Numerical investigation and analysis of indoor gas explosion: A case study of “6·13” major gas explosion accident in Hubei Province,China

Taking the ' 6·13 ′ major gas explosion accident in Shiyan, Hubei Province, China as an example, three problems were studied in this work: (1)The determination of the volume of natural gas involved in the explosion; (2)The propagation process of shock wave inside the building and the damage evolution process of the accident-related building; (3)The overpressure and fragment injury to the person outside the building. Through the numerical simulation in ANSYS/LS-DYNA software, the volume of natural gas involved in the explosion is determined to be 10240 × 1400 × 400 cm (length × width × height) from three perspectives: the damage to the building, the distribution of overpressure inside the building, and the TNT equivalent of the explosion energy. The simulation results are in good line with the accident, which verifies the effectiveness of the scheme and the accuracy of the numerical model. Based on the reasonable filling scheme, the propagation process of shock waves inside the building, the damage evolution process of the building, and the injury ranges of overpressure and fragments outside the building are analyzed. It can be found that the propagation of shock waves in confined space is complex and variable. The explosion shock waves are first reflected and superimposed in the watercourse, resulting in pressure rise. At about 8ms, the shock waves rushed into the first-floor space of the building, and the maximum overpressure was about 0.56 MPa. At about 50 ms, the shock waves rushed into the second-floor space, and the maximum overpressure was about 0.139 MPa. The first and second-floor slabs and infilled walls were almost completely destroyed. The interior walls of the infilled walls are mainly collapsed, and the exterior walls are ejection around the building as the center. The peak displacement and peak velocity of the interior walls of each floor are about 15% of the exterior walls. The fragments which cause fragment injury mainly come from the retaining wall above the watercourse, the maximum velocity is about 89 m/s, and the maximum displacement is 8.9 m. The safety distance of fragment injury is about 8.8 m, while the safety distance of overpressure injury is about 4.6 m. The lethal distance of fragment injury is greater than that of overpressure injury. Compared with the distance between different damage levels of overpressure injury, the difference in fragment injury is small. Therefore, the safety assessment at the engineering level only needs to consider the safety distance of fragment injury. This study can provide suggestions for evaluating the damage of natural gas cloud explosions in confined spaces and is helpful for accident investigation and safety protection.     

Comparative study on standardized ignition sources used for explosion testing

For the determination of safety characteristics of gases, vapors and dusts different types of ignition sources are used in international standards and guidelines. The paper presents test results of a comparative calorimetric and visual study between four different types of ignition sources. The ignition procedures were analyzed visually with a high-speed camera and electric recordings. In addition to that, the influence of the electrode-orientation, -distance as well as ignition energy on the reproducibility of the exploding wire igniter was tested.The exploding wire is already in use for standardized determination of safety characteristics of gases, first tests on the suitability of the exploding wire igniter for dust testing have been carried out but are not standardized yet. Using the exploding wire, the ignition energy can be varied from 2 J to 10 000 J (2 x 5000 J) and thus it could be used for gases, vapors, dusts and hybrid mixtures. Moreover it can be used at high initial pressures and it is the only ignition source with an easily measurable ignition energy release. Furthermore, it does not introduce another chemical reaction into the system.Finally, a proposal for a standard ignition source for explosion tests on hybrid mixtures is derived from the test results.     

辐射制冷技术在安全帽上的应用研究*

为缓解夏季配戴安全帽导致的头部高温不适,采用具有光谱选择特性的辐射降温涂料对安全帽表面光学性能进行改性,经光学测试,安全帽的太阳辐射反射率由45%提升至89%,大气窗口发射率由92%提升至95%。对安全帽进行降温效果测试,并基于测试结果建立热力学模型。结果表明:在阳光直射下,改性安全帽内部温度低于普通白色安全帽,温差最大12.2 ℃;在热力学模型中,即使在夏季最热时间段（12∶00～14∶00）,改性安全帽内部温度仍可比普通安全帽低8 ℃,预测平均评价值由普通安全帽的3.5降低至1.0,预测不满意百分比从100%降低至20%。     

机场货站易爆危险品存储区外部安全防护距离研究

为合理设定机场货站易爆危险品存储区外部安全防护距离,基于爆炸威力计算模型,利用有限元分析软件AUTODYN模拟包装约束下爆炸品爆炸冲击波特性,通过引入包装约束系数,描述包装材料对爆炸威力影响,计算航空运输易爆危险品存储区外部安全防护距离.结果表明:1 mm厚度聚碳酸酯、钢和铝材质外包装的包装约束系数分别为0.9047,...     

