instrument valve seat leak standard
instrument valve seat leak standard
(OP)
I am working on verification for many our valves. For seat leakage (internal leak), as my experience, API, AWWA, FM etc. they have the standards for leak rate and test specification. But my current company product line is instrument valves with low flow (small Cv). We use HE sniffer to detect external leak (10e-5) and seat leakage is check by bubble in water or liquid leak detector. The time duration is variant depend on operator, also the connect tube size is different too. So, is there standard or common rule for leakage? Out instrument valve are for petrochemical, refinery and so on.





RE: instrument valve seat leak standard
Although attached link are for control valves and regulators there are some comments and pointers for small Cv valves that could possibly be to your interest.
As a thought wouldnt the best procedure be to be at least at par with competitors, or hopefully better by proving you can go below leakage at known tests, if possible?
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RE: instrument valve seat leak standard
bcd
RE: instrument valve seat leak standard
I know that frequency signiture can be obtained upstream and downstream of the valve as turbulence of the throttled gas is created. The only thing one surely can not tell with this method is the leakage rate specified by API598.
I need to hear your ideas.
RE: instrument valve seat leak standard
RE: instrument valve seat leak standard
In more general terms, EN 1779 standard (Edition 1999 + Amendment 1 dated 2003) about Non-destructive testing - Leak testing - Criteria for method and technique selection may be helpful when choosing how to detect a gas leakage based on the type and shape of the object under test and on the entity of the leakage itself; moreover, the typical accuracy ranges for each method (e.g. tracer gas, vacuum, pressure change, bubbles, etc...) are also given and the influence of pressure, temperature and nature of gas on leakage is also studied.
Unluckily, this standard excludes hydrostatic, ultrasonic or electromagnetic methods (for which other reference documents must be applied).
See also thread408-150132: "Zero Leakage" conept and EN 1779 std... within this Forum...
Coming back to reysor's question, I would also suggest the pressure change method: of course this is feasible if there is another valve tight enough (or if it is possible to blind the pipe off) downstream the instrument valve under examination...
In any case, I believe that it should be the plant on the field to dictate the allowable leak rate and not just a standard on the paper. In other terms: why taking the valve off the line if you can't even notice the leakage?
Hope this helps, 'NGL
RE: instrument valve seat leak standard