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:
- Non-metallic gaskets or soft gaskets (flat, soft, sheet and die-cut gaskets)
- Semi-metallic gaskets (Kammprofile, Spiral Wound, and Metal Jacketed gaskets)
- Metallic gaskets (Ring Joint gaskets, type R, RX, and BX)
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.
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) |
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.
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:
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 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).
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
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
| 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 |
| 1¼ | 42 | 76 | 83 | 83 | 83 | 89 |
| 1½ | 48 | 86 | 95 | 95 | 95 | 98 |
| 2 | 60 | 105 | 111 | 111 | 111 | 143 |
| 2½ | 73 | 124 | 130 | 130 | 130.2 | 165 |
| 3 | 89 | 137 | 149 | 149 | 149 | 168 |
| 3½ | 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
| 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
| 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 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.
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
- 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:
MATERIALS FOR SPIRAL WOUND GASKET
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
|
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
- 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
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:
SPIRAL WOUND GASKET DIMENSIONS (ASME B16.20 FOR ASME B16.5 FLANGES)
Spiral Wound Gasket Class 150 Dimensions
| 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 |
| 1¼ | 38.1 | 47.8 | 60.5 | 76.2 |
| 1½ | 44.5 | 54.1 | 69.9 | 85.9 |
| 2 | 55.6 | 69.9 | 85.9 | 104.9 |
| 2½ | 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
%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 |
| 1¼ | 38.1 | 47.8 | 60.5 | 82.6 |
| 1½ | 44.5 | 54.1 | 69.9 | 95.3 |
| 2 | ||||
