What are Flange Gaskets?

What are Flange Gaskets?

Flange Gaskets are used to create a static seal between two flanges faces, at various operating conditions, with varied pressure and temperature ratings. A gaskets fills the microscopic spaces and irregularities of the flange faces, and then it forms a seal that is designed to keep liquids and gases. Correct installation of damage-free gaskets and demage-free flange faces is a requirement for a leak-free flange connection.
If it would be technically possible, in order to manufacture flanges perfectly flat and smooth, and perfectly compatible with one another under all operating conditions, a gasket would not be necessary. But in normal practice it is not possible, because flange connections under ANY circumstances should be made. Small impurities and a small bit of dirt, is in practice not be avoided and therefore it is necessary to use a gasket.

Types of flange gaskets

Flange gaskets can be classified in multiple ways. The most common taxonomy is based on the gasket material type:

ASME B16.21 covers types, sizes, materials, dimensions, tolerances, and markings for nonmetallic flat gaskets for pipe flanges. ASME B16.20 covers metallic and semi-metallic gaskets for pipeline flanges.

gasket flange - What are Flange Gaskets?

THE 5 GASKETS SELECTION FACTORS

Flange gasket shall be selected based on multiple process parameters, such as operating temperature/pressure, type of fluid conveyed by the pipeline, flange type, size, pressure rating, material grade, and specifications. The key factors to consider to select proper gaskets are:

1 – TYPE OF FLUID CONVEYED BY THE PIPELINE

The flange gasket should not be affected by the fluid conveyed by the pipeline over the whole range of operating conditions (pipeline operating temperature and pressure). The chemical resistance chart shows how different flange gasket materials resist specific temperatures, pressures, and fluids.

Gaskets Chemical Resistance Chart

Gasket Material Max temperature (F) Max Pressure (psi) Gasket Thickness Gasket Service Recommended
Butyl -40 to 225 150 1/16 to 1/4 Gases, inorganic acids & alkalis. Excellent weather/abrasion resistance.
EPDM -40 to 212 150 1/16 to 1/4 Water, steam, animal/vegetable oils, oxygenated solvents. Excellent weather resistance.
Natural (Pure Gum) -20 to 140 100 1/32 to 1 Acids, organic salts & alkalis. Non-toxic. Abrasion resistant. Soft.
Neoprene -20 to 170 150 1/32 to 2 Oil/gasoline. Excellent weather resistance.
Neoprene – Cloth Inserted -20 to 170 150 1/32 to 1/4 Oil/gasoline. Excellent weather resistance. Handles movement. High tensile strength.
Nitrile (NBR, Buna-N) -25 to 170 150 1/32 to 2 Oil/Aromatic fuels, mineral, animal and vegetable oils, solvents and hydraulic fluid. Available in commercial, premium and FDA grades.
SBR (Red Rubber) -20 to 170 150 1/32 to 1/4 Air, hot/cold water.
SBR – Cloth Inserted -20 to 170 150 1/16 to 1/4 Air, hot/cold water, saturated/ low-pressure steam. Excellent for high compression loads. Handles movement.
Silicone to 400 150 1/32 to 1/4 High-temperature air or water (not oil or steam). Soft. Available in FDA grade.
Vinyl 20 to 160 150 1/16 to 1/4 Water, oxidizing agents. Excellent weather/abrasion resistance
Viton to 400 150 1/32 to 1/4 Oil/Aromatic fuels, mineral, animal and vegetable oils, solvents and hydraulic fluid.
Gasket Material Max temperature (F) Max Pressure (psi) Creep
Relaxation
(%)
Gasket Service Recommended
Non-Asbestos/EPDM 800 1200 15 Steam/oxygenated solvents/
mild organic acids/alkalis. Excellent aging properties.
Non-Asbestos/Hypalon 400 900 40 Strong organic & inorganic acids/oils/aromatic hydrocarbons, powerful oxidizing agents.
Non-Asbestos/Neoprene 800 1200 15 Fuel/oils. Good general purpose material.
Non-Asbestos/Nitrile 800 1500 15 Steam/oil/fuel/solvent. Excellent general purpose material with wide chemical resistance.
Non-Asbestos/Nitrile
(with metal insertion)
850 2500 15 Hot gases. High load/stress environments. Available with galvanized low carbon steel foil or mesh insert.
Non-Asbestos/SBR 800 1500 15 Steam/industrial gases.
Low pressure/temperature.

