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。     

金属摩擦火花的发生及引燃特性研究

为保障新时期工贸冶金煤矿行业的安全发展，以典型金属材料——TC4钛合金、Q235钢、304不锈钢及铝、镁、锌、铜合金的摩擦火花颗粒为研究对象，探究金属材料摩擦区域温度、火花颗粒表面形貌、粒度特征及引燃特性。结果表明：金属材料的物理特性对摩擦火花的发生情况具有明显影响；高熔点、高硬度、低热导率金属材料——TC4钛合金、Q235钢、304不锈钢更易产生摩擦火花颗粒，其摩擦接触点最高温度分别为462℃、750℃、801℃。摩擦试件的压力和旋转圆盘的转速直接影响摩擦火花颗粒的粒径和单位时间的火花量：随着摩擦试件压力增大、旋转圆盘转速增加，摩擦火花颗粒粒径、单位时间火花量呈现增长趋势。摩擦火花颗粒能够引燃氢气空气混合物与酒精液雾，所形成的爆炸燃烧环境又加剧了摩擦火花颗粒的爆裂燃烧，加大了摩擦火花颗粒的危险性。     

危险品仓库中“搬运工具”静电与摩擦火花的防护

本文阐述了危险品仓库中“搬运工具”静电和摩擦火花防护的必要性,分析了“搬运工具”静电和摩擦火花产生的原因,提出了“搬运工具”静电及摩擦火花的防护措施。     

危险品仓库静电隐患的测量、评估与防护危险品仓库中"搬运工具"静电与摩擦火花的防护

本文阐述了危险品仓库中"搬运工具"静电和摩擦火花防护的必要性,分析了"搬运工具"静电和摩擦火花产生的原因,提出了"搬运工具"静电及摩擦火花的防护措施.     

头部隔热防护的改进

<正>在冶炼行业的炉前作业环境中,除了热辐射强度大,还伴有金属火花、飞屑、粉尘等伤害眼睛、面部、颈部,可能对作业人员的健康造成伤害。如何有效地保护高温炉窑作业工人的头颈部安全?目前,已有企业根据多年来的科学试验和实际应用,研发出新型隔热防护面罩。在炼钢、炼铁、炼焦等冶炼行业中,高温炉窑温度一般在1 000℃~2 000℃,在此温度下的炉前工作业岗位,除了热辐射强度大外,还伴有金属火花、飞屑、粉尘及坠落物体等伤害眼睛、面部、颈部,可能对作业人员的健康造成伤害。在这种特殊高温、强热辐射的作业环境中,炉前工人身穿阻燃铝     

高硅铝合金粉尘云燃爆特性研究

通过开展硅质量分数25%高硅铝合金粉尘燃爆特性研究,揭示了硅质量分数25%高硅铝合金粉尘的最小点火能、最低着火温度、爆炸下限和最大爆炸压力。研究结果表明,在实际生产中要防止高硅铝合金粉尘云与雷电、静电、生产中摩擦或碰撞所产生的火花等能量源接触,避免达到高硅铝合金粉尘云的最小点火能0.1～0.2 mJ而引发爆炸事故;要防止出现明火与发热设备热表面温度达到高硅铝合金粉尘云最低着火温度960℃;对高硅铝合金生产场所、工艺设备等进行抗爆设计时,约束爆炸压力措施承受最大爆炸压力的冲击至少要在0.525 MPa或以上。     

防爆工具及其应用

为避免因碰撞与摩擦等原因产生火花而引起周围可燃性物质燃烧和爆炸,易燃易爆场所使用的手工具,应采用非钢质材料。如有色金属铝、镁、铜等。这类采用非钢材制成的、用于易燃易爆场所的手工具,被称为防爆工具,也称无火花工具或抗火花工具。一、防爆工具的发展随着工业的不断发展,因工具火花带来的火灾爆炸事故越来越突出,这种因工具火花带来的灾害,国内外屡有发生。如:1983年3月7日,我国西南某化工厂一名工人在往油罐卸汽油时,用铁扳手开桶盖产生的火     

