ASME B16.20 — Spiral wound gasket — Class 1500
ASME B16.20 Spiral wound gasket — Class 1500 — 19 sizes.
| NPS | Inner ring ID (d1) (mm) | Sealing element ID (d2) (mm) | Sealing element OD (d3) (mm) | Centering ring OD (d4) (mm) |
|---|---|---|---|---|
| 1/2 | 14.2 | 19.1 | 31.8 | 63.5 |
| 3/4 | 20.6 | 25.4 | 39.6 | 69.9 |
| 1 | 26.9 | 31.8 | 47.8 | 79.5 |
| 1-1/4 | 33.3 | — | — | — |
| 1-1/2 | 41.4 | — | — | — |
| 2 | 52.3 | 58.7 | 85.9 | 143 |
| 2-1/2 | 63.5 | 69.9 | 98.6 | 165.1 |
| 3 | 78.7 | 92.2 | 120.7 | 174.8 |
| 4 | 97.8 | 117.6 | 149.4 | 209.6 |
| 5 | 124.5 | 143 | 177.8 | 254 |
| 6 | 147.3 | 171.5 | 209.6 | 282.7 |
| 8 | 196.9 | 215.9 | 257.3 | 352.6 |
| 10 | 246.1 | 266.7 | 311.2 | 435.1 |
| 12 | 292.1 | 323.9 | 368.3 | 520.7 |
| 14 | 320.8 | 362 | 400.1 | 577.9 |
| 16 | 374.7 | 406.4 | 457.2 | 641.4 |
| 18 | 425.5 | 463.6 | 520.7 | 704.9 |
| 20 | 476.3 | 514.4 | 571.5 | 755.7 |
| 24 | 577.9 | 616 | 679.5 | 901.7 |
- NPS 3–20: HGFF, Piping-World and SJ Senersol agree. NPS 1/2, 2, 24: Piping-World + Wermac. NPS 3/4, 2-1/2: Piping-World (3/4 also SJ Senersol). NPS 1: HGFF.
- NPS 1-1/4 and 1-1/2: only inner ring ID confirmed (Piping-World/Wermac 33.3, 41.4); other cells not recovered. Global Supply Line PDF gives 38.1/44.5 (Class 150-style) — rejected.
- An SJ Senersol row giving NPS 1 d4 85.9 mm is the Class 2500 value; rejected.
- Thickness: inner/centering ring 2.97–3.33 mm, sealing element 4.45 mm (Wermac). For RF flanges to ASME B16.5.
Sources: piping-world.com/spiral-wound-gasket-dimensions-class-1500 · wermac.org/gaskets/dim_gaskets_sw1500.html · hgffgroup.com/spiral_wound_gasket/class-1500-nps-1-2-24/ · sjsenersol.com/wp-content/uploads/2025/07/Technical-Specific