4 Common Types of metal sealing gaskets
author: www.qishine.com
2026-02-26
1. Spiral Wound Gasket
A spiral wound gasket is a semi-metallic composite gasket made by alternately winding pre-formed metal strips (typically 304, 316 stainless steel, Hastelloy, titanium, etc.) and non-metallic filler materials (graphite, PTFE, ceramic fiber, etc.).
A spiral wound gasket is a semi-metallic composite gasket made by alternately winding pre-formed metal strips (typically 304, 316 stainless steel, Hastelloy, titanium, etc.) and non-metallic filler materials (graphite, PTFE, ceramic fiber, etc.).
Based on their structure, spiral wound gaskets can be classified into the following types:
Type A (Basic Type): No inner nor outer ring.
- Suitable for: General service conditions with pressure below 5.0 MPa and temperatures from -200°C to +600°C.
- Typical Applications: Pipeline flange connections for non-corrosive media like regular water, oil, and steam.
- Matching Flanges: Raised face (RF) flanges, requiring sufficient bolt load to ensure sealing.
- Suitable for: General service conditions with pressure below 5.0 MPa and temperatures from -200°C to +600°C.
- Typical Applications: Pipeline flange connections for non-corrosive media like regular water, oil, and steam.
- Matching Flanges: Raised face (RF) flanges, requiring sufficient bolt load to ensure sealing.
Type A Spiral Wound Gasket Only the Basic Ring
Type B Spiral Wound Gasket Include Basic Ring and Inner Ring
Type B (With Inner Ring): Equipped with an inner ring.
- Suitable for: Applications with frequent pressure fluctuations, thermal cycling, or prone to blow-out.
- Key Advantage: The inner ring prevents over-compression of the gasket, controls bolt load, and shields the inner windings from erosion by the medium.
- Typical Applications: Heat exchangers in petrochemical plants, high-temperature steam systems, inlet/outlet flanges of reciprocating pumps.
- Matching Flanges: Raised face flanges; inner ring material must be compatible with the medium.
- Suitable for: Applications with frequent pressure fluctuations, thermal cycling, or prone to blow-out.
- Key Advantage: The inner ring prevents over-compression of the gasket, controls bolt load, and shields the inner windings from erosion by the medium.
- Typical Applications: Heat exchangers in petrochemical plants, high-temperature steam systems, inlet/outlet flanges of reciprocating pumps.
- Matching Flanges: Raised face flanges; inner ring material must be compatible with the medium.
Type C (With Outer Ring): Equipped with an outer ring.
- Suitable for: High-pressure (up to 25 MPa), high-temperature applications and situations requiring high flange alignment.
- Core Function: The outer ring provides centering, prevents radial displacement of the gasket, and facilitates installation alignment.
- Special Applications: Flange connections on large equipment where maintenance is difficult, or where precise alignment is critical.
- Matching Flanges: Raised face flanges; the outer ring protects the wound layer from mechanical damage.
- Suitable for: High-pressure (up to 25 MPa), high-temperature applications and situations requiring high flange alignment.
- Core Function: The outer ring provides centering, prevents radial displacement of the gasket, and facilitates installation alignment.
- Special Applications: Flange connections on large equipment where maintenance is difficult, or where precise alignment is critical.
- Matching Flanges: Raised face flanges; the outer ring protects the wound layer from mechanical damage.
Type C Spiral Wound Gasket Include Basic Ring and Outer Ring
Type D Spiral Wound Gasket Include Basic Ring, Inner Ring and Outer Ring
Type D (With Inner & Outer Rings): Equipped with both inner and outer rings.
- Suitable for: Critical sealing points under extreme conditions, demanding the highest overall performance.
- Condition Characteristics: High pressure (up to 42 MPa), severe thermal cycling (temperature differential >300°C), corrosive media.
- Typical Applications: Main steam systems in nuclear power plants, hydrogenation reactors, critical connections in supercritical boilers.
- Key Advantage: The outer ring ensures centering and alignment, while the inner ring prevents blow-out and media erosion, providing the most reliable seal.
- Suitable for: Critical sealing points under extreme conditions, demanding the highest overall performance.
- Condition Characteristics: High pressure (up to 42 MPa), severe thermal cycling (temperature differential >300°C), corrosive media.
- Typical Applications: Main steam systems in nuclear power plants, hydrogenation reactors, critical connections in supercritical boilers.
- Key Advantage: The outer ring ensures centering and alignment, while the inner ring prevents blow-out and media erosion, providing the most reliable seal.
