The design of bolted flange connection is required to comply with the ASME Boiler & Pressure Vessel VIII, Division 1, Mandatory Appendix 2, stress requirement and rigidity index check. The requirement for flange rigidity index has been applied to all types of flange design. However the flange rigidity does not consider design parameters, such as temperature variation, different thermal expansion, and effects of shell and tube sheet thickness. Furthermore, the flange rigidity indexes were originally designed within the temperature range of -20F to 366F and below the design pressure of 150psi. Therefore, the flange rigidity index may not be able to accommodate all operation conditions for bolted flange joint.

In this paper, parametric study was performed for standard flanges with 3D finite element model to investigate the flange rigidity. The FE model, which includes flange, gasket and bolt,   was built using the ABAQUS FE software package. To accommodate operation cycle, bolt pre-tension, heat up, and cool down operations were considered in the analysis. NPS 3, 6, 12, 18, 24 for classes 300, 400, 600, 900, 1500, 2500 flanges were selected. For verification parameters, bolt pre-tension, temperature and internal pressure were considered for each flange model. The flange rotation angle was changed to the rigidity index (J). Therefore, the flange rotation angle calculated by FE model was divided by rigidity factor (KI) and it was compared the flange rigidity index. The accuracy of flange rigidity index was verified with FE model.


Verification of Flange Rigidity Index for Standard Flanges Using Finite Element Analysis

Division / Sponsors: 
Pressure Vessels & Piping (PVP)


Paper Proceedings: https://asmedigitalcollection.asme.org/PVP/PVP2020/volume/83815

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