TJ 
 
Class JTlZXL 
 Book -S ^5 
 
 Copyright N°_ 
 
 COPYRIGHT DEPOSIT. 
 
REYNOLDS COMBINED VERTICAL 
 POWER CYLINDERS, 44x88x60. 
 
 AND HORIZONTAL ENGINE 12,000 HORSE 
 BUILT BY ALLIS-CHALMERS COMPANY. 
 
Twentieth Century Hand-Book 
 
 FOR 
 
 Steam Engineers and Electricians 
 
 WITH QUESTIONS AND ANSWERS 
 
 A PRACTICAL NONTECHNICAL TREATISE 
 
 On the Care and Management of Steam Engines, Boilers and Dynamos. 
 With Full Instructions in Regard to the Intelligent Management of all 
 Classes of Steam Engines, Making Evaporation Tests on Boilers, 
 Hydraulics for Engineers, the Adjustment of the Slide Valve, Corliss 
 Valve, etc., Fully Described and Illustrated, together with the Applica- 
 tion of the Indicator and Diagram Analysis. All Problems are Solved 
 in Plain Figures, thus Enabling the Man of Limited Education to readily 
 comprehend their meaning. 
 
 New 1905 Revised and Enlarged Edition 
 
 TO WHICH IS ADDED FULL AND COMPLETE CHAPTERS 
 ON THE STRENGTH OF BOILERS, MECHANICAL 
 STOKERS, AND CLEAR DESCRIPTIONS OF 
 THE STEAM TURBINE, ITS CONSTRUC- 
 TION AND MANAGEMENT 
 
 By C. F. SWINGLE, M.E. 
 
 ELECTRICAL DIVISION 
 
 Containing only such information as Steam Engineers should know 
 
 to successfully and economically run or manage an electrical plant 
 
 BY 
 
 HENRY C. HORSTMANN & VICTOR H. TOUSLEY 
 
 ILLUSTRATED 
 
 CHICAGO 
 
 FREDERICK J. DRAKE & CO., PUBLISHERS 
 
 1905 
 
uBRARY o! 3QNGRESS 
 fwu Copies rtecwveU 
 
 CQcyn^nt tntfjf 
 CUCSS « XXc. Not 
 
 //37/ 2^ 
 
 COPY 8. 
 
 COPYRIGHT, 1905 
 
 BY 
 
 FREDERICK J. DRAKE & COMPANY 
 
 CHICAGO, U. S. A. 
 
 , ' 
 
 t 
 
 1 
 
 
 
 TYPOGRAPHY BY 
 
 MARSH, AITKEN & CURTIS COMPANY, CHICAGO 
 
LIST OF ILLUSTRATIONS 
 
 PART I STEAM ENGINEERING 
 
 American Thompson indicator, 
 
 176. 
 Amsler's polar planimeter, 263. 
 Ashcroft steam gauge, 36. 
 
 Baragwanath closed heater, 53. 
 
 Baragwanath open heater, 55. 
 
 Babcock and Wilcox water 
 tube boiler, 16. 
 
 Berryman closed heater, 57. 
 
 Baragwanath siphon conden- 
 ser, 272. 
 
 Coffin averager or planimeter, 
 
 261. 
 Crosby indicator, sectional view, 
 
 170. 
 Crosby indicator, with reducing 
 
 wheel, 183. 
 Cross compound Allis-Chalmers 
 
 engine, 266. 
 Center oiler for crank pin, 279. 
 
 Davis belt-driven feed pump, 48. 
 Differential valve for Davis 
 
 pump, 47-49. 
 Detroit lubricator, 277. 
 
 Green's fuel economizer- 
 construction, 94. 
 
 -under 
 
 Hamilton Corliss engine— cro 
 
 compound, 268. 
 Horizontal boiler setting, 12. 
 Heine water tube boiler, 14. 
 Hot water thermometer, 59. 
 
 Inside view of pop valve, 41 „ 
 
 Knowles jet condenser, 269. 
 
 Lahman shaking grate, 67. 
 
 Martin rocking grate, 68. 
 Marsh steam pump, 50. 
 Metropolitan injector, 52. 
 McClave shaking grate, 33-35. 
 
 Pop safety valve, 40. 
 Pickering governor, 276. 
 Penberthy injector — sectional 
 view, 285. 
 
 Schaefer and Budenberg steam 
 
 gauge, 38. 
 Sectional view of pressure gauge, 
 
 37. 
 Sectional view of Corliss cylinder 
 
 and valve chests, 158. 
 Shaft governor, 281. 
 
 Tandem compound Buckeye 
 
 engine, 267. 
 U. S. Automatic injector, 51. 
 Wickes vertical water tube 
 
 boiler, 13. 
 Worthington duplex feed pump, 
 
 49. 
 Worthington surface condenser, 
 
 271. 
 
INDEX 
 
 PART I STEAM ENGINEERING 
 
 Absolute pressure, 190. 
 Absolute back pressure, 191. 
 Absolute zero, 193. 
 Action of slide valve, 134-139. 
 Adiabatic curve, 194-252-254. 
 Adjustable cut-off, 145-203. 
 Admission, 1C8. 
 Admission line, 208. 
 Adjustment of governor, 164- 
 165. 
 
 Air — 
 
 Composition of, 91. 
 
 Cubic feet per lb. of coal 
 
 burned, 70-93. 
 Leaks in boiler settings, 33-34. 
 How to admit to furnace, 
 
 70-71. 
 
 Angular Advance — 
 
 Necessity of, 136. 
 
 Effect of decreasing, 144. 
 
 Effect of increasing, 148-149. 
 
 Definition of, 201. 
 Analysis of coal, 92. 
 Apparatus for making tests, 
 
 118-120. 
 
 Area — 
 
 Of circles, 204-205. 
 
 Of fire box, 61. 
 
 Of grate surface, 121. 
 
 Of heating surfaoe, 61. 
 
 Of safety valve, 39. 
 
 Of segments, 22. 
 
 Sectional of braces, 21-22-23. 
 
 Ash— 
 
 Dry, 123. 
 
 Removal of, 29-121 
 
 Weight of, 127. 
 Atoms, 106-107. 
 Atmospheric line, 186. 
 Automatic stoker, 94. 
 Automatic cut-off, 202. 
 
 Back pressure, 190, 
 Blow-off- 
 Pipes, 45-47. 
 
 Cock, 46. 
 
 Surface, 47. 
 Boiler — 
 
 Air leaks in brick work, 34. 
 
 Back arches, 29-31-34. 
 
 Bridge Walls, 28. 
 
 Bracing, rules for, 22-23-24. 
 
 Bursting pressure, 18. 
 
 Cleaning, 71-73. 
 
 Combustion chamber, 29. 
 
 Contraction of plates, 43. 
 
 Expansion of plates, 44. 
 
 Factor of safety, 21. 
 
 Force tending to rupture, 19, 
 
 Flue cvlindrical, 11.' 
 
 Grate surface, 32-33. 
 
 Horse power of, 131. 
 
 How to prevent alternate ex- 
 pansion and contraction, 
 72-73. 
 
 Incrustation, 104. 
 
 Insulation, 33-34. 
 
 Inspection, 73-74. 
 
 Operation of, 66. 
 
 Plain cylinder, 11. 
 
 Return tubular, 12. 
 
 Rivets, 15-16. 
 
 Settings, 27. 
 
 Set in battery, 28-122. 
 
 Shell material, 14-15. 
 
 Types of, 11. 
 
 Tubes, renewing of, 74. 
 
 Water tube, i3. 
 
 What causes alternate ex- 
 pansion and contraction. 73. 
 Boyle's law, 194. 
 Box valve, 157. 
 Brumbo pulley, 181. 
 British thermal unit, 98-99. 
 Buck stays, 31-32. 
 
Ill 
 
 Calorimeter, 124. 
 
 Chimney draft, 124. 
 
 Circulating system, 47. 
 
 Cleaning fires, 67. 
 
 Cleaning flues, 71-72. 
 
 Clearance, 193-236-245-246. 
 
 Combustion, 91-94. 
 
 Coal- 
 Analysis of, 92. 
 Moisture in, 124. 
 
 Composition of matter, 106. 
 
 Connecting steam gauge, 38. 
 
 Connecting boiler to main head- 
 er, 75-76. 
 
 Corliss valves, 158-163. 
 
 Corliss valve gear, 158-160. 
 
 Condenser pressure, 191. 
 
 Counter pressure, 260. 
 
 Compression, 194-202-236-238. 
 
 Condenser- 
 Jet, 270. 
 Surface, 270. 
 Siphon, 271. 
 
 Water required per H. P. per 
 hour, 274-276. 
 
 Curves — 
 
 Adiabatic, 194-252-254. 
 Compression, 236-238. 
 Expansion, 194. 
 Isothermal, 194-246-251. 
 Theoretical expansion, 246- 
 251. 
 
 Cut-off- 
 Automatic, 202. 
 Adjustable, 203. 
 At half stroke, 149. 
 Equalizing, 212-226. 
 FLxed, 202. 
 
 - Of slide valve, 137-142. 
 
 Cylinder condensation, 200. 
 
 Dash pot, 162-165. 
 Diagrams — 
 
 From Corliss centennial en- 
 gine, 232-235. 
 From Hamilton Corliss en- 
 gine, 235-236. 
 From Buckeve engine, 208- 
 
 216-218-226-227. 
 From Bates vertical Corliss 
 engine, 209-212. 
 
 Diagrams— 
 
 From Bullock horizontal Cor- 
 liss engine, 213-216. 
 From Atlas riding cut off 
 
 engine, 218. 
 From cross compound con- 
 densing engine, 219-220. 
 From Fishkill Corliss con- 
 densing engine, 222-224. 
 From vertical slide valve en- 
 gine, 224-225. 
 Friction, 260. 
 
 Showing lines and curves, 207. 
 Domes — 
 
 Purpose of, 43 
 Bracing, 24. 
 Draft gauge, 125. 
 Duplex Pump — 
 
 How to set valves of, 81-82. 
 How to operate with one 
 water piston disabled, 82- 
 83._ 
 Dynamics, 195. 
 
 Economy in fuel, 51-57. 
 Economizers, 94. 
 Eccentric — 
 
 Adjustment of, 156-161. 
 
 Definition of, 200. 
 
 Position, 138-139-201. 
 
 Rod, length of, 153-154. 
 
 Throw, 201. 
 Efficiency test, 122. 
 Efficiency of plant, 197. 
 Energy in one pound of coal, 
 
 102.' 
 Engine — 
 
 Corliss, 158. 
 
 Compound, 268. 
 
 Compound, distribution of 
 steam in cvlinders, 221-222. 
 
 Changing of speed, 287-288. 
 
 Efficiency of, 196-197. 
 
 Four valve, 157-159. 
 
 How to place on center, 
 150-153. 
 
 Keying up, 281-282. 
 
 Operation of, 266-288. 
 
 Steam consumption of, 198- 
 236-238-242. 
 
 Single valve, 134. 
 
Equivalent evaporation, 127. 
 Evaporation — 
 
 Factor of, 128-129. 
 Exhaust — 
 
 Cramped, 225. 
 
 Injector, 57-58. 
 
 Heater, 53-54-55-57. 
 
 Line, 208. 
 Expansion curve, 194-208. 
 
 Factor of safety, 20. 
 
 Factor of evaporation, 128-129. 
 
 Feed pipes, 43-45. 
 
 Feed Pumps — 
 
 Belt driven, 47. 
 
 Best water valves for, 80. 
 
 Double acting, 48. 
 
 Selection of, 48-50. 
 • Setting steam valves of du- 
 plex pump, 81-82. 
 Feed Water- 
 Heating by exhaust steam, 
 283-285. 
 
 Proper supply of, 74-75. 
 
 Quantity required, 49-51. 
 
 Temperature of, 43. 
 
 What to do if supply is cut 
 off, 75. 
 Feed Water Heaters — 
 
 Closed, 53. 
 
 Capacity of, 56-57. 
 
 Economy of, 52. 
 
 Live steam, 58. 
 
 Open, 53. 
 Fire tools, 68. 
 
 Firing, proper method of, 69-71. 
 Fire brick lining, 28-33. 
 First law of thermo-dvnamics, 
 
 194. 
 First law of motion, 194-195 
 Fixed cut-off, 202. 
 Foaming, 76. 
 Formula — 
 
 For ascertaining friction loss 
 in water pipes, 87. 
 
 For decreasing speed of en- 
 gine, 288. 
 
 For double riveting, 20. 
 
 For efficiency of boiler, 130. 
 
 For estimating quantity of 
 condensing water, 274. 
 
 Formula — 
 
 For finding bursting pres- 
 sure, 20. 
 For finding heating surface, 
 
 62-64. 
 For increasing speed of en- 
 gine, 287. 
 For per cent, of saving by 
 use of exhaust heater, 56. 
 For single riveting, 21. 
 Force, definition of, 195. 
 Friction of water in pipes, 
 
 86-88. 
 Fusible plugs, 40-42. 
 Furnace temperature, 93. 
 
 Gauges — 
 
 Draft, 125. 
 
 Steam, connecting, 38-39-40. 
 
 Vacuum, 192. 
 Gauge pressure, 190. 
 Generation of steam, 107. 
 Governor — 
 
 Throttling, 202-276. 
 
 Automatic cut-off, 276. 
 
 Isochronol, 202-281. 
 Grate Surface — 
 
 Length and width of, 32. 
 
 Ratio of to heating surface, 33. 
 
 Ratio of to safety valve area, 
 39-40. 
 
 Square feet of, 121. 
 Gridiron valve, 157. 
 
 Hand firing, 95. 
 
 Hand holes, reenforcing, 24. 
 
 Heater — 
 
 Closed, 53-57. 
 
 Capacity of, 56. 
 
 Live steam, 57. 
 
 Open, 54-55. 
 
 Economy of, 52. 
 Heating Surface — 
 
 Of horizontal boilers, 61. 
 
 Of vertical fire box boilers, 61 . 
 Heat — 
 
 A form of energy, 96. 
 
 External work of, 108. 
 
 Internal work of, 108. 
 
 Intensity of, 95. 
 
 Latent, 102-103. 
 
Heat — 
 
 Mechanical equivalent of, 99. 
 
 Original source of, 97. 
 
 Sensible, 99-101. 
 
 Specific, 99. 
 
 Theories regarding nature of 
 95-96. 
 
 Unit of,' 98-99. 
 High speed engines, 157. 
 Hook rod, adjusting length of, 
 
 160-161. 
 Horizontal boiler setting, 12. 
 Horse Power — 
 
 Definition of, 102-193. 
 
 Constant, 197-228-230. 
 
 Indicated, 193. 
 
 Net, 194. 
 Hot water thermometer, 58-59. 
 Hydraulics, 83-87. 
 Hydrogen, 91. 
 Hyperbolic logarithms, 188. 
 
 Internally fired boilers, 23. 
 Initial pressure, 190. 
 Injector — 
 
 Care of, 286. 
 
 Exhaust, 285. 
 
 Live steam, 286. 
 
 Principles of, 285-286. 
 Indicator — 
 
 By whom invented, 168. 
 
 Care of, 185-223-224. 
 
 Description of, 171-175. 
 
 How to attach, 183-185. 
 
 Principles of, 168-171. 
 
 Spring, 172. 
 
 Study of diagrams, 207-230. 
 
 Taking diagrams, 186-187- 
 188. 
 Isochronol governor, 202-281. 
 
 Joule's experiments with heat, 
 97-98 
 
 Latent heat, 102-103. 
 Lap — 
 
 Effect of increasing, 134- 
 145-146. 
 
 Inside, 135-144-201. 
 
 How to measure, 154-155. 
 
 Lap — 
 
 Meaning of, 201. 
 
 Of Corliss valves, 164. 
 
 Outside, 135-141-201. 
 Lead — 
 
 Adjustments for, 156. 
 
 Definition of, 201. 
 
 Equalized, 156-164. 
 
 Necessity of, 134. 
 
 Of Corliss valves, 164. 
 Logarithms, 197. 
 Lubrication — 
 
 Of crank pin, 279. 
 
 Of guides, 278. 
 
 Of pillow blocks, 280. 
 
 Of piston, 277. 
 
 Of valves, 277. 
 
 Margin of safety, 13. 
 Material for boilers, 14. 
 Manholes, reenforcing, 24. 
 Maximum theoretical duty of 
 
 steam, 195. 
 Measuring lap, 154. 
 Measuring chimney draft, 124- 
 
 125. 
 Mean Effective Pressure — 
 
 Definition of, 190. 
 
 Figuring by ordinates, 255- 
 259. 
 
 Finding bv planimeter, 262- 
 263. 
 
 Rule for finding, 220-227. 
 Mechanical equivalent of heat, 
 
 98-99. 
 Momentum, 195. 
 Moisture — 
 
 In steam, 123-124. 
 
 In coal, 124. 
 Mud-drums, 43. 
 
 Obliquity of connecting rod, 
 
 147. 
 Operation of boilers, 65. 
 Ordinates, 200-255-257. 
 Outside lap, 146. 
 
 Packing for feed pumps, 80. 
 Pantograph, 182-183. 
 Pendulum motion, 177-182. 
 
VI 
 
 Piston — 
 
 Clearance, 193. 
 
 Displacement, 193. 
 
 Speed, 193. 
 
 Valve, 157. 
 Placing engine on dead center, 
 
 151-152. 
 Planimeter, 262-263. 
 Power — 
 
 Calculations, 254-259. 
 
 Definition of 194. 
 Priming, 76. 
 
 Questions — 
 
 On boiler operation, 87-90. 
 On boiler construction, 24- 
 
 25-26. 
 On boiler settings, 64-65. 
 On combustion, 115-116. 
 On definition of words, terms, 
 
 and phrases, 204. 
 On diagram analysis, 230- 
 
 231-263-265. 
 On engine operation, 288-290. 
 On evaporation tests, 131— 
 
 132. 
 On indicator, 188-189. 
 On valve setting, 166-167. 
 
 Radius of eccentricity, 140-141. 
 Ratio of expansion, 191. 
 Reevaporation, 251-252. 
 Reducing mechanism, 176-183. 
 Relative positions of crank pin 
 
 and eccentric, 139. 
 Release, 142. 
 
 Rocker arm, how to adjust, 150. 
 Rules — 
 
 For ascertaining required size 
 
 of feed pump, 50-51. 
 For calculations in hydraulics, 
 
 83-86. 
 For finding piston speed of 
 
 pumps, 83-84. 
 For finding strength of solid 
 
 plate, 15. 
 For finding strength of rivets, 
 
 16 
 For finding strength of riveted 
 seams, 15. 
 
 Rules — 
 
 For finding area of segment 
 
 of circle, 22. 
 For finding velocity of flow 
 
 of water in pipes, 84-85. 
 For finding weight of water 
 
 discharged per second, 85- 
 
 86. 
 For finding initial pressure, 
 
 220. 
 For finding mean forward 
 
 pressure, 220. 
 For finding mean effective 
 
 pressure, 220-227-228. 
 For finding terminal pressure, 
 
 242. 
 For finding indicated horse 
 
 power, 228. 
 For safety valve calculations, 
 
 78-79. 
 For spacing braces, 23. 
 
 Safe working pressure, 15. 
 Safety Valve- 
 How to keep in good working 
 order, 80. 
 
 Problems, computation of, 
 78-79. 
 
 U. S. marine rule for, 77. 
 Sensible heat, 99-101. 
 Shaking grates, 67-68. 
 Smoke prevention, 94-95. 
 Specific heat, 99. 
 Steam line, 209. 
 
 Strength of riveted seams, 15. 
 Strength of solid plate, 15. 
 Strength of rivets, 15. 
 Steam — 
 
 Consumption per H. P. per 
 hour, 198-236-238-242. 
 
 Clearance, 193. 
 
 Density of, 109. 
 
 Dry, 108. 
 
 Gaseous nature of, 107. 
 
 In its relation to the engine, 
 109. 
 
 Efficiency of, 195-196. 
 
 Generation of, 106. 
 
 Method of testing drvness of 
 109-124. 
 
 Nature of, 107. 
 
Steam — 
 
 Percentage of moisture in, 
 123-124. 
 
 Physical properties of, 110- 
 114. 
 
 Relative volume of, 109-110. 
 
 Saturated, 107. 
 
 Superheated, 107-108. 
 
 Temperature of, 107 
 
 Total heat of, 108. 
 
 Volume of, 109. 
 
 Wet, 108. 
 Surface blow off, 46-47. 
 Tables- 
 Analysis of coal, 92. 
 Areas and circumferences of 
 circles, 204-205. 
 
 Constants for areas of seg- 
 ments, 22. 
 
 Factors of evaporation, 129. 
 
 Constants for steam consump- 
 tion per I. H. P. per 
 hour, 228. 
 
 Hyperbolic logarithms, 199. 
 
 Lap and lead of Corliss 
 valves, 164. 
 
 Physical properties of steam, 
 110-114. 
 
 Specific heat, 99. 
 
 Weight of water, 105. 
 Temperature — 
 
 Of escaping gases, 93. 
 
 Of feed water, 74-123. 
 
 Of furnace, 93. 
 Tensile strength, 14. 
 Terminal pressure, 190-242. 
 Tests- 
 Evaporation, object of, 117. 
 
 Preparing for, 119-121. 
 
 Duration of, 123. 
 
 Closing of, 124. 
 
 Record of, 127. 
 
 Provisions for, 58-60. 
 
 Tanks for, 59-60. 
 
 For efficiency of boiler and 
 furnace, 126. 
 
 For efficiency of boiler, 126. 
 Thermo dynamics, first law of, 
 
 96-97-194. 
 Theoretical clearance, 243-246. 
 Three-way cock, 175. 
 
 Throttling governor, 202-276. 
 Tie rods — 
 
 For boiler walls, 31-32. 
 
 Transverse, where to locate, 
 32. 
 Total heat of evaporation, 102- 
 
 103. 
 Travel of valve, 137. 
 Triple riveted butt joints, 18. 
 
 Unit of work, 194. 
 
 Vacuum, 192. 
 Valve — 
 
 Adjustment of travel, 156. 
 
 Corliss, how to adjust, 162. 
 
 Diagrams, 145-148. 
 
 Decreasing travel of, 145. 
 
 Gear of Corliss engine, 159- 
 160. 
 
 Lap and lead of, 134-156. 
 
 Placing central, 154-155. 
 
 Rotative, 158. 
 
 Slide, 133-157. 
 
 Setting of, 133-160. 
 
 Stem, length of, 154-155. 
 
 Travel of, 134-137-140-155- 
 201. 
 
 Types of, 134. 
 Valve, Safety — 
 
 Frequent testing of, 79. 
 
 Lever, 39-40-77. 
 
 Pop, 39. 
 
 Ratio of area to grate sur- 
 face, 39-40. 
 
 U. S. Marine rule for, 77. 
 Valves — 
 
 For feed pump, 80. 
 
 Water — 
 
 Boiling point of, 105-106. 
 Chemical treatment of, 104. 
 Composition of, 103. 
 Contraction and expansion of, 
 
 104-105. 
 Foaming, 76. 
 Impurities in, 104. 
 Quantity required for con- 
 denser, 273-276. 
 Weight of, 105. 
 
VTII 
 
 Washing out Boiler; — 
 Preparing for, 72. 
 Proper method of, 73-74. 
 
 Water Columns — 
 
 Proper location of, 34-35. 
 How to connect to boiler, 
 
 35-36. 
 Dangerous condition of, 37. 
 
 Wire drawing, 191. 
 
 Work- 
 Definition of, 195. 
 External, 108. 
 Internal, 108. 
 
 Wrist Plate- 
 Vibration of, 162. 
 Adjustment of, 163. 
 
 Zeuner valve diagrams, 
 145-148. 
 
 139- 
 
PART II 
 
 STEAM ENGINEERING 
 LIST OF ILLUSTRATIONS 
 
 American underfeed stoker, Electrically operated valve 
 348. (Curtis turbine), 380. 
 
 Branca's steam turbine, 358. 
 Burke furnace, 353. 
 
 Cahall boiler fitted with auto- 
 matic stoker, 337. 
 
 Curtis steam turbine (general 
 view), 372. 
 
 Curtis steam turbine, under 
 construction, 373. 
 
 Curtis steam turbine — station- 
 ary and revolving buckets, 
 374. 
 
 Curtis steam turbine — nozzle 
 diaphragm, 375. 
 
 De Laval steam motor — gen- 
 eral view, 394. 
 
 De Laval diverging nozzle, 392. 
 
 De Laval turbine wheel and 
 nozzles, 393. 
 
 De Laval steam turbine — work- 
 ing parts, 396. 
 
 De Laval steam turbine — plan 
 view, 398. 
 
 De Laval steam turbine— sec- 
 tional view, 399. 
 
 De Laval steam turbine — gov- 
 ernor and valve, 402. 
 
 De Laval steam turbine — cross 
 section of wheel, 404. 
 
 Diagram of nozzles and buckets 
 in a Curtis steam turbine, 
 376. 
 
 Double riveted lap joint, 305. 
 
 Double riveted butt joint, 306. 
 
 Double crow foot stay, 318. 
 
 Governor of Curtis steam tur- 
 bine, 379. 
 
 Hamilton-Holzwarth steam 
 
 turbine, 385. 
 Hero's steam turbine, 357. 
 
 Jones underfeed stoker, 351. 
 
 Mansfield chain grate stoker, 
 
 338. 
 Murphy furnace, 344. 
 
 Playford stoker, 339. 
 
 Quadruple riveted butt joint, 
 309. 
 
 Roney stoker, 346. 
 
 Triple riveted butt joint, 307. 
 
 Vanderbilt locomotive fire box, 
 
 314. 
 Vicars mechanical stoker, 341. 
 
 Wilkinson mechanical stoker, 
 
 342. 
 Westinghouse - Parsons steam 
 
 turbine (general view), 360. 
 Westinghouse - Parsons steam 
 
 turbine (sectional view), 362. 
 Westinghouse - Parsons steam 
 
 turbine — open for inspection, 
 
 361. 
 Westinghouse -Parsons steam 
 
 turbine governor, 367. 
 
PART II 
 
 STEAM ENGINEERING 
 
 INDEX 
 
 Accumulator, 372. 
 
 Action of steam in turbine en- 
 gines, 364-377-398. 
 
 Adiabatic expansion, 392. 
 
 Admission of steam to turbine 
 engines, 370-379. 
 
 American stoker, 347-348-349. 
 
 Angle irons, 314. 
 
 Of segments, 320-321. 
 
 Of surface to be stayed, 319. 
 
 Balancing pistons, 365. 
 Barometric condenser, 408. 
 Boiler — 
 
 Care of, 327. 
 
 Braces and stays, 311. 
 
 Belpaire type, 313. 
 
 Fire cracks, 331. 
 
 How to prepare for washing 
 
 out, 328. 
 How to fire up, 331-332. 
 How to connect with main 
 
 header, 332. 
 Inspection of, 330. 
 Rivet material, 298. 
 Stay bolts, 313. 
 Steel plate — specifications 
 
 for, 296. 
 Tensile strength of plate, 
 
 296. 
 Thurston's specifications for 
 rivets, 298. 
 
 Calculating strength of stayed 
 
 surfaces, 319. 
 Channel bar, 317. 
 Clearance in turbine engines, 
 
 365-374-383. 
 Clinker on furnace walls, 330. 
 Coxe mechanical stoker, 338. 
 
 Crown — 
 
 Bars, 313. 
 
 Bolts, 313. 
 
 Sheet, 313. 
 Crow foot brace, 311-312. 
 Curtis steam turbine, 370. 
 
 Action of steam in, 377. 
 
 Efficiency of, 381. 
 
 Expanding nozzles of, 371 . 
 
 Guide bearings of, 373. 
 
 Lubrication of, 371. 
 
 Ratio of expansion in four 
 stage machine, 371. 
 
 Stationary blades — function 
 of, 374. 
 
 De Laval steam turbine, 392. 
 
 Action of steam in, 397-400. 
 
 Conversion of heat into work, 
 395. 
 
 Diverging nozzles of, 392. 
 
 Efficiency, tests of, 404-405. 
 
 Flexible shaft of, 400-402. 
 
 Gear wheels of, 400. 
 
 Governor, 402-403. 
 
 Vacuum valve, 403. 
 Diameters of rivets, 299-300. 
 Dished heads, 325. 
 Double riveted butt joints, 299- 
 
 303-306. 
 Double riveted lap joints, 300- 
 
 305-306. 
 Double crow foot brace, 318. 
 
 Efficiency — 
 
 Of double riveted lap joint, 
 
 305-306. 
 Of double riveted butt joint, 
 
 307. 
 Of triple riveted butt joint, 
 
 307. 
 
Efficiency — 
 
 Of quadruple riveted butt 
 
 joint, 309-310 
 Of Westing-house - Parsons 
 
 steam turbine, 368. 
 Of Curtis steam turbine, 380- 
 
 381. 
 Of De Laval steam turbine, 
 
 404. 
 
 Factor of safetv, 324. 
 Flexible coupling, 366-387. 
 Flexible shaft, 400. 
 Floating journal, 366. 
 Floating fulcrum, 367. 
 Fusible plug, 329. 
 
 Gusset stays, 314. 
 
 Hamilton - Holzwarth steam 
 
 turbine, 382. 
 Action of steam in, 385-386. 
 Development of, 382. 
 Distribution of steam in, 
 
 386. 
 Device for changing speed of, 
 
 389. 
 Flexible couplings of, 387. 
 Governor, 387-388. 
 Lubrication of, 390. 
 Regulating mechanism, 388- 
 
 389. 
 Running wheels, 384. 
 Stationary disks, 383. 
 Thrust ball bearing, 387. 
 
 Inspectors, U. S. Board of, 
 
 296-311. 
 Inspection of boilers, 330. 
 
 Jones underfeed stoker, 351- 
 352. 
 
 Kinetic energy of steam, 357- 
 391-400. 
 
 Lost work, 368. 
 
 Man-holes for boilers, 330. 
 Mechanical stokers, 334. 
 Murphy furnace, 341-342-343. 
 
 Nozzle — 
 
 Expanding, 391-395. 
 Valves, 395. 
 
 Outside furnaces, 353-354. 
 
 Parallel flow of steam in tur- 
 bine engines, 359. 
 
 Pitch— 
 
 Of rivets, 299-300. 
 For stays, 319. 
 
 Playford stoker, 339. 
 
 Punched and drilled boiler 
 plates, 297. 
 
 Quadruple riveted butt joint, 
 
 308. 
 Quintuple riveted butt joint, 
 
 308. 
 
 Rivets — 
 
 Crushing resistance of, 305. 
 
 Diameter and pitch of, 300. 
 
 Material for, 297. 
 
 Shearing strength of, 298. 
 Riveted joints — 
 
 Calculations for efficiencies 
 of, 306-307-308-309-310. 
 
 Double lap and butt, 302. 
 
 Single lap, 302. 
 
 Triple riveted butt, 303. 
 
 Quadruple riveted butt, 309. 
 
 Quintuple riveted butt, 309. 
 Riveting machine, 302. 
 Roney stoker, 345-346 
 
 Stayed surfaces — 
 
 Areas of, 320. 
 
 Strength of, 319-320-323. 
 Steam turbine — 
 
 Branca's turbine, 359. 
 
 Disposal of exhaust steam, 
 406. 
 
 Efficiency of, 381. 
 
 Hero's turbine, 359. 
 
 Main requisite for quiet run- 
 ning, 387. 
 
 Two- main sources of econ- 
 omy, 380-411. 
 
 Types of, 359. 
 
Tables- 
 Diameters of rivets, 298. 
 
 Diameters and pitch of rivets 
 in double riveted joint, 
 300. 
 
 Kent's rules for thickness of 
 plate and diameter and 
 pitch of rivets, 301. 
 
 Lloyd's rules for thickness of 
 plate and diameter of riv- 
 ets, 300. 
 
 Proportions of single riveted 
 lap joints, 302. 
 
 Proportions of double riveted 
 lap and butt joints, 303. 
 
 Proportions of triple riveted 
 butt joints, 304. 
 
 Through stays, 314-316-317. 
 
 Thurston's table of joint ef- 
 ficiencies, 301. 
 
 Triple riveted butt joint, 303- 
 304-307. 
 Turbines (steam) — 
 
 Branca's turbine, 359. 
 
 Disposal of exhaust steam, 
 406. 
 
 Efficiency of, 380. 
 
 Hero's turbine, 359. 
 
 Main requisites for quiet run- 
 ning, 387. 
 
 Types of, 359. 
 
 Unstayed surfaces — 
 » Rule for finding strength of, 
 324. 
 
 Vacuum — 
 
 Advantages of, 407-409. 
 
 Valve, 403. 
 Vanderbilt locomotive fire box, 
 
 313. 
 Velocity — 
 
 Force of, 380. 
 
 Of escaping steam, 360-361. 
 
 Work done by, 377-378. 
 Vicars mechanical stoker, 340. 
 
 Water column for boiler, 330. 
 Welded seams, 325. 
 Westinghouse - Parsons steam 
 
 turbine — 
 
 Action of steam in, 364-365. 
 
 Clearances in, 364. 
 
 Efficiency of, 369. 
 
 Floating journal, 367. 
 
 Governor, 367. 
 
 Principles of, 359. 
 
 Perfect balance of, 368. 
 
 Speed of, 360. 
 
 Stationary and moving 
 blades of, 363-364. 
 Wheels — 
 
 Impulse, 360. 
 
 Reaction, 360. 
 
 Running, 384. 
 Wilkinson stoker, 340-341 
 
PART III 
 INDEX 
 
 ELECTRICITY FOR ENGINEERS 
 
 Ammeters, 137. 
 
 alternating current, 143. 
 
 shunt, 138. 
 Ampere, definition of, 7. 
 
 hour, definition of, 9. 
 
 milli, definition of, 10. 
 
 turns, definition of, 42. 
 Arc Lamp, alternating current, 
 168. 
 
 brush, 155. 
 
 constant current, 154. 
 
 constant potential, 165. 
 
 enclosed, 167. 
 
 principle of, 153. 
 
 Thomson-Houston, 160. 
 
 Western Electric, 169. 
 Armature, location of faults, 61. 
 
 Balanced three- wire system, 
 
 23. 
 Booster, 198. 
 Brush system, 77. 
 
 controller, 84. 
 Brushes, care of, 53. 
 
 construction of, 53. 
 
 shifting of, 62. 
 
 setting of, 59. 
 
 staggered, 55. 
 
 Calculation of wires, 25. 
 Center of Distribution, 25. 
 Circuit breakers, 117. 
 Circular mil, definition of, 26. 
 Collector rings, 125. 
 Coulomb, definition of, 10. 
 Commutator, area allowed for 
 current, 51. 
 
 care of, 53. 
 
 construction of, 49. 
 Conductivity, definition of, 16. 
 Conductors, 7. 
 Constant current system, 20. 
 
 Constant potential system, 20. 
 Current, 5. 
 
 generation of, 40. 
 
 single phase, 129. 
 
 two and three phase, 130. 
 Cut-out box, 25. 
 
 Distributing center, 24. 
 Divided circuits, 16. 
 Dvnamos, alternating current, 
 122. 
 
 brush, 77. 
 
 care of, 64. 
 
 compound wound, 47. 
 
 failure to generate, 67. 
 
 operation of constant cur- 
 rent, 75. 
 
 operation of constant poten 
 tial, 65. 
 
 operation in parallel, 69. 
 
 reversal of current, 44. 
 
 separate exciting, 123. 
 
 series, connections of, 45 
 
 shunt, connections of, 46. 
 
 test for polarity, 70. 
 
 Thomson-Houston, 89. 
 
 Electromagnet, 41. 
 Electromotive force, definition 
 
 of counter, 108. 
 Electroplating, 199. 
 Electrolysis, 199. 
 Electrolytic action, 9. 
 Equalizer bar, 72. 
 
 Feeders, 24. 
 Fuses, 117. 
 
 Gramme Ring, 44. 
 Ground detectors, 185. 
 
 Heating by electricity, 201= 
 Horse power, 15. 
 
Incandescent lamps, 172. 
 
 current required, 175. 
 
 efficiency tables, 173. 
 Insulators, 7. 
 
 Joints in wires, 31. 
 Joule, 15. 
 
 Kilowatt hour, 15. 
 
 Laminated armature, 53. 
 Light, absorbtion of, 176. 
 Lightning arresters, 204. 
 
 Thomson, 206. 
 Lines of force, definition of, 41. 
 
 direction of, 42. 
 Loss in wires, 27. 
 
 Magnet, soft iron, 5. 
 
 steel, 5. 
 Meters, reading of, 147. 
 Mil, circular, 26. 
 
 square, 26. 
 Motors, 107. 
 
 alternating current, 116- 
 
 compound, 112. 
 
 series, 111. 
 
 shunt, 110. 
 Multiple arc system, 20 
 Multiple series system, 21. 
 
 Negative wire, 23. 
 Nernst lamp, 177. 
 Neutral point of dynamo, 49. 
 Neutral wire, 22. 
 
 Ohm, 13. 
 Ohm's law, 14. 
 
 Parallel system, 19. 
 Photometer, Bunsen, 190. 
 
 Rumford's, 191. 
 Polarity indicator, 142. 
 Positive wire, 23. 
 Potential, difference of, 10. 
 Prony brake, 187. 
 
 Regulator, Brush, 85. 
 series dynamo, 45. 
 
 Resistance box. 46. 
 
 definition of, 13. 
 
 effect of heat on, 13. 
 Rheostat for shunt dynamo, 66. 
 
 Series arc system . 20. 
 
 circuit, 6. 
 
 multiple sj^stem, 20. 
 Service wires, 25 
 Short circuit, 11. 
 Speed controller, 114. 
 Square mil, 26. 
 Static electricity, 12. 
 Storage batteries, 193. 
 
 connections for, 197. 
 Switchboard, arc, 101. 
 
 arc, 104. 
 
 constant potential, 73. 
 
 Testing lines, 181. 
 
 dynamo efficiency, 187. 
 
 grounds, 184. 
 
 open circuits, 181. 
 
 short circuits, 183. 
 Thomson-Houston system, 89. 
 
 controller, 97. 
 Three-wire system, 22. 
 Transformer, principle of, 130 
 
 rotary, 128. 
 
 Volt, definition of, 10. 
 Voltameter, 9. 
 Voltmeter, 10. 
 
 alternating current, 143. 
 
 magnetic vane, 137. 
 
 Weston, 133. 
 
 Watt, definition of, 14. 
 
 hour, definition of, 15. 
 Wattmeters, 144. 
 
 Thomson, 145. 
 Wires, carrying capacity of, 38. 
 
 properties of, 39. 
 
 weights of copper, 37. 
 Wiring tables, 32. 
 Wiring systems, 19. 
 
INTRODUCTION 
 
 ENGINEERING DIVISION 
 
 In the following pages the author proposes to oleal 
 mainly with the operation of steam engines, boilers, 
 feed pumps, and all the necessary adjuncts of a steam 
 plant, rather than with the co?istmctioii and erectio?i of 
 the same, although the designing and construction of 
 steam machinery will receive some attention. 
 
 In order to successfully operate a steam plant the 
 engineer in charge should, in addition to his other 
 accomplishments, have at least sufficient technical 
 knowledge to enable him to ascertain, by measure- 
 ments and calculations, such very important points as 
 the safe working pressure of his boiler, the most eco- 
 nomical point of cut off for his engine, whether engine 
 and boiler are properly proportioned for the work to 
 be performed, and many other details which will be 
 treated upon in their proper place. 
 
 Without a doubt the most successful operating 
 engineers are those who combine practice with theory, 
 and in order to obtain a practical working knowledge 
 of steam engineering it is absolutely necessary that 
 the young man who desires to become a successful 
 engineer should start in the boiler-room, that he 
 should thoroughly familiarize himself with' all of the 
 details of boiler management, and while his hands 
 and eyes are thus gradually being trained to the prac- 
 tical part of the work he should at the same time be 
 training his mind in the theoretical part by reading 
 and studying technical books and journals relative to 
 steam engineering. In order to facilitate this work a 
 9 
 
10 . INTRODUCTION 
 
 series of practical questions will follow the close of 
 each chapter, the answers to which may be found in 
 the matter contained in the chapter. And now with 
 the hope that a study of the following pages may prove 
 to be a help to all into whose hands this book may 
 come, the author respectfully dedicates it to his fellow 
 craftsmen, the engineers of America. 
 
 C. F. S. 
 
Engineering 
 
 CHAPTER I 
 THE BOILER 
 
 Description of various types — Construction — Rules for ascertain- 
 ing strength of sheet before and after punching — Strength of 
 rivets — Single and double riveted seams — Triple riveted butt 
 joints, strength of — Force tending to rupture a boiler — Rules 
 for finding the safe working pressure of boilers — gracing — 
 Rules for bracing — Bracing domes. 
 
 It is hardly within the scope of this book to describe 
 the many and varied types of metallic vessels known 
 as steam boilers in use to-day for the generation of 
 steam for power and other purposes. The author will 
 deal mainly with those types most commonly used in 
 this country for stationary service. 
 
 Description. These may be divided into four differ- 
 ent classes. The first and most simple type, and the 
 one from which the others have gradually evolved, is 
 the plain cylinder boiler in which the heated gases 
 merely pass under the boiler, coming in contact only 
 with the lower half of the shell and then pass to the 
 stack. These boilers are generally of small diameter 
 (about 30 in.) and great length (30 ft.). Next comes 
 the flue cylindrical boiler, which is somewhat larger in 
 diameter than the former, generally 40 in. diameter 
 and 20 to 30 ft. long, with two large flues 12 to 14 in. 
 diameter extending through it. The return tubular 
 boiler, consisting of a shell with tubes of small diam- 
 11 
 
12 
 
 ENGINEERING 
 
 eter (2 to 4 in.) extending from head to head through 
 which the hot gases from the furnace pass on their 
 way to the stack. This boiler, which comes in the 
 third class, is probably more extensively used in the 
 United States for stationary service than any other 
 type. The fourth class comprises the water tube boil- 
 ers, in which the water is carried in tubes 3 to 4 in. in 
 diameter, sometimes vertical and sometimes inclined, 
 and connected at the top to one end of a steam drum, 
 
 STANDARD HORIZONTAL BOILER WITH FULL-ARCH FRONT SETTING. 
 
 and having the lower ends of the tubes connected to a 
 mud drum, which is also connected to the opposite end 
 of the steam drum, thus providing for a free circula- 
 tion of the water. Of the latter type there have been 
 many different kinds evolved during the last one hun- 
 dred years, the majority of them having had but a 
 brief existence, being compelled to obey the inex- 
 orable law of the survival of the fittest, and to-day 
 there are a few excellent types of water tube boilers 
 
THE BOILER 
 
 IS 
 
 which have become standard and are being extensively 
 used. The margin of safety as regards disastrous 
 
 WICKES VERTICAL WATER TUBE BOILER, 
 
 explosions appears to be in favor of the water tube 
 boiler. It is not contended that they are entirely 
 
14 
 
 ENGINEERING 
 
 exempt from the danger of explosion. On the con- 
 trary, the percentage of explosions of water tube boil- 
 ers in proportion to the number in use is probably as 
 large, if not larger, than it is with boilers of the shell 
 or return tubular type, but the results are seldom so 
 destructive of life or property, for the reason that if 
 one or more of the tubes give way the pressure is 
 released and the danger is past. 
 
 500 HORSE POWER HEINE WATER TUBE BOILER. 
 
 Construction. As the four classes of boilers above 
 referred to are constructed of similar material, although 
 assembled in different ways, the standard rules for 
 calculating strength of joints, bracing, etc., may be 
 applied to all. 
 
 The shell should be made of homogeneous steel of 
 about 60,000 lbs. tensile strength. The thickness 
 depending upon the pressure to be carried. The term 
 
THE BOILER 15 
 
 tensile strength means that it would take a pull of 
 60,000 lbs. in the direction of its length to break a bar 
 of the material one inch square, or two inches wide by 
 one-half inch thick, or three-eighths of an inch thick 
 by 2.67 in. wide. 
 
 The heads are generally made one-eighth of an inch 
 thicker than the shell. 
 
 Riveting. Boiler rivets should be of good charcoal 
 iron, or a soft, mild steel of 38,000 lbs. to 40,000 lbs. 
 T. S. No boiler is stronger than its weakest part, and 
 it is evident that a riveted joint has not the full 
 strength of the solid plate. In order to ascertain the 
 safe working pressure of a boiler it is necessary to first 
 determine the strength of the riveted seams, and the 
 method of doing this is as follows: Assume the boiler 
 to be of the horizontal tubular type, 60 in. in diameter 
 by 16 ft. in length. The plates to be of steel ^ in. 
 thick, having a tensile strength of 60,000 lbs. per 
 square inch, the longitudinal seams to be double 
 riveted and the girth seams to be single riveted. The 
 pitch of the rivets, that is the distance from the center 
 of one rivet hole to the center of the next one in the 
 same row, to be for the double riveted seams 3^ in. 
 and for the single riveted seams 2}i in. The diameter 
 of the rivets to be yk in. and diameter of holes to be 
 \\ in. Assume the rivets to have a T. S. of 38,000 lbs. 
 per square inch of sectional area. First, find strength 
 of a section of solid plate 3^ in. wide, which is the 
 width between centers of rivet holes before punch- 
 ing. 
 
 Rule 1. Pitch x thickness x T. S. Thus, 3.25 x .375 x 
 60,000 = 73,125 lbs., strength of solid plate. 
 
 Second, find strength of net section of plate, mean- 
 ing that portion of plate left after deducting the diam- 
 
16 
 
 ENGINEERING 
 
 eter of one hole || in., which expressed in decimals 
 = .9375 in. from the width of plate before punching. 
 
 Rule 2. Pitch - diameter of hole x thickness x T. S. 
 Thus, 3.25 - .9375 x .375 x 60,000 = 52,031 lbs., strength 
 of net section of plate. 
 
 Third, find strength of rivets. In calculating the 
 strength of rivets in a double riveted seam, the sec- 
 tional area of two rivets must be considered, taking 
 
 BABCOCK AND WILCOX BOILER. 
 
 one-half the area of two rivets in the first row, and the 
 area of another rivet in the second row. The area of 
 a %-in. rivet is .6013 in., but when in position it is 
 assumed to fill the hole \\ in. Consequently, its area 
 would then be .69 in. and its strength is found by 
 Rule 3. 
 
 Rule j. Sectional area x T. S. Thus, .69x38,000 = 
 26,220 lbs. , strength of one rivet, and multiplying by 2, 
 as there are two rivets, the result is 26,220 x 2 = 52,440 
 
THE BOILER 
 
 17 
 
 Jbs., strength of. rivets in the seam under considera- 
 tion. It thus appears that the plate is the weakest por- 
 
 VERTICAL FIRE BOX BOILER. 
 
 tion and the percentage of strength retained is found 
 by multiplying $2,031 by 100 and dividing by 73,12$, 
 
18 ENGINEERING 
 
 the strength of solid plate. Thus, =71.1 
 
 per cent. 
 
 The query might arise, why is the diameter of one 
 rivet hole deducted from the pitch when figuring the 
 strength of net plate? The answer is, that in punching 
 the holes one-half the diameter of each hole is cut 
 from the section designated, thereby reducing its width 
 by just that amount. 
 
 The 71. 1 per cent, obtained by the calculation rep- 
 resents the strength of the boiler as compared to the 
 strength of the sheet before punching, and should enter 
 into all calculations for the safe working pressure. 
 
 It is usual in practice to figure the strength of a 
 double-riveted seam at yo per cent, of the strength of 
 the solid plate. The strength of triple-riveted butt 
 joints may be calculated by taking a section of plate 
 along the first row of rivets and estimate it as a single- 
 riveted joint, then add to this result the strength of 
 rivets in the second and third rows for a section of the 
 same width. In properly designed triple-riveted butt 
 joints the percentage of strength retained is 88, and 
 some recent achievements in designing have shown the 
 remarkable result of quadruple-riveted butt joints 
 retaining as high as 92 to 94 per cent, of the strength 
 of the solid plate. 
 
 Bursti?ig Pressure. The query might arise, why 
 should the longitudinal or side seams require to be 
 stronger than the girth or round about seams? The 
 answer is, that the force tending to rupture the boiler 
 along the line of the longitudinal seams is proportional 
 to the diameter divided by two, while the stress tend- 
 ing to pull it apart endwise is only one-half that, or 
 proportional to the diameter divided by four. 
 
THE BOILER 19 
 
 To illustrate, let Fig. i represent the shell of the 
 boiler heretofore referred to, ignoring for the time 
 being the tubes and braces, and consider the boiler 
 simply as a hollow cylinder. Now the total force 
 tending to rupture the boiler along the line of the girth 
 seams or in the direction of the horizontal arrows = area 
 of one head in square inches x pressure in pounds per 
 square inch. It is true that the pressure is exerted 
 against both heads, but the area of one head can- only 
 be considered for the reason that the two stresses are 
 exerted against each other just as in the case of two 
 horses pulling against each other, or in opposite direc- 
 tion on the same chain. The stress on the chain will 
 
 g A B 
 
 be what each horse (not both) pulls. To further illus- 
 trate, suppose one of the horses to be replaced by a 
 permanent post or wall and let one end of the chain be 
 attached thereto. One head or one side of the boiler 
 pulls against the other, and the stress on the seams is 
 the force with which each (not both) pulls. Referring 
 again to Fig. I, area of one head = 6cr x .7854 = 2827.4 
 sq. in. Suppose there is a pressure of 10 lbs. pet- 
 square inch in the boiler. Then total stress on the 
 girth seams = 2827.4 x 10 = 28,274 lbs. Opposed to this 
 pull is the entire circumference of the boiler, which is 
 60 x 3.1416= 188.5 m - Therefore, dividing total pres- 
 sure (28,274 lbs.) by the circumference in inches (188. 5) 
 will give 150 lbs. as the stress on each inch of the 
 
c 20 • ENGINEERING 
 
 girth seams. While the stress on each inch of the 
 longitudinal seams or along the line A B, Fig. i, and 
 which is exerted in the direction of the vertical arrows, 
 is pressure (10 lbs.) x one-half the diameter (30 in.) 
 = 300 lbs. One-half the diameter is used because the 
 pressure in any direction is effective only on the sur- 
 face at right angles to that direction. 
 
 The formula for finding the bursting pressure of a 
 boiler may be expressed as follows: 
 
 T S x T . 
 B = ' in which B = bursting pressure. 
 
 T.S. = tensile strength. 
 T= thickness of sheet. 
 R= radius or one-half the cliam. , 
 Example. T. S. = 55,000 lbs. per square inch. 
 
 T = ys in. (expressed decimally = .375 
 
 in.). 
 R = 30 in. 
 Then 55,000 x .375 -f- 30 = 687.5 l° s - P er square inch, 
 which is the pressure at which rupture would take 
 place provided there were no seams in the boiler and 
 the original strength of the sheet was retained, but, as 
 has been seen, a certain percentage of strength is lost 
 through punching or drilling the necessary rivet holes, 
 and this must be taken into account. 
 
 The formula now becomes, for double riveting, 
 
 B =— — '- — = — , in which the letters preserve the same 
 
 value as in the original formula, but the result is 
 reduced by multiplying by the decimal .70, which rep- 
 resents the percentage of strength retained by double- 
 riveted seams. Consequently B will now = 
 
 55.ooox.375x.70 8llbs . 
 30 
 In case the seams are all single riveted .56 must be 
 
THE BOILER 21 
 
 substituted for .70, and with triple-riveted butt joints 
 .88 can safely be used. 
 
 Safe Working Pressure. In order to ascertain the safe 
 working pressure of a boiler it is necessary first to cal- 
 culate the bursting pressure and divide this by another 
 factor called the factor of safety. The one most com- 
 monly used for boilers is 5, or in other words the safe 
 working pressure = one-fifth the bursting pressure. In 
 the case of the boiler under consideration, the safe 
 pressure would be 481 ■*- 5 = 96 lbs., at which point the 
 safety valve should blow off. 
 
 Bracing. Every engineer can easily ascertain for 
 himself whether the boilers under his charge are 
 properly braced or not. The parts that require bra- 
 cing are: all flat surfaces, such as the sides and top of 
 the fire-box in boilers of the locomotive type, and 
 those portions of the heads above and below the tubes 
 in horizontal tubular boilers, also the top of the dome. 
 
 The stress per square inch of sectional area on braces 
 and stays should not exceed 6,000 lbs. It is custom- 
 ary to consider the flange of the head and the top row 
 of tubes as sufficient bracing for a space two inches 
 wide above the tubes and the same distance aruund the 
 flange. Therefore the part of the head to be braced 
 will be the segment contained within a line drawn two 
 inches above the top row of tubes and two inches inside 
 the flange. 
 
 In order to ascertain the number of braces required 
 for a given boiler he^ad, three factors are necessary: 
 first, the area of the segment in square inches; second, 
 the diameter and T. S. of the braces, and third, the 
 pressure to be carried. By the use of Table No. 1 the 
 areas of segments of boiler heads ranging from 42 to 72 
 in. in diameter can easily be obtained. Assume the 
 
ENGINEERING 
 
 boiler to be 60 in. in diameter, distance from top of 
 tubes to top of shell 24 in. Deduct 4 in. for surface 
 braced by top row of tubes and flange, leaving the 
 height of segment to be braced 20 in. 
 
 TABLE I 
 
 Diameter 
 of Boiler. 
 
 Ditsance from 
 Tubes to Shell. 
 
 Height of 
 Segment. 
 
 Constant. 
 
 42 in. 
 
 15 in. 
 
 11 in. 
 
 .16314 
 
 44 in. 
 
 17 ni. 
 
 13 in. 
 
 .1936 
 
 48 in. 
 
 19 m. 
 
 15 m. 
 
 .20923 
 
 54 m. 
 
 21 m. 
 
 17 in. 
 
 .21201 
 
 60 in. 
 
 24 in. 
 
 20 in. 
 
 .22886 
 
 66 in. 
 
 25 m. 
 
 21 in. 
 
 .214 
 
 72 in. 
 
 29 in. 
 
 25 in. 
 
 .24212 
 
 Rule. Multiply the square of the diameter of the 
 boiler by the constant number found in right hand col- 
 umn opposite column headed diameter. 
 
 Example. 60 x 60 x .22886 = 823.89 sq. in., area of 
 segment to be braced. Find number of braces 
 required. Assume the braces to be ij4 in. in diam- 
 eter and of a T. S. of 38,000 lbs. per square inch of 
 section. The area of one brace will be .994 sq. in., 
 which x 6,000 lbs. gives 5,964 lbs. as the stress allow- 
 able on each brace. Suppose the pressure to be car- 
 ried is 100 lbs. per square inch. There will be area of 
 segment (823.89 sq. in.) x pressure (100 lbs.) = 82,389 
 lbs., total stress. Dividing this result by 5,964 lbs. 
 (the capacity of each brace) gives 13.8 braces as the 
 number needed. In practice there should be fourteen. 
 
 Having a T. S. of 38,000 lbs. and using 6 as the 
 factor of safety, each brace could safely sustain a pull 
 of 6,295 lbs. Therefore it is evident that the above 
 mentioned load for each brace is well within the limit. 
 For convenience in calculating the areas of segments 
 
THE BOILER 
 
 of circles, other than those mentioned in Table I, the 
 following rule is given: 
 
 Referring to Figure 2 it is desired to find the area of 
 t/-'e segment contained within the lines A B C E. It 
 will be necessary first to find the area of the sector 
 bounded by the lines A B C D. This is done by mul- 
 tiplying one-half the length of 
 the arc, A B C, by the radius, 
 D B. Having obtained the 
 area of the sector, the next / 
 step is to find the area of the 
 triangle bounded by the lines 
 A E.C D and subtract it from 
 the area of the sector. The 
 remainder will be the area of 
 the segment. Having found 
 
 the area of the surface to be braced, and the number 
 of braces required, it now becomes necessary to con- 
 sider the spacing of the same. 
 
 Rule. Divide area to be braced by the number of 
 braces, and extract the square root of quotient. 
 
 Example. 823.89- 14= 58.8 sq. in. to be allotted to 
 each brace. Extract square root of 58.8 and the 
 result is 7.68 inches, which is the length of one side of 
 the square which each brace will be required to sus- 
 tain. 
 
 For internally fired boilers the same rules can be 
 applied except that the surfaces to be braced are 
 generally of rectangular shape and consequently the 
 area is more easily figured than in the case of seg- 
 ments. That part of the head below the tubes also 
 requires to be braced, and two braces are generally 
 sufficient, as at A and B, Fig. 3. In the case of domes 
 it is safe to consider the portion of the head within 
 
24 
 
 ENGINEERING 
 
 three inches of the flange as sufficiently braced. Then 
 suppose the dome to be 36 in. in diameter, there will 
 remain a circle 30 in. in diameter to be braced. The 
 circumference of this circle is 94.2 in. and the pitch, 
 or distance from center to center of the braces, being 
 
 7.6 in., the number of 
 braces required is 
 found by dividing 94.2 
 b y 7-6, giving 12 
 braces. These braces 
 should be located 
 along a line which is 
 one-half the pitch, or 
 3.8 in., within the cir- 
 cumference of the 30- 
 in. circle. The space 
 immediately surround- 
 ing the hole cut for 
 the steam outlet will 
 be sufficiently reen- 
 forced by the flange riveted on for the reception of the 
 steam pipe. All holes cut in boilers, such as man 
 holes, hand holes, and those for pipe connections, 
 above two. inches should be properly reenforced by 
 riveting either inside or outside a wrought-iron or steel 
 ring or flange of such thickness and width as to con- 
 tain at least as much material as has been cut from 
 the hole. 
 
 Questions 
 
 1. How many types of steam boilers are there? 
 
 2. What kind of boilers are included in type one? 
 
 3. Describe a boiler belonging to type two. 
 
 4. Describe a boiler of the third type. 
 
 figure 3. 
 
THE BOILER 25 
 
 5. How is a boiler of the fourth type constructed? 
 
 6. In what respect do water tube boilers have the 
 advantage over other types as regards explosions? 
 
 7. What kind of material should be used in the con- 
 struction of boilers? 
 
 8. What does the term tensile strength (T. S.) 
 mean? 
 
 9. What is the usual T. S. of steel boiler plates? 
 
 10. How much thicker than the shell plates should 
 the heads be? 
 
 11. Of what material and of what T. S. should the 
 rivets be? 
 
 12 Is a riveted joint as strong as the solid plate? 
 
 13. What is meant by the pitch of the rivets? 
 
 14. What is the usual pitch for a double riveted 
 seam? 
 
 15. Give the rule for finding the strength of the solid 
 plate before punching. 
 
 16. What is meant by net section of plate? 
 
 17. What is the rule for finding strength of net sec- 
 tion of plate? 
 
 18. How is the strength of rivets in a double riveted 
 seam calculated? 
 
 19. What percentage of the strength of solid plate is 
 usually retained in a double riveted seam? 
 
 20. How is the strength of a triple riveted butt strap 
 joint calculated? 
 
 21. What per cent, of the original strength of the 
 sheet is retained in a properly designed triple riveted 
 butt strap joint? 
 
 22. Why should the side seams be stronger than the 
 girth seams? 
 
 23. What is the rule for finding the bursting pressure 
 of a boiler? 
 
26 ENGINEERING 
 
 24. How is the safe working pressure of a boiler 
 calculated? 
 
 25. What parts of a boiler require bracing internally? 
 
 26. What stress per square inch of sectional area 
 may be allowed on braces? 
 
 27. How is the number of braces required for any 
 part of the boiler obtained? 
 
 28. How should domes.be braced? 
 
CHAPTER II 
 BOILER SETTINGS AND APPURTENANCES 
 
 Foundations — Brick work, etc. — Grate surface — Insulation — Water 
 columns — Steam -gages— Safety valves — Rules for finding 
 areas of — Fusible plugs and where to place them — Domes and 
 mud drums — Feed pipes — A good arch for the back connec- 
 tion — Blow off pipes and cocks — Surface blow off and circulat- 
 ing system — Feed pumps and feed water heaters— Injectors — 
 Saving effected by heating the feed water with exhaust 
 steam — Apparatus for making coal tests— Heating surface — 
 Rules for figuring the same. 
 
 Settings. In the case of internally fired boilers the 
 matter of setting resolves itself into the simple point 
 of securing a sufficiently solid foundation, either of 
 stone or brick laid in cement, for the boiler to rest 
 upon. 
 
 But with horizontal tubular or water tube boilers the 
 matter of brick work becomes important, and partic- 
 ular attention should be paid to securing a good foun- 
 dation for the walls and great care exercised in building 
 them in such manner that the expansion of the inner 
 wall or lining will not seriously affect the outer walls. 
 This can be done be leaving an air space of two inches 
 in the rear and side walls, beginning at or near the 
 level of the grate-bars and extending as high as the 
 fire line, or about the center line of the boiler. Above 
 this height the wall should be solid. Fig. 4 shows a 
 plan and an end elevation illustrating this idea. The 
 ends of some of the bricks should be allowed to project 
 at intervals from the outer walls across the air space, 
 so as to come in touch with the inner walls. 
 27 
 
28 
 
 ENGINEERING 
 
 Where boilers are set in batteries of two or more the 
 middle or party walls should be built up solid from 
 the foundation. All parts of the walls with which the 
 
 FIGURE 4. 
 
 fire comes in contact should be lined with fire brick, 
 every fifth course being a header to tie the lining to 
 the main wall. 
 
 Bridge walls should be built straight across from 
 wall to wall of the setting, and should not be curved to 
 conform to the circle of the boiler shell. The proper 
 
 -4 
 
 FIGURE 5. 
 
 distance from the top of the bridge wall to the bottom 
 of the boiler varies from eight to ten inches, depend- 
 ing upon the size of the boiler. The space back of the 
 
BOILER SETTINGS AND APPURTENANCES 
 
 29 
 
 bridge wall, called the combustion chamber, can be 
 filled in with earth or sand, and should slope gradually 
 downward from the back of the bridge wall to the floor 
 level at the rear wall, and should be paved with hard 
 burned brick. The ashes and soot can then be easily 
 cleaned out by means of a long-handled hoe or scraper 
 inserted through the cleaning out door, which should 
 always be placed in the back wall of every boiler set- 
 ting. 
 
 Back Arches. A good and durable arch can be made 
 
 FIGURE 6. 
 
 for the back connection, extending from the back wall 
 to the boiler head, by taking flat bars of iron S/ 8 x 4 in., 
 cutting them to the proper length and bending them 
 in the shape of an arch, turning four inches of each 
 end back at right angles, as shown in Fig. 5-. The 
 distance O-B should equal that from the rear wall to 
 the boiler head, and the height, O-A, should be about 
 equal to O-B, and should bring the point A about two 
 inches above the top row of tubes. The clamp thus 
 formed is filled with a course of side arch fire brick, 
 
30 
 
 ENGINEERING 
 
 Fig. 6, and will form a complete and self-sustaining 
 arch, the bottom, B, resting on the back wall, and the 
 top, A, supported by an angle iron riveted across the 
 boiler head about three inches above the top row of 
 tubes. See Figs. 7 and 8. 
 
 Enough of these arches should be made so that when 
 laid side by side they will cover the distance from one 
 side wall to the other across the rear end of the boiler. 
 A fifty-four-inch boiler would thus require, six clamps, 
 
 FIGURE 7. 
 
 a sixty-inch boiler seven clamps, and a seventy-two- 
 inch boiler would require eight clamps; the length of 
 a fire b*rick being about nine inches. In case of needed 
 repairs to the back end of the boiler the sections can 
 be lifted off, thus giving free access to all parts, and 
 when the repairs are completed the arches can be reset 
 with very little trouble and much less expense than the 
 building of a solid arch would necessitate. This form 
 of segmental arch allows ample freedom for expansion 
 
BOILER SETTINGS AND APPURTENANCES 
 
 31 
 
 of the boiler, in the direction of its length, without 
 leaving an opening when the boiler contracts. 
 
 The crosswise construction of arch bars, while afford- 
 ing equal facility in repair work, is necessarily more 
 expensive than the form here described, and is also 
 open to the objection that it cannot follow the con- 
 tracting boiler and maintain a tight joint or connection 
 
 FIGURE 8. 
 
 between the back arch and the rear head above the 
 tubes. 
 
 Boiler walls should always be well secured in both 
 directions by tie rods extending throughout the entire 
 length and breadth of the setting, whether there be one 
 boiler or a battery of several. The bottom rods 
 should be laid in place at the floor level when starting 
 the brick work, and the top rods extending transversely 
 across the boilers can be laid on top of the boilers. 
 
32 ENGINEERING 
 
 The top rods extending from front to back can be laid 
 in the side walls or rest on top of them. All tie rods 
 should be at least one inch in diameter, and for batter- 
 ies of several boilers they should be larger. The rods 
 should extend three or four inches beyond the brick 
 work, with good threads and nuts on each end to 
 receive the buck stays. In laying down the transverse 
 tie rods they should be located so as to allow the buck 
 stays to bind the brick work where the greatest con- 
 centration of heat occurs. 
 
 Horizontal boilers should always be set at least one 
 inch lower at the back end than at the front, to make 
 sure that the rear ends of the tubes will be covered 
 with water so long as any appears in the gauge glass, 
 provided of course that the lower end of the glass is 
 properly located with reference to the top row of 
 tubes, which will be discussed later on. Upon the 
 brick work and immediately under each lug of the 
 boiler there should be laid in mortar a wrought or cast 
 iron plate several inches larger in dimension than the 
 bearing surface of the lug and not less than one inch in 
 thickness. Upon each of these plates there should be 
 placed two rollers made of round iron ion^ in. in 
 diameter, and as long as the width of the lug. These 
 rollers should be placed at right angles to the length 
 of the boiler, in such a position that the lug will bear 
 equally upon them. The object of the rollers is to 
 prevent disturbance of the brick work by the endwise 
 expansion and contraction of the boiler. 
 
 Grate Surface. The number of square feet of grate 
 surface required depends upon the size of the boiler. 
 A good rule and one easy to remember is to make the 
 length of the grates equal to the diameter of the boiler. 
 The width, of course, will depend upon the construe- 
 
BOILER SETTINGS AND APPURTENANCES 33 
 
 tion of the furnace. If the fire brick lining is built 
 perpendicular, the width of grate will be about equal 
 to the diameter of the boiler. On the other hand, if 
 the lining is given a batter of three inches, starting at 
 the level of the grate, then the width will be reduced 
 six inches. It is customary to allow one square foot 
 of grate surface to every 36 sq. ft. of heating surface. 
 The distance of the grate-bars from the shell of the 
 boiler varies from 24 to 28 in., according to the dimen- 
 sions of the boiler. 
 
 Insulation. All boilers should be well protected 
 from the cooling influence of outside air, if economy 
 
 M CLAVE' S GRATES. 
 
 of fuel is any object. The tops of horizontal boilers 
 should be covered with some kind of heat insulating 
 material, or arched over with common brick, leaving a 
 space of two inches between the boiler and the arch. 
 The resulting saving in fuel will far more than com- 
 pensate for the extra expense in a very short time. 
 All cracks in the side and rear walls should be care- 
 fully pointed up with mortar or fire clay. One source 
 of heat loss in return flue boilers is short circuiting 
 from the furnace to the breeching, caused by the 
 arches over the fire doors becoming loose and shaky, 
 and allowing considerable of the heat to escape directly 
 to the stack instead of passing under the boiler and 
 
34 ENGINEERING 
 
 through the tubes. Another bad air leak often occurs 
 at the back connection when the arch rests wholly 
 upon iron bars imbedded in the side walls. This leak, 
 as has already been noted, is caused by the expansion 
 of the boiler, which gradually pushes the arch away 
 from the back head until, in the course of time, there 
 will be a space of $/% in. and sometimes y± in. between 
 the head and the arch. The obvious remedy for this 
 is an arch that will go and come with the movement 
 of the boiler, and such an arch can be secured by build- 
 ing it in sections, as illustrated by Fig. 3, and then 
 riveting a piece of angle iron to the boiler head, above 
 
 m' clave' s grates. 
 
 the top row of tubes for the upper ends of the sections 
 to rest upon, as already described. It will be seen 
 that within all possible range of boiler movement in 
 either direction the arch will, with this construction, 
 always remain close to the head. 
 
 Water Columns. Water columns should be so located 
 as to bring the lower end of the gauge glass exactly on 
 a level with the top of the upper row of tubes, thus 
 always affording a perfect guide as to the depth of 
 water over the tubes. Many gauge glasses are placed 
 too low, and water tenders and firemen are- often 
 deceived by them unless their positions with relation to 
 the tubes are carefully noted. 
 
BOILER SETTINGS AND APPURTENANCES 35 
 
 The only safe plan for an engineer to pursue in 
 taking charge of a steam plant is to seize the first 
 opportunity for noting this relation. When he has 
 washed out his boilers he may leave the top man-hole 
 plates out while refilling them, and when the water 
 stands at about four inches over the top row of tubes, 
 the depth of water in the glass should be measured. 
 He should do this with every boiler in the plant, and 
 make a memorandum for each boiler. He will then 
 know his bearings with regard to the safe height of 
 water to be carried in the several gauge glasses. If he 
 finds any of them are too low, he should lose no time 
 
 m' clave' s grates, 
 
 in having them altered to comform to the requirements 
 of safety. The position of the lower gauge cock 
 should be three inches above the top row of tubes. 
 
 In making connections for the water column plugged 
 crosses should always be used in place of ells. Brass 
 plugs are to be preferred if they can be obtained; but 
 whether of brass or iron, they should always be well 
 coated with a paste made of graphite and cylinder oil 
 before they are screwed in. They can then be easily re- 
 moved when washing out the boiler, so as to allow the 
 scale, which is sure to form in the lower connection, to 
 be cleaned out. The best point at which to connect the 
 lower pipe with the boiler is in the lower part of the 
 
36 ENGINEERING 
 
 head just below the bottom row of tubes, and near the 
 side of the boiler on which the water column is to 
 stand; \% or \y 2 in. pipe should be used in all cases. 
 The top connection can be made either in the head 
 near the top, or in the shell. A 24 or I in. drain pipe 
 should be led into the ash pit, fitted with a good reli- 
 
 AUXILIAEY SPRING PRESSURE GAUGE. 
 
 able valve which should be opened at frequent intervals 
 to allow the mud and dirt to blow out of the water col- 
 umn and its connections. This is a very important 
 point, and great care should be taken to keep the 
 water column and all its connections thoroughly clean 
 at all times. 
 
 One of the best indications that some portion of the 
 
BOILER SETTINGS AND APPURTENANCES 37 
 
 connections between the water glass and the boiler is 
 choked or plugged with scale, is when there is no per- 
 ceptible movement of the water in the glass. When 
 the connections are free and the boiler is being fired, 
 
 AUXILIARY SPRING PRESSURE GAUGE, SECTIONAL VIEW. 
 
 there is always a slight movement of the water up and 
 down in the glass, and when there is no perceptible 
 movement it is time to look for the cause at once. 
 Many instances of burned tubes have occurred, and 
 
38 
 
 ENGINEERING 
 
 even explosions caused by low water in boilers while 
 the gauge glass showed the water to be at a safe 
 height. But owing to the connections having become 
 plugged with scale, the water in the glass had no con- 
 nection whatever with that in the boiler, and the water 
 column was therefore worse than useless. 
 
 Steam Gauges. As water columns are made at pres- 
 ent the steam gauge is usually connected at the top of. 
 the column. This makes a handsome and convenient 
 connection, although theoretically the proper method 
 would be to connect the steam gauge directly with the 
 dome or the steam space of the shell. There should 
 always be a trap or siphon in the gauge pipe in order 
 
BOILER SETTINGS AND APPURTENANCES 39 
 
 to retain the water of condensation, so as to prevent 
 the hot steam from coming in contact with the spring. 
 
 If at any time the water is drained from the siphon, 
 care should be exercised in turning on the steam 
 again by allowing it to flow in very slowly at first until 
 the siphon is again filled with water. 
 
 The steam gauge and the safety valve should be com- 
 pared frequently by raising the steam pressure high 
 enough to cause the valve to open at the point for 
 which it is set to blow. 
 
 Safety Valves. The modern pop valve is generally 
 reliable, but, like everything else, if it is allowed to 
 stand idle too long it is likely to become rusty and 
 stick. Therefore it should be allowed to blow off at 
 least once or twice a week in order to keep it in good 
 condition. 
 
 Most pop valves for stationary boilers are provided 
 with a short lever, and if at any time the valve does 
 not pop when the steam gauge shows the pressure to 
 be high enough, it can generally be started by a light 
 blow on the lever with a hammer. 
 
 The ratio of safety valve area to that of grate surface 
 is, for the old style lever and weight valve, I sq. in. of 
 valve area for each 2 sq. ft. of grate surface, and 
 for pop valves I sq. in. of valve area for each 3 sq. ft. 
 of grate surface. 
 
 Each boiler in a battery should have its own safety 
 valve, and, in fact, be entirely independent of its mates 
 as regards safety appliances. 
 
 One example of safety valve computation will be 
 given. Suppose the grate surface of a boiler is 
 5 x 6 = 30 sq. ft, what should be the diameter of the 
 lever safety valve? The required area of the valve is 
 30-2= 15 sq. in. Then 15^.7854=19, which is the 
 
40 ENGINEERING 
 
 square of the diameter of the valve. Extracting the 
 square root of 19 gives 4.35 in. diameter of valve. In 
 actual practice one 5 in. or two 3 in. lever safety 
 valves would be required. If a pop valve is to be used 
 the required area is 30 ■*■ 3 = 10 sq. in. Then 10 - .7854 = 
 12.73 = square of diameter of valve. Extract the 
 
 POP VALVE. 
 
 square root of 12.73 and the result is 3.6 in, = diam- 
 eter of valve. In practice a 4 in. valve would be 
 required. 
 
 Fusible Plugs. A fusible plug should be inserted in 
 that part of the heating surface of a boiler which is 
 first liable to be overheated from lack of water. 
 
BOILER SETTINGS AND APPURTENANCES 
 
 41 
 
 In a horizontal tubular or return flue boiler the 
 proper location for the fusible plug is in the back head 
 
 INSIDE VIEW OF A POP SAFETY VALVE. 
 
 about ij^ or 2 in. above the top row of tubes. In fire- 
 box Doilers the plug can be put into the crown sheet 
 
42 ENGINEERING 
 
 directly over the fire. These plugs should be made of 
 brass with hexagon heads and standard pipe threads, 
 in sizes y 2 , ^, I in., or even larger if desired. A hole 
 drilled axially through the center and counter sunk in 
 the end that enters the boiler is filled with an alloy of 
 such composition that it will melt and run out at the 
 temperature of the dry steam at the pressure carried 
 in the boiler. Thus, if the water should get below the 
 plug the dry steam, coming in contact with the fusible 
 alloy, melts it and, escaping through the hole in the 
 plug, gives the alarm, and in case of fire-box or inter- 
 nally fired boilers the steam will generally extinguish 
 the fire also. The hole is counter sunk on the inner 
 end of the plug so as to retain the fusible metal against 
 the boiler pressure. These plugs should be looked 
 after each time the boilers are washed out, and all dirt 
 and scale should be cleaned off in order that the fusible 
 metal may be exposed to the heat. 
 
 Another type of fusible plug consists of a small brass 
 cylinder into one end of which is screwed a plug filled 
 with a metal which will fuse at the temperature of dry 
 steam at the pressure which is to be carried in the 
 boiler. The other end of the cylinder is reduced and 
 fitted with a small stop valve and threaded to screw 
 into a brass bushing inserted into the top of the boiler 
 shell. This bushing also receives at its lower end a 
 piece of ^ or 3^ in. pipe which extends downwards to 
 within 2 in. of the top row of tubes, or the crown sheet 
 if the boiler is internally fired. The principle of the 
 device is that in case the water falls below the lower 
 end of the pipe, steam will enter, fuse the metal in the 
 plug, and be free to blow and give warning of danger. 
 Some of these appliances are fitted with whistles 
 which are sounded in case the steam gets access to 
 
BOILER SETTINGS AND APPURTENANCES 43 
 
 them. But even with such devices no engineer can 
 afford to relax his own vigilance and depend entirely 
 upon the safety appliances to prevent accidents from 
 low water. 
 
 Domes and Mud-Drums. As a general proposition, 
 both mud drums and domes are useless appendages to 
 steam boilers. There are, no doubt, instances where 
 they may serve a purpose, but as a rule their use is of 
 no advantage to a boiler. Neither are the so-called 
 circulating systems, sometimes attached to return 
 tubular boilers, of any real value. These consist of 
 one or more 4 to 6 in. pipes extending under the boiler 
 from front to back through the furnace and the com- 
 bustion chamber and connected to each end of the 
 boiler. 
 
 Feed Pipes. Authorities differ in regard to the 
 proper location of the inlet for the feed pipe, but 
 upon one point all are agreed, namely, that the feed 
 water, which is always at a lower temperature than the 
 water in the boiler, should not be allowed to come 
 directly in contact with the hot boiler sheets until its 
 temperature has been raised to within a few degrees of 
 the temperature of the water in the boiler. Cer- 
 tainly one of the most fruitful sources of leaks in the 
 seams and around the rivets is the practice of intro- 
 ducing the feed water into the bottom either at the 
 back or front ends of boilers, as is too often the case. 
 The cool water coming directly in contact with the hot 
 sheets causes alternate contraction and expansion, and 
 results in leaks, and very often in small cracks in the 
 sheet, the cracks extending radially from the rivet 
 holes. It would appear that the proper method is to 
 connect the feed pipe either into the front head just 
 above the tubes, or into the top of the shell. The 
 
44 ENGINEERING 
 
 nipple entering the boiler should have a long thread 
 cut on the end which screws into the sheet, and to this 
 end inside the boiler there should be connected another 
 pipe which shall extend horizontally at least two- 
 thirds of the length of the boiler, resting on top of the 
 tubes, and then discharge. Or, what is still better, 
 allow the internal pipe to extend from the entering 
 nipple at the front end to within a few inches of the 
 back head, then at right angles across the top of the 
 tubes to the other side, and from there discharge 
 downward. By this method the feed water is heated 
 to nearly, if not quite, the temperature of the water in 
 the boiler before it is discharged. One of the objec- 
 tions to this system is the liability of the pipe inside 
 the boiler to become filled with scale and finally 
 plugged entirely. In such cases the only remedy is to 
 replace it with new pipe. But the great advantage of 
 having the water thoroughly heated before being dis- 
 charged into the boiler will much more than compen- 
 sate for the extra expense of piping, and the general 
 idea of introducing the feed water at the top instead of 
 at the bottom of the boiler is therefore recommended 
 as being the best. 
 
 The diameter of feed pipes ranges from I in. for 
 small sized boilers, up to 1% and 2 in. for boilers of 54 
 to 72 in. in diameter. It is not good policy to have 
 the feed pipe larger than necessary for the capacity of 
 the boiler; because it then acts as a sort of cooling 
 reservoir for the feed water, and may cause considerable 
 loss of heat. 
 
 For batteries of two or more boilers it is necessary to 
 run a main feed header, with branch pipes leading to 
 each boiler. The header should be large enough to 
 supply all the boilers at the same time, should it ever 
 
BOILER SETTINGS AND APPURTENANCES 45 
 
 become necessary to do so. The header can be run 
 along the front of the boilers just above the fire doors 
 with the branch pipes running up on either side, clear 
 of the flue doors and entering the front connection, or 
 smoke arch, and the boiler head at a point two inches 
 above the tubes. There should always be a valve in 
 each branch pipe between the check valve and the 
 header for the purpose of regulating the supply of 
 water to each boiler, and also for shutting off the 
 pump pressure in case of needed repairs to the check 
 valve. Another valve should be placed between the 
 check valve and the boiler. By this arrangement it is 
 always possible to get at the check valve when it is 
 out of order. 
 
 Blow off Pipes. Blow off pipes should always be 
 connected with the lowest part of the water space of a 
 boiler. If there is a mud-drum, then of course the 
 blow off should be connected with it; but if there is no 
 mud-drum, the blow off should connect with the bot- 
 tom of the shell, near the back head, extend down- 
 wards to the floor of the combustion chamber, and 
 thence horizontally out through the back wall, where 
 the blow off cock can be located. 
 
 The best blow off cocks are the asbestos packed 
 iron-body plug cocks, which are durable and safe. 
 A globe valve should never be used in a blow off pipe, 
 because the scale and dirt will lodge in it and prevent 
 its being closed tightly. A straight way or gate valve 
 is not so bad, but an asbestos packed plug cock is 
 undoubtedly the best and safest. 
 
 In order to protect the blow off pipe from the 
 intense heat, a shield consisting of a piece of larger 
 pipe can be slipped over the vertical part before it is 
 connected. 
 
46 
 
 ENGINEERING 
 
 Blow off cocks should be opened for a few seconds 
 once or twice a day, to allow the scale and mud to be 
 blown out. If neglected too long they are liable to 
 become filled with scale and burn out. A plan which 
 is said to give good results is to connect a tee in the 
 horizontal part of the pipe, and from this tee run a I in. 
 
 FIGURE 9. 
 
 pipe to a point in the back head at the water level. 
 It is claimed that this will cause a circulation of water 
 in the pipe and prevent the formation of scale. 
 
 A surface blow off is a great advantage, especially 
 if the water is muddy or liable to foam. By having 
 the suiface blow off connected on a level with the 
 
BOILER SETTINGS AND APPURTENANCES 47 
 
 water line a large amount of mud and other matter 
 which is kept on the surface by the constant ebullition 
 can. be blown out. 
 
 A combination surface blow off, bottom blow off, 
 and circulating system can be arranged by a connec- 
 tion such as illustrated in Fig. 9. By closing cock A 
 and opening cocks B and C the bottom blow off is put 
 in operation; by closing B and opening A and C the sur- 
 face blow off is started, and by closing C and leaving 
 A and B open the device will act as a circulating sys- 
 tem. The pipe should be of the same size throughout. 
 Blow off pipes should be of ample size, never less than 
 i}£ in-. an d from that to 2^ in., depending upon the 
 size of the boiler. 
 
 Feed Pumps and Injectors. The belt driven power 
 pump is the most economical boiler feeder, but is not 
 
 DIFFERENTIAL VALVE, DAVIS PUMP. 
 
 the most convenient nor the safest. When the engine 
 stops, the pump stops also, and sometimes it happens 
 that the belt gives way and the pump stops at iust 
 
48 
 
 ENGINEERING 
 
 the time when the boiler is being worked the hard- 
 est. 
 
 The modern double acting steam pump, of which 
 there are many different makes to choose from, is 
 without doubt the most reliable boiler feeding appli- 
 ance and the one best adapted to all circumstances 
 and conditions, although it is not economical in the 
 
 DAVIS BELT DRIVEN FEED PUMP. 
 
 use of steam, since the principle of expa-nsion cannot 
 be carried out with the pump as with the engine. 
 
 In selecting a feed pump care should be exercised to 
 see that it is of the proper size and capacity to supply 
 the maximum quantity of water that the boiler can 
 evaporate. This may be ascertained by taking into 
 consideration the amount of heating surface and the 
 required consumption of coal per square foot of grate 
 surface per hour. First, take the coal consumption. 
 Assume the boiler lo have 30 sq. ft. of grate surface, 
 
BOILER SETTINGS AND APPURTENANCES 
 
 49 
 
 and that it is desired to burn 15 lbs. of coal per square 
 foot of grate per hour, which is a good average with 
 the ordinary hand fired furnace using bituminous coal. 
 
 SECTIONAL VIEW OF DIFFERENTIAL VALVE. 
 
 Suppose the boiler is capable of evaporating 8 lbs. of 
 water per pound of coal consumed. Then 30 x 15x8 = 
 3,600 lbs. of water, evaporated per hour. Dividing 
 
 WORTHINGTON DUPLEX BOILER FEED PUMP. 
 
 3.600 by 62.4 (the weight of a cubic foot of water in 
 pounds) gives 57.6 cu. ft. per hour, which, divided by 
 60, gives 0.96 cu. ft. per minute. This multiplied by 
 
50 
 
 ENGINEERING 
 
 1,728 ( number of cubic inches in a cubic foot) gives 
 1,659 cu. in. per minute which the pump is required to 
 supply. Suppose the pump is to make forty strokes 
 per minute, and the length of stroke is five inches. 
 Then 1659 -5-40 = 41.47 cu. in. per stroke, which, divided 
 by 5 (length of stroke in inches) gives 8.294 sq. in. as 
 • the required area of water piston. 8.294-^.7854 = 
 10.56, which is the square of the corresponding diam- 
 
 jri m i 
 
 1 — *«* 
 
 jiiiil i J^0S. 
 
 ;:'<3i'M 
 
 im. 
 
 Sffli|«l|l§l 
 
 ti MI..W- .. 
 
 iitii a ^ :i ' f 
 
 PHANTOM VIEW OF MARSH INDEPENDENT STEAM PUMP. 
 
 eter, and the square root of 10.56 = 3.25. So, theo- 
 retically, the size of the water end of the pump would 
 be 3^ in. in diameter by 5 in. stroke; but as it is 
 always safer to have a reserve of pumping capacity, 
 the proper size of the pump would be 3^ in. in diam- 
 eter by 5 in. stroke, with a steam cylinder of 6 or 7 in. 
 in diameter. 
 
 There is another rule for ascertaining the size of the 
 
BOILER SETTINGS AND APPURTENANCES 
 
 51 
 
 feed pump, by taking the number of square feet of 
 heating surface in the boiler and allow a pump capacity 
 of I cu. ft. per hour for each 15 sq. ft. of heating sur- 
 face. Thus, let the total heating surface of the boiler 
 be 786 sq. ft. Dividing this by 15 gives 52.4 as the 
 number of cubic feet of water required per hour, from 
 which the pump dimensions may be found in the same 
 way as in the preceding case. 
 
 In figuring on the capacity of a feed pump for a bat- 
 tery of two or more boilers, the total quantity of water 
 required by all the boilers 
 must be taken into consid- 
 eration. All boiler-rooms 
 should be supplied with at 
 least two feed pumps, so 
 that if one breaks down 
 there may always be an- 
 other one available. 
 
 The injector is a reliable 
 boiler feeder, and is in fact 
 more economical than the 
 steam pump, because the 
 heat in the steam used is 
 all returned to the boiler, 
 
 excepting the losses by radiation. But the disad- 
 vantage attending the use of the injector is that it will 
 not work well with the feed water at a temperature 
 very much in excess of ioo° F. , while a good steam 
 pump, fitted with hard rubber valves, will handle water 
 at a temperature as high as 200 ° or 208° F. , when the 
 water flows to the pump by gravity from a heater, or 
 it will raise water from a receiving tank on a short 
 suction lift at a temperature of 150 or 160 F. 
 
 Feed Water Heaters. One great source of economy 
 
 AUTOMATIC INJECTOR. 
 
52 
 
 ENGINEERING 
 
 in fuel is the utilization of all the available exhaust 
 steam for heating the feed water before it enters the 
 boiler. Of course if the main engine is a condensing 
 engine, the exhaust from that source is not directly 
 available, except by interposing a closed heater 
 between the cylinder and the condenser, or by using 
 
 METROPOLITAN INJECTOR, MODEL O. 
 
 the water of condensation for feeding the boilers. 
 This can be clone with safety, provided a surface con- 
 denser is used, but with a jet condenser or an open 
 heater in which the exhaust mingles with the water, it 
 is advisable to have an oil separator to prevent the oil 
 from getting into the boilers. 
 
BOILER SETTINGS AND APPURTENANCES 
 
 ,:; 
 
 Exhaust heaters are of two kinds, open and closed. 
 In the open heater the exhaust steam mingles directly 
 with the water and a portion of it is condensed. A 
 well-designed open exhaust heater will raise the tem- 
 perature of the water to very 
 nearly the boiling point, 212 
 F. These heaters should be 
 set so that the water will flow 
 by gravity from them to the 
 feed pump In the closed type 
 of exhaust heaters, the exhaust 
 steam and the water are kept 
 separate. In some styles the 
 steam passes through tubes, 
 which are surrounded by water, 
 while in others the water fills 
 the tubes, which are in turn 
 surrounded by the steam. In 
 either case the water in the 
 closed heater is under the. full 
 boiler pressure while the feed 
 pump is in operation, because 
 the heater is between the pump 
 and the boiler, while with the 
 open heater the pump is be- 
 tween the heater and the boiler. 
 
 The saving effected by heat- 
 ing the feed water with exhaust 
 steam can be easily ascertained 
 by the use of a thermometer, 
 a steam table, and a simple 
 tion. First, find by 
 
 BARAGWANATH STEAM 
 
 JACKET FEED WATER 
 
 HEATER. 
 
 arithmetical calcula- 
 thermometer the temperature 
 of the water before entering the heater; find its tem- 
 perature as it leaves the heater. Next ascertain by 
 
54 
 
 ENGINEERING 
 
 the steam table the number of heat units above 32 
 F. in the water at each of the two temperatures. Sub- 
 tract the less from the greater, and the remainder will 
 be the number of heat units added to the water by the 
 heater. Next find by the table the number of heat 
 units above 32 F. in the steam 
 at the pressure ordinarily car- 
 ried in the boiler, and subtract 
 from this the number of heat 
 units in the water before it 
 enters the heater. The result 
 will be the number of heat 
 units that would be required to 
 convert the water into steam of 
 the required pressure, provided 
 no heater were used. Then to 
 I* find the percentage of saving 
 effected by the heater, multiply 
 the number of heat units added 
 to the water by the heater by 
 100, and divide by the number 
 of heat units required to con- 
 vert the unheated water into 
 steam, from the initial temper- 
 ature at which it enters the 
 heater. 
 
 Example. Assume the boiler 
 to be carrying 100 lbs. gauge 
 pressure. Suppose the temper- 
 ature of the water before entering the heater is 
 60 ° F. , and that after leaving the heater its tem- 
 perature is 202 F. , what is the percentage of saving 
 due to the heater? The solution of the problem is as 
 follows: 
 
 INTERIOR VIEW OF OPEN 
 HEATER. 
 
BOILER SETTINGS AND APPURTENANCES 5.5 
 
56 ENGINEERING . 
 
 Boiler pressure by gauge = ioo lbs. 
 
 Initial temperature of feed water = 6o° F. 
 
 Heated temperature of feed water = 202 F. 
 
 From the steam table (see Chapter IV., Table 5) it 
 is found that 
 
 Heat units in water at 202 F. = 170. 7. 
 
 Heat units in water at 6o° F. = 28.01. 
 
 Heat units added to water by heater = 170.7 - 28.01 = 
 142.69. 
 
 Heat units in steam at 100 lbs. gauge pressure = 
 1 185.0. 
 
 Heat units to be added to water at 6o° F. to make 
 steam of 100 lbs. gauge pressure = 1 185.0- 28.01 = 
 1156.99. 
 
 Percentage of saving effected by the use of the 
 
 142.69 x 100 
 
 heater = ^ =12.33 per cent. 
 
 1156.99 DD F 
 
 Suppose the coal consumed under this boiler amounts 
 to two tons per day at a cost of $3.00 per ton, or a fuel 
 cost of $6.00 per day. Then the saving in dollars and 
 cents due to the heater in the foregoing example would 
 be 12.33 per cent of $6.00, or $0.7398 (74 cents) per 
 day. 
 
 Heaters, especially those of the closed type, should 
 have capacity sufficient to supply the boiler for fifteen 
 or twenty minutes. There would then be a body of 
 water continually in the heater in direct contact with 
 the heating surface, and as it passes slowly through it 
 will receive much more heat than if rushed through a 
 heater that is too small. All heaters and feed pipes 
 should be well protected by some good insulating 
 covering to prevent loss of heat by radiation. In 
 some cases the exhaust steam, or a portion of it at 
 least, can be used to advantage in an exhaust injector. 
 
BOILER SETTINGS AND APPURTENANCES 
 
 57 
 
 This device, where it can be used at all, is economical 
 in that it not only feeds the boiler, but also heats the 
 
 CLOSED FEED WATER HEATER. 
 
 water without the use of live steam. But it will not 
 force the water against a pressure much above 75 lbs. 
 
58 ENGINEERING 
 
 to the square inch, and if the initial temperature of 
 the water is much above 75 F. the exhaust injector 
 will not handle it. Heaters which use live steam 
 direct from the boilers heat the feed water to a much 
 higher temperature, so that they act as purifiers by 
 removing a large portion of the scale-forming impu- 
 rities before the water enters the boiler. Live steam 
 heaters, however, are not to be considered as econo- 
 mizers of heat. 
 
 Provisions for Testing. While considering feed pipes 
 and other apparatus necessarily appertaining to the 
 feeding of boilers, it is well to devote a short space 
 also to the fittings and other devices required for suc- 
 cessfully conducting tests of the boiler and furnace. 
 This subject is mentioned here for the reason that the 
 author considers that the necessary fittings and appli- 
 ances for making evaporative tests properly belong to, 
 and in fact are a part of, the feed piping, and can be 
 put in while the plant is being erected at much less 
 cost and trouble than if the matter is postponed until 
 after the plant is in operation. 
 
 Beginning then at the check valve, there should be a 
 tee located in the horizontal section of the feed pipe, 
 as near to the check valve as practicable, and between 
 it and the feed pump; or a tee can be used in place of 
 an ell to connect the vertical and horizontal sections 
 of the branch pipe where it rises in front of the boiler. 
 One opening of this tee is reduced to V& or }4 in. to 
 permit the attachment of a hot water thermometer. 
 These thermometers are also made angle-shaped at the 
 shank, so that if desired they can be screwed into a tee 
 placed in vertical pipe and still allow the scale to 
 stand vertical. The thermometer is for the purpose 
 of showing at what temperature the feed water enters 
 
BOILER SETTINGS AND APPURTENANCES 
 
 59 
 
 the boiler during the test, and there- 
 fore should be as near the boiler as 
 possible. After the test is completed 
 the thermometer may be taken out 
 and a plug inserted in its place. 
 
 The next requirement will be a de- 
 vice of some kind for ascertaining the 
 weight of water pumped into the 
 boiler during the test. In some well 
 ordered plants each boiler is fitted 
 with a hot water meter in the feed 
 pipe, but as this arrangement is hardly 
 within the reach of all, a substitute 
 equally as accurate can be made by 
 placing two small water tanks, each 
 having a capacity of eight or ten cubic 
 feet, in the vicinity of the feed pump. 
 These tanks can be made of light 
 tank iron, and each should be fitted 
 with a nipple and valve near the bot- 
 tom for connection with the suction 
 side of the pump. The tops of the 
 tanks may be left open. If an open 
 heater is used, and it is possible to 
 place the tanks low enough to allow 
 a portion of the water from the heater 
 to be led into them by gravity, it will 
 be desirable to do so. A pipe leading 
 from the main water supply, with a 
 branch to each tank, is also needed 
 for filling them. One of the feed hot water ther- 
 
 r i-i-i 1 ill MOMETER. 
 
 pumps, ot which there should always 
 
 be at least two, as already stated, is fitted with a tee 
 
 in the suction pipe near the pump to receive the pipe 
 
60 
 
 ENGINEERING 
 
 leading from the tanks. During the test the main suc- 
 tion leading to this pump from the general supply 
 should be kept closed, so that only .the water that 
 passes through the tanks is used for feeding the boiler. 
 If the plant be a small one, with but one or two boil- 
 ers and only a single feed pump, the latter can be 
 made to do duty as a testing pump, because during 
 the test there will be no other boilers to feed besides 
 the ones under test. 
 
 F££ fLtynT£ t 
 
 HSUPp L y 
 
 TOF&PPUMP 
 
 FIGURE 10. 
 
 If metal tanks are considered too expensive, two 
 good water-tight barrels can be substituted. Fig. 10 
 will give the reader a general idea of what is needed 
 for obtaining the weight of the water by the method 
 just described. If a closed heater is used and no other 
 boilers are in service during the test, the cold water 
 can be measured in the tanks and pumped directly 
 through the heater, but if it is necessary to feed other 
 boilers besides those under test, then either a separate 
 
BOILER SETTINGS AND APPURTENANCES 61 
 
 feed pipe must be run to the test boilers, or else hot 
 water meters will have to be put into the branch pipes. 
 
 In cases where a separate feed pipe must be put in 
 for the test boiler and the water which is used for 
 testing cannot be passed through a heater, there 
 should be a % or I in. pipe connected to the feed main 
 or header and leading to the testing tanks, in order to 
 allow a portion of the hot feed water to run into and 
 mix with the cold water in the tanks as they are being 
 filled, thus partially warming the water before it goes 
 to the boiler. 
 
 Heating Surface. The heating surface of a boiler 
 consists of that portion of the boiler which is exposed 
 to the heat on one side and water on the other. In a 
 horizontal boiler of either the flue or tubular type, the 
 available heating surface is, first, the lower half of the 
 shell; second, the area of the back head below the 
 water line minus the combined cross sectional area of 
 all the tubes or flues; third, the inside area of the 
 flues; fourth, the area of the front head minus the sec- 
 tional area of the flues. 
 
 For a fire-box boiler of the vertical type, the area of 
 the flue sheets minus the sectional area of the flues, 
 plus the area of the fire-box plus the inside area of the 
 flues constitutes the heating surface. If the boiler is a 
 horizontal internally fired boiler, the heating surface 
 will consist of, first, area of three sides of the fire- 
 box; second, area of the crown sheet; third, area of 
 flue sheets minus sectional area of flues; fourth, inside 
 area of the flues. 
 
 In estimating the area of the fire-box, the area of the 
 fire door should be subtracted therefrom. If the fire- 
 box be circular, as in the case of a vertical boiler, the 
 area may be obtained by first finding by measurements 
 
62 ENGINEERING 
 
 the: diameter, which multiplied by 3.1416 will give the 
 circumference. Then multiply this result by the 
 height or the distance between the grate bars and 
 the flue sheet. In the case of water tube boilers the 
 outside area of the tubes must be taken. Two exam- 
 ples will be given illustrating methods of calculating 
 heating surface: 
 
 First, take a horizontal tubular boiler, diameter 72 
 in., length 18 ft., having sixty-two 4^ in. flues; find 
 area of lower half of shell. 
 
 Circumference = diameter x 3. 1416 = 18.8496 ft. 
 
 One-half of the circumference multiplied by the 
 length = required area. Thus, 18.8496 42x18= 169.64 
 sq. ft. 
 
 Next find heating surface of back head below the 
 water line. Total area = 72 s x .7854 = 4071.5 sq. in. 
 Assume two-thirds of this area to be exposed to the 
 heat. 2 /i of 4071.5 = 2714.3 sq. in. From this must be 
 deducted the sectional area of the tubes. In giving 
 the size of boiler tubes the outside diameter is taken. 
 The tubes being 4^2 in.; the area of a circle 4^ in. in 
 diameter is 15.9 sq. in. Number of flues, 62 x 15.9 = 
 985.8 sq. in. = sectional area of tubes. The heating 
 surface of the back head therefore = 2714.3 — 985.8 = 
 1728.5 sq. in. Dividing this by 144, to reduce to feet, 
 we have 12 sq. ft. 
 
 Next find inside area of tubes. The standard thick- 
 ness of a 4)4, in. tube = .134 in. The inside diameter 
 therefore will be 4.5 - (2 x . 134) = 4.23 in., and the cir- 
 cumference will be 4.23x3.1416=13.29 in., and the 
 inside area will be 13.29 x length, 18 ft., = 216 in. 
 Thus 216 x 13.29 - 144 = 19.93 sq. ft., inside area of one 
 flue. There being 62 flues, the total heating surface of 
 tubes is 19.93x62= 1235.66 sq. ft. The heating sur- 
 
BOILER SETTINGS AND APPURTENANCES 
 
 63 
 
 face of the front head is found in the same manner as 
 that of the back head, with the exception that the 
 whole area should be figured instead of two-thirds, for 
 the reason that the entire surface is exposed to the 
 heat, although that portion above the water line may 
 be considered as superheating surface. The heating 
 
 surface of front head would be: area 4071 
 
 area of tubes 985.8 = 3085.7 sq. in. = 21.43 
 
 The total heating surface of the boiler 
 
 to be 1438.73 sq. ft, divided up as follows 
 
 Lower half of shel 
 Back head, 
 Tubes, 
 Front head, 
 
 169.64 sq. 
 12.00 
 1235.66 
 21.43 
 
 5 - sectional 
 
 sq. ft. 
 
 is thus found 
 
 ft. 
 
 1438-73 
 
 Next taking a vertical fire-box boiler of the follow- 
 ing dimensions: diameter of flue sheet, and also of fire- 
 box, 50 in.; height of fire-box above grate bars, 30 in ; 
 number of flues, 200; size of flues, 2 in.; length of 
 flues, 7 ft. 
 
 First, find heating surface in flue sheet. 
 
 Area of circle, 50 in. in diameter = 1,963.5 sq. in. 
 
 Sectional area of 2 in. flue = 3.14 sq. in., which mul- 
 tiplied by 200 = 628 sq. in., total sectional area of 
 tubes. The heating surface of one flue sheet therefore 
 will be 1,963. 5 - 628 -*- 144 = 9 sq. ft. 
 
 Assuming that the tops of the flues are submerged, 
 the area of the top flue sheet will also be 9 sq. ft. 
 Then heating surface of flue sheets = 9 x 2 = 18 sq. ft. 
 
 Second, find heating surface of tubes. The standard 
 thickness of a 2 in. flue is .095 in. The inside diameter 
 will consequently be 2 — (.095 x 2) = 1.8 in., and the 
 circumference will be 1.8x3.1416=5.66 in. The 
 
64 ENGINEERING 
 
 length of the flue being 7 ft., or 84 in., the inside area 
 will be 5.66 x 84 -h 144 = 3.3 sq. ft., and multiplying this 
 result by 200 we have 20c x 3.3 = 660 sq. ft. as the 
 heating surface of the flues. 
 
 Third, find heating surface of the fire-box. Diam- 
 eter of fire-box = 50 in., which multiplied by 
 3.1416=157.08, which is the circumference. The 
 height being 30 in., the total area will be 157.08 x 30 * 
 144 = 32.7 sq. ft. Allowing 1 sq. ft. as the area of the 
 fire door, will leave 31.7 sq. ft. heating surface of fire- 
 box. The heating surface of the boiler will be: 
 
 For the flue sheets, 18 sq. ft. 
 
 For the flues, 660 
 
 For the fire-box, 31.7 
 
 Total, 709-7 
 
 The above methods may be applied in estimating the 
 heating surface of any boiler, provided in the case of 
 water tube boilers that the outside in place of the 
 inside area of the tubes be figured. 
 
 Questions 
 
 1. How should the bridge wall of a horizontal boiler 
 be built? 
 
 2. How should the brick work of a boiler be secured 
 in order to prevent damage by expansion and contrac- 
 tion? 
 
 3. Which end of a horizontal boiler should be the 
 lowest, and why? 
 
 4. How should the. water column be located? 
 
 5. How high abo\ r e the top row of tubes should the 
 lower gauge cock be? 
 
 6. What is the proper ratio of safety valve area to 
 grate surface? 
 
BOILER SETTINGS AND APPURTENANCES 6,5 
 
 7. Where should the fusible plug be located? 
 
 8. Where should the feed pipe enter the boiler? 
 
 9. Where should the blow off pipe be connected? 
 
 10. What is the most economical device for feeding 
 a boiler? 
 
 11. In selecting a feed pump, how may the required 
 size of pump be ascertained? 
 
 12. What is the disadvantage in the use of the 
 injector for feeding a boiler? 
 
 13. What is gained by using a feed water heater? 
 
 14. How many kinds of exhaust heaters are there? 
 
 15. How may the saving effected by using the 
 exhaust steam for heating the feed water be estimated? 
 
 16. What should the capacity of the heater be? 
 
 17. What provision should be made for testing coal 
 and other fuel? 
 
 18. What is the heating surface of a boiler? 
 
CHAPTER III 
 
 BOILER OPERATION 
 
 First care of the engineer on entering his boiler-room — Cleaning 
 fires — Fire tools, etc. — Firing — Suggestions as to best method 
 of firing — Quantity of air required per pound of coal — Clean- 
 ing tubes — Washing out, etc. — Why it is dangerous to cool a 
 boiler too quickly — Repairing tubes — Cleaning inside of 
 boiler — Pitting — How to feed a boiler — What to do in cases of 
 emergency — Connecting with main — Foaming, priming, etc. — 
 Safety valve calculations— Rules for safety valve calcula- 
 tions — Feed pumps — Care of feed pumps — Directions for set- 
 ting steam valves of duplex pumps — Hydraulics for engineers. 
 
 Operation. Having considered in the previous chap- 
 ters the principal details in the construction and 
 erection of boilers with which the working engineer is 
 interested, it is now in order to devote a space to their 
 operation. 
 
 Duties. The first act of the careful engineer on 
 entering his boiler-room when he goes on duty should 
 be to ascertain the exact height of the water in his 
 boilers. This he can do by opening the valve in the 
 drain pipe of the water column, allowing it to blow 
 out freely for a few seconds, then close it tight and 
 allow the water to settle back in the glass. This 
 should be done with each boiler under steam, not only 
 once, but several times during the day. No engineer 
 should be satisfied with a general squint along the line 
 of gauge glasses, but he should either go himself or 
 else instruct his fireman or water tender to make the 
 rounds of each boiler and be sure that the water is all 
 right. 
 
 60 
 
BOILER OPERATION 
 
 67 
 
 The next thing to be looked after is the fire. If the 
 plant is run continuously clay and night it is the duty 
 of the firemen coming off watch to have the fires clean, 
 the ash pits all cleaned out, a good supply of coal on 
 the floor, and everything in good order for the on 
 coming force. A good fireman will take pride in 
 always leaving things in neat shape for the man who 
 is to relieve him. 
 
 Cleaning Fires. With some varieties of coal this is 
 
 lahman's grate. 
 
 a comparatively easy task, especially if the boilers are 
 fitted with shaking grates. With a coal that does not 
 form a clinker on the grate bars, the fires can be kept 
 in good condition by cleaning them twice or three 
 times in twenty-four hours, as the larger part of the 
 loose ashes and noncombustible can be gotten rid of 
 by shaking the grates and using the slice bar at inter- 
 vals more or less frequent; but such coals are generally 
 considered too expensive to use in the ordinary manu- 
 facturing plant, and cheaper grades are substituted. 
 
68 
 
 ENGINEERING 
 
 Fire Tools. For cleaning fires successfully and 
 quickly the following tools should be provided: a slice 
 bar, a fire hook, a heavy iron or steel hoe, and a light 
 hoe for cleaning the ash-pit. It is unnecessary to 
 describe these tools, as they are familiar to all 
 engineers. A suggestion as to the kind of handles 
 with which they should be fitted may be of benefit. 
 The working ends of the aforesaid tools having been 
 made and each welded to a bar of I ori^ in. round 
 
 MARTIN ANTI-FRICTION ROCKING GRATES. 
 
 iron and 10 or 12 in. long, take pieces of 1 or 1% in. 
 iron pipe cut to the length desired for the handles and 
 weld the shanks of the tools to them. To the other 
 end of the pipe weld a handle made of round iron 
 somewhat smaller than the shank. By using pipe 
 handles the weight of the tools is considerably lessened, 
 and they will still be sufficiently strong. The labor of 
 cleaning the fire will thus be greatly lightened. When 
 a fire shows signs of being foul and choked with 
 
BOILER OPERATION 69 
 
 clinker, preparations should be made at once for clean- 
 ing it by allowing one side to burn down as low as pos- 
 sible, putting fresh coal on the other side alone. When 
 the first side has burned as low as it can without 
 danger of letting the steam pressure fall too much, 
 take the slice bar and run it in along the side of the 
 furnace on top of the clinker and back to near the 
 bridge wall, then using the door jamb as a fulcrum, give 
 it a quick strong sweep across the fire and the greater 
 part of the live coals will be pushed over to the other 
 side. What remains of the coal not yet consumed can 
 be pulled out upon the floor with the light hoe and 
 shoveled to one side, to be thrown back into the 
 furnace after the clinker is taken out. Having now 
 disposed of the live coal, take the slice bar and run it 
 along on top of the grates, loosening and breaking up 
 the clinker thoroughly, after which take the heavy hoe 
 and pull it all out on the floor. A helper should be 
 ready with a pail of water, or, what is still better, a 
 small rubber hose connected to a cold water pipe run- 
 ning along the boiler fronts for this purpose, and put 
 on just enough water to quench the intense heat of the 
 red hot clinker as it lies on the floor. ' When the 
 grates are cleaned, close the door, and with the slice 
 bar in the other side push all the live coal over to the 
 side just cleaned, where it should be leveled off and 
 • fresh coal added. After this has become ignited, treat 
 the other side in the same way. An expert fireman 
 will thus clean a fire with very little loss in steam 
 pressure, and practically no waste of coal. 
 
