CO2 cyl pressure

1-tonmudder

1-tonmudder

Doin my part to stir the pot.
Joined
Apr 17, 2005
Location
Greeneville TN
I have a 20lb CO2 cyl to air up tires and such with and would like to put a gauge in it to monitor how much I have left.I have a reg that is preset at 150 PSI so I wont need a adj reg.How many psi does a full 20lb cylinder have and any recommendations on a gauge???
 
CO2 pressure changes with temperature. At room temperature it's ~850 psi. At 120F it's ~2200 psi. CO2 fire extinguishers don't have gauges because the internal pressure will change depending on the temperature. When they recharge a CO2 extinguisher they fill it to a weight versus a pressure. Your 20 LB tank will hold 20 LBS of CO2. I have a 5 LB tank for my kegerator. The gauge on the regulator will read 800 - 850 PSI at room temperature. When I put the tank in the kegerator at ~ 37F the pressure shown on the gauge drops, even if its a brand new tank. There's still 5 LBS of CO2 in the tank but the pressure drops due to the lower temperature.
 
Ok,thats brings up another ???.I have always heard that your not supposed to let a No2 bottle sit in direct sunlight due to it building pressure.I know No2 and Co2 are different but will that apply to the Co2 also or is that false info.This will be in the back of my M-1009 and we run all summer with no top so it will be in direct sunlight.
 
A full one is heavy and when they are close to empty they aren't too bad.
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Yeah I understand that,but I would like to know for sure how much I had (I'm anal like that).I would hate to be in Harlan for 3-4 days or along the interstate 300 miles from home and need it and it run out 1st thing.
 
Wiegh your bottle, the tare wieght should be written on the side of the bottle. Total wieght minus the tare wieght and that how much co2 you have left.
 
Not sure about direct sunlight but the pressure in a CO2 tank will increase when the tank is exposed to heat. I'd imagine if your tank was black it'd heat up more than a light colored tank - but that's just a guess on my part. All of the CO2 tanks I've tested have been in an environmental chamber.
 
One point about regulators. I think most people don't run a reg on a tank that's going to be strapped into an offroad rig is that they're relatively fragile. I know it wouldn't take me long to be a dumbass and break the thing right off. It's only like what $30 for a refill? Let it run empty before the trip and have it filled.
 
If you have a guage on your regulator, you can tell when its low because the pressure will get below about 500psi. However, that is a round figure, and Ive seen mine on really cold days show 450psi and still have a lot of fluid left.
 
CO2 i na canister is compressed into a liquid, it isn't a gas. That's why it's measured by eight.
B/c it's a liquid, that also means that "pressure" is not really a good indication of the amount remaining. The pressure drop is not a linear change with fluid drop - it will stay high until close to teh end, then drop off quickly.
If you plan to mount it, and leave it mounted, and use it from a mounted location, then a guage would be convenient b/c you won't have to unbolt it and lift i tu pto get a "feel" for if you're close or not.
 
1-tonmudder said:
Ok,thats brings up another ???.I have always heard that your not supposed to let a No2 bottle sit in direct sunlight due to it building pressure.I know No2 and Co2 are different but will that apply to the Co2 also or is that false info.This will be in the back of my M-1009 and we run all summer with no top so it will be in direct sunlight.
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don't mount the c02 tank in a place that gets direct sunlight or you'll probably be replacing burst disc on hot days. 100 deg weather + sunlight + tank = c02 gas out the burst disc. get a gauge for before the reg for 0-3000 psi its really nice to know when you should get your tank out of the heat. i worked at a paintball field for a years and c02 burns are just as bad as fire burns.
 
rockcity said:
why not run nitrogen? heat doesn't affect the pressure nearly as much as CO2
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Nitrogen wouldn't give you anywhere close to the cu. ft. of usable air as compressed Co2.

1-ton, I've seen guys use a little luggage scale (or any type of hanging scale) to measure the weight of the bottle. You should measure it when full and when empty. The weight difference should be 20lbs.

awww.americanweigh.com_images_h_series_main.jpg
 
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