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Old 12-10-2012, 03:08 AM   #1
jamesdawsey
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Default Force carbing vs. CO2 leak?

Hey folks,

Long story short: I'm wondering if force carbing takes several adjustments due to CO2 being progressively absorbed into solution, or if I have a systemic problem.

Long story long:
So i've been force carbonating my beers ever since I started kegging; about 3 months/4 brews ago. Every time I have kegged, carbed, then put the keg in the fridge, and returned to maintain the carbonation as the beer cools throughout the next day. Now here's the weird thing: I understand that the actual PSI will lower as the temperature inside the keg lowers(keg day/carbing at about 65*F), but up to three days after kegging I am still adding CO2 up to 20 lbs. because the pressure reading tends to drop, even all the way to 0 psi in as few as 8 hrs. I've progressively began with more CO2 at the initial keg day from 20 up to 40 psi according to my regulator since I put this system together. One suggestion is that I have a leak. I don't think so because after about 3 days I can level it out at 8-10 psi and it's well carbed, but due to the strange looks I've gotten from folks when recounting my methods I'm curious as to whether this happens only on my system.

Am I wasting CO2 due to a leak?
Is this a normal/expected occurence due to temp. changes?
Is my regulator unreliable?

Purely curious. I don't currently understand the chemistry/physics of suspending a gas in a liquid solution, and certainly appreciate any helpful advice.

Thanks!

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Old 12-10-2012, 04:12 AM   #2
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So you keep turning your tank valve off in between bursts of pressurizing the keg?

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Old 12-10-2012, 12:57 PM   #3
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I do.

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Old 12-10-2012, 01:09 PM   #4
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The pressure will drop as the CO2 dissolves into the beer. You can hear it happening if you shake your keg to speed things up. Every time you shake the keg and CO2 dissolves, the gas will flow for a while refilling to the set pressure. Chemistry is so cool

Things will go faster if you keep the tank connected and turned on at a constant temperature throughout the whole process.

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Old 12-10-2012, 01:20 PM   #5
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You may or may not have a leak. It's hard to tell from your report and there are several variables. If, as you indicate, things eventually stabilize and the pressure in the keg stays at some fixed value you 1) have reached equilibrium and 2) don't have a leak. Cornelius kegs aren't the greatest at holding pressure long term because the large O ring eventually gets hard as it ages and cold makes it harder still. There is a silcone O-ring that solves this problem but that cost about $7 20 years ago.

You seem to have the mechanism down. You put CO2 in the headspace and some of it migrates to the beer until the partial pressure of CO2 in the beer is the same as the partial pressure of CO2 in the headspace. As a fair amount of CO2 moves to the beer the pressure in the headspace is lower than it was when you disconnected the gas. "Top up" with CO2 and the process repeats until the partial pressure of CO2 in the beer is the same as the pressure at top up. At that point no more CO2 will dissolve.

Keep in mind that the smaller the headspace (i.e. the fuller the keg) the less CO2 is in it and the more times you will have to top up.

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Old 12-10-2012, 11:22 PM   #6
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jsmcclure and ajdelange thank you both for your suggestions. You make good sense. Particularly the point about the headspace.

So I have a follow-up question. Bobby_M seems to be confounded as to why I would turn my CO2 off, and I have gotten this response from other homebrewers before. This puzzles me. The reason I have to turn it off is because the pressure continues to rise much higher than I would like it to when I leave it on, even if ever so slightly (at which point it just rises slowly). Is there some common sense way to leave the tank open and un-watched without pushing the keg's internal pressure to detrimental amounts?

@jsmcclure: You make it sound like you never turn your tank off. Is this true, and what prevents you from over-pressurizing your keg?

equipment - dual gauge regulator 0-60/0-2000 PSI, 5 lb. CO2 tank, 5 gallon Cornelius kegs, freshly cleaned, sanitized, and O-rings replaced.

*sidenote: Only the keg side of my regulator has ever given any meaningful readings. My tank side meter has never given any reading greater than 0. I'm not convinced that's a worthy problem for real concern though. Am I wrong?

Again, any helpful thoughts or suggestions are greatly appreciated. Not the end of the world, but an interesting puzzle, I think.

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Old 12-10-2012, 11:56 PM   #7
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Quote:
Originally Posted by jamesdawsey View Post
So I have a follow-up question. Bobby_M seems to be confounded as to why I would turn my CO2 off, and I have gotten this response from other homebrewers before. This puzzles me. The reason I have to turn it off is because the pressure continues to rise much higher than I would like it to when I leave it on, even if ever so slightly (at which point it just rises slowly). Is there some common sense way to leave the tank open and un-watched without pushing the keg's internal pressure to detrimental amounts?
I guess that's why I'm confused. I've NEVER turned my co2 tank off- ever. I have three, four, or five kegs hooked up at any given time. The psi for my system is always at 12 psi. I don't know why anybody would turn off the tank- unless they were going out of town for two months or something.

