Diagnosis quantification of control valves

Evaluation of control loop performance becomes of great importance to realize safe and highly efficient plant operations. Typical plant has hundreds or thousands of control loops and it is impossible to investigate all the control loops manually. Various researchers have been investigated automatic methods to evaluate performance of control loops. After the evaluation of control loop performance, root cause of poor performance should be diagnosed. One of the most common cause to produce oscillating behavior in control loops is the stiction of control valves. The author proposed a diagnosis method of stiction based on qualitative shape analysis. In this paper, the method is extended to quantify stiction by showing the width of sticky movements. The method is successfully applied to several data sets of industrial control loops.