Combustible dusts may be found in a variety of sectors, including chemicals, food and beverage, rubber, plastics, and the majority of fossil fuel power plants. They can be found as finely ground organic or metallic particles. Dust explosions may cause terrible damage to a variety of businesses, including the death of workers and innocent bystanders.
The likelihood of dust explosions may be considerably decreased, though, by taking a number of preventative actions. Let's explore each one in turn.
According to the Combustible Dust Incident Reports published by the Dust Safety Science, dust explosions resulted in 163 fires and 53 explosions in 2021, killing 69 people and injured 215 others. Some companies cannot prevent the buildup of flammable dust in a plant due to the nature of their operations and the enormous size of the space. Additionally, processing facilities in many sectors run the danger of producing explosive dust since any solid combustible element can do so.
Any surface in a work area may get covered in combustible dust that has accumulated inside machinery or has escaped from it. And when these accumulations scatter into the air while being near an ignition source, an explosion happens. Dust explosions are therefore a severe safety concern for process companies that work with chemicals that produce flammable dust.
Why Are Dusts Combustible?
OSHA defines combustible dust as "a solid material composed of distinct particles or pieces, regardless of size, shape, or chemical composition, which presents a fire or deflagration hazard when suspended in air or some other oxidising medium over a range of concentrations."
The majority of solid organic materials (sugar, flour, cereals, wood, etc.), many metals (aluminium, bronze, magnesium, zinc, etc.), some non-metallic inorganic materials, and textile fibres (cotton) are often organic or metallic dusts that are finely ground into very small particles.
Generally speaking, some of these compounds are not flammable, but at the correct quantity and concentration, they have the potential to burn or explode. In your workspace, these particles may collect on rafters, roofs, dust collectors, ducts, gaps, drop ceilings, and even other machinery.
What Causes Combustible Dust Explosions?
When tiny particles are exposed to oxygen and come into touch with an ignition source like a spark, metallic ember, or cigarette butt, a dust explosion occurs. Known as deflagration, this quick burning process creates a high-pressure airwave. A deflagration is a common fire, such as one caused by a gas stove, the burning of wood or paper, the combustion of petrol within an automobile's cylinder, etc.
With the speed at which deflagration processes occur, the hot air and gaseous byproducts of fire (carbon dioxide) create an extraordinary atmospheric pressure that may blow down walls and level buildings.
What Makes a Dust Explosion?
A dust explosion requires the presence of five factors, according to OSHA. The explosion won't happen if any of these components is absent.
A fire requires the first three components of the Fire Triangle:
1. flammable fuel (dust);
2. Heat as the ignition source;
3. airborne oxygen (oxidizer);
A combustible dust explosion requires the presence of two factors:
4. the scattering of dust particles in an adequate number and concentration;
5. Restricting the dust cloud.
The "explosion pentagon" is formed when the last two components are added to the fire triangle.
The two eruptions of dust
Primary and secondary explosions are frequently seen in combustible dust explosions. When dust suspended in a small area (duct, tank or collector, processing chamber) is exposed to a heat source, it ignites and bursts, causing the principal explosion to happen first. The initial explosion disrupts and agitates dust that has been inert on various surfaces for a long period of time. This extra dust also ignites and causes the second wave, or secondary explosion, to happen. Because there is such a great quantity and concentration of extra dust available to ignite them, secondary explosions frequently do more damage than first ones.
What Can Be Done To Stop And Manage Dust Explosions?
Due to the nature of their processes and the materials they utilise, dust formation is unavoidable in several industries. According to the Combustible Dust Incident Reports, food production (11.6%), agricultural activities (36.6%), and wood processing and wood products (18.5%) make up the majority of all fire and explosion occurrences in 2021.
The likelihood of dust explosions can be considerably decreased by implementing a number of preventative measures. Risk assessment comes first and is the most crucial of these. These evaluations must take into account a number of factors, such as dust particle size, mode of dispersion, air currents, ignition sources, ventilation system features, containment of the dust cloud, physical barriers, etc. The good news is that today's adjustable risk assessment software may include a thorough dust explosion evaluation that can be tailored to the unique operations and architecture of each organisation.
An enterprise must implement a Risk prevention Plan encompassing the following topics to avoid and control dust explosions:
The method of risk assessment
The following steps should be taken as part of the risk assessment process for dust explosion prevention:
Identify all combustible dust sources, including industrial processes and the materials utilised in those operations.
Find any possible hotspots for flammable dust accumulation, whether they are obvious or not.
Determine the mechanisms that let dust into the air or produce dust clouds,
evaluate the effectiveness of the steps taken to reduce dust collection,
Identify the likelihood and severity of dust becoming a flash fire or explosion threat.
Identify any possible sources of ignition (flames, heat sources, friction points, sparks, electrostatic discharges, etc.),
Calculate the possibility of an explosion or flash fire caused by flammable dust that might harm, maim, or kill employees.
assessment of processes
Examine production procedures including abrasive blasting, cutting, grinding, sieving, polishing, cleaning, etc. that might produce flammable dust (materials and by-products).
In order to regulate hot work (welding, grinding wheel operations, etc.), evaluate the permit-to-work system.
Identifying the origins of ignition
Look for potential ignition sources, such as sparks, fire, flames, stoves, heat sources, welding, etc.
Analyse the possibility of dust forming on or entering electrical enclosures,
Analyse the effectiveness of the no-smoking policy at work.
education and training for workers
When it comes to averting and containing fires and explosions, employees are the first line of defence. They ought to get instruction on the dangers of flammable dust. The business must provide instruction on appropriate cleaning practises, housekeeping regulations, and steps to decrease dust and remove ignite sources.
preliminary information collecting and study
Compile instances of items that have been linked to flammable dust explosions at work that have been published in the literature (such as the USA OSHA flammable Dust poster). Some nations, including Canada, mandate the mention of the potential for flammable dust hazards.
Protocol for cleaning is a crucial component of dust explosion avoidance that is frequently disregarded. Any open spaces and overhanging structures where dust could collect must be kept in mind. Look for concealed areas where dust may collect, such as ducts, equipment for interior ventilation or conveyance, or behind ceilings. The right hoover cleaners (made for low-combustibility organic granules and dust) should be given to the housekeeping staff.
