4 ms·
For high vacuum (i.e. NOT UHV), Viton gaskets are fine basically anywhere. They leak water however. If you have some odd shapes that are hard to clamp you can
by avsteele 5y ago
For high vacuum (i.e. NOT UHV), Viton gaskets are fine basically anywhere. They leak water however. If you have some odd shapes that are hard to clamp you can use any variety of epoxies (from e.g. https://www.epotek.com/ https://www.epotek.com/)
Glass to metal is the only tough nut at the low end of high vacuum. Glue works but you will always have to worry about thermal stresses crating a leak someday.
There's a new fs pulse laser technique for directly bonding glass to stainless, but its still not quite there yet.
At my company we developed a new type of all-metal seal as drop in replacement for viton gaskets. These can get you way below where viton can, and work well for arbitrarily shaped ports. It's awesome. Still a few bugs to work out to make sure you get a tight seal before cracking the glass.
- MengerSponge 5y agoAre those all-metal seals commercially available yet? Got a link to a product page, or to your company's contact page?
- avsteele 5y agoYou can email me adam@zerok.com
- rainbowzootsuit 5y agoIsn't Kovar to borosilicate a well accepted method of joining glass for vacuum applications? I mostly worked with UHV, as your disclaimer excluded, so am not widely with high vacuum applications. I'd think that there would be an issue with thermal coefficients going directly to stainless.. https://en.wikipedia.org/wiki/Kovar https://en.wikipedia.org/wiki/Kovar
- fuzzfactor 5y agoOn a mass spectrometer I recently replaced an old-fashioned triode gauge tube and these are the same size glass as the 9-pin miniature radio tubes of the 1950's. The base looks like an audio 12AX7 and fits the same size socket, the metal pins are supposed to be Kovar coming through the glass. But this electron tube is not sealed at the top, it is wide open with a Kovar metal precision adapter ring fused to the glass instead, and a Viton o-ring is used to lock it into the vacuum measurement port. As a vacuum tube, it "simply" behaves differently depending on residual trace gases present. It is connected to a circuit optimized to give calibrated vacuum readings. No doubt I could connect it to an audio circuit instead, and get some excellent output. It's a well-made tube, only a single triode though.
- avsteele 5y agoKovar sleeve viewports are fine yes down into UHV. We don't use them because standard viewport shapes are very limiting. I guess you could have an operation large enough to custom fabricate something, but that's not in my experience
- rainbowzootsuit 5y agoI've used a feed throughs that came as CF bored out with a borosilicate stubs already attached, so that you can fabricate your own glass without having to know about the metal-glass bonding. I'm not sure how big those get if you're trying for viewport style usage.
- syntaxing 5y agoWait, why are Viton not ok for UHV? Viton KF seals are used everywhere for UHV (maybe not to the -12 but -10 is definitely achievable).