KEVOS® MAKEOS · Fasteners
Gasketed Flange Bolt Load Check
Do these flange bolts give enough load to seat the gasket and hold the pressure, and what torque do they need?
Bolt load check for a gasketed bolted flange by the widely used ASME Section VIII Appendix 2 approach: hydrostatic end force and gasket load at operating pressure (gasket factor m), gasket seating load (seating stress y), the required bolt area at the allowable bolt stress, the area provided by the bolts, the load per bolt and the tightening torque from the nut factor.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Design pressure | MPa | Internal design pressure. |
| Diameter at gasket load reaction | mm | Gasket load reaction diameter (per the code: the gasket mean diameter or outside of the contact width less 2b). |
| Effective gasket seating width | mm | Effective gasket seating width from the code’s basic width. |
| Gasket factor m | Gasket factor m for the gasket type (from the code or gasket maker). | |
| Gasket seating stress y | MPa | Minimum design seating stress y for the gasket. |
| Number of bolts | Number of flange bolts. | |
| Bolt diameter | mm | Bolt diameter. |
| Thread pitch | mm | Thread pitch. |
| Allowable bolt stress | MPa | Allowable bolt stress (at ambient for seating; at temperature for operation). |
| Nut factor | Nut factor for the bolt condition. |
Method and formulas
- End force H = π ÷ 4 × G² p; gasket load H_p = 2π b G m p; operating W_m1 = H + H_p.
- Seating W_m2 = π b G y.
- Required bolt area A_m = max(W_m1, W_m2) ÷ S_a; provided = bolts × A_t, A_t = π ÷ 4 (d − 0.9382 P)².
- Load per bolt = max(W_m1, W_m2) ÷ bolts; torque = K F d.
- Example: the flange needs 346.83 kN of bolt load, 28.903 kN and 115.61 N·m per bolt.
Limitations
- Bolt load only; flange ring stresses, rotation and leakage tightness need the full code analysis.
- Gasket factors are user inputs from the code or gasket maker.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Check bolts on a pipe or vessel flange
- Set tightening torque for a gasketed joint
- Compare gaskets by the bolt load they need
Who it is for
- Mechanical engineers
- Maintenance engineers
- Pipefitting supervisors
What you get
- Operating and seating bolt loads
- Required and provided bolt area
- Load and torque per bolt
Interpreting the result
- Soft gaskets need little seating load; spiral-wound and metal gaskets need much more.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1521–1536, 3392–3404. Topic reference; no source tables or recommended settings are reproduced.
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