How much liquid co2 in a tank?

[hitech]

I have to hand it to you, looks like math won out after all. i really believed the old 60% "rule".

Congratulations!

[trains are bad]

Judging by the condensation patterns on my prefrozen and therefore frosty 20oz tanks, that I observe during filling, I say there's about 3-4 inches of liquid in the vertical tank at that temperature.

I take a tank out of the freezer, set it down til it has actual frost all over it, screw it into the fill station and dump the co2 to it. At that temperature it quickly fills to the 18 ozs I put in them. There is a band of frost left at the bottom of the tank about 3-4" tall. Sorry, even with the xray I don't believe it. Because I can also tell that they are less than 1/2 full because of the angles at which a bottomlined tank starts shooting snow.

[Wat]

Well, i guess you can believe what you want. But i ran my calculations by my Thermo advisor at MIT and he knew it was right. He also explained to me how the fill rating is determined. I had assumed that the safety threshold on CO2 was determined by how much CO2 it could hold under the worst case scenario that all the CO2 boiled off and the pressure skyrocketed.

Thats actually not true, as a gas, co2 really isn't exceptionally dangerous since the burst disk provides a mechanism to vent high gas pressures. What is dangerous is CO2 as a liquid. The fill rating is determined by finding the maximum specific volume (thats 1/density) of liquid co2 and seeing how much would fill in the tank. As a liquid, co2 expands and contracts depending on temperature. If you were to 100% fill a co2 with liquid co2 below its critical temperature (that is, the temperature at which co2 can no longer exist as a liquid) and the temperature rose, the liquid would expand and the hydraulic pressure applied to the whole vessel would result in a catastrophic failure, even with a burst disc. Your max fill would be 100% liquid co2 at critical density. Put in a few percentage points for safety and you're getting somewhere around 95% liquid fill at the critical temperature around 82 degrees.

You can also easily disprove that the tank cannot be 30-40% full. You can look up the density of liquid co2 and gaseous co2 at various temperatures and you can easily show that if its only 40% liquid than you are no where near a full fill.

[Hellbore]

Wow, I thought for sure nobody would disagree with such obvious evidence.

Isn't it clear to you people that your methods (looking at frost, gun shooting snow) are FAR less precise than actually x-raying the tank and seeing the liquid level? There are all kinds of possible explanations for your anecdotal evidence, whereas the empirical evidence of the x-ray is pretty easy to interpret.

[hitech]

Wow, I thought for sure nobody would disagree with such obvious evidence.

[elprup]

I haven't read this page in full nor have I researched this topic, but I came across the page while searching for something else.

http://www.warpig.com/paintball/technical/gasses/co2dynamics.shtml