Argon regulator leak

[robsthomson]

Hi, after going to do some welding after a few months of not using my powertig welder (with the regulator left installed and the tank valve closed), I found that there is now a large leak at the argon regulator. At first I thought it might have been from around the tank valve stem, but it seems to be coming from the CGA fitting between the tank and regulator.

I've tried removing and reinstalling the regulator several times with no luck.

It seems like one or both of the fittings may have been damaged somehow, but both the tank and the regulator were securely chained to a steel column and not even touched during this time. I'm using the regulator that came with my powertig welder. I couldn't see anything visibly wrong with the fittings.

Is there anything I should try before I take the tank and regulator to a welding shop?

Mostly, I'd really like to know what might have happened to cause this and how I can prevent it from happening again.

[performance]

Overtightening can deform the mating faces or crack the nut. Or a particle of dirt left on the face from a mud wasp or something can scar up the faces. You should give a long blast of argon from the cylinder and wipe down the mating surfaces with a clean dry rag before you tighten them up.

To confirm the exact place of the leak, coat the regulator in a sudsy mixture of Dawn dish detergent and water. Liberally "paint" the areas and bubbles should form right around the area of the leak. This will help you pinpoint and possibly correct the source of the problem.

[robsthomson]

Well, I can confirm that the leak location is definitely the connector.

I should also say that by "bad leak", I mean that when I open the tank valve I get a blast of argon blowing on everything from around the connector thread, not just a loud hissing noise. Its about what I'd expect if the connector was just loosely screwed in and not tightened at all.

There doesn't seem to be any visible damage on the mating surfaces. The regulator side is as clean and smooth as when it came with the machine. The only thing notable about the tank side is a ring where the brass is discolored where the fittings press together, which I think was there when I bought the tank.

I've always wiped off the connectors and cracked the valve before attaching the regulator, so there shouldn't have been any dirt.

I don't think I've been over tightening them. I've generally tightened it either "very hand tight with gloves", or the same amount with a wrench. How much torque should I actually be using?

I'm also wondering if temperature change could have caused some damage. The last time I used the welder, it was winter and my unheated shop was very cold. Since then, it got fairly warm in the summer and it is now about room temperature. So, in the meantime, the tank and regulator have been through a temperature range of at least 80F.

[Wrenchtamer]

If those fittings were left tightened I would not be shocked if the regulator side of that connection was warped a little bit since the two dissimilar metals contract at different rates. I see this sometimes on a fitting between the high and low sides of a refrigerant system and although it has never been confirmed by the manufacturer, I believe that the difference in thermal characteristics has something to do with it.

[jakeru]

Has anyone had good luck with the "hand tight" versions of the CGA fittings? I'm talking about the tank fittings often found on helium balloon filling regulators that have a little rubber o-ring to make the seal, and a large plastic handle around the nut so you can just tighten the fitting with your hand.

The rubber o-ring seems like it would seal with a lot less pressure. I'm just wondering if anyone has tried it on an argon regulator, and if so, did you find that it worked well, were you pleased with it, etc.

PS - for the original poster, inspect the cylinder side of the fitting for knicks, dings, and any galling or scoring marks, and try to polish/clean it with a little scotch brite pad or steel wool. Similarly, you can inspect the regulator side of the fitting, and polish that mating surface as well. A smoother surface should seal more reliably with less force. Oh and also, make sure the CGA nut spins freely with low friction compared to the rest of the fitting. You don't want the fitting twisting at all when tightening the nut. If there is friction, identify it (dirty? galled surfaced?) and eliminate it. Any burrs can be filed down to reduce friction. I've also tried putting a dab of oil on the surfaces where the nut bears on the back of the fitting, and found it was helpful to make it tighten up much nicer. That may not be recommended however.

PPS - anyone know how much torque are we supposed to tighten the CGA nut to? I have been usually tightening mine down pretty hard, with a pretty big wrench.

[robsthomson]

Wow. I was wrong about the problem. The fitting wasn't the leak at all. The argon was just blowing across it a lot.

The regulator body had a hairline crack running between the gauge and cylinder ports. It was nearly invisible, but under pressure it would spread apart enough to let gas out. Thankfully it didn't explode.

My guess is that it was probably cracked before I got it and only spread enough to leak later.

Anyway, problem solved, I've ordered a new regulator.