Gasket Material Max temperature (F) Max Pressure (psi) Creep
Relaxation
(%)
Gasket Service Recommended
Pure PTFE 500 800 35 – 55 Excellent chemical resistance.
Filled PTFE 500 1200 11 – 40 Excellent chemical resistance.
Filled PTFE – Metal Inserted 500 2500 20 Excellent chemical resistance. 316 SS perforated core.
Expanded PTFE 600 3000 30 Excellent chemical resistance. Highly compressible.

 

Gasket Material Max temperature (F) Max Pressure (psi) Creep
Relaxation
(%)
Gasket Service Recommended
Carbon or Graphite/Nitrile 840 1900 20 Excellent for steam. Excellent chemical resistance except for powerful oxidizing agents.
Carbon or Graphite/SBR 900 2000 14 Excellent for steam. Excellent chemical resistance except for powerful oxidizing agents.
Pure Flexible Graphite 950 2100 5 Excellent chemical resistance except for powerful oxidizing agents. Available laminated or homogeneous.
Pure Flexible Graphite – Metal Inserted 950 2800 7 Excellent chemical resistance except for powerful oxidizing agents. Available with 316 SS Foil, Mesh or Tang Core. Available laminated or homogeneous.
Gasket Material Max temperature (F) Gasket Service Recommended
Copper 600 Excellent for steam. Excellent chemical resistance except for powerful oxidizing agents.
Brass 500 Excellent for steam. Excellent chemical resistance except for powerful oxidizing agents.
GHL 212 Excellent chemical resistance except for powerful oxidizing agents. Available laminated or homogeneous.
Grafoil ® 800 Excellent chemical resistance except for powerful oxidizing agents. Available with 316 SS Foil, Mesh or Tang Core. Available laminated or homogeneous.
Titanium 1000 Similar strength to 300 series stainless, but tougher and much less dense. Excellent resistance to chloride solutions (sea water) and bleaching solutions.
Soft Iron, Low Carbon Steel 1000 Soft. Will corrode in water. Mostly used where immersed in liquid hydrocarbons.

Stainless Steel,

Type 304

1000 A general-purpose, soft, corrosion-resistant, non-magnetic stainless that will not harden under heat.

Stainless Steel,

Type 316

1000 Not as strong as 304, but more corrosion-resistant in chemical solutions (except for a limited range of oxidizing acids)

Stainless Steel,

Type 321

1600 Stronger than 304. Used when similar performance to 304 is needed at higher temperatures.

Stainless Steel,

Type 347

1600 More corrosion-resistant and harder than 321.

Stainless Steel,

Type 410

1200 Commonly referred to as “Chrome”. This stainless will harden when heat-treated. It is highly magnetic, hard and strong, but not very corrosion-resistant.

Stainless Steel,

Type 430

1400 More corrosion-resistant than 410, but will not harden when heat-treated. This stainless is soft and no stronger than 300 series stainless.
Nickel 1400 Exhibits good corrosion and erosion resistance at moderate temperatures.
Monel® 1500 A family of nickel/copper alloys that offer greater corrosion and erosion resistance than nickel alone. Particularly useful in seawater applications.
Inconel® 2000 A family of nickel/chromium alloys that are non-magnetic and take corrosion resistance to elevated temperatures.
Hastelloy® 2000 A family of Nickel/chromium/molybdenum alloys for use in highly aggressive chemical environments at elevated temperatures

2 – PROCESS TEMPERATURE

The selected flange gasket should have a reasonable service life expectancy considering the most demanding conditions that the pipeline may experience (highest expected temperature-pressure conditions for high-temperature applications, and lowest temperatures for low-temperature applications).

The temperature-pressure ratings of the common gasket materials are shown in the image below as a general reference.

gaskets and temperaryre - What are Flange Gaskets?

Gasket materials are designed to compress under load to seal the flanges. However, to retain such seal, the gasket should be able to keep a proper sealing surface and not creep significantly (an adverse phenomenon that may be activated by temperature).

