The facing of a flange decides how the gasket is compressed and, in turn, how well the joint seals. Choosing the wrong facing is one of the most common causes of leaking flanged joints in process piping.
Raised Face (RF) is the most widely used facing in ASME B16.5 piping. The small raised area concentrates the bolt load on a smaller gasket area, which produces a higher seating stress and a more reliable seal at moderate pressures.
Flat Face (FF) is used where the mating component is cast iron or another brittle material. The full-face gasket and full contact area avoid the bending stress that a raised face would put into a brittle flange.
Ring Type Joint (RTJ) uses a metal ring seated in a machined groove and is the usual choice for high pressure and high temperature service, typically Class 900 and above in oil and gas duty.
When you specify a flange, confirm the facing, the facing finish, the pressure class and the material grade together — all four must match the mating flange and the gasket.
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