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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).
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. 3.2.5 Inner Ring. Inward buckling of spiral-wound gaskets has been identified as a potential problem. Inner rings shall be furnished with all spiral-wound gaskets having PTFE (polytetrafluoroethylene) filler material. Inner rings forflexible graphite-filled,spiral-wound gas- kets shall be furnished unless the purchaser specifies otherwise. For all filler materials, inner rings shall be furnished in spiral-wound gaskets for (a) NPS 24 and larger in Class 900 (b) NPS 12 and larger in Class 1500 (c) NPS 4 and larger in Class 2500 Inner rings are required for these gaskets due to high available bolt loads, which may result in outer ring damage. The inner ring thickness shall be from 2.97 mm to 3.33 mm (0.117 in. to 0.131 in.). Tables 12 through 14 (Tables I-7 through I-9 of Mandatory Appendix I) show inner ring inside diame- ters that may extend a maximum of 1.5 mm (0.06 in.) into the flange bore under the worst combination of flange bore, eccentric installation, and tolerance. Gaskets with inner rings should be used only with socket welding, lapped, welding neck, and integral flanges. Reference Table 15 for minimumpipe wall thick- ness for use with gaskets with inner rings. Reference Tables 16 through 18 (Tables I-10 and I-11 of Mandatory Appendix I) for maximum allowable bore for use with gaskets without inner rings. 3.2.6 Gasket Compression. Spiral-wound gaskets NPS 1 ⁄ 2 , NPS 3 ⁄ 4 , and NPS 1 in Classes 150, 300, and 600 shall be designed so thata uniform boltstress of172 MPa (25,000 psi), based on the nominal bolt root diameter, will compress the gasket to a thickness of 3.30 mm ± 0.13 mm (0.130 in. ± 0.005 in.). All other gasket sizes and classes shall be designed so that a uniform bolt stress of 207 MPa (30,000 psi) will compress the gasket to a thickness of3.30 mm± 0.13 mm (0.130 in. ± 0.005 in.).
5.3 Materials 5.3.1 Covering. Covering material shall be selected from Table 29. 5.3.2 Core. Core material shall be selected from Table 29. 5.3.3 Centering Ring. When carbon steel centering rings are selected, they shall be painted, metal plated, or otherwise coated to inhibit atmospheric corrosion. 5.4 Marking 5.4.1 General. The centering ring shall be perma- nently marked. The lettering height shall be a minimum of 2.5 mm (0.1 in.), except where space requirements dictate use of a smaller size character. The following information shall be included: (a) manufacturer’s name or trademark. (b) flange size (NPS). (c) pressure class. (d) metal core abbreviation (Table 29). (e) covering material abbreviation (Table 29). (f) centering ring metal abbreviation (Table 29), except when carbon steel is used. (g) flange identification. Gaskets used for ASME B16.47 flanges shall be marked B16.47 A or B16.47 B, as applicable. Illustrative marking examples are shown in Table 30 (see also Fig. 4). (h) ASME B16.20 designation.

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