CO2 Tank Weights

[MrLang]

I'm hoping someone can basically tell me I'm being an idiot, I'm right, and I can move along. Alternatively, I think maybe someone might tell me that the tank doesn't actually hold 20 oz and I should assume it's going to cut out well in advance of my logical answer below:

I have a 20 oz CO2 tank. 1 ounce is 28 grams, so 20 oz should be 560g. The whole tank full weighs 1374g. Can I assume I can run it until 1374 - 560 or 814g or is this a poor assumption. Will the gas cut out before then? How much before then in your personal experience?

More importantly, rather than tell me my math and logic are right... can anyone confirm or deny this BASED ON EXPERIENCE WEIGHING THE TANKS BEFORE AND AFTER USE?

Thanks in advance to those giving input based on personal experience.

[dillan2020]

I would think it is 20oz by vollume not weight and without knowing what 20oz of co2 weighs it's impossible to guess.

[MrLang]

The weight, volume, and space occupied is a static function across all gases - it's the noble gas law.

They sell you 20 oz of CO2 by weight and the volume and pressure are dictated by the size of the container it's in, which doesn't matter to me.


What I'm actually asking here is if people actually sell you 20 oz when they fill a tank and if they do, does the CO2 tank function to release gas for the entire 20 oz or does it fizzle out before the 20 oz mark.

[Erndogg]

I can't help you on the math side of things but from my days playing painful I can tell you to things: 1) (based on what i was told years ago) when the Co2 is filled, it is pressurized becoming a liquid instead of gas. This may or may be part of your trouble with calculations. 2) the rate of expansion from liquid to gas varies incredibly based on the temp of surroundings. So when it's hotter gas expands much faster. So when we chrono in the morning to make sure velocity was safe, by noon we would have to chrono again because.every one with co2 would be shooting hot at unsafe velocity.

Again sorry I can't help you with the math part of your problem. Just trying to lend you a hand from my past experience with co2 use.

As far as if they actually sell you 20 oz I don't think so. I think they fill it short so to allow for expansion. I can't tell you for certain and I am not airsmith.

[JohnNJ]

I don't know about paintball canisters but...

I purchased used tanks from a fire extinguisher business. One tank is called a 10 pounder and it weighs approx. 10 pounds empty. When full it weighs a little over 15 pounds.

I have not weighed it during use but I know the tank gets lighter quickly but then the tank seems to last forever, even though it feels empty. I can't tell you why there's a big weight drop initially.

What I'm saying is that weight may not be a good indicator of what's left in the tank.

[John Marker]

The weight, volume, and space occupied is a static function across all gases - it's the noble gas law.

They sell you 20 oz of CO2 by weight and the volume and pressure are dictated by the size of the container it's in, which doesn't matter to me.


What I'm actually asking here is if people actually sell you 20 oz when they fill a tank and if they do, does the CO2 tank function to release gas for the entire 20 oz or does it fizzle out before the 20 oz mark.

Yes, if they fill the tank correctly, they are selling you 20oz of CO2. There are some shops out there that short fill them and tell their customers that they need to do that to allow for expansion, but that is a load of crap. The tanks are built to hold the amount of CO2 that is specified on the label and stamped into the neck of the tank.

When the tank is full and at normal room temperatures, the CO2 that is in the tank should be about 80% liquid and 20% gas. As the tank is emptied, the amount of liquid CO2 decreases as the liquid converts into a gas to maintain the pressure in the tank, which should be around 600-700 psi. When enough CO2 has been used that there is no longer liquid CO2 in the tank, the pressure will very rapidly drop and the tank is basically empty, although there is still CO2 in the tank but it is no longer pressurized enough to propel it out of he tank and not the atmosphere.

You will not be able to utilize all 20oz, but it should be close, I would think 19oz or so realized from a fill, especially for euthanizing rodents. In paintball you can bet on losing a few ounces of CO2 from each tank because of the lack of pressure when the CO2 levels become low, but you shouldn't have this problem when not trying to pressurize a paintball marker.

Hope this helps,

John

[MrLang]

Yes, if they fill the tank correctly, they are selling you 20oz of CO2. There are some shops out there that short fill them and tell their customers that they need to do that to allow for expansion, but that is a load of crap. The tanks are built to hold the amount of CO2 that is specified on the label and stamped into the neck of the tank.

When the tank is full and at normal room temperatures, the CO2 that is in the tank should be about 80% liquid and 20% gas. As the tank is emptied, the amount of liquid CO2 decreases as the liquid converts into a gas to maintain the pressure in the tank, which should be around 600-700 psi. When enough CO2 has been used that there is no longer liquid CO2 in the tank, the pressure will very rapidly drop and the tank is basically empty, although there is still CO2 in the tank but it is no longer pressurized enough to propel it out of he tank and not the atmosphere.

You will not be able to utilize all 20oz, but it should be close, I would think 19oz or so realized from a fill, especially for euthanizing rodents. In paintball you can bet on losing a few ounces of CO2 from each tank because of the lack of pressure when the CO2 levels become low, but you shouldn't have this problem when not trying to pressurize a paintball marker.

Hope this helps,

John

Exactly what I was looking for... thanks everyone