Issue link: https://www.e-digitaleditions.com/i/1380119
28 / June 2021 powderbulk.com vention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids. Not only must a DHA be completed for new processes, but the NFPA also requires DHA updates every 5 years. Using the results from your DHA, a dust collector man- ufacturer can design your dust management equipment in a way that mitigates the risk of a dust explosion. Identify dust collection points Identifying the main places where dust is produced in your process is vital to dust management, as collecting the dust at its source is the most efficient means of air pollution control. Mapping out the areas and processes that are generating dust will allow you to determine where your primary collection points should be. Dust collection points include obvious dust- generating material handling equipment, such as conveyor belts, bucket elevators, bagging equipment, or pneumatic conveyors, and any grinding, screening, or drying equipment. The specific dust collection point for your equipment type can be found by consulting Indus- trial Ventilation: A Manual of Recommended Practice for Design by the ACGIH. Taking a proactive approach with your current system setup so that it offers sufficient capacity for any additional collection points that may need to be added in the future is best practice. Bulk density, commonly expressed in grams per cubic centimeter (g/cm 3 ) or in pounds per cubic foot (lb/ft 3 ), is a weight-per-unit-volume measurement. Knowing your dust's bulk density is important because a high bulk density dust requires a more powerful and higher energy dust management system than a low bulk density dust. By quantifying your dust's bulk or apparent density, you can request that your filter vendor create specialty filters that are optimized for your dust collection needs and allow you to more easily diagnose any dust re-entrainment issues, which is when the dust is mixed back into the original airstream. Particle size distribution refers to the particle size range present in a dust sample. This is typically expressed in terms of particle size versus the cumu- lative percentage of total weight or volume. Plotting a sample's particle size distribution on a log-probability graph allows you to determine the dust particles' mass- mean diameter, which quantifies the average particle size of the mass that you're analyzing. For example, lime- stone typically has a fairly large particle size range, with some fine and some fairly large particles, while carbon black has a very narrow range of fine particles. Particle size distribution and the resulting mass-mean diameter can be used to predict filter performance and thus serve as good theoretical qualification prior to other physical tests such as a bag filter failure analysis. The finer and narrower your particle size distribution, the more efficient your filter media needs to be. A particle analysis can be done by an independent lab or a filter media supplier if you provide them with an appropriate dust sample. The analysis will result in a particle analysis report, similar to the example shown in Figure 1. Perform a dust hazards analysis If you're handling combustible dust, then you'll need to perform a dust hazards analysis (DHA) to stay com- pliant with regulations. A DHA is a systemic review of your facility and processes to identify any potential combustible dust hazards with the goal of improving facility safety. In addition to OSHA-led initiatives, the National Fire Protection Association (NFPA) recently implemented NFPA 652: Standard on the Fundamentals of Combustible Dust, which requires that all applicable facilities that have the potential for a dust explosion perform a DHA. NFPA 652 creates a unique standard separate from industry- and commodity-specific regulations by build- ing upon other standards, such as NFPA 61: Standard for the Prevention of Fires and Dust Explosions in Agricultural and Food Processing Facilities; NFPA 484: Standard for Combustible Metals; and NFPA 654: Standard for the Pre- FIGURE 1 A particle analysis report example