In this paper, the concepts of preventive maintenance are pres¬ented in first part, and second part of the paper present several mathematical models for prediction service life as a base for preventive maintenance forecasting. These models aid in determining the frequency of inspec¬tions that will allow the condition of a piece of equipment to be determined in order to plan an appropriate maintenance action. The problem of determination of the service life is directly related to geometry, multiaxial loadings, materials and appropriate models for prediction of the failure propagation. The more precise modelling of these input parameters the more precise and reliable the results are. Therefore in the paper we will present models and procedures for calculations service life, remain service life and/or service control cycle.