粉尘云电火花点火研究

分析了粉尘云电火花点火研究的主要目的。对工业实际中常见的电火花点火源及其放电能量和现有实验装置中的火花触发电路与喷粉系统进行了研究,分析了实验过程中以电容能量和火花能量来衡量粉尘云电火花点火敏感性的主要误差。     

注氮辅助蒸汽吞吐工艺过程井筒爆炸事故分析方法

在注氮气辅助蒸汽吞吐开采原油的工艺过程中,由于地层条件复杂,存在发生油井爆炸事故的风险.以某油田注氮作业过程的井筒爆炸事故为例,结合现场调研和理论计算分析了事故的爆炸性质和点火源类型.通过对物理爆炸和化学爆炸的爆炸能量和爆炸压力进行理论计算,结合本次爆炸事故的总能量及井口装置的破坏压力,确定此次井筒爆炸事故类型为化学爆炸.此外,通过对比分析3种不同类型的点火源,确定此次井筒爆炸事故的点火源为注气速度过快导致油套管相互碰撞产生的碰撞火花.通过全面分析某油田井筒爆炸事故原因和性质,形成了一种系统性的井筒爆炸事故分析方法.     

铝粉厂粉尘爆炸危险性影响因素的灰关联分析

本文对粉尘爆炸的机理、条件、影响因素和预防措施进行了阐述,对已发生的粉尘爆炸事故进行了统计分析.本文在论述灰色系统及灰关联分析原理的基础上,总结了灰关联分析的适用条件及国内外研究现状,针对电气点火源进行具体分析,阐述了电火花、静电火花产生的原因及易发生部位等,提出了预防电气点火源的具体措施.     

石化装置泄漏事故点火源及点火概率的确定

简要综述石化企业常见点火源的分类及点火概率的确定方法。首先介绍点火源的常见分类方式,通过事件树展示泄漏发生后立即点火和延迟点火造成的不同事故后果;其次总结目前国内外确定点火概率的两种方法,即基于事故统计的点火概率以及基于点火源分类和统计的方法。在基于事故统计的点火概率中,给出国外在易燃液体运输、井喷、储罐破裂、管道运输等行业发生泄漏事故后的点火概率。在基于点火源分类及统计的点火概率计算中,给出TNO、HSE推荐的点火概率计算方法。同时对国内的研究情况进行了总结,给出已发表的点火概率计算方法。最后简要介绍目前国内关于点火过程的试验研究。针对国内工厂实际情况确定不同点火源的点火概率的工作亟待开展。     

煤矿瓦斯爆炸事故特征与耦合规律研究

分析瓦斯爆炸事故的瓦斯积聚原因、引爆火源和引爆地点等事故特征及其分类,统计并分析1988—2008年发生的563次瓦斯爆炸事故的基本特征和耦合规律,结果表明:通风混乱等通风系统问题导致瓦斯缓慢积聚的瓦斯爆炸事故占90.6%;电火花和放炮火焰引爆瓦斯占事故的78.6%;发生在采掘工作面的瓦斯爆炸事故占69.4%;通风系统问题导致瓦斯积聚的瓦斯爆炸事故主要发生在采掘工作面和巷道,占81.3%;通风系统问题导致瓦斯积聚的事故其引爆火源主要是电火花,占72.8%;电火花和放炮火焰引爆瓦斯主要发生在采掘工作面和巷道,占73.2%。有效预防和控制煤矿瓦斯爆炸事故需切实加强通风管理、电气管理和严格放炮操作与程序。     

井喷点火过程天然气爆炸后果分析

井喷失控事故发生后，尽快点火是减少人员伤亡的最有效措施之一。然而，点火过程中一旦发生天然气爆炸，其可能的爆炸伤害范围、破坏范围以及是否在可接受风险范围，就成为决策能否点火的关键。本文应用蒸汽云爆炸的肿当量模型和冲击波峰值超压模型，提出了天然气井喷失控后，发生天然气爆炸的人员死亡区、重伤区和轻伤区的计算方法；假设井喷的天然气无阻流量，计算了可能的人员伤害范围，并对计算结果进行了分析。分析发现，在井喷失控后，最大限度地减少井喷失控时间，以及最大限度地防止天然气在某一区域的大量积聚，是减轻井喷失控天然气爆炸后果的最佳措施。     

