Gas and non-gas PTFE

[polygonum]

A little while ago I posted about an MDPE weeping connection - thanks for responses.

Having prepared for destroyed olive, no insert or whatever, opened it up and found it was what it initially seemed to be - not done up properly to begin with and a bit of dirt/scale/slight scoring allowing the tiniest moistness. So I wrapped the olive neatly with some PTFE tape, tightened it up properly, and it is nice and sound.

For the first time, I used gas PTFE tape. Lovely and decent thickness, not flying away with static, easy to wrap neatly. Now I am wondering why they bother making non-gas PTFE. Is there any good reason? Or is it simply a cheaper and crappier product without other merit? (Not that Toolstation's finest was expensive!)

[The Medway Handyman]

I've had similar experiences and thoughts. Gas tape is so much better IMO.

21p as opposed to 50p. Spose it might matter if you use hundreds of rolls.

[polygonum]

And 12m as opposed to 5m. Still at the ignorable end of the scale unless, as you say, using miles of it.

[Roger Mills]

I bought a pack of (I think) 10 rolls of gas PTFE a few years ago for not very much when SF were doing an offer. It's brilliant stuff - I've not used 'ordinary' PTFE ever since. Because it's thicker, you need less of it - and it doesn't get shredded by the threads like the regular stuff does.

[newshound]

I'm inclined to agree, the only possible advantage I can see for the thinner is that the "shredding" might allow it to fill up threads on a male item a little more effectively. Also you have a little more control if there is an unthreaded pin-bush clearance to fill.

[Brian Gaff]

I think the gas one does not produce static, which I guess if there is gas about might not be very nice. Of course its not pure ptfe, as it contains a semi conductive part. I can well remember when emi decided to use ptfe liners in their audio cassettes, most people started hearing clicks on their tapes, and a good fast rewind made it most likely you would get a shock taking it out of its machine.

Very good stuff to use to make static electricity generators with, if a little expensive. I blame the ions. Brian

[Fredxxx]

In which case you would have thought the thin stuff would be good for gas?

[DerbyBorn]

Just an observation (and from watching helpful videos on Youtube), I think some people reach for the PTFE when it should not be used. I have removed compression fittings where the PTFE has been used on the threads and on tap connectors. We need to identify what performs the sealing - and what provides the clamping force. I guess some people might jump in and say they use it everywhere as it does no harm.

[polygonum]

I think it can help to lubricate a thread so it is easier to tighten up

- and probably helps to ensure it can be undone in future. But shouldn't really be necessary.

[bert]

In message , polygonum writes

Perhaps it's safe to use with drinking water and the gas one isn't?

[Tim Watts]

Not that I know of.

[newshound]

That's exactly why I *do* use it on threaded connections, even compression joints with an olive. I don't wind it over the olive, although to be honest I do not believe it would adversely affect the sealing because the metal to metal contact is at a pressure related to the yield stress of the brass, copper, or whatever and this is *very* much higher than the flow stress of PTFE.

It also helps when used liberally on the threads of immersion heaters, because it fills up the gaps and prevents water penetrating and depositing limescale. A friend of mine has some which do a lot of work in his brewery, and need replacing every year or so. This has been much easier since I trained his fitter to use at least 10 turns.

[bert]

From Wiki colours of spools.

White ? used on NPT threads up to 3/8 inch Yellow ? used on NPT threads 1/2 inch to 2 inch, often labeled "gas tape" Pink ? used on NPT threads 1/2 inch to 2 inch Green ? oil-free PTFE used on oxygen lines and some specific medical gasses Gray ? contains nickel, anti-seizing, anti-gailling and anti-corrosion, used for stainless pipes Copper ? contains copper granules and is certified as a thread lubricant but not a sealer

[Fredxxx]

My policy is to only use PTFE to seal tapered thread, otherwise I avoid the stuff.

[DerbyBorn]

polygonum wrote in news: [e-mail]:

A smear of grease would work as well. This is my usual approach.

[amcmaho]

On Sunday, March 1, 2015 at 11:58:26 AM UTC, polygonum wrote: Now I am wondering why

The only difference is in the density of the tape.

Voids open up in the material when PTFE is stretched, as part of the manu facturing process.

SFAIK, there is no BS for ordinary plumbing PTFE tape (sold by length), w hile the gas tape is manufactured to some British Gas specification (can't be arsed to look it up). There is an incentive for the manufacturers to str etch the PTFE as much as possible to yield the maximum length of PTFE tape.

With the gas tape, you're buying more PTFE and less hole.

Goretex is stretched PTFE, so for that material the microscopic holes mus t be large enough to allow water vapour through while keeping water out.

[charles]

Yes, I'm sure the PTFE tape I buy nowadays is much thinner than the stuff I used 40+ years ago when installing a CH system.

[Roger Mills]

That would have been hemp, wouldn't it?

[The Medway Handyman]

Or Oakum :-)