208 HYDROELECTRIC PLANTS. COSTS. Fig. 192 gives the cost per foot of reinforced concrete pen- stock. The data from which this curve is plotted was derived largely from Gillette's book, " Cost Data," but also from numerous other sources. FIG. 191. Reinforcing costs about three cents per pound for steel, and C.5 cent to instal. The concrete costs bout $10.00 per cubic yard, including every item. Round rods cost about Gasfjoer/vof of Penstock FIG. 192. $34.00 per ton. Brick penstocks require 570 bricks per cubic yard and 1.25 barrels of cement. A mason should lay 1200 bricks in eight hours at a cost of $6.00 Figs. 193 to 195 show the three common forms of steel riveted HYDRAULIC CONSTRUCTION. 209 PLANCED ENTRANCE TAPER BOLTED TO PRESSURE BOX FIGS. 193-195. UNIVERSITY OF CALIFORNIA ANDREW SMITH HALLIDIE: 1868^1 1901 DESIGN AND CONSTRUCTION OF HYDROELECTRIC PLANTS INCLUDING A SPECIAL TREATMENT OF THE DESIGN OF DAMS BY R. C. BEARDSLEY NEW YORK McGRAW PUBLISHING COMPANY 1907 |\\ Copyrighted, 1907, by the McGraw Publishing Company, New York. To my father, E. R. Beardsley, to whom we owe the gravity dam, and the discovery of the existence and effects of vacuums under dams. ' CONTENTS. CHAPTER. PAGE. I. HYDRAULIC PRINCIPLES 1 Hydrostatics 1 Hydrodynamics 2 II. MEASUREMENT OF FLOW 10 Weirs 10 Dams 12 Velocity of Approach 15 The Nappe 17 Venturi Meters 18 Penstocks and Pipes 20 Established Values of n 22 Circular Penstocks 23 Flow in Penstocks 25 Short Pipes 29 Flow of Air in Pipes 30 Limiting Velocities for Air 30 Canals 31 Effect of Ice on the Flow 32 Rivers, Preliminary Measurements 33 Current Meters 35 Extensive Measurements 37 III. RECONNAISSANCE OF WATER POWER 39 Power Measurement 39 Value of Government Reports to the Hydraulic En- gineer 40 Relation of Pondage and Reservoirs to the Valuation of Power 45 Penstock with Reservoir 51 Ice Evils 55 Soundings 56 Flowage Height 58 Cost of Surveys 61 Engineer's Report 62 Engineer's Measurements 62 Form of Report 65 IV. MATERIALS 68 Wood 68 Metals 69 vi CONTENTS. CHAPTER, PAGE. IV. MATERIALS (Continued). Cement and Concrete 69 Testing 70 Uses 85 Sand Cement 88 Burnt Clay and Gumbo 88 Costs . 89 Hand-Mixed Concrete 90 Machine Mixed Concrete 92 Forms 94 Surfacing 96 Concrete Laid under Water 98 General Remarks 99 Peculiarities of Concrete 100 Concrete-Steel 102 Strength of Materials 113 Columns and Foundations 122 Design of Machine Elements 130 V. HYDRAULIC CONSTRUCTION 137 Piling 137 Drilling 149 Explosives 155 Cableways 159 Bridges 164 Coffer Dams 169 Caissons 175 Costs 179 Pumps 179 Hydraulic Ram 183 Embankments 185 Canals 187 Tunnels 192 Penstocks 199 The Design of Dams ". 210 Costs 274 Flashboards 281 Head Gates 289 Sluice Gates 296 Head Racks 298 VI. POWER HOUSE CONSTRUCTION 301 Foundations 301 Structure 303 Architecture 330 VII. POWER HOUSE EQUIPMENT 331 Waterwheels 331 Hydro-Compressor 370 Auxiliary Plants 381 CONTENTS. vii CHAPTER. PAGE. VII. POWER HOUSE EQUIPMENT (Continued). Electric Generators 393 Switch Boards 398 Switches and Instruments 402 Lightning Arresters 413 Transformers 415 Storage Battery 421 Motor Generators 429 Frequency Changers 429 Alignment of Machinery 43 1 VIII. POWER TRANSMISSION 434 Couplings 434 Friction Clutches 435 Keys 436 Quill Shafts 436 Shafting 436 Gears .< 440 Belting 446 Rope Transmission 449 High Tension Electric Transmission 460 Efficiencies 486 Efficiency of Old Wheels 493 IX. TABLES AND FORMULAS 495 Various Units 495 Power and Energy and Their Equivalents 495 Application of Energy Formulas 496 Comparison of the Value of Power when Expressed in Horse-Power per Year or Kilowatt per Year. . 501 CHAPTER I HYDRAULIC PRINCIPLES. HYDROSTATICS. Water is chemically known as H 2 O. Its weight varies from 62.3 pounds to 62.5 poi.nds per cubic foot. In all estimates on water power the value should be used which gives results on the safe side. Thus, in finding the power of the stream 62.3 should be used, but in obtaining the pressure on the dam or against a gate, 62.5 is the safest figure. In turbine testing, where great accuracy is required, the water should be weighed during the test. 1 cubic foot of water = 6.232 imperial gallons = 7.48 United States gallons. 1 imperial gallon = .1605 cubic foot = 1.2 United States gallons. 1 United States gallon = .1337 cubic foot = .331 imperial gallons. 1 United States gallon = 8.355 pounds = 231 cubic inches. 1 miners inch = 11.219 United States gallons =1.5 cubic foot. The miner's inch is not the same in all parts of the country, but the value given above is becoming universally acknowledged. x ater is but slightly compressible, therefore the pressure, P, is for all practical purposes directly proportional to the depth, H, and can be represented by a diagram as shown in Figs. 1, 2 and 3. The total pressure on any submerged surface is equal to the area of the pressure diagram (a b c. Fig. 1 ; d e c b, Figs. 2 and 3), and the center of pressure passes through its center of gravity G perpendicular to the submerged surface. The moment of the pressure about c is M = Py. 1 2 HYDROELECTRIC PLANTS. The pressure in pounds per square inch at any point is p = 0.433 Depth. The pressure is always normal to the submerged surface (Fig. 4). The total pressure exerted on a submerged body is P = 0.433 H S wherein 5 is the area of the surface and H the depth of water over the geometrical center of the body. Any body submerged in water will suffer an apparent loss of weight which is equal to the weight of the displaced volume of water. If a unit volume of water is heavier than a unit volume of the substance the latter will float. FIG. 1. FIG. 2. FIG. 4. HYDRODYNAMICS. Water in motion is governed by the same law as falling bodies, i.e., m v 2 mgh - __. wherein m g h represents the potential energy due to its position and m v 2 represents the kinetic energy due to its velocity. This equation holds true only for an efficiency of 100 per cent. HYDRAULIC PRINCIPLES. 3 The quantities which enter into the equation are the mass, m, head, h, velocity, v, and the gravity constant, g = 32.16, m g = w = weight and v = V2gh = 8.03V h When h is given in feet, v is the velocity in feet per second. The flow of water through an opening expressed in cubic feet per second is Q = vA wherein v is the velocity in feet per second and A is the area in square feet, of the opening. FIG. 5. For rectangular openings of length, /, and depth, d, the for- mula for Q is Q = c I d x/277* (Fig. 5) For circular openings of diameter d the formula for Q is (Fig. 5) _ ,12 / 1 M ,74 \ Q = c^-V2gh (1-JL1_-_J_^L_....) 4 V 128 h 2 16384 h 4 / for values of h > 2 d ' Q-c- . r v'2H wherein <: is a coefficient which depends on the form of the orifice and may be taken as 0.61 for openings in thin plates or planks such as head gates; Q is given in cubic feet per second when h. I and d are measured in feet. 4 HYDROELECTRIC PLANTS. The above formulas for flow through orifices supposed that there is no velocity of approach and are correct to within 0.5 per cent, when A f ^> 10 A wherein A' is the area of cross-section of the canal or tank and A that of the orifice. When , The velocity of approach should be taken into consideration. Let h be the head due to the velocity of approach, i.e., V ^7 T t FIG. 6. Then Q = c\ FIG. 7. c --= 0.61 FIG. 8. (Fig- 6. for rectangular openings of length /. For submerged orifices the discharge is practically the same as in the case of a free discharge except that the head, h, is taken between the two levels (Fig. 7). Q = c A \/2 h g c = 0.6 The weir is a special case of a rectangular orifice where h l =0. Q = r/V2j(fe 2 + fc )! (Fig. 8.) n =-- 1.0- 1.5 c = 0.60 Suppose water to be conducted through a pipe line from HYDRAULIC PRINCIPLES. 5 one reservoir to another. The difference between the levels being h (Fig. 9). If pressure tubes are inserted at intervals along the pipe line their levels will coincide with the line a b called the hydraulic gradient when the line is open and with the line a a' when the valve at B is closed. This reduction in pressure head is due to two things, namely, frictibn losses and conversion of pressure head into velocity head. The velocity head is represented by h v and FIG. 9. The friction head lost at the entrance to the pipe is expressed thus C 2g c = 0.5 (approximately) The friction head lost in the pipe is directly proportional to the length of the pipe, inversely proportional to the diameter of the pipe, directl> proportional to the square of the velocity and is expressed thus / I/ 2 C d 2f~ c is the coefficient of friction . 6 HYDROELECTRIC PLANTS The total available sta:ic head is h = h Q + h f + h v From Figs. 9 and 10 it is seen that a pipe laid along the hy- draulic gradient would not be subjected to pressure except when the pipe is closed at the lower end and open at the upper, FIG. 10. and that at all portions of the pipe line which lie below the hydraulic gradient are subjected to the pressure h p from the inside while those that lie above it are subjected to the pres- sure h p from the outside. When the pipe line rises above the hydraulic gradient it is FIG. 11. called a siphon. A siphon requires an air tight pipe because its operation depends upon the possibility of raising the hy- draulic gradient by an amount equal to the head due to the atmosphere as shown in Fig. 10. Even though the pipe be air tight some air will be carried in by the water and will collect in the pipe at the highest point. At this point a tank with HYDRAULIC PRINCIPLES. 7 a valve must be inserted to collect and carry off the air. It is also used to start the siphon. The operation is explained as follows (Fig. 11) : To operate the pipe, the valves at B and C are closed, D opened and the whole siphon and reservoir E filled with water. B and C are now opened, D being left open. Then, as the air forms during the operation of the pipe, the air drives the water out of E, but E having some capacity, it requires time to do this and, before E is entirely emptied, the valve D is closed and E filled with water, after which D is opened again. In this way, the siphon may be caused to operate continuously. If the head lost by friction in the pipe exceeds 20 to 25 feet the pipe will not operate successfully. In a siphon, the pressure to be contended with is that due to air pressure and the pipe must be strong enough against collapsing to stand 15 pounds per square inch. FIG. 12. Siphons may form a part of the penstock when it is cheaper than tunnelling. Large siphons may be built of wooden staves though riveted steel pipe is, in all cases, preferable. From Fig. 10 it is seen that the hydraulic gradient is raised by an amount equal to the head due to the atmospheric pres- sure and that the pipe should work as well above as below the apparent hydraulic gradient. This is true enough in theory, but in practice pipes will leak and allow air to enter and the water will carry air which will collect at the high points and form air plugs, and shift the hydraulic gradient from its normal position to that shown in Fig. 12, so that the part of the pipe above the point C will be under pressure and the discharge will take place at C, the rest of the pipe acting simply as a channel to convey the water from there to the end. This will cause a material decrease in the velocity and consequently the flow of the water. Water 8 HYDROELECTRIC PLANTS. carried from a great height is often utilized at a nozzle by absorbing its kinetic energy as in a Pelton wheel. In this case the velocity is kept low in the pipe so as to reduce the head lost in friction and the greater part of velocity head de- veloped in a nozzle. Fig. 13 shows the hydraulic gradient for a case of this sort. In the cases which went before, the gradient was taken as a straight line from one end of the pipe line to the other, but this is only true where the pipe itself follows approximately a straight line between the reservoir and the discharge. The impulse pressure at the nozzle is obtained by assuming that this velocity was produced by the action of a force F for a period of one second; then the product of the force, F, and the distance, , through which the weight W moves in one FIG. 13. second, is the work and is equal to the kinetic energy, thus .,. V W = V V 2 V 2 q = w a = 2w a wherein q is the volume per second, w the specific weight of water, and a the area of the orifice. Thus, it is seen that were there no losses the head, h, corresponding to the velocity, v, would produce an impulse pressure equal to that produced by a static head, 2 h. This demonstrates that the sudden closing of a valve in a pipe line may subject the pipe to enormous pressure. HYDRAULIC PRINCIPLES. u The time, T, which it takes the water to attain its final ve- locity in a frictionless pipe or to come to rest when a valve is closed is, r 0.249 vT seconds, wherein / is the length of the pipe in feet. The kinetic energy in foot pounds possessed by a pipe full of water in motion is, E R = 0.765 d I v> = h = 49.2 J//* wherein d is the diameter of the pipe in feet, / the length in feet, h the head in feet, and v the velocity in feet per second. CHAPTER II. MEASUREMENT OF FLOW The flow is the amount of water which passes a given point in a given time, and is determined by substituting experimental constants in theoretical formulas which are derived for the aperture through which it is desired to measure the flow. WEIRS. Weirs are used in measuring the flow in small streams or the discharge of turbines, pumps, etc. FIG. 14. Wire for small streams. The author has found that the construction shown in Fig. 14 is very satisfactory when the flow of small streams is to be measured. The weir may be of any length or si?e, and built on any bottom and is easily and quickly constructed in swift water. 10 MEASUREMENT OF FLOW. 11 The posts, .4, are driven with a maul at equal distances apart across the stream and as nearly as possible in line. Then the floor is made on shore, in sections of, say, 12 feet in length and as wide as thought necessary, for that particular bottom and height of weir. Holes are cut in the floor so that it may be dropped down over the posts. The sections are then placed over the posts and sunk on to the bed of the stream and weighted down with rock. The tops of the posts are cut tapering and all on the same level except the four end posts which are left long to form the abut- ments. Then the first plank, E, is fitted to the floor so that its upper edge is perfectly level. If the river bed is of sand a row of sheet piling must be driven at C before the floor or mat is placed, but for most bottoms this will not be necessary. Having placed the plank, E, fill above it with earth to prevent the water cutting under the floor when the head is increased. FIG. 15. FIG. 15a. The height of these planks will depend on the depth of the water as the top or weir plank must be at least a foot above the lower water level. Champfer the edge of the weir plank, B, to a thin edge, and place plenty of earth at the ends. A stake, D, is driven up stream a distance of six feet or more from the we r so that its top is exactly on a level with the top edge of the weir plank. The total cubic feet of water per minute flowing in the stream is obtained by measuring the depth of water over the stake, D, and from the weir table (see Table II) finding the cubic feet of water flowing each minute per foot width of weir then multiplying this quantity by the width of the weir in feet. Since a cubic foot of water weighs 62.5 pounds, the pounds of water flowing per minute are equal to the flow in cubic feet per minute, times 62.5. A formula which takes end contraction into account is as follows : 12 HYDROELECTRIC PLANTS. Q, the cubic feet of water flowing over the weir per min- ute = 199.8 (L -0.1 n D) D 3/2. D = depth of water in feet above A , measured at a point some six feet to ten feet up stream from the weir, n = the number of end contractions. Thus in Fig. 15a at B, n = 0, at C, n= 1, and at D, n = 2; for n = 0, the formula is, Q = 199.8 LD3/2. Frequently it is of advantage to have the weir plank B below the lower water level, in which case the weir is called a sub- merged weir. In this case the depths h and H are measured but instead of referring to the table, substitute these measure- ments in the following equation: Q = (Q x (width of weir in feet) X (8.025 \/a) X (h + f a), in TABLE I. h/H C .20 618 to .628 .40 590 to .600 .60 583 to .593 .70 580 to .590 .80 581 to .591 .90 590 to .600 .95 610 to .615 which Q = cubic feet of water per second, a = H-h, and C is a coefficient depending on h+H (see Table I). DAMS. While the flow over the standard weir can be obtained from Table II, which is based on Francis' formula, it has been found that for the forms of crest found on power dams the flow varies a good deal from that for the sharp crested weir. The experi- ments made at Cornell are the latest and best data we have on the subject, and Figs. 16 to 21 give the coefficients C for six different dams and for depths of water up to six feet as given by these experiments. It will be seen that the coefficient C varies considerably from 3.33 as used in the Francis formula. EXAMPLE: If the depth of water on a dam 230 feet long, MEASUREMENT OF FLOW. 13 TABLE II. WEIR TABLE USING FRANCIS' FORMULA Q - 3.33 1 Kf. Discharge in cubic feet per minute per foot length of Weir. ead H in s. ft. Cu. ft. per min. Head H Cu. ft. per min Head H Cu. ft. per min. Head H Cu. ft. per min. HeadH Cu. ft. per min. In Ins. in ft. In Ins in ft. In Ins. In ft. In Ins. In ft. 01 .18 7 .58 88.26 13 i 1.15 246.42 20f 1.72 450.72 27 A 2.29 692.40 .02 .54 7A .59 90.54 13 10 1 .16 249.60 20 'i 1.73 454.62 271 2.30 696.90 .03 1.02 7A .60 92.88 14 1 J 1.17 252.84 20 J 1.74 458.58 27$ 2.31 701.46 04 1.62 7 A .61 95.16 14 r 1 .18 256.08 > 1.75 462.54 27 H 2.32 706.02 j .05 2.22 7 ? .62 97.56 14 i 1 .19 259.38 > 1.76 466.50 28 2.33 710.58 06 2.94 7 re .63 99.90 14 i 1.20 262.62 2 1.77 470.52 28 1 2.34 715.20 H -07 3.72 711 1 6 .64 102.30 14 v 1.21 265.92 2 1.78 474.48 2.35 719.76 TJ .08 4.50 7 * 3 .65 104.70 14 i 1 .22 269.22 2 1.79 478.50 28 A 2.36 724.38 ft 09 5.40 7 1 .66 107.16 14 i 1.23 272.58 2 1.80 482.52 28 A 2.37 729.00 ft .10 6.30 8 .67 109.56 14 \ 1 .24 275.88 2 1.81 486.54 28, 9 6 2.38 733.62 7.26 8| .68 112.02 15 1.25 279.24 2 1.82 490.56 28 H 2.39 738.24 A :i2 8.23 8J .69 114.54 If) 1.26 282.60 22 1.83 494.64 28 1| 2.40 742.86 i -13 9.36 8| .70 117.03 L5 1 .27 285.96 22J 1 .84 498.66 28 it 2.41 747.54 \ -14 10.44 .71 119.52 15 1.28 289.32 22 A 1.85 502.74 29 A 2.42 752.16 .15 11.58 81 .72 122.04 15 1 .29 292.74 22 A 1 .86 506.82 29 A 2.43 756.84 H .16 12.78 8i .73 124.62 5 1.30 296.16 22 A 1.87 510.90 29J 2.44 761.52 A -17 13.98 8| .74 127.23 5 1 .31 299.58 22 v. 1.88 515.04 29i 2.45 766.20 .18 15.24 9* .75 129.73 .->' 1.32 303 .00 22 H 1.89 519.12 29^ 2.46 770.88 .19 16.56 .76 132.36 i; I .33 306.48 22 t? 1.90 523.26 29 j 2.47 775.62 .20 17.88 gi .77 135.53 IK 1.34 309 .90 22 1 i 1.91 527.40 29: 2.48 780.30 .21 19.20 9i .78 137.64 6 1 .35 313.38 23 1.92 531 .54 29 2.49 785.04 .22 20.64 .79 143.23 H '< f 1.36 316.86 23 J 1.93 535.74 30 2.50 789.78 .23 22.02 SI .83 142.93 8 \. 1.37 320 . 40 23J 1.94 539.88 30 i 2.51 .24 23.52 i] .81 145.63 i) ' ( L.33 323 .88 230 1.95 544.08 30J 2.52 .25 24.96 .82 143.33 6 I 1.39 327.42 23 1.96 548.28 .26 26.46 io s .83 151.03 6 1 ' 1 .40 330.96 23 1.97 552.48 .27 23.02 10 .84 153.84 H 1 .41 334.50 23; 1.S8 556.68 .23 29.58 10* .85 156.63 7 c 1 .42 338.10 23; .99 560.88 .29 31.20 10 A .86 159.36 7 < 1.43 341 .64 24 .00 564 . 1 4 .30 32.82 [0 A .87 162.12 7 1 .44 345.24 24 J .01 569.34 .31 34.50 [0 A .83 164.94 7; 1 .45 348.84 24i .02 573.60 M .32 36.18 10 H .89 167.76 7 1 .46 352.50 24| .03 577.86 .33 37.86 [0 f-| .90 170.53 7: 1.47 356.10 24i .04 582.18 8 l -34 39.60 [0 ff .91 173.46 7 1.48 359.76 245 .05 586 . 44 k .35 41.40 11 .92 176.34 17 1 .49 363.42 24? .06 590.76 A -36 43.14 111 .93 179.22 1S 1 .50 367.08 24^ .07 595.02 ft .37 44.94 111 .04 182.10 IS I .51 370.74 24 1 .08 599.34 A .38 46.81 Hi .95 184.93 IS 1 .52 374.40 25 A .09 603.72 H -39 48.66 111 .96 187.92 IS 1 .53 378.12 25 A .10 608.04 \i -40 50.52 111 .97 190.86 IS 1 .54 381 .84 25 A .11 612.36 H -41 52.44 111 .98 193.86 IS 1.55 385.56 25 * .12 616.74 A -42 54.36 111 .99 196.80 18 I .56 389.28 25| .13 621.12 A -43 56.34 12 .00 199.80 18 H 1 .57 393.06 .14 625.50 k -44 58.32 12 .01 202.80 19 1.58 396.78 253 .15 629.88 .45 60.30 .02 205.80 19A .59 400.56 25 ii .16 634.26 .46 62.34 12| .03 208.86 19 ;\ .60 404.34 26 A .17 638.70 .47 64.38 12i .04 211.92 19 A .61 408.18 .18 643.08 .48 .49 .50 .51 66.42 68.52 70.62 72.78 121 12! 12M 12 H .05 .06 .07 .08 214.98 218.04 221 .16 224.22 19A 19^ 19 ]-, i9fi .62 .63 .64 .65 411 .96 415.80 419.64 423.48 26 1 26| 26? .19 .20 .21 .22 647.52 651 .96 656.40 660.90 .52 74.34 13A .09 227.40 19| .66 427.32 26 1 .23 665.34 1 -53 77.10 .10 230.52 20 .67 431.22 26J .24 669.84 * .54 79.26 13A .11 233.64 20 i .68 435.06 27 .25 674.34 i .55 81.48 13* .12 236.82 20 I .69 438.96 27 J .26 678.84 ! .56 83.70 134 .13 240.00 20 .70 442.86 27 i .27 683.34 H -57 85.98 .14 243.18 20 I .71 446.76 27 .28 687.84 14 HYDROELECTRIC PLANTS. ^.8 Depth of water in ft. over crest * Rounding corner is equivalent to an increase of H=0.7 R, FIGS. 16 to 21. Cornell Experiments. MEASUREMENT OF FLOW. io of section shown in Fig. 18, is five feet, what will be the quantity of water passing over the dam? For h = 5 we find that C = 3.7 Q = Clhl= 3.7X230X51 51 = v/5 3 = 11.18 and Q = 9514 cubic feet per second. Francis' constant, 3.33, would only have given 8571 cubic feet per second. Fig. 22, from Cornell experiments shows the form taken by the top surface of the water flowing over four different dam crests and in depths up to six feet. Fig. 23 shows the under and outer surface of the water pouring FIG. 22. Form taken by water passing over a dam (Cornell). over the dam shown and plotted from measurements made by the author under a gravity dam at Waldron, 111. During these experiments it was observed that there was a very strong current as indicated at x. VELOCITY OF APPROACH. In most cases met with in actual practice, the water ap- proaches the dam with a greater velocity than that where the formulas here given were evolved, therefore such velocity must be allowed for in applying the formulas. Let H be the true head of water on the dam (Fig. 24) ; h = the observed head at a distance of six or ten feet above the dam; Q-, = discharge over the dam due to the head h in cubic feet 16 HYDROELECTRIC PLANTS. per second per foot width of weir. ; Q = discharge due to the head H; v = velocity of approach in feet per second. - x/64.4~(H-fc) -.7- Then " H ~ h =I 6?~4 " Fig 24.) (1) PIG. 23. Form taken by water passing over a darn (Beardsley). FIG. 24. To apply these formulas obtain Q from the discharge for- mula, Q = C lk\, and substitute for Q in (1). This gives an v 2 approximate value for v, which substituted in = H v 64.4 gives the approximate velocity head, H v . Then H v +h = H, gives a close approximation to the true head, H, from which MEASUREMENT OF FLOW. 17 by again substituting in the formula for flow in cubic feet per second, a more nearly exact value for Q can be found. If till greater accuracy is desired the process may be gone through again. Where possible the value of v should be determined with a meter and substituted direct in = H. 64.4 THE NAPPE. In discussing the flow over dams much is said about this and that form of nappe. Nappe is the name given to that part of the crest of the dam which is in direct contact with the water. The various forms of nappe are as follows: Depressed, wetted, adhering and free. A depressed nappe is due to the formation of a vacuum; the sheet of water is more or less pressed in upon the crest. An adhering nappe is partly caused by the vacuum but ap- plies to all cases where there is no air at all between the water and the crest. Wetted nappe is where the air has free access behind the over- pour and the crest is smooth. Free nappe is where there is no vacuum at all. The effect on the coefficient C of the different nappes on the same dam is shown by the following experiment on a short low dam. Q (1) Free nappe, under surface open to air 4 . 33 3 . 47 (2) Depressed nappe, imprisoning a certain amount of air at a pressure below normal 4 . 60 3 . 69 (3) Nappe wetted, no air imprisoned; level of tail water at least 4.2 feet below level of crest .... 4 . 97 3 . 99 (4) Adhering nappe . . . 5 . 54 4 . 45 These experiments would show a variation of 20 per cent., but as they were for a low and short dam, and as all peculiari- ties tend to disappear for h^avy discharges, in practice the difference would not be so noticeable. The curves for the six dams in the Cornell experiments are plotted for free nappes. It will be seen that the gravity dam will pass more water 18 HYDROELECTRIC PLANTS. for a given depth of water on the crest than will a thin edged weir, or any other form of dam. VENTURI METERS. Next to the standard weir, the Venturi meter is the most important aid in the measurement of water, and when properly installed and calibrated it excels the weir in accuracy. Many of the largest cities of the country are using Venturi meters to measure the flow of water in the water systems, and in a few instances such meters are being used to measure the flow to turbines. About 1887, Mr. Clemens Herschel brought the Venturi to the attention of American engineers and since that time it has been steadily growing in favor. Fig. 25 shows the proportions (all dimensions in feet) for the Venturi meter used by Mr. Herschel. When used for FIG. 25. head gates, however, (see Fig. 26) the meter may be mate- rially shortened. Fig. 26 shows the Venturi meter for measuring the flow to a turbine serving the double purpose of a meter and a head gate. Mr. Herschel states that a Venturi meter placed in a nine-foot penstock in which the mean velocity is about '2.5 to three feet per second, the total loss in head will be one foot and if the velocity is two feet per second the loss will be only six inches. Therefore in all but water powers of the lowest head the Venturi meter can be used to measure the water. Since it does not affect the accuracy of the meter if the cones, a and b (Fig. 25), are rough, these parts may be constructed of reinforced concrete. It is essential, however, that the throat c be made accurately and of metal lined with bronze or brass. The Builders' Iron Foundry of Providence, R. I., make a spe- cialty of Venturi meters. The air chambers D and E, Fig. 26, MEASUREMENT OF FLOW. 19 must also be of metal. Fig. 27 shows one form of air chamber. The effect would, however, be just as satisfactory if the air space was not divided into segments and if but a single pipe was inserted at the top. About the only condition that effects the efficiency of the Venturi is the falling off in the velocity of the water when the demand is low. This would not be an objection where used for turbines, as the flow would never be below about 20 per cent, of the full flow. Mr. Frizell states that the area at the throat must be more than 1/16 to 1/20 of the area of the penstock at C Fig. 26, in order that the meter should accurately measure FIG. 26. Venturi meter used as a head gate. the flow. Herschel says that the velocity through the throat must not be less than five feet per second. This limits the shortening of the meter as the taper of the cones meeting at the throat must be as given in Fig. 25. When used for head gates, as in Fig. 26, several Venturi meters should be placed side by side, in wnich case if all the turbines are running at part gate, one or more meters can be cut out and the remaining meters used to their full capacity and efficiency. When so arranged the meters may be made comparatively short. Noth- ing can clog up a Venturi meter even saw logs will be metered as water. Mr. Herschel claims that the Venturi meter is accu- rate to within about two per cent. 20 HYDROELECTRIC PLANTS The pipes A and B, Fig. 26, lead up to the indicating in- strument F. This instrument is made in various forms by the Builders' Iron Foundry and gives the flow in cubic feet per minute. PENSTOCKS AND PIPES. We are indebted to Kutter and D'Arcy for our most reliable data on the flow of water through pipes; they performed many experiments with pipes of various sizes and lengths, and their formulas may be depended on as being exact to within five per cent. We will only give one formula, and the accompanying tables, the author's purpose being to give only the best and easiest, rather than to give a variety. FIG. 27 Q = A C^XVs v - CVTs = C x/r XV? 7 v = velocity of water in feet per second. A == wet area of penstock =96, Fig. 29. C = a coefficient depending on s, n, r , 5 = the fall of water surface per foot length or hydraulic gradient fall in feet per mile 5280 ^ r = = mean hydraulic depth, P = wetted perimeter (see Figs. 28-30). MEASUREMENT OF FLOW. 21 TABLE III (Kent). Q discharge in cubic feet per second, -4= area in square feet, v = velocity in feet per second, r = mean hydraulic depth, i diam. for pipes running full, * = sine of slope. Size of Pipe Clean Cast-iron Old Cast-iron Pipes Pipes. Value of Lined w th Deposit. A C>/Fby A= area Kutter's = 52,491 and from Table V we find that for a fall of one foot per mile V^ = .013762. There- fore Q = .013762X52,491 = 722.38 cubic feet per second, or 43,342 cubic feet per minute. This is not a large enough flow, so we next try a 16 foot pipe for which A C \/r = 74,191 and -x/5 = -013762 and A C \/7 \/^ = 61,260 cubic feet per minute. Knowing the size of pipe and the quantity of water flowing C7/ f O./ O. O.3 O.-4 O.-5 O.ff 0.7" O.3 O.9 /O // /-? ft~oporfron or^frea, D/schsfrige or Ife/oc/fy FIG. 31. the velocity is obtained by dividing the quantity Q, by the area of the pipe in square feet. The velocity may also be obtained from the curves, Fig. 31, and it is a good policy to use both methods as a check on the calculations. Table V will be found useful in getting the square roots of the various values of s. FLOW IN PENSTOCKS. We have Kutter's formula, v = C \/7T where HYDROELECTRIC PLANTS. S3 0-0 radius (rj O.S ~06 0.7 08 O.f O3 0-4 03 JL FIG. 32, MEASUREMENT OF FLOW. 27 C = n .5521 + 23 [ This is a rather laborious equation and in Fig. 32 is given a set of curves from which C may be easily found. Each curve is for a certain value of n as given on page 22 and a corresponding hydraulic mean radius, r. These curves give very close results for all slopes greater than 5 = .0005 or 3 feet per mile, and pipes of greater diameter than 10 inches. For smaller slopes or penstocks the curves give fairly approximate values. EXAMPLE. 20,000 cubic feet of water per minute is to be carried one mile with a fall of 5 feet. What is the proper size FIG. 34. FIG. 35. for the penstock if built of planed lumber and well constructed? For a trial size assume a section as shown in Fig. 33, 5 = .000947, n= .01, r = (6x6)^(6 + 6 + 6) = 2. Now from curve for n = .01, Fig. 32, and r = 2, we find that C = 172. Substituting these values in v = C \/r s we have v = 172 V2X. 000947 = 7.5026 feet per second, or 450 feet per 28 HYDROELECTRIC PLANTS. minute. As the area of the penstock = 36 square feet, cubic feet per minute = 450X36 = 16,200 which is not large enough, so we take a section, say, 7X7 = feet. Then r = 2.33 and C = 175. 175X%/r7= v = 175X.047, TABLE V. (Kent). FALL IN FEET PER MILE, SLOPE, SINE OF SLOPE AND SQUAPE ROOT OF THE SINE. Fall in ft. per mile. Slope 1 ft. in- Sine of angle of slope Fall in ft. per mile. Slope 1 ft. in- Sine of angle of slope. H H L Vs H L 5 v7 0.25 .30 21120. 17600 . .0000473 .0000568 .003881 .007538 17. 18. gto.a 293.3 .0032197 .0034091 .056742 .058388 .40 13200 . .0000758 .008704 19. 277.9 .0035985 .059988 .50 10560 . .0000947 .009731 20. 264. .0037879 .061546 .60 8800. .0001136 .010660 22 240. .0041667 .064549 .702 7520. .0001330 .011532 24. 220. .0045455 .067419 .805 6560. .0001524 .012347 26. 203.1 .0049242 .070173 .904 5840 . .0001712 .013085 28. 188.6 .0053030 .072822 1. 5280. .0001894 .013762 30. 176. .0056818 .075378 1.25 4224. .0002367 .015386 35.20 150. .0066667 .081650 1.5 3520. .0002841 .016854 40. 132. .0075758 .087039 1.75 3017. .0003314 .018205 44. 120. .0083333 .091287 2. 2640. .0003788 .019463 48. 110. .0090909 .095346 2.25 2347. .0004261 .020641 52.8 100. .010 .1 2.5 2112. .0004735 .021760 60. 88. .0113636 .1066 2.75 1920. .0005208 .022822 66. 80. .0125 .111803 3. 1760. .0005682 .023837 70.4 75. .0133333 .115470 3.25 1625. .0006154 .024807 80. 66. .0151515 . 123091 3.5 1508. .0006631 .025751 88. 60. .0166667 .1291 3.75 1408. .0007102 .026650 96. 55. .0181818 .134839 4. 1320. .0007576 .027524 105.6 50. .02 .141241 5. 1056. .0009470 .030773 120. 44. .0227273 .150756 6. 880. .0011364 .03371 132. 40. .025 .158 14 7. 754.3 .0013257 .036416 160. 33. .0303030 .174077 8. 660. .0015152 .038925 220. 24. .0416667 .204124 9. 586.6 .0017044 .041286 264. 20. .05 .223607 10. 528. .0018939 .043519 330. 16. .0625 .25 11. 443.6 .0020833 .045643 440. 12. .0833333 .288675 12. 440. .0022727 .047673 528. 10. .1 .316228 13. 406.1 .0024621 .04962 660.0 8. .125 .353553 14. 377.1 .0026515 .051493 880. 6. .1666667 .408248 15. 352. .0028409 .0533 1056. 5 . .2 .447214 16. 330 . .0030303 .055048 1320. 4. .25 .5 which gives a velocity of 8.225 feet per second, and a flow of 24,180 cubic feet per minute, which is too much. Another trial gives a section of 6 feet 4 inches X 7 feet as having a capacity of 21,360 cubic feet per minute, which is about right. MEASUREMENT OF FLOW. 29 SHORT PIPES. The flow through such pipes is affected by three quantities; frictional resistance such as has been already considered, losses due to setting quiet water into motion and a loss due to the shape of the orifice. TABLE VI (Kent). Values of \/~^ for circular pipes, sewers, and penstocks of different diameters, r = mean area hydraulic depth = full. perimeter diameter for circular pipes running full or exactly half Diam. ft. in. /- in ft. Diam. ft. in. \/r in ft. Diam. ft. in. Vr in ft- Diam ft. in. Vr in ft- i .088 2 .707 4 6 1.061 9 1.500 i .102 2 1 .722 4 7 1.070 9 3 1.521 l .125 2 2 .736 4 8 1.080 9 6 1.541 i .144 2 3 .750 4 9 1.089 9 9 1.561 11 .161 2 4 .764 4 10 1.099 10 1.581 H .177 2 5 .777 4 11 1.109 10 3 .601 if .191 2 6 .790 5 1.118 10 6 .620 2 .204 2 7 .804 5 1 1.127 10 9 .639 2* .228 2 8 .817 5 2 1.137 11 .658 3 .251 2 9 .829 5 3 1.146 11 3 .677 4 .290 2 10 .842 5 4 .155 11 6 .696 5 .323 2 11 .854 5 5 .164 11 9 .714 6 .354 3 .866 5 6 .173 12 .732 7 .382 3 1 .878 5 7 .181 12 3 .750 8 .408 3 2 .890 5 8 .190 12 6 .768 9 .433 3 3 .901 5 9 .199 12 9 .785 10 .456 3 4 .913 5 10 .208 13 .083 11 .479 3 5 .924 5 11 .216 13 3 .820 .500 3 6 .935 6 .225 13 6 .837 1 .520 3 7 .946 6 3 .250 14 .871 2 .540 3 8 .957 6 6 1.275 14 6 .904 3 .559 3 9 .968 6 9 1.299 15 .936 4 .577 3 10 .979 7 1.323 15 6 .968 5 .595 3 11 .990 7 3 1.346 16 2. 6 .612 7 6 1.369 16 6 2.031 1 7 .629 1 .010 7 9 1.392 17 2.061 1 8 .646 2 .021 8 1 .414 17 6 2.091 1 9 .661 3 .031 8 3 1.436 18 2.121 1 10 .677 4 .041 8 6 1.458 19 2.180 1 11 .692 5 .051 8 9 1 .479 20 2.236 To find the diameter D of a short pipe of length L, which is to carry a given quantity Q of water per minute under a head H, substitute values for D in the formula (37.6 D+L) until the equation is satisfied. 30 HYDROELECTRIC PLANTS. If the orifice is given a slant as per dotted line (Fig. 34) the flow will be materially reduced. The inlet on short penstocks where the entrance loss would be an important portion of the whole lost head, should be pro- vided with a conical entrance piece as in Fig. 35; to avoid a large gate, the cone may project out into the head water as shown. FLOW OF AIR IN PIPES. Air flows in a pipe under the same laws as water in a penstock, the only difference being in the coefficient of friction. v 2 L H = 10,000 D 5 d wherein D is the diameter of the pipe in inches, L the length of the pipe in feet, V the volume of air delivered in cubic feet per minute, H the pressure lost in transmission, and d a constant. A hydro-compressor delivers the air to the pipe line at the temperature of the water and, therefore, does not require cooling. In other words, the pressure will not drop off due to cooling while being transmitted through the pipes. TABLE VII. LIMITING VELOCITIES FOR AIR. Diameter of pipe in feet 4 6 8 10 12 Velocity in feet per second... 18 12 11 10 9 8 The above velocities are extreme and should be avoided. TABLE VIII (F. Richard). a FOR WROUGHT IRON PIPE. Diameter Pipe in inches. Diameter Pipe in inches. a 1 .35 5 0.934 H .50 6 1.00 H .662 8 1 .125 2 .665 10 1.2 2* .65 12 1.26 3 .73 16 1.34 3} .787 20 1.40 4 .84 24 1.45 MEASUREMENT OF FLOW. 31 TABLE IX (F. Richard). POWER OBTAINABLE FROM ONE POUND OF COMPRESSED AIR USED WITHOUT HEATING Pressure Ibs. per sq. in. H.p. per cubic ft. of air per sec. Of Compression. Alter cooling to 60 F. 100 57.34 56.6 95 55.30 55.4 90 53.17 54.0 85 51.11 52.7 80 48.96 51.2 75 46.59 49.2 70 44.53 47.7 65 42.24 45.8 60 39.92 43.7 55 37.52 41.4 50 35.06 38.7 45 32.58 35.8 40 29.94 32.4 35 27.21 28.4 30 24.39 23.7 CANALS. The calculations for the flow in canals are even more com- plicated than for penstocks on account of the greater variation of n. This coefficient varies for each particular soil and lining and may equal .012 for one section and .035 for the next. In selecting the value for n always take a value .01 larger than called for in the list given on page 22. The form of cross- section depends principally on the soil through which the canal is cut. The velocity is selected so that the linings will not be disturbed by the flowing water and sufficient velocity given to the flow so that silt will not be deposited. The banks of the canal must be made so flat that when they are wet they will not run down into the canal or change their form in any way. Grass will form in most canals, but this can be mowed out and need not be considered. 32 HYDROELECTRIC PLANTS. TABLE X. SAFE VELOCITIES FOR CANALS, AT WHICH THE VARIOUS SOILS WILL NOT WASH. Soft brown earth ......... Safe mean velocity ft. per sec. Soft loam ........ . ...... " " " " Sand ................... Gravel .................. " Pebbles (most gravel) ____ Broken stones, flint ...... " " " Conglomerate, soft slate. . " . " Pure clay ............... " Stratified rock ........... " " Hard rock ............ ... " " These values are recommended by Kutter as being safe. 0.328 .656 1.312 2.625 3.938 5.579 6.564 7.000 8.204 13.127 ' EFFECT OF ICE ON THE FLOW. In all northern latitudes, due allowance must be made for the ice forming in the canal, which not only reduces the area FIG. 36. but also increases the wetted perimeter. The coefficient n for the surface of the ice may be assumed to be equal to that for a canal in earth or .024. EXAMPLE. Find the difference between the capacities of the canal shown in Fig. 36 having a fall of one foot to the mile when free from ice, and when frozen over as shown. (1) Canal 1200 free from ice: The area, A, = 1200 square feet, r = n - .024. n From Kutter 's formula MEASUREMENT OF FLOW. 33 Substituting 23 + I .00155 .024 .000189 .024 XV 9.68 X. 000189 IV9.68 91. 7X. 0428 = 3.92 feet per second, and Q = 1200X3.92 = 4700 cubic feet per second. (2) Canal frozen over with ice 24 inches thick. 1000 A = 1000. r = 220 = 4.545, n .024 Solving for v, v = 2.31 and Q = 1000X2.31 = 2310. Thus it will be seen that the ice causes a loss in the efficiency of the canal of about 49 per cent. In the case of a shallow, broad canal with rough bottom, the loss is proportionately greater. S FIG. 37. Therefore, in selecting the size of section do not fail to allow for ice. RIVERS, PRELIMINARY MEASUREMENTS. As most frequently happens the stream to be measured 13 .too wide and deep to warrant the construction of a weir, in which case some other method must be adopted. Select some place along the river where for from 50 to 100 feet the water is of uniform depth and width, and measure off along the banks a certain distance, say 100 feet, as in Fig. 37. Divide this distance into 10-foot lengths, and mark the divi- sions with stakes. Take a dry piece of wood and w r eight one end so that when thrown into the water it will stand almost upright, and, as it floats, just clear the bottom of the stream. A piece of lead pipe is a handy thing for this purpose as it may be cut to any length, and easily nailed to the float. 34 HYDROELECTRIC PLANTS. Have an assistant on the bank with a watch and note book. Throw the float into the stream above the first stake and when it has floated down even with it, the assistant takes the time. Then run down and stand ready to catch the float when it gets even with the last stake, and as it arrives at that point call out and the assistant catches the time. The number of seconds it has taken the float to move 100 feet is then entered in the note book. A large number of these readings should be taken, and the float thrown in at different places across the stream so as to get the average velocity of the water. All these measurements added up and divided by their number, now gives the average time it takes the float to move 100 feet. The average velocity of the river will be from 85 to 95 per cent, of this, depending on the unevenness of the river bed. Now take a rod divided into feet and inches, and, starting across the stream even with the first stake, measure the depth FIG. 38. every three or four feet, as at 1, 2, 3, 4, etc., being careful to set the rod on top of the inequalities rather than down in be- tween them. Repeat this operation across from every one of the ten stakes and then add up all the soundings and divide the sum by the number of the readings taken. This gives the aver- age depth in feet. Next get the width of the stream opposite each stake, as A A ', B B f , etc., and divide by the number of measurements, getting the average width. Now to get the cubic feet of water flowing per minute mul- tiply the average width by the average depth and this product by the velocity of the water in feet per minute. A cubic foot of water weighs slightly more than 62J pounds. Therefore the number of cubic feet of water found to be flowing each minute multiplied by 62 J (62J is generally used) , gives the pounds of water flowing each minute. The writer has found that in this way remarkably close re- MEASUREMENT OF FLOW. 35 suits can be obtained, not varying more than five per emit, from measurements made with a standard weir. One of the most reliable floats consists of a jointed tube closed at one end. Fig. 38. The joints are short enough to easily pack away and about 2 inches in diameter. In making the measurements enough joints are screwed together so that when sufficient shot is put in to sink the bottom to within a few inches of the river bed, the top is just out of water. Cur- rent meters are often used for measuring the velocity of a stream. CURRENT METERS. Fig. 39 shows the two types of current meters which are commonly used. The one at the right, is of the cup vane FIG. 39. Revolving type current-meter. type, and the one at the left of the helical. In each case the meter is mounted on a long pole or rod and lowered into the water. The current causes the vanes to revolve and the in- strument is so calibrated that a certain number of revolutions of the vanes indicates a certain velocity of the water. By proper gearing one of the gears is made to revolve once for each passing foot of water. The revolution of this gear is made known to the observer either by electrically ringing a bell or by causing a click which may be heard along the rod. It will be seen that these instruments depend for their accu- racy upon the constancy of the coefficient of friction of the 36 HYDROELECTRIC PLANTS. numerous bearings. These bearings are in agate mostly and yet a small piece of river grass or a grain cf sand can cause a great inaccuracy in the reading. On this account they mvst be frequently inspected, cleaned and re-calibrated. It was to avoid, as much as possible, these sources of error, that the author designed the current meter shown in Fig. 40. In this meter the current strikes the vane, causing it to rotate on the pivot g ; attached to the pivot is a light i-inch brass tube a having at its upper end a pointer c. Being rigidly connected FIG. 40. Direct reading type current-meter. to the vane the pointer c indicates the exact position of the vane /. Now to bring the vane back when acted on by the flow to its position at right angles to the current and the pointer c to 0, the thumb screw, h, is turned. This thumb screw is attached to the torsion wire d and the wire is attached to the pivot g. Therefore by turning the screw h the vane is moved back and the pointer k attached to the thumb screw, to some position, say 175. The torsion in the wire is directly proportional to the pressure on the vane, or the velocity of the water, so the reading will be 175 feet per minute. On the dial the scale, made MEASUREMENT OF FLOW 37. from actual tests, is placed, and gives the velocity in feet per minute (see plan view). When a velocity is wanted all that is necessary is to stick the meter in tne water with the va.ne about perpendicular to the current and then rotate the thumb screw till C comes to 0. By taking the highest reading of the pointer k, C being kept at 0, it will be known that the vane is per- pendicular to the current. In tnis instrument there is no rotation of delicate parts, the vane only moving through an arc of some 30. Therefore grit and grass have little effect on it. Depending on the torsion of a steel wire for its accuracy it is at all times ready for use and readings can be made as easily as time can be taken from a watch. The vanes are detachable and a set of four goes with each instrument so that the greatest sensitiveness of the instrument may be used for all currents. Thus for a very slow current a large vane is used and for a swift current a small vane. When using any but the standard vane the readings have to be multiplied by a constant. This meter is made jointed so that it may easily be carried in a suit case, its weight being but two or three pounds. EXTENSIVE MEASUREMENTS. If the measurements are to be made on a stream of great width and to continue during times of flood, a cable way is suspended over the selected spot and a car is used. The cable is marked every five or ten feet depending on the roughness of the river bottom, and the measurements made at these points every time. In taking accurate measurements it is well to take a mean of three general methods. These methods are as follows: Six tenths single point method; numerous experiments have shown that the average velocity of the entire area is found at a depth equal to six tenths the whole depth. Therefore in taking these measurements the meter is held at that depth under the water at each five or ten foot mark on the cable. The average of these mean values gives the average velocity of the section. Surface single point method; here the meter is held but a foot under the water at each point across the stream and the average taken. This average is then multiplied by .85 to .95 to get the average velocity for the section. .95 would be 38 HYDROELECTRIC PLANTS. used for streams having smooth bottoms. The rougher the bottom, the lower would be the average velocity. In- tegrating method; in this case the meter is lowered slowly and with a uniform motion from the surface to the bottom and back again. From the gauging car measurements of depth are also taken at each interval. The widths are not taken as the profile made at the start shows the location of each interval. CHAPTER III. RECONNOISSANCE OF WATER POWER. Up to a short time ago the common practice has been to purchase a water power and install water wheels as required by the increasing business, without first obtaining exact knowledge of the true value of the full power of the stream. Now, how- ever, when organized capital and business foresight are the governing factors in nearly all power developments, and each horse power obtained is becoming more and more valuable, it behooves us to know as nearly as possible the actual power to be had under the given conditions. It is seldom indeed that the power to be derived from a stream is not over-estimated. This is usually due to the anxiety of the owner to impress the engineer with the fact that he expects a certain amount of power, and the willingness of the engineer to make his report agree with the owner's wishes. Any man of average intelligence should be able to make measurements of his water power which will serve as a check on those taken by the engineer, and in most cases can be used as a basis for the preliminary estimates. POWER MEASUREMENT. Water power is measured by two quantities: pounds of water flowing down the stream each minute, and the " fall " or " head." The amount of head should be found by a competent surveyor, and as the limiting factor is the cost of the overflowed lands, the owner should accompany the surveyor when the levels are run to see that no little brooks or drainage ditches are overlooked. Sometimes a very innocent ditch is a drain for many acres of valuable farm land and if you back it full of water you are liable to heavy damages. The surveyor can from time to time set his level up so that the glass is on a level with the crest line of the proposed dam, and by sweeping around over the river 39 40 HYDROELECTRIC PLANTS. bottoms, get a very good idea of the overflow. A county map is a great aid in getting the acreage of the submerged land. Having obtained the levels, the area of the reservoir as it will be when full should be roughly approximated, as its extent will be of use in determining the value of the power. The head in feet being obtained, the next item should be the pounds of water flowing in the stream each minute. Great care should be exercised in determining this item. ' To be safe these measurements should extend over several years as the yearly flow varies between wide limits, but usually this is impossible. Measurements taken at any other than during the time of low water will be untrustworthy as it is with the minimum we usually have to deal. In determining these periods of low water, if the observer is a stranger in the vicinity of the proposed dam, he may ask several of the old fishermen and hunters, but should not depend upon merchants and bankers for this most important information. On many of the rivers government reports may be obtained, but the author would advise caution in their use. The methods of determining the flow are fully explained in Chapter II. VALUE OF GOVERNMENT REPORTS TO THE HYDRAULIC ENGINEER. Wishing to make all possible use of the various reports on rainfall, run-off, etc., annually issued by the United States Government, the writer made an extended study of the subject with the following results: No reliable data can be obtained from the reports on preci- pation which will aid in estimating the maximum flood flow. Nor will the rainfall data be of use in predicting the day, week or month when these extreme floods will occur. An average can be taken, but outside of this average are such widely scattered variables that for practical purposes there is no in- formation given. For example, take the Table XI and note that during August, 1903, the rainfall was 6.93 inches, and in October it was 6.26. Yet there is no corresponding increase in the run-off. Note that for March, 1904, the time of the terrible flood which cost many lives and millions of money, the rain was only 3.08 inches. This flood was caused entirely by a sudden thaw which melted RECONNAISSANCE OF WATER POWER. 41 TABLE XI. RAINFALL AND RUN-OFF DATA, SUSQUEHANNA RIVER. AVERAGE OF NINETEEN STATIONS. Month. 19C Run- Off. 3 Rain- fall. 190 Run- Off. 4 Rain- fall. Month. 19 Run- Off. 33 Rain- fall. 19 Run- Off. 04 Rain- fall. Cu. ft. per sec. per sq. mile. inches Cu. ft per sec. per sq. mile. inches Cu. ft. per sec. per sq. mile. inches Cu. ft. per sec. per sq. mile. inches January. . . . 1.626 2.60 1.280 3.46 July 1.331 4.20 0.800 5.16 February. . . 3.552 2.50 1.620 2.24 August. . . . 1.053 6.93 0.519 4.21 March 5.023 4.93 4.280 3.08 September . 1.277 1.64 0.413 3.56 April 2.910 2.01 2.930 2.79 October 1.822 6.26 0.698 3.01 May 0.628 0.85 1.750 3.64 November. . 1.151 2.24 0.498 1.17 June 1.115 6.70 1.290 2.99 December. . . 0.737 2.20 0.407 2.18 Total rainfall for year = 25 inches (1903), and 18.7 inches (1904). TABLE XII. RUN-OFF AND RAINFALL DATA FOR VARIOUS RIVERS. Date Drainage area sq. miles Run-orf cu. ft. per sec. per sq. mile Chippewa R Eau Claire Wis 1904 G740 1 362 Flambeau R,. Ladysmith, Wis 1904 2,120 1.230 Wisconsin R Merrill Wis 1904 2,630 1 850 Rock R Rockton 111 1904 6,150 * 761 Illinois R., Minooka, 111 Youghiogheny R., Friendsville, Md Mahoning R., Youngstown, O Licking R., Pleasant Valley, O New R., Radford, Va New R., Fayette, W. Va 190* 1904 1904 1904 1904 1904 6,480 295 958 696 2,725 6,200 1.953 f2.120 1.247 .792 .968 .929 Greenbrier R Alderson, W Va 1903 1 344 1 480 Greenbrier R Alderson, W Va 1904 1 344 911 Scioto R., Columbus, O Olentangy R., near Columbus, O Wabash R., Logansport, Ind Tippecanoe R., Delphi, Ind White R. (E. Branch), Shoals, Ind French Broad R., Oldtown, Tenn leniessee R Knoxville, Tenn 1904 1904 1904 1904 1904 1904 1904 1,051 520 3,163 1,890 4,900 1,737 8 990 1.017 1.103 1.600 off 10% .947 1.050 842 Pigeon R Newport, Tenn 1904 655 070 Nolichucky R., Granville, Tenn Halston R. (S. Fork), Bluff City, Tenn Watauga R., Elizabethton, Tenn Little Tennessee R., Judson, N. C Tuckasegee R Bryson, N C 1904 1904 1904 1904 1904 1,099 828 408 675 662 .030 .862 .280 .650 470 Hiwassee R Murphy, N C . 1904 410 290 Hiwassee R., Reliance, Tenn Nottely R., Ranger, N. C Susquehanna R., McCall's Ferry, Pa 1904 1904 1,180 272 1,370 .200 1.140 Average value. . . . 1.23 1.357 * Minimum is 62% too low. t Maximum is 58% too high. 42 HYDROELECTRIC PLANTS. TABLE XII. (Continued.) Name of River. Date. Drainage area sq. miles. Run-off cu. ft. per sec. per sq. mile. Colorado R., Yuma, Arizona Gila R., Yuma, Arizona Virde R., McDowell, Arizona 1903 1903 1903 225,049 6,000 .069 .085 .0533 Salt R., McDowell, Arizona 1903 6,260 .041 Salt River, Roosevelt, Arizona 1903 5,756 .061 Tonto Creek Roosevelt Arizona 1903 1,030 038 Grand R Klmwood Springs Colo 1903 5,838 47 Whiterocks R Whiterocks Utah 1903 114 1 23 Bear R., Collinston, Utah 1903 6,000 .20 Sevier R Gunnison Utah 1903 3,986 027 San Pitch R Gunnison Utah 1903 836 045 Humboldt R Oreana Nev 1903 13,800 .009 Humboldt R., Golconda, Nev 1903 10,780 .0158 Humboldt R., Palisade, Nev 1903 5,014 .066 South Fork of Humboldt R., Elko, Nev 1903 1,150 .153 East Fork of Walker R., Yerington, Nev West Fork of Walker R., Coleville, Cal Walker R., Wabuska, Cal 1903 1903 1903 1,130 306 2,420 .103 1.02 .0704 Carson R., Empire, Nev 1903 988 .43 East Fork of Carson R., Gardnerville, Nev West Fork of Carson R.. Woodfords, Cal Truckee R Tahoe Cal 1903 1903 1903 381 70 519 1.21 1.70 .40 Truckee R Vista Nev 1903 1,519 .52 Truckee R Pyramid Lake, Nev 1903 2,130 .40 Truckee R Mystic Cal 1903 955 .79 Donner Creek Trucker Cal 1903 30 2.57 Cache Creek Yolo, Cal 1903 1,280 .43 Cache Creek Lower Lake, Cal 1903 500 .67 Feather R Oroville Cal . 1903 3,350 2.11 Stony Creek Fruto Cal 1903 760 .71 Sacramento R , Red Bluff Cal 1903 9,295 1.50 Tuolumin R , Lagrange Cal 1903 1,501 1.82 Merced R , Merced Falls Cal 1903 1,090 1.28 King R., Sanger, Cal 1903 1,742 1.31 Yule R , Portersville Cal 1903 437 .34 Kern R., Bakersfield, Cal 1903 2,345 .32 Santa Anna R Waumpingo Cal 1903 182 .46 Mohave R Victorville Cal 1903 400 .37 Yakima R., Kiona, Wash Yakima R Union Gap Wash 1903 1903 5,230 3,300 1.12 1.83 Naches R North Yakima Wash . . 1903 1,000 2.57 Triton R North Yakima Wash 1903 289 3.15 Missoula R., Missoula, Mont Brittmort R Grantsdale Mont 1903 1903 5,960 1,550 .571 1.007 Weiser R., Weiser, Idaho Boise R Boise Idaho . . 1903 1903 1,670 2.450 .80 1 .28 RECONNAISSANCE OF WATER POWER. 43 the accumulated snow, and such a thaw may occur at any time of the winter. In the summer we are no more sure of the flood periods. There may have been a drought and then a terrible rainfall. In this case the dry soil takes up so much of the precipation that there is no flood. Another year is damp but has slight precipation. A heavy rain comes and the soil being saturated, all the rain runs into the river and a flood is the result. There- fore it is impossible to predict the flood periods from rain fall data. For the same river the run-off changes between wicle limits, for the same rainfall and for the same time of the year. The rainfall at one station bears no resemblance to that at other stations on the same drainage area. From the government reports on run-off per square mile of drainage area, data can be obtained, which is of use in com- puting the yearly power to be depended upon. If the reports have extended over a period of several years, a table like table XI, covering that period will give an annual run-off per square mile which will be very close to the actual. An enterprise properly handled will not figure on the results of the poorest year, but will base the investment on the average income for a long period. In this case the above average run-off for all the years will furnish a safe basis for estimating the power. As will be seen by referring to Tables XI to XIII, the run-off per square mile of drainage area, varies somewhat for different rivers, and for the same river it varies with the year, but the average results are not so erratic as to preclude their use as a basis for estimates. It will be noticed that the Western rivers are much more erratic than those of the Eastern or Middle States, but even in their case, by using judgment in considering the location 'of those rivers having abnormal run-off, a safe average value can be estimated for the average annual run-off per square mile of drainage area. The maximum flood to be expected, no matter when it occurs, is a matter of great importance, as the safety of the enterprise largely depends upon it. There is one way, and only one way, to compute this, whether done by the Government or the engineer, and that is by meas- urements made on the spot. Where the Government gauging 44 HYDROELECTRIC PLANTS. -IOO OfO t w c So *o b> O 9 M CO^"-O?0 ^ O C 10 eg o S^ ^1 econd. Then Q = A C ^/rX \/7, or, 40 = 302.9 XV^ and \/s~= .132. From Table VI we find the slope = one foot in 55. v = 10.8 feet per second. (4) 24 inch steel riveted pipe 2150 + 3450 feet long. From_ Table III A C \/r for cast iron pipes = 247.57. Q A C \A-X\A and 40 = 247.57 v^, \ 7 * = .00161. From Table V the slope = one foot in 36 feet. In this way the total head lost between the reservoir and power house is found to be about 200 feet. Thus, if one foot head is lost for every 36 feet of the 24 inch pipe, the length of ;he pipe divided by 36 gives the total loss of 155 feet. Adding this to the loss in the 26 inch pipe a loss of nearly 200 feet is obtained. The gravity pipe line pierced the mountains in 19 places in order that its center line might coincide with the hydraulic gradient, The total length of tunnels was 7,490 feet. This should encourage the engineer who has the ordinary proposition under consideration. ICE EVILS. In making a reconnoissance, the engineer should always take into consideration the probable trouble to be expected from cold weather. The author recently (1906) made a tour of the great water power plants in the northern states during the extremely cold season, and made a special study of the ice troubles experienced in operation. A resume' of the conclusions drawn from the investigation is given below: 56 HYDROELECTRIC PLANTS. Narrow channels parallel with the dams and head works were seldom troubled with ice ; plants having short mill ponds ending in rapids or long shallow ponds ending in rapids were invariably troubled with anchor ice; in ponds which were frozen over to a good depth the anchor ice lost its form before it got to the racks; tail races which were not protected were frozen over and clogged unless they were deep enough to take care of the water; turbines running in unprotected steel flumes were, in some cases, so bothered by water freezing in the flumes that housings had to be built around the flume and fires kept burning ; FIG. 45. the lowest flow in the winter was about the same as that during the low water period in summer. SOUNDINGS. Test Holes. The natural impulse of engineers and investors is to rush into a job without preliminary soundings which are to tell what the foundations will be. Not long ago the author was called upon to inspect a site for a dam and found that be- cause the banks on either side of the river were stone, the owners had jumped at the conclusion that the bottom was also stone. $20,000 was spent in getting ready to build a masonry dam and then it was found that there was no rock bottom. Often the rock bottom drops perpendicularly down for from 50 to 100 feet as shown in Fig. 45. The continual wearing of the valleys fills the river bed below the ledge with sand and gravel, and to the eye presents the appearance of a uniform river bed. Unfortunately this condition is most likely to exist RECONNAISSANCE OF WATER POWER, 57 at the narrowest part of the river and between cliffs, just where the dam would naturally be wanted. Again there may be mud holes under what is apparently solid rock bottom, as at M, Fig. 46, and there may be several inches of mud between the layers of rock. Another condition often found is shown in Fig. 47. A founda- FIG. 46. tion is excavated for the power house in the hard blue clay and unless soundings are made it would not be suspected that at the shore side the foundations rested on only a few inches of clay, the rest being quicksand. In this case the power house would settle badly and in time be destroyed. These three cases (there are many more) should serve to urge the engineer and investor to spend some money on sounding the bottom. FIG. 47. Rock. On extremely large and important work a diamond drill is used in getting a sample of the river bed. The diamond drill brings to the surface a solid core of rock, an examination of which tells exactly the nature of the bottom. An accurate measurement must be made of the depth of the diamond below the surface so that if there are seams in the rock their thickness may be determined. Soft Bottoms. The common way of sounding soft bottoms is to drive a gas pipe of from 2J to 4 inches diameter in the same 58 HYDROELECTRIC PLANTS. way a drive-well is sunk. The pipe is divided into 8 foot sec- tions and driven with a plug in the top end. Every 2 feet, 4 feet, or 8 feet, the plug is removed and the pipe cleaned out with a sand pump. Water is used to loosen up the materials in the pipe. By examining the materials thus removed a record is made of the bottom. It is a good plan to empty the pump each time into a tall glass jar, the water being drained off. The exact composition of the materials may then be ascertained. From time to time the pipe will become plugged with stone, in which case a drill such as shown in Fig. 115 is screwed into a gas pipe and two men, using it as a churn drill, drill out the obstruction. The driver used is usually made in the form of a small pile driver, a heavy section of some hard-wood tree being used for the hammer. The hammer may be lifted by man power. "Where only a few holes are required a 2 inch pipe may be driven with a heavy post maul. Much may be learned of the character of the substratas by sounding with a f-inch round iron rod, and the engineer should never be without such a rod when making a hasty preliminary inspection. Only a year ago the author learned this at a cost of about $6000. After the contract was secured, a little -inch _. rod showed that where it was without a doubt solid granite, the bottom dropped down 14 feet, making much more ex- cavation necessary than had been figured on, and necessitating the building of more dam. By listening to the rod you can tell whether any rock struck is solid or only a boulder. For most soft soils a common 2-inch wood auger having a auger handle, or, for deep boring, a handle several feet long, is handy for sounding. There are several earth augers on the market, but for soft loams and clay a common auger is good. In this manner one or two men can sound over a large area. FLOWAGE HEIGHT. When a dam is to be built it becomes a question of great moment, just how high the water will be raised at different points above the dam. There may be a city up the river whose drainage rights must not be affected, or there may be another water power above the proposed dam whose tail water limits RECONNAISSANCE OF WATER POWER. 59 the height of the proposed dam. In these cases it must be known what the flowage height will be. Water flowing in the stream obeys the same laws as when flowing in a canal or penstock. It merely becomes a greater question of judgment in selecting the coefficient of roughness. The first step is to go over the reservoir with a competent surveyor and take accurate profiles of the cross-section similar to Fig. 48, say at half-mile intervals. Here A B is the assumed elevation of the water when backed up by the dam, C D is a line on the exact level of the dam's crest, E F is the level of the water in the river at the particular section before the dam is built. While on the ground decide about what the coefficient of roughness will be, making allowance for bends in the river, undulating ground, stumpages, etc. f/J FIG. 48. The fall F in feet between any two points along the stream above the dam can be found from the formula F = wherein F is the fall between two consecutive points where the section of the river has been determined, v is the velocity of the stream in feet per second, D is the distance in feet be- tween the points, C, a coefficient depending upon the ratio of the wet perimeter to the cross-section of the stream and r is the mean hydraulic radius. wherein Q is the cubic feet of water flowing per second, and A is the area of the cross-section in square feet. t>0 HYDROELECTRIC PLANTS. C may be taken from the table given below. ,4 r -=p- wherein P is the length of the wet perimeter. The area A = A B F G E. can be estimated from the pro- file curves of the cross-section at the point in question. Taking the profiles of the cross-sections every half mile and solving for F in the above formula a curve of flowage height, F can be plotted. EXAMPLE. A river having a flow of 100,000 cubic feet per minute is to be dammed with a 12-foot dam. At one mile intervals the sections 1, 2, 3, etc., are taken each at the middle of the interval. Fig. 49 shows the section one-half mile above the dam. For TABLE XIV. VALUES FOR C COMMONLY USED BY ENGINEERS. For rivers, and canals in earth. Fairly regular. For values of r less than 0.5 u " from han 5 c - 30 5 to 1 C 45 1 " 2 c 55 2 " 3 c 65 3 " 4 .. .. c = 80 4 "10 30 "75. . c . .c = 100 = 125 the first mile there should not be more than J-inch fall, so A B will be assumed to be on the same level as the top of the dam C D. With a planimeter, or otherwise, the area A = 4800 square feet may be found. The wet perimeter P = 480 feet, therefore = hydraulic mean radius = r = 10. From Ta- ble XIV C would be 100. cu. it. per min. "4X60 100,000 4800X60 = .0347. D = 5280. RECONNAISSANCE OF WATER POWER. 61 ' - - Profile 2 (Fig. 50) is located a mile above the first section and 1J miles above the dam. Profiting by the first calculations A B is placed one inch above C D (Fig. 48) the area A then = 100 000 2600 square feet and r = 3.24, D = 5280, v =- - - .64. C *> H$sr= FIG. 50. and so on with all the sections taken. When a section is reached where the area A divided into fhe flow Q gives exactly the same velocity as that found in the stream at that section before the dam is built, we know that we are where the dam does not affect the flow at all. In other words the line A B coincides with the normal surface of the water in the river at that point before the building of the dam. COST OF SURVEYS. The cost of a survey depends entirely on the density of under- brush, and forests, on the variation of levels and on the weather. Where it is only desired to get an approximate and hasty 62 HYDROELECTRIC PLANTS. level showing the possible head obtainable a level may be run without checking back, for about $2 per mile. More accurate levels such as would be used for the basis of an investment, would cost about $5 per mile. Precise levels will cost $20 to $30 per mile. A fairly accurate survey of the overflowed land can be made for from $0.25 to $0.50 per acre. This includes running the levels and staking out the high water level. Topographical surveys with about 50 foot contour intervals will cost, for densely wooded and irregular surface, about $200 per square mile, for more open country about $80 to $90, and for extensive valleys, bare of all brush and trees and with gently sloping sides, about $50. The same surveys with 5-foot intervals and very precisely made, may cost from $1000 to $2000 per square mile. ENGINEER'S REPORT. GOVERNMENT REPORTS. Great importance is attached by all capitalists to the reports of the Government. It is the only unbiased report they have to rely upon. It is therefore well to give the Government reports a prominent place. If these reports, as is often the, case, give a minimum flow which there is reason to believe is too small or too large, every effort should be made to obtain from the office of Hydrography a detailed description of exactly how the measurements were taken. A visit to the gauging station may be necessary to determine the value of the reports. All the topographical maps prepared by the department, re- lating to the drainage area should be procured. The Weather Bureau of the Department of Agriculture should be consulted and the rainfall for the driest year in ten tabulated and the average taken as in Table XIII. It is also a good plan to prepare curves showing the rainfall (average) for each month on the whole drainage area for, say, ten years. The run-off reports furnish data for another curve showing the average run-off over a long .period. ENGINEER'S MEASUREMENTS. (1) From the measurements made by the engineer curves are plotted showing the run-off for as long as they were taken. RECONNAISSANCE OF WATER POWER. 