静电喷漆作业的防火防爆

静电喷漆工艺应用普及很快,但其生产过程的火灾危险性属甲类。其火灾危险主要在于使用的漆料或有机溶剂,喷漆作业中存在电火花、静电火花、高温热表面、自然发热等引火源。为防止火灾爆炸发生,要注重防火防爆安全管理和强化必要的安全技术措施。     

液化石油气站储罐区火灾爆炸危险性分析与安全措施

选择具体的液化石油气储配站,分析了该站的危险特性、危险产生的途径及可能造成的后果。在没有任何防护措施的情况下,采用蒸气云爆炸和沸腾液体扩展蒸气云爆炸模型,对该站一个50m3储罐发生泄漏造成的火灾爆炸事故后果进行预测,得出火灾爆炸后的安全距离为大于211．0m。在储配站不能满足此安全距离的基础之上,从防止产生爆炸性气体环境、消除点火源和抑制事故扩大三方面来提出有效的安全措施,降低事故发生的概率及事故造成的损失。其中,站址选在全年最小频率风向的上风侧且周围空旷的地区,罐上设置液位计、压力表、温度计及可燃气体报警器可防止产生爆炸性气体环境;罐及管道设静电接地,法兰用铜线跨接,站内设警示标志可消除点火源;生产区与辅助区间设置隔离墙,罐区周围设置砖混围堤,罐上设安全阀可抑制火灾爆炸事故扩大。     

对称障碍物条件下瓦斯爆炸火焰与压力波耦合作用研究

为了研究对称障碍物条件下瓦斯爆炸压力波与火焰传播的耦合作用,在150 mm×150 mm×1 700 mm的有机玻璃瓦斯爆炸管道中,距离点火端不同距离安装0.5阻塞率的对称障碍物,进行8.5%甲烷体积分数的爆炸试验,采集瓦斯爆炸的超压信号并同步拍摄火焰传播图像。结果表明:火焰穿越板式对称障碍物的过程经历了火焰加速、火焰降速到火焰再加速的过程,火焰降速的时间仅为5 ms。距离点火焰源不同长度的对称障碍物在火焰加速过程中的作用存在明显差异,近点火源的障碍物作用主要为诱导湍流,远离点火源的障碍物作用主要为湍流增强。     

煤气火灾如何预防

统计资料表明,现代厨房常见煤气火灾,主要是管道、炉灶等安装不当、质量不过关或因腐蚀损坏等,造成气遇明火发生火灾或爆炸事故;或发现漏气时,错误地使用明火寻找泄漏点,引起燃烧或爆炸事故;由于使用不当(如先开气、后点火)或由于停气、回火、风吹使火焰熄灭,或使用锅、壶烧水时,因水满沸腾后溢出将火泼熄时没有及时关闭阀门,致使漏出的煤气被第二次点火的火源引爆等,因此有效防止煤气火灾,必须做到以下两点:     

可燃制冷剂空调用开关元件点燃危险及防爆试验分析

随着全球范围对环境问题的日益重视,R290,R32等新型制冷剂因优良的环保性能和节能效果被广泛应用于空调行业,但其属于IIA级爆炸性气体,为了进一步分析其运行过程中的防爆安全性能。通过文献数据和测试分析,可燃制冷剂空调电气元件的点燃源主要来自其工作过程中产生的电气火花。其中空调开关元件最容易产生电火花、电弧,且通过试验验证这些火花或电弧能点爆（6.5±0.5）%乙烯/空气混合物。综合IEC 60335-2-40,GB 4706.32标准要求和空调开关元件的结构特征,分析确定其应符合“nC”型防爆技术要求,并能通过“nC”型爆炸试验。针对开关元件结构尺寸小、存在爆炸试验中爆炸性混合气体多次置换和负载通、断电操作的难点问题,提出一套合理可行的爆炸试验实施方案,并通过测试应用得到验证。     

纺织工业中火花探测熄灭系统的应用

纺织行业的火灾和粉尘爆炸的发生,点火源是导致事故发生的条件之一,若能在事故发生前检测到火花并灭之,完全可以预防事故的发生.火花探测熄灭系统能够胜任此项任务.本文介绍了火花探测熄灭系统的工作原理和管道火花探测熄灭系统的基本组成,分析了纺织厂火花源的产生,探讨了火花探测熄灭系统的安装位置,以及该技术在纺织行业大力推广还要做的大量试验实践工作.本火花探测熄灭系统的最大优点是发现火花立即熄灭,而不会影响生产的继续运行,属于预防纺织行业粉尘爆炸的积极方式.但是,目前国内纺织工业企业中使用该技术的较为少见,那么建立相应产品的国内生产标准和安装规范迫在眉睫,它是该技术统一、规范和推广的法规性保障.     

