Detection and Quantification of Control Valve Stiction

Stiction is one of the most common problems in the spring-diaphragm type control valves, which are widely used in the process industry. Although there have been many attempts to understand and detect stiction in control valves, none of the current methods can simultaneously detect and quantify stiction. There is thus a clear need in the process industry for a non-invasive method that can not only detect but also quantify stiction so that the valves that need repair or maintenance can be identified, isolated and repaired. This work describes a method that can detect and quantify stiction that may present in control valves using routine closed loop operating data obtained from the process. No additional excitation or experimentation with the plant is required. Over a dozen industrial case studies have demonstrated the wide applicability and practicality of this method as an useful diagnostic aid in control-loop performance monitoring.