The flange face is the surface area where the gasket seats to seal the flanged connection. During fabrication the flange is always fitted perpendicular to the pipe to prevent any leakage of the connecting joint. The most common types of flange faces are the Raised Face or RF, the Flat Faced or FF, and the Ring Type Joint or RTJ.
The Raised Face
The Raised Face is the most common for the ANSI B16.5 and ASME B16.47 Flanges. The main scope of the Raised Face design is to concentrate the pressure of the two mating Flanges on a small surface area to increase the strength of the seal. The Raised Face is machined inside the bolt circle and is 1/16” in height for the 150# and 300# classes and ¼” for the 400# and above classes. For the 150# and 300# classes this dimension is included in the overall length of the Flange. For the 400# and above class Flanges the ¼” must be added to the overall length of the Flange.
The Standard Facing for the B16.5 and B16.47 Flanges is known as a Phonographic Finish which is a continuous groove which is generated by using a 1/16” Radius round nose tool with a cutting speed of 1/32” per revolution, this results in a 125-250 RMS finish. The customer may specify a different finish for special applications.
The Flat Face
The contact surface for Flat Faced Flanges will have the same height across the face of the Flange. Per ASME B31.3 a Raised Face Flange should never be bolted to a Flat Faced Flange as this could result in a leak at the Flanged joint.
The Ring Type Joint
The Ring Type Joint Flange has a circular groove machined in the Face and is used for high pressure and high temperature applications. The RTJ as well as the other facings will be covered at a later time.
Please contact Coastal Flange with any questions or to receive a bid winning quote tailored to your needs.
Other related posts: