Dry Ice

Fexo180 · Wed Mar 21, 2012 2:49 am

Not sure if this is the relevant area to be posting this question, however.. Could one use dry ice in a pressure vessel to use as a portable pressure source.. think it be be ideal for a qev/slide valve combo.
using 2 chambers on the gun..
1 with the dry ice and water.. bit of plumbing for the secondary chamber & qev/slide. e.t.c ??

thoughts..

i suppose water in the system could be problematic?

Crna Legija · Wed Mar 21, 2012 4:08 am

dry ice can produce a lot of pressure, something like 3000psi if left long enough at the right temp, if your tank can take the strain sure it'll work but would be much better off with a c02/HPA tank reged down.

inonickname · Wed Mar 21, 2012 4:16 am

Crna Legija wrote:dry ice can produce a lot of pressure, something like 3000psi if left long enough at the right temp, if your tank can take the strain sure it'll work but would be much better off with a c02/HPA tank reged down.

I'd suggest that at around 830 psi or so at room temperature the pressure increase is probably going to drop off...

Crna Legija · Wed Mar 21, 2012 5:26 am

inonickname wrote:
Crna Legija wrote:dry ice can produce a lot of pressure, something like 3000psi if left long enough at the right temp, if your tank can take the strain sure it'll work but would be much better off with a c02/HPA tank reged down.
I'd suggest that at around 830 psi or so at room temperature the pressure increase is probably going to drop off...

anyway still very high

saefroch · Wed Mar 21, 2012 2:10 pm

Water isn't a problem, no reaction occurs. Usually it's combined with dry ice for better thermal contact, and thus heating. If your vessel can take the pressure, packing it full of dry ice and letting it warm up will give you a fair amount of liquid CO<sub>2</sub> in the tank, and will last fairly long at ~830psi.

killerbanjo · Wed Mar 21, 2012 4:10 pm

I have always wondered if you could fill paintball co2 tanks with dry ice, weigh it and put it in then leave it overnight or a day or two and in theory it should fill the co2 canister with co2. Never tried it though...

Fnord · Wed Mar 21, 2012 6:21 pm

I have always wondered if you could fill paintball co2 tanks with dry ice, weigh it and put it in then leave it overnight or a day or two and in theory it should fill the co2 canister with co2. Never tried it though...

Yeah, it works. Add a shot of silicone lube when you do it, and possibly put the thing in some (cold) water so the rubber gasket doesn't get exposed to -120F. Great way to save a few bucks if you have a ton of tanks laying around. Just be careful with the weighing part.

If your vessel can take the pressure, packing it full of dry ice and letting it warm up will give you a fair amount of liquid CO2 in the tank, and will last fairly long at ~830psi.

I don't know how much dry ice expands when phase shifting into a liquid at room temp, but keeping it at near-solid density at that temperature would send the pressure way, waaay up. You'll pop the burst disk on the tank if it has one. If it doesn't, well, I hope no one is around it

A number I heard that was commonly used is 2.7 cubic inches of tank volume per ounce of CO2, which allows for expansion.

Fexo180 · Wed Mar 21, 2012 7:12 pm

I have made my fair share of dry ice bombs in the past.. 3-4 pellets, some water, an empty soda bottle and very VERY quick hands..

the pressure chamber would have to be fairly gnarly with a burst disk or some sort of pressure relief valve so that to dosn't become a shrapnel maker.

ramses · Thu Mar 22, 2012 6:11 pm

I'm curious. How did you get the dry ice into the paintball CO2 tank? Did you take the valve off and just shove it through the hole?

Fnord · Thu Mar 22, 2012 9:08 pm

^Crushed them up into powder, weighed it, then unscrewed the top and funneled it in. I let it warm up in a big piece of steel tubing, just for safety reasons. For a 9oz tank it takes a few hours for the temp start equalizing.