How to calculate the set pressure of a safety valve?

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1. The concept of setting pressure: Setting pressure, also known as opening pressure, is an important parameter in the operation of safety valves. The value of this setting pressure has a direct impact on the safety of equipment operation. 2. Determination of the setting pressure: The setting pressure of a safety valve is generally not higher than the design pressure of the pressure vessel or pipeline. Unless there are special process requirements, the setting pressure of the safety valve is 1.10 times the normal operating pressure, with a minimum of 1.05 times. 3. Adjustment of set pressure: Within the specified operating pressure range, the set pressure can be adjusted by rotating the adjustment screw, thereby changing the amount of spring pre-tension compression. Remove the valve cover cap and loosen the lock nut in order to adjust the adjustment screw. First, increase the inlet pressure to cause the valve to open once; if the opening pressure is too low, tighten the adjustment screw in a clockwise direction ； If the set pressure is too high, loosen it counterclockwise. After adjusting to the desired set pressure, tighten the lock nut and put on the cap. If the required setting pressure exceeds the operating pressure range of the spring, it is necessary to replace it with another spring whose operating pressure range is suitable, and then make the adjustments. After replacing the spring, the corresponding values on the nameplate should be changed. When adjusting the set pressure, the following points should be noted: (1) When the medium pressure approaches the set pressure (reaching over 90% of the opening pressure), do not rotate the adjustment screw; otherwise, the valve disc may also rotate, thereby damaging the sealing surface. 　　(2) To ensure the accuracy of the set pressure value, the medium conditions used for adjustment, such as the type of medium and its temperature, should be as close as possible to the actual operating conditions. When the type of medium changes, especially when transitioning from a liquid phase to a gas phase, the set pressure often varies. As the operating temperature increases, the set pressure decreases. Therefore, when it is adjusted at normal temperature for use at high temperatures, the set pressure value at normal temperature should be slightly higher than the required opening pressure value.