Old Welding Cylinder Re-use & Repainted?

[HotRodHudson]

A buddy gave me this old cylinder he had used for welding a few years ago. I have no idea what the certification is or when last done as I’m new to this. Before I just take it down to get it filled for use with my mig welder, what should I know or be prepared for, when I do go to have it filled?

Which set of gauges should I use assuming they both work? Can I glass bead blast this bottle and paint it or would that be dangerous even If emptied? Is there a safe way to repaint it?

I was told it was empty but I don’t want to go...BOOM!










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[MoonRise]

If you are going to 'use' the cylinder as a high-pressure cylinder, then do NOT 'clean up' the cylinder.

Take the regulator off, take cylinder to local welding supply/store (aka LWS), exchange for a filled cylinder, pay at the counter. Done. They may or may not check the cylinder or require a 'recert' fee.

 

[bczygan]

Is it an old aluminum scuba tank?

Bill

 

[rlitman]

Is it an old aluminum scuba tank?

Bill

No, but close. That's an aluminum CO2 cylinder. They're mostly used with soda fountains. Look at the valve. It's externally threaded. And the 1800 pressure rating is a givewaway too. (edit: and now I also see "20#CO2" after looking again)

Being aluminum, I would not suggest painting it. It will not rust anyway.

 

[MoonRise]

And for GMAW, you can use straight CO2 (what that cylinder looks like) as the shielding gas for welding mild steel.

You have to adjust the parameters a bit (slightly higher voltage compared to using C25 gas ) and you have a slightly 'hotter' arc and a bit more spatter than when using C25 gas. Probably not the best gas choice for welding thin automotive sheet metal (use C25 there).

Not the right shielding gas for stainless steel GMAW. And not the right gas for GTAW (aka TIG), which uses straight argon for pretty much everything (except when it uses argon-helium blends for 'thicker' workpieces).

And unless you have a 250-class of 'bigger' machine, you will NOT be using FCAW-G wire (which some of those 'dual-shield' FCAW-G wires use CO2 as the shielding gas).

 

[bczygan]

Painting:
https://www.luxfercylinders.com/support/paint-removal-and-repainting-all-metal-composite-cylinders-made-6061-aluminum-alloy-l6x

 

[rlitman]

Painting:
https://www.luxfercylinders.com/support/paint-removal-and-repainting-all-metal-composite-cylinders-made-6061-aluminum-alloy-l6x

Good link, but that cylinder is not 6061, and it should probably be condemned (though CO2 service is far less of a risk than compressed gas service with that tank). Sorry to be the bringer of bad news, but bad news is better than "bang".

Looking closely, I see that the stamping says "DOT E6498" with a test stamping from 1979. That is one of the notorious Luxfer 6351 alloy cylinders.

https://www.luxfercylinders.com/img...uminium_scuba_cylinders_safety_alert_2217.pdf

Because of that, I'd recommend verifying that it is empty and turning it into a nice gong, or mailbox, or something along those lines.

 

[HotRodHudson]

Old Welding Cylinder Re-use & Repainted?

That is a lot if information & made me a bit worried. I called Luxfer & am waiting on a reply. The document notes just the “scuba” tanks so I’ll have to gather more info.


I also called one of the big welding supply houses & told him what I had. He believed if it is a CO2 tank it should be fine for an exchange. I don’t want to pull a “fast one” so I’ll wait to hear from Luxfer & then go see the welding company & talk to them.


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[5ktq]

I'd think most place will exchange it. they might charge you hydrotest fee because it is out of service

(need test every 5 or 10 years.. looks like yours was made in 79, tested in 86, 91)

 

[rlitman]

Re: Old Welding Cylinder Re-use & Repainted?

That is a lot if information & made me a bit worried. I called Luxfer & am waiting on a reply. The document notes just the “scuba” tanks so I’ll have to gather more info.


I also called one of the big welding supply houses & told him what I had. He believed if it is a CO2 tank it should be fine for an exchange. I don’t want to pull a “fast one” so I’ll wait to hear from Luxfer & then go see the welding company & talk to them.


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That's just the document I linked. This document lists Luxfer CO2 cylinders:
http://www.ocascuba.org/misc/DOT Advisory AL 6351-T6 Cylinders.pdf

Neither Luxfer nor any of the other manufacturers that used this alloy have ever recalled these cylinders, but the DOT has mandated special procedures for testing them, because they present risks not found in other cylinders. The problem is that his alloy is susceptible to cracking under sustained load. So, if it were stored empty for decades, it might be in better shape than if stored full.

Some shops will fill these, some won't. Personally, I'd never try to fill it. Cylinders aren't that expensive, but the results of a failed one are. But if your shop is willing to take it, that's their call. I wouldn't be willing to accept one in return.

See how reading this makes you feel about it:
http://biobug.org/scuba/scubatank/

 

[pcmeiners]

rlitman/ others...... thanks for the info, I have one of the 6351 tanks