Recommended stud bolt dimensions for API 6B Flanges to accommodate both R and RX gaskets from 2000 psi to 20000psi rating flanges. Bolt dimensions are based on two nuts. If three nuts are required for bolt tensioning add one nut height to these dimensions.
Nut height may taken equal to bolt diameter.
Bolt dimensions for API 6B 2000 psi flanges
| Flange Size (Inches) |
API Rating (psi) |
Bolt Dia (Inches) |
Length (Inches) |
Length (mm) |
| 26-3/4 | 2000 | 1.75 | 14.25 | 365 |
| 30 | 2000 | 1.625 | 14.5 | 370 |
Bolt dimensions for API 6B 3000 psi flanges
| Flange Size (Inches) |
API Rating (psi) |
Bolt Dia (Inches) |
Length (Inches) |
Length (mm) |
| 26-3/4 | 3000 | 2 | 17.5 | 445 |
| 30 | 3000 | 1.875 | 17.75 | 455 |
Bolt dimensions for API 6B 5000 psi flanges
| Flange Size (Inches) |
API Rating (psi) |
Bolt Dia (Inches) |
Length (Inches) |
Length (mm) |
| 13-5/8 | 5000 | 1.625 | 12.75 | 325 |
| 16-3/4 | 5000 | 1.875 | 14.75 | 375 |
| 18-3/4 | 5000 | 2 | 17.75 | 455 |
| 21-1/4 | 5000 | 2 | 19 | 485 |
Bolt dimensions for API 6B 10000 psi flanges
| Flange Size (Inches) |
API Rating (psi) |
Bolt Dia (Inches) |
Length (Inches) |
Length (mm) |
| 1-13/16 | 10000 | 0.75 | 5.5 | 140 |
| 2-1/16 | 10000 | 0.75 | 5.5 | 140 |
| 2-9/16 | 10000 | 0.875 | 6.5 | 170 |
| 3-1/16 | 10000 | 1 | 7.25 | 185 |
| 4-1/16 | 10000 | 1.125 | 8.5 | 220 |
| 5-1/8 | 10000 | 1.125 | 9.25 | 235 |
| 7-1/16 | 10000 | 1.5 | 11.75 | 300 |
| 9 | 10000 | 1.5 | 13.5 | 345 |
| 11 | 10000 | 1.75 | 15.25 | 390 |
| 13-5/8 | 10000 | 1.875 | 17.75 | 455 |
| 16-3/4 | 10000 | 1.875 | 17.75 | 455 |
| 18-3/4 | 10000 | 2.25 | 22.75 | 580 |
| 21-1/4 | 10000 | 2.5 | 24.75 | 630 |
Bolt dimensions for API 6B 15000 psi flanges
| Flange Size (Inches) |
API Rating (psi) |
Bolt Dia (Inches) |
Length (Inches) |
Length (mm) |
| 1-13/16 | 15000 | 0.875 | 6 | 155 |
| 2-1/16 | 15000 | 0.875 | 6.5 | 170 |
| 2-9/16 | 15000 | 1 | 7.25 | 185 |
| 3-1/16 | 15000 | 1.125 | 8 | 205 |
| 4-1/16 | 15000 | 1.375 | 9.75 | 250 |
| 5-1/8 | 15000 | 1.5 | 11.5 | 295 |
| 7-1/16 | 15000 | 1.5 | 13 | 335 |
| 9 | 15000 | 1.875 | 16 | 410 |
| 11 | 15000 | 2 | 19.5 | 500 |
| 13-5/8 | 15000 | 2.25 | 21.25 | 540 |
| 18-3/4 | 15000 | 3 | 26.75 | 680 |
Bolt dimensions for API 6B 20000 psi flanges
| Flange Size (Inches) |
API Rating (psi) |
Bolt Dia (Inches) |
Length (Inches) |
Length (mm) |
| 1-13/16 | 20000 | 1 | 7.75 | 200 |
| 2-1/16 | 20000 | 1.125 | 8.5 | 220 |
| 2-9/16 | 20000 | 1.25 | 9.5 | 245 |
| 3-1/16 | 20000 | 1.375 | 10.25 | 265 |
| 4-1/16 | 20000 | 1.75 | 12.5 | 320 |
| 7-1/16 | 20000 | 2 | 17.75 | 455 |
| 9 | 20000 | 2.5 | 21.75 | 555 |
| 11 | 20000 | 2.75 | 23.75 | 605 |
| 13-5/8 | 20000 | 3 | 29.75 | 760 |