How to spot and eliminate combustible dust hazards

Nicola Brittain

Preventing dust-related explosions is essential for good plant management, here we provide some tips on how to do just this.

Combustible dust refers to the fine particles that can ignite and explode when suspended in the air in certain concentrations. They come from materials such as wood and plastics and can pose a significant risk to workers and facilities in process manufacturing plants.

Industries at risk might include agriculture, manufacturing, and food processing and combustible dust might be made up of common materials including flour, sugar, coal, and metal powders. The accumulation of dust in confined spaces or on surfaces can create an explosive atmosphere, leading to catastrophic consequences.

Understanding the associated properties and risks

Understanding the properties and risks associated with combustible dust is therefore crucial for maintaining a safe working environment.

The primary hazards of combustible dust include fire and explosions and are most likely to be caused by an electrical spark or other ignition sources, resulting in property damage, injuries, and even fatalities.

When dealing with combustible dust, it’s essential to conduct accurate laboratory testing to determine combustibility or explosibility. Testing helps to indentify hazards associated with the problem, while a thorough risk assessment will help to indentify and mitigate the risks associated with combustible dust at your facility.

A consultancy company called Sigma-HSE, specialises in providing expert consulting and testing services to assess and then manage the likelihood of combustible dust in a processing plant. 

Elements to a combustible dust explosion

There are five key elements to a combustible dust explosion; these  include the conventional fire triangle—fuel, oxidant, and an ignition source —  as well as confinement and dispersion.. When all five elements are present simultaneously, there is a high risk of an explosion. Understanding and managing these elements are crucial for preventing and mitigating the hazards associated with combustible dust in the workplace.

Safety operators should also be aware that an initial explosion can create a shockwave that disturbs settled dust, leading to subsequent explosions. Fuelled by the dispersed dust cloud, the increased surface area of the dispersed dust allows for rapid combustion, resulting in a more extensive and devastating fire.

While the initial explosion will cause damage, it is often the secondary explosion that is most devastating.

As an expert from HSE Sigma explains, ease of ignition must also be understood, taking into consideration factors that include minimum ignition energy; minimum ignition temperature, cloud; minimum ignition temperature, layer and self-heating/thermal instability.

Potential effects of an explosion should be considered

Following this, the potential effects of an explosion should be considered including determining the maximum energy release, pressure exertion, burning velocity, and rate of reaction of the material.

Such insights are crucial for deciding whether protective or preventive measures against explosion events are warranted. Identifying the minimum amount of material required for ignition and managing oxygen levels are other fundamental safety considerations. Understanding the minimum explosible concentration and controlling oxygen levels can also enhance safety by ensuring that combustion processes are adequately supported or suppressed.

To effectively recognise combustible dust hazards, it’s essential to understand the aforementioned signs and be aware of and use preventive measures and hazard control strategies to reduce the likelihood of combustible dust incidents occurring in industrial situations.

Implementing rigorous housekeeping practices, conducting regular equipment inspections, and employing explosion protection measures, such as explosion venting and suppression systems are good ways of doing this.. Similarly, controlling ignition sources, such as sparks from friction or electrical equipment, are also necessary for hazard control.

By prioritising these preventive measures and strategies, businesses can significantly reduce the likelihood of combustible dust incidents thereby creating safer working environments.