ASME B16.20a:2000 pdf free download.METALLIC GASKETS FOR PIPE FLANGESRing-Joint, Spiral-Wound, and Jacketed.
The distance of the first weld from the termrnal 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 centering ring.
32.4 Centering Ring. All spiral-wound gaskets shall be furnished assembled into a cenlering ring. The centering ring thickness shall be from 0.117 in. to 0.131 in. and suitably grooved on the inside diameter so as to retain the gasket.
3.2.5 Inner Ring. Inner rings shall be furnished with all spiral-wound gaskets having PTFE (polytetiafluomethylene) tiller material, It is recommended that inner rings be specified by the user for flexible graphite and other filler materials (if appropriate for flanges and bore sizes used). particulaily where experience has demonstrated inward buckling of the gaskets to be a problem. Inner rings shall be furnished in spiral-wound gaskets for flanges NPS 24 and larger in Class 900, NPS 12 and larger in Class 1500. and NPS 4 and Larger in Class 2500. Gaskets with inner rings should be used only with socket welding. lapped. welding neck, arid integral flanges.
The inner-ring thickness shall be from 0.117 in, to 0.131 in. Tables 12 through 14 show inner-ring inside diameters that may extend a maximum of 0.06 in. into the flange bore under the worst combination of flange bore, eccentric installation, and tolerance.
3.2.6 Gasket Compression. Spiral-wound gaskets
NPS “2. NPS 3/4, and NPS I in Classes 150. 300, and 600 shall be designed so that a uniform bolt stress of 25.000 psi. based on the nominal boll rool diameter, will compress the gasket to a thickness of 0.130 in. ±0.005 in, All other gasket sizes and classes shall be designed so that a uniform bolt stress of 30.000 psi will compress the gasket to a thickness of 0.130 in. ±0.005 in.
3.3 Materials
Metal windings and filler materials shall be in accordance with Table 19. The inner ring shall be of a material that has corrosion resistant characteristics equivalent to or better than that of the metal winding. The centering ring may be carbon steel that is painted, metal plated. or otherwise coated to inhibit atmospheric corrosion.
ASME B16.20a:2000 pdf free download
