ENGINEER'S BRAKE VALVES 141 



which will force the extended portion of release valve 14 

 against the upper projection of the double-seated check-valve, 

 forcing the latter downwards from its seat and allowing the 

 driver-cylinder air to pass by the check-valve through the 

 vertical grooves in its circumference, and to the atmosphere 

 through the brake-valve exhaust opening. 



The operation when applying the brakes by straight-air is 

 the same as with the S-3 brake, except that the brake-cylinder 

 pressure is on top of the check-valve 23 and forces it to its 

 lower seat, thus preventing brake-cylinder air from escaping 

 through the triple-valve exhaust port by way of connection to 

 the automatic side of the double check-valve. The release can 

 be made by using either release or running position, but after 

 releasing the brakes the handle should invariably be returned 

 to and left in running position. 



Cleaning and Oiling. In cleaning and oiling the straight-air 

 brake valve, all parts should be wiped clean and the applica- 

 tion and release valves replaced without oil; a little heavy 

 oil or brake-cylinder grease, however, can be used to good 

 advantage on the main shaft and its gasket. The slide-valve 

 reducing valve should be thoroughly cleaned and a small 

 amount of valve oil used on its piston and slide-valve. The 

 double check- valves and safety valves should be cleaned, but 

 no oil is required. 



CARE OF BRAKE VALVES 



There is a wide range of variation in the time a rotary valve 

 will continue working satisfactorily in general service. Some 

 valves will run 3, 4, or 6 mo. while others will not run as many 

 weeks. Tallow or vaseline are good lubricants for the rotary, 

 but oil of any kind should be used sparingly on any part of 

 the brake apparatus, except the steam end of the pump. Oil 

 that has a tendency to gum should never be used. 



Whenever the rotary valve works hard, the brake valve 

 should be taken apart and the rotary cleaned and oiled, to 

 prevent cutting. At the same time, the packing ring should 

 be cleaned, but without removing it, since, if removed, it 

 is liable to be sprung out of true, which will necessitate refitting 



