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Setting of safety valve
Created on 03.20
1 Adjustment of opening pressure (set pressure)
Within the specified working pressure range, the opening pressure can be adjusted by rotating the screw and changing the amount of spring preload compression. After removing the valve cover cap and loosening the lock nut, the adjustment screw can be adjusted. First, the inlet pressure is increased, so that the valve jumps once, and if the opening pressure is low, the adjustment screw is tightened in a clockwise direction; If the opening pressure is too high, rotate and loosen it in a counterclockwise direction. When the required opening pressure is adjusted, tighten the lock nut and attach 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 adjust the corresponding data on the nameplate after replacing the spring.
2 When adjusting the opening pressure, the following points should be noted:
When the medium pressure is close to the opening pressure (reaching more than 90% of the opening pressure), the adjustment screw should not be rotated to avoid the valve disc rotating and damaging the sealing surface. In order to ensure the accuracy of the opening pressure value, the medium conditions used for adjustment, such as the type of medium and the temperature of the medium, should be as close to the actual working conditions as possible. The opening pressure often changes when the medium type changes, especially when it changes from the liquid phase to the gas phase. When the operating temperature increases, the opening pressure decreases. Therefore, when adjusted at room temperature and used for high temperature, the set pressure value at room temperature should be slightly greater than the opening pressure value of the ball.
3 Adjustment of discharge pressure and return pressure
After the opening pressure is adjusted, if the discharge pressure or return pressure does not meet the requirements, the adjustment ring on the valve seat can be used to adjust it. Unscrew the fixing screw of the adjustment ring and insert a tool such as a thin iron rod from the exposed screw hole to pluck the teeth on the adjustment ring to rotate the adjustment ring left and right. When the adjustment ring rotates counterclockwise to the right, its position will increase, and the discharge pressure and return pressure will decrease. On the other hand, when the adjustment ring rotates clockwise to the left, its position decreases, and the discharge pressure and recoil pressure increase. During each adjustment, the rotation amplitude of the adjustment ring should not be too large (generally within 5 teeth). After each adjustment, the set screw should be tightened so that the end of the screw is in the groove between the two teeth of the adjustment ring to prevent the adjustment ring from rotating, but no lateral pressure should be generated on the adjustment ring. Then a motion trial is performed. For safety reasons, the inlet pressure of the safety valve should be appropriately reduced (generally less than 90% of the opening pressure) before the adjustment ring is toggled to prevent accidents caused by the sudden opening of the valve during adjustment.
It must be noted that the discharge pressure and return pressure test of the safety valve 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 of the safety valve is reached). The capacity of the test bench usually used to check the opening pressure of the safety valve is very small, and the valve cannot reach full opening, and its return pressure is also false. When calibrating the opening pressure on such a test bench, in order to make the starting action obvious, the adjustment ring is usually adjusted to a relatively high position, but this is not suitable under the actual operating conditions of the valve, and the position of the adjustment ring must be readjusted.
4 Lead seal
After the safety valve is fully adjusted, the lead seal should be carried out to prevent arbitrary changes to the adjusted condition. When the safety valve leaves the factory, except in special cases, it is usually adjusted with room temperature air according to the upper limit of the working pressure level (i.e., high pressure). Therefore, users generally need to adjust it according to the actual working conditions. Then re-lead seal.
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