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.
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. In some areas it is common to refer to the size not in liters but in beers. In areas where 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:
|Size (US gal)||Size (litres)||No. of 12 fl oz drinks||No. of 16 fl oz drinks||No. of 20 fl oz drinks||Weight of full keg (lb)||Also known as|
|1.32||5||14||10.6||8.5||-||Mini Keg / Bubba (single-use/recycleable)|
|5||18.9||53||40||32||55-60||Soda syrup / Corny Keg / Home Brew|
|6.6||25||70||50.25||42||-||"Half Barrel" (Europe)|
|7.75||29.3||82||62||49||90||Quarter Barrel / Pony Keg|
|13.2||50||140||105||84||-||Import Keg (standard European "Barrel")|
|15.5||58.7||165||124||99||140 - 170||Half Barrel / Full Keg|
Accepted specifications for a standard keg are:
|Height of keg||23.3 inches|
|Diameter of keg||16.1–17.15627 inches|
|Contents||1984.0 U.S. fluid ounces|
|15.5 U.S. gallons|
|12.91 imp. gallons|
|Full keg weight||160.5 pounds (72.8 kg)|
|Empty keg weight||29.7 pounds (13.5 kg)|
|Beer weight||130.8 pounds (59.3 kg)|
|24×12 fl oz case equivalent||6.9 cases|
|12 fl oz servings||165.333|
|16 fl oz (1 U.S. pint) servings||124|
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.
As with any pressurized container, a keg can cause injury, even at normal operating pressure, whether with compressed air or carbon dioxide:
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
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.
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.
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.
It is recommended that kegs not be sanitized with bleach to avoid unpleasant residuals. Iodine based solutions or specialty sanitizers such as Star-San 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.
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.