Class , oJ % Book. ,4 ex GopyrigTrtN°_. *2 COPYRIGHT DEPOSIT. Complete Examination Questions and Answers for Marine and Stationary Engineers A Complete Engine Operator's Catechism Giving the Latest and Most Approved Answers to all Leading Questions which will be Asked for the Purpose of Examining and Determining the Quali- fications of Applicants for Licenses for Engineers and for Persons having Charge of Steam Boilers as Approved by all Muni- cipalities and Government Boards of Examining Engineers, both Stationary and Marine Special Reference to Modern Types of Oil Engines BY CALVIN Fv SWINGLE, M.E. Author of "Twentieth Century Hand-Booh for Steam Engineers and Electricians,''' "Modem Locomotive Engineering Hand-Book," "Steam Boilers: Their Con- struction, Care and Operation" Etc. ILLUSTRATED CHICAGO FREDERICK J. DRAKE & CO. PUBLISHERS -T5 1 <=°l Copyright 1922, 1917, 1914 and 1906 By Frederick J. Drake & Co. Printed in U. S. A. & fi < MmR 10 1922 §)C!.A654901 CONTENTS CHAPTER I PAGE Steam, Heat, Combustion and Fuels 7 CHAPTER II The Boiler 25 CHAPTER III Boiler Construction 65 CHAPTER IV Boiler Settings and Appurtenances 81 CHAPTER V Boiler Operation 128 CHAPTER VI Types of Engines — Classification 173 CHAPTER VII Condensers — Air- Pumps — Sea-Water 211 CHAPTER VIII Auxiliary Machinery and Fittings 240 CHAPTER IX The Indicator — Principles of the Indicator 270 CHAPTER X The Steam Turbine — Fundamental Principles 304 CHAPTER XI Modern Types of Oil Engines 361 INTRODUCTION The development of the science of steam engineering and the continually increasing demand for more power for manufacturing purposes and for transportation, both on land and sea, have in these modern times resulted in the creation of power plants, which are truly marvelous in their details when compared with the steam machinery of forty years ago. Even the last twenty years have witnessed tremendous developments along these lines, and we may imagine the effect it would have upon an engineer, who twenty years ago was counted as first class in his business, but who, having taken a Rip Van Winkle sleep of twenty years, is suddenly awakened and finds him- self set down in the engine room of a first-class ocean steamer, or in the midst of one of our modern up-to-date power plants. The facts are, he would have hard work to recognize his surroundings. Even the steam gaugee would indicate a pressure of 150 to 175 pounds more per square inch than did the old-time gauges. Therefore, in view of the remarkable improvements in steam machinery which have been made and are continually being made, it certainly behooves engineers to do their utmost to keep step with the march of progress. The author has endeav- ored, in the following pages, to place before his readers information in a catechetical form which will be found to cover all of the various details appertaining to the opera- tion of modern steam plants, both stationary and marine. C. F. S. CHAPTER I STEAM, HEAT, COMBUSTION, AND FUELS Ques. 1. — What is steam? Ans. — Steam is vapor of water. Ques. 2. — At what temperature will water evaporate (boil) in the open air at sea level? Ans. — 212 degrees Fahrenheit. Ques. 3. — If 1 cubic foot of water is evaporated at 212 degrees into steam at atmospheric pressure, how many cubic feet of steam will there be? In other words, what will the volume of the steam be? Ans. — 1,646 cubic feet. Ques. 4. — Then what is the relative volume of steam at atmospheric pressure, and the water from which it was evaporated at 212 degrees? Ans.— 1,646 to 1. Ques. 5. — What is the relative volume of steam at 200 pounds gauge pressure, and the water from which it was generated? Ans.— 132 to 1. Ques. 6. — What is meant by the terms atmospheric pressure, gauge pressure, and absolute pressure, as applied to steam and other gases? Ans. — The pressure in pounds exerted by the steam, or gas, on each square inch of the interior surface of the containing vessel, tending to rupture it. 7 8 QUESTIONS AND ANSWERS Ques. 7. — What is vacuum? Ans. — The absence of all pressure in the interior of a vessel. Table 1, which follows, shows the physical properties of saturated steam from a perfect vacuum up to 1,000 pounds absolute pressure. It will be found convenient for reference. TABLE I Properties of Saturated Steam ►> SI Total Heat s 40 O u o Absolute Pressure Lbs. per Sq. Inc J* P. CO Q above 32 U F. latent Heat H-h Heat units > •S3 "a; .5 M O • So i> to u a In the Water h Heat-units In the Steam H Heat-units ~ 29.74 089 32. O. IO9I.7 I09I.7 208,080 3333.3 .0005 29.67 .122 40. 8. IO94. 1 1086. 1 154,330 2472.2 .0004 2Q.56 .176 50. 18. 1097.2 IO79.2 107,630 I 724. I .0006 29.40 .254 60. 28.01 II00.2 I072.2 76,370 1223.4 .0008 29.19 •359 7o. 38.02 1 103. 3 1065.3 54,660 875.61 .0011 28.90 .502 80. 48.04 1106.3 1058.3 39,690 63 s. So .0016 28.51 .692 90. 58.06 110Q.4 I05L3 2Q,290 469. 20 .0021 28.00 •943 100. 68.08 1112.4 1044.4 21,830 34970 .0028 27.88 I. 102. 1 70.09 1113.1 IO43.O 20,623 334.23 .0030 25.85 2. 126.3 94.44 1120.5 I026.O 10,730 173.23 .0058 23.83 3- 141. 6 109.9 1125.1 1015.3 7,325 118.00 .0085 21.78 4. I53.I 121. 4 1128.6 1007.2 5,538 89. So .0111 19.74 5. 162.3 130.7 II3I-4 1000. 7 4,. c 30 72.50 .0137 17.70 6. 1 70. 1 138.6 1133.8 995-2 3,8i6 61.10 .0163 15.67 7. 176.9 145.4 II35.9 990.5 3.302 53.00 .0189 13.63 8. 1S2.9 I5I.5 1137.7 9S6.2 2,912 46.60 .0214 II.60 9. 188.3 156.9 H39-4 982.4 2,607 41.82 .0239 9.56 10. 193.2 161.9 1140.9 979.0 2,361 37.8o .0264 7.52 11. 197.8 166.5 1142.3 975.8 2,159 34.61 .0289 5-49 12. 202.0 170.7 II43.5 972.8 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 II45.9 967.4 1,721 27.50 .0363 o.OO 14.7 212.0 180.9 1 146. 6 965.7 1,646 26.36 .0379 STEAM, HEAT, COMBUSTION, AND FUELS Table I — Continued Total Heat cu a p4 Above 32° F. ■4-» d co S CO 6* 0) ex be . a to cu o* £ cu > '■*■* 5i U rt 0"-5 < +, cu a w ; « psS t-i H t— < H-t O.3 15 213.3 181. 9 II46.9 965.O 1,614 25.90 .0387 i-3 16 216.3 185.3 II47.9 962.7 1,519 2403 .0411 2.3 17 219.4 188.4 II48.9 96O.5 1,434 23.00 .043? 3.3 18 222.4 191.4 1 149. 8 958.3 1,359 2I.80 .0459 4-3 19 225.2 194.3 1 1 50.6 956.3 1,292 20.70 .O483 5-3 20 227.9 i97.o II5I.5 954-4 1,231 19.72 .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 17.30 .0578 9-3 24 237.8 207.0 "54.5 947.4 1,038 16.62 .0602 10.3 25 240.0 209.3 "55-1 945.8 998 ID.OO .062 5 ".3 26 242.2 211. 5 "55.8 944-3 962 15.42 .O649 12.3 27 244.3 213.7 1156.4 942.8 929 I4.90 .0672 13.3 28 246.3 215.7 "57.1 94L3 898 I4.40 .0696 14.3 29 248.3 217.8 "57-7 939-9 869 13.91 .0719 15.3 SO 250.2 219.7 "58.3 938.9 841 13.50 .0742 16.3 31 252.1 221.6 1158.8 937-2 816 I3.07 .0765 17.3 32 254.0 223.5 "59-4 935.9 792 12.68 .0788 18.3 33 255.7 225.3 "59-9 934-6 769 12.32 .0812 19-3 34 257.5 227.1 1 160. 5 933-4 748 12.00 .0835 20.3 35 259.2 228.8 1161.0 932.2 728 11.66 .O858 21.3 36 260.8 230.5 1161.5 931.0 709 11.36 .088O 22.3 37 262.5 232.1 1162.0 929.8 691 11.07 .O9O3 23-3 38 264.0 233.8 1 162. 5 928.7 674 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.^ 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 43 271.5 241.4 1164.7 923.3 600 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 .1086 31.3 46 275.7 245.7 1166.0 Q20.4 563 9.02 .IIO8 32.3 47 277.0 247.0 1 166. 4 9I9.4 552 8.84 .1131 33-3 48 278.3 248.4 1166.8 918.5 541 8.67 ."53 34-3 49 279.6 249.7 1167.2 917.5 531 8.50 .1176 35.3 5o 280.9 251.0 1167.6 916.6 520 8-34 .1198 36.3 51 282.1 252.2 1168.0 915.7 5" 8.19 .1221 37.3 52 283.3 253.5 1168.4 914.9 502 8.04 .1243 10 QUESTIONS AND ANSWERS Table i — Co?iti?i tied m cf C- u ~ z. it . •Z 09 38.3 39-3 40-3 41.3 42.3 43 3 44-3 45-3 46.3 47-3 48.3 49-3 50.3 51.3 52.3 53 3 54.3 55.3 56.3 57.3 53.3 59-3 60.3 61.3 62.3 63.3 64.3 65.3 66.3 67.3 68.3 69.3 70.3 71-3 72.3 73-3 74.3 75-3 3 a Irt < 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 7i 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 c ■ c o Hg Q 284.5 285.7 286.9 288.1 289.1 290.3 291.4 292.5 293.6 294-7 295.7 296.8 297.8 293. S 299.8 300. s 301.8 302.7 303.7 304.6 305.6 306.5 307.4 308.3 309.2 3 10. 1 310.9 311. 8 312.7 313.5 3U4 315.2 316.0 316.8 317.7 3IS.5 319.3 320.0 Total Heat above 32 F. 254-7 256.0 257.2 253.3 259.5 260.7 261.8 262.9 264.0 265.1 266.2 267.2 26S.3 269.3 270.4 271.4 272.4 273.4 2 74-4 275.3 276.3 277.2 27S.2 279.1 2S0.0 2S0.9 2S2.7 2S3.6 2S4.5 2S5.3 2S6.2 2S7.0 2S7.9 288.7 2S9.5 290.4 291.2 5 2 168.7 169. 1 169.4 169.8 170. 1 170.5 170.S 171. 2 171. 5 171. S 172. 1 172.4 172.8 173- 1 173-4 173-7 174.0 174-3 174-6 174.8 175. 1 175-4 175-7 176.0 176.2 176.5 176.S 177.0 177.3 177.6 177.S 173. 1 178.3 178.6 178.8 1 79- 1 179.3 179.6 -r - 914.0 492 913-1 484 912.3 476 911.5 46S 910.6 460 909.3 453 909.0 446 903.2 439 Q07.5 432 906.7 425 905.9 419 005.2 413 904.5 407 903.7 401 903.0 395 902.3 390 901.6 3S4 000.9 379 900.2 374 899-5 369 89S.9 365 89^.2 360 897.5 356 896.9 351 S96.2 347 895.6 343 895.0 339 394.3 334 893.7 331 893.1 327 892.5 323 891.9 320 891.3 316 890.7 313 890.1 309 889.5 306 8S8.9 303 8S8.4 299 5* 7.90 7.76 7.63 7.50 7.38 7.26 7.14 7.03 6.92 6.S2 6.72 6.62 6.53 6.43 6.34 6.2> 6 6 6 17 09 01 93 5.S5 7i 63 57 50 5-43 5-37 5.31 5.25 5.iS 513 5.07 5.02 4.96 4.91 4.36 4.S1 STEAM, heat;, combustion, and fuels Table i — Continued 11 a Total Heat CD 5 •** fid 53 »h =3 d cm— 1 en a 4> above 32 F. a en E 3 - * . CO • to a* Cu >- cu -D - v P. be . S3 CO Oj-O " 4 " > Cl cojo Q j3 (Z •3 ffi *cd M & CM ^ H-t d ►* t-H a as g 76.3 91 320.8 292.0 1179.8 887.8 296 4.76 .2102 77.3 92 321.6 292.8 1 180.0 887.2 293 4.71 .2123 78.3 93 322.4 293.6 1180.3 886.7 20>0 4-66 .2145 79-3 94 323.1 294.4 1180.5 886.1 287 4.62 .2166 80.3 95 323.9 295.1 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 83.3 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 85.3 100 327.6 298.9 1181.8 882.9 271 4.36 .2296 86.3 IOI 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 88.3 103 329.7 30I. I 1182.5 881.4 264 4.24 .2360 89.3 104 330.4 30I.9 1182.7 880.8 26l 4.20 .2382 90-3 105 33i. 1 302.6 1182.9 880.3 259 4.16 .2403 9!-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 III 335-2 306.8 1184.2 877.4 246 3.95 .2531 97.3 112 335-9 307.5 1 1 84.4 876,9 244 3.92 .2553 98.3 113 336.5 308.2 1184.6 876.4 242 3.88 .2574 99-3 114 337.2 308.8 1184.8 875.9 24O 3.85 .2596 100.3 115 337.8 309.^ 1185.0 875.5 238 3.82 .2617 101.3 Il6 338.5 310.2 1185.2 875.0 236 3-79 .2638 I02.3 117 339-1 3I0.8 1185.4 874.5 234 3.76 .2660 103.3 Il8 339-7 311. 5 1185.6 874.1 232 3-73 .2681 104.3 119 340.4 312.1 1185.8 873.6 230 3-70 .2703 105.3 120 341.0 312.8 1185.9 873.2 228 3.67 .2764 106.3 121 341.6 313.4 1 186. 1 872.7 227 3-64 .2745 107.3 122 342.2 314. 1 1186.3 872.3 225 3.62 .2766 108.3 123 342.9 314.7 1186.5 871.8 223 3-59 .2788 109.3 124 343.5 315.3 1186.7 871.4 221 3.56 .2809 no. 3 125 344.1 316.0 1186.9 870.9 220 3.53 .2830 in. 3 120 344-7 316.6 1187.1 870.5 218 3.51 2851 112.3 127 345-3 317.2 1187.3 870.0 216 3.48 .2872 «3.3 128 345-9 317.8 1187.4 869.0 215 3.46 .2894 12 QUESTIONS AND ANSWERS Table i — Continued Total Heat CD S 2d 9d CO>— » co . 1x1 Above 32° F. rt co £ c a) fct, CO S o 1 *3 rv to E XI - s? •"• 4-1 3 CO Q 2 x «i 5d OJ <^ ^3 4 feet, depen ng upon the size >f the boiler. Ques. 90.— How ar? these furnace flues secured in :he boiler? 4 <-* o OS (4 U> H Ui a 3 o M s o « o 5 A ns# — One end of the flue is riveted into the front ^ead of the boiler, and the back end of the flue is rivetf 1 28 QUESTIONS AND ANSWERS Ques. 91. — Describe the combustion chamber of th< Scotch boiler. Ans. — It is a chamber built of steel boiler plate located at the rear end of the boiler, and entirely sur rounded by water. A nest of tubes extends from th< front sheet of the combustion chamber, above the cor- rugated furnace flue, to the front head of the shell. Fig. 2. Standard Horizontal Boiler with Full-arch Front Setting. Ques. 92. — Describe the course of the heated gases ii the Scotch boiler. Ans. — The furnaces proper, are placed within the cor rugated flues, near the front end. The gases and smoke pass through the flues to the combustion chamber, anc from thence return through the small tubes to the smoke box in front, and from there out through the stack. Ques. 93. — How are the flat sides of the combustion chamber staved? THE BOILER Fig. 3, Vertical Tubular Boiler, with Fuel-Length Tubes. SA QUESTIONS AND ANSWERS Ans. — By stay-bolts connecting with the shell and th< back head. The small tubes serve as stays for the front sheet. Fig. 4. Vertical Marine Boiler, Showing Details of Bracing. Ques. 94. — What is meant by double-ended Scotd boilersf Ans. — Boilers having furnaces at each end. A double- ended Scotch boiler is in fact two single-ended boilen placed back to back. THE BOILER 31 Ques. 95. — What advantage has the Scotch boiler over other types? Ans. — A very large amount of heating surface in proportion to its cubic contents. Ques. 96. — What are the disadvantages connected with the use of the Scotch boiler? •• oooosra 0000000000 0000000000 000000 000000 000000 0000000000 0000000000 OOOOOOOOOo Fig. 5. Single-Ended Scotch Marine Boiler. Ans. — First, defective water circulation; second, iability to leaky tubes; third, unequal expansion of the )arts, thereby setting up severe strains. Ques. 97. — Is the Scotch boiler much used? &ns. — It is in almost universal use in the large ocean- orng mercnanr vessers. 32 QUESTIONS AND ANSWERS Ques. 98. — What are the distinctive features of the flue and return-tube boiler? Ans. — This form of boiler is cylindrical in shape in that part of the shell containing the large flues and small return tubes, but resembles a locomotive boiler in that portion containing the fire-box. Fig. 6. Double-Ended Scotch Marine Boiler, Sectional View. Ques. 99. — Describe the action of the heat in this boiler. Ans. — The furnace or fire-box, resembling that of a locomotive, is located in the front end of the boiler. From thence large flues conduct the heated gases to the combustion chamber in the rear, similar to that of a Scotch boiler, and from there the gases return through the small tubes to the uptake. THE BOILER 3* S « o u w (4 P w CCS 6 34 QUESTIONS AND ANSWERS Ques. 100. — Describe the Western river boiler. Ans. — This boiler is usually very long (25 to 30 feet) ji proportion to its diameter. It consists of a cylindrical shell having two or more flues of large diameter (12 to 14 inches) extending its entire length. It is set in brick- work in the same manner as the horizontal tubular boiler is, tie gases passing underneath the shell to the rear, and thence returning through the large flues to the uptake Fig. 8. The Bonus-Freeman Water-Tube Boiler. leacirg to the stack. It is a very simple boiler, and willj withstand high pressures and hard usage. Ques. 101. — Describe the locomotive boiler. Ans. — The locomotive boiler consists essentially of al rectangular fire-box and a cylindrical shell. A large number of tubes of small diameter (2 inches) -?ass| through the shell from the fire-box to the smoke-box, continuation of the barrel at the front end. THE BOILER 3» 36 QUESTIONS AND ANSWERS Ques. 102. — How is the fire-box joined to the outer shell at the bottom? Ans. — By a forged ring called the mud-ring, made of wrought iron or steel, through which long rivets pass, uniting the fire-box sheet and the outer sheet. Ques. 103. — How are the flat sides of the fire-box stayed? Ans. — By stay-blots screwed through the outer shell, into and through the fire sheet, and having both ends riveted down cold. Ques. 104. — How is the flat crown-sheet of a locomo- tive boiler stayed? P^5S^S-5s waaa L_ Fig. 10. Cornish Boiler. Ans. — By a system of crown-bars, made in the shape of double girders, the ends of which rest upon the side sheets of the fire-box. Crown-bolts pass up through the crown-sheet and crown-bars, and are secured by nuts resting upon saddles on top of the crown-bars. The heads of the bolts support the crown-sheet. Ques. 105. — Is the locomotive boiler an economical boiler for stationary purposes? Ans. — It is not. Ques. 106. — Are there any other forms of cylindrical •hell boilers besides those already referred to? Ans. — Yes; the Cornish boiler, having a large central THE BOILER 31 flue, in one end of which the furnace is located; the Lan- cashire boiler, a modification of the Cornish, containing two internal furnace flues, and the Continental boiler. Ques. 107. — What is meant by Galloway tubes as applied to a boiler? Ans. — Galloway tubes are conical-shaped water tubes which stand in an inclined position in the large flues of the Lancashire boiler back of the furnaces, and serve to circulate the water from the space below, to the space above the flues. They also act as bafflers to the gases In their passage through the flues, and thus provide increased heating surface. §§I?=is==sssrag *■ "" n Fig. 11 The Lancashire Boiler. Pig. 12. The Gai^oway Boiler. Ques. 108. — Describe the Continental boiler. Ans. — The Continental boiler is a modification of the Scotch boiler, and is used to a large extent in the marine service. It is provided with a Morison corrugated fur- nace, and its efficiency as a steam generator has been established by a long series of practical tests. Ques. 109. — What are the leading characteristics of the Bonson boiler? Ans. — The Bonson boiler is a combination of the tubular and water-tube types. The water-tube member is in the form of a flat arch, and serves as a roof to the furnace. The cylindrical shell rests upon and is con- 38 QUESTIONS AND ANSWERS nected with front and rear steel saddles (water-chambers) and the water-tubes are connected with the lower portion of these saddles. * Ques 110. — What route do the gases take in passing from the furnace of the Bonson boiler to the smoke- stack? Fig. 13. Continental Boiler, with Morison Corrugated Furnace, eor Marine or Stationary Service. Ans. — They pass first under the water-tubes, which are lined with a special tile made of fire-clay, the sides of the furnace being also lined with fire-brick. The gases, after passing into the combustion chamber, at the rear, ascend and return through the fire-tubes in the shell, and from thence into the uptake at the front. Ques. 111. — What are the leading characteristics of water-tube boilers? v THE BOILER 39 Ans. — In water-tube boilers the larger part of the heating surface consists of tubes of moderate size (1 to 4 inches in diameter). There is always some form of separator, drum or reservoir into which the tubes lead. In this drum the steam is separated from the water. In some forms of water-tube boilers this shell or drum is of considerable size. Fig. 14. The Bonson Boiler and Setting. Ques. 112. — Is this drum exposed directly or indi- rectly to the heat? Ans. — It is generally exposed indirectly, as the upper part is used for steam space. Ques. 113. — What advantage is there in having a large size steam and water-drum? Ans. — The advantage of having a good free water surface for the disengagement of the steam. The water occupies about one-third of the lower portion of the drum. iO QUESTIONS AND ANSWERS Quef. 114. — Are the upper ends of the tubes in all water-trbe boilers entirely filled with water? Ans. — Not in all cases. In some forms of water-tube boilers the upper ends of the tubes extend above the water level. Ques. 115. — How are these different forms of water- tube boilers designated? Ans. — First, as drowned tubes; second, as priming \ubes. Fig. 15. Steee Saddle of Bonson Boieer. Ques. 116. — What are some of the advantages of water-tube boilers? Ans. — They may be made light, powerful and able to withstand high pressures. They are quick steamers, that is, steam may be raised rapidly from cold water; also, the circulation of the water in them is good gen- erally. Ques. 117. — What are some of the disadvantages attending the use of water-tube boilers? Ans. — They are difficult to inspect and clean. Also, owing to the large number of joints, leaks are liable to occur. THE BOILER 41 Ques 118. — Describe briefly the Babcock & Wilcox vater-tube boiler. Ans. — There is a large horizontal cylindrical shell at he top for the purpose of supplying steam and water- pace. The lower half of this shell contains water, and he upper half steam. The tubes are expanded into leaders at each end. At the front end these headers are Fig. 16. Babcock and Wilcox Boiler, for Land Service. rought up near the shell, to which they are connected y a cross connection. The back end headers are con- ected to a mud-drum at the bottom, and to the shell at he top by slightly inclined tubes. The back headers eing lower than the front headers, the tubes are thus nclined from front to back. Ques. 119. — In what style are the tubes connected to le headers? Ans. — They are staggered. 42 QUESTIONS AND ANSWERS Ques. 120. — What is meant by staggered tubes? Ans. — Staggered tubes are those which are not placed in vertical rows, that is, one directly above the other. Fig. 17. Babcock and Wilcox "Alert" Type Marine. Boiler. FromB. & W. "Book Marine Steam," p. 154. Ques. 121. — What are the facilities for cleaning thes< tubes? Ans. — At each end of each tube there are hand-hole: provided. Ques. 122. — Describe the course of the gases for th( Babcock & Wilcox boiler. THE BOILER 43 Ans. — A brick bridge wall at the baca. tnu ot the fur- nace, together with special tiles placed among the tubes, compel the gases to first pass up among the tubes until they come in contact with the bottom of the shell for about two-thirds of its length from the front end. At this point a hanging bridge wall and special tiles deflect the gases downward in their course, and they again circulate among the tubes, passing underneath the tiles and up among the tubes again. The products of com- bustion thus pass over and around the tubes three times on their way to the uptake. Ques. 123. — What portions of this boiler constitute the heating surface? Ans. — The tubes, headers, and the lower half of the shell. Ques. 124. — What course does the water take in its circulation in this boiler? Ans. — Down from the shell at the rear to the water- tubes, thence forward and upward through the tubes. In its course through the tubes it becomes partially vap- orized and of less density. It then passes up into the shell at the front, where the steam is disengaged. Ques. 125. — Is the Babcock & Wilcox boiler much used in the marine service? Ans. — Yes, it is used extensively in the British and United States navies, also in merchant steamers. Ques. 126. — Is the form of this boiler the same for marine as for land service? Ans. — It is not. The chief features in which it differs from the land boiler are, first, a verv much larger grate 44 QUESTIONS AND ANSWERS area; second, the cylindrical shell is set transversely to the direction of the tubes; third, the fire-doors are located at what would be the rear of the land boiler; fourth, the tubes are much shorter, owing to the contracted space allowed on ocean steamers; fifth, the brickwork is sur- rounded outside by a metal casing. Fig. 18. The Caldweu, Boiler. Ques. 127. — Are there any other forms of water-tube boilers patterned after the Babcock & Wilcox boiler? Ans. — There are several, prominent among which are the Caldwell and the Root boilers. Ques. 128. — Describe the Caldwell boiler. Ans. — It is similar in construction to the Babcock & Wilcox, except that the tubes, instead of being staggered vertically, are placed one directly above the other, with specially shaped fire-brick laid across alternate spaces between the tubes to deflect the gases. THE BOILER 45 Ques. 129. Describe the Root water-tube boiler. Ans. — It consists of a nest of 4-inch tubes expanded into headers which are connected at front and back with a set of steam and water-drums about 15 inches in diameter. The tubes are inclined at an angle of about 20 degrees from the horizontal. At the rear end of each overhead water and steam-drum is a connection leading to the ■■■ Fig. 19. The Root Water-Tube Boiler. steam-collecting header above, placed transversely to the direction of the other drums, and from this header two connecting pipes lead to a large steam-drum located at about the center of the boiler, and above all. Ques. 130. — How does the water circulate in the Root boiler r Ails. — It descends through vertical connecting pipes If rom the feed-drum at the rear to the mud-drum beneath^ 46 QUESTIONS AND ANSWERS From thence it passes into the back and lower ends of the tubes, and on up through the tubes, and into the over- head drums, into the upper halves of which the steam is disengaged. Ques. 131. — Describe the Cahall water-tube boiler. Anc —The Cahall boiler is vertical, having a nest of Fig. 20. The Cahall Vertical Boiler. water-tubes standing nearly vertical. These tubes are connected with a shallow water-drum at the bottom, and a larger and deeper water and steam-drum at the top. The furnace is located alongside of the mud-drum, and the gases traverse among the tubes in a circuitous manner owing to bafflers placed among the tubes. THE BOILER 4T Oues. 132. — How do Lie £*ses escape to the stack . ; a his boiler? Fig. 21. -Wickes Vertical Water-Tube Boiler. Ans. — Extending through the center of the annular rum at the top is a flue through which the products of ombustion find their way to the uptake. 48 QUESTIONS AND ANSWERS Ques. 133. — Of what form is the Wickes boiler? Ans. — The Wickes boiler consists of upper and lower vertical drums connected by vertical tubes. The furnace is external. Fig. 22. The Stirling Boiler. Ques. 134. — What course do the gases take in their passage to the stack, in the Wickes boiler? Ans. — A thin partition wall of fire-brick is built between two adjoining middle rows of tubes. This wall causes the erases first to ascend to the top, and then down- THE BOILER 4& wards to the chimney flue at the bottom and opposite to the furnace. Ques. 135. — Describe the Stirling boiler. Ans. — In the Stirling water-tube boiler there are three horizontal steam and water-drums at the top, an^ Fig. 23. Thornycroft Boiler. one water-drum at the bottom. These drums are co** nected by three divisions of inclined and curved tubes. Ques. 136. — How are the products of combustion led from the furnace to the uptake, in the Stirling boiler? Ans. — Bafflers of fire-brick are placed back of the two first divisions of tubes. The first baffler cause* the gases 50 QUESTIONS AND ANSWERS to ascend to the top of the first division of tubes; the second baffler deflects the gases downwards, around and among: the tubes of the second division. The draught is tlw : i upwards again, surrounding the tubes composing tb' third division, thence to the stack. Fig. 24. The Niclausse Boiler. Ques. 137. — Describe the Thornycroft boiler. Ans. — The Thornycroft boiler is adapted for use on torpedo boats and high-speed yachts. A large horizontal steam-drum at the top is connected to a water-drum at the bottom by two groups of curved tubes of small THE BOILER 51 diameter. The grates are located on each side of the water-drum. There are also two smaller drums at the bottom, one on each side, connected to the middle drum by small pipes. Fig. 25. The Niceausse Boiler— Side View. Ques. 138. — How does the water circulate in this boiler? Ans. — Down from the top drum to the middle lower drum through special return water-tubes of large diameter, and from thence through the smaller tubes to 52 QUESTIONS AND ANSWERS the side drums. From there the water passes up through the curved tubes to the upper portion of the top drum, where the steam is disengaged. Ques. 139. — Describe the Niclausse boiler. Ans. — The Niclausse boiler is made up of a series of slightly inclined tubes. These tubes are double, that is, one inside the other, and they are connected to the front header in such a manner that the colder water flows down the inside tubes and returns to the front between the two tubes when heated by the action of the fire and hot gases on the larger outside tubes. Each vertical row of tubes is connected at the front end to a separate header, the headers being placed side by side, and all leading into a top drum or steam-collector. Ques. 140. — How is the entering feed-water at the front kept separate from the hot ascending currents of water? Ans. — By a diaphragm in the top drum that keeps the cooler water separate from the hot water and steam. Ques. 141. — How are the tubes connected to the headers in the Niclausse boiler? Ans. — By coned surfaces on the ends of the tubes bearing on similar coned surfaces in the headers, and kept in contact by outside dogs and nuts. These joints appear to cause no trouble by leakage. Ques. 142. — Is the Niclausse boiler much used? Ans. — It is used to some extent in the British navy, and also in several large United States war-ships. Ques. 143. — Of what type is the Normand boiler? Ans. — The Normand boiler is a marine water-tube THE BOILER 53 boiler of the Thornycrof t type. The two outer rows of tubes are formed into a wall of tubes, and in the vicinity of the furnace the tubes are arched upwards in order to form a combustion chamber. Back of the furnace the Part front "View Part section through furnace. Fig. 26. The Normand Boiler. curvature is not so great, although all of the tubes are curved more or less, to permit of expansion when heated. Ques. 144. — What course do the gases take in this boiler? b'4 QUESTIONS AND ANSWERS Ans. — The gases proceed from the fire among the tubes, and traverse the length of the boiler to the rear end, where they pass below a brick deflecting plate to the space surrounding those tubes that are less curved. Fig. 27. The Yarrow BoitER. Ques. 145. — What other peculiar feature character- izes the Normand boiler? Ans. — Provision is made for tne admission of air Aoove the fire. THE BOILER 55 Ques. 146. — How is this accomplished? Ans. — By means of a small air casing at the front and back, and a series of small holes one inch in diameter lead- ing through the brickwork to the space above the fire. Ques. 147. — For what kind of service is the Normand boiler mainly adapted? Ans. — For torpedo-boat destroyers. Ques. 148. — What is the distinguishing feature of the Yarrow boiler, among boilers having water-tubes of small diameter? Ans. — The Yarrow boiler lias straight tubes. It also has at the bottom on each side a small water-chamber or mud-drum with nearly flat tube-plates, into which the tubes are expanded. The tubes run in an inclined direc- tion from these water-drums to the steam and water- drum at the top. Ques. 149. In what manner does the water circulate in the Yarrow boiler? Ans. — Those tubes which receive the most heat con- duct the water from the lower drums to the upper drum, into which the steam is delivered. Other tubes which are cooler carry the water from the upper drum to the lower drums. Ques. 150. — Describe the Mosher boiler. Ans. — The Mosher boiler has two upper steam-drums and two lower and smaller water-drums, the water- drums being directly underneath the steam-drums. These drums are connected by curved generator pipes of small diameter, the pipes entering the steam-drums above the water-line. 56 QUESTIONS AND ANSWERS Ques. 151. — How does the water find its way from the upper to the lower drums? Ans. — By means of two external downtake pipes 4 inches in diameter. The boiler is cased in, the casing being lined with fire-brick. Ques. 152. — For what class of service is the Mosher boiler mainly adapted? Ans. — Torpedo boats and high-speed yachts. Fig. 28. The Mosher Boiler. Ques. 153. — Describe the construction of the Almy boiler. Ans. — It is made principally of short lengths of pipe screwed into return bends and into twin unions. At the bottom there is a larger pipe or header that surrounds the two sides and back of the grates, and there is a similar structure at the top, the two headers being con- nected by the smaller pipes. THE BOILER 5? Ques. 154. — How is the steam separated from the water in the Almy boiler? Fig. 29. The Aemy Boiler. Ans. — The steam and water are together discharged from the upper header into a separator in front of the boiler, and from this separator the steam is drawn, while 58 QUESTIONS AND ANSWERS the separated water and the feed-water pass down through circulating pipes to the lower header. Ques. 155. — What other peculiar feature attaches to this boiler? Fig. 30. The Du Temple Boiler. Ans. — It is provided with a coil feed-water heater above the main boiler. Ques. 156. — Describe in general terms the Du Tempi boiler. THE BOILER 59 Ans.— It is of the same general character as the 'hornycroft type, except that the generating tubes dis- harge into the steam-drum below the water-line. Ques. 157. — How are these tubes connected to the trums? Fig. 31. Rsed's Boiler. Ans. — By cones and nuts. Ques. 158.— Is the Du Temple boiler used to any ;reat extent? Ans. — Yes; it is used extensively in the French navy, specially on vessels of the torpedo-boat type. Ques. 159.— Describe Reed's boiler. 60 QUESTIONS AND ANSWERS Ans. — This boiler resembles the Du Temple boiler. I has the usual top collector drum, and two lower drum with curved generating pipes connecting them. Ques. 160. — How are the tubes attached to th drums? Fig. 32. The Seabury Boiler. Ans. — By screwed connections at each end, witl nuts inside the chambers. Ques. lGl.-^-How are the gases caused to travers< the heating surface in this boiler? Ans. — By means of diaphragms fitted to the tubes. Ques. 162. — What class of service is this boile: largely used in? THE BOILER 61 Ans. — British torpedo-boat destroyers, and also on hird-class cruisers. Ques. 163. — Describe the Seabury boiler. Ans. — The Seabury boiler has three lower water- rums, the middle drum being smaller than the two out- ide drums. These drums are connected to one large team and water-drum above by curved pipes of small iameter and the furnace is divided into two sections by he central nest of pipes. Above the boiler tubes and nside the casing there is a coil feed-water heater. Ques. 164. — Describe the latest type of Belleville oiler? Ans. — The Belleville boiler is a water-tube boiler, and ; of extensive use on large ships. It is made up of two istinct series of straight tubes, larger in diameter than hose of the curved type. These tubes are placed nearly orizontal, each alternate horizontal row being slightly nclined in the opposite direction to the row above it. The generator proper has a water-chamber below and a team-drum or chamber on top, and the zigzagged tubes re connected to these respective chambers, Ques. 165. — What kind of a furnace has this boiler? Ans. — A rectangular brickwork furnace inclosed in a teel casing, and the generating tubes are placed directly >ver the grates, the bottom row of tubes being about two eet above the grates. Baffle plates are secured at inter- als among the tubes for the purpose of causing the hot ;ases to traverse the whole of the heating surface. Ques. 166. — How is circulation of the water secured n the Belleville boiler? 6? QUESTIONS AND ANSWERS Ans. — By means of external return water-pipes, one on each side connecting the ends of the top drum with ♦be lower water-chamber, the cooler water thus passing Teed/ outlet Feed inlet to Boiler cfter leaving iconom/ser* Fig. 33. BellevwAB Bviui* wii* Economise*. THE BOILER 63 down through these pipes into the lower drum, and from thence the heated water passes up through the generating tubes, discharging into the top drum, where the steam is disengaged. Ques. 167. — What are the usual dimensions of the* generating tubes? Ans. — Four and one-half inches in diameter and seven feet six inches in length. The ends are connected by- being screwed into malleable cast-iron boxes. Ques. 168. — How is the economizer or feed-water heater attached to this boiler? Ans. — It is placed directly above the generator, a space called the combustion chamber being left between the two series of tubes. The tubes of the economizer are smaller, being 2}i inches in diameter. The general form of the economizer resembles that of the generator. Ques. 169. — What is the course of the feed-water in this boiler? Ans. — It enters the bottom of the economizer and is forced upwards to and fro through the zigzagged tubes to the top, and from thence it falls to the bottom of the hot water collector at the top, and then flows to the return pipes, through which it passes to the generator. Ques. 170. — -Mention another peculiar feature of this boiler. Ans. — An automatic feed-regulating device worked by a float in a chamber acting upon the feed-valve. Ques. 171. — Is the Belleville boiler an economical boiler? Ans. — It is; an actual evaporation of from 9.3 poun^j 64 QUESTIONS AND ANSWERS to 9.9 pounds of water per pound of coal having been obtained under test, with the feed-water at a temperature of 68 degrees. Pipe connected to upper part of element view of A JFeeol inlefr. U. Aotomatic Feed Regulator for Belleville Boiler. ^ CHAPTER III BOILER CONSTRUCTION Ques. 172. — What is the best material to use in the construction of the shell of the boiler? Ans. — Open-hearth steel, having a tensile strength of from 55,000 pounds to 60,000 pounds per square inch. Ques. 173. — What is meant by the expression tensile strength (T- S.)? Ans. — The expression 60,000 pounds tensile strength means that it would require a pull of 60,000 pounds in I -CJ /£ Aboi/tz* I &-i£i!±-ya*&± i Fig. 35. Test Piece. the direction of its length to break a bar of the material 1 inch square, or 2 inches wide by ^2 inch thick, or 2.67 inches wide by Yz inch thick. Ques. 174. — How are steel sheets for boiler construc- tion tested? Ans. — A small piece, called a test piece, is cut from each sheet and placed in a testing machine. Ques. 175. — What is the working test for steel boiler sheets? Ans. — A piece from each sheet is heated to a dark 65 66 QUESTIONS AND ANSWERS cherry red, plunged into water at 60° temperature, and bent double cold under the hammer, such piece to show no flaw or crack after doubling. Ques. 176. — Of what material should the tubes of fire-tube boilers be made? Ans. — A good quality of homogeneous iron. Ques. 177. — What is the working test for boiler tubes? Ans. — They should show no flaw when expanded into the flue-sheet and beaded. i^ I Fig. 36. Crow Foot Braces. Ques. 178. — What should the specifications be regard- ing rivets? Ans. — All rivet material should be of good charcoal iron, or mild steel, tough and soft. Test, a good rivet should bend double cold, without showing fracture. Ques. 179. — Of what material are the tubes of water- tube boilers usually made? Ans. — Of good charcoal iron or mild steel specially prepared for the purpose, and lap welded, or drawn. BOILER CONSTRUCTION 67 Ques. 180. — What is the test for tubes from 3 T A to 4 inches in diameter and No. 10 wire gauge? Ans. — A piece V/2 inches in length is cut from one end of a tube, and this piece must stand hammering down cola vertically without showing a crack or split, when down solid. Ques. 181. — Of what material should stay-bolts be made? Ans. — Of iron or mild steel, especially manufactured for the purpose. Fig. 37. Gusset Stays. Ques. 182. — What should be the tensile strength of stay-bolt material? Ans. — For iron, not less than 46,000 pounds; for steel, not less than 55,000 pounds. Ques. 183. — What kind of material are braces and stays made of? Ans. — The material for braces and stays should be of :he same quality as the best stay-bolt stock. Ques. 184. — What is the object sought in staying the lat surfaces of a boiler internally? Ans. — The object is to strengthen those surfaces Iufficiently to enable them to withstand the maximum aternal working pressure to which thev will be subjected. 