Steam:
Its Generation and Use

water at or about the freezing point, t° Fahren- heit. A French “Caloric” is the heat required to raise one kilogramme of water i° centigrade, and is equal to 3.96832 British thermal units. A pressure of 1 lb. per sq. in. is exerted by a col- umn of water 2.3093 ft., or 27.71 in. high, at 62° F. The following table gives the number of British thermal units in a pound of water at different tem- peratures. They are reckoned above 32° Fah., for, strictly speaking, water does not exist below 320, and ice follows another law. WATER BETWEEN 32° AND 212ü F. Tcm. 1 Heat Weight, 1 Tem- Heat Weight, pera- Units lbs. per Units lbs. per ture Fah. 1 per lb. cub. ft. 1 Fah. per ]b. cub. ft. 32° 35 0. 3. 62.42 62.42 M5 146 113.28 I 114.28 1 61.28 61.26 8. 62.42 ’47 115.29 61.24 45 J3- 62.42 148 116.29 1 61.22 50 18. 62.41 149 117.30 61.20 52 20. 62.40 ’5° 118.31 61.18 54 22.01 62.40 151 119.31 61.16 56 24.OI 62.39 152 120.32 61.14 58 26.01 62.38 153 121.33 61.12 60 28.01 62.37 J54 122-33 61.10 62 30.01 62.36 ’55 123.34 61.08 64 32.01 62.35 156 ’24-35 61.06 66 34.02 62.34 T57 125-35 61.04 68 36 02 62.33 158 126.36 61.02 7° 38.02 62.31 159 127-37 61.00 40.02 62.30 160 128.37 60.98 74 42-03 62.28 161 129.38 60.96 76 44 °3 62.27 162 130.39 60.94 78 46.03 62.25 163 I3T-4O 60.92 80 48.04 62.23 164 132.41 60.90 82 50. °4 62.21 ’65 I33'4I 60.87 84 52. °4 62.19 166 1,34 -42 60.85 86 54-°5 62.17 167 135-43 60.83 88 i 56.05 62.15 168 136-44 60.81 QO 58.06 62.13 169 137-45 60.7g 60.06 62.11 170 i38-45 60.77 94 62.06 62.09 171 139.46 60.75 96 64.07 62.07 I72 140.47 60.73 98 66.07 62.05 x73 141.48 60.70 100 68.08 62.02 174 142.49 60.68 102 70.09 62.00 ’75 M3-5O 60.66 104 72.09 61.97 176 '44-51 60.64 I06 74-10 61.95 T77 I45-52 60.62 IO8 76.10 61.92 178 146.52 60.59 78.11 61.89 179 147-53 60.57 80.12 61.86 180 148.54 60.55 113 114 8l. 12 61.84 181 149-55 60.53 82.13 8^.11 61.83 61.82 182 183 150.56 i5!-57 60.50 60.48 JI5 116 84.13 61.80 184 152.58 60.46 117 118 85.14 61.78 185 153-59 60.44 86.14 61.77 186 154-6° 60.41 119 87.15 61-75 187 155-6' 60.39 88.15 6i.74 188 156.62 60.37 89.15 61.72 180 157-63 60.34 90.16 61.70 190 158.64 60.32 61.68 191 159-65 60.29 123 124 125 92.17 93-'7 94.17 61.67 61.65 61 63 192 *93 194 160.67 161.68 162.69 60.27 60.25 60.22 127 128 95.18 q6. 18 61.61 61.60 195 196 163.70 164.71 60.20 60.17 129 130 *3* fß2 133 134 135 97->9 98. !9 1 99.20 61.58 61.56 61.54 107 198 199 165.72 166.73 167.74 60.15 60.12 60.10 100.20 IOI.21 102.21 IO3.22 61.52 61.51 61.49 61.47 200 201 202 203 168.75 169.77 170.78 1 I7I-79 60.07 60.05 60.02 60.00 1 >6 104.22 61.45 204 ; 172.80 59-97 137 138 139 140 141 I42 M3 144 105.23 106.23 61.43 61.41 205 206 >73-8t 174-83 59-95 59-92 107.24 108.25 109.25 110.26 61.39 61.37 61.36 61.34 207 208 2(X) 210 V5-84 176.85 177.86 178.87 56.89 59-87 59-84 