HP Gas test for ball valves

[BFZHA]

Hi,
We have required a HP gas test for ball valve for gas service.
At the end of the test, we want to require visual inspection of seat and the internals in order to verify eventually damage of this parts. Since this check can not be made without dismantling the valve ie impact on price and production schedule, my question is:

From previous experience, is there a damage risks on valve internals due to HP gas test with nitrogen?

In this case, Is this final check necessary for all valves or only one valve by diameter and series?

Regards.

 

[zdas04]

The final test is not only not necessary, it is irresponsible. A competent mechanic can disassemble, inspect, and re-assemble a valve with a reasonable probability of not introducing a new problem, but that probability is not zero. The responsible thing to do is to verify that the valve is still bubble tight after re-assembly. Oh yeah, your procedure calls for an inspection after a test. See where this is heading?

If you were testing with CO2 above the gas/dense-phase boundary, I would be very concerned about the integrity of the seals after the test. I'm not aware of any phase-change drama that you need to avoid with a nitrogen test.

I would certainly revisit that test procedure and rethink the whole disassembly step.

David

 

[BigInch]

If its not for leakage testing, what's the difference if you use water or gas. Pressure is pressure.

If its for leakage, you don't need to go higher than the working pressure. If for some reason I don't understand, you want to, why not calibrate your expected leakage with your working gas to what you get with a helium test done at a lower pressure.

 

[blacksmith37]

The test frequency depends on the specification and purchase order. eg. API 6A, for wellhead valves has 4 product specification levels (PSL), requiring different levels of NDE and other verifications. The highest level required air under water tests at rated pressure (like 20,000 psi). Also cycling at these conditions (which can be very exciting).
( I have been off API 6 committee for years, so am unfamiliar with the current requirements).

 

[BFZHA]

Thanks for your replies;
The test with Nitrogene is required by our Client as a complementary test because valves are going to be used in gas service; This test shall be made in manufacturer shop.

I conclude that, it is not advisable nor necessary to dismantel the valve. Since service conditions are less stringent than test conditions and if valve HP test is positif, there is no need to expose a valve to a supplementary operations in manufacturing process.

Regards.