There are many different flittings standards to be found worldwide. To allow easy functionality and interchangeability, these are designed to have standardised dimensions.
Moreover, common world standards include ASA / ANSI / ASME (USA), PN / DIN (European), BS10 (British/Australian), and JIS / KS (Japanese/Korean).
In addition, most cases Fittings are interchangeable as most local standards have been aligned to ISO standards, however some local standards still differ (e.g. an ANSI/ASME flange will not mate against an ISO 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/ASME 150 will not mate with an ANSI/ASME 300). These pressure classes also have differing pressure and temperature ratings for different materials.
Additionally, unique pressure classes for piping can also be developed for a process plant or power generating station. These may be specific to the corporation, engineering procurement and construction (EPC) contractor, or the process plant owner.
In addition, the ANSI/ASME pressure classes for Flat-Face flanges are 125# and 250#. The classes for Ring-Joint, Tongue & Groove, and Raised-Face flanges. The come in 150#, 300#, (400# – unusual), 600#, 900#, 1500#, and 2500#.
Finally, the Fittings and flange faces are also made to standardized dimensions. They come in “flat face”, “raised face”, “tongue and groove”, or “ring joint” styles, although other obscure styles are possible.
In conclusion, the flange designs are available as “weld neck”, “slip-on”, “lap joint”, “socket weld”, “threaded”, and also “blind”.