Bolted Flange for Pressure Components

delta

I request if someone can give me some details on how to proceed step by step with a verification of a joint composed by:
- n°2 flange (one blind and one flat) in carbon steel
- n°1 circular flat gasket in klingerite material (asbestos free)
- set of bolt composed by stud-bolt plus 2 washer / 2 nuts each bolt
the joint is subject to internal pressure

thank in advance

delta

In details, my concerning are on how to consider the pretension of bolts, bolt and gasket reactions on Mecaway.

Victor

For bolt pretension, you could use thermal stress to apply a pretension force on solid elements. Alternatively, if you aren't interested in the details of the bolts you could use a spring element with a specified free length so that it's pretensioned. The bolt head would have to be fixed to the flange face using a matching mesh because Mecway doesn't have contact elements yet.

I'm not sure what you mean by bolt and gasket reactions. Do you mean the stresses at the interface between gasket and flange?

Pipe joints aren't my area of expertise so you might have to explain a little more detail.

delta

Dear Victor,
Thanks for answe regarding pretention; I will try and revert you asap.
Regarding bolt and gasket reaction I'm referring to :
- gasket reaction Ht (mean pressure along gasket surface).
- bolt reaction Hg (load on gasket surface determinated by bolt tightening).

Victor

Thanks, I think I understand now -

For gasket reaction, you can turn off visibility of the flange's component(s) in the post-processor (right click the component under Solution, uncheck Visible), leaving the gasket visible, then it'll show the stress on the surface. If you also align the surface with the global coordinates, you can read off the normal stress as Stress XX, YY or ZZ. To obtain numerical values, make a named selection containing the element faces of the gasket, then in the postprocessor, use the Table (right click Solution -> Table) and check that named selection in the list to show only the stress values on the gasket surface.

To separate stress due to bolt tightening from stress due to the fluid pressure, you can use two or three load cases (right click Loads & Constraints -> New load case). One for fluid pressure, one for bolt pretension, and one for both combined.

Heinrich

Hi all (flange calc),
I'm a bit late here, but my advice would be to first do a Appendix 2 calculation in ASME Section VIII, Division 1 or other similar codes.
Determine the gasket loads from this calculation. Use as input in your FEA model, including pressure and depending on external loads you can use symmetry and perform the calc. I've attached a file (picture) on this.