Approximate Calculations of Maintenance Policies for Weibull Distribution Using Exponential Distribution

It is always easy to get analytical formulas of optimal maintenance policies with exponential failure times in reliability theory, however, it might be difficult sometimes to discuss them theoretically with a Weibull distribution. This chapter proposes several approximate calculations for failure times and age replacement of operating units, MTTF and replacement of parallel systems, and inspection models with Weibull failure times. It has been well known that when failure times are exponential, any finite maintenance time does not exist. Introducing deviation and variance times between failure and maintenance times, it is shown analytically in this chapter that finite times exist for exponential failure times, and using them, approximate maintenance times are given for Weibull failure times. These approximate calculations would become useful references to optimal maintenance policies, and be applied for maintenance plans in practical fields.