ASME B16.20a:2000 pdf download METALLIC GASKETS FOR PIPE FLANGES Ring-Joint, Spiral-Wound, and Jacketed
1 SCOPE
1.1 General
This Standard covers materials, dimensions, tolerances, and markings for metal ring-joint gaskets, spiral-wound metal gaskets, metal-jacketed gaskets, and fillermaterial. These gaskets are dimensionally suitable foruse with flanges described in reference flange standardsASME B16.5，ASME B16.47，and API Specification6A. This Standard covers spiral-wound metal gasketsand metal-jacketed gaskets for use with raised-face andflat-face flanges.
1.2 Quality Systems
Requirements relating to the product manufacturersquality system programs are described in Annex A.
1.3 References
Standards and specifications adopted by reference inthis Standard are shown in Annex I, which is part ofthis Standard.
2 RING-JOINT GASKETS
2.1 Types
Ring-joint gaskets shall be either octagonal or ovalin cross section.
2.2 Size
Ring-joint gaskets shall be identified by an R，RXor BX number that relates to flange size (NPS) pressureclass，and the appropriate fange standards (ASMEB16.5，ASME B16.47、or API Specification 6A)
2.3 Materials
2.3.1 General. Ring-joint gasket materials, someof which are listed in Table 1,shall be selected bythe user based on suitability for the service conditions
It is recommended that ring-joint gaskets be of a lesserhardness than that of the mating flanges.
2.3.2 Hardness. Ring-joint gaskets of materialslisted in Table I shall have a hardness equal to orlcss than that shown in Table l.
2.4 Marking
The outer surface of each gasket shall carry themanufacturer’s name or identification trademark andgasket number prefixed by the letters R，RX, or BXfollowed by the gasket material identification. Materialsshall be identified as shown in Table 2. The gasketshall also be marked with an ASME B16.20 designation.The marking shall be applied so as not to harmfullydistort the gasket or affect the integrity of the scal.
2.5 Dimensions and Tolerances
Dimensions and tolerances for ring-joint gaskets shallbe as shown in Tables 3 through 8.
2.6 Surface Finish
Types R and RX gaskets shall have a finish notrougher than 63 in. roughness. Type BX gaskets shallhave a finish not rougher than 32 pin. roughness. Surfacefinishes shall pertain to the gasket-sealing surfaces It is recommended that ring-joint gaskets be of a lesserhardness than that of the mating flanges.
2.3.2 Hardness. Ring-joint gaskets of materialslisted in Table l shall have a hardness equal to orless than that shown in Table 1.
2.4 Marking
The outer surface of each gasket shall carrythemanufacturer’s name or identification trademark andgasket number prefixed by the letters R， RX, or BXfollowed by the gasket material identification. Materialsshall be identified as shown in Table 2. The gasketshall also be marked with an ASME B16.20 designation.The marking shall be applied so as not to harmfullydistort the gasket or affect the integrity of the seal.
2.5 Dimensions and Tolerances
Dimensions and tolerances for ring-joint gaskets shallbe as shown in Tables 3 through 8.
2.6 Surface Finish
Types R and RX gaskets shall have a finish notrougher than 63 in. roughness. Type BX gaskets shallhave a finish not rougher than 32 win. roughness. Surfacefinishes shall pertain to the gasket-sealing surfaces.

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