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What Caused Thread Damage?

Zman
Zman Member Posts: 7,611
edited October 2021 in THE MAIN WALL
I came across this one today while investigating a regulator overpressure issue.
This aluminum regulator has stripped inner threads, the debris plugged the regulator and caused it to fail. The pipe was a factory threaded steel nipple and did not appear to be damaged. The contractor is a very experienced pipefitter, it is possible his apprentice did the work.
I am leaning towards either overtightening or poorly machined threads. Any thoughts?

"If you can't explain it simply, you don't understand it well enough"
Albert Einstein

Comments

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 9,378
    edited October 2021
    If that was factory installed then the knucklehead at the factory did something wrong. Bad tap at factory. If that was a field install part... then it is still a factory defect... that way you get a free one under warranty.

    Tell the helper the 48" pipe wrench is a little overkill for 1/2" threads

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • mattmia2
    mattmia2 Member Posts: 10,920
    edited October 2021
    Are the chips aluminum or steel? Looks like it wasn't drilled far enough and the tap was forced in past the bottom of the hole.

    or the tap was turned in too many turns
    STEVEusaPA
  • Zman
    Zman Member Posts: 7,611
    The chips are aluminum. I wondered about that. The female threads on the other side and the replacement look good. Mabe bad machining on the one.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 16,467
    @Zman

    It's common for aluminum threads to gall. I have seen it many times on gas valves. Teflon tape with some anti seize on the tape and a very light brushing of anti seize on the inside threads is the fix

    The reason you see this at the far end is if you DON't dope the inside with anti seize and just dope the outside threads the dope gets pushed off the end when the nipple is screwed in
    Zman
  • mattmia2
    mattmia2 Member Posts: 10,920
    @ChrisJ is the machinist here. The fact that the shoulder at the bottom of the tapping is all galled makes me think that the nipple didn't do it.
  • ChrisJ
    ChrisJ Member Posts: 16,315
    It doesn't look like the threads that were engaged are damaged in those pictures.  Just the ones further in.  

    It doesn't look like galling to me and I wouldn't expect galling with steel and aluminum. 

    Single pipe 392sqft system with an EG-40 rated for 325sqft and it's silent and balanced at all times.

    Zman

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