Drop in Tank pressure with force carb

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broadbill

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Hey everyone;

I'm still working out the kinks in my kegging setup and had a question about force carbing and tank PSI...

Here is the deal, I recently filled up my CO2 tank (a 4lb tank...actually a converted medical O2 cylinder that came as part of keg package from an online vendor) then used it to force carb 5 gallons of Jamil's West Coast Blaster (not that beer type matters...).

Force carbing was something like 30psi for 48 hours, followed by venting and resetting regulator to 14psi for 2-3 days.

Before force carbing the tank pressure read 1000psi, but after a few days at 14psi the tank now reads 500psi (almost down to the red line on the tank gauge)! Is it normal to have this big of a drop with force carbing? I know gas is going into solution, but this much?

I did check for a gas leak (soapy water test) but didn't find anything between the tank and regulator, at any of the regulator connections or at any of the seals on the keg.

I have the gas off while I figure out the problem and turn it on only dispense but it would be nice to leave it on all the time.

Any other tricks/tips for searching out gas leaks? Anyplace I should check more thoroughly?

Assuming its not a gas leak, is it normal for 5 gal of beer to take that much gas during force carbing?

Also, would tank temperature effect what the tank pressure is? IIRC, the 1000psi reading was when the tank was at room temp, but then it went into the fridge and read the 500 psi a few days later...

Thanks in Advance!
 

Chad

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If you put the CO2 tank in the fridge with the keg you'll notice a big drop on the pressure gauge. It's not unusual for mine to drop into the red once it's been in the refrigerator for a bit, even if it has just been filled. Pressure is temperature dependent.



Chad
 

ElPresidente77

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What kind of kegs do you use. If they are corney kegs, make sure gas is not leaking out of the top of the keg. Did you use a food grade lubricant on the O-ring?? Did you hit the keg with about 30psi to seat the head of the keg? You def. should not be losing gas that fast.
 
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broadbill

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What kind of kegs do you use. If they are corney kegs, make sure gas is not leaking out of the top of the keg. Did you use a food grade lubricant on the O-ring?? Did you hit the keg with about 30psi to seat the head of the keg? You def. should not be losing gas that fast.
I did hit the keg to seal the top, and my leak test didn't show any bubbles around the lid. It is hard to test the QDs for leaks and I did not use any lube on the posts...good pt. on that. However, the gas is now off but it looks like the gas pressure on the keg is holding steady. If the QDs were leaking I would expect the keg to be losing pressure. Still, good idea on putting lube on o-rings...

Thanks!
 
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broadbill

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If you put the CO2 tank in the fridge with the keg you'll notice a big drop on the pressure gauge. It's not unusual for mine to drop into the red once it's been in the refrigerator for a bit, even if it has just been filled. Pressure is temperature dependent.



Chad
good to know, thanks! I did think it could be a pressure/temp thing but wanted to confirm...
 

shortyjacobs

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Also, would tank temperature effect what the tank pressure is? IIRC, the 1000psi reading was when the tank was at room temp, but then it went into the fridge and read the 500 psi a few days later...
This is exactly it, and completely normal.

To expand on this, that little gauge is useless. The way a CO2 tank works is there is mostly liquid CO2 in the tank, with a bit of gaseous CO2. As you suck gaseous CO2 out of the tank, some of the liquid boils and becomes gas to replace it.

The end result of this is: the pressure is always the same in the tank (at a given temperature), whether it is full or almost empty. Only when the last bit of CO2 boils off, (which is right before the tank goes empty), does the reading change.

So it's not like a fuel gauge on a car. Instead, it will read 500 psi until JUST before it runs out, then it will quickly drop to 0.
 
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