The ASTM A335 Gr. P11 seamless pipes, with nominal chemical composition of “1.25Cr-0.5Mo” or “1.25Cr-0.5Mo-Si”, can be used for ASME B31.3 process piping. The ASME B31.3 Code has designated ASTM A335 Gr. P11 as a listed material and provided the basic allowable stresses in tension at various temperatures. Allowable stresses in shear shall be 0.80 times the basic allowable stresses in tension. Allowable stress in bearing shall be 1.60 times that value. Allowable stresses in compression shall be no greater than the basic allowable stresses in tension.
|Temp. °F||S ksi|
ASME B31.3 has specified the design minimum temperature of -20°F [-29°C] for which ASTM A335 P11 is normally suitable without impact testing requirements. However, in engineering practices, the use of ASTM A335 Gr. P11 shall be limited at the minimum temperature of 0°F [-18°C]. According to the referencing API RP 934-C, the minimum Charpy V-notch impact values at 0°F [-18°C] shall be 40 ft-lbs [54 Joules] average of three specimens and 20 ft-lbs [27 Joules] for a single specimen. In addition, if the minimum design metal temperature (MDMT) is less than 0°F [-18°C], ASME Code requirements for impact testing must also be met. If the impact tests at the MDMT of less than 0°F [-18°C] meet the 40/20 ft-lbs [54/27 Joules] criteria, retesting at 0°F [-18°C] is not needed.