> the most common type used in process plant applications and easily to identify.
> It is referred to as a raised face because the gasket surfaces are raised above the bolting circle face.
> This face type allows the use of a wide combination of gasket designs, including flat ring sheet types and
metallic composites such as spiral wound and double jacketed types.
> The purpose of a RF flange is to concentrate more pressure on a smaller gasket area and thereby increase the
pressure containment capability of the joint.
2. Flat Face Flange (FF)
> It has a gasket surface in the same plane as the bolting circle face.
> Applications using flat face flanges are frequently those in which the mating flange or flanged fitting is made
from a casting.
> Flat face flanges are never to be bolted to a raised face flange.
3. Ring Joint Flange (RTJ)
> The Ring Type Joint flanges are typically used in high pressure (Class 600 and higher rating) and/or high
temperature services above 800°F (427°C).
> They have grooves cut into their faces which steel ring gaskets.
> The flanges seal when tightened bolts compress the gasket between the flanges into the grooves, deforming (or
Coining) the gasket to make intimate contact inside the grooves, creating a metal to metal seal.
> An RTJ flange may have a raised face with a ring groove machined into it.
