Becht Engineering Blog

This posting (November 2019) is an update to an October 2013 post which reflects changes to the ASME B31.3 Code relative to severe cyclic service that have occurred since the original post. There has been a fair amount of confusion as to when the rules for severe cyclic conditions in ASME B31.3 should be used, and the rules themselves can be somewhat confusing to apply. In the 2016 edition of ASME B31.3 the definition of when the rules for severe cyclic service are applicable were changed, which may reduce the confusion.  The definition as to when the rules of severe cyclic apply is in the 300.2, Definitions.  Prior to the 2016 edition, it stated that severe cyclic conditions are: Conditions applying to specific piping components or joints in which SE computed in accordance with para. 319.4.4 exceeds 0.8SA (as defined in para. 302.3.5); and The equivalent number of cycles (N in...

In addition to the many clarifications, updated references to codes and standards, updates to basic allowable stresses, and added listed materials, there are several substantive changes to the 2016 Edition of ASME B31.3, Process Piping, which is scheduled to be issued mid-January 2019. These substantive changes are: Owner Added specific permission for the owner to designate a representative to carry out selected responsibilities required by this Code, and noted that the owner retains ultimate responsibility for the actions of the representatives. Flange Design Added the ASME B&PV Code Section VIII, Division 2, para. 4.16 flange calculation method as an acceptable way to design flanges for B31.3 applications. The Division 2 procedure considers pressure, gasket seating, and externally applied axial forces and net-section bending moments. Stress Intensification and Flexibility Factors Added specific references to ASME B31J-2017 as a resource for stress intensification and flexibility factors as an alternate to Appendix D. High Cycle Fatigue...

Risk based inspection (RBI) is a powerful tool to identify and manage mechanical integrity risks in fixed equipment and piping but is only one part of a robust reliability program.  RBI informs inspection decision making on where, when and how to inspect most of equipment but is frequently misinterpreted as a “Silver Bullet” that covers all necessary inspection activities in a refinery.  Most RBI programs have significant gaps that can result in costly reliability issues or unjustified maintenance costs.  RBI gaps can exist where risk assessments require input from outside of an inspection department or mechanical integrity group.  Examples of these gaps are when failures have process consequences but not mechanical integrity concerns, such as tube leaks in shell and tube heat exchangers and cyclones in an FCC Unit.  Another example is when mechanical integrity is dependent upon other systems functioning per design, such as fired heater tubes.  Quantitative RBI Programs...

Reducing Loss of Primary Containment (LOPC's) or commonly referred to as “leaks” in a refinery is a key factor to improve reliability.  Historically, most refiners reduced the high consequence leaks to avoid major incidents; however, lower consequence related leaks were not given high priority.  Today high reliability is required, and reduction of all leaks is desired due to greater legal and regulatory oversight of the industry.  Approximately 90% of the leaks occur in piping systems.  These leaks typically fall into 3 categories; internal corrosion, flange leaks and external corrosion.  Many refiners have programs in place for internal corrosion and programs for flanged joints; however, many lack comprehensive programs for external corrosion. To fully reduce LOPCs a comprehensive internal and external corrosion management system is necessary. Background Many refineries have had Mechanical Integrity related audits performed during the last decade.  These audits have found many areas for improvements and programs were initiated...