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ASME Section VIII Division 1 does not provide rules to evaluate thermal stresses, stresses at attachments and supports, stresses in nozzles due to force and moment loading, fatigue (even just fluctuating pressure), and so on. In part, the reason is that the generalized treatment of these items cannot be easily reduced to a rule-based procedure. That is the purpose of the cited code paragraph below (paragraph U-2(g)): to instruct and enable the designer to seek design methodologies that can address these types of issues but that also provide design margins consistent with ASME Section VIII Division 1:
“You can use the design by analysis methods of ASME Section VIII Division 2 ("VIII-2") part 5 for an ASME Section VIII Division 1 ("VIII-1") vessel pursuant to paragraph U-2(g) of VIII-1... so long as we use the same design margins as VIII-1. This "as safe as" clause of paragraph U-2(g) means we cannot use design by analysis to justify a minimum thickness less than the value arrived at by a paragraph in VIII-1. So the "in lieu of" phrase of VIII-2 4.1.1.5 has no effect.”
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