2. Metallic Ring Joint Gasket
A metallic ring joint gasket is a solid, one-piece metal ring with a cross-section precisely machined to achieve sealing via line or area contact.
A metallic ring joint gasket is a solid, one-piece metal ring with a cross-section precisely machined to achieve sealing via line or area contact.
Metallic Ring Joint Gasket Include Type R - Octagonal, Type R - OVAL, Type RX, Type Bx, etc.
Based on cross-sectional shape, metallic ring gaskets can be divided into:
R Type Octagonal Ring Gasket
- Cross-section: Regular octagonal shape, with both inner and outer angled surfaces at 23°.
- Dimensions: The gasket's mean diameter is 0.1-0.4 mm larger than the groove's mean diameter for an interference fit.
- Contact Characteristic: Forms 23° angled surface contact with the groove, creating a "wedging effect."
- Applicable Flanges: Modern flat-bottom groove flanges (API 6A Type 6B groove).
- Sealing Mechanism: Initial line contact transforms into area contact under bolt preload; sealing stress is enhanced by high internal pressure.
- Applications: High-pressure pipelines in petrochemical plants, Christmas tree equipment, main seals for pressure vessels. Working pressure typically 15-70 MPa.
- Cross-section: Regular octagonal shape, with both inner and outer angled surfaces at 23°.
- Dimensions: The gasket's mean diameter is 0.1-0.4 mm larger than the groove's mean diameter for an interference fit.
- Contact Characteristic: Forms 23° angled surface contact with the groove, creating a "wedging effect."
- Applicable Flanges: Modern flat-bottom groove flanges (API 6A Type 6B groove).
- Sealing Mechanism: Initial line contact transforms into area contact under bolt preload; sealing stress is enhanced by high internal pressure.
- Applications: High-pressure pipelines in petrochemical plants, Christmas tree equipment, main seals for pressure vessels. Working pressure typically 15-70 MPa.
R Type Oval Ring Gasket
- Cross-section: Oval shape with continuously changing curvature radius.
- Contact Method: Initial two-point line contact develops into an oval contact band upon compression.
- Compatibility: Suitable for both circular and flat-bottom groove flanges.
- Relative Efficiency: Sealing efficiency is about 80-90% of the octagonal ring's, but offers better flexibility.
- Special Advantage: Has some compensation ability for flange misalignment and rotation.
- Typical Applications: Traditional refinery units, medium-to-high pressure heat exchangers, older high-pressure valves.
- Cross-section: Oval shape with continuously changing curvature radius.
- Contact Method: Initial two-point line contact develops into an oval contact band upon compression.
- Compatibility: Suitable for both circular and flat-bottom groove flanges.
- Relative Efficiency: Sealing efficiency is about 80-90% of the octagonal ring's, but offers better flexibility.
- Special Advantage: Has some compensation ability for flange misalignment and rotation.
- Typical Applications: Traditional refinery units, medium-to-high pressure heat exchangers, older high-pressure valves.
RX Type Pressure-Energized Ring Gasket
- Improvement Basis: Optimized from the R type octagonal ring with a specially designed cross-section.
- Key Feature: Outer surface has pressure-activation grooves; internal cavity structure is optimized.
- Pressure Response: Medium pressure enters behind the gasket via the outer grooves, increasing sealing contact pressure with rising internal pressure.
- Standards: Fully compliant with the latest API 6A and ASME B16.20 specifications.
- Pressure Range: Design pressure up to 34.5 MPa (5,000 PSI).
- Special Applications: Deep-sea drilling equipment, high-pressure water injection systems, sour gas (H₂S-containing) environments.
- Installation Note: Requires strict control of bolt tightening sequence to avoid gasket distortion.
- Improvement Basis: Optimized from the R type octagonal ring with a specially designed cross-section.
- Key Feature: Outer surface has pressure-activation grooves; internal cavity structure is optimized.
- Pressure Response: Medium pressure enters behind the gasket via the outer grooves, increasing sealing contact pressure with rising internal pressure.
- Standards: Fully compliant with the latest API 6A and ASME B16.20 specifications.
- Pressure Range: Design pressure up to 34.5 MPa (5,000 PSI).
- Special Applications: Deep-sea drilling equipment, high-pressure water injection systems, sour gas (H₂S-containing) environments.
- Installation Note: Requires strict control of bolt tightening sequence to avoid gasket distortion.
BX Type Ultra-High Pressure Ring Gasket
- Design Breakthrough: A special octagonal ring gasket developed for extreme high-pressure environments.
- Core Innovation: Incorporates internal pressure-balancing holes to ensure uniform pressure distribution on sealing faces.
