O-Ring or U-Cup seal at 450F 1

[Letuch]

Kalrez O-ring and spring energized PTF U-cup seal work perfectly as static seal between metal shaft and metal/ceramic body with bore, at elevated temperatures up to 450F. Now, design requires Dialectric material for shaft sealed in the metal body at elevated temperatures. I performed test with MACOR ceramic in the presense of water steam and observed decomposition of the MACOR to the certain depth permanent change of mechanical properties (decreased density and 1.4% increase of dimensions. Next test have been performed with Glass Filled Peek, but dimensional unstability at elevated temperatures caus U-cup seal failure.
Does any one know prooven solution for metal/plastic sealing at elevated temperatures?
Thanks.

 

[StoneCold]

Ask the technical people at John Crane, Chesterton, or Flowserve. I am sure they have seen this a million times.

 

[Letuch]

The only option they offer is packing, but that is not acceptable solution for me. Packing requires maintainance and consume space for compression mechanism. I am lookin for permanent static seal. I wish it is possible to braze ceramic to metal.

 

[ApC2Kp]

Letuch,
If a permanent static seal is required, then it could be you could use a hermetic seal similar to that provided for elecrical feedthru fittings from ELECPAC Div. of Wilbrecht Electronics. There was a 800 deg F seal that was matched for thermal expansion of glass and KOVAR metal body and KOVAR signal wires in a ceramic core. The metal body had an internal shoulder to retainer the ceramic core against drifting from pressure during thermal cycling. see

http://www.wilbrecht.com