Optimal Age-replacement Policy for Series Systems Considering Maintenance Time

Age-replacement is one of the most commonly usedmaintenance policies based on preventive action to prevent system failure. Inmany age-replacement settings, it assumed that maintenance time can beignored since short compared with operation time. However, maintenance,especially corrective maintenance, may take a non-negligible amount dueto various factors such as ordering replacement parts, equipping themaintenance team, and transporting equipment. Neglectingmaintenance when optimizing for multi-unit systems maythus lead sub-optimal or even incorrect solutions problem, resultingin higher costs. We present an optimal policy forsystems consisting multiple independent units connected in series. Thefailure any causes entire fail, which isimmediately detected. formulated model integrates both andcorrective times determining replacementinterval, minimizing expected long run cost per unit The sufficientconditions existence uniqueness corresponding optimalsolution are derived. performance proposed wasevaluated by comparing conventional does not intoaccount Numerical examples illustrate effects downtimecost policy.