Gas-tight fittings

[Tim+]

Well if that *isn?t* what you?re looking for does this mean you?re looking for a similar coupling to be used in-line rather than to just connect to a cylinder? Never seen such a fitting as an in-line fitment.

Incidentally, for gas cylinder connecting, the male end is domed whilst the female (cylinder end) is an inverse cone.

Tim

[newshound]

POL seems fairly commonplace, here is another explanation.

"The POL (derived from the company, Prest-O-Lite, who first made the fittings) fitting is found on larger 4kg to 9kg cylinders. This is a female fitting and points out sideways from the bottle."

[SH]

Which is what I said in teh first place, a POL connector!

And POL stands for Prest-o-lite :-)

[SH]

And herewith a table of connector types:

[newshound]

Well done. Wikipedia is usually one of the first places I look, not sure how I missed it this time.

[Robin]

I can only repeat the apology in my follow-up post

[SH]

Come to think of it, a similar connector can be found on the ends of flexible hydraulic hoses where they are screwed into the brake caliper as shown:

The connnector size is smaller than that of a POL connector but the hose may not be rated for carrying gas.... So a metal braided flexible hose might be more suitable lke this:

[SH]

or

provided the inner pipe material is gas compatible (such as PTFE or FEP (fluoroethylene polymer))

[Cursitor Doom]

I think we're still at cross-purposes here. I'm not claiming rubber O rings are infinitely re-useable. What I'm saying is "the system" I'm describing *is* infinitely re-useable. O rings will degrade over time and doing/undoing them will accelearate that wear. OTOH, "the system" (we are still awaiting the name of it) is such that it only gets

*better* over time. Yes, the more times it's screwed and unscrewed, the better the seal becomes as the two mating faces bed in and polish up against each other. What's a tribologist? I'm a pure-bred Angle but I don't go on about it. :-)

[Cursitor Doom]

I don't think so. That seems to rely on the squishing-up of an O ring. The system I'm on about doesn't need anything deformable to effect a seal. See the O ring on this POL connector:

[Cursitor Doom]

I still don't think it's been identified correcly in this thread. Here's the *actual* coupling I'm talking about:

It seals in the way you describe and requires no O-ring, no PTFE tape, no sealant - not even a thin smear of vaseline. And it is *infinitely* reusable as there is no deformation involved. Sounds too good to be true, doesn't it? But it is. The sealing principle is very similar to that used between ground glass unions in lab glassware inasmuch as a shiny ring forms on the seating surfaces where they contact each other. Nearest I've found so far is CGA350 standard. But smaller!

[The Natural Philosopher]

Materials scientist I think

[Robin]

Read the Wikipedia article and you'll see POL is sometimes with and sometimes without. I've no idea what current British Standards require.

[PeterC]

Just as well! An internal room at work (Plessey Caswell), CO2-cooled oven, I noticed that the cylinder was not right for CO2. Went in to check (nothing to do with me but I was concerned about what they'd managed to get). Um, CO in an open system - LH thread is good!

[Cursitor Doom]

Okay, but there is NO O-ring on the system I'm referring to in this thread.

[Cursitor Doom]

Flamable gases have a nick machined out of the nut that does-up anticlockwise to indicate it's a left-hooker. Makes it easier to tell Left Hand-Threaded nuts at a glance.

[Andy Burns]

bull-nose & cone?

[Andy Burns]

Shouldn't BS 341 be on that list?

[newshound]

Friction, wear, lubrication. And contact mechanics.

[newshound]

It's still a POL connector.