Cornelius Kegs
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Homebrewing: Cornelius Kegs

Forum moderator Chris (known to his friends as Daft as a Brush) 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.

 
 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.
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 O2is lighter than CO2 so it will always rise above it.

 

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.

 

 

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.

 

 

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.

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