 Firing. No definite set of rules for hand firing can 
 be laid down that will be suitable for all steam plants, 
 or for the many different kinds of coal used. Some 
 kinds of coal need very little stirring or slicing, while 
 
70 ENGINEERING 
 
 others that have a tendency to coke and form a crust 
 on top of the fire need to be sliced quite often. 
 
 Every engineer, if he is at all observant, should be 
 able to judge for himself as to the best method of 
 treating the coal he is using, so as to get the most 
 economical results. A few general maxims may be 
 laid down. First, keep a clean fire; second, see that 
 every square inch of grate surface is covered with a 
 good live fire; third, keep a level fire, don't allow hills 
 and valleys and yawning chasms to form in the fur- 
 nace, but keep the fire level; fourth, when cleaning the 
 fire always be sure to clean all the clinkers and dead 
 ashes away from the back end of the grates at the 
 bridge wall, in order that the air may have a free pas- 
 sage through the grate bars, because this is one of the 
 best points in the furnace for securing good combus- . 
 tion provided the bridge wall is kept clean from the 
 grates up. By keeping the back ends of the grate bars 
 and the face of the bridge wall clean, the air is per- 
 mitted to come in contact with the hot fire brick, and 
 thus one of the greatest aids to good combustion is 
 utilized. Don't allow the fire to become so deep and 
 heavy that the air cannot pass up through it, because 
 without a good supply of air good combustion is 
 impossible. When the chimney draft is good the 
 quantity of cold air admitted underneath the grate 
 bars may be easily regulated by leaving the ash-pit 
 doors partly open. The amount of opening required 
 can be ascertained by a little experimenting and 
 depends upon the intensity of the draft and the condi- 
 tion of the fire. With a clean, light fire and the air 
 spaces in the grates free from dead ashes, a slight 
 opening of the ash-pit doors will suffice to admit all 
 the air required beneath the grates. But if the fire is 
 
BOILER OPERATION 71 
 
 heavy and the grates are clogged, a larger opening 
 will be necessary. In firing bituminous coal contain- 
 ing a large percentage of volatile (light or gaseous 
 matter) the best results can be obtained by leaving the 
 fire doors slightly open for a few seconds immediately 
 after throwing in a fresh fire. The reason for doing 
 this is that the volatile matter in the coal flashes into 
 flame the instant it comes in contact with the heat of 
 the furnace, and if a sufficient supply of oxygen is not 
 present just at this particular time the combustion will 
 be imperfect and the result will be the formation of 
 carbon mon-oxide or carbonic oxide gas, anct the loss 
 of about two-thirds of the heat units contained in the 
 coal. This loss can be guarded against in a great 
 measure by a sufficient volume of air, either through 
 the fire doors directly after putting in a fresh fire, or, 
 what is still better, providing air ducts through the 
 bridge wall or side walls which will bring the air in on 
 top of the fire. Each pound of coal requires for its 
 complete combustion 12 lbs. or about 150 cu. ft. of air, 
 and the largest volume of air is needed just after fresh 
 coal has been added to the fire. 
 
 Cleanli?iess. In order to get the best results great 
 care should be taken that the tubes be kept clean and 
 free from soot. Especially does this apply to horizon- 
 tal return tubular boilers, for the reason that when the 
 tubes become clogged with soot the efficiency of the 
 draft is destroyed and the steaming capacity of the 
 boiler is greatly reduced. Soot not only stops the 
 draft, but it is a non-conductor of heat. In some 
 batteries of boilers where an inferior grade of coal is 
 used and the draft is poor, it is absolutely necessary 
 to scrape or blow the tubes at least once a day in 
 order to enable the boilers to generate sufficient steam. 
 
72 ENGINEERING 
 
 As to the process of cleaning there are various 
 devices on the market, both for blowing the soot out 
 by means of a steam jet and also for scraping the 
 inside of the tubes. The steam jet, if properly made 
 and used with a high pressure and dry steam, does 
 very satisfactory work, but it should not be depended 
 upon exclusively to keep the tubes clean, because in 
 process of time a "scale will form inside the tubes that 
 nothing but a good scraper will remove. For that 
 reason it is good practice to use the scraper two or 
 three times a week at least. When the boiler is 
 cooled down for washing out, the bottom of the shell 
 should be cleaned of all accumulations of dust and 
 ashes, the combustion chamber back of the bridge wall 
 cleaned out, and the back flue sheet or head swept off 
 and examined, and if there is a fusible plug in the back 
 head the scale should be scraped from it, both inside 
 and outside the boiler, because if it is covered with 
 scale neither the water nor the heat can come in con- 
 tact with it, and it will be non-effective. 
 
 Washing Out. The length of time that a boiler can 
 be run safely and economically after having been 
 washed out depends upon the nature of the feed water. 
 If the water is impregnated to a considerable extent 
 with scale forming matter, the boiler should be washed 
 out every two weeks at the least, and in. some cases of 
 particularly bad water it becomes necessary to shorten 
 the time to one week. To prepare a boiler for washing 
 the fire should be allowed to burn as low as possible 
 and then be pulled out of the furnace, the furnace 
 doors left slightly ajar and the damper left wide open 
 in order that the walls may gradually cool. It is as 
 bad a practice to cool a boiler off too suddenly as it is 
 to fire it up too quick, because the sudden change of 
 
BOILER OPERATION 16 
 
 temperature either way has an injurious effect on the 
 seams, contracting or expanding the plates, according 
 as it is cooled or warmed, and thus creating leaks and 
 very often small cracks radiating from the rivet holes, 
 and becoming larger with each change of temperature, 
 until finally the strength of the seam is destroyed and 
 rupture takes place. After the boiler has become 
 comparatively cool and there is no pressure indicated 
 by the steam gauge the blow off cock may be opened 
 and the water allowed to run out. The gauge cocks 
 and also the drip to the water column should be left 
 open to allow the air to enter and displace the water. 
 Otherwise there will be a partial vacuum formed in the 
 boiler and the water will not run out freely. 
 
 A boiler should not be blown out, that is, emptied 
 of water while under pressure. The sudden change of 
 temperature is sure to have a bad effect upon the 
 sheets and seams. Suppose for instance that all the 
 water is blown out of a boiler under a pressure of 
 20 lbs. by the steam gauge. The temperature of steam 
 at 20 lbs. is 260 F., and it may be assumed that the 
 metal of the boiler is at or near that temperature also. 
 Assume the temperature of the atmosphere in the 
 boiler-room to be 6o° F. There will then be a range 
 of 260 — 6o° = 200 temperature for the boiler to pass 
 through within a short time, which will certainly have 
 a bad effect, and besides this the boiler shell will be so 
 hot that the loose mud and sediment left after the 
 water has run out is liable to be baked upon the 
 sheets, making it much harder to remove. 
 
 While inside the boiler the boiler washer should 
 closely examine all the braces and stays, and if any are 
 found loose or broken they should be repaired at once 
 before the boiler is used again. The soundness of 
 
74 ENGINEERING 
 
 braces, rivets, etc., can be ascertained by tapping 
 them with a light hammer. 
 
 Renewing T?tbes. As it is practically impossible to 
 prevent scale from forming on the outside of the tubes 
 of horizontal tubular boilers unless the feed water is 
 exceptionally good, and as the tubes will in course of 
 time become leaky where they are expanded into the 
 heads, the engineer if he has a battery of two or more, 
 should take advantage of the first opportunity that 
 presents itself to take out of service the boiler that 
 shows the most signs of deterioration and take out the 
 tubes, and after cleaning them of scale by scraping and 
 hammering or rolling in a tumbling cylinder, he should 
 select those that are still in good condition and have 
 them pieced out at the ends, making them almost as 
 good as new. 
 
 The flues being out of the boiler will give the boiler 
 washer a good opportunity to thoroughly clean the 
 inside also, and if there are any loose rivets they 
 should be replaced and leaky or suspicious looking 
 seams chipped and caulked. If there are indications 
 of corrosion or pitting, a stiff paste or putty made of 
 plumbago mixed with a small proportion of cylinder 
 oil may be applied to the affected parts with good 
 results. 
 
 Feed Water. There is no steam plant of any conse- 
 quence that does not have more or less exhaust steam 
 or returns from a steam heating system which can be 
 utilized for heating the feed water before it enters the 
 boiler. Cold water should never be pumped into a 
 boiler that is under steam when it is possible to 
 prevent it. 
 
 In feeding a boiler the speed of the feed pump 
 should be so gauged as to supply the water just as fast 
 
BOILER OPERATION 75 
 
 as it is evaporated. The firing can then be even and 
 regular. 
 
 If the supply of feed water should suddenly be cut 
 off, owing to breakage of the pump or bursting of a 
 water main, and no other source of supply was avail- 
 able, the dampers should be immediately closed, or if 
 there should be no damper in the breeching, the draft 
 may be stopped by opening the flue doors. The fires 
 should then be deadened by shoveling wet or damp 
 ashes in on top of them, or if the ashes cannot be 
 readily procured, bank the fires over with green coal 
 broken into fine bits. This, with the draft all shut off. 
 will deaden the fires, while the engine still running 
 will gradually use up the extra steam. If the water 
 should get dangerously low in the boilers the fires 
 may be pulled, provided they have become deadened 
 sufficiently, but they should never be pulled while they 
 are burning lively, because the stirring will only serve 
 to increase the heat and the danger will be aggra- 
 vated. 
 
 Comiecting a Recently Fired Up Boiler. After a boiler 
 has been washed out, filled with water, and fired up, 
 the next move is to connect it with the main battery. 
 The steam in the boiler to be connected having been 
 raised to the same pressure as that in the battery, the 
 connecting valve should be opened slightly, just 
 enough to permit a small jet of steam to pass through, 
 which can be heard by placing the ear near the body of 
 the valve. This jet of steam may be passing from the 
 battery into the newly connected boiler or vice versa. 
 Whichever way it passes, the valve should not be 
 opened any farther until the flow of steam stops, 
 which will indicate that the pressure has been equal- 
 ized. It will then be found that the valve will move 
 
70 ENGINEERING 
 
 much easier and it may be gradually opened until it is 
 wide open. 
 
 Foaming. Water carried with the steam from the 
 boiler to the engine, even if in small quantities, is very 
 detrimental to the successful operation of the engine, 
 as it washes the oil from the walls of the cylinder, 
 thereby increasing the friction, and unless a plentiful 
 supply of oil is entering the cylinder cutting of the 
 piston rings will take place. There is also danger of 
 breaking a cylinder head or of bending the piston rod 
 if the water comes in too large quantities. 
 
 There are certain kinds of water which have a natu- 
 ral tendency to foam, especially such as contain con- 
 siderable organic matter, and the more severe the 
 service to which the boiler is put the more will the 
 water foam, until it is practically impossible to locate 
 the true level of the water in the boilers, and the only 
 recourse the water tender has is to keep his feed pump 
 running at such a speed as will in his judgment supply 
 the water as fast as it goes out of the boilers. It is a 
 dangerous condition to say the least, and the only 
 remedy for it is either a change to a different kind of 
 water, or if this is not possible, then an increase in 
 the number of boilers, which would make it possible 
 to supply sufficient steam for the engine without being 
 compelled to fire the boilers so hard. 
 
 Pi r imi?ig. By which is meant the carrying over of 
 water in the form of fine spray mingled with the 
 steam, is not so dangerous as foaming and yet it 
 causes much loss in the efficiency of a boiler or 
 engine. It can be prevented to a large extent by 
 placing a baffle plate in the steam space of the boiler 
 directly under the dome or outlet to the connection 
 with the steam main. 
 
BOILER OPERATION 77 
 
 Safety Valves. Rules are given in Chapter II. for 
 guidance in making calculations relating to spring pop 
 valves, which are now almost universally used on 
 boilers, and which, without doubt, are the most reliable 
 appliance for relieving a boiler of surplus steam; 
 
 A short space will be devoted to the consideration 
 of the lever safety valve also, as it may be of interest 
 to some students. 
 
 The U. S. marine rule for lever valves is here 
 repeated: "Lever safety valves to be attached to 
 marine boilers shall have an area of not less than one 
 square inch to every two square feet of grate surface in 
 the boiler, and the seats of all such safety valves shall 
 have an angle of inclination of 45 to the center line 
 of their axis." 
 
 In order to arrive at accurate results in lever safety 
 valve calculations it is necessary to know first the num- 
 ber of pounds pressure exerted upon the stem of the 
 valve by the lever itself, irrespective of the weight, 
 also the weight of the valve and stem, as all these 
 weights together with the weight of the ball suspended 
 upon the lever tend to hold the valve down against 
 the pressure of the steam. The effective weight of the 
 lever can be ascertained by leaving it in its position 
 attached to the fulcrum and connecting a spring bal- 
 ance scale to it at the point where it rests on the valve 
 stem. The weight of the valve and stem can also be 
 found by means of the scale. When the above weights 
 are known, together with the weight at the end of the 
 lever and its distance from the fulcrum, also the area 
 of the valve and its distance from the fulcrum, the 
 pressure at which the valve will blow can be found by 
 the following rules: 
 
 Rule 1. Multiply the weight by its distance from the 
 
78 ENGINEERING 
 
 fulcrum. Multiply the weight of the valve and lever 
 by the distance of the stem from the fulcrum and add 
 this to the former product. Divide the sum of the 
 two products by the product of the area of the valve 
 multiplied by the distance of its stem from the 
 fulcrum. The result will be pressure in pounds per 
 square inch required to lift the valve. 
 
 Example. Diameter of value, 3 in. 
 
 Distance of stem from fulcrum, 3 in. 
 
 Effective weight of lever, valve and stem, 20 lbs. 
 
 Weight of ball, 50 lbs. 
 
 Distance of ball from fulcrum, 30 in. 
 
 Required pressure at which the valve will blow off, 
 50 x 30 + 20 x 3 = 1560. 
 
 Area of valve, 7.0686 x 3 = 21.2058. 
 
 1560 -*- 21.2058 = 73-57 lbs. pressure. 
 
 When the pressure at which it is desired the valve 
 should blow off is known, together with the weights of 
 all the parts, the proper distance from the fulcrum at 
 which to place the weight is ascertained by'Rule 2. 
 
 Ride 2. Multiply the area of the valve by the pres- 
 sure and from the product subtract the effective weight 
 of the valve and lever. Multiply the remainder by the 
 distance of the stem from the fulcrum and divide hy 
 the weight of the ball. The quotient will be the 
 required distance. 
 
 Example. Area of valve, 7.07 sq. in. 
 
 To blow off at 75 lbs. 
 
 Effective weight of lever and valve, 20 lbs. 
 
 Weight of ball, 50 lbs. 
 
 Distance of valve stem from fulcrum, 3 in. 
 
 7.07 x 75 - 20 = 510.25. 
 
 510.25x3^-50 = 30.6 in., distance from fulcrum at 
 which to place the ball. 
 
BOILER OPERATION 79 
 
 When the pressure is known, together with the 
 distance of the weight from the fulcrum, the weight ot 
 the ball is obtained by Rule 3. 
 
 Rule j. Multiply the area of the valve by the pres- 
 sure and from the product subtract the effective weight 
 of the lever and valve. Multiply the remainder by 
 the distance of the stem from the fulcrum and divide 
 by the distance of the ball from the fulcrum. The 
 quotient will be the required weight. 
 
 Example. Area of valve, . . . . 7.07 sq. in. 
 
 Pressure in pounds per square inch, . . 80 lbs. 
 
 Effective weight of lever and valve, . . 20 lbs. 
 
 Distance of stem from fulcrum, .... 3 in. 
 
 Distance of weight from fulcrum, ... 30 in. 
 
 7.07 x 80-20 = 545.6. 
 
 545.6 x 3 -i- 30 = 54.56 lbs., weight of ball. 
 
 Safety valves, especially those of the lever type, are 
 liable to become corroded and stick to their seats if 
 allowed to go any great length of time without blow- 
 ing. Therefore it is good practice to raise the steam 
 pressure to the blowing off point at least two or three 
 times a week, or oftener, for the purpose of testing 
 the valve. If it opens and releases the steam at the 
 proper point all is well, but if it does not, it should be 
 looked after forthwith. Generally the mere raising of 
 the lever by hand, or a few taps with a hammer it it 
 be a pop valve, will free it and cause it to work all 
 right again; but if this treatment has to be resorted to 
 very often the valve should be taken down and over- 
 hauled. In too many steam plants not enough import- 
 ance is attached to the safety valve. The fact is, 
 it is one of the most useful and important adjuncts of 
 a boiler, and if neglected serious results are sure to 
 follow. 
 
80 ENGINEERING 
 
 Feed Pumps. A good engineer will always take a 
 pride in keeping his feed pump in good condition, and 
 if he has two or more of them, which every steam 
 plant of any consequence should have, he will have an 
 opportunity to keep his pumps in good shape. The 
 water pistons of most boiler feed pumps are fitted to 
 receive rings of fibrous packing. The best packing for 
 this purpose and one that will stand both hot and cold 
 water service is made of pure canvas cut in strips of 
 the required width, y 2 , $/&, Y\ in., etc., and laid 
 together with a water proof cement having the edges 
 for the wearing surface. This packing is called square 
 canvas packing, and can be purchased in any size 
 required for the pump. The size is easily ascertained 
 by placing the water piston, minus the follower plate, 
 centrally in the water cylinder and measuring the 
 space between the piston and cylinder walls. This 
 packing should not be allowed to run for too long a 
 time before renewing, for the reason that pieces of it 
 are liable to become loose and be forced along with 
 the feed water on its way to the boiler and lodge 
 under the check valve, holding it open and causing no 
 end of trouble. If the feed pump has to handle hot 
 water, or has to lift the water several feet by suction, 
 the packing rings should be looked after at least once 
 a month. 
 
 Hard rubber valves are, all things considered, the 
 best for a boiler feed pump, as they are not affected 
 by hot water and do not hammer the seats like metallic 
 composition valves do. Every boiler feed pump 
 should be fitted with a good sight-feed lubricator for 
 cylinder oil. The steam valve mechanism of a steam 
 pump is very sensitive and delicate and requires good 
 lubrication in order to do good work. In too many 
 
BOILER OPERATION 81 
 
 cases feed pumps are fitted with an old style cylinder 
 oil cup and there is generally more oil on the outside 
 of the valve chest than there is inside, while the valve 
 is bulldozed into working by frequent blows from a 
 convenient club. 
 
 The steam valves of all steam pumps are adjusted 
 before they are sent out from the factory, and most of 
 them are arranged so that the stroke may be 
 shortened or lengthened as the engineer desires. It 
 is best as a rule to allow a pump to make as long a 
 stroke as it will without striking the heads, because 
 then the parts are worn evenly. 
 
 Sometimes an engineer is called upon to set the 
 valves of a duplex pump which have become disar- 
 ranged. In such a case he should proceed as follows: 
 Place both pistons exactly at mid-stroke. This may 
 be done in two ways. First, by dropping a plummet 
 line alongside the levers connecting the rock shafts 
 with the spools on the piston rods. Then bring the 
 rods to the position where the centers of the spools 
 will be in a vertical line with the centers of the rock 
 shafts. 
 
 The second method is to move the piston to 
 the extreme end of the stroke until it comes in contact 
 with {he cylinder head. Then mark the rod at the 
 face of the stuffing box gland. Next move the piston 
 to the other end of the stroke and mark the rod at the 
 opposite gland. Now make a mark on the rod exactly 
 •half way between the two outside marks and move the 
 piston back until the middle mark is at the face of the 
 gland and the piston will be at mid-stroke. Having 
 placed both pistons at mid-strike, remove the valve 
 chest covers and adjust the valves in their central posi- 
 tion, viz., so that they cover the steam ports. The 
 
82 ENGINEERING 
 
 valve rod being in position and connected to the 
 rocker arm by means of the short link, the nut or nuts 
 securing the valve to the rod should be so adjusted as 
 to be equidistant from the lugs on the valve, say fa or 
 yi of an inch according to the amount of lost motion 
 desired, which latter factor governs the length of 
 stroke in some makes of duplex pumps, while in 
 others it is controlled by tappets on the valve rod 
 outside of the valve chest. Care should be taken 
 while making these adjustments that the valve be 
 retained exactly in its central position. 
 
 Having set the valves correctly, move one of the 
 pistons far enough from mid-stroke to get a small 
 opening of the steam port on the opposite side, then 
 replace the valve chest covers and the pump will be 
 ready to run. As these valves are generally made 
 without any outside lap, a slight movement of one of 
 the pistons in either direction from its central position 
 will suffice to uncover one of the ports on the other 
 cylinder sufficiently to start the pump. 
 
 Sometimes duplex pumps "work lame," that is, 
 one piston will make a quick full stroke while the 
 other piston will move very slowly and just far enough 
 to work the steam valve of the opposite side. In the 
 majority of cases this irregular action is due to 
 unequal friction in the packing of the rods, or the 
 packing rings on one of the pistons may be worn out. 
 
 If one side of a duplex pump becomes disabled from 
 any cause, as breaking of piston rod in the water 
 cylinder, for instance, which is liable to happen, the 
 pump may still be operated in the following manner 
 until duplicate parts to replace the broken ones have 
 been .secured. Loosen the nuts or tappets on the 
 valve stem of the broken side and place them far 
 
BOILER OPERATION 83 
 
 enough apart so that the steam valve will be moved 
 through only a small portion of its stroke, thereby 
 admitting only steam enough to move the empty 
 steam piston and rod, and thus work the steam valve 
 of the remaining side. The packing on the broken 
 rod should be screwed up tight, so as to create as 
 much friction as possible; there being no resistance in 
 the water end. In this way the pump may be oper- 
 ated for several days or weeks and thus prevent a shut 
 down. 
 
 Hydraulics for Engineers. Among the many difficult 
 problems that are continually coming up for engineers 
 to solve, there is none more perplexing than the cor- 
 rect calculation of the quantit}' of water which will be 
 discharged in a given time from pipes of various sizes 
 and under the many different heads or pressures. 
 Problems in hydraulics, as given by the majority of 
 writers on engineering, are usually in elaborate alge- . 
 braical equations, which, to the ordinary working 
 engineer, are very perplexing, at least the author has 
 found them to be so in his experience. Therefore 
 with a view of assisting his brother engineers in the 
 solution of problems along this line which they may 
 be called upon to solve, the author has spent consider- 
 able time and labor in searching for and compiling a 
 few rules and examples for hydraulic calculations in 
 plain arithmetic which he hopes may be of benefit. . 
 
 First, to find velocity of flow in the pump, or in 
 other words, piston speed. 
 
 Rule. Multiply number of strokes per minute by 
 length of stroke in feet, or fractions thereof. 
 
 Second, the velocity of flow in the discharge pipe 
 is in inverse ratio to the squares of the diameters of 
 the pipe and the water cylinder of pump. 
 
84 ENGINEERING 
 
 Thus, a pump cylinder is 6 in. in diameter, and the 
 piston speed is ioo ft. per minute; the discharge pipe 
 being 3 in. in diameter. What is the velocity of. flow 
 in the pipe? 
 
 Exajnple. 3^=4. In this case the velocity in the 
 pipe is four times that in the pump, and 100 x 4 = 400 ft. 
 per minute, velocity for water in the discharge pipe. 
 
 Third, to find velocity in feet per minute necessary 
 to discharge a given quantity of water in a given 
 time. 
 
 Rule. Multiply the number of cubic feet to be dis- 
 charged by 144 and divide by area of pipe in inches. 
 
 Fourth, to find area of pipe when the volume and 
 velocity of water to be discharged are known. 
 
 Rule. Multiply volume in cubic feet by 144 and 
 divide by the velocity in feet per minute. 
 
 Fifth, one of the first requisites in making correct 
 calculations of the quantity of water discharged from 
 any sized pipe is to obtain the velocity of flow per 
 second. There are several rules for doing this, among 
 which the following appear to be the plainest and 
 most simple: 
 
 Rule 1 Multiply the square root of the head in 
 inches by the constant 27.8. For instance, assume 
 the head to be 100 ft. = 1200 in. The square root of 
 1200 is 35 nearly, then 35 x 27.8 = 973 in. = 81 ft. per 
 second velocity. 
 
 Rule 2. Multiply the square root of the head in feet 
 by the constant 8, as follows: The square of 100= 10 
 and 10 x 8 = 80 ft. velocity per second. 
 
 Rule j. Multiply twice the acceleration of gravity 
 by the head in feet and extract the square root of 
 product. The acceleration of gravity may be consid- 
 ered the constant number 32, neglecting decimals. 
 
BOILER OPERATION 85 
 
 32 x 2 x 100 = 6400. Square root of 6400 = 80 ft. per 
 second. 
 
 In many instances it is more convenient to use the 
 pressure in pounds per square inch as shown by gauge 
 instead of the height or head, and we can then apply 
 Rule 4. 
 
 Rule 4. Multiply the square root of the pressure in 
 pounds per square inch by the constant number 12.16 
 as follows: Pressure due to 100 ft. head = 44 lbs., 
 nearly. Square root of 44 = 6.6, which multiplied by 
 12.16 = 80.2 ft. velocity per second. 
 
 Having ascertained the velocity of flow, we may 
 now proceed to calculate the weight of water in 
 pounds per second discharged from any size of pipe, 
 neglecting for the time being the loss in pressure 
 caused by friction from elbows and bends in the pipe 
 and also the peculiar shape assumed by a stream of 
 water flowing through pipes or conduits when there is 
 no resistance except the pressure of the atmosphere 
 and friction caused by long distance transmission. 
 
 We will take for our calculation a four-inch pipe 
 from which the water has a free flow under a head of 
 100 ft., which gives a velocity of 80 ft. per second. 
 
 Rule 5. Divide the velocity in feet per second by the 
 constant 2.3, and multiply the quotient by the area of 
 discharge pipe in square inches. 80 + 2.3 = 34.7. 
 Now the area of a four-inch pipe is 12.57 sq. in., and 
 34.7 x 12.57 = 436 lbs. discharged per second. 
 
 In order to get the matter clearly before us, let us 
 assume that we have a section of four-inch pipe just 
 80 ft. in length and that it lies in a horizontal position 
 and is filled solidly full of water. It will contain area, 
 12.57 sq. in. x length, 960 in. = 12,067.2 cu. in. of water, 
 and as one pound of water occupies a space of 
 
80 ENGINEERING 
 
 2j.j cu. in. , we therefore have 1,2067.2 -f- 27.7 = 436 lbs. 
 of water, and at a velocity of 80 ft. per second our 
 pipe will be emptied and refilled continuously each 
 second. We have also Rule 6 to find the number of 
 cubic feet discharged per minute when the velocity 
 per minute is known. 
 
 Rule 6 Multiply the area of pipe in square inches 
 by the velocity in feet per minute and divide by the 
 constant 144. 
 
 Example. Area of 4 in. pipe = 12.57 sq. in. Velocity 
 of flow = 80 ft. per second = 4,800 ft. per minute. Then 
 i2^x4 i 80o = 4I9 cu> ft _ per m i nut e = 6.99 cu. ft. per 
 second, which multiplied by 62.3 lbs. (weight of 1 cu. 
 ft.) = 435.4 lbs. per second. 
 
 As stated before, no allowance is made by the above 
 rules for friction or other retarding influences, but foi 
 ordinary purposes in connection with a steam plant a 
 deduction of 25 per cent, is probably sufficient. Of 
 course if the water is being discharged into an elevated 
 tank or against direct pressure of any kind, the resist- 
 ance in pounds per square inch or the height in feet 
 must be deducted from the impelling pressure or head. 
 Let us assume, for instance, that our 4 in. pipe is dis- 
 charging water into a tank at an elevation of 75 ft. 
 above the level of the pump, and that to reach the 
 tank requires 100 ft. of pipe with two 90° ells and one 
 straight-way valve. We wish to discharge 500 gal. 
 per minute into the tank ana will therefore require a 
 velocity of about 13 ft. per second, which will necessi- 
 tate a pressure of a little more than 1 lb. per square 
 inch to be maintained at the pump over and above all 
 resistance. Now the resistance to be overcome in this 
 case will be: 
 
BOILER OPERATION 87 
 
 Pressure per square inch due to 75 ft. head, 32.5 lbs. 
 Friction loss due to length of pipe and velocity, 7.43 ' 
 Friction loss due to two 90 ells, 2.16 ' 
 
 Friction loss due to straight way valve, .2 
 
 Total, 42.29 lbs. 
 Requiring a pressure of say 43 lbs. per square inch, 
 or about the equivalent of 100 ft. head at the pump. 
 
 Again, suppose that in place of the elevated tank 
 we have 1,000 ft. of 8 in. horizontal pipe with a 4 in. 
 delivery at the end farthest from the pump, and three 
 branch pipes each 100 ft. long and 4 in. in diameter 
 with one 90 ell and one straight-way valve, connected 
 at intervals to the 8 in. main, and it is required to dis- 
 charge in all 1,000 gals, per minute, or at the rate of 
 250 gals, per minute for each 4 in. delivery. The 
 friction loss for each 100 ft, in length of 8 in. pipe at 
 a velocity of 13 ft. per second is .94 lbs., and for each 
 100 ft. of 4 in. pipe it is 1.89 lbs. Likewise the 
 friction loss for each- 90 ell is 1.08 lbs., and for a 
 straight way valve .2 lbs., at the above velocity. The 
 total resistance therefore to be overcome is as follows: 
 For 1,000 ft. of 8 in. pipe, .94 lbs. x 10 = 9.4 lbs. 
 For 300 ft. of 4 in. pipe, 1.89 lbs. x 3 = 5.67 
 For four 90 ells, 1.08 lbs. x 4 = 4.32 " 
 
 For four straight-way valves, .2 lbs. x 4= .8 
 
 Total, 20.19 l° s - 
 Consequently the pressure required at the pump will 
 be about 22 lbs. per square inch, equal to a head of 
 50 ft. 
 
 Questions 
 
 1. What should be the first care of an engineer on 
 entering his boiler room when he goes on watch? 
 
88 ENGINEERING 
 
 2. What is one of the duties of the fireman before 
 coming off watch? 
 
 3. Name the various tools necessary for cleaning 
 fires properly. 
 
 4. Describe the operation of cleaning fires. 
 
 5. What general rules should be observed in firing? 
 
 6. How may the best results be obtained in firing 
 bituminous coal? 
 
 7. What will be the result if a sufficient supply of 
 oxygen is not admitted to the furnace? 
 
 8. What quantity of air (cubic feet or pounds 
 weight) is required for the complete combustion of 
 one pound of coal? 
 
 9. Suppose there is a fusible plug in jthe boiler and 
 it becomes covered with scale, what will be the result? 
 
 10. How long may a boiler be run safely after wash- 
 ing it out? 
 
 11. What should be done with a boiler in order to 
 prepare it for washing out? 
 
 12. What effect does the too sudden cooling off or 
 firing up of a boiler have upon the seams? 
 
 13. What other bad result takes place within the 
 boiler when it is emptied of water while hot? 
 
 14. What should be done with tubes that have 
 become badly scaled? 
 
 15. How fast should the feed water be supplied? 
 
 16. What should be done in case the supply of feed 
 water be cut off suddenly? 
 
 17. What is the proper method of connecting a 
 recently fired up boiler to the main header? 
 
 18. What are some of the dangerous results of 
 foaming? 
 
 19. What can be done to prevent or at least to 
 modify foaming in boilers? 
 
BOILER OPERATION 89 
 
 20. Which are the most reliable pop valves or lever 
 safety valves? 
 
 21. What is the rule regulating the area of lever 
 safety valves? 
 
 22. What two factors must first be known before cor= 
 rect calculations can be made as to the weight and posi- 
 tion of the ball on a lever safety valve? 
 
 23. How may the effective weight of the lever and 
 that of the valve and stem be found? 
 
 24. When the area in square inches of the valve, the 
 weight of the valve and stem, the effective weight of 
 the lever, the weight of the ball and its distance from 
 the fulcrum are known, how is the pressure at which 
 the valve will blow off ascertained? 
 
 25. When the pressure at which the valve should 
 blow off is known, together with the weights of all the 
 parts, how may the distance the ball should be from 
 the fulcrum be ascertained? 
 
 26. When the pressure is known, together with the 
 distance of the ball from the fulcrum, how is the 
 weight of the ball found? 
 
 27. What should be done with a safety valve in 
 order to keep it in good working condition? 
 
 28. Describe the process of setting the steam valves 
 of a duplex pump. 
 
 29. How may a duplex pump be operated in case 
 one of the water pistons becomes disabled? 
 
 30. How is the velocity of flow or piston speed per 
 minute of a pump ascertained? 
 
 31. The piston speed being known, how is the velo- 
 city of flow in the discharge pipe found? 
 
 32. When it is required to discharge a certain quantity 
 of water from a given size of pipe in a given time, how 
 may the velocity of flow in feet per minute be found? 
 
90 ENGINEERING 
 
 33. When the volume of water to be discharged and 
 the velocity of flow are known, how is the area of the 
 pipe obtained? 
 
 34. What is meant by "acceleration of gravity," and 
 what constant number represents it in connection with 
 hydraulics? 
 
 35. What per cent, of allowance is ordinarily made 
 for friction in water pipes? 
 
CHAPTER IV 
 
 COMBUSTION -WATER— STEAM 
 
 Combustion — Composition of air — Carbon — The principal constit- 
 uent of fuels — Hydrogen, its nature and heating value — 
 Table, giving analysis of various coals — Process of combus- 
 tion described — Quantity of air required — Furnace tempera- 
 ture — How to utilize the heat in the escaping gases — Heat, 
 what it is and how produced — Joule's researches — The heat 
 unit — Specific heat — Sensible heat and latent heat — Experi- 
 ments of Professor Black — Total heat of evaporation — Water, 
 its composition, nature, etc. — Steam, its expansive nature, 
 temperature, etc. — Saturated steam, etc. — Total heat of 
 steam — Density of steam. 
 
 Combustion. The subject of the combustion of fuels 
 being one in which every engineer is vitally interested, 
 it is proper that its leading features and principles be 
 discussed. One of the main factors in the combustion 
 of coal is the proper supply of air. Air is composed 
 of two gases, oxygen and nitrogen, in the proportion, 
 by volume, of 21 per cent, of oxygen and 79 per cent, 
 of nitrogen, or by weight, 23 per cent, of oxygen and 
 J7 per cent, of nitrogen. 
 
 The composition of pure dry air, as given by Kent 
 in Steam Boiler Economy, is as follows: 
 
 By volume, 20.91 parts O. and 79.09 parts N. 
 
 By weight, 23.15 parts O. and 76.85 parts N. 
 
 Air is a mixture and not a chemical combination of 
 these two elements. The principal constituent of coal 
 and most other fuels, whether solid, liquid or gaseous, 
 is carbon. Hydrogen is a light combustible gas and 
 combined either with carbon or with carbon and 
 91 
 
92 
 
 ENGINEERING 
 
 oxygen, in various proportions, is also a valuable con- 
 stituent of fuels, notably of bituminous coal. The 
 heating value of one pound of pure carbon is rated at 
 14,500 heat units, while one pound of hydrogen gas 
 contains 62,000 heat units. 
 
 Analysis of coal shows that it contains moisture, 
 fixed carbon, volatile matter, ash and sulphur in vari- 
 ous proportions according to the quality of the coal. 
 The following table deduced from a few of the many 
 valuable tables of analysis of the coals of the United 
 States, as given by Mr. Kent, will show the composi- 
 tion of the principal bituminous coals in use in this 
 country for steam purposes. Two samples are selected 
 from each of the great coal producing states, with the 
 exception of Illinois, from which four were taken. 
 
 Table 2 
 
 State 
 
 Kind of Coal 
 
 Moist- 
 ure 
 
 Vola- 
 tile 
 Matter 
 
 Fixed 
 Carbon 
 
 Ash 
 
 Sul- 
 phur 
 
 Pennsylvania 
 
 Youghiogheny 
 
 1.03 
 
 36.49 
 
 59.05 
 
 2.61 
 
 0.81 
 
 " 
 
 Connellsville 
 
 1.26 
 
 30.10 
 
 59.61 
 
 8.23 
 
 0.78 
 
 West Virginia 
 
 Quinimont 
 
 0.76 
 
 18.65 
 
 79.26 
 
 I. II 
 
 O.23 
 
 ' ' 
 
 Fire Creek 
 
 0.61 
 
 22.34 
 
 75-02 
 
 I.47 
 
 0.56 
 
 E. Kentucky 
 
 Peach Orchard 
 
 4.60 
 
 35-70 
 
 53-28 
 
 6 42 
 
 1.08 
 
 
 Pike County 
 
 1. So 
 
 26.80 
 
 67.60 
 
 3.80 
 
 0.97 
 
 Alabama 
 
 Cahaba 
 
 1.66 
 
 33-28 
 
 63.04 
 
 2.02 
 
 o.53 
 
 " 
 
 Pratt Co.'s 
 
 1.47 
 
 32.29 
 
 59 50 
 
 6-73 
 
 1.22 
 
 Ohio 
 
 Hocking Valley 
 
 6-59 
 
 35-77 
 
 49-64 
 
 8.00 
 
 1-59 
 
 " 
 
 Muskingum " 
 
 3-47 
 
 37-88 
 
 53-30 
 
 5-35 
 
 2.24 
 
 Indiana 
 
 Block 
 
 8.50 
 
 31.00 
 
 57-50 
 
 3.00 
 
 
 ' ' 
 
 
 2.50 
 
 44-75 
 
 51-25 
 
 1.50 
 
 
 W. Kentucky 
 
 Nolin River 
 
 4.70 
 
 33-24 
 
 54-94 
 
 11.70 
 
 2-54 
 
 1 ' 
 
 Ohio County 
 
 3-70 
 
 30.70 
 
 45.oo 
 
 3.16 
 
 I.24 
 
 Illinois 
 
 Big Muddy 
 
 6.40 
 
 30.60 
 
 54.6o 
 
 8.30 
 
 I.50 
 
 ' ' 
 
 Wilmington 
 
 15.50 
 
 32.80 
 
 39-90 
 
 11.80 
 
 
 " 
 
 ' ' screenings 
 
 14.00 28.00 
 
 34.20 
 
 23.80 
 
 
 
 Duquoin 
 
 8.90 I 23.50 
 
 60.60 
 
 7.00 
 
 
 The process of combustion consists in the anion of 
 the carbon and hydrogen of the fuel with the oxygen 
 
COMBUSTION — WATER STEAM 93 
 
 of the air. Each atom of carbon combines with two 
 atoms of oxygen, and the energetic vibration set up by 
 their combination is heat. Bituminous coal contains a 
 large percentage of volatile matter which is released 
 and flashes into flame when the coal is thrown into the 
 furnace, and unless air is supplied in large amounts at 
 this stage of the combustion there will be an excess of 
 smoke and consequent loss of carbon. On the other 
 hand there is a loss in admitting too much air because 
 the surplus is heated to the temperature of the furnace 
 without aiding the combustion and will carry off to 
 the chimney just as many heat units as were required 
 to raise it from the temperature at which it entered 
 the furnace to that at which it enters the uptake. It 
 will therefore be seen that a great advantage will be 
 gained by first allowing the air that is needed above 
 the fire to pass over or through heated bridge walls or 
 side walls. Some kinds of coal need more air for 
 their combustion than do others, and good judgment 
 and close observation are needed on the part of the 
 fireman to properly regulate the supply. 
 
 Some boilers will make steam more economically by 
 partly closing the ash-pit doors, while others require 
 the same doors to be kept wide open. The quantity 
 of air required for the combustion of one pound of 
 coal is, by volume, about 150 cu. ft.; by weight, about 
 12 lbs. 
 
 The temperature of the furnace is usually about 
 2500 , in some cases reaching as high as 3000 . The 
 temperature of the escaping gases should not be much 
 above nor below 400 F. for bituminous coal. The 
 waste heat in the escaping gases can be utilized to 
 great advantage by passing them through what are 
 called economizers before they escape into the chim- 
 
94 
 
 ENGINEERING 
 
 ney. These economizers consist of coils or stacks of 
 cast iron pipe placed within the flue or breeching lead- 
 ing from the boilers to the chimney and are enveloped 
 in the hot gases, while the feed water is passed 
 through the pipes on its way to the boilers, the result 
 being that considerable heat is thus imparted to the 
 feed water that would otherwise go to waste. 
 
 In order to attain the highest economy in the burn- 
 ing of coal in boiler furnaces two factors are indispen- 
 
 GREEN S FUEL ECONOMIZER UNDER CONSTRUCTION. 
 
 sable, viz., a constant high furnace temperature and 
 quick combustion, and these factors can only be 
 secured by supplying the fresh coal constantly just as 
 fast as it is burned, and also by preventing as much as 
 possible the admission of cold air to the furnace. 
 This is why the automatic or mechanical stoker, if it 
 be of the proper design, is more economical and 
 causes less smoke than ,hand firing. The fireman 
 when he puts in a fire is prone to shovel in a good 
 supply all at once, and this has the tendency to 
 
COMBUSTION — WATER — STEAM 95 
 
 greatly reduce the temperature of the furnace, while 
 at the same time it retards combustion. On the other 
 hand the mechanical stoker supplies the coal continu- 
 ously only as fast as it is required and no faster, and 
 the furnace doors do not need to be opened at all, by 
 which a large volume of cold air is prevented from 
 entering the furnace and reducing the temperature. 
 The author does not wish to be understood as recom- 
 mending the adoption and use of mechanical stokers 
 to replace hand firing, but he draws this contrast 
 between the two methods of firing in order that it 
 may be of some benefit to the thousands of honest 
 toilers who earn a livelihood by shoveling coal into 
 boiler furnaces. 
 
 The problem of the economical use of coal and the 
 abatement of the smoke nuisance, especially in our 
 large cities, has of late years become so serious that it 
 is to the interest of every engineer, and especially 
 every fireman, to use the utmost diligence, care and 
 good judgment in the use of coal, and to emulate as 
 much as possible the methods of the mechanical 
 stoker. 
 
 Heat. All matter, whether solid, liquid or gaseous, 
 consists of molecules or. atoms, which are in a state of 
 continual vibration, and the result of .this vibration is 
 heat. The intensity of the heat evolved depends upon 
 the degree of agitation to which the molecules are 
 subject. 
 
 Until as late as the beginning of the nineteenth 
 century two rival theories in regard to the nature of 
 heat had been advocated by scientists. The older of 
 these theories was that heat was a material substance, 
 a subtle elastic fluid termed caloric, and that this fluid 
 penetrated matter something like water penetrates a 
 
ENGINEERING 
 
 sponge. But this theory was shown to be false by the 
 wonderful researches and experiments of Count Rum- 
 ford at Munich, Bavaria, in 1798. 
 
 By means of the friction between two heavy metallic 
 bodies placed in a wooden trough filled with water, 
 one of the pieces of metal being rotated by machinery 
 driven by horses, Count Rumford succeeded in raising 
 the temperature of the water in two and one-half 
 hours from its original temperature, of 6o° to 212 F., 
 the boiling point, thus demonstrating that heat is not 
 a material substance, but that it is due to vibration or 
 motion, an internal commotion among the molecules 
 of matter. This theory, known as the Kinetic theory 
 of heat, has since been generally accepted, although it 
 was nearly fifty years after Rumford advocated it in a 
 paper read before the Royal Society of Great Britain 
 in 1798, before scientists generally became converted 
 to this idea of the nature of heat and the science of 
 Thermo Dynamics placed on a firm basis. 
 
 During the period from 1840 to 1849 Dr. Joule made 
 a series of experiments which not only confirmed the 
 truth of Count Rumford's theory that heat was not a 
 material substance but a form of energy which may be 
 applied to or taken away from bodies, but Joule's 
 experiments also established a method of estimating 
 in mechanical units or foot pounds the amount of that 
 energy. This latter was a most important discovery 
 because by means of it the exact relation between heat 
 and work can be accurately measured. 
 
 The first law of thermo dynamics is this: Heat and 
 mechanical energy or work are mutually convertible. 
 That is, a certain amount of work will produce a 
 certain amount of heat, and the heat thus produced is 
 capable of producing by its disappearance a fixed 
 
COMBUSTION — WATER — STEAM 
 
 07 
 
 amount of mechanical energy if rightly applied. The 
 mechanical energy in the form of heat which, through 
 the medium of the steam engine, has revolutionized 
 the world, was first stored up by the sun's heat 
 millions of years ago in the coal which in turn, by 
 
 ^feTy^rr/ti 
 
 P ~fiadd.te$ 
 
 FIGURE 11 
 
 1^ 
 
 combustion, is made to release it for purposes of 
 mechanical work. 
 
 The general principles of Dr. Joule's device for 
 measuring the amount of work in heat are illustrated 
 in Fig. ii. It consisted of a small copper cylinder 
 
98 ENGINEERING 
 
 containing a known quantity of water at a known 
 temperature. Inside the cylinder and extending 
 through the top was a vertical shaft to which were 
 fixed paddles for stirring the water. Stationary vanes 
 were also placed inside the cylinder. Motion was 
 imparted to the shaft through the medium of a cord 
 or small rope coiled around a drum near the top of the 
 shaft and running over a grooved pulley or sheave. 
 To the free end of the cord a known weight was 
 attached. This weight was allowed to fall through a 
 certain distance, and in falling it turned the shaft 
 with its paddles, which in turn agitated the water, 
 thus producing a certain amount of heat. To illus- 
 trate, suppose the weight to be 77.8 lbs., and that by 
 means of the crank at the top end of the shaft it has 
 been raised to the zero mark at the top of the scale. 
 (See Fig. 11.) One pound of water at 39. i° F. is 
 poured into the copper cylinder, which is then closed 
 and the weight released. At the moment the weight 
 passes the 10 ft. mark on the scale, the thermometer 
 attached to the cylinder will indicate that the temper- 
 ature of the water has been raised one degree. Then 
 multiplying the number of pounds in the weight by 
 the distance in feet through which it fell will give the 
 number of foot pounds of work done. Thus, 
 77.8 lbs. x 10 ft. = 778 foot pounds. 
 
 The heat unit or British thermal unit (B. T. U.) is 
 the quantity of heat required to raise the temperature 
 of one pound of water one degree, or from 39 to 
 40 F., and the amount of mechanical work required 
 to produce a unit of heat is 778 foot pounds. There- 
 fore the mechanical equivalent of heat is the energy 
 required to raise 778 lbs. one foot high, or 77.8 lbs. 
 10 ft. high, or 1 lb. 778 feet high. Or again, suppose 
 
COMBUSTION — WATER — STEAM 99 
 
 a one-pound weight falls through a space of 778 ft. or 
 a weight of 778 lbs. falls one foot, enough mechanical 
 energy would thus be developed to raise a pound of 
 water one degree in temperature, provided all the 
 energy so developed could be utilized in churning or 
 stirring the water, as in Joule's machine. Hence the 
 mechanical equivalent of heat is 778 foot pounds. 
 
 Specific Heat. The specific heat of any substance is 
 the ratio of the quantity of heat required to raise a 
 given weight of that substance one degree in temper- 
 ature to the quantity of heat required to raise an equal 
 weight of water one degree in temperature when the 
 water is at its maximum density, 39. i° F. To illus- 
 trate, take the specific heat of lead, for instance, which 
 is .031, while the specific heat of water is 1. That 
 means that it would require 31 times as much heat to 
 raise one pound of water one degree in temperature as 
 it would to raise the temperature of a pound of lead 
 one degree. 
 
 The following table gives the specific heat of differ- 
 ent substances in which engineers are most generally 
 
 interested. 
 
 TABLE 3. 
 
 Water at 39. i° F 1.000 
 
 Ice at 32 F 504 
 
 Steam at 212 F 480 
 
 Mercury 033 
 
 Cast iron 130 
 
 Wrought iron 113 
 
 Soft steel 116 
 
 Copper 095 
 
 Lead 03 1 
 
 Coal 240 
 
 Air 238 
 
 Hydrogen 3.404 
 
 Oxygen 218 
 
 Nitrogen 244 
 
 Sensible Heat and Latent Heat. The plainest and 
 most simple definition of these two terms is that given 
 
 L. OF C. 
 
100 ENGINEERING 
 
 by Sir Wm. Thomson. He says: "Heat given to a 
 body and warming it is sensible heat. Heat given to 
 a body and not warming it is latent heat." Sensible 
 heat in a substance is the heat that can be measured in 
 degrees of a thermometer, while latent heat is the heat 
 in any substance that is not shown by the ther- 
 mometer. 
 
 To illustrate this more fully a brief reference to 
 some experiments made by Professor Black in 1762 
 will no doubt make the matter plain. It will be 
 remembered that at that early date comparatively 
 little was known of the true nature of heat, hence Pro- 
 fessor Black's investigations and discoveries along this 
 line appear all the more wonderful. He procured 
 equal weights of ice at 32 F. and water at the same 
 temperature, that is, just at the freezing point, and 
 placing them in separate glass vessels suspended the 
 vessels in a room in which the uniform temperature 
 was 47 F. He noticed that in one-half hour the 
 water had increased 7 F. in temperature, but that 
 twenty half hours elapsed before all of the ice was 
 melted. Therefore he reasoned that twenty times 
 more heat had entered the ice than had entered the 
 water, because at the end of the twenty half hours 
 when the ice was all melted the water in both vessels 
 was of the same temperature. The water having 
 absorbed J° of heat during the first half hour must 
 have continued to absorb heat at the same rate during 
 the whole of the twenty half hours, although the ther- 
 mometer did not indicate it. From this he calculated 
 that 7 x 20 = 140 of heat had become latent or hidden 
 in the water. 
 
 In another experiment Professor Black placed a 
 lump of melting ice, which he estimated to be at a 
 
COMBUSTION — WATER — STEAM 101 
 
 temperature of 33 F. on the surface, in a vessel con- 
 taining the same weight of water at 176 F., and he 
 observed that when the whole of the ice had been 
 melted the temperature of the water was 33 F., thus 
 proving that 143 of heat (i76°-33°) had been 
 absorbed in melting the ice and was at that moment 
 latent in the water By these two experiments Pro- 
 fessor Black established the theory of the latent heat 
 of water, and his estimate was very near the truth 
 because the results obtained since that time by the 
 greatest experimenters show that the latent heat of 
 water is 142 heat units, or B. T. U. 
 
 Black's experiment for ascertaining the latent heat 
 in steam at atmospheric pressure was made in the 
 following simple manner: He placed a flat, open tin 
 dish on a hot plate over a fire and into the dish he put 
 a small quantity of water at 50 F. In four minutes 
 the water began to boil, and in twenty minutes more 
 it had all evaporated. In the first four minutes the 
 temperature had increased 212 - 50 = 162 , and the 
 temperature remained at 212 throughout the twenty 
 minutes that it required to evaporate all the water, 
 despite the fact that the water had been receiving heat 
 during this period at the same rate as during the. first 
 four minutes. He therefore reasoned that in the 
 twenty minutes the water had absorbed five times as 
 much heat as it had in the four minutes, or 162 x 
 5 = 810°, without any sensible rise in temperature. 
 Therefore the 8io° became latent in the steam. Owing 
 to the crude nature of the experiment Professor 
 Black's estimate of the number of degrees of latent 
 heat in steam was incorrect, as it has been proven by 
 many famous experimenters since then that the latent 
 heat of steam at atmospheric pressure is 965.7 B. T. U. 
 
102 ENGINEERING 
 
 It will thus be perceived that what is meant by the 
 term latent heat is that quantity of heat which 
 becomes hidden or latent when the state of a body is 
 changed from a solid to a liquid, as in the case of 
 melting ice, or from a liquid to a gaseous state, as 
 with water evaporated into steam. But the heat so 
 disappearing has not been lost, on the contrary it has, 
 while becoming latent, been doing an immense amount 
 of work, as can easily be ascertained by means of a 
 few simple figures. It has been seen that a heat unit 
 is the quantity of heat required to raise one pound of 
 water one degree in temperature and also that the 
 mechanical equivalent of heat, or, in other words, the 
 mechanical energy stored in one heat unit is equal to 
 778 foot pounds of work. 
 
 A horse power equals 33,000 ft. lbs. of energy in 
 one minute of time, and a heat unit = 778 -*- 33,000 = 
 .0236, or about -£$ of a horse power. The work done 
 by the heat which becomes latent in converting one 
 pound of ice at $2° F. into water at the same temper- 
 ature = 142 heat units x 778 ft. lbs. = 110,476 ft. 
 lbs., which divided by 33,000 equals 3.34 horse 
 power. Again, by the evaporation of one pound 
 of water from 32 F. into steam at atmospheric 
 pressure, 965.7 units of heat become latent in the 
 steam and the work done = 965.7 x 778 = 751,314 ft. 
 lbs. = 22.7 horse power. It will thus be seen what 
 tremendous energy lies stored in one pound of coal, 
 which contains from 12,000 to 14,500 heat units, pro- 
 vided all the heat could be utilized in an engine. 
 
 Total Heat of Evaporation. In order to raise the tem- 
 perature of one pound of water from the freezing 
 point, 32 F., to the boiling point, 212 F., there must 
 be added to the temperature of the water 212 — 32 = 
 
COMBUSTION WATER — STEAM 103 
 
 i8o°. This represents the sensible heat Then to 
 make the water boil at atmospheric pressure, or, in 
 other words, to evaporate it, there must still be added 
 965.7 B. T. U., thus 180 + 965.7= 1,145.7, or in round 
 numbers 1,146 heat units. This represents what is 
 termed the total heat of evaporation at atmospheric 
 pressure and is the sum of the sensible and latent heat 
 in steam at that pressure. But if a thermometer were 
 held in steam evaporating into the open air, as, for 
 instance, in front of the spout of a tea-kettle, it would 
 indicate but 212 F. 
 
 When steam is generated at a higher pressure than 
 212 , the sensible heat increases and the latent heat 
 decreases slowly, while at the same time the total heat 
 of evaporation slowly increases as the pressure 
 increases, but not in the same ratio. As, for instance, 
 the total heat in steam at atmospheric pressure is 
 1,146 B. T. U. , while the total heat in steam at 100 lbs. 
 gauge pressure is 1,185 B. T. U., and the sensible tem- 
 perature of steam at atmospheric pressure is 212 , 
 while at 100 lbs. gauge pressure the temperature is 338 
 and the latent heat is 876 B. T. U. See table. 
 
 Water. The elements that enter into the composi- 
 tion of pure water are the two gases, hydrogen and 
 oxygen, in the following proportions: 
 
 By volume, hydrogen 2, oxygen I. 
 By weight, 11.1, " 88.9. 
 
 Perfectly pure water is not attainable, neither is it 
 desirable nor necessary to the welfare of the human 
 race, because the presence of certain proportions of air 
 and ammonia add greatly to its value as an agent for 
 manufacturing purposes and for generating steam. 
 The nearest approach to pure water is rain water, but 
 even this contains 2.5 volumes of air to each 100 vol- 
 
104 ENGINEERING 
 
 umes of water. Pure distilled water, such for instance 
 as the return water from steam heating systems, is not 
 desirable for use alone in a boiler as it will cause cor- 
 rosion and pitting of the sheets, but if it is mixed with 
 other water before going into the boiler its use is 
 highly beneficial, as it will prevent to a certain degree 
 the formation of scale and incrustation. Nearly all 
 water used for the generation of steam in boilers con- 
 tains more or less scale-forming matter, such as the 
 carbonates of lime and magnesia, the sulphates of lime 
 and magnesia, oxide of iron, silica and organic matter, 
 which latter tends to cause foaming in boilers. 
 
 The carbonates of lime and magnesia are the chief 
 causes of incrustation. The sulphate of lime forms a 
 hard crystalline scale which is extremely difficult to 
 remove when once formed on the sheets and tubes of 
 boilers. Of late 'years the intelligent application of 
 chemistry to the analyzing of feed waters has been of 
 great benefit to engineers and steam users, in that it 
 has enabled them to properly treat the water with 
 solvents either before it is pumped into the boiler, or 
 by the introduction into the boiler of certain scale 
 preventing compounds made especially for treating 
 the particular kind of water used. Where it is neces- 
 sary to treat water in this manner great care and 
 watchfulness should be exercised by the engineer in 
 the selection and use of a boiler compound. 
 
 From ten to forty grains of mineral matter per 
 gallon are held in solution by the waters of the differ- 
 ent rivers, streams and lakes; well and mine water 
 contain still more. 
 
 Water contracts and becomes denser in cooling until 
 it reaches a temperature of 39. i° F. , its point of great- 
 est density. Below this temperature it expands and 
 
COMBUSTION WATER STEAM 
 
 105 
 
 at 32 F. it becomes solid or freezes, and in the act of 
 freezing it expands considerably, as every engineer 
 who has had to deal with frozen water pipes can tes- 
 tify. 
 
 Water is 815 times heavier than atmospheric air. 
 The weight of a cubic foot of water at 39. i° is approx- 
 imately 62.5 lbs., although authorities differ on this 
 matter, some of them placing it at 62.379 lbs., and 
 others at 62.425 lbs. per cubic foot. As its tempera- 
 ture increases its weight per cubic foot decreases until 
 at 212 F. one cubic foot weighs 59.76 lbs. 
 
 The table which follows is compiled from various 
 sources and gives the weight of a cubic foot of water 
 at different temperatures. 
 
 Table 4 
 
 Temper- 
 
 Weight per 
 
 Temper- 
 
 Weight per 
 
 Temper- 
 
 Weight per 
 
 ature 
 
 Cubic Foot 
 
 ature 
 
 Cubic Foot 
 
 ature 
 
 Cubic Foot 
 
 32° F. 
 
 62.42 lbs. 
 
 1 32° F. 
 
 61.52 lbs. 
 
 230° F. 
 
 59-37 lbs. 
 
 42° 
 
 62.42 
 
 142 
 
 61.34 
 
 240° 
 
 59.IO 
 
 52° 
 
 62.40 
 
 152 
 
 61.14 
 
 '250° 
 
 58.85 
 
 62° 
 
 62.36 
 
 162° 
 
 60.94 
 
 260° 
 
 58.52 
 
 72° 
 
 62.30 
 
 172° 
 
 60.73 
 
 270° 
 
 58.21 
 
 82° 
 
 62.21 
 
 182 
 
 60.50 
 
 300° 
 
 57-26 
 
 92° 
 
 62.II 
 
 IQ2° 
 
 60.27 
 
 330° 
 
 56.24 
 
 102° 
 
 62.OO 
 
 202° 
 
 60.02 
 
 360° 
 
 55.16 
 
 112° 
 
 61.86 
 
 212° 
 
 59-76 
 
 3 90° 
 
 54.03 
 
 122° 
 
 61.70 
 
 220° 
 
 59-64 
 
 420 ° 
 
 52.86 
 
 The boiling point of water varies according to the 
 pressure to which it is subject. In the open air at sea 
 level the boiling point is 212 F. When confined in a 
 boiler under steam pressure the boiling point of water 
 depends upon the pressure and temperature of the 
 steam, as, for instance, at 100 lbs. gauge pressure the 
 temperature of the steam is 338 F., to which temper- 
 
106 ENGINEERING 
 
 ature the water must be raised before its molecules 
 will separate and be converted into steam. In the 
 absence of any pressure, as in a perfect vacuum, water 
 boils at 32 F. temperature. In a vacuum of 28 in., 
 corresponding to an absolute pressure of .943 lbs., 
 water will boil at ioo°, and in a vacuum of 26 in., at 
 which the absolute pressure is 2 lbs., the boiling point 
 of water is 127 F. On the tops of high mountains in 
 a rarefied atmosphere water will boil at a much lower 
 temperature than at sea level, for instance at an 
 altitude of 15,000 ft. above sea level water boils at 
 184° F. 
 
 Steam. Having discussed to some extent the phys- 
 ical properties of water, it is now in order to devote 
 some time to the study of the nature of steam, which 
 is simply water in its gaseous form made so by the 
 application of heat. 
 
 As has been stated in another portion of this book, 
 matter consists of molecules or atoms inconceivably 
 small in size, yet each having an individuality, and in 
 the case of solids or liquids, each having a mutual 
 cohesion or attraction for the other, and all being in a 
 state of continual vibration more or less violent 
 according to the temperature of the body. 
 
 The law of gravitation which holds the universe 
 together, also exerts its wonderful influence on these 
 atoms and causes them to hold together with more or 
 less tenacity according to the nature of the substance. 
 Thus it is much more difficult to chip off pieces of iron 
 or granite than it is of wood. But in the case of water 
 and other liquids the atoms, while they adhere to each 
 other to a certain extent, still they are not so hard to 
 separate, in fact, they are to some extent repulsive to 
 each other, and unless confined within certain bounds 
 
COMBUSTION — WATER — STEAM 107 
 
 the atoms will gradually scatter and spread out, and 
 finally either be evaporated or sink out of sight in the 
 earth's surface. Heat applied to any substance tends 
 to accelerate the vibrations of the molecules, and if 
 enough heat is applied it will reduce the hardest sub- 
 stances to a liquid or gaseous state. 
 
 The process of the generation of steam from water 
 is simply an increase of the natural vibrations of the 
 molecules of the water, caused by the application of 
 heat until they lose all attraction for each other and 
 become instead entirely repulsive, and unless confined 
 will fly off into space. But being confined they con- 
 tinually strike against the sides of the containing 
 vessel, thus causing the pressure which steam or any 
 other gas exerts when under confinement. 
 
 Of course steam, like other gases, when under pres- 
 sure is invisible, but the laws governing its action are 
 well known. These laws, especially those relating to 
 the expansion of steam, will be more fully discussed in 
 the chapters on the Indicator. The temperature of 
 steam in contact with the water from which it is 
 generated, as for instance in the ordinary steam boiler, 
 depends upon the pressure under which it is gener- 
 ated. Thus at atmospheric pressure its temperature 
 is 212° F. If the vessel is closed and the pressure 
 increased the temperature of the steam and also that 
 of the water rises. 
 
 Saturated Steam. When steam is taken directly from 
 the boiler to the engine without being superheated, it 
 is termed saturated steam. This does not necessarily 
 imply that it is wet and mixed with spray and 
 moisture. 
 
 Superheated Steam. When steam is conducted into 
 or through a vessel or coils of pipe separate from the 
 
108 ENGINEERING 
 
 boiler in which it was generated and is there heated to 
 a higher temperature than that due to its pressure, it 
 is said to be superheated. 
 
 Dry Steam. When steam contains no moisture it is 
 said to be dry. Dry steam may be either saturated or 
 superheated. 
 
 Wet Steam. When steam contains mist or spray 
 intermingled it is termed wet steam, although it may 
 have the same temperature as dry saturated steam of 
 the same pressure. 
 
 During the further consideration of steam in this 
 book, saturated steam will be mainly under discussion 
 for the reason that this is the normal condition of 
 steam as used most generally in steam engines. 
 
 Total Heat of Steam. The total heat in steam includes 
 the heat required to raise the temperature of the water 
 from 32 F. to the temperature of the steam plus the 
 heat required to evaporate the water at that tempera- 
 ture. This latter heat becomes latent in the steam, 
 and is therefore called the latent heat of steam. 
 
 The work done by the heat acting within the mass of 
 water and causing the molecules to rise to the surface 
 is termed by scientists internal work, and the work 
 done in compressing the steam already formed in the 
 toiler or in pushing it against the superincumbent 
 atmosphere, if the vessel be open, is termed external 
 work. There are, therefore, in reality three elements 
 to be taken into consideration in estimating the total 
 heat of steam, but as 'the heat expended in doing 
 external work is done within the mass itself it may, for 
 practical purposes, be included in the general term 
 latent heat of steam. 
 
 De?isity of Steam. The expression density of steam 
 means the actual weight in pounds or fractions of a 
 
COMBUSTION WATER STEAM 109 
 
 pound avoirdupois of a given volume of steam, as one 
 cubic foot. This is a very important point for young 
 engineers especially to remember, so as not to get the 
 two terms, pounds pressure and pounds weight, mixed, 
 as some are prone to do. 
 
 Volume of Steam. By this term is meant the volume 
 as expressed by the number of cubic feet in one pound 
 weight of steam. 
 
 Relative Volume of Steam. This expression has refer- 
 ence to the number of volumes of steam produced 
 from one volume of water. Thus the steam produced 
 by the evaporation of one cubic foot of water from 
 39 F. into steam at atmospheric pressure will occupy 
 a space of 1646 cu. ft., but, as the steam is compressed 
 and the pressure allowed to rise, the relative volume of 
 the steam becomes smaller, as for instance at 100 lbs. 
 gauge pressure the steam produced from one cubic 
 foot of water will occupy but 237.6 cu. ft., and if the 
 same steam was compressed to 1,000 lbs. absolute or 
 985.3 lbs. gauge pressure it would then occupy only 
 30 cu. ft. 
 
 The condition of steam as regards its drvness may 
 be approximately estimated by observing its appear- 
 ance as it issues from a pet cock or other small open- 
 ing into the atmosphere. Dry or nearly dry steam 
 containing about 1 per cent, of moisture will be trans- 
 parent close to the orifice through which it issues, and 
 even if it is of a grayish white color it may be esti- 
 mated to contain not over 2 per cent, of moisture. 
 
 Steam in its relation to the engine should be consid- 
 ered in the character of a vehicle for transferring the 
 energy, created by the heat, from the boiler to the 
 engine. For this reason all steam drums, headers and 
 pipes should be thoroughly insulated in order to 
 
110 
 
 ENGINEERING 
 
 prevent, as much as possible, the loss of heat or energy 
 by radiation. 
 
 Table 5, showing the properties of saturated steam, 
 is compiled mainly from Kent's Steam Boiler Eco?wmy. 
 The decimals have not been carried out in the columns 
 headed Relative Volume and Weight of 1 cu. ft. of 
 steam, as their absence will affect the results very 
 little. 
 
 TABLE 5 
 Properties of Saturated Steam 
 
 
 
 
 Total 
 
 Heat 
 
 
 
 S 
 
 
 
 3 
 
 a 
 
 
 above 
 
 32" F. 
 
 _^ 
 
 g 
 
 2 2 
 
 £j 
 
 
 
 
 
 
 Mjc'l 
 
 "p 
 
 £0 
 
 
 «2 
 
 5 w 
 
 a £ 
 
 
 > g 
 
 S 
 
 Q 
 
 £ 1 
 
 C I " L ' 
 
 £ '2 
 
 C/3-pi t 3 
 
 ►4 
 
 (4 
 
 ^3 
 
 
 29.74 
 
 .089 
 
 32. 
 
 O. 
 
 1091.7 
 
 IO9I.7 
 
 208,080 
 
 3333-3 
 
 .0003 
 
 29.67 
 
 
 122 
 
 40. 
 
 8 
 
 
 1094. 1 
 
 IO86. 1 
 
 154,330 
 
 2472.2 
 
 .0004 
 
 29.$6 
 
 
 176 
 
 50. 
 
 18 
 
 
 1097.2 
 
 IO79.2 
 
 107,630 
 
 1 724. 1 
 
 .0006 
 
 29.4O 
 
 
 254 
 
 60. 
 
 28 
 
 01 
 
 I IOO. 2 
 
 IO72.2 
 
 76,370 
 
 1223.4 
 
 .0008 
 
 29.I9 
 
 
 359 
 
 70. 
 
 38 
 
 02 
 
 1 103. 3 
 
 IO65.3 
 
 54,66o 
 
 875.61 
 
 .0011 
 
 28.9O 
 
 
 502 
 
 80. 
 
 48 
 
 04 
 
 1106.3 
 
 I058.3 
 
 39,690 
 
 635.80 
 
 .0016 
 
 28.51 
 
 
 692 
 
 90. 
 
 5S 
 
 06 
 
 1109.4 
 
 I05 I..3 
 
 2Q.290 
 
 469.20 
 
 .0021 
 
 28 OO 
 
 
 943 
 
 100. 
 
 68 
 
 08 
 
 1112.4 
 
 I044.4 
 
 21,830 
 
 349-70 
 
 .0028 
 
 2y.88 
 
 1 
 
 
 102. 1 
 
 70 
 
 09 
 
 1113.1 
 
 IO43.O 
 
 20,623 
 
 334-23 
 
 .0030 
 
 25 85 
 
 2 
 
 
 126.3 
 
 94 
 
 4A 
 
 1120.5 
 
 1026.0 
 
 10,730 
 
 173-23 
 
 .0058 
 
 23.83 
 
 3 
 
 
 141. 6 
 
 109 
 
 9 
 
 1125.1 
 
 IOI5.3 
 
 7,325 
 
 118.00 
 
 .0085 
 
 21.78 
 
 4 
 
 
 I53-I 
 
 121 
 
 4 
 
 1128 6 
 
 IOO7.2 
 
 5,588 
 
 89.S0 
 
 .0111 
 
 19-74 
 
 5 
 
 
 162.3 
 
 130 
 
 7 
 
 1131-4 
 
 IOOO. 7 
 
 4,530 
 
 72.50 
 
 .0137 
 
 17.70 
 
 6 
 
 
 170. 1 
 
 138 
 
 6 
 
 1133.8 
 
 995-2 
 
 3,8i6 
 
 61.10 
 
 .0163 
 
 15.67 
 
 7 
 
 
 176.9 
 
 145 
 
 4 
 
 H35-9 
 
 990- 5 
 
 3,302 
 
 53-oo 
 
 .0189 
 
 13.63 
 
 8 
 
 
 182.9 
 
 151 
 
 5 
 
 1 137- 7 
 
 986.2 
 
 2,912 
 
 46.60 
 
 .0214 
 
 11.60 
 
 9 
 
 
 188.3 
 
 156 
 
 9 
 
 U39-4 
 
 982.4 
 
 2,607 
 
 41.82 
 
 .0239 
 
 9-56 
 
 10 
 
 
 193.2 
 
 161 
 
 9 
 
 1 1 40. 9 
 
 979.0 
 
 2,361 
 
 37-So 
 
 .0264 
 
 7.52 
 
 11 
 
 
 197.8 
 
 166 
 
 5 
 
 1142 3 
 
 975-8 
 
 2,159 
 
 34.61 
 
 .0289 
 
 5-49 
 
 12 
 
 
 202.0 
 
 170 
 
 7 
 
 H43-5 
 
 972.8 
 
 1,990 
 
 31.90 
 
 .0314 
 
 3-45 
 
 13 
 
 
 205.9 
 
 174 
 
 7 
 
 1 144. 7 
 
 970.0 
 
 1,846 
 
 29.60 
 
 .0338 
 
 1. 41 
 
 14 
 
 
 209.6 
 
 178 
 
 4 
 
 1145.9- 
 
 967.4 
 
 1,721 
 
 27-5o 
 
 .0363 
 
 0.00 
 
 M 
 
 7 
 
 212.0 
 
 180 
 
 9 
 
 1 1 46. 6 
 
 965./ 
 
 1,646 
 
 26.36 
 
 .0379 
 
COMBUSTION WATER— STEAM 
 
 111 
 
 Table 5 — Continued 
 
 
 
 
 Total 
 
 Heat 
 
 
 
 2 
 
 c 
 
 31—1 
 
 5 c" 
 
 fc 
 
 Above 
 
 32° F. 
 
 rt co 
 
 1 
 
 2 2 
 
 ■ 
 
 P-I •" 
 
 
 p*S 
 
 m 
 
 S a, 
 
 ffi^"| 
 
 > 
 
 -"C/2 
 
 2 - 
 
 
 3 °* 
 
 Q 
 
 
 
 
 % 
 
 IS? 
 
 3 • 
 
 u 3 
 
 0-1 
 
 -D.-I 
 
 
 a * 
 
 a ffi 
 
 
 ' X 
 
 _] 
 
 -J ° 
 
 0.3 
 
 15 
 
 213-3 
 
 181. 9 
 
 1 146. 9 
 
 965.O 
 
 1,614 
 
 25.90 
 
 .O3S7 
 
 I 
 
 3 
 
 16 
 
 216.3 
 
 185.3 
 
 1147.9 
 
 962.7 
 
 1,519 
 
 24-33 
 
 .O4II 
 
 2 
 
 3 
 
 17 
 
 219.4 
 
 188.4 
 
 1148.9 
 
 960.5 
 
 i,434 
 
 23.OO 
 
 •0435 
 
 3 
 
 3 
 
 18 
 
 222.4 
 
 191.4 
 
 1149-8 
 
 958.3 
 
 i,359 
 
 2I.8o 
 
 .0459 
 
 4 
 
 3 
 
 19 
 
 225.2 
 
 194.3 
 
 1150.6 
 
 956.3 
 
 1,292 
 
 20.70 
 
 .0483 
 
 5 
 
 3 
 
 20 
 
 227.9 
 
 197.0 
 
 II5I.5 
 
 954-4 
 
 1,231 
 
 I9.72 
 
 .0507 
 
 6 
 
 3 
 
 21 
 
 230.5 
 
 199.7 
 
 1152.2 
 
 952.6 
 
 1,176 
 
 18.84 
 
 .0531 
 
 7 
 
 3 
 
 22 
 
 233-0 
 
 202.2 
 
 H53-0 
 
 950.8 
 
 1,126 
 
 18.03 
 
 .0555 
 
 8 
 
 3 
 
 23 
 
 235-4 
 
 204.7 
 
 II53.7 
 
 949-1 
 
 1,080 
 
 I7.30 
 
 .0578 
 
 9 
 
 3 
 
 24 
 
 237.8 
 
 207.0 
 
 II54.5 
 
 947-4 
 
 1,038 
 
 16.62 
 
 .0602 
 
 10 
 
 3 
 
 25 
 
 240.0 
 
 209.3 
 
 II55.I 
 
 945-8 
 
 998 
 
 lo.OO 
 
 .062 5 
 
 11 
 
 3 
 
 26 
 
 242.2 
 
 211. 5 
 
 H55.8 
 
 944- 3 
 
 962 
 
 15.42 
 
 .0649 
 
 12 
 
 3 
 
 27 
 
 244-3 
 
 213-7 
 
 1156.4 
 
 942.8 
 
 929 
 
 14.90 
 
 .0672 
 
 13 
 
 3 
 
 28 
 
 246.3 
 
 215-7 
 
 H57-I 
 
 94L3 
 
 898 
 
 I4.4O 
 
 .0696 
 
 14 
 
 3 
 
 29 
 
 248.3 
 
 217.8 
 
 H57-7 
 
 939-9 
 
 869 
 
 I3-9I 
 
 .O7I9 
 
 15 
 
 3 
 
 30 
 
 250.2 
 
 219.7 
 
 1158.3 
 
 938.9 
 
 841 
 
 I3.50 
 
 .0742 
 
 16 
 
 3 
 
 31 
 
 252.1 
 
 221.6 
 
 1158.8 
 
 937-2 
 
 816 
 
 13.07 
 
 .0765 
 
 17 
 
 3 
 
 32 
 
 254.0 
 
 223.5 
 
 II59-4 
 
 935-9 
 
 .792 
 
 12.68 
 
 .0788 
 
 iS 
 
 3 
 
 33 
 
 255.7 
 
 225.3 
 
 "59.9 
 
 9346 
 
 769 
 
 12.32 
 
 .08l2 
 
 19 
 
 3 
 
 34 
 
 257.5 
 
 227.1 
 
 1 160. 5 
 
 933-4 
 
 748 
 
 12.00 
 
 .O835 
 
 20 
 
 3 
 
 3^ 
 
 259.2 
 
 228.8 
 
 1161.0 
 
 932.2 
 
 72S 
 
 11.66 
 
 .0858 
 
 21 
 
 3 
 
 36 
 
 260.8 
 
 230.5 
 
 1161.5 
 
 931 
 
 709 
 
 11.36 
 
 .0880 
 
 22 
 
 3 
 
 37 
 
 262.5 
 
 232.1 
 
 1162.0 
 
 929. S 
 
 691 
 
 11.07 
 
 .0903 
 
 23 
 
 3 
 
 38 
 
 264.0 
 
 233.8 
 
 1 162. 5 
 
 92S.7 
 
 674 
 
 10.80 
 
 .0926 
 
 24 
 
 3 
 
 39 
 
 265.6 
 
 235.4 
 
 1162.9 
 
 927.6 
 
 658 
 
 10.53 
 
 .0949 
 
 25 
 
 • 3 
 
 40 
 
 267.1 
 
 236.9 
 
 1163.4 
 
 926.5 
 
 642 
 
 10.28 
 
 .0972 
 
 26 
 
 3 
 
 4i 
 
 268.6 
 
 238.5 
 
 1163.9 
 
 925.4 
 
 627 
 
 10.05 
 
 •0995 
 
 27 
 
 3 
 
 42 
 
 270.1 
 
 240.0 
 
 1164-3 
 
 924.4 
 
 613 
 
 9-83 
 
 .IOI8 
 
 28 
 
 3 
 
 43 
 
 27L5 
 
 241-4 
 
 1 164. 7 
 
 923 3 
 
 600 
 
 9.61 
 
 .1040 
 
 29 
 
 3 
 
 44 
 
 272.9 
 
 242.9 
 
 1165.2 
 
 922.3 
 
 587 
 
 9.41 
 
 • IO63 
 
 30 
 
 3 
 
 45 
 
 274.3 
 
 244-3 
 
 1165.6 
 
 921.3 
 
 575 
 
 9.21 
 
 .IO86 
 
 3i 
 
 • 3 
 
 46 
 
 275-7 
 
 245-7 
 
 1 166.0 
 
 920.4 
 
 563 
 
 9.02 
 
 .IIO8 
 
 32 
 
 3 
 
 47 
 
 277.0 
 
 247.0 
 
 1 166. 4 
 
 919.4 
 
 552 
 
 8.84 
 
 . 1 1.3 I 
 
 33 
 
 3 
 
 48 
 
 278.3 
 
 248.4 
 
 1166.8 
 
 918.5 
 
 54i 
 
 8.67 
 
 ■1153 
 
 34 
 
 • 3 
 
 49 
 
 279.6 
 
 249.7 
 
 1167.2 
 
 917.5 
 
 53i 
 
 8.50 
 
 .II76 
 
 35 
 
 ■3 
 
 5o 
 
 280.9 
 
 251.0 
 
 1167.6 
 
 916.6 
 
 520 
 
 8-34 
 
 .II98 
 
 36 
 
 ■3 
 
 5i 
 
 282.1 
 
 252.2 
 
 1168.0 
 
 915.7 
 
 5ii 
 
 8.19 
 
 .1221 
 
 37 
 
 •3 
 
 52 
 
 283.3 
 
 253-5 
 
 1168.4 
 
 914.9 
 
 502 
 
 8.04 
 
 •1243 
 
112 
 
 ENGINEERING 
 
 
 
 
 Table 5 — Continued 
 
 
 
 
 <u 
 
 
 Total Heat 
 
 
 
 a 
 
 
 
 £c 
 
 g d 
 
 
 above 
 
 32° F. 
 
 ^ 
 
 E 
 
 c £ 
 
 
 
 [In m 
 
 
 4) <U 
 
 II 
 
 
 
 
 > 
 
 1° 
 
 , Xj 
 
 vw 
 
 P* £ 
 
 rt •- 
 
 1 5 
 
 1^ 
 
 <u ft 
 
 to . 
 
 s* 
 
 H g 1 
 
 *c? 
 
 "V ? 
 
 fe^ rt 
 
 »3 
 
 ■~B 
 
 M 0) 
 
 03X1 
 
 S-O 
 
 Q 
 
 | | 
 
 5 ° 
 
 3 = 
 
 P4 
 
 h 
 
 0^ 
 
 
 < 
 
 
 c S- 
 
 a **" 
 
 
 
 
 5° 
 
 33-3 
 
 53 
 
 284.5 
 
 254-7 
 
 1168.7 
 
 9I4-0 
 
 492 
 
 1 - 
 7.90 
 
 1266 
 
 39-3 
 
 54 
 
 285.7 
 
 256.0 
 
 1 [65. 1 
 
 9I3.I 
 
 .484 
 
 7-76 
 
 1288 
 
 40.3 
 
 55 
 
 286.9 
 
 257.2 
 
 1169 4 
 
 912.3 
 
 476 
 
 7-63 
 
 1311 
 
 4i-3 
 
 56 
 
 288.1 
 
 258.3 
 
 1 169. 8 
 
 9H-5 
 
 468 
 
 7- 50 
 
 1333 
 
 42.3 
 
 57 
 
 289.I 
 
 259-5 
 
 1 1 70. 1 
 
 910.6 
 
 460 
 
 7.38 
 
 1355 
 
 43 3 
 
 58 
 
 29O.3 
 
 260.7 
 
 1170.5 
 
 909.8 
 
 453 
 
 7.26 
 
 1377 
 
 44-3 
 
 59 
 
 291.4 
 
 261.8 
 
 1 170.8 
 
 909.0 
 
 44<J 
 
 7-14 
 
 1400 
 
 45-3 
 
 60 
 
 292.5 
 
 262.9 
 
 1171.2 
 
 908.2 
 
 439 
 
 7-03 
 
 1422 
 
 46.3 
 
 61 
 
 293.6 
 
 264.0 
 
 II7I.5 
 
 Q07-5 
 
 432 
 
 6.92 
 
 1444 
 
 47-3 
 
 62 
 
 294.7 
 
 265.1 
 
 1171.8 
 
 906.7 
 
 425 
 
 6.82 
 
 1466 
 
 483 
 
 63 
 
 295-7 
 
 266.2 
 
 1172.1 
 
 905-9 
 
 419 
 
 6. 72 
 
 1488 
 
 49-3 
 
 64 
 
 296.8 
 
 267.2 
 
 1172.4 
 
 905.2 
 
 413 
 
 6.62 
 
 1511 
 
 50.3 
 
 65 
 
 297.8 
 
 268.3 
 
 1172.8 
 
 9045 
 
 407 
 
 6-53 
 
 1533 
 
 5i.3 
 
 66 
 
 298.8 
 
 269.3 
 
 H73-I 
 
 903-7 
 
 401 
 
 6 43 
 
 1555 
 
 52.3 
 
 67 
 
 299.8 
 
 270.4 
 
 H73-4 
 
 903.0 
 
 395 
 
 6-34 
 
 1577 
 
 53 3 
 
 68 
 
 300.8 
 
 271 4 
 
 H73-7 
 
 902.3 
 
 390 
 
 6.25 
 
 1599 
 
 54-3 
 
 69 
 
 301.8 
 
 272.4 
 
 1174-0 
 
 901.6 
 
 384 
 
 6.17 
 
 1621 
 
 55-3 
 
 ~o 
 
 302.7 
 
 273-4 
 
 H74-3 
 
 900.9 
 
 379 
 
 6.09 
 
 1643 
 
 56.3 
 
 7i 
 
 3037 
 
 274.4 
 
 H74-6 
 
 900.2 
 
 374 
 
 6.01 
 
 1665 
 
 57-3 
 
 72 
 
 304.6 
 
 275.3 
 
 H74-8 
 
 899-5 
 
 369 
 
 5-93 
 
 1687 
 
 53.3 
 
 73 
 
 305-6 
 
 276.3 
 
 H75-I 
 
 89S.9 
 
 305 
 
 5.85 
 
 1709 
 
 59-3 
 
 74 
 
 306.5 
 
 277.2 
 
 1175.4 
 
 898.2 
 
 360 
 
 5.78 
 
 1731 
 
 60.3 
 
 75 
 
 307-4 
 
 278.2 
 
 H75-7 
 
 897-5 
 
 356 
 
 5.71 
 
 1753 
 
 61.3 
 
 76 
 
 308.3 
 
 279.1 
 
 1176.0 
 
 896.9 
 
 35i 
 
 5.63 
 
 1775 
 
 62.3 
 
 77 
 
 309.2 
 
 280.0 
 
 1176.2 
 
 896.2 
 
 347 
 
 5-57 
 
 1797 
 
 63-3 
 
 78 
 
 310. 1 
 
 280.9 
 
 1176.=; 
 
 895.6 
 
 343 
 
 5.50 
 
 1819 
 
 64.3 
 
 79 
 
 310.9 
 
 281.8 
 
 1176.8 
 
 895.0 
 
 339 
 
 5-43 
 
 1840 
 
 65 3 
 
 80 
 
 311. 8 
 
 2827 
 
 1177.0 
 
 894-3 
 
 334 
 
 5-37 
 
 1862 
 
 66.3 
 
 81 
 
 312.7 
 
 283.6 
 
 II77-3 
 
 893-7 
 
 33i 
 
 5-31 
 
 1884 
 
 67.3 
 
 ' 82 
 
 313-5 
 
 284.5 
 
 11*77.6 
 
 893.1 
 
 327 
 
 5-25 
 
 1906 
 
 68.3 
 
 83 
 
 3144 
 
 285 = 3 
 
 1177.S 
 
 892.5 
 
 323 
 
 5.18 
 
 1928 
 
 69-3 
 
 84 
 
 315-2 
 
 286.2 
 
 1178.1 
 
 891.9 
 
 320 
 
 5-13 
 
 1950 
 
 70 3 
 
 35 
 
 316.0 
 
 287.0 
 
 1178.3 
 
 891.3 
 
 316 
 
 5.07 
 
 1971 
 
 71.3 
 
 86 
 
 316.8 
 
 287.9 
 
 IT 78.6 
 
 890.7 
 
 313 
 
 5.02 
 
 1993 
 
 72.3 
 
 87 
 
 317.7 
 
 288.7 
 
 it 78. 8 
 
 890.1 
 
 309 
 
 4.96 
 
 2015 
 
 73-3 
 
 88 
 
 318.5 
 
 289. 5 
 
 1179.1 
 
 889.5 
 
 306 
 
 4.91 
 
 2036 
 
 74-3 
 
 89 
 
 3190 
 
 2904 
 
 1179.3 
 
 8S8.9 
 
 303 
 
 4.86 
 
 2058 
 
 75-3 
 
 90 
 
 320.0 
 
 291.2 
 
 1179.6 
 
 888.4 
 
 299 
 
 4.81 
 
 2080 
 
COMBUSTION WATER STEAM 
 
 113 
 
 
 
 
 
 Table 5 — Continued 
 
 
 
 
 
 (0 
 
 
 Total 
 
 Heat 
 
 
 
 E 
 
 
 
 3~ 
 
 3 C 
 
 
 above 
 
 32° F. 
 
 ca tn 
 
 E 
 
 .5 " 
 
 . 
 
 (jr. m 
 
 en 6" 
 
 £ 6* 
 
 0h OT 
 
 d« 
 
 « a 
 
 E m 
 
 5^1 
 
 > 
 
 
 
 <u ft 
 
 03 X! 
 
 3 a 
 
 Q 
 
 
 1 = 
 
 -4-> <D 
 
 3 a 
 
 "3 
 
 3 x 
 U 3 
 
 *: 
 
 76.3 
 
 91 
 
 320.8 
 
 292.0 
 
 1179.8 
 
 887.8 
 
 296 
 
 4.76 
 
 .2102 
 
 77 
 
 3 
 
 92 
 
 321.6 
 
 292.8 
 
 1180.0 
 
 887.2 
 
 293 
 
 4 
 
 7i 
 
 • 2123 
 
 78 
 
 3 
 
 93 
 
 322.4 
 
 293.6 
 
 1180.3 
 
 886.7 
 
 290 
 
 4 
 
 66 
 
 ■2145 
 
 79 
 
 3 
 
 94 
 
 323.1 
 
 294.4 
 
 1180.5 
 
 886 1 
 
 287 
 
 4 
 
 62 
 
 .2166 
 
 So 
 
 3 
 
 95 
 
 3239 
 
 295.1 
 
 1180 7 
 
 885.6 
 
 285 
 
 4 
 
 57 
 
 .2188 
 
 81 
 
 3 
 
 96 
 
 324.6 
 
 295-9 
 
 1181.0 
 
 885.0 
 
 282 
 
 4 
 
 53 
 
 .2210 
 
 82 
 
 3 
 
 97 
 
 325.4 
 
 296.7 
 
 1181.2 
 
 884.5 
 
 279 
 
 4 
 
 48 
 
 .2231 
 
 S3 
 
 3 
 
 98 
 
 326.1 
 
 297.4 
 
 1181.4 
 
 884.0 
 
 276 
 
 4 
 
 44 
 
 •2253 
 
 84 
 
 3 
 
 99 
 
 326.8 
 
 298.2 
 
 1181.6 
 
 883.4 
 
 274 
 
 4 
 
 40 
 
 .2274 
 
 85 
 
 3 
 
 100 
 
 3276 
 
 298.9 
 
 1181.8 
 
 882.9 
 
 271 
 
 4 
 
 36 
 
 .2296 
 
 86 
 
 3 
 
 101 
 
 328.3 
 
 299.7 
 
 1182.1 
 
 882.4 
 
 268 
 
 4 
 
 32 
 
 .2317 
 
 87 
 
 3 
 
 102 
 
 329.0 
 
 300.4 
 
 1182.3 
 
 881.9 
 
 266 
 
 4 
 
 28 
 
 .2339 
 
 S3 
 
 :■ 
 
 103 
 
 32Q.7 
 
 301. 1 
 
 1182.5 
 
 881.4 
 
 264 
 
 4 
 
 24 
 
 .2360 
 
 89 
 
 3 
 
 104 
 
 330.4 
 
 301.9 
 
 1182 7 
 
 880.8 
 
 261 
 
 4 
 
 20 
 
 .2382 
 
 90 
 
 3 
 
 105 
 
 331 1 
 
 302.6 
 
 1182.9 
 
 880.3 
 
 259 
 
 4 
 
 16 
 
 .2403 
 
 9i 
 
 3 
 
 106 
 
 331.8 
 
 303.3 
 
 1183.1 
 
 879.8 
 
 257 
 
 4 
 
 12 
 
 ■2425 
 
 92 
 
 3 
 
 107 
 
 332.5 
 
 304.0 
 
 1183.4 
 
 879.3 
 
 254 
 
 4 
 
 09 
 
 .2446 
 
 93 
 
 3 
 
 108 
 
 333-2 
 
 304.7 
 
 1183.6 
 
 878.8 
 
 252 
 
 4 
 
 05 
 
 .2467 
 
 94 
 
 3 
 
 109 
 
 333-9 
 
 305-4 
 
 1183.8 
 
 878.3 
 
 250 
 
 4 
 
 02 
 
 .2489 
 
 95 
 
 3 
 
 no 
 
 334-5 
 
 306.1 
 
 1184.0 
 
 877.9 
 
 248 
 
 3 
 
 98 
 
 .2510 
 
 96 
 
 3 
 
 in 
 
 335-2 
 
 306.8 
 
 1184.2 
 
 877.4 
 
 246 
 
 3 
 
 95 
 
 .2531 
 
 97 
 
 3 
 
 112 
 
 335-9 
 
 307.5 
 
 11S4.4 
 
 876,9 
 
 244 
 
 3 
 
 92 
 
 •2553 
 
 9 S 
 
 3 
 
 113 
 
 336-5 
 
 308.2 
 
 1184.6 
 
 876.4 
 
 242 
 
 3 
 
 88 
 
 • 2574 
 
 99 
 
 3 
 
 114 
 
 337-2 
 
 308.8 
 
 1184.8 
 
 875.9 
 
 240 
 
 3 
 
 85 
 
 .2596 
 
 100 
 
 3 
 
 115 
 
 337.8 
 
 309-. 
 
 1185.0 
 
 875.5 
 
 238 
 
 3 
 
 82 
 
 .2617 
 
 101 
 
 3 
 
 116 
 
 338.5 
 
 310.2 
 
 1185.2 
 
 875.o 
 
 236 
 
 3 
 
 79 
 
 .2638 
 
 102 
 
 3 
 
 117 
 
 339-1 
 
 310.8 
 
 1185.4 
 
 874.5 
 
 234 
 
 3 
 
 76 
 
 .2660 
 
 103 
 
 3 
 
 1 1.8 
 
 339-7 
 
 311.5 
 
 1185.6 
 
 874.1 
 
 232 
 
 3 
 
 73 
 
 .2681 
 
 104 
 
 3 
 
 119 
 
 3404 
 
 312. 1 
 
 1185.8 
 
 873.6 
 
 230 
 
 3 
 
 70 
 
 .2703 
 
 105 
 
 3 
 
 120 
 
 341.0 
 
 312 8 
 
 1185.9 
 
 873.2 
 
 22S 
 
 3 
 
 67 
 
 .2764 
 
 106 
 
 3 
 
 121 
 
 341.6 
 
 3134 
 
 1 186. 1 
 
 872.7 
 
 227 
 
 3 
 
 64 
 
 • 2745 
 
 107 
 
 3 
 
 122 
 
 342.2 
 
 314. i' 
 
 1186.3 
 
 872.3 
 
 225 
 
 3 
 
 62 
 
 .2766 
 
 108 
 
 3 
 
 123 
 
 342.9 
 
 314-7 
 
 1 186. 5 
 
 871.8 
 
 223 
 
 3 
 
 59 
 
 .2788 
 
 109 
 
 3 
 
 124 
 
 343-5 
 
 315.3 
 
 1186.7 
 
 871.4 
 
 221 
 
 3 
 
 56 
 
 .280Q 
 
 no 
 
 3 
 
 125 
 
 344- 1 
 
 316.0 
 
 1 186.9 
 
 870.9 
 
 220 
 
 3 
 
 53 
 
 .2830 
 
 III 
 
 3 
 
 126 
 
 344-7 
 
 316.6 
 
 1187.1 
 
 870.5 
 
 218 
 
 3 
 
 5i 
 
 2851 
 
 112 
 
 3 
 
 127 
 
 345-3 
 
 317.2 
 
 1187.3 
 
 870.0 
 
 216 
 
 3 
 
 48 
 
 .2872 
 
 113 
 
 3 
 
 128 
 
 345-9 
 
 3I7.S 
 
 1187.4 
 
 869.0 
 
 215 
 
 3 
 
 46 
 
 .2894 
 
114 
 
 ENGINEERING 
 
 
 
 
 
 Table $ — Continued 
 
 
 
 
 <u 
 
 
 Total Heat 
 
 
 
 S 
 
 
 
 SH 
 
 3 d 
 
 
 Above 
 
 32° F. 
 
 ^ 
 
 a 
 
 c 2 
 
 £j 
 
 
 
 
 
 
 M 
 
 "0 
 > 
 
 
 
 3h J- 
 
 v tn 
 
 B w 
 
 XI .. 
 
 
 
 
 
 
 
 
 
 U a 
 
 
 ;S ft 
 
 t -1 oj 
 
 *J? 
 
 3LJ 
 
 2 
 
 •S 
 
 "^ 
 
 HJS 
 
 3 tn 
 rt-Q 
 
 8x> 
 
 Q 
 
 1 £ 
 
 J3 X 
 
 X! rt 
 
 a x 
 
 & 
 
 h 
 
 • O 
 
 "4-3 
 
 129 
 
 346.5 
 
 318.4 
 
 1187.6 
 
 869.2 
 
 213 
 
 3-43 
 
 .2915 
 
 115 
 
 3 
 
 130 
 
 347- 1 
 
 319-1 
 
 1187.8 
 
 868.7 
 
 212 
 
 3-4i 
 
 .2936 
 
 116 
 
 3 
 
 131 
 
 347.6 
 
 319-7 
 
 1188.0 
 
 868.3 
 
 210 
 
 3-38 
 
 .2957 
 
 117 
 
 3 
 
 132 
 
 348.2 
 
 320.3 
 
 1188.2 
 
 867.9 
 
 209 
 
 3-36 
 
 .2978 
 
 ti6 
 
 3 
 
 133 
 
 348.8 
 
 320.8 
 
 1188.3 
 
 867.5 
 
 207 
 
 3-33 
 
 .3000 
 
 119 
 
 3 
 
 134 
 
 349-4 
 
 321.5 
 
 1188.5 
 
 867.0 
 
 206 
 
 3.3i 
 
 .3021 
 
 120 
 
 3 
 
 i35 
 
 350.0 
 
 322.1 
 
 1188.7 
 
 866.6 
 
 204 
 
 3-29 
 
 .3042 
 
 121 
 
 3 
 
 136 
 
 350.5 
 
 322.6 
 
 1188.9 
 
 866.2 
 
 203 
 
 3-27 
 
 .3063 
 
 1 22 
 
 3 
 
 137 
 
 35r. 1 
 
 323.2 
 
 1189.0 
 
 865.8 
 
 201 
 
 3-24 
 
 .3084 
 
 123 
 
 3 
 
 138 
 
 351-8 
 
 323.8 
 
 1189.2 
 
 865.4 
 
 200 
 
 3.22 
 
 .3I05 
 
 124 
 
 3 
 
 139 
 
 352.2 
 
 324.4 
 
 1 189.4 
 
 865.0 
 
 199 
 
 3.20 
 
 .3126 
 
 125 
 
 3 
 
 140 
 
 352.8 
 
 325.0 
 
 1189.5 
 
 864.6 
 
 197 
 
 3-i8 
 
 .3147 
 
 126 
 
 3 
 
 141 
 
 353-3 
 
 325-5 
 
 1189.7 
 
 864.2 
 
 196 
 
 3.16 
 
 .3169 
 
 127 
 
 3 
 
 142 
 
 353-9 
 
 326.1 
 
 1189.9 
 
 863.8 
 
 195 
 
 3.14 
 
 .3190 
 
 I 28 
 
 3 
 
 H3 
 
 354-4 
 
 326.7 
 
 1 190.0 
 
 863.4 
 
 193 
 
 3-" 
 
 .3211 
 
 129 
 
 3 
 
 144 
 
 355.o 
 
 327.2 
 
 1190.2 
 
 863.0. 
 
 192 
 
 3-09 
 
 .3232 
 
 130 
 
 3 
 
 i45 
 
 355.5 
 
 327.8 
 
 1 190 4 
 
 862.6 
 
 191 
 
 3-07 
 
 •3253 
 
 131 
 
 3 
 
 146 
 
 356.o 
 
 328.4 
 
 1 1 90. 5 
 
 862.2 
 
 190 
 
 3-05 
 
 .3274 
 
 133 
 
 3 
 
 148 
 
 357-1 
 
 329.5 
 
 1 190.9 
 
 861.4 
 
 187 
 
 3.02 
 
 .3316 
 
 135 
 
 3 
 
 150 
 
 358.2 
 
 330.6 
 
 T191.2 
 
 860.6 
 
 1S5 
 
 2.98 
 
 .3358 
 
 140 
 
 3 
 
 155 
 
 360.7 
 
 333-2 
 
 1192.0 
 
 858.7 
 
 179 
 
 2.89 
 
 .3463 
 
 MS 
 
 3 
 
 160 
 
 363.3 
 
 335-9 
 
 1192.7 
 
 856.9 
 
 174 
 
 2. So 
 
 .3567 
 
 150 
 
 3 
 
 165 
 
 365.7 
 
 338.4 
 
 "93 5 
 
 855.1 
 
 169 
 
 2.72 
 
 •3671 
 
 155 
 
 3 
 
 170 
 
 36S.2 
 
 340.9 
 
 1 194. 2 
 
 853-3 
 
 164 
 
 2.65 
 
 •3775 
 
 160 
 
 3 
 
 175 
 
 370.5 
 
 343-4 
 
 1194.9 
 
 851.6 
 
 160 
 
 2.58. 
 
 .3879 
 
 165 
 
 3 
 
 180 
 
 372.8 
 
 345-8 
 
 "95-7 
 
 849.9 
 
 156 
 
 2.51 
 
 •3983 
 
 170 
 
 3 
 
 185 
 
 375-1 
 
 348.1 
 
 1196,3 
 
 848.2 
 
 152 
 
 2-45 
 
 .4087 
 
 175 
 
 3 
 
 190 
 
 377-3 
 
 35o.4 
 
 1197.0 
 
 846.6 
 
 148 
 
 2-39 
 
 .4191 
 
 1 So 
 
 3 
 
 i95 
 
 379-5 
 
 352.7 
 
 1197.7 
 
 845.0 
 
 144 
 
 2-33 
 
 .4296 
 
 [85 
 
 3 
 
 200 
 
 381.6 
 
 354-9 
 
 1198.3' 
 
 843.4 
 
 141 
 
 2.27 
 
 .4400 
 
 [90 
 
 3 
 
 205 
 
 383-7 
 
 357-1 
 
 1 199.0 
 
 841.9 
 
 138 
 
 2.22 
 
 .4503 
 
 195 
 
 3 
 
 210 
 
 385-7 
 
 359-2 
 
 1199.6 
 
 840.4 
 
 135 
 
 2.17 
 
 .4605 
 
 200 
 
 3 
 
 215 
 
 387 7 
 
 361.3 
 
 1200.2 
 
 838.9 
 
 132 
 
 2.12 
 
 .4707 
 
 2" 5 
 
 3 
 
 220 
 
 389-7 
 
 362.2 
 
 1 200. 8 
 
 838.6 
 
 129 
 
 2.06 
 
 .4852 
 
 245 
 
 3 
 
 260 
 
 404.4 
 
 377-4 
 
 1205.3 
 
 827.9 
 
 no 
 
 1.76 
 
 .5686 
 
 285 
 
 3 
 
 300 
 
 417.4 
 
 390.9 
 
 1209.2 
 
 818.3 
 
 96 
 
 i-53 
 
 .6515 
 
 485 
 
 3 
 
 500 
 
 467.4 
 
 443- 5 
 
 1224.5 
 
 781.0 
 
 59 
 
 •94 
 
 1.062 
 
 685 
 
 3 
 
 700 
 
 504.1 
 
 482.4 
 
 1235.7 
 
 753-3 
 
 42 
 
 .68 
 
 I.470 
 
 9853 
 
 1000 
 
 546.8 
 
 528.3 
 
 1248.7 
 
 720.3 
 
 30 
 
 .48 
 
 2.082 
 
COMBUSTION — WATER — STEAM 115 
 
 Questions 
 
 1. What is combustion? 
 
 2. What is one of the main factors in combustion? 
 
 3. Of what is air composed? 
 
 4. In what proportion are these two gases combined? 
 
 5. What is the principal constituent of coal and 
 other fuels? 
 
 6. What other valuable constituent is contained in 
 bituminous coal? 
 
 7. What is the usual temperature of a boiler furnace 
 when in active operation? 
 
 8. About what should be the temperature of the 
 escaping gases? 
 
 9. W T hat two factors are indispensable in the eco- 
 nomical use of coal? 
 
 10. What is heat? 
 
 11. What is the heat unit? 
 
 12. What is the mechanical equivalent of heat? 
 
 13. How many heat units are there in one pound of 
 carbon? 
 
 14. How many heat units are there in one pound of 
 hydrogen gas? 
 
 15. What is specific heat? 
 
 16. What is sensible heat? 
 
 17. What is latent heat? 
 
 18. Is the latent heat imparted to a body lost? 
 
 19. What is meant by the total heat of evaporation? 
 
 20. How much heat expressed in heat units is 
 required to evaporate one pound of water from a tem- 
 perature of 32 into steam at atmospheric pressure? 
 
 21. Name the two elements composing pure water. 
 
 22. In what proportion are these two gases combined 
 in the formation of water? 
 
116 ENGINEERING 
 
 23. Is perfectly pure water desirable for use in steam 
 boilers? 
 
 24. What causes scale to form in boilers? 
 
 25. What proportion of mineral matter is usually 
 found in water? 
 
 26. What is steam? 
 
 27. Of what does matter consist? 
 
 28. How does the application of heat to any sub- 
 stance affect its molecules? 
 
 29. In what particular manner does heat affect the 
 molecules of water? 
 
 30. Is steam under pressure visible? 
 
 31. What is saturated steam? 
 
 32. What is dry steam? 
 
 33. What is superheated steam? 
 
 34. What is meant by the term total heat in steam? 
 
 35. What is meant by the density of steam? 
 
 36. What is meant by the volume of steam? 
 
 37. What is the weight of a cubic foot of water at 
 39. 1 ° temperature? 
 
 38. What is the weight of a cubic foot of water at a 
 temperature of 212 ? 
 
 39. What is the boiling point of water in the open 
 air at sea level? 
 
 40. At what temperature will water boil in a perfect 
 vacuum? 
 
 41. What is meant by the relative volume of steam? 
 
CHAPTER V 
 
 EVAPORATION TESTS 
 
 Evaporation tests, object of — Preparing for a test — Suggestions as 
 to apparatus needed — Taking the temperature of the feed 
 water — Precautions necessary to obtain accurate results — 
 Duration of test — Feeding a boiler during a test — How to pro- 
 ceed if the boiler is fed by an injector — Determining the per- 
 centage of moisture in the steam — Moisture in the coal — 
 Chimney draft — Draft gauge — Rules for determining the 
 results of a test — "Equivalent evaporation," how to com- 
 pute — Factors of evaporation — Boiler horse power. 
 
 Evaporation Tests. The object of making evapora- 
 tion tests of steam boilers is primarily to ascertain how 
 many pounds of water the boilers are evaporating per 
 pound of coal burned; but these tests can and should 
 be made to determine several other important points 
 with reference to the operation of the boilers, as for 
 instance: I. The efficiency of the boiler and furnace 
 as an apparatus for the consumption of fuel and the 
 evaporation of water; whether this apparatus is per- 
 forming its guaranteed duty in this respect, and how it 
 compares with a known standard. 2. To determine 
 the relative economy of different varieties of coal, also 
 to determine the relative value of fuels other than 
 coal, such as oil, gas, etc. 3. To ascertain whether or 
 not the boilers as they are operated under ordinary 
 every day conditions are being run as economically as 
 they should be. 4. In case the boilers, owing to an 
 increased demand for steam, fail to supply a sufficient 
 quantity without forcing the fires, whether or not addi- 
 tional boilers are needed, or whether the trouble could 
 117 
 
118 ENGINEERING 
 
 be overcome by a change of conditions in operating 
 them. 
 
 As was stated in the chapter oh boiler setting, every 
 steam plant can and should be equipped with the 
 necessary apparatus for making evaporation tests, and 
 every engineer should take pride in making a good 
 showing in the economical use of coal, and, be it said 
 to their credit, the majority of engineers do this, 
 although many of them are working under conditions 
 that prevent them from doing all that they might 
 desire along this line. Too many engineers are com- 
 pelled to look after work entirely outside of and 
 foreign to their vocation as engineers, often having to 
 go to some distant part of the building to make repairs 
 to some part of the machinery, leaving their boiler and 
 engine to care for themselves for the time being, thus 
 not only endangering the safety of property, but of 
 life as well. But conditions are gradually changing 
 for the better in this respect, and employers and own- 
 ers of steam plants are coming more and more to rec- 
 ognize the fact that the engineer is something more 
 than a mere handy man about a factory, in fact, that 
 he has a distinct and responsible vocation to be ful- 
 filled, viz., the safe and economical operation of the 
 plant where the power comes from. 
 
