Air pressure test in API 6D 1

Hi there,
We are purchasing some ball valves used in LNG services. And the valves are manufactured based on API 6D standards. The leakage tests required in API 6D are mostly hydrostatic tests which are shell test(2200psi) and closure test(1650 psi). However, we request additional air closure test at the pressure of 77kg/cm2(1095psi) based on the reason that the operation pressure of our natural gas will reach as high as 60kg/cm2(853 psi). My question is,"Does the passing of hydrostatic tests will ensure the same air tightness for our high pressure service gas." Our vendor said the 77kg-air-test is apparently deviated from API standard and also unnecessary. Anything wrong with our request?
Any comments or helps will be much appreciated.

 

[PAN]

I understand that the hydrostatic test is acceptable without air test in such high pressure.

In ANSI B16.34, closure test by gas would be 80 psi. Can we use this standard as a reference compare to API 6D?

 

[msmedesign]

API6D does not require high pressure air test, but of course you can add high pressure test requirement to your PO. ( it will cost a little more)
It is very common to have that kind of requirement even not only air also nitrogen test.

Please email me msmedesign@yahoo.com if you have any further question. My company can provide you those valves without any problem.

 

[WRCrowley]

I am looking for performance statistics on API 6D pipeline valves by different valve manufacturers. Hopefully, this would be independent industry data and not manufacturer data.

Ideally , I would like the data divided by gate valve and ball valve.

I have already asked API and the Office of Pipeline Safety.

Contact me directly at compete@catsites.com if you have any suggestions, or post them here.

 

[scalleke]

I work for a valve manufacturer and see nothing wrong with your request however. One question is always the leakage rate that will be allowed.

Zero leak does not exist and high differential pressure seat tests must mention a maximum allowed leak rate. Especially since mass flow meters and other tools can measure leakage rates that cannot be detected with a rotameter.

Best regards.

Scalleke

 

[NGiLuzzu]

I agree with Scalleke: "Zero Leakage" does not exist and "No Visible Leakage" depends on the measurement methods and instruments.

Let me quote the European standard EN 1779, para. 6, just for a general principle:
"Zero leakage rate shall not be specified. The required leak tightness shall be related to the function of the object under consideration"

Bye to all, 'NGL

 

[WRCrowley]

Scalleke, Anegri,

Thanks for the feedback. I understand the "zero leakage" comments.

API lists 200+ certified manufacturers of 6D valves. Has anyone ever done a performance study of these products?

API has not.

WRCrowley

 

[Hush]

I know some users such as Shell, BP, Gazprom, & Exxon
have data because I've had to submit equipment for testing. Whether it's published for public consumption is another matter.