• Journal of the Korean earth science society
• /
• v.41 no.5
• /
• pp.478-489
• /
• 2020

This study presents an analysis of infrasonic signals from two accidental explosions in Gwangyang city, Jeonnam Province, Korea, on December 24, 2019, recorded at 12 infrasound stations located 151-435 km away. Infrasound propagation refracted at an altitude of ~40 km owing to higher stratospheric wind in the NNW direction, resulting in favorable detection at stations in that direction. However, tropospheric phases were observed at stations located in the NE and E directions from the explosion site because of the strong west wind jet formed at ~10 km. The transmission losses on the propagation path were calculated using the effective sound velocity structure and parabolic equation modeling. Based on the losses, the observed signal amplitudes were corrected, and overpressures were estimated at the reference distance. From the overpressures, the source energy was evaluated through the overpressure-explosive charge relationship. The two explosions were found to have energies equivalent to 14 and 65 kg TNT, respectively. At the first explosion, a flying fragment forced by an explosive shock wave was observed in the air. The energy causing the flying fragment was estimated to be equivalent to 49 kg or less of TNT, obtained from the relationship between the fragment motion and overpressure. Our infrasound propagation modeling is available to constrain the source energy for remote explosions. To enhance the confidence in energy estimations, further studies are required to reflect the uncertainty of the atmospheric structure models on the estimations and to verify the relationships by various ground truth explosions.

• Explosives and Blasting
• /
• v.18 no.3
• /
• pp.15-28
• /
• 2000

국내에서는 Heavy ANFO로 더 잘 알려져 있는 Emulsion Blends는 왁스 대신 오일을 사용 하여 상온에서 펌핑이 가능하도록 한 에멀젼과 ANFO(또는 초안)의 혼합물을 일컫는다. ANFO는 저렴하고 안전하며 장약이 쉽고 밀장전되는 장점이 있지만, 내수성이 거의 없고 폭발 속도가 느리며 장약 비중이 0.75∼0.90g/cc 정도로 낮아 폭약으로서 그 위력이 작은 단점을 갖고 있다. Blends는 수용성 ANFO 입자 사이의 빈 공간을 내수성 에멀젼이 태우고 있는 형태로서 에멀젼 함량 25%부터 내수성이 나타나기 시작하여 에멀젼 함량 40% 이상에서는 완전한 내수성을 갖게 되며, 에멀젼의 함량이 증가할수록 폭발속도는 카트리지 에멀젼 폭약에 근접하게 된다. 장약 비중은 에멀젼의 함량이 증가하여 45% 근처에서 1.25∼ 1.30g/cc의 최대 값을 갖지만, 그 이상의 에멀젼 함량에서는 기폭 감도 저하로 예감제를 사용하여 비중을 감소시키는 것이 바람직하다. Blends는 자체에 물을 함유하고 있으므로 열역학적으로 계산된 단위 중량당 반응열은 ANFO에 비해 매우 적지만, 폭발속도, detonation pressure(폭굉압), borehole pressure(폭발압력) 등이 ANFO에 비해 크므로 폭발압력에서부터 암석의 파괴가 가능한 압력가지의 단위 중량당 유효한 에너지의 양은 암석의 강도가 커질수록 ANFO에 비해 매우 적지만, 폭발속도, ANFO와 비슷해진다. 따라서 장약 비중이 ANFO의 130∼145%로 높은 Blends는 동일한 천공에 더 많이 장약할 수 있어 단위 천공당 암석 파괴에 이용되는 유효 에너지의 총 양이 커지게 되므로, 공간격과 저항선을 늘릴 수 있어 총 천공수를 감소시킬 수 있다. 결론적으로, Blends의 장점은 내수성과 함께 비장약량은 비슷하거나 약간 증가하는데 비해, 천공수는 크게 감소하여 전체적으로는 발파 현장의 경제성이 향상된다는데 있다.

• Korean Chemical Engineering Research
• /
• v.58 no.3
• /
• pp.356-361
• /
• 2020

Propylene is widely used in petrochemical manufacturing at over 200 ℃. However, since propylene is a flammable gas with fire and explosion risks, inert nitrogen is injected to prevent them. In this study, experiments were conducted using propylene-nitrogen-oxygen upon pressure changes at 200 ℃. At 21% oxygen, as pressure increased from 0.10 MPa to 0.25 MPa, lower explosion limit (LEL) decreased from 2.2% to 1.9% while upper explosion limit (UEL) increased from 14.8% to 17.6%. In addition, minimum oxygen concentration (MOC) decreased from 10.3% to 10.0%, indicating higher risks with the expanded explosive range as pressure increased. With increase of pressure from 0.10 MPa to 0.25 MPa, explosion pressure increased from 1.84 MPa to 6.04 MPa, and the rate of rise of maximum explosion pressure increased drastically from 90 MPa/s to 298 MPa/s. It is hoped that these results can be used as basic data to prevent accidents in factories using propylene.

• Journal of the Korean Society of Safety
• /
• v.19 no.4 s.68
• /
• pp.150-154
• /
• 2004

Gas explosion characteristics of hydrogen and liquefied petroleum gas(LPG) were measured in 6L cylindrical vessel, and experiment for explosion to fire transition phenomena of the gases were carried out using the 270L vessel. Explosion characteristics were measured using the stain type pressure transducer and explosion to fire transition phenomena was analyzed with the hish-speed camera. Base on the experiment, it was found that explosion pressure was most high slightly above the stoichiometric concentration, and explosion pressure rise rate and flame propagation velocity were proportional to the combustion velocity. And we find that those kind of explosion characteristics affect the explosion-to-fire transition, in addition, explosion flame temperature, flame residence time, are important parameters in explosion-to-fire transition.

