Specifications:

The CAPITAL CONTROLS® Series 71P11A Gas Pressure Reducing and Shut-Off Valve is a diaphragm-type gas pressure regulating valve designed for use on chlorine, sulfur dioxide and ammonia gas service. The valve is used in a gas dispensing system to prevent liquefaction of the gas by providing a controlled pressure drop in the piping system. Downstream pressure is regulated to a reduced value by adjustment of the control setting. If the downstream pressure exceeds the pressure at which the valve is set, gas flow will be shut off.
There are three models for use with a variety of control applications:
71P11A01 Manual
71P11A02 Pneumatic 
71P11A03 Electric/hydraulic

All models are constructed with materials resistant to corrosion from the gases being controlled. The valve body is constructed of ASTM A105 forged steel to meet the recommendations of The Chlorine Institute for Class IV piping. Valves use a self-centering ball stem with a soft TFE seat for positive shut-off.

The control setting for the manual and electric valves are made by adjustment of a 
mechanical adjustment screw that applies spring tension to the loading diaphragm. The pneumatically actuated unit is controlled by pneumatic or hydraulic pressure applied to the diaphragm.

Fail-safe operation can be accomplished using either the electrically-actuated or pneumatic/hydraulically-actuated units. Either can be configured to permit valve closure on power failure (venting of 3-way solenoid valve for pneumatic unit)

• Replaceable inlet capsule
• Exceeds Chlorine Institute and ASME recommendations
• Manual and automatic operation
• Capacities to 12000 lb/day (240 kg/h)
• For Chlorine, Sulfur Dioxide and Ammonia
• Rugged field-proven design

Operation:

Gas at supply pressure enters the inlet connection and passes through the capsule assembly which houses the valve plug and seat. When the downstream pressure falls below the control pressure, the spring-loaded or pilotoperated diaphragm opens the valve plug and gas flows through the valve entering the downstream piping at the outlet connection. When the downstream pressure 
exceeds the control pressure, the diaphragm permits the valve plug to seat and gas flow stops. The desired downstream control pressure should be determined by the type of gas being controlled. Should the downstream pressure exceed the control pressure setting, the diaphragm will move to close the valve, shutting off the gas flow.