Flange Bolt Torque Chart: EN 1092-1 PN10 and PN16
A flanged joint seals only when its bolts are tightened to the right load. Too little and it leaks; too much and the gasket is crushed or the bolts yield. This page gives bolt sizes and recommended tightening torques (Nm) for EN 1092-1 PN10 and PN16 flanges.
Bolts and torque by nominal size
Values for grade 8.8 steel bolts, lubricated threads and fibre or spiral wound gaskets. Torque is applied per bolt with a torque wrench.
| DN | PN10 bolts | PN10 torque (Nm) | PN16 bolts | PN16 torque (Nm) |
|---|---|---|---|---|
| 15 | 4 × M12 | 50 | 4 × M12 | 50 |
| 20 | 4 × M12 | 50 | 4 × M12 | 50 |
| 25 | 4 × M12 | 50 | 4 × M12 | 50 |
| 32 | 4 × M16 | 120 | 4 × M16 | 120 |
| 40 | 4 × M16 | 120 | 4 × M16 | 120 |
| 50 | 4 × M16 | 120 | 4 × M16 | 120 |
| 65 | 8 × M16 | 120 | 8 × M16 | 120 |
| 80 | 8 × M16 | 120 | 8 × M16 | 120 |
| 100 | 8 × M16 | 120 | 8 × M16 | 120 |
| 125 | 8 × M16 | 120 | 8 × M16 | 120 |
| 150 | 8 × M20 | 235 | 8 × M20 | 235 |
| 200 | 8 × M20 | 235 | 12 × M20 | 235 |
| 250 | 12 × M20 | 235 | 12 × M24 | 405 |
| 300 | 12 × M20 | 235 | 12 × M24 | 405 |
| 350 | 16 × M20 | 235 | 16 × M24 | 405 |
| 400 | 16 × M24 | 405 | 16 × M27 | 595 |
| 500 | 20 × M24 | 405 | 20 × M30 | 810 |
| 600 | 20 × M27 | 595 | 20 × M33 | 1,100 |
DN65 PN10 flanges with 4 holes, from older DIN practice, are still common. The bolt size is the same (M16), so the torque does not change. See PN10 and PN16 flange compatibility.
Torque by bolt size
The same bolt size appears in several pressure classes. This table gives values by bolt size and grade.
| Bolt | Stress area (mm²) | Preload (kN) | 8.8 lubricated (Nm) | 8.8 dry (Nm) | A2-70 stainless, lubricated (Nm) |
|---|---|---|---|---|---|
| M12 | 84.3 | 27.0 | 50 | 65 | 35 |
| M16 | 157 | 50.2 | 120 | 160 | 85 |
| M20 | 245 | 78.4 | 235 | 315 | 165 |
| M24 | 353 | 113.0 | 405 | 540 | 285 |
| M27 | 459 | 146.9 | 595 | 795 | 420 |
| M30 | 561 | 179.5 | 810 | 1,075 | 570 |
| M33 | 694 | 222.1 | 1,100 | 1,465 | 775 |
How the values were calculated
Values target a bolt preload of about 50% of yield strength, using:
T = K × F × d
T: torque (Nm), K: nut factor, F: preload (kN), d: nominal bolt diameter (mm)
- Grade 8.8: yield strength 640 MPa (EN ISO 898-1).
- A2-70 stainless: yield strength 450 MPa (EN ISO 3506-1).
- Lubricated: K ≈ 0.15 (machine oil or assembly paste). Dry: K ≈ 0.20.
Values are rounded to 5 Nm.
The gasket matters
- Fibre and spiral wound gaskets: the chart values apply.
- Rubber (EPDM, NBR) gaskets: common in water lines. They need less torque and are crushed if overtightened. Use the gasket maker's value.
- PTFE gaskets: they creep. Re-check the torque 24 hours after assembly.
Tightening sequence
Never go straight to final torque. Snug the bolts by hand, then tighten in a star pattern to about 30%, 60% and 100% of the final value. Finish with one pass round the flange at 100%.
EN 1092-1 flanges from Yazıcı Endüstri
Yazıcı Endüstri has manufactured flanges and pipe fittings in Istanbul since 1998 and exports to more than 37 countries. We produce EN 1092-1 flanges from PN 2.5 to PN 400 in carbon and stainless steel, including custom sizes up to DN 3000. See also the flange facing types guide.
Frequently asked questions
What torque for a DN100 PN16 flange?
A DN100 PN16 flange has 8 M16 bolts. For grade 8.8 lubricated bolts with a fibre or spiral wound gasket, about 120 Nm per bolt.
Is the same torque used with rubber (EPDM) gaskets?
No. Rubber gaskets need less torque. Use the gasket maker's value.
Why does lubrication change the torque?
Lubrication lowers friction, so the same torque gives more bolt load. Lubricated bolts are tightened to a lower torque.
This guide is for general information. For project decisions, follow the gasket maker's data, the project specification and, where required, an EN 1591-1 calculation.