What determines the design pressure of pressure vessels?

GB150 3.4.3 states that the design pressure refers to the maximum pressure specified at the top of the vessel; together with the corresponding design temperature, it serves as the design load condition, and its value shall be no lower than the operating pressure. Generally, 1.1 times the maximum operating pressure is used.

Reply to 2# zzw212: Why is 1.1 times chosen?

Reply to 3# yxbtm1975: According to the regulations, the design pressure should be no lower than the maximum operating pressure. The factor of 1.1 mentioned earlier is also based on experience; in actual calculations, the relevant design pressure can be determined in accordance with regulations such as the “Pressure Vessel Code” (the current revised version is in use). 1. When a safety valve is installed on the vessel, considering the delay in the valve’s activation, the vessel cannot release pressure promptly, so the design pressure must not be lower than the opening pressure of the safety valve (the opening pressure of the safety valve should be less than or equal to 1.05–1.1 times the vessel’s operating pressure). 2. When a burst disc is installed on the vessel, the design pressure must not be lower than the burst pressure of the disc; this value can be determined based on the type of burst disc, by taking the designed burst pressure of the disc plus the upper limit of its manufacturing range. Typically, this can range from 1.15 to 1.3 times the maximum operating pressure. 3. When a safety valve is installed on the pipeline at the vessel’s outlet side, the design pressure should be no lower than the opening pressure of the safety valve plus the pressure drop from the vessel to the safety valve. 4. When a safety valve is installed on the inlet pipeline of the vessel and a stop valve or other shut-off device is installed on the outlet side, the design pressure shall be the higher of the following two values: a) the opening pressure of the safety valve; b) the vessel’s operating pressure increased by an appropriate margin. 5. When the vessel is located on the inlet side of a pump and there are no safety control devices, the design pressure should correspond to that of a vessel without any safety relief devices, with verification being carried out using an external pressure of 0.1 MPa. 6. When the vessel is located on the outlet side of a pump and there are no safety control devices, the design pressure shall be the highest of the following three values: a) the normal inlet pressure of the pump plus 1.2 times the normal operating head of the pump; b) the maximum inlet pressure of the pump plus the normal operating head of the pump; c) the normal inlet pressure of the pump plus the shut-off head. 7. When a safety control system is installed in the vessel system, but individual vessels do not have such systems, and it is difficult to determine the pressure drop between vessels, the design pressure shall be selected according to the table below: Operating pressure Pw (MPa) Design pressure p (MPa) Pw ≤ 1.8 Pw + 1.8 1.8 < Pw ≤ 4.0 1.1Pw 4.0 < Pw ≤ 8.0 Pw + 0.4 Pw > 8.0 1.05Pw 8. For vessels containing liquefied gases without cooling facilities, since the vessel pressure is closely related to the critical temperature and operating temperature of the medium, the design pressure should be no lower than the saturated vapor pressure of the liquefied gas at 50°C. For vessels containing mixed liquefied petroleum gases for which there are no actual composition data, the saturated vapor pressure of the relevant components at 50°C shall be used as the design pressure. The design pressure is usually specified by the client and, along with the design temperature, serves as one of the design conditions; generally, you just need to carry out the design as required

It is specified in Table 4-1 on page 6 of HG20580

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