Beer kegs are made of stainless steel. A beer keg has a single opening on the top, from where a tube extends inside the keg to the bottom of the keg. There is a self-closing valve that is opened by a coupling fitting which is attached to the top of the keg. There is also an opening at the top of the spear that allows carbon dioxide/nitrogen to drive the beer out of the keg. The coupling fitting has one or two valves that control the flow of beer out of and gas into the keg. The keg should always be placed in upright position.
Keg sizes are not standardized. In North America a full keg, or half-barrel, equals 15.5 U.S. gallons, or 58.66 liters. Read more about beer keg sizes
You can tap from a beer keg in 2 ways:
- With an air pump utilizing outside air. This adds bacteria and oxygen into the keg, which affects the taste. A beer keg, tapped with a pump, should be used within 24 hours from the first glass is served.
- With a gas tap. Using a gas tap and maintaining the right gas pressure can preserve the keg of beer up to 120 days.