Published March 31, 2024 Authored by Dr. Chris Cloney and Jon Barrett of Dust Safety Science
A picture of a Combustible Dust Fire and Hazard, and bags of Grain, inside a Grain Manufacturing Facility
Key Takeaways:
- Industry Dynamics: The grain and agriculture industry plays a pivotal role in global food production and supply. However, this multifaceted sector also harbors an often-overlooked hazard: combustible dust, derived from the processing and handling of grains and agricultural materials like wheat, corn, barley, and rice.
- Hazards of Combustible Dust: Combustible dust, prevalent in grain facilities, poses a significant risk due to its inherent flammability. Factors such as fine particulate nature, dust suspension in confined spaces, and susceptibility to ignition sources contribute to the potential for explosions or fires.
- Specific Concerns: Grain bins, essential for storing harvested crops, represent a key concern due to the potential for smoldering incidents leading to combustible dust accumulation. Equipment used in handling and processing, such as conveyors and dryers, contributes to dust generation and increases the risk of mechanical sparks, elevating the hazard level.
Understanding the Combustible Dust Hazards in the Grain and Agricultural Industries
The grain and agriculture industry stands as an indispensable cornerstone of our global economy, providing sustenance to populations worldwide and serving as a linchpin for various industries. The Occupational Safety and Health Administration, (OSHA), identifies Grain as a Combustible Dust. Fine particles generated during various stages of grain and agricultural processing, such as mixing, drying, and transporting, constitute the primary source of combustible dust in these facilities. This multifaceted sector encompasses the cultivation, harvesting, processing, and distribution of grains, cereals, oilseeds, flours, and other agricultural commodities. It not only fuels the food supply chain but also contributes significantly to biofuels, animal feed, and various industrial products. However, within this industrious domain lies a hidden risk—a potential hazard that has garnered increased attention over the years: combustible dust.
In the grain and agriculture industry, the presence of combustible dust represents a significant peril. This fine particulate matter is often a byproduct of processing and handling grains or agricultural materials like wheat, corn, barley, and rice, and is inherently combustible. The nature of these materials, when finely ground, such as flour, during various processing stages or stored in silos, elevates the risk of dust accumulation. These particles, when suspended in the air in certain concentrations, as a dust cloud, can ignite swiftly when exposed to an ignition source, triggering dust explosions or fires with devastating consequences. This dust, composed of organic materials, possesses the potential for rapid combustion when exposed to ignition sources, setting the stage for combustible dust explosions or fires within grain processing facilities, silos, or storage areas.
The fine, granular composition of these materials facilitates the dispersion and suspension of dust particles, increasing the likelihood of their interaction with ignition sources such as electrical equipment, friction, sparks, or even static electricity. As grains are processed and handled—whether through milling, grinding, conveying, or storage—a considerable amount of dust is produced. This dust, when allowed to accumulate, creates an environment ripe for disaster. Factors like particle size, concentration in the air, and the presence of oxygen contribute to the combustibility of this dust, emphasizing the critical need for stringent safety protocols and preventive measures.
Moreover, the confined spaces inherent in grain storage facilities and processing plants exacerbate the combustible dust hazard. Grain silos, a fundamental aspect of the industry, provide an enclosed environment where dust accumulation can occur unnoticed. The combination of combustible dust, confined spaces, and potential ignition sources poses a considerable risk to the safety of workers, infrastructure, and surrounding communities. Understanding these specific challenges is pivotal for implementing proactive strategies to mitigate the potential hazards posed by combustible dust in the grain and agriculture sectors.
A picture of the NFPA 61 Guide and the NFPA 61 Standard for the Prevention of Fires and Dust Explosions in Agricultural and Food Processing Facilities
The Grain and Agriculture Industry-Specific Concerns and Root Causes with Combustible Dust
Within the grain and agriculture industry, specific equipment and operational procedures can exacerbate the risks associated with combustible dust. Grain bins, vital structures for storing harvested crops, present a notable concern due to the potential for smoldering incidents. When grains are stored in bulk, heat generated by microbial activity or chemical reactions within the stored material can lead to spontaneous combustion. This smoldering process, if undetected or unmanaged, can accelerate and contribute to the accumulation of combustible dust, augmenting the hazard within the storage facility.
Moreover, the handling and processing equipment used in grain facilities, such as conveyors, grinders, separators, and dryers, can generate significant dust as a byproduct. The intricate machinery involved in these operations increases the risk of friction or mechanical sparks, which, when combined with the combustible dust suspended in the air, heightens the potential for catastrophic incidents.
Combustible dust is a serious workplace hazard that can lead to catastrophic incidents if not properly managed. To mitigate the risks associated with combustible dust, various standards and regulations have been put in place. In the year 1923, was when the NFPA published the first standard on combustible dust, as no national regulations were enacted to address the problem of combustible dust directly, and dust-related explosions and fires, along with loss of life and property, continued to occur. Listed are the important combustible dust standards and regulations, and why they are crucial for the safety of workers and the prevention of industrial disasters:
- NFPA 61, Standard for the Prevention of Fires and Dust Explosions in Agricultural and Food Processing Facilities NFPA 61 protects lives and property from fires and dust explosions in facilities handling, processing, or storing bulk agricultural materials, their by-products, or other agricultural-related dust and materials.
