A multi-criteria decision model to determine intervals of preventive maintenance with equipment reliability degradation due to imperfect maintenance

The present paper presents a method to define preventive maintenance interval considering possible equipment degradation caused by imperfect maintenance actions and the preference of maintenance planner for high reliability or maintenance cost minimization. To model imperfect maintenance the method considers coefficients that modify equipment failure rate along operational life. The decision-making method used to select the most suitable preventive maintenance period aiming at keeping the equipment reliability higher than a target value and minimizing total maintenance costs is the multi-criteria model with the application of the PROMETHEE method. The method is applied on the analysis of equipment of a speed regulator system used in hydro generators. The objective of the analysis is to define the preventive maintenance plan during a typical operational mission aiming at no failure occurrence with minimum total maintenance costs. The maintenance planner preference is easily model by the method and has great effect on maintenance interval.