GATES AND VALVES 



151 



on a panel. The upper contact on the switch operates the valve, 

 and the lower is for the bell, which will ring only when the valve is 

 closed or open. This depends on how the connections are made, 

 and the operator can at all times ascertain what position the valve 

 is in. If the valve is connected so that the bell will ring when the 

 valve is closed, and the operator closes the bell circuit, and the 

 bell will not ring, he will readily understand the valve is open; 

 if he closes the valve circuit, or upper pole of switch for a few 

 seconds, and again closes the lower or bell circuit and the bell 



Valve Circuit 



FIG. 77. Connections for Electro-Hydraulic Valve Shown in Fig. 76. 



rings, he will understand the valve is closed. The valve can be 

 operated by hand simply by lifting the small armature on the con- 

 trolling device. 



Cylinder valves are, as a rule, more economical for smaller 

 sizes, while for larger the electric motor operated valve (Fig. 78) 

 is to be recommended. Such valves are very reliable and can be 

 closed in a comparatively short time. Besides this, remote 

 control from the main control board in the power-house can readily 

 be provided. 



The service of valve motors is exceedingly intermittent and 

 may vary from comparatively short intervals, such as once every 



