﻿Bui. 1136, U. S. Dept. of Agriculture. 



PLATE VII. 



Thermostatic Air Valves and Traps. 



In those illustrated the thermostatic element consists of a flexible capsule C and 

 a volatile or nonvolatile liquid, the expansion of which shuts the valve. The 

 capsules serve as springs to open the valves. The traps are provided with ad- 

 justing nuts A to compensate for variations in the steam pressure in the system. 



' * 



