THE FEED WATER 31 



water space. The steam space may be drained before 

 starting the engine, in order to prevent water from being 

 thrown from the smoke-stack. Both water and steam 

 space must be drained in cold weather, to prevent freezing. 

 The "Case" steel-shell feed-water heater, as shown in 

 Fig. 8, is constructed in the same manner as a small tubu- 

 lar boiler. The tubes are expanded in the flanged heads 

 at each end of heater. The exhaust inlet and outlet elbows 

 are clamped tight against the ends of heater by a long bolt 



FIG. 8. SECTIONAL VIEW OF "CASE" STEEL-SHELL HEATER. 



(or bolts) passing from one to the other. The feed water 

 surrounds the tubes and the exhaust steam passes through 

 them. The hot water is discharged to the boiler on the un- 

 der side of heater, but it is taken from the top, the water 

 passing behind an annular flanged plate that leads it to the 

 outlet. Only the pressure of exhaust steam is brought to 

 bear against the packing joints. This form of heater has 

 proved to be very efficient, and the interior is readily acces- 

 sible by removing the exhaust inlet and outlet elbows. 



