Summary of Technical Requirements for Pressure Vessels (16)

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Mandatory requirements for low-temperature vessels: The mandatory requirements for low-temperature vessels (≤ -20°C) are as follows: 01 Low-temperature steel forgings with a nominal thickness greater than 200 mm shall be of grade III or IV. 02 Steel studs of 30CrMoA, 35CrMoA, and 40CrNiMoA types: when used at temperatures below -20°C, impact tests at those operating temperatures must be conducted (the minimum temperature for 30CrMoA is -100°C, for 35CrMoA it is -70°C, and for 40CrNiMoA it is -50°C). The impact energy required is specified in Table 14. 03 30CrMoA steel for studs: when used at temperatures < -40°C to -70°C, P ≤ 0.020% and S ≤ 0.010% ； When the operating temperature is < -70°C to -100°C, P ≤ 0.015% and S ≤ 0.008%. 04 35CrMoA is a steel used for studs; when the operating temperature is between -40°C and -70°C, P should be ≤0.020% and S should be ≤0.010%. 05 Strain-hardened S30408 bolt blanks intended for use at temperatures below -100°C shall undergo impact testing at the operating temperature, with a KV2 value of ≥41 J. 06 The inner diameter corners at the connection points should be rounded, with the radius of the fillet generally taken as min{δnt/4, 19mm}. 07 Low-temperature and low-stress condition: A condition in which the maximum overall membrane + bending stress actually experienced by the pressure-bearing components of the container is ≤ ReL/6, and is not greater than 50 MPa. 08 The design documents shall specify the low-temperature and low-stress operating conditions: T(∆)=design temperature + 50°C (40°C in the case of no post-weld heat treatment) serves as the basis for material selection and the determination of technical requirements.