Helium seat leak test for Swing Check valves

[engineer2385]

Hello,
If Helium seat leak test is required by a customer for a swing check valve, what should govern test duration and the leakage criteria? Gas Pressure for seat test is 80 Psi minimum as per SP-61. MSS-SP-61 gives leakage rates for seat leak tests with Air and Gas. Does that mean it includes Helium?

 

[Danlap]

Hello,

Different customer may refer to different standard.
Metal to metal swing check valve, by nature (aside from hydrotest) is allowed to have greater leakage rate. Compare to different type of valves with same sizes and classes.
It is used as back flow (surge) preventer, and seldom used as a block valve (several condition may applied).

Therefor, in my humble opinion I find two things from your statement quite amusing:
a. MSS-SP-61, probably your customer is used to with mass production / incoming goods. Therefor practical and fast testing procedure may applied.
PS: Be careful on testing period. those x seconds start counting after the pressure test are for sure already balanced.
b. Helium medium
In practice, all (compressible) medium can be used as testing medium. All subjected for same designated pressure and leakage rate. However come with some advantages and disadvantages:
[ul]
[li]Air (environment) --> very cheap, however may need a big compressor and accumulator for high pressure purging[/li]
[li]Nitrogen --> can be transported (for offshore) in Liquid form, quite practical[/li]
[li]Helium --> quite expensive (especially when you need large volume), smaller particle (I am not surprised when valves was air tight, but when it is retested with Helium its leaking), suitable for Fugitive Emission testing since the apparatus called Helium sniffer.[/li]
[/ul]
So, Seat testing a swing check valve (leakage rate approximately 0.1% of its circumferential) using Helium when you only requires bubble counter?

Regards,
MR

Greenfield and Brownfield have one thing in common; Valve(s) is deemed to "run to fail" earlier shall compared to other equipments

 

[engineer2385]

Muktiadi, some opine that Helium leakage criteria should not be taken from SP-61. Here, Helium seat leak test(low pressure leak test) is in addition to Air seat test. My question is what should be the governing criteria for this kind of Helium seat leakage test?

 

[Danlap]

Engineer2385,

To be honest you've lost me.
If there is some prohibition of not using Helium kindly show us the exact official statement. Some opinion does not count as engineering answer. Most likely the one who gave the opinion fail to perform leak tight seat test using helium.
In testing practice helium often used (seat, body, fugitive emission) for cryogenic test, high temp test and back seat (to test Fugitive).

Revert back to your customer what standard they are governed with. They must have this when deciding the valve selection and SIL criteria.
I can imagine two general standard which is ISO 5208 (however you should now your check valve leakage class) and or API 621.

Regards
MR

Greenfield and Brownfield have one thing in common; Valve(s) is deemed to "run to fail" earlier shall compared to other equipments

 

[engineer2385]

Muktiadi, I agree with you. I found that the customer has specified Helium seat leakage criteria as per SP-61. Also, SP-61 specifies inert gas a medium for seat closure tests.

 

[gerhardl]

Hello guys!

Great that you already have it sorted out!

I was about to comment on two points: it is always wise to google for references and information before you drop a question in this forum, and likewise before you give an answer.

Secondly: most answers of practical application of customers requirements (but not always and not always clarly defined) can be found in customers reference standards and notes.

(

http://www.heliumleakdetection.net/Helium-Leak-Testing/what-is-helium-leak-detection.html)

 

[israelkk]

Helium is 7 times lighter than Nitrogen (4 grams/mole) compared to (28 gram/mole) for Nitrogen. Therefore, the flow rate will be SQRT(7)=2.645 times volume flow rate of Nitrogen or Air.