Mig gas leak

[Jim mcgrath]

I bought a new cylinder of gas today and when I screwed the regulator to the top of the gas bottle, it leaked. I would imagine this is a common problem. I was wondering how other people fixed a gas leak like this because when I googled the question: should I use ptfe tape , it said not to use it. In the end I could only get it to stop leaking by using tape. Also I was wondering about where the tape should be placed. There is a taper on the end of the regulator fitting which seems to correspond to a taper which is in the fitting at the top of the gas bottle. I wrapped the Teflon tape around the taper on the regulator fitting, see photo. The arrow is pointing to where I placed the tape. I don’t know if this is correct but it seems to have worked.

 

[addjunkie]

Should be metal to metal, suggest the sealing face is marked.

 

[voipio]

The circular line, where the conical surfaces meet, is the point where the seal is formed in a bullnose connector. Look closely within this contact line area for dinks, or foreign material. Usually it's the male bullnose part on the regulator, that's maybe been put down roughly on a hard surface, but it's not always the case. Smoothing the metal around the contact line area, using wire wool, or fine emery paper, will often succeed in eliminating the leak. The abrasive movements should follow a circular motion around the bullnose. Basically hold the abrasive between thumb and forefinger, and use a twist of the wrist movement.

 

[addjunkie]

Id suggest braso, or a bit if duraglit

 

[brightspark]

you can also slightly tighten the bulnose in the bottle and turn the regulator round back and forth then re tighten sometimes makes a better seal. if it still leaks take it off and see where its been scoring or sealing after turning it

 

[tom2207]

ive used a copper washer at the bullnose before today , when you really have to ,, but Im religious about turning the bottle off at the end of a job , or the end of a day , its no fun to come back to a bottle that should be full and now is empty , especially when you pay for your own gas.

 

[Hitch]

As Brightspark said...

Check the regulator for damage, carefully clean up any high spots if it is.
Then do the old back and forth trick and tighten the nut.
Then give it a bit more using a decent spanner and mallet if necessary.

Never not managed to get one to seal or had to use sealant yet in over 25years in the industry.

 

[Morrisman]

you can also slightly tighten the bulnose in the bottle and turn the regulator round back and forth then re tighten sometimes makes a better seal. if it still leaks take it off and see where its been scoring or sealing after turning it

Yes, I’ve done that a few times, always sealed after a few twists back and forth.

 

[tom2207]

another old school tip I still do is to piff a bit of gas out of the cylinder and over the bull nose before screwing them together ,,, same as blowing water off a set of regs at a gas swap if you dive ,,, just in case theres anything in the fitting , dont know if it makes any odds , its just the way I was shown by a very old hand a long time ago.

 

[voipio]

A quick snift of gas before fitting the regulator helps to clear the cylinder bullnose, and also gets rid of fine dust that could drift back into the cylinder valve, once the regulator is fitted, cylinder valve opened, and the high pressure side has equalised. Regulator internals don't like dust, either, although they're usually protected to some extent by a sintered filter. A visual inspection of the bullnose connectors (both cylinder and regulator) is worth doing.

 

[Jim mcgrath]

I removed the ptfe tape and cleaned the bullnose with wire wool. I tightened the fitting down and sure enough, no leaks this time

 

[Jim mcgrath]

I’am not sure if it was cleaning the bullnose or maybe I just tightened it a bit harder. I think that someone saying “hit it with a mallet” gave me courage.
I better just say that when I was removing the ptfe tape, I noticed some had gone down inside the bullnose fitting, I got it out with a needle. It would have blocked the gas supply for sure.
Thanks everyone!