[clavius]

Hi all,

Been lurking here for a while, lots of interesting stuff to take in. I have noted in some of the "troubleshooting" discussions here and elsewhere there has been mention of making sure that you don't have "bad" gas (argon, CO2, mix, etc) or contaminated gas messing up your welds. Just curious if anyone has actually had this happen to them.

It's easy to see how in all of the handling and processing that a gas bottle could get filled either with the wrong gas, or mixed in the wrong proportions, or not purged properly before being filled. Just curious how common that might be. In my job we often use lots of high purity bottled gas (not welding gas, mostly N2 and Helium) and have only once suspected this but found after we had the gas in the bottle in question analyzed, it was not actually the issue.

Any insights? just wondering...

[Jim FLinchbaugh]

Along those same lines of questions, how would you prove out that you indeed
did have bad gas?

[LtBadd]

Along those same lines of questions, how would you prove out that you indeed
did have bad gas?

If you have a 2nd bottle, hook it up and if the problem is gone...

[GreinTime]

Along those same lines of questions, how would you prove out that you indeed
did have bad gas?

If you have a 2nd bottle, hook it up and if the problem is gone...

Elegantly simple, if not blunt description of checking.

To elaborate further, if everything was going fine before you changed the bottle, and now it's not, first step would be spray the fittings on the bottle, regulator, and back of the welder to see if you have a leak. Sometimes the leak is very small, but will draw atmosphere into the line due to pressure differential as the gas flows past.

The biggest issue with swapping bottles, or having someone fill yours, is that it's too time consuming in most cases for them to pull vacuum on entire cylinder gang, when they can get away with pumping argon back in a few times and not have any issues. When the pressure get low, moisture accumulates in the bottle from the pressure/temperature change. A little moisture is less than ideal, but when you fill the bottle multiple times, leaving 1-2ppm of contaminates in the bottle (in the form of moisture) every time you fill it back up, now you have 10-15ppm, I. E. It's a constantly compounding problem until you have it filled again.

One solution, if you own your bottles, is to purchase a small vacuum pump and make the appropriate adapter line to pull vacuum on the bottle yourself. If you let the gas shop know that you've already pulled vacuum, and you'd like them to fill your cylinder and give it back, they'll normally have no problems doing it if they fill in house. It's less work they have to do and you seriously reduce your chances of getting a bad bottle.

Finally, most gas shops will swap bottles for you if you believe it to be a case of bad gas.

Sent from my SM-G900V using Tapatalk

[clavius]

In the one instance were we thought this was an issue, we had the gas sampled and analyzed at a lab. I don't know what that cost but suspect it was not inexpensive but it could be worth it depending upon the application. Just asking as I have seen several references to that in various posts here.

[exnailpounder]

I had an issue just like Greintime outlined. My bottle was getting down to about 500psi and I was noticing my aluminum welds were grainy after having looked great when the bottle was fuller. Otto explained what was happening and I switched bottles and the problem was gone. When I went for a bottle exchange, I mentioned the problem to the manager and he gave me a free fill. He told me that they draw down bottles twice when filling them but I find that hard to believe and more of a consolation to get me to shut up. He said I was the only one that complained about the problem. I told him that maybe I was the only one that gives a shit about what my welds look like and I kind of resented the inferrence that I was trying to get a free fill or a discount. Both my Argon bottles are full right now so it will be awhile before I find out if the problem returns. IMO it is rare to get actual contaminated gas but probably pretty common to get moisture coming out at lower bottle pressures. I am sure it's cheaper to give some idiot welder a free fill or a couple flap discs as a consolation than it is to draw a vacuum in every bottle they fill.

[Braehill]

Clavius,
I've explained the moisture situation on more than one occasion here, but one thing I haven't touched on in a while is this. When cylinders are filled in most larger welding gas supply companies they're filled on a manifold of sometimes upwards of 100 cylinders. If one of those cylinders is not tightened down at the valve, the leak isn't found until they are refilling the cylinder so it's been pulling in atmosphere (moisture) into all the cylinders on the manifold. When they start to refill them they hear the leak and it's tightened and in their mind all is well and they finish filling them. Now every cylinder on that manifold has moisture in it.

We complain about high prices for Argon and if they have to analyze every cylinder to insure it's purity the price will go up considerably, if you need proof of this, ask for a cylinder of Ultra High Purity Argon and see what you pay. It's filled from the same tank of liquid Argon (99.9997%) as the other cylinders, then it's analyzed to be sure of it's total purity, that's the only difference.

Seldom if ever are you going to get a cylinder with the wrong gas in it unless you are buying a mix and it's mislabeled. Most times the fittings are not interchangeable from tank to tank to keep this from happening.

We've gone over ways to check your system for leaks and ways to see if it's indeed a gas problem at all and not some other issue. Most times it's something else that's causing your issue, but gas issues can never be totally eliminated even by switching bottles from the same supplier because of what I mentioned earlier, you may get another cylinder from the same lot. Adding a cheap desiccant filter in your low pressure side of your system will lessen the chances of getting moisture to the weld gas envelope. You can buy these at Harbor Freight or most automotive paint supply places.

As to the question of how do you know if it's bad gas, ask them to run your cylinder on the analyzer to see how much moisture is in it and give you a total purity to see if it's up to industry standards, If it's not, they should give you a free replacement cylinder that does. If they refuse, go somewhere else for your gas.

Len