All API ring gaskets manufactured by Vanco are circular with various cross-sectional profiles to obtain different sealing characteristics. The purpose of these gaskets is to create a static seal between two stationary members of a mechanical assembly and to maintain that seal under various operating temperatures and pressures. Typical mechanical assemblies include bolted flanges or clamps that are constructed of a material with a hardness value higher than that of the gasket. This hardness differential forces the ring gasket to plastically deform instead of the ring grooves. The diagram below illustrates the longitudinal cross-section of the flanges while the black shading represents the cross-section of the gasket.

The mating flanges will have a machined ring groove on the face of each flange to act as the gasket seating surface. The seal is located along small bands of contact between the sealing angles of the ring gasket, which are located on the OD and ID, and the ring grooves located on the face of the mating flanges or connectors. The seal is established by compressing the gasket material, through high bolt loads, and causing the gasket material to flow into the voids and imperfections of the gasket seating surfaces so that intimate contact is made between the gasket and the gasket seating surfaces, therefore, preventing the escape of the contained fluid. Due to this plastic deformation of the gasket, it is recommended that a new gasket be used each time a connection is made-up. API 6A and ASME B16.20 define Type R, RX and BX ring gasket designs while API 17D defines Type SBX ring gasket designs.

There are three categories of API ring type joints: R, RX and BX and range in size from 1/2″ to over 40″ in outside diameter and are manufactured in carbon steel, stainless steel and various other materials. Vanco maintains an inventory of ring-joints in carbon steel, 304 stainless steel and 316 stainless steel. Other materials can be made in a timely manner, based on customer requirements.

Type R

The Type R ring-joint gasket was the first metal gasket design standardized within the oil and gas industry and has been in service since the 1930′s. Type R ring-joint gaskets are manufactured with either an oval or octagonal cross-section. Since the pitch diameter of the Type R gaskets are equivalent to the pitch diameter of their mating ring grooves, no radial interference exists between the ring gasket and the ring groove. Type R ring gaskets are not designed to be pressure energized and do not allow face-to-face contact of the flanges or hubs.

Type RX

The Type RX ring-joint gasket is manufactured with a diameter slightly larger than that of the mating ring grooves, which allows radial interference to exist. The OD sealing angle of Type RX ring gaskets is considered to be the primary seal since both radial and axial loads are applied to the OD sealing angles causing the sealing force on the OD sealing angles to be substantially greater than the sealing force on the ID sealing angles. The RX ring-joint gaskets are designed to be pressure-energized, and do not allow face-to-face contact of the flanges or hubs. Axial through-holes are drilled only in certain RX ring-joint gasket sizes to ensure pressue equalization between each face of the ring-joint gasket and the mating ring grooves.

Type BX

The Type BX ring-joint gasket is manufactured with a diameter slightly larger than that of the mating ring grooves, which allows radial interference to exist. The OD sealing angle of Type BX ring gaskets is considered to be the primary seal since both radial and axial loads are applied to the OD sealing angles causing the sealing force on the OD sealing angles to be substantially greater than the sealing force on the ID sealing angles. Type BX ring-joint gaskets are designed to be pressure-energized, and do allow face-to-face contact of the flanges or hubs. Axial through-holes are drilled in each BX ring-joint gasket to ensure pressue equalization between each face of the ring-joint gasket and the mating ring grooves.

Type SBX

The Type SBX has the same dimensions and sealing characteristics as its BX counterpart. However, Type SBX ring gasket designs have additional ports drilled in the rings to allow them to be installed in connectors that are located under water. The additional ports allow for the evacuation of water that can be trapped between the faces of the ring gasket and each ring groove once the mating sealing surfaces first come into contact.