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BUTTERFLY VALVE STOCK PROBLEM.

BUTTERFLY VALVE STOCK PROBLEM.

(OP)
Hello everyone just want to ask for some suggestions on how i might resolve my problem on butterfly valves what happen i didn't indicated the medium what will be flowing on the valves knowing that the medium is for sea water application and the disc material is just a GGG40 that made the disc corroded and the valve cant completely closed it is a pneumatic controlled actuator.

Any suggestions how can i make a solution to this problem.

Thank you very much for your help and suggestions.

---------------------------------------------------------------

RE: BUTTERFLY VALVE STOCK PROBLEM.

Only you can do is shut down the system, remove the damaged valve, and install a new vale with correct material.

RE: BUTTERFLY VALVE STOCK PROBLEM.

Hi RMA28,

Your information is not complete enough for detail assessment.
Is this valve already removed from the line? Or is this preliminary root cause still a hypothesis?
Stuck? to close, complete stuck on its wherever position
Butterfly valve type? Soft seated zero or double offset OR metal seated double or triple offset?
Spindle material?

The GGG10 or ductile iron is less prone for corrosion compare to stainless or carbon steel. Nonetheless, due to the butterfly design where the disc is not in contact with seat until it reaches 97 to 100% close position, then this is unlikely to be the stuck root cause problem. Especially when this is soft seated, small corrosion on the disc edge should be able to still create relatively tight sealing.
The spindle/stem however is a different case, when the material is not suitable and design wise prone for exposing seawater to reach the surface between stem vs body or stem vs packing, then once corroded it may cause excessive friction between above sealing area, hence stuck.
Alternative material can be considered is aluminum bronze, duplex or others.

I assume this is soft seated (usually rubber made from either EPDM or NBR), then it is highly recommended to tighten the pipe-to-valve flanges during the valve in open position. When valve in close position during pipe installation, the seat is slightly bulge, hence it cannot "relaxed" when the flange already tightened. and will act as obstruction when the valve is operated to open position. This bulge seat will prevent the valve from fully close if required.

Adding force by means of adding instrument air into actuator or by using cheater bar on spindle will only damage the seat further.

Success
regards,
MR



https://nosuchvalve.com
All valves will last for years, except the ones that were poorly manufactured; are still wrongly operated and or were wrongly selected

http://www.eng-tips.com/faqs.cfm?&rat1=2&f...

RE: BUTTERFLY VALVE STOCK PROBLEM.

If this is warm aerated seawater, my guess is you actually don't have a full disc left, especially if it has been used in any sort of throttling service.

"Any suggestions how can i make a solution to this problem."
Yes - replace it with a valve or disc which is suitable for your service. Seawater is not an easy fluid to deal with and requires specialist materials as noted in the posts above.

You've made an error in not listing the fluid service in the data sheet - don't compound this mistake by trying to do something cheap and nasty which won't last. Replace the valve / disc.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: BUTTERFLY VALVE STOCK PROBLEM.

(OP)
Thank you for your attention everyone. The butterfly valve type is a Wafer type, we've already removed the valve from the line and seen the corrosion from the valve. Just a correction regarding my post it is completely stuck up. Any other suggestion that will make the disc move easier on operation. Your response is highly appreciated.

Thank you very much everyone for your suggestions. We'll try to change the valve disc.

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