Important Changes in the 2012 Edition of ASME B31.3
The 2012 edition of ASME B31.3, Process Piping, brings many important changes to the 2010 edition of the code. These changes are essential for a piping stress engineer to understand and take into account when designing and verifying process piping systems. This article will provide an overview of the key changes included in the latest edition.
Clarifications Related to Codes & Standards
The 2012 edition of ASME B31.3 provides clarifications related to codes and standards applicable to piping systems. These clarifications include the addition of new requirements related to the application of ASME B31.1, Power Piping Code and ASME B31.4, Liquid Transportation Systems for Hydrocarbons, as well as changes to the requirements for welding, fabrication, inspection, and acceptance criteria for piping systems.
Updates to Basic Allowable Stresses
The 2012 edition of ASME B31.3 includes updates to the basic allowable stresses for various piping materials. These updates include changes to the allowable stresses for carbon steel, austenitic stainless steel, and other alloys. The updates also include the addition of new materials to the list of materials approved for use in piping systems.
Additional Listed Materials
The 2012 edition of ASME B31.3 includes the addition of several new materials to the list of materials approved for use in piping systems. These materials include high-strength low-alloy steel and duplex stainless steel. The code also provides guidance on the selection and application of these materials.
Displacement Stress Range Allowable
The 2012 edition of ASME B31.3 limits the allowable displacement stress range to 414 MPa (60,000 psi). While high strength steels generally have higher tensile and yield strengths, they also have similar fatigue strengths as common steels, which is why the limit was added.
Stress Equation for Flexibility
The 2012 edition of ASME B31.3 includes the axial stress in the flexibility stress equation, whereas the 2010 edition only addressed this in Appendix P. While axial stress may not be a significant factor in most piping systems, it can be important in jacketed or buried piping.
Category D Fluid Service
The definition of Category D fluid service in the 2012 edition has been revised to include a piping system with design minimum temperatures below -29 degrees Centigrade (-20 degree Fahrenheit). This applies when the lower temperature is generated from ambient conditions.
Preheating
The 2012 edition requires all metals to be preheated to 10 degrees centigrade (50°F) or higher before welding, whereas the 2010 edition only recommended preheat temperatures.
Other Changes
In addition to the changes mentioned above, the 2012 edition of ASME B31.3 includes a new Appendix N, Application of ASME B31.3 Internationally, and revises Appendices H and J. It also removes restrictions to acceptance of previously qualified welding procedures, and adds specific language about the use of standard welding procedures as permitted by ASME Boiler and Pressure Vessel Code, Section IX. Finally, the qualification needs for an Owner’s Inspector are broadened in the current 2012 Edition.