ASME B31T-2010 pdf download

ASME B31T-2010 pdf download.Standard Toughness Requirements for Piping.
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., −20°F (−29°C)].
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.” Ifthe design min- imum temperature is equal to or warmer than this value, then low-temperature requirements do not apply. Mate- rial within a group may be used at this temperature or temperatures warmer than this limit without imposing any of the requirements of this Standard. This limit con- siders material properties and the influence of fabrica- tion processes 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 material permitted tem- perature. When a temperature is listed, this is the design minimum temperature permitted for the material group regardless of impact testing or any other requirements except as permitted by column 18. 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. A figure 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 temperature with stress limits are provided for by utilizing columns 10 through 18 instead of column 6 as discussed in para. 3.6 below.
3.6.2 Stress Ratio. The stress ratio is defined as the maximum of the following: (a) nominal pressure stress (based on minimum pipe wall thickness less allowances) divided by the allowable stress at the design minimum temperature. (b) for piping components with pressure ratings, the pressure for the condition under consideration divided by the pressure rating at the design minimum temperature. (c) combined longitudinal stress due to pressure, dead weight, and displacement strain (stress intensifica- tion factors are not included in this calculation) divided by the allowable stress at the design minimum tempera- ture. In calculating longitudinal stress, the forces and moments in the piping system shall be calculated using nominal dimensions, and the stresses shall be calculated using section properties based on the nominal dimen- sions lesscorrosion, erosion, andmechanical allowances. Indetermining the stress ratio, the loadings coincident with the metal temperature under consideration may be used in lieu of maximum design values. Where there are several low-temperature design conditions, each shall be evaluated to determine the stress ratio. The curve used to generate columns 10 through 17 is provided in Mandatory Appendix II and may be used as an alternative to columns 10 through 17. Column 18 lists the minimum low-temperature ser- vice limit achievable by limiting stresses to less than 10% of the tensile strength (i.e., SR ≤0.3) and may be used without any additional low-temperature service requirements. At these stress levels, the design margin is considered adequate to prevent a brittle fracture failure mode.