• Journal of Magnetics
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• v.18 no.2
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• pp.202-206
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• 2013

In this paper, the MFL (magnetic flux leakage) signals of complex defects on the underground gas pipeline are analyzed and their depths are estimated. Since closely-located defects (complex defects) affect each other, accelerate the progress of defection, and are finally combined to one (cluster), it's meaningful to differentiate complex defects from single defects by analyzing their characteristics. Various types of complex defects are characterized and analyzed by defining the safety distance for interference. 26 artificial defects are carved on the pipeline simulation facility (PSF) to analyze the characteristics of complex defect and demonstrate the accuracy of the proposed complex defect estimation. The proposed method shows average length error of 5.8 mm, average width error of 15.55 mm, and average depth error of 8.59%, respectively.

• Journal of the Korean Society of Safety
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• v.33 no.3
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• pp.33-38
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• 2018

Defects in piping caused by corrosion or external impact of underground piping can lead to high risk of rupture of the piping due to high pressure. Flammable gas can be immediately ignited when discharged from piping, causing a jetfire. The damage of the radiant heat not only threatens the health of the workers who work in the industry but also the health of the people living in the neighboring residential areas. It is important to prevent and prepare before an accident occurs. In this study, three types of flammable gas underground piping accident scenarios were investigated, and the ranges of influence were determined using Phast ver7.2. and finally regression models were formulated to predict the ranges using excel and Matlab.

• Journal of the Korean Institute of Gas
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• v.2 no.1
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• pp.23-27
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• 1998

To protect the underground pipeline from the mechanical damage and to enhance the cathodic protection effect, the river sand has been backfilled traditionally around the buried pipeline. However, river sand became depleted and expensive. One has to seek for the economic alternative materials. Crashed stone is a good candidate for the backfill material. In this study, how much the particle size and shape of the crashed stone can effect on the gas pipeline coating was examined. A series of laboratory and field test was performed. In the Lab, the increasing loads were applied to the coated pipeline surrounded by the crashed stone, where no significant damage was observed.

• 한국가스학회:학술대회논문집
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• 2002.05a
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• pp.111-121
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• 2002

천연가스 수송배관은 매설환경시의 방식 및 외부충격 등에 대비하여 배관을 보호할 목적으로 폴리에틸렌(polyethylene)으로 피복(coating)되어 있다. 가스배관이 전국으로 확장됨과 더불어 배관피복 기술도 초기 사용하던 1층(one-layer), 2층피복으로 발전되어 현재는 3층피복시스템을 적용한 배관들이 전국에 매설되고 없다. 그러나 강관에 적용된 폴리에틸렌 피복이 경우에 따라 장기간 사용에 따른 자연균열등이 발생하여 피복의 안정성에 문제를 일으키기도 하므로, 그동안 전국에 매설되어있는 배관 피복재들의 물성변화 여부를 확인하여 천연가스수송용 배관의 내성 데이터베이스를 구축, 향후 배간운영의 신뢰성 평가에 참고하고자 하였다. 이를 위하여 선진외국에서 폴리에틸렌 배관의 내구성과 장기사용 안정성 평가를 위해 오래전부터 활용되고 있는 저속균열저항성(slow crack growth resistance : SCGR) 측정과 배관 피복층의 산화유도시간(OIT : oxidation induction time)을 측정하여 국내 배관 피복재들의 내구성을 평가하고 이를 근거로 하여 국내사용판정에 적합하고 수출도 고려한 폴리에틸렌 물성치의 목표값을 제안하였다.

• Journal of the Korean Institute of Gas
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• v.18 no.5
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• pp.66-71
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• 2014

Gas pipelines are the core facilities in the gas facilities and the most pipelines are buried underground and are exposed to the risk of corrosion caused by the soil characteristics and the environmental impact. The anti-corrosion potential and the corrosion status of the underground pipelines are measured periodically in accordance with the relevant laws and regulations. A study on the cathodic protection measurement system was carried out in order to solve the problems of the conventional measurement system. This paper describes the survey on the standards and the specifications of the cathodic protection measurement and the the reference electrode to meet the relevant regulations, and the development of the measuring circuit and the data transmission module to build the cathodic protection measurement system. This study verified the field applicability through the testing of the developed prototype and investigated on the problems of the previous studies and the future research and development direction.

• Journal of Magnetics
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• v.18 no.3
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• pp.357-360
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• 2013

A modified SQI method using magnetic leakage flux (MFL) signal for underground gas pipelines' defect detection and characterization is presented in this paper. Raw signals gathered using MFL signals include many unexpected noises and high frequency signals, uneven background signals, signals caused by real defects, etc. The MFL signals of defect free pipelines primarily consist of two kinds of signals, uneven low frequency signals and uncertain high frequency noises. Leakage flux signals caused by defects are added to the case of pipelines having defects. Even though the SQI (Self Quotient Image) is a useful tool to gradually remove the varying backgrounds as well as to characterize the defects, it uses the division and floating point operations. A modified SQI having low computational complexity without time-consuming division operations is presented in this paper. By using defects carved in real pipelines in the pipeline simulation facility (PSF) and real MFL data, the performance of the proposed method is compared with that of the original SQI.

• Smart Structures and Systems
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• v.30 no.5
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• pp.433-446
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• 2022

Despite efforts to reduce unexpected accidents at confined construction sites, choking accidents continue to occur. Because of the poorly ventilated atmosphere, particularly in long, confined underground spaces, workers are subject to dangerous working conditions despite the use of artificial ventilation. Moreover, the traditional monitoring methods of using portable gas detectors place safety inspectors in direct contact with hazardous conditions. In this study, a long-range (LoRa)-based wireless safety monitoring system that features the network organization, fault-tolerant, power management, and a graphical user interface (GUI) was developed for underground construction sites. The LoRa wireless data communication system was adopted to detect hazardous gases and oxygen deficiency within a confined underground space with adjustable communication range and low power consumption. Fault tolerance based on the mapping information of the entire wireless sensor network was particularly implemented to ensure the reliable operation of the monitoring system. Moreover, a sleep mode was implemented for the efficient power management. The GUI was also developed to control the entire safety-monitoring system and to manage the measured data. The developed safety-monitoring system was validated in an indoor testing and at two full-scale water pipeline construction sites.

• Corrosion Science and Technology
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• v.2 no.3
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• pp.161-163
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• 2003

With the development of Chinese petroleum and gas industry, about 20,000 km long-distance pipeline and 250,000 km gathering pipeline have been constructed in China. After operating for many years, most of the coatings on buried pipelines have aged so severe that the steel pipes are subject to corrosion environment underground. Focusing on the need of external coating for buried pipeline rehabilitation, a new type of coating has been developed. The development and application of the coatings has been introduced in this paper.

• The Journal of Society for e-Business Studies
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• v.23 no.2
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• pp.33-47
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• 2018

City gas pipelines are buried underground. Because of this, pipeline is hard to manage, and can be easily damaged. This research proposes a real time prediction system that helps experts can make decision about pressure anomalies. The gas pipline pressure data of Jungbu City Gas Company, which is one of the domestic city gas suppliers, time variables and environment variables are analysed. In this research, regression models that predicts pipeline pressure in minutes are proposed. Random forest, support vector regression (SVR), long-short term memory (LSTM) algorithms are used to build pressure prediction models. A comparison of pressure prediction models' preformances shows that the LSTM model was the best. LSTM model for Asan-si have root mean square error (RMSE) 0.011, mean absolute percentage error (MAPE) 0.494. LSTM model for Cheonan-si have RMSE 0.015, MAPE 0.668.

• Journal of the Korean Society for Environmental Technology
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• v.19 no.6
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• pp.576-585
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• 2018

Systematic management during the whole life cycle from construction to operation and maintenance is very important for the seven underground pipelines (waterworks, sewerage, electricity, telecommunications, gas, heating, oil including waterworks and sewerage). Especially, it is the construction process that affects the whole life cycle of underground buried pipeline. In order to construct a new city or to maintain different underground pipes, it is always necessary to dig the ground and carry out construction and related work. There is a possibility that secondary and tertiary breaks frequently occur in the pipeline construction process after the piping constructed first in this process. To solve this problem, a system is needed which can monitor damage in real time. However, the supply of electric power for continuous operation of the system is limited according to the environment of underground buried pipelines, so it is necessary to develop a stable electric power supply system using natural energy rather than existing electric power. In this study, we developed a system that can operate the pipeline monitoring system for long time (24 hours and 15 days) using natural energy using wind and solar light.