CAN YOU USE PTFE TAPE ON GAS CYLINDER CONNECTION?

Discussion in 'Motorhome Chat' started by wingman, Jul 2, 2014.

  1. wingman

    wingman Funster

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    Can one use PTFE tape to ensure a gas-tight fit on the cylinder union? The brass hose-to-cylinder connection never seems competent enough to me. Yes, I take care of my brass hose coupling, but the cylinders must get plenty of abuse from previous owners? Even the slightest dinge (technical term?) on the cylinder coupling could allow gas to escape.

    Certainly, there have been a few times that I've had a whiffy gas locker - even though it's vents are clear and hose etc is new. A dealership once told me that "you have to really nip the nut up tight with a spanner". Well, I've given my spanner and nut plenty of 'Isaacs' and even hung off it a-la Robin Knox Johnston! BUT a brass- to-brass connection seems doomed to fail at some stage, especially with road movement and metal-metal imperfections.

    I'm aware that there's two different types of PTFE - one for general plumbing and one for gas. Sooo, apart from getting over-zealous with tape and blocking up the aperture, is there any reason why tape can't be used
     
  2. scotjimland

    scotjimland Funster Life Member

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    No.. do not use PTFE on a bottle seal..

    the seal on a propane bottle is a brass, face to face seal.. the thread does not make the seal..
    As the bottle seal is female connection.. it is unlikely and unusual for it to be damaged..
    the seal on your pitail or regulator, which is male, is far more likely to get damaged..

    Inspect the male, if it is scored either replace or if only minor scratches, try rubbing with some very fine emery cloth..
     
    Last edited: Jul 2, 2014
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  3. tofo

    tofo Funster

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    I always assumed you shouldn't

    As the faces of the joint

    Are ground to fit each other

    tape on the thread won't stop gas coming from
    The inner gas carrier pipe on the connection

    Only my thoughts
     
  4. Terry

    Terry Funster

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    Well I disagree with Jim on this :D cannot see what harm it can do and yes use the gas stuff --I would buy yourself a can of gas leak detector spray as well --I know I have given some of my own bottles plenty of torques but still detected the odd wiff of gas in the locker ---The gas SS pipe I just got off Tecno has a rubber connection on the bottle side and hand tighten knob/no spanners so I cannot see why no PTFE
    I can stand to be corrected it won't be the first time :Dedit I am assuming you mean on the threaded bits
    terry
     
  5. Gromett

    Gromett Funster

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    I was always led to believe no PTFE on any gas connection. Plumbed in my whole van 3-4 years ago and no problems at all.
    Occasionally got a smelly bottle before I started on the refillable, but a quick tweak always sorted it.
     
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  6. scotjimland

    scotjimland Funster Life Member

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    no problem.. as is your prerogative .. :)

    I don't give advice on topics I have no qualifications, training or experience.
     
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  7. The Wino

    The Wino Funster

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    The seal is the face of the domed end so ptfe wont help it might mean you cant tighten the connector fully so no (in my opinion).

    David
     
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  8. scotjimland

    scotjimland Funster Life Member

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    you have it in one.. (y)

    There is another valid reason for not using PTFE tape,
    If a small part of it gets into the pipework it can block the regulator or a gas jet causing all sorts of problems..

    PTFE should only be used on taper threads where it is used as a lubricant and sealer.. taking great care not to wrap it over the edge of the thread where it could break off when tightened. .. (see above).

    Never use on parallel threads or gas compression joints .
     
    Last edited: Jul 2, 2014
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  9. Jaws

    Jaws Funster Life Member

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    No. one son is a gas safe approved fitter.
    I asked him about this a while ago.
    There is a specific type of ptfe tape made for gas joints and ordinary white stuff should not be used ( an installation will fail commissioning tests if it is used and they will not issue a Gas Safe certificate )

    But as others have already mentioned, the seal is on the domed end not the thread
     
  10. Terry

    Terry Funster

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    The gas PTFE IS BLUE -still don't see any reason it cannot be used on the threaded bits -we always use gas it paste on any of the compression /olives joints but that stuff is red and gets everywhere -I have several mates who are gas safe reg and I admit I did not know they even did a gas PTFE tape until a couple of yrs ago -so will ask them about it's use
    terry
     
