ASME B31T:2015 pdf download

ASME B31T:2015 pdf download.Standard Toughness Requirements for Piping
2 GLOSSARY
CVN: abbreviation for Charpy V-notch. design minimum temperature: the lowest component tem- perature expected in service. fully deoxidized steel: steel that has been deoxidized either by the addition of strong deoxidizing agents or by vac- uum 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. Limitations on the use of steels that are not fully deoxidized may be imposed by the applicable piping code or specification. lower critical temperature: the temperature at which the first phase change occurs when heating a metal.low-temperature service limit: the design minimum tem- perature where additional requirements for low- temperature service do not apply. NDTtemperature: the nilductilitytransitiontemperature. stress ratio: the ratio of the design stress to an allowable stress. (See para. 3.6.2.) T-number: a number assigned to a group of similar mate- rials with similar low-temperature requirements. The number consists of the material type, a temperature characteristic, and possibly a suffix.
3 LOW-TEMPERATURE RANGES AND REQUIREMENTS
3.1 Low-Temperature Service Requirements Low-temperature service requirements are contained in Table 3.1-1. These requirements are established for T-number groups of materials with similar require- ments. In addition to T-number group, in some cases requirements are dependent on thickness and/or other characteristics as listed in Table 3.1-1. 3.2 Material Groupings (Column 1 of Table 3.1-1) Material T-number groups for each covered material specification are provided in Table 3.2-1. (In addition, a table sorted by material type and T-number group that lists all materials in each T-number group is provided inMandatory Appendix III.) In determining the applica- ble T-numbergroup fora material fromthe table, consid- eration shall be given to the material specification, grade, and any other variables as established in the notes. The table separates the materials into types (car- bon steel, low-alloy steel, etc.), and the group number is representative of the low-temperature service limit for the material; however, the low-temperature service limit may vary based on the design and fabrication requirements. Low-temperature service limits shall be determined from Table 3.1-1. An “(A)” in the T-number group [e.g., CS −20(A)] indicates that materials of that group may not be used at temperatures colder than the group number [e.g., −29°C (−20°F)]. 3.3 Nominal Thickness and Notes (Columns 2 and 3 of Table 3.1-1) For material T-number groups where the low- temperature suitability varies significantly according to the thickness, a thickness is listed in column 2 of Table 3.1-1. Note that the thickness is the nominal thick- ness as defined in the code or specification referencing this Code. The variation based on thickness applies to carbon steel T-number groups CS A, CS B, CS C, and CS D where Table 3.1-1 lists thickness at each 10°F incre- ment. 3.4 Low-Temperature Service Limit (Column 4 of Table 3.1-1) Column 4, the first temperature column in Table 3.1-1, is the low-temperature service limit. If the design mini- mum temperature is equal to or warmer than this value, then low-temperature requirements do not apply. Mate- rials within a group may be used at this temperature or temperatures warmer than this limit without imposing anyofthe requirements ofthis Code. This limitconsiders material properties and the influence of fabrication pro- cesses on the material properties. 3.5 Material Requirements for Low-Temperature Service (Columns 5 and 6 of Table 3.1-1) Column 5 lists the minimum permitted temperature of the material. When a temperature is listed, this is the designminimumtemperature permitted forthe material group regardless of impact testing or any other require- ments except as permitted by column 18, where the applied stress is limited to 30% of the allowable. Column 6 is the minimum temperature without impact testing for the material. If the design minimum temperature is equal to or warmer than this value, the material does not require impact testing. If the design minimum temperature is colder than this value, impact testing of the material in accordance with section 3 is required. For carbon steels, this limit might vary with material thickness (T-number groups CS A, CS B, CS C, and CS D) or with stress levels. Additional rows are provided in the table for thickness variations. Interpola- tion between thicknesses is permitted. Figures and a table for the curves of the variation of temperature with thickness are provided in Mandatory Appendix I and these may be used as an alternative to the values in Table 3.1-1. Permitted temperatures with stress limits are provided for by using columns 10 through 18 instead of column 6 as discussed in para. 3.6 below.