CHAPTER IV 



TEMPERATURE CONTROLLERS AND RECORDERS 



In order that uniformly good results in the pas- 

 teurization of milk may be obtained, it is abso- 

 lutely necessary that the temperature to which the 

 milk is heated be controlled in such a way that 

 there will be no great variation. In order to con- 

 trol this properly, three things are necessary 

 first, a uniform, even flow of milk; second, a steam 

 pressure which does not vary; and third, that the 

 steam which is admitted to the heater be so con- 

 trolled that whatever variations there may be in 

 the temperature of the inflowing cold milk may be 

 met by varying amounts of steam, admitted to the 

 heater. This control will, of course, also prevent 

 any excessive heating which would follow if too 

 much steam entered the heating apparatus. 



The matter of an even milk flow has been dis- 

 cussed in the previous chapter. 



The control of steam pressure may be accom- 

 plished in various ways. It is, of course, necessary 

 that there be sufficient boiler capacity to insure 

 that the steam pressure does not fall below a cer- 

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