浅谈静电火灾或爆炸的成因及预防

本文从静电产生的原因、产生条件及危险性进行分析入手,对不同情况和条件下静电火灾或爆炸的预防措施和方法进行了探讨。     

粉体料仓静电燃爆风险与防控措施

针对聚烯烃、聚酯粉体物料在风送、包装过程中静电高能放电造成料仓闪爆、静电打火问题,总结了国内外粉体料仓静电防控技术与装备研究及应用情况;根据料仓装置特点,从料仓静电放电、可燃气体两方面分析料仓装置静电引燃危险性;分析了料仓工艺操作、反吹风系统设置、管道粉体静电监测、管道粉体静电消除和包装粉体静电控制技术与装备研究与应用现状,阐明了石化料仓企业需加强安全管理,落实与优化控制料仓粉体静电的关键和重要措施。     

油品储运作业静电火灾成因及防治对策

分析油品储运过程中静电产生的机理,通过控制油品液面静电电位静电接地等控制对策,以减少消除静电火灾事故,确保油品储运系统的安全运行。     

浅谈矿井火灾防治技术

矿井火灾的防治工作主要包括三个方面：煤层自然发火危险性评价、煤层自然发火的预测预报和矿井火灾的防治技术。煤层自然发火危险性评价的目的是要在火灾发生之前对火灾发生的可能性做出科学性的评价,煤层自然发火的预测预报是在煤矿生产过程中对可能或已经发生的火灾进行监测和预测,而矿井火灾防治技术则是对即将发生或已经发生的火灾采取措施,阻止火灾的发生。     

粉体含能材料生产与储运中的静电安全及防护

分析了静电产生的原因,阐述了粉体含能材料生产中的静电起电现象、静电的危害、静电安全性评估标准以及建立在此标准基础上的静电放电危险的评价办法,提出了粉体含能材料在生产、运输中所需要采取的静电防护措施。     

粉体含能材料生产与储运中的静电安全及防护

分析了静电产生的原因,阐述了粉体含能材料生产中的静电起电现象、静电的危害、静电安全性评估标准以及建立在此标准基础上的静电放电危险的评价办法,提出了粉体含能材料在生产、运输中所需要采取的静电防护措施。     

静电的产生原因及解决办法

因为薄膜的运动及摩擦都难以避免的,静电对生产的影响主要有以下几个方面.     

粉体静电起电的试验研究

采用静电电荷仪和法拉第筒 ,测定了两种导电性能完全不同的粉体在机械振动筛中静电起电量的参数。结果表明 :无论是导电的金属粉体还是非导电的粮食粉体所产生的静电均已超出《静电安全导则》规定的安全界限     

印刷包装行业静电的产生及解决方案

生活中的静电现象,大家并不陌生,在工业生产中产生的静电现象,人们往往对此不以为然,认为只是轻微的电量,在印刷包装生产过程中,不会有什么危害。这种麻痹大意的观念是不对的,当一定量的静电必然会对生产造成明显的影响。一定量的静电作用于一定量的易燃气体时,那么火     

流化床反应静电的产生与消除

本文阐述了流化床中的静电产生的原因,将静电与结片现象关联起来,并以生产的角度阐述了静电消除和控制方法。     

MIKE 3 versus HARTMANN apparatus: comparison of measured minimum ignition energy (MIE)

In this study, MIE values measured with two different explosion tubes, HARTMANN and MIKE 3, are compared. Generally, MIKE 3 apparatus provides MIE results, which are equal or lower to those measured with the HARTMANN apparatus; this is particularly true for the energy ranges between 1 and 10mJ and higher than 100mJ. Differences observed can modify samples classification according to their sensitivity to electrostatic ignition sources. Nevertheless, ignition of a dust cloud by an electrostatic discharge is complex, and implies a different mechanism from that occurring during MIE tests. Thus, it seems difficult to synchronise dust dispersion and spark triggering to obtain optimal concentration in the spark area. Moreover, spark characteristics such as duration or energy feeding rate of spark cannot reproduce exactly industrial-world ones. On this point, it is not possible to conclude if characteristics of MIKE 3 electric circuit, e.g., resistance and inductance, are more relevant than HARTMANN circuit ones.     

New class of electrostatic energy analyzers with a cylindrical face-field

A new class of electrostatic energy analyzers based on a cylindrical face-field is presented. The focusing field used is a solution of a Laplace equation ²U(R,Z)=0 with boundary conditions U(R₁,Z)=U(R,0)=U(R,L)=0 and U(R₂,Z)=V and restricted by concentric cylindrical surfaces and two flat surfaces perpendicular to the axis of symmetry. Regimes of a second-order focusing were found for different types of sources, including a point-source, an extended surface source of large angular size and a flow parallel to the symmetry axis, while charged particles entered into the analyzer through a face-window arranged in a boundary electrode. Some results are described showing the capability of utilizing the prototype cylindrical face-field-analyzer for distant surface chemistry monitoring.     

Simulation of ionic crystals and calculation of electrostatic potentials

By assuming complete ionicity, an efficient algorithm was performed for the evaluation of the electrostatic interactions. There are no symmetry restrictions for the application of this algorithm. The lattice self-potentials for distinct ion positions and the Madelung constant were computed for a wide variety of ionic crystals. The simulation was carried out using the conventional Ewald method. This work highlights the significance of the Coulomb potential in lattice effects and the existence of differences in potentials for complicated compounds. Finally, we remark that the general framework presented in this paper is more appropriate to study structural phase transitions.     

