anyway to identify which gas is in this cylinder?

disney · Mar 5, 2025

Greetings all. I was given this cylinder from a retired gentleman (who has no idea what gas it was), and honestly thought it was empty, but after freeing up the cylinder/valve protective cap (took a while as it was rusted..), if I crack the valve, I get what i believe is the sound of gas still under high pressure. is there an easy /cheap way to tell what gas it is, or would there be a marking stamped somewhere? Even just having a bottle to trade would be great, but I would hate to turn it in, if I could still use the gas in it.

thank you for any help you are able to provide

flyerdan · Mar 5, 2025

Put a regulator on it and fill a balloon to test for density. Unregulated, tip on side and blast some out so you have ice, put it in water and see if it carbonates. That will confirm / exclude helium and CO2

Too many Kubotas · Mar 5, 2025

Smell it, and try lighting it. Should narrow it down some.

zzvyb6 · Mar 5, 2025

Place to start. But: a few things to consider. Is the tank too old to recertify? If its other than the color suggests, is it worth trying to use? Would it make a better wind chime that a welding surprize ? If the top end is corroded and the valve breaks off, the tank will try to go flying, perhaps going thru whatever it wants, including you.

D&D · Mar 5, 2025

disney said:
Greetings all. I was given this cylinder from a retired gentleman (who has no idea what gas it was), and honestly thought it was empty, but after freeing up the cylinder/valve protective cap (took a while as it was rusted..), if I crack the valve, I get what i believe is the sound of gas still under high pressure. is there an easy /cheap way to tell what gas it is, or would there be a marking stamped somewhere? Even just having a bottle to trade would be great, but I would hate to turn it in, if I could still use the gas in it.

thank you for any help you are able to provide

what size tank is it?

alexpops · Mar 5, 2025

^^ What ZZ said. be careful lighting. & check the test date to see if it can be traded in or you'll need to get it re-tested before anyone will fill. the top around the valve looks sketchy, like it sat outside for a while & the cap trapped water against the valve threads. I would make sure both ends are pointed in safe directions before messing with it too much. You can buy a new tank online or at your local weld gas supplier for relatively cheap & the safety factor isn't a question.

WranglerX · Mar 5, 2025

Look at valve body closely and see if it has a "CGA XXX" designation.... Certain valve body types have different configuration for different gasses..... Its a first clue to what type of gas may be in cylinder....

CGA Fitting Reference | CONCOA

A CGA fitting is the standardized system for the attachment of a compressed gas cylinder to the required regulator or transfer line. Examples of CGA fittings would be CGA-580 for Non-flamable, Non-oxidizing gases such as Nitrogen, Argon, or Helium. CGA-590 is used for compressed air and CGA-326...

www.concoa.com

alexpops · Mar 5, 2025

Looks like CGA 580 on the valve so either argon or argon co2 mix? Unless this gentleman retired from AC business in which case maybe nitrogen.

etpm · Mar 5, 2025

Argon has no smell. Pure CO2 can have an acidic sensation for some people, which can be perceived as kind of an odor. C25, which is 75% argon and 25% CO2 has no odor. It's not acetylene, which has a strong odor, because the cylinder and valve are wrong for acetylene. The valve threads don't look like a CO2 valve and the cylinder doesn't look like a CO2 cylinder. CO2 is relatively low pressure. C25 is high pressure because of the argon. It could be a gas that will harm you pretty fast if you smell it. Unlikely, but you never know. All high pressure cylinders that contain flammable or toxic gasses or mixtures that contain toxic gasses will have left hand threads. So check if it has left hand threads. If it does then maybe it is best to trade it in, don't smell it. I sure wouldn't. If you have a regulator for oxygen then see if it threads in. Set the pressure on the regulator to zero and hold a lit match or similar near the output of the regulator and slowly increase the pressure on the reg. As the gas starts to flow out if it is oxygen the match will start to burn really fast. If it just goes out then the cylinder is filled with an inert gas. If inert gas fill a balloon with the inert gas and see if it rises. If it does then you have helium. If it sinks then either argon or C25 or nitrogen is most likely.
Eric

WranglerX · Mar 5, 2025

alexpops said:
Looks like CGA 580 on the valve so either argon or argon co2 mix? Unless this gentleman retired from AC business in which case maybe nitrogen.

Could be...

BlueKnife · Mar 5, 2025

Bring it to a welding gas supply place and ask them. It's not a rental tank, so you're good there. It's got relatively new-ish looking barcode stickers on it, so it's not way out of date. If I had to guess just based on the pics, I'd say Mig gas of some sort.

disney · Mar 6, 2025

thank you for all your replies, it will be some time before I am able to check it. I will update once I know more. thanks again.

MoArk Willy · May 20, 2025

You only have a couple of choices.
You can take it to a gas supplier and see what they say. If it can be re-certified they may help you with it.
Without the tag and with the amount of rust on the neck ring they may not want to touch it.
It's worth exactly what you paid for it.
Whatever you do....don't light it....that's a reckless move.

yomax4 · May 21, 2025

Tank has a 580 CGA valve. I'd bet it's Helium, Nitrogen, Argon or Argon CO2 Mix. The Distributor won't be able to tell you what it is and they will suggest that you blow it down, purge and refill. As would I.

disney · May 25, 2025

ok. so I filled a balloon to the size of a tennis ball, and then with a long aim 'n' flame lighter, tried to light it, and as soon as the balloon melted, it flew away (5ft). but clearly not flammable. I then verified with golf ball sized filled balloon that it puts out a flame. so that should narrow it down to Nitrogen, Argon or Argon CO2 (as Helium would have made the balloon float.) is there any way to see if I connect it to my welding regulator (the type with the ball) and see if the ball floats higher or lower than with a known gas?

WranglerX · May 25, 2025

disney said:
ok. so I filled a balloon to the size of a tennis ball, and then with a long aim 'n' flame lighter, tried to light it, and as soon as the balloon melted, it flew away (5ft). but clearly not flammable. I then verified with golf ball sized filled balloon that it puts out a flame. so that should narrow it down to Nitrogen, Argon or Argon CO2 (as Helium would have made the balloon float.) is there any way to see if I connect it to my welding regulator (the type with the ball) and see if the ball floats higher or lower than with a known gas?

Ball type regulator move ball up on volume/flow (CFM or CFH) not of whether gas is heavier/lighter than air (gas type) ....

ultrarunner · May 25, 2025

I had a good side business in school picking up cylinders and taking them to the gas plant Cylinder Clinic.

For a fee they would hydro, replace the valve, paint and fill.

Only CO2 could not be converted to other gases because CO2 leaves a residue.

I would then advertise in the penny mart with the new documentation.

Hydro, Paint and New Valve was $35 when I stopped.

Going to a jobber would have doubled my cost so having a full scale plant nearby made it work.

Age of the cylinder was never a issue and on occasion I’m seeing nearly 100 year old cylinders in medical oxygen rotation.

5030 · May 25, 2025

Considering how crusty the bottle is as well as the threaded bung, I'd never put any of my regulators on it, sure way to screw up a good regulator. I'd blow it down (outside) and repurpose it into something else. Maybe a 'bowling ball cannon'...lol

I own all the bottles that are used in the shop I own and I get them all refilled as well and never exchange. Kind of **** about nice, clean and unscratched bottles.