68 QUESTIONS AND ANSWERS Ques. 185. — Does the cylindrical portion of a boiler need bracing? Ans. — It does not, for the reason that the internal pressure tends to keep it cylindrical. Ques. 186. — What is the maximum direct pull per square inch of section that may be allowed on braces and stay-rods? Fig. 38. Through Stay Rods. Ans. — For iron, 6,500 pounds; for steel, 8,000 pounds; and this point should be kept in view when spac« ing the braces. Ques. 187. — What is meant by spacing braces? Ans. — The distance from center to center that the stays are from each other at the point of their connection to the stayed surface. Ques. 188. — Give an example. Ans. — The stays in a certain boiler are spaced 8 inches apart, center to center, therefore each stay supports BOILER CONSTRUCTION 69 1x8=64 square inches. Assuming the working pressure o be 100 pounds per square inch, the sectional area of ach stay should be 1 square inch. f/M/IU(UJtrCQ-£4A Fig. 39. Vertical Tubular Boiler, with Submerged Tubes. Ques 189. — Suppose the working pressure is 250 ounds per square inch and the stays are spaced 6 inches 70 QUESTIONS AND ANSWERS center to center, what should be the sectional area of eacF stay? Ans. — The pressure to be sustained by each stay would be 6x6 = 9000 pounds. Assume the stays to be of BOILER CONSTRUCTION 71 steel and unwelded, and allowing a direct pull of 7,200 pounds per square inch, the sectional area of each stay should be tSBS = 1-25 square inches; or, if the stays are 1.5 inches smallest diameter, and a direct pull of 8.000 pounds per square inch of section is allowed, they may be spaced 7 inches, center to center. Ques. 190. — Of what forms are boiler stays usually made? Ans. — For low-pressure boilers, crow-foot stays; for high-pressure boilers, through stay-rods and gusset-stays. Fig. 41. Common Stay -Bolt. Ques. 191. — Where are stay-bolts used? Ans. — In fire-box boilers, and all boilers of the loco- motive type, to tie the fire-box to the external shell. Ques. 192. — How are stay-bolts applied? Ans. — A continuous thread is cut on the stay-bolt rod, the same thread being also tapped in the holes in the external plate, and the inside sheet. The steel stay-bolt is then screwed through the plates and allowed to project far enough at each end to permit of its being riveted down cold. 72 QUESTIONS AND ANSWERS Ques. 193. — What is the principal cause of the break ing of stay-bolts? Ans. — The unequal expansion of the sheets into which they are screwed. Ques. 194. — Why are stay-bolts sometimes drilled partly through their length? Ans. — In order that, if the bolt breaks, the steam or water may blow out through the small hole and give warning of the break. Ques. 195. — Describe the Tate flexible stay-bolt. Fig. 42. Tate Flexible Stay Bolt. Ans. — The outer head is ball shaped, and is inclosed within a socket formed by a sleeve that screws into the outer sheet and a cap that screws onto the sleeve. The other end of the bolt is screwed into and through the fire- sheet a sufficient distance to allow of riveting. Ques. 196. — What is meant by the efficiency of a riveted joint? Ans. — It is the per cent, of strength of the solid plate that is retained in the joint. Ques. 197. — What is the efficiency of a properly proportioned double riveted butt-joint? BOILER CONSTRUCTION 73 Ans. — From 71 to 75 per cent. Ques. 198. — What is the efficiency of a properly pro- portioned triple riveted butt-joint with inside and outside welts or butt-straps? Ans. — From 85 to 88 per cent. Fig. 43. Tate Feexibee Stay-Boi/t, Unthreaded. Ques. 199. — Where is the weakest portion of the triple riveted butt-joint? Ans. — At the outer row of rivets. Table 4 Table of Diameters of Rivets* Thickness of Plate Diameter of Rivet Thickness of Plate Diameter of Rivet V4 inch 8 /ie " 3 / 8 " 7 /l6 " % " V2 inch 9/ i{ 716 n /l6 " 3/ 4 « 13 /l6 " 9 /i6 inch Vs " S U " v. " 1 " 7 /s inch 15 /l6 " IVm " IVs " l 1 /* " ♦Machine design— W. C. Unwin. Ques. 200. — What percentage of efficiency may be retained in a properly designed quadruple riveted butt- joint having both inside and outside butt-straps? Ans. — 94 per cent. n QUESTIONS AND ANSWERS Ques. 201. — Where is the weakest portion of such joint? Ans. — At the outer row of rivets. Fig. 44. Double Riveted Butt-Joint. Ques. 202. — How may boiler heads be constructed which will not require to be stayed? Ans. — By being dished, or "bumped up." Fig. 45. Triple Riveted Butt-Joint. Ques. 203.— What is the depth of dish, as adopted by 6teel-plate manufacturers? BOILER CONSTRUCTION 75 Ans. — One eighth of the diameter of the head, when langed. Ques. 204. — What should be the thickness of the head is compared to the thickness of the shell? Fig. 46. Quadruple Riveted Butt-Join t, Lloyd's rules, condensed, are as follows: ,loyd's Rules — Thickness of Plate and Diameter of Rivets 1 Thickness of Diameter of Thickness of Diameter of 1 Plate Rivets Plate Rivets 1 y% inch Vi inch Y\ inch 7/$ inch 1 7 /l6 5/8 " 13 /l6 " Vs " 1 V* " Va " n - 1 " 1 °/l6 " Va " 15 A« " 1 " 1 5 /8 " Va " 1 " 1 " 1 Hie " % " Ans. — The heads should be as thick, or slightly thicker, tan the shell plate. 76 QUESTIONS AND ANSWERS Ques. 205. — What method other than riveting may- be, and sometimes is employed in the formation of boiler seams? Ans. — Boiler seams may be welded if the material from which the plates are rolled is of the best, and great care and skill are exercised. Ques. 206. — Mention two of the advantages possessed by welded seams over riveted seams? Table 5 Proportions of Triple-riveted Butt Joints with Inside and Outside Welt Thickness of Diameter of Pitch of Pitch of Efficiency Per Cent Plate Eivet Rivet Outer Rows Inches Inches Inches Inches s / 8 13 /l6 3.25 6.5 84 T /ii 13 /l6 3.25 6.5 85 Vi 13 /l6 3.25 6.5 83 %6 Vs 3.50 7.0 84 5 / 8 1 3.50 7.0 86 3 U lYii 3.50 7.0 85 % IVs 3.75 7.5 86 1 1V 4 3.87 7.7 84 Ans. — First, 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; second, the welded joint, having a smooth surface inside the boiler, is much less liable to collect scale and sediment than is the riveted joint. Ques. 207. — Why should the longitudinal or side seams of a boiler be stronger than the girth or round- about seams? BOILER CONSTRUCTION 7? Ans. — Because 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 tending to pull it apart endwise is only one-half that, or propor- tional to the diameter divided by^four. Ques. 208. — What is the formula for ascertaining the bursting pressure of a boiler? TSXTXE _ . Ans. — 5 — B, in which TS = Tensile strength T = Thickness of sheet E = Efficiency of joint R = Radius (one-half the diameter) B = Bursting pressure Ques. 209. — How is the safe working pressure of a boiler ascertained? Ans. — First calculate the bursting pressure, then divide this by the factor of safety, which usually is five, although in some instances a safety factor of eight is used. Ques. 210. — In addition to the regular bracing and staying, how are the heads of return tubular and Scotch narine boilers greatly reenforced? Ans. — By the tubes, which are expanded into the leads and beaded down on the ends. Ques. 211. — Are the tubes always expanded into the ube-sheets? Ans. — They are in fire-tube boilers. In some forms >f water-tube boilers the tubes are screwed into the ^ders or chambers. 78 QUESTIONS AND ANSWERS Ques. 212 — What type of furnace is largely used in internally fired boilers? Ans. — The Morison corrugated furnace. Ques. 213. — Mention three advantages gained by the use of corrugated furnaces. Ans. — First, the corrugations (if properly made) add great rigidity and strength to resist the crushing strain to which the furnaces are subjected; second, there is more heating surface in a corrugated than in a smooth surface; third : the alternate expansion and contraction of the Fig. 47. Section of Tube Expanded into Sheet. corrugated surface tends to loosen any scale that ma; form on the surface inside the boiler. Ques. 214. — In regard to riveted seams, which is th< better method, to drill or to punch the rivet-holes? Ans. — The rivet-holes should be drilled. In goo boiler work this method is now always followed. Ques. 215. — What other important point should bj kept in view in joining the plates of a boiler? Ans. — To get the joint tight without caulking, or a| least with as small an amount of caulkiner as oossible. BOILER CONSTRUCTION 79 Ques. 216. — Mention some of the injurious effects of excessive caulking. Ans. — First, it is one of the most fruitful causes of grooving along the edges of the seams; second, it tends to raise the edge of the plate that is caulked, thereby causing looseness at the joint. Ques. 217. — What other very important point should be secured in the construction of the boiler? Ans. — The rivet-holes in the plates should come fair before the rivet is put in. ^^ X. * -^ -^"/ V r '-:^v^ -: v**',i/"\-/ -#*' -' Fig. 48. Morison Corrugated Furnace. Ques. 218. — If the rivet-holes do not come fair what should be done with them? Ans. — They should be made exactly true by the use of a rimer. Ques. 219. — What should not be done with the rivet- holes in case they do not come fair? Ans. — They should not be drifted. A drift-pin is often the primary cause of starting a crack in a sheet. Ques. 220. — What can be said generally concerning the construction of a boiler, especially one intended for high pressures? 80 QUESTIONS AND ANSWERS Ans. — Only the best material should be used, and great care and skill should be exercised in all the detail of assembling it. By reference to Chapter I, Part 2, of Swingle's "Twentieth Century Hand Book for Engineers and Elec- tricians," the student will be enabled to obtain much more detailed information concerning boiler construction, the strength of riveted joints, bracing and staying, strength of material, etc., as all of these important feat- ures are dwelt upon at length and fully discussed. CHAPTER IV BOILER SETTINGS AND APPURTENANCES. Ques. 221. — What kind of a setting is required for internally fired boilers? Ans. — First, a good solid foundation, second, the Doiler should be covered with non-conducting, non-com- Dustible material of some sort, to prevent radiation of heat, and the whole should be encased in a sheet-metal jacket. mm m Fig. 49. Plan and Elevation oe Boiler Setting, Showing Air Spaces. Ques. 222. — What kind of a setting is required for horizontal tubular and water-tube boilers? Ans. — Brick walls with an inner lining of fire brick. When the boiler is supported by lugs resting upon the walls, a heavy iron plate should be imbedded in the brickwork, for each lug to rest upon. The walls should also be tied together, both endwise and transversly, by iron rods not less than 1/4 inch in diameter, extending clear through in both directions, the bottom rods to be laid in place as the walls are being built. These rods are \o have a thread and nut on each end, and are secured 81 82 QUESTIONS AND ANSWERS to heavy cast or wrought iron bars called buck stays, placed vertically against the outside of the walls. Ques. 223. — How may boiler walls be greatly pro- tected from the injurious action of the heat? Ans. — By leaving an air-space of 2 inches between the fire-brick lining and the outer wall, beginning at the level of the grate bars and extending as high as the cen- ter of the boiler. Above this height the walls should be solid. ■4*\ Fig. 50. Clamp for Back Arch. Ques. 224. — What is the duty of bridge-walls and bafflers? Ans. — To present a hot surface for the unconsumed gases to impinge against, and also to divert the gases towards the heating surface of the boiler. Ques. 225. — How may a good and durable back arch for a horizontal tubular boiler be constructed? Ans. — Take flat bars of iron H inch thick by 4 inches ua width, cut them to the proper length, bend them to the BOILER SETTINGS AND APPURTENANCES 8J shape of an arch, and turn 4 inches of each end back at right angles. The clamp thus formed is to be filled with a course of side arch fire-brick, and will form a complete and self-sustaining arch 9 inches wide and with sufficient spring to cover the distance between the back wall and the back head of the boiler above the tubes. 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. Fig. 51. Back Arch Complete. Ques. 226. — What advantages do this form of back arch possess over the ordinary flat cover? Ans. — First, it can come and go with the expansion and contraction of the boiler; second, it always maintains a practically air-tight cover at this important point; third, in case of needed repairs to the back end of the boiler the sections may be easily removed, one at a time, and when the repairs are completed they may be reset with very small expense. 84 OURSTIOXS AND ANSWERS Ques. 227. — Give an easy rule for ascertaining the dimensions of the grates. Ans. — For a horizontal tubular, the length of the grates should equal the diameter of the boiler. The width depends upon the construction of the furnace. If the fire-brick lining is built perpendicular, the width of grate will also equal the diameter of the boiler, but if Fig. 52. Back Arch in Pi«ace. the lining is given a batter of 3 inches, starting at the level of the grates, then the width of grate will be 6 inches less. Ques. 228. — What is the ordinary ratio of grate sur- face to heating surface for land boilers, with natural draught? Ans. — One square foot of grate surface to every 36 square feet of heating: surface. BOILER SETTINGS AND APPURTENANCES 85 Ques. 229. — What ratio of grate surface to heating surface is usually chosen with forced draught? Ans. — One square foot of grate surface to 40 square feet of heating surface, and in some instances the ratio is as high as 1 to 50. Ques. 230. — How many different styles of grate-bars are in general use? Ans. — Four; first, the common stationary grate, consisting of a plain cast-iron bar tapered in cross PLAIN GRATE (STANDARD PATTIRN ) TUPPER OR HERRING-BONE CRATE SAW-DUST AND WOOD GRATF Fig. 53. Grate Bars. section and having small projections cast on the sides to keep the bars apart a sufficient distance; second, herring- bone grates, consisting of channel-shaped cast-iron bars having V-shaped openings on top to allow the air to pass through to the fire; third, shaking or rocking grates, fourth, dumping grates. Ques. 231. — What percentage of the total grate area is usually allowed for the admission of air through the grates? 86 QUESTIONS AND ANSWERS Ans. — From 30 to 50 per cent, depending upon the kind of coal used. Ques. 232. — What is the heating surface of a boiler? Ans. — All the surfaces that are in contact with and covered by water on one side and surrounded by flame or hot gases on the other side. The areas of these surfaces are estimated in square feet and added together. Fig. 54. M'Clave's Grates. PLATE NO 3. Fig. 55. M'Clave's Grates. Ques. 233. — Is it possible to estimate the horse-power of a boiler from its heating surface? Ans. — It is in a general way, but not accurately. Ques. 234. — How many square feet of heating surface are usually allowed per horse-power? Ans. — From 10 to 16 square feet, depending entirely upon the type of boiler. Ques. 235. — Give seme examples. BOILER SETTINGS AND APPURTENANCES 8? Ans. — For water-tube boilers 10 to 12 square feet of leating surface; for horizontal fire-tube, 12, for vertical iire-tube, 12 to 15, and for locomotive boilers, 12 to 16 square feet of heating surface per horse-power. Ques. 236.— Why this difference? Ans. — Because the heating surface is more effective n some types of boilers than it is in others. Ques. 237. — What is the rule for calculating the heat- ng surface of a horizontal tubular boiler? Ans. — Taking the dimensions in inches, multiply two- :hirds of the circumference of the shell by its length. Multiply the inside circumference of one of the tubes by ts length, and this product by the number of tubes. Add hese two products together, and to this sum add two- hirds of the combined areas of both tube-sheets and rom this latter sum subtract twice the combined sec- ional areas of all the tubes. The result will be the leating surface in square inches, which, divided by .44, will give the number of square feet of heating urface. Ques. 238. — What is the rule for finding the heating urface of vertical fire-box boilers? Ans. — Multiply the circumference of the fire-box by ts height above the grate. Find the heating surface of he tubes by the process given in the former rule and add hese two products together, and to this add the area of he lower tube sheet. From this sum deduct the sectional rea of all the tubes. The dimensions having been taken inches, the result should be divided by 144 to ascertain e number of square feet of heating surface. 88 QUESTIONS AND ANSWERS Ques. 239. — Why is the inside circumference of the tubes taken? Ans. — Because in fire-tube boilers this is the portion that is directly exposed to the heat. Ques. 240. — Why are the combined sectional areas of the tubes subtracted from the area of that portion of the tube-sheets that is exposed to the heat. Ans. — Because the effective heating surface of a tube-sheet is the surface remaining after the areas of the openings through the tubes is deducted. Ques. 241. — What is implied in the expression "a 3-inch boiler tube?" Ans. — It means a tube 3 inches in external diameter. Ques. 242. — Such being the case, which diameter should be considered in calculating the heating surface of fire-tubes? Ans. — Only the inside diameter, which equals the out- side diameter minus twice the thickness of the tube. Ques. 243. — In calculating the heating surface of the tubes of water-tube boilers which diameter should be taken? Ans. — The outside diameter, for the reason that the outside circumference is exposed to the heat. Ques. 244. — How is the heating surface of a water- tube boiler ascertained? Ans. — Much depends upon the style of boiler. A general rule and one that will apply in all cases, is to multiply the outside circumference of one of the tubes by its length, and this product by the number of tubes that are of a similar length and diameter. If there are vari- his sections of tubes of va^v:ng lengths, the heating urface of each section must be ascertained separately nd the whole added together. To this sum must be dded the combined areas of those portions of the headers hat are directly exposed to the heat, having first deducted he sectional area of the tubes. All of those portions of he steam and water-drums that are directly exposed to he heat should be estimated as heating surface also. BOILER SETTINGS AND APPURTENANCES 89 Fig. 56 Door op a Belleville Boiler. The door proper has an outer and inner plate, the former being a screen plate nth edges open for the admission of air The door is perforated with holes at he lower part, through which the air is drawn, and the inner plate, which is of ast iron, is closed at the bottom, and has holes for the discharge of air at t:he op. When the fires are alight, there is a continuous current of air flowing into he furnace through these plates. Ques. 245. — What is the rule for ascertaining the eating surface of a Scotch boiler? Ans. — The grates being set in the large main flues, nly one-half of each flue area is available as heating urface. The following rule applies: To one-half the ombined area of the main flue add the area of one head between the grate and water-line, minus the total cross- ection of the tubes, plus one-half the cross-section of » QUESTIONS AND ANSWERS fc.dritt rfues, plus the combined inside area of the tubes, F*ms the inside area of the combustion chamber. Ques. 245. — Give the rule for finding the heating surface of a corrugated flue. Ans. — Multiply the average inside diameter in feet by the iength of the flue in feet, and this product by the Fig. 57. . Shows another variety, the air being admitted tht**C*fc holes at the bottom o the wrought-steel door proper, a perforated inner cast-ir^/i plate being fitted t< shield the door. The wrought-steel furnace frame which carries the door ai has an inner shield plate of cast-iron perforated with holes. constant 4.93. The result is square feet of heating surface. Ques. 247. — What is the duty of a safety valve? Ans. — To automatically relieve the boiler of all pressure above a certain prescribed working pressure b; allowing the surplus steam to escape into the atmosphere.| Ques. 248. — If a boiler had no safety valve, o r if th< BOILER SETTINGS AND APPURTENANCES 91 safety valve should refuse to work, and all other exit from the boiler be closed, and heat continuously applied, what would be the result? Ans. — An explosion must of necessity occur. Fig. 58. Pop Vai^ve. Ques. 249. — How many types of safety valves are in use? Ans. — Two; the lever safety valve, and the spring- pop safety valve. Ques. 250. — Which is the best adapted to all kinds of service? Ans. — The spring-loaded pop safety valve is, for the 92 QUESTIONS AND ANSWERS reason that any inclination o* "~ L e boiler, such as that caused by the vessel's pitching ana rolling in a heavy sea, does not interfere with the working of a spring-pop valve, Fig. 59. Inside View of a Pop Safety Valve. while on the other hand the leverage of a weighted lever valve decreases with any inclination of the boiler that BOILER SETTINGS AND APPURTENANCES 93 would momentarily put the lever in an inclined position. Ques. 251. — What is the United States marine rule :or determining the area of lever safety valves for boilers? Ans- — "Lever safety valves to be attached to marine >oilers shall have an area of not less than 1 square inch to Fig. 60. Triplex Pop Safety Valve. very 2 square feet of grate surface in the boiler, and the seats of all such safety valves shall have an angle of inclination of 45 degrees to the center line of their axis." Ques. 252. — What is the rule regarding spring pop safety valves? 94 QUESTIONS AND ANSWERS Ans. — f hree square feet of grate surface are allowed to each square inch of safety-valve area. Ques. 253. — What other and more reliable method is there of calculating safety-valve area? Ans. — The method by which the area of the valve is based upon the quantity of steam that the boiler is capable of generating. Ques. 254. — Why is this method more reliable? Ans. — For the reason that the rate of combustion varies greatly under different conditions, as, for instance, when forced draught is employed, a much higher rate of combustion is attained than is possible with natural draught. Ques. 255. — Do the standard rules given in answers 251 and 252 hold good for safety-valve areas for all pressures? Ans. — No; because the rate of efflux for steam increases as the pressure increases. Therefore, for the higher pressures the total safety-valve area may be reduced. Ques. 256. — What should be the lift of a safety valve in order to allow the proper area of escape? Ans. — One-fourth of the diameter of valve. Ques. 257. — What is the rule for ascertaining the pressure at which a lever safety valve will lift when the weight and its distance from the fulcrum are known, as also the effective weight of the valve, stem, and lever? Ans. — Multiply the weight by its distance from the fulcrum. Multiply the weight of the valve and lever by the distance of the stem from the fulcrum, and add to the BOILER SETTINGS AND APPURTENANCES 95 >rmer product. Divide the sum of the two products by le product of the area of the valve multiplied by its dis- mce from the fulcrum. The result will be the pressure i pounds at which the valve will lift. Ques. 258. — What is the rule for finding the distance lat the weight should be placed from the fulcrum for a jquired pressure? Ans. — Multiply the area of the valve by the pressure Fig. 61. Davis Belt Driven Feed Pump. t which it is desired to have it lift, and from this product ibtract the effective weight of the valve and lever, lultiply the remainder by the distance of the stem from le fulcrum, and divide by the weight. The quotient will the required distance. Ques. 259. — What is the rule for ascertaining the eight required when all of the other factors are known? 96 QUESTIONS AND ANSWERS Ans. — Multiply the area of the valve by the pressure, and from the product deduct the effective weight of the valve and lever. Multiply the remainder by the distance of the stem from 'the fulcrum and divide by the distance of the ball or weight from the fulcrum. The quotient wiU be the required weight in pounds. Fig. 62. Phantom View oe Marsh Independent Steam Pump. Ques. 260. — What can be said in general regarding the safety valve? Ans. — It is one of the most useful and important adjuncts of a steam boiler, and if neglected, serioas results are apt to follow. Ques. 261. — Mention the two standard methods of supplying the feed-water to boilers under pressure? Ans. — First, by the feed-pump; second, by the injector. BOILER SETTINGS AND APPURTENANCES 97 Ques. 262. — What advantage has the feed-pump over the injector? Ans. — The advantage of being able to draw its supply of water from a heater, in which the exhaust steam is utilized for heating the feed-water before it enters the boiler. Great economy in fuel is thereby effected. Ques. 263. — What is a duplex pump? Ans. — A duplex pump consists of two steam-cylinders and two water-cylinders, each having the necessary pistons and valves. The steam-valves of one side are Fig. 63. Worthington Duplex Boiler Feed Pump. operated by the other side, and vice versa. Both water cylinders discharge into the same main. A common suction main serves both water-cylinders also. Ques. 264. — If one side of a duplex pump becomes disabled from any cause, how may the other side be operated for the time being? Ans. — Loosen the nuts or tappets on the valve-stem of the broken side and place them far enough apart so that the steam- valve will be moved through only a small por- tion of its stroke, thereby admitting only steam enough to move the empty steam-piston and rod, and thus work the 98 QUESTIONS AND ANSWERS steam-valve of the remaining side. The packing on the piston-rod of the broken side should be screwed up tightly, so as to create as much friction as possible, there being no resistance in the water end. In this manner the pump may be operated for several days or weeks, and thus prevent a shut-down. OVERFLOW SUCTION Fig. 64. The Hancock Inspirator. Ques. 265. — How is the velocity of flow, or piston* ;peed per minute of a pump ascertained? Ans. — Multiply the number of strokes per minute by the length of stroke in feet, or fractions thereof. This will give the piston-speed in feet per minute. Ques. 266. — How is the velocity of flow in the dis- charge-pipe ascertained? Ans. — Divide the square of the diameter of the water* k BOILER SETTINGS AND APPURTENANCES 99 :ylinder in inches by the square of the diameter of the iischarge-pipe in inches, and multiply the quotient thtia 831109 OJL obtained by the piston-speed in feet per minute of the pump. Ques. 267.— When the velocity in feet oer minute If 100 QUESTIONS AND ANSWERS koown, how may the number of cubic feet discharged per minute be ascertained? Ans. — Multiply the area of the pipe in square inches by the velocity in feet per minute, and divide by the con- stant 144. The result will be the number of cubic feet of water or other fluid discharged per minute. Ques. 268. — How may the required size and capacity of feed-pump for a certain boiler be ascertained? Fig. 66. The Self- Acting Injector Ans. — Multiply the number of square feet of grate surface by the number of pounds of coal it is desired to burn per hour per square foot of grate. This will give the total coal consumed per hour, which, multiplied by the number of pounds water evaporated per pound of coal will result in the total number of pounds water required per hour. Ques. 269. — How may the required size of the feed- pump be ascertained from the number of square feet of heating surface? BOILER SETTINGS AND APPURTENANCES 101 Ans. — Allow a pump capacity of 1 cubic foot of watei per hour for each 15 square feet of heating surface. Ques. 270. — How can an injector lift and force watei into the boiler against the same or even higher pressure than the pressure of the steam supplied to the injector? Ans. — An injector works because the steam imparts sufficient velocity to the water to overcome the pressure in the boiler. 102 QUESTIONS AND ANSWERS Ques. 271. — What is the velocity of a jet of steam under 180 pounds pressure issuing from a nozzle? Ans. — About 3,600 feet per second. Ques. 272. — What is the velocity of a jet of water under a pressure of 180 pounds issuing from a nozzle? Ans. — Only 164 feet per second. Ques. 273. — Why docs the steam have so much greater velocity than the water, when the pressure in both instances is the same? BOILER SETTINGS AND APTORTENANCES 103 Ans. — Because of the latent heat that is stored in the steam. Ques. 274. — What is the purpose of the combining tube in an injector? Ans. — To bring the jet of steam and the jet of water into close contact in order that the steam may be con- WA.TEP CONN *TO* Fig. 69. Water Column. densed and the size of the jet reduced sufficiently to allow it to enter the delivery tube, which is of smaller diameter than the combining tube. Ques. 275. — What is the velocity of the combined jet of water and condensed steam as it leaves the combining tube and enters the delivery tube, assuming the steanr 104 QUESTIONS AND ANSWERS pressure in the boiler to be 180 pounds per square inch? Ans. — 198 feet per second. Ques. 276. — What velocity is actually needed to cause the jet to enter the water-space of the boiler carrying 180 pounds pressure? Ans. — Only 164 feet per second. The excess of 34 feet per second imparted to the velocity of the jet serves to overcome the friction of the feed-pipe and the resistance of the main check-valve. Ques. 277. — In general terms, then, to what is the action of the injector due? Ans. — The action of the injector is due to the high velocity with which a jet of steam strikes the water enter- ing the combining tube, imparting to it its momentum and forming with it during condensation a continuous jet of smaller diameter, having sufficient velocity to over- come the pressure in the boiler. Ques. 278. — What is the object in fitting a boiler with a check-valve in the feed-pipe? Ans. — A check-valve is for the purpose of preventing the water in the boiler from backing up into the feed main and feed-pump. Ques. 279. — Where should the check-valve be located? Ans. — In the feed-pipe, as near to the boiler as possible. Ques. 280. — For what purpose are gauge-cocks and water-gauge glasses? Ans. — They are for the purpose of indicating the height of the water in the boiler while it is under pressure. BOILER SETTINGS AND APPURTENANCES 105 Ques. 281. — Describe the construction and operation of a glass water-gauge? Ans. — A water-gauge, otherwise known as a water column or combination, is a cast-iron or brass cylinder connected to the steam-space of the boiler at the top, and to the water-space near the bottom. The normal position of the safe water-level is near the middle of the water- Fig. 70. Ivow Water Alarm. Fig. 71. Combined High and how Water Aearm. column, into one side of which are screwed brass fittings for the glass tube or water-glass, which is a strong tube of special manufacture. Each end of this tube passes through a stuffing box in the brass fittings. The joint is made steam tight by a rubber ring that fits around the tube and is compressed by a follower screwed onto it. The fittings that connect the water-column with the boiler are, or at least should be, equipped with automatically closing ball valves which will act in case the gauge-glass breaks. 10G QUESTIONS AND ANSWERS Ques. 282. — Where are the gauge-cocks or test-cocks usually connected? Ans. — They are usually connected to the water-column cylinder in such a position that the lowest one is at the desired water-level, one a few inches above that, and the third near the highest point of the heating service. These test-cocks should be opened several times a day in order to keep them clear for use in case the gauge-glass breaks. Ques. 283. — What is liable to happen to the water- column? Ans. — Unless the water and sediment are frequently blown out of it through the valve at the bottom provided for this purpose, the tubes and connections will become clogged, thus preventing a free circulation of the water, and the true water-level in the boiler will not be indicated as it should be. Ques. 284. — What is a fusible plug? Ans. — A fusible plug is a 1-inch brass pipe threaded plug, having its center drilled out to a diameter of not less than /^ inch, and the hole filled with Banca tin or other fusible metal. Ques. 285. — Where should a fusible plug be attached to a boiler? Ans. — A fusible plug should always be attached to that portion of the boiler that is first liable to become overheated on account of the water-level becoming too low. Ques. 286. — Mention some proper locations for fusible plugs in various types of boilers? Ans. — The back head of a horizontal tubular boiler. BOILER SETTINGS AND APPURTENANCES 107 about 3 inches above the top row of tubes, the crown- sheet of a horizontal fire-box boiler; the lower tube-sheet of a vertical boiler, or sometimes in one of the tubes a few inches above the tube-sheet; in the lower side of the upper drum of a water-tube boiler. The fusible metal which fills the center of the plug is of con- ical form in order to prevent its being blown out by the pressure behind it. On the other hand, the melting point of this fusible metal is such that when the water falls below it, and the steam under pressure in the boiler comes in contact with it, the metal is melted and runs out, thus allowing the steam to escape through the hole and give the alarm. If the melted plug is located in the crown- sheet of a fire-box boiler, the escaping steam and water will quench the fire and thus lessen the danger of burning the sheet. Fig. 72a. Klinger's Water Gauge Mounting.— The usual round thin gauge glasses give trouble with high-pressure steam, owing to frequent fractures, while the water level is often indistinct. Klinger's glass, designed to obviate these defects, gives promise of success. It consists of a thick fl t glass, with smooth front and serrated back, shown in section Fig. 72. a and b, the front and back of the mounting, are bolted together with the glass and packing, shown by thick lines, between them. The serrations, when clean, cause the water to appear black., as in Fig. 72a. Ques. 287. — For what purpose is a steam-gauge attached to a boiler? Ans. — For the purpose of indicating the number of pounds pressure per square inch in the boiler. 108 QUESTIONS AND ANSWERS Ques. 288. — What type of steam-gauge is in most general use? Ans. — The Bourdon spring tube gauge. Ques. 289. — Describe the construction of this gaug^ and the principle upon which it operates? Ans. — The Bourdon gauge consists of a thin, curved, FaG. 73. Auxiliary Spring Pressure Gauge. flattened metallic tube closed at both ends and connected to the steam-space of the boiler by a small pipe bent at some portion of its length into a curve or circle that becomes filled with water of condensation, and thus pre- vents the live steam from coming directly in contact with the tube or spring, while at the same time the full BOILER SETTINGS AND APPURTENANCES 109 pressure of steam in the boiler acts upon the tube, tending to straighten it. The end or ends of the spring tube being free to move, and connected by a suitable geared rack and pinion with the pointer of the gauge, causes it Fig. 74. Auxiliary Spring Pressure; Gauge, Section ai« View. to move across the face of the dial, thus indicating the pressure of the steam in pounds per square inch on the inner surface of the boiler. When there is no pressure n the boiler the pointer shouJd stand at ()• 110 QUESTIONS AND ANSWERS Ques. 290. — How should steam-gauges be cared for? Ans. — They should be tested frequently by comparing them with a gauge that has been tested against a column of mercur}'. Ques. 291. — How should the steam-space of the boiler be connected to the main steam-pipe or header? Ans. — There should be a steam stop-valve placed in the connection between the boiler and the header. The valve Fig. 75. Sectional View American Pressure Gauge. used for this purpose is usually an angle-valve, and should be constructed so as to close automatically, especially in a battery of two or more boilers. Ques. 292. — Why should this valve be self-closing in case the pressure in the header is higher than the pressure in the boiler? Ans. — In order that in case of an accident to one of a battery of boilers the steam may be prevented from pass- ing out of the neader and into the disabled boiler. BOILER SETTINGS AND APPURTENANCES 111 Ques. 293. — Describe the construction and operation of an automatic steam stop-valve. Ans. — The valve is opened and closed by means of a screw-stem passing out through the stuffing box, and fitted with a hand-wheel outside. In large-size valves this screw-thread is carried in a strong yoke outside the cas- ing. The pressure from the boiler is on the under side of the valve-disk, thus tending to open it. The stem or spindle is independent of the valve, and is hollow to allow a smaller size sliding spin- dle connected to the valve to pass into it. This spin- dle serves to guide and hold the valve steady, while at the same time the valve is free to close automatically any time that the pressure in the main exceeds the pressure in the boiler. Ques. 294. — How is the steam admitted to the Fig. 76. Section oe an Angle Stop- Valve. whistle or the steam siren? Ans. — Through a special stop-valve, usually of the self-closing type, being worked by a spring on the valve. Ques. 295. — Describe the action of the steam whistle. Ans. — The steam whistle produces its sound by the vibrations of a thin stationary metallic cylinder, under the impact of the steam. 112 QUESTIONS AND ANSWERS Ques. 296. — How does the steam siren produce its sound? Ans. — By means of the rotations of a small slotted wheel which in turning opens and closes narrow slots in the casing. Ques. 297. — How may the passage of water from the boiler into the steam-pipe be prevented to a large extent? Ans. — By means of an in- ternal pipe-extension called a dry pipe, that collects the steam from all parts of the steam-space through narrow slots on its upper side. The shape of these slots has a straining action on the steam. Ques. 298.— What is the object in equipping a boiler with a surface blow-off? Ans. — In order that it may catch and pass off impurities, such as grease, oil, and scum, floating on the surface of the water. Ques. 299. — Describe the construction and operation of the surface blow-off. Ans. — It is connected to the boiler near the water- ievel, and carries an internal pipe-extension that ends in a flat pan, directly below the water-line. It should be Fig. 77. Steam Fog- Whistle. BOILER SETTINGS AND APPURTENANCES 113 opened quite frequently, especially when muddy water is being fed to the boiler. This will allow the accumulated scum to pass out. Fig. 78. Section of a Steam Siren. Ques. 300. — Where and how should the bottom blow- off be connected? Ans. — The bottom blow-off should be connected to the lowest section of the boiler, and should be fitted with iI4 QUESTIONS AND ANSWERS ► ruvfffAn :: Lie 30 a straight-way valve, or a cock, in order that there may be no obstruction to the free passage of the mud and other sediment when the boiler is being cleaned. Ques. 301. — For what purpose is the hydrometer-cock, and where is it located? Ans. — In the marine serv- ice the water used in the boilers is more or less impreg- nated with solid matter, and it becomes necessary to test the density of the water in the boilers at certain intervals. The hydrometer- cock is for the purpose of drawing off a quantity of water from the I boiler for testing, and is fitted to the water-space of the boiler. Ques. 302. — Describe the construction and use of the hydrometer. Ans. — It is an instrument having a long, slender stem, made of either glass or metal. There are two bulbs in the stem. The smaller one is loaded and the larger one is hollow and filled with air, which gives the instrument buoyancy, and keeps it in a vertical position. The stem is graduated in degrees, each degree representing the presence of one-tenth the solid Fig. 79. Hydrometer. mutter in sea-water. BOILER SETTINGS AND APPURTENANCES 115 Ques. 303. — What prooortion of sea-water is solid atter? Ans. — One thirty-second part. Ques. 304. — Upon what principle are the readings aken from the hydrometer based? Ans. — Upon the principle that when any body floats reely, the weight of the liquid displaced is equal to the weight of the body floating, so that the higher the density )f the liquid the less depth will the body sink in it. If the nstrument sinks only to the zero mark on the scale, the vater is fresh: if it sinks to 10 degrees, it indicates the presence of one-thirty-second part of solid matter, and f it sinks to 40 degrees, it indicates a density caused by he presence of four times as much solid matter as there s in sea-water. Ques. 305. — How is the water in the boiler tested with the hydrometer? Ans, — A quantity of water is drawn off through the ydrometer-cock, fitted for this purpose into a long pot, into which the instrument is inserted. Ques. 306. — How are boiler hydrometers graduated, with reference to temperature? Ans. — They are usually graduated to suit a tempera- ture of 200 degrees Fahrenheit, as that is about the temp- erature of the water a few seconds after being drawn off for testing. Ques. 307. — How are the expansion and contraction of steam-pipes provided for? Ans. — In the smaller sized pipes a bend can be put in the length of pipe that will answer the purpose, but in the 110 QUESTIONS AND ANSWERS large pipes an expansion joint, having a stuffing box foi the pipe to slide in and out of the adjacent pipe is fitted, Ques. 308.