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Up Topic Welding Industry / Technical Discussions / Filling oxygen tank with argon.
- - By seagull369 (*) Date 10-24-2007 06:26
I obtained a small oxygen tank on the cheap lately and was wondering if it'd be possible to convert it to hold argon so I can use it with my MIG welder. Right now there is no valve on there, just the bare 1/2" NPT female thread. The legit MIG tanks I've seen in the weld shops have a larger diameter orifice than that (maybe 3/4?).

Do you folks think It'd be possible to use the tank, find the valve size I need and actually have a shop fill it for me?

Thanks for reading.  
Parent - - By aevald (*****) Date 10-24-2007 06:58
Hello seagull369, I doubt very much that any legitimate welding supply or filling facility will accommodate your wishes to use this tank for the purpose you are proposing. I know it sounds like a very simple task, yet pressure vessels, such as the tank that you have, go through a considerable and rigorous testing regimen to make them safe and liability free for you and the facilities that fill and keep them up to snuff on their hydro-testing and other sorts of safety items. The fact that the valve has been removed from this tank might indicate that it has possibly been condemned from being in service already. If your curiosity needs to be satisfied take the tank to a welding supplier/filler and inquire about the tank, they should be able to look at it and tell you by the stampings and such on the tank a lot about it's history and possibly explain, as I have, some of the issues here. Good luck and be safe. Best regards, aevald
Parent - - By Lawrence (*****) Date 10-24-2007 10:14
Allan is right.

Besides,  You reall don't want all those little spiders shootin out into your puddle do ya?
Parent - - By bozaktwo1 (***) Date 10-24-2007 16:32
Absolutely not.  Those cylinders are made with different sized orifices and threads to avoid exactly what you propose.  I can't prove it, but an old acquaintance of mine once told me that some cylinders are made differently (materials and process) depending on what service they're intended for.
Parent - - By rlitman (***) Date 10-24-2007 20:23 Edited 10-24-2007 20:26
Not true.  The valves have different threads for several safety purposes, but oxygen cylinders and argon cylinders are of the same construction.
It is true that not all cylinders are the same.  C02 cylinders have a gas over liquid, and are not up to the pressures of cylinders that contain just plain compressed gas, but at the factory, oxygen, argon, helium, and nitrogen cylinders are interchangeable (before the valve is installed).
Like Allen said, a reputable filler should be able to look at the markings in the cylinder and tell you the service pressure, and if its testing is up to date.
They would probably also be able install a cga-580 valve for you (that part is unlikely to be in stock).

The good news for you, is that converting FROM oxygen to an inert gas, is easier than converting TO oxygen, because argon tanks do not absolutely need to be "oxygen clean".
The bad news, is that with the valve off, dirt can get into the tank and cause corrosion of the inside.  So, your tank definately needs a good visual inspection of the inside.
Anyway, your filler should be well versed with this, or they can send it out for recertification.  You're probably looking at $15 for a new hydro test (with no guarantee of passing), and another $20-30 for the valve to get this usable (plus the fill).

-- Robert
Parent - - By DaveBoyer (*****) Date 10-25-2007 03:10
Depending on the gas company, You might be able to trade that cylinder if it turns out to be OK and is a standard size etc. in against a cylinder that suits Your needs. This is up to the company. Airgas for instance is not cooperative in this way.
Parent - - By seagull369 (*) Date 10-27-2007 02:40
Thanks for al the great responses everyone.

To get one thing str8, There actually was a valve/ regulator/flow meter on the tank recently. Fearing I might scare off any welding shops who saw the funky contraption that it was on there, I figured I better yank it off and corked it up, which I did.

I did end up bringing the tank to a shop- in fact 3 of 'em. Unfortunately none wanted to touch the thing. It didnt seem to be for reasons that there wuddnt any valve on it, but rather it probably wasnt a shape/size they were used to seeing in the tanks they handled that have argon in it. And besides that, like I mentioned, the orifice diameter on mine is smaller than what one of those cg-580 valves will screw into. Of course, most I talked to were more than happy to suggest the argon tanks they sold for me to purchase.

Anyway just out of curiousity, does anyone out know if they make a variant of the cg-580 who's tank side  has a 1/2" male NPT fitting? I figured I might have better luck having someone fill it someday if it at least has valve that looks the part. 

Thanks again everyone. 
Parent - By ctacker (****) Date 10-27-2007 02:52
good luck, with liability issues you may never find a reputable business to fill it!
Parent - By DaveBoyer (*****) Date 10-27-2007 03:42
You might have a medical oxy tank, they are different in size, and have a valve more like a SCUBA tank.
Up Topic Welding Industry / Technical Discussions / Filling oxygen tank with argon.

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