, multiplying the result by the total heat 
 of combustion of the fuel. The heat of combustion can be obtained 
 by calculation, or by means of a fuel calorimeter. 
 
 Under a short test the boiler must be in good working order and 
 fired for some hours before the beginning of the test, so that the brick- 
 work and chimney may be thoroughly heated. Shortly before the 
 test is begun, the fire may be allowed to burn low; and by reducing 
 the amount of steam taken from the boiler, the pressure can be kept 
 constant. The fire may then be drawn, the grate cleaned, and a new 
 fire quickly started, with wood and fresh coal. Toward the end of the 
 test the fire may be allowed to burn low, and at the close may be drawn 
 and quenched with water, the unburned fuel being allowed for. In 
 a long test of twenty-four hours or more, this is not necessary. 
 
102 BOILER ACCESSORIES 
 
 If the boiler is fed by a steam pump, the pump should be run b) 
 steam taken from some other boiler, if convenient; if not, the amount 
 of steam used by the pump must be determined and allowed for. If 
 the feed-water is supplied by an injector, it will take steam .from the 
 boiler itself. About 2 per cent of this steam is consumed in forcing the 
 water into the boiler, the remainder going to heat the feed-water. 
 
 During the boiler trial, observations of temperatures and pres- 
 sures should be made at the same time, and at about 15-minute inter- 
 vals. In order to obtain the result of the test, the following must be 
 known : 
 
 1. Amount (in pounds) of coal burned, and number of pounds of ashes 
 left; 
 
 2. Number of pounds of water pumped into boiler; 
 
 3. Temperature of feed- water when it enters boiler; 
 
 4. Pressure of steam in boiler; 
 
 5. Quality of steam discharged from boiler that is, the per cent of 
 moisture in the steam. 
 
 The coal for the furnace can be conveniently weighed in barrels, 
 and may be fired directly from these barrels or dumped on the fire- 
 room floor. The barrels should be carefully weighed when full and 
 empty, and the time recorded, so that there may be no possibility of 
 counting one barrel twice or omitting any. The rate of combustion 
 will be fairly uniform, and the calculations at the times of emptying 
 the barrel will fairly indicate whether or not an error has been made. 
 Any unburned coal should be weighed, and the amount subtracted. 
 
 The condition of the fire for a twenty-four-hour test should be the 
 same at the beginning and the end. This condition is estimated by 
 the eye; and unless great care is used, an appreciable error is likely 
 to be made If the coal consumption is 15 to 20 Ibs. per square foot of 
 grate surface, an error of two inches in estimating the thickness of the 
 fire may cause an error of as much as 2 per cent in the final results. 
 The wood used in starting the fire should be carefully weighed, 
 and may be considered as equal to -fa of the same weight of coal. 
 The clinker and ashes should be carefully collected and weighed, and 
 a sample of the ashes examined to obtain the amount of unburned 
 fuel. 
 
 There are several ways of determining the amount of water 
 pumped into the boiler. The best method is to weigh it in tanks or 
 barrels set upon standard scales. There should be two or more 
 
BOILER ACCESSORIES 103 
 
 barrels of sufficient size, so that the filling and emptying may not be 
 hurried. They should be set high enough to discharge readily into 
 the tank or hot well from which the feed-water is drawn. The valves 
 should be large and should open quickly, so that the emptying may 
 not be delayed. If barrels are used, they should be numbered, and the 
 weight of each accurately noted, so that there may be no mistake in de- 
 ducting the weight of a barrel from the total weight of barrel and water. 
 When one barrel is being emptied, the other may be filled. The 
 weigher must use care and intelligence; otherwise he may become 
 confused in his records, as in a boiler of considerable size the barrels 
 fill and empty rapidly. At the beginning of the test, the level of the 
 water in the hot well should be recorded, and at the end of the test 
 should be brought to the same mark. If inconvenient to weigh the 
 water, it may be measured by a meter ; but if a meter is used, it should be 
 tested and its error determined under like conditions of temperature 
 and pressure. The feed-water should be free from air, as otherwise 
 too large a meter reading will be recorded. 
 
 The level in the water-glass of the boiler should be carefully noted 
 at the beginning and end of the test. If possible, the level should be 
 constant throughout the test; and if there is any difference between 
 the beginning and the end, due allowance should be made for it. 
 
 The temperature of the feed -water can be taken best by means of a 
 thermometer in a cup filled with oil screwed into the feed-pipe near the 
 check-valve. If the temperature is nearly constant, readings at 15- 
 minute intervals will suffice; otherwise readings should be taken 
 every five minutes. 
 
 The steam pressure shown by the gauge should be as nearly con- 
 stant as possible throughout the test, and should be practically the 
 same both at the beginning and at the end. Gauge readings should be 
 recorded every 15 minutes, and the fireman should see that the pres- 
 sure is constant. The gauge should be tested, and corrected if neces- 
 sary. 
 
 Barometric readings should also be taken, two or three being 
 sufficient for a ten-hour run. These readings, in inches, may be made 
 to indicate pounds pressure by multiplying by .491, this being the 
 weight of one cubic inch of mercury. If the trial is on a vertical boiler 
 which furnishes superheated steam because of the heat being in con- 
 tact with the tubes above the water-level, both the pressure-gauge and 
 
104 BOILER ACCESSORIES 
 
 the thermometer should be used, so that the amount of superheating 
 can readily be found by subtracting the temperature due to pressure 
 (obtained from the steam tables) from the temperature readings. 
 
