You who weld, need information:

Last Saturday I bought a couple of storage units at an auction. Inside one was some welding equipment, and there were two small tanks I can't identify. At first, I thought they were oxygen tanks for a person on a breathing device, but then I noticed the tag that said "welding" on it.

They are Praxaor Nitrogen tanks with a gauge, like a torch setup has. The only info on the tag is UN 1066. I asked my Son and he said he has heard of nitrogen for welding, but that is all he knows.

What do I have ? Thanks,


Don

I may have just gotten an answer. I called the guys we get our o/a and mig gas from and he says plumbers use these to purge lines before they put freon in them. Think I'll throw them on Craigslist and see.

Don

That's right. After opening a system for compressor change outs and such, we pressurized with nitrogen to check for leaks.

Then we pull the system down into a vacuum.

Then charge the system.

you may be able to trade them in at your welding shop for tanks that you use like argon/co2 or straight argon. It's nice to have spares.

That's a good idea, thanks.

Don

Don,

Nitrogen is also used to purge steel and stainless pipe (like headers) when welding. Keeps the oxidation away from the inside of the joint especially on stainless.

Memory may not be serving me, but I believe you can tig weld copper using straight nitrogen shielding gas too...

Oooooh, we might want to keep them then and use them for that purpose.

Don

Well, at least they used to use it... sounds like availability is an issue now.

Shielding gases for welding are argon, helium and nitrogen or mixes of two or more of these. Pure argon may be used for TIG welding up to a thickness of some 2mm and for MIG welding up to approximately 5mm - above these thicknesses an argon-helium mixture will give better results with greater heat input and less risk of lack of fusion defects.

Nitrogen and argon-nitrogen gas mixes have been used in the past with some advantages being gained in terms of increased heat input from the high voltage nitrogen arc but such gases are not commercially available and argon-helium or helium shield gases are now the preferred choice. The high thermal conductivity of copper means that not only are high heat input shielding gases required as thickness increases, but preheat is necessary at section thicknesses exceeding 2mm.