ASME B16.20a-2000 pdf – METALLIC GASKETS FOR PIPE FLANGESRing-Joint, Spiral-Wound,and Jacketed.
2.7 Identification Number
1)imensional refercncc edeiitihcjtion iiiuiibers arc asigned to nnoinI ga%kets and arc shown in Tables 3 through H.
31 Size and Class
SpraI.wiund gaskets. including centering ring and inner nng (paras. 3.2.4 and 3.2.5i. are idenlilied hy flange si,c I NPSi. pressure clas. and the app tipnalc ti.ingc sLiniLsrtl (AS’siF Rlhi or ASMF Rl47l.
3.2 Dimensions and Tolerances
3.2.1 General l)imcnsi.ns and ioIer-anes br spiral-wound gaskcs. eeiuenn nugs. and inner flogs shall
in .Mxnrdancc with rabIes 9 through Ii and as specitwd In this sceuon,
3.2.2 Construction. Spiral-wound gasLis shall be consrucied as alternate phes fi.ircular layers criunted as resolutions) ol prelormed metal windings and plaint hIkes that are spirally wound, 14w the hiiishi:d gasLct. the tiller %haiI be csscntially flush with. hut not below. the metal winding on both wnLKt Iaics ut Ihe gasket. The metal stop in the winding shjll be (lOOt’ in to 0(X)’) itt thick, The hiler material thicknei.s shall be dctennincii by the nianulaclurer
3.2.3 Metal Joining. Thi: inner wmdingi shall lust a minimum of three pbes at strip without hllcr, The ,n,tial two plies shall he spot- welded circumlerenlially with a minimum of three welds spaced at a masimum distance of . in The outer wmdins, which dull hjvc a minimum of three plies of prdormed metal without filler. shall be spot welded cireunilcrcntially with a minimum of three welds, the bra of which shall he the terminal weld.
The distatice of the lion weld 1mm the terminal weld shall he no greater than IS in Lip to four additional loose preformed nictal wmdings beyond the terminal weld may he used to retain the gasket Into the centering ring,
3.2.4 C.nt.ring Ring All spiral-wound gaskets shall he lumished asseinhkd Into a centering ring. The ccnienng ring thi1ns haIl be from 0.117 in, to 0131 in, and suitably groused on the inside diameter so as to retain the gie.kct.
3.2.5 Inner Ring. Inner nngs shall be furnished with all spiral wound gasket, having PTFE (polyleira. ltuiiruethyknc tiller nuterial. Ii is recommended that inner rings hc specified by ihe user for l1ciblc graphite and other tiller materials tif apprupnate fur flanges and bore sigcs used). particularly where esperiencc has demonstrated inward buckling of thc gaskets to he 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 Cbss 15410. and PS 4 and largev in Class 2500. (laskets with nnei rings shouW he used only with socket welding, lapped. ssslsling ncck. and integral flanges.
The inner ring thickness shall be from 0.117 in. to 0 131 in. laNes 12 through 14 show tnncr-nng inside diameters that may cstcnd a masimuni of 0.06 in. info lh flange kite under the worst combination of flange bore. cccentnc installation, and tolerance. Reference Table IS for minimum pipe wall itliLkibess hit use with gaskets with inner rings Refrrence Tables 16, 17. and IS lot mavitnuni allowable bore br use with gaskets without inner rings.
3.2.6 Gasket Compression. Spiral-wound gaskets NI’S … M’S and sPS I in Classes ISO. 3(I). and (rOb) shall be designed so that a uniform bolt stress of 25,000 psi. based on the nominal bolt root diameter, will compress the gasket to a thickness of 0.1 34.) in. ±000’S in. All other gasket sizes and classes shall be designed so that ii unifonn boll stress of 10.004) psi will compress the gasket to thickness of 4)1 0 in ±0.005 in.