THE FEED WATER. 27 



Feed-Water Heaters. A feed-water heater heats the feed 

 water delivered by the pump, by passing it through pipes 

 surrounded by exhaust steam from the engine. In this way, 

 the feed water carries into the boiler the heat it has absorbed 

 from the exhaust steam, and which would otherwise be 

 wasted. The interior of the "Case" heater is shown in the 

 accompanying sectional view. Tubes (A), (three or more 

 in number), are tightly calked in the inner heads (B). Gas 

 pipes (C) pass through the tubes, their ends being held in 

 place by sockets cast on the outer heads. The outer heads 

 are secured by four stud bolts, which screw into the heater 



FIG. 5. SECTIONAL VIEW OF CASE HEATER. 



body, and are made tight by gaskets. The exhaust from 

 the engine enters the heater at E, surrounding the tubes, 

 and passing out at F. The water from the pump enters 

 through the head at D, passes out at the other end and 

 into the pipe G to the boiler. In going through the heater, 

 the water is obliged to pass through the annular spaces, 

 formed by the inside of tubes and the outside of gas pipes, 

 in films about one-eighth of an inch thick. Two cocks 

 are screwed into the bottom of the heater, one of which 



