Probabilistic models for analyzing the availability and profit of a deteriorating 2-out-of-4 system

This paper deals with modelling and evaluating the availability and profit of a linear consecutive 2-out-of-4 system exposed to three consecutive stages of deterioration before failure. The system will pass through three consecutive stages of deterioration: slow, medium and fast before failure. The failure and repair times are assumed to be exponentially distributed. Explicit expressions for the system avail-ability, the probability of a repairman being busy due to the failure of a unit, or due to the replacement of failed units, and the profit function have been derived using a probabilistic approach. The impacts of the failure and repair rate on system availability and profit have been investigated. The results of this paper will enhance system performance and ensure the timely execution of appropriate maintenance and improvement, and thus is a major tool for decision making, planning and optimisation.