Spiral Wound Gasket

Written by Matt Milbury on . Posted in Gasket

Dwg spiral wound gasketSpiral wound gasket

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.

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

SizesTolerances
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"

Identification Markings Required by ASME B16.20

Dwg spiral wound gasket identification marking