Thepmanee, Teerawat

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Thepmanee, Teerawat
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teerawat.th@kmitl.ac.th

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    Item type:Publication,
    Reliability enhancement of LNG fuel gas supply system in combined-cycle power plant
    (2020-12-01)
    Thepmanee, Teerawat
    ;
    Nachasingha, Chakri
    ;
    Kummool, Sart
    This article aims to present a technique to enhance reliability of liquefied natural gas (LNG) fuel gas supply system (FGSS) of gas turbine unit in a combined-cycle power plant. In order to prevent unplanned plant shutdowns, the proposed technique is based on the use of failure modes, effects, and diagnostic analysis (FMEDA) to identify and evaluate the effects of possible failure modes, to determine what could minimize the chance of failures, and to design a new safety interlock. The studied FGSS consists of gas analytical system (GAS) in 2-out-of-2 voting scheme, shutdown valve system (SDV) in 1-out-of-2 voting scheme, fuel gas controller (FGC), and engineering/operator workstations. Two automatic GAS subsystems with different measurement methods are installed in the GAS. One of two GAS subsystems uses three gas chromatography analyzers in 2-out-of-3 voting scheme. The gas chromatography results and diagnostic alarm historian are utilized to consider the failure behavior. The reliability models for the GAS subsystem using gas chromatography and the overall FGSS are also included to confirm the effectiveness of utilizing diagnostic information from the gas analyzers. Based on the FMEDA results, the new safety interlock with no additional software and hardware costs can be achieved. The workability of the proposed safety interlock is demonstrated by test results.
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    Item type:Publication,
    PFD analysis of LNG fuel gas supply system for improving combined-cycle power plant safety
    (2022-04-01)
    Thepmanee, Teerawat
    ;
    Julsereewong, Amphawan
    ;
    Pongswatd, Sawai
    In order to determine an unavailability of each safety function subsystem that influences on an overall unavailability of entire protection system for safety analysis and enhancement, a modeling is required. This article presents a safety system modeling to evaluate the detected–undetected failures and repairable behaviors of each safety function subsystem in the studied fuel gas supply system (FGSS), which is utilized in a combined-cycle power plant. The proposed modeling deals with probability of failure on demand (PFD) analysis for calculation of the unavailability of three safety function subsystems, which are gas analytical subsystem (GAS), fuel gas controller subsystem (FGC), and shutdown valve subsystem (SDV). The interested GAS includes two different groups of gas analyzers in 2-out-of-2 (2oo2) voting scheme, when using three gas analyzers in each group in 2-out-of-3 and diagnosis (2oo3D) voting scheme. The interested FGC consists of two controllers in 2oo2 voting scheme, when the structure of each controller is in 1-out-of-1 and diagnosis (1oo1D) voting scheme. The interested SDV consists of two shutdown valves, which are installed in 1-out-of-2 (1oo2) voting scheme. The reliability block diagram is utilized for representative of combination of all three safety function subsystems, and the fault tree is utilized for calculation of PFD unavailability of each safety function subsystem. As the results obtained from the proposed safety function modeling, the influence of three safety function subsystems on the total unavailability of the FGSS is described. In addition, an example of the proposed modeling application to provide two guidelines for effective engineering design and operation is also presented. The first is a guideline to implement an effective human machine interface (HMI) at an operator workstation for real-time monitoring of the studied FGSS in the presence of failures that can be automatically detected by device diagnosis. The latter is a guideline to maintain and troubleshoot the failures that can be revealed by proof test. Based on diagnostic information and proof test results, operation and maintenance savings can be achieved.