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PROCESSING
Minimising the risk of dust explosion on
food conveyors Del Williams
On conveyor systems in the food processing industry, some powdered and bulk solid materials can be ignition sensitive in specific concentrations (ie, grains, sugar, creamer, etc), particularly when exposed to static electricity discharge. A key point of concern is conveyor system connection points such as inlets, outlets and storage bins. Here, the concentration of dust can become sufficiently high for a deflagration to occur with accidental exposure to an ignition source, such as static electricity, a spark, flame or even high heat or friction.
T
he characteristics of the material conveyed and the type of conveyor along with its associated component parts and connection points should be considered in the system’s design to avoid a serious risk of dust combustion and explosion. By carefully selecting and integrating the conveyor system and its components, food processors can help to minimise the risk of dust explosions while safely conveying materials in a hygienic and energy-efficient manner. “When conveying powders, understanding the requirements is critical because an explosion can injure people as well as destroy essential equipment, causing lengthy downtime. So, any conveyor system that handles such material must be designed and engineered to comply with all safety codes and have dust mitigation procedures in place,” said Gary Schliebs, a Process Engineer and Director of Plus One Percent…Engineered Solu22
January/February 2022
tions, a consulting firm that works in the food industry and markets food industry conveyor equipment. Ignition sensitivity One of the key factors in determining the risk for dust explosion is the product’s sensitivity to static electricity discharge in specific concentrations and fuel-to-air ratios, as well as its sensitivity to ignition in ambient air or processing conditions. In general, static electricity can ignite a combustible dust cloud inside a food processing conveyor system if the minimum ignition energy of the dust is very low. Powder and dust conveyed at high-velocity speeds through metal pipe or ducting can build up an electrostatic charge in the dust and potentially ignite. Because static charge can accumulate at different points in the system, the equipment should be fully grounded to earth so it does not discharge into the line.
www.foodprocessing.com.au
