Pressure equipment presents inherent hazards due to the potential energy of its content, especially for gases. Consequently most industrialized countries have, for many decades, regulated these products. In European countries, each national authority developed regulations that were significantly different from each other: some were very detailed (e.g., in France), some contained only general requirements (e.g., in the UK), and others included very detailed conformity assessment procedures (e.g., in Germany).

The Code has separate requirements for boiler external and non-boiler external piping. Boiler external piping is actually within the scope of ASME BPVC, Section I. ASME BPVC, Section I refers to ASME B31.1 for technical requirements. Non-boiler external piping falls entirely within the scope of ASME B31.1. Thus, boiler external piping is treated as part of the boiler and subject to the Boiler and Pressure Vessel Code, whereas non-boiler external piping is not.

ASME B31.1 provides requirements for piping systems in Part 6 of Chapter II. Requirements for boiler external piping that were transferred from ASME BPVC, Section I in 1972, as well as requirements for systems with specific types of fluids or equipment, can be found here.

ASME B31.1 requires leak testing of all piping systems other than lines open to the atmosphere, such as vents or drains downstream of the last shut-off valve. For boiler external piping, a hydrostatic test in accordance with PG-99 of ASME BPVC Section I, conducted in the presence of the Authorized Inspector, is required.

The ASME Boiler and Pressure Vessel Code was first published by the ASME in 1915 as the “Rules for the Construction of Stationary Boiler and for Allowable Working Pressures” in the Report of the Committee to Formulate Standard Specifications for the Construction of Steam Boilers and Other Pressure Vessels and their Care in Service . The Committee was officially known as the Boiler Code Committee. The document was 114 pages , and the scope was identified as follows: These Rules do not apply to boilers which are subject to federal inspection and control, including marine boilers, boilers of steam locomotive and other self-propelled railroad apparatus . The Rules are divided into two parts. PART I applies to new installations (Section I, Power Boilers; Section II, Heating Boilers). PART II applies to existing installations . The purpose of the Code was to address the needs of the industry with regard to safety of fired steam boilers. The problem the Code was intended to address was that explosions of steam boilers were killing hundreds of people each year and causing great damage. From the turn of the century to 1915, thousands of deaths were caused by boiler explosions. The ASME addressed the issue by requesting engineers from industry to volunteer their time to write a set of engineering rules that could be adopted into state laws to ensure the proper construction of steam boilers [1]. In the 50 years after the Code was first published, the number of deaths caused by explosions of properly operated boilers and pressure vessels was reduced to essentially zero when the construction rules of the ASME Code were met. Subsequently, this outstanding record of safety has remained intact. No other industry has a better safety record.

In the first Edition, the principal author, Mr. Thomas J. Am, made extensive references to Section VIII, Division 2, and these references remain in both the second and third Editions. Users of this Chapter of the Companion Guide should be aware that in the 2007 Edition of the ASME Boiler and Pressure Vessel Code, Section VIII, Division 2, Alternative Rules for Construction of Pressure Vessels, was completely rewritten and revised. This “New” Section VIII, Division 2 has little conformity with the rules of “Old” Section VIII, Division 2. The rules for “Design by Analysis” were first embodied in the 1963 Edition of Section III, Nuclear Vessels, for Class A Vessels (today's Class 1 vessels), and later used as the Alternative Rules published in the 1968 Edition of Section VIII, Division 2. These design rules utilized Design Stress lntensities based on the Maximum Shear Stress Theory of Failure (the Tresca Criterion) and the design values were based on a design factor of of the Tensile Strength and of the Yield Strength. Permitted materials were restricted, and temperature limits were established at 700_F for carbon and low alloy steels, and 800_F for austenitic and high temperature alloys. Many fabrication details permitted in Section VIII, Division 1, were not included in construction details for the Alternative Rules. Section III, Class 2 vessels designed by analysis in NC-3200 still abide by the rules of the “Old” Section VIII, Division 2, up to the 2004 Edition, including the 2005 and 2006 Addenda. The “New” Section VIII, Division 2, 2007 Edition, still refers to “Design Stress Intensities,” but they are based on the Maximum Stress Theory of Failure (von Mises Criteria), and they are based on a design factor of 1/2.4 of the Tensile Strength. Many of the construction details not previously permitted have been included. Section III has not even begun to study this disparity in design and construction, and has not considered approval of the “New” Section VIII, Division 2. Therefore, in using this Chapter, do not reference the 2007 Edition of Section VIII, Division 2. All references are to the “Old” Section VIII, Division 2, 2004 Edition with 2005 and 2006 Addenda. For a complete discussion on the rewrite, please refer to Chapter 22.