— Why is il necessary to place a sepa rator in the line of pip< leading from the boiler i the engine? Ans. — The object of a separator is to provide an additional safeguard against priming, by preventing any water in the steam-pipe from entering the cylinder. Ques. 309. —Describe the ordinary separator. Ans. — It is a metal cyl- inder larger in diameter than the steam-pipe, and connected to the pipe near the engine, by flange con- nections in such a manner that the larger portion of the separator hangs in a vertical position below the pipe. It is divided from the top nearly to the bottom by a diaphragm, and the steam Fig. 80. Expansion Joint. enters on one side, near to the top, and impinges against the diaphragm, passes underneath it. and out on the other side near the top. ggg ^^ BOILER SETTINGS AND APPURTENANCES 11? Any water that reaches the separator is mostly left at the bottom, only the steam passing on to the engine cylinder. A valve is provided at the bottom of the eparator for drawing off the water. The height of the water in the separator is shown by a glass gauge. Ques. 310. — Describe the automatic steam separator. Ans. — In addition to the isual diaphragm, it is fitted vith an automatic blow-out pparatus, having a float that s raised as the water accumu- ates, and which by a system f levers opens a valve of arge area for drainage. The utomatic separation also has hand blow-off valve. Ques. 311. — What is an sbestos-packed cock, and vhere is it used? Ans. — An asbestos-packed ock has its top and bottom lands packed with asbestos, yhile the shell also has longi- udinal grooves found in it which are packed with sbestos. These cocks are very suitable to use on boilers nd steam piping where high pressures are carried, and t locations where cocks are more convenient than valves rould be. Ques. 312. — What are funnel dampers, and for what urpose are they attached? Fig. 81. Separator. 118 QUESTIONS AXD ANSWEH? Ans. — They are hinged dampers fitted in the uptakes leading from the boilers to the funnel, in order that each 'SlEMOVTLEr G/sc"f#c* • . x , » ^ « £ % • i 2> * 1 • | 1 ^^^^ mm wr •DftAtM Fig. 82. Automatic Separator. boiler may be shut off from the draught when not in use, and they are also for use when the fires are being cleaned BOILER SETTINGS AND APPURTENANCES 119 These dampers should be fitted so that there are no means of closing them permanently, but that if released they will at once assume the open position. Ques. 313. — What are funnel stays? Ans. — Wire ropes carried from the top of the funnel to the ship's sides, and fitted with adjusting screws for the purpose of regulating the strains. Fig, 83. Asbestos-Packed Cock. Ques. 314. — What precautions should be taken with these stays before raising steam in the boilers? Ans. — The adjusting screws should be slackened in order to allow for the expansion in the length of the funnel as it becomes heated. Ques. 315. — What is the usual height of the funnels of modern vessels? Ans. — Ninety to 100 feet, measured f rom the furnaces. 120 QUESTIONS AND ANSWERS ^ A / I I ZOUBLt BOTTOM i i Fig. 84. Section of Armored Cruiser, Showing Stoke-hold and Funnels. BOILEP SETTINGS AND / PPURTENANCES 121 Ques. 316- — For what purpose is the funnel cover? Ans.— It is fitted over the top of the funnel for use Fie. 85. Section of Armored Cruiser, Showing Air Screen and Coai, Bunker. 122 QUESTIONS AND ANSWERS when the ship is in harbor, or if any of the funnels are not in use, in order to prevent rain-water from entering and corroding the uptakes. These covers are kept a little above the top of the funnel, in order to allow sufficient space for the escape of smoke from small fires used for airing and warming the boilers while they are lying idle. Ques. 317. — How is the stoke-hold of a steamer ventilated? Ans. — When natural draught only is used, screens are required to keep the downward current of cool air separate from the upward current of warm or vitiated air, otherwise the circulation will not be as good as it should be. Ques. 318. — When forced draught is employed for the furnaces, how is the air supplied? Ans. — One of the oldest and at the same time most expensive methods is to admit a jet of high-pressure steam directly from the boilers to the base of the funnel. This is known as the steam blast. Another plan of using the steam blast is to admit small jets of steam into the furnace, over the fire. Ques. 319. — What other principal plans for creating forced draught are employed? Ans. — First, admitting jets of compressed air into the base of the funnel, in a manner similar to the steam- jet; second, fitting a centrifugal fan in the uptake; third, blowing the air into closed ash-pits; fourth, closing the stoke-hold and keeping it filled with slightly compressed air. ^ BOILER SETTINGS AND APPURTENANCES 123 Ques. 320. — Of the plans iust mentioned, which one is probably the most efficient? Ans. — Closed stoke-holds, although the third plan, viz., blowing the air into closed ash-pits, is an efficient method, but a certain degree of danger attaches to it, on account of the pressure in the furnaces being greater Fig. 86. Cross Section of Stoke-hoed, Showing Air Lock. than that in the stoke-hold, and unless proper precautions re taken before opening the furnace doors for the pur- pose of replenishing the fires, the flames may be blown nto the stoke-hold and serious results follow. Ques. 321. — Is this latter system of closed ash-pits much in vogue? 124 QUESTIONS AND ANSWERS Ans. — It is used to a large extent in the United States navy, also many ships of the mercantile marine service. The British and other navies also use it to some extent. Ques. 322. — How may this system of creating a forced draught be made safe, so as to guard against the flame being Mown into the stoke-hold? Fig. 87. Elevation of Stoke-hold, Showing Air Lock. Ans. — By fitting a device that automatically closes the air-supply to the ash-pit when the furnace door is opened for firing. Ques. 323. — What is the object of providing air-locks in the hold of a vessel? BOILER SETTINGS AND APPURTENANCES 125 Ans. — In order to provide for passage to and from he stoke-holds, when under pressure. Ques. 324. — Describe the construction and operation f an air-lock? Ans. — An air-lock consists of a small air-tight cham- >er fitted with two hinged doors opening against the air WATER LINC Fig. 88. See's Ash Ejector. In this apparatus, which is fitted in many large passenger steamers in which ie raising of ashes on deck is objectionable, the ashes are placed in a trough jading to a pipe, a jet of water at a pressure of about 200 pounds per square inch rom one of the pumps is then admitted, and scours the ashes along the pipe into ie sea. A small valve is fitted to permit the entry of air into the pipe during ie discharge. The apparatus is simple and efficient. 126 QUESTIONS AND ANSWERS pressure. In passing through only one door is open at a time which makes it possible to enter or leave the stoke- hold without allowing much air to escape and thus reduce the air-pressure in the stoke-hold. Ques. 325. — At what places aboard a ship are air-locks necessary? "STK 8 I I B IT B IT B I T B 1FB 7T T- BpT' yij^^JUL— j^-jLJL— -Q=J^ CZD C=) (=> CZD 1=1 C= □ □ 1= C= EZ1 □ C= □ □□ F rrf : i — I o i — i cm Cm Cm Cm Cm cm cm cmi r— i ^SJ Fig. &>. Shaking Grates. Ans. — At all places where communication is had between the compartments under pressure and any other part of the ship. Ques. 326. — What are the advantages in general possessed by closed stoke-holds over other systems? Ans. — First, a reduction in the space and weight BOILER SETTINGS AND APPURTENANCES 1B7 equired by the boilers, since, by the addition of fans and creens, which are light and inexpensive, and supply the lecessary air under pressure to the furnaces, the boilers nay be made to develop from 20 to 25 per cent more )ower, than they would with natural draught; second, by he employment of blowing fans, a continuous supply of resh air in the stoke-hold is assured and the health and omfort of the men working there is much better provided or than it would be with natural draught. Ques. 327. — How are the ashes raised from the stoke- ?<*ld to the deck, to be thrown overboard? Ans. — By means of the ash-tube and engine; the ash* ube leading from stoke-hold to deck, and the engine aising the ashes in an ash-bucket, that passes through he tube. Another method is by means of the ash-ejector, vhich is simply an inclined tube running from the stoke* eld to above the water-line, and overboard. At the ower end of this tube is a hopper, into which the ashes re shoveled, and at the bottom of this hopper they are icked up by a jet of water of high velocity, and forced trough the inclined tube overboard. CHAPTER v BOILER OPERATION Ques. 328. — What should be the first cart of an engineer, or water-tender, when he goes on watch? Ans. — He should ascertain the exact height of th< water in his boilers by opening the valve in each of th< drain-pipes of the water-columns, allowing it to blow ou freely for a few seconds, then closing it tight, and allowinj the water to settle back in the glass. Ques. 329. — What is one of the important dut es o the firemen coming off watch? Ans. — They should have the fires clean, the ash-pit all cleaned out, a good supply of coal on the floor, anc everything in good condition for the oncoming force. Ques. 330. — What implements are needed for success fully and quickly cleaning a fire? Ans. — A slice-bar, a fire-hook, a heavy iron or stee hoe, and a lighter hoe for cleaning the ash-pit. Ques. 331. — How may these tools be made, so tha they will be light and easy to handle and at the sam time strong and durable? Ans. — After the working ends have been fashioned t< the desired shape, let each be welded to a bar of 1-inch o 1 Ms -inch round iron 10 or 12 inches in length. Thci take pieces of 1-inch or 1/4-inch iron pipe, cut to th< length desired for the handles, and weld the shanks of th< tools to one end of the pipe handles and to the other en< 129 _ BOILER OPERATION 129 weld a ring handle or a short cross-bar to facilitate hand- ling the tools. Ques. 332. — When a fire shows signs of being foul and choked, what should be done at once? Ans. — Prepare to clean it by allowing one side to burn as low as possible, putting fresh coal on the other side alone. Ques. 333. — Describe the process of cleaning a fire. Ans. — When the first side has burned as low as it can, without danger of letting the steam-pressure drop too low, take the slice-bar and shove it in along the side of the fur- nace, 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 portion 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 removed. Having thus disposed of the live coal, take the slice-bar and shove it in on top of the grates, under the clinker, loosening and breaking it up, after which take the heavy hoe and pull it all out upon the floor, where the intense heat contained in the clinker should be quenched by a helper, with a pail of water, or water discharged from a small rubber hose. Ques. 334. — Having gotten one side of the fire cleaned, what is the next move? Ans. — Close the door for that side, and with the slice bar in the other side, push all the liw coal over to the side just cleaned, where it should be leveled off, and fresh coal 130 QUESTIONS AND ANSWERS added. After this has become ignited treat the other side in the same manner. Ques. 335. — Can a definite code of rules for hand firing, be laid down, that will suit all conditions? Ans. — No; owing to the fact that there are so many different varieties of coal, some of which need very little stirring or slicing, while others, that have a tendency to coke and form a crust on top of the fire, need to be sliced quite often. Ques. 336. — Mention a few general maxims that are applicable to all boiler-rooms. Ans. — First, keep a clean fire; second, see that every square inch of grate surface is covered with a good live fire; third, keep as level a fire as possible; fourth, when cleaning the fire, be sure to clear all the clinkers and dead ashes away from the back end of the grates at the bridge- wall. Ques. 337. — Why should the face of the bridge-wall, especially, be kept clean and free from ashes and clinker? Ans. — For the reason that this is one of the best points in the furnace for securing good combustion, provided that the bridge-wall is kept clean from the grates up, and by keeping the back ends of the grates clean, the air is allowed a free passage through them and is per- mitted to come directly in contact with the hot fire-brick, and thus one of the greatest aids to good combustion is utilized. Ques. 338. — In firing bituminous coal, what is a good plan to pursue in regard to the fire-doors, with some types of boilers? BOILER OPERATION 131 Ans. — They should be left slightly ^pen for a few seconds, immediately after throwing in a fresh fire. Ques. 339. — Give the reason for doing this. Ans. — Bituminous coal contains a large percentage of volatile (light or gaseous) matter, which flashes into flame the instant it comes in contact with the live fire in the furnace, and if a sufficient supply of oxygen is not present just at this particular time, the combustion w r ill be imperfect, and the result will be the formation of carbon monoxide, or carbonic oxide gas, and the loss of about two-thirds of the heat units contained in the coal. Ques. 340. — How may this great loss of heat be guarded against, in a great measure? Ans. — By admitting 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 above the fire. Ques. 341. — What quantity of air is required for the complete combustion of 1 pound of coal? Ans. — By weight, 12 pounds; by volume, about 150 cubic feet. Ques. 342. — Is there any advantage gained by heating this air before admitting it to the furnace? Ans. — There is a great advantage, provided the heat used for this purpose would otherwise be wasted. Great economy in fuel, and much better combustion, result from supplying heated air to the furnaces. Ques. 343. — Describe the Howden draught system, as used in the marine service. 182 QUESTIONS AND ANSWERS Ans. — There is a nest of tubes in the uptake that is enveloped by the hot gases on their way to the stack. The air is caused to pass through these tubes by a ■» — >. .:."- *.:* A- / \ J£l J3= 4 v\ / / N • 6 boo poooo boooo poooo JOOOO poooo poooo — kOGOO poooo )0000 >oooo )OOOC o.ooc oooo ooooooooooo oooooooooooo oooooooooooo oooooooooooo oooooooooooo ooooooooooooo oo ooooooooooo •ooooooooo oooo ooooooooooooo ooooooooooooo, // h * / / Vu^ Fig. 90. Arrangement of the Howden Draught System. blower-fan, and as a consequence is heated to a higb degree before passing into the ash-pit. Some of this hot air is also directed into the furnace above the fire, thus securing a good combustion of the fuel. _ BOILER OPERATION 13a Ques. 344. —What precautions should be taken regard- ing cleanliness of the tubes? Ans. — The tubes of all boilers shoula ce kept clean and free from soot, and especially does this apply to fire- Fig. 91. Air Heater oe the Howden Draught System. tube boilers, for the reason that, when these tubes become clogged with soot, the efficiency of the draught is destroyed and the steaming capacity of the boiler is greatly reduced, because soot not only stops the draught but it is also a non-conductor of heat. 134 QUESTIONS AND ANSWERS Ques. 345. — What methods are ordinarily employed for cleaning the soot and dust from tubes? Ans. — First, the steam jet, if properly made and connected by steam hose so as to get dry steam of high pressure, will do very effective work; second, a scraper having steel blades expanded by springs so as to fit the inside of the tubes snugly, should be pushed through each tube once or twice during each twenty-four hours of service. This will cut the soot loose from the inside sur- face of the tubes, and greatly facilitate blowing it out with the steam jet. For the tubes of water-tube boilers Fig. 92. Scraper for Cleaning Fire Tubes. the steam jet may be employed to advantage in cleaning the outside surfaces, and a rotary scraper driven by a small steam turbine is used for cleaning the scale forma- tion from the inside. Ques. 346. — How often should a boiler be washed out and cleaned inside? Ans. — If the feed-water is impregnated to a consider- able extent with scale-forming matter, the boiler should be washed out every two weeks, and if the water is very bad, the time should be shortened to one week. Ques. 347. — How should a boiler be prepared for washing out? BOILER OPERATION 135 Ans. — The fire should be allowed to burn as low as possible, and then be all pulled out of the furnace, the fire-doors left slightly ajar, and the dampers left wide open in order that the boiler may gradually cool. Ques. 348. — Should a boiler be blown out, that is, emptied of water, while there is any steam-pressure in it? Ans. — It should not. Ques. 349.— Why not? Ans. — For the reason that the sudden change of temperature from hot to cold has an injurious effect on the seams and braces. It is as bad a practice to cool a boiler down too suddenly as it is to fire it up too quickly. Fig. 93. Turbine Cleaner for Water Tubes. Ques. 350. — What effect does the too sudden contrac- tion or expansion of the boiler-plates have upon the riveted seams? Ans. — Leaks are created, and very often small cracks radiating from the rivet-holes are started, and these becoming larger with each change of temperature, will finally destroy the strength of the seam and serious results will follow. Ques. 351. — Suppose that all of the fire has been pulled from the furnace and that the boiler has stood until the steam-gauge indicates 20 pounds pressure, 136 QUESTIONS AND ANSWERS would it then be safe to blow a!l of the water out of the boiler? Ans. — It would not, for the reason that the tempera- ture of steam at 20 pounds pressure is 260 degrees Fahrenheit, and it may be assumed that the temperature of the metal of the boiler is at or near this temperature also. Assuming the temperature of the atmosphere in the boiler-room to be 60 degrees Fahrenheit there will be a range of 260 degrees — 60 degrees = 200 degrees Fahren- heit 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 become baked upon the bottom sheets, making it much harder to remove. Ques. £c2. — Under what conditions is it best to empty a boiler of water preparatory to washing it out? Ans. — 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 drip-valve 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. Ques. 353. — Mention some of the important duties of the boiler-washer. Ans. — After the water has all run out and the boiler has cooled sufficiently to permit it, he should go inside (provided there is a man-hole) and after having thoroughly BOILER OPERATION t37 cleaned the inside of the boiler, he should closely examine all of the braces and stays, and if any are found loose or broken, they should be repaired at once, before the boiler is put in service again. The soundness of braces, rivets, etc., can be ascertained by tapping them with a light hammer. Ques. 354. — What should be done with the tubes of fire-tube boilers when they become coated with scale on their outside surfaces? Ans. — The boiler should be taken out of service, laid up temporarily, and the tubes taken out, cleaned, and those that are not corroded or pitted too badly may be made almost as good as new by cutting off 8 or 10 inches of the ends and welding pieces of new tubing on, to bring the tubes back to their original length, after which they may be put back in the boiler and be good for a long term of service. While the tubes are out of the boiler for re- pairs the boiler-washer will have a good opportunity to get inside and clean and inspect every portion of the inside. Ques. 355. — What precautions should be taken when connecting a recently fired-up boiler with the steam main or header? Ans. — First, the steam in the boiler to be connected should be raised to the same pressure as that in the main, then the dampers should be closed and the steam stop- valve should be opened slightly, just enough to permit a amall 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 main into the newly connected boiler, or vice versa. Whichever way it is Fig. 94. Square Open Heater. BOILER OPERATION 139 going, the valve ought not to be opened any farther until the flow of steam stops. This will indicate that the pres- sure has been equalized be- tween the boiler and the main, and it will then be found that the valve will move much easier, and it may be gradually opened until it is wide open. Ques. 356.— Should cold feed-water ever be pumped into a boiler that is under steam? Ans. — It should not, if it is possible to prevent it. Ques. 357. — How may the feed-water be heated econo- mically? Ans. — By passing it through a feed-heater in which the heating agent employed is the exhaust steam from the engines. Ques. 358. — How should the feed-water be supplied to a boiler while the boiler is being fired? Ans. — It should be supplied just as fast as it is evap- orated. The firing can then be even and regular. Ques. 359. — If the supply of feed-water should sud- denly be cut off owing to breakage of the pump or some other cause, and no other source of supply was available, what should be done? Fig. 95. Interior View OF Open Heater. 140 QUESTIONS AND ANSWERS Ans. — The dampers should be closed immediately, and all of the draught stopped. The fires should be deadened by shoveling wet or damp ashes in on top of them, or if ashes can not readily be procured, bank the fires over with green coal broken into fine bits. This, with the draught all shut off, will keep the fires dead, and if repairs to the feed-supply can not be made within a short time, the fires should be pulled, that is, if they have become deadened sufficiently. Ques. 360.— Should the fires be pulled while they are burning lively? Ans. — No; because the stirring will only serve to increase the heat, and the dan- ger will be aggravated. Ques. 361.— What is the primary object of making evaporation tests of boilers? Ans. — To ascertain how many pounds of water per pound of coal the boiler is evaporating. Ques. 362. — What other important details relating to the operation of the boilers may be ascertained through « Veil-conducted evaporation test? Ans. — First, the efficiency of the boiler and furnace as tfic 96. Baragwanath Steam Jacket Feed Water Heater. BOILER OPERATION 141 an apparatus for the consumption ni fuel and the evap- oration of water; second, the relative value of different varieties of coal, and other fuels, as heat- producers; third, whether the boilers, as they are operated un- der ordinary every- day conditions, are being operated as economically as they should be; fourth, in case the boilers, owing to an increased de- mand for steam, fail to supply a sufficient quantity, whether or not additional boilers are needed, or whether the trouble could be overcome by a change of conditions in the op- eration of the boilers. Ques. 363.— What are the principal data to be noted down dur- ing the progress of an evaporation test? Ans.— First, time— the number of hours that the test is conducted; second, the kind of coal burned; third. Fig 97. Closed Feed Water Heateb. 142 QUESTIONS AND ANSWERS weight of coal consumed; fourth, weight of water evap- orated during the test; fifth, weight of dry ash returned; sixth, moisture in the coal per cent, seventh, dry coal corrected for moisture- eighth, weight of combustible; ninth, moisture in the steam, per cent; tenth, water corrected for moisture in the steam, eleventh, average temperature of the feed -water; twelfth, average tempera ture of the escaping gases; thirteenth, square feet of grate surface; fourteenth, square feet of heating sur- face; fifteenth, ratio of grate surface to heating surface. Ques. 3G4. — How may the weight of the coal consumed during the test be ascertained? Ans. — By having a small platform scales fitted with a wooden platform large enough to accommodate a wheel- barrow, or, in lieu of a barrow, a box large enough to contain two or three hundred pounds of coal. Each wheel-barrow load, or boxful of coal that goes to the boiler undei test can then be weighed and the figures be placed upon a tally-sheet and added together at the close of the test, thus giving the total weight of coal consumed during the test. If, at the close of the test, there is any of the weighed coal left on the floor, it should be weighed back and deducted from the total weight. Ques. 3G5. — How may the weight of water evaporated during the test be ascertained? Ans. — By having a hot-water meter fitted in the branch feed-pipe leading to the boiler under test, or if this is not to be had, a substitute equally as accurate can be made by placing two small water-tanks, each having a capacity of 8 or 10 cubic feet, in the vicinity of the feed-pump. BfJILEK OPERATION 143 These tanks can be made of light tank-iron, and each should be fitted with a nipple and valve, near the bottom, for connection with the suction side of the feed-pump. The tops of the tanks may be left open. A pipe leading from the main water-supply, with a branch to each tank, is also needed for filling them. If an open feed-water heater is used, and it is possible to place the tanks low enough to allow a portion of the hot water from the F£:e f^WRT£ H SUPp L y TOFEEPPUMP Fig. 98. heater to be led into them by gravity, it will be desirable to do so. If this can not be done, some other provision should be made for at least partially warming the water before it goes to the boiler. The exact capacity of each one of these two tanks, either in cubic feet or in pounds of water, should be ascertained, and then all of the feed- water that is supplied to the boiler during the test is to be first passed through the tanks, which should be numbered 144 QUESTIONS AND ANSWERS one and two respectively, in order to prevent confusion in keeping a record of the number of tanksfull of water used during the test. Two tanks should be provided, in order that while the feed-pump is drawing the water from one, the other one may be filled. The feed-pump that is used to supply the boiler under test should have no connection whatever with the main feed-supply. By keeping tab of the number of tanksfull of water used during the test, and TABLE 6 WEIGHT OF WATER AT VARIOUS TEMPERATURES Temper- Weight per Temper- Weight per Temper- Weight per ature Cubic Foot ature Cubic Foot ature Cubic Foot 32 F. 62.42 lbs. 132 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 26o° 58.52 72° 62.30 172 60.73 2 70° 58.21 82° 62.21 182 60.50 3 00° 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 3QO° 54.03 122° 61.70 220° 59-64 420 52.86 multiplying this by the capacity of each tank, the total weight of water evaporated is ascertained. Ques. 3GG. — How is the weight of dry ash ascertained? Ans. — No water should be allowed to come in contact with the ashes during the test, or if it is absolutely neces- sary to use water, it should be used as sparingly as possible, and as the ashes are pulled from the furnace or ash-pit, they should be thrown to one side, and allowed to become dry, after which the weight can be ascertained by means of the scales that was used for weighing the coal. BOILER OPERATION 145 Ques. 367. — How is the amount of moisture in the coal ascertained? Ans. — This can generally be obtained from the reports of the geologist of the state in which the coal was mined. Ques. 368. — How is the weight of dry coa! corrected for moisture ascertained? Ans. — Deduct the percentage of moisture in the coal from the total weight of coal consumed. Ques. 369. — How is the weight of combustible ascer- tained? Ans. — Deduct the weight of dry ash returned from the Weight of dry coal corrected for moisture. Ques. 370. — How is the percentage of moisture in the steam determined? Ans. — By means of an instrument called a calorimeter, or if such an instrument is not at hand, the condition of the steam as regards its dryness may be approximately estimated by observing its appearance as it issues from a pet-cock, or other small opening into the atmosphere. Dry, or nearly dry steam, containing about 1 per cent of moisture, will be transparent close to the orifice through which it issues, and if it is of a grayish white color it may be estimated to contain not over 2 per cent of moisture. Ques. 371. — How is water corrected for moisture in the steam arrived at? Ans. — Deduct the percentage of moisture in the steam from the total weight of water evaporated during the test. Ques. 372. — How is the average temperature of the feed- water obtained? 146 QUESTIONS AND ANSWERS Ans. — By means of a hot-water tnermometer connected to the feed-pipe near to the check-valve, but between it and the feed-pump. If the thermometer is not attached to the feed-pipe, the temperature of the water in each tank should be taken and noted down, during the time that the feed-pump is drawing from it. From these notations, made at regular intervals during the progress of the test, the average temperature of the feed-water is easily calculated. Ques. 373. — How is the average temperature of the escaping gases determined? Ans. — By readings taken at regular intervals from a thermometer con- nected in the uptake. Ques. 374. — What should be done with the boiler and furnace before be- ginning an evaporative test? Ans. — The boiler should be thor- oughly cleaned, both inside and out- side, and especially the heating sur- face, by scraping and blowing the soot out of the tubes, if it be a return-tu- bular 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 out- side of the shell, and also from the ^Thermometer.™ TOILER OPERATION 14? combustion chamber ana smoKe connections. The grate- bars and sides of the furnace should be cleared of all clinker, and all air-leaks made as tight as possible. Ques. 375. — What should be done with the water- connections? Ans. — The boiler and all of its water-connections should be perfectly 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. Ques. 376. — Why is it required that especial care be exercised regarding the water-connections? Ans. — For the reason that the test is made for the pur- pose of ascertaining the exact quantity of water that the toiler will evaporate with a given weight and kind of coal, md if any of the water fed to the boiler during the test is allowed to leak away, or if any water, other than that which has been measured by passing it through the tanks, is allowed to get into the boiler during the test, the results will be misleading and unreliable. Ques. 377. — Before starting the test, what other details regarding the boiler should be attended to carefully? Ans. — The boiler should be thoroughly heated, by having been run for several hours at the ordinary rate. The fire should then be cleaned and put in good condition to receive the fresh coal that has been weighed for the test. Ques. 378. — What should be done regarding the water-level? Ans. — At the time of beginning the test, the water- level in the boiler should be at or near the height ordi- narily carried, and its position should be marked by tying 148 QUESTIONS AND ANSWERS a cord around one of the guard-rods of the gauge-glass and, to prevent any possibility of enor, the height of th< water in the glass should be measured in inches, and i memorandum made of it. Ques. 379. — What data regarding the steam-pressure should be recorded? Ans. — The steam-pressure as indicated by the gauge should be noted at the time of starting the test, and alsc at regular intervals during the progress of the test, ir order that the average pressure may be obtained. Ques. 380. — When should the test begin? Ans. — When all of the conditions just described have been complied with and the first lot of weighed coal ha! been fed to the furnace and the feed-pump is receiving water from one of the measuring tanks, the time shoulc be noted and recorded as the starting time. Ques. 381. — What length of time should an evapora- tion-test be conducted? Ans. — Ten houis, if it is possible to continue it that long. Ques. 382. — What conditions regarding the steam- pressure, condition of the fire and the water-level shoulc prevail at the close of the test? Ans. — They should be as nearly as possible the same at the close as they were at the beginning. The water- level should be the same and the quantity and the condition of the fire, also the steam pressure. Ques. 383. — How may this be accomplished? Ans. — Only by very careful work toward the close of the test. BOILER OPERATION 149 Ques. 384. — If any of the weighed coal is left on the oor at the close of the test, what should be done with it? Ans. — It should be weighed back and its weight educted from the total weight. Ques. 385. — If a portion of water is left in the last ank tallied, what disposition should be made of it? Ans. — It should be measured and deducted from the otal. Ques. 386. — In making a test of the efficiency of the oiler, what is one of the most essential conditions to be aken into consideration? Ans. — The boiler should be operated at its fullest apacity, from the beginning to the end of the test, and rrangements should be made to dispose of the steam as ast as it is generated. Ques. 387. — How may this be done? Ans. — If the boiler is in a battery and connected to & ommon header, the other boilers can be fired lighter dur- ng the test; but if there is but the one boiler in use, a vraste-steam pipe should be temporarily connected, hrough which the surplus steam, if there is any, can be ischarged into the open air, through a valve regulated s required. Ques. 388. — If the boiler under test is fed by an njector instead of a pump during the test, from whence hould the steam-supply for the injector be taken? Ans. — The steam for the injector should be taken lirectly from the boiler under test, through a well- >rotected pipe. The steam for the pump, if one is used, hould also be taken from the same source. 150 QUESTIONS AND ANSWERS Ques. 389. — How should the temperature of the feed* water be taken when an injector is used? Ans. — It should be taken from the measuring tanks* or at least from the suction side of the injector. Ques. 390.— Why? Ans. — Because the water in passing through the injector receives a large quantity of heat imparted to it by live steam directly from the boiler, and the tempera- ture of the water after it leaves the injector would not be a true factor for use in calculating the results of the test. Ques. 391. — For obtaining reliable and economical results in an evaporation-test, what conditions are essential regarding the draught? Ans. — There should be a good, strong draught, which can be regulated by a damper, as desired. There should also be a draught-gauge connected to the uptake, for the purpose of measuring the draught. Ques. 392. — Why is it necessary to measure the draught? Ans. — The principal reason for measuring the draught is that in making comparative tests of the heating value of different varieties of coal, the conditions should be the same as near as possible in all of the tests made, and especially should this be the case with the draught. Therefore, by using a draught-gauge and measuring the draught during each test, there will be no uncertainty regarding this very important element. Ques. 393. — Describe the construction and operation cf a draught-gauge. BOILER OPERATION 151 Ans. — The usual form of drr^ght-gauge is a glass tube bent in the shape of the letter U. One leg i s con- nected to the uptake by a small rubber hose, while the other leg is open to the atmosphere. A scale marked in tenths of an inch is fitted between the two legs of the gauge. The glass tube is partly filled with water, which will, when there is no draught, stand at the same height in both legs, provided the instrument stands perpendicular, which is its normal position. When connected to the uptake, the suction caused by the draught will cause the water in the leg to which the hose is attached to rise, while the level of the water in the leg that is open to the atmos- phere will be equally depressed, and the extent of the variation in frac- tions of an inch is the measure of the draught. Thus the draught is referred to as being .5 .7 or .75 inch. Ques. 394.— What is the least iraught that should be used, in or- ler to obtain good results? Ans.— The draught should not be less than .5 inch. Better results may be obtained with a draught of .7 inch. Ques. 395.— If the test is made for the purpose of letermining the efficiency of the boiler and setting as a vhole, including grate, draught, etc., and also for compar- Fig. 100. Draught Gauge, 152 QUESTIONS AND ANSWERS ing the heating qualities of different kinds of coal* what must the result be based upon? Ans. — Upon the number of pounds of water evapo- rated per pound of coal burned. Ques. 396. — What is implied in the expression "per pound of coal burned' ' as used in this connection? Ans. — It includes not only the purely combustible matter in the coal, but the non-combustible also, such as ash, moisture, etc. Some varieties of Western coal con- tain as high as 12 to 14 per cent of moisture, and the ability of the furnace 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. Ques. 397. — If the test is to determine the efficiency of the boiler itself as an absorber and transmitter of heat, what must be the factor for working out the result? Ans. — The weight of the combustible alone must be considered. Ques. 398. — When making a series of tests for the purpose of comparing the economical value of different kinds of coal, what conditions should prevail? Ans. — The conditions should be as nearly uniform as possible; that is, let the tests all be made under ordinary working conditions, and with the same boiler or boilers, and if possible with the same fireman. Ques. 399. — What is meant by the term "equivalent evaporation, ' ' as applied to the results of an evaporation- test? Ans. — The term "equivalent evaporation/' or t le evaporation from and at 212 degrees, assumes that the BOILER OPERATION 153 feed-water enters the boiler at a temperature of 212 degrees and is evaporated into steam at 212 degrees tem- perature, and at atmospheric pressure, as, for instance, if the top man-hole plate were left out, or some other large opening in the steam-space of the boiler allowed the steam to escape into the atmosphere as fast as it was generated. Ques. 400. — Why is it necessary to introduce this feature into calculations of the results of evaporation- tests? Ans. — Owing to the variation in the average tem- perature of the feed-water used in different tests, and also- the variation in the average steam-pressure, it is absolutely necessary that the results of all tests be brought by computation to the common basis of 212 degrees in order to obtain a fair and just comparison. Ques. 401. — Describe the method of calculation by which this is done. Ans. — Suppose an evaporation-test to have been made, and that the average steam-pressure by the gauge was 85 pounds, which equals 100 pounds absolute pressure, and that the average temperature of the feed-water was 141 degrees. By reference to Table 1, Chapter 1, it will be found that in a pound (weight) of steam at 100 pounds absolute pressure there are 1,181.1 heat units or thermal units, and in a pound of water at 141 degrees temperature there are 109.9 heat units. It therefore required 1,181.1 — 109.9 = 1,071.9 heat units to convert 1 pound of feed- water at 141 degrees temperature into steam at 85 pounds gauge, or 100 pounds absolute pressure. Now 154 QUESTIONS AND ANSWERS to convert a pound of water at 212 degrees temperature into steam at atmospheric pressure and 212 degrees tem- perature, requires (according to Table l) 965.7 heat units, and the 1,071.9 heat units would evaporate 1,071.9 -*- 965.7 = 1.11 pounds of water from and at 212 degrees. The 1.11 is the factor of evaporation for 85 pounds gauge pressure, and 141 degrees temperature of feed-water, Ques. 402. — What use is made of this factor of evap- oration in the calculation? Ans. — One of the results of the test was "weight of water corrected for moisture in the steam," and by mul- tiplying this result by the factor of evaporation, the "equivalent evaporation" is ascertained. Ques. 403. — Upon what is the factor of evaporation based, in any test? Ans. — Upon the steam-pressure and the temperature of the feed-water. Ques. 404. — Give the formula for finding this factor for any test. TT L. Ans. — The formula is: Factor =——,in which H = 9bo.7 total heat in the steam, h = total heat in the feed-water, and 965.7 = the number of heat units in a pound of steam at atmospheric pressure and 212 degrees tempera- ture. Table 7 gives the factor of evaporation, already calculated, for various pressures and temperatures. Ques. 405. — If it is desired to ascertain the cost of coal for generating the steam used for operating an engine that uses 30 pounds of steam per horse-power per hour, what is the method of calculation? Ans.— If the engine uses 30 pounds of steam per horse- ower per hour, and it has been found by the test that pound of the coal used would evaporate 9 pounds of ater into steam of the pressure at which it is supplied to le engine, the actual consumption of fuel by the engine Table 7, Factors of Evaporation BOILER OPERATION 155 D g 12 00° K 82° 73° 6 4 ° 52° 43° 34° 25° 13° 04° 95° 86° 77° 65° 56° 47° 38° &A I.027 I.039 I.049 I.05S I.O67 I.077 I.O89 I.099 I. I08 I.II8 I.I30 I.I38 I.I4Q 1.158 1.167 1. 180 1. 189 1. 199 1.208 CO 1.030 1.042 1.052 1. 061 1.070 1.080 1.092 1. 102 I. Ill 1. 121 1. 133 1. 142 1. 