High Temp O-rings

[MadMango]

I am looking for an o-ring material that can withstand about 850-900F. I have found a perflouroelastomer material from Parker (FFKM) but it is only rated to 590F. This is for centering a .50" diameter "soldering tip" that is 12" long.

Am I running down an infinitely long and dark tunnel?

"Art without engineering is dreaming; Engineering without art is calculating."

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[MintJulep]

Certainly not an infinitely long tunnel.

I think you will quickly find it to be a dead-end.

I'm not aware of any elastomer that's good to 900F. I think you need to be looking for a ceramic.

 

[hydtools]

Some suppliers may be able to diecut rings from sheet of mica or glass. No elastomers for that temperature.

http://www.usseals.com/grafoil.htm

Ted

 

[Timelord]

MadMango,

In my experience, 600 deg F is the very best you can do with an o-ring. Since this application is just a centering ring it is probably not required to seal anything. If this is the case, just make a ring out of ceramic. Macor can certainly take the temp and is machineable and readily available.

Timelord

 

[MadMango]

Alumina Silicate ceramic rings are my next choice. I liked the idea of an elastomer since they are conformal and "give".

Thanks all.

"Art without engineering is dreaming; Engineering without art is calculating."

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[MiketheEngineer]

Talk to NASA -- they might know something about high temp O-rings - on the other hand - Maybe not!!

 

[GBor]

I thought PEEK would come close, but PTFE filled still only shows about 720F. A search on

http://www.matweb.com

didn't show up anything of interest other than your fallback. Good luck!

 

[unclesyd]

We fabricated our own heaters where we had to roughly center a heater in a roll. As the hole had a cast profile we used a ceramic fiber saturated with a cement that allowed heater to centered.

Here is one of many companies that make potting compounds for similar applications.

http://www.aremco.com/a2.html

Sauereisen is another supplier but the website is down.

If conductivity between parts isn't a problem.
In another fabrication we used a metal o-ring to center the two parts and then added the ceramic potting compound. If you use this approach make sure the ring is vented.

 

[Cockroach]

I think UncleSyd is on the right track. In the oilfield, superheated stream is used to breakdown the viscosity of petroleum byproduct in the tar sands, getting an off-the-shelf elastomer to hold this temperature has long been known to be impossible.

Rather, you need to be thinking in terms of graphoil or similar materials as used in the valve industry. I've used pure lead before, soft malable and readily accessable but cannot remember the melt point. Maybe a ceramic or specialty metal would work for you.

Good luck with your research.

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada

 

[btrueblood]

MM, it's not totally clear from your posts if you are trying to achieve: a compliant, sealed, joint from metal tube to metal? sleeve, with thermal or electrical insulation or both...

so, a few more random thoughts:

Boron nitride, as a pressed powder, is much more machinable, and has better (lower) thermal conductivity than alumina, but not quite as good as silica. Foamed silica even better, but weaker.

A tightly fit ceramic tube, especially one cemented/potted around the metal, may fracture if you don't take care with CTE differences.

A good way to keep the ceramic from cracking due to vibration/handling is to pot it in place with some silicone RTV, if you can engineer a spot to put the RTV where the temp. stays below 500F or so.

There are solder glasses that can bond ceramics to metal.

http://www.cotronics.com

is another supplier of ceramics in various guises.

 

[ShaggyPE]

Talk to NASA -- they might know something about high temp O-rings - on the other hand - Maybe not!!

Ouch!!!!! There's a jab.

-Dustin
Professional Engineer
Certified SolidWorks Professional

 

[MadMango]

Based on feedback here, the o-rings are out, we are going to a machined alumina silicate ring. The rings are more of a guide for the "solder tip", so there will be a loose fit between the rod that makes the "solder tip" and the guide rings (.002" clearance). We wanted the rings to provide thermal insulation because we are probably going to epoxy them into a 7075 housing.

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[leftyone]

I know in Semiconductor industry they use conflat, a sort of copper type metalic seal for temps. above 650F. No elastomer will tolerate above 600F no matter what the datasheet says. Don't be fooled. Gumlast has a seal that tolerates 650F for short period of time.

 

[MadMango]

Thanks for the conflat information and direction, I learn something new everyday. The machined alumina silicate rings designed performed "good enough" for this project to be successful.

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