Most Prevalent Flange Facing Types

There are mainly 4 prevalent facing types for flanges which are manufactured as per miscellaneous international standards.

1) Raised Face(RF): This is the most common facing type of pipe flanges. The face is typically raised 1.6mm for class 150 and 300, and 6.35mm for class 400, 600, 900, 1500 and 2500. For other international standards, the RF thickness differs from different pressure ratings and sizes. Since the face is raised, the gasket diameter is smaller than the bolt circle.

2) Flat Face(RF): For American standard flanges, flat faces are typically used in cast iron class 125 and 250 flanges. Flat faces are also widely applied to slip on plate flanges and blind flanges in EN1092-1, BS10, BS4504, DIN, JIS, UNI, GB/HGT and GOST standards with pressure ratings ranging from PN6 to PN16. It requires a full-faced gasket which has a large contact area that even extends beyond the bolt circle. Thus, the fastening force can be distributed over a widest area avoiding cracking damage to the flange face.

3) Lap Joint(LJ): This type of flange are always used along with a stub end acting as a raised face.

4) Ring Type Face(RTJ): A ring groove is machined out precisely to fit the mating metallic ring either in oval or octagonal shape.