mariog,
Thanks for your response. Just calling it like I see it. One of the plates in the annular bottom ring is different than all the others. It has a much larger surface area than the others to account for the 48" field cut tank inlet. This plate is butt welded per API 650 just like the remainder of the annular bottom ring plates.
For this reason any "opening" in annular plates should be avoided.
I don't consider myself an API 650 expert. Just curious, is the above statement in API 650? If so, could you please cite the section within API 650? FYI, this tank was designed and built in the 1970s.
Without FEA tools at my disposal, it seems that the most logical thing to do would be to model as danb stated (thanks danb); recreate the old and compare the old connection loads to the new config connection loads. If the client accepts this approach, I'll pursue this approach.
it is very difficult to count realistic "imposed displacements and rotations" in these two points other than by following a FEA analysis.
Utilizing CII, if I approach the problem as danb states (comparing the old tank line config to the new), it would seem to me that the difficultly to account for realistic "imposed displacements and rotations" would basically be simplified into whatever is assumed for the old config should be assumed for the new config. For example, if the old tank line connection to tank bottom is modeled as rigid, the new tank line connection would be modeled as a rigid. If one is flexible, the other has the same flexibility. If one has imposed displacements and rotations, the other would have the same imposed displacements and rotations, etc., etc......in any case the new loads at this connection should be less than the old. Thoughts anyone?