63 TABLE XV RUN-OFF AND XV.AIN FALL DATA. Branch of River to be developed Run-off of Similar River, cu. it. per sec. per sq. mile. Ratio. f b Rainfall inches. Run-off cu. ft. per sec. per sq. mile. Ratio b a Sta Y StaZ *+_' - * 2 T Month. (a) 80 (O (d) w (/) (g) June 2.70 2.420 0.896 0.56 0.46 0.510 0.211 July 6.75 5.854 0.807 0.44 0.47 0.455 0.078 August .... 0.94 0.818 0.870 0.27 0.31 0.290 0.356 TABLE XVI. RUN-OFF AND RAIN FALL DATA. (DRY YEAR). Branch of River to be Developed. Run-off of River to be Developed. Rainfall dry year, inches. Run-off. h Xc = * Cu. ft. per sec. per sq. mile. i Xg = j Cu. ft. per sec. per 570 sq. miles. 570 X; = k. Month. 0b) <) (/) ( June 1.67 1.496 0.315 179.55 July 3.88 3.364 0.261 148.77 August .... 3.88 3.364 0.261 148.77 TABLE XVII. RESERVOIR EVAPORATION. inches. Cubic feet corresponding to area 15 sq. miles, area Xl = m V) (m) 6.10 212,572,800 6.90 240,451,200 5.60 195,148,800 TABLE XVIII. WATER FOR MINIMUM YEAR Total Run-off, sec. Xk = Power Draught @ 400 cu. ft. per sec. sec. X400 = Total Draught o + m = p Net Volume cu. ft. n-p = q Month. June. (K) 465 393 600 (o) 1 036 800 000 (P} 1 249 372 800 ( 90 % net. Step-up Transformers . . .97% 92. 1% " Transmission line 95% 87.5% " Step down Transformers 97% 84 . 6% " Distribution to Sub-stations 93% 79 . 0% " Rotary Converters 90% 71 . 1% " Some branch of the river to be developed for which rainfall data is available, is selected and the run-off measured for each month. The ratio between run-off and rainfall being estab- lished for this branch, the rainfall for the driest year is multi- plied by this ratio in order to obtain the run-off of the branch. At the same time the run-off of this branch is compared with that of the similar river, the average of two gauging stations y and Z being taken, and another ratio determined- then mul- tiplying the flow of the branch for the dry year by this second ratio the approximate flow of the river is obtained. RECONNAISSANCE OF WATER POWER. 65 Tables XV to XVIII show the method of computing the ap- proximate run-off of a river when that of a similar river is known, the evaporation being taken into account. From these four tables curves may be plotted showing the level of the water in the reservoir each month for one or more years. Two of the driest years may be taken. Another table may be prepared in connection with the ones given herewith, which will show the area of the reservoir for every foot of elevation between the points of maximum and minimum head. FORM OF REPORT. Having compiled the foregoing data the report might take the following form, subject to those modifications which each particular proposition will make necessary: Introduction. DEAR SIR: I beg to submit, etc. General Description. The site of the proposed development, etc. Flow of the Stream. Curves relating to the measurements made by engineers and Government. Table developing the " ratio " of run-off. Table giving run-off for stream under consideration. Table giving evaporation. Table giving net run -off for use through turbines, etc. Power Capacity of the Stream. Table giving the efficiencies of each mechanism commencing with the turbine and ending at the point where power is sold. Curves showing the delivered power for each year when meas- urements were taken. Market for the Power. Table or curves showing the load of the various customers, the rate of increase of the power used by these companies for a few years back and the estimated power which they will use for a number of years in the future. Curve showing the char- acter of the probable daily load. Auxiliary Steam Operation. Curve showing the power in the river during a dry year and a shaded portion showing the part of the load which would have to be carried by steam. Table showing the per cent, of 66 HYDROELECTRIC PLANTS TABLE XX. MAINTENANCE AND DEPRECIATION. Maintenance. Depreciation. Buildings 1.0 1.0 Auxiliary Mechanism 1.0 1.0 Exciters 5.0 2.0 Storage Battery 5.0 2.0 Generators 2.0 5.0 Transformers 2.0 1.0 Station Wiring 1.0 5.0 Lightning Protection 15.0 0.8 Transmission Line 10.0 0.0 Turbines 3.5 18.0 Gates and Racks . . 1.0 7.5 TABLE XX-A. COST OF OPERATING STEAM POWER. Year to which figures are assumed to apply Total yearly demand at ( ) per kw-hr. Average output rate for year kw Average output rate for year (max. day) kw Engine and generating capacity kept ready for use (h p nom ) 1905 1910 1915 n Boilers retained in station Per cent, of demand required by steam Total output by steam for year kw-hr Cost of coal for actual running at ( ) per kw-hr . . . . . Cost of coal for banking (at 10, 8, 6, 4 and 3%).. Emergency labor (.0075, 0070, .004 cts. per kw-hr. Permanent force at station Maintenance of boilers at 80c. per h.p. . . . Maintenance of engine at 60c. per h.p. . . . Total cost of operating steam auxiliary Cost per kw-hr. output RECONNAISSANCE OF WATER POWER. 67 steam operation based on the load for a few years back and covering a number of years in the future. Back Water Conditions. Full description with curves showing the duration, etc. Pondage. Table giving cubical contents of reservoir for each foot of depth the pond will be drawn down. Curves of the power with shaded portion showing the part of the load the stored-up water will carry (similar to the steam load). Detailed Description of the Work. Power house, transmission lines, canals, head gates, dam, miscellaneous. Estimates of Cost of Construction. Dam, power house, etc. Operating Charges. Maintenance and Depreciation. Table showing per cent, of depreciation and maintenance on each detail of the work; labor and small supplies. (Table XX.) Cost of operation of auxiliary power, taxes, interest, office expenses, etc. (Table XXA.) Revenue. Full reasons for believing power can be sold at the given price, etc. Summary. Gross receipts .....$ Operating expenses $. . . Net profit $ Interest on the investment $ As an appendix the report may contain small scale drawings of the dam, power house, etc. Photographs made from the tracings are good for this purpose. CHAPTER IV. MATERIALS. Before taking up hydraulic construction it is well to consider the relative suitability of the various materials. Many times structures are subjected to alternate exposure of air and water, and this condition is a severe one which comparatively few materials can successfully withstand. WOOD. It is a well known fact that practically all woods, if submerged in water, will be preserved from decay. Therefore, where pos- sible, all timber should be submerged. The condition most conducive to decay is that of continual change from dry to wet and wet to dry. The most rapid decay ever witnessed by the writer was where the posts of a flume came in contact wit^ gumbo, a soil common alcr-g western rivers, and at the water line. In this case 8x8-inch pine timber lasted only six years. Ordinarily, pine timber under most unfavorable conditions, lasts from eight to twelve years. With few exceptions, all timber decays first in the sapwood. Hence specifications should exclude the sap. Certain woods are wholly unsuited for work in contact with varying degrees of moisture. Some of these are as follows: Elm (except rock elm), soft maple, willow, poplar, baswood, all oaks (except white, pin oak and live oak), spruce, pine and hemlock. Among the best, and in order of superiority for such work, are the following: Texas and Oregon fir, red and white cedar, " Hart " yellow pine, live oak, white oak, pin oak, white pine (free from sap), beech, spruce pine, tamerack and hemlock. Hemlock is given in both lists, as it is on the border-line. The upland hemlock lasts fairly well. Yellow pine, when free from sap, makes a very satisfactory material, and the cost is moderate. For most rivers, white oak makes good timber, yet 68 MATERIALS. 69 there are cases on record where the acid in the oak was attacked by some chemical in the water and the timber destroyed in a few years. No matter what wood is used, or how well it may be dry-seas- oned, after it has been exposed to water for a few years, it will shrink. Of course, the more thoroughly it is dried, the less will be the contraction. The first effect of the water is to swell the wood. Plank, when continually wet on one side so that the wood is saturated, will last indefinitely. Soft wood is worn away less rapidly by running water than is hard wood. METALS. Among the cheaper metals, cast iron resists the corroding effect of water the best. Steel corrodes much more rapidly. All metals corrode more rapidly when exposed to running water, and the higher the velocity the more rapid the corrosion. Steel penstocks wear away rapidly and become rough, increasing the coefficient of friction. Nothing thinner than J-inch should be used. For work under high heads such as several hundred feet or more the water frequently bores holes through cast iron turbine runners, and nothing but bronze should be used for such parts. CEMENT AND CONCRETE. Five years ago we were in the steel age, but to-day it is the concrete-steel age. Bridges on all the great railways were then built of steel; to-day the best practice points to the concrete- steel bridge. The price of steel remains at about the same figure. The price of timber is steadily going up, having increased fully 50 per cent, in 10 years. Interest on money is steadily going down. Cement is each year getting cheaper. The tendency of the limes is toward more permanent construction. These facts have con- tributed to usher in the concrete-steel age. The characteristics of steel have been thoroughly worked out. It has high tensile strength, is quite flexible, has good elasticity, and is uniform in all its features. But cement is not so well understood. In fact, there are as many ideas concerning its proper combinations as there are engineers. 70 HYDROELECTRIC PLANTS. There are two distinct kinds of cement, natural or Rosendale, and Portland. Some of the largest works have used Rosendale, as, for instance, the Croton dam, but in the last few years Port- land cement has been made in the United States in much larger quantities and of such splendid quality that the use of any other is no longer advisable. Frost affects Rosendale cement, and under no circumstances should it be used when frost can reach it. For the interior portions of large monolithic dams and where it is desired to save a few dollars (a questionable policy) Rosendale might be used. The price of Portland has now gained a point where, on account of its superior strength, there is no real economy in the use of cheap cement. There are innumerable brands of cement made in the United States to-day, most of which are equal to the English and Ger- man cements. Among the best might be mentioned Giant Portland, Lehigh, and Atlas. TESTING. All cement, no matter of what brand, should be tested before being used on important works. The following tests are those recommended by the American 1 Society of Civil Engineers in 1902*, and which are without doubt the most authorative we have to-day. Sampling. Selection of Sample. The selection of the sample for testing is a detail that must be left to the discretion of the engineer; the number and the quantity to be taken from each package will depend largely on the importance of the work, the number of tests to be made and the facilities for making them. The sample shall be a fair average of the contents of the package; it is recommended that, where conditions permit, one barrel in every 10 should be sampled. All samples should be passed through a sieve having 20 meshes per linear inch, in order to break up lumps and remove foreign material; this is also a very effective method for mixing them together in order to obtain an average. For determining the characteristics of a shipment *Report of the American Society of Civil Engineers' Committee on Uniform tests of Cement. MATERIALS. 71 of cement, the individual samples may be mixed and the average tested; where time will permit, however, it is recommended that they be tested separately. Method of Sampling. Cement in barrels should be sampled through a hole made in the center of one of the staves, midway between the heads, or in the head, by means of an auger or sampling iron similar to that used by sugar inspectors. If in bags it should be taken from surface to center. Chemical A nalysis . Significance. Chemical analysis may render valuable service in the detection of adulteration of cement with considerable amounts of inert material, such as slag or ground limestone. It is of use, also in determining whether certain constituents, believed to be harmful when in excess of a -certain percentage, as magnesia and sulphuric anhydride, are present in inadmis- sible proportions. While not recommending a definite limit for these impurities, the committee would suggest that the most recent and reliable evidence appears to indicate that for Portland cement magnesia to the amount of 5 per cent, and sulphuric anhydride to the amount of 1.75 per cent., may safely be con- sidered harmless. The determination of the principal constituents of cement silica, alumina, iron oxide and lime is not conclusive as an indication of quality. Faulty character of cement results more frequently from imperfect preparation of the raw material or defective burning than from incorrect proportions of the con- stituents. Cement made from very finely-ground material, and thoroughly burned, may contain much more lime than the amount usually present and still be perfectly sound. On the other hand, cements low in lime may, on account of careless preparation of the raw materials, be of dangerous character. Further, the ash of the fuel used in burning may so greatly modify the composition of the product as largely to destroy the significance of the results of analysis. Method. As a method to be followed for the analysis of cement that proposed by the Committee on Uniformity in the Analysis of Materials for the Portland Cement Industry, of the New York Section of the Society for Chemical Industry, and pub- lished in the Journal of the Society, for January 15, 1902, is recommended. 72 HYDROELECTRIC PLANTS. Specific Gravity. Significance. The specific gravity of cement is lowered by underburning, adulteration and hydra tion, but the adulteration must be in considerable quantity to effect the results appre- ciably. Inasmuch as the difference in specific gravity are usually very small, great care must be exercised in making the deter- mination. When properly made, this test affords a quick check for underburning or adulteration. Apparatus and Method. The determination of specific gravity is most conveniently made with Le Chatelier's apparatus. This consists of a flask (D), Fig. 51, of 120 cubic centimeters (7.32 FIG. 51. cubic inches) capacity, the neck of which is about 20 centi- meters (7.87 inches) long; in the middle of this neck is a bulb (C), above and below which are two marks (E) and (F) ; the volume between these marks is 20 cubic centimeters (1.22 cubic inches). The neck has a diameter of about 9 millimeters (0.35 inch), and is graduated into 1-10 cubic centimeters above the bulb. Benzine (62 Baume naphtha), or kerosene free from water, should be used in making the determination. The specific gravity can be determined in two ways: 1. The flask is filled with liquid to the lower mark (E), and 64 grains (2.25 ounces) of powder, previously dried at 100 C. MATERIALS. 73 (212 F.) and cooled to the temperature of this liquid, is gradually introduced through the funnel (B) [the stem of which extends into the flask to the top of the bulb (C)], until the upper mark (F) is reached. The difference in weight between the cement remaining and the original quantity (64 grains) is the weight which has displaced 20 cubic centimeters. 2. The whole quantity of the powder is introduced, and the level of the liquid rises to some division of the graduated neck. This reading plus 20 cubic centimeters is the volume displaced by 64 grains of the powder. The specific gravity is then obtained from the formula: . . Weight of cement Specific gravity = A . , Displaced volume. The flask, during the operation, is kept immersed in water in a jar (A), in order to avoid variations in the temperature of the liquid. The results should agree within 0.01. A convenient method for cleaning the apparatus is as follows : The flask is inverted over a large vessel, preferably a glass jar and shaken vertically until the liquid starts to flow freely; it is then held still in a vertical position until empty ; the remaining traces of cement can be removed in a similar manner by pouring into the flask a small quantity of clean liquid and repeating the operation. More accurate determinations may be 'made with the picnometer. Fineness. Significance. It is generally accepted that the coarser par- ticles in cement are practically inert, and it is only the extremely fine powder that possesses adhesive or cementing qualities. The more finely cement is pulverized, all other conditions being the same, the more sand it will carry and produce a mortar of a given strength. The degree of final pulverization which the cement receives at the place of manufacture is ascertained by measuring the residue retained on certain sieves. Those known as the No. 100 and No. 200 sieves are recommended for this pur- pose. Apparatus. The sieve should be circular, about 20 centimeters (7.87 inches) in diameter, 6 centimeters (2.36 inches) high, and provided with a pan 5 centimeters (1.97 inches) deep, and a cover. 74 HYDROELECTRIC PLANTS. The wire cloth should be woven (not twilled) from brass wire having the following diameters: No. 100, 0.0045 inch; No. 200, 0.0324 inch. The wire cloth should be mounted on the frames without distortion; the meshes should be regular in spacing and be within the following limits: No. 100, 96 to 100 meshes to the linear inch; No. 200, 188 to 200 meshes to the linear inch. Fifty grams (1.76 ounces) or 100 grains (3.52 ounces) should be used for the test, and dried at a temperature of 100 C. (212 F.) prior to sieving. Method. The committee, after careful investigation, has reached the conclusion that mechanical sieving is not as prac- tical or efficient as hand work, and, therefore, recommends the following method: The thoroughly dried and coarsely screened sample is weighed and placed on the No. 200 sieve, which, with pan and cover attached, is held in one hand in a slightly inclined position, and moved forward and backward, at the same time striking the side gently with the palm of the other hand, at the rate of about 200 strokes per minute. The operation is con- tinued until not more than 0.1 per cent, passes through after one minute of continuous sieving. The residue is weighed, then placed on the No. 100 sieve and the operation repeated. The work may be expedited by placing in the sieve a small quantity oia large shot. . The result should be reported to the nearest tenth of 1 per cent. Normal Consistency. Significance. The use of a proper percentage of water in making the pastes* from which pats, tests of setting and bri- quettes are made, is exceedingly important, and affects vitally the results obtained. The determination consists in measuring the amount of water required to reduce the cement to a given state of plasticity, or to what is usually designated the normal consistency. Various methods have been proposed for making this determination, none of which have been found entirely satisfactory. The committee recommends the following: Method: Vicat Needle Apparatus. This consists of a frame K, Fig. 52, bearing a movable rod L, which has a cap A at one end, and at the other end a cylinder B, 1 centimeter (0.39 inch *The term " paste " is used in this report to designate a mixture of cement and water, and the word " mortar " a mixture of cement, sand and water. MATERIALS. 75 in diameter, the cap, rod and cylinder weighing 300 grains (10.57 ounces). The rod, which can be held in any desired position by a screw jp, carries an indicator, which moves over a scale (graduated to centimeters) attached to the frame K. The paste is held by a conical, hard-rubber ring 7, 7 centimeters (2.76 inches) in diameter at the base, 4 centimeters (1.57 inches) high, resting on a glass plate /, 10 centimeters (3.94 inches) square. In making the determination, 500 grains (17.64 ounces) of cement are kneeded into a paste, as described in a succeeding paragraph, and is then formed into a ball with the hands, com- FIG. 52. pleting the operation by tossing it six times from one hand to the other, maintained 6 inches apart; the pall is then pressed into the rubber ring, through the larger opening, smoothed off and placed on a glass plate (on its large end), and the smaller end smoothed off with a trowel; the paste, confined in the ring resting on the plate, is placed under the rod bearing the cylinder which is brought in contact with the surface and quickly released. The paste is of normal consistency when the cylinder penetrates to a point in the mass 10 millimeters (0.39 inch) below the top of the ring. Great care must be taken to fill the ring exactly to the top. The trial pastes are made with varying percentages of water 76 HYDROELECTRIC PLANTS. until the correct consistency is obtained. The committee be lieves that the normal consistency should produce a rather wet paste, since this consistency tends to greater uniformity in the mixing, and since there is less liability of compressing the bri- quettes during the molding. Having determined in this manner the proper percentage of water required to produce a neat paste of normal consistency, the proper percentage required for the sand mortars is obtained from an empirical formula. The com- mittee hopes to devise such a formula. The subject proves to be a very difficult one, and, although the committee has given it much study, it is not yet prepared to make a definite recom- mendation. Time of Setting. Significance. The object of this test is to determine the time which elapses from the moment water is added until the paste ceases to be fluid and plastic (called the " initial set "), and also the time required for it to acquire a certain degree of hardness (called the " final " or " hard set.") The former of these is the more important, since, with the com- mencement of setting, the process of crystallization or harden- ing is said to begin. As a disturbance of this process may produce a loss of strength, it is desirable to complete the opera- tion of mixing and molding or incorporating the mortar into the work before the cement begins to set. It is usual to measure arbitrarily the beginning and end of the setting by the pene- tration of weighted wires of given diameters. Method. For this purpose the Vicat needle, which has al- ready been described, should be used. In making the test, a paste of normal consistency is molded and placed under the rod L, Fig. 52; the cylinder and the cap A are replaced by the needle H, one millimeter (0.039 inches) in diameter, and the cap D, the rod L with cap D and needle //, weighing 300 gr. (10.57 ounces). The needle is then carefully brought in con- tact with the surface of the paste and quickly released. The setting is said to have commenced when the needle ceases to pass a point five millimeters (0.20 inches) above the upper surface of the glass plate, and is said to have terminated the moment the needle does not sink visibly into the mass. The test pieces should be stored in moist air during the test ; this is accomplished by placing them on a rack over water MATERIALS. 77 contained in a pan and covered with a damp cloth, the cloth to be kept away from them by means of a wire screen; or they may be stored in a moist box or closet. Care should be taken to keep the needle clean, as the collection of cement on the sides of the needle retards the penetration, while cement on the point reduces the area and tends to increase the penetration* The determination of the time of setting is only approximate, being materially affected by the temperature of the mixing water, the temperature and humidity of the air during the test, the percentage of water used, and the amount of molding the paste receives. FIG. 53. Standard Sand. The committee recognizes the grave objections to the standard quartz now generally used, especially on account of its high percentage of voids, the difficulty of compacting in the molds, and its lack of uniformity ; it has spent much time in investigat- ing the various natural sands which appeared to be available and suitable for use. For the present, the committee recom- mends the natural sand from Ottawa, 111., screened to pass a sieve having 20 meshes per linear inch and retained on a sieve having 30 meshes per linear inch; the wires to have diameters 78 HYDROELECTRIC PLANTS. of 0.0165 and 0.0112 inches, respectively, i.e., half the width of the opening in each case. The Sandusky Portland Cement Co., of Sandusky, O., has agreed to undertake the preparation of this sand, and to furnish it at a price only sufficient to cover the actual cost of preparation. While the form of the briquette recommended by a former committee of the society is not wholly satisfactory, this com- mittee is not prepared to suggest any change, other than round- ing off the corners by curves of J-inch radius, Fig. 53. Molds. The molds should be made of brass, bronze or some equally non-corrodible material, having sufficient metal in the sides to FIG. 54. prevent spreading during molding. Gang molds, which permit molding a number of briquettes at one time, are preferred by many to single molds; since the greater quantity of mortar that can be mixed tends to produce greater uniformity in the re- sults. The type shown in Fig. 54 is recommended. The molds should be wiped with an oily cloth before using. Mixing. All proportions should be stated by weight; the quantity of water to be used should be stated as a percentage of the dry MATERIALS. 79 material. The metric system is recommended because of the convenient relation of the gram and the cubic centimeter. The temperature of the room and the mixing water should be as near 21 C. (70 F.) as it is practicable to maintain it. The Sand and cement should be thoroughly mixed dry. The mixing should be done on some non-absorbing surface, preferably plate glass. If the mixing must be done on an absorbing surface it should be thoroughly dampened prior to use. The quantity of material to be mixed at one time depends on the number of test pieces to be made; about 1000 gr. (35.28 ounces) makes a convenient quantity to mix, especially by hand methods. The committee, after investigation of the various mechanical mixing machines, has decided not to recommend any machine that has thus far been devised, for the following reasons: (1) The tendency of most cement is to " ball up " in the machine, thereby preventing the working of it into a homogeneous paste; (2) there are no means of ascertaining when the mixing is complete without stopping the machine, and (3) the diffi- culty of keeping the machine clean. Method. The material is weighed and placed on the mixing table, and a crater formed in the center, into which the proper percentage of clean water is poured; the material on the outer edge is turned into the crater by the aid of a trowel. As soon as the water has been absorbed, which should not require more than one minute, the operation is completed by vigorously kneading with the hands for an additional 1J minutes, the process being similar to that used in kneading dough. A sand- glass affords a convenient guide for the time of kneading. During the operation of mixing the hands should be protected by gloves, preferably of rubber. Molding. Having worked the paste or mortar to the proper consistency, it is at once placed in the molds by hand. The committee has been unable to secure satisfactory results with the present molding machines; the operation of machine molding is very slow, and the present types. permit of molding but one briquette at a time, and are not practicable with the pastes or mortars herein recommended. Method. The molds should be filled at once, the material 80 HYDROELECTRIC PLANTS. pressed in firmly with the fingers and smoothed off with a trowel without ramming; the material should be heaped up on the upper surface of the mold, and, in smoothing off, the trowel should be drawn over the mold in such a manner as to exert a moderate pressure on the excess material. The mold should be turned over and the operation repeated. A check upon the uniformity of the mixing and molding is afforded by weighing the briquettes just prior to immersion, or upon removal from the moist closet. Briquettes which vary in weight more than three per cent, from the average should not be tested. Storage of the Test Pieces. During the first 24 hours after molding, the test pieces should be kept in moist air to prevent them from drying out. A moist closet or chamber is so easily devised that the use of the damp cloth should be abandoned if possible. Covering the test pieces with a damp cloth is objectionable, as commonly used, because the cloth may dry out unequally, and, in consequence, all the test pieces are not maintained under the same condition. Where a moist closet is not available a cloth may be used and kept uniformly wet by immersing' the ends in water. It should be kept from direct contact with the test pieces by means of a wire screen or some similar arrangement. \ moist closet consists of a soapstone or slate box, or a metal- lined wooden box the metal lining being covered with felt and this felt kept wet. The bottom of the box is so constructed as to hold water, the sides are provided with cleats for holding glass shelves on which to place the briquettes. Care should be taken to keep the air in the closet uniformly moist. After 24 hours in moist air, the test pieces for longer periods of time should be immersed in water maintained as near 21 C. (70 F.) as practicable; they may be stored in tanks or pans, which should be of non-corrodible material. Tensile Strength. The tests may be made on any standard machine. A solid metal clip, as shown in Fig. 55, is recommended; this clip is to be used without cushioning at the points of contact with the test specimen. The bearing at each point of contact should be J-inch wide, and the distance between the center of contact on the same clip should be 1J inches. MATERIALS. 81 Test pieces should be broken as soon as they are removed from the water. Care should be observed in centering the briquettes in the testing machine, as cross-strains, produced by improper centering, tend to lower the breaking strength; the load should not be applied too suddenly, as it may produce vibration, the shock from which often breaks the briquette before the ultimate strength is reached. Care must be taken that the clips and the sides of the briquette be clean and free from grains of sand or dirt, which would prevent a good bearing. The load should be applied at the rate of 600 pounds per minute. The average of the briquettes of each sample tested should be FIG. 55. taken as the test excluding any results which are manifestly faulty. Constancy of Volume Significance. The object is to develop those qualities which tend to destroy the strength and durability of a cement. As it is highly essential to determine such qualities at once, tests of this character are for the most part made in a very short time, and are known, therefore, as accelerated tests. Failure is revealed by cracking, checking, swelling or disintegration, or all of these phenomena. A cement which remains perfectly sound is said to be of constant volume. Methods. Tests for constancy of volume are divided into 82 HYDROELECTRIC PLANTS. two classes: (1) normal tests, or those made in either air or water maintained at about 21 C. (70 F.), and (2) accelerated tests, or those made in air, steam or water, at a temperature of 45 C. (115 F.) and upward. The test pieces should be allowed to remain 24 hours in moist air before immersion in water or steam. For these tests, a pat about 7J centimeters (2.95 inches) in diameter, 1J centimeters (0.49 inches) thick at the center, and tapering to a thin edge, should be made, upon a clean glass plate (about 10 centimeters (3.94 inches) square), from cement paste of normal consistency. Normal Test. A pat is immersed in water maintained as near 21 C. (70 F.) as possible for 28 days, and observed at intervals; the pat should remain firm and hard and show no signs of cracking, distortion or disintegration. Accelerated Test. (a) A pat is placed on a shelf in a suitable vessel filled with fresh water, but without allowing it to touch the bottom. The water is then gradually raised to a tempera- ture of 45' C. (115 F.) and maintained, at this temperature for 24 hours; or (b), a pat is exposed in any convenient way in an atmosphere of steam, above boiling water, in a loosely closed vessel, for three hours. To pass these tests satisfactorily the pats should remain firm and hard and show no signs of cracking, distortion or disintegration. Should the pat leave the plate, distortion may be detected best with a straight-edge applied to the surface which was in contact with the plate. In the present state of our knowledge it cannot be said that cement should necessarily be condemned simply for failure to pass the accelerated tests; nor can a cement be considered entirely satisfactory simply because it has passed these tests. Submitted on behalf of the committee: George S. Webster, chairman; Richard L. Humphrey, secretary; George F. Swain, Alfred Noble, Louis C. Sabin, S. B. Newberry, Clifford Richard- son, W. B. W. Howe, F. H. Lewis. Simple Tests. The tests recommended by the Society are quite exhaustive and are those used on very large works where a man is detailed to the testing work alone. For less extensive work, however, a more rapid and less expensive test is desired. MATERIALS. 83 The following simple tests can be made by the engineer him- self, with an outfit costing not over $4, and which can be stored in a desk pigeon-hole. The tests thus made will be interesting in themselves, and will be effective and convincing aids in re- jecting most bad cements which may be offered, and will also have the preventive effect of causing manufacturers to send their lower grades of cement elsewhere and to send only their best products to the places where such tests are probable: (1) For Fineness. Sift three to four ounces of cement through a standard test sieve of 100 meshes per linear inch. Reject ce- ment of which 10 per cent, by weight is retained on the sieve. This is conservative, and the limit may be made smaller, for many Portland cements are now in the market which will leave less than four per cent. A test by 200-mesh sieve, with a 30 per cent, limit, is desirable, but takes time. (2) For Quickness of Setting. Make a pat of four ounces of neat cement, adding one-quarter to one-fifth its weight of water and making a putty-like ball which can be dropped on the table and retain its form without falling to pieces. Press this upon a 3x4-inch glass plate, leaving it ^-inch thick in the center and sloping to thin edges all around. Note time required to take initial set. Reject cement which sets in less than 25 minutes. It may take three hours or more, but it will be better for paving if it sets in one hour. The instant of " initial set " is determined by nothing when the surface will support a 4-ounce weight resting upon the smooth flat end of a 11/12-inch diameter wire. (3) For Soundness. Use the pat on glass above described and note when it sets enough more to make it difficult to indent it with the thumb nail, or when it will support one pound on the smooth flat end of a 1/24-inch wire, which may be con- sidered as indicating " a hard set." Then put the pat with its glass plate over boiling water until the steam has heated them, and then immerse and keep them in the boiling water for three hours. Reject Portland cement if the pat shows radiating cracks in the center, or shows blow-holes on the surface, or curls up from the glass, or cracks at the thin edges. Good natural cements may fail to endure this test (which is a severe one) , and it may properly cause the rejection of some Portland cements which would endure it after being " air- slacked " or " seasoned." 84 HYDROELECTRIC PLANTS. (4) For Purity. Provide a glass-stoppered bottle of muriatic acid, two shallow white bowls or two J-inch by 6-inch test tubes, a glass rod and a pair of rubber gloves. Put in a bowl or a tube as much cement as can be taken on a nickel 5-cent piece; moisten it with half a teaspoonful of water; cover with clear muriatic acid poured slowly upon the cement while stirring it with the glass rod. Pure Portland cement will effervesce slightly, and will give off some pungent gas and will gradually form a bright yellow jelly without any sediment. Powdered limestone or powdered cement-rock mixed with the pure cement will cause a violent effervescence, the acid boiling and giving off strong fumes until all the carbonate of lime has been consumed, when the bright yellow jelly will form. Powdered sand or quartz or silica mixed with cement will produce no other effect than to remain undissolved as a sedi- ment at the bottom of the yellow jelly. Reject cement which has either of these adulterants. Powdered slag mixed with cement unfits it for pavement work. The adulteration is indicated in the dry cement (when coloring matter does not conceal it) by a lilac tint, and it is also indicated on the surface of a test-pat after drying by brown and green and yellow discolorations. A chemical test will show the presence of slag if made as follows: Provide an ounce of mixture of methylene iodide (CH 2 I 2 ) and benzine, in which the methylene (the specific gravity of which is 3. 292 , being the heaviest organic liquid) is reduced to the specific gravity of 2. 95 by addition of benzine. The methylene is uncommon and costs $1 an ounce. Into a i-inch test tube put J-inch of the dry suspected cement and pour in a little of the mixture, stirring to a thin grout Then cork the tube and let it stand. If slag is present, it will remain at the top, while the cement will settle to the bottom. The separation cannot be seen if coloring matter is present. Coloring matter in any cement will show itself in the acid test by giving a black or gray color to the resultant jelly, which would otherwise be yellow. The coloring matter may or may not be injurious in itself, but its presence shows that the manu- facturer wished to disguise the cement, which should be re- jected, because there are a plenty of good cements which need no disguise. MATERIALS. 85 Weight. The several kinds of cement differ materially in weight, and any cement that varies much from these average weights should be examined specially. The standard barrel contains 3.65 cubic feet, and the standard bag is one-fourth of a barrel. The average weight of a cubic foot of packed cement is: Portland, 104 to 114 pounds; puzzolan, 90 pounds; natural, 75 to 82 pounds for Eastern and 70 to 72 for Western, the average net weight of each per barrel being 375 pounds, 330 pounds, 300 pounds and 265 pounds. Results. These tests will be conclusive as far as they go, and will cause the rejection of no good cements. The makers of high-grade cements would not object to these requirements and would not increase the price because of them. Beam Test. The best test of all is to construct small beams of the actual materials to be used and then select that cement and mixture which gives the best results. Of course tests should be made to determine the freedom from slag, etc. For testing use a beam 2x2x24 inches. A heavy timber lever can easily be made for the center load test. Then the formula P_L_ s_bd* 4 6 gives the safe load P. (see Table XXIX) USES. During the process of manufacturing the cement is frequently over or under burned, making an inferior quality. This is usually mixed in with the other cement and sold. There are times when this inferior cement is sold to the small buyer with the idea that it will not be tested. It is to discourage such acts that the cement is tested. Cement which has been over burned sets with great rapidity and there are times when the hydraulic engineer wants just such cement. By sending to the factory such cement can usu- ally be procured, and if wanted in sufficient quantity it will be made especially to suit the requirements. It must be borne in mind, however, that such cement is only about half as strong as the perfect article. 80 HYDROELECTRIC PLANTS. By reading over the tests for cement, the virtues desired in a good cement will be understood. Cement should be put up in barrels though it adds somewhat to the cost. Paper sacks preserve the cement from loss and moisture better than cloth sacks but are more liable to injury from rough handling. The most common form for shipping is the cloth sack, the sacks being saved and sent back to the factory. Cement alone, neat cement, is seldom used unless it is for pointing or plastering, the usual way being to mix it with sand and crushed stone; sand and slag; sand and burnt clay or gumbo, gravel, cinders, etc. This added material is called the aggregate. The aggregate must always be clean and, when dirty, must be well washed. TABLE XXI. Weight Volume Volume Name. per bbl. in Ibs. perbbl. incu. ft. per bbl. in cu. ft net. Portland 380 4 3.6 Natural . . 300 4 3.6 TABLE XXII. WEIGHT OF CONCRETE. Cinder concrete about 105 Ibs. per cubic foot. Crushed stone concrete " 140 Gravel concrete 150 Slag concrete " 135 Cement mortar 1-2 " 116 The proportions of the aggregate and cement depend not only on the aggregate but also on the character of the work for which it is used. Here is where the judgment of the engineer is brought into play. The walls for flumes, penstocks, canal lining, floors, etc., should be in the proportion of 1J barrels Portland cement to the cubic yard of gravel having the proper proportion of sand and gravel, or if crushed stone is used, the proportion, one cement, two sand and four stone is good practice. For less important work one barrel of cement to the cubic yard of gravel and 1-3-6 if stone is used. MATERIALS. 87 The amount of water used in mixing is one of the open ques- tions. The best engineering practice, however, outside of the laboratories, seems to be to use enough water so that when the concrete is tamped into the forms water stands on the surface and the whole mass quakes when tamped. A wet concrete is more apt to be well made than a more dry TABLE XXIII. CONCRETE AGGREGATES. Cement. Sand. Gravel. Crushed Character of Work. Stone. 1 6 Culvert sides and bottom. 1 5 Culvert arch. 1 4 Culvert arch especially strong. 1 1 Water-tight under high pres- sure. 1 2 or 2J 4 Water-tight under high pres- sure equally good. 1 2J 5 Penstocks, lining for reser- voirs. 1 3 6 Generator and building foun- dations. 1 2 3 Lining for reservoirs. 1 3 6 Backing for reservoirs. 1 3 5 Piers and abutments. 1 7 Steel concrete bridges 25 foot to 35 foot span. 1 2 4 Steel concrete bridges arches span 40 feet to 60 feet. 1 6 Sewers. 1 7 Large breakwater. 1 3 Steel concrete piling, 5000- pound hammer. 1 2 J 5 Floor slabs. 1 2 4 Beams. mixture. Special work which is under the eye of the engineer can be done with the minimum amount. Numerous experi- ments have proven that a wet concrete gets practically as strong as the more dry mixture. In Table XXIII are given some of the mixtures used on im- portant works, actually built, in the United States. 88 HYDROELECTRIC PLANTS. SAND CEMENT. In the West, when, owing to high freight rates and difficulties of transportation, the price of cement reaches a high figure, the conditions are such that sand cement demands recognition. F. L. Smidth is the inventor and a royalty of 10 cents per barrel is charged. The silica sand is placed in a revolving drum in which are pebbles of great hardness. These pebbles grind the sand and equal volume of cement up into a much finer dust than was even the cement before it was put in. The combined mixture of half sand and half cement is then assumed as being all cement, and used with the usual proportions of gravel or sand and stone. Experience with it in California indicates that it gives good results. The following is the itemized cost of a barrel of sand cement, given in Water Supply and Irrigation: One-half barrel Portland cement $5 . 00 One-half barrel sand .18 Grinding sand .20 Royalty 05 Total cost of 375 pounds sand cement $5 . 43 The above was ground so that 95 per cent, passed a 180-mesh sieve. Using 340 pounds of the above per cubic yard of concrete we have the following cost per cubic yard of concrete: Cement sand $4.93 Sand 50 Crushed rock and gravel 2 . 50 Labor . . 1 . 00 Total $8. 93 BURNT CLAY AND GUMBO. The engineer is often called upon to do concreting where there is no stone or gravel. In such localities there is usually clay or gumbo which may be burned and used in the place of the broken stone. The clay or gumbo is burnt as follows: Cord wood is piled in a pile, say 12x12x1 foot. On this spread a layer of coal or slack about four inches thick, and on top of all 15 to 20 inches of clay or gumbo. MATERIALS. 89 On firing the wood enough air enters the pile to enable slow combustion without vitrifying the material. This process costs from 25 to 40 cents per cubic yard. Shrinkage of these clays is about 12 per cent, during burning, and the crushing strength of the burnt product is often as high as 400 pounds per square inch. Gumbo is a black, sticky mud, found along most of the rivers of the United States, especially in the Central and Western States. It is now being used to quite an extent for railroad ballast and highways. Table XXIV shows how the various items of expense are dis- tributed. Of course, the items of labor, forms, mixing and placing, will vary with every case. The costs are given in dollars per cubic yard. TABLE xxrv. COST IN DOLLARS OF CONCRETE WORK PER CUBIC YARD. Character of the Work. Labor and General Expenses. Forms. Lumber in Forms. Mixing and Placing. Power house walls. Surface finished in rock work .20 to .30 .60 to .75 .40 to .60 1. to 1.5 Power house walls. Surface rough .20 to .25 .50 to .60 .35 to .50 1 . to 1 .25 Foundations for buildings, generators, etc. .15 to .20 .15 to .25 .10 to .12 .8 to 1 00 Canal slopes and bottoms (filling) Canal slopes and bottoms (surface) .10 to .20 12 to 25 .10 to .15 25 to 35 .01 to .05 01 to 10 .8 to 1 25 1 25 to 1 5 Walls having numerous windows, etc. Fancy work .25 to .40 1 .50 to 2.0 .75 to 1 .00 1.5 to 1 75 COSTS. A few years ago the idea obtained that concrete should cost at least $6 per yard, but experience has robbed concrete of all its mystery and we must accept it as the best friend the engineer has to-day. In 1903 the author built a large power-house, the concrete for which cost as follows: Hand Mixed All labor (hand-mixing).. Gravel Labor on forms Cement, li barrels. . . $0.75 per cubic yard 25" " " .68 ' " " 2.52 ' " Total $4.20 " 90 HYDROELECTRIC PLANTS. The forms were built of the plank and timber used in the construction of the dam and so cost nothing. The outside of the power-house was finished to represent coursed masonry. The concrete was all hand-mixed, the gravel being dumped from wagons holding just one cubic yard, directly upon the mixing platform. This cost is for the concrete tamped in place, and allows for all shrinkage from the batch measurements. HAND-MIXED CONCRETE. In mixing by hand or machine the crushed stone should be well washed off by means of a stream of water as it comes on to the platform. If wheel-barrows are used they should be of steel and have numerous holes drilled through the bottom to allow the water to drip off. The cement should not be taken from the sack to measure, simply allow 9/10 cubic feet per sack of TABLE XXV. SIZES OF GAUGE BOXES. Proportions. / Sand Box. Size. Vol. cu.ft. , Stone Size. Box. x Vol. cu.ft. 1 2J 4 2'9"X2' XI '8" 9.25 5'X4' 5F 14.80 13 6 2' 9" X2' X2' 0" 11.10 5'X6'8" 22.20 12 5 2'9*X2'X1' 4" 7.40 5'X6' 6i* 18.50 i_2J 6J 2'9"X2'X1'8" 9.25 * 5' X7' 2Y 24.05 95 to 100 pounds. If gravel is used it should not be washed unless the gravel has more than 10 per cent, by weight of loam or 15 per cent, of clay, as it has been found that up to these pro- portions the strength is improved by the loam or clay. When the mixing is in a cramped-up place where wheel- barrows have to be used and the foreman is of the second class, the JDest plan is to have the wheel-barrows dumped into gauge boxes. Table XXV gives the sizes of some gauge boxes found convenient for the proportions given. The sand box is placed on the platform and filled level full. The desired amount of cement is then mixed with the sand, the box having been re- moved, and alongside the sand cement the stone box is filled with the washed stone, the box removed and the cement sand mixed with it once over, the necessary water being played on it through a garden sprinkler. MATERIALS. 91 The more the concrete is mixed the better, but the above mixing ensures good work. For arch construction use fine crushed stone or gravel, of an even size, not to exceed one-inch grade. To determine the exact mixture, take a vessel full of stone or gravel and fill the space in same with sand, by shaking the sand into the stone until the bulk begins to enlarge, showing that no interstices remain unfilled, then measure the proportions of sand and stone. Use one portion of Portland cement to three portions of sand, and proportion of crushed rock as the test may determine. Beams are always tension, and the floor above acts as the compression member, consequently the highest quality of ten- sion concrete is required, which is gravel or fine crushed stone of not over one-half-inch grade. Cinders are not as valuable for beam as for floor or arch con- struction, where their lightness is a consideration. Under ordinary conditions, unless exposed to excessive heat or excessive rain, the following is a safe table for the strength of concrete: TABLE XXVI. When 30 days old 60 per cent, of full strength 60 " " 75 90 " " 85 " 120 ' " CO " 180 " " 95 " 360 " " ICO The extent to which concrete is hurt by freezing can be ascer- tained by estimating that after freezing it will not develop more than 40 per cent, of the balance of the strength it would have attained had it not frozen. The most economical and expeditious method for hand mixing is to dump the gravel or sand and stone directly from the wagons holding one cubic yard on to a large mixing board having an area of about 24x32 feet. If stone and sand are used for the aggregate, two wagon loads of stone are dumped, making two piles in line on the board. A wagon having a fixed partition extending down the middle of the wagon box, and loaded so that one-half of the load of 92 HYDROELECTRIC PLANTS. sand is just right for the cubic yard of stone, is then driven over the stone piles and a half dumped on top of each pile. Four men with square pointed shovels (two at each end of the pile) then commence at the ends and turn the sand and stone over, working toward the middle. When it is all turned over the board men turn around and work the pile back into its former position. The cement is now scattered over the top of the pile by the man who usually acts as a sub foreman. The board men then repeat the first mixing operation, water being sprinkled on the mixture in the meanwhile, through a garden sprinkler. Wheelbarrows take the concrete away, having been filled by the board men. The board men should be the pick of the work- men and should receive 10 per cent, more pay. Three batches FIG. 56 should be run all the time in order to get the most efficient results, and all the men should be employed necessary to take care of every detail of the work. It is very poor policy to skimp the help in concrete mixing. An ordinary No. 4 tank pump, worked by two men, will raise enough water 20 or 30 feet to wet 100 cubic yards of concrete per day. If the concrete is made of sand gravel the first mixing is, of course, unnecessary, and the cement is spread directly over it and mixed twice over by the four board men. MACHINE MIXED CONCRETE. On large work it becomes necessary to handle the concrete in such bulk that hand mixing becomes too slow and expensive. MATERIALS 93 For a small job the cost of transporting and setting up a mixer makes the cost more than if done by hand, but when thousands of cubic yards are made the machine mixed concrete is much cheaper. There are many forms of mixers on the market, though all may be divided into two classes, gravity and mechan- ical. The gravity mixer (see Fig. 56) depends on the force of gravity to mix the aggregate as it falls down a spout lined FIG. 57. Concrete plant. with projections which deflect the concrete from side to side, and thus mix it. These mixers are quite cheap and simple, but there is reason to believe that they do not give as good results as do the mechanical mixers, though they compare favorably with the usual hand mixed cement. Of the mechan- ical mixers the cubical mixer is one of the best. It consists simply of a square metal box mounted on an axis passing through two opposite corners and revolved by steam, electric ; 94 HYDROELECTRIC PLANTS. gasoline or other power. The proper amount of water is fed into the box through a pipe and the batch is dumped in through a door. Where the work to be done is extensive it will pay to fix up a good concrete plant. In Fig. 57 is shown an elevation view of a mixing plant. A large bin is provided for the stone and sand. Under the bin is a measuring box having a movable partition so that any proportion of sand and stone can be obtained. The cement is dumped into a sheet iron chute which empties into the measuring box. The measuring box dumps into the mixer through a canvas tube. The mixer is placed high enough above the ground so that cars or one horse carts may pass under for filling. All mixers into which a certain amount of aggregate is dumped, mixed and drawn off after the motion of the machine has stopped, are called batch mixers. That is a batch is mixed and emptied and then another is put in. To avoid the delay of waiting to fill and dump, continuous mixers are sometimes used. In these mixers the proper aggre- gates are fed in at one end of the mixer continuously, and taken out at the other end. It is generally conceded that machine mixed concrete is the best. The cost of mixing concrete by machine is from 50 to 70 cents per cubic yard. This includes all machine expense and placing the concrete in the forms, but does not include the forms, tamping or cost of material. FORMS. Next in importance to the mixture of the concrete is the building of the forms. It requires the constant vigilance of the engineer to produce good results with the class of labor usually to be procured. The forms must be so built that there will be no springing of the plank. When the work is rushed the green concrete may be several feet deep in the forms and the top being constantly tamped, causes great pres- sure on the sides. If, after the concrete has partly set, the forms spring ever so little, the concrete assumes a new position and a large part of its strength is gone. On large engineering jobs there is usually a great amount of rough lumber used in which case the forms may be built of it, using the heavy timber for posts and the two-inch plank surfaced MATERIALS. 95 on one side and edged for the sheeting. It must be remembered that the concrete will reproduce the finest cracks and grain in the wood sheeting, so great care must be taken to have the surface perfectly smooth and level. The forms should be washed with soft soap just before filling and any cracks or rough places should be filled with hard soap, putty, or any other filling which will not discolor the concrete. Opposite posts should be tied together by means of soft iron wire passed through several times, then twisted up tightly. This is the safest and cheapest method of stiffening. One-half inch bolts may be used but they cost more and are more difficult to obliterate from the exposed surface of the finished concrete. Arches are formed over centers something like that shown FIG. 58. in Fig. 58. No part of the form work should be more rigid than the centers. Plenty of bracing should be used especially when the timbers can afterwards be used on the works so that their only cost is the putting in place. The center above the spring- ing line A B, is built in any convenient place and then carried out and stood upon the posts. The ribs should not be more than two feet apart. Great care must be taken not to remove the forms too soon. A common rule is to allow them to stand nine days, but while this is longer than necessary for some work, it is not enough for other. A long arch should stand two or three weeks, while thin walls only meant to maintain a vertical pressure, can be uncovered in three or four days if necessary. 96 HYDROELECTRIC PLANTS. ROCK WORK. Plain concrete looks too much like plaster to present a good appearance, so the surface is usually made to resemble rock work by tacking strips to the sheeting as in Fig. 59. The appearance thus procured will add from three to four cents per square foot to the cost of the form but will be worth much more than that where a fine appearance is desired. Arches may be given the proper appearance as shown in Fig. 60. The strips used to form this rock work are surfaced all FIG. 59. over and must be of clear stuff, the size may be made to suit the taste, but the section given in the lower part of Fig. 60 gives good results. SURFACING. Where a fine appearance is desired the following method of surfacing is used: As soon as the forms are removed and while the concrete is somewhat soft, the surface is rubbed with pieces of grindstone or blocks of concrete having handles moulded in and composed of one part cement to two parts sand. The sur- MATERIALS. 97 face is then wet down; washed with a coat of grout, of one part cement to one part sifted sand, and rubbed with a wooden float. This finish will not peel and is hard and of uniform color. The concrete may be pricked or tooled to make it more nearly resemble real rock. FIG. 60. Use sheets of steel, called facing boards, for the purpose of holding the coarse concrete away from the surface which it is desired to finish, and have thin grout of one part cement to two parts sand filled in between the facing boards and the form as shown in Fig. 61. " . * FIG. 61. When strips are used to get the rock- work effect, the facing board is merely a sheet of iron or steel with holes in the top corners to admit of their being lifted. But when the surface is plain the facing boards have ribs attached as in Fig. 62 to keep them an inch or so away from the form. 98 HYDROELECTRIC PLANTS. The size of the boards will depend on the size of the walls and usually several lengths are used. The width should be about 12 inches. A coal scuttle having a straight edged snout is handy for pouring the grout in between the boards and the form. Where possible, build the forms up to full height at the start FIG. 62. and dump the concrete at all stages of the work from the top level. In hydraulic work this can usually be done as the em- bankments have to be built to the top levels and the mixing boards may be placed on the embankment. The necessary shoveling of the concrete back into place counteracts the ten- dency of the concrete to unmix in falling FIG. 63. CONCRETE LAID UNDER WATER. Concrete properly laid under water will have a greater strength than if laid in the air. All currents must be avoided, and if this is impossible, the mixture must be enough richer in cement to allow for that washed out. There are several methods for depositing concrete under the water, the best of which is shown in Fig. 63. A large square, steel or wood bucket is made having trap doors as shown. By pulling the wire A the bottom is let MATERIALS. 99 down and the concrete deposited. The box may hold as much as a cubic yard or more of concrete and is handled by means of a derrick. A tube as in Fig. 64 is often used on small work or even a canvas bag, the idea being to get the concrete on to the bottom without washing out the cement. Concrete simply dumped into the water, unless it is very rich and the water shallow, is worthless. When the current cannot be stopped concrete may be depos- ited in sacks partly filled and tamped with a heavy tamp. A large piece of canvas held against the current and the concrete deposited against it often keeps one out of a serious difficulty. GENERAL REMARKS. In depositing the layers of concrete in the forms it is neces- sary to keep the courses level, otherwise the facing boards FIG. 65. cannot be successfully used and the exterior finish will show scars. Courses should be run clear across arches as in Fig. 65. Concrete begins to set the moment it is wet and the quicker it is placed in the form, and the less it is disturbed when so placed, the stronger will it be. Thus, if the forms spring after a few hours of setting the strength is greatly impaired. No blasting should 'be done near the concrete till it has set for at least two| to five days. Before each course is laid the preceding layer must be thor- oughly swept off and wet down. All surfaces between layers must be left as rough as possible, and where a first class job is desired these partly dried surfaces after being wet down should be coated with a thin layer of grout of one part cement and two parts sand. This greatly increases the strength of the joint. 100 HYDROELECTRIC PLANTS. If concrete is deposited and left exposed to the sun, the result will be that at least one-half an inch of the top surface will be absolutely dead and will form a serious parting line in the wall, as the next layer will not adhere to it. Keep the surfaces wet, covered with a damp canvas, straw, etc. The edges of the coping may be rounded with a Crafts edger or with a wood fillet and the joints struck with a Crafts jointer. PECULIARITIES OF CONCRETE. Concrete expands from heat and about the same amount from absorption of moisture. The deck of a reinforced concrete dam will expand about -J-inch per 100 feet when the water is raised upon it. An iron rod embedded in the concrete is gripped firmly by the contraction and the average resistance to pulling out is about 500 pounds per square inch of surface. Anchor bolts grouted in with neat cement will resist ex- tracting better than if set in lead or sulphur. The sun shining on a concrete pier tends to warp it. Slag cements have not yet been proved reliable for hydraulic work. Natural cements should never be used, especially where ex- posed to frost. Concrete has no safe tensile strength. Concrete allowed to set in a pipe contracts so that it may be shaken out. Good concrete contracts or expands for each degree ^uu,uuu Fahrenheit change in temperature. A concrete strut placed between two unyielding abutments will set up a pressure within itself of 15 pounds per square inch for each change of one degree Fahrenheit temperature. CONCRETE IN FREEZING WEATHER. It frequently becomes necessary to lay concrete in freezing weather. If the concrete freezes its strength is less than half what it would otherwise be. To prevent freezing the water used is made quite salt. Barrels half full of salt are kept full of hot water and frequently stirred up. All the water used is taken from them. The concrete is then rushed into the forms MATERIALS. 101 and covered with a canvas and a layer of manure or compact straw or hay. If deposited in water, the water keeps out all frost. If freezing cannot be prevented use plenty of cement and salt. Salt does not affect the strength of the concrete. Concrete so made sets very slowly and is dangerous where it is to sustain pressure in less than two or .three months time. Large fires built on the windward side will keep the tem- perature below freezing. Often a large tent may be placed over the work during construction, and heated by means of large piles of cordwood kept burning constantly. A tent 150 feet long and 60 feet wide can be bought for from $500 to $600. Concrete must not be placed on frosty steel reinforcing as the concrete drops away on the under side when forms are removed. TABLE XXVII. EFFECT OF AGE AND FROST IN STRENGTH OF CONCRETE. Age. days. Strength pounds per square inch. Remarks. 9 213 Tested in usual way. 28 275 Tested in usual way. 7 123 Tested in dry room. 28 130 Tested in dry room. 7 80 ( Frozen every night and 28 100 ( thawed every day. 7 88 Frozen all the time. 28 108 Frozen all the time. There is no absolute necessity of using salt. Shelters should be placed over mixer and stoves placed inside the structures. Hot water should be used and the sand heated. As far as could be determined without actual tests, the salt does not retard setting, as where the concrete was kept heated it set quickly. After the concrete has been deposited it should be immedi- ately covered with tar paper and over the paper should be spread about 10 inches of manure. As long as the interior of the structures is kept heated the concrete on the exterior and next to the forms will not freeze. 102 HYDROELECTRIC PLANTS The concrete under the tar paper will not freeze and will get very hard. Exposed concrete which can not be heated from within can be encased with manure outside the forms. It has been found convenient to provide a trap door in the outside lagging so that the setting of the concrete could be watched. Some authorities claim that Improved Union cement is the best to use in cold weather. One rule is that slow setting Portland must not freeze in less than four days after placing, and quick setting can freeze in 12 hours if kept frozen till set. Some interesting experiments were recently made on slag cement (not slag Portland) with the results shown in Table XXVII. CONCRETE-STEEL. Concrete possesses the qualities of permanence and great crushing strength but little or no tensile or shearing strength. It is the purpose of steel reinforcing to give to the concrete these two items of strength which it lacks. The ideal reinforcing is such as to form a beam which will always fail at the center by pulling apart the steel bars, and at no other part. When con- crete fails by shearing it fails between wide limits and a large factor of safety is necessary, but when all the tension is carried by the reinforcing, the factor of safety need be only such as is used for steel work. Scientific reinforcing does not teach the filling up of the concrete with large steel beams as is sometimes done, but to distribute the proper amount of comparatively small rods throughout the mass and in such a way as to take up all ten- sional moments. Steel expands .0000064 part of its length for each degree Fahrenheit, while concrete expands about .0000057 of its length for each increase of one degree Fahrenheit. This means that in the case of a steel beam 20 feet long imbedded in concrete, there will be a difference in the expansion and con- traction from maximum to minimum temperatures, of about 1/16 inch, Though this is a small amount, it is enough where the reinforcing is large beams, to destroy all adhesion between the steel and concrete. Concrete shrinks on setting about . 1UUU part of its dimensions. Therefore, if there is a large I-beam MATERIALS. 103 imbedded in its mass as in Fig. 66 there is a tendency to form a crack as shown. The crack does not necessarily occur, but a strain is set up which weakens the wall. For these reasons FIG. 66. large steel beams should not be used for reinforcing, but some of the many patent reinforcing bars made especially for the purpose. The Ransom bar is one of the best known and con- sists of a square bar, say one inch square twisted many times. FIG. 67. FIG. 68. The International Fence and Fireproofing Company of Comm- bus, O., make a stranded cable which is used in connection with woven wires as in Figs. 67-68. 104 HYDROELECTRIC PLANTS. The Trussed Concrete Steel Company of Detroit, Mich., have perfected a system of reinforcing which is undoubtedly one of the best we have, They have conducted numerous tests o. beams and slabs which should be of great value to the engineer. It will be seen that the heavier beams are about half as strong as steel beams of the same depth. Figs. 69-72 show a few of the uses for the reinforcement. Fig. 73 shows the bar. The cost of the International cables is about 2J cents per foot, and their metallic sheeting costs 3 cents per square foot. The FIG. 69. Kahn bars cost about 3.9 cents per pound for the small bars, and 3.25 cents for the larger. In Fig. 74 is shown a type of hollow concrete steel construction (Ransom) which possesses many valuable features. Any form of reinforcing may be used. The cost is about 25 to 35 cents per square foot of exterior surface. Fig. 75 shows one method of forming the air cells a, a', etc. The corner curve posts B are covered on the sides c, c', with sheet iron and are not fastened to the rest of the form. The two parts D, D' are separate from the posts. The brace E is a piece of 2x6-inch timber, and two are used to hold each form in place. MATERIALS. 105 The forms are about four feet high. The brace is removed first and the posts pulled out when the entire form easily comes out. The posts are allowed to project enough above the form to permit a chain being attached for pulling them out. At Charles City, la., the writer has just completed a re- inforced concrete penstock, 1100 feet long and having a capacity of 18,000 cubic feet per minute. The loss of head will be 12 inches. 2.C 1 J .4-4-4- -r-T-i- -1 t- rr "IJ! 1-i-t- 1 -4-,-L-i 14~ -4-4-4-j 1 1 ! ! i ' ; ; | > \ , FIG. 70. Fig. 76 shows how the forms were constructed. The lagging was -J inch flooring, 3 inch being used on the curves. The sections were 12 feet long and had five ribs per section. Fifteen sections were built which made 182 feet of penstock. The outer forms were made of 2 inch surfaced plank and 6 by 8 inch posts, on 4 foot centers. 