 The author proposes to present in as brief a manner 
 as possible a few simple suggestions and rules for the 
 benefit of engineers who desire to make evaporation 
 tests with a view of determining one or more of the 
 points mentioned at the beginning of this chapter. 
 
 Tests for the last three purposes named can be made 
 by the regular engineering force of the plant, but in 
 case a controversy should arise between the maker of 
 the boiler and the purchaser regarding the first men- 
 
EVAPORATION TESTS 119 
 
 tioned point, viz., the guaranteed efficiency of the 
 boiler or the furnace, the services of experts in boiler 
 testing may be resorted to. 
 
 Preparing for a Test. All testing apparatus should be 
 kept in such shape that it will not take three or four 
 days to get it ready for making a test. On the con- 
 trary, it can be and should be always kept in condition 
 ready for use, so that the preparations for making a 
 test will occupy but a short time. A small platform 
 scale sufficiently large for weighing a wheel-barrow 
 load of coal should also be provided in addition to the 
 apparatus referred to in Chapter II. 
 
 The capacity of each of the two tanks therein men- 
 tioned, and which are illustrated in Fig. 10, can be 
 determined in two ways, either by measuring the 
 cubical contents of each or by placing them one at a 
 time on the scales, filling them with water to within a 
 few inches of the top, and note the weight. Also make 
 a permanent mark on the inside at the water level. 
 The water should then be permitted to run out until 
 within an inch or so of the outlet pipe near the bottom, 
 where another plain mark should be made, after which 
 the empty tank should be again weighed, then by sub- 
 tracting the last weight from the first the exact number 
 of pounds of water that the tank will contain between 
 the top and bottom marks can be determined and a 
 note made of it. 
 
 It is much more convenient to have each tank con- 
 tain the same quantity of water, although not abso- 
 lutely necessary. The tanks should also be numbered 
 I and 2 respectively in order to prevent confusion in 
 keeping a record of the number of tanks full of water 
 used during the test. Care should be exercised to 
 have the water with which the tanks are filled while on 
 
120 ENGINEERING 
 
 the scale, at or near the same temperature as that at 
 which it is to be fed into the boiler during the test. 
 Otherwise there is liability of error owing to the varia- 
 tion in the weight of water at different temperatures. 
 In order to guard against this, the capacity in cubic 
 feet of each tank between the top and bottom marks 
 should be ascertained by measuring the distance 
 between the marks, also the diameter, or, if the tanks 
 be square, the length of one side, after which the 
 cubical contents can be easily figured and noted down. 
 By knowing the capacity in cubic feet of each tank all 
 possibility of error in the weight of feed water will be 
 eliminated. 
 
 The scales for weighing the coal can be fitted with a 
 temporary wooden platform large enough to accom- 
 modate a wheel-barrow, and after it has been balanced 
 with the empty barrow on it, the record of weight of 
 coal burned during the test can be easily kept. 
 
 The same barrow should be used throughout the 
 test, and to save complications in estimating the 
 weight, the same number of pounds of coal should be 
 filled in the barrow each load. The coal passer will 
 learn in a short time to fill the barrow to within a few 
 pounds of the same weight each load by counting the 
 shovelsful and the difference can easily be adjusted by 
 having a small box of coal near the scale from which 
 to take a few lumps to balance the load, or if there is 
 too much coal in the barrow some of it can be thrown 
 into the box. 
 
 At least two separate tally sheets should be provided, 
 marked respectively coal and water, and the one for 
 coal placed near the scale, and care should be taken 
 that each load is tallied as soon as it is weighed. The 
 tally sheet for water should be near the measuring 
 
EVAPORATION TESTS 121 
 
 tanks and as soon as a tank is emptied it should be 
 tallied. The temperature of the feed water should be 
 taken at least every thirty minutes, or oftener if pos- 
 sible, from a thermometer placed in the feed pipe near 
 the check valve, as described in Chapter II. The 
 readings should be noted and, at the expiration of the 
 test, the average taken. 
 
 If the object of the test is to ascertain the efficiency 
 of the boiler and furnace it is absolutely necessary that 
 the boiler and all its appurtenances be put in good 
 condition, by cleaning the heating surface both inside 
 the boiler and outside, scraping and blowing the soot 
 out of the tubes if it be a return tubular boiler, and 
 blowing the soot and ashes from between the tubes if 
 it is a water tube boiler. All dust, soot and ashes 
 should be removed from the outside of the shell and 
 also from the combustion chamber and smoke connec- 
 tions. The grate bars and sides of the furnace should 
 be cleared of all clinker, and all air leaks made as 
 close as possible. The boiler and all its water connec- 
 tions should be free from leaks, especially the blow-off 
 valve or cock. If any doubt exists as to the latter it 
 should be plugged or a blind flange put on it. It is 
 very essential that there should be no way for the 
 water to leak out of the boiler, neither should any 
 water be allowed to get into the boiler during the test 
 except that which is measured by passing through the 
 tanks. 
 
 The engineer making the test should know the num- 
 ber of square feet of grate surface and also the 
 area of the heating surface in square feet. Rules 
 for computing the latter are given in Chapter II. 
 If the boiler is a water tube boiler the outside diameter 
 of the tubes must be used in estimating the heating 
 
122 ENGINEERING 
 
 surface. A correct knowledge of the above points is 
 essential in making a test for determining any one of 
 the four objects mentioned at the commencement of 
 this chapter, but especially is it needed in conducting 
 a test of the efficiency of the boiler and furnace. 
 
 In making an efficiency test it is essential that the 
 boiler should be run at its fullest capacity from the 
 beginning to the end of the test. Therefore arrange- 
 ments should be made to dispose of the steam as fast 
 as it is generated. If the boiler is in a battery con- 
 nected with a common header, its mates can be fired 
 lighter during the test, but if there is but. the one 
 boiler in use a waste steam pipe should be temporarily 
 connected through which the surplus steam, if there is 
 any, can be discharged into the open air through a 
 valve regulated as required. Before starting the test 
 the boiler should be thoroughly heated by having 
 been run several hours at the ordinary rate. The fire 
 should then be cleaned and put in good condition to 
 receive fresh coal. 
 
 At the time of beginning the test the water level 
 should be at or near the height, ordinarily carried and 
 its position marked by tying a cord around one of the 
 guard rods of the gauge glass, and, to prevent all pos- 
 sibility of error, the height of the water in the glass 
 should be measured and a note made of it. Note also 
 the time that the first lot of weighed coal is fed to 
 the furnace and record it as the starting time. The 
 steam pressure should be noted at the beginning of 
 the test and at regular intervals during the progress of 
 the test in order that the average pressure may be 
 obtained. 
 
 At the close of the test all of the above conditions 
 should be as nearly as possible the same as at the 
 
EVAPORATION TESTS 123 
 
 beginning; the quantity and condition of the fire 
 should be the same, also the steam pressure and water 
 level. This can be accomplished only by careful work 
 towards the close of the test. 
 
 During the progress of the test care should be exer- 
 cised to prevent any waste of coal, especially in clean- 
 ing the fire. The ash made during the test must not 
 be wet down until after it is weighed, as in all calcula- 
 tions for combustible and non-combustible matter in 
 the coal the ash should be dry. 
 
 The duration of the test should be at least ten hours 
 if it is possible to continue it for that length of time. 
 The feed pump should be kept running at such speed 
 as will supply the water to the boiler as fast as it is 
 evaporated, and no faster. If at the close of the test 
 a portion of water is left in the last tank tallied it can 
 be measured and deducted from the total. And if any 
 weighed coal is left on the floor it should be weighed 
 back and deducted from the total weight. If the 
 boiler is fed by an injector instead of a pump during 
 the test, the injector should receive steam directly 
 from the boiler under test through a well protected 
 pipe. Also, the temperature of the feed water should 
 be taken from the measuring tanks, or at least from 
 the suction side of the injector, for the reason that the 
 water in passing through the injector receives a large 
 quantity of heat imparted to it by live steam directly 
 from the boiler. Therefore the temperature of the 
 water after it leaves the injector would not be a true 
 factor for figuring the evaporation. 
 
 Determination of the Perce?itage of Moisture in the 
 Steam. This is an important point in estimating the 
 results of an evaporation test for the reason that each 
 pound weight of moisture in the steam as it leaves the 
 
124 ENGINEERING 
 
 boiler represents a pound of water that has not been 
 evaporated into steam, and should therefore be 
 deducted from the total weight of water fed into the 
 boiler during the test. 
 
 The steam should be tested for moisture by taking 
 samples of it from the steam pipe or header as near 
 the boiler as possible in order to guard against addi- 
 tional moisture caused by condensation. For making 
 expert boiler tests for scientific and other purposes, an 
 instrument called a calorimeter is used for ascertaining 
 the quantity of moisture in the steam. But most 
 engineers are not so fortunate as to possess one of 
 these instruments, nor even to induce their employers 
 to purchase one, therefore space will not be taken up 
 in describing it here. A method of testing the 
 quality of the steam by noting the appearance of a 
 small jet blowing into the atmosphere is mentioned 
 near the close of Chapter IV, which in the absence of 
 a calorimeter would answer very well for ordinary 
 purposes. 
 
 Moisture in the Coal. This can generally be obtained 
 from the reports of the geologist of the state in which 
 the coal is mined or from the dealer, although the 
 former is the most reliable. The percentage of mois- 
 ture must be deducted from the total weight of coal in 
 figuring the weight of combustible. 
 
 Measuring the Chimney Draft. A good draft is indis- 
 pensable for obtaining economical results in an evap- 
 oration test. The draft can be easily regulated by a 
 damper to suit the conditions. Chimney draft is ordi- 
 narily measured by a draft gauge connected with the 
 smoke flue near the chimne}'. The usual form of draft 
 gauge is a glass tube bent in the shape of the letter U. 
 (See Fig. 12.) One leg is connected to the flue by 3 
 
EVAPORATION TESTS 
 
 125 
 
 small rubber hose, while the other is open to the 
 atmosphere. The tube is partly filled with water, 
 which will, when there is no draft, stand at the same 
 height in both legs. When connected to the chimney 
 or flue the suction will cause the 
 water in the leg to which the 
 hose is attached to rise, while 
 the level of the water in the 
 other leg will be equally de- 
 pressed, and the extent of the 
 variation in fractions of an inch 
 is the measure of the draft. Thus 
 the draft is referred to as being 
 .5, .7 or .75 inches. The draft 
 should not be less than .5 inches 
 in any case to insure good results. 
 
 Having thus successfully con- 
 ducted the test to its close, and 
 being armed with all the data 
 heretofore noted, the engineer 
 is now ready to compute the 
 results. 
 
 If the test is made for the pur- 
 pose of determining the effi- 
 ciency of the boiler and setting 
 as a whole, including grate, 
 chimne}^ draft, etc., then the 
 result must be based upon the 
 number of pounds of water evap- 
 orated per pound of coal. This latter phrase includes 
 not only the purely combustible matter in the coal, 
 but the non-combustible also, as ash, moisture, etc. 
 Some varieties of western coal contain as high as 12 to 
 14 per cent, of moisture, and the ability of the furnace 
 
 FIGURE 12. 
 
126 ENGINEERING 
 
 to extract heat from the mass is to be tested, as well 
 as the ability of the boiler to absorb and transmit that 
 heat to the water. Therefore the efficiency of the 
 boiler and furnace = 
 
 Heat absorbed per pound of coal. 
 Heating value of one pound of coal. 
 
 If the test is to determine the efficiency of the boiler 
 itself as an absorber of heat, then the combustible 
 alone must be considered in working out the final 
 result. Thus, 
 
 Efficiency of boiler = 
 
 Heat absorbed per pound of combustible. 
 Heating value of one pound of combustible. 
 
 When making a series of tests for the purpose of 
 comparing the economical value of different varieties 
 of coal the conditions should be as nearl}^ uniform as 
 possible; that is, let the tests be made under ordinary 
 working conditions and with the same boiler or boil- 
 ers, and if possible with the same fireman. 
 
 The following is a record of one of many evapora- 
 tion tests made by the author, and is introduced here 
 for the purpose of illustrating methods of computing 
 the results to be obtained from the various data. The 
 rather large quantity of coal burned per square foot of 
 grate surface per hour (25 lbs.) is owing to the fact 
 that the boiler was run to its full capacity, the coal 
 burning clean and forming no clinker. The chimney 
 draft also was exceptionally good, giving a large unit 
 of evaporation per square foot of heating surface per 
 hour. The low temperature of the escaping gases is 
 due to the fact that they were returned over the top of 
 the boiler before passing to the chimney. 
 
EVAPORATION TESTS 127 
 
 Date of test 
 
 Duration of test, 12 hours. 
 Boiler, return tubular, 72 in. diameter, 18 ft. long, 62-41^ in. tubes. 
 Kind of coal, Pocahontas; average steam pressure.. 85 lbs. 
 
 Weight of coal consumed 11 , 100 
 
 Weight of water apparently evaporated 107,187 
 
 Weight of dry ash returned 8.1 per cent.= goo 
 
 Moisture in the coal 2.0 " = 222 
 
 Moisture in the steam 1.0 " = 1,071 
 
 Dry coal corrected for moisture . . 10,878 
 
 Weight of combustible 9,978 
 
 Water corrected for moisture in the steam 106,116 
 
 Water evaporated into dry steam, from and at 212 . . 117,788 
 Water evaporated per lb. of coal, actual conditions. . 9.65 
 
 Water evaporated per lb. of coal, from and at 212 . . 10.61 
 
 Water evaporated per lb. of combustible, from and 
 
 at 212 11. 81 
 
 Water evaporated per lb. of dry coal, from and at 212° 10.82 
 
 Water evaporated per hr. per sq. ft. of heating surface 6. 22 
 
 Coal burned per sq. ft. of grate surface per hour .... 25 
 
 Horse power developed by boiler during test 284.5 
 
 Temperature of feed water, average 141 ° 
 
 Temperature of chimney gases, average 400 
 
 Square feet of grate surface 36 
 
 Square feet of heating surface 1576 
 
 Ratio of grate surface to heating surface 43.7 
 
 The results obtained will be taken up in their regu- 
 lar order beginning with, first, water evaporated into 
 dry steam from and at 212 . As it may be of benefit 
 to some, a short definition of the meaning of the above 
 expression is here given. 
 
 The term "equivalent evaporation," or the evapora- 
 tion from and at 212 , assumes that the feed water 
 enters the boiler at a temperature of 212 and is evap- 
 orated into steam at 212 temperature and at atmos- 
 pheric pressure. As for instance, if the top man hole 
 plate were left out or some other large opening in the 
 steam space allowed the steam to escape into the 
 atmosphere as fast as it was generated. Owing to 
 the variation in the temperatures of the feed water 
 used in different tests, and also the variation in the 
 steam pressure, it is absolutely necessary that the 
 
128 ENGINEERING 
 
 results of all tests be brought by computation to 
 the common basis of 212 in order to obtain a just 
 comparison. 
 
 The process by which this is done is as follows: 
 Referring to the record of th£ test it is seen that the 
 steam pressure average was 85 lbs. gauge pressure, or 
 100 lbs. absolute, and that the temperature of the feed 
 water was 141 °. Referring again to Table No. 5, phys- 
 ical properties of steam, it will be seen that in a pound 
 of steam at 100 lbs. absolute pressure there are 1,181.8 
 heat units, and in a pound of water at 141 ° temperature 
 there are 109.9 heat units. It therefore tooku8i.8- 
 109.9 = I07I-9 heat units to convert one pound of feed 
 water at 141 ° into steam at 85 lbs. pressure. To con- 
 vert a pound of water at 212 into steam at 
 atmospheric pressure, and 212 temperature requires 
 965.7 heat units, and the 1,071.9 heat units w T ould evap- 
 orate 1,071.9 + 965.7 = 1. 11 lbs. water from and at 212 . 
 The 1. 1 1 is the factor of evaporation for 85 lbs. gauge 
 pressure and 141 ° temperature of feed water, and by 
 multiplying "water corrected for moisture in the 
 steam" (see record of test), 106,116 lbs., by 1.11, the 
 weight of water which could have been evaporated into 
 steam from and at 212 , is obtained, which is 117,788 
 lbs. The factor of evaporation is based upon the 
 steam pressure and the temperature of the feed water 
 in any test and the formula for ascertaining it is as 
 
 follows: Factor = —? , in which H = total heat in 
 
 965.7 
 
 the steam, and h = total heat in the feed water. It 
 is used in shortening the process of finding the evap- 
 oration from and at 212 , and Table No. 6 gives the 
 factor of evaporation for various pressures and tem- 
 peratures. 
 
EVAPORATION TESTS 
 
 129 
 
 Table 6 
 Factors of Evaporation 
 
 u V 
 
 X 
 
 X 
 
 X! 
 
 X 
 
 i 
 
 X 
 
 X 
 
 XI 
 
 X 
 
 ►? rt 
 
 3 iri 
 
 %S 
 
 S R 
 
 
 | a 
 
 bt>~° 
 
 bo's 
 
 So 8 
 
 80 S- 
 
 
 
 ^ r/i 
 
 
 
 as tfl 
 
 03 . 
 
 
 
 rt . 
 
 1 B 
 
 ^ g 
 
 <S 8 
 
 ^ £ 
 
 ^ s 
 
 g 
 
 O g 
 
 O gj 
 
 £ 
 
 O % 
 
 
 
 
 
 
 
 
 
 
 
 fen 
 
 D-, 
 
 Ph 
 
 P4 
 
 Ph 
 
 £ 
 
 £ 
 
 £ 
 
 £ 
 
 £ 
 
 212° 
 
 I.027 
 
 1.030 
 
 1.032 
 
 I-035 
 
 1.037 
 
 I.O39 
 
 1. 041 
 
 1.043 
 
 1.047 
 
 200° 
 
 I.O39 
 
 1.042 
 
 I.045 
 
 I.O47 
 
 1.050 
 
 I.052 
 
 1.054 
 
 1.056 
 
 1.059 
 
 I 9 I° 
 
 I.O49 
 
 1.052 
 
 I.054 
 
 I.057 
 
 1.059 
 
 I. 06l 
 
 1.063 
 
 1.065 
 
 1.069 
 
 182° 
 
 I.O58 
 
 1. 061 
 
 I.O64 
 
 I.066 
 
 1.069 
 
 I. 07I 
 
 r.073 
 
 1.075 
 
 1.078 
 
 173° 
 
 I.067 
 
 1.070 
 
 1.073 
 
 I.O76 
 
 1.078 
 
 I.OSO 
 
 1.082 
 
 1.0S4 
 
 1.087 
 
 164 
 
 I.077 
 
 1.080 
 
 I.O83 
 
 1.085 
 
 1.087 
 
 I.O9O 
 
 1. 091 
 
 1.093 
 
 1.097 
 
 152 
 
 I.089 
 
 1.092 
 
 1-095 
 
 I.09S 
 
 1. 100 
 
 1,102 
 
 1. 104 
 
 1. 106 
 
 1. 109 
 
 H3° 
 
 I.O99 
 
 1. 102 
 
 1. 105 
 
 I. I07 
 
 1. 109 
 
 I. Ill 
 
 1. 113 
 
 1.115 
 
 1. ng 
 
 134° 
 
 I. IO8 
 
 1. in 
 
 1. 114 
 
 I. Il6 
 
 1. 119 
 
 1. 121 
 
 1. 123 
 
 1. 125 
 
 1. 128 
 
 125° 
 
 I.II8 
 
 1. 121 
 
 1. 123 
 
 I. 126 
 
 I. 128 
 
 1. 130 
 
 1. 132 
 
 1134 
 
 1. 137 
 
 113° 
 
 I. I30 
 
 i.133 
 
 1. 136 
 
 I. I38 
 
 1. 140 
 
 I- 143 
 
 1. 145 
 
 1. 146 
 
 1. 150 
 
 104° 
 
 1. 138 
 
 1. 142 
 
 1. 145 
 
 I. I48 
 
 1. 150 
 
 1. 152 
 
 1154 
 
 1. 156 
 
 1. 159 
 
 95° 
 
 1. 149 
 
 1. 152 
 
 i- 154 
 
 T.I57 
 
 I- 159 
 
 I.l6l 
 
 1. 163 
 
 1. 165 
 
 1. 169 
 
 86° 
 
 I.I58 
 
 1. 161 
 
 1. 164 
 
 I. 166 
 
 1. 169 
 
 I.I7I 
 
 1. 173 
 
 1. 174 
 
 1. 178 
 
 77° 
 
 1. 167 
 
 1. 170 
 
 I.I73 
 
 1.176 
 
 1. 178 
 
 I. ISO 
 
 1. 182 
 
 1. 1 84 
 
 1. 187 
 
 65° 
 
 1. 180 
 
 1. 183 
 
 1. 186 
 
 I. 188 
 
 I. T90 
 
 I. I92 
 
 1. 194 
 
 1. 196 
 
 1.200 
 
 56° 
 
 1. 189 
 
 1. 192 
 
 1. 195 
 
 I. 197 
 
 1.200 
 
 I.202 
 
 1.204 
 
 1.206 
 
 1.209 
 
 47° 
 
 1. 199 
 
 1. 201 
 
 1.204 
 
 I.207 
 
 1.209 
 
 I. 211 
 
 1. 213 
 
 1. 215 
 
 .1.218 
 
 38° 
 
 1.208 
 
 1. 211 
 
 1. 214 
 
 I. 2l6 
 
 1. 218 
 
 I.220 
 
 1.222 
 
 1.224 
 
 1.228 
 
 Second, water evaporated per pound of coal actual 
 conditions = water apparently evaporated divided by 
 coal consumed = 9.65 lbs. No accurate estimate 
 regarding the quality of the coal or the efficiency of 
 the boiler can be made from this figure (9.65 lbs.). It 
 can be used, however, in estimating the cost of fuel for 
 generating the steam; as, for instance, if the boiler is 
 supplying steam to an engine that uses 30 lbs. of steam 
 per horse power per hour, it will require 30 -s- 9.65 = 3.1 
 lbs. of coal per horse power per hour; the "actual 
 conditions" under which the boiler is being operated 
 being the pressure of steam required by the engine 
 and the temperature of the feed water. 
 
1 30 ENGINEERING 
 
 Third, water evaporated per pound of coal from and 
 at 212° = water evaporated into dry steam from and at 
 212° divided by coal consumed = 10.61 lbs. This fig- 
 ure is the proper one to use in comparing the relative 
 economic values of different varieties of coal tested 
 with the same boiler or boilers. 
 
 Fourth, water evaporated per pound of combustible 
 from and at . 212 = water evaporated into dry steam 
 from and at 212 divided by weight of combustible 
 = 1 1. 81 lbs. This result is the one to be used for 
 ascertaining the efficiency of the boiler, and the per- 
 centage of efficiency is found by. dividing the heat 
 absorbed by the boiler per pound of combustible by 
 the heat value of one pound of combustible. The 
 average heat value of bituminous and semi-bituminous 
 coals is not far from 15,000 heat units per pound of 
 combustible. In the evaporation of 11. 81 pounds of 
 water from and at 212° the heat absorbed was 11. 81 x 
 965.7= 11,404.9 heat units. The efficiency of the boiler 
 
 ,, r 11,404.9X100 „*■ . 
 
 therefore was 1500J — = 76 per cent. 
 
 In like manner to ascertain the efficiency of the 
 boiler and furnace as a whole, the water evaporated 
 from and at 212 per pound of coal is taken. Thus, 
 10.61 x 965.7 = 10,246 heat units absorbed from each 
 pound of coal. Now assuming that there were 13,500 
 heat units in each pound of the coal used in the test, 
 the per cent of efficiency of boiler and furnace was 
 
 10,246X100 
 
 13,500 ~ 75- 9- 
 
 Fifth, water evaporated per pound of dry coal from 
 and at 212 = water evaporated into dry steam from 
 and at 212 divided by coal corrected for moisture. 
 
 Thus, 117,788 -5- 10,878 = 10.82 lbs. This result is useful 
 for calculating the results of tests of the same grade 
 
EVAPORATION TESTS 131 
 
 of coal, but differing in the degree of moisture in 
 each. 
 
 Sixth. Boiler horse power. The latest decision of 
 the American Society of Mechanical Engineers (than 
 whom there is no better authority) regarding the horse 
 power of a boiler is as follows: "The unit of commer- 
 cial horse power developed by a boiler shall be taken 
 as 34^ units of evaporation per hour. That is, 34^ 
 lbs. of water evaporated per hour from a feed temper- 
 ature of 212 into steam of the same temperature. 
 This standard is equivalent to 33,317 B. T. U. per hour. 
 It is also practically equivalent to an evaporation of 
 30 lbs. of water from a feed water temperature of ioo° 
 F. into steam of 70 lbs. gauge pressure." 
 
 According to this rule the horse power developed 
 by the boiler during the test under consideration = water 
 evaporated into dry steam from and at 212 , 117,788 
 lbs ■*■ 12 hrs. •*■ 34. 5 = 284.5 horse power. 
 
 Questions 
 
 1. What is the primary object of an evaporation 
 test? 
 
 2. Name four other important points which can be 
 determined by evaporation tests. 
 
 3. In making a test of the efficiency of the boiler 
 and furnace, what precautions should be observed? 
 
 4. How is the heating surface of water tube boilers 
 estimated? 
 
 5. What length of time should a test be conducted? 
 
 6. In case the boiler is fed by an injector, what pre- 
 cautions are necessary? 
 
 7. If the steam contains any moisture, what should 
 be done? 
 
 8. How is the weight of combustible determined? 
 
132 ENGINEERING 
 
 g. What is a calorimeter, and for what purpose is it 
 used? 
 
 io. By what other method may the moisture in the 
 steam be estimated approximately? 
 
 11. What should be done with the percentage of 
 moisture in the coal? 
 
 12. How is the chimney draft measured? 
 
 13. Describe a draft gauge. 
 
 14. Give the formula for ascertaining the efficiency 
 of the boiler and setting. 
 
 15. If the test is to determine the efficiency of the 
 ooiler alone, what factors are used? 
 
 16. If a series of tests is made for comparing differ- 
 ent varieties of coal, what should be done? 
 
 17. What is meant by equivalent evaporation? 
 
 18. Why should the results of all tests be computed 
 from and at 212 ? 
 
 ig. What is a factor of evaporation? 
 
 20. How is it determined? 
 
 21. What is a boiler horse power? 
 
 22. How many heat units per hour is this equiv- 
 alent to? 
 
CHAPTER VI 
 
 VALVES AND VALVE SETTING 
 
 Valves and valve setting — Importance of correct adjustment — The 
 D slide valve — Single valve engines— Four valve engines — 
 Various positions of the slide valve during one revolution — 
 Relative positions of the crank pin and eccentric during the 
 stroke — Valve diagrams — Placing the engine on the center — 
 Adjusting the length of eccentric rod — Measuring the inside 
 and outside lap — Setting the valve — Fixed cut off engines — 
 Variable automatic cut off —Factors affecting the distribution 
 of the steam — Why the four valve engine is the most eco- 
 nomical — Description of corliss valves and valve gear and 
 directions for adjusting the same. 
 
 Valves and Valve Setting. It goes without saying that 
 every man who aspires to be an engineer should en- 
 deavor to thoroughly acquaint himself with the princi- 
 ples governing the action of valves as well as the details 
 of valve setting. But it must be remembered that this 
 knowledge can not be acquired in a day or a week, or 
 even months. True, a man maybe able to learn some 
 of the alphabet of valve lore in a comparatively short 
 time, but the more practical experience he has in the 
 work the more will he realize the supreme need of 
 mastering all the details of the process. 
 
 The common D slide valve, simple as it appears, is 
 capable of furnishing problems over which savants 
 have puzzled themselves. 
 
 The development of the full amount of power of 
 which the engine is capable, its efficiency and eco- 
 nomical use of steam, and its regular and quiet action 
 are, in the largest degree, dependent upon the correct 
 adjustment of its valve or valves. 
 133 
 
134 ENGINEERING 
 
 There are many different types of valves for control- 
 ling the admission and release of steam to and from the 
 cylinders of engines, but the basic principles govern- 
 ing the adjustment of all, whether slide, poppet, rota- 
 tive, piston, etc., are exemplified in the action of the 
 common D slide valve, viz., the admission of the 
 steam to the cylinder, its cut off and release, and 
 the closure of the exhaust, each and all of which 
 events are to take place at the proper moment during 
 one stroke of the piston. 
 
 In order to properly perform these important func- 
 tions the valve must have lead and lap. The various 
 terms relating to valve action are plainly defined 
 in Chapter VIII on "Definitions," and it is unnec- 
 essary to repeat them here. If the outside lap is 
 increased admission will be later and cut off earlier, 
 and if it be desired to keep the lead the same it will be 
 necessary to move the eccentric forward, which will 
 make the other events, cut off, release, and compres- 
 sion, earlier also. If the inside lap is increased the 
 result will be an earlier closing of the exhaust and 
 increased compression. 
 
 These propositions refer mainly to engines of the 
 single valve variety in which one valve controls the 
 admission and distribution of the steam for both ends 
 of the cylinder. In engines of the four valve type, 
 having a separate steam and exhaust valve for each 
 end of the cylinder, each individual valve may be 
 adjusted independently of the others, as will be 
 explained later on, and in the case of engines having 
 separate eccentrics, one for the steam and one for the 
 exhaust valves, the adjustment becomes still more 
 perfect. 
 
 We will first study the action of the D slide valve by 
 
VALVES AND VALVE SETTING 
 
 135 
 
 referring to Fig. 13, which is a sectional view of a 
 valve, valve seat and ports. The valve is represented 
 at mid travel or in its central position. S P, S P are 
 the steam ports, and E P is the exhaust port. The 
 projections marked X at each foot of the arch inside 
 
 L 
 
 1 1 
 
 1 1 
 
 s*^ 
 
 L 
 
 1 | 
 l | 
 1 
 
 ' ' k 
 
 ^^^^ 
 
 \ l 
 
 ' ' ^S 
 
 *L* *A 
 
 
 JP^i 
 
 FIGURE 13. 
 
 W p y@ 
 
 the valve, represent inside lap and may be added to or 
 taken from the inside edges of the valve, according as 
 more or less compression is desired. The dotted lines, 
 L, L represent outside lap. 
 
 Motion is imparted to the valve through the medium 
 
 leaoT 
 
 FIGURE 14. 
 
 of the eccentric. If the valve had neither lap nor lead 
 the position of the eccentric on the crank shaft would 
 be just 90 or one-quarter of a circle ahead of the 
 crank, but as more or less lap as well as lead is 
 required, it becomes necessary to move the eccentric 
 
136 ENGINEERING 
 
 still farther ahead of the crank, and this farther 
 advance is termed angular advance, lap angle for lap 
 and lead angle for lead. 
 
 Assuming the piston to be at the end of the stroke 
 towards the crank, in other words, the engine to be 
 
 on the dead center, the first function of the valve is 
 lead or admission, illustrated by Fig. 14. Owing to 
 the valve having both lap and lead, the position of the 
 highest point of the eccentric will be assumed in this 
 case to be 120 ahead of the crank, the position of the 
 latter being at o°. 
 
 Exhaust opening has also occurred at the opposite 
 
 FIGURE 16. 
 
 end of the cylinder. The second function is full port 
 opening, Fig. 15, the crank having moved through 60 ° 
 and the eccentric is now at 180 , the farthest point of 
 its throw in that direction, the valve being at the end 
 of its travel. At this point it might be well to note a 
 
VALVES AND VALVE SETTING 
 
 137 
 
 matter about which some persons are liable to become 
 confused, simple as it is, viz., that the travel of a slide 
 valve equals twice the port opening plus twice the out- 
 side lap. For instance, suppose the width of each 
 steam port to be \% in. and the outside lap to be I in. 
 In Fig, 15 the valve is at the extreme end of its travel 
 
 FIGURE 17. 
 
 towards the right and is about to return. It first 
 covers port number one = \% in. Next it moves to 
 mid travel lap number one = 2% in. Its next move is 
 lap number two = 3^ in., and lastly it uncovers port 
 number two = 4^ in., which is its travel. 
 To return to the third function of the valve or cut 
 
 FIGURE 18. 
 
 off, Fig. 16. The crank has now traversed 120 and 
 the highest point of the eccentric is at 60 ° on the 
 return circle, a point equivalent to 240 ° of the circle 
 described by the crank. 
 
 The fourth function is when compression begins at 
 the head end of the cylinder, Fig. 17. The crank is 
 
138 
 
 ENGINEERING 
 
 now at 150 , the piston being near the end of the stroke 
 and the eccentric has reached 90 of the return circle 
 or three-quarters of the crank circle, while the crank 
 has still to travel 30 in order to complete the first one- 
 half of its circle. At this point we can study the effect 
 of inside lap, because if the valve has no inside lap, 
 release on the crank end will begin almost at the same 
 moment that compression takes place at the head end, 
 
 /to' 
 
 90* 
 
 FIGURE 19. 
 
 but by adding inside lap, compression can be caused 
 to take place earlier and release later. 
 
 The next event is admission at the head end of the 
 cylinder, Fig. 18. The crank has now arrived at 180 , 
 having completed one-half of a revolution; the piston 
 is at the end of the stroke, and the eccentric is at 
 120 on the return path. Fig. 19 serves to better illus- 
 trate the relative positions of the crank pin and 
 
VALVES AND VALVE SETTING 189 
 
 eccentric during the stroke. The inner circle repre- 
 sents the path described by the high point of the 
 eccentric, and the large circle that of the crank pin. 
 The radius C 2 of the small circle represents the throw 
 of the eccentric, and the distance C L is the lap of the 
 valve plus the lead. The point of intersection of the 
 vertical line, L 1, with the eccentric circle locates the 
 position of the highest point of the eccentric, and 
 the line C B, drawn from the center of the crank shaft 
 through this point, indicates the angular advance, 
 which in this case is 30 represented by the angle 
 ABC. The figures 1, 2, 3, 4, 5 indicate the position 
 of the high point of the eccentric at the moment of 
 each function of the valve. The action of the valve 
 can be moregraphically illustrated by means of valve 
 diagrams, of which there are several different kinds, 
 notably the Bilgram and Zeuner. The Zeuner dia- 
 gram will be made use of in this instance. 
 
 Fig. 20 shows the total movement of the valve, 
 regardless of lap and lead. First draw line C 1 to 
 represent the center line of the engine. Next draw 
 line C 4 perpendicular to the line of centers, with C as 
 the center of the crank shaft. The radius of the semi- 
 circle D, 1, 2, 3, 4,^5, 6 equals the radius of eccentri- 
 city. Line C D represents the position of the crank 
 when the valve is at mid travel or in its central posi- 
 tion, D being the location of the crank pin. Referring 
 back to Fig. 13 the valve is there shown in its central 
 position and supposed to be moving in the direction of 
 the arrow in order to admit steam to the crank end ot 
 the cylinder. Again referring to Fig. 20, draw line 
 C A in such a position that the angle ABC will 
 equal the angular advance of the eccentric, which we 
 will assume in this case to be 30 . . This will bring the 
 
140 
 
 ENGINEERING 
 
 high point of the eccentric at B while the crank, as 
 before stated, is at D. Next using line C A as the 
 diameter draw a circle about it called the valve circle. 
 
 A, 
 
 [Tfi- 
 
 C\ 
 
 
 \ 
 
 **■" 
 
 Va}vs Ttavet = ?%* 
 
 FIGURE 20. 
 
 Now suppose the crank to be turning in the direction 
 of the arrows. At position D the crank line is just 
 about to cut into the valve circle, the valve being 
 central. When the crank gets to position I the valve 
 
VALVES AND VALVE SETTING 141 
 
 has moved the distance C E. When the crank is at 2 
 the valve has moved the distance C M, and when the 
 crank arrives at 3 the valve has moved to the limit of 
 its travel from its central position and it now begins 
 the return movement. The motion of the valve is 
 comparatively slow at this point for the reason that the 
 high point of the eccentric is now passing the center 
 at 7. The distance the valve has moved backward 
 while the crank has moved from 3 to 4 is the distance 
 B F, while F C represents its distance from the central 
 position, and G C the same when the crank is at 5. 
 When the crank arrives at 6 and its line has left the 
 valve circle, the valve is again central. Fig. 20 merely 
 shows the movement of the valve through one-half of 
 its travel without giving any details regarding port 
 openings, cut off, etc. 
 
 In Fig. 21 the influence of outside lap is delineated. 
 According to the dimensions of the valve under con- 
 sideration the outside lap is one inch. The diagram is 
 drawn precisely as in Fig. 20, and in addition strike an 
 arc representing the outside lap, using C as the center 
 with a radius equal to the outside lap. As before, the 
 crank is at D and the valve central. When the. crank 
 has moved to E and its line cuts the intersection of 
 the outside lap and valve circles, the valve has moved 
 the distance C H, just equal to the outside lap, and 
 the port begins to uncover at this point. Then by the 
 time the crank gets to the center, 1, the port is open' 
 the distance L O, which is the lead, in this case yi in. 
 This position of the valve is shown in Fig. 14. 
 
 The position of the crank when cut-off takes place is 
 ascertained by drawing a line, C G 5, through the inter- 
 section of the outside lap and valve circles, where the 
 valve is on its return movement (see Fig. 16). Thus 
 
Wl 
 
 ENGINEERING 
 
 far no account has been taken of release and compres- 
 sion, and in order to determine the position of the 
 crank when these events occur it will be necessary to 
 
 
 =* Z?*'* 
 
 / — 
 
 FIGURE 2L 
 
 draw the valve circle for the opposite movement of the 
 valve, for be it remembered that the movement of the 
 valve so far considered has been only one-half of its 
 
VALVES AND VALVE SETTING 
 
 143 
 
 
 
 
 1 
 
 
 
 \><> 
 
 i / I \ 
 
 
 / \\T\ 
 
 Je )%T \ 
 
 
 /l/ji^' 
 
 7 
 
 
 Xm/. ^\ 
 
 
 S 
 
 
 
 \<2 x J 7->L 
 
 
 
 1 ^^y^t 
 
 X/q '\ 
 
 
 
 \^^"""~^ s^/l f J %s 
 
 7&y \ 
 
 1 
 
 e 
 
 
 
 
 
 \ 
 
 10 
 
 A-? \ 
 ft \ 
 
 
 
 
 
 
 
 
 
 Vedve 7kaveC 
 
 = «t'~ \ 
 
 
 
 
 latrurof ?ecenit< ct 
 
 ^ = *v V 
 
 
 
 
 Out-r/tte £oa 
 
 
 
 
 bir</>e La/> 
 
 = A- ^ 
 
 \ 
 
 
 f'/ect/rt L eac/ 
 
 - \~ 
 
 
 FIGURE 22. 
 
 travel; that is, it has moved from its central position 
 towards the head end of the cylinder and back again. 
 We have seen how it has thus performed the functions 
 
] 44 ENGINEERING , 
 
 of admission, full port opening and cut off for the 
 crank end of the cylinder, and now by referring to 
 Fig. 22 it will be seen at what point of the stroke tJru 
 remaining events, viz., release and compression, 
 occur. 
 
 Draw a second valve circle, Fig. 22, diametrically 
 opposite the first. Also draw an arc with a radius 
 equal to the inside lap, which in this case is assumed 
 to be one-half inch. When the crank gets to the 
 position 7 its center line cuts the intersection of the 
 inside lap and valve circles and release begins. When 
 the crank arrives on the center 8, the valve has moved 
 the distance C T from central position; but C X of this 
 distance has been occupied by the inside lap, therefore 
 the lead on the exhaust is represented by the distance 
 X T. When the crank on its return stroke arrives at 
 the position marked 10, its line again cuts the inter- 
 section of the inside lap and valve circles and com- 
 pression takes place, as in Fig. 17. By dropping 
 perpendiculars from the positions of the crank at 1, 5, 
 7 and 10 an indicator diagram may be drawn showing 
 the performance of an engine with this style of valve. 
 
 Fig. 23 shows the effect of decreasing the angular 
 advance, that is, setting the eccentric back towards the 
 crank. In this instance the eccentric is set back io°, 
 thus making the angle of advance 20 instead of 30 as 
 before. The full lines represent the new angle, while 
 the dotted circles and lines indicate the valve and its 
 movements as drawn at first. A shows the original 
 point of admission and A' the position of the crank 
 when admission takes place with the lesser angle of 
 advance. Similarly R and R' show the old and new 
 points of release, and C and C the compression The 
 two different points of cut off are also indicated. It 
 
VALVES AND VALVE SETTING 
 
 145 
 
 will be observed that all of these events occur later 
 and the lead also is diminished. 
 
 In locomotives, and also in some types of adjustable 
 cut off engines, the travel of the valve may be varied 
 at will, and the effect of decreasing the valve's travel 
 
 
 TO 
 
 /^^ 
 
 FIGURE 23. 
 
 is illustrated by Fig. 24, the full lines showing the 
 decreased travel and its influence, and the dotted lines 
 showing the original. Admission and release occur 
 later, while cut off and compression take place earlier, 
 and the lead is less. The travel of the valve as indicated 
 
146 
 
 ENGINEERING 
 
 in Fig. 24 has been decreased one inch, making it 3^ 
 in. in place of 4^ in. as before. 
 
 Fig. 25 shows the result of increasing the outside 
 lap. The lap has been increased in this case from 1 
 in., as originally drawn, to 1% in. as indicated by the 
 
 C ' 
 
 W 
 
 '17 
 
 FIGURE 24 
 
 full lines, while the dotted lines show the lap as it was 
 before being changed. The effect of this change is to 
 cause less lead, a later admission and an earlier cut 
 off, but compression and release are not affected for 
 the reason that these latter events are controlled by 
 the inside lap, which has not been changed, 
 
VALVES AND VALVE SETTING 
 
 147 
 
 In Fig. 22 the valve is shown as cutting off the steam 
 when the crank has completed 120 or two-thirds of 
 the half revolution, but the point of cut off on the indi- 
 cator diagram shows that the piston has traveled I of 
 the stroke. This discrepancy is due to the obliquity 
 
 /€*■ 
 
 && 
 
 .*y 
 
 FIGURE 25. 
 
 of the connecting rod, as it will be seen by looking at 
 the valve diagram, Fig. 22, that the crank must travel 
 farther to complete the stroke from this point than the 
 piston does. In order to cause the valve to cut off 
 earlier, say at one-half stroke, it will be necessary to 
 do one of two things, either to increase the outside 
 
148 
 
 ENGINEERING 
 
 FIGURE 26. 
 
 lap, which would have a tendency to cause admission 
 to occur too late, or the angle of advance may be 
 
VA1/VES AND VALVE SETTING 149 
 
 increased sufficient to cause cut off to take place at 
 half stroke, but to do this alone would cause admission 
 to occur too early. Therefore the proper thing to do 
 is to increase both the angle of advance and the out- 
 side lap. Fig. 26 shows how this can be done without 
 decreasing the travel of the valve. The angle of 
 advance, A B C, is now 50 , where before it was 30 , 
 as in Fig. 22. 
 
 The valve is central when the crank is at position 1; 
 the high point of the eccentric being at point 4. The 
 outside lap which before was 1 in. has had ^\ in. added 
 to it, making it i T 7 g- in. When the crank gets to D the 
 port is just commencing to open, and with the crank 
 on the center at 2, the lead is }( in. 
 
 It will readily be seen at this point that by increasing 
 the outside lap still more the lead can be diminished, 
 and the point of cut off made still earlier, but this 
 would result in a still further reduction of the power of 
 the engine, which has already been considerably 
 reduced, as shown by the diminished area of the indi- 
 cator diagram as compared with the one in Fig. 22. 
 When the crank gets to position 3 the valve has 
 reached the limit of its travel, and the port is open the 
 distance A a, which is as far as the outside lap will 
 permit. With the crank at point 4 cut off occurs. But 
 with the increased angular advance and the inside 
 lap remaining as it was before, viz., j4 in., release 
 would occur too early. Therefore it will be nec- 
 essary to increase the inside lap sufficient to cause 
 release and compression to take place at as near 
 the proper points as possible. In this instance 3/s 
 in. has been added, making the inside lap 7^ in., 
 and release takes place with the crank at position 5, 
 while compression begins at 6. These points may 
 
150 
 
 ENGINEERING 
 
 also be changed by simply adding to or decreasing 
 the inside lap. 
 
 It should be noted that in the foregoing discussion 
 of valve gear it is understood that the valve stem 
 moves in the same direction as the eccentric rod, that 
 is, the direction of motion is not reversed by a rocker 
 arm interposed between the eccentric and the valve. 
 
 r 
 
 FIGURE 27. 
 
 In case there should be a rocker arm connected so as 
 to reverse the motion and thereby cause the valve to 
 move opposite to the eccentric rod, it will be neces- 
 sary to set the eccentric behind the crank, as in Fig. 27. 
 Most engines are fitted with a rocker arm for trans- 
 mitting the motion of the eccentric to the valve stem, 
 
 r 
 
 FIGURE 28. 
 
 but the usual practice is to attach them so that the 
 direction of motion is not reversed, as in Fig. 28 
 
 The first step in the operation of valve setting is to 
 place the engine on the dead center, which means that 
 
VALVES AND VALVE SETTING 15 1 
 
 the piston is at the end of the stroke, and the centers 
 of the main shaft, crank pin and crosshead pin, or 
 wrist pin as it is sometimes called, are in line (see Fig. 
 31). When moving the engine to place it on the cen- 
 ter it should always be turned in the direction in which 
 it is to run. This is to guard against any errors which 
 might result from lost motion or looseness in the 
 reciprocating parts. Turn the fly wheel around until 
 the crosshead is almost to the end of the stroke, say 
 within a half inch of it, as at A, Fig. 29. Then with a 
 
 figure 29. 
 
 steel scriber or penknife mark the location of the 
 crosshead on the guides A, also provide a secure rest- 
 ing place upon the floor of the engine-room for a 
 markef to be placed against the rim of the wheel. 
 This rest should be firmly fastened to the floor in order 
 that its position may not be changed during the opera- 
 lion of valve setting. Place the marker against the 
 wheel as at B and mark the point with a center punch 
 or cold chisel. Next turn the engine carefully until 
 the crosshead completes the stroke and moves back on 
 the return stroke until the mark A is in line again. 
 Make another mark on the rim of the wheel opposite 
 the marker at C. This position of the engine is 
 shown in Fig. 30, and it will be seen that the crank is 
 now as much above the center as it was below in Fig. 
 
152 
 
 ENGINEERING 
 
 29. Now with a pair of large dividers ascertain the 
 middle or half distance between marks B and C and 
 put another mark, D, at this point. Then turn the 
 
 FIGURE 30. 
 
 engine a complete revolution until mark D comes 
 opposite the pointer, Fig. 31, and the engine will be 
 on the true center. 
 
 At this point the question may arise, why not simply 
 reverse the motion and back the wheel up until the 
 mark D is in line with the marker? The answer is, 
 
 figure 31. 
 
 that while this would undoubtedly save considerable 
 labor, yet it would almost certainly result in an error, 
 on account of the lost motion of the moving parts 
 which would permit of considerable movement of the 
 wheel before any movement of the crosshead would 
 take place if the wheel was turned back. The result 
 would be that when mark D came to be opposite to the 
 
VALVES AND VALVE SETTING 
 
 1.53 
 
 pointer, the crank would not be on the true center. 
 The next move is to see that the eccentric rod is 
 adjusted to the proper length. If there is a rocker 
 arm, connect the eccentric rod in its proper place, 
 leaving the valve rod disconnected for the time being. 
 
 
 ^ 
 
 £eceni/i/c &><* 
 
 t 
 
 
 K.y 
 
 \ 
 
 FIGURE 32. 
 
 Then adjust the length of the rod so that when the 
 eccentric is turned around on the shaft the rocker arm 
 will vibrate equal distances on each side of a plummet 
 line suspended through the center of the pin upon 
 which the arm turns, as in Fig, 32. Before connecting 
 
154 
 
 ENGINEERING 
 
 the valve rod the valve should be put in its central 
 position and marked. To do this it will be necessary 
 to first ascertain the outside lap. 
 
 The most accurate method of doing this is to take the 
 valve out and measure the distances between the out- 
 side edges of the steam ports as at B, Fig. 33. Then 
 measure the width of the valve from edge to edge as 
 at A. Then A - B + 2 = the outside lap. For instance, 
 A = 8.5 in., B-6.5 in. Then 8.5-6.5-2, and 2 
 
 FIGURE 33. 
 
 divided by 2 = 1 in., which is the lap. The inside lap. 
 should also be measured at this point for convenience, 
 and the measurements preserved for future reference. 
 The inside lap is ascertained by measuring the distance 
 between the inside edges of the ports and the distance 
 across the arch of the valve from one inside edge to 
 the other (see Fig. 33) and dividing the difference 
 by 2. For instance, the distance F is 4 in., and E is 
 3 in. ; then A ^ = .5 in., making the inside lap }4 in. 
 To place the valve central, measure the width of the 
 
VALVES AND VALVE SETTING 155 
 
 outside lap each way from the outside edges of the 
 steam ports and mark the points on the valve seat with 
 a sharp lead pencil. Then place the valve with edges 
 on the marks and it will be central. To insure accu- 
 racy measurements should also be taken from the out- 
 side edges of the steam ports to the ends of the seats. 
 Having fixed the valve in its central position, replace 
 the stem and if it is secured in the valve by nuts, as in 
 Fig. 33, care should be taken to leave a little play for 
 the valve between the nuts, otherwise it is liable to 
 become stuck and held off the seat when it gets hot 
 and expands. Make a, center punch mark C, on the 
 edge of the valve chest directly over the valve stem, 
 and placing one leg of a tram or pair of dividers in the 
 mark, with the other leg describe a mark on the top of 
 the Valve as at D, thus marking the valve in its central 
 position. 
 
 Now with the rocker arm perpendicular, the eccen- 
 tric rod having been previously adjusted, connect the 
 valve rod to the rocker, and turn the eccentric to the 
 limit of its throw in one direction, and measure 
 the distance the valve has traveled from its central 
 position. Then turn the eccentric around to its 
 extreme throw in the other direction, and if the valve 
 travels the same distance from its central position in 
 the opposite direction the lengths of the rods are cor- 
 rect, but if not correct the necessary change can 
 usually be made by shifting the nuts on the valve stem, 
 or if the valve is secured to the stem by a yoke the 
 change can be made in the rod. 
 
 Having succeeded in getting the correct travel for 
 thejvalve, the next step is to set the eccentric. With 
 the engine -on the dead center, turn the eccentric 
 around on the shaft in the direction in which the 
 
156 ENGINEERING 
 
 engine is to run, so as to take up all the play in the 
 valve stem and other moving parts, and with the tram 
 or dividers watch the valve until it has moved away 
 from its central position by the amount of its outside 
 lap, plus the lead it is desired to give the valve. For 
 instance, if the valve has one inch outside lap and the 
 lead is to be }i in., the valve should be moved away 
 from its central position 1^5 in., and also away from 
 the end of the cylinder at which the piston is. The 
 steam port for that end should now be open }i in., and 
 the eccentric should be ahead of the crank one-quarter 
 turn plus the angular advance required for the outside 
 lap and lead, or if as previously explained, the motion 
 of the eccentric is reversed by a rocker arm the eccen- 
 tric should be behind the crank by the same amount. 
 Tighten the set screws holding the eccentric on to the 
 shaft and turn the engine around until it is on the 
 opposite center. Then if the lead is the same on each 
 center the valve is set correctly. If the lead is not the 
 same, move the valve on the stem toward the end 
 having the most lead, a distance equal to one-half the 
 difference between the two leads. If the lead as 
 equalized is more than is desired, move the eccentric 
 back on the shaft until the correct lead opening is 
 secured, then tighten the set screws permanently, and 
 with a sharp cold chisel make a plain mark on the 
 shaft and opposite to this another mark on the 
 eccentric. This will save considerable trouble in case 
 the eccentric should slip or be accidentally moved 
 from its true position at any time. 
 
 Although the common D slide valve as applied to 
 stationary engines usually has its point of cut off 
 fixed, yet there are many types of variable automatic 
 cut off engines with single slide valves of various pat- 
 
VALVES AND VALVE SETTING 157 
 
 terns, such as box valves in which the steam passes 
 through the valve, piston valves in which the steam 
 either passes through or around the ends of the valve, 
 so-called gridiron valves and various other types. 
 Such valves are generally applied to high speed 
 engines and are actuated by eccentrics which are 
 under the control of shaft governors which vary the 
 position of the eccentric with relation to the crank 
 according to the load that is on the engine, thus regu- 
 lating the point of cut off so as to maintain a constant 
 speed, while the throttle is kept wide open. While 
 the details of setting all the various styles of valves, 
 including the corliss or four valve type, differ consider- 
 ably from those required in setting the D valve, yet 
 the same principles govern the operation, no matter 
 what kind of a valve is to be adjusted 
 
 In all types of reciprocating engines the same fac- 
 tors affecting the distribution of the steam are present, 
 viz., the outside or steam lap affecting admission and 
 cut off, and the inside or exhaust lap affecting release 
 and compression. While the D valve (and other 
 types of single valves) combines these four principal 
 factors within itself (that is, two steam laps and two 
 exhaust laps), it should be noted that in the four valve 
 type of engine the same factors are distributed among 
 four valves, each valve performing its own particular 
 function in controlling the distribution of the steam 
 for the end of the cylinder to which it is attached. 
 Also each valve may be adjusted to a certain degree 
 independently of the others, and this fact goes far 
 towards explaining why engines of this type, with the 
 disengaging valve gear, are so much more economical 
 in the use of steam than are those with the ordinary 
 fixed cut off. Thus, for instance, the steam valves of 
 
158 
 
 ENGINEERING 
 
 a corliss engine may be adjusted to cut off the steam 
 at any point, from the very beginning up to one-half 
 of the stroke, without in the least affecting the release 
 or compression because these events are controlled by 
 the exhaust valves. 
 
 As the corliss engine is a prominent and familiar 
 type of the four valve detaching cut off engine, and 
 embodies the main features of nearly all engines 
 belonging to that class, it will be used to illustrate the 
 method of setting the valves on a four valve engine. 
 
 figure 34. 
 
 Fig. 34 is a sectional view of the cylinder, steam and 
 exhaust chests, and the valve chambers of a corliss 
 engine. I and 2 are the steam valves and 3 and 4 the 
 exhaust valves. The valves work in cylindrical cham- 
 bers accurately bored out, the face of the valve being 
 turned off to fit steam iight. They are what is termed 
 rotative valves, that is, they receive a semi-rotary 
 motion from the wrist plate, which in turn is actuated 
 by the eccentric. 
 
 In some of the modern improved makes of four 
 valve engines there are two eccentrics, one for the 
 
VALVES AND VALVE SETTING 
 
 159 
 
 steam and the other for the exhaust valves. This 
 arrangement permits of still greater latitude in adjust- 
 ments for the economical use of steam. 
 
 In Fig. 34 the piston is shown as just ready to begin 
 the stroke towards the left. Admission is taking 
 place at valve 2 and release at valve 3, valves 1 and 4 
 being closed. The arrows show the direction in which 
 the valves move. Motion is transmitted from the wrist 
 plate to the valves by means of short connecting rods 
 and cranks attached to the valve stems. These rods 
 
 <s 
 
 
 
 
 
 
 
 
 
 
 
 l$k 
 
 9 
 
 /W""T 
 
 //* 
 
 
 
 
 
 
 1 ; 
 
 B 
 
 
 1 ®\ 
 A V 
 
 ®1 
 
 ;J^2 
 
 \c 
 
 
 ©1 
 
 3 
 
 
 ^ 
 
 F$ 
 
 
 
 L * 
 
 in iff 
 
 d «f 
 
 TWf-y 
 
 FTGURE 35. 
 
 are, or at least should be, fitted with right and left hand 
 threads or turn buckles for the purpose of lengthening 
 or shortening the rods while setting the valves. 
 
 The valve gear of a corliss engine with a single 
 eccentric is shown in Fig. 35. The connections of the 
 exhaust valves with the wrist plate are positive, and 
 the travel of these valves is fixed, being a constant 
 quantity, but the connections of the steam valves with 
 the wrist plate are detachable, being under the control 
 of the governor. Various designs of releasing mechan- 
 
160 ENGINEERING 
 
 ism are in use by different builders, but the same gen- 
 eral principles govern the operation of all, viz., that 
 the valve is quickly opened at the commencement of 
 the stroke when the wrist plate has its fastest motion, 
 and that the governor trips the releasing meehanism at 
 that point in the stroke at which it is desired that cut 
 off should take place, and that the valve is then 
 quickly closed by means of a vacuum dash pot or, as in 
 some types of engines, by a spring. Connection is 
 made between the wrist plate and rocker arm by 
 means of the hook rod, so-called because it hooks over 
 the wrist plate pin, and can easily be disconnected in 
 case it is desired to work the valves by hand, as in 
 warming up the engine preparatory to starting up. 
 
 Referring to Fig. 35, A is the wrist plate, B and C 
 are the dash pot rods, D, D' the dash pots and H R the 
 hook rod. G and G' represent the governor rods, and 
 the figures 1, 2, 3 and 4 indicate the valve rods with 
 turn buckles for changing their lengths. 
 
 As in setting the slide valve, the first requisite in 
 setting corliss valves is to put the engine on the cen- 
 ter, the method of doing which has been fully 
 described. Next adjust the length of the hook rod, if 
 it is adjustable, if not, then the eccentric rod so that 
 the wrist plate will vibrate equal distances each way 
 from its central position which is marked on top of 
 the hub. (See Fig. 36.) It will be noticed that there 
 are four marks, A, B, C and D. Marks A and B are on 
 the hub of the wrist plate and the stationary flange 
 against which it turns, and when they are in line, indi- 
 cate that the wrist plate is central. Marks C and D 
 are on the stationary flange at equal distances each 
 way from B, and when the engine is running mark A 
 should travel to the right until it is in line with D and 
 
VALVES AND VALVE SETTING 
 
 161 
 
 to the left until in line with C, or it may happen that 
 A will travel past C and D or perhaps not quite to 
 them, but which ever it does, it should stop at equal 
 distances from them. This adjustment should be care- 
 fullv made before setting the valves, because if any 
 
 FIGURE 36. 
 
 change is made in the lengths of the eccentric rod or 
 hook rod after the valves are once set it will seriously 
 affect the action of all the valves. 
 
 The method of adjusting the rocker arm so that it 
 will vibrate correctly has been already described and 
 it is very desirable that its travel should be equidistant- 
 
162 
 
 ENGINEERING 
 
 in either direction from a vertical position, but if it is 
 found that the hook rod is non-adjustable as to length 
 and that the wrist plate still vibrates too far in one 
 direction, then the adjustment must be made on the 
 length of the eccentric rod, which can be screwed into 
 or out of the strap. The vibration of the wrist plate 
 should then be tested by turning the eccentric around 
 on the shaft in the direction the engine is to run. 
 When this is found to be correct the next step is to 
 remove the back bonnets from the valve chambers. 
 Fig. 37 represents one of the steam valves and Fig. 38 
 
 (0) 
 
 />> — 
 
 : / 
 
 '-■ \ 
 
 : 
 
 : ) 
 
 * ( 
 
 ^ 
 
 FIGURE 37. 
 
 one of the exhaust valves, each with back bonnet 
 removed, showing the ends of the valves. 
 
 The working edges of the valves, as well as the 
 ports of a corliss engine, cannot be seen when the 
 valves are in place, owing to the fact that the circular 
 ends of the valves fill the spaces at the ends of the 
 valve chambers, but certain marks will be found on the 
 ends of the valves, and corresponding marks on the 
 faces of the chambers which serve as a guide in set- 
 ting the valves. Referring to Fig. 37, mark V on the 
 .end of the valve is in line with the edge of the valve, 
 and P indicates the edge of the porr. The same let' 
 
VALVES AND VALVE SETTING 
 
 163 
 
 ters apply to Fig. 38. Having removed the bonnets 
 and found the marks, temporarily secure the wrist 
 plate in its central position by tightening one of the 
 set screws on the eccentric. Then connect the valve 
 rods, adjusting their lengths so that the steam valves 
 will have from % to j\ in. lap, as in Fig. 37, and the 
 exhaust valves from ^- 2 - to T 3 ¥ in. opening, as in Fig. 38. 
 These figures vary according to the size of the engine, 
 the smaller figures being for small size engines and the 
 larger figures apply to large sizes. 
 
 In adjusting the steam valves be sure and note the 
 
 figure 38. 
 
 direction in which they turn to open. In most corliss 
 engines the arm of the crank to which the valve rod is 
 connected extends downwards from the valve stem, 
 as in Fig. 35. This will cause the valve to move 
 towards the wrist plate in opening. After the valve 
 rods have been properly adjusted as to length, place 
 the engine on either center by the method previously 
 explained and move the eccentric around on the shaft 
 in the direction in which the engine is to run until it is 
 far enough ahead of the crank to allow the steam 
 valve the proper amount of lead opening, which will 
 vary according to the size of the engine. Table 7 
 
164 
 
 ENGINEERING 
 
 gives the lap and lead for various sizes of corliss 
 engines from 12 to 42 in. bore. Having tightened the 
 
 TABLE 7. 
 
 Size of Engine. 
 
 Lap of Steam 
 Valve. 
 
 Lead Opening of 
 Steam Valve. 
 
 Lead Opening of 
 Exhaust Valve. 
 
 12 inches 
 
 \ inch 
 
 ^ inch 
 
 sh inch 
 
 14 
 
 5 " 
 Te 
 
 32 
 
 
 3V " 
 
 16 
 
 5 < 1 
 
 _1_ 
 
 
 JL << 
 
 T6 
 
 16 
 
 
 32 
 
 18 
 
 3 11 
 
 8 
 
 16 
 
 
 A " 
 
 20 " 
 
 3 " 
 8 
 
 A 
 
 
 ¥ J 
 
 22 " 
 
 3 u 
 
 ft 
 
 
 1 1 6 
 
 24 
 
 r 7 e " 
 
 3 
 3"2 
 
 
 3\ " 
 
 26 
 
 7 '< 
 
 T6 
 
 3 
 32 
 
 
 3 " 
 32 
 
 28 
 
 r 7 e " 
 
 3 
 32 
 
 
 ft •: 
 
 30 
 
 i " 
 
 A 
 
 
 I !! 
 
 32 
 
 i " 
 
 #2 
 
 
 1 
 
 34 
 
 1 '< 
 2 
 
 1 
 
 
 1 " 
 
 36 " 
 
 fr " 
 
 1 
 
 
 1 << 
 
 "S" 
 
 38 " 
 
 1% " 
 
 i 
 
 
 1 3 6 " 
 
 40 
 
 .ft " 
 
 1 
 
 8 
 
 
 A " 
 
 42 
 
 T 9 6 " 
 
 8 
 
 r 3 e " 
 
 eccentric set screws, turn the engine around, to the 
 opposite center and note whether the lead is the same 
 on each end. If there is a difference it can generally 
 be equalized by slightly altering the length of one of 
 the valve rods. The valves should also be adjusted 
 by means of the indicator at the first opportunity, as 
 that is the only absolutely correct method. 
 
 The next point to receive attention is the adjustment 
 of the lengths of the horizontal rods extending from 
 the governor to the releasing mechanism, so that the 
 steam valves will cut off at equal points in the stroke. 
 This is done by raising the hook rod clear of the wrist 
 plate pin, and with the bar provided for the purpose 
 move the wrist plate to either one of its extreme posi- 
 tions as shown by the marks on the hub (see Fig. 36) 
 
VALVES AND VALVE SETTING 165 
 
 and holding it in this position adjust the length of the 
 governor rod for the steam valve (which will then be 
 wide open) so that the boss or roller which trips the 
 releasing mechanism is just in contact, or within ^ in. 
 of it. Then move the wrist plate to the other extreme 
 of its travel and adjust the length of the other rod in 
 the same manner. To prove the accuracy of the 
 adjustment, raise the governor balls to their medium 
 position, or about where they would be when the 
 engine is running at its normal speed and block them 
 there. Then having again connected the hook rod to 
 the wrist plate, turn the engine around in the direction 
 in which it is to run, and when the valve is released, 
 measure the distance upon the guide that the crosshead 
 has traveled from the end of the stroke. Now con- 
 tinue to turn the engine in the same direction until the 
 other valve is released, and measure the distance that 
 the crosshead has traveled from the opposite end of 
 the stroke, and if the cut off is equalized these two 
 distances will be the same. If there is a difference, 
 lengthen one rod and shorten the other until the point 
 of cut off is the same for both ends. 
 
 The lengths of the dash pot rods should also be 
 adjusted so that when the plunger is at the bottom of 
 the dash pot the valve lever will engage the hook. 
 
 After all adjustments have been made tighten the 
 lock nuts on all the rods. 
 
 Questions 
 
 i. What important features in the operation of an 
 engine are dependent upon a correct adjustment of the 
 valves? 
 
 2. How many different types of valves are there in 
 general use? 
 
166 ENGINEERING 
 
 3. What are the basic principles governing the 
 adjustment of the valves of an engine? 
 
 4. Name two important functions of a valve. 
 
 5. What is the effect of increasing the outside lap? 
 
 6. What is the result of increasing the inside lap? 
 
 7. What advantage has an engine of the four valve 
 type over one with but a single valve? 
 
 8. Suppose a valve had neither lap nor lead, what 
 would be the position of the eccentric in relation to 
 the crank? 
 
 9. What is meant by the term "angular advance," 
 and why is it necessary? 
 
 10. What is the first function of the valve at the 
 commencement of the stroke? 
 
 11. What is the second function? 
 
 12. What is the travel of a slide valve equivalent to? 
 
 13. What is the third function of the valve? 
 
 14. What is the fourth function? 
 
 15. What will be the effect if a valve has no inside 
 lap? 
 
 16. How can the action of a slide valve be graphically 
 illustrated? 
 
 17. Name the two most commonly used valve dia- 
 grams. 
 
 18. What is meant by the expression, "radius of 
 eccentricity"? (See Chapter VIII.) 
 
 19. Why must a valve have outside lap? 
 
 20. What is the object in giving a valve inside 
 lap? 
 
 21. What is the result of decreasing the angular 
 advance? 
 
 22. What will be the result if the travel of the valve 
 is decreased? 
 
 23. What three changes must be made in order to 
 
VALVES AND VALVE SETTING 167 
 
 cause an earlier cut off in an engine that has a fixed 
 cut off? 
 
 24. What is the first step in the operation of valve 
 setting? 
 
 25. When is an engine on the dead center? 
 
 26. What precautions should be observed in turning 
 an engine to place it on the center? 
 
 27. Why is this necessary? 
 
 28. Describe briefly the process of placing an engine 
 on the dead center. 
 
 29. What is the next move in the routine of valve 
 setting? 
 
 30. What should be done with the valve before con- 
 necting it to the valve rod? 
 
 31. How may the outside lap be ascertained? 
 
 32. How is the amount of inside lap found? 
 
 33. Should the valve be rigidly secured to the stem? 
 
 34. Describe the proper method of adjusting the 
 length of the rod in order that the valve may travel 
 correctly. 
 
 35. How is the correct position of the eccentric on 
 the shaft ascertained? 
 
 36. If the lead is not the same at each end of the 
 stroke, how may it be equalized? 
 
 37. If there is more lead than is desired, how may it 
 be decreased? 
 
 38. What is the function of a shaft governor in rela- 
 tion to the eccentric? 
 
 39. Why is the four valve type of engine more eco- 
 nomical in the use of steam than the single valve type 
 with fixed cut off? 
 
 40. How should the wrist plate be adjusted? 
 
 41. If the wrist plate does not vibrate correctly what 
 will be the result? 
 
168 ENGINEERING 
 
 42. How should the rods connecting the governor 
 with the releasing mechanism be adjusted? 
 
 43. How may this adjustment be tested? 
 
 44. How should the dash pot rods be adjusted as to 
 length? 
 
CHAPTER VII 
 
 THE INDICATOR 
 
 The indicator — Its invention and improvement — Principles 
 governing its operation — Diagrams from condensing and non- 
 condensing engines — Sizes of springs to be used for various 
 pressure — Reducing mechanism — The reducing wheel — 
 Different forms of pendulum reducing motion — Brumbo pul- 
 ley — The pantograph — Attaching the indicator — Parts of the 
 cylinder to which indicator pipes should not be connected — 
 Care of the insirument — Cleaning, oiling, etc. — Directions for 
 taking diagrams. 
 
 The Indicator. One of the greatest aids to the eco- 
 nomical operation of the steam engine is the indicator, 
 and it is the privilege of every engineer to have at least 
 an elementary, if not a thorough knowledge of its prin- 
 ciples and working. The time devoted to the study of 
 the indicator, and in its application to the engine, is 
 time well spent, and in the end will well repay the 
 student of steam engineering. 
 
 Inve?itor. The indicator was invented and first ap- 
 plied to the steam engine by James Watt, whose restless 
 genius was not satisfied with a mere outside view of his 
 engine as it was running, but he desired to know more 
 about the action of the steam in the cylinder, its pressure 
 at different portions of the stroke, the laws governing its 
 expansion after being cut off, etc. Watt's indicator, 
 although crude in its design and construction, con- 
 tained embodied within it all of the principles of the 
 modern instrument. 
 
 Principles. These principles are: 
 
 First. The pressure of the steam in the engine 
 - 169 
 
170 
 
 ENGINEERING 
 
 cylinder throughout an entire revolution, against a 
 small piston in the cylinder of the indicator, which in 
 turn is controlled or resisted in its movement by a 
 
 SECTIONAL VIEW CROSBY INDICATOR. 
 
 spring of known tension, so as to confine the stroke of 
 the indicator piston within a certain small limit. 
 
 Second. The stroke of the indicator piston is com- 
 municated by a multiplying mechanism of levers and 
 parallel motion to a pencil moving in a straight line. 
 The distance through which the pencil moves being 
 
THE INDICATOR 
 
 171 
 
 governed by the pressure in the engine cylinder and 
 the tension of the spring. 
 
 Third. By the intervention of a reducing mechan- 
 ism and a strong cord, the motion of the piston of the 
 engine throughout an entire revolution is communi- 
 cated to a small drum attached to and 
 forming a part of the indicator. The 
 movement of the drum is rotative and 
 in a direction at right angles to the 
 movement of the pencil. The forward 
 stroke of the engine piston causes the 
 drum to rotate through part of a revo- 
 lution and at the same time a clock 
 spring connected within the drum is 
 wound up. On the return stroke the 
 motion of the drum is reversed and the 
 tension of the spring returns the drum 
 to its original position and also keeps 
 the cord taut. 
 
 To the outside of the drum a piece of 
 blank paper of suitable size is attached and held in place 
 by two clips. Upon this paper the pencil in its motion 
 up and down traces a complete diagram of the pressures 
 and other interesting events transpiring within the en- 
 gine cylinder during the revolution of the engine. In 
 fact the diagram traced upon the paper is the compound 
 result of two concurrent movements. First, that of the 
 pencil caused by the pressure of the steam against 
 the indicator piston; second, that of the paper drum 
 caused by, and coincident with, the motion of the 
 engine piston. The upper end of the indicator cylin- 
 der is always open to the atmosphere, the steam acting 
 only upon the underside of the small piston, and when 
 the cock connecting the cylinders of the engine and 
 
 CROSBY INDI- 
 CATOR SPRING. 
 
172 ENGINEERING 
 
 indicator is closed, both ends of the indicator cylinder 
 are open to atmospheric pressure, and the pencil then 
 stands at its neutral position. If now the pencil is 
 held against the paper and the drum rotated either by 
 hand or by connecting it with the cord, a horizontal 
 line will be traced. - This line is called the atmospheric 
 line, meaning the line of atmospheric pressure, and it 
 is a very important factor in the study of the diagram. 
 
 If the engine is a non-condensing engine the pencil 
 in tracing the diagram will, or at least, should not fall 
 below- the atmospheric line at any point, but will on 
 the return stroke trace a line called the line of back 
 pressure at a distance more or less above the atmos- 
 pheric line and very nearly parallel with it. If the 
 engine is a condensing engine the pencil will drop 
 below the atmospheric line while tracing the line of 
 back pressure on the diagram, and the distance this 
 line is below the atmospheric line will depend upon 
 the number of inches of vacuum in the condenser. 
 
 As before stated, the length of stroke of the indi- 
 cator piston and the pencil movement as well is 
 controlled by a spiral steel spring which acts in resist- 
 ance to the pressure of the steam. These springs are 
 made of different tensions in order to be suitable to 
 different steam pressures and speeds, and are numbered 
 20, 40, 60, etc., the number meaning that a pressure per 
 square inch in the engine cylinder corresponding to the 
 number on the spring will cause a vertical movement of 
 the pencil through a distance of one inch. Thus, if a 
 number 20 spring is used and the pressure in the 
 cylinder at the commencement of the stroke is 20 lbs. 
 per square inch, the pencil will be raised one inch, or 
 if the pressure is 30 lbs., the pencil will travel 1^ in., 
 and if there is a vacuum of 20 in. in the condenser, 
 
THE INDICATOR 
 
 ra 
 
 the pencil will drop y% in. below the atmospheric line 
 for the reason that 20 in. of vacuum corresponds to a 
 
 IMPROVED TABOR INDICATOR WITH OUTSIDE CONNECTED SPRING. 
 A.SHCROFT MFG. CO., N. Y. 
 
 pressure of about. 10 lbs. less than atmospheric pressure 
 or an absolute pressure of about 4 lbs. If a 60 spring 
 is used a pressure of 60 lbs. in the engine cylinder will 
 
174 
 
 ENGINEERING 
 
 be required to raise the pencil one inch, or 90 lbs. to 
 raise it \y 2 in. 
 
 The Ashcroft Manufacturing Co. of New York, 
 makers of the well known Tabor indicator, have 
 recently introduced a new feature in indicator work by- 
 connecting the spring on top of the cylinder and in 
 plain view of the operator. This arrangement removes 
 the spring from the influence of direct contact with the 
 
 figure 40. 
 
 steam, and it is subject only to the temperature of the 
 surrounding atmosphere. It is claimed that as a result 
 of this the accuracy of the spring is insured and that 
 no allowance need to be made in its manufacture for 
 expansion caused by the high temperature to which it 
 is subject when located within the cylinder. Another 
 good feature of this design is, that the spring can be 
 easily removed without disconnecting any one part of 
 the instrument in case it is desired to change springs. 
 
THE INDICATOR 
 
 175 
 
 A cut of the improved instrument is herewith pre- 
 sented. 
 
 Fig. 39 is a sectional view of the American Thomp- 
 son improved indicator. Fig. 40 shows the spring. 
 Fig. 41 is a three way cock for attaching the indicator 
 to thecylinder. 
 
 Reducing Mechanism. Probably the only practically 
 universal mechanism for reducing the motion of the 
 crosshead is the reducing wheel, a device in which, by 
 
 FIGURE 41. 
 
 the employment of gears and pulleys of different diam- 
 eters, the motion is reduced to within the compass of 
 the drum, and the device is applicable to almost any 
 make of engine, whether of high or low speed. Some 
 makers of indicators attach the reducing wheel directly 
 to the indicator, thus producing a neat and very con- 
 venient arrangement. Fig. 42 shows the indicator 
 complete with reducing wheel attached. 
 
 One of the most accurate and easily applied devices 
 for reducing the motion of the piston is the wooden 
 
176 
 
 ENGINEERING 
 
 pendulum in its various forms. (See Figs. 43, 44 and 
 45.) It consists of a flat strip of pine or other light 
 wood of a length net les , than one ard a half times the 
 stroke of the engine, a:id if made longer it will be 
 better. It should be from % to ]/b in. thick and have 
 an average width of abjut4in. If the engine to be 
 
 FIGURE 42. 
 
 indicated is horizontal the bar or pendulum is to be 
 pivoted at a fixed point directly above and in line with 
 the side of the crosshead, as that is generally the most 
 convenient point of attachment. The pivot can be 
 fixed to a permanent standard bolted to the frame of 
 the engine (Fig. 46), or it may be secured to the ceil- 
 
THE INDICATOR 
 
 177 
 
 ing of the room or even to a post fastened to the floor. 
 It the engine is vertical the bar can be pivoted to the 
 wall of the room or a strong post firmly secured to the 
 floor. The .connection with the crosshead is best 
 accomplished by means of a short bar or link. A con- 
 venient length for this bar is one-half the stroke of the 
 engine. To locate the correct point for the pivot, 
 
 figure 43. 
 
 assuming the length of the short bar to be one-half the 
 length of the stroke, proceed as follows: 
 
 Place the engine on the center with the crosshead at 
 the end of the stroke towards the crank. Then having 
 previously bored a hole for the pivot in one end of the 
 pendulum bar and in the other end a hole for connect- 
 ing with the link, suspend the pendulum by a tem- 
 porary pin, as a large wood screw, directly above and in 
 
178 
 
 ENGINEERING 
 
 line with the stud or bolt hole which has previously 
 been tapped into the crosshead at any convenient 
 point. The pendulum should be temporarily sus- 
 pended at such a height that when it hangs perpendic- 
 ular the hole in its lower end will line up accurately 
 with the hole or stud in the crosshead. Now swing 
 the pendulum in either direction a distance equal to 
 the length of the link (one-half the stroke of the 
 
 FIGURE 44. 
 
 engine) from the crosshead connection and note the 
 distance that the bottom hole is above a straight edge 
 laid horizontal and in line with the center of the stud 
 in the crosshead. This will give the total vibration of the 
 free end of the link from a line parallel with the line 
 of the engine and the permanent location of the pivot 
 should be one-half of this distance below the tem- 
 porary point of suspension. This will allow the link 
 
THE INDICATOR 
 
 179 
 
 to vibrate equally above and below the center of its 
 connection with the crosshead. Fig. 47 shows a com- 
 plete connection of this character. 
 
 Sometimes the end is slotted and thus directly con- 
 nected to the stud in the crosshead, dispensing with 
 the link. In this case it is necessary to locate the 
 pivot at a point perpendicular to the center of travel 
 of the stud in the crosshead. (See Fig. 43.) The link 
 
 FIGURE 45. 
 
 connection is to be preferred, however. The cord can 
 be attached to the pendulum at a point near the pivot 
 which will give the desired length of diagram. This 
 point can be determined by multiplying the length of 
 the pendulum by the desired length of diagram and 
 dividing the product by the stroke. For convenience 
 these terms should be expressed in inches. Thus, 
 assume stroke of engine to be 48 in., length of pendu- 
 
180 
 
 ENGINEERING 
 
 lum \y 2 times length of stroke = 72 in. Desired length 
 of diagram 3 in. Then 72 x 3 -5- 48 = 4.5 in., which is 
 
 figure 46. 
 
 the distance from center of pivot to point of connec- 
 tion for the cord. This can be either a small hofe 
 
 FIGURE 47. 
 
THE INDICATOR 
 
 181 
 
 bored through the pendulum or a wood screw to which 
 the ccrd can be attached. From this point the cord 
 should be led over a guide pulley located at such 
 height that when the pendulum is vertical the cord 
 will leave it at right angles. After leaving the guide 
 pulley the cord can be carried at any angle desired. 
 The Brumbo Pulley. Another method of connecting 
 the cord to the pendulum is to run the cord over a 
 grooved segment, called a Brumbo pulley, connected 
 
 FIGURE 48. 
 
 with the pivoted end of the pendulum (Fig. 48), but 
 with this arrangement, owing to the curved travel of 
 the pendulum, there is greater liability to distortion of 
 the diagram than in the first method. In case it is 
 desired to use the Brumbo pulley, the radius of the 
 segment can be found by the same process as that 
 used for finding the point for connecting the cord 
 directly to the pendulum. 
 
 One of the neatest and most easily applied devices 
 
182 
 
 ENGINEERING 
 
 for reducing the motion of the crosshead is the panto- 
 graph. (See Fig. 49.) No dimensions are essential 
 except that it shall be made reasonably strong of some 
 light, tough variety of wood, and that the pins and 
 holes be nicely fitted to each other so that while the 
 movement may be free there shall at the same time 
 not be too much lost motion. The pantograph should 
 be of such capacity that it will just close up nicely 
 when the engine is at mid stroke and open out nicely 
 when at its extreme travel. The two ends, C and D, 
 
 figure 49. 
 
 are each to be fitted with a pin extending through far 
 enough so that pin C can be hooked into a hole or 
 socket on the crosshead, while pin D rests in a socket 
 in the top of a post secured to the floor at a 
 point opposite the center of travel of the crosshead 
 and of such height as will allow the pantograph to lie 
 in a horizontal position. Also the distance of the post 
 from the guides must be adjusted so as to allow the • 
 device to close up at mid stroke and open out at full 
 stroke without any straining of the parts. The point 
 F of connection for the cord will always have a motion 
 
THE INDICATOR 
 
 183 
 
 parallel with, and simultaneous with, that of the cross- 
 head; the pin to which the cord is attached can be set 
 in any one of the holes that will give the desired 
 length for the diagram. The motion given by this 
 device is accurate, although it may become necessary 
 
 CROSBY REDUCING WHEEL. 
 
 in some cases, especially with long stroke engines, to 
 introduce a guide pulley to carry the cord from the 
 pantograph. 
 
 Attaching the Indicator. The cylinders of most 
 engines at the present time are drilled and tapped for 
 
184 ENGINEERING 
 
 indicator connections before they leave the shop, 
 which is eminently proper, as no engine builder, or 
 purchaser either, should be satisfied with the perform- 
 ance of a new engine until after it has been accurately, 
 tested and adjusted with the indicator. 
 
 The main requirements in these connections are that 
 the holes shall not be drilled near the bottom of the 
 cylinder where water is likely to find its way into the 
 pipes, neither should they be in a location where 
 the inrush of steam from the ports will strike them 
 directly, nor where the edge of the piston is liable to 
 partly cover them when at its extreme travel. An 
 engineer before he undertakes to indicate an engine 
 should satisfy himself that all these requirements are 
 fulfilled. Otherwise he is not likely to' obtain a true 
 diagram. The cock supplied with the indicator is 
 threaded for one-half inch pipe and unless the engine 
 has a very long stroke it is the practice to bring the 
 two end connections together at the side or top of the 
 cylinder and at or near the middle of its length, where 
 they can be connected to a three way cock. The pipe 
 connections should be as short and as free from elbows 
 as possible in order that the steam may strike the 
 indicator piston as nearly as possible at the same 
 moment that it acts upon the engine piston. 
 
 The work of taking diagrams is very much simplified 
 by having both ends of the cylinder connected to one 
 common tee or a three way cock as above described, 
 but for long stroke engines there should be two indi- 
 cators, one for each end and the diagrams should be 
 taken simultaneously if it is desired to adjust the 
 valves by the indicator. In this case an assistant 
 would be required to manipulate one of the instru- 
 ments. 
 
TTTE INDICATOR 185 
 
 The pipes should always be thoroughly blown out 
 by allowing- the steam to blow through the open cock 
 during several revolutions of the engine, before con- 
 necting the indicator. If this is not done there is a 
 moral certainty that grit and dirt will get into the 
 cylinder of the indicator, where the pressure of the 
 least atom of grit will cause the delicate instrument to 
 work badly. 
 
 Selecting a Spring. The proper number of spring to 
 use depends upon the boiler pressure in the case of an 
 automatic cut off engine, but for an engine with a 
 fixed cut off and throttling governor the number of the 
 spring to be selected will depend upon the initial 
 pressure in the cylinder. A convenient rule is to 
 select a spring numbered one-half as high as the pres- 
 sure; for instance, if the boiler pressure is 80 lbs., use a 
 No. 40 spring, which will give a diagram 2 in. in height. 
 
 Care of the Instrument. The indicator should be 
 cleaned and oiled both before and after using. The 
 best material for wiping it is a clean piece of old soft 
 muslin of fine texture, as there is not so much liability 
 of lint sticking to or getting into the small joints. Use 
 good clock oil for the joints and springs, and before 
 taking diagrams it is a good practice to rub a small 
 portion of cylinder oil on the piston and the inside of 
 the cylinder, but when about to put the instrument 
 away these should be oiled with clock oil also. None 
 but the best cord should be used for connecting the 
 paper drum with the reducing motion, as a cord that is 
 liable to stretch will cause trouble. Suitable cord and 
 also blank diagrams can generally be secured from 
 firms manufacturing and selling indicators. After the 
 indicator has been screwed on to the cock connecting 
 with the pipe, the cord must be adjusted to the proper 
 
180 ENGINEERING 
 
 length before hooking it on to the drum. This must 
 be done while the engine is running, by taking hold 
 of the loop on the cord connected with the reducing 
 motion with one hand, and with the other hand grasp 
 the hook on the short cord attached to the drum, then 
 by holding the two ends near each other during a revo- 
 lution or two it will be seen whether the long cord 
 needs to be shortened or lengthened. 
 
 The length of the diagram is determined by the 
 point of connection of the cord to the pendulum as has 
 been heretofore explained. Care should be exercised 
 in placing the paper on the drum to see that it is 
 stretched tight and firmly held by the clips. The 
 pencil point having been first sharpened by rubbing it 
 on a piece of fine emery cloth or sand paper should be 
 adjusted by means of the pencil stop with which all 
 indicators should be provided, so that it will have just 
 sufficient bearing against the paper to make a fine, 
 plain mark. If the pencil bears too hard on the paper 
 it will cause unnecessary friction and the diagram will 
 be distorted. The best method of ascertaining this 
 fact and also whether the travel of the drum is equally 
 divided between the stops, is to place a blank diagram 
 on the drum, connect the cord and while the engine 
 makes a revolution hold the pencil against the paper. 
 Then unhook the cord, remove the paper and if the 
 travel of the drum is not divided correctly it can be 
 changed. 
 
 Having thus arranged all the preliminary details, 
 place a fresh blank on the drum, being careful to keep 
 the pencil out of contact with it, connect the cord, 
 open the cock admitting steam to the indicator and 
 after the pencil has made a few strokes to allow the 
 cylinder to become warmed up, then gently swing it 
 
THE INDICATOR 187 
 
 around to the paper drum and hold it there while the 
 engine makes a complete revolution. Then move the 
 pencil clear of the paper, close the cock and unhook 
 the cord. Now trace the atmospheric line by holding 
 the pencil against the paper while the drum is revolved 
 by hand. This method of tracing the atmospheric line 
 is preferable to that of tracing it immediately after 
 closing the cock and while the drum is still being 
 moved by the engine, for the reason that there is not 
 so much liability of getting the atmospheric line too 
 high owing to the presence of a slight pressure of 
 steam remaining under the indicator piston for a 
 second or two just after closing the cock; also the line 
 drawn by hand will be longer than one drawn while 
 the drum is moved by the motion of the engine and 
 will therefore be more readily distinguished from the 
 line of back pressure. 
 
 Having secured a truthful diagram, it now remains 
 to take as many as are desired, and if the object is to 
 set the valves of the engine, the diagrams from each 
 end of the cylinder should follow each other as quickly 
 as possible in order that the conditions of load and 
 steam pressure may be the same. When the indicator 
 is connected so that diagrams can be taken from both 
 ends without changing it, the above conditions can 
 generally be realized. But if diagrams can only be 
 taken from one end at a time, the only way to arrive 
 at correct conclusions in relation to the adjustment of 
 the valves will be to see that the boiler pressure is 
 practically the same at the time of taking diagrams 
 from either end and that the position of the governor 
 is also the same, assuming that the load on the engine 
 is practically constant. This applies of course to an 
 automatic cut off. 
 
188 ENGINEERING 
 
 As soon as the diagrams are taken the following 
 data should be noted upon them: The end of the 
 cylinder, whether head or crank; boiler pressure; and 
 time when taken. Other data can be added after- 
 wards. If the engine is an automatic cut off of the 
 corliss type and the point of cut off on one end does 
 not coincide with the other, the difference can gener- 
 ally be adjusted while the engine is running by chang- 
 ing the length of the rods extending from the governor 
 to the tripping device. These rods are, or should be, 
 fitted with right and left threads on the ends for this 
 purpose. Any changes in the valves, such as giving 
 them more lead, compression, etc., and which neces- 
 sitates changing the length of the reach rods connect- 
 ing them with the wrist plate, will have to be made 
 while the engine is stopped, although with slow speed 
 engines and the exercise of caution it is possible to 
 make alterations in these rods while the engine is 
 running. 
 
 Questions 
 
 1. What instrument is a necessary part of an 
 engineers outfit? 
 
 2. Who invented the indicator? 
 
 3. Name the principles governing the action of the 
 • indicator. 
 
 4. What will a truthful diagram from a steam 
 cylinder show? 
 
 5. Does the steam act upon both sides of the indi- 
 cator piston? 
 
 6. What does the atmospheric line show? 
 
 7. Is this line important in the study of the dia- 
 gram ? 
 
 8. Where should the line of back pressure appear in 
 a diagram from a non-condensing engine? 
 
THE INDICATOR 189 
 
 9. Where will the line of back pressure appear on a 
 diagram from a condensing engine? 
 
 10. What controls the length of stroke of the indi- 
 cator piston? 
 
 11. What does the number on the spring mean? 
 
 12. What is one of the most convenient appliances 
 for reducing the motion of the crosshead within the 
 compass of the drum? 
 
 13. What other appliances besides the reducing 
 wheel may be employed for this purpose? 
 
 14. What is a Brumbo pulley? 
 
 15. What are the main requirements in indicator 
 connections? 
 
 16. What should be done with the pipes before 
 attaching the indicator? 
 
 17. Upon what does the selection of the scale of 
 spring depend? 
 
 18. What is a convenient rule to be observed in the 
 selection of a spring? 
 
 19. What is the best method of tracing the atmos- 
 pheric line? 
 
 20. What data should be noted on the diagram as 
 soon as it is taken? 
 
CHAPTER VIII 
 
 DEFINITIONS AND TABLES 
 
 Definition of words, terms and phrases — Table of hyperbolic 
 logarithms — Table of areas and circumferences of circles. 
 
 In order to facilitate the study and analysis of indi- 
 cator diagrams, the following definitions of technical 
 terms, some of which have already been explained in 
 another part of this book, are here given. 
 
 Absolute pressure. Pressure reckoned from a perfect 
 vacuum. It equals the boiler pressure plus the atmos- 
 pheric pressure. 
 
 Boiler pressure or gauge pressure. Pressure above the 
 atmospheric pressure as shown by the steam gauge. 
 
 Initial pressure. Pressure in the cylinder at the be- 
 ginning of the stroke. 
 
 Terminal pressure (T. P.). The pressure that would 
 exist in the cylinder at the end of the stroke provided 
 the exhaust valve did not open until the stroke was 
 entirely completed. It may be graphically illustrated 
 on the diagram by extending the expansion curve by 
 hand to the end of the stroke. It is found theoretically 
 by dividing the pressure at point of cut off by the ratio 
 of expansion. Thus, absolute pressure at cut off = ioo 
 lbs., ratio of expansion = 5; then 100 + 5 = 20 lbs., abso- 
 lute terminal pressure. 
 
 Mean effective pressure (M. E. P.). The average 
 pressure acting upon the piston throughout the stroke 
 minus the back pressure. 
 
 Back pressure. Pressure which tends to retard the 
 forward stroke of the piston. Indicated on the dia- 
 gram from a non-condensing engine by the height of 
 190 
 
DEFINITIONS AND TABLES 191 
 
 HjC back pressure line above the atmospheric line. In 
 a condensing engine the degree of back pressure is 
 shown by the height of the back pressure line above 
 an imaginary line representing the pressure in the 
 condenser corresponding to the degree of vacuum in 
 inches, as shown by the vacuum gauge. 
 
 Total or absolute back pressure, in either a condensing 
 or non-condensing engine, is that indicated on the 
 diagram by the height of the line of back pressure 
 above the line of perfect vacuum. 
 
 Ratio of expansion. The proportion that the volume 
 of steam in the cylinder at point of release bears to 
 the volume at cut off. Thus, if the point of cut off is 
 at one-fifth of the stroke, and release does not take 
 place until the end of the stroke, the ratio of expan- 
 sion, or in other words, the number of expansions, is 
 5. When the T. P. is known the ratio of expansion 
 may be found by dividing the initial pressure by 
 the T. P. 
 
 Wire drawing. When through insufficiency of valve 
 opening, contracted ports, or throttling governor, the 
 steam is prevented from following up the piston at full 
 initial pressure until the point of cut off is reached, it 
 is said to be wire drawn. It is indicated on the dia- 
 gram by a gradual inclination downwards of the steam 
 line from the admission line to the point of cut off. 
 Too small a steam pipe from boiler to engine will also 
 cause wire drawing and fall of pressure. 
 
 Conde?iser pressure may be defined as the pressure 
 existing in the condenser of an engine, caused by the 
 lack of a perfect vacuum. As, for instance, with a 
 vacuum of 25 in. there will still remain the pressure 
 due to the 5 in. which is lacking. This will be about 
 2.5 lbs. 
 
VM ENGINEERING 
 
 Vacuum. That condition existing within a closed 
 vessel from which all matter, including air, has been 
 expelled. It is measured by inches in a column of 
 mercury contained within a glass tube a little over 30 
 in. in height, having its lower end open and immersed 
 in a small open vessel filled with mercury. The upper 
 end of the glass tube is connected with the vessel in 
 which the vacuum is to be produced. When no 
 vacuum exists the mercury will leave the tube and fill 
 the lower vessel. When a vacuum is maintained in 
 the condenser, or other vessel, the mercury will rise in 
 the glass tube to a height corresponding to the degree 
 of vacuum. If the mercury rises to the height of 30 
 in. it indicates a perfect vacuum, which means the 
 absence of all pressure within the vessel, but this con- 
 dition is never realized in practice; the nearest 
 approach to it being about 28 in. 
 
 For purposes of convenience the mercurial vacuum 
 gauge is not generally used, it having been replaced 
 by the Bourdon spring gauge, although the mercury 
 gauge is used for testing. 
 
 The vacuum in a condenser is generally maintained 
 by an air pump, although it can be produced and 
 maintained by the mere condensation of the steam as 
 it enters the condenser by allowing a spray of cold 
 water to strike it. The steam when it first enters the 
 condenser drives out the air and the vessel is filled 
 with steam which, when condensed, occupies about 
 1,600 times less space than it did before being con- 
 densed, hence a partial vacuum is produced. 
 
 While the vacuum in a condenser cannot be consid- 
 ered as power at all, yet it occupies the anomalous 
 position of increasing, by its presence, the capacity of 
 the engine for doing work. This is owing to the fact 
 
DEFINITIONS AND TABLES 193 
 
 that the atmospheric pressure or resistance which is 
 always ahead of the piston in a non-condensing engine 
 is, in the case of a condensing engine, removed to a 
 degree corresponding to the height of the vacuum, thus 
 making available just so much more of the pressure 
 behind the piston. Thus, if the average steam pres- 
 sure throughout the stroke is 30 lbs. and there is a 
 vacuum of 26 in. maintained in the condenser, there 
 will be 13 lbs. of resistance per square inch removed 
 from in front of the piston, thus making available 
 30+ 13 = 43 lbs. pressure per square inch. 
 
 Absolute zero has been fixed by calculation at 461. 2° 
 below the zero of the Fahrenheit scale. 
 
 Piston displacement. The space or volume swept 
 through by the piston in a single stroke. Found by 
 multiplying thearea of piston by length of stroke. 
 
 Piston clearance. The distance between the piston 
 and cylinder head when the piston is at the end of the 
 stroke. 
 
 Steam clearance, ordinarily termed clearance. The 
 space between the piston at the end of the stroke and 
 the valve face. It is reckoned in per cent, of the total 
 - piston displacement. 
 
 Horse power (H. P.). 33,000 pounds raised one foot 
 high in one minute of time. 
 
 Indicated horse power {I. H. P.). The horse power 
 as shown by the indicator diagram. It is found as 
 follows: 
 
 Area of piston in square inches x M. E. P. x piston 
 speed in feet- 33,000. 
 
 Piston speed. The distance in feet traveled by the 
 piston in one minute. It is the product of twice the 
 length of stroke expressed in feet multiplied by the 
 number of revolutions per minute. 
 
104 ENGINEERING 
 
 R. P. M. Revolutions per minute. 
 
 Net horse pozver. I. H. P. minus the friction of the 
 engine. 
 
 Compressio?i. The action of the piston as it nears the 
 end of the stroke, in reducing the volume and raising 
 the pressure of the steam retained in the cylinder 
 ahead of the piston by the closing of the exhaust 
 valve. 
 
 Boyle's or Mariotte s law of expanding gases. "The 
 pressure of a gas at a constant temperature varies 
 inversely as the space it occupies." Thus, if a given 
 volume of gas is confined at a pressure of 50 lbs. per 
 square inch and it is allowed to expand to twice its 
 volume, the pressure will fall to 25 lbs. per square inch. 
 
 Adiabatic curve. A curve representing the expansion 
 of a gas which loses no heat while expanding. Some- 
 times called the curve of no transmission. 
 
 Isothermal curve. A curve representing the expan- 
 sion of a gas having a constant temperature but 
 partially influenced by moisture, causing a variation in 
 pressure according to the degree of moisture or satura- 
 tion. It is also called the theoretical expansion 
 curve. 
 
 Expansion curve. The curve traced upon the dia- 
 gram by the indicator pencil showing the actual 
 expansion of the steam in the cylinder. 
 
 First law of thermody?iamics. Heat and mechanical 
 energy are mutually convertible. 
 
 Power. The rate of doing work, or the number of 
 foot pounds exerted in a given time. 
 
 Unit of work. The foot pound, or the raising of one 
 pound weight one foot high. 
 
 First law of motion. All bodies continue either in a 
 state of rest or of uniform motion in a straight line, 
 
DEFINITIONS AND TABLES 195 
 
 except in so far as they may be compelled by 
 impressed forces to change that state. 
 
 Work. Mechanical force or pressure cannot be con- 
 sidered as work unless it is exerted upon a body and 
 causes that body to move through space. The product 
 of the pressure multiplied by the distance passed 
 through and the time thus occupied is work. 
 
 Momentum. Force possessed by bodies in motion, 
 or the product of mass and density. 
 
 Dynamics. The science of moving powers or of 
 matter in motion, or of the motion of bodies that 
 mutually act upon each other. 
 
 Force. That which alters the motion of a body, or 
 puts in motion a body that was at rest. 
 
 Maximum theoretical duty of steam is the product of 
 the mechanical equivalent of heat, viz., 778 ft. lbs. 
 multiplied by the total heat units in a pound of steam. 
 Thus, in one pound of steam at 212 reckoned from 32 
 the total heat equals 1,146.6 heat units. Then 
 778 x 1,146.6 equals 892,054.8 ft. lbs. = maximum duty. 
 
 Steam efficiency may be expressed as follows: 
 
 Heat converted into useful work . . „ . 
 
 i =^ : — = and maximum effic- 
 
 Heat expended 
 
 iency can only be attained by using steam at 
 
 as high an initial pressure as is consistent with safety 
 
 and at as large a ratio of expansion as possible. The 
 
 percentage of efficiency of steam used at atmospheric 
 
 pressure in a non-expansive engine is very low; as, for 
 
 instance, the heat expended in the evaporation of one 
 
 pound of water at 32 into steam at atmospheric 
 
 pressure = 1,146.6 heat units, and the volume of steam 
 
 so generated = 26.36 cu. ft. 
 
 One cubic foot of steam at 212 contains energy 
 
 equal to 144x14.7 = 2,116,8 ft. lbs., and 26.36 cu. 
 
196 ENGINEERING 
 
 ft. = 2, 1 16.8 x 26.36 = 55,798.84 ft. lbs., which divided by 
 the mechanical equivalent of heat, viz., 778 ft. 
 lbs. = 71.72 heat units, available for useful work. The 
 per cent, of efficiency therefore is 71 fi46 6°° = 6.28 per 
 cent. But suppose the initial pressure to have been 
 200 lbs. absolute, and that the steam is allowed to 
 expand to thirty times its original volume. The heat 
 expended in evaporating a pound of water at 32 into 
 steam at 200 lbs. absolute pressure = 1,198.3 heat units, 
 and the volume of steam so generated = 2.27 cu. ft. 
 The average pressure during expansion would be 29.34 
 lbs. per square inch and the volume when expanded 
 thirty times would equal 2.27 x 30 = 68. 1 cu. ft. 
 
 One cubic foot of steam at 29.34 lbs. pressure equals 
 144 x 29.34 = 4,224.96 ft. lbs., and 68. 1 cu. ft. will equal 
 4224.96x68.1=287,719.7 ft. lbs. of energy, which 
 divided by the equivalent, 778, equals 370.2 heat units, 
 and the per cent, of efficiency will be 37 ^ 9 g 3 10 ° = 30.8 
 per cent. 
 
 Engine efficiency. If the engine is considered merely 
 
 as a machine for converting into useful work the heat 
 
 energy in the steam regardless of the cost of fuel, its 
 
 efficiency may be expressed as follows: 
 
 Heat converted into useful work 
 
 Total heat received in the steam 
 
 Example. Assume an engine to be receiving steam 
 at 95 lbs. absolute pressure, that the consumption of 
 dry steam per horse power per hour equals 20 lbs., that 
 the friction of the engine amounts to 15 per cent., and 
 that the temperature of the feed water is raised from 
 6o° to 170 by utilizing a portion of the exhaust. 
 
 In a pound of steam at 95 lbs. absolute there are 
 1,180.7 heat units, and in a pound of water at 170 there 
 
DEFINITIONS AND TABLES 197 
 
 are 138.6 units of heat, but 28.01 of these heat units 
 were in the water at its initial temperature of 6o°. 
 Therefore the total heat added to the water by the 
 exhaust steam equals 138.6 -28.01 = no. 59 heat units, 
 and the total heat in each pound of steam to be 
 charged up. to the engine is 1,180.7 - 1 10.59 = 1,070. 1 1, 
 and the total for each horse power developed per hour 
 will be 1,070. n x 20 - 21,402.2 heat units. 
 
 A horse power equals 33,000 ft. lbs. per minute, or 
 sixty times 33,000 = 1,980,000 ft. lbs. per hour. From 
 this must be deducted 15 per cent, for friction of the 
 engine, leaving 1,683,000 ft. lbs. for useful work. 
 Dividing this by the equivalent, viz., 778 ft. lbs., 
 gives 2,163.2 heat units as the heat converted into one 
 horse power of work in one hour, and the percentage 
 
 of efficiency of the engine will be ^f^l™ = iai P er 
 cent. 
 
 Efficiency of the plant as a whole includes boiler and 
 engine efficiency and is to be figured upon the basis of 
 Heat converted into useful work 
 Calorific or heat value of fuel 
 
 Horse power constant of an engine is found by multi- 
 plying the area of the piston in square inches by the 
 speed of the piston in feet per minute and dividing the 
 product by 33,000. It is the power the engine would 
 develop with one pound mean effective pressure. To 
 find the horse power of the engine, multiply the M. 
 E. P. of the diagram by this constant. 
 
 Logarithms. A series of numbers having a certain 
 relation to the series of natural numbers, by means of 
 which many arithmetical operations are made com- 
 paratively easy. The nature of the relation will be 
 understood by considering two simple series, such as 
 the following, one proceeding from unity in geomet- 
 
198 ENGINEERING 
 
 rical progression and the other from o in arithmetical 
 progression: 
 
 Geom. series, I, 2, 4, 8, 16, 32, 64, 128, 256, 512, etc. 
 
 Arith. series, o, 1, 2, 3, 4, 5, 6, 7, 8, 9, etc. 
 
 Here the ratio of the geometrical series is 2 and any 
 term in the arithmetical series expresses how often 2 
 has been multiplied into 1 to produce the correspond- 
 ing term of the geometrical series. Thus, in proceeding 
 from 1 to 32 there have been 5 steps or multiplications 
 by the ratio 2; in other words, the ratio of 32 to 1 is 
 compounded 5 times of the ratio of 2 to 1. The above 
 is the basic principle upon which common logarithms 
 are computed. 
 
 Hyperbolic logarithms. Used in figuring the M. E. P. 
 of a diagram from the ratio of expansion and the 
 initial pressure. Thus, hyperbolic logarithm of ratio 
 of expansion -f 1 multiplied by absolute initial pres- 
 sure and divided by ratio of expansion = mean forward 
 pressure. From this deduct total back pressure and 
 the remainder will be mean effective pressure. The 
 hyperbolic logarithm is found by multiplying the com- 
 mon logarithm by the constant 2.302585. Table 8 
 gives the hyperbolic logarithms of numbers usually 
 required in calculations of the above nature. 
 
 Steam co?isnmption per horse power per hour. The 
 weight in pounds of steam exhausted into the atmos- 
 phere or into the condenser in one hour divided by the 
 horse power developed. It is determined from the 
 diagram by selecting a point in the expansion curve 
 just previous to the opening of the exhaust valve and 
 measuring the absolute pressure at that point. Then 
 the piston displacement up to the point selected, plus 
 the clearance space, expressed in cubic feet, will give 
 the volume of steam in the cylinder, which multiplied 
 
DEFINITIONS AND TABLES 
 
 199 
 
 Table 8. 
 
 Hyperbolic Logarithms. 
 
 No. 
 
 Log. 
 
 No. 
 
 Log. 
 
 No. 
 
 Log. 
 
 No. 
 
 Log. 
 
 No. 
 
 Log. 
 
