sealing of threaded joints
sealing of threaded joints
(OP)
Having a wee spot of bother with the reliability of threaded joints , particulary stainless steel 2" pipe. Trying to find a reliable sealant to do the job , any ideas ?
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sealing of threaded joints
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RE: sealing of threaded joints
what temperatures, highs and lows?
how is this pipe supported, and how often? (vibration?)
how are you threading the pipe....what kind of cutting fluids?
are the dies in good shape and made for stainless?
how are the threads turning out, nice and sharp or torn and rough?
are the threads to the correct depth? (a quick rule of thumb is to make the fitting onto the pipe by hand until it binds up, then back it off and if the dies are set correctly it should be 3 to 3 1/2 rounds. proper fitting tightness will usually be five rounds. this does not substitute for ring and plug guages.)
what kind of fittings are you using?
what type of stainless?
just a few questions.
what kind of pipe dope are you now using?
you might try using an anaerobic type of pipe dope, clean the threads to remove the cutting fluids, dope the male threas, assemble the joint, and depending on type of dope and conditions it might need to cure before putting into service. loctite makes some very good pipe dope.
most pipe dopes will state that they are only good upto two inch.
if you are already using an anaerobic type of dope do not apply teflon tape to the threads, the teflon will act as a barrier between the threads and will not let the dope get to both sets of threads. this kind of dope hardens in the presence of metal and the absence of air, and if it can't touch the metal it will not work properly.
just my two cents worth.
G3
RE: sealing of threaded joints
Maybe "seal welds"?
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RE: sealing of threaded joints
RE: sealing of threaded joints
Have you looked at previous threads? A few posts back there was a very good discussion on threaded stainless steel joints:
thread378-154496
RE: sealing of threaded joints
But, stainless NPT threads can be problematical and teflon does not always lube enough to prevent galling, or seizing of the two parts before'seating' is accomplished.
A better lube is a nickel based compound such as "Never-Seixe". It eliminates galling and allows tightening until a proper 'seat' and sealing are achieved.
RE: sealing of threaded joints
If the threading machine being used has an adjustable head, it needs to be set such that the fitters can get 3 to 4 turns to hand-tight, on clean dry threads. It's not very often that you can just set the die head exactly to the increments marked on the scale, and have it where it needs to be. Also, are the same dies being used to thread carbon steel pipe? Ridgid makes dies & cutting oil specifically for stainless. I had a Ridgid rep tell me that if the dies for SS are being used for carbon steel, that will cause problems when you go back to threading stainless.
RE: sealing of threaded joints
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RE: sealing of threaded joints
My recommendations: first, get dies with the correct cutting angles for stainless steel, otherwise you won't get decent surface finish. And the threading machine needs to be very rigid so it won't deform under the stresses involved (no surprise, Ridgid still makes the best threading tooling on the market IMHO). Use plenty of a good cutting fluid. As to sealants, for 2" stainless, the only thing we've found which works reliably is teflon tape top-dressed with a good quality anaerobic pipe thread sealant- Henkel Loctite has quite a few formulations to offer but there are other brands as well. There's plenty of metal on the female pipe threads to cure the sealant so the teflon tape won't really interfere with this too badly, and the teflon provides better galling resistance than paste alone can provide. And a good anaerobic sealant never sets up hard anyway- it crosslinks and forms a gel but never really solidifies. And don't over-tighten- it won't make the joints more leak resistant, all it will do is increase the likelihood of galling.
RE: sealing of threaded joints
RE: sealing of threaded joints