Enhancing Reliability of Fuel Gas System at Combined Cycle Power Plant

This paper presents a methodology to boost the reliability of a combined natural gas and associated petroleum gas system (fuel gas system, FGS) for a gas turbine unit in a combined cycle power plant. The use of failure mode, effects, and diagnostic analysis (FMEDA) is proposed to avoid unplanned shutdowns of the power plant. This method identifies and evaluates potential types of failures, develops measures to reduce them, and establishes a new protection system. The system includes a gas analysis system (GAS), a shut-off valve system (SVS), a fuel gas controller (FGC), and workstations for an engineer and operator. The gas analysis system has two automatic subsystems with different measurement methods. One of them includes three gas chromatograph analyzers that operate according to the 2-out-of-3 voting. The results of gas chromatography and the diagnostic archive of alarms serve as the basis for analyzing the causes of possible failures. Reliability models were developed to confirm the effectiveness of using diagnostic data from gas analyzers within the gas subsystem. They employ a gas chromatography and a common fuel gas controller. The FMEDA findings demonstrate that a new safety interlock can be implemented without any additional financial outlay for software and hardware