• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.4
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• pp.311-316
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• 2010

Defects positioning of underground gas pipelines using MFL(magnetic flux leakage) inspection which is one of non-destructive evaluation techniques is proposed in this paper. MFL signals acquired from MFL PIG(pipeline inspection gauge) have nonlinearity and distortion caused by various external disturbances. SQI(self quotient image), a compensation technique for nonlinearity and distortion of MFL signal, is used to correct positioning of pipeline defects. Through the experiments using artificial defects carved in the KOGAS pipeline simulation facility, it is found that the performance of proposed defect detection is greatly improved compared to that of the conventional DCT(discrete cosine transform) coefficients based detection.

• Journal of the Korean Institute of Gas
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• v.20 no.5
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• pp.89-95
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• 2016

Keeping the gas pipelines in the common utility tunnel is useful because it has a lower risk of corrosion than conventional burial, and can prevent from excavating construction. But, explosions in common utility tunnels can cause greater damage from the blast overpressure compared to outdoor explosions, due to nature of the confined environment. Despite this fact, however, research on common utility tunnels has been limited to fire hazard and little has been studied on the dangers of explosions. This study developed scenarios of methane gas explosion caused by gas leak from gas piping within the common utility tunnel followed by unknown ignition; the study then calculated the extent of the impact of the explosion on the facilities above, and suggested the needs for designing additional safety measures. Two scenarios were selected per operating condition of safety devices and the consequence analysis was carried out with FLACS, one of the CFD tools for explosion simulation. The overpressures for all scenarios are substantial enough to completely destroy most of the buildings. In addition, we have provided additional measures to secure safety especially reducing incident frequency.

• Industry Promotion Research
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• v.4 no.1
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• pp.1-9
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• 2019

This study is a technology related to a seismic protection device for a fire pipe for installation in a building such as an apartment or a building. The fire pipe is fixed to the base panel by fastening bolts so as to flow left and right. The present invention relates to an earthquake-resistant apparatus for a fire-extinguishing piping, which is capable of minimizing damages caused by an earthquake in order to prevent damages and breakage of a fire-extinguishing pipe by mitigating earthquakes, vibrations, It is connected to an insert plate embedded in concrete or ceiling hanger bolts formed at regular intervals on the ceiling to keep the piping constant from the ceiling and to keep the horizontal condition of the piping always constant so that the piping relaxes or sags And to effectively prevent damage to the piping. The can get.

• Proceedings of the KIEE Conference
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• 2005.07e
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• pp.61-63
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• 2005

In present, most of underground metallic structures, especially gas pipeline, have adopted in order to protect against a corrosion. If a coating defect is be on the surface of gas pipeline, the pitting corrosion is occur normally. So, in the corrosion field, investigation of coating defect is very important activity. In this paper, DCVG(Direct Current Voltage Gradient) method which is can detect a coating defect of gas pipeline is introduced. And also, the assesment of coating defect position according to the position of temporary anode of ICCP(Impresed Current Cathodic Protection) system is presented.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.12
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• pp.2019-2029
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• 2001

Up to now a wide variety of researches on inpipe inspection robots have been introduced, but it still seems to be difficult to construct a robot providing mobility sufficient to navigate inside the complicated configuration of underground pipelines. This paper introduces a robot called MRINSPECT IV(Multifunctional Robotic Crawler for inpipe inSPECTion IV) for the inspection of urban gas pipelines with a nominal 4-inch inside diameter. The proposed robot can freely move along the basic configuration of pipelines such as along horizontal or vertical pipelines. Moreover it can travel along reducers, elbows, and steer in the branches by modulating the speeds of driving modules. Especially, its capability for steering in tile three-dimensional pipeline configuration has a competative edge over the other ones and provides excellent mobility in navigation. Its critical points in the design and construction are introduced and results of experiments are given.

