• Proceedings of the Korean Society of Disaster Information Conference
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• 2023.11a
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• pp.241-243
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• 2023

아파트 신축공사 흙막이 가시설 현장에 근접 매설된 상수관의 누수 및 파열 사고로 터파기 공사 현장에 토사 유실 및 지반 함몰이 발생되었으며, 흙막이 가시설의 토류판이 파손되었다. 흙막이 가시설의 안정성 확보를 위해 벽체구간은 레이커로 보강하고 사보강재는 1단과 2단을 묶어 힘을 분산시키고 종방향으로 보강 및 토류판 보강을 시행하였다.

• Proceedings of the Korean Society of Disaster Information Conference
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• 2023.11a
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• pp.244-246
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• 2023

아파트 신축공사 흙막이 가시설 현장에 근접 매설된 상수관의 누수 및 파열 사고로 인접 건물이 공사현장 방향으로 58~188mm 기울어졌으며, 지중수평경사계 계측결과 21.07.20일 22.64mm가 21.10.18.일 101.46mm로 급격하게 78.82mm의 큰 수평 변위가 발생되었으며, 이로 인해 흙막이 가시설의 사보강재가 변형되고 토류판 일부가 파손되었다.

• Korean Chemical Engineering Research
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• v.55 no.3
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• pp.322-331
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• 2017

District heating was first introduced in Korea in 1985. As the service life of the underground thermal piping network has increased for more than 30 years, the maintenance of the underground thermal pipe has become an important issue. A variety of complex technologies are required for periodic inspection and operation management for the maintenance of the aged thermal piping network. Especially, it is required to develop a model that can be used for decision making in order to derive optimal maintenance and replacement point from the economic viewpoint in the field. In this study, the analysis was carried out based on the repair history and accident data at the operation of the thermal pipe network of five districts in the Korea District Heating Corporation. A failure probability model was developed by introducing statistical techniques of qualitative analysis and binomial logistic regression analysis. As a result of qualitative analysis of maintenance history and accident data, the most important cause of pipeline damage was construction erosion, corrosion of pipe and bad material accounted for about 82%. In the statistical model analysis, by setting the separation point of the classification to 0.25, the accuracy of the thermal pipe breakage and non-breakage classification improved to 73.5%. In order to establish the failure probability model, the fitness of the model was verified through the Hosmer and Lemeshow test, the independent test of the independent variables, and the Chi-Square test of the model. According to the results of analysis of the risk of thermal pipe network damage, the highest probability of failure was analyzed as the thermal pipeline constructed by the F construction company in the reducer pipe of less than 250mm, which is more than 10 years on the Seoul area motorway in winter. The results of this study can be used to prioritize maintenance, preventive inspection, and replacement of thermal piping systems. In addition, it will be possible to reduce the frequency of thermal pipeline damage and to use it more aggressively to manage thermal piping network by establishing and coping with accident prevention plan in advance such as inspection and maintenance.

• Journal of Korean Society of Disaster and Security
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• v.16 no.1
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• pp.71-80
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• 2023

Fuel cells are low-carbon power sources that can expand distributed energy system and electric vehicle charging infrastructure when installing fuel cells in gas stations. In order to ensure safety for fuel cells in gas stations, quantitative risk assessments were conducted after deriving accident scenarios based on accident data of domestic and foreign gas stations and fuel cells. It calculates the expected extent of damage from fire and explosion that can occur in reality, not the worst accident scenario, and analyzes the damage impact. The separation distance of more than 9.0 m from a dispenser, 15.5 m from a car under refueling, 4.1 m from the ventilation pipe, 1.1 m from the gas adjustment device prevent the severe damage caused by the expected accident. This study result can be used to deploy fuel cells in gas stations and establish safety measures.

• Journal of the Korea Convergence Society
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• v.6 no.3
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• pp.13-18
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• 2015

This paper is the study on the safe design of joint controling the pressure and temperature by connecting between pipes laying with the flexible joint. This study aims at decreasing the excessive pressure applied in the pipe and preventing the accident occurrence in order to solve the pipe damage by extraction and contraction due to the pressure of open air and transport gas. The flow properties of each model are investigated through the simulation analysis by applying three kinds of the flexible joints. When transport gas passes the flexible joint, the flow characteristics of heat, pressure and velocity at pipe laying are analyzed. It is thought to be contributed to the safe design due to the shape of the flexible joint by using the result of this study. And it is possible to be grafted onto the convergence technique at design and show the esthetic sense.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.2
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• pp.177-184
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• 2017

Many ground subsidence accidents have happened in Korea. The accident was caused by the subsidence and leakage of the deteriorated sewage pipe. This study aims to establish the empirical data of the ground penetration radar(GPR) detection for ground subsidence. A test bed was also manufactured for the same purpose. The GPR detection variables are embedment depth and horizontal distance of embedded cast iron pipe and expanded polystyrene(EPS). From the detection results, the EPS embedded by a depth of 1.5m was difficult for detection. The EPS closely embedded to the cast iron pipe within a 0.5m distance had a very strong cast iron pipe signal. Therefore, the detection was impossible. This study developed an image processing program, called the GPR image processing program(GPRiPP), to process the GPR detection results. Its major function is the gain function, which amplifies the wiggle wave signal. Compared to the existing programs, the GPRiPP is capable of showing a similar image processing performance.

