Transient behaviour of systems with perpetual operation-repair cycles

Many systems or items to through cycles of operation-repair in their lifetime in which the system/component is either up and running or under repair. It is common in many items that repair time depends on cause of failure which is a reflection of time to failure of the time. Several studies have relaxed this constraint by assuming independence between operation time and repair time. It will be shown that the limiting behaviour is in fact the same although the transient behaviour is significantly different depending on the time distributions applied. In sensitive situations where start-up behaviour is of concern such variations in availability cannot be ignored. This paper aims at derivation of the availability function of a single component with dependent exponentially distributed time to failure and repair time which is operating until failure, repaired and back to operation immediately. The techniques used to estimate the necessary parameters involved an numerically generated availability functions are introduced and compared with results under independent assumptions.