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16 / May 2020 powderbulk.com DUST DOCTOR PBE A brief introduction to dust collection hoods John A. Constance The Engineers Collaborative carries that dust to the exhaust duct system. It doesn't matter if the dust collection system has the proper exhaust air quantity available or the ductwork is sized properly. If the dust capture hood isn't well-engi- neered and -designed, the system won't be effective. Concerns with canopy hoods If a dust-generating source such as a hot furnace or open-top melt- ing pot emits hot, contaminated air, the air will rise due to thermal buoyancy. This is where installing a canopy hood over the contam- inated air source can be effective — if properly designed. A can- opy hood, which is installed on a wall or suspended from above, is a hood specifically designed to capture and exhaust dust, fumes, and vapors from a hot process that isn't enclosed. Other hoods, such as side draft hoods, would typically fail where canopy hoods succeed because side draft hoods have difficulty capturing contam- inants thermally driven upward. The industrial ventilation manual provides the necessary details for designing a canopy hood, includ- ing explanations of different hood types, the dimensions needed for hoods along with diagrams, and the equations needed to figure out the best fit for your process. While T he manual Industrial Ventila- tion: A Manual of Recommended Practice for Design, published by the American Conference of Governmental Industrial Hygien- ists (ACGIH), is probably the most well-known textbook on the topic of industrial ventilation. Its cover- age of dust collection topics — such as capture hood design, ductwork design, and exhaust fan and air cleaning equipment selection — is extensive. The manual discusses ventilation's general principles, which cover supply and exhaust systems, airflow, acceleration of air and hood entry losses, duct losses, and multiple-hood exhaust systems. By following the principles set forth in the manual and properly applying them to your actual dust collection issue, you can engineer and design an effective dust collec- tion system. Some dust collection systems used by manufacturers in the powder and bulk solids industry — manufacturers of food, pharma- ceuticals, chemicals, and cosmetics — fail in getting the desired results. Many times, these systems fail because the dust capture hoods aren't properly doing their job; they haven't been accurately fitted for the application at hand. A dust cap- ture hood is a hood that captures dust or contaminated air and then • Lean, dense phase, plug-flow conveying of powders & small particles • Gentle - segregation & damage free • Conveying rates up to 10,000 lbs/hr • Safe, explosion free • Quiet, hygienic, reliable • No tools assembly Simply the best vacuum conveyor 609-265-0101 www.volkmannUSA.com PUT US TO THE TEST Volkmann_PBE_two-color-ad-May-2020.indd 1 3/30/20 4:04 PM