Typical time duration from closed to open? 1

[nickelkid]

What is a typical time (or range of times) for a double acting pneumatically controlled plug valve?

 

[JLSeagull]

I have more experience with spring opposed - single acting actuators and ball valves. In this case a throw-down number is one second per inch pipe size.

 

[BigInch]

Works for me.

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[Sircrashalot]

JLSeagull is right,

Anywhere between 1-2 seconds per inch of pipe diameter works pretty well for two reasons:

1) generally slow enough to prevent water hammer in system
2) can usually be supplied with reasonably sized control circuits and solenoids.

Andy

 

[gerhardl]

... and 'typical time' for one diameter can of course be somewhat manipulated (or vary) depending on one, or several in combination, of:

-actual torque -> selection of actuator size
-air pressure
-airline pipe diameter and length
-solenoid valve diameter (capacity, Kv)
-throttle valves on solenoid outlets/inlets (if allowed by construction of solenoid valve)
-throttle valves on actuator
-actuator air inlet and outlet diameter and inside construction (length and diameter of inside air tubing)
-actuator size, type and producer

Both short operating time (for instance emergency shutdown) and prolonged (as long as practically limited by equipment) can be 'engineered' by above.

Time limits for control circuits automatically acting on signals from air actuators limit switches therefore either to be given 'ample time' ot to be tested at site if critical for next step.

 

[dcasto]

I like to use the sindered aluminum or brass vent plugs available from Whitey and others as a way to regulate the venting of air and hence the time.

 

[JLSeagull]

Several manufacturers make a "speed control" that amounts to a two parallel check valves each with a series needle valve. The arrangement permits slowing the opening or closing time by use of the needle valve. These are not suitable for safety shutdown in the closing direction, or blowdown valves in the opening direction because the valve can be closed. Further any mechanical restriction can plug.

I prefer to select a tubing size that causes some restriction if needed to slow the opening or closing time. More often, a quick exhaust is required to accellerate the closing time for large valves.

The MMS requires offshore shutdown valves to close within 45-seconds. This is difficult with a 36 NPS or larger valve in high pressure gas service. BTW, the valve torque is greater thus closing speed slower when closing against 1200 psig gas in comparison to ambient pressure air.