3" throgh 6" rubber seated butterfly valve popping out of seat

[tsmith62]

I have several 3", 4" and 6" butterfly valves with double acting air to air actuators on them. The valve seat is a dovetail design. The actuators have no travel stops. When solenoid is energized to open the valve the valve disc suddenly pops out of the seat.

I have heard that a cartridge design seat may work better.

I do not think the seat is being attacked by any chemicals.

I think the actuators should also have closed travel stops to prevent the disc from going to far into the seat.

The media flowing through the valve is clean.

Does anyone have any experience with this problem? What was the cause and what was the cure?

 

[MikeHalloran]

Air actuators behave like that in response to loads that change with position, because of the energy stored in the air. If it's causing a problem, please describe the problem.





Mike Halloran
Pembroke Pines, FL, USA

 

[chief]

Sounds like the seat material is Buna. This is too soft for the application. Try Viton or EPDM for better adherence to the valve body and less deflection. Also set your travel stops on the actuators by closing the valve manually and setting the maximum travel. This position prevents over-travel of the butterfly and prevents pushing out the seat.

Offshore Engineering&Design

 

[gerhardl]

Hello frog123,

Advice given above from both MikeHalloran and chief is sound (provided your fluid is compatibel with sealings suggested).

You could also try to throttle the air out of the actuator to soften the opening movement. (You do not say anything about line and air pressure.)

If you still, after 'redisigning' your application within reasonable limits have the same problem still reoccuring, you could do one of two things:

Either cange to a recognised brand of proven designed centric or double eccentric BFL valve (I presume centric BFL valve is what you have) for your exact application, with actuator from the same supplier. The problem is well known and with a correct total design you will have a better chance avoiding trouble.

The second option is to change to electrical actuators. Good electrical actuator brands for theese small valves will have considerable higher price than pneumatic actuators (approx 3 to 5 times higher), but should be considered for soft opening and closing actuation, and no air consumption.

 

[JimCasey]

rubber-seated butterfly valves are >supposed< to be shipped and stored with the disc in a partially-open condition. If they sat on the shelf closed for months before installation, the liner may have permanently deformed around the edge of the disc. This aggravates the "pop" you experience. One step further, when initially installing the valve- partially open the valve before torquing the flange bolts so the liner does not envelop the edge of the disc as it is compressed between the flanges.

Raising your air pressure or increasing the actuator size both contribute to actuator "Stiffness" and will reduce the effect/magnitude of the "pop". Unless you are using the valves for modulating service the pop is merely annoying and is not harmful unless it keeps the actuator from opening the valve at all.

 

[amitplasma]

try epdm seat material or for best valves contact Crane / Sounders