- Pressure: Working pressure up to 138 MPa (20,000 PSI), with special designs reaching 207 MPa.
- Standards: Manufactured strictly per API 6A, specifically for API 6BX type flanges.
- Safety Feature: Internal channels balance cavity pressure, preventing sudden pressure shocks.
- Typical Applications: Wellhead equipment for ultra-deep wells (>6000 meters), high-pressure hydrogen storage, supercritical water oxidation systems.
- Installation Requirement: Requires hydraulic torque wrenches and multi-stage preloading following a specific sequence.
- Design Breakthrough: A special octagonal ring gasket developed for extreme high-pressure environments.
- Core Innovation: Incorporates internal pressure-balancing holes to ensure uniform pressure distribution on sealing faces.
- Pressure: Working pressure up to 138 MPa (20,000 PSI), with special designs reaching 207 MPa.
- Standards: Manufactured strictly per API 6A, specifically for API 6BX type flanges.
- Safety Feature: Internal channels balance cavity pressure, preventing sudden pressure shocks.
- Typical Applications: Wellhead equipment for ultra-deep wells (>6000 meters), high-pressure hydrogen storage, supercritical water oxidation systems.
- Installation Requirement: Requires hydraulic torque wrenches and multi-stage preloading following a specific sequence.
3. Serrated Metal Gasket
A serrated metal gasket is a high-precision gasket made from a metal plate with concentric serrated grooves precisely machined on both sides. Its features include:
- Double-sided symmetrical serrations: Both sides have concentric circular serrations with a depth of 0.05-0.1 mm.
- Serration Parameters: Pitch 0.5-1.0 mm, tooth angle 60-90°, crest width 0.05-0.1 mm.
- Material Selection: Soft iron, low-carbon steel, stainless steel, aluminum, copper, etc., with hardness ranging HB90-250.
- Surface Treatment: Often tin-plated, silver-plated, or coated with graphite to reduce the friction coefficient.
- Flexible Design: Gasket thickness is typically 1.5-3.0 mm to ensure sufficient elastic deformation capacity.
A serrated metal gasket is a high-precision gasket made from a metal plate with concentric serrated grooves precisely machined on both sides. Its features include:
- Double-sided symmetrical serrations: Both sides have concentric circular serrations with a depth of 0.05-0.1 mm.
- Serration Parameters: Pitch 0.5-1.0 mm, tooth angle 60-90°, crest width 0.05-0.1 mm.
- Material Selection: Soft iron, low-carbon steel, stainless steel, aluminum, copper, etc., with hardness ranging HB90-250.
- Surface Treatment: Often tin-plated, silver-plated, or coated with graphite to reduce the friction coefficient.
- Flexible Design: Gasket thickness is typically 1.5-3.0 mm to ensure sufficient elastic deformation capacity.
Serrated Metal Gasket include Outer Guide Ring, Serrated surface made from solid metal core and soft facing filler material
Applicable Conditions
- Medium-to-high pressure range: Working pressure 4.0-20 MPa, up to 42 MPa maximum.
- Temperature range: -200°C to +600°C.
- Media types: Steam, oil & gas, hydrogen, ammonia, organic solvents, etc.
- Flange types: Raised face (RF), flat face (FF), male-and-female (MFM) flanges.
- Medium-to-high pressure range: Working pressure 4.0-20 MPa, up to 42 MPa maximum.
- Temperature range: -200°C to +600°C.
- Media types: Steam, oil & gas, hydrogen, ammonia, organic solvents, etc.
- Flange types: Raised face (RF), flat face (FF), male-and-female (MFM) flanges.
Special Application Scenarios
- Hydrogen systems: The serrated structure effectively prevents hydrogen molecule permeation and leakage.
- Reciprocating equipment: Inlet/outlet flanges for compressors and pumps, resistant to vibration and pressure pulsation.
- High-temperature bolting: Reduces sealing failure caused by bolt creep at high temperatures.
- Hard-to-access maintenance points: Long-term reliability reduces maintenance frequency.
- Hydrogen systems: The serrated structure effectively prevents hydrogen molecule permeation and leakage.
- Reciprocating equipment: Inlet/outlet flanges for compressors and pumps, resistant to vibration and pressure pulsation.
- High-temperature bolting: Reduces sealing failure caused by bolt creep at high temperatures.
- Hard-to-access maintenance points: Long-term reliability reduces maintenance frequency.
