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Help with co2 tank issue

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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Help with co2 tank issue

Unread postAuthor: skyjive » Sat Dec 06, 2008 5:26 pm

So I am trying to connect my regulator to my co2 tank but the problem is that the regulator has a 1/4" female in port, which does not directly connect to the threading on the cylinder, which is 1/2" male. I used a few fittings to bridge the gap but they are leaking profusely due to the 1800 psi pressure on the upstream side of the regulator. I used pipe paste which has always worked for me, and tightened the fittings up really tight, but to no avail. The threads on the cylinder seemed kinda weird, like they weren't tapered and it was hard to get the fitting onto them, so this might be the trouble spot. If anyone has encountered this type of problem or has experience with co2 setups like this, any help would be appreciated, as I can't get my just-completed semi-auto to run until this stops leaking.

The regulator, cylinder, and fittings:
Image

The suspected trouble spot:
Image
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Re: Help with co2 tank issue

Unread postAuthor: Gippeto » Sat Dec 06, 2008 7:33 pm

The threads on your tank valve are NOT tapered. And the seal gets made INSIDE the threaded portion.

Go to a shop that sells welding supplies, and get the proper fitting for your tank. Take your tank to make sure.

Clean and check the threads on your valve before you go. You may have to "fix" them with a file if you've buggered them with the pipe coupler.

Good luck. :)
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Unread postAuthor: jitup » Sat Dec 06, 2008 8:02 pm

Gippeto is right on the money. btw in total how much do you have in your setup? what is the max psi you can reach with it?

I ask because mine dose not go that high, or atleat that is what my dad said (I used an extra oxygen regulator so I thought if it can handle the forces of a full size oxy bottle, It will handle my 20 oz Co2 tank. PLEASE correct me if I am wrong, it is to cold to shoot and I do not want to blow my arm off because the reg. can't handle the pressure.)
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Unread postAuthor: grumpy » Sat Dec 06, 2008 8:10 pm

Maybe it's because you are using NPT threaded fittings and the valve has CGA threads .
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Unread postAuthor: skyjive » Sat Dec 06, 2008 8:23 pm

Thanks for the advice. I hope I haven't ruined the threads :(
@ jitup: The tank is I think at 1800 psi, and the regulator has a max ouput of 2500 psi, so I can go as high as tank pressure. I am not gonna take it above a few hundred though.
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Unread postAuthor: jitup » Sat Dec 06, 2008 8:28 pm

that is good. since this disscussion is about Co2 set ups, what is the max PSI an Oxygen reg can accept, and put out. Is it safe to use with a 20 oz Co2 tank?
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Unread postAuthor: scavies » Sun Dec 07, 2008 10:35 am

Watch out, that steel has a bad habit of tearing up brass.

Right now I'm looking for teflon tape on there. If you don't have it on, well do it.

Anyway, the threads shouldn't be too much of a problem. I have just layered a ton of teflon on top of mismatching threads plenty of times and they stop leaking after a few tries.

Oh yea, I'm not too sure that your CO2 pressure is right. Vapor pressure of CO2 at about 55 degrees is around 600 psi and that's before it start cooling from expansion...Where's that chart???

Ah here it is Image
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Unread postAuthor: Gippeto » Sun Dec 07, 2008 1:05 pm

scavies; " just layered a ton of teflon on top of mismatching threads plenty of times "

This is half assing things at its finest. :roll:

Half assing things at high pressures can and likely WILL result in injury or death.

I strongly suggest that you do it RIGHT.

As to the pressure handling capability of the bottle, the working pressure is likely stamped into the bottle around the neck area.

With my CO2 bottle, it says 1800psi. The proof pressure of the bottle is 3000psi.

The pressure of CO2 is highly temperature dependant. On a hot day(~32C) I've seen it as high as 1000psi. Yesterday, when I brought the same bottle in from the truck (it was below freezing outside) the bottle pressure was around 400psi.

Oxygen regulators should handle the supply pressure of CO2.(Max inlet pressure is usually 3000psi) Whether or not the "soft parts" are compatable is a question though.

As well, the output pressure will be very low. In the neighborhood of 100-125psi.
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Unread postAuthor: skyjive » Sun Dec 07, 2008 2:17 pm

yeah, this is my first time working with high pressure (non bike-pump) and frankly that co2 tank scares me to death, so I'm certainly not gonna half-ass anything. It does say 1800 psi on the tank shoulder. I ordered an adapter off mcmaster that should solve the problem (cga-320 -> 1/4" npt)
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Unread postAuthor: Gippeto » Sun Dec 07, 2008 2:21 pm

Don't let it scare you.

Just be respectful and aware of its abilities, and treat it accordingly. :)
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Unread postAuthor: tomthebomb137 » Sun Dec 07, 2008 2:26 pm

with gippetao, i will half ass and build crummy setups for everything BUT my high pressure lines. there is an absurd about of power in these tanks and they dont have much concern for human, or any other form of life. mess around with anything EXCEPT high pressure lines, oxy, co2, or whatever else youd want to run. and you are probably aware of this, but jut so you know, carefull if your using plastic after the reg setup, co2 gets veryyy cold upon expansion, and will compromise the strength of your pipe and fittings
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Unread postAuthor: skyjive » Sun Dec 07, 2008 3:01 pm

yeah, the only post-reg stuff that isn't copper is 2750 psi hydraulic line (and a cardboard magazine, but that hardly counts) :wink:
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Unread postAuthor: scavies » Sun Dec 07, 2008 4:05 pm

Oh yea ur right. I only half ass with 12 gram CO2s which decrease pressure right away in the chamber according to ideal gas law. That is a pretty massive tank, so yea, I take that back.
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Unread postAuthor: grumpy » Sun Dec 07, 2008 4:31 pm

just keep one thing in mind , co2 is not an ideal gas!
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