59-82 111.26 112.27 61.32 61.30 2" 212 179.89 180.90 59-79 59-76 HEATING FEED-WATER. The feed-water furnished to steam boilers has to be heated from the normal temperature to that of the steam before evaporation can com- mence, and this generally at the expense of the fuel which should be utilized in making steam. This temperature at 75 lbs. pressure is 320°, and if we take 6o° as the average temperature of feed, we have 260 units of heat per pound, which, as it takes 1151 units to evaporate a pound from 6o°, represents a loss of 22.5 per cent, of fuel. All of this heat, therefore, which can be imparted to the feed-water is just so much saved, not only in cost of fuel, but in capacity of boiler. But it is essential that it be done by heat which would otherwise be wasted. All heat imparted to feed- water by injectors and “live-steam heaters,” comes from the fuel and represents no saving. There are two sources of waste heat available for this purpose — exhaust steam and chimney gases. By the former, water may be heated to 2oo°, or possibly to 210°, in a well proportioned heater. The gases going to the chimney carry off on an average, according to good authority, 51 Per cent, of the fuel, and in the most economical boiler this cannot be reduced below 12 percent. Some proportion of this is always available for heating the feed-water, by what are known as ‘ ‘ economizers, ’ ’ and frequently it may be carried nearly to the temperature of high pressure steam, making a saving in some instances of 20 per cent. The more wasteful the boiler, the greater the benefit of the economizer; but for large plants it is always a valuable adjunct. In many cases water heated by exhaust steam may be still further heated in an economizer, to advantage. SAVING OF FUEL BY HEATING FEED-WATER. UN PER CENT.) (steam at sixty pounds.) Initial Tem. of Water. FINAL TEMPERATURE OF FEED-WATER. 120 140 160 180 200 250 300 32° 7-5° 9.20 10.90 12.36 14 -3° 19.03 22.90 35 7.25 8.96 10.66 12.09 14.09 18.34 22.60 4° 6.85 8.57 10.28 12.00 I3-7I 17-99 22.27 45 6-45 8.17 9-9° 11.61 T3-34 17.64 21.94 5° 6.05 7.71 9-5° 11.23 13.00 17.28 21 .61 55 5.64 7-37 9.06 10.85 13.60 16.93 21.27 60 5.23 6-97 8.72 10.46 12.20 16.58 20.92 65 4.82 6.56 8.32 10.07 11.82 16.20 20.58 7° 4-4° 6.15 7.91 9.08 Ji-43 15-83 20.23 75 3.98 5-74 7-5° 9.28 11.04 15-46 19.88 80 3-55 5-32 7-09 8.87 10.65 15-08 19-52 85 3.12 4-9° 6.63 8.46 10-25 14.70 19.17 9° 2.68 4-47 6.26 8.06 9-85 M • 32 18.81 95 2.24 4.04 5-84 7-65 9-44 13-94 18.44 100 1.80 3.61 5-42 7-23 9-°3 1.3-55 18.07 IIO .90 2-73 4-55 3-38 8.20 12.76 17.28 120 0 T.84 3-67 5-52 7-36 ii-95 16.49 130 .92 2.77 4-64 6-99 II. 14 15-24 140 150 160 170 180 IQO 200 0 1.87 •94 0 3-75 2.83 1.91 .96 0 CS CM 01 O'O O 0 0 t^OO 00 O O 1 tn m o m 10.31 9-46 8-59 7.71 6.81 5-9° 1 4.8s 14.99 14.18 13-37 12.54 11.70 10.82 9-93