 I.OI 
 
 . OO99 
 
 3.00 
 
 1 .0986 
 
 5.00 
 
 I . 6094 
 
 7.0c 
 
 1-9459 
 
 9.00 
 
 2. 1972 
 
 i 05 
 
 O.0487 
 
 3.05 
 
 1. 1151 
 
 5.05 
 
 1 .6194 
 
 7.05 
 
 I.9530 
 
 9-05 
 
 2.2028 
 
 1 . 10 
 
 0.0953 
 
 3- 10 
 
 I.I34I 
 
 5-IO 
 
 1.6292 
 
 7.IC 
 
 I .9600 
 
 9. 10 
 
 2.2083 
 
 1. 15 
 
 0.1397 
 
 3.15 
 
 1. 1474 
 
 5.15 
 
 I . 6390 
 
 7.15 
 
 I. 967 1 
 
 9-15 
 
 2.2137 
 
 1.20 
 
 0.1823 
 
 3.20 
 
 1 .1631 
 
 5.20 
 
 I.6486 
 
 7 .2C 
 
 I . 9740 
 
 9.20 
 
 2.2192 
 
 1.25 
 
 0.2231 
 
 3-25 
 
 1. 1786 
 
 5.25 
 
 I.6582 
 
 7.25 
 
 I .9810 
 
 9.25 
 
 2.2246 
 
 1.30 
 
 0.2623 
 
 3.30 
 
 1. 1939 
 
 5.30 
 
 I.6677 
 
 7.30 
 
 L9879 
 
 9.3o 
 
 2.23IO 
 
 i-35 
 
 0.3001 
 
 3-35 
 
 1 .2090 
 
 5-35 
 
 I. 6771 
 
 7.35 
 
 L9947 
 
 9-35 
 
 2.2354 
 
 1.40 
 
 O.3364 
 
 3.40 
 
 1.2238 
 
 5.40 
 
 I.6864 
 
 7.4c 
 
 2 . OOI 5 
 
 9.40 
 
 2 . 2407 
 
 1-45 
 
 0.37I5 
 
 3-45 
 
 I.2384 
 
 5-45 
 
 I.6956 
 
 7.45 
 
 2.00I8 
 
 9-45 
 
 2 . 2460 
 
 1.50 
 
 O.4054 
 
 3.50 
 
 I.2527 
 
 5.50 
 
 I . 7047 
 
 7.50 
 
 2.OI49 
 
 9 -5o 
 
 2.2513 
 
 1.55 
 
 0.4382 
 
 3-55 
 
 I.2669 
 
 5-55 
 
 I. 7138 
 
 7.55 
 
 2.02I5 
 
 9-55 
 
 2.2565 
 
 1.60 
 
 O.4700 
 
 3.6o 
 
 1.2809 
 
 5.60 
 
 I.7228 
 
 7.60 
 
 2.028I 
 
 9.60 
 
 2.26l8 
 
 1.65 
 
 0.5007 
 
 3.65 
 
 1.2947 
 
 5.65 
 
 I. 7316 
 
 7.65 
 
 2.0347 
 
 9-65 
 
 2.267O 
 
 1.70 
 
 0. 5306 
 
 3 -7o 
 
 1.3083 
 
 5.7o 
 
 I • 7405 
 
 7.70 
 
 2.0412 
 
 9.70 
 
 2.2721 
 
 1-75 
 
 0.5596 
 
 3-75 
 
 I. 3217 
 
 5-75 
 
 I. 7491 
 
 7.75 
 
 2.0477 
 
 9-75 
 
 2.2773 
 
 1.80 
 
 0.5877 
 
 3.80 
 
 1.3350 
 
 5.80 
 
 1.7578 
 
 7.80 
 
 2.0541 
 
 9.80 
 
 2.2824 
 
 1.85 
 
 O.6151 
 
 3.85 
 
 i.348o 
 
 5.85 
 
 I.7664 
 
 7.85 
 
 2.0605 
 
 9-85 
 
 2.2875 
 
 1.90 
 
 0.641S 
 
 3.90 
 
 I .3610 
 
 5.90 
 
 1.7750 
 
 7.90 
 
 2.0668 
 
 9.90 
 
 2.2925 
 
 1-95 
 
 0.6678 
 
 3-95 
 
 1.3737 
 
 5-95 
 
 1.7834 
 
 7.95 
 
 2.0731 
 
 9-95 
 
 2.2976 
 
 2.00 
 
 0.6931 
 
 4.00 
 
 1.3863 
 
 6.00 1. 79 1 8 
 
 8.00 
 
 2.0794 
 
 10.00 
 
 2.3026 
 
 2.05 
 
 0.7178 
 
 4.05 
 
 1.3987 
 
 6.05 
 
 I . 8000 
 
 8.05 
 
 2.0857 
 
 10.25 
 
 2.3273 
 
 2.10 
 
 0.7419 
 
 4. 10 
 
 1. 4010 
 
 6. 10 
 
 I.8083 
 
 8.IO 
 
 2.0918 
 
 10.50 
 
 2.3514 
 
 2.15 
 
 0.7654 
 
 4.15 
 
 1.4231 
 
 6.15 
 
 I. 8164 
 
 8.15 
 
 2.0988 
 
 io.75 
 
 2.3749 
 
 2.20 
 
 O.7885 
 
 4.20 
 
 1. 4351 
 
 6.20 
 
 I.8245 
 
 8.20 
 
 2. IO4I 
 
 11 .00 
 
 2.3979 
 
 2.25 
 
 0.8110 
 
 4-25 
 
 1 . 4469 
 
 6.25 
 
 I.8326 
 
 8.25 
 
 2. II02 
 
 12.00 
 
 2.4849 
 
 2.30 
 
 0.8329 
 
 4.30 
 
 1.4586 
 
 6.30 
 
 I . 8405 
 
 8.30 
 
 2. I 162 
 
 13.00 
 
 2.5626 
 
 2-35 
 
 0.8544 
 
 4-35 
 
 1. 4701 
 
 6.35 
 
 I.8484 
 
 8.35 
 
 2. 1222 
 
 14.00 
 
 2.639O 
 
 2.40 
 
 0.8755 
 
 4.40 
 
 I. 4816 
 
 6.40 
 
 I.8563 
 
 8.40 
 
 2.1282 
 
 15.00 
 
 2.7I03 
 
 2-45 
 
 0.8961 
 
 4-45 
 
 1.4929 
 
 6.45 
 
 I . 8640 
 
 8.45 
 
 2.1342 
 
 16.00 
 
 2.7751 
 
 2.50 
 
 O.9163 
 
 4.5o 
 
 1 . 5040 
 
 6.50 
 
 I. 8718 
 
 8.50 
 
 2 . I40O 
 
 17.00 
 
 2.8332 
 
 2.55 
 
 O.9361 
 
 4.55 
 
 I.5J5I 
 
 6.55 
 
 1.8795 
 
 8.55 
 
 2.1459 
 
 18.00 
 
 2.8903 
 
 2.60 
 
 o.9555 
 
 4.60 
 
 I.5260 
 
 6.60 
 
 I.8870 
 
 8.60 
 
 2.I5I8 
 
 19.00 
 
 2 . 9444 
 
 2.65 
 
 0.9746 
 
 4.65 
 
 1.5369 
 
 6.65 
 
 I.8946 
 
 8.65 
 
 2.1576 
 
 20.00 
 
 2.9957 
 
 2.70 
 
 0.9932 
 
 4.70 
 
 1.5475 
 
 6.70 
 
 I. 902 1 
 
 8.70 
 
 2.1633 
 
 21 .00 
 
 3.0445 
 
 2-75 
 
 1.0116 
 
 4-75 
 
 1. 558i 
 
 6.75 
 
 !.9095 
 
 8.75 
 
 2. 169O 
 
 22.00 
 
 3.0910 
 
 2.80 
 
 1 .0296 
 
 4.80 
 
 1.5686 
 
 6.80 
 
 1 .9169 
 
 8.80 
 
 2.1747 
 
 23.00 
 
 3.035 5 
 
 2.85 
 
 I.0473 
 
 4.85 
 
 1.5790 
 
 6.85 
 
 1.9242 
 
 8.85 
 
 2. 1804 
 
 24.00 
 
 3.1780 
 
 2. go 
 
 1.0647 
 
 4.90 
 
 1.5892 
 
 6.90 
 
 L93I5 
 
 8.90 
 
 2.l860 
 
 25 .00 
 
 3.2189 
 
 2.95 
 
 I. 0818 
 
 4.95 
 
 1.5994 
 
 6.95 
 
 T.9387 
 
 8.95 
 
 2.I9I6 
 
 30.00 
 
 3.3782 
 
200 ENGINEERING 
 
 by the weight per cubic foot of steam at the pressure 
 as measured will give the weight of steam consumed 
 during one stroke. From this should be deducted the 
 steam saved by compression as shown by the diagram, 
 in order to get a true measure of the economy of the 
 engine. Having thus determined the weight of steam 
 consumed for one stroke, multiply it by twice the num- 
 ber of strokes per minute and by 60, which will give 
 the total weight consumed per hour. This divided by 
 the horse power will give the rate per horse power per 
 hour. 
 
 Cylinder condensatiofi a?id re evaporation. When the 
 exhaust valve opens to permit the exit of the steam 
 there is a perceptible cooling of the walls of the 
 cylinder, especially in condensing engines when a high 
 vacuum is maintained. This results in more or less 
 condensation of the live steam admitted by the open- 
 ing of the steam valve; but if the exhaust valve is 
 caused to close at the proper time so as to retain a 
 portion of the steam to be compressed by the piston on 
 the return stroke, a considerable portion of the water 
 caused by condensation will be reevaporated into steam 
 by the heat and consequent rise in pressure caused by 
 compression. 
 
 Ordinates. Parallel lines drawn at equal distances 
 apart across the face of the diagram, and perpendic- 
 ular to the atmospheric line. They serve as a guide to 
 facilitate the measurement of the average forward 
 pressure throughout the stroke, or the pressure at any 
 point of the stroke if desired. 
 
 Eccentric.. A mechanical device used in place of a 
 crank for converting rotary into reciprocating motion. 
 An eccentric is in fact a form of crank in which the 
 crank pin, corresponding to the eccentric sheave, 
 
DEFINITIONS AND TABLES 201 
 
 embraces the shaft, but owing to the great leverage at 
 which the friction between the sheave and the strap 
 acts, compared with its short turning leverage, it can 
 only be used to advantage for the purpose named 
 above. 
 
 Eccentric throw is the distance from the center of the 
 eccentric to the center of the shaft. This definition 
 also applies to the term "radius of eccentricity." 
 
 Eccentric position. The location of the highest point 
 of the eccentric relative to the center of the crank pin, 
 measured or expressed in degrees. 
 
 Angular advance. The distance that the high point 
 of the eccentric is set ahead of a line at right angles 
 with the crank. In other words, the lap angle plus 
 the lead angle. If a valve had neither lap nor lead, 
 the position of the high point of the eccentric would 
 be on a line at right angles with the crank; as for 
 instance, the crank being at o° the eccentric would 
 stand at 90 . 
 
 Valve travel. The distance covered by the valve in 
 its movement. It equals twice the throw of the eccen- 
 tric. This refers to engines having a fixed cut off. In 
 the case of an engine with a variable automatic cut off 
 the travel of the cut off valve is regulated by the gov- 
 ernor. 
 
 Lap. The amount that the ends of the valve project 
 over the edges of the ports when the valve is at mid 
 travel. 
 
 Outside or steam lap. The amount that the end of 
 the valve overlaps or projects over the outside edge of 
 the steam port. 
 
 * Inside lap. The lap of the inside or exhaust edge of 
 the valve over the inside edge of the port. 
 
 Lead. The amount that the port is open when the 
 
202 ENGINEERING 
 
 crank is on the dead center. The object of giving a 
 valve lead is to supply a cushion of live steam which, 
 in conjunction with that already confined in the clear- 
 ance space by compression, shall serve to bring the 
 moving parts of the engine to rest quietly at the end 
 of the stroke, and also quicken the action of the piston 
 in beginning the return stroke. 
 
 Compression. Closing of the exhaust passage before 
 the steam is entirely exhausted from the cylinder. 
 A certain quantity of steam is thus compressed into 
 the clearance space. 
 
 Throttling governor. Used to regulate the speed of 
 engines having a fixed cut off. The governor controls 
 Ihe position of a valve in the steam pipe, opening or 
 closing it according as the engine needs more or less 
 steam in order to maintain a regular speed. 
 
 Automatic or variable cut off. In engines of this type 
 the full boiler pressure is constantly in the valve chest 
 and the speed of the engine is regulated by the gov- 
 ernor controlling the point of cut off, causing it to take 
 place earlier or later according as the load on the 
 engine is lighter or heavier. 
 
 Fixed cut off. This term is applied to engines in 
 which the point of cut off remains the same regardless 
 of the load, the speed being regulated by a throttling 
 governor as explained above. 
 
 Isochronal or shaft governor. This device in which 
 the centrifugal and centripetal forces are utilized, as 
 in the fly ball governor, is generally applied to auto- 
 matic cut off engines having reciprocating or slide 
 valves. It is attached to the crank shaft and its func- 
 tion is to change the position of the eccentric, which 
 is free to move across the shaft within certain pre- 
 scribed limits, but is at the same time attached to the 
 
ENGINEERING 
 
 203 
 
 Table 9. 
 Areas and Circumferences of Circles. 
 
 Diam. 
 
 Area. 
 
 Circum. 
 
 Diam. 
 
 Area. 
 
 Circum. 
 
 Diam. 
 
 Area. 
 
 Circum. 
 
 •25 
 
 .049 
 
 .7854 
 
 15.5 
 
 18S.692 
 
 48.694 
 
 31 
 
 754.769 
 
 97.389 
 
 • 5 
 
 .1963 
 
 1.5708 
 
 16 
 
 201.062 
 
 50.265 
 
 31-25 
 
 766.992 
 
 98.175 
 
 1.0 
 
 .7854 
 
 3.1416 
 
 16.25 
 
 207.394 
 
 5L05I 
 
 3i-5 
 
 799.3I3 
 
 98.968 
 
 1-25 
 
 1. 2271 
 
 3.9270 
 
 16.5 
 
 213.825 
 
 51.836 
 
 32 
 
 804.249 
 
 100.53 
 
 1.5 
 
 1. 7671 
 
 4.7124 
 
 17 
 
 226.980 
 
 53.407 
 
 32.25 
 
 816.86 
 
 101.31 
 
 2 
 
 3.1416 
 
 6.2832 
 
 17-25 
 
 233.705 
 
 54.192 
 
 33 
 
 855.30 
 
 103.67 
 
 2.25 
 
 3.9760 
 
 7.0686 
 
 17-5 
 
 24O. 5 20 
 
 54-978 
 
 33.25 
 
 868.30 
 
 I04.45 
 
 2.5 
 
 4.9087 
 
 7.8540 
 
 18 
 
 254-469 
 
 56.548 
 
 33-5 
 
 881.41 
 
 105.24 
 
 3 
 
 7.0686 
 
 g.4248 
 
 18.25 
 
 261.587 
 
 57.334 
 
 34 
 
 907.92 
 
 106.81 
 
 3-25 
 
 8.2957 
 
 I0.2IO 
 
 18.5 
 
 268.803 
 
 58.119 
 
 34.25 
 
 921.32 
 
 107.60 
 
 3-5 
 
 9. 62 1 1 
 
 IO.995 
 
 19 
 
 283-529 
 
 59.690 
 
 34-5 
 
 934.82 
 
 108.38 
 
 4 
 
 12.566 
 
 12.566 
 
 19-25 
 
 29I. O39 
 
 60.475 
 
 35 
 
 962.11 
 
 106.95 
 
 4-25 
 
 14.186 
 
 13.351 
 
 19-5 
 
 298.648 
 
 61.261 
 
 35.25 
 
 975.90 
 
 110.74 
 
 4.5 
 
 15.904 
 
 14.137 
 
 20 
 
 314.160 
 
 62.832 
 
 35-5 
 
 989.80 
 
 in. 52 
 
 5 
 
 I9-635 
 
 I5.708 
 
 20.25 
 
 322.063 
 
 63.617 
 
 36 
 
 1017.8 
 
 113-09 
 
 5-25 
 
 21.647 
 
 16.493 
 
 20.5 
 
 33O.064 
 
 64.402 
 
 36.25 
 
 1032.06 
 
 113.88 
 
 5-5 
 
 23.758 
 
 17.278 
 
 2f 
 
 346.361 
 
 65.973 
 
 36.5 
 
 1046.35 
 
 114.66 
 
 6 
 
 28.274 
 
 18.849 
 
 21.25 
 
 354-657 
 
 66.759 
 
 37 
 
 1075.21 
 
 116.23 
 
 6.25 
 
 30.679 
 
 I9.635 
 
 21.5 
 
 363.05I 
 
 67.544 
 
 37-25 
 
 1089.79 
 
 117.01 
 
 6.5 
 
 33.183 
 
 20.420 
 
 22 
 
 380.I33 
 
 69.115 
 
 37-5 
 
 1104.46 
 
 117. 81 
 
 7 
 
 38.484 
 
 21.991 
 
 22.25 
 
 388.822 
 
 69.900 
 
 38 
 
 H34-II 
 
 119.38 
 
 7-25 
 
 41.282 
 
 22.776 
 
 22.5 
 
 397.6o8 
 
 70.686 
 
 38.25 
 
 1149.08 
 
 120.16 
 
 7-5 
 
 44.178 
 
 23.562 
 
 23 
 
 415.476 
 
 72.256 
 
 38.5 
 
 1164. 15 
 
 120.95 
 
 8 
 
 50.265 
 
 25.132 
 
 23.25 
 
 424-557 
 
 73.042 
 
 39 
 
 1194.59 
 
 122.52 
 
 8.25 
 
 53-456 
 
 25.918 
 
 23-5 
 
 433.731 
 
 73-827 
 
 39.25 
 
 1209.95 
 
 123.30 
 
 8.5 
 
 56.745 
 
 26.703 
 
 24 
 
 452.390 
 
 75.398 
 
 39-5 
 
 1225.42 
 
 124.09 
 
 9 
 
 63.617 
 
 28.274 
 
 24.25 
 
 461.864 
 
 76.183 
 
 40 
 
 1256.64 
 
 125.66 
 
 9-25 
 
 67.200 
 
 29.059 
 
 24.5 
 
 47I.436 
 
 76.969 
 
 40.25 
 
 1272. 3g 
 
 126.44 
 
 95 
 
 70.882 
 
 29.845 
 
 25 
 
 49O.875 
 
 78.540 
 
 40.5 
 
 1288.25 
 
 127.23 
 
 10 
 
 78.540 
 
 3I.4I6 
 
 25-25 
 
 500.741 
 
 79.325 
 
 4i 
 
 1320.25 
 
 128.80 
 
 10.25 
 
 82.516 
 
 32.201 
 
 25.5 
 
 5IO.706 
 
 80.IIO 
 
 41.25 
 
 1336.40 
 
 129.59 
 
 10.5 
 
 86.590 
 
 32.986 
 
 26 
 
 530.930 
 
 81.681 
 
 41.5 
 
 1352.65 
 
 130.37 
 
 11 
 
 95-033 
 
 34-557 
 
 26.25 
 
 54LI89 
 
 82.467 
 
 42 
 
 1385.44 
 
 I3I-94 
 
 11.25 
 
 99.402 
 
 35-343 
 
 26.5 
 
 551-547 
 
 83.252 
 
 42.25 
 
 1401.98 
 
 132.73 
 
 11. 5 
 
 103.869 
 
 36.128 
 
 27 
 
 572.556 
 
 84.823 
 
 42.5 
 
 1418.62 
 
 133.51 
 
 12 
 
 113.097 
 
 37-699 
 
 27.25 
 
 583.208 
 
 85.608 
 
 43 
 
 1452.20 
 
 I35-08 
 
 12.25 
 
 II7-859 
 
 38.484 
 
 27.5 
 
 593.958 
 
 86.394 
 
 43-25 
 
 1469.13 
 
 135.87 
 
 12.5 
 
 122.718 
 
 39.270 
 
 28 
 
 615.753 
 
 87.964 
 
 43-5 
 
 1486.17 
 
 136.65 
 
 13 
 
 132.732 
 
 40 840 
 
 28.25 
 
 626.798 
 
 88.750 
 
 44 
 
 I52C53 
 
 138.23 
 
 13-25 
 
 137.886 
 
 41.626 
 
 28.5 
 
 637.941 
 
 89.535 
 
 44.25 
 
 1537-86 
 
 139.01 
 
 13-5 
 
 143.130 
 
 42.411 
 
 29 
 
 660.521 
 
 91.106 
 
 44-5 
 
 1555.28 
 
 139.80 
 
 14 
 
 I53-938 
 
 43-982 
 
 29.25 
 
 671.958 
 
 91.891 
 
 45 
 
 1590.43 
 
 I4I.37 
 
 14-2 5 
 
 I59-485 
 
 44. 767 
 
 29-5 
 
 683.494 
 
 92.677 
 
 45-25 
 
 1608.15 
 
 142.15 
 
 14.5 
 
 165.130 
 
 45-553 
 
 30 
 
 706.860 
 
 94.248 
 
 45-5 
 
 1625.97 
 
 142.94 
 
 15 
 
 176.715 
 
 47-124 
 
 30.25 
 
 718.690 
 
 '95.033 
 
 46 
 
 1661.90 
 
 I44.5I 
 
 15.25 
 
 182.654 
 
 47-Qog 
 
 30.5 
 
 730.618 
 
 95.818 
 
 46.25 
 
 1680.01 
 
 145.29 
 
£04 
 
 DEFINITIONS AND TABLES 
 
 Table 9 — Continued. 
 
 Diam. 
 
 Area. 
 
 Circum. 
 
 Diam. 
 
 Area. 
 
 Circum. 
 
 Diam. 
 
 Area. 
 
 Circum. 
 
 46.5 
 
 1698.23 
 
 146.08 
 
 62 25 
 
 3043-47 
 
 195-56 
 
 73 
 
 4778.37 
 
 245.04 
 
 47 
 
 1734.94 
 
 147-65 
 
 62.5 
 
 3067.96 
 
 196.35 
 
 78. 25 
 
 4809.05 
 
 245.83 
 
 47.25 
 
 1753-45 
 
 14S.44 
 
 63 
 
 3117.25 
 
 197.92 
 
 73.5 
 
 4339.83 
 
 246.61 
 
 47-5 
 
 [772.05 
 
 149.22 
 
 63.25 
 
 3142.04 
 
 198.71 
 
 79 
 
 4901.68 
 
 248.19 
 
 4 3 
 
 1809.56 
 
 150.79 
 
 63.5 
 
 3166.92 
 
 I99-50 
 
 79-25 
 
 4932.75 
 
 248.97 
 
 48.25 
 
 1828 46 
 
 I5L58 
 
 64 
 
 3216.99 
 
 201.06 
 
 79 5 
 
 4963.92 
 
 249. 76 
 
 48.5 
 
 1S47.45 
 
 152.36 
 
 64.25 
 
 3242.17 
 
 201.85 
 
 80 
 
 5026.56 
 
 25L33 
 
 49 
 
 1885.74 
 
 153-93 
 
 64-5 
 
 3267.46 
 
 202.68 
 
 80.5 
 
 5089.58 
 
 252.90 
 
 49-25 
 
 1905.03 
 
 154-72 
 
 65 
 
 33I8.3I 
 
 204.20 
 
 81 
 
 5I53-00 
 
 254-47 
 
 49-5 
 
 1924.42 
 
 I55.50 
 
 65.25 
 
 3343-88 
 
 204.99 
 
 81.5 
 
 5216.82 
 
 256.04 
 
 50 
 
 1963.50 
 
 157.08 
 
 65-5 
 
 3369-56 
 
 205.77 
 
 82 
 
 5281.02 
 
 257.61 
 
 50.25 
 
 1983.18 
 
 157.86 
 
 66 
 
 3421..20 
 
 207.34 
 
 S2.5 
 
 5345-62 
 
 259.18 
 
 50.5 
 
 2002.96 
 
 158.65 
 
 66.25 
 
 3447.16 
 
 20S.13 
 
 83 
 
 5410.62 
 
 260.75 
 
 5i 
 
 2042.82 
 
 160.22 
 
 66.5 
 
 3473.23 
 
 208.91 
 
 33.5 
 
 5476.00 
 
 262.32 
 
 51-25 
 
 2062.90 
 
 161.00 
 
 67 
 
 3525.66 
 
 210.49 
 
 84 
 
 554L78 
 
 263.89 
 
 51.5 
 
 2083.07 
 
 161.79 
 
 67-25 
 
 3552.01 
 
 211.27 
 
 84.5 
 
 5607.95 
 
 265.46 
 
 52 
 
 2123.72 
 
 163.36 
 
 67-5 
 
 3573.47 
 
 212.06 
 
 S5 
 
 5674.51 
 
 267.04 
 
 52.25 
 
 2144.19 
 
 164.14 
 
 68 
 
 3631.68 
 
 213.63 
 
 85-5 
 
 5741-47 
 
 268.60 
 
 52.5 
 
 2164.75 
 
 164.19 
 
 68.25 
 
 3658.44 
 
 214.41 
 
 86 
 
 5808.81 
 
 270.17 
 
 53 
 
 2206.18 
 
 166.50 
 
 68.5 
 
 3685.29 
 
 215.20 
 
 86.5 
 
 5876.55 
 
 271.75 
 
 53-25 
 
 2227.05 
 
 167.29 
 
 69 
 
 3739-28 
 
 216.77 
 
 37 
 
 5944.66 
 
 273.32 
 
 53-5 
 
 2248.01 
 
 168.07 
 
 69.25 
 
 3766.43 
 
 217-55 
 
 87.5 
 
 6013.21 
 
 274.89 
 
 54 
 
 2290.22 
 
 169.64 
 
 69.5 
 
 3793-^7 
 
 218.34 
 
 88 
 
 6082.13 
 
 276.46 
 
 54-25 
 
 2311.48 
 
 170.43 
 
 7o 
 
 3848.46 
 
 219.91 
 
 88.5 
 
 6151.44 
 
 278.03 
 
 54-5 
 
 2332.83 
 
 171. 21 
 
 70.25 
 
 3875-99 
 
 220.70 
 
 89 
 
 6221.15 
 
 279.60 
 
 55 
 
 2375-83 
 
 172.78 
 
 70.5 
 
 390;. 63 
 
 221. 48 
 
 89.5 
 
 6291.25 
 
 281.17 
 
 55-25 
 
 2397.48 
 
 173-57 
 
 7i 
 
 3959-2Q 
 
 223.05 
 
 90 
 
 6371.64 
 
 282.74 
 
 55-5 
 
 2419.22 
 
 ^74-35 
 
 71-25 
 
 3987-I3 
 
 223.84 
 
 90.5 
 
 6432.62 
 
 284.31 
 
 56 
 
 2463.01 
 
 I75.92 
 
 71-5 
 
 4015.16 
 
 224.62 
 
 91 
 
 6503.89 
 
 285.88 
 
 56.25 
 
 2485.05 
 
 176.71 
 
 72 
 
 4071.51 
 
 226.19 
 
 9i-5 
 
 6573.56 
 
 287.46 
 
 56.5 
 
 2507.19 
 
 177-5 
 
 72.25 
 
 4099.83 
 
 226.98 
 
 92 
 
 6647.62 
 
 289.03 
 
 57 
 
 2551.76 
 
 179.07 
 
 72.5 
 
 4128.25 
 
 227.75 
 
 92-5 
 
 6720.07 
 
 290.60 
 
 57.25 
 
 2574.19 
 
 179.85 
 
 73 
 
 4135.39 
 
 229.34 
 
 93 
 
 6792.92 
 
 292.17 
 
 57-5 
 
 2596.72 
 
 ,180.64 
 
 73-25 
 
 4214. 11 
 
 230.12 
 
 93-5 
 
 6866.16 
 
 293-74 
 
 58 
 
 2642.08 
 
 182.21 
 
 73-5 
 
 4242. 92 
 
 230.91 
 
 94 
 
 6939-79 
 
 295.31 
 
 58.25 
 
 2664.91 
 
 182.99 
 
 74 
 
 4300.85 
 
 232.48 
 
 94-5 
 
 7013.81 
 
 296.88 
 
 58.5 
 
 2687.83 
 
 183.78 
 
 74-25 
 
 4329-95 
 
 233.26 
 
 95 
 
 7088.23 
 
 298.45 
 
 59 
 
 2733-97 
 
 185.35 
 
 74-5 
 
 4359.16 
 
 234-05 
 
 95-5 
 
 7163.04 
 
 300.02 
 
 59-25 
 
 2757.19 
 
 186.14 
 
 75 
 
 4417.37 
 
 235.62 
 
 96 
 
 7238.25 
 
 301.59 
 
 59-5 
 
 2780.51 
 
 1S6.92 
 
 75-25 
 
 4447-37 
 
 236.40 
 
 96.5 
 
 73i3-8o 
 
 303.16 
 
 60 
 
 2827.44 
 
 188.49 
 
 75-5 
 
 4476.97 
 
 237.19 
 
 97 
 
 7389-3I 
 
 304.73 
 
 60.25 
 
 2851.05 
 
 189.28 
 
 76 
 
 4536.37 
 
 238.76 
 
 97-5 
 
 7466.22 
 
 306.30 
 
 50.5 
 
 2874.76 
 
 190.06 
 
 ,76.25 
 
 4566.36 
 
 2 39-55 
 
 98 
 
 7542.89 
 
 307.88 
 
 61 
 
 2922 47 
 
 191.64 
 
 76.5 
 
 4596.35 
 
 240.33 
 
 93-5 
 
 7620.09 
 
 309 44 
 
 61.25 
 
 2946.47 
 
 192.42 
 
 77 
 
 4656.63 
 
 241.90 
 
 99 
 
 7697.70 
 
 311.02 
 
 61.5 
 
 2970.57 
 
 193.21 
 
 77 25 
 
 4686.92 
 
 242.69 
 
 99-5 
 
 7775.63 
 
 312.58 
 
 62 
 
 3019.07 
 
 194.78 
 
 77-5 
 
 47i7.3o 
 
 243-47 
 
 100 
 
 7854.00 
 
 314.16 
 
DEFINITIONS AND TABLES £05 
 
 governor. The angular advance of the eccentric is 
 thus increased or diminished, in fact is entirely under 
 the control of the governor, and cut off occurs earlier 
 or later according to the demands of the load on the 
 engine. 
 
 Adjustable cut off. One in which the point of cut off 
 may be regulated or adjusted by hand by means of a 
 hand wheel and screw attached to the valve stem, the 
 supply of steam being regulated by a throttling gov- 
 ernor. 
 
 Questions 
 
 i. What is absolute pressure? 
 
 2. What is gauge pressure? 
 
 3. W 7 hat is initial pressure? 
 
 4. What is terminal pressure and how may it be 
 ascertained theoretically? 
 
 5. What is back pressure? 
 
 6. Whatis absolute back pressure? 
 
 7. What is meant by ratio of expansion? 
 
 8. What does the term wire drawing mean when 
 applied to an indicator diagram? 
 
 9. What is condensor pressure? 
 
 10. What does the term vacuum imply? 
 
 11. What is absolute zero? 
 
 12. What is meant by the term piston displacement? 
 
 13. What is piston clearance? 
 
 14. What is steam clearance? 
 
 15. What is a horse power? 
 
 .16. What is meant by piston speed? 
 
 17. Define Boyle's law of expanding gases. 
 
 18. What is an adiabatic curve? 
 
 19. What is an isothermal curve? 
 
 20. What is the first law of thermodynamics? 
 
 21. What is the unit of work? 
 
-206 
 
 ENGINEERING 
 
 22. Define the first law of motion. 
 
 23. What is momentum? 
 
 24. What is the maximum theoretical duty of steam? 
 
 25. What is meant by the term steam efficiency? 
 
 26. How may the term engine efficiency be defined? 
 
 27. What is meant by the term efficiency of the 
 plant, and how may it be ascertained? 
 
 28. How is the horse power constant of an engine 
 found, and what does it mean? 
 
 29. What are common logarithms? 
 
 30. What are hyperbolic logarithms, and how are 
 they found? 
 
 31. What are ordinates as applied to an indicator 
 diagram? 
 
 is an eccentric? 
 
 is meant by the throw of an eccentric? 
 is meant by position of the eccentric? 
 is angular advance? 
 is valve travel? 
 s lap? 
 
 s inside lap? 
 s outside lap? 
 s lead? 
 
 s a throttling governor? 
 s meant by the term fixed cut off? 
 s meant by an automatic cut off? 
 s an isochronal governor? 
 s an adjustable cut off? 
 
 32. 
 
 What 
 
 33- 
 
 What 
 
 34- 
 
 What 
 
 35- 
 
 What 
 
 36. 
 
 What 
 
 37- 
 
 What 
 
 38. 
 
 What 
 
 39- 
 
 What 
 
 40. 
 
 What 
 
 41. 
 
 What 
 
 42. 
 
 What 
 
 43- 
 
 What 
 
 44. 
 
 What 
 
 45- 
 
 What 
 
CHAPTER IX 
 
 DIAGRAM ANALYSIS 
 
 Diagram analysis — Figure illustrating the various points in an 
 indicator diagram — Disadvantage of unequal cut off — Dia- 
 gram from compound condensing engine — Rules for finding 
 M. E. P. when the initial and terminal pressures are known, 
 and the ratio of expansion — Equalizing the work done in the 
 high and low pressure cylinders — Misleading diagrams caused 
 by dirt in indicator cylinder — Diagrams showing effect of 
 cramped exhaust — Table of factors for calculating the steam 
 consumption fiom the terminal pressure. 
 
 In the following study of indicator diagrams all the 
 illustrations are reproductions of actual diagrams taken 
 under ordinary working conditions. Figs. 50 and 51 
 are here introduced in order to define the different 
 
 FIGURE 50. 
 
 points, lines and curves. Fig. 50 was taken from a 
 large vertical engine with the corliss valve motion. 
 
 The engine being of slow speed and extremely long 
 stroke (10 ft.) with a clearance of but 1 per cent., the 
 compression beginning at C and ending at B is some- 
 what lighter than is ordinarily given to shorter stroke 
 207 
 
208 
 
 ENGINEERING 
 
 engines. From B to D is the admission line, which 
 being practically perpendicular to the atmospheric 
 line A, shows sufficient lead and ample port area. 
 From D to E is the steam line. Cut off occurs at E, 
 and from E to F is the expansion curve. At F the 
 point of release is quite sharply defined, as it should 
 be. From F to G is the exhaust line,, and from G to C 
 the line of back pressure, sometimes called the line of 
 counter pressure for the reason that the pressure indi- 
 cated by it acts counter or in opposition to the forward 
 pressure of the steam on the piston. This engine, is a 
 
 FIGURE 51. 
 
 simple condensing engine and the nearness of the 
 back pressure line to the line of perfect vacuum V 
 shows that an excellent vacuum was maintained in the 
 condenser. 
 
 Fig. 51 is from a Buckeye automatic cut off engine 
 having a shaft governor and what is termed a riding 
 cut off, that is the cut off valve slides to and fro on 
 the back of the main valve. The engine is horizontal 
 non-condensing, the cylinder being 28 in. bore by 56 
 in. stroke, and, at the time the diagram was taken, 
 
DIAGRAM ANALYSIS 209 
 
 developed 357. 58 horse power with a piston speed of 
 728 ft. per minute. The steam consumption per I. H. 
 P. per hour was 26 lbs., a rather high rate, but this was 
 owing to the fact that the engine was located too far 
 from the boilers, and as there were a large number of 
 elbows in the steam pipe the pressure was greatly- 
 reduced at the engine. Thus wire drawing of the 
 steam was caused, which is plainly indicated by the 
 downward inclination of the steam line, D E. 
 
 In a well proportioned engine having a steam pipe 
 of sufficiently large area, the steam line should paral- 
 lel the atmospheric line up to the point of cut off. 
 Fig. 51 indicates proper release of the steam at F, and 
 the back pressure from G to C, which is 3 lbs. above 
 the atmospheric line, shows a reasonably free passage 
 of the exhaust steam. 
 
 Figs. 52 to 57 illustrate diagrams from three new 
 vertical corliss engines supplying power for an electric 
 lighting plant, which the author was requested to test 
 and adjust after they had been in operation a few 
 months. The valves had previously been set by the 
 erecting engineer at the time the engines were set up. 
 Each one of these engines exhausted into a separate 
 condenser of the Jet type, into which the condensing 
 water was forced under pressure and from which the 
 overflow was discharged by gravity into a sewer. 
 There was no air pump and as a consequence the 
 vacuum maintained was very low, usually from 10 to 
 15 in., and at times still less, so that the beneficial 
 results of condensing were only partially realized. 
 
 For convenience the diagrams from each engine will 
 be treated in numerical order, beginning with engine 
 No. I. This engine was 24 x 48 in., running 70 R. P. 
 M., with a boiler pressure of 68 lbs. A 40 spring was 
 
210 
 
 ENGINEERING 
 
 used in the indicator. The principal defect was the 
 lack of sufficient lead on both ends, as indicated by 
 the inclination inward of the admission lines and the 
 rounded corners of the steam lines at the beginning of 
 
 FIGURE 52. 
 
 the stroke. (See Fig. 52.) There was also more com- 
 pression, especially on the bottom end, than was neces- 
 sary, considering the size of the engine and the speed. 
 The necessary changes having been made, the indi- 
 cator was again applied and the diagram Fig. 53 was 
 
 FIGURE 53. 
 
 obtained, which shows the distribution of the steam to 
 be satisfactory, although at the time of taking this 
 diagram the boiler pressure was only 60 lbs., while it 
 should have been 68 or 70 lbs., because with the latter 
 
DIAGRAM ANALYSIS 
 
 211 
 
 pressure still better results could have been attained. 
 The I. H. P. was 235 and the steam used per I. H. P. 
 per hour was 18 lbs. 
 
 Fig. 54 is the original diagram from engine No. 2, 
 
 figure 54. 
 
 and shows bad valve adjustment all around, with the 
 exception of lead on the top end. The variation in 
 the points of cut off is the worst feature; cut off 
 taking place on the bottom at 29 per cent, of the 
 stroke, while on the top end it does not occur until 
 
 __1 
 
 -A 
 
 -V 
 
 FIGURE 55. 
 
 the piston has traveled through 42 per cent, of the 
 stroke. There is more compression also than is 
 needed. This engine was 18 x 42 in., running at a 
 speed of 78 R. P. M., and the steam consumption, 
 
2F2 
 
 ENGINEERING 
 
 according to diagram Fig. 54, was 33 lbs. per I. H. P. 
 per hour. Having equalized the cut off and reduced 
 the compression by making the necessary changes in 
 the valve gear, the indicator was again applied, result- 
 ing in diagram Fig. 55, which maybe considered prac- 
 
 FIGURE 56. 
 
 tically perfect. The boiler pressure was 68 lbs. and 
 the spring used was a No. 40. The steam consump- 
 tion was reduced to 22 lbs. per I. H. P. per hour as 
 compared to 33. lbs. in Fig. 54. 
 
 Figs. 56 and 57 represent diagrams from engine No. 
 3, which w£s the same size as No. 1, viz., 24x48 in., 
 
 FIGURE 57. 
 
 and running at 72 R. P. M. The original diagram, 
 Fig. 56, shows too little lead on both ends, but espe- 
 cially on the top. There is also lack of compression 
 on the bottom end. The boiler pressure was 60 lbs. 
 and the scale of spring 40. Fig. 57, taken after the 
 
DIAGRAM ANALYSIS 
 
 21.3 
 
 necessary adjustments had been made, shows much 
 better valve performance. The horse power developed 
 was 251 and the steam consumption was 20.5 lbs. per 
 I. H. P. per hour. The rather high rate of steam 
 consumption for this engine as compared with engine 
 No. 1, which was the same size but consumed only 18 
 lbs. of steam per I. H. P. per hour, was due to two 
 causes. First, a low vacuum; second, low initial pres- 
 sure necessitating a late cut off. 
 
 Figs. 58 to 61 , inclusive, are diagrams from a Bullock 
 horizontal non-condensing corliss engine which had 
 
 figure 58. 
 
 been running about eight or nine months when it fell 
 to the author's lot to apply the indicator to the engine, 
 not only for the purpose of adjusting the valve motion, 
 but also to make a series of tests for the purpose of 
 ascertaining the amount of power delivered by the 
 engine to each one of several different departments 
 which were receiving power from this source. 
 
 The dimensions of the engine were as follows: bore 
 of cylinder, 32 in.; stroke, 5 ft. At the time Fig. 58 
 was taken the engine was making 62 R. P. M. and the 
 boiler pressure was only 50 lbs. A 30 spring was 
 used. Although the load on the engine was very light 
 
214 
 
 ENGINEERING 
 
 at the time, yet the diagram served as a guide to some 
 extent in setting the valves, and by taking off the bon- 
 nets from the valve chests and making the necessary 
 changes in the adjustment by the marks on the valves 
 
 FIGURE 59. 
 
 a pretty fair job was made of it, as will be seen by 
 referring to Fig. 59. The reducing motion was a 
 pantograph, described in Chapter VIII, and as it is 
 very easy to vary the travel of the paper drum with 
 this motion, diagrams of different lengths were taken 
 until the one which appeared to be the most satisfac- 
 
 FIGURE 60. 
 
 tory was obtained. The slight hump in the expansion 
 curve immediately after cut off was probably caused 
 by a speck of dirt or grit which momentarily checked 
 the indicator piston on the down stroke. The com- 
 
DIAGRAM ANALYSIS 
 
 215 
 
 pression on the crank end is not sufficient and the 
 exhaust valve rod on that end was slightly lengthened, 
 resulting in the production of diagram Fig. 60. In 
 this diagram the familiar hump in the crank end expan- 
 sion curve reappears, but in a different location, being 
 nearer the end of the stroke. It will also be noticed 
 that the length of Fig. 60 has been considerably 
 reduced from that of Figs. 58 and 59, it being about 
 one inch shorter. 
 
 Hc*d 
 
 FIGURE 61. 
 
 The boiler pressure and the load on this engine were 
 gradually increased from time to time, from 50 lbs. 
 and a light load, (as shown by Fig. 58) to 60 lbs. and 
 335 horse power, (as indicated by Fig. 59 taken some 
 three months later) and when Fig. 61 was taken, about 
 two years and eight months later, the boiler pressure 
 had been increased to 87 lbs. and the I. H. P. was 
 over 700. 
 
 Diagram Fig. 61 shows good economy in the use of 
 
nc> 
 
 ENGINEERING 
 
 steam in spite of the fact that the cut off occurs rather 
 late. There is no back pressure worth mentioning, the 
 back pressure line forming part of the atmospheric 
 line through the largest part of the stroke. The reason 
 for this is that the areas of the exhaust ports as well 
 as the exhaust pipe were sufficiently large to permit a 
 free passage for the steam. The exhaust pipe, also, 
 was made as short and direct as possible and all super- 
 fluous elbows were dispensed with. The steam con- 
 
 I5h 
 
 figure 62. 
 
 sumed per I. H. P. per hour as per diagram Fig. 61 
 was 22.3 lbs., and the horse power developed was 710.6. 
 Figs. 62 to 64, inclusive, represent diagrams from a 
 Buckeye engine 24 x 48 in., and are introduced for the 
 purpose of emphasizing the need of caution and good 
 judgment in setting valves by the indicator when the 
 load on the engine is variable. Fig. 62, which was the 
 first to be taken, would seem to indicate that the valve 
 was badly adjusted, but when Fig. 63 was taken imme- 
 diately afterwards, the cause of the trouble became 
 apparent. The engine was furnishing power for 
 
DIAGRAM ANALYSIS 
 
 217 
 
 operating an electric street railway on a small scale, 
 and the variation in the points of cut off was caused 
 by the stopping and starting of the cars. 
 
 Fig. 63 is a notable example of the quick and deli- 
 cate action of the shaft governor, as it will be seen 
 that during four successive revolutions there was a 
 different load each time, as shown by the diagram 
 from the crank end. 
 
 
 
 
 
 
 
 
 
 
 
 
 ^ 
 
 ^ 
 
 \ 
 
 
 
 
 
 
 
 
 
 
 cy 
 
 ^ 
 ^ 
 
 \ 
 
 
 
 
 
 
 
 
 
 
 ^s 
 
 N. 
 
 
 
 
 
 
 
 
 
 
 
 a. 
 
 *fc 
 
 
 
 
 
 
 
 
 
 
 
 Ui 
 
 <*> 
 
 
 
 
 
 
 
 
 
 
 
 sr 
 
 * 
 
 5 
 
 
 <5^ 
 
 
 
 v. 
 
 *»». 
 
 ^ ^ W 
 
 
 
 m 
 
 M 
 
 s\ 
 
 
 
 
 •^ 
 -S 
 
 ^ 
 
 
 
 
 
 FIGURE 63- 
 
 Fig. 64 was secured by quick manipulation of the 
 instrument when it was known that the load was to be 
 steady for a few seconds. 
 
 Fig. 65 is from an Atlas single valve automatic cut 
 off engine with shaft governor. This engine was 
 16 x 24 in., running at 105 R. P. M., and at the time 
 the diagram was taken the boiler pressure was only 50 
 lbs. The spring used was a No. 30. The diagram is a 
 
218 
 
 ENGINEERING 
 
 fairly good one for the type of engine. Owing to the 
 variation in the angular advance of the single eccentric 
 
 actuated by a shaft governor, the degree of compres- 
 sion varies with the point of cut off in the single valve 
 engine, the compression being higher with an early 
 
 figure 65. 
 
 cut off than it is when cut off occurs later in the 
 stroke. The loop at A is caused by too much lead 
 
DIAGRAM ANALYSIS 
 
 219 
 
 which, together with the compression, caused a 
 momentary rise in the pressure above the normal. 
 The lead at B is approximately correct. The differ- 
 
 HP 
 
 ence in terminal pressures at C and D is the result of 
 shifting of the points of cut off caused by variations in 
 the load. The back pressure lines are almost identical 
 with the atmospheric line, showing that the exhaust is 
 
 figure 67. 
 
 in no way restricted or cramped. I. H. P. is 65.7 and 
 steam consumption 21 lbs. per I. H. P. per hour. 
 
 Figs. 66 and 67 are diagrams taken from a cross 
 
220 ENGINEERING 
 
 compound condensing corliss engine. The high 
 pressure cylinder was 24 x 48 in., and the low pressure 
 cylinder was 44 x 48 in. The steam from the high 
 pressure exhausted into a receiver and from thence 
 into the low pressure cylinder. The receiver pressure 
 was 5.3 lbs. above atmospheric pressure. The ratio of 
 piston areas was 3.36 toi. That is, the area of the low 
 pressure piston was 3.36 times the area of the high 
 pressure piston, which was about the correct ratio for 
 the pressure carried, viz., 84 lbs. gauge or 99 lbs. 
 absolute. A No. 40 spring was used on the high 
 pressure and a No. 12 on the low pressure cylinder. 
 The number of expansions in the two cylinders was 14. 
 Thus, the ratio of expansion in the high pressure cylin- 
 der was 4.5 and in the low pressure the ratio was 3.1. 
 Then 4.5 x 3.1 = 14; or, Thus, initial pressure = 99 lbs. 
 absolute, terminal pressure in L. P. cylinder = 7 lbs. 
 absolute; then 99 -*- 7 = 14. 
 
 To illustrate the process of finding the M. E. P. with- 
 out the use of ordinates when the absolute initial and 
 terminal pressures and the number of expansions in 
 each cylinder are known, the following problems will 
 be worked out: 
 
 Find M. E. P. in L. P. cylinder. 
 
 First, find initial pressure. 
 
 Rule. T. P. multiplied by number of expansions. 
 Thus, 7x3.1 = 21.7 lbs. absolute initial pressure in 
 L. P. cylinder. 
 
 Second, find mean forward pressure (M. F. P.). 
 
 Rule. Multiply initial pressure by hyperboli< 
 logarithm of number of expansions plus I, and divid< 
 product by number of expansions. Thus the hyper 
 bolic logarithm of 3. 1 = 1. 13 14, to which add 1 = 2.1314 
 Then 2L7 ^- 1314 = 14.9 lbs. M. F. P. Deduct from 
 
DIAGRAM ANALYSIS 221 
 
 this the back pressure, which was 5 lbs. absolute. 
 Thus, 14.9- 5 = 9.9 lbs. M. E. P. in L. P. cylinder. 
 
 Next find M. E. P. in H. P. cylinder. 
 
 First, find T. P. in H. P. cylinder. 
 
 This will equal the initial pressure in the L. P. 
 cylinder + 2 per cent for loss in the receiver. Thus, 
 21.7 + .4 = 22.1 lbs., terminal pressure in H. P. cylinder- 
 Second, find initial pressure in H. P. cylinder. 
 
 Ride. Multiply T. P. by number of expansions. 
 Thus, 22.1 x 4.5 =99.4 lbs., absolute initial pressure in 
 H. P. cylinder. 
 
 Third, find mean forward pressure (M. F. P.). 
 
 The hyperbolic logarithm of 4.5 = 1. 5041, add 
 1=2.5041. Then 55^41^1 =55 lbs., M. F. P. in H. 
 P. cylinder. Deduct back pressure 22.1; thus, 55 lbs. 
 -22.1 lbs. = 32.9 lbs., M. E. P. in H. P. cylinder. 
 
 The ratio of piston areas being 3.36 to I, it may be 
 of interest to pursue the subject a little farther and 
 ascertain how the distribution of the steam in the two 
 cylinders corresponds to the ratio of areas. The ratio 
 and pressures may be expressed as follows: 
 Ratio of areas — H. P. cylinder, 1; L. P. cylinder, 3.36. 
 M. E. P. — H. P. cylinder, 32.9; L. P. cylinder, 9.9 lbs. 
 which is very nearly correct; sufficiently so for all 
 practical purposes, and clearly demonstrates that with 
 the intelligent use of the indicator it is possible to so 
 adjust the valves and establish the points of cut off on 
 a compound or triple expansion engine that the work 
 done in each cylinder will be practically the same. 
 As for instance, the product of the area of the H. P. 
 piston and the M. E. P. = 14,883.6 lbs., and that of the 
 L. P. piston x M. E. P. = 15,052.9 lbs., a difference 
 of only 169.3 lbs. If the two products had been equal, 
 
222 
 
 ENGINEERING 
 
 the horse power exerted in the two cylinders would 
 have been the same. As it was, the horse power of 
 the H. P. cylinder was 263.4 and that of the L. P. 
 cylinder was 266.4, showing a difference of only three 
 horse power in the amount of work done in each 
 cylinder. 
 
 Fig. 68 was taken from one of a pair of Fishkill Cor- 
 liss engines connected to a common crank shaft. The 
 engines were each 24 x 48 in., and run at 65 R. P. M., 
 with a boiler pressure of 65 lbs. They were equipped 
 with a jet condenser and a bucket plunger air pump 
 served for both engines. These engines had been in 
 
 figure 68. 
 
 continuous service for nearly seventeen years when the 
 author was called upon to indicate them and adjust 
 the valves. A diagram taken at the same time from 
 the mate of this engine was very nearly an exact 
 counter part of Fig. 68. The horse power, as shown 
 by Fig. 68, was 248, and the steam per I. H. P. per 
 hour was 15.2 lbs. The vacuum gauge showed 27 in. 
 and a 50 spring was used. 
 
 Figs. 69 and 70 are from an old Fishkill corliss 
 engine 16 x 42 in., to which the author applied the 
 indicator after he had set the valves, according to the 
 ordinary rules for valve setting, by the marks placed 
 
DIAGRAM ANALYSIS 
 
 223 
 
 on the ends of the valves and valve chests. These 
 diagrams are introduced especially for the purpose of 
 showing the need of exercising the greatest of care to 
 prevent dirt or grit of any kind from getting into the 
 
 FIGURE 69. 
 
 indicator cylinder. After the indicator pipes had been 
 blown out sufficiently, as it was thought, the indicator, 
 which was a thoroughly reliable instrument, was 
 attached and diagram Fig. 69 was obtained. It 
 showed the valve adjustment to be very nearly correct, 
 but the perfectly straight steam lines and the sharp 
 
 FIGURE 70. 
 
 corners and sudden drop at cut off were a puzzle, espe- 
 cially in an old engine where the valves and valve 
 seats were known to be much worn down. After 
 taking several more diagrams with precisely the same 
 
224 ENGINEERING 
 
 result, the indicator was removed, and upon taking 
 out the piston a quantity of dirt was found on it and 
 also on the inside of the cylinder. This fully 
 explained the cause of the sharp corners, etc., on the 
 diagram. After the indicator had been cleaned and 
 oiled it was again connected and Fig. 70 was produced, 
 which is a truthful presentation of the performance of 
 the steam in the cylinder. 
 
 Many diagrams are misleading, owing to causes 
 similar to the above, and a diagram with too sharp 
 angles at cut off or release should be regarded with 
 suspicion until it is proved beyond all doubt to be 
 truthful. 
 
 FIGURE 71. 
 
 Fig. 71 represents a diagram from a vertical non- 
 condensing engine 14 x 16 in. with riding cut off, 
 which the author was called upon to adjust. This 
 engine was nearly new, having been run but a few 
 months, and although the size of it was ample to do 
 all the work required, yet it had failed, so far, to supply 
 one-half the power needed. After taking the diagram 
 and making a few outside investigations, the cause of 
 the trouble was apparent. Indeed, the wonder was that 
 the engine had supplied as much power as it had 
 under the circumstances. 
 
 First. It was situated too far from the boiler plant, 
 being fully 1,200 ft., -and although a pressure of 85 lbs. 
 
DIAGRAM ANALYSTS 225 
 
 was carried at the boilers and the steam was conveyed 
 through a 6-inch pipe, yet owing to the many drains on 
 the pipe for heating buildings, running other small 
 engines, etc., by the time the steam reached the engine 
 in question the pressure was reduced so much that a 30 
 spring was found to be too strong, although that was 
 the scale of Fig. 71. 
 
 Second, the end of the exhaust pipe was found to 
 be submerged in a nearby pond of water to which it 
 had been carried, probably with a view of making a 
 condensing engine out of it! It was also found that 
 
 FIGURE 72. 
 
 there were no less than four superfluous elbows in the 
 exhaust pipe that could easily be dispensed with. The 
 diagram shows that the cut off was practically useless. 
 That the back pressure was nearly 6 lbs. above the 
 atmosphere, and that the engine was using 55 lbs. of 
 steam and 7 lbs. of coal per horse power per hour, all 
 of which conditions were about as bad as they could 
 be. 
 
 After increasing the lead and adjusting the cut off a 
 No. 16 spring was used and Fig. 72 was produced 
 which, although still showing late admission, is an 
 improvement over the original diagram. The initial 
 
226 ENGINEERING 
 
 pressure being only 30 lbs, above the atmosphere, 
 further work with the indicator was deferred until 
 changes were made in the steam and exhaust pipes, 
 by which the initial pressure was increased to 55 lbs. 
 and the exhaust pipe was freed of extra turns and 
 raised from its watery, grave into the open air. The 
 engine has since then given perfect satisfaction. 
 
 Fig. 73 is from a Buckeye automatic cut off engine 
 18 x 36 in. The engine had been running for several 
 years with the valves in the condition shown by the 
 diagram, and in the meanwhile, the load having been 
 increased from time to time, the engine finally refused 
 
 FIGURE 73. 
 
 to run up to speed and something had to be done. 
 The superintendent of the plant said that he had an 
 idea that something was the matter with the engine 
 but could not ascertain what it was, and so he finally 
 called upon the author to apply the indicator. The 
 result was that diagram Fig. 73 was obtained, showing 
 that the principal cause of the trouble was unequal cut 
 off. After equalizing the cut off and increasing the 
 lead on the crank end by a small fraction diagram 
 Fig. 74 was taken, and after this the engine gave no 
 further trouble. The depression in the steam lines 
 might have been rectified to some extent by increasing 
 
 
DIAGRAM ANALYSIS 227 
 
 the boiler pressure, thus giving a higher initial pressure 
 and an earlier cut off. The speed of the engine was 
 94 R. P. M., with a boiler pressure of 70 lbs. A 40 
 spring was used with the indicator. 
 
 In order to more fully illustrate the process of ascer- 
 taining the M. E. P. without dividing the diagram into 
 ordinates, the following computation is given together 
 with rules, etc. In this process two important factors 
 are necessary, viz., the absolute initial pressure and 
 the absolute terminal pressure, and they can both be 
 obtained from the diagram by measuring with the 
 
 figure 74. 
 
 scale adapted to the spring used. Thus, in Fig. 74 the 
 absolute initial pressure measured from the line of 
 perfect vacuum V to line B is 'jy lbs., and the absolute 
 terminal pressure measured from V to line B' is 21 lbs. 
 The ratio, or number of expansions, is found thus: 
 
 Rule. Divide the absolute initial pressure by the 
 absolute terminal pressure; thus, yj -5- 21 = 3.65 = num- 
 ber of expansions. 
 
 Second. Find mean forward pressure. 
 
 Rule. Multiply absolute initial pressure by the 
 hyperbolic logarithm of number of expansions plus I, 
 and divide product by number of expansions. Thus, 
 
228 
 
 ENGINEERING 
 
 referring to Table 8, it will be seen that the hyperbolic 
 logarithm of 3.65 is 1.2947, to which 1 must be 
 
 added. Then 
 
 48.4 lbs., which is the abso- 
 
 lute mean forward pressure. From this deduct 
 the absolute back pressure, which is 16 lbs. or 1 lb. 
 above atmosphere; thus, 48.4- 16= 32.4 lbs. M. E. P. 
 
 Third. Find I. H. P. 
 
 Area of piston minus one-half area of rod x M. E. P. 
 x piston speed in feet per minute, divided by 33,000. 
 
 Ti_ /i.u J' i. c J U • „ • \ 250.96X32.4X564 
 
 lnus (the diameter or rod being 3 in.), ^^ = 
 
 138.9 I. H. P. 
 
 The steam consumption per I. H. P. per hour may 
 also be computed by means of Table 10, which was 
 originally calculated by Mr. Thomson, and is based 
 upon the following theory: 
 
 TABLE 10. 
 
 T. P. 
 
 w. 
 
 T. P. 
 
 w. 
 
 T. P. 
 
 w. 
 
 3 
 
 117.30 
 
 13 
 
 466.57 
 
 23 
 
 798.10 " 
 
 3-5 
 
 135.75 
 
 13-5 
 
 483.43 
 
 23-5 
 
 814.39 
 
 4 
 
 153-88 
 
 14 
 
 500.22 
 
 24 
 
 830.64 
 
 4-5 
 
 171.94 
 
 14.5 
 
 517.07 
 
 24.5 
 
 846.96 
 
 5 
 
 186.75 
 
 15 
 
 533.85 
 
 25 
 
 863.25 
 
 5-5 
 
 207.60 
 
 15-5 
 
 550.64 
 
 25.5 
 
 879.49 
 
 6 
 
 225.24 
 
 16 
 
 567-36 
 
 26 
 
 895.70 
 
 6.5 
 
 242.97 
 
 16.5 
 
 584.10 
 
 26.5 
 
 911.86 
 
 7 
 
 260.54 
 
 17 
 
 600. 78 
 
 27 
 
 927.99 
 
 7-5 
 
 278.06 
 
 17-5 
 
 617.40 
 
 27-5 
 
 944- 07 
 
 8 
 
 295-44 
 
 18 
 
 633.96 
 
 28 
 
 960.12 
 
 8.5 
 
 312.80 
 
 18.5 
 
 650.46 
 
 28.5 
 
 976.27 
 
 9 
 
 330.03 
 
 19 
 
 666.90 
 
 29 
 
 992.38 
 
 9-5 
 
 347.27 
 
 19-5 
 
 683.38 
 
 29-5 
 
 1008.46 
 
 10 
 
 364.40 
 
 20 
 
 699.80 
 
 30 
 
 1024.50 
 
 10.5 
 
 381.57 
 
 20.5 
 
 716.27 
 
 30.5 
 
 1040.51 
 
 11 
 
 398.64 
 
 21 
 
 732.69 
 
 31 
 
 1056.48 
 
 11. 5 
 
 415-73 
 
 21-5 
 
 749-06 
 
 31-5 
 
 1072.42 
 
 12 
 
 432.72 
 
 22 
 
 765.38 
 
 32 
 
 1088.32 
 
 12.5 
 
 449.69 
 
 22.5 
 
 781.76 
 
 32.5 
 
 1104.35 
 
DIAGRAM ANALYSIS 229 
 
 A horse power = 33,000 ft. lbs. per minute, or 1,980,- 
 000 ft. lbs. per hour, or 1,980,000 x 12 = 23,760,000 in. 
 lbs. per hour, meaning that the same amount of energy 
 required to lift 33,000 lbs. one foot high in one minute 
 of time would lift 23,760,000 lbs. one inch high in one 
 minute of time. Now if an engine were driven by a 
 fluid that weighed one pound per cubic inch, and the 
 mean effective pressure of this fluid upon the piston 
 was one pound per square inch, it would require 
 23,760,000 lbs. of the fluid per horse power per hour. 
 But, if in place of the heavier fluid we substitute pure 
 distilled water of which it requires 27.648 cu. in. to 
 weigh one pound, the consumption per I. H. P. per 
 hour will be considerably less; as, for instance, 23,760,- 
 000-27.648 = 859,375 lbs., which would be the rate 
 per hour of the water driven engine if the M. E. P. of 
 the water was one pound per square inch and if the 
 M. E. P. was increased to 20 lbs.; then twenty times 
 more power would be developed with the same volume 
 of water, but the weight of water consumed per H. P. 
 per hour would be proportionately less. Now if the 
 engine is driven by steam it will consume just as 
 much less water in proportion as the water required to 
 make the steam is less in volume than the steam used. 
 Therefore if the above constant number, 859,375, be 
 divided by the M. E. P. of any diagram and by the 
 volume of the terminal pressure, the quotient will be 
 the water (or steam) consumption per I. H. P. per 
 hour. 
 
 Referring to Table 10, the numbers in the W columns 
 are the quotients obtained by dividing the constant, 
 859,375, by the volumes of the absolute pressures 
 given in the columns under T. P. and which represent 
 terminal pressures. The table is considerably abridged 
 
230 ENGINEERING 
 
 from the original, which was very full and complete, 
 the pressures advancing by tenths of a pound from 3 
 bs. to 60 lbs.; but it is seldom that in ordinary practice 
 there is needed such accuracy. If at any time, how- 
 ever, a diagram should show a terminal pressure not 
 given in the table, the correct factor for that pressure 
 can be easily found by dividing the constant 859,375, 
 by the relative volume of the pressure as found in 
 Table 5 of the properties of saturated steam given in 
 another chapter. 
 
 Referring again to Fig. 74, it is seen that the^ ter- 
 minal pressure is 21 lbs. absolute, and by reference to 
 Table 10 and glancing down column T. P. until 21 is 
 reached, it will be seen that the number opposite in 
 column W is 732.69. This number divided by the M. 
 E. P. of the diagram Fig. 74, which is 32.4 lbs., gives 
 22.6 lbs. per I. H. P. per hour as the steam consump- 
 tion. The rate thus found makes no allowance for 
 clearance and compression, however, and these two 
 very important items will be treated in a succeeding 
 chapter together with the method of correction for the 
 above, viz., clearance and compression, as they enter 
 largely into the steam economy of an engine. 
 
 Questions 
 
 1. What effect has back pressure upon the work of 
 an engine? 
 
 2. Name some of the causes of wire drawing of the 
 steam. 
 
 3. What relation should the steam line of an indi- 
 cator diagram bear to the atmospheric line? 
 
 4. What is the effect of insufficient lead upon the . 
 admission line of a diagram? 
 
DIAGRAM ANALYSIS 231 
 
 5. How does an unequal cut off affect the working 
 of an engine? 
 
 6. How is the number of expansions in a compound 
 engine ascertained? 
 
 7. What is the rule for finding the initial pressure by 
 calculation? 
 
 8. Give the rule for finding the mean forward 
 pressure. 
 
 9. When the M. F. P. is known, how may the mean 
 effective pressure be found? 
 
 10. How should the steam be distributed in the 
 cylinders of a compound engine? 
 
 11. What is the rule for finding the horse power 
 developed by an engine? 
 
 12. What is meant by the steam consumption of an 
 engine? 
 
 13. What is considered an economical rate of steam 
 consumption for a non-condensing engine? 
 
 14. What is a fairly good rate of steam consumption 
 for a condensing engine? 
 
CHAPTER X 
 DIAGRAM ANALYSIS— CONTINUED 
 
 Diagram analysis continued — Corliss Centennial engine and dia- 
 grams from it— Calculating steam consumption from indicator 
 diagrams — Clearance and compression, and how to correct a 
 diagram for the same — How to estimate the theoretical clear- 
 ance from a diagram — Measuring the volume of the clearance 
 space with water — The theoretical expansion curve — Illustra- 
 tion of hyperbolic law in its application to the expansion of 
 gases — The adiabatic curve and how to draw it — Power cal- 
 culations — Method of finding the M. E. P. of a diagram — The 
 planimeter and how to use it. 
 
 Figs. 75 to 77 are reproductions of diagrams taken 
 by the author from the once famous engine built by 
 Geo. H. Corliss for the Centennial Exposition which 
 was held at Philadelphia in 1876. A brief description 
 of this engine may not be out of place here, as it will 
 enable the reader to study the diagrams to a better 
 advantage. 
 
 This engine is, in fact, two simple condensing beam 
 engines, exactly alike in every detail, standing verti- 
 cal side by side and connected to a common- crank 
 shaft by means of the working beams overhead which 
 are pivoted at their centers to the A frame of the 
 engine. The cylinders are 40 in. bore by 10 ft. stroke 
 and the engine runs at a speed of 36 R. P. M., thus 
 giving a piston speed of 720 ft. per minute. The valve 
 gear is of the regular corliss type adapted to a vertical 
 engine, and motion is transmitted from the eccentric 
 through the medium of a rock shaft placed horizontally 
 on the frame. The steam and exhaust valves are 
 232 
 
DIAGRAM ANALYSIS 
 
 233 
 
 located in the cylinder heads, thereby reducing the 
 clearance to 1.5 per cent. Each engine has its own 
 jet condenser and air pump, which latter is of the 
 regular bucket plunger type and receives its motion 
 from the overhead beam through long connecting rods. 
 The crank shaft is 18 in. in diameter and carries a gear 
 fly-wheel 30 ft. in diameter, weighing 56 tons, the 
 teeth of which mesh into another gear wheel 10 ft. in 
 diameter carried on the jack shaft through which the 
 power is transmitted to the various departments of the 
 works. The face of the rim of the gear wheel is 24 in. 
 
 figure 75 
 
 in width, which allows the length of the teeth to be 
 24 in., while the pitch, or distance from center to cen- 
 ter of the teeth, is 5 in. The steam pipe is 18 in. inside 
 diameter and the cylinders are jacketed with live 
 steam. 
 
 This engine showed remarkable economy in the use 
 of steam when working at or near the capacity for 
 which it was designed by Mr. Corliss, which was 1,400 
 horse power. At the time Fig. 75 was taken the load 
 was 1,122 horse power and the boiler pressure was 32,5 
 lbs. gauge, or 47.5 lbs. absolute. The spring used was_ 
 
234 ENGINEERING 
 
 a No. 20, although a much better appearing diagram 
 would have been obtained by using a No. 30 spring. 
 
 The diagram shows very slight compression, but the 
 lead is correct. The point of cut off is not so clearly 
 defined as it should be, and the author attributes the 
 cause of this to the spring being too weak for the 
 reason that when Fig. 76 was taken some eight months 
 later from the same end of the same cylinder, but with 
 a spring of the proper tension for the pressure, the 
 point of cut off is much more plainly defined. (See 
 Fig. 76.) 
 
 FIGURE 76. 
 
 The absolute initial pressure, as shown by Fig. 75, 
 was 47.5 lbs., and the absolute terminal pressure was 
 8.5 lbs. The ratio of expansion would therefore be 
 47-5 "*" 8-5 = 5-6. The steam consumption per I. H. P. 
 per hour was 14 lbs. 
 
 Fig. JJ is from the same engine, and is here intro- 
 duced for the purpose of showing the great advantage 
 resulting from a good vacuum. In fact the largest 
 portion of the work in this case was done through the 
 help of the vacuum, as indicated by much the largest 
 portion of the area of the diagram being below the 
 line of atmospheric pressure. The diagram would 
 appear to be a kind of connecting link between the 
 
DTAGRAM ANALYSIS 
 
 23.5 
 
 times of Watt and Newcomen, when the vacuum did 
 all the work, and these modern times of high steam 
 pressure. 
 
 The circumstances under which Fig. 77 was obtained 
 were as follows: At certain times it became necessary 
 to run a part of the shops overtime, and the load at 
 such times being light, the boiler pressure was allowed 
 to drop to the point at which the engine would run the 
 most quietly, and that point was found to be about 7 
 lbs. gauge pressure. A No. 10 spring was used. The 
 horse power developed was 227.5, which multiplied by 
 
 "a 
 
 Vqcuu/rj 27 *l 
 Joi/es fressvre nfi, 
 
 Hep in. 
 
 FIGURE 77. 
 
 2, as there were two engines, would equal 455 I. H. P. 
 But the rate of steam consumption, which was 
 23.3 lbs. per I. H. P. per hour, was considerably 
 higher than it was with the ordinary load, as when 
 Fig- 75 was taken, showing that it is very poor econ- 
 omy to run an engine very much below its rated 
 capacity. 
 
 Fig. 78 is from a Hamilton corliss non-condensing 
 engine 32^/3 in. bore by 72 in. stroke. A No. 60 spring 
 was used, the boiler pressure being 85 lbs. gauge. The 
 I. H. P. was 652.2 and the steam consumption per 
 I. H. P. per hour was 22.9 lbs. 
 
23f> 
 
 ENGINEERING 
 
 There are but few points about the diagram that are 
 open to criticism. The compression is rather high for 
 so large an engine and the steam lines should be main- 
 tained more nearly horizontal up to the point of cut. 
 off. 
 
 Steam Consumption from Indicator Diagrams. In cal- 
 culating the steam consumption of an engine, two very 
 important factors must not be lost sight of, viz., clear- 
 ance and compression. Especially is this the case in 
 regard to clearance when there is little or no compres- 
 sion, for the reason that the steam required to fill the 
 clearance space at each stroke of the engine is prac- 
 
 figure 78. 
 
 tically wasted, and all of it passes into the atmosphere 
 or the condensor, as the case may be, without having 
 done any useful work except to merely fill the space 
 devoted to clearance. On the other hand, if the 
 exhaust valve is closed before the piston completes 
 the return stroke, the steam then remaining in the 
 cylinder will be compressed into the clearance space 
 and can be deducted from the total volume which, 
 without compression, would have been exhausted at 
 the terminal pressure. 
 
 Figs. 79 and 8o, which are reproductions of diagrams 
 taken by the author while adjusting the valves on a 
 16 x 42 in. corliss engine, will serve to graphically 
 
DIAGRAM ANALYSIS 
 
 237 
 
 illustrate this point. Fig. 79, which was the first one 
 to be taken, shows no compression. The point of 
 admission at A is plainly defined by the square corner 
 at the extreme end of the stroke. The clearance of 
 
 FIGURE 79. 
 
 this engine is 4 per cent, of the volume of the piston 
 displacement. The engine being 16 in. bore by 42 in. 
 stroke, the piston displacement is found by the follow- 
 ing calculation: Area of piston, 201.06 sq. in. x stroke, 
 
 FIGURE 80. 
 
 42 in. = 8444.52 cu. in. The volume of clearance 
 space is equal to 8444.52 cu. in. x .04 = 337.78 cu. in., 
 which divided by 1,728 = .195 cu. ft. 
 
 By reference to Fig. 80, taken after adjusting the 
 
238 ENGINEERING 
 
 valves for compression, it will be noticed that the 
 steam is there compressed to 37 lbs., the compression 
 curve beginning at C and ending at B. There is 
 therefore compressed during each stroke a volume of 
 steam equal to .195 cu. ft. at a pressure of 37 lbs. 
 gauge, or 52 lbs. absolute. 
 
 One cubic foot of steam at 52 lbs. absolute pressure 
 weighs .1243 lbs., and .195 cu. ft. will weigh .1243 x 
 .195 = .0242 lbs. 
 
 The engine was running at 70 R. P. M., or 140 
 strokes per minute. Thus, according to Fig. 80, the 
 total weight of steam compressed and doing useful 
 work during one hour, and which without compression 
 would have passed out through the exhaust pipe, is 
 equal to .0242 x 140 x 60 = 203.28 lbs. 
 
 Now in order to estimate the steam consumption of 
 the above engine from diagram Fig. 79, it would be 
 necessary to account for all the steam occupying not 
 only the volume of the piston displacement at the end 
 of the stroke, but the clearance as well, for the reason, 
 as before stated, that it would all be released before 
 exhaust closure. This would equal 8444.52 cu. in. 
 + 337-78 cu. in = 8782.3 cu. in., which divided by 
 1,728=5.08 cu. ft. each stroke, or 10.16 cu. ft. each 
 revolution. 
 
 The absolute terminal pressure of Fig. 79 is 20 lbs. 
 One cubic foot of steam at this pressure weighs .0507 
 lbs., and the weight of steam consumed each revolu- 
 tion would therefore be 10.16 x .0507 = .515 lbs., which 
 multiplied by 70 R. P. M. = 36.05 lbs. per minute, or 
 2,163 l°s. P er hour. The horse power developed by 
 the engine at the time was 80. Therefore the steam 
 consumption per I. H. P. per hour = 2, 163 -*■ 80 = 27 
 lbs. 
 
DIAGRAM ANALYSIS 239 
 
 Referring again to Fig. 80 it will be remembered 
 that the total weight of steam compressed during one 
 hour was 203.28 lbs. The weight of steam consumed 
 per hour, therefore, equals 2, 163 — 203.28 = 1959.7 lbs. 
 
 Owing to compression, the work area of Fig. 80 is 
 somewhat smaller than that of Fig. 79, amounting in 
 fact to the area of the irregular figure enclosed between 
 the points A, B and C. The work represented by this 
 figure amounts to a very small proportion of the total 
 work indicated by Fig. 79, still in order to arrive at 
 correct conclusions, it should be deducted therefrom. 
 
 Assuming the negative work to be equal to .55 horse 
 power, we have 80 -.55 = 79.45 I. H. P. as the work 
 represented by Fig. 80. As the total weight of steam 
 consumed in one" hour was 1959.7 lbs., the steam con- 
 sumption per I, H. P. per hour will be 1959.7 + 
 79.45 = 24.67 lbs., a saving by compression of 2.33 lbs. 
 per H. P. per hour, besides the great advantage of 
 having a cushion of steam in contact with the piston at 
 the termination of the stroke, thus bringing the mov- 
 ing parts of the engine to rest quietly without shock 
 or jar. 
 
 The steam consumption may also be computed from 
 the diagram, regardless of the dimensions of the 
 cylinder or the horse power developed. The mean 
 effective pressure and also the absolute terminal pres- 
 sure must, however, be known. This method was 
 referred to in the preceding chapter, but in the com- 
 putation therein made no correction was made for 
 clearance and compression. 
 
 Having reviewed these two factors at considerable 
 length it will now be in order to more fully explain 
 the methods of treating diagrams when it is desired to 
 make these corrections. 
 
240 
 
 ENGINEERING 
 
 First, draw vertical lines C and D, Fig. 81, at each 
 end of the diagram, and perpendicular to the atmos- 
 pheric line. Draw line V, representing perfect vacuum, 
 14.7 lbs. below the atmospheric line, as indicated on 
 the scale adapted to the diagram, which in this case is 
 50 lbs. to the inch. Continue the expansion from R, 
 where release begins, until it intersects line Li V, from 
 which point the absolute terminal pressure can be 
 measured. 
 
 Having ascertained the terminal pressure, which for 
 Fig. 81 is 30 lbs., draw line D E, which may be called 
 
 JJ£. 
 
 FIGURE 81. 
 
 the consumption line for 30 lbs. The terminal 
 being 30 lbs., refer to Table 10 and find in column W, 
 opposite 30 in column T. P., the number 1,024.5. 
 Divide this number by the M. E. P which in Fig. 81 is 
 41 lbs., and the quotient, which is 24.99 lbs., is the 
 uncorrected rate of steam consumption. This rate 
 stands for the total consumption throughout the whole 
 stroke represented on the diagram by the distance 
 from D to C, which measures 3.25 in., but it is evident 
 that there is a small portion of the return stroke, that' 
 indicated by the distance from E to C, during which 
 
DIAGRAM ANALYSIS 241 
 
 the steam compressed in the clearance space should 
 not be charged to the consumption rate, but should 
 be deducted therefrom. In order to do this, 
 multiply the uncorrected rate by the distance from D 
 to E, which is 3^ in, or 3.125 in., and divide the pro- 
 duct by the distance from D to C, 3^ in., or 3.25 in. 
 Thus, 24.99 x 3- I2 5 + 3- 2 5 = 2 4-03 lbs., which is the cor- 
 rected rate and represents a saving by compression of 
 24.99 — 24.03 = .96 lbs., or nearly 3.7 per cent. 
 
 In many cases the terminal pressure greatly exceeds 
 the compression, an illustration of which is given in 
 Fig. 82 which is a reproduction of a diagram from an 
 
 FIGURE 82. 
 
 old Wheelock engine. It now becomes necessary to 
 extend the compression curve to L, a point equidistant 
 from the vacuum line with the terminal at R. The 
 consumption line R. L. now becomes longer than the 
 stroke line R. M., therefore the corrected rate will 
 exceed the uncorrected rate by just so much; as for 
 instance, terminal pressure = 34 lbs. The factor, as 
 per Table 10, = 1152.26, and the M. E. P. of the diagram 
 is 47 lbs. Then, 1,152.26-47 = 24.5 lbs., uncorrected 
 rate; 24.5 x 3.125 in. (distance R. L.) - 3 in. (distance 
 R. M.) = 25.52 lbs., corrected rate, a loss of a little 
 more than one pound, or about 4 per cent. 
 
242 
 
 ENGINEERING 
 
 There is another class of diagrams very frequently 
 encountered in which the terminal pressure is con- 
 siderably below the compression curve, and in order to 
 compute the consumption rate by the above method it 
 becomes necessary to continue the compression curve 
 downwards until it meets the terminal, as illustrated at 
 A, Fig. 83, which is a friction diagram from a Buckeye 
 engine. R is the point of release, D A represents the 
 consumption line, and D C the stroke. The terminal 
 
 FIGURE 83. 
 
 is 8.5 lbs., and the factor for that pressure, according 
 to Table 10, is 312.8. Dividing this number by the M. 
 E.P., which was 7 lbs., gives 44.6 lbs. as the uncor- 
 rected rate. The distance D to A, where the com- 
 pression curve intersects the consumption line, is 
 2.625 in., and the total length of the diagram C to 
 D is 3-375 ln - Then 44.6x2.625^3.375 = 35 lbs. as 
 the corrected rate. The extremely high rate is owing 
 to the fact that the engine was running light, no load 
 except a line of empty shafting. 
 
DIAGRAM ANALYSIS 243 
 
 Theoretical Clearance. The expansion and compres- 
 sion curves of a diagram are created by the expansion 
 and compression of all the steam admitted during the 
 stroke. This includes the steam in the clearance space 
 as well as in the" cylinder proper. It is evident, 
 therefore, that the volume'of the clearance is one of 
 the factors controlling the form of these curves, and 
 when the clearance is known a correct expansion or 
 isothermal curve maybe theoretically constructed, as 
 will be explained later on. Also if the actual curves, 
 either expansion or compression, of a diagram assume 
 an approximately correct form, the clearance, if not 
 already known, may be determined theoretically from 
 them; although too much confidence should not be put 
 in the results as they are liable to show either too little 
 or too much clearance, generally the latter, especially 
 if figured from the compression curve. 
 
 For the benefit of those who may desire to test this 
 method of ascertaining the percentage of clearance of 
 their engines, several illustrations will be given of its 
 application to actual diagrams taken from engines in 
 which the clearance was known. 
 
 Fig. 84 is from an engine in which the clearance 
 was known to be 5 per cent. As compression cuts but 
 a very small figure in this diagram, the expansion 
 curve alone will be utilized for obtaining the theoreti- 
 cal clearance, and the process is as follows: 
 
 Select two points, C and R, in the curve as far apart 
 as possible, but be sure that they are each within the 
 limits of the true curve. Thus C is located just after 
 cut off takes place, and R is at a point just before 
 release begins. From C draw line C D parallel with 
 the atmospheric line. From D draw line D R, and 
 from C draw line C E, both perpendicular to the 
 
244 
 
 ENGINEERING 
 
 atmospheric line. Then from R draw line R E, form- 
 ing a rectangular parallelogram, C D R E, with two 
 opposite corners, C and R, within the curve. Now 
 through the other two corners, D and E, draw the 
 diagonal D E, extending it downwards until it inter- 
 sects the vacuum line V. From this point erect the 
 vertical line V W, which is the theoretical clearance 
 line. 
 
 To prove the result proceed as follows: Measure 
 the length of diagram from F to G, which in this case 
 
 FIGURE 84. 
 
 is 3.75 in., representing piston displacement. Next 
 measure the distance from F to the clearance line V W, 
 which is 3.91 in., representing piston displacement 
 with volume of clearance added. Then 3.91-3-75 = 
 .16, which represents volume of clearance; and . 16 x 
 100 ^3.75 = 4-3 per cent., which is approximately near 
 the actual clearance, which, as before stated, was 5 per 
 cent. 
 
 Fig. 85 serves to illustrate the same method applied 
 to the compression curve. This diagram is a repro- 
 
DIAGRAM ANALYSIS 
 
 245 
 
 duction of one taken from the low pressure cylinder of 
 a large compound condensing corliss engine in which 
 the actual clearance was 2.25 per cent. Two points, G 
 and H, are selected in the compression curve, and 
 from them the parallelogram GHI'K is erected 
 with two of its opposite corners, G and H, well within 
 the limits of the curve, while through the other two 
 corners, I and K, the diagonal I K C is drawn 
 intersecting the vacuum line at C, thus locating the 
 
 J 
 
 1 
 
 
 
 
 
 H 
 
 I 
 
 
 
 c 
 
 1 
 
 
 
 V 
 
 FIGURE 85. 
 
 point from which the clearance line C D can be drawn. 
 The measurements in this case are as follows: 
 
 Total length of diagram, E to F = 3.75 in. 
 
 Distance from clearance line, DC, to F = 3.875 in. 
 
 Volume of clearance = 3.875 — 3.75 = . 125 in. 
 
 . 125 x 100 -*■ 3.75 = 3.33 per cent, clearance, which is 
 1.08 per cent, more than the known clearance. 
 
 However, notwithstanding the liability to error in 
 many cases, still this method of computing clearance 
 may often be utilized to good advantage. 
 
 Another and more practical method of measuring 
 clearance is as follows: Place the engine on the dead 
 center. Remove the valve chest cover and take out 
 the valve. Close the cylinder cock on that end of the 
 cylinder to which the piston has been moved, leaving 
 
9A() ENGINEERING 
 
 the cock on the opposite end of the cylinder open and 
 disconnected from its drip pipe, so as to give an 
 opportunity for catching any water that may leak past 
 the piston while measuring the clearance space. Then 
 having first provided a known weight of water, always 
 making sure of having a little more than enough, pour 
 it into the steam port until the clearance space is filled 
 to a level with the valve seat. When this is done, 
 weigh the water that is left and deduct it from the 
 original quantity, and the remainder will be the num- 
 ber of pounds of water required to fill the clearance, 
 from which it is an easy matter to compute the number 
 of cubic inches or cubic feet in the space devoted to 
 clearance. If any water leaks past the piston during 
 the operation it should be weighed and deducted from 
 the total quantity poured into the port. 
 
 In the case of an engine having the valve chest on 
 the side of the cylinder it will be necessary to close 
 the steam port either by blocking the valve against it 
 or by fitting a piece of soft wood into it, making it 
 water tight. The water can then be poured into the 
 clearance space through a pipe conncted to the indi- 
 cator opening in that end of the cylinder. Care should 
 be exercised to allow a vent for the air to escape as it 
 is displaced by the water. 
 
 The Theoretical Expansion Curve. According to 
 Boyle's law the volume of all elastic gases is inversely 
 as their pressures, and steam being a gas conforms sub- 
 stantially to this law; although the expansion curves 
 of indicator diagrams are affected more or less by the 
 loss of heat transmitted through the cylinder walls, 
 and by the change in the temperature of the steam 
 produced by the changes in pressure during the prog- 
 ress of the stroke. The pressure generally falls more 
 
DIAGRAM ANALYSIS 
 
 247 
 
 rapidly during the first part of the stroke, and less 
 rapidly during the last portion than it should in order 
 to conform strictly to the above law, and the terminal 
 pressure usually is greater than it should be to agree 
 with the ratio of expansion. But this fullness of the' 
 expansion curve of the diagram near the end compen- 
 sates in a measure for the too rapid fall near the begin- 
 ning of the stroke. Therefore, if the engine is in 
 fairly good condition with the valves properly adjusted 
 and not leaking, and the piston rings are steam tight, 
 
 Jj 
 
 ) 
 
 I 
 
 1 
 
 «--— ^"^ 
 
 
 
 
 1 -=4 
 
 
 
 
 Af 
 
 JO C$ A 
 
 it may be assumed that the expansion of the steam in 
 the cylinder takes place according to Boyle's law and 
 it is found that the expansion curve drawn by the indi- 
 cator practically coincides with a hyperbolic curve 
 constructed according to that law. 
 
 Fig. 86 graphically illustrates the application of the 
 hyperbolic law to the expansion of gases. The hori- 
 zontal lines represent volumes and the vertical lines 
 represent pressures. The base line, A F, represents 
 the full stroke of a piston in the cylinder of an engine, 
 
248 ENGINEERING 
 
 and the vertical line A I represents the pressure of 
 the steam at the commencement of the stroke. 
 
 Suppose there is no clearance and that the steam has 
 been admitted up to point H when it is cut off. The 
 rectangle A B H I is the product of the pressure mul- 
 tiplied by the volume of the steam thus admitted. 
 When the piston has traveled from A to C the volume 
 of the steam has been doubled and the pressure C L 
 has been reduced to just one-half what it was at A I, 
 but the area of the rectangle A C L M is equal to the 
 area of the initial rectangle, and, as before, is the pro- 
 duct of the pressure C L multiplied by the volume A C. 
 As the piston travels still farther, as from A to D, the 
 steam is expanded to four volumes while the pressure 
 at D K will only be one-fourth that of the initial 
 pressure; but the new rectangle A D K N is still equal 
 in area to either of the others, A B H I or A C L M. 
 
 'The same law applies to each of the remaining rect- 
 angles; A E G O representing five volumes and one- 
 fifth of the initial pressure, and A F R P representing 
 six times the initial volume and one-sixth of the initial 
 pressure, but each having the same area as the initial 
 rectangle A B H I. Now the area of the rectangle 
 A B H I represents the work done by the steam up to 
 the point of cut off, and the area of the hyperbolic fig- 
 ure enclosed by the lines B H R F represents the work 
 done by the expansion of the steam after cut off 
 occurs. This area and the amount of work it repre- 
 sents may be computed by means of the known rela- 
 tions of hyperbolic surfaces with their base lines; as 
 for instance, if the base lines A B, A C, A D, etc., 
 extend in geometrical ratio, as r, 2, 4, 8, 16, etc., the 
 successive areas, B H L C, B H K D, B H G E, etc., 
 increase in arithmetical ratio, as 1, 2, 3, 4, etc. 
 
DIAGRAM ANALYSIS 
 
 249 
 
 On the principles of common logarithms, which 
 represent in arithmetical ratio natural numbers in 
 geometrical ratio, tables of hyperbolic logarithms have 
 been computed for the purpose of facilitating the cal- 
 culation of areas of work due to different degrees of 
 expansion. Such a table is given elsewhere in this 
 book, and in Chapter IX is described the method of 
 calculating the M. E. P. by this means. 
 
 A theoretical curve may be constructed conjointly 
 with the actual expansion curve of a diagram by first 
 locating the clearance and vacuum lines and then pur- 
 
 figure 87. 
 
 suing the method illustrated by Fig. 87. A curve so 
 produced is called an isothermal curve, meaning a 
 curve of the same temperature. 
 
 Referring to Fig. 87, suppose, first, that it is desired 
 to ascertain how near the expansion curve of the dia- 
 gram coincides with the isothermal curve, at or near 
 the point of cut off. Select point R near where 
 release begins, but still well within the expansion 
 curve. From this point draw the vertical line, R T, 
 parallel with the clearance line, V S. Then draw the 
 horizontal line, S T, parallel with the atmospb^'c line, 
 
250 ENGINEERING 
 
 and at such a height above it as will equal the boiler 
 pressure as measured by the scale adapted to the dia- 
 gram; such measurement to be made "from the atmos- 
 pheric line to correspond with the gauge pressure. 
 From T draw the diagonal T V, and from R draw the 
 horizontal line R D parallel with the atmospheric line. 
 From D, where this line intersects T V, erect the 
 perpendicular D E, thus forming the parallelogram 
 R D E T, and as line T V passes through two of its 
 opposite angles and meets the junction of the clear- 
 ance and vacuum lines, the other two angles, R and 
 E, will be in the theoretical curve, and R being the 
 starting point, it is obvious that this curve must pass 
 through E, which would be the theoretical point of 
 cut off on the steam line S T. 
 
 Two important points in the theoretical curve have 
 now been located, viz., E as the cut off, and R as the 
 point of release. In order to obtain intermediate 
 points, draw any desired number of lines downward 
 from points in S T, as I, 2, 3, 4, 5, etc., and continue 
 them downwards far enough to be sure that they will 
 meet the intended curve, and from the same points in 
 S T draw diagonals 1 V, 2 V, 3 V, 4 V, 5 V, etc., all 
 to converge accurately at V. From the intersection of 
 these diagonals with D E draw horizontal lines paral- 
 lel with V V, and the points of junction of these lines 
 with the vertical lines will be points in the theoretical 
 curve. It will now be an easy matter to trace the 
 curve through these points. If, on the other hand, it 
 be desired to compare the curves toward the exhaust 
 end of the diagram, draw lines E D and E T, Fig. 88, 
 also T R, locating R near where release commences, 
 after which draw line R D, completing the parallelo- 
 gram E T R D, fixing R as a point in the theoretical 
 
DIAGRAM ANALYSIS 
 
 251 
 
 curve started at E. After drawing the diagonal T V, 
 proceed in the same manner as before to locate the 
 intermediate points. 
 
 It will be observed that in order to ascertain the 
 performance of the steam near the beginning of the 
 stroke, the starting point of the isothermal curve must 
 be near the point of release, and conversely, if the 
 starting point of the curve is located near the point of 
 cut off and coincident with the actual curve, the test 
 will apply towards the end of the stroke. It is not to 
 be expected that the expansion curve of any diagram 
 taken in practice will conform strictly to the lines of 
 
 figure 88. 
 
 the isothermal curve, especially towards the latter end 
 of the stroke, owing to the reevaporation of water 
 resulting from the condensation of steam which was 
 retained in the cylinder by the closing of the exhaust 
 valve. This reevaporation commences just as soon as 
 the temperature of the steam, owing to reduction of 
 pressure due to expansion, falls below the temperature 
 of the cylinder walls, and it continues at an increasing- 
 rate until release occurs. The tendency of this 
 reevaporation or generation of steam within the 
 cylinder during the latter portion of the stroke is to 
 
ENGINEERING 
 
 raise the terminal pressure considerably above what it 
 would be if true isothermal expansion took place. 
 The terminal pressure may also be augmented by a 
 leaky steam valve, while, on the other hand a leaky 
 piston would cause a lowering of the terminal and an 
 increase in the back pressure. 
 
 The Adiabatic Curve. If it were possible to so pro- 
 tect or insulate the cylinder of a steam engine that 
 there would be absolutely no transmission of heat 
 either to or from the steam during expansion, a true 
 adiabatic curve or "curve of no transmission" might 
 
 r 
 
 
 Ic 
 
 
 s 
 
 
 t -^~~ 
 
 
 
 / 
 
 / 
 
 
 7 
 
 
 ' / 
 
 u 
 
 
 / / 
 
 
 
 
 
 
 .ss 
 
 
 // 
 
 
 
 ss 
 
 
 
 ~<^ 
 
 
 
 
 
 
 ^^z^-~ 
 
 
 H 
 
 -js-s- 51 """^ 
 
 -2L 
 
 c 
 
 J 
 
 A 
 
 V 
 
 V 
 
 be obtained. The closer the actual expansion curve 
 of a diagram conforms to such a curve, the higher will 
 be the efficiency of the engine as a machine for con- 
 verting heat into work. 
 
 Fig. 89 illustrates a method of figuring a curve 
 which, while not strictly adiabatic, will be near 
 enough for all practical purposes, while at the same 
 time it will give the student an opportunity to study 
 the laws governing the expansion of saturated steam. 
 
 To draw the curve, first locate the clearance anc 
 vacuum lines V S and V V. Next locate point R in 
 
DIAGRAM ANALYSIS 253 
 
 the expansion curve near where release begins, making 
 this the starting point, and also the point of coinci- 
 dence of the expansion curve with the adiabatic curve. 
 The other points in the curve are located from the 
 volumes of steam at different pressures during expan- 
 sion; the pressures being measured from the line of 
 perfect vacuum, and the volumes from the clearance 
 line. 
 
 The absolute pressure at R, Fig. 89, is 26 lbs. From 
 point R erect the perpendicular R T. Also draw hori- 
 zontal line R 26 parallel with the vacuum line and at a 
 height equal to 26 lbs. above vacuum line V V, as 
 shown by the scale, which in this case was 40. The 
 length of line R 26, measured from R to the clearance 
 line, is 3 T V in., or 3.0625 in. By reference to Table 5 
 it will be seen that the volume of steam at 26 lbs. abso- 
 lute, as compared with water at 39 , is 962. Now if 
 the length of line R 26 be divided by this volume, and 
 the quotient multiplied by each of the volumes of the 
 other pressures represented at points 30, 35, 40, 45, 
 etc., up to the initial pressure, the products will be 
 the respective distances from the clearance line of 
 points in the adiabatic curve. These points can be 
 marked on the horizontal lines drawn from the 
 clearance line to line R T. 
 
 Starting with line R 26, it has been noted that its 
 length is 3.0625 in., and that the volume was 962. 
 3.0625-962^.003. Then the volume of steam at 30 
 lbs. is 841, which being multiplied by .003 = 2.5 in., the 
 length of line 30. Next the volume at 35 lbs. = 728. 
 Multiplying this volume by .003 = 2.1 in., length of 
 line 35, and so in like manner for each of the other 
 points. 
 
 The process involves considerable figuring and care- 
 
254 ENGINEERING 
 
 ful and accurate measurements, which should be made 
 with a steel rule with decimal graduations. It is not 
 expected that the cut Fig. 89 will be found accurate 
 enough in its measurements to serve as a standard; it 
 being intended only to serve as an illustration of the 
 process. The diagram from which the illustration was 
 drawn was taken from a 600 H. P. engine situated 
 some 200 ft. from the boilers, and there was a con- 
 siderable cooling of the steam by the time it reached 
 the engine, the effect of which is apparent. The 
 curve produced by the measurements is shown by the 
 broken line. The process can be applied to any dia- 
 gram. 
 
 Power Calculations. The area of the piston (minus 
 one-half the area of rod) multiplied by the M. E. P., as 
 shown by the diagram, and this product multiplied by 
 the number of feet traveled by the piston per minute 
 (piston speed) will, give the number of foot pounds of 
 work done by the engine each minute, and if this pro- 
 duct be divided by 33,000, the quotient will be the 
 indicated horse power (I. H. P.) developed by the 
 engine. 
 
 Therefore one of the first requisites in power calcu- 
 lations is to ascertain the M. E. P. Beginning with 
 the most simple, though only approximately correct, 
 method of obtaining the average pressure, as illus- 
 trated by Fig. 90, draw line A B touching at A and 
 cutting the diagram in such manner that the space D 
 above it will equal in area spaces C and E taken 
 together, as nearly as can be estimated* by the eye. 
 Then with the scale measure the pressure along the 
 line F G at the middle of the diagram, which will be 
 the M. E. P. 
 
 The process is based upon the theory that the 
 
DIAGRAM ANALYSIS 
 
 255 
 
 average width of any tapering figure is its width at 
 the middle of its length. This method should not be 
 relied upon as accurate, but is convenient at times 
 when it is desired to make a rough estimate of the 
 horse power of an engine. 
 
 Figuring the M. E. P. by Ordinates. This is a very 
 common method and one which can be relied upon to 
 give accurate results, provided care is exercised in its 
 use. 
 
 The process consists in drawing any convenient 
 
 P 
 
 FIGURE 90. 
 
 number of vertical lines perpendicular to the atmos- 
 pheric, line across the face of the diagram, spacing 
 them equally, with the exception of the two end 
 spaces, which should be one-half the width of the 
 others, for the reason that the ordinates stand for the 
 centers of equal spaces, as for instance, line I, Fig. 91, 
 stands for that portion of the diagram from the end to 
 the middle of the space between it and line 2. Again, 
 line 2 stands for the remaining half of the second 
 space and the first half of the third, and so on. This 
 
&5(i 
 
 ENGINEERING 
 
 is an important matter, and should be thoroughly under- 
 stood, because if the spaces are all made of -equal 
 width, and measurements are taken on the ordinates, 
 the results will be incorrect, especially in the case of 
 high initial pressure and early cut off, following which 
 the steam undergoes great changes. 
 
 If the spaces are all made equal, the measurements 
 will require to be taken in the middle of them, and 
 errors are liable to occur, whereas if spaced as before 
 described, the measurements can be made on the 
 
 CrqnKEntL 
 
 ¥1 
 
 JS 
 
 S 
 
 '9 
 to. I 
 
 167./ + /0 - zL. 7/ {^ fl.FP 
 
 trrjr. m.£.p 
 
 FIGURE 91. 
 
 ordinates, which is much more convenient and will 
 insure correct results. Any number of ordinates can 
 be drawn, but ten is the most convenient and is amply 
 sufficient, except in case the diagram is excessively 
 long. For spacing the ordinates, dividers may be 
 used, or a parallel ruler may be procured from the 
 makers of the indicator; but one of the most con- 
 venient and easily procurable instruments for this pur- 
 pose is a common two-foot rule, and the method of 
 using it is illustrated in Fig. 91. 
 
 First draw vertical lines at each end of the diagram, 
 
DIAGRAM ANALYSTS 2.57 
 
 perpendicular to the atmospheric line and extending 
 downwards to the vacuum line, or below it if neces- 
 sary, in order to have a point on which to lay the 
 rule. In Fig. 91 points A and B are found to be the 
 most convenient. Now lay the rule diagonally across 
 the diagram, touching at A and B, and the distance 
 will be found to be 3% in., or 60 sixteenths. 
 
 Suppose it be desired to draw 10 ordinates. Divide 
 63 by 10, which will give 6 sixteenths, or 3/s in. as the 
 width of the spaces, but as the two end spaces are to 
 be one-half the width of. the others, there will be 11 
 spaces altogether, the two outer ones having a width 
 equal to one-half of ^ or T \. Now apply the rule 
 again in the same manner, touching at points A and B, 
 and with a sharp pointed pencil begin at A and mark 
 the location of the first ordinate according to the rule, 
 at a distance of y\- from the end. "Then 3/s from this 
 mark make another one, which will locate the second 
 ordinate, and proceed in like manner to locate the 
 others. The last two or three marks generally come 
 below the diagram, and if the diagram be taken from a 
 condensing engine it may be necessary to tack it on to 
 a larger sheet of paper in order to get these points. 
 Having correctly located the ordinates, they may now 
 be drawn perpendicular to the atmospheric line or 
 vacuum line, either of which will answer. 
 
 It should be noted that, owing to the diagonal posi- 
 tion of the rule with relation to the atmospheric line, 
 the spaces are not of the actual width as described by 
 the rule, but this is unimportant, so long as they are of 
 a uniform width. This method can be applied to any 
 diagram, no matter what its length may be, and point 
 B may be located at any distance below the atmos- 
 pheric or vacuum lines, wherever it is the most con- 
 
258 ENGINEERING 
 
 venient for the subdivisions on the rule, sixteenths, 
 eighths, etc., so long as it is in line with the e'nd of 
 the diagram. Having thus drawn the ordinates, the 
 M. E. P. may.be found by measuring the pressure 
 expressed by each one, using for this purpose the 
 scale adapted to the spring used, adding all together 
 and dividing by the number of ordinates which will 
 give the average pressure. 
 
 Referring to Fig. 91, begin with ordinate No. 1 on 
 the diagram, from the head end of the cylinder. In 
 this case a 40 spring was used. Lay the scale on the 
 ordinate with the zero mark where it intersects the 
 compression curve. The pressure is seen to be 49 lbs. 
 Set this down at that end of the card and measure the 
 pressure along ordinate No. 2, which is 55 lbs. Pro- 
 ceed in this manner to measure all the ordinates, 
 placing the resulting figures in a column, after which 
 add them together and divide by 10. The result is 
 26.71 lbs., which is the mean forward pressure (M. 
 F. P.). To obtain the mean effective pressure, deduct 
 the back pressure, which is represented by the distance 
 of the exhaust line of the diagram above the atmos- 
 pheric line in a non-condensing engine, and in a con- 
 densing engine the back pressure is measured from the 
 line of perfect vacuum, 14.7 lbs., according to the scale 
 below the atmospheric line. 
 
 In Fig. 91 the back pressure is found to be 3 lbs. 
 Therefore the M. E. P. of the head end will be 
 26.71 - 3 = 23.71 lbs. On the crank end the M. F. P. 
 is 27.23 lbs, and 27.23 - 3 - 24.23 lbs. = M. E. P. The 
 average effective pressure on the piston, therefore, will 
 be 23.71 + 24.23 * 2 = 23.97 lb s - 
 
 Unless great care is exercised in the measurements, 
 errors are liable to occur in applying this method, 
 
DIAGRAM ANALYSIS 259 
 
 especially with scales representing high pressures, as 
 60, 80, etc. The most convenient and reliable method 
 is to take a narrow strip of paper of sufficient length, 
 and starting at one end, apply its edge to each ordinate 
 in succession and mark their lengths on it consecu- 
 tively with the point of a knife blade or a sharp pen- 
 cil, Having thus marked on the paper the total length 
 of all the ordinates, ascertain the number of inches and 
 fractions of an inch thereon, the fractions to be 
 expressed decimally, and divide by the number of 
 ordinates. The quotient will be the average height of 
 the diagram, and as the scale expresses the number of 
 pounds pressure for each inch or fraction of an inch in 
 height, if the average height of the diagram be multi- 
 plied by the number of the scale, the product will be 
 the M. F. P. 
 
 Referring again to Fig. 91, if the lengths of the 
 ordinates drawn on the head end diagram be measured, 
 their sum will be found to be 6 T 8 ¥ or 6.666 in. Divid- 
 ing this by 10 gives .666 in. as the average height. 
 The mean forward pressure will then be as follows: 
 .666 x 40 = 26.64 lbs., or oractically the same as found 
 by the other method. 
 
 Fig. 92 illustrates a type of diagram frequently met 
 with, and one which requires somewhat different 
 treatment in estimating the power developed. It will 
 be noticed that, owing to light load and early cut off, 
 the expansion curve drops considerably below the 
 atmospheric line, notwithstanding that the engine 
 from which this diagram was taken is a non-con- 
 densing engine. When release occurs at R, and the 
 exhaust side of the piston is exposed to the atmos- 
 phere, the pressure immediately rises to a point equal 
 to, or slightly above, that of the atmosphere. 
 
260 
 
 ENGINEERING 
 
 Fig. 92 was taken during a series of experiments 
 made by the author for the purpose of ascertaining the 
 friction of shafting and machinery, and the engine it 
 was obtained from is a Buckeye 24 x 48 in. The 
 boiler pressure at the time was only 40 lbs., and a No. 
 20 spring was used. The ordinates are drawn accord- 
 ing to the method illustrated in Fig. 91. By placing 
 the rule on points A and B, the distance between 
 those two points is found to be 3^8 in., or 58 sixteenths. 
 Dividing this by 10 gives 5.8 sixteenths, or nearly ^ 
 
 
 Sp'typ 
 
 FIGURE 92. 
 
 in., as the width of the spaces; the two end spaces 
 being one-half of this, or T \ in. wide. The first five 
 ordinates, counting from A, express forward pressure, 
 represented by the arrows. The remaining five ordi- 
 nates, counting from B, express counter or back pres- 
 sure, represented by the arrows pointing in the 
 opposite direction. Measuring the pressures along 
 the first five ordinates, and adding them together, 
 gives 63.1 lbs., which divided by 5 gives 12.65 ^s. as 
 the mean forward pressure (M. F. P.). 
 
DIAGRAM ANALYSIS 
 
 261 
 
 Then figuring up the counter pressure in the same 
 manner on the other five ordinates, beginning at B, 
 
 COFFIN AVERAGER OR PLANIMETER. 
 
 the result is 4.25 lbs. The M. E. P. therefore will be 
 12.65 ~4- 2 5 = 8.4 lbs. 
 
 Obtaining the M. E. P. with the Planimeter. The area 
 of the diagram represents the actual work done by the 
 
262 ENGINEERING 
 
 steam acting upon the piston. In a non-condensing 
 engine the lower or exhaust line of the diagram must 
 be either coincident with or slightly above the atmos- 
 pheric line in order to express positive work. Any 
 deviation of this line, either above or below the atmos- 
 pheric line, represents counter pressure, the amount of 
 which may be ascertained by measurements with the 
 scale, and should be deducted from the mean forward 
 pressure. 
 
 On the other hand, the exhaust line of a diagram 
 from a condensing engine falls more or less below the 
 atmospheric line, according to the degree of vacuum 
 maintained, and the nearer this line approaches the 
 line of perfect vacuum, as drawn by the scale, 14.7 lbs. 
 below the atmospheric line, the less will be the counter 
 pressure, which in this case is expressed by the dis- 
 tance the exhaust line is above that of perfect vacuum. 
 
 The prime requisite therefore in making power cal- 
 culations from indicator diagrams is to obtain the 
 average height or width of the diagram, supposing it 
 were reduced to a plain parallelogram instead of the 
 irregular figure which it is. 
 
 The planimeter, Fig. 93, is an instrument which will 
 accurately measure the area of any plane surface, no 
 matter how irregular the outline or boundary line is, 
 and it is particularly adapted, for measuring the areas 
 of indicator diagrams, and in cases where there are 
 many diagrams to work up, it is a very convenient 
 instrument and saves much time and mental effort. In 
 fact, the planimeter has of late years become an almost 
 indispensable adjunct of the indicator. It shows at 
 once the area of the diagram in square inches and 
 decimal fractions of a square inch, and when the area 
 is thus known it is an easy matter to obtain the aver- 
 
DIAGRAM ANALYSIS 
 
 263 
 
 age height by simply dividing the area in inches by 
 the length of the diagram in inches. Having ascer- 
 tained the average height of the diagram in inches or 
 fractions of an inch the mean or average pressure is 
 found by multiplying the height by the scale. Or the 
 process may be made still more simple by first multi- 
 plying the area, as shown by the planimeter in square 
 
 figure 93. 
 
 inches and decimals of an inch, by the scale, and 
 dividing the product by the length of the diagram in 
 inches. The result will be the same as before, and 
 troublesome fractions will be avoided. 
 
 Questions 
 i. What advantage is gained by placing the valves 
 of a corliss engine in the cylinder head? 
 
264 ENGINEERING 
 
 2. What two important factors must be considered 
 in calculating the steam consumption of an engine? 
 
 3. What advantage, in an economical way, is gained 
 by compression? 
 
 4. How is the piston displacement of an engine 
 ascertained? 
 
 5. How is the steam consumption per horse power 
 per hour calculated? (See Figs. 79 and 80.) 
 
 6. What effect does compression have upon the work 
 area of an indicator diagram? (See Fig. 80.) 
 
 7. How can the steam consumption, as shown by 
 the diagram, be corrected for clearance and compres- 
 sion? (See Figs. 81, 82 and 83.) 
 
 8. What do the expansion and compression curves 
 of a diagram show? (See theoretical clearance.) 
 
 9. If the clearance of an engine is not known, how 
 may it be determined theoretically from an indicator 
 diagram? (See Figs. 84 and 85.) 
 
 10. What other method may be employed to ascer- 
 tain the clearance? 
 
 11. What is Boyle's law for gases? 
 
 12. Is steam a gas? 
 
 13. What is a hyperbolic curve? (See Fig. 86.) 
 
 14. How may a theoretical curve be constructed 
 from an indicator diagram? (See Fig. 87.) 
 
 15. What effect does reevaporation have upon the 
 expansion curve? 
 
 16. When does reevaporation take place within the 
 cylinder? 
 
 17. How does a leaky steam valve affect the ter- 
 minal pressure? 
 
 18. If the piston rings leak, what is the result? 
 
 19. W T hat is an adiabatic curve, and what conditions 
 are necessary in order to produce it? 
 
DIAGRAM ANALYSIS °265 
 
 20. What is the rule for computing the horse power 
 developed by an engine? 
 
 21. What important factor is necessary in all power 
 calculations? 
 
 22. How may the M. E. P. be found? (See Figs. 
 91 and 92.) 
 
 23. What does the area of the diagram represent? 
 
 24. In a diagram from a non-condensing engine, 
 where should the exhaust line be? 
 
 25. If the exhaust line of a diagram is above the 
 atmospheric line, what does it show? 
 
 26. Where should the exhaust line of a diagram from 
 a condensing engine be? 
 
 27. How is the M. E. P. ascertained by the plani- 
 meter? 
 
CHAPTER XI 
 
 ENGINE OPERATION 
 
 Engine operation — Simple engines — Compound engines — Con- 
 densing and non-condensing engines — Condensers — Surface 
 and jet condensers — Starting a condensing engine — Rules for 
 estimating quantity of condensing water required — The gov- 
 ernor — Speed regulation — How to keep a governor in good 
 working condition — Lubrication of an engine — Running 
 "over" or "under" — Oiling the bottom guide on horizontal 
 engines — Oiling the crank pin and main bearings — Shaft gov- 
 ernors—Keying up an engine — What to do with a hot pillow 
 block — Feed water heaters — Economy of using exhaust steam 
 for heating feed water — Changing the speed of an engine. 
 
