Anti-surge control valve - Quick opening 1

[MDP]

I have to purchase anti-surge control valves which require an opening stroke time of 2 sec. max.

The valves are globe+cage type with spring-diaphragm actuator (fail-open) with a "flow tends to open" plug.

The valve supplier propose me two ways to achieve the fast opening feature :

option 1 : a quick exhaust valve to speed up the valve opening ensured by the spring return

option 2 : an air booster to increase the supply pressure to the actuator

What is the more appropriate solution for anti-surge application ?

In addition, is there any trap or hint in the selection of anti-surge control valve ?


Many thanks in advance for your help and advise.

MDP

 

[spud1]

The most appropriate method of control depends on how you want the valve to act.

If you need the valve to stoke fully open on 'trip' within two seconds but do not require modulating control within the two seconds then a separate high capacity solenoid can be used as a dump valve to evacuate the actuator and a standard positioner can be used for control once the valve is fully open.

If you require control modulation in 2 seconds then the first step would be to select a high capacity positioner which may meet the speed requirements(Masoneilan 7400-200 is a high capacity pneumatic unit, there are high capacity electropneumatic positoners available). Depending on how accurate you wish to control, flow boosters and/or quick exhaust valves can be used (boosters/exhaust valves tend to increase overshoot on position)

The speed achievable depends on the volume of the actuator and the stroke of the valve - the higher the volume & stroke, the more boosters etc will be required.

Depending on the fluid and duty you need to be aware of auto-refrigeration (Joule-Thompson effect)which will reduce the valve operating temperature. Many anti-surge valve have low design temperatures because of this effect.

 

[RobV]

I think you should explain in more detail where the valve is situated.

Centrifugal compressor anti-surge systems can have differnt solution.
1. A unit with two valves. One called the hot-bypass which is a true emergency valve that can suited with the solution of a high capacity solenoid. This valve doesn't need control! It take its feed from the compressor discharge before the cooler so this automatically means that the valve cannot be open for too long as the compressor would trip of high suction temperature. The second valve, would take the discharge gas after the cooler. This valve would be the one that would control the compressor by recycling the gas. It would require modulating control within two seconds, thus high capacity positioners and volume boosters plus a solenoid override in case of surge. If surge still occurs they you trip the hot-bypass wide open.
2. Units with a 1 valve where both functions decribed above are handled by one valve. The gas is always taken from after the cooler

Depending on the supplier of the compressor and the selected compressor controls supplier additional and/or other requirements may be neccessary.

And yes, there are traps in designing/selecting the right valve.
Drop me some info at robert_verwey@hotmail.com of the compressor suction and discharge and flow rates and I'll have a look.

 

[stanier]

If this a fluid application I suggest you look for details from Mannesmann, Mokveld or Noreva. They have surge relif valves that open instantaneously. Sharing knowledge is a way to immortality

 

[MortenA]

I not sure if its a compressor anti surge valve or a pipeline anti surge valve. If its fpr pipeline try Mokveld

http://www.mokveld.com/

Best regards

Morten

 

[rotamato]

Selecting anti-surge valve is not a big deal, because all manufacturers will promise you the moon.
Solution with boosters is giving us a big trouble, with opening times over 10 sec in control, while no problem in opening in less than 1 sec through the solenoid.
Moreover valves get stuck if closed 100% and we had surge twice already, thanks must be to to ESD push-botton.

I strongly suggest you to specify in data sheet that opening time in less than 2 sec is in CONTROL mode, not only in trip mode. Expedite the manufacturer many times and put in the spc that they must prove the opening time via controller at their factory and at the final location.

Good luck.