Pressure equilibrium within keg to determine volumes of co2

[Brewmegoodbeer]

Hello all,

I have literally been thinking about the carbonation of beer for about 9 hours now. It is questionable how I am getting through the day. Haha. I like to burst carbonate by setting the pressure at about 40 PSI for around 24 hours. I want to estimate the volumes of co2 that I have at this point. I have thought of turning off the gas, purging the keg head space to 0 psi, and waiting a few hours for the pressure to exit the liquid and fill the head space to the point of equilibrium where the pressure gauge becomes stable. If the pressure of the head space build up to my target at this point (12 psi at 38 deg F), I am at desired ~2.5 volumes of co2. At this point, I would turn my gas back on, and set regulator to 12 psi and enjoy. Is this a good way to determine keg equilibrium?

 

[FunkedOut]

Sounds good to me.
I skip the part where you turn off the gas and wait.
I usually use 50psi for 12 hours @ 34*F, then purge and put on 10psi at 34*F (~2.5 volumes).
It's pretty good right away, but is great after a couple of days.

 

[Brewmegoodbeer]

How do you know it reaches 2.5 volumes at 50 psi at 12 hours though? Im looking for a way to messure the pressure that the keg contains at equilibrium. I figure I can purge head space after turning off gas and see what pressure gets built back up in head space from liquid to judge where my pressure is at. If its not there, then ill adjust time on 40 psi.

 

[FunkedOut]

I don't.
I've settled on this based on previous keggings, where I sample some beer and use my senses to make the call the it's not enough. then use the same method a couple days later to see that its has gotten to a steady state.
not scientific at all.

your method allows a test of what the dissolved CO2 is.
please keep a log and share here.
it's going to depend on temperature and volume as well.
if you can keep those two variables constant, you can build a table of psi, time and resulting equilibrium.
then you can stop measuring and just trust the table.

 

[Brewmegoodbeer]

I don't.
I've settled on this based on previous keggings, where I sample some beer and use my senses to make the call the it's not enough. then use the same method a couple days later to see that its has gotten to a steady state.
not scientific at all.

your method allows a test of what the dissolved CO2 is.
please keep a log and share here.
it's going to depend on temperature and volume as well.
if you can keep those two variables constant, you can build a table of psi, time and resulting equilibrium.
then you can stop measuring and just trust the table.

Ill follow up with my results with a table! Cheers

 

[helibrewer]

Hello all,

I have literally been thinking about the carbonation of beer for about 9 hours now. It is questionable how I am getting through the day. Haha. I like to burst carbonate by setting the pressure at about 40 PSI for around 24 hours. I want to estimate the volumes of co2 that I have at this point. I have thought of turning off the gas, purging the keg head space to 0 psi, and waiting a few hours for the pressure to exit the liquid and fill the head space to the point of equilibrium where the pressure gauge becomes stable. If the pressure of the head space build up to my target at this point (12 psi at 38 deg F), I am at desired ~2.5 volumes of co2. At this point, I would turn my gas back on, and set regulator to 12 psi and enjoy. Is this a good way to determine keg equilibrium?

You could use something like this: https://www.morebeer.com/products/carbonating-keg-lid.html with a pressure gauge connected to your keg gas post. Just monitor your head pressure and adjust the carb stone pressure as required until there is equilibrium.....then you can vent the keg, put a standard lid on it and be ready for the next batch.

 

[Brewmegoodbeer]

You could use something like this: https://www.morebeer.com/products/carbonating-keg-lid.html with a pressure gauge connected to your keg gas post. Just monitor your head pressure and adjust the carb stone pressure as required until there is equilibrium.....then you can vent the keg, put a standard lid on it and be ready for the next batch.

Thanks for the idea! Say if I set the co2 stone on carbonation lid to 15 psi (2 psi wetting pressure+ 1psi pressure from beer above stone+ 12 psi goal). would the head pressure (read from the gauge connected to gas post) not read 12 psi until at equilibrium or would it read 12 psi almost immediately even though not yet carbed due to continuous addition of co2 to keg from co2 tank? If i just check every couple of hours until gauge read 12, this would be perfect!

 

[helibrewer]

Thanks for the idea! Say if I set the co2 stone on carbonation lid to 15 psi (2 psi wetting pressure+ 1psi pressure from beer above stone+ 12 psi goal). would the head pressure (read from the gauge connected to gas post) not read 12 psi until at equilibrium or would it read 12 psi almost immediately even though not yet carbed due to continuous addition of co2 to keg from co2 tank? If i just check every couple of hours until gauge read 12, this would be perfect!

The head pressure will be in equilibrium with the beer. At the brewery where I work, we set the carb stones to about 25PSI then monitor head pressure looking for our desired volume of CO2 (temp/pressure)....we then verify the CO2 volume with an Anton-Paar device.....because the gauges on fermenters are just not that accurate.