Thread Sealers, Gap Fill and Large Threads.

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On my roll of yellow PTFE tape for gas lines, it says to use it for lines no larger than 1 1/2in.

I assume larger threads have larger gaps that the tape cannot fill. So, the question that arises is - what do you use on large dia threads?
 
loctite-thread-sealant-with-teflon.jpg
 
I like this stuff:
ss16-softset-off.jpg

The same brand also has a version specifically for use with E85 and one for worn threads.
 
Originally Posted By: George7941
On my roll of yellow PTFE tape for gas lines, it says to use it for lines no larger than 1 1/2in.

I assume larger threads have larger gaps that the tape cannot fill. So, the question that arises is - what do you use on large dia threads?


I don't know why your roll of tape says that it's only good up to 1-1/2" pipe. It may be that the manufacturer offers a wider tape, and wants you to use that. Teflon tape is commonly available in 1/2", 3/4", and 1" widths. Having said that, as pipe gets bigger, it is harder to seal. A few years ago, I did a gas piping job that involved several hundred feet of galvanized pipe from 4" down to 1/2" diameter, all threaded. We used mostly X-Pando, which is an industrial thread sealant that expands as it dries. It worked well. On at least a couple of 4" threads, we used a combination of Key-Tite and teflon tape, which also worked well. We were required to use a 24-hour recording gauge to test this pipe, and we passed.

Another factor to consider is the contents of the pipe. There are different sealants for different liquids and gases. If it's water or compressed air, pretty much any pipe dope will be OK, although on the big sizes some are better than others.
 
Originally Posted By: 1foxracing
loctite-thread-sealant-with-teflon.jpg



These paste sealants also have pipe size limits. I am looking at a Loctite industrial products catalogue and these are the pipe size limits
Loctite 545 2"
565 2"
567 3" (this is the thread sealer I use)
561 sealant stick 3"

I was just curious as to what is used on large pipes, I am thinking 6 to 8" dia.
 
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The X-pando sealant mentioned looks like it is a good candidate for large dia threads since it expands. The X-pando website however does not list gap-fill specs. For Locite, gap-fill varies from 10 thou for 545 to 20 thou for 567.
 
Originally Posted By: George7941
On my roll of yellow PTFE tape for gas lines, it says to use it for lines no larger than 1 1/2in.

I assume larger threads have larger gaps that the tape cannot fill. So, the question that arises is - what do you use on large dia threads?


Oakum can be used for large diameter pipe. AKA horsehair and hemp rope it is still common in Germany and other Euro countries.
 
Originally Posted By: Stelth
George, are you actually trying to seal some big pipes, or is this just idle curiosity?


Just idle curiosity.

I have taken apart house heating pipes that were assembled with some kind of fibrous material, probably oakum.

I have never worked with pipe threads larger than 1 1/2 inch.
 
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