Combustible dust has become a primary focus of OSHA and the National Fire Protection Agency (NFPA) due to the recent explosions resulting in catastrophic damage and loss of human life. An explosion in a sugar refinery claimed 14 lives in February of 2008. Since that time OSHA has created the Nation Emphasis Program (NEP) which focuses on industries working with explosive dust. All manufacturing facilities are required to comply with NFPA 652 by September 7th, 2020 to assist manufactures in identifying fire, flash fire and combustible dust hazards.
Having your dust tested for combustibility is part of the dust hazard analysis to provide designers and engineers vital information. Some important information we need as industrial ventilation design specialist includes; minimum ignition energy (MIE) which tells us the minimum electrical energy measured in millijoules to ignite the dust. The MIE is required as static electricity charge generated in a duct system is enough to provide an ignition source. That’s why for wood dust collection systems the duct should be grounded, or pharmaceutical processes should be using anti-static flex hose.
We can also learn the Kst value from a dust explosion severity test which tells us how high the energy (pressure) will rise over a given period of time. This information is important to establish explosion relief panels and chemical suppression requirements. The higher the Kst value, the more energy is generated over a short period. Think in terms of burning wood. When you use smaller pieces of wood to create fire, the wood will burn faster. That’s because there is more surface area of wood to burn. The volume could be the same. Take a 12 inch diameter log, put it on a fire and it burns slowly. Take the same log split it 18 times and place them all on the fire and the intensity increases.
So what dust do you test? Take a sample of the finished product as mixing chemicals will dry them out or create different compounds that are more explosive when batched. This would be a representative sample of what you’re working with. The test results should be shared with your designer so we can incorporate safety features such as abort gates, isolation dampers, chemical suppression equipment, grounded duct systems, rotary air locks and more.
OSHA states almost 40% of all dust explosions occur in the dust collector. As this is where the fuel resides, the cleaning mechanism can create explosion.
Clean Air can provide a compliant dust collection system design that will be granted approval by your local code official. We can include in our system design;
- Spark detection & suppression
- Isolation gates
- Abort gates
- Explosion vent
- Flameless explosion vent
- Chemical suppression
- Fire break shutters