Converting co2 tank to hold argon/co2

Date 03-07-2008 03:37

Hi folks. My apologies if this question has been posted before (I tried searching, but didn't come up with much).

Someone locally here is selling an empty 10lb co2 tank (in test), and I was wondering if I could convert it to hold an argon &/or an argon/ co2 mix.

I've heard that since the tank has held co2 previously, that all but rules out using it to hold straight argon. As far as the mix goes, tho, I was told all I'd need to do is swap in a cga-580 valve and I shouldnt have a problem getting it filled.

Before I go and actually buy the thing, I'll be sure to stop by airgas to confirm this, tho, in the meantime I just wanted to run this past you all to to see what you thought

By the way, anyone know how the 10 lbs. converts to cubic feet? I did some googling and it seemed to be generically 7 cu ft. per lb.

Thanks for any thoughts.

By rlitman (***)

Date 03-07-2008 04:18

Sorry, but nope. Its not so much about the previous contents, as it is about the pressure it was designed and tested for.
Argon tanks (which store highly pressurized gas) need to be able to withstand a much higher pressure than CO2 tanks (which store mostly liquid CO2 in a similar way to an LP tank, but at a much higher pressure than LP), and any argon mix, is also a pressurized gas.
So, you can put CO2 in an argon tank, but no argon, or mix into a CO2 tank.

As for volume of CO2:
With a molecular weight of 44, there are around 10.3mol of CO2 in a pound. Since there are 22.4L of ideal gas at STP per mole, 1 pound yields 231L, or:
8.15 Cubic Feet per pound of CO2. A heavier gas (such as propane), would yield less volume per mass (propane should be around 6.18 Cubic Feet per pound).

By DaveBoyer (*****)

Date 03-07-2008 04:23

Some welding supliers will let You trade a tank for the one You need, Airgas is generally not helpfull in this regard, company policy. However, You might ask, just in case You find someone more lenient.

By seagull369 (*)

Date 03-07-2008 05:34

Wow... I feel like I'm back in chem. class again after that one, rlitman :-D

Thank you both for the great replies. I doubt anyone could've answered that any better.