METHOD AND APPARATUS FOR DIAGNOSING PNEUMATIC CONTROL VALVE BY USING POSITIONER MODEL

摘要

Provided is a method for diagnosing a pneumatic control valve by using a positioner model. The method may comprise the steps of: establishing a relational expression for outputting a valve stem displacement according to control pressure, the relational expression including parameters for the characteristics of a positioner, an actuator, and a valve; determining an initial parameter value by adjusting the values of the parameters until the difference between a measured value for a normal operation of the pneumatic control valve and an output value obtained by the relational expression is smaller than a predetermined error limit; determining a diagnostic parameter value by adjusting the values of the parameters until the difference between a measured value for a diagnostic operation of the pneumatic control valve and an output value obtained by the relational expression is smaller than a predetermined error limit; and comparing the initial parameter value and the diagnostic parameter value so as to determine whether the pneumatic control valve has an abnormality. Accordingly, it is possible to diagnose the state of the pneumatic control valve by estimating variations of the parameters in real time when the pneumatic control valve is operated and comparing the same with the values of the parameters in the normal state.