 The following general suggestions regarding the 
 operation of engines are made with the object in view 
 
 CROSS COMPOUND DIRECT CONNECTED . CORLISS ENGINE, ALLIS 
 CHALMERS CO. 
 
 of assisting young engineers or those whose experience 
 has been limited to one or two types of engines. 
 
 In many cases a young man starts in as a fireman in 
 266 
 
ENGINE OPERATION 267 
 
 a certain plant, and by industry and a strict devotion 
 to duty becomes able in course of time to handle not 
 only the boilers successfully, but is at times required 
 to run the engine in the absence of the engineer. He 
 thus acquires the ability to operate that particular 
 engine, while at the same time he may be compar- 
 atively ignorant of the peculiarities of other types. 
 Or an engineer may have had years of experience with 
 simple non-condensing engines, but if called upon to 
 operate a compound condensing engine, he would find 
 that he had a great deal to learn. 
 
 TANDEM COMPOUND ENGINE, BUCKEYE ENGINE CO. 
 
 Engines may be divided into two general classes, 
 viz., simple and compound. 
 
 A simple engine may be either condensing or non- 
 condensing, but its leading characteristic is, that the 
 steam is used in but one cylinder, and from thence it is 
 exhausted either into the atmosphere or into a con- 
 denser. 
 
 A compound engine is one in which the steam is 
 made to do work in two or more cylinders before it is 
 allowed to exhaust, and this class of engine may be 
 either condensing- or non-condensing;. 
 
ENGINEERING 
 
 *:':tf% 
 
ENGINE OPERATION 
 
 2G9 
 
 In a non-condensing engine the pressure of the 
 atmosphere, amounting to 14.7 lbs. per square inch at 
 sea level, is constantly in resistance to the motion of 
 
 EXHAUST 
 INLET 
 
 KNOWLES JET CONDENSER. 
 
 the piston. Therefore the exhaust pressure cannot 
 fall below the atmospheric pressure, and is generally 
 from two to five pounds above it, caused by the resist- 
 ance of bends and turns in the exhaust pipe, or other 
 
270 ENGINEERING 
 
 causes which tend to retard the free passage of the 
 steam. 
 
 The advantage, from an economical point of view, 
 of exhausting the steam into a condenser in which a 
 vacuum is maintained, is fully set forth in Chapter 
 VIII. on Definitions. (See" Vacuum.) 
 
 Condensers are of two classes, viz., jet condensers 
 and surface condensers. 
 
 In a jet condenser the steam is exhausted into an 
 air-tight iron vessel of any convenient shape, gener- 
 ally cylindrical and of suitable size, and is there con- 
 densed by coming in contact with a jet of cold water, 
 admitted in the form of a spray. The air pump, which 
 also maintains a vacuum in the condenser, draws this 
 water, together with the condensed steam, away from 
 the condenser. 
 
 The surface condenser, like the jet condenser, con- 
 sists of an air-tight iron vessel, either cylindrical or 
 rectangular in shape, but unlike the jet condenser, it 
 is fitted with a large number of brass or copper tubes 
 of small diameter, through which cold water is forced 
 by a pump, called a circulating pump. A vacuum is 
 also maintained in the body of the condenser by the 
 air pump, and the steam exhausting into this is con- 
 densed by coming in contact with the cool surface of 
 the tubes. Or, as is often the case, the exhaust steam 
 passes through the tubes in place of around them, and 
 the condensing water is forced into and through the 
 body of the condenser, the vacuum in this case being 
 maintained in the tubes. Owing to the fact that in a 
 surface condenser the steam does not mix with the 
 water, a larger quantity of condensing water is required 
 than in a jet condenser, but on the other hand, an 
 advantage is gained by having the pure water of con- 
 
ENGINE OPERATION 
 
 271 
 
 densation; in other words, the condensed steam, which 
 may be returned to the boilers along with the regular 
 feed water supply, and will greatly aid in preventing 
 the formation of scale, while the water of condensation 
 as it comes from a jet condenser, being mixed with 
 oil and other impurities, is not, as a rule, suitable to 
 be fed to boilers. 
 
 There are many different types of jet condensing 
 
 WORTHINGTON SURFACE CONDENSER, WITH AIR AND CIRCU- 
 LATING PUMP- 
 
 apparatus, in some of which no air pump is used; their 
 action being based somewhat upon the principle of the 
 injection used for feeding boilers. In this type of jet 
 condenser the supply of condensing water is drawn from 
 outside pressure, either from an overhead tank or other 
 source, and passing into an annular enlargement of the 
 exhaust pipe, is discharged downwards in the form of 
 a cylindrical sheet of water into a nozzle which gradu- 
 ally contracts. The exhaust steam, entering at the 
 
272 
 
 ENGINEERING 
 
 same time, is condensed, and the contracting neck of 
 the cone shaped nozzle gradually brings the water to a 
 solid jet, and it rushes through the nozzle with a veloc- 
 ity sufficient to create a vacuum. This type of con- 
 denser can only be used where the discharge pipe has 
 a free outlet. 
 
 The jet condenser with air pump attached is the 
 most reliable as well as econom- 
 ical for general purposes, for the 
 reason that with this type the sup- 
 ply of condensing water may be 
 drawn from a well or other source 
 lower than the level of the con- 
 denser. These condensers are also 
 generally fitted with a "force in- 
 "ection," as it is called, which is 
 simply a connection between the 
 condenser and water main or tank, 
 for the purpose of letting cold water 
 into the condenser to condense the 
 exhaust steam when starting the 
 engine, and thus aid in forming a 
 vacuum. When a good vacuum has 
 been established and the engine is 
 running up to speed, the force injection may be shut 
 off, and the water will flow into the condenser from 
 the well by suction. The above refers to engines in 
 which the air pump receives its motion directly from 
 the engine. 
 
 Another type of jet condensing apparatus is the 
 independent air pump and condenser, which is still 
 better, for the reason that the air pump, which is sim- 
 ply an ordinary double acting steam pump, may be 
 started independently of the engine, and, in fact, 
 
 SIPHON CONDENSER. 
 
ENGINE OPERATION 273 
 
 before the engine is started, thus creating a vacuum in 
 the condenser, and greatly facilitating the starting of 
 the engine. Another great advantage in the inde- 
 pendent condensing apparatus is that there is not so 
 much danger of the water backing up into the cylinder 
 in case of a sudden shut down of the engine, because 
 the air pump may be kept in operation, thus relieving 
 the condenser of water; whereas, if the air pump gets 
 its motion from the engine, it will of course stop when 
 the engine stops, and unless the injection water is shut 
 off immediately after closing the throttle there is 
 great danger of the cylinder becoming flooded with 
 water, resulting very often in a broken cylinder head, 
 or a bent piston rod. 
 
 The quantity of water required to condense the 
 exhaust steam of an engine is determined by three 
 factors: First, the density, temperature and volume of 
 the steam to be condensed in a given time; second; 
 the temperature of the overflow or discharge, and 
 third, the temperature of the injection water. For 
 instance, the temperature of the injection water may 
 be 35 in the winter and 70 ° in the summer. Or it 
 may be desired to keep the overflow at as high a tem- 
 perature as possible for the purpose of feeding the 
 boilers. Again, the pressure, and consequently the 
 temperature of the exhaust steam as it enters the con- 
 denser, varies with different engines, and often with 
 the same engine, according as the load is light or 
 heavy. Therefore the only accurate method of esti- 
 mating the amount of condensing water required per 
 minute or per hour, under any and all conditions, is to 
 first ascertain the weight of water required to con- 
 dense one pound weight of steam at the temperature 
 and pressure at which the steam is being exhausted. 
 
274 ENGINEERING 
 
 In these calculations the total heat in the steam must 
 be considered. This means .not only the sensible heat, 
 but the latent heat also. 
 
 The formula for solving the above problem may be 
 
 FT — T 
 
 expressed as follows: ~ — ~ = W, in which 
 
 H = total heat in the steam, 
 T = temperature of the overflow, 
 I = temperature of the injection water, 
 
 W = weight of water required to condense one pound 
 weight of steam. 
 
 To illustrate, suppose the absolute pressure of the 
 exhaust, as shown by the indicator diagram, is y lbs. 
 Referring to Table 5, it will be seen that the total heat 
 in steam at 7 lbs. absolute is 1 135.9 heat units. 
 Assume the temperature of the overflow to be no°, 
 which is as high as is consistent with a good vacuum 
 Now the total heat to be absorbed from each pound 
 weight of steam in this case would be 1135.9—110 = 
 1025.9 B. T. U. 
 
 Suppose the temperature of the condensing water to 
 be 55 and the temperature of the overflow being uo°, 
 there will be no° — 55 = 55 of heat absorbed by each 
 pound of water passing into and through the con- 
 denser, and the number of pounds of water required to 
 condense one pound weight of steam under the above 
 conditions will equal the number of times 55 is con- 
 tained in 1025.9. Expressed in plain figures the cal- 
 culation is "nHl™ = 18.65 lbs. 
 
 In order to ascertain the quantity of condensing 
 water required per horse power per hour, it is only 
 necessary to know the number of pounds weight of 
 steam consumed by the engine per horse power per 
 hour, as shown by the indicator diagram, and multiply 
 
ENGINE OPERATION 275 
 
 this by the weight of condensing water required per 
 pound of steam, as found by the above solution. 
 
 Thus, suppose the steam consumption of the engine 
 to be 17 lbs. per I. H. P. per hour. Then 17 x 18.65 
 = 317.05 lbs. per hour, which reduced to gallons = 38.2 
 gals. 
 
 Or, if the steam consumption is not known, and the 
 weight only of condensing water required per hour is 
 desired, regardless of the horse power developed by 
 the engine, it will be necessary, first, to estimate the 
 total volume of steam exhausted per hour and calcu- 
 late its weight from its known pressure. 
 
 Thus, assume the engine to be 24x48 in., and the 
 R. P..M. to be 80. Then the piston displacement will 
 equal area of piston less one-half area of rod multi- 
 plied by length of stroke. Referring to Table 9, the 
 area of a circle 24 in. in diameter = 452.39 sq. in. 
 Suppose the piston rod to be 4.5 in. in diameter, its 
 area, according to Table 9, is 15.904 sq. in., one-half 
 of which = 7.952 sq. in. The effective area of the pis- 
 ton now becomes 452.39 — 7.952 = 444.43 sq. in., and 
 the piston displacement equals 444.43 x 48 = 21332.64 
 cu. in. Dividing this by 1728 (number of cubic inches 
 in a cubic foot) gives 12.34 cu. ft. of piston displace- 
 ment. The total volume of steam exhausted per min- 
 ute, therefore, will be 12.34 x 2 x 80 = 1974.4 cu. ft. 
 
 The absolute pressure of the exhaust may again be 
 assumed to be 7 lbs. per square inch. Referring to 
 Table 5, the weight of one cubic foot of steam at 7 
 lbs. absolute is .0189 lbs., and the total weight of steam 
 exhausted per minute, therefore, would be 1974.4 x 
 .0189 = 37.3 lbs., and if 18.65 lbs. water is required to 
 condense one pound of steam, the quantity required 
 per minute would be 37.3 x 18.65=695.8 lbs., or per 
 
27G 
 
 ENGINEERING 
 
 hour, 41748 lbs., equal to 5029 gals. This is at the. 
 rate of 8.7 lbs., or a little more than one gallon per 
 revolution for a 24 x 48 in. simple condensing engine. 
 The Governor. The proper regulation of speed is a 
 very important point in the operation of engines, and 
 in order to attain this most desirable object, due atten- 
 tion must be paid to the governor. 
 If it be a throttling governor (see 
 Chapter VIII, on Definitions), care 
 should be taken to not pack the 
 small valve stem too tight, nor allow 
 the packing to become hard from 
 long usage. The packing nut should 
 be left loose enough to allow a 
 slight leakage of steam past the 
 stem. This will keep it lubricated 
 and the slightest variation of the 
 governor balls will be transmitted 
 to the valve, and the speed will be 
 regular. 
 
 If the engine has an automatic 
 cut off mechanism actuated by a fly 
 ball governor, it is obvious that all 
 the moving parts of the governor 
 should work with as little friction as possible. Good 
 oil and enough of it should be used. Particular atten- 
 tion should be paid to the dash pot connected with the 
 governor, the object of which is to regulate the varia- 
 tions of the governor and prevent a jerky movement. 
 It often happens, especially with new engines, that 
 the small piston in the dash pot fits too snug, and the 
 consequence is that it sticks; causing the governor to 
 be slow in responding to changes in the speed of the 
 engine. 
 
 PICKERING HORI- 
 ZONTAL GOVERNOR 
 
ENGTNE OPERATION 
 
 277 
 
 It is a good plan sometimes to take the dash pot pis- 
 ton out, and putting it in a lathe, reduce its diameter 
 slightly, and also round off the sharp edges. The oil 
 used in the dash pot should not be allowed to become 
 gummy by being used too long without changing it for 
 fresh oil. 
 
 Lubrication. The proper lubrication of all the work- 
 ing parts of an engine is a matter of prime importance, 
 
 DOUBLE CONNECTION LUBRICATOR. 
 
 not only in prolonging the life of the engine, but in 
 reducing friction, and thus increasing efficiency. 
 Various types of lubricators have been devised for 
 introducing oil into the valve chest and cylinder, but 
 probably the most reliable and easily managed appa- 
 ratus for this purpose is a good oil pump worked by 
 the engine itself, for the reason that it is positive and 
 the flow of oil is not easily affected by changes in 
 
278 
 
 ENGINEERING 
 
 temperature. In the case of large horizontal engines 
 especially, it is good practice to introduce a little 
 graphite along with the cylinder oil once or twice a 
 day. 
 
 In many cases trouble is experienced with the bot- 
 
 f^s* 
 
 FIGURE 94. 
 
 torn guides of horizontal engines, especially if the 
 engine "runs over," as illustrated by Figs. 94 and 95, 
 where it will be seen that in addition to the weight of 
 the crosshead, the thrust or pressure consequent upon 
 the pull, Fig. 94, and push, Fig, 95, also comes upon 
 the bottom guide both with the inward and outward 
 
 figure 95. 
 
 strokes; whereas with an engine "running under," the 
 thrust is just in the opposite direction, and the pres- 
 sure comes upon the top guide. 
 
 The best method of lubricating the lower guide of a 
 horizontal engine is to drill through from the under- 
 
ENGINE OPERATION 
 
 279 
 
 side at a point near the center of the guide, and con- 
 nect a small size pipe, ^ or ^ in., to which an oil or 
 grease cup can be attached. The oil thus forced up 
 from beneath will serve a much better purpose than if 
 dropped on the guide, to be instantly scraped off by 
 the crosshead. 
 
 One of the best devices for oiling fhe crank pin is 
 the center oiler, illustrated in Fig. 96. An oil hole is 
 drilled along the center line of the pin to a point about 
 midway of its length, and another hole from the 
 
 figure 96. 
 
 wearing surface of the pin at right angles to the first 
 hole. The two holes meet at the center of the pin 
 and form a route by which the oil is conducted to the 
 point where it is most needed. The hole at the outer 
 end of the pin is enlarged and threaded to receive the 
 oil pipe, one end of which is connected to the pin by 
 means of a short nipple and elbow, while the other 
 end is in line with the center of the main shaft and 
 remains in that position while the crank revolves. 
 The oil is fed into this end of the pipe through an 
 
280 ENGINEERING 
 
 elbow or hollow ball screwed to the end of the pipe, 
 and the supply may be regulated at will by the engi- 
 neer, as the cup is at all times under his control. 
 
 The pillow block or main bearing of an engine 
 demands and should receive the most careful attention 
 from the engineer, for the reason that there is where 
 the greatest friction occurs, and if neglected for even 
 a short time, trouble will occur. 
 
 The main bearings of most engines are fitted with 
 apparatus for oiling them by which the oil is dropped 
 upon the top of the journal, when in fact the place that 
 the oil is most needed is at the bottom or underside of 
 the bearing. In horizontal engines, especially, there is 
 a constant pressure on the bottom of the bearing, due 
 to the weight of the flywheel and main shaft, and this 
 pressure prevents the greater part of the oil, if fed in 
 on top, from reaching the lower surface. Therefore 
 the lubrication of pillow blocks may be greatly facil- 
 itated by connecting, whenever it is possible to do so, 
 at least one oil pipe in such a way that it will conduct 
 the oil to the bottom of the bearing. In case a pillow 
 block or other bearing shows signs of warming up, 
 good results may often be obtained by using from 25 
 to 50 per cent, of cylinder oil mixed with the regular 
 engine oil. 
 
 Every engineer should establish a regular system of 
 oiling his engine, as for instance, by having regular 
 intervals of time for going around the engine and 
 inspecting all the working parts. A good rule is to 
 make the rounds about every twenty minutes. In this 
 way no part will be neglected, and the danger of 
 having hot bearings or of other accidents happening 
 will be greatly lessened. 
 
 Many automatic cut off engines, especially those of 
 
ENGINE OPERATION 281 
 
 the high speed type, are fitted with isochronal or shaft 
 governors. There are various styles of these gov- 
 ernors, but all or nearly all of them control the admis- 
 sion of steam to the cylinder, and consequently the 
 point of cut off by varying the angular advance of the 
 eccentric, which in such engines is free to move across 
 the shaft, being entirely under the control of the 
 governor. 
 
 Very close regulation is generally obtained by the 
 
 ISOCHRONAL OR SHAFT GOVERNOR, BUCKEYE ENGINE CO. 
 
 use of shaft governors, but particular attention should 
 be given to the lubrication of the steam valve, which, 
 with this class of engines, is generally a slide valve of 
 some description, and although it may be ever so 
 nicely balanced, yet if it does not get sufficient oil, the 
 friction due to dry surfaces rubbing together, will put 
 extra work on the governor, and the speed is liable to 
 be irregular. 
 
 Keying Up. To keep the working parts of an engine 
 properly keyed up so as to take up the lost motion 
 
282 ENGINEERING 
 
 without causing the bearings -to heat, is one of the 
 most delicate and exacting duties of the engineer. 
 Every engineer worthy of the name should aim to have 
 a smooth and quietly running engine. In fact, this 
 is one of the principal tests of his skill as an engineer. 
 
 A few general suggestions may be given here, but 
 much more depends upon the good judgment of the 
 engineer himself. 
 
 In connecting up an engine, as for instance, the 
 crank pin and crosshead, the key should first be driven 
 in until it is solid, that is, until the brasses clamp the 
 pin tightly. Then place a small ruler across the face 
 of the gib and key, and with the point of a knife blade, 
 or a steel scriber, make a fine mark along the edge of 
 the ruler. This will be the "solid mark.'' Now back 
 the key up by light blows with the hammer, which 
 should be of copper, until the brasses are just loose 
 enough on the pin to permit a side movement of the 
 rod. If the rod is very heavy, hold a block of wood 
 against the side of the rod near the pin and give it a 
 blow with a sledge. If there is no movement, back 
 the key a little more, and keep trying until there is a 
 side movement. There should be a space of at least 
 3V in. between the sides of the brasses and the flange 
 of the pin, so as to allow a slight side play. If it is 
 found, after running a while, that there is too much 
 lost motion, causing the engine to pound, put the ruler 
 across the gib and key again, and with a lead pencil 
 draw a line. Then loosen the set screw and drive the 
 key in a distance equal to the width of the line, and 
 no more. This process should be repeated at intervals 
 until the pound is all gone, or the bearing begins to 
 warm up slightly, indicating that the brasses are up as 
 close as they will run. 
 
ENGINE OPERATION 283 
 
 The adjustment of pillow blocks also requires a large 
 measure of skill and good judgment, and should be 
 done by degrees; but when once adjusted properly and 
 kept well oiled, the matter of keeping them in good 
 working condition becomes greatly simplified. 
 
 If a pillow block, or other bearing filled with babbit 
 metal, should become heated to such a temperature as 
 to cause the metal to run, do hot shut down the engine 
 at once and turn on a stream of cold water, because 
 this will only make matters worse, causing the metal 
 to stick to the journal, and the labor and trouble of 
 cleaning it out will be increased. The best method to 
 pursue in such an emergency is to gradually slow the 
 engine down and keep it moving at as slow a speed as 
 it will run, and in the meantime a small stream of 
 cold water may be allowed to flow over the bearing, 
 applying it to all parts as nearly as possible until it is 
 cooled, after which the engine may be stopped and 
 repairs made. 
 
 Heating Feed Water. Every steam plant should be 
 provided with one or more heaters for the purpose of 
 utilizing the exhaust steam for heating the feed water, 
 and the exhaust, not only of the engine, but of the 
 feed pumps and all other steam pumps connected with 
 the plant, should be led into it if possible. This 
 applies especially to non-condensing engines, and 
 even if the engine be a condensing engine the exhaust 
 may be passed through a closed heater before going 
 into the condenser. 
 
 The percentage of saving in heat effected by heating 
 the feed water with exhaust steam which would other- 
 wise go to waste, may be ascertained by the following 
 rule: 
 
 Multiply the difference in the total heat in the 
 
284 ENGINEERING 
 
 water above 32 , before and after heating, by 100, and 
 divide the product by the total heat required to con- 
 vert the water into steam from the initial temperature. 
 The quotient will be the per cent, of saving. 
 
 The following example will serve to illustrate the 
 process: Suppose the initial temperature of the water 
 to be 50 , and that by means of the heater its tem- 
 perature is increased to 183 before entering the 
 boiler. The steam pressure being 100 lbs. gauge, or 
 115 lbs. absolute. By referring to Table 5, it will be 
 seen that 
 
 Water at 182. g° temp, contains 151. 5 heat units, 
 
 « 5ao o << „ Ig • „ 
 
 The difference = 133.5 neat units. 
 
 One pound of steam at 115 lbs. absolute pressure 
 contains above 32 , 1,185 neat units, and for each 
 pound of water, at 50 , converted into steam at the 
 above pressure, there would be required 1,185—18 = 
 1 167 heat units; but 133.5 hear, units having been 
 added to the water while passing through the heater, 
 the problem now becomes — y^— =11.44 per cent., 
 saving in heat. 
 
 Two classes of heaters are available for this purpose, 
 viz., open heaters and closed heaters. 
 
 In the open heater the exhaust steam comes in con- 
 tact with and mingles with the water, and a portion of 
 it is condensed and returns to the boiler. In this 
 respect the open heater has an advantage over the 
 closed type, in which the water is kept separate from 
 the exhaust steam by passing it through tubes that are 
 surrounded by the steam which is confined in the outer 
 shell of the heater. In some types of the closed heater 
 the steam passes through the tubes, which are in turn 
 
ENGINE OPERATION 
 
 285 
 
 surrounded by the water. A heater of either class 
 should be sufficiently large to allow the water to pass 
 through it slowly, in order thai it may absorb all the 
 heat possible. About one-third of a square foot of 
 heating surface should be allowed per horse power for 
 a closed heater, and it should have sufficient volume 
 to contain water enough to supply the boilers for a 
 quarter of an hour. If a heater is too small for the 
 engine it is liable to cause ,„_. 
 
 *=> STEAM 
 
 back pressure on the ex- 
 haust. 
 
 There is no saving in 
 heat, but rather a loss in 
 using live steam to heat 
 the feed water, but on the 
 other hand, if the water is 
 bad, it can be purified to a 
 certain extent by passing 
 it through a live steam 
 heater on its way to the 
 boiler. 
 
 Probably the most eco- 
 nomical device for feed- 
 ing boilers is the exhaust 
 injector, which not only 
 feeds the boiler, but utilizes all the available heat in the 
 exhaust steam and returns it to the boiler. The diffi- 
 culties attending the use of the exhaust injector are 
 that it cannot force water against a pressure above 75 
 or 80 lbs., and that it will not lift its water supply by 
 suction. 
 
 The principle by which an injector is able to force 
 water against a higher pressure than that of the steam 
 by which it is operated, lies in the fact that the mix- 
 
 SECTIONAL VIEW OF PEN- 
 BERTHY INJECTOR. 
 
*!8b ENGINEERING 
 
 ture of water and steam rushes with such velocity into 
 the vacuum formed by the condensation of the steam, 
 that the momentum thus acquired carries it into the 
 boiler against the higher pressure. 
 
 Live steam injectors, while being much less econom- 
 ical than the steam pump with heater, are, neverthe- 
 less, a valuable adjunct of a steam plant. They are 
 lifting and non-lifting. A lifting injector in good con- 
 dition, with no air leaks in the suction pipe, will raise 
 the water by suction about 20 ft. With the non-lifting 
 injector the water supply must flow into the injector, 
 and it may be handled at a temperature as high as 
 150 , although not so reliable as at lower temperatures. 
 
 A good free working check valve and one that will 
 not leak, is one of the most important requisites in the 
 feeding of boilers, and especially is this the case when 
 an injector is used. 
 
 Sometimes an injector is prevented from working by 
 dirt being drawn in through the suction pipe. This 
 trouble can be avoided by fitting the pipe with a 
 strainer. If the tubes become clogged with scale, they 
 should be soaked in a dilute solution of muriatic acid, 
 say one part of acid to ten parts of water. All the 
 joints and connections should be air tight, and the 
 valves should be properly packed, otherwise the 
 injector will be a constant source of trouble. 
 
 Changing the Speed of an Engine. It sometimes hap- 
 pens that it is desired to permanently change the speed 
 of an engine, and the method of doing this is as fol- 
 lows: 
 
 If it is desired to increase the speed but two or three 
 revolutions, it can generally be accomplished by mov- 
 ing the counter balance (which most governors have) 
 farther out on the lever, although there is a limit to 
 
ENGINE OPERATION 287 
 
 this, because if moved too far, either in, to decrease 
 the speed, or out to increase the speed, the effect will be 
 to destroy the true action of the governor, and its move- 
 ments will be jerky. The location of the counter bal- 
 ance should be at that point where the governor works 
 the best at the speed at which it was designed to run, 
 and which is generally marked on the governor. And 
 this can only be determined by much patient experi- 
 menting on the part of the engineer. If moving the 
 counter balance does not bring about the desired 
 increase of speed, the next move is to increase the 
 diameter of the governor pulley so that the propor- 
 tions of the pulleys on the engine shaft and the gov- 
 ernor will be such that the governor will continue to 
 run at its normal speed, while the speed of the engine 
 has been increased the desired number of revolu- 
 tions. 
 
 To illustrate, assume the engine to be making 75 
 revolutions per minute, and that the pulley on the 
 engine shaft, upon which the governor belt runs, 
 is 12 in. in diameter, and that the governor pulley is 8 
 in. in diameter. 
 
 Suppose it is desired to increase the speed of the 
 engine to 85 revolutions per minute. First find the 
 speed of the governor with the engine running at 75 
 revolutions. 
 
 The formula is, 
 Speed of engine x diameter of shaft pulley , . 
 
 Diameter of governor pulley ^ 
 
 governor. Thus, <5 * 12 = 112. 5, revolutions for gov- 
 ernor. 
 
 Next find what the diameter of the governor pulley 
 must be to allow the governor to still run at 112. 5 revo- 
 lutions while the engine runs at 85 revolutions. 
 
288 ENGINEERING 
 
 The formula is, 
 
 Speed of engine x diameter of shaft pulley ,. 
 
 ^ i ^ — Qiameter 
 
 Speed or governor 
 
 of governor pulley. Thus, ^fip = 9.06 in., diameter 
 
 of new pulley required for governor. 
 
 Should it be desired to decrease the speed of the 
 
 engine, the same rules and formula will apply for 
 
 ascertaining the diameter of the governor pulley, which 
 
 in this case would have to be reduced in size. 
 
 Questions 
 
 1. Into what two general classes may engines be 
 divided? 
 
 2. In what respect do they differ? 
 
 3. What advantage has a compound engine over a 
 simple engine? 
 
 4. What advantage economically has a condensing 
 engine over a non-condensing engine? 
 
 5. How many kinds of condensers are there? 
 
 6. Describe a jet condenser. 
 
 7. Describe a surface condenser. 
 
 8. Is an air pump absolutely necessary with all jet 
 condensers? 
 
 9. What is meant by an independent air pump and 
 condenser? 
 
 10. What three factors determine the quantity of 
 condensing water required by an engine? 
 
 11. What is the rule for ascertaining the quantity of 
 condensing water required by an engine? 
 
 12. How may the quantity of condensing water 
 required per horse power per hour be ascertained? 
 
 13. What precautions should be observed with a 
 throttling governor? 
 
ENGINE OPERATION 289 
 
 14. What general rules should be followed in the 
 operation of an automatic cut off governor? 
 
 15. What is the most reliable device for introducing 
 oil into the valve chest and cylinder? 
 
 16. How may the bottom guide of a horizontal 
 engine be best lubricated? 
 
 17. What reliable device may be used in the lubri- 
 cation of the crank pin? 
 
 18. What precautions should be observed in the 
 lubrication of the main bearings or pillow blocks? 
 
 19. What should be done with a pillow block that 
 shows signs of warming up? 
 
 20. How does an isochronal, or shaft governor, regu- 
 late the speed of an engine? 
 
 21. How is the shaft governor affected if the steam 
 valve is not properly lubricated? 
 
 22. Describe the proper method of keying up an 
 engine. 
 
 23. What should be done in case a main bearing 
 becomes heated sufficiently to melt the babbitt? 
 
 24. How may the exhaust be utilized to an advan- 
 tage? 
 
 25. What is the rule for ascertaining the percentage 
 of saving in heat when an exhaust heater is used? 
 
 26. What two classes of heaters are available? 
 
 27. What is an open heater? 
 
 28. Describe a closed heater. 
 
 29. Is there a saving in heat effected by using alive 
 steam heater? 
 
 30. What advantage then is derived from its use? 
 
 31. Upon what principle does an injector work? 
 
 32. Into what two types are injectors divided? 
 
 33. What particular valve in the feed pipe of a boiler 
 should always be kept in good condition? 
 
290 ENGINEERING 
 
 34. How may an injector that has become clogged 
 with dirt or scale be cleaned? 
 
 35. What precautions should be observed in fitting 
 up an injector? 
 
 ^6. How may the speed of an engine be slightly 
 increased? 
 
 37. If it is desired to increase the speed consider- 
 ably, how may it be done? 
 
 38. If it is desired to decrease the speed, what 
 changes are necessary? 
 
Engineering 
 
 PART II 
 
INTRODUCTION TO PART II 
 
 In Chapters I, II and III of Part I the construction, 
 setting and operation of steam boilers is treated upon 
 at some length, but as there is a constant demand in 
 the manufacturing world for higher steam pressures, 
 the author considers that it would no doubt be of great 
 benefit to his readers if these topics were dealt with 
 more in detail. This is done in Chapters I and II, and 
 the subject of mechanical stokers and furnaces is 
 taken up in Chapter III. 
 
 Since the inauguration of the twentieth century there 
 has been introduced to the engineering profession a 
 comparatively new prime mover, in the shape of the 
 steam turbine, and judging from present indications it 
 has come to stay. Therefore it behooves engineers to 
 make themselves acquainted with it, and the sooner 
 they do so the more will they be benefited by the 
 advent of this stranger. 
 
 In the remaining portion of Part II the author has 
 endeavored to lay before his readers a plain, practical 
 description of each one of the four leading types of 
 steam turbines that are being manufactured and used 
 in this country at the present time. 
 
 C. F. S. 
 
 April, 1905. 
 
 293 
 
Engineering 
 
 PART II 
 
 CHAPTER I 
 THE BOILER 
 
 Importance of correct knowledge of the construction and 
 strength of steam boilers— Tensile strength of steel boiler 
 plates — Dr. Thurston's specifications — Specifications of U. S. 
 board of inspectors of steam vessels — Punched and drilled 
 plates — Rivets and rivet iron and steel — Efficiency of the 
 joints — Proportions of double riveted butt joints — Lloyd's 
 rules for thickness of plate and diameter of rivets— Cor- 
 rect design of triple riveted butt joints — Calculations for 
 efficiency of different forms of joints — Discussion of various 
 ways in which failure may occur in different styles of joints 
 — Necessity for higher efficiencies in riveted joints — Quad- 
 ruple and quintuple butt joints— Staying flat surfaces — 
 Different methods of staying a boiler — Correctly designed 
 stays — Stay bolts for fire box boilers — The Belpaire boiler — 
 Vanderbilt Locomotive with Morison fire box — Gusset stays — 
 Through stay rods — Calculating strength of stayed surfaces — 
 Area of segments — Proper spacing of stays — Strength of un- 
 stayed surfaces — Dished heads — Welded seams. 
 
 As it is of the highest importance, not only to the 
 engineer in charge of the plant, but also to his assist- 
 ants, and in fact to all persons whose business com- 
 pels them to be in the vicinity of the boiler-room, that 
 there should be absolutely no doubt as to the safe 
 construction of the boilers and their ability to with- 
 stand the pressures under which they are operated, the 
 295 
 
Z\)b ENGINEERING 
 
 author has compiled the following additional data 
 regarding the construction and strength of boilers. 
 The deductions and reports of tests and experiments 
 made by such eminent authorities as Dr. Thurston, 
 Prof. Wm. Kent, Dr. Peabody, D. K. Clark, Hutton 
 and many other experts have been consulted, and the 
 author has also added the results of his own obser- 
 vations, collected during an experience of thirty-five 
 years as a practical engineer. 
 
 When steel was first introduced as a material for 
 boiler plate, it was customary to demand a high tensile 
 strength, 70,000 to 74,000 lbs. persq. in., but experience 
 and practice demonstrated in course of time that it 
 was much safer to use a material of lower tensile 
 strength. It was found that with steel boiler plate of 
 high tenacity there was great liability of its cracking, 
 and also of certain changes occurring in its physical 
 properties, brought about by the variations in tem- 
 perature to which it was exposed. Consequently 
 present-day specifications for steel boiler plate call for 
 tensile strengths running from 55,000 to 66,000 lbs., 
 usually 60,000 lbs. per sq. in. Dr. Thurston gives 
 what he calls "good specifications" for boiler steel as 
 follows: "Sheets to be of uniform thickness, smooth 
 finish, and sheared closely to size ordered. Tensile 
 strength to be 60,000 lbs. per sq. in. for fire box sheets 
 and 55,000 lbs. per sq. in. for shell sheets. Work- 
 ing test: a piece from each sheet to be heated to a 
 dark cherry red, plunged into water at 6o° and bent 
 double, cold, under the hammer. Such piece to show 
 no flaw after bending. The U. S. Board of Supervising 
 Inspectors of Steam Vessels prescribes, in Section 3 of 
 General Rules and Regulations, the following method 
 for ascertaining the tensile strength of steel plate for 
 
THE BOILER 297 
 
 boilers: "There shall be taken from each sheet to be 
 used in shell or other parts of boiler which are sub- 
 ject to tensile strain, a test piece prepared in form 
 according to the following diagram: 
 
 -jdSn&L. n &. Jkr<sJ/e/ Section 
 T , ¥~ f M>t/e r ssTM,n9 r ' 
 
 ! C - ! tjk 
 
 Aboi/J-Z 
 — * 
 
 A J .:.{:.^:..Mo U fys~. 
 
 TEST PIECE. 
 
 The straight part in center shall be 9 in. in length 
 and 1 in. in width, marked with light prick punch 
 marks at distances 1 in. apart, as shown, spaced so as 
 to give 8 in. in length. The sample must show, when 
 tested, an elongation of at least 25 per cent in a length 
 of 2 in. for thickness up to % in. inclusive; in a length 
 of 4 in., for over % in. to T \ in. inclusive; in a length 
 of 6 in., for all plates over T \ in. and under 1% in. in 
 thickness. The samples shall also be capable of being 
 bent to a curve of which the inner radius is not greater 
 than i T /i times the thickness of the plates, after having 
 been heated uniformly to a low cherry red and 
 quenched in water of 82 ° F." 
 
 Punched and Drilled Plates. Much has been written 
 on this subject, and it is still open for discussion. If 
 the material is a good, soft steel, punched sheets are 
 apparently as strong and in some instances stronger 
 than drilled, especially is this the case with regard to 
 the shearing resistance of the rivets, which is greater 
 with punched than with drilled holes. 
 
 Concerning rivets and riv.et iron and steel Dr. 
 
298 
 
 ENGINEERING 
 
 Thurston has this to say in his "Manual of Steam 
 Boilers": "Rivet iron should have a tenacity in the 
 bar approaching 60,000 lbs. per sq. in., and should be 
 as ductile as the very best boiler plate when cold. A 
 good ^-in. iron rivet can be doubled up and hammered 
 together cold without exhibiting a trace of fracture." 
 The shearing resistance of iron rivets is about 85 per 
 cent and that of steel rivets about 77 per cent of the 
 tenacity of the original bar, as shown by experiments 
 made by Greig and Eyth. The researches made by 
 Wohler demonstrated that the shearing strength of 
 iron was about four-fifths of the tensile strength. 
 
 The tables that follow have been compiled from the 
 highest authorities and show the results of a long and 
 exhaustive series of tests and experiments made in 
 order to ascertain the proportions of riveted joints that 
 will give the highest efficiencies. 
 
 The following Table 11 gives the diameters of rivets 
 for various thicknesses of plates and is calculated 
 according to a rule given by Unwin. 
 
 TABLE 11 
 
 Table of Diameters of Rivets* 
 
 Thickness of 
 Plate 
 
 Diameter of Rivet 
 
 Thickness of Plate 
 
 Diameter of Rivet 
 
 V4 inch 
 
 5 /l6 " 
 
 3 / 8 " 
 7 / 16 " 
 V 2 " 
 
 V 2 inch 
 
 9 /l6 " 
 U /l6 " 
 
 3 / 4 " 
 13 /l6 " 
 
 9 /ie inch 
 5 /s " 
 3 / 4 " 
 Vs " 
 
 1 
 
 V 8 inch 
 
 15 /l6 " 
 lVl6 " 
 IVs " 
 
 1V4 " 
 
 The efficiency of the joint is the percentage of the 
 strength of the solid plate that is retained in the joint, 
 
 * Machine design— W. C. Unwin. 
 
THE BOILER 
 
 299 
 
 and it depends upon the kind of joint and method of 
 construction. 
 
 If the thickness of the plate is more than y 2 in., the 
 joint should always be of the double butt type. 
 
 The diameters of rivets, rivet holes, pitch and 
 efficiency of joint, as given in the following Table 12, 
 which was published in the "Locomotive" several 
 years ago, were adopted at the time by some of the 
 best establishments in the United States.* 
 
 TABLE 12 
 
 Proportions and Efficiencies of Riveted Joints 
 
 Inch 
 
 Inch 
 
 74 
 
 5 U 
 
 b /« 
 
 "/ifi 
 
 n U 
 
 3 /4 
 
 2 
 
 2Vi« 
 
 3 
 
 3Vs 
 
 .66 
 
 .64 
 
 .77 
 
 .76 
 
 Inch Inch 
 
 Thickness of plate 
 
 Diameter of rivet 
 
 Diameter of rivet-hole 
 
 Pitch for single riveting 
 
 Pitch for double riveting 
 
 Efficiency — single-riveted joint 
 Efficiency — double-riveted joint 
 
 3 /s 
 3 / 4 
 
 13 /l6 
 
 2Vs 
 3V 4 
 .62 
 .75 
 
 Vl6 
 13 /l6 
 
 Vs 
 2 3 /ie 
 3 3 / 8 
 .60 
 .74 
 
 v 2 
 
 15 /l6 
 
 2V 4 
 
 3V 2 
 .58 
 .73 
 
 Concerning the proportions of double-riveted 
 butt joints, Prof. Kent says: "Practically it may 
 be said that we get a double-riveted butt joint 
 of maximum strength by making the diameter of 
 the rivet about 1.8 times the thickness of the plate, 
 and making the pitch 4.1 times the diameter of the 
 hole." 
 
 Table 13 as given below is condensed from the report 
 of a test of double-riveted lap and butt joints. f In 
 
 * Thurston's "Manual of Steam Boilers.' 
 tProc. Inst. M. E., Oct., 1888. 
 
300 
 
 ENGINEERING 
 
 this test the tensile strength of the plates was 56,000 to 
 58,000 lbs. per sq. in., and the shearing resistance of 
 the rivets (steel) was about 50,000 lbs. per sq. in. 
 
 TABLE 13 
 
 Diameter and Pitch of Rivets — Double-riveted Joint 
 
 Kind of Joint 
 
 Thickness of 
 Plate 
 
 Diameter of 
 Rivet 
 
 Ratio of Pitch to 
 Diameter 
 
 Lap 
 Butt 
 Butt 
 Butt 
 
 | inch 
 
 1 " 
 3 " 
 
 1 " 
 
 0.8 inches 
 0.7 " 
 1.1 " 
 1.3 " 
 
 3 . 6 inches 
 3.9 " 
 4.0 " 
 3.9 " 
 
 Lloyd's rules, condensed, are as follows: 
 Lloyd's Rules — Thickness of Plate and Diameter of Rivets 
 
 Thickness of 
 
 Diameter of 
 
 Thickness of 
 
 Diameter of 
 
 Plate 
 
 Rivets 
 
 Plate 
 
 Rivets 
 
 3 /s inch 
 
 5 / 8 inch 
 
 3 / 4 " 
 
 7 Is inch 
 
 Vie " 
 
 5 / 8 " 
 
 13 /l6 " 
 
 Vs " 
 
 V2 " 
 
 3 / 4 " 
 
 Vs " 
 
 1 
 
 9 /l6 " 
 
 3 / 4 " 
 
 15 /l6 " 
 
 1 
 
 5 /8 " 
 
 3 / 4 " 
 
 1 
 
 1 
 
 n /l6 " 
 
 Vs " 
 
 
 
 The following Table 14 is condensed from one calcu- 
 lated by Prof. Kent,* in which he assumes the shearing 
 strength of the rivets to be four-fifths of the tensile 
 strength of the plate per square inch, and the 
 excess strength of the perforated plate to be 10 per 
 cent. 
 
 * Kent's "Mechanical Engineer's Pocket-Book," page 362. 
 
THE BOILER 
 
 301 
 
 TABLE 14 
 
 
 
 Pitch 
 
 Efficiency 
 
 Thickness 
 of Plate 
 
 Diameter 
 of Hole 
 
 
 
 
 Single 1 
 
 Double 
 
 Single 
 
 Double 
 
 
 
 Riveting 
 
 Riveting 
 
 Riveting 
 
 Riveting 
 
 Inches 
 
 Inches 
 
 Inches 
 
 Inches 
 
 Per Cent 
 
 Per Cent 
 
 3 /s 
 
 Vs 
 
 2.04 
 
 3.20 
 
 57.1 
 
 72:7 
 
 Vie 
 
 1 
 
 2.30 
 
 3.61 
 
 56.6 
 
 72.3 
 
 Va 
 
 1 
 
 2.14 
 
 3.28 
 
 53.3 
 
 70.0 
 
 V2 
 
 IVs 
 
 2.57 
 
 4.01 
 
 56.2 
 
 72.0 
 
 7l6 
 
 1 
 
 2.01 
 
 3.03 
 
 50.4 
 
 67.0 
 
 9 /l6 
 
 IVs 
 
 2.41 
 
 3.69 
 
 53.3 
 
 69.5 
 
 9 /l6 
 
 1V4 
 
 2.83 
 
 4.42 
 
 55.9 
 
 71.5 
 
 Vs 
 
 - 1 
 
 1.91 
 
 2.82 
 
 47.7 
 
 64 6 
 
 Vs 
 
 IVs 
 
 2.28 
 
 3.43 
 
 50.7 
 
 67.3 
 
 5 / 8 
 
 1V4 
 
 2.67 
 
 4.10 
 
 53.3 
 
 69.5 
 
 Another table of joint efficiencies as given by Dr. 
 Thurston* is as follows, slightly condensed from the 
 original calculation: 
 
 Vt fi " 
 
 V*' ' 
 
 5 /s' 
 
 3 / 4 ' 
 
 Vs' 
 
 1' 
 
 .53 
 
 .52 
 
 .48 
 
 .47 
 
 .45 
 
 .43 
 
 TABLE 15 
 
 Single riveting 
 
 Plate thickness. 5 / 16 ' ' 3 /s' 
 
 Efficiency 55 .55 
 
 Double riveting 
 
 Plate thickness. 3 /s" 7 / 16 " V2" 3 U" V 1" 
 Efficiency 73 .72 .71 .66 .64 .63 
 
 The author has been at considerable pains to compile 
 Tables 16, 17 and 18, giving proportions and efficiencies 
 of single lap, double lap and butt, and triple-riveted 
 butt joints. The highest authorities have been con- 
 sulted in the computation of these tables and great 
 care exercised in the calculations. 
 
 * Thurston's "Manual of Steam Boilers," page 119. 
 
302 
 
 ENGINEERING 
 
 TABLE 16 
 
 Proportions of Single-riveted Lap Joints 
 
 Thickness of Plate 
 
 Diameter of Rivet 
 
 Pitch of Rivet 
 
 Efficiency 
 
 Inches 
 
 Inches 
 
 Inches 
 
 Per Cent 
 
 716 
 
 9 /l6 
 
 1.13 
 
 50.5 
 
 
 5 /s 
 
 1.33 
 
 53.3 
 
 " 
 
 n /l6 
 
 1.55 
 
 55.7 
 
 3 /s 
 
 3 / 4 
 
 1.60 
 
 53.3 
 
 
 7 /s 
 
 2.04 
 
 57.1 
 
 7 /l6 
 
 7 /s 
 
 1.87 
 
 53.2 
 
 
 1 
 
 2.30 
 
 56.6 
 
 ^k 
 
 1 
 
 2.14 
 
 53.3 
 
 
 IVs 
 
 2.57 
 
 56.2 
 
 9 /l6 
 
 1 
 
 2.01 
 
 50.4 
 
 
 IVs 
 
 2.41 
 
 53.3 
 
 " 
 
 1V4 
 
 2.83 
 
 55.9 
 
 5 /s 
 
 IVs 
 
 2.28 
 
 50.7 
 
 
 1V4 
 
 2.67 
 
 53.3 
 
 It will be noticed that in single-riveted lap joints the 
 highest efficiencies are attained when the diameter of 
 the rivet hole is about 2^3 times the thickness of the 
 plate, and the pitch of the rivet 2^ times the diameter 
 of the hole. 
 
 With the double-riveted joint it appears, according 
 to Table 17, that in order to obtain the highest 
 efficiency the joint should be designed so that the 
 diameter of the rivet hole will be from if to 2 times 
 the thickness of plate, and the pitch should be from 
 3,M3 to 3^ times the diameter of the hole. Concerning 
 the thickness of plates Dr. Thurston has this to say:* 
 "Very thin plates cannot be well caulked, and thick 
 plates cannot be safely riveted. The limits are about 
 % of an inch for the lower limit, and % of an inch for 
 the higher limit." The riveting machine, however, 
 overcomes the difficulty with very thick plates. 
 
 ■■* Thurston's "Manual of Steam Boilers," page 120. 
 
THE BOILER 303 
 
 TABLE 17 
 Proportions of Double-riveted Lap and Butt Joints 
 
 Thickness of 
 
 Diameter of 
 
 
 
 Plate 
 
 Rivet 
 
 Pitch of Rivet 
 
 Efficiency 
 
 5 /ie inch 
 
 9 /ie inch 
 
 1 .71 inches 
 
 67 . 1 per cent 
 
 5 /l6 " 
 
 5 / 8 " 
 
 2.05 " 
 
 69.5 ' 
 
 
 3 / 8 " 
 
 3 / 4 " 
 
 2.46 " 
 
 69.5 ' 
 
 
 3 / 8 " 
 
 7 U " 
 
 3.20 " 
 
 72.7 ' 
 
 
 7 /l6 " 
 
 3 U " 
 
 2.21 " 
 
 66.2 ' 
 
 
 Vl6 " 
 
 Vs " 
 
 2 86 " 
 
 69.4 
 
 
 Vl6 " 
 
 1 
 
 3 61 " 
 
 72.3 « 
 
 
 Vi " 
 
 1 
 
 3.28 " 
 
 70.0 ' 
 
 
 Vi " 
 
 IVs " 
 
 4.01 " 
 
 72.0 ' 
 
 
 9 /l6 " 
 
 1 
 
 3.03 " 
 
 67.0 ' 
 
 
 9 /l6 " 
 
 IVs " 
 
 3.69 " 
 
 69.5 ' 
 
 
 9 /l6 " 
 
 1V4 " 
 
 4.42 " 
 
 71.5 ' 
 
 
 5 /s " 
 
 IVs' " 
 
 3.43 " 
 
 67.3 ' 
 
 
 5 / 8 " 
 
 1V4 " 
 
 4.10 " 
 
 69.5 ' 
 
 
 3 / 4 " 
 
 1 
 
 2.50 " 
 
 72.0 ' 
 
 
 7 / 8 " 
 
 IVs " 
 
 3.94 " 
 
 74.2 ' 
 
 
 1 
 
 1V4 " 
 
 4.10 " 
 
 76.1 ' 
 
 
 The triple-riveted butt joint with two welts, one in- 
 side and one outside, has two rows of rivets in double 
 shear and one outer row in single shear on each side 
 of the butt, the pitch of rivets in the outer rows being 
 twice the pitch of the inner rows. One of the welts is 
 wide enough for the three rows of rivets each side of 
 the butt, while the other welt takes in only the two 
 close pitch rows. 
 
 When properly designed, this form of joint has a 
 high efficiency, and is to be relied upon. Table 18 
 gives proportions and efficiencies, and it will be noted 
 that the highest degree of efficiency is shown when the 
 diameter of rivet hole is from ij£ to 1% times the 
 thickness of plate, and the pitch of the rivets is from 
 lY 2 to 4 times the diameter of the hole. This, of 
 
304 
 
 ENGINEERING 
 
 course, refers to the pitch of the close rows of rivets, 
 and not the two outer rows. 
 
 TABLE 18 
 
 Proportions of Triple-riveted Butt Joints with Inside and 
 Outside Welt 
 
 Thickness of 
 
 Diameter of 
 
 Pitch of 
 
 Pitch of 
 
 Efficiency 
 Per Cent 
 
 Plate 
 
 Rivet 
 
 Rivet 
 
 Outer Rows 
 
 Inches 
 
 Inches 
 
 Inches 
 
 Inches 
 
 7s 
 
 u /ie 
 
 3.25 
 
 6.5 
 
 84 
 
 Vic 
 
 M /ie 
 
 3.25 
 
 6.5 
 
 85 
 
 72 
 
 U /lG 
 
 3.25 
 
 6.5 
 
 83 
 
 7io 
 
 Vs 
 
 3.50 
 
 7.0 
 
 84 
 
 7s 
 
 1 
 
 3.50 
 
 7.0 
 
 86 
 
 74 
 
 lVl6 
 
 3.50 
 
 7.0 
 
 85 
 
 Vs 
 
 IVs 
 
 3.75 
 
 7.5 
 
 86 
 
 l 
 
 1V4 
 
 3.87 
 
 7.7 
 
 84 
 
 Some simple rules are given in Chapter I, Part I, for 
 finding the percentage of efficiency, or in other words 
 the ratio of the strength of the riveted joint to the 
 strength of the solid plate. In those calculations the 
 tensile strength of the rivets was assumed to be 38,000 
 to 40,000 lbs. per sq. in. The highest efficiency is 
 attained in a riveted joint when the tensile strength of 
 the rods from which the rivets are cut approaches that 
 of the plates, and when the proportions of the joint 
 are such that the tensile strength of the plates, the 
 shearing strength of the rivets, and the crushing 
 resistance of the rivets and plate, for a given section 
 or unit strip, are as nearly equal as it is possible to 
 secure them. 
 
 A few examples of calculations for efficiency will be 
 given, taking the three forms of riveted joints in most 
 common use. The following notation will be used 
 throughout: 
 
THE BOILER 
 
 305 
 
 T.S. = Tensile strength of plate per square inch. 
 T = Thickness of plate. 
 
 C = Crushing resistance of plate and rivets. 
 A = Sectional area of rivets. 
 S = Shearing strength of rivets. 
 D = Diameter of hole (also diameter of rivets 
 
 when driven). 
 P = Pitch of rivets. 
 In the calculations that follow T.S. will be assumed 
 to be 6o,000 lbs., S will be taken at 45,000 lbs., and the 
 value of C may be assumed to be 90,000 to 95,000. 
 
 Fig. 97 shows a double-riveted lap joint. The style 
 of riveting in this joint 
 is what is known as 
 chain riveting. 
 
 In case the rivets are 
 staggered, the same 
 rules for calculating 
 the efficiency will hold 
 as with chain riveting, 
 for the reason that 
 with either style of 
 riveting the unit strip 
 of plate has a width equal to the pitch or distance p, 
 Fig. 97. ^ 
 
 The dimensions of the joint under consideration are 
 as follows: P = 3^ in., T = T 7 6 - in., D = I in. (which is 
 also diameter of driven rivet). 
 
 The strength of the unit strip of solid plate is 
 PxTxT.S. =85,312. 
 
 The strength of net section of plate after drilling is 
 P - D x T x T.S. = 59,062. 
 
 The shearing resistance of two rivets is 2A x S = 70, 
 686. 
 
 FIGURE 97. 
 
.306 
 
 ENGINEERING 
 
 The crushing resistance of rivets and plate is 
 Dx2xTxC = 78,750. 
 
 It thus appears that the weakest part of the joint is 
 the net strip or section of plate, the strength of which 
 is 59,062 and the efficiency = 59,062 x 100 -*- 85,312 = 
 69.2 per cent. 
 
 A double-riveted butt joint is illustrated by Fig. 
 98, and the dimensions are as follows: 
 
 P, inner row 
 of rivets = 2^ 
 in. 
 
 P', outer row 
 of rivets = 5^ 
 in. 
 
 Tof plate and 
 butt straps = T \ 
 in. 
 
 Dof hole and 
 driven rivet = 1 
 in. 
 
 Failure may 
 
 occur in this joint in five distinct ways, which will be 
 taken up in their order. 
 
 1. Tearing of the plate at the outer row of rivets. 
 The net strength at this point is P-DxTxT.S., 
 which, expressed in plain figures, results as follows: 
 5.5- 1 x .4375 x 60,000= 118,125. 
 
 2. Shearing two rivets in double shear and one in . 
 single shear. Should this occur, the two rivets in the 
 inner row would be sheared on both sides of the plate, 
 thus being in double shear. Opposed to this strain 
 there are four sections of rivets, two for each rivet. 
 Then at the outer row of rivets in the unit strip there 
 is the area of one rivet in single shear to be added, 
 
 FIGURE 98. 
 
THE BOILER 
 
 307 
 
 The total resistance, therefore, is 5A x S as follows: 
 .7854 x 5 x 45,000 = 176,715. 
 
 3. The plate may tear at the inner row of rivets and 
 shear one rivet in the outer row. The resistance in 
 this case would be P' — 2D x T x T.S. + A x S as 
 follows: 5.5 -2 x .4375 x 60,000 + .7854 x 45,000 = 
 127,218. 
 
 4. Failure may occur by crushing in front of three 
 rivets. Opposed to this is 3D xTxC, or 1 x 3 x -4375 x 
 95,000= 124,687. 
 
 5. Failure may occur by crushing in front of two 
 rivets and shearing one. The resistance is represented 
 by 2D x T x C + iA x S; expressed in figures, Ix2x 
 •4375 x 95.000 + .7854 x 45,000 = 1 18,468. 
 
 The strength of a solid strip of plate 5^ in. wide 
 before drilling is P' x T x T.S. , or 5. 5 x .4375 x 60,000 = 
 144,375, an d tne efficiency of the joint is 1 18,125 x 100 ■*■ 
 144,375 = 81. 1 per cent. 
 
 A triple-riveted butt joint is shown in Fig. 99, the 
 dimensions of 
 which are as fol- 
 lows: 
 
 T~*.in. 
 
 D = |f in. 
 
 A = .69 in. 
 
 P =3 3 /s in. 
 
 P' = 6^ in. 
 
 Failure may 
 occur in this 
 joint in either 
 one of five 
 ways. 
 
 I. By tearing the plate at the outer row of rivets 
 where the pitch is 6% in. The net strength of the unit 
 
 FIGURE 99. 
 
308 ENGINEERING 
 
 strip at this point isP'-DxTx T.S., found as follows: 
 675 - -9375 x -4375 x 60,000 = 152,578. 
 
 2. By shearing four rivets in double shear and one 
 in single shear. In this instance, of the four rivets in 
 double shear, each one presents two sections, and 
 the one in single shear presents one, fc thus making 
 a total of nine sections of rivets to be sheared, 
 and the strength is 9A x S, or .69 x 9 x 45,000 = 
 279,450. 
 
 3. Rupture of the plate at the middle row of rivets 
 and shearing one rivet. Opposed to this strain the 
 strength is P' - 2D x T x T.S. t iA x S, equivalent to 
 6-75 - (-9375 x 2) x .4375 x 60,000 + .69 x 90,000 = 
 190,068. 
 
 4. Crushing in front of four rivets and shearing one 
 rivet. The resistance in this instance is 4D x T x C + 
 1 A x S, or .9375 x 4 x .4375 x 90,000 + .69 x 45,000 = 
 178,706. 
 
 5. Failure may be caused by crushing in front of 
 five rivets, four of which pass through both the 
 inside and outside butt straps, while the fifth rivet 
 passes through the inside strap only, and the resist- 
 ance is 5D x T x C, equivalent to .9375 x 5 x 90,000 = 
 184,570. 
 
 The strength of the unit strip of plate before drilling 
 isP'xTx T.S., or 6.75 x .4375 x 60,000 = 177,187, and 
 the efficiency is 152,578x100-177,187 = 86 per 
 cent. 
 
 With the constantly increasing demand for higher 
 steam pressures, the necessity for higher efficiencies in 
 the riveted joints of boilers becomes more apparent, 
 and of late years quadruple and even quintuple-riveted 
 butt joints have in many instances come into use. The 
 quadruple butt joint when properly designed shows a 
 
THE BOILER 
 
 309 
 
 high efficiency, in some cases as high as 94.6 per cent. 
 Fig. 100 illustrates a joint of this kind, and the 
 dimensions are as follows: 
 
 T=y 2 in. 
 
 D = i| in. 
 
 A = .69 in. 
 
 P, inner rows = 3^ in. 
 
 ?', 1st outer row = jy 2 in. 
 
 P", 2d outer row = 15 in. 
 
 The two inner rows of rivets extend through the 
 
 FIGURE 100. 
 
 main plate and both the inside and outside cover 
 plates or butt straps. 
 
 The two outer rows reach through the main plate 
 and inside cover plate only, the first outer row having 
 twice the pitch of the inner rows, and the second 
 outer row has twice the pitch of the first. 
 
310 ENGINEERING 
 
 Taking a strip or section of plate 15 in. wide (pitch 
 of outer row), there are four ways in which this joint 
 may fail. 
 
 1. By tearing of the plate at the outer row of rivets. 
 The resistance is P" — DxTxT.S., or 15 — .9375 x 
 .5 x 60,000 = 421,875. 
 
 2. By shearing eight rivets in double shear and three 
 in single shear. The strength in resistance is 19A x S, 
 or .69 x 19 x 45,000 = 589,950. 
 
 3. By tearing at inner rows of rivets and shearing 
 three rivets. The resistance is P" - 4D x T x T.S. + 
 3A x S, or 15 -(.9375 x 4) x .5 x 60,000+ .69 x 3 x45,000 = 
 430,650. 
 
 4. By tearing at the first outer row of rivets, where 
 the pitch is 7^ in., and shearing one rivet. The 
 resistance is P" — 2D x T x T.S. + A x S, or 15 — (.9375 x 
 2) x .5 x 60,000+ .69 x 45,000 = 424,800. 
 
 It appears that the weakest part of the joint is at the 
 outer row of rivets, where the net strength is 421,875. 
 The strength of the solid strip of plate 15 in. wide 
 before drilling is P" x T x T.S., or 15 x .5 x 60,000 = 
 450,000, and the efficiency is 421,875 x 100 ■*■ 450,000 = 
 93.7 per cent. 
 
 Staying Flat Surfaces. The proper staying or bracing 
 of all flat surfaces in steam boilers is a highly important 
 problem, and while there are various methods of 
 bracing resorted to, still, as Dr. Peabody says, "the 
 staying of a flat surface consists essentially in holding 
 it against pressure at a series of isolated points which 
 are arranged in regular or symmetrical pattern." The 
 cylindrical shell of a boiler does not need bracing for 
 the very simple reason that the internal pressure tends 
 to keep it cylindrical. On the contrary the internal 
 pressure has a constant tendency to bulge out the flat 
 
THE BOILER 
 
 311 
 
 FIGURE 101. 
 
 surface. Rule 2, Section 6, of the rules of the U. S. 
 Supervising Inspectors provides as follows: "No braces 
 or stays hereafter to be employed in the construction 
 of boilers shall be 
 allowed a greater 
 strain than 6,000 lbs. 
 per sq. in. of sec- 
 tion." 
 
 The method to be 
 employed in staying 
 a boiler depends upon the type of boiler and the pressure 
 to be carried. Formerly when comparatively low pres- 
 sures were used (60 to 75 lbs. per sq. in.) the diagonal 
 crow foot brace was considered amply sufficient for stay- 
 ing the flat heads of boilers of the cylindrical tubular 
 type, both above and below the tubes, but in the present 
 age, when much higher pressures are demanded, 
 through stay rods are largely employed. These are 
 soft steel or iron rods i}( to 2 in. in diameter, extend- 
 ing through from head to head, with a pull at right 
 angles to the plate, thus having a great advantage 
 over the diagonal stay in that the pull on the diagonal 
 
 tay per square inch of 
 section is more than 5 
 per cent in excess of 
 what a through stay 
 would have to resist 
 under the same condi- 
 tions of pressure, etc. 
 The method of calculation for diagonal bracing is 
 given in Chapter I and will not be discussed here. 
 
 The weakest portion of the crow foot brace when in 
 position is at the foot end, where it is connected to the 
 head by two rivets. With a correctly designed brace 
 
 figure 102. 
 
312 
 
 ENGINEERING 
 
 FIGURE 103. 
 
 the pull on these rivets is direct and the tensile strength 
 of the material needs to be considered only, but if the 
 form of the brace is such as to bring the rivet holes 
 above or below the center line of the 
 brace, or if the rivets are pitched too 
 far from the body of the brace, there 
 will be a certain leverage exerted upon 
 the rivets in addition to the direct pull. 
 Fig. 101 shows a brace of incorrect 
 design and Figs. 102 and 103 show 
 braces designed along correct lines. 
 
 Other methods of staying, besides 
 the crow foot brace and through stays, 
 consist of gusset stays, and for locomo- 
 tives and other fire box boilers screwed 
 stay bolts are employed to tie the fire 
 box to the external shell. The. holes for these stay 
 bolts are punched or drilled before the fire box is put 
 in place. After it is in and riveted along the lower 
 edge to the foundation ring, or mud ring as it is some- 
 times called, a continuous thread is tapped in the 
 holes in both the outside plate and the fire sheet 
 by running a long tap through both plates. The 
 steel stay bolt is then screwed through the plates 
 and allowed to project enough at each end to permit 
 of its being riveted cold. Stay bolts are liable 
 to be broken by the unequal expansion of the fire 
 box and outer shell, and a small hole should be 
 drilled in the center of the bolt, from the outer end 
 nearly through to the inner end. Then in case a bolt 
 breaks, steam or water will blow out through the small 
 hole, and the break will be discovered at once. The 
 problem of properly staying the flat crown sheet of a 
 horizontal fire box boiler, especially a locomotive 
 
THE BOILER 313 
 
 boiler, is a very difficult one and has taxed the inven- 
 tive genius of some of the most eminent engineers. 
 
 Before the invention of the Belpaire boiler, with its 
 outside or shell plate flat above the fire box, the only 
 method of staying the crown sheet was by the use of 
 cumbersome crown bars or double girders extending 
 across the top of the crown sheet and supported at the 
 ends by special castings that rest on the edges of the 
 side sheets and on the flange of the crown sheet. At 
 intervals of 4 or 5 in. crown bolts are placed, having 
 the head inside the fire box and the nut bearing on a 
 plate on top of the girder. There is also a thimble for 
 each bolt to pass through, between the top of the 
 crown sheet and the girder. These thimbles maintain 
 the proper distance between the crown sheet and 
 girder and allow the water to circulate freely. 
 
 The Belpaire fire box dispenses with girders and 
 permits the use of through stays from the top of the 
 fiat outside plate through the crown sheet and secured 
 at each end by nuts and copper washers. 
 
 For simplicity of construction and great strength the 
 cylindrical form of fire box known as the Morison 
 corrugated furnace has proved to be very successful. 
 This form of fire box was in 1899 applied to a loco- 
 motive by Mr. Cornelius Vanderbilt, at the time assist- 
 ant superintendent of motive power of the New York 
 Central and Hudson River R. R. This furnace was 
 rolled of fy-'m. steel, is 59 in. internal diameter and 11 
 ft. 2% in. in length. It was tested under an external 
 pressure of 500 lbs. per sq. in. before being placed in 
 the boiler. It is carried at the front end by a row of 
 radial sling stays from the outside plate, and supported 
 at the rear by the back head. Figs. 104 and 105 show 
 respectively a sectional view and an end elevation of 
 
314 
 
 ENGINEERING 
 
 this boiler. It will 
 be seen at once 
 that the question 
 of stays for a fire 
 box of this type 
 becomes very sim- 
 ple. The boiler 
 has proved to be 
 so satisfactory that 
 the company has 
 since had five more 
 of the same type 
 constructed. 
 
 Gusset stays are 
 used mainly in 
 boilers of the Lan- 
 cashire model and 
 are triangular- 
 shaped plates 
 sheared to the 
 proper form and 
 having- two angle 
 irons riveted to the 
 edges that come 
 against the shell 
 and the head. The 
 angle irons are 
 then riveted to the 
 shell and the flat 
 head. This form 
 of brace is simple 
 and solid, but its 
 chief defect is, 
 that it is very rigid 
 
THE BOILER 
 
 1515 
 
 and does not allow for the unequal expansion of the in- 
 ternal furnace flues and the shell. Fig. 106 illustrates a 
 gusset stay and the method of applying it. 
 
 Coming now to through stay rods, it is safe to say 
 that whenever and wherever it is possible to apply 
 them they should be used. In all cases they should 
 
 Vertical Section A-B. 
 
 nog 
 
 End Elevation, 
 Sfiowing Attachment of Long. Stays. 
 
 fc— fl^'-H Half End Elevation 
 Half Section C-D. j of Smoke-Box. 
 
 FIGURE 105. 
 
 be placed far enough apart to allow a man to pass 
 between them for the purposes of inspection and wash- 
 ing out of the boiler. Through stay rods are usually 
 spaced 14 in. apart horizontally and about the same 
 distance vertically. The ends, as far back as the 
 threads run, are swaged larger than the body, so that 
 the diameter at the bottom of the thread is greater 
 than the diameter of the body. There are several 
 
316 
 
 ENGINEERING 
 
 methods of applying through stays. One of the most 
 common, especially for land boilers, is to allow the 
 ends of the rod • to project through the plates to be 
 stayed, and holding them in place by a nut and copper 
 washer, both inside and outside the plate. Another 
 and still better plan is to rivet 6-in. channel bars across 
 
 the head, inside above 
 ' the tubes, the number 
 of bars depending 
 upon the height of the 
 segment to be stayed. 
 The channel bars 
 are drilled to corre- 
 spond with the holes 
 that are drilled in the 
 plate to receive the stay rods, which latter are then 
 secured by inside and outside nuts and copper washers. 
 
 jTTSW' T 
 
 10 x 
 
 i° / u 
 
 
 FIGURE 106. 
 
 FIGURE 107. 
 
 These channel bars act as girders and serve to greatly 
 strengthen the head or flat plate. Fig. 107 will serve 
 to illustrate this method. 
 
THE BOILER 
 
 317 
 
 Sometimes a combination of channel bar and 
 diagonal crow foot braces is used, as shown by Fig. 108. 
 
 A good form of diagonal crow foot stay is obtained 
 by using dou- 
 ble crow feet, 
 made of pieces 
 of boiler plate 
 bent as shown 
 by Fig. 109 
 and riveted to 
 the plate by 
 four rivets. A 
 hole is drilled 
 through the 
 body of the 
 crow foot, and 
 a bolt pass- 
 ing through 
 this secures th 
 
 0000( t 
 
 FIGURE 108. 
 
 forked end of the stay. 
 
 Another method of securing through stays to the 
 
 heads is shown by Fig. no and is applied where too 
 
 many stay rods would be required 
 
 to connect all the points to be 
 
 stayed. A tee iron is first riveted 
 
 to the flat plate to be stayed, and 
 
 two V-shaped forgings are bolted 
 
 to it as shown. The through stay 
 
 is then bolted to the forgings, and 
 
 thus two points in the flat head 
 
 are supported by one stay. It will 
 
 readily be seen that this method will reduce the number 
 
 of through stay rods required. 
 
 Calculating the Strength of Stayed Surfaces. In cal- 
 culations for ascertaining the strength of stayed sur- 
 
 figuke 109. 
 
318 
 
 ENGINEERING 
 
 faces, or for finding the number of stays required for 
 any given flat surface in a boiler, the working pressure 
 being known, it must be remembered that each stay 
 is subjected to the pressure on an area bounded by 
 lines drawn midway between it and its neighbors. 
 Therefore the area in square inches, of the surface to 
 
 FIGURE 110. 
 
 be supported by each stay, equals the square of the 
 pitch or distance in inches between centers of the 
 points of connection of the stays to the flat plate. 
 Thus, suppose the stays in a certain boiler are spaced 
 8 in. apart, the area sustained by each stay = 8x8 = 
 64 sq. in., or assume the stay bolts in a locomotive fire 
 box to be pitched 4^ in. each way, the area sup- 
 ported by each stay bolt = 4^2 x 4>2 = 20*4 sq. in. 
 Again taking through stay rods, suppose, for example, 
 
THE BOILER 319 
 
 the through stays shown in Fig. 107 to be spaced 15 
 in. horizontally and 14 in. vertically, the area sup- 
 ported by each stay = 15 x 14 = 210 sq. in. 
 
 The minimum factor of safety for stays, stay bolts 
 and braces is 8, and this factor should enter into all 
 computations of the strength of stayed surfaces. 
 
 The pitch for stays depends upon the thickness of 
 the plate to be supported, and the maximum pressure 
 to be carried. 
 
 In computing the total area of the stayed surface it 
 is safe to assume that the flange of the plate, where it 
 is riveted to the shell, sufficiently strengthens the plate 
 for a distance of 2 in. from the shell, also that the 
 tubes act as stays for a space of 2 in. above the top 
 row. Therefore the area of that portion of the flat 
 head or plate bounded by an imaginary line drawn at 
 a distance of 2 in. from the shell and the same dis- 
 tance from the last row of tubes is the area to be 
 stayed. This surface may be in the form of a segment 
 of a circle, as with a horizontal cylindrical boiler, or 
 it may be rectangular in shape, as in the case of a 
 locomotive or other fire box boiler. Other forms of 
 stayed surfaces are often encountered, but in general 
 the rules applicable to segments or rectangular figures 
 will suffice for ascertaining the areas. 
 
 The method, of finding the area of the segmental 
 portion of the head above the tubes is given in Chapter 
 I, pages 22 and 23, and will not be enlarged upon here, 
 except to add Table 19, which covers a much greater 
 number of segments than Table 1, page 22, does. The 
 diameter of the circle and the rise or height of the 
 segment being known, the area of the segment may 
 be found by the following rule: 
 
 Rule. Divide the height of the segment by the 
 
320 
 
 ENGINEERING 
 
 TABLE 19 
 
 Areas of Segments of a Circle 
 
 Ratio 
 
 Area 
 
 Ratio 
 
 Area 
 
 Ratio 
 
 Area 
 
 Ratio 
 
 Area 
 
 .2 
 
 11182 
 
 .243 
 
 14751 
 
 .286 
 
 18542 
 
 .329 
 
 . 22509 
 
 '201 
 
 11262 
 
 .244 
 
 14837 
 
 .287 
 
 18633 
 
 .33 
 
 . 22603 
 
 .202 
 
 11343 
 
 .245 
 
 14923 
 
 .288 
 
 18723 
 
 .331 
 
 . 22697 
 
 .203 
 
 11423 
 
 .246 
 
 15009 
 
 .289 
 
 18814 
 
 .332 
 
 . 22792 
 
 .204 
 
 11504 
 
 .247 
 
 15095 
 
 .29 
 
 18905 
 
 .333 
 
 . 22886 
 
 .205 
 
 11584 
 
 .248 
 
 15182 
 
 .291 
 
 18996 
 
 .334 
 
 . 22980 
 
 .206 
 
 11665 
 
 .249 
 
 15268 
 
 .292 
 
 19086 
 
 .335 
 
 . 23074 
 
 .207 
 
 11746 
 
 .25 
 
 15355 
 
 .293 
 
 19177 
 
 .336 
 
 .23169 
 
 .208 
 
 11827 
 
 .251 
 
 15441 
 
 .294 
 
 19268 
 
 .337 
 
 . 23263 
 
 .209 
 
 11908 
 
 .252 
 
 15528 
 
 .295 
 
 19360 
 
 . 338 
 
 . 23358 
 
 .21 
 
 11990 
 
 .253 
 
 15615 
 
 .296 
 
 19451 
 
 . 339 
 
 . 23453 
 
 .211 
 
 12071 
 
 .254 
 
 15702 
 
 .297 
 
 19542 
 
 .34 
 
 . 23547 
 
 .212 
 
 12153 
 
 .255 
 
 15789 
 
 .298 
 
 19634 
 
 l -341 
 
 . 23642 
 
 .213 
 
 12235 
 
 .256 
 
 15876 
 
 .299 
 
 19725 
 
 .342 
 
 . 23737 
 
 .214 
 
 12317 
 
 .257 
 
 15964 
 
 .3 
 
 19817 
 
 .343 
 
 . 23832 
 
 .215 
 
 12399 
 
 .258 
 
 16051 
 
 .301 
 
 19908 
 
 .344 
 
 . 23927 
 
 .216 
 
 12481 
 
 .259 
 
 16139 
 
 .302 
 
 20000 
 
 .345 
 
 . 24022 
 
 .217 
 
 12563 
 
 .26 
 
 16226 
 
 .303 
 
 20092 
 
 .346 
 
 .24117 
 
 .218 
 
 12646 
 
 .261 
 
 16314 
 
 .304 
 
 20184 
 
 .347 
 
 .24212 
 
 .219 
 
 12729 
 
 .262 
 
 16402 
 
 .305 
 
 20276 
 
 .348 
 
 . 24307 
 
 .22 
 
 12811 
 
 .263 
 
 16490 
 
 .306 
 
 20368 
 
 .349 
 
 . 24403 
 
 .221 
 
 12894 
 
 .264 
 
 16578 
 
 .307 
 
 20460 
 
 .35 
 
 . 24498 
 
 .222 
 
 12977 
 
 .265 
 
 16666 
 
 .308 
 
 20553 
 
 .351 
 
 . 24593 
 
 .223 
 
 13060 
 
 .266 
 
 16755 
 
 .309 
 
 20645 
 
 .352 
 
 . 24689 
 
 .224 
 
 13144 
 
 .267 
 
 16843 
 
 .31 
 
 20738 
 
 .353 
 
 . 24784 
 
 .225 
 
 13227 
 
 .268 
 
 16932 
 
 .311 
 
 20830 
 
 .354 
 
 . 24880 
 
 .226 
 
 13311 
 
 .269 
 
 17020 
 
 .312 
 
 20923 
 
 .355 
 
 . 24976 
 
 .227 
 
 13395 
 
 .27 
 
 17109 
 
 .313 
 
 21015 
 
 . 356 
 
 . 25071 
 
 .228 
 
 13478 
 
 .271 
 
 17198 
 
 .314 
 
 21108 
 
 . 357 
 
 .25167 
 
 .229 
 
 13562 
 
 .272 
 
 17287 
 
 .315 
 
 21201 
 
 .358 
 
 . 25263 
 
 .23 
 
 13646 
 
 .273 
 
 17376 
 
 .316 
 
 21294 
 
 .359 
 
 . 25359 
 
 .231 
 
 13731 
 
 .274 
 
 17465 
 
 .317 
 
 21387 
 
 .36 
 
 . 25455 
 
 .232 
 
 13815 
 
 .275 
 
 17554 
 
 .318 
 
 21480 
 
 .361 
 
 . 25551 
 
 .233 
 
 13900 
 
 .276 
 
 17644 
 
 .319 
 
 21573 
 
 .362 
 
 . 25647 
 
 .234 
 
 13984 
 
 .277 
 
 17733 
 
 .32 
 
 21667 
 
 .363 
 
 . 25743 
 
 .235 
 
 14069 
 
 .278 
 
 17823 
 
 .321 
 
 21760 
 
 .364 
 
 . 25839 
 
 .236 
 
 14154 
 
 .279 
 
 17912 
 
 .322 
 
 21853 
 
 .365 
 
 . 25936 
 
 .237 
 
 14239 
 
 .280 
 
 18002 
 
 .323 
 
 21947 
 
 .366 
 
 . 26032 
 
 .238 
 
 14324 
 
 .281 
 
 18092 
 
 .324 
 
 22040 
 
 .367 
 
 .26128 
 
 .239 
 
 14409 
 
 .282 
 
 18182 
 
 .325 
 
 22134 
 
 .368 
 
 . 26225 
 
 .24 
 
 14494 
 
 .283 
 
 18272 
 
 .326 
 
 22228 
 
 .369 
 
 . 26321 
 
 .241 
 
 14580 
 
 .284 
 
 18362 
 
 .327 
 
 22322 
 
 .37 
 
 .26418 
 
 .242 
 
 14666 
 
 .285 
 
 18452 
 
 .328 
 
 22415 
 
 .371 
 
 .26514 
 
THE BOILER 
 
 TABLE 1 9 — Contin tied 
 
 321 
 
 Ratio 
 
 Area 
 
 Ratio 
 
 Area 
 
 Ratio 
 
 Area 
 
 Ratio 
 
 Area 
 
 .372 
 
 .26611 
 
 .405 
 
 . 29827 
 
 .438 
 
 .33086 
 
 .471 
 
 .36373 
 
 .373 
 
 . 26708 
 
 .406 
 
 . 29926 
 
 .439 
 
 .33185 
 
 .472 
 
 .36471 
 
 .374 
 
 . 26805 
 
 .407 
 
 .30024 
 
 .44 
 
 . 33284 
 
 .473 
 
 .36571 
 
 .375 
 
 .26901 
 
 .408 
 
 .30122 
 
 .441 
 
 .33384 
 
 .474 
 
 .36671 
 
 .376 
 
 . 26998 
 
 .409 
 
 .30220 
 
 .442 
 
 . 33483 
 
 .475 
 
 .36771 
 
 .377 
 
 . 27095 
 
 .41 
 
 .30319 
 
 .443 
 
 .33582 
 
 .476 
 
 .26871 
 
 .378 
 
 .27192 
 
 .411 
 
 .30417 
 
 .444 
 
 .33682 
 
 .477 
 
 .36971 
 
 .379 
 
 . 27289 
 
 .412 
 
 .30516 
 
 .445 
 
 .33781 
 
 .•478 
 
 .37071 
 
 .38 
 
 . 27386 
 
 .413 
 
 .30614 
 
 .446 
 
 . 33880 
 
 .479 
 
 .37171 
 
 .381 
 
 . 27483 
 
 .414 
 
 .30712 
 
 .447 
 
 .33980 
 
 .48 
 
 .37270 
 
 .382 
 
 . 27580 
 
 .415 
 
 .30811 
 
 .448 
 
 .34079 
 
 .481 
 
 .37370 
 
 .383 
 
 . 27678 
 
 .416 
 
 .30910 
 
 .449 
 
 .34179 
 
 .482 
 
 .37470 
 
 .384 
 
 . 27775 
 
 .417 
 
 .31008 
 
 .45 
 
 .34278 
 
 .483 
 
 .37570 
 
 .385 
 
 . 27872 
 
 .418 
 
 .31107 
 
 .451 
 
 .34378 
 
 .484 
 
 .37670 
 
 .386 
 
 . 27969 
 
 .419 
 
 .31205 
 
 .452 
 
 .34477 
 
 .485 
 
 .37770 
 
 .387 
 
 . 28067 
 
 .42 
 
 .31304 
 
 .453 
 
 .34577 
 
 .486 
 
 .37870 
 
 .388 
 
 .28164 
 
 .421 
 
 .31403 
 
 .454 
 
 .34676 
 
 .487 
 
 .37970 
 
 .389 
 
 . 28262 
 
 .422 
 
 .31502 
 
 .4*5 
 
 .34776 
 
 .488 
 
 .38070 
 
 .39 
 
 . 28359 
 
 .423 
 
 .31600 
 
 .456 
 
 .34876 
 
 .489 
 
 .38170 
 
 .391 
 
 . 28457 
 
 .424 
 
 .31699 
 
 .457 
 
 .34975 
 
 .49 
 
 .38270 
 
 .392 
 
 . 28554 
 
 .425 
 
 .31798 
 
 .458 
 
 .35075 
 
 .491 
 
 .38370 
 
 .393 
 
 . 28652 
 
 .426 
 
 .31897 
 
 .459 
 
 .35175 
 
 .492 
 
 . 38470 
 
 .394 
 
 . 28750 
 
 .427 
 
 .31996 
 
 .46 
 
 .35274 
 
 .493 
 
 .38570 
 
 .395 
 
 . 28848 
 
 .428 
 
 .32095 
 
 .461 
 
 . 35374 
 
 .494 
 
 . 38670 
 
 .396 
 
 . 28945 
 
 .429 
 
 .32194 
 
 .462 
 
 . 35474 
 
 .495 
 
 .38770 
 
 .397 
 
 . 29043 
 
 .43 
 
 .32293 
 
 .463 
 
 . 35573 
 
 .496 
 
 . 38870 
 
 .398 
 
 .29141 
 
 .431 
 
 .32392 
 
 .464 
 
 .35673 
 
 .497 
 
 . 38970 
 
 .399 
 
 . 29239 
 
 .432 
 
 .32941 
 
 .465 
 
 .35773 
 
 .498 
 
 . 39070 
 
 .4 
 
 . 29337 
 
 .433 
 
 . 32590 
 
 .466 
 
 . 35873 
 
 .499 
 
 .39170 
 
 .401 
 
 . 29435 
 
 .434 
 
 .32689 
 
 .467 
 
 .35972 
 
 .5 
 
 .39270 
 
 .402 
 
 . 29533 
 
 .435' 
 
 .32788 
 
 .468 
 
 .36072 
 
 
 
 .403 
 
 .29631 
 
 .436 
 
 .32887 
 
 .469 
 
 .36172 
 
 
 
 .404 
 
 . 29729 
 
 .437 
 
 .32987 
 
 .47 
 
 .36272 
 
 
 
 diameter of the circle. Then find the decimal opposite 
 this ratio in the column headed "Area." Multiply this 
 area by the square of the diameter. The result is the 
 required area. 
 
 Example. Diameter of circle = 72 in. Height of 
 segment = 25 in. 25 + 72 = .347, which will be found in 
 the column headed "Ratio," and the area opposite this 
 
5WI ENGINEERING 
 
 is .24212. Then .24212x72x72=1,255 sq. in., area 
 of segment. 
 
 A boiler is 66 in. in diameter, the working pressure 
 is 100 lbs. per sq. in. The distance from the top row 
 of tubes to the shell is 25 in. Required, the number 
 of diagonal crow foot braces that will, be needed to 
 support the heads above the tubes, also the sectional 
 area of each brace. The thickness of the heads is ^ 
 in. and the T.S. = 55,000 lbs. per sq. in. 
 
 Assume the head to be sufficiently strengthened by 
 the flange for a distance .of 2 in. from the shell, the 
 diameter of the circle of which the segment above the 
 tubes requires to be stayed is reduced by 2 + 2 = 4 in. 
 and will therefore be 66 — 4 = 62 in. The rise or height 
 of the segment above the tubes is 25-4 = 21 in. 
 Required, the area.* 21 -5- 62 = .338. Looking down 
 the column headed "Ratio" in Table 19, area opposite 
 .338 is .23358. Area of segment = .23358 x 62 x 62 = 
 897.88 sq. in. The total pressure on this area will be 
 897.88 x 100 = 89,788 lbs. 
 
 Assume the braces to be made of \}i in. round steel 
 having a T.S. of 50,000 lbs. per sq. in. and to be 
 designed in such a manner as to allow for loss of 
 material in drilling the rivet holes in the crow feet. 
 Each brace will have a sectional area of .994 sq. in., 
 and using 8 as a factor of safety, the strength or safe 
 holding power of each stay may be found as follows: 
 .994x50,000-8 = 6,212 lbs., and the number of stays 
 required = 89,788 lbs. (total pressure) divided by 6,212 
 lbs. (strength of each stay) = 14 5, or in round numbers 
 15. If the stays are made of flat bars of steel the 
 sectional area should equal that of the round stays, 
 and the dimensions of the crow feet of all stays should 
 
 * See rule for Table 19. 
 
THE BOILER 323 
 
 be such as to retain the full sectional area of the body 
 after the rivet holes are drilled. 
 
 Each stay is connected to the plate by two ^-in. 
 rivets, having a T.S. of 55,000 lbs. per sq. in. and a 
 shearing strength of 45,000 lbs. per sq. in. These 
 rivets are capable of resisting a direct pull of 10,818 
 lbs., using 5 as a factor of safety; ascertained as fol- 
 lows: 2A x 45,000 ■*- 5 = 10,818 = strength of two rivets. 
 They are also subjected to a crushing strain, and the 
 resistance to this is DxC-5, which expressed in 
 figures is .875 x 90,000 -*- 5 = 15,750 lbs. 
 
 The proper spacing comes next, and is arrived at in 
 the following manner: 
 
 Area to be stayed = 897.88 sq. in. 
 
 Number of stays = 15. 
 
 Area supported by each stay = 897.88 ■*- 15 = 59.8 
 sq. in. 
 
 The square root of 59.8 = 7.75 nearly, which is the 
 distance in inches each way that the stays should be 
 spaced, center to center. 
 
 If through stay rods are used in place of diagonal 
 braces for staying the boiler under consideration, the 
 number and diameter of the rods may be ascertained 
 by the following method: 
 
 Assuming the heads to be supported by channel 
 bars, as previously described, and that the stays are 
 pitched 14 in. apart horizontally and 13 in. vertically, 
 each stay would be required to support an area of 14 x 
 13=182 sq. in., and the number of stays would be 
 897.88- 182 = 4.9, in round numbers 5. See Fig. 107. 
 The pressure being 100 lbs. per sq. in., the total stress 
 on each stay = 182 x 100 = 18,200 lbs. Assume the 
 stay rods to be of soft steel having a T.S. of 50,000 
 lbs. per sq. in., and using a factor of safety of 8, the 
 
3^4 ENGINEERING 
 
 sectional area required for each stay will be found as 
 follows: 18,200x8^50,000 = 2.9 sq. in., and the 
 diameter will be found as follows: 2.9^.7854 = 3.69, 
 which is the square of the diameter, and the square 
 root of 3.69= 1.9 in., or practically 2 in. The same 
 methods of calculation are applicable to the staying of 
 the heads below the tubes, also for stay bolts in fire 
 box boilers. 
 
 Strength of Unstayed Surfaces. A simple rule for 
 finding the bursting pressure of unstayed flat surfaces 
 is that of Mr. Nichols, published in the "Locomotive," 
 February, 1890, and quoted by Prof. Kent in his 
 "Pocket-book." The rule is as follows: "Multiply the 
 thickness of the plate in inches by ten times the tensile 
 strength of the material used, and divide the product 
 by the area of the head in square inches." Thus, 
 Diameter of head = 66 in. 
 Thickness of head = $/% in. 
 Tensile strength = 55,000 lbs. 
 Area of head = 3,421 sq. in. 
 
 $/<& x 55,000 x 10 -5- 3,421 = 100, which is the number 
 of pounds pressure per square inch under which the 
 unstayed head would bulge. 
 
 If we use a factor of safety of 8, the safe working 
 pressure would be 100^8= 12.5 lbs. per sq. in., but as 
 the strength of the unstayed head is at best an 
 uncertain quantity it has not been considered in the 
 foregoing calculations for bracing, except as regards 
 that portion of it that is strengthened by the flange. 
 
 In all calculations for the strength of stayed surfaces, 
 and especially where diagonal crow foot stays are 
 used, the strength of the rivets connecting the stay to 
 the flat plate must be carefully considered. A large 
 factor of safety, never less than 8, should be used, and 
 
THE BOILER 325 
 
 the cross section of that portion of the foot of the stay 
 through which the rivet holes are drilled should be 
 large enough, after deducting the diameter of the hole, 
 to equal the sectional area of the body of the stay. 
 
 Dished Heads. In boiler work where it is possible to 
 use dished, or "bumped up" heads as they are some- 
 times called, this type of head is rapidly coming into 
 use. Dished heads maybe used in the construction of 
 steam drums, also in many cases for dome-covers, thus 
 obviating the necessity of bracing. The maximum 
 depth of dish, as adopted by steel plate manufacturers 
 April 4, 1901, is y& of the diameter of the head when 
 flanged, and if the tensile strength and quality of the 
 plate from which the heads are made are the same as 
 those of the shell plate, the dished head becomes as 
 strong as the shell, provided the head has the same 
 thickness or is slightly thicker than the shell plate. 
 
 Welded Seams. A few boiler manufacturers have 
 succeeded in making welded seams, thus dispensing 
 with the time-honored custom of riveting the plates 
 together. A good welded joint approaches more 
 nearly to the full strength of the material than can 
 possibly be attained by rivets, no matter how correctly 
 designed the riveted joint may be. The weld also 
 dispenses with the necessity of caulking, and a boiler 
 having a perfectly smooth surface inside, such as would 
 be afforded by welded seams, would certainly be much 
 less liable to collect scale and sediment than would 
 one with riveted joints. But in order to make a 
 success of welded seams the material used must be of 
 the best possible quality, and great care and skill are 
 required in the work. 
 
 The Continental Iron Works of Brooklyn, New 
 York, exhibited at the St. Louis World's Fair in 1904 
 
326 ENGINEERING 
 
 a welded steel plate soda pulp digester without a 
 single riveted joint. The dimensions of this vessel, 
 which may be likened to a cylinder boiler without flues, 
 were as follows: Thickness of plate, % in.; diameter, 
 9 ft.; length, 43 feet. The heads were dished to the 
 standard depth. The safe working pressure was 125 
 lbs. per sq. in. It appears not only possible, but 
 probable, that the process of welding boiler joints may 
 in time supplant the older custom of riveting. 
 
CHAPTER II 
 
 CARE OF THE BOILER 
 
 Washing out the boiler — Duties of the boiler washer — How to pre- 
 pare a boiler for washing — How to clean and inspect the 
 inside of a boiler— Fusible plugs — Advantage of manholes, 
 giving free access to top and bottom of boiler — Responsibility 
 resting upon the boiler washer — Necessity of keeping water 
 column clean — Scraping the flues — Fire cracks and how to 
 deal with them — Firing up and how it should be done — Danger 
 in too sudden heating up of a boiler — Advantages of filling a 
 recently washed out boiler with warm water — Connecting 
 with the main header and the safest method of procedure. 
 
 Washing Out. In order to get the best results from 
 the burning of coal or any other fuel in a boiler furnace 
 it is absolutely necessary to keep the boiler as clean as 
 possible, both Inside and outside. In large plants the 
 boiler washer and his helper are detailed to look after 
 this part of the work, and while the job is by no means 
 a very desirable one, it is at the same time a very 
 responsible one, and much depends upon the thorough- 
 ness with which the work is done. In small plants, 
 consisting of one or two boilers, the engineer generally 
 has to attend to the details of the work himself, and 
 no matter whether the plant be large or small, the 
 engineer in charge is the man above all others who 
 should be most interested in seeing that thorough 
 work is done, not only as a matter of safety, but for 
 the sake of his reputation as an engineer. The boiler 
 that is to be washed out should be allowed to gradually 
 cool for ten or twelve hours. It will then be in a 
 condition which will permit a man to go inside of it ' 
 327 
 
328 ENGINEERING 
 
 and do effective work, and no boiler can be thoroughly- 
 cleaned and inspected unless the boiler washer does 
 go inside. 
 
 These remarks apply, of course, to horizontal tubular 
 or flue boilers and water tube boilers having drums 
 large enough for a man to crawl into. Some types of 
 internally fired boilers are provided with man-holes, 
 but the majority of them have only hand-holes into 
 which the hose for washing out may be inserted. 
 
 After the water has been allowed to run out, the first 
 step in washing out a boiler is to remove all the loose 
 mud and scale possible by means of a steel scraper 
 fitted to a long handle and introduced through the 
 man-hole in the bottom part of the head. This will 
 prevent the scale from getting into the blow-off pipe 
 and stopping the flow of the water used for washing 
 the boiler. If there is a man-hole on top, the next 
 thing in order is to take the hose in through it and 
 give the sides of the shell and also the tubes a good 
 cleaning. 
 
 Sometimes it happens that where an exhaust heater 
 of the open type is used, oil will find its way into the 
 boiler and, mixing with the mud, will form a thick 
 pasty-like substance on the sides of the boiler along 
 the water line. This should be carefully scraped off 
 and removed, as any matter containing oil or grease is 
 a very dangerous thing to have inside a boiler. 
 
 After cleaning the upper part of the boiler, it should 
 be inspected for loose braces or rivets. This can best 
 be accomplished by tapping the parts with a light 
 hammer. A solid rivet will give a clear metallic 
 sound, and a little practice will enable one to easily 
 detect the sound of a loose brace or broken rivet. 
 
 Signs of corrosion or pitting of the shell along the 
 
CARE OF THE BOILER 329 
 
 water line should also be carefully searched for. 
 Fusible plugs, to be effective, must be kept clean, and 
 the only opportunity for cleaning them is at the time 
 of washing out the boiler. Therefore while working on 
 the upper part of the boiler, attention should be given 
 to the fusible plug. If it is one of the ordinary kind, 
 screwed into the back head above the tubes, it should 
 be taken out and cleaned and before replacing it the 
 thread should be well coated with a mixture of cylinder 
 oil and plumbago, which will prevent it from sticking. 
 If the fusible plug is one of the type consisting of a 
 brass tube extending from the top of the shell to the 
 water level, the lower end of this tube should be 
 cleaned of all mud or scale. 
 
 Having thus finished above the tubes, the mud and 
 scale should again be scraped from the bottom, after 
 which the hose should be inserted through the front 
 man-hole that should be in every horizontal boiler. 
 
 Some authorities argue that a man-hole should not 
 be cut in the bottom part of a boiler head, giving as 
 their reason that it weakens the head, but the logic is 
 not sound, for the reason that the man-hole can be 
 reenforced in such a manner as to make it fully as 
 strong as the solid sheet, and when we consider the 
 great advantage of having a man-hole in the bottom, 
 both as- regards washing out and also for repairs, it is 
 plain that it is really a necessity. 
 
 After washing out all the loose mud and scale that 
 it is possible to get from the bottom, the boiler washer 
 should next go inside and, with scrapers and tools 
 made for the purpose, he should scrape and chip off 
 all the scale that he can from the bottom, because 
 there is where lies the greatest danger from burnt 
 sheets caused by accumulations of scale preventing the 
 
330 ENGINEERING 
 
 water from getting to the metal. Much good work 
 may be accomplished in this way and no boiler washer 
 should consider the job complete until he has gone 
 through the boiler both top and bottom, and not only 
 cleaned but inspected it. Any loose rivets, broken or 
 loose braces, signs of corrosion or pitting should be at 
 once reported to the chief engineer or superintendent. 
 
 It will thus be seen that great responsibility rests 
 with the boiler washer, for the reason that he is the 
 man that is in closest touch with the inside of the 
 boiler, and it is due to the manner in which he does 
 his work inside the boiler whether a defect is discovered 
 and repaired in 'time or whether it is allowed to go 
 until the result is often a grave disaster. The author 
 desires to enter a plea for this hard-worked and too 
 often underpaid craftsman, and hereby expresses the 
 wish that his services were better appreciated. 
 
 The water column or combination should receive 
 particular attention each time the boiler is washed out. 
 The lower pipe leading to the boiler is liable to become 
 clogged with scale, and if not cleaned regularly it is 
 sure to cause trouble by preventing a free flow of the 
 water from the boiler to the gauge glass. 
 
 If the boiler is of the horizontal tubular type, the 
 tubes should be scraped inside, and with water tube 
 boilers use the steam jet to blow the soot and ashes 
 from between the tubes. Soot, in addition to choking 
 the draft, is also a non-conductor of heat. 
 
 After the hand-hole and man-hole plates have been 
 replaced the boiler may be filled with water to the 
 proper level, and while this is being done it is in order 
 to take a look into the furnace for any broken grates 
 or accumulations of clinkers on the side walls or bridge 
 wall. These clinkers should be chipped off, also the 
 
CARE OF THE BOILER 331 
 
 bottom of the boiler should be swept clean of ashes and 
 examined for any defects, such as fire cracks about 
 the rivets most exposed to the heat. These cracks 
 may often exist some time before being discovered 
 unless a close inspection is made. They are small 
 cracks radiating from the rivet holes outward past the 
 rivet heads one-half to three-quarters of an inch, and 
 are always liable to extend farther until they become a 
 source of danger unless arrested in time. They may 
 be closed up sometimes with the caulking tool, but if 
 one should be found several inches in length, a hole 
 should be drilled at the outer end of the crack and a 
 rivet put in. This will generally stop it. Fire cracks 
 occur in the girth seams only, and especially the seam 
 nearest the fire. 
 
 It is essential that the bridge walls of horizontal 
 boilers be kept in good repair, in order that as much 
 fire brick surface as possible may be exposed to the 
 heat. This will greatly aid combustion and prevent 
 smoke. 
 
 • Firing Up. After the boiler washer has completed 
 his task the next thing in order is firing up, and in 
 doing this if care and good judgment are not exercised 
 there is danger of doing much damage to the boiler, 
 especially if it has been filled with cold water. A 
 very light fire should be started at first and kept that 
 way until the water gets to the boiling point at least, 
 after which the fire may be gradually increased until 
 the steam gauge shows a few pounds pressure, when it 
 will be safe to urge the fire still more. The bad effects 
 resulting from the unequal expansion or contraction 
 of the sheets and undue stress upon the rivets, all 
 caused by rapid changes of the temperature of the 
 boiler from hot to cold or vice versa, cannot be 
 
36% ENGINEERING 
 
 guarded against too carefully, and they are liable to be 
 brought about in two ways: first, by haste in cooling 
 down a hot boiler that is to be washed out, and 
 secondly, by starting a heavy fire under a cold boiler. 
 That part of the boiler most exposed to the heat will 
 become hot while other parts farthest removed from 
 the fire may still be cold. Very often there is a 
 difference of 150 or 200 in the temperature of 
 different parts of the boiler for a time during the firing 
 up process, and the same dangerous conditions may be 
 caused also by blowing all the water out of a boiler 
 while under a pressure of 15 or 20 lbs., as is the custom 
 of some persons when preparing a boiler for washing 
 out. Either custom cannot be too strongly condemned. 
 
 Sometimes a boiler is needed in a hurry after having 
 been washed out, and in such an emergency it should 
 be filled with warm water; in fact, it is better to always 
 fill a boiler with warm water if it is possible to do so 
 after washing out. 
 
 Connecting with the Main Header. When the gauge 
 shows a pressure that is within 10 or 15 lbs. of being 
 the same as that carried on the other boilers it should 
 be watched closely, and when the pressure becomes 
 the same as that in the main the connecting valve 
 should be opened slightly, just sufficient to allow a 
 light flow of steam through it, which can be easily 
 detected by placing the ear near the valve chamber. 
 This steam may be passing from the boiler to the 
 header or vice versa, but whichever way it is going the 
 valve should not be opened any farther until the pres- 
 sure in the main pipe and in the boiler is equalized, 
 when it will be found that the valve may be opened 
 easily. While connecting the boiler the dampers 
 should be closed. 
 
CARE OF THE BOILER 333 
 
 Care should always be exercised in connecting a 
 recently fired up boiler, "and the engineer should be 
 certain that the steam gauge and pop valve are in 
 good working order. Otherwise there is liability of a 
 serious accident occurring, either in breakage of the 
 steam pipe, or what is still worse, a boiler explosion. 
 
CHAPTER III 
 MECHANICAL STOKERS 
 
 Principles involved in the action of automatic stokers — Advan- 
 tages and disadvantages attending their use— Classification 
 and general description of stokers — Coal-handling machinery 
 — Under-feed stokers — Mansfield chain grate stoker — Play ford 
 stoker — Vicars mechanical stoker — The Wilkinson stoker- 
 Murphy stoker — Roney stoker— The American under-feed 
 stoker — The Jones under-feed stoker — Outside furnaces — Con- 
 ditions required in a boiler furnace to ensure good combus- 
 tion — Hindrances to good combustion — Description of Burke 
 ' outside furnace. 
 
 The principles governing the operation of mechan- 
 ical or automatic stokers are in the main correct, viz., 
 that the suppl}' of coal and air is continuous and. that 
 provision is made for the regulation of the supply of 
 fuel according to the demand upon the boiler for 
 steam; also that the intermittent opening and closing 
 of the furnace doors, as in hand firing, thereby 
 admitting a large volume of cold air directly into the 
 furnace on top of the fire, is avoided. 
 
 Mechanical stokers have within the last twelve years 
 been largely adopted in the United States, especially 
 in sections where bituminous coal is the principal fuel. 
 The disadvantages attending their use are: 
 
 First, that the cost of properly installing them is so 
 great that their use is practically prohibited to the 
 small manufacturer. 
 
 Second, that in case of a sudden demand upon the 
 boilers for more steam the automatic stoker cannot 
 respond as promptly as in hand firing, although 
 334 
 
MECHANICAL STOKERS 33.5 
 
 this objection could no doubt be met by skillful 
 handling. 
 
 Third, the extra cost for power to operate them, 
 although this is probably offset by the diminished 
 expense for labor required, as compared to hand firing. 
 
 There are many different types of mechanical stokers 
 and automatic furnaces, but they may for convenience 
 be grouped into four general classes. In class one the 
 grate consists of an endless chain of short bars that travel 
 in a horizontal direction over sprocket wheels, operated 
 either by a small auxiliary engine or by power derived 
 from an overhead line of shafting in front of the boilers. 
 
 In class two may be included stokers having grate 
 bars somewhat after the ordinary type as to length and 
 size, but having a continuous motion up and down or 
 forward and back. This motion, though slight, serves 
 to keep the fuel stirred and loosened, thus preventing 
 the firing from becoming sluggish. The grate bars in 
 this class of stokers are either horizontal or inclined at 
 a slight angle, and their constant motion tends to 
 gradually advance the coal from the front to the back 
 end of the furnace. 
 
 Class three includes stokers having the grate bars 
 steeply inclined. Slow motion* is imparted to the 
 grates, the coal being fed onto the upper end and 
 forced forward as fast as required. 
 
 Class four includes an entirely different type of 
 stoker, in that the fresh coal, is supplied underneath 
 the grates, and is pushed up through an opening left 
 for the purpose midway of the furnace. The gases, on 
 being distilled, immediately come in contact with the 
 hot bed of coke on top and the result is good com- 
 bustion. In this type of stoker steam is the active agent 
 used for forcing the coal up into the furnace, either 
 
336 
 
 ENGINEERING 
 
 ••;.-: 
 
 
MECHANICAL STOKERS 
 
 337 
 
 by means of a long, slowly-revolving screw, as in the 
 American stoker, or a steam ram, as with the Jones 
 under-feed stoker. A forced draft is employed, and 
 the air is blown into the furnace through tuyeres 
 When these stokers are intelligently handled they 
 give good results, especially with cheap bituminous 
 coal. The clinker formed on the grate bars or dead 
 plates is easily removed. 
 
 The coal is supplied to mechanical stpkers either by 
 being shoveled by hand into hoppers in front of and 
 above the grates, or, as 
 is the case in most of 
 the large plants using 
 them, it is elevated by 
 machinery and depos- 
 ited in chutes, through 
 which it is fed to 
 each boiler by gravity. 
 Stokers of the chain 
 grate variety are usu- 
 ally constructed so that 
 they may be withdrawn 
 from underneath the 
 boiler in case repairs are 
 necessary. The coal, 
 either nut or screen- 
 ings, is fed into a hop- 
 per in front of and 
 above the level of the grate 
 along towards the rear end. 
 
 FIGURE 112. 
 
 CAHALL VERTICAL BOILER WITH 
 
 CHAIN GRATE STOKER ATTACHED 
 
 and is slowly carried 
 The ash drops from 
 the grate as it passes over the sprocket wheel at 
 the rear. 
 
 Fig. in shows a battery of Babcock and Wilcox 
 water tube boilers fitted with chain grate stokers. The 
 
838 
 
 ENGINEERING 
 
 buckets for elevating the coal to bins overhead, from 
 whence it is fed by gravity to the stokers, are not 
 shown. These buckets or carriers may also be utilized 
 for conveying the ashes from the boiler-room. 
 
 O H 
 K g 
 
 Fig. 112 is a sectional view of a vertical Cahall 
 boiler with a Mansfield chain grate stoker, and Fig. 113 
 shows the same stoker withdrawn from the boiler. 
 
 The Coxe mechanical stoker operates upon the same 
 
MECHANICAL STOKERS 
 
 339 
 
 general principles as do those previously described, 
 being of the chain grate type, but it has in addition a 
 series of air chambers just underneath the upper 
 traveling grate. These air chambers are made of sheet 
 iron and are open at the top and provided with dampers 
 for regulating the air pressure for different sections of 
 the grate. The air blast is supplied by a fan. Another 
 featureof this stoker is a water chamber for the bottom 
 section of the grate to travel through on its return. 
 
 FIGURE 114. 
 
 The Playfor.d stoker has wrought iron T bars extend- 
 ing across the furnace and attached to the traveling- 
 chains. These T bars carry the small cast iron sections 
 composing the grate. A screw conveyor is also 
 placed in the ash pit for the purpose of carrying the 
 ashes from the rear to the front of the pit. Fig. 114 is 
 a sectional view of the Playford stoker attached to a 
 water tube boiler. 
 
 In class two may be included stokers having the 
 grates inclined more or less. In some varieties the 
 grates incline from front to rear, while in others they 
 
340 ENGINEERING 
 
 are made to incline from the side walls towards the 
 center line of the furnace. 
 
 In the Vicars mechanical stoker the grate bars are 
 somewhat of the shape of the ordinary grate and lie in 
 two tiers in a horizontal position. The lower or back 
 tier next the bridge wall is stationary and is placed 
 there for the purpose of catching what coal is carried 
 over the ends of the upper or moving grate bars. 
 These have a slow reciprocating motion which 
 gradually moves the hot coke back towards the bridge 
 wall The coal is fed from a hopper into two com- 
 partments, from which it is pushed by reciprocating 
 plungers onto a coking plate and from thence it 
 passes to the grate bars. The motion of these bars 
 has several intermediate variations, from a state of. 
 rest to a movement of 3^ in. They have a simul- 
 taneous movement forward by which the fuel is 
 advanced, but on the return movement the bars act at 
 separate intervals. In this manner the fuel remains 
 undisturbed by the return motion of the grates. Fig. 
 115 illustrates this stoker. 
 
