A survey of maintenance policies of deteriorating systems

Simple preventive maintenance (Maintenance type 1P) and preventive replacement (maintenance type 2P) are scheduled in such a way that the system does not drop below a minimum reliability. Failure rate after maintenance type 1P lies between "good as new" and "bad as old". The degree of improvement in failure rate after maintenance type 1P is cailed the improvement factor. A set of curves for the improvement factor as a function of cost for maintenance type 1P and age of the system is proposed. The cost rate for a system is formulated as a ratio of an average cost for a cycle (time between replacements) to an average cycle length. An optimum number of type 1P maintenance actions before type 2P maintenance is obtained by minimizing the cost rate when the failure times are Weibull distributed. The optimum solutions are a function of improvement factors and predetermined upper limit of failure rate.

An Algorithm for Preventive Maintenance Policy

Joint redundancy and maintenance optimization for multistate series–parallel systems

Extended optimal replacement model with random minimal repair costs

In extreme shock models, only the impact of the current, possibly fatal shock is usually taken into account, whereas in cumulative shock models, the impact of the preceding shocks is accumulated as well. A shock model which combines these two types is called a `combined shock model'. In this paper we study new classes of extreme shock models and, based on the obtained results and model interpretations, we extend these results to several specific combined shock models. For systems subject to nonhomogeneous Poisson processes of shocks, we derive the corresponding survival probabilities and discuss some meaningful interpretations and examples.

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On new classes of extreme shock models and some generalizations

The reliability behavior of systems is investigated if two types of failures can happen. Type 1 is removed by minimal repair, Type 2 by replacement. Reliability expressions are derived. The results are used for calculating the s-expected long-run cost rate for a generalized age replacement policy and repair limits.

Klaus Fischer

Papers

General Failure Model Applied to Preventive Maintenance Policies