联合站储油罐区火灾危险性分析及维修控制安全探讨

本文分析了联合站储油罐区的火灾危险性,阐明了引起火灾的各种原因如明火、静电火花、雷击、碰撞和摩擦火花、电气设备故障、自燃等。一旦发生火灾,具有爆炸危险性大、易形成大面积燃烧、燃烧速度快、扑救难度大,损失大等特点。对储油罐动火维修的安全控制提出建议。     

闪光烟火剂感度变化因素的实验研究

研究铝粉的粒度、形状和粘合剂的含量对闪光烟火药剂感度的影响。发现由铝粉和高氯酸钾配制的二元药剂对摩擦和冲击比较钝感，而对静电火花和火焰敏感；当加入粘合剂后，冲击感度和摩擦感度均明显提高。而静电火花感度和火焰感度均明显下降。粒度和形状对感度的影响是铝粉比表面积变化引起的；粘合剂对感度的影响是由于加入粘合剂后形成的微胶囊的脆性和硬度较大，且易藏有气泡，容易形成热点。     

试论摩擦撞击火花及其事故预防

阐述了煤矿井下摩擦撞击产生火花的种类、形式、机理和危害，提出了预防措施和对策。     

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.     

Safe handling of combustible powders during transportation,charging, discharging and storage

The knowledge of the ignition behavior of dust–air mixtures due to electrical sparks (MIE, Minimum Ignition Energy) and hot surfaces (MIT, Minimum Ignition Temperature) is important for risk assessments in chemical production plants. The ignition behavior determines the extent and hence the cost of preventive protection measures.This paper describes the use of the minimum ignition energy and minimum ignition temperature as very important safety indexes in practice.     

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.     

Simulation of the flow of an explosive atmosphere exposed to a hot surface

The accidental ignition of combustible atmospheres by hot surfaces is of great concern for chemical and process plant safety. In this paper, we present our research regarding the evolution of thermal plumes originating from hot hemispheres and discs. In particular, we focus on the effect of the orientation of the surface on the ignition process. The auto-ignition temperatures and ignition locations were studied experimentally. To get further insight, we conducted detailed numerical simulations and validated them with measurements. Three-dimensional simulations were performed on hot hemispheres and hot discs for different orientations ranging from 0° to 180°. The solver employs a transient, implicit scheme which is based on the coupled heat transfer and flow equations. The mesh in the vicinity of the hot surfaces is refined to resolve the steep temperature gradients and to capture the boundary layer separation. The influence of the orientation on critical hot spots in the gas mixture is analysed by examining the flow structures and the temperature evolution of the buoyancy-driven flow. Using the obtained results, we discuss the change of the onset and location of the ignition.     

典型静电放电火花点燃危险性评价方法研究

通过研究典型静电放电火花的实际点燃能力 ,对实际生产工艺工程中的静电放电火花的点燃危险性进行定量评价。静电放电火花的放电相当能量、放电火花空间分布范围和放电火花持续时间 ,决定了静电放电火花实际点燃可燃物的可能性大小 ,因此不同类型的静电放电火花点燃可燃物的差异性很大。根据数据序列理论分析 ,引入静电放电火花点火源序列和可燃物危险性序列之间存在的关联性 ,反映了静电放电火花点燃可燃物的危险程度 ,可用于对静电放电火花的实际点燃危险性进行量化评价。对聚烯烃粉体生产工艺过程中典型和频发性的静电放电火花的点燃危险性进行了定量评价。     