LFT-G注塑工艺在玻璃钢安全帽生产中的应用

玻璃钢安全帽因具有强度高、耐高温,耐水、酸、碱、油、化学腐蚀及良好的绝缘性等特点,被广泛应用于石油化工、矿山、电力、冶炼等多个行业。目前,玻璃钢安全帽的生产工艺仅有两种,一是手糊,二是模压。但这两种生产工艺不仅存在粉尘、噪声、有毒物质等多种职业危害因素,而且由于部分关键工序采用手工制作,因而造成玻璃钢安全帽的质量性能的不稳定。使用LFT-G（长纤维增强热塑性塑料颗粒）作为原材料,将注塑工艺引进玻璃钢安全帽的生产中,实现了玻璃钢安全帽的注塑生产。这种工艺,不仅职业危害因素大大减少,而且也因关键工序中不存在手工作业,从而大大增加了玻璃钢安全帽质量的稳定性,同时,由于LFT-G粒料的长度增加,经过加工后,安全帽成品中的纤维长度也会增加,使得安全帽的抗冲击性能等满足标准要求。为此,以LFT-G为基础的玻璃钢安全帽的注塑工艺具有广阔的应用前景。     

Parametric approach of the domino effect for structural fragments

More specific and accurate probabilistic models of the numbers of fragments generated respectively by Boiling Liquid Expanding Vapor Explosions (BLEVEs), Mechanical Explosions (MEs), Confined Explosions (CEs), and Runaway Reactions (RRs) of a horizontal cylindrical vessel were developed using the maximum entropy principle based on historical accident data. The theoretical results from the four probability density functions were compared to the observed data, and the numbers of fragments followed discrete exponential distributions in the interval [1, 9]. Beside the summary of the probabilistic distributions of the other random variables in the process of fragment projection, the effects on the fragment trajectory and target terms were investigated using a parametric approach. The results showed that using the complete model, wind shear, turbulence, and absence of fragment rotation caused the fragments to impact within shorter distances; fragment rotation and lack of wind decreased the probability of impact within a given distance, but the rupture probability of the target was not affected by fragment rotation or wind. The probabilistic confidence intervals of fragment range, impact, and target penetration became narrower with the number of simulation runs, but the accuracy of the results increased. The probability of fragment impact increased with the volume of the target vessel and the degree of filling of the explosion vessel, but did not depend on the kind of explosion. The probability of target rupture increased slowly with the degree of filling of the explosion vessel, but was little influenced by the volume of the target vessel or the kind of explosion.     

浅谈国内外安全帽生产技术

安全帽作为对自然人头部受坠落物体或其他特定因素引起的伤害所采用的个人防护用品,越来越受到世界各国的安全防护行业的重视。特别是在发达国家,不断进行技术创新,更新安全帽标准。本文从安全帽技术领域方面．详细介绍各国制造安全帽常用材料的性能与特点,安全帽的模具材料、加工工艺、先进生产技术以及主要国家的安全帽检测标准差异。     

