In some cases, additional information such as test results will be available from chemical manufacturers. Different dusts of the same chemical material will have different ignitability and explosibility characteristics, depending upon many variables such as particle size, shape, and moisture content. Additionally, these variables can change while the material is passing through process equipment. For this reason, published tables of dust explosibility data may be of limited practical value.
In some cases, dusts will be combustible even if the particle size is larger than that specified in the NFPA definition, especially if the material is fibrous. Industrial settings may contain high-energy ignition sources such as welding torches. In these situations, test methods for dust ignition and explosion characteristics from ASTM International originally the American Society for Testing and Materials would be of value.
Combustible Dust Fires and Explosions: Recent Data and Lessons Learned
A discussion of these test methods is in reference 8, and the relevant OSHA and other standards are listed in the "Sources of Additional Information" section of this document. The facility analysis must identify areas requiring special electrical equipment classification due to the presence or potential presence of combustible dust.
However, NFPA 70 does not define combustible dusts. The overall dust hazard designation for electrical requirements is Class II. This is further broken down into Divisions which represent the probability of dust being present at any given time. Additionally, each dust is assigned a group E, F, or G , representing the dust types metal, carbonaceous, and other, respectively with different properties. For instance, group E dusts are electrically conductive and electric current can pass through a layer of such dust under favorable circumstances, causing short circuits or arcs.
The amount of dust accumulation necessary to cause an explosive concentration can vary greatly.
Combustible Dust Fires and Explosions: Recent Data and Lessons Learned
This is because there are so many variables — the particle size of the dust, the method of dispersion, ventilation system modes, air currents, physical barriers, and the volume of the area in which the dust cloud exists or may exist. As a result, simple rules of thumb regarding accumulation such as writing in the dust or visibility in a dust cloud can be subjective and misleading. The hazard analysis should be tailored to the specific circumstances in each facility and the full range of variables affecting the hazard.
Many locations need to be considered in an assessment. One obvious place for a dust explosion to initiate is where dust is concentrated. In equipment such as dust collectors, a combustible mixture could be present whenever the equipment is operating.
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Other locations to consider are those where dust can settle, both in occupied areas and in hidden concealed spaces. A thorough analysis will consider all possible scenarios in which dust can be disbursed, both in the normal process and potential failure modes. The references and information sources at the end of this document will assist in the decision process for the methods suitable to specific work sites. Additional guidance and requirements may be available from local or state fire and building code officials as well as OSHA Area or Regional Offices. The following are some of its recommendations:.
Additionally, 29 CFR The use of proper electrical equipment in hazardous locations is crucial to eliminating a common ignition source.
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The classification of areas requiring special electrical equipment is discussed in the Facility Dust Hazard Assessment section above. Once these areas have been identified, special Class II wiring methods and equipment such as "dust ignition-proof" and "dust-tight" must be used as required by 29 CFR Hazardous atmospheres including dust concentrations are addressed in paragraph c of this standard.
Where coal-handling operations may produce a combustible atmosphere from flammable dust, employers covered by the Electric Power Generation, Transmission, and Distribution standard must eliminate or safely control ignition sources. See 29 CFR The following are some suggested protection methods:.
Workers are the first line of defense in preventing and mitigating fires and explosions. While OSHA standards require training for certain employees, all employees should be trained in safe work practices applicable to their job tasks, as well as on the overall plant programs for dust control and ignition source control.
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- Prevention of dust explosions in the food industry.
They should be trained before they start work, periodically to refresh their knowledge, when reassigned, and when hazards or processes change. Employers with hazardous chemicals including combustible dusts in their workplaces are required to comply with 29 CFR This includes having labels on containers of hazardous chemicals, using material safety data sheets, and providing employee training. A qualified team of managers should be responsible for conducting a facility analysis or for having one done by qualified outside persons prior to the introduction of a hazard and for developing a prevention and protection scheme tailored to their operation.
Supervisors and managers should be aware of and support the plant dust and ignition control programs.http://lastsurestart.co.uk/libraries/listen/570-how-to-put.php
Dust Explosions in the Process Industries 1 | University of Bergen
Their training should include identifying how they can encourage the reporting of unsafe practices and facilitate abatement actions. Eckhoff, Rolf K. Hatwig, M. Frank, Walter. Amyotte, P. Ebidat, Vahid. Note: This SHIB was developed using the latest information and requirements from the references below. Editions are not listed here, since users of this document should refer to the most current editions. Chemical Safety and Hazard Investigation Board. ASTM International.
Avbryt Send e-post. Eckhoff Dust Explosions in the Process Industries Unfortunately, dust explosions are common and costly in a wide array of industries such as petrochemical, food, paper and pharmaceutical. Les mer. Om boka Dust Explosions in the Process Industries Unfortunately, dust explosions are common and costly in a wide array of industries such as petrochemical, food, paper and pharmaceutical.
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- Dust Explosions in the Process Industries by Rolf K Eckhoff?
It is imperative that practical and theoretical knowledge of the origin, development, prevention and mitigation of dust explosions is imparted to the responsible safety manager. The material in this book offers an up to date evaluation of prevalent activities, testing methods, design measures and safe operating techniques. Also provided is a detailed and comprehensive critique of all the significant phases relating to the hazard and control of a dust explosion.