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PTFE tape

GreenNeedle

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I've been digging around the forum (and others) gauging the quality and opinions/reviews on various regulators and setups etc. I'm not a first time user of pressurised BTW. I sold my last one about 18 months ago, however am sourcing a new setup at the moment.

Off the topic of parts really but I notice that loads of people use PTFE tape on their regulator threads. Can someone explain why?

When I was working as a welders mate a few years ago, the welders would go mad at anyone who used it on the regulator. I would go as far to say they were in for a yellow card (disciplinary) for doing so!!!

I was told that only gas grade PTFE can be used (not normal stuff) and definitely not on the regulator. Its only used to join pipes (like compression fittings.)

The reason I noticed the use of PTFE is because it is appearing in many pictures where a leak is occuring in their system!!!!

Now I am by no meas knowledgable on this subject after all I was just the labourer however you remember these kind of things especially as I had a setup at home. Maybe its old school thinking.

I found this thread which seems to concur with them but we all know we can find info to agree or disagree on any subject!!!

http://www.chromforum.org/viewtopic.php?f=2&t=2074

Any opinions from those who are knowledgable?

p.s. I never used PTFE on mine and had zero problems. Just screwed the reg to the cylinder. Also just screwed the needle valve straight into the reg. 500g bottles lasted for a couple to 3 months with no leaks.

Regards
AC
 

chris1004

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27 Dec 2008
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Hi Andy,

:oops: :oops:

I use PTFE tape on anything and everything. Never had a problem and it has helped me out of a jam on more than one occasion. My regulator has taped threads at every connection and its never leaked. That doesn't mean its right though.

I'm just a DIYer with no formal training so I will be following this thread with some interest.

Regards, Chris.
 

Dan Crawford

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I've done setups with and without PTFE, I do think CO2 lasts longer with PTFE on every seal. In my view it stands to reason, be it to "correct" stuff or not, it creates a better seal, doesn't it?

I'm like Chris in that I have no formal training, just seems like common sense to me.
 

Stu Worrall

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the local chap who supplies my gas said that the seal is on the neck of the bottle, not in the threads. On mine there is a plastic/rubber gromet that goes between the flat bit of the bottle top and the reg. Im not an expert on it, just took the advice of the local chap as his gas supply company has been in his family for many years

From below it also points out that particles of ptfe can get into the reg and cause it to send full pressure downstream to your tank :woot: (probably only happens in extreme cases though)

a few from google i found.

big thread on it here - http://www.reefcentral.com/forums/showthread.php?t=826326 with some quotes below

Teflon tape is not meant to be used with compressed gas. The theory is that small pieces can break free (and DO while tightening the threaded fitting) and become lodged in the regulator. There are specific plastic rings that are meant to be seated in the female portion of the regulator, and then the regulator is tightened with a correct-sized spanner. The plastic ring allows you to tighten the fitting down properly, and upon compression, provides a leak-free seal.

Ask anyone who deals with compressed gas for a living, and I'm certain they'll tell you the same.

With the correct gaskets (and appropriate spanner), there is no leak.
-E.

Compressed Gas Association (CGA) defines the safety standards for working with compressed gases and associated equipment. Reputable safety documentation typically references CGA.

I recall seeing one manufacturer recommend teflon for their regulator, but most likely that was some employee's "common sense" recommendation, and not anything from CGA.

More info:

http://www.scottecatalog.com/ScottTe...5?OpenDocument

Pertinent section states:

"Valve Outlet Connections and Fittings: Be sure all fittings and connection threads meet properly - never force. Dedicate your regulator to a single valve connection even if it is designed for different gases. NEVER cross thread or use adapters between nonmating equipment and gas cylinders. Most valve outlet connections are designed with metal-to-metal seals; use washers only if indicated. Do not use Teflon® tape on the valve threads to prevent leaking, it may become powdered and get caught on the regulator poppet causing full pressure downstream. Never use pipe dope on pipe threads. Also, never turn the threads the wrong way. This may produce brass particles that might get caught in the regulator’s poppet."

People make a lot of assumptions and overlook a lot of things with regard to compressed gas safety. I reviewed this recently with several people who should have known better, and they were very surprised when I gave them the urls in these posts. They only had been working with compressed gases for the last 30 years. It probably had been a while since they last had RTFM.


http://www.barrreport.com/showthread.php/2020-CO2-reg-choices-which-one
In general teflon tape should not be used with any other type of straight threaded connectors. (It will usually cause leaks). There are many hundreds of non-NPT connectors such as: Swagelok, BSPT (Brittish Straight Pipe Thread), Prestolok, or anything that uses a rubber o-ring or gasket to make a seal. Non Tapered pipe threads do not use the threads to make the seal, instead they use the threads only to apply a force to squeeze two surfaces together and the surfaces make the seal. Teflon tape usually prevents this seal.

