High Vacuum Feedthrough For Heated Vapor

Welcome to CR4. Why not use a hollow metal seal like they use on sparkplugs?

That's a possibility. Not wanting to start a project specifically on designing a new feedthrough for injecting hot vapors into a vacuum chamber I was hoping to find something "off-the-shelf". The "fluid" feedthroughs currently on the shelf come in two varieties. One is just a tube welded to a feedthrough (conflat, KF, and thread+bolt+washer). The other actually includes a double-walled, evacuated tube similar to what you're suggesting. The problem I'm facing with the latter is that I need to heat the entire feedthrough to keep the vapors from condensing. With the hollow tube design, I can heat the outer wall, but the inner wall (which is vacuum insulated) will not be heated, and condensation will occur). The former design of a tube welded to a conventional feedthrough is my best solution but I need to use a thread+bolt+washer design. The best washer solution I have right now is Kalrez which can go up to about 320C (I was hoping to go even higher, like 350-400C). I was just wondering if someone knew of a higher temperature washer (like perhaps a flexible, compressible ceramic). I'm thinking that 320C is the highest that's out there though.

I'll keep the hollow seal idea in mind though. Thanks.

Does it have to be a washer seal or could you have a mini Conflat with copper seals?

Never tried this with vacuum but maybe a metal O ring?

You need a knife-edge seal to an annealed copper washer/gasket. If you are using High vacuum and vapor transfer, then you MUST use all metal and ceramic and glass components or your seals will corrupt your vacuum and your condensate.

A thin plate of copper silver soldered to the tube as a flange/seal might work for you. Use a large diameter outer and secure it around the perimeter with a steel ring and screws. If this has to be serviced regularly, then the seal ring should be separate from the assembly.

If you could make use of sparkplus for this do it! They are very handy starting points for vacuum systems, including electrical feed through at High voltage and low/high pressures.

If you used an alumina ceramic feedthrough the thermal conductivity is sufficient to allow you to fit a heater to the outside.

There are silicone rubbers that will cope with 300 C.

Commonly used to seal the ends of tubular heating elements, etc

Dow Corning have such - ^{_{from memory - no time to do the search for you}}.