ASME B31T-2015 pdf – Standard Toughness Requirements for Piping.
The low-temperature service limit established 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 transition temperature for a given material specification will vary based on actual heat chemistry of the material and subsequent processing. 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 referring code and the design engineer (when permitted by the referring code).
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 systenm are listed, scow are not, and these unlisted materials are not addressed in this Code. Where permitted by code or specification invoking this Code, these requirements may be used for unlisted materials. The invoking code or specification may establish the correct T-number group for the material or may invoke the testing and other requirements of this Code using the worst-ease assumption that the design minimum temperature is colder than the temperatures that would allow exemption from any of the requirements of this Code. The
guidelines for establishing the correct T-number group are provided in Nonmandatory Appendix B.
CVN: abbreviation for Charpy V-notch.
design rnimrnum tenpenzture: the lowest component temperature expected in service.
fully deoxidized ffil: steel that has been deoxidiied either by the addition of strong deoxidizing agents or by vacuum treatment, to reduce the oxygen content to such a level that no reaction occurs between the carbon and oxygen during solidification, Also known as killed steel, SteeLs that are not fully deoxidized include rimmed, semi-killed, and capped steels. Umitations on the use of steels that are not fully deoxidized may be imposed by the applicable piping code or specification.
(c) The data for development of the temperature adjustment (T5g) shall be developed by performing additional Charpy V-notch tests on either the welding precedure qualification heat-affected zone or the unaffected base matenal, or both, at temperatures that pro. ‘ide toughness values that meet oreicceed those required lot the thickness of material to be welded in production. The average toughness data for the heat-affected zone and the unaffected base material shall be plotted on a property-temperature chart. The temperatures at which these two sets of data exhibit a common acceptable value of toughness for the production thickness involved shall be determined. The determined temperature for the unaffected base material shall be subtracted from th similarly determined temperature for the heat-affected zone. This difference shall be used in (d) below as
If the temperature difference is zero or is a negative number, no adjustment is required for the base material to be welded in production, and the minimum temperature established by this Code will still apply as stated in (a) above. The Charpv V-notch testing results shall be recorded on the Welding PQR. and any offsetting TADI or increased toughness requirements shall be noted on the Welding PQR and an the Welding Procedure Specification (WI’S).
(d) At least one of the following methods shall be used to compensate for the heat-affected zone toughness decrease due to the welding procedure. More than one compensation method may be used on a par basis.
(e) The low-temperature service limit for all of the material to be welded in production WPSs supported by this PQR shall be increased by the adjustment temperature TAN.
(2) The specified testing temperature for the production material may be reduced by Tsnt.
(3) The materials to be welded may be welded using th WI’S provided they exhibit Charpy V-notch values that are no less than the minimum required lateral expansion value required for the material plus the difference in average lateral expansion values between the unaffected base metal and the HAZ.
3.7.3 FormIng and Bending Processes. Any pnwess may be used to hot form, cold form, or bend material, including weld metal, provided the impact properties of the material, when required, are not reduced below the minimum specified values, or they are effectively restored by heat treatment following the forming operation.