ASME B16.20 Spiral Wound Gasket Dimensions
Gasket OD, ID & Centering Ring OD for ASME B16.5 Flanges
About
ASME B16.20 defines dimensions for metallic gaskets used with pipe flanges. The table below contains data from Table SW 2.1-1 of ASME B16.20-2017, covering spiral wound gasket dimensions for ASME B16.5 flanges in NPS 1/2 through 24.
Use the dimension dropdown to switch between gasket inside diameter, gasket outside diameter, and centering ring outside diameter views. Each view shows dimensions by pressure class.
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Spiral Wound Gasket Table
Select a dimension type and optionally filter by flange size. All dimensions are in inches.
| NPS | 150 (in) | 300 (in) | 400 (in) | 600 (in) | 900 (in) | 1500 (in) | 2500 (in) |
|---|---|---|---|---|---|---|---|
| 1/2 | 0.75 | 0.75 | — | 0.75 | — | 0.75 | 0.75 |
| 3/4 | 1 | 1 | — | 1 | — | 1 | 1 |
| 1 | 1.25 | 1.25 | — | 1.25 | — | 1.25 | 1.25 |
| 1-1/4 | 1.88 | 1.88 | — | 1.88 | — | 1.56 | 1.56 |
| 1-1/2 | 2.13 | 2.13 | — | 2.13 | — | 1.88 | 1.88 |
| 2 | 2.75 | 2.75 | — | 2.75 | — | 2.31 | 2.31 |
| 2-1/2 | 3.25 | 3.25 | — | 3.25 | — | 2.75 | 2.75 |
| 3 | 4 | 4 | — | 4 | 3.75 | 3.63 | 3.63 |
| 3-1/2 | 4.5 | 4.5 | — | 4.13 | — | — | — |
| 4 | 5 | 5 | 4.75 | 4.75 | 4.75 | 4.63 | 4.63 |
| 5 | 6.13 | 6.13 | 5.81 | 5.81 | 5.81 | 5.63 | 5.63 |
| 6 | 7.19 | 7.19 | 6.88 | 6.88 | 6.88 | 6.75 | 6.75 |
| 8 | 9.19 | 9.19 | 8.88 | 8.88 | 8.75 | 8.5 | 8.5 |
| 10 | 11.31 | 11.31 | 10.81 | 10.81 | 10.88 | 10.5 | 10.63 |
| 12 | 13.38 | 13.38 | 12.88 | 12.88 | 12.75 | 12.75 | 12.5 |
| 14 | 14.63 | 14.63 | 14.25 | 14.25 | 14 | 14.25 | — |
| 16 | 16.63 | 16.63 | 16.25 | 16.25 | 16.25 | 16 | — |
| 18 | 18.69 | 18.69 | 18.5 | 18.5 | 18.25 | 18.25 | — |
| 20 | 20.69 | 20.69 | 20.5 | 20.5 | 20.5 | 20.25 | — |
| 24 | 24.75 | 24.75 | 24.75 | 24.75 | 24.75 | 24.25 | — |
Data sourced from ASME B16.20-2017, Table SW 2.1-1.
How to Use This Chart
Spiral wound gaskets consist of alternating layers of metal strip and filler material wound into a spiral. Key dimensions include:
- Gasket ID — inside diameter of the gasket sealing element, varies by pressure class
- Gasket OD — outside diameter of the gasket, grouped by class range (150–600 and 900–2500)
- Centering Ring OD — outside diameter of the centering ring used to locate the gasket on the flange