 The quality of steam can readily be determined by a calorimeter. 
 If there is sufficient steam space within the boiler, from 1 to 2 per cent 
 priming will generally result. If the steam space is inadequate, there 
 will be more priming. If more than 2 per cent priming is present, the 
 steam will blow white from the gauge-cocks when opened ; if less than 
 2 per cent, it will appear blue. 
 
 The above observations are of the more important class, and must 
 be taken. In addition to these, it is well to take samples of the flue gas 
 at intervals and from various places in the furnace or chimney, the 
 object being to determine whether there is a sufficient supply of air 
 admitted, or whether there is too much. The draft of the chimney 
 may be measured by means of a U-tube partially rilled with water, or 
 by a draft-gauge. 
 
 It is well to bear in mind that in making the boiler test the utmost 
 care must be used, both in taking observations and in recording them, 
 and in working up the results of the trial. A committee of the Ameri- 
 can Society of Mechanical Engineers has recommended a code of 
 rules for boiler trials, and the following standard form for recording 
 results. These are too voluminous for complete reproduction, and 
 they can be found in full in Vol. XXI of the Proceedings of the above 
 Society for the year 1900. The following code of rules is practically 
 an abstract of the above-mentioned code: 
 
 PRELIMINARIES TO A TEST 
 
 1. In preparing for and conducting trials of steam boilers, 
 the specific object of the proposed trial should be clearly defined and 
 steadily kept in view. 
 
 2. Measure and record the dimensions, position, etc., of grate 
 and heating surfaces, flues, and chimneys; proportion of air-space in 
 the grate-surface; kind of draught, natural or forced. 
 
 3. Put the boiler in good condition. Have heating surface 
 clean inside and out; grate-bars and sides of furnace free from clinkers; 
 dust and ashes removed from back connections; leaks in masonry 
 stopped; and all obstructions to draught removed. See that the 
 damper will open to full extent, and that it may be closed when desired, 
 
BOILER ACCESSORIES 105 
 
 Test for leaks in masonry by firing a little smoky fuel and immediately 
 closing damper. The smoke will escape through the leaks if there be 
 such. 
 
 4. Have an understanding with the parties in whose interest 
 the test is to be made, as to the character of the coal to be used. The 
 coal must be dry; or, if wet, a sample must be dried carefully, and a 
 determination of the amount of moisture in the coal must be made, 
 the calculation of the results of the test being corrected accordingly. 
 Wherever possible, the test should be made with standard coal of a 
 known quality. For that portion of the country east of the Alleghany 
 mountains, good anthracite egg coal or Cumberland semi-bituminous 
 coal may be taken as the standard for making tests. West of the 
 Alleghany mountains and east of the Missouri river, Pittsburg lump 
 coal may be used. 
 
 In all important tests, a sample of coal should be selected for 
 chemical analysis. 
 
 5. Establish the correctness of all apparatus used in the test 
 for weighing and measuring. These are: 1. Scales for weighing 
 coal, ashes, and water. 2. Tanks or water-meters for measuring 
 water. Water-meters, as a rule, should only be used as a check on 
 other measurements. For accurate work the water should be weighed 
 or measured in a tank. 3. Thermometers and pyrometers for taking 
 temperatures of air, steam, feed-water, waste gases, etc. 4. Pressure- 
 gauges, draft-gauges, etc. 
 
 6. Before beginning a test, the boiler and chimney should be 
 thoroughly heated to their usual working temperature. If the boiler 
 is new, it should be in continuous use at least a' week before testing, so 
 as to dry the mortar thoroughly and heat the walls. 
 
 7. Before beginning a test 3 the boiler and connections should 
 be free from leaks; and all water connections, including blow and 
 extra feed-pipes, should be disconnected or stopped with blank flanges, 
 except the particular pipe through which water is to be fed to the 
 boiler during the trial. In locations where the reliability of the power 
 is so important that an extra feed-pipe must be kept in position, and in 
 general when, for any other reason, water-pipes other than the feed- 
 pipes cannot be disconnected, such pipes may be drilled so as to leave 
 openings in their lower sides, which should be kept open throughout 
 the test as a means of detecting leaks or accidental or unauthorized 
 
106 BOILER ACCESSORIES 
 
 opening of valves. During the test the blow-off pipe should remain 
 exposed. 
 
 If an injector is used it must receive steam directly from the boiler 
 being tested, and not from a steam-pipe or from any other boiler. 
 
 See that the steam pipe is so arranged that water of condensation 
 cannot run back into the boiler. If the steam pipe has such an inclina- 
 tion that the water of condensation from any portion of the steam- 
 pipe system may run back into the boiler, it must be trapped so as to 
 prevent this water getting into the boiler without being measured. 
 
 8. A test should last at' least ten hours of continuous running, 
 and twenty-four hours whenever practicable. 
 
 9. The conditions of the boiler and furnace in all respects 
 should be, as nearly as possible, the same at the end as at the beginning 
 of the test. The steam pressure should be the same, the water-level 
 the same, the fire upon the grates should be the same in quantity and 
 condition, and the walls, flues, etc., should be of the same temperature. 
 To secure as near an approximation to exact uniformity as possible 
 in conditions of the fire and in temperatures of the walls and flues, 
 the following method of starting and stopping a test should be 
 adopted. 
 
