Class 600 Flange Dimensions (ASME B16.5)
Class 600 flanges per ASME B16.5 are designed for high-pressure piping applications. At ambient temperature, a Class 600 carbon steel (ASTM A105) flange is rated for approximately 102 bar (1,480 psi). Class 600 is commonly specified for high-pressure steam, hydrocarbon processing, and gas transmission systems.
Specs Table: Class 600 WN Flange Dimensions (ASME B16.5)
| NPS | DN | Flange OD (mm) | Thickness (mm) | Raised Face Dia. (mm) | Bolt Circle (mm) | No. of Bolts | Bolt Dia. (in) | Bolt Hole Dia. (mm) |
|---|---|---|---|---|---|---|---|---|
| 1/2 | 15 | 95.3 | 14.2 | 34.9 | 66.5 | 4 | 1/2 | 15.7 |
| 3/4 | 20 | 117.5 | 15.7 | 42.9 | 82.6 | 4 | 5/8 | 19.1 |
| 1 | 25 | 124.0 | 17.5 | 50.8 | 88.9 | 4 | 5/8 | 19.1 |
| 1-1/4 | 32 | 133.4 | 20.6 | 63.5 | 98.6 | 4 | 5/8 | 19.1 |
| 1-1/2 | 40 | 155.4 | 22.4 | 73.2 | 114.3 | 4 | 3/4 | 22.4 |
| 2 | 50 | 165.1 | 25.4 | 92.1 | 127.0 | 8 | 5/8 | 19.1 |
| 2-1/2 | 65 | 190.5 | 28.4 | 104.6 | 149.4 | 8 | 3/4 | 22.4 |
| 3 | 80 | 210.0 | 31.8 | 127.0 | 168.1 | 8 | 3/4 | 22.4 |
| 4 | 100 | 273.1 | 38.1 | 157.2 | 215.9 | 8 | 7/8 | 25.4 |
| 5 | 125 | 330.2 | 44.5 | 185.7 | 266.7 | 8 | 1 | 28.4 |
| 6 | 150 | 355.6 | 47.8 | 215.9 | 292.1 | 12 | 1 | 28.4 |
| 8 | 200 | 419.1 | 55.6 | 269.7 | 349.3 | 12 | 1-1/8 | 31.8 |
| 10 | 250 | 508.0 | 63.5 | 323.9 | 431.8 | 16 | 1-1/4 | 35.1 |
| 12 | 300 | 558.8 | 66.5 | 381.0 | 489.0 | 20 | 1-1/4 | 35.1 |
| 14 | 350 | 603.3 | 69.9 | 412.8 | 527.1 | 20 | 1-3/8 | 38.1 |
| 16 | 400 | 685.8 | 76.2 | 469.9 | 603.3 | 20 | 1-1/2 | 41.1 |
| 18 | 450 | 742.9 | 82.6 | 533.4 | 654.1 | 20 | 1-5/8 | 44.5 |
| 20 | 500 | 812.8 | 88.9 | 584.2 | 723.9 | 24 | 1-5/8 | 44.5 |
| 24 | 600 | 939.8 | 101.6 | 692.2 | 838.2 | 24 | 1-7/8 | 50.8 |
Dimensions per ASME B16.5-2020 for welding neck flanges. Raised face height is 6.4 mm (1/4 in) for Class 600, included in the thickness value.
Class 600 vs Lower Classes
| NPS | CL 150 OD (mm) | CL 300 OD (mm) | CL 600 OD (mm) | CL 150 Thickness (mm) | CL 300 Thickness (mm) | CL 600 Thickness (mm) |
|---|---|---|---|---|---|---|
| 4 | 228.6 | 254.0 | 273.1 | 23.9 | 31.8 | 38.1 |
| 6 | 279.4 | 317.5 | 355.6 | 25.4 | 36.6 | 47.8 |
| 8 | 342.9 | 381.0 | 419.1 | 28.4 | 41.1 | 55.6 |
| 10 | 406.4 | 444.5 | 508.0 | 30.2 | 47.8 | 63.5 |
| 12 | 482.6 | 520.7 | 558.8 | 31.8 | 50.8 | 66.5 |
The dimensional increase from Class 300 to Class 600 is substantial. Class 600 flanges at NPS 12 are over twice as thick as Class 150, significantly increasing weight and cost.
When Class 600 Is Specified
- High-pressure hydrocarbon gas lines (typically > 50 bar design pressure)
- High-pressure steam systems (ASME B31.1 power piping)
- Gas transmission pipelines at valve stations
- Services requiring ring joint gaskets (RTJ face) for enhanced sealing integrity
- Wellhead and Christmas tree piping connections in upstream applications
Gasket and Bolt Considerations
Class 600 flanges commonly use spiral wound gaskets (ASME B16.20) for raised face applications and ring joint gaskets for RTJ face configurations. The stud bolt sizes are significantly larger than Class 150/300, requiring higher torque values and often hydraulic tensioning for NPS 10 and above.
For complete welding neck flange dimensions across all ASME B16.5 pressure classes, see the reference tables.
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