COMBUSTIBLE DUST: What you must know!
COMBUSTIBLE DUST
Many known materials are hazardous and can also result in big explosions. Combustible dust may be minute and barely visible to the naked eye, but it is among the destructive materials. Combustible dust is the finest material that can cause a dust explosion when it comes in contact with fire and air.
So, any dust particle can become flammable, like sugar, flour, grain, wood, metals, and even non-metallic or inorganic materials. OSHA considers cohesive dust, regardless of particle size, shape, or content, flammable. So, it may result in a fire if not handled with care.
Conditions Required for Combustible Dust Explosions
A dust explosion requires these five conditions:
- A combustible dust
- Highly concentrated dispersion of dust in the air
- Presence of an oxidant, usually atmospheric oxygen
- A source of ignition
- Confined space such as in a building
Sources of Dust
Many common flammable materials, such as coal and sawdust, can emit dust. Additionally, the dispersion of otherwise harmless organic materials can form combustible dust clouds.
These include grain, flour, starch, sugar, powdered milk, cocoa, coffee, and pollen. Aluminum, magnesium, titanium, and other powdered metals can also form explosive suspensions in the air, increasing the risk of explosion.
Dust explosions can result from activities such as transporting grain. Authorities often violently demolish grain silos, increasing the risk of dust explosions. Coal mining leads to coal dust. Flour milling leads to large amounts of flour dust.
A gigantic explosion of flour dust destroyed a mill in Minnesota on May 2, 1878, killing 18 workers at the Washburn A Mill and another four in nearby buildings. Sawmills and other woodworking facilities are exposed to similar risks.
Although not strictly dust, paper particles emitted during processing are also known to pose a dust explosion hazard. Enclosed paper mills exposed to such dangers commonly use humidifiers to reduce the risk of airborne paper dust explosions.
Sources of Ignition
A dust explosion can be ignited through many sources. A naked flame may not necessarily be the only source of a dust explosion. OSHA training will enable workers to identify the most common sources of ignition, include:
- Electrostatic Discharge
- Friction
- Electrical Arcing From Machinery or Other Equipment
- Hot Surfaces
- Fire
- Self-Ignition
However, it is not easy to determine the exact source of ignition when investigating a dust explosion or any other explosion.
Ignition is often attributed to static electricity when a source of explosion cannot be clearly identified.
External sources can generate static charges. They can also be internally generated by friction at the surfaces of particles themselves as they collide or move past one another.
EXAMPLES OF COMBUSTIBLE DUST EXPLOSIONS
Dust explosions may cause fatalities and injuries to employees, as well as the destruction of a whole building. Examples of dust explosions are: in 2010, three workers were killed by a titanium dust explosion in West Virginia.
In 2008, fourteen workers lost their lives in a sugar dust explosion in Georgia. There were 146 fatalities, along with another 114 injuries, due to a metal powder explosion in Kunshan, China, in 2014.
PREVENTION OF DUST EXPLOSION
How to prevent combustible dust explosions; the basis of this prevention is only thorough hazard assessment, according to OSHA. In the prevention studies, the first thing to study is flammable dust control recommendation, which includes implementing an explosive dust inspection in the factory or building with testing of dust and its controlling program.
Dust prevention also encourages the use of proper dust collection systems and filters. To avoid dust particles settling in the vents, roofs, and ceilings, a complete checkup of the ventilation system is required. Keep the working areas clean, facilitate the cleaning process, and use surfaces that minimize dust growth.
During the inspection, provide access to all the areas, including hidden ones like basements, attics, storerooms, etc., and, from time to time, check for dust particles inside and outside.
Make sure to use a vacuum for the cleaning process, and if any source of fire is present near areas, kindly use cleaning methods that do not generate dust clouds.
Prevention of fire is another important task after finding all possible ways of combustible dust existence. Fire safety is necessary for those hazardous conditions and, the first step of preventing required to look for a source of fire in the enclosure.
The ignition source can be controlled using suitable electrical equipment and wiring methods. It also controls static electricity, including bonding equipment to the ground, smoking, open flames, sparks, frictions, and mechanical sparks. Use different devices to remove foreign materials capable of igniting combustibles from process materials.
Constantly remember to separate the dust from heated surfaces and heating systems. Use an equipment preventive maintenance program.
OSHA GUIDELINES
OSHA also provides guidelines for damages and injuries from a combustible dust explosion. Training the workers is the primary and most important thing, and a supervisor is responsible for inspecting the possible circumstances of hazards at the workplace. If an injury occurs, the first response is to remove the victims from the damaged areas.
A fire-specialized suppression system should be installed with the explosion protection system. Activate the spark detection system, develop emergency plans with emergency exit routes, and find first aid. To avoid hazards, organizations must ensure that employers save the lives of their employees and educate and train workers.
