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Sealing NPT threads, tape v. anaerobics ?

Sealing NPT threads, tape v. anaerobics ?

Sealing NPT threads, tape v. anaerobics ?

I also posted in the piping thread, but specific application is hydraulics.

The perennial discussion of teflon tape vs. anaerobic sealants for NPT threads goes on forever on boards. My opinion, your opinion, etc.

Is anyone aware of actual test research between the various methods? Teflon tape, Loctite PST, Megaloc, Rectorseal, etc?

My rule is eliminate NPT, but it is not always possible.


RE: Sealing NPT threads, tape v. anaerobics ?

My rule is absolutely no thread tape on any joint in any sysytem!

If I come across any, I remove it and replace it with anaerobic sealant.

I have replaced many pumps that have suffered from taking in pieces of thread sealing tape. I have also seen many valves jammed with tape.

No tape!

Better still...no tapered threads!


RE: Sealing NPT threads, tape v. anaerobics ?

See same thread in Piping & fluid mechanics engineering.

I agree with eliminating NPT threads in fluid systems.


RE: Sealing NPT threads, tape v. anaerobics ?

Tape when used correctly is just fine(or even better!). However, in my experience I have rarely seen it used correctly. Many company's have now enforced a no tape policy as a result.

That said...

I also agree with eliminating NPT threads. There are other options available that seal more reliably and can be reused repeatedly over time.


RE: Sealing NPT threads, tape v. anaerobics ?

Tape is good for temporary joints that are intended to be disassembled often or soon.  For permanent istallations, anaerobics are the way to go.  Ones that assist in the area of galling (as some materials do) are even better.

RE: Sealing NPT threads, tape v. anaerobics ?

I have used all of these.

The problem with an anaerobic sealant is that the pieces to be sealed have to be free of oil.  This makes it difficult to use after an a fitting has been ran. Anaerobic sealants are the only way to go when sealing steel into Aluminum bodies.  I have never seen tape or anything else be able to seal steal to aluminum becuase the Alumiminum moves too much with temperature.  My suggestions:

Always use O-ring, JIC, Flat Face, or Flange  ports if possible.

When assembling new system use anaerobic sealant and clean out the threads of they appear to be wet with brake cleaner and an old tooth brush and blow dry.  Don't wait too long when tightening the fittings, they will set pretty fast when not exposed to air. I seal gauges with tape, because I may need to get it apart.

Use teflon tape as secondary sealing compound with wet joints.  I have had great success but you have to know your limit when tightening the joint. Also wrap the tap 1 1/2 turns only.  More then that and it will just ball up. Start a few threads from the tip wit your wrap so it can't get into your plumbing. Keep the tape flat on the fitting.

Don't use Schedule 40 fittings, they stretch too much and leak.

Good Luck


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