Flour, a well-known product that people use widely in making bread, pizza and snacks, can sometimes turn into a hazardous and fatal “dust bomb”. On May 2, 1878, a tragic explosion stroke the Washburn “A” Mill which was the largest flour mill in the United States at that time. It killed 17 people and pulverized the main building. The mill exploded when flour dust suspended in the air ignited. However, Washburn did not put any dust filters into use, because it didn’t raise much attention on dust explosion precaution even though several explosive incidents had happened in Europe.
Overall, more than 10 explosion incidents occur in the food processing industry yearly in the USA only. Every incident should be a warning for other manufacturers. But why is this happening? And how can Food manufacturers be protected from combustible flour explosions?
We know that 5 elements, namely āExplosion Pentagonā, should be present before a dust explosion happens:
- Combustible dust (fuel)
- Ignition source (heat)
- Oxygen in air (oxidizer)
- Dispersion of dust particles in sufficient quantity and concentration
- Confinement of the dust cloud
Read more Explosion Safety here: Explosion Safety
Basically, when fuel (combustible dust) is dispersed and confined in an enclosed space or building, ignition will result in an explosion, like a flour dust explosion. Regarding flour production, explosions may occur in processing factories where flour dust particles are suspended in air, accumulating into sufficient quantity and concentration (60g/m3), dispersing into a dust cloud, and finally ignited by sources such as frictional heat during the grinding process and sparks generated by surrounding equipment in the plants. For instance turning on a lightbulb can generate a big enough spark to enlighten the dust cloud and cause a flour bomb.
Why is Flour dust (wheat) so explosive?
Wheat dust is highly explosive due to its physical and chemical properties. Hereās why:
- Fine Particles: Wheat dust consists of tiny particles with a large surface area relative to their mass. This makes it highly reactive when exposed to oxygen.
- Combustibility: Wheat dust is organic and contains carbon, which burns easily. When dispersed in the air, the particles can ignite if they reach the right concentration and are exposed to a heat source.
- Suspension in Air: In confined spaces, suspended wheat dust can form an explosive dust cloud. If ignited, the combustion spreads rapidly, leading to a dust explosion.
- High Heat Release: The combustion of wheat dust releases a significant amount of heat and energy, increasing the explosion’s intensity.
- Chain Reaction: A primary explosion can disturb more settled dust, creating secondary explosions, which are often more destructive.
This is why effective dust management, proper ventilation, and explosion mitigation systems are critical in industries handling wheat or similar organic materials.
How can we protect manufacturers from combustible flour explosion?
By taking one of the five elements causing the explosion away. Therefore, a factory should make sure there are no places where flour dust can accumulate. This means smooth ceilings and sloping surfaces. Having the right extraction systems in place, and preferably as close to the dust production as possible.
Take away things that sparks, ignites or creates friction or heat sources. Keep static electricity under control. And make sure that the mechanical and electrical equipment have regular maintenance. Make sure the factory has isolation barriers and that workers are using the appropriately designed screw conveyors.
This is why it is important to have dust collection systems tailored to you specific situation. As all these aspect need to be aligned perfectly for smooth operation. Want to know more about what is important in dust collection systems? Download the Whitepaper below and find out!