Friction spark generation and incendivity of several metal alloys

When metal alloys are used as mechanical equipment or tools in explosive atmospheres, the occurrence and incendivity of mechanically generated sparks as ignition sources should be taken into consideration. The formation of mechanically generated sparks was investigated for seven metals, including Q235 steel, 304 stainless steel, TC4 titanium alloy, 6061 aluminum alloy, H62 bronze alloy, AMAK3 zinc alloy, and AZ31B magnesium alloy. The relationship between the physical-chemical properties and generation and incendivity of friction sparks was evaluated. For 6061 aluminum alloy, H62 bronze alloy, AMAK3 zinc alloy, and AZ31B magnesium alloy, no bright friction sparks were observed in the maximum friction velocity of 12 m/s and maximum surface pressure of 3.75 N/mm², because of low hardness, high thermal conductivity, low melting point, and the absence of carbon content. Ignition testing indicated that nano titanium dust layers with MIEL (minimum ignition energy of dust layer) of 1 mJ were not ignited by friction particles from the four metal alloys. However, bright particles were clearly observed for 304 stainless steel, Q235 steel, and TC4 titanium alloy. Friction sparks at the maximum power densities showed incendivity with micro titanium layers having an MIEL of 17.5–25 mJ but not with PMMA, corn starch, and wood dust having MIELs greater than 1 J. Two different particle burning behaviors with different fragmentation mechanisms during the friction process were determined, namely the micro explosion phenomenon for TC4 titanium alloy and particle burst for Q235 steel. Results indicate that the physical-chemical properties of friction metal rods are useful for preliminary evaluation of spark generation. Powder layers with known MIEL can be considered as indicator testing materials to evaluate spark incendivity.     

基于FLACS的海上钻探平台井喷爆炸事故后果模拟分析*

为研究海上钻探平台井喷燃爆事故后果,运用FLACS软件对某深海钻探平台井喷爆炸事故进行模拟,研究在不同事故场景下气云爆炸发展过程及平台荷载分布规律,讨论井喷速率、风向、点火位置等对爆炸超压的影响。研究结果表明:随泄漏速率增加,爆炸强度和爆炸范围均增大,爆炸严重程度不仅与井喷速率密切相关,同时也受平台结构影响;点火位置会对爆炸超压产生影响,在可燃气体与空气混合气体比例为化学理论当量比处点燃气体,生活区承受的爆炸超压最大;在设施及建构筑物分布较为密集、拥塞度较高的地方产生的爆炸超压更大。研究结果可为可为平台的阻隔防爆性能设计与应急响应提供指导。     

Hot surfaces generated by sliding metal contacts and their effectiveness as an ignition source

Frictional processes caused by malfunctions may lead to hot surfaces and mechanical sparks. Whenever mechanical sparks occur due to friction, there are also hot surfaces. The time until the ignition source becomes effective is largely dependent on the thermal conductivity of the friction partners. Based on this, it was examined whether classification into the explosion groups and temperature classes of IEC 60079-0 is possible and useful. This research therefore focuses on the development of hot surfaces and their effectiveness. To assess the formation of hot surfaces, tests for temperature development according to the applied power density and the different materials were performed in a friction apparatus. The experimental setup is realised via a friction pin which is pressed onto a rotating friction disc. The variation of the power density was carried out by changing the velocity and load per area. The temperature distribution was detected by thermocouples, two pyrometers and an infrared camera. For the investigation of the incendivity of hot surfaces, the ignition curves were determined by characteristic reference gases and vapours of the IEC explosion groups and temperature classes. Tests have been carried out with hydrogen, ethylene, diethyl ether, propane and pentane. The experiments have shown that a larger thermal conductivity of the steel used can lead to slow down heating of the pin material. With an increasing wear rate the maximum temperature decreases. It was possible to determine the maximum temperatures at specific power inputs. The ignition tests show that ignitions are possible even at low velocities. The effective ignition source was thereby always the hot surface. The result was a graduation of the explosion limits analogous to the order of Maximum experimental safe gap (MESG) values. In contrast, no significant relationship between the ignition limits and the temperature class of the respective substances was revealed.     

