Quality Technology and Quantitative Management Reliability Monitoring and Performance Measuring for the Exponential Failure Process

Reliability monitoring and performance measuring of a failure process are important issues for complex products or repairable systems. Xie et al. proposed a new type of control chart called the t-chart for monitoring processes reliability with low nonconforming rates. In this paper, the t -chart is used as a first controlling stage to monitor an exponential failure process. But, being in control of a process by statistical process control is not enough since an in- control process can produce bad or out of specification products. To measure the performance of the exponential failure process, a lifetime capability index denoted as L_tp is proposed. By taking past in- control sample data of t -chart from the first controlling stage without additional sampling efforts, we develop the second controlling stage that the sampling error is considered to obtain the lower confidence bound of L_tp and to make a decision on how well the process reliability meets specifications.