On December 31, 1973, the American Society of Mechanical Engineers (ASME) published Subsection NF [1] of the ASME Boiler and Pressure Vessel Code Section III, Division 1 (hereafter addressed as Subsection NF) as part of the winter 1973 addenda to the 1971 Code edition [2]. This was a historic publication; prior to it, supports (also called pipe hangers and restraints) were not addressed as part of ASME Section III. Existing nuclear plants and plants under construction during that time were using ANSI B31.1 [3], ANSI B31.7 [4], MSS-SP58 [5], and the AISC Manual of Steel Construction [6] to design supports. ASME Section III, Subsection NF, provided a stabilizing position for future nuclear plant support design by designating a single source of rules for the design, construction, fabrication, and examination of supports. This criteria-and-commentary chapter provides information on the origins and evolution of design rules and is intended to allow designers, engineers, and fabricators to make better use of Subsection NF of the ASME Code. Topics of greatest interest are discussed and addressed from both a technical and historical viewpoint. It is not the intent, however, to address every detail or anticipate every question associated with the use of the subsection. However, there will be situations when engineering judgment and special considerations will be used in conjunction with Subsection NF to qualify supports. ASME Boiler and Pressure Vessel Code Section III, Division 1, Subsection NF, was developed in an attempt to provide rules for the estimated 10,000 piping and component supports existing in a typical nuclear power plant. These rules have evolved so dramatically that the existing support rules seldom resemble the original rules of 1973. This document follows the evolution of Subsection NF as the industry attempted to apply the subsection's rules. Commentary is provided to explain how the criteria are used, the source and technical basis for the equations and the rationale, and the reasons for change. It is anticipated that readers will develop a better understanding of Subsection NF to appreciate its complexities and usefulness.