152 I. l6l 1. 170 I.183 1. 192 1. 20I 1. 211 CO ed o co CO CO Si <3 CO u Ph 1.032 I 045 1.054 1.064 1.073 1.083 1.095 1. 105 1. 114 1. 123 1.136 1. 145 1.154 1. 164 1.173 1.186 1. 195 1.204 1. 214 1.035 1.047 1.057 1.066 1.076 1.085 1.098 1. 107 1.116 1. 126 1. 138 1.148 1. 157 1. 166 1. 176 1. 188 1. 197 1.207 1. 216 1.037 1.050 1.059 1.069 1.078 1.087 1. 100 1. 109 1. 119 1. 128 1. 140 1. 150 1. 159 1. 169 I.I78 1. 190 I.200 I.209 1. 218 CO 10 O a . O g CO u en bfl 2 3 M CTj . Geo CO CD u V n bfl CN 3 M a . Oco CO D 1.039 1.052 1. 061 1. 071 1.080 1.090 1. 102 I. Ill 1. 121 1. 130 1. 143 1.152 1. 161 1. 171 1. 180 1. 192 1.202 I. 211 I.220 I. O4I I.054 I.063 I.073 1.082 1. 09 1 1. 104 1. 113 I.I23 1. 132 1. 145 I. 154 I. I63 I.I73 1. 182 I. 194 I.204 1. 213 1.222 I.O43 I.O56 I.065 I.O/5 I.034 I.093 1. 106 I.II5 1. 125 1. 134 1. 146 1. 156 1. 165 I.I74 1. 1 84 1. 196 1.206 1. 215 1.224 to %■ I.047 I.059 I.069 I.078 I.087 1.097 I. IO9 1. 119 1. 128 1. 137 1. 150 1. 159 1. 169 1. 178 1. 187 1.200 I.209 1. 218 1.228 vould be as follows: 30 -5- 9 = 3.33 pounds of coal per lorse-power per hour, which, multiplied by the total horse- >ower developed by the engine, will give the total weight )f coal consumed in one hour's run. Ques. 406. — What is the meaning of the expression 'boiler horse-power?' ' 156 QUESTIONS AND ANSWERS Ans. — The latest decision of the American Society o Mechanical Engineers regarding the horse-power oi a boiler is "that the unit of commercia 1 horse-power de veloped by a boiler shall be taken as 34j/2 units of evapor« ation." That is, 34^2 pounds of water evaporated pel hour from a feed temperature of 212 degrees into steai of the same temperature. This standard is equivalent to 33,317 heat units per hour. It is also practically equivalent to an evaporation of 30 pounds of water from a feed temperature of 100 degrees Fahrenheit into steam of 70 pounds gauge- pressure. Ques. 407. — According to this rule, what would be the horse-power of a boiler in which during a 10-hour test, the evaporation from and at 212 degrees was found by calculation to have been 86,250 pounds of water? Ans. — The horse-power developed would be 86,250 - 10-^ 34.5 = 250 horse-power. Ques. 408. — In what way can the maximum economy in the consumption of coal be obtained? Ans. — There is only one way, and that is by keeping a continuous supply of coal on the fires and admitting a regular and sufficient quantity of air for its combustion, Ques. 409. — Can these conditions be reached by hand firing? Ans. — They can not, no matter how careful and skil- ful the firemen may be. Ques. 410. — Mention two of the principal disadvan- tages attending hand firing. Ans. — First, during the time of firing the furnace BOILER OPERATION J57 door is wide open, thus admitting a large volume of cold air ; second, immediately after throwing in a fresh supply of coal, there is a sudden generation of gas, a large per- centage of which escapes without being entirely consumed, and much heat is thus wasted. Ques. 411.— What are the principles governing the operation of mechanical or automatic stokers? Ans. — First, a continuous supply of coal and air; second, thorough regulation of the supply of fuel and air, according to the demand upon the boilers for steam; third, the intermittent opening and closing of the furnace doors is entirely prevented. Ques. 412.— What are some of the disadvantages attending the use of mechanical stokers? Ans.— First, the great cost of installing them; second, in case of a sudden demand upon the boilers for more steam, the mechanical stoker can not respond as promptly as in hand firing; third, the extra cost for power to operate them. Ques. 413.— How many different classes of mechanical stokers are in use? Ans. — Four general classes. Ques. 414.— Describe the construction and operation )f stokers belonging to Class 1. Ans.— The grate consists of an endless chain of short >ars, that travels in a horizontal direction from the front o the back of the furnace, over sprocket wheels operated ither by a small auxiliary engine or by power derived rom an overhead line of shafting in front of the boilers, "he motion of the endless chain of grates is of course very 158 QUESTIONS AND ANSWERS I BOILER OPERATION 159 slow, but it is continuous and regular, receiving the supply of coal at the front and depositing the ashes at the bacK nd, where they drop into the ash-pit. o in o o <% «« W Q a O a Ques. 415. — What type of stokers is included iu [lass 2 ? Ans. — Stokers having grate-bars somewhat after the rdinary hand-fired type, but having a continuous motion 160 QUESTIONS AND ANSWERS no and down, of- forward and back. Although this motion is slight, it serves to keep the fuel stirred and loosened, thus preventing the fire from becoming sluggish Ques. 416. — What position do the grate-bars in Oass 2 occupy? Fig. 103. Vicars Mechanical Stoker. Ans. — Either horizontal, or slightly inclined, and their constant motion tends to gradually advance the coal from the front to the back end of the furnace. Ques. 417. — What kinds of stokers are included in Class 3 ? Ans. — Stokers in which the grates are steeply inclined. BOILER OPERATION 161 The coal is fed onto the upper ends of the gates, whicfop - having a slow motion, gradually force the coal forward as fast as required. In some stokers of this class, as, for instance, the Murphy, the grates incline from the sides towards the middle of the furnace, but in the majority of cases the inclination is from the front towards the back. Fig. 104. The Murphy Automatic Furnace. Ques. 418. — What is the leading feature governing the operation of stokers ^belonging to Class 4 ? Ans. — Thecoal is supplied from underneath the grates, and is pushed iffT through an ppening left for the purpose midway of the length of the furnace. The gases, on being distilled, come in contact immediately with the hot | bed of coke on top, and the result is good combustion. Ques. 419. — What are. stokers belonging to Class A I called? 162 QUESTIONS AND ANSWERS Ans. — Under-feed stokers. Ques. 420. — What methods are employed for forcing the coal up into the furnace with under-feed stokers? Ans. — Steam is the active agent, either by means of a steam-ram, or a long, slowly revolving screw, driven by a small engine. BOILER OPERATION 163 Ques. 421. — How is the air supplied when an under- feed stoker is used? § 55 HI n o U tn P hi o >< w I Compound, in which the cylinders are tandem to each other, and one piston rod, cross-head, connecting rod, and valve-gear is common to both, although each cylinder has 176 QUESTIONS AND ANSWERS its own valve or valves for controlling the admission and release of the steam. Ques. 458. — What is implied in the expression "triple expansion ?" Ans. — Triple expansion means that the steam has been allowed to expand through three successive stages, doing Fig. 115. Shows a Triple Ex- pansion Engine in which the Hich Pressure is Tandem with The Intermediate Cylinder. Fig. 115a. Shows the Ordinary Ar« RANGEMENT OF CYLINDERS FOR A TrI« i'le Expansion Engine. a fixed amount of work in each stage, before release occurs. Ques. 459. — How many cylinders are required on a triple-expansion engine? Ans. — Never less than three, and for large, high-speed engines it often becomes necessary to have two lowr TYPES OF ENGINES CLASSIFICATION 17? pressure cylinders, thus making a four-cylinder triple- expansion engine. Ques. 460. — Are four cylinder triple-expansion en- gines much in use? Ans. — They are in the marine service, and especially in the British navy, and they are also used to a large extent in the mercantile service. Ques. 461. — Describe the action of the steam in a quadruple-expansion engine. MOMBOILBB ma — m — cm — mn Fig. 116. Arrangement of Four Cylinder Trifle Expansion Engine for Marine Service. Ans. — In a quadruple-expansion engine, the expansion of the steam is divided up into four stages by causing it to pass through four successive cylinders, termed respectively the high-pressure, first intermediate, second intermediate, and low-pressure. In some of the larger engines of this type there are two low-pressure cylinders,, thus making five cylinders in all. Ques. 462. — What pressures of steam are usuallv used in this type of engine? 178 QUESTIONS AND ANSWERS Ans. — From 200 to 250 pounds per square inch. Ques. 463. — What are some of the advantages that ire to be gained in the use of steam by stage expansion? TYPES OF ENGINES CLASSIFICATION 179 Ans. — First, that the cylinder into which steam directly from the boiler is admitted is never open to the cooling influence of the atmosphere, or condensor, hence there is not so much cooling and condensation of the entering steam; second, the steam that is condensed and reevaporated in the first cylinder reappears as working steam in the second cylinder; third, the loss from con- densation in the second and third cylinders is also reduced, owing to the smaller range of temperature, between admission and exhaust in those cylinders. Ques. 464. — What are the mechanical advantages of compound and triple-expansion engines, for heavy duty? Ans. — First, the facility with which high rates of expansion may be carried out without bringing excessive strains and stresses on the framing of the engine; second, a greater uniformity of twisting moment on the shaft. Ques. 465. — What are the usual ratios of cylinder volumes in compound and triple and quadruple-expansion engines? Ans. — For compound engines 1 to 4 between high and low-pressure cylinders. For triple-expansion engines, the ratios are about 1, 3 and 7, for high, intermediate and low-pressure cylinders. For quadruple-expansion engines the ratios are as follows: 1, 2, 4/4 and 10/4 for high-pressure, first intermediate, second intermediate and low-pressure respectively. Ques. 466. — What is meant by the term receiver, a9 used in connection with the stage-expansion of steam? Ans. — In the case of a compound engine the receiver is the whole of the space between the high-pressure 180 QUESTIONS AND ANSWERS piston, when at the end of its stroke, and the back of the low-pressure steam-valve, whether it be slide rotative, or piston-valve. In the case of a triple-expansion engine, the space between the piston at the end of its stroke and the back of the intermediate steam-valve is called the intermediate receiver, and the space between the inter- Fic. 118. Sectional View of Tandem Compound Cylinders, Showing Arrangement of Steam Chests and Valves. mediate piston at the end of its stroke and the low-pres- sure steam-valve is the low-pressure receiver. Ques. 4G7. — What is the usual volume of these receivers in modern practice? Ans. — After many experiments with large reservoirs as receivers, it has been found that all that is necessary is a comparatively large exhaust pipe from the exhaust TYPES OF ENGINES — CLASSIFICATION 181 orifice of the high-pressure cylinder to the steam inlet of the next lower pressure cylinder, it having been demon- strated that the volume of the exhaust passage and pipe from the high-pressure cylinder and the low-pressure valve-chest supplied sufficient space to allow for the com- pression that occurs between release from the high-pres- sure cylinder and admission to the low-pressure cylinder. Jroytitota* Q ues - 468.— Does this law apply in the case of triple and quadruple-expansion engines? Ans. — It does. Ques. 469. — Upon what does the power of any stage- expansion engine depend? Ans. — The power of a stage-expansion engine work- ing at any given rate of ex- pansion depends entirely upon the dimension of its low- pressure cylinder or cylinders, Fig. 119. Tandem Quadruple Ex- an( J j s not affected by the size pansion Marine EngineShowing j of its high-pressure cylinder, carries out but one stage in the Arrangement of Cylinders. which latter, in fact, expansion. Ques. 470. — What does the capacity of the low-pres- sure cylinder or cylinders of such an engine require to be? Ans. — The same as that of the whole of the cylinders of a simple engine of the same power, working at the same initial pressure and total ratio of expansion. Ques. 471.— Why is this? 182 QUESTIONS AND ANSWERS Ans. — For the reason that, since the initial pressures and ratios of expansion are the same in bot.i engines, it follows that the terminal pressures and volumes must also be identical in both cases. In the simple engine the whole of the steam at the end of the stroke fills all of the cylinders, while in the compound engine it is contained in the low-pressure cylinder or cylinders only, hence the capacity of this cylinder must be equal to the capacity of all the cylinders of the simple engine. r r\ "N LP ^ /&/.P 2* IP □W ~7 N.P. «> PROM BOILCR I Fig. 119a. Quadruple Expansion Engine, with Cylinders as Ordinaril* Arranged — Arrows Show Course Taken by the Steam. Ques. 472. — Why is it necessary in some cases to employ two low-pressure cylinders? Ans. — For the reason that in very large engines one low-pressure cylinder would be too large and unwieldy, therefore it is divided into two equal parts. Ques. 473. — Are compound and triple-expansion engines much in use outside of the marine service? Ans. — They are to a large extent, owing to the great gain in economy over the simple engine. Practically all large manufacturing plants u c/ * them. TYPES OF ENGINES CLASSIFICATION 183 Ques. 474. — What other types of engines are in use in the marine service? Ans. — The vertical walking-beam engine is largely in use on the lakes, bays, and rivers of the United States, Fig* 120. Belleville Reducing Valvts. Ques. 475. — What is the leading characteristic of this type of engine? Ans. — It has usually but a single cylinder^ with a very 184 QUESTIONS AND ANSWERS long stroke in proportion to its diameter, the length of the stroke varying from 7 to 12 feet. Ques. 476. — What pressures of steam are usually employed in beam engines? Ans. — Owing to the fact that the steam is expanded in a single cylinder only t the pressure carried is low — 50 to 60 pounds per square inch. Ques. 477. — Mention another type of engine that is in common use on Western rivers. Fig. 121. Fig. 121 is a sectional view of the cylinder, steam, and exhaust-chests, and the valve-chambers of a Corliss engine. 1 and 2 are the steam-valves and 3 and -4 the exhaust-valves. The valves work in cylindrical chambers accurately bored •ut, the face of the valve being turned off to fit steam tight. They are what is termed rotative valves, that is, they receive a semi-rotary motion from the wrist' ~iate, which in turn is actuated by the eccentric. Ans. — The stern-wheel engine, consisting of a pair ot engines, one cylinder on either side of the boat, and directly connected to the shaft of the stern-wheel. Like the beam engine, the stroke is long in proportion to the cylinder diameter. Ques. 478. — Are these engines simple or compound? Ans. — In former years simple engines were used alto- TYPES OF ENGINES — CLASSIFICATION 185 gether, but the later types are compound, either tandem or cross-compound. Ques. 479. — What styles of valves and valve-gears are in use on these engines? Ans. — Poppet-valves, actuated by long cam-driven! levers, are the most generally used. Other styles of valves, such as rotative valves, common slide and piston- valves, are also quite frequently used. Q 9 A*/?* c i - 8 3 xoS ffl Ifcf *% Wm Fig. 122. The valve-gear of a Corliss engine with a single eccentric is shown in Fig. 122» 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 connection! of the steam-valves with the wrist-plate are detachable, being under the control of the governor. Ques. 480.- — What is meant in speaking of a fo« ^ valve engine? Ans. — An engine having two steam-valves and tvJ3 exhaust-valves located near each end of the cylinder. Ques. 481. — What type of four-valve engine has met with great favor since its introduction? Ans. — The Corliss engine, invented by Mr. Geo. H# Corliss, of Providence, R. L 186 QUESTIONS AND ANSWERS Ques. 482. — What advantage does the four-valve engine possess over the single-valve type? Ans. — The advantage that each valve may be adjusted to a certain degree independently of the others, the steam- valves tor admission and cut-off and the exhaust-valves for compression and release. Ques. 483. — What is one of the oldest forms of valve, and one that is still used extensively, especially on marine engines? Ans. — The D slide-valve. L Fig. 123. Fig. 123 represents a slide-valve at mid-travel. S P— S P are the steam- ports and E P is the exhaust-port; the projections marked x at each foot <,£ the arch inside 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 O L — O h represent outside lap. Ques. 484. — What are the functions of the slide- valve? Ans. — It controls the admission, expansion and release of the steam and the closure of the exhaust. Ques. 485. — Upon what does the development of the full power of the engine and its efficient and economical use of steam, as well as its regular and quiet action, largely depend? Ans. — Upon the correct adjustment of its valve or valves. TYPES OF ENGINES CLASSIFICATION 187 Ques. 486. — How is the slide-valve fitted to the :ylinder? Ans. — The slide-valve has a flat face and it works on the corresponding flat face of the cylinder. In the cylinder face there are three passages called ports, the two smallest, called steam-ports, leading to each end of the cylinder, and the larger one, called the exhaust-port, eading to either the receiver, condensor, or the atmos- phere, as the case may be. The valve is contained in a team-tight chest or casing, either 'cast with the cylinder, Fig. 124. Fig. 124 shows the slide-valve in .the position of lead — exhaust opening has also occurred at the opposite end of the cylinder. The arrows show the course of the steam, also the direction in which the valve is traveling. or bolted to it. This casing or valve-chest is filled with live steam while the engine is working. Ques. 487. — How must the slide-valve be constructed, in order that it may properly perform the four important functions of admission, cut-oflf, release, and exhaust closure? Ans. — It must have lap and lead. Ques. 488.— What is lap? Ans. — Lap is the amount that the ends of the valve project over the edges of the ports when the valve is at mid-travel. 188 QUESTIONS AND ANSWERS Ques. 489. — What is steam lap, or outside lap? Ans. — The amount that the end of the valve projects over the outside edge of the steam-port. Ques. 490. — What is inside or exhaust lap? Ans. — The lap of the inside or exhaust edge of th< valve over the inside edge of the port. Ques. 491.— What is lead? Ans. — The amount that the steam port is open when the piston is just commencing its stroke. This is the instant of admission. Ques. 492. — When is the instant of cut-off? / Z Fig. 125. Fig. 125 shows the slide-valve at the end of its travel— full port opening. Ans. — When the admission of steam to the cylinder is stopped by the steam edge of the valve closing the steam- port and the piston is pushed the balance of the stroke by the expansion of the steam admitted before cut-off occurred. Ques. 493. — When is the instant of compression? Ans. — When the two inside or exhaust edges of the valve coincide with the inner edges of the ports, the piston being near the end of its stroke and the valve at mid- travel, Ques. 494. — When is the instant of release? TYPES OF ENGINES CLASSIFICATION 189 Ans. — When the inner edge of the valve commences to ;>pen the steam-port to the exhaust-passage. Ques. 495. — What is the advantage gained by com- ression? £ Ans.- — A portion of steam is confined ahead of the >iston, thus forming an elastic cushion to absorb the Inomentum of the piston and other moving parts con- mected with it and bring all to rest quietly at the end of the stroke. Ques. 496.— -How may this compression be increased | or diminished? Fig. 126. Fig. 126 illustrates the instant of cut-off. The valve is now traveling in the opposite direction. S • ' t " ' Ans. — By adding to or taking away from the inside lap of the valve. Ques. 497.— What is the object of giving a valve lead? Ans. — The effect of lead is to cause the engine to be quick and not to lag at the beginning of the stroke. The live steam admitted through the lead opening also assists in forming a cushion for the piston at the end of the stroke. Ques. 498. — Do the principles governing the adjust- ment and action of the slide-valve necessarily have to be applied in the adjustment and action of rotative, piston, 190 QUESTIONS AND ANSWERS and other forms of valves for controlling the distributio] of steam in the cylinders of engines? Ans. — They do. The same general principles applj in all cases. Ques. 499. — How is motion generally imparted to th| slide-valve or other types of valves? Ans. — By means of an eccentric, which is simply a cir| cular cast-iron or cast-steel sheave having a hole bored ii it eccentrically with its own circumference, and larg< enough to permit of its being fitted on the engine shaft The eccentric-sheave is either keyed on the shaft or helc Fig. 127. Fig. 127 shows the slide-valve at the instant of compression. in its place by set-screws, and therefore revolves with th< shaft. On the circumference of the eccentric, which is of sufficient width to present a good bearing surface, ring, called the eccentric-strap, works, and attached tc this ring is the eccentric-rod, which is either directly con- nected to the valve-rod, or valve-stem, or else impart! motion to the valve through the agency of a rocker-arm, and in many engines a link motion is used. The center of revolution of the eccentric being several inches apart from its center of formation, will, when the sheav< revolves with the shaft, cause the eccentric to convert th< TYPES OF ENGINES CLASSIFICATION 191 rotary motion into a reciprocating motion, which through the agency of the rod is imparted to the valve or valves. Ques. 500. — What is meant by the throw of an eccentric? Ans. — The distance be- tween the center of the eccen- tric-sheave and the center of the crank-shaft. This dis- tance is also called the radius of eccentricity. Ques. 501. — What is meant by eccentric position? Ans. — The location of the highest point of the eccentric relative to the center of the crank-pin, expressed in de- grees. Ques. 502. — What is ang- ular advance? Ans. — 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. Ques. 503. — If a valve had neither lap nor lead, what Fig. 128. Fig. 128 shows an eccentric with its strap and rod. E is the sheave, the center of which is shown at D. A is the center of the shaft. The WOUld be the position of the distance A D represents the throw of the eccentric and twice that distance hicrh nninf rvf tVi£» t*rr(*n+rii* equals the travel of the end B of the fll & n P umi UI tne CCCCIUTC rod along the line A F. S is the ec- centric strap relative to the crank? 192 QUESTIONS AND ANSWERS motion, using twoth ends, the required change may be made by moving ie eccentric ahead or b*cV -in tf\e *Vaf*- 204 QUESTIONS AND ANSWERS Ques. 534. — Is the position of the eccentric on the 'ihaft necessarily fixed on all types of engines? Ans. — It is not. Many high-class stationary engines Fig. 138. Piston Valve, arc 6tted \tith isochronol or inertia governors, whi control the position of the eccentric and vary the poin t cfc I TYPES OF ENGINES CLASSIFICATION 205 of cut-off according as the load on the engine is light or heavy, thus maintaining a regular speed. Ques. 535. — What types of valves are used with isochronol governors? Ans. — Slide-valves of various patterns; 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. Ques. 536. — In all types of reciprocating engines the same factors affecting the distribution of the steam are )resent. What are they? Ans. — Outside lap, affecting admission and cut-off, md inside lap, affecting release and compression. Ques. 537. — How are these factors distributed in the our-valve type of engine? Ans. — They are distributed among the four valves, ach valve performing its own particular function in the istribution of the steam for the end of the cylinder to rhich it is attached. Ques. 538. — What advantage is there connected with etting the valves of a four-valve engine, as compared rith a single valve? Ans. — Each valve may be adjusted to a certain degree ldependently of the others, thus, for instance, the steam- alves of a Corliss engine may be adjusted to cut off the :eam at any point from the beginning up to one-half the :roke, without in the least affecting the release or com- ression, because these latter events are controlled by the thaust- valves. Ques. 539.— What is the first requisite in setting the Ives of a Corliss 206 QUESTIONS AND ANSWERS Ans. — To place the crank on the dead center. Ques. 540. — What is the next move? Ans. — To adjust the length of the hook-rod, if it is adjustable; if not, then the length of the eccentric-rod, so that the wrist-plate will vibrate equal distances each C WKtst ptafe ) ^i r -r. w Fig. 139. Wrist Plate op Corliss Engine. way from its central position, which is marked on top of the hub. Ques. 541. — How should the rocker-arm, that carries the eccentric-rod, and hook-rod be adjusted? Ans. — The length of the eccentric-rod should be such TYPES OF ENGINES CLASSIFICATION 207 that the rocker-arm will vibrate equal distances each way from a vertical position. Ques. 542. — How may the vibration of the wrist-plate and rocker-arm be tested? Ans. — By connecting the eccentric-rod and the hook- rod in their proper places, and turning the loose eccentric around on the shaft in the direction the engine is to run. Ques. 543. — Having gotten these important adjust- ments correctly made, what is the next step in setting Corliss valves? Ans. — Remove the back bonnets from the four valve Fig. 140. Steam- Vaeve of Corliss Engine. chests, and while neither the working edges of the valves nor the ports can be seen, yet certain marks will be found on the ends of the valves and corresponding marks on the faces of the chests, which serve as a guide in setting the valves. Ques. 544. — Having removed the bonnets and found the marks, what is to be done next? Ans. — Temporarily secure the wrist-plate in its central position by tightening one of the set-screws on *He eccentric. Then connect the valve-rods to the wrist- 208 ^QUESTIONS AND ANSWERS plate and to the small crank-arms attached to the ends of the valves, adjusting their lengths so that the steam- valves will have from Y\ to t 9 6 inch lap, and the exhaust valves from ^V to tV inch opening. Ques. 545. — In adjusting the steam-valves, what par* ticular detail should be carefully noted? Ans. — The direction in which the valves turn to open should be noted. In most Corliss engines the arm of the small crank to which the valve-rod is connected, extends Fig. 141. Exhaust- Vai«vE otf Coruss Engine. downwards from the valve-stem. This will cause the valve to move towards the wrist-plate in opening. Ques. 546. — After the valve-rods have been properly adjusted as to length, what is the next move? Ans. — Place the engine on the dead center — either center will do — and move the eccentric around on the shaft in the direction the engine is to run, until the eccentric is far enough ahead of the crark to allow the steam-valve for that end of the cylinder the proper amount of lead opening, which will vary according to the size of the engine. Then tighten the eccentric set screws TYPES OP ENGINES — CLASSIFICATION 209 and tr.rn the engine around to the opposite center and note whether the lead is the same on both ends. Ques. 547. — In case there is a difference in the lead for the two ends, how may it generally be equalized? Ans. — By slightly altering the length of one of the valve-rods. Ques. 548. — What is the next point to receive atten- tion, in setting Corliss valves? TABLE 8 LAP AND LEAD OF CORLISS VALVES Size of Engine. Lap of Steam Lead Opening of Lead Opening of Valve. Steam Valve. Exhaust Valve. 12 inches J inch ^s inch i % inch 14 " A " A " A " 16 " t 5 t " * A " 18 1 " 1 <« 1* ,. A " 20 " 8 a A " 22 " 24 k" A A ' a * 26 A " a : A " 28 h " A ft •; 30 •• k " A " * : 32 i " a :: i ** 34 4< h " 1 « 8 1 ** 36 ■' \ " * ' * « 38 ■• 1% " *■ A 40 A " ^ A 42 ft " 8 " A " Ans. — The adjustment of the lengths of the rods extending from the governor to the releasing mechanism^ so that the valves will cut off at equal points in the stroke. Ques. 549. — How is this adjustment accomplished? Ans. — By raising the hook-rod clear of the wrist-plate pin and with the bar provided for the purpose, move the •210 QUESTIONS AND ANSWERS wrist-plate to either one of its extreme positions, as shown by the marks on the hub, and, holding it in this position, adjust the length of the governor-rod for that 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 ?V inch 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. Ques. 550. — How may the accuracy of this adjust- ment be tested? Ans. — 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 by the trip, measure the distance upon the guide that the cross-head has traveled from the end of the stroke. Now continue to turn the engine in the same direction until the other valve is released, and measure the distance that the cross- head has traveled from the opposite end of the stroke, and if these two distances are the same, the cut-off is equalized. 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* The io*k-nuts on all rods should then be securely tightened. (4 *« M «< CHAPTER VII CONDENSERS — AIR-PUMPS — SEA- WATER Ques. 551. — What is the average composition of sea- water? Ans. — Sea-water contains about 3*2 part of its weight of solid matter, of which common salt (sodic chloride) is the principle constituent. The average composition of the solid matter in sea-water may be taken as follows: Sodic chloride, or common salt 76 per cent Magnesic chloride .10 Calcic sulphate, or gypsum 5 Magnesic sulphate 6 Carbonate of lime, and organic*matter 3 Ques. 552. — Does the common salt in sea-water cause much trouble for the marine engineer? Ans. — It does not, for the reason that it remains soluble in water at all temperatures, and there is no deposit of salt, except under extreme circumstances. Ques. 553. — What is the principal scale-forming ingredient in sea-water? Ans. — Sulphate of lime, or calcic sulphate. Deposit is also formed by sulphate of magnesia, although it is less objectionable than the lime deposit. Ques. 554. — At what temperature does the sulphate of lime become insoluble in water and form a deposit on the boiler plates? Ans. — At a temperature of 280 degrees to 295 degrees 311 212 QUESTIONS AND ANSWERS Fahrenheit, corresponding to a pressure of 35 to 45 pounds pressure of steam by the gauge. As the tem- perature of the water rises, the other sulphates become insoluble, and at 350 degrees Fahrenheit, or 120 pounds gauge-pressure, sea-water is incapable of holding any sulphates in solution. Ques. 555. — What other cause, besides a high tempera- ture, tends to precipitate these salts? Ans. — Increase of density, caused by evaporation of the water, even if the temperature remains about 212 degrees Fahrenheit. Sulphate of calcium is thus deposited at a density of sV Common salt does not crystallize out until a density of about A is reached. Ques. 556. — When was it possible to use sea-water for feeding boilers? Ans. — In the early days of marine engineering, when a low-pressure (35 to 45 pounds) was carried, and the jet condenser was used, in which the steam was exhausted into the condensing chamber, where it came into actual contact with and was condensed by a jet of cold sea- water. The feed-water for the boilers was drawn from this mixture of sea-water and condensed steam, conse- quently a large quantity of sea-water was sent into the boilers, but as the temperature was low and the density was not allowed to exceed ?*, the salts were held in solution fairly well. Ques. 557. — How was the increase of density pre- vented? Ans. — By blowing off a portion of the denser boiler- water at stated times, and making up the loss by ad- CONDENSERS — AIR-PU M PS — SEA-WATER 213 mitting a larger quantity of salt water. This was termed "brining the boiler.' ' Ques. 558. — What led to the introduction of the surface condenser? Ans. — With the advent of high pressures, it was found impossible to prevent the deposit of scale, and all of its attendant evils. It was therefore found necessary to condense the exhaust steam without bringing it into actual contact with the condensing water, hence the sur- face condenser was designed. Ques. 559. — Mention two of the principal advantages gained by the use of the surface condenser. Ans. — First, by its use fresh feed-water is obtained for the boilers; second, the condition of the condensing water is of no importance, as regards the feed-water so that, no matter whether it is salt, muddy, acid, or other- wise impure, pure water is always obtained for the boilers, provided the condenser is maintained in good condition and no leakage is allowed to occur. Ques. 560. — What is the meaning of the word vacuum? Ans. — That condition existing within a closed vessel during the absence of all pressure, including atmospheric pressure. Ques. 561. — How is a vacuum measured? Ans. — It is measured in inches of a column of mer- cury contained within a glass tube a little more than 30 inches 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 214 QUESTIONS AND ANSWERS 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 within 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 a height of 30 inches it indicates a per- fect vacuum, which means the absence of all pressure within the vessel, but this condition is never realized in practice, the nearest approach to it being about 28 inches. Ques. 562. — Is the mercurial vacuum-gauge used in every-day practice? Ans. — For purposes of convenience it is not generally used, it having been replaced by the Bourdon Spring- gauge, although the mercury-gauge is used for testing. Ques. 563. — What is the advantage, from a purely economic standpoint, in allowing the exhaust steam to pass into a condenser in which a vacuum is maintained rather than to allow it to exhaust into the open air? Ans. — In a non-condensing engine, that is, an engine in which the exhaust steam passes into the open air, the pressure of the atmosphere, amounting to 14.7 pounds per square inch at sea-level, is constantly in resistance to the motion of the piston. Therefore the exhaust or ter- minal pressure can not fall below the atmospheric pres- sure and is generally from 2 to 5 pounds above it, caused by the resistance of bends, and turns in the exhaust pipe, or other causes which tend to retard the free passage of the steam. On the other hand, if the steam were allowed to exhaust into a condenser in which a vacuum of 25 inches CONDENSERS AIR-PUMPS SEA- WATER 215 is being maintained, the terminal pressure or back pres- sure in resistance to the forward motion of the piston would be but 2.5 pounds, and if a vacuum of 28 inches existed in the condenser there would be practically no back pressure, thus making available for useful work the 14.7 pounds of steam which in the non-condensing engine was required to overcome the resistance of the atmos- pheric pressure. Ques. 564. — Is it proper, then, to consider the vacuum in a con- denser as power? Ans. — The vacuum can not be considered as power at all. It oc- cupies the anomalous position of increasing, by its presence, the ca- pacity of the engine for doing work. Ques. 565. — How is the vacuum in a condenser usually maintained? Ans. — By a pump called an air- pump, although a partial vacuum can be produced by the mere conden- sation of the exhaust 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 at a low pressure, which 3 when con- densed, occupies about 1,600 times less space than it did be- fore being condensed, hence a partial vacuum is produced. The action of the siphon injector is based upon this principle. Ques. 566. — Describe the construction and action of the siphon condenser. Fig. 142. Siphon Condenser. *16 QUESTIONS AND ANSWERS Ans. — The siphon condenser is a form of jet condenser in which no air-pump is used. In this t3 r pe of condenser the supply of condensing water is drawn from outside pressure, either from an overhead tank, or other source, iXHAUST tNter Fig. 143. Knowles Jet Condenser. 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 gradually contracts. The exhaust steam, entering at the same time, is con- CONDENSERS AIR-PUMPS SEA-WATER 21? densed 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 velocity sufficient to create a vacuum. This type of condenser can only be used where the discharge pipe has a perfectly free outlet. Ques. 567. — Describe in general terms the construc- tion and action of the jet condenser. Ans. — The jet condenser is usually a vertical, cylindri- ifi * "">" /hr&u7i£> Fig. 144. Sectionae View of a Surface Condenser and Independent Air and Circulating Pumps'. cal, cast-iron vessel, made air-tight, and which receives the exhaust steam from the low-pressure cylinder. In modern plants, condenser-shells are often made of sheet steel in cylindrical shape, reenf orced with stiffening rings. The exhaust steam enters at the top and the condensing water enters usually at the side, flowing in through the spraying nozzle, and, discharging through a large num- ber of small holes, comes in contact with the steam in the 218 QUESTIONS AND ANSWERS form of spray, thus producing a quick condensation while falling to the bottom of the condenser, to be drawn off by the air-pump. A cock or valve is fitted in the injection pipe, for the purpose of regulating the supply of cooling water. Ques. 568. — Why is an air-pump a necessary part of a ^reliable jet-condensing apparatus? Ans. — The mixture of condensing water and con- densed steam must be pumped away constantly, also the condensing water always contains a certain volume of air in solution, which may be liberated, either by boiling it or by reducing the pressure to which it is subjected. This air is liberated in the condenser, and if it is not pumped away regularly, it is liable to accumulate and spoil the vacuum. Ques. 569. — How may the dimensions of a single-act- ing air-pump for a given sized engine be determined? Ans. — In the solution of this problem, two factors must be considered: First, the total volume of the low- pressure cylinder; second, the density of the exhaust steam. The volume of the air-pump cylinder is then found by the following rule: Multiply the volume of the low-pressure cylinder in cubic feet by 3.5, and divide the product by the number of cubic feet contained in 1 pound weight of exhaust steam at the pressure at which it enters the condenser. This rule applies only to jet con- densers. Ques. 570. — Describe the construction and action of the surface condenser. tins. — The surface condenser, like the jet condenser. CONDENSERS — AIR-PUMPS — SEA- WATER 219 is an air-tight iron or steel 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 (generally about Yz inches), through which cold water is forced by a pump called a circulating Fig. 145. Side view of large cylindrical horizontal surface-condenser having two exhaust-inlets. The tubes are not shown. The steam enters at the orifices marked A, and is withdrawn, when condensed, through the orifice B by the air-pump. The circulating water enters at C, and is confined by the diaphragm D to the lower half of the tubes, and, having traversed these tubes, it returns through the upper half of the tubes, being finally discharged to the sea through the pipe E. I T. T. are the tube-plates near the ends of the condenser casing. pump. A vacuum is maintained in the body of the con- denser by the air-pump, and the steam exhausting into this vacuum is condensed by coming in contact with the cool surface of the tubes. Or, as is often the case, the exhaust steam passes through the tubes instead of around 220 QUESTIONS AND ANSWERS them, and the cooling water is forced into and through the body of the condenser, the vacuum in this case being maintained in the tubes. The tubes may be placed either vertical or horizontal. When the steam is passed through the tubes, they are generally placed vertical, while, on the Ct*cut*rm6 **r& ouutf Fig. 146. End Sectional View op Cylindrical Horizontal Surface Condenser, Showing a Portion op the Tubes. other hand, if the water circulates through them they are placed horizontal. The system of causing the water to circulate through the tubes, the steam surrounding them, is the more general. CONDENSERS AIR-PUMPS SEA- WATER 221 Ques. 571. — How are the tubes generally arranged in a surface condenser? Ans. — They are arranged in one or more systems, so that the condensing water passes through the condenser, usually twice, the coldest water entering at the bottom and coming in contact with the steam at its lowest tem- perature, and the warmest water at the top meeting the hottest steam. The exhaust steam enters at the top and after passing over the cold tubes is removed in the form of water, by the air-pump. The steam is directed in its downward course by baffle- plates, thus securing complete utilization of the cooling sur- face. A space is provided at the bottom of the condenser for the accumulation of the water of condensation below the cooling surface. The con- denser casing or shell for naval vessels is either cast in brass or else built up from com- position sheets, in order to save weight and prevent cor- rosion and galvanic action, which would be more liable to take place with an iron or steel shell. Ques. 572. — How are the tules secured in their places? Ans. — Brass or composition tube-plates are placed in the shell, near each end, sufficient space being' left between the outside cover-plates and the tube-plates iv» Fig. 147. Detail of Wick and Gland Packing for the Tubes of a Surface Condenser. 