Research On Periodical Preventive Maintenance Policies For A K-OUT-OF-N: F System

The research of preventive maintenance (PM) has received wideattention for its ability to improve production system reliability, reduceproduct costs and accelerate the enterprise’s reacting speed to market needs.In this research, three optimal periodic preventive maintenance models fork-out-of-n:F systems are established.A k-out-of-n: F system consists of n components and fails if at least k ofthe n components fails. The systems have two types of failures: type I failuresin which the failure components number is less than k, and type II failures inwhich the system’s failure components number is no less than k.The first model is to determine an optimal replace period for ak-out-of-n:F system. In this model, type I failures are removed by minimalrepairs. Type II failures are removed by replacements. If the system survivesto time T without type II failures, it will be subject to PM at time T.In the second model, we consider a two-phase preventive replace modelfor k-out-of-n:F systems. The maintenance period is divided into two phases.Each failure of a component of the system is removed by a minimal repair inthe first phases. If type I failures take place in the second phase, it can belying idle. Corrective maintenance on the failed components are performed ifthe number of failed components reaches k, or preventive maintenance isperformed once the total operating times reaches T, whichever occurs first.In the third model, we assume that PM is imperfect, which means afterPM a k-out-of-n:F system is as good as new with probability p and is as badas old with probability q=1-p. other assumption and notations are identical tothose in the second model. A renew circle in determined upon the type IIfailure, or the first perfect maintenance whichever occurs first.All the three preventive maintenance optimization models are providedto minimize the system maintenance cost rate. Finally numerical examplesare given by using Matlab program to find out the optimal solution andpresented the sensitivity analysis for major parameters.