STEAM ENGINES 203 



Injection Water for Jet Condenser. The quantity of injec- 

 tion water required for a jet condenser may be found by the 

 formula 



H-(t-32) 



t-h ' 

 in which Q = number of pounds of injection water required to 



condense 1 Ib. of steam; 

 H = total heat above 32 of 1 Ib. of steam at pressure 



at release; 

 t = temperature of mixture of injection water and 



condensed steam on leaving the condenser; 

 ti = temperature of injection water on entering the 



condenser. 



EXAMPLE. Steam is exhausted into a jet condenser from 

 an engine cylinder at a pressure of 10 Ib., absolute; the temper- 

 ature of the injection water on entering is 60 P., and on leaving 

 140 F. How much injection water is required per pound of 

 steam? 



SOLUTION. The total heat above 32 of 1 Ib. of steam at 

 10 Ib. absolute, from the Steam Table, is 1,140.9 B. T. U. 

 Then, substituting the values of H, t, and h in the formula, 

 1,140.9-(140-32)_1.032.9 

 140-60 80 



ENGINE MANAGEMENT 



STARTING AND STOPPING 



Warming Up. About 15 or 20 min. before starting the 

 engine, the stop-valves should be raised just off their seats 

 and a little steam should be allowed to flow into the steam 

 pipe. The drain cock on the steam pipe just above the throttle 

 should be opened. When the steam pipe is thoroughly warmed 

 up and steam blows through the drain pipe, the drain cock 

 should be closed and the throttle opened just enough to let a 

 little steam flow into the valve chest and cylinder; or if a 

 by-pass around the throttle is fitted, it may be used. The 

 cylinder relief valves, or drain cocks, and also the drain cocks 



