• Fire Science and Engineering
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• v.33 no.4
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• pp.112-120
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• 2019

Benzene is a class 4 hazardous material according to the Act on the Safety Control of Hazardous Substances. This study qualitatively evaluated the damage size of a "toxic" accident and "pool fire" accidents based on benzene in a virtual scenario of a fire and leakage accident during unloading at a port facility. The KORA program was used as an evaluation method, which is supported as a universal program by the National Institute of Chemical Safety. The range of damage effects of a benzene-induced fire and leakage accident was predicted. In the case of toxic damage range, the accident's damage effect range for the "worst case scenario" was reduced by up to 5.11% with a decrease in the size of the leakage hole. In the case of the leakage time, the damage effect range increased to 145.12% with a 10 min leakage time compared to that of a 5 min leakage time and went up to 20 min (212.29%) with a 20 min leakage time. In the case of pool-fire-induced damage, the damage effect range by radiant heat in the "worst case scenario" was 228.8 m in radius from the center of the handling facility. In the "alternative scenario," the damage effect range by radiant heat was reduced by up to 8.26% compared to that in the "worst case scenario" since the size of the leakage hole was decreased by reducing the cross-sectional area of the pipe.

• Journal of the Korean Institute of Gas
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• v.24 no.2
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• pp.15-21
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• 2020

Currently, in KS C IEC 60079-10-1, the leakage hole radius of secondary leakage is expressed as a recommendation. Underestimation of leak hole size can lead to underestimation of the calculated values for leak rates, and conservative calculations of leak hole sizes, which are considered for safety reasons, can be overestimated, resulting in an overestimated risk range. This too should be avoided. Therefore, a careful and balanced approach is necessary when estimating the size of leaking holes.Based on this logic, this study examines the stability by grasping the concentration inside the gas box when leaking dangerous substances as a result of experiments based on SEMI S6, an international safety standard applied in the semiconductor industry and The scope of explosion hazardous area was determined by applying the formula of KS C IEC 60079-10-1 according to SEMI F15 leak rate criteria and SEMI S6 leak rate criteria. Based on this, we will examine whether the exhaust performance needs to be improved as an alternative to FAB facilities that are difficult to apply to explosion hazards such as semiconductor industry.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.2_2
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• pp.315-325
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• 2023

Recently, various dynamic risk analysis methods have been suggested for estimating the risk index by predicting the possibility of accidents and damage. It is necessary to maintain and support the safety system for responding to accidents by continuously updating the probability of accidents and the results of accidents, which are quantitative standards of ship risk. In this study, when a LNG leakage that may occur in the LN G Fuel Gas Supply System (FGSS) room during LN G bunkering operation, a reliability physical model was prepared by the change in monitoring data as physical parameters to estimate the accident probability. The scenario in which LNG leakage occur were configured with FT (Fault Tree), and the coefficient of the covariate model and Weibull distribution was estimated based on the monitoring data. The possibility of an LNG leakage, which is the top event of FT, was confirmed by changes in time and monitoring data. A method for estimating the LNG leakage based on the reliability physical analysis is proposed, which supports fast decision-making by identifying the potential LNG leakage at the accident.

• Journal of ILASS-Korea
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• v.20 no.2
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• pp.101-106
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• 2015

Gas leakage and dispersion in the underground LNG power plant can lead to serious fire and explosion accident. In this study, computational fluid dynamics simulation was applied to model the dynamic process of gas leakage and dispersion phenomena in a closed space. To analyze the risk assessment factor, such as the flammable volume ratio, transient simulations were carried out for different scenarios. The simulation results visualized the gas distribution with time in the closed space. The flammable volume ratio was introduced for quantitative analysis the fire/explosion probability.

• Journal of Hydrogen and New Energy
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• v.30 no.1
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• pp.29-34
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• 2019

Safety of hydrogen handling facilities is needed as supply of hydrogen cars has been expanded recently. In this study, the adequacy of safety regulations of hydrogen handling facilities and the risk of damage with hydrogen leakage were studied. The range of explosion hazard location of the hydrogen filling plant was investigated using the computational fluid dynamics (CFD) method, Explosive hazardous area is influenced by leakage type, hole size and sectional area. When the conditions of KS standard are applied, range explosive hazardous area is expanded 7.05 m, maximum. It is about 7 times larger than exceptional standard of hydrogen station. Meanwhile, distance from leakage point to 25% LEL of hydrogen is investigated 1.6 m. Considering the shape of charging hose, regulation of hydrogen station is appropriate.

