An innovative processing method for the direct bathtub calculation

\In many plants, industries, etc. unavailability, often due to neglected or not well performed maintenance, results in reduced revenue and decreasing profitability. It is proved that with good maintenance management methods (usually called Computer Maintenance Management Systems, CMMS) these economic losses can be reduced and the availability improved. But a better result may be obtained intervening at level of maintenance planning. For its improvement, an optimal compromise between the costs of failures repairs and of maintenance operations, carried-out to avoid such failures, has to be found in respect of prefixed constraints on the system availability, reliability, etc. To this aim, reliability criteria must be considered. In this frame, the knowledge of the failure rate of the single components (suitably obtained by the processing of exploitation data previously collected) and, in particular, of its variation in the time has a particular importance. The present paper describes a now method for the processing of the much less than total much greater than failure rate of each component type of an industrial system on the basis of historical data previously collected on it and its possible use for the selection of the only components on which maintenance must be applied and its preliminary definition.