Measurement of minimum ignition energies (MIEs) of dust clouds – History,present, future

Nearly 130 years ago Holtzwart and von Meyer (1891) demonstrated by experiments that explosible dust clouds could be ignited by inductive electric sparks. Then more than half a century passed before the publication of the important quantitative research of Boyle and Llewellyn (1950) and Line et al. (1959). They worked with capacitive electric sparks and found that the minimum capacitor energies ½CU² required for ignition of various dust clouds in air decreased substantially when a large series resistance, in the range 10⁴–10⁷ Ω, was introduced in the discharge circuit. When considering that the net energies of the sparks themselves were only of the order of 10% of the ½CU² discharged, the minimum net spark energies required for ignition with a large series resistance were only a few per cent of the net energies required without such a resistance.Line et al. observed that the essential effect of increasing the series resistance, and hence increasing the discharge time of the sparks, was to reduce the disturbance of the dust cloud by the blast wave from the spark. This phenomenon was explored further by Eckhoff (1970, 2017), and subsequently by some simple experiments by Eckhoff and Enstad (1976). Franke (1974, 1977) and Laar (1980) confirmed the additional finding of Line et al. (1959) that the minimum ½CU² for ignition is also substantially reduced by including a series inductance in the discharge circuit, rather than a series resistance. The basic reason is the same as with a large series resistance, viz. increased spark discharge time and hence decreased disturbance of the dust cloud by blast wave from the spark. For this reason inclusion of an appreciable series inductance in the spark discharge circuit is an essential element in current standard MIE test methods.In experiments with spark ignition of transient dust clouds produced by a blast of air in a closed vessel, it is necessary to synchronize the occurrence of the spark with the formation of the dust cloud. The precision required from this type of synchronization is typically of the order of 10 ms, which can be obtained even by mechanical arrangements, such as rapid change of spark gap length, or of the distance between two capacitor plates. The present paper reviews some methods that have been/are being used for achieving adequate synchronization of dust cloud appearance and spark discharge. Some current standard experimental methods for determining MIEs of dust clouds experimentally have also been reviewed. The same applies to some theories of electric-spark ignition of dust clouds.At the end of paper some suggestions for possible future modifications of current standard methods for measuring MIEs of explosible dust clouds are presented. With regard to justifying significant modifications of existing standard methods, the “bottom line” is, as quite often in many connections, that any modifications should be based on realistic cost/benefit evaluations.     

High voltage and break spark ignition of propylene/air mixtures at various initial pressures

The original break spark test apparatus for intrinsically safe circuits was modified to allow the measurements of minimum ignition currents (MICs) at different initial pressures between 20 and 120 kPa. The MICs of different propylene/air mixtures at ambient temperature and at both atmospheric and sub-atmospheric pressures were measured. The corresponding minimum ignition energies (MIEs) using break sparks were calculated and compared with those derived from MIE/quenching distance correlations using high voltage sparks between flanged electrodes.     

不同物质组合摩擦火花引燃特性的研究

在本研究中,对碳钢、铍青铜和铜镍锰合金等三种金属与砂轮和45号钢轮摩擦时产生火花的能力和引燃能力作了对比实验。用于实验的可燃混合气为液化石油气/空气和氢/空气。实验表明,碳钢和砂轮摩擦产生的火花最强烈,但仍很难引燃液化石油气/空气混合气;铍青铜与砂轮摩擦时几乎看不到火花,铜镍锰合金在同样条件下产生火花的几率销大。在摩擦时间较长的条件下,两者均能引燃极易爆炸的氢/空气混合气,但爆炸却并不是在火花出现时立即发生的。可以推断:在上述条件下,摩擦造成的炽热表面是引燃的主要原因,而材料的引燃能力的强弱,不能只以是否产生火花为判断基准。