What does low temperature and low stress mean? (Explain it in simple terms)
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What does low temperature and low stress mean? (Explain it in simple terms)
Clause C1.5 in Appendix C of GB150-98 \"Steel Pressure Vessels\" provides the definition of low-temperature, low-stress conditions. Specifically, low-temperature, low-stress conditions refer to those situations in which the design temperature of the vessel shell or its pressure-bearing components is below or equal to -20 degrees Celsius, but the circumferential stress is less than or equal to one-sixth of the yield strength of the steel at normal temperature, and not greater than 50 MPa. Low-temperature and low-stress operating conditions are not suitable for low-temperature vessels whose standard minimum tensile strength of steel is greater than 540 MPa.
Low-temperature and low-stress conditions refer to those in which the design temperature of the shell or its stressed components is below or equal to -20 degrees Celsius, but the hoop stress is less than or equal to one-sixth of the yield strength of the steel at normal temperature, and not greater than 50 MPa. See GB150, page 141, C1.5 for details
In other words, when designing equipment for low-temperature and low-stress operating conditions, even if the design temperature is below -20 degrees, it is not necessary to follow the design standards for low-temperature pressure vessels! I wonder if saying this is vulgar!
(Sorry, correction) Let’s use an example. Suppose a vessel is designed for a temperature of -69 degrees Celsius; since -69 + 50 = -19, and -19 > -20, the material used is 16MnR (Q345R). If the thickness of the vessel’s shell is sufficient, the circumferential stress calculated using formula 5-2 in GB150 will be 49 MPa. This value is less than 57.5 MPa (345 MPa/6 = 57.5 MPa) as well as less than 50 MPa. Therefore, a pressure vessel with a shell made of 16MnR (Q345R) of this thickness meets the requirements for low-temperature and low-stress conditions specified in clause C1.5 of Appendix C of GB150, and it is not necessary to follow the procedures outlined in Appendix C for its design and manufacture.
Clause C1.5 in Appendix C of GB150-98 defines the low-temperature and low-stress condition: a low-temperature and low-stress condition refers to a situation in which the design temperature of the shell or its pressure-bearing components is less than or equal to -20 degrees Celsius, but the hoop stress is less than or equal to one-sixth of the yield strength of the steel at normal temperature, and not greater than 50 MPa. Low-temperature and low-stress operating conditions are not suitable for low-temperature vessels whose standard minimum tensile strength of steel is greater than 540 MPa. According to this requirement, you generally need to calculate the circumferential stress of the cylinder and the head; note that the formula for the circumferential stress of the head is not the one specified in GB150
C1.5 in Appendix C of GB150-98 \"Steel Pressure Vessels\": When the shell or pressure-bearing components are used under \"low-temperature and low-stress conditions\", it is not necessary to comply with the provisions of this appendix if the design temperature increased by 50°C is still above -20°C. ““A low-temperature and low-stress condition” refers to a condition in which the design temperature of the shell or its stressed components is below or equal to -20°C, but the hoop stress is less than or equal to one-sixth of the yield strength of the steel at normal temperature, and not greater than 50 MPa. “The “low temperature and low stress condition” does not apply to low-temperature vessels whose standard minimum tensile strength of steel is greater than 540 MPa
A low-temperature and low-stress condition, literally, refers to a condition that is both low in temperature and low in stress. The threshold for low temperature is -20°C, while the threshold for low stress is when the circumferential stress is less than or equal to one-sixth of the steel’s yield strength at normal temperature, and not greater than 50 MPa. Low-temperature and low-stress operating conditions are not suitable for low-temperature vessels whose standard minimum tensile strength of steel is greater than 540 MPa. Furthermore, when housings or compressed components are used under \"low-temperature and low-stress conditions\", it is not necessary to comply with the provisions of this appendix if the design temperature increased by 50°C results in a value higher than -20°C