Research On Oscillation Factors Of Industrial Control Valves

As a terminal actuator in industrial control,the control valve is extremely important.The performance of the control valve directly affects the safety of industrial sites and the quality of industrial products.At the beginning of the application of the control valve,the positioning control performance of the control valve is relatively superior.However,as the control valve is operated for a long time under high temperature and high pressure conditions or fails to maintain in time,and abnormalities such as impurities appear in the medium or pipeline,the control valve and the control system where the control valve is located will eventually oscillate.Such oscillations can cause large fluctuations in industrial products and can even cause serious industrial accidents.Therefore,it is of great significance to explore the basic causes of the oscillation of the control valve and to avoid these reasons in the design stage in the future.Based on the mechanism model of the control valve and the liquid level control mechanism model,the causes of the oscillation of the control valve are analyzed respectively on the pneumatic actuator part of the control valve and the flow characteristic part of the control valve.Firstly,the mechanism model of the control valve is analyzed and verified to ensure the feasibility of exploring the pneumatic execution of the control valve.Based on the mechanism model of the control valve,the causes of the partial oscillation caused by the aerodynamics are analyzed and simulated.The difference between the dynamic and static frictional force of the control valve is positively correlated with the amplitude of the control valve oscillation.At the same time,the influences of the control parameters and the set signal on the amplitude of the oscillation are explored,which proves that they are the key factors affecting the oscillation.Secondly,the mechanism model of the liquid level control model simulating a real working condition is modeled,and the open-loop and closed-loop verification are carried out to ensure the accuracy of the model.Based on the liquid level control model,the vibration of the liquid level control object caused by the flow characteristic curve is analyzed and simulated.When the flow characteristic curve of the control valve is distorted,the controlled liquid level object will oscillate.in conclusion.According to the degree of distortion of the flow characteristic curve,the conclusion that the more severe the distortion of the flow characteristic curve is,the more serious the oscillation of the control system is.At the same time,the degree of oscillation of the control system is simulated by the distortion mode with different flow characteristics and the degree of tilt,which proves that it all causes the basic factors of the control system oscillation.