I used the search function as I thought this would be a very basic question, but I couldn't find the answer.

When using API 650 appendix P.2.5 formulas to calculate shell deflection and rotation the value "t" is used. This is the shell thickness at the opening connection.
In my assumption using the local thickness near the opening (shell + reinforcement plate) would be OK for local stresses near the opening. But for shell deflection and rotation I would suspect the overall shell thickness to be much more important than the local thickening.

Is my interpretation of the code correct (use thickened shell in all formulas) and if so, what's the reason to do this for shell deflection and rotation?

Thanks in advance for your reply,
With regards,
Corné

Actually the curves in Appendix P for stiffness, if you indicate "reinforcing on the shell" assume that there is a pad with a thickness equal to the shell thickness. You really shouldn't specify a value in the "pad thickness" field. (This field exists simply to appease users who insisted, and I got tired of arguing with them.)

All other equations in Appendix P use "t", as you state, which is the overall shell thickness.

Note that Appendix P doesn't really compute shell stresses. To qualify the nozzle you have to draw those figures. Also note that Section P.3 has been deleted from the latest Code Addendum.

Richard thanks for your reply.

Well, I didn't use Tank for the calculations, but I needed to calculate this for the CII analysis and wanted to do this by hand to get a feeling with the formulas.

The formulas for deflection and rotation don't use curves (in my older version of the code that is). But my versions says "t = shell thickness at the opening connection". Which I assumed is shell thickness and pad thickness together.

But if I understand you correctly for all formulas t should be the shell thickness only?

In my version Section P.3 is available. Is this deleted because of the errors it apperently has? It was an easier calculation method than that with the figures. Will something like P.3 be re-instated?

Thanks in advance for your reply,
With regards,
Corné

Yes.



My guess would be "yes", but the Code doesn't give a reason for its changes.



I didn't find it easy, the examples contradicted the body of the Code and there were curves mis-labeled. I couldn't get through it (computation wise) which is why I never put it in our software. Will something like this come back - I don't know. This was a massaged WRC107 method and I'm not a big fan of that bulletin either. Whatever they put in the Code has to be complete, correct, and computationally possible.