What is the reasoning behind UG-45 in Sect VIII, Div 1

[nutriarat]

Can someone explain the purpose of the UG-45 for min wall thickness of nozzle necks? If a nozzle opening has sufficient reinforcement and the nozzle neck is thick enough for the service pressure then why is UG-45 necessary?

 

[TomBarsh]

UG-45(a) requires only the minimum thickness "for the loadings", same as for a cylindrical shell. This applies to process connections and to access and inspection openings).

UG-45(b) provides for more stringent requirements for process connections, anything that presumably has a pipe or pipe-like something attaching to it. There will be loads from the attached piping. I suppose the UG-45(b) requirements account for these loads in a general sort of way so that there is a reasonably matching nozzle neck. ie: might not be a good idea to hook up a fire hose to a 1/16" min thk nozzle, might not take the induced loads. If it weren't for these minimum practical requirements we might be forced to be checking every nozzle to assure that it could carry the weight of whatever is attached to it: flanges, piping, etc.

That's my take at least.