106 HYDROELECTRIC PLANTS. As the work progressed many improvements were made in the inner forms and these are shown in the figures. It was found to be very difficult to clean the bottom at d, and the bottom forms, e, were made so that they could be moved in toward the center 8 inches and without disturbing the upper forms resting on the posts, /. TRA/M5VER5E 5ECT1O/M. - * "~"^| 'h'ttt Hahn Pairs tf'o*.. frfrodo* ,. _ * __ Irrfrfjt*. _ or UPPER ARcn~~p/y. MALP FIG. 71. Penstock reinforced with Kahn Bars. To take out the forms the lower forms were moved toward the center and removed. Then one half of the upper forms was taken out by dropping the side at g, first. The section to the left was that built where the ice would pound and the half on the right where the penstock passed into the excavation. Where the penstock left the cliff it was carried on three MATERIALS, 107 masonry piers, but where it was rock up to the bottom of the penstock it was built as shown. On the side where there was no rock cliff dowel pins were set as shown. The rough surface .CROSS BAR TO RESIST CTF.CTA IISVCRTE..D COMT AND GE.NJE.KAL. PLAN 'A ^ . -SrafTioN J3-J3., FIG. 72. Types of reinforced floors. FIG. 73. Kahn bar. of the rock was smoothed with concrete but no attempt was made to fill it up to the gradient. The outer forms were taken off in three days and the inner, in five days. The weather was cool and almost freezing. 108 HYDROELECTRIC PLANTS. FIG. 75. FIG. 74. Ransome system of reinforced concrete building. runwau jolank universal cement\ v%y? sacks per yd i-:?:: " /e-ffiods 82 Steel, placing 10 Cement 3.30 $5.45 per yard. The power house was entirely of reinforced concrete and built for three 35 in. turbines under a head of 13 feet. Each turbine is in a separate wheel pit. The walls are mostly 10 in. and 16 in. thick. The cost of the concrete in the power house was as follows: Forms, labor \$2.12 Forms, lumber 2 . 00 Pump 40 Concrete, labor 2 . 00 Concrete, cement 3 . 30 Sand 50 Washing and trimming concrete 10 Steel, at $183 , 1 . 10 Steel, placing .50 $12.02 per yard. MATERIALS. Ill The forms in all cases were carried up full height of the struc- ture before the concrete was placed. While this costs more for lumber work is much more rapid. The above power house was built in three weeks, and in winter weather. BUILDING BLOCKS. There are now on the market many patent moulds for making concrete building blocks, but there is no reason why the engineer should not make his own moulds, as it frequently happens that it is desired to make many special blocks. In Fig. 77 is shown a mould which is easily made, and which gives good results and a cheap block. The face board A has fillets D nailed to it to from the joints as shown. The sides E are set up and the spacing boards F slipped into the grooves formed 0838& FIG. 77. by the fillets on the facing boards and the corresponding slits in the side boards. The face of the facing boards is lined per- fectly smooth with metal before the fillets are nailed on. All the wood which comes in contact with the concrete must be thor- oughly soaked in oil to prevent warping and sticking to the concrete. Both sides of the spacing boards should also be lined with iron. When the mould is all assembled the clamps G are put on, then mortar 1 to 2 is poured in so that it stands at the top edge of the fillets. The concrete (mixed rather damp) is then filled in so that it comes about up to the centre of the cores H. The cores are then pressed down between the spacing boards and into the concrete and the mould then filled up over and around the cores. The cores should be covered with sheet metal or 112 HYDROELECTRIC PLANTS. made entirely of it. These are put in the mould by guess, a half- inch one way or the other making no difference. The facing plank should be two or three inches thick, and can be from 12 to 14 or 16 feet long. When filled, the mould should be left for at least four days, when the clamps are knocked off, the blocks taken out and the cores driven out. The cores should have a slight taper. One of the good points of this mould is that the face of the block is at the bottom of the mould, so that it is an easy matter to get a fine, smooth face on the block. Where the face is formed in a vertical position there is sure to be a difference in the hardness and color of the top and bottom edges. The moulds, while drying, must be sprinkled twice a day and kept shaded from the sun. A 1-3-5 mixture makes a strong enough block for all ordinary purposes. If desired, projections may be put on the spacing boards so that there will be cavities in the blocks to fill with mortar while laying, thus binding the whole wall more strongly together. The actual cost of these blocks is from 10 to 12 cents per super- ficial square foot. A wall built of building blocks and nine inches thick equals a brick wall 13 inches thick. To lay a nine-inch wall which would have the same superficial area as a 13-inch brick wall, using 1000 bricks, would cost 7. By adding about J to 3 per cent, of red iron oxide by weight to the cement sand (1 to 1 mixture), the concrete blocks may be made to represent sandstone. Ultra-marine blue added in the same proportion produces a slate or bluish limestone effect. The strength of the concrete is slightly increased by the coloring matter. Ultra-marine green and vermilion can also be used. Bus hammering the surface of the concrete gives it a fine appearance, and only costs 1J to 2 cents per square foot. A wall of blocks will require one-fourth the mortar and one- third the labor that a 13-inch brick wall will. A brick wall 13 inches thick, faced with pressed brick, will cost, per superficial square foot, as follows : 7 pressed brick @ $30 per 1000 $0.02 per square foot 14 common brick @ $10 per 1000 14 " Mortar and Labor .30 Total.. .65 " MATERIALS. 113 The same wall, built of building blocks would cost from 15 to to 20 cents per square foot. It takes one-third cubic yard of mortar to lay 100 blocks 24x8x8 inches, and a mason should lay ten blocks per hour. Labor and mortar costs four to five cents per superficial square foot. STRENGTH OF MATERIALS. It is the purpose of the author to here give a clear and concise treatment of the subject without going into laborious explana- tions and complicated reasoning. The engineer wants the strength of a beam or column and wants it quick. It does not matter if the result is not exact so long as it gives a reasonable degree of accuracy. DEFINITIONS. A moment at a given point is the product of a force and the distance between the given point and the point of application. The neutral line is a line which passes through that part of the section in which there is no strain, neither compression nor tension. The moment of inertia of a section about a certain axis is the sum of the products of the elementary particles of the section and the square of their distance from that axis. The moment of resistance of a section is the quotient obtained by dividing the moment of inertia by the distance of the outside fibers (in which the strain is a maximum) from the neutral line. The radius of gyration of a section is the distance from the axis at which the sections if concentrated would have the same moment of inertia as before. SYMBOLS. P = Concentrated safe load at any point. p Safe pressure per square inch of area for columns. A = Area of section in square inches. F = Factor of safety. W = Load, uniformly distributed, in pounds = total safe load H- weight of beam. L = Length of clear span in inches. / = Length of column in inches. M = Bending moment, in inch pounds, any section. d = Depth or height of section from out to out, in inches. 114 HYDROELECTRIC PLANTS. n = Distance of center of gravity of section, from top or from bottom in inches. 5 = Safe stress per square inch in extreme fibers of beam either top or bottom, in pounds according as n relates to distance from top or from bottom of section = safe strength. D = Maximum deflection, in inches. / '= Moment of inertia of the section, neutral axis through the center of the section. R = Section modulus = moment of resistance. 'Given in tables for standard sections.) r = Radius of gyration, in inches. E = Modlus of elasticity. GENERAL FORMULAS. Beams : a * * l I T __S. R--. r-^ - S/ -SR S - - IT / -R Steel columns in buildings p = 17100-57- Steel struts in trusses p = 13500-50 Wrought iron columns 9000 p - 36000 r 2 MATERIALS. 115 TABLE XXVIII. STRENGTH OF MATERIALS IN POUNDS PER SQUARE INCH. E VIodulus of Elasticity Ultimate Strength per square inch. (Tension) Ultimate Strength per square inch. (Single shear) across grain) Ultimate Strength per square inch. Columns, etc. (Compression) Ultimate Strength or Beams, Flecture Ash 1,600,000 16,000 6,800 5,000 Beech 1,300,000 11,500 7,000 5,000 Birch 1,400,000 15,000 8,000 480 Brass, cast 9,200,000 18,000 10,300 Brass, wire 14,2000,00 49,000 Cedar 3,500 Chestnut 1,000,000 4,000 320 Copper, cast. . . 18,000,000 30,000 Copper, wire . . . 18,000,000 60,000 Concrete, 6 mos. old 700 Concrete, 1 year old 1,000 Elm 1,000,000 4,200 Glass 8,000,000 Iron, cast 12,000,000 16,000 20,000 80,000 33,000 to to 23,000,000 100,000 Iron, cast, aver- age 17,500,000 100,000 Iron, wrought \ 18,000,000 50,000 47,000 36,000 bars, sheets ( to and plates ) 40,000,000 Iron, wire 26,000,000 56,000 Iron, wire ropes 15,000,000 Lead, sheet .... 720,000 3,300 Granite 8,000 to 32,000 ( 1,000,000 2,000 to 10,000 400 t4,000 4,000 Oak (white) 3 to to to / 2,000,000 700 7,000 Oak, average. . . 1,500,000 Pine, white. . . . 1 , GOO, 000 7,000 200 to 500 t 750 f3,500 3,200 Pine, yellow. . . . 1,600,000 1 2,000 250 to 600 t!400 t5,000 5,400 Spruce 1,600,000 8,000 200 to 500 t 600 t4,000 3.700 Hemlock 6,000 3,000 3,000 Steel bars 29,000,00 45,000 45,000 64,000 to to to 42,000,000 120,000 120,000 Steel, average. . 35,500,000 100,000 60,000 Oregon Pine 4,500 Sycamore 1 ,000,000 4,000 Brick and ce- ment 280 1,000 Limestone 2,600 to 18,000 750 Sandstone 2,800 to 16,000 1,000 Best Leather belting 1,000 t Cross grain. 116 HYDROELECTRIC PLANTS. C/2 ii (N Sec T^ hk MATERIALS. 117 ! I ^ 118 YDROELECTRIC PLANTS. i tp f IN -, + X X X 2 (N MATERIALS. 119 CO Bj Sect 120 HYDROELECTRIC PLANTS. BEAMS. Mr. A. L. Johnson gives the following method for designing reinforced concrete beams: All beams are considered as being 12 inches wide and as having e = . (See Fig. 78.) For ordinary concrete of 1-3-6 mixture or where 1-2-5 is used but the mixing not of the best, so that the modulus of elasticity, E c of the concrete = 3,000,000 per square inch, and where E s the modulus of the steel = 29,000,000 pounds per square inch. Elastic limit of the steel 50,000 pounds per square inch. // = 200, f c = 2000. Then y l = .33lh;~-j- = .64 per cent. = percentage of the r-^-l j a*/* -i . 78. whole area of beam which is steel, wherein d = spacing of bars and a = area of one bar. M Q = 3620 h 2 = resisting moment = M F, where F is the factor of safety used, and M = bending moment. For a better grade of concrete such as would be made of trap rock, good gravel or good limestone in the proportion of 1-2-4, and well made. In this case E, the modulus for the con- crete, = 2,400,000. f c = the compressive strength (breaking) = 2400 pounds per square inch, ft = tensile strength of the con- crete 200 pounds per square inch and the same values for the steel as the above. MATERIALS 121 Then, y l - .418 h = -j- = .132* = 1.1 per cent. M = 5505 /i 2 = M F. In the above, F should be taken at 5 or 6. M = bending moment in inch pounds for beam loaded. (See case 4, page 123.) EXAMPLE: A beam 12 inches wide and of 10 foot span sus- tains a uniform load of 20 feet of water. Find the necessary area of the reinforcing bars: mixture good, and of 1 :2:4 concrete. TABLE XXIXa. TABLE FOR USE IN DESIGNING REINFORCED CONCRETE BEAMS. A. L. JOHNSTON. BEAMS 12" WIDE. 1:2:5 CONCRETE. M h* <7t MO h Q 50,000 3.00 .397 1,000,000 13.4 1.77 100,000 4.24 .530 1,500,000 16.4 2.17 150,000 5.20 .687 2,000,000 19.0 2.50 200,000 6.00 .793 2,500,000 21.25 2.80 250,000 6.71 .886 3,000,000 23.25 3.00 300,000 7.33 .971 3,500,000 25.10 3.32 350,000 7.94 .048 4,000,000 27.00 3.55 400,000 8.48 .120 4,500,000 28.50 3.76 450,000 9.00 .188 5,000,000 30.00 3.97 500,000 9.48 .252 5,500,000 31.5 4.16 550,000 9.94 .313 6,000,000 33.00 4.34 600,000 10.38 .373 6,500,000 34.25 4.52 650,000 10.81 .428 7,000,000 35.50 4.69 700,000 11.22 .482 7,500,000 36.75 4.85 750,000 11.61 .535 8,000,000 38.00 5.01 800,000 12.00 .585 8,500,000 39.00 5.17 850,000 12.36 .633 9,000,000 40.25 5.32 900,000 12.72 1.68 9,500,000 41.5 5.47 950,000 13.07 1.726 10,000,000 42.5 5.60 * h is the depth of beam in inches from top to bottom surface of concrete, t q is the area of steel in square inches. The load W = 12,600. Neglecting dead load of beam. S = .132 h = 1.1 percent. M = 5505 h 2 = M F. M = 5(12600X10X12) 5505 W = 945,000, and h = 13 inches. The area of the steel then is, 13 inches X 12 inches X .011 = 1.71 square inches. 122 HYDROELECTRIC PLANTS. These formulas will serve for any reinforcing which is especially prepared to prevent slipping.* Tables giving safe loads on floors and beams may be had from the various companies. The Trussed Concrete-Steel Company of Detroit publish a useful booklet. COLUMNS AND FOUNDATIONS. Numerous experiments seem to indicate that columns made of reinforced concrete and less than 20 to 25 diameters in height do not fail by flexture (bending) but invariably crush. There- fore under these conditions the column need not be calculated for flexture. The crushing strength of the concrete may be taken at from 1500 pounds per square inch to 1800. Using a factor of safety of 5 to 6 we have the safe strength of 250 to 350 pounds per square inch. Concrete-steel columns wound with wire or hooped may have a safe strength of 800 to 1400 pounds per square inch. The building ordinances of Chicago allow a maximum load on concrete of 8 to 15 tons per square foot. Trautwine gives the crushing strength as follows: For concrete 1 month old 12 to 18 tons per square foot. 6 " " 48 " 72 " 12 " " 74 " 120 " Kidder gives 14J tons per square foot as the safe load. A factor of safety of irom 6 to 10 should be used. Crushing strength for neat (all cement) cement = 25 to 60 tons per square foot. *The author has lately been using nothing but plain round mild steel bars which may be purchased for about $0.018 per pound delivered. One and one-fourth per cent, of mild steel is used in this case, and in all cases where rods lap the ends pass each other 40 diameters. Where high carbon rods are used they stretch long before their full strength is utilized, and the concrete cracks. Therefore the only value of the more expensive steel is lost. MATERIALS. 123 TABLE XXX. PROPERTIES OF BEAMS. Bending Moment M max Max. Load Pressure at Support P* Deflection D Case (1) P L S R p PL 9 U L-dr 3 L 3EI Case (2) ^QOOOOOOO WL 5 R P WL 3 ^. -L .1 2 2L 8 E I Case (3) Q PL 45 R P PL 9 R^ L fc^ 4 L 2 48 El Case (4) OOOOQOO WL 85 R P b WL 9 P L *d 8 L 2 384 El Case (5) Pab SRL P b Pa P L 9 a 2 b* It^*-^ L ab L T L 3EIL* Case (6) > ft P a (L - a) 2SRL P 2PL 3 a 2 (L-o) 2 lr-L- k ^ L a (L - a) 2 3 E I V Case (7) P (2 b + LJ i ' l ' 2L &) L gd 2 KS-P 5 a or P (2 a + LJ 2 L NOTE. All lengths are measured in inches, and all forces in pounds. The moments of resistance and inertia will be found under the prop- erties of sections. 124 HYDROELECTRIC PLANTS. TABLE XXXI (Kidder). SAFE BEARING LOAD FOR DIFFERENT SOILS IN TONS PER SQUARE FOOT. Minimum. Maximum Rock, hardest kind 200 Rock, equal to Ashler masonry 25 30 Brick, equal to Ashler masonry 15 20 Brick, of poor quality 4 7 Clay in thick beds, always dry 4 6 Clay in thick beds, moderately dry 2 4 Clay in thick beds, soft and wet 1 2 Gravel and coarse sand 8 10 Sand, fine and compact 4 6 Sand, fine, clean and dry 2 4 Alluvial soils and uncertain sand 0.5 1 Safe pressures are given by Rankine to be 1 to 1J tons pel square foot on tamped earth; 2 to 3 tons per square foot on compact gravel and dry sand ; or 4 to 6 tons per square foot where a few inches settlement may be allowed; 1 to 2J tons per square foot safe load no pure soft clay ; 2 tons per square foot on silty soil will settle 3 to 12 inches in a few years. TABLE XXXII (Kidder). MAXIMUM SAFE LOAD IN POUNDS PER SQUARE INCH ON DIFFER- ENT KINDS OF MASONRY FOR BEARING PLATES UNDER COL- UMNS AND GIRDERS. For granite 1000 best grades of sandstone 700 soft sandstone 400 " hard stone rubble 150 to 250 extra hard brick in cement mortar 150 to 200 good hard brick (Eastern) in cement mortar. . . . 120 common brickwork 100 " good Portland cement concrete 200 " good Portland cement concrete reinforced 400 One or more holes through bottom of column bearing plates should be left so that it can be determined whether or not the grout fills up underneath. MATERIALS. 125 FACTORS OF SAFETY. The factor ot safety is that figure by which the ultimate strength is divided in order to get the safe strength, and there- fore is the most important of all engineering data. The reck- less engineer adopts a low factor of safety trusting to luck for future fame as a close calculator while the conservative engineer selects the higher values. It is, therefore, largely a personal equation. In Table XXXIII the factors of safety are given as recom- mended by Unwin, Gordon, etc., and Pencoyd, Carnegie & Cam- brian Steel Companies. They are very conservative; judgment must be exercised in their use however. Where the material is exposed to wear or rust a certain amount of the area must be allotted to this loss and the factor applied to the remaining portion. If samples of the materials are frequently tested, a much lower factor may be used based on these tests. TABLE XXXIII. FACTORS OF SAFETY. Name of Material. Steady Load, No Vibration Dead Load. Fluctuating Loads. Vibrations. Shocks as Machine. Temporary Structure. Tensile Dead Load. Steel 5 5 to 7 15 4 8 to 12 Cast Iron 6 15 20 Very uncertain Steel Shafting 5 8 12 4 Leather Belts 10 12 14 6 Stay Bolts 6 7 12 4 .. Wood Dry 6 12 20 8 10 Wood Green Brickwork 15 15 18 25 30 30 12 14 Steel Columns 6 6 to 10 12 3 Nickel Steel 5 5 to 7 10 3 8 Bronze 5 6 8 3 7 EXAMPLES. In nearly all pocket-books there are tables giving the proper- ties of standard sections of structural steel and "Sample's." " Properties of Steel Sections " gives the properties of all sorts 126 HYDROELECTRIC PLANTS. of built-up sections*. It is assumed that the reader possesses such a table in solving the following examples: Beams. EXAMPLE l.-^Given a 24-inch I-beam of 16-foot span weighing 100 pounds per foot: what is the safe uniform load it will sustain? From the tables for standard section, 7 is 2380; n, the distance of the neutral axis, A A from the extreme fibers is 12 inches, therefore (Fig. 79) *--! tal 9M R is given in the tables in the column headed Section Modulus. From case (4), 857? Load = where 16,000 - safe strength of the steel. 25 R 2X1-6000X198.3 W = 3L 3X1*6" 132,200 Ibs. ' FIG. 79 FIG. 80. Q ^- 7~> c\ C* TO The difference between = and ' . is due to the fact L o L that the equations in properties of sections gives inch pound SS R 2SR values thus ^j- j-. If the beam is built up as shown in Fig. 80, and we have no tables giving the value oil or R, I may be found as follows: The moment of inertia of any built-up section about an axis is equal to the sum of the moments of inertia of those sections through whose centers of gravity the axis may pass, plus the sum of the moments of all sections through whose centers of gravity the axis does not pass, plus the area of all such sections multiplied by the square of their distances from the axis. *With permission of the publishers several of Sample's tables are given in Chapter IX. MATERIALS. 127 EXAMPLE 2. Find / for Fig. (80), first about the axis m n, which passes through the center of gravity of I-beam (l),and is at the distance n from the center of gravity of (2) and (3), then 1=1 for beam (1)+ 2 [area of beam (2) or (3) Xn 2 ] +2 (moment of inertia of beam 2 or 3). Figured on this axis, the load should be in the direction of the arrow, because the neutral axis passes at the point where there is neither tension nor compression. 1 FIG. 81. PIG. 82. In the case of the axis passing through the center of gravity of all the members as in Fig. (Si), I = [moment of inertia of the I-beam] + 2 [moment of inertia of one of the two channel beams.] FIG. 83. FIG. 84. Care must be exercised in selecting / for the various sections, as in the tables / is given for both axes. In the case of a latticed beam, Fig. 82, the lattice is not con- sidered. Thus 7 = twice the / for one channel. For Fig. 83 / = 2 I - -f b t n n I + 4 [(area of angle Xn 2 ) + (/ of angle)] , r The distance X, Fig. 84, is foUnd by deducting the values 128 HYDROELECTRIC PLANTS. given in tables for standard sections for the perpendicular dis- tance from center of gravity to back of flanges, from the dis- tance y. I for two angles (Fig. 84) = twice I for a single angle. EXAMPLE 3. Find the safe center load, P, which two 4x4xJ-inch angles will support. Span = 6 feet, Z = 1 inch. From case (3), P = ~r^~ From tables for standard sections, 7 on axis 1, 1. =5-56. Therefore 7 for the two angles = 11.12. In the tables x is given for the above angle, as 18.-,w=d-#=4-l. 18= 2.82 FIG. 85 . 11.12 3.94X.16000 EXAMPLE 4. Design the beam shown in Fig. 85 of rectangu- lar section made of cast iron. To start with assume a thickness b of 2 inches. From Table XXVIII the ultimate strength of cast iron in flexture, is 36,000. The load is to be a steady stress, therefore the factor of safety is 6 and the safe strength is 6,000 pounds. b d? Now M = 5 R or, W L = 6000 and substituting the proper 2 y d? values, 5000X48 = 6000 ^ = 120, and d = 10. 95 inches; o call this 11 inches. MATERIALS. 129 To get the depth at any other point, say 30 inches from the end, proceed as before, only substituting 30 inches instead of 48 inches. In the design of shafting we frequently have the condition shown in Fig. 80, and have to find the maximum bending moment M. Suppose the gear or pully weighs 1111 pounds, and the belt chain or tooth pull tending to rotate it, regardless of 7 or r. p. m. = 4111 pounds, then 5 for steel is about 10,000. Substituting and solving for d we have a shaft about 5| inches in diameter. If the wheel is at the center of the span. ,, (4111 + 1111)X(3 + 6)X12 PL. M = - - - = m inch pounds. I 3'---+^ tf'-. FIG. 6. EXAMPLE 5. A standard 7 beam, 20 feet span, is loaded at the center with a load P, of 10, COO pounds. Find proper size of beam: From case (3) R = 3 P L S Therefore 3 x 1) 16,000 From tables for standard steel I-beams we find that the section having a section modulus of 37.5 is a 12-inch-35 pound beam. Columns. The radius of gyration r = ^| -r- plays an important part in the design of columns. 130 HYDROELECTRIC PLANTS. If the column is a built-up section /, the moment of inertia, is found in the same way as for beams. EXAMPLE 1. Find r about axis 11, for column (Fig. 87) composed of two latticed 12-inch channels weighing 40 pounds per foot each, and placed six inches apart. / = 2[(area of each channel X by X 2 ) + (/ for each beam)] From tables for standard channels we find, x for axis, 11, and a 12 inch-40-pound channel to be . 722, therefore X = . 722 + 3 inch, or 3.722 inches: area of channel =11.76. 7 for one one channel = 6.63. Substituting, 1=2 (11.76X3.722 + 6.63) = 339 [/ | 339 = 9 '* A "\2X11.76 lr r n -4J_ FIG. 87. FIG. 88. Example: The column shown in Fig. 88, is built up ol four 3x3xJ-inch angles. Find r I = 4[(area of one angle X^ 2 ) + (7 for one angle)] From tables for standard shapes x == . 84. : A' =5 .84=4.16. Area of one angle = 1 . 44. I for one angle = 1 . 24. 104.6 7 == 4(1. 44X4. 16 2 f 1.24) = 104.6 r = ^ i 44 = 4 - 26 DESIGN OF MACHINE ELEMENTS. THE SCREW. F = forc'e in pounds applied at circumference of hand wheel A at a point B, R inches from center line of screw. P = the distance between threads in inches = pitch of screw = distance MATERIALS. 131 which one complete revolution of hand wheel will raise screw. W = weight lifted. W P Then F ' 283* where 6.283 = a constant. EXAMPLE. What pull must be applied at B to just raise 5000 pounds hanging to the screw? The screw itself weighs 111 pounds and has a pitch of one inch. R = 24 inches. / = .2 Then Weight of screw Ill Friction due to screw, 111X.2 22.2 Weight lifted 5000.0 Friction due to the weight, 5000X.2 1000.0 And F = 6133.2X1 W .6133.2 6.283X24 = 40.7 pounds. FIG. 89 and 90. A man turning the wheel A would exert an equal pressure on each side and in the above case would exert 20.35 pounds pressure with each hand. The work of lifting is measured in foot pounds and in the 70 above case would = 40.7 X 2 x X N where 2 n is the circumference of the hand wheel in feet and N the revolutions. A man can, for a minute or two, perform work equal to 17280 foot pounds per minute. In the above example one revolution = 40.7X12.566 = 511.4 foot pounds, and the number of revo- 17280 lutions a man could turn the wheel per minute = ^ - = 33.8. 511.4 132 HYDROELECTRIC PLANTS. In 33. S revolutions the screw would lift the weight 33.8 XP or in the above case 2.82 feet. Often the screw itself does not move vertically, but is sup- ported on a collar C, Fig. 90, the nut attached to a weight traveling along the screw and lifting the weight W. In this case the friction of the collar is added to that of the nut D. Knowing the pitch of the screw and the weight it is to sus- tain, it is a simple matter to design it for strength. From the table giving the shearing strength of materials the safe strength for the material in the threads is found and sufficient area is provided so that the threads will not strip. If it is six inches in diameter at the root of the thread and the thread is one inch thick (see Fig. 91), the safe strength of the thread making one turn around the shaft would be 6X~Xl inch X 5 where 5 = safe strength of the metal, The same reasoning would apply to the nut. WINCHES. Heavy winches usually employ the worm and gear, Fig. 92 for at least one power increase. L is the distance in inches, a tooth on worm gear moves in one revolution of screw. For a one threaded worm L = P for a two threaded worm L = 2 P, three threaded L = 3 P, there- fore, for a two threaded worm and a gear of 50 teeth the shaft A will make one complete revolution for every 25 of the crank C; or disregarding friction one pound exerted at C should lift 25 at B a distance 2 P. If the worm is single threaded the ratio would be 1 to 50 and the distance moved P. Efficiency of a worm gear is about 40 per cent, for starting MATERIALS. 133 loads; 50 per cent, for pitch line velocity of 10 feet per minute; SO per cent, for velocities of 100 feet. Therefore, in the above case of 50 teeth in gear and single threaded worm of J pitch, P, R = 7 inches, we would have the force F, applied at C, necessary to start the worm against a resistance at the pitch line at B, of 2000 pounds, ,., 2000XJX1.6 F =-*5&xr- = 36 - 6 p unds - 1.6 is gotten from the efficiency being 40 per cent. 36.6 pounds, acting at the 7-inch radius, travels 3.665 feet per revolution. It requires 48 revolutions to raise the gate 24 inches, therefore if the gate is to be raised in one minute, 36 . 6 X 3 . 665 X 48 = 6432 foot pounds per minute are required, which is less than half the power a man can exert for short periods. FIG. 92. For steady work during several hours, a man can only exert about 3500 foot pounds per minute. Now if the rope lifting the weight is run over a smaller wheel, A, say ^ the diameter of B, the leverage will be increased in the D proportion of r- ; but the time of lifting is also increased in the same proportion; 36.6 pounds at C will now lift 8000 pounds at A. If a pinion is placed at A and a spur gear D is used, the lifting power on the pitch circle F will be increased in proportion to the ratio of the gears. Suppose this ratio is 1 to 4 in the above axample, then the 36.6 pounds exerted at C will lift 2000X4 or 8000 pounds at F. The efficiency of a pair of well- cut gears should be 97 per cent., and that of uncut and poorly designed gear 90 per cent. Therefore the power delivered at A , in the abo^e example = 2000 X -^ X efficiency of gears, or if 134 i HYDROELECTRIC PLANTS. the pitch diameter of A = J that of B, and the diameter of E is i that of Z), 8000 pounds will be transmitted at .a loss of 3 to 10 per cent ; if 10 per cent is lost 7,200 pounds will be the actual weight lifted at F, and so on through any number of reductions. Force is increased at the expense of motion, when the energy remains constant. HOISTING BY ROPE OVER A DRUM. 5 = stress in rope in pounds at A Fig. 93. When the weight W is suddenly lifted, owing to slack in the rope, the stress is greatly increased. R = weight of the whole rope in pounds. F = equivalent friction in pounds = weight of all moving parts x by /. / = coefficient of friction. FIG. 93. Then 5 = 2 W + R + F. W = weight lifted. / = .01 for vertical hoisting and .02 to .04 for inclined. EXAMPLE : Required size of rope to hoist vertically, 5,000 pounds through 1500 feet; S = [(5000X2) + (2 X 1500)]. 01 (5,000 4-3,000) == 13080 pounds. If the factor of safety = 7 select rope having ultimate strength of 100,000. (See table LXIII). If the hoisting is done on an incline, S = (2 W + R) sin a + F and F = f (W + R) cosine . See Fig. 93. As the rope passes over the drum the strain is greatly increased, due to the bending of the fibres. If the drum is 45 times the diameter of rope the bending strain = 8/9 of the whole strain on rope and leaves 1/9 of the ultimate load available. If 80 times the diameter of rope the bending strain will have 1 (5 of MATERIALS. 135 the ultimate strength of the rope available for use. The bending stress on different ropes are given in the tables. STEEL CABLES. E = 28,500,000 = modulus of elasticity. A = net area of steel. R = radius of drum or sheave. d = diameter of each wire in the rope. The net working stress for which the rope is safe will then be the difference in S, found as above, and the safe strength given in Table LXIII for the particular rope. EXAMPLE: Find safe load for a one-inch cast steel rope run- ning over a six-foot sheave. From Table LXIV the bending stress = 9937 pounds and from Table LXIII the maximum safe stress for a one-inch rope = 22667 pounds. The difference, 12730 pounds, is the safe working load. The stress due to weight of rope and weight lifted as found by the first formula for S must not exceed this safe load PULLEY OR GEAR. When we have a pulley or gear transmitting power we usually wish to know the tension on the belt or rope, in case of a pulley or the pressure on a tooth of a gear. EXAMPLE : A pulley 38 inches in diameter runs at 116 revolu- tions per minute, and transmits 110 horse power. What is the pull at the rim? 110X33,000 38X. 2618X116 .2618 = a constant. If a gear has the same diameter at the pitch circle the pressure would be the same and would be considered as all acting on one tooth. CENTRIFUGAL FORCE IN WHEELS. Let W = weight in pounds of entire rim of pully, gear or fly wheel. R = radius in feet to center of gravity of rim section. S r = revolutions per minute. S = total strain on the cross section of rim in pounds. Then 5= .00005427 WxRXS r 2 . S, divided by the area of the section gives the strain on the metal per square inch. 136 HYDROELECTRIC PLANTS. SHAFTING. Consider one end of the shaft, A Fig. 94, fast and on the other end a lever / inches long, with a weight of W pounds. Suppose, for example, we give the shaft a safe strength 5 of 10,000 pounds per square inch, then the formula for the safe diameter under that stress is Wl = .196d 3 X 10,000; from this d may be found, or having d, S may be obtained. FIG. 95. For square shafts (Fig. 95) W I = .28J 3 5 For hollow shafts (Fig. 95) W I = A D ^f- \ = area of circle of diameter D. a = area of circle of diameter d For maximum bending moment see Table XXX. CHAPTER V. HYDRAULIC CONSTRUCTION PILING No feature of engineering work is more disappointing and at the same time more important than piling. There is always more or less uncertainty as to the cost before beginning, and then as to the efficiency of the job when completed. Many I FIG. 96 times piles will appear to drive all right, when in reality they are being sheared off, as in Fig. 96. Sheet piles may look well at the top, when, in fact, there are large holes between them further down. There are two patent types of wooden sheet piling, the Wake- FIG. 97. FIG. 98 field (Fig. 97), and the Beardsley (Fig. 98). The Wakefield consists of three planks all of the same width, while the Beards- ley pile is composed of two widths. Each pile has its advantages for certain conditions. The planks for the Beardsley pile being in two widths are sawed out of the log to better advantage than if all of the same width. 137 138 HYDROELECTRIC PLANTS. Where the pounding will not be too heavy, the planks may be spiked together with 60d wire spikes, and clinched, but generally four to eight- . five -eighth-inch carriage bolts are used. Of course, the groove of one pile must be slightly wider than the tongue of the next, otherwise it will bind in driv- ing. The usual method in the case of the Wakefield pile is to place a three-sixteenths-inch shim at a. The narrowest planks FIG. 99. in'the Beardsley pile are all sawed three-sixteenths-inch thicker than the wide plank to get the desired result. It requires great experience and a good head to successfully drive sheet piling. Experience with round piling alone is worse than none, as far as sheet piling is concerned. Each pile must FIG. 100 be given just the proper edge bevel, as at a (Fig. 99), or side bevel as at b. The edge bevel causes the pile to hug to the pre- ceding one, but if too much is given the piling may get to run- ning in the direction of the line A B. The side bevel 6, is given where the previous pile has run, as shown by the line B C. If the bevel is too great the foot of the pile may run out of the groove. The top of the pile is held securely against HYDRAULIC CONSTRUCTION. 139 the preceding pile by the rope D, which passes back to the steam wench, in the case of a steam driver, or to a pair of double blocks in the case of a horse driver. Too. great a pull on this rope will throw the foot of the pile out. If the pile runs, as shown in Fig. 100, one or more peavies are used to bring it back into line. Timbers E, E are laid along the line and bolted together with spacers, F, F between, to aid in keeping the piling straight, as the piling approaches the spacers, a bolt is put through the timbers and the pile nearest the spacer and the spacer removed. One -inch bolts should be used with heavy washers, so that the timbers may be brought back into place rF"they have spread any. It is often necessary to put iron points on the piling, as at M, Fig. 99. These may consist of iron 2x4-inch, bent to fit the bevel. The common dimensions of the plank are 2x12 inches and f Vz'ao/teJ -.rt-^ wfi---..-..-.r s. =.i i i: ^.-.-.-Jtf's 7rrj".rs-------.-^.---.---i^^i 1 ivrw*.a. FIG. 101. 2x8 inches, and the wood used may be beach, oak, Southern pine, gum, hard maple, cypress, elm, or any close-grained hard wood. The head of the pile should be banded with a band of the best Norway iron x3 inches, and several bands should be used, so that two or three banded piles will always be ready for use. Where the piling is quite long, say 25 to 40 feet, it must be much heavier, and is made as in Fig. 101. Strips (a) are bolted to the pile with J-inch carriage bolts to form the tongue and groove. PILE DRIVERS. The smaller drivers are usually operated by horse-power, but for large, quick work a steam driver is used, the pile driver being similar to the horse power, except that the engine is set in the frames. The most rapid and satisfactory pile driver is the steam-head driver. The parts work between the leaders the same as a drop hammer, but rests continually on top of the pile. The piston and weight are caused to reciprocate by 140 HYDROELECTRIC PLANTS. steam acting on a piston in the cylinder, at the rate of 80 strokes or less per minute. The rapidity of hitting may be nicely regulated. Piling may be driven in quicksand, hard pan, etc., with this driver, where it would be impossible with the slower type. In quicksand the pile is buoyed up by an amount equal to the weight displaced, and where the blows are few and far between the pile rises between strokes; but with the steam-hammer the weight is on the pile at all times and blow follows blow in such rapid succession that the displaced particles of sand and water do not have time to settle back 'into place. Also much cheaper grades of wood may be used for the piling, as the splinter- ing effect is less. A common horse-power pile driver with a 2CCO-pound drop hammer costs all complete from &10 to 200. The same outfit, with a suitable boiler and engine, will cost from $800 to $1,CCO. A steam-head driver of the same comparative size will cost from $1,500 to $3,000. COST OF DRIVING PILING. TABLE XXXIV. COST OP DRIVING ROUND WOOD PILING AND NUMBER DRIVEN PER DAY. Horse Power. Steam. Steam-Hammer. Depth in Compact Clay. (Feet) Depth in Strong Gravel. (Feet) Depth in Wet Sand. (Feet) No. of Piles Cost per Pile No. of Piles Cost per Pile No. per day Cost 6 to 12 $1.75 8 to 10 $3.50 15 to 30 $1.50 to $2. 20 12 to 14 $5 to $6 ?5 to 35 4 to 6 $2 to $2.50 6 to 8 $4 to $6 20 to 50 $* to $1.50 14 8 to 10 $2.50 to $3 $2.50 12 13 $2.75* 16 * Labor was high. The above costs do not include the pile itself, and represent costs actually attained on various jobs. The cost of driving sheet piling is about the same per foot, measured across the stream, as that of round piling. It will cost about $1.50 per foot width to drive 12 to 16-foot piles, when the driving is easy, and from $2.50 to $3.00 where it is hard. HYDRAULIC CONSTRUCTION. 141 The lowest average bid for driving round piling on a large pile dam by several reliable contractors was 45 cents per foot of pile. This included the pile and the sawing off under water. The current was strong and driving average. The piles cost from 10 to 15 cents per foot. In charging so much per linear foot (the usual method) the pile is measured from its point to the sawed-off head, the penetration not being measured, though it, of course, influences the price. Ordinary round piles for hydraulic work should not cost more than 8 to 15 cents per linear foot for driving. METHOD OF DRIVING. Fig. 104 shows a few of the common pile points for round piles. The first is a soft iron strap and the second and third are of cast iron. FIG. 104. The author has found that for soft soils such as sand, silt, and soft clay, the piles drive much better if not pointed at all, but left with a square end; in fact, experience with the round piling indicates that the large end should be the down end in such soils. Sand is somewhat like a liquid, and has a buoyant force, which will always act to force the pile out of the ground, and depends entirely upon the volume of the pile submerged. When the pile is driven point first this force lifts it out as fast as it can be driven, but when driven butt first tnis force acts in the same way, but is opposed by a great frictional resistance which would have to be overcome before the pile could be removed. This resistance represents the work which would have to be done in displacing the shaded volume of sand (Fig. 105.) Western rivers, such as the Platt and Elkhorn, demonstrated that it was far better practice to drive the piles with the butt-end 142 HYDROELECTRIC PLANTS. down. Of course in this case the small end must be of good proportions so as not to break or broom under the hammer. With this way the pile does not spring back, and, instead of the " flare " hitting towards the sand, it drives away from it. When the pile driver is mounted on a scow, scattered round piles may be driven twice as rapidly as on land, but when the piling is along the edge of a platform or mat, the cost is less for the land driver. A heavy hammer and short fall is the most satisfactory, as the pile will be shattered less and more blows can be given. This is especially true for quicksand. FIG. 105. Trautwine gives the adhesive power of ice to a pile as 30 to 40 pounds per square inch of surface. The friction of a metallic pile is about three-tenths that of wood jet Driving. The most successful way to sink round or sheet piling in wet sand is by means of a jet of steam or water. The author had an experience with the Elkhorn River in Nebraska, which thor- oughly demonstrated the value of the jet. After vainly trying to drive sheet piles in the sand of the river bed for two months, with an ordinary pile driver, an Edson pile sinking outfit, costing about $150 was used. This is shown in Fig. 106. Two men handled the 1-inch tube, which was constantly moved about so as to loosen up the sand under and around the pile. Two men worked the pump and two men guided the pile. The pile was handled in the leaders of a pile driver, and a 2,000-pound hammer left resting on the head of the pile. When the pile stuck, a few blows of the hammer started it again. With this HYDRAULIC CONSTRUCTION. 143 simple outfit an average of from 20 to 30 piles, 14 feet long by 12 inches in diameter, were driven per day, at a cost of $1.50 per pile. Steam can be used in the place of the water. Jetted piles may be of the soft wood. With the jet, round piles averaging 14 inches in diameter can be sunk by means of a strong jet at the rate of a foot per second. Large cylinders may be rapidly sunk in the worst sands, and it seems very strange that this FIG. 106. method is not more generally adopted. Of course, the jet can only be used for sands, or other soft soils. CONCRETE PILES. Wooden piles rapidly decay unless entirely submerged in water. If exposed to sea water they are eaten up by insects. Concrete piles are permanent, and it is only a question of a few years when wooden piles will be a curiosity, having been entirely displaced by the concrete. There are several patent concrete piles, a noteworthy one being the Raymond pile. This is made by sinking a thin casing of metal the size of the pile and filling it with concrete. Fig. 107 shows the adaptation of the concrete pile, and how eight concrete piles displaces 22 wooden piles. Reinforcing bars may be placed in the molds before filling. 144 HYDROELECTRIC PLANTS. Fig. 108 illustrates a concrete-steel pile, which is made before placing it in the ground. As here shown it is reinforced by three f-inch Kahn bars, making 160 pounds of steel for a 20-foot pile. At the bottom end of the pile the three rods converge to oooo oo ooooo oocoooooooo FIG. 107. a point, and are welded together. The concrete used is made of high-grade Portland cement and clean river gravel, in the pro- portion of 1 to 3. The method of constructing the piles is as follows: The molds or forms are set up on one corner, and the concrete placed FIG. 108. in them. Piles can be built in this way in lengths varying from 16 to 26 feet, as required. When molded complete the pile is left to set for about a day, without water, and then kept in the form for a week longer, with continual sprinkling. By that time the concrete has hardened sufficiently to allow the HYDRAULIC CONSTRUCTION. 145 piles to be lifted out of the form and set away for another period of a week or more, during which time they are kept constantly wet. After this they can be removed for transportation or storage. The piles can be driven by steam hammers weighing as much as 5000 pounds, with a fall of about 5 feet. The head of the pile is protected from damage in driving by a cushion cap made of alternate layers of iron plate, wood and lead, which is clamped to the pile head. This cap also serves to guide the pile in the leads. Such a pile 20 inches across corners at the top and 6 inches at the bottom would cost about $9.00 all complete, and give the bearing power of four wooden piles. Protection of wooden piling from the Teredo can be secured by grouting a concrete jacket around the pile after it is in place, as shown in Fig. 109. STEEL PILING. Within the last few years there has been a startling advance made in the construction of piling, due chiefly to the advent of the steel pile. One of the best known steel piles is that made by the Interlocking Steel Sheeting Company of Chicago, and called the Jackson pile. Fig. 110 will sufficiently explain the style and use of this pile. Great depths may be obtained by its use, and by using concrete to fill between the channels, it may be made absolutely water-tight. Of course the cost of this pile is great, a linear foot of 12-inch pile, if made of the lightest 146 HYDROELECTRIC PLANTS. ; channels and I-beams, will weigh 72 pounds, which would make the cost of steel at two cents per pound, about $1.50 per foot. Steel piling costs about $40 per ton f.o.b. factory. How- ever, they may be withdrawn and driven many times, thus bringing the cost down to a reasonable figure. Almost every form in steel has now been worked into sheet piling and patented, but the author gives one to the public which is not patented and FIG. 110. which possesses some good features. (See Fig. 111.) In this pile Phoenix columns, boiler plates and angle-irons are used. The columns act as stiffeners to the webs formed by the boiler plates. Any width plate may be used and corners turned by simply bending the plate. The column may be of any size and can be filled with concrete. The weight per foot of a pile 12 inches FIG. 111. 'wide is 34 pounds, which, at three cents per pound, would cost $1.02 per foot of pile. By using a 5f-inch Phanix column the pile will weigh 25 pounds per foot. i IRON PILING. .. The cast iron pile is used to quite an extent where the iron .alone is depended on for supporting the load and resisting .corrosion, The smaller iron piles are usually sunk by means -.of a screw. Fig. 112. The screw has about one complete turn, and HYDRAULIC CONSTRUCTION. 147 is from 18 to 60 inches in diameter. The shaft usually consists of a piece of heavy shafting. Though in the pile shown in Fig. 113 a hollow 27-inch cast iron shell 1 inches thick, and made in 7-foot sections was used. These large ^iles were driven by the FIG. 112. Erie railroad for the purpose of sustaining a tunnel under the Hudson River. A large ratchet and pawl (Fig. 113), driven by two hydraulic cylinders, was used for screwing down the V m m FIG. 113. pile, each cylinder tested to 1500 pounds pressure per square inch. A dead load of 440,000 pounds, placed on top of the pile was found necessary to cause the 5-inch screw to penetrate 35 feet, and 40 revolutions were made. One pile was driven (ex- 148 \ HYDROELECTRIC PLANTS. elusive of all such work as placing new sections, etc.) in 10 hours. Under a test load of 500,000 pounds for 15 days and 600,000 pounds for another month, the pile settled a little over J inch. SAND PILES. Sand, the great foe to pile driving, is made to act as a pile in some cases where the soil is treacherous. A large wooden or steel pile is driven six or eight feet in the mud, and then pulled out. The hole thus left is filled with sand, well tamped in place. The hole may be dug like a well and then filled. The particles of sand transmit the load equally throughout the area of the hole. Another form of pile which can be used in sandy and gravelly soils is made by jetting down a IJ-inch gas pipe having perfora- tions at the lower end about J inch in diameter, and then forcing through it a cement grout, the tube being slowly withdrawn. This fills the interstices in the soil and forms a concrete pile of from 12 to 48 inches in diameter. Sand which is too compact cannot be successfully cemented in this wa\ . BEARING POWER OF PILES. The bearing power may be approximately determined by the formula (Trautwine) : VFallinltTxWt. of Hammer in Ibs. X .023 Extreme Load = - - .- : Last sinking in inches -f 1. The safe load would be one-fourth to one-tenth this. Great caution must be observed in driving piles meant to sustain important loads, which would be injured by settling. A pile may drive into sand with great resistance but under a steady load settle rapidly. The earth's crust is full of strata of varying density and unless test borings are made down past the foot of the pile, it may be resting immediately over a strata of silt or quicksand. Maj. J. Sanders, United States Engineer, gives the following formula for obtaining the bearing power: W_n 8 d where P Safe load on pile in pounds. W weight of hammer in Ibs. n = fall of hammer in inches. d = penetration in inches caused by each of the last few blows. The objection to this last formula is that the selection of the HYDRAULIC CONSTRUCTION. 149 factor of safety is not left to the engineer. However, as his experiments were made in river mud on the Delaware River, the factor of safety should be about ten in which case this formula gives a much larger safe load than does Trautwine. The Engineering News formula is simple and safe and will serve as a check on other estimates. Safe load in tons is 2 X wt. of hammer in tons X fall of hammer in ft. Penetration of pile in ins. for last blow + 1 in. When the pile is driven to rock or unyielding hard pan it acts as a column and can be figured as such. A grillage is placed over the heads of piles to distribute the load evenly on each pile as in Fig. 114. Steel beams may also be used. FIG. 114. A more permanent way to distribute the load is by the use of concrete placed a foot or so deep around and over the heads of the piling as in Fig. 107. Reinforcing should be used so that if any pile or cluster of piles settles, the foundation will hold together. DRILLING. HAND DRILLING. On small jobs hand drilling is much the cheapest and in fact many times on large work, hand drilling though much slower has been found as cheap as power drilling. The two methods used in hand drilling are churn drilling and jump drilling. In jump drilling a comparatively light drill is held by one man and struck by one or two strikers. The drill is made of tool steel one inch to one and one-fourth inch in diameter and sharpened as in Fig. 115. Between blows the drill is revolved a quarter turn. 150 HYDROELECTRIC PLANTS. A short drill called a starter is used to start the hole. It is given a slightly larger diameter across the bit than the finishing drills, the shoulders at (a) are made parallel and about one-half inch long. An eight-pound striking hammer is used. A spoon, Fig. 116, or a pump, Fig. 117, is used to keep the hole clean. The pump is made of three-quarter inch gas pipe. A marble b is placed in the bottom as shown and by moving the pipe up and down, water and stone dust fill it and it is^then emptied by removing from the hole. When the rock is seamy, the shoulder a should be lengthened and for very difficult work a wing c, Fig. 115, welded to each side of the drill will help materially. For straight vertical drilling, churn drilling is the most satisfactory. The body of the drill is made of ordinary iron 1 to 1J inch diameter and from six to eight feet long. The drill point or bit is made of tem- pered steel welded to the bar. In churn drilling the workman (often two) lifts the bar and drops it, giving it a quarter turn each blow. The weight of the bar is relied on to do the cutting. This is the best drill to use for sinking anchor bolts for dams, locks, etc. The cost of drilling by hand depends on the position of the holes and the character of the rock. The author's experience has been that with jumper drilling, holes 1J inch in diameter and 24 inches to 36 inches deep, for anchor bolts in the beds of streams can be drilled in one hour with three men. Trautwine gives seven to eight feet of 1} inch hole in granite as a fair day's work for three men and eight to nine feet in marble or limestone. A churn drill worked by one man will drill about the same amount as a jumper with three men. HYDRAULIC CONSTRUCTION. 151 MACHINE DRILLING. Among the machine drills the diamond drill ranks the highest in rate of cutting and depth of hole, but as it is intended more for mineral prospecting or deep well boring, we will not give a detailed description of it. A diamond drill, drilling a IJ-inch hole 200 to 300 feet deep costs about $1250 and will drill one to two feet per hour at a cost of from $1 to $2 per foot. 162 HYDROELECTRIC PLANTS. The drill commonly used is shown in Fig. 118. This drill may be worked with steam or air, the only difference being in the packing of the glands. The price of such a drill varies from $200 to $500 depending on depth and diameter of hole it will drill and the depth of feed. The feed is from 12 to 30 inches and this, limits the depth of drilling before a longer drill is put in. If driven by steam the steam pipe will have to be one inch for the smaller drills, 1J inches for medium and 1J inches for the large drill having 30 inches feed and drilling a 2-inch to 5-inch hole 27 feet. FIG. 119. If driven by air (see page 192 " Tunnels "), the operation of the drill will be understood by referring to Fig. 118 where X32 is the hand feed, X24 is the piston, X27 the rifle bar which causes the drill to revolve slightly each stroke, X25 the rifle nut which causes the rifle bar to rotate the bar and with it the ratchet wheel X30. Thus each time the piston reciprocates along the bar, the ratchet turns a notch and on the down stroke the piston with the piston rod and drill rotates. Extra charge is made for the tripod which costs from $30 to $80 depending on the size of the weight. Fig. 119 shows H YDRA ULIC CONSTR UCTION. 153 a Sullivan drill all complete except the hose pipe. Hose pipe suitable for the modern drills costs 60 cents per foot. Con- FIG. 120. nections will add $4 to this per hose. A mining column, Fig 121, for tunneling costs about $50. FIG. 121. For use in hard rock a drill having a bit shaped like a 4- is best, but for seamy rock where the drill tends to bind it should 154 HYDROELECTRIC PLANTS. be shaped like an X In soft sandstone a chisel bit is recom- mended. Each drilling machine should have three sets of drills Fip. 122. Channeler at work on canal. of three drills per set. These cost $3 to $5 per set for the smaller drills. FIG. 123. Channeler at work on tail race. Each drilling machine requires one man to operate it and takes two to three men to move it. One man can attend the HYDRAULIC CONSTRUCTION. 155 air compressor plant or steam plant. One blacksmith will sharpen drills for five or six machines if he is provided with special hammers which give the correct form to the bits. Among the best drills are those made by the Sullivan Ma- chinery Company, Chicago, 111., the Ingersoll Rock-Drill Com- pany, New York, Burleigh Rock-Drill Company, Fitchburg Mass., and the Gray don & Denton Manufacturing Company of New York. Only since the Chicago Drainage Canal was built has the channeling machine come into use for canal cutting, but since then several large hydraulic plants have used them. Canals cut with a channeling machine require no lining. Fig. 122 shows a channeler at work. Where it was not necessary to preserve the rock for building purposes, the channeler merely cuts a channel about one inch across and six or seven feet deep along the edge of the canal, and then the rock is blasted out in the usual way. This leaves a smooth surface, unshattered by the explosion. The drill is given a slight slant, as in Fig. 123, so that the general contour of the wall will be perpendicular. The channeler shown in Fig. 122 costs about $2000 with boiler, but on a large job the canal lining saved will more than pay for it. Such a channeler should cut from 100 to 150 square feet of channels per day, at a cost of twenty cents per square foot. EXPLOSIVES. Dynamite is the most common form of explosive, and is used on all kinds of work. It is commonly put up in half-pound sticks wrapped in oilei paper. These sticks are 1J inches in diameter and Q inches long. Any strength may be had, the most common being from 30 to 40 per cent, nitre-glycerine, up to 80 per cent. Dynamite is ordinarily quite safe to handle, though under certain conditions it is extremely unstable, and should be handled intelligently. In small quantities good dynamite may be burned and this widely advertised fact has caused the death of many men. When exposed to the sun or boiling water (as is often done when thawing it out) it rots. This condition usually, but not always, may be detected by the appearance of a greenish tinge. In this state it will explode when burnt or even jarred. In lar^e masses dynamite may be exploded by its own heat while burning. 156 YDROELECTRIC PLANTS. Dynamite will explode if struck between irons, but not by blows of wood upon wood. A drop of pure nitro-glycerine may ooze from a stick on thawing, and falling three or four inches explode on striking a hot surface. The electric spark and also lightning will explode dynamite. We do not give these defects space here to scare the inexperienced, but to make known that dynamite, when rotting, is dangerous. When in good condition and handled with any degree of care, it is as safe as any explosive. To thaw frozen dynamite, place in a warm place, but do not boil. To use the dynamite a stick is opened at one end (Fig. 124), and with a punch of the suitable size, a hole is punched two or three inches deep, as at (A). Then a cap ir placed over the end 12.7 FIGS. 124 to 127. Preparing a dynamite charge. of the fuse, as in Fig. 125, and the end of the cap crimped down on to it. The cap is the most dangerous part of the charge, and great care must be exercised to in no way injure the ends con- taining the fulminate of mercury. In cutting the fuse off to insert in the cap, use a sharp knife, and be careful not to spill the powder out. Many failures are attributable to lack of powder near the fulminate. The cap and fuse is then pushed solidly into the hole in the dynamite, and the loose paper around the stick is twisted about the fuse and tied solidly with string (Fig. 126). If the charge is under water, or in a damp hole, the exterior around the fuse and string should be coated with axle grease, soap, or some such water-proofing compound. The charge is now placed in the hole and tamped in on top, filling the hole. Dry sand is the best for tamping, but rock dust is also good. The end of the fuse is now slit (see Fig. 127), and the charge is ready for firing. H YDRA ULIC CONSTR UCTION. 157 When a charge fails to explode, great caution should be ob- served in going near it, as often the fuse hangs fire for two or three minutes. Do not tamp the holes with anything but wood. Rather than attempt to dig out an unexploded stick, drill another hole eight or ten inches from it and fire another charge. The charges may be varied by cutting the sticks into different lengths. Deep drilling is necessary to produce the best results. D _T FIG. 128. Connections for electrically firing dynamite. The harder the material, the higher the per cent, of nitro-glycer- ine used. For soft clay, the holes are bored with an ordinary two-inch auger and giant powder used, or mild 15 per cent dynamite. On large work, or where all the charges must be fired at once, the charges are all connected to an electric circuit as in Fig. 128, FIG. 129. by turning the handle of the magneto (a) the charges are all exploded, A special cap is used. This method is especially good for under-water work. When it is desired to get in an unusually heavy charge, a small charge, called a " squib," is first fired, making a cavity, as at (6), Fig. 129. This is then filled with dynamite taken from the paper cases and tamped in. For work under a building, and where it is desired to avoid jarring, about two inches of a stick is fired at a time, the stronger grade of dynamite being used. 158 HYDROELECTRIC PLANTS. To blast ice, the charges are placed several feet under water. Large boulders may be cracked by simply placing the charge on top and resting a heavy stone on the charge. Old piling may be cut off under water by boring a- hole partly through and sticking in the dynamite. The author once had to drive sheet piling where the sand was filled with saw logs in some places to a depth of eight feet. A place was cut through these by driving two-inch gas pipes, as shown in Fig. 130. The log was first located with a J-inch rod ; in the lower ends of the pipe were plugs. When the pipes were driven the plugs were rammed out and the charges placed in the pipes. A rammer then held the charges in while the pipes were withdrawn. It often required two men one day to cut off a large log, but all were finally cut. FIG. 130. Jovite is a more modern production than dynamite, and possesses several advantages over that explosive. It will burn without exploding; jarring will not set it off. It will not rot and become dangerous. It can be hammered iron on iron with perfect safety. For the same strength it is lighter than dyna- mite. It may be dropped on hot iron. Lightning will not ex- plode it. It contains no liquid, as does dynamite. It cannot freeze. A stick may explode within two inches of another with- out exploding the latter. Dynamite gives off poisonous fumes, which cause severe headaches. It has affected the author to such an extent that walking, was impossible. It has even caused death. Therefore, * ) H YDRA U'LIC CONSTRUCTION. 159 when working with it in tunnels or deep cuts, the workmen do not return to the work immediately, but wait for the clearing away of the fumes. Jovite does not give off injurious fumes, and therefore much time is saved in its use. Jovite is put up in sticks, the same as dynamite, or in bulk. It is graded as: No. 1, which has the strength of 20 per cent, dyna- mite; No. 2 is equivalent to 40 per cent, dynamite ; No. 3XX equivalent to 60 per cent dynamite. It is exploded in exactly the same way as dynamite. In bulk form it may be used to fill into cracks and seams, thus saving much drilling. To get a lifting effect where it is desired to produce quarry stone, No. 1 is used, and where the stone is to be broken up into small pieces, No. 3XX. For under-water work jovite possesses no especial advantage over dynamite, except in its safety before using. It must not be left in the water any great length of time, as the nitrate of soda leaks out. It can be procured put up in water-tight bags. The cost of jovite is slightly less than dynamite on account of its lesser weight, the price per pound being about the same. Ordinary electric fuses with a cap attached and with from four to eight feet of wire for each fuse, cost from $3 to $4 per 100. A blasting machine which will fire 20 charges costs $25. Dynamite costs about 14 cents per pound for the lower percent- ages of nitro-glycerine, and up to 16 cents for 60 per cent, nitro glycerine. CABLEWAYS. In building long dams the cableway is the best of all methods for handling materials. There are innumerable systems of cable tramways now in use, but the following are the funda- mental types. Fig. 131 shows a splendid arrangement for making large fills. There are a number of cars A , or skips which travel around on the stationary cable 5, being moved by the traction rope C. The terminal D is the same at both ends, one or both being used as filling stations. The cars can be loaded automatically as they pass around the terminal and automatically dumped at any point along the cable. Intermediate supports may be placed between the terminals. By adding another rope which is car- ried around with the car or skip, and a set of falls the car may be stopped at any point and lowered. 160 HYDROELECTRIC PLANTS. Fig. 132 illustrates the most common form used for construct- ing dams, etc. The carriage is pulled along the cable and may be lowered at any point by a man stationed on the shore. Loads as high as 10 to 20 tons may be handled on spans of over 1000 feet. By making the towers movable the whole field of operation may be covered. FIG. 131. FOR SMOKB-STACK GUYS, TROLLEY-LINE SPAN WIRE AND OTHER PURPOSES. COMPOSED OF SEVEN CAL. STEEL WIRES TWISTED TOGETHER. Price in cents per 100 feet. Diameter in inches. Weight per 100 feet in pounds. Approximate breaking strain in pounds. 315 1/2 52 8,320 250 7/16 40 6,000 200 3/8 30 4.700 160 5/16 22 3,300 115 1/4 13 1,750 80 3/16 8 1,000 60 5/32 5 / 700 45 1/8 3.50 375 35 3/32 2.25 320 Fig. 133 shows a very good plan where a cheap cableway is desired. By simply varying the elevation of the boom fall blocks, the bucket or skip may be made to run out over the cable and back again by aid of its gravity alone. The dimensions given are for a cablewa.y built by Parker & Flynn of Waterford, HYDRAULIC CONSTRUCTION. 161 162 HYDROELECTRIC PLANTS. N. Y. The total span was 900 feet, arid the load five cubic feet of wet concrete. The cable was a J-inch st-eel hoisting cable. This plan could be well adapted to dan building. A set of falls would be carried by the skip so as to permit the lifting and lower- ing of materials. There being no heavy towers, it would be an easy matter to shift the cable up or down stream. z *-i w m n + W n for n= S_ 2 wS 2 +2WS do) 164 HYDROELECTRIC PLANTS. If the tension is desired, transpose and solve for t, thus in (10) t _ BRIDGES. The bridge in some one of its many forms enters so frequently into the design of hydraulic plants that it is deemed advisable to give the design of a few of the more simple forms brief treat- ment here. FIG. 135. One of the simplest trusses is shown in Fig. 135. This truss is adapted to spans of from 30 to 40 feet. Total compressive stress on D~C Total tensile stress on B C or Total compressive stress in D C = W, wherein W is the total concentrated transient load. FIG. 136. These formulas are for a concentrated load: For a uniformly loaded truss W would be divided by 4 in the above. For a truss with random load, as in Fig. 136: Total compressive stress on A Total tensile tress on BCXAD BC = ABXCD XW HYDRAULIC CONSTRUCTION. 165 Total tensile stress in ACXDB Compressive stress in D C = W. For a truss, as shown in Fig. 137, having equal loads at two points we have: Total compressive stress on AB = V FIG. 137. Total tensile stress on A C or *j>-4f Total tensile stress on Compressive stress on E C or F D = W In Fig. 138 is shown the truss Fig. 135, inverted and adapted to a roof truss. As such, the total load of rafters or purlines, supported by the braces A C and B C, produces the same stress .xtv. FIG. 138. as would one-half the load concentrated at the apex C. The horizontal thrust in the rafters at either end equals the tension in the rod C D. Any of these trusses may be turned over, in which case the compression members become tension members. When the spans are longer than about 40 feet a truss, having a number of panels, as in Fig. 139, is used. This is the Burr truss, and as shown here has five panels. . 166 HYDROELECTRIC PLANTS. Four-fifths of the total load of truss and transient load is taken as being divided evenly between the four points of sup- port, C, D, E and F, One-fifth is supported by the abutments. Total compressive stress on A G or B J = 2WX 7^-7^- (jr C Total tensile stress on G C or / F = 2 W. TT X- Total compressive stress on H C or I F = Wx -^-pr fi L) w _ Total wt. of load and truss Number of panels The diagonals H E and I D receive no stress unless the truss is unequally loaded. The rods H D and / E each sustain a Total compressive stress = W. A C Total compressive stress inG H or / J = 2WX >^- Total compressive stress in H I = 3 W X GC AC GC A C Total tensile stress in A C or F E = 2 Wx ^~ (j G A C Total tensional stress in C D, D E or E F = ,3 Wx ^-^ G C For large trusses the cords and even the braces frequently have to be built up. A properly built up timber is better than a solid timber of the same area, for though the strength may be less, it will last longer, the interior being ventilated. Fig. 140 shows some of the splices used by the Pullman Car Mfg. Co. and recommended by the Master Car Builders' Asso- HYDRAULIC CONSTRUCTION. lt>7 ciation. Fig. 141 shows a met hod of building up a chord com- posed of a number of planks, a, b, c, d, e, etc. The leaves, x, are made of hard wood one third the thickness ^6/os7>. V: " FIG. 211. Beardsley mat. In Fig. 211 the essential features of a patent mat possessing all the above features are given. The mat is built so that it is at all times submerged. It can therefore be built of any sound lumber. The mud sills A are first laid in the river bed. Where possible the river bed should be excavated rather than filled up to a level. That is, the top surfaces of the mud sills should be placed level with the natural river bed, the trenches being dug for them. When this cannot be done the fill may be made with any material that will not be dissolved by the action of the water. An architect's level is indispensable in laying these sills. One man holds the staff on the ends of the sills and the other men tamp under the sills until they are level, then the timbers are HYDRAULIC CONSTRUCTION. 