222 QUESTIONS AND ANSWERS the circulation of the cooling water. Into these plates, which are thick enough to furnish a good bearing for the tubes, the ends of the tubes are fitted and packed thor oughly tight, sometimes with a wood packing, sometimes with small screwed stuffing boxes with glands and fol« lowers, which tighten upon wick packing. The wood packing consists of a small soft wooden sleeve, which is forced into the small hole over the tube end in a dry state, and after becoming wet it swells and clamps the Fig. 148. Method op Packing Tubes of a Worthington Surface Condense*. One end of each tube is flanged and rigidly held in the tube head by means of a screw follower; the other end of the tube passes through an adjustable gland, which permits of free movement of the tube during expansion and contraction. This method of securing rigidly one end of the tube reduces the number of glands or stuffing-boxes to just one-half the number found in ordin- ary condensers. The glands can be readily removed and the packing replaced if it becomes leaky from long use. I tube, thus forming and preserving a tight joint so long as it is kept wet. Ques. 573. — Which kind of packing is the most reli- able for condenser tubes? Ans. — The gland and wick, for the reason that it always remains tight, while on the other hand the wood packing will shrink and become loose if the condenser is out of service for a time. , CONDENSERS AIR-PUMPS — SEA-WATER 223 Ques. 574. — What are the usual dimension* of the tubes of surface condensers? Ans. — They are generally about % inches in diameter, are made of brass, about ?V of an inch thick, of a com- position consisting of not less than 70 per cent of coppei and not less than 1 per cent of tin, the remainder being zinc, the small quantity of tin being added to prevent galvanic action. The tubes are pitched not less than |J Fig. 149. Worthington Surface Condenser, with Air and Circulating Pump. inches apart in order to allow sufficient material for the gland. They are zigzagged so as to occupy as small a volume as possible. Condenser tubes vary considerably in length, depending upon the size of the condenser, the usuai length in large condensers being from 8 to 10 feet,, while in some very large condensers the tubes are 14 or 15 feet in length. The tube-plates are about 1 inch thick, in order to provide sufficient depth for the gland and packing for the tubes. *£4 QUESTIONS AND ANSWERS Ques. 575. — What type of air-pump is generally used? Ans. — The vertical single-acting air-pump has been cover removed. Throuoh muft cyhncter. ptwrmmg.^wB^i^wA Fic. 150. Section cf Blake independent air-pump, fitted in many vessels, including several U. S. warships. There are two steam-cylinders and two single acting vertical air-pumps of the usual type. It works at slow speed and give* excel* tent results. ^ CONDENSERS AIR-PUMPS SEA-WATER 225 found to be the most efficient. In vertical engines the air- pump generally receives its motion from the cross- head of the engine, through the medium of a short walking-beam. There are, however, a great many engines fitted up with an independent air-pump and condenser, in which the air-pump is simply an ordinary double-acting steam-pump, having its own steam- cylinder, and may be operated independently of the engine, which is a great advantage, as there is not so much danger of the water from the condenser backing up into the cylinder in case of a sudden shut-down of the engine, which is liable to occur with a jet condenser. Ques. 576. — Describe the parts of the vertical single- acting air-pump. Ans. — It consists of the barrel, or cylinder, the suc- tion-channel way at the bottom, the cover, with delivery- channel way and the hot well, the whole being made air- tight. The moving parts are the bucket, or piston, with its valves, the foot-valves and the head-valves. Ques. 577. — Describe the arrangement of the air- pump in connection with the condenser. Ans. — The suction-channel way is in connection with the lowest part of the condenser, in order that the water can be readily and completely removed from the condenser. It usually supports the foot-valves and all joints and! |valve-seat division-plates require to be fitted air-tight, 'he barrel is generally connected to a flange or facing of ;he suction-channel way, and it is constructed of com- position or cast iron with a composition sleeve pressed in ind bored out truly cylindrical, in order to form a smooth 226 QUESTIONS AND ANSWERS and durable working-cylinder for the buckc jr piston, which is kept tight against the barrel, either by water- Fig. 151. Sectional View op Vebticai, Single Acting Air-pump. grooves, or, more commonly, by packing, consisting vine ^r more split metallic packing rings. Sometime* icJ CONDENSERS AIR-PUMPS SEA-WATER 227 fibrous soft packing, held in place and compressed by a follower ring, is used. A stuffing box is provided in the top cover, through which the piston-rod or trunk, as the case may be, has water-tight passage. Ques. 578. — What kind of valves are used in air- GUARO QOfr^Q tmjO Seating pumps r Ans. — Rubber valves, either of hard or soft rub- ber, but since the introduc- tion of mineral oil as a lubricant for the engine cyl- inders, it has been found that the ordinary rubber valves deteriorate under its influence, and metal valves are now largely coming into use, especially in the navies. They may be made of thin sheet metal, are light, and not affected by grease, if cleaned occasionally, and will last a long time. In form, air-pump valves are either single rectangular flaps that lift on one edge igainst a curved metallic guard, or else there are a number )f smaller circular valves, lifting bodily from their seats, tnd secured to the seat by a central stud, which also carries metal guard above the valve. The valve-seats are usually dependent, being constructed of composition metal, and Fig. 152. Details op Rubber Valve, Valve- seat and Guard for Air-pump. 228 QUESTIONS AND ANSWERS pressed into their places. They are divided into small spaces by gratings, so that the unsupported area of the valve may not be too large. The bucket carries the bucket-valves, which allow the air and water to pass through to the delivery side. Air-pump valves are some- times fitted with spiral springs of bronze wire on top, to secure quick closing. The flap valves are clamped to the seat, on the stationary edge, by their curved guards. Ques. 579. — How is the bucket or piston of the air- pump actuated? ") / Light Springs sometimes x^ i fitted here on bucket ANO fOOTVALVES 1*ig. 153. Section of Metal Valve, Valve-seat and Guard for Air-pump. Ans. — Either by a solid piston-rod, or by a hollow trunk, made entirely of composition, or covered by a composition sleeve. With the piston-rod type it is neces- sary to have a connecting rod and guides above the top cover of the air-pump, while the trunk type contains the connecting rod bearing in the trunk, near the bucket, and requires no extra guides. Ques. 580. — What is the function of the hot well? Ans. — It acts as a small reservoir, for the accumula- tion of the discharge- water from which the feed-pumps CONDENSERS AIR-PUMPS SEA- WATER 229 draw their supply. The later vessels in the English navy are fitted with "feed-tanks" in which the discharge from the air-pumps is allowed to accumulate, and from which the feed-pumps draw their supply of water for feeding the boilers. There is a feed-tank for each engine-room, AttCMic* f | C«hau»t raon KXvWeJI T^y j\ i — f lG. 154. WORTHINGTON CENTRAL CONDENSER 1*OR A I*ARGE SVA*IOWARY PLANl % Showing Pumps j»nd Piping. md they are connected by a pipe running between the two, :ngine-rooms, fitted with a shut-off \alve worked fron? ither engine-room. These feed-tanks, are fitted with [lass water-gauges and zinc slabs. 230 QUESTIONS AND ANSWERS Ques. 581.— What is the function of the circulating puitfp In connection with the surface condenser? F* 155. Transverse Section op a Centrifugal Pump. B, Casing, D E. Curved Vanes. Ans. — It either forces or draws the cooling watei through the tubes or the body of the condenser. ^ CONDENSERS AIR-PUMPS SEA-WATER £31 Oues. 582. — What type of pump has beei, xcund to be best adapted to this work? Ans. — The centrifugal pump worked by an indepen- dent auxiliary engine, for the reason that the pump works smoothly, there are no valves, and having a separate engine, it can be kept working and the condensers kept cool when the main engines are stopped, which is not the case with a pump that receives its motion from the main engines. Another great advantage possessed by the independent system is, that the speed may be regulated so as to supply the required quantity of water. Ques. 583. — Describe the construction and action of the centrifugal circulating pump. Ans. — The pump consists of an impeller wheel or fan evolving inside a casing. The impeller and casing are made of gun metal, and the spindle or shaft carrying the mpeller is either cast of gun metal in one piece with the mpeller, or formed separately of forged bronze and keyed to it. This spindle runs in lignum-vitae bearings and is ubricated with water. The impeller generally consists }f a central web guiding the incoming water, with two side-plates that gradually approach each other as they lear the circumference and between which runs a series )f curved vanes. These vanes are curved away from the iirection of rotation as they proceed from the boss to the :ircumference. The water enters the central part of the mpeller through the inlet pipe and is thrown by the apidly revolving vanes outwards and around into the :asing which surrounds the circumference of the wheel, *he casing is of gradually increasing area and leads to 232 QUESTIONS AND ANSWERS the delivery pipe, through which it is forced by the cen- trifugal action to the condenser, where, after traversing the tubes, it is discharged overboard. The casing is tMf Fig. 156. Longitudinal Section op a Centrifugal Pump. A, Central W*b C C, Side Plates. E, Inlet. F, Discharge. formed in two parts to enable the impeller to be inserted and also to facilitate insoection. CONDENSERS — AIR-PUMPS SEA-WATER 233 Ques. 584. — How is the quantity of water required to condense the exhaust steam of an engine determined? Ans. — The quantity of cooling water required for a condensing system depends primarily upon the system, whether it is surface condensing or whether the condenser is a jet condenser The surface condenser needs a greater quantity of water than does the jet condenser. This is due to the fact that in the surface condenser the water, not being mixed with the steam, can not absorb the heat so rapidly. Ques. 585. — About how much more water does a sur- face condenser require than is needed by a jet condenser? Ans. — About 15 per cent more. Ques. 586. — What three factors determine the quantity of cooling water required? Ans. — First, the density, temperature, and volume of the steam to be condensed in a given time; second, the temperature of the overflow and third, the temperature of the injection water. For instance, it may be desired to keep the overflow at as high a temperature as possible, for the purpose of feeding the boilers, or the temperature of the injection or cooling water varies greatly. It may be 35 degrees in the winter and 70 degrees in the summer. In the marine service the temperature of sea-water varies considerably, depending upon the locality, in the tropics the temperature of the sea-water in the summer being often as high as 85 degrees Fahrenheit. Ques. 587. — What quantity of condensing water would be required in a jet condenser into which the exhaust steam under an absolute pressure of 7 pounds is passing. 234 QUESTIONS AND ANSWERS assuming the temperature of the cooling water to hi 55 degrees and the temperature of the overflow to b< 110 degrees? Ans. — In these calculations the total heat in the stearr must be considered. This means not only the sensible heat, but the latent heat also. Now in 1 pound weight oi steam at 7 pounds absolute pressure the total heat h 1,135.9 heat units. The temperature of the overflow being 110 degrees, the total heat to be absorbed from each poun< weight of steam in this case would be 1,135.9 — 110 = 1025.9 thermal units. The temperature of th< condensing water being 55 degrees and the temperature of the overflow being 110 degrees, there will be 110 degrees — 55 degrees = 55 degrees of heat absorbed b)> each pound of cooling water passing into and through th< condenser, and the number of pounds of water requirec to condense each pound weight of steam under thes< conditions will equal the number of times 55 is con- tained in 1,025.9, thus, 1 jV =z 18.65 pounds. Assuminj the steam consumption of the engine to be 17 pounds pel indicated horse-power per hour, then 17 X 18.65 = 317.0i pounds of water is required per horse-power per hour foi condensing purposes. Ques. 588. — How is the weight of cooling watei required per hour determined, when the steam consumptior per indicated horse-power per hour is not known? Ans. — In this case the volume of steam exhausted pel hour must be considered. Thus, assume the cylinder f rorr which the steam is exhausted to be 24 X 48 inches anc the revolutions per minute to be 80. The piston dis« CONDENSERS AIR-PUMPS SEA-WATER 235 placement will equal area of piston less one-half area of rod, multiplied by length of stroke. The area of a circle 24 inches in diameter = 452.39 square inches. Suppose the piston-rod to be 4.5 inches in diameter, its area is 15.904 square inches, one-half of which = 7.952 square Table No. 9 Jet Condensing Quantity of Injection Water per Revolution of Engine, injection water 50° overflow 110° Low-pressure Cylinder. Single-cylin- der, Water per Rev. Two-cylinder. Water pei Rev. Three-cylif> der, Water per Rev. Lbs. Galls. Lbs. Galls. Lbs. Galls. 20x36 ii 22x36 24x42 26x42 28x48 30x48 32x54 34x54 36x60 38x60 40x66 44x66 48x72 52x72 56x72 60x72 64x72 iches 4.2 5.1 7. 8.3 11. 12.6 16.2 18.3 22.8 25.5 31. 37.5 48.5 57. 66. 75.6 85. .5 .61 .84 1. 1.45 1.52 1.95 2.2 2.75 3.07 3 73 4.51 5.84 6.89 7,9 9. 10. 3.9 4.8 6.6 7.8 10.4 11.7 15. 17.0 21.2 23.7 28.8 34.8 45. 53.1 61.5 70.5 80. .47 .57 .79 .93 L24 1.41 1.81 2.05 2.55 2.85 3.45 4.2 5.42 6.4 7.41 8.5 9.6 3.6 4.4 6. 7.2 9.5 10.8 13.9 15.8 19,6 21.9 26.7 32.2 41.7 49.2 57. 65.3 74. .43 u .53 a .72 a .87 tt 1.14 u 1.3 tt 1.68 tt tt 236 t« 2J4 a 3,2 a as tt 6. tt 5.9 u 6.8 tt 7,8 tt as (Table No. 9. troit, Mich. ) -From Book on Compound Engines. By James Tribe, Dd- inches. The effective area of the piston is therefore 452.39 — 7.952 = 444.4 square inches and the piston displacement equals 444.4 X 48 = 21,332.64 cubic inchfc*. It is necessary in this calculation to express the total volume of steam exhausted per minute in cubic feet, therefore 21,332.64 ■*• 1.728 (number of cubic inches in a 236 QUESTIONS AND ANSWERS cubic foot) gives 12.34 cubic feet of piston displacement, and the engine running at a speed of 80 revolutions per minute will send into the condenser a volume of steam equal to twice the piston displacement multiplied by the number of revolutions per minute, expressed thus: 12.34 X 2 X 80 = 1,974.4 cubic feet per minute. Assuming the absolute pressure of the exhaust to be 7 pounds per square inch, the weight of 1 cubic foot of steam at 7 pounds absolute is .0189 pounds and the total weight of steam exhausted per minute would be 1,974.4 X .0189 = 37.3 pounds, and if 18.65 pounds of water is required to condense 1 pound weight of steam at 7 pounds absolute, the total weight of water required per mirute in this case would be expressed as follows: 37.3 Y 18.65 = 695.8 pounds, or per hour 695.8 X 60 = 41,74$ pounds, equal to 5,029 gallons. Ques. 589. — What quantity of condensing water would be required in a surface condenser, assuming the condi- tions to be the same as described in the answer to question 587? Ans. — A surface condenser requires about 15 to 20 per cent more condensing water \han a jet condenser does. It was seen in the answer referred to that 18.65 pounds of water were required to condense 1 pound weight of steam, therefore the quantity of water requirec by the surface condenser woul'i 'be about 22 or 23 pounds for each pound of steam. Ques. 590. — What provision is made on board oi vessels for obtaining a snp^V of water for the condenseri and for other p'rpoaei? CONDENSERS — AIR-PUMPS — SEA- WATER 237 Table io Areas and Circumferences of Circles. Diam. •25 • 5 I.O 1.25 1-5 2 2.25 2.5 3 3.25 3-5 4 425 4.5 5 5.25 5.5 6 6.25 6.5 7 7.25 7-5 8 8.25 8.5 9 9-25 9-5 10 10.25 10.5 11 11.25 11- 5 2 12.25 a-5 3 325 3-5 4 4.25 4.5 5 5 25 Area. .049 .1963 .7854 1. 2271 I.7671 3.I4I6 3.9760 4.9087 7.0686 8.2957 9.6211 12.566 14.186 15.904 I9-635 21.647 23.758 28.274 30.679 33.183 38.484 41.282 44.178 50.265 53.456 56.745 63.617 67.200 70.882 78.540 82.516 86.590 95.033 99.402 IO3.869 II3.O97 117.859 122.718 132.732 137.886 143.130 153.938 I59-485 165.130 176.715 182.654 Circum. Diam. Area .7S54 I.5708 3.I4I6 3.9270 4.7124 6.2832 7.0686 7.8540 9.4248 IO.210 IO-995 12.566 13.351 14.137 I5.708 16.493 17.278 18.849 I9-635 20.420 21.991 22.776 23.562 25.132 25.918 26.703 28.274 29.059 29.845 3I.4I6 32.201 32.986 34.557 35-343 36.128 37.699 38.484 39- 270 40. 840 41.626 42.411 43.982 44» 767 45.553 47.124 47-909 15.5 16 16.25 16.5 17 17.25 17.5 18 18.25 18.5 19 19.25 19-5 20 20.25 20.5 21 21.25 21.5 22 22.25 22.5 23 23.25 23.5 24 24.25 24.5 25 25.25 25.5 26 26.25 26.5 27 27.25 27.5 28 28.25 28.5 29 29.25 29.5 30 30.25 30.5 i.692 201.062 207.394 213.825 226.980 233.705 240.520 254-469 261.587 268.803 283.529 291.039 298.648 314.160 322.063 330.064 346.361 354.657 363.051 380.133 388.822 397.6o8 415.476 424.557 433.731 452.390 461.864 471.436 490.875 500.741 510.706 530.930 541.189 55L547 572.556 83.208 593.958 615.753 626,798 637.941 660.521 671.958 683.494 706.860 718.690 730.618 Circum. Diam 48.694 50.265 5L05I 51.836 53.407 54.192 54.978 56.548 57.334 58.II9 59.690 60.475 61.261 62.832 63.617 64.402 65.973 66.759 67.544 69.115 69.900 70.686 72.256 73.042 73.827 75.398 76.183 76.969 78.540 79.325 80.110 81.681 82.467 83.252 84.823 8 5. 60S 86.394 87.964 88.750 89.535 91.106 91.891 92.677 94.248 95.033 95.8i8 31 31.25 31.5 32 32.25 •33 33.25 33-5 34 34.25 34-5 35 35.25 35.5 36 36.25 36.5 37 37.25 37.5 38 38.25 38.5 39 39-25 39-5 40 40.25 40.5 4i 41.25 41.5 42 42.25 42.5 43 43-25 43.5 44 44.25 44.5 45 45.25 45-5 46 46.25 Area. Circum, 754.769 766.992 799.313 804.249 816.86 855.30 868.30 881.41 907.92 921.32 934.82 962.II 975.90 989.80 1017.8 1032.06 1046.35 1075.21 1089. 79 1104.46 1134.11 1149.08 1164.15 1 [94.59 1209.95 1225.42 1256.64 1272.39 1288.25 1320.25 1336.40 1352.65 1385.44 1401.98 1418.62 1452.20 1469.13 1486.17 1520.53 1537.86 1555.28 1590.43 1608.15 1625.97 1661.90 1680.01 97.389 98.175 98.968 100. 53 101.31 103.67 104.45 105.24 106.81 107.60 108.38 106.95 110.74 in. 52 113.09 113.88 114.66 116.23 1 17.01 117.81 119.38 0.16 120.95 122.52 123.30 124.00. 125.66 126.44 127.23 128.80 129.59 130.37 131.94 132.73 133.51 135.08 135.87 136.65 138.23 1 39- 01 139.80 141.37 142.15 142.94 144.51 145.29 838 QUESTIONS AND ANSWERS Table lO—Coramued. Diam. Area. Circum. Diam. Area. Circum. Diam. Area. Circum.. 46.5 l6g8.23 146.08 62.25 3043.47 195.56 7S 4773.37 245.04 47 1734.94 147.65 62.5 3067. 96 196.35 7S.25 4809,05 245.83 47.25 i753-*5 148.44 63 3117.25 197.92 73. 5 4S39.83 246.61 47.5 1772.05 149.22 63.25 3142.04 198.71 79 4901. 6S 248.19 4 3 1809.56 150.79 63.5 3166.92 I99.50 79^3 4932.75 24S.97 48.25 1828.46 I5L58 64 3216.99 20I.06 79.5 4963.92 249.76 48. 5 1847.45 152.36 64.25 3242.17 201.85 80 5026.56 25L33 49 1885.74 153-93 6+5 3267.46 202. 63 80.5 5089. 5S 252.90 49.25 1905.03 154.72 65 3318.31 204.20 81 5i53.oo 25447 49-5 1924.42 I55.50 65.25 3343.83 204.99 81.5 5216.S2 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 82.5 5345-62 259.18 5o.5 2002.96 153.65 66.25 3447.16 20S.13 83 5410.62 260. 75 51 2042.82 160.22 66.5 3473.23 208.91 83.5 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 357S.47 212.06 85 5674.51 267.04 52.25 2144.19 164.14 63 3631.68 213.63 85.5 5741-47 268.60 52.5 2164.75 164.19 6S.25 3658.44 214.41 86 5808.81 270.17 53 2206.18 166.50 68.5 36S5.29 215.20 86.5 5376.55 27L75 53.25 2227.05 167.29 69 3739.28 216.77 87 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 3793.67 218.34 88 6082.13 276.46 54.25 2311.48 170.43 7o 3S48.46 219.91 8S.5 6151.44 278.03 54-5 2332.83 171. 21 70.25 3875.99 220.70 89 6221.15 279.60 55 2375.83 172.73 7o.5 3903.63 221.48 89.5 6291.25 281.17 55.25 2397.48 173.57 7i 3959.20 223.05 90 6371.64 2S2.74 55-5 2419.22 174.35 71.25 39S7-I3 223.84 90.5 6432.62 284.31 56 2463.01 175.92 71.5 4015.16 224.62 9i 6503.89 2S5.88 56.25 2485.05 176.71 72 4071.51 226.19 91.5 6573.56 287.46 56.5 2507.19 177.5 72.25 4099.83 226. 9S 92 6647.62 289.03 57 2551.76 I79.07 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 ISO.64 73.25 4214. 11 230.12 93.5 6866.16 293.74 58 2642. oS I82.2I 73.5 4242.92 230.91 94 6939.79 295.31 58.25 2664.91 I82.99 74 4300.85 232.48 94-5 7013.81 296.88 58.5 2687.83 183.73 74-26 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 IS6.I4 75 4417.87 235.62 96 7238.25 301.59 59-5 2780.51 186.92 75.25 4447.37 236.40 96.5 7313.80 303.16 60 2S27.44 183.49 75.5 4476.97 237.19 97 7389.81 304.73 60,25 2851.05 189.28 76 4536.37 238.76 97-5 7466.22 306.30 60.5 2874.76 I9O.06 176.25 4566.36 239-55 98 7542.89 307.88 61 2922.47 I9I.64 76.5 4596.35 240.33 98.5 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 1242.69 99.5 7775.63 312.58 62 3019.07 194.78 77-5 4717.30 243.47 100 7854.00 314.16 CONDENSERS AIR-PUMPS SEA-WATER 239 Ans. — All holes in the hull of a ship below the water- line for the supply or discharge of condensing wa- ter, or for any other purpose, are fitted with valves having long spindles which are brought inside the vessel through stuff- ing boxes, in order that the valves may be worked from inboard. The cir- culating pumps take their suction from a large screw-down inlet valve on the bottom of the ship, while the dis- charge is through simi- lar valves on the ship's side. Ques. 591.— What type of valve is largely used for this purpose? Ans. — The Kingston sea-valve. Strainers are placed over all inlets, to prevent the entrance of weeds and other impuri- tieSc Fig. 157. Sea-valve. A CHAPTER VIII AUXILIARY MACHINERY AND FITTINGS Oues. 592. — Besides the air and circulating purnps, what other pumps are required in well-equipped steam plants, or aboard steam-ships? Ans. — Boiler feed-pumps, fire service, pumps for hydraulic elevators, and other service requiring water- pressure, and in addition, on ship-board, pumps are required for emptying the bilges and tanks and for supply- ing water for washing the decks, evaporator service and for sanitary purposes. Ques. 593. — Is there a special pump provided for each sei vice? Ans. — Not in all cases, but one pump may be con- nected in such a manner as will permit of its being used alternately for several different purposes. However, a special pump is, or at least should always be provided for teeding the boilers. Also a special bilge-pump is usually supplied, for the reason that it handles very dirty water, that should not be passed through any other pipe system. In small vessels one pump (the donkey) usually serves for nearly all purposes, including auxiliary boiler-feed, and on Western river steamers an independent pump (the doctor) having a steam-cylinder and walking-beam, drives a system of pumps for feed, fire and bilge-pumping service. 240 AUXILIARY MACHINERY AND FITTINGS 241 Ques. 594. — What special features should appertain to the boiler feed-pump? Ans. — It should be simple, durable, of great strength and ample capacity to insure regular and reliable service under the most severe conditions. It is always best to have the main and auxiliary feed-pumps duplicates of each other if possible, for the reason that in cases of emergency the different parts are interchangeable. In the marine service the main feed-pump draws its supply of water from the hot well, feed-heater or the feed-tank, as the case may be. The auxiliary or du- plicate feed-pump may be arranged so as to draw from either of these sources,, and also from the sea, thus making provision for emergency. Ques. 595. — W here should the feed-pumps be located? Ans. — As near to the boiler-room as possible, in order that the engineer in charge of the boilers may have fult control of the feed-water supply. On board of vessels, when the feed-pump is worked from the main engine, the auxiliary, or injector is usually placed in the stoke-holcL Ques. 596.— What type of boiler feed-pump has FlG. 158. The Worthington Boiler- feed Pump, Admiralty Pattern. For 250 Pounds Pressure. 242 QUESTIONS AND ANSWERS been found to be the most reliable for all kinds of service? Ans. — The double acting steam-pump, working inde- pendently of all other machinery. The horizontal variety is principally used for land service, while on board steam vessels the vertical type is preferred, for the reason that it occupies less floor space. In both the horizontal and vertical types, the water valve-chambers have removable covers, allowing a ready access to the valves and valve- seats. The steam-valves of these pumps are actuated in various ways. In the duplex variety, which consists of two pumps combined into one, the steam-valve of one side is moved from the piston-rod of the other, and vice versa, while with a pnmp having but a single steam-cylin- der, the steam-valve is worked by a tappet action from w>»t»»/M»rrr7K rao ountr STCAkt QUVLtT Fig. 161. Kirkaldy's Feed-heater. • the passage leading to the suction chamber, so that a small quantity of water is always escaping from the water- cylinder, which causes the pump to keep slowly in motion, even when the feed-valves on the boilers are closed. Ques. 599. — Are feed-water heaters much in use in the marine service? Ans. — They are largely used in the mercantile service, and results justify their adoption. Ques. 600. — Describe the construction and operation of Kirkaldy's feed-heater. AUXILIARY MACHINERY AND FITTINGS 247 Ans. — It is constructed along lines similiar to a sur- face condenser, having tubes rolled into tube-plates in the ordinary manner, the whole surrounded by an outside shell, leaving spaces at each end between the tube-plates and end-covers. The feed-water does not mix with the heating steam, but is drawn through the tubes, on thej mm mm* Fig. 162. Weir's Feed-heater and Regulator. outside of which is the steam, which is usually the exhaust from various auxiliary engines, or it may be drawn from the boilers. By-pass valves are fitted, so that when necessary the feed-water can be passed direct, without passing through the heater. 248 QUESTIONS AND ANSWERS Ques. 601. — Describe the construction and operation of Weir's feed-heater and regulator. Ans. — It takes steam from the final receiver of the engine after it has done most of its work. The steam enters the heating chamber through a circular perforated ring and there mixes with the cold feed-water, which is admitted through the spring-loaded valve on the cover. Fig. 163, The Harris Grease Filter. The heated water falls to the bottom of the heater s from whence it is removed by the feed-pump. A galvanized iron float is fitted to the bottom of the heater, which communicates by means of levers with the steam-valve leading to the feed-pump, thus keeping the water-level constant in the heater and preventing the pumps from drawing air. AUXILIARY MACHINERY AND FITTINGS 249 Ques. 602. — What provision is made on board steam- vessels for the prevention of oil or grease passing into the boilers along with the feed-water? Ans. — Numerous types of grease-filters are in use- In the Harris grease-filter the feed-water is caused to pass- through a series of gratings, on each of which is fitted one or two sheets of filtering material, consisting of toweling or flannel, supported by wire gauze. When the- cloths become dirty they are cleaned by a steam jet, and washed off by a reverse current of water. Ques. 603. — What is the object of placing a governor on an engine? Ans. — To maintain regularity of speed of the engine when the load is varied from any cause. Ques. 604. — Upon what principle do the most of the jovernors for land engines operate? Ans. — Upon the principle of centrifugal force causing wo balls or weights, each suspended or attached to a lever iwinging on a fulcrum, fixed near the top of a vertical 5 evolving spindle, to fly outward as the speed increases; ,nd the force of gravitation which acts in the opposite lirection as the speed decreases. The outward movement f the balls or weights is utilized to either close the throt- le or shorten the point of cut-off, while the inward move- nent has the opposite effect. Ques. 605. — Are governors required on marine en- p ines? Ans. — They ere, for the reason that in a marine engine onsiderable diminution in resistance may ensue in rough r stormy weather, from the pitching motion of the vessel* 250 QUESTION^ AND ANSWERS which causes the propellers to rise partly out of the water, thus causing what is technically known as "racing of the engines." Ques. 606. — Is the centrifugal type of governor suit- able for marine service? Ans. — It is not, for the reason that the forces acting upon the balls or weights would be affected by the motion of the ship and the action would be irregular. Other forms of governors for marine engines are in use with various degrees of success, but all, or nearly all of them, possess the one defect of requiring an increased speed of the engine to cause them to act, and even then their action is sluggish, the throttle-valve being generally closed after the racing is over. Ques. 607. — What type of marine governor is likely to prove the most successful in marine service for the prevention of "racing?" Ans. — A governor that acts by variations of pressure at the stern of the vessel near the propeller, and not from engine-speed variations. Racing being caused by diminished immersion of the propeller, it is accompanied by a diminution of pressure of water at that part, which can be utilized to actuate the throttle-valve. Such gov- ernors may therefore anticipate and prevent any increase of speed due to the above cause, although they would have no effect in case of a serious increase of speed, due to such an accident as a broken shaft or propeller. Ques. 608. — Describe Dunlop's governor, which is of the latter type. Ans.-— It consists of a sea-cock at the stern of the AUXILIARY MACHINERY AND FITTINGS £51 ship, opening into an air-vessel or air-chamber, so con- structed that, by opening the sea-cock, water flows into the air-vessel and compresses the air contained therein to a pressure equivalent to the head of water outside the ship. From the top of the air-chamber a pipe is led to the under side of an air-tight elastic diaphragm, forming Dart of an apparatus in the engine-room. On the upper side of the diaphragm is a spiral spring, with means of adjusting its compression to balance the air pressure )elow the diaphragm. From the center of the diaphragm i connection is made to the slide-valve of a small steam- :ylinder so constructed that its piston moves in exact iccordance with the movements of the diaphragm. This >team-piston is connected by suitable gear to the throttle- valve of the engine whose speed is to be controlled. The iction is as follows: The sea-cock being open, any varia- ;ion of head of water outside the ship is accompanied by in inflow or outflow of water through it and consequently i variation in the pressure of the air contained in the air- camber, and also under the diaphragm of the engine-room ipparatus, causing the diaphragm to move through such >art of its travel as is requisite to enable the compression )f spring and the air-pressure to balance each other again, ivery movement of the diaphragm is followed by a torresponding movement of the governor steam-piston, ind consequently of the throttle-valve of the engines inder control, the time taken between the variation in he head of water at the stern of the ship and the moving >f the throttle-valve being practically nothing. The :overnor therefore anticipates any increase in the speed 252 QUESTIONS AND ANSWERS of the engines due to the propeller rising out of the wate and does not depend upon a variation in speed of th< engines to be controlled, before it acts. By adjusting th balance between the spring and the air-pressure under th diaphragm the diaphragm begins to fall and the throttle valve to close, when the tips of the propeller-blades ris ^ B P/PELEO TO C THE BOTTOk OF A/R-TlGHr Diaphragm A A/r Vessel AT Stern of Sn/p Engine Room Apparatus Sea Cock fir teo here Fig. 164. Dunlop's Governor. to any desired distance above the surface of the water The air-vessel should be fitted as far aft in the screw-tun« nel as possible, the hole through the side of the vesse being placed about one-fourth the diameter of th* propeller below the level of the center of the shaft. Th< reports of the action of this governor in the mercantile AUXILIARY MACHINERY AND FITTINGS 253 narine are very satisfactory. It is fitted in the "Cam- >ania," "Paris," and many other vessels. Ques. 609. — How is the fresh water needed on board hip for drinking, washing, culinary purposes, and for naking up for the waste of feed-water for the boilers and or various other purposes, obtained? Hr*r?*Mit ftta Normandy's Evaporator. Ans. — By means of evaporators and distillers. The vaporators are really small boilers, with heat obtained rom steam passing through tubes, while the water to be vaporated surrounds the tubes. There is no coal used i these boilers, the steam being obtained from the main 254 QUESTIONS AND ANSWERS boilers. The vapor produced is conducted to the distillii apparatus, where it is condensed into fresh drinkin water, and a portion of it goes to the condensers for tl purpose of making up the deficiency of boiler feed-watei The condensed primary steam is returned to the boilers. Ques. 610. — Describe Normandy's evaporator. Aps. — In this type of evaporator the tubes are a straight and rolled into tube-plates at their ends. Th steam from the main boilers enters these tubes through pipe at the top and evaporates the surrounding sea-wat< contained in the shell, and is itself condensed and pass< out through the bottom, returning to the boilers. Th vapor generated outside the tubes is conveyed by a vah and pipe, either to the auxiliary condenser for feed-wat( make-up, or else to the distilling condensers for th production of drinking water. The resulting scale deposited in the evaporator, from whence it is cleaned intervals. The sea-water for the evaporator is supplie by a pump. It takes its supply from a feed-box contain ing a float which maintains a constant level in the feed box. Ques. 611. — Describe Normandy's condenser. Ans. — The steam from the evaporator enters the con denser through a pipe at the top and passes downward through two series of tubes, the upper set being th condensing and the lower the cooling tubes. These tube are surrounded by a casing, which is kept filled with col( lea-water that enters at the bottom and flows out at th top through an overflow pipe that is connected to tto casing at a point a short distance below the top and AUXILIARY MACHINERY AND FITTINGS 255 then carried to some distance above the top of the cham- ber before discharging overboard. By means of this arrangement the hottest sea-water is not discharged over- board, but instead may be used in the evaporator, in connection with the condenser, and thus promote economy of evaporation. An air-pipe is fitted to allow the air evolved from the condensing water in the casing by heat to pass into the overflow pipe leading to the sea. The condensed water rises from the lower chamber through a stand-pipe connected at the bottom and overflows from this pipe into and down another pipe leading to the suction of a small steam donkey pump, which pumps it into test- tanks, from whence it flows by gravity to the water-tanks in the hold of the vessel. By this arrangement the cool- ing tubes of the condenser are always kept full of water and the fresh water is drawn off cold. Ques. 612. — On vessels carrying cargoes of fresh meat and other perishable articles that are affected by the heat, what provision is made for their preservation? Ans. — Various types of refrigerating machinery are in use, some using the cold-air system, others the carbonic- acid system, and a few of the smaller ships are fitted with machines for making ice only. Ques. 613. — Describe the cold-air system. Ans. — The machine consists of a tandem compound engine having piston slide-valves both on the same valve- rod and worked by a single eccentric. This engine supplies the motive power of the apparatus. Two air- ylinders, one called the compressing cylinder and the other one the expanding cylinder, are placed side by side and in 256 QUESTIONS AND ANSWERS line with the low-pressure cylinder of the engine. These air-cylinders are double acting, the pistons receiving their motion from the crank-shaft driven by the engine. The action of the device is simple and is as follows: The revolving shaft, through the medium of connecting rods and guides, moves the pistons up and down. Air is drawn into the compressing cylinder through inlet-valves from the surrounding atmosphere or from the cold room. It is compressed on the return stroke of the piston and passes into the cooling chamber, which is constructed similar to a surface condenser, having a pump to circu late the cooling sea-water through it. The work done thus far appears as heat in the air and this heated air, passing through the tubes of the air-cooler, is cooled by the cir- culating water and is then led to the valve-chamber of the expanding cylinder. The valve arrangement of this cylinder consists of a slide-valve and an expansion valve working on the back of the slide-valve. This arrange- ment supplies a means of sharply cutting off the inlet of air when it enters the expanding cylinder. The compress- ing cylinder is provided with a water-jacket through which the circulating pump delivers the cooling water op its way from the air-cooler to the sea. The slide-valve* are so arranged in the expanding cylinder that when the proper quantity of air is admitted the supply is cut off and during the remainder of the stroke the air expands and therefore does work on the piston and heat is expended in the process in exactly the converse manner to the generation of heat in the compressing cylinder, As, however, the air has been deprived of its surolus beat AUXILIARY MACHINERY AND FITTINGS 251 CM} ,_, (M) „ — n — n CONOEHSER Pic 165. Cold -£ir System oe Refrigeration. 258 QUESTIONS AND ANSWERS in the cooling chamber, the heat equivalent of the work it does in the expanding cylinder is absorbed from itself and the result is a considerable lowering of its temperature. This cold air is then exhausted through the orifice of the slide-valve in the usual manner, and conducted first to the Brine to col 4 chamber. Fig. 166. Carbonic-Acid System of Refrigeration. 