• Journal of the Korea Society of Computer and Information
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• v.19 no.7
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• pp.95-102
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• 2014

There are a variety of structures below the surface are buried. In particular, if It is experiencing problems in the city gas pipe or electrical wire, our safety would be greatly jeopardized. Therefore, the underground structures which encounter a variety of pollutants are highly sensitive to corrosion. So if you are not identify the degree of corrosion, it can lead to large accidents such as gas leakage. Until now, person visit directly every underground structure to measure and record manually, but This approach requires a lot of human and material resources and the continuity of management. Therefore, the research to find out the risk factors quickly via the continuous management is needed, and in this paper the structures management systems in the vehicle being moved by combining ICT underground structures for state information wirelessly collects and analyzes system is proposed.

• Journal of the Korean Institute of Gas
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• v.20 no.6
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• pp.16-22
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• 2016

Coating pipe(PLP) has been generally used in buried site for protecting the corrosion. To prevent the damage by occurring the defect, other construction or execution works, an anti-oxidation environment was forcibly made by using protective potential. Coating and protective potential are applied simultaneously, but corrosion rate or defects are not easy to observe because soil composition has many uncertainty. Also, defect of coating pipe can not be directly observed. A corrosion coupon can easily measure a corrosion rate directly. The corrosion rate was measured with 6 scenarios using corrosion coupon during about 1 year(6 scenarios are based on soil type and protective potential or not in this research. Resultingly, the corrosion coupon has not occurred in the case of protected by potential current, but corrosion has occurred in a non-protected site. The corrosion rate was measured at least in the clay, and the propensity of corrosion rate was similar in other soil(sand and loams). The local corrosion has occurred in the clay because of high water content. On the other hand, general corrosion was occurred in sand and loams. Commonly, sand is not to corrosive soil. Although, corrosion occurred in sand can be estimated by chemical component and valid with chemical analysis report.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.6
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• pp.937-957
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• 2017

Urban roads are not only congested with vehicles and pedestrians, but also have many pipelines buried to provide convenience for inhabitants. In addition, urban inhabitants live comfortably in buildings adjacent to the road for residence, business, commerce, rest and so on. Therefore, despite the high cost of land, urban underground buildings with high land use efficiency are constantly being built. Recently, the construction of underground buildings has caused social problems such as the collapse of surrounding roads and adjacent buildings. Institutional improvement is being actively carried out to improve this. In this study, a new type of MSRC diaphragm wall was developed and a study on the construction method of underground building was carried out. It is intended to secure the underground excavation safety of underground buildings in urban areas and effectively prevent land subsidence complaints. Also, a reasonable design method of MSRC diaphragm walls using the ultimate strength design method is presented through the flexural performance Experiment.

• Journal of the Korean Institute of Gas
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• v.5 no.3 s.15
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• pp.63-72
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• 2001

An alternating current (AC) corrosion using coupon and electric resistance (ER) probe has been studied. Coupon coupled with ER probe were applied in terms of AC voltage from high value to low value through the survey of AC voltages on buried gas transmission pipeline over the country. Parameters such as AC current density of coupon, AC voltage, cathodic protection potential, soil resistivity and frequency were monitored continually. Corrosion induced by AC was observed even under cathodically protected condition that met cathodic protection criterion (below -850mv vs. CSE). Corrosion rate was affected mainly not by AC voltage but by both of frequency and AC current density. An experimental corrosion rate relationship could be obtained statistically, In which AC corrosion rate increased linearly with effective AC current density and its slope was 0.619 in case of coupon and 0.885 in case of ER probe.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.6
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• pp.568-576
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• 2010

It is widely known that the leak locating of underground plastic pipelines is much more difficult than that of cast iron pipelines. The precision of the leak locating depends upon the speed of leak signal and the time delay estimation between the two sensors on the pipeline. In this paper, six different windowing filters are considered to improve the time delay estimation especially for the plastic pipelines. The time delay is usually estimated from the peak time of cross-correlation functions. The filtering windows including rectangle, Roth, Wiener, SCOT, PHAT and maximum likelihood are applied to derive the generalized cross-correlation function and compared each other. Experimental results for the actual plastic underground water supply pipeline show that the introduction of the filtering windows improved the precision of time delay estimation. Some window functions provide excellent leak locating capability for the plastic pipe of 98 m long, which is less than 1 % of the pipe lengths. Also a new probabilistic approach that the combinations of all results from each filtering window is suggested for the better leak locating.