Background
There are two standards that deal with bending moments on flanged
connections and give a simplified calculation method:- ASME III div.1 par. 3658. Here the equivalent
pressure is calculated from the axial force and bending
moments.
- ASME B31.8 Appendix E Note 14 of table E1. Here
the bending moment to produce leakage of a flanged joint is
calculated.
Both equations are used for an estimation
only. On this web-page both methods are combined in a calculator. In
this way one can manipulate with different figures.
The equivalent pressure method is based on the stresses in the
flange. The ASME B31.8 approach is based on leakage. It is now
possible to determine the maximum bending moment fulfilling both
criteria.
Thus making a quick estimate for different conditions. The final
result can than be calculated with a more detailed analysis.
If the calculated equivalent pressure remains below the allowable
limits than no detailed analysis is necessary.
Example of use:
- Fill out pressure
- Choose bolts and number of
bolts
- Fill out Bolt circle
- Fill out average gasket
diameter
- 'Fill out the horizontal
bending moment
- Press '+ Equivalent Pressure' button. This will add-up the equivalent pressure to the original pressure
- Reduce the elevated pressure
back to its original value
- Press 'Allow. Bending' button
The calculated allowable bending moment will
be higher than the original Horz. bending moment. The newly
calculated boltforce fulfils both the ASME III criteria and the ASME B31.8
criteria. |
