Seal interspace leak test

[fred2002]

Greetings!

I have been asked to come up with a method of checking the sealing integrity of a double O-ring static seal arrangement. There is an interspace with a test tapping point. The seals are pressurised from the outside.

The acceptance criteria for the seal integrity is a specific volume of air within a set time with a differential pressure across the seal of 0.2 bar.

The pressure outside the seals will be ambient, and I will create a vacuum within the interspace. The interspace volume is fixed at about 4 litres and over 250 seconds no more than 0.8 litres must enter the interspace.

Do I have enough information to design/specify some test equipment?

Is it just a case of measuring a pressure rise?

Thanks in advance.

 

[EdStainless]

So in service is the space between the seals at vacuum? Or is the outside pressurized?
And if test by pulling a vac in between then aren't you testing both o-ring seals at once?
Is the 0.2 bar across one seal or both?
So if you take 4 l to 0.8 bar abs you will have removed 0.8 l of air.
And since that is your leak criteria you can't rely on simple pressure decay.
You could have a larger tank (40 l) that you pump to 0.8bar, and then connect to the test piece with a sensitive flow meter (roughly 3cc/sec at max leak rate).

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P.E. Metallurgy, consulting work welcomed

 

[Compositepro]

That seems to be a very large leak rate for a seal. I believe such a large leak rate would result in soon destroying the seal or it would self-seal to a much lower rate.