 10. Standard Method. Steam being raised to the working 
 pressure, remove rapidly all the fire from the grate, close the damper, 
 clean the ash-pit, and as quickly as possible start a new fire with 
 weighed wood and coal, noting the time of starting the test and the 
 height of the water-level while the water is in a quiescent state, just 
 before lighting the fire. 
 
 At the end of the test, remove the whole fire, clean the grates.and 
 ash-pit, and note the water-level when the water is in a quiescent 
 state ; record the time of hauling the fire as the end of the test. The 
 water-level should be as nearly as possible the same as at the beginning 
 of the test. If it is not the same, a correction should be made by com- 
 putation, and not by operating pump after test is completed. It wil 
 generally be necessary for a time to regulate the discharge of steam 
 from the boiler tested, by means of the stop-valve, while fires are being 
 hauled at the beginning and at the end of the test, in order to keep 
 the steam pressure in the boiler at those times up to the average during 
 the test. 
 
 11. Alternate Method. Instead of the Standard method above 
 
BOILER ACCESSORIES 107 
 
 described, the following may be employed where local conditions 
 render it necessary : 
 
 At the regular time for slicing and cleaning fires, have them 
 burned rather low, as is usual before cleaning, and then thoroughly 
 cleaned ; note the amount of coal left on the grate as nearly as it can 
 be estimated ; note the pressure of steam and the height of the water- 
 level which should be at the medium height to be carried throughout 
 the test at the same time; and note this time as the time of starting 
 the test. Fresh coal, which has been weighed, should now be fired. 
 The ash-pits should be thoroughly cleaned at once after starting. 
 Before the end of the test the fires should be burned low, just as before 
 the start, and the fires cleaned in such a manner as to leave the same 
 amount of fire, and in the same condition, on the grates as at the start. 
 The water-level and steam pressure should be brought to the same 
 point as at the start, and the time of the ending of the test should be 
 noted just before fresh coal is fired. 
 
 12. Keep the Conditions Uniform. The boiler should be run 
 continuously, without stopping for meal-times or for rise or fall of 
 pressure of steam due to change of demand for steam. The draught, 
 being adjusted to the rate of evaporation or combustion desired before 
 the test is begun, should be retained constant during the test, by 
 means of the damper. 
 
 If the boiler is not connected to the same steam pipe with other 
 boilers, an extra outlet for steam with valve in same should be pro- 
 vided, so that in case the pressure should rise to that at which the 
 safety-valve is set, it may be reduced to the desired point by opening 
 the extra outlet, without checking the fires. 
 
 If the boiler is connected to a main steam pipe with other boilers, 
 the safety-valve on the boiler being tested should be set a few pounds 
 higher than those of the other boilers, so that in case of a rise in pres- 
 sure the other boilers may blow off, and the pressure be reduced by 
 closing their dampers, allowing the damper of the boiler being tested 
 to remain open, and firing as usual. 
 
 All the conditions should be kept as nearly uniform as possible, 
 such as force of draught, pressure of steam, and height of water. The 
 time of cleaning the fires will depend upon the character of the fuel, 
 the rapidity of combustion, and the kind of grates. When very good 
 coal is used, and the combustion not too rapid, a ten-hour test may be 
 
108 BOILER ACCESSORIES 
 
 run without any cleaning of the grates other than just before the 
 beginning and just before the end of the test. But in case the grates 
 have to be cleaned during the test, the intervals between one cleaning 
 and another should be uniform. 
 
 13. Keeping the Records. The coal should be weighed and 
 delivered to the fireman in equal portions, each sufficient for about 
 one hour's run; and a fresh portion should not be delivered until the 
 previous one has all been fired. The time required to consume each 
 portion should be noted, the time being recorded at the instant of 
 firing the first of each new portion. It is desirable that at the same 
 time the amount of water fed into the boiler be accurately noted and 
 recorded, including the height of the water in the boiler and the 
 average pressure of steam and temperature of feed during the time. 
 By thus recording the amount of water evaporated by successive 
 portions of coal, the record of the test may be divided into several 
 divisions, if desired, at the end of the test, to discover the degree of 
 uniformity of combustion, evaporation, and economy at different 
 stages of the test. 
 
 14. Priming Tests. In all tests in which accuracy of results is 
 important, calorimeter tests should be made of the percentage of 
 moisture in the steam, or of the degree of superheating. At least 
 ten such tests should be made during the trial of the boiler, or so many 
 as to reduce the probable average error to less than one per cent; 
 and the final records of the boiler test should be corrected according 
 to the average results of the calorimeter tests. 
 
 On account of the difficulty of securing accuracy in these tests, 
 the greatest care should be taken in the measurements of weights and 
 temperatures. The thermometers should be accurate within a tenth 
 of a degree; and the scales on which the water is weighed, to with' n 
 one-hundredth of a pound. 
 
 15. As each fresh portion of coal is taken from the coal-pocket, 
 a representative shovelful should be selected from it and placed in a 
 barrel or box, to be kept until the end of the trial, for analysis. The 
 samples should then be thoroughly mixed and broken. This sample 
 should be put in a pile, and carefully quartered. One quarter may 
 then be put in another pile,, and the process repeated until five or six 
 pounds remain. One portion of this sample is to be used for the 
 
BOILER ACCESSORIES 109 
 
 determination of the moisture and heating value; the other, for chemi- 
 cal analysis. 
 
