• Title, Summary, Keyword: Pipe defects

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ON-POWER DETECTION OF PIPE WALL-THINNED DEFECTS USING IR THERMOGRAPHY IN NPPS

  • Kim, Ju Hyun;Yoo, Kwae Hwan;Na, Man Gyun;Kim, Jin Weon;Kim, Kyeong Suk
    • Nuclear Engineering and Technology
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    • v.46 no.2
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    • pp.225-234
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    • 2014
  • Wall-thinned defects caused by accelerated corrosion due to fluid flow in the inner pipe appear in many structures of the secondary systems in nuclear power plants (NPPs) and are a major factor in degrading the integrity of pipes. Wall-thinned defects need to be managed not only when the NPP is under maintenance but also when the NPP is in normal operation. To this end, a test technique was developed in this study to detect such wall-thinned defects based on the temperature difference on the surface of a hot pipe using infrared (IR) thermography and a cooling device. Finite element analysis (FEA) was conducted to examine the tendency and experimental conditions for the cooling experiment. Based on the FEA results, the equipment was configured before the cooling experiment was conducted. The IR camera was then used to detect defects in the inner pipe of the pipe specimen that had artificially induced defects. The IR thermography developed in this study is expected to help resolve the issues related to the limitations of non-destructive inspection techniques that are currently conducted for NPP secondary systems and is expected to be very useful on the NPPs site.

A Study for Tubing Pipe Flaw Sizing by Using Guided Ultrasonic Wave (유도초음파기법을 이용한 튜빙 결함측정에 관한 연구)

  • Joo, Kyung Mun;Cheon, Keun Young;Lee, Jeong Seok
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.5 no.1
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    • pp.20-24
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    • 2009
  • There is extensive tubing pipe in the nuclear power plant under high temperature and pressure. Erosion and corrosion defects are expected on this tubing pipe due to environmental and mechanical factors. In this study, Guided Ultrasonic Wave technique was applied to detect defects. The technique explores the advantages of the Guided Ultrasonic Wave method that inspects along the wall of the pipe and can travel long distances, providing rapid collection of data. This paper presents a case study of the Guided Ultrasonic Wave testing of 3/8" tubing pipe. This study offers to understand detected signals through correlation between amplitude and depth of defects.

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A Study on Proper Location of Welding Defect in Three Point Bend Testing with MDPE Pipe

  • Lai, Huan Sheng;Yoon, Kee Bong;Kil, Seong Hee
    • Journal of Energy Engineering
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    • v.24 no.1
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    • pp.1-9
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    • 2015
  • Welding defects affect the performance of welded pipe joints. In this study, a three point bend test of welded steel and medium density polyethylene (MDPE) pipe joints with defects of various defect locations and defect materials was studied using the finite element method. The defect was assumed to be located at 12 o'clock, 3 o'clock or 6 o'clock direction. The results showed that pipes failed more easily on the compression side due to stress or local buckling. The air defect was more dangerous than the steel defect if the defect was located in the compression side; otherwise, the defect material effect on the integrity of pipes was ignorable. It is argued that the integrity of pipes with defects in the compression side is weaker than that in other regions, and the defect should be located in the compression side or the 12 o'clock position in the three point bend test to maximize the effect of defect existence on the pipe structural integrity.

The Evaluation of GFRP Pipe by NDT Methods (비파괴시험에 의한 GFRP Pipe의 평가)

  • Lee, J.S.;Cho, K.S.;Chang, H.K.;Lee, S.H.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.9 no.1
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    • pp.48-55
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    • 1989
  • It is desirable to develop the effective NDT techniques to evaluate the strength of composite structures. In this study several of acoustic NDT techniques were applied to investigate useful parameters for evaluating the filament wound GFRP structures and following results were obtained. 1. Propagation velocity of stress wave to axial direction in the filament wound GFRP pipe depends on the effective modulus along the propagation direction and source location was parcticable from the a measured velocities. 2. By the application of acoustic emission techniques to GFRP pipe during hydraulic test, it was proven to be possible to detect the damage initiating pressure which could be evaluated nondestructively through the measuring of stress wave energy factor(SWEF). 3. The final failure pressure of GFRP was greatly influenced in the presence of pass through defects, and void-like defects were more dangerous than the laminar type defects.