氢化锆对太安空中爆炸及热安全性能影响的研究*

为研究氢化锆对太安空中爆炸及热安全性的影响,分别对氢化锆/太安混合炸药（ZrH2/PETN）和太安单质炸药开展空中爆炸实验和热分析实验,得到相应的压力时程曲线和TG、DSC热分解曲线。研究结果表明:氢化锆的添加会降低混合炸药的压力峰值,但能显著提高其正相作用时间,氢化锆含量为10%、20%时,氢化锆/太安混合炸药的正相冲量与太安相当。同时与纯太安相比,氢化锆/太安混合组分的最大质量损失速率下降约51.07%~60.04%,热爆炸临界温度及自加速分解温度最大提高约8.78%和9.93%,但混合组分中氢化锆的加入并未改变太安的热分解机理,说明氢化锆作为惰性热稀释剂能够改善其热安全性。     

基于机器学习方法的安全帽佩戴行为检测

施工现场作业人员是否佩戴安全帽主要依靠人工检查,存在监管效率低、时效性差等问题,为了实时自动监管作业人员是否佩戴安全帽,提出1种基于机器学习的安全帽佩戴行为检测方法。首先利用深度学习YOLOv3算法检测出现场视频中的施工人员脸部位置,根据安全帽与人脸的关系估算出安全帽潜在区域;然后对安全帽潜在区域图像进行增强处理,使用HOG（方向梯度直方图）提取样本的特征向量;再利用SVM（机器学习的支持向量机）分类器对脸部上方是否有安全帽进行判断,进而实现对施工人员安全帽佩戴行为的实时检测与预警。以某高铁站施工现场为例进行验证,研究数据表明在施工通道和塔吊作业区域,该方法可实时有效检测出工人未佩戴安全帽的行为,识别率达90%。     

Investigations into the influence of dustiness on dust explosions

A new safety characteristic the “dustiness” according to VDI 2263 – part 9 (Verein Deutscher Ingenieure, 2008) is investigated. Dustiness means the tendency of a dust to form clouds. The paper deals with the influence of the dustiness on vented dust explosions. In order to look into the effects of the dustiness on dust cloud formation and explosion properties experiments and simulations in a vertical dust dispersion glass tube apparatus were carried out.Preliminary explosion experiments showed that the dustiness has an influence on the reduced explosion pressure in a vented 75 L test apparatus. Dusts with comparable p_max and K_St values and different dustiness were tested. Dusts with higher dustiness produced higher overpressures, despite comparable safety characteristics. In order to verify the results for applications in the process industries further tests with different settings are planned as well as industrial scale experiments. Characteristics of the dust such as particle size, density, specific surface area and particle shape, which influence the dispersibility, have been determined experimentally.The Euler/Lagrange and the Euler/Euler approaches are compared for simulating an exemplary dust/air mixture. Especially sedimentation and the ability of the approaches to simulate the tendency of dust to stay airborne were investigated. The Euler/Lagrange approach is better suited for simulating local dust concentrations, particle size distributions and particle forces. It could be used to point out regions of high dust concentrations in a vessel. With the Euler/Euler method it is possible to achieve fast solutions for one specified diameter, but the simulated dust/air mixtures are always more homogenous than in reality. ANSYS CFX version 13 was used in all simulations.     

储罐爆炸碎片最可能抛射距离的Monte-Carlo(蒙特卡罗)数值模拟

在总结前人工作的基础上,推导了储罐爆炸碎片抛射距离的理论计算公式,并给出具体的计算方法;分析了计算参数的不确定性,同时介绍用Monte-Carlo方法模拟高压储罐爆炸时碎片抛射距离的算法;在数值模拟结果的基础上,计算了碎片抛射距离的分布函数和概率密度函数,引入最可能抛射距离的概念,并指出可以用此来确定碎片抛射的危害范围。该方法对于定量评价储罐爆炸碎片危害性,减缓和控制碎片产生的风险,具有重要的意义。     

焊接面罩的发展历程

焊接面罩是一种焊工防护装备,也是重要焊接辅助工具。本文主要介绍自焊接面罩出现100多年以来,经历了众多的改进,从手持式焊接面罩到头戴式焊接面罩、从黑玻璃焊接面罩到自动变光焊接面罩、从单一功能焊接面罩到多种功能集结的焊接面罩。同时指出,基于材料和技术的进步,焊接面罩不会停止创新的步伐,焊接面罩将在保护焊工、提高焊接质量和效率方面扮演重要角色。     

