INTERVAL ESTIMATION OF AVAILABILITY OF A SERIES SYSTEM

A system consists of n independent subsystems connected in series. Based on a sample of complete periods for each subsystem, an approximate interval estimate of the steady-state availability of the system is presented for 3 cases: Each lifetime and repair-time has an exponential distribution Each lifetime has an exponential distribution; each repair-time has a log-normal distribution Each lifetime and repair-time has a log-normal distribution. For a large system it often costs less to test subsystems than to test the system. Consequently, it is more economical to estimate the steady-state availability of the system by using the data from each subsystem. Moreover, it is time-saving since subsystems can be tested simultaneously prior to assembly of the system. Numerical examples show that equations (12) & (15) give quite good confidence bounds for the steady-state availability. I believe this method will prove useful in practice.