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How is the setting pressure of the safety valve on a pressure vessel determined? According to Appendix B of GB150.1, when a vessel is equipped with a relief device, the design pressure of the vessel is generally used as the starting point for determining the overpressure limit. B4.2.1 When a relief device is installed on a vessel, its operating pressure should not exceed the design pressure, and the overpressure limit for that vessel should not be more than 10% of the design pressure or 20 kPa, whichever is greater. B4.2.2 When multiple relief devices are installed on a vessel, the operating pressure of one of these devices should not exceed the design pressure; the operating pressures of the other devices can be higher, but they must not exceed 40% of the design pressure. The overpressure limit for this space shall not exceed 12% of the design pressure, or the greater of the two values, 30 kPa. B4.2.3 When a vessel is at risk of encountering a fire or coming into contact with unexpected external heat sources that could pose a hazard, auxiliary relief devices should be installed to ensure that the overpressure inside the vessel does not exceed 1600 times the design pressure. In any of the following situations, it can be considered a vessel, and only one relief device needs to be installed in the hazardous area (on the vessel or pipeline). However, when calculating the discharge volume of the relief device, the connecting pipes between containers must be included. a) A pressure vessel connected to a pressure source and which does not generate pressure on its own; the design pressure of this vessel reaches the design pressure of the pressure source ； b) When the design pressures of the pressure vessels are the same or only slightly different, and the vessels are connected by pipes of sufficient size without any valves in between. B4.4 For the same pressure vessel that has two or more design pressures due to various operating conditions, the operating pressure of the vessel’s relief device shall be suitable for the design pressures under all such conditions, and shall meet the requirements of B4.2. B4.5 If the pressure inside a container may be lower than atmospheric pressure, and the container cannot withstand such negative pressure, a relief device to prevent negative pressure should be installed. B4.6 For pressure vessels such as heat exchangers, if there is a risk that the high-temperature medium could leak into the low-temperature medium and generate steam, a venting device should be installed in the low-temperature area. B4.7 Generally, any type of relief device can be chosen, but a rupture disc device must be used if one of the following conditions is met. a) Rapid increase in pressure, b) Higher requirements for sealing, C) Materials inside the container can cause the safety valve to fail ； d) Other situations where safety valves cannot be used