Dust explosions occurs due to the rapid combustion of high concentrations of combustible dust particles in an enclosed space. When mixed with oxygen, these fine particles can be ignited when they come into contact with a spark or any other ignition source. Known as deflagration, the quick combustion process leads to a high-pressure airwave.
Deflagration, or rapid combustion, is not only caused by the presence of oxygen, heat and fuel (dust). It can also be caused by the dispersion of dust particles in sufficient quantity and concentration. If deflagration occurs in an enclosure such as in a room, vessel or a process equipment, the resulting pressure rise may lead to an explosion. Based on the "Dust Explosion Pentagon", an explosion can occur when all five factors are present: Oxygen, heat, fuel, dispersion and confinement.
Common materials that are susceptible to fire such as coal and sawdust, can potentially generate a dust explosion. Organic materials which may seem mundane such as grain, sugar, starch, corn starch peat, flour, soot and pollen can also be dispersed into a hazardous dust cloud. Another example is powdered metals including Aluminium, Magnesium, Zinc, Iron Carbonyl and Titanium, which can create explosive suspensions in air when they are finely divided.
Some examples of workplaces and industries which face a greater risk of dust explosions include but is not limited to the following:
• Put in place a hazardous dust inspection, testing, housekeeping, and control programme;
• Utilise proper dust collection systems & filters;
• Reduce the dust escaping from process equipment or ventilation systems;
• Utilise surfaces that help to reduce dust accumulation and facilitate cleaning;
• Perform regular inspection for dust residues in both open and hidden areas;
• Only use vacuum cleaners that have been approved for dust collection; and
• Situate relief valves away from dust deposits.
• Utilise appropriate frame-proof equipment or non-sparking tools in areas which handle combustible powders;
• Control static electricity, this includes the bonding of equipment to ground;
• Regulate smoking, open flames, and sparks;
• Regulate mechanical sparks and friction;
• Remove foreign materials susceptible to igniting combustibles from process materials with the usage of separator devices;
• Isolate heated surfaces or heating systems away from dusts; and
• Put in place an equipment preventive maintenance programme.
• Separate the hazard by isolating with distance;
• Segregate the hazard by isolating with a barrier;
• Put in place deflagration isolation/venting;
• Install pressure relief venting for equipment;
• Move vents away from working areas;
• Install specialised fire suppression systems;
• Install explosion protection systems;
• Implement spark/ember detection for suppression activation; and
• Develop an emergency response plan.
• Provide training and refresher courses on combustible dust hazards and its controls for people who are involved in working with combustible dusts.
• Communicate the combustible dust hazards, its physical properties, safe handling practices and precautions to be taken.
Organisations that are aware of the hazards of combustible dusts and how to manage or eliminate the dangers they pose can effectively avoid the catastrophic effects of dust explosions: the loss of life and property, injury, interrupted production, damages, litigation and adverse publicity.
There have been several incidents, one in the recent past, which was caused by "a combustible dust explosion", leading to fatal workplace incident, further highlighting the importance of workplace safety. It is the duty and responsibility of the employers to look after the health and safety of employees at work.
As a SAC-accredited certification body with extensive experience in auditing and certifying against ISO management systems, TÜV SÜD PSB Singapore can support organisations in improving the levels of workplace safety, preventing injuries in workplaces and putting in place a global standard of quality and safety management system:
Contact us today to improve workplace safety!
Author:
Chin Chee Chow
Senior Auditor & Team Lead
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