• Title/Summary/Keyword: Corrosion detection

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Defect detection of wall thinning defect in pipes using Lock-in photo-infrared thermography technique (위상잠금 광-적외선 열화상 기술을 이용한 감육결함이 있는 직관시험편의 결함 검출)

  • Kim, Kyoung-Suk;Jang, Su-Ok;Park, Jong-Hyun;Choi, Tae-Ho;Song, Jae-Geun;Jung, Hyun-Chul
    • Proceedings of the KSME Conference
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    • 2008.11a
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    • pp.317-321
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    • 2008
  • Piping in the Nuclear Power plants (NPP) are mostly consisted of carbon steel pipe. The wall thinning defect is mainly occurred by the affect of the flow accelerated corrosion (FAC) of fluid which flows in carbon steel pipes. This type of defect becomes the cause of damage or destruction of piping. Therefore, it is very important to measure defect which is existed not only on the welding partbut also on the whole field of pipe. Over the years, Infrared thermography (IRT) has been used as a non destructive testing methods of the various kinds of materials. This technique has many merits and applied to the industrial field but has limitation to the materials. Therefore, this method was combined with lock-in technique. So IRT detection resolution has been progressively improved using lock-in technique. In this paper, the quantitative analysis results of the location and the size of wall thinning defect that is artificially processed inside the carbon steel pipe by using IRT are obtained.

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Study on the Fugitive Emissions of a PFA Lined Ball Valve through Helium Leak Detection (PFA 라이닝 볼밸브의 헬륨누설 검출 및 비산배출에 관한 연구)

  • Lee, Won-Ho;Kim, Dong-Yeol;Lee, Jong-Chul
    • The KSFM Journal of Fluid Machinery
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    • v.19 no.4
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    • pp.39-42
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    • 2016
  • A PFA lined ball valve, which is machined with fluorinated resin PFA to its inner part for improving corrosion resistance, non-stickness, heat-resistance, has been widely used to the chemical/pharmaceutical industries, the semiconductor/LCD manufacturing processes, etc. with the high purity chemicals as working fluid. EPA stated that 60% of all fugitive emissions come from the valve stem packing in a typical petroleum or chemical processing plant. They monitor regulated components for leaks and maintain seal performance at acceptable levels. Korean industrial standards only deals with the bubble test for in-line leakage of valves, which has the detectable leak rate of $10^{-4}$ [$mbar{\cdot}L{\cdot}s^{-1}$], therefore, it is not sufficient to check fugitive emissions. In this study, we conducted Helium leak detection from a PFA lined ball valve and evaluated fugitive emissions according to ISO 15848-1, which has the detectable leak rate of $10^{-9}$ [$mbar{\cdot}L{\cdot}s^{-1}$], for manufacturing the high-reliable PFA lined ball valves against fugitive emissions.

Development of Non-contact Detector for Broken Cords of Steel-Cord Conveyor Belt (컨베이어벨트의 비접촉식 스틸코드파선 검사장치 개발)

  • Yoo, Jae-Sang;Son, Boong-Ho
    • Proceedings of the KIEE Conference
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    • 2000.07d
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    • pp.2535-2537
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    • 2000
  • In order to detect and monitor the broken cords of steel-cord belt from being damaged by impact of large lump of materials and the corrosion of steel cord, we developed a non-contact magnetic coil detection system. This measures the deterioration of reinforcing cables in steel cord conveyor belt which transport the ores in raw material plant. In this research, magnetic coil sensor of broken-cord detection system has exciting part and sensing part. The broken-cord detection system is operated by supplying a transmitter coil with electric power to generate magnetic field, and then the change of induced voltage is detected in each receiver coils due to resultant magnetic flux effected by the broken steel cords at the inside of the conveyor belt. By the informations such as the position and size of the broken steel cords obtained by SCBMS(Steel Cord Belt Monitoring System), it is expected that not only the span of belt life will be lengthened, but also this system can enable operators to plan scheduled maintenance and prevent the enlargement of damaged parts in steel cord belt at an early stage

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Development of a Guided Wave Technique for the Inspection of a Feeder Pipe in a Pressurized Heavy Water Reactor

