Non-Metalic Spacers for High Vacuum/Cryogenics

[weeeds]

Is anyone familiar with the type of non-metalic, non-thermally conductive, material that can be used in high vacuum and will also withstand touching a metal at cryogenic temperature?
Thank you

 

[EdStainless]

I am sure that ours were nylon.
You need low density and low thermal conductivity.

= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[israelkk]

ANd low outgasing

 

[IRstuff]

What exactly do these spacers do?

TTFN

 

[weeeds]

The spacers sit in the vacuum between a liquid oxygen vessel and the vacuum jacket. The tank sits horizontally and the idea is to place the spacers at the center of each head to take any shock loads that may result from the vessel being hit. We have a 10,000 lb load that can act on the contact surface between the two vesels and we do not want to put any additional stresses on the inner vessel suspension system. Therefore we need a spacer that is suitable for full vacuum without gassing off, can withstand the cryogenic temperature, and can absorb an impact load. We have seen some fiberglass-like tube material in the past but have no idea what it is or where to get it.
Any ideas?
Thank you

 

[israelkk]

Try NASA they have an outgasing information web

http://outgassing.nasa.gov/

 

[rd400guy]

Teflon?

 

[plastx]

I was thinking of Teflon too. I've seen it for sealing cryogenic products. DuPont states to -400F to +550F as a usable temperature range for PTFE. Would be important to know the stresses involved and chemicals that the seal may contact. There are fiberglass filled PTFE products out there. Check the following link for plastic seals including PTFE:

http://www.rulon-meldin.com/home.asp

 

[IRstuff]

Frankly, I think that it's bad idea. The vacuum jacket is designed to eliminate all conductive thermal paths. There is no material that can do as good a job as a vacuum for insulation. Whatever material you pick will substantially degrade the thermal insulation of the vacuum jacket. The only material that might come close in thermal properties is a sol-gel, but those are not designed for structural strength.

If there is shock problem, you really should look elsewhere to solve the problem, either with a larger gap, thicker walls or materials, etc.

TTFN

 

[unclesyd]

Here are several approaches to your problem. The first is CRS-Wrap, the next two are for Perlite products and the last is for a foam material. The CRS-Wrap has built in spacers.
Make sure you check the material performance at your vacuum level. The breakpoint in most systems is 10^-4 Torr.

http://www.lydallthermal.com/products_catalog-detail.cfm?PID=37&cid=41

http://www.silbrico.com/lowtmp.htm

http://www.perlite.net/redco/pvs_07.pdf

http://www.jm.com/insulation/performance_materials/products/hpi31_cryolite.pdf