Check Valve Leakage Acceptance
Check Valve Leakage Acceptance
(OP)
We have a few ball check valves with SW ends. The valve body and the piping are heat treated after welding. Now the check valves seem not seal. Would anyone advise the acceptance criteria for the leakage rate of the valves?
Thanks,
Henry
Thanks,
Henry





RE: Check Valve Leakage Acceptance
Thats a subjective question.
Personally I detest backflow on a check valve, its not really serving its function is it?
I have however seen plants leave ball check valves in with contaminants in the seat causing backflow for periods and didn't seem to care.
You need to look at time, cost, application, and decide.
I've had SW ball check valves installed and not had a problem with internals.....what makes you think the heat treat casued something?
Frank "Grimey" Grimes
You can only trust statistics 90% of the time.
RE: Check Valve Leakage Acceptance
David Simpson, PE
MuleShoe Engineering
www.muleshoe-eng.com
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
The harder I work, the luckier I seem
RE: Check Valve Leakage Acceptance
RE: Check Valve Leakage Acceptance
RE: Check Valve Leakage Acceptance
My new rule is, piston checks at the pumps, keep the check at the contactor, AND NEVER EVER use a SW check valve.
PS, I kept my objection letter and was spared a horrible death and I got all the funding I needed when I rebuilt the system.
RE: Check Valve Leakage Acceptance
I didn't ask because I wanted to know, I posed a question that you need to answer for your process. If you have backflow from the header to the vessels, what bad thing happens? If it is a lot of backflow is the bad thing worse?
All check valves leak some, the acceptable magnitude of "some" is something that needs to be assessed based on your facility. We just can't do it from our desks all over the world.
I'm with dcasto that SW checks are pretty dumb, but they go in all the time--company specs don't like threads or small diameter flanges.
David
RE: Check Valve Leakage Acceptance
To further clarify, these valves are installed on the vessel maintenance drain lines. They are all 1-1/2" CL800.
My main concern at this moment is that if the leakage is the result of PWHT which may have damaged the valve seat. If a small amount of leakage is the nature of this type of check valve, I will accept the current condition.
RE: Check Valve Leakage Acceptance
Did the welding cause debree, and thus lodge in the seat?
Did the welding damage the seal? I would think so.
Test a virgin valve, see how it performs before welding and heat treating. If it performs well, then you may want to test it after welding to see if it damaged the valve. Welding can melt a seal and or deform the metal so that the geometry no longer lets it seal correctly.
Charlie
www.facsco.com
RE: Check Valve Leakage Acceptance