Analyses of Cascading Failure in Mine Ventilation System and Its Effects in a Serious Mine Gas Explosion Disaster

In 2009, a serious gas explosion happened in Tunlan coal mine at Shanxi province, P.R. China, which claimed the lives of 78 miners. 114 miners got injured, and nearly 4 million dollars of economic loss was reported. According to the investigation report, the mine gas explosion was originally from a buildup of gas catching a flame in the underground. The happening of such accumulation was actually caused by functional failures of the mine ventilation system so that the concentration of gas reached the lower flammable limit. Technically speaking, the mine ventilation system is an integrity system. Any unit’s failure can lead to other units losing their normal functions until the whole system breaks down. In other words, a cascading failure may happen. Based on the Tunlan mine disaster, this article introduces the concepts of cascading failure in the subject of mine ventilation engineering, which include the development process of failure, the mechanism, and the corresponding failure criteria, etc. The software “VentGIS simulator” is used as a tool to investigate the failure that occurred and its effects in the mine ventilation system. The coupled relationships between the failure mechanism and the gas explosion and its propagation are quantitatively studied in-depth. The research efforts show that (1) unreasonably installed the ventilation regulators directly caused the buildup of mine gas, which means an initial failure in a local ventilation system had appeared. Thus, one requirement of the gas explosion was provided; (2) failures of the early-warning system and mitigation measures led to the propagation of gas explosion shock in the underground mine network. Hence, impacts by the explosion are greatly enhanced. The research results presented in this article can be used as theoretical guidelines for improving the safety of a mine ventilation system or assisting to design a new one in the future.     

Correlates of coal mine accidents and injuries: A literature review

Coal mining is the most dangerous occupation in the United States, with injury frequency and severity rates several times the average for all industries. Although mine safety improved slightly during the early 1970's, recent trends indicate small decreases in accidents and injuries and, in some cases, increases in accident severity. Experienced miners have lower risks of fatal injuries than inexperienced miners. Workers in small mines are more likely to receive fatal injuries than those in large mines. The various engineering methods of extracting coal from its natural deposit do not produce different fatality rates. The thickness of the coal seam mined is not related to the incidence of fatalities. Although conflicting evidence appears in the literature, recent studies find younger miners with much higher disabling injury rates than older miners. Whether a collective bargaining agreement is in effect is unrelated to accident and injury occurrence at a mine site. Studies of the relationships of accident and injuries to the effectiveness of safety training, the number of shifts each day at a mine site, and the time elapsed during a shift until an accident occurs have produced ambiguous results, often as a result of analysis of inadequate data.     

包头铝厂焙烧炉煤气爆炸反分析

从爆破的角度分析了包头铝厂焙烧炉煤气爆炸事故，发现不仅是煤气爆炸损坏了耐热砼墙体，在煤气爆炸之前，砼墙体的强度已因其他原因被破坏，煤气爆炸只是使其明显化。     

包头铝厂焙烧炉煤气爆炸反分析

从爆破的角度分析了包头铝厂焙烧炉煤气爆炸事故，发现不仅是煤气爆炸损坏了耐热砼墙体，在煤气爆炸之前，砼墙体的强度已因其他原因被破坏，煤气爆炸只是使其明显化。     

列车追尾事故的故障树分析兼谈复杂系统安全

温州动车组追尾事故是我国铁路大发展时期发生的特别重大事故.为更深入了解事故的可能原因,以列车追尾事故为顶事件,开展故障树分析,探讨事故的各种发生模式,剖析造成事故的各种事件,并从宏观的角度讨论了复杂安全关键系统的安全要素和策略,给出了一些建议.     

煤矿综采面安全生产评价研究

[摘要]矿井事故高发区域是煤矿综采工作面,煤矿环境的特殊在很大程度上增加了确保安全生产的难度系数,矿井生产具有其他行业所不具有的特殊性、复杂性以及多变性,其中发生率较高的矿井事故类型有透水、煤炭自燃、瓦斯或煤尘爆炸以及职业病等。本文首先介绍了综采工作面常见事故类型,其次阐述了构建煤矿综采面安全生产评价指标体系应遵循的原则,最后对确定综采工作面安全生产评价指标权值加以探讨。     

Analysing the risk of LNG carrier operations

This paper presents a generic, high-level risk assessment of the global operation of ocean-going liquefied natural gas (LNG) carriers. The analysis collects and combines information from several sources such as an initial hazid, a thorough review of historic LNG accidents, review of previous studies, published damage statistics and expert judgement, and develops modular risk models for critical accident scenarios. In accordance with these risk models, available information from different sources has been structured in the form of event trees for different generic accident categories. In this way, high-risk areas pertaining to LNG shipping operations have been identified. The major contributions to the risk associated with LNG shipping are found to stem from five generic accident categories, i.e. collision, grounding, contact, fire and explosion, and events occurring while loading or unloading LNG at the terminal. Of these, collision risk was found to be the highest. According to the risk analysis presented in this paper, both the individual and the societal risk level associated with LNG carrier operations lie within the As Low As Reasonable Practicable (ALARP) area, meaning that further risk reduction should be required only if available cost-effective risk control options could be identified. This paper also includes a critical review of the various components of the risk models and hence identifies areas of improvements and suggests topics for further research.     

