Common problems of safety valve

Safety valve is used as overpressure protection device for pressurized equipment, container or pipeline When the pressure in the equipment, container or pipeline exceeds the allowable value, the valve will open automatically, and then discharge completely to prevent the pressure in the equipment, container or pipeline from rising continuously; when the pressure drops to the specified value, the valve shall close automatically in time to protect the safe operation of the equipment, container or pipeline 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 medium pressure acting on the valve 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 mode, the safety valve is divided into direct acting type and pilot type The safety valve can be opened in proportion in the whole range of opening height, in a considerable range of opening height, or only in a small range of opening height, and then suddenly open to the full open position Therefore, the safety valve can be divided into proportional type and full open type The construction, use and determination of safety valves shall conform to the regulations or be approved by the statutory authorities Constraints and definitions may vary by specification When applying safety valves, the requirements of their applicable codes must be followed Safety valve take-off and leakage three possibilities: your safety valve check has a small leak, but it is not easy to find, so small leakage point will expand in the erosion The test method is to test the pressure test, the more stringent method is to seal the sealing surface test, the water will cover the cover, after pressure whether there is a bubble The safety valve procedure states that the soft seal must be bubble free, and the hard seal may be available, but the bubble generation speed must be within a certain range This should be done after the calibration is complete as the safety valve may break the sealing surface during the calibration The second is the fatigue of the spring The spring is greatly affected by the temperature and environment (if the safety valve is closed, the influence of the medium should also be considered) If the reason is the selection of the safety valve or the quality problem Three is the pipeline factors, such as vibration, impact, resulting in the safety valve set pressure is too large, the valve core from the seat sealing surface, resulting in damage, slag and so on In fact, the manufacturing requirements for safety valves are quite high, especially for power station safety valves As the sealing force of the safety valve is equal to the spring force - medium pressure, which is close to the general places 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 Under the low action, good sealing is expected The sealing surface should be processed with high precision and high material requirements Third: the performance of the spring must be very stable, because the medium temperature is high, which will cause the output of the spring to drop, which is not tightly sealed In particular, the steam safety valve is equipped with a backflushing plate, and the leakage may cause the safety valve to jump, thus affecting the power supply Do not suggest self maintenance! Safety valve is an important part to ensure the safe operation of the equipment Only qualified inspection unit can inspect and maintain the safety valve It is recommended to dismantle once a year and submit for inspection.