SCIENCE OF SUCCESSFUL THRESHING 



way, the feed water carries into the boiler the heat it has 

 absorbed from the exhaust steam, which would otherwise 

 be wasted. The interior of the "Case" heater with cast 

 shell is shown in section in Fig 1 . 7. . Tubes (three or more 

 in number), are tightly calked in the inner heads and inner 

 pipes pass through the tubes, their ends being held in place 

 by sockets cast on the outer heads. These heads are se- 

 cured by four stud bolts, which screw into the heater body, 



, OUTER HEAD 



/INNER HEAD 



EXHAUST ~ 

 STEAM 



HEATER SHELL 



INNER PIPE { OUTER TUBE 



INNER PIPE 



HOT WATER 

 TO BOILER 



INNER HEAD' 

 DRAIN - 

 OUTER HEAD" 



FIG. 7- SECTIONAL VIEW OF "CASE" CAST-SHELL HEATER. 



and are made tight by gaskets. The exhaust from the en- 

 gine enters the heater from the cylinder, surrounding the 

 tubes, and passing out to the smoke stack at the opposite 

 end as shown. The water from the pump enters through 

 the head at the right and passes out at the other end into 

 the pipe leading 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 pipes, in 

 films about one-eighth of an inch thick. 



Two cocks are screwed into the bottom of the heater, 

 one of which drains the steam space and the other the 