 16. The ashes refuse should be weighed dry, and a sample 
 frequently taken to show the amount of combustible material passing 
 through the grate. To get a representative ash sample, the ash-pile 
 should be quartered as required for the coal. 
 
 17. The quality of the fuel should be determined by heat test, by 
 analysis, or by both. 
 
 18. The analysis of the flue gases is an especially valuable 
 method of determining the relative value of different methods of 
 firing or of different kinds of furnaces. Great care should be taken 
 to procure average samples, since the combustion of the gases mav 
 vary at different points in the flue ; and as the combustion of flue gas 
 is liable to vary from minute to minute, the sample of gas should be 
 drawn through a considerable period of time. 
 
 19. It is desirable to have a uniform system of determining and 
 recording the quantity of smoke produced. This is usually expressed 
 in percentages, depending upon the judgment of the observer. 
 
 20. In tests for the purpose of scientific research in which the 
 determination of all variables is desirable, certain observations should 
 be made which in general are not necessary such as the measure- 
 ment of air-supply, the determination of its moisture, the determina- 
 tion of the heat loss by radiation, the infiltration of air through the 
 setting, etc. but as these determinations are rarely undertaken, no 
 definite instructions are here given. 
 
 21. Two methods of defining and calculating the efficiency of 
 the boiler are recommended. They are: 
 
 Heat absorbed per pound of combustible 
 
 (1) Efficiency of the boiler = ^n ^~ ~T ~j t 
 
 Calorific value of one pound of combustible 
 
 Heat absorbed per. pound of coal 
 
 (2) Efficiency of boiler and grate = ~ = ^ 5 j .- 
 
 Calorific value of one pound of coal 
 
 The first of these is the one usually adopted. 
 
 22. An approximate statement of the distribution of the heating 
 value of the coal among the several items of heat utilized, may be 
 included in the report of a test when analyses of the fuel and chimney 
 gases have been made. 
 
 23. Record of the Test. The data and results of the trial 
 should be recorded in a systematic manner, according either to Table 1 
 
110 BOILER ACCESSORIES 
 
 (see Vol. XXI, Transactions of the American Society of Mechanical 
 Engineers), or Table 2, taken from those "Transactions." 
 
 TABLE 2 
 Data and Results of Evaporative Test 
 
 Arranged in accordance with the short form advised by the Boiler Test Committee 
 of the American Society of Mechanical Engineers, Code of 1899: 
 
 Made by on boiler, at 
 
 To determine 
 
 Kind of fuel 
 
 Kind of furnace 
 
 Method of starting and stopping the test (Standard or Alternate, Arts. X 
 
 and XI, Code) 
 
 Grate surface . . . . sq. ft. 
 
 Water-heating surface " " 
 
 Superheating surface " " 
 
 Total Quantities 
 
 1. Date of Trial 
 
 2. Duration of Trial hours 
 
 3. Weight of coal as fired Ibs. 
 
 4. Percentage of moisture in coal per cent 
 
 5. Total weight of dry coai consumed Ibs. 
 
 6. Total ash and refuse " 
 
 7. Percentage of ash and refuse in dry coal per cent 
 
 8. Total weight of water fed to boiler Ibs. 
 
 9. Water actually evaporated, corrected for moisture or 
 
 superheat in steam " 
 
 10. Equivalent water evaporated into dry steam from and 
 
 at 212 F " 
 
 Hourly Quantities 
 
 11. Dry coal consumed per hour Ibs. 
 
 12. Dry coal per square foot of grate surface per 
 
 hour " 
 
 13. Water evaporated per hour corrected for 
 
 quality of steam " 
 
 14. Equivalent evaporation per hour from and 
 
 at 212 F " 
 
 15. Equivalent evaporation per hour from and at 
 
 212 F. per square foot of water-heating 
 
 surface " 
 
 Average Pressures, Temperatures, Etc 
 
 16. Steam pressure by gauge Ibs. per sq. in. 
 
 17. Temperature of feed-water entering boiler degrees 
 
 18. Temperature of escaping gases from boiler 
 
 19. Force of draught between damper and boiler. . . ins. of water 
 
 20. Percentage of moisture in steam, or number or 
 
 degrees of superheating .per oent or degrees 
 
BOILER ACCESSORIES 
 
 111 
 
 Horse-Power 
 
 21. Horse-power developed (item 14 -~ 34^) H. P. 
 
 22. Builder s rated horse-power " 
 
 23. Percentage of builder's rated horse-power developed . . .per cent. 
 
 Economic Results 
 
 24. Water apparently evaporated under actual conditions per 
 
 pound of coal as fired (item 8 -f- item 3) Ibs. 
 
 25. Equivalent evaporation from and at 212 F. per pound 
 
 of coal as fired (item 10 -f- item 3) " 
 
 26. Equivalent evaporation from and at 212 F. per pound of 
 
 dry coal (item 10 -j- item 5) " 
 
 27. Equivalent evaporation from and at 212 F. per pound of 
 
 combustible [item 10 ~ (item 5 item G)] " 
 
 If items 25, 26, and 27. are not corrected for quality of steam, the fact should be 
 stated. 
 
 Efficiency 
 
 28. 
 29. 
 30. 
 31. 
 
