Safety valve discs are not stable.
The valve disc frequently pops or flutters. Frequently popping refers to the fact that after the safety valve
gets back on its seats, it will open again after the pressure rises a little, which will appear repeatedly. This phenomenon is called the frequently popping of the safety valve. The occurrence of frequently popping is extremely unfavorable to the sealing of the safety valve, and it is very easy to cause leakages of the sealing surface. The vibration of the safety valve in the discharge process is called the flutter of the safety valve. The flutter can easily cause metal fatigue, reduce the mechanical performance of the safety valve, and cause serious hazards for the equipment. The reason for the unstable valve disc are as follows:
(1) The spring's stiffness is too great, and the valve disc can not rise to the opening height; the discharge volume is too small, and the pressure continues to rise after the safety valve is opened, resulting in reopening. Using a spring with appropriate stiffness can solve this problem.
(2) The adjustment ring is improperly adjusted, and the channel area is too large. After the safety valve is opened, the pressure drops sharply below the working pressure. The valve will be closed with the violent impact of the valve disc on the valve seat. Since the source of the pressure increase has not been eliminated, the valve disc opens again, forming a frequent popping. This problem can be solved by readjusting the position of the adjustment ring.
(3) The resistance of the discharge pipeline is too great, and the momentum of the outflowing medium decreases sharply, resulting in excessive discharge back pressure, which can be solved by reducing the resistance of the discharge pipe and removing the obstacles of the discharge pipe.
(4) The valve is not used properly, and the discharge capacity of the selected valve is too great. Make the rated discharge of the selected valve as close as possible to the required discharge of the equipment.
The valve seat is not normal.
After the exhaust, the pressure continues to rise. The reasons are as follows:
(1) The discharged amount of the selected safety valve is less than the safe discharge capacity of the equipment. After the safety valve is opened, it is too late to discharge the overpressure medium, and the pressure of the pressure vessel continues to rise. Select the appropriate safety valve again.
(2) The centerline of the valve stem is not correct or the spring is rusted, so that the valve disc cannot rise to the proper height, which reduces the discharge amount of the safety valve. Reassemble the valve stem or replace the spring, and pay attention to the anti-rust measures of the spring.
(3) The cross-section of the exhaust pipe is not enough, so that the discharged amount of the safety valve is smaller than the safe discharge amount of the equipment. Use an exhaust pipe that meets the safe discharge area.
(4) The spring's grade does not meet the requirements. Because the stiffness is too poor, the spring compression is too great during adjustment, resulting in insufficient opening height. Replace the spring of the corresponding grade, and the stiffness of the spring should be appropriate.
The valve disc does not return to its seat after discharge. This is mainly because: