Silicone O-Ring in Oxygen service?

[ProjEngInstrument]

We're designing a pressure sensor for Cryogenic gas measurement that uses a solenoid valve containing several O-Ring seals.

The gas of concern is Oxygen, our solenoid valve manufacturer recommended EPDM or Silicone O-Rings for oxygen service.

We tried the EPDM but the valves leak at our low temperature limit (-40C). The silicone seals nicely at the cold temperatures but there may be safety concerns using the silicone seal material with oxygen (gaseous)?

Material compatibility looks good for cold oxygen with silicone o-rings, but I have read that silicone seals aren't recommended with oxygen above 130PSI (our application typicially up to 200 PSI). Valve vendor states they use the valves in fighter jet oxygen applications up to 80 PSI. What is the safety issue (if any) with oxygen and silicone seals?

Viton is preferred with oxygen service but may not work well at -40C and vendor doesn't have this option anyways (one of the O-rings is non standard so this would probably be hard to find in alternate materials).

I'm hoping we can make a good case for using the silicone seals for this application?

 

[btrueblood]

Less an issue with pressure than with temperature for gaseous oxygen, the different compounds will oxidize with time and temperature. Get yourself a copy of the Parker O-ring handbook(*). It lists a silicone polymer as preferred for O2 above 300 F, Viton for 200-300 F, and neoprene for "cold" oxygen. EPDM and all the above are given a "satisfactory" rating for "cold" oxygen. If EPDM at -40 is not sealing well, ask for a softer compound (most EPDM rings are 70 durometer, try using a 50-durometer ring).

(*)

http://www.parker.com/literature/ORD 5700 Parker_O-Ring_Handbook.pdf

 

[Demon3]

You could contact Peter Reimer at RxC Technologies. I know he specialized in o-ring formulations that have additives to protect them against plasma and other aggressive conditions.

Chris DeArmitt PhD FRSC CChem

 

[unclesyd]

You need to checkout the ASTRA seal from Creavey. Seal it and forget it.

http://www.creavey.com/downloads/Creavey-Brochure.pdf