I am trying to determine wether a tangential nozzle (with external loadings) on a pressure vessel needs a reinforcing pad. Does ASME address this issue?
Yes, it does. But not completely. Neglecting the external loadings, you need to determine the size of the cut (long dimension) that you're making into the vessel to see whether you'll need additional reinforcement. A 2" NPS true tangential nozzle might easily have a cutout which exceeds 3" and thus requires reinforcement to be considered.
The external loadings can be evaluated using FEA or a WRC107/297 approach. Just use the appropriate opening size depending on the loading, and translate the loadings to be on a "normal" radial nozzle coordinate system relative to the shell i.e. a "radial" load relative to the tangential nozzle is a shear load as far as the shell is concerned, etc. Use UG-24(e) for evaluating your results.
Now, to throw some more fuel into what started as a reasonably simple thread... If you do not require a repad for the external loadings but you do for internal pressure you can consider using Fig. UG-37 provided you are not using a repad. This will allow you to reduce the area of reinforcement required depending on what plane you are looking at. The tangential nozzle cutout will have a short dimension parallel to the long seam and a long dimension parallel to a circ seam. The force applied to the cutout in each direction will vary (stress*area), but keep in mind that the circ stress is double the long stress. So... with perhaps a LWN nozzle you may wind up not needing reinforcement if you recognize that the loading on the hole varies and apply the F factor presented in Fig. UG-37. Note that the F factor must be 1 unless you are dealing with an integrally reinforced nozzle [see UW16(c)(1)]. Weld buildup may be used to augment the area of reinforcement while maintaining the status of "integrally reinforced." Note that weld buildup "which is an integral part of the shell or nozzle wall" may be used, not merely oversized fillet welds.
