• 한국안전학회지
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• 제32권5호
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• pp.168-178
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• 2017

In order to prevent major and chemical accidents, some of the plants which would like to install and operate hazard chemicals handling facilities must submit Off-site Consequence Analysis due to recent arisen leak accidents since 2015. A lot of chemical industrials choose gas detectors as mitigation equipment to early detect gas vapor. The way of placement of gas detectors has two methods; Code-based Design(CBD) and Performance-based Design. The CBD has principles for gas detectors to be installed with consideration for the place that is expected to accumulate gas, and the leak locations according to legal standards and technical guidelines, and has a possibility to be unable to detect by these rules to locate gas detectors by vapor density information. The PBD has two methods; a Geographic Method and Scenario based Method. The Scenario-based Method has been suggested to make up for the Geographic Coverage Method. This Scenario-based Method draw the best optimum placement of gas detectors by considering leak locations, leak speed information, leak directions and etc. However, the domestic placement guidelines just refers to the CBD. Therefore, this study is to compare existing placement location of gas detectors by the domestic CBD with placement locations, coverages and the number of gas detectors in accordance with the Scenario-based Method. Also this study has measures for early detecting interest of Vapor Cloud and suitable placement of gas detectors to prevent chemical accidents. The Phast software was selected to simulate vapor cloud dispersion to predict the consequence. There are two cases; an accident hole size of leak(8 mm) from API which is the highst accident hole size less than 24.5 mm, and a normal leak hole size from KOSHA Guide (1.8 mm). Detect3D was also selected to locate gas detectors efficiently and compare CBD results and PBD results. Currently, domestic methods of gas detectors do not consider any risk, but just depend on domestic code methods which lead to placement of gas detectors not to make personnels recognize tolerable or intolerable risks. The results of the Scenario-based Method, however, analyze the leak estimated range by simulating leak dispersion, and then it is able to tell tolerable risks. Thus it is considered that individuals will be able to place gas detectors reasonably by making objectives and roles flexibly according to situations in a specific plant.

• 한국안전학회지
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• 제23권3호
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• pp.1-7
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• 2008

As a clean fuel, LNG or LPG is widely used in large restaurants or plants instead of coal. These fuels are easy to use and cheap. However, they are inflammable very much and easily exploded at the worst. So there are many laws and regulations legislated for the handling and usage of the gas facilities. Nevertheless, very harsh explosions occurred in several domestic or foreign places. In this paper a gas detection and alarm system was developed for large facilities. A new concept for connecting many gas detectors was proposed and based upon that a system including hardware and software have been developed and tested. Although up to 16 gas detectors apart 1 km from main controller can be connected currently, this system can be easily expanded for more detectors because each gas detector receiver communicates with main controller using industrial standard RS-485 multi drop technique. Furthermore several additive functions was included for the installation and maintenance convenience.

• Journal of Radiation Protection and Research
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• 제29권1호
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• pp.25-31
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• 2004

Results of EGS4 based calculations to study the spatial resolution of gas detectors are described. The calculations include radial distribution of electrons generated by photons of various energies penetrating into variable thickness of Ar and Xe gas layers. Given a desired spatial resolution, the maximum allowed thickness of gas layer for each energy level is determined. In order to obtain 0.1mm spatial resolution, the maximum thickness for the Ar gas is found to be 2mm for photon energies below 14keV while the optimum energy of photons for Xe gas with the same thickness is about 45keV. The results of calculations performed to compare the number of electrons generated by CsI coated micro-channel plate and the number of electrons generated by the Ar and Xe gas layers are described. The results show that the number of electrons generated by the gases is about 10 times higher than the one generated by CsI coated micro-channel plate. A few sample gray scale images generated by these calculations are included.

• Journal of Advanced Marine Engineering and Technology
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• 제32권3호
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• pp.455-460
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• 2008

The flammable gas monitoring system is to be provided in cargo pump rooms of tankers in accordance with the requirements of SOLAS regulations, and flammable gas detectors are to be arranged in a proper position. In this paper, simulation tests and CFD analysis are carried out under the actual ventilation conditions of pump rooms in the ship in service. Based on the results, a new guidelines for an arrangement of flammable gas detectors are suggested.

