. Electric railway review . ill thus be noted that no engine is operative with a suf-ficiently small number of pounds of steam per horsepower,nor is any steam pump sufficiently wasteful of steam to war-rant running a feed pump condensing, even though it is pos-sible to reduce the steam consumption of a feed pump tothat of the most economical unit known. Another method of delivering water to a heater by meansof a suction pump from a low-down type of jet condenser isby elevating the discharge to such a height that the waterwill flow into the open heater by gravity as shown in Figure227-(G
. Electric railway review . ill thus be noted that no engine is operative with a suf-ficiently small number of pounds of steam per horsepower,nor is any steam pump sufficiently wasteful of steam to war-rant running a feed pump condensing, even though it is pos-sible to reduce the steam consumption of a feed pump tothat of the most economical unit known. Another method of delivering water to a heater by meansof a suction pump from a low-down type of jet condenser isby elevating the discharge to such a height that the waterwill flow into the open heater by gravity as shown in Figure227-(Gl-3). When considering such a connection it should beremembered that for every foot the discharge is raised, asshown by the dimension line, a, this lift is equivalent toraising the feed water 30 times this amount as the quantitythus lifted is ordinarily about 30 times that fed to the only advantage in this style of connection is the elim-ination of one pump. If a house pump is used to supply the cold water it may. Figure 227—(G1-3). be found better practice to utilize this same pump for sup-plying water to the heater rather than by increasing theduty on the air pump by raising the head. To make a comparison of the relative economy of thetwo practices it may be assumed that a, in Hgure 227. is 5feet, that the condenser uses 30 pounds of water per poundof steam condensed, that the temperature of the intake wateris 55 degrees and the discharge water 90 degrees and that thepump dequires 100 pounds of steam per horsepower. Thenfor each pound of feed water there will be required the fol-lowing additional British thermal units necessary to raisethe water 5 feet: B. t. u. = (30 lb. x 5 ft. x 100 lb. steam perh. p. X 50 B. t. u. per lb. steam) -^ = 23. If cold water 938 ELECTRIC RAILWAY REVIEW November, 1906. is used 1-30 of the result just obtained will be required forpumping, thus % B. t. u. plus the difference between the heatunits and water of 90 degrees, or 58 B
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