It would be hard for the co2 in the beer to be in equilibrium if the tank was off, and a beer was poured. Leaving it on means it works perfectly all the time.

Unless you are carbing at a higher pressure ("burst" carbing), the psi will always be at the amount set on your regulator.
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Old 12-11-2012, 04:46 AM   #8
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Quote:
Originally Posted by jamesdawsey View Post
The reason I have to turn it off is because the pressure continues to rise much higher than I would like it to when I leave it on, even if ever so slightly (at which point it just rises slowly). Is there some common sense way to leave the tank open and un-watched without pushing the keg's internal pressure to detrimental amounts?

@jsmcclure: You make it sound like you never turn your tank off. Is this true, and what prevents you from over-pressurizing your keg?
A properly functioning regulator keeps you from overpressurizing the keg. What was the pressure reading on the low pressure gauge before you hooked up the keg? That should be the pressure you eventually get in the keg. It will run lower for some time while CO2 is being absorbed, then eventually settle in at that pressure again. If you are motivated and pressed for time, with sufficient agitation you can reach that equilibrium in a surprisingly short period of time. Most of the time I let the kegs get there without agitation in a week (the "set and forget" method).

As mentioned above, the CO2 dissolved in the beer will come to equilibrium with the CO2 in the headspace of the keg, whatever that pressure is. When you give internittent doses of CO2, it will take a while to get to your desired pressure. If the regulator is set at your final desired pressure, the commonly accepted time frame for equilibrium at room temperature is a week. If you agitate the keg, you are increasing the interaction between the CO2 and the beer, and can get the CO2 into solution much faster, just like you can get the CO2 out of solution faster with agitation. I like to lay my kegs on their side, gas in side up, and roll them back and forth a couple of inches, with the gas set on my final target pressure. I can hear the gas flow for a while, then eventually silence ensues. With this technique I can keg a beer and serve it in 20 minutes or so, nicely carbonated. Be sure to use a carbonation table or application to get the right pressure setting.

The high pressure gauge isn't worth much. It will drop only when your tank is almost empty. If you want to know if your tank is only 1/4 full, get a scale. Or better yet, keep an eye on Cragslist and just get a backup tank.
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Old 12-11-2012, 04:48 AM   #9
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Quote:
Originally Posted by jamesdawsey View Post
This puzzles me. The reason I have to turn it off is because the pressure continues to rise much higher than I would like it to when I leave it on, even if ever so slightly (at which point it just rises slowly). Is there some common sense way to leave the tank open and un-watched without pushing the keg's internal pressure to detrimental amounts?
If the pressure continues to rise the regulator isn't regulating i.e. it isn't doing what it is supposed to do.

I too keep gas pressure on all kegs all the time as do most people here and any bar you have ever been in. That is what a regulator is for: to keep a selected amount of pressure at all times irrespective of whether conditions are static or beer is being drawn once a day or once a minute.

Pressure creeping steadily upward suggests that there is dirt in the regulator needle valve so that it can't close completely no matter what the diaphragm and spring pressures.
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Old 12-11-2012, 06:43 AM   #10
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Quote:
Originally Posted by jamesdawsey View Post
jsmcclure and ajdelange thank you both for your suggestions. You make good sense. Particularly the point about the headspace.

So I have a follow-up question. Bobby_M seems to be confounded as to why I would turn my CO2 off, and I have gotten this response from other homebrewers before. This puzzles me. The reason I have to turn it off is because the pressure continues to rise much higher than I would like it to when I leave it on, even if ever so slightly (at which point it just rises slowly). Is there some common sense way to leave the tank open and un-watched without pushing the keg's internal pressure to detrimental amounts?

@jsmcclure: You make it sound like you never turn your tank off. Is this true, and what prevents you from over-pressurizing your keg?

equipment - dual gauge regulator 0-60/0-2000 PSI, 5 lb. CO2 tank, 5 gallon Cornelius kegs, freshly cleaned, sanitized, and O-rings replaced.

*sidenote: Only the keg side of my regulator has ever given any meaningful readings. My tank side meter has never given any reading greater than 0. I'm not convinced that's a worthy problem for real concern though. Am I wrong?

Again, any helpful thoughts or suggestions are greatly appreciated. Not the end of the world, but an interesting puzzle, I think.
There is something wrong if your high pressure side always reads 0 and the low pressure side climbs uncontrolled. You sure you have that regulator configured properly? There may be a failure within your regulator.
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