AskDefine | Define keg

Dictionary Definition



1 the quantity contained in a keg [syn: kegful]
2 small cask or barrel

User Contributed Dictionary




  1. A round wooden container that has a flat top and bottom, often used to store beer.


round wooden container that has a flat top and bottom

Extensive Definition

A keg is a cylindrical container, usually constructed of aluminum, steel or wood. It is commonly used to store, transport, and serve beer. Other alcoholic or non-alcoholic drinks, carbonated or non-carbonated, may be housed in a keg as well. Such liquids are generally kept under pressure.
Formerly a keg was a small barrel made by a cooper used to transport items such as nails and gunpowder.


Since keg sizes are standardized, the keg can be used as a standard unit of measure for liquid volumes. This size standard, however, varies from country to country, with many countries using the metric system rather than U.S. gallons.
A full keg is a 15.5 U.S. gallon barrel, routinely called a half-barrel. A half keg or pony keg is therefore called a quarter-barrel and has a volume of 7.75 U.S. gallons. Generally a keg is a vessel smaller than a barrel; thus, it is 30 gallons or smaller. In the U.S. the terms half-barrel and quarter-barrel are derived from the fact that a U.S. beer barrel is legally defined as being equal to 31 U.S. gallons (note that this is not the same volume as some other units commonly known as barrels). A 15.5 U.S. gallon keg is also equal to:
In European countries where the metric system is used, kegs come in 25 and 50 liters as a standard. It is common to refer to the size not in liters but in beers. The standard beer size is .5 liters i.e.: a 50 liter keg would be 100 beers.
However, beer kegs can come in many sizes:

Specifications for a U.S. 1/2 barrel keg

Accepted specifications for a standard keg are:

Differences between a keg and a cask

In brewing parlance, a keg is different from a cask. The keg is built with a downtube located in its center with a valve to force gases out when filling and air in when dispensing. Kegs are artificially pressurized after fermentation with carbon dioxide or a mixture of carbon dioxide and nitrogen gas. A cask has a tap hole near the edge of the top, and a spile hole on the side used for conditioning the unfiltered and unpasteurised beer. Casks are simply gravity-fed for the dispensing of liquids. Additionally, kegs have a simple concave bottom whereas a cask is flat on the bottom. The concavity allows for sediment to be captured away from the flow pipe in the keg. Lastly, kegs have straight sides, unlike the traditional barrel or cask shape.

Keg beer

Keg beer is a term for beer which is served from a pressurized keg. While often considered synonymous to draught beer, keg beer refers specifically to beer served under pressure, while draught beer may refer to any beer served from a larger container, including both keg beer and cask ale. Keg beer is often filtered and/or pasteurized, both of which are processes that render the yeast inactive, increasing the shelf life of the product at the expense of flavor.
Keg has become a term of contempt used by some since the 1960s as pasteurized draught beers were replacing traditional cask beers. The quality of the kegging process was not as good then as it is today, and sometimes the keg beers are referred to as plastic beer. Some people believed that chemicals (adjuncts) were used to create a foam head.
Despite this consumer concern, keg beer was replacing traditional cask ale in all parts of the UK, primarily because it requires less care to handle. Since the mid-1970s, the Campaign for Real Ale (CAMRA) has been conducting a successful consumer campaign which focused attention on those consumers who preferred traditional cask beer. As well as this, CAMRA has successfully lobbied the British Parliament to ensure support for cask ale. New, small microbreweries have sprung up to serve those consumers who prefer traditional cask beer. Today most pubs in the UK will serve both keg and cask beer.

Tapping a keg

There are two different types of tapping equipment that are available for kegs, party pumps and gas taps. Party pumps utilize outside air, which may introduce bacteria inside the keg, and will cause the beer to go "flat" or lose carbonation, reducing the quality of the beer. Kegs operating a party pump should be used within 18–24 hours otherwise the beer may become unpalatable. Gas pumps normally use CO2, but certain brewers require a mix of other gases (Guinness requires 25% CO2 and 75% nitrogen). Gas pumps can preserve a keg up to 120 days with proper refrigeration.
As with any pressurized container, a keg can cause injury, even at normal operating pressure, whether with compressed air or carbon dioxide:
"The tapping system and pressure regulator both should be equipped with a pressure relief (blow off) device. If you are not familiar with tapping equipment, consult your retailer..." (printed on an Anheuser-Busch's keg cap)
Generally, in the US and Australia kegs or the beer coil are kept in a bucket of ice and/or water, in order to keep the beer cool. Keg use is somewhat different in the UK.Kegless

Other types of kegs

Mini keg

The mini keg is a 5-liter keg produced for retail sales. Some brands come with a spout and pour from the bottom via gravity, while others may use a low cost pressurized tap. Mini kegs are typically not returned to the manufacturer for cleaning and refilling. The kegs, being made of aluminum, may be recycled.
In Canada, Molson brewery dubbed the mini keg "Bubba." Much like other brand names, the name is now generally applied to all 5-liter mini kegs in Canada. This might cause confusion, as a company called Bubba Keg is established in the U.S., and appears to not be associated with Molson.
Another type of mini keg is the "beer ball", a disposable plastic ball that usually holds around 5.2 gallons, roughly the equivalent of fifty five twelve-ounce beers, though they can also be found in a smaller, 3.8 gallon size. Like kegs, it is necessary to tap the ball before the beer inside it can be served.

