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  1. #27
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    Quote Originally Posted by jmac00 View Post
    there is ONE guaranteed way to "seal" NPT threads.

    Use Teflon tape and then put pipe dope over the Teflon tape. This is about the only way you can run anti-freeze through screwed pipe without leaks. An old pipe fitter told me that trick. Just use caution because you can screw fittings together so far that you will crack the fitting.
    glycol dissolves teflon pastes. should use that black goo called grip. think hercules makes it. and don't get it on your clothes

  2. #28
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    May 2000
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    Quote Originally Posted by heavymetaldad View Post
    glycol dissolves teflon pastes. should use that black goo called grip. think hercules makes it. and don't get it on your clothes

    aaah, the guy that told me that was "old school", and it was 20-25 years ago but it did work?
    I only drink a little, but when I do
    I turn into another person and THAT person drinks a lot

  3. #29
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    Quote Originally Posted by jmac00 View Post
    aaah, the guy that told me that was "old school", and it was 20-25 years ago but it did work?
    hey old timer!

  4. #30
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    Sep 2002
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    Hampton Roads, Virginia
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    Back when I did steam piping I was taught:
    Pipe dope on the Pipe threads
    Never-seize on the union threads and the shoulder the nut half sits on.

    Never had any leakage problems, and you could undo the union years later.

    Kevin
    "There are 10 types of people in the world.. those who understand binary, and those who don't."

  5. #31
    Join Date
    May 2004
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    Rapid City, SD
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    Using a bit of dope on the threads as a means to keep things from seizing up is a good idea, and if you're like me, open the bottle and you'll have dope all over yourself almost immediately.

    Using anti-seize instead of dope, well it accomplishes the same purpose and probably works as good or better... but when you become covered with this silver (or copper) colored substance... it's nearly impossible to wipe off and often just keeps smearing until you give up even trying and are mostly silver...
    "If you call that hard work, a koala’s life would look heroic."

  6. #32
    Join Date
    Jul 2005
    Location
    North Central Ontario Canada
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    624
    Have only ever saw one union with pipe dope on the threads. Was on the valve train on a 105 boiler horsepower 2 1/2 inch union. This needed to come apart on a regular basis for maintenance. Made it easier to come apart so I was told.

    Apart from that one time never put dope on any threads on unions for steam, hot water, fuel oil or heavy process oils.

    Using Masters Metallic on the male threads makes a difference.

    http://www.gfthompson.com/pipes.html

    I am sure there is a similar product in the USA.

    Come across the odd union with pinholes that leaks...usually stamped China on the fitting but thats another story
    Here's your sign...

  7. #33
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    Jun 2007
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    Here. I'm right here i tell you!
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    Quote Originally Posted by heavymetaldad View Post
    glycol dissolves teflon pastes. should use that black goo called grip. think hercules makes it. and don't get it on your clothes
    I learned that the hard way on a York YCIV while changing out the coolant pump. Does not matter which glycol either. They both do it!. It even did it with Locktite 567 . That glycol is something else!

  8. #34
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    May 2000
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    Rochester, NY, USA
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    Quote Originally Posted by heavymetaldad View Post
    hey old timer!

    that's me: I maybe used, but I ain't used up
    I only drink a little, but when I do
    I turn into another person and THAT person drinks a lot

  9. #35
    Join Date
    Mar 2003
    Posts
    7,326
    Well, I'd say this argument could go on for a long time, BUT pipe dope or never seize definately help to get unions apart in many cases. Example...for almost twelve years I had the service contract on a pro football stadium that used 350 degree hot water for heating. All piping was socket weld. Had over two hundred reheats, plus preheat coils in the 68 AHU's, some of which were face/bypass. Once a year for two weeks while the team was away at camp, we did a shutdown to rework things like control valves, coil replacements, thattype of thing. If you didn't use either dope or never seize, you were not getting the onions apart, period. with it, no problem. We also liked to hit the faces a bit, in the event of misalignment of the piping, it seemed to allow for easier movement of the ground joint when tightening, without scarring the face. For me, 1/2" gas line no, but for any sort of process piping, hot water etc, its on there. We do a lot of bigger equipment that most would consider industrial, and it just makes life easier.

  10. #36
    Join Date
    Dec 2007
    Location
    Northeast Wisconsin
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    482
    I put dope on the union THREADS only, not on the union mating surfaces. I wasn't taught this, it is just something that works well. As some others in this thread have mentioned, I use it this way to facilitate dis-assembly at a later date, not to create a better seal. Why don't I use something like anti seize? Because I already have the dope right next to me and it works fine.

  11. #37
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    Sep 2002
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    Hampton Roads, Virginia
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    Quote Originally Posted by Lurch77 View Post
    I put dope on the union THREADS only, not on the union mating surfaces. I wasn't taught this, it is just something that works well. As some others in this thread have mentioned, I use it this way to facilitate dis-assembly at a later date, not to create a better seal. Why don't I use something like anti seize? Because I already have the dope right next to me and it works fine.
    As already stated I always used anti-seize on the threads, but I guess some types of dope will work as well, but I would use the Teflon (white) type not something like Permatex.


    Kevin
    "There are 10 types of people in the world.. those who understand binary, and those who don't."

  12. #38
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    Feb 2008
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    Waffleville
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    wonder if he is putting pipe dope on flare fitting too lmao
    If Guns Kill People, Do Pencils Misspell Words?

    http://www.youtube.com/watch?v=An2a1...eature=related

    Before we work on artificial intelligence why don't we do something about natural stupidity?

  13. #39
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    Jan 2008
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    Quote Originally Posted by beachtech View Post
    wonder if he is putting pipe dope on flare fitting too lmao
    a couple of drops of oil (or a tiny bit of never seize) on the male face works wonders. ran across one where some knuckle head used loctite reefer sealant on all servicable flares on a machine.
    (i also thin out a fresh can of never sieze with oil)

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