Flange design??

[Jade24]

Hi,

There is something about flange calculations that I don't understand.
The norm tells you to calculate the loads, and based on the loads how to calculate the moments and then how to calculate the thickness.
Shouldn´t it, at some point, divide the loads through the number of screws?

Because if not, the norm is considering that all the loads are acting at one point, and one big bolt(that has the total area of all the actual bolts)is taking the stress.
For instance, we have that form that gives the gasket seating load(w=(Am+Ab)*S/2), from what I see, the form is considering that the stress caused by the overbolting of all bolts will act at one point when actually the stress is devides at diferent points along the flange.

Of course that I am not saying that the norm is wrong, but I would apreciate if someone would give me a light, and explain me why is the calculation done like that.

Thanks and sorry for english mistakes

 

[jamesl]

It is not necessary to divided by bolts because the forces in opposite direction used in the calc are also total force, not divided among bolts. It will be all cancelled out if the calculation is based on each bolt.

 

[TGS4]

If you think of a flange in a 2D-axisymmetric sense, there really is only one "big" bolt (smeared out around the circumference), etc.