基于可变模糊集理论的硫化矿炸药自爆危险性评价

为了判定某高硫矿山的炸药自爆危险性,采用可变模糊集理论对矿山中的黄铁矿含量、装药时间等8个影响炸药自爆的因素进行评价。根据可变模糊评价模型确定指标评价区间矩阵Iab、可变范围评价区间Icd和点值矩阵M,利用熵权法确定各影响因素权重,并根据指标特征值xij,Mih得到综合相对隶属度矩阵,结合判断准则得出该矿山炸药自爆危险性等级。研究结果表明:该矿山的炸药自爆危险等级为Ⅱ级,自爆危险性一般,与实际生产情况相符,可变模糊集理论在评价炸药自爆危险性时具有有效性。     

Pressure characteristics and dynamic response of coal mine refuge chamber with underground gas explosion

Coal mine refuge chambers are new devices for coal mine safety which can provide basic survival conditions after gas explosion. In order to simulate the propagation of underground methane/air mixture blast wave, and check structural safety of coal mine mobile refuge chamber, an underground tunnel model and a refuge chamber model have been established based on explicit nonlinear dynamic ANSYS/LS-DYNA 970 program. Results show that the reflected wave pressure on the impact surface was about two times higher than that on the incident one. The relationship between the pressure fields of the chamber was analyzed. The maximum pressure of gas explosion reached about 0.71 MPa, and the pulse width was 360 ms. The maximum absolute displacement and stress occurs at the main door center and the connection of stiffeners and the front plate, respectively. The entire coal mine mobile refuge chamber was in elastic state and its strength and stiffness meet the safety requirements. The cabin door, the front plate and the connecting flange at cabin back as well as the stiffeners on each side were the most critical components. Suggestions were put forward for the refuge chamber.     

Method of Testing the Penetration of Acid Solutions Through Safety Gloves

Because they cause burns that are difficult to heal, acids are dangerous, and steps should be taken to ensure that the human skin does not come into contact with them. For this purpose safety gloves are generally used by workers who have to handle acids. Such gloves need to be tested to ensure that they are acid resistant. Standard EN 374 (European Committee for Standardization [CEN], 1993c) specifies a method of testing the permeation of liquid chemicals, on a molecular level, through glove material, but it may be difficult to ensure the fitness of the joints of a two-compartment cell, when gloves are lined with jersey. To deal with this a simple pH-meter method to test the permeation of acid and alkali solutions through safety gloves has been developed. The permeation of H₂S0₄, HCI, HN0₃, and CH₃COOH through gloves made from neoprene, nitrile, and PVC was tested. This method seems to be simple and economical.     

浅谈提高爆炸容器使用安全性的技术措施

针对爆炸容器工作时 ,产生的爆炸冲击波、破片、有害气体、振动及噪声等危害因素 ,简述了国内外使用爆炸容器时 ,采取的一些相关安全技术措施 ;提出了将结构健康监测技术应用于爆炸容器寿命安全评估的构想     

Effect of initial temperature on explosion characteristics of 2, 3, 3, 3–Tetrafluoropropene

The flammability of refrigerants is a major cause of refrigerant explosion incidents. Studying the explosion characteristics of refrigerants at different initial temperatures can provide significant benefits for solving the safety problems of refrigerants under actual working conditions. This paper studied the effects of the initial temperature and refrigerant concentration on the explosion characteristics of refrigerant 2, 3, 3, 3-tetrafluoropropene (R1234yf) at 0.1 MPa. The curves of explosion characteristics with different initial temperature revealed the same variation trend ranged from 25 °C to 115 °C. Specifically, as the refrigerant concentration was raised, the peak overpressure, the maximum rate of pressure rise, and laminar burning velocity increased initially and decreased afterwards, along with maximum values at the refrigerant concentration of 7.6%. When the refrigerant concentration was 7.6%, the peak overpressure declined exponentially with the initial temperature rise, while the maximum rate of pressure rise increased linearly. The laminar burning velocity calculated from the spherical expansion method indicated that the flame propagation was gradually accelerated by the increase of initial temperature, which coincided with the change of the maximum rate of pressure rise. Meanwhile, experiments and CHEMKIN simulation results demonstrated the effects of elevated temperature from 20 °C to 50 °C on the explosion limits of R1234yf. The lower explosion limit reduced and the upper explosion limit increased with rising initial temperature. In general, R1234yf exhibited moderate combustion and lower explosion risk, compared with traditional refrigerants.     

