90 



AIR COMPRESSORS 



forms the maximum limit of main-reservoir pressure. Thus, 

 when the brake-valve handle is in running position, the excess- 

 pressure side of the governor limits the main-reservoir pressure 

 to 20 Ib. above the feed-valve pressure, no matter what feed- 

 valve pressure is being carried. The maximum-pressure side 

 forms a limit beyond which the main-reservoir pressure can- 



TO fSEo Mi ve f/pE (E r.). 

 ro BKAKE P/PE (ontat sc* 



not rise. Therefore, a change in feed-valve regulation auto- 

 matically produces a corresponding change in the governing 

 pressures. As each governor head has a vent port 22, from 

 which a small amount of air escapes whenever pressure is 

 present in the chamber above the governor piston, to avoid 

 an unnecessary waste of air, one of these should be plugged 

 with a vent-port screw 22. 



