Sealant Needed to Reduce Vapor Leakage

There are several types of epoxy and silicone sealants that withstand high temperatures, in different values, that you can find easily browsing the internet.

However, if it's a pressure vessel or pipe subject to internal pressure, depending on the value of the internal pressure, a sealant will not help you. It will build up pressure behind the sealant and leak. This leakage is comming probably through the weld itself, meaning that there's actually a discontinuity, that can develop to a crack sooner or later.

Welds in pressure vessels are supposed to be inspected and need to be leak tight, and they are if properly done. And they need to with stand the proof test after the process anyway, which can be dangerous in the conditions mentioned.

I recommend you to rework the weld (cut the place with a grinder enough to remove the damage in the weld, then re-weld correctly).

Thank You, it has 5 lbs of pressure do you feel a sealant would be helpful.

I still recommend rebuild the weld.

If you still want to do something that's wrong, you could apply a layer or two of fiberglass cloth dampened in sealant, around all the tube. Choose an epoxy or silicone for high temp. The fiberglass will make your repair stronger, because will anchor in itself to withstand the pressure.

Pay attention to choose a sealant for the temperature and product compatibility.

There are companies that do a vacuum sealing process. We used it all the time when we got a lot of leakage in our aluminum castings. This was used on water pumps that produced a lot of internal pressure like 60 to 80 psi.

There are many in the market, each suitable for a particular service.

Search for keyword. 'on line sealing, hot sealing and like'.

Futmanite is one such sealant and service provider with wide range...

Go to your closest Tire Store and buy a can of Alloy Wheel Sealer.

End of problem.

What's your temperature range?

Greg

Loctite makes a thread locking product that will also work as a sealer.

Loctite 290 Threadlocker

It is a thin liquid that will wick into gaps of .004" and cure. It is an anaerobic and cures by crosslinking. A primer will speed the cure time and I expect the surfaces need to be cleaned to get good results.