Process and controller performance monitoring: overview with industrial applications

SUMMARYComplex processes depend on regulatory control systems to operate. Changes made to the sensor systemand the process itself as well as the natural degradation over time of the equipment may cause somecontrollers’ and process performance to suffer. Since there are hundreds of controllers in most complexprocesses, it is virtually impossible to monitor their performance manually. This work reviews the state-of-the-art in controller performance monitoring including both feedforward and feedback control. Theexperiences of the DuPont Company in the deployment of a system for performance monitoring arepresented. Information as to how such a monitoring system is implemented in the operation of a chemicalprocess and examples of its operation are included. Copyright # 2003 John Wiley & Sons, Ltd. KEY WORDS : compliance metrics; chemical processes; real-time monitoring; controller performance 1. INTRODUCTIONMost modern industrial plants have hundreds and even thousands of automatic control loops.These loops can be simple proportional-integral-derivative (PID) or more sophisticated model-based linear and non-linear control loops. It has been reported that as many as 60% of allindustrial controllers have performance problems [1]. Having an automated means of detectingwhen a loop is not performing well and then diagnosing the root cause is essential because theyplay a vital role in product quality, safety and ultimately economics.Some of the obstacles that prevent this automatic assessment, from being a part of the day-to-day maintenance program include a lack of: user-friendly interface, readily understandablereport generation, diagnosis information in text form, a single composite index ranking the loopperformance and reliable computational software tools. In addition, education of the operationsstaff is essential to make full use of some of the currently available time and frequencymethodologies.

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