Thread locker on pipe unions

Discussion in 'HVAC Heating & Cooling' started by Alessandro Bortoloni, Mar 18, 2020.

  1. Alessandro Bortoloni

    Alessandro Bortoloni New Member

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    Hello, I am having issues keeping pipe unions tight. The company i work for makes industrial sized gas dryers. We use a 2" pipe union on each end of our gas train. We build the machines, ship them out cross country to customer sites, and by the time my technicians arrive, the unions are all loose. Is there a sealer or a type of loctite that I can use on the union threads to keep it from coming loose?
     
  2. Sylvan

    Sylvan Still learning

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    If the unions are made up properly there is no valid reason for them to become loose
     
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  4. Reach4

    Reach4 Well-Known Member

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  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    I think you may need bigger wrenches.
     
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  6. fitter30

    fitter30 Member

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    Tighten as usual then hit it on a flat of the nut with a 2 lb hammer retighten. It won't come loose. When your 5' 6" 160 sometime you need some tricks.
     
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  7. Sylvan

    Sylvan Still learning

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    I really do not having my wrenches hit with a hammer

    This is why I have wrenches 6" - 48" or Chain Tongs and can easily add a pipe on the handle for more leverage when making up 6" threaded pipe

    When loosing an old union I use a ball peen hammer and cold chisel as I replace lots of expansion compensators (expansion joints)
     

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  8. WorthFlorida

    WorthFlorida The wife is still training me.

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    Are these unions installed at the factory with the machines for the gas connections? What part of the union has worked loose? Is this something new? Has the supplier of the union been changed or another manufacture? Are all fittings NPT?

    Assuming the union is becoming loose at the pipe joint, not the union joint. When the union is placed on the pipe stub, the thread (NPT) may be cut wrong (too narrow and not tapered). Or the union is tapped too wide. The pipe thread is tapered so as you tight the union, the pipe is squeezed into the union and it should be extremely hard to bottom out the pipe inside the union. Or during assembly of the union on the machine, it is being over torqued and distorting the tapered connection.

    If it is loosening at the union fitting, it is not being tighten enough or the unions are not manufactured to spec.

    Google "npt union connection"
    NPT stands for National Pipe Tapered thread. It is also sometimes called National Pipe Thread, NPTF (F for Fuel), American Standard Taper, or simply "pipe". Most other plumbing fittings have straight or parallel threads, but NPT fittings have a tapered thread profile. Sep 11, 2012

    Both NPT and NPS have the same thread angle, shape, and pitch (threads per inch). However, NPT threads are tapered and NPS threads are straight (parallel). ... Straight Pipe Threads need a gasket or O-ring to create a seal. While NPT and NPS threads will engage, they do not seal properly with each other. Feb 4, 2020
     
  9. fitter30

    fitter30 Member

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    Have you changed how the gas train is supported for shipping, using a different brand - quality.
     
  10. Sylvan

    Sylvan Still learning

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    I use Ward black unions or Anvil and never had a failure both are domestic
     
  11. fitter30

    fitter30 Member

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    Need to read my post again i didn't hit the wrench i hit the flat of the nut. When your in a pipe chase like your pics hammer and chisel is the only way without opening up the wall more. Any screwed thread bigger than 4" calls for a torch, stick welder and slip on flange. Never used or seen a machine that did larger than 4" .
     
  12. Sylvan

    Sylvan Still learning

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    IF you need to thread larger pipe

    Do like I do and use a Rigid 161 4" - 6" ONE person can thread it using a Rigid 700 with the adapter for the 141 and 161 stock and you need a vise and oiler

    The 700 is also great for threading pipe in place just hold back
     

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  13. Sylvan

    Sylvan Still learning

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    The above picture is before and this is after one man with a sawzall that cut the nut and then the rest of the union out saving the existing took about 11/2 hrs start to finish

    Materials needed sawzall blade, 2 black nipples , 1 expansion compensator 1 Ward Union (rated) and try not to laugh when handing them a bill for $3,967

    Most plumbers fear trying save the 43 year old black piping on a heating and cooling system . I Figured it is not my home or piping just try my best

    https://www.nyrpcorp.com/keflex/
     

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  14. fitter30

    fitter30 Member

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    I carried a 700 & 300 on my truck for up to 2" . Phone call can have a 2" -4" machine. Never
     
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  15. Sylvan

    Sylvan Still learning

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    For low pressure steam lines and older (before Victaulic) stand pipes it was all threaded , Ever see 7" black steel
     
  16. fitter30

    fitter30 Member

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    Yes and 5" ,left threading couplings and 90s. All long gone.
     
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