Flange Specification and Identification
A flange is specified by the following information:
Type and Facing. The flange is specified according to whether it is, for example, ‘‘weld-neck RTJ’’ or ‘‘socket-weld RF.’’ Ring joint facing and RTJ gasket dimensions for ASME B16.5.
Nominal Pipe Size (NPS). This is a dimensionless designation to define the nominal pipe size (NPS) of the connecting pipe, fitting, or nozzle. Examples include NPS 4 and NPS 6.
Flange Pressure Class. This designates the pressure temperature rating of the flange, which is required for all flanges. Examples include Classes 150, 300, 900, and 1500.
Standard. Basic flange dimensions for ASME B16.5. Examples include ASME B16.5, BS 1560, DIN or API 6A.
Material. A material specification for flanges must be specified and be compatible to the piping material specifications.
Pipe Schedule. This is only for WN, composite lap-joint and swivel-ring flanges where the flange bore must match that of the pipe, such as schedule 40, 80, 120, and 160.