• JSTS:Journal of Semiconductor Technology and Science
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• v.8 no.2
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• pp.164-169
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• 2008

The effects of the antisite related defects on the electronic structure of silica and the gate leakage current have been investigated using first-principles calculations. Energy levels related to the antisite defects in silicon dioxide have been introduced into the bandgap, which are nearly 2.0 eV from the top of the valence band. Combining with the electronic structures calculated from first-principles simulations, tunneling currents through the silica layer with antisite defects have been calculated. The tunneling current calculations show that the hole tunneling currents assisted by the antisite defects will be dominant at low oxide field whereas the electron direct tunneling current will be dominant at high oxide field. With increased thickness of the defect layer, the threshold point where the hole tunneling current assisted by antisite defects in silica is equal to the electron direct tunneling current extends to higher oxide field.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.3
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• pp.83-87
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• 2012

Computational Fluid Dynamics (CFD) method has been used to investigate the axial force of automotive water pump. As the excessive axial force can make some unexpected problems like impeller interference and coolant leakage we have focused on finding the cause of axial force and its reduction in this paper. First, we have tested the closed type water pump with and without balance hole by the calculation methods. By examining the pressure contour around the impeller, we have found that the axial force arises not only from the pressure difference around shroud but also from the pressure difference around hub. So we have tested two impellers - one is normal open type impeller and the other is open type impeller with modified hub. The results show that the axial force reduction is about 150~200N for normal one and 700N@3000RPM for modified impeller. And the hydraulic efficiency which is important in aspect of engine fuel efficiency is reduced about 6.5% for normal one but increased 4%@3000RPM for modified impeller.

• Journal of Welding and Joining
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• v.19 no.3
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• pp.285-291
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• 2001

Large steel water pipes are joined prevalently by the bell end method, and are welded both at inside and outside of lapped parts. In practice, welded joints of water pipes are very critical, because in most cases failure of pipes causing leakage occurs at the welded joint. Therefore some methods have been developed to ensure the soundness of welded joints of water pipes, like leakage tests and nondestructive tests (NDTs). But one of the major characteristics that affects the soundness of welded Joints is the stress distribution caused by welding and external forces. Some studies have been carried out on the residual stress of steel water popes, but complex stress distributions by welding and external forces are rarely studied. In this study, temperature and stress distributions in steel water pipes produced by welding are predicted by a three-dimensional finite element method(FEM). Also, stress values are measured from real steel water pipes by the hole-drilling methods, and compared with predicted ones. The influence of some typical post weld treatments on residual stress distribution was also investigated by residual stress measurements.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.308-327
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• 2004

As use of tunnels and subways increase there also are accidents proportionate to it. Daegu Subway Station fire, Hongjimoon tunnel fire led people to be conscious of disaster protection and as a result, there is a trend to adopt standards for fire protection. Accordingly, this thesis is focused on investigating various fire and water protection related issues for subaqueous tunnel under Ran river. The thesis developed evacuation and disaster prevention plan as fire level increases and have identified the suitability of disaster prevention through evacuation and fire simulation, countermeasure of a water leakage during construction and operation considering the subaqueous tunnel. And we selected EPB shield TBM equipment considering the ground condition and effect of boring hole, and accomplished reasonable water protection design through setting goals using event-tree method, as well as examining model test of boring hole and flooding in heavy rain. Also included structured total system consist of water leakage sensing system, water protection gate, pumping system and fire protection system to respond systematically in emergency.

• Journal of Hydrogen and New Energy
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• v.20 no.5
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• pp.378-383
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• 2009

Hydrogen is the primary fuel in fuel cell systems. Because of high inflammation and explosion possibility of hydrogen, fuel cell systems require safety measures to prevent hydrogen hazard upon leakage. In this study, a model enclosure was made by referring to a commercial residential fuel cell system and hydrogen leakage experiments and computational simulations were conducted therein. Hydrogen was injected into the cavity through leakage holes located at the bottom while its flow rate was precisely controlled using MFC. The transient sensor signals from hydrogen sensors installed inside the enclosure were recorded and analyzed. The hydrogen sensor signals showed different delay times depending on their position relative to a leakage point, which indicated that hydrogen generally moves upward and accumulates at the upper region of a closed cavity. The inflammable regions with hydrogen concentration over 4% LEL were observed to locate near the leakage hole initially, and broaden towards the upper cavity region afterward. The simulation result showed that detection time at the hydrogen sensor was similar to the pattern of experimental results. However, the maximum concentration of hydrogen had a gap between experiment and simulation at detect point due to measurement errors and reaction rate.