A review of one aspect of the thermal-explosion theory

The historical development of the thermal-explosion theory is examined and reviewed, It is shown that the original formulation of the problem by Semenov accurately defines the phenomenon and explains the reason for the explosion. He showed that, when the heat generation within the solid exceeds the heat dissipation to the surroundings, explosion occurs. Frank-Kamenetskii’s disapproval of Semenov’s logic theorized that the difference between the temperatures at the center of the solid and its surface is the cause of the explosion. His famous and ingenious small-temperature model and the solution to the differential equation that resulted from that distorted the problem and delayed the progress to a full understanding of the problem. He concluded that explosion occurs when no solution to the problem exists. The exact solution to the problem by Shouman, Donaldson and Tsao reaffirmed the validity of the Semenov formulation. Further examination of the effect of reactant consumption on the problem produced full understanding of the physics of the problem.     

Rate dependent constitutive modelling of laminated FRP composites degraded by fire

A constitutive theory is proposed for FRP laminated composite materials that is designed to account for both temperature and strain rate dependent response, such as would occur during, and after, exposure to the elevated temperatures due to fire. The theory is physically based, and in particular, is based on a kinematical framework fixed on the fabric laminates; full accounting of laminate reorientation and anisotropic response is thus achieved. The theory is numerically implemented and FEM analysis of compressive deformation of a sandwich panel, given as an example, demonstrates how common material failure modes such as kinking are naturally included in the theory and in analyses using the theory. The theory accounts for finite strains and thus the extent of deformation is arbitrary. The theory and its numerical implementation are designed specifically to perform numerical analysis of structural response of FRP structures subject to fire degradation.     

大空间内着火位置对火灾增长的影响

以大空间展厅为例,利用火源辐射模型和烟气辐射模型并结合CFAST6．0区域模拟软件的计算结果,对比分析了大空间内不同着火位置下火灾增长的情况。研究结果表明仅考虑火源热辐射的情况下,展厅内着火位置越处于左右中间对称处,其火灾增长越快,热释放速率峰值也越大,达到热释放速率峰值的时间和火灾的持续时间越短,处于展厅中心位置时所有值达峰值。对火源热辐射和烟气辐射综合考虑时,到达热释放速率峰值时间与火灾持续时间的规律同仅考虑火源辐射模型时一致,但热释放速率峰值均有不同程度的提高。     

Effects of fire on small commercial gas cylinders

Current standards on the safety of small portable gas cylinders only define the pressures at temperatures of up to 50 °C and therefore have limited applicability in situations where cylinders are close to fires. Cylinders containing a pressurised liquid butane–propane mixture were heated in a small barbecue. The cylinders underwent a boiling liquid expanding gas explosion (BLEVE) at a liquid temperature of 90–100 °C. Failure was at the rolled seam where gas could escape thus provoking the BLEVE. Previous hydrostatic pressure testing of the cylinders showed that collapse of the spherical cap base occurred at a pressure of 1.8 MPa and that this was followed by failure of the rolled seam at a pressure of 2.0 MPa. These pressures were lower than that required to produce longitudinal cracks in the cylinder wall. Analysis of the pressure created as the temperature is raised by means of the Clausius–Clapeyron equation indicated the temperature for failure of the seam to be about 100 °C. After the BLEVE the cylinder broke into two fragments, an end cap and a tub rocket. The velocity of the tub rocket was estimated to be 65 m s⁻¹, giving a kinetic energy of 309 J. By comparison with the ballistics of rubber bullets it is believed that any injuries will be non-penetrating blunt trauma injuries and be less likely to cause severe injuries than those created by rubber bullets. The range over which the kinetic energy is likely to be capable of creating injuries is estimated to be less than 30 m.     

Diagnostics of pulsed vacuum arc discharges by optical emission spectroscopy and electrostatic double-probe measurements

In this work the study of plasma characteristics by means of two of the most common techniques employed by the scientific community dedicated to the experimental plasma research is presented. The plasma was generated in a vacuum reaction chamber which was filled with hydrogen gas. Inside the chamber, two opposite electrodes were placed: the cathode, which was formed by a target of highly oriented pirolitic carbon and the anode. The electron temperature T_e and the electron density n_e were measured by using optical emission spectroscopy and electrostatic double probe, obtaining very close values for each case. T_e was calculated as approximately 0.7 eV and n_e of the order of 10¹³ cm⁻³. The optical emission measurement allows one to identify the substances that are in the plasma like C I, C II, C III, H I and H₂ and some possible reactions. The double-probe technique showed the plasma potential of about 24 V. The characteristic curve of the double probe exhibited oscillational plasma instabilities which could be attributed to the charge density variation or other factors, such as the employed AC signal and the geometric probe.     

Deterioration of the fire structural resistance of sandwich composite under tension due to water absorption

The effect of water absorption on the fire structural resistance of a sandwich composite is investigated. A sandwich material consisting of E-glass/vinyl ester laminate skins and balsa wood core was environmentally aged in hot (70 °C) and humid (85% relative humidity) conditions for an increasing period up to and exceeding the saturation time. The face skins displayed Fickian diffusion behaviour in the absorption of water whereas the core exhibited significant mass loss due to water causing hydrolysis of bioorganic compounds in the wood. Water absorption decreased the fire structural resistance of the sandwich composite under tensile loading. The saturated sandwich composite exposed to fire failed at lower tensile stresses and within shorter times compared to the dry composite. The reduction in fire resistance was primarily due to moisture-induced weakening of the laminate skins. The reduction to the fire structural resistance caused by water absorption was predicted using a thermal–mechanical model.