Flange calculation per EN 1092-1 / AD 2000-B7
Look up EN 1092-1 dimensions and pre-size the bolted joint: required bolt force from internal pressure (assembly, operating and test condition per AD 2000-B7), equivalent pressure for external axial force and bending moment, plus tightening torque and utilisation per bolt. This stage covers pre-sizing, not the full EN 1591-1 verification.
Flange calculator (EN 1092-1 / AD 2000-B7)
Scope: pre-sizing, not the full EN 1591-1 verification
Stage 1 covers pre-sizing per EN 1092-1 / AD 2000-B7 (dimensions, bolt forces, equivalent pressure, tightening torque). The full EN 1591-1 verification (iterative force balance with gasket parameters per EN 13555) is NOT included – it requires manufacturer-specific gasket parameters and the original standards.
Gasket parameters are reference values (only the soft flat gasket is documented); for a verification use manufacturer data per AD 2000-B7 / EN 13555.
Override dimensions and parameters
Forces per load case
| Condition | hydrostatic end force | gasket force | total bolt force |
|---|---|---|---|
| Assembly (seating) | 0 kN | 84.6 kN | 84.6 kN |
| Operating (with pe) | 22.8 kN | 50.7 kN | 73.5 kN |
| Test (p') | 32.6 kN | 42.3 kN | 74.8 kN |
governing: Assembly · Equivalent pressure pe: 16 bar (1.6 N/mm²)
Bolt force, tightening torque, utilisation
Utilisation 13 %- required total force FS,req
- 84.6 kN
- force per bolt
- 10.6 kN
- perm. assembly force FM,perm
- 78.9 kN
- tightening torque MA
- 230 Nm
Tightening torque and permissible assembly preload per VDI 2230 (utilisation 0.9·Rp0.2, tightened to FM,perm). Utilisation = FS,req / (n·FM,perm).
Pre-sizing per EN 1092-1 / AD 2000-B7. Tightness and force estimate, not a flange-ring strength verification and not a full EN 1591-1 verification. Responsibility for the design remains with the user.
Formulas and fundamentals
Internal pressure separates the flanges via the hydrostatic end force FH = (π/4)·dD²·p on the effective gasket diameter dD. A residual seating stress must remain on the gasket: FD,B = π·dD·bD·SD·k1 with the effective width bD, the operating factor k1 and the safety SD = 1.2. The required operating bolt force is FS,B = FH + FD,B.
During assembly the gasket must be seated for the first time. The seating force FD,V = π·dD·bD·k0·KD often exceeds the operating force for soft gaskets and then governs. The test condition uses the test pressure p' (typical 1.43·p). The design value is the maximum: FS,req = max(FD,V, FS,B, FS,P), per bolt FS,req/n.
External piping loads are captured via the Kellogg equivalent pressure: pe = p + 16·|Mb|/(π·G³) + 4·Fax/(π·G²) with G = dD. The bending moment Mb acts as a magnitude, the axial force Fax with its sign (tension increases, compression relieves). The operating force is then recomputed with pe instead of p.
The tightening torque per bolt follows the VDI 2230 approach MA = FM·(0.16·P + 0.58·µG·d2 + µK·dKm/2). The joint utilisation is FS,req against the permissible assembly preload of all bolts n·FM,perm.
Worked example
Example DN100/PN16 (AD 2000-B7): the EN 1092-1 table gives 8 bolts M16 on the bolt circle k = 180 mm. Flat gasket with dD = 134 mm, bD = 8 mm, bore di = 107 mm, internal pressure p = 16 bar = 1.6 N/mm².
Hydrostatic end force FH = (π/4)·134²·1.6 ≈ 22.6 kN (exact from the pressure parts FR ≈ 14.4 kN and FF ≈ 8.2 kN). Operating residual gasket force with k1 = 10 N/mm² and SD = 1.2: FD,B = π·134·8·1.2·10 ≈ 40.4 kN, so FS,B ≈ 63.0 kN.
Seating force during assembly with k0·KD = 20 N/mm²: FD,V = π·134·8·20 ≈ 67.4 kN. It governs (larger than operating and test), so FS,req ≈ 67.4 kN and per bolt ≈ 8.4 kN. Against the permissible assembly force of an M16 8.8 there is ample reserve, the traffic light is green.
Equivalent-pressure example: an additional bending moment Mb = 500 Nm and an axial tension Fax = 2 kN at the same flange give pe = 1.6 + 16·500000/(π·134³) + 4·2000/(π·134²) = 1.6 + 1.06 + 0.14 = 2.80 N/mm² (28 bar). The moderate moment raises the effective pressure by about 75 percent.
Frequently asked questions
Which standards does the flange calculation cover?
The connection dimensions (outside diameter, bolt circle, number and size of bolts, hole diameter) come from EN 1092-1 as a curated selection of common DN/PN combinations. Bolt forces follow the methodology of AD 2000 code sheet B7, the tightening torque uses the VDI 2230 approach and the equivalent pressure follows the Kellogg method.
Is this the full verification per EN 1591-1?
No. This stage covers pre-sizing: dimensions, bolt force from internal pressure and external loads, tightening torque and utilisation. The full EN 1591-1 verification (iterative force balance with gasket parameters per EN 13555, all component compliances and load conditions) is not included, because it requires manufacturer-specific tested gasket parameters and the original standards.
Why does the seating force often govern during assembly rather than the operating pressure?
Soft gaskets must be seated for the first time during assembly with a high surface pressure k0·KD so that they seal at all. This seating force is often larger than the operating sum of hydrostatic end force and residual seating stress. That is why the calculation takes the maximum over all load conditions.
How are external piping loads included?
An external axial force and a bending moment at the flange are converted via the Kellogg equivalent pressure pe into an additional internal pressure that has the same separating effect on the gasket joint. The bolt force is then recomputed with pe instead of p. This is a tightness and lift-off check, not a local flange-ring strength calculation.
Where do the gasket parameters k0·KD and k1 come from?
The default (soft flat gasket, k0·KD = 20, k1 = 10 N/mm²) matches the worked example. The other gasket types are rough, editable order-of-magnitude reference values. For a reliable verification the actual parameters per AD 2000-B7 or the gasket manufacturer (EN 13555) must be used.
Can I enter my own dimensions instead of DN/PN?
Yes. The DN/PN selection fills the outside diameter, bolt circle, number and size of bolts and hole diameter automatically from the EN 1092-1 table. The advanced inputs let you override all dimensions as well as the gasket diameter, effective width and parameters manually.