Safety valve set pressure
Release time:
2024-11-27
The set pressure, also known as the opening pressure, is an important parameter for the operation of safety valves. The setting of the set pressure directly relates to the safety of equipment operation.
The set pressure refers to the predetermined pressure at which the safety valve disc begins to open under operating conditions, measured as gauge pressure at the valve inlet. At this pressure, under specified operating conditions, the force generated by the medium pressure that causes the valve to open is balanced by the force that keeps the disc on the valve. At this pressure, measurable opening height begins to occur, and the medium is discharged in a continuous state that can be perceived visually or audibly.
The set pressure of a safety valve generally does not exceed the design pressure of the pressure vessel or pipeline. If the design drawings or nameplates indicate a maximum allowable working pressure, this can also be used to determine the set pressure of the safety valve.
Within the specified working pressure range, the set pressure can be adjusted by rotating the adjustment screw to change the pre-compression of the spring. After removing the valve cover, loosen the locking nut to adjust the adjustment screw. First, increase the inlet pressure to make the valve jump once. If the opening pressure is too low, tighten the adjustment screw clockwise; if the opening pressure is too high, loosen it counterclockwise. Once the desired set pressure is reached, tighten the locking nut and reattach the cover.
If the required set pressure exceeds the working pressure range of the spring, a different spring that is suitable for the working pressure range needs to be replaced, and then adjustments should be made. After replacing the spring, the corresponding data 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 more than 90% of the opening pressure), the adjustment screw should not be rotated to avoid damaging the sealing surface as the valve disc rotates.
(2) To ensure the accuracy of the set pressure value, the conditions of the medium used during adjustment, such as the type of medium and the temperature of the medium, should be as close as possible to the actual working conditions. Changes in the type of medium, especially when transitioning from liquid to gas, often result in changes in the set pressure. When the working temperature increases, the set pressure decreases. Therefore, when adjusting at room temperature for use at high temperatures, the set pressure value at room temperature should be slightly higher than the required opening pressure value.
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