Nozzle neck x manhole thickness

[torsani]

Hi
What are the reasons to consider UG-45(b)(1), (2), (3) and (4) only for nozzle neck thickness and not for manhole thickness?

 

[gr2vessels]

torsani,
The Manway is a nozzle, perhaps less stressed than a process nozzle connected to the plant piping. That is, the UG-45 applies in full for the sizing of the Manway nozzle neck thickness.
cheers,
gr2vessels

 

[vesselfab]

manholes and other inspection openings are not subject to external loads from piping

 

[doct9960]

torsani,

UG-45(a) applies to nozzle necks or other connections (INCLUDING access openings and inspection openings)

UG-45(b) applies to nozzle necks or other connections (EXCEPT for access openings and inspection openings)

A manhole is basically an access opening. Therefore, UG-45(a) is the applicable paragraph for determining its minimum neck thickness.

The probable reason why the ASME Committee formulated UG-45(b) is to account for external loads from piping.

 

[gr2vessels]

gents,
The design of a manway could be simple or complex, therefore the various sub-clauses of UG-45 may apply selectively or in full. It is not unusual to lift the vertical vessel by the lugs welded to the top manway cover, as well as inserting a pressure relief nozzle / valve on the manway cover, including some piping with their own loads, affecting the design of the manway. Sometimes, you hang a few internals to the manway cover also, hence the manway design turns into a ordinary nozzle design.
cheers,
gr2vessels