Increase thickness of raised face of a flange 2

[ElCidCampeador]

Hi,
suppose that you have a flange in contact with its identical counterflange, both special WN raised faced with RF thickness=2mm. Suppose also a spiralwounded gasket between the two.
This configuration could be easily designed using ASME VIII Div.1 appendix 2.

Now suppose, keeping the other parameters equal, to increase thickness of raised faces to 30mm each one (thickness of the flange "t" used in appendix 2 is kept the same).
Do you think that there are now different stresses in the flanges than previous configuration? It seems that appendix 2 doesn't take into account of this additional height, but do you think it's necessary an additional calculation?

I mean, the length of tie rods for tightening of the flanges should be higher...I could deduce that bolt torque and then forces acting of flanges should be different.

Thank you

 

[r6155]

Do the calculation and see the result.

Regards

 

[ElCidCampeador]

Do the calculation and see the result.

Regards

I've already run appendix 2 calculation with a pressure vessel software and new geometry seems not possible to be integrated...what kind of calculation should I do?

 

[r6155]

Hand calculation.
Regards

 

[ElCidCampeador]

Hand calculation.
Regards

I also suppose by fingers, right?

Why appendix 2 doesn't include this calcs, if so important?

 

[LittleInch]

The forces on the flange are not impacted by the gap between the flange faces.

By "tie rods" do you mean stud bolts??

They will stretch more but the forces will be the same.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[ElCidCampeador]

The forces on the flange are not impacted by the gap between the flange faces.

By "tie rods" do you mean stud bolts??

They will stretch more but the forces will be the same.

Thank you for your answer, so if the thickness of RF would increase more and more, at some point stud bolts could highly plasticize/break, right?

I don't understand why ASME or calculation softwares themselves do not include this case. I've seen many raised face with various dimensions...
More in general, if I put a ring or a plate between 2 flanges that will increase gap between raised faces...as conseguence the length of stud bolts will increase, so I should check against bolts failure, right?

 

[LittleInch]

"at some point stud bolts could highly plasticize/break, right?"

No.

Stud bolts stay below yield stress so yes as they get longer they "stretch" more, but only the same length per unit length (mm/m) which gives the same axial force per bolt.

"I've seen many raised face with various dimensions..."
Have you? Care to mention some?


"so I should check against bolts failure, right?"

Errr, no just make them longer and tighten them to the same axial force as before.

You seem to have not understood how stud bolts work in flanges I think. Length is irrelevant to force or stress if you keep them at the same % of yield stress.

A few sketches might help though.


Remember - More details = better answers
Also: If you get a response it's polite to respond to it.