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A Study on the Forming Process Development of a Long-neck Flange Using a Long Pipe (긴 관을 이용한 롱넥플랜지 성형공정 개발에 관한 연구)

  • Choe, Gan-Dae;Gang, U-Jin;Bae, Won-Byeong;Jo, Jong-Rae
    • Journal of the Korean Society for Precision Engineering
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    • v.19 no.8
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    • pp.212-219
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    • 2002
  • The pipe with a long-neck flange is widely used in power plants, chemical plants, and shipbuilding companies. Now the pipe with a long-neck flange is manufactured by welding a thick flange to a pipe. But this long-neck flange pipe has some defects in the welding region such as unfitting and local thermal fatigue, which weaken the strength around the neck of the flange. Moreover, after welding the flange, the contacting surfaces of the flange have to be machined flat. So, that is uneconomical. Therefore, to solve the above problems of the long-neck flange pipe, a new process, which has no defects around the flange neck, is required. In this study, three forming processes are suggested to get an enhanced long-neck flange. First suggested process consists of conical forming and flange forming. Second and third suggested processes consist of the bulging of a long pipe locally heated by induction coils and the flange forming. The differences between second and third suggestions are the thickness and local heating area of the pipe. That is, the thickness of the initial pipe of third suggestion is larger than that of the final product, and the local heating area is smaller than that of second suggestion. These three suggestions for forming a long-neck flange are simulated by FE analyses with a commercial code DEFORM 2D. Especially, the theoretical result of FE analysis on the first suggestion for forming a long-neck flange is verified by the experiment with aluminum 6063 pipes. From the theoretical and experimental results, it is concluded that three suggested processes are very useful in order to manufacture the pipe with a long-neck flange without any defects.

Mechanically Fabricated Defects Detection on Underwater Steel Pipes using Ultrasonic Guided Waves (유도초음파를 이용한 수중 강관의 기계적 결함 검출)

  • Woo, Dong-Woo;Na, Won-Bae
    • Journal of Ocean Engineering and Technology
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    • v.24 no.1
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    • pp.140-145
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    • 2010
  • This study presents a detection method for mechanically fabricated defects on underwater steel pipes, using ultrasonic guided waves. Three different diameters (60, 90, and 114 mm) of 1000-mm long steel pipes were considered, along with several experimental design factors such as incident angles, incident distances, and the degrees of defects, to investigate how these factors affected the experimental results - the detectability of the mechanical defects. From the experimental results, we determined that the amplitude and arrival time of the first received wave signals gave a promising clue for distinguishing the existence of the defects and their severities. Between the amplitude and arrival time, the arrival time gave a more promising indication since it was affected by the experimental factors in a constant manner. Therefore, it was shown that the use of ultrasonic guided waves for underwater pipe inspection is feasible.

Analysis of Weld Beads for Wall Thinning Defects in the Weld Zone of the Boost Pump Recirculation Pipe for Power Plants and Evaluation of Their Integrity (플랜트 승압펌프 재순환 배관 용접부의 용접비드에 의해 발생한 감육결함 분석 및 건전성 평가)

  • Nam, Ki-Woo;Ahn, Seok-Hwan;Do, Jae-Yoon
    • Journal of Ocean Engineering and Technology
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    • v.24 no.4
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    • pp.38-46
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    • 2010
  • The wall thinning phenomenon of pipes was simulated as metal loss due to erosion and corrosion. Such wall thinning defects in the pipes of power plants are a very important safety consideration. In this study, we analyzed wall thinning defects that occurred by weld bead of weld zone of boost pump recirculation pipe. From the results of the analysis of pipe failures, numerical analysis was performed by Fluent v6.3.26 using the standard k-$\varepsilon$ model of the weld bead shape, such as an elliptical or a spherical shape, on the inner wall of the pipe. Using the results obtained, we showed the overlap effect by cavitations corrosion and erosion-corrosion at the bottom of the wall-thinning defect.

Technology for the Detection of Corrosion Defects in Buried Pipes of Nuclear Power Plants with 3D FEM (3D 유한요소법을 이용한 원전 매설배관 부식결함 탐상기술 개발)

  • Kim, Jae-Won;Lim, Bu-Taek;Park, Heung-Bae;Chang, Hyun-Young
    • Corrosion Science and Technology
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    • v.17 no.6
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    • pp.292-300
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    • 2018
  • The modeling of 3D finite elements based on CAD data has been used to detect sites of corrosion defects in buried pipes. The results generated sophisticated profiles of electrolytic potential and vectors of current distributions on the earth surface. To identify the location of defects in buried pipes, the current distribution on the earth surface was projected to a plane of incidence that was identical to the pipe locations. The locations of minimum electrolytic potential value were found. The results show adequate match between the locations of real and expected defects based on modeling. In addition, the defect size can be calculated by integrating the current density curve. The results show that the defect sizes were $0.74m^2$ and $0.69m^2$, respectively. This technology may represent a breakthrough in the detection of indirect damage in various cases involving multiple defects in size and shape, complex/cross pipe systems, multiple anodes and stray current.

Burst capacity of pipe under corrosion defects and repaired with thermosetting liner

  • Akram, Ali;Mustaffa, Zahiraniza;Albarody, Thar M. Badri
    • Steel and Composite Structures
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    • v.35 no.2
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    • pp.171-186
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    • 2020
  • This paper aims at providing insights on the use of thermosetting liner for the repair of offshore pipelines exposed to corrosion and leakage. The work which covers both experimental and numerical approaches were aspired due to the high cost of repair for pipelines, limitations of thermoplastic material and limited study of reinforced thermosetting liner. The experiment involves a destruction test called the burst test, carried out on an API 5L X42 carbon steel pipe under four case studies, namely (i) intact pipe, (ii) pipe with corrosion defect, (iii) pipe with corrosion defect and repaired with thermosetting liner and (iv) pipe with leakage and repaired with thermosetting liner. The numerical simulation was developed to first validate the experimental results and later to optimize the design of the thermosetting liner in terms of the number of layers required to restore the original strength of the pipe. The burst test shows an improvement in 23% of the burst capacity for the pipe with corrosion defects, after being repaired with a three-layer thermosetting liner. The parametric studies conducted showed that with an addition of thermosetting layers, the burst capacity improves by an average of 1.85 MPa. In conclusions, the improvement in strength can be further increased with increasing thickness of the thermosetting liner. The thermosetting liner was also determined to fail first inside the host pipe.

FUZZY SUPPORT VECTOR REGRESSION MODEL FOR THE CALCULATION OF THE COLLAPSE MOMENT FOR WALL-THINNED PIPES

  • Yang, Heon-Young;Na, Man-Gyun;Kim, Jin-Weon
    • Nuclear Engineering and Technology
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    • v.40 no.7
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    • pp.607-614
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    • 2008
  • Since pipes with wall-thinning defects can collapse at fluid pressure that are lower than expected, the collapse moment of wall-thinned pipes should be determined accurately for the safety of nuclear power plants. Wall-thinning defects, which are mostly found in pipe bends and elbows, are mainly caused by flow-accelerated corrosion. This lowers the failure pressure, load-carrying capacity, deformation ability, and fatigue resistance of pipe bends and elbows. This paper offers a support vector regression (SVR) model further enhanced with a fuzzy algorithm for calculation of the collapse moment and for evaluating the integrity of wall-thinned piping systems. The fuzzy support vector regression (FSVR) model is applied to numerical data obtained from finite element analyses of piping systems with wall-thinning defects. In this paper, three FSVR models are developed, respectively, for three data sets divided into extrados, intrados, and crown defects corresponding to three different defect locations. It is known that FSVR models are sufficiently accurate for an integrity evaluation of piping systems from laser or ultrasonic measurements of wall-thinning defects.