Re: good technical kegging reference

On 22 Jun 2006 08:09:46 -0700, <naramsey@xxxxxxxxx> wrote:
1) How does the regulator physically work. What does turning that
little screw actually do behind the scenes in there?

My understanding is that the screw pushes against a spring on the inside
which itself puts pressure against a diaphram. Changing the pressure on
the diaphram adjusts how much gas the regulator will allow to come through.

If you're *really* curious, there are rebuild kits for regulators that
replace the internal components. They probably have instructions sheets
with them that show you what everything looks like inside. You could
probably find a copy of the instructions online somewhere, or maybe
someone else has a copy they can scan for you?

2) Fix a volume and temperature of beer in a keg, as well as a
carbonation level in volumes of CO2. Am I to understand that there is
a PSI which, when applied to the keg, puts it in "equilibrium" in the
sense that no more CO2 will dissolve and no CO2 will gas out (pretend
there is no check valve or whatever so that gas is free to go either
way). Is this moreover the PSI you find in that force carbonation
table everywhere? If so, does it really not depend on the volume of
beer in the keg?

Exactly. How much gas goes into solution depends on temp and pressure.
By looking up the temp your beer is at and the amount of carbonation
you want, there is a specific PSI that you set the regulator to. Then
the keg will slowly absorb gas (becomes carbonated) until an equilibrium
is reached. At that point, no gas will come out or go in. Think
of it as the pressure of the gas in the beer being the same as the
pressure of the gas outside the beer. The PSI you use has nothing to
do with the volume of the beer. Once you reach equilibrium, as far as
distribution of gas goes, I don't think the CO2 even cares that the beer
is there. For example, my understanding is that if you pressurized an
empty keg and a full keg to the same PSI and allowed the full keg to
come to equilibrium (beer fully carbonated), you would end up with the
exact same amount of CO2 in both kegs. Gas is funny that way. Common
sense says that a keg full of beer won't hold as much gas, but it
doesn't really work that way. The gas and beer don't even know each other
are there, as far as how much will fit.

The next step is serving the beer. IMO, the best way to do this is to
use the same PSI to serve the beer as you use for carbonation. That way
the level of carbonation will not change.

In order to get a smooth pour (no foaming), you also want the resistance
of your tubing to equal the PSI of your dispensing pressure. Different
kinds of tubing are rated at a certain PSI/foot depending on size of
the tubing and to a lesser extent the material it is made from. The
standard beverage tubing is 3/16" ID and has a resistance rating of
~2 PSI/foot.

So, if you look on the chart based on your temp and level of carbonation
preferences and find that you need 12 PSI to carbonate your beer, you would
also use 12 PSI to serve your beer and need to supply 12 PSI of resistance
in your tubing (6 feet of tubing rated at 2 PSI/foot). Using too much tubing
is better than using too little though, so generally it's a good idea to
start out with it being a little long and then trim back if you need to.

12 PSI carbonation = 12 PSI dispensing = 12 PSI resistance.

This is called having a "balanced" system, and all of the values are
constant over the life of the keg. None of them depend on the volume
of beer. So it's a truly "set and forget" system.


John.
.

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