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Helium valve seal

Helium valve seal

Helium valve seal

(OP)
Problem: I need to seal and then open quickly a 30 inch orfice. It is to hold 0.18 psi helium at -45 deg C with minimal leaks. My best sealing material I beleive is silicone. How could the valve best seal helium? a flat gasket design? o-ring design? other?

RE: Helium valve seal

Why do you think silicone is your best sealing material?  Silicone rubber is very permeable to gas/vapor.  Butyl rubber is a much less permeable sealing material.   

RE: Helium valve seal


looking theoretically at your problem (no further details than given - especially on opening/closing mechanism) the best sealing material could be butyl rubber as stated above.

Best sealing constructions for flanges or lid-like sealings would probably be o-ring in groove engineered to fit together (dept and width of groove to give just enough room for the O-ring to compress and fill grove at given conditions - (this is an art) - counterface flat).

If you really want to put money into quality the O-ring would be of PTFE to cover (more than required) of the lower temperature range or FEP - construction (rubber covered by PTFE).

Note: a lot of cheaper solutions exists, both for form and material just check what is reasonable result and cost for you.

Ask a top quality sealing producer/supplier!

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