How kegs work

In first article we wrote about the differences between a keg and a cask.

In this article we will see how they work and what are they made of.

During kegs manufacturing process, the factory melts a particular steel, copper, nickel and manganese alloy which ensures to leave a smooth joint so there are no gaps in which bacteria could shelter and spoil the beer.

The result is an incredibly resistant keg capable of enduring the pressure of the inside fluid without busting, and resist the blows it will receive during the transportation to its destination.

Kegs of more than 5 liters are all reusable, which means that are returned to the brewery for refilling. The 5 liter mini keg is recyclable and it’s usually never returned back for refilling.

Barrels of beer must be sealed or oxygen could penetrate inside which would mean that beer would be spoiled within days. But since the beer must go out somehow, all pressurized barrels are equipped with a valve at the top that allows fluid to go out. This valve is connected to a tube called spear that almost reach the bottom of the keg, the spear is going to be used by the beer for raising to the valve.

Inside of a beer keg

In the other hand casks come equipped with a spigot at the bottom and an oxygen inlet at the top (if they operate by gravity) or an outlet for beer and a valve for pumping air (if they operate by air pressure).

For more information about Cask and Keg barrels types please visit this link.

Keg barrels type use CO2 or N2 as gas, the reason is that the CO2 gas is the same gas that beer naturally produce and it’s the gas that generates the bubbles and foam so inserting CO2 into the barrel does not harm the flavor or smell of the beer. Nitrogen is also near neutral so it usually doesn`t introduce any strange taste or flavor in beer.

The downside of CO2 is that dissolves rather easily in beer and it might turn the beer into a large pool of foam while serving it, this does not happen with nitrogen because it dissolves worse in beer.  Therefore sometimes a mixture of CO2 and N2 is used in order to maintain perfect balance in the keg gas mixture.

Kegs require different gas pressures depending on where in the world the beer is going to be drunk. USA kegs follow “D” standard while the German ones follow “A” standard. Commonly the more aromatic and flavorful the beer is, the less gas pressure it needs and therefore the less pressure is required to maintain its level of carbonation.

This is the strength cask type barrels, by not introducing pressurized CO2, carbonation level is lower and therefore the beer contained is more flavorful and aromatic. This fact is reinforced by the type of beer casks use to contain (unpasteurized and unfiltered beer).

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