| Initial temp. of feed. | Initial temp. of feed. | |||||||||||
| Pressure of steam in boiler, lbs. per sq. inch above atmosphere | ||||||||||||
| 0 | 20 | 40 | 60 | 80 | 100 | 120 | 140 | 160 | 180 | 200 | ||
| 32° | .0872 | .0861 | .0855 | .0851 | .0847 | .0844 | .0841 | .0839 | .0837 | .0835 | .0833 | 32 |
| 40 | .0878 | .0867 | .0861 | .0856 | .0853 | .0850 | .0847 | .0845 | .0843 | .0841 | .0839 | 40 |
| 50 | .0886 | .0875 | .0868 | .0864 | .0860 | .0857 | .0854 | .0852 | .0850 | .0848 | .0846 | 50 |
| 60 | .0894 | .0883 | .0876 | .0872 | .0867 | .0864 | .0862 | .0859 | .0856 | .0855 | .0853 | 60 |
| 70 | .0902 | .0890 | .0884 | .0879 | .0875 | .0872 | .0869 | .0867 | .0864 | .0862 | .0860 | 70 |
| 80 | .0910 | .0898 | .0891 | .0887 | .0883 | .0879 | .0877 | .0874 | .0872 | .0870 | .0868 | 80 |
| 90 | .0919 | .0907 | .0900 | .0895 | .0888 | .0887 | .0884 | .0883 | .0879 | .0877 | .0875 | 90 |
| 100 | .0927 | .0915 | .0908 | .0903 | .0899 | .0895 | .0892 | .0890 | .0887 | .0885 | .0883 | 100 |
| 110 | .0936 | .0923 | .0916 | .0911 | .0907 | .0903 | .0900 | .0898 | .0895 | .0893 | .0891 | 110 |
| 120 | .0945 | .0932 | .0925 | .0919 | .0915 | .0911 | .0908 | .0906 | .0903 | .0901 | .0899 | 120 |
| 130 | .0954 | .0941 | .0934 | .0928 | .0924 | .0920 | .0917 | .0914 | .0912 | .0909 | .0907 | 130 |
| 140 | .0963 | .0950 | .0943 | .0937 | .0932 | .0929 | .0925 | .0923 | .0920 | .0918 | .0916 | 140 |
| 150 | .0973 | .0959 | .0951 | .0946 | .0941 | .0937 | .0934 | .0931 | .0929 | .0926 | .0924 | 150 |
| 160 | .0982 | .0968 | .0961 | .0955 | .0950 | .0946 | .0943 | .0940 | .0937 | .0935 | .0933 | 160 |
| 170 | .0992 | .0978 | .0970 | .0964 | .0959 | .0955 | .0952 | .0949 | .0946 | .0944 | .0941 | 170 |
| 180 | .1002 | .0988 | .0981 | .0973 | .0969 | .0965 | .0961 | .0958 | .0955 | .0953 | .0951 | 180 |
| 190 | .1012 | .0998 | .0989 | .0983 | .0978 | .0974 | .0971 | .0968 | .0964 | .0062 | .0960 | 190 |
| 200 | .1022 | .1008 | .0999 | .0993 | .0988 | .0984 | .0980 | .0977 | .0974 | .0972 | .0969 | 200 |
| 210 | .1033 | .1018 | .1010 | .1003 | .0998 | .0994 | .0990 | .0987 | .0984 | .0981 | .0979 | 210 |
| 220 | — | .1029 | .1019 | .1013 | .1008 | .1004 | .1000 | .0997 | .0994 | .0991 | .0989 | 220 |
| 230 | — | .1039 | .1031 | .1024 | .1018 | .1012 | .1010 | .1007 | .1003 | .1001 | .0999 | 230 |
| 240 | — | .1050 | .1041 | .1034 | .1029 | .1024 | .1020 | .1017 | .1014 | .1011 | .1009 | 240 |
| 250 | — | .1062 | .1052 | .1045 | .1040 | .1035 | .1031 | .1027 | .1025 | .1022 | .1019 | 250 |
NOTE.—An approximate rule for the conditions of ordinary practice is a saving of 1 per cent. made by each increase of 11° in the temperature of the feed water. This corresponds to .0909 per cent. per degree. The calculation of saving is made as follows: Boiler pressure, 100 lbs. gauge; total heat in steam above 32° = 1,185 B.T.U. feed water, original temperature 60°, final temperature 209°F. Increase in heat units, 150. Heat units above 32° in feed water of original temperature = 28. Heat units in steam above that in cold feed water, 1,185-28 = 1,157. Saving by the feed water heater = 150 ÷ 1,157 = 12.96 per cent. The same result is obtained by the use of the table. Increase in temperature 150° × tabular figure .0864 = 12.96 per cent. Let total heat of 1 lb. of steam at the boiler pressure = H; total heat of 1 lb. of feed water before entering the heater = h', and after passing through the heater = h"; then the saving made by the heater is (h"-h') ÷ (H-h').
Under usual conditions the plans of an electrical station are readily drawn, as they are generally of a simple nature. The engines and generators will occupy the majority of the space, and these are usually placed in one large room; in some stations, however, they are located respectively in two adjacent rooms. The boilers are generally located in a room apart from the engines and dynamos, and in some cases a separate building is provided for them; the pumps, etc., must be installed not far from the boilers, and space must also be allowed near the boilers for coal and ashes.
Fig. 2,720.—Floor plan of an electrical station having a belted drive with counter shaft.
Fig. 2,720 shows the floor plan of an electrical station, in which a countershaft and belted connections are used between the engines and generators. Referring first to the plan of the building itself, A represents the engine and dynamo room, B denotes the boiler room, C the office, D the store room, and E the chimney connected with the boilers by means of the uptake w. Referring next to the apparatus installed, S, S, S, S represents a battery of four boilers; these are connected by steam piping VV to the two steam engines, M and M, which are belted to the countershaft O. Belted to the countershaft are the generators, T, T, T, T, the circuits from which are controlled on the switchboard, H.
Ques. What are the objections to the arrangement shown in [fig. 2,720].?
Ans. The large space required by the belt drive especially in locations where land is expensive. Another objection is the frictional loss due to the belt drive with its countershaft, etc.