Chapter 3 has multiple authors, and in Chapter 3.1, History of Materials in the ASME Boiler and Pressure Vessel Code , Domenic Canonico traces the chronological evolution of materials and associated technologies, from the need for materials to accommodate riveted construction to the acceptance of fusion welding as a fabrication process. Included in this discussion are the application of advanced materials, the revisions to the basis for setting allowable stress values, and the acceptance of Material Specifications other than those approved by ASTM. Also covered is the evolution of materials, from their humble beginning as a 35-page inclusion in the 1914 Edition of the Boiler Code to the 3994-page, four-Part 2001 Edition of Section II of the ASME B&PV Code. Chapter 3.1 provides some insight not only into the materials needed for the design and fabrication of power boilers but also into the determination of the Maximum Allowable Working Pressure. With the aid of tables, Domenic discusses the Material Specifications from the 1914 through the present Code Editions. Chapter 3.2, authored by Richard Moen and Elmar Upitis, discusses Code Section II, Part A— Ferrous Material Specifications , adopted by ASME for the construction of boiler, pressure vessel, and nuclear power plant components. They note that all materials accepted by the various Code Sections and used for construction within the scope of the Code Sections' rules must be furnished in accordance with the Material Specifications contained in Section II, Parts A, B, or C, or referenced in Appendix A of Part A—except where otherwise provided in the ASME Code Cases or in the applicable Code Section. Discussions in Chapter 3.2 include The Organization of Section II, Part A, Guideline on the Approval of New Materials, Appendices, and Interpretations. In Chapter 3.3, Dennis W. Rahoi provides the basis of and commentary on Section II, Part B— Nonferrous Material Specifications , adopted by ASME for the construction of boiler, pressure vessel, and nuclear power plant components. He notes that all materials allowed by the various Code Sections and used for construction within the scope of the Code Sections' rules must be furnished in accordance with the Material Specifications contained in Section II, Part B or referenced in Appendix A of Part B-except where otherwise provided in the ASME Code Cases or in the applicable Code Section. Dennis discusses alloy definitions; the organization of Section II, Part B Appendices; the acceptable ASTM Editions; Nonmandatory guidelines; the guideline on the Approval of New Materials; the allowable stresses for alloys; and the basis for material acceptance for Code Construction. Dennis also provides cross-references to weldability; ASME Code Sections I, III, IV, VIII, and IX; and Piping Codes B31.1 and B31.3. Chapter 3.4, authored by Marvin Carpenter, discusses Section II, Part C— Specification for Welding Rods, Electrodes, and Filler Metals . Welding plays a major role in the fabrication of pressure vessels and related components to the requirements of the ASME B&PV Code. Marvin provides the basis for the Specifications and Standards enveloped by Section II, Part C and their relations to the ANSI/AWS specifications. Marvin indicates that Section II, Part C does not include all the welding and brazing materials available to the industry—only those Specifications applicable to ASME Code Construction. Discussions also include Code Cases pertinent to this chapter. Chapter 3.4 highlights the major features of the Welding Material Specifications contained in Section II, Part C and the relationship of these Specifications to other Sections of the Code, including Section IX. Included are the electrode classification system, material descriptions, welding material applications, welding material procurement, and filler-metal certification. Chapter 3.4 should prove useful for one to gain a basic understanding of ASME/AWS Welding Material Classification and Specification. Chapter 3.5, authored by Richard Moen and Elmar Upitis, covers Section II, Part D— Properties . The coverage includes properties of ferrous and nonferrous materials adopted by the Code for design of B&PV and nuclear power plant components. This coverage includes tables of maximum allowable stresses and design-stress intensities for the materials adopted by the various Code Sections, as well as a discussion of yield strength and tensile strength at various temperatures, external-pressure charts, and other properties for the design of items covered by the various Code Sections. With the aid of several tables, they provide in-depth information about “where is what” in Section II, Part D, and in addition, they note that although much of the information in the various Subparts and Appendices of Section II, Part D was compiled in several places in earlier Code Section Editions, in current editions it is compiled entirely in Section II, Part D to reduce the length of, avoid the duplication of, and facilitate the use of the Code Sections. Thus their commentary can be a useful “road map” even for Users of earlier Code Sections, because it encapsulates—all in one place-information crucial to Designers and Practicing Engineers.

In Chapter 4, Roger Reedy provides commentary for the understanding and application of the principles of the ASME B&PV Code. Roger traces the history of the Code, from its initial charter and the voluntary effort of engineers for establishing a Code with a safety record to the current Code developed by a consensus process. Roger suggests that Code Users apply common sense when using the Code and for understanding Code requirements. He emphasizes that “the Code is not a handbook and cannot substitute for the use of engineering judgment.” Also, Roger emphasizes the need for a better understanding of the basic principles of the Code Interpretations in the application of safety factors for the Section III Nuclear Code, the Section VIII Pressure Vessels, and the Section I Boiler Code. Roger states that the term safety factor is both incorrect and misleading, because a reduction in the factor seems to indicate a reduction in safety. In fact, when the Code Committee considers a reduction in design factor, it allows the reduction only after it determines that other changes in Code requirements have compensated for the reduction.

Chapter 6 originally authored by John Hechmer for the first edition and updated by Greg Hollinger for the second edition has been largely revised by David Jones for the current third edition. Authors cover Subsection NB, Class 1 Components . In presenting the rules and requirements for Section III, Subsection NB, the authors discuss 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. The chapter emphasizes the analytical rules and requirements, and 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 that is considered the basis document for Sections III and VIII. John provided 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, commentary is provided 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.”—The authors emphasize that the design by analysis theme of NB is to provide high assurance that the failure modes of burst, plastic collapse, excessive plastic deformation, fatigue, ratcheting, brittle fracture, elastic instability (buckling), stress corrosion, and corrosion fatigue. The intent of the rules of NB is to provide 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 and David Jones to the 2007 version of the Code including discussions of the differences between Section VIII Division 2 and Section III NB. Discussions have been added on the Section VIII Division 2 rules dealing with Limit Analysis, Finite Element Analysis and Environmental Fatigue, and new methods for fatigue of weldments.

