Experience refilling argon or 75/25 cylinders yourself?

[BukitCase]

I stand corrected - Bottled gas - Wikipedia, the free encyclopedia (see Case 2)

and Carbon dioxide - Wikipedia, the free encyclopedia " it undergoes a phase transition from gas to liquid at room temperature at an attainable pressure of approximately 60 bar (870 psi, 59 atm), allowing far more carbon dioxide to fit in a given container than otherwise would."

Learn somethin' new every day... Steve

 

[xring100]

We used to have liquid argon in the lab at work as well as hydrogen because we used large volumes and compressed gas was not feasible. Problem with these is that these tanks if not refrigerated at extremely cold temps bled off gas or they would explode. Thus unless you use a lot of gas regularly you'd be wasting money

Argon boils at ~−300°F at standard pressue

 

[BukitCase]

Same here, but I wasn't directly involved - we had an argon and nitrogen plant (extraction), cryo tanks for liquid nitrogen, oxygen, hydrogen, probably others (200 acre rare metals plant) - There are times when I think it would have been fun to start over in a different profession there just so I could learn more, then I wake up and the nightmare's over :=)

 

[PILOON]

Hooking the 2 tanks together will result in both attaining the same pressure which will be lower after each transfer.
Rapid transfer could cause the valves to freeze so slow would be suggested.
Naturally the small tank needs to be rated for the high pressure that the large one is and hoses fittings also need to meet pressure specs.
I used to scuba dive, filled my own tanks and did occasional transfers as well.

 

[yomax4]

If you transfill, You should have the small tank in a pail of water because it will get Hot! This can be dangerous.. You will only be able to split the difference in pressure from the big tank to the small one. If you have 2000# in the big tank you will only get 1000# in the small one unless you manifold 4 or 5 tanks together. I have done it a lot with 40CF Helium tanks back in the day. Works the same with other inert gases like Argon etc.. As for CO2.it is filled as a Liquid. You use the gas off the top unless you have a Siphon tank that has a dip tube in it which makes it dispense liquid from the bottom. Often used in POP bulk clusters

 

[Sodo]

OK now we're getting down to it. But I don't see how you can get ~2000psi if the pressure of liquid CO2 is 870psi.

I think the pressure will hold steady at (~2000psi) until the last drop of liquid is gone then the pressure will drop like letting air out of a tire.

So can I transfer liquid by turning the bigger tank upside-down? And do I transfer (liquid) until the 20cf tank reaches a certain weight? It makes sense that I'd have to cool the smaller tank to fit it all in.

Somebody knows how to do this.

 

[Arc weld]

Lots of confusing info on here. In a mix gas like C-25, CO2 can be measured/filled in the gas form because it is a small portion of the total mix. It can also be measured in liquid (weighed before the argon is added to get the same C-25 mixture. For a 100% CO2 cylinder, it is always filled as a liquid. Very similar to propane. There's a fancy term for it but the CO2 is basically boiling/vaporizing inside the cylinder and that creates the gas pressure. A dip tube on the valve will allow liquid CO2 to be withdrawn. Again, similar to propane. The pressure of a CO2 cylinder varies depending on the rate of vaporizing but the maximum pressure is about 850 PSI. A full cylinder is usually between 600 and 800 PSI. Not anywhere close to high pressure gasses at 2200 PSI. CO2 is filled by weight not pressure on a scale the same as propane. Cylinders are referred to by their weight, such as 50 or 75 pounds. The easiest way to know this is to take a 200 cu. ft. oxygen cylinder and put it beside a similar sized 50 lb. CO2 cylinder and load both into the back of a truck. The CO2 will be 50 lbs. heavier because it's filled with liquid. A 100 Lb CO2 like used for fire extinguishing is the last cylinder you ever want to have to pick up by hand.

You can get high pressure braided hoses for filling smaller cylinders from large ones but it's not recommended. Just get at least an 80 cu. ft. C-25 and be done with it. A 125 cu. ft. would be better. A 20 cu. ft. cylinder is a waste of time and will only last about 15 or 20 minutes. If I had to fill a cylinder every 20 minutes of welding, I'd throw the MIG out and use stick! ullinghair:Straight CO2 used for welding usually needs a special regulator to prevent freezing from too fast of withdrawal rate.

Just about anyone needing high volumes of gas can get cryogenic tanks with liquid in them. The problem is you can't let them sit around or all the gas created will vent off when the pressure gets too high.

 

[Sodo]

Thx for the info. I have an 80cf cylinder. Loading it into the truck at the store it did not strike me as a good portable size. Keeping the 80 at the shop and getting a 20cf for the truck sounds like a better idea. I've been setting my flow at 20cf per hour so I assumed there would be about 60 minutes of welding from a 20cf tank.

Where did you get the "15 minutes" estimate for 20 cf?

 

[Arc weld]

Never heard of anyone being happy with 20 cu. ft. cylinder. They're tiny. They might last a little longer than 15 minutes but there's always some wasted gas. You lose some even disconnected the line when transfilling too. Anywhere you go to use MIG, you need to be inside anyway. An 80 cu. ft. cylinder isn't hard to move around but why not use stick since your machine does both? Wouldn't it suck to run out of gas in the middle of a job? A 20 cu. ft, cylinder makes no sense unless you need to carry it to the top of a skyscraper.

 

[adirondackmtnman]

CO2 certainly goes to liquid at some pressure. Gary, Steve do you know for a fact that CO2 at 2200psi in a welding cylinder does not have some liquid at the bottom? In other words, of you have 80cf of CO2 in an 80cf cylinder, is there some liquid at the bottom?.

Also interested in Argon and the 75/25 mix. Somebody on this forum knows this for a fact.

:thumbsup:If it's not liquid,,,, then my plan gets simpler. :thumbsup:

I think if there were a chance of it being in a liquid state in the cylinder, the warning placard would have to state 'liquified carbon dioxide' or something similar. Chances are it indicates compressed gas.

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