THE FEED WATER 23 



procure all of them and try one after another until the 

 injector works properly. Any unused jets that have not 

 been inserted may be returned. 



Independent Pumps. This is the name given to pumps 

 for feeding a boiler, which are operated independently of 

 the engine. They are, in fact, small engines in themselves, 

 connected directly to double-acting pump plungers. An 

 independent pump can be run whether the engine is run- 

 ning or not, but as the heater is effective only when the en- 

 gine is running, it is best, on boilers having both pump and 

 injector, to use the injector when the engine is not running. 

 The Marsh pump has an exhaust valve for turning the ex- 

 haust of the pump in with the feed water. This, of course, 

 heats the feed water and renders the pump more economi- 

 cal. If, for any reason, it is desired to use the pump when 

 the engine is not running, the exhaust should be turned in, 

 in order to heat the water before it enters the boiler. At 

 other times, however, we advise engineers to allow the 

 pump to exhaust into the air. The most of the trouble 

 with these pumps is due to insufficient lubrication, and the 

 successful operators use plenty of cylinder oil. If the ex- 

 haust be turned in at all times, this cylinder oil is carried 

 into the boiler where it accumulates, in some cases in suf- 

 ficient quantities to render it dangerous to the plates of the 

 boiler. Consequently, for this reason and also because the 

 pump is more easily "kept up" when exhausting in the air, 

 we do not advise turning the exhaust into the feed water. 