3 – PROCESS PRESSURE

The flange gasket should be able to withstand the maximum pressure expected in the pipeline; this is often the test pressure, which can be at least 2 times the flange rating at ambient temperature.

4 – FUGITIVE EMISSIONS LEGISLATIVE CONSTRAINTS

More and more stringent procedures and legislation are coming about in the field of allowed fugitive emissions, and such constraints shall be duly considered during the design of a pipeline and its flanged joints.

5 – OTHER ASPECTS

The other key factors to consider for a proper gasket selection are listed below:

a) Pipeline vibration and oscillation: the gasket shall withstand the oscillations and the vibrations that may affect the pipeline

b) Fluid erosion: a properly selected flange gasket shall withstand the erosion and the corrosion coming from the fluid conveyed by the pipeline. This aspect impacts either the gasket mat, rial, type and size

c) Fluid contamination risk: For some applications, it is important to select flange gaskets materials that do not contaminate the fluid conveyed by the pipeline (for example; pharmaceutical and food applications, or gas pipelines)

d) Flanges corrosion: Some flange materials, such as austenitic stainless steel, are subject to stress corrosion cracking. Therefore, the flange gasket selection should consider the possible impurities that may induce corrosion of the flange’s metal

e) Integrity: When the integrity of a gasket is of prime importance (e.g. when sealing a highly toxic chemical), the choice of the gasket may be influenced by the requirement for a larger safety margin. As an example, a spirally wound gasket with an outer retaining ring may be selected in place of a compressed asbestos fiber gasket.

f) Potential financial impact of gaskets failures: Although a gasket is a relatively inexpensive item in the overall pipeline cost, due care should be given to the proper selection of gaskets to prevent leakages and failures that may generate way larger financial impact

As a general reference, the following table shows the recommended types of gaskets by service, pipeline temperature and pressure rating, and flange facing types:

Guidance gaskets selection 1 - What are Flange Gaskets?

Non-metallic gaskets or soft gaskets (flat, soft, sheet and die-cut gaskets)

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 gasketsspiral woundKammprofile and metal jacketed) are under more demanding service conditions.

die cut gaskets - What are Flange Gaskets?

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).

FF and Ring Gasket - What are Flange Gaskets?

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

soft gaskets - What are Flange 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

gaskets sizes 2 - What are Flange Gaskets?

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

gaskets sizes 2 - What are Flange Gaskets?

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

gaskets sizes 2 - What are Flange Gaskets?

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

Semi-metallic gaskets (Kammprofile, Spiral Wound, and Metal Jacketed gaskets)

SPIRAL WOUND GASKET

Spiral wound gaskets are “semi-metallic” gaskets whose sealing element is a metal strip filled with graphite, PTFE, ceramic fibers and, non-asbestos fibers (filler materials). The metal component of the spiral wound gasket provides strength to the seal, whereas the added fibers enhance conformability and resilience. Inner and outer rings can be added to the core sealing element to facilitate the installation and enhance pressure rating. 

Spiral Wound Gaskets - What are Flange Gaskets?

The dimensions of spiral wound gaskets range from few mm up to 5.000 mm, and the typical thicknesses are 3.2, 4.5, 6.4, and 7.2 mm.

A Spiral wound gasket may be ordered with different shapes, such as oblong, rectangular, oval, pear and diamond. The round type is, of course, the standard shape for raised face (RF), male-and-female (M&F), and tongue-and-groove flanges (T&G) for petrochemical applications.

Flexitallic USA introduced spiral wound gaskets in the petrochemical market back in 1912 to cope with an increasing demand for leak-proof sealing solutions in applications with higher and higher (and fluctuating) temperatures and pressures. Spiral wound gaskets are designed to withstand the mechanical stress generated by severe service conditions of pipeline’s flanged joints with enhanced features than compressed fiber gaskets.

SPIRAL WOUND GASKET TYPES

Spiral wound gaskets are available in different designs depending on:

  • the number of rings (outer and inner)
  • the materials of the inner and the outer ring of the gasket

spiral wound gaskets types - What are Flange Gaskets?

  • Type 00: Spiral Wound Gasket without rings: they are used for tongue and groove, male and female flanges.
  • Type 01: Spiral Wound Gasket with inner ring: they are used for male and female or special flange types.
  • Type 10: Spiral Wound Gasket with outer ring: they are used for raised face flanges.
  • Type 101: Spiral Wound Gasket with inner and outer rings: they are used for raised face flanges.
  • Special Section: Spiral Wound Gasket with special rings: they are used for special flanges and special usage.