 In the Wilkinson stoker, Fig. 116, the grate bars 
 are hollow and are set at an angle of 20°, the inclina- 
 tion being from front to back. Each bar is stepped 
 along its fire surface and on the rise is perforated with 
 a long, narrow slot. A steam pipe extends along the 
 front of the furnace and from this pipe small branch 
 pipes lead into the ends of the grate bars, which latter 
 are in fact a series of hollow trunks with their front 
 ends open. When in operation a steam blast is 
 admitted to each of the several trunk grate bars 
 through the small branch pipes, and this blast induces 
 an air current of more or less pressure, which finds an 
 outlet through the narrow slots in the stepped fire 
 
MECHANICAL STOKERS 
 
 341 
 
 surface of the grates and directly into and through the 
 burning mass of fuel. A slow reciprocating motion is 
 imparted to the grates by means of cranks and links 
 operated from an overhead shaft; see Fig. 117, These 
 cranks are set alternately at 90° with each other, thus 
 giving a forward movement to one-half of the grate 
 bars while at the 
 same time the 
 other half is 
 moving back- 
 ward. In this 
 manner the fuel 
 is kept slowly 
 moving down 
 the inclined 
 grates. 
 
 The Murphy 
 Automatic Fur- 
 nace, a sectional 
 view of which is 
 shown in Fig. 
 1 1 8, has the 
 grates inclined 
 inwards from 
 the side walls, 
 while a fire 
 brick arch is 
 sprung from 
 
 FIGURE 115. 
 
 side to side to cover the entire length of the grate. 
 The coal is shoveled or fed by carrier into the 
 coal magazines, one on each side, as shown in the 
 cut If the furnace is placed directly under the boiler 
 it necessitates putting these coal magazines within the 
 side walls, but as the Murphy furnace is usually con- 
 
342 
 
 ENGINEERING 
 
 structed at the present day as an outside furnace, the 
 coal magazines are independent of the boiler walls. 
 The bottom of each magazine is used as a coking 
 
 plate, against which the upper ends of the inclined 
 grates rest. On the central part of this plate is an 
 inverted open box. This is termed the "stoker box," 
 
MECHANICAL STOKERS 
 
 343 
 
 and it is moved back and forth across the face of the 
 coking plate by means of a shaft with pinions that 
 mesh into racks under each end of the box. By means 
 
 FIGURE 117. WILKINSON STOKER. 
 
 of this motion of the stoker boxes the coal is pushed 
 forward to the edge of the coking plate and from 
 thence it slowly passes down over the inclined grates 
 
344 
 
 ENGINEERING 
 
 toward the center of the furnace. At this point [he 
 slowly rotating clinker breaker grinds the clinker and 
 other refuse and deposits them in the ash pit. 
 
 1 1 1 1 I-. 1 1 
 
 1 j 1 1 1 1 
 
 1 ' 1 1 1 1 1 
 
 ! 1 1 1 J 1 
 
 
 
 ' IPIT | 1 
 
 
 
 
 FIGURE 118. THE MURPHY AUTOMATIC FURNACE. 
 
 Above the coking plates are the "arch plates," upon 
 which the bases of the fire brick arch rest. These 
 plates are ribbed, the ribs being an inch apart, and, the 
 arch resting upon these ribs, there is thus provided a 
 series of air ducts by means of which the air, already 
 heated by having been admitted in front and passed 
 through the flues over the arch, is conducted into the 
 furnace above the grates and comes directly in contact 
 with the gases rising from the coking fuel. Air is also 
 admitted under the coking plate and, passing up 
 through the grates, serves to keep them cool and also 
 furnishes the needed supply to the burning coke as it 
 slowly moves down toward the center. 
 
MECHANICAL STOKERS 345 
 
 The fuel is aided in its downward movement by the 
 constant motion of the grates, one grate of each pair 
 being moved up and down by a rocker at the lower 
 end. 
 
 Motion is imparted to the various moving parts of 
 this furnace by means of a reciprocating bar extending 
 across the outside of the entire front, and to which all 
 the working parts are attached by links and levers. 
 This bar is operated by a small engine at one side of 
 the setting, the power required being about one horse- 
 power per furnace. 
 
 The Roney stoker consists of a set of rocking stepped 
 grate bars, inclined from the front towards the bridge 
 wall. The angle of inclination is 37 . A dumping 
 grate operated by hand is at the bottom of the incline 
 for the purpose of receiving and discharging the clinker 
 and ash. This dumping grate is divided into sections 
 for convenience in handling. 
 
 The coal is fed onto the inclined grates from a 
 hopper in front. The grate bars rock through an arc 
 of 30 , assuming alternately the stepped and the 
 inclined position. Fig. 119 is a sectional perspec- 
 tive view of this stoker and illustrates the working 
 parts. 
 
 The grate bars receive their motion through the 
 medium of a rocker bar and connecting rod. A shaft 
 extending across the front of the stoker under the 
 coal hopper carries an eccentric that gives motion to 
 the connecting rod and also to the pusher in the coal 
 hopper. This pusher, working back and forth, feeds 
 the coal over the dead plate onto the grates," and its 
 range of motion is regulated by a feed wheel from no 
 stroke to full stroke, according to the demand for coal. 
 The motion of the grate bars may also be regulated by 
 
340 
 
 ENGINEERING 
 
 a sheath nut working on a long thread on the connect- 
 ing rod. Each grate bar consists of two parts, viz., a 
 cast iron web fitted with trunnions on each end that 
 rest in seats in the side bearer and a fuel plate having 
 the under side ribbed to allow a free circulation of 
 air. 
 
 The fuel plate is bolted to the web and carries the 
 
 FIGURE 119. 
 
 SECTTONAL PERSPECTIVE OF THE RONEY MECHANICAL STOKER. 
 
 fuel. The grates lie in a horizontal position across 
 the furnace in the form of steps, and ample provi- 
 sion is made for the admission of air through the 
 slotted webs. A fire brick arch is also sprung 
 across the furnace, covering the upper portion of the 
 grate. 
 
 This arch, being heated to a high temperature, serves 
 in a measure to partly coke the coal as it passes under 
 it. Air is also admitted on top of the coal at the 
 front. This air is heated by its passage through a 
 perforated tile over the dead plate and adjoining the 
 
MECHANICAL STOKERS 
 
 347 
 
 fire brick arch. Fig. 120 shows the location of the 
 arch and tile. 
 
 In mechanical stokers of the uncler-feed type the air 
 is supplied by forced draft. 
 
 The American stoker consists of a horizontal con- 
 veyor pipe into which the coal is fed from a hopper. 
 The diameter cf this pipe depends upon the quantity 
 of coal to be burned, and varies from 4% in. for the 
 smaller sizes up to 9 and 10 in. for the larger sized 
 stokers. The length of the conveyor pipe for the 
 
 figure 120. 
 
 standard 10-in. stoker is 72 in. Attached to the outer 
 end of this conveyor pipe, and forming a part of it, is 
 an iron box containing a reciprocating steam motor 
 which, through the medium of a rocker arm and pawl 
 and ratchet wheel, drives a screw conveyor shaft that 
 slowly revolves within the pipe, thus forcing the coal 
 forward and up through another box or trough, which 
 latter is wholly within the furnace. Extending around 
 the top edges of this box, and on a level with the grate 
 bars, there is a series of tuyeres through which the air 
 is forced. 
 
348 
 
 ENGINEERING 
 
 These tuyeres, being at a high temperature, serve to 
 heat the air in its passage through them, thus greatly 
 
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 aiding combustion. Fig. 121 is a longitudinal sectional 
 view of this stoker. 
 
 The speed of the screw conveyor is regulated by the 
 hand throttle of the motor, according to the demand 
 
MECHANICAL STOKERS 
 
 349 
 
 for coal. With the 9-in. standard stoker from 350 to 
 1,200 lbs. of coal per hour may be burned. Fig. 122 
 is a view of the American stoker before being placed 
 in position in the furnace. 
 
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 The air jets, passing out from the tuyeres in- a 
 horizontal direction, and from opposite sides, cut 
 through the rounded bed of coal and the gases are thus 
 ignited and consumed immediately after being distilled 
 
350 ENGINEERING 
 
 from the coal, while the pressure of the coal- rising 
 from underneath forces the already coked fuel over the 
 edges of the trough or box onto the grates which 
 occupy the space between^ the side walls and the coal 
 trough. The air is first delivered from the fan into 
 the air box that surrounds the coal trough on three 
 sides and from thence it passes to the tuyeres. If this 
 stoker is properly handled very good results may be 
 obtained by its use, but, like all other devices for burn- 
 ing coal under boilers, it is bad policy to endeavor to 
 force it beyond its capacity. 
 
 In the Jones under-feed stoker the coal is pushed for- 
 ward and up into the furnace through a cast iron retort or 
 trough. The impelling force is a steam ram connected 
 to the outer end of the retort, and the speed of the ram is 
 regulated automatically by the steam pressure, or by 
 hand as desired. The coal is supplied to the ram through 
 a cast iron hopper having a capacity of 125 to 140 lbs. 
 
 Forced draft is also employed in this stoker, the air 
 being conducted from the fan or blower through 
 galvanized iron pipes into the closed ash pit, which 
 really forms an air box, as the space on either side of 
 the retort that is usually occupied by grate bars is in 
 this case covered by solid cast iron dead plates upon 
 which the coked fuel lies until it is consumed. These 
 plates, being hot, serve to heat the air coming in con- 
 tact with them in its passage to the cast iron tuyeres 
 through which it passes to the bed of burning fuel in 
 the retort. Air entirely surrounds the retort on the 
 sides and back end, and is at a constant pressure in 
 the ash pit, but can only pass into the furnace through 
 the tuyeres, the jets of air cutting through the rounded 
 heap of incandescent fuel from opposite sides and in 
 a direction inclined upwards. 
 
MECHANICAL STOKERS 
 
 351 
 
 Coal is supplied to the hopper either by hand, or by 
 mechanical means where the plant is fitted with coal- 
 handling machinery. The opening through which it 
 passes from the hopper to a position in front of the 
 ram is 8 x 10 in. in size. Each charge of the steam 
 
 FIGURE 123. 
 
 ram carries forward 15 to 20 lbs. of coal. Connected 
 to the ram and moving in conjunction with it is a long 
 rod extending through the retort near the bottom. 
 Upon this rod are carried shoes that act as auxiliary 
 plungers and facilitate the movement of the coal. 
 
 FIGURE 124. 
 
 Fig. 123 is a sectional view of the Jones stoker, 
 showing the machine full of coal, with the ram ready 
 to make a charge. Fig. 124 shows the stoker complete 
 before being placed in the furnace. 
 
352 ENGINEERING 
 
 It is claimed by the builders of under-feed stokers, 
 and the claim appears to have good foundation, that 
 by pushing the green coal up so as to meet the upper 
 crust of glowing fuel the gases on being distilled 
 immediately come in contact with and are consumed 
 by the burning mass, and the formation of smoke is 
 thus prevented. Both the Jones under-feed and the 
 American stokers have proved to be very successful in 
 the burning of the cheaper bituminous coals of the 
 West. One feature tending to commend them is the 
 fact that practically all of the coal is utilized, there 
 being no waste caused by the slack coal or fine screen- 
 ings dropping through the grate bars into the ash pit 
 unconsumed. 
 
 A good substitute for the mechanical stoker is an 
 outside furnace, by which is meant a boiler installation 
 having the furnace in front of instead of underneath 
 the boiler. One of the principal hindrances to good 
 combustion in the ordinary type of boiler furnace is 
 the fact that the temperature of the boiler shell or 
 water tubes with which the gaseous products of com- 
 bustion come in contact can never be higher than the 
 temperature of the water contained within the boiler. 
 This temperature ranges from 297° for steam at 50 lbs. 
 gauge pressure, up to 407° for 255 lbs. pressure, while 
 the temperature of the furnace, according to Dr. 
 Thurston and other high authorities, ranges from 2,010° 
 to 2,550°. 
 
 It is evident that perfect combustion does not take 
 place until these high temperatures are reached. Each 
 time the furnace is charged with fresh coal, especially 
 if the boiler be hand-fired, a large volume of volatile 
 gases is liberated but not consumed. If these gases 
 are allowed to immediately come in contact with a 
 
MECHANICAL STOKERS 
 
 353 
 
 comparatively cool surface, as for instance the heating 
 
 surface of the boiler, the result is a cooling of the 
 
 gases, incomplete combustion and the formation of 
 
 smoke and soot. If on the other hand the furnace is 
 
 so constructed that these gaseous products first impinge 
 
 against hot surfaces, such as fire brick arches or bafflers 
 
 that have a temperature 
 
 corresponding to that 
 
 of the furnace, good 
 
 combustion is assured. 
 
 This condition is in a 
 
 large degree attained 
 
 by the use of outside 
 
 furnaces that permit the 
 
 construction of a fire 
 
 brick arch to cover the 
 
 entire grate surface. 
 
 The Burke furnace, 
 patented by James V. 
 Burke of Chicago, is a 
 notable example of this 
 type of furnace. It is 
 applicable to any type 
 of stationary boiler. 
 Fig. 125 shows this fur- 
 nace as applied to 
 tubular boilers. It con- 
 sists of a fire brick arch 
 extending from 6 to 8 
 ft. outwards from the boiler front and of a width to 
 correspond to the diameter of the boiler. The arch 
 rests securely upon brick work inclosed in a well 
 ventilated iron casing. There is practically no heat 
 radiated from this furnace, all the heat generated 
 
 Front View. 
 
 FIGURE 125. 
 
354 
 
 ENGINEERING 
 
 by it passing to the boiler. The central portion of the 
 grate bars consists of shaking grates, while the side 
 bars are stationary and inclined. 
 
 Fig. 126 is a sectional view and will serve to illustrate 
 the construction of this furnace. The coal is fed 
 through pockets on top on each side of the arch, the 
 larger furnaces having two pockets on each side and 
 the smaller sizes one. The doors in front are only 
 
 C/foss Seer; 0//. 
 FIGURE 126. 
 
 opened for the purpose of cleaning fires or when first 
 starting fires. The air is supplied by way of the ash 
 pit, passing up through the grate bars. A portion of 
 the air supply is also drawn through the ventilators and 
 passes to the upper part of the furnace. The arch 
 extends under the front end of the boiler 6 or 8 in. , and 
 there is a bridge wall about 4 ft. back from the front 
 against which the gases from the furnace impinge. 
 There are 42 sq. ft. of grate surface in the larger 
 
MECHANICAL STOKERS 355 
 
 sizes, and 22 sq. ft. in the smaller size. Good com- 
 bustion is attained in this furnace, owing to the fact 
 that the gases as they are distilled from the coal come 
 immediately in contact with the highly heated surface 
 of the arch directly over the fire, 
 
CHAPTER IV 
 THE STEAM TURBINE 
 
 The steam turbine — Lack of information concerning steam tur- 
 bines — Points of difference between the turbine and the 
 reciprocating engine — Kinetic energy in steam — Hero's steam 
 turbine — Branca's steam turbine — Fundamental principles of 
 the steam turbine — Types of steam turbines built in the 
 United States — The Westinghouse-Parsons turbine — Theo- 
 retical velocity of steam exhausting into a vacuum — Relation 
 of bucket speed to steam speed — Speed of the Westinghouse- 
 Parsons turbine — Description of cylinder and blades — Rela- 
 tion of stationary to moving blades — Curvature of blades — 
 Action of the steam within the turbine explained — Balancing 
 pistons — Construction of bearings — A floating journal — Lubri- 
 cation of bearings — Water seal packing — Speed regulation — 
 Description and diagram of governor — Efficiency of steam 
 turbines — Tests of Westinghouse-Parsons turbines. 
 
 Although the turbine principle of utilizing the energy 
 in steam and converting it into useful work has been 
 experimented upon for many years, it is only since the 
 inauguration of the twentieth century that steam 
 turbines have been brought to the front as efficient 
 power producers. 
 
 There are to-day in this country four distinct types 
 of steam turbines, each one of which has its own 
 characteristic features distinguishing it from the 
 others, but in each the kinetic energy and velocity of 
 the expanding steam constitute the source of power. 
 
 Notwithstanding the fact that much has been said 
 
 and written during the past four years regarding the 
 
 steam turbine, the machine is to-day a mystery to 
 
 thousands of engineers, not because they do not desire 
 
 356 
 
THE STEAM TURBINE 
 
 357 
 
 information upon the subject, but because of a lack of 
 opportunities for obtaining that information. The 
 author therefore considers that a space devoted to 
 this subject would no doubt be of benefit to his 
 readers. 
 The piston of the reciprocating engine is driven back 
 
 FIGURE 127. 
 
 and forth by the static expansive force of the steam, 
 while in the steam turbine not only the expansive force 
 is made to do work, but a still more important element 
 is utilized, viz., the kinetic energy or heat energy 
 latent in the steam and which manifests itself in the 
 rapid vibratory motion of the particles of steam 
 
358 
 
 ENGINEERING 
 
 expanding from a high to a lower pressure, and this 
 motion the steam turbine transforms into work. 
 
 One of the earliest descriptions of a device for con- 
 verting the power of steam into work was recorded by 
 Hero, a learned writer who flourished in the city of 
 Alexandria in Egypt, in the second century before 
 Christ. Hero describes a machine called an ^Eolipile 
 or "Ball of yEolus,' 1 illustrated in Fig. 127. B is the 
 boiler under which a fire was made. G is a hollow 
 
 
 .FIGURE 128. 
 
 metallic globe that revolved on trunnions C and D, 
 one of which terminated in a pivot at E, while the 
 other was hollow and conveyed the steam generated in 
 the boiler B to the interior of the globe or ball, from 
 which it escaped through the hollow bent tubes H and 
 I, and the reaction of the escaping steam caused the 
 globe to revolve. This was the first steam turbine, and 
 it worked on the reaction principle. 
 
 Many centuries later, in the year A.D. 1629, Branca, 
 an Italian, described an engine which marks a change 
 
THE WESTINGHOUSE PARSONS STEAM TURBINE 359 
 
 in the method of using the steam. Branca's engine 
 consisted of a boiler A, Fig. 128, from which the steam 
 issued through a straight pipe and impinged upon the 
 vanes of a horizontal wheel carried upon a vertical 
 shaft, causing it to revolve. This device was the germ 
 of the impulse turbine, and these two principles, viz., 
 reaction and impulse, either one or the other and 
 sometimes a combination of both, are the fundamental 
 principles upon which the successful steam turbines of 
 the present age operate. 
 
 As previously stated, there are four types of steam 
 turbines being manufactured in this country at present, 
 viz., 
 
 The Westinghouse-Parsons Turbine, 
 
 The General Electric Curtis Turbine, 
 
 The Hamilton-Holzwarth-Rateau Turbine, and 
 
 The De Laval Turbine. 
 Each will be taken up in its regular order and its 
 distinctive theoretical features studied. 
 
 The Westinghouse-Parsons Steam Turbine is funda- 
 mentally based upon the invention of Mr. Charles A. 
 Parsons, who, while experimenting with a reaction 
 turbine constructed along the lines of Hero's engine, 
 conceived the idea of combining the two principles, 
 reaction and impulse, and also of causing the steam to 
 flow in a general direction parallel with the shaft of 
 the turbine. This principle of parallel flow is common 
 to all four types of turbines, but is perhaps more 
 prominent in the Westinghouse-Parsons and less so in 
 the De Laval. 
 
 A cubic foot of steam under 100 lbs. pressure, if 
 allowed to discharge into a vacuum of 28 in., would 
 attain a theoretical velocity of 3,860 ft. per second and 
 would exert 59,900 ft. -lbs. of energy. A law of turbo 
 
360 ENGINEERING 
 
 mechanics specifies that in order to obtain the highest 
 efficiency in the operation of turbines (whether water 
 or steam) the relation between bucket speed and fluid 
 speed (steam in this case) should be as follows: 
 
 For purely impulse wheels, bucket speed equals 
 one-half of jet speed. 
 
 For reaction wheels, bucket speed equals jet speed. 
 
 Assuming the velocity of the jet of steam issuing 
 from the nozzle to be 4,000 ft. per second, this would 
 mean a peripheral speed of 2,000 ft. per second for an 
 impulse wheel, and for a wheel 1 ft. in diameter the 
 
 figure 129. 
 
 speed would be 38,100 R. P. M. But such a speed is 
 beyond the limits of strength of material. 
 
 As before stated, the Westinghouse-Parsons turbine 
 operates on both impulse and reaction principles, and 
 by a system of compounding, which will be explained 
 later on, the peripheral velocity of the machine has 
 been so reduced as to bring it within practical limits 
 while at the same time the power value of the steam is 
 utilized to a high degree of efficiency. 
 
 The speed of the Westinghouse-Parsons turbine 
 
THE WESTINGHOUSE-PARSONS STEAM-TURBINE 361 
 
 varies from about 750 R. P. M. for a 5,000 K. W. 
 machine to 3,600 R. P. M. for a 400 K. W. turbine. 
 
 Fig. 129 is a general view of a 400 K. W. turbine 
 generator unit. Fig. 130 shows a 600 H. P. machine 
 with the upper half of the cylinder, or stator as it is 
 termed, thrown back for inspection. Fig. 131 is a 
 sectional view of a Westinghouse-Parsons turbine, and 
 it will be noticed that there are three sections or drums, 
 gradually increasing in diameter from the inlet A to 
 
 figure 130. 
 
 the third and last group of blades. This arrange- 
 ment may be likened in some measure to the triple 
 compound reciprocating engine. 
 
 By reference to Fig. 130 it will be seen that t the 
 inside of the cylinder is studded with rows of small 
 stationary blades and that the rotor or revolving part 
 of the machine is also fitted with rows of small blades, 
 similar in shape and dimensions to the stationary 
 
362 
 
 ENGINEERING 
 
 blades. When the upper half of the cylinder is in 
 position, each row of stationary blades fits in between 
 two corresponding rows of moving blades. This 
 arrangement may perhaps be better understood by 
 reference to Fig. 132, which illustrates the relation of 
 the stationary blades to the moving blades when in 
 position, and also shows by the arrows the course of 
 the steam and its change of direction caused by the 
 stationary blades. 
 
 For the purpose of explanation the moving blades or 
 
 FIGURE 131. 
 
 vanes may be considered as small curved paddles pro- 
 jecting from the surface of the rotor, and there is a 
 large number of them, as, for instance, taking a 400 
 K. W. machine, there are 16,095 moving blades and 
 14,978 stationary blades, a total of 31,073. 
 
 The stationary vanes, as previously explained, project 
 from the inside surface of the cylinder. Both station- 
 ary and moving vanes are similar in shape, and are 
 made of hard drawn material, and they are set into 
 
THE WESTINGHOUSE-PARSONS STEAM TURBINE 363 
 
 their places and secured by a caulking process. The 
 blades vary in size from ^ to 7 in. in length, accord- 
 ing to where they are used. Referring to Fig. 130, it 
 will be observed that the shortest blades are placed at 
 what might be termed the steam end of each section or 
 drum of the rotor and cylinder, and that their length 
 gradually increases, corresponding with the increased 
 volume of steam, until a mechanical limit is reached, 
 when a new group of blades begins on a succeeding 
 drum of larger diameter. Referring to Fig. 132, 
 which is a sectional view of four rows of blades, it will 
 
 1 I C^CCCCC^CCC STATIOI 
 
 1 )) )) )) i).l)Tn ^ BLADES 
 
 ) )) } ))Jb) )Ti 
 
 STATIONARY BLADES 
 
 MOVING BLADES 
 
 FIGURE 132. 
 
 be noticed that all the blades, whether stationary or 
 moving, have the same curvature. Also that the curves 
 are set opposite each other. The reason for this will 
 be apparent as the diagram is studied. The steam at 
 pressure P first comes in contact with row I of station- 
 ary blades. It expands through this row, and in 
 expanding the pressure falls to P'. 
 
 The energy in the steam is converted into velocity, 
 and it impinges upon row 2 of moving blades, driving 
 them around in their course by impulse. A second 
 expansion now occurs in row 2 and again the energy is 
 converted into velocity, but this time the reaction of 
 
364 ENGINEERING 
 
 the steam as it leaves the blades of row 2 also tends to 
 impel them around in their course. The moving 
 blades thus receive motion from two causes — the one 
 due to the impulse of the steam striking them, and the 
 other due to the reaction of the steam leaving them. 
 
 This cycle is repeated in rows 3 and 4, and soon 
 throughout the length of the rotor until the exhaust 
 end is reached. 
 
 It should be noted that the general direction taken 
 by the steam in its passage through the turbine is in 
 the form of a spiral or screw line about the rotor. The 
 clearance between the blades as they stand in the rows 
 is }i in. for the smallest size blades and % in. for the 
 larger ones, gradually increasing from the inlet to the 
 exhaust. In the 5,000 K. W. machine the clearance at 
 the exhaust end between the rows of blades is 1 in. It 
 will thus be seen that there is ample mechanical 
 clearance, also allowance for lateral motion for adjust- 
 ment of the rotor, although this is very slight, as the 
 rotor is balanced at all loads and pressures by the 
 balancing pistons PPP, Fig. 131, to which reference 
 is now made. These pistons revolve within the 
 cylinder, but do not come in mechanical contact with 
 it; consequently there is no friction. The diameter of 
 each piston corresponds to the diameter of one of the 
 three drums. 
 
 The steam entering the chamber A through valve V 
 presses against the turbine blades and goes through 
 doing work by reason of its velocity. It also presses 
 equally in the opposite direction against the first piston 
 P, and so the shaft or rotor has no end thrust. On leav- 
 ing the first group of blades and striking the second 
 group the pressure in either direction is again equalized 
 by the balance port E allowing the steam to press against 
 
THE WESTINGHOUSE-PARSONS STEAM TURBINE 365 
 
 the second balance piston P. The same event occurs at 
 group three, the steam acting upon the third piston P. 
 
 The areas of the balancing pistons are such that, no 
 matter what the load may be or what the steam pres- 
 sure or exhaust pressure may be, the correct balance 
 is maintained and there is practically no end thrust. 
 Below is shown a pipe E connecting the back of the 
 balancing pistons with the exhaust chamber. This 
 arrangement is for the purpose of equalizing the 
 pressure at this point with the pressure in the exhaust 
 chamber B. 
 
 It might be thought that the blades, on account of 
 their being so light and thin, would wear out very fast, 
 but experience so far shows that they do not. This 
 may be accounted for in two ways. First, the reduc- 
 tion of the velocity of the steam, the highest velocity 
 in the Parsons turbine not exceeding 600 ft. a second; 
 secondly, the light steam thrust on each blade, said to 
 be equal to about 1 oz. avoirdupois. This is far within 
 the bending strength of the material. A steam strainer 
 is also placed in the admission port, to prevent all 
 foreign substances from entering the turbine. 
 
 A rigid shaft and thrust or adjustment bearing 
 accurately preserves the clearances, which are larger in 
 this turbine than in other types, owing to the fact that 
 the entire circumference of the turbine is constantly 
 filled with working steam when in operation. 
 
 The bearings shown in Fig. 131 are constructed 
 along lines differing from those of the ordinary 
 reciprocating engine. The bearing proper is a gun 
 metal sleeve that is prevented from turning by a loose- 
 fitting dowel. Outside of this sleeve are three con- 
 centric tubes having a small clearance between them. 
 This clearance is kept constantly filled with oil sup- 
 
366 ENGINEERING 
 
 plied under light pressure, which permits a vibration 
 of the inner shell or sleeve and at the same time tends 
 to restrain or cushion it. This arrangement allows the 
 shaft to revolve about its axis of gravity, instead of 
 the geometrical axis, as would be the case if the bear- 
 ing were of the ordinary construction. The journal is 
 thus to a certain degree a floating journal, free to run 
 slightly eccentric according as the shaft may happen 
 to be out of balance. 
 
 A flexible coupling is provided, by means of which 
 the power of the turbine is transmitted to the dynamo 
 or other machine it is intended to run. The oil from 
 all the bearings drains back into a reservoir, and from 
 there it is forced up into a chamber, where it forms a 
 static head, which gives a constant pressure of oil on 
 all the bearings. A secondary valve is located at Vs, 
 by means of which high pressure steam may be admitted 
 to the steam space E on the same principle that 
 high pressure steam is admitted to the low pressure 
 cylinder of a compound engine. This valve opens 
 automatically in cases of emergency, such as overload, 
 failure of the condenser to work, etc. 
 
 The shaft, where it passes through either cylinder 
 head, is packed with a water seal packing, consisting 
 of a small paddle wheel attached to the shaft, which, 
 through centrifugal action, maintains a static pressure 
 of about 5 lbs. per sq. in. in the water seal, thus pre- 
 venting all leakage while at the same time it is 
 frictionless. 
 
 The speed of the Westinghouse-Parsons turbine is 
 regulated by a fly ball governor constructed in such 
 manner that a very slight movement of the balls 
 serves to produce the required change in the supply of 
 steam. Fig. 133 is a diagram of the governor 
 
THE WESTINGHOUSE-PARSONS STEAM TURBINE 367 
 
 mechanism. The ball levers swing on knife edges 
 instead of pins. The governor works both ways, that 
 is to say, when the levers are oscillating about their 
 mid position a head of steam corresponding to full 
 load is being admitted to the turbine, and a move- 
 ment from this point, either up or down, tends to 
 increase or to decrease the supply of steam. 
 
 Referring to Fig. 133, B is a piston directly con- 
 
 FIGURE 133. 
 
 nected to the admission valve. Steam is admitted to 
 this piston under control of the pilot valve A, which 
 has a slight but continuous reciprocating motion 
 derived from the eccentric rod C, and the function of 
 the governor is-to vary the plane of oscillation of this 
 valve, thus causing it to admit more or less steam to 
 piston B. The admission valve, being actuated 
 exclusively by piston B, is thus caused to remain open 
 for a longer or shorter period of time, according to the 
 load upon the turbine. 
 
368 ENGINEERING 
 
 The vibrations of the admission valve, although very 
 slight, are continuous and regular, about 165 per 
 minute, and are transmitted primarily by means of an 
 eccentric, the rod of which is shown at C, Fig. 133. 
 
 The governor sleeve is used as a floating fulcrum, and 
 the points D and E are fixed. By means of this very 
 ingenious device the steam is admitted to the turbine in 
 puffs, either long or short, according to the demand for 
 steam. At full load the puffs merge into an almost con- 
 tinuous blast. When the load has increased to the point 
 where the valve is wide open continuously, a full head of 
 steam is being admitted. Beyond this the secondary 
 valve comes into action, thus keeping the speed up to 
 normal. 
 
 The rotor requires perfect balancing to insure quiet 
 running, but this is easily accomplished in the shop by 
 means of a balancing machine used by the builders. 
 
 Steam turbines generally show higher efficiency in 
 the use of steam than reciprocating engines do, and 
 this fact is due to three leading causes. First, it is 
 possible with the turbine to use highly superheated 
 steam which, owing to the difficulties attending 
 lubrication, could not be used in the reciprocating 
 engine. Second, a larger proportion of the heat con- 
 tained in the steam is converted into work, for the 
 reason that the steam is allowed to expand to a much 
 lower pressure and into a higher vacuum. In addition 
 to this, the velocity of the expanding steam is utilized 
 in a much higher degree in the turbine as compared 
 with the reciprocating engine. Third, mechanical fric- 
 tion or lost work is reduced to the minimum. Under 
 test a 400 K. W. Westinghouse-Parsons steam turbine, 
 using steam at 150 lbs. initial pressure and superheated 
 about 180 , consumed 11. 17 lbs. of steam per Brake 
 
THE WESTINGHOUSE-PARSONS STEAM TURBINE 369 
 
 horse power hour at full load. The speed was 
 3,550 R. P. M. and the vacuum was 28 in. With 
 dry saturated steam the consumption was 13.5 lbs. 
 per B. H. P. hour at full load, and 15.5 lbs. at one-half 
 load. 
 
 A 1,000 K. W. machine, using steam of 150 lbs. 
 pressure and superheated 140 , exhausting into a 
 vacuum of 28 in., showed the very remarkable economy 
 of 12.66 lbs. of steam per E. H. P. per hour. 
 
 A 1,500 K. W. Westinghouse-Parsons turbine, using 
 dry saturated steam of 150 lbs. pressure with 27 in. 
 vacuum, consumed 14.8 lbs. steam per E. H. P. hour 
 at full load, and 17.2 lbs. at one-half load. 
 
CHAPTER V 
 
 THE CURTIS STEAM TURBINE 
 
 The Curtis turbine an impulse and reaction machine — Admission 
 of the steam — System of expanding nozzles — Ratio of expan- 
 sion in four stage machine — Step bearing — Method of lubri- 
 cation — Action of the steam in a two stage machine — Static 
 force, and force of velocity compared — Speed regulation in 
 Curtis turbine — Accomplished in first group of nozzles — How- 
 admission of steam is controlled — Velocity of the steam is 
 constant, with light or full load — Two main sources of econ- 
 omy in the steam turbine — Efficiency tests of Curtis turbine. 
 
 In the Curtis turbine the heat energy in the steam is 
 imparted to the wheel, both by impulse and reaction, 
 but the method of admission differs from that of the 
 Westinghouse-Parsons in that the steam is admitted 
 through expanding nozzles in which nearly all of the 
 expansive force of the steam is transformed into the 
 force of velocity. The steam is caused to pass through 
 one, two, or more stages of moving elements, each 
 stage having its own set of expanding nozzles, each 
 succeeding set of nozzles being greater in number and 
 of larger area than the preceding set. The ratio of 
 expansion within these nozzles depends upon the 
 number of stages, as, for instance, in a two-stage 
 machine the steam enters the initial set of nozzles at 
 boiler pressure, say 180 lbs. It leaves these nozzles 
 and enters the first set of moving blades at a pressure 
 of about 15 lbs., from which it further expands to 
 atmospheric pressure in passing through the wheels 
 and intermediates. From the pressure in the first 
 stage the steam again expands through the larger area 
 370 
 
THE CURTIS STEAM TURBINE 371 
 
 of 'the second stage nozzles to a pressure slightly 
 greater than the condenser vacuum at the entrance to 
 the second set of moving blades, against which it now 
 impinges and passes through still doing work, due to 
 velocity and mass. 
 
 From this stage the steam passes to the condenser. 
 If the turbine is a four-stage machine and the initial 
 pressure is 180 lbs., the pressure at the different stages 
 would be distributed in about the following manner: 
 Initial pressure, 180 lbs.; first stage, 50 lbs.; second 
 stage, 5 lbs.; third stage, partial vacuum, and fourth 
 stage, condenser vacuum. 
 
 The Curtis turbine is built by the General Electric 
 Co. at their works in Schenectady, New York, and 
 Lynn, Mass. The larger sizes are of the vertical type, 
 and those of small capacity are horizontal. 
 
 Fig. 134 gives a general view of a 5,000 K. W. 
 turbine and generator. The generator is shown at the 
 top, while the turbine occupies the middle and lower 
 section. A portion of the inlet steam pipe is shown, 
 ending in one nozzle group at the side. There are 
 three groups of initial nozzles, two of which are not 
 shown. The revolving parts of this unit are set upon 
 a vertical shaft, the diameter of the shaft correspond- 
 ing to the size of the unit. For a machine having the 
 capacity of the one illustrated by Fig. 134 the diameter 
 of the shaft is 14 in. 
 
 The shaft is supported by and runs upon a step 
 bearing at the bottom. This step bearing consists of 
 two cylindrical cast iron plates, bearing upon each 
 other and having a central recess between them into 
 which lubricating oil is forced under pressure by a 
 steam or electrically driven pump, the oil passing up 
 from beneath. A weighted accumulator is sometimes 
 
372 
 
 ENGINEERING 
 
 installed in connection with the oil pipe as a con- 
 venient device for governing the step bearing pumps, 
 and also as a safety device in case* the pumps should 
 fail, but it is seldom required for the latter purpose, as 
 
 FIGURE 134. 
 
 5,000 K.W. CURTIS STEAM TURBINE DIRECT CONNECTED TO 5,000 
 
 K.W. THREE-PHASE ALTERNATING CURRENT GENERATOR. 
 
 the step bearing pumps have proven, after a long 
 service in a number of cases, to be reliable. The 
 vertical shaft is also held in place and kept steady by 
 three sleeve bearings, one just above the step, one 
 between the turbine and generator, and the other near 
 
THE CURTIS STEAM TURBINE 
 
 373 
 
 the top. These guide bearings are lubricated by a 
 standard gravity feed system. It is apparent that the 
 amount of friction in the machine is very small, and 
 as there is no end thrust caused by the action of the 
 steam, the relation between the revolving and station- 
 ary blades may be maintained accurately. As a con- 
 
 FIGURE 135. 
 
 500 K.W. CURTIS STEAM TURBINE IN COURSE OF CONSTRUCTION. 
 
 sequence, therefore, the clearances are reduced to the 
 minimum. 
 
 The Curtis turbine is divided into two or more stages, 
 and each stage has one, two or more sets of revolving 
 blades bolted upon the peripheries of wheels keyed to 
 the shaft. There are also the corresponding sets of 
 stationary blades, bolted to the inner walls of the 
 cylinder or casing. As in the Westinghouse-Parsons 
 
374 ENGINEERING 
 
 type, the function of the stationary blades is to give 
 direction to the flow of steam. 
 
 Fig. 135 illustrates one stage of a 500 K. W. turbine 
 in course of construction. It will be observed that 
 there are three wheels, and that in the spaces between 
 these wheels the stationary buckets or vanes are 
 
 REVOLVING BUCKETS FOR CURTIS STEAM TURBINE. 
 
 STATIONARY BUCKETS FOR CURTIS STEAM TURBINE. 
 FIGURE 136. 
 
 placed, being firmly bolted to the casing. Fig. 136 
 shows sections of both revolving and stationary 
 buckets ready to be placed in position. The illustration 
 in Fig. 135 shows the lower or last stage. The clear- 
 ance between the revolving and stationary blades is 
 from 3V to T V in., thus reducing the wastage of steam 
 to a very low percentage. The diameters of the 
 
THE CURTIS STEAM TURBINE 375 
 
 wheels vary according to the size of the turbine, that 
 of a 5,000 K. W. machine being 13 ft. 
 
 Fig. 137 shows a nozzle diaphragm with its various 
 openings, and it will be noted that the nozzles are set 
 at an angle to the plane of revolution of the wheel. 
 
 Fig. 138 is a diagram of the nozzles, moving blades 
 ancf stationary blades of a two-stage Curtis steam 
 turbine. The steam enters the nozzle openings at the 
 top, controlled by the valves shown, the regulation of 
 which will be explained later on. In the cut Fig. 138 
 two of the valves are open, and the course of the 
 steam through the first stage is indicated by the arrows. 
 
 FIGURE 137. NOZZLE. 
 
 After passing successively through the different sets cf 
 moving blades and stationary blades in the first stage, 
 the steam passes into the second steam chest. The 
 flow of steam from this chamber to the second stage 
 of buckets is also controlled by valves, but the function 
 of these valves is not in the line of speed regulation 
 but for the purpose of limiting the pressure in the stage 
 chambers, in a manner somewhat similar to the control 
 of the receiver pressure in a two-cylinder or three- 
 cylinder compound reciprocating engine. 
 
 The valves controlling the admission of steam to the 
 second and later stages differ from those in the first 
 group in that they partake more of the nature of slide 
 
376 
 
 ENGINEERING 
 
 valves and may be operated either by hand or auto- 
 matically; in fact, they require but very little regulation, 
 
 St:<sorT-> er/nest. 
 
 
 i<«««««««(a 
 
 ~mm~ ~ 
 
 /\Sfovt'r->sr £9 /oc/e-S 
 
 Ato22fe Z7/<pjo/^mo'gr/- 1 
 
 Afovrrt^ jB/QOfiss 
 
 cccccccccccccccccccccc 
 
 /V7ov/r>gr /3/ocfes 
 
 I(<««<« «(««(«««« 
 
 Afo v/ir>jp/3/&afG 3 
 
 III I I.J 
 
 FIGURE 138. 
 DIAGRAM OF NOZZLES AND BUCKETS IN CURTIS STEAM TURBINE. 
 
 as the governing is always done by the live steam 
 admission valves. 
 Action of the Steam in a Two-stage Machine. As 
 
 previously stated, the steam first strikes the moving 
 blades in the first stage of a two-stage machine at a 
 
THE CURTIS STEAM TURBINE 377 
 
 pressure of about 15 lbs. above atmospheric pressure, 
 but with great velocity. From this wheel it passes to 
 the set of stationary blades between it and the next 
 lower wheel. These stationary blades change the 
 direction of flow of the steam and cause it to impinge 
 the buckets of the second wheel at the proper angle. 
 
 This cycle is repeated Until the steam passes from 
 the first stage into the receiving chamber or steam 
 chest for the second stage. Its passage from this 
 chamber into the second stage is controlled by valves, 
 which, as before stated, are regulated either by hand 
 or automatically. The course of the steam through 
 the nozzles and blades of the second stage is clearly 
 indicated by the arrows, and it will be noted that 
 steam is passing through all the nozzles. 
 
 At this point it might be well to consider the ques- 
 tion which no doubt arises in the mind of the student 
 in his efforts to grasp the underlying principles in the . 
 action of the steam turbine. Why is it that the 
 impingement of the steam, at so low a pressure, against 
 the blades or buckets of the turbine, imparts such a 
 large amount of energy to the shaft? 
 
 The answer is, because of velocity, and a good 
 example of the manner in which velocity may be 
 made to increase the capacity of an agent to do work 
 is illustrated in the following way: Suppose that a 
 man is standing within arm's length of a heavy plate 
 glass window and that he holds in his hand an iron 
 ball weighing 10 lbs. Suppose the man should place 
 the ball against the glass and press the same there with' 
 all the energy he is capable of exerting. He would 
 make very little, if any, impression upon the glass. 
 But suppose that he should walk away from the 
 window a distance of 20 ft. and then exert the same 
 
378 ENGINEERING 
 
 amount of energy in throwing the ball against the 
 glass, a different result would ensue. The velocity 
 with which the ball would impinge the surface of the 
 glass would no doubt ruin the window. Now, not- 
 withstanding the fact that weight, energy and time 
 involved were exactly the same in both instances, yet 
 a much larger amount of work was performed in the 
 latter case, owing to the added force imparted to the 
 ball by the velocity with which it impinged against 
 the glass. 
 
 Speed Regulation. The governing of speed is 
 accomplished in the first set of nozzles, and the control 
 of the admission valves here is effected by means of 
 a centrifugal governor attached to the top end of the 
 shaft. This governor, by a very slight movement, 
 imparts motion to levers, which in turn work the valve 
 mechanism. The admission of steam to the nozzles 
 is controlled by piston valves, which are actuated by 
 steam from small pilot valves which are in turn under 
 the control of the governor. Fig. 139 shows the form 
 of governor for a 5,000 K. W. turbine, and Fig. 140 
 shows the electrically operated admission valves for 
 one set of nozzles. 
 
 Speed regulation is effected by varying the number 
 of nozzles in flow, that is, for light loads fewer nozzles 
 are open and a smaller volume of steam is admitted to 
 the turbine wheel, but the steam that is admitted 
 impinges the moving blades with the same velocity 
 always, no matter whether the volume be large or 
 small. With a full load and all the nozzle sections in 
 flow, the steam passes to the wheel in a broad belt and 
 steady flow. 
 
 The Curtis Steam Turbine is the result of the investi- 
 gations and experiments of Mr. C. G. Curtis of New 
 
THE CURTIS STEAM TURBINE 
 
 370 
 
 York, and while retaining the advantage of the expand- 
 ing nozzle of De La\ r al, it at the same time utilizes the 
 energy acquired by velocity, by causing the steam to 
 
 FIGURE 139. GOVERNOR FOR 5,000 K.W. TURBINE. 
 
 impinge the moving buckets of two or more wheels in 
 succession. A portion of this velocity force is given 
 up in the first stage, and another portion in the second 
 stage, and this process is repeated, the steam in each 
 
380 
 
 ENGINEERING 
 
 case being first caused to expand in divergent nozzles 
 and thus acquire new velocity before it is allowed to 
 impinge the moving blades of the next lower stage. The 
 pressure in each succeeding stage of expansion becomes 
 lower and lower, until finally vacuum is reached. 
 
 As previously stated, two of the main sources of 
 economy that the steam turbine possesses in a much 
 higher degree than does the reciprocating engine are: 
 
 first, its adaptability 
 for using super- 
 heated steam, and 
 second, the possibil- 
 ity of maintaining a 
 higher degree of 
 vacuum. 
 
 k The efficiency 
 
 I 
 
 I shown by the steam 
 
 HH 1 turbine is certainly 
 
 ^ mx ^"- - ■ ' ; remarkable, and one 
 
 \ .jr peculiar feature re- 
 
 ^**— _ — _——*_- ' garding the machine 
 
 is, that its efficiency 
 is not affected by 
 variations in load to the same degree as is the efficiency 
 of the reciprocating engine. 
 
 A 600 K W. Curtis turbine operating at 1,500 
 R P. M., with steam at 140 lbs. gauge pressure and 
 28.5 in. vacuum, showed a steam consumption as fol- 
 lows, steam superheated 150 : 
 
 At full load, 12.5 lbs. per E. H. P. per hour.. 
 At half load, 13.25 lbs. per E. H. P. per hour. 
 At one-sixth load, 16.2 lbs. per E. H. P. per hour. 
 And at one-third overload, 12.4 lbs. per E. H. P. per 
 hour. 
 
 FIGURE 140. ELECTRICALLY OPER- 
 ATED VALVE. 
 
THE CURTIS STEAM TURBINE 381 
 
 This would seem to indicate that the efficiency of 
 the steam turbine increases with overload, at least up 
 to a certain point. 
 
 In another test of a Curtis turbine, using dry 
 saturated steam of 145 lbs. gauge pressure, the steam 
 consumption at full load was 14.76 lbs. per E. H. P. 
 hour, and at half load the rate was 15.95 lbs. per 
 E. H. P. hour. The same machine using steam super- 
 heated 150 showed a steam consumption of 
 13.27 lbs. per E. H. P.hour, at full load. 
 
 A Curtis turbine carrying a commercial load on a 15- 
 hour run showed an average coal consumption as 
 follows; the turbine was operated with one boiler 
 independently of the other boilers in the battery, and 
 the steam was not superheated: Coal consumed per 
 E. H. P. hour, 1.86 lbs. 
 
 The highest type of modern reciprocating engine, 
 triple expansion, condensing, having steam jacketed 
 cylinders, shows a coal consumption of 1.5 to 2 lbs. per 
 H. P. per hour, assuming the evaporation to be 8 lbs. 
 water per pound of coal. 
 
CHAPTER VI 
 
 THE HAMILTON-HOLZWARTH STEAM TURBINE 
 
 The Hamilton-Holzwarth steam turbine — Points of difference 
 between it and the Westinghouse- Parsons — Small clearances 
 necessary — Stationary discs and guide vanes — Running 
 wheels— Expansion of the steam and where it occurs — Action 
 of the steam within the machine — Various stages in high and 
 low pressure casings — Curvature of vanes — Purpose of sta- 
 tionary discs — Thrust ball bearings — Description of the gov- 
 ernor and regulating mechanism — Close regulation — Method 
 of changing speed while running. 
 
 This turbine resembles the Westinghouse-Parsons 
 turbine in some respects, prominent of which is that 
 it is a full stroke turbine, that is, that the steam flows 
 through it in one continuous belt or veil in screw line, 
 the general direction being parallel with the shaft. 
 But, unlike the Parsons type, the steam in the Hamil- 
 ton-Holzwarth turbine is made to do its work only by 
 impulse, and not by impulse and reaction combined. 
 It might thus be termed an action turbine. 
 
 The Hamilton-Holzwarth steam turbine is based 
 upon and has been developed from the designs of Prof. 
 Rateau, and is being manufactured in this country by 
 the Hooven-Owens-Rentschler Co. of Hamilton, Ohio. 
 It is horizontal and placed upon a rigid bed plate 
 of the box pattern. All steam, oil and water pipes 
 are within and beneath this bed plate, as are also 
 the steam inlet valve and the regulating and by-pass 
 valves. 
 
 The smaller sizes of this turbine are built in a single 
 casing or cylinder, but for units of 750 kilowatts and 
 382 
 
THE HAMILTON-HOLZWARTH STEAM TURBINE 383 
 
 larger the revolving element is divided into two parts, 
 high and low pressure. 
 
 There are no balancing pistons in this machine, the 
 axial thrust of the shaft being taken up by a thrust 
 ball-bearing. The interior of the cylinder is divided 
 into a series of stages by stationary discs which are set 
 in grooves in the cylinder and are bored in the center 
 to allow the shaft, or rather the hubs of the running 
 wheels that are keyed to the shaft, to revolve in this 
 bore. 
 
 The clearance allowed is as small as practical, as it 
 is in this clearance between the revolving hub and the 
 circumference of the bore of the stationary disc that 
 the leakage losses occur. It should be noted that 
 between each two stationary discs there is located a 
 running wheel, and that the clearance between the run- 
 ning vanes and the stationary vanes is made as slight 
 as is consistent with safe practice; otherwise leakage 
 would occur here also, and besides this there would be 
 a distortion of the steam jet and entrainment of the 
 surrounding atmosphere, resulting in a rapid decline in 
 economy if the clearance between the stationary and 
 moving elements was not reduced to as small a fraction 
 as possible. 
 
 As before stated, the stationary discs are firmly 
 secured to the interior walls of the casing. At intervals 
 on the outside periphery of these discs are located the 
 stationary or guide vanes. These are made of drop 
 forged steel. They are set in a groove on the outside 
 edge of the disc and fastened with rivets. Both disc 
 and vanes are then ground, giving the vanes the profile 
 that they should have for the most efficient expansion 
 of the steam. After this is done a steel ring is shrunk 
 on the outside periphery of the vanes and the steam 
 
384 ENGINEERING 
 
 channels in the disc. These discs are then placed in 
 the grooves in the casing at regular intervals, and in 
 the spaces between them are the running wheels. 
 
 The casing is divided into an upper and lower half. 
 The running wheels are built with a cast steel hub 
 having a steel disc riveted on to each side, thus forming 
 a circumferential ring space into which the running 
 vanes are riveted. A thin steel band or rim is tied on 
 the outer edge of the vanes, thus forming an outer wall 
 to the steam channels and confining the steam within 
 the vanes. These vanes are also milled on both edges, 
 on the influx and efflux side of the wheel, thus forming 
 them to the shape corresponding to the theoretical 
 diagram. 
 
 The running vanes conform in section somewhat to 
 the Parsons type, but the action of the steam upon 
 them and also within the stationary vanes is different. 
 The expansion of the steam and consequent develop- 
 ment of velocity takes place entirely within the station- 
 ary vanes, which also change the direction of flow of 
 the steam and distribute it in the proper manner to the 
 vanes of the running wheels, which, according to the 
 claims of the makers, the steam enters and leaves at 
 the same pressure, thus allowing the wheel to revolve 
 in a uniform pressure. 
 
 Fig. 141 shows a general view of the Hamilton- 
 Holzwarth turbine, and the action of the steam within 
 the machine may be described as follows: After leaving 
 the steam separator that is located beneath the bed 
 plate, the steam passes through the inlet or throttle 
 valve, the stem of which extends up through the floor 
 near the high pressure casing and is protected by a 
 floor stand and equipped with a hand wheel, shown in 
 Fig. 141. The steam now passes through the regulat- 
 
THE HAMILTON-HOLZWAKTH STEAM TURBINE 
 
 385 
 
 ing valve, which will be described later on. From this 
 valve it is led through a curved pipe to the front head 
 
 of the high pressure cas- 
 ing or cylinder. In this 
 head is a ring channel 
 into which the steam 
 enters, and from whence 
 it flows through the first 
 set of stationary vanes. 
 In these vanes the first 
 stageof expansionoccurs, 
 the velocity of the flow 
 is accelerated, and the 
 direction of flow is 
 . changed by the curve of 
 2J the vanes in such man- 
 § ner that the steam im- 
 o pinges the vanes of the 
 fe first running wheel at the 
 proper angle and in a full 
 cylindrical belt, impart- 
 ing by impulse a portion 
 of its energy to the wheel. 
 Passing through the 
 vanes of this wheel, the 
 steam immediately enters 
 the vanes of the second 
 stationary disc, which are 
 larger in area than those 
 of the first, and here 
 occurs the second stage 
 of expansion, another acceleration of velocity, and also 
 the proper change in direction, and the steam leaves 
 this distributer and impinges the vanes of the second 
 
386 ENGINEERING 
 
 running wheel. This cycle is repeated throughout the 
 several stages of the turbine, a certain percentage of 
 the heat energy in the steam being imparted by impulse 
 to each wheel and thence to the turbine shaft. From 
 the last running wheel the steam is led through re- 
 ceiver pipes to the front head of the low-pressure 
 cylinder, or, if there is but one cylinder, directly to 
 the condenser or the atmosphere. 
 
 In the low-pressure casing, which is larger in diam- 
 eter than the high-pressure the steam is distributed in 
 the same manner as it is in the high-pressure casing. 
 There is, however, in the front head of the low-pres- 
 sure casing an additional nozzle through which live 
 steam may be admitted in case of overload. The 
 design of this nozzle is such that the live steam entering 
 and passing through it and controlled by the governor 
 exerts no back pressure on the steam coming from the 
 receiver, but, on the contrary, its action is similar to 
 the action of an injector, that is, it tends to suck the 
 low-pressure steam through the first set of stationary 
 vanes of the low-pressure turbine. 
 
 The first stationary disc of the low-pressure turbine 
 has guide vanes all around its circumference, so that 
 the steam enters the turbine in a full cylindrical belt, 
 interrupted only by the guide vanes. To provide for 
 the increasing volume as the steam expands in its 
 course through the turbine, the areas of the passages 
 through the distributers and running vanes must be 
 progressively enlarged. The gradual increase in the 
 dimensions of the stationary vanes permits the steam 
 to expand within them, thus tending to maintain its 
 velocity, while at the same time the vanes guide the 
 steam under such a small angle that the force with 
 which it impinges the vanes of the next running wheel 
 
THE HAMILTON-HOLZWARTH STEAM TURBINE 387 
 
 is as effective as possible. The curvature of the vanes 
 is such that the steam while passing through them will 
 increase its velocity in a ratio corresponding to its 
 operation. 
 
 The purpose of the stationary discs is, as has been 
 stated, to distribute the steam to the running wheels. 
 They also take the back pressure of the steam as it 
 impinges the vanes of the running wheels, thus in a 
 sense acting as balancing pistons. 
 
 In all 'steam turbines one of the main requisites for a 
 quiet-running machine is that the revolving element 
 or rotor shall be perfectly balanced. The rotary body 
 of the Hamilton-Holzwarth turbine consists of a plu- 
 rality of running wheels, each one of which is balanced 
 by itself before being placed upon the shaft. All the 
 bearings are lubricated in a thorough manner by oil 
 forced up into the bottom bushing or shell under slight 
 pressure. Flexible couplings are used between the 
 high and low-pressure shafts, and for connecting the 
 turbine shaft to the generator shaft or other shaft to be 
 driven. By means of the thrust ball-bearing on the 
 exhaust end of the turbine the shaft may be adjusted 
 in an axial direction in such manner as to accurately 
 preserve the desired position of the running wheels 
 with relation to the stationary discs. 
 
 The governor is of the spring and weight type, 
 adapted to high speed, and is designed especially for 
 turbine governing. It is directly driven by the turbine 
 shaft, revolving with the same angular velocity. Its 
 action is as follows: Two discs keyed to the shaft 
 drive, by means of rollers, two weights sliding along a 
 cross bar placed at right angles through the shaft and 
 compressing two springs against two nuts on the cross 
 bar. Every movement of the weights, caused by 
 
388 ENGINEERING 
 
 increasing or decreasing the angular velocity of the 
 turbine shaft, is transmitted by means of levers to 
 a sleeve which actuates the regulating mechanism. 
 These levers are balanced so that no back pressure is 
 exerted upon the weights. The whole governor is 
 closed in by the discs, one on each side, and a steel 
 ring secured by concentric recesses to the discs. In 
 order to decrease the friction within the governor and 
 regulating mechanism, thrust ball-bearings and friction- 
 less roller-bearings are used. 
 
 As previously stated, the regulating valve is located 
 beneath the bed plate. One side of it is connected by 
 a curved pipe with the front head of the high-pressure 
 cylinder and the other side is connected with the inlet 
 valve. The regulating valve is of the double-seated 
 poppet valve type. Valves and valve seats are made 
 of tough cast steel, to avoid corrosion as much as 
 possible, and the valve body is made of cast iron. 
 
 Immediately below the regulating valve and forming 
 a part of it in one steam chamber is located the by- 
 pass regulating valve. Thus the use of a . second 
 stuffing box for the stem of this valve is avoided. 
 The function of this valve is to control the volume of 
 the live steam supply that flows directly to the by-pass 
 nozzles in the front head of the low-pressure casing. 
 This valve is also a double-seated poppet valve. 
 
 The main regulating valve is not actuated directly by 
 the governor, but by means of the regulating mechan- 
 ism. The construction and operation of this regulat- 
 ing mechanism is as follows: The stem of the 
 regulating valve is driven by means of bevel gears by 
 a shaft that is supported in frictionless roller-bearings.. 
 On this shaft there is a friction wheel that the governor 
 can slide across the face of a continuously revolving 
 
THE HAMILTON-HOLZWARTH STEAM TURBINE 389 
 
 friction disc by means of its sleeve and bell crank 
 lever. This revolving disc is keyed to a solid shaft 
 which is driven by a coupling frorn a hollow shaft. 
 This hollow shaft is driven by the turbine shaft through 
 the medium of a worm gear. The solid shaft, with the 
 continuously revolving friction disc, can be slightly 
 shifted by the governor sleeve so that the two friction 
 discs come into contact when the sleeve moves, that 
 is, when the angular velocity changes. If this change 
 is relatively great, the sleeve will draw the periodically 
 revolving friction disc far from the center of the always 
 revolving one, and this disc will quickly drive the 
 stem of the regulating valve and the -flow of steam will 
 thus be regulated. As soon as the angular velocity 
 falls below a certain percentage of the normal speed, 
 the driving friction disc is drawn back by the governor, 
 the regulating valve remains open and the whole regu- 
 lating mechanism rests or stops, although the shaft is 
 still running. 
 
 Should the angular velocity of the shaft reach a point 
 2.5 per cent higher than normal, the governor will shut 
 down the turbine. If an accident should happen to 
 the governor, due to imperfect material or breaking or 
 weakening of the springs, the result would be a shut- 
 down of the turbine. 
 
 In order to change the speed of the turbine while 
 running, which might be necessary in order to run the 
 machine parallel with another prime mover, a spring 
 balance is provided, attached to the bell crank lever 
 of the regulating mechanism. The hand wheel of this 
 spring balance is outside of the pedestal for regulating 
 mechanism and near the floor-stand and hand wheel. 
 With this spring balance the speed of the turbine may 
 be changed 5 per cent either way from normal. 
 
390 ENGINEERING 
 
 All the bearings of the unit are thoroughly lubricated 
 with oil forced under pressure by the oil pump driven 
 by means of worm-gearing by the turbine itself. After 
 flowing through the bearings the oil is passed through 
 a filter and from thence to the oil tank located within 
 the bed plate, from whence it is taken by the oil pump. 
 All revolving parts are enclosed, and the principal 
 part of the regulating mechanism operates in a bath 
 of oil. 
 
CHAPTER VII 
 
 DE LAVAL STEAM TURBINE 
 
 De Laval steam turbine — High velocity — The De Laval divergent 
 nozzle — Adiabatic expansion of steam within nozzle — Conver- 
 sion of static energy into kinetic — Form of De Laval wheel — 
 Speed of buckets — Speed of turbine shaft, and how it is 
 reduced — Construction of the wheel — Number of buckets 
 required — Number of nozzles — Gear and flexible shaft — 
 Description of governor — Vacuum valve — Operation of gov- 
 ernor — Efficiency tests — Steam consumption— Cross section 
 of wheel showing correct design — Table of sizes, giving speed 
 and weight. 
 
 The De Laval steam turbine, the invention of Carl 
 De Laval of Sweden, is noted for the simplicity of its 
 construction and the high speed of the wheel —10,000 
 to 30,000 R. P. M. The difficulties attending such 
 high velocities are, however, overcome by the long, 
 flexible shaft and the ball and socket type of bearings, 
 which allow of a slight flexure of the shaft in order 
 that the wheel may revolve about its center of gravity, 
 rather than the geometrical center or center of position. 
 All high speed parts of the machine are made of forged 
 nickel steel of great tensile strength. But one of the 
 most striking features of this turbine is the diverging 
 nozzle, also the invention of De Laval. 
 
 It is well known that in a correctly designed nozzle 
 the adiabatic expansion of the steam from maximum 
 to minimum pressure will convert the entire static 
 energy of the steam into kinetic. Theoretically this is 
 what occurs in the De Laval nozzle. The expanding 
 steam acquires great velocity, and the energy of the jet 
 391 
 
ENGINEERING 
 
 of steam issuing from the nozzle is equal to the amount 
 of energy that would be developed if an equal volume 
 of steam were allowed to adiabatically expand behind 
 the piston of a reciprocating engine, a condition, how- 
 
 ever, which for obvious reasons has never yet been 
 attained in practice with the reciprocating engine. 
 But with the divergent nozzle the conditions are 
 different. 
 
 Referring to Fig. 142, a continuous volume of steam 
 
DE LAVAL STEAM TURBINE 
 
 393 
 
 at maximum pressure is entering the nozzle at E, and, 
 passing through it, expands to minimum pressure at F, 
 the temperature of the nozzle being at the same time 
 constant and equal to the temperature of the passing 
 steam. The principles of the De Laval expanding 
 nozzle are in fact more or less prominent in all steam 
 
 FIGURE 143. THE DE LAVAL TURBINE WHEEL AND NOZZLES. 
 
 turbines. The facilities for converting heat into work 
 are increased by its use, and the losses by radiation 
 and cooling influences are greatly lessened. 
 
 The De Laval steam turbine is termed by its builders 
 a high-speed rotary steam engine. It has but a single 
 wheel, fitted with vanes or buckets of such curvature as 
 
394 
 
 ENGINEERING 
 
 has been found to be best adapted for receiving the 
 impulse of the steam jet. There are no stationary or 
 
 guide blades, the augular position of the nozzles giving 
 direction to the jet. Fig. 143 shows the form of wheel 
 
DE LAVAL STEAM TURBINE 395 
 
 and the nozzles. The nozzles are placed at an angle of 
 20° to the plane of motion of the buckets, and the 
 course of the steam is shown by the illustration. 
 
 The heat energy in the steam is practically devoted 
 to the production of velocity in the expanding 01 
 divergent nozzle, and the velocity thus attained by the 
 issuing jet of steam is about 4,000 ft. per second. To 
 attain the maximum of efficiency the buckets attached 
 to the periphery of the wheel against which this jet 
 impinges should have a speed of about 1,900 ft. per 
 second, but, owing to the difficulty of producing a 
 material for the wheel strong enough to withstand the 
 strains induced by such a high speed, it has been found 
 necessary to limit the peripheral speed to 1,200 or 
 1,300 ft. per second. 
 
 Fig. 144 shows a De Laval steam turbine motor of 
 300 H. P., which is the largest size built up to the 
 present time, its use having been confined chiefly to 
 light work. 
 
 The turbine illustrated in Fig. 144 is shown directly 
 connected to a 200 fe.VV. two-phase alternator. The 
 steam and exhaust connections are plainly shown, as 
 also the nozzle valves projecting from the turbine 
 casing. The speed of the turbine wheel and shaft is 
 entirely too high for most practical purposes, and it is 
 reduced by a pair of very perfectly cut spiral gears, 
 usually made 10 to 1. These gear wheels are made of 
 solid cast steel, or of cast iron with steel rims pressed 
 on. The teeth in two rows are set at an angle of go° to 
 each other. This arrangement insures smooth running 
 and at the same time checks any tendency of the shaft 
 towards end thrust, thus dispensing ,with a thrust 
 bearing. 
 
 The working parts of the machine are clearly illus- 
 
396 
 
 ENGINEERING 
 
 FIGUKE 145. 
 
 trated in Fig. 145, and a fairly good conception of the 
 assembling of the various members, and especially the 
 reducing gears, may be had by reference to Fig. 146, 
 
DE LAVAL STEAM TURBINE 397 
 
 which shows a 110 H. P. turbine and rotary pump with 
 the upper half of the gear case and field frame removed 
 for purposes of inspection. The slender shaft is seen 
 projecting from the center of the turbine case, and upon 
 this shaft are shown the small pinions meshing into the 
 large spiral gears upon the two pump shafts. 
 
 Referring to Fig. 145, A is the turbine shaft, B is the 
 turbine wheel, and C is the pinion. As the turbine 
 wheel is by far the most important element, it will be 
 taken up first. It is made of forged nickel steel, and 
 it is claimed by the builders, the De Laval Steam 
 Turbine Co. of Trenton, New Jersey, that it will with- 
 stand more than double the normal speed before 
 showing any signs of distress. A clear idea of the 
 construction of the wheel and buckets may be had by 
 reference to Fig. 143. The number of buckets varies 
 according to the capacity of the machine. There are 
 about 350 buckets on a 300 H. P. wheel. The buckets 
 are drop forged and made with a bulb shank fitted in 
 slots milled in the rim of the wheel. 
 
 Fig. 147 is a sectional plan of a 30 H. P. turbine con- 
 nected to a single dynamo, and Fig. 148 is a sectional 
 elevation of the same. 
 
 The steam, after passing the governor valve C, Fig. 
 148, enters the steam chamber D, Fig. 147, from 
 whence it is distributed to the various nozzles. The 
 number of these nozzles depends upon the size of the 
 machine, ranging from one to fifteen. They are 
 generally fitted with shut-off valves (see Fig. 144) by 
 which one or more nozzles can be cut out when the 
 load is light. This renders it possible to use steam at 
 boiler pressure, no matter how small the volume 
 required for the load. This is a matter of great 
 importance, especially where the load varies con- 
 
398 
 
 ENGINEERING 
 
 siderably, as, for instance, there are plants in which 
 during certain hours of the day a 300 H. P. machine 
 may be taxed to its utmost capacity and during certain 
 
DE LAVAL STEAM TURBINE 
 
 899 
 
400 ENGINEERING 
 
 other hours the load on the same machine may drop to 
 50 H. P. In such cases the number of nozzles in action 
 may be reduced by closing the shut-off valves until the " 
 required volume of steam is admitted to the wheel. 
 This adds to the economy of the machine. After pass- 
 ing through the nozzles, the steam, as elsewhere 
 explained, is now completely expanded, and in imping- 
 ing on the buckets its kinetic energy is transferred to 
 the turbine wheel. Leaving the buckets, the steam 
 now passes into the exhaust chamber G, Fig. 147, and 
 out through the exhaust opening H, Fig. 148, to the 
 condenser or atmosphere as the case may be. 
 
 The gear is mounted and enclosed in the gear case I, 
 Fig. 147. J is the pinion made solid with the flexible 
 shaft and engaging the gear wheel K. This latter is 
 forced upon the shaft L, which, with couplings M, 
 connects to the dynamo or is extended for other 
 transmission. 
 
 O, Fig. 148, is the governor held with a taper shank 
 in the end of the shaft L, and by means of the bell 
 crank P operates the governor valve C. The flexible 
 shaft is supported in three bearings, Fig, 147. Q and 
 R are the pinion bearings and S is the main shaft bear- 
 ing which carries the greater part of the weight of the 
 wheel. This bearing is self-aligning, being held to its 
 seat by the spring and cap shown. 
 
 T, Fig. 147, is the flexible bearing, being entirely 
 free to oscillate with the shaft. Its only purpose is to 
 prevent the escape of steam when running non-con- 
 densing, or the admission of air to the wheel case when 
 running condensing. The flexible shaft is made very 
 slender, as will be observed by comparing its size with 
 that of the rotary pump shaft in Fig. 146. It is by means 
 of this slender, flexible shaft that the dangerous feature 
 
DE LAVAL STEAM TURBINE 
 
 401 
 
402 
 
 ENGINEERING 
 
 of the enormously high speed of this turbine is 
 eliminated. 
 
 The governor is of the centrifugal type, although 
 differing greatly in detail from the ordinary fly ball 
 governor, as will be seen by reference to Fig. 149. It 
 is connected directly to the end of the gear wheel shaft. 
 Two weights B are pivoted on knife edges A with 
 
 figure 149. 
 
 hardened pins C, bearing on the spring seat D. E is 
 the governor body fitted in the end of the gear wheel 
 shaft K and has seats milled for the knife edges A. It 
 is afterwards reduced in diameter to pass inside of the 
 weights and its outer end is threaded to receive the 
 adjusting nut I, by means of which the tension of the 
 spring, and through this the speed of the turbine, is 
 adjusted. When the speed accelerates, the weights, 
 
DE LAVAL STEAM TURBINE 403 
 
 affected by centrifugal force, tend to spread apart, and 
 pressing on the spring seat at D push the governor pin 
 G to the right, thus actuating the bell crank L and 
 cutting off a part of the flow of steam. 
 
 It has been found necessary with this turbine, when 
 running condensing, to introduce a valve termed a 
 vacuum valve, also controlled by the governor, as it has 
 been found that the governor valve alone is unable to 
 hold the speed of the machine within the desired limit. 
 The function of the vacuum valve is as follows: The 
 governor pin G actuates the plunger H, which is 
 screwed into the bell crank L, but without moving the 
 plunger relative to said crank. This is on account of 
 the spring M being stirrer than the spring N, whose 
 function is to keep the governor valve open and the 
 plunger H in contact with the governor pin. When 
 a large portion of the load is suddenly thrown off, the 
 governor opens, pushing the bell crank in the direction 
 of the vacuum valve T. This closes the governor 
 valve, which is entirely shut off when the bell crank is 
 pushed so far that the screw O barely touches the 
 vacuum valve stem J. Should this not check the speed 
 sufficiently, the plunger H is pushed forward in the 
 now stationary bell crank and the vacuum valve is 
 opened, thus allowing the air to rush into the space P 
 in which the turbine wheel revolves, and the speed is 
 immediately checked. 
 
 The main shaft and dynamo bearings are ring oiling. 
 The high-speed bearings on the turbine shaft are fed 
 by gravity from an oil reservoir, and the drip oil is 
 collected in the base and maybe filtered and used over 
 again. 
 
 The fact that the steam is used in but a single stage 
 or set of buckets and then allowed to pass into the 
 
404 
 
 ENGINEERING 
 
 exhaust chamber might appear at first thought to be a 
 great loss of kinetic energy, but, as has been previously 
 stated, the static energy in the steam as it enters the 
 nozzles is converted into kinetic energy by its passage 
 through the divergent nozzles, and the result is a 
 greatly increased volume of steam leaving the nozzles 
 at a tremendous velocity, but at a greatly reduced 
 
 L23 
 
 FIGURE 150. 
 
 pressure — practically exhaust pressure — impinging 
 against the buckets of the turbine wheel and thus 
 causing it to revolve. 
 
 Efficiency tests of the De Laval turbine show a high 
 economy in steam consumption, as, for instance, a test 
 made by Messrs. Dean and Main of Boston, Mass, on 
 a 300 H P. turbine, using saturated steam at about 
 200 lbs. pressure per sq. in. and developing 333 Brake 
 
DE LAVAL STEAM TURBINE 
 
 405 
 
 H. P., showed a steam consumption of 15.17 lbs. per 
 B. H. P., and the same machine, when supplied with 
 superheated steam and carrying a load of 352 B. H. P., 
 consumed but 13.94 lbs. per B. H. P. These results 
 compare most favorably with those of the highest type 
 of reciprocating engines. 
 
 Fig. 150 shows a cross section of a 300 H. P. De 
 Laval wheel, showing the design necessary for with- 
 standing the high centrifugal stress to which these 
 wheels are subjected. All De Laval wheels are tested 
 to withstand the centrifugal stress of twice their normal 
 velocity without showing signs of fatigue. 
 
 The following table gives the sizes and weights of 
 some of these turbines, together with revolutions per 
 minute of the turbine shaft and the main shaft. 
 
 Horse Power 
 
 Revolutions 
 Turbine Shaft 
 
 Revolutions 
 Main Shaft 
 
 Approximate 
 Weight 
 Pounds 
 
 5 
 
 - 10 
 
 20 
 
 75 
 
 110 
 
 225 
 
 300 
 
 30,000 
 24,000 
 20,000 
 16,400 
 13,000 
 11,060 
 10,500 
 
 3,000 
 2,400 
 2,000 
 1,500 
 1,200 ■ 
 900 
 900 
 
 330 
 
 650 
 
 1,250 
 
 5,000 
 
 8,000 
 
 15,000 
 
 20,000 
 
CHAPTER VIII 
 
 DISPOSAL OF THE EXHAUST STEAM OF STEAM 
 TURBINES 
 
 Advantages of exhausting into a condenser — Possible to maintain 
 higher vacuum in condenser of a turbine than with reciprocat- 
 ing engine — Surface condensers — Bulkley injector condenser 
 — Steam turbine condensing apparatus at St. Louis Exposition, 
 1904 — Dry air pump — Gain in economy from high vacuum — 
 Cost of operating auxiliaries — Necessity of excluding all air 
 from condensing system — Ways in which air may be en- 
 trained — Comparative efficiency of turbines and reciprocating 
 engines — Percentage of saving per each inch increase in 
 vacuum above 25 inches — Advantages of superheating the 
 steam — Outlook for future of steam turbines. 
 
 As in the case of the reciprocating engine, the 
 highest efficiency in the operation of the steam turbine 
 is obtained by allowing the exhaust steam to pass into 
 a condenser, and experience has demonstrated that it 
 is possible to maintain a higher vacuum in the con- 
 denser of a turbine than in that of a reciprocating 
 engine. This is due, no doubt, to the fact that in the 
 turbine the steam is expanded down to a much lower 
 pressure than is possible with the reciprocating engine. 
 
 The condensing apparatus used in connection with 
 steam turbines may consist of any one of the modern 
 improved systems, and as no cylinder oil is used within 
 the cylinder of the turbine, the water of condensation 
 may be returned to the boilers as feed water. If the 
 condensing water is foul or contains matter that would 
 be injurious to the boilers, a surface condenser should 
 be used. If the water of condensation is not to be used 
 406 
 
DISPOSAL OF THE EXHAUST STEAM 407 
 
 in Hie boilers, the jet system may be employed. 
 Another type of condenser that is being successfully 
 used with steam turbines is the Bulkley injector 
 condenser. 
 
 Among the steam turbines that were on exhibition at 
 the St. Louis exposition in 1904 the Westinghouse- 
 Parsons and the General Electric Curtis turbines were 
 each equipped with Worthington surface condensers, 
 fitted with improved auxiliary apparatus consisting of 
 dry vacuum pumps, either horizontal of the well-known 
 Worthington type, or rotative motor-driven, a hot well 
 pump, and a pump for disposing of the condensed 
 steam from the exhaust system. The two latter pumps 
 were of the Worthington centrifugal type. The 
 Hamilton-Holzwarth turbine was equipped with a 
 Smith-Vaile surface condenser, fitted with a duplex 
 double-acting air pump, a compound condensing 
 circulating pump, and a rotative dry vacuum pump, 
 motor-driven. The vacuum maintained was high, 28 
 to 28.5 in. 
 
 As an instance of the great gain in economy effected 
 by the use of the condenser in connection with the 
 steam turbine, a 750 K. W. Westinghouse-Parsons 
 turbine, using steam of 150 lbs. pressure not super- 
 heated and exhausting into a vacuum of 28 in., showed 
 a steam consumption of 13.77 l° s - P er B. H. P. per 
 hour, while the same machine operating non-condensing 
 consumed 28.26 lbs. of steam per B. H. P. hour. 
 Practically the same percentage in economy effected by 
 condensing the exhaust applies to the other types of 
 steam turbines. 
 
 With reference to the relative cost of operating the 
 several auxiliaries necessary to a complete condensing 
 outfit, the highest authorities on the subject place the 
 
408 ENGINEERING 
 
 power consumption of these auxiliaries at from 2 to 7 
 per cent of the total turbine output of power. A por- 
 tion of this is regained by the use of an open heater 
 for the feed water, into which the exhaust steam from 
 the auxiliaries may pass, thus heating the feed water 
 and returning a part of the heat to the boilers. 
 
 A prime requisite to the maintenance of high vacuum, 
 with the resultant economy in the operation of the 
 condensing apparatus, is that all entrained air must be 
 excluded from the condenser. There are various ways 
 in which it is possible for air to find its way into the 
 condensing system. For instance, there may be an 
 improperly packed gland, or there may be slight leaks 
 in the piping, or the air may be introduced with the 
 condensing water. This air should be removed before 
 it reaches the condenser, and it may be accomplished 
 by means of the "dry" air pump. 
 
 This dry air pump is different from the ordinary air 
 pump that is used in connection with most condensing 
 systems. The dry air pump handles no water, the 
 cylinder being lubricated with oil in the same manner 
 as the steam cylinder. The clearances also are made 
 as small as possible. These pumps are built either in 
 one or two stages. 
 
 A barometric or a jet condenser may be used, or a 
 surface condenser. The latter type lessens the danger 
 of entrained air, besides rendering it possible to return 
 the condensed steam, which is pure distilled water, to 
 the boilers along with the feed water, a thing very much 
 to be desired in localities where the water used for feed- 
 ing the boilers is impregnated with carbonate of lime 
 or other scale-forming ingredients. 
 
 In comparing the efficiency of the reciprocating 
 engine and the steam turbine it is not to be inferred 
 
DISPOSAL OF THE EXHAUST STEAM 400 
 
 that reciprocating engines would not give better results 
 at high vacuum than they do at the usual rate of 25 to 
 26 in., but to reach and maintain the higher vacuum of 
 28 to 28.5 in. with the reciprocating engine would 
 necessitate much larger sizes of the low-pressure 
 cylinder, as also the valves and exhaust pipes, in order 
 to handle the greatly increased volume of steam at the 
 low pressure demanded by high vacuum. 
 
 The steam turbine expands its working steam to 
 within I in. of the vacuum existing in the condenser, 
 that is, if there is a vacuum of 28 in. in the condenser 
 there will be 27 in. of vacuum in the exhaust end of 
 the turbine cylinder. On the other hand, there is 
 usually a difference of 4 or 5 in. (2 to 2.5 lbs.) between 
 the mean back pressure in the cylinder of a recipro- 
 cating condensing engine and the absolute back pres- 
 sure in the condenser. 
 
 It therefore appears that the gain in economy per 
 inch increase of vacuum above 25 in. is much larger 
 with the turbine than it is with the reciprocating 
 engine. Mr. J. R. Bibbins estimates this gain to be 
 as follows: between 25 and 28 in. there is a gain of 3^ 
 to 4 per cent per inch of increase, and at 28 in. 5 per 
 cent. These results have been obtained by means of 
 exhaustive tests conducted by Mr. Bibbins. Other 
 high authorities on the steam turbine all agree as to the 
 great advantages to be derived by incurring the extra 
 expense of erecting a condensing plant that is capable 
 of maintaining the high vacuum necessary to high 
 efficiency. 
 
 Another method by which the steam consumption of 
 the turbine may be materially decreased and a great 
 gain in economy effected is by superheating the steam. 
 The amount of superheat usually specified is ioo°, and 
 
410 ENGINEERING 
 
 the apparatus employed for producing it maybe easily 
 mounted in the path of the waste gases. The steam 
 may thus be superheated without extra cost in fuel, and 
 an increase of 8 to 10 per cent in economy effected. 
 The independent superheater requires extra fuel and 
 labor, and the gain in this case is doubtful, but there 
 can be no question as to the wisdom of utilizing the 
 waste flue gases for superheating the steam. 
 
 As previously stated, the steam turbine is peculiarly 
 adapted for the use of highly superheated steam and 
 high vacuum, and in these two particulars it excels the 
 reciprocating engine At the present time many large 
 plants are equipped with turbine engines that are giving 
 the best of results, and the outlook for the future 
 employment of this type of power producer is certainly 
 very promising. 
 
PART III 
 Electricity for Engineers 
 
Electricity for Engineers 
 
 CHAPTER I 
 
 The Electric Current— The Ampere— The Volt— The Ohm— The 
 Watt — Divided Circuits. 
 
 The Electric Current. All electrical phenomena with 
 which we have to deal are produced through the 
 medium of the electric current. This current flows 
 only in a conductor of electricity. Among the most 
 noteworthy of the conductors are the various metals; 
 the most useful, and in fact the only one in general 
 use for light and power purposes, being copper. 
 
 Every conductor offers some resistance to the flow 
 of current, just as every pipe offers resistance to the 
 flow of steam or water. Just how this resistance varies 
 we shall see later on. In order to familiarize ourselves 
 with the most important electrical phenomena let us 
 consider Fig. I. The current is assumed to leave the 
 battery at the +, or positive, pole and flow along the 
 wires, etc., to the negative, or - pole, and as it passes 
 through the coils of wire wound about the iron bar it 
 produces magnetism in the bar. If the bar is of soft 
 iron the magnetism lasts only while the current is 
 flowing, but a bar of hardened steel will permanently 
 retain its magnetism. The current will also heat the 
 incandescent lamp until it emits light, and the fine 
 wire, R, to the melting point, if desired. In passing 
 through the water in the jar, it will decompose it, 
 forming oxygen and hydrogen gas. If, instead of 
 5 
 
6 
 
 ELECTRICITY FOR ENGINEERS 
 
 water, the jar is filled with a proper solution, one of 
 the copper plates in the solution will be gradually 
 eaten away and the other added to. If we now discon- 
 nect our wires from the battery and connect I at 2, and 
 2 at I, the chemical action in the jar will be reversed, 
 the lamp and fine wire, R, will heat as before, no differ- 
 ence being noticeable. The iron bar will also be a 
 magnet as before, but the end that before attracted 
 the north seeking end of a compass needle will now 
 reDel it and attract the south seeking end of the same 
 
 figure 1. 
 
 needle. The wire which connects the various devices, 
 and the devices themselves, constitutes an electric cir- 
 cuit, and the current is said to flow in such a circuit 
 along the wire, just as water flows in a pipe. The 
 solid lines form what is known as a series circuit, 
 while the dotted lines form a multiple circuit. In the 
 latter case, each piece of apparatus receives current 
 independent of the others. In the series circuit the 
 same current passes through all. If the small wire a 
 is connected to b, no current will flow through R; it 
 
ELECTRICITY FOR ENGINEERS 7 
 
 will all flow through a and b. If the wire X be con- 
 nected to Y, all current will flow through it and none 
 through any other part of the circuit. The current 
 obeys the same law as does water; it takes the path 
 which offers the least resistance to its flow. 
 
 Such substances as effectually prevent current from 
 flowing through them are known as insulators. Some 
 of them are 
 
 Dry Air, Mica, 
 
 Glass, Shellac, 
 
 Silk, Oil, 
 
 Asbestos, Paraffine, 
 
 Porcelain, Wool, 
 
 Cotton, Paper, 
 
 Rubber, Gutta Percha, 
 
 and because the following substances have a low resist- 
 ance they are known as conductors of electricity. 
 Their relative conductivity is in the following order, 
 silver being the best: 
 
 Silver, 
 
 Copper, 
 
 Gold, 
 
 Platinum 
 
 Iron, 
 
 Tin, 
 
 Lead, etc. 
 
 The Ampere. The ampere is the unit of volume or rate 
 of flow, and in speaking of a flow of so many amperes, 
 we mean substantially the same thing, electrically 
 speaking, as though we referred to so many gallons of 
 water, mechanically speaking. The number of amperes 
 flowing over a wire deliver power, much or little, pro- 
 
8 ELECTRICITY FOR ENGINEERS 
 
 portional to the electromotive force or pressure under 
 which they flow; just as the number of gallons of water 
 flowing through a pipe toward a water wheel deliver a 
 large or small quantity of power to the wheel, propor- 
 tional to the pressure under which the water flows. If 
 ioo amperes were flowing at a pressure of 10 volts they 
 would produce the same power as though there were 
 io amperes flowing at ioo volts, exactly as ioo gals, of 
 water flowing at a pressure of io lbs. to the square inch 
 would produce the same power as io gals, flowing at a 
 pressure of ioo lbs. to the square inch. In both cases, 
 however, for convenience, we have not considered the 
 size of either wire or pipe, but with the wire, as with 
 the pipe, as we increase the diameter we decrease the 
 friction or resistance. In speaking of the gallon we, 
 of course, have something material on which we can 
 base the unit gallon. We may take a vessel I ft. wide, 
 I ft. long and I ft. high, and this vessel will hold I cu. 
 ft. of water. This cubic foot would contain jy^ gals.; 
 but in the case of the ampere we must adopt another 
 method. We shall take an earthenware tank in which 
 is contained a solution of copper sulphate and add one- 
 tenth of one per cent, sulphuric acid. We shall next 
 take two copper plates and hang them into this solu- 
 tion, keeping them spaced one inch apart, vertically. 
 Having washed these plates in clear water, rounded off 
 the corners and dried them thoroughly, we must next 
 weigh them very carefully before submerging them in 
 the liquid. We may now connect both plates to a 
 source from which we can obtain a -current of electri- 
 city and allow the current to flow from one plate to 
 another, through the liquid, for a period of time which 
 we must measure by a watch or clock. After current 
 has flowed for several hours we will remove the plates, 
 
ELECTRICITY FOR ENGINEERS 1) 
 
 wash them in clean water, and then dip in a bath of 
 water containing a very small amount of sulphuric acid 
 to prevent oxidization, dry them and carefully weigh 
 them again. It will be found that the negative plate 
 has increased in weight by what is called electrolytic 
 action. Now weigh the negative plate and ascertain 
 the exact number of grammes of copper deposited on 
 its surface, or, in other words, find how many grammes 
 heavier the plate is now than it was before it went into 
 the bath. With these data in our possession we will 
 multiply the time in seconds that current was passing 
 through the plates by .000329 and divide the number 
 of grammes deposited on the plate by the result. The 
 quotient will be the number of amperes that passed 
 from plate to plate. This I give simply to show you 
 the manner in w r hich the ampere can be ascertained. 
 It is that current which will deposit .000329 gramme 
 per second on one of the plates of a voltameter, as 
 above described. It is also the current produced by 
 one volt acting through a resistance of one ohm. 
 
 In other words, the ampere is that current which 
 would be forced over a wire having a resistance of one 
 ohm by a pressure of one volt. 
 
 The ampere-hour is the unit of electrical quantity in 
 general use. It is the quantity of electricity conveyed 
 by one ampere flowing for one hour, or one-half 
 ampere flowing for two hours; or again, one-fourth 
 ampere flowing for four hours. In each case the sum 
 total would be one ampere-hour." It must, however, 
 be noted that an ampere-hour with the pressure at no 
 volts would deliver just one-half as much power as an 
 ampere-hour at 220 volts. 
 
 An ordinary 16 *candle-power no volt incandescent 
 lamp requires a current of about one-half an ampere, 
 
10 ELECTRICITY FOR ENGINEERS 
 
 while a lamp of the same candle-power at 220 volts 
 requires but one-fourth of an ampere, and a 52 volt 
 lamp about one ampere. 
 
 A milli-ampere is the one-thousandth (yoW) P ai "t °f 
 an ampere. 
 
 The Coulomb. The Coulomb is the unit of quantity. 
 It is the quantity of current delivered by one ampere 
 flowing for one second. 
 
 The Volt. By electromotive force, volts, or potential, 
 we mean electrically about the same as we do when 
 speaking of pounds pressure as indicated on a steam 
 gauge. If we connect a volt-meter between a positive 
 and a negative wire we find that it indicates a certain 
 number of volts; the volt-meter then indicates electrical 
 pressure just as a steam gauge indicates steam pressure. 
 The difference in potential or pressure between two 
 wires we will assume to be 100 volts, and the difference 
 of potential between the inside of a pipe and the atmos- 
 phere also at 100 lbs. to the square inch. The steam 
 gauge is closed at one end of the tube which operates it, 
 and hence, the pressure from the interior of the pipe 
 does not flow into the atmosphere; in other words, the 
 resistance offered to the pressure prevents the water 
 from escaping into the atmosphere. In the case of 
 the volt-meter the resistance of the wires used in its 
 construction prevents any great quantity of electricity 
 from flowing out of the positive wire and into the 
 negative through the volt-meter coil. If the gauge 
 were accidentally broken off the pipe, the resistance to 
 the pressure on the inside of the pipe would be greatly 
 lowered and allow the water to flow into the atmos- 
 phere. If a piece of ordinary wire were connected to 
 the positive and negative wires, where we have just 
 connected our volt-meter, it would form a path of such 
 
ELECTRICITY FOR ENGINEERS 11 
 
 low resistance and allow all the current to flow through 
 it, so there would be no pressure indicated in the volt- 
 meter. This would "be called a "short circuit." With 
 a volt-meter there is always a small amount of current 
 flowing from a positive to a negative wire through the 
 coil in the meter. This current is neccesary to produce 
 the reading on the meter, but we need not consider 
 this current at present, the quantity being very small. 
 
 One volt (unit of pressure) will force one ampere 
 (unit of current) over one ohm (unit of resistance). 
 
 Potential is a term quite frequently used to express 
 the same idea as voltage or electromotive force, but its 
 meaning is somewhat different. Suppose that a steam 
 engine is working with ioo lbs. of pressure at the 
 throttle valve, and exhausting into a heating system or 
 system of piping that offers a back pressure of 5 lbs. to 
 the square inch; in other words, the resistance to the 
 flow of steam out of the exhaust pipes of this engine is 
 such that the remaining pressure, when the engine has 
 exhausted, is 5 lbs. Now it will readily be seen that 
 the total pressure utilized to do the work would be 100 
 lbs. less 5 lbs., or 95 lbs., and therefore the potential 
 would be 95 lbs. Now, if we are using electricity at 
 100 volts pressure, and lose 5 volts in overcoming 
 resistance, we have a potential of 95 volts left. When- 
 ever work is done by a steam engine a certain amount 
 of pressure is lost by condensation, doing work and by 
 overcoming friction. This loss may be considered the 
 same as a loss of potential, for in the use of electricity 
 any loss in pressure of volts that may occur from 
 doing work or overcoming resistance is called a loss of 
 potential. 
 
 In open arc lamps the loss of potential across the 
 terminals or binding posts is about 50 volts; that is, 50 
 
12 ELECTRICITY FOR ENGINEERS 
 
 volts have been absorbed or used in producing light. 
 You can now readily understand that electromotive 
 force means force, pressure, energy, and that by 
 potential we mean the capacity to do work or the 
 effective pressure to do work. While we are speaking 
 of electromotive force we may consider some of the 
 advantages of high and low electromotive forces. 
 High electromotive force, like steam at high pressure, 
 is far more economical in transmission or utilization 
 because the quantity may be that much smaller. 
 
 When transmitted to great distances, high electro- 
 motive forces, like high water or steam pressures, are 
 far more desirable on account of the reduction in fric- 
 tion losses; but this is partially offset by the necessity 
 of using, in water transmission, a much stronger pipe 
 for the high pressure than would be necessary for the 
 low pressure, and in the transmission of current at a 
 high electromotive force or pressure it becomes neces- 
 sary to use wires with far better insulating material 
 than would be required for the transmission of elec- 
 tricity at low pressure. Increasing the pressure or 
 electromotive force always means more danger, even if 
 you know the pipes are extra strong or the insulation 
 of the wire is of unusuallv high resistance; for if any- 
 thing should happen the consequences would be far 
 more serious with high than with low pressures. But 
 notwithstanding all this, engineers are continually 
 increasing the pressures of electrical machinery. 
 
 Static electricity is a term applied to electricity pro- 
 duced by friction, and a static discharge of electricity 
 usually consists of an infinitely small quantity but a 
 very high electromotive force or pressure. Discharges 
 of lightning are extremely high in voltage, but the 
 quantity of current that flows is very small. 
 
ELECTRICITY FOR ENGINEERS 13 
 
 The Ohm. The ohm is the unit of resistance. Resist- 
 ance, electrically speaking, is much the same thing as 
 friction in mechanics. If a wire or pipe of a certain 
 length is delivering 10 gals, or 10 amperes at a pressure 
 of ioo lbs. or ioo volts, and we propose to double the 
 flow without increasing the pressure, it will be necessary 
 for us to increase the diameter of the pipe and wire in 
 order to lower the resistance of the wire and the friction 
 of the pipe to one-half of what it was before. If we 
 desire the best results from the pipe, we lower its fric- 
 tion by reaming out all burrs and avoiding all unneces- 
 sary bends and turns; likewise if we desire the best 
 results from the wire we will have the copper of which 
 it is constructed as nearly pure as possible, and we 
 will install the wire where its temperature will not be 
 unnecessarily high, avoiding boiler rooms and other 
 hot places. Resistance of the wire increases slightly 
 with an increase in temperature. 
 
 For every additional degree centigrade the resistance 
 of copper wire increases about 0.4 per cent., or for 
 every additional degree Fahrenheit about 0.222 per 
 cent. Thus a piece of copper wire having a resistance 
 of 10 ohms at 32 F. would have a resistance of n.ic 
 ohms at 82 F. An annealed wire is also of lower 
 resistance than a hard drawn wire of the same size. 
 A good idea of the value of an ohm may be had from 
 the following table, which gives the length of differ- 
 ent wires required to make one ohm resistance. 
 
 FEET PER OHM OF WIRE (B. & S.). 
 
 94 feet of No. 20 605 feet of No. 12 
 
 150 " 18 961 " 10 
 
 239 " 16 1529 " 8 
 
 380 " 14 2432 " 6 
 
 3867 feet of No. 4 
 
14 ELECTRICITY FOR ENGINEERS 
 
 We have not as yet established a unit of mechanical 
 friction, therefore when we speak of mechanical fric- 
 tion we refer to it as requiring a certain quantity of 
 power to overcome it. When, however, resistance to 
 the flow of electricity is spoken of it is referred to as 
 so many ohms. It can be measured in Several ways, 
 the most reliable and convenient being by an instru- 
 ment called the Wheatstone Bridge. It can also be 
 calculated if the length and diameter of the wire or 
 conductor is known, as will be shown later on. 
 
 The basis of all electrical calculation is Ohm's law. 
 This law reads: 
 
 "The strength of a continuous current in a circuit is 
 directly proportional to the electromotive force acting 
 on that circuit, and inversely proportional to the resist- 
 ance of the circuit." In other words, the current is 
 equal to the volts divided by the ohms. Expressed in 
 symbols, C = E/R; C being current, E voltage, and R 
 resistance. If an incandescent lamp having a resist- 
 ance of 200 ohms be placed in a socket where the 
 pressure is 115 volts, the resulting current through 
 such a lamp would be 115 divided by 200, or .575 of an 
 ampere. 
 
 From the formula C = E/R, two others are deduced. 
 The volts divided by the amperes equal the ohms, 
 E/C = R. 
 
 The amperes multiplied by the ohms equal the volts, 
 CxR = E. 
 
 The Watt. The watt is the unit of power. It is an 
 ampere multiplied by a volt; just as the unit of mechan- 
 ical power, called the foot pound, is the result of the 
 pound multiplied by the space in feet through which it 
 moves. If a current of say 100 amperes, flews over a wire 
 at a pressure of 10 volts, the power delivered will equal 
 
ELECTRICITY FOR ENGINEERS " 15 
 
 ioo amperes x 10 volts = 1,000 watts. If a current of 
 io amperes flows over a wire at a pressure of ioo volts, 
 the power would be exactly the same, io amperes x ioo 
 volts, or 1,000 watts. But, of course, in the first case it 
 would require a wire ten times as large to deliver the 
 1,000 watts as would be necessary in the latter case. 
 If a weight of 10 pounds were being elevated through 
 space at the rate of ioo ft. per minute the power 
 equivalent would be io lbs. x ioo ft., or 1,000 ft. lbs. 
 If an arc lamp consumes 10 amperes at a pressure of 
 70 volts, its power consumption is 10 x 70, or 700 watts. 
 One watt is the power developed when 44.25 ft. lbs. 
 of work are done per minute. Seven hundred forty- 
 six' watts equal one horse power. The watt-hour 
 is the unit of electric work, and is a term employed to 
 indicate the expenditure of one watt for one hour. 
 The kilo watt-hour is the term employed to indicate 
 the expenditure of an electric power of 1,000 watts for 
 one hour. 
 
 The work done per second when a power of one watt 
 is being developed is called the joule, and a joule is 
 equal to .7375 ft. lbs. 
 
 Electromotive force times current equals watts. 
 The square of the current multiplied by the resistance 
 equals watts; and the voltage multiplied by itself and 
 divided by the resistance equals watts. Expressed in 
 symbols, these explanations would look like this: 
 W.fExQ. W = C 3 x R. W = E'^R. 
 
 First. If we have an electromotive force or voltage of 
 10 volts and a current of 20 amperes, we have 10 x 20 = 
 200 watts. 
 
 Second. If we have a current of 10 amperes and a 
 resistance of 30 ohms, we would have 10 x 10 x 30 = 3,000 
 watts. 
 
16 ELECTRICITY FOR ENGINEERS 
 
 Third. If we have an electromotive force or voltage 
 of 10 volts and a resistance of 20 ohms, we would have 
 10 x 10, or 100 ■*■ 20, or 5 watts. 
 
 In the above formulas E stands for voltage, C for 
 current, R for resistance and W for watts. 
 
 Divided Circuits. Currents of electricity, although 
 they have no such material existence as water or 
 steam, still obey the same general law; that is, they 
 flow and act along the lines of least resistance. If a 
 pipe extending to the top of a ten story building had 
 a very large opening at the first floor, it would be im- 
 possible to force water to the top floor. All the water 
 would run out at the first floor. If the opening at the 
 first floor were small only a part of the water would 
 escape through it, some would reach the top of the 
 building. The flow of water in each case is inversely 
 proportional to the resistance offered to it by the dif- 
 erent openings. 
 
 The same thing is true of currents of electricity. 
 Where several paths are open to a current of electri- 
 city the flow through them will be in proportion to 
 their conductivities, which is the inverse ratio of their 
 resistances. As an illustration, the current flow 
 through all of the lamps, Fig. 2, is the same, because 
 
 figure 2. 
 
 each lamp offers the same resistance. But if we 
 arrange a number of lamps as in Fig. 3, the lamps in 
 series will offer twice as much resistance as the single 
 
ELECTRICITY FOR ENGINEERS 
 
 17 
 
 A, 
 
 OB 
 
 FIGURE 3. 
 
 lamps, and will receive but half the current of the 
 single lamp. In Fig. 4 we have still another arrange- 
 ment. The lamp A limits the current which can flow 
 through B and C, and that current which does flow 
 
 FIGURE 4. 
 
 divides between B and C in proportion to their con- 
 ductivities. If B has a resistance of no ohms and C 
 220 ohms, then B will carry two parts of the current 
 and C only one. The combined resistance of all 
 lamps, Fig. 2, equals the resistance of one lamp 
 divided by the number of lamps. The combined resist- 
 ance, Fig. 3, equals the sum of the resistances of the 
 two lamps at A multiplied by the resistance of B and 
 divided by the sum of all the resistances. If the resist- 
 ance of each of the lamps were no ohms, the problem 
 would work out thus: ^g^ = 73 /s. 
 
 In Fig. 4 the total resistance is |}o+So + 1 10 = l8 3^- 
 
 One practical illustration of the above law may be 
 
 found in the method of switching series arc lamps, 
 
18 
 
 ELECTRICITY FOR ENGINEERS 
 
 Fig. 5. As long- as the switch S is open the arc lamp 
 burns, but as soon as the switch is closed the lamp is 
 
 FIGURE 5. 
 
 extinguished because the resistance of the short wire 
 and the switch S is so much less than that of the arc 
 lamp that practically all the current flows through S. 
 
CHAPTER II 
 
 WIRING SYSTEMS — CALCULATION OF WIRES — WIRING 
 TABLES. 
 
 Wiring Systems. The system of wiring which is most 
 generally used for incandescent lighting and ordinary 
 power purposes is called the two wire parallel system. 
 In this system of wiring the two wires run side by side, 
 one of them being the positive and one the negative. 
 The lamps, motors and other devices are then con- 
 nected from one wire to the other. A constant pressure 
 of electricity is maintained between the two wires, and 
 the number and size of lamps, or other apparatus, 
 connected to these two wires, determine how many 
 amperes are required. Each lamp or motor is inde- 
 pendent of the others and may be turned on or off 
 without disturbing the others. 
 
 A diagram of such a system is shown in Fig. 6. 
 
 FIGURE 6. 
 
 In this system the quantity of current varies in pro- 
 portion to the number of devices connected to it. 
 Suppose that we are maintaining a pressure or poten- 
 tial or electromotive force of no volts on such a sys- 
 tem, and that we have connected to the system ten 16 
 candle power incandescent lamps, consuming one-half 
 19 
 
20 ELECTRICITY FOR ENGINEERS 
 
 ampere each. The total quantity of current to supply 
 these lamps would be 5 amperes. If we should now 
 switch on ten more lamps the quantity of current 
 would be 10 amperes, and the pressure would remain 
 no volts. This system is also known as the "constant 
 potential system," or multiple arc system, and among 
 the numerous devices used in connection with it are 
 the constant potential arc lamp, the shunt motor, the 
 compound wound motor, the series motor, incandes- 
 cent lamps, etc. Electric street railways are also 
 operated on this system. The electricity supplied 
 through this system of wiring may be either direct or 
 alternating current. 
 
 The series arc system, Fig. 7, is a loop; the greatest 
 electrical pressure being at the terminal or terminal ends 
 
 FIGURE 7. 
 
 of the loop. The current in such a system of wiring is 
 constant, and the pressure varies as the lamps or other 
 apparatus are inserted in or cut out of the circuit. 
 This system is also called the constant current system. 
 The same current passes through all of the lamps, and 
 the different lamps are also independent of each other. 
 
 At the present time the series system is used mostly 
 for operating high tension series arc lamps. The use 
 of motors with it has been almost entirely abandoned. 
 
 The series multiple system, Fig. 8, is simply a num- 
 ber of multiple systems placed in series. This method 
 of wiring was at one time employed to run incandes- 
 
ELECTRICITY FOR ENGINEERS 
 
 21 
 
 cent lights from a high tension series arc light circuit, 
 but on account of the danger connected with the use 
 
 figure 8. 
 
 of incandescent lamps, operated from a high tension arc 
 lamp circuit, the system has been abandoned. It is 
 not approved by insurance companies, and conse- 
 quently is not often used. 
 
 The multiple series system consists of a number of 
 small series circuits, connected in multiple, as shown 
 in Fig. 9. This system of wiring is used on constant 
 
 FIGURE 9. 
 
 potential systems, where the voltage is much greater 
 than is required by the apparatus to be used, as, for 
 instance, connecting eleven miniature lamps, whose 
 individual pressure required is 10 volts, into a series, 
 and then connecting the extreme ends of such a series 
 to a multiple circuit whose pressure is no volts. In 
 electric street cars, where the pressure between the 
 
22 ELECTRICITY FOR ENGINEERS 
 
 trolley wire and the running rail is 500 volts, it will be 
 noticed that the lighting circuits in the car consist of 
 five 100 volt lamps in series, and one end of this series 
 is connected to the trolley line, the other end being 
 grounded on the trucks. 
 
 The three wire system, Fig. 10, is a system of 
 multiple series. In this system, as its name implies, 
 three wires are used, connected up to the machines in 
 
 FIGURE 10, 
 
 the manner shown in the diagram. Both machines are 
 in series when all lights are turned on, but should all 
 lights on one side of the neutral or center wire be 
 turned off the machine on the other side alone would 
 run the other lights. 
 
 One of these wires is positive, the other is negative, 
 and the remaining one or center wire is neutral. In 
 ordinary practice from positive to negative wire, a 
 potential of 220 volts is maintained, while from the 
 neutral wire to either of the outside wires a potential 
 of no volts exists. The advantages of such a system 
 are many, principally among them is the use of double 
 the voltage of the two wire system; this reduces the 
 current one-half and allows the use of smaller wires. 
 This system only requires three wires for the same 
 amount of current that would require four in the other 
 system. Motors are supplied at 220 volts, while 
 lights operate at no. Incandescent lighting circuits 
 
ELECTRICITY FOR ENGINEERS 23 
 
 can be maintained from either outside wiie to the 
 neutral wire. The saving in copper by dispensing 
 with the fourth wire is not the only advantage in the 
 saving of conductors. The neutral wire may be much 
 smaller than the outside wires because it will seldom 
 be called upon to carry much current. 
 
 Inside of buildings, however, where overheating of 
 a wire is always dangerous, the neutral wire should be 
 of the same size as the others. By tracing out the 
 circuits in Fig. 10, it will readily be seen that, so long 
 as all lamps are burning, the current passes out of 
 dynamo I into the positive wire and from there through 
 the lamps (always two in series) to the negative 
 or — wire, returning over it to the — pole of dynamo 2. 
 So long as an equal number of lamps is burning on 
 each side of the neutral, no current passes over the 
 neutral wire in either direction. But if the positive 
 or + wire should be broken, say at a, dynamo 1 will no 
 longer send current and the lamps between the positive 
 and neutral wire will be out. 
 
 Dynamo 2 will now supply the lamps between the 
 neutral and the negative wire and for the time being 
 the neutral wire will become positive. Should the 
 negative wire break at b, the lamps connected to it 
 would be out and dynamo 1 would supply the lights on 
 its side, the neutral wire becoming negative. When 
 motors of one or more H. P. are used on this system, 
 it is usual to connect them to the outside wires using 
 220 volts. It is important also to arrange the wiring 
 so that an equal number of lights are installed on each 
 side of the neutral. When the lights and motors are 
 so arranged, the system is said to be "balanced." It 
 is also very important to arrange so that the neutral 
 wire cannot readily be broken. Should the neutral 
 
*4 ELECTRICITY FOR ENGINEERS 
 
 wire be opened while, for instance, fifty lamps were 
 burning on one side and say ten or twenty on the 
 other, the ten or twenty would be broken by the excess 
 voltage. Grounded wires ordinarily cause more 
 trouble than anything else on electric light or power 
 circuits, but with the three wire system, the neutral 
 wire is often grounded. Grounds on this wire are less 
 objectionable than on other wires, because it carries 
 very little current, and that current is constantly vary- 
 ing in direction, so that no great amount of electrolysis 
 can occur at any one place. For full descriptions and 
 drawings of methods of wiring, see Wiring Diagrams 
 and Descriptions by Horstmann and Tousley, published 
 by Frederick J. Drake & Co., Chicago. 
 
 Feeders (see Fig. n), as the name implies, is a term 
 used to designate wires which convey the current to 
 
 any number of other wires, and the feeders become a 
 part of the multiple series, multiple and three wire 
 systems. 
 
 Distributing mains are the wires from which the wires 
 entering buildings receive their supply. 
 
ELECTRICITY FOR ENGINEERS 
 
 25 
 
 Service zvires are the wires that enter the buildings. 
 
 The center of distribution is a term used for that part 
 of the wiring system from which a number of branch 
 circuits are fed by feeder wires. In most buildings 
 the tap lines are all brought to one point, and ter- 
 minate in cut-out boxes. These cut-out boxes are 
 supplied by the main. Each floor of the building may 
 have a cut-out box, or each floor of the building may 
 have several cut-out boxes of the above description. 
 
