Explosive dusts are one of the biggest hazards in the dust collecting industry. An inadequate dust collector can cause losses of life and great damage to property. In 2008, the Georgia Imperial Sugar refinery explosion was an industrial disaster and one of the biggest dust collector explosions ever seen. A total of fourteen people lost their lives and forty were injured by the explosion. According to many investigations, this was due to negligence and indifference on behalf of Imperial Sugar and could easily have been avoided. Adequate equipment and a dust collector could have saved the lives lost on February 7th, 2008.
Here are ways to understand and identify explosive dusts and how to prevent fatal accidents.
What is combustible dust?
To put it simply, combustible dust is any fine material that can catch fire and create an explosion when it is mixed with air. Many of these materials would never be suspected of being explosive, but in the right size and the right quantity, they become a very big risk.
We could divide these dusts into three categories, solid organic materials, metals, and non-metallic inorganic material.
Here are just some examples of combustible dusts:
|Solid Organic Materials||Sugar, Flour, Grain, Wood|
|Metals||Aluminium, Magnesium, Manganese, Zinc|
|Non-metallic Inorganic Materials||Textile Fiber, Polyester Dust, Cement, Epoxy|
To learn more about combustible dusts, refer to the OSHA combustible dust poster. They present a very helpful and complete list of potential combustible dusts.
Why does my dust explode?
To be explosive, dust needs five very particular conditions. The dust explosion pentagon helps show how these five conditions interact with each other to create an explosion.
- Dust: This is the source of all dust collector explosions, dust acts as a fuel and combustion to continue burning. The difference with a fire and an explosion, in our case, is that a fire burns static material whereas explosions come from the rapid ignition of multiple dust particles creating an intense hot expansion of fire and pressure. For this, a cloud of dust is required. This dust can be from metal, flour, sugar, wood or even sand.
- Oxidant: One of the most basic elements for a fire to burn is oxygen, which is found practically everywhere. This element is a necessary component of air to breath, making it very hard to remove from the work environment and even harder to remove from the dust explosion pentagon.
- Ignition: The ignition is the starter for all other elements to create an explosion. The smallest spark is necessary to create a deadly explosion, whether it be small pieces of metal coming into contact with each other, static electricity or even a cigarette. The explosion can also come from overheating, which ignites something near by.
- Dispersion: This happens when the dust entering the collector and the accumulated dust spread out in the air and create dust clouds. This kind of disturbance can be caused by simple daily activities like using compressed air or sweeping. Dispersion can also happen when a very small explosion sends stagnant dust into the air creating a much bigger explosion.
- Confinement: The space holding the dust can range from a small dust collector to a whole warehouse or even a factory. An ignition of the dust confined in an enclosed space such as a dust collector will cause a rapid expansion of the cloud. Due to the confined space, the overpressure will keep rising until the dust collector literally explodes. The dust suspended in the air can accumulate over a period of days and create a bigger explosion. When the cloud combusts, the pressure can be so intense, it has been seen where roofs from buildings have lifted.
Knowing all the potential factors is key to saving lives and money, which is why referring to a professional for dust collecting should be a top priority.
How do I prevent explosions?
To prevent a dust explosion, you need to prevent at least one of the five elements of the dust explosion pentagon. The key is always proper cleaning of the combustible dusts. Without fuel, the explosion cannot occur, the events of a fire are also much less likely to happen. For hazardous dust cleaning, the NFPA 654 standard outlines the best methods of cleaning, which should be executed by a trained professional. Any type of open flame or potential spark source should be removed, and equipment overheat must be monitored at all times.