METHOD AND APPARATUS FOR DETECTING A FAULT OF A CONTROL VALVE ASSEMBLY IN A CONTROL LOOP

A method and apparatus for detecting a fault of an automatically operated control valve assembly. Data consisting of several values of the control signal (i) and corresponding values of the position (h) of the control valve is measured and recorded. A mathematical model for the control valve assembly is defined. The mathematical model is fitted to the data measured from the control signal (i) and the position (h) of the control valve. At least one critical parameter for each component of the valve assembly, that is the valve (2) itself, the actuator (3) and the positioner (5), is chosen. The values and changes of the critical parameters are computed from the mathematical model fitted to the measured data. The component in which the fault is located is detected on the basis of the computed values of the critical parameters.