40 Bolted-Flange Joints and Connections

In Chapter 40, William J. Koves addresses the design of bolted-flange joints and connections, perhaps one of the crucial safety aspects of the power and petrochemical industries because entire piping systems and components are ultimately held together by connections and welded joints. Addressed in this chapter are flanged joints, which are essential and complex components in nearly all pressurized systems. Many factors determine the successful design and operation of a flange joint in service. William notes that the bolted-flange joint involves the interaction between the bolting, flange, and gasket, with important nonlinear variables such as friction and gasket properties considered. The Code design rules provide a method for sizing the flange and bolts to be structurally adequate for the specified design conditions; however, these rules do not address assembly or special requirements, nor do they guarantee a leak-tight joint for all transient-operating conditions. The purpose of Chapter 40 is to provide the background and basis for the bolted-flange joint design rules contained in the ASME Codes in addition to a discussion of how the rules are applied. Considering this topic's interaction with several ASME Code Sections and Piping and related Codes, William, who has several years of experience serving in ASME Code Committees, translates his professional and Code experience in the writing of this chapter by providing cross-references to the various Codes and Standards. He discusses Codes that address flange-joint design, including design requirements and applicability, and he discusses flange standards as well as flange design for pressure vessels and piping. He provides an in-depth discussion of flange-stress design methods, including the ASME design methodology; the historical background and technical basis; the scope and design philosophy; and the flange types. He comments on flange designs not addressed by ASME: design for external loads, leak-tightness—based design, and flange joint assembly, including ASME Appendix S, bolting and gasket considerations.