1, Typical flange facings 1) Flat Face (FF): Sealing is also by compression of a flat non-metallic gasket (very rarely a flat metallic gasket), the phonographic/ concentric grooved surfaces of the mating FF flanges. 2) Raised Face (RF): Sealing on a RF flange is by a flat non-metallic gasket (or a flat metallic gasket for special applications), which fits within the bolts of the flange. 3) Ring ..
