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Metal to Metal Ball Valve Leakage

Metal to Metal Ball Valve Leakage

Metal to Metal Ball Valve Leakage

(OP)
Hello Everybody,

we have a series of Ball valves ( BSE) size 6"to 12" Class 600 , metal to metal , and they are leaking.
the requested leakage rate by customer was Rate B ISO 5208, while we test them with Rate D ( by mistake ) and all passed.
now the problem is:
we took 1 valve 10" as a sample and that did not leak @6 bar gas test , but at 10 and 21 bar hydrotest it had 50 drop /min leakage.
after 2 set of 15 times cycling of the valve we had gas leak ( heavy leak like 110 bubble /min) at 6 bar and at 10 and 21 bar hydro test 50 drop /min leakage in one seat.
we used O-ring instead of packing and there were no leakage.

we did consider the dimension of the packing which as stated our technical department it is correct and ...( they are not being involved in solving the problem ...)
we are still investigating , but I was really wondering what other possibilities could exist apart from misalignment of ball and seat or seat and ball not being properly adopted ...
packing material is graphite.
we also applied pressure on seat A and B which there was a leakage at seat B and then on both of them and again leakage at Seat B not A.
I myself believe that we should study more about the packing design and dimension but my boss believes that it is too easy to focus on and it must have more complicated reason..
I guess he is right but I need to brainstorm ( which is not very common in our factory) with more professional people to learn more about the possibilities.

valves are not in our factory they are in our other branch near customer location , we are sending a technician there but he might not be useful if we do not have any pre thoughts about the cause.

Thanks,
susan

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