Regarding the design temperature of GB/T150.1

I. Implementation of the maximum design temperature: Determination of design loads: The maximum design temperature, together with the maximum design pressure, serves as the design load conditions to determine the maximum thermal stress that a pressure vessel can withstand under normal operating conditions. In the design documents, the maximum design temperature must be clearly specified, and it is essential to ensure that all design calculations are based on this temperature. Material selection: Based on the maximum design temperature, select materials that can meet the performance requirements at that temperature. The selection of materials requires consideration of factors such as high-temperature strength, creep resistance, and oxidation resistance, to ensure that pressure vessels can operate safely at the highest design temperature. Structural design: When designing a structure, it is necessary to take into account the effects of the maximum design temperature on factors such as material expansion and thermal stress. Through reasonable structural design, such as the use of expansion joints and flexible connections, the impact of thermal stress on pressure vessels can be reduced. Safety verification: In the design documents, it is necessary to verify the safety of the pressure vessel at the highest design temperature. This includes strength checks, stability checks, etc., to ensure that the pressure vessel meets safety requirements at the highest design temperature. II. Implementation of the minimum design temperature: Determination of the design load: The minimum design temperature is used to determine the load-bearing capacity of pressure vessels in low-temperature environments. In the design documents, the minimum design temperature must be clearly specified, and it is essential to ensure that all design calculations take into account the changes in material properties at that temperature. Material selection: Based on the minimum design temperature, select a material with sufficient low-temperature toughness. Low-temperature toughness is the ability of a material to resist brittle fracture at low temperatures, and it is crucial for ensuring the safety of pressure vessels in low-temperature environments. Structural design: When designing a structure, it is necessary to take into account the effects of the minimum design temperature on factors such as material contraction and thermal stress. The low-temperature load-bearing capacity of pressure vessels can be improved through reasonable structural design, such as increasing wall thickness and using special connection methods. Safety verification and protective measures: In the design documents, it is necessary to verify the safety of the pressure vessel at the lowest design temperature, including strength verification and toughness verification. In low-temperature environments, special protective measures may be necessary, such as installing insulation layers or using electric heating, to prevent pressure vessels from being damaged or becoming ineffective due to low temperatures.

I don’t understand what it means by how to carry out the process; the highest value (as before), the lowest value (considering material selection/impact; indicated in the drawing data fields, not shown in the calculation sheet)

If a device has only one operating condition, such as an operating temperature of 120°C and an operating pressure of 0.5 MPa, how should the highest and lowest design temperatures be indicated in the diagram? Is it sufficient to specify just one design temperature? Does the minimum design temperature need to take the ambient temperature into account?

At the minimum design temperature, the focus is on testing the material’s low-temperature toughness (it must have sufficient toughness reserves); there is no need to calculate strength

The temperature should be a range; values outside this range need to be taken into consideration, as the design requires a comprehensive approach. For example, whether steel with a temperature difference of 100°C during operation will exceed its fatigue limit or what impact this will have on its strength, and whether the steel can maintain sufficient toughness at low temperatures.