• Title/Summary/Keyword: Pipe wall thinning

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Development of Inspection Methodology for a Nuclear Piping Wall Thinning Caused by Erosion Using Ultrasonic B-Scan Measurement Device (B-Scan 초음파 측정장비를 이용한 원전 배관 침식손상 검사법 개발)

  • Lee, Dae Young;Suh, Heok Ki;Hwang, Kyeong Mo
    • Corrosion Science and Technology
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    • v.11 no.3
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    • pp.89-95
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    • 2012
  • U.S. Electric Power Research Institute (EPRI) has developed CHECWORKS program and applied it to power plant piping lines since some lines were ruptured by flow-accelerated corrosion (FAC) in 1978. Nowadays the CHECWORKS program has been used to manage pipe wall thinning phenomena caused by FAC. However, various erosion mechanisms can occur in carbon-steel piping. Most common forms of erosion are cavitation, flashing, liquid droplet impingement erosion (LDIE), and Solid Particle Erosion (SPE). Those erosion mechanisms cause pipe wall thinning, leaking, rupturing, and even result in unplanned shutdowns of utilities. Especially, in two phase condition, LDIE damages a wide scope of plant pipelines. Furthermore, LDIE is the major culprit to cause such as power runback by pipe leaking. This paper describes the methodologies that manage wall thinning and also predict LDIE wall thinning area. For this study, current properties of two-phase condition are investigated and LDIE areas are selected. The areas are checked by B-Scan method to detect the effect of wall thinning phenomena.

Comparison of Wall Thinning Analysis Results between CHECWORKS and ToSPACE (CHECWORKS와 ToSPACE 프로그램의 배관감육 해석결과 비교)

  • Hwang, Kyeongmo;Yun, Hun;Seo, Hyeokki
    • Corrosion Science and Technology
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    • v.17 no.6
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    • pp.317-323
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    • 2018
  • Assumptions have always been that wall thinning on the secondary side piping in nuclear power plants is mostly caused by Flow-Accelerated Corrosion (FAC). Recent studies have showed that wall thinning on the secondary side piping is caused by Liquid Droplet Impingement Erosion (LDIE), Solid Particle Erosion (SPE), cavitation, and flashing. To manage those aging mechanisms, several software such as CHECWORKS, COMSY, and BRT-CICERO have been used in nuclear power plants. Korean nuclear power plants have been using the CHECWORKS program since 1996 to date. However, many site engineers have experienced a lot of inconveniences and problems in using the CHECWORKS program. In order to work through the inconveniences and to remedy problems, KEPCO-E&C has developed a "3D-based pipe wall thinning management program (ToSPACE)" based on the experience of over 30 years in relation to the pipe wall thinning management. This study compares the results of FAC and LDIE analysis using both the CHECWORKS and ToSPACE programs with respect to validation of the wall thinning analysis results.

Evaluating on the Effects of Circumferential Thinning Angle and Bending Load on the Failure Pressure of Wall-Thinned Elbow through Burst Tests (파열 시험을 통한 감육곡관의 손상압력에 미치는 원주방향 결함 폭과 굽힘하중의 영향 평가)

  • Kim, Jin-Weon;Na, Yeon-Soo;Lee, Sung-Ho
    • Journal of the Korean Society of Safety
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    • v.21 no.6 s.78
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    • pp.14-19
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    • 2006
  • This study performed burst tests using real-scale pipe elbow containing simulated local wall-thinning to evaluate the effects of circumferential thinning angle and bending load on the failure pressure of wall-thinned elbow. The tests were carried out under the loading conditions of internal pressure and combined internal pressure and bending loads. Three circumferential thinning angles, ${\theta}/{\Pi}=0.125,\;0.25,\;0.5$, and different thinning locations, intrados and extrados, were considered. The test results showed that the failure pressure of wall-thinned elbow decreased with increasing circumferential thinning angle for both thinning locations. This tendency is different from that observed in the wall-thinned straight pipe. Also, the failure pressure of intrados wall-thinned elbow was higher than that of extrados wall-thinned elbow with the same thinning depth and equivalent thinning length. In addition, the effect of bending moment on the failure pressure was not obvious.

Development of Wall-Thinning Evaluation Procedure for Nuclear Power Plant Piping-Part 1: Quantification of Thickness Measurement Deviation

  • Yun, Hun;Moon, Seung-Jae;Oh, Young-Jin
    • Nuclear Engineering and Technology
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    • v.48 no.3
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    • pp.820-830
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    • 2016
  • Pipe wall thinning by flow-accelerated corrosion and various types of erosion is a significant and costly damage phenomenon in secondary piping systems of nuclear power plants (NPPs). Most NPPs have management programs to ensure pipe integrity due to wall thinning that includes periodic measurements for pipe wall thicknesses using nondestructive evaluation techniques. Numerous measurements using ultrasonic tests (UTs; one of the nondestructive evaluation technologies) have been performed during scheduled outages in NPPs. Using the thickness measurement data, wall thinning rates of each component are determined conservatively according to several evaluation methods developed by the United States Electric Power Research Institute. However, little is known about the conservativeness or reliability of the evaluation methods because of a lack of understanding of the measurement error. In this study, quantitative models for UT thickness measurement deviations of nuclear pipes and fittings were developed as the first step for establishing an optimized thinning evaluation procedure considering measurement error. In order to understand the characteristics of UT thickness measurement errors of nuclear pipes and fittings, round robin test results, which were obtained by previous researchers under laboratory conditions, were analyzed. Then, based on a large dataset of actual plant data from four NPPs, a quantitative model for UT thickness measurement deviation is proposed for plant conditions.

