Spiral wound gasket 20" Class 900 — ASME B16.20
Spiral wound gasket 20" Class 900 to ASME B16.20: inner ring id 482.6 mm, sealing element id 520.7 mm, sealing element od 571.5 mm, centering ring od 698.5 mm.
Dimensions of Spiral wound gasket 20" Class 900
| Symbol | Dimension | Value |
|---|---|---|
| d1 | Inner ring ID | 482.6 mm (19.000 in) |
| d2 | Sealing element ID | 520.7 mm (20.500 in) |
| d3 | Sealing element OD | 571.5 mm (22.500 in) |
| d4 | Centering ring OD | 698.5 mm (27.500 in) |
SKU TSH-GASKET-ASME-B16-20-CLASS-900-20 · Standard ASME B16.20 · verified by 2+ sources
Purchase description
SPIRAL WOUND GASKET, 20", CLASS 900, SS316 + GRAPHITE, CS RINGS, ASME B16.20
Available materials: SS316 + graphite, CS rings, SS316 + PTFE, CNAF (non-asbestos), Neoprene / EPDM rubber, Soft iron / SS316 (ring joint).
Notes
- NPS 3–24: flanges.co, Wermac and Piping-World agree. NPS 1/2–1: Piping-World + Wermac + HGFF. NPS 1-1/4–2-1/2: Piping-World; NPS 2 d2/d4 also confirmed by a second source.
- NPS 1-1/4 d1: Piping-World 33.4 vs flanges.co/Wermac/HGFF 33.3 mm; 33.3 kept.
- There are no Class 900 flanges NPS 1/2–2-1/2 in practice — Wermac says use Class 1500.
- XSSeal NPS 2 d2 69.9 / d4 142.7 rejected.
- Thickness: inner/centering ring 2.97–3.33 mm, sealing element 4.45 mm (Wermac). For RF flanges to ASME B16.5.
Same size, other ratings
Other sizes — Spiral wound gasket, Class 900
Frequently asked questions
What are the main types of pipe flanges?
Weld neck (WN), slip-on (SO), blind (BL), socket weld (SW), threaded (THD), lap joint (LJ) and plate flanges. Special types include orifice, long weld neck, reducing flanges and spectacle blinds.
When should I use a weld neck flange instead of a slip-on?
Use weld neck flanges for high pressure, high or cycling temperature, and lines with vibration or fatigue loading. The tapered hub and full-penetration butt weld spread stress smoothly. Slip-on flanges are cheaper and easier to align, but their fatigue life is roughly one third of a WN.
What does Class 150, 300 or 600 mean on a flange?
The ASME class is a pressure-rating designation, not a pressure in psi. The allowable pressure depends on the material group and temperature. A Class 150 A105 flange is rated 19.6 bar at 38 °C but 13.8 bar at 200 °C.
Is a 150# flange rated for 150 psi?
No. A Class 150 carbon-steel flange is rated about 285 psi (19.6 bar) at ambient temperature, and about 170 psi (11.7 bar) at 260 °C. The "150" is a class number.