 Calorific value of the dry coal per pound B. T. IT. 
 
 Calorific value of the combustible per pound " 
 
 Efficiency of boiler (based on combustible) per cent. 
 
 Efficiency of boiler, including grate (based on dry coal) " 
 
 Cost of Evaporation 
 
 Cost of coal per ton of - Ibs. delivered in boiler-room $ 
 
 Cost of coal required for evaporating 1.000 Ibs. of water 
 
 from and at 212 F 
 
 A log of the test should be kept on properly prepared blanks 
 containing headings as follows: 
 
 TABLE NO. 
 
 
 PRESSURES 
 
 TEMPERATURES 
 
 FUEL, 
 
 FEED- WATER 
 
 
 Fn 
 
 &c 
 
 O> 
 
 "I 
 
 o 
 
 
 1 
 
 
 
 
 
 (3 
 
 
 TIME 
 
 Baromet 
 
 Steam ga 
 
 c3 
 
 SO 
 
 Q 
 
 External 
 
 Boiler-ro 
 
 I 
 
 e3 
 
 1 
 
 2 
 3 
 
 s 
 
 Pounds 
 
 1 
 
 
 
 Hi 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 FIRING 
 
 Starting the Fire. The fireman should first ascertain the water- 
 level; as the gauge-glass is not always reliable, on account of im- 
 purities, foam, etc., the gauge-cocks should be tried. In a batter}' 
 
112 BOILER ACCESSORIES 
 
 of boilers, the gauge-cocks of each should be opened, for the water 
 may not stand at the same level in each. The safety-valve should be 
 raised slightly from its seat. If the fire has been banked over night, 
 open the draughts, and rattle down the ashes and clinkers from the 
 grate. In case the fire has been allowed to go out, a new one may be 
 started if the gauge-glass shows the proper amount of water, and the 
 valves work well. 
 
 If anthracite coal is used, first throw a thin layer of coal all over 
 the grate, then place a piece of wood across the mouth of the furnace 
 just inside the door and lay other pieces of wood at right angles to 
 the cross-piece with the ends resting on it. This allows a space under 
 the wood for air. Now throw on coal until the wood is covered. The 
 fire may be started with oily cotton waste, shavings, or any combustible 
 material. 
 
 Keep the furnace door open and the draught-plate closed until 
 the wood is burning freely, which causes the flame to pass over and 
 through the coal and to ignite it. The fire is then spread or pushed 
 back evenly over the furnace bars; the furnace door closed; the ash- 
 pit door opened, as the draught requires; and more coal added when 
 necessary If bituminous coal is used, do not spread a thin layer over 
 the grate bars under the wood. 
 
 The fire at the start should be slow, to cause gradual, uniform 
 heating of the water and various parts of the boiler. If steam is 
 raised too rapidly, enormous strains are set up, due to unequal expan- 
 sion, thereby causing leakage at joints, and perhaps rupture. 
 
 If the boiler is of the water-tube type, steam may be raised more 
 rapidly, because the amount of water is less and the joints are usually 
 placed at some distance from the intense heat of the fire. 
 
 The fire being started, the method of adding coal depends upon 
 the fireman, the kind of coal, the type of boiler,, and the rate of com- 
 bustion. There are three general methods of firing spreading, 
 alternate or side firing, and coking. 
 
 Spreading is accomplished by placing small amounts of coal 
 uniformly over the entire surface of the grate at short intervals. By 
 this method, the coal is thrown just where it is wanted and then not 
 disturbed. The fire should be hollowed in the center; that is, it 
 should be thicker at the sides. Good results are obtained from this 
 method, since the fire can be kept in the right condition at all times, 
 
BOILER ACCESSORIES 1 13 
 
 if the coal is of the right sort. During the operation of firing, the 
 door should be kept open as little as possible, or the fire will be cooled 
 by the entrance of cold air. For a short time, while the coal is giving 
 off gas, the draught-plate of the furnace door should be opened, in 
 order that sufficient air may be admitted above the coal to burn the 
 hydrocarbons. 
 
 When the alternate or side firing method is used, coal is spread 
 so as to cover one side of the fire completely at one firing, leaving the 
 other side bright. At the next firing, the bright side is covered. The 
 hydrocarbons given off by the fresh coal are burned by the hot gases 
 from the incandescent coal. This method is superior to spreading, 
 because the entire furnace is not cooled off by the addition of fresh 
 fuel. 
 
 Side firing is most advantageous with two furnaces leading to 
 a common combustion chamber. The furnaces are fired at regular 
 intervals with moderate charges of coal, and the draught-plates are 
 opened while the coal is giving off gas. 
 
 The two systems described above are best adapted to anthracite 
 coal, since it burns with comparatively little smoke. 
 
 With bituminous coal, which is soft and burns with considerable 
 smoke, the coking method is used. The coal is piled on the grate just 
 inside the door, and allowed to coke from 15 to 30 minutes. During 
 this time, the hydrocarbons are driven off and burned by the heat 
 from the fire. In order fully to accomplish this, air must be admitted 
 above the grate through the draught-plates of the furnace door. 
 The coke is then pushed backward over the fire, and a new supply 
 placed on the front of the grate. The air admitted prevents the form- 
 ing of carbon monoxide gas and smoke. At the same time, however, it 
 cools the furnace somewhat and reduces the rate of evaporation; but 
 this objection is not serious unless a boiler must be worked to its maxi- 
 mum capacity in order to furnish the required amount of steam. If 
 this is the case, economy is sacrificed to rapidity, for a low rate of 
 combustion is usually more economical than a high rate. 
 