 Calculation of Wires. If we desire to transmit or 
 deliver a certain quantity of liquid through a pipe, 
 we estimate the size of the pipe and 
 the comparison of sizes in the pipes 
 by squaring the diameter, in inches, 
 and multiplying the result by the 
 standard fraction .7854. By way 
 of explanation we will dwell upon 
 the above method for a short time. 
 In Fig. 12 we have a surface which 
 measures one inch on all four 
 sides, and which has an area of one square inch. 
 
 Now in a circle which is contained in this figure, and 
 which touches all four sides of the square, we would 
 only have .7854 of a square inch. If the diameter of 
 this circle is 2 in., instead of 1, you can readily see by 
 Fig. 13 that its area is four times as great or 2 x 2 = 4. 
 We then multiply by the standard number .7854 in 
 order to find the area contained in the two-inch circle; 
 and if the diameter were 3" in., then 3x3 = 9, and 
 9 x .7854 would be the area in square inches contained 
 in the three-inch circle. 
 
 Again, if we had a square one inch in area, like Fig. 
 14, and we took one leg of a carpenter's compass and 
 placed it on one corner of this square, striking a 
 
 FIGURE 12. 
 
26 
 
 ELECTRICITY FOR ENGINEERS 
 
 quarter-circle from one adjacent corner to the other 
 adjacent corner, the area inscribed by the compass 
 would again be .7854 of a square inch. 
 
 The above will explain to the reader the relation 
 
 figure 13, 
 
 between the circular and square mil. The circular 
 mil is a circle one mil (-joVo °f an inch) in diameter. 
 The square mil is a square one mil long on each side. 
 In the calculation of wires for electrical purposes, the 
 circular mil is generally used, because we need only 
 multiply the diameter of a wire by 
 itself to obtain its area in circular 
 mils. If we used square mils we 
 should have to multiply by .7854. 
 
 The resistance of a conductor 
 (wire) increases directly as its length, 
 and decreases directly as its diameter 
 is increased. A wire having a diam- 
 eter of one mil and being one foot 
 long has a resistance at ordinary temperature of 10. 7 
 ohms. If this wire were two feet long, it would have 
 
 FIGURE 14. 
 
ELECTRICITY FOR ENGINEERS 27 
 
 a resistance of 21.4 ohms, but if it were two mils in 
 diameter and one foot long, it would have a resistance 
 one-fourth of 10.7, or about 2.67. 
 
 Every transmission of electrical energy is accom- 
 panied by a certain loss. We can never entirely pre- 
 vent this loss any more than we can entirely avoid 
 friction. But we can reduce our loss to a very small 
 quantity simply by selecting a very large wire to carry 
 the current. This would be the proper thing to do if 
 it were not for the cost of copper, which would make 
 such an installation very expensive. As it is, wires 
 are usually figured at a loss of from 2 to 5 per cent. 
 
 The greater the loss of energy we allow in the wires 
 the smaller will be the cost of wire, since we can use 
 smaller wires with the greater loss. 
 
 In long distance transmission and where the quality 
 of light is not very important, a loss of 10 or 20 per 
 cent, is sometimes allowed, but in stores, residences, 
 etc., the loss should not exceed 2 or 3 per cent., other- 
 wise the candle power of the lamps will vary too much. 
 
 Where the cost of fuel is high the saving in first cost 
 of copper is soon offset by the continuous extra cost 
 of fuel to make up for the losses in the wires. 
 
 To determine the size of wire necessary to carry a 
 certain current at a given number of volts loss, we may 
 proceed in the following manner: Multiply the num- 
 ber of feet of wire in the circuit by the constant 10.7, 
 and it will give the circular mils necessary for one ohm 
 of resistance. Multiply this by the amperes, and this 
 will give the circular mils for a loss of one volt. Divide 
 this last result by the volts to be lost, and the answer 
 will be the number of circular mils diameter that a 
 copper wire must have to carry the current with such a 
 loss. After obtaining the number of circular mils 
 
28 ELECTRICITY FOR ENGINEERS 
 
 required, refer to the table of circular mils, and select 
 the wire having such a number of circular mils. 
 The formula is as follows: 
 
 Feet of wire x 10.7 x amperes . . .. 
 
 T7 —. : — r-^ = circular mils. 
 
 Volts lost 
 
 By simply transposing the above terms we obtain 
 another formula, which can be used to determine the 
 volts lost in a given length of wire of a certain size, 
 carrying a certain number of amperes. 
 
 The formula is as follows: 
 
 Feet of wire x 10. 7 x amperes , 7 , . 
 
 ^ = ~ - = Volts lost. 
 
 Circular mils * 
 
 And again, by another change in the terms we 
 obtain a formula which shows the number of amperes 
 that a wire of given size and length will carry at a 
 given number of volts lost: 
 
 Circular mils x volts lost A 
 
 — = — - — ;= — -. = Amperes. 
 
 Feet of wire xio.7 
 
 In computing the necessary size of a service or main 
 wire, to supply current for either lamps or motors, it 
 is necessary to know the exact number of feet from the 
 source of supply to the center of distribution. When 
 the distance of center of distribution is given it is well 
 to ascertain whether it is the true center or not. It 
 may be only the distance from a cut-out box that has 
 been given, when it should have been the distance 
 from the point at which the service enters the building 
 or, perhaps, from the point at which the service is con- 
 nected to the street mains. For when the size is deter- 
 mined it is for a certain loss which is distributed over 
 the entire length of the wire to be installed. The trans- 
 mission of additional current on the mains in the build- 
 ing increases the drop in volts in the main, and likewise 
 
ELECTRICITY FOR ENGINEERS 29 
 
 in the service. Most buildings are wired for a certain 
 per cent loss in voltage, estimated from the point 
 where the service enters the building. All additions 
 should be estimated from that point. 
 
 In using the formula for finding the proper size wire 
 to carry current, the first thing to be determined is the 
 length of the wire; remember that the two wires are in 
 parallel, and therefore the total length of the wire is 
 twice the total distance from the commencement to 
 the end of the circuit. If the proposed load on this 
 circuit is given in lamps, you may reduce it to amperes, 
 and if the proposed load is given in horsepower, you 
 may reduce it to amperes. The voltage on the circuit 
 is known in either case. You take the loss of the 
 voltage and divide the product of amperes, multiplied 
 by the length, as found, and 10.7 by it; this answer 
 will be the size in circular mils of a wire necessary to 
 carry the amperes. 
 
 Example : What is the size of wire required for a 50 
 volt system, having 100 lamps at a distance of 100 £t. , 
 with a 4 per cent loss? 
 
 Answer: The load of 100 lamps on a 50 volt system 
 is 100 amperes, and a 4 per cent loss of 50 volts is 2 
 volts. Multiply the total length of the wire, which is 
 twice the distance, or 200 ft., by the 100 amperes of 
 current; this gives us 20,000. Then multiply this by 
 the constant, which is 10.7; this gives us 214,000. 
 Divide this by 2, which is the loss in volts, and you 
 have 107,000 circular mils diameter of wire required 
 
 When determining the size of wire to be used it is 
 always necessary to consult the table of carrying 
 capacities, and this will very often indicate a wire 
 much larger than that determined by the wiring for- 
 mula, especially if a somewhat high loss is figured on. 
 
?>() ELECTRICITY FOR ENGINEERS 
 
 When estimating the distance it is not always cor- 
 rect to take the total distance. 
 
 To illustrate: Suppose one lamp is ioo ft. from the 
 point at which the distance is determined, and the 
 farthest lamp is 400 ft., the remaining lamps being 
 distributed evenly between these two points; we would 
 average the distances between the first and last lamp, 
 which would be 200 ft. It is necessary to use judg- 
 ment in estimating the mean or average distance, as 
 the lamps or motors are bunched differently in each 
 case 
 
 In a series system the loss in voltage makes con- 
 siderable difference to the power, but does not affect 
 the quality of the light as much as in a multiple arc or 
 parallel system. In a parallel system the lamps 
 require a uniform pressure, and this can only be had 
 by keeping the loss low. In a series system the lamps 
 depend upon the constant current and the voltage 
 varies with the resistance, in order to keep the current 
 constant. This is accomplished by a regulator on the 
 dynamo, which is designed to compensate for the 
 changes of resistance in the circuit and to increase or 
 decrease the pressure as required. 
 
 In estimating the size of wire for a series system you 
 consider the total length of the loop. There is no 
 average distance as the total current travels over the 
 entire circuit. We will assume that you have an arc 
 light circuit of a No. 6 Brown & Sharp gauge wire and 
 want to find what loss there is in this circuit. You 
 have the area of a No. 6 wire, which is 26,250 circular 
 mils, and the length of the circuit, and from this we 
 will figure the loss in this manner: Assuming the 
 circuit to be 10,000 ft. long, and the current 10 
 amperes, we will multiply 10,000 ft. by 10 amperes, 
 
ELECTRICITY FOR ENGINEERS 
 
 31 
 
 and this by 1.07, which gives us 1,070,000, and divide 
 this by 26,250. The answer is 40 volts, lost in the 
 circuit, 
 
 fteeip bva\b S\oyn coracxd untt\ 
 
 
 Such a circuit would operate at perhaps 2,000 or 
 3,000 volts, and a loss of 40 volts would not be exces- 
 
32 ELECTRICITY FOR ENGINEERS 
 
 sive. It would be wasting a little less energy than is 
 required to burn one large arc lamp. 
 
 The multiple series system is a number of small wires 
 connected in multiple, and is the same as the multiple 
 arc or parallel system. The wire is figured in the same 
 way as for the multiple arc system. 
 
 The series multiple system is a number of small paral- 
 lel systems, and these are connected in series by the 
 main wire. The wire is figured the same as for the 
 series system. 
 
 The Ediso?i three-wire system is a double multiple, and 
 the two outside wires are the ones considered when 
 carrying capacity is figured. When this system is 
 under full load or balanced, the neutral wire does not 
 carry any current, but the blowing of a fuse in one of 
 the outside wires may force the neutral wire to carry 
 as much current as the outside wire and it should, 
 therefore, be of the same size. The amount of copper 
 needed with this system is only three-eighths of that 
 required for a two-wire system. 
 
 Wiring Tables. On the following pages are presented 
 wiring tables for 110,220 and 500 volt work. These 
 tables are used in the following manner: Suppose we 
 wish to transmit 60 amperes a distance of 1,800 ft. at 
 1 10 volts and at a loss of 5 per cent. We take the col- 
 umn headed by 60 in the top row and follow it down- 
 ward until we come to 1,800, or the number nearest to 
 it. From this number we now follow horizontally to 
 the left, and under the column headed by 5 we find 
 the proper size of wire, which is 500,000 c. m. The 
 same current, at a loss of 10, would require only a 0000 
 wire, as indicated under the column at the left, headed 
 by 10. 
 
 Before making selection of wire, always consult the 
 
~~ ELECTRICITY FOR ENGINEERS 33 
 
 table of carrying capacities, page 38. This table is 
 taken from the rules of the National Board of Fire 
 Underwriters, and is in general use. 
 
 The first three of the following tables are wiring 
 tables for the three standard voltages, no, 220, 500 
 From these tables ; can be found the sizes of wire 
 required to carry various amounts of current (in am- 
 peres) different distances (in feet) at several percent- 
 ages of loss, or the distance the different sizes of wire 
 will carry various amounts of current at several per- 
 centages of loss can be found. 
 
 These tables are figured on safe carrying capacity for 
 the different sizes of wire. The distances in feet are 
 to the center of distribution. 
 
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 122475 
 97107 
 77012 
 61105 
 48202 
 382S2 
 30457 
 24155 
 19140 
 
 12077 
 9570 
 7614 
 6039 
 4785 
 3819 
 3019 
 2392 
 1910 
 1510 
 1195 
 950 
 755 
 597 
 475 
 377 
 298 
 
 <N 
 
 578700 
 
 460645 
 
 347220 
 
 244950 
 
 194215 
 
 154025 
 
 122210 
 
 96405 
 
 76565 
 
 60915 
 
 48310 
 
 38282 
 
 30457 
 
 24155 
 
 19140 
 
 15229 
 
 12077 
 
 9570 
 
 7039 
 
 6039 
 
 4785 
 
 3819 
 
 3019 
 
 2392 
 
 1910 
 
 1510 
 
 1195 
 
 950 
 
 755 
 
 597 
 
 5| • 
 3 o a) 
 
 -. © M> 
 
 2m^ 
 
 P Ml o 
 
 bos g 
 
 O 
 i-H 
 
 CO 
 
 coooooo-«M*ii3fflc-xcf.o--nM*in» • • • 
 ooooo tH '""' '~ l "" '"' *"* " • • ■ 
 
 oSo° : : : 
 
 
 OOOOOOOHNMtiOiDMBaO-WM^iOS • • 
 
 ll| S ° : ! : 
 
 
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 00-JWMOO-JWi(i.»©-JQO*©OM"JOOOOOO 
 OS 00 *>■ >-» OS O tO 
 
 Circular 
 
 Mils 
 
 Square Mils 
 
 ►-;• os- o»- en 
 
 ^ 01 U M 
 
 Pounds 
 per 1000 feet 
 
 00»«<0t( 
 
 Pounds 
 per mile 
 
 a os eo o -3 to * 
 
 Feet per 
 Pound 
 
 Pounds 
 per 1000 feet 
 
 WOOimok 
 
 Pounds 
 per Mile 
 
 § 52 
 
 <x<tos*.4>.oototo^>-i 
 
 00*.mOOOMWOO)C05D<!Oi 
 - - 1 on to 00 -1 h^ O OS <! 
 
 -^oixj^ooa 
 
 Feet 
 
 per Pound 
 
 <s?oi\3on«o 
 oooo^oj^j 
 
 ooooonoo?ooo©^c 
 Go<tosoo©to*-too 
 
 »oooo 
 
 Pounds 
 per 10 feet 
 
 *-p-'M(JMW*.0'aa)OMG- OS CO © *>■ to 
 *0'»00OW0'.O0)W"ii : , <S -I OS GO 4-^ 
 
 ►— ►-»0n.N*-<5CnaeC0tOGCaOOn©O0On4».CO-<l<aiOO©~3 
 
 wsoonas^ooascooo^-oopsoasGOfcaovoo-cj 
 
 soccffim^osMM^ 
 
 s>OO0O— ©OOOOCOnc 
 
 Pounds 
 per Mile 
 
 Feet 
 
 per Pound 
 
 -ootooa 
 
 ,0GC-Ci~5^^0n« 
 
 ROhms 
 per 1000 feet 
 
 >— osoooooo 
 toccooona 
 
 WMOffloa 
 
 K-jffiow»m»)ooocac 
 
 Ohms 
 per Mile 
 
 
 OOCI^OOpOiUiOi-W-DMCOiOO*-^^^ 
 
 Feet 
 per Ohm 
 
 OIMMhCOOOOOOCOOC 
 
 SII-311 
 
 . . . 
 
 »©COOS 
 
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 Ohms 
 per Pound 
 
38 ELECTRICITY FOR ENGINEERS 
 
 TABLE OF CARRYING CAPACITY OF WIRES. 
 UNDERWRITERS' RULES. 
 TABLE A. TABLE B. 
 
 Rubber Other 
 
 Insulation. Insulations. Circular 
 
 B. & S. G. Amperes. Amperes. Mils. 
 
 iS 3 5 1,624 
 
 16 6 8 2,583 
 
 14 12 16 4,107 
 
 12 17 23 6,530 
 
 10 24 32.., 10,380 
 
 8 33 46 16,510 
 
 6 46 65 26,250 
 
 5 54 77 33,ioo 
 
 4 65 92 41,740 
 
 3 76 no 52,630 
 
 2 90 131 66,370 
 
 1 107 156 83,600 
 
 o 127 185 105,500 
 
 00 150 220 133,100 
 
 000 177 262 ,. 167,800 
 
 0000 210.... 312 211,600 
 
 Circular Mils. 
 
 200, 000 200 300 
 
 300, 000 270 400 
 
 400,000 330 500 
 
 500,000 390 590 
 
 600,000 450 68o- 
 
 700,000 500 760 
 
 800,000 550 840 
 
 900,000 600 920 
 
 1,000,000 650 1,000 
 
 1,100,000 690 1,080 
 
 1,200,000 730 1,150 
 
 1,300,000 770 1,220 
 
 1,400,000 810 1,290 
 
 1,500,000 850 1,360 
 
 1,600,000 890 1.430 
 
 1,700,000 930 1,490 
 
 i,8oo,oco 970 i,55o 
 
 1,900,000 1,010 1,610 
 
 2,000,000 1,050 1,670 
 
 The lower limit is specified for rubber-covered wires 
 to prevent gradual deterioration of the high insula- 
 tions by the heat of the wires, but not from fear of 
 igniting the insulation. The question of drop is not 
 taken into consideration in the above tables. 
 
ELECTRICITY FOR ENGINEERS 39 
 
 TABLE OF DIMENSIONS OF PURE COPPER WIRE.* 
 
 
 
 Arfia. 
 
 Weight and Length. 
 
 No. 
 
 Diam. 
 Mils. 
 
 
 
 
 Sp. Gr. 8.9. 
 
 
 B. & S. 
 
 Circular 
 
 Square 
 
 Lbs. 
 
 Lbs. 
 
 Feet 
 
 
 
 Mils. 
 
 Mils. 
 
 per 
 1000 feet. 
 
 per 
 
 Mile. 
 
 per 
 Pound. 
 
 0000 
 
 460.000 
 
 211600.0 
 
 166190.2 
 
 640.73 
 
 3383.04 
 
 1.56 
 
 ouo 
 
 409.640 
 
 167805.0 
 
 131793.7 
 
 508.12 
 
 2682.85 
 
 1.97 
 
 00 
 
 364.800 
 
 133079.0 
 
 104520.0 
 
 402.97 
 
 2127.66 
 
 2.48 
 
 
 
 324. 950 
 
 105592.5 
 
 8i932.2 
 
 319.74 
 
 1688.20 
 
 3.13 
 
 1 
 
 289. aoo 
 
 83694.5 
 
 65733.5 
 
 253.43 
 
 1338.10 
 
 3.95 
 
 2 
 
 257.630 
 
 66373.2 
 
 52129.4 
 
 200.98 
 
 1061.17 
 
 4.98 
 
 3 
 
 229.420 
 
 52633.5 
 
 41338.3 
 
 159.38 
 
 841.50 
 
 6.28 
 
 4 
 
 204.310 
 
 41742.6 
 
 32784.5 
 
 126.40 
 
 667.38 
 
 7.91 
 
 5 
 
 181.940 
 
 33102 2 
 
 25998.4 
 
 100.23 
 
 529.23 
 
 9.98 
 
 6 
 
 162.020 
 
 26250.5 
 
 20617.1 
 
 79.49 
 
 419.69 
 
 12.58 
 
 7 
 
 144.280 
 
 20816.7 
 
 16349.4 
 
 63.03 
 
 332.82 
 
 15.86 
 
 8 
 
 128.490 
 
 16509.7 
 
 12966.7 
 
 49.99 
 
 263.96 
 
 20.00 
 
 9 
 
 114.430 
 
 12094.2 
 
 10284.2 
 
 39.65 
 
 209.35 
 
 25.22 
 
 10 
 
 101.890 
 
 10381.6 
 
 8153.67 
 
 31.44 
 
 165.98 
 
 31.81 
 
 11 
 
 90.742 
 
 8234.11 
 
 6407.06 
 
 24.93 
 
 137.65 
 
 40.11 
 
 12 
 
 80.808 
 
 6529.94 
 
 5128.60 
 
 19.77 
 
 104.40 
 
 50.58 
 
 13 
 
 71.961 
 
 5178.39 
 
 4067.07 
 
 15.68 
 
 82.792 
 
 63.78 
 
 14 
 
 64.084 
 
 4106.76 
 
 3225.44 
 
 12.44 
 
 65.658 
 
 80.42 
 
 15 
 
 57 068 
 
 3256.76 
 
 2557.85 
 
 9.86 
 
 52.069 
 
 101.40 
 
 16 
 
 50.820 
 
 2582.67 
 
 2028.43 
 
 7.82 
 
 41.292 
 
 127.87 
 
 17 
 
 45.257 
 
 2048.20 
 
 1608.65 
 
 6.20 
 
 32.746 
 
 161.24 
 
 18 
 
 40.303 
 
 1624.33 
 
 1275.75 
 
 4.92 
 
 25.970 
 
 203.31 
 
 19 
 
 35.890 
 
 1288.09 
 
 1011.66 
 
 3.90 
 
 20.594 
 
 256.39 
 
 20 
 
 31.961 
 
 1021.44 
 
 802.24 
 
 3.09 
 
 16.331 
 
 323.32 
 
 21 
 
 28.462 
 
 sio.oa 
 
 636.24 
 
 2.45 
 
 12.952 
 
 407.67 
 
 22 
 
 25.347 
 
 642.47 
 
 504.60 
 
 1.95 
 
 10.272 
 
 514.03 
 
 23 
 
 22.571 
 
 509.45 
 
 400.12 
 
 1.54 
 
 8.1450 
 
 648.25 
 
 24 
 
 20.100 
 
 404.01 
 
 317.31 
 
 1.22 
 
 6.4593 
 
 817.43 
 
 25 
 
 17.900 
 
 320.41 
 
 251.65 
 
 .97 
 
 5.1227 
 
 1030.71 
 
 26 
 
 15.940 
 
 254.08 
 
 199.56 
 
 .77 
 
 4.0623 
 
 1299.77 
 
 27 
 
 14.195 
 
 201.50 
 
 158.26 
 
 .61 
 
 3.2215 
 
 1638.97 
 
 28 
 
 12.641 
 
 159.80 
 
 125.50 
 
 .48 
 
 2.5548 
 
 2066.71 
 
 29 
 
 11.257 
 
 126.72 
 
 99.526 
 
 .38 
 
 2.0260 
 
 2606.13 
 
 30 
 
 10.025 
 
 100.50 
 
 78.933 
 
 .30 
 
 1.6068 
 
 3286.04 
 
 31 
 
 8.928 
 
 79.71 
 
 62.603 
 
 .24 
 
 1.2744 
 
 4143.18 
 
 32 
 
 7.950 
 
 63.20 
 
 49.639 
 
 .19 
 
 1.0105 
 
 5225.26 
 
 33 
 
 7.080 
 
 50.13 
 
 39.369 
 
 .15 
 
 .8015 
 
 6588.33 
 
 34 
 
 6.304 
 
 39.74 
 
 31.212 
 
 .12 
 
 .6354 
 
 8310.17 
 
 35 
 
 5.614 
 
 31.52 
 
 24.153 
 
 .10 
 
 .5039 
 
 104; 8.46 
 
 36 
 
 5.000 
 
 25.00 
 
 19.635 
 
 .08 
 
 .3997 
 
 13209.98 
 
 37 
 
 4.453 
 
 19.83 
 
 15.574 
 
 .06 
 
 .3170 
 
 16654.70 
 
 38 
 
 3.965 
 
 15.72 
 
 12.347 
 
 .05 
 
 .2513 
 
 21006.60 
 
 39 
 
 3.531 
 
 12.47 
 
 9.7923 
 
 .04 
 
 .1993 
 
 26487.84 
 
 40 
 
 3.144 
 
 9.88 
 
 7.7635 
 
 .03 
 
 .1580 
 
 33410.05 
 
 *1 mile pure copper wire 13.59 ohms at 15.5° C. or 
 
 1-16 in. diam. ~ 59.9* F. 
 
 1 circular mil is .7854 square mil. 
 
CHAPTER III 
 
 Current Generation in Dynamos — Dynamos — Brushes and 
 Commutators. 
 
 Current Generation in Dynamos. If we take a coil of 
 wire, Fig. 15, and rapidly thrust a magnet into it, we 
 shall observe a certain deflection of the galvano- 
 meter needle shown with it. This deflection con- 
 tinues only while the magnet is in motion. After 
 
 FIGURE 15. 
 
 we have inserted the magnet and it has come to 
 rest the galvanometer needle will return to its normal 
 position. When we withdraw the magnet the deflec- 
 tion of the needle will be in the opposite direc- 
 tion. If the magnet is inserted or withdrawn with 
 a veiy quick motion, the deflection will be consider- 
 able. If the magnet is very slowly inserted or with- 
 drawn the deflection will hardly be noticeable. The 
 40 
 
ELECTRICITY FOR ENGINEERS 
 
 41 
 
 same phenomena will occur if instead of moving the 
 magnet, we hold it stationary and move the coil, or if 
 both of them be moved towards or from each other. 
 The deflection of the compass needle indicates that a 
 current of electricity is passing along the wire, and the 
 experiments above described show exactly how cur- 
 rents of electricity are produced in dynamos. 
 
 An electromotive force is induced by rapidly cutting 
 
 "lines of force," that is, by moving either a magnet 
 
 over a wire or a wire over or near a magnet. The 
 
 current in turn is the result of this electromotive force 
 acting in a closed circuit. A bar of iron becomes an 
 electromagnet if we wind about it a few turns of wire 
 and cause a current of electricity to flow along the 
 wire, Fig. 16. The magnetism is conceived to consist 
 of lines of force, which leave the bar at one end and 
 enter it at the other, the direction of these lines 
 depending upon the direction in which the current 
 circulates about the bar of iron. The number of these 
 lines of force depends upon the number of ampere 
 turns in the iron bar and on the diameter, length and 
 quality of the iron bar. 
 
42 ELECTRICITY FOR ENGINEERS 
 
 Ampere turns is a term used to indicate the mag- 
 netizing force; it is the number of turns of wire on a 
 magnet multiplied by the current in amperes flowing 
 through these turns of wire. 
 
 Haskins, in Electricity Made Simple, explains this 
 thus: "If, for instance, we have a current of one 
 ampere flowing through a single turn of wire around a 
 bar of soft iron and we have developed enough mag- 
 netism to lift a keeper or other piece of iron, weighing 
 one ounce, then with one-half the amount of current 
 and two coils around the bar, we would obtain the 
 same result, and with three turns of wire we would 
 require but one-third the current to develop the same 
 lifting power in the bar or magnet." 
 
 The law of magnetic flow is very much the same as 
 the law of current flow. If the iron bar is of low mag- 
 netic resistance, the flow will be quite great; if of high 
 resistance, the flow will be small. 
 
 Lines of force can also be shunted just as a current 
 of electricity can; that is, they will follow the path of 
 lowest resistance just as a stream of water or a current 
 of electricity will. 
 
 Now let us consider the elemental sketch of a 
 dynamo, Fig. 17. The wire a represents the armature 
 and we have also the iron bar and the coil of wire 
 wound on it and, for the present, we may consider the 
 battery B as the source of the current which produces 
 the magnetism or lines of force in the iron bar. The 
 battery current magnetizes the iron bar (which in 
 dynamos is known as the field magnet) and produces 
 the lines of force indicated by arrows. 
 
 These lines of force leave the field magnet of our 
 dynamo at the north pole marked N, and pass through 
 the air-gap and armature into the south pole marked S. 
 
ELECTRICITY FOR ENGINEERS 
 
 43 
 
 As we begin to move the wire or armature, it cuts 
 through these lines of force and begins to generate an 
 electromotive force, which in turn will cause the cur- 
 rent to flow if the circuit is ciosed through a lamp or 
 other device. 
 
 This current reverses in direction as the wire a passes 
 from the influence of the south pole into that of the 
 north pole and the brushes B' and B", which transmit 
 
 FIGURE 17. 
 
 the current to the outside wires, are so set that they 
 change the connection of the wire a at the time that it 
 passes from one pole to the other. By this means the 
 current in the external circuit is kept constant in 
 direction, although it alternates in the armature. 
 
 The faster we turn our wire or armature, the greater 
 will be the electromotive force generated. Instead of 
 using onlv one wire, as in Fig. 17, we may take many 
 
44 
 
 ELECTRICITY FOR ENGINEERS 
 
 turns before bringing the end out, and in so doing 
 obtain the well known drum armature, or, by a slightly 
 different method of winding, the gramme ring arma- 
 ture, Fig. 18. Here we have many wires cutting the 
 lines of force at once and our electromotive force with 
 the same number of revolutions of the armature is cor- 
 respondingly increased, and the more turns of wire we 
 arrange to cut those lines of force per second the 
 greater will be our E. M. F. Instead of providing 
 
 FIGURE 18. 
 
 more wire or increasing the speed of our armature we 
 can increase the magnetism, or number of lines of force, 
 by sending more current through the fields, that is 
 increasing the "ampere turns." 
 
 If we wish to reverse the current flow we can do so 
 by revolving the armature in the opposite direction, 
 or by reversing the current through the fields. 
 
 Dynamos. Having so far considered the generation 
 of currents in dynamos, we may now consider different 
 types of dynamos and their uses. Fig. 19 shows adia- 
 
ELECTRICITY FOR ENGINEERS 
 
 45 
 
 gram of the wires and connections of a series dynamo. 
 The principal use of this dynamo at present is in con- 
 nection with series arc circuits. (See Fig. 7.) This 
 dynamo is usually equipped with an automatic regu- 
 lator (which will be explained later) to raise or lower 
 the voltage as the number of lamps increases or 
 
 figure 19. 
 
 decreases, the current remaining constant at about 10 
 amperes. By reference to the figure, we can trace the 
 current as it flows from the 4- brush, in the direction of 
 the arrows, around both field magnets and through the 
 lamps, returning to the - brush on the dynamo. In 
 our elementary sketch of a dynamo we used battery 
 current to magnetize our fields; we need not consider 
 
46 
 
 ELECTRICITY FOR ENGINEERS 
 
 that any more, for in practice all direct current 
 dynamos produce their own magnetism by circulating 
 some or all of their current through the field coils. 
 
 In the shunt wound dynamo, Fig. 20, the wire in the 
 field winding is of such size and connected in such a 
 manner as to have a resistance so high that only a 
 
 ^mtrf) 
 
 FIGURE 20. 
 
 portion of th(^ main generated current of electricity 
 passes around the field magnets. The quantity of cur- 
 rent passing around these field magnets is also regu- 
 lated by a resistance sometimes called a rheostat shown 
 at R. The resistance to the flow of current through 
 this box is adjusted by hand by the attendant and the 
 flow of current through this rheostat and around the 
 
 
ELECTRICITY FOR ENGINEERS 4? 
 
 field magnet is what determines the electromotive force 
 of the dynamo. 
 
 This type of dynamo is used for electric lighting and 
 for operating motors. The electromotive force of such 
 a dynamo remains nearly constant, but the current 
 varies with the number of lights or motors used. If it 
 were connected to too many lights it would deliver too 
 much current and become overheated and perhaps 
 burn out. The current leaves at the + brush, passes 
 through whatever lamps happen to be switched on and 
 returns to the — brush. 
 
 Fig. 21 shows a diagram of a compound wound 
 dynamo. This is really a combination of the series 
 and shunt dynamos. If the current in a series dynamo 
 is not kept constant the magnetism in the fields will 
 vary as the current varies, and consequently its volt- 
 age will be very unsteady. This makes such a dynamo 
 unfit for use with variable currents. 
 
 The voltage of a shunt dynamo is quite constant with 
 variable loads, but still it leaves much room for 
 improvement; not because of any variation in the 
 induced electromotive force, but because of the losses 
 occurring in the armature and wires conveying current. 
 The loss of voltage in the armature and line equals the 
 current multiplied by the resistance; consequently, as 
 the current increases more and more volts are lost and 
 the pressure goes down. If we would have the pressure 
 remain at its normal value, we must find some way to 
 increase the field magnetism as the current delivered 
 by the dynamo increases, and this is the purpose of 
 the compound winding. The compound winding car- 
 ries the total current of the dynamo around the fields, 
 but only a few times, just often enough so that the 
 increase in magnetism resulting from this current may 
 
48 
 
 ELECTRICITY FOR ENGINEERS 
 
 make up for the loss in the armature or line. Dyna- 
 mos may be compounded for any per cent, of loss 
 desired. 
 
 The foregoing descriptions are those of direct cur- 
 rent dynamos, and they are called direct or continuous 
 
 FIGURE 21. 
 
 current dynamos because the current flow continues in 
 one direction out of the positive or + side of the 
 dynamo, to the external circuit, and back again to the 
 negative or - side of the dynamo. The current as it 
 is generated in the coils of the armature which 
 
ELECTRICITY FOR ENGINEERS 49 
 
 revolves between the field or pole pieces, is alter- 
 nating; that is to say, if the armature wires were con- 
 nected to collector rings the current in the outside 
 wires would be reversed every time the position of the 
 wire in the armature were changed from the influence 
 of one pole piece to that of the other. If the coils 
 constituting the armature are connected to a device 
 called the commutator, they will be commutated or 
 rectified. 
 
 Such a commutator is formed of alternate sections of 
 conducting and non-conducting material, running 
 parallel with the shaft with which it turns. It is 
 
 FIGURE 22. 
 
 placed on the shaft of the armature so that it rotates 
 with it, as shown in Fig. 22. The brushes press upon 
 its surface and collect the current from the bars. (See 
 Fig. 31.) The function of the commutator is to change 
 the connections of the armature coils from the + or 
 positive to the negative or — side of the circuit at the 
 time at which the coil connected to the bar under the 
 brush passes from the influence of one pole piece into 
 that of the other. This is the time at which the cur- 
 rent in the coil reverses in direction, and is called the 
 neutral point. If we consider, for the sake of simplic- 
 ity, an armature having only one turn of wire on it, 
 as Fig. 17, there will be a time while the coil is in the 
 
50 ELECTRICITY FOR ENGINEERS 
 
 position indicated by dotted lines at c and d when no 
 current is being generated. The brushes on any 
 dynamo should always be set at this point, for this is 
 the point of least sparking. In actual practice all 
 commutators have quite a number of bars and it is 
 impossible to avoid, in passing under the brushes, that 
 at least two of them are in contact with a brush at the 
 same time. If a brush did leave one bar before it 
 touches another, the current would be entirely broken 
 for that length of time and much sparking would 
 result. The nature of all armature windings is such 
 that while the brush is in contact with the commutator 
 bars it short circuits that coll between them. This is 
 the main reason why the brushes must be kept at a 
 point at which the coil which is short circuited gener- 
 ates no current. 
 
 Although the electromotive force generated in one 
 coil of a dynamo is very small, the resistance of the 
 "short circuit" formed by the dynamo brush is also 
 very small and therefore the current may be quite large. 
 This current is the main cause of sparking in dynamos. 
 The number of bars constituting a commutator depends 
 upon the winding of the armature, and the number of 
 coils grouped thereon. By increasing the number of 
 coils and commutator sections the tendency to spark 
 at the brushes is decreased, and the fluctuations of the 
 current are also decreased. However, there are many 
 reasons against making the number of bars on a com- 
 mutator very great. Increasing the number of bars in 
 a commutator increases the cost of manufacture, and 
 in smaller dynamos if the number of bars be increased 
 beyond a certain extent, each bar becomes so thin 
 that a brush of the proper thickness to collect the cur- 
 rent from the commutator would lap over too many 
 
ELECTRICITY FOR ENGINEERS 51 
 
 bars of the commutator at one time. Each commu- 
 tator bar should be of the size that will present suffi- 
 cient metal for the carrying capacity of the current 
 generated in the coil to which it is connected. Differ- 
 ent builders of dynamos have different ideas as to the 
 number of amperes that maybe carried per square inch 
 in a commutator bar, but where a commutator is made 
 
 FIGURE 23. 
 
 of 95 per cent, copper it is usual to allow for each ioo 
 amperes a commutator bar surface of i% sq. in. 
 
 The method of electrical connection between the 
 commutator bar and the coil of the armature varies in 
 different designs. Some builders solder the terminals 
 of the coils to the commutator bars; others bolt the 
 terminals of the coils to the bars; and some makers 
 use hard drawn copper and "form" the armature coii 
 in such a manner that both ends of the coil become 
 
5 L Z ELECTRICITY FOR ENGINEERS 
 
 commutator bars, making the coil continuous from one 
 end of the commutator bar to the end of the diametric- 
 ally opposite commutator bar. 
 
 In Fig. 23 we show a so-called "formed" armature 
 coil, after it has been prepared by properly insulating 
 it and bending it into shape ready to be applied to the 
 laminated armature body. 
 
 In Fig. 24 is shown a "formed" coil armature with 
 
 FIGURE 24. 
 
 the winding almost finished. The commutator is yet 
 to be placed on the shaft and the coil terminals con- 
 nected to the commutator bars. 
 
 In Fig. 25 we have an armature shaft with the lami- 
 
 figure 25. 
 
 nated armature body keyed on to the shaft ready to be 
 wound. 
 
ELECTRICITY FOR ENGINEERS 53 
 
 The body on which the armature coils are to be 
 wound is made up of sheet iron punchings and placed 
 on the armature shaft in the same manner that you 
 would put ordinary iron washers on a lead pencil. 
 These punchings or discs are insulated from one 
 another by having previously been painted with a coat 
 of shellac; for there is the same tendency to produce 
 current in the iron part of the armature, due to the 
 cutting of the magnetic lines, as there is in the copper 
 wire which is wound on its surface. If the iron core 
 were solid, there would be a very large current circu- 
 lating in the same direction as that which flows through 
 the wires. Such a current would be entirely useless 
 and would heat the armature; to prevent this the 
 armature is built up of thin sheet iron discs. 
 
 Brushes and Commutators. Figs. 26 to 30 show differ- 
 ent arrangements of modern brushes and brush-holders. 
 These are used to take the current from the commu- 
 tator and deliver it to the outside wires in the case of a 
 dynamo, and for the opposite in the case of a motor. 
 
 There are many different designs and constructions 
 of brushes and brush-holders, and these designs are 
 brought about by the various ideas of different builders 
 in their attempt to produce various advantageous 
 results, but the electrical connections and underlying- 
 principles remain the same whether a copper or a car- 
 bon brush be used. 
 
 In any construction of brush holding device, if great 
 care is not exercised in keeping it thoroughly clean, 
 trouble is sure to be the result, and trouble of this 
 nature increases so rapidly that unless the attendant 
 immediately sets about to right it, a burned out arma- 
 ture is almost sure to be the consequence sooner or 
 later. In alternating current dynamos, where brushes 
 
"A ELECTRICITY FOR ENGINEERS 
 
 rest on collector rings instead of commutators, it is 
 much easier to keep out of trouble, because the 
 brushes in this case merely collect the current from 
 the rings and do not commutate or rectify it. 
 
 The brushes and commutator of a dynamo or motor 
 
 figure 26. 
 
 are probably the most important parts with which the 
 engineer has to deal. Great care should be taken that 
 the brushes set squarely on the commutator and that 
 the surface of the brushes and commutator are as 
 smooth as possible. It is a good plan, and in some 
 
ELECTRICITY EOR ENGINEERS 
 
 55 
 
 cases the brush-holders are so made, that the brushes 
 set in a staggering position, that is to say, in a posi- 
 tion so that all the brushes will not wear in the same 
 place over the circumference of the commutator and 
 
 -^ZS 
 
 FIGURE 27. 
 
 cause uneven wear across the length of the commutator 
 bars. In most machines the armature bearing is left 
 so that there is more or less side motion, which, when 
 the armature is running, causes a constant changing of 
 the position of the brushes and commutator. 
 
56 
 
 ELECTRICITY FOR ENGINEERS 
 
 Whatever style of brush is used, the commutator 
 should be kept clean and allowed to polish or glaze 
 itself while running. No oil is necessary unless the 
 brushes cut, and then only at the point of cutting. A 
 cloth (not cotton waste) slightly greased with vaseline 
 and applied to the surface of the commutator while 
 
 figure 28. 
 
 running is best for the purpose of preventing the com- 
 mutator from cutting. Should the commutator 
 become rough, it should be smoothed with sandpaper, 
 never using emery cloth, because emery cloth is con- 
 ductor of electricity, and the particles of emery are 
 liable to lodge themselves between the commutator 
 bars in the mica and short circuit the two bars, thereby 
 
ELECTRICITY FOR ENGINEERS 57 
 
 burning a small hole wherever such a particle of emery- 
 has lodged itself. The emery will also work into the 
 brushes and copper bars and wear them down; it being 
 almost impossible to remove all the emery. 
 
 In the end-on carbon brushes, Fig. 30, the contact 
 surface of the brushes should be occasionally cleaned 
 by taking a strip of sandpaper, with the smooth side 
 of the paper to the commutator, and the sanded side 
 toward the contact surface of the brush, and then by 
 
 FIGURE 29. 
 
 leaving the tension of the brush down on the sand- 
 paper, it is an easy matter to move the sandpaper to 
 and fro and throughly clean off the glazed and dirty 
 surface from the carbon, leaving it with a concave that 
 will exactly fit the commutator. 
 
 The advantages of carbon brushes are many. 
 Among the cardinal points are: The armature may 
 run in either direction without it being necessary to 
 alter the brushes; the carbon can be manufactured with 
 a quantity of graphite in its construction, thereby 
 
58 
 
 ELECTRICITY FOR ENGINEERS 
 
 lowering the mechanical friction of the brushes on the 
 commutator; they do not cut a commutator so much 
 by sparking; the commutator has a longer life, the 
 wear being more evenly distributed. 
 
 Carbon brushes, due to their rather high resistance, 
 will often heat up considerably, but, although this 
 heat is objectionable, their resistance tends to cut 
 down the sparking. The brushes are sometimes coated 
 with copper to reduce their resistance. Often a car- 
 
 FIGURE 30. 
 
 bon brush will be found which is very hard. As a rule 
 such a brush should be thrown away, as it will heat 
 abnormally and at the same time wear the commu- 
 tator. 
 
 In Fig. 31 we have one of the various so-called old 
 styles of leaf brush-holders. The end-on brushes are 
 more generally used in modern practice, because their 
 contact surface area is not increased or decreased by 
 wear. Consequently the brushes always remain in a 
 diametrically opposite position. With the old style 
 
ELECTRICITY FOR ENGINEERS 
 
 59 
 
 brush-holding device, where the brushes rest on the 
 commutator at a tangent, great care should be exer- 
 
 FIGURE 31. 
 
 cised not to allow the brushes to wear in a position so 
 that their points will be out of diametrical opposition. 
 
 
 FIGURE 32. 
 
 In Fig. 31 we show the correct way that this type of 
 brush should be set. 
 
00 ELECTRICITY FOR ENGINEERS 
 
 In Figs. 32 and 33 we show the incorrect way. 
 
 By remembering that each one of the commutator 
 bars is the end of a coil, and then just mentally tracing 
 the current through the coils from one brush to the 
 other, we can readily understand what the results are 
 when the brushes are neglected and left in a relative 
 position, as shown in these figures. 
 
 Sparking is the usual result of brushes allowed to 
 wear to such an extent. Overloading of a dynamo or 
 motor will also cause serious sparking, and no amount 
 
 figure 33. 
 
 of care can prevent damage to armature, commutator 
 or brushes, if a machine is permitted to be overloaded. 
 Sometimes the commutator will contain one or more 
 bars which, as the commutator gets old and wears 
 down, will wear away either too fast or too slow, due 
 to the metal being harder or softer than the rest of the 
 bars forming the commutator. This causes a rough- 
 ness of the commutator and results in the flashing of 
 the brushes and heating of both the commutator and 
 brushes. About the only satisfactory method of 
 
ELECTRICITY FOR ENGINEERS 
 
 61 
 
 remedying this evil is to take out the armature and 
 have the commutator turned down in a lathe. 
 
 A short-circuited coil in the armature, or a broken 
 armature connection, will also cause considerable 
 sparking. Either of these conditions can be located 
 by means of a Wheatsone bridge or by what is known 
 as the fall of potential method. To make a test with 
 this latter method, connect in series with the armature 
 to be tested some resistance capable of carrying the 
 necessary current, also an ammeter. Some apparatus 
 for varying the current strength, such as a water rheo- 
 
 
 M^.MS 
 
 
 
 
 
 
 
 
 
 
 
 A / \A A A 
 
 —C\- 
 
 10 ■ ff n" 
 
 
 
 WR 
 
 
 
 vvvvv 
 
 VA>- 
 
 xv v y J? 
 
 FIGURE 34. 
 
 stat or lamp rack, must be connected in the circuit, a 
 diagram of which is shown in Fig. 34. 
 
 In the diagram, WR is the water rheostat or lamp 
 rack, R the known resistance, A the ammeter and M 
 the armature to be tested. By means of the water 
 rheostat regulate the -current passing over the appa- 
 ratus until it is of such strength that a deflection can 
 be obtained on a voltmeter when it is connected to two 
 adjacent bars on the commutator. Suppose the arma- 
 ture coil between bar 1 and 2 on the commutator were 
 broken. The voltmeter connected across these two 
 bars would give the same reading as when connected 
 
62 ELECTRICITY FOR ENGINEERS 
 
 across the two points 10 and 11. If the voltmeter were 
 connected between any other two points on the com- 
 mutator on the same side as the broken coil no deflec- 
 tion would be obtained, while connecting the voltmeter 
 between any two adjacent bars on the other side of the 
 commutator would give practically the same reading 
 irrespective of which bars were used. The resistance 
 of one or more sections of the armature winding could 
 also be found by using Ohm's law, R = E/C, or the 
 resistance would be equal to the voltage divided by the 
 current as shown on the ammeter. It must be remem- 
 bered that this latter will be true only when there is an 
 open coil in one side of the armature, for in this case 
 only will the whole current flow through the one side. 
 If the coil between bars I and 2 were short circuited, 
 the voltmeter would show practically no reading 
 between these bars; while between any other bars some 
 deflection would be obtained. An open circuit or 
 short circuit will nearly always be found by examina- 
 tion, as the trouble usually happens very close to the 
 commutator connections in the case of an open circuit 
 and may very often be found between the commutator 
 bars themselves, in the case of a short circuit. If the 
 trouble is not at these places it will usually be in the 
 windings, in which case the only remedy is to have it 
 re-wound. Temporary repairs may be made in the case 
 of an open circuit by short circuiting the commutator 
 bars around the open circuit, but this method should 
 only be used in emergency, as the sparking will in time 
 destroy the commutator. 
 
 With many dynamos, especially of older types, it is 
 necessary to shift the brushes with every change of 
 load. The current produced by the armature makes a 
 magnet out of it and the magnetism of the armature 
 
ELECTRICITY EOR ENGINEERS 
 
 63 
 
 opposes that of the fields. In Fig. 35 the armature is 
 working with a very light load and the lines of force 
 of the field magnets are only slightly opposed by those 
 
 FIGURE 35. 
 
 of the armature. In Fig. 36 we assume a heavy load 
 on the dynamo and consequently the magnetism of the 
 armature opposes that of the fields. This changes the 
 location of the neutral point (when the coils under the 
 brush generate no current) and it becomes necessary to 
 
 FIGURE 36. 
 
 shift the brushes accordingly, or great sparking would 
 result. The amount of shifting necessary with changes 
 of load varies in different dynamos. If the field is 
 
64 ELECTRICITY FOR ENGINEERS 
 
 very strong compared to the armature, it will be but 
 little. If the armature (as in some arc dynamos) is 
 very strong compared to the field, it will be consider- 
 able. 
 
 In dynamos, with increasing load, the brushes should 
 be shifted in the direction of rotation and in the oppo- 
 site direction when the load decreases. 
 
 Never allow a dynamo or motor to stand in a damp 
 place uncovered. Moisture is apt to soak into the 
 windings and cause a short circuit or ground when 
 started. Great care should also be used should it ever 
 be found necessary to use water on a heated bearing. 
 If the water is allowed to reach the armature or com- 
 mutator, it is bound to cause trouble. Water should 
 only be used in case of emergency, and then sparingly* 
 
CHAPTER IV 
 OPERATION OF DYNAMOS 
 
 Constant Potential Dynamos. In order to thoroughly 
 explain the operation of dynamos, let us assume that 
 we have the task of starting a new shunt dynamo, one 
 that has never generated any current. Our first step is 
 to open the main switch and turn the rheostat or field 
 
 FIGURE 37. 
 
 resistance box so that all the resistance is in circuit. 
 A rheostat consists of a number of resistances, Fig. 37, 
 so arranged that they can be cut in or out of the circuit 
 without opening the circuit. By reference to the figure 
 it will be seen that the current enters at the handle and 
 from there passes to the contact point upon which the 
 65 
 
()() 
 
 ELECTRICITY FOR ENGINEERS 
 
 handie happens to rest. If the handle is at i the cur- 
 rent must pass through all the wire in the box; if it is 
 at 2 it simply passes through the handle and out. 
 
 Rheostats for the shunt circuit of a dynamo should 
 have sufficient resistance, so that when it is all inserted 
 the voltage of the dynamo will slowly sink to zero. 
 This method of stopping the action of a dynamo is 
 
 FIGURE 37. 
 
 perfectly safe and should be followed wherever pos- 
 sible. 
 
 We are now running our dynamo with all resistance 
 in the shunt circuit. This is simply as an extra pre- 
 caution because we know nothing about this particular 
 dynamo. When it is known that the dynamo is in 
 good order, the engineer or attendant usually cuts out 
 all the resistance, and as the generator builds up or, in 
 other words, generates current, he proceeds, by the aid 
 of the resistance box, to cut down or diminish the flow 
 of electricity around the field magnets of the dynamo, 
 
ELECTRICITY FOR ENGINEERS 67 
 
 and thereby diminish the magnetic density of the 
 field magnets and the electromotive force of the 
 dynamo. 
 
 We must now gradually turn our rheostat so as to 
 cut out resistance and watch the voltmeter, which is 
 connected as shown at V in Fig. 20, and receives cur- 
 rent whenever the dynamo is operating. Suppose that 
 the voltmeter indicates nothing, and we find that the 
 dynamo will not generate. On examination of all the 
 connections we find everything correct, and we now 
 discover that the dynamo field magnets do not contain 
 what is termed "residual magnetism" sufficient to start 
 the process of generating current. 
 
 Before an armature can generate current it must cut 
 lines of force, that is, it must revolve in a magnetic 
 field. If the dynamo has been generating current it is 
 likely that the iron cores of the field magnets will 
 retain sufficient magnetism to start the generation of 
 current again. This magnetism which remains in the 
 iron is known as residual magnetism. It will make 
 itself manifest by attracting the needle of a compass, 
 or if strong, a screw driver or a pair of pliers. If we 
 find no magnetism in the iron core of the field mag- 
 nets, we may take the ends of the shunt winding on the 
 field magnets and pass current over them from a bat- 
 tery. This current will produce sufficient magnetism 
 to cause the generator to build up; in other words, if 
 we disconnect these batteries, and connect the wires 
 back again from where we got them, we will find that 
 we can generate current with the machine. 
 
 When the machine begins to generate, we watch the 
 voltmeter and cut resistance in or out of the circuit 
 according whether we need to lower or raise the volt- 
 age. If we have only one dynamo we may close the 
 
f>8 ELECTRICITY FOR ENGINEERS 
 
 main switch before we begin generating or after we 
 have attained full voltage. 
 
 Again referring to the pole pieces on the dynamo, it 
 is possible that there is a sufficient quantity of residual 
 magnetism in the pole pieces, and that the polarity of 
 both field magnets, between which the armature is 
 revolving, is the same. This would also cause the 
 dynamo to fail in generating current. If sending bat- 
 tery current through the coils does not make one field 
 a north pole and the other a south pole, one of the 
 fields must be connected wrong, and we must make 
 some changes in the connection. 
 
 Referring to Fig. 20, a and b are the terminals of the 
 shunt winding on the fields. If the winding of the 
 fields is correctly put on it will be as in the little sketch 
 at lower corner; that is, if both field magnets were 
 taken out of their places and put together, the wind- 
 ing should run as one continuous spool. But if the 
 winding on one field is wrong, we need simply change 
 its connection, as, for instance, transferring c to a and 
 a to c. 
 
 In order that a dynamo may excite itself, it is neces- 
 sary that the current produced by the residual magnet- 
 ism shall flow in such a direction as to strengthen this 
 residual magnetism. If the current produced by the 
 residual magnetism flows through the field coils in the 
 opposite direction this will tend to weaken the residual 
 magnetism and consequently to reduce the current 
 which flows. 
 
 For this reason if the first attempt to start a dynamo 
 with battery current fails, the battery should be applied 
 with the opposite poles so that the magnetism it pro- 
 duces in the fields will be in the opposite direction. 
 
 The magnetism, the fields, and all parts of the 
 
ELECTRICITY FOR ENGINEERS 69 
 
 dynamo may be in perfect working order and yet a 
 short circuit in any part of the wiring will prevent 
 the dynamo from building up This short circuit 
 will furnish a path of such low resistance that all cur- 
 rent will flow through it and none can flow through the 
 fields to induce magnetism. Often dynamos fail to 
 generate because of broken wires in the field coils, 
 poor contacts at brushes, or loose connections. Some- 
 times also part of the wiring may be grounded on 
 the metal parts of the dynamo frame. A faulty posi- 
 tion of the brushes may also be a cause for the machine 
 not generating. In some machines the proper position 
 for the brushes is opposite the space between the pole 
 pieces, while in other machines their proper position is 
 about opposite the middle of the pole piece. If the 
 exact position is not known, a movement of the brushes 
 will sometimes cause the generator to build up. 
 
 If there are several dynamos to be started great care 
 must be taken to see that the second machine is oper- 
 ating at full voltage before the switch is closed con- 
 necting it to the switch board. The voltage should be 
 exactly the same as that of the first machine and the 
 rheostat worked to keep it so. If it is less, it is pos- 
 sib?e that the first machine will run the second as a 
 motor; if it is more, the second machine may run the 
 first as motor, the machine having the higher voltage 
 will always supply the most current. 
 
 It is also necessary before throwing in the second 
 machine (connecting it to the switch board) to see that 
 its polarity is the same as that of the machine with 
 which it is to run. By reference to Fig. 38 it will be 
 seen that the + poles of both machines connect to the 
 same bar, and if one of these machines is running and 
 we wish to connect the other with it, we must first be 
 
70 ELECTRICITY FOR ENGINEERS 
 
 sure that the wire of the second machine which leads 
 to the top bus-bar is of the same polarity. That is, if 
 the top bus-bar is positive, or sends out current, the 
 wire or all dynamos connected to it must also be posi- 
 tive. The simplest way to find the positive pole of a 
 dynamo is with a cup of water. Take two small wires 
 and connect one to each of the main wires of the 
 dynamo and then insert the bare ends of both wires 
 into the water, small bubbles will soon be seen to rise 
 in the water from one of the wires. That wire which 
 gives off the bubbles is the negative wire. Take care 
 that in making this test you do not get the ends of the 
 small wires together or against the metal of the cup or 
 you will form a short circuit. The polarity of both 
 dynamos must be tested and wires of same polarity 
 connected to the same bus-bar. 
 
 Where several machines are to be operated in paral- 
 lel, compound dynamos are generally used, because it 
 is troublesome to keep two shunt machines working in 
 harmony. 
 
 The starting of a compound wound dynamo is the 
 same as that of a plain shunt dynamo, but in connect- 
 ing a compound wound dynamo to its circuit it is 
 necessary to be sure that the shunt coils and series coils 
 tend to drive the lines of force around the magnetic cir- 
 cuit in the same direction. If the series coil is con- 
 nected up in the opposite direction to the shunt coil 
 the dynamo will build up all right and will work satis- 
 factorily on very light loads. When, however, the 
 load becomes even, five or ten per cent, of full load, 
 the voltage drops off very rapidly and it is impossible 
 to get full voltage with even half the load on. This is 
 because the ampere turns due to the series coils 
 decrease the total ampere turns acting on the magnetic 
 
ELECTRICITY FOR ENGINEERS 
 
 71 
 
 circuit instead of increasing them as the load comes 
 on. This lowers the magnetic flux and of course 
 lowers the resulting voltage. In such a case it will be 
 necessary to reverse either the field or series coils. 
 
 Fig. 38 and the following description of compound 
 dynamos and their connections is taken from Wiring 
 Diagrams and Descriptions, by Horstmann and Tousiey, 
 published by Frederick J. Drake & Co., Chicago. 
 
 figure 38, 
 
 Fig. 38 shows connections for two compound wound 
 dynamos run in parallel. When two or more com- 
 pound wound dynamos are to be run together, the 
 series fields of all the machines are connected together 
 in parallel by means of wire leads or bus-bars which 
 connect together the brushes from which the series 
 fields are taken. This is known as the equalizer, and 
 is shown by the line running to the middle pole of the 
 dynamo switch. By tracing out the series circuits it 
 
72 ELECTRICITY FOR ENGINEERS 
 
 will be seen that the current from the upper brush of 
 either dynamo has two paths to its bus-bar. One of 
 these leads through its own fields, and the other, by 
 means of the equalizer bar, through the fields of the 
 other dynamo. So long as both machines are gener- 
 ating equally there is no difference of potential between 
 the brushes of No. I and No. 2. Should, from any 
 cause, the voltage of one machine be lowered, current 
 from the other machine would begin to flow through 
 its fields and thereby raise the voltage, at the same 
 time reducing its own until both are again equal. The 
 equalizer may never be called upon to carry much cur- 
 rent, but to have the machines regulate closely it 
 should be of very low resistance. It may also be run 
 as shown by the dotted lines, but this will leave all 
 the machines alive when any one is generating. The 
 ammeters should be connected as shown. If they 
 were on the other side they would come under the 
 influence of the equalizing current and would indicate 
 wrong, either too high or too low. The equalizer 
 should be closed at the same time, or preferably a lit- 
 tle before the mains are closed. In some cases the 
 middle, or equalizer, blade pf the dynamo switch is 
 made longer than the outside to accomplish this. The 
 series fields are often regulated by a shunt of variable 
 resistance. To insure the best results compound ma- 
 chines should be run at just the proper speed, other- 
 wise the proportions between the shunt and series coils 
 are disturbed. 
 
 GENERAL RULES 
 
 1. Be sure that the speed of the dynamo is right. 
 
 2. Be sure that all the belts are sufficiently tight. 
 
 3. Be sure that all connections are firm and make good contact. 
 
 4. Keep every part of the machine and dynamo room scrupu- 
 lously clean. 
 
ELECTRICITY FOR ENGINEERS 73 
 
 5. Keep all the insulations free from metal dust or gritty sub- 
 stances. 
 
 6. Do not allow the insulation of the circuit to become impaired 
 in any way. 
 
 7. Keep all bearings of the machine well oiled. 
 
 8. Keep the brushes properly set and see to it that they do not 
 cut or scratch the commutator. 
 
 9. If the brushes spark, locate the trouble and rectify it at once. 
 
 10. The durability of the commutator and brushes depends on 
 the care exercised by the person in charge of the dynamos. 
 
 11. At intervals the dynamos must be disconnected from the 
 circuit and thoroughly tested for leakage and grounds. 
 
 12. In stations running less than twenty-four hours per day, the 
 circuit should be thoroughly tested and grounds removed (if any 
 are found) before current is turned on. 
 
 13. Before throwing dynamos in circuit with others running in 
 multiple, be sure the pressure is the same as that of the circuit; 
 then close the switch. 
 
 14. Be sure each dynamo in circuit is so regulated as to have its 
 full share of load, and keep it so by use of resistance box. 
 
 15. Keep belting in good order; when several machines are 
 operating in parallel and a belt runs off from one, the others will 
 run this machine as a motor. 
 
 16. In the same way if you shut down an engine driving a 
 generator, the other generators will run the generator and the 
 engine. 
 
 Constant Potential Switchboard. In Fig. 39 we show 
 the usual type of switchboard employed to connect, 
 or switch various dynamos and to feed various circuits 
 from. These types, sizes and arrangements of switch- 
 boards vary and depend entirely on the type and size 
 of the plant, the number of dynamos used and the num- 
 ber of circuits to be controlled. The switchboard in 
 this cut has three dynamo panels and one load panel. 
 At the left of the board and near the top is the volt- 
 meter, while on the three left panels are the dynamo 
 main switches and their respective amperemeters. On 
 the lower part of these three machine panels will be 
 
74 
 
 ELECTRICITY FOR ENGINEERS 
 
 noticed the protruding hand wheels of the field resist- 
 ance boxes, which are hidden back of the board. The 
 meter at the top of the right hand panel is the load 
 amperemeter and registers the total number of amperes 
 
 *i 
 
 I M 1 
 
 . 0$ ■ 
 
 XL 
 
 
 Wk 
 
 
 *k3*rf 
 
 i 
 
 FIGURE 39. 
 
 that are being supplied to the circuits whose several 
 switches are just' below the meter. 
 
 Fig. 40 shows diagrammatically the reverse side of a 
 similar switchboard. Below all of the switches there 
 are installed fuses in each wire. The object of these 
 fuses is to protect the wires and also the dynamos. 
 These fuses consist of an alloy which melts at a com- 
 
ELECTRICITY FOR ENGINEERS 
 
 75 
 
 paratively low temperature. If, for instance, a short, 
 circuit occurs in any line, the current will suddenly 
 become very great and will generate considerable heat. 
 This heat will cause the fuse to melt and open the cir- 
 cuit. If the fuse did not melt the current would con- 
 tinue and overheat the wires, causing considerable 
 
 IO..S O! 
 
 :*■»■ 
 
 ■jfj 
 
 E ^ualhie v 
 
 Q Q QT O TX 
 
 Fuses' 
 
 I 
 
 9 9 9 "t~9 9 9 " 9 9 9 
 
 cr 
 
 
 
 o 
 h 
 6 <t 
 
 < 
 
 i 6 
 
 
 JJJIII 
 
 Switches 
 
 § 9 r | ? g _? 
 
 FIGURE 40. 
 
 damage and perhaps fires. The fuses should always 
 be chosen of such a size that they will melt before the 
 current rises enough to do any damage. 
 
 Operation of Constant Current Dynamos. Constant cur- 
 rent dynamos differ from constant potential dynamos 
 mainly in the higher voltage for which they are usually 
 
76 ELECTRICITY FOR ENGINEERS 
 
 constructed. Such machines are always more or less 
 dangerous to life, and great care must be taken not to 
 touch any of the current-carrying parts with bare hands. 
 
 When such parts must be handled rubber gloves are 
 very convenient and useful if kept dry. High voltage 
 machines should always be surrounded by insulating 
 platforms of dry wood, or rubber mats, so arranged 
 that one must stand on them in order to touch any 
 part of the machine. By reference to Fig. 19 it will 
 be seen that the constant current dynamo is not 
 equipped either with a voltmeter or a field rheostat; 
 but an amperemeter should always be used. The 
 troubles encountered with these dynamos are much the 
 same as those of constant potential dynamos. Most of 
 them are referred to in the following descriptions and 
 instructions for different systems and to avoid repeti- 
 tion need not be mentioned here. 
 
 The type of dynamo generally used with constant 
 currents is shown in Fig. 19 and is series wound; that 
 is, the same current that passes through the lights also 
 passes through the fields and excites them. The fields 
 of this dynamo are connected with a short circuiting 
 switch, S, which is generally used when the machine is 
 to be shut down. When this switch is closed it forms 
 a path of much lower resistance than do the fields of 
 the dynamo and all current passing through it and the 
 dynamo loses its magnetism and stops generating. 
 A constant potential dynamo will not begin genera- 
 ting if there is a short circuit anywhere in the wiring 
 connected with it, but with the constant current 
 dynamo it is often necessary to provide a short circuit 
 in order to start it. If there is very much resistance 
 in the line or if it is entirely open the dynamo will fail 
 to generate. 
 
ELECTRICITY FOR ENGINEERS 77 
 
 . In order to start generation a small wire may be 
 attached to one of the terminals of the dynamo and 
 the other end brought in contact with the other ter- 
 minal for a fraction of a second or the shortest possible 
 instant. If the circuit happens to be arranged some- 
 what as shown in the figure, the plug may be inserted 
 so that ihe dynamo is started through only one lamp. 
 When this lamp is burning properly the plugs may be 
 suddenly withdrawn and the current will now force 
 itself through the other lamps. This process is known 
 as "jumping in" and should be used only in an emer- 
 gency, as much damage may be caused, especially if a 
 dynamo is already running a large number of lamps 
 and is then "jumped into" a bad circuit. This is also 
 often done, but is just as dangerous as it would be to 
 attempt to start a heavy steam engine by opening up 
 the throttle valve with a quick jerk. 
 
 Constant current dynamos are always equipped with 
 automatic regulators and before the dynamo is started 
 special attention must be given the regulator to see 
 that it is in proper working order. 
 
 Often it may be desirable and even necessary to run 
 two dynamos in series, as, for instance, if a circuit has 
 been extended beyond the capacity of -one machine. 
 In such a case the regulator of one machine is cut out 
 and that machine set to operate at about its highest 
 electromotive force, and, the variations are taken care 
 of by the other dynamo. 
 
 The Brush System. The brush arc dynamo is quite 
 distinct from other constant current dynamos in general 
 use. We shall therefore give the following descrip- 
 tion of it taken from literature furnished by the Gen- 
 eral Electric Company. 
 
 The brush arc generator is of the open coil type, the 
 
78 ELECTRICITY FOR ENGINEERS 
 
 fundamental principle of which is illustrated in Fig. 
 41. Two pairs of coils, placed at right angles on an 
 iron core, are rotated in a magnetic field. The hori- 
 zontal coils represented in the diagram are producing 
 their maximum electromotive force, while the pair of 
 coils at right angles to them is generating practically 
 no electromotive force. The brushes are placed on 
 the segments of the four-part commutator, so as to col- 
 lect only the current generated by the two horizontal 
 
 FIGURE 41. 
 
 coils. The other coils are open circuited or com- 
 pletely cut out of the circuit. 
 
 Such a machine will generate current, continuous in 
 direction, but fluctuating considerably in amount. 
 These fluctuations will be diminished by the addition 
 of more coils to the armature. 
 
 Fig. 42 shows the connections of an eight-coil brush 
 arc generator. Each bobbin is connected in series 
 with the one diametrically opposite. The connection 
 is not shown on the diagram. It will be noticed that 
 of those coils connected to the outer ring on which the 
 brushes A and A 1 bear, only 3, 3 1 are in circuit, 1, I 1 
 
 
ELECTRICITY FOR ENGINEERS 
 
 79 
 
 being entirely cut out; while on the inside ring all 
 coils 2, 2 1 and 4, 4 1 are in circuit, the two pairs being 
 parallel; 4, 4 1 are coming into the field of best action; 
 in other words, they are approaching that part of the 
 field in which there is most rapid change of magnetic 
 flux, while 2, 2 1 are approaching that part in which the 
 flux is uniform. In 4, 4 1 there is an increasing electro- 
 
 figure 42. 
 
 motive force being generated, and the current is rising; 
 while in 2, 2 1 , the electromotive force is decreasing and 
 the current falling. Unless 2, 2 1 were cut out of the 
 circuit, a point would soon be reached where the elec- 
 tromotive force in 2, 2 1 would be zero, and conse- 
 quently 4, 4 1 would be short circuited through 2, 2 1 . 
 Just before this occurs, however, 2, 2 1 have passed from 
 under the brush and the small current still flowing 
 
80 ELECTRICITY FOR ENGINEERS 
 
 draws out the spark one sees on the commutator of all 
 open coil machines. 
 
 Setting the Brushes. A pressure brush should always 
 be used over the under brush in the same holder, as it 
 improves the running of the commutator and secures 
 better contact on the segment. The combination is 
 referred to as the "brush." The brushes should be 
 set about 5^3 in. from the front side of the brass brush- 
 holder. 
 
 In setting the brushes, commence with the inner pair 
 and set one brush about 5^3 in. from the holder to tip 
 of the brush, then rotate the rocker or armature until 
 
 figure 43. 
 
 the tip of the brush is exactly in line with the end of a 
 copper segment, as shown in Fig. 43. The other 
 brush should be set on the corresponding segment 90 
 removed (the same relative position on the next for- 
 ward segment); but if the length of the brush from the 
 holder is less than $}i in., move both brushes forward 
 until the length of the shorter brush from the holder 
 is 5^ in. Now set the two extreme outer brushes in 
 the same manner, clamping firmly in position, and by 
 using a straight edge or steel rule, all the brushes can 
 be set in exactly the same line and firmly secured. 
 The spark on one of the six brushes may be a trifle 
 
ELECTRICITY FOR ENGINEERS 81 
 
 longer than on the others. In this case, move the 
 brush forward a trifle so as to make the sparks on the 
 six brushes about the same length. Equality in 
 the spark lengths is not essential, but it gives at a 
 glance an indication of the running condition of the 
 machine. 
 
 Brushes should not bear on the commutator less than 
 }i in. from the point of the brush, or, as illustrated in 
 Fig. 44 (a), they will tend to drop into the commu- 
 tator slots and pound the copper tip of the wood block, 
 causing the fingers of the brushes to break off. If, on 
 the other hand, the bearing is too far from the end, or 
 the brushes are set too long, as in Fig. 44 (b), the 
 
 figure 44a. figure 44b. figure 44c. 
 
 point of the brush will not be in contact with the seg- 
 ment, thereby prolonging the break, and allowing the 
 spark to follow the tip with consequent burning of the 
 segments and brushes. 
 
 Fig. 44 (c) shows correct seating with the tip of the 
 brush nearly tangential and stiff on the segment as it 
 leaves. 
 
 Care of Commutator. If the commutator needs lub- 
 rication, oil it very sparingly. Once or twice during 
 a run is ample. If the oil has a tendency to blacken 
 the commutator instead of making it bright, wipe the 
 commutator with a dry cloth. Too much oil causes 
 flashing. 
 
 The machine, of course, generates high potential, 
 and the cloth, or whatever is used to oil the commu- 
 
82 ELECTRICITY FOR ENGINEERS 
 
 tator, should therefore be placed on a stick so that the 
 hand is not placed in any way between the brushes. 
 
 A rubber mat should be provided for the attendant 
 to stand on when working around the commutator or 
 brushes. 
 
 One hand only should be used, and great care exer- 
 cised not to touch two brush clamps or brushes at the 
 same time; never with switches closed. 
 
 As soon as current is shut off from the machine the 
 commutator should be cleaned. A piece of very fine 
 sandpaper held against the commutator under a strip 
 of wood for about a minute before the machine is 
 stopped, will scour the commutator sufficiently. The 
 brushes need not be removed. An effort should be 
 made to have the machine cleaned immediately after 
 it is shut down. Five minutes at that time will give 
 better results than half an hour when the machine is 
 cold. Never use a file, emery cloth or crocus, on the 
 commutator. New blocks will sometimes cause flash- 
 ing, due to the presence of sap in the wood. The 
 machine should be run for a few hours with a slightly 
 longer spark, say y 2 in., and the commutator then 
 thoroughly cleaned with fine sandpaper. 
 
 All constant current arc machines require an auto- 
 matic regulator to increase the voltage as more lamps 
 are cut into the circuit and decrease it as lamps are 
 cut out. 
 
 We will give only one of the several forms of regu- 
 lators used with this system. 
 
 The form I regulator is placed on the frame of the . 
 machine beneath the commutator, and a constant 
 motion is imparted to its main shaft through a small 
 belt running around the armature shaft. (See Fig. 
 46.) By means of magnetic clutches and bevel gears, 
 
ELECTRICITY FOR ENGINEERS 83 
 
 a pinion shaft is rotated, which moves the rack and the 
 rocker arm and so shifts the brushes on the commu- 
 tator to maintain a spark of about $/% in. on short cir- 
 
 To Controller 
 
 \ To Controller 
 
 FIGURE 46. 
 
 cuit and }i in. at full load; at the same time the 
 rheostat arm is moved over the contacts to cut 
 resistance in or out of the shunt around the field 
 circuit. 
 
84 
 
 ELECTRICITY FOR ENGINEERS 
 
 The current for the magnetic clutches is regulated by 
 the controller. 
 
 The controller consists principally of two magnets 
 which are energized by the main current and act when 
 the current is too high or too low by sending a small 
 current to one of the clutches. 
 
 A careful examination of the controller (see Fig. 
 47), in connection with Fig. 46, will give a clear idea 
 
 CONNECTIONS OF BRUSH CONTROLLER 
 
 To Held &\ Ar-vT) /^ To Circuit or Ammeter 
 
 HI! (T-j-^P r ' y i_j_- r U 
 
 Changed S June's 
 
 FIGURE 47. 
 
 of its regulating action. It is generally advantageous 
 to make the yoke which carries the brushes on the 
 machine and the arm moving the rheostat, rather 
 tight. As the magnetic clutches act with considerable 
 force, it is not necessary to adjust these moving parts 
 so loosely that they will move without considerable 
 pressure on the rocker handle. Less difficulty will 
 then be experienced in adjusting the controller. 
 
ELECTRICITY FOR ENGINEERS 85 
 
 For shunt lamps, the controller may be adjusted to 
 permit a variation of .4 ampere above or below normal; 
 for differential lamps, the variation above and below 
 normal should not exceed .2 ampere. The limits 
 given in the following instructions are for differential 
 lamps, and may be extended .2 ampere above or below 
 for shunt lamps. 
 
 If the controller is out of adjustment and fails to 
 keep the current normal, do not try to adjust the ten- 
 ions of both armatures at the same time. For exam- 
 ple, suppose the current is too high, either one of the 
 two spools may be out of adjustment. The left-hand 
 spool I may not take hold quickly enough, or the 
 spool F may take hold too quickly. To make the 
 adjustment, screw up the adjusting button K on the 
 right hand spool, increasing the tension. This will 
 have a tendency to let the current fall much lower 
 before the armature comes in contact with H, to cause 
 the current to increase. By simply tapping the arma- 
 ture G quickly with a pencil or piece of wood, forcing 
 it down to its contact, and at the same time watching 
 the ammeter, the current may be brought up to 6.8 
 amperes if 6.6 amperes is normal, or to 9.8 if 9.6 
 amperes is normal. With the current at 6.8 amperes, 
 which is .2 ampere high, the adjusting button L should 
 be turned. to increase the tension on this spring until 
 the armature M comes in contact with contact N, 
 which will force current down through O. The clutch 
 which pulls the brushes forward and rocks the rheostat 
 back for less current will thus be energized. Repeat 
 this adjustment two or three times, but do not touch 
 the adjusting button K; adjust L until it is just right. 
 
 At the side of the armature M a little wedge is 
 screwed in by means of an adjusting button, and 
 
80 ELECTRICITY FOR ENGINEERS 
 
 increases or decreases the leverage on this armature. 
 See that this wedge is fairly well in between the core 
 or frame of the spool and the spring of the armature. 
 The armature M may have to be taken out and the 
 spring slightly bent. It is advisable to have the screw 
 which passes through the adjuster button L about half 
 way in, to allow an equal distance up and down for 
 adjusting this lighter spring after the wedge shaped 
 piece is in the right position to give the necessary 
 tension on the spring which is fastened to the arma- 
 ture M. 
 
 In the right-hand corner P, a small bent piece of 
 wire is placed for tightening up the screw which fas- 
 tens the spring to the frame of the spool. As the con- 
 tact made by the spring and the frame of the spool 
 held together by a screw and button is a part of the 
 magnetic circuit, it will be almost impossible to get 
 this spring back to exactly the same tension after once 
 removing it. Therefore, the adjusting buttons of the 
 controller must be turned slightly in order to bring it 
 back to its proper adjustment. This, however, is an 
 after consideration, and care should be taken to have 
 the screw which holds the spring and frame together 
 always tight. 
 
 Having adjusted the spool I so that the current will 
 not rise above 6.8 amperes (or 9.8 amperes), move the 
 armature M up to contact N with a pencil or piece of 
 wood, causing the current to be reduced to about 6.2 
 (or 9.2). After the current settles at this point, decrease 
 the tension on the spring which is fastened to armature 
 G, allowing this armature to fall down to contact H. 
 Current will then flow through Q, which will rock the 
 brushes back and also move the rheostat arm for more 
 current. As the spool I has been adjusted for 6.8 (or 
 
ELECTRICITY FOR ENGINEERS 87 
 
 9.8) amperes, the current cannot rise above that amount 
 no matter how the spool F is adjusted. 
 
 With very little practice in moving the armature of 
 one spool with a pencil, the other can be adjusted 
 much more readily than if an attempt is made to adjust 
 the screws K and L at the same time. 
 
 The two small shunt coils, R and S, are connected 
 around the two contacts simply to decrease the spark 
 between the silver and platinum contacts. If they 
 should" become short circuited in any way, so that 
 their resistances become diminished, sufficient current 
 may pass through either of them to operate the regu- 
 lator. If unable to locate the trouble disconnect these 
 coils at points T and U, when a thorough examination 
 can be made. M and G need not move more than just 
 enough to open the contact; ^ m - ls ample. 
 
 In starting the machine, the lower switch, which 
 short circuits the field, should be opened last. 
 
 The switch in the left-hand corner of the controller, 
 figure 47 cuts out the two resistance wires which are 
 used to force the current through wires O and Q to 
 the clutches. Open this switch, which leaves the 
 automatic device of the controller in circuit, so that it 
 will move the brush rocker. Unclamp the brush rocker 
 from the rheostat arm rocker. Move the brushes by 
 hand to give the proper spark, allowing the rheostat 
 arm, however, to be moved by the controller. After 
 the switches are opened, the rheostat arm will go clear 
 around to a full load position, and then, as the current 
 rises, the controller takes hold and brings the arm 
 back. In the meantime, rock the brushes forward or 
 backward and keep the spark about the proper length, 
 say }& in., at full load to ^ in., on short circuit. 
 Gradually the rheostat arm will settle, the spark will 
 
88 
 
 ELECTRICITY FOR ENGINEERS 
 
 become constant, and the machine will give its proper 
 current. Then clamp the rocker and rheostat- arm 
 together and let the machine regulate itself. 
 
 This method is much better than opening the 
 switches on the machine and allowing the wall con- 
 troller to take care of the machine from the start. By 
 allowing the controller to start the machine, a trifle 
 longer spark is obtained than by the other method, 
 
 PULLEY END 
 
 COMMUTATOR END 
 
 figure 48. 
 
 unless the machine is run from the beginning on a very 
 full load. 
 
 The machine will require a trifle longer spark on 
 light load, or on bad circuits, than when running at 
 full load. This fact should be borne in mind in wet 
 weather, when trouble with grounds is experienced. 
 
 A reliable ammeter should always be connected in 
 the circuit of an arc generator, so that the exact cur- 
 rent may be read at a glance. It should be connected 
 into the negative side of the line where the circuit 
 leaves the regulator. 
 
ELECTRICITY FOR ENGINEERS 
 
 89 
 
 The Thomson-Houston System. The Thomson-Hous- 
 ton dynamo differs from other arc dynamos principally 
 in the nature of its armature winding. This is shown 
 in Fig. 48. One end of each of the three coils is con- 
 nected to a copper ring common to all. The other end 
 of each coil terminates at one of the three commutator 
 segments. The management and operation of the 
 machine will appear from the following instructions 
 taken from pamphlets furnished by the General Elec- 
 tric Company. 
 
 FIGURE 50. 
 
 Setting the Cut-out. After the brushes are in position 
 the cut-out must be set. This is done by turning the 
 commutator on the shaft in the direction of rotation 
 (if the commutator is set in position the whole arma- 
 ture must be revolved) until any two segments are just 
 touching the primary brush on that side, as segments A' 
 and A'" touch brush B 4 in Fig. 50. 
 
 Under these conditions brush B 1 should be at the 
 left-hand edge of upper segment. Then turn commu- 
 tator until the same two segments are just touching 
 
90 ELECTRICITY FOR ENGINEERS 
 
 brush B 2 , when the end of brush B 3 should just come 
 to the right-hand edge of the lower segment. If the 
 secondary brush projects beyond the edge of the seg- 
 ment the regulator arm should be bent down; if it does 
 not come to the edge of the segment, the arm should 
 be bent up. 
 
 Care must be taken that the regulator armature is 
 down on the stop when the cut-out is being set. 
 These adjustments by bending regulator arm are 
 always made in the factory before testing the machine, 
 and should never be made on machines away from the 
 factory, unless the regulator arm has been bent by 
 accident. If it becomes necessary to make any adjust- 
 ments they should be made by means of the sliding 
 connection attached to the inner yoke. 
 
 Always try the cut-out on both primary brushes. If 
 it does not come the same on both, turn one over. If 
 the brush-holders are correctly set by the gauge, there 
 should be no trouble in getting the cut-out set properly 
 after one or two trials. 
 
 To set the commutator in the proper position on a 
 right-hand machine, with a ring armature, find the 
 leading wire of No. I coil. It is the custom in the 
 factory to paint this lead red, also to paint a red mark 
 on the center band between two groups of coils, 
 namely, the last half of No. I coil and the first half of 
 No. 3 coil. The first half of a coil is that group from 
 which the lead comes. The last half is diametrically 
 opposite the first half and the lead wire belonging to 
 it is- connected with the brass ring on the outside of 
 the connection disk on the commutator end. 
 
 In Fig. 51 the first halves of the. three coils are rep- 
 resented by 1, 2 and 3, and the last halves by i', 2' 
 and 3', 
 
ELECTRICITY FOR ENGINEERS 9; 
 
 A narrow piece of tin with sharply pointed ends is 
 bent up over the sides of the middle band at the cen- 
 ter of the red mark so that the points are opposite each 
 other. 
 
 When the red mark and red lead have been found, 
 turn the armature until the last half of No. I coil has 
 wholly disappeared under the left field and until the 
 left-hand edge of the first coil to the right of the red 
 
 FIGURE 51. 
 
 mark (No. 3 in Fig. 51) is just in line with the edge of 
 the left field. The red lead will then be in position 
 shown in Fig 51, and the armature is in proper posi- 
 tion to set the commutator. 
 
 In the case of the right-hand drum armature 'he 
 leading wire of the first coil should be found. This lead 
 may be recognized from the fact that it is more heavily 
 insulated than the rest, and is found in the center of 
 
92 
 
 ELECTRICITY FOR ENGINEERS 
 
 FIGURE 52. 
 
 the outer coil, on the commutator end. With this 
 wire turned underneath, rotate the armature forward, 
 or counter-clockwise, until the pegs on the right-hand 
 
 Red mark painted 
 on center band. 
 
 FIGURE 53. 
 
ELECTRICITY FOR ENGINEERS 
 
 93 
 
 side of this coil just disappear under the left field. 
 (See Fig. 52.) 
 
 The position of the red lead and the red mark on the 
 band are the same on all armatunes, but their positions 
 in the fields of the machines called left-hand (clock- 
 wise rotation), should be as shown in Fig. 53 and 54 
 when setting the commutator. 
 
 When the armature of a right-hand machine is in 
 position, the commutator is turned on the shaft until 
 
 figure 54. 
 
 segment No. 1 is in the same relative position as the 
 last half of No. 1 coil; segment No. 2 should corres- 
 pond with the last half of No. 2 coil, and segment No. 
 3 with the last half of No. 3 coil, as shown on Figs. 51 
 and 52. 
 
 For left-hand machines, see Figs. 53 and 54. 
 
 The distance from the tip of the brush, which is on 
 top, to the left-hand edge of No. 2 segment on a right- 
 hand machine, or to the right-hand edge of No. 3 seg- 
 
f)4 ELECTRICITY FOR ENGINEERS 
 
 ment in a left-hand machine is called the lead, and 
 should be made to correspond with the following 
 table. 
 
 TABLE OF LEADS 
 DRUM ARMATURES. RING ARMATURES. 
 
 C 12 \ inch positive K 12 ^g inch positive 
 
 E 12 / F " " M 12 i " negative 
 
 E 2 J «' « M 2 I " 
 
 H 12 4 " " LD 12 \ " positive 
 
 H 2 J « « . LD* i " 
 
 MDi 2 ^| " 
 
 MD 2 if •< 
 
 Place the screws in the binding posts at the lower 
 ends of the sliding connections, and put on the dash 
 pot connections between the brushes, with the heads 
 of the connecting screws outward. In every case the 
 barrel part of the dash pot is connected to the top 
 brush-holder, and plunger part to the bottom brush- 
 holder. 
 
 See that the field and regulator wires are connected 
 and that all connections are securely made. 
 
 When all connections have been made, make a care- 
 ful examination of screws, joints and all moving parts. 
 They must be free from stickiness and not bind in any 
 position. 
 
 To determine when the machine is under full load, 
 notice the position of the regulator armature, which 
 should be within }i in. of the stop. At full load the 
 normal length of the spark on the commutator should 
 be about T 3 g in. If it is less than this, shut' down the 
 machine and move the commutator forward or in the 
 direction of rotation until the spark is of the desired 
 length. If the spark is too long, move the commu- 
 tator back the proper amount. 
 
 A general view of the complete dynamo is given in 
 
ELECTRICITY FOR ENGINEERS 
 
 95 
 
 Fig. 55, and will help explain the regulator used with 
 this system. 
 
 The regulator is fastened to the frame of the machine 
 by two short bolts. On the right»hand machine its 
 position is on the left-hand side, as shown in Fig. 55. 
 On the left-hand machine, i.e., one which runs clock- 
 wise, its position is on the opposite side. Before fill- 
 
 FIGURE 55. 
 
 ing the dash pot D with glycerme, see that the 
 regulator lever and its connections, brush yokes, etc., 
 are free in every joint, and that the lever L can move 
 freely up and down. Then fill the -dash pot D with 
 concentrated glycerine. The long wire from the 
 regulator magnet M is connected with the left-hand 
 binding post P of the machine, and the short wire with 
 
96 
 
 ELECTRICITY FOR ENGINEERS 
 
 the post P 2 on the side of the machine. The inside 
 wire of the field magnet, or that leaving the iron flange, 
 of the left-hand field should be connected into post P 2 
 also, as shown in Fig. 55. The electric circuit (see 
 Fig. 56) should be complete from post P l , on the con- 
 troller magnet, through the lamps to the post N on the 
 machine, through the right-hand field magnet C, to 
 the brushes B 1 B 1 , through the commutator and arma- 
 ture to the brushes B B, through the left-hand field C, 
 
 IGURE 56. 
 
 to posts P 2 and P, thence to posts P 2 and P on the con- 
 troller magnet, through the controller magnet to P 1 . 
 The current passes in the direction indicated by the 
 arrows 
 
 When an arc machine is to be run frequently at a 
 small fraction of its normal capacity, the use of a light 
 load device is advisable to secure the best results in 
 regulation. 
 
 The rheostat for this purpose (see Fig. 57) is con- 
 nected in shunt with the right field of the generator. 
 
ELECTRICITY FOR ENGINEERS 97 
 
 Facing the rheostat with the right binding posts at the 
 bottom, the contact on the right side or No. I gives 
 open circuit and throws the rheostat out of use. Point 
 No. 2 gives a resistance of 44 to 46 ohms and Point 
 No. 3 gives a resistance of 20 to 22 ohms. 
 
 This rheostat with a 75-light machine allows the fol- 
 lowing variations: Point 1, 75 to 48 lights; Point 2, 
 48 to 25 lights; Point 3, 25 lights or less. For use with 
 
 FIGURE 57. 
 
 other sizes of generators, the adjustment of the rheo- 
 stat must be made to suit the conditions. 
 
 When the rheostat is in use, the sparks at the com- 
 mutator will be somewhat larger than normal, but will 
 not be detrimental. 
 
 The controller magnet (see Fig. 58) is to be fastened 
 securely by screws to the wall or some rigid upright 
 support, taking care to have it perfectly plumb. It is 
 connected to the machine in the manner shown in Fig. 
 55, i.e., the binding post P 2 on the controller magnet is 
 
98 
 
 ELECTRICITY FOR ENGINEERS 
 
 connected to the binding post P 2 (see Fig. 55) on the 
 end of the machine, and likewise the post P on the 
 controller to the post P on the leg of the machine; 
 the post P 1 forms the positive terminal from which the 
 circuit is run to the lamps and back to N. 
 
 Great care should be taken to see that the wires P P 
 
 FIGURE 58. 
 
 and P 2 P 2 are fastened securely in place; for if connec- 
 tion between P and P should be impaired or broken, 
 the regulator magnet M would be thrown out of action, 
 thus throwing on the full power of the machine, and if 
 the wire P 2 P 2 should become loosened, the full power 
 of the magnet M would be thrown on, and the regu- 
 
ELECTRICITY FOR ENGINEERS 99 
 
 lator lever L, rising in consequence, would greatlj- 
 weaken or put out the lights. 
 
 The wires leading from the controller magnet to the 
 machine should have an extra heavy insulation. 
 
 Care should be taken in putting up the controller 
 magnet that the following directions are followed: 
 
 1. The cores B of the axial magnets CC must hang 
 exactly in the center, and be free to move up and 
 down. 
 
 2. The screws fastening the yoke or tie pieces to the 
 two cores must not be loosened. 
 
 3. The contacts O must be firmly closed when the 
 cores are not attracted by the coils C C, which is the 
 case, of course, when no current is being generated by 
 the machine, and when the cores are lifted, the con- 
 tacts must open from g- 1 ^ in. to ^ in.; a greater open- 
 ing than ^ in. has the effect of lengthening the time 
 of action of the regulator magnet. This tends to ren- 
 der the current unsteady, and in case of a very weak 
 dash pot or short circuit might cause flashing. Adjust- 
 ment must be made if necessary by bending the lower 
 contact up or down, taking care that it is kept parallel 
 with the upper contact, so that when they are closed, 
 contact will be made across its whole width. If this 
 adjustment is not properly made there will be destruc- 
 tive sparking on a small portion of the contact surfaces. 
 
 4. All connections must be perfectly secure. 
 
 5. The check nuts N must be tight. 
 
 . 6. The carbons in the tubes L must be whole. These 
 carbons form a permanent shunt of high resistance 
 around the regulator magnet M, and if broken will 
 cause destructive sparking at contacts O, burning them 
 and seriously interfering with close regulation of the 
 generator. In case a carbon should become broken, 
 
100 ELECTRICITY FOR ENGINEERS 
 
 temporary repairs may be made by splicing the broken 
 pieces with a fine copper wire. 
 
 To keep the action of the controller perfect the con- 
 tacts O should be occasionally cleaned by inserting a 
 folded piece of fine emery cloth and drawing it back 
 and forth. 
 
 The amount of current generated by each machine 
 
 FIGURE 59. 
 
 depends upon the adjustment of the spring S. If the 
 tension of this spring is increased the current will be 
 diminished; if the tension is diminished, the current 
 will be increased. 
 
 In starting these dynamos when the armature has 
 reached its proper speed, the short circuiting switch on 
 the frame should be opened. This method allows the 
 
ELECTRICITY FOR ENGINEERS 
 
 101 
 
 generator to take up its load gradually, and is a very 
 important point in the handling of the machine. 
 
 Arc Switchboards. Fig. 59 shows a general view of 
 the Thomson-Houston plug switchboard. A rear view 
 of the same board is given in Fig. 60. 
 
 In a standard panel the number of horizontal rows 
 of holes equals one more than the number of gener- 
 ators. The vertical holes are always twice the number 
 of generators. The positive leads of the generators are 
 
 FIGURE 60. 
 
 attached to the binding posts on the left-hand ends of 
 the horizontal conductors. The negative leads are 
 connected to the corresponding binding posts at the 
 right-hand end of the board. 
 
 The positive line wires are connected to the vertical 
 straps on the left, and the negative wires to the similar 
 straps on the right of the center panel. 
 
 If a switchboard plug be inserted in any of the holes 
 of the board, it puts the corresponding generator lead 
 
102 ELECTRICITY FOR ENGINEERS 
 
 and the line wire in electrical connection, but as the 
 positive line wires are back of the positive generator 
 leads only, it is not possible to reverse the connection 
 of the line and the generator accidentally, though any 
 other combinations of lines and generators can be 
 made readily and quickly. 
 
 The holes of the lower horizontal rows have bushings 
 connected with the vertical straps only. Plugs con- 
 nected in pairs by flexible cable and inserted in the 
 holes put the corresponding vertical straps in connec- 
 tion as needed, and normally independent lines may be 
 connected when one generator is required to supply 
 several circuits. 
 
 Lines and generator leads may be transferred, while 
 running, by the use of these cables, without shutting 
 down machines or extinguishing lamps. 
 
 The standard boards are arranged for an equal num- 
 ber of generators and circuits, but special boards for 
 any ratio of circuits to generators can be built. 
 
 As it is sometimes convenient, even in small plants, 
 to interchange lines and generators without shutting 
 down machines, a special transfer cable with plugs has 
 been devised. This serves the same purpose as the 
 regular transfer cable, but the plugs may be used in 
 any of the holes of the switchboard, as they are insu- 
 lated, except at the tip, and when inserted connect 
 with the line strips only. 
 
 The transfer of circuits from one generator to 
 another gives trouble to dynamo tenders who are not 
 familiar with the operation of these plug switchboards. 
 Fig. 61 illustrates the successive steps for transferring 
 the lamps of two independent circuits from two genera- 
 tors to one without extinguishing the lamps on either 
 circuit. 
 
ELECTRICITY FOR ENGINEERS 
 
 103 
 
 4- 
 
 12 3 4 
 
 12 3 4 
 
 
 1 , ' 
 
 -•(boo • — vO/— e — ©■ 
 
 1 , 1 
 
 1 2 
 
 3 
 
 (J • LJ LJ u • u u 
 OOOO OOOO 
 OOOO OOOO 
 
 2 1 
 
 3 
 
 ♦ — # 
 
 o o 
 o o 
 
 OOOO 
 OOOO 
 
 rt 
 
 OOOO 
 OOOO 
 
 ^1 
 
 3 
 
 
 1 
 
 
 
 c 
 
 
 
 1 
 
 
 
 
 
 ?/■ 
 
 -H 
 
 i> o. 
 
 o 
 
 4- 
 
 -y>r 
 
 
 r\ 
 
 
 1 1 
 
 \J 
 
 <J 
 
 1 1 
 
 1 
 
 i 
 
 C 
 
 ) o 
 
 o 
 
 o 
 
 1 
 
 
 
 1 
 
 1 2 
 
 ^ 
 
 •^ 
 
 u 
 
 L> 
 
 2 1 
 
 . 1 
 
 3 
 
 
 
 C 
 
 ) o 
 
 o 
 
 o 
 
 o 
 
 o 
 
 o 
 
 1 
 3 
 
 
 o 
 
 C 
 
 2) O 
 
 o 
 
 o 
 
 o 
 
 o 
 
 o 
 
 
 FIGURE 61. 
 
104 ELECTRICITY FOR ENGINEERS 
 
 This process is a very simple example of switch- 
 board manipulation, but illustrates the method used 
 for all combinations. 
 
 The location of plugs is shown by the black circles, 
 which indicate that the corresponding bars of the 
 horizontal and vertical rows are connected. 
 
 Circuit No. I and No. 2, running independently from 
 generators No. 1 and No. 2 respectively, are to be 
 transferred to run in series on generator No. 2. 
 
 In A, Fig. 61, are two circuits running independently; 
 in B the positive sides of both generators and circuits 
 are connected by the insertion of additional plugs. 
 
 At C both generators and circuits are in series. 
 
 Next insert plugs and cables as shown in D. Then 
 withdraw plugs on row corresponding to generator No. 
 1, and the circuits No. 1 and No. 2 are in series on 
 machine No. 2, and machine No. 1 is disconnected as 
 at E. ■ • 
 
 Similar transfers can be made between any two cir- 
 cuits or machines, and by a continuation of the process 
 additional circuits can be thrown in the same machine. 
 The transfer of the two circuits to independent genera- 
 tors is accomplished by reversing the process illus- 
 trated. 
 
 Fig. 62 shows the wiring and connections of the 
 Western Electric Co.'s series arc switchboard. At the 
 top of the board are mounted six ammeters, one being 
 connected in the circuit of each machine. On the 
 lower part of the board are a number of holes, under 
 which, on the back of the board, are mounted spring 
 jacks to which the circuit and machine terminals are 
 connected. For making connections between dynamos 
 and circuits, flexible cables terminating at each end in 
 a plug, are used; these are commonly called "jump- 
 
ELECTRICITY FOR ENGINEERS 
 
 105 
 
 ers." The board shown has a capacity of six machines 
 and nine circuits, and with the connections as shown 
 machine I is furnishing current to circuit I, machine 2 
 is furnishing current to circuits 2 and 3, and machine 4 
 is furnishing current to circuits 4, 5 and 7. In con- 
 necting together arc dynamos and circuits the positive 
 of the machine (or that terminal from which the cur- 
 rent is flowing) is connected to the positive of the cir- 
 
 FIGURE 62. 
 
 cuit (the terminal into which the current is flowing). 
 Likewise the negative of the machine is connected to 
 the negative of the circuit. Where more than one cir- 
 cuit is to be operated from one dynamo, the - of the 
 first circuit is connected to the + of the second. At 
 each side of the name plate (at 3, for instance) there 
 are three holes. The large hole is used for the per- 
 manent connection, while the smaller holes are used 
 for transferring circuits, without shutting down the 
 
100 ELECTRICITY FOR ENGINEERS 
 
 dynamo. Smaller cables and plugs are used for 
 transferring. If it is desired to cut off circuit 5 from 
 machine 4, a plug is inserted in one of the small holes 
 at the right of 4, the other plug being inserted in one 
 of the holes at the left of 7. Circuit 5 would now be 
 short circuited, and the plug in the + of 5 can now be 
 transferred to the permanent connection in the + of 7, 
 and the cords running to 5 removed. If it is desired 
 to cut in a circuit, say circuit 6 onto machine 2, insert a 
 cord between the — of circuit 2 and the -f-of 6 and an- 
 other between the — of 6 and the + of 3. Now pull the 
 plug on the cord connecting — of 2 and the + of 3 and 
 insert the permanent connections. In cutting in cir- 
 cuits, if they contain a great number of lights, a long 
 arc may be drawn when the plug between 2 and 3 is 
 pulled, and it is sometimes advisable to shut down the 
 machine when making a change of this kind. 
 
CHAPTER V 
 
 MOTORS. — ALTERNATING CURRENT MOTORS. 
 
 Motors. Any dynamo may be used as a motor and con- 
 sequently we have as many types of motors as there are 
 types of dynamos. The pull of a motor depends upon 
 the repulsion and attraction between the lines of force, 
 or magnetism of the wire and core of the armature and 
 that of the fields. We have seen that in a dynamo, as 
 we force a wire through a magnetic field, current is 
 generated. The more current there is generated or 
 flowing in such a wire, the greater will be the expendi- 
 ture of power necessary to force such a wire through a 
 magnetic field; in other words, the currents flowing in 
 the wires of a dynamo armature, always tend to drive 
 the armature in a direction opposite to that in which it 
 is being driven. 
 
 If, then, instead of revolving a dynamo armature by 
 mechanical means, we connect it to a source of elec- 
 tricity and allow a current to flow through it we must 
 obtain motion, and the direction of this motion will 
 depend upon the direction in which the current flows, 
 so long as this current does not alter the magnetism of 
 the fields. 
 
 We have already seen that the electric motor is built 
 exactly like a dynamo; consequently, as its armature 
 revolves it not only does useful work, such as turning 
 whatever machinery it is belted to, but it also gener- 
 ates an electromotive force. For instance, if a motor, 
 running at full speed and receiving current from a 
 107 
 
108 ELECTRICITY FOR ENGINEERS 
 
 dynamo (Fig. 63), were suddenly disconnected by 
 opening the main switch, it would at once begin acting 
 as a generator and sending out current. This can be 
 easily seen with any motor equipped with a starting 
 box, such as shown; for the current from the motor 
 will continue to energize the fields and the little mag- 
 net M so as to hold the arm of the starting box until 
 the motor has nearly come to rest. If it were not for 
 the current generated by the motor, this arm would fly 
 back the instant the switch is opened. 
 
 The electromotive force set up by a motor always 
 opposes that of the dynamo driving it; that is, the 
 current which the motor tends to send out would flow 
 in the opposite direction to that which is driving it. 
 
 This may be compared, and is somewhat similar, to 
 the back pressure of the water which a pump is forcing 
 into a tank. If the check valves were removed and 
 the steam pressure shut off, the water would tend to 
 force the pump backward. 
 
 This electromotive force is called the counter elec- 
 tromotive force of the motor. The counter electro- 
 motive force of the motor varies with the speed of the 
 motor and also limits the speed of the motor, for it is 
 obviously impossible that a motor should develop 
 higher counter E. M. F. than the E. M. F. of the 
 dynamo driving it. 
 
 This highest possible speed of a motor is, then, that 
 speed at which its counter E. M. F. becomes equal to 
 the E. M. F. of the dynamo supplying the current, and 
 this is the speed which would be obtained were the 
 motor doing no work and running without friction. 
 This condition is impossible in practice, and the 
 counter E. M. F. of the motor is always less than the 
 E. M. F. of the dynamo. In order to speed up a 
 
ELECTRICITY FOR ENGINEERS 109 
 
 motor we must arrange it so that it must run faster in 
 order to develop an E. M. F. equal to that of the 
 dynamo; we can do this by lessening the number of 
 turns of wire on the armature, or by lessening the 
 magnetism of the fields. In doing so, however, we 
 also lessen the capacity of the motor for performing 
 work. 
 
 The power that can be obtained from an electric 
 motor depends upon two things: the current flowing in 
 its armature coils and the strength of magnetism devel- 
 oped in the fields. 
 
 Assuming the fields as remaining constant, the power 
 of the motor must then vary as the current flowing 
 through it. Suppose we have a motor being driven by 
 an E. M. F. of no volts and it is doing no work; it 
 will be running at full speed and its counter E. M. F. 
 will therefore also be very near no volts. If now a 
 load be thrown on this motor, it must get more current 
 .in order to develop the necessary power to carry the 
 load. 
 
 Throwing on the load will decrease the speed of this 
 motor, and consequently its counter E. M. F. will fall, 
 say to ioo volts. The E. M. F. of the dynamo being 
 no and the counter E. M. F of the motor ioo, there 
 will be considerable current forced through the arma- 
 ture of the motor, so that it can now handle the load. 
 
 The current in the armature at all times will equal 
 
 E - E' 
 
 — ~ — where E is the electromotive force of the 
 K 
 
 dynamo, E' the counter electromotive force of motor, 
 
 and R the resistance of the motor armature. In order 
 
 that a motor should keep a nearly uniform speed, for 
 
 varying loads, the resistance of its armature should be 
 
 very low, for then a slight drop in counter E. M. F 
 
no 
 
 ELECTRICITY FOR ENGINEERS 
 
 will allow considerable current to flow through the 
 armature. The above applies particularly to the shunt 
 motor shown in Fig. 63. In this diagram C is a double 
 pole fuse block, S the main controlling switch, R the 
 starting box, or rheostat, M the magnet, which holds 
 the arm of the starting box in place when it is broughc 
 
 figure 63. 
 
 over against it, F the fields, and A the armature of the 
 motor. 
 
 The current enters, say at the right hand fuse, and 
 passes to the starting box and along the fine wires 
 shown in dotted lines through the fields of the motor 
 and coil M to the other fuse. The fields of the motor 
 and the little magnet M are now charged, but as yet 
 
ELECTRICITY FOR ENGINEERS 111 
 
 there is no current passing through the armature and 
 no motion. We now slowly move the arm on the start- 
 ing box to the right; this admits a little current, 
 limited by the resistance in the starting box, to the 
 motor armature and it begins to revolve, and as we 
 continue to move the arm to the right, the armature 
 gains in speed because we admit more current to it by 
 cutting out more and more resistance. When the 
 armature attains full speed, the arm comes in contact 
 with the little magnet M, and is held there by magnet- 
 ism. The whole object of the starting box is to check 
 the inrush of current, while the armature is developing 
 its counter E. M. F. or back pressure. 
 
 When the armature has attained its normal speed, 
 the starting box is no longer in use. If for any reason 
 the current ceases to flow, the little magnet M loses its 
 magnetism and releases the arm, which (actuated by a 
 spring) flies back and opens the circuit so that, should 
 the current suddenly come on again, the sudden inrush 
 will not damage the armature. 
 
 In Fig. 64 are shown the connections of a series 
 wound motor with an automatic release spool on the 
 starting box of a sufficiently high resistance so it can be 
 connected directly across the circuit. This becomes 
 necessary since the field windings are in series with the 
 armature. 
 
 The speed of a series motor may be decreased by 
 connecting a resistance in series with the motor and 
 may be increased in speed by cutting out some of the 
 field windings. In electric railway work where two 
 motors are used on one car, they are usually connected 
 in series with each other in starting up and then in 
 parallel with each other while running at full or nearly 
 full speed. The series motor is well adapted to such. 
 
112 
 
 ELECTRICITY FOR ENGINEERS 
 
 work as electric railway work, or for cranes and so 
 forth, because it will automatically regulate its speed 
 to the load to be moved, exerting a powerful torque 
 at a low speed while pulling a heavy load. Such a 
 motor, however, requires constant attendance when the 
 
 FIGURE 64. 
 
 load becomes light, as it will tend to "run away" 
 unless its speed is checked. 
 
 In Fig. 65 we have a diagram of a compound wound 
 motor connected with a type of starting box that cuts 
 out the armature when current has been cut off the 
 lines supplying the motor, as before explained. In 
 addition to this there is another electro magnet which 
 is traversed by the main current on its path to the 
 armature. Should the motor be overloaded by some 
 
ELECTRICITY FOR ENGINEERS 
 
 113 
 
 means, the current flowing to the armature would 
 exceed the normal flow. The magnetism thus pro- 
 duced would overcome the tension of a spring on the 
 armature of the so-called "overload magnet" and cause 
 it to short circuit the magnet which holds the resist- 
 ance lever and allow it to fly back and open the arma- 
 
 FIGURE 65. 
 
 ture circuit. By so doing the liability of burning out 
 the armature due to overload is reduced to a minimum. 
 The compound motor may be made to run at a very 
 constant speed, if the current in the series winding of 
 the fields is arranged to act in opposition to that of the 
 shunt winding. In such a case an increase in the load 
 of a motor will weaken the fields and allow more cur- 
 rent to flow through the armature without decreasing 
 
114 
 
 ELECTRICITY FOR ENGINEERS 
 
 the speed of the armature, as would be necessary 
 in a shunt motor. Such motors, however, are not 
 very often used, since an overload would weaken the 
 fields too much and cause trouble. 
 
 If the current in the series field acts in the same 
 
 FIGURE 66. 
 
 direction as that of the shunt fields, the motor will 
 slow up some when a heavy load comes on, but will 
 take care of the load without much trouble. Fig. 66 
 shows a starting box arranged as a speed controller. 
 It differs from other starting boxes only in so far that 
 the resistance wire is much larger and that the little 
 
ELECTRICITY FOR ENGINEERS 115 
 
 magnet will hold the arm at any place we desire, so 
 that if we leave the arm at any intermediate point the 
 motor will run at reduced speed. This sort of speed 
 regulation can be used only where the load on the 
 motor is quite constant. If the load varies, the speed 
 will vary. Another and a better way of varying the 
 speed of motors consists in cutting a variable resist- 
 ance into the field circuit, as more resistance is cut 
 into the circuit the fields become weaker and the 
 motor speeds up. If possible, motors should be so 
 designed that they can operate at their normal speed, 
 and they will then cause little trouble. 
 
 Motors have much the same faults as dynamos, but 
 they make themselves manifest in a different way. 
 An open field circuit will prevent the motor from start- 
 ing and will cause the melting of fuses or burning out 
 of an armature. The direction of rotation can be 
 altered by reversing the current through either the 
 armature or the fields. If the current is reversed 
 through both, the motor will continue to run in the 
 same direction. A short circuit in the fields, if it cuts 
 out only a part of the wiring, will cause the motor to 
 run faster and very likely spark badly. If the brushes 
 are not set exactly opposite each other, there will also 
 be bad sparking. If they are not at the neutral point, 
 the motor will spark badly; brushes should always be 
 set at the point of least sparking. If it becomes neces- 
 sary to open the field circuit, it should be done slowly, 
 letting the arc gradually die out; a quick break of a 
 circuit in connection with any dynamo or motor is not 
 advisable, as it is very likely to break down the insula- 
 tion of the machine. 
 
