Getting a Handle on Your Combustible Dust Exposure – Part 2
Last week, we reviewed the definition of combustible dust, the “Dust Explosion Pentagon”, and identified several historic dust explosions that have resulted in the tragic loss of many lives. This week, we’ll review applicable industry standards and provide a few recommendations for facilities that handle combustible dust.
In response to the combustible dust explosions that have occurred in the U.S., OSHA established a Combustible Dust National Emphasis Program on March 11, 2008, CPL 03-00-008, that targets facilities that create or handle combustible dusts, and establishes policies and procedures for inspecting those facilities. This emphasis program increased OSHA enforcement activities with a focus on specific industry groups that have experienced frequent or catastrophic dust incidents.
The targeted inspections may result in citations for housekeeping (29 CFR 1910.22) where dust accumulations are found, for electrical classification violations (29 CFR 1910.307), or citations may be issued under the General Duty Clause [Section 5 (a) (1)] of the OSH Act.
OSHA also recently released a new fact sheet aimed at helping to protect workers from combustible dust explosion hazards.
Applicable Industry Standards (NFPA & FM)
There are numerous industry standards and guidelines that may apply to facilities with combustible dust exposures, some of which are listed below.
- NFPA 61, Standard for the Prevention of Fires and Dust Explosions in Agricultural and Food Processing Facilities
- NFPA 68, Standard on Explosion Protection by Deflagration Venting
- NFPA 69, Standard on Explosion Prevention Systems
- NFPA 70, National Electrical Code [NEC]
- NFPA 77, Recommended Practice on Static Electricity
- NFPA 484, Standard for Combustible Metals
- NFPA 499, Recommended Practice for the Classification of Combustible Dusts and Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas
- NFPA 652, Standard on the Fundamentals of Combustible Dust
- NFPA 654, Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids
- NFPA 664: Standard for the Prevention of Fires and Explosions in Wood Processing and Woodworking Facilities
- FM DS 7-73, Dust Collectors and Collection Systems
- FM DS 7-76, Prevention and Mitigation of Combustible Dust Explosions and Fire
In the document Combustible Dust in Industry: Preventing and Mitigating the Effects of Fire and Explosions, OSHA references NFPA 654 to provide guidance on dust control, ignition sources, and consequence controls including the following recommendations:
- Minimize the escape of dust from process equipment or ventilation systems
- Use dust collection systems and filters
- Utilize surfaces that minimize dust accumulation and facilitate cleaning
- Provide access to all hidden areas to permit inspection
- Inspect for fugitive dust residues in open and hidden areas and remove dust accumulations at regular intervals
- Only use vacuum cleaners approved for dust collection
- Use cleaning methods that do not generate dust clouds, if ignition sources are present
- Locate relief valves away from dust hazard areas
- Develop and implement a hazardous dust inspection, testing, housekeeping, and control program (in writing with established frequency and methods)
- Use appropriate electrical equipment and wiring methods
- Control smoking, open flames, and sparks
- Control static electricity, including bonding of equipment to ground
- Control mechanical sparks and friction
- Proper use and type of industrial trucks
- Proper use of cartridge activated tools
- Use separator devices (magnets) to remove foreign materials capable of igniting combustibles from process materials
- Separate heated surfaces from dusts
- Separate heating systems from dusts
- Adequately maintain equipment
- Separation of the hazard (isolate with distance)
- Segregation of the hazard (isolate with a barrier)
- Deflagration venting of a building, room, or area
- Explosion venting for equipment
- Provision of spark/ember detection and extinguishing systems
- Sprinkler systems and specialized explosion suppression systems
Find a Professional
Evaluation of exposures from combustible dust is a complex process that should only be performed by someone with specialized knowledge and experience in conducting these evaluations.
The combustible dust consultants at Harrington Group can take you through the process step-by-step. The first step is generally a Combustible Dust Audit, which typically proceeds as follows:
- Site visit to understand the materials, equipment, and processes at the facility
- Evaluation of management controls such as employee training, management of change, and emergency response procedures relative to combustible dust hazards in the workplace
- Evaluation of operational procedures to prevent or mitigate fires, deflagrations, and explosions
- Review of inspection, testing, and maintenance programs for all explosion prevention and protection measures relied upon for safety
- Collection of dust/powder sample(s) for laboratory testing, if warranted
- Evaluation of electrical classifications in powder handling areas
- Review of process and equipment documentation (P&ID’s, PFDs, Equipment approval drawings, air flow rates etc.)
- Review of Basis of Safety (BOS) documentation for each piece of powder handling equipment (Dust Collectors, Silos, Hoppers, Mills, etc.), or identification of apparent gaps
- Recommendations identifying opportunities for improvement to the site’s management of combustible dust related hazards.
After the audit and associated report is complete, the facility can then take steps to address any gaps identified in the audit by:
- Engaging a contractor to implement engineering control recommendations
- Establishing a task force to implement management control recommendations
- Maintaining the BOS through a formal change-management protocol
If you need help assessing your facility/processes for combustible dust exposures, the engineers at HGI can help. Fill out the contact form at the bottom of this page.
References & Additional Resources:
Guidelines for Safe Handling of Powders and Bulk Solids, CCPS, 2005
Dust Explosions in the Process Industries, R.K. Eckhoff, 3rd Edition, 2010