• 동력기계공학회지
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• 제13권6호
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• pp.35-42
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• 2009

The piping systems in the steam-driven power engines lie under the cyclic condition of thermal expansion and contraction by superheated steam. These phenomena might cause some severe damages on the pipes and the accessory devices. To avoid these damages, the calculation of the proper strength and the consideration of the reduced resultant forces on the materials are needed. In the present study, numerical investigations on the effects of the thermal deformation of the industrial piping system were performed with comparison of the design data. Commercial software, ABAQUS with the thermal-fluidic loadings based on the design conditions was used for the thermal stress analysis of the piping system. From the analysis of the initially-designed pipe supporters, the rearrangement was suggested to improve the piping design.

• Nuclear Engineering and Technology
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• 제46권5호
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• pp.633-640
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• 2014

In this research, the surface roughness affecting the pressure drop in a pipe used as the steam generator of a PWR was studied. Based on the CFD (Computational Fluid Dynamics) technique using a commercial code named ANSYS-FLUENT, a straight pipe was modeled to obtain the Darcy frictional coefficient, changed with a range of various surface roughness ratios as well as Reynolds numbers. The result is validated by the comparison with a Moody chart to set the appropriate size of grids at the wall for the correct consideration of surface roughness. The pressure drop in a full-scale U-shaped pipe is measured with the same code, correlated with the surface roughness ratio. In the next stage, we studied a reduced scale model of a U-shaped heat pipe with experiment and analysis of the investigation into fluid-structure interaction (FSI). The material of the pipe was cut from the real heat pipe of a material named Inconel 690 alloy, now used in steam generators. The accelerations at the fixed stations on the outer surface of the pipe model are measured in the series of time history, and Fourier transformed to the frequency domain. The natural frequency of three leading modes were traced from the FFT data, and compared with the result of a numerical analysis for unsteady, incompressible flow. The corresponding mode shapes and maximum displacement are obtained numerically from the FSI simulation with the coupling of the commercial codes, ANSYS-FLUENT and TRANSIENT_STRUCTURAL. The primary frequencies for the model system consist of three parts: structural vibration, BPF(blade pass frequency) of pump, and fluid-structure interaction.

• 한국가스학회지
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• 제17권2호
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• pp.70-77
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• 2013

본 연구는 화력발전소 최종과열기에서 고압터빈 사이 배관과 고압터빈을 지난 곳에 있는 체크밸브와 1차 재열기 사이 배관을 포함한 수증기 배관시스템에서 터빈의 급작스런 사고로 인해 터빈으로 들어가는 수증기를 차단할 때 발생하는 수증기 충격이 배관시스템에 미치는 영향을 분석하는 연구이다. 이를 위해서 수격현상 해석에 많이 사용하는 Flowmaster 소프트웨어로 배관시스템을 모델링하고 시간 변화에 따라 배관 내부의 압력, 질량유량률의 특성을 파악하였다. 이러한 특성으로부터 수증기 충격이 주로 영향을 미치는 곡관에서 수증기 충격에 의한 힘을 도출하였다. 본 연구를 통해서 수증기 충격은 주증기 차단 밸브 직전의 곡관과 체크밸브 이후에 바이패스 배관과 연결되는 곡관에서 수증기 충격에 의한 힘이 가장 크게 나타남을 밝혀냈다. 본 연구에서는 이렇게 도출한 힘의 기본 자료를 이용하여 차후 연구에서 화력발전소 수증기 배관시스템의 수증기 충격 시 곡관과 지지대의 안전성을 진단하는 토대를 구축하였다.

• 열병합발전
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• 통권27호
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• pp.5-9
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• 2002

High pressure steam pipe in power plants is subjected to service conditions under which creep processes take place limiting the component's lifetime. To ensure a safe and economic operation it is necessary to get accurate information about the lifetime situation of single components as well as of the whole system. Careful evaluation is combined with FEM analysis, NDT, microstructure evaluation. Especially, 14MoV63 steel is used as material for main steam pipe for 30 years old power plants. In service inspections have shown an increasing number of cracks and creep cavities beside stress concentration parts. A detailed analysis came to the conclusion that lifetime has been consumed to a high degree, 80%level.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2023년도 추계학술대회
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• pp.111-113
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• 2023

자율운항선박 기술개발사업 중 2세부(자율운항선박 핵심 기관시스템 성능 모니터링 및 고장예측 진단 기술 개발)과제에서 자율운항선박 핵심장비 중 증기 배관(Steam Pipe)의 모니터링 및 고장예측 시스템 중 열화상 카메라에 의한 증기 배관(Steam Pipe)을 브라우저에서 모니터링 하는 시스템을 연구 및 개발 목표로 한다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.886-891
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• 2000

