Online valve diagnostic monitoring system

An online plant operation monitoring system for monitoring operational units in a plant, comprising:

• sensor means for continuously sensing conditions of the operational units in the plant to produce sensor signals;
• data storage means for storing baseline data and historical data for each of the operational units;
• data acquisition means for transmitting the sensor signals;
• extraction means for extracting characteristic features of each of the operational units from the sensor signals corresponding thereto by comparing the sensor signals with the baseline data to determine deviations therefrom in proportion to the baseline data, whereby the characteristic features are dimensionless;
• and
• diagnosis means for evaluating the characteristic features by application of an expert system rule base.

An online valve monitoring system for monitoring valves in a piping system, the valves having a valve stem actuated by a motor, said valve monitoring system comprising:

• sensors for outputting sensor signals, each of the valves having at least three sensors corresponding thereto, the at least three sensors comprising:
• a motor current sensor for detecting current drawn by the motor operating a corresponding valve;
• a strain sensor, directly coupled to the valve stem, for sensing strain of the valve stem of the corresponding valve;
• and
• a position sensor, coupled to the valve stem, for sensing a position of the valve stem of the corresponding valve;
• data acquisition means for transmitting the sensor signals from the valves to a remote location;
• timing means for storing baseline data and historical data for each of the valves;
• signal processing means for extracting characteristic features of the sensor signals from each of the valves by comparing the sensor signals with the baseline data to determine deviations therefrom in proportion to the baseline data, whereby the characteristic features are dimensionless, and for providing a deviation significance indication for each of the characteristic features in dependence upon the magnitude of the deviations between the sensor signals and the baseline data corresponding thereto;
• diagnosis means for evaluating the characteristic features by application of an expert system rule base to provide a diagnosis of a malfunction capable of causing the deviations between the baseline data and the sensor signals corresponding thereto, for each valve and comparing the deviations corresponding to each valve to determine a confidence factor for the diagnosis thereof;
• analysis means for analyzing the historical data to detect a trend in changes in the sensor signals and for providing maintenance scheduling recommendations;
• output means for providing an immediate indication when said diagnosis means diagnoses the malfunction of one of the valves and for outputting at least one of the trend and the scheduling recommendations upon at least one of a request and a scheduled basis;
• and
• updating means for updating the baseline data after maintenance of one of the valves without affecting the expert system rule base and for updating the expert system rule base without requiring changes in the processing of the sensor signals.