Safety valves are used for pressurizing equipment, containers or pipes as overpressure protection devices. When the pressure in the equipment, container or pipeline exceeds the allowable value, the valve will automatically open and then be fully discharged to prevent the pressure in the equipment, container or pipeline from continuing to rise; when the pressure drops to the specified value, the valve should automatically close in time to Protect the safe operation of equipment, vessels or pipes.

       The safety valve can be directly driven by the system pressure at the valve inlet. In this case, the mechanical load provided by the spring or hammer overcomes the pressure of the medium acting under the disc. They can also be controlled by a mechanism that releases or applies a closing force to open or close the safety valve. Therefore, according to the above driving method, the safety valve is divided into a direct acting type and a pilot type.

       It can also be proportionally opened within a small opening height range, and then suddenly opened to the fully open position. Therefore, the safety valve can be divided into proportional and fully open.

       The construction, use and determination of safety valves shall comply with regulations or be approved by legal authorities. Constraints and definitions may vary by specification. When applying a safety valve, the requirements of its applicable code must be followed.

       There are three possibilities if there is an internal leak without starting the safety valve:

       First of all, there is a small leak when your safety valve is inspected, but it is not easy to find. Such a small leak point will expand in the erosion. The test method is to test the pressure test, and the stricter method is to seal the sealing surface. In the test, the water will cover the sealing surface and there is no foam at the rear pressure. The safety valve procedure stipulates that the soft seal must be bubble-free and a hard seal may be available, but the rate of bubble generation must be within a certain range. This should be done after the calibration is completed, as the safety valve may damage the sealing surfaces during the calibration.

       Secondly, it is the fatigue of the spring. The spring is relatively affected by temperature and environment (if the safety valve is closed, it must also consider the influence of the medium). If this reason is the safety valve selection or quality problem.

       Then there are pipeline factors, such as vibration and shock, which cause the pressure of the safety valve to be set too large, and the valve core is detached from the sealing surface of the valve seat, causing damage and slag inclusion. In fact, the safety valve manufacturing requirements are quite high, especially for power station safety valves. Since the sealing force of the safety valve is equal to the spring force-medium pressure, and close to the general place such as the main steam, feed water pressure and working pressure safety valve of the power plant, the actual sealing force of the sealing surface is not too large, and it is expected to be good under low effects The sealing and sealing surfaces must be processed with high precision and high requirements for materials.

       On the other hand, the performance of the spring must be very stable, because the high temperature of the medium will cause the output of the spring to drop, which is not tightly sealed. In particular, the steam safety valve has a recoil plate. Generally, the leakage may cause the safety valve to jump and affect the power supply.

       Safety valve is an important part to ensure the safe operation of the equipment. Only qualified inspection units can inspect and maintain safety valves. It is recommended to disassemble once a year and submit for inspection.