A method for detecting and characterizing an occurrence of at least one event during operation of a valve actuator as one of a deviation, malfunction or failure, the method comprising the steps of: detecting a series of signals received from a plurality of sensors, where each signal represents a condition of a different operational variable associated with the actuator ; determining from the signals one or more of the operational variables that caused the occurrence of the at least one event; the method being characterized : determining at least one relationship between the one or more operational variables and the at least one event, determining a time-related succession of intermediate states of operation associated with the valve actuator, wherein each state of operation is a group of one or more of the operational variables being in a normal operation zone, a deviation zone, a malfunction zone or a failure zone, and wherein the states are interconnected by transition paths which are automatically quantified by cause-and-effect relationships and temporal and likelihood factors; characterizing each at least one event by the one of the operational related variables being in one of the normal mode of operation zone , the deviation zone , the malfunction zone or the failure zone ; and communicating the at least one relationship through an output device. detecting a series of signals received from a plurality of sensors, where each signal represents a condition of a different operational variable associated with the actuator ; determining from the signals one or more of the operational variables that caused the occurrence of the at least one event; the method being characterized : determining at least one relationship between the one or more operational variables and the at least one event, determining a time-related succession of intermediate states of operation associated with the valve actuator, wherein each state of operation is a group of one or more of the operational variables being in a normal operation zone, a deviation zone, a malfunction zone or a failure zone, and wherein the states are interconnected by transition paths which are automatically quantified by cause-and-effect relationships and temporal and likelihood factors; characterizing each at least one event by the one of the operational related variables being in one of the normal mode of operation zone , the deviation zone , the malfunction zone or the failure zone ; and communicating the at least one relationship through an output device. determining at least one relationship between the one or more operational variables and the at least one event, determining a time-related succession of intermediate states of operation associated with the valve actuator, wherein each state of operation is a group of one or more of the operational variables being in a normal operation zone, a deviation zone, a malfunction zone or a failure zone, and wherein the states are interconnected by transition paths which are automatically quantified by cause-and-effect relationships and temporal and likelihood factors; characterizing each at least one event by the one of the operational related variables being in one of the normal mode of operation zone , the deviation zone , the malfunction zone or the failure zone ; and communicating the at least one relationship through an output device. <EOS>