Author Topic: Basic Question of Kegging Science  (Read 717 times)

Offline Nagel Family Brewing

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Basic Question of Kegging Science
« on: April 06, 2010, 12:10:23 PM »
How does the science work?  When you put 10 PSI pressure into a keg does the keg eventually equalize to 10 PSI until it is tapped.  Aggitation just makes the liquid and head space pressure equalize quicker correct?  How do professional keg fillers work?  Do they aggitated the keg to get it carbonated quicker for distribution?

Offline weithman5

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Re: Basic Question of Kegging Science
« Reply #1 on: April 06, 2010, 12:49:11 PM »
as long as you can keep the 10psi blanket on it it will stabilize. if you pressurize to 10psi then isolate the keg from the pressure source it will drop some as the gas diffuses in to the liquid.  the amount absorbed in to the liquid is proportional to the partial pressure of the gasses on top.  (so if you had a 10 pound pressure but 2/3 of it was nitrogen and 1/3 co2, that is typically the way it will be dissolved in the beer)
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Offline narvin

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Re: Basic Question of Kegging Science
« Reply #2 on: April 06, 2010, 12:53:58 PM »
The head space in the keg will immediately equalize at 10 psi.  However, what we care about is the volume of CO2 that will dissolve in the beer.  This is why there are charts that tell you how much CO2 will dissolve at a give temperature and pressure. 

Ideally you want the carbonating pressure and the serving pressure to be the same.  This way the equilibrium from carbing doesn't change once you put it on tap.  It doesn't matter as much at bars that serve the keg in less than a week, but eventually CO2 will come out of solution (or the keg will become overcarbonated) if the serving pressure is less/more than what the keg was carbonated at.
« Last Edit: April 06, 2010, 01:07:04 PM by narvin »
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Offline yugamrap

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Re: Basic Question of Kegging Science
« Reply #3 on: April 06, 2010, 01:00:05 PM »
If you keep a keg under pressure, it will equilabrate as the gas (CO2) is absorbed by the beer.  Agitation will accelerate that process, as will colder temperature (a liquid will hold more dissolved gas at colder temperatures).  As long as the keg is not isolated from the gas source, the beer will continue to absorb gas until it reaches its equilibrium for that particular temperature and pressure which, hopefully, is the intended carbonation level for the beer.  A chart like this is helpful: http://www.kegkits.com/carbonation.htm

Commercial breweries fill kegs (and bottles and cans) with beer that's already been carbonated - usually by some means of "natural" carbonation like krausening.  They have counter-pressure equipment for kegging and bottling carbonated beer.
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