Open-keg systems are characterized by their barrel shape and bunghole on the side by which the interior can be readily accessed without extracting the valve body or spear.
Closed-keg systems are identified by their typically straight sides, with a rim, called a chime, on each side. The top chime has integrated handles for easy handling. The top also contains a concentric valve fitting in the center allowing for easy cleaning and filling by automated systems. Draught accounts prefer closed-keg systems over open-keg systems for several reasons including ease of tapping, ease of storage and handling, and the improved profit margin due to the reduction of beer loss that is commonly associated with older keg styles.
The newer, more common single-valve keg (SVK) or "Sankey" keg (see Figure 18.1) has a valve arrangement that consists of a stainless steel, rod housing, called a combination fitting that is permanently installed into the top center of the keg and sealed with a spring-loaded check ball. The tapping device, or tavern head, fits into the lug housing of the valve.
Click on the following topics for more information on kegging beer.