Measuring the violence of dust explosions with the “20 l sphere” and with the standard “ISO 1 m vessel”: Systematic comparison and analysis of the discrepancies

On the basis of a systematic testwork with a number of different dusts, the explosion indices as determined within the 20 l sphere and with the ISO-VDI 1 m³ vessel have been compared. The repeatability has been assessed and since some systematic deviations appear a refined physical analysis of the explosion processes is developed. It appears in particular that the cube root law supposed to link both vessels is not verified. A striking illustration of this appears when a dust with a significant explosion severity inside the 20 l sphere is not even explosible in the larger vessel. It is strongly suggested that the ignition energy is forcing very significantly the explosion in the smaller vessel inducing several tens of Celsius degrees of preheating. It is shown also that the inner level of turbulence is decreasing very fast in the 20 l sphere during the flame development so that difficult-to-ignite mixtures would tend to burn at a lower combustion rate. It is further demonstrated that the major bias between the chambers can be explained and quantified with these elements. A correlation with the standard 1 m³ vessel and a grid of interpretation of the data is proposed.     

模糊数学在爆炸危险性评价中的应用

在爆炸危险性分析与评价中应用模糊数学的一些方法是客观的需要,本文简单介绍了模糊综合评判和模糊故障树的原理和评价步骤。     

当代世界50起重大毒性灾害初析

本文对当代世界１９３０～１９９２年５０起重大毒性灾害进行了分析。其中药物中毒６起，食物中毒７起，环境污染８起，毒气泄漏５起，有毒化学品与有毒气体爆炸９起，核爆炸与核辐射６起，恐怖行为２起，其它毒性灾害７起。本文还对减轻毒性灾害的基本对策进行了探讨。     

一起有机过氧化物爆炸事故的调查和分析

阐述一起重大爆炸伤亡事故的现场调查和原因分析，介绍如何通过人证物证材料，用鱼刺图法找出可能引起事故的诸原因，逐项加以分析，将与人证或物证材料相矛盾的原因子以排除，最后剩下无法排除亦即能与人证物证相符的那个原因，就是事故的真正原因。笔者是这起事故调查专家组组长，取证和数据可靠。     

粉尘爆炸技术的最新发展

系统论述了爆炸防护技术的最新发展，为了选择最佳防护措施必须恰当鉴定和评估，包括材料的性质。借助一些经验公式，可估算温度对各种材料操作参数的影响。用情化法不仅可防止可爆混合物的形成还可防止其着火。对设备的“结构防爆”措施，近年来已制造出买用的容器。可以确信，工业爆炸防护领域必将拥有足够的技术以有效地战胜爆炸危险。     

Numerical investigation of surface conduit parallel gas pipeline explosive based on the TNT equivalent weight method

With the rapid development of petroleum industry, the transport pipelines of oil and gas are increasingly constructed to minimize land use conflicts. Therefore, the parallel pipelines are unavoidable in order to save land resource, reduce the pipeline construction and maintenance costs. The economy and security of pipeline laying and running is the primary problem considered in pipeline construction, which the parallel spacing plays a decisive role to. The leakage of natural gas is very serious and dangerous due to its flammable and combustible. The explosive of leak gas causes impact failure to parallel pipeline. Specific to the surface conduit parallel gas pipeline, numerical simulation of leak natural gas explosive was carried out based on TNT equivalent weight method. Explosive damage degree of pipeline decreased with the pipeline distance increasing. Consulting with the pipeline ovalization strain design criteria and the combustion effect, the safety parallel natural gas pipeline space maybe at least 4 m to ensure the surface conduit parallel pipeline safely and steadily operation.     

Three accidents in European dynamite production plants: An attempt to improve the external lessons learning

Three serious accidents occurred in three dynamite manufacturing plants within three European countries during a relatively short time period triggering the question of effective external learning. The article discusses the lessons for the prevention of accidents learned from retrospective comparative analysis. It advocates for a better process for learning lessons. It attempts to show how a two level approach to accident analysis may help to reveal a common deeper learning hidden under diverse routine lessons.     