 The necessary thickness of a bed for the best results, is found by 
 experiment. It depends on the draught and the kind of coal used. 
 If the former is strong, and the coal in large lumps, the bed may be 
 thick (about one foot); but if the draught is weak, or if the coal is 
 small, the bed must be thin (about three or four inches), so that suffi- 
 
114 BOILER ACCESSORIES 
 
 cient air may pass through. In marine and locomotive work, with 
 forced draught, the bed must be very thick to get a large coal con- 
 sumption per square foot per hour. With the same draught, bitu- 
 minous coal can be fired more thickly than anthracite 
 
 After finding from experiment the best thickness for the bed, keep 
 it at that thickness. Always keep the bed of uniform thickness, and 
 never let the fire burn holes in the bed, and do not let the rear of the 
 grate become bare. If a larger amount of steam is required, fire 
 smaller quantities at more frequent intervals. Do not fire a large 
 amount of coal, and wait for the pressure to rise; The firing of fresh 
 coal chills the furnace and temporarily retards combustion. The 
 coal should be fired in small quantities and as quickly as possible. 
 Keep the fire free from ashes and clinkers, but do not clean the fires 
 oftener than is necessary. 
 
 Four tools are used for cleaning the fire the slice-bar, the prick- 
 bar; the clinker hook, sometimes called the devil's claw; and the hoe 
 or rake. 
 
 . The slice-bar is a long, straight bar, with the end flattened . It 
 is used to break up clinkers by thrusting it between the grate and the 
 fire. It is also used to break up caking coaL The prick-bar is similar 
 to the slice-bar, except that the end is bent at right angles like a hook. 
 To remove ashes, the prick-bar is run along, up between the grate 
 bars, from underneath. This bar is often made with detachable hook, 
 so that the end may be replaced when burned off. The clinker hook, 
 or devil's claw, is used to haul the fire forward. The hoe, or rake, is 
 used to draw out cinders, to haul the fire forward, etc. 
 
 In cleaning the fire, the fireman first looks to the water and steam. 
 There should be enough water and sufficient steam pressure to last 
 during cleaning. Then he breaks up the clinkers with the slice-bar, 
 and removes the ashes with the prick-bar. If necessary, he pushes the 
 fire to the rear, thoroughly cleans the front of the grate bars, and then 
 hauls it forward and cleans the back of the furnace bars. Some fire- 
 men clean one side at a time, instead of first the front and then the 
 rear. The fire should be allowed to burn down before cleaning; but 
 sufficient fuel, called chaff, should be left to start the fire quickly. 
 Before cleaning, partly close the dampers, so that the amount of cold air 
 admitted will be small. For this reason and to prevent loss of pressure, 
 clean as rapidly as possible. 
 
BOILER ACCESSORIES 115 
 
 Banking the fire depends upon the condition of the fire, the 
 fireman himself, and the length of time it is to remain banked. First 
 clean and place all the coal in a small space at the bridge ; then cover 
 with fresh coal to a depth depending on the length of time .the fire 
 is to remain banked. Then close all dampers and open the door. 
 Some firemen cover the front of the furnace bars with ashes. 
 
 To start from a banked fire, first examine the condition of the 
 water-level, steam pressure, safety-valves, etc. Then clean the fire 
 with the slice-bar, and rattle down the ashes with the prick-bar. After 
 spreading the coal evenly over the grate, cover with a thin layer of coal, 
 and open the dampers. 
 
 CARE OF BOILERS 
 
 Any amount of time spent in the proper care of a steam boiler' 
 will be amply repaid, for this is of great importance. The boiler, of 
 course, should be so designed and constructed that all parts can be 
 inspected readily; but this is of little benefit unless proper and rigid 
 inspections are made. All internal fittings, such as fusible plugs, 
 water alarms, feed-pipes, and the like, should occasionally be examined 
 to see if they are tight and in good working order. If due care is not 
 given to the boiler, its life will be materially shortened. 
 
 The following rules for the management and care of boilers have 
 been established by the Hartford Steam Boiler Inspection & Insur- 
 ance Company, and should be carefully followed, whether the boiler 
 is insured by the above-mentioned company or not: 
 
 1. Condition of Water. The first duty of an engineer, when he 
 enters his boiler-room in the morning, is to ascertain how many gauges 
 of water there are in his boilers. Never unbank or replenish the fires 
 until this is done. Accidents have occurred, and many boilers have 
 been entirely ruined from neglect of this precaution. 
 
 2. Low Water. In case of low water, cover the fires immedi- 
 ately with ashes; or, if no ashes are at hand, use fresh coal, and close 
 ash-pit doors. Do not turn on the feed under any circumstances, nor 
 tamper with or open the safety-valve. Let the steam outlets remain 
 as they are. 
 
 3. In Case of Foaming. Close throttle, and keep closed long 
 enough to show true level of water. If that level is sufficiently high, 
 feeding and blowing will usually suffice to correct the evil. In case 
 
116 BOILER ACCESSORIES 
 
 of violent foaming, caused by dirty water or by change from salt to 
 fresh water or vice versa, in addition to the action above stated, check 
 draught, and cover fires with fresh coal. 
 
