co2 pressure

nsane-spuds · Tue Nov 04, 2008 6:34 pm

Alright, so here is my question:

Is the pressure of co2 constant? I mean, if i have a full 12g co2 cartridge, and i empty out will the pressure in it always be at around 800 psi until its pretty much completely empty?

Thanks in advance.

covey12 · Tue Nov 04, 2008 6:47 pm

you mean emptying all of the gas in one chamber, for one shot, or using it for multiple shots, because if your going for the multi shots, i suggest finding a regulator (i have no idea where to get one) becuase it will always allow the same psi out of the 12gram

grumpy · Tue Nov 04, 2008 7:04 pm

it would depend on the size of pressure chamber.

nsane-spuds · Tue Nov 04, 2008 7:25 pm

The reason i'm asking is because i was wondering if this would work to regulate co2. Beacause if i remember properly, in a tank, co2 pretty much stays at 800 psi until its empty...

VH_man · Tue Nov 04, 2008 7:32 pm

That is Basically a Regulator, Except for the fact you need a VERY STRONG spring.........

In fact, that IS a regulator. Congrats.

nsane-spuds · Tue Nov 04, 2008 7:41 pm

Well, its a co2 regulator.

This wouldn't work with air since the pressure in the tank drops unlike with co2. Right?

TurboSuper · Tue Nov 04, 2008 7:51 pm

Well air doesn't really have a liquid (highly compressed) state, since it's not a gas but a mix of gases. So therefore it ends up losing pressure as the tank is discharged, following P1V1=P2V2.

frankrede · Tue Nov 04, 2008 7:51 pm

The pressure will drop if you let some out.
Ever had a co2 bb gun?
The velocity drops the more you shoot it.

nsane-spuds · Tue Nov 04, 2008 7:56 pm

I dont have a bb gun but my friend has a paintball gun and if i remember right he told me that there is no use to have a gauge on a paintball tank since the pressure only drops at the few lasts shots. Also, co2 tanks are filled by weight wich leads me to think that the pressure wont drop unless there isint any more liquid co2 left in the tank.

VH_man · Tue Nov 04, 2008 8:11 pm

CO2 tanks TECHNICALLY do not loose pressure. However, as you let gas out, energy is required to turn the liquid CO2 into a gas.

This energy is taken as Heat, and therefore makes the temerature of your CO2 tank drop, Causing your Vaopr pressure to drop.

So yes, the Pressure drops, but if you regulate it, you will notice it gives as constant a pressure as ever, although it might take longer as you fire it faster.

All in all, i say go with one of the Air tanks for Paintball. It uses the same threads, and gives out the same overall pressure as a CO2 tank, except without cooldown, and the filling is cheaper.

biged · Wed Nov 05, 2008 6:05 am

For a 12 gram CO2 cartridge:

4200 / Chamber Cubic Inches = PSI

5.25 CI is 800 psi
15 CI is 280 psi
25 CI is 168 psi
35 CI is 120 psi
45 CI is 93.3333333 psi
55 CI is 76.3636364 psi

I unfortunately don't have the calculation for modifying the formula for temperature. The hotter it gets the greater the pressure.

///ed///

VH_man · Wed Nov 05, 2008 6:08 am

I THINK you guys are missing the point (correct me if im wrong)

He wants to Regulate a CO2 cartrige for use in some sort of Airgun, not fill up his spudgun chamber.

And also, i think you should know that a well-designed regulator will keep the output constant untill the input falls below the desired output pressure.

grumpy · Wed Nov 05, 2008 7:11 am

nsane-spuds wrote:, co2 tanks are filled by weight wich leads me to think that the pressure wont drop unless there isint any more liquid co2 left in the tank.

this is correct , once all liquid is gone the pressure will rapidly fall. not sure but maybe this will help in what you want to know about co2.

http://www.doomlabs.com/science/CO2_Science.html

Ragnarok · Wed Nov 05, 2008 8:23 am

VH_man wrote:In fact, that IS a regulator. Congrats.

Sorry, this is not a regulator:

It's a check valve, and all it will do is let CO2 through from right to left until the pressure is the same on both sides.

Well, to be more specific, it will let CO2 through until the force on the ball is the same on both sides. What it will actually do is create a fixed pressure difference between the 2 sides.
As CO2's storage pressure is reasonably fixed, it would very crudely regulate CO2, but it cannot be called a regulator.

If you want an idea of how a regulator works, this animation of mine gives the crude basics:

The spring has to be the opening force - not the closing one. It also has to be opposed to the regulated side, not the high pressure one.
In this case, the high pressure side has no impact on the opening force.