Effects of ignition energy on fire and explosion characteristics of dilute hybrid fuel in ventilation air methane

Deflagration explosions of coal dust clouds and flammable gases are a major safety concern in coal mining industry. Accidental fire and explosion caused by coal dust cloud can impose substantial losses and damages to people and properties in underground coal mines. Hybrid mixtures of methane and coal dust have the potential to reduce the minimum activation energy of a combustion reaction. In this study the Minimum Explosion Concentration (MEC), Over Pressure Rise (OPR), deflagration index for gas and dust hybrid mixtures (K_st) and explosive region of hybrid fuel mixtures present in Ventilation Air Methane (VAM) were investigated. Experiments were carried out according to the ASTM E1226-12 guideline utilising a 20 L spherical shape apparatus specifically designed for this purpose.Resultsobtained from this study have shown that the presence of methane significantly affects explosion characteristics of coal dust clouds. Dilute concentrations of methane, 0.75–1.25%, resulted in coal dust clouds OPR increasing from 0.3 bar to 2.2 bar and boosting the K_st value from 10 bar m s⁻¹ to 25 bar m s⁻¹. The explosion characteristics were also affected by the ignitors’ energy; for instance, for a coal dust cloud concentration of 50 g m⁻³ the OPR recorded was 0.09 bar when a 1 kJ chemical ignitor was used, while, 0.75 bar (OPR) was recorded when a 10 kJ chemical ignitor was used.For the first time, new explosion regions were identified for diluted methane-coal dust cloud mixtures when using 1, 5 and 10 kJ ignitors. Finally, the Le-Chatelier mixing rule was modified to predict the lower explosion limit of methane-coal dust cloud hybrid mixtures considering the energy of the ignitors.     

Explosion prevention and weighting analysis on the inerting effect of methane via grey entropy model

Explosion prevention is vital for process safety and daily life. In practice, inerting is viewed as an ideal method to reach basic explosion prevention as well as to diminish flammability risk in normal operation, storage, and transportation of materials. This study deals with the inerting effect on the explosion range for methane via grey entropy model, comparatively detected under the different inert gases of nitrogen (N₂), argon (Ar), and carbon dioxide (CO₂), which have various loading inerting concentrations: 10 (90 vol% air), 20 (80 vol% air) and 25 vol% (75 vol% air). The inert influences were determined via the experimental 20-L-apparatus investigations under 1 atm, 30 ^OC, combined with the grey entropy model, which is one of the most prevailingly used grey system theories for weighting analysis and decision-making of the fire and explosion assessment for practical operations. The results indicated that CO₂ had better inerting capacity than the others, as derived from our grey entropy theoretical soft computing calculations. Through the combination of the grey entropy weighting analysis model and the flammability investigations in this study, the concluded decision-making was feasible and useful for the practical applications of inert gases for preventing fire and explosion hazards in relevant processes.     

Wire-mesh inhibition of jet fire induced by explosion venting

Explosion venting is widely applied in industrial explosion-proof designs due to the convenient, economical and practical features of this method. Natural gas is usually stored in storage tanks. If the gas in the vessel is mixed with air and encounters an ignition source, explosion venting might occur, producing jet fire, generating new secondary derivative accidents and causing casualties and property losses. In this paper, a set of test platforms including wire-mesh suppression devices is established to study the inhibition of jet fire induced by explosion venting by wire mesh. The experimental research shows that a wire mesh significantly inhibits the jet fire induced by explosion venting. The flame propagation velocity and pressure clearly decrease with increasing numbers of wire-mesh layers. The wire-mesh structure significantly affects the flame propagation, and the more layers of mesh there are, the better the suppression effect is. The flame temperature gradually decreases with the addition of the wire mesh. The mesh size significantly affects the pressure propagation of explosion venting. The explosion pressure gradually decreases with the addition of the wire mesh. With increasing distance between the wire mesh and the explosion vent, the maximum temperature first increases and then decreases, and the maximum explosion pressure first decreases and then increases. In the case of single gas cloud, the flame suppression effect is the most obvious when the wire mesh is 0.2 m away from the explosion vent. In the case of double gas clouds, the flame suppression effect is the most significant when the distance between the wire mesh and the first gas cloud is 0.4 m.