Dust collector fires and explosions can cause tremendous damage to facilities and be fatal for workers caught in the immediate vicinity. These hazards are almost entirely preventable with proper equipment selection, placement and maintenance. Here is what you need to know to protect your workers and your facility.
How Dust Collector Fires Start
All fires need a combination of three elements to ignite and spread: fuel, an ignition source and oxygen. Together, these elements are known as “the fire triangle.”
Dust collectors provide the perfect environment for a fire to start and spread. Many industrial processes requiring dust collection—such as welding, cutting and grinding—also produce a large number of sparks. If these sparks make it through the ductwork to the dust collector, they will find the perfect fuel in the form of filter media and collected dust. Finally, dust collectors are continually pulling air in and through the filter media, creating a steady flow of fresh oxygen into the machine.
Preventing Dust Collector Fires
To prevent fires from starting or spreading, you need to shut down one or more of the legs of the “fire triangle.” An ideal fire prevention system addresses all three.
Step 1: Stop the Sparks
The first priority is to stop sparks from reaching the filter media or collected particulate. If your processes have the potential to generate sparks, even in small numbers, your duct system or dust collector should be fitted with a spark arrestance system.
Spark arrestors work by impeding the journey of the spark through the ductwork, actively stripping it of its thermal envelope and allowing the flaming particle to cool to safe temperatures before it reaches flammable material. Common approaches include:
- Plates placed in front of the duct inlet to deflect sparks from entering the ductwork
- Baffles and metal mesh filters that bounce the sparks off multiple metal surfaces to extinguish the spark
- Fixed-blade mixing vanes that create strong turbulence in the air stream to cool the spark
The RoboVent Delta3 Spark Arrestance System was developed using Computational Fluid Dynamics (CFD) and extensive laboratory and field testing to find the right balance of forces to extinguish practically 100% of sparks.
Step 2: Cut off Access to the Fuel Supply
Fire suppression systems may also include elements that provide a physical separation between the fire and additional fuel. Damper systems provide a physical barrier between the cabinet and ductwork.
Step 3: Eliminate Oxygen
Effective spark arrestance will substantially reduce your fire risk. However, in the event that a spark does make it through, you need a backup plan. The next step in fire safety is eliminating sources of oxygen to smother the developing fire before it can spread. Dust collectors should be equipped with temperature or smoke sensors (or both) that quickly detect smoldering within the filter media or cabinet. These sensors, in addition to sounding an alarm, can trigger systems that cut off the airflow.
- Blowers should automatically shut down when a possible fire is detected so oxygen is no longer actively flowing into the machine.
- Automated damper systems can shut down airflow immediately while a heavy fan wheel is still slowing down.
- Fire suppression systems smother the fire using water, carbon dioxide or a chemical fire suppressant. These are the last line of defense in a dust collector fire. They may not extinguish the fire completely, but are designed to keep it suppressed until professional firefighters arrive.
Fire Suppression Options
Internal, automated fire suppression systems are an essential fire safety element. There are three basic types of fire suppression systems to choose from.
- Sprinkler System: A water-based sprinkler system is a simple and economical option for dust collector fire suppression. The sprinkler head port is mounted directly into the filter cabinet and connected to the facility water system. It sprays the cabinet with water if a fire is detected, extinguishing the flames.
- CO2 Fire Suppression: Carbon dioxide (CO2) gas smothers the fire by displacing the oxygen. Look for a heat-activated system that does not require external power. CO2 is cleaner than a sprinkler system, avoiding the potential mess of water inside the filter cabinet.
- Chemical Fire Suppression: Chemical systems like the RoboVent Suprex-200™ Fire Suppression System are even more effective than CO2 systems. They can target fire suppressant chemicals right where they are needed as soon as a fire is detected. Look for a clean-agent system with chemicals that are not harmful to humans, have minimal environmental impact, and do not leave hard-to-clean powder deposits.
Working with Combustible Dusts
Combustible dusts are, by definition, susceptible to combustion via fire or explosion. If you are working with combustible dusts, you must have a system design and configuration that complies with NFPA standards. These systems often include the following components:
- Explosion vents to safely release pressure in the event of an explosion.
- Rotary airlocks between the dust containment drums and the main dust collector cabinet to prevent the deflagration from propagating in the event of an explosion.
- Isolation valves in between the filter compartment and the facility ductwork to prevent fires or a pressure wave from a deflagration from spreading back through the ductwork into the facility, potentially causing additional damage.
Read more about combustible dust safety.
Safety First: Putting Together a Dust Collector Fire Safety Plan
Dust collector fires can cause tens of hundreds of thousands of dollars in facility damage and put lives in danger. Make sure you have an adequate fire prevention strategy in place. You also need to ensure that your dust collector system design meets all applicable OSHA and NFPA standards for dust collector fire safety.
RoboVent can help you design a dust collection system that is fully compliant with industry standards and guidelines for fire prevention and select the right combination of fire safety elements for your application and dust type. Talk to a RoboVent expert today.