Spiral Wound Gasket 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.
| Metal
|
Abbrev.
|
Min. Temp.
|
Max. Temp.
|
Guide Ring Color
|
Guide Ring Color
|
| 304 Stainless Steel
|
304
|
-320 °F
|
1400 °F
|
Yellow
|
|
| 304L Stainless Steel
|
304L
|
|
|
|
|
| 310 Stainless Steel
|
310
|
|
|
|
|
| 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
|
|
| 410 Stainless Steel
|
410
|
|
1560 °F
|
No Color
|
|
| 430 Stainless Steel
|
430
|
|
|
|
|
| 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
|
|
| 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
| Metal
|
Abbrev.
|
Min. Temp.
|
Max. Temp.
|
Guide Ring Color
|
Guide 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
| Sizes
|
Tolerances
|
| Winding
|
Inner & Outer Ring(s)
|
Gasket Thickness
|
Gasket Tolerance
|
Min. Width
|
Max. Width
|
Compressed 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"
|
- Gasket thickness is measured across the metallic ring.
Identification Markings Required by ASME B16.20
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