Each manufacturer, of course, has a specific way to code such configurations of spiral wound gaskets.

The image shows how the different available types of spiral wound gaskets fit a flanged connection:

profiles of spiral wound gaskets - What are Flange Gaskets?

MATERIALS FOR SPIRAL WOUND GASKET

spiral wound gasket - What are Flange Gaskets?

SPIRAL WOUND GASKET WINDING MATERIALS

The sealing element of a spiral wound gasket is produced by interleaving plies of alternating metal winding strip combined with a filler material. Such formed metal strip in the key sealing element of a spiral wound gasket. The filler material used for the metal strip is usually graphite, even if different materials such as PTFE, ceramic fibers, and non-asbestos materials may be used.

  • SS 304L
  • SS 316L
  • SS 321
  • Titanium
  • Nickel
  • Nickel alloys
  • Duplex

FILLER MATERIALS FOR SPIRAL WOUND GASKET

  • Graphite
  • PTFE
  • Ceramic fibers
  • Non-asbestos

MATERIALS FOR INNER AND OUTER RINGS

The inner and the outer rings of a spiral wound gasket may be the same material of the winding core or a different one. Solid inner rings are required by the ASME B16.20 specification for flanges with pressure rating 900# NPS 24 and larger, 1500# NPS 12 and larger, pressure class 2500#, NPS 4 and larger. The inner ring improves the pressure rating of the spiral wound gasket, as it provides additional compression to the flanged joint and provides a heat and corrosion barrier protecting the gasket windings and the flanges from erosion.

SPIRAL WOUND GASKET MATERIALS MECHANICAL PROPERTIES

 Use scrollbar at the bottom of table.
Spiral Wound Gasket Material
(Commercial Name)
DIN
SPECIFICATION
DIN
MATERIAL NR.
AISI &
UNS
B.S &
ASTM
HARDNESS
HV 10
TEMPERATURE RANGE in C° VOLUMETRIC MASS [G/CM3]
MIN. MAX.
Soft Iron (Armco) 1.1003 90 – 100 -60 500 7.85
Steel (LCS) RSt.37.2 1.0038 100 – 130 -40 500 7.85
Stainless Steel 304 X5CrNi 18 1.4301 304 304S15/16/31 130 – 180 -250 550 7,9
Stainless Steel 304 L X2CrNi 189 1.4306 304L 304S11 130 – 190 -250 550 7,9
Stainless Steel 309 X15CrNiMo 2012 1.4828 309 309S24 130 – 190 -100 1000 7,9
Stainless Steel 316 X5CrNiMo 1810 1.4401 316 316S31/33 130 – 180 -100 550 7,9
Stainless Steel 316 L X2CrNiMo 1810 1.4404 316L 316S11/13 130 – 190 -100 550 7,9
Stainless Steel 316 Ti X10CrNiMoTi 1810 1.4571 316Ti 320S31 130 – 190 -100 550 7,8
Stainless Steel 321 X10CrNiTi 189 1.4541 321 321S12/49/87 130 – 190 -250 550 7,9
Stainless Steel 347 X10CrNiNb 189 1.4550 347 347S31 130 – 190 -250 550 7,9
Nickel 200 Ni 99.2 2,4066 NO2200 3072-76 NA11 90 – 120 -250 600 8,9
Monel 400 NiCu 30 Fe 2.4360 NO4400 3072-76 NA13 110 – 150 -125 600 8,8
Inconel 600 NiCr 15 Fe 2.4816 NO6600 3072-76 NA14 120 – 180 -100 950 8,4
Incoloy 800 X10NiCrAITi 3220 1.4876 NO8800 3072-76 NA15 140 – 220 -100 850 8,4
Incoloy 825 NiCR 21 Mo 2.4858 NO8825 3072-76 NA 16 120 – 180 -100 450 8,14
Hastelloy B2 NMo 28 2.4617 N10665 170 – 230 -200 450 9,2
Hasetlloy C276 ‘NiMo 16Cr15W 2.4819 N10276 170 – 230 -200 450 8.9
Titanium Ti 99,8 3.7025 110 – 140 -250 500 4,5

SPIRAL WOUND GASKET COLOR CODES

Spiral wound gaskets feature colored markings for the winding and the non-metallic fillers

spiral wound gaskets - What are Flange Gaskets?

