ASME B16.20 octagonal ring type gaskets
Size: R32, R35, R39, R46
Ring-joint gaskets shall be either octagonal or oval in cross section.
Ring-joint gaskets shall be identified by an R, RX, or BX number that relates to flange size (NPS), pressure class, and the appropriate flange standards (ASME B16.5, ASME B16.47, API Specification 6A, or ISO 10423).
3.1 General. Ring-joint gasket materials, some of which are listed in Table 1, shall be selected by the user based on suitability for the service conditions.
It is recommended that ring-joint gaskets be of a lesser hardness than that of the mating flanges.
3.2 Hardness. Ring-joint gaskets of materials listed in Table 1 shall have a hardness equal to or less than that shown in Table 1.
The outer surface of each gasket shall carry the manufacturer’s name or identification trademark and gasket number prefixed by the letters R, RX, or BX, followed by the gasket material identification. Materials shall be identified as shown in Table 2. The gasket shall also be marked with an ASME B16.20 designation. The marking shall be applied so as not to harmfully distort the gasket or affect the integrity of the seal.
5. Surface Finish
Types R and RX gaskets shall have a surface finish not rougher than 1.6 μm (63 in.) roughness. Type BX gaskets shall have a surface finish not rougher than 0.8μm (32 in.) roughness. Surface finish shall pertain to the gasket-sealing surface.