ASME B16.5 Class 600 raised-face weld-neck flange dimensions NPS 1/2 through NPS 24: outside diameter O, bolt circle, bolt hole, stud count, stud size and flange thickness tf. High-pressure step in the B16.5 range (60–100 bar service in oil, gas, chemical, refinery and offshore piping). Class 600 keeps 4 studs to NPS 1-1/2, steps to 8 at NPS 2, to 12 at NPS 6, then 16 at NPS 10, 20 at NPS 12–18 and 24 at NPS 20+.
ASME B16.5 Class 600 is the high-pressure step in the B16.5 range, used for 60–100 bar service in oil, gas, chemical, refinery and offshore piping. The class number fixes the bolt pattern, so a Class 600 NPS 4 flange from any maker shares the same 275 mm outside diameter, 215.9 mm bolt circle and eight 7/8-inch studs.
| NPS | OD O (mm) | Bolt circle (mm) | Bolt hole (mm) | No. of studs | Stud size | Flange tf (mm) |
|---|---|---|---|---|---|---|
| 1/2 | 95 | 66.7 | 15.7 | 4 | 1/2 in | 22.4 |
| 3/4 | 115 | 82.6 | 19.1 | 4 | 5/8 in | 25.4 |
| 1 | 125 | 88.9 | 19.1 | 4 | 5/8 in | 27.7 |
| 1-1/4 | 135 | 101.6 | 19.1 | 4 | 5/8 in | 28.4 |
| 1-1/2 | 155 | 114.3 | 22.4 | 4 | 3/4 in | 31.8 |
| 2 | 165 | 127.0 | 19.1 | 8 | 5/8 in | 31.8 |
| 2-1/2 | 190 | 149.4 | 22.4 | 8 | 3/4 in | 35.1 |
| 3 | 210 | 168.3 | 22.4 | 8 | 3/4 in | 38.1 |
| 4 | 275 | 215.9 | 25.4 | 8 | 7/8 in | 44.5 |
| 5 | 330 | 266.7 | 28.4 | 8 | 1 in | 50.8 |
| 6 | 355 | 292.1 | 28.4 | 12 | 1 in | 55.6 |
| 8 | 420 | 349.3 | 31.8 | 12 | 1-1/8 in | 63.5 |
| 10 | 510 | 431.8 | 34.9 | 16 | 1-1/4 in | 69.9 |
| 12 | 560 | 489.0 | 34.9 | 20 | 1-1/4 in | 76.2 |
| 14 | 605 | 527.1 | 38.1 | 20 | 1-3/8 in | 82.6 |
| 16 | 685 | 603.3 | 41.3 | 20 | 1-1/2 in | 88.9 |
| 18 | 745 | 654.1 | 44.5 | 20 | 1-5/8 in | 101.6 |
| 20 | 815 | 723.9 | 44.5 | 24 | 1-5/8 in | 108.0 |
| 24 | 940 | 838.2 | 50.8 | 24 | 1-7/8 in | 120.7 |
Bolt holes are drilled 1/8 in larger than the stud (ASME B16.5 §5.3.4). Class 600 keeps 4 studs to NPS 1-1/2, steps to 8 at NPS 2, to 12 at NPS 6, then to 16 at NPS 10, 20 at NPS 12–18 and 24 at NPS 20 and above. Class 600 studs are ASTM A193 B7 for most services and A193 B16 or B8 for high-temperature or corrosive service.