1, the output force of the pneumatic valve actuator is insufficient. The pneumatic actuator is the power component that drives the spool action. The output force is greater than the force required to close the valve. Otherwise, slack closing will occur. The pneumatic valve will be opened with medium pressure, which will cause internal leakage.
2, open the regulating valve diaphragm actuator spring stiffness is insufficient. The pneumatic diaphragm valve closes the valve by the force of the spring. When it opens, it requires less driving force, but when it closes, it requires more power. In order to overcome the pressure difference between the front and back of the valve, when the force of the spring is not enough to overcome the pressure difference, it will close slack.
3, control valve selection is not correct. Valves are also concerned about the right door. Different control valves have different allowable differential pressures. Sleeve control valves and double-seat control valves have a greater differential pressure than single-seat control valves. Angle stroke V control ball valve and eccentric rotary ball valve allowable differential pressure is larger. In the large differential pressure conditions, the reasonable choice of control valves is critical.
4, the control valve internal impurities, foreign matter caused by blockage. The bonnet of the control valve needs to be disassembled and the spool needs to be disassembled and cleaned. Damage to the sealing surface needs to be reground and reassembled.