 4. Leaks. When leaks are discovered, they should be re- 
 paired as soon as possible. 
 
 5. Blowing Off. Clean furnace and bridge wall of all coal and 
 ashes. Allow brickwork to cool down for two hours at least before 
 opening blow-off. A pressure exceeding 20 Ibs. should not be allowed 
 when boilers are blown out. Blow out at least once in two weeks. 
 In case the feed becomes muddy, blow out six or eight inches every 
 day. When surface blow-cocks are used, they should be frequently 
 opened for a few minutes at a time. 
 
 6. Filling Up the Boiler. After blowing down, allow the 
 boiler to become cool before filling again. Cold water pumped into 
 hot boilers is very injurious, from the sudden contraction set up. 
 
 7. Exterior of Boiler. Care should be taken that no water 
 comes in contact with the exterior of the boiler, either from leaky 
 joints or from other causes. 
 
 8. Removing Deposit and Sediment. In tubular boilers, the 
 handholes should be frequently opened, all collections removed, and 
 fore-plates carefully cleaned. Also, when boilers are fed in front and 
 blown off through the same pipe, the collection of mud or sediment in 
 the rear end should be removed frequently. 
 
 9. Safety= Valves. Raise the safety-valves cautiously and 
 frequently, as they are liable to become* fast in their seats and useless 
 for the purpose intended. 
 
 10. Safety= Valve and Pressure=Qauge. Should the gauge at any 
 time indicate the limit of pressure allowed by the insurance 
 company, see that thd safety-valves are blowing off. In case of dif- 
 ference, notify the company's inspector. 
 
 11. Qauge=Cocks, Glass Gauge. Keep gauge-cocks clear and 
 in constant use. Glass gauges should not be relied on altogether. 
 
 12. Blisters. When a blister appears, there must be no delay 
 in having it carefully examined and trimmed or patched, as the case 
 may require. 
 
 13. Clean Sheets. Particular care should be taken to keep 
 sheets and parts of boilers exposed to the fire, perfectly clean; also 
 
BOILER ACCESSORIES 117 
 
 all tubes, flues, and connections well swept. This is particularly 
 necessary where wood or soft coal is used for fuel. 
 
 14. General Care of Boilers and Connections. Under all cir- 
 cumstances, keep the gauges, cocks, etc., clean and in good order, and 
 things generally in and about the engine-room in a neat condition. 
 
 15. Getting Up Steam. In preparing to get up steam after 
 boilers have been open or out of service, great care should be exercised 
 in making the manhole and handhole joints. Safety-valve should 
 then be opened and blocked open, and the necessary supply of water 
 run in or pumped into the boilers, until it shows at second gauge in 
 tubular and locomotive boilers; a higher level is advisable in vertical 
 tubulars as a protection to the top ends of tubes. After this is done, 
 fuel may be placed upon the grate, dampers opened, and fires started. 
 If chimney or stack is cold and does not draw properly, burn some 
 oily waste or light kindling at the base. Start fires in ample time, so 
 that it will not be necessary to urge them unduly. When steam 
 issues from the safety-valve, lower it carefully to its seat and note 
 pressure and behavior of steam-gauge. 
 
 If there are other boilers in operation, and stop-valves are to be 
 opened to place boilers in connection with others on a steam-pipe 
 line, watch those recently fired up, until pressure is up to that of the 
 other boilers to which they are connected; and, when that pressure is 
 attained, open the stop-valves very slowly and carefully. 
 