• 센서학회지
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• 제24권1호
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• pp.6-9
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• 2015

Conventional leak detectors are widely based on helium gas sensors. However, the usage of hydrogen sensors in leak detectors has increased because of the high prices of helium leak detectors and the dearth in the supply of helium gas. In this study, a hydrogen leak detector was developed using solid-state hydrogen sensors. The hydrogen sensors are based on Park-Rapp probes with heterojunctions made by oxygen-ion conducting Yttria-stabilized zirconia and proton-conducting In-doped $CaZrO_3$. The hydrogen sensors were used for determining the potential difference between air and air balanced 5 ppm of $H_2$. Even though the Park-Rapp probe shows an excellent selectivity for hydrogen, the sensitivity of the sensor was low because of the low concentration of hydrogen, and the oxygen on the surface of the sensor. In order to increase the sensitivity of the sensor, the sensors were connected in series by Pt wires to increase the potential difference. The sensors were tested at temperatures ranging from $500-600^{\circ}C$.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.285-288
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• 2002

In this study, we investigate electron transport properties in xenon gas by using a Monte Carlo technique for electrons with energies below 10 keV. First of all, we determine a set of electron collision cross sections with xenon by scrutinizing the cross section data taken from many publications. Then, the W value and the Fano factor for electrons in gaseous xenon are computed by the Monte Carlo simulation on the assumption that electrons undergo single collision events including elastic, excitation and ionization processes. We also evaluate the production number of excited atoms.

• 에너지공학
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• 제25권1호
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• pp.145-152
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• 2016

가스사고 연감에 의하면 최근 가연성 및 독성 가스로 인한 사고가 끊임없이 발생하고 있다. 이러한 사고를 예방하기 위하여 위험지역에서도 안전하게 가스 누출여부를 검사할 수 있는 검지기를 개발하고자 한다. 따라서 본 논문에서는 적외선 가스센서의 응답특성에 근사하는 방정식을 선형회귀를 이용하여 도출하였다. 선형회귀방정식을 통해 도출된 결과를 Neville 반복 보간법을 활용하여 알고리즘을 제안하였다. 또한, 제안한 알고리즘을 시판중인 가연성 가스누출검지기와 한국가스안전공사에서 제조한 7종의 표준가스를 이용하여 시험을 한 결과 성능이 향상될 수 있음을 확인하였다. 향후 경년변화, 온 습도 조건에 따른 성능변화를 분석하고, 방폭구조를 적용한 회로를 적용함으로서 신뢰성과 안정성을 향상시키고자 한다.

• 한국산업융합학회 논문집
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• 제26권6_3호
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• pp.1251-1258
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• 2023

Traditional markets are infrastructure with facilities and characteristics of very high population density. Recently, arcades have been installed through traditional market modernization policies, and aging infrastructure has been repaired. However, gas and electrical facilities of traditional markets cannot be easily replaced because of its high density. And because regular inspections are not conducted, management of facilities is on very poor condition. In addition, when a fire occurs in a traditional market, the fire easily spreads to nearby stores and is likely to spread to a large fire because of a lot of highly flammable substances. Smoke detectors and heat detectors are installed in most traditional markets to monitor fires, but malfunctions are frequent due to the nature of smoke detectors and heat detectors, and network facilities are not properly maintained. Therefore, in this study, gas detection sensors and flame detectors are additionally installed in Gwangmyeong Traditional Market, and a digital twin-based traditional market fire monitoring system is implemented in conjunction with existing sensors in the market's 3D model. With this digital twin based fire monitoring system, we can reduce the malfunctions of fire detect sensors, and can easily guide the evacuation route.

• 설비공학논문집
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• 제16권10호
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• pp.889-894
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• 2004

Infrared (IR) detectors are widely used for many applications, such as temperature measurement, intruder and fire detection, robotics and industrial equipment, thermoelstic stress analysis, medical diagnostics, and chemical analysis. Quantum detectors commonly need to be refrigerated below 80 K, and thus a cooling system should be equipped together with the detector system. The cooling load, which should be removed by the cooling system to maintain the nominal operating temperature of the detector, critically depends on the insulation efficiency of the cryochamber housing the detector. Thermal analysis of cryochamber includes the conduction heat transfer through a cold well, the gases conduction and gas outgassing, as well as radiation heat transfer, The transient cooling characteristics of an infrared detector cryochamber are investigated experimentally in the present study. The transient cooling load increases as the gas pressure is increased. Gas pressure becomes significant as the cooling process proceeds. Cool down time is also increased as the gas pressure is increased. It is also found that natural convection effects on cool down time become significant when the gas pressure is increased.

• 대한기계학회논문집B
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• 제26권3호
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• pp.439-447
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• 2002

The microchannel flow in miniature TCDs (thermal conductivity detectors) is investigated numerically. The solutions based on the boundary layer approximation are not very accurate in the region of the duct inlet for low Reynolds numbers. In this study, two-dimensional Navier-Stokes equations are considered to analyze the gas flow in a miniature TCD. Effects of channel size, inlet and boundary conditions on the heat transfer rate are examined. When the gas stream is not preheated, the distances for a miniature TCD to reach the conduction-dominant region for duct flow are found to be approximately two and three times the thermal entry length for duct flow with constant properties, respectively, leer constant wall temperature and constant wall heat flux boundary conditions. If the gas temperature at the channel inlet is close to the mean gas temperature in the conduction-dominant region, the entrance region is much shorter compared to other cases considered in this study.