Optimum allocations for reliability and maintainability for series system with buffers under imperfect repair

System reliability enhancement and maximization is now a crucial issue in large scale industries like oil refineries and petrochemical processes. Redundancies such as multiple units in parallel or standby units are neither structurally nor economically feasible. Alternatively, series sub-systems with inprocess buffers are commonly used. In these plants, buffers are essential to guarantee the steady output flow in case of having failed equipment or having equipment under maintenance and repair. In these series systems, the capacity of each sub-system should be greater than the targeted capacity of the plant by a specified margin. This is to maximize the system availability within constraints of allocated budgets. In the proposed work the problem of optimal allocations of reliability and maintainability to such series continuous flow systems, for example the series systems in oil & gas upstream and downstream industries, is considered. Optimum capacity margins, capacity of in-process buffers will be considered as decisions variables in addition to other variables describing the performance of the system. The optimal reliability and maintainability is allocated based on multiple objectives to assure that minimizing the total cost will not affect the system integrity.