• Fire Science and Engineering
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• v.25 no.6
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• pp.32-38
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• 2011

As the using rate of an explosive gas has been increased in the industrial site, the regional residents adjacent to the site as well as the site workers have frequently fallen into a dangerous situation. Damage caused by accident in the process using hydrogen gas is not confined only to the relevant process, but also is linked to a large scale of fire or explosion and it bring about heavy casualties. Therefore, personnel in charge should investigate the kinds and causes of the accident, forecast the scale of damage and also, shall establish and manage safety countermeasures. We, in Anti-Calamity Research Center, forecasted the scope of danger if break out a fire or/and explosion in hydrogen gas facilities of MLCC firing process. We selected piping leak accident, which is the most frequent accident case based on an actual analysis of accident data occurred. We select and apply piping leak accident which is the most frequent case based on an actual accident data as a model of damage forecasting scenario caused by accident. A jet fire breaks out if hydrogen gas leaks through pipe size of 10 mm ${\Phi}$ under pressure of 120 bar, and in case of $4kw/m^2$ of radiation level, the radiation heat can produce an effect on up to distance of maximum 12.45 meter. Herein, we are going to recommend safety security and countermeasures for improvement through forecasting of accident damages.

• Transactions of the Korean hydrogen and new energy society
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• v.35 no.1
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• pp.66-74
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• 2024

This study addresses the escalating issue of worldwide hydrogen gas accidents, which has seen a significant increase in occurrences. To comprehensively evaluate the risks associated with hydrogen, a two approach was employed in this study. Firstly, a qualitative risk assessment was conducted using the bow-tie method. Secondly, a quantitative consequence analysis was carried out utilizing the areal locations of hazardous atmospheres (ALOHA) model. The study applied this method to two incidents, the hydrogen explosion accident occurred at the Muskingum River power plant in Ohio, USA, 2007 and the hydrogen storage tank explosion accident occurred at the K Technopark water electrolysis system in Korea, 2019. The results of the risk assessments revealed critical issues such as deterioration of gas pipe, human errors in incident response and the omission of important gas cleaning facility. By analyzing the cause of accidents and assessing risks quantitatively, the effective accident response plans are proposed and the effectiveness is evaluated by comparing the effective distance obtained by ALOHA simulation. Notably, the implementation of these measures led to a significant 54.5% reduction in the risk degree of potential explosions compared to the existing risk levels.

• 한국전산유체공학회:학술대회논문집
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• 2005.10a
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• pp.39-44
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• 2005

In HANARO, a multi-purpose research reactor of 30 MWth, the emergency water supply system consists essentially of an emergency water storage tank located in the level of about thirteen meter (13 m) above the reactor core, a three inch ('3\%') diameter water injection pipe line including injection valves from the tank to the reactor cooling inlet pipe and a test loop to do periodic system performance test. When the water level of the reactor pool comes down to the extremely low due to a loss of reactor pool water accident the emergency water stored in the tank should be fed to the core by the gravity force and at that time the design flow rate is eleven point four kilogram per second (11.4 kg/s). But it is impossible periodically to measure the injection flow rate under the emergency condition because the normal water level should be maintained during the reactor operation. This paper describes a flow network analysis to simulate the flow rate under the emergency condition. As results, it was confirmed through the analysis results that the calculated flow rate agrees with the design requirement under the emergency condition.

• Journal of Power System Engineering
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• v.14 no.5
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• pp.36-40
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• 2010

The ultrasonic guided wave propagates along with the given structure's wall direction. Because of this specific character, the ultrasonic guided waves arc used in many other fields. Especially, it can be readily utilized for nondestructive inspection of various structures that are made up of gas pipes, heat exchanger tubes, and thin plates. Further, the guided wave technology can be readily utilized when inspecting pipes or thin plates which pose high risk of the accident but for which the nondestructive inspection itself is impossible because it is difficult to get to them since they are coated or buried underground. In the other hand, conventional ultrasonic testing such as thickness gauging uses bulk waves and only tests the region of structure immediately below the transducer. As a result of the application about inlet and outlet cooling water line using guided wave test, we conformed that the overall corrosions were in the lower side of the 304.8 mm inlet valve and these corrosions were engaged in not locally but through the lower side of the valve line. In the near future, we can expect that the detectable defect size is smaller than before along with the development of the sensing technology.