Performance Testing of Gaskets Nitrogen vs Methane

[johnthebest]

Hello everyone, I received a technical clarification from the contractor about Performance Testing of Gaskets and I want your opinions:

"Dear Sir
This is regarding procurement of Spiral Wound Gaskets.( as per ASME B 16.20 2017 Edn )
We are in the process of placing Orders(Manufacturer of Spiral Wound Gaskets).

Here, would like to bring one code requirement on Performance Testing of Gaskets.

Please see the below appended Clause SW-2.6 a) of ASME B 16.20 2017 Edn.
(a) The test fixture shall have a surface finish per ASME B16.5, be capable of shielding the gasket so as to direct any leakage to the monitoring probe, and be capable of
applying a uniform load on the test gasket sealing element while internally pressurizing the gasket with methane (minimum 97% purity)

As shown, this performance need to conducted with Methane Gas.

As per Vendor’s response, they are able to do the test with Nitrogen Gas ( which is more lighter than Methane Gas).
[Molar Mass : Methane =16.04 , Nitrogen =14.0067]

Needless to say, with Nitrogen Gas Vendor is able to Performance Test with more sensitivity.

On availability as well as safety point of view , Vendor’s view of Performance Test with Nitrogen Gas observed to be fine.

Kindly please have a look and be reverted with your acceptance/opinion on the same.

(Note: In all of our past projects, we procured Spiral Wound Gaskets performance tested with Nitrogen Gas only) "

What are your thoughts?

 

[danschwind]

I may be entirely wrong in my assessment, so take what I will say with a grain of salt, but I don't think you can correlate the sensitivity of the performance test with the molar mass of the gas, instead, you should correlate with the molecular diameter.

 

[johnthebest]

Thx for ur reply. is there any major differences between using methane and nitrogen gas?

 

[danschwind]

A quick google search indicates that the molecular diameter of nitrogen is smaller than that of methane. This would indicate that yes, the sensitivity with nitrogen would be higher.

Now, with basic logic, we can deduce that there should be a reason for the standard to specify testing with methane. I'm unaware of the reason, sorry. Let's hope someone with more experience in that field can clarify it.

 

[RVAmeche]

I'd guess it's because methane is frequently tested for natural gas systems, as well as the smell that provides additional indication.

 

[jari001]

Materials of construction may vary between methane and nitrogen based on operation temperature and pressure.