• 한국산학기술학회논문지
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• 제15권1호
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• pp.482-487
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• 2014

본 연구(I)의 목적은 현재 K-water에서 실시하는 대구경 노후관로 개량사업시 매설관의 노후도를 판단할 수 있는 방법을 제시하였다. 대구경 관로의 노후도 평가모형을 개발하기 위해 국내의 대표적 평가기법 중 1995년 평가법, 2002년 평가법, 상태평가법 등 3개를 분석하였다. 대구경 관로의 노후도를 평가하기 위하여 기존의 3가지 평가방법별 인자의 우선순위를 바탕으로 공통 인자와 대구경 관로의 특성을 고려할 수 있는 인자를 함께 고려하여 10개 인자를 선정하였다. 또한 개발모형의 인자별 가중치는 국내의 대구경 관로의 실험 및 분석 값을 바탕으로 한 회귀식과 전문가 의견과 관리경험 등을 고려하여 산정하였다. 따라서 기존의 3가지 모형의 특성을 고려하여 개발된 평가모형은 대구경 관로의 노후도를 평가하기에 보다 신뢰성 있는 모형으로 판단된다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.264-267
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• 2004

Wall thinning of carbon steel pipe components due to Flow-Accelerated Corrosion (FAC) is one of the most serious threats to the integrity of steam cycle piping systems in Nuclear Power Plants (NPP). Since the mid-1990s, secondary side piping systems in Korean NPPs have experienced wall thinning, leakages and ruptures caused by FAC. Korea Electric power Research Institute (KEPRI) and Korea Hydro & Nuclear Power Co., LTD. (KHNP) have conducted a study to develop the methodology for systematic pipe management and established the Korean Thinned Pipe Management Program (TPMP). To effectively maintain the integrity of piping system, FAC engineer should understand the criterions of the structural integrity evaluation and the safety margin assessment for the thinned pipe component. This paper describes the technical items of TPMP, and shows the example of the integrity evaluation and safety margin assessment for three thinned pipe component of a NPP.

• 한국압력기기공학회 논문집
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• 제17권1호
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• pp.28-35
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• 2021

The flow accelerated corrosion (FAC) is one of significant aging and degradation mechanism and can affect structural integrity of CANDU feeder pipes. Pipe burst can occur under normal operation pressure (min. 10 MPa) if wall-thinning of the feeder pipe due to FAC is accumulated. Previous studies considered simple shapes of feeder pipe with local wall-thinning in order to conservatively assess structural integrity of wall-thinned feeder pipe. In this paper, a new FE model is developed, having an actual shape of the feeder pipe (double bent) as well as the actual wall-thinning shape and location based on the in-service inspection result. Then, the burst pressure assessment of the wall-thinned feeder pipe is performed using lower bound limit load analysis considering elastic-perfectly plastic material. In addition, an improved formulation to predict the burst pressure of the wall-thinned feeder pipe is presented and the safety margin is compared with an existing assessment method.

• 한국산학기술학회논문지
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• 제15권2호
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• pp.1096-1101
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• 2014

본 연구(II)는 연구(I)에서 제안한 대구경 관로의 노후도 평가 모형을 수도권 광역상수도 1단계를 대상으로 이를 적용하였다. 노후도 평가 방법별 적용 결과에서, 총 30개 관로 중에서 1995년 평가방법은 24개, 2002년 평가방법은 27개 관로가 개량이 필요한 것으로 나타났다. 또한 개발된 모형과 기존의 2개 평가방법의 결과는 거의 일치하는 것으로 산정되었다. 즉, 본 연구에서 개발한 간편모형은 기존의 많은 인자를 이용하여 노후도를 평가하는 방법과 비교에서 신뢰할 수 있는 부합되는 결과를 보여 주었다. 따라서, 본 연구에서 개발한 모형은 기존의 노후관 평가방법과 비교시 실험 및 분석 등에 필요한 시간적 경제적 비용을 절약할 수 있어 실무적 적용에 많은 도움을 줄 수 있으리라 기대된다.

