DS 7-76 Prevention and Mitigation of Combustible Dust ... - FM Global

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7-76 Combustible Dust Explosion Page 2 FM Global Property Loss Prevention Data Sheets 3.1.13 Dust Collector Operating Pressures (2.3.3.1.17) ............................................................... 31 3.1.14 Explosion Isolation (2.3.3.2) .............................................................................................. 31 3.1.15 Explosion Isolation: Use of Active Devices (2.3.3.3.4) ...................................................... 31 3.1.16 Rapid-Action Float Valves (2.3.3.3.5) .................................................................................. 32 3.1.17 Vacuum Operation (2.3.3.6) ............................................................................................... 32 3.1.18 Spark Extinguishing Versus Explosion Suppression (2.3.4.1) ........................................... 32 3.1.19 Minimum Ignition Energy (MIE)(2.3.4.2) ............................................................................. 33 3.1.20 Foreign Material Separators, Magnetic or Other (2.3.4.3) ................................................. 33 3.1.21 Clean Versus Dirty Side of Dust Collectors (2.4.2) ............................................................ 33 3.1.22 Cyclone Explosion Venting (2.4.2.3) .................................................................................. 34 3.1.23 ‘‘Conductive’’ Dust Collector Bags (2.4.3.1) ....................................................................... 34 3.1.24 Connecting Ducts (2.5) ....................................................................................................... 34 3.1.25 Silos (2.6) ............................................................................................................................ 35 3.1.26 Bucket Elevators (2.7) ......................................................................................................... 35 3.1.27 Size-Reduction Equipment (Grinders, Pulverizers, Hammer Mills, etc.) ............................ 36 3.2 Loss History ..................................................................................................................................... 36 4.0 REFERENCES ...................................................................................................................................... 38 4.1 FM Global ....................................................................................................................................... 38 4.2 Other ................................................................................................................................................ 38 APPENDIX A GLOSSARY OF TERMS ...................................................................................................... 39 APPENDIX B DOCUMENT REVISION HISTORY ...................................................................................... 41 APPENDIX C RESEARCH INFORMATION ON DUST EXPLOSION HAZARDS ...................................... 42 C.1 Reprint from Journal of Loss Prevention in the Process Industries: Improved Guidelines for the Sizing of Vents in Dust Explosions .......................................................................................... 42 APPENDIX D BIBLIOGRAPHY ................................................................................................................... 56 List of Figures Fig. 1. Preferred locations for processes or equipment handling combustible dusts ................................... 6 Fig. 2. Schematic of rooftop explosion vents that project above the roof line ............................................. 8 Fig. 3. Rotary Air Lock ................................................................................................................................. 14 Fig. 4. Rapid-action valve (gate type) ......................................................................................................... 15 Fig. 5. Rapid action float valve (Ventix ESI ®) ............................................................................................ 15 Fig. 6. Acceptable design parameters for explosion diverters .................................................................... 16 Fig. 7. Explosion diverter .............................................................................................................................. 17 Fig. 8. Indoor installation of explosion diverter ............................................................................................ 17 Fig. 9. High-speed abort gate ...................................................................................................................... 17 Fig. 10. Example of duct explosion venting at an elbow ............................................................................ 22 Fig. 11. FM Approved explosion quench pipe (Photo courtesy of Rembe GmbH) ................................... 28 List of Tables Table 1. Construction for Dust Handling Occupancies ................................................................................... 6 Table 2. Typical Dust Bulk Density .............................................................................................................. 26 Table 3. Losses by Industry (by Number of Losses) ................................................................................... 36 Table 4. Losses by Cause (Ignition Source) ................................................................................................ 37 Table 5. Losses by Dust Type ...................................................................................................................... 37 Table 6. Losses by Equipment Type ............................................................................................................ 38 ©2008 Factory Mutual Insurance Company. All rights reserved.
Combustible Dust Explosion 7-76 FM Global Property Loss Prevention Data Sheets Page 3 1.0 SCOPE This data sheet describes recommended preventive measures to reduce the frequency of combustible dust explosions, and protection features to minimize damage from a combustible dust explosion. The hazards of dust fires can be found in other data sheets containing detailed occupancyspecific recommendations. However, an overview of loss history related to dust fires is included in this document. This data sheet does not include dust explosion prevention and protection schemes unique to grain handling, storage, and processing. Loss prevention recommendations for these occupancies are covered in Data Sheet 7-75, Grain Storage and Milling. However, recommendations in this data sheet do apply to hazards at grain handling facilities that are not unique to those facilities. The technology of dust explosion hazard evaluation is primarily discussed in metric (SI) units and those are the units used in this data sheet. 1.1 Changes January 2012. Terminology related to ignitable liquids has been revised to provide increased clarity and consistency with regard to FM Global’s loss prevention recommendations for ignitable liquid hazards. 2.0 LOSS PREVENTION RECOMMENDATIONS 2.1 General 2.1.1 Treat all equipment that handles combustible dusts, as well as any rooms or buildings where combustible dusts can be present and might be put into suspension, as having a dust explosion hazard. 2.1.2 Implement a management-of-change process in all facilities handling combustible dusts to be certain that no changes occur that could increase the severity or consequence of an existing dust hazard or introduce a dust hazard where none previously existed. Examples of such changes include the following: • Adding new equipment such as blenders, grinders, cutting tools, dust collectors, cyclones, etc. • Increasing temperatures in the process that could result in drier material being handled • Adding new materials • Changing product formulation by adding combustible materials or reducing the proportion of inert materials • Making process changes that reduce the particle size of in-process materials 2.1.3 Where process, equipment, raw material, or product changes are planned that could significantly change the dust properties, retest the dust for its explosibility. 2.1.4. Ensure your management-of-change process has the following minimum characteristics: a) Provides a method for identification of changes that should be subject to the management-of-change process b) Provides documentation of the proposed change c) Provides a formal analysis of the loss prevention considerations involved in the proposed change d) Identifies the need for updated personnel training e) Provides for communication of the change and the loss prevention consequences to appropriate personnel such as maintenance, operators, safety, and emergency responders f) Establishes any administrative procedures needed (documentation, checklists that cover hazards, training, etc.) g) Identifies any required authorizations 2.1.5 Where potential for a dust explosion exists, eliminate the potential or minimize the consequences using one of the following methods: a) Control fugitive dust releases using enclosures, collection systems and equipment design. ©2008 Factory Mutual Insurance Company. All rights reserved.
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DS 7-76 Prevention and Mitigation of Combustible Dust ... - FM Global

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