Draught or Draft beer is almost always un-pasteurized and therefore is more fragile.  It should be consumed after being "tapped", and is generally truer to the flavors of the ingredients as pasteurization exposes the beer to heat and changes the flavor profile. A keg has a concentrically located downtube and a valve that allows beer in and gas out when filling and vice versa when beer is dispensed. Also kegs have a simple concave bottom. This aspect of keg design meant that all the beer in the keg was dispensed which therefore required that the beer be processed by filtration, fining or centrifuging, or some combination of these, to prevent sediment formation. Lastly, kegs have straight sides unlike the traditional barrel or cask shape. In order to get the beer out of a keg and into a customer’s glass, it can be forced out with gas pressure, although if air or gas at low pressure is admitted to the top of the keg it can also be dispensed using a traditional hand pump at the bar. By the early 1970s most beer in Britain was keg beer, filtered, pasteurized and artificially carbonated. This change was largely driven by the customer's dislike of sediment in his beer.

How To Clean Draft Beer and Equipment

Keg Facts and Conversion Tables
(Currently this includes the U.S. standard kegs.)
 
Kegs(Typical Kegs used in the U.S.)

Using a 12 ounce glass with 20% head, one 1/2bbl will pour an average 206 12 ounce glasses.

1/2 Barrel Keg...............................1/4 Barrel Keg

23 1/4 inches.........Height.................14 3/4 inches

17.0 inches............Diameter.............17.0 inches

1984 ounces..........Contents..............992 ounces

160.5 pounds.........Full Weight........ 82.2 pounds

29.7 pounds...........Empty Weight.....17.3 pounds

130.8 pounds.........Beer Weight........64.9 pounds

29°F.......................Freezing Point....29°F
Conversion Tables

Keg Size..............# of Gallons.............# of Ounces............Metric Equiv.

One Full bbl...........31 gallons................3968 ounces.............107.348 liters

One Half bbl..........15.5 gallons..............1984 ounces.............58.674 liters

One Quarter bbl.....7.75 gallons...............992 ounces..............29.337 liters

So, as you see, 10hl  = 8 1/2bbls
Cases per 1/2 BBL by Package Size

12 oz. Package (24-12oz.)..........6.888 Cases per 1/2 bbl

16 oz. Package (24-16oz.)..........5.166 Cases per 1/2 bbl

32 oz. Package (12-32oz.)..........5.166 Cases per 1/2 bbl

Weight of Draught Beer

One Ounce of Draught Beer by Volume = One Ounce by Weight

Foam

Foam is approximately 25% beer, 75% Carbon Dioxide