• Fire Science and Engineering
• /
• v.12 no.4
• /
• pp.13-19
• /
• 1998

We investigated the weight loss according to temperature using Thermal Gravimetric Analysis(TGA) in order to find the thermal hazard of carbon black(Hi-Black 10, Hi-Black 50L) dusts, and the properties of dust explosion in variation of the surface functional groups and specific surface area of their dust with the same particle size. Using Hartman's dust explosion apparatus which estimate dust explosion by electric ignition after making dust disperse by compressed air, dust explosion experiments have been conducted by varying concentration and size of carbon black dust. The explosion pressure of both carbon black increased as the specific surface area increased. The results indicated that Hi-Block 50L of which specific surface area was larger three to four times than that of Hi-Black 10 was much easier of dust explosion.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1995.05a
• /
• pp.531-537
• /
• 1995

본 논문에서는 증기폭발의 전파과정을 해석하기 위한 수학적 모델을 제시하였다. 이 모델은 용융물, 용융파편, 그리고 냉각재 기상과 액상 둥 4상 유체의 2차원적인 천이거동을 지배방정식 및 관련상관식의 수치적 해를 구함으로써 증기폭발의 전파속도 및 폭발압력 등을 예측할 수 있다. 모델에 사용된 주요 상관식은 용융물 분쇄, 냉각재 상변화, 에너지 교환, 그리고 운동량 교환함으로 구성되어 있다. 냉각재의 상태를 결정하는데 있어서 냉각재의 기상과 액상 사이의 열역학적인 비평형을 허용할 수 있도록 냉각재의 상태방정식을 구성하였다. 주석/물의 증기폭발에 대한 예제계산을 수행한 결과 폭발의 전파속도 및 압력 등에 있어서 합당한 것으로 밝혀졌다. 또한 중요한 초기변수(중기 분율, 용융물 분율) 및 관련상관식에 대한 민감도 분석을 수행함으로써 모델개선을 위한 중요인자를 제시하였다.

• Explosives and Blasting
• /
• v.33 no.3
• /
• pp.1-13
• /
• 2015

Accidents related to gas explosion are frequently happened in foreign countries and in Korea. For the evaluation and the analysis of gas explosions, TNT equivalent methods are used. In this study, the influence of the selection of chemical equation in TNT explosion and the selection of enthalpy of the products on the explosion energy, detonation pressure, velocity of detonation, and temperature was calculated. Depending on the chemical equations, the maximum detonation pressure can be 2 times higher than the minimum. As an example for applying TNT equivalent method, an explosion of methane gas in a confined volume was assumed. With the TNT equivalent, it was possible to predict the variation of peak overpressure and impulse with the distance from the explosion location.

• Journal of the Korean Institute of Gas
• /
• v.3 no.3 s.8
• /
• pp.51-57
• /
• 1999

A study on the vented gas explosion characteristics were carried out with the liquified petroleum gas(LPG) which is used in domestics and industries fuel. To evaluate a damage by gas explosion and to predict a explosion hazards, a series of experiment have been performed in the regular hexahedron vessel of 270${\iota}$. A side of the vessel was made to setting a polyester diaphragm which was ruptured by explosion to simulate an accidental explosion which ruptured the window by explosion. Experimental parameters were LPG concentration, ignition position, venting area, a strength of diaphragm which was ruptured and distances from venting, Experimental results showed that vented gas explosion pressure was more affected by the diaphragm strength than the gas concentration, and the vented gas explosion pressure and blast wave pressure was increased with decreasing the venting area and increasing the strength of diaphragm. In this research we can find that a damage by vented explosion at the outside can be larger than the inside by blast wave pressure near the venting.

• Explosives and Blasting
• /
• v.37 no.4
• /
• pp.10-16
• /
• 2019

Information on overpressure, positive phase duration, and impulse are required to assess the effects of shock waves or pressure waves on the structure. In this study, the overpressure and positive phase duration were determined by applying the Multi-Energy Method, which is found to be effective in analyzing the explosion of vapor clouds. Based on the total heat of combustion estimated in the cyclohexane vapor cloud explosion in the Nypro Ltd(UK), overpressure and positive phase duration at the distance of 40, 80, 120, 160, 200, 240, 280, 320, 360(m) from the source of explosion were evaluated. Overpressure was shown to decrease exponentially and positive phase duration increased almost linearly with distance. A probit function was used to assess the probability of damages for the structures at each distance using the overpressure and impact obtained at the above mentioned distances. The Analyses of probability of damages have shown that there is a high probability of collapse at distances within 120m, major damage to structures within 240m, and minor damage and breakage of window panes of structures occur over the entire distances.

• Fire Science and Engineering
• /
• v.13 no.2
• /
• pp.26-32
• /
• 1999

We had investigated combustion pro야$\pi$ies of rice bran dusts. Decomposition of rice bran d dusts with temperature were investigated using DSC and the weight loss according to t temperature using TGA in order to find the thermal hazard of rice bran dusts, and the p properties of dust explosion in variation of their dust with the same particle size. Using H Hartman's dust explosion apparatus which estimate dust explosion by electric ignition after m making dust disperse by compressed air, dust explosion experiments have been conducted by v varying concen$\sigma$ation and size of rice br뻐 dust. According to the results for thermodynamic stability of rice bran dust, there are little change of initiation temperature of heat generation 때d heating value for used particle size. But i initiation temperature of heat generation decreased with high heating rate whereas d decomposition heat increased with particle size. Also, the explosion pressure was increased as t the ignition energy increased and average maximum explosion pressure was 13.5 kgv'cnt for 5 BJ/60 mesh and 1.5 뼈Ie미 dust concentration.