Quantitative safety assessment of the ventilation recirculation system in an undersea mine

This paper describes a quantitative safety study carried out on a system which monitors the environmental conditions in an undersea mine. Of particular importance are the concentrations of methane and carbon monoxide present in the mine. Although the presence of these gases is of concern in all mines it is of particular concern in this undersea mine since up to 37 per cent of the return air of the ventilation system is recirculated. When high methane or carbon monoxide levels are detected recirculation is halted. Fault trees were constructed to represent two system failure modes for each of the trip conditions; failure to trip on demand and spurious trip. These logic diagrams were then analysed to produce the minimal cut sets and the probabilities for the system failure events. From this prediction of system performance the degree of improvement attainable by changing the system design, component repair times or test frequencies was investigated.     

N2O基单组元气体推进剂的爆炸事故分析

针对新型N₂O基单组元气体推进剂在发动机试车过程中发生的爆炸事故,通过推进剂的基础安全特性实验与管道阀门的结构分析,开展了事故原因分析。气体推进剂点火能量的实验结果表明,临界点火能量在0.25~0.50 mJ之间。在实验管道中的火焰传播速度能达到410 m/s。临界着火温度的实验结果显示,样品的最低着火温度为135 ℃。阀门的工作原理与结构分析结果显示,在阀门通电开启过程中,会对活塞上方4.06 mL的气体产生压缩作用。根据绝热方程计算可知,气体在压缩过程中温度可升至193.7 ℃。对比实验与理论计算可以推知,阀门启动过程中的压缩作用,可能是发生爆炸事故的根本原因。     

试揭世界三大自然之谜之一──明代京师王恭厂火药厂爆炸探因

３７０年前，明王朝京师王恭厂火药制造厂发生大爆炸，北京城百姓死亡逾万人，该事故被称为世界三大自然之谜的一个谜。我们在耿庆国等人的考证及分析基础上，从爆炸的力学效应入手，剖析了这次事故，并以此文来缅怀北京城３７０年前在灾难中罹难的先人。     

试揭世界三大自然之谜之一──明代京师王恭厂火药厂爆炸探因

３７０年前，明王朝京师王恭厂火药制造厂发生大爆炸，北京城百姓死亡逾万人，该事故被称为世界三大自然之谜的一个谜。我们在耿庆国等人的考证及分析基础上，从爆炸的力学效应入手，剖析了这次事故，并以此文来缅怀北京城３７０年前在灾难中罹难的先人。     

一起配制特种混合气时发生的气瓶爆炸

介绍一起在配制混合气时的气瓶爆炸事故 ,造成 1个死亡 ,3人受伤 ,对爆炸事故进行了全面分析 ,确定为化学爆炸     

Full-scale experiment to evaluate the combustion hazard of refrigerants with low global-warming potential in a conceivable accident scenario

A full-scale experiment based on a realistic foreseeable leak accident scenario was conducted with two refrigerants with low global-warming potential (GWP). The assumed accident scenario was that of the leakage of low-GWP refrigerant from a variable-refrigerant-flow air-conditioning system into a general narrow karaoke space, with an open flame present in the region where the low-GWP refrigerant accumulated. Even in the absence of mechanical ventilation, neither ignition nor flame propagation occurred if the amount of “LFL equivalent”, that the calculated interior concentration corresponded to the lower flammable limit, was leaked and mixed sufficiently. Even when the leak amount was “UFL equivalent”, that the calculated interior concentration corresponded to the upper flammable limit, ignition and flame propagation could be prevented by means of a suitable ventilation system. The maximum pressure rise was 4–6 kPa. Finally, no transition from laminar combustion to turbulent combustion was observed.     

薄壳结构内气体爆炸破坏后果数值模拟研究

为研究气体爆炸对结构的破坏效应,依据分析得出的事故数据,计算高压气体主要参数得出高压气团模型,采用AUTODYN,设置合理的流出边界及联接强度,建立Shell/Euler耦合模型,模拟了二甲苯气体爆炸效应。结果较好地描述了结构内爆炸演化过程,二甲苯爆炸导致箱式梁产生一定程度的结构破坏,箱式梁顶板与侧板的焊接点部分断裂,底板与侧板联接失效。仿真结果与事故特征基本吻合,验证了所用模拟方法的有效性。提出的高压气团模拟法基于气体性质,分析爆炸事故特征,确定爆源气体种类并定量其体积及分布。分析仿真结果发现内部加强筋可强化箱式梁。该研究进一步确定二甲苯的燃爆危险性,为二甲苯使用场所提供安全依据及设计参考。     

煤矿瓦斯爆炸事故数值模拟分析

对某煤矿瓦斯爆炸事故现场破坏情况和有关资料进行了分析,利用AutoReaGas计算软件对爆炸过程进行数值模拟,得出瓦斯爆炸过程中流场各参数的变化规律,探讨了事故发生的原因及发展过程,并与事故现场所搜集的爆炸参数相比较,为事故调查研究提供了科学的依据。     

Knowledge-based support for event tree construction

A prototype system called EventMAP has been developed to provide knowledge-based support for event tree construction. It comprehends an event tree model of a physical system, which represents the possible event sequences following an initial incident. This model can be used to identify potentially hazardous accident or failure scenarios, to help in assessing the possible outcomes of an observed incident, and to support decisions about appropriate actions. It can also be used during modification to provide insights into the needs for specific safety features.

