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Howdy,

The first issue I foresee is the o-ring material. If the seals are
standard O-rings, great, then you can just order Viton O-rings. But I
thought those fittings used custom seals with odd cross-sections.

Sigh...you're right. Here's a high-res photo of some gaskets:



They look mainly flat, with a ridged part around them, and the flanges have an O-ring
groove in them. I suppose the advantage of that is you don't need a centering ring
like with KF flanges.

You can get Buna-N (nitrile) gaskets easily, and fortunately some sites (found one EBay
store ) sell Viton gaskets.

Another possibility to think about is that they don't have to be
absolutely gas-tight for dairy operations, small leaks may be permitted.

Could be, although I would've thought that for hygienic reasons they'd
ensure there's no places where stuff could get trapped or porosity.

Another thing to think about: for the most part, high vacuum fittings
are designed such that when assembled together, very little "trapped"
volume remains in the conjoined system, that is, space that is
connected to the pumped volume, but has low conductance, IOW, "nooks
and crannies".

The large flat gaskets might give rise to this.

But I agree that these do resemble KFs an awful lot, and I'm going to
start comparing prices out of curiosity - if they are drastically
cheaper than what I can get from Duniway et al, then an experimental
purchase and test would seem in order!

Would be very interested to hear how it goes! It turns out I can get them in the UK,
just searching under "tri clamp fitting" instead.

On a related hardware topic, have you ever come across the convoluted metal
hose used for domestic gas main installations? Stuff like this -



Maybe things are different in the US, but there's always a bit of that stuff used between
the gas main and house regulator. It looks to be very nice for vacuum use - not quite
as flexible as proper vacuum bellows tubing, but still pretty good. Also see ebay for
"flexible exhaust" - for example item 230830064598. Again, bellows tubing just like
that used for vacuum. No ends unfortunately!

Cheers,

Lindsay

- Bill "Gomez" Lemieux,
The Highland Tinker