Optimization of inspection strategy and status monitoring for standby equipment avaiability enhancement

Abstract

In many cases, the plant safety greatly depends on the successful operation of specific standby equipment at the time of demand arrival. For the effective management of safety critical standby equipment, unavailability measures are introduced and widely applied. In this study, we propose an age-dependent unavailability model for standby equipment, which considers aging relevant information, such as the number of actual operation, the elapsed time from its installation, in an integrated manner. Based on the proposed model, we present two availability enhancement strategies, Online Monitoring based Inspection Method (OMIM) and Shortening Surveillance Test Interval Method (SSTIM). In OMIM, "elapsed time sensitive' elements are monitored, without actual operation, at the differentiated monitoring interval with the help of sensing devices. For the rest parts of the elements, actual testing is applied with the adaptive interval for each standby turn by SSTIM. The effectiveness of the proposed enhancement schemes is demonstrated via a case study for the motor operated valve (MOV). To our belief, the proposed schemes can have wide applications such as equipment tests, dynamic probabilistic safety assessment (PSA), and risk-informed regulations.