EventMAP incorporates explicit knowledge about safety engineering and good event tree construction practice. This assures that model building will be more systematic, and will produce more complete and correct event trees. Assumptions underlying the model are tracked explicitly, allowing ‘what-if’ exploration. Moreover, the safety-related design rationale will be preserved despite personnel changes over time. EventMAP incorporates knowledge about: plant structure in terms of subsystems, components, and interconnections; cause/effect relationships and other interactions among subsystems; and failure modes, including human errors. The role of EventMAP is to act as an ‘intelligent assistant’ for the event tree developer; it monitors the evolving model and issues suggestions and warnings to the user as appropriate.     

Failure Analysis of Physical Explosion due to Gas Jetting from High-Pressure Pipeline

Jetting of the combustible gas with high pressure is a prelude to bringing into action of the chemistry explosion of gas cloud. Comparing with the leakage and diffusion of combustible gas and the chemistry explosion effect of gas cloud, the distribution of pressure, temperature and velocity formed by high-pressure gas jetting after the destruction of a pipeline, has been paid less attention to in the related field. There are a few fundamental data on the subject of evaluation of physical explosion parameters. In this paper, a physical explosion case of hydrogen gas transported through a high-pressure pipeline is reported, and a cause analysis of the explosion accident is proposed. Numerical simulation yields the field state parameters and the damage characteristics in the process of high-pressure gas jetting. In front of the leakage gas flow, a shock wave forms due to high-pressure gas jetting. The physical explosion can trigger the combustion of leaked hydrogen gas. Though the pressure rapidly attenuates behind the shock wave, a relatively high velocity is maintained until the control valve in the pipeline system is closed down or the jetting finishes. In the given accident case, the shock wave pressure reaches an order of 1 MPa and the temperature reaches 200–300 °C. This temperatures is obviously less than the igniting temperature of hydrogen gas, 400 °C. But the combustion of leaked gas may be triggered by the spark caused by the impact of instrument plates. Since the instrument plates near the leaking port of pipeline has been damaged already before the leaked gas burns, the electric spark from the line short or the strike spark between metal parts are also completely possible to trigger this combustion.     

地铁开式通风系统喷嘴送风研究

地铁开式通风系统事故时风机联动范围大,时滞长,可靠性和及时性较差,主要针对地铁开式通风系统喷嘴送风进行研究。采用Fluent数值模拟方法,从送风角度、布置位置对顶置和侧置喷嘴进行了优化,获得了顶置和侧置喷嘴最佳布置形式。对两种喷嘴形式下隧道风机进行了选型计算。最后采用SES对区间隧道火灾喷嘴送风风机动作模式进行模拟,结果表明,通过喷嘴送风,可减小风机动作数量,通过动作事故区间相邻车站的隧道风机即可满足区间风速要求,系统可靠性和及时性大大提高。     

A feasibility study for transportable 241Am-in-lung and 241Am-in-nose-blow monitoring systems for use following a weapons accident

In a nuclear weapon accident involving fire or conventional explosion, most of the radiation dose received by people in the immediate vicinity would result from inhalation of 239Pu. This is accompanied by the nuclide 241Am, which is much easier to determine by external counting because of the 60 keV gamma ray emission. In the event of an accident, a priority would be to identify any people who have had intakes of 239Pu which were so large that decorporation therapy should be considered. Direct measurement of lung content provides the most rapid and convenient method for assessing intakes by inhalation. A transportable system has been considered as this could be deployed close to the site of the accident and would allow rapid measurements to be made. The feasibility of a transportable 241Am-in-nose-blow and nasal swab measurement system has also been considered. This would be used to help select people for 241Am-in-lung measurements.     

响水化工厂爆炸TNT当量估算

为了使人们更清楚地了解爆炸的危险性,需要对爆炸事件的TNT当量进行计算,以2019·响水化工厂爆炸事件为例,对该爆炸事件的TNT当量进行了估算。在分析此次爆炸原因的同时,对比分析了多种TNT当量的计算方法,确定此次爆炸事故以建筑物的破坏程度计算TNT当量。根据爆炸事故现场建筑物的破坏情况,先确定出在爆炸周边不同距离处空气冲击波的超压范围,再运用萨道夫斯基公式计算出不同距离处不同TNT当量炸药爆炸产生的空气冲击波超压,将计算值与确定出的空气冲击波超压范围值进行对比,最终确定出爆炸事故的TNT当量。估算此次爆炸事故的TNT当量在400～500 t。