 The ordinary starting box for motors is wound with 
 comparatively fine wire and will get very hot if left in 
 
116 ELECTRICITY FOR ENGINEERS 
 
 circuit long. The movement of the arm from the first 
 to the last point should not occupy more than thirty 
 seconds, and if the armature does not begin to move at 
 the first point the arm should be thrown back and the 
 trouble located. 
 
 Alternating Current Motors. By a proper combination 
 of two phase or three phase currents it is possible to 
 produce a revolving magnetic pole. By placing inside 
 of the apparatus which produces this revolving mag- 
 netic pole a suitable short circuited armature, this 
 armature will be dragged around by the revolving pole 
 in much the. same way that a short circuited armature 
 in a direct current machine would be dragged around 
 if the fields were revolved. Such a machine is called 
 an induction motor. The armature will revolve with- 
 out any current entering it from the external circuit. 
 This does away with commutators, collector rings, 
 brushes, brush-holders, and in fact many of the parts 
 which are so necessary in direct current machines. 
 The rapidity of the alternations in the external circuit 
 determines the speed of the motor. 
 
 Some alternating current motors are known as 
 "synchronous" motors. What is meant by synchro- 
 nous is, occuring at the same time, or in unison. As 
 an example, suppose two clocks are ticking just alike 
 so that the pendulums start and stop at the same time; 
 we would hear but one tick. These two clocks would 
 then be in synchronism. If an alternating current 
 generator has 32 field coils and revolves at the rate of 
 60 R. P. M., then a synchronous motor with only 4 
 field coils would revolve at the rate of 480 R. P. M. 
 This motor would operate in synchrony with the gener- 
 ator and yet would make 480 R. P. M. while the 
 generator made 60 R. P. M. 
 
CHAPTER VI 
 
 Fuses and Circuit Breakers. Fuses are metal wires or 
 strips, generally made of an alloy of lead and antimony, 
 the amount of each metal used being so proportioned 
 that the wire will melt at a certain temperature. This 
 metal is very similar to that used in the fusible plugs 
 in boilers. These fuse strips or fuse wires are placed 
 in the various circuits in such a manner that the current 
 must first flow through the fuse before entering the lights, 
 motors or other electrical apparatus. If a short circuit 
 should occur, there would be an excessive amount 
 of current flow through the fuse and the temperature 
 of the metal would be raised to the point where it would 
 melt and open the circuit. This would cut off the current 
 and save the electrical apparatus from being damaged 
 by the excessive current. Fuses are placed in the var- 
 ious circuits in accordance with the rules and regulations 
 of the National Board of Fire Underwriters. These rules 
 require a fuse to be placed in the circuit of every piece 
 of electrical apparatus liable to be short circuited, and 
 also at points where small wires are tapped onto larger 
 ones, unless the main fuse in the larger wire is small 
 enough to protect the smallest wire in the circuit. The 
 ordinary commercial fuse wire is not intended to melt 
 until the current has reached a strength of about twice 
 the number of amperes marked on the fuse. A few 
 good points to remember in regard to fuses are as fol- 
 lows: Unless the fuses are of the new enclosed type 
 (fuses entirely encased in small tubes) or unless they 
 are under the eye of a constant attendant, they should 
 be enclosed in fireproof boxes. This should be done 
 to minimize the chance of the red hot metal from a 
 117 
 
118 ELECTRICITY FOR ENGINEERS 
 
 melted fuse dropping into some inflammable material. 
 It is a very good plan to enclose all fuses. Fuses 
 placed in a hot room will blow at a lower increase in 
 current than those in a cool room. Always use copper 
 tipped fuses, both for the purpose of getting a good 
 contact at the binding screw and for the reason that 
 the blowing point of a fuse wire depends on the length 
 of the wire. Two pieces of fuse wire of the same 
 diameter, but of different lengths, will not blow with the 
 same current because the cooling effect of the terminals 
 is greater with the shorter fuse. 
 
 In the larger size fuse strips see that the contacts 
 between the fuse terminal and the binding post are free 
 from dirt and that there is plenty of contact between 
 them, otherwise the poor contact will heat up the ter- 
 minal and the fuse strip and cause it to blow at a much 
 lower current strength than that for which it is marked. 
 Oil between the contacts will cause heating and the 
 same result. 
 
 From the fact that when a fuse strip has blown the 
 current will be off the circuits which are protected by 
 the strip until the fuse has been replaced, and this 
 takes some time, another device known as the circuit 
 breaker has come into general use. The circuit breaker 
 is simply a knife switch equipped with a spring which 
 tends to open it, and is held in place by a small catch. 
 The current passing through the switch also passes 
 through the winding of a small solenoid on the inside 
 of which is an iron core. When the current passing 
 through the solenoid exceeds a certain amount, the 
 iron core is drawn up into the solenoid, and in doing 
 so strikes the catch holding the switch and releases it, 
 thus opening the switch and cutting off the current. 
 Circuit breakers are nearly always installed in the cir- 
 
ELECTRICITY FOR ENGINEERS 
 
 119 
 
 FIGURE 67. 
 
120 ELECTRICITY FOR ENGINEERS 
 
 cuits of generators, although fuses are also used. The 
 fuse is rated higher than the circuit breakei, so that 
 the circuit breaker will operate first and the fuse only 
 operates when the circuit breaker fails to work. Cir- 
 cuit breakers are also used to a large extent in protect- 
 ing large motors, and the small overload devices used 
 on motor starting boxes are simply circuit breakers. 
 Fig. 67 shows a view of an I-T-E circuit breaker. S is 
 the solenoid and I the moveable iron core. This core 
 is adjustable, by means of the washer W, so that it will 
 operate at whatever current desired. L is the catch 
 which holds the switch. Carbon contact pieces, C C, 
 are so arranged that the current is broken on them, 
 thus taking the arc off the blades. In Fig. 68 a dia- 
 gram of a circuit breaker used for the protection of a 
 motor is shown. In this case the circuit breaker is 
 double pole; while the one shown in the preceding fig- 
 ure is single pole. 
 
 For small work, such as tap lines and small motors, 
 the circuit breaker is too expensive to warrant its use, 
 but for capacities of 50 amperes and over it is advisible 
 to use the circuit breaker. . Circuit breakers are also 
 designed and used to prevent the liability of short cir- 
 cuits between generators connected in parallel, due to 
 the reversal of polarity of one of the dynamos. In other 
 words, should one of the dynamos become reversed in 
 polarity while working in parallel with other machines, 
 the polarity circuit breaker would open the machine- 
 switch and cut it out. Circuit breakers of this descrip- 
 tion are also used in charging storage batteries. Some- 
 times circuit breakers are referred to as overload 
 switches. The mechanical operation of these instru- 
 ments can be readily understood when examined, as 
 they are all of a very simple mechanical construction. 
 
ELECTRICITY FOR ENGINEERS 12 J. 
 
 LINE 
 
 ;r CIR CUIT 
 BREAKER 
 
 D.P.S.T. 
 SWITCH 
 
 FIGURE 68 
 
CHAPTER VTI 
 
 ALTERNATING CURRENT DYNAMOS 
 
 Alternating current dynamos^are operated upon the 
 same general principle of magnetic induction as that 
 involved in continuous current dynamos. The 
 mechanical construction, however, differs considerably 
 in the two types of machines. The current produced 
 in the two types is identical, but in the direct current 
 machine this current is rectified by means of a com- 
 mutator; that is, the current constantly flows out or; ; 
 wire and back in the other wire, never changing in 
 direction in the external circuit. In the alternating 
 current dynamo the current is sent to the line exactly 
 as it is generated in the armature, flowing out one wire 
 and back on the other and then reversing and flowing 
 out on the wire on which it has just flowed in, and back 
 on the wire on which it had formerly flowed out. An 
 illustration which will more fully explain this action 
 can be found by supposing the two ends of the cylinder 
 of a piston pump were connected by means of a pipe 
 and then, having done away with all the valve move- 
 ments, the pumps were started. At the beginning of 
 the stroke, water would be forced out one side of the 
 cylinder around the pipe into the other side of the 
 cylinder, and after the piston had reached the end of 
 the stroke and started back, the water would then take 
 a return course back to where it had started. In this 
 case the pump could be likened to the dynamo and 
 the pipe to the wires, and the current to the water 
 flowing back and forth. The form and winding of 
 122 
 
 s 
 
ELECTRICITY TOR ENGINEERS 
 
 123 
 
 alternating current dynamos varies considerably, but 
 they generally follow the plan shown in Fig. 69. In 
 the figure the pole pieces are alternately north (N) and 
 south (S), while the armature is wound with the same 
 number of poles, with the winding so arranged that 
 the poles alternate. The fields are excited by direct 
 current passing over the field coil windings. This 
 
 figure 69. 
 
 direct current is usually obtained from another source 
 aside from the current generated in the armature of 
 the alternating current dynamo. A separate dynamo, 
 called an exciter, is employed for supplying the cur- 
 rent to the fields. There are some types of so called 
 "composite wound alternating current dynamos" in 
 which a part of the current from the alternator arma- 
 
124 
 
 ELECTRICITY FOR ENGINEERS 
 
 ture is rectified or commutated by means of a commu- 
 tator mounted on the same shaft with the armature, 
 
 Armatures are wound 
 in two layers. 
 
 .__ upper coil. 
 
 lower » 
 
 FIGURE 70. 
 
 and this commutated current passed around the field 
 coils in a manner similar to the direct current com- 
 
ELECTRICITY FOR ENGINEERS 125 
 
 pound wound dynamo. In Fig. 70 we have a diagram 
 of connections of a composite wound machine made by 
 the General Electric Company. It will be noticed that 
 in connection with this dynamo we still employ a sepa- 
 rate direct current exciting machine. The object of this 
 composite winding is the same as with the compound 
 wound direct current dynamo, namely, regulation 
 under variable loads without the necessity of changing 
 the strength of the field exciting current from the 
 exciter dynamo. The winding of the alternate current 
 armature consists of the same number of armature coils 
 as there are pole pieces in the fields of the machine. 
 The outer end of the first armature coil is left free to 
 be connected to one of the collector rings, while the 
 other end of the coil is connected to the inner end of 
 the second coil; the outer end of the second coil is 
 connected to the outer end of the third coil, and so on 
 through the entire armature. In this class of winding 
 you can readily see that while the coils connected from 
 the underside or inner ends are under the influence of 
 one polarity of field magnetism, the armature coils 
 connected from the outer side are under an opposite 
 magnetic influence. The purpose of forming the arma- 
 ture circuit m this manner may be fully understood 
 when it is remembered that the magnetism from the 
 north pole of a magnet will induce a flow of electricity 
 in a coil of wire in a given direction, while the mag- 
 netism of the south pole will induce a flow of current 
 in an opposite direction. Now, for the reasons just 
 explained, the current in all of the coils of the arma- 
 ture will flow in the one direction, but as the armature 
 is rotated sufficiently to move the coils from the influ- 
 ence of one pole to the influence of the opposite pole 
 which is next to it, the action of all the magnetic poles 
 
126 ELECTRICITY FOR ENGINEERS 
 
 of the field reverse all the inductions in the armature 
 coils and cause the current to flow in an opposite 
 direction. The number of reversals occurring during 
 a revolution is determined by the number of poles that 
 the armature coils pass during one revolution. One of 
 these armature coils we will assume to be under a 
 north magnetic influence and in its rotation it passes 
 through a south magnetic influence, thence into a 
 north magnetic influence again. The current has now 
 alternated or reversed its direction of flow twice and 
 has passed through what is called one cycle. If the 
 current were making 120 alternations or passing 
 through 60 cycles in one second, it would be known as 
 making 60 cycles or alternating at the rate 7,200 alter- 
 nations per minute. These are the general terms used 
 in designating alternating currents. 
 
 By tracing out the circuits' in Fig. 70, it will be seen 
 tnat, assuming the current to be flowing into the col- 
 lector ring R, it will pass through the upper half of the 
 armature winding and out to the commutator C, where 
 a part of it will be commutated (or changed into direct 
 current), then flowing back around the lower half of 
 the armature windings and out to the other collector 
 ring R\ On the commutator C the upper line coming 
 from the armature is connected to each alternate seg- 
 ment, while the lower line is connected to the remain- 
 ing segments. The amount of current which is thus 
 rectified and flows around the two halves of the field 
 winding, which are connected in parallel, is regulated 
 by means of the German silver shunt. The fields are 
 also energized by the current generated in the small 
 dynamo known as the exciter. 
 
 In Fig. 71 is shown an alternating current dynamo 
 with its separate exciter The two collector rings are 
 
ELECTRICITY FOR ENGINEERS 
 
 127 
 
 shown immediately at the right of the armature, while 
 at the right of the collector rings is shown the commu- 
 tator from which the current for the composite winding 
 of the fields is taken. The current generated by the 
 alternator is regulated in the same way as with direct 
 current dynamos; that is, by varying the current sent 
 around the field windings. This is accomplished by 
 the use of a resistance box in series with the exciting 
 
 FIGURE 71. 
 
 current or by means of a resistance box connected in 
 the fields of the exciting dynamo. This latter regula- 
 tion is of course the more economical, as there would 
 be considerable energy wasted were a resistance used 
 in the main exciting circuit. Alternating currents are 
 generally used where currents are to be transmitted 
 long distances, as for instance, where power is derived 
 from a water fall situated some distance from the 
 
128 
 
 ELECTRICITY FOR ENGINEERS 
 
 point of use Its adaptability for such work is 
 apparent, because it can be generated at high voltages 
 and transformed down to any voltage desired. It 
 requires less copper to transmit it, due to the higher 
 voltages employed. By the aid of transformers it can 
 either be stepped up to a higher pressure or stepped 
 down to as low a pressure or voltage as .desired. 
 Another great advantage is that, after it has been 
 transmitted a considerable number of miles, by the aid 
 
 figure 72. 
 
 of a rotary converter it can be converted into direct 
 current. 
 
 Rotary transformers which transform the alternating 
 current to a direct current are simply alternating cur- 
 rent motors connected to direct current dynamos. 
 Sometimes these machines are mounted on the same 
 shaft; sometimes they are belted together, and in some 
 cases the same windings are used for both machines; a 
 commutator being mounted at one side of the armature 
 
ELECTRICITY FOR ENGINEERS 129 
 
 from which direct current is taken while the alter- 
 nating current is taken into the armature on a pair of 
 collector rings on the opposite end of the shaft. In 
 Fig. 72 is shown a view of a rotary transformer where 
 the alternating current is taken in at the right, and 
 direct current taken off at the commutator on the left. 
 By single phase we understand that the current flows 
 out, gradually increasing in strength, then dying away 
 and reversing in direction and again increasing and 
 dying away. This action is shown by the curve in 
 
 figure 73. 
 
 Fig. 73. Although the single phase alternating cur- 
 rent system is in advance of the direct current system 
 for electrical power transmission, because permitting 
 electrical power to be transmitted long distances at 
 high potential, which can be readily increased or 
 reduced by means of transformers, the single phase 
 system is limited by the difficulty in obtaining a satis- 
 factory self starting motor; therefore the use of the 
 single phase current has been confined almost entirely 
 to transmitting current for lighting. The development 
 of the polyphase (two phase_ and three phase) alter- 
 
130 
 
 ELECTRICITY FOR ENGINEERS 
 
 nating systems possess all the advantages of the single 
 phase system and at the same time permits the use of 
 motors having not only most of the valuable features 
 of the continuous current motors, but also some advan- 
 
 figure 74. 
 
 tages over them. In the two phase system two cur- 
 rents displaced 90 degrees from each other and 
 otherwise exactly similar to the single phase currents 
 are used. In the three phase system three currents 
 separated 120 degrees are used. These currents are 
 shown in Fig. 74. 
 
 FIGURE 75. 
 
 In Fig. 75 is shown the principle upon which the 
 transformer used in alternating current work are opera- 
 ted. Two separate coils of wire are wound on a ring 
 
ELECTRICITY FOR ENGINEERS 
 
 LSI 
 
 of laminated iron. One of the coils contains a num- 
 ber of turns of fine wire, while the other contains only 
 a few turns of large wire. When an alternating cur- 
 rent is sent around the coils of fine wire, generally 
 called the primary, a current will be induced in the 
 coil of heavy wire, or secondary. The amount of cur- 
 rent induced in the larger wire will be relatively 
 greater in amperes and less in potential than that of 
 the fine wire circuit. This ratio is almost entirely 
 dependent upon the relative number of turns existing 
 
 FIGURE 76. 
 
 between the large and the small wires. To illustrate, 
 suppose we had a current of 10 amperes at a pressure 
 of 1,000 volts in the primary, and there were ten times 
 as many turns of wire in the primary coil as in the 
 secondary, then we would get a current of ioo amperes 
 at a pressure of ioo volts in the secondary coil. This 
 same relation would hold true whatever the ratio 
 between the number of turns on the two coils might 
 be. In Fig. 76 is shown a core of iron having on one 
 end a primary coil connected to a battery. On the 
 other end of the core is another coil connected to the 
 
132 ELECTRICITY FOR ENGINEERS 
 
 ends of which is an incandescent lamp. By making 
 and breaking the battery circuit the lamp may be made 
 to flash up, due to the great voltage induced in the 
 secondary coil. This is a good thing to remember 
 when working with a dynamo or motor. Do not 
 quickly break the shunt field connection, as the 
 increased voltage due to the current induced by the 
 field magnet when the circuit is broken is liable to 
 puncture the insulation and necessitate the re-winding 
 of the field coil. 
 
CHAPTER VIII 
 METERS 
 
 Volt and Ampere Meters. Two of the most important 
 instruments used in electrical work are the voltmeter 
 and amperemeter, the latter generally called ammeter. 
 Classed with these instruments, is a meter of an im- 
 portant nature called the wattmeter. We will first 
 become acquainted with the voltmeter, which is an 
 instrument, as its name implies, for measuring the 
 voltage or potential or electromotive force between two 
 wires. The general construction of this instrument .is 
 shown in Fig. JJ. 
 
 In this diagram we show an instrument on the order 
 of the Weston meter. This will serve as a good illus- 
 tration that the operation of meters is very similar to 
 the operation of motors. A permanent magnet, M, 
 causes a magnetic flux across the air gap G, and 
 situated in this gap is a bobbin, B, on which is wound a 
 number of convolutions or turns of copper wire. The 
 bobbin is made to revolve on jeweled bearings. The 
 object of the jewel bearing is to have the instrument as 
 much devoid of mechanical friction as possible. Two 
 springs, S, one above and one below the bobbin, carry 
 the current to the movable part of the meter. If the 
 current is now caused to flow around the coil of wire, 
 it will produce a torque or twist which will move the 
 bobbin again the two hair springs, S. Like magnetic 
 poles repel each other and unlike magnetic poles 
 attract each other. The current flowing around the 
 133 
 
134 
 
 ELECTRICITY FOR ENGINEERS 
 
 movable bobbin produces magnetism, and the quantity 
 or strength of magnetism so produced is proportional 
 to the amount of current which the pressure or voltage 
 
 figure 77. 
 
 will force through the winding of the movable bobbin 
 so that the bobbin will continue to move until the 
 torque exerted by the current equals the counter torque 
 exerted by the spiral springs. A pointer, fastened to 
 
ELECTRICITY FOR ENGINEERS 135 
 
 the shaft upon which the bobbin is mounted, passes 
 over a graduated scale and indicates the pressure or 
 volts. The capacity of this meter in volts will vary as 
 the resistance of the wire connected in series with the 
 bobbin varies. We will assume that we have a meter 
 whose pointer reads from o to 125 volts. If we desired 
 this same meter to read from o to 250 volts, we would 
 put a resistance in the meter which would be twice as 
 great as the one contained in the meter when reading 
 from o to 125 volts. The permanent magnet of this 
 meter is made of Tungsten steel, and this steel is arti- 
 ficially aged so that when the instrument leaves the 
 factory the magnetizing power of the magnet will 
 remain constant for a number of years. The current 
 is brought into the instrument through the binding 
 posts A and C, but before passing through the wire on 
 the bobbin the current must pass over a path of very 
 high resistance, R. This resistance is proportioned to 
 the amount of pressure the meter is made to indicate, 
 and in commercial construction instead of making 
 bobbins of variable resistances, the bobbins are all 
 made alike, and this dead resistance, R, is varied to 
 comply with the pressure that it is to indicate with the 
 instrument. In voltmeters used on a 500 to 600 volt 
 circuit, this resistance will measure from 65,000 to 
 75,000 ohms. The current which flows through the 
 winding on the bobbin at full voltage is very small, and 
 when registering no volts amounts to about one seven- 
 hundredth of an ampere. Since it is the number of 
 ampere turns that produces the magnetic density in an 
 electro magnet, it can be seen that even one seven- 
 hundredth of an ampere, if passed around a bobbin a 
 considerable number of times, will produce quite a 
 strong magnetic flux and pull. Voltmeters are often 
 
136 ELECTRICITY FOR ENGINEERS 
 
 referred to as being "dead beat." What is meant by 
 dead beat is the tendency of the pointer to move from 
 one position to another with very little or no swinging 
 to and fro. In this type of voltmeter this dead beat 
 effect is producedin the following manner: The core 
 of the bobbin B being constructed of copper, when a 
 current flows over the winding of the bobbin and causes 
 it to revolve, eddy currents are produced in the copper 
 (in much the same way that current is produced in the 
 revolving armature of a dynamo), and these eddy cur- 
 rents tend to arrest the motion of the bobbin. In the 
 best voltmeter construction the resistance wire used is 
 made of a metal which will not vary much in resistance 
 at different temperatures. It can readily be seen that, 
 were a meter which was constructed and correctly 
 calibrated at 70 ° F., surrounding temperature, mounted 
 on switchboard in an engine-room with the temperature 
 at 90 or 95°, the meter would uot register absolutely 
 correct, because the resistance of the wire would be 
 considerably increased, due to the increase of the sur- 
 rounding temperature. The effect of this would be a 
 smaller flow of current at an equal voltage through 
 the bobbin in the meter, and consequently a smaller 
 amount of magnetism and a lower reading of the in- 
 strument. 
 
 We will assume that a copper cable of about the size 
 of one's wrist is conducting a current of about 
 three thousand amperes. Now, if a monkey wrench or 
 hammer were to be lying within a few inches of this 
 cable, before current was flowing, the monkey wrench 
 or hammer would be attracted to the cable. The 
 rapidity with which the monkey wrench would be 
 attracted to the cable would be proportional to the 
 weight of the iron in the wrench and the amount of the 
 
ELECTRICITY FOR ENGINEERS 137 
 
 current flowing through the cable. This, I think, will 
 explain an electrical phenomenon which will assist us 
 to understand what are called the magnetic vane volt- 
 meters and ammeters. This principle is shown in 
 Fig. 7 S. 
 
 A certain amount of current passing over the path 
 A, which consists of several turns of wire, will attract 
 an iron form, B, mounted on the spindle with the 
 
 FIGURE 78. 
 
 pointer. The attraction will be proportional to the 
 amount of current flowing over the copper conductor. 
 The advantage of such an instrument is its simplicity, 
 but the disadvantage is its inaccuracy. Its simplicity is 
 apparent, and its inaccuracy is due to the residual 
 magnetism that remains in the iron part B when the 
 current through the conductor has been reduced. 
 When the indicator is caused 1o move upward on the 
 scale, the instrument will register practically correct, 
 
138 ELECTRICITY FOR ENGINEERS 
 
 but as the flow of current over the conductor A dimin- 
 ishes or decreases, the residual magnetism remaining 
 in the iron part B will have a tendency to cause it to 
 lag back. Amperemeters are constructed on practi- 
 cally the same lines as explained in the construction of 
 voltmeters, except that in ammeters the whole current 
 to be measured passes through the coil A, this coil 
 being made of comparatively few turns of large wire, 
 while in voltmeters the resistance is very high. 
 Ammeters are placed in series with one of the leads 
 and voltmeters in shunt with the current to be meas- 
 ured. In some ammeters a resistance block, usually 
 called a shunt, is employed, over which the main cur- 
 rent is caused to flow, and the ammeter is connected to 
 both ends of this resistance block. In this way only a 
 very small portion of the total current is caused to 
 flow through the ammeter. In this case a milli-volt- 
 meter, with the scale graduated to amperes, is 
 employed. By Ohm's law we know that the voltage is 
 equal to the current times the resistance, E = CR. 
 The resistance remaining constant, the voltage is pro- 
 portional to the current, so that the amount of current 
 sent through the milli-voltmeter or ammeter is exactly 
 proportional to the current flowing through the shunt. 
 Fig. 79 shows connections for ammeters which carry 
 the entire current and those used with a shunt. 
 
 The object of such a construction is apparent. In 
 the installation of the switchboard, where each 
 ammeter registers several thousand amperes, it is not 
 necessary to construct the large conductors in such a 
 manner that the total current is caused to flow through 
 the ammeter. For each 1,000 amperes passing over 
 the shunt only about one-half an ampere will pass 
 through the ammeter, and the little bobbin will then 
 
ELECTRICITY FOR ENGINEERS 
 
 139 
 
 cause a deflection of the pointer in the meter and the 
 pointer will register 1,000 amperes. Meters of this 
 description are usually connected to their resistance 
 blocks by a pair of No. 16 flexible lamp cords. When 
 installing meters of this class, never cut off any of the 
 
 /~\ 
 
 </ 
 
 gHUHt 
 
 t<* 
 
 FIGURE 79. 
 
 flexible cord which is supplied with the ammeter, as 
 the resistance of the cord becomes a part of the resist- 
 ance in the meter. By cutting off some of this cord 
 it can be readily seen that the meter will register more 
 current than it should. 
 
140 
 
 ELECTRICITY FOR ENGINEERS 
 
 Another kind of meter is constructed on the 
 solenoid principle, and is shown in Fig. 80. In this 
 instrument the helix is a bare copper wire and is wound 
 in an open coil form. It is curved in the shape of a 
 segment of a circle, the center of which is at the pivot 
 on which the needle is suspended. The pointer or 
 needle is attached and projects downward to the scale. 
 The helix is made of copper rod or is cast to the shape 
 
 
 ./^ * ^^"^ m 
 
 
 \ \ / 1\ \ 
 \ » / / 1 1 
 
 V * / / J I 
 
 \ V / / J 
 
 FIGURE 80. 
 
 required. Being of an open coil type, it is not neces- 
 sary that it be insulated with insulating material 
 because the air spaces between the turns becomes the 
 insulation. Although not the best insulator by any 
 means, there are few substances which possess better 
 insulating qualities than air, although on account of its 
 absorption of moisture, it becomes often a much poorer 
 insulator than many other materials. In this type of 
 
ELECTRICITY FOR ENGINEERS 
 
 141 
 
 instrument it will be seen that as the number of 
 amperes flowing over the coil is increased it produces 
 an increased electromagnetic pull on the iron section 
 or core entering it. As this electro magnetic pull is 
 
 FIGURE 81. 
 
 increased, the core moves up into the helix and causes 
 a deflection of the pointer across the scale on the 
 instrument. This type of instrument has the same 
 objection as that of the magnetic vane instrument, 
 
142 ELECTRICITY FOR ENGINEERS 
 
 namely, residual magnetism of the iron, and hence 
 error in the reading while the current flowing is being 
 diminished. 
 
 Another style of simple ammeter or voltmeter is 
 shown in Fig. 81. This instrument consists of a frame 
 made of non-magnetic material, around which the wire 
 is wound, the ends of the wires being connected to the 
 binding posts. The armature of this instrument, as in 
 all other similar instruments, is connected to the 
 pointer, and may be constructed of several pieces of 
 iron. The principle of its working is similar to that 
 described above, in that the armature tends to set 
 itself at right angles, to the wire through which the 
 current passes. This style of instrument is used where 
 current is liable to flow in either direction. 
 
 A simple form of meter for measuring current is 
 shown in Fig. 82. Here we have an amperemeter 
 which consists of a strip of copper fastened to a block 
 of wood or other insulating material, as shown at A. 
 A piece of magnetized steel, B, to which a needle, C, is 
 attached, swings on a pivot or shaft which is suspended 
 at the bridge D. A scale is provided from which the 
 number of amperes flowing can be obtained. The 
 needle is rigidly attached to the magnetized steel B and 
 moves with it. The action of this instrument is as fob 
 lows: When a magnetized piece of steel is brought near 
 to a conductor through which a current of electricity 
 is passing, the magnetized steel tends to set itself at 
 right angles to the direction of the current. The 
 stronger the current becomes, or the more highly mag- 
 netized the piece of steel may be, the nearer to a posi- 
 tion of right angles the armature will assume. It is 
 not practical to use this construction of an instrument 
 to cover a range of more than one-half of a right 
 
ELECTRICITY FOR ENGINEERS 
 
 143 
 
 angle, for when the needle moves through an angle of 
 about 50 degrees, it will require a much greater 
 increase of current in proportion to the movement to 
 obtain the deflection and the additional degree of the 
 indicating needle. Such an instrument as the above 
 may also be used to determine the direction of flow of 
 
 FIGURE 82. 
 
 current in a wire and is sometimes quite- convenient on 
 arc circuits which are liable to have their currents 
 reversed either by wrong plugging of the board or the 
 reversing of polarity in the dynamo. 
 
 Voltmeters and ammeters used with alternating cur- 
 rents must, of course, differ in some respects from 
 
144 ELECTRICITY FOR ENGINEERS 
 
 those employed for continuous currents. Alternation 
 of the current does not permit the utilizing of the mag- 
 netic effect of the current to the same extent or in 
 exactly the same manner as continuous currents, but 
 when the cores of magnets are built up of soft iron 
 wires of small diameter, the resulting attraction 
 between coil and core is similar, though not so strong 
 as between a coil carrying direct current on a solid 
 iron core. 
 
 Another type of ammeter and voltmeter used with 
 alternating or direct current is known as the hot wire 
 instrument. A rather long, thin platinum wire is 
 placed in the circuit and so arranged that its elonga- 
 tion or expansion resulting from the heating effect of 
 the current passing over it is made to operate a pointer 
 mounted on a jeweled bearing. These instruments 
 absorb but little current and are claimed to be per- 
 manently correct. This class of instrument may be 
 used on either direct or alternating current, and when 
 used on alternating current the frequency or alterna- 
 tions make no difference in the operation of the instru- 
 ment. It is also unaffected by external magnetic fields, 
 such as a neighboring dynamo or motor, and can be 
 used close to a wire conducting current without being 
 affected in its accuracy. When used as an ammeter it 
 is connected in shunt with a resistance placed in the 
 main circuit in the same manner as described for direct 
 current ammeters, and in this way but a very small 
 proportion of current is made to pass over the instru- 
 ment. Separate resistances are also furnished with the 
 instruments; so that by connecting these in series with 
 the instrument they can be used over a very wide range. 
 
 Wattmeters. A few years ago, where current was 
 sold by central stations to consumers, or in any other 
 
ELECTRICITY FOR ENGINEERS 145 
 
 place where it was desirable to measure the power fur- 
 nished in the form of electricity, there were several 
 kinds of differently constructed meters used to measure 
 the amount of current. Some of these meters were 
 based on the chemical action of the current; the current 
 in passing to the work depositing metal from one plate 
 to another. The plates or terminals of the meters 
 were weighed before being placed in the circuit and 
 again weighed on being taken out, the amount of metal 
 having been deposited determining the amount of cur- 
 rent used, as explained in the fore part of the book. 
 Of late, however, most of the recording wattmeters in 
 use are operated on the principle of the Thomson 
 wattmeter. As has been explained under the definition 
 of units, the work done (watts) is equal to the current, 
 (amperes) multiplied by the electromotive force (volts), 
 or W = C x E. For a wattmeter to register correctly it 
 must take a record of the volts and amperes. 
 
 The Thomson wattmeter is simply a small motor in 
 which the armature is used as a voltmeter and the 
 fields as an ammeter. The armature is wound with fine 
 wire and is connected to a small commutator made up 
 of metal bars. Two very thin metal brushes bear on 
 this commutator and carry the current to and from the 
 armature. The armature is connected across the mains 
 in just the same wav as a voltmeter would be connected. 
 The fields are wound with a coarse wire and are con- 
 nected in series with the main circuit, thus acting as an 
 ammeter. It can readily be seen that with the arma- 
 ture influenced only by the voltage, and the fields by 
 the current passing through the mains, the two acting 
 together will correctly measure the power supplied. 
 As the voltage rises or lowers, the speed of the arma- 
 ture will be affected accordingly, and as the current 
 
146 
 
 ELECTRICITY FOR ENGINEERS 
 
 through the fields varies the electromagnetic effect 
 produced by the fields and in which the armature 
 revolves will vary, thus also varying the speed. By 
 reference to Fig. 83, the fields F F are connected in 
 series with one of the mains and the armature A is. 
 
 FIGURE 83. 
 
 connected across the mains. Fig. 84 is a simplified 
 diagram. Attached to the shaft on which the arma- 
 ture rotates is a copper disc which revolves between 
 the poles of a permanently magnetized steel magnet. 
 Eddy currents are generated in this copper disc as the 
 
ELECTRICITY FOR ENGINEERS 147 
 
 armature rotates, thereby acting as a brake against 
 which the armature must work. Connected to the top 
 of the shaft is a train work of wheels which move small 
 pointers over the dials on the face of the instrument 
 and record the amount of current which has passed 
 through the meter. As no iron is used in either the 
 armature or fields of the motor, the meter can be used 
 on either alternating or direct current. 
 
 In Fig. 85 we show a two wire meter with the case 
 removed. 
 
 In Fix. 86 a three wire meter is shown. 
 
 Directions for Reading Meter Dials. To correctly read 
 the sum indicated on the dial of a recording meter, the 
 
 MA/VSWVWV 
 
 directions given herewith should be thoroughly under- 
 stood and carefully followed. 
 
 The figures (1,000, 10,000, etc.) under or over each 
 dial refer to a complete revolution of the hand at that 
 dial. 
 
 Therefore, each division on the dial to the extreme 
 right indicates not one, two, three, or four thousands 
 of units, but one, two, three, or four hundreds of units. 
 
 A complete revolution of the hand counts one thou- 
 sand, and will have moved the hand on the second dial 
 one division. Thus in reading Diagram No. 6, Fig, 
 87 the first dial (that on the extreme right) indicates 
 700, not 7,000. 
 
148 
 
 ELECTRICITY FOR ENGINEERS 
 
 A hand to be read as having completed a division, 
 must be confirmed by the dial before it (to the right). 
 It has not completed the division on which it may 
 appear to rest, unless the hand before it has reached 
 
 FROM GENERATOR 
 
 FIGURE 85. 
 
 or passed o, or, in other words completed a revolution. 
 For this reason it will be found easier and quicker to 
 read a dial from right to left, as shown by reading Dia- 
 gram No. 2, Fig. Sy. 
 
ELECTRICITY FOR ENGINEERS 
 
 149 
 
 The first dial (the extreme right) indicates 900. The 
 second hand apparently rests on o, but since the first 
 rests only on 9 and has not completed its revolution, 
 
 FIGURE 86. 
 
 the second dial also indicates 9. This 9, placed before 
 the 900 already obtained, gives 9,900. 
 
 This is also true of dial 3. The second hand, at 9, 
 has not quite completed its revolution, so the third has 
 not completed its division, therefore another 9 is 
 
1/50 ELECTRICITY FOR ENGINEERS 
 
 obtained, making 99,900. The same is true of dial 4, 
 making 999,900. 
 
 The last dial (the extreme left) appears to rest on 1, 
 but since the fourth is only 9, the last has not com- 
 pleted its division, and therefore reads o. The total 
 reading is 999,900. 
 
 The hands are sometimes slightly misplaced. In 
 Diagram No. 8 the first diagram (the extreme right) 
 reads o, which gives. 000. The hand of the second 
 dial is misplaced. As the first registers o, the second 
 should rest exactly on a division; therefore it should 
 have reached 8, making 8,000. The third hand is 
 apparently on 3, but since the second hand is at 8, the 
 third cannot have completed a division and must, 
 therefore, indicate 2. The two remaining dials are 
 correct, and make a total of 9,928,000. 
 
 In Diagram No. 9, the second dial hand is mis- 
 placed, for since the first indicates 1, the second should 
 have just passed a division. As it is nearest to 8 it 
 must have just passed that figure. The remaining 
 three dials are approximately correct. The total indi- 
 cation is 9,918,100. 
 
 In Diagram No. 10, the second and fourth dial 
 hands are slightly behind their correct position, but 
 not enough to mislead in reading. The total indica- 
 tion is 9,928,300. 
 
 By carefully following these directions little diffi- 
 culty will be found in reading the dial, even when the 
 hands become misplaced. . 
 
 Note whether there is a constant marked on the 
 dial. If there is, multiply the dial reading by the 
 constant. With constant y 2 , multiply by l / 2 ; that is, 
 divide by 2. 
 
 The "constant" of a meter is the term applied when 
 
ELECTRICITY FOR ENGINEERS 
 
 151 
 
 <0 
 
 No.l- 1.111/100 
 
 o^ (6 
 
 No.6 = 99.700 
 
 ^OtASON REC0« 0//V( 
 WATT METER 
 
 ioooooooqenERAL ELECTRIC CO. ,0 °° 
 
 WWatt Hrs. Constant Watt Hrs.CJ 
 
 WATT METER, 
 
 --GENERAL ELECTRIC CO. "><"» ^ 
 
 (Jwart Hrs Constant Watt Hrs.vJ 
 No. 3- 1.000.100 
 
 ioooooooqeneral ELECTRIC CO. 100 ° -. 
 vJwatt Hrs. Constant Wan HrsW 
 
 No.4 =9.999.400 
 
 'O 
 
 c 
 
 (fS , \^SON RE CO^ c ^o'^ 
 X^y WATT METER X^fV 
 
 .oooooooQENERAL ELECTRIC CO. ">°° 
 
 vJWatt Hrs. Constant Watt Hrs.CJ 
 
 No. 5 =^909.100 
 
 O 
 
 'b 
 
 WATT METER 
 
 100000006ENERAL ELECTRIC CO. «><>° ^ 
 VJWatt Hrs. Constant Watt Hrs.Vj 
 
 \^sj/ WATT METER 
 
 10 oooooo G ENERAL ELECTRIC CO 1000 ^ 
 
 (J Watt Hrs. Constant Watt Hrs VJ 
 
 No.7 = 9.912.100 
 
 o 
 
 Ov 
 
 o 
 
 WATT METER 
 
 GENERAL ELECTRIC CO. 100 ° 
 
 Hrs. Constant Watt Hh. 
 
 Q 
 
 No. 8 =9.928.000 
 
 o 
 
 WATT METER 
 
 iooooooogenERALELECTRIC CO " 00 ~ 
 
 \J Watt Hrs. Constant Watt Hrs \Jj 
 
 No.9=9.918.100 
 
 <0 
 
 WATT METER 
 
 .ooooowqenERAL ELECTRIC CO. ,00 ° ^ 
 
 \Cj Watt Hrs. Constant Watt Hrs.CJ 
 
 '6~ 
 
 No.10 = 9. 928.300 
 
 1000000 100000 
 
 "31 
 
 Vjj/ WATT METER XjjJ 
 
 .oooooooqenERAL ELECTRIC CO. ,00 ° ~ 
 .Uwatt Hrs. Constant Watt HrsJJ 
 
 FIGURE 87. 
 
152 ELECTRICITY FOR ENGINEERS 
 
 the meter is constructed to run at a lower speed than 
 what would be necessary to measure the true number 
 of watts which has passed through it. For instance, 
 if the constant is 2 and the meter has registered 5,000 
 watt-hours, then the meter having run only half as fast 
 as it should, we multiply 5,000 by 2, which gives us 
 10,000 watts as the actual amount that has passed 
 through the meter. This scheme becomes necessary in 
 order to register a large amount of current with a 
 meter small in bulk or size. For convenience the 
 maker often takes a 220 voltmeter which would read 
 the number of watts direct on the dial at 220 volts and 
 sells it for a 110 voltmeter by marking a constant on 
 the dial of the meter. 
 
CHAPTER IX 
 
 Arc Lamps. The principle on which the arc lamp oper- 
 ates is shown in Fig. 89. Current is caused to flow 
 from one carbon point to another through a space or gap 
 between the carbons. The heat of the arc is sufficiently 
 high to disintegrate the carbon and reduce it to a vapor, 
 this vapor filling the space between the carbon points. 
 The current passes over this space in a bow-shape path 
 or arc, and it is from this fact that the lamp gets its 
 name. The arc is constantly moving, and generally 
 revolves around the carbon points. This can be easily 
 seen by looking closely at a burning lamp through a 
 smoked glass. After a lamp has been burning for 
 some time on direct current the carbons assume the 
 shape shown in Fig. 88, the upper or positive carbon 
 assuming a cup shape, while the lower carbon gener- 
 ally burns to a point. This cup shape formation on 
 the upper or positive carbon acts as a reflector to 
 throw the light downward. The positive carbon burns 
 away about twice as fast as the negative carbon and 
 lamps must be trimmed accordingly. Sometimes the 
 current feeding arc lamps (on direct current systems) 
 becomes reversed, either through the dynamo reversing 
 its polarity or through wrong plugging of the switch- 
 board. The lamps will now burn "upside down," or, 
 in other words, the bottom carbon will be the positive 
 one. In such a case, if let go, the carbon holders of 
 the lamp will be burned and the lamp will burn for 
 only half the time for which it was intended, owing to 
 the fact that the lower or negative carbon is only one- 
 half as long as the upper or positive carbon. Such 3 
 153 
 
154 ELECTRICITY FOR ENGINEERS 
 
 condition can be determined by either of the following 
 ways: See if the light is being thrown downwards. 
 See which carbon is burning away the faster. Raise 
 the carbons and notice the formation of the carbon 
 tips. When the carbons are separated it will be 
 noticed that the tip of one carbon is considerably hot- 
 ter than the other and is heated a longer distance from 
 the point; this is the positive carbon. 
 
 FIGURE 88. 
 
 The action of the arc lamp used on direct current 
 constant current systems is shown in Fig. 89. Current 
 passes through wire T and over the coarsely wound 
 solenoid M, thence down to the carbon, across the 
 arc or crater, into the negative carbon and out again 
 on the wire T'. The regulating action is as follows: 
 A coil M', constructed of fine wire and of high resist- 
 ance, is connected in shunt across the arc. The action 
 of the current flowing through the solenoid M across 
 
ELECTRICITY FOR ENGINEERS 
 
 155 
 
 Q T 
 
 to 
 
 the crater or arc produces a magnetic pull on the 
 solenoid core A and causes a separation of the car- 
 bons. As these carbons burn away the resistance 
 across the crater increases and a very small portion of 
 the main current is caused to flow through the shunt 
 coil M\ The magnetic pull of the shunt solenoid 
 overcomes that of the series solenoid with the result 
 that the solenoid core A is drawn into coil M' and the up- 
 per carbon thus lowered, de- 
 creasing the gap at the arc. In 
 this way a constant regulation 
 is going on, tending to keep 
 the two carbons at a uniform 
 distance apart. The upper car- 
 bon rod is held by means of a 
 clutch. When the carbons have 
 burned away, so that the lower- 
 ing of the solenoid does not 
 lower them to the proper ex- 
 tent, the clutch is released and 
 the carbon drops, thus feeding 
 the lamp. Some lamps are 
 manufactured wherein the lower 
 
 carbon is positive. This causes the light emitted from 
 the crater to be projected upwards. The arc lamp 
 frame is supplied with a shade on which the light cast 
 from the arc is reflected downward. The advantage of 
 this system is to obtain a better diffusion and distribu- 
 tion of the light beneath the arc lamp. This lamp 
 is not now generally used. 
 
 Fig. 90 shows a diagram of connections for the 
 improved Brush arc lamp. These lamps are used on 
 constant current or series systems and their action is 
 as follows; 
 
156 
 
 ELECTRICITY FOR ENGINEERS 
 
 The carbons should rest in contact when the lamp is 
 cut out. When the switch is opened, part of the cut- 
 
 figure 90. 
 
 rent from the positive terminal hook P goes through 
 the adjuster to the yoke and thence through the carbon 
 
ELECTRICITY FOR ENGINEERS 157 
 
 rod and carbons to the negative terminal hook N. 
 The remainder of the current goes to the cutout 
 block, but. as the cutout block is closed at first, the 
 current crosses over through the cutout bar to the 
 starting resistance, and so to the negative side of 
 the lamp. A part of it, however, is shunted at the 
 cutout block through the coarse wire of the magnets 
 and so to the upper carbon rod and carbons and- out. 
 This shunted current energizes the magnet and so 
 raises the armature which opens the cutout and at the 
 same time establishes the arc by separating the car- 
 bons. 
 
 The fine wire winding is connected in the opposite 
 direction from the coarse wire winding, and its attrac- 
 tion is therefore opposite. When the arc increases in 
 length, its resistance increases, and consequently the 
 current in the fine wire is increased. The attraction of 
 the coarse wire winding is therefore partly overcome 
 and the armature begins to fall. As it falls, the arc is 
 shortened and the current in the fine wire decreases. 
 The mechanism feeds the carbons and regulates the 
 arc so gradually that a perfect, steady arc is main- 
 tained. 
 
 The fine wire of the magnets is connected in series 
 with the winding of a small auxiliary cutout magnet 
 at the top of the mechanism. 
 
 This magnet, which also has a supplementary coarse 
 winding, does not raise its armature unless the voltage 
 at the arc increases to 70 volts. The two windings 
 connect at the inside terminal on the lower side of 
 auxiliary cutout magnet, and the current from the fine 
 wire of the main magnets passes through both wind- 
 ings and then to the cutout block and so to the starting 
 resistance and out. 
 
158 ELECTRICITY EOR ENGINEERS 
 
 If the main current through the carbon is interrupted 
 (as by breaking of the carbons) the whole current of 
 the lamp passes through the fine wire circuit. Before 
 this excessive current has time to overheat the fine 
 wire circuit, it energizes the auxiliary cutout mag- 
 net, and closes a circuit directly across the lamp 
 through the coarse wire on the auxiliary cutout to 
 the main cutout block, and thence to the negative 
 terminal. 
 
 The auxiliary cutout operates instantly, and prevents 
 any danger to the magnets during the short period 
 required for the main armature to drop and throw in 
 the main cutout. When the main cutout operates, the 
 armature of the auxiliary cutout falls, because there is 
 not sufficient current in that circuit to energize the 
 magnet. 
 
 The voltage at which the auxiliary cutout magnet 
 operates depends on the position of its armature, 
 which is regulated by the screw securing the armature 
 in position. It should not be adjusted to operate at 
 less than yo volts. 
 
 One of the three methods of suspension maybe used 
 for Brush lamps. If chimney suspension, which is the 
 most common, is adopted, the wire, cable or rope used 
 :o suspend the lamp must be carefully insulated from 
 the chimney. For this purpose a porcelain insulator 
 should be inserted between the support and the lamp, 
 as shown in Fig. 91. 
 
 Hook suspension may be used to advantage in some 
 places, but great care must be taken to insulate the 
 supporting wires from any conductors, as the hooks 
 form the terminals of the lamps. 
 
 The most convenient arrangement for indoor use is 
 to suspend the lamp from a hanger board. The porce- 
 
ELECTRICITY FOR ENGINEERS 
 
 1.59 
 
 iain base of the hanger board prevents short circuits 
 or grounds. 
 
 A protecting hood is not necessary for outdoor use, 
 as the lamp chimney and its base are one casting and 
 effectual^' exclude rain or 
 snow water. 
 
 The lamps run on circuits 
 of 6.6 amperes for 1,200 and 
 9.6 amperes fcr 2,000 nom- 
 inal candlepower. In case 
 it is necessary to run a lamp 
 on a circuit differing from 
 the standard, the lamp may 
 be adjusted by moving the 
 contact on the adjuster. 
 About one ampere either 
 above or below the normal 
 may be compensated for by 
 this means. 
 
 Permanent adjustment for 
 special circuits of variation 
 greater than one ampere is 
 made by filing the soft iron 
 armature. The clutch should 
 be so adjusted that the cen- 
 ter of the armature is f|- in. 
 above the plate when the trip 
 on the first rod is touching 
 the bushing, and \\ in. when 
 
 the trip on the second rod is in a similar position. 
 A small gauge is convenient for adjusting the clutch. 
 The position of the trip of the clutch determines the 
 feeding point of the lamp. 
 
 After thoroughly repairing and cleaning the lamp, it 
 
 FIGURE 91. 
 
160 ELECTRICITY FOR ENGINEERS 
 
 should be run a short time before installing. Lamps 
 should not be tested in an exposed place, as a strong 
 draft of air will cause unpleasant hissing which may be 
 mistaken for some internal trouble. 
 
 Lamps should not hiss or flame if good carbons are 
 used. A voltmeter should always be used when adjust- 
 ing or testing. 
 
 The lamp terminals are marked P (positive) and N 
 negative) and should be connected into circuit accord- 
 ingly. 
 
 The carbons should be solid and of uniform quality. 
 For the best results, the upper carbon should be 
 12 in. x T 7 g in., and the lower 7 in. x T 7 g in. The stub 
 of the upper carbon may then be used in the lower 
 holder when retrimming. 
 
 At each trimming the rod should be carefully wiped 
 with clean cotton waste. If any sticky or dirty spots 
 ; ppear, which cannot be readily removed with waste, 
 ^se a piece of well-worn crocus cloth, always being 
 careful to use a piece of clean waste before pushing 
 the rod into the lamp. It should never be pushed up 
 'rto the lamp in a dirty condition. 
 
 The carbon rod maybe unscrewed and removed by a 
 small screw driver or small strip of metal inserted in 
 the slot cut in the rod cap. The cap will remain in 
 the hole through the yoke when the rod is taken 
 out. 
 
 In Fig. 92 an interior view of the Thomson-Houston 
 arc lamp is shown. This lamp is also used on con- 
 stant current systems. 
 
 The lamps should be hung from the hanger boards 
 provided with each lamp, or from suitable supports of 
 wire or chain. 
 
 As the hooks on the lamp form also its terminals, 
 
ELECTRICITY FOR ENGINEERS 
 
 101 
 
 they should be insulated, where a hanger board is not 
 used, from the chains or wires used to support the 
 lamp. 
 
 figure 92. 
 
 When the lamps are hung where the}/ are exposed to 
 the weather, they should be covered with a metal 
 hood, to prevent injury from rain and snow. 
 
162 ELECTRICITY FOR ENGINEERS 
 
 In such cases, care should be taken that the circuit 
 wires do not form a contact on the metal hood and 
 short circuit the lamp. 
 
 Before the lamps are hung up they should be care- 
 fully examined to see that the joints are free to move, 
 and that all connections are perfect. 
 
 No lamp should be allowed to remain in circuit, 
 with the covers removed and the mechanism exposed. 
 Such practice is dangerous, and in violation of insur- 
 ance rules. 
 
 The object of testing the lamps in the station is to 
 find any defects, if such exist, and to test all the con- 
 ditions of running before delivering them to custom- 
 ers. The lamps should not be hung up in their 
 respective places in the external circuit, until every- 
 thing is running with perfect satisfaction. 
 
 The tension of the clamp which holds the rod is 
 adjusted by raising or lowering the arm at the top of 
 the guide rod. (See Fig. 93.) If the tension is too 
 great the rod and clutch will wear badly and the feed- 
 ing will be uneven, causing unsteadiness in the lights. 
 Too little tension will not allow the clutch to hold up 
 the rod and any sudden jar to the lamp will cause the 
 rod to fall and the light to go out. 
 
 The double carbon, or M lamp, should have the ten- 
 sion of the second carbon a trifle lighter than the first 
 one. 
 
 When adjusting the tension, be sure to keep the 
 guide rod perpendicular and in perfect line with the 
 carbon rod; it should be free to move up and down 
 without sticking. 
 
 The tension of the clutch in the D lamp should be 
 the same as that of the K lamp. It is adjusted by 
 tightening or loosening the small coil spring from 
 
ELECTRICITY FOR ENGINEERS 
 
 lt>3 
 
 the arm of the clutch to the bottom of the clamp 
 stop. 
 
 To adjust the feeding point in the K lamp, press 
 down the main armature as far as it will go, then push 
 
 FIGURE 93. 
 
 up the rod about one-half its length, let go the arma- 
 ture and then press it down slowly and note the dis- 
 tance of the bottom side of the armature above the 
 base of the curved part of the pole. When the rod 
 
1()4 ELECTRICITY FOR ENGINEERS 
 
 just feeds, this distance should be ]/^ in. If it is not, 
 raise or lower the small stop which slides on the guide 
 rod passing through the arm of the clutch, until the 
 carbon rod will feed when the armature is ^ in. from 
 the rocker frame at base of pole. 
 
 To adjust the feeding point of the M lamp, adjust 
 the first rod as in the K lamp. Then let the first rod 
 down until the cap at the top rests on the transfer 
 lever. The second rod should feed with the armature 
 at a point T V in. higher than it was while feeding the 
 first rod, that is, it should be T 5 g in. from rocker frame 
 at base of pole. 
 
 The feeding point of the D lamp is adjusted by slid- 
 ing the clamp stop up or down, so that the rod will 
 feed when the relative distances of the armature of the 
 lifting magnet and the armature of the shunt magnet 
 from rocker arm frame are in the ratio of I to 2. 
 There should be a slight lateral play in the rocker, 
 between the lugs of the rocker frame. 
 
 The armatures of all the magnets should be central 
 with cores, and come down squarely and evenly. 
 There should be a separation of ^ m - between the sil- 
 ver contact points, when the armature of the starting 
 magnet is down. This contact should be perfect when 
 the armature is up. The arm for adjusting the tension 
 should not touch the wire or frame of the lamp when 
 at the highest point. There should be a space of %\ in. 
 or }i in. between the body of the clutch and the arm 
 of the clutch, to allow for wear on the bearing surfaces. 
 
 Always trim the lamp with carbons of proper length 
 to cut out automatically, that is, have twice as much 
 carbon projecting from the top as from the bottom 
 holder. Always allow a space of }{ in., when the lamp 
 is trimmed, from the round head screw in the rod, near 
 
ELECTRICITY FOR ENGINEERS 
 
 165 
 
 the carbon holder, to the edge of the upper bushing, so 
 that there will be sufficient space to start the arc. 
 
 The arcs of the 1,200 candlepower lamps should be 
 adjusted to ¥ 3 ¥ in., with full length of carbon. Arcs of 
 2,000 candlepower lamps should be adjusted from y 1 ^ 
 to 3 8 *- in. when good carbons are used. 
 
 The action of a lamp that feeds badly may often be 
 confounded with a badly flaming carbon. The distinc- 
 tion can readily be made after a short observation. 
 The arc of a lamp that feeds badly will gradually grow 
 long until it flames, the clutch will let go suddenly, the 
 upper carbon will fall until it touches the lower carbon, 
 and then pick up. A bad carbon may burn nicely and 
 feed evenly until a bad spot in the carbon is reached, 
 when the arc will suddenly become long and flame and 
 smoke, due to impurities in the carbon. Instead of 
 dropping, as in the former case, 
 the upper carbon will feed to its 
 correct position without touching 
 the lower carbon. 
 
 In a series arc lamp the shunt 
 coil is used to regulate the voltage 
 over the arc. With constant po- 
 tential arc lamps this shunt coil 
 is not needed, owing to the fact 
 that the voltage over the lamp 
 is practically constant. Fig. 94 
 shows a diagram of an arc lamp 
 for use on constant potential cir- 
 cuits. The upper carbon is sup- 
 ported by means of an iron yoke 
 which forms a core to the two 
 
 solenoids M M. Current entering binding post T 
 passes through the windings of these two solenoids and 
 
 FIGURE 94. 
 
166 ELECTRICITY FOR ENGINEERS 
 
 then through the carbons and through the resistance 
 coil R to the other terminal of the lamp. The action 
 of the lamp is as follows: Current passing over the 
 solenoids M M is regulated by the resistance across 
 the arc. This current produces an electromagnetic 
 pull on the iron core and floats, magnetically, the core 
 and upper carbon. When the carbons burn away at 
 the crater the distance from point to point of the car- 
 bons is increased and a corresponding increase in 
 resistance to the flow of the current takes place. This 
 reduces the flow of current around the solenoids and 
 correspondingly reduces the electromagnetic pull on 
 the core; the iron core and carbon fall a slight dis- 
 tance by gravity. In so doing the distance at the 
 crater is decreased and the flow of current increased, 
 thus increasing the flow of current around the solenoids 
 and drawing up the core and carbons. In this way a 
 very nice equilibrium between gravity and magnetic 
 pull is maintained. It will be noticed that this lamp 
 has no automatic cutout as has the constant current 
 arc lamp. In a series arc lamp when the carbons are 
 all consumed, the automatic cutout closes the circuit 
 from the positive and negative binding posts of the 
 individual arc lamp, thereby maintaining a path 
 through the arc lamp over which the current can con- 
 tinue to flow to supply the remaining arc lamps in the 
 series circuit. 
 
 The series arc, as its name would indicate, is the 
 most simple of all lighting circuits. The lamps are 
 arranged so that all the current from the positive pole 
 of the dynamo goes through each, and from the last on 
 the conductor leads back to the dynamo. The series 
 system is more generally used where it is desired to 
 illuminate a large district, as in street lighting. It is 
 
ELECTRICITY FOR ENGINEERS 167 
 
 also used to some extent in store lighting, although the 
 series arc is fast being replaced with the constant 
 potential arc for this purpose. 
 
 In the low tension or constant potential arc lamp the 
 use of a cutout mechanism is not necessary, because 
 these lamps burn singly across the system of wiring, 
 where a constant potential is maintained, and hence 
 when the carbons are all consumed, current simply 
 ceases to flow across them. In the open arc lamp the 
 potential across the crater is usually from 45 to 50 
 volts, while in the inclosed arc lamp the potential 
 across the crater is from 68 to 75 volts. This is due to 
 the increased resistance through the crater, because of 
 the peculiar nature of the gases emitted from the 
 crater burning in a condition with practically no atmos- 
 phere. When such an arc lamp is connected across a 
 no volt circuit, the lamp contains a resistance coil in 
 the mechanism box over which the current must flow 
 before producing the arc, R (Fig. 94). This resistance 
 coil assists to reduce the pressure from no volts down 
 to the pressure required by the arc or crater. If, for 
 instance, the electromotive force across the wires 
 supplying current to a low tension arc lamp is no 
 volts and the pressure required to maintain the arc or 
 crater is 70 volts, then the resistance coil chokes down 
 the electromotive force from no to 70, or 40 volts. If 
 the arc consumes 4 amperes of current then the loss is 
 4 (amperes) times 40 (volts), or 160 watts. This 160 
 watts is lost by heat radiating to the atmosphere from 
 the wire of the resistance coil. The constant potential 
 lamp is usually referred to as the low tension arc lamp. 
 The high tension arc lamp generally burns with the arc 
 in the open air, while the low tension lamp burns with 
 the arc encased in a small glass bulb so arranged as to 
 
168 ELECTRICITY FOR ENGINEERS 
 
 permit the upper carbon to slide into the bulb in a 
 manner that will maintain, as near as possible, a condi- 
 tion whereby the arc burns in a gas containing no 
 oxygen. The enclosed arc lamp has the advantage of 
 burning a considerable number of hours without being 
 recarboned or trimmed; but it also has the disadvantage 
 that the bulb enclosing the arc turns black after burn- 
 ing for some time, caused by the gases emitted from 
 the arc. This renders the bulb partially opaque, 
 consequently imprisoning a considerable quantity of 
 useful light. Enclosed arc lamps are also operated in 
 series systems, and where they are so used the objec- 
 tion of loss due to the cutting down of the voltage (as 
 in constant potential lamps) is overcome. Enclosed 
 lamps are also operated on alternating current systems. 
 
 The operation of the alternating arc lamp and the 
 mechanism in the lamp is very similar to that of the 
 direct current arc lamp, but the magnets instead of 
 being constructed of solid iron, are laminated in a 
 similar manner as the system of lamination explained 
 in the construction of armatures. These laminated 
 cores and other parts forming the magnetic circuit 
 in the arc lamp are necessary to avoid eddy cur- 
 rents. The crater has neither a cup shape on the 
 upper carbon nor a point on the lower carbon, because 
 current flows through the crater alternately positive 
 and negative with each alternation. In the alternating 
 arc lamp the upper and lower carbons burn away with 
 almost equal rapidity, and the same quantity of light 
 is projected upward as downward. 
 
 In Fig. 95 is shown an arc lamp with case removed. 
 The two upper coils are the coarsely wound series 
 coils, while the two lower coils are the finely wound 
 shunt coils. This lamp is adapted for an enclosed arc 
 
ELECTRICITY FOR ENGINEERS 
 
 169 
 
 bulb. The magnetically attracted cores are U shaped, 
 and both cores are connected together mechanically by 
 non-magnetic metal, such as brass or zinc, so that the 
 magnetism set up in the shunt coils will not be affected 
 by the magnetism set up by the 
 series coils. This scheme is used in 
 alternating current lamps, while in 
 direct current lamps the cores are 
 made of H shaped iron not lami- 
 nated. 
 
 In Figs. 96 to 98 are shown three 
 views of series enclosed alternating 
 current arc lamps of the Western 
 Electric Company. 
 
 Fig. 96. Side view of lamp, show- 
 ing one series and one shunt spool, 
 lever movement and adjusting 
 weight. This weight is fastened 
 upon a threaded rod, and the finest 
 adjustment can be obtained by 
 screwing the weight backward or for- 
 ward. Threads can be clamped in 
 position when the correct adjustment 
 is obtained. 
 
 Fig. 97. Front view of lamp, show- 
 ing shunt spools, supporting resist 
 ance and cutout. Note that lever 
 carries no current when in normal 
 working position, but that insulated bridge forms con- 
 nection across two contacts, completing cutout circuit 
 when in position shown in cut. 
 
 Fig. 98. Rear view of lamp, showing series spool, 
 short circuiting switch and manner of suspending dash 
 pot. Note that the dash pot is inverted, allowing sucn 
 
 figure 95 
 
170 
 
 ELECTRICITY FOR ENGINEERS 
 
 dirt as may accumulate therein to fall out rather than 
 in the clash pot. 
 
 The three cuts show the manner of suspending the 
 spools and their accessibility, it being possible to 
 remove any spool by simply taking out the two screws 
 
 FIGURE 96. 
 
 FIGURE 97. 
 
 FIGURE 98. 
 
 which fasten it lo the frame, and lifting it off the 
 lower support. 
 
 The carbons used in arc lamps are extremely hard 
 and dense. They are made from a mixture of pow- 
 dered gas house coke, ground very fine, and a liquid 
 like molasses, coal tar, or some similar hydro-carbon, 
 forming a stiff, homogeneous paste. This is molded 
 
ELECTRICITY FOR ENGINEERS 171 
 
 into rods or pencils of required size and length, or 
 other shapes, being solidified under powerful hydro- 
 static pressure. The carbons are now allowed to dry, 
 after which they are placed in crucibles or ovens, 
 thoroughly covered with powdered carbon, either lamp- 
 black or plumbago, and baked for several hours at a 
 high temperature. After cooling, they are sometimes 
 repeatedly treated to a soaking bath of some fluid 
 hydro-carbon, alternated with baking, until the product 
 is dense as possible, all pores and openings having 
 been filled solid. Arc carbons are often plated with 
 copper, by electrolysis, to insure better conductivity. 
 
 It is said that one 2,000 candlepower arc lamp will 
 light in open yards 20,000 sq. ft.; in railroad stations, 
 14,000 sq. ft.; in foundries and machine shops, 5000 
 to 2,000 sq. ft. Where good, even illumination is 
 desired, it is advisable to use a greater number of 
 smaller lamps evenly distributed. 
 
CHAPTER X 
 
 Incandescent Lamps. As nearly every one is familiar 
 with the construction of the incandescent lamp no 
 detailed description will be undertaken, suffice it to 
 say that the incandescent lamp comprises a carbon 
 filament enclosed in a glass bulb from which the air 
 has, as far as possible, been withdrawn, the carbon 
 filament being soldered to the ends of small platinum 
 wires entering the glass shell. Incandescent lamps can 
 be burned either in series or in multiple; the multiple 
 system being the most used. Series incandescent 
 lamps are used to a considerable extent in the smaller 
 towns for street lighting and also for the small minia- 
 ture lamps burned in series on a constant potential sys- 
 tem and used for decorative purposes. They are also 
 used in street car lighting. 
 
 When incandescent lamps are to be used in series, 
 they should be carefully selected; there is quite a 
 difference in the current consumed by different lamps, 
 even of the same make, and when they are all limited 
 to the same current quite a difference in candlepower 
 may be noticeable. Some will be above their rated 
 candlepower and others below. 
 
 The resistance of an incandescent lamp when cold is 
 very high, varying in the ordinary 16 candlepower no 
 volt lamp from 600 to 1,000 ohms. When the lamp 
 becomes heated, as when current is passing through it, 
 the resistance reduces considerably, being in the 16 
 candlepower no volt lamp about 220 ohms. 
 
 The current required by the various incandescent 
 lamps varies considerably for lamps of the same volt- 
 172 
 
ELECTRICITY FOR ENGINEERS 173 
 
 age and candlepovver, but a good average which can be 
 used in figuring currents is y 2 ampere for a 16 candle- 
 power no volt lamp and % ampere for the 220 volt 
 16 candlepower lamp. The amount of power, in watts, 
 consumed by a lamp is equal to the voltage multiplied 
 by the current, or W = C x E. A 16 candlepower no 
 volt lamp taking y 2 ampere would consume uox 
 y 2 = 55 watts, while a 220 volt lamp taking y± ampere 
 would consume 220x^ = 55 watts. It will thus be 
 seen that while the current and voltage may vary, the 
 amount of power consumed will be approximately the 
 same for all 16 candlepower lamps. Lamps are rated 
 at a certain number of watts per candle, the amount 
 varying from 3 to 4 watts for 16 candlepower no volt 
 lamps. The proper lamp to be used varies according 
 to the conditions. While less power is consumed in 
 a 3.1 watt lamp, the life of the lamp is comparatively 
 shorter, so that the lamps will have to be renewed 
 oftener. With a 4 watt lamp a greater amount of cur- 
 rent is consumed, but the life of the lamp is longer. 
 Another point of great importance in burning incan- 
 descent lamps is the voltage. The table below shows 
 what effect variation in voltage has on the candlepower 
 and efficiency. 
 
 An increase in voltage increases the candlepower. 
 This increases the efficiency and shortens the life as 
 follows: 
 
 A lamp burning at — 
 
 Normal voltage gives ioo per cent. C. P, and consumes 3.1 Watts per C. P. 
 
 1 per cent, above normal gives 106 per cent. C. P. and consumes 3. Watts per C P. 
 
 2 " 
 3 
 4 
 5 
 6 
 
 A lamp burning at normal voltage should give its 
 
 112 " " " 
 
 2.9 
 
 118 " " 
 
 2,8 
 
 125 " " 
 
 2,7 
 
 132 " " 
 
 2.6 
 
 140 " " " 
 
 2.5 
 
174 
 
 ELECTRICITY FOR ENGINEERS 
 
 full candlepower at its rated efficiency. A 3.1 watt 
 lamp burning below its voltage loses its efficiency and 
 candlepower as follows: 
 If burned — 
 
 1 per cent, below normal it gives 95 per cent.C. P. and consumes 3.2 Watts per C. P. 
 
 3-35 " " 
 
 3 i 
 3-6 
 
 3-75 
 
 4- 
 
 4.6 
 
 By referring to the table it will be seen that with the 
 voltage raised 3 per cent, (on a no volt system to a 
 little over 113 volts) the candlepower will increase 18 
 per cent., or in other words, a 16 candlepower lamp 
 would be raised to nearly 19 candlepower. At the 
 same time raising the voltage will decrease the life of 
 the lamp. This is shown in the following table where, 
 with an increase of 6 per cent, in the voltage, the life 
 of the lamp is reduced 70 per cent. A lamp at normal 
 voltage has 100 per cent. life. 
 
 The same lamp i per cent, above normal loses 18 per cent. life. 
 
 " " " 2 " " " 
 
 " 3o 
 
 " 3 " 
 
 " 44 
 
 4 " 
 
 " 55 
 
 " " " s, " 
 
 " 62 
 
 6 " 
 
 11 yo 
 
 To obtain satisfactory results, the voltage should be 
 kept constant at just the proper value. 
 
 Considerable heat is generated in an incandescent 
 lamp, so that as a general rule it is a bad plan to use 
 paper shades which come very close to the bulb. 
 Where lamps are hung so that there is a liability of 
 their coming in contact with surrounding inflammable 
 material, such as in warehouses and store-rooms, it is a 
 good plan to enclose the lamp in a wire guard. 
 
 The following table will prove a handy reference for 
 estimating the number of lamps (8 to 50 C. P.) that 
 can be run per horsepower or kilowatt. The table is 
 
ELECTRICITY FOR ENGINEERS 
 
 175 
 
 figured for theoretical values, so that the actual horse- 
 power or kilowatts delivered must be used, or else 
 values less than those given must be used to allow for 
 loss in the lines. 
 
 Candle-power. 
 
 Efficiency. 
 
 Total Watts. 
 
 Per 
 
 Horsepower. 
 
 Per Kilowatt. 
 
 8 
 
 3-5 
 
 28 
 
 26.6 
 
 35-7 
 
 8 
 
 4 
 
 32 
 
 23-3 
 
 31.2 
 
 16 
 
 3 
 
 48 
 
 15.5 
 
 20.8 
 
 16 
 
 3-i 
 
 50 
 
 14.9 
 
 20 
 
 16 
 
 3-5 
 
 56 
 
 13.3 
 
 17.8 
 
 16 
 
 4 
 
 64 
 
 ir. 6 
 
 15.6 
 
 ?.o 
 
 3 
 
 60 
 
 12.4 
 
 16.6 
 
 20 
 
 3-1 
 
 62 
 
 12 
 
 16. 1 
 
 20 
 
 3-5 
 
 7o 
 
 10.6 
 
 14.2 
 
 25 
 
 3 
 
 75 
 
 9-9 
 
 13-3 
 
 25 
 
 3-i 
 
 77- 5 
 
 9.6 
 
 12.9 
 
 25 
 
 3-5 
 
 87.5 
 
 8-5 
 
 11. 4 
 
 25 
 
 4 
 
 100 
 
 7 4 
 
 10 
 
 32 
 
 3 
 
 96 
 
 7 
 
 10.4 
 
 32 
 
 3-1 
 
 99.2 
 
 7.5 
 
 10 
 
 32 
 
 3-5 
 
 112 
 
 6.6- 
 
 8.9 
 
 50 
 
 3 
 
 150 
 
 4.9 
 
 6.6 
 
 50 
 
 3-i 
 
 155 
 
 4.8 • 
 
 6.4 
 
 50 
 
 3-5 
 
 175 
 
 4-2 
 
 5-7 
 
 The first column gives the candlepower. The second 
 column gives the number of watts consumed for each 
 single candlepower obtained, and is called the effi- 
 ciency of the lamp. Multiply the total candlepower 
 by the efficiency and you get the total number of watts 
 consumed by the lamp. The fourth column shows the 
 number of lamps per 746 watts, and the last column 
 the number of lamps per 1,000 watts. 
 
 The current and watts consumed by 110 volt lamps 
 
 of the different candlepowers are approximately given 
 
 below. 
 
 4 candlepower o. 18 amperes, 20 watts 
 
 8 " .0.29 " 32 " 
 
 16 " 0.5 " 55 " 
 
 32 1.0 " no " 
 
176 ELECTRICITY FOR ENGINEERS 
 
 The light given off by an incandescent lamp varies 
 according to the position from which it is viewed. In 
 some makes of lamps most of the light is given off 
 directly downward, while in other lamps the maximum 
 light is given off in a horizontal direction. The best 
 lamp to use must be determined by the location of the 
 lamp and the place where the light is required. By 
 the use of suitable reflectors or shades the light can be 
 thrown in any direction desired. A 16 candlepower 
 lamp if placed seven feet above the floor will light up 
 a floor space of ioo sq. ft., providing the walls are of a 
 light color. If the walls are of a dull color, or if a 
 bright illumination is desired more lamps should be 
 used. Glass globes placed over the lamps reduce the 
 light to a considerable extent, as is shown in the fol- 
 lowing table: 
 
 Clear glass 10 per cent. 
 
 Holophane 12 " 
 
 Opaline 20 to 40 " 
 
 Ground . 25 to 30 " 
 
 Opal 25 to 60 " 
 
CHAPTER XI 
 
 The Nernst Lamp. Very recently a new type of elec- 
 tric lamp has been introduced which has a few charac- 
 teristics of the arc lamp and many of the characteristics 
 of the incandescent lamp. It is a lamp that can be 
 successfully operated only on alternating currents. 
 That part of the lamp from which the light is emitted 
 is called the glower. The glower performs about the 
 same functions as does the filament in an incandescent 
 lamp. 
 
 In Fig. 99 a diagram of a six glower lamp is shown. 
 The six glowers are shown at 6. These glowers are in 
 the shape of small rods and are composed of an oxid r. 
 which, at the normal temperature, is of very high 
 resistance, the resistance being so high that practically 
 no current can flow through them. When these rods 
 become heated, the resistance reduces considerably, so 
 that they will conduct current. The heaters which are 
 composed of a considerable length of fine platinum 
 wire embedded in porcelain, are shown at 5. The 
 action of the lamp is as follows: Current enters at 1, 
 and being unable to flow over the glowers on account 
 of their high resistance, passes to the cutout 4', then 
 through the platinum wire of the heaters back to the 
 other side of the cutout 4. As the platinum wire in 
 the heaters becomes heated, the glowers, which are 
 placed directly below them, also heat up and in time 
 their resistance becomes so reduced that current will 
 pass through them. The current will now pass through 
 the glowers to what is known as the ballast, 7. This 
 177 
 
178 
 
 ELECTRICITY FOR ENGINEERS 
 
 ballast is composed of fine iron wire and its purpose is 
 to steady the current through the glower. From the 
 fact that iron wire increases in resistance with increase 
 of current, this wire acts as a regulator, tending to cut 
 
 FIGURE 99. 
 
 down any fluctuations in the current strength. It will 
 be noticed that there is a separate ballast for each 
 glower. From the ballast the current flows around the 
 coil of wire 3. Inside of this coil is an iron core which 
 
ELECTRICITY FOR ENGINEERS 
 
 179 
 
 moves up and down, and connected to the lower end 
 of this core are the cutouts 4,4'. As the glower 
 becomes heated, more current is sent around this coii, 
 until it becomes of such strength that the core is 
 drawn in, thus opening the cutouts. All of the cur- 
 rent will now flow through the glowers. The Nernst 
 lamp does not operate successfully on direct current, 
 
 FIGURE 100. 
 
 due to the blackening of the glower caused by decom- 
 position of the platinum contacts with which they are 
 connected. These lamps are made in sizes of from 1 
 to 30 glowers, and they consume about 88 watts per 
 glower. The light resembles very closely the light 
 from a Welsbach gas burner, although the green tinge 
 of the Welsbach is not present. 
 
180 ELECTRICITY FOR ENGINEERS 
 
 In Fig. ioo is shown the single glower lamp 
 assembled, which can be inserted in an ordinary Edi- 
 son socket. 
 
 In Fig. 101 the six glower lamp, with dome attached, 
 is shown. 
 
CHAPTER XII 
 
 Line Testing. In the operation of electric light and 
 power circuits three principal causes of trouble are 
 continually encountered. These are the open circuit, 
 the short circuit, the ground, and also combinations of 
 these, as there is nothing which prevents the existence 
 of all three defects on any line at the same time. In 
 order to study these properly, let us refer to Fig. 102, 
 which shows an ordinary incandescent circuit equipped 
 with the necessary cutout and a switch. 
 
 An open circuit may be caused by poor contact, or 
 
 H F 
 
 
 FIGURE 102. 
 
 failure to make any contact at all, of the fuse. If this 
 is the cause, the light can be made to burn by connect- 
 ing the fuse terminals A and B or C and D by means 
 of short pieces of wire. Such wire must, however, be 
 used only for an instant to make sure of the trouble, 
 and proper fuses must then be provided. Another 
 method of locating an open circuit in the fuse consists 
 of moistening the finger tips and placing the tips of 
 two fingers of the same hand on B and D. If the fuses 
 are in order, a slight shock will be felt; this method is 
 applicable only on low voltage systems and must never 
 be used where the voltage exceeds 250. 
 181 
 
182 ELECTRICITY FOR ENGINEERS 
 
 If the fuses are found all right, the next place to look 
 for the cause of an open circuit is at the switch. The 
 contact points of switches are often so badly burned 
 or covered with dirt and grease that they do not make 
 proper connection and hence the lights will not burn. 
 
 The switch can be tested with the fingers just as we 
 tested the cutout, and if the shock is felt the line is 
 all right to this point. In testing the switch, be sure 
 you test at the proper point (i and 2) in the figure 
 which shows a switch, the blades of which cross. 
 Some switches make connection straight along without 
 crossing. In testing with a wire, as shown above, be 
 very careful not to connect the points 1 and 2 at the 
 switch, or you will have a short circuit. 
 
 If the line is found alive at the far side (points 1 and 
 2) of the switch shown, and still the lights do not burn, 
 it is quite likely that there is a broken wire between 
 the switch and the lamps. This break in the wire is 
 not always visible, as often the wire is entirely con- 
 cealed, and even when the wire is in plain view, the 
 break may extend only to the copper and leave the 
 outer insulation apparently perfect. 
 
 If we are dealing with concealed wires that appear 
 only where the lights are connected, we must first 
 examine the connections at all such places and see 
 whether they are in good order. If we find nothing 
 wrong there we may proceed to locate our open circuit 
 (which we shall assume to be at E) by the following 
 method: In place of one of the fuses AB or CD, con- 
 nect any incandescent lamp (if plug cutouts are used 
 the lamp can be screwed in instead of the plug). Now 
 connect a wire from 1 or 2 of the switch to 3 or 4 of 
 the nearest lamp. 
 
 If we happen to connect our wire from 1 to 4 we 
 
ELECTRICITY FOR ENGINEERS 183 
 
 shall make a short circuit and the lamp at the cutout 
 will burn at full candlepower, but none of the other 
 lamps will burn at all. Now disconnect the test wire 
 from 4 and connect it at 3; if the broken wire is at E, 
 as we have assumed, all the lights will now burn in 
 series with the lamp in the cutout. If there are but 
 few lights connected in the circuit, this lamp will burn 
 at about half candlepower; if there are many lamps 
 connected it will come nearly to full candlepower, and 
 the lamps in the circuit will show nothing. 
 
 If instead of an open circuit the cause of our trouble 
 is a short circuit, it will first make itself evident by a 
 burned out fuse in the cutout at AB or CD. 
 
 A little experience will soon enable one to judge 
 whether a burned out fuse is due to an overload or a 
 short circuit; the damage to terminals and the evi- 
 dence of burning will be much greater from a "short" 
 than from a slight overload. 
 
 Often the current that "blows" the fuse will also 
 burn out the wire which caused the "short," so that 
 the line will seem perfectly clear when a new fuse is 
 inserted. 
 
 If an inspection of the wires and apparatus does not 
 reveal the location of the trouble, we may fuse up one 
 side of the circuit and connect an incandescent lamp 
 in place of the other fuse. If the "short" is still on, 
 the lamp will burn at full candle power. 
 
 A short circuit may consist of anything of low elec- 
 trical resistance that brings the wires of opposite 
 polarity into electrical connection with each other. 
 Thus, if the two points, F and G, although several 
 hundred feet or even yards apart, were in connection 
 with gas or water piping of low electrical resistance, 
 all current would flow through the piping from F to G, 
 
184 ELECTRICITY FOR ENGINEERS 
 
 and there would be none to flow through the lamps. 
 Short circuits are also often caused by small wires in- 
 side of sockets or fixtures coming in improper contact. 
 In one instance a short circuit which caused a search 
 of several hours was finally located in the butt of an 
 Edison base lamp, the center contact piece of which 
 had been put on crooked in such a manner that when 
 the lamp was screwed into its socket this center piece 
 made connection with opposite poles within the socket. 
 
 If a careful examination does not reveal the "short" 
 it will be necessary to cut the wires, say at H; if this 
 clears the line so that all lamps nearer the cutout than 
 H burn, the trouble must be beyond H; if not, the line 
 must be cut again nearer the cutout until finally the 
 exact location of the trouble is found. 
 
 Any connection of any part of an electrical circuit to 
 earth is called a "ground," and wires so connected are 
 said to be grounded. One ground on a system will 
 not necessarily do much harm or interfere with the 
 operation of the system. It will, however, greatly 
 increase the probability of electric shocks to people 
 coming in contact with any part of the wiring. Also, 
 if there is a ground on one side of a system, the 
 appearance of a second ground on the other side of the 
 system will be equal to a short circuit, if both are of 
 low resistance, and probably cause the burning out of 
 fuses or wires. 
 
 If a ground is of high resistance, it may merely 
 waste energy through leakage of current; or it may 
 cause slow destruction of a wire or sometimes a gas or 
 water pipe by electrolytic action. Aside from direct 
 contact with metal parts of buildings, the most prolific 
 cause of grounds is found in dampness. 
 
 Grounds may be located by means of the Wheatstone 
 
ELECTRICITY FOR ENGINEERS 
 
 185 
 
 bridge, magneto or a common bell and battery. After 
 removing the fuses from the grounded part of the 
 system, connect one side of the apparatus to a good 
 ground, such as a water pipe, and the other side to the 
 system. Proceed in the same way as explained for 
 short circuits; that is, cut the lines until the ground is 
 located, or the line shows clear. Where the wiring is 
 concealed and there are a number of switches control- 
 ling chandeliers, grounds can very often be located by 
 switching off one fixture at a time, for when the 
 grounded fixture is switched off the line will show 
 clear. 
 
 To facilitate the discovery of grounds as soon as they 
 come on, most switchboards are equipped with ground 
 detectors of some kind. 
 
 The cheapest and easiest to install of these consists 
 of two lamps in series, as shown in Fig. 103. So long 
 
 ~3 
 
 LSi 
 
 + 
 
 £ 
 
 2L 
 
 FIGURE 103. 
 
 as both sides of the system are clear of grounds, the 
 lamps will both burn at equal candlepower (rather dim) 
 no matter whether the buttom C be pressed or not. 
 But should a ground come on the 4- wire, say at B, and 
 the button C be then pressed, the lamp 2. will be 
 deprived of current and lamp I will burn at full candle- 
 power. In such a case the current passes from the 
 -f wire to the ground B, through the ground to C, 
 
186 
 
 ELECTRICITY FOR ENGINEERS 
 
 button C and lamp I to the — wire. Should a ground 
 come at A, lamp I would be cut out and 2 womd 
 
 
 pq 
 
 w 
 
 OO-i 
 
 DO- 1 
 
 DP 
 
 m> 
 
 * + 
 
 burn at full candlepower. The great disadvantage of 
 the lamp ground detector lies in the fact that it is not 
 very sensitive; that is, unless the ground is of quite 
 
ELECTRICITY FOR ENGINEERS 
 
 187 
 
 low resistance the difference in the brilliancy of the 
 lamps will hardly be noticeable. 
 
 A much more satisfactory arrangement is that shown 
 in Fig. 104, where a voltmeter is connected for that 
 purpose. With the two single pole switches A and B 
 in the position shown, the voltmeter indicates the 
 pressure of the dynamo; if B is thrown over, the 
 current from the 4- wire passes through the voltmeter 
 to the ground, and if there is a ground on the - wire it 
 will indicate it. If B is thrown back and A over, a 
 
 _$! S$- 
 
 ©. 
 
 FIGURE 105. 
 
 ground on the + wire will be indicated. If the system 
 is perfectly clear, the voltmeter will indicate nothing 
 with either one of the switches thrown over. This test 
 of lines and circuits should be quite frequently made. 
 
 Testing Efficiency of Dynamos and Motors. The simplest 
 means of testing the efficiency of motors is shown in 
 Fig. 105. 
 
 This is known as the Prony brake, and consists of a 
 pair of clamps arranged for thumb screws and fastened 
 to the pulley of the motor, and a set of scales. 
 
 We will assume that we are testing the efficiency of 
 
188 ELECTRICITY FOR ENGINEERS 
 
 a motor. We will arrange the clamps over the pulley- 
 as shown in the figure and on the long end of the 
 clamp w r e will arrange a bolt, from which we may 
 impart the pressure obtained to the platform of a pair 
 of scales. In the circuit supplying the motor with cur- 
 rent we will connect an amperemeter and a voltmeter. 
 We will now start the motor and press down on the 
 clamps by means of the thumb screw, until the 
 mechanical energy expended is sufficiently high to 
 cause the desired consumption of current shown by the 
 amperemeter at the pressure shown by the voltmeter. 
 With a tachometer or speed indicator we will find the 
 number of revolutions of the motor per minute. When 
 this has been done, we will take the weights on the 
 scales and balance the pressure brought down on the 
 platform. Now stop the motor. The weight indi- 
 cated by the scales is that weight which the motor 
 would have revolved through a circle, the radius, or 
 half the diameter of which is the distance from the 
 center of the motor shaft to the center of the bolt 
 pressing on the scale platform, Fig. 105. To find the 
 horsepower exerted, multiply the distance between the 
 bolt and the armature shaft by 2.. This will be the 
 diameter of the circle described. Multiply this by 
 3.1416. This will be the circumference of the circle 
 described. Multiply this by the number of pounds 
 indicated by the scales, multiply this by the number of 
 revolutions per minute, and divide the answer by 
 33,000. 
 
 Suppose your amperemeter registered 50.9 amperes 
 and your voltmeter registered no volts. This would 
 be 50.9 x no = 5,599 watts consumed. Divided by 746 
 watts, the electrical horsepower would be 7^ horse- 
 power consumed. 
 
ELECTRICITY FOR ENGINEERS 189 
 
 Suppose the dynamometer proved that you obtained 
 six actual mechanical horsepower. Then 6 divided by 
 7^ would be 80 per cent, efficiency which the motor 
 would have for changing electrical energy into mechan- 
 ical energy. 
 
 To test the efficiency of a dynamo we must first find 
 how much power is being delivered to it by the engine. 
 This is done in the usual manner by means of the indi- 
 cator, etc. Having obtained this, it is simply neces- 
 sary to connect an ammeter and voltmeter and, taking 
 simultaneous readings of both, find the power given 
 out by the dynamo by multiplying together the volts 
 and amperes. 
 
 As an example, suppose we have found that our 
 engine is delivering 40 H. P. while we are obtaining 
 from our dynamo 200 amperes at no volts pressure. 
 200 x no divided by 746 will give us the electrical 
 energy we are receiving; in this case a trifle less than 
 29.5 H. P. To find the efficiency of the dynamo we 
 divide the power received from the dynamo by that 
 delivered to it by the engine, 29.5 divided by 40 equals 
 .737, which is the efficiency of this dynamo. When 
 testing dynamos it is usual to provide an artificial load 
 which can be kept constant. Large metal plates, 
 preferably copper, are connected to the positive and 
 negative mains of the dynamo and immersed in a 
 barrel of water. The quantity of current that will flow 
 from one plate to the other can be regulated by dis- 
 solving more or less salt in the water and by immers- 
 ing the plates more or less and also by bringing them 
 closer together. The greater the surface of the plates 
 immersed in the water and the nearer they are brought 
 together, the greater will be. the current. Be very care- 
 ful and do not let the plates touch each other. Before 
 
190 
 
 ELECTRICITY FOR ENGINEERS 
 
 accepting a new dynamo a test run of twenty-four 
 hours at full load is usually made and the water rheo- 
 stat need be used only to keep the load constant when 
 lights are switched on or off. 
 
 Photometer. The amount of light given off by an 
 incandescent lamp is measured in candlepower. To 
 determine the candlepower of a lamp, an appaiatus 
 known as the photometer is used. Fig. 106 shows a 
 diagram of what is known as the Bunsen photometer. 
 S is a scale divided into inches, meters, or any suitable 
 divisions, at one end of which is placed a standard 
 lamp and at the other end the lamp to be measured. 
 
 FIGURE 106. 
 
 A small screen, made of white paper having a grease 
 spot in the center, is mounted on a stand so that it can 
 be moved along the scale. To operate the instrument, 
 move the screen to such a point that the grease spot 
 becomes invisible from either side. The two candle- 
 powers are now to each other as the squares of their 
 distances from the screen. For instance, suppose the 
 lamp A is a standard 16 candlepower lamp and at the 
 point where the grease spot is invisible the distance 
 from B to the screen is 20 in., and from A to the 
 screen 40 in., then B is to A as 20 squared is to 40 
 squared, or as 400 is to 1,600 or one-fourth as 
 great; therefore B is a 4 candlepower lamp. Care must 
 
ELECTRICITY FOR ENGINEERS 
 
 191 
 
 be taken that the two lamps are burning at just the 
 proper voltage, otherwise the comparison will not be 
 accurate. Instruments of the kind just described are 
 made in a variety of different patterns, but their prin- 
 ciple remains the same. Candlepowers may also be 
 compared by a method known as Rumford's.' Take a 
 pencil or other opaque rod and place it in front of a 
 white piece of paper or light-colored wall. Now place 
 
 in front of it, but separated so that there will be two 
 separate shadows cast, the two lamps to be compared. 
 By moving one of the lamps away from, or closer to, 
 the screen, at some point the two shadows will become 
 of the same density. Now measure the distances of the 
 two lamps from the screen, and their candlepowers 
 will be to each other as the squares of the distances; 
 (Fig. 107). 
 
192 ELECTRICITY FOR ENGINEERS 
 
 If the current consumed by a lamp and the voltage 
 maintained at its terminals are measured by an amme- 
 ter and voltmeter, as shown in Fig. 106, we need only 
 find the watts (current times volts) and divide by the 
 candlepower to find the efficiency of the lamp. If, for 
 instance, the 4 candlepower lamp B is taking J ampere 
 at no volts, we have 18^3 watts expended on it; this 
 divided by the candlepower 4 shows an efficiency of 
 4 T \ watts per candle. 
 
CHAPTER XIII 
 
 Storage Batteries. The storage battery is often 
 referred to as an accumulator. An accumulator is an 
 appliance for storing electricity. It depends upon the 
 chemical changes undergone by certain substances 
 when subjected to the action of an electric current. 
 Strictly speaking, it is not correct to say that electri- 
 city is stored in an accumulator, although as far as 
 external results is concerned such appears to be the 
 case. What it really does is this: The current flowing 
 into the accumulator produces a gradual chemical 
 change or decomposition of the active elements of 
 which the battery is constructed. This change con- 
 tinues to take place as long as the charging current is 
 applied. This is known as electrolytic action. As soon 
 as the current ceases, so also does the chemical decom- 
 position of the elements cease, and if the terminals be 
 then connected by a wire, a reversal of the chemical 
 process commences. Particles gradually reform them- 
 selves into original chemical combinations, and by so 
 doing produce a current of electricity which flows in 
 opposite direction to that originally used for charging. 
 
 An early form of accumulator, though more of 
 experimental than practical interest, was Grove's gas 
 battery. This was composed of a series of cells, each 
 cell comprising two tubes, closed at the upper ends, 
 and dipping down into a glass jar containing acidu- 
 lated water. Each tube had a platinum wire fused into 
 the closed end, from which a strip of platinum foil 
 extended downwards into the liquid. The outer ends 
 193 
 
194 ELECTRICITY FOR ENGINEERS 
 
 of the platinum wires were provided with terminals, by 
 means of which several of these cells were connected 
 together. A charging current was then applied and 
 resulted in the gradual decomposition of the water in 
 the various glass jars. Hydrogen collected on one of 
 the platinum plates in each of the cells and oxygen on 
 the other. If after a short time the charging source 
 was disconnected from the wires joined to the outer 
 terminals of the cells and a galvanometer substituted, 
 it was found that a current would then flow in the 
 reverse direction until all the separated hydrogen and 
 oxygen gases had recombined to form water again. 
 
 From a practical point of view the gas battery was 
 deficient, inasmuch as it would only supply current for 
 a very short-time, and several workers set themselves 
 the task of contriving an arrangement to obviate this 
 defect. The most successful of these early workers 
 was Plante, and he found in the course of his experi- 
 ments that the best results were to be obtained by 
 using lead plates or electrodes in a dilute solution of 
 sulphuric acid. He made a cell by taking two long 
 strips of sheet lead, placed one over the other with 
 pieces of insulating material between, and coiling 
 these up into spiral form. These plates were provided 
 with separate terminals and were placed in a jar con- 
 taining a solution of sulphuric acid. The action of the 
 charging current was to decompose the water in the 
 solution, the oxygen combining with the metal of the 
 positive plate and thus forming peroxide of lead, 
 whereas the hydrogen was simply deposited on the 
 negative plate and there remained in gaseous form. 
 On discontinuing the charging current, the hydrogen 
 combined with the oxygen in the solution to form 
 water again, while the peroxide of lead was deoxidized, 
 
ELECTRICITY FOR ENGINEERS 195 
 
 the lead remaining on the surface of the plate as 
 spongy lead, and the oxygen reentered the solution to 
 compensate for the oxygen which was extracted there- 
 from by the hydrogen in forming water. Plante found 
 that this method of construction enabled him to get an 
 electromotive force of from 2 to 2.5 volts, as against 
 1.47 volts given by Grove's gas battery. 
 
 Plante's experiments did not, however, terminate 
 with this achievement, and he next introduced a 
 method for considerably increasing the available 
 metallic surface of the electrodes. This plan is known 
 as "forming" the plates, and consists of repeating for 
 a considerable time the following series of operations: 
 (1) charge the accumulator, (2) discharge ditto, (3) 
 recharge, but with the charging current entering in the 
 reverse direction, (4) again discharge. This series of 
 reversals in charging and discharging, if kept up for 
 several days, has the effect of causing the lead plates 
 to become very porous or spongy in character, and, 
 therefore, by reason of the additional surface of con- 
 tact between electrolyte and electrode thus provided, 
 enables the cell to retain a much greater charge than 
 it would otherwise. 
 
 It is not difficult to see that this work of forming 
 is of a somewhat tedious and expensive character, and 
 with the object of reducing this process to a minimum, 
 another inventor, Faure, conceived the idea of using 
 plates coated with a paste of lead-oxide, a plan which 
 made it possible to use an accumulator with success 
 after being charged only two or three times. When first 
 introduced, some difficulty was found in making the 
 lead-oxide paste adhere properly to the plates, and 
 various means were devised to overcome this drawback. 
 Scratching and indenting the lead plates was tried, 
 
196 ELECTRICITY FOR ENGINEERS 
 
 but this was ultimately superseded by the plan of 
 making perforated plates in the form of grids, the 
 paste being pressed into the perforations. With vari- 
 ous slight modifications, in the shape of perforations, 
 this device has been found to answer exceedingly well, 
 and is now very generally adopted. 
 
 When an accumulator is freshly charged, it would be 
 found to have an electromotive force of about 2.25 to 
 2.5 volts, but after being used a short time this falls to 
 about 2 volts, at which figure it remains until the cell 
 is nearly exhausted. For many purposes, however, a 
 higher voltage than this is required, and it then 
 becomes necessary to have several cells joined in 
 series, so as to give a total voltage equal to the 
 number of cells multiplied by 2. Thus 20 cells of 2 
 volts each, if joined in series, would give an electro- 
 motive force of 40 volts; 50 cells would give 100 volts, 
 and so on. 
 
 The quantity of current which a cell will accumulate 
 or store depends upon the area of its plates; thedarger 
 the plates the greater the capacity of the cell, and the 
 higher the permissible rate of discharge. As it is not 
 always convenient to use very large plates where great 
 capacity is required, the same result may be obtained 
 by using a number of small plates to increase the 
 available plate surface, but in such cases the plates 
 must be connected in parallel. That is, the positive 
 plates must all be connected to one terminal, and the 
 negative plates all to the other terminal, thus forming 
 practically two plates divided into a number of 
 branches. 
 
 The capacity of an accumulator is usually measured 
 in ampere hours. Thus an accumulator which will 
 discharge a current of ten amperes for one hour, or of 
 
ELECTRICITY FOR ENGINEERS 
 
 197 
 
 five amperes for two hours, or of one ampere for ten 
 hours, is said to have a capacity of ten ampere hours. 
 As a general rule, it maybe estimated that an accumu- 
 lator has a capacity of six ampere hours for each 
 square foot of positive plate surface. 
 
 For charging storage batteries the shunt dynamo is 
 generally used, and the voltage must be kept as nearly 
 constant as possible. Fig. 108 shows a very simple 
 installation where the battery is intended to be charged 
 during the running time of the dynamo and to carry 
 the lights during such time as the dynamo is not in 
 
 FIGURE 108. 
 
 action. The ammeter A, in the battery line, should 
 be of a kind which indicates the direction of the cur- 
 rent passing through it. The rheostat R is used to 
 regulate the charging current and the voltmeter V is 
 connected so that either the voltage of the dynamo or 
 the battery may be taken. In addition to this volt- 
 meter a low reading meter should also be provided to 
 test single cells. An automatic circuit breaker is also 
 often provided to open the circuit should the current 
 through it flow in the wrong direction. Should, for 
 any reason, the voltage of the dynamo fall below that 
 
198 ELECTRICITY FOR ENGINEERS 
 
 of the battery while charging, the battery would begin 
 to discharge through the dynamo. Where it is import- 
 ant that the voltage supplied by the battery shall be 
 at the same voltage as that supplied by the dynamo, a 
 "booster" is employed to help charge the battery. 
 Such a booster increases the electromotive force at 
 the terminals of the battery sufficient to allow it to be 
 charged to the full pressure of the dynamo. In setting 
 up and charging storage batteries, detailed instructions 
 should be obtained from the makers and rigidly 
 followed. 
 
CHAPTER XIV 
 
 Electrolysis. Electrolysis is chemical decomposition 
 effected by means of the flow of an electric current. 
 Bydectrolytic action it is possible to deposit metals, 
 such as gold, silver, nickel, etc., over the exterior 
 surface of other metals. This process is ordinarily 
 called nickel plating, gold plating, etc., and is carried 
 on by means of tanks in which there are liquids hold- 
 ing in solution some of the various metallic salts. By 
 placing over these tanks a bar or number of bars made 
 of brass or copper, we may hang articles from these 
 bars by means of wires, so that they are submerged in 
 the' solution. Now by using a dynamo whose output 
 is low in pressure or electromotive force and high in 
 quantity or amperes, and connecting the positive or 
 outgoing terminal of this machine to a piece of metal, 
 such as copper, nickel, gold, or silver, and submerging 
 this metal in the liquid contained in the tank, the flow 
 of current from this piece of gold or silver into the 
 liquid or bath will carry with it, by electrolysis or 
 electrolytic action, some of this gold or silver and 
 deposit it on the articles suspended in the liquid, from 
 the brass or copper bars to which the negative terminal 
 of the plating dynamo is connected. The use of the bath 
 containing metallic salts reduces the resistance from 
 the metal to be deposited on the articles that are to be 
 plated, which are the negative electrodes. This effects 
 an equal deposit of metal over the entire surfaces 
 being subjected to the electrolytic or plating action. 
 
 Where it is desired to cover such metals as steel or 
 199 
 
200 ELECTRICITY FOR ENGINEERS 
 
 iron with silver or gold, it becomes necessary to subject 
 the articles to De plated to what is called a striking 
 bath. 'This striking bath consists of a system of elec- 
 trolytic action as above described, where copper is first 
 deposited over the surfaces of iron or steel. The more 
 precious metals will distribute themselves over this 
 copper surface more uniformly and in a finer grained 
 manner than if the article had not been copper plated 
 first. After the plated article has had sufficient metal 
 deposited on its surface, it is put through a buffing and 
 polishing process for its final finish. 
 
 Electrolysis has also been applied where it is desired 
 to reclaim the precious metals from ores without smelt- 
 ing them. This method consists of immersing the ore 
 in tanks filled with a solution. The ore receives cur- 
 rent from the positive element of a dynamo through 
 the liquid solution, and the metal in the ore is depos- 
 ited on the negative plate in the vat, which is con- 
 nected to the negative terminal of the dynamo. Thus 
 by employing a process similar to electro plating it is 
 possible to extract the metal from the ores in almost 
 its pure state from the negative plate. The solution 
 mentioned is water in which various kinds of metallic 
 salts have been dissolved which bear a chemical rela- 
 tion to the metals to be extracted. 
 
 This short description will assist in explaining how 
 electrolytic action takes place in water and gas pipes 
 buried under the surface of the ground, when, for 
 instance, electric railroads, operated in the vicinity 
 are not properly constructed. In the construction of 
 an electric street railroad or trolley line the generators 
 are connected to the trolley wires usually at the posi- 
 tive terminals of the dynamos. 
 
 The current passes from the trolley line through the 
 
ELECTRICITY FOR ENGINEERS 201 
 
 .car to the rails and back to the negative pole of the 
 dynamo. If the rails are not of sufficient carrying 
 capacity, or if there is a pipe line of better carrying 
 capacity near the rails, it is quite certain that some of 
 the current will be carried by the pipes. Wherever 
 the current leaves a pipe it carries some of the metal 
 with it, and if there is much current a hole will soon 
 be eaten into the pipe. As the pipes are mostly 
 covered with rust, which is a partial insulator, the 
 current will be most likely to enter and leave the pipe 
 at some point which is comparatively bright and the 
 electrolytic action will be concentrated at such points. 
 
 Heating by Electricity. The electric heater is simply 
 a coil of wire through which enough current is caused 
 to flow to produce quite an appreciable amount of 
 heat. In the use of resistance coils for nearly all elec- 
 trical purposes the function of the resistance coil is to 
 cut down the flow of current required at some point, as 
 for instance, where a resistance coil is used as a start- 
 ing box on a motor. The flow of current across or 
 through such a coil or coils, will produce heat, and 
 shows one way in, which electric power can be con- 
 verted into heat. Another instance, if a contact is 
 poorly made, the resistance to the flow of current 
 offered by this contact produces heat and a consequent 
 loss of watts. The voltaic arc in an arc lamp is 
 another instance where resistance to the flow of current 
 is interposed in the circuit and consequently produces 
 heat. 
 
 The incandescent lamp is another instance where 
 resistance is the cause of the production of heat, but, 
 of course, in both the arc and incandescent light, the 
 result desired is a maximum amount of light with a 
 minimum amount of heat. 
 
202 ELECTRICITY FOR ENGINEERS 
 
 If we were to construct a coil of small wire, whose 
 total resistance would be the. same as that of another 
 coil of large wire, it would be found that the coil of 
 small wire would contain much less wire than the coil 
 of large wire, both resistances being the same in ohms. 
 Now if both these coils were connected across a circuit, 
 we will say of no volts, the same amount of current 
 would flow over both the coils, because their resist- 
 ances are alike, but the smaller coil would get quite 
 hot, while the larger coil would perhaps be just 
 slightly warmed. The number or quantity of heat 
 units gi en out by both coils are the same. The sur- 
 face from which these heat units pass out into the 
 atmosphere is much less in the smaller coil than in the 
 large one, hence the smaller coil gets quite hot, some- 
 times even red hot. If we were to permit current to 
 flow over this small coil and maintain its temperature 
 at a low red heat, it would in time become oxidized by 
 the chemical action of the oxygen in the air. To pre- 
 vent this oxidization we may imbed this small coil in 
 a porcelain cement, and after it has been properly 
 imbedded in this cement we will put the entire coil 
 and cement through a baking process, making the 
 cement quite hard and sealing the wire coil from the 
 influence of the oxygen in the atmosphere. Then 
 we can take this coil so constructed and produce 
 heat in a flat iron, or in a stove, in a curling iron, 
 soldering iron, and in fact anywhere. The coil being 
 so hermetically se-aled it can also be used in chafing- 
 dishes, tea kettles, water urns, glue pots, etc. The 
 principle of producing heat by electricity remains the 
 same no matter where or how it is applied, the only 
 difference necessary being in the form given to the 
 heater coils. 
 
ELECTRICITY FOR ENGINEERS 203 
 
 Heating by electricity is quite an expensive and 
 uneconomical proposition, and an idea can be obtained 
 as to the quantity of current necessary to do electric 
 heating, when we consider that in very cold weather it 
 requires nearly as much power to operate the heaters 
 in a street car system as it does to propel the cars. 
 
CHAPTER XV 
 
 Lightning Arresters. Lightning arresters are needed 
 on overhead, outdoor lines only. The simplest form 
 of lightning arrester consists of two bare metal plates 
 set very close together, but under no circumstances 
 allowed to touch each other. (See Fig. 109.) One of 
 these plates is connected to the overhead line and the 
 other to the ground. 
 
 A sudden flow of current meets with an enormous 
 opposition when it encounters the coils of a large 
 electro magnet. Although the resistance of the air 
 space between the two plates forming the lightning 
 arrester may be several millions of ohms, it is far 
 easier for the current to jump this air space in such a 
 very short time as is taken up by a lightning-discharge 
 than it would be to force its way around the coils of 
 the magnet. The reason for this is, that a current of 
 electricity flowing through the coils of an electro mag- 
 net creates magnetism or lines of force. These lines 
 of force cut through the coils on the magn-et and in 
 that way tend to produce a counter current, or counter 
 electromotive force, which, for a very short time, is 
 almost equal to the electromotive force creating it. 
 Were the current flow to continue for any appreciable 
 time this counter electromotive force would disappear 
 entirely as soon as the magnetism reached its final 
 strength. 
 
 In order, therefore, to facilitate as much as possible 
 a lightning discharge towards the ground and away from 
 the machinery and buildings, the wires leading from 
 204 
 
ELECTRICITY FOR ENGINEERS 
 
 205 
 
 the arresters to the earth should be run in as straight a 
 line as possible and be kept well separated from metal 
 parts, especially iron, of the building. Under no cir- 
 
 TO 
 
 LINE 
 
 WWVWVWWVWV 
 AAA/NAAAAAAAAAAAA 
 
 TO 
 GROUND 
 
 FIGURE 109. 
 
 cumstances should the ground wire be run in an iron 
 pipe, nor should lead covered wires be used. 
 
 With the simple lightning arrester shown above there 
 is great liability of the current from the dynamo fol- 
 lowing the arc caused by the lightning discharge to 
 
200 
 
 ELECTRICITY FOR ENGINEERS 
 
 ground, and, as there must be two arresters, one on eauh 
 side of the dynamo, this amounts almost to a short 
 circuit and is very likely to put the dynamo out of 
 service. Should such an arc continue for a few min- 
 utes, it may fuse the plates of the arrester. The arc 
 can readily be extinguished by blowing it out or caus- 
 ing a strong blast of air to strike it. 
 
 To prevent trouble of this kind the Thomson light- 
 
 FIGURE 110. 
 
 ning arrester, shown in Fig. no, was devised. This 
 consists of the two diverging metal plates shown at 
 the top of the figure, one of which is connected to the 
 earth and the other to the line to be protected and an 
 electro magnet, as shown. The current from the 
 dynamo traverses the coils of the electro magnets. 
 The action is as follows: When a lightning discharge 
 through the arrester takes place, it forms an arc 
 
ELECTRICITY FOR ENGINEERS £()7 
 
 between the lower points of the plates above the mag- 
 nets. These plates are very close together at the 
 bottom. Now the electric arc is always strongly 
 repulsed by a magnet, and hence the arc formed is 
 forced upward where the plates diverge, and the space 
 becomes too great for it to be maintained and it is 
 then broken. The arc is virtually blown out by the 
 magnetism. 
 
22 .500