3 'snow-box" a small accessible chamber in which the snow formed from the moisture is deposited, and from thence to the cold chamber, in which the supply of meat or provi- sions is kept and where it displaces air of a higher tem- perature. The refrigerating chamber is insulated by lagging its bulkheads, ceiling, and floor with silicate cottuk AUXILIARY MACHINERY AND FITTINGS 259 or other non-conductor, a teak lining being fitted o\ cr this to form the inside surface. Ques. 614. — Describe the carbonic-acid system. Ans. — A very successful and efficient device is the carbonic-anhydride system of Messrs. J. & E. Hall, in which carbonic anhydride is passed round continually in the circuit. The apparatus consists of three parts: a compressor, a condenser, and an evaporator. The com- pressor draws in heated and expanded gas from the evaporator and compresses it. The compressed gas then passes to a condenser, consisting of coils in which the warm compressed gas is cooled and liquefied by reduction of temperature caused by the action of the cooling sea- water. From the condenser the cool liquid carbonic anhydride is conveyed into the evaporator consisting of coils, where it vaporizes and expands, absorbing heat in the process and cooling the surrounding brine, which is in contact with the coils. This cold brine is circulated by a small pump to the refrigerating chamber, where it is conducted through a long series of rows of cooling pipes, termed "grids/ y which are placed at the roof of the chamber. The cold-brine "grids" in this position set up a circulation of air, the cold air descending and being replaced by air not so cold, which is cooled in its turn. Any moisture in the air is condensed on the "grids" and appears as frost on the pipes. The theory of the action of this system is as follows : Under atmospheric pressure the liquid C0 2 would evaporate at a temperature of 120 degrees Fahrenheit below zero, but its temperature of evaporation rises with the pressure, in a similar manner as 260 QUESTIONS AND ANSWERS water. At a pressure of 500 pounds per square inch it boils at a temperature of 30 degrees Fahrenheit so that cold water may be used to supply the heat for boiling it. The pressure in the evaporator is therefore regulated to the required temperature of the cooling water, so that a considerable pressure is necessary in the evaporator. The compressor draws the gas from the evaporator and com- presses it to the liquefying pressure, the heat due to the compression being absorbed by the cooling water in the condenser coils and the gas in these coils becomes liquid before its exit. The liquid is then boiled in the evapora- tor coils, cooling the surrounding brine by the heat absorbed during evaporation. The compressor gland is made tight by cupped leathers with glycerine forced between them at a higher pressure than that in the com- pressor, so that no escape of gas can take place. The carbonic anhydride is supplied in steel cylinders to replenish the supply. Ques. 615. — What types of dynamos are used on board ships for generating electric current for internal illumi- nation and for working search-lights and motors? Ans. — They are usually of the two-pole type, direct driven and carried on an extension of the engine-bed. They have drum armatures and the field-magnets are compound wound, to give a constant pressure of 80 or 100 volts for any current from zero to the maximum, while the speed is maintained constant. The usual speed is 320 revolutions per minute. The machines are con- nected to a switchboard located in a central position, from which the current is distributed to the various circuits for AUXILIARY MACHINERY AND FITTINGS 261 lighting, motors, etc. This board is so arranged that a circuit can be quickly changed from one machine to another, but no circuit can receive current from two 262 QUESTIONS AND ANSWERS machines at the same time. The most recently fitted dynamos for the marine service are of the iron-clad type, the field coils and the armature being almost entirely surrounded by iron, to reduce to a minimum the leak- age of magnetic lines of force which may affect com- passes or chronometers in the neighborhood. Ques. 616. — How are these dynamos usually driven? Ans. — By vertical two-cylinder engines, generally compounded, although in some ships, where the steam- pressure is low, the engines are simple. All parts are carefully balanced and a heavy fly-wheel is fitted on the engine-shaft, at the dynamo end, which conduces to steady running. The speed is regulated by an isochronal governor fitted on the shaft. Ques. 617. — Describe the construction of the arma- ture. Ans. — The armature-core is built up of thin disks of soft iron slipped over metal sleeves, which are keyed on the shaft. The disks are insulated from each other by thin sheets of asbestos paper, to prevent loss of energy and heating due to eddy currents, and are kept in place by clamping-plates and end-nuts. The conductors on the armature, which carry the current, are made up of copper wires, twisted together, and pressed to a rectangular section. They are insulated by a covering of varnished tape. Usually two lengths of bars are used. They are placed around the periphery of the armature, longitudi- nally, long and short bars alternating, their ends overhang- ing the core. All the ends at one end of the armature project the jame distance. Projections are fitted into the AUXILIARY MACHINERY AND FITTINGS 263 core at intervals, which drive the conductor-bars. These projections are insulated by mica slips. The bars are kept in place by bands of steel or bronze binding wire, tightly wound on and soldered. Mica strips are placed under the bands to prevent injury to the insulation of the bars. Each bar is connected at each end by bent copper strips to another bar almost diametrically opposite to it, so that the whole of the bars and end-connections form one closed circuit. The projecting end of each long bar is also connected to the nearest commutator segment, the number of segments being equal to the number of long Fig. 168. Armature bars. Two or more pairs of brushes bear on the commu- tator, to collect the current, so that any brush may be lifted off without interrupting the circuit. Ques. 618. — Describe the construction of the field- magnet coils. Ans. — The field-magnet winding consists of shunt and series coils wound on a frame which fits over the upper pole-piece. The shunt coils are of small wire and high resistance. The ends of the wire are connected to the machine terminals. The greater part of the magnetism is due to these coils, so that at full speed, and when no current is being taken from the xi 264 QUESTIONS AND ANSWERS machine, the electric pressure is normal, that is, 80 or 100 volts. The series coils are formed of thick copper bars and convey the whole current generated. They provide additional magnetism, proportional to the current flowing in them, and so compensate for the additional Fig. 169. Compound Wound Dynamo. pressure required to force this current through the machine. By the combination of the two sets of coils, the pressure is thus independent of the current, so long as the speed is constant. In the largest machines there are two distinct armature windings laid on side by side, the bars ^ AUXILIARY MACHINERY AND FITTINGS 265 of the two windings alternating, as also do their respec- tive commutator segments. The two windings are con* nected in parallel by the brushes, which all have a bearing rather wider than the angular width of two commutator segments. Ques. 619. — In order to obtain satisfactory working, what should be done with the commutator occasionally? Ans. — It should be turned up, by using a lathe slide- rest clamped to the bed-plate and running the engines as slowly as possible, and after turning, the commutator should be polished. This truing up is necessary in order to remove any flat places which are liable to form on the segments. The brushes also should be carefully filed to fit the commutator curve. The brushes must be care- fully set in the holders, with all the tips of each set in a line, and the tips of the two sets bearing simultaneously on diametrically opposite commutator segments. Gener- ally two segments are marked at their ends, with crosses, to assist in this adjustment. Ques. 620. — How is the electric current carried to the different parts of the ship? Ans. — By wires of the best copper, thoroughly insu- lated and protected from injury by being placed in wooden mouldings, or what is still better, iron tubes lined with insulating material. The junction boxes have safety fuses and connections, arranged in incombustible porce- lain or lava blocks. Ques. 621. — How are the lamps and motors arranged? Ans. — The lamps are attached to substantial supports With good protection to the insulation of the wires at their r 266 QUESTIONS AND ANSWERS connection. For exposed places extra globes or wire screens are provided to prevent breaking of the bulbs. The motors are fitted on substantial foundations, with switches for handling in convenient positions. The use of electric motors is becoming more and more general on board vessels as their convenience and freedom from waste is known. They can be used for working ven- tilating fans, etc., in confined spaces where the heat of steam would be objectionable. They also avoid the waste due to condensation, radiation and leakage in pipes, require very little attention when running and are always ready for starting. Ques. 622. — What facilities are provided for pumping the water out of steam-ships in case of a serious leak? Ans. — All steam-ships, including war-vessels, were formerly fitted with bilge-pumps worked direct from the main engines, and this is still the common practice in the mercantile marine. In addition to these pumps, the circulating pumps are fitted with bilge as well as sea connections, and in some of the larger vessels there are four centrifugal pumps which can be used for pumping out the bilges, each of these pumps having a capacity of at least 1,200 tons of water per hour. Ques. 623. — What are some of the requirements of a reliable bilge-pumping outfit? Ans. — The pump itself should be close to the bilge, but the engine for working it should if possible be at a high level, so as to be out of the reach of the water in case of its rising rapidly. Another point that should be kept in view is the provision of large engine-power foi AUXILIARY MACHINERY AND FITTINGS 26? working the pumps. The valves for changing the suction of the centrifugal pumps from the sea to the bilge are, or at least should be, arranged to be worked from the start- ing platform, and to enable this to be done quickly in case of need, the valves in the sea and bilge-suction pipes r \ 7~~T I , I 3 t i \Q_©_©/ 2ZE Fig. 170. Fire and Bilge Pumps. are often coupled together so that they may be worked by a single lever. Ques. 624. — Describe the type of fire and bilge-pump- ing engines that are used to a large extent in the English navy. ^ 268 QUESTIONS AND ANSWERS Ans. — Each pumping engine consists of two double- acting pumps and two steam-cylinders, fitted with slide-valves, having very little lap, to insure the engines starting readily from any position of the cranks, economy in the use of steam being in these cases a minor considera- tion. In the large battle-ships and cruisers there are four [of these pumps, two in each engine-room, each one of the four having a capacity of 80 to 120 tons of water per hour. The pumps are large enough to remove these quantities of water at a speed not exceeding 60 revolu- tions per minute, with a steam-pressure of two-thirds the maximum boiler-pressure, and they form a means of pumping water out of the ship, auxiliary to the main circulating pumps. They can be used for either fire ser- vice or for clearing the bilges of water. Ques. 625. — Describe Friedmann's bilge-ejector. Ans. — This apparatus is a modification of Giffard's injector, the number of nozzles being increased so as to give the steam several suction orifices instead of one. The steam is conducted to a tuyere about one-half the diameter of the steam-pipe, and then passes successively through a series of intermediate tuyeres, through which the water is drawn from the hold and expelled from the ship through the discharge. The device occupies little space and has considerable capacity, but its consumption of steam is large. Ques. 326. — Describe the suction and discharge arrangements of fire and bilge pumps. Ans. — They are fitted with separate suction-pipes leading to the following parts of the vessel: Forward n. AUXILIARY MACHINERY AND FITTINGS 269 and after ends of engine-room, with a continuation to the screw tunnel from the latter, main engine save-all, each boiler compartment, the main suction-pipe, salvage system of the vessel and to the sea. The valve-boxes and pipes are so arranged that each pump can draw from any of these parts. The pumps deliver water either over- board direct, to the engine-room or to the fire-main, a large air-vessel being fitted in connection with the latter. J)/SCHAROe TO enginc room*' r"n D ,0*0*9 CCNHCCTIOM T=»i /BtTWeCJ?, SVCTtON BOXCS \ MAIM SUCT/OAt pUf SUCTION r/tOM SCA. S£A [VALV£ , sue TIOW FACM SSA. Fig. 171. Suction and Discharge Arrangements oe Fire and Bilge Pumps. A A A A, pumps; B B, directing valve-boxes; C C, shut-off valves from the sea, and bilge directing valve-box respectively; D D, directing valves for discharge, either to fire main, overboard or to engine-room. Ques. 627. — How is the fire-main arranged? Ans. — The fire-main is a pipe extending fore and aft in the ship, with branches leading to different parts as required. Delivery-valves, with screwed nozzles for hose- connections, i are located at various points in the fire-main. Non-return valves are fitted at the junction of delivery- pipes from the pumping engines. CHAPTER IX THE INDICATOR — PRINCIPLES OF THE INDICATOR Ques. 628. — By whom was the indicator invented and first applied to the steam-engine? Fig. 172. Sectional View Crosby Indicator. Ans. — The indicator was invented and first applied to the steam-engine by James Watt, whose restless genius 270 k> THE INDICATOR PRINCIPLES OF INDICATOR 271 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 differ- ent portions of the stroke, the laws governing its expan- sion after being cut off, etc. Watt's indicator, although crude in its design and construction, contained embodied within it all of the principles of the modern instrument. Ques. 629. — What are the principles governing the action of the indicator? Ans. — First, the pressure of the Steam in the; engine-cylinder throughout an entire revolution, against a small pis- ton in the cylinder of the indicator, which in turn is controlled or resisted in its movement by a spring of known tension, so as to confine the stroke of the indica- tor piston within a certain small limit. Second, the stroke of the indicator pis- ton is communicated by a multiplying mechanism of levers and parallel motion to a pencil moving in a vertical straight line, the distance through which the pencil moves being governed by the pressure in the engine-cylinder and the tension of the spring. Third, by the intervention of a re- ducing mechanism and a strong cord, the motion of the pis- ton of the engine throughout an entire revolution is com- municated 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 Fig. 173. Crosby Indicator Spring. * 272 QUESTIONS AND ANSWERS the drum to rotate through part of a revolution 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. Ques. 630. — Describe in general terms the construc- tion of an indicator. Ans. — An indicator con- sists of a small cylinder, open to the atmosphere at the top and having its bot- tom end connected by suit- 1 able pipes and stop-cocks to both ends of the engine- cylinder in such a manner that the steam-pressure in either end may be caused to act upon the indicator FlG piston, as required. The S.CTIONAI, View Thom'pson Indicator. cyHnder q£ ^ indicator stands vertical, and is of a known area, usually about one square inch. It contains a piston, upon which the steam acts only on the under side, the top of the cylinder being open to the atmosphere. The length of stroke of this piston is regulated and controlled by a steel spiral spring of known tension, which acts in resistance to the pressure of the steam. When the cock connecting the cylinders of the engine and indicator is closed, both ends of the indi- cator cylinder are open to atmospheric pressure, and the ^ THE INDICATOR PRINCIPLES OF INDICATOR 273 pencil, which is connected to the piston by a system oj levers, stands at its neutral position. Ques. 631. — Describe the construction and action \d the spiral spring in connection with the indicator pistou. Ans. — 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 No. 20 spring is used and the pressure in the cylinder at the commencement of the stroke is 20 pounds per square inch, the pencil will be raised one inch, or if the pressure is 30 pounds, the pencil will travel V/2 inch, and if there is a vacuum of 20 inches in the condenser, the pencil will drop /. inch below the atmospheric line for the reason that 20 inches of vac- uum correspond to a pressure of about 10 pounds less than atmospheric pressure or an absolute pressure of about 4 pounds. If a 60 spring is used a pressure of 60 pounds in the engine-cylinder will be re- quired to raise the pencil one inch, or 90 pounds to raise it V/2 inch. Ques. 632. — Are these springs placed inside the cylinder in all types of indicators? Ans. — The Ashcroft Manufacturing Company of New Fig. 175. Thompson Indica- tor Spring. . 274 QUESTIONS AND ANSWERS 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 FlG, 176. Improved Tabor Indicator with Outside Connected Sprinc. Ashcroft Mfg. Co., N. Y. view of the operator. This arrangement removes the spring from the influence of direct contact with the steam, and it is subject only to the temperature of the THE INDICATOR — PRINCIPLES OF INDICATOR 275 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. Ques. 633. — What precautions should be observed in attaching the indicator to an engine-cylinder? Ans. — 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. These pipes should always be thoroughly blown out and cleaned, by 276 QUESTIONS AND ANSWERS allowing the steam to blow through the open three-way cock during several revolutions of the engine before con- necting the indicator. If this is not done there is a moral certainty that dirt and grit will get into the cylinder of the indicator and cause it to work badly and give diagrams that are misleading. Ques. 634. — How is an indicator diagram or card drawn? Fig. 177. Three-way Cock. Ans. — 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 engine- 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 THE INDICATOR PRINCIPLES OF INDICATOR 277 piston; second, that of the paper drum caused by, and coincident with the motion of the engine-piston. Ques. 635. — How is the atmospheric line drawn? Ans. — By holding the pencil to the paper, and causing the drum to be rotated, when the pencil stands at its neutral position, that is with the steam shut off from the indica- tor cylinder. Ques. 636. — What is meant by the term atmospheric line? Ans. — The atmospheric line is a horizontal line drawn on the diagram and means the line of atmospheric pres- sure. 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 atmospheric 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. Ques. 637. — Is the atmospheric line a necessary part of an indicator diagram? Ans. — The atmospheric line is a very important factor in the study of the diagram. Ques. 638. — How are the dimensions of the diagram regulated? Ans. — It is a convenient practice to select a spring numbered one-half of the boiler-pressure as, for instance, A 278 QUESTIONS AND ANSWERS suppose gauge-pressure or boiler-pressure is 200 pounds per square inch, then a 100 spring would give a diagram 2 inches in height, which is a convenient height. As to the length of the diagram, this is regulated by adjustment Fig. 178. Crosby Reducing Wheel Attached to Indicator. of the cord in its travel, by means of the reducing wheeL Any length of diagram up to four inches may be obtained, but two and a half to three inches is a very good length for analysis. Ques. 639. — How is the motion of the crosshead of THE INDICATOR PRINCIPLES OF INDICATOR 279 the engine reduced and utilized for rotating the drum of the indicator? Ans. — There are various mechanisms used for this purpose. Probably the only practically universal mechanism ior reducing the motion of the crosshead is the reducing wheel, a device in which, by the employment of gears and pulleys of different diameters, the motion is reduced to within the compass of the drum, and the 280 QUESTIONS AND ANSWERS device is applicable to almost any make of engine] whether of high or low speed. Some makers of indicator; attach the reducing wheel directly to the indicator, thui producing a neat and very convenient arrangement, Ques. 640. — Describe the construction of the woodei pendulum for reducing the motion. Ans. — It consists of a flat strip of pine or other lightl Wooden Pendulum, Reducing Motion. wood of a length not less than one and a half times the stroke of the engine, and if made longer it will be better. It should be from Z A to 7 /s inch thick and have an average width of about 4 inches. If the engine to be 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 cross- head, as that is generally the mo^t convenient point of attachment. The pivot can be fixed to a permanent THE INDICATOR PRINCIPLES OF INDICATOR 281 standard bolted to the frame of the engine or it may be secured to the ceiling of the room or even to a post fastened to the floor. If 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 convenient length for this bar is one-half the stroke of the engine. Ques. 641. — When the short bar is one-half the length of the stroke, how is the correct point for the loca- tion of the pivot for the pendulum found? Ans. — Place the engine on the center with the cross- head 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 con- necting with the link, susoend the pendulum by a temporary pin, as a large wood screw, directly above and in line with the stud or bolt hole which has previously been tapped into the crosshead at any convenient point. The pendulum should be temporarily suspended at such a height that when it hangs perpendicular the hole in its lower end will line up accurately with the hole or stud in the crosshead. Now swing the pendulum in either direc- tion a distance equal to the length of the link (one-half the stroke of the 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 282 QUESTIONS AND ANSWERS the pivot should be one-half of this distance below th< temporary point of suspension. This will allow the link to vibrate equally above and below the center of its con nection with the crosshead. Ques. 642. — How is the correct point of attachment of the cord to the pendulum found? Ans. — The cord can be attached to the pendulum at point near the pivot, which will give the desired length ol diagram. This point can be determined by multiplyinj the length of the pendulum by the desired length of dia- gram and dividing the product by the stroke. Foi convenience these terms should be expressed in inches. Thus, assume stroke of engine to be 48 inches, length of pendulum V/2 times length of stroke = 72 inches. Desired length of diagram 3 inches. Then 72X3-^48 = 4.5 inches, which is the distance from center of pivot to point of connection for the cord. This can be either a smal hole bored through the pendulum or a wood screw to which the cord 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 wil leave it at right angles. After leaving the guide pulley the cord can be carried at any angle desired. Ques. 643. — How shoulu the indicator be cared for? Ans. — 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 ioints and springs, and before taking diagrams it is a good THE INDICATOR PRINCIPLES OF INDICATOR 283 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. Ques. 644. — How may the cord be adjusted to proper length? Ans. — None but the best cord should be used for con- necting the paper drum with the reducing motion, as a cord that is liable to stretch will cause trouble. After the indicator has been screwed on to the cock connecting with the pipe, the cord must be adjusted to the proper ength before hooking it on to the drum. This must be lone while the engine is running, by taking hold of the oop on the cord connected with the reducing motion with one hand, and with the other hand grasp the hook )n the short cord attached to the drum, then by holding :he two ends near each other during a revolution or two t will be seen whether the long cord needs to be shortened r lengthened. Ques. 645. — What precautions are necessary in regard o the paper and pencil in order to secure a truthful liagram? Ans. — Care should be exercised in placing the paper >n the drum to see that it is stretched tight and firmly leld by the clips. The pencil point having been first harpened by rubbing it on a piece of fine emery cloth or and paper should be adjusted by means of the pencil |top with which all indicators should be provided, so that will have just sufficient bearing against the paper to lake a fine, plain mark. If the pencil bears too hard on 284 QUESTIONS AND ANSWERS the paper it will cause unnecessary friction and the di; gram will be distorted. The best method of ascertain^ this fact and also whether the travel of the drum equally divided between the stops, is to place a blank die gram on the drum, connect the cord and while the engir makes a revolution hold the pencil against the pape Then unhook the cord, remove the paper and if the trav of the drum is not divided correctly it can be changed. Ques. 646. — Describe the process of taking an indica tor diagram. Ans. — Place a fresh blank on the drum, being carefi to keep the pencil out of contact with it, connect the con open the cock admitting steam to the indicator and aft< the pencil has made a few strokes to allow the cylinder t become warmed up, then gently swing it around to th paper drum and hold in there while the engine makgs complete revolution. Then move the pencil clear of th paper, close the cock and unhook the cord. Now trac the atmospheric line by holding the pencil against th' paper while the drum is revolved by hand. This metho< of tracing the atmospheric line is preferable to that o tracing it immediately after closing the cock and whili the drum is still being moved by the engine, for the reasoi that there is not so much liability of getting the atmos« pheric line too high owing to the presence of a sligh pressure of steam remaining under the indicator pistol for a second or two just after closing the cock; also th< line drawn by hand will be longer than one drawn whil< the drum is moved by the motion of the engine and wi therefore be more readily distinguished from the line oi back pressure. THE INDICATOR— PRINCIPLES US? INDICATOR 3§§ Ques. 647. — What other details should be observed in the taking of indicator diagrams? Ans. — 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 afterwards. Ques. 648. — What needed changes in the cut-off of a Corliss engine, as shown by a diagram, may be made while the engine is running? Ans. — 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 generally be adjusted while the engine is running by changing 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 necessitates changing the length of the reach rods connecting 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. Ques. 649. — What important details will a truthful indicator diagram show? Ans. — First, the pressure of the steam against the piston of the engine at any point in the stroke during a complete revolution; second, diagrams from a condensing engine show the amount of vacuum that is being maint- ained in the condenser, measured from the line of perfect 286 QUESTIONS AND ANSWERS vacuum; third, the point of cut-off is clearly shown, als< the point in the return stroke at which compressioi begins; fourth, the expansion curve, and how near i approaches the theoretical expansion curve; fifth, an] fault in the setting of the valves is clearly shown 01 the diagram; sixth, diagrams taken from the differen cylinders of a compound or stage expansion engine ma; be combined in such a manner as to show whether or no the cylinders are properly proportioned, and whether th< steam is being distributed correctly. Ques. 650. — What is absolute pressure? Ans. — Pressure reckoned from a perfect vacuum. It equals the boiler-pressure plus the atmospheric pres sure. Ques. 651 — What is boiler-pressure or gauge-pres- sure? Ans. — Pressure above the atmospheric pressure as shown by the steam gauge. Ques. 652. — What is initial pressure? Ans. — Pressure in the cylinder at the beginning of the stroke. Ques. 653. — What is meant by terminal pressure (T. p.)? Ans. — 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 extend- ing 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 THE INDICATOR — PRINCIPLES OF INDICATOR 287 pressure at cut-off =100 pounds, ratio of expansion=5; then 100-^-5^=20 pounds, absolute terminal pressure. Ques. 654. — What is mean effective pressure (M. E. p.)? Ans. — The average pressure acting upon the piston througnout the stroke minus the back pressure. Ques. 655. — What is back pressure? Ans. — Pressure which tends to retard the forward stroke of the piston. Indicated on the diagram from a non-condensing engine by the height of the 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. Ques. 656. — What is total or absolute back pressure? Ans. — Total or absolute back pressure, in either a ondensing 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. Ques. 657. — How is the line of perfect vacuum drawn Dn an indicator diagram? Ans. — The line of perfect vacuum is drawn parallel with the atmospheric line and at a distance below the atter, representing 14.7 pounds, as measured by the scale :orresponding to the spring that was used in taking the liagram. Different scales are supplied for the different prings used. Ques. 658. — What is meant by ratio of expansion? Ans. — The Drooortion that the volume of steam in the 288 QUESTIONS ANEf ANSWERS 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 expansion, or in other words, the number oi expansions, is 5. When the T. P. is known the ratio oJ expansion may be found by dividing the initial pressure by the T. P. Ques. 659. — What is rteart by wire drawing? Ans. — 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 diagram 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. Ques. 660. — What is condenser pressure? Ans. — Condenser pressure may be defined as the pres- sure existing in the condenser of an engine, caused by the lack of a perfect vacuum. As, for instance, with a vacuum of 25 inches there will still remain the pressure due to the 5 inches which is lacking. This will be about 2.5 pounds. Ques. 661. — What 'is absolute zero? Ans. — Absolute zero has been fixed by calcula- tion at 461.2 degrees below the zero of the Fahrenheit scale. Ques. 662. — What is piston displacement? Ans. — The space or volume swept through by the THE INDICATOR — PRINCIPLES OF INDICATOR 289 piston in a single stroke. Found by multiplying the area of piston by length of stroke. Ques. 663. — What is piston clearance? Ans. — The distance between the piston and cylinder head when the piston is at the end of the stroke, Ques. 664. — What is steam clearance, ordinarily termed clearance? Ans. — 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. Ques. 665. — What is the meaning of the expression horse-power as applied to a steam-engine? Ans. — 33,000 pounds raised one foot high in one minute of time. Ques. 666. — What is indicated horse-power (I. H. P.)? Ans. — The horse-power as shown by the indicator diagram. It is found as follows: Area of piston in square inchesXM. E. P. X piston speed in feet-^33,000. Ques. 667.— What is meant by the term piston speed? Ans. — 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. Ques. 668.— What is net horse-power? Ans. — I. H. P. minus the friction of the engine. Ques. 669. — What is compression? Ans. — The action of the piston as it nears the end of he stroke, in reducing the volume and raising the pres- ure of the steam retained in the cylinder ahead of the rfston by the closing of the exhaust valve. 290 QUESTIONS AND ANSWERS Ques. 670. — What is Boyle's law of expanding gases? Ans. — "The pressure of a gas at a constant tempera- ture varies inversely as the space it occupies." Thus, if a given volume of gas is confined at a pressure of 50 pounds per square inch and it is allowed to expand to twice its volume, the pressure will fall to 25 pounds per square inch. Ques. 671. — What is an adiabatic curve? Ans. — A curve representing the expansion of a gas which loses no heat while expanding. Sometimes called the curve of no transmission. Ques. 672. — What is an isothermal curve? Ans. — A curve representing the expansion of a gas having a constant temperature but partially influenced by moisture, causing a variation in pressure according to the degree of moisture or saturation. It is also called the theoretical expansion curve. Ques. 673. — What is the expansion curve? Ans. — The curve traced upon the diagram by the indicator pencil showing the actual expansion of the steam in the cylinder. Ques. 674. — What is power? Ans. — The rate of doing work, or the number of foot pounds exerted in a given time. Ques. 675. — What is the unit of work? Ans. — The foot pound, or the raising of one pound weight one foot high. Ques. 676. — Define the first law of motion. Ans. — All bodies continue either in a state of rest or of rjiifarm motion in a straight line, except in so far as THE INDICATOR— PRINCIPLES OF INDICATOR 291 they may be compelled by impressed forces to change that state. Ques. 677.— What is work? Ans.— Mechanical force or pressure can not 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. Ques. 678.— What is momentum? Ans.— Force possessed by bodies in motion, or the product of mass and density. Ques. 679.— What is the meaning of the word dynam- ics? Ans.— The science of moving powers or of matter in motion, or of the motion of bodies that mutually act upon each other. Ques. 680.— What is force? Ans.— That which alters the motion of a body or puts in motion a body that was at rest. Ques. 681.— What is the maximum theoretical duty of steam? Ans.— The maximum theoretical duty of steam is the product of the mechanical equivalent of heat, viz., 778 foot pounds multiplied by the total heat units 'in a pound of steam. Thus, in one pound of steam at 212 degrees reckoned from 32 degrees the total heat equals 1,146.6 heat units. Then 778X1,146.6 = 892,054.8 foot oounds=maximum duty. Ques. 682.— What is steam efficiency? Ans.— Steam efficiency mav be expressed as follows: 292 QUESTIONS AND ANSWERS H,eat converted into useful work . Heat expended and maxunum efficiency 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. Ques. 683. — What is meant by the term efficiency o{ the plant as a whole? Ans. — Efficiency of the plant as a whole includes boiler and engine efficiency, and is to be figured upon the - Heat converted into useful work Calorific or heat value of fuel Ques. 684. — What is the horse-power constant of an engine? Ans. — The horse-power constant of an engine is founc by multiplying the area of the piston in square inches b] the speed of the piston in feet per minute and dividing the product by 33,000. It is the power the engine woul<* develop with one pound mean effective pressure. To fin(f the horse-power of the engine, multiply the M. E. P. ol the diagram by this constant. Ques. 685. — What is meant by the expression steam consumption per horse-power per hour? Ans. — The weight in pounds of steam exhausted info the atmosphere 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 pfston displacement up to the point selected, plus the clearance space, expressed in cubic feet, will THE INDICATOR — PRINCIPLES OF INDICATOR 293 give the volume of steam in the cylinder, which multiplied 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 jto 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 number 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. Ques. 686. — What is cylinder condensation and reevaporation? Ans. — 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 opening 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 poition of the water caused by condensation will be reevaporated into steam by the heat and consequent rise in pressure caused by compression. Ques. 687. — What are ordinates, as applied to indi- cator diagrams? Ans. — Parallel lines drawn at equal distances apart across the face of the diagram and perpendicular to the atmospheric line. They serve as a guide to facilitate the 294 QUESTIONS AND ANSWERS ■measurement of the average forward pressure through- out the stroke, or the pressure at any point of the stroke if desired* Ques. 688. — What is a throttling governor? Ans. — A governor that is used to regulate the speed of engines having a fixed cut-off. The governor controls the position of a valve in the steam-pipe, opening or clos« *W Fig. 180. Illustrating the Process of Obtaining the Mean Eeeectiv* Pressure by Means oe Ordinates. ing it according as the engine needs more or less steam in order to maintain a regular speed. Ques. 689. — What is an automatic or variable cut- off engine? AnSc — 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 governor 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. THE INDICATOR PRINCIPLES OF INDICATOR 295 Ques. 690.— What is a fixed cut-off? Ans. — 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. Ques. 691. — What is an adjustable cut-off? Ans. — One in which the point of cut-off may be regu- lated 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 governor. Ques. 692. — What is an isochronal or shaft governor? Fig. 181. Indicator Diagram Taken from a Condensing Engine. A, atmospheric line. V, line of perfect vacuum. B to D, admission line. D to E, steam line. E, point of cut-off. E to F, expansion line. F to G, ex- haust. G to C, line of back pressure; and from C to B shows compression. Ans. — This device in which the centrifugal and cen- tripetal forces are utilized, as in the fly-ball governor, is generally applied to automatic cut-off engines having reciprocating or slide valves. It is attached to the crank shaft and its function is to change the position of the eccentric, which is free to move across the shaft within certain prescribed limits, but is at the same time attached to the governor. The angular advance of the eccentric is thus increased or diminished; in fact is entirely under 296 QUESTIONS AND ANSWERS the control of the governor, and cut-off occurs earlier of later according to the demands of the load on the engine. Ques. 693. — If the valves of an engine are properly adjusted and the distribution of the steam is approxi- mately correct, what particular features should character- ize an indicator diagram taken from it? Ans. — First, the admission line at the beginning of the stroke should be perpendicular to the atmospheric line; second, the steam line, as it is called, extending from the beginning of the stroke to the point of cut-off, should be Fig. 182. Diagram Showing Insufficient Lead. parallel with the atmospheric line; third, the point of cut-off should be sharply defined; fourth, the expansion curve, extending from the point of cut-off to the point of release, should conform as near as possible with the isothermal curve, which can easily be applied to any dia- gram; fifth, the exhaust line, extending from point of release to that point in the return stroke where compres- sion begins, should be parallel with and practically coin- cident with the atmospheric line, if the engine is non-condensing:, or if the engine be a condensing engine, THE INDICATOR PRINCIPLES OF INDICATOR 29? this line should approach within a few pounds of the line of perfect vacuum. Ques. 694. — If the admission line inclines inward from the perpendicular, what defect in the valve setting is indicated? Ans. — Insufficient lead. Ques. 695.— How is wire drawing of the steam detected by the indicator diagram? Ans. — By the downward inclination of the steam line toward the point of cut-off. Fig. 183. Diagram Showing Effects of Wire Drawing the Steam. Ques. 696. — What is a very necessary factor in the calculation of the horse-power of an engine as shown by a diagram taken from it? Ans. — The mean effective pressure. Ques. 697.— How is the M. E. P. of a diagram ascer- tained? Ans. — There are two methods commonly used. First, by means of ordinates, and secondly, by the use of the planimeter. 