Composition of Nitrogen/Helium for Leak Test of process piping

[Johan Rivera]

All,

Having a leak rate acceptance criteria of 50 SCF/y in a mixture of 99% Nitrogen/ 1% helium for leak test of process piping, shall such criteria be different if the presence of helium by composition in the mixture is not guaranteed to be 1%?.

I appreciate your valuable feedback.

 

[EdStainless]

As long as it is close it will the same.
For small leaks all of the leaking gas will be He.
I presume that this is low pressure and that you will be sniffing for the He with a mass spec?

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P.E. Metallurgy, consulting work welcomed

 

[Johan Rivera]

Thanks Ed...
It is high pressure in most cases (200 barg) for for corrosive and toxic service in process systems. Yes, mass spect is there but no assurance on the composition of N2/He mixture

 

[EdStainless]

If you are looking for small leaks the pressure doesn't matter.
2 bar and 200 bar will give you same result if it is molecular flow.
You do need a guaranteed minimum on the He.

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P.E. Metallurgy, consulting work welcomed