Square opening in cylindrical vessel

[cn1109]

Hello all, I hope to get some guidance from experienced vessel designers in the forum on the following problem.

I have a 40" OD x 0.25" WALL shell that has a 30" square cutout for a radial branch connection. Stiffener plates (0.25" thick) perpendicular to the shell axis have been welded at the edges and mid-span of the cutout. The stiffener plates do not span the entire circumference of the shell, only a few inches beyond the edges of the cutout. Based on my reading of the Code, there are no rules in VIII-1 to cover this geometry. Without doing FEA, are there other ways to assess the strength of this opening subject to internal pressure?

A colleague suggested that I should determine if the stiffener plates are sufficient to prevent the shell from collapsing subject to an equivalent external pressure. If the shell doesn't collapse then the opening can be deemed adequately reinforced for internal pressure. Is there merit to this approach?

 

[racookpe1978]

Draw the penetration - It doesn't "look" right, "feel" right, nor "smell right" to me.

What pressure do you think this vessel is going to face?
What service?
What fluid/gas/
What cyclic rate of pressure/depressurize?

 

[cn1109]

Attached pdf is a simplified schematic of my problem.

It should be noted that this is an existing design. We would like to increase the operating pressure from 80 psi to 150 psi. Service fluid is water at 200F. Pressure cycling is not a concern.