Combustible Dust: Fire and Explosion Prevention Requires a Comprehensive Approach|
Article- June 2012 By Magnalight.com
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Most people are aware in some way or another of the problems that dust and dirt accumulations can present. We regularly dust off our furniture, we remark with disgust on how filthy the top of the refrigerator has become, we groan in dismay when the day after washing the care it is covered in a film of dusty grime. However, when it comes to the workplace, dust suddenly seems to become invisible and we pay it little mind until either a serious problem arises or we find ourselves in the midst of a cleaning program. Particularly in the industrial workspace where machining and manufacturing is a part of daily operations, dust is something that for all intents should always be a foremost concern.
The problems that dust in the industrial work area present are numerous and range from cost and maintenance concerns to safety and health issues. Dusts can increase maintenance costs by speeding the wear of machinery as it gets into moving parts like bearings, or clogs air intakes and fans and causes overheating, which in turn increases the frequency of needed servicing. As well as increasing the costs of repairs, maintenance costs are also increased by the need to frequently perform cleaning and inspections to ensure dust accumulations do not reach problematic levels.
Dusts in the industrial workplace can also pose serious problems with increased risk of fires and explosions, and this is probably the most acute area of concern for any operation where combustible dusts are created. There are many well documented instances of explosions and fires as a result of combustible dust accumulation and poor preventative and control procedures. Although reliable hard data is in truth somewhat scarce and figures from OSHA considered low, media reports and investigation suggest as many as 10 combustible dust related incidence per week occur. Certainly, new reports make clear the hazards with more severe instances appearing at least several times a year in news stories and special reports.
The dangers of combustible dusts range from minor fires that can disrupt operations and potentially injure workers, to major explosions and conflagrations where entire facilities and surrounding properties are damaged or destroyed and fatalities occur. Since 1980 there have been at least 350 combustible dust explosions in the US, and some media reports put that number higher, with an average of 10 occurring every week. On Oct, 29, 2003, the Hayes Lemmerz factory in Huntington, Ind., exploded due to the ignition of accumulated aluminum dust produced by the manufacture of aluminum wheels. In 2003, 15 people died in combustible dust explosions. Another explosion in 2003 occurred at West Pharmaceutical Industries in Kinston, N.C when approximately a ton of plastics dust which had accumulated in the buildings ceiling ignited.
Incidents such as these and many others underscore the severity of the combustible dust problem. Given the well established nature of combustible dust and its prevalence in the industrial workspace, one would assume that such explosive material would be as heavily addressed by OSHA as are other flammable compounds such as petrochemicals or solvents. In fact, OSHA has in place clear guidelines and regulations regarding flammable liquids, vapors and gases in the industrial workplace, but when it comes to combustible dusts such detailed efforts at control and prevention are obvious only by the lack of their presence. Although Hazardous Location Classifications do indeed include dusts in their descriptions, standards and regulation specifically regarding the actual control and management of dusts in the workplace is lacking.
OSHA’s traditional stance on dust safety has been to refer to their established “housekeeping standard”, which in essence takes a proactive approach by emphasizing control and cleanup of dust to prevent dangerous dust accumulations and suspension which can lead to fires and explosions. The problem here however, is that this is not a comprehensive or reliable way to address the problems presented by combustible dusts. Even with good housekeeping practices in place, it is still possible to unseen and unrealized dust threats to exist and create the potential for dangerous ignitions.
To more fully address the problems of combustible dusts it is necessary to operators to acknowledge the lack of cohesive regulation and guidelines and take a more proactive and independent approach. A good starting point would be to consider the well known “Fire triangle”, which tells us that Heat, Fuel, and Oxygen must be present for a fire to exist and work from there to collapse at least two sides of the triangle if possible to achieve effective ignition prevention. Good housekeeping practices do in fact work to help remove one side of the fire triangle, however, as we noted earlier it is still possible for the danger to exist dues to the ease with which mistakes and unforeseen issues can occur.
A more effective route takes into account more than one side of the fire triangle and removes as many sides as possible in order to achieve a higher and more reliable level of protection. With good housekeeping practices in place which represents removing fuel, we are left with oxygen and heat as potential areas to address. Since removing oxygen is impractical under all but the most controlled of conditions, we are left with removing heat, also known as sources of ignition. Ignition sources with combustible dusts can be anything electrical, from the small spark created by turning on a power switch to the heat created by a light fixture. Additionally, since dust can accumulate in layers and act as an insulator, equipment which normally operates at safe temperatures can become a potential ignition source if dust accumulates in sufficient quantities and prevents the normal dissipation of heat from the device. A classic example of this is the accumulation of dust on top of high bay light fixtures where it is difficult to detect and can eventually lead to overheating of the fixture and eventual ignition.
As a result, operators need to not only practice good housekeeping, but commit to utilizing the proper explosion proof lighting, hazardous location approved electrical equipment, and ensuring employees are trained in the proper use of such equipment in hazardous atmospheres where combustible dusts are present. By combining both good housekeeping and ensuring the installation of and proper use of explosion proof approved lighting and equipment, two sides of the fire triangle are collapsed, and the highest possible protection against combustible dust ignition is achieved.