Study on time-dependent unavailability evaluation

Hioki, Kazumasa 

A method to evaluate time dependent unavailability of components and systems was developed and applied to a real-sized systems. With the component failure rate and the information on test and maintenance, the method first calculates the unavailability of each component included in minimal cutsets that is obtained through a fault tree analysis, and then calculates both the time-dependent and time-averaged unavailability of the system. It was shown that the method can be utilized to set a test schedule which gives higher reliability with the same manpower. Also shown is that the method can help develop the operational procedures such as the allowable outage time or the test intervals using the peak value instead of the time-averaged value of system unavailability.