• 품질경영학회지
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• 제48권4호
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• pp.597-608
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• 2020

Purpose: The purpose of this paper is to present a probability distribution of the burst pressure of API 5L X65 pipes for the reliability assessment of corroded gas pipelines. Methods: Corrosion is a major cause of weakening the residual strength of the pipe. The mean residual strength on the corrosion defect can be obtained using the burst pressure code. However, in order to obtain the pipe reliability, a probability distribution of the burst pressure should be provided. This study is concerned with estimating the burst pressure distribution using Monte Carlo simulation. A response surface method is employed to represent the distribution parameter as a model of the corrosion defect size. Results: The experimental results suggest that the normal or Weibull distribution should be suitable as the probability distribution of the burst pressure. In particular, it was shown that the probability distribution parameters can be well predicted by using the depth and length of the corrosion defect. Conclusion: Given a corrosion defect on the pipe, its corresponding burst pressure distribution can be provided at instant. Subsequently, a reliability assessment of the pipe is conducted as well.

• 반도체디스플레이기술학회지
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• 제21권2호
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• pp.117-122
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• 2022

This paper proposes a method for evaluating the work of manufacturing workers using MediaPipe as a risk factor for musculoskeletal diseases. Recently, musculoskeletal disorders (MSDs) caused by repeated working attitudes in industrial sites have emerged as one of the biggest problems in the industrial health field while increasing public interest. The Korea Occupational Safety and Health Agency presents tools such as NIOSH Lifting Equations (NIOSH), OWAS (Ovako Working-posture Analysis System), Rapid Upper Limb Assessment (RULA), and Rapid Entertainment Assessment (REBA) as ways to quantitatively calculate the risk of musculoskeletal diseases that can occur due to workers' repeated working attitudes. To compensate for these shortcomings, the system proposed in this study obtains the position of the joint by estimating the posture of the worker using the posture estimation learning model of MediaPipe. The position of the joint is calculated using inverse kinetics to obtain an angle and substitute it into the REBA equation to calculate the load level of the working posture. The calculated result was compared to the expert's image-based REBA evaluation result, and if there was a result with a large error, feedback was conducted with the expert again.

• 한국압력기기공학회 논문집
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• 제11권2호
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• pp.51-60
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• 2015

Local wall thinning and integrity degradation caused by several mechanisms, such as flow accelerated corrosion, cavitation, flashing and/or liquid droplet impingement, is a main concern in secondary steam cycle piping system of nuclear power plants in terms of safety and operability. Thinned pipe management program (TPMP) has being developed and optimized to reduce the possibility of unplanned shutdown and/or power reduction due to pipe failure caused by wall thinning. In this paper, newest technologies, standards and regulations related to the integrity assessment, repair and replacement of thinned pipe component are reviewed. And technical improvement items in TPMP to secure the reliability and effectiveness are also presented.

• International Journal of Internet, Broadcasting and Communication
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• 제13권2호
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• pp.93-102
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• 2021

In this research, we present a natural lighting system with transmission distance of 30m and lighting efficiency of 35% (30m standard) for operating hours of 7h/day (based on clear sky). The system is composed of parabolic reflective mirror and modified light pipe that can secure more than 88% of light concentration efficiency. The light loss rate of newly designed light pipe transmission system is demonstrated to 0.8 %/m in the straight-line part and 2%/m in the curved part. Modified light pipe daylighting system shows better performance over fiber optic daylighting system in terms of transmission distance (1.5 times longer) and illuminance (3.05 times higher).

• Nuclear Engineering and Technology
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• 제49권2호
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• pp.349-359
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• 2017

During the past 25 years, in the context of probabilistic safety assessment, efforts have been directed towards establishment of comprehensive pipe failure event databases as a foundation for exploratory research to better understand how to effectively organize a piping reliability analysis task. The focused pipe failure database development efforts have progressed well with the development of piping reliability analysis frameworks that utilize the full body of service experience data, fracture mechanics analysis insights, expert elicitation results that are rolled into an integrated and risk-informed approach to the estimation of piping reliability parameters with full recognition of the embedded uncertainties. The discussion in this paper builds on a major collection of operating experience data (more than 11,000 pipe failure records) and the associated lessons learned from data analysis and data applications spanning three decades. The piping reliability analysis lessons learned have been obtained from the derivation of pipe leak and rupture frequencies for corrosion resistant piping in a raw water environment, loss-of-coolant-accident frequencies given degradation mitigation, high-energy pipe break analysis, moderate-energy pipe break analysis, and numerous plant-specific applications of a statistical piping reliability model framework. Conclusions are presented regarding the feasibility of determining and incorporating aging effects into probabilistic safety assessment models.

• 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.