ASME B16.20:2012 pdf download

ASME B16.20:2012 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 grooved metal gaskets with covering layers. These gas- kets are dimensionally suitable for use with flanges described in reference flange standards ASME B16.5, ASME B16.47, API Specification 6A, and ISO 10423. 1.2 Quality Systems Requirements relating to the product manufacturers’ quality system programs are described in Nonmandatory Appendix A. 1.3 References Standards and specifications adopted by reference in this Standard are shown in Mandatory Appendix II, which is part of this Standard. 1.4 Relevant Units This Standard states values in both SI (Metric) and U.S. Customary units. These systems of units are to be regarded separately as standard. Within the text, the U.S. Customary units are shown in parentheses or in separate tables that appear in Mandatory Appendix I. The values stated in each system are not exact equiva- lents; therefore, it is required that each system of units be used independently of the other. Combining values from the two systems constitutes nonconformance with the 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 B16.5, ASME B16.47, API Specification 6A, or ISO 10423).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 ofa lesser hardness than that of the mating flanges. 2.3.2 Hardness. Ring-joint gaskets of materials listed in Table 1 shall have a hardness equal to or less than that shown in Table 1. 2.4 Marking The outer surface of each gasket shall carry the manu- facturer’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. 2.5 Dimensions and Tolerances Dimensions and tolerances for ring-joint gaskets shall be as shown in Tables 3 through 8 (Tables I-1, I-2, and I-3 of Mandatory Appendix I). 2.6 Surface Finish Types R and RX gaskets shall have a surface finish not rougher than 1.6 m (63 in.) roughness. Type BX gaskets shall have a surface finish not rougher than 0.8 ?m (32 ?in.) roughness. Surface finish shall pertain to the gasket-sealing surface. 2.7 Identification Number Dimensional reference identification numbers are assigned to ring-joint gaskets and shown in Tables 3 through 8 (Tables I-1, I-2, and I-3 of Mandatory Appendix I).
3 SPIRAL-WOUND GASKETS
3.2.1 General. Dimensions and tolerances for spi- ral-wound gaskets, centering rings, and inner rings shall be in accordance with Tables 9 through 14 (Tables I-4 through I-9 of Mandatory Appendix I) and as specified in this section (see also Figs. 1 and I-1). 3.2.2 Construction. Spiral-wound gaskets shall be constructed as alternate plies (circular layers counted as revolutions) of preformed metal windings and pliant 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 in the winding shall be 0.15-mm (0.006-in.) to 0.23-mm(0.009-in.) thick. The fillermaterial thickness shall be determined by the manufacturer. 3.2.3 MetalJoining. The inner windings shall have a minimumofthree plies ofpreformedmetal strip without filler. The initial two plies shall have spot welds spaced around the inner circumference. The minimum number of welds shall be three. The maximum distance between welds shall be 76 mm (3.0 in.). The outer windings, which shall have a minimum of three plies of preformed metal without filler, shall be spot-welded circumferen- tially 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 38 mm (1.5 in.). Up to four additional loose preformed metal windings beyond the terminal weld may be used to retain the gasket into the centering ring. 3.2.4 Centering Ring. All spiral-wound gaskets shall be furnished assembled into a centering ring. The centering ring thickness shall be from 2.97 mm (0.117 in.) to 3.33 mm (0.131 in.) and suitably grooved on the inside diameter so as to retain the gasket.