ASME Boiler Pressure Vessel Code, Section III, Division 1, Subsection NC, Class 2 components, and Subsection ND, Class 3 components, have significant technical and administrative similarities. The ASME BPV III Standards Committee has a long-standing goal of combining these two subsections (NC and ND). Consolidating Subsections NC and ND will simplify, reduce repetitions and make the Code easier to use. Additionally, a combined Subsection NC/ND will simplify Code maintenance. To facilitate this consolidation, the Subgroup on Component Design, under the BPV III Standards Committee assigned a Task Group to develop a strategy to combine the two subsections into a single subsection while maintaining both Class 2 and Class 3 as separate classes of construction.
Both Subsections NC and ND of the Code have been completely reviewed, compared and the technical bases for the differences have been established. The conclusion of this review is that there are only a few major technical differences between the two code class rules; however, there are a significant number of editorial differences. Based on the review, the Task Group developed a strategy that completes the consolidation within two publishing cycles of Code edition. For the Code Edition 2019, two separate Subsections NC and ND books will be published to resolve editorial differences and otherwise align the two subsections. For the Code Edition 2021, a single merged subsection will be published. This paper provides the background for the proposed code change, discusses the detailed result of the NC/ND comparison, and provides the basis for the major technical differences. The paper will also update the status of the project and code actions needed to consolidate to a single subsection.