New reliability data processing methods for maintenance improvement

ENEA (an Italian Research Institute) developed, in collaboration with some European companies (ATC, ANSALDO, SIVECO France and IIS sa) and within a Project financed by the European Commission (Contract No BRPR - CT96-0211), a software tool to be applied for the improvement of the maintenance planning of each type of complex system (industrial production lines, networks, power production plants, transport systems, etc.) on the basis of reliability and costs criteria. To achieve the prefixed goals, the developed software includes a database for the end-users direct recording of historical data on the components of their equipments and interactively connected with appropriate computer methods to process suitable reliability data on the basis of the rough data so collected. Other computer methods allow the automatic selection of the components on which maintenance must be applied together with its preliminary definition and its improvement at system level. The paper includes a detailed description of the above methods (integral part of the main software tool) for the processing of reliability data. Different methods were set-up to this aim; one of them allows the processing of the total failure rate independently of the failure causes searching the bathtub distribution (or part of it) better approximating all the available rough data. Other methods allow the processing of failure rates referring to the failure cause; to this aim the classical and bayesian statistics were applied.