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What are the key differences between ASME Section VIII Division 1 and Division 2 codes?

a. General Scope: Both Division 1 (D1) and Division 2 (D2) cover fabrication, inspection, testing, materials, and design. They also define responsibilities, though D2 formalizes them more deeply.

b. Design By Analysis (DBA): D2 includes Part 5, which is the section dedicated to DBA in Division 2. Division 1 does not include a section on DBA; though it does not prohibit its use. Division 1 allows DBA to supplement the rules included in it, but DBA may not be used to replace rules in Division 1. The user of DBA in D2 may be used to get a more favorable answer for the designer. For example, if a designer is working on a D1 stamped vessel and an aspect of the design is clearly in scope of the D1 method, DBA cannot be used to get around that. A D2 vessel design can get around a DBR method using a DBA method.

c. Design By Rule (DBR): The DBR methods in D2 are often identical or near identical to methods in D1. However, in many cases, the methods have additional scope of coverage or are a different method altogether. For example, the ellipsoidal head method in D2 is the same as Appendix 1-4(f) in D1. The custom flange method in D2 4.16 is the same as Appendix 2 in D1, though the hub factors are determined in an updated way, and 4.16 has built-in support for external loads. The external pressure method in D2 4.4 is a completely different method from the external pressure methods in D1 UG-28, UG-29 and UG-33. It is often more favorable to the designer as well.

d. Style: D1 is in two-column style with figures, nomenclature, tables, etc, placed throughout the text. D2 is in a one-column style with text later followed by nomenclature, tables, and figures in a consistent and ordered fashion in line with ISO standards.

e. Harmonization: As an additional note, the common rules effort is eliminating design rules in D1 that are common with design rules in D2. Instead, the D1 location will point to the D2 location for these common rules. There is also language guiding the D1 user to D2 to supplement D1 methods with the D2 methods, including DBR and DBA.

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