DUST EXPLOSION HAZARD ASSESSMENT 粉尘爆炸危害评定
INTRODUCTION简介
The majority of powders that are used in the processing industries are combustible. An explosion will occur if the concentration of the combustible dust that is suspended in air is sufficient for flame propagation when ignited by a sufficiently energetic ignition source. It should be noted that as far as dust clouds are concerned, the terms “combustible”, “flammable”, and “explosible” all have the same meaning and could be used interchangeably.
大多数加工行业中的粉尘是“可燃的”。当悬浮在空气中的可燃性粉尘达到支持火焰传播的浓度时,同时点火源有足够能量,爆炸就会发生。就粉尘云而言,术语“可燃”,“易燃”,和“易爆”都具有相同的含义,可以互换使用。
To eliminate/control dust cloud explosion hazards the following activities are required:为了消除/控制粉尘云爆炸危害,应采取以下措施:
- Understanding of the explosion characteristics of the dust, 了解粉尘的爆炸特性,
- Identification of locations where combustible dust clouds are or could be present during normal and abnormal conditions,
- 识别在正常和异常情况下,可燃性粉尘云存在或可能会存在的场所
- Identification of potential ignition sources that could be present under normal and abnormal conditions,
- 识别在正常和异常情况下,可能存在的点火源,
- Proper plant design to eliminate and/or control the occurrence of dust explosions and protect people and facilities.
- 正确的厂房设计以消除和/或控制粉尘爆炸的发生,保护人员和设备。
As is highlighted above, in order to assess the risk of a dust explosion in a facility and to select the most appropriate basis of safety, explosion characteristics of the dust(s) that are being handled / processed in the facility should be determined. The explosion characteristics of dusts normally fall within two groups, “likelihood of an explosion (Ignition Sensitivity)” and “consequences of an explosion (Explosion Severity)”. These two groups of tests are discussed below:
如上文所强调的,为了评价粉尘在设施中爆炸的风险及选择适当的安全基本要求,应先确定设施中需处理/处置的粉尘的爆炸特性。粉尘的爆炸特性通常分为两类,“爆炸的可能性(点火感度)”和“爆炸的后果(爆炸烈度)”。关于这两类特性的测试在下文中讨论:
Laboratory Tests to Determine the “Likelihood of an Explosion (Ignition Sensitivity)”
实验室测试确定“爆炸的可能性(点火感度)”
Explosion Classification (Screening) Test爆炸分类(筛选)测试
The Explosion Classification test determines whether a dust cloud will explode when exposed to an ignition source. The test results in a material being classified as either combustible or non-combustible.爆炸分类测试用来确定粉尘云暴露在点火源环境下发生爆炸的可能性。测试结果将可以区分材料的可燃或不可燃。
Minimum Explosible Concentration (ASTM E151)最小爆炸浓度(ASTM E151)
The Minimum Explosible Concentration (MEC) test determines the lowest concentration of dust cloud in air that can give rise to flame propagation upon ignition. This test answers the question “how easily can an explosible dust cloud be formed?”
最小爆炸浓度(MEC)测试确定的粉尘云在空气中产生火焰传播所需的最小浓度。这个测试可以回答“为何这么容易形成爆炸性粉尘云?”
Minimum Ignition Temperature (ASTM E-2021)最小点火温度(ASTN E-2021)
The Minimum Ignition Temperature (MIT) test determines the lowest temperature capable of igniting a dust dispersed in the form of a cloud. The MIT is an important factor in evaluating the ignition sensitivity of dusts to such ignition sources as heated environments, hot surfaces, and friction sparks.
最小点火温度(MIT)测试确定能点燃扩散的粉尘云所需的最低温度。MIT是一个评价粉尘对加热的环境,高温热表面及摩擦火花等点火源点火感度的重要参数。
Minimum Ignition Energy (ASTM E2019) 最小点火能量(ASTM E 2019)
The Minimum Ignition Energy (MIE) test determines the lowest electrostatic spark energy that is capable of igniting a dust cloud at its optimum concentration for ignition. The test is used primarily to assess the susceptibility of dust clouds to ignition by static sparks.
最小点火能量(MIE)测试确定点燃粉尘云最佳浓度时所需的最小静电火花能量。本试验主要用于评估粉尘云被静电火花点燃的感度。
Electrostatic Volume Resistivity (ASTM D257)静电体电阻率(ASTM D257)
Volume Resistivity classifies powders as low, moderately, or highly insulating. Insulating powders have a propensity to retain static charge and can produce hazardous electrostatic discharges when exposed to grounded facilities, equipment, or personnel.按体积电阻率将粉末分为低,中等或高绝缘。绝缘粉末具有携带静电电荷的特质并能在接触到的设施,设备,人员时产生危害性静电释放。
Electrostatic Chargeability (General Accordance with ASTM D257)静电负荷(与ASTM D257总体一致)
Electrostatic Chargeability is a measure of the propensity of powder particles to become charged when flowing through conveyances or when handled in containers. The test provides data that can be used to develop appropriate materials handling guidelines from an electrostatic hazards point of view.
静电负荷是粉尘粒子在传输过程中流动或用容器进行处理时释放静电的能力。该实验用来提供物质的相应数据,从而从控制静电危害的角度制定处理此类物质的方针。
Limiting Oxidant Concentration极限氧浓度
The Limiting Oxidant Concentration (LOC) test determines the minimum concentration of oxygen (displaced by an inert gas such as nitrogen) capable of supporting combustion. An atmosphere having an oxygen concentration below the LOC is not capable of supporting combustion and thus cannot support a dust explosion. 极限氧浓度(LOC)测试确定能够支持燃烧的最小氧浓度(实验中通过惰性气体进行置换,例如氮气)。低于LOC的大气环境无法燃烧,因此也不能产生粉尘爆炸。
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