Chapter 6
Subsection NB—Class 1 Components


Chapter 6, authored by John Hechmer, covers Subsection NB, Class 1 Components. In presenting the rules and requirements for Section III, Subsection NB, John discusses the theories on which the rules and requirements are based, the appropriate application for applying the rules and requirements, and the interfaces for design, analysis, and construction. He emphasizes the analytical rules and requirements, and in his discussions he makes reference to the Criteria of the ASME Boiler and Pressure Vessel Code for Design by Analysis in Sections III and VIII, Division 2, 1968, considered the basis document for Sections III and VIII. John provides the design theory and ramifications of the key considerations, with cross-references to other Code Sections discussing the subtle differences between the Section III design criteria and the Section I and Section VIII, Division 1 design criteria.

In addition, John provides commentary on the Code requirements of Class 1 for design by analysis “because of the prominent role played by stress analysis in designing vessels by the rules of Section III … and because of the necessity to integrate the design and analysis efforts.” He states that the theme of the design criteria for Class 1 vessels is the need for a complete, thorough assessment of the stresses to ensure that failure does not occur from the various failure modes. Thus the true intent is that the analyses give an added assurance that high quality is reached; therefore, stress analysis is added to the “NB rules for all of the disciplines … and their interaction” in an effort to reach high quality. Chapter 6 has been updated by Greg Hollinger to the current Code and additional write-up has been provided by Greg dealing with Limit Analysis, Finite Element Analysis and Environmental Fatigue.

  • 6.1 Introduction
  • 6.2 Design
  • 6.3 Analysis
  • 6.4 Primary Stress Limits
  • 6.5 Primary-Plus-Secondary Stress Limits
  • 6.6 Fatigue
  • 6.7 Special Procedures
  • 6.8 References
  • 6.9 Summary of Changes

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