Metal or Plastic Pipe Flanges
Flanges are the connectors used in process piping to connect pipe to tees, elbows, tanks, valves, pumps and whatever other equipment may be necessary. Other methods of connection are threaded, welded or tri-clamp ends.
Flanges in North America are standardized by the ASME Boiler Code and ANSI B16.5 Pipe Flanges and Flanged Fittings. Each flange has a rating which are in a series which runs 150, 300, 600, 900, 1500, 2500. Each series mates only with itself and this defines the maximum pressure at various temperatures that the flanged item can be subjected to. However, this maximum pressure depends on the material of construction of the item. The sizes defined go from 1/2" up to 24". Flanges larger than 24" are defined elsewhere or are specially engineered as per the Boiler Code.
Similar classification systems are used in Europe as defined by DIN and Japan where they are defined by JIS.
Between mating flanges, a gasket is placed. Then the flanges are bolted together squeezing or crushing the gasket which creates an effective seal.
A significant detail of a flange is whether it has a raised face onto which the gasket is placed or if it has a flat face. Flat face flanges are typically used with cast iron materials whereas raised face is used almost everywhere else. Other types of faces are around as well, such as ring type joints, large or small male/female flanges or tongue in groove faced flanges.
Pottery Flanges
In pottery, a flange is a shoulder or step on one part, say a lid, designed to mate with another part that has a hole in it, say a pot.