Miller Magazine Issue: 135 March 2021

76 ARTICLE MILLER / march 2021 secondary explosion, which starts with the puncture of the wall of the equipment, such as silos, pipes and etc., spreads to the whole enterprise within approximately 200 ms. Fire triangle is the combination of combustible mate- rial (fuel), caustic material (oxygen) and ignition (igni- tion source) which are required for a normal combus- tion event to start and continue. In dust explosions, five different chains have to come together in order to create an explosive at- mosphere [10]. These are; • Explosive atmosphere (confined space) • Explosive materials (Organic substances such as food and agricultural products, synthetic organics such as pesticides, pigments and plastics, -Coal etc.) • Explosive Dust concentration (dust cloud hung in the air) • Spark or energy source that will ignite the explo- sive atmosphere. • Air (sufficient amount of oxygen) This is called the explosion pentagon. If any of these five components can be prevented from interacting with each other, the risk of explosion will be eliminated. The first precaution to be taken in protection from dust explosions is to isolate the mentioned environments from each other and avoid formation of explosions. However, if there is still a risk of explosion, counter- measures must be taken. It has been reported that ef- fects such as electric arcs and/or sparks, hot surfaces, sparks caused by friction and static electricity that may come from electrical devices are sufficient for the dust in enterprises to explode [10]. For example, selecting spark-free devices and/or isolating such devices (use of ex-proof units) could be a solution. However, in order to limit the impact of explosion, measures such as es- tablishing explosion-proof structures, fire extinguish- ing installations and isolating the environments where explosion may occur from other regions have been rec- ommended [10]. Pursuant to the regulations in force in Turkey (Reg- ulation on Equipment and Protective Systems Used in Possible Explosive Atmospheres (2014/34/EU), it is necessary to create a risk matrix considering the prob- ability of the ignition source to be activated, the ex- plosion concentration in the environment, the duration the explosive material is kept and the effect that will occur as shown in Figure 1 and take measures accord- ingly. 2. Reasons of Dust Explosions In Tables 1-4, the reasons of dust explosions, the sectors most affected by dust explosions, the facilities where dust explosions are observed and the properties of various explosive dusts in the food sector are pre- sented respectively. As it is seen, there is a risk of dust explosion in almost all industries. In a sector such as Figure– 4: Explosion pentagon [18] Figure – 5: Risk Matrix [14] Risk Matrix Damage Effect Level Very Slight Slight Moderate Severe Very Severe Very Small Low Low Low Low Low Small Low Low Low Moderate Moderate Moderate Low Low Moderate Moderate High High Low Moderate Moderate High High Very High Low Moderate High High Unpredictable Possibility Figure – 3: Fire triangle [17]