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. By using flanges, pipes can be assembled or disassembled very easily.
Plumbing or Piping
Although flange generally refers to the actual raised rim or lip of a fitting, many flanged plumbing fittings are themselves known as ‘flanges’:
Surrey FlangeCommon 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 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.
A closet flange provides the mount for a toilet.
There are many different flange standards to be found worldwide. To allow easy functionality and inter-changeability, these are designed to have standardised dimensions. Common world standards include ASA/ANSI (USA), PN/DIN (European), BS10 (British/Australian), and JIS/KS (Japanese/Korean).
ANSI designations such as ANSI 150, ANSI 300 and so on are often followed by a # (hash symbol). The ANSI number does not directly relate to a pressure rating, but to a class of flange. For example, the hash (#) or ‘pound’ reference; e.g. 300 pound, can be misleading in that an ANSI 300 flange is actually rated for a test pressure of 740 psi (~5100 kPa), and only within a certain working temperature range (-20 to 100 deg F.)
In most cases these are not interchangeable (e.g. 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 (e.g. an ANSI 150 will not mate with an ANSI 300). These “pressure classes” also have differing pressure and temperature ratings for different materials. “Pressure Classes” of piping are usually developed for a process plant or power generating station; these “pressure classes” may be unique to the specific corporation, Engineering Procurement and Construction (EPC) contractor, or the process plant owner.
The flange faces are made to standardized dimensions and are typically “flat face”, “raised face”, “tongue and groove”, or “ring joint” styles, although other obscure styles are possible.
Flange designs are available as “welding neck”, “slip-on”, “boss”, “lap joint”, “socket weld”, “threaded”, and also “blind”.
ASME standards (U.S.)
Pipe flanges that are made to standards called out by ASME B16.5 or ASME B16.47 are typically made from forged materials and have machined surfaces. B16.5 refers to nominal pipe sizes (NPS) from 1/2 to 24. B16.47 covers NPSs from 26 to 60. Each specification further delineates flanges into classes 150, 300, 400, 600, 900, 1500 and 2500 for B16.5. B16.47 delineates its flanges into classes 75, 150, 300, 400, 600, 900.
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). In addition, there are many “industry standard” flanges that in some circumstance may be used on ASME work.
Flanges in other countries also are manufactured according to the standards for materials, pressure ratings, etc. Such standards include DIN, and/or ISO standards.