Adjustment of safety valve opening pressure (set pressure):
Within the specified working pressure range, the opening pressure can be adjusted by rotating the adjusting screw and changing the pre compression amount of the spring. After removing the valve cover and loosening the locking nut, the adjustment screw can be adjusted. Firstly, increase the inlet pressure to make the valve jump once.
If the opening pressure is low, tighten the adjusting screw clockwise; If the opening pressure is too high, loosen it counterclockwise. After adjusting to the required opening pressure, tighten the locking nut and install the hood.
If the required opening pressure exceeds the working pressure range of the spring, it is necessary to replace another spring with a suitable working pressure range, and then make adjustments. After replacing the spring, the corresponding data on the nameplate should be changed.
When adjusting the opening pressure of the safety valve, the following points should be noted:
When the medium pressure approaches the opening pressure (reaching more than 90% of the opening pressure), the adjusting screw should not be rotated to prevent the valve disc from rotating and damaging the sealing surface.
To ensure the accuracy of the opening pressure value, the medium conditions used for adjustment, such as the type and temperature of the medium, should be as close as possible to the actual working conditions. When the type of medium changes, especially when transitioning from liquid to gas, the opening pressure often changes. When the working temperature increases, the opening pressure decreases. Therefore, when adjusting at room temperature for high temperatures, the set pressure value at room temperature should be slightly higher than the opening pressure value of the ball.
Adjustment of safety valve discharge pressure and reseating pressure:
After adjusting the opening pressure, if the discharge pressure or reseating pressure does not meet the requirements, the adjustment ring on the valve seat can be used for adjustment. Unscrew the fixing screw of the adjustment ring, insert a thin iron rod or similar tool into the exposed screw hole, and then move the gear teeth on the adjustment ring to rotate left and right.
When the adjusting ring rotates counterclockwise to the right, its position increases, and the discharge pressure and reseating pressure both decrease; On the contrary, when the adjusting ring rotates clockwise to the left, its position decreases, and the discharge pressure and reseating pressure both increase. During each adjustment, the adjustment ring should not rotate too much (usually within 5 teeth).
After each adjustment, the fixing screw should be tightened so that the end of the screw is located in the groove between the two teeth of the adjustment ring to prevent the adjustment ring from rotating, but it should not generate lateral pressure on the adjustment ring. Then conduct action tests. For safety reasons, before moving the adjustment ring, the inlet pressure of the safety valve should be appropriately reduced (generally lower than 90% of the opening pressure) to prevent accidents caused by sudden opening of the valve during adjustment.
Note that conducting safety valve discharge pressure and reseating pressure tests is only possible when the flow rate of the air source is large enough to prevent the valve from opening (i.e. when the rated discharge capacity of the safety valve is reached).
The capacity of the test bench commonly used to verify the opening pressure of the safety valve is very small, and at this time, the valve cannot reach full opening, and its reseating pressure is also false. When calibrating the opening pressure on such a test bench, in order to make the takeoff action obvious, the adjusting ring is usually set at a relatively high position. However, under the actual operating conditions of the valve, this is not appropriate, and the position of the adjusting ring is readjusted.
Lead sealing
After all safety valves have been adjusted, they should be sealed with lead to prevent arbitrary changes to the adjusted condition. When the safety valve leaves the factory, unless otherwise specified, it is usually adjusted using room temperature air according to the upper limit (i.e. high pressure) of the working pressure level.
Therefore, users generally need to make adjustments based on actual working conditions. Then re seal with lead.
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