ASME B16.20a:2000 pdf download

ASME B16.20a:2000 pdf download.METALLIC GASKETS FOR PIPE FLANGES
1 SCOPE
1.1 General This Standard covers materials, dimensions, toler- ances, and markings for metal ring-joint gaskets, spiral- wound metal gaskets, metal-jacketed gaskets, and filler material. These gaskets are dimensionally suitable for use with flanges described in reference flange standards ASME B 16.5, ASME 816.47, and API Specification 6A. This Standard covers spiral-wound metal gaskets and metal-jacketed gaskets for use with raised-face and flat-face flanges. 1.2 Quality Systems Requirements relating to the product manufacturers’ quality system programs are described in Annex A. 1.3 References Standards and specifications adopted by reference in this Standard are shown in Annex I, which is part of this Standard.
2 RING-JOINT GASKETS
2.1 Types Ring-joint gaskets shall be either octagonal or oval in cross section. 2.2 Size 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 B 16.5, ASME B 16.47, or API Specification 6A). 2.3 Materials 2.3.1 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. 2.3.2 Hardness. Ring-joint gaskets of materials listed in Table I shall have a hardness equal to or less than that shown in Table I . 2.4 Marking 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 B 16.20 designation. The marking shall be applied so as not to harmfully distort the gasket or affect the integrity of the seal. 2.5 Dimensions and Tolerances Dimensions and tolerances for ring-joint gaskets shall be as shown in Tables 3 through 8. 2.6 Surface Finish Types R and RX gaskets shall have a finish not rougher than 63 pin. roughness. Type BX gaskets shall have a finish not rougher than 32 pin. roughness. Surface finishes shall pertain to the gasket-sealing surfaces.
3 SPIRAL-WOUND GASKETS
3.1 Size and Class Spiral-wound gaskets, including centering ring and inner ring (paras. 3.2.4 and 3. 25). are identified by flange size (NPS), pressure class. and the appropriate flange standard (ASME B 16.5 or ASME B 16.37). 3.2 Dimensions and Tolerances 3.2.1 General. Dimensions and tolerances for spi- ral-wound gaskets, centering rings, and inner rings shall be in accordance with Tables 9 thr-ough I I and as specified i n this section. 3.2.2 Construction. Spiral-wound gaskets shall be constructed as alternate plies (circular layers counted as revolutions) of preformed metal windings and plaint fillers that are spirally wound. For the finished gasket, the filler shall be essentially flush with. but not below, the metal winding on both contact faces of the gasket. The metal strip i n the winding shall be 0.006 in. to 0.009 in. thick. The filler matet-ia1 thickness shall be determined by the manufacturer. 3.2.3 Metal Joining. The inner windings shall have a minimum of three plies of preformed metal strip without filler. The initial two plies shall be spot- welded circumferentially with a minimum of three weld spaced at a maximum distance of 3 in. The outer windings. which shall have a minimum of three plies of preformed metal without filler, shall bc spot- welded circumferentially with a minimum of three welds, the last of which shall be the terminal weld. The distance of the first weld from the terminal weld shall be no greater than 1.5 in. Up to four additional loose preformed metal windings beyond the terminal weld may be used to retain the gasket into the center- ing ring. 3.2.4 Centering Ring. All spiral-wound gaskets shall be furnished assembled into a centering ring. The centering ring thickness chal1 be from 0.1 17 in. to 0.1 3 1 in. and suitably grooved on the inside diameter so as to retain thc gasket.