92 AIR COMPRESSORS 



adjusted for 20 Ib. excess pressure, and spring 19 for a pressure 

 ranging from 120 to 140 Ib., depending on the service. 



Pipe Connections to Old-Standard Equipment. The 

 method of connecting an SF governor with the old standard 

 equipment is shown in Fig. 5. When so connected it is appli- 

 cable to the high-speed brake or the double-pressure control 

 equipments without changing or moving any of the governor- 

 pipe connections. By regulating the maximum -pressure side 

 to, say, 140 Ib., duplex main-reservoir regulation may be 

 obtained, for feed-valve pressures up to 110 Ib, since the excess- 

 pressure head will stop the pump at 130 Ib. thereby giving 

 an excess pressure of 10 Ib. 



PIPING DIAGRAMS FOR TWO AIR COMPRESSORS 



For two O^-in. compressor installations, a 1 J-in. steam supply 

 pipe should be used together with an SF-5 (IJ-in.) governor 

 and a IJ-in. steam valve. A 1-in. supply pipe, governor, and 

 steam valve are too small and throttle the supply of steam, 

 reducing the speed of the compressors too much. Where both 

 pumps are on one side of the locomotive, they should be con- 

 nected up as in Fig. 6 (a); where they are on opposite sides 

 of the locomotive, connected up as in (b). For two 11-in. 

 pumps, a 1^-in. supply pipe, governor, and steam valve 

 should be used, the pumps being connected up as shown. 



AIR-STORAGE RESERVOIRS 



The necessity for an air reservoir in connection with nearly 

 all air compressor plants is well understood. It receives the 

 air in pulsations from the compressor and delivers it at uni- 

 form pressure. The reservoir also acts as a depository for 

 such moisture, oil, and other foreign matter as passes through 

 the compressor. The condensation of water resulting from the 

 compression of air can never be entirely prevented, but 

 the amount may be lessened by obtaining the coolest and 

 driest air possible for the air intake to the compressor, and 

 by locating the reservoir and radiating pipe in the coolest 

 possible place. These conditions are requisite for the most 

 satisfactory service. Each reservoir should have a drain 