Chapter 47 has been updated with Anne Chaudouet as the lead for this revision with other authors Peter Hanmore and Guido Karcher from the previous editions continuing to be co-authors for this edition, as well. The authors, Francis Osweiller, Peter Hanmore and Guido Karcher all have considerable experience of the US pressure equipment market as well as that in Europe. They have provided a background to the methodology and objectives of the pressure equipment directive and CE marking in general before attempting to portray the detail. The directive is a document of only 55 pages, yet it is applicable to all equipment that can operate at a pressure greater than 0.5 bar and is a mandatory requirement for all pressure equipment to be put into service in the European Union. In common with other European directives the pressure equipment directive specifies general safety objectives which the manufacturer must meet and this leaves considerable scope for interpretation. Having accumulated considerable experience in the implementation of the directive since its application in November 1999, the authors have provided details of how to design and build pressure equipment to meet the European requirements and thus permit its CE marking and its free movement throughout Europe. After describing the system used to categorize pressure equipment and the conformity assessment requirements that are linked to them the authors go on to explain the routes that can be followed to meet the directive including an explanation of “harmonized standards” and “Notified Bodies”. Each of the essential safety requirements relating to design, manufacture and testing is discussed and guidance provided to assist manufacturers to comply, thus providing the potential exporter to Europe with a wealth of valuable information. A special attention has been given in this revision to material aspects and to the use of ASME Codes with PED. The areas of compliance of the new Section VIII Division 2 with PED are also highlighted. The authors close with a brief look into a crystal ball and consider the possibility of these “performance based” requirements becoming the basis of global trade.

In Chapter 47 the authors, Francis Osweiller, Peter Hanmore and Guido Karcher all have considerable experience of the US pressure equipment market as well as that in Europe. They have provided a background to the methodology and objectives of the pressure equipment directive and CE marking in general before attempting to portray the detail. The directive is a document of only 55 pages, yet it is applicable to all equipment that can operate at a pressure greater than 0.5 bar and is a mandatory requirement for all pressure equipment to be put into service in the European Union. In common with other European directives the pressure equipment directive specifies general safety objectives which the manufacturer must meet and this leaves considerable scope for interpretation. Having accumulated considerable experience in the implementation of the directive since its application in November 1999, the authors have provided details of how to design and build pressure equipment to meet the European requirements and thus permit its CE marking and its free movement throughout Europe. After describing the system used to categorize pressure equipment and the conformity assessment requirements that are linked to them the authors go on to explain the routes that can be followed to meet the directive including an explanation of “harmonized standards” and “Notified Bodies”. Each of the essential safety requirements relating to design, manufacture and testing is discussed and guidance provided to assist manufacturers to comply, thus providing the potential exporter to Europe with a wealth of valuable information. The authors close with a brief look into a crystal ball and consider the possibility of these “performance based” requirements becoming the basis of global trade.