298 QUESTIONS AND ANSWERS Ques. 698. — Describe the method of finding the M E. P. by ordinates. Ans. — The process consists in drawing any convenienl number of vertical lines perpendicular to the atmospheric line across the face of the diagram, spacing them equally with the exception of the two end spaces, which shoul< be one-half the width of the others, for the reason tha the ordinates stand for the centers of equal spaces. This is an important matter, and should be thoroughly under Cr/fn/(£/jil SS 3 '9 to./ 8 7 2 7 2 'Jr/6.Jju>/7& 'fit* Fig. 184. Finding M. E. P. Stood, because if the spaces are all made of equal width, and measurements are taken on the ordinates, the result! will be incorrect, especially in the case of high initial pres- sure and early cut-off, following which the steam undergoes great changes. If the spaces are all made equal, the meas- urements 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 ordinates, which is much more convenient and will insure correct results. Any number of ordinates can be drawn, but ten THE INDICATOR PRINCIPLES OF INDICATOR 299 is the most convenient and is amply sufficient, except in case the diagram is excessively long. Ques. 699. — Having succeeded in drawing the ordi- nates across the face of the diagram, what is the next step? Ans. — The pressure represented by each line is meas- ured from the exhaust line to the steam line, and so on, FlG. 185. Pl^ANIMETER. along the expansion curve throughout the length of the diagram, using for this purpose the scale adapted to the fpring used, and having thus obtained measurements on each line, add all together and divide the sum total by the number of lines, which will give the mean forward pressure. To obtain the mean effective pressure, deduct the back pressure, which is represented by the distance 300 QUESTIONS AND ANSWERS of, the exhaust line above the atmospheric line in a non- condensing engine, and in a condensing engine the back pressure is measured from the line of perfect vacuum. Fig. 186. Coffin Averager or Planimeter. Ques. 700. — What is a planimeter? ^ rs# — The planimeter is an instrument which will THE INDICATOR PRINCIPLES OF INDICATOR 301 accurately measure the area of any plane surface, no matter how irregular the outline or boundary line is. Ques. 701. — What is the main requirement in ascer- taining the M. E. P. of a diagram? Ans. — The prime requisite In making power calcula- tions 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. Ques. 702. — What advantage is gained by using the planimeter in measuring diagrams? Ans. — 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 average 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 multiplying the area, as shown by the planimeter in square 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. Ques. 703. — Having obtained the M. E. P., as shown by the diagram, how may the horse-power developed by the engine be ascertained? Ans. — The area of the piston (minus one-half the are* of rod) multiplied by the M. E. P., as shown by the dia- 302 QUESTIONS AND ANSWERS gram, 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 product be divided by 33,000, the quotient will be the indicated horse-power (I. H. P.) developed by the engine. Ques. 704. — Mention two important factors in calcu- lations of steam consumption. Ans. — In calculating the steam consumption of an engine, two very important factors must not be lost sight of, viz., clearance and compression. Especially is this the case in regard to clearance when there is little or no compression, for the reason that the steam required to fill the clearance space at each stroke of the engine is prac- tically wasted, and all of it passes into the atmosphere or the condenser, 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. Ques. 705. — When, owing to light load and early cut-off, the expansion curve drops below the line of back pressure, how must the area of the diagram be calculated? Ans. — The area of the loop below the back pressure line must be subtracted from the remainder of the diagram. If the planimeter is used, the instrument will make the sub- traction automatically, but if the diagram is divided into THE INDICATOR PRINCIPLES OF INDICATOR 303 parts by ordinates, the pressure shown by the ordinates in the lower loop must be subtracted from that shown by the loop above the back pressure line in order to ascertain the M. E. P. or average pressure. Ques. 706. — What is meant by the adiabatic curve? 7 ,'C s So 7* 7° IS / / ~7 ~T / / t>o / / 5S 'Jr 5o S> HS ^'^ 3S •f^^^ 3o R s-*^*^ 1 Zi J A V V Fig. 187. The dotted line R C shows what the true adiabatic curve would be on the diagram, provided it could be realized. Ans. — If it were possible to so protect or insulate the cylinder of a steam engine that there would be absolutely no transmission of heat either to or from the steam dur- ing expansion, a true adiabatic curve or "curve of no transmission" might 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 converting heat into work. CHAPTER X THE STEAM TURBINE — FUNDAMENTAL PRINCIPLES Ques. 707. — What are the basic principles governing the action of steam turbines? Ans. — There are two fundamental principles upon which all steam turbines operate, viz., reaction and impulse. In some types of turbines the reaction principle alone is utilized, and in others the impulse, while in still others, and probably the most successful ones, both principles are combined. Ques. 708. — In what general direction does the steam flow 7 when used in a turbine? Ans. — Parallel with the shaft or rotor, and also in a screw-like direction around it. This definition does not apply, however, to turbines of the purely impulse type, like the De Laval, for instance. Ques. 709. — What causes the rotor to revolve? Ans. — The action of the steam, coming, as it does, with tremendous velocity and great force against the small buckets or vanes with which the rotor is fitted, causes it to revolve, and as there is a continuous current of steam passing into the cylinder, the motion is continue ous. Ques. 710. — What law of turbo-mechanics governs the relation of bucket-speed, and fluid or steam speed? _ Ans. — For purely impulse-wheels, bucket-speed equals one-half of jet-speed. For reaction wheels, bucket-speed equals jet-speed. 804 STEAM TURBINE — FUNDAMENTAL PRINCIPLES 305 Ques. 711, — With what velocity would steam of 100 pounds pressure discharge into a vacuum of 28 inches? Ans. — The theoretical velocity would be 3,860 feet per second. Ques. 712. — What amount of energy would a cubic foot of steam under 100 pounds pressure exert if allowed to discharge into a vacuum of 28 inches? Ans. — 59,900 foot pounds. Ques. 713. — Does the steam impinge against the first rows or sections of buckets at full pressure? Ans. — In turbines of the Parsons type, the initial pressure of the steam is practically boiler-pressure, but it gradually falls as it p __cs on through the cylinder, which becomes larger in diameter as the exhaust end is approached. In other types of turbines, the steam is admitted to and directed against the blades or buckets, through expanding nozzles, and by the time it strikes the first stage, or section of moving vanes, the pressure has fallen to one-third or less of the original boiler-pressure, but the velocity is very great. Ques. 714. — In what particular respect does the steam turbine appear to possess an advantage over the recipro- cating engine, in the use of steam? Ans. — The turbine, if designed along correct lines, is capable of utilizing in the highest degree one of the most valuable properties of steam, viz., velocity. Ques. 715. — Give an example of the great increase in the amount of work performed by an agent when velocity is one of the factors made use of. Ans. — Suppose that a man is standing within arm's 306 QUESTIONS AND ANSWERS length of a heavy plate-glass window and that he holds in his hand an iron ball weighing 10 pounds. 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 feet, and then exert the same amount of energy in throwing the ball against the glass, a different result would ensue. The velocity with which the ball would impinge against the surface of the glass would no doubt ruin the window. Now, notwithstanding 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. Ques. 716. — Describe the construction and action of the De Laval steam turbine. Ans. — 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 curva- ture as has been found to be best adapted for receiving the impulse of the steam-jet. There are no stationary or guide-blades, the angular position of the nozzles giving direction to the jet. The nozzles are placed at an angle of 20 degrees to the plane of motion of the buckets. The heat energy in the steam is practically devoted to the production of velocity in the expanding or divergent nozzle, and the velocity thus attained by the issuing jet of steam is about 4,000 feet per second. To attain the STEAM TURBINE — FUNDAMENTAL PRINCIPLES 307 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 feet per second, but, owing to the difficulty of producing a material for the wheel strong enough to withstand the strains induced by Fig. 188. The De Lavai, Turbine Wheei, and Nozzles. such a high speed, it has been found necessary to limit the peripheral speed to 1,200 or 1,300 feet per second. Ques. 717. — Describe the action of the steam in its passage through the De Laval diverging nozzle. Ans.— It is well known that in a correctly designed nozzle the adiabatic expansion of the steam from max- 308 QUESTIONS AND ANSWERS imum 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 of steair 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, however, which for obvious reasons has never yet been attained in practice STEAM TURBINE FUNDAMENTAL PRINCIPLES 309 with the reciprocating engine. But with the divergent nozzle the conditions are different. Ques. 718. — What is the usual speed of the De Laval steam-turbine wheel? Ans. — From 10,000 to 30,000 revolutions per minute, according to the size of the machine. Ques. 719. — How are the difficulties attending such high velocities overcome? Ans. — 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. Ques. 720. — How is the speed of the De Laval turbine -wheel and shaft reduced and transmitted for practical purposes? Ans. — 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 90 degrees 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. Ques. 721. — How are the buckets made and fitted to the De Laval wheel? Ans. — The buckets are drop-forged and made with a bulb shank, fitted in slots, that are milled in the rim of the wheel. Ques. 722. — How many buckets are there? 310 QUESTIONS AND ANSWERS Ans. — The number of buckets varies according to the capacity of the machine. There are about 350 buckets U.S g __ u a 1 2 = > «■ /J ^-- y rt * S *r C c u-g y u a 3 ^ ~- c u -*&* y w o " w *j 2 art « a 2 *£~ ~S-2 rt 2 2 u rtjq on a 300 norse-power wheel, which is the largest size built up to the present time. STEAM TURBINE FUNDAMENTAL PRINCIPLES 311 Ques. 723. — How many of the diverging nozzles are fitted to each wheel? Ans. — 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 by which one or more nozzles can be cut out when the load is light. This fc Fig. 191. Working Parts of the; De Laval Steam Turbine. A. — Turbine shaft. I. — Gear wheel shaft. B. — Turbine wheel. J. — Gear wheel bearing, two parts. C— Pinion. K.—Oil ring. D. — Pinion bearing, two parts. L,. — Gear wheel bearing in position. E. — Pinion bearing, two parts. M. — Coupling. F. — Wheel bearing with spring. N. — Centrifugal governor. G. — Flexible bearing. O. — Gland ad-justing nut. H. — Gear wheel. P. — Adjusting nut for flexible bearing 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 considerably, as, for instance, there are plants in which during certain hours of the day a 300 horse-power machine may be taxed to its utmost capacity and during 312 QUESTIONS AND ANSWERS certain other hours the load on the same machine may drop to 50 horse-power. 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 passing through the nozzles, the steam, as elsewhere explained, is now completely expanded, and in impinging on the buckets its kinetic energy is transferred to the turbine wheel. Leaving the buckets, the steam now passes into the exhaust-chamber, and out through the exhaust-opening, to the condenser or atmosphere, as the case may be. Ques. 724. — How is the speed of this turbine regu- lated? Ans. — The governor is of the centrifugal type, although differing greatly in detail from the ordinary fly-ball governor. It is connected directly to the end of the gear-wheel shaft. Ques. 725. — Describe the methods of lubricating the bearings on the De Laval turbine. Ans. — 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 may be filtered and used again. Ques. 726. — What can be said regarding the steam- consumption of this turbine? Ans. — Efficiency tests of the De Laval turbine show a high economy in steam-consumption, as, for instance, a test made by Messrs. Dean and Alain, of Boston, Mass., on a 300 horse-power turbine, using saturated steam at STEAM TURBINE FUNDAMENTAL PRINCIPLES 313 about 200 pounds pressure per square inch and develop- ing 333 brake horse-power, showed a steam-consumption of 15.17 pounds per brake horse-power, and the same machine, when supplied with superheated steam and carrying a load of 352 brake horse-power, consumed but Fig. 192. The De Lavae Steam Turbine Governor. Two weights B are pivoted on knife edges A with hardened pins C, bearingr on the spring seat D. E is the governor body fitted in the end of the gear wheeJ 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, 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. 13.94 pounds per brake horse-power. These results compare most favorably with those of the highest type of reciprocating engines. Ques. 727. — Since the steam is used in but a single 314 QUESTIONS AND ANSWERS stage or section of buckets in the De Laval turbine, why such good economy in the use of steam? Ans. — 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 tre- mendous velocity, but at a greatly reduced pressure- practically exhaust pressure — impinging against the buckets of the turbine wheel and thus causing it to revolve. Table No. 11 Capacities and Speed of De Laval Turbines 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 Ques. 728. — Describe in general terms the Curtis steam-turbine. Ans. — The Curtis turbine is built by the General Electric Company at their works in Schenectady, N. Y., and Lynn, Mass. The larger sizes are of the vertical type, and those of small capacity are horizontal. In the vertical type the revolving parts are set upon a vertical chaft, the diameter of the shaft corresponding to the size of the machine. The shaft is supported by and runs upon a step-bearing at the bottom. This step-bearing STEAM TURBINE FUNDAMENTAL PRINCIPLES 315 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 FiC. 193. 5,000'K. W. Curtis Steam Turbine Direct Connected to 5,000 K. W. Three-phase Alternating Current Generator. beneath. A weighted accumulator is sometimes installed n connection with the oil pipe as a convenient device for governing the step-bearing pumps, and also as a safety ievice in case the pumps should fail, but it is seldom required f^r the fotter purpose, as the step-bearing pumos 316 QUESTIONS AND ANSWERS have proven, after a long service in a number of cases to be reliable. The vertical shaft is also held in place an kept steady by three sleeve bearings, one just above th step, one between the turbine and generator, and th other near the top. These guide bearings are lubricate by a standard gravity feed system. It is apparent tha the amount of friction in the machine is very small, an as there is no end-thrust caused by the action of th steam, the relation between the revolving and stationar blades may be maintained accurately. As a consequence therefore, the clearances are reduced to the minimum The Curtis turbine is divided into two or more stage* and each stage has one, two or more sets of revolvin blades bolted upon the peripheries of wheels keyed to th shaft. There are also the corresponding sets of station ary blades, bolted to the inner walls of the cylinder o casing. Ques. 729. — What is the diameter of the vertical shaf for a 5,000 kilowatt turbine and dynamo? Ans. — Fourteen inches. Ques. 730. — How is the heat energy in the stean imparted to the wheel of the Curtis turbine? Ans. — Both by impulse and reaction. The steam i; admitted through expanding nozzles in which nearly all o: the expansive force of the steam is transformed into th< force of velocity. The steam is caused to pass throug one, two, or more stages of moving elements, each stag< having its own set of expanding nozzles, each succeedinj set of nozzles being greater in number and of larger are; than the preceding set. The ratio of expansion within STEAM TURBINE FUNDAMENTAL PRINCIPLES 317 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 pounds. It leaves these nozzles and enters the first set of moving blades at a pressure of about 15 pounds, from which it further expands to atmospheric pressure in passing Fig. 194. One Stage of a 500 K. W. Curtis Steam Turbine in Course op Construction. through the wheels and intermediates. From the pres- ure in the first stage the steam again expands through the larger area 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 318 QUESTIONS AND ANSWERS steam passes to the condenser. If the turbine is a four stage machine and the initial pressure is 180 pounds, th< pressure at the different stages would be distributed ii •S^^Cfrrt 0*>«.s£ DD)»D])])D)DW])DD])DDDD])DD9 ~~*v*-*~ Atovmg B/acHes A#ov/r*£f JQ/o '*"*hes? 340 QUESTIONS AND ANSWERS Ans. — In comparing the efficiency of the reciprocating engine and the steam-turbine it is not to be inferred that reciprocating engines would not give better results at high vacuum than they do at the usual rate of 25 to 26 inches, but to reach and maintain the higher vacuum of 28 to 28.5 inches 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. Ques. 774. — What advantage has the turbine over the reciprocating engine, in the disposal of its exhaust steam? Ans. — The steam-turbine expands its working steam to within 1 inch of the vacuum existing in the condenser, that is, if there is a vacuum of 28 inches in the condenser there will be 27 inches of vacuum in the exhaust end of the turbine cylinder. On the other hand, there is usually a difference of 4 or 5 inches (2 to 2.5 pounds) between the mean back pressure in the cylinder of a reciprocating condensing engine and the absolute back pressure in the condenser. Ques. 775. — Mention the two principal sources of economy that the steam-turbine possesses in a high degree. Ans. — 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 superheated steam, and second, the possibility of maintaining a higher degree of vacuum. ^ (4 < CO o$ W < U O 342 QUESTIONS AND ANSWERS Ques. 776. — What can be said of the steam turbine, regarding friction of rubbing parts, such as reciprocating pistons, cross-heads, etc? Ans. — There are no rubbing surfaces in the turbin except the bearings of the rotor. Ques. 777. — Of what type is the Allis Chalmers steam- turbine? Ans. — It is of the reaction, or Parsons type, with a number of modifications in details of construction. Ques. 778. — Give an elementary description of the "Parsons" steam-turbine. Ans. — It consists essentially of a fixed casing, or cylinder, usually arranged in three stages of different diameters, that of the smallest diameter being at the high- pressure, or admission end, and that of the largest diam- eter at the low-pressure or exhaust end of the casing. Inside of this casing is a revolving drum, or rotor, the ends of which are extended in the form of a shaft, and carried in two bearings, just outside each end of the cyl- inder. Ques. 779. — What causes the drum to revolve within the cylinder? Ans. — The drum is fitted with a large number of small curved blades, or paddles arranged in straight rows around its circumference. The blades in each stage, or step, are also arranged in groups of increasing length, those at the beginning of each larger stage being shorter than those at the end of the preceding stage, the change being made in such a manner that the correct relation of blade length to drum diameter is secured. These rows of STEAM TURBINE FUNDAMENTAL PRINCIPLES 343 revolving blades fit in and run between corresponding rows of stationary blades that project from the walls of the cylinder. These stationary blades have the same cur- vature as the revolving blades, but are set so that the curves incline in the opposite direction to those of the revolving blades. The steam entering the cylinder at the smallest or first stage, is deflected in its course by the first row of stationary blades, and immediately impinges with a pressure but slightly reduced from boiler pressure, against the first row of revolving blades. It then passes EXHAUST FIG.I ELEMENTARY PARSONS TYPE STEAM TURBINE Fig. 206. Main bearings, A and B. Thrust bearing, R. Steam pipe, C. Main throttle valve, D. which is balanced, and operated by the governor. Steam enters the cylinder through passage E, passes to the left through the alternate rows of stationary and revolving blades, leaving the cylinder at F and passes into the condenser, or atmosphere through passage G. H, J and K are the three steps or stages of the machine. L,, M and N are the three balance pistons. O, P and Q are the equalizing passages, connecting the balance pistons with the corres- ponding stages. to the next row of stationary blades, which again deflect its course so as to cause it to strike the next row of mov- ing blades at the proper angle. Thus the continual pressure and reaction of the steam against the cuivetf surfaces of the moving blades causes the drum, or rotor to revolve. Pic 207. Spindle or Rotor, Aixis Chalmers Steam Turbine. The rings which carry the blades are pressed on. ^ STEAM TURBINE FUNDAMENTAL PRINCIPLES 345 Ques. 780. — Does not the action of the steam against the revolving blades tend to produce a strong end thrust? Ans. — It does — but this thrust is neutralized by three "balance-pistons" so called, which are fitted upon the revolving drum at the high-pressure end of the cylinder. The diameter of each "piston" corresponds with the diameter of that stage of the cylinder with which it is connected by an equalizing passage which permits the steam to act upon it, and thus balance the thrust. Fig. 208. Fig. 208 showing arrangement of blading and course of the steam in Parson* iteam turbine. Ques. 781. — Do the revolving blades come in contact ith the stationary parts? Ans. — They do not. The high speeds which are nec- essary in the steam turbine prohibit any continuous con- 346 QUESTIONS AND ANSWERS tact between moving and stationary parts, except in the lubricated bearings. Ques. 782. — How much clearance is allowed between the moving and stationary parts in the "Parsons" steam- turbine? Ans. — The tips of the revolving blades just clear the walls of the cylinder, and the tips of the stationary blades just clear the surface of the rotor. B ( R GUUU6T Fig. 209. Sectional view of elementary Parsons steam turbine, with Allis Chalmers modifications. L and M are the two balance pistons at the high pressure end. Z is a smaller balance piston placed in the low pressure end, yet having the same effective area as did the larger piston N shown in Fig. 206. O and Q are the two equalizing passages for. pistons L and M. Passage P is omitted in this construction and balance piston Z is equalized with the third stage pressure at Y. Valve V is a by-pass valve to allow of live steam being admitted to the second stage of the cylinder in case of a sudden overload. This by-pass valve is the equivalent of the by-pass valve used to admit live steam to the low pressure cylinder of a compound reciprocating engine. Valve V is arranged to be operated, either by the governor or by hand, as the conditions may require. Frictionless glands made tight by water packing are provided at S and T where the shaft passes out of the cylinder. The shaft is extended at U and connected to the generator shaft by a flexible coupling. Ques. 783. — How are the clearances between the edges of the revolving and stationary blades preserved? Ans. — The position of the drum, as regards end play, is definitely fixed by means of a small "thrust bearing" provided inside the housing of the main bearing. This so-called thrust bearing can be adjusted to locate* STEAM TURBINE — FUNDAMENTAL PRINCIPLES 347 and hold the revolving spindle or rotor in such position as will allow sufficient clearance between the moving and stationary blades, and yet reduce the leakage of steam to a minimum. Ques. 784. — Is there not danger of out leakage of steam, and in leakage of air, where the shaft passes out of the high and low-pressure ends of the cylinder? Ans. — There is; but this is provided for by glands that are made practically frictionless by water packing, without metallic contact. Ques. 785. — How is the power of the "Parsons" type of steam-turbine transmitted to the electric generator, or other machine to be run? Ans. — The shaft is extended at the low-pressure end, nd coupled to the shaft of the generator by means of a lexible coupling. Ques. 786. — What provision is made in this type of team-turbine for speed regulation? Ans. — The speed of the "Parsons" turbine is regu- ated by a very sensitive governor driven from the turbine >haft by means of cut gears working in an oil bath. The jovernor operates a balanced throttle-valve, and may be idjusted for speed while the turbine is in motion if lecessary for the synchronizing of alternators, and divid-, ng the load. Ques. 787. — Suppose there should be an accidental ierangement of the governing mechanism, what provision s made for preventing dangerous over speed? Ans. — A separate safety governor is provided, driven iirectly by the turbine shaft, without the intervention of 348 QUESTIONS AND ANSWERS gearing, and so adjusted that if the speed of the turbin should reach a predetermined point above that for whic the main governor is set, the safe:j governor will com into action, and trip a valve, thus shutting off the stean and stopping the turbine. Ques. 788. — Is the arrangement of "balance-pistons described in answer to question 780 carried out in a sizes of steam-turbines of the "Parsons" type? Ans. — No. In the larger sizes of the Allis Chalmer steam-turbine, the. largest one of the three pistons at th high-pressure end is replaced by a smaller balance-pistoi located at the low-pressure end of the turbine, and work ing inside a supplementary cylinder. This piston presents the same effective area for th< steam to act upon, as did the larger piston, because th« working area of the latter in its original location con sisted only of the annular area included between it periphery, and the periphery of the next smaller piston. Ques. 789. — How is the pressure of the steam brough to bear upon this equalizing piston in its new position? Ans. — By means of passages through the body of th< rotor, connecting the third stage of the cylinder wit the supplementary cylinder in which the piston revolves Ques. 790.— How are the blades or paddles fitted to and held in the rotor, and cylinder of the Allis Chalmen steam-turbine? Ans. — Each blade is individually formed by specia machine tools, so that its root or foot is of an angular dove-tail shape, and at its tip there is a projection. Foundation rings are provided for each row of blade*. ^ © d a CJ +■» CO wa en be c ■ — 1 o •s 0) c o & u 03 bfl .s 354 QUESTIONS AND ANSWERS and have thus been enabled to make such a distribution of the metal, as to cause an equal expansion of all parts of the cylinder. Ques. 799. — What effect does the accidental carrying over of water with the steam, have upon the steam-tur- bine? Ans. — The sudden presence of a quantity of water with the steam, caused by foaming or priming of the boil- ers, would cause no more serious results than the slowing down of the turbine during the time necessary to permit the water to be discharged from the exhaust end. Ques. 800. — What may be said in general of the steam-turbine? Ans. — It has passed through the experimental stage, and has come to the front, as an efficient power pro- ducer, having a bright future before it. DE LAVAL STEAM TURBINE. CLASS C. Ques. 801. — In what respect does the Class C De Laval Turbine differ mainly from the regulation type of De Laval Turbine referred to on pages 304 to 314? Ans. — In the construction of the buckets, and guide vanes ; also in the accessibility of the parts. Ques. 802. — Describe the construction of the buckets in this type of steam Turbine. Ans. — The buckets are made of nickel-bronze and are secured to the rim of the wheel by bulb shanks. They may also be replaced individually without disturb- ing other buckets. STEAM TURBINE FUNDAMENTAL PRINCIPLES 355 Ques. 803. — Describe the construction of the guide vanes in the Class C Turbine . Ans. — The guide vanes are of nickel-bronze, and are attached to steel retaining rings in the same manner as are the rotating buckets. Ques. 804.— What can be said in favor of this meth- od of attaching guide vanes, and buckets ? Ans. — It is superior to the common method of cast- ing these important parts of the turbine in with a por- tion of the casing, or the rim of the wheel. Ques. 805. — Give a reason for this. Ans. — If guide vanes, or buckets that are cast in, should become corroded, and need replacing, it is neces- sary to replace a portion of the casing, or the wheel rim, in order to bring the turbine back to its original effi- ciency. Ques. 806. — What amount of work is necessary in order to replace one, or more of these parts in the Class C De Laval Steam Turbine? Ans. — See answer to question 802. Ques. 807. — How are changes in boiler pressure, or in vacuum, provided for in the Class C Turbine ? Ans. — By simply replacing the nozzles by others de- signed for the new ratio of expansion. Ques. 808. — Is this possible in turbines in which the nozzles are a permanent part of the main turbine struc- ture? Ans. — It is not. Ques. 809.— How is the speed of the Class C De Laval Turbine controlled? 356 QUESTIONS AND ANSWERS Ans. — Two governors are provided, one of which is called the emergency governor. Ques. 810. — In what way may a turbine governor be rendered useless, and still retain all its parts unbroken? Ans. — By the valves becoming clogged with scale, waste or other foreign matter. Ques. 811. — What special provision does this type of steam turbine possess for the prevention of accidents in case the emergency governor should fail ? Ans. — The wheel itself is designed to withstand the highest speed, and in addition to this precaution, the en- tire wheel is encircled by a steel ring which would ef- fectually prevent the penetration of detached parts. Ques. 812. — How may the rotating parts of the De Laval Class C Turbine be removed entirely from the casing when repairs are necessary ? Ans. — By lifting the casing cover, and loosening and removing the bearing caps of the shaft. Ques. 813. — Why is it possible to maintain indefinite- ly a high steam economy with this type of steam tur- bine? Ans. — This is due to the fact that provision is made for the easy and quick replacement of those parts sub- ject to wear. Ques. 814. — Is the Type C De Laval Steam Turbine built in the larger sizes? Ans. — It is not, at present. Ques. 815. — Mention some of the principal uses fcr which this turbine is adapted. Ans. — It is especially adapted to the driving ol cen- STEAM TURBINE FUNDAMENTAL PRINCIPLES 357 trifugal pumps, blowers, exciters, and small dynamos. Ques. 816. — Describe the various conditions of op- eration for which the Class C Steam Turbine is built. Ans. — It may be operated high pressure condensing, or high pressure non-condensing. It may also be op- erated with a certain degree of back pressure. Again, it may be operated as a low pressure condensing turbine, or it may be operated on mixed flow service. EXTRACTS FROM UNITED STATES GOVERN- MENT RULES FOR THE EXAMINATION OF APPLICANTS FOR ENGINEERS' LICENSE. Ques. 817. — Give some of the principal regulations relative to Marine Engineers. Ans. — Before an original license is issued to any per- son to act as engineer, he must personally appear be- fore some local board, or a supervising inspector for examination; but upon the renewal of such license, when the distance from any local board, or supervising inspector is such as to put the person holding the same to great inconvenience, and expense to appear in person, he may upon taking the oath of office before any per- son authorized to administer oaths, and forwarding the same, together with the license to be renewed, to the local board, or supervising inspector of the district in which he resides, or is employed, have the same renewed by the said inspectors, if no valid reason to the contrary be known to them, and they shall attach such oath to the stub end of the license, which is to be retail *n 358 QUESTIONS AND ANSWERS f}le in their office. And inspectors are directed, when licenses are completed, to draw a broad pen and ink red mark through unused spaces in the body thereof, so as to prevent a6 far as possible, illegal interpolation after issue. Ques. 818. — Give in brief the classification of engi- neers on the lakes, and seaboard. Ans. — The classification of engineers on the lakes, and seaboard shall be as follows : Chief Engineer. First Assistant Engineer. Second Assistant Engineer. Third Assistant Engineer. Ques. 819. — What limitations are placed upon chief engineers, and assistant engineers relative to their spliere of action? Ans. — Inspectors may designate upon the certificate of any chief, or assistant engineer the tonnage of the vessel on which he may act." Ques. 820. — What additional restrictions are placed upon assistant engineers? Ans. — First, second, and third assistant engineers may act as such on any steamer of the grade of which they hold a license, or as such assistant engineer on any sfeamer of a lower grade than those to which they hold a license. Ques. 821. — On what grades of steamers may assist- ant engineers act as chief engineers? Ans. — Assistant engineers may act as chief engi- neers on high pressure steamers of one hundred tons bur- STEAM TURBINE FUNDAMENTAL PRINCIPLES 359 den and under, of the class and tonnage, or particular steamer for which the inspectors, after a thorough ex- amination, may find them qualified. In all cases where an assistant engineer is permitted to act as first (chief) engineer, the inspector shall state on the face of his cer- tificate of license, the class and tonnage of steamers, or the particular steamer on which he may so act. Ques. 822. — What is the duty of an engineer when he assumes charge of the boilers and machinery of a steamer ? Ans. — His duty is to forthwith thoroughly examine the same, and if he finds any part thereof in bad con- dition, caused by neglect or inattention on the part of his predecessor, he shall immediately report the facts to the local inspectors of the district, who shall thereupon investigate the matter, and if the former engineer has been culpably derelict of duty, they shall suspend or re- i voke his license. Ques. 823. — What are some of the important require- ments regarding service that will entitle a person to re- ceive an original license as engineer or assistant engi- neer? Ans. — He must have served at least three years in the engineers' department of a steam vessel; provided that any person who has served as a regular machinist in a marine engine works for a period of not less than three years ; and any person who has served for a period of not less than three years as a locomotive engineer, stationary engineer, regular machinist in a locomotive, or stationary engine works, and any person who has 360 QUESTIONS AND ANSWERS graduated as a mechanical engineer from a duly recog- nized school of technology, may be licensed as engineer on steam vessels, after having had not less than one year's experience in the engine department of a steam vessel. Ques. 824. — What are the requirements regarding education? Ans. — No original license shall be granted any engi- neer, or assistant engineer, who cannot read and write, and does not understand the plain rules of arithmetic. Ques. 825. — What are the requirements regarding the age of an applicant? Ans. — He must be not less than twenty-one, nor more than thirty years of age in order to receive an appoint- ment as second assistant engineer. Ques. 826. — What is the penalty for making a false statement before a board of examination, or of produc- ing a false certificate as to age, time of service or char- acter? Ans. — Any person found guilty of such action will be dropped immediately. CHAPTER XI MODERN TYPES OF OIL ENGINES Ques. 827. — What is the propelling force behind the piston of an oil engine? Ans. — The heat energy evolved by the combustion of a mixture of vaporized fuel oil and air under compres- sion. Ques. 828. — How is the vaporization of the oil accom- plished ? Ans. — There are four methods, classified as follows: (1) Vaporization caused by the heat evolved by the en- gine. (2) Vaporization in an external chamber which is heated from external sources. (3) Vaporization in an internal chamber heated wholly or in part from external sources. (4) Combustion caused by the heat of highly compressed air, without previous vaporization of the oil. Ques 829. — Which one of these methods of vaporiza- tion has proved to be the most practicable and best adapted to all conditions of service? Ans. — The one belonging in class 4, owing to its sim- plicity and the absence of much auxiliary equipment, vap- orization taking place within the cylinder itself. Ques. 830. — Explain the principles of a two-cycle oil engine. Ans. — A two-cycle engine receives a charge of the :xplosive mixture, compresses it, ignites it and discharges he products of combustion while the piston makes one 361 362 QUESTIONS AND ANSWERS complete travel backward and forward. Consequently it has a working stroke or power impulse for each revo- lution of the crank shaft. Ques. 831. — Explain the principles of a four-cycle oil engine. Ans. — The four-cycle engine requires four strokes of the piston, or two revolutions of the crank shaft to com- plete the cycle. Consequently there is but one power im- pulse for every two revolutions of the crankshaft, or one working piston stroke out of four. Ques. 832. — Which is the most simple type from a constructive point of view? Ans. — The four-cycle engine. Ques. 833. — Give reasons for this. Ans. — The two-cycle engine requires a scavenging air pump to discharge the exhaust gases ; also special devices for the admission of cooling water to the piston. In the four-cycle engine this apparatus is not required. Ques. 834. — Which type of engine is the most eco- nomical in the use of fuel oil? Ans. — The fuel consumption per brake horsepower of a four-cycle engine is from 7 to 10 per cent less than that of the two-cycle engine. Ques. 835. — To which one of the four classes of oil engines as enumerated in the answer to Question 828 does the Diesel Engine belong? Ans. — To class 4. Ques. 836. — How is combustion effected in the Diesel oil engine? MODERN TYPES OF OIL ENGINES 363 Ans.— The Diesel engine admits a large volume of air to the cylinder and compresses it to such an extent that upon the introduction of oil in the form of spray by a blast of air at still higher pressure, combustion occurs at once without previous admixture. Ques. 837.— Explain in brief the action taking place within the cylinder of a Diesel engine at the beginning of a power stroke. Ans. — The oil fuel is injected through the fuel valve located in the top of the cylinder, which is vertical. This valve is opened by a cam just before the piston has reached its top center, and the injection of the fuel then commences and continues until the piston after passing the top dead center has moved through about 10 per cent of its downward stroke. Owing to the high pressure now prevailing in the combustion chamber, which is that por- tion of the cylinder space above the piston a tempera- ture is produced which exceeds the ignition point of the fuel oil, and as a result the oil, having entered the cylin- der in an extremely pulverized state, is at once ignited, and is combusted under approximately constant pressure. Ques. 838. — How is this constant pressure maintained during the period of oil admission ? Ans. — In two ways. First, by the compression pres- sure exerted by the piston on its up-stroke ; second, by the admission of compressed air under a pressure exceeding that of compression this air is required for the injection of the charge of fuel oil. Ques. 839.— What pressure is usually required for 364 QUESTIONS AND ANSWERS injection of the fuel oil into the combustion chamber of an oil engine of the Diesel type? Ans. — From 450 to 600 lbs. per sq. in., depending upon the style or make of the engine, and also upon local conditions. Ques. 840. — From whence is this supply of com- pressed air obtained? Ans. — From one or more high pressure air compres- sors usually driven from the main crosshead of the en- gine by means of links and beams. Ques. 841. — How many working cylinders are there in the ordinary Diesel oil engine? Ans. — Four, and in some cases six. Ques. 842. — Give a brief description of the construc- tion and action of the high pressure air compressors al- ready referred to. Ans. — They are of the tandem compound type, two or three stage, the low pressure stage being double acting, while the intermediate and high pressure stages are single acting. Cooling coils are provided for each stage. The piston and discharge valves of the low r pressure stage are of the flat disk type, while those of the higher stages are of the poppet type. The high pressure air is delivered to a pipe, common to all the cylinders of the engine. This pipe conveys the air through separators to the spray-air bottle from whence it leads to the fuel inlet valve bodies in the cylinder heads. Ques. 843. — What is the function of the spray-air bottle? MODERN TYPES OF OIL ENGINES 365 Ans.