A modern keg is more than just a vessel to hold beer. It is built to be part of the dispensing system. Regardless of the size, each one contain a valve mechanism that 1) seals the contents from the outside environment; 2) allows compressed gas in to push the contents out; 3) provides an exit for the contents to flow out with the help of a
The valve serves as an inlet for pressurized gas and an outlet for the beer. Each valve consists of a spring loaded valve mechanism connected to a tube that extends to the bottom of the keg. When the spring is compressed by activating the coupler, compressed gas is let in. This gas escapes into the head space (above the beer) via an exit on the underside of the valve.
The pressure of the gas pushes down on the beer forcing it up through a tube that extends from the valve down to the bottom of the keg. From the valve the beer enters the transport and dispense system.
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