金属热颗粒引燃可燃堆积材料的实验研究

电焊操作、烟花燃放、工业磨削和高压电线碰撞等过程容易产生高温热颗粒。这些热颗粒一旦接触可燃材料就有可能引燃材料,导致火灾。该文对热颗粒引燃可燃堆积材料的行为进行实验研究,从而为工业堆积材料的火灾防控方法提供参考。实验加热一系列不同直径(6mm,8mm,10mm,12mm,15mm,20mm)的黄铜金属颗粒作为热源,并采用三种常见的工业堆积材料(木粉,炭粉,羟丙基甲基纤维素HPMC)作为可燃材料的代表物,研究不同功率金属热颗粒对材料的引燃行为,分析金属热颗粒引燃材料的临界功率。结果表明,材料本身的性质会影响热颗粒的引燃行为,HPMC的引燃时间最长,木粉的引燃时间最短。随着热颗粒直径的增加,热颗粒引燃三种材料所需的功率值整体呈增大的趋势。由于燃烧空腔的形成,HPMC的引燃临界功率相对较高。     

New approach to calculate the probability of ignition

The probabilistic approach to the evaluation of fire hazard and the effectiveness of fire-precaution measures enables a rational response to the randomness of fire outbreaks. This article employs the statistical analysis methods to elucidate the causes for the ignition of fire on a random sample of industrial buildings in the Republic of Slovenia. The analyses are based on the Structural Equation Modeling (SEM), which is a well established and important statistical analysis technique in the fields of social science, biology, psychology and medicine, but hitherto rarely applied in safety research. The results of the study demonstrate that for the analyzed random sample of industrial buildings the frequency of fire outbreaks statistically significantly depends only on the presence and the probability of exposure to the heat sources (flames, sparks, and hot surfaces), but does not significantly depend on the available quantity of flammable materials within the industrial structure.     

热颗粒和热辐射共同作用阴燃点燃松针燃料床：数值研究

建立了热颗粒和热辐射共同作用下阴燃点燃松针燃料床的二维数值模型,计算得到了热颗粒和热辐射单独点燃以及共同作用点燃的临界条件,分析了燃料床的点燃过程。与前人实验数据对比表明数值模型能够较好预测临界点燃条件。金属热颗粒单独作用时点火所需的临界温度与颗粒直径呈双曲线关系。金属热颗粒与热辐射共同作用时,临界辐射热通量呈现出随颗粒温度和直径的增加而显著减小的趋势。热辐射持续供热能有效维持表层炭氧化反应,两者共同作用下点燃危险性增加。研究同时发现,燃料含水率对共同作用下的临界辐射热通量有较大影响。     

Ignition of hydraulic fluid sprays by open flames and hot surfaces

A study of the ignition of non-fire-resistant hydraulic fluid sprays was conducted by the National Institute for Occupational Safety and Health. Both an open flame and a hot steel surface were used as the external heat sources. With the open flame as the heat source, the minimum oil temperature and minimum spray nozzle pressure that resulted in an ignition were measured. The effects of the distance between the open flame and the nozzle and the nozzle orifice diameter on the ignitability of the hydraulic fluid sprays were examined. With the hot surface as the heat source, the minimum surface ignition temperature was determined. The degree of oil atomization and the relative direction of oil injection with respect to the hot surface are discussed. The ignition of oil sprays from the impingement of oil jets onto a vertical surface was also investigated. Finally, the results are compared with those obtained for fire-resistant hydraulic fluids.     

木材在线性增长热流下着火的复合判据研究

为探索木材在热流变化时的着火特点并提出着火判据,通过试验研究了木材在线性增长热流条件下的自发着火性能,测定了泡桐、椿木、榆木和刺槐4种木材的点燃时间、木材表面的入射热流以及试样内部的温度.结果表明.当热流增长率大于等于0.199kw/(m~2·s)时,试验的所有木材均可以被点燃,点燃这些木材的临界热流增长率介于0.065～0.103 kw/(m~2·s).建立了木材着火的计算模型,计算得出木材自发着火时的表面温度约为500℃.根据试验和计算的结果提出了-结合表面温度和临界热流增长率的木材自发着火复合判据.