- NFPA 68, Standard on Explosion Protection by Deflagration Venting applies to the design, location, installation, maintenance, and use of devices and systems that vent the combustion gases and pressures resulting from a deflagration within an enclosure so that structural and mechanical damage is minimized. Chapter 8 of the NFPA 68 provides guidance on Venting of Deflagrations of Dusts and Hybrid Mixtures, Effects of Vent Ducts, Bins, Hoppers, and Silos, Venting of Dust Collectors Using Bags, Filters, or Cartridges, Bucket Elevators, Venting Internal to Building with Flame-Arresting and Particulate Retention Device, Venting Silos or Other Storage Vessel Provided with Integral Bin Vents, and Deflagration Venting of Enclosures Interconnected with Pipelines.
- NFPA 654 Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids. The NFPA 654 Standard is referenced by OSHA’s Combustible Dust National Emphasis Program (NEP) to identify dust hazards and define mitigation strategies that help protect life and property. The standard provides industry-recognized safety practices for facility and systems design, process equipment protection, fugitive dust control and housekeeping, ignition source identification and control, fire protection, training and procedures, inspection, and maintenance. Annexes offer guidance on the application of area electrical classification for various dust accumulation levels.
A picture of a detailed analysis and percentages of several Industries, including Grain and Agriculture and Food Products, affected by Combustible Dust, from Dust Safety Science
Historic Grain and Agriculture Industry Related Combustible Dust Explosions
Combustible dust incidents, continue to occur worldwide and in the Grain and Agriculture and Agribusiness industry, as presented in this combustible dust research and incident database from Dust Safety Science. In addition, statistics of the most prevalent industries, regarding combustible dust incidents, are also captured in this Annual Incident Report Database, from Dust Safety Science. During 2022, the Grain and Agriculture dust occurred in 38% of combustible dust incidents. In addition, the Dust Safety Science Podcast educates the public on Safety Share – Explosion at Wood Pellet Receiving Port. Some of the historic Grain and Agriculture Industry combustible dust explosions and incidents include:
- The Great Mill Disaster (1878): Also known as the Washburn A Mill explosion, occurred on May 2, 1878, in Minneapolis, Minnesota, United States Two professors from the University of Minnesota, S. F. Peckham and Louis W. Peck, later confirmed that abundant flour dust had been the cause of the explosion after reviewing controlled experiments regarding flour dust combustion They concluded that two dry millstones had rubbed against each other and caused a spark that ignited the dust, causing the explosion.
- According to the NFPA, the Year 1919 was especially trying. On May 20, a blast at a feed grinding plant in Milwaukee, Wisconsin, destroyed the facility and killed three people. Two days later, in Cedar Rapids, Iowa, an immense explosion—one reportedly felt 30 miles away—levelled the Douglas Starch Works, killing 43 and injuring 30. In September, a large grain elevator in Kansas City, Missouri, exploded, killing 14 and injuring 10. In all of these incidents and many more, dust was identified as the culprit. Source: NFPA Journal A Century of Dust
- The Murray Grain Elevator Explosion of 1919: The Murray Grain Elevator was torn apart by a dust explosion on September 13, 1919, fourteen men were killed and 10 seriously injured. The elevator failed two inspections in the same month and was pronounced ‘dangerous’ both times. After inspecting the damage and interviewing witnesses, they concluded that the explosion originated in the basement. It propagated up through the man lift tower on the side of the elevator and blew out the walls with unusually aggressive force. Pieces of the 16-inch concrete wall were found dozens and, in some cases, hundreds of feet from the site, and the entire working shed was blown away, leaving a demolished grain dryer behind.
Historical incidents of combustible dust explosions within the grain and agriculture industry provide the continuous risks inherent in this vital sector. From grain silos to processing facilities, these incidents have highlighted the devastating consequences of combustible dust accumulation and ignition. Each explosion serves as a stark reminder of the need for continuous vigilance, robust safety protocols, and proactive risk management strategies to prevent future tragedies.
Conclusion
Combustible dust incidents continue to pose significant risks worldwide, particularly in industries such as Grain and Agriculture and Agribusiness. The data compiled in the Dust Safety Science research and incident database sheds light on the prevalence and severity of these incidents, with the Grain and Agriculture Industry accounting for 38% of reported incidents in 2022. Additionally, historic events such as the Great Mill Disaster of 1878 and the Murray Grain Elevator Explosion of 1919 serve as poignant reminders of the catastrophic consequences of combustible dust mishaps. These incidents underscore the critical importance of proactive safety measures and ongoing education to prevent future combustible dust explosion tragedies.
Through incident analysis, it becomes evident that factors such as dust accumulation, confined spaces, equipment malfunction, and ignition sources contribute to the occurrence and severity of these incidents. However, amidst the statistics, there is hope in the form of education, lessons learned, and preventive measures implemented. Industry-wide initiatives, improved equipment design, enhanced ventilation systems, and comprehensive training programs have all played pivotal roles in mitigating the risks associated with combustible dust in the grain and agriculture industry.
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For more from Dr. Chris Cloney on Combustible in the Grain and Agriculture Industry, visit this podcast episode: Typical Hazards in Grain Milling, Sifting, and Sorting Applications With Matt Williamson and Case Study – The Murray Grain Elevator Explosion of 1919
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