A non-asbestos gasket (die-cut) is an economical type of gasket used to seal ANSI/ASME or EN flanges for low-pressure, low-temperature and non-critical applications. ASME B16.21 covers the dimensions and tolerances for this type of flange gaskets. Other types of gaskets, metallic and semi-metallic (such as ring joint gaskets, spiral wound, Kammprofile and metal jacketed) are under more demanding service conditions.

 

Non Asbestos gaskets have fully replaced asbestos gaskets for decades as studies demonstrated the risks (for human health) associated with the production, use, and disposal of asbestos materials.

The sizes, types, materials, dimensions, dimensional tolerances, and marking requirements for non-asbestos gaskets are covered by the ASME B16.21 specification when it comes to gaskets for ASME B16.5 and ASME B16.47 flanges.

The two main types of non-asbestos gaskets are the “full face” (FF) for FF flanges and the “flat ring” type for raised face flanges (RF).

Full face and ring gasket

 

Non asbestos gaskets are produced with compressed fiber sheets cut by water pressure machines.

Non asbestos gaskets have dimensions ranging from 5 to 5.000 mm. Larger sizes are produced by joining multiple fiber sheets.

The terms, “flat-cut gaskets”, “die-cut gaskets”, “compressed sheet gaskets” and “asbestos-free gaskets” are synonyms to define soft gaskets.

 

NON ASBESTOS MATERIALS FOR GASKETS

Materials for soft gaskets

The most common materials used to for soft gaskets are aramid fibers (Kevlar), glass fibers, elastomers, Teflon (PTFE), graphite, neoprene mixed with various binder materials:

  • Aramid NBR binder
  • carbon graphite reinforced
  • glass reinforced (steam service gasket)
  • PTFE bi-axially oriented (silica filler)
  • SBR (styrene-butadiene)
  • CR-chloroprene (Neoprene)
  • EPDM gasket (ethylene propylene)
  • fluorocarbon (Viton)
  • graphite
  • BUNA-n-rubber (nitrile, NBR gasket)
  • chlorosulfonated polyethylene (Hypalon gasket)
  • aramid + SBR binder (premium type gasket)
  • graphite + ss316/316l insert
  • PTFE biaxially oriented (with hollow glass microsphere) blue
  • PTFE biaxially oriented (pigment-free)-gray
  • expanded PTFE gasket
  • PTFE joint sealant
  • PTFE envelope slit type
  • PTFE envelope milled type
  • PTFE envelope formed type
  • MICA sheet
  • ceramic fiber

Non asbestos gaskets can also be coated with graphite, for non-stick and steam resistance, mixed with PTFE for excellent chemical resistance, or with EPDM for potable water applications.

 

NON ASBESTOS GASKET DIMENSIONS (ASME B16.21)

NON ASBESTOS GASKET DIMENSIONS FOR ASME B16.5 RF FLANGES

soft gaskets sizes

NPS d1
(ID)
d2 (GASKET OUTSIDE DIAMETER)
Class 150 Class 300 Class 400 Class 600 Class 900
1/2 21 48 54 54 54 64
3/4 27 57 67 67 67 70
1 33 67 73 73 73 79
42 76 83 83 83 89
48 86 95 95 95 98
2 60 105 111 111 111 143
73 124 130 130 130.2 165
3 89 137 149 149 149 168
102 162 165 162 162
4 114 175 181 178 194 206
5 141 197 216 213 241 248
6 168 222 251 248 267 289
8 219 279 308 305 321 359
10 273 340 362 359 400 435
12 324 410 422 419 457 498
14 356 451 486 483 492 521
16 406 514 540 537 565 575
18 457 549 597 594 613 638
20 508 606 654 648 683 699
24 610 718 775 768 791 838

All values in millimeters

 

NON ASBESTOS GASKET DIMENSIONS FOR ASME B16.47-SERIES A

soft gaskets sizes

NPS d1 (ID) d2 (GASKET OUTSIDE DIAMETER)
Class 150 Class 300 Class 400 Class 600
26 660 775 835 832 867
28 711 832 899 892 914
30 762 883 953 946 972
32 813 940 1006 1003 1022
34 864 991 1057 1054 1073
36 914 1048 1118 1118 1130
38 965 1111 1054 1073 1105
40 1016 1162 1114 1127 1156
42 1067 1219 1165 1178 1219
44 1118 1276 1219 1232 1270
46 1168 1327 1273 1289 1327
48 1219 1384 1324 1346 1391
50 1270 1435 1378 1403 1448
52 1321 1492 1429 1454 1499
54 1372 1549 1492 1518 1556
56 1422 1607 1543 1568 1613
58 1473 1664 1594 1619 1664
60 1524 1715 1645 1683 1721

All values in millimeters

 

NON ASBESTOS GASKET DIMENSIONS FOR ASME B16.47-SERIES B

soft gaskets sizes

NPS d1 (ID) d2 (GASKET OUTSIDE DIAMETER)
Class 150 Class 300 Class 400 Class 600
26 660 725 772 746 765
28 711 776 826 800 819
30 762 827 886 857 879
32 813 881 940 911 933
34 864 935 994 962 997
36 914 987 1048 1022 1048
38 965 1045 1099
40 1016 1095 1149
42 1067 1146 1200
44 1118 1197 1251
46 1168 1256 1318
48 1219 1307 1368
50 1270 1357 1419
52 1321 1408 1470
54 1372 1464 1530
56 1422 1514 1594
58 1473 1580 1656
60 1524 1630 1705

All values in millimeters. Dimensional tolerances:

  • For outside diameter NPS 12 and smaller: +0 / -1.5 mm.; NPS 14 and larger: +0 / -3.0 mm.
  • For inside diameter NPS 12 and smaller: ± 1.5 mm; NPS 14 and larger: ± 3.0 mm

 

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