有限元在安全帽设计中的应用

安全帽可以防止高空坠落物对人员头部造成伤害。在材料和工艺一定的前提下,安全帽的结构对发挥安全帽的作用尤为重要。本文首先对安全帽作用机理及使用情况进行分析,指出改善安全帽帽壳缓冲性能有利于更好地发挥安全帽的作用。然后简要介绍ANSYS的建模方案以及网格划分和自由度约束情况,通过对安全帽的ANSYS有限元分析,得出安全帽的变形和应变图,并通过分析安全帽从最低端到顶端的变形和应变情况,指出安全帽在撞击过程中的能力吸收规律,根据分析数据提出建立双层安全帽帽壳的改进方案,并再次通过有限元分析得出变形和应变图,验证了双层安全帽帽壳在缓冲方面更有效果,这种分析结果可以为安全帽帽壳的设计提供参考。     

Severity and patterns of injury in helmeted vs. non-helmeted motorcyclists in a rural state

Introduction: Under current law in our rural state, there is no universal requirement for motorcyclists to wear helmets. Roughly 500 motorcycle crashes are reported by the state each year and only a fraction of those riders wear helmets. We sought to determine the difference in injury patterns and severity in helmeted versus non-helmeted riders. Methods: Retrospective review (2014–2018) of a single level 1 trauma center’s registry was done for subjects admitted after a motorcycle collision. Demographic, injury and patient outcome data were collected. Patients were stratified by helmet use (n = 81), no helmet use (n = 144), and unknown helmet use (n = 194). Statistical analysis used Student’s t-test or Pearson’s χ² p-value ≤0.05 as significant. State Department of Transportation data registry for state level mortality and collision incidence over the same time period was also obtained. Results: Of the 2,022 state-reported motorcycle collisions, 419 individuals admitted to our trauma center were analyzed (21% capture). State-reported field fatality rate regardless of helmet use was 4%. Our inpatient mortality rate was 2% with no differences between helmet uses. Helmeted riders were found to have significantly fewer head and face injuries, higher GCS, lower face, neck, thorax and abdomen AIS, fewer required mechanical ventilation, shorter ICU length of stay, and had a greater number of upper extremity injuries and higher upper extremity AIS. Conclusions: Helmeted motorcyclists have fewer head, face, and cervical spine injuries, and lower injury severities: GCS and face, neck, thorax, abdomen AIS. Helmeted riders had significantly less mechanical ventilation requirement and shorter ICU stays. Non-helmeted riders sustained worse injuries. Practical Applications: Helmets provide safety and motorcycle riders have a 34-fold higher risk of death following a crash. Evaluating injury severities and patterns in motorcycle crash victims in a rural state with no helmet laws may provide insight into changing current legislation.     

火炸药、弹药工厂和企业中重大事故隐患的定量评估:爆炸危险源系统的现实危险度方程

火药、炸药、弹药工厂和企业存在着极大的燃烧爆炸危险性,对这类企业的重大事故隐患进行危险性评估是非常必要的。提出了危险源现实危险度(DAH)即事故隐患严重度的判据H的评估方程,而火炸药燃烧爆炸危险源系统的现实危险度H与下列因素有关,即与火炸药的危险指数W、系统的固有危险度B、未受控系数K、以及距该系统安全距离不足的建筑物和设施受危险源爆炸事故影响的破坏程度等因素有关。讨论了对这些因素的评估和计算。