221 weighed down to prevent floating out should the pumps stop. When the sills are levelled they are filled flush to their tops, a straight edge being used to level with. If too much fill is used the nailing of the plank will draw the sills up, and if too little there will be uneven settling. Next, the planking B is nailed down. Unless these planks are edged and well dried they should be battened water tight on that part of the mat over which the water will be conducted during the building of the last half. It is a good plan to make this deck of two layers of 1-inch boards, breaking joints at edges and ends. This makes the mat more flexible. The row of sheet piling C is driven as deep as possible and a water-tight connection made with the mat. The row D is not attached to the mat, and the spaces usually left will permit the seepage water to find an outlet without exerting an uplift on the mat. It is also desirable to permit the mat to settle, which it could not do if it were fastened to the piling. The intermediate sills E run up and down stream, being placed a distance apart equal to the distance between the dam bents, so that each bent will rest directly over a sill. The sills F run lengthwise of the dam, thus forming, with the sills E, a series of compartments, each as wide as the distance between dam bents, and as long as the mat. These compartments are filled with gravel or stone, and the top planks G are then laid. The top planks are merely for the purpose of conducting the water over the mat without allowing it to wash out the gravel, so they need not be edged or the cracks battened. Along the up-stream edge of the mat is built the breast wall. The posts H are placed five or six feet apart and should be from four to ten feet in height, depending on the height of dam. The tops should not come near enough to the surface to be struck by floating ice, logs, etc. The breast wall serves two very important purposes: During construction it is used to shift the water from one part of the mat to another, so as to aid in building the dam. By its use the water may be raised, a plank at a time, until the fill above it is completed. It also serves to hold the fill over the edge of the mat, the only place where the water could possibly find an outlet. This fill is made as high as the current going over the breast wall will permit. The breast wall is not placed on top of the plank G, but on the lower course. In this way greater flexibility is obtained between the mat directly under the dam and where it 222 HYDROELECTRIC PLANTS. is attached to the piling. Also a small amount of fill can be made over the edge of the mat without filling above the top level. The posts are held by means of rods, or may be braced. The timbers used for heads up to 20 feet are 8x8 inches, and for very low heads 6x8 inches. The length of the mat should be such that the foot boards will not strike the breast wall in being dropped, and that the down stream edge of apron will just come to the edge. Water from the overpour should never be allowed to strike the mat. It will be seen that it is a physical impossibility for water to ever cut under such a mat. In an experience with over 60 such mats the author has never known the water to get under one. Owing to cheap construction several have been under- mined from below, but never injured along the breast wall. -!* S77<7/ FIG. 212. ^Fig. 196, gives a good idea of the construction of such mats. In this case the water was all turned through the power house, seen in the distance, and the breast wall was filled full depth at once. The trench shown to the left was to make the driving of the sheet piling more easy. Each alternate sill should be drifted to the mud sills with at least 2 f x!4-inch drift spikes. The planking is done with 30d spikes. In the majority of cases it is necessary to build half of the mat at a time. During the building of the first half (or as much more than half as possible) the water is turned to the other side of the river, but while building the last half it runs over the com- pleted portion. (See Fig. 212.) In this case the entire surface of the mat is exposed to the HYDRAULIC CONSTRUCTION. 223 water, and if there is any leakage it will follow along the sills toward the uncompleted mat, when the water is pumped out, unless a cut-off wall, A, is put in. It will pay to do a good job on this cut-off. The author has found that a concrete wall as shown at A Figs. 212 and 213 is the best. This wall is built before the mat is laid near to it on either side, and should go down to firm bottom if possible. The top must not be more than an inch or so above the top of the mat, and only extend to the up and down-stream row of piling; along the top is embedded a plank or timber to which temporary planks may be nailed. These temporary planks are tongued and grooved and keep out the water. The mat simply abuts against the wall and does not project into it at any place. A row of piling may be used in place of the wall. FIG. 213. The cost of laying a mat is about 3 cents per square foot, including digging the trenches for mud sills, leveling, planking, etc., but does not include the fill above breast wall. Three kegs of 30d nails are required to 1000 square feet of mat. A timber mat requires from 5J to 7 square feet of lumber per superficial square foot. The dam and the abutments are placed on the mat. The dam may be of the crib type if desired, though commonly the frame dam is used. It may, of course, be fastened down to the mat by means of drifts, but this is wholly unnecessary, as once the water pressure is on nothing could stir the dam. A few years ago, to demonstrate to an incredulous city board that the dam would not slip off the mat, a model dam was built and placed on the slimy floor of an old penstock. The dam was four feet high and just fitted into the penstock, without quite touch- ing at the ends. The water was turned on all at once and the 224 HYDROELECTRIC PLANTS. model only slid one inch and then settled solidly upon the floor. Figs. 214 and 215 show dams of the frame type and are suited either to place on mats or solid rock. There should be no mortise and tenon joints about a dam, as experience has proved that such joints are the first places to decay. A plain sawed butt joint is all that is necessary, there being no side, strains at all. Four 40d spikes are used at each joint to hold the parts in place. The designing of a frame gravity dam is a very simple operation. Take the example of a 20-foot dam with 5 feet of water going over it. (Fig. 215.) First, assume the slant of the deck to be 23, and draw the decking. Then at 5-foot intervals erect verticals to get the depth or head of water at those points. Multiply the depth by 62.5 to obtain the pressure per square foot on the deck. Thus, at vertical (1), when the depth is 22 feet the pressure is 1375 pounds per square foot. Now the up-stream plate A must, in most cases, be high enough above the mat to allow the passage of the water underneath. This makes the length of the foot board B about six feet, and the plate A will then have to sustain practically half the weight on these foot boards. If the distance between bents is four feet, 1469X3X4 is the part of the pressure on the foot boards held by the plate. It will also hold half the weight on the 3-foot span to the next plate, which is 1375X1.5 X4. The sum of the two is 25,876 pounds. From table (55*) an oak beam one inch thick and 10 inches deep will safely sustain a load of 2640 pounds, therefore a lOxlO-inch beam will sustain 26,400 pounds. At depth (2) the pressure per square foot is 1250 pounds and the area supported by the plate C is 4JX4 = 17 square f eet ; therefore , the load on C is 4JX4.X 1250 =21,250 pounds, for which an SxlO-inch timber is found to be right. As it is not best to use a smaller timber than an 8x8-inch in a dam of this size, all the remaining plates will be made of SxS-inch timbers, and they should be spaced up and down stream so that the full strength of the decking will be utilized. At (3) they could safely be four feet apart, and at (7) six feet, so six feet will be taken as the maximum distance at the crest and then gradually diminish the span toward the toe. The posts, if made of 8x8-inch timbers, will be many times stronger than necessary, but a smaller size would make the pressure at the ends too severe. From table (54*) a post six * See Chapter IX. HYDRAULIC CONSTRUCTION. 225 226 HYDROELECTRIC PLANTS. HYDRAULIC CONSTRUCTION. 227 feet long and 8x8 inches section will safely sustain 41,000 pounds for white pine, and for oak about 52,000 pounds. At D the lock block is bolted to the sill with a J-inch bolt. This block stiffens the dam against the horizontal forces acting at crest of dam, such as ice expansion. The design of the apron is more important perhaps, than any other part of the dam. If the water is given no object to strike against the only way 'the apron can be injured is by wearing out under the friction of the water. In this design a curved apron, having a crest formed to prevent the water from falling perpendicularly over on to it, is shown. This crest can be covered with boiler iron. The curve is obtained by nailing together segments made of 3-inch plank. The straight part of the apron is made of 3-inch white oak or yellow pine, and the lower portion is built up like the crest, the segments all being sawed to template before placing on the frame of the dam. The only strain on the timbers is that due to the weight of the water, and when passing over the apron this is in a very thin sheet. The segments of the apron should be sawed so that the grain will run with the current. The foot-boards B, are of 4-inch plank. Each bottom board is notched on one edge so that it will bear its part of the pressure. If the bottom boards were water-tight no pressure would come on to the top boards at all. Curve (Fig. 258) gives the thou- sands of feet of lumber in 100 feet of dam similar to that just designed. Fig. 216 shows a gravity dam, made principally of steel. The details of construction may be worked out in a great many different ways, but the design shown will serve to illustrate the principle. The deck is of tongue and grooved plank, as in the timber dam. As the deck is at all times in direct contact with the water it is preserved from decay. The apron is made of segments as shown. If, for any reason, the sill cannot be placed under water, another channel should be used in its place, forming, with the one shown, a box girder. Fig. 220 shows a design for a concrete-steel dam. This form of dam is the combination of all that is good in both the timber gravity dam and the concrete dam. The use of the steel re- inforcing makes the design as certain as it would be for an all- steel dam. The compressive strength of the concrete is used 228 HYDROELECTRIC PLANTS. HYDRAULIC CONSTRUCTION. 229 to the fullest extent, but all tensional stress is thrown upon the steel. The steel being embedded in the concrete will not rust, and therefore the permanence of the structure is secured. For rock bottom the apron may be omitted (Figs. 218 and 219). The passageway is for the free admission of air to the interior and to permit inspection. There are certain conditions under which even a concrete- steel dam will fail to give perfect satisfaction. Thus, if the 230 HYDROELECTRIC PLANTS. bottom yields ever so little, the dam will crack. The steel will hold it together, but leaks will start, which, in time, will cause damage and loss of power. Again, such a dam must necessarily be constructed entirely in place in the river bed, which means more or less risk from floods during the building. v~ZL Designed for the Roberts & Abbott Co. FIG. 219. Reinforced gravity dam. The design (Fig. 220) shows a dam that is composed of indi- vidual reinforced members, each of which is built on shore, and thoroughly tested and seasoned before placing in the dam. The deck is made up of these segments C, and the apron deck is .nade of similar segments, the only difference being that the apror HYDRAULIC CONSTRUCTION. 231 segments are of less depth and have more anchor bolts. Each segment has recesses, F, moulded along the sides, so that when cemented between, as G, the whole is bound together. Each segment is a beam eight inches deep and 12 inches wide, in the dam shown, and as long as the distance between bents, each sustains eight times the actual pressure per square foot,, and may be designed from tables in Chapter IV. // YDR A ULIC CONS TR UCTION. 233 234 HYDROELECTRIC PLANTS. l HYDRAULIC CONSTRUCTION. 235 236 HYDROELECTRIC PLANTS. Referring to Table XXIXa, page 121, we find that the segments near the toe of the dam should be 10 inches deep and be reinforced with 1.31 square inches of mild steel to sustain the load. The first segment supports three feet of the the foot boards, or 3X8 = 24 square feet of surface; therefore, 24X1000 = 24,000 pounds is the pressure upon it. For this beam of 14-inch depth two inches of steel are required. At each end of the segments is molded a half recess to permit of bolting to the deck and apron plate. When the segments are all in place on the dam a rich cement-sand mortar is filled in between, making the joints water tight. Now as these segments only run from one bent to the next, it is evident that one bent could sink a good deal without impairing the strength of the dam. Also if the deck warps, the only place a crack would occur would be between the segments and not across them, where the rein- forcing is. In a dam of the size shown (Fig. 220), the sill A is made all in one piece, but for higher dams it may be made in more pieces. Where each post comes, a steel plate E is molded. The four holes have the same spacing as the reinforcing rods in the posts, so that when the post is set up the rods slip onto them. At H a plate is molded into A , so that the bolts connecting it with the sill will have greater shearing value. The holes for these bolts are cored into the plate. The apron plate is made in the same way, a number of anchor bolts being molded in, to hold the apron segments. The sill is 10x1 0-inch and reinforced with Ix3-inch bars. The dimensions of the posts are obtained from the formula: Safe Load = 350 (area of concrete +15 X area of reinforcing steel). This dam may be placed upon a timber mat the same as a timber dam. Gravel should be placed on the deck so that if a crack should occur leakage will be prevented. WING DAMS. On navigable rivers, wing dams are sometimes built to avoid obstructing navigation. These dams are run part way across the river and frequently quite a distance up the stream. The head thus acquired is necessarily low, but usually in such cases there is plenty of water. At Rock Island, 111.; there is a very large power created by a wing dam and used by the United States Government at its arsenal. HYDRAULIC CONSTRUCTION. 237 The wing dam is built in the same way as others described except at the end which receives the full force of the current. At this point every precaution must be taken to provide against undermining. The pier A, Fig. 225, is built first, a coffer being built so that the bottom of the river may be excavated. FIG. 225. The foundation of this pier must go down below the level of possible wash. Having built a safe end the building of the dam possesses no unusual difficulties. BOW DAMS. Dams, especially masonry dams, are often bowed up stream, as shown in Fig. 226, in an exaggerated form. The idea is to get the strength of an arch. When the ends of vertical faced masonry dams are given a secure anchorage, as in Fig. 226, there is no doubt but that a great increase in strength is secured, by the arch, but the ends must make an angle with the stream such that a line CD, coinciding with them, passes inside the center of curvature. The water pressure, being perpendicu 1 ar to the surface at all points, presses every part towards the center 238 HYDROELECTRIC PLANTS. of curvature, and if the ends are given a less slant, as A B, the pressure at P tends to shove the end away from the cliffs and the dam is no stronger than if built straight. The author knows of two bowed masonry dams, each of which failed at both ends. For timber, or gravity dams of any material, the bow adds no degree of safety. The old-style crib dam, unless very short, would gain little by the arching, as it would fail, due to local weakness at some one point, and disintegrate without giving an FIG. 226. end thrust. The gravity dam depends on the vertical water pressure to hold it in place, therefore the arch would add nothing to its security. MASONRY DAMS. The search for permanence has developed the masonry dam. Its great first cost would have made its use impossible had there not been a strong prejudice against all other forms. The feeling of security given by the use of masonry often made a proper disposition of the materials a secondary consideration, with the result that the list of masonry dam casualties contain almost as many failures as that of timber dams. With the passing of the forest and the decreasing cost of concrete, however, it becomes more and more important that we perfect the masonry or concrete dam. Assuming that the concrete or masonry is properly laid, there are eight prime factors which must be determined and provided for before the actual work of construction begins: // YDRA ULIC CONSTR UCTION. 239 1. Wall being sheared by the horizontal push of the water. 2. Undermining below the dam, due to weak apron. 3. Resistance to sliding on its base. 4. Effect of vacuums. 5. Effect of flotation on the weight of materials. 6. Effect of ice expansion. 7. Liability of seepage under the dam. 8. Weakness of green concrete or masonry. To convince the reader that it is worth while to study the above points well before indulging in hasty construction, the cross-sections of a few masonry or concrete dams which have failed, are given in Figs. 227 and 228, these costing millions of FIGS. -227, 228. dollars and a great many lives. The cause of these failures may be found among the above eight factors, and the probable factors which caused the failure have been indicated on each section. The author contends that the cause of so many disasters is because the factors 4, 5, 6, 7 and 8 have not been understood, and by merely building to oppose the hydraulic pressure, instead of turning them in to. factors of safety. By referring to these sections it will be seen that without an exception the up-stream face of the dams are vertical, or prac- tically so, and that all are apparently of heavy proportions, when the water pressures alone are considered. In discussing the above eight factors it must be borne in mind that there are 240 HYDROELECTRIC PLANTS. but two forces, the amount of which can be figured with any degree of accuracy. These are the hydraulic pressure and the crushing strength of the masonry. It is an undisputed fact that the tensile strength of masonry or concrete is so uncertain that it can not be relied upon at all. Also the shearing strength is unreliable. The weight of the material is a quantity which is equally difficult to compute, owing to the factor of flotation- Of course, it is at once apparent that the portion of the dam which is below the surface of tail water is lifted up by the amount of the weight of the displaced water, and that this lifting effect is increased by 'the backwater caused by floods. It has been contended that the water which soaked into the masonry owing to the hydraulic pressure did not affect the weight of the material thus soaked, but lately leading engineers are taking the stand that the weight is very materially affected, though as to just what extent they are still at variance. This loss in the effective weight of the material the author calls the factor of flotation, as the tendency is to float the masonry, and has demonstrated to his own satisfaction that it is not safe to figure the effective weight of the affected masonry at more than two-thirds its actual weight. In the following table is given the amounts of water which a cubic foot of sand and some common rocks will absorb: TABLE XXXVII. Material. Water absorbed per cubic foot. Material. Water absorbed per cubic foot. Sand Quarts. 10 Dolomite ' Quarts. 1 to 10 2 to 6 Chalk g Triassic sandstone 4 Granite 1/100 to 1 Trenton limestone JtolJ Bearing in mind these points, it will be seen how very uncertain is the material which has been looked upon in the past as the most trustworthy agent to resist the hydraulic forces. Its one factor upon which reliance may be placed (the crushing strength) has never been made use of in the past, as all masonry dams which have failed, however scant their dimensions may have HYDRAULIC CONSTRUCTION. 241 been, were absolutely safe against crushing. This is because the structures were built so weak in other ways that the limit of the crushing strength could not possibly be reached before there was a wash-out due to some other cause. We will now take up the eight factors in their order and con- sider their importance in the design of dams: 1. If the dam should give way at G D, Fig. 232, owing to the horizontal down-stream push of the hydraulic pressure, it is sheared at that point. Even an approximate value for the shearing strength is impossible to predetermine, as it depends on variables, such as evenness of mixing the mortar or concrete; parting lines formed between bodies of the materials laid^at different times; strains set up in the materials, owing to uneven setting, etc. 2. One of the most common causes of disaster is due to the dam being undermined on the down-stream edge of the structure, and to the sucking force of vacuums. To prevent this a massive extension mat must be provided. (See design on page 234). 3. Referring to the sections of the above dams it will be seen that all the pressure is directly down stream, because it is a well known law that water pressure is always perpendicular to the exposed surface. Therefore the only thing to hold these dams in place is the friction between the bed of the stream and the dam. The Austin dam is a very noteworthy example of a dam which failed by sliding on its base. A large section slid bodily down stream and still stands erect, several hundred feet below its original position. Of course, the heavier the materials, the greater the friction. The crushing strength of the masonry, however, does not enter into consideration. 4. In considering the fourth factor the reader is referred to the result of the Cornell experiments, given on page 14. These experiments prove that, for even a small fall and overpour, a powerful vacuum is formed. In the case of the eight-foot dam it had to sustain the equivalent of five feet of head in addition to the eight feet, or over half again as much. This means 312 pounds per square foot of surface. Where the dam is from 40 to 100 feet high and the sheet of water flowing over the apron is six or eight feet thick, the vacuum must be almost perfect. It has been found that the vacuum adds fully 1000 pounds pe'r square foot to the pressure on the dam where the dam is 20 or 30 242 HYDROELECTRIC PLANTS. feet high and the sheet four feet or more thick. The presence of a vacuum can be qualitatively demonstrated by noting the in- rush of air at the inlets provided in dams for the relief of the vacuum. The Columbus, Anderson and the Upper and Lower Tallassee dams all failed within a day or two of each other, and in each case the hydraulic pressure (owing to the back- water) was less than at any other time in the history of the dam. Then why did they fail ? Simply because of the terrible vacuum pressure and the floating effect produced by the increased back- water below the dam. In order to more clearly demonstrate the action of vacuums, the following reasoning is given: Referring to Fig. 229, the sec- FIG. 229. tion of the overflowing water is similar to that of the dam. Now there are two fundamental laws of motion which we must accept as being correct. 1. A body under motion will continue so unless acted on by some external force. 2. Action and reaction are equal and oppositely directed. The action of the air pressure when a vacuum is formed is to deflect the mass of falling water from its normal path, as shown by the dotted lines. Of course there can be no question but that to deflect tons of rapidly falling water force is required. This force shows itself by the difference in elevation of the water behind the pour, and that below, as the levels a and b. Accord- ing to the second law there must be some reaction to the air pressure on the overflow. Suppose Fig. 229 to take more simple form, as in Fig. 230, the impended water not being considered. HYDRAULIC CONSTRUCTION. 243 Now the water between the overflow and the dam is held to the level a, by the partial vacuum V. In other words, the water is sucked up in between the dam and the overpour, creating a suction on, not only the wall of water on the right, but also on the wall of masonry on the left. Can there be any question on this point? Mr. Frizell, in his very excellent treatise on hydraulics, says, " Its greatest possible deleterious effect would be to press the stream against the down stream face of the dam," and claims that the vacuum tends to sustain the dam. Of course this view is faulty, as it does not consider the reaction on the pond-side of the dam. Filling the pond above the dam does not change the above reasoning, as the air pressure is perfectly transmitted through the imponded water. The water and the wall tend to be sucked into the vacuum, and to resist this suction a certain factor of safety must be allowed. FIG. 230. " Suction is the act of exhausting air from a cavity, but it acts upon the air within the cavity, not upon the walls of the cavity, nor upon any substance heavier than the air; a piece of paper upon the floor of the cavity would not be disturbed by the suction. Suction is the primary cause and vacuum is the effect. The breaking of the walls of the cavity is the effect of a secondary cause -atmospheric pressure forcing in the walls to fill the vacuum. Its action may be better understood from the following illustration: A piece of pliable leather having a cord attached to its center, when saturated with water and pressed upon a stone, adheres with such force that in many instaces it is possible to lift the stone. The pull on the cord reduces the atmospheric pressure on top of the stone, and in cases where the stone is not heavier than the total pressure on the leather it is possible to reduce the pressure on top of the stone to such an extent that the atmospheric pressure from below will lift the stone. 244 HYDROELECTRIC PLANTS. The operation of this familiar experiment is precisely the same as that of vacuum suction on dams. The sheet of water is represented by the piece of pliable leather, the dam by the stone against which the sheet is pressed, and the projectile force of the sheet by the pull upon the cord. If, in the experiment, the atmospheric pressure is greater than the weight of the stone, the stone will be lifted and no vacuum formed, and so the dam may receive a pull equal to the projectile force of the sheet, even though the over-pour does not leap away from the apron and, without causing a vacuum, develop an unseen, unsuspected force, which may have the power to destroy the dam. Since it is evident that suction brings into action a secondary force against the outside face of the cavity or wall only, we are driven to the conclusion that the facings on the lower half of aprons are not displaced by suction. The more probable cause of the defacement of aprons is found in a deficient resisting power of the masonry, the erosion of weak mortar from poorly-constructed joints, and the develop- ment of vibrations caused by great columns of water pounding upon the facings with a force of many thousands of tons. This theory is the more probable since the facings are not torn off at points above the lower half of the apron where vacuums do occur, but are torn off at a point where, in all probability, they do not occur."* Now as to the amount of this air pressure: At first thought it would seem that the effective pressure would only be figured as pressing the dam from the crest down to the surface of the water a, Fig. 231, but this is not so. Referring to Fig. 231, the column of water behind the over-pour caused by the vacuum reacts on the dam, tending to neutralize the vacuum pressure. The pressure against the dam considering only the vacuum pressure and that due to the level E D, at the water level C D the pressure is zero, but at level A B and H I it equals the pressure due to the level E D and therefore equals the vacuum pressure. The line E A H therefore is the line of pressures at any point along E F. due to the backwater against the dam, and the line C F is the line of vacuum pressure. As the *E. R. Beardsley. H YDRA ULIC CONSTR UCTIOX. 245 air pressure acts against the up-stream face of the dam, through the emponded water, it must be perpendicular to that surface of the dam, and will be uniformly distributed along the face. We may, therefore, represent this vacuum by the line C' G' parallel to this face and at a distance from it equal to the vacuum pressure. The line C' F f is CF transferred. Now the center of gravity of this shaded, area F f E' G r C', which represents the entire vacuum pressure, may be found and the whole pressure considered as acting at that point, and tending to slide or overturn the dam. The amount of vacuum pressure for any particular dam is very difficult to determine, owing to the lack of data on the sub- ject. The author has made the following experiments with dams fitted with air inlets: FIG. 231. A~dam 565 feet long, with a total head six feet, and a head over the crest of three feet, showed a vacuum pressure of three feet of water or 1 . 31 pounds per square inch ; a dam 300 feet long, with a total head of 12 feet, and a head over the crest of 30 inches, showed a vacuum of three feet of water or 1 . 31 pounds per square inch; a dam 275 feet, with a total head of 30 feet, and a head over the crest of four feet, showed a vacuum of 14 feet of water or six pounds per square inch. At Cornell a weir [six feet high, with 18 inches of water, showed a vacuum pressure of two feet of water or . 86 pounds per square inch ; and a dam eight feet high, with two feet of water, showed a vacuum of five feet of water or 2. 16 pounds per square inch. From these examples a fair guess may be made as to the probable pressure due to vacuums. 246 HYDROELECTRIC PLANTS. One of the results of the formation of the vacuum is to set up vibrations which may seriously affect the stability of the structure. Water falling perpendicularly into the river bed or upon the apron, gives a series of rapid blows, keeping the entire structure in a tremulous condition. A body placed on t'he floor may be easily moved if the floor is vibrated. Now add to the effect .of these constant vibrations, the heavy rhythmic vibration caused by the vacuum, and the conditions are perfect for the down-stream movement of the dam. When the overpour is not too heavy the vacuum forms more or less perfectly until the sheet of water can resist the inward pressure of 'the air no longer, when it breaks through the sheet, thus restoring the equilibrium. This process is repeated with great regularity and results in an intense horizontal push and pull on the dam. If the vacuum inlets are too small, this action takes place, causing a puffing noise, similar to a locomotive pulling a heavy train up hill. 5. It will at once be apparent that that portion of the dam which is entirely below tail water (see Fig. 232) is floated up with a force equal to the weight of the displaced water, but it will possibly require a little study before the reader will under- stand how the water which seeps into the solid masonry can cause a diminution of weight in the affected portions. One of the most widely known and popular experiments to illustrate the action of water pressure is the bursting of a stout keg by means of a high but thread-like column of water. This is the action which takes place through the finest seam of the most minute interstices and exerts a lifting or floating effect on the particles which go to make up the mass of the structure. Re- HYDRAULIC CONSTRUCTION. 247 f erring to the sketch (Fig. 232) all that masonry on the up-stream side of the line D C will be affected in this way, and there is such a small amount of dam left unaffected that the only safe way is to suppose the entire structure as affected. A fairly safe method is to figure the mass of the dam above tail water as losing one-third its weight, and that below tail water as losing 62 pounds per cubic foot. Mr. J. B. Francis held that solid concrete deposited on bed rock would be lifted or floated, and to prove this, placed a pipe provided with a pressure gauge, in the concrete of a dam and found that the gauge registered the full pressure. 6. Ice expansion, the sixth factor, becomes, in our northern climate, a most deadly foe to all dams, and especially to masonry dams. The co-efficient of ice expansion is nine-tenths of an inch to the 100 feet, and a sheet of ice one mile long will expand nearly four feet. It is evident that dams do not receive all this expansion. If they did the first severe winter would destroy them. A large per cent, is already expanded when the sheet is first attached to the dam, but the expansion will be continued as long as severe weather lasts. The following is taken from the Architect and Building .News: ' A short railway was once built in the Province of Ontario which crossed a fresh- water pond, known as Rice Lake, by a bridge two and one-half miles long. The bridge was mostly corn- composed of trestle-work, very strongly built, with uprights driven in hard bottom and thoroughly braced. The middle portion, over the deepest part of the lake, was composed of trusses eighty feet in span, supported by piers measuring 12x24 feet and filled with stone. Early in the first winter after the bridge was built the lake froze over to a depth of about seven inches. Before snow came to protect the ice, the weather moderated, the sun shone out brightly, the ice expanded, and in a few minutes the bridge was in ruins its whole length, the trestles being pushed over in the direction of the principal expansion. Afterwards the trestles were repaired and filled in with gravel, the top of which is eight feet above the level of the water, yet the expansion of ice during sunny days is so great that it frequently creeps up the embankment, and, by successive move- ments, is pushed upon the rails." 248 HYDROELECTRIC PLANTS. The extent of the lake is not given, but with an open ice field of from three to four miles, and all the conditions favorable, the expansion would be as stated. Many instances have been known on lakes and rivers, where, under the enormous pressure, acres of ice have been hurled into the- air as if by an explosion of dyna- mite. An instance of this kind came under the writer's obser- vation a few years since, on the Kankakee River, Illinois, at the mouth of Baker Creek. The expansive power of ice is plainly shown along the shores of the small northern lakes, more especially those having firm bluffs on one side and low, marshy lands on the opposite side, which receive the full force of the expansion, and which after many years of repeated action have pushed inland the frozen earth of the shore up into parallel windrows, dykes or moraines from one to several feet in height. A singular phenomenon attending expansion is that it is greatest when the sun comes out and shines upon the ice while freezing. Short dams suffer less than long ones, because the abutments and banks offer great resistance, and expansion is thrown in the direction of least resistance. If the dam is long, the shore protection is diminished and its central portions more exposed. For this reason the dam is rarely moved at the abut- ments, but always at the center, with decreasing ratio towards the ends. If the dam is on rock bottom and bolted down, however fast, the repeated strain, winter after winter, tear it loose from its fastenings. If built on pilings, the movement is imparted to them, loosening the foundations, disturbing the general solidity of the structure, causing leakage and assisting in the work of general dissolution. The only way the vertical faced concrete dam can be built to be safe against ice expansion, is to give it enough strength to actually crush the ice against its up-stream face. Otherwise the ice will crush the dam, as there is no give and take to masonry. Trautwine gives 12 to 14 tons per square foot as the compressive strength of ice. This means that if a field of 12-inch ice gets a grip on to the crest of the dam it can push it with a force of from 12 to 14 tons for each foot of the length of the dam. 7^ , Seepage exists to a certain extent under all dams, and while it does not always indicate a weakness may prove to be HYDRAULIC CONSTRUCTION. 249 a destructive factor. If the resistance to the escape of the water below the dam at E Fig. 232, is greater than that to its entrance under the dam at F, there will be a back pressure created in direct proportion to this difference. If in Fig. 232 we suppose the water has free access under the dam as shown by the double shaded portion, then the whole bottom area of the dam will be lifted up with a pressure due to the head of water H and the dam floated out of position. Therefore, the up-stream toe of th3 dam must be made more nearly water-tight than the down- stream edge. In fact, drains should be placed under the dam to conduct away the water which does seep through the toe at F. Fig. 237, shows a dam of excellent design with the cutoff duct a to catch the seepage and the seepage trench b to make the toe as tight as possible. The seep holes c need be only about six or eight inches in diameter and about 10 feet be- tween centers lengthwise of the dam. AVith this design the effect of vacuum is allowed for and the dam allowed to rest with all possible weight upon the foundation. 8. The eighth factor we believe to be a very important one. The time taken to complete a heavy masonry dam varies from two to five years. To hasten the construction, large quantities of masonry or concrete are laid each season, with the result that the interior of the dam does not get a chance to dry out, and hence has very little strength. However, it is rushed to comple- tion late in the season and is compelled to withstand whatever floods may come its way. If there are no floods, well and good; but if, as in the case of the Cloumbus, Anderson, Upper Tallassee and Lower Tallassee dams, the floods come at once, the dams are in great danger of destruction. The four above-named dams were new dams, but all were destroyed by the same flood. In Fig. 233 we have attempted to show graphically the propor- tions of the three great agents of destruction water pressure, ice expansion and vacuum. Of course, the dam does not have to be of such great proportions, as, fortunately, when the ice can fasten to a dam there would be no vacuums, there being so much water that the ice could not fasten to the dam; but the sketch will show the importance of each of these factors. Each section is completed without a factor of safety and shows a dam just ready to be overturned by the particular force. In calculating 250 HYDROELECTRIC PLANTS. the ice expansion, the very low value of 8000 pounds pressure per foot of dam has been taken. Trautwine gives 24,000. The vacuum pressure has been taken as 625 pounds per square foot of surface exposed and the exposed surface called the area 10 feet below crest of dam. However well designed a vertical faced masonry or concrete dam may be, yet we must acknowledge that it is in the nature of a dangerous experiment. Every great masonry dam that was ever built has called forth heated discussions among the most noted engineers. The Croton dam was delayed years on account of such conflicting opinions. As this book goes to press the professors of University College, of London, England, come out with the startling announcement that all previous dams have been designed without taking into account a force tending to burst the dam vertically. Following is given a clipping from FIG. 233. a London paper, which shows how the best laid plans go oft agley.: " The new theory regarding the strain upon masonry of dams, brought forward by Atcherley and Pearson, mathema- ticians of the University College of London, has, at least for the time being, put an end to Sir William Garstin's plan of raising the gigantic dam at Assouan, which has already proved such a blessing to Egypt. ' This was an important part of a huge plan for further irriga- tion of Egypt, destined to bring millions of acres under cultiva- tion. Lord Cromer's last report dealt minutely with the scheme, the outlines of which then were cabled. " Sir William, through calculations of the engineering staff, was satisfied that according to all accepted theories of dam HYDRAULIC CONSTRUCTION. 251 construction the factor of safety was amply sufficient to permit the dam being raised, but in October he was informed of the new theory that the vertical sections of dams under water pressure were more severely strained than the horizontal parts. ' Therefore, while the dam was designed according to rules hitherto applied and may be safe as regards cracking horizontally, it may crack vertically. ' The Egyptian Government asked Sir Benjamin Baker to give an opinion on the raising of the dam. After inspecting the dam Baker reported that all thoughts of raising it should be postponed another 20 years. ' He is of the opinion, basing it on the new theory, that there now is little hope of raising the dam to any appreciable extent, although calculations submitted to and passed by him before the new theory was correct in all respects. He adds that the vibrations on the masonry dam are due to the rushing water in the sluices, and that the dam as constructed is perfectly safe. " 'There should be ' he said, ' perfect confidence and no need of anxiety in the permanent stability for centuries without difficult or costly works for its maintenance.' ' Masonry Dam Design in Detail. The design of masonry dams will now be treated in detail. First, take the case of a dam (Fig. 234) having the water level FIG. 234. with the crest and the up-stream side (face) perpendicular. The TV pressure at P = y X62.5X// and, in effect, is applied at the point J H from the bottom. The pressure P acts perpendicular to the face, and in turning the dam over, uses the lever A B. That is, the pressure P in pounds times A B in feet, is the over- turning moment. 252 HYDROELECTRIC PLANTS. The center of gravity G is found by drawing lines from C to .the middle of B D, and taking ^ of it. The weight of the masonry , (due allowance being made for the flotation factor) may now be supposed to act at this point, and in holding the dam against .the overturning force of the water, use the lever BE, EX being drawn through the center of gravity and perpendicular to D B, therefore the resisting moment due to the weight of the dam js WxBE where W is the effective weight of the dam. The factor of safety of the dam is PXAB In all these examples one linear foot of the dam is considered, i.e., the pressure for 100 feet of dam would be 100P. Suppose the dam to be turned around, as in Fig. 235. The water pressure acts perpendicular to the face and at a point FIG. 235. P, J the height as before. P acts in overturning the dam with the leverage A B, which is the perpendicular distance between the projection of P and the toe of the dam B. It will be seen that the flatter the face C D the greater will be the moment of the vertical force. That is, the more nearly the dam approaches the gravity type the less the tendency of the water to tip it over. The center of gravity is found as before and the perpenidcular, % E, is drawn. Then the effective weight of the dam will act, in resisting the water pressure, through the leverage E B, there- fore the factor of safety is WXEB PXBA Now take the case of Fig. 236, where the water is flowing over the dam at a depth h< HYDRAULIC CONSTRUCTION. 253 In this case P is not applied at a distance of J H from the base, but at a distance V = 3 h_ + X The overturning moment of the water then = PxA B. < i To get the center of gravity of a section like this, draw a line connecting the centers of the lines D B and F C. Lay off RF equal to D B, and D S equal to F C. Then where R.S crosses the center line, will be the center of gravity. The resist- ing moment of the dam = W X E B and the factor of safety is WXEB s = PXAB If this section is turned as in Fig. 235 the same reasoni i g is true. FIG. 236. A common method of determining the safety of any section is to" lay off to scale from / (Fig. 236) the line / K equal to the pressure P, and from 7 the line 7 N, to the same scale representing the effective weight of the dam. In gravity type the weight of the water should be considered. Then the resultant, 7 M, should intersect the base B D in the middle third. Such a method is faulty, as it does not take into consideration the factors 2, 3, 4. 6, 7 or 8 (page 239), but will serve for the basis of further design. After getting this preliminary section the forces due to vacuums, ice expansion, character of bottom, etc., can be considered and extra area of section added. As shown by Fig. 235 the dam is safest against the water 254 HYDROELECTRIC PLANTS. pressure with the slope up stream. Especially is the factor of safety against sliding increased, but there is the overpour to be considered. In order to conduct the water away from the dam in safety, an apron is required, and if, in addition to the apron, the dam is sloped up stream the result is a dam too expensive to build. For this reason practically all masonry dams are built with the face about perpendicular, the slight up-stream slope given to some being merely a temporizing between cost and safety. Therefore to design a masonry dam, first design the apron, giving the necessary slope to prevent vacuum (Fig. 237), and then lay off the section c f d 6, as found for Fig. 236, having the resultant of the water pressure and gravity of the dam strike FIG. 237. in the middle third of the base. Now add the section / r t d of area sufficient to make the dam safe against ice expansion, seepage, shearing and the weakness of green masonry. The flotation will have been allowed for in determining W, and undermining will have been provided for in building a liberal apron. Such a masonry dam should be safe, providing foun- dations are good, and the materials are well laid. After the sec- tion has been decided upon it is well to investigate the critical points to see if the safe crushing strength has not been ex- ceeded. In General Gillmore's reports we find the following table of the crushing strength in tons per square foot (2240 pounds) for various stones: H YDRA ULIC CONSTR UCTION. 255 99 specimens of granite. 43 " limestone. 12 " " marble. 62 " " sandstone. Highest 1541 tons. 1600 " 1284 " 1136 " Lowest 497 tons. " 221 " 488 " " 251 " The lowest values are from the poorest quarries in the United states, so it would seem that by taking one-tenth of the minimum values one would have reached the extreme of safety. However, in the design of the Quaker Bridge dam (Croton dam) for the New York City water supply, the engineers limited the safe crushing strength to 13.5 tons or 30,000 pounds per square foot. Crushing stresses are determined as follows: In Fig. 238, let L equal the base of the dam, d the distance FIG. 238. between a point where a perpendicular passing through the center of gravity cuts the base and the up-stream edge of the dam. Then L d is the distance from B to D. Let p be the maximum unit stress then and P = P' W (L-d) Ld Ld wherein W is the effective weight of the dam. The resultant MI is found as in Fig. 238. By measure- ment on the drawing the distance d is found, and substi- tuting in the above, p for the segment d may be deter- mined, this gives the maximum compressive stress in the base at that point in pounds per square foot, when the pond is empty. To find the stress near B due to the water pressure measure d' and substitute in the above formula. The answer will be the pressure near B in pounds per square foot. 256 HYDROELECTRIC PLANTS. In designing a very high dam the first operation is similar to the preceding: the top section assuming H = 100 feet (Fig. 239) is taken first. Find the point of application of the water pressure P, as in Fig. 236. Find the center of gravity g and g' of each of the triangles ABC and A E D as already explained. Find the center of gravity of these two triangles as follows: / W \ distance g G = g g' ( w+w ,) wherein W and W are the weights or areas of the triangles whose centers of gravity are respectively g and g'. A' e distance (4 ' \ I j-y- I where A g and A ' g are the areas of Ag + A g/ FIG. 239. the triangles, of which they are the center of gravity. The triangle ABC is added on to give a strong crest. The base E D is arbitrarily taken as two-thirds the height //. The resultant / M is next obtained, and from p = W (L - d] Ld the maximum pressures are found. Second, if the pressures of the first section are within the limits of safety another section of 50 feet is added (Fig. 240), the tip-stream face being given a batter of 15 feet in the 50, and the apron a batter of 40 feet in the 50. (These proportions conform to the standard sections for such dams, (see Fig. 241.) The center of gravity of the entire figure A B C D H F E is now found. The center of gravity of E D H F being found as HYDRAULIC CONSTRUCTION. 257 in Fig. 236, and then that of the two centers of gravity G and g", found from wherein w and w" are the weight or areas of the sections whose centers of gravity are G and g" respectively. G f is the center of gravity of the entire section. Find P for the dam now 150 feet high and its point of appli- cation in the same way as for the 100-foot section. As the face of the dam has now been given a batter of 15 feet FIG. 240. up stream, there will be a certain component of force, due to the water holding the dam down. This will be 50 (100 + 10 +-^-) X 62. 5X15 = 126,562. 5 pounds. Thiswillact perpendicular to the base F H and at a point half way between E and F. This large component is not generally considered in the design of the dam, and while its neglect is on the side of safety, in finding the pressure on the toe H, it adds to the pres- sure on the base at F, and the author believes that if there is any reliability at all in the designing of a dam, every factor should be allowed for. Therefore, to allow for this force con- 258 HYDROELECTRIC PLANTS sider the 126,562.5 pounds as being so much area or weight of masonry concentrated at O, after having divided it by the weight of a cubic foot of the dam materials to reduce it to the same standard with the former calculations. Thus, if the masonry weighs 140 pounds the equivalent at O = 904.02 square feet. Now connect O and G' and find the center of gravity of these two areas, and from the point so found, drop a perpendicular to the base F H and on this new component lay off to scale the FIG. 241. amount of the combined forces due to G' and and draw the resultant S M f . The effect has been to throw the resultant more toward the center of the base, which is as it should be. The pressure of the dam when the pond is empty may be too great at F and possibly exceed the stress allowed, therefore the slope E F may have to be increased. From p = j^ the pressure at F can be calculated for either d or d" and at H for either d f or d'" . If the pressures are satisfactory lay down another 50-foot HYDRAULIC CONSTRUCTION. 259 section and proceed as before. Each of the succeeding sections batter 50 feet down stream, up stream the third section batters 20 feet, the fourth 30 feet, the fifth 50 feet, etc. Of course these batters are arbitrary and are only to serve as a preliminary guide. EXAMPLE. As example, assume a dam 250 feet high, with 10 feet of water going over its crest ; also assume the masonry weighs 130 pounds per cubic foot, allowing 10 pounds for flota- tion, and that the safe bearing strength is 20,000 for d and 15,000 for d'. Now assume the section to be the same as the standard dam (shown in Fig. 241 by the dotted outline). Then the crest is 20 feet wide and formed of a triangle 20 feet wide at base and 30 feet high superimposed on the triangle 100 feet high and with a base two-thirds the height or 66| feet. The calculations for this first section follow: First section. The center of gravity for each triangle is found and the center of gravity G of the two areas determined as explained above. Then calculate the water pressure against (TT \ -j + h), which for this section is, P = 62.5 X 100 ( + lo = 375,000. The point at which P is applied is the distance Y above the base thus, -R A , Jt_\ " 3 V JT+21J which here is 100 3 The force P is projected horizontally as shown by the arrow heads. A perpendicular line is dropped from the center of gravity G, and projected till it intersects P. From this inter- section measure, to any convenient scale, the force P, horizon- tally, and the weight of the section, W, downward, as shown, complete the rectangle and draw the resultant. Now measure the distance from the intersection of this resultant with the base of the dam to the right hand edge of dam, this is d' and 260 HYDROELECTRIC PLANTS. in this case equals 14.5'. Also measure the distance from the perpendicular from the center of gravity to the up-stream edge of the dam, d = 21.5 feet. Areas about G = 300 + 3333.5 = 3633.5. W = (300 + 3333.5) 130 = 472,355 pounds. W(L-d) Maximum pressure p max = ~ 7 L/ d and for d, 472355 (67- 21.5) max g^vxoi g O/ X ^1 O for d', 472355 (67- 14.5)' pmax = - A7 1 A - - o/ X 14 . o = 14,989 pounds per square foot. 25,525 pounds per square foot. This gives a pressure on the up-stream side of dam below the assumed allowable stress of 20,000, but the pressure on the down- stream side is much too high, therefore the section is altered giving the base a width of 80 feet. Then the area about G is 240 + 4,000 = 4240. W = 4240X130 = 551,200 pound*. 551,200 (80- 26) Pmax at d --= - 8QX26 = 14,310 pounds per square ft. 551,200 (80- 30) pmax ^ d' = - 80X30 - = n ' 525 P unds P ers( l uareft - We now have the pmax at d r somewhat lower than the lim- iting value but this is necessary to keep the slope further down from becoming too flat. In all these calculations it is assumed that the extreme edge of the down-stream toe would not crumble if the dam should turn on it as a pivot. This would not be true as it would break back to some point, A and therefore d' should only be figured to that point. This would greatly increase the p m jx* How- ever, the authorities do not generally allow for it. Neither has the vertical component of the water pressure which would greatly increase the p max at the up-stream edge of the dam been allowed for here. HYDRAULIC CONSTRUCTION. 261 Second section. Now add 50 feet more of dam as shown and, 62.5X150 + 10 = 796,875 pounds. Areas about G' = 240 + 4000 + 5625 = 9865 square feet. W = 9860X130 = 1,282,450 pounds. Completing the parallelograms of forces, for d, 1,282,450 (145-53) Anax = ~ 145 v^r" = pounds per square foot. ford', 1,282,450 (145-59) - -- 145 x59 - 13120 pounds per square foot. These values being sufficiently safe, another 50 feet of dam is added. 200 Third section. P = 62.5X=^ (200 + 10) = 1,375,000 pounds. 200 /, 10 Areas about G" = 240 + 4000 + 5625 + 9250 = 19,115 square feet. W = 19,115X130 - 2,484,950 pounds. Completing the parallelogram, ford, 2,484,950 (225-87) max = - 225X87 = 1751 P unds P er square foot. and for d', 2,484,950 (225-99) />max= - 225x99"" = pounds per square foot. Each of these pressure seems to be approaching our assumed limits so another 50 foot section is added. 262 HYDROELECTRIC PLANTS. Fourth section. P = 62.5X250 (250/2 + 10) = 2,109,375. 250 / 10 ) Areas about G" f =240 + 4000 + 5625 + 9250+13,750 32865 square feet. W = 32865X130 = 4,272,450 Completing the parallelogram of forces, ford, 4,272,450(324-138.5) 324X138.5 and for d', 4,272,450 (324 - 143) 17.661 pounds per square foot. = 13, 187 pounds per square foot. max 324X143 The values assumed above for the compressive strength of the masonry are very low, but will serve to illustrate the method. If the drawing is made to a scale of J-inch to the foot, and carefully done, the degree of accuracy will be well within all requirements. The crest would, of course, have to be given a different shape as explained on page 254 for an overflow dam. The outline of a standard dam section is shown in Fig. 241. This is for a dam which allows for no overflow and which as- sumes a cubic foot of masonry at 140 pounds. The assumption of weight is very important and the writer thinks, that owing to the difference in opinion on the subject, this is much too high. Again the crushing strength on the up-stream side is limited by the strength of the mortar, and not the stone. Also, in 'finding the value for p max on the up-stream side, the maximum weight of the masonry must be used because it is when the reservoir is empty, and there is no flotation, that this stress will reach a maximum. This involves the construction of a second parallelogram for each section, having W figured with the weight of masonry at 170 to 180 pounds per cubic foot. Again, suppose the back water stands at the level of the top of last section, then the weight of this section must be figured as having lost 62.5 pounds per cubic foot of masonry at all times. Being buried in the earth does not alter the calcula- tions, all of which are figured from solid rock bottom. HYDRAULIC CONSTRUCTION. 263 The height of such a dam is only limited by the compressive strength of the masonry (the tensile strength is not considered) and the cost. The Croton, or Quaker Bridge dam is 300 feet high at the highest point. Examining the four sections of the preceding examples for this factor of safety we find: 44 X 551 200 First section factor of safety = 36> Ix375>oou = 1-78. c t t t + 82X1,282,450 Second section factor of safety = -=: __- _. = 2.48. Third section factor of safety - = 3.21. In the above we have taken 44.82 and 124 as the leverage to the probable breaking line of toe. As the factors are increasing, we need not begin the fourth section. The above factors do not allow for the tensional strength, which is the only safe way to figure, and it therefore would seem that the first section is weak. In no other branch of engineering would such a small factor of safety be used. On the first section there is no vertical component of water pres- sure to add to the factor of safety, the safety of this is out of all proportion to the other sections. In the second section if the vertical component of the water pressure is to be allowed for, proceed as follows: Vertical pressure P = 135X62.5X15 = 126,562.5 pounds. This acts at a point midway between B and C and, in effect, acts the same as so much masonry, whose center of gravity is at that point; there- fore connect this point by a horizontal line with the perpen- dicular G f T, and get the center of gravity of 126,562.5 pounds at R, and 1,282,450 pounds at S, as follows: By measurement, RS = 46 feet. R U - 46 1 ' 282 ' 450 1,282,450 + 126,562 and .911X46 - 41.9 feet. 264 HYDROELECTRIC PLANTS. W now = 1,282,450+126,562 = 1,409,012 pounds and acts through U. Lay off from U the vertical U F to same scale as W and construct the parallelogram of forces, P remaining the same. The resultant now strikes the base at Z and the factor of sa is now, ' I ' ' ^ = 2.87 instead of 2.48 as before. oox /yo,o o The p max for d is also increased for the second section. 7Q 5\ = 1,409,012 145X49 ' 5 = !8,750 pounds per square foot instead of 15,350 as before. The /? max is, of course, decreased on d' but this is of no importance. There are several methods of solving the above problem, FIG. 242. but the center of gravity method is the one most readily under- stood by the average engineer. Such dams are now frequently made of concrete, and when properly made are superior to masonry. Large quantities of concrete hastily built are dangerous in any structure, but es- pecially so for dams. Severe stresses are set up by the shrink- age of the mass on setting. The outside contracts first and later the interior, causing intense strains* which result in cracks or cause the dam to give way under small added pressures. Therefore, the concrete should be deposited in blocks as in Fig. 242. The blocks A, C and B are built in place by suitable forms and after they have set for two or three weeks, the blocks E, D and F are laid. A, B and C are lower by a foot or so than the others, so as to afford the proper friction between the layers. The blocks may be attached to each other by means of steel anchors as shown in the block D. HYDRAULIC CONSTRUCTION. 265 Steel bars placed as shown by dots on Fig. 242 will make the factor of safety what it should be; this reinforcing will be especially' advisable in the case of high dams where the factor against overturning is small near the crest. Edward Wigman, a noted authority on masonry dam con- struction, states the following in his admirable book: " As the theory of masonry dams has to be based upon hypotheses which are only approximately correct, we may permit," etc. He also gives the following for the safety of a masonry dam against sliding: / W = horizontal thrust, P, of the water. W = weight of dam, and / = coefficient of friction of masonry on masonry usually figured as .67 to .75. EARTH DAMS. The earth dam is, without doubt, the oldest form of dam, yet in this country it has been looked upon with a good deal of suspicion. Hundreds of the largest cities in the country are to-day depending on earth dams to hold the water which is to save their millions from thirst and fire. For all this when the engineer is asked to consider the building of an earth dam for a water power, there is at once a vigorous protest. There are several very good reasons why an earth dam may be superior to the solid concrete or masonry dam, given that it be properly constructed. No sudden crack can destroy the whole structure. Any trouble which may develop will or- dinarily give warning in time to permit of repairs. The Johns- town flood is pointed to as an example of the insecurity of such dams. However the cause of this disaster was due to insuffi- cient spillways and no one claims that an earth dam is built for spillway purposes. A large majority of the failures of earth dams have been due to this cause. The second in order of the causes of failure is the placing of pipes through the embankment. Build the dam so that the spillway is ample and in the proper place, place no pipes through the fill and use the proper materials and the earth dam is, without question, the best and cheapest dam that can be built. Mr. Burr Bassell in his book, " The Earth Dam," treats the subject at length. There have been built eleven dams over 100 feet high, ten 266 HYDROELECTRIC PLANTS. over 90 feet high, and six over 80 feet high. In Europe the earth dam has received considerable study and many dams are standing which are exceedingly old. That an earth dam should be suited to a site there must be present three conditions. First, the conditions must be such that the maximum flood which has ever occurred at the place can be taken care of without washing out the uncompleted structure. Second, the conditions must be such that the maximum floods which are to be expected" can be diverted around one end of the dam, over the rim of the containing cliffs or through some new channel so that at no time in the future can the waters top the embankment. Third, the materials must be suited to the work. Mr. Burr Bassell advises that where a tunnel of sufficient size to carry all the flood water can not be cut around the dam through solid rock, or where the channel can not be entirely FIG. 243. changed to bring about the same degree of safety during con- struction, that the earth dam should not be built! This is certainly worthy advice from the strongest advocate of an earth dam, but it should be possible to use the idea shown in sketch, Fig. 243. The author was called upon to pass on the leasibility of an earth dam near Baltimore where it was impossible to take care of the water in any other way than in the one shown in the sketch. The arches of the concrete bridge could be made of great span so as to take care of the greatest floods during construction. When the earth fills were completed a dry period would be selected and the water made to run through a com- paratively small pipe until all the space under the arches was filled with concrete. Then the small pipe could be closed also or left with a gate for future use. The best form of spillway is where the dam is of such height HYDRAULIC CONSTRUCTION. 267 that by slight excavation the water may be made to spill over the rim of the basin above the dam. The capacity of this spillway may be determined by computing the maximum flow as explained in Chapter III. Where the flood flow is small the tunnel may be resorted to. There are certain materials which are of no use for building earth dams. It is the author's opinion that all these dangerous materials contain what is commonly called quicksand. The test for such earths is to mix the material up fairly wet in a box and pack it with a tamp. If it quakes on being tamped it belongs to the dangerous class. Good earth should pack solidly into place. Another test is to find at what angle the earth will stand when piled up in water. This angle should not be less than 20 degrees. The best soils for the purpose contain some clay. fli'-t FIG. 244. Puddle is a term given to that part of the fill which is made of selected materials mixed together to form a core to prevent seepage. Many engineers contend that the best earth dam is one of homogeneous section. Mr. Bassell placed the core of the Tabaud dam on the up-stream edge (see Fig. 244), and this is undoubtedly the proper place for it if it is used at all. Mr. Herbert M. Wilson advises the following mixture for puddle: Coarse gravel 1.0 cubic yard Fine gravel 35 Sand... 15 " - " Clay 20 ' 1.70 " which, when rolled in embankment, gives 1J yards. All clay shrinks on drying, and if allowed to dry out while being compacted the result will be a leaky and dangerous dam. 268 HYDROELECTRIC PLANTS. Pure clay shrinks about five per cent, on drying. Dry clay as usually excavated will absorb one-sixth its weight of water and when perfectly dry about one-third. Some clayey mix- tures while hard to excavate will run like oil when wet. The cost of well-made puddle varies between wide limits, but should not cost more than from 20 to 40 cents per cubic yard. The safest way to test materials for imperviousness is to fill the ends of glass tubes all to the same depth with the materials and fill the tubes with water. The tube which holds the water the longest is the most impervious. Mr. Bassell advises building the dam up in layers which have a slope toward the center as shown in Fig. 245. This is to prevent the water used in compacting from going to waste over the sides of the embankment and to insure the con- tinued dampness of the layers exposed to the air. The thinner the layers the more thoroughly can they be compacted. Six inch layers were used near the bottom of the Tabaud dam and nine inch at the top. FIG. 245. The process then s as follows: The earth is brought to the dam in wagons or by aerial cable and deposited in regular heaps over the proper area. Road graders drawn by six horses then spread out the piles and a sprinkling cart drawn by four horses wets it down. A five to eight ton roller passes to and fro over the wet earth and finally before the next layer is de- posited, a harrow roughens up the surface. Every surface is kept wet at all times. While all the most impervious materials should be deposited on the up-stream side, no great expense should be incurred in doing so as it will be better to spend that extra amount in making the dam wider at the base. Where the fill is made by hydraulicing it is impossible to sort out the materials, but in that case it is not necessary. Common practice seems to make the top width about 25 feet, the up-stream slope 1:3, and the down-stream slope 1:2. HYDRAULIC CONSTRUCTION. 269 There can be no hard and fast rule, however, as the slopes depend on the angle of repose of the materials, and the width at the top is merely the factor of safety for the particular con- dition. Fig. 246 shows a section of the Jerome Park Reservoir for the City of New York. Here the masonry core rests on quick- sand. It would seem that in the light of the recent development of steel sheet piling, that piling driven to bed rock would be a much better arrangement. The greatest chance for seepage is along the original surface which the dam rests on, and every precaution must be taken to break the continuity. Plowing and harrowing should be thoroughly done and all soft mud pockets cleaned out. If the bottom is earth, a row of steel sheet piling should be driven. FIG. 246. The force required to take care of and compact 2000 cubic yards per day of materials delivered on the dam will be about as follows: Three rollers, one ten-ton and two five-ton, drawn by six horses. Two graders, drawn by six horses. Three water tanks, drawn by four horses. Two harrows, drawn by two horses. Three carts, drawn by one horse. One plow, drawn by two horses. The total cost of this equipment would be, exclusive of horses, about $2500 and the cost per cubic yard of the com- pacted materials, exclusive of the equipment, about four cents per cubic yard. The question of drainage is one of great importance. There is sure to be more or less spring water at the site and this must all be provided with some means of exit without letting it wash out the earth composing the dam. If the bottom is of rock, trenches as in Fig. 247 should be excavated. 270 HYDROELECTRIC PLANTS. In the bottom of the trenches tile covered with concrete are placed. The trench thus made serves a double purpose as it not only takes care of the spring water but also acts as a pre- ventative to seepage along the natural surface. Where the bottom is earth the spring water must be conducted away with great care. FIG. 248. Each spring must be thoroughly boxed over with reinforced concrete and a drain built as in Fig. 248 to conduct the water away. This drain should not run at right angles to the axis of the dam, as it would then tend to produce a leak through the dam, but it should have a small angle with the axis, making ' FIG. 249. Earth dam. as long a drain as possible before it reaches the down stream edgewof the dam. In Figs. 249 and 250 are shown sections of the Belle Fourche dam now under contract in South Dakota, the contract price for this dam containing 1,600,000 cubic yards of gumbo was at the rate of 61 cents per cubic yard (government contract), but this included spillways. The author's experience with HYDRAULIC CONSTRUCTION. 