ASME VIII-1, Appendix-46 Discussion.

[mechengineer]

Hello everyone,

ASME VIII-1, Appendix 46.
"The design-by-rule requirements in Division 2, Part 4 may be used to design the components for a Division 1 pressure vessel, provided the following conditions are met:
(a) If the thickness of a shell section or formed head is determined using the design rules in Division 2, 4.3
(1) For design of nozzles, any nozzle and its reinforcement attached to that shell section or formed head shall be designed in accordance with Division 2, 4.5."
It looks like that Division 1, UG-27 shall not use for determining shell thickness if use Division 2, 4.5 for opening
The shell thickness is determined by using Division 1, UG-27, which is more conservative option than Division 2, 4.3. In fact, there is a very slight different on the thickness between Division 1, UG-27 and Division 2, 4.3 when use a same allowable stress. Code shall allow to use Division 2, 4.5 (pressure area method for opening reinforcement) to instead of UG-37 (opening area replacement method) & Appendix 1-7 (large opening) and shell, head & nozzle neck thicknesses are determined per Division 1, UG-27.
Division 2, 4.5 is Design Rule for Nozzle Opening. It is the "Pressure Area Method' for opening reinforcement, previous Appendix 1-10 in VIII-1.

 

[TGS4]

Your logic is backwards.

The only thing that is not permitted is to set the wall thickness using VIII-2 using 4.3, and then to return to VIII-1 and use UG-37 for nozzle reinforcement. All other combinations are permitted.