Spiral Wound Gasket

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Dwg spiral wound gasketA spiral wound gasket is a type of mechanical seal used in piping and pressure vessel applications to prevent leaks and maintain a seal in environments with high temperature and pressure.  It is a combination of metal and filler materials designed to provide resilience, strength, and sealing efficiency.

Spiral Wound Gasket Index

primary components of a spiral wound gasket

  • Metal Winding Strip  -  Typically made of stainless steel, the metal winding strip is wound in a circular fashion, forming the central structural component of the gasket.  The winding strip provides strength and resiliency to the gasket.
  • Filler Material  -  The filler material is usually a soft, compressible material such as graphite, PTFE (polytetrafluoroethylene), or other materials with sealing properties.  The filler material is placed between the layers of the metal winding strip and contributes to the gasket's ability to conform to irregularities in flange surfaces.
  • Outer Ring  -  An outer ring, often made of carbon steel or stainless steel, is added to the outer circumference of the gasket.  It provides additional structural support and helps to center the gasket within the flange.
  • Inner Ring (Optional)  -  In some designs, an inner ring may be included to enhance stability and prevent the filler material from flowing into the pipeline.  The inner ring is often made of the same material as the outer ring.

The winding strip and filler material combination allows the spiral wound gasket to effectively seal joints in flanged connections, preventing the leakage of fluids or gases.  The design enables the gasket to maintain a seal under varying temperature and pressure conditions.  The spiral wound configuration provides resilience, allowing the gasket to adapt to flange surface irregularities and variations.

Spiral wound gaskets are commonly used in industries such as petrochemical, chemical, oil and gas, power generation, and others where there is a need for reliable sealing in demanding conditions.  Proper selection of materials and correct installation are crucial for the effective performance of spiral wound gaskets.

Spiral Wound Gasket per ASME B16.20

  • ASME B16.20 - Metallic Gaskets for Pipe Flanges: Ring-Joint, Spiral-Wound, and Jacketed
  • Inner rings are recommended for all graphite filled gaskets, required for all PTFE filled gaskets, and for NPS 24 and larger in Class 900, NPS 12 and larger in Class 1500, and NPS 4 and larger in Class 2500.
  • The gasket outside diameter tolerance for NPS 1/2 through NPS 8 is ±0.03"; for NPS 10 through NPS 24, +0.06", –0.03".
  • The gasket inside diameter tolerance for NPS 1/2 through NPS 8 is ±0.016"; for NPS 10 through NPS 24, ±0.03".
  • The centering ring outside diameter tolerance is ±0.03".
  • There are no Class 400 flanges in NPS 1/2 through NPS 3 (use Class 600), Class 900 flanges in NPS 1/2 through NPS 2-1/2 (use Class 1500), or Class 2500 flanges NPS 14 and larger.

Spiral Wound Gasket Styles

  • Style RW
    • General purpose gasket suitable for flat face and raised face flanges up to Class 2500 (*)
    • Centering ring accurately locates the gasket on the flange face, provides additional radial strength, and acts as a compression limiter.
    • Spiral winding (sealing element) consists of preformed metal and soft filler material.
  • Style RWI
    • Suitable for flat face and raised face flanges up to Class 2500 (*).
    • Recommended for higher pressure applications, for use with PTFE fillers, and when mandated by ASME B16.20 as follows: NPS 24 and larger in Class 900, NPS 12 and larger in Class 1500, and NPS 4 and larger in Class 2500.
    • Inner ring acts as compression limiter and protects sealing elements from process media attack.
  • Style SW
    • Suitable for tongue and groove, male-female, or groove-to-flat face flanges (**).
    • Spiral winding only, containing preformed metal and soft filler material.
    • Also available with inner rings—Style SWI.

(*) Depending on gasket size, an inner ring is recommended for applications above Class 600, due to the high available bolt load.

(**) This design does not have a compression limiter.


Spiral Wound Gasket Metallic Color Code

In accordance with ASME B16.20 spiral wound gaskets are identified by color coding.  The inside ring of the gasket is paint per the following colors.

MetalAbbrev.Min. Temp.Max. Temp.Guide Ring ColorGuide Ring Color
304 Stainless Steel 304 -320 °F 1400 °F Yellow  
316L Stainless Steel 316L -150 °F 1400 °F Green  
317L Stainless Steel 317L -150 °F 1400 °F Maroon  
321 Stainless Steel 321 -320 °F 1400 °F Turquiose  
347 Stainless Steel 347 -320 °F 1700 °F Blue  
Alloy 20 A-20 -300 °F 1400 °F Black  
Carbon Steel CRS -40 °F 1000 °F Silver  
Hastelloy B HAST B -300 °F 2000 °F Brown  
Hastelloy C276 HAST C -300 °F 2000 °F Beige  
Incolony 800 IN 800 -150 °F 1600 °F White  
Incolony 825 IN 825 -150 °F 1600 °F White  
Inconnel 600 INC 600 -150 °F 2000 °F Gold  
Inconnel X750 INX -150 °F 2000 °F No Color  
Monel 400 MON -200 °F 1500 °F Orange  
Nickel 200 NI -320 °F 1400 °F Red  
Titanium TI -320 °F 2000 °F Purple  


Spiral Wound Gasket Non-Metallic Color Code

MetalAbbrev.Min. Temp.Max. Temp.Guide Ring ColorGuide Ring Color
Ceramic CER -350 °F 2000 °F Light Green  
Flexible Graphite FG -350 °F 950 °F Gray  
PTFE/Teflon 321 -400 °F 500 °F White  
Verdicarb (Mica Graphite) VC -350 °F 600 °F Pink  


Spiral Wound Gasket Thickness

WindingInner & Outer Ring(s)Gasket ThicknessGasket ToleranceMin. WidthMax. WidthCompressed Thickness
0.125" 3/32" 0.125" ±0.005" 3/16" 1" 0.090-0.100"
0.175" 1/8" 0.175" ±0.005" 1/4" 1 1/2" 0.125-0.135"
0.25" 3/16" 0.250" ±0.005" 5/16" 1 1/2" 0.180-0.200"
0.285" 3/16" 0.185" ±0.005" 5/16" 1 1/2" 0.200-0.220"


Spiral Wound Gasket Advantages and Disadvantages

  • Spiral wound gaskets are versatile and can be used in a wide range of applications, including those involving high temperature and pressure.
  • They are designed to withstand high pressures and temperatures, making them suitable for challenging industrial environments.
  • Spiral wound gaskets provide excellent sealing performance and are effective in preventing leaks in flanged connections.
  • They are available in various materials, allowing for compatibility with a wide range of chemical substances.
  • Spiral wound gaskets are durable and have a long service life, making them a reliable choice for sealing applications.
  • The design of spiral wound gaskets allows them to conform to irregularities in flange surfaces, ensuring a tight seal.
  • Compared to some other types of gaskets, spiral wound gaskets can be more expensive.  The cost can vary depending on the materials used.
  • Proper installation is crucial for effective sealing with spiral wound gaskets.  Achieving the correct compression and alignment during installation can be more challenging compared to some other gasket types.
  • The effectiveness of spiral wound gaskets depends on the condition of the flange surfaces.  Smooth and flat flanges are essential for optimal performance.
  • While they are durable, spiral wound gaskets may not be as resilient as certain elastomeric gaskets.  They may not be suitable for applications requiring significant vibration or movement.
  • Selecting the appropriate material for the specific application is critical.  Incompatible materials may lead to corrosion or other issues.


Identification Markings Required by ASME B16.20

Dwg spiral wound gasket identification marking


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