butterfly valve bottom cover repetative leak

[ajeeb]

I'm seeking your support to findout the reason of the repetative leak from the bottom cover in butterfly valve in our site.
the process is low temp hydrocarbon and frequently leaking from the bottom cover.
the fluid pressure is around 800 psig. however we don't have any leakage from the flanges while they are (flange gasket and bottom cover gasket) are the same type.

 

[bcd]

Could be many possible reasons. Scratch across sealing surface, inadequate bolt strength, casting porosity, creep of gasket material, bolts loosening because of vibration, etc., etc. One quick test is to check the bolt torque once it is leaking. Have the bolts "loosened" considerably? And when they are retightened, does the leak stop? If so, it would seem that it is a poor gasketed joint design.

 

[Dean8573]

You may have a shaft which is sitting untrue or miss shaped and therefor not allowing for adequate squeeze on your seal resulting in the leak witnessed.

 

[gerhardl]

Please explain: Bottom cover? Normally a BFL valve is mounted with spindle horizontally oriented. If vertical and leaking, remount to horizontal position. If already horizontal and leaking: picture or constructional details, please! I also agree with postings above.

 

[Roberto1956]

I believe that in your butterfly valve is a high performance and the stem thightness is done by O-ring assembly.
So the bolts of botton cover don't works for thightness.
If during the hidrostatic test you got approval of the valve, the problem is the valve design for low temperature and material selection.