2025 Update to ASME Section VIII, Division 2, Part 5 – Design by Analysis

Abstract The 2025 Edition of ASME Section VIII, Division 2 contains the most substantial revision since the entire Section VIII, Division 2 was rewritten in the 2007 Edition. Below are the highlights of the changes made. The entirety of Part 5 underwent a significant editorial revision. The entire Part is brought into conformance with the ASME Style Guide. Cross-references to paragraphs, equations, figures, and tables have been fixed. Variables in the nomenclature have been cleaned up. And a variety of paragraphs have been simplified using the “Clarity Rewrite” approach that other portions of the Section VIII Code are undergoing. In paragraph 5.2, two stress limits that were in the Code prior to the 2007 rewrite are reinstated: Bearing Stress Limits and Shear Stress Limits. These limits are identical to the limits previously contained in the 2004 Edition. The fatigue screening methods in paragraph 5.5 are also updated. Method B had been updated in the 2023 Edition. A new Method C is introduced, which is almost identical to Method B, except that instead of the smooth-bar fatigue curves, the Structural Stress welded fatigue curves are used. The fatigue analysis methods themselves are also updated, in order to bring them into harmony with API 579-1/ASME FFS-1 (2021), as well as proposed and approved changes that are not yet published in that document. The ratcheting assessment is also updated substantially. The elastic analysis ratcheting limits are changed. Additionally, a new elastic analysis method, based on the Bree Diagrams, is also introduced. A new Section is inserted into Paragraph 5.6, titled, “Protection Against Creep Damage”. This new section details new damage modes that require demonstrating protection against. The first subsection is “Protection Against Stress Rupture From Load-Controlled Loads”. Design-By-Rule methods are referenced, as is an elastic stress analysis method. The second subsection is “Protection Against Stress Rupture From Load-Controlled Loads Plus Occasional Loads”. Again, Design-By-Rules methods are referenced. The third subsection is “Protection Against Creep Buckling”. In this subsection, the analyst is referred to Method B in paragraph 5.4, with modification appropriate for creep - namely using an isochronous stress-strain curve instead of the elastic-plastic curve. The fourth subsection is “Protection Against Failure from Creep Fatigue”. Here, creep-fatigue screening methods are introduced. A specific creep-fatigue analysis methodology has not yet been introduced, although the framework for one is laid out in the form of the paragraph. The fifth and final subsection is “Protection Against Creep Ratcheting”. In this subsection, an elastic analysis methodology is presented. Note that these subsections generally follow the flow of the prior paragraphs in Part 5.