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Preventing explosions with gentle handling

06 November 2023

In 2008 an explosion in a sugar refinery near Georgia in the US killed 14 people. The disaster was a turning-point in raising awareness of dust explosions — but are UK food manufacturers doing all they can to mitigate the risks? Stephen Harding discusses the role materials handling equipment has to play in improving worker safety and reducing the risk of hazardous incidents.

When it is finely divided or dispersed as dust clouds in air sugar is combustible. Because of this, dust explosions can occur throughout the sugar production process — including during heating, sieving, transferring, loading or storing. This means that safety regulations need to be strictlyadhered to. 

The ATEX directives — short for Atmosphere Explosible — are two EU regulations that, since they were established in 2003, prescribe the minimum safety requirements for workplaces and equipment used in explosive atmospheres. The regulations have a vital place in the food and drink industry where workers can be exposed to daily risks. 

A 2008 joint study by the Health and Safety Executive (HSE) and Health Services Laboratories (HSL), Dust Explosion in Sugar Silo Tower: Investigation and Lessons Learnt, examined a dust explosion that occurred in a British sugar refinery in Norfolk, UK, in 2003. “Evidence suggests that from the very early stages, the explosion progressed through the system in both directions,” stated the report. “Because of the linking chute, the pressure in the production/bulk export elevators would also have increased during these early stages and airflow and vibration would begin to stir up sugar fines to form an explosive cloud.”

Exposure to oxygen and an ignition source caused the cloud of sugar fines to combust. To avoid this, a recommended solution is the use of sealed, or closed, chutes and feeders that 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 also be earthed to reduce risk of an igniting electrostatic charge.

But what about the other main contributing factor cited in the HSE and HSL’s report: vibration? Today smart sensors are able to assess the vibrations caused by equipment. This is useful for preventative maintenance, to predict the health of machinery and anticipate when it might breakdown or require maintenance. 

But, vibrations are a more pressing issue than a cause for spillages in sugar refining. In some circumstances, vibrations can create combustible dust clouds. 

Automated conveying 
Managing dust emissions is one the biggest challenges in conveying powders. To address the above challenges, Gough Engineering has developed an automated conveying system that is fully enclosed to reduce dust to reasonable levels during the conveying process. The system is driven by twin vibrator motors mounted on roster mounts or coil springs which gives a smooth vibration for feeding granular and powdered products through harsh environments. 

Choosing the right material handling equipment for a production line will depend on a variety of different factors, including the transported food material’s particles, properties and behaviour. But another consideration is the equipment’s design –, such as its vibratory motion type and drive mechanism – and whether it complies with the ATEX directives. Key ATEX regulations include ATEX Category 2D for hazardous areas categorised by high-risk power and dust, and Category 3D for areas with medium-risk powder or dust. 

Stephen Harding is managing director at Gough Engineering.


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