A flange is an external or internal rib, or rim (lip), for strength, as the flange of an iron beam or I-beam (or a T-beam); or for a guide, as the flange of a train wheel; or for attachment to another object, as the flange on the end of a pipe, steam cylinder, etc, or on the lens mount of a camera. Thus a flanged rail is a rail with a flange on one side to keep wheels, etc., from running off. The term "flange" is also used for a kind of tool used to form flanges.
Common flanges used in plumbing are the Surrey flange or Danzey flange, York flange, Sussex flange and Essex flange. Surrey and York flanges fit to the top of the hot water tank allowing all the water to be taken without disturbance to the tank. They are often used to ensure an even flow of water to power showers. An Essex flange requires a hole to be drilled in the side of the tank. There is also a Warix flange which is the same as a York flange but the shower output is on the top of the flange and the vent on the side. The York and Warix flange have female adapters so that they fit onto a male tank, whereas the Surrey flange connects to a female tank.
In most cases these are not interchangeable (eg an ANSI flange will not mate against a JIS flange). Further many of the flanges in each standard are divided into "pressure classes", allowing flanges to be capable of taking different pressure ratings. Again these are not generally interchangeable (eg an ANSI 150# will not mate with an ANSI 300#). These "pressure classes" also have differing pressure and temperature ratings for different materials.
Flange designs are available as "welding neck", "slip-on", "boss", "lap joint", "socket weld", "threaded", and also "blind".
Pipe flanges that are made to standards called out by ASME/ANSI B16.5 or ASME/ANSI B16.47 are typically made from forged materials and have machined surfaces. They are typically in "Pressure Classes" such as 150#, 300#, 600#, 900# 1500#; however, ASME B16.47 still recognizes the 75# or "Class 75" flange for certain low pressure and low temperature applications.
The gasket type and bolt type are generally specified by the standard(s); however, sometimes the standards refer to the ASME Boiler and Pressure Vessel Code (B&PVC) for details (see ASME Code Section VIII Division 1 - Appendix 2 ). These flanges are recognized by ASME Pipe Codes such as ASME B31.1 Power Piping, and ASME B31.3 Process Piping.
Materials for flanges are usually under ASME designation: SA-105 (Specification for Carbon Steel Forgings for Piping Applications) , SA-266 (Specification for Carbon Steel Forgings for Pressure Vessel Components) or SA-182 (Specification for Forged or Rolled Alloy-Steel Pipe Flanges, Forged Fittings, and Valves and Parts for High-Temperature Service).
Part of the process of blocking a felt hat is called flanging.
Several different microwave RF flange types exist.