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Combustible Dust Hazards and Abatement Techniques There are many different methods of minimizing or eliminating dust hazards at wood pellet facilities, the first of which is a dust hazard analysis. BY ADAM HAROZ
By now, most companies and people throughout the manufacturing sector have heard of combustible dust, as it has become a widely discussed topic. As a review, combustible dust fires and explosions are caused when a combustible atmosphere of dust, or a layer of flammable solids, is introduced to an ignition source. These ignitions can be made worse if there are significant levels of dust accumulation present in surrounding areas, and hazard mitigation techniques are not properly utilized. One of the best ways to identify these dust fire and explosion hazards, as well as being the first step in putting a mitigation action plan together is a combustible dust hazard analysis (DHA). Besides being a great first step, it is also a required one according to the NFPA standards 652 and 61.
Dust Hazard Analysis A DHA is a systematic method for conducting a risk analysis of a facility and process to identify any pieces of equipment and areas that pose potential for combustible dust to be present, as well as identifying the potential ignition sources to which the dust can be exposed. According to NFPA standards, the DHA “shall be led by a qualified person, who possessed a recognized degree, certificate, professional standing, or skill and who, by knowledge, training, and experience, has demonstrated the ability to deal with problems related to the subject matter, the work or project.” Besides the notion of a DHA being a good practice and the requirements to have one conducted in accordance with national consensus standards, there is the question
of “Can these requirements be enforced?” The answer is yes, but not always in the ways industry typically thinks about safety and enforcement. NFPA writes the standards, but they do not have enforcement powers on their own. The Occupational Safety and Health Administration does not have regulations specifically covering combustible dust, though they do have some industry-specific regulations (e.g.,1910.272 for grain handling facilities), as well as a combustible dust National Emphasis Program. NEP states that OSHA prioritizes combustible dust-related inspections and utilizes the general duty clause to cover combustible dust hazards not otherwise covered by regulatory requirements like lockout/tagout, fire protection, electrical, etc. Also, we have been seeing an increase in insurance carriers requiring industrial facilities conduct a DHA before awarding coverage, and local fire marshals and building code enforcement requiring a DHA be conducted to determine building occupancy codes or before awarding a building permit. Hazards and Associated Mitigation Techniques While there are several potential hazards that translate across the manufacturing sector, especially related to combustible dust fires and explosions, there are some inherent to the pellet industry that correlate to the materials and equipment used, as well as some to the particular processing techniques involved. One such example relates to the widespread use of bucket elevators as a method of mechanical conveyance. Bucket elevators commonly have a hazardous dust atmosphere, as they convey dry material. Additionally, there can be quite a few ignition sources present, from a bearing that may overheat, metal buckets that could generate a spark, tramp metal entering the system, etc. In accordance with NFPA 652, some mitigation techniques include: • Bearings should be external. • Elevators should be outside and equipped with protection and venting. • Magnets at the elevator infeed. • Monitors for bearing temperature, with
CONTRIBUTION: The claims and statements made in this article belong exclusively to the author(s) and do not necessarily reflect the views of Pellet Mill Magazine or its advertisers. All questions pertaining to this article should be directed to the author(s). 28 PELLET MILL MAGAZINE | ISSUE 2 2022