Finite Element Based Stress Concentration Factors for Pipes with Local Wall Thinning (유한요소해석을 이용한 국부 감육배관에 대한 응력집중계수 제시)

  • Son, Beom-Goo;Kim, Yun-Jae;Kim, Young-Jin
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.28 no.7
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    • pp.1014-1020
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    • 2004
  • The present work complies the elastic stress concentration factor for a pipe with local wall thinning, based on detailed three-dimensional elastic FE analysis. To cover practically interesting cases, a wide range of pipe and defect geometries are considered, and both internal pressure and global bending are considered. Resulting values of stress concentration factors are tabulated for practical use, and the effect of relevant parameters such as pipe and defect geometries on stress concentration factors are discussed. The present results would provide valuable information to estimate fatigue damage of the pipe with local wall thinning under high cycle fatigue.

Development of Portable Vibration Signal-Based Pipe Wall Thinning Inspection Device (진동신호기반 배관감육 측정시스템 개발)

  • Han, Soon-Woo;Park, Jin-Ho;Kang, To;Sohn, Ki Sung
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2014.10a
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    • pp.545-547
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    • 2014
  • The portable vibration signal-based pipe wall thinning inspection device was developed in this work. Compared to wall-thinning detection using conventional ultrasonic thickness measurement gauge, the proposed device can estimate average wall thickness of wide range and be applied to in-service pipes. The measurement principle of the device was briefly described and the configrations of hardware and software were explained. It was shown that the device can gauge average wall-thickness of test specimens with high precision.

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Monitoring Method for Pipe Thinning using Accelerometers (가속도계를 이용한 배관 감육 감시 방법)

  • Choi, Young-Chul;Park, Jin-Ho;Yoon, Doo-Byung;Sohn, Chang-Ho;Hwang, Il-Soon
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2006.11a
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    • pp.156-162
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    • 2006
  • Pipe thinning is one of the major issues for the structural fracture of pipes of nuclear power plants. Therefore a method to inspect a large area of piping systems quickly and accurately is needed. In this paper, we proposed the method for monitoring pipe thinning. Our basic idea come from that a group velocity of impact wave is different as wall thickness. If the group velocity is measured, wall thickness can be estimated. To obtain the group velocity, time-frequency analysis is used. This is because an arrival time difference can be measured easily in time-frequency domain rather than time domain. To test the performance of this technique, experiments have been performed for a plate and U type pipe. Results show that the proposed technique is quite powerful in the monitoring pipe thinning.

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Monitoring Pipe Thinning Using Time-frequency Analysis (시간-주파수 기법을 이용한 배관 감육 감시 방법)

  • Sohn, Chang-Ho;Park, Jin-Ho;Yoon, Doo-Byung;Chong, Ui-Pil;Choi, Young-Chul
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.16 no.12 s.117
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    • pp.1224-1230
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    • 2006
  • Pipe thinning is one of the major issues for the structural fracture of pipes of nuclear power plants. Therefore a method to inspect a large area of piping systems quickly and accurately is needed. In this paper, we proposed the method for monitoring pipe thinning. Our basic idea come from that a group velocity of impact wave is different as wall thickness. If the group velocity is measured, wall thickness can be estimated. To obtain the group velocity, time -frequency analysis is used. This is because an arrival time difference can be measured easily in time-frequency domain rather than time domain. To test the performance of this technique, experiments have been performed for a plate and U type pipe. Results show that the proposed technique is quite powerful in the monitoring pipe thinning.

Development of Numerical Algorithm of Total Point Method for Thinning Evaluation of Nuclear Secondary Pipes (원전 2차측 배관 감육여부 판별을 위한 Total Point Method 전산 알고리즘 개발)

  • Oh, Young Jin;Yun, Hun;Moon, Seung Jae;Han, Kyunghee;Park, Byeong Uk
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.11 no.2
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    • pp.31-39
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    • 2015
  • Pipe wall-thinning by flow-accelerated corrosion (FAC) and various types of erosion is a significant and costly damage phenomenon in secondary piping systems of nuclear power plants (NPPs). Most NPPs have management programs to ensure pipe integrity due to wall-thinning that includes periodic measurements for pipe wall thicknesses using ultrasonic tests (UTs). Nevertheless, thinning evaluations are not easy because the amount of thickness reduction being measured is often quite small compared to the accuracy of the inspection technique. U.S. Electric Power Research Institute (EPRI) had proposed Total Point Method (TPM) as a thinning occurrence evaluation method, which is a very useful method for detecting locally thinned pipes or fittings. However, evaluation engineers have to discern manually the measurement data because there are no numerical algorithm for TPM. In this study, numerical algorithms were developed based on non-parametric and parametric statistical method.

Review on the Integrity Evaluation and Maintenance of Wall-Thinned Pipe (감육배관의 건전성평가 및 정비 관련 기술기준 고찰)

  • Lee, Sung Ho;Lee, Yo Seob;Kim, Hong Deok;Lee, Kyoung Soo;Hwang, Kyeong Mo
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.11 no.2
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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.