360 PRESSURE-RETAINING VALVES 



PC. No. Ref. No. Name of Part 



7,871 5 Handle. 



7.870 6 Cock key. 

 7,875 7 Cock cap. 

 2,231 8 Key spring. 



7.879 9 Weight-lifting rod. 

 10,976 10 Outside weight, complete. 



The 25-50 pound, high- and low-pressure retaining valve, 

 shown in Fig. 2, regulates the pressure at 25 and 50 Ib. It is 

 used on 6-in., 8-in., and 10-in. brake cylinders and weighs 

 7f Ib. The piece and reference numbers of the valve and of 

 its various parts are given in the accompanying list. 



PC. No. Ref. No. Name of Part 



7.880 Type 25-50 pressure-retaining valve, com- 



plete. 



9.610 Body, complete, includes 5, 6, 7, and 8. 



7.877 2 Body, bushed. 



7.869 3 Case. 



7.878 4 Inside weight, complete. 



7.871 5 Handle. 



7.870 6 Cock key. 

 7,875 7 Cock cap. 

 2,231 8 Key spring. 



7.879 9 Weight-lifting rod. 



9.611 10 Outside weight, complete. 



Operation. This type of pressure-retaining valve operates 

 like the older types, except that the weight can be increased 

 so as to make it a two-pressure retainer. The weights 4 and 

 10 are equal. The weight 10 is cylindrical and surrounds the 

 weight 4- It can be raised off of weight 4 or lowered on to it 

 by turning the handle 5 to the proper position. With the 

 handle straight down, the retainer is cut out of service. In 

 this position the handle engages rod 9 and raises weight 10 

 off of weight 4 so as to reduce the wear of the valve seat. With 

 the handle in its intermediate position, the weight 10 rests 

 on the weight 4- This doubles the amount of retainer weight, 

 so that the high pressure is retained, as the pressure must 

 raise both weights to escape. With the handle horizontal, 

 the weight 10 is raised off the weight 4 so that the weight 4 

 alone is in use; thus the low pressure is retained. 



