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Author: search.filters.author.Thepmanee, TeerawatSubject: search.filters.subject.Reliability

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    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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    Design and Implementation of Functional Safety for Repairable Systems
    (2018-10-15)
    Julserccwong, Amphawan
    ;
    Thepmanee, Teerawat
    This paper focuses on a practical technique based on IEC 61508 and IEC 61511 standards to design and implement the functional safety for repairable systems. A pilot plant for pressure control under real-world operating conditions is employed as a case study to demonstrate the effectiveness of the proposed design and implementation. The fault trees are utilized to model and analyze the reliability of two sensing elements, two logic solvers, and two final elements used in the designed safety instrumented function (SIF) in terms of probability of failure on demand (PFD). The values of mean time to restore (MTTR) as well as the impacts of proof test effectiveness are considered in reliability modeling of the designed SIF for the case study. Plotting the created PFD equations in MATLAB shows the impacts of perfect and imperfect proof tests during the mission time of the designed SIF. The safety integrity level (SIL) verification shows that the designed SIF can meet the target SIL. The hardware installation for implementing the designed SIF is also described.
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    Reliability modeling of emergency shutdown function for heat recovery steam generator control
    (2016-10-01)
    Chairuan, Chaichan
    ;
    Julsereewong, Amphawan
    ;
    Thepmanee, Teerawat
    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.