 OK THE 
 
 UNIVERSITY 
 
 OF 
 
INDEX 
 
 Page 
 
 Angle valve _ 37 
 
 Ashton valve 44 
 
 B 
 
 Barrel calorimeter G7 
 
 Blow-out apparatus 45 
 
 Boiler coverings 78 
 
 Boiler explosions 88 
 
 causes of 90 
 
 defective design 91 
 
 defects of workmanship . . 92 
 
 deterioration 91 
 
 low water 90 
 
 mismanagement 92 
 
 energy, determination of 89 
 
 investigation 93 
 
 prevention 94 
 
 Boiler setting 1 
 
 Boiler supports 6 
 
 Boilers, care of 115 
 
 blisters 116 
 
 blowing off 116 
 
 clean sheets 116 
 
 condition of water 115 
 
 exterior of boiler 116 
 
 filling up boiler 1 16 
 
 foaming. . . 115 
 
 gauge-cocks 116 
 
 getting up steam 117 
 
 leaks 116 
 
 low water 115 
 
 removing deposit and sediment. 116 
 
 safety-valves 116 
 
 Boilers, horse-power of 
 
 Bucket trap 64 
 
 C 
 
 Calorimeters 66 
 
 barrel 67 
 
 separator "0 
 
 throttling 71 
 
120 INDEX 
 
 Page 
 
 Check valves 38 
 
 Circulating apparatus 56 
 
 Cochrane feed- water heater 59 
 
 Cochrane steam separator 63 
 
 Competition valve 37 
 
 Corrosion 81 
 
 external '. 81 
 
 internal 82 
 
 D 
 
 Dial gauge 29 
 
 Differential steam trap 65 
 
 Down-draft furnaces I ........ 15 
 
 Draft-gauge 22 
 
 Drafts 22 
 
 forced , ... . . 22 
 
 closed ash-pit system 23 
 
 closed stoke-hold system 23 
 
 Ellis & Eaves system 24 
 
 Howden system 24 
 
 induced system 24 
 
 natural 22 
 
 E 
 
 Eames differential draft-gauge 22 
 
 Ellis & Eaves system of forced draft 24 
 
 Equalizing valve .; 66 
 
 Evaporators 57 
 
 External corrosion 81 
 
 F 
 
 Feed apparatus . . . -. : 48 
 
 circulating apparatus ....;.. v ... 56 
 
 evaporators 57 
 
 feed-water heaters ... .Y. 58 
 
 injectors or inspirators 54 
 
 pumps 53 
 
 Feed-water heaters 58 
 
 Firing.... .V ..' /. . Ill 
 
 Float trap 64 
 
 Forced draft , 22 
 
 Foster reducing valve 45 
 
 Fuel economizers 17 
 
 Fuel used in steam production 94 
 
 artificial fuels 101 
 
 charcoal 97 
 
 coal .. . .".' 94 
 
 coke ., ... ...-.,. ,;vW : - ..... 97 
 
 culm . :i 97 
 
 gas 100 
 
INDEX 121 
 
 Page 
 Fuel used in steam production 
 
 liquid fuels 98 
 
 peat 97 
 
 straw 98 
 
 wood 97 
 
 Furnaces 7 
 
 bridge 12 
 
 door 9 
 
 down-draft 15 
 
 fuel economizers 17 
 
 fusible plugs 20 
 
 grate 9 
 
 hollow arch 15 
 
 mechanical stokers 19 
 
 prevention of smoke 13 
 
 special 12 
 
 Fusible plugs 20 
 
 G 
 
 Gate valve 38 
 
 Gauges 
 
 steam and vacuum '. 29 
 
 water 32 
 
 Globe valve 36 
 
 Grates . '. 9 
 
 circular 10 
 
 herring bone 10 
 
 rocking 11 
 
 Grooving 83 
 
 H 
 
 Hancock inspirator 55 
 
 Handholes 29 
 
 Herring bone grate 10 
 
 Hollow arch 15 
 
 Holt reducing valve 45 
 
 Horse-power of boilers 79 
 
 Howden system of forced draft 24 
 
 I 
 
 Incrustation 84 
 
 carbonate of lime 85 
 
 corbonate of magnesia 86 
 
 iron salts 86 
 
 sulphate of lime - . 86 
 
 Induced draft 24 
 
 Injectors or inspirators 54 
 
 Hancock 55 
 
 Internal corrosion .* 82 
 
122 INDEX 
 
 K 
 
 Page 
 
 Kelley standard rocking grate 12 
 
 "Klinger Patent" gauge-glass 35 
 
 L 
 
 Lagging ,. r . 75 
 
 Lever safety-valve 40 
 
 M 
 
 Manholes 28 
 
 Mason reducing valve 45 
 
 Mechanical stokers 19 
 
 Muffler safety-valve 44 
 
 N 
 
 Natural draft 22 
 
 P 
 
 Pipe coverings 76 
 
 Piping , 73 
 
 Pitting 83 
 
 Pop regulator 43 
 
 Pop safety-valve 42 
 
 Priming 61 
 
 Pumps : . . 53 
 
 steam-driven : 53 
 
 R 
 
 Reducing valves 44 
 
 Foster 45 
 
 Holt 45 
 
 Mason 45 
 
 Return traps 66 
 
 Rocking grates 11 
 
 S 
 
 Safety-valves 39 
 
 lever '.- 40 
 
 muffler 44 
 
 pop ;. .. ... 42 
 
 Scale or sludge 84 
 
 Separator calorimeter 70 
 
 Smoke, prevention of . . 13 
 
 Star Marine pop safety-valve 44 
 
 Steam boiler trials 101 
 
 alternate method 106 
 
 keeping records 108 
 
 preliminaries to a test 104 
 
 priming tests 108 
 
 record of test ~. 109 
 
 standard method ..-...'.- 106 
 
 uniform conditions. . 107 
 
INDEX 123 
 
 Page 
 
 Steam jets .' 25 
 
 Steam separators 62 
 
 Cochrane 63 
 
 Stratton 63 
 
 Steam traps 64 
 
 bucket 64 
 
 differential 65 
 
 floaj 64 
 
 return / 66 
 
 Steam and vacuum gauges . . . 29 
 
 Stratton steam separator , 63 
 
 T 
 Tables 
 
 coals, analysis and heat value of various 95 
 
 evaporation, factors of : 80 
 
 evaporative test, data and results of 110 
 
 gases, evaporative power of 100 
 
 heat, relative values of preventatives of radiation of . . 77 
 
 heat loss, variation of, with pressure 76 
 
 heat losses in bare pipes 76 
 
 log of test Ill 
 
 Throttling calorimeter 71 
 
 Try-cocks 33 
 
 Tube-cleaners 26 
 
 Tube-stoppers 26 
 
 V 
 
 Valves 36 
 
 angle. 37 
 
 check 38 
 
 gate 38 
 
 globe 36 
 
 materials for 39 
 
 reducing 44 
 
 safety 39 
 
 W 
 
 Water gauges 32 
 
 gauge-glasses v 33 
 
 try cocks 33 
 
 Water-tube boilers 6 
 
 Worthington duplex steam pump 53