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FTG-05 · 09-20-2012, 05:29 PM

While I've never bought CO2, I do buy C25, which is a welding gas. It didn't matter whether I brought a leased tank or my personally owned tank - they just got traded out, an empty for a full one. The cost for a very large C25 is about $45 or so; this is probably a 35-40 lb CO2 equivalent. I fail to see how you can buy dry ice for less.

There is also the matter of taking off and putting back on the high pressure valve. Unless you have the specialized wrenches to precisely fit the valve, I used to do this for living, you're going to have some trouble even taking the valve off. And then there is the matter of correctly installing the valve plus the wear and tear of constantly taking it off and on. They're supposed to be taken off once every 5 years or so at a minimum. You're planning to do that for every "refill". Not smart.

Fooling with high pressure cylinders like this falls into the same category as +120 VAC electricity: Not something to be forked with.

Buy the gas, not the dry ice.

alchemedes · 09-21-2012, 09:10 AM

I know this isn't co2 in the video (co2 isn't flammable), but check out what happened to this guy that removed the valve off an oxygen tank. Just sayin...

http://www.youtube.com/watch?v=9lw_fhNAIQc

mattd2 · 09-21-2012, 09:33 AM

Dry ice sublimes at -78°C at atmoshperic pressure. From what I have seen a dot3aa (is that the right standard?) cylinder has a lower working temperature of -20°C. I would be cautious of the cylinder getting cold and cracking due to brittle fracture.

**Homercidal** · 09-21-2012, 11:59 AM

I have a 5# tank and it costs $16 to refill at the local supply store. A 20# tanks only costs $19 to fill.

I'll be upgrading my tank when my EHERMS system is built. $3 more for 4 times as much? Yes please.

**iaefebs** · 09-21-2012, 10:17 PM

Quote:

Originally Posted by Homercidal

I have a 5# tank and it costs $16 to refill at the local supply store. A 20# tanks only costs $19 to fill.

I'll be upgrading my tank when my EHERMS system is built. $3 more for 4 times as much? Yes please.

I would guess that it is not so much the amount of CO2, but the labor to fill a tank. The process of filling a 5# is the same as a 20# and probably takes close to the same time.

**jpc** · 09-21-2012, 11:25 PM

Quote:

Originally Posted by alchemedes

I know this isn't co2 in the video (co2 isn't flammable), but check out what happened to this guy that removed the valve off an oxygen tank. Just sayin...

http://www.youtube.com/watch?v=9lw_fhNAIQc

Technically, oxygen is not flammable, either, nor can it "explode". It is an oxidizer, and will provide oxygen to a fire, but there needs to be a fuel of some sort in order to have such a thing happen.

Rbeckett · 09-21-2012, 11:34 PM

Derek.
The prices fpr compressed gasses and the hazmat fees has risen astronomucally in the last 12 months. The current best price I can find around town is at a fire extinguisher service co. The welding gas places are just too expensive to fool with right now. Since a 5 lb cylinder will last a while I haven't had to fill any lately but am aware it is gonna hurt when I do. You can thamk mr Obama and the DOT for this little issue. Hazmat background checks are not cheap and every one is paying the cost of that due to 9/11. Sorry I dont have concrete prices, but I use non medical grade gasses because they are much cheaper than medical grade helium, argon or CO2.
Bob

alchemedes · 09-22-2012, 02:24 AM

I don't understand why the prices would differ so astronomically across the US. I guess some places just know they can rip you off.

**copyright1997** · 09-22-2012, 03:02 AM

Not to thread jack, but do any of you have an adapter to do co2 canister to co2 canister transfers? I have a 20#, 5#, and 4#, and would like to use the 20# to refill the smaller ones. Any idea if what parts I need?

jolsen · 09-22-2012, 06:26 AM

Quote:

Originally Posted by acidrain

To answer your question, it is possible, but I think you would need to remove the valve to do it, and that can be dangerous itself depending on your skill and knowledge of compressed gas cylinders. You would need to measure (in weight) the dry ice, and not exceed the bottle rating.

That said, you should be able to find a used 5 or 10 lb bottle on craigslist for around $50... more if it includes a regulator.
Take that puppy to your nearest welding shop and exchange it for a new, filled tank (doesn't matter if it's out of date as long as it's NOT a rented tank) for exchange.
I pay $11 for each 5 lb exchange, and the tanks I get look brand new. I understand it's only $20 or so to upgrade from a 5 to 10 lb., and the fills are only a couple dollars more.

Im jealous, up here I've searched everywhere and the cheapest I can find is 40$ n change for a 5# and I just mean refill...