So if it's not a NPT thread do not use teflon tape unless directed to by the MFR.

Most regulators have NPT connections for the pressure gauges and for the output line, but usually have a different type where they connect to the bottle.


http://www.mig-welding.co.uk/forum/showthread.php?t=9315
Do not use grease, oil or ptfe tape on the regulator or valve thread/seat.
 

GreenNeedle

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Dan -The link in the first post and those above explain the reasoning.

The threads that you use Teflon tape on are tapered in that they decrease in diameter the further you go down the thread. Like a wedge if you like. So the further in ti goes the harder it is to tighten. PTFE tape is not a sealant. It is a lubricant and lets you tighten a little further. In effect it's like putting some grease in the hole ad then the wedge hammers in a little further.

The threads on the reg are not tapered. They are the same diameter all the way down so teflon tape will be of no use at all. It could even mean shards break off as you are tightening, get between the 2 metal surfaces where they meet the plastic washer and CAUSE a leak.

So far from being a reassurance or a 'backup, just in case' application it could actually cause the leak.



From what I've read last night (been searching quite heavily brands of regulators and problems with them etc.)

Its the sort of thread that is there just to keep the 2 items in position. It is the washer that creates the seal.


I remember once when we had a new welder start (young lad ;) ) I walked into the fab shop and he was changing a bottle over.

The 'old boy' I was with suddenly spotted the white tape peeking out from the bottle neck, grabbed the young lad by the collar and marched him into the office. lol It is often used at the join of the actual reg body and the pipe that leads to the bottle attachment though. I think that is a different type of thread there.


AC
 

Dan Crawford

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A wealth of information there fellas, nice work. Maybe we should somehow link it to Sam's Thread about setting up a Fire Extinguisher CO2 System.
 

chris1004

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Ditto Dan's sentiments.

I'll be modifying my working practices with this in mind from now on. Thanks guys for the useful info.

Regards, Chris.
 

GreenNeedle

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I've used your picture here Sam to show where the PTFE is not be used. The 'can be used' one is based on what I have read up on. apparently it is a different type of thread there.

FEclose.jpg


AC
 

Mortis

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Just out of curiousity what do welders use CO2 for anyway ? Is it to control the flame temperature ?
 

milla

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Mortis said:
Just out of curiousity what do welders use CO2 for anyway ? Is it to control the flame temperature ?

Shielding gases[CO2] are necessary for gas metal arc welding to protect the welding area from atmospheric gases such as nitrogen and oxygen, which can cause fusion defects, porosity, and weld metal embrittlement if they come in contact with the electrode, the arc, or the welding metal.
 

JohnC

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Wow, excellent thread. I need to look at my washer/ring on my reg next time i switch bottle. must be knackered.

RE: Gas tape. it is MUCH thicker and does not work around threads.
 

Drouthie

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I've just finished a gas safety course at my work and another reason given for not using PTFE tape was that it can be used as a bit of a fudge, letting people use something that really isn't fit for purpose anymore. As soon as you start messing around with a regulator and modifying it in any way, legally you become the manufacturer with all of the burden of safety and responsibility if something goes wrong. The advice I was given was don't use it for anything at all. I believe that there is other safety problems with some lubricated PTFE tapes and more flammable gases but I can't remember at the moment, I'll check my notes at home.
 

O'Neil

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You can use PTFE Tape as long as it is fit for purpose (i.e. one wrap gas PTFE) and don't apply it near the edge of the male thread, ideally you want to be a thread or two away from the edge, this way when your screwing the nut down in theory the PTFE is being pushed back. The rubber/teflon washer should be all that is required, but if you are concerned in any way you should carefully apply gas paste to the face of the fitting, not on the washer or threads.
Use a good gas paste ROCOL is by far the best Gastite is garbage, the idea of the gas paste is to make up for any tiny imperfections (invisible to the naked eye) that have been left behind after the manufacturing process.
If you do take my advice apply it sparingly you simply need a thin coat around the face of the fitting.
The confusion comes from when the old paste and hemp method was replaced by PTFE on screwed steel fittings as all of the older gas pipework started to leak after the natural gas degraded the hemp.
PTFE is fine with gas but most often than not paste only is used.
Most of the old school plumbers and heating engineers will shun the use of PTFE on a regulator simply because it comes with the washer and that is all that should be required to make the seal.
 

GillesF

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Belgium
I use Locktite sealant. Very easy to use, just a bead on the threads and then you can screw it on. I've also never had to redo a connection for leaks, so it seals very well.
 
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