One of the domestic co-generation plants have undergone excessive vibration problems of turbine attributed to external force for years. The root cause of turbine vibration may be shan alignment problem which sometimes is changed by thermal expansion and external farce, even if turbine technicians perfectly performed it. To evaluate the alignment condition from plant start-up to full load, a strain measurement of turbine and main steam piping subjected to thermal loading is monitored by using strain gages. The strain gages are bonded on both bearing housing adjusting bolts and pipe stoppers which. installed in the x-direction of left-side main steam piping near the turbine inlet in order to monitor closely the effect of turbine under thermal deformation of turbine casing and main steam piping during plant full load. Also in situ load of constant support hangers in main steam piping system is measured by strain gages and its results are used to rebalance the hanger rod load. Consequently, the experimental stress analysis by using strain gages turns out to be very useful tool to diagnose the trouble and failures of not only to stationary components but to rotating machinery in power plants.

• 한국산학기술학회논문지
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• 제14권1호
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• pp.33-38
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• 2013

여러 종류의 증기발생기 검사정비 로봇의 엔드이펙터 모션 구동에 전부 사용할 수 있도록 ARM Cotex M3-107 MCU 기반의 제어기와 엔드이펙터 모션 프로그램 생성 응용소프트웨어로 구성된 범용 엔드이펙터 모션구동 제어시스템을 개발하였다. 범용 제어시스템을 적용하여 엔드이펙터의 직선이송 및 회전이송의 위치 결정의 오차는 무시할만한 수준이며, 재현성은 0.04% 오차를 보여줌으로써 실제로 사용 가능한 범용 엔드이펙터 모션구동 제어시스템을 개발하였다.

• Nuclear Engineering and Technology
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• 제53권1호
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• pp.322-336
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• 2021

This paper presents a numerical prediction of the transient hydraulic loads acting on the tubes and external supports of a pressurized water reactor (PWR) steam generator (SG) during blowdown following a sudden feedwater line break (FWLB). A simplified SG model was used to easily demonstrate the prediction. The blowdown discharge flow was treated as a flashing flow to realistically simulate the transient flow fields inside the SG and the connected broken feedwater pipe. The effects of the SG initial pressure or the broken feedwater pipe length on the intensities or magnitudes of transient hydraulic loads were investigated. Then predictions of the decompression pressure wave-induced impulsive pressure differential loads on SG tubes and the transient blowdown loads on SG external supports were demonstrated and the general aspects of transient responses of such transient hydraulic loads to the FWLB were discussed.

• KEPCO Journal on Electric Power and Energy
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• 제2권4호
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• pp.583-588
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• 2016

The high-temperature steam pipes of thermal power plants are subjected to severe conditions such as creep and fatigue due to the power plant frequently being started up and shut down. To prevent critical pipes from serious damage and possible failure, inspection methods such as computational analysis and online piping displacement monitoring have been developed. However, these methods are limited in that they cannot determine the life consumption rate of a critical pipe precisely. Therefore, we set out to develop a life assessment system, based on a three-dimensional piping displacement monitoring system, which is capable of evaluating the life consumption rate of a critical pipe. This system was installed at the "M" thermal power plant in Malaysia, and was shown to operate well in practice. The results of this study are expected to contribute to the increase safety of piping systems by minimizing stress and extending the actual life of critical piping.

• Corrosion Science and Technology
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• 제15권4호
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• pp.182-188
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• 2016

Significant piping wall thinning caused by Flow-Accelerated Corrosion (FAC) and Erosion-Corrosion (EC) continues to occur, even after the Mihama Power Station unit 3 secondary pipe rupture in 2004, in which workers were seriously injured or died. Nuclear power plants in many countries have experienced FAC and EC-related cases in steam cycle piping systems. Korea has also experienced piping wall thinning cases including thinning in the downstream straight pipe of a check valve in a feedwater pump line, the downstream elbow of a control valve in a feedwater flow control line, and failure of the straight pipe downstream of an orifice in an auxiliary steam return line. Cause analyses were performed by reviewing thickness data using Ultrasonic Techniques (UT) and, Scanning Electron Microscope (SEM) images for the failed pipe, and numerical simulation results for FAC and EC cases in Korea Nuclear Power Plants. It was concluded that the main cause of wall thinning for the downstream pipe of a check valve is FAC caused by water vortex flow due to the internal flow shape of a check valve, the main cause of wall thinning for the downstream elbow of a control valve is FAC caused by a thickness difference with the upstream pipe, and the main cause of wall thinning for the downstream pipe of an orifice is FAC and EC caused by liquid droplets and vortex flow. In order to investigate more cases, additional analyses were performed with the review of a lot of thickness data for inspected pipes. The results showed that pipe wall thinning was also affected by the operating condition of upstream equipment. Management of FAC and EC based on these cases will focus on the downstream piping of abnormal or unusual operated equipment.