Page 1 of 1

co2 tank to fill with air

Posted: Fri Feb 19, 2021 11:13 am
by bravootome
hi, i got a sh 9 on( or oz ..) co2 paintball tank ( with the gun too) . the tank is made of Al and i want to know if and to what pressure (bar) can i fill it with my hill pump - with air. ( as i know co2 is more "low pressure than air"). i can not read the markings on it as it is pretty beat off ...... It is pretty heavy for it's size so it should work with 200 bar ??

Re: co2 tank to fill with air

Posted: Fri Feb 19, 2021 11:48 am
by mrfoo
Avoid beating off in public. It'll get you on a list.

Sorry, that was a cheap joke.

An aluminium tank can only, AIUI, be rated up to 3000 psi. That's around 200 bar, and the absolute maximum safe rating, tank direct from the factory, you can possibly expect. However, liquid CO2 only requires a bit more than 5 bar, so your tank may only have been rated for that. If you can't read the markings on the tank (and pressure rating should be stamped into the metal, not just painted on), either the tank is extremely beaten up, or it's intended only for liquid CO2 and has not been high pressure rated. Or quite possibly both. In any case, you can't trust it to not grenade if used for high pressure air unless you have hydrostatically tested it beforehand. This means pressurising it to some margin above the pressure at which you intend to use it, using *only* an incompressible fluid such as water - a potential failure when pressurised with water will be much less "dramatic" than the same failure using a compressible gas. This can be done "on the cheap" using, for example, a grease gun, some hydraulic line and a pressure gauge that can handle the pressures you expect, but even then I'd be very wary of a battered tank.

Re: co2 tank to fill with air

Posted: Fri Feb 19, 2021 12:01 pm
by bravootome
mrfoo wrote:
Fri Feb 19, 2021 11:48 am
Avoid beating off in public. It'll get you on a list.
either the tank is extremely beaten up, or it's intended only for liquid CO2 and has not been high pressure rated.
no, the tank has some markings stampted, but i could not read them clearly .... it is very heavy for his size and aluminum material, so it must hold some pressure. i put 100 bar in a diy tank. Anyhow i shall try read what is written .....
Anyone here turned a painball gun (point zero model) into a 6 mm one ?

Re: co2 tank to fill with air

Posted: Fri Feb 19, 2021 1:31 pm
by Rumpler
CO2 tanks have a nominal pressure of about 58bar at 20°C, that's why all those paintball air regulators reduce the pressure from whatever is in the bottle to that level (850psi) so air and co2 is interchangeable.

About the max. working pressure, looking at the steel tank I have here I think the markings say 1800psi, but better look at the markings on yours and google what they mean (English isn't my first language, so I'm not sure I read that right). Here the TÜV test pressure for Co2 bottles usually is 250bar. There should be a burst disk on your bottle, maybe it's marked wiuth the burst pressure. Anyway, that is not the working pressure, just the one it didn't explode when the bottle was new.

https://www.catalinacylinders.com/faqs/ ... -cylinder/

I would be very wary to go to any limits or misuse pressure bottles, if something goes wrong, it goes seriously wrong. Fast. If an aluminum bottle is so beat of that you can't even read the stamped in markings (neck/bottom) I would really consider to not use it again. I also would be concerned about corrosion, when you fill with air you get water and oxygen into a bottle propable designed for niether of that.
With an DIY tank, I would at least hydrotest it to 1,5 of the intended working pressure (just my guess, I'm sure there are good recommendations about that around here).

Re: co2 tank to fill with air

Posted: Sun Feb 21, 2021 7:24 am
by jackssmirkingrevenge
Some pictures of the tank would help. You say it's heavy, are you sure it's aluminum?

Personally I wouldn't go beyond 100 bar if it's aluminum. If it's steel, you'd need to inspect it properly for corrosion.
Rumpler wrote:
Fri Feb 19, 2021 1:31 pm
I would be very wary to go to any limits or misuse pressure bottles, if something goes wrong, it goes seriously wrong. Fast. If an aluminum bottle is so beat of that you can't even read the stamped in markings (neck/bottom) I would really consider to not use it again. I also would be concerned about corrosion, when you fill with air you get water and oxygen into a bottle propable designed for niether of that.
Wise words worth heeding.