Reliability modeling of emergency shutdown function for heat recovery steam generator control

Abstract

This paper presents a method for evaluating reliability and unreliability of emergency shutdown function for a control system of heat recovery steam generator (HRSG), which is operated with active redundant for providing safety and protection. The studied triple-pressure HRSG for driving the steam turbine in a power plant consists of three sections: high pressure section, intermediate pressure section, and low pressure section. A safety shutdown is based on level and pressure sensing system with three pressure transmitters and three level transmitters in each section for implementing a voting algorithm in order to tolerate the failure ofone sensor. Fault tree analysis (FTA) is employed as a tool for analyzing probability functions ofsuccess and failure for three possible voting algorithm configurations. Based on the obtained modeling, complex data of the studied system are transformed to accurate prediction of its reliability and unreliability.