In API 650 appendix P.1 it states

"This appendix shall be used (unless specified otherwise by the Purchaser on Line 29 of the Data Sheet) for tanks larger than 36 m
(120 ft) in diameter, and only when specified by the Purchaser for tanks 36 m (120 ft) in diameter and smaller. See W.2(5) for
additional requirements."

My question is that for tanks under 36m in diameter if using this appendix has not been specified on the tank datasheet can it still be used to determine acceptable nozzle loads?

I believe that it can. After reading the appendix it seems that the vendors only responsibility in appendix P is providing the and the unrestrained stiffenesses and deflections and then evaluating if the loads are acceptable as per P.2.8.1

"The Manufacturer is responsible for furnishing to the Purchaser the shell stiffness coefficients (see P.2.4) shell deflection and rotation (see P.2.5). The Purchaser is responsible for furnishing to the Manufacturer the magnitude ofthe shell-opening loads (see P.2.6). The Manufacturer shall determine, in accordance with P.2.7, the acceptability of the shell opening loads furnished by the Purchaser. If the loads are excessive, the piping configuration shall be modified so that the shellopening
loads fall within the boundaries of the nomograms constructed as in P.2.7.1."

Since there is nothing physically being done to the tank to make it compliant I would think that if I meet the criteria of appendix P.2 the tank will be safe although it may shift liability for the Nozzle Loadings.

As well since API 650 does not specify any method for determining loads for tanks under 36m. I believe I am not breaking the code by using appendix P.

Any comments from a Safety or Code Compliance stand point?