4. Corrugated Metal Gasket
A corrugated metal gasket is a flexible gasket formed by thin metal sheets (0.1-0.5 mm) precision-rolled or stamped into a regular corrugated pattern. Its features include:
- Corrugation Geometry: Sine wave, rectangular wave, or trapezoidal wave, with wavelength 2-10 mm and wave height 0.3-2.0 mm.
- Multi-layer Structure: Typically 2-4 layers of corrugated metal are laminated, with non-metallic materials optionally sandwiched between layers.
- Material Combination: Stainless steel corrugated sheets + graphite filler, or special alloy corrugated sheets + ceramic fiber.
- Edge Treatment: Edges are often enclosed by a metal outer ring or fitted with locating tabs.
- Cross-section Optimization: Precise control of crest and trough radii ensures uniform stress distribution.
A corrugated metal gasket is a flexible gasket formed by thin metal sheets (0.1-0.5 mm) precision-rolled or stamped into a regular corrugated pattern. Its features include:
- Corrugation Geometry: Sine wave, rectangular wave, or trapezoidal wave, with wavelength 2-10 mm and wave height 0.3-2.0 mm.
- Multi-layer Structure: Typically 2-4 layers of corrugated metal are laminated, with non-metallic materials optionally sandwiched between layers.
- Material Combination: Stainless steel corrugated sheets + graphite filler, or special alloy corrugated sheets + ceramic fiber.
- Edge Treatment: Edges are often enclosed by a metal outer ring or fitted with locating tabs.
- Cross-section Optimization: Precise control of crest and trough radii ensures uniform stress distribution.
Corrugated metal gasket Formed through precise rolling or stamping, include metal corrugations and soft facing material
Applicable Scenarios
- Low-load sealing: Situations with limited bolt load, requiring only about 30% of the compressive force needed for flat gaskets.
- High-temperature fluctuations: -250°C to +800°C (up to +1000°C without filler layers).
- Large-diameter flanges: Diameters up to 3000 mm and above, compensating for flange deflection.
- Dissimilar material connections: Connecting carbon steel to stainless steel, or metal to non-metal flanges.
- Low-load sealing: Situations with limited bolt load, requiring only about 30% of the compressive force needed for flat gaskets.
- High-temperature fluctuations: -250°C to +800°C (up to +1000°C without filler layers).
- Large-diameter flanges: Diameters up to 3000 mm and above, compensating for flange deflection.
- Dissimilar material connections: Connecting carbon steel to stainless steel, or metal to non-metal flanges.
Structural Variants and Applications
A. All-Metal Corrugated Gasket
- Structure: Multiple layers of the same metal corrugated sheets laminated.
- Advantages: High-temperature resistance, radiation resistance, non-contaminating.
- Applications: Nuclear reactors, high-temperature cracking furnaces, vacuum metallurgy equipment.
A. All-Metal Corrugated Gasket
- Structure: Multiple layers of the same metal corrugated sheets laminated.
- Advantages: High-temperature resistance, radiation resistance, non-contaminating.
- Applications: Nuclear reactors, high-temperature cracking furnaces, vacuum metallurgy equipment.
B. Corrugated Gasket with Filler Layer
- Structure: Corrugated metal + graphite/PTFE/mica filler layer.
- Advantages: Good low-temperature sealing, chemical corrosion resistance.
- Applications: Chemical pipelines, low-temperature storage tanks, food & pharmaceutical equipment.
- Structure: Corrugated metal + graphite/PTFE/mica filler layer.
- Advantages: Good low-temperature sealing, chemical corrosion resistance.
- Applications: Chemical pipelines, low-temperature storage tanks, food & pharmaceutical equipment.
C. Corrugated Gasket with Outer Ring
- Structure: Corrugated core + locating outer ring.
- Advantages: Accurate installation positioning, strong blow-out resistance.
- Applications: Large heat exchangers, tower flanges, hard-to-maintain locations.
- Structure: Corrugated core + locating outer ring.
- Advantages: Accurate installation positioning, strong blow-out resistance.
- Applications: Large heat exchangers, tower flanges, hard-to-maintain locations.
Metallic seal gaskets, as critical components in industrial sealing, directly impact equipment safety, energy consumption control, and environmental protection. Engineers should make scientifically sound selections based on specific operating parameters, medium characteristics, flange conditions, and economic factors, incorporating the technical details provided herein. Strict adherence to specifications during installation and maintenance is essential to ensure the long-term, reliable operation of the sealing system.
Qishine is ideal choice for EPC companies and project contractors.
Website: www.qishine.com
Email: qishine@qishine.com
Tel: 0592-5225595
Email: qishine@qishine.com
Tel: 0592-5225595
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