— The spray-air bottle has an overflow valve whereby air in excess of that necessary for spraying is passed into a bottle for storing the starting air. Ques. 844.— What is meant by the expression "start- ing air" as used in conection with the Diesel oil engine ? Ans.— In starting the engine, compressed air at about 650 lbs. pressure is admitted to those cylinders whose cranks are in the proper position for running in the de- sired direction. After the engine begins to turn, starting air is admitted to each cylinder from 10 degrees past the top center to 85 degrees past the top center until the en- gine has attained sufficient speed for fuel admission, (These remarks apply to the two-cycle type.) Ques. 845.— Give further details regarding the process of starting. Ans. — Just before fuel admission occurs clean air from the scavenging receiver has been compressed in the working cylinders to about 450 lbs. pressure, and when the engine is running normally fuel admission to each cylinder occurs as follows : When the piston on the up stroke is within 2^ degrees of the top center the fuel admission valve opens and remains open until the piston has reached a point $jy 2 degrees past the top center when the valve closes and combustion takes place. Ques. 846. — Describe events in connection with the exhaust. Ans.— The exhaust ports are uncovered 35 degrees before the piston has reached bottom center, and 2^ degrees before the exhaust ports start to be uncovered, 366 QUESTIONS AND ANSWERS two scavenger valves in the cylinder head are opened by the cam shaft, admitting fresh air at 7 or 8 lbs. pressure to the cylinder for scavenging. The exhaust ports are ag f ain covered by the piston at 35 degrees past bottom center, and compression begins. Ques. 847. — What length of time do the scavenger valves remain open ? Ans. — Until 31^ degrees after the exhaust ports are closed by the piston, from which point compression oc- curs until 2j4 degrees before the top center is reached, when the fuel valve opens as stated in answer to ques- tion 845. Ques. 848. — How is the speed of the Diesel oil engine regulated ? Ans. — By the control of certain factors in connection with its operation, as for instance, the amount of fuel injected, the amount and pressure of the compressed air required for vaporizing and injecting the fuel, also the variable admission of fuel by the vaporizer valve in ac- cordance with the amounts of air and fuel. Ques. 849. — What means are employed for controlling the amount of fuel, and the pressure of the injection air? Ans. — These factors are adjusted directly from the regulator. The air pressure supply is controlled by ad- justing a slide fitted into the suctions of the low or first stage cylinders of the air compressor. The quantity and pressure of the spray or injector air is thus easily regu- lated. The duration of opening of the fuel valve is ad- justed by the action of the regulator in conjunction with MODERN TYPES OP OIL ENGINES 367 a pilot valve which is operated by the pressure from one of the stages of the air compressor. Ques. 850. — What type of governor is employed to effect the above mentioned regulation ? Ans. — A centrifugal governor, usually of the fly wheel design. Ques. 851. — Give a brief description of the first two Diesel engines built by the United States Government. Ans. — These engines constitute the power plant of the fuel ship "Maumee." Each engine will develop 2,500 horse power at 136 r. p. m. and is of the two-cycle, six cylinder, cross head type. The scavenging pumps are mounted on the outboard columns of the even numbered cylinders and are driven by links and beams from the main cross heads. Each scavenging pump is double act- ing and draws the air from both sides of the piston. Di- rectly under each scavenging compressor, and driven by the same cross head, are two water pumps. Ques. 852. — What are the functions of these pumps? Ans. — To supply fresh water for cooling the pistons, lubrication for the main crank pin, cross head and thrust block bearing ; salt water for cooling all the engine parts except the pistons ; also service for bilge and sanitary systems. Ques. 853. — Where are the high pressure air compres- sors located on these engines? Ans. — They are mounted on the outboard columns of the odd numbered cylinders, and are driven from the main cross head by links and beams. 368 QUESTIONS AND ANSWERS Ques. 854. — Describe the construction of the bedplate and main bearings. Ans. — The bed plate consists of three cast iron sec- tions bolted together. Each section contains three main bearings consisting of a flat bottomed cast iron piece sup- ported in the bed plate saddle, a lower main bearing brass cored for water circulation capable of being rolled out of the saddle without removing the crank shaft; and a flat topped upper bearing brass. The binding cap is of forged steel, and the bearing brasses are lined with a white metal consisting of 80 per cent tin, 15 per cent antimony and 5 per cent copper. Ques. 855. — What is the diameter of the crankshaft for the engines of the "Maumee?" Ans. — i$y 2 inches. It is made of special forgings having a tensile strength of 71,000 to 78,000 lbs. and an elongation of 18 to 20 per cent. The sections are bored hollow and drilled for the forced lubrication system. Ques. 856. — Describe the piston rod. Ans. — The piston rod is of forged steel and bored hollow for the passage of the fresh water to and from the working piston. Ques. 857. — Describe in brief the construction of the piston. Ans. — The piston is divided into two parts, the work- ing piston, which consists of a specially lined casting cored for water circulation and ribbed for strength ; and a lower iron casting which is bolted to the piston rod. The two sections are not bolted to each other, although both are MODERN TYPES OF OIL ENGINES 369 secured to the rod. The working piston is dished on top and is machined with greater clearance at its top than at its bottom. It carries six cast iron snap rings varying in width from the top to the bottom, the upper rings being given more clearance than the lower ones on account of the greater heat. The lower part of the main piston merely serves as a guide and is fitted with two cast iron snap rings at the bottom. Ques. 858. — What is the function of these two snap rings ? Ans. — To prevent the escape of gas into the engine room. Ques. 859. — Describe the process of cooling the piston while the engine is running. Ans. — Fresh water coming up from the rod enters the central compartment of the piston, passes out toward the side through cored passages at the top and finally reaches the concentric space in the piston rod through four pipes set at 45 degrees, returning from the highest point of the water space, and thus insuring a flow of water along the hottest parts of the piston. Ques. 860. — What advantage does this system of cool- ing possess ? Ans. — The advantage of simplicity. Ques. 861. — What is the disadvantage in connection With it ? Ans. — The disadvantage of heating the water entering the piston by that just leaving the piston. 370 QUESTIONS AND ANSWERS Ques. 862. — Describe the construction of the mail cylinder. Ans. — It is made up of two parts, a cast iron jackel carrying the exhaust belt and a plain cylindrical liner of special cast iron. The space between the cylinder jacket and the liner forms the water jacket for the salt cooling water. The top of the liner is securely held in place by the cylinder head, while the lower end is free to expand through the stuffing box in the bottom of the jacket which prevents salt water leakage. The surface of the liner passing through the tight fit at the exhaust belt has sev- eral shallow grooves for the purpose of collecting any slight water leakage. These grooves are about 34 mcn in depth, by )A inch in width, and are connected to pet cocks on the outside of the jacket. These are kept open and serve as leak indicators. Ques. 863. — Describe the construction of the cylinder head. .Ans. — The cylinder head is secured to the cylinder by 12 studs. The joint between the head and liner is made tight by a thin copper gasket. The head has five openings to receive the valve cages. The center one is for the fuel valve, and the two largest openings on either side are for the scavenging valves ; the inboard opening is for the cylinder release valve, and the outboard open- ing is for the air starting valve. Ques. 864. — How is the cylinder head cooled ? Ans. — It is divided into two compartments for cool- ing. The water from the cylinder jacket is by-passed MODERN TYPES OF OIL ENGINES 371 around the cylinder head joint into the lower compart- ment of the head through which it must all go before rising to the upper compartment. Ques. 865. — Describe the fuel spray valve and its operation. Ans. — This valve is located in the center of the head. It consists of a cast iron body, within which is housed a long forged steel needle valve that opens upward. This valve is opened by the cam shaft, and is ordinarily held shut by heavy springs. The compressed air for fuel in- jection is connected to the valve body at the top and maintains a constant pressure in the valve body, there being a safety valve in the air line at each cylinder. Ques. 866. — Where is the camshaft located? Ans. — It is located on the inboard side of the engine and is in four sections. The first section carries the cams for cylinders 1 and 2 ; the second the governor, the cam for cylinder No. 3 and an eccentric for driving the fuel pump for cylinders 1 and 2 ; the third carries the cam for cylinder No. 4 and the gear that transmits the motion of the vertical shaft to the cam shaft which is horizontal; and the fourth carries the cams for cylinders 5 and 6. Ques. 867. — Of what does the high pressure air sys- tem for one engine consist? Ans. — It consists of three attached air compressors, the spray flask of about 5 cubic feet capacity, the six start- ing-air flasks with a capacity of about 180 cubic feet, air separators, piping and release valves. There is also one auxiliary air compressor independently driven by steam, 372 QUESTIONS AND ANSWERS with a capacity equal to that of one of the attached compressors. Ques. 868.— What is the function of the auxiliary a compressor ? Ans.— To provide air for charging the spray and stai ing flasks when all the other air is gone. Ques. 869.— Of what does the salt water cooling sy tern consist? Ans.— Two attached plunger pumps under the middl scavenger pump and an independently driven steam plut ger pump, together with the necessary piping and connec tion. Both attached pumps have a common suction, am each is of sufficient capacity to supply the salt wate system at normal power. Ques. 870.— Describe the course taken by the sal water used for cooling. Ans.— It is discharged by the pumps into a large mail at the back of the engine beneath the floor plate. From this main a branch leads upward to the bottom of each intercooler for the high pressure air compressors and to the bottom of each cooler in the scavenger pump cast- ings. The main then continues around the forward end of the engine, where a branch leads upward on the out- board side of the main bearing cap. Continuing around to the inboard side of the engine under the floor plate, the main supplies a branch to the bottom of each ahead crosshead guide. A collecting main runs around the en- gine at the height of the cylinder base. On the inboard side it receives the return cooling water from the main MODERN TYPES OF OIL ENGINES 373 bearing and thrust block. On the outboard side of the engine it receives the cooling water from the scavenger cooler. Ques. 871. — Describe the further course of the cool- ing water at the back of the engine. Ans. — Back of the engine all the water in the collect- ing main enters the bottom of the main cylinder jackets, two' branches leading to each jacket. The cooling water leaving the high pressure inter-coolers of each compressor, is carried to the lower end of the jacket of the middle stage air compressor cylinder, from whence it is forced upward into the jacket of the low stage cylinder through two ferrules set partly into each cylinder at the joint. From the low stage jacket, the water enters the high stage jacket through two by-passes around the cylinder joint, and from the high stage jacket the water is forced into the high stage cylinder head through two by-passes around the joint between the head and cylinder. From the head of each high stage cylinder the water is led into the exhaust pipe jacket and from here is finally discharged into an overboard discharge main. Ques. 872. — How is the fresh cooling water carried to the piston ? Ans. — Fresh cooling water is drawn from a compart- ment in the double bottom, where it is cooled, to the piston through a swivel joint on the after beam bearing, a pipe secured to the beam, another swivel joint on the cross- head end of the beam, the main crosshead, a nickle-steel pipe running up through the center of the piston rod, and 374 QUESTIONS AND ANSWERS four collecting pipes reaching the highest part of th| outer cooling space in the piston, and from thence retun ing through the concentric space in the piston rod, finally reaches a discharge main back of the engine vil links and beams and the forward end of the crosshead 11 a manner similar to that by which it entered. Ques. 873. — Describe the facilities for maneuverinj the engine. Ans. — On the operator's platform is the maneuverinj control wheel, which controls the starting, stopping anc reversal of the engine by means of compressed air. Thu wheel also cuts off the fuel and spray air from the cylin ders during maneuvering and until the engine is turning over in the desired direction. Above the maneuvering control is a dial on which a pointer indicates the running position of the engine. There is also a hand cutout by which the engine can be instantly stopped. It operates to raise the suction valves of the fuel pumps thus rendering them inoperative. Ques. 874. — What other facilities are provided for hand control? Ans. — A fuel control wheel by means of which the quantity of fuel pumped into each cylinder may be con- trolled. A dial and pointer above the fuel control indi- cate in eight equal steps the quantity of fuel pumped, from a minimum to the maximum. Coming out from the shaft of the fuel control wheel is the needle stroke con trol which varies the stroke of the fuel spray needle from maximum to minimum. There is also a hand control f*»r MODERN TYPES OP OIL ENGINES 375 the high pressure a i r which regulates the opening of the suctions of the low stage cylinders of the air compres- sors. The quantity and pressure of the spray air is thus controlled. Ques. 875. — What kind of oil is used in engines of the Diesel type ? Ans. — Crude petroleum having a heat value of 18,000 to 20,000 b. t. u. per pound. Ques. 876. — How does fuel oil compare with coal in heat value ? Ans. — To compare the fuel consumption per brake horse power of an oil engine with that of a steam engine one pound of oil may be considered as equivalent to ij4 lbs. of coal. Ques. 877. — What is the usual rate of fuel oil con- sumption per brake horse-power-hour for oil engines? Ans. — Recent tests of a 500 horse power engine of the Diesel type show an average oil consumption of 0.483 lbs. of oil per brake horse-power-hour. Ques. 878. — Did the load on the engine vary to any extent during the course of these tests ? Ans. — It varied from 25 per cent below, to 113 per cent above normal rating. Ques. 879. — Regarding efficiency, what can be said of the Diesel type oil engine? Ans. — It gives a high efficiency in service, in fact is said to be one of the most efficient prime movers known at present (1917). 376 QUESTIONS xVND ANSWERS Ques. 880. — Is auxiliary ignition apparatus required in the Diesel engine? Ans. — It is not. The fuel oil is ignited by the tem- perature of compression. This fuel does not explode as in a gasoline engine, but burns in the cylinder, and by the heating and expansion of the air and gases within the cylinder, the piston is forced out on its working stroke. Ques. 881. — What other type of oil engine resembles the Diesel engine in the process of ignition? Ans. — The Hornsby-Ackroyd Engine. In this engine the oil is first introduced into a vaporizer located at the back or side of the cylinder, the heat necessary for vapor- ization being supplied at starting by external lamps, but when the engine is in operation the continued combustion of the fuel supplies sufficient heat for both vaporization and ignition. Ques. 882. — How is the air necessary for combustion introduced into the cylinder? Ans. — This being a four-cycle engine, air enters the cylinder during the suction period of the cycle. Thus the cylinder becomes charged with air, and the vaporizer becomes filled with a spray of oil simultaneously. Dur- ing the compression period the air in the cylinder, being forced into the vaporizer, becomes properly mixed with the oil and an explosive mixture is formed. Ques. 883. — How is the oil fuel supplied to the Hornsby-Ackroyd engine ? Ans. — By an oil pump, the stroke of which is under MODERN TYPES OP OIL ENGINES 377 control of the governor, thus giving close regulation of speed. This engine is built either horizontal or vertical. Ques. 884. — Describe some of the peculiar features of the Remington Oil Engine. Ans. — This engine is valveless, the gases being moved into and out of the cylinder through ports uncovered by the movement of piston, which itself also performs the function of a pump. Ques. 885. — How does this action take place? Ans. — The engine is of the vertical type, operating on the two-stroke cycle. On the up-stroke of the piston a partial vacuum is created in the enclosed crankcase, and when the bottom of the piston uncovers the inlet port which is directly under the exhaust port, the air rushes in and fills the crankcase at atmospheric pressure. On the next down stroke this air is compressed in the crank case to four or five pounds pressure ; while at the same time the mixture of oil-vapor and air already in the cylin- der is burning and expanding, thus forcing the piston down on its working stroke. When the piston approaches the end of its down stroke it uncovers the exhaust port on the side of the cylinder, permitting the burnt charge to escape to the atmosphere. Immediately after this event takes place the transfer port on the opposite side of the cylinder is uncovered by the piston, thus allowing a por- tion of the air compressed in the crank case to pass into the cylinder, where it is deflected upwards by the shape of the piston, and caused to fill the cylinder, thereby expell- ing the remainder of the burnt charge. The piston now 378 QUESTIONS AND ANSWERS starts on another up-stroke, compressing the fresh charg of air into the hot cylinder head. Ques. 886. — How is the fuel oil admitted to th cylinder ? Ans. — When the piston is near the end of the upwan compression stroke, an oil pump mounted on the crank case and controlled by the governor injects the prope amount of oil through the nozzle into the space above th piston now occupied by the compressed and heated aii This oil is atomized in a vertical direction through ai opening near the end of the nozzle, and is thus vaporizec and gasified before it reaches the cylinder walls. Ques. 887. — How is ignition effected in the Remingtoi oil engine? Ans. — By means of a nickel steel plug located in th< center of the cylinder head, and kept red hot by the ex- plosions. By the burning of the oil spray in the com- pressed air the pressure is increased and the piston i: now forced downward on its power stroke. Ques. 888. — Of what type is the Remington oil en- gine? Ans. — It is a two-cycle engine, since the operations hitherto described take place with every revolution of th crank shaft. Therefore each down stroke is a power stroke. Several sizes of this engine are built especially to operate on semi-refined fuels, such as distillate, solar oil, gas oil, etc. All sizes of Remington oil engines are built to operate on all grades of ordinary kerosene oil. MODERN TYPES OF OIL ENGINES 379 Ques. 889. — Does the use of kerosene and other distil- ates of petroleum as fuel for internal combustion engines five satisfactory results? Ans. — It does, provided the engine has been designed for using that grade of fuels. Ques. 890. — What are the principal characteristics of the Nordberg high compression oil engine? Ans. — This engine ignites its fuel of its own compres- ion. It therefore requires no hot bulb, torch, or other auxiliary ignition device. It has no valve gear or valves subject to the working pressure and heat, there being but one valve on the engine and it is located at a point where it is not affected by the heat. It operates its own fuel pump by means of an eccentric on the crank shaft. Ques. 891. — Of what type is the Nordberg engine? Ans. — It is of the two-cycle type. Ques. 892. — Describe the operations of the exhaust, and the admission of the scavenging air to the cylinder. Ans. — Near the end of the working stroke the piston uncovers the exhaust ports, and after these have been opened a certain amount, the scavenging port is also un- overed by the piston and fresh air from the scavenging space is blown into the cylinder and through the exhaust openings, thus cleaning out the burned gases and provid- ing fresh air for the next cycle. Ques. 893. — Describe the processes of compression md ignition in this engine. Ans. — With the piston on the return stroke, the air entrapped in the cylinder is compressed to a pressure of -* 380 QUESTIONS AND ANSWERS approximately 450 pounds, and at the end of the strol fuel oil is injected through the fuel nozzle located in t cylinder head, and ignition occurs, due to the heat the compressed air. Ques 894. — How is this fuel supplied to the noz; under the required pressure? Ans. — By the fuel pump driven by an eccentric on t crank shaft. Ques. 895. — How is the quantity of fuel oil requir by the engine controlled in order to maintain a unifoi speed at varying loads ? Ans. — By means of a centrifugal shaft governor whi acts on the fuel pump through a rod, and determines t amount of oil which is by-passed by the pump, that the amount not used. Ques. 896. — Describe the construction of the fu pump and appurtenances. Ans. — This oil pump is a simple plunger pump, of very strong construction. The plunger receives its m< tion from a driving cam operated by an eccentric on t crank shaft. The plunger has a constant stroke, and t capacity of the pump is for a much greater quantity oil than the engine would ever use, but as before state< the amount of oil actually pumped to the fuel nozzle always under the control of the shaft governor. The fu pump and driving cam are located in a cast iron box ke] filled with oil, so that the pump operating mechanism continually submerged in this oil. MODERN TYPES OF OIL ENGINES 381 Ques. 897. — How is the Nordberg oil engine started ? Ans. — By means of compressed air at a pressure of 250 pounds admitted to the cylinder, behind the piston. Ques. 898. — Describe the starting valve, and its opera- ;ion. Ans. — The starting valve is of the quick opening type, ind is manipulated by the operator who gives the cylinder ;he proper charge of compressed air for the right portion )f the stroke. After one or two revolutions the operator starts the fuel pump by means of a lever which throws he pump cam into connection, thus starting the flow of fuel oil to the cylinder. The engine usually fires on the hird or fourth revolution. Ques. 899. — How is compressed air at 250 pounds Dressure supplied to the engine for starting? Ans. — From a welded steel storage tank kept charged kr means of a two-stage air compressor furnished with the engine. This air compressor is designed for a work- ng pressure of 250 pounds, and is provided with an inter- :ooler. It may be driven by a belt from the engine, or from a motor or line shaft. Ques. 900. — Does this compressor run continuously? Ans. — It does not. It is used only for short periods when recharging the air-storage tank after the oil engine las been put in operation. Ques. 901. — How is the scavenging air supplied to the cylinder? Ans. — The space between the piston and the front end of the cylinder is used as a compression space. On the . 382 QUESTIONS AND ANSWERS back stroke of the piston, air is drawn into this spa through a piston valve driven by an eccentric on the mi crank shaft. On the forward stroke of the piston this i is slightly compressed in the space between cylinder he and piston, until at the end of the stroke, the scavengi port is opened by the piston, as already described. Ques. 902. — Describe the action of the fuel nozzle. Ans. — The fuel nozzle atomizes the fuel oil by din mechanical pressure from the fuel pump ; and not means of highly compressed air. Ques. 903. — What types of fuel oil can be used the Nordberg oil engine? Ans. — The leading types, such as regular fuel o kerosene, and other distillate. Ques. 904. — Describe the method of providing t required storage for this fuel. Ans. — A reservoir fitted with compartments for t different types of fuel oil is provided. This reservoir kept supplied with fuel oil by means of a small pum driven from the engine. This pump lifts the fuel oil froi the underground storage tank, and delivers it into th reservoir which stands at a level sufficiently high to allo^ the fuel oil to run by gravity to the fuel pump on the en gine. The overflow from this fuel reservoir can be pipe back to the underground tank. Ques. 905. — At what times is kerosene or distillat used as fuel on this engine? Ans. — Usually in starting, when the regular fuel oi is heavy or viscous. ^ MODERN TYPES OF OIL ENGINES 383 Ques. 906. — What changes are required in order to change from distillate to the regular fuel, or vice versa? Ans. — It is necessary only to turn a three-way cock. Ques. 907. — How is the cylinder cooled? Ans. — It is water jacketed, and the jacket spaces are provided with hand-holes for cleaning. Ques. 908. — What quantity of water is required for cooling? Ans. — From four to seven gallons per brake horse power hour, depending upon the temperature of the water. Ques. 909. — Is the Nordberg oil engine equipped with a cross-head? Ans. — It is provided with a cross-head running in bored guides. Ques. 910. — Of what type is the Lawson kerosene engine ? Ans. — It is of the vertical, four-cylinder type ; de- signed primarily to operate on kerosene, although it may be operated on power distillate, or gasoline. Ques. 911. — How is the fuel for this engine admitted to the cylinders? Ans. — By means of inlet poppet valves, located in the cylinder heads. These valves are operated by overhead tappets which receive their motion from a cam-shaft. Ques. 912. — How are the products of combustion ex- hausted from the cylinders? Ans. — By means of exhaust valves also located in the cylinder heads, and operated by the same cam-shaft. 384 QUESTIONS AND ANSWERS Ques. 913. — Describe the fuel feeding device in v on the Lawson kerosene engine. Ans. — It is of the venturi atomizer type, the functi of which is to maintain a uniformly high velocity of through a venturi tube having radial holes in its restrict portion through which the fuel is admitted by suction. Ques. 914. — How is the speed of this engine cc trolled:* Ans. — By means of a fly-ball governor, driven from bevel gear on the cam-shaft, and acting to control the a mission of fuel to the cylinder. The governor acts rectly upon a two-ported barrel valve whose ports coinci with the ports in the valve housing when the engine is rest. When the engine has attained full speed the ban valve is rotated by the governor, thereby closing the low port and decreasing the amount of fuel and air admitt into the cylinder. At the same time the upper port also closed, deflecting more air through the nozzle a: maintaining practically a constant velocity of air at t point. Ques. 915. — How is adjustment made for no load ai full load? Ans. — By means of a fuel needle valve, in conjun tion with a butterfly valve in the air inlet. Ques. 916. — Is each cylinder equipped with a fu feeding device such as described? Ans. — A separate carburetor, or atomizer as it called, is provided for each cylinder, in order to prevei liquefying of the fuel before it reaches the cylinder. MODERN TYPES OF OIL ENGINES 385 Ques. 917. — What provision is made to prevent pre- mature ignition on full load? Ans. — A water feed is provided for this purpose. Ques. 918. — Describe the cooling system in use on the Lawson engine. Ans. — The cylinders and cylinder heads are water jacketed. The heads carry the valves which seat directly against the water jacket, thereby bringing the water as close as possible to the valve heads, and thus prevent undue heating of the same, which is exceedingly detri- mental in a kerosene engine. Ques. 919. — What kind of piston is in use on this engine ? Ans. — The pistons are of the barrel or trunk type, each piston being equipped with four rings, three on its extreme upper end, and one on its extreme lower end. Ques. 920. — Describe the valve operating mechanism. Ans. — The cam-shaft is carried in five bronze bear- ings within the crank-case. The cams for each cylinder, viz., exhaust, inlet and igniter, are integral, and keyed to the cam-shaft. The push-rods acting upon the valve tappets are provided with hardened slides which are fitted with rollers for contact with the cams. The tappet levers are adjustable for wear. Ques. 921. — How is cooling water supplied to the Lawson kerosene engine? Ans. — By means of a circulating pump mounted on the engine, and driven directly from the crank-shaft through the medium of a chain and sprocket gear. 386 QUESTIONS AND ANSWERS Ques. 922. — Describe the course of the water in its circulation through the jacket? Ans. — Water is admitted to the cylinder jacket on one side, directly in line with the lower line of the com- pression chamber, the cooling water not passing directly through the lower portion of the jacket, owing to the fact that the exhaust water is taken out of the top of the head by means of a polished brass manifold which is provided with expansion joints to avoid cracking. Ques. 923. — What system of ignition is used on this engine ? Ans. — The ignition is of the standard make and break type, and is arranged with two timing adjustments, one individual, and one simultaneous. The latter adjust- ment is used in starting, and is so arranged that all igniters may be stopped by shifting the timing lever. Directly over the igniter is mounted an insulated brass bar which is charged with current from a gear-driven magneto, alternating current. The igniters are provided with a spring coming in contact with this brass bar, thus eliminating wiring connection. Ques. 924. — How is the engine started? Ans. — An air starter is used which admits air into each cylinder through an automatic air valve in the head. As soon as the engine fires, the pressure within the cylinder holds this valve in its seat, thereby preventing admission of air. The starter consists of a main body, having four radial air ports connected by piping to the different cylinders. These ports are covered, and un- MODERN TYPES OF OIL ENGINES 387 covered by a rotary disc valve having one port. This disc is held on its seat by the pressure of the air and is free to rotate when the air is shut off. The starter is connected to the end of the cam-shaft by means of a flexibld coupling. To start the engine, all that is necessary is to turn it on the center and open the air cock, no shifting of cams and gears being required. Ques. 925. — What kind of fuel is used in starting? Ans. — Gasoline is used until the engine has attained full speed, when it may be turned over until it runs on kerosene. Ques. 926. — Of what type is the Fairbanks-Morse marine oil engine? Ans. — It is a two-stroke cycle engine, securing igni- tion from a moderate compression and localized heat. Ques. 927. — Where is the combustion chamber lo- cated ? Ans. — Entirely outside the cylinder. The fuel oil is injected into this chamber. Ques. 928. — Does any portion of the fuel oil enter the cylinder? Ans. — Not in the form of oil. Ques. 929. — What advantage is gained by this action ? Ans. — The lubrication of cylinder and piston is not impaired. Ques. 930. — Is the electric spark used for ignition in this engine? Ans. — No. The heat retained in the combustion cham- ber is sufficient to cause ignition. INDEX A PAGE Absolute pressure 286 Absolute zero 288 Adiabatic curve 290-303 Admission — Instant of 188 Air- Admission to furnace 85 Advantage in heating 131 Composition of 17 Locks, object of 124-126 Product of 18 Volume required for combustion 17-19 Air pump — Description of 225-226 Dimensions of 218 Types of 224-225 Valves for 227 Angular advance 191 Apparatus — Condensing, for steam turbines 338 Ash- Dry 144 Ash ejector 127 Ash pits — Closed 123 B Blow-off- Surface 112 Bottom 113 Boilers — Bracing 66 Back arch for horizontal tubular 82-83 INDEX PAGE Connecting up 138-139 Feed pump 97 Heating surface 86-87 Horsepower 86-87 Leaks 135 Marine 169 Material 65 Operation 128 Rivets 66 Seams, welded 76 Steam space of 110 Types of 25-64 Washing out 134-136 Boiler construction 65 Boyles law 14, 290 Braces 66 Bucket speed 304 Bursting pressure 77 C Calorimeter 145 Carbon 17 Carbon, monoxide 21 Clearance 302 Piston 289 Steam 289 Coal — Composition of 22 Consumption of 156 Dry 145 Heating value of one pound 24 Method of ascertaining cost 154-155 Moisture in 145 Cocks — Asbestos packed 117 Gauge 104 Hydrometer 114 Combustible — Weight of 145 Combustion 17 INDEX PAGE Rate of 20 Compression 302 Advantage of 189 Instant of 188 Meaning of 289 Condensation 233-235 Cylinder 293 Condenser — Advantages in use of ' 214-215 For steam turbines 338 Jet 217 Siphon 216 Surface 213 Corrosion 168 Cause of 169 Prevention of 170 Curves — Adiabatic 290-30! Expansion 290 Isothermal 290 Cut-off- Adjustable 2& Fixed 29£ Instant of 18£ D Dampers — Funnel 117-111 Dead-center 202-20* Diagram — Characteristics of 29( Details of 285-28( Method of taking 284-28^ Distillers 253-2^ Draught li Artificial 19-125 Essentials for 15(] Forced 122-lfl Measuring 150-15! Natural 19, 191 INDEX PAGE Systems 131-132 Draught gauge 150 Dry-pipe 112 Dynamics 291 Dynamos — For marine service 260-264 E Eccentric — Description of 190 Position 191-204 Throw of 191 Efficiency — Plant 292 Steam 291 Ejector — Ash , 127 Engine — Automatic 294 Classes of 173-178 Four- valve 185 Marine 192 Variable cut-off 294 Evaporation — Equivalent 152 Factor of 153-154 Of water 152 Evaporation tests — Apparatus for 141 Data for 148 Duration of 148 Method of conducting 141 Objects of 140 Preparing for 146-147 Evaporators — For marine service 253-254 Exhaust steam — Disposal of 337 Expansion 13 Advantages of 179 INDEX PAGE Curve 290 Joint 116 Rate of 181 Ratio of 288 F Feed pumps 97 Feed water — Average temperature of 145-146 Heaters 247-248 How supplied to boiler 139 Stoppage of supply 140 Fire cleaning 129 Firing — Hand 130 Fire-main 269 Fire tools 128 Foot pound 290 Force 291 Forced draught 122-124 Friction — In steam turbines 341 Fuels 167 Funnel-stays 119 Funnel cover • . 121-122 Furnace — Corrugated 26- 78 Petroleum 165 Temperature of 21 Fusible plug 106-107 G Galvanic action 170 Cause of 170 Prevention of 171 Gases — Escaping 146 Gauge — Cock 104 Steam 107-110 INDEX Governor — page Adjustment of 209-210 Curtis steam turbine - 321 Dunlop's 250-253 Inertia 204-205 Isochronal 204-295 Marine 250 Object of 249 Principle of '. 249 Shaft 295 Throttling 294 Grate-bars — Dimensions of 84 Types of 85-86 Grate-surface 84-85 Grease filters 249 H Hand firing 130 Disadvantages of 156 Heat- Latent 15 Loss of 131 Mechanical equivalent of 16 Radiation of 16 Sensible 15 Specific 14 Transmission of 16 Horsepower — Boiler 155 Constant 289 Engine 289 Indicated 289 Net 289 Hot-well 228-229 Hydrometer 115 Hydrometer cock * 114 I Indicator — Care of 282-283 Construction of 272-273 INDEX PAGE Diagram 276-277 Principles of 271 Injector — Principles of 101 Isothermal curve 290 j Jet condenser 217 Jet speed 304 L Lap 187 Inside 188 Outside 188 Latent heat 15 Lead 188 Decreasing 203 Equalizing 203 Object of 189 Lighting— In marine service 265-266 Link — Block 195 Curvature of 194 Slip of 195 Link-motion 192 Locks — Air 124-126 M Mean effective pressure 287-297 Method of finding 299 Mechanical stokers 157 Types of 157-161 Moisture — In coal 145-152 In steam 145 Momentum 291 Motion- First law of 290 INDEX o Oil — PAGE Composition of 24 Engines 361 Fuel 24 Heating value of 24 Ordinates 293 Oxidation 169 P Petroleum — Advantages in use of 166-167 Analysis of 164 Heating value of 165 Method of inducting to furnace 166 Objection to 167 Piston — Balancing 202 Piston clearance 289 Piston displacement .« 289 Piston speed 289 Plaximeter 300-301 Plates- Oxidation of 169 Power — Definition 290 Pressure — Absolute 286 Absolute back 287 Back 287 Boiler 286 Bursting 77 Condenser 288 Expansion of 13 Gauge 286 Initial 286 Mean effective 287 Safe working 77 Terminal 286-287 Pumps — Air 215 Bilge 266-267 INDEX PAGB Boiler feed 241 Centrifugal 231 Circulating 230 Double acting 242-246 Dry air 339 Duplex 97 Fire, marine 267-268 For marine service 240 Location of 241 Petroleum 166 R Ratio — Of cylinder volumes 179 Receiver 179-180 Reducing motion 280 Reducing wheel 279 Re-evaporation — Cylinder 293 Refrigeration — Cold air system 255-258 Carbonic acid system 259-260 Release — Instant of 188 Rivets — Material for 66 Test for 66 Riveted joints — Efficiency of 72-74 Lloyd's rules for 75 Rocker arm — Adjustment of 206 Rules— For finding heating surface of various types of boilers. .87-89 For finding heating surface of corrugated flues 90 For finding area of lever safety valves 93 For finding speed of pump 98 For finding velocity of flow in discharge pipe 98-99 For finding required size of feed pump 100-101 For finding boiler horsepower 156 INDEX PAGR For finding weight of condensing water 234-235 Rules— For finding I. H. P 301 For finding bursting pressure 77 For finding safe working pressure 77 S Safe working pressure 77 Safety valve — Duty of 90 Types of 91-92 Scale 137 Sea water 170 Composition of 211 Disadvantages in using 212 Sensible heat 15 Separator 1 16-118 Siphon condenser 216 Siren, steam 112-113 Smoke and soot 21 Specific heat 14 Speed — Bucket 304 Jet 304 Piston 289 Regulation in Curtis turbine 321 Regulation in Hamilton-Holzworth turbine 335-336 Steam 304 Stays- Gusset 67 Funnel 119 Material for 67-68 Stay bolts 71-72 Steam 7 Action of in engine cylinder 173 Clearance 289 Consumption per H. P. hour 292 Dry 145 Gauge 107 Maximum theoretical duty of 291 Moisture in 145 INDEX PAGE Physical properties of 8-12 Relative volume of 7 Theoretical velocity of 305 Volume of 7 Wire drawn 288 Steam efficiency 291 Steam gauge 107-110 Steam siren 112-113 Steam speed 304 Steam turbine — Action of steam in 304 Advantage over reciprocating engine 305-306, 322-340 Allis-Chalmers 342 Curtis (descriptive) 314-321 De Laval (descriptive) 306-314 Friction in 341 Hamilton-Holzworth 330-337 Principles of 304 Westinghouse-Parsons 323-330 Stoke-hold — Closed 126-127 Stokers — For marine service 164 Fuel for. 164 Mechanical 157 Method of supplying coal to 163-164 Underfeed 162-163 Surface condenser — Advantages of 213 Construction and action of 219 Tubes of 221-288 T Tables- Analysis of coal 23 Areas and circumferences of circles 237-238 Capacities and speed of De Laval turbines 314 Diameters of rivets 73 Factors of evaporation 155 Lap and lead of Corliss valves 209 Physical properties of saturated steam 8-12 INDEX PAGE Proportion of triple riveted butt joints 7€ Specific heat of various substances 14-15 Water required for jet condensers 235 Weight of water at various temperatures 144 Tests- Evaporation 140 For efficiency of boiler 149-152 Test piece 65-66 Thermal unit 16 Thermo-dynamics 15 Thermometer — Hot water 146 Tubes- Cleaning 133-137 Fire 25 Galloway 37 Material for 66 Submerged 25 Water 25 Working test for 66 Turbines — Action of steam in 304 Advantage over reciprocating engine 305-306, 322-340 Allis-Chalmers 342 Curtis (descriptive) 306-314 De Laval (descriptive) 314-321 Friction in 341 Hamilton-Holzworth 330-337 Principles of 304 Westinghouse-Parsons 323-330 V Vacuum — How measured 213 How maintained 215-219 In turbine condensers 340 Meaning of 213 Perfect 287 Vacuum gauge — Mercurial 214 Spring 214 INDEX Valves— page Check 104 Double-ported 199 Piston 202 Poppet 199 Treble-ported 200 Safety 90 Setting 202-205 Sea 239 Slide 186-187 Steam stop 110 Steam stop, automatic Ill Valve gear — Joy 196 Marshall 195 Reversing 194-195 Valve-setting 202-205 Defects in 297 W Water- Evaporation per pound of coal 152 Sea 170-211 Quantity required for condenser 233 Water column 105-106 Whistle- Steam 111-112 Wire drawing 288-297 Wood- Composition of 24 Disadvantage of as fuel 24 Heating value of, in thermal units 24 Work- Definition of 291 Unit of 290 Wrist-plate — Vibration of 207 Z Zero- Absolute 288 Zinc slabs 171-1T2