B16.5

Flanges are fabricated per ASTM and ASME Standards. 

Flange Face

It refers to the area of contact with the gasket used for sealing. Typically, a gasket sits between the two opposing flange faces. Examples of flange faces are:

Flat Face (FF): The entire surface is flat, similar to a raised face (RF) flange but without the raised area. This means the entire surface contacts the gasket when two flanges mate.

Raised Face (RF): It’s the most widely used type of flange face. This is referred to as “Raised” because the elevated surface of this flange is above the bolting circle where the gasket sits.

Ring-Type Joint (RTJ): This type has a metal ring with a deep groove cut into its surface. In the process of tightening the bolts, the metal ring in the groove compresses.

Tongue and Groove: The tongue flange has a raised ring while the groove flange has a corresponding depression machined onto the faces.

Lap Joints: This type are two-piece pipe flange connections that are easy to assemble and disassemble. Lap joint flanges are important since they can allow minor misalignments.

Male and female (M/F): In this type, the male flange has a raised ring while the female has a matching depression.