high temperature o'rings 2

[breaker34]

does anyone have experience with High Temperature o'rings? I am talking fire tested rings, so will see 1300F

 

[MikeHalloran]

No.
See "Challenger".

I dimly recall some removable high temperature metallic seals called "Clam Seals". I don't think they are in production anymore. The only reference I can find is a highly simplified typewriter sketch here:
ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.../19750071373_1975071373.pdf
See Figure 6(b).
They were axially stiff and sealed by Brinelling their way into the gland faces, which means they only worked once if they worked at all.

Caterpillar uses what amounts to a two-hump bellows as a gasket between their turbochargers and downstream pipes. It is axially flexible, and requires perfect faces to sort of seal at all. Mostly, it either leaks until the leaks are clogged by soot, or it burns out immediately, and is then replaced with a flat composition gasket, which fits apparently by happenstance.




Mike Halloran
Pembroke Pines, FL, USA

 

[moltenmetal]

There is no such thing as an o-ring which will survive 1300 F.

There are hollow torroidal metal gaskets made by some (Haskel amongst others) that some people call "metal o-rings", but these do not behave the same way as some fictitious elastomer which survives 1300 F.

There are also metal gaskets designed to be somewhat pressure-loaded, such as the seal ring used in the Grayloc connector.

 

[israelkk]

Rubber such as Buna-N for example is an ablation material therefore, it can stand even much higher temperatures for a short period of time (minutes). You should describe your application more precisely.

 

[btrueblood]

Similarly silicones will withstand brief exposures to fire before they leak (ablate through). Thus, Challenger made it 90-some seconds into flight...

 

[Burdy]

We changed our o rings out to graphite rings as the seal was static. Metal orings were just far too expensive to incorporate into the product. B

 

[NGiLuzzu]

breaker34,
as rule of thumb, I usually consider the maximum allowable temperature for o-rings made of engineered polymers around +325°C = +615°F (with reference to DuPont™ KALREZ®, for example: see

http://www.kalrez.com).

In presence of oxygen, graphite faces high risks of oxydation above approx. +450°C = +840°F.

So I believe You have to switch to graphite o-rings for the temperature You mention, as well as to adopt design solutions capable to reduce temperature in the area where o-rings are assembled onboard the valve, if possible.

Hope this helps,
'NGL
_______________________

 

[breaker34]

thank you to everyone.

 

[NGiLuzzu]

Sorry, I made a copy/paste error!!! ;-)
The last sentence should have been:
"So I believe You have to switch to metal o-rings for the temperature You mention..."

Thanks and Regards,
'NGL
_______________________

 

[moltenmetal]

Flexible graphite is a valuable gasket material, but you can't make a true o-ring out of it.