ASME B16.5 Class 900 — NPS 8" Flange Dimensions
An ASME B16.5 Class 900 NPS 8" flange (DN 200) is a forged steel pipe flange rated to153.2 bar (2220 psi) at ambient temperature for Group 1.1 carbon steel. It is used in process piping systems wherever the design pressure and temperature fall within the Class 900 pressure-temperature rating envelope defined in ASME B16.5.
| Dimension | Imperial (in) | Metric (mm) |
|---|---|---|
| Flange OD | 21.75" | 552.4 mm |
| Bolt Circle Diameter (BCD) | 18.00" | 457.2 mm |
| Number of Bolt Holes | 12 | — |
| Bolt Hole Diameter | 1.62" | 41.1 mm |
| Bolt Size (stud) | 1-1/2" | 38.1 mm |
| Raised Face OD | 10.62" | 269.7 mm |
| Minimum Thickness | 3.25" | 82.5 mm |
| Approx. Weight — Weld Neck (kg)* | 204.1 kg | — |
Disclaimer: These dimensions are provided for reference only. Always verify against the current edition of ASME B16.5 before using in engineering calculations, fabrication drawings, or procurement documents. Dimensions for Class 900, 1500, and 2500 are reference approximations — class-specific tolerances and ratings must be confirmed from the standard.
Common Materials
Class 900 NPS 8" flanges are typically carbon steel ASTM A105 (forged) or stainless steel ASTM A182 F304 / F316L. For elevated temperatures above 340 °C (650 °F), chrome-moly grades such as A182 F11 or F22 are specified. Confirm the material group against the ASME B16.5 pressure-temperature tables for your design conditions. Use the Flange Weight Calculator to estimate weights for different materials and flange types.
Frequently Asked Questions
What is an ASME B16.5 Class 900 NPS 8" flange?
A forged steel pipe flange conforming to ASME B16.5, NPS 8" (DN 200), pressure class 900. The flange OD is 21.75" (552.4 mm) with 12 bolt holes on a 18" bolt circle. It is rated to approximately 153.2 bar (2220 psi) at ambient for Group 1.1 carbon steel.
What material is a Class 900 NPS 8" flange?
Common materials include ASTM A105 (carbon steel, forged), ASTM A182 F304/F316L (stainless steel), and ASTM A182 F11/F22 (chrome-moly alloy for high-temperature service). The choice depends on the fluid service, maximum design temperature, and corrosion requirements.
How does Class 900 differ from Class 1500 for NPS 8"?
Class 900 is rated to 153.2 bar (2220 psi) at ambient, while Class 1500 is rated to 255.3 bar (3705 psi). The Class 1500 flange for NPS 8" has a larger OD and heavier bolting to achieve the higher pressure rating. Always confirm the required class from the piping design specification before procurement.