CO2 Tank Pressure

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beilber

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Hi All,

I just started kegging and had my 5# co2 tank filled a few days ago. When i hooked up my regulator it read the tank pressure at 800psi. The regulators goes up to 2000psi which made me wonder if It wasn't filled completly. I saw this post a little bit ago:

Word of warning : Don't Leave Full CO2 Tanks in Hot Car!

My wife went to get it filled so I am hoping that having it in her trunk wile at work was the cause, even though it wasn't that hot out, rather than being taken advantage of because she is a woman.

I don't know too much about CO2 tanks and how they are filled. Any thoughts?

Thanks!
 
Is the CO2 tank currently cold? When cold, the tanks read a different pressure than warm. Even at room temperature, they won't max out the gauge.

Chances are @ 800#, your tank is fine.
 
Beilber your co2 pressure is fine this should help.


What's the pressure in a CO2 tank?

As long as there is liquid in the tank, the pressure in a CO2 tank is determined ONLY by the temperature. At room temperature (70 degrees F) its about 853 psi. (You can check this and the pressure for other temperatures in the little table at the top left of the CO2 diagram.)

The pressure in a CO2 cartridge, as long as there's any liquid in it, can be calculated roughly from:

p = p0 * exp(T/T0)

where p is pressure in psi, T is temperature (Fahrenheit), and

p0 = 314.04 psi
T0 = 69.64 F

Cheers...:mug:
 
CO2 only has so much pressure depending on the temp. Around 800-900 is right for room temp. If you put it in the fridge, expect it to drop to around 600. If you blow a burst disk by letting the tank get too hot, you lose it at. It's a fail safety, not a blow off valve that resets below a certain PSI.

CO2 is not compressed air. It's a liquid in the tank that only boils off gas to maintain its vapor pressure. See the link here.

co2 tank care

As you use CO2, the tank pressure won't drop until all the liquid has boiled off. After that, the gauge will fall rather quick as you use the remaining pressure with no more liquid to boil off.

Mike
 
Thanks All I feel less dumb now :)

I have it at room temp, but I did put it in the fridge and saw the pressure internally drop too around 600, good call blk and thanks for the link!

So basically, as the CO2 "liquid state" evaporates CO2 "Gas state" is released. And the temperature will affect the state change, higher temp more evaporation and lower temp less.

I appreciate the help, but one more thing. I used 5 gal Cornys for kegging, how many kegs will i be able to force carb and dispense off of my 5# tank, on average? I know every beer has different carbonation i just want a rough idea.

Thanks again,
 
Weigh the tank!

As was pointed out...CO2 pressure from the tank while it has liquid in it is just a function of temperature.

CO2 tanks are designed to be filled ONLY to about 2/3's of the way with Liquid CO2. The head space is very important to keep you from blowing the burst disc on the Valve when the tank gets exposed to higher ambient temperature.

Most tanks are stamped with a TARE weight. If you weigh your tank...and subtract the Tare weight...you'll know how full your tanks is. I have a couple of tanks that don't have the weight stamped on them...so I just weighed them empty...and put a label on them for future reference.

You're cylinders should also have the MAX working pressure stamped on them. All my CO2 tanks are stamped for 1800 psi. I think the burst disc is 2000 psi...but I'm not sure of that. The other important marking on the tank is the Hydro test date. You'll need to get your tank recertified at a test facility every 5 years.

You can get a lot of good info from manufacturers websites...Like Catalina and Luxfer. They are a good resource for learning more about your CO2 tanks...and the proper safety procedures.
 
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