ASME B31T:2021 pdf free download – Standard Toughness Requirements for Piping
Suitability of piping systems for low-temperature service is a function ofseveral variables, including mate- rial properties, design loadings, and fabrication proce- dures. The three primary factors that generally control the susceptibility for brittle fracture are material tough- ness, crack size, and tensile stress level. There are a wide variety of services where low-temperature suitability need not even be considered; however, a screening criterion is necessary to determine this. One objective of this Standard is to provide a simple approach to evaluate whether additional consideration is necessary to evaluate suitability for low-temperature service. This is done by establishing a low-temperature service limit for various materials. Services at or warmer than this limit are not considered low tempera- ture, and additional considerations relative to suitability are not required.
Forservicescolderthanthislimit,variousrequirements are provided that, when met, qualify the material for low- temperature services. These requirements include impact testing, qualification of welding and other fabrication procedures, and limiting the design loadings. The low-temperature service limitestablished herein is based on a reasonable degree of assurance that at this temperature, the material will have a ductile failure mode. The actual ductile-to-brittle transitiontemperature fora given material specification will varybased on actual heatchemistryofthematerialandsubsequentprocessing. For critical applications, the design engineer can select materials with a lower low-temperature service limit or require impact testing. On less-critical applications, material with a higher low-temperature service limit may be acceptable. The final selection is left to the code, standard, or specification referencing this Standard and the design engineer (when permitted by the code, standard, or specification referencing this Standard).
To keep the number of sets of requirements to a minimum, material groupings have been established, and a unique set of requirements have been provided for each group. These groups are assigned “T- numbers” for easy reference. Although most materials used in piping systems are listed, some are not, and these unlisted materials are not addressed in this Stan- dard. Where permitted by the code, standard, or specifi- cation referencing this Standard, these requirements may beusedforunlistedmaterials.Thecode,standard,orspec- ification referencing this Standard may establish the correct T-number group for the material or may invokethetesting and other requirement softhisStandard usingtheworst-caseassumptionthatthedesignminimum temperature is colder than the temperatures that would allow exemption from any of the requirements of this Standard. The guidelines for establishing the correct T- number group are provided in Nonmandatory Appendix B.
Either International System (SI, also known as metric) or U.S. Customary (USC) units may be used with this edition. Localcustomaryunits mayalso be usedto demon- strate compliance with this Standard. One system ofunits shouldbeusedconsistentlyforrequirementsapplyingtoa specific installation. It is the responsibility of the organ- izationperformingcalculations to ensurethataconsistent system of units is used. The ASME B31 Committee is organized and operates under procedures of ASME that have been accredited by the American National Standards Institute. The Committee is continuing and keeps all Code Sections and Standards current with new developments in methods, materials, construction, and industrial practice. This Standard may be invoked in whole or in part by various codes, standards, or specifications and is only mandatory when so invoked. The applicable edition of this Standard shall be as specified by the code, standard, or specification referencing this Standard. It is intended that this edition ofthe ASME B31T Standard not be retro- active. Users of this Standard are cautioned against making use of Standard revisions without assurance that they are acceptable to the proper authorities in the jurisdiction where the material is to be installed.