  • Metallic winding materials: the metallic winding material is designated by a solid color identification around the outside edge of the centering, as shown in the image below
  • Non-metallic filler color coding: the gasket filler materials are designated by a number of stripes placed at equal distances around the edge of the centering ring

swg color coding - What are Flange Gaskets?

WINDING MATERIALS COLOR CODING

Metallic Winding Material for Spiral Wound Gasket Abbreviated Winding
Material Name
Color Code
Carbon steel CRS Silver
304 SS 304 Yellow
304 L SS 304 L No color
309 SS 309 No color
316 L SS 316 L Green
347 SS 347 Blue
321 SS 321 Turquoise
Monel 400 MON Orange
Nickel 200 NI Red
Titanium TI Purple
Hastelloy B HAST B Brown
Hastelloy C HAST C Beige

FILLER MATERIALS COLOR CODING

Polytetrafluoroethylene PTFE White stripe
Mica-graphite Manufacturer’s designation Pink stripe
Flexible graphite F.G. Gray stripe
Ceramic CER Light green stripe
Inconel 600 INC 600 Gold
Inconel 625 INC 625 Gold
Incoloy 800 IN 800 White
Incoloy 825 IN 825 White

MARKINGS ON SPIRAL WOUND GASKET

The illustration shows the configuration of a typical spiral wound gaskets and the usual manufacturers’ markings:

marking of SWG - What are Flange Gaskets?

SPIRAL WOUND GASKET DIMENSIONS (ASME B16.20 FOR ASME B16.5 FLANGES)

Spiral Wound Gasket Class 150 Dimensions

spiral wound - What are Flange Gaskets?

NPS Inner Ring Sealing Element Outer Ring
Inside Diameter (d1) Inside Diameter (d2) Outside Diameter(d3) Outside Diameter (d4)
1/2 14.2 19.1 31.8 47.8
3/4 20.6 25.4 39.6 57.2
1 26.9 31.8 47.8 66.8
38.1 47.8 60.5 76.2
44.5 54.1 69.9 85.9
2 55.6 69.9 85.9 104.9
66.5 82.6 98.6 124
3 81 101.6 120.7 136.7
4 106.4 127 149.4 174.8
5 131.8 155.7 177.8 196.9
6 157.2 182.6 209.6 222.3
8 215.9 233.4 263.7 279.4
10 268.2 287.3 317.5 339.9
12 317.5 339.9 374.7 409.7
14 349.3 371.6 406.4 450.9
16 400.1 422.4 463.6 514.4
18 449.3 474.7 527.1 549.4
20 500.1 525.5 577.9 606.6
24 603.3 628.7 685.8 717.6

NOTES: • All dimensions are in millimeters • Spiral Wound gasket with Inner – and Outer ring • d1 = Inside diameter Inner ring. • d2 = Inside diameter sealing element when no Inner ring is used. • d3 = Outside diameter of sealing element. • d4 = Outside diameter of an Outer ring

The thickness of inner and outer ring: 2.97 mm – 3.33 mm. • Thickness sealing element: 4.45 mm. • Tolerance Outside diameter for NPS 1/2 through NPS 8 is ± 0.8 mm; for NPS 10 through NPS 24 tolerance is + 1.5 mm – 0.8 mm. • There is no class 400 flanges NPS 1/2 thru NPS 3 (use Class 600), class 900 flanges NPS 1/2 thru NPS 2½ (use Class 1500), or class 2500 flanges NPS 14 or larger. 

Spiral Wound Gasket Class 300 Dimensions

spiral wound - What are Flange Gaskets?

%0

NPS Inner Ring Sealing Element Outer Ring
Inside Diameter (d1) Inside Diameter (d2) Outside Diameter (d3) Outside Diameter (d4)
1/2 14.2 19.1 31.8 54.1
3/4 20.6 25.4 39.6 66.8
1 26.9 31.8 47.8 73.2
38.1 47.8 60.5 82.6
44.5 54.1 69.9 95.3
2

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