Chapter 3 has multiple authors, and in Chapter 3.1, History of Materials in the ASME Boiler and Pressure Vessel Code, Domenic Canonico traces the chronological evolution of materials and associated technologies, from the need for materials to accommodate riveted construction to the acceptance of fusion welding as a fabrication process. Included in this discussion are the application of advanced materials, the revisions to the basis for setting allowable stress values, and the acceptance of Material Specifications other than those approved by ASTM. Also covered is the evolution of materials, from their humble beginning as a 35-page inclusion in the 1914 Edition of the Boiler Code to the 3994-page, four-Part 2001 Edition of Section II of the ASME B&PV Code. Chapter 3.1 provides some insight not only into the materials needed for the design and fabrication of power boilers but also into the determination of the Maximum Allowable Working Pressure. With the aid of tables, Domenic discusses the Material Specifications from the 1914 through the present Code Editions. Chapter 3.2, authored by Richard Moen and Elmar Upitis, discusses Code Section II, Part A—Ferrous Material Specifications, adopted by ASME for the construction of boiler, pressure vessel, and nuclear power plant components. They note that all materials accepted by the various Code Sections and used for construction within the scope of the Code Sections' rules must be furnished in accordance with the Material Specifications contained in Section II, Parts A, B, or C, or referenced in Appendix A of Part A—except where otherwise provided in the ASME Code Cases or in the applicable Code Section. Discussions in Chapter 3.2 include The Organization of Section II, Part A, Guideline on the Approval of New Materials, Appendices, and Interpretations. In Chapter 3.3, Dennis W. Rahoi provides the basis of and commentary on Section II, Part B—Nonferrous Material Specifications, adopted by ASME for the construction of boiler, pressure vessel, and nuclear power plant components. He notes that all materials allowed by the various Code Sections and used for construction within the scope of the Code Sections' rules must be furnished in accordance with the Material Specifications contained in Section II, Part B or referenced in Appendix A of Part B—except where otherwise provided in the ASME Code Cases or in the applicable Code Section. Dennis discusses alloy definitions; the organization of Section II, Part B Appendices; the acceptable ASTM Editions; Nonmandatory guidelines; the guideline on the Approval of New Materials; the allowable stresses for alloys; and the basis for material acceptance for Code Construction. Dennis also provides cross-references to weldability; ASME Code Sections I, III, IV, VIII, and IX; and Piping Codes B31.1 and B31.3. Chapter 3.4, authored by Marvin Carpenter, discusses Section II, Part C—Specification for Welding Rods, Electrodes, and Filler Metals. Welding plays a major role in the fabrication of pressure vessels and related components to the requirements of the ASME B&PV Code. Marvin provides the basis for the Specifications and Standards enveloped by Section II, Part C and their relations to the ANSI∕AWS specifications. Marvin indicates that Section II, Part C does not include all the welding and brazing materials available to the industry—only those Specifications applicable to ASME Code Construction. Discussions also include Code Cases pertinent to this chapter. Chapter 3.4 highlights the major features of the Welding Material Specifications contained in Section II, Part C and the relationship of these Specifications to other Sections of the Code, including Section IX. Included are the electrode classification system, material descriptions, welding material applications, welding material procurement, and filler-metal certification. Chapter 3.4 should prove useful for one to gain a basic understanding of ASME∕AWS Welding Material Classification and Specification. Chapter 3.5, authored by Richard Moen and Elmar Upitis, covers Section II, Part D—Properties. The coverage includes properties of ferrous and nonferrous materials adopted by the Code for design of B&PV and nuclear power plant components. This coverage includes tables of maximum allowable stresses and design-stress intensities for the materials adopted by the various Code Sections, as well as a discussion of yield strength and tensile strength at various temperatures, external-pressure charts, and other properties for the design of items covered by the various Code Sections. With the aid of several tables, they provide in-depth information about “where is what” in Section II, Part D, and in addition, they note that although much of the information in the various Subparts and Appendices of Section II, Part D was compiled in several places in earlier Code Section Editions, in current editions it is compiled entirely in Section II, Part D to reduce the length of, avoid the duplication of, and facilitate the use of the Code Sections. Thus their commentary can be a useful “road map” even for Users of earlier Code Sections, because it encapsulates—all in one place—information crucial to Designers and Practicing Engineers.

In Chapter 4, Roger Reedy provides commentary for the understanding and application of the principles of the ASME B&PV Code. Roger traces the history of the Code, from its initial charter and the voluntary effort of engineers for establishing a Code with a safety record to the current Code developed by a consensus process. Roger suggests that Code Users apply common sense when using the Code and for understanding Code requirements. He emphasizes that “the Code is not a handbook and cannot substitute for the use of engineering judgment.” Also, Roger emphasizes the need for a better understanding of the basic principles of the Code Interpretations in the application of safety factors for the Section III Nuclear Code, the Section VIII Pressure Vessels, and the Section I Boiler Code. Roger states that the term safety factor is both incorrect and misleading, because a reduction in the factor seems to indicate a reduction in safety. In fact, when the Code Committee considers a reduction in design factor, it allows the reduction only after it determines that other changes in Code requirements have compensated for the reduction.

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.