271 umbo has been very disastrous and it would be considered a dangerous material for earth dams unless the slopes were at least 3:1 and the top 50 feet wide. Figs. 251 to 252 illustrate the weir which is to be built intc the top of the earth dam. This is always a dangerous thing to do. 272 HYDROELECTRIC PLANTS. Longitudinal Section 1 J _ Center Line* Half Plan Plan . Section A-B. FIGS. 251-252. // YDRA ULIC CONSTR UCTION. 273 Fig. 250 shows how the concrete pipe is laid through the dam which is also bad engineering. Hydraulic Fills. To placer mining in the West we owe the cheapest and best method for making a fill where the local conditions are favorable. Where a giant is used, water must be delivered to it at a head of 100 to 150 feet. In exceptional cases this water is found within reasonable distance to the materials and at a sufficient elevation to produce the necessary head. However, in the great majority of cases the water must be pumped from the river to be dammed. To pump the water a centrifugal pump may be used. In such cases the power required for pumping is a serious FIG. 253. The cross sections of several of the world's most famous earth dams. item and wherever possible the water used should be collected at the level of the giant and used over and over again. Thus a pump of comparatively small size would pump the water from the river up to the giant and a large pump at the giant would pump the pressure necessary for it. Fig. 254 shows the method of using the giant. The grade of seven to ten per cent, from the cliff to the sluice is maintained, at all times. The sluice may be a metal lined box or may be simply a ditch dug in the earth. If a metal lined box it must have a slope of from six to ten per cent., and if a ditch, 25 per cent. The sluices lead the earth and water down to the dam where the 274 HYDROELECTRIC PLANTS, semi-liquid is collected in a lake on top of the fill. At some suitable location a timber spillway is provided so that the surface water is drawn off without any of the earth going with it. The amount of water used depends largely on the head at the giant and the materials, but roughly it may be taken at from 900 to 1500 cubic feet of water per cubic yard of materials in the dam. If, as was the case with the La Mesa dam in California, there is no embankment upon which to work a giant, then a large area of soil is plowed and scraped into the sluices. At the La Mesa dam 11 acres were excavated to a depth of two feet. In this way 700 cubic yards per day were delivered to the dam with a use of 50,000 cubic feet of water. FIG. 254. Giant washing earth into sluice. About the largest daily average fill was made on a long railway fill where for 60 days the average was 1100 cubicjyards per day. In this case the head at the giant was 160 feet and the water used was 960 cubic feet per minute, the sluices were 4x2 feet. The costs per yard on several large fills averaged six to eight cents including all costs of plant, etc. The cost of the plant in the above instance was SI 0,000. COSTS. Figs. 255-263 show graphically the cost per foot of width and amount of materials required per foot of width, for dif- ferent types of dam. Figs. 255 and 256 refer to the type of dam shown in Fig. 213 and give respectively the quantity of material and cost for different heights of dam. Figs. 257 and 258 refer to the type of dam shown in Fig. 214 and give re- spectively the cost and the quantity of material. Figs. 259 HYDRAULIC CONSTRUCTION. 275 (M -%o ^ &T so *x> std v^cmcfe FIG. 255. so tOoMar^i FIG. 256. FIG. 257. 276 HYDROELECTRIC PLANTS. ^ ^ ^" if I 1 [)0- > *^^*" i no r L J^ i ^j iff bj i " X tf< ^ ^ ^ X ] ^ \ \\ ^/ x 40! ^ \\ \ s ' / / <* ^ j\ ^1 \ \ 5 / ,< xi \\ s \ \\ s\ f / x^ f^ ^ ^N N\ s V \\ \ \ V V 8 16 2* 32 VO 8 56 64 72 60 68 Thousand of feet FIG. 258. M 'Li cL po too foo Poun&s , 300 I i O& 3 300 FIG. 259. 750 ISO C W0 1 D ' , ^ ^^ ffc-C gr ^ ^^- ' ^ x^r *? r ' | ^ ^^ - " a j / 3 ^p ^~~ & ^ <* XI J F i? g'/ 3 ^ / / IOOO 2000 3000 4000 /.yJs. , FIG. 260. 6O00 rtC7(? OOOO SOOO 600 roo BOO 900 HYDRAULIC CONSTRUCTION. 277 /ooo 900C 600- I FIG. 261. O /OO //e/gftf of Darn fn FIG. 262. 54 oo 90 jus /yo of Dam //? FIG. 263. 278 HYDROELECTRIC PLANTS. and 260 show the cost of building and the amount of steel re- quired for reinforced concrete dams of the gravity type, built respectively for low and high heads. Figs. 261, 262, and 263 show cost data for low solid concrete, high solid concrete, and high concrete steel dams respectively. These costs do not in- clude foundations. ABUTMENTS. Where the dam is on soft bottom and rests upon a mat, the abutment should in all cases stand on the same mat. The more weight on the mat the better. FIG 264. The earth fill behind the abutments must be put in with great care. The earth should be selected and tamped in six-inch layers well wet down. Fig. 264 gives the amount of material in solid concrete abutment shown in Fig. 265. The reinforced concrete abutment, Fig. 266, is much cheaper and better. The plan view of the solid abutment shows the wing is given a turn up stream. The object of this is to form a pocket so that any leakage is stopped by the earth falling into the corner. If a liberal wing is not provided and of this shape there will always be a leak along the abutment. The reinforced abutment has so many wings that the pocket is not necessary. Fig. 267 gives the amount of material used in the abutment shown in Fig. 266. H YDRA ULIC CONSTR UCTION. 279 280 HYDROELECTRIC PLANTS. ">"^^ FIG. 2GG. Cubic terete of Concrete FIG. 267. HYDRAULIC CONSTRUCTION. 281 FLASHBOARDS. The height of a dam is only limited by the value of the over- flowed lands, and as it is usually only during high water that the lands are damaged, the height of the dam in summer is lower than is actually necessary. It is to increase the height of the dam during low water (just when head is most needed) that the dashboard is used. There has never been a flashboard designed that suited all requirements and yet its value is so great that most dams are equipped with some one of the various varieties. One of the simplest forms, see Fig. 268, has proved the most satisfactory. It consists of wooden or iron posts set into the crest of the dam and supporting vertical planks against the water pressure. The posts are so designed that when the - rr _ f/ ITr FIG. 268. water exceeds a certain amount they break off and plank and posts go down stream. The planks are fastened to the posts by means of staples through which pass the posts, otherwise, when the water was drawn down below the crest of the dam the plank would fall off. In calculating the dimensions of posts, First find the pressure against the post. P =62.5 H (Ii/2 + h) (Fig. 263), in the case where the water flows over the boards at a depth h\ and P = i 7/X62.5XH when it comes to some depth H, at or below the top of board. Having P, the moment of pressure against the post is found by, PXl = inch pounds = M. I is found where water flows over the boards by / = (l-f- 77 r-p ) and for o \ H + 2 h I water at top of boards / = H/3. / must be given In inches. Having determined the permissible height of water over*the 282 HYDROELECTRIC PLANTS. boards, find the moment of pressure for that height and then for the water at the top of the board. The resisting moment of the post M is then found for both cases, as follows: Let s = the safe strength per square inch of the post. Then if post is of round section M = . 098 + s + d* See properties of sections page. For example: A flashboard three feet high and posts of round white pine and three feet between centers with a depth of not more than 12 inches of water over the boards; find the diameter of the post. First, when water is 12 inches deep over boards, P = 62.5X3 r+l = 469 pounds per foot length or 469X3 = 1407 pounds pressure against one post. This pressure P acts at a 3 / 1 \ height of-- I 1+ .TT-O) = 1.2 fee tor 14. 4 inches from the bottom. o \ tj-r Z/ Therefore the moment of pressure against the post is M = 14.4 X 1407 = 20,261 inch pounds. Second, when the water is at top of boards: p = | x 62.5X3 = 281 pounds per foot ft or 28iX 3 = 843 pounds on post. / = | = 1 foot = 12 inches. o The moment of pressure is M' =843X12 - 10,116 inch pounds. The moment of posts' resistance in the first case is M= .098 xs x d 3 If we take s = 3200 as the breaking strength of white pine and substitute, we have .098X3200 d 3 = 20,261 and d 5 = > d == 4 - in - With water at top of board 3200 d 3 x .098 = 10,116; d= 3.2 in. HYDRAULIC CONSTRUCTION. 283 inches. Therefore, the post should be slightly more than 3 inches in diameter. From this it is seen that the posts will be safe with water at top of the boards, but will break when the water is a few inches above, as Table 53 gives the breaking strength of white pine as 4000 pounds square inch. For square posts After a few seasons of actual test the exact size of the posts will have been determined. The loss of the boards in most cases is of small moment as the dam is only a few hundred feet long, and in many cases the plank can be caught below. However, the posts do not always break at the right time, often breaking too soon and causing a waste of water. They may also concentrate the current where a few posts have broken prematurely, thus causing uneven wear on the dam crest. In the plans for the Yorktown dam Fig. 300 is shown a form of flashboard designed by the author. It is especially adapted to short dams, though it can be applied to any length. By turning the shaft all the posts are lowered or raised at the same time. In lowering, however, as the top of the posts get below the center of the first plank, that plank tips over and goes down stream. As the tops come to the centers of the next plank they also pass over and so on with as many planks as the boards are high. After the flood has subsided it is an easy matter for a man to walk out on the crest and place new boards. Such flashboards are seldom over three feet high though they have been built four feet. Quite a severe vacuum forms under the water sheet and unless air inlets are provided the posts will fail much sooner than the above calculations would indicate. A form of flashboard patented by J. H. Shedd and O. P. Sarle is shown in Figs. 269 to 270. These were used at Norwich, Conn., on a dam 432 feet long and have apparently given sat- isfaction Referring to Fig. 270 the board m is pivoted on a toothed cam roller e. The object of e is to vary the center of resistance to suit the varying center of water pressure due to an increasing 284 HYDROELECTRIC PLANTS. now of water over the boards. With the water at the top the center of water pressure is slightly below the teeth then in contact. As the flood comes on, the center of pressure FIG. 270. rises and gradually tilts the gate until when the water has reached a certain stage it lies in a horizontal position resting on the Z bar g, which runs full length of the dam. As the HYDRAULIC CONSTRUCTION. 285 flood recedes the boards automatically resume their normal position. Fig. 270 is a view of the entire flashboard mounted on the dam, and Fig. 269 a detail of one section of flashboard. While possessing some very valuable features this form has certain defects. There are a great many obstructions for drift wood to strike against and lodge upon. It gives the water a perpendicular fall upon the dam, causing heavy vibrations. There is a serious liability to damage from ice floes and heavy logs. All the sections do not assume the same relative position at all stages of flood water. There is some leakage between the sections, etc. FIG. 272. Fig. 272 shows a mechanism invented by S. C. Irwan and A. M. Bournan which, though more especially meant for a mov- able dam, is well adapted for flashboards. The part u is in the form of the sector of a circle, is hollow and extends either the full length of the dam or in long sections. The sector u floats upon the water admitted into the chamber x when it is wished to elevate the crest, any water contained within u being pumped or drained out through the pipe a. To lower the crest, water is let out of x and pumped or admitted into u causing u to settle down. This form of flashboard may be made of any 286 HYDROELECTRIC PLANTS. height, the limitations being the permissible widening of the crest of dam and the factor of safety of the dam under the increased head. The top slope of the sector affords a good spill- way for the water and there are no projections for the lodgment of trash or to cause vibrations. The joints can all be made practically water-tight and the entire mechanism may be raised or lowered at any time from the shore by merely operating the air and water valves. FIG. 273. The water pressure against this form of flashboard is hori- zontal, and in applying it to dams must be allowed for in the design of the structure. Fig. 273 shows a form of flashboard which possesses the con- trolling features of Fig. 270 and the principal of Fig. 272. Fig. 273 shows it adapted to the timber dam, and this particular board raised the water three feet. The board C is all in one length and bolted together with one-inch bolts. It is pivoted on the bronze trunions H. Every four feet along the crest is a bearing which bears on the pivot H. The pivot is supported HYDRAULIC CONSTRUCTION. 287 by the timber A. The deck planks M have a small crack left between them so that the water pressure has free access to the chamber R. About 20 feet apart are the valves L which are operated by means of a steel cable from the shore. With the valves shut the gate is as shown, but when these are open the water pressure on the left hand side of the board causes it to assume the position shown dotted. During ice flows or very high water the board is let down leaving a clear crest for the passage. When up this flashboard will leak no water, and when down leaves nothing for objects to strike against or lodge upon. Fig. 222 shows the same type of flashboard used on a masonry dam. Spaced at intervals across the length of dam are beams A pivoted on a shaft or trunion B. Riveted to the top of these FIG. 274. Drum Dam. beams is the wood or steel decking. A steel plate C bent to the proper circle is attached to angle-iron imbedded in the masonry. D is a floor covering the chamber E, its only purpose being to exclude stones, sticks, etc., which might interfere with the operation of the leaf A. It is provided with sufficient openings to supply the chamber with water. The operation then is as follows: The water pressure has free access to the entire surface of the movable deck and, with the water even with the crest G, the center of this pressure P is one -third the depth from the edge F to the surface and strikes the deck at P. As the water rises, P also rises till with the water six feet above the level H, it arrives at P r . P' travels rapidly along toward G, after it passes B, permitting of very accurate adjustment. By. making 288 HYDROELECTRIC PLANTS. F B may be more nearly horizontal if for mechanical reasons it is so desired. If it is desired to control the movement from the shore the web H, the Tee -iron 7 and valve N are added, the web and Tee -iron making a more or less perfect shut-ofT of the water, so that by pumping water into the space L under the deck, the pressure P is reduced to zero and the crest will fall. If necessary, by pumps, the pressure in L may be made to exceed P. FIG. 275. If thought necessary, a steel apron M (shown dotted) may be hinged to the crest to form a spillway. This mechanism is suited to almost any range of variation in water levels, and may serve equally well as a movable dam. It may also be applied to the gravity dam as the component of the water pressure may be made to act as nearly vertical as desired. In the design shown the range of movement was HYDRAULIC CONSTRUCTION. 289 3J feet and necessitated a width of crest of 19 feet. By making the beam A straight the crest could be narrowed somewhat. The vacuum which forms underneath at will help in actuating the leaf since for a thin sheet of water over the crest it will be slight and for a heavy overpour quite severe. By controlling this vaccuum with suitable inlet pipes it may be increased when it is desired to lower the crest, thus sucking it downward. A float may be used to open the vacuum inlet automatically at a certain stage of the water, and if necessary, start the pumps. Fig. 275 illustrates what is perhaps the most unique and heavy of all movable dams or flashboards. It was built in the city of Schweinfurt, on the river Main, Germany. At this place the law forbade any structure being placed in the river bed above a certain height and it was to gain the permit, that this mechanism was designed. An e-xperimental dam was put in operation having a cylinder 13J feet in diameter and 59 feet long and it gave perfect satisfaction. The one shown is 6J feet in diameter and 114 feet long. The steel shell is 1.1 inch thick and weighs 193,600 pounds. This clyinder is lifted to a height of 13 feet by means of an 18 horse-power electric motor and may also be operated by 12 men in which case it takes three hours to lift. The concentric cylinder C is filled with water when the cylinder is down to give added weight, but as it turns in raising this water spills out. The lifting is all done at one end but at each end there is a cog wheel and rack. HEAD GATES. What the safety valve is to the steam engine, the head gate is to the water power. Every water power should possess such a safety device, for there comes a time in the history of every water power when it is desired to empty the head race, flumes, etc., of water and it is at such times that a reliable head gate is wanted. As the office of the head gate is to protect, it should be placed at the very entrance of the head race. The form shown in Fig. 276 is one of the most common and we think the best. The fill a is made wide enough to form a roadway and heavy enough to resist the overturning force of the water. When the bottom is soft, this form of head gate 290 HYDROELECTRIC PLANTS. is placed upon a mat the same as a gravity dam. In nearly every case, one row of sheet piling should be driven along the up-stream edge of the mat used under head gates. The length % should generally be about equal to the depth of the water. The ends of the head gates should be well protected against the water cutting around and the down-stream wings (Fig. 276) should be extended well down stream to prevent the wash of the water after it has passed through the gates. A velocity of 200 to 300 feet per minute may be allowed to the gates as the up and down stream length is so small that the loss of head will be inappreciable. Where the banks are a sandy loam, or other easily washed material, every joint must be water tight. A good plan is to sheet all wooden bulkheads I//// FIG. 276. Head gates. exposed to hydraulic pressure with " all heart " yellow pine flooring. In the last described head gate, all parts above water and for a foot or so below should be of concrete or masonry as the wood at the water line decays rapidly. The piers can also be of masonry or concrete in which case greater permanence is secured. On large work the head gate frequently reaches heavy pro- portions. Fig. 277 gives a design for a gate 20x50 feet. In this design the gate proper weighs about 66,500 pounds, and to balance this, a counter balance A is used. The counter balance consists of a box girder 50 feet long and having a space 24 inches by 42 inches by 50 feet inside, which is filled with concrete, thus giving the necessary 66,500 pounds. The chain at each end of gate passes over a wheel B, the links fitting into the rim similar HYDRAULIC CONSTRUCTION. 291 FIG. 277. 292 HYDROELECTRIC PLANTS. to a chain hoist. To operate the gate the hand wheel C is turned until the eccentrics lift the gate away from the bearing on the pier. This throws the pressure on the eight wheels and makes FIG. 278. the lifting of the gate by means of the worm gear D, an easy matter. The horizontal down stream thrust on the gate is about FIG. 279. Common head gates. 630,000 pounds. Therefore the piers E must weigh 4/3 of 630,000 or 840,000 pounds to be in equilibrium against sliding and twice that for a factor of safety of two. In the design given HYDRAULIC CONSTRUCTION. 293 this factor is attained. In almost all cases instead of having some means of throwing the pressure on the wheels, a small gate would be provided to let in the water slowly and thus takeoff the pressure, but sometimes this is not desired as when it is necessary to control the water and limit the amount supplied to the canal. On the Chicago drainage canal and the great power at St. Mary's river, gates similar to the one shown are FIG. 280. used for this purpose. The cost of this gate would be about $8000 all complete. Fig. 278 shows a common type of head gate suited to heads up to 20 feet. Fig. 279 shows the most common head gate and one which is plenty good enough for all ordinary circum- stances. The stem a should be made of an 8x8-inch or a 6x8- inch timber. The planks e should be seasoned and edged. The braces c are nailed on and the stem is bolted with f-inch 294 HYDROELECTRIC PLANTS. carriage bolts. The guides for the gates should be as at E and not as at D on account of the liability of weeds and sticks getting caught and causing the gate to bind. This gate may have two stems where the area is great or the head high. The hoists shown in Figs. 280 to 282 are suited to this gate; Fig. 282 being used for all the gates of a series except the one used to raise whrle the full pressure is on. FIG. 281. For gates under high heads (40 to 100 feet), the type shown in Fig. 283 is used. For larger gates and heads of 30 to 50 feet the hoist shown in Fig. 280 may be employed. The elements of the design of gates is given below. The force necessary to lift is found as follows: According to usual practice the friction between oak and iron is about 62 HYDRAULIC CONSTRUCTION. 295 per cent. That is, it will take 62 per cent, of the water pressure against the gate to keep the gate moving. Assuming for example a bronze gate 2 feet by 2J feet working on bronze guides under a head of 30 feet, the horizontal pressure will be 62.5x29x6.25 = 11,325 pounds; 25 per cent, of this (for FIG. 282. bronze on bronze) = 2831 pounds, which is the force required to move the gate. General Morin states that it requires about one-eighth more force to start the gate, therefore to be safe, 3200 pounds will be taken as the starting force. Now suppose FIG. 283. the gate weighs 500 pounds Friction of screw = (500 + 7021) Xcoefficient .25. . . 1880 Equivalent weight of gate due to friction 11.325X .25 3200 Friction of nut = (500 + 7021) Xcoefficient .15 1128 Total equivalent weight, W = 6708 296 HYDROELECTRIC PLANTS. Now for the hoist shown in Fig. 283 when the hand wheel is 24 inches in diameter and the pitch of the screw on the stem is 1 inch, W = F X * R where W = 6708; F = force re- quired to start gate; R = radius of hand wheel =12 inches; P = 1. Substituting, F = 890 pounds. This is too large for a hand wheel and such a gate would be lifted with two such screws or a set of gears would be used to reduce the required pressure, as in Fig. 280. SLUICE GATES. In Fig, 284 a very common form of umbrella waste gate is FIG. 284, shown. This gate is often made a part of the dam. The size shown is that usually selected, there being as many gates dis- tributed along as thought necessary to pass the water. As here shown, the down stream thrust of the water is horizontal and heavy masonry walls arc necessary to resist it. The plan shown HYDRAULIC CONSTRUCTION. 297 in the Noblesville plant (Fig. 352) throws most of the pressure in a vertical direction. Experiments made by the author on old head gates show that F is about 85 per cent, of the hori- zontal pressure against the gate. Fig. 285 shows a hydraulically operated gate. This gate is about the best of all the types where some form of power is available at the power house at all times. Usually when it is required FIG. 285. to operate the gates it is for the purpose of a shut-down, and therefore the power ceases. When there is a storage battery plant or where current can be brought to the power house from some other plant, a motor can be used to drive a force pump. Pressures of 500 to 1000 pounds per square inch should be used. The piston rod will not require packing or piston rings as some waste of water during the lift will do no harm. The valve a lets the water in on one side and out on the other, and by pulling on the cord b, the water will be admitted to either side of the piston. 298 HYDROELECTRIC PLANTS. HEAD RACKS. As the uninterrupted working of the plant depends largely on keeping driftwood and other objectionable trash out of the turbines, it becomes of the first importance to properly con- struct the racks. In a large majority of cases, their area is made much too small, due allowance not being made for the area occupied by the rack bars. The net area of the rack should be such that not more than 40 to 60 cubic feet of water per minute will pass per square foot of area. The cheapest form of rack bars are those made as shown in Fig. 286. The bars a should be from one to three inches apart depending on the size of turbine they are to protect and should be built in sections of say, from six to eight bars held together by J-inch bate FIG. 286. bolts b. The sections are not fastened to the rack frame and so may be easily removed for repairs. If the length of the bars is not over ten feet the brace B is unnecessary. Iron is much the best material for the bars, and, though the first cost is somewhat more than for wood, it will be found the cheapest in the long run. The bars may be of iron from Jx2 inches to |x4 inches. For heads of from 6 to 14 feet the use of f x3-inch iron strengthened every six feet of its length by a J-inch bolt, is advised, a piece of f-inch gas pipe should be strung on between each pair of bars for spacers. There should be two racks, one a coarse rack above the other. The coarse rack should have 3-inch spaces between the bars and the fine rack 1 inch to 1J inch. For small turbines under 15 inches a brass wire screen affords excellent protection. The HYDRAULIC CONSTRUCTION. 299 meshes should be f , f , or f inch square. Instead of the second coarse rack a deflecting boom, a, may be used (Figs. 286 and 287). Several buoyant timbers are strung together across the head race as shown, the bars being given a slant towards the dam and projecting down into the water several feet. Such a boom will catch a large proportion of the trash and most of it will glance off and pass over the dam. FIG. 287. TABLE XXXVIII. WEIGHT OF ONE SQUARE FOOT OF RACK. Size of Bar and Weight of One Bar per Foot. Distance Between Bars. I" 1" iF H" 1J" 2" 2*" 3" 4" i"x3" 2.55 Ibs. 30.6 24.5 20.5 17.5 15.3 13.6 I" x3" 3.83 Ibs. 41. 33.4 28.3 24.5 21.7 19.5 16. \" x 4" 6.8 Ibs. 40.8 36.25 30. 27.25 23.4 18 Rack bars cost about three cents per pound. Anchor ice is the worst foe to the head rack and has been known to render a valuable water power practically useless during the winter months. The cause of anchor ice is a much disputed question, but it is the belief of the writer that it is formed by the coagulation, as it were, of the water as it passes from a pool of comparatively quiet water over a shoal or rapid. When water freezes on the pond, a certain amount of the air is imprisoned in the ice making its specific gravity less than that of water but when the water has been quiet and the tempera- ture below freezing, the water assumes a temperature below freezing and yet does not congeal until it is agitated on the rapids where it instantly freezes and contracts into solid pasty ice slightly heavier than water, so that it drifts along at all 300 HYDROELECTRIC PLANTS. depths and finally lodges against the racks much to the disgust of the power user. However, if proper precautions are taken, shut-downs will never be found necessary on that account. At Norfolk, on Raquette River, the Remington Paper Co. overcame the diffi- culty, which at first seemed serious, by building a house over the rack and keeping it warm. Men were also kept at work with rack hooks cleaning out the anchor ice. In Fig. 288 a sketch of a patent rack is shown which gives complete protection against every head rack- ill. FIG. 288. The rack is made in 6-foot sections. The wire netting a is such as is used for reinforcing concrete and is caused to run over the steel rack bars b by means of the friction drum C. The netting may be made to run as slowly as desired and only runs when it is found necessary to clear the rack. A rack similar to this was used at the Mill Creek power, only it was caused to revolve by means of a current-wheel placed behind the rack and in the penstock. CHAPTER VI. POWER HOUSE CONSTRUCTION. Together with head gates, racks, penstocks, etc., the accesso- ries to the power house have been treated, some of them being at times a part of it. The power house proper, however, is the subject of this chapter. FOUNDATIONS. There is no one thing more important in all building ' opera- tions than the foundations. After the soundings have been properly made, it should be an easy matter to design the founda- tions, and yet how few heavy buildings are there which do not FIG. 289. settle and show cracks. Most of the skyscrapers of Chicago are steadily sinking, as are also those of New Orleans. This is to be expected on such foundation material as those cities have, but the architect shows his skill by so designing the foundations that a 20-story building always remains plumb no matter how much it may settle. Building a power house on the bank of a river introduces a little problem in foundations. Fig. 289 shows a power plant the flume of which rests on the solid hardpan eight feet below tail water. The power house containing the generators extends back on to the bank and rests on gravel. Also see Fig. 47. 301 302 HYDROELECTRIC PLANTS. Now, if special provision is not made to give the base of the power house foundations sufficient area, there will be a crack at a as shown. The flume will not settle but the generator house will. Abutments resting on mats, and heavy wing walls running FIG. 290. back into the shore are also subject to cracks unless carefully designed. Safe pressures for foundations are given on page 124. All soils will settle some, therefore the pressures must be met with sufficient bearing surface in the foundations. FIGS. 291, 292. For heavy concrete power houses four feet of firm soil under the base is sufficient, especially w T hen placed on a mat as in Fig. 290. Wet sand will sustain almost any load if it is held in place by sheet piling. The mat M should make a close fit with the piling but not be fastened to it. In this case the POWER HOUSE CONSTRUCTION. 303 strata* of clay need only be about a foot thick as the pressures are evenly distributed over it by the sand above. To pre- vent the piling from spreading, strap iron anchors, 5, are bolted to the wales and to the mat as shown. This permits settling of the mat. Where heavy loads are to be borne on columns the arrange- ment shown in Fig. 291 may be employed. The concrete must be of rich mixture. For engine foundations where it is desired to avoid all vibra- tions the pier is placed on a bed of clean dry sand. As long as no sand is allowed to escape the pier will not settle, and to make this sure a copper sheet a should be embedded as shown, Fig. 292. The heavier the foundations the less the vibration. About 300 pounds of foundation per one horse-power is good practice for engines up to 25 horse-power, 200 pounds 25 to 100 horse- power, and 175 pounds for those of 100 to 5*00 horse-power. Of course this only applies to foundations on soft shaky soils. The safe bearing pressures per square foot of the soil must not be exceeded (see Table XXXI), and this often makes a foundation of much larger base necessary. STRUCTURE. There should be only one type of power house and that type the best, but unfortunately the majority of the power plants must be built as cheaply as possible. The flume is that part which contains the turbine. The cheapest arrangement is that in which the flume is a part of the dam. Figs. 293 and 294 show two views of such a flume, built into a gravity dam. In building this flume it must be remembered that a part of the gravity virtue of the dam is taken away and a horizontal down stream push added, therefore caution must be used in bracing the down stream bulkhead. The plan shown is for a 30-inch turbine taking 5000 cubic feet of water per minute. If the water is drawn one foot below the crest of the dam the velocity in the flume would be 90 feet per minute, which is good practice. With 12 feet of water in the flume the horizontal pressure at x = 35,500 pounds. A rod 1J inches in diameter will hold this and as one such rod is a small item of cost, its use is advised. Frequently 304 HYDROELECTRIC PLANTS. the down stream sill A splits along the line of mortises when a rod is not used. This arrangement could be used for two turbines in line with the dam, though it would be better to place FIG. 293. Timber wheel pits at end of dam. FIG. 294. Timber wheel pits at end of dam. them up and down stream. By building a masonry pier be- tween the flume and the dam, any number of wheels could be -set, as the masonry would resist the horizontal pressure. POWER HOUSE CONSTRUCTION. 305 Two posts are shown under the wheel setting at B. These are to support the wheel and are slanted off to each side of tail race. All planks are edged and seasoned. The head gate stems have holes two inches in diameter bored to permit the gates being lifted with a bar. A light frame house should be erected over the gears. This same flume could, of course, be used for horizontal wheels. One plan is to have the shaft project through the down stream FIG. 295. Timber wheel pits for soft bottoms. bulkhead and have a rope drive to the machine back on the bank. Fig. 295 shows two views of a timber flume built entirely separate from the dam and on a sand bottom, and Fig. 296 shows a section of the same flume. The wheel pit is first dug and the mat O laid. A concrete wall TV is built as shown serving to resist the pressure of the sand under the upper mat and also as a deflection for the water discharged from the draft tubes. The timber frame serving to support 306 HYDROELECTRIC PLANTS. the turbines rests partly on this wall. The down stream sill, however, does not, and as it would have to sustain about 37,000 pounds of water, and a center load of about 5000 pounds, there must be placed at H, H, steel columns. Four-inch gas pipes with large cast iron bearing plates will serve this purpose. As shown, there are settings for two turbines, but the same plan may be adapted to any number. Heavy rods are used to take up the larger part of the horizontal pressure. These rods are anchored to the up stream edge of the fore-bay mat by means of bolts put in before the sheet piling is driven. In this plan the fore-bay is widened to give liberal rack area. Sheet piling should be driven along both the up stream edge and the ends as shown. The plan view shows how the earth fill FIG. 296. is only carried around to X. The wings C D E F would be more lasting if made of concrete, which if reinforced and braced, need only be 12 inches thick. Where earth comes in contact with wet timber decay is very rapid. Frequently sound timber will, under such conditions, rot out in six years. The fore-bay mat must be made water-tight and the piling bolted and ce- mented to it. Two thicknesses of plank should be laid on the mat under the wheel pit. The greatest difficulty is experienced in building a power house so that water will not follow around its sides, but the plan here shown should be safe from such accidents. All earth fills must be thoroughly tamped while wet. Where there is no danger from back water, this plan may be used for horizontal wheels. POWER HOUSE CONSTRUCTION. 307 A compromise between the all timber and all concrete power house, is shown in plan and side elevation in Figs. 297 and 298. This is a very good plan for a power house of moderate cost. The cost could be further reduced by substituting timber for the concrete end walls shown at x. The only defect that de- veloped in this plant was the splitting of the sill as shown. The use of a IJ-inch rod running through all three flumes would have remedied this weakness. Each flume contains one quarter turn 35-inch Morgan & Smith horizontal turbine. This complete power house with a timber dam 22 feet high and 300 feet long cost $15,000. Fig. 299 shows a late design of a concrete steel power house, The design of this power house embodies a novel and very im- portant improvement. The waste gates, of which there are three for each, are used to draw down the head in time of flood. As shown here, the gates not only serve to pass large quantities of water, but they also act to increase the power of the turbines in times of high back water. This action is quite similar to that of a steam injector. Fig. 300 shows a concrete steel power house of the most permanent kind. On account of being cramped for room the exciters and switch board are here placed on a plat- form above the generators. In reality the governors and generators are in the basement. It is seldom that the at- tendant has to tend the generators, the most of his time being spent with the switchboard and exciters, therefore this arrange- ment is permissible under the circumstances. The battle- mented cornice shown on the building is made of building blocks but below this the building is built on the Thatcher plan. A feature of this plant is the method of emptying the reservoir. That part of the flume floor above the head gates is a continua- tion of the dam. At Y instead of the usual foot boards, boards are stood on end as shown, each board having a ring in the top by means of which it may be pulled out. The large window shown at end of generator room is to admit the generators, there being no other way in this case. The stairs are all steel and concrete. The floor and walls of the generator room are made water-tight up to the down stream windows to keep out the back water. Fig. 301 shows the section of a power house which is designed 308 HYDROELECTRIC PLANTS. POWER HOUSE CONSTRUCTION. 309 ,.. F 310 HYDROELECTRIC PLANTS. POWER HOUSE CONSTRUCTION. 311 312 HYDROELECTRIC PLANTS. POWER HOUSE CONSTRUCTION. 313 to waste the water above the dam through the wheel pits. Immediately above each draft tube a concrete wall c is built serving as a deflector and to protect the draft tube from the FIG. 302. force of the water coming through the waste gates. Above the waste gates this wall is thinned to two feet, serving to support FIG. 303. Excessive reinforcing. the flume floor. At the up stream end the wall is only 12 inches thick. Fig. 302 shows a view of the pier at A B. 314 HYDROELECTRIC PLANTS. The rack D is of heavy steel and serves to keep the trash out of the waste gates. At E is shown a steel rack which need not be used if the rack F has sufficient width. Fig. 303 shows one of eight flumes, each containing two pairs of turbines. The head was only 20 feet though the heavy re- inforcing would give the idea of a very high pressure. This power house was built to cost as much as possible, and does not show good engineering. The arrangement of the deflectors is, however, very good. They serve also as piers under the flume floor. The part showing through the draft hole is curved to deflect the water while the up stream end is pointed so as to not choke the discharge from the turbines above. The " Soo " plant is shown in Fig. 304. This is the largest low head power plant in the world. Each flume is built as shown in Fig. 305. Two sides are of I-beams filled in between with concrete and the end is of -J-inch steel plates. This form of flume is patented, and the advantage claimed is that it takes up a minimum of space. It is a question in the author's mind how the expansion of the heavy steel beams will affect the adhesion of the concrete. Concrete reinforced with wire netting should be more efficient and less costly. -J-inch steel is apt to rust out too quickly and sweats badly, causing a damp generator room. The space at A being of no value, would it not be a better plan to run the sides straight out and make the end square and of reinforced concrete ? Or leave it round and make it of concrete reinforced with cables ? Fig. 306 shows in detail the setting of high pressure turbines. This plan is the latest in turbine installation for heads of 75 feet or more, and is the product of the Stillwell, Bierce & Smith Vail Company. All necessary relief valves and piping are here shown. The main valves are operated by water pressure. When the head exceeds about 20 to 30 feet it is necessary to conduct the water to the wheels through penstocks. Figs. 307 and 308 show the power house of the Hannawa Falls Water Power Company. The head is about 85 feet. The plan view shows an arrangement of penstocks made necessary by local topographical conditions and one not to be recommended. The head racks have an area of 200 square feet and since each 10 foot penstock carries 30,000 cubic feet per minute, the velocity through the racks, not allowing for the POWER HOUSE CONSTRUCTION. 315 316 HYDROELECTRIC PLANTS. space taken up by the bars, would be 150 feet per minute, while it should be only 90. Another defect is the shallowness of the water under the draft tube, it being but five feet. The area of the tail race is about 500 square feet and the water discharged when all turbines are in use is 100,000 cubic feet per minute, giving a velocity of 200 feet per minute. As the percentage of head lost by this high velocity is small it may m -^~-^~-~ "_r-_^_n4^^r- - -CONCRETE- =~t_ ^ - FIG. 305. Details of the " Soo " plant. be considered a good design. The penstocks are of 5/16-inch and f-inch mild steel, containing less than .06 per cent, of phos- phorous. The turbines are special, having gun metal bronze runners of the Samson type. The gates are of cast steel, the case and draft- tubes .of rolled steel and the remainder of cast iron. The upper part of the building is for manufacturing purposes. Fig. 309 shows a well designed plant built for the largest paper mill in the world at Millinocket, Me. The part of the plant here shown is for the generation of 3000 kw. in three units. Three pairs of 36-inch turbines of 1500 h.p. each, drive three POWER HOUSE CONSTRUCTION. 317 318 HYDROELECTRIC PLANTS. CBOSS-SECTION OF TUB POWBB HOUSE. FIG. 307. Power-house. O FIG. 308. Power-house. POWER HOUSE CONSTRUCTION. 319 1000 kw. generators. Allowing for 80 per cent, efficiency in the turbines, 26,000 cubic feet of water are required per minute and for the exciters 1440, making 27,440 cubic feet per minute in all. This gives a velocity of five feet per second in the 11-foot penstock. It will be noted that 1125 kw. turbines are used to drive 1000 kw. generators. This is evidently much too small as 10 per FIG. 309. Power-house. cent, of the turbine power is required 'for regulation and all generators should take a 50 per cent, overload for one half hour without overheating, therefore the full peak load capacity of these generators can never be used and fully 20. per cent, of the money invested in them is bringing no return. Each pair of turbines should be of 1400 kw. capacity, because most turbines are most efficient on J gate, the turbines depreciate in efficiency 320 HYDROELECTRIC PLANTS. ffiODODQQQQ OQQQi FIG. 310. Power-house. POWER HOUSE CONSTRUCTION. 321 much more rapidly than do the generators with the result that in five or ten years the turbine power will become too weak for the maintenance of the proper voltage in the generators. An interesting feature of this plant is the manner of bringing in the penstock under the turbine. Fig. 310 shows common type of power house for medium heads. In this case the head is about 40 feet. The steel penstocks are FIG. 311. Foreign design for hydroelectric power-house. brought into the power house through a masonry wall. A second wall separates the turbine cases from the generator room, thus insuring a dry generator room. The power house was on a soft bottom and rests on a heavy timber mat, no piling being driven to sustain it. This plant is at Red Bridge, Mass. To give the reader some idea of foreign practice a typical plant is shown in Figs. 311 and 312. In Europe vertical direct 322 HYDROELECTRIC PLANTS. POWER HOUSE CONSTRUCTION. 323 324 HYDROELECTRIC PLANTS. POWER HOUSE CONSTRUCTION. 325 326 HYDROELECTRIC PLANTS. connected generators are quite common. This plant works under an 85-foot head and develops over 2000 h.p. Three of the generators are 500 h.p. driven by turbines of 650 h.p. In this case partial allowance has been made for regulation and the peak load of the generator so that the full efficiency of the generators can be obtained. Under test the turbines gave 81 per cent, efficiency, at f load and 79 per rent, at full load. Therefore, when developing 487 h.p. the turbines are the most efficient. When the highest efficiency is desired, even in this case, the turbine capacity is too small, as at f load it should drive the generator under a 50 per cent, overload and the Transverse . Sec-tier FIG. 316. Power-house for high heads. governors. However, the above is better than the average American practice. Governors made by Escher, Wyse & Co. (Allis-Chalmers Co. are the American manufacturers) are used, these being a standard make in Europe, and are becoming better known in America. Figs. 313 and 314 illustrate the power plant now being built for the utilization of the waters of the Chicago drainage canal. It would be difficult, indeed, to criticize the design of this plant, except that more reinforcing might have been used in the con- crete, but on the whole this plant marks a distinct advance in such construction. Figs. 315 to 317 give a good idea of a pelton water wheel plant built for the Pike's Peak Power Company. The effective head is 1160 feet. Each of the four peltons driving the gen- POWER HOUSE CONSTRUCTION. 327 f I t t^ .-i co I 328 HYDROELECTRIC PLANTS. FIG. 318. Power-house at Niagara Falls. POWER HOUSE CONSTRUCTION. 329 erators is of 610 h.p., though by using one of the two wheels comprising each unit and by using different sized nozzles, almost any power can be obtained at full efficiency. Each pelton unit drives a 500 h.p. generator at 450 r.p.m. This plant was tested and the efficiency from water to switchboard was 78 per cent. All piping was tested to 800 pounds pressure per square inch. Fig. 318 shows a 5000 h.p. unit in the most noted hydro- electric plant in the world, namely, the Niagara plant. The turbines were designed by Escher, Wyse & Company of Zurich, FIG. 319. Example of power-house architecture. Switzerland, and built by I. P. Morris Co., of Philadelphia. The governors were the design of the same Swiss company, and were built by A. Falkinan of Philadelphia. These governors permit a speed variation of five per cent, from full to no load, and for ordinary load variation is as good as modern steam engine practice. The generators are of the two-phase type. Much of the power is used by electric furnaces using single phase current. This unbalances the generator load and taxes the regulation to the utmost. The regulation of voltage is within ten per cent. ; the efficiency of the generators is 98 per cent.; the working head on the turbines is 161 feet. 330 HYDROELECTRIC PLANTS. ARCHITECTURE. It costs but very little more to give to the exterior of a power house or head works a fine appearance, and in after years the appearance may be an important factor in the price for which the property will sell. FIG. 320. Architecture suitable for head-gates, arches, etc. Figs. 319 and 320 show some types of construction which have been used on numerous well-know structures, and may aid the engineer in the design of hydroelectric power plants. CHAPTER VII. POWER HOUSE EQUIPMENT. WATERWHEELS. TURBINES. Like all other matters pertaining to hydraulics, the turbine has made slight progress in the last 50 years. In 1840 the Swain turbine gave 80 per cent, efficiency on test and the LeiTel 74 -per cent. The following is a list of some of the most prom- inent turbines. The efficiency given is the catalogue value, and even an efficiency of 80 per cent, is seldom guaranteed. The only improvement has been in size, and speed and efficiency at part gate. TABLE XXXIX. COMPARISON OF VARIOUS MAKES OF WHEELS. Wheels. Diam- eter. Head. Revolu- tions. H.P. Water cu. ft. per mm. Effi- ciency. Hercules : . . . . 30 inches 20 feet 174 119.59 3,960 80% Samson McCormick 30 " 30 20 " 20 " 242 186 162.00 142 70 5,312 4 721 80% 80% Victor 30 " 20 " 210 165.35 5,471 80% Rice's Victor Hunt 30 " 30 20 " 20 " 222 187 183.72 111 52 6,079 3 556 80% 80% 30 20 " 107 100 78 3 273 827n Most of the turbine makers give the results of tests performed at testing flumes, proving high efficiency, but it is the author's opinion that little dependence should be placed on these. There is no question but that the tests are correctly performed but the wheel makers do not give to the public all the data connected with the test. This is known to have been the case in several 331 332 HYDROELECTRIC PLANTS. \ instances. The only safe way is to have a written guarantee from the makers. | Turbines may be divided into three general classes which will serve the purposes of this book: Register gate, wicket, and cylinder gate. All turbines are now made in both the horizontal and vertical forms. They all have a runner of the same general type. Fig. 321 shows a Victor runner and it typifies many others. This is the part of the turbine which revolves. The buckets are usually of steel cast into the cast iron frame. FIG. 321. Among the wicket gate turbines the Leffel and American are the most prominent. The former has a greater speed than any other, and in construction is one of the strongest. In the latest Leffel and Victor wheels the gates are operated by a ring and lever (Figs. 360 and 324) instead of the numer- ous rods shown in Figs. 322-323. This is an important improve- ment where a sensitive governor is used as the number and weight of the moving parts are greatly reduced. This wheel POWER HOUSE EQUIPMENT. 333 can be used for heads up to 40 feet. They have a good part load efficiency. Turbines built by the S. Morgan Smith Company are for the most part of the cylinder gate type. A form of wicket gate as made by the above-mentioned company, is shown in Fig. 324. It's mode of operation is immediately apparent from the illus- tration. Fig. 325 shows a double turbine built by the S. FIG. 322. Morgan Smith Company. This turbine, as will be seen from the controlling devices, is of the cylinder gate type. It was built to operate under a head of 85 feet. The greater proportion of turbines are of the cylinder type. Fig. 326 shows a sectional view of a Victor turbine made by the Platt Iron Works Company of Dayton, Ohio. This is their latest wheel and the invention of A. C. Rice ; A and A ' are the runners, and F and F' the cylinder gates operated in the direction of shaft by the rods a and a' . The gears operating these gate rods are run in oil and project through the bulkhead 334 HYDROELECTRIC PLANTS. into the power house. All cylinder gate turbines have a gate similar to the Victor gate. The cylinder gate is more nearly water tight than the registering gates, but taken with the counter weight used to balance them they are heavier than the register. The Platt Iron Works Company makes a high pressure tur- bine which can be used with heads of from 70 to TOO feet. They thus fill in the gap between the ordinary turbine and the FIG. 323. Pelton. In operating turbines under high heads it is imperative that all grit be removed from the water before it is passed through the wheels, otherwise the wheels soon wear out. On such wheels all running parts should be made of bronze. The action of water under high pressure is such that holes are often bored through solid cast iron by the impact of the fluid. Under heads above 50 feet, an efficiency of 75 per cent, is very good, and for the average gate opening this is too high, for heads above 200 feet 80 per cent, is a fair efficiency. POWER HOUSE EQUIPMENT. 335 Wheels tested at Holyoke, Mass., are tested under the most favorable conditions. The wheel is new and smoothed up un- usually well. The setting is perfect, and all parts are new and water-tight. After a year or so of use all turbines become more or less leaky, out of alignment and the buckets become dented and rough. It is no uncommon thing for the J-inch steel buckets to get knocked partly, out of the casting. There are numerous forms of turbine settings, a few of which FIG. 324. are given in Figs. 327 to 341. Cf course any slant may be given the various pipes and draft tubes. There has been such a fad for horizontal turbines that they were often installed where the vertical type would be prefer- able. The horizontal turbine allows the placing of two or more turbines on one shaft, thus getting increased speed with the same power or increased power with the same speed. How- ever, their use usually necessitates a generator of slower speed than would the vertical type, and hence of more cost and makes regulation within wide limits of head an impossibility. When 336 HYDROELECTRIC PLANTS. the frequency is not of prime importance, the ordinary ex- citation of a generator can take care of a 10 per cent, reduction in speed, but beyond this the voltage will fall, therefore, where * "*' X severe reduction in head is to be apprehended, the vertical turbine with its noisy gearing may be the best practice as with POWER HOUSE EQUIPMENT. 337 a proper ratio of gearing and a sufficient number of turbines the speed of the line shaft can be kept up. The determining factors as to the selection of the horizontal turbine should be: One, the speed variation under all probable stages of head and back water; two, additional cost of ma- chinery, due allowance being made for the increased efficiency FIG. 326. of the horizontal wheel. (The same wheel mounted in a hori- zontal position would have an efficiency about three per cent, less than in the vertical position, but since about 10 per cent, or more is lost in the gearing, etc., the turbine will be about seven per cent, more efficient in the horizontal position than in the vertical;) three, cost of turbine setting. 338 HYDROELECTRIC PLANTS. FIGS. 327-331. FIGS. 332-333. FIGS. 334-336. FIGS. 337 339. FIGS. 340-341. Typical Turbine Settings POWER HOUSE EQUIPMENT. 339 There must be at all times, from six feet to ten feet of water at A y Fig. 335, to prevent air bubbles and whirlpools. Horizon- tal wheels have been used on heads as low as 15 feet. The great Soo plant has 16 feet head and the turbines (Hunt) gave 84 per cent, efficiency on test It sometimes happens that a water power is to be developed at a head considerably below that to which it will be increased later on, and it is desired to install generators and turbines which will answer for both heads. The following setting was designed by Mr. M. E. Powers (Fig. 342). The gears were so FIG. 342. proportioned that at the reduced head the generator had the proper speed. The turbines were selected so that under the increased head, the generator shown in sketch could be moved directly over it and direct connected to it. A second generator was then installed and. set over the other turbine. The gears were therefore all there was to be discarded. Wherever possible it is best to place two, four or six turbines on a shaft so as to balance the end thrust (see Figs. 329, 332, 335 and 339). An open setting, Figs. 327, 335, 336 and 337, should be ob- tained when possible, the efficiency being greater and the governing better. 340 HYDROELECTRIC PLANTS. Fig. 341 shows about the only alternative where the varia- tion between high and low water exceeds the maximum prac- ticable length of draft tube, and where it is desired to maintain the speed and power with direct connected units. The back water wheel No. 1, runs idle during normal water, but is used when the back water reaches the draft tube. Next to lack of water during the months of minimum flow, the reduction of head by back water is the most serious osbtacle the hydraulic engineer has to contend with. One good feature, however, is that we have plenty of water, so that by installing enough turbines and properly gearing them, we may keep up the speed of the line shaft and also the power. Ordinarily building the dam does not affect the stage of back water. Its cause lies below the dam, and is due to the choking effect of the river banks, islands, bends, etc. Usually the high FIG. 343. water mark can be distinguished by the driftwood along the banks. It is seldom indeed that there are not somewhere sure indications of the high water mark. Farmers along the river can corroborate the evidence, so that there should be no trouble in determining the back water stage. The depth of water over the dam is, as a rule, more difficult to pre-determine. If there is a dam anywhere above , the problem is an easy one. As a rule, if you build a dam in a river having parallel shores, as in Fig. 343, the water will pile up below the dam twice as much as it does above. If the dam is narrower than the average width of the stream, the difference will of course be less. Take an example where we have 20 feet of head at normal stages. Suppose we frequently have the head -diminished five feet due to back water, and in extreme cases our head is reduced to ten feet. Then for a series of turbines all having the same pwer with same head, we have the following: POWER HOUSE EQUIPMENT. 341 EXAMPLE: We wish to drive a 350 h.p. generator at 290 r.p.m. and we do not want the speed to fall below 260 as the field rheostats of the generator will not take care of a greater variation. The normal flow of the stream will just supply the one wheel. Referring to tables for the Samson turbine we find that a 50-inch Samson will give 451 h.p., at 145 r.p.m. under a 20-foot head. First. Under normal conditions the first pair of gears (Fig. 344) will be in the ratio of 2 to 1 and turbine No. 2 will be thrown out of gear. Second. The head becomes reduced to 15 feet and the speed of the generator falls to 252 r.p.m. Now if but one turbine were in gear the ratio of the gears would be 1 to 2.3 to keep the speed at 290, as under 15-foot head a 50-inch Samson has 126 r.p.m.; FIG. 344. but the power would be too low, being only 293 h.p. We there- fore gear turbine No. 2 in the ratio of 1 to 2.6. The speed of the line shaft will then be a mean between the two sets of gears. ^1? = 2.3 and 2.3 X 126 = 298.8. With the two turbines we have under 15-foot head 586 h.p. We have therefore kept up the speed and power. Third. Head reduced to 10 feet; three 50-inch Samsons under 10-foot head will give 480 h.p. at 103 r.p.m. With turbines No. 1 and 2 geared as above the speed will be 237 r.p.m. Now if we add a third turbine we do not double the power as before, but have to allow for the action of a one- third power acting on the two-third power. We have the following formulas for any number of turbines: 342 HYDROELECTRIC PLANTS. where X = the ratio to be found; R = the number of revolu- tions desired on the line shaft. TV = the number of turbines including the turbine the ratio of whose gears it is desired to find; R' = the revolutions of the turbines under the reduced head (found from turbine tables) at which the n'th turbine is thrown into gear. .4 = the ratio of the gears of turbine No. 1. B = ratio of gears of turbine No. 2. C would = ratio of No. 3, etc. Thus in the above example, X = - - (2 + 2.6) ; X 3.846. If we add another turbine for a head of only eight feet we find that all the turbines will have a velocity of 92 r.p.m. 9QO v4 and X = ^--(2 + 2.6 + 3.73) =4.27 as the ratio of the fourth set of gears. The power is 456 h.p. Care must be taken in keeping the proper proportions for the gears; that is, the speed of the teeth, pressure, etc. It is this ability to regulate the speed and keep up the power that often makes it desirable to install vertical rather than horizontal turbines. Of course, the head works must be given sufficient area to take care of the great quantity of water used under the reduced head. During periods of flood, a velocity of 100 feet may be used through the racks and 200 feet through the tail race as efficiency is not so important at high water as are speed and power. Since every turbine has a certain velocity at which it is most efficient the above arrangement will not be of high efficiency, but at the time the extra turbines are thrown into gear there is plenty of water. The lower geared turbines are made to race while the higher gears cause the turbines to work at a low speed. Under extreme conditions of back water the low geared wheels may develop no power at all in which case they would be cut out.. By the use of the draft tube any turbine may be placed above tail water. This distance B, Figs. 327 and 336, is theo- retically 34 feet, but in practice there are reasons why the length should be about as given in the table by Mr. John Wolf Thurso. POWER HOUSE EQUIPMENT. 343 Diameter of draft tube in feet. = 0.5 1 23 4567 8 9 10 11 12 13 14 Draft head in feet. =32.5 30 27.5 25 22.5 20 18 16 14.5 13 12 11 10.5 10 9.5 By draft head is meant the vertical distance between the center of shaft and the tail water for horizontal wheels and between the center of the guide buckets for vertical turbines, as B in Fig. 327. This table gives draft heads slightly too small for turbines under steady loads and working at full gate and too great a head for rapidly fluctuating loads and partial gate. Draft tubes should always be conical. The proper diameter for any particular draft tube may be figured, using the above table as follows: A conical draft tube must not be more than / V 2 \ 12 feet in diameter, at a height of (10-5 ^ ;) feet above tail water, where V = .285 \/64.4 H. Short and small tubes must dip into the tail water 6 in- ches to 12 inches and 20 inches to 24 inches for long and large tubes. A greater dip permits a greater draft head within limits. Where heads fluctuate badly and a sensitive governor is used, the wheels should set close to tail water to avoid oscillations. Even where the turbine sets below tail water a draft tube increases the efficiency. Frequently with large draft tubes when running at part gate the draft tube does not fill with water at all, and the turbine runs under a severe loss of head. Draft tubes are gen- erally made much too thin, 3/1.6 inch is a common thickness, while good practice would be nothing thinner than J-inch. The velocity of the water amounting to about twice the peripheral speed may be calculated from V = .285 \/64.4 H, where V is velocity in feet per second and H is the total head acting on turbines in feet. All turbine settings should be provided with a gauge, A, Fig. 345, to indicate the pressure at turbine due to the head, and a vacuum gauge B to indicate the vacuum in the draft tube due to the draft head. Throttling gates should never be used to regulate the speed, on account of the great waste of power. 344 HYDROELECTRIC PLANTS. All turbine makers supply books giving dimensions of flumes for different sized wheels and tables of speed, power and quan- tity of water for different sized turbines under various heads. FIG. 345. Whether the turbine chamber is of wood, masonry or steel, the water should be admitted to the wheel and conducted away from it at a velocity of about 80 feet to 90 feet per minute. FIG. 346. Setting for cylinder gate turbine. Of course, if to gain this condition necessitates an expenditure of more than the head gained is worth, a higher velocity is ad- visable. By referring to the tables giving the water used by POWER HOUSE EQUIPMENT. 345 the selected wheels and dividing this quantity of water by 80 or 90, the proper area of the wheel chamber, that is A H (Fig. 346) is obtained. The area C D should also equal A H where practicable, though often the added cost of a deep wheel pit will not warrant a lower velocity than 100 feet per minute. The effective depth of tail water should be take.n as D E. Where the desired depth is not attainable, a diffuser K, or a concrete diffuser should be used. The tail race is not usually continued down stream at the depth D, but is gradually shallowed and widened so that the FIG. 347. area A' E r = A B, Fig. 347, the race discharging into the river on an angle. As the speed of a turbine grows less with the increase in size ? two or more small turbines may be mounted on the same hori- zontal shaft. There is a further advantage in having several small wheels rather than one large one, in that there is less trouble with the draft tubes. The floor upon which the turbine rests must be perfectly unyielding. It supports not only the water but also the tur- bine. Whenever the depth of water over turbines will permit, set the wheels high enough above tail water so that a man can pass under the floor of the flume, and by removing a man-hole 346 HYDROELECTRIC PLANTS. cover provided for the purpose in the draft tube, adjust the step of the turbine (Fig. 348). Some form of step adjustment FIG. 348. 1T FIG. 350. other than that usually used should be designed. Figs. 349 and 350 are given as suggestions. POWER HOUSE EQUIPMENT. 347 THE PELTON WHEEL. Pelton is the name commonly given to that form of water wheel which receives its water power from the force of one or more jets of water directed against the numerous cup-like vanes situated around its periphery. This wheel is also called the hurdy-gurdy wheel, or tangential wheel. Fig. 351 shows a Pelton mounted in an iron frame. The water after leaving the vanes drops down to tail water utilizing none of the fall from the bucket down. Thus on a low head, especially when there is liability of back water, a serious pro- portion of the head is lost. FIG. 351. Pelton water wheel. As now constructed, the Pelton uses a nozzle so small that the power derived from it is quite insignificant comparatively. To increase the power of the Pelton, the velocity being fixed by the machinery they are to drive, two expedients are resorted to. One. The diameter of the wheel may be increased to as great a diameter as required to give the power. 33 feet is the greatest diameter in use; 12 feet is rather uncommon, and six feet is the largest standard size. Two. The number of nozzles may be increased. The Pelton Water Wheel Company built a quintex Pelton or a five-nozzle 348 HYDROELECTRIC PLANTS. wheel. Again for any large units more than one wheel may be mounted on the same shaft. Of course, all this complicates the plant and there comes a time when the complication makes the high pressure turbine preferable to the Pelton. For heads up to about 150 feet and for powers of over 500 h.p. the turbine has as great an efficiency, is cheaper, and is preferable to the Pelton. For higher heads up to 300 feet and large powers the field is open to both the Pelton and the turbine, but above this head the Pelton begins to rapidly out-distance the turbine in point of cost and efficiency. There are quite a number of plants in operation where a head of from 1200 to 1GOO feet is utilized successfully. Tables giving the sizes and powers of the standard Pelton may be obtained from the manufacturer. In these tables the " ef- fective " head is given, that is, the vertical distance between surface of the head water and the point where the water strikes the vanes, and not the distance down to tail water as for the turbine. As will be seen from Fig. 351 the weights of the revolving parts are quite light and therefore add very little to the regula- tion of speed under a fluctuating load. It is therefore quite necessary to use a heavy fly wheel where good government is essential. In many large plants the weight of the generator- armatures or fields is depended on. Where the generator is of the revolving field type this may be sufficient. For high efficiency the velocity of the water issuing from the nozzle must remain at a maximum. The Pelton Water Wheel Company regulate their wheels in four different ways. (1) By deflecting the nozzle so that the water does not hit the vanes. (2) A cut-off hood is placed in front of the nozzles by means of which the discharge area of the nozzle is varied. (3) A deflecting plate is used to deflect the water. (4) A plug nozzle is used. In this nozzle a tapering pin or needle is placed like the valve of a steam, water injector, the operation of which regulates the quantity of discharge without materially affecting the velocity. The Doble needle regulating nozzle (Fig. 366) is the best on the market. It is made by Abner Doble Co., San Francisco, Cal. Any form of water wheel governor may be used with the Pelton, either to deflect the nozzle or to alter the area of discharge. POWER HOUSE EQUIPMENT. 