An improved algorithm for automatic quantification of valve stiction in flow control loops

Stiction is a common cause of loop performance deterioration. The presence of stiction in the spring-diaphragm type valve is the most frequently found valve problem in the process industry. Methods have been proposed fitting an ellipse to the PV-OP plot and the maximum width of the ellipse is reported as "apparent stiction". An improvement on these methods is here proposed for situations where the PV-OP plot is similar to a parallelogram, resulting in a better estimation of stiction. The application of this quantification algorithm together with the cross-correlation detection method to several examples is used to demonstrate the superiority of the proposed approach.