70 A Handbook for Dairymen 



ters will tell you whether there is enough ammonia 

 in the line, whether it returns superheated, whether 

 the cooling of the compressor — either by water 

 jacket or liquid injection — is correct. By record- 

 ing both the suction and discharge temperatures of 

 the compressor, the operator has an accurate and 

 continuous picture of what is going on while the 

 plant is in operation. 



These are only a few isolated instances of what 

 can be done in the refrigerating room alone by an 

 intelligent use of recorders. Wherever possible in 

 the boiler room and the refrigerating room, record- 

 ing instruments should be installed. Their slightly 

 additional cost above indicating instruments is far 

 offset by the greater value gained by the continuous 

 records which the operator can compare and study. 

 If properly installed and faithfully used, these in- 

 struments will provide the engineer with th€ most 

 valuable information on all the conditions upon 

 which the productive efficiency and economy of the 

 plant depend. 



It is worth emphasizing that, where it is a ques- 

 tion of temperature, or pressure, guessing is un- 

 scientific, uneconomical, and unsafe. In the power 

 plant, knowledge alone is power ; not memory — that 

 is too treacherous ; not scraps gathered at irregular 

 intervals by glancing at an indicator ^ — that is the 

 little knowledge which is a dangerous thing. What 

 is needed is complete recorded knowledge of what is 

 happening all the time in and around the boiler and 

 the refrigerating equipment. And this is just what 

 recording instruments give. They are not only per- 

 petual guides to the operators, but they give the 

 engineer an opportunity to compare various records 

 and thus establish an efficient operating standard. 



Finally, cheap indicating and recording instru- 