349 An excellent plan where for certain periods the power is greatly reduced is to have several nozzles, any one of which may be shut off by hand, leaving, say, one nozzle to carry the reduced load This gives the maximum efficiency. REGULATION. Long pipes carrying water for power purposes are subject to great abnormal pressures due to the quick shutting off of the water from the turbines. The water under motion has acquired a certain amount of mo- mentum which is proportional to the product of the weight and velocity. To arrest this momentum requires power or some means must be provided for the escape of the energy. In the early history of the development of water powers under high heads, some of our best engineers met with serious accidents such as the bursting of huge steel pipes and the flooding of power houses; but now that the agents of destruction are known, provision is made for their subjection. To secure the best regulation, what is known as an open setting should be approached as nearly as the conditions will permit. That is, the conditions secured in the design for. the power house at Nobelsville, Ind. (see Figs. 352 and 353), where the water stands directly over the turbines with no appreciable loss of head at any point. The Yorktown plant (Fig. 300) is also an example. Where a long penstock is used, this condition may be approximated by providing a small reservoir at the outlet of the penstock. The size of this reservoir will depend on the sensitiveness of the governor, and should equal the amount of water the penstock will carry in twice the time necessary to close the turbine gates. If the gate is left closed the reservoir will run over unless its level is above the inlet of the penstock and its capacity about equal to that of the entire penstock. Usually a standpipe made of steel, see Fig. 354, of only a few feet diameter is used, in which case the water immedi- ately runs out at the top, when the gates are quickly shut. This relieves the pressure on the pipe line and the water stored in the pipe under the increased head supplies the succeeding demand for power while the water is getting up to speed again. The overflow of the standpipe should be on a level with the surface of high water at the inlet of penstock, unless the fall 350 HYDROELECTRIC PLANTS. L..J POWER HOUSE EQUIPMENT. 351 352 HYDROELECTRIC PLANTS. in the line is so great that the pressure on the penstock (head H, Fig. 354), would be excessive when the standpipe is filled. In this case the standpipe would give place to safety valves along the line of penstock. Standpipes must be protected from freezing. In Fig. 355, c is a standpipe with a tank at the upper end and large enough to take care of the fluctuating water. FIG. 354. Safety valves similar to those on a steam boiler are built. They should be able to discharge, when open, the full flow of the penstock. Fig. 355 indicates the location of the safety valve at a. This should be so placed that the overflowing water will escape into the tail race. Where there is a high place in the FIG. 355. penstock air valves must be placed as at b, to prevent the formation of air plugs, or, where the height is not too great, a better plan is to place standpipes at these points. Galvanized sheet iron will often serve the purpose as at 6'. The ordinary steel standpipe such as is used by city water works and here shown at c, Fig. 355, makes an excellent standpipe. It must be heated in winter to prevent freezing. POWER HOUSE EQUIPMENT. 353 Fig. 356 shows a good design for a concrete-steel stand pipe. Figs. 357 and 358 show two types of cheap governor made by the Woodward Governor Company. These are considered by the author to be the best cheap governors on the market. FIG. 356. Governors. The selection of governors should first be made after a thor- ough study of the situation. Sensitive governing means severe wear and tear on the gates, and should be avoided where pos- 354 HYDROELECTRIC PLANTS. o tuO 1 POWER HOUSE EQUIPMENT. 355 sible. Many lighting plants are successfully operated where it requires 20 seconds to close the gates and while 20 seconds may be the extreme, it has been the author's experience that for all but the most important, or special plants, 5 seconds is quite satisfactory. The approximate energy necessary to operate turbine gates, which are properly balanced and installed, is given in Table XL. Where it is desired to obtain the energy necessary to op- erate gates which are already installed, the test can be made DIMENSIONS, SIZE B. HORIZONTAL MODEL Compensating Type Governor ALL shafts may revolve in either direction desired. NOTE optional positions for Speed Governor Pulley. MAIN SHAFT may be extended on either end of governor to take Main Pulley. BACK SHAFT nay extend on either or both ends to connect to gate. FIG. 358. Horizontal Woodward governor. by turning a hand wheel of known radius through the medium of a spring balance. The test should include a measurement of the pounds necessary to start the gate; to move it when 0.25 open; to move it when 0.5 open, and to move it when 0.75 open. From these measurements the average foot pounds is found by multiplying average pull in pounds by the product of the circumference, in feet, of the hand-wheel and the num- ber of turns necessary to close the gate. A powerful governor is one which will in a given number of 356 HYDROELECTRIC PLANTS. seconds from rest bring up to a high velocity a mass of iron sometimes weighing several thousand pounds. Every moving part connected to the gates must be set in motion regardless of friction. In the case of cylinder gate turbines the cylinder c is counter- FIG. 359. balanced by means of a weight W (Fig. 359). The governor must therefore move the weight and cylinder as well as the gears, shafts, etc. The turbine having wicket gates as in Fig. 324 is balanced by water pressure so does not require a counter-balance. There FIG. 360. are more parts to get out of order than with a cylinder gate, but the regulation may be more perfect and requires a less powerful governor. In Fig. 359 the governor operates the gate stem 5 only, which may be reciprocated or revolved to suit the conditions. Fig. 360 shows a plan view of a wicket gate turbine. Until POWER HOUSE EQUIPMENT. 357 recently the collar C was operated by gear wheels and a rod running to each gate, but in the present form of Leffel and Smith turbines the parts are reduced in number and also the weight. The governor works the draw bar R to cause the rotation of the collar C. All bearings for the various parts of turbine gates should be of bronze and of liberal proportions. TABLE XL. FOOT POUNDS REQUIRED TO OPERATE TURBINE GATES. H.P. of Turbine Head of Water. 10 15 20 25 30 35 40 50 60 80 100 25 400 360 330 310 290 265 250 220 50 700 630 580 540 500 470 440 390 350 310 75 1000 900 830 770 720 660 625 550 500 440 400 100 1200 1080 1000 935 860 800 750 665 600 530 465 150 1600 1450 1320 1240 1150 1060 1000 880 800 700 640 200 2000 1800 1660 1550 1440 1330 1250 1110 1000 880 800 250 2400 2170 2000 1870 1730 1600 1500 1330 1200 1060 930 300 2800 2530 2330 2180 2000 1870 1750 1550 1400 1240 1100 400 3600 3250 3000 2800 2600 2400 2250 2000 1800 1600 1400 600 3900 3600 3360 3120 2880 2700 2400 2160 1920 1680 GOO 4500 4200 3920 3640 3360 3150 2800 2520 2240 1960 800 5800 5400 5000 4650 4300 4000 3600 3240 2880 2500 1000 6000 5580 5160 4800 4500 3900 3450 3000 Location of the plant should influence the selection of a gov- ernor and where the plant is in some isolated place, the less complicated the governor, the better. Of course extra parts could be kept always on hand where the item of expense is second in importance to good design. Again if the super- intendence of the plant is to be given to incompetent men (a common and costly experiment) the less complicated the gov- ernor the better. Throttling valves should never be used to regulated turbines. Fig. 361 shows a standpipe with a damping pipe a. The object of this pipe is to prevent the water oscillating in the standpipe under the action of the governor. The one shown 358 HYDROELECTRIC PLANTS. is three feet in diameter and connects to the standpipe one foot above the surface of the water in the distant reservoir. For heads above 100 feet or so the standpipe loses part of its effi- ciency on account of the inertia of the mass of water it contains. The cost also becomes prohibitive and recourse is had to safety valves and heavy fly-wheels. In fact, all turbines, where good regulation is desired, should be provided with them. These fly-wheels range in weight from 5000 pounds to almost any weight, and peripheral speeds of from 5000 to 10,000 feet per minute, and are made of built-up plates, or cast steel with steel tires shrunk on. Fly-wheels serve to take care of all the FIG. 361. Stand pipe with dampening pipe. smaller and more rapid fluctuations due to surging in the pen- stock, draft tubes or changes of load. The governor does not have to act so quickly and the pressures on the penstock are more easily controlled and are not so severe. Vibrations of the foundation are minimized and most of the noise eliminated. For fluctuating loads the draft tubes should be short, as severe oscillations are set up in long tubes tending to cause vibrations, uneven power and even to damage the turbine. The best governors on the market are the Lombard, the Im- proved Sturgess, the Woodward and the Replogle. The first-three makes, which use energy stored in tanks to operate the gates, are called hydraulic gjvernors, while the Woodward and Re- POWER HOUSE EQUIPMENT. 359 plogle which operate the gates by friction derived from inertia balls similar to those on a steam engine governor, are called mechanical governors. All governors are set into operation by the change of speed in the line shaft. A pulley on the line shaft drives the friction cones, and a second pulley drives the governor balls. A change of speed then varies the position of the balls which causes the friction cones on the gate shaft to operate, or causes the hy- draulic piston to act on the friction cones. It will thus be seen that the speed has to change perceptibly in order to actuate the governor, a fact which of itself makes perfect government impossible. It would seem to the writer that the first word " go " should come from the switchboard rather than from the line shaft. It is the fluctuation in the power that brings about the change of speed which we wish to avoid. Therefore if a special ammeter sets the governor in motion a full second will be clipped off of the time taken by the best governors in starting the gates. The inherent difficulty in attaining perfection in water power government is the impossibility of setting in motion the dead water in the pipe or flume the instant the gate is opened. However, if the ammeter is used to start the governor, all well-designed water powers may be made to regulate with a variation in speed of less than three per cent, on throwing off 75 per cent, of the full load, or two per cent, under changes amounting to 50 per cent, full load. There is a limit to the speed with which a gate can be closed, due to mechanical rea- sons, 1 to 1 seconds is about this limit. Therefore when a second is lost in getting the initial impulse to the governor it is a serious loss. The curves, Fig. 362, show the action of a governor when the load is suddenly increased from 25 kw. to 75 kw. These curves are taken from Mr. M. A. Replogle's paper read before the American Society of Mechanical Engineers, May, 1906. Mr. John Sturgess gives a set of curves which are exactly like Mr. Replogle's in showing that valuable time is lost in start- ing the governor. In these curves it will be seen that the speed does not increase perceptibly for fully 0.25 second. This is due to the inertia of the moving machinery and shows the importance of providing a fly-wheel effect where possible. It 360 HYDROELECTRIC PLANTS. also shows that this effect retards the action of the governor at the start, though it helps it in the end. Hence with a gov- ernor started from the ammeter we will have the governor acting 0.25 second to 0.5 second before the speed varies at all and in another second the gates will be wide open and, if a proper fly-wheel is provided, the regulation will be practically perfect. All governor experts are agreed that the cylinder gate turbine, especially those with the lip, 6, Fig. 363, are the most difficult so 85 ^7, A ? 102 101 100 99 98 9? L ^ c ^ j 1 | ^ ^ ^ c> j t -, ^ * J NORMAL , SPEED J > ^N s - ->. " . | ?- f S^ > - N \ _ ~ 5 r^ - x; \ ^ C 1 > 3 \ j -*, \ / -I r V 3 ^ * ^ ^ \, >w *^. ^ S gTC^ / ~r _c ^ C ^ \ J x o -L -.1 r V ij .. ~ - 2 . After getting the mean radius of the t)4 . 4 armature, shafts and pulleys, calculate the fly-wheel effect. Say that this is found to be 20,000 foot pounds per second, then 220,000 - 20,000 = 200,000 foot pounds to be supplied by the fly-wheel. If the mean diameter of the fly-wheel rim is 12 feet and the maximum revolutions per second of the fly- wheel is 10, then V l = 12X7TX10 = 377 feet per second; and V 2 = 12X7T (10 -.12) = 372+; then 200,000 - ~ 3722) - 3420 pounds. Therefore a fly-wheel having a rim weighing 3420 pounds would have prevented the fall in speed. Of course this would be a very small fly-wheel, but in this example the fall in speed was slight and the load small. JFig. 365 shows an ideal arrangement of standpipe and tur- bine unit. The penstock is continued on through the power house and ends in the reservoir. Mr. G. A. Buivinger describes such a plant. Much difficulty had been experienced with this power plant due to long pen- stocks (6200 feet by 8 feet), long draft tubes, etc. A 10,000 364 HYDROELECTRIC PLANTS. pound fly-wheel was placed on the shaft, and while this aided the regulation, it did not perceptibly effect the pressures on the pipe. Finally a reservoir 50 feet in diameter and 12 feet deep was built as shown. The capacity of the power plant was 800 horse power under 47-foot head, and this reservoir supplied 2000 cubic feet of water for each foot in depth and there- fore one foot of water supplied 2000xG2.oX47 =5,875,000 foot pounds per minute and for 30 seconds twice that, or 11,750,- 000, which is about half the full load output of the plant. This arrangement gives the water in the penstock a free path into the reservoir. The reservoir can frequently be built of FIG. 365. concrete on top of a near-by cliff, and in such cases (where no tower is required) there should be no limit to the height. The efforts made to reduce the pressures in the above plant by installing a 10,000 pound fly-wheel would indicate that the re- lation between pipe pressures, fly-wheel and regulation is not well understood. Water hammer can not be prevented by the use of a fly-wheel and the present day governor. The gov- ernor acts from the line shaft and the fly-wheel retards the action of the governor. The presence of the fly-wheel would, other things being equal, permit the more gradual opening of the gates, but owing to the fact that it takes longer to get the line shaft up to speed again with a fly-wheel, if the gates operate slowly the result will be that the speed will not fall so POWER HOUSE EQUIPMENT. 365 low but the period will be increased and where the load fluctuates rapidly the second peak may come before speed is restored. Therefore it is fully as important to have quick gate action with a fly-wheel as it is without. The dash and dotted line above the speed curves illustrates the effect of a fly-wheel. The only safety from water hammer is the standpipe or relief valves. The function of a standpipe is not to take the place of the fly-wheel, its duty being to prevent water hammer. Water flowing in a long penstock must be suddenly arrested, the doing of which produces a bursting tendency. If we let P equal the normal working pressure per square inch on the penstock, due to the hydrostatic head; P 1? the pressure which will be produced by shutting the gates a certain percentage of the opening, v = the velocity in feet per second in the pipe at the time the gate is moved. Then P! = i (P + 62.92 Xv)+Vi (P + 62.92 X?;) 2 - 62.92 XPX?;X p = the percentage of the normal output remaining after a reduction of load. Thus if the wheels are running under full load and half the load is thrown off, p = .50. In the above, the penstock is not supposed to increase in volume under the pressures. Governing High Head Systems. In the development of power from water under high pressure, certain .difficulties arise which must be carefully considered, else disaster will follow. As already explained water hammer is a great danger to the pipe line. It has been stated in the preceding pages that safety valves and standpipes were the two methods employed to prevent water hammer. The following refers to heads above 200 to 300 feet where standpipes cannot be employed. Where tangential wheels are used and the head too great for a standpipe, the deflecting needle nozzle serves to prevent water hammer and gives the highest efficiency where the state laws require that the natural flow of the stream be uninterrupted. Here the waste of water can not.be avoided, but where it is pos- sible to store the flow during light loads great economy is de- sirable. In this case the needle nozzle shown in Fig. 366 gives the highest efficiency and the best regulation. The force re- quired to operate this nozzle is very slight. 366 HYDROELECTRIC PLANTS. POWER HOUSE EQUIPMENT. 367 It is evident that when the needle is suddenly thrust outward water hammer is produced. To relieve this excessive pressure safety valves must be provided and as there is no more im- portant part of the power equipment it should be carefully designed. The common type is built similar to the safety valve on a steam engine and is open to the danger of sticking in the seal. This failure to operate at the critical time has caused the loss of many thousands of dollars. To be safe against sticking, the valve should be made to rotate constantly, or con- structed as in Fig. 366. In this safety valve water stands normally at some level, a, in the pipe, b, compressing the air in b. As the pressure in- creases the water rises in 6, till the hollow ball c floats up and completes the circuit between the switchboard and the solenoid S, thus causing the balanced valve d to descend and the valve e to open. Instead of operating the valve, e, this same arrangement could be used to deflect the nozzle. The governor operates the needle at g. TESTING. There can be no object in insisting on a guarantee for a machine unless a test is performed to ascertain whether the guarantee has been made good or not. Such tests cost a good deal and it is seldom indeed that large turbines are tested after being guaranteed and placed. However, if a test shows up a loss of a few per cent, on, say, a 500 h.p. turbine, and the water wheel company can be held for this loss, the amount saved will more than pay for the in- vestment. For a deficiency of five per cent., 25 h.p. would be lost, which at $20 means $500 clear cash lost each year and at ten cents per kw.-hr. (3000 hours per annum), would mean $5595. The turbine manufacturers send their wheels, that is, one of each pattern, to Lowell or Holyoke, Mass., where there are companies that make a business of such work. However, the engineer in charge of the power plant should from the start plan to make a test, because the testing flume efficiency is seldom attained in practice. During construction, while the wheel pit is free from water, a weir W, Fig. 367, should be put in. It is often placed 368 HYDROELECTRIC PLANTS. under the power house, but usually it may be placed fur- ther down stream, the greater the distance from the turbine the better. This weir should be so constructed that after the test it can be easily removed. If it is necessary to put the weir close to the wheels, an equalizing rack is placed parallel to and at distance of five or six feet from the weir. This rack has numerous small openings equal to about one-fourth or one- fifth the entire area. FIG. 367. Fig. 367 shows how the exact depth over the weir is obtained by means of a hook gauge and a water-tight box communi- cating through a f-inch lead pipe with head water. As shown this gauge may be placed above the equalizer and it will give the same reading as if placed below. Air must be ad- mitted under the overpour at V, otherwise the formulas given in Chapter II will give too large a flow. Fig. 369 shows the general arrangement of the friction brake as arranged for testing a vertical turbine. If the friction-pulley is heavier than the gear ordinarily used, it is suspended by means of cords passing over pulleys and attached to counter weights. This is a refinement which would not be necessary POWER HOUSE EQUIPMENT. 369 in ordinary tests. The brake is suspended in the proper position around the pulley by means of ropes and weights W. A bell crank C is used to transmit the turning effort from the brake arm to the scales (Fig. 369). The operation is best demonstrated by an actual example. Let the dimensions of the bell crank C be M = 5 feet and N = 6 feet; the effective length of the brake lever 0, Fig. 370, be 10 feet. Then the total leverage acting on the friction-pulley ^ or lt)xj = 12ft. FIG. 359. and the total force acting on the pulley face is W O = 10 W = 12 W. M o wherein W is the weight as measured at the end of the bell crank arm N. The weight, W is used to counter-balance the brake rigging. The power of the turbine = 6.28X0XJFXr.p.m. 6.28X12X.20Q 33,000 33,000 = 457 h.p. where 6. 28 = 2?r, = effective inches, W= weight on scale arm. At the start everything must be in balance. As shown in Fig. 369 the bell crank is the heaviest to the left of the knife edge, and in practice an arm P, would be attached to balance 370 HYDROELECTRIC PLANTS. the scale pan, etc. The friction pulley should have about 100 square inches frictional surface per h.p., and may be from 18 inches to 120 inches in diameter. Heavy cylinder oil may be used as a lubricant, however, green pig fat is the best. During the test the exact head is obtained by getting the level of the water over the wheels. Then, having the quantity HeadX62JxQ of water per minute the i.h.p. is found from * . oo,UUU The h.p. measured with the brake, divided by the i.h.p., gives the efficiency. Undoubtedly one of the best all-around dynamometers is that shown in Fig. 370. This dynamometer has been thoroughly FIG. 370. tested at Purdue University. The wood shoes are placed two or three inches apart and are fitted to the face of the pulley. Wrought iron straps press these against the face. The flanges shown in the part sectional view are intended to hold water which is poured in for cooling purposes. The Westinghouse Company have found that for piling the break shoes " green " pig fat is the best. A large slice is laid upon the top of the shoes and the" heat allowed to melt it. To get the proper area for brake shoes, the author has the following formula: A = ^ ^ , wherein A is the total POWER HOUSE EQUIPMENT. 371 area of the shoes in square inches ; P the power in horse power to be dissipated; S the speed in revolutions per min., and R the radius, in feet, of the pulley. This is derived from dynamometers actually made and used by various engineers. About one-half to one-fourth of the area of the pulley face should be covered by the shoes. p For brakes not cooled by water use A = The capacity P of this dynamometer in horse power (the prin- ciple is the same for other types) is found from the following formula: Ififll v A v jh v 7? v t* TV -v UU J. /\ ^1 XX /' /\ JV /N I . JJ.II1. j 33,000 ' where A the area in square inches of the frictional surfaces of all the shoes; p = the assumed pressure per square inch of the shoe on the rim of the wheel, and may be taken at about three pounds. 1.001 is a constant found by multiplying the coefficient of friction, .35, by TT; R is the radius of the wheel in feet. This formula must not be confused with that for the measure- ment of the power as in that case R is the radius at which W is applied and = 0, Fig. 370. It is only used to get at the proper size of the brake. For testing large turbines a less expensive, and at the same time a very satisfactory way is to test the electrical generators driven by them. Of course this can only be done when there is direct connection as the efficiency of a line of shafting would otherwise have to be found. HYDRO-COMPRESSORS. No book on hydraulics would be complete without something on hydro-compressors, a method of power development that is to become quite common in the future. Fig. 371 shows in its entirety such a compressor. The letters show the important parts as follows: A, the penstock; B, the receiver; C, the compressor pipe ; D, the air chamber or collector; E and F, the tail. race; G, timbering used, where shaft is sunk in earth, to support the walls ; 77, the blow-off pipe ; 7, the com- pressed air-feed pipe; /, the air head consisting of; a, the tel- 372 HYDROELECTRIC PLANTS. w FIG. 371. Hydro-compressor. POWER HOUSE EQUIPMENT. 373 escoping pipe with bell-mouthed casting, b, opening upwards; c, the cylindrical and conical casting; d, the vertical air supply pipes, each having at its lower end a number of smaller inlet pipes radiating from it towards the center of compressor pipe ; e, the adjusting screws for raising the air-head; K, the diffuser; L, the apron; M, the pipes to allow the escape of air from be- neath apron and dispenser; A/", the legs by which the separating tank is raised above the bottom of the shaft to allow egress of the water.; P, the automatic regulating valve. The water is conveyed to the tank B through the penstock A, where it rises to the same level as the source of supply. In order to start the compressor the head piece / must be lowered by means of the hand-wheel / so that the water may be ad- mitted between the two castings b and c. The supply of water to the compressor, and consequently the quantity of com- pressed air obtained, is governed by the depth to which the head piece is lowered into the water. The water enters the com- pressing pipe between the two castings b and c, passing among, and in the same direction as, the small air inlet pipes d. A partial vacuum is created by the water at the ends of these small pipes, and hence atmospheric pressure drives the air into the water in innumerable small bubbles, which are carried by the water down the compressing pipe C. During their downward course with th~ water the bubbles are compressed, the final pressure being proportional to the column of water sustained in the shaft E and tail race F. When they reach the disperser K their motion is changed, along with that of the water, from the vertical to the horizontal. The disperser directs the mixed water and air towards the circumference of the separating tank D. Its direction is changed again towards the center by the apron L. From thence the water flows upward, and, free of air, passes under the lower edge of the separating tank. During this process of travel in the separating tank, whiqii is slow compared with the motion in the compressing pipe C, the air, by its buoyancy, has been rising through the water and pipes M, M, from under the apron and disperser, to the top of the air chamber D, where it displaces the water. The air in the chamber is kept under a nearly uniform pressure by the weight of the return water in the shaft and tail race. 374 HYDROELECTRIC PLANTS. The air is conveyed through the main 7, up the shaft to an automatic regulating valve, and from thence to the engines, etc. The air pressure in the main and air chamber increases one pound per square inch for each two feet three and a half inches that the water is displaced downwards in the air chamber by the accumulating air. The variation in pressure from this source will not be more than three pounds per square inch in a working plant. As the automatic valve requires a change of only one pound per square inch pressure to close it completely it will be evident that, by properly adjusting the valve, some air can always be retained in the air chamber, and that the water can be prevented from ever reaching the inlet to the air main. If a large quantity of air has accumulated in the air chamber, the valve allows of its free passage along the main; but when the air is being used more quickly than it is accumulating, and the pressure decreases below a certain point because the chamber is nearly emptied of air, the valve shuts partially, or completely, adjusting itself to the supply from the compressor. When the air has displaced the water almost to the lower end of the compressing pipe, it escapes through blow-off pipe H. A hydro-compressor was built at Magog, P. Q., and tested by a number of experts and was found to have an efficiency in re- lation to the power of the falling water of from 55 to 71 per cent. An old steam engine driven with the compressed air gave 51.2 h.p. for each 100 h.p. in the falling water. When the compressed air was heated to 267 degrees F., the efficiency was 61.5 per cent. If this heated compressed air had been used in a modern hot air jacket engine the efficiency would have been 87J per cent. Another compressor at Ainsworth, B. C., gave 71 per cent, efficiency. Much depends on the number of the air pipes and the air-head should be so made that pipes may be added or taken out. The number should be greatest when about half the water is used and reduced at full flow. A new and very large compressor plant is that located at Victoria Mines in Michigan. The author is indebted to Mr. W. O. Webber for the following data: The minimum quantity of water available is 29,000 cubic feet a minute. The power available is 4000 h.p. ; the dam is 28 POWER HOUSE EQUIPMENT. 375 feet in height, and is a mile above the site of the compressor, and the extreme height from the top of the dam to the outlet of the compressor is 72 feet. There are three downflow pipes in solid rock, 5 feet in diameter, and 334 feet deep; they are lined with 6 inches of concrete. The air chamber at the bottom has a capacity of 82,000 cubic feet of air. The surface pipe is 24 feet in diameter, and the blow-off pipe 12 inches in diameter. Each one of the downflow shafts can be operated independently, and furnishes an equivalent of 1300 h.p. The air is furnished at a pressure of 118 pounds per square inch. The total cost of compressor, including dam, was $200,000. The water is received into the downflow shafts over a cir- cular shaped apron five feet in diameter. The apron is of steel TABLE XLI DATA FROM EXISTING HYDRO-COMPRESSORS. H.P. developed. Diam of. tube, inches. Diam. of shaft, feet. Gauge press, pounds. Head, feet. Depth of shaft, feet. Location of Plant. 587 33 7. 46 107 210 Ainsworth, B. C. 300 18 3.5 25 14 64 Petersborough, Canada. 150 44 7. 52 16 150 Magog, P. Q. 1500 168 24 91 18.5 240 Norwich, Conn. 4000 eat 60 118 72 334 Victoria Mine% Mich. t There are three of these 5-foot tubes. construction, and weighs 11 tons. Five iron pipes, six inches in diameter, extend above the water to a distance of four feet, and connect several inches below the water line with 2000 small pipes, 0.25 inches in diameter, each small pipe pointing toward the center of the apron. The small pipes are about 18 inches in length, and, being arranged in a circle, there remains a space in the center of the shaft 3.5 feet in diameter. As the water flows into the shaft, air is drawn down through the larger pipes, and is forced into the water as it passes over the ends of the small pipes. The separating chamber and separator consists of expanding tubes downwardly projecting into the air chamber, with conical concrete diffusers formed on the floor of the separator chamber below them. It must not be supposed that the compressor pipe has in all 376 HYDROELECTRIC PLANTS. cases to be placed in a well. It may take the form shown in Fig. 372. Frizell obtained an efficiency of 52 per cent, under a 5-foot head. The compressor is especially adapted to low heads. In designing a compressor the head and quantity of water being given, first decide on the pressure for the air. Of course the higher the pressure the cheaper the engines and pipe line, but the efficiency of the compressor is less for high pressures. The loss due to absorption of air by the water averages about four per cent, and varies as the square of the pressure. FIG. 372. About 80 pounds pressure per square inch should be at- tained, though the costs of all the various machines will have to be the determining factor. Having decided on the pressure, find the length of the compressor pipe C, by multiplying the pressure by 2.3, which gives the length in feet. The diameter of this pipe depends on the volume of the water and the amount of head which can be lost. Its diameter is figured in the same way as that of a penstock. See pages 26 and 199. The effective head acting on this pipe is that due to the difference between' the head and tail water levels, minus the head lost by the water ascending the shaft. The velocity in the shaft E should not exceed four feet per second. POWER HOUSE EQUIPMENT. 377 . The diameter of the air reservoir or collector is more a matter of judgment, but its area may be from 10 to 15 times that of the compressor pipe. The air mixing pipes d may be of gas pipe of from f-inches to two inches in diameter and having radial pipes as shown in Fig. 373. The holes in the radial pipes are on the underside so that the water falling about them sucks the air down and out of the pipes. Fig. 374 shows the Norwich compressor. The air head is mounted on a pipe which telescopes into the compressor pipe allowing an up and down movement equal to the variation of the level of head water. Where the fluctuations are more than a foot or so the level should be controlled at the head gates. The same head gates and racks suitable for a turbine plant are used FIG. 373. for a hydro-compressor, the rack, however, having a fine brass wire screen to catch every particle of drift. That part of the steel work containing the compressed air must be air-tight. The receiver must be protected from the cold in the northern climates as the air inlet pipes will freeze solid when the com- pressor shuts down. Where the water used exceeds, say six to ten thousand cubic feet per minute the plant should be divided up into units, there being a common shaft and air chamber, but separate compressor pipes, receivers, diffusers and aprons. To avoid obstructing the flow. as much as possible the author would suggest as arrange- ment of inlet pipes as shown in Fig. 375, the pipes being open at both ends and also having small holes drilled at the lower ends. The curve in the pipes corresponds to the flow of the falling water, so that the water runs along instead of against them. 378 HYDROELECTRIC PLANTS. By passing the compressed air through a heater and raising it to about 300 degrees Fahrenheit, 50 per cent, more power is obtained. To do this, according to Mr. Wm. Webber, requires FIG. 374. about 7J per cent, of the power in the river, figured on the basis of the amount of coal used. Moistening the dry compressed air in the engine cylinder also POWER HOUSE EQUIPMENT. 379 adds to the power. To saturate the air, the water has to be forced into the engine cylinder against the air pressure. Each h.p. in the river requires about 3.7 pounds per minute of water for this saturation, and the work performed by the pumps is - (P X W X 3.7) 2 tound by : QQ nnn = power required, where p _ 33,000 Pressure of air in Receiver .434 and W is the theoretical horse- power of river. The minuend is multiplied by two as the efficiency of a pump is about 50 per cent. The power thus found is about 4J per cent, of the river power. It only requires a glance at a compressor to see that as com- pared with a turbine plant it is simplicity itself. There are no moving parts to wear out. No expensive and troublesome governors are required. No attendance. No oil or wear. No FIG. 375. fire insurance, and practically no depreciation. Everything is automatic and it can be built under any and all conditions of foundation. Professor Unwin states that it is practical to transmit power by compressed air to a distance of 20 miles with a loss of 12 per cent. The cost is less than a turbine plant, as there are no journals, shafting, gearing, etc., the only cost being for the boiler iron and excavation. The cost of excavation will of course vary with the condition. Rock excavation will cost $5 to $8 per cubic yard and earth from 50 cents to $3. Mr. Webber places the cost of a 5,000 h.p. compressor at $42,000. The boiler iron ought not to cost more than four cents per pound erected. Of course the same dam, head gates, canals 380 HYDROELECTRIC PLANTS. and racks are required as for a turbine plant, but no power house. For distances less than five or six miles (and no doubt the future will see this increased), the transmission of the power by means of compressed air is as efficient as by any other means, a two per cent, loss being usually allowed. A velocity of 60 feet per second, may be allowed in the pipes, 'and as each horse- power at 85 pounds pressure takes about 1.44 cubic feet of air per minute, the area of the pipe may be determined. Webber gives the cost of a 20-inch steel pipe four miles long carrying 5,000 horse power at 85 pounds pressure as $3.05 per foot laid, making the cost per mile $18,500, and for four miles $74,000. An electric transmission would cost as follows: Two governors (for two units) $2,000 Generator house 5,000 Switch board 2,000 Four miles transmission line 4,500 Generators and exciters. . 50,000 Step up and step down transformers. . . . 30,000 $93,000 The cost is more in favor of the hydro-compressor plant, as the distance grows less and vice versa. Compressed air may be used in the engines already operating a factory, but the greatest efficiency is obtained when each machine is driven by its own air engine, in which case the effi- ciency is about that of the electric motor. Water is sprayed into the cylinder of the air engine, but any engine may be fitted with a spray. Small air motors of about \ h.p. require as high as 14 cubic feet of air at 80 pounds pressure per square inch per minute per horse power. AUXILIARY PLANTS. The same course of reasoning as applied to a storage battery plant, see page 421, should be pursued in selecting the proper size of the auxiliary plant, the chief difference being that the auxiliary plant is used to tide over the months of low water rather than the daily fluctuations of load, and the curves show- ing the monthly fluctuations of the river flow are used in de- termining the proper size of the plant rather than the hourly POWER HOUSE EQUIPMENT. 381 Variations in the power output. Usually the size of the auxiliary has to be guessed at, as accurate data on the river flow is seldom to be had. STEAM PLANT. Boilers. In considering an auxiliary plant for a water power it must be borne in mind that ordinarily it will be in use but about one- third of the time. Therefore a boiler should be selected which will depreciate the least when not in use. The kind of boiler selected should next depend upon the price of coal. Table XLII gives relative economy, etc., of the various types of boilers. TABLE XLII. COMPARISON OF VARIOUS TYPES OP BOILERS. Type of Boiler. Sq. ft. of heating surface for 1 h.p. Coal per sq. ft. Heating Surface per hour. Relative economy. Relative Rapidity of steaming. Authority. Water-tube Tubular . 10 to 12 14 to 18 .3 25 1.00 91 1.00 50 Isherwood. Flue 8 to 12 .4 .79 .25 Prof. Trowbridge Plain Cylinder 6 to 10 .5 .69 .20 Locomotive 12 to 16 .275 .85 .55 Vertical Tubular 15 to 20 25 .80 .60 In actual practice, all day firing, and for small lighting plants having compound condensing engines, 10 pounds of coal is burned for each kw-hr at the switch board. In badly designed, small, isolated plants the consumption may reach 15 pounds per kw-hr. The coal item is about half the entire cost of steam power. A locomotive boiler will evaporate (usual practice) from 6 to 8 pounds water per pound of coal, while a water tube boiler will evaporate 7J to 9 pounds. Therefore, if we wish to install a 1000 h.p. boiler plant where fair coal costs $1 per ton (2240 pounds is always considered a ton of steam coal), and where the plant will be run 1000 hours per season of 382 HYDROELECTRIC PLANTS. drought, the value of the difference between the coal used by the water tube and the locomotive boilers is first determined. TABLE XLIII. FUEL AND WATER REQUIRED FOR THE PRODUCTION OF MECHANICAL ENERGY. Lbs. water from and at 212 per Ib. of coal. Lbs. coal per h p. per hour. 9 3.83 Good coal and boiler 10 3.45 Fair coal and boiler 8.6 4. 8. 4.31 7. 4.93 Poor coal and boiler 7. 5. 6. 5.75 5. 6.90 Lignite and poor boiler. 3.5 10. From Table XLIII it is seen that for a first class boiler of the water tube type about 3 . 7 pounds, of coal will be used per h.p. per hour, and 1000 h.p. for 1000 hours will use 1,000,000X3.7 which, at $1, will will consume about or in the above case 2240 cost $1,652. six pounds of 1,000,000X6 1652 tons A locomotive boiler fair coal per h.p.-hr., = 2,680 tons costing $2,680. Table XLII also gives the relative efficiencies for the same coal. The water tube boilers will cost, set up, about $10,000, not counting buildings or smoke stacks, as they would cost about the same for all boilers, except where building sites are very expensive and fine buildings are erected. The locomotive boilers would cost about $7000. The difference in cost of operation is about $1000 per season in favor of the water tube boilers, airi difference in cost of plant is as follows: Difference in first cost .................. $3,000 ' interest on investment ...... 180 " "maintenance.. 300 Total $3,480 v POWER HOUSE EQUIPMENT. 383 About 3J to 4 years service would pay for a first class boiler plant if the coal cost $3. In one season's run, the water tube boilers would save $3000 over the cheaper boiler, an amount which just pays the difference in their cost. Another strong argument for the water tube boiler is its free- dom from disastrous explosions and ease of repair. The author would strongly advise the intending purchaser to look up the second-hand boiler market. Frequently half the cost of a new boiler plant can be saved by the use of a second- hand boiler, which is practically as good as new. Of course great care must be taken in selecting such boilers. The Babcock & Wilcox and the Heine water tube boilers are among the best. Table XLV and diagram will give a good idea of the dimen- sions of a boiler plant. The general proportions will hold good for any number of fire tube boilers. The setting shown is of brick, but it may readily be made of concrete, using the same dimensions. The setting is for tubular boilers ; water tube boilers are taller, but will take up about the same floor space. It is impossible to give the table of sizes for water tube boilers, as the various types vary so widely, but below is given the rela- tive dimensions of three of the most prominent makes: TABLE XLIV. OUTSIDE DIMENSIONS OF WATER TUBE BOILERS. Make and Nominal Rated Size of Boiler. Width. Length. Height. Babcock & Wilcox, 370 h.p Babcock & Wilcox 2 in battery 13' 8" 26' 6" 17' 9i" 17 / g^" 19' 6" 19' 6" Sterling 500 h p lg> o" ig/ Q" 23' 0" Babcock & Wilcox 15' 5" 23' 5" 20' 0" Vertical Wickes, 400 h.p 22' 11" 19' 5" 34' 0" Roughly, each horse power requires about 0.666 square foot of floor space. The volume occupied by water tube boilers is about as follows, for the largest sizes: VOLUME OF WATER TUBE BOILERS PER H.P. Babcox & Wilcox 13. 75 cubic feet Sterling 15.73 " Wickes.. 18.70 " 384 HYDROELECTRIC PLANTS. aoBjans s,a}BJ3 ui ;aaj aoBj-ins jo 'oj^ cr O5 ^ CM * C! 3 * 00 3 t>. 00 sqiuBf aippiui jo ssaujpiijj. > S T T 3 T ' CM CM ^H CM C \ I I N u -pBq PUB }oos jo mptjvi D c * CO CD p C III! >0 O O CO ci \ T T CO t^ 3 P s}id IJSB jo tpSuai H .H T T T T ' ? p co "saoBtunj jo u.}pi/y^ CO .S nn: :n saoBuanj jo q}3uaq * .S T T T ^ 00 rt 1 1 suoadB jo u^Suaq O S nn; 5 co co 1 ! CO squreC spis}no t o siaujpiuj. * c T>O -! CO C 1 1 1 CM CM CM CM C >* o * 1 1 ^ CM CM c O O 1 1 1 i 1 1 STIBAV apis jo ui 3ui -sop 0} aaijoq jo aaiua;) c OS 00 00 00 C 1 CO rH S[JBM JO ^ c ^ CO CO CO t ~ 00 CO jj O 2 H jo ia}uao 0} au'j aooj^ J -J LUU , 1 i. W C/2 pua }uoJj 'saajioq ;o ja^uao 0} auij Jooi^ .S ^ iO iO 00 G LkliJ : 1 1 'S}UOJJ aag jo do} 0} auji aoo[^ - .S CM CM CM CM C 1 1 1 1 O5 O O O C 1 1 1 3AJBA A}8JBS jo do} 0} aui[ aoo^ ( i .S T T T T ' CM CM CM CO C B b. I i i .uop.puao^o^p,,, M ' S CM CO CO * ' CM CM CM CM C o p co i ! i. ^ CM CM "**- ' I*-" O .S T T T T ' O5 Oi ** O5 ^ ^H CM -H ! ! ! M CM CM 'Sa^ppBS 5^DB}S JO lT}p{AV - c O5 O> O5 t^. 1 1 1 1 1 rc co co -t T ? T * 1C iO sjajioq jo }uo-ij 0} auiop paiaAU jo aa}uaQ w c CO CO CO CO r- t~- oo t>- O CO CO X3 00 00 .S o o o en ;uapuadapui jo ja}uaQ Q Jl 00 00 O 00 i i i j 5 aSuBy atuoQ jo do} 0} saanpq jo dox O d t- t~- N- CO CM CM CM CO CO CO CO CO n M* ^ co ^ .O CO CO VM saanoqjo^auzBiQ < .5 (M Tjt T}1 O iO C 1C CO O CO CM ) CO l> jajioq qDBa jo 'd'lj pa}BJ {BUHUO^J O O O O O CO l^ l> o o *o X O C^ POWER HOUSE EQUIPMENT. 385 The capacity of the boiler plant is found for all ordinary loads as follows: The kilowatt capacity of generators times 75 equals horse power of the boilers. Nominal rating is used in above , of course, where a water power is to take all the peak loads this would give too much. Then one-half the kilowatt capacity of gen- erators would be sufficient. By heating the feed water with the exhaust about 6 to 10 per cent, of the fuel will be saved, besides saving the boilers from the evil effects of filling with cold water. If slack coal is used it should be blown into the furnace. 386 HYDROELECTRIC PLANTS. The boiler house should be separated from all other rooms by a thin wall. In most cases steel smoke stacks will -be found the most eco- nomical for an auxiliary plant. There should be at least two for plants of any size, and for large plants about one stack per 1000 h.p. One stack for 1000 h.p. will cost, all set up, about $1,500, and for 500 h.p., $500. A Weber reinforced concrete chimney, 10 feet inside diameter, and 200 feet high, with founda- tion, will cost about $7,000. TABLE XLVI (Kent). SIZE OF CHIMNEYS AND PROPER H.P. BOILER. Height of Chimney in Feet. Diam. of j chimney 50 60 70 80 90 100 110 125 150 " *Vip; Commercial H.P. 18 23 25 27 21 35 38 41 24 49 54 58 62 27 65 72 78 83 30 84 92 100 107 113 33 115 125 133 141 36 141 152 163 173 182 39 183 196 208 219 42 216 231 245 258 271 , 48 311 330 348 365 389 54 363 427 449 472 503 551 60 505 539 565 593 632 692 66 658 694 728 776 849 72 792 835 876 934 1023 78 995 1038 1107 1212 84 1163 1214 1294 14^8 90 1344 1415 1496 1639 96 1537 1616 1720 1876 The quality of the coal has much to do with the size of the chimney. The height should be about 75 feet for free burning bituminous coal, 115 feet for slow burning bituminous coal or slack, and 125 to 150 feet for anthracite. The steel stack rests on a concrete or masonry foundation and should be bolted firmly to it. Galvanized iron cable is used to guy the stack and these and the anchorage should be designed to withstand a wind pressure of 25 pounds per square foot against the stack. Suppose we have the case shown in POWER HOUSE EQUIPMENT. 387 Fig. 377. The guys, supposing there are four, will support 68 lineal feet of the pipe against the wind pressure or a pressure of 5X60X25 = 7,500 pounds. If the guy is at an angle of 45 degrees the tension will be 7,500 x2 since the tension is proportional to the distance D L therefore the cable will have to sustain 15,000 pounds (see Table LXIII). This is more than would be ordinarily given to one guy, as another set would be attached further down, but the above will serve to caution the builder against the usual practice of using any and all kinds of anchorage and cables, in the blind hope that no great storm will strike the stack. A good boiler should, under forced firing, be capable of evapo- rating twice normal. Therefore in selecting the proper capacity of the boiler plant take the peak load, as found on page 426, and make the boiler capacity one-half the peak. Boilers should be operated 25 per cent, above the rated capacity to give best results. It often occurs in the case of a water plant, that, while there is not enough water to carry the average load there is enough, using a storage reservoir, to carry the peak loads. In this case the water is all reserved for the peaks and the boilers run steadily and efficiently on the average load. In which case the capacity of the boilers is made equal to three- fourths the average load. In a large plant there should always be at least one spare boiler. The feeding should not be left to an injector alone, but both an injector and a pump should be used in all cases. 388 HYDROELECTRIC PLANTS. Steam Engines. The engine best fitted for auxiliary work is, undoubtedly, the high-speed automatic cut-off engine, though, as in the case of boilers, the price of coal has much to do with the selection. TABLE XLVII. COMPARATIVE EFFICIENCV OF ENGINES. Kind of Engine. H.P. Steam Press. Water per I.H.P.. non- condensing. Per hour, condensing Plain slide valve with long ^troke, cut-off f 25 to 100 75 to 80 40 to 50 30 to 40 Automatic, high speed, single valve, cut-off J 50 to 150 75 to 80 25 to 35 20 to 25 Automatic, four valve, and Corliss, high speed, cut-off 1/5 50 to 500 110 to 120 22 to 30 16 to 24 Compound automatic, four valve and Corliss, high speed 400 and up 110 to 120 20 to 27 13 to 20 Triple expansion 500 an 1 up 120 to 160 20 to 27 12? to 18 The true criterion of the engine's efficiency is the amount of water used per i.h.p. < By use of the above table in connection with Table XLIII it can be easily figured what the coal bill will be with the different engines. Of course the less efficient engine will require more boiler capacity, and this must be allowed for. The high-speed engine governs to within 2 per cent from normal load to a sudden no load. Where space is valuable they are the thing, especially those of the vertical type, such as the Westinghouse. When not compounded they consume about 35 pounds of water per indicated h.p. per hr. Roughly, a high-speed automatic cut-off engine will cost $14 to $17 per h.p., all set up. A Corliss cross compound slow-speed high-pressure engine will cost all set up about $30 to $40. Usually second-hand engines may be purchased at half price, which will answer every purpose. As the engine's power is given by the formula H.P. 2PLAN 33,000 where P is the mean effective steam pressure in pounds per square inch on piston, A the area of the piston in square inches, A^ the POWER HOUSE EQUIPMENT. 389 number revolutions per minute, and L length of the stroke in feet, it is evident that by varying the cut-off and therefore P, the power of the engine can be varied. All engines are designed for a certain mean effective pressure, at which they are most efficient, and in selecting the proper size its capacity should just equal the average load, unless the per- missible change in cut-off for the particular engine will not increase the power sufficiently to take care of the peak load. Suppose the case of a 100 h.p. engine cutting off at J stroke, boiler pressure at 100 pounds; r.p.m. = 250, length of stroke L = 1 foot, and the area of the cylinder = 113 square inches. Then at J cut-off 2 ^ N = 102 h.p. And at } cut-off 2PLAN 33,000 Boiler pressure multiplied by C taken from table XLVIII is sub- stituted in the above for Pin each case. By changing the cut-off from J to J we add about 50 per cent to the engine's capacity. While this is at the expense of efficiency, it will be good practice to make 165 h.p. the peak load capacity of the engine. Even | cut-off is advisable in this case. Engines having heavy fly- wheels can carry a 100 per cent, overload for a few seconds. As in the case of boilers, where possible, let the water power take care of the peak loads and keep the engines working as nearly as possible at full load and efficient cut-off. TABLE XLVIII. MEAN EFFECTIVE PRESSURE FOR DIFFERENT CUT-OFFS. Point of cut-off C Point of cut-off C i .5965 | .9188 J .6995 .9370 i .7428 f .9657 i .8465 J .9917 Boiler pressure X C = Mean Effective Pressure. Condensing engines should not ordinarily be used for auxiliary work. 390 HYDROELECTRIC PLANTS. The common single valve engines have a very limited range of cut-off and cannot be depended upon to carry a prolonged overload of more than 25 per cent. If the engine carries a heavy fly-wheel a momentary over load of from 50 to 75 per cent, may be carried. On the other hand the Corliss and other four valve engines have a very large range of cut-off (0 ), an d will safely carry a momentary overload of 100 per cent. THE INTERNAL COMBUSTION OR GAS ENGINE. " The gas engine has probably developed more slowly than any other piece of modern apparatus, as it is now 30 years since the Otto gas engine was introduced. It is only within the last ten years that the larger type of engine, from 500 to 2,000 h.p. in size, has appeared. The delay in bringing forward the most efficient motive power known is chiefly due to the difficulty experienced in developing an efficient and inexpensive method of making gas. As far as the production of gas from anthracite and non-caking bituminous coal is concerned this problem has apparently been solved, but it is still in a more or less unsolved condition for the richer bituminous and semi-bituminous caking coals of the Eastern States. " The following heat balance is believed to represent the best results obtained in Europe and the United States up to date in the formation and utilization of producer gas "Analysis of the average losses in the conversion of one pound of coal containing 12,500 B.t.u. into electricity: B.t.u. % 1. Loss in gas producer and auxiliaries 2,500 20 2. Loss in cooling water in jackets 2,375 19 3. Loss in exhaust gases 3,750 30 4. Loss in engine friction 813 6.5 5. Loss in electric generator 62 0.5 6. Total losses 9,500 76.0 7. Converted into electrical energy 3,000 24.0 12,500 100.0 : "The great objection to the use of the gas engine for electrical purposes has been: First, its lack of uniform angular velocity; POWER HOUSE EQUIPMENT. 391 secondly, its uncertainty in action and high cost of maintenance; and thirdly, its inability to carry heavy overloads. Recent developments have removed the first and second objections ; and a period of vigorous development has resulted in placing the gas engine in the front rank of claimants for attention as a prime mover. "The total investment for a gas-producer plant, all auxiliaries, gas engines and electric generators, has been reduced by the elimination of the gas-holding tank to a point where it is now practically on a par with a first-class steam plant using high- grade reciprocating engines. " Where natural gas or blast-furnace gas can be obtained, the gas engine has outdistanced all competitors ; and now that some of our large manufacturers have taken up in earnest the problem of designing producer-gas plants, it is safe to say that rapid developments will result. " The records of operation of several important installations of gas engines in power plants abroad and in this country seem to indicate that only one important objection can be raised to this prime mover, and that is that its range of economical load is practically limited to between 50 per cent, load and full load. This lack of overload capacity is probably a fatal defect for the ordinary power plant, more especially for the average railroad plant operating under a violently fluctuating load, unless pro- tected by a storage-battery of comparatively large capacity. " Over a year ago, while watching the effect of putting a large steam turbine having a sensitive governor in multiple with reciprocating engine-driven units having sluggish governors, it occurred to the author that here was the solution of the gas- engine problem; for the turbine immediately proceeded to act like an ideal storage-battery; that is, a storage-battery whose potential will not fall at the moment of taking up load, for all the load fluctuations of the plant w r ere taken up by the steam turbine, and the reciprocating units went on carrying almost constant load, while the turbine load fluctuated between and 8,000 kw. in periods of less than 10 seconds. " The combination of gas engines and steam turbines in a single plant offers possibilities of improved efficiency while at the same time removing the only valid objection to the gas engine. " A steam-turbine unit can easily be designed to take care of 392 HYDROELECTRIC PLANTS. 100 per cent, overload for a few seconds; and as the load fluctu- ations in any plant will probably not average more than 25 per cent, with a maximum of 50 per cent, for a few seconds, it would seem that if a plant were designed to operate normally with 50 per cent, of its capacity in gas engines and 50 per cent, in steam turbines, any fluctuations of load likely to arise in practice, could be taken care of. " We have seen that the thermal losses in the gas-engine jacket- water amounted to approximately 19 per cent., and as the water is discharged at a temperature above 100 it can be used to advantage for boiler feed " The jacket-water necessary for an internal combustion engine will probably be about 40 pounds per kilowatt-hour, assuming that the jacket-water enters at 50 F.; then the discharge tem- 11 1 - r\ ^, ., __ . n -.^ ,, perature will be oO+ = 109.4 F." 4U X J.UU The above is quoted from Mr. H. G. Stott, and is one of the most authoritative and important discussions of the gas engine subject ever given, and marks the latest word in that branch of engineering. Mr. Stott is in charge of the largest steam power plant in the world, and being a man of great integrity and ability, he stands in a prominent position to treat the subject in a classic manner. Therefore, from what he says the gas engine producer plant is, by far, the best auxiliary to install in connection with a water power having large storage capacity. The water power would take the fluctuating loads, leaving the steady average load for the gas engines. In some cases the jacket-water could be used for heating, though, as a rule, this would be lost. The gas engine is without doubt the ideal auxiliary power. There are no boiler plants to depreciate. The engine is ready at all times to take up its load. The modern gas engine is easily started, has good regulation and is as easily operated as the steam engine. There are many new makes on the market, but it is in the nature of an experiment when any but the standard engine is used. The Westinghouse, Otto&Priestman, Crosley, Koerting Cockrell and Snow are among the best. The gas used may be a mixture of gasoline and air, lighting POWER HOUSE EQUIPMENT. 393 gas taken from the city mains or producer gas. Usir j gasoline, the average engine will consume J gallon of gasoline per effect- ive h.p-hr. Using city gas, the consumption will be 21 to 22 cubic feet of gas per effective h.p.-hr. Using producer gas an engine should develop one i.h.p. per hr. with from 1 to 2 pounds good coal. For plants of all sizes a producer plant should be installed. If the producer gas is made directly from the coal, and as indicated by the above the saving in coal is enormous The price of coal here again enters as a factor. A gas engine producer plant all complete with producer set up and ready for operation, would cost about $35 per brake h.p. using soft coal, wood, etc., and about $16 for a producer using hard coal, coke, etc. These figures do not include the engine. Producer gas may be made from cheap bituminous coals, anthracite and coke. Usually small anthracite coal or coke is used, but bituminous coal, lignites and wood may be employed. Tests show that a 16 h.p. producer plant gave one horse power for each 1 . 1 pounds of coal, and plants above 50 h.p. gave 1 h.p. for each J pounds of coal. Gas engines without producers cost at the factory as follows: Small engines of from 10 to 30 h.p. about $45 per h.p. Engines up to 100 h.p. $40 per h.p., and above that about $35 per h.p. The complete plant will cost about $85 per b.h.p. ELECTRIC GENERATORS. The type of generator depends upon the character of the load and the system of distribution. Therefore the various systems of distribution will de described in connection with the gener- ators. SYSTEMS OF DISTRIBUTION. Continuous Current. There are two general systems of continuous current distribu- tion: the constant current and the constant potential systems. The constant current or series system is seldom used in this country except for series arc lighting. The lamps take about 10 amperes at about 50 volts per lamp. The generator must have a voltage equal to 50 times the number of lamps in series and a current capacity in amperes equal to 10 times the number of series circuits in parallel. 394 HYDROELECTRIC PLANTS. Knowing the number of arcs to be supplied for city lighting, and those for commercial lighting, the peak load can be decided on. Arc machines will carry '25 per cent, overload for a half hour, and their capacity need therefore only be 75 per cent, of the peak load. < . ... .. ., - (Voltage of the machine) The size being limited by - ^-^ j r = to about Voltage of the lamp 75 kw or less, the generator will be of the belted type. It should rest on a heavy timber frame well oiled, and bolted with deeply countersunk bolts so as to well insulate it from the ground. The load is generally quite constant, and cheap gov- ernors may be employed for regulation. The constant potential or parallel system is in almost universal use in this country. In this system the current capacity in amperes is equal to the current capacity of the lamp used times the number of lamps in multiple. There are three general methods of wiring, namely ; the two-wire method for lamps and small motors (110 volts); the three-wire method, lamps and motors (220 to 440 volts) and the five-wire method for lamps and motors (440 volts). Sharp peaks are sure to occur and the safe overload capacity of the generators must be at least three times the average load. First class governing is an essential feature in the successful operation of this system. The best practice is to have two machines, each being of sufficient size to carry the entire probable load as an overload of 25 per cent. The machines may, and usually are, operated in parallel. No precautions are necessary to insulate the frame from the ground. Alternating Current. In alternating systems there are two general classes, the single phase and the polyphase. The single phase system may be high tension at the generator and stepped down at the load, or may be stepped up to very high tension at the generator and stepped down at the load. The former has only one set of transformers, those for stepping down the voltage from 1000 to 5000 volts to 50, 100 or 200 volts. The secondary may be two or three-wire. POWER HOUSE EQUIPMENT: 395 The latter has two sets of transformers, one for stepping up and one for stepping down. The transmission voltage may be from 5000 to 60,600 volts. The advent of a single-phase motor has brought the single- phase system into great prominence, since, aside from the added cost in long transmissions, it possesses the following advantages > M >/Ss liRTT Unrr FIG. 378. over the polyphase systems: By using single-phase a saving of 10 to 40 per cent, of the first cost of the motor transformer instal- lation is affected; fewer transformers are required with a conse- quent saving in transmission losses of 10 to 20 per cent. Fewer meters are required, which is a good saving, as each small meter consumes about 1 per cent, of the power measured ; also the labor 8== FIG. 379. of installing each of the numerous meters is materially lessened ; it costs less to erect the pole line, etc. The above are very important facts and should be well con- sidered. The working voltage may be 100, 120, 200, or 240 volts. One of the most common two-wire systems is that shown in Fig. 378, the two generators and the lamps being in parallel. 396 HYDROELECTRIC PLANTS. Two hundred and twenty-volt lamps are now used to some extent, in which case the distribution is materially cheapened. In the three-wire system (Fig. 379) the transformers T are of large size, supplying a long line of lamps or small motors. Either of the transformer connections shown may be used, care being taken to connect unlike terminals at P. The polyphase system may be divided into the two-phase and the three-phase. The two-phase, four- wire system, shown in Fig. 380, consists of two single-phase circuits differing in phase by 90. The chief advantage claimed for this system is that a rotating field may be established, which permits the use of two-phase FIG. 380. induction motors and the self-starting of synchronous motors. The two-phase induction motors will start up under full load, but the synchronous motors will not, being run up to speed unloaded. The success of the single-phase motor, of course, lessens these advantages so that the single-phase should be considered the better system up to 30 h.p. Street railways have frequently been operated from this system synchronous converters supplying the continuous current. For long transmissions step up and step down transformers would be used. This system requires the same amount of copper as the single- phase. The three-phase system shown in Fig. 381 is by far the most POWER HOUSE EQUIPMENT. 397 important alternating current system in use to-day. Especially is this true when considered in connection with hydro-electric power plants. By it power is being successfully transmitted at a pressure of 60,000 volts for distances as high as 150 miles. As shown above, no step up transformers are used, though, of course, for higher voltages than 10,000, and preferably voltages above 4300, the voltage is stepped up for transmission and then stepped down for use. In comparing the actual operation of two-phase and three- phase systems there is little to choose between them. The three- phase saves 25 per cent, in copper over the single and two-phase systems on the transmission. FIG. 381. The selection of the proper size for the generators is one of the very important problems, and while an easy one, it is usually the cause for the most inexcusable mistakes. At Constantine, Mich., there is a modern hydro-electric power plant built by a Chicago company. They have two 600 kw. generators having a maximum capacity (allowing for 50 per cent, overload,) of 2460 h.p. To drive these generators they have turbines with a maximum capacity, allowing for loss in gearing, of 1700 h.p. This, too, is for the maximum working head of 11 feet. Fre- quently the head is reduced by back water to 6 feet, in which case they can hardly carry their small lighting load, though at the same time thousands of horse power are passing over the dam and going to waste. 398 HYDROELECTRIC PLANTS. This is not an extreme case, but one much better than is often found. Generators are rated at a unity power factor. Therefore if the power factor is .80 the generator will have only about .80 of its rated capacity. While electrical manufacturers do not guarantee it, yet it is a fact that any of the standard generators will carry a 25 per cent, overload right along and a 50 per cent, overload for two or three hours without doing them any injury. Exciters for these generators should, in all cases, be belted to the shaft to give the most uniform velocity. Where the head fluctuates it is bad engineering to drive the exciter with one turbine, the speed of which cannot be controlled. The generator line shaft, when the plant is properly designed, is the best to drive the exciter from. In the case of horizontal turbines and direct connection it is very difficult to keep up the speed. The latest method is to drive one exciter with a motor. The loss of speed through diminished head reduces the voltage of the line current and also reduces the frequency. Where lamps are operated or where the hydraulic plant is operated in connec- tion with some distant steam plant this reduction of the frequency is a very serious thing. The lamps refuse to work and the distant generators will not run in parallel. A variation of 2 per cent, from the normal frequency may seriously affect the operation of the plant. To get the proper size of generator, first find the greatest peak loads which are apt to occur. Divide this peak load by 1.5; this will give the rated capacity of the generator for a unity power factor. Now if the load is an inductive one and the power factor is .80 multiply, the rated capacity as found from the above, by 1.2. This gives the commercial rating of the generator. The exciter capacity should be about 30 per cent, greater for an .80 power factor than for a unity power factor. The exciter capacity for an .80 power factor should be about 4 per cent, of the generator capacity, as found from the above. SWITCH BOARDS. The switch board is the most variable factor in the design of the power house and one of the least understood. Everything POWER HOUSE EQUIPMENT. 399 about the switch board should be thoroughly made and of the best materials. Marbelized slate for boards up to 600 volts is a good substitute for marble, the chief objection being that it scratches easily. Whether of slate or marble care should be exercised in select- ing slabs free from mineral veins. White Italian marble IJ-inch to 2-inch thick is, in the long run, the most satisfactory. The Standard Marble Company of Cincinnati, O., sell a very good grade of marble. One and a quarter-inch costs about 65 cents, IJ-inch costs about 80 cents, and If to 2-inch costs about $1.10 per square foot. The frame is in almost all cases made of angle irons as shown in Fig. 382, though especially prepared wood boiled in paraffin FIG. 382. or linseed oil has been used for high tension work. A 1J to 2-inch angle iron is plenty large for the ordinary board. Fancy heads are used on the face side of the board. The iron work must be painted before setting up. Felt washers are used between the iron and marble. The holes c are for fastening the various panels together. There is no good reason why the engineer should not make the complete switch board on the site, and it is certainly a good plan for him to select the instruments with great care. For eight or ten dollars a drill press, such as is used by black- smiths, can be purchased with which to drill holes in the marble. It should be attached to a plank A, as shown in Fig. 400 HYDROELECTRIC PLANTS. 