  11. Plumberman

    Plumberman Read Only Funster

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    Hi Wingman,
    PTFE tape should not be used on Gas Unions as there is a risk if it stopping the two machined faces of the union sealing properly.
    Also as posted earlier there is a risk of causing a blockage in the connecting pipe work / fittings.
    You can use an approved LPG jointing paste if you have problems with leaks but be careful not to get any inside the pipe work ,just a very light coating should do the job.
    PTFE is only a thread sealing tape.
    If you smell gas in your Gas locker buy a can of leak detection spray which is quite cheap from a plumbers merchants and will detect where the leak is coming from.
    Leaks will show up by foaming bubbles around the leaking areas,even micro leaks can be dangerous if allowed to build up.
    Don't be tempted to use washing up liquid as an alternative as this has been proved to be corrosive to hoses and fittings .
    This should be used every time you undo or disturb a fitting.
    LPG is heavier than air so gas will collect at the lowest point,which is why you should have drop holes under all cylinders and appliances which should be kept clear of debris at all times.
    Also the base of cylinders should be kept clear as this is an integral part of the surface area of the cylinder to allow gas to be drawn off at the correct rate.
    The sealant mentioned by Terry in previous post is Stag Red Sealant and is for use on permanent joints not cylinder unions .
    Most modern sealants are non setting to allow for easy removal of fittings.
    Hope this helps you.
    Alex.
     
    Last edited: Jul 2, 2014
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  12. Tootles

    Tootles Funster

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    Tyres????? :whistle::whistle::whistle:
     
  13. wingman

    wingman Funster

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    Thanks Alex and all other contributors. Really interesting replies.
    When I'd sat down and thought about it, all made complete sense, doh!

    What was equally interesting (and quite a gem) was the locker space itself. I've always understood about keeping the vents clear and I have two contoured platforms for the cylinders BUT, I have a bad habit of using the locker to bung all sorts of stuff. As of now, I've stuffed in levellers, a flat hose reel, dust sheet to kneel on and an adjustable parrot-nosed spanner contained in anti-rattle bubble wrap to give the nut a few more Newtons!!! The locker's not full, but the advice about an air flow around the bottles is something I've never thought about!

    Bugger; where am I going to put this stuff now???

    Thanks guys
    James
     
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  14. Terry

    Terry Funster

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    Spoken to 3 different gas safe plumbers now and all say it's safe to use on the threaded bit ---It is now white tape but comes with a yellow top and is slightly thicker than normal PTFE, normal ptfe which incidentally is pressure tested up to 20 bar where gas is normally at 2 bar at the most -All 3 said gas is measured in millibars unlike water and all said it was OK to use or use the paste just be careful not to get the paste into the pipe :)All said use the leak detector spray after making the seal if you are unsure,
    terry
     
  15. funflair

    funflair Funster Life Member

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    I think the question has to be WHY would you want to put ptfe tape on the thread as it will not help with a gas seal, if the male into female joint is leaking the threads are not there to stop it as gas would still get up the inside of the nut.

    To lubricate the threads OK.

    Martin
     
  16. mentaliss

    mentaliss

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    Well can't speak for the others BUT GasLow ( my system) technical says absolutely not !!!! no tape, no sealing gue..........
     
  17. gasman2008

    gasman2008 Read Only Funster

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    If you suspect a leak cover the joint with leak detection fluid, if you want to help the seal put a small (VERY) amount of gas tap grease (this must be for 3rd family gas) on the male end before you put the hose onto the bottle
     
  18. Techno

    Techno Funster Life Member

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    Shall we have a vote?
    No tape !
     
  19. gasman2008

    gasman2008 Read Only Funster

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    Tape will not help. So I vote NO
     
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  20. timdownieuk

    timdownieuk Funster

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    Given that these gas safe plumbers have no idea about cylinder pressures I wouldn't put too much store in anything they say. Were they qualified to work with LPG? Not all are I believe.

    I vote NO too. As has been repeatedly said, the threads don't make the seal.
     
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