11 replies to this topic

[BarelyBrews]

I just bought a refreshed CO2 tank , feels full to me. When i hook it up to my set-up it reads 600 , which is definitely not all the way up the gauge. A co-worker whom has kegged for years says the gauges on the regulators are never accurate. Is this normal for others too? I have the dual regulator , pressure to the keg and what i beleive is supposed to read the tank. Thanks.

[Sidney Porter]

the high pressure gauge measures the head space pressure. Which should always be the same until all the liquid is gone. The you start pushing with gas and the high pressure gauge will start to drop. What you head space pressure is varies with temp.

[ncbeerbrewer]

+1. Every refill of my tank its always cold as can be even after I get home. I have noticed it takes a day or so for the high pressure gauge to read completely full. It goes up as the gas heats up to room temperature.

[MoreAmmoPlz]

Mine continually reads 625psi. Not sure if it's a faulty gauge or the 58 degrees it is sitting in but I don't start to worry about getting a new tank until I see the pressure begin to continually drop.

[3rd party JKor]

If you keep it at constant temperature, it will read a constant pressure until the liquid CO2 is gone. If you move it to a different temperature, the pressure will change regardless of liquid level. Liquid carbon dioxide in a cylinder is at equilibrium with the CO2 gas in the head space. Putting a curve fit through data I pulled from a carbon dioxide saturation table, you can calculate the pressure you regulator should read with this equation:P = 0.0489T² + 4.183T + 306.24Pressure is in psigTemperature is in FahrenheitThis equation is valid for normal storage temps, approx. -20°F to 100°FAccording to the equation, at 58°F the pressure on the regulator should read:.0489*58²+4.183*58+306.24 = 713.4 psigOf course, the tank gauge on a CO2 tank doesn't need to be accurate at all. The pressure it reads doesn't tell you anything about the level in the tank, unless all the liquid is gone, then it will start dropping. At that point, the tank is 99% empty anyway. If you really want to monitor your CO2 tank level, you should do it by weight.

Edited by JKoravos, 12 May 2009 - 08:37 AM.

[stellarbrew]

The pressure gauge will read lower when the tank is cold because the saturated pressure of CO2 is lower at colder temperatures. As long as you have any liquid CO2 remaining in the tank, then the gas will be at the saturated pressure (vapor pressure) for whatever temperature it is at. Once all of the liquid is gone, then the tank pressure will begin to fall below the saturation pressure, and you will know that you will very soon be out of CO2.To get an idea if your gauge is working correctly, here are some approximate readings you should see on your gauge at a range of tank temperatures (if there is liquid iremaining in the tank):33 F - 496 psig35 F - 512 psig37 F - 527 psig39 F - 563 psig51 F - 644 psig59 F - 720 psig71 F - 845 psig81 F - 962 psigIf you deviate more than a few psig from these numbers, when the tank is stabilized at the given temps, then that represents someinaccuracy in your gauge.

[3rd party JKor]

My post has an equation in it, that makes it cooler.

[stellarbrew]

My post has an equation in it, that makes it cooler.

I loved your curve fit method. You explained it so well, that I wouldn't have bothered posting if I had seen your post before I started.

[3rd party JKor]

I loved your curve fit method. You explained it so well, that I wouldn't have bothered posting if I had seen your post before I started.

Awww, how sweet.

[BarelyBrews]

Sweet , learned something new today. Thanks for the help .My tank was more frozen than not frozen , and i do keep in inside the fridge for now at 42 degrees. That is what my fridge has been steady for a few weeks.

[djinkc]

My post has an equation in it, that makes it cooler.

I thought we had an agreement, no math on Tuesdays..........nevermind that was someplace else........

[3rd party JKor]

I thought we had an agreement, no math on Tuesdays..........nevermind that was someplace else........

Well, wherever that place is, I don't want to be there!