358 PRESSURE-RETAINING VALVES 



PC. No. Ref. No. Name of Part 



7,813 Type 15-B pressure-retaining valve, com- 



plete. 



9,602 Body, complete, includes 5 to 14 inclusive. 



8,786 2 Body, bushed. 



2.457 3 Case. 



2.458 4 Weight, complete. 



7.672 5 Handle. 

 7,812 6 Cock key. 

 2,367 7 Cock cap. 

 2,231 8 Key spring. 

 7,811 9 Extension socket. 

 8,049 10 Extension-socket cotter. 

 7,674 11 Extension-socket sleeve. 

 7,676 12 Extension-socket sleeve pin. 



7.673 13 Handle plate. 

 2,238 14 Handle pin. 



OPERATION OF RETAINING VALVES 



With the retaining valve in release position, or straight down, 

 the air that escapes from the exhaust port of the triple valve 

 passes through the retainer pipe and out through the exhaust 

 port without passing up into the valve case, thus giving a 

 free exhaust for the air from the brake cylinder. If the handle 

 is turned up to the horizontal, or retaining, position the free 

 exhaust opening is closed and the air from the cylinder must 

 then pass around the plug valve and up against the weight 

 valve. This valve is held on its seat by the weight 4, which is 

 heavy enough to hold the valve down against a pressure of 

 15 Ib. If the air coming from the brake cylinder has a pressure 

 exceeding 15 lb. t it will raise the valve and pass up into the 

 retainer case 8. It must then pass out through a small vent 

 port, the diameter of which at its smallest part is & in. This 

 retards the flow of air so that it takes about 20 to 25 sec. for 

 the air to pass out of an 8-in. cylinder with 8-in. travel and 

 reduce the pressure from 50 to 15 Ib.; thus, sufficient time is 

 given for the auxiliaries to recharge from 50 to 70 Ib. before 

 the pressure is reduced to 15 Ib. The brake-cylinder pressure 

 reduces gradually during the recharging, and the retainer 

 finally keeps 15 Ib. until the handle 5 is turned down to the 

 vertical position, and opens the exhaust port. With larger 

 cylinders, the use of this size retainer makes the time for 