383, and should be driven with a 1 h.p. motor The drill should have a speed of about 170 r.p.m., a table on which to lay the slab is very handy, though of course the floor (if perfectly level) will serve the purpose. It would take about one day to bore the holes for the board shown in Fig. 382. The ordinary twist drill is used, plenty of water being fed to the cutting edge. Holes up to 7-16-inch may be drilled in one drilling; up to J-inch use two drills, and from that to IJ-inch, use three different sizes. If the holes are not true file them with a rat-tail file. To lay out the holes for drilling use an indelible pencil and prick punch. Where the drill has chipped the marble at back of FIG. 383. board fill out with plaster of Paris. When the individual panels are completed they are bolted together with f-inch bolts and temporarily stood up while the bus work is done. The back of a switch board is where the workman's skill is shown. In bus work use what is known as half hard copper bar. This may be had of the Detroit Copper & Brass Rolling Mills, Detroit, Mich. A bar thicker than 7-16-inch is very difficult to bend. Aluminum makes excellent bus-bars, as it has a large area to dissipate heat and is light in weight. All connections to it have to be bolted. One thousand amperes per square inch of copper and 750 amperes per square inch of aluminum is common practice for switches and bus-bars. All copper parts carrying currents of POWER HOUSE EQUIPMENT. 401 opposite polarity must have a certain amount of air space be- tween, as given in the table XLIX. This table may be used for either alternating or continuous current. Due allowance must be made for the conditions at the board during operation, and if the atmosphere will be damp a wider arcing distance must be allowed. TABLE XLIX. SPACING OF Bus BARS AND SWITCH BLADES. Voltage volts. Current amperes. Distance between nearest metal parts, inches. to 125 to 10 10 to 25 25 to 50 0.75 1.00 1.25 125 to 250 to 10 10 to 35 35 to 100 100 to 300 300 to 1000 1.50 1.75 2.25 2.50 3.00 250 to 600 Oto 10 10 to 35 35 to 100 3.50 4.00 4.50 600 to 1000 Oto 10 100 5.00 7.00 Fig. 384 represents a simple bus-bar for boards of moderate size. On very heavy bus-bar work instead of bending the bars, t':ey are attached as shown in Fig. 385. Care must be taken to maintain the proper arcing distance from the steel frame of the board. The flexible connecting FIG. 384. cables are soldered into the lugs as shown in Fig. 386 at a, but all strip connections as c, are bolted to the bus-bars with from one to four bolts. Where the bus-bars are over T \ inch thick it is well to make them of two or more strips with air spaces between for ventila- tion. A contact surface of one square inch per 100 amperes should be allowed at joints. 402 HYDROELECTRIC PLANTS. For heavy alternating currents the bus-bars may be m^de of tubing to keep down the losses due to skin effect. In high tension work (6000 or more volts) the bus-bars are not usually placed on the board, but mounted on porcelain insulators behind it. Where the boards are of such large size that a single attendant can not operate them the heavy switches are operated from a control board. Each switch is operated by an electric, pneu- matic or hydraulic motor, which is put in motion from a small board representing on a small scale the large one. All the measuring instruments are mounted on the control board: fine wires connect them to the large bus-bars on the main board. FIG. 385. FIG. 386. In an alternating current plant the current for operating the large switches is derived from a motor-generator in connection with a storage battery. Where the hydraulic head is sufficient, hydraulic pistons may be used, the valves being actuated by electro magnets. SWITCHES AND INSTRUMENTS. Each switch is proportioned to the current and voltage. The higher pressures broaden and complicate them, while the heavy currents make the switch heavy and bulky. They may consist of one or more blades and are designated by letters which indi- cate the type of instrument as follows: S.P.S.T. means single pole (one blade), single throw (handle of switch in Fig. 386 does not open more than 90). D.P.D.T. means double pole and double throw, as in Fig. 387, etc. Then the switches may or may not have fuses as in Fig. 388. POWER HOUSE EQUIPMENT. 403 All contact surfaces must be so proportioned as to carry but 50 amperes per square inch of surface. These contacts should at full load not heat to more than 50 degrees Fahrenheit above the atmosphere. A standard size for switch board panels is 62x30x2 inches for the main upper part, with a sub-base 28x30x2 inches. In polyphase work, where there are several units, the usual practice is to have one panel for each generator and one panel for each exciter. The generator panel has the ammeter, volt meters, generator switches, fuses, field switch fuses, pilot lamp for generator, and on the back of the panel a lightning arrester for each phase, a station transformer and a ground detector. Table XLIX gives the proper spacing distances for the me- tallic parts. Only in very small switches of high voltage should the- hinge a, Fig. 388, be made to carry the current. FIG. 388. For switch board work the switches have lugs of sufficient length to project through the board and receive the strips, washer and nuts. For higher tension switches of from 600 to 10,000 volts a bar- rier of marble, slate or glass is inserted between the poles or blades of the switch to prevent arcing, as in Fig. 389. This is really a single throw switch with one added contact making it a double throw suited for as high as 20,000 volts, though for tensions of from 6,000 to 20,000 volts an oil switch is considered the best. Fig. 390 shows a high tension switch in which A is a copper piston and C a lever on the front of the board by which the eight pistons are brought into contact with the eight contacts B. The eight cylinders D are of porcelain and divided into pairs, 404 HYDROELECTRIC PLANTS. each pair having a connection for a ;vire from the generator and one to the line. The eight tubes therefore take care of four circuits. Actual practice has demonstrated the oil switch to be the best, especially for inductive loads, and most compact for voltages up to 10,000, while for voltages above this a long break switch, is considered the most reliable, dependance being placed on the length of break alone, which for 6,600 volts is 30 inches, for 22,000 volts 6 feet. FIG. 389. FIG. 390. It is necessary to know the voltage of all machines connected to the board and also the voltage on the out-going feeders. The best, and what has become the standard voltmeter for direct currents is the Weston. It is mounted on the front of the board and a lamp provided to light the dial. All voltmeters must be dead beat and accurate to within 1 per cent, at all loads. It is quite essential to have at least two voltmeters so that one may be used as a check on the other, but it is not necessary to have one for each machine and feeder, as a multi-contact switch may be used to connect them with any circuit it is wished to get the voltage of. (See Fig. 391.) For alternating currents it is customary to connect the volt- meters through a transformer, so as not tc submit the instru- POWER HOUSE EQUIPMENT. 405 ment to the high tension. These potential transformers are attached to the back of the board, or placed on the wall. They are very small transformers and should not carry any other load than the voltmeter. Voltmeters are often mounted on swinging brackets at the ends of the board. The range of all voltmeters should be about 50 per cent, above normal load. For voltages of 10,000 and more an electrostatic voltmeter is often used. It may be connected in parallel across high ten- sion lines without the use of a transformer. Some voltmeters are so designed as to work on either alter- nating or continuous current. FIG. 391. A voltmeter switch which is largely in use is shown in Fig. 391. By plugging in between a and b and a' 6', any of the generators or feeders can be connected to the instrument. One of the feeder lines in Fig. 391 could be replaced by pilot wires run back to the center of distribution. Then by con- necting with the voltmeter the pressure at the far end of the line could be read. This method is only adapted for lines under two or three miles in length. A better way is to use a compensa- tor. This is a device by which the voltmeter Dreading is decreased by an amount equal to the drop in the line. The Westinghouse Mershon type is one of the best. The connections for the Mershon compensator are given in 406 HYDROELECTRIC PLANTS. Fig. 392. A is an ordinary potential transformer, B is an induc- tance and C a non-inductive resistance, and D and E are small transformers. This is the most common arrangement and is suitable for the most inductive loads, such as motors or motors FIG. 392. and lamps. For a small village lighting plant it is not thought necessary to use any such device as the telephone may be relied on to give warning of any dissatisfaction on the part ot the cus- tomers. FIG. 393. The Westinghouse Company manufactures a compensator suitable for lines having little self-induction, such as incandescent lighting. The connections are as in Fig. 393; / is the ordinary potential transformer. The voltmeter V is of the coil and POWER HOUSE EQUIPMENT. 407 plunger type. When the voltage at the distributing end is correct the hand of the voltmeter is at 0. The adjustment is obtained by plugging in along a, and by rotating the contact c. The Weston ammeter is the most widely used, whether direct or alternating, and is accurate to within 1 per cent, at all loads, and is also dead beat; that is, the oscillations soon cease after a change of load. Usually, where the current is moderate, say less than 250 am- peres, and the voltage not above 5,000, alternating current ammeters are connected directly in the main circuit, as in Fig. 394, but for high voltages and large currents a current trans- former is connected as shown in Fig. 395. A recording ammeter, whether for continuous or alternating current, should be part of every switch board equipment in order that the peak may be studied and due charges made. The Bristol Company of Waterbury, Conn., make both recording ammeters and voltmeters. - FIG. 394. FIG. 395. There should be an ammeter in each phase and one for the field exciting connections in addition to the watt-hour meters. The circuit-breaker is the safety valve of a switchboard. Its purpose is to open the circuit at times of short circuit and overloads. It commonly consists of a solenoid which operates a trigger, releasing the switch when the current exceeds a certain predetermined amount. These instruments are quite expen- sive and may be considered as a luxury in view of the fact that the ordinary fuses can be relied on to a certain extent. How- ever, it is an excellent plan to equip each generator and each feeder with a single -pole circuit-breaker. Circuit-breakers serve to protect against lightning, though they should not be relied on for this purpose. They may also take the place of a switch. A great advantage possessed by circuit-breakers over fuses is the ease and quickness with which the broken circuit may again be put in operation. They are 408 HYDROELECTRIC PLANTS. also much more accurate than a fuse. The circuit-breakers should be so constructed that the main line breaker will act somewhat behind the branch line breaker, otherwise the main breaker may operate at the same time the branch opens, thus needlessly interrupting the service. The contacts should be of carbon and the breaker should be able to carry a 75 per cent, overload. They may be had of as many poles as desired. A good plan is to have a circuit-breaker on each side of the circuit, in which case one side will open automatically if it is attempted to close the other, while the short remains. If a single- pole breaker is used connecting the generator to the board it is best practice to place it on the negative side. There are circuit- breakers which open the circuit for both too high and too low currents. These are used in connecting generators to storage batteries. Circuit-breakers are not quite so common on alternating current boards as they are on continuous current boards, but for high-tension transmission work they should certainly be used. When there is any uncertainty about the generators keeping in step, as in the case where turbines have no governors, it is advisable to connect them to the board through a breaker. After years of experience with the Niagara transmission to Buffalo, a circuit-breaking switch has recently been installed on each phase of the outgoing feeders. Thus three three-phase transmission lines have nine breakers. The voltage is 22,000 and it was found that the break of the switch had to be fully six feet. The best type for high tension work is undoubtedly the oil circuit-breaker. In this type the break may be much shorter, as the oil quenches the arc. Many boards have one oil circuit-breaker on each feeder panel, thereby protecting the board from overloads and shorts on the transmission line, but leaving the generators and exciters to the care of fuses. Fuses form the most common method of providing an auto- matic interruption of the circuit during overloads and shorts. It is to their cheapness that they owe their popularity, for they are the most unsatisfactory part of a board's equipment. De- pending on the fusing point of a metal, they are not at all accurate. POWER HOUSE EQUIPMENT. 409 A common way is to have the fuses a part of the switch for low-tension work, but for high-tension boards it is advisable to have the fuses on the back of the board. In Fig. 396 a General Electric fuse box is shown. The entire box may be pulled off the board, the slips c being only in fric- tional contact with the terminals t. These fuses are made for as high as 150 amperes and 2,500 volts. For higher tension boards the fuse blocks are placed at back of board and the blocks removed by means of an insulated pole some three or four feet in length to protect the operator from shocks. All fuses should be enclosed, and a common form is enclosed in a fiber or hard rubber tube. On alternating current switch boards the practice seems to be to eliminate fuses as much as possible, though it is still common to place fuses on the feeders. The wattmeter is to the power station what the journal and ledger are to the successful business man. In order to improve or FIG. 396. maintain the efficiency of the plant one should know the amount of power being sent out by each machine and by each feeder. These instruments are usually mounted on the board, though if the board is crowded or for any other reason, they may be placed near the generator. The power on a continuous current line may be obtained at any time by taking the product of the voltmeter and ammeter readings at the same instant, thus getting the power in watts, from which the horse power is obtained by dividing by 746 or the kilowatts by dividing by 1000. The wattmeter, however, indicates this product so that the watts may be read off directly by simply pushing a button. However, it is usually desirable to keep a record of the watt- hours, as the watt-hour is the unit on which the charge for power is based. To get this continuous all-day record the watt-hour meter 410 HYDROELECTRIC PLANTS. is used. The best known instrument for this purpose is the Thomson, which may be used with either alternating or con- tinuous current. In this instrument there are a number of dials at the top from which the total watt-hours may be read like the readings on a gas meter. Fig. 397 shows a Thomson watt-hour meter connected to a two wire line. FIG. 397. The power in alternating current circuits is equal to the pro- duct of the current and the in phase component of the e.m.f., and is obtained directly by connecting a wattmeter in each separate phase. In single-phase circuits the connections are precisely the same as in continuous current circuits. In un- FIG. 398. balanced two-phase circuits there should be a wattmeter in each phase. The total power equals the sum of the two readings, but in balanced two-phase circuits, such as motor load, there need be only one meter, and its reading, multiplied by two, will give the total power. In three-phase circuits only two meters are necessary, connected as shown in Fig. 398. The total power POWER HOUSE EQUIPMENT. 411 is equal to the sum of the readings. The energy, which is equal to the product of the power and the time, is obtained with a watt-hour meter. For single-phase circuits the connections are the same as for continuous current circuits. In two-phase circuits there should be two instruments if the load is unbalanced and one if balanced. The connection is the same as for single -phase, and the total energy is equal to the sum of the two readings, or twice the reading in one phase. In three-phase, star-connected loads, one meter will measure one third the energy; in some cases the meter may be connected FIG. 399. with an artificial neutral, as shown in Fig. 399. In unbalanced three-phase circuits two instruments connected as shown in Fig. 400 should be used. Where the pressure is over 550 and under 3,000 volts it is not thought advisable to pass the line voltage directly through the instrument, so small transformers (t) are used, as in Fig. 401. Induction watt-hour meters are sometimes used. These are for alternating currents only, and have to be adjusted to the par- ticular frequency of the line. They, however, have no com- mutator to get out of order. For series arc lighting the Thomson meter is connected as 412 HYDROELECTRIC PLANTS. in Fig. 402, a cut out, a, being provided to short circuit the line in case of an open circuit beyond. In the case of very heavy currents a special meter is used, shown in Fig. 403. FIG. 400. All meters should be accurate to within 3 per cent. They should maintain this accuracy throughout the load and be of sufficient size to carry the peak loads. They should not waste more than 1 per cent, of the energy delivered to them. FIG. 401. FIG. 402. The drop in voltage caused by its presence in the circuit should not exceed 0.25 per cent. It often becomes advisable to charge two rates, one for the short heavy peak loads, and another for the more steady average POWER HOUSE EQUIPMENT. 413 loads. For measuring this kind of a load a two rate meter is used. This instrument will record the two periods of load sepa- rately, thus allowing the desired rates to be changed. There are meters which record the ampere-hours instead of watt-hours, but these are not to be recommended for power house work. FIG. 403. LIGHTNING ARRESTERS. White some arresters work equally well on direct and alter- nating current circuits, the greater number do not. A very reli- able arrester is the Garton, which is shown in Fig. 404. The Westinghouse arrester is largely used on direct-current circuits up to 700 volts. FIG. 404. FIG. 405. r~ The General Electric Company puts out a magnetic blow-out arrester which has been largely used, especially on electric rail- way lines, etc., connections are shown in Fig. 405. These arresters are made for voltages up to 850. There should be one on each side of the line for added safety. 414 HYDROELECTRIC PLANTS. For alternating current practice the only satisfactory arresters are those using a series of cylinders, discs or spheres, having small air gaps between them and connected in series, the number depending on the voltage of the system. The Wurts arrester, made by the Westinghouse, and the FIG. 406. General Electric arresters are representative of this class. They are made for 1,000 volts, and when a line of higher voltage is to be protected enough are placed in series to sum up the required voltage, as in Fig. 406. To Switchboard -@ ToSwitchboarct FIG. 407. The General Electric arrester, shown in Fig 407, is installed for 10,000 volts. The choke coil for arresters may be made by coiling up about 150 feet of the line wire, .making a coil, about 15 inches in diameter. The ground indicated in the figures by must be very carefully made. A steel penstock or head POWER HOUSE EQUIPMENT. 415 rack makes a good ground, or a galvanized iron pipe driven 12 or 14 feet Into moist earth makes a good ground. All con- nections must be made as directly as possible and of ample size to carry the whole current. In remodeling the Niagara plant Westinghouse low-equivalent arresters were installed, as shown in Fig. 408. These protect a 22,000 volt system. Each phase of each circuit has an arrester. They are mounted on marble boards and each board is mounted on castors, so that if damaged it may be wheeled out and replaced by a spare. The arresters are connected to the feeder line through fuses. KAAAAAAAAAAAA FIG. 408. TRANSFORMERS. The office of the transformer is to change the voltage of an alternating current circuit from one value to another, or to change the system from one phase to another. They come in all sizes, from the potential transformer used on switch boards for voltmeters to those of thousands of watts capacity. In the large transformers above 25 kw. and below 75 kw. the case is usually filled with oil, which serves as an insulator. In some this oil is pumped in and out and cooled, while in others the case is given a large area to dissipate the heat by radiation. Still others are air cooled, a blower being constantly at work forcing air through the transformer. In the power house we have to deal with the small transformers 416 HYDROELECTRIC PLANTS, used in connection with the switchboard instruments and the large step up transformers connected to the main lines. The switch board potential transformers, etc., are only large enough to serve the instruments and are not intended to carry a load. They come all ready to place on the switch board and need no description. The same type of transformer is used for any number of phases, a separate transformer being placed in each phase. The following are the methods of cooling: (1) Self-cooling dry transformer, made for voltages up to 15,000 (2) Self-cooling oil-filled " " " 80,000 (3) Cooled by forced air curents " " 4) " " " water " " " (5) Cooled by both oil and water " " The over-heating of the transformer must be carefully guarded against and should never run above 80 degrees Centigrade. Thus, if the temperature of the room is 40 degrees Centigrade the interior of the transformer must not exceed it by more than 40 degrees Centigrade. Types (1) and (2) are more expensive to build than the other types, as more iron has to be used, but are the best, all things considered. The air cooled transformers are provided with air pipes con- necting with a blower. In large plants they are set over air- tight rooms or pipes having openings in the ceiling through which the air passes to the transformers setting over the holes. The air pressure, amount of air, etc., is given in Table L. TABLE L DATA ON THE COOLING OF AIR-BLAST TRANSFORMERS. Totai capacity of trans- formers, kw. Capacity of trans- formers, kw. Ounce pressure per cu. in. Cu. ft. air required per min. per transformer Size of blower, inches . Speed of blower, r.p.m. Output of blower cu. ft. per min. Power to drive blower, h.p. 300 50 .30 250 40 375 1,800 .25 900 100 .40 350 50 350 3,200 .60 1800 200 .50 600 CO 325 5,900 1.10 2700 300 .GO 850 70 310 8,300 2.25 4500 500 .80 1.300 80 310 13,000 4.25 6700 750 .90 1,800 90 295 17,600 6.75 7500 1 ,250 1.00 3.000 100 280 23,600 12.00 POWER HOUSE EQUIPMENT. 417 The power consumed in cooling an air cooled transformer is about 0.3 per cent., or less, of the power delivered. The approximate cost of transformers is from $4 to $7 per kw. An oil cooled transformer may simply have its case filled with oil, or the oil may be circulated by means of a pump. The case is- sometimes rilled with oil and water caused to circulate around and through the case to cool the oil. About one gallon of water per minute per 300 kw. is necessary in this case. These artificially cooled transformers are smaller in size than those depending alone on the radiation of the cases, but have the dis- advantage that should the pumps or blowers fail to act the tem- perature will run up. However, such transformers will stand such usage for an hour, and most faults can be remedied in that time. The pumping outfit should in all cases consist of two separate pumps. Thin transformer cases should be avoided, as in case of fire they become punctured and the oil escapes. The casing should be at least -inch thick. TABLE LI. Watts capacity. Core loss watts. Full load copper loss in watts. Regula- tion per cent . Efficiency. Weight in Ibs. Approx. cost. Full load. 1 load. i load. i load. 600 25 16.7 2.93 93.5 92.9 91.1 85.2 70 1,000 32 27.4 2.80 94.4 94.0 92.8 88.1 95 1,500 38 37.5 2.63 95.2 95.0 94.0 90.3 125 2,000 45 50.0 2.58 95.5 95.4 94.5 91.2 155 2,500 50 54.0 2.23 96.0 95.9 95.1 92.1 195 3,000 55 62.0 2.13 96.2 96.1 95.5 92.7 220 4,000 63 85.0 2.19 96.4 96.4 95.9 93.6 270 5,000 70 105.0 2.17 96.6 96.6 96.2 94.2 350 7,500 110 147.0 2.50 96.7 96.6 96.2 94.6 470 10.000 140 177.0 1.90 96.9 96.9 96.4 94.3 535 15,000 175 272.6 1.90 97.2 97.1 96.8 95.1 850 20,000 190 356.0 .94 97.3 97.4 97.2 95.9 995 25,000 220 460.0 .98 97.3 97.5 97.3 96.1 1210 30.000 250 495.0 .81 97.5 97.7 97.5 96.3 1500 40,000 390 590.0 .65 97.6 97.6 97.4 95.8 1780 50,000 460 690.0 .48 97.7 97.7 97.5 96.1 1900 The transformer is the weak link, and every precaution must be taken for its protection. If there is a break-down on the system the chances are three to one that the fault is with the 418 HYDROELECTRIC PLANTS. transformers. Lightning is the most dangerous foe and hence the latest and best arresters are none too good. A good plan, suggested by Professor Thomson, is that of interposing a metallic shield, connected to earth, between the primary and secondary windings. Another safety device invented by Professor Thomson con- sists of a thin paper film between two metallic points, one of which is connected to the line and the other to the ground. This automatically grounds the line, though it is not at all certain to act. One of the heroic measures for protection is to ground the secondary circuit. This is now permitted by the underwriters. All secondary circuits should be frequently tested for shorts. This is done by running test wires to the transformers and test- u u 4$$ n iS-S-3- LIH2I a cb FIGS. 409-412. ing with a ground detector on the board. Each year a complete insulation test should be made of every transformer. Trans- formers are also inserted in the primary to add to the protection given by the arresters. The cases of all large station trans- formers should be thoroughly grounded to protect the workmen. Figs. 409-412 show the most common methods of connecting the ordinary protective devices. Transformers being almost invariably used for constant poten- tial circuits they must be protected against heavy surges of current due to shorts on the line. The fuse, therefore, becomes a very important part of the transformer. The Stanley Company, the General Electric Company, West- inghouse and many others make fuses especially for transformers. They have removable blocks, so that the fuses may safely be replaced. Transformers may be wound tor polyphase, but the POWER HOUSE EQUIPMENT. 419 best practice is to use the single phase. Though requiring more iron the single phase arrangement permits the banking of the transformer, so that the disabling of one does not completely cripple the system. In selecting the size and efficiency of transformers it must be borne in mind that it is not always best practice to install transformers of the highest efficiency. The more efficient transformers are higher priced, and when the difference between the costs of two transformers becomes greater than the power saved by the more efficient transformer could be sold for, the cheaper transformer would be the proper one to adopt. The best power house practice is to use four, six, ten or more transformers banked together and having one transformer in reserve ready to be rolled into place. There is always danger of a transformer, especially the oil cooled type, catching fire, and it is quite important to provide for such contingencies. They should be in a separate room arid have switches arranged on their cases so that by merely opening the switch the transformer is disconnected from the line and ground. It is a good plan to have each transformer mounted on a truck to facilitate quick movement. Never, under any circumstances, install a cheap transformer. The standard transformers are quite reliable, but those which are not well known should be avoided. Table LII gives the proper sizes for transformers on three-phase motor circuits. Transformers will carry as great an overload as the generators, so their normal rating should be the same as that of the gen- erators. Small transformers, below 25 kw., may be placed on poles. The common practice nowadays, however, is to use a few large transformers at sub-stations rather than numerous small ones mounted on poles at the houses. It is not good practice to mount transformers on the walls of houses, though at times this has to be done, in which case precautions must be taken to insu- late them from the brick or woodwork. Parallel connection is not advisable for small transformers where it can be avoided. Transformers are often wound in sections, so that for high vol- tage they may be connected in series. Where it is wished to increase the primary voltage on an old 420 HYDROELECTRIC PLANTS. TABLE LII. PROPER CAPACITY OF TRANSFORMERS FOR S-PHASE MOTORS. Capacity of \Iotor in h.p. Capacity of transformers in kw. Two transformers. Three transformers. 1 O.G 0.0 2 1.5 1 .0 3 2.0 1.5 5 3.0 2.0 7 * 4.0 3.0 10 5.0 4.0 15 7.5 5.0 20 10.0 7.5 30 15.0 10.0 50 25.0 15.0 75 25.0 system, the primary windings of the old transformers may be connected in series. In four- wire, two-phase systems, unless motors are to be operated, the transformers are connected to each phase in the same manner as for a single phase, but where motors are run there E V3 FIG. 413. FIG. 414. must be one transformer for each phase, each having a capacity of one-half that of the motor or its rated overload. In three-phase work two types of connections are used, namely, the delta, J, and the star, Y, connections. The relative voltages and currents for 1:1 ratio are given in Figs. 413 and 414. POWER HOUSE EQUIPMENT. 421 Transformers may be used as phase changers (see Fig. 415). That is, a two-phase generator may be installed in the power house and the current changed to three-phase for transmission. This might be advisable where a part of the load is near by. This is the system at Niagara and in Fig. 415 are shown the connections for changing from two-phase to three-phase and then from three-phase back to two-phase. One transformer should have a transformation ratio of 100:10 and the other 100:8.67. This latter ratio for small transforma- tion is, in practice, made at 100:9. If the two transformers are wound the same or are interchangeable they must have a com- bined capacity of 12 per cent, more than the load. The 100:9 transformer is called a teaser and need be but 4 per cent, larger than would be normally required. For transforming the phases two transformers are usually used, which are made especially FIG. 415. for the work, having two connections, one giving 50 per cent, and the other 86. 7 per cent, the full voltage. In this case either transformer may serve as the teaser. STORAGE BATTERY. The storage battery is seldom used essentially in its storage sense, its cost prohibiting this, but invariably in the capacity of a regulator. Its importance is in almost direct proportion to the rapidity and magnitude of the fluctuations. The cost of a storage battery plant is high, but in all cases of engineering the only disideratum should be the relation between the total first cost and the future dividends, and when so considered the use of a battery plant will usually become a necessity for the follow- ing reasons: (1) The capacity of the generating units required to carry the abnormal peak loads is decreased, thus minimizing the first cost of the plant. 422 HYDROELECTRIC PLANTS. (2) The maintenance of better voltage regulation on the whole system. (3) The creation of a reserve force which may be utilized to carry a minimum load for a short time to permit of repairs, etc. (4) A reduction in the annual cost of producing a unit of energy. A generating unit, when run at full load, is from 10 to 30 per cent, more efficient than when running on such loads as are common to all power plants not equipped with batteries. The wear and tear on a plant carrying a fluctuating load is quite severe, and plays an important part in the depreciation item. Especially is this true of a turbine plant where the action of a powerful governor on the gates causes great wear and vibrations. (5) Increase of the capacity of transmission lines by carrying the peak loads at the point of use, thus making the line only carry the normal load. FIG. 416. FIG. 417. The most prominent makers of batteries are the Electric Storage Battery Company of Philadelphia and the Gould Stor- age Battery Company of New York. The Electric Storage Battery Company build the chloride battery and the Gould Company the Gould battery. For central station use, the cells are best made in the form of lead lined wooden tanks, eac.h cell or tank lining made somewhat longer than necessary to hold the plates first installed, so as to allow more plates to be added later on if found advisable. Being receptacles for the storage of energy under electrical pressure the cells themselves must be thoroughly insulated from the earth. This may be accomplished by placing each cell in a box of sand as in Fig. 416, and setting the box on four oil insulators, shown in Fig. 417, or, as is most frequently done, on porcelain insulators. The room must be provided with special ventilation to carry off the acid fumes. The frame work supporting the cells must POWER HOUSE EQUIPMENT. 423 be very strong, of wood and painted with an acid-proof paint. The plates contained in the cell constitute the element. The connections are all made by burning the terminals together. Great care must be taken to get pure acid and distilled water. The capacity of storage batteries is given in ampere-hours or watt-hours under a certain rate of discharge. Every battery has Its most efficient rate and if this is exceeded the capacity is lessened. If a cell can deliver 100 amperes for 10 hours on normal discharge its capacity will be 1000 ampere-hours, but If discharged in five hours its capacity may only be 800 ampere- hours. For this reason a sufficient number of batteries should be installed to carry at least 75 per cent, of the peak on a normal discharge. The watt-hour capacity is more trustworthy than the ampere- hour, for while the latter efficiency may be as high as 95 per cent, the former is seldom above 70 per cent, to 80 per cent. The new Edison battery weighs 57 pounds per kw.-hour capacity, and has a voltage per cell of from 1.1 to 1.5 volts. A battery having a capacity of 1000 kw.-hour capacity will, if all cells are on the same floor, take up about 100 square yards. The largest cells may consist of from 80 to 100 plates. A single cell, such as used in the power house, gives from 6 to 7 ampere-hours. Storage batteries must be charged at a slightly higher voltage than they are discharged at. This charging voltage averages from 2 to 2.5 volts per cell, and the discharging voltage will average from 2.5 to 1.8. While charging, the voltage is gradually increased so that two cells may require 40 volts at the start and 50 at the finish. This is usually done by means of the booster or cutting-out resistance from the generator field. Without some regulating device the voltage delivered to the line would drop off from 20x2.5 = 44 volts to 1.8x20 = 36.0 volts. To counteract this drop cells are added so that they may be thrown in one after another to keep up the pressure. These are called end cells. Cells should never be completely discharged, 1.8 volts being the minimum voltage of the discharge. To get the desired voltage for any system enough batteries are placed in series to give it: thus: 424 HYDROELECTRIC PLANTS. Desired Battery Voltage . T-TT : - r - - 7 ^h = number of cells. Minimum voltage of cell. Then to get the desired current groups of the cells in series as given by the above formula are connected in parallel, as in Fig. 418, where each cell has a capacity of 10 amperes. Sometimes there are not enough cells to take up the voltage of the machine , in which case a resistance is placed in series with the cells. The amount of this resistance is found by dividing the difference between the voltage of the batteries and the gen- erators, by the amperage of the battery. The usual office of a storage battery makes it necessary to automatically cause the cells to be charged during hours of light load and discharged during peak loads. In large plants, such as we are more especially treating, the regulation of the battery must be more rapid than hand regula- tion, and therefore a booster is used. This booster is a small FIG. 418. generator usually driven by a motor, and its action is as follows: The battery and the armature of the booster are in series. The booster field has two windings, one is a fine wire shunt, and the other a few turns of heavy wire in series with the main line. The field current may be adjusted by means of a shunt rheostat. The effect of the booster is that of a number of cells added in series with the battery. The shunt and field coils of the booster oppose each other in such a way that on normal discharge there is no e.m.f. generated. But when the line current falls below normal, the shunt coil, excited by the battery, takes effect and the booster delivers an e.m.f. which aids the generator in charging the batteries. When the line current is above normal due to a heavy load on the line, the series coil takes effect and forces the battery into helping carry part of the load. POWER HOUSE EQUIPMENT. 425 The electrolyte, consisting of sulphuric acid and water, must be of the purest ingredients. The water is placed in the cell first and the acid poured slowly into the water. After the mixture has cooled and within two hours, the plates are placed in position, connected, and the batteries slowly charged. It is advocated by some makers to charge the batteries for the first time at about one-third the normal rate. Charging at a higher rate than recommended by the makers should never be attempted A little overcharging does no harm, but results in a waste of current. When the cells are fully charged the following facts are ap- parent: Number of ampere-hours, i.e., the product of the reading of the ammeter and the time comes to the desired amount; the voltage reaches the maximum; the positive plate becomes very dark; gasing takes place, that is, gas is given off, making the electrolyte boil. When this last phenomenon has gone on 10 or 15 minutes the battery is charged. To prevent the escape of the gas the electrolyte is often covered an inch deep with paraffine and an inch-hole bored through to prevent the accumulation of pressure. Every cell must be easily accessible for examination and the plates and electrolyte frequently inspected. The plates become buckled in time and particles of the paste fall out and lodge between them. For this reason, frequent inspection is necessary to prevent short circuiting of the plates. Each cell must be thoroughly insulated from the earth. Cells should not be left standing for any great length of time without being charged, else sulphating will take place. Sulphating causes a scale to form over the plates, espe- cially on the positive plates, reducing the capacity of the cell and causing a buckling of the plates. Sulphating is removed by carefully scraping the plates, after which they are charged at a slow rate for some time. If a storage battery is to be put out of use for any great length of time, they should be fully charged, the electrolyte drawn off and the cells then filled with pure water. They should then be discharged at their normal rate. After the water has stood in the cells for some 48 hours it is then drawn off and the battery will remain in good condition. If the plates become slightly buckled they may be straightened by pressing, not pounding, between two boards. In Fig. 419 and 420 are given two load curves which were 426 HYDROELECTRIC PLANTS. taken at a large lighting and power station. The curve in Fig. 419 is a representative winter curve, and that shown in Fig. 420 was taken in the spring. The double hatched portion shows 1 i' | I 1*1 i* I I 1*1 l' I I I I I I I FIG. 419. the load carried by the battery, and the single hatched shows the charging load of the power plant. The battery was of the chloride type, having a 10,000 kw.-hr. capacity. Vtof. FIG. 420. It will be seen that the maximum peak load amounts to 1600 kw. above the average. That is, had there been no battery used, 1600 kw. more power would necessarily have been generated by POWER HOUSE EQUIPMENT. 427 machinery. Aside from the first cost, interest and depreciation of all this added machinery, it would have worked at full load only a small part of the day, so that its efficiency would have been very low. If the power had been generated by steam the boilers necessary for the peak loads would all have to be heated up and then allowed to cool down a very costly and injurious thing to do. The use of the storage battery, therefore, equalizes the load and permits a lesser number of generating units to work at their most efficient output. In Fig. 419 it will be seen that the batteries could have easily carried all the load there was between 1 and 5 a^m., if it had been necessary for a short time. However, if the battery had been installed with this point in view more battery power would have been required, as it is during those hours that the batteries must be charged. The efficiency of a storage battery being about 70 per cent, the power of the machinery must be so proportioned that the double shaded portion of the power curves is 70 per cent, of the single shaded portion, i.e., the battery should have a capacity 30 per cent, larger than the double shaded portion. In designing a plant, curves should be drawn approximating as nearly as possible what the actual practice will be, and the battery and machine capacity worked out from them ; then after the plant is in operation the curves may be brought to the desired form by regulating the charges for current. To generate the 1600 kw. by steam would cost, for machinery, about $130,000, and the added yearly maintenance cost of the machinery would be about as follows: Depreciation at 8 per cent, on $130,000 worth of machinery $10,400 Interest and insurance on $130,000 worth of machinery 8,000 Added cost of operating $130,000 worth of machinery . . 4,000 2 per cent, added depreciation due to operating 4860 kw., or $390,000 worth of machinery on uneven loads 7,800 $30,200 To get the watt-hour capacity of the battery multiply the hours the load is on by the average watts: thus take the case of the first peak in curve, Fig. 419; the average time is 4J hours 428 HYDROELECTRIC PLANTS. and the average load is about 1000 kw., which makes 4250 kw.- hrs., as the capacity required for that part of the load. Each peak is figured in the same way and the sum multiplied by 1 . 3 gives the necessary capacity of the battery. In the above case the required 10,000 kw.-hr. battery would cost $40,000 and the yearly cost of operation, depreciation, interest, etc., would be about $4000. Several companies guar- antee the maintenance to be 5 per cent, or less. Fig. 421 shows the load curves on a large central station plant for a week day and for Sunday. Taking the week day card: The station was provided with a 1000 kw. unit which was thrown on to the load at 12 a.m. It carried the load with good efficiency until about 7 o'clock, when another, a 3500 kw., unit was thrown in. At this time the ammeter did not show up a full load so the storage battery was connected and charging commenced. The ammeter showed the load was increasing on the line, so at 2.30 a 1500 kw. unit was put into service and the battery thrown out until 3 p.m., when the battery was put into the line. The three units kept up their load until midnight by feeding the battery as shown. In this case the battery saved 4000 kw. capacity in machinery. The Sunday card shows how the battery carried the entire load from 12 midnight until 2 p.m. In hydraulic transmissions the battery is placed at the far end of the line at the center of distribution. For alternating cur- rents a motor generator is required to change to direct current, in which case an attendant is required constantly at the sub-station. But where the transmission is by direct current only an occa- POWER HOUSE EQUIPMENT. 429 sional visit to inspect the battery is necessary, the booster being located at the power house. The location of the battery at the consumer's end of the line adds another valuable feature to the battery installation. It permits the use of a smaller feeder, or for the same size of wire reduces the line drop. This is because the peak current is never sent over the line, the battery supplying all excesses. Old plants find this method a good one for increasing their capacity without changing the size of feeders or installing extra machinery. On lighting loads a booster is used only to add a few volts to the generators, but on railway work the booster is so made that it regulates the batteries, causing them to charge and discharge. An end-cell switch is used in connection with the boosters. This sometimes consists of a sliding contact caused to move along the threaded shaft by means of a small motor made espe- cially for the purpose. A double throw single-pole switch is used to connect the battery either to the generator through the booster or directly to the line. MOTOR GENERATORS. Motor generators are motor-driven generators. They com- monly consist of a synchronous motor driving a direct current generator on either end of its shaft. The losses are those due to a synchronous motor and the losses of the two direct current generators. The most common use for the motor-generator is for convert- ing alternating current into continuous current for electric rail- ways, though it is also frequently used for lighting and power. In this way power may be transmitted by three-phase current to great distances and then changed to direct current for the use of the consumer. It serves the same purpose as the synchronous converter, but differs from the converter in that it operates perfectly on the higher frequencies. FREQUENCY CHANGERS. The frequency may be changed to suit the requirements by using a frequency changer. This consists of a synchronous motor directly connected to an induction motor. The current to be changed is led into the stationary field winding of the induction motor, called the primary, and taken from the rotor called the 430 HYDROELECTRIC PLANTS. secondary. The frequency and voltage of the out-put will depend on the speed of the secondary. If the frequency is to be increased the induction motor must be driven backwards, and if the frequency is to be decreased it is driven forwards. To change a frequency of 40 cycles to 60 cycles, the secondary would be run backivards at half speed, and to obtain 25 cycles from a 60 cycle current, the secondary would run forwards at about 0.4 times its rated speed. The capacity of the primary will have the same proportion to the out-put that the initial frequency has to the final. In table LIII data for a frequency changer of 100 kw. capa- TABLE LIII. INDUCTION MOTOR AS FREQUENCY CHANGER. Initial fre- quency. Final fre- quency. Primary capacity of ind. motor in kw. Secondary capacity of syn. motor in kw. Capacity of fre- quency changer in kw. Speed of ind. motor r.p.m. Speed of syn. motor r.p.m. Direction and speed of running. 40 60 33 66 100 400 800 Half speed back. 30 60 50 50 100 400 800 Full speed back. 25 60 58 42 100 400 800 336 forward. 60 25 42 58 100 400 800 1920 r.p.m.back. 60 30 50 50 100 400 800 Half-speed ahead. 60 40 66 33 100 400 800 Half-speed ahead. city are given. The proportions would remain the same for other sizes. The efficiency would not, of course, be 100 per cent., as has been assumed, but would depend on the efficiency of the two motors used. In each there would be a loss of from 4 to 10 per cent., depending on the size and running conditions. When driven backwards all mechanical losses are supplied by the driving motor, but when driven forwards the frequency converter may supply a part or all of the mechanical losses in the set. The object of a frequency changer is to permit the use of synchronous converters on a system where a high frequency is demanded and to reduce line drop. A synchronous converter will not operate satisfactorily on the higher frequencies, about POWER HOUSE EQUIPMENT. 431 25 being the best. Lighting service demands 60 cycles or more, and for long transmissions 25 cycles gives the smallest voltage drop. Therefore, to reconcile these oppositions recourse is had to the frequency changer. ALIGNMENT OF MACHINERY. One of the most necessary instruments for this work is the architect's level. Such an instrument costs about $60. It should be a 14-inch level with a vernier for getting angles. Reliable straight edges are indispensable. These should be three in number and 4, 6, and 8 feet long. Fig. 422 shows the best form. Where the engineer has much shaft aligning to do it will pay to have the instrument shown in Fig. 423. The blades G and frame are made of tool steel. By turning the thumb wheel C the screw H is revolved in the nut at F. The screw turns in Z7, which moves up and down with it. E is another nut in which the FIG. 422. left-handed thread on the screw works. In operation the blades are placed astride the shaft and the screw run down till it just touches the top of the shaft to be aligned. As H moves down- ward the nut E moves upward. In this way the pivot of the wings B always remain the same distance from the center line of the shaft. This makes it very handy where the line shaft consists of several different sizes. In leveling the point A is brought into line with the tight wire. To get the shaft level in the horizontal plane the architects' level is set up and the pivot B is leveled at different points along the shaft. Plumb lines should be very fine silk lines or steel wire. Plumb bobs should be heavy. Those filled with quick silver and weighing several pounds are the best. After the shafting is all in place it should be given a very careful aligning. The loss of power in shafting is mostly due to poor alignment. Where the bearings of a line shaft pass over masonry walls 432 HYDROELECTRIC PLANTS. the bearings are anchored to the wall, as in Fig. 424. The taper- ing boxes A should be well made, planed perfectly smooth on the outside and where placed in concrete well soaped or oiled. After the base of the bearing is placed and aligned the holes left by the removal of the boxes are filled with 1 to 1 cement-sand. At least i inch is left between the bottom of the bearing base and FIG. 423. the top of the masonry. This is to allow for any small error in the first alignment and to permit pouring underneath the iron, and also into the bolt holes, a strong mixture of cement. The tapering holes left by the boxes allow of shifting the bolt heads two inches or more each way before pouring the mixture. Fig. 424 shows one taper box removed, and the bearing in place ready to pour. The foundation bolts for engines and gen- erators are made in the same way. POWER HOUSE EQUIPMENT. 433 To avoid making a mistake in the spacing of the bolts a tem- plate should always be made, having the holes bored to exactly fit those in the base of the bearing or bed-plate. On this tem- plate the center lines may be marked to aid in aligning. It is of extreme importance on extensive work to make accu- rate measurements. Instrument makers now make steel tapes which at a certain temperature and tension are exact. Tension handles are made by Keuffel & Esser Co., of New York, so that the engineer will know when the tension is exact. A scale is also made giving the correction for different temperatures. A 100-foot tape is about J inch longer at summer heat than at the standard temperature of 62 degrees Fahrenheit. The en- gineer can have his tape certified at Washington by paying a dollar or so extra. Fie. JIM. FIG. 425. When working around power houses, the great foe to the steel tape is rust. The tapes may be nickel plated for from 50 cents to $2. The common way to get a line at right angles to another is to measure off certain distances as A B and A C (Fig. 425), and then to make the distance 2 + A O- The distances usually taken are 6 and 8, then V6 2 +8 2 = 10 Where great accuracy is required greater distances may be taken. There should be a vernier on the level, in which case it may be used for getting right angles. CHAPTER VIII. POWER TRANSMISSION There are in general four ways of driving machines from tur- bines, namely: direct connection; gears and shafting; belting; and rope drive. COUPLINGS. The line shaft is divided up so that there are as many lengths as there are pinions. Heavy shafts are seldom longer than 20 feet. Couplings are used to connect the various pieces. These may be the plain disc coupling, the plate coupling or the com- pression. The proportions of a disc coupling are given in terms of the shaft's diameter, in Fig. 426. The size and number of bolts used to hold the halves together may be found from: horse power transmitted x 33,000 Velocity of one bolt, ft. per min. XAfXGOOO = N = number of bolts. ; 6000 = safe shearing strength per square inch of bolt. Example: There is 500 h.p. to be transmitted. Shaft speed 225 r.p.m. Diameter of circle of bolt centers 16 inches. N. = .6 434 POWER TRANSMISSION. 43S bolts. The velocity of the bolts is 884 feet per minute, therefore, 500X33,000 = 52 884X6X6000 mches. The bolt of standard size nearest to this area is J-inch. In connecting the generators a coupling is often used which has a little give-and-take motion called a wabbler, so that if the line shaft and generator are not quite in line there will be no binding. (Fig. 427.) FIG. 427. A jaw clutch coupling, Fig. 428, is a handy arrangement where it is necessary to uncouple frequently and quickly. FIG. 428. FRICTION CLUTCHES. The friction clutch is a form of coupling which can be thrown in while one shaft is at full speed. They are made in all sizes itp to several thousand horse power. Clutches should be used only where absolutely necessary, as they are a weak link in the chain and get out of order easily. The bushings should be of bronze and self-oiling. The power transmitted by a clutch is proportional to the speed. 436 HYDROELECTRIC PLANTS. KEYS. Referring to Fig. 429, all dimensions being given in inches: for/2, /= + - Where the pinions are slid on the shaft there should be two keys, one on each side of the shaft. They should fit snugly, but loose enough to permit the gear being slid back by hand. Screws are used to hold the key and gear in place. QUILL SHAFTS. Fig. 430 shows an arrangement by means of which a gear or machine may be thrown out without affecting the line shaft. Thus two generators may be placed end to end on the same shaft, the generator next to the turbines being attached to the quill. Then this generator may be thrown out without stopping No. 2. No. 2 may be uncoupled, or uii-clutched, without stopping No. 1. While certain conditions often make a quill advisable, it should be avoided where possible, as it introduces complications. SHAFTING. In the every day transmission of power by shafting a large per cent, of the power is lost due to poor design. If the shaft springs, not only is the friction of the bearings increased, but also that of the gearing. Shafting should always be calculated for bending moments and torsional moments. The curves in Fig. 431 will quickly give the proper size of shaft for safe tensile strength of 7500 and shearing of 6000 pounds per square inch. Fig. 432 is for the purpose of getting the size for any other strength. Thus, if we find by Fig. 431 that a 6-inch shaft is required and we wish to know the proper size for POWER TRANSMISSION. 437 a safe strength of 20,000 pounds per square inch ; following up the vertical ordinate from 6, Fig. 432, it strikes the 20,000 pound curve at the horizontal line which indicates a 4 J-inch shaft. One of the largest of manufacturing plants some time ago, while building their plant, guessed at the size of some shafts on the heavy conveyors. The designer had figured them for the FIG. 431. Curves giving proper size of shaft for given twisting and bend- ing moments. FIG. 432. Diagram for getting new diameters when shaft has been figured from Fig. 431 POWER TRANSMISSION. torsional moments alone. When the plant started up six of the 24 shafts broke, and the author learned from good authority that the total cost caused by the accident amounted to over $20,000. Fig. 433 gives the proper allowance for different fits. These curves may be used for obtaining the size of bore in the gears or pulleys. FIG. 433. Diameters of shafts for various fits. The following formulas, given by Thurston and modified by Jones & Laughlins, will be found fairly safe, though where first class work is desired they may sometimes give a shaft too small. For head shafts well supported against springing For line shafting hangers 8 feet apart For transmission only, no pulleys; or short counters H.P. = H.P. = H.P. = H.P. = , but the bearing B gives the necessary rigidity. The bearing B should be at all times out of water. This view also shows how -the shaft is enlarged at the pinion. In this case the different turbines were thrown out of use by simply slipping the pinion out of gear. In Fig 436 two rods A are 446 HYDROELECTRIC PLANTS. shown. These run from bridge-tree to bridge-tree and tend to steady the entire harness. All bearing should be of the ball- and-socket ring oiling type. Roughly, a bridge- tree will cost $100, or about 4 cents per pound (without bearings). BELTING. Modern practice is to dispense with belts wherever possible, substituting an electric, a compressed air or a rope drive. How- ever, as they are still used to some extent, a briet treatment of the subject will be necessary. For steady, hard usage in dry places a good leather belt is preferable to all others. Leather belts will stand rubbing, such as caused by crossed belts, shifters, etc. For damp places the rubber or gandy belt is used. The power trans- mitted by the rubber and leather belt is about the same for the same tension. Ordinary belts will safely stand a tension of 45 pounds per inch of width for single belt and 75 pounds per lineal inch for double. This tension is exerted at the periphery of the pulley and becomes a measure of the power transmitted ; thus a single belt 10 inches wide runs over a pully at a speed of 1000 feet per minute, therefore 1000x10x45 , -33500- = 13 - 7h 'P- POWER TRANSMISSION. 447 The longer the belt the better, because a less tension has to be maintained, as the sag increases the arc of contact. It must be remembered that the effective tension is the differ- ence between the tension on the tight and loose sides when run- ning with a load. Therefore, calculate the tension necessary to pull the load and make the tension on the belt when idle equal to the safe tension less this effective tension. In selecting a belt it must be borne in mind that while the power transmitted is directly proportional to the tension, it is often a bad policy to get the necessary tension by merely tight- ening the belt or taking up the slack. On short spans it is better to get the necessary tension by adding to the weight of the belt, Fig. 438. This increases the sag and arc of contact. For pulleys over 12 inches diameter use a double or triple leather belt or a correspondingly heavy rubber or cotton belt. The latter when 6 to 7-ply has an effective pull 6/7 that of first-class single ply leather. FIG. 438. Wave motion on the slack side and running from side to side of pulley under light loads is caused by too thin a belt. This wave motion wears out bearings, shafting and belts. Avoid vertical belts. The angle should be at least 45 degrees. Avoid such long heavy belts that the allowable tension is exceeded. While the tensions given in the tables are considered good practice by some of the most reliable manufacturers, Taylor claims that if half the tension is used the life will be increased about 2.6 times. The efficiency will also be increased and the life of the bearings. For leather belts always place the hair side of the belt next the pulley as so placed it will transmit 30 per cent, more power than if the hair side is placed outside. For narrow belts run over small pulleys the distance between center should be at least 15 feet. For larger belts, say 6 to 12 inches, 20 to 25 feet and for the largest sizes 25 to 30 feet. Whang leather lacing makes the best fastening especially 448 HYDROELECTRIC PLANTS. for small pulleys, but large belts should be made continuous by splicing and cementing. Belts run best at high speeds (not more than 5000 feet per minute for single nor more than 4000 feet per minute for double leather belts). All belting should be laid out so that the slack side of the belt is on top, the pull being on the lower belt. The idler should be placed as close as possible to the smallest pulley regardless whether it is the driver or the driven. An idler (or tightener) is absolutely necessary on vertical belts; speed should not exceed 5000 feet per minute. A splendid splice for rubber belts is that shown in Fig. 439. The surfaces of one end of belt as a, a are given a coat of rubber dissolved in gasoline. The surfaces b, b of the other end are coated with rubber dissolved in bisulphide of carbon. Place in a press till dry. V* ' is, FIG. 439. The horse power per inch width is found from the following formula : S k = horse power, wherein 5 is the speed in feet per minute and k = 0.001665 for single leather belts and k = 0.002666 for double leather belts. For special cases we find the proper width from the above formula and then multiply by the coefficient C, given in the following: Double horizontal crossed belts C = 1.2 Single vertical open belts C = 1.8 Double vertical driver C = 2.0 Single horizontal, large driver to smal.l pulleys C 1.2 Double horizontal, large driver to small pulleys C = 1.3 Quarter turn single belts (7=1.5 Quarter turn double belts C = 1.8 Large belts transmit power with a loss of from 6 to 12 per cent. This includes the loss in the four bearings supporting the two pulleys. POWER TRANSMISSION. 449 ROPE TRANSMISSION. Rope transmission deserves a prominent place among trans- mitting devices. In cleanliness, efficiency and cheapness it is much superior to shafting and belts. It is adapted to the lightest or the heaviest power transmission. MANILLA HEMP AND COTTON ROPES. The usual transmission rope for long distances is of steel and consists of six strands having 19 wires to the strand. A hemp core is placed at the center to give pliability, but for short drives such as could be made with a belt a number of hemp or manilla ropes of three strands are used. TABLE LVI (C. W. Hunt). HORSE POWER OF MANILLA ROPE AT VARIOUS SPEEDS. u' P Speed of Rope in Feet per Minute. Smallest Diam. of Pulley. 1500 2000 2500 3000 3500 4000 4500 5000 6000 7000 2.2 8000 i 1.45 1.9 2.3 2.7 3. 3.2 3.4 3.1 2.2 20 in. I i 2.3 3.3 4.5 3.2 4.3 5.9 3.6 5.2 7.0 4.2 5.8 8.2 4.6 5.0 5.3 4.9 3.4 3.4 24 " 30 " 36 " 9.1 9.8 10.8 9.3 6.9 6.9 1 5.8 7.7 9.2 10.7 11.9 12.8 13.7 12.5 8.8 8.8 42 " 11 9.2 12.1 14.3 16.8 18.6 20.0 21.4 19.5 13.8 13.8 54 " H 13.1 17.4 20.7 23.1 26.8 28.8 30.8 28.2 19.8 19.8 60 " 11 18. 23.7 28.2 32.8 36.4 39.2 41.8 37.4 27.6 27.6 72 " 2 23.2 30.8 36.8 42.8 47.6 51.2 54.8 50.0 35.2 35.2 84 ' TABLE LVII (C. W. Hunt). PROPER SAG OF MANILLA ROPE. Distance between pulleys, feet. Driving side. Slack Side of Rope. All speeds. 80 ft. per sec. 60 ft. per sec. 40 ft. per sec. 40 4 inches 7 inches 9 inches 11 inches 60 10 17 20 " 23 80 17 " 28 " 34 39 100. 24 " 44 53 " 62 " 120 35 63 " 75 " 88 " 140 46 " 86 105 117 160 60 " 111 135 " 168 " 450 HYDROELECTRIC PLANTS TABLE LVIII. PROPER TENSION ON SLACK PART OF ROPE Speed of Rope, ft. per sec. Diameter of Rope and pounds tension on slack rope. 1" if* iy 11" 2" \ 8 4 s" 20 10 27 40 54 71 110 162 216 283 30 14 29 42 56 74 115 170 226 296 40 15 31 45 60 79 123 181 240 315 50 16 33 49 65 85 132 195 259 339 60 18 36 53 71 93 145 214 285 373 70 19 39 59 78 101 158 236 310 406 80 21 43 64 85 111 173 255 340 445 90 24 48 70 93 122 190 279 372 448 One or more grooves may be used the bottom of the groove being lined with wood or leather filling (Fig. 440), which lessens the wear on the rope. The wood filling is apt to get loose when e'xposed to the weather, and even the leather if left idle will loosen up. A filling consisting of alternate pieces of leather and rubber is the best. FIG. 441. ~~&ttp. azfy>. The efficiency of a rope drive is quite high, being about 96 per cent, in a single span drive and decreasing 2 per cent, for each relay or sub-division of the system as shown in Fig. 441. When several grooves are used they may be turned out of POWER TRANSMISSION. 451 the solid metal as shown in Fig. 442, no filling being used and the ropes not touching the bottom. The iron must be smooth and free from all flaws. TABLE LIX. HEMP ROPE, THREE STRANDS. Diameter of pulley* feet". Size of Rope. Strength Weight per ft., pounds. Length per lb., feet. Diameter, inches. Circum., inches. Breaking strength, Ibs. Safe strength. 21 6 17.1 324.000 10,800 9.4 .1064 19 5i 15.7 272,000 9,070 7.9 .1266 16.5 5 14.25 225,000 7,800 6.52 .1533 14 ' 4* 12.1 182,000 6,100 5 28 .1894 12 4 11.4 144,000 4,850 4.18 .2392 11 3J 10.7 126,000 4,100 3.67 .2725 10 3* 10. 110,000 3,500 3.2 .3125 9 3J 9.27 95,000 2,970 2.76 .3613 8 3 8.57 81,000 2,530 2.35 .4255 7 21 7.85 68,000 2,100 1.97 .5076 6 *ft 7.14 56,200 1,800 1.63 .6135 5.25 2J 6.43 45,500 1,420 1.32 .7575 4.25 2 5.70 36,000 1,100 1.04 .9615 3.4 If 5.10 27,500 900 .80 1.25 2.75 11 4.28 20,200 630 .588 1.700 2.1 11 3.97 14,000 430 .407 2.457 1.5 1 2.86 9,000 280 .261 3.831 1.22 1 2.5 6,900 210 .200 5.000 .97 I 2.14 5,050 150 .147 6.803 .74 1 1.78 3,500 100 .102 9.803 .53 .34 .18 i 1 1 1.43 1.07 .71 2,240 1,260 560 75 .065 .036 .016 15.38 27.77 62.5 The horse power transmitted by one rope is vD 2 II 825 where v is the velocity in feet per second, and D the diameter of rope in inches. 452 HYDROELECTRIC PLANTS. The tension on the slack rope when working is where 7 is the tension due to the transmitting of the power 4- the tension due to the weight of rope; F the centrifugal force, F== PV* ~ 32.2' where p is the weight of one foot of rope in pounds and v the velocity of rope in feet per second. The tension 7, due to 33000 XH the power is V , when V is the velocity of rope in feet per minute. In solving the above equation t may be taken from Table LVIII in finding 7. ~ c/ ~ -M*j a - e - c - *, $ FIG. 442. Table LVII gives the sag on the slack side of the rope to pro- duce the proper tension, or, the sag which would be produced by the tension given in Table LVIII. The most efficient drives are made with a large number of small ropes. A 5/16-inch rope running over 30-inch sheaves is the best for drives up to 20 h.p., ^-inch for drives of from 20 to 40 h.p. and f-inch for 40 to 80. Where the sheaves are of different diameters the ropes do not pull alike and therefore the angle of the grooves on the smaller pulley must be made less so as to get the same friction on both pulleys. On long out-door transmissions the large sheaves re- ceive heavy side pressures from the force of the wind and must be made strong laterally. It is advisable to place idlers to support the rope where on account of the space, the tension becomes excessive. POWER TRANSMISSION. 453 STEEL ROPES. Steel ropes are largely used for out-door work. The sheaves or pulleys are the same as for the soft ropes though they are more often without filling. As in the case of the soft ropes there must be a sufficient amount of friction between the sheaves and the rope to prevent slipping. This, having selected the proper diameter of pulley, is obtained by regulating the tension on the cable by means of a tail sheave and counter weight. The coefficient of friction, /, for sheaves is given as follows: Dry Wet Greasy Rope on a grooved iron pulley 120 .085 .070 Rope on a wood-filled pulley 235 .170 .140 Rope on a rubber and leather filling 495 .400 . 205 Then to find the proper weight W on the counter balance, W = C P, where P = ~ , is the useful pull on the rope, and C.is a constant depending on the above values of / and the number of ropes, N, used. C is given in Table LX. TABLE LX. VALUES OF C IN FINDING PROPER COUNTER WEIGHT. N. Number of ropes used on half laps. f. 1 2 3 4 5 6 .07 9.130 4.623 3.141 2.418 1.999 1.729 .085 7.536 3.833 2.629 2.047 1.714 1.505 120 5.345 2.777 1.953 1.570 1.358 1.232 .140 4.623 2.418 1.729 1.416 1.249 1.154 170 3.833 2.047 1.505 1.268 1.149 1.085 .205 3.212 1.762 1.338 1.165 1.083 1.043 235 2.831 1.592 1.245 1.110 1.051 1.024 .400 1.795 1.176 1.047 1.013 1.004 1.001 .495 1.538 1.095 1.019 1.004 1.001 Example: There are 400 h.p. to be transmitted; 2-inch rope; speed of rope = 3600 feet per minute ; 33000x400 3600 3666 pounds useful pull on the rope. 454 HYDROELECTRIC PLANTS. Find N, the number of ropes. The actual horse power trans- mitted may be found approximately from H = 3.1D 2 X*>, where D = diameter of rope and v = velocity in feet per second, therefore H = 3.1x4x60 = 74.4. But we have 400 h.p. to transmit, therefore, 400 =-7- -. = 5 . 37 = n ropes. 74.4 Taking 6 as the proper number and referring to Table LX for a wet rope on an iron pulley, C = 1 .505, W = C P. W = 1.505x3666 = 5517 pounds. TABLE LXI. PROPER DEFLECTION FOR WIRE ROPE. Span in feet ............. 50 100 150 200 250 300 350 400 450 Deflection in inches ...... 