43 www.drivesncontrols.com February 2024 HAZARDOUS AREAS n Containing the risk of sugar explosions In 2008, there was an explosion in a sugar re nery in the US in which 14 people died. Sugar production is more dangerous than most people realise, involving combustible dust which has the potential to explode or burn. The disaster was a turning point in raising awareness of dust explosions – but are manufacturers doing all they can to mitigate the risks? Sugar is combustible when it is nely divided or dispersed as dust clouds in air. Because of this, dust explosions can occur throughout the production process – including during heating, sieving, transferring, loading or storing. This makes it imperative to apply safety regulations and to comply with Atex regulations. The Atex (atmosphere explosible) directives are two EU regulations that, since they were established in 2003, prescribe the minimum safety requirements for workplaces and equipment used in explosive atmospheres. Key Atex regulations include Category 2D for hazardous areas (high-risk powder and dust) and 3D for medium-risk areas. The regulations have a vital role in plants producing or using combustible materials such as our or sugar. The potential for industrial disasters needs to be avoided at all costs. Fortunately, material-handling equipment can help to achieve this. Lessons learned Sugar cane re neries, and sugar beet factories, use a variety of automated material-handling technologies such as bucket elevators, conveyors and sieves. These systems are used to lter or transport the sugar to dierent parts of the production process, often in large volumes. It’s vital that dust leakages are minimised. But how do explosions in sugar re neries occur? To answer this question, the Health and Safety Executive and Health Services Laboratories, produced a study in a 2008 called Dust Explosion in Sugar Silo Tower: Investigation and Lessons Learnt. It examined a dust explosion that occurred in a sugar re nery in Norfolk in 2003. “Evidence suggests that from the very early stages, the explosion progressed through the system in both directions,” states the report. “Because of the linking chute, the pressure in the production/bulk export elevators would also have increased during these early stages and airow and vibration would begin to stir up sugar nes to form an explosive cloud.” Exposure to oxygen and an ignition source caused the cloud of sugar nes to combust. To avoid this, the report recommends using sealed or closed chutes and feeders to prevent dust from escaping and making contact with the air. Closed feeders can also transport the sugar more accurately and consistently without leaks or spillages. The equipment should be earthed to reduce the risk of ignition by an electrostatic charge. But what about the other main contributing factor cited in the report – vibration? Vibrations caused by equipment are an issue in food manufacturing, with raw materials being prone to spoilage and spillage. Manufacturers can use techniques such as condition monitoring to assess these vibrations. This is useful for preventative maintenance, to predict the health of the machinery, and to anticipate when it might break down or need maintenance. But, in sugar re ning, vibrations are a more pressing issue than merely causing spillages. In some circumstances, vibrations can create combustible dust clouds. Managing dust emissions is one the biggest challenges when conveying powders. To address this challenge, Gough Engineering has developed an automated conveying system known as a tubular feeder. It uses covers, with gaps sealed as much as possible, to reduce dust to reasonable levels during the conveying process. The enclosed system gives a smooth, consistent and predictable product feed. It prevents combustible products, such as sugar nes, from reaching the external atmosphere. Twin vibrator motors mounted on roster mounts or coil springs produce a smooth vibration that feeds granular and powdered products through harsh environments. There are no exposed moving parts, so the risks of damage or contamination are much lower than with open feeders. Removable end-caps make cleaning quick and safe. Choosing the right material-handling equipment for production lines depends on a variety of factors, including the transported material’s particle properties and behaviour. Another vital consideration is the equipment’s design, such as its vibratory motion and drive mechanisms, and whether it complies with the Atex directives. n Stephen Harding, managing director of Gough Engineering, explains the vital role that materialshandling equipment can play in improving worker safety and reducing the risk of explosive incidents when transporting powdery materials such as sugar and our. Conveying explosive materials such as sugar in sealed systems reduces the risk of accidents
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