Homebrewing: Cornelius Kegs
Forum moderator Chris (known to his friends as DaaB) expounds on
his favourite subject!
Cornelius kegs are stainless
steel pressure vessels, originally designed to dispense soft drinks syrups
and are ideal for dispensing beers and wines under pressure.
CO2 gas is
injected in through the post marked IN on top of the keg and is connected
via a Grey Disconnect. The gas enters the keg through a short dip tube
exerting pressure on the beer which is in turn forced up the long dip tube
and out through a tap connected by a Black Disconnect to the post marked
OUT.
Beer is delivered from the bottom of the
keg so before it is racked to the keg, ideally it should be allowed to fall
bright with the aid of finings in a secondary fermenter or barrel.
Alternatively the long dip tube can be shortened by ˝” and the beer can be
racked to the keg as normal with priming sugars and natural carbonation can
take place. The resultant sediment will be left behind but so will a pint or
two of beer. Should the dip tube be shortened and the performance found to
be unsatisfactory the dip tube can be lengthened again by pushing on a piece
of 1/4”/6mm siphon tubing and cutting to length. |
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The disconnects are attached to the
posts by withdrawing the collar which releases 4 ball bearings on the inner
diameter, its then pushed onto the post, and the collar released locating
the balls into a machined groove. A plunger in the disconnect depresses a
poppet valve built into the post allowing the flow of gas or liquid. When
the disconnect is removed a spring automatically closes the poppet valve
preventing the loss of any pressure or liquid. It also prevents the ingress
of any O2
protecting the contents from oxidation. The grey (gas) disconnect
will not fit the OUT post and the black (liquid) disconnect will not fit the
IN post. |
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One last fitting to mention on the keg
top is a pressure release valve. This not only safe guards it against over
pressurising but after injecting with CO2
it can be used to purge any
O2 out
of the keg by pulling up on the ring as O2 is lighter than
CO2
so it will
always rise above it.
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The Gas Supply
There are three main sources of pressurised CO2 available to ‘drive’ your beverage out of
the keg.
S30 Cylinder & Valve
The simplest of all is the S30 cylinder.
This requires a specially modified lid, and only metal lids can have this
modification done to them. It is done by drilling an 18mm hole in a suitable
place and bolting on an S30 valve much like any other homebrew keg on the
market. The S30 cylinder is screwed onto the valve until a flow of gas is heard
and unscrewed to stop the flow. These cylinders are pressurised to 800 psi and
injecting your Corni keg in this manner is a bit of a hit and miss affair
although with a bit of experience it has served many users well. Refills are
done on an exchange basis
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Widget World
Slightly more complex is the
Widget World system. It consists of a cylinder similar to the S30 but 40% larger
containing 40% more gas. Attached to it is a control handle that regulates the
discharge pressure from 800 psi to 65 psi. There are a few Widget World
configurations but a typical Cornelius keg setup consists of a discharge
manifold with pressure release valve and pressure gauge. Attached to the
manifold is a hose either via a barbed hose fitting or a John Guest Speed Fit
fitting. On the other end of the hose is the Grey (gas) disconnect which
connects to the Cornelius Kegs gas IN post. The control handle and pressure
gauge allow you to inject CO2
to precisely achieve the level of pressure you require in the keg
and as long as it is attached to the keg it will monitor the
pressure allowing you to easily check for leaks. Finally you can get a N2/CO2mix, ideal for the Guinness drinkers who want a smooth creamy head on their
pint. Again refills for this cylinder are available on an exchange basis.
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Pub Style Cylinder and Regulator
This is the set up for the brewer who can’t resist gadgets
although its only really practical if you are lucky enough to find a reliable
source for these CO2
cylinders.
They come in several sizes and
like the other two methods, refills come on an exchange basis. Buying
CO2 this
way is far cheaper than the other two systems but the initial outlay can be
expensive particularly as some suppliers want an initial deposit, some even want
a monthly rental and that’s if they will even let you, as Joe public rent one at
all!
To connect the cylinder to the keg a regulator is
required, to step the cylinder pressure down to the required delivery
pressure. Welding suppliers are a good source for these. These can be 1 or 2
gauge regulators, the single gauge regulators just show discharge pressure and
the two gauge regulators show cylinder contents pressure and discharge
pressure. One thing to look out for on regulators designed for (mig) welding
sets, is that the discharge pressure gauge can sometimes be calibrated for flow
in Litres/Min which isn’t much good if you want to set a specific pressure for
delivery or forced carbonation. Fortunately all that is required is a simple
cheap replacement gauge, calibrated in PSI (pounds per square inch) and Bar. It
should be noted that a flow gauge rated at 5 bar must be replaced with a
pressure gauge rated at 5 Bar.
With that sorted out, a connection between the regulator
is required, this is usually in the form of 3/8” pvc gas line available from
brewery suppliers and the better homebrew shops. It is connected to the
regulator using either John Guest ‘Speed Fit’ fittings or barbed fittings and
connected to the grey disconnect in the same manner.
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Unlike the previous two systems, this method constantly
supplies CO2 to the keg, so as liquid is drawn off the pressure is
maintained at the level set by the pressure regulator, usually between 3-5 psi .
The extra capacity of these cylinders means they are ideal for pressurising more
than one keg at a time by splitting the gas supply using Speed Fit or Barbed Tee
or Y pieces.
The larger volumes of gas available and the constant supply of
CO2 under pressure also make this system ideal for forced
carbonation. Forced carbonation and the serving of carbonated beer can become
rather a complex subject but in most cases setting the regulator to 12 psi and
allowing the CO2 to become absorbed in its own time, will produce
good results. When it comes to serving though, the regulator must be reset to a
much lower pressure to avoid excessive foaming. After the last drink of the
session has been delivered, the pressure can be returned to maintain
carbonation. The process of carbonation can be sped up
by chilling the keg either by putting it in the fridge or leaving it outside on
a cold winters night. This is because CO2 is more readily absorbed
into a cold liquid and carbonation can occur in as little as a few hours.
Rocking the keg from side to side can further reduce the time taken to
carbonate, this increases the surface area of the liquid presented to the gas,
speeding up the absorption rate. Care should be taken not to set to high a
pressure when doing this as the beer can become over carbonated, if this happens
the pressure should be periodically released over time until a level is reached
where the beer can be served without producing excessive amounts of foam.
These attributes make the Cornelius keg an ideal alternative to
bottles when storing and dispensing homebrewed lager. They are also far easier
to clean and rinse than 40 glass bottles too! Chris |