1.75 7 15.5 27.62 42.25 62.25 84.62 110.62 140 A less deflection than 3 inches corresponding to a span of 54 feet does not give satisfactory results. The maximum tension on the rope occurs at the ends and is given by when p is the weight of one foot of rope ; / the horizontal distance between pulleys in feet, and h the deflection given in Table LXI. To this tension must be added that due to transmitting the power or the useful pull, as above found. The horizontal pull on the pulley is the useful pull 4- 2 T'. If the tension T f is the W in the above formulas there will be no counter weight required, and in all cases the counter weight should equal W minus T. The sheaves should be of large diameter, as not only does the efficiency of the drive depend largely upon it, but also the wear of the ropes. For ropes of 7- wire strands the pulley should ha-e a diameter equal to 150 D; for 12 strands, 115 D; for 19 strands, 90 D, D being the diameter of the rope. POWER TRANSMISSION. 455 TABLE LXII. HORSE POWER OP WIRE ROPES. Diam. of wheel, feet. No. of revs. min. of pulley. Diam. of rope. H.P. Diam. of wheel, feet. No. of revs, per min. Diam. of rope. H.P. 3 80 i 3 7 140 A 35 3 100 i 3* 8 80 f 26 3 120 i 4 8 100 i 32 3 140 1 4i 8 120 f 39 4 80 1 4 8 140 f 45 4 100 1 5 9 80 f 47 4 120 1 6 9 100 I 59 4 140 i 7 9 120 f 70 5 80 A 9 9 140 1 83 5 100 A 11 10 80 H 66 5 120 A 13 10 100 H 83 5 140 A 15 10 120 H 97 6 80 * 14 10 140 H 116 6 100 \ 17 12 80 f 96 6 120 i 20 12 100 f 120 6 140 * 23 12 120 I 145 7 80 A 20 12 140 I 173 7 100 A 25 14 80 H 145 7 120 A 30 14 100 1ft 180 In figuring the strain on the rope the actual area of all the wires in the rope must be taken. Safe stress for iron rope is 24,640 pounds per square inch. Steel ropes are preferable to iron. For a long transmission such as several thousand feet, select a larger rope than the tables call for and run it at a low velocity over large sheaves. Support the ropes on large idlers every hundred feet or so. Such a trans- mission is well suited to hydraulic powers where the factory is some distance away from the power house. CARE OF THE ROPES. All steel or iron rope must be frequently oiled with linseed oil, tar or any oil free from acid. It should be very carefully uncoiled from the shipping coil to avoid kinks. 456 HYDROELECTRIC PLANTS. The nominal diameter of the rope is the diameter of the circle which just encloses it, and this diameter must always be given in ordering. Hoisting Ropes TABLE LXIII. 6 Strands of 19 Wires Each. Iron. Cast-Steel. Extra Strong Plow-Steel. II II Cast Steel. | 1 eg % c <0 H 0.39 8,800 2,933 17,600 5,867 20,200 6,733 22,800 7,600 F A n 0.30 6,800 2,267 13,600 4,533 15,600 5,200 17,700 5,900 'x 1 u 0.22 5,000 1,667 10,000 3,333 11,560 3,853 13,100 4.367 a A i 0.15 3,400 1,133 6,800 2,267 8,100 2,700 f f 0.10 2,400 800 4,800 1,600 5,400 1.800 ~r. Tensile strength 75,000 to 150,000 to 190,000 to 225,000 to of wire per sq. in. 90,000 ibs. 200,000 ibs. 225,000 ibs. 275,000 Ibs. TABLE LXIV. Bending Stresses 19- Wire Rope. Diam. of Bend. 6 8 10 12 14 16 18 20 22 24 26 Diam. of Rope. i 1,801 1,390 1,131 965 827 726 654 586 535 495 455 A 3,308 2,568 2,098 1,774 1,536 1,355 1,212 1,096 1,000 920 852 1 3,776 3,094 2,620 2,273 2,006 1,796 1,626 1,485 1,366 1,265 tr 5,351 4,546 3,951 3 494 3 132 2 838 2594 2 389 2 214 i 6,609 5,755 5,096 4,573 4,147 3,793 3,495 3,241 A 8,337 7,393 6,642 6,029 5,519 5,089 4,721 I 11,565 10,270 9,237 8,392 7,689 7,095 6,586 13,360 12,027 10,936 10,027 9,257 8,597 f 15,309 13,932 12 782 11 807 10 971 7 21 403 19 662 18 183 16 910 1 27 612 25 707 U 35,620 POWER TRANSMISSION. TABLE LXIV .Continued. 457 Diam. of Bend.j 28 30 36 48 1 60 72 84 | 96 108 120 Diam. 01 Rope. 1 i 423 398 338 250 200 167 144 126 112 101 A 795 742 621 468 376 314 270 236 210 189 1 1,178 1,102 924 698 561 469 403 353 314 283 A 2,063 1,931 1,620 1,226 986 824 708 621 553 498 * 3,021 2,829 2,376 1,800 1,448 1,212 1,042 913 813 733 ft 4,403 4,125 3,468; 2,630 2,118 1,773 1,525 1,338 1,191 1,074 1 6,145 5,759 4,847 3,680 2,967 2,485 2,135 1,876 1,671 1,506 H 8,024 7,524 6,201 4,818 3,886 3,257 2,802 2,459 2,191 1,976 1 10,245 9,609 8,101 6,165 4,977 4,173 3,591 3,153 2,809 2,534 1 15,805 14,835 12,528 9,556 7,724 6,481 5,583 4,886 4,371 3,943 i 24,047 22,589 19,113 14,614 11,830 9,937 8,566 7,528 6,714 6,059 H 33,347 31 ,347 26,566 20,357 16,500 13,872 11,966 10,523 9,387 8,474 U 42,036 35,683 27,400 22,239 18,713 16,153 14,209 12,682 11,452 H 48,109 37,028 30,096 25,350 21,897 19,272 17,209 15,545 H 61,238147,229 38,436 32,403 28,008 24,662 22,030 19,906 if J59,094 48,152 40,629 35,140 30,957 27,664 25,005 if . . |74,565 60,844 49,919 44,476 39,203 35,048 31,689 IX 90 325 73,795 62,379 54,022 47,639 42,606 38,534 1 8 2 88,409 74,795 64,814 57,183 51,160 46,285 2i 125,387 106,265 92,203 81,428 72,908 66,002 H 145,246 126,185 111,546 99,951 90,540 Tables LXIII and LXIV were calculated by Mr. William Hewitt, and are published here by his permission. The original, with other data on wire ropes, appeared in a pamphlet entitled "Wire Rope and its Ap- plication to Power Transmission," 1901, issued by Trenton Iron Com- pany, Trenton, N. J., from whom copies can be obtained. FRICTION AND BEARINGS. The coefficients of friction are designated by /, and to get the horse power required to drive a .shaft against this friction, we have : H = 4112 fWdn 33,000 where W is the total weight on the journal in pounds; d the diam. of journal in inches, n the revolutions per minute. A journal carries 10 feet of 6-inch shaft and a mortise gear weighing 2400 pounds. The shaft runs at 150 r.p.m. and weighs 900 pounds, therefore W = 3300 pounds and the horse power lost is 41 12x. 2x3300x150 33,000 '- is here taken for a mineral oil and 16 pounds pressure per square 458 HYDROELECTRIC PLANTS. inch, as .2. In addition to the above weights there may be the equivalent weight of the thrust due to the driving gear In the above example suppose 500 h.p. is transmitted. . The driving wheel is 6 feet in diameter and the pinion 4 feet. There will therefore be 500x33,000 velocity of tooth in feet per min. pounds pressure against the bearing due to this thrust or 8760 pounds. Adding this to the weight of shaft and gear, we have 41 12x. 2x12060x150 33,000 4.5 h.p. lost or about 1 per cent. Thvtrston gives the following coefficients of friction. TABLE LXV. VALUES OF f. Oils. Pressures. 8 Ib. per sq. in. 161b.persq. in. 321b.persq.in. 48 Ib.per sq. in. Sperm, lard, neat's foot, etc. .159 to .25 .138 to .192 .086 to .141 .077 to .144 Olive, cotton-seed, rape, etc. .16 to .283 .107 to .245 .101 to .168 .079 to .131 Cod and Menhaden .248 to .278 .124 to .167 .097 to .102 .081 to .122 Mineral oils .154 to .261 .145 to .233 .086 to .178 .094 to .222 Always place a bearing each side of a gear. Allow no over- hung gear. The standard size of shafting is given in inches, halves, and quarters of an inch, but in reality they are 1-16-inch smaller than their listed size. Thus a 5-inch shaft is actually 4 15-16 in diameter. For line shafts driving from vertical turbines at ordinary speed the length of the journal should be four times the diameter of shaft. Where necessary three times the diameter will do. Thurston gives the following list of proper lubricants : Low temperature as in rock j Light mineral lubricating oils, drills driven by compressed air. ( Very great pressures, low speed j Graphite, soapstone and other 1 solid substances. POWER TRANSMISSION. 459 Heavy pressures, low speed. j The above, and lard, tallow ( and other greases. Heavy pressures, high speed. ( Sperm-oil and heavy mineral ( oils, castor oil. Light pressures and high speed. ( Sperm, refined petroleum, olive ( rape, and cotton-seed oil. Ordinary machinery. TLard, oil, tallow oil, heavy min- heavy vegetable fLard, oil, tal < eral oils, t oils. Practically all bearings must be babited. Different work requires different grades of babit. For the bearings on turbine vertical and horizontal shafts hard babit is usually the best. FIG. 443. To babit the boxes, take the two halves of the box off the bridge- tree and bolt together with a piece of thin cardboard B between and center a piece of shaft A, Fig. 443. This shaft must be a full |-inch smaller than the regular shaft. With clay or cement, close up the ends and form at one end a funnel. Heat the whole bearing up so that it is so hot you cannot hold your hand upon it. Heat the babit in a ladle and pour quickly. Now take the halves apart, and with a pean, hammer the babit evenly over its surface to compress it somewhat. Then scrape the edges at C so that the bearing will come solidly together. Bolt the halves together and place in a lathe and bore out the bearing to fit the shaft. Such a bearing will wear much longer and run cooler than the usual cheaply made affair. Fig. 444 shows a bearing 460 HYDROELECTRIC PLANTS. of good design. It has a thrust collar and an oiling ring, also dust-proof ends which are filled with carded wool. FIG. 444. HIGH TENSION ELECTRIC TRANSMISSION. In high tension work it becomes exceedingly important to take the best possible care of the line from the time it leaves the FIG. 445. FIG. 446. switch-board. In leaving the building care must be taken to so locate the line that there will be no dripping eaves over it. POWER TRANSMISSION. 461 One method is to take the line out through the roof, as in Fig. 445. This was the plan adopted for the Missouri River 50,000-volt transmission plant. It has the defect of being open to snow drifts and sleet. A roof added as in Fig. 446 would serve as a great protection. POLES. The best practice to-day is to have two separate and distinct pole lines wherever the continuous operation of the plant is considered of great importance. The Missouri River transmis- sion line is 65 miles long and has two pole lines the whole distance, The pole lines should be far enough apart so that one line could not possibly fall across the other. Each line must have a cleared path wide enough so that no tree or limb can fall upon it. Highways should be avoided where a private right of way can be procured, on account of the danger of the insulators being thrown at or shot at by passing boys and nimrods. Wires pass- ing houses and play-grounds are constantly being crossed by kite strings, etc., and where the line has to pass such places 65-foot poles should be used. The proper height of the poles will depend entirely on the topography of the country, but generally speaking, outside of towns and in a clear field 35-foot poles should suffice. In Fig. 447 is shown a pole top used on the 50,000-volt transmission referred to above, Fig. 448 being a section of the glass insulator. The pin is of oak boiled in paraffin, and it was found that the pin alone would stand a pressure of 50,000 volts. The glass sleeve is to keep the pin dry. Poles carrying smaller wires than the above, say Nos. 6 to 2, could be placed 125 feet apart. There is a growing tendency to place the poles farther apart and make each pole a more per- fect insulating medium and approaching more nearly the tower. There are now a number of plants transmitting over steel towers placed several hundred feet apart. All wooden poles set in earth should be of good, sound, well- shaped, live cedar wood, not less than 7 or 8 inches in diameter at the top. They should be cut square at both ends and stripped of their bark. All knots should be trimmed off and no pole should have more than one curve in it. Standard specifications for cedar poles, with 5-inch tops 462 HYDROELECTRIC PLANTS. FIG. 448. POWER TRANSMISSION. 463 and 25 feet long and upwards, are as follows: All poles must be cut from live growing timber, peeled and reasonably well proportioned for their height. Tops must be reasonably sound and when seasoned must measure as follows: 5-inch tops must measure 15 inches in circumference ; 6-inch tops, 18j- inches; and 7-inch tops, 22 inches. If poles are green, fresh-cut or water soaked, the 5-inch tops must be 5 inches plump in diam- eter; 6-inch tops 19 J in circumference and 8-inch tops 22 J inches. TABLE LXVI. Height of Pole, 35 ft. to 45 ft. 50 " 55 ' 60 " 80 ' Depth of Hole. 5 feet. One way sweep allowable not exceeding one inch for every 5 feet. The part of the pole in the ground is not included in measure- ments for sweep. Butt rot in the center, including small ring rot outside the center must not exceed 10 per cent, the area of the butt. Butt rot which plainly seriously impairs the strength of the pole above ground is a defect. WinH shake is not a defect unless very unsightly. Rough, large knots, if sound and trimmed smooth are not a defect. W/XWJA FIG. 449. The depth a pole should be set in the ground depends on many conditions, such as character of soil, weight of the wires sup- ported, exposure to heavy winds, etc., but roughly, Table LXVI will give the depths which meet average conditions. The part of the pole in the ground is, of course, the first to decay, and though many methods have been adopted to preserve the wood, there is no definite knowledge on the subject yet. Hot tar and 464 HYDROELECTRIC PLANTS. carbolineutn are sometimes used. A good plan to preserve the poles from decay and also to protect them from grass fires is shown in Fig. 449. The hole is dug about 12 inches larger in diameter than the pole, the pole set in place and concrete rammed in. The concrete is mixed in a wagon fixed up especially for the purpose (see Fig. 450) ; and the holes all having been dug a gang of men go ahead and have each pole ready by the time the concrete wagon gets to it. This plan adds about $1.50 to $2 to the cost of the pole, but more than doubles the life. The FIG. 450. holes may be a foot shallower than given in Table LXVI, as the area of the concrete is greater than that of the bare pole. The strain on one pole carrying a heavy transmission line and tending to break it off at right angles to the line, may amount to as much as 4000 pounds, applied at top end, though this would only be the case where the wind amounted to a gale ; 2000 pounds is usually taken. Cedar is rapidly becoming exhausted, and within the last five years has almost doubled in price. It therefore becomes important to find a substitute. Oak is stouter than cedar, but POWER TRANSMISSION. 465 rots in the ground. The setting shown in Fig. 449 protects the pole from rot, and should permit the use of less durable woods. Fig. 451 shows a pole which depends for its lateral support upon three side guys of galvanized strand cable rather than upon the earth. Such a setting makes the installation of poles in rock an easy matter, as no holes have to be blasted. It is especially adapted to boggy or sandy ground, and serves to protect the poles from prairie fires, etc. Poles should not be guyed to trees or buildings. The average life of poles when set in the ground is given below: FIG. 451. Norway pine 7 years Chestnut 15 " Cypress 13 " White cedar 10 " By setting up longer poles than actually necessary at the start the decayed ends may be cut off and the reduced pole set in a new hole, thus doubling the life. The earth around the pole must be thoroughly tamped. The number of men required to set up a pole is given in Table LXVII though the number given may be somewhat re- duced in the case of poles 60 feet and over in length by having a good derrick mounted on a wagon especially fitted up for the purpose. Climbing spikes are made of 9/16 inch square iron 9 inches long and one man can drive about 200 to 250 per day. 466 HYDROELECTRIC PLANTS. TABLE LXVII. LABOR REQUIRED TO SET POLES. Height of Pole. No. men required. No. of poles set per day including digging 30 feet 40 " 6 with 7 " pikes 18 13 60 " 10 - derrick 70 " 12 " 80 " 15 " This is the age of concrete-steel construction and in no way is its application shown to better advantage than in concrete- steel poles. Fig. 452 shows a 35 foot concrete-steel pole ; at the top is cored a hole D to receive the top pin. The gain for the cross arm is one inch deep and the arm is bolted as shown in detail A B. The bolt is passed around the pole rather than through it to avoid touching the bars n. The reinforcing as here shown consists of I"x3" Kahn bars, but any other rein- forcing will make a good pole. POWER TRANSMISSION. 467 A 35-foot pole costs about $20, depending on the cost of the concrete, about J yard being required. A 45-foot pole will cost about $45. Such a pole will stand a greater transverse strain than will cedar pole and will last indefinitely; 2000 pounds horizontal pull at the top is usually allowed for large poles. FIG. 453. Frequently rivers, ravines or even bays have to be crossed with the transmission line, in which case the pole becomes a tower. The tower shown in Figs. 453 was built to carry four J-inch cables over a span of 6200 feet. The tower shown 468 HYDROELECTRIC PLANTS. is 65 feet high and the one at the other end is 225 feet high. Fig. 454 shows one of the four saddles carried on each tower. Each layer fastened with. FIG. 454. Fig. 455 shows the insulating link connecting the anchor and the cable, there being two connected to each cable. POWER TRANSMISSION. 469 The oil shown in Fig. 455 is for the purpose of keeping the micanite in a good state for insulation, it having been found to deteriorate. A span of 500 feet over a river was successfully accomplished by bringing the wires, No. 1, a complete turn over an 8xlO-inch timber, properly supported as in Fig. 456. Each of the four anchors is built on suspension bridge principles and resists a pull of 12 tons. The cables have a conductivity equal to No. FIG. 455. 2 copper, weigh 7080 pounds each, and have a sag 100 feet and have a breaking stress of 98,000 pounds. The voltage used is 60,000. The same principle may be carried out for smaller spans, building the towers of timber and using less massive insulators. On account of wind pressure and added strain due to the FIG. 456. falling of one or more poles, it is necessary to thoroughly brace up the line. Also at every turn of the line the corner pole must be well braced. On straight transmission line work every eighth pole should be thoroughly guyed. The rule is to allow 50 poles to the mile, the extra 6 or 10 poles serving for bracing and anchors. If the poles are of the type shown in Fig. 451 this will, of course, be unnecessary. At the end of a line the poles should be guyed as in Fig. 457, slack being left in the proportion shown, so that only a part of 470 HYDROELECTRIC PLANTS. the strain comes on any one of the poles. The dead men A (see Fig. 457) are usually slanted in the direction of the guy unless the soil is very hard. There are several patent anchors on the market, which are simply driven into the ground and expanded in place. A post hole auger may be used for sinking anchors. FIG. 457. CROSS ARMS. Cross arms may be of yellow pine, white oak, creosoted white pine, chestnut or any other first-class wood. For ordinary lighting lines the dimensions vary from 30 inches long, 3Jx4|-inches section, for 2-4-pin arms to 8 feet long, 3fx4f inches to 4x5-inches section, for 6-8-pin arms. They are fastened to the pole by means of two -J-inch to f-inch bolts or lag screws and gained into the pole J-inch. All arms of more than 4 pins must be braced with flat iron braces not less than 14"xjx27" bolted to the cross arm with f-inch carriage bolts and the two ends fastened to the pole with 4"xf" lag screw. On very high tension transmission lines these braces are sometimes made of wood, see Fig. 447. A general practice on transmission lines is to give the arms a thorough dipping in hot asphaltum compounds, sometimes a coating J-inch thick being obtained. This is applied after the wood has been well-seasoned and helps to prevent a break- down should an insulator give out. Boiling the arms in linseed oil is also a good plan. Cross arms should be placed so as to alternately face each other on adjacent poles and be back to back on the next two. This is to add safety to the bolts should several wires break or a pole fall. POWER TRANSMISSION. 471 Double cross arms, that, is one on each side of the pole must be placed at all abrupt changes in direction and on all end poles. PINS. Pins should be made of the very best material and are made of oak or locust or iron. If oak is used it must be well boiled in paraffin or linseed oil else they will decay inside of six or eight years. On the Missouri River transmission line, see Fig. 448, the pin is de- pended on to a certain extent for insulation. All pins should be bolted into the cross arm as in Fig. 447 FIG. 458. especially when the line passes over very hilly country, as other- wise a pole may be placed between two more lofty ones in which case there is a tendency to pull the pin out of its socket. If nailed, the moisture which collects around the pin will soon rust the nail off. The cost of the pin shown in Fig. 448 is about 25 cents. INSULATORS. In selecting the proper insulators it is sometimes hard to choose between glass and porcelain. Glass is transparent, which enables internal defects to be detected and renders the cavities undesirable tenements for insects. It does not present a very good mark to the small boy and lunatic. It is cheaper than porcelain. On the other hand porcelain may now be obtained in dull colors which do not attract the eye. They i72 HYDROELECTRIC PLANTS. may be chipped by bullets or stones without being entirely disabled. It is stronger than glass and less hydroscopic. How- ever, in actual practice both glass and porcelain have been used with good success. r FIG. 459. FIG. 460. On the 40,000 volt Provo transmission line, a glass insulator is used over 105 miles of line, see Fig. 459. The Edison Electric Company's 83 mile, 23,000 volt-line uses a porcelain insulator of about the same size as the glass one used in tne Provo system, and there seems to be much less FIG. 461. leakage of current. Much may be said for and against either glass or porcelain, but in view of the increased experience in porcelain manufacturing and the superior satisfaction now procured it is the author's opinion that porcelain is much the better for high tension work. POWER TRANSMISSION. 473 Porcelain insulators are made white or chocolate colored, the latter being preferred on account of being less conspicuous. For all ordinary pressures up to 2000 volts it might be well, on account of cheapness, to use a glass double petticoat insu- lator, something like Fig. 460. These cost $40 per thousand. FIG. 462. For potentials between 2000 and 5000, a glass insulator having more petticoats as in Fig. 461, costing about $55 per thousand should be used. For higher voltages, all things considered, porcelain should FIG. 463. be used. These larger porcelain insulators are made in two or more parts so as to avoid large pieces of porcelain, which could not be vitrified properly. These parts are fastened to- gether by means of sulphur (Fig. 458). Frequently a combina- 474 HYDROELECTRIC PLANTS. tion of glass and porcelain is used as in Fig. 462, made by the Locke Company. A porcelain insulator about 10 inches high and 9 inches in diameter, good for 30,000 to 40,000 volts, costs $500 to $750 per thousand. The R. Thomas & Company of East Liverpool, O., make a good line of insulators, one of which is shown in Fig. 463. This particular insulator was tested to 120,000 volts, it weighs 23 pounds and costs about $2500 per thousand. The common rule is to test the insulator with twice its work- FIG. 464. ing voltage, that is, it is given a factor of safety of 2, which is, for a three-phase line, equivalent to a factor of 3 between the wire and earth. It is a good plan to adapt the insulator to the conditions peculiar to the location even if a special design is required. The makers of the best insulators announce that they are ready to make insulators from designs furnished by the engineers. In Fig. 464 is shown the Niagara type used for a 11,000-volt transmission ; the one at the left is the old one and the one at tl:e right is the new one. POWER TRANSMISSION. 475 THE LINE. Transmission lines are frequently made of medium hard drawn copper or aluminium, though a large proportion are of hard- drawn copper. This latter has a breaking tensile strength of from 60,000 to 70,000 pounds per square inch, and while the conductivity is from 2 to 4 per cent, less than the annealed, and somewhat difficult to string up without injury, it is to be preferred. If the wires are larger than No. 1 or 0, it is best to use a stranded hard-drawn cable as it will be more flexible and is especially adapted to alternating current work. Aluminium has not been generally adopted yet, though there are some very important transmissions using it. It at first proved to be unreliable and is still difficult to solder. It has some very valuable features, however. It is cheaper than copper for the same conductivity and is 1.3 times larger in diameter than copper, and half as heavy. Its tensile strength should not be taken at more than 15,000 to 17,000 pounds per square inch. This increase in size of aluminium wire over copper would be a disadvantage were it not for the fact that the larger the wires the less the leakage between them. Were it not for the low tensile strength and added area ex- posed to wind pressure, the poles could be separated more for aluminium than for copper, but owing to these facts the same spacing is used in both cases. However, the strain is much less on the insulators. All aluminium transmission wires must be stranded to insure against breaking. All fastenings must be especially solid to prevent slipping as it wears rapidly. Wherever aluminium is joined with any other metal as solder, etc., it must be covered with a waterproof covering as otherwise a galvanic action will be set up which would soon destroy the joint. The Mclntyre joint is one of the best for this purpose. It consists of a tube slipped over the wires and then twisted together by means of a special tool. For long transmission allowance has to be made for the added electric capacity of aluminium wires, being about 5 per cent, more than for copper. A smaller copper wire than No. 5 should not be used for transmissions on account of its lack of strength. 476 HYDROELECTRIC PLANTS. On transmission lines the wires are strung in the top of the insulators in which case they are fastened as shown in Fig. 464 However, on the smaller side lines they are tied to the side as in Fig. 465. When a series tap is taken off, the connections are as shown in Fig. 466. In certain localities the wires have to be insulated with some continuous covering. This consists of an insulating compound and a protective covering. The best insulation has for the first covering some rubber composition and for the outer a moist FIG. 465. FIG. 466. hard cotton braid. If the wire is to be continually gutta-percha is better than rubber. The length of wire on a long transmission must be carefully figured as the sag between poles amounts to considerable amount. The length L (Fig. 467) between two poles A and B is Sd 2 L = and d = H + -. H 2 W 8 T where d is the sag in feet, at middle of span, H the span from A to B in feet, T the tension in pounds in wire at C and W the weight in pounds of wire per foot. FIG. "467. Due allowance must be made for changes in temperature, the tension, of course, being greatest in cold weather. From Table LXVIII it will be seen that if a wire is being strung between poles 100 feet apart, when the temperature is 80 degrees Fahren- heit, and give it a sag of If feet, the sag will only be .158 feet When the temperature falls to 10 degrees Fahrenheit. Then H 2 W the tension at that temperature and sag may from T = be found. Sd POWER TRANSMISSION. 477 In Table LXVIII. the column under the - 10 F. gives this sag when the wire is under a tension of 30,000 pounds per square inch, which is only allowing a factor of safety of 2 for medium hard drawn copper. It should be 4 as the tension T is directly proportional to the sag d. In the above case, by doubling the sag, the desired factor of safety will be obtained. Allowance must be made for an added weight of sleet and wind which together may add 20 to 30 pounds to the total weight per wire. A telephone is more than a luxury to a power station and should be one of the first things provided for. It is also of TABLE LXVIII. TEMPERATURE IN DEGREES F. Span in teet. -10 30 40 50 60 70 80 90 100 Deflection in Feet. 50 .041 .5 .666 .75 .75 .833 .916 .916 1 60 .0583 .666 .833 .916 .916 1.00 1.083 1.083 1.166 70 .0833 .833 .916 1.00 1.083 1.166 1.25 1.25 1.41 80 .100 .916 1.083 1.166 1.25 1.33 1.41 1.5 1.58 90 .133 1.083 .166 1.33 1.41 1.5 1.58 1.66 1.75 100 .158 1.166 .33 1.41 1.58 1.66 1.75 1.92 2.00 110 .192 1.33 .5 1.58 1.75 1 .83 2.00 2.08 2.18 120 .233 1.41 .58 1.75 1.83 2.00 2.18 2.25 2.33 140 .308 1 .66 .92 2.08 2.25 2.33 2.50 2.66 2.75 160 .408 1.92 2.18 2.33 2.50 2.66 2.83 3.00 3.16 180 .516 2.18 2.41 2.66 2.83 3.08 3.25 3.42 3.58 200 .641 2.58 2.75 3.00 3.16 3.42 3.58 3.75 4.00 great value during construction. The telephone line may be strung on the transmission pole line. It will then also serve as a leakage detector, as any great amount of leakage or a cross may be heard in the .receiver. In running the telephone lines on the transmission pole line the transpositions are sometimes made by placing brackets on the poles with both brackets on the same side of the pole, and at transpositions, placing the brackets on opposite sides of the pole, as in Fig. 468, one of the brackets being made long in the sketch simply to indicate the upper bracket, and shows how the upper wire is brought down under the bracket on the pole to the left. 478 HYDROELECTRIC PLANTS. These transpositions should be made about once to the mile on short lines and say six to eight times for the full length on longer ones. A very common way is to provide a two-pin arm for the telephone line and use a double type two-groove insula- tor at the transpositions. A No. 6 Bell lightning arrester should be installed at each end of the line, though not absolutely nec- essary. The greater the distance between the wires the greater the induciiion and therefore the greater the drop in voltage. There are, however, good reasons why the wires should be as far apart as possible. Birds frequently fly into the wires, especially owls; therefore if the wires are several feet apart, the wings of the birds cannot span them. In the West great trouble was experienced from cranes alighting on the wires, so that a dis- tance of from six to seven feet was found necessary between wires. FIG. 468. Sticks are often thrown across the wires, but if they are far enough apart it would take such a heavy stick that it could not be successfully thrown up to the line. The farther the wires are apart the greater may be the sag and therefore there will be less strain on the wires and insulators. The farther the wires are apart the less will be the leakage across the intervening air. It is well to calculate the inductive drop or inductive react- ance, as it is called, of the line, due to the spacing of the wires, where the distance is unusually great. The following method of calculating the line losses for alter- nating currents was given in the American Electrician of June, 1897, and as it takes into account the different spacing of the transmission wires, it is given here. EXAMPLE. Power to be delivered to the consumer is 250,000 watts; e.m.f. at the consumer's end of the line is 2000 volts; distance of transmission, 10,000 feet; distance between wires is 18 inches. POWER TRANSMISSION. 479 To start with, assume the size of wire as No. 0. The power factor is .80, and the frequency 60 cycles per second, or 7200 alternations per minute single -phase. orrj 000 - = 312,500 apparent watts to be delivered. 31 9 500 = 156.25 amperes (current in each wire). From Table LXIX, under the heading 18 inches and corre- sponding to a No. wire, we find .228. Then we have, 156.25 X10X.228 = 356.3 reactance volts. This amounts to 17.8 per cent, of the 2000. From the column headed resistance volts, we have for a No. wire and 18 inch spacing, .197. Therefore we have 156.25 X 10 X. 197 = 307.8 as the resistance volts lost. This is 15.4 per cent, of the 2000 volts. Now referring to the curves, Fig. 469, we follow up the ver- tical .8 to the first circle. At this point lay off the resistance volts in a horizontal direction to the right. From the end of this horizontal line thus laid off erect a perpendicular equal to the reactance volts lost. In this case, as shown, the top of the vertical comes nearly to the circle denoting a drop of 24 per cent. Therefore the drop in terms of the generator e.m.f. is We have found the resistance volts to be 307.8 and the cur- rent to be 156.25 amperes. Hence the power lost 307.8 X 156.25 = 48.1 kw. The per cent, loss is - - - r = 16.1 per cent. . 1 For two and three phase transmissions find the current in the conductors as in the following method (General Electric) and proceed as in the above example. 480 HYDROELECTRIC PLANTS, V POWER FIG. 469, POWER TRANSMISSION. 481 TABLE LXIX. DROP DUE TO INDUCTIVE REACTANCE. 1 J +J '~ H 2 '3 resistance volts per 1000ft. pole line. For 1 amp. Rea (\ be stance volts per IOC (0 ft. of pole line for one ampere 200 cycles per min. for distances given. /mean square). 7 tween conductors 1" 2" 3" 6" 9" 12" 18" 24" 30" 36" 0000 639 .098 .046 .079 .111 .130 .161 .180 .193 .212 .225 .235 .244 000 507 .124 .052 .085 .116 .135 .167 .185 .199 .217 .230 .241 .249 00 402 .156 .057 .090 .121 .140 .172 .190 .204 .222 .236 .246 .254 319 .197 .063 .095 .127 .145 .177 .196 .209 .228 .241 .251 .259 1 253 .248 .068 .101 .132 .151 .183 .201 .214 .233 .246 .256 .265 2 201 .313 .074 .106 .138 .156 .188 .206 .220 .238 .252 .262 .270 3 159 .394 .079 .112 .143 .162 .193 .212 .225 .244 .257 .267 .275 4 126 .497 .085 .117 .149 .167 .199 .217 .230 .249 .262 .272 .281 5 100 .627 .090 .121 .154 .172 .204 .223 .236 .254 .268 .278 .286 6 79 .791 .095 .127 .158 .178 .209 .228 .241 .260 .272 .283 .291 7 63 .997 .101 .132 .164 .183 .214 .233 .246 .265 .278 .288 .296 8 50 1.260 .106 .138 .169 .188 .220 .238 .252 .270 .284 .293 .302 A few years ago it was thought good engineering to allow a loss of 10 per cent or more in transmissions, but to-day a 5 per cent, loss on full load is the general rule for all but extremely long transmissions. This small loss is made possible by selecting high voltages an empirical rule being to use 1000 volts per mile approximately. Of course there are often other considerations which enter to influence the selection of voltage. The wiring formulas here given are about the simplest and most exact of any and are in the form .gotten out and used by the General Electric Company. They may be used to determine the size of copper conductors, volts loss in lines, current per conductor, and weight of copper per circuit for any system of electrical distribution. Area of conductor, circular mils = DXWXC PXE 2 Volts loss in lines = PXEXB 100 482 HYDROELECTRIC PLANTS. Current in main conductors = - = / Lbs. copper PXE 2 X 1,000,000 W = Total watts delivered. D = Distance of transmission (one way) in feet. P = Loss in line in per cent, of power delivered, that is of W E = Voltage between main conductors at receiving or con- sumer's end of circuit. For continuous current C = 2160, 7=1,5 = 1, and A = 6.04. Table LXX gives values of the constants C t T, B and A when applied to a. c. calculations. FIG. 470. FIG. 471, Vfce formulas are applicable to direct and alternating cur- rent systems, and may be used to find the size of wire to transmit any amount of power to any kind of load known to electrical engineering. In all alternating current transmissions the wires should be transposed at equal intervals, and be placed equidistant from one another, to equalize the inductive drop in the phases. Many transmissions have the wires 36 inches apart, though a greater distance is sometimes to be recommended. The two circuits of a quarter phase must be arranged as in Fig. 470 or Fig. 471. Fig. 471 shows the two circuits side by side though they may be above each other or in any position if that position is main- tained. The three wires of a three-phase transmission must be ar- POWER TRANSMISSION. 483 B 6,0 ^5 jS| H i o <-H 10 ^H Ifl So o X X S! 2 2 < O = 99 CO (N O5 H H NT. CTO PE OW O tr X CO CO Tj*oO^iOOiO be K K 'ffi ffi ffi o a W . o to Q to Q "> Q to Q to O ^ G "" W -7 a ^ a ffi 1 a 1 a 1 ffi o" 1 T3 g i 1 5 rt bo *& 5 i H a 1 Qf o H a rf -* O5 Si d W K ffi ffi W w ^ g II d i to X c5 1 a 1 3 1 a 1 0' | |t I*J|j w co" ffi CO K i ^ -M" .a* OH .! >i O f- s 3 w i t 1 00 H a E i ( co h ffi i a tn * t>. W d * 8'| 1 a 4- 1 * S3 1 8 ffi i-H co 5 ffi o o tc i (5 ffi !s n^ Jjl II S w x ^H * i ii O "tn fd 1 G 8 a -^ 8 00 o 00 t> H ^ -0 rfc* (]j W ( - u 1 CO 498 H YDROELECTRIC PLAN TS. The application of the kilowatt-hour formulas is exactly similar to the examples given above. EXAMPLE 2: Suppose that we have a reservoir whose super- ficial area is 12 acres and that we are able to draw down the surface two feet and utilize the water under a head of 20 feet. What is the number of horse-power-hours per acre, assuming an efficiency of 60 per cent. Referring to the proper formula in Table LXXII we have 0.825X20X12 = 198 horse-power hours per acre foot. Since we are going to use two feet, there will be twice this amount or 396 horse-power hours per acre. If this energy is utilized during 10 hours we would have 39.6 horse-power; if it TABLE LXXIII. THE HORSE-POWER IN WATER, FLOWING AT THE RATE OF ONE CUBIC FOOT PER MINUTE AND OPERATING UNDER VARIOUS HEADS AT AN EFFICIENCY OF 85 PER CENT. Head h.p. of in 1 cu. ft. feet, of water. Head. h.p. Head. h.p. Head. h.p. Head. 'h.p. 1 .0016088 36 .057953 100 .160980 320 .515136 640 1 .030272 2 .0032196 38 .061172 105 . 169029 330 .531234 650 .04637 3 .0048294 40 .06439 110 .177078 340 .547332 660 .062468 4 .0064392 42 .067612 115 .185127 350 .563430 670 .078566 5 .008049 44 .070831 120 .193176 360 .579528 680 .094664 6 .0096588 46 .074051 125 .201225 370 .595626 690 1.110762 7 .0112686 48 .07727 130 .209274 380 .611724 700 1.12686 8 .0128784 .08049 135 .217323 390 .627822 710 1.142958 9 .0144882 52 .08371 140 .225372 400 .643920 720 1.159056 10 .016089 54 .086929 145 .233421 410 .660018 730 1.175154 11 .0177078 56 .090149 150 .241470 420 .676116 740 12 .0193176 58 .093368 155 .249519 430 .692214 750 1.20735 13 .020927 60 .096588 160 .257568 440 .708312 760 14 .022537 62 .099807 165 .265617 450 .724410 780 15 .024147 64 . 103027 170 .273666 460 . 740508 790 16 .025757 66 . 106247 175 .281715 470 .756606 800 1.28780 17 .027366 68 . 109466 180 .289764 480 .772704 820 18 .028876 70 .112686 185 .297813 490 .788802 840 19 .030586 72 .115906 190 .305862 500 .804900 860 20 .032196 74 .119125 195 .313911 510 .820998 880 21 .0338058 76 .122345 200 .321960 520 .837096 900 1.44882 22 .0354156 78 .125564 210 .338058 530 .853194 920 23 .037025 80 .128784 220 .354156 540 .869292 940 24 .038635 82 .132004 230 .370254 550 .885690 960 25 .040245 84 .135223 240 .386352 560 .901488 980 26 .041855 86 . 138443 250 .402450 570 .917586 1000 1.60980 27 .043464 88 .141662 260 .418548 580 .933684 28 .045074 90 .144882 270 .434646 590 .949782 29 .046684 92 .148102 280 .450744 600 .965880 30 .048294 94 .151321 290 .466842 610 .981978 32 .051514 96 .154508 300 .482940 620 .998076 34 .054733 98 .157760 310 .499038 630 1 .014174 TABLES AND FORMULAS. 499 TABLE LXXIV. THEORETICAL KILOWATTS IN WATER FLOWING AT THE RATE OF ONE CUBIC FOOT PER MINUTE AND OPERATING UNDER VARIOUS HEADS. Head. kw. Head. kw. Head. kw. Head. kw. Head. kw. 4 .00565 100 .1413 330 .4663 560 .7913 790 .116 5 .00706 105 .1483 335 .4734 565 .7984 795 .123 6 .00848 110 .1554 340 .4804 570 .8054 800 .130 7 .00989 115 .1625 345 .4875 575 .8125 805 .137 8 .01130 120 .1659 350 .4946 580 .8195 810 .145 9 .01271 125 .1766 355 .5016 585 .8266 815 .1516 10 .01413 130 .1837 360 .5087 590 .8337 820 .159 11 .01554 135 .1907 365 .5 57 595 .8407 825 .166 12 .01695 140 .1978 370 .5288 600 .8478 830 .173 13 .01837 145 .2049 375 .5299 605 .8548 835 .181 14 .01978 150 .21195 380 .5369 610 .8619 840 .188 15 .02159 155 .2190 385 .5440 615 .8690 845 .195 16 .0226 160 .2260 390 .5510 620 .8760 850 .201 17 .02402 165 .2331 395 .5580 625 .8830 855 .208 18 .0254 170 .2402 400 .5650 630 .8902 860 .215 19 .02684 175 .2477 405 .5720 635 .8970 865 .2222 20 .02826 180 .2543 410 .5790 640 .9040 870 1.229 21 .02967 185 .2614 415 .5864 645 .9112 875 1.2364 22 .031086 190 .2684 420 .5935 650 .9184 880 1.2434 23 .03259 195 .2755 425 .6005 655 .9255 885 1.2505 24 .03391 200 .2826 430 .6076 660 .9326 890 1.2576 25 .0353 205 .2895 435 .61466 665 .9396 895 1.2646 26 .0367 210 .2966 440 .62173 670 .9467 900 1.2717 27 .03815 215 .3037 445 .6288 675 .9538 905 1.2787 28 .03956 220 .3107 450 .6359 680 .9608 910 1.2858 29 .04097 225 .3179 455 .6429 685 .9674 915 1 . 2929 30 .0424 230 .3245 460 .6500 690 .9750 920 1.2300 32 .0452 235 .3320 465 .6570 695 .9820 925 1.307 34 .04804 240 .3390 470 .6640 700 .9890 930 1.314 36 .05086 245 .3462 475 .6712 705 .9960 935 .3211 38 .0537 250 .3530 480 .6782 710 .003 940 .3282 40 .0565 255 .3603 485 .6853 715 .0103 945 .3353 42 .05934 260 .3674 490 .6924 720 .0173 950 .3423 44 .06217 265 .3744 495 .6994 725 .0244 955 .3494 46 .065 270 .3815 500 .7065 730 .0315 960 .3565 48 .0677 275 .3886 505 .71360 735 .1390 965 .3635 50 .07065 280 .3956 510 .72060 740 .0426 970 .37 55 .0777 285 .4027 515 .7277 745 .053 975 .377 60 .08478 290 .4098 520 .7348 750 .0600 980 .384 65 .09184 295 .4168 525 .7418 755 .067 985 .391 70 .0989 300 .4239 530 .7489 760 .074 990 .399 75 .1059 305 .4310 535 .7560 765 .081 995 .406 80 .11304 310 .4380 540 .7630 770 .088 1000 .413 85 .1211 315 .4451 545 .7700 775 .095 90 .12717 320 .4522 550 .7770 780 .103 95 .1342 325 .4592 555 .7842 785 .110 500 HYDROELECTRIC PLANTS. is utilized in one hour we would have 396 horse-power. If this energy can be sold for lighting purpose and brings for ex- ample seven cents per horse-power-hour each acre-foot of reser- TABLE LXXV. THE THEORETICAL KILOWATT-HOURS AND HORSE-POWER-HOURS PER ACRE-FOOT OF STORAGE AREA FOR DIFFERENT HEADS. Head ft. En h.p.-hr. ergy. kw.-hr. Head ft. En h.p.-hr. ergy. kw.-hr. Head ft. En h.p.-hr. ergy. kw.-hr. . 4 5.5 4.103 150 206 . 25 153.863 580 797.50 594.93 5 6.88 5.129 160 220. 164.120 590 811.25 605 . 19 6 8.25 6.155 170 233 . 75 174.378 600 825.00 615.45 7 9.62 7.180 180 247.50 184.635 610 838.75 625.71 8 11.00 8.206 190 261.25 194.893 620 852.50 635.96 9 12.37 9.232 200 275.00 205.150 630 866.25 646.22 10 13.75 10.258 210 288.75 215.408 640 880.00 656.48 11 15.12 11.283 220 302.50 225.666 650 893.75 666.74 12 16.50 12.309 230 316.25 235.923 660 907.50 676.99 13 17.90 13.335 240 330.00 246.180 670 921.25 687.25 14 19.24 14.361 250 343.75 256.438 680 935.00 697.51 15 20.62 15.386 260 357.50 266 . 69 690 948.75 707 . 77 16 22.00 16.412 270 371.25 276.95 700 962.50 717.92 17 23.37 17.438 280 385.00 287.21 710 976.25 728.18 18 24.75 18.464 290 398.75 297.47 720 990.00 738.44 19 26.13 19.489 300 412.50 307.72 730 1003.75 748.70 20 27.50 20.515 310 426 . 25 317.98 740 1017.50 758.95 21 28.87 21.54 320 440.00 328.24 750 1031.25 769.21 22 30.25 22.566 330 453.75 338.50 760 1045.00 779 . 47 23 31.62 23.592 340 467.50 348.75 770 1058.75 789.72 24 33.00 24.618 350 481.25 359.01 780 1072.50 799.98 25 34.37 25.644 360 495.00 369.27 790 1086.25 810.24 26 35.75 26.670 370 508.75 379.53 800 1100.00 820.50 27 37.12 27.699 380 522.50 389.78 810 1113.75 830.76 28 38.49 28.72 390 536.25 400.04 820 1127.50 841.01 30 41.25 30.772 400 550.00 410.30 830 1141.25 851.27 32 44.00 32.824 410 563.75 420.56 840 1155.00 861.53 35 48.12 35.901 420 577.50 430.81 850 1168.75 871.79 40 55.00 41.030 430 591.25 441.07 860 1182.50 882.04 45 61.87 46 . 159 440 605.00 451 .33 870 1196.25 892.30 50 68.75 51.288 450 618.75 461.59 880 1210.00 902.56 55 75.62 56.416 460 632.50 471 .84 890 1223.75 912.82 60 82.50 61.538 470 646.25 482 . 10 900 1237.50 923.07 65 89.37 66.667 480 660.00 492.36 910 1251.25 933 . 43 70 96.25 71 .803 490 673.75 502.62 920 1265.00 943.69 75 103.12 76.931 500 687.50 512.87 930 1278.75 953.95 80 110.00 82.060 510 701.25 523.13 940 1292.50 964.20 90 123.75 92.318 520 715.00 533.39 950 1306.25 974 . 46 100 137.50 102.575 530 728.75 543.65 960 1320.00 984.72 110 151.25 112.833 540 742.50 553.90 970 1333.75 994.98 120 165.00 123.092 550 756.25 564.16 980 1347.50 1005 . 23 130 178.80 133.348 560 770.00 574 . 42 990 1361.25 1015.49 140 192.50 143.605 570 783.75 584.68 1000 1375.00 1025.75 voir area will bring $13.86 each time it is passed through the turbines. TABLES AND FORMULAS. 501 COMPARISON OF THE VALUE OF POWER WHEN EXPRESSED IN HORSE-POWER PER YEAR OR KlLOWATT PER YEAR. Since the power of a stream is usually sold in terms of kilowatt- hours, it is often necessary to transfer horse-power-hours to kilowatt-hours; for example, if one horse-power is used every hour of the year (8,760) there would be used 8,760 horse-power- hours per year. This expressed in kilowatt-hours would equal 6,535 kilowatt-hours. If one horse-power is used 10 hours a day for a year (3,598 hours) the total energy would be 3,598 horse-power-hours which is 2,684 kilowatt-hours. Table LXXVI gives the value for different periods of use of one horse-power when sold at one cent per kilowatt-hour and vice versa. For any other price, multiply the values given in Table LXXVI by the price in cents. TABLE LXXVI. COST OF POWER FOR DIFFERENT PERIODS OF USE. Hours one kw. is used per day. Cost per kw. year at Ic. kw. (1) and h.p. per per kw.-hr. h.p. (2) Cost per h.p. year at Ic. ] h.p. (3) and kw. per aer h p.-hr. kw. (4) Hours used per year. 24 $87.60 $65.70 $87.60 $109.50 8.760 10 31.30 23.47 31.30 34.12 3,130 8 29.20 21.09 29.20 36.50 2,920 8* 25.04 18.78 25.04 31.30 2,504 6* 21.90 16.42 21.90 27.37 2,190 * Including Sundays. APPLICATION OF TABLE LXXVI. If horse-power is worth $50.00 for a year of 3,130 hours and, it is desired to know how much this will be per kilowatt-hour divide $50.00 by the price per horse-power in column 2. Thus, $50.00 23.47 = 2.13 cents per kilowatt-hour. Again suppose the price to be $25.00 per kilowatt for a year of 2,920 hours the price per kilowatt-hour being desired, then $25.00 divided by the cost of one kilowatt at one cent per hour, that is, $29.20 gives 0.856 cents per kilowatt-hour. INDEX. ABUTMENTS, amount of material in, 278. design of, 278. reinforced concrete, 280. solid concrete, 279. Air engine. See Motors. Air flow in pipes, 30. heating of, 379. moisting of, 378. motors. See Motors. valves in penstocks, 352. Alignment of machinery, 43 1 . Aluminum for bus-bars, 400. line, wire, 475. tensile strength, 475. Ammeter. See Instruments. Anchor ice, 299. protecion against, 300. Anderson Dam, profile of, 239. Angle of repose, rule for, 189. Arches, concrete forms for, 95. Architecture for power house, 330. Austin Dam, profile of, 239. BACK water conditions, 340. Batch mixer, 93. Beams, concrete-steel, 120. design of, 126, 128. general formulas, 114. properties of, 123. Beardsley current meter, 36. Bearing strength of various mate- rials, 124. Bearings. See Power Transmis- sion. alignment of, 431. installation of, 432. Belle Fourche dam, 270. Belting. See Power transmission. Blasting machine, cost of, 159. Boilers, See Power plants. Boosters, 424. Bouzey Dam, profile of, 239. Brick wall, cost of, 112. Bridges, design of, 164. Bridge-trees, 445. cost of, 446. Building blocks, 111. cost of, 112. moulds for, 111. Buoyancy, 2. Burnt clay, 88. Bus-bars, contact surface, 401. design of, 400, 401. high-tension, 402. skin effect, 402. CABLES, deflection of, 162. Cableways, 159. cheap, 160. for dam construction, 160. Caisson, cost of excavation from, 179. cost of sinking, 179. design of, 175. Canals, banks, shape of, 31. excavation, cost, 191. flow in, 31. lining of, 189. cost of, 190. effect on flow, 190. location of, 187. masonry, 192. reinforced concrete, 192. velocities, for various soils, 32. Cement, 69. chemical analysis, 71. consistency of, 74. fineness of, 73-83. kinds of, 70 purity, 84. sampling of, 70. soundness, 83. specific gravity, 72. testing, 70. beam test, 85. constancy of volume, 81. mixing, 78. molding, 79. molds, 78. simple, 82. storage of pieces, 80. tensile strength, 80. time of setting, 76-83. uses of, 85. weight, 85. Center of gravity, method of find- ing, 256. Channeling machine, 155. cost of, 155. 503 504 INDEX. Chimneys, design of, 386. foundations, 386. guying of, 386. Churn drilling, 149. Circuit-breaker, 407. high tension, 408. installment, 408. Clay, shrinkage of, 268. Coefficient of roughness, values of, 22. Coffer dams, 169. cost of, 174. horse type, 171. cost of, 173. ordinary type, 174. sand bag type, 169. sacks necessary to build, 171. truss bridge type, 173. Columbus Dam, profile of, 239. Columns, design of, 122, 129. general formulas, 114. Compensator, 405, 406. Compressed air, See Air. Concrete, 69. abutments, cost of, 110. aggregates, for various pur- poses, 87. amount of water used in mix- ing, 87. bus hammering, 112 coloring of, 112. crushing strength, 122. expansion of, 100. exposed to sun, 100. facing boards, 97. forms, building of, 94. freezing weather, 91-100. hand mixed, cost of, 89. hand mixing methods, 90. laid under water, 98. laying of, 99. machine mixing, methods, 92. piles, See Piles. rock work, 96. shrinkage of, 102. strength, effect, of age and frost, 101. strength of, for various ages, 91. surfacing of, 96. tensile strength, 100. weight of, 86. work, cost of, 88. Concrete-steel, 102. beams, design of, 120. hollow construction, 104. forms for, 104. power house, cost of, 110. Copper bus-bars, 400. line, wire, 475. Cornell experiments on flow-over dams, 14. Cost of: brick penstocks, 208. walls, 112. bridge-trees, 446. building blocks, 112. canal lining, 190. channeling machine, 155. coffer dam, 174. compressed air transmission system, 380. concrete abutments, 110. concrete work, 89. concrete-steel chimney, 386. penstocks, 109, 208. poles, 467. power houses, 110. construction equipment for earth dams, 269. diamond drill, 151. drill tripod, 152. drills, 152, 154. earth dams, 270. Edson pile sinking outfit, 142. electric power transmission, 380. energy, 501. excavation from caissons, 179. explosives, 159. gas engines, 393. gas producers, 393. hand drilling, 150. high speed engines, 388. horse coffer dam, 173. hose pipe, 153. hydraulic fill plant, 274. hydro-compressor installation, 379. insulator pins, 471. insulatore, 473, 474. laying mats, 223. locomotive boiler, 382. maintenance of steam power plant, 427. marble, 399. mining column, 153. operation steam boiler, 382. pile drivers, 140. pile driving, 140. puddle, 268. reinforced concrete penstocks, 109, 208. round piles, 141. sand cement, 88. sawing outfit for penstock staves, 204. setting poles, 464. sheet piling, 140. sinking caissons in different soils, 179. INDEX. 505 Cost of: slow speed engines, 388. steam power plant, 51, 427. steel stacks, -386. storage batteries operation, 428. surveys, 61. switchboards, 399. transformers, 417. turbine harness, 446. various types of dams, 274-278. water tube boiler, 382. Couplings. See Power transmission. Cross arms, See Power transmis- sion. Croton Dam, profile, 258. Current density in bus-bars, 400. meters, 35. direct reading type, 36. revolving type, 35. DAMS, effect on back water, 340. agents of destruction, graph- ically represented, 250. amounts of material required for various types, 274. apron, design of, 227. bow, 237. coffer, See Coffer, concrete, deposition of, 264. concrete-steel, 233. cost of various types, 274. design of, 210. down-stream push, 241. earth, 265. building of, 268. construction equipment, 269. construction equipment, cost of, 269. cost, 270. drainage of, 269. hydraulic fills, cost of plant 274. hydraulic fills, waters re- quired for, 274. materials for, 267. most famous, 273. profiles for, 273. puddle mixture, 267. site, 266. weir in, 271. factors in, design of, 238. flash boards. See Flash boards. design of, 281. floatation of, 247. flow over, 12. frame type, 224. friction on bed of stream, 241. gravity, choice of slope, 218. concrete-steel design, 227. Dams, gravity, concrete-steel, rock bottom, 229, 230. concrete-steel, segmental, 231. frame type, design of, 224. reinforced concrete, 234. segmental, 231. steel, 227. theory of, 216. timber, rock bottom, 225. timber, soft bottom, 226. ice expansion, 247. masonry, 238. apron, design of, 254. center of gravity, 256. crushing stresses, 255. design of, 251. design, practical example, 259. safety of any section, 253. standard profile, 258. mats. See Mats, movable, 235, 285-289. nappe, form of, 17. over pour, form of, 15. pressures on, 217. sand bottom, 218. seepage under, 248. standard section, 262. steel, 232. Tainton gate, 350. timber, choice of material, 219. vacuums, 241. action of, 242. which have failed, 239. wing, 236. Depreciation and maintenance charges, 66. Diamond drill, cost of, 151. Distribution a.c., 394. polyphase, 396. single-phase, 394. three-wire, 396. systems, 394. two-phase, vs. three-phase 397. continuous current, 393. parallel, 394. series system, 393. wiring methods, 394. systems, 393. Draft head, 343. Draft tubes, 342. conical forms, 343. deflector for, 313. diameters for different heads, 343. installation of, 343. Drill hose pipe, cost of, 153 Drill, mining column, cost of, 153. 506 INDEX. Drilling, 149. by hand, cost of, 150. by machine, 151. machine, attendance required, 154. size of air pipe, 193. Drills, blacksmiths required for sharpening, 155. cost of, 152, 154. steam required by, 152. tripod, cost of, 152. Drum hoist, design, 134. Dynamite, cost of, 159. handling of, 155. preparation of, 156. Dynamometer, absorption. See Prony brake. EARTH dams, see dams. Edson pile sinking outfit, 142. Efficiency as affected by power factor, 487. of various machines, 64, 487. Ejector gates. 310. Electric fuses, cost of. 159. Electric generators. See Gener- ators. Electric transmission. See Power transmission. Embankments, 185. design, 187. materials suitable for, 186. preparation of ground for, 185. puddle wall, design of, 186. riprap for, 187. slope, height of, 186. Energy cost, 501. formulas, 497. application of, 497. Engine foundations, 303. gas. See Power plants, gas. steam. See Power plants. steam. Excavation, cost of, 179. Exciters, See Powei -house. Expander, 205. Explosions, boilers, 383. Explosives, 155. FACTORS of safety, 125. Feed water. See Power plants. Flash boards, 281. adjustable, 285-289. design of posts, 283. forms of, 281. short dam, 283. vacuum under, 283. Floatation, 2. Floats, 35. Flood, maximum determination of, 43. Flood periods, determination of, 43. Flow, curves showing, 50. effect of ice on, 32. measurement of, 10. integrating method, 38. single point method, 36. six tenths single point method, 37. of air, See Air. of water. See Water. Flowage height, 58. Flume, 303. area of, 345. built in gravity dam, 303. discharge velocity, 344. effect of depth of tail water, 345. floor of, 345. interior velocity, 344. tail race, 345. timber, 305. Fly-wheels, energy stored in, 363. use of, 358. Forms for concrete work, 94 Formulas and tables, 495. Foundations, 301. design of, 122. engine, 303. materials, strength of, 302. Frequency changers, 429. efficiency, 430. Friction. See Power transmission. clutches. See Power transmis- sion. coefficient, 453, 458. head, 5. head in rivers, 60. Fuses, 408, 409. GAS engines. See Power plants. Gate hoists, 294. Gauge boxes, size of, 90. Gauges on turbine settings, 343. Gears. See Power transmission. Generators, 393, efficiency, 487. rating of, 398. selection of, 397. voltage, 489. work, 394. Giant used for hydraulic fills, 273. Governing of high speed turbine insulations, 365. Government reports, value of, 40. Governors, actuated from switch- board, 359. cheap, 353. hydraulic, 358. mechanical, 359. operation of, 359. INDEX. 507 Governors, turbine, 353. requirements for, 361. types on market, 358. Woodward, types C and D.354. Gravity mixer, 93. Grounded guard wire, 485. Guard wire, grounded, 485. Gumbo, 88. HABRA Dam, profile of, 239. Hand drilling, 149. Hard pan, 211. Harness for turbines, 445. Head gates, 289. cost of, 293. design of, 294. force to start, 295. high heads, 294. hoists, 296. hydraulically operated, 297. large work, "290. medium heads, 293. most common form, 289. soft bottom, 289. velocity through, 290. Head racks, 298. anchor ice, 299. boom, 299. cheapest form, 298. cost of, 299. net area, 298. velocity permissible during floods, 342. weight of, 299. Heads of water, conversion table, 495. High head turbine, installations governing of, 365. Hoists for gates, 294. Hook gauge, 368. Horse-power in water at various heads, 498. stored in water, 500. Hydraulic construction, 137. fills, 273. gradient, 5. power formulas, 497. radius for different size pipe, 29. ram, 183. calculation of, data, 184. capacity of the several sizes, 185. Hydro-compressors, 371, 372. Ainsworth, 374. air head, 377. mixing pipe, 377. reservoir, 377. compressor pipe, not in well, 376. Hydro-compressors, data, 375. design of, 376. efficiency, 374, 376. head gates, 377. inlet pipes, 377. installation cost, 379. Magog, P. Q., 374. pressure, selection of, 376. variation, 374. velocity in, 376. Victoria mines, Michigan, 374. Hydrodynamics, 2. Hydrostatics, 1. ICE, blasting of, 158. effect on flow, 32. evils, 55. expansion of, 247. expansive power of, 248. Imperial gallons, 1 . Impulse pressure, 8. Inductive reactance in transmission lines, 481. Instruments. ammeter, recording, 407. West on, 407. ampere-hour meters, 413. two rate meters, 413. voltmeter, a.c., 404. d.c., 404. electrostatic, 405. watt-hour meters, 409. accuracy of, 411. connections, 411. induction, 411. Thomson, 410. wattmeters, 409. Insulator pins. See Power trans- mission. Internal combustion engine. See Power plants. Iron piling. See Piling. JEROME Park reservoir, 269. Jovite, 158. cost of, 159. Jump drilling, 149. KAHN bar, reinforcement, 104. Keys. See Power transmission. Kilowatt-hours in water in stored water, 500. Kilowatts in water at various heads 499. Kutter's formula, values of C, 26. LEFFEL turbine, 333. Lightning. arresters, 413. a.c., 413. 508 INDEX. Lightning, arresters, connections of, 413-415. Garton, 413. General Electric, 413. grounding of, 484. low-equivalent, 415. West high ouse, 413. protection, 407, 484. Lower Tallasee Dam, profile of, 239. Lubricants, 458. MACHINES, alignment of, 431. Maintennace and depreciation charges, 66. Masonry, bearing strength, 124. Materials, 68. Mats, Beardsley, concrete steel, cost of, 214. cost of laying, 223. extension, 215. cheapest kind, 216. for abutments and walls, 302. length of, 222. rock bottom, 213. sand bottom, 212. soft bottom, 210. Measurements, engineer's, 62. Mershon diagram, 480. Metals, 69. Meters, See instruments. Venturi meter, 18. Instruments. Mill Creek penstock system, calcu- lation of, 53. power plant, 52. Miner's inch, 1. Mining column, cost of, 153. Moment, definition of, 113. inertia, definition of, 113. in built-up sections, 126. resistance, definitions of, 113. Motors. air, 378, 380. air consumption of, 380. water required to saturate air, 379. electric, single-phase, 395. induction, as frequency changers, 430. efficiency, 489. single-phase advantages, 395. synchronous, efficiency, 489. starting current, 488. Motor-generators, 429. efficiency, 490. NAPPES, form of, 17. Needle nozzle, 365, 366. Neutral line, definition of, 113. Niagara Falls power house, 328. ORIFICES. See Water. PELTON wheel, 347. regulation of, 348, 349. needle nozzle, 365. Penstocks, abnormal pressures in, 349. brick, cost of, 208. bridge, 168. circular, 23, 203. concrete-steel, 105. cost of, 109. data, 200. definition of, 199. expander, 205. flow in, 20, 22. Kutter's, formula, 25. gravity type, 53. hoops for, 206. joints, method of making, 203. means of shutting off water, 361. reinforced concrete, cost of, 208. staves, material for, 203. safety valves in, 352. joint sawing outfit, 204. steel, 208. joints, 210. stresses in, 207. timber, design of, 200. on trestle, 202. vibration in, prevention of, 349 Pile drivers, 139. cost of, 140. methods, 141. Pile screw outfit, 147. Piles, bearing power of, 148. concrete, 143. hammers used with, 145. cost of driving, 140. iron points, 139. jet driving, 142. jet piles, cost of, 142. in quicksand, 140. sand, 148. Piling, 137. iron, 146. sheet, driving of, 138. steel, 145. Pins, insulator. See Power trans- mission. Pipes, abnormal pressures in, 349. capacity, diagram, 25. capacity, table, 21, 24. flow in, 20. INDEX. 509 Plant maintenance and deprecia- Powerhouse, steam, boilers, water tion charges, 66. tube, space oc- Plumb lines, 431. cupied by, 383. Pole lines. See Power transmission. coal required, 381. Poles. See Power transmission. cost of, 427. Pondage, relation to value of power, cost of maintenance, 427. 45. engines, 388. Portland cement, 70. comparison of, 388. Power in a.c. circuits, 410. cost, 388. Power and energy expressions, 495. cut-off, 389. Power factor, effect on rating of design, 389. generator, 398. efficiency, 388. Power house, al gnment of machin- foundation, 432, 433. ery, 431. overload capacity,390 architecture, 330. power formula, 388. auxiliary, 380. feed water heating, 385. Chicago drainage canal, 323- fuels, comparison of, 382. 326. smoke stacks, 386. concrete-steel, 307. cost of, 386. construction, 301. turbines, overload capa- cost of, 307. city, 391. with ejector gates, 310. storage batteries. See Storage equipment, 331. batteries, exciters, 398. structure, 303. capacity, 398. switchboards, 398. flume, 303. building of, 399. foreign types, 321. bus work, 400. foundations, 301. cost of, 399. gas capacity, 391. frame, design of, 399. gas consumption, 393. instruments. See Instru- engines, 390. ments. efficiency, 393. materials, 399. heat balance, 390. remote control, 402. investment, 391. spacing of bus-bars and mixture used, 392. switches, 401. producers, cost of, 393. switches, See Switches, generators, electric. See gen- timber and concrete, 307. erators. Power, measurement of, 410. selection of, 397. per cubic foot of air at different high heads, 325, 326. pressures, 31. lightning protection. See Light- single-phase circuit, 410. ning. three-phase circuits, 410. load curves, 426, 428. Power transmission, 433. low head, 314. air, 379. medium heads, 309, 321. belting, splicing of, 448. Niagara Falls, 328. cost, 380. reinforced concrete, 310, 311, couplings, disc, 434. 312. efficiency, 486. steam, boilers, 380. diagram, 491. comparison of types, tested, 492. 381. electric, cost, 380. cost of, 382. cross-arms, 470. efficiency of, 382. efficiency, 486. feeding, 387. entrance to buildings, 460. house, 386. frequency, 486. operation, cost, 382. general instructions, 485. overload capacity, 387 insulator pins, 471. plant capacity, 385. cost of, 471. setting, dimensions, insulators, cost of, 473, 383, 384. 474. 510 INDEX. Power transmission, electric, in- sulators, selection of, 471. line, 475. design of, 476, 478. lightning protection, ' 484. loss, 478-484, 488. sag, 476. ' spacing of, 478, 485. temperature, effect of, on sag, 476. transposition, 478. pole lines, 461. bracing of, 469. pole top, design, 462. poles, 461. concrete-steel, 466. cost of 467. strength of, 467. life of, 465. guying of, 465. installation of, 465, 466. preservation of, 464 . setting of, 463-465. cost of, 464. specifications for, 461 strains on, 464. regulation, 486. towers, 467. voltages, 486. mechanical, 434. bearings, 445. babitting of, 459. installation of, 458. belting, 446. efficiency of, 448. leather, 446. operation of, 447. power of, 448. rubber, 446. speeds on, 448. clutches, friction, 435. couplings, 434. design, 434. flexible, 435. jaw, 435. friction, 457. gears, 440. design of, 440-444. strength of, 442. keys, 436. quill, shafts, 436. rope, 449. care of, 455. centrifugal force, 452. design, 452. efficiency, 450, 486. horse-power, 449. Power transmission, mechanical rope, manilla and copper, 449. sag, 449. sheaves, 454. steel, 453. steel, design, 453-457. strength, 451. tension, 450. shafting, 436. design of, 438, 439. efficiency, 487. friction, 457. worm and gear, 444. Power in unbalanced two-phase circuits, 410. in water, curves, 49. measurement of, 39. at various heads, 498. Pressure, submerged surface, 1. Prony brakes, 368-371. capacity, 371. design of, 370. shoes, area, 370-371. Properties of various sections, 116 Puddle, cost of, 268. walls, design of, 186. Puentes Dam, profile of, 239. Pulley or gear, design, 135. Pumps. centrifugal, 179. adjustable lining for, 180. choice of motor for, 181. horse-power of, 180. operation of, 182. QUILL shafts. See Power transmis- sion. RADIUS of gyration, definition of, 113. Rainfall data, 40. Ransom bar, reinforcement, 103. Reconnoissance of water power, 39. Reinforcement, 103. Reinforcing of concrete, 102. Reports, form of, 65. engineer's, 62. government, 62. Reservoirs in connection with pen- stock, 349. relation to value of power, 45. Rivers, flow measurement, 33, 37. of United States, run-off and rainfall data for, 41, 42. Rock work, 96. Roofs, design of, 165. Rope drive. See Power transmis- sion. Rosendale cement, 70. INDEX. 511 Rotary converter, efficiency, 490. Run-off data, 40. determined without run-off re- port, 64. Safety factors, 125. valves for high pressure pipe line, 366, 367. in penstocks, 352. Sand cement, 88. cost of, 88. Sand, seepage through, 212. standardized, 77. Scott system, 421. Screw design, 130. Sections, properties of, 116. Shafting. See Power transmission. alignment of, 431. design, 129, 136. Sheet piling. See Piling. Short pipes, flow in, 29. Siphon, 6. operation of, 7. Slag cements, 100. Slope, fall in feet per mile, etc., 28. Sluice gates, 296. S. Morgan Smith turbine gate, 334. Soils, angle of repose, 188. bearing strength of, 124. " Soo " plant, 314. Soundings, 56. rock bottom, 57. soft bottom, 57. Speed regulation, throttling gates, 343. Standard profile for masonrv dam, 258. Standpipe, 357. function of, 365. ideal arrangement with tur- bine unit, 363, 364. Steam engines. See Power plants, steam. plant. See Power plants. cost of, 51. Steel piling. See Piling. Stones, strength of, 255. water absorbed by various kinds, 240. Storage battery, 421. boosters, 424. buckling, 425. capacity, calculation of, 427. charging of, 423. cost of, 428. cost of operation, 428. design, 423. design for central station, 422. discharging, 423. efficiencies, 427. electrolyte, 425. Storage battery, end cell switch, 429 end cells," 423. location of, 429. operation, 425. rating of, 423. reasons for using, 421. room ventilation, 422. sulphate, 425. Straight edge, 431. Stranded cable, reinforcement, 103. Strength of materials, 113. of various materials, table, 115. Surveys, cost of, 61. Suspension bridge, design of, 168. Susquehanna River, run-off and rainfall data, 41-44. Switches, 402. contact surface, 403. design of, 401, 402. high tension, 403. oil, 404. voltmeter, 405. Switchboards. See Power house. Svnchronous converter, efficiency, 490. TABLES and formulas, 495. Tail race, design of, 344. velocity, permissible during floods, 342. Tainton gate, 350. Tapes, steel, 433. Telephone lines on a transmission line, 477. Tent, cost of, 101. Test holes, 56. Testing of turbines, 367. Throttling gates, 343. Timber, suitable for hydraulic con- struction, 68. built up, 166. Transformers, 415. air-blast, data of, 416. . banking of, 419. capacity of, 420. connection of, 420. connections, Scott system, 421. cooling methods, 416. cost of, 417. current, 407. data, 417. efficiency, 488, 489. oil, 417. phase changers, 421. potential, 405. power required to air cool, 417. protection of, 418. selection of, 489. temperature, 416. water required to cool, 417. Transpositions, 478. 512 INDEX. Truss bridges, design of, 164. roofs, design of, 165. Tunnels, blasting, charges, 195. cost of, 198. drilling of, 193. earth, 195. cost of excavations, 198. rock, 192, 193. itemized cost of, 199. Turbine chamber. See Flume. 344. setting, " Soo " plant, 316. special, 339. Turbines, 331. choice of capacity, 319. classification of, 332. comparison of various makes, 321. efficiency, 331, 334, 487. gates, 333. energy required to oper- ate, 355. time required to close, 355 governors, 353. harness, 445. high pressure, 334, 348. setting for, 314. horizontal, 335. efficiency, 337. Leffel, 333. old, efficiency of, 493, 494. regulation, back water condi- tions, 340, 341. choice of gate, 360. cylinder gate, balancing of, 356. draft tubes, effect on, 358. energy required to operate gates, 357. energy stored in fly-wheel, 363. fly-wheels, use of, 358. governors, 358. high head system, 365. influence of plant location on, selection of gover- nor, 357. relation between stand- pipe pressure, fly-wheel and regulation, 364. requirements of governor, 361. set, 362. standpipe with damping pipe, 357. time required to close gates, 355. wicket gate, balancing of, 356. relation of speed to size, 345. runners, 332. running parts, 334. Turbines, selection of, 337. settings, 335. typical, 338. speed of, 331. step bearing, 346. testing of, 367. equalizing rack. 368. hook gauge, use of, 368. wheel pit, weir, 367. vertical, efficiency, 337. water used by, 331. wear, 335. wicket gate, 356. UNITED STATES gallon, 1. Upper Tallasee Dam, profile of, 239. VACUUM, experiments, 245. Vacuums, action of, 242. values of, 244. Valves used with centrifugal pumps 183. Velocity of approach, 4, 15. limits of air in pipes, 30. Venturi meters, 18. as head gates, 19. Victor turbine runner, 332. Voltmeter. See Instruments. WASTE gates, 296. hydraulically operated, 297. umbrella type, 296. Water, 1. flow of, 3. orifice, submerged, 4. through circular orifice, 3. through rectangular ori- fice, 3. hammer, prevention of, 349. relieve of, 367. power, measurement of, 39. weight of, 1. Waterwheels, 331. Watt -hour meters. See Instruments Wattmeters. See Instruments. Weirs, 10. submerged, 11. in earth dam, 271. for wheel pit, 367. table, 13. Winches, design, 132. Wiring formula for a.c. and d.c., 481. Woods, 68. life of, 465. suitable for construction, 68. Woodward governor, type B, 355. types C and D, 354. Worm wheel. 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