  • Cheong, Yong-Moo;Lee, Dong-Hoon;Kim, Sang-Soo;Jung, Hyun-Kyu
    • Corrosion Science and Technology
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    • v.4 no.3
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    • pp.108-113
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    • 2005
  • One of the recent safety issues in the pressurized heavy water reactor (PHWR) is the cracking of the feeder pipe. Because of the limited accessibility to the cracked region and a high dose of radiation exposure, it is difficult to inspect all the pipes with the conventional ultrasonic method. In order to solve this problem, a long-range guided wave technique has been developed. A computer program to calculate the dispersion curves in the pipe was developed and the dispersion curves for the feeder pipes in PHWR plants were determined. Several longitudinal and/or flexural modes were selected from the review of the dispersion curves and an actual experiment has been carried out with the specific alignment of the piezoelectric ultrasonic transducers. They were confirmed as L(0,1)) and/or flexural modes(F(m,2)) by the short time Fourier transformation(STFT) and were sensitive to the circumferential cracks, but not to the axial cracks in the pipe. An electromagnetic acoustic transducers(EMAT) was designed and fabricated for the generation and reception of the torsional guided wave. The axial cracks were detected by a torsional mode(T(0,1)) generated by the EMAT.

ASSESSMENT OF WALL-THINNING IN CARBON STEEL PIPE BY USING LASER-GENERATED GUIDED WAVE

  • Kim, Do-Youn;Cho, Youn-Ho;Lee, Joon-Hyun
    • Nuclear Engineering and Technology
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    • v.42 no.5
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    • pp.546-551
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    • 2010
  • The objective of this research is to estimate the crack location and size of a carbon steel pipe by using a laser ultrasound guided wave for the wall thinning evaluation of an elbow. The wall thinning of the carbon steel pipe is one of the most serious problems in nuclear power plants, especially the wall thinning of the carbon steel elbow caused by Flow-Accelerated Corrosion (FAC). Therefore, a non-destructive inspection method of elbow is essential for the nuclear power plants to operate safely. The specimens used in this study were carbon steel elbows, which represented the main elements of real nuclear power plants. The shape of the wall thinning was an oval with a width of 120mm, a length of 80mm, and a depth of 5mm. The L(0,1) and L(0,2) modes variation of the ultrasound guided wave signal is obtained from the response of the laser generation/air-coupled detection ultrasonic hybrid system represent the characteristics of the defect. The trends of these characteristics and signal processing were used to estimate the size and location of wall thinning.

Small Crack Detection in Bolt Threads by Predictive Deconvolution (예측디콘볼루션에 의한 볼트 나삿니의 미세 균열 검출)

  • Suh, Dong-Man;Kim, Whan-Woo
    • The Journal of the Acoustical Society of Korea
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    • v.16 no.1
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    • pp.5-9
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    • 1997
  • If small cracks in stud bolts are not detected early enough, they grow rapidly and cause total fracture. It is difficult to detect, prior to failure, flaws such as stress-corrosion cracking in thread roots and corrosion wastages using conventional ultrasonic testing methods during inservice inspection. This study show a method of detecting a small crack by digital signal processing. When ultrasonic beams travels into threads in parallel way, the echoes from each successive threads has almost the same intervals between any two signals. We can estimate the next thread signal based on previous thread signal by the predictive distance. The optimized operator is used to remove the predicted successive thread signals so that a small crack signal can be detected.

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Nondestructive inspection of spent nuclear fuel storage canisters using shear horizontal guided waves

  • Choi, Sungho;Cho, Hwanjeong;Lissenden, Cliff J.
    • Nuclear Engineering and Technology
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    • v.50 no.6
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    • pp.890-898
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    • 2018
  • Nondestructive inspection (NDI) is an integral part of structural integrity analyses of dry storage casks that house spent nuclear fuel. One significant concern for the structural integrity is stress corrosion cracking in the heat-affected zone of welds in the stainless steel canister that confines the spent fuel. In situ NDI methodology for detection of stress corrosion cracking is investigated, where the inspection uses a delivery robot because of the presence of the harsh environment and geometric constrains inside the cask protecting the canister. Shear horizontal (SH) guided waves that are sensitive to cracks oriented either perpendicular or parallel to the wave vector are used to locate welds and to detect cracks. SH waves are excited and received by electromagnetic acoustic transducers (EMATs) using noncontact ultrasonic transduction and pulse-echo mode. A laboratory-scale canister mock-up is fabricated and inspected using the proposed methodology to evaluate the ability of EMATs to excite and receive SH waves and to locate welds. The EMAT's capability to detect notches from various distances is evaluated on a plate containing 25%-through-thickness surface-breaking notches. Based on the results of the distances at which notch reflections are detectable, NDI coverage for spent nuclear fuel storage canisters is determined.

