Control Valve Questions

A

Thread Starter

Anil Bathra

Can spring return single acting actuator for fail safe position of control valve be a satisfactory solution for higher sizes?

Is it possible to get fail safe position if we use double acting actuator for control valve?

Email - [email protected]
 
R

Raymond Mpofu

Failsafe with regards to control valves implies either you require your process line to close or open on failure of control air supplies to the pneumatic actuator, it will vary depending on whether upstream of your control valve will pressurise or depressurize when control valve fails either open or closed position

Example: If I install a pneumatic actuator such that it controls discharge pressure of a pump by throttling part of the fluid to a bypass line, Then the valve will tend close if pressure is less than the setpoint and open when pressure on the pump discharge line is increasing above setpoint. In such a case if I use a air to open actuator, when I loose the control air supply to the actuator, the valve will close and my pump discharge will overpressurise. But a failsafe option would be to use an air to close so that air failure opens the valve and my pump discharge is not pressurized. This is just an example to understand things to consider when designing a failsafe option......hope it helps
 
A
Thanx Raymond.

But how double acting Piston type control valve will work for fail safe position?
 
Top