Mastering ASME B16.5 Flange Dimensions
A flange size chart ensures proper fit-up, bolt alignment, and gasket seating. Misreading tables leads to costly mistakes.
Key Dimension Parameters
- NPS
- Nominal Pipe Size (not actual OD for 14 inch+)
- Class
- Pressure rating: 150, 300, 600, 900, 1500, 2500
- Outside Diameter
- Overall flange diameter
- Thickness
- Flange thickness at hub
- Bolt Circle
- Diameter through bolt hole centers
- Number of Bolts
- Increases with NPS and class
Class 150 Dimensions
| NPS | OD | Thickness | Bolt Circle | Bolts |
|---|---|---|---|---|
| 1/2 | 3.50 | 0.44 | 2.38 | 4 |
| 1 | 4.25 | 0.56 | 3.12 | 4 |
| 2 | 6.00 | 0.69 | 4.75 | 4 |
| 4 | 9.00 | 0.81 | 7.50 | 8 |
| 6 | 11.00 | 0.94 | 9.50 | 8 |
| 8 | 13.50 | 1.06 | 11.75 | 8 |
| 10 | 16.00 | 1.12 | 14.25 | 12 |
| 12 | 19.00 | 1.19 | 17.00 | 12 |
Class 300 Dimensions
| NPS | OD | Thickness | Bolt Circle | Bolts |
|---|---|---|---|---|
| 1/2 | 3.75 | 0.56 | 2.62 | 4 |
| 1 | 4.88 | 0.69 | 3.50 | 4 |
| 2 | 6.50 | 0.88 | 5.00 | 4 |
| 4 | 10.00 | 1.12 | 7.88 | 8 |
| 6 | 12.50 | 1.38 | 10.62 | 8 |
| 8 | 15.00 | 1.56 | 13.00 | 8 |
| 10 | 17.50 | 1.69 | 15.25 | 12 |
| 12 | 21.00 | 1.81 | 18.50 | 12 |
Common Mistakes
- Confusing NPS with actual dimensions
- Mixing pressure classes (150 won’t bolt to 300)
- Ignoring facing type (RF vs RTJ)
Songhai Flange provides dimension tables and CAD drawings for all products.
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