Gaskets

Ring Joint Type

Ring joint gaskets come in two basic types, an oval cross section and an octagonal cross section. These basic shapes are used in pressures up to 10,000 psi (64 MPa). The dimensions are standardized and require specially grooved flanges. The octagonal cross section has a higher sealing efficiency than the oval and would be the preferred gasket.
However, only the oval cross section can be used in the old type round bottom groove. The newer flat bottom groove design will accept either the oval or the octagonal cross section.
The hardness of the ring should always be less than the hardness of the flanges to prevent flange deformation. Dimensions for standard ring joint gaskets and grooves are covered in ASME B16.20 and API 6A, API 17D and ASME B16.5/B16.20.
 

  • Type - R (Octagonal)

    Type - R (Octagonal)
    Type - R  Octagonal

  • Type - R (Oval)

    Type - R (Oval)
    Type - R (Oval)

  • Type - RX

    Type - RX
    Type RX gaskets fit in the same currently specified grooves as Type R gaskets and offer a greater capacity to support weight and resist vibration without leaking. Type RX gasket cross sections seen in profile have 8 "sides", but seal using different forces from Type R octagonal gaskets. API has referred to them as "self-sealing" or "pressure energized" ring gaskets.

  • Type - BX

    Type - BX
    Type BX gaskets, used in API 6 BX, 17D SS and SV flanges, and API 16 BX clamp hubs also have cross sections seen in profile to have 8 "sides." They have a pitch diameter slightly larger than the groove into which they fit; the diameter difference between gasket and groove provides an additional sealing force by maintaining intimate with the outside diameter of the groove, even if the flanges move slightly away from each other under pressure.