In general, the raised face design is most commonly used. Mating face is flat but portion inside bolt holes are raised 1/16″ (1.6mm) or 1/4″ (6.4mm). Once assembled, the gaskets may be removed easily without springing the flange. Steel flanges that are to mate with cast iron should have flat faces to prevent breaking the cast iron flange during bolt tightening. Gaskets are unconfined.
Mating face of both flanges are flat. Ring type gaskets are commonly used on this facing, covering essentially the entire face both inside and outside the bolts. Gaskets are unconfined.
These facings are commonly used in the bonnet of valves, the cover of pressure vessels and tanks subject to high pressures. Depth of recessed face normally equal to, or less than, height of male or raised face to prevent possibility of flanges coming together metal-to-metal when gasket is compressed. Raised outside diameter not more than 1/16″ (1.6mm) larger than outside diameter of male face. Joints must be pried apart for disassembly. Gaskets are semi-confined.
These facings are commonly used in the bonnet of valves, the cover of pressure vessels and tanks subject to high pressures. Depth of groove equal to, or less than, height of tongue. Groove normally not over 1/16″ (1.6mm) wider than tongue. Although this joint must be pried apart for disassembly, tongue-and-groove flange do produce a high gasket pressure. Gaskets are fully confined.