When a dust explosion occurs, employees and management are usually caught off‐guard because of the unseen risk factors that are present at the time. Materials that are completely safe can be extremely combustible and potentially deadly in dust form. Industries that are prone to combustible dust particles in the air and on surfaces include pharmaceuticals, chemical processing plants, metals refining, bulk solids handling, food and beverage processing, and furniture manufacturing.
A dust explosion is the rapid combustion of fine particles suspended in the air, often but not always in an enclosed location. Dust explosions can occur where any dispersed powdered combustible material is present in high enough concentrations in the atmosphere or other oxidizing gaseous medium such as oxygen.
These industries and others that are prone to airborne ignitable materials require an explosion protection system that can detect airborne ignitables and diminish the risk of an explosion or fire. A dust explosion can be easily ignited by a small spark from a dull tool, an overheated motor, and an exhaustive list of other destructive combinations. The process of eliminating these risks begins with identifying and testing for explosive dust collections, followed by the installation of an active detection and explosion mitigation system.
According to the Occupational Health and Safety Administration (OHS), ignitable dust is a major cause of industrial fires and explosions, and while these incidents may start as a small, localized fire, they are often the beginnings of a massive chain reaction:
If there’s dust in the area, the primary explosion will cause that dust to become airborne. Then, the dust cloud itself can ignite, causing a secondary explosion that can be many times the size and severity of the primary explosion. If enough dust has accumulated, these secondary explosions have the potential to bring down entire facilities, causing immense damage and fatalities.
A safe plant is one that operates within the acceptable limits of hazardous airborne particulates and has in place a safe method for handling and storing materials that are explosion hazards. This process may begin with an explosibility testing service provider that can help companies identify and mitigate combustible particle explosions.
How an explosion protection system works
Identifying hazardous dust risks
An explosion detection system is one that can recognize the critical warning signs of an imminent dust explosion and makes the decision to activate mitigation protocols. This early identification works to prevent an explosion, and thereby protecting life, limb, an property by detecting sources of ignition. Knowing and eliminating some of the root causes of dust ignition is also considered:
- sparks and arcs from normal equipment operation
- heat‐producing equipment that result in high temperatures
- failure of electrical equipment such as a short circuit
With a specialty fire detection system, innovative equipment that can sample the air for dust particulates, or by using an optical smoke and fire sensor which can sense smoke by using a light source to detect extremely small, scattered smoke particles to sounds an alarm. Explosion detection systems are usually installed in conjunction with special hazards fire suppression systems that will safely extinguish fires while protecting valuable electronic or mission critical assets.
Mitigation of dust explosions
Once the dust particulate levels present a hazardous condition, an explosion can be mitigated or isolated to prevent the spread of ignitable dust and subsequent flames to other areas. This can be accomplished using explosion isolation valves which close upon the detection of an explosion to prevent the travel of dust into other areas. Or the explosion can be isolated by release of a chemical that suppresses the explosion and prevents fire from spreading to adjacent process areas.
With the right specialty fire detection system, a possible dust explosion can be detected in its early stages and mitigated in milliseconds, avoiding costly damage and employee injury or fatality. If the beginning phases of ignition do occur, the secondary line of defense is the fire suppression system that controls the explosion by reducing the build‐up of pressure and prevents the spread of toxic and hazardous dust.