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Maximum CO2 pressure- ABS gas reservoir.

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Maximum CO2 pressure- ABS gas reservoir.

Unread postAuthor: chpiai » Tue May 01, 2007 3:32 am

Given that liquid CO2 has a vapour pressure of about 830 PSI, about 55 atmospheres; if I have a compressed gas reservoir with a volume not significantly greater than 160 ml (10 ci), or any reservoir volume less than this figure, and it were to be exposed directly to an unregulated 16g (0.56 oz) CO2 cartridge, it would theoretically fill the reservoir to something approaching its own vapour pressure (830 PSI). Were this to occur, it is presumably highly likely that the ABS reservoir will rupture. Has anyone had this happen? What is the highest pressure an ABS reservoir can reliably handle?
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Unread postAuthor: FreakyShotGlass » Tue May 01, 2007 3:36 am

Unless the ABS is pressure rated to 830psi, which it isn't, then this is possibly one of the dumbest things I've heard. The ABS would rupture and would have a lot of energy, meaning that you wouldn't want to be anywhere near it when it went off. I dont think anyone has been stupid enough too try this.
Bottom line, don't use ABS for any pneumatics, let alone an unregulated CO2
setup.
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Unread postAuthor: jackssmirkingrevenge » Tue May 01, 2007 3:38 am

FreakyShotGlass wrote:Bottom line, don't use ABS for any pneumatics, let alone an unregulated CO2
setup.


Only a 16g capsule of CO2 was proposed, so in a chamber of significant dimensions the pressure's going to be much less than 830 psi. Still, why not use pressure rated PVC and be safe?
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Unread postAuthor: Hotwired » Tue May 01, 2007 3:47 am

You can get pressure rated ABS but even so, putting unregulated CO2 into it is still going to frag you.

The highest rated ABS I've seen in the UK is Class E pipe which has a working pressure of 15bar - 217psi. You'd have to be missing something to want to fill it with four times that pressure.
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Re: Maximum CO2 pressure- ABS gas reservoir.

Unread postAuthor: FreakyShotGlass » Tue May 01, 2007 3:48 am

chpiai wrote: if I have a compressed gas reservoir with a volume not significantly greater than 160 ml (10 ci), or any reservoir volume less than this figure, and it were to be exposed directly to an unregulated 16g (0.56 oz) CO2 cartridge, it would theoretically fill the reservoir to something approaching its own vapour pressure (830 PSI).


He is proposing to make a chamber small enough to reach the vapour pressure of CO2. If the chamber proposed was larger and PVC then it would be able to and has been done safely.
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Last edited by FreakyShotGlass on Tue May 01, 2007 3:55 am, edited 1 time in total.
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Unread postAuthor: Hotwired » Tue May 01, 2007 3:52 am

So how does he get propane in his gas chamber after starting with a 16g CO2 cartridge?
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Unread postAuthor: FreakyShotGlass » Tue May 01, 2007 3:54 am

lol, Im still thinking of propane, I just wrote a PM about it. Man thats funny. :oops:
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Unread postAuthor: chpiai » Tue May 01, 2007 4:40 am

I should probably clarify, I'm not actually proposing deliberately filling a reservoir to that kind of pressure; I'm simply trying to assess the danger in the event that it was accidentally over-pressurised.
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Unread postAuthor: chpiai » Tue May 01, 2007 5:04 am

I am thinking ABS because the consensus seems to be that it will deform and rupture in the event of failure, where PVC will fragment and shred me.
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Unread postAuthor: FreakyShotGlass » Tue May 01, 2007 5:09 am

At pressures as extreme as 830psi I dont know if ABS will still rupture, it might fragment. My advice would be to find the thickest metal pipe you can and then bury it in the densest material you can find, ie, soil, sand, cement.
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Unread postAuthor: jimmy101 » Tue May 01, 2007 12:02 pm

If you are worried about something happening that isn't supposed to happen (like a valve or regulator freezing open) then the usuall solution is to include one or more pop-off valves (safety release valves) in the chamber. If the pipe is rated at say 200 PSIG then a 150 PSIG pop-off would be a good idea.

If you use pop-offs you have to make sure that the throat of the pop-off is at least as big as the hole though which the gases are being supplied. A pop-off with a 1/16" ID throat might not be able to keep up if you are pressurizing the chamber through a 1/2" ID line.

Your local hardware store might have pop-off valves. Check near the compressors. McMaster-Carr has many kinds of pop-offs.

You might also be able to use the safety release valve used on hot water heaters. IIRC, they are usually rated at about 100 PSIG and have pretty large throats (> 1/2" ID).
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Unread postAuthor: chpiai » Tue May 01, 2007 2:13 pm

jimmy101 wrote:If you are worried about something happening that isn't supposed to happen (like a valve or regulator freezing open) then the usuall solution is to include one or more pop-off valves (safety release valves) in the chamber. If the pipe is rated at say 200 PSIG then a 150 PSIG pop-off would be a good idea.

If you use pop-offs you have to make sure that the throat of the pop-off is at least as big as the hole though which the gases are being supplied. A pop-off with a 1/16" ID throat might not be able to keep up if you are pressurizing the chamber through a 1/2" ID line.

Your local hardware store might have pop-off valves. Check near the compressors. McMaster-Carr has many kinds of pop-offs.

You might also be able to use the safety release valve used on hot water heaters. IIRC, they are usually rated at about 100 PSIG and have pretty large throats (> 1/2" ID).



Thanks a lot. That's what I shall do.
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