Best tape for tapered LP72 threads?

[MrVegas]

I'm going to take two old LP72s with 1/2 inch tapered threads in for hydro and visual pretty soon. I was just curious what tape people usually use on the threads when putting the valve back in the tank. (I'm not going to try to do anything myself, but I might actually provide the tape.)

 

[runsongas]

Teflon tape. Mil spec or the NIBS aa58092 grade.

 

[2airishuman]

I have been using 99%+ teflon tape intended for oxygen service. It seals much better than the thin white stuff in the plumbing department at the big-box home center.

The stuff I got is no longer available on Amazon, but here's the link. You might be able to find something similar:

https://www.amazon.com/Green-Thread...tape&qid=1549856633&s=gateway&sr=8-5-fkmrnull

Also, it helps considerably to chase the threads on the valve and cylinder with a die and tap to get the last of any crud out. Threadcutting is not in compliance with DOT regulations but my interpretation is that using a tap for cleaning purposes without cutting new threads is OK.

And I have had problems with them leaking when they come back from hydro, so your concern is not misplaced.

 

[rjack321]

Also, it helps considerably to chase the threads on the valve and cylinder with a die and tap to get the last of any crud out. Threadcutting is not in compliance with DOT regulations but my interpretation is that using a tap for cleaning purposes without cutting new threads is OK.

I don't know anyone with actual tapered taps?
You can just go round and round with a dental pick too.

 

[Bob DBF]

I don't know anyone with actual tapered taps?

One more reason to know a plumber.


Bob

 

[MrVegas]

You guys are great! Thanks for the help. I ordered some of this, hopefully that will do the trick:

https://www.amazon.com/Green-Thread...tape&qid=1549856633&s=gateway&sr=8-5-fkmrnull

 

[2airishuman]

I don't know anyone with actual tapered taps?
You can just go round and round with a dental pick too.

Or a wire brush. You have to be careful to clean out any debris that falls into the cylinder.

1/2" NPT taps are available at any home center in the plumbing department. They are not expensive. 3/4" NPSM taps are more difficult to get.

 

[divad]

Or a wire brush. You have to be careful to clean out any debris that falls into the cylinder

Or a brass wire brush.

 

[Ghetto Diver]

I believe these are 1/2 nGt not npt.
They are close, but not the same.
I use a ss wire brush. Plumbing tape worked too.
Ymmv

Eta: I seen this spec'ed somewhere else but here's one. (At work)
SCUBA Valves | Dive Gear Express®

I meant to confirm when I pulled mine, but did not.
No way would I chase these with a npt tap/die

 

[2airishuman]

The only difference between NGT and NPT is the minimum number of mating threads. It's the same thread form, size, spacing, etc.