Application of Functional Safety Theories in Furnace Safety Supervisory System

Furnace safety supervisory system (FSSS) plays an important role in protecting the boiler of thermal power plant from danger. In order to evaluate the performance of FSSS itself, functional safety theories are applied in this paper to achieve hazard and risk analysis, target safety integrity level (SIL) determination and functional safety evaluation. The most important safety instrumented function (SIF) of FSSS-master fuel trip (MFT) is considered, and the probability of failure on demand (PFD) is calculated based on the method of fault tree analysis (FTA). According to the analysis result, target SIL for FSSS is 2, but the actual system does not meet the requirement. Through corrective measures of making one-out-of-two (1oo2) redundant configuration for each actuator and compressing the functional testing cycle, the safety index of MFT ultimately reaches the target value.