When a nozzle under internal pressure is put at a vertex of a conical or toriconical head is neck thickness calculate by UG-45 or only by UG-27 and 1-5 ?
UG-27 is implicitly called for by UG-45, that is always applicable to nozzles (though I wouldn't define it as a calculation, just minimum requirements).
Then UG-32(g) is of application, and it calls for 1-5. Note that if 1-5 requires a reinforcement on nozzle side and this one is provided by means of a stiffening ring (never seen that though), the nozzle thickness is governed by UG-45.