Pony keg

A pony keg is a beer vessel containing 7.75 U.S. gallons (29.33 liters) of fluid. It is half the size of the standard beer keg and equivalent to a quarter of a barrel. It will serve roughly 82 twelve ounce cups. The shape of a pony keg resembles that of a full-sized keg, while being much easier to move manually. However, it shares many inconveniences with the bigger kegs, such as: often requiring a deposit when purchased; needing a tap to serve the contents; and posing difficulties in determining the amount of beer remaining (weighing the keg or observing its buoyancy are common techniques). Despite this, a pony keg can be a cheap way to provide beer for a medium-sized party.

UK keg supply structure

The beer vessel supply structure in the UK is quite different, whilst the couplers for kegs have been largely standardised to sankey, grundy and interbrew, a couple of others exist such as UEC and U-Type; however these are much less common. The kegs themselves are either steel or increasingly the more lightweight aluminum variety. The standard keg size is 11 imperial gallons (50 liter/88 imperial pints approx) and the vast majority of keg beers are supplied in this keg size. There are also smaller 30 liter (54 imperial pints approx) kegs usually reserved for more specialist and or premium European beers.
A number of manufacturers also produce 18 imperial gallon (approximately 82 litres/144 imperial pints) and 22 imperial gallon (approximately 100 litres/172 imperial pints) kegs, however owing to their size they are not so popular as manual handling is seen by some to be difficult, and as a result they tend to be used only for large scale events and bars with high throughput.
For bars that sell an excessive volume of beer there is the 33 imperial gallon (150 litre/260 imperial pint) keg, however due to its very large size few people can move them making it an impractical choice.

Homebrewing kegs

Homebrewers often use kegs for aging, filtering, and storing beer. These are seldom the standard kegs used by major brewers to transport draught beer to wholesalers, but instead are reconditioned Cornelius kegs (colloquially known as "cornies") that were originally manufactured to store soda—these vessels are much easier to fill, clean and maintain than standard beer kegs.
These kegs are stainless steel cylinders that hold approximately 5 U.S. gallons of liquid. The keg is filled with liquid (wort or beer) via a removable hatch on the top, which is then closed and sealed. Carbon dioxide is added to pressurize the keg via an inlet port on the top and is facilitated by gently rocking the brew back and forth. Liquid is dispensed via an outlet port attached to a tube that extends to the bottom of the keg. Pin-lock and ball-lock fittings (or posts) are the two types of couplings used on the inlet and outlet ports. Coke distributors used pin-lock fittings, while Pepsi distributors used ball-lock fittings. Ball-lock are most used. The pin-lock style is often referred to as a "Coke" keg or style and the ball-lock is often referred to as a "Pepsi" keg or style, though the fittings themselves are removable, serviceable, and contain interchangeable parts.
Homebrewers often use 15.5 U.S. gallon kegs for boiling vessels in creating wort. The kegs are drilled for a drain at the bottom, and the top cut open to create a large stainless steel cooking kettle. Many times, the piece of metal cut out of the top is re-used to create a false bottom for straining wort during the mashing process, as well as to strain the boiled wort when adding hops without using a mesh grain bag.
Alternatively, kegs specifically designed for home brewing are available. The capacity may be matched to commercial extract brewing kits—typically 12 and 23 litres. Smaller 2.5 gallon kegs are also made for ease of transporting to a function.

Cleaning and care

All kegs may have residual pressure, and this must be vented to avoid having the valve explode and injure or kill a person as the valve shoots out. Conventional 15.5 U.S. gallon kegs have circle spring clips that can be removed to release the tap valve. Some kegs such as those used by Miller have threaded valves from Micro Matic that, after venting, can be opened by lightly tapping the valve ears with a mallet or using a pry bar spun out counterclockwise. These valves then need to have the ball lock depressed while the valve head is lifted to overcome a safety. The safety prevents the valve from releasing under pressure.
It is recommended that kegs not be sterilized with bleach to avoid unpleasant residuals. Iodine based solutions or specialty cleansers such as PBW are most commonly used. The ball lock valves may be unscrewed using wrenches to allow further cleaning or replacement of O-rings or poppet valves.

Keg laws

In the U.S. as of 2005, there are 21 states and numerous localities that have keg registration laws. The laws vary widely in terms of whom they target, what their intended purpose is, and how strongly they are enforced.



External links

keg in Belarusian (Tarashkevitsa): Кег
keg in German: Keg
keg in French: Fût (bière)
keg in Italian: Fusto (contenitore)
keg in Dutch: Fust
keg in Polish: Keg
keg in Russian: Кег
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