FEA Flange Study

[PVnew80]

I recently asked a customer for a verification that their custom Flange would be safe to use at a designated pressure - they responded by supplying me with an FEA study that included the following screen shots - see attached.

I'm far from being an FEA expert (infact rarely ever used it) but to me this is in no way representative of the real life scenario, I was just after a more qualified response really?

To start with why model the whole flange when it is axisymmetric, the constraints seem all wrong and the loads wrong - there doesnt seem to be a hydrostatic end force or a gasket load applied and surely the maximum stress is at the hub discontinuity? I think the FEA was performed in solidworks which I am not familiar with.

 

[PVnew80]

here is second image

 

[TGS4]

Good thing you trusted your gut.

You are correct that you should be seeing flange assembly and operating loads - particularly bolt loads as boundary conditions or loads. You should also expect gasket loads.

Punt it back to them. Trust your instincts. Perhaps they can run some VIII-1, Appendix 2 calcs...???

 

[corus]

I can't make out what the restraints or loads are but strictly speaking it's not axisymmetric, if only because of the bolt holes. A better analysis might have been to use symmetry across a 30 or 60 degree segment of the flange. As an approximation it could be said it's axisymmetric if you assumed tha bolts acted around the full circumference, and were well away from the area of interest, say at the intersection of the flange/hub discontinuity only.

 

[PVnew80]

Thanks guys, you're right Corus i should have said cyclic symmetry not axis! Out of interest I had a go at running a study on promechannica using a 60deg section and applying the relevent flamge loads and the results were much more as I'd expect them to be, that said I've managed to get all the details I need and have done some ASME VIII appendix 2 calcs now to make sure!

I always think back to this phrase "Don't confuse convenience with intelligence" when dealing with FEA!