• Nuclear Engineering and Technology
• /
• v.46 no.2
• /
• pp.225-234
• /
• 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.

• Transactions of the Korean Society of Pressure Vessels and Piping
• /
• v.19 no.2
• /
• pp.93-101
• /
• 2023

In this study, a deep learning algorithm was used to diagnose electric potential signals obtained through CIPS and DCVG, used indirect inspection methods to confirm the soundness of buried pipes. The deep learning algorithm consisted of CNN(Convolutional Neural Network) model for diagnosing the electric potential signal and Grad CAM(Gradient-weighted Class Activation Mapping) for showing the flaw prediction point. The CNN model for diagnosing electric potential signals classifies input data as normal/abnormal according to the presence or absence of flaw in the buried pipe, and for abnormal data, Grad CAM generates a heat map that visualizes the flaw prediction part of the buried pipe. The CIPS/DCVG signal and piping layout obtained from the 3D finite element model were used as input data for learning the CNN. The trained CNN classified the normal/abnormal data with 93% accuracy, and the Grad-CAM predicted flaws point with an average error of 2m. As a result, it confirmed that the electric potential signal of buried pipe can be diagnosed using a CNN-based deep learning algorithm.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.11 no.2
• /
• pp.77-84
• /
• 2007

The elastic buckling strength of a corrugated pipe made of orthotropic material was evaluated. The height and length of a corrugated wave and the thickness of the pipe were considered as factors affecting the buckling strength of the pipe. And also, the ratio of the longitudinal stiffness and transverse stiffness were considered as parameters affecting on the buckling strength of a pipe made of orthotropic material. Buckling strengths of various corrugated pipes with different shapes and stiffness ratio were evaluated by FE analyses. And a formula to estimate the elastic buckling strength was suggested by regression of FE analysis results. Analysis results show that a corrugated pipe has superior buckling strength to a general flat pipe and the suggested formula estimates accurate buckling strength of the corrugated pipe made of orthotropic material.

• Journal of the Korean Society of Safety
• /
• v.25 no.4
• /
• pp.42-47
• /
• 2010

Recently, many techniques have been developed for the inspection of pipelines using guided waves. However, few researches have been made on the application of those techniques for buried underground pipes. Guided wave motions in the buried pipes are somewhat different from those of on-ground pipes which have traction-free (air) boundary condition on outer pipe walls and thus are strongly affected by the mechanical property of the surrounding soils. Therefore, it should be investigated the effect of soil properties on the guided wave behavior in buried pipe. On the other hand, the mechanical property of soil is largely depending on its moisture conditions nevertheless of other influential factors such as void ratio. In this study, the effect of moisture conditions in soils on mode attenuation of guided waves in the buried pipe is investigated. To this end, numerical study is performed to characterize mode attenuation behavior in buried pipes and the effective mode which is suitable for long range inspection is identified.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.14 no.1
• /
• pp.33-38
• /
• 2013

The general purposed control system for driving a motion of many different typed robot end-effector, which consists of a controller based on ARM Cotex M3-11017 MCU and an application software for generating a motion of end-effector, was developed. Experimental results show that a positioning error is nearly negligible and a repeatability error is 0.04%. Accordingly the developed control system can be applied practically to actuate a robot end-effector for inspection and maintenance of steam generator heat pipe in nuclear power plant.

• 제어로봇시스템학회:학술대회논문집
• /
• 2005.06a
• /
• pp.963-968
• /
• 2005

For worm robots applied to pipe inspection and colonoscopy, earthworm-like robots that have a locomotion pattern in backward wave or green caterpillar-like robots that have a locomotion pattern in forward wave have been studied widely. Note however that a method using a single and fixed locomotion pattern is not desirable in the sense of mobility cost, if there are various changes in pipe diameter. In this paper, locomotion patterns are considered for a semi-looper-like robot, which adopts a locomotion pattern of green caterpillars as the basic motion and sometimes can realize a locomotion pattern of looper, whose motion approximately consists of two rhythms or relatively low rhythm.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.2 no.3
• /
• pp.168-175
• /
• 1998

This study investigated the structural performance of the precast prestressed cylinder pipe having cracked under construction. The finite element formulation of PPC pipe incorporates Asoild elements using SAP90 program and the radial prestress force was transformed into the eqivalent external pressure. The analytical results were compared with the experimental results of full scale tests on PPC pipes subjected to static load. It is shown that the proposed modelling gives a realistic represention of the actual behavior. The analytical procedure is used to calculate the stresses in the PPC pipes and to check the crack opening under various situations such as bedding angle, earth pressure, and earth cover. Finally, the proposed modelling and analytical procedure should be especially usefull for the safety assessment of the PPC pipes under general loading conditions.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.20 no.6
• /
• pp.167-173
• /
• 2020

A lot of research has been done on pipe climbing robots to investigate the aging pipe structures of nuclear power plants and petrochemical plants. Nevertheless, most of the research on pipe climbing robots focused on the structural design and foundational motion control of pipe climbing robots. So, For the operator to control the pipe climbing robot, it has many difficulties to climb the pipe and avoid obstacles by manual operation. In this paper, propose an algorithm that recognizes obstacle by using camera images of pipe climbing robots, estimates the distance between pipe climbing robots and obstacles, and determines the position where pipe climbing robots can catch pipes to avoid obstacles between pipes.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.8 no.1
• /
• pp.221-229
• /
• 2004

In Recent experimental research results of connection method between steel pipe pile and concrete footing are provided based on various experimental observations. It gives a shedding light toward developing better connection method for steel pipe pile at the field application. In this study, the newly developed method is tested for compressive, pull put and combination load including moment with carefully designed monitoring system. The measured data show that new method have at least equivalent or better load resistant capacities compared with those of specified method in Korea Road Design Specification. It is also tried to define and investigate the load transfer mechanism for new method.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.10 no.2
• /
• pp.91-101
• /
• 2006

Lately, massive concrete structures are increasingly built. In such massive structures, the heat of hydration of mass concrete causes thermal cracks. To avoid thermal crack, methods widely acceptable for practical use are pre-cooling, pipe cooling and control of placing height. Thermal stress analysis is performed to find the way of controlling the thermal crack of pier footing mat in this paper. The footing mat model for the analysis is $12m{\times}14m$area and 3m height. The analysis results are compared with method of control of lift height and method of pipe cooling. The analysis results show that thermal crack can be removed by method of placing control and pipe cooling at footing mat placed on the ground.