A component has time to failure X with denstiy f(ë). Opportunities arise as a Poisson process of rate λ. At an opportunity the component may at choice, be replaced at cost cÅ2. At failure the components can either be minimally repaired at cost cÅ1 or replaced at cost cÅ4. Finally the component may be replaced at any time at an ‘interrupt’ cost of cÅ3. The author derives expressions for the long-run expected cost rate, and gives examples of numerical optimisation with respect to control limits on age at an opportunity, and at an interrupt replacement.
