84 



AIR COMPRESSORS 



gasket into the port. When the brake valve is in running posi- 

 tion, the air in port /is at main-reservoir pressure; when this 

 pressure reaches 90 Ib. it operates the governor, which shuts 

 off steam from the pump. During an application of the brake or 

 while the brake valve is on lap, the pressure in port /is shut off 

 from the main reservoir and is much lower than 90 Ib. Usually 

 it is the same as that in the brake pipe, and cannot be raised to 

 90 Ib.; consequently, the low-pressure side of the governor 

 being cut out by the brake valve, does not operate, and the 



To Train P/pe 



FIG. 3 



pump continues to work and raises main-reservoir pressure 

 until the high-pressure side of the governor (usually set at 

 110 Ib. and operated by main-reservoir air) stops it. 



TYPE SF-5 COMPRESSOR GOVERNOR 



The piece number of the SF-5, compressor governor, com- 

 plete, shown in Fig. 4, is 21,799; for the steam portion, 

 complete, which includes No. 2 to No. 11, inclusive, it is 

 17,879; for the excess-pressure head, complete, 20,783; for the 



