ASME B16.20:2017 pdf free download

ASME B16.20:2017 pdf free download.Metallic Gaskets for Pipe Flanges.
SW-I SIZE AND CLASS
Spiral-wound gaskets, including centering ring and Inner ring (paras. SW-2.4 and SW-2.S). are identified by flange sise (NPS), pressure class, and the approprl..te flange standard (ASME 816.5 or ASME 816.47).
SW-2 DIMENSIONS AND TOLERANCES SW-2.l General
Dimensions and tolerances for spiral-wound gaskets. centering rings, and inner nngs shall be in accordance with Figure SW-2.I-1 and Tables SW-2.l-1 through SW-2.I.6. and as specified en this Part
SW-2.2 Construction
Spiral-wound gaskets shall be constructed as alternate plies (circular layers counted as revolubons) opcefurmed metal windengs and pliant fillers that are spirally wound.
Pliant fillers shall not extend below the metal winding on both contact laces of the gasket Metal winding thickness shall he 0.190mm 20.040mm (0.0075 in, ±00015 in.). For all filler materials, filler thickness and density shall be determined by the manufacturer such that ihe performance testing criteria in sara SW-2.6 will be met. In addition, for gaskets with flexible graphite filler material, filler thickness and density shall be determined by the manufacturer such that each finished gasket will compress to a thickness no less than 3.43 mm (0.135 in.) when suhlected to the following uniform gasket stress, and where the gasket contact area Is calculated using the inside and outside diameters as shown In Tables SW. 2.1-1 through SW’2.l’3:
(a) 52 MPa (7.500 psi) for Class ISO flanges
(6) 70 MPa (10.000 psi) for Class 300 through Gaas 600 flanges
(c) 140 MPa (20,000 psi) for Class 900 and above
SW-2.3 Metal ioln4ng
The Inner windings shall have a minimum of three phes of preformed metal imp 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 havea minimum of three plies of preformed metal withoutfiller. shall be spot-welded circumferentially with aminimum of three welds, the last of which shall be theterminal weld.
The distance of the first weld from the terminal weldshall be no greater than 38 mm (1.5 in.J. Up to four addi-tional loose preformed metal windings beyond the term-inal weld may be used to retain the gasket into thecentering ring.
Sw-2.4 Centering Ring
All spiral-wound gaskets shall be furnished assembledinto a centering ring.The centering-ring thickness shall befrom 2.97 mm to 3.33 mm (0.117 in. to 0.131 in.) andsuitably grooved on the inside diameter so as to retainthe gasket.
sw-2.5 Inner Ring
lnward buckling of spiral-wound gaskets has been iden-tified as a potential problem.Innerrings shall be furnishedwith all spiral-wound gaskets having polytetrafluoroethy-lene (PTFE) filler material. Inner rings for flexiblegraphite-filled. spiral-wound gaskets shall be furnishedunless the purchaser specifies otherwise.
For all filler materials, inner rings shall be furnished inspiral-wound gaskets for NPS 24 and larger in Class 900by NPS 12 and larger in Class 1500c) NPS 4 and larger in Class 2500
lnner rings are required for these gaskets due to highavailable bolt loads, which may result in outer ringdamage.