Joint Optimization Of Redundancy Allocation And Spares Inventory For A Series System

With the coming of capital intensive industrial era,people's requirement for the system availability become higher and higher.Redundancy allocation and spares inventory for a repairable system are two important methods for improving the system availability.However,in the existing research on the availability of repairable systems,these two aspects are generally considered separately.Occasionally a few joint optimization papers of redundancy allocation and spares inventory has emerged recently,but those researchers only focus on the most fundamental hot-standby redundancy and on(S-1,S)ordering policy.On the basis of existing joint optimization reliability model,this paper proposes a joint optimization model of redundancy allocation and spares inventory for a series system.Specifically,in our model,hot-standby,warm-standby and cold-standby are considered as redundant components respectively and a more general ordering policy(s,S)is adopted.Firstly,this paper formulates the system operating mechanism and gives the corresponding model assumptions.According to these conditions,the Markov state-space of system is formulated.Next,based on the knowledge of continuous time Markov process,the system steady availability,the mean time between failures and other related reliability probability indices are derived to solve this problem.What's more,maximizing the system steady availability is considered as an objective,cost budgets and spares availability are considered as constraints,the mathematical programming model of joint optimization system is formulated.It can be solved by branch and bound method.Finally,by comparing and researching the related reliability probability indices and the optimal solutions for the joint optimization model,the conclusion that the proposed joint optimization model is definitely and significantly superior to the previous joint optimization model can be proved.Besides,main conclusions are as follows:The optimal batch ordering policy is,as same as,sometimes even better than the optimal one-for-one spares replenishment policy when other conditions are identical.On the same case,cold-standby and warm-standby redundancy can obtain better system steady availability.On the one hand,this paper proposed joint optimization model can enrich the related reliability knowledge.On the other hand,this paper also has certain practical significance to the design,application and management decision of system reliability.