ASME B16.20 is the international standard for spiral-wound metal gasket — gb/t 4622 / asme b16.20 (series 090). This page sets out what the standard governs, the size range it specifies, and the related standards you will see referenced in datasheets.
ASME B16.20 — Scope
ASME B16.20 specifies the dimensions and tolerances of spiral-wound metal gasket — gb/t 4622 / asme b16.20 (series 090). Material, property class, surface finish and packaging are governed by separate documents in the same standards family (for example ISO 898-1 for the mechanical property classes of bolts and screws).
Tolerance & Product Grades
ASME B16.20, alongside the related GB/T 4622 / ASME B16.20 entries on this site, specifies product grades (typically A or B for fine work and C for general engineering) and tolerance classes for the controlling dimensions. Choose the grade against the precision your application requires.
Dimensions Specified by ASME B16.20
| Nominal pipe size | Inner diameter d1 (mm) | Outer diameter d2 (mm) | Thickness t (mm) | Winding material | Reference standard |
|---|---|---|---|---|---|
| DN15 | 22 | 42 | 4.5 | 304SS + flexible graphite | GB/T 4622 / ASME B16.20 |
| DN20 | 27 | 49 | 4.5 | 304SS + flexible graphite | GB/T 4622 / ASME B16.20 |
| DN25 | 34 | 59 | 4.5 | 304SS + flexible graphite | GB/T 4622 / ASME B16.20 |
| DN32 | 43 | 69 | 4.5 | 304SS + flexible graphite | GB/T 4622 / ASME B16.20 |
| DN40 | 49 | 75 | 4.5 | 304SS + flexible graphite | GB/T 4622 / ASME B16.20 |
| DN50 | 61 | 87 | 4.5 | 304SS + flexible graphite | GB/T 4622 / ASME B16.20 |
| DN65 | 77 | 109 | 4.5 | 304SS + flexible graphite | GB/T 4622 / ASME B16.20 |
| DN80 | 89 | 121 | 4.5 | 304SS + flexible graphite | GB/T 4622 / ASME B16.20 |
| DN100 | 115 | 149 | 4.5 | 304SS + flexible graphite | GB/T 4622 / ASME B16.20 |
| DN150 | 169 | 205 | 4.5 | 304SS + flexible graphite | GB/T 4622 / ASME B16.20 |
Companion Standards
ASME B16.20 controls only the geometry of spiral-wound metal gasket — gb/t 4622 / asme b16.20 (series 090). The mechanical strength is set by ISO 898-1 (bolts and screws) or ISO 898-2 (nuts); the surface finish is governed by separate finish standards (e.g. ISO 4042 for electroplating). For corrosion testing, the relevant document is ISO 9227 (neutral salt spray).
When to Specify ASME B16.20
ASME B16.20 is the inch-based reference; for metric programs choose the ISO equivalent instead.