The explosive danger of dust particles
Tuesday, May 09, 2017
Combustible dust explosions are a risk in many areas of a facility.
Facilities can create dust particles that can become airborne and dispersed throughout the plant. It's when these particles are in a combustible environment that they represent a significant risk for an industrial accident. The serious hazards associated with handling fine dusts and powdered materials may be overlooked by many plant personnel because they are not fully understood.
The presence of dust in a factory is now at the top of the list of items to inspect during an audit. Facilities must now implement a strategic plan for managing combustible dust at their locations and be proactive in mitigating these dust issues.
The National Fire Protection Association (NFPA) sets standards and codes to protect buildings against fire and explosion risks, and the Occupational Safety & Health Administration (OSHA) is enforcing these standards with increasing vigilance.
Regulatory standards (NFPA) and what it means for dust control
NFPA 652: Standard on the Fundamentals of Combustible Dust, 2016 Edition was issued by the NFPA in 2015. The scope of the standard is to provide the basic principles of and requirements for identifying and managing the fire and explosion hazards of combustible dusts and particulate solids.
The intent is to provide overarching minimum requirements for combustible dust and to reference the appropriate specific NFPA standards for a given industry or material that is being handled, but it does not supersede those existing standards.
One of the crucial aspects of NFPA 652 is the requirement of the Dust Hazard Analysis (DHA). The owner/operator of a facility is responsible for ensuring a DHA has been completed in accordance with the standard where materials have been determined to