Finite Element Modeling of Perturbation Fields due to Colonies of Stress Corrosion Cracks(SCCs) in a Gas Transmission Pipeline (가스공급배관에서 응력부식균열 군에 의해 교란된 자속의 유한요소 모델링)

  • Yang, Sun-Ho
    • Journal of the Korean Society for Nondestructive Testing
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    • v.21 no.5
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    • pp.493-500
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    • 2001
  • The detection of axial cracks using conventional MFL pig is a significant challenge in the gas pipeline inspection. In this study, a technique using interaction of circumferentially induced torrents with axial stress corrosion crack is presented. The feasibility of this technique is investigated using finite element modeling. Finite element analysis of such interaction is a difficult problem in terms of both computation time and memory requirements. The challenges arise due to the nonlinearity of material properties, the small sire of tight cracks relative to that of the magnetizer, and also time stepping involved in modeling velocity effects. This paper presents an approach based on perturbation methods. The overall analysis procedure is divided into 4 simple steps that can be performed sequentially. Modeling results show that this technique can effectively detect colonies of SCC as well as single SCC.

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Evaluation of Half Cell Potential Measurement in Cracked Concrete Exposed to Salt Spraying Test (염해에 노출된 균열부 콘크리트의 반전위 평가)

  • Kim, Ki-Bum;Park, Ki-Tae;Kwon, Seung-Jun
    • Journal of the Korea Concrete Institute
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    • v.25 no.6
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    • pp.621-630
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    • 2013
  • Several techniques for steel corrosion detection are proposed and HCP (half cell potential) technique is widely adopted for field investigation. If concrete has cracks on surface, steel corrosion is rapidly accelerated due to additional intrusion of chloride and carbon dioxide ions. This study is for an evaluation of HCP in cracked concrete exposed chloride attack. For this work, RC (reinforced concrete) beams are prepared considering 3 w/c ratios (0.35, 0.55, and 0.70) and several cover depths (10~60 mm) and various crack widths of 0.0~1.0 mm are induced. For 35 days, SST (salt spraying test) is performed for corrosion acceleration, and HCP and corrosion length of rebar are evaluated. With increasing crack width, w/c ratios, and decreasing cover depth, HCP measurements increase. HCP evaluation technique is proposed considering the effects of w/c ratios, crack width, and cover depth. Furthermore anti-corrosive cover depths are obtained through Life365 program and the results are compared with those from this study. The results shows relatively big difference in cracked concrete, however provide similar anti-corrosive conditions in sound concrete.

Damage Detection on Thin-walled Structures Utilizing Laser Scanning and Standing Waves (레이저 스캐닝 및 정상파를 이용한 평판 구조물의 손상탐지)

  • Kang, Se Hyeok;Jeon, Jun Young;Kim, Du Hwan;Park, Gyuhae;Kang, To;Han, Soon Woo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.41 no.5
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    • pp.401-407
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    • 2017
  • This paper describes wavenumber filtering for damage detection using single-frequency standing wave excitation and laser scanning sensing. An embedded piezoelectric sensor generates ultrasonic standing waves, and the responses are measured using a laser Doppler vibrometer and mirror tilting device. After scanning, newly developed damage detection techniques based on wavenumber filtering are applied to the full standing wave field. To demonstrate the performance of the proposed techniques, several experiments were performed on composite plates with delamination and aluminum plates with corrosion damage. The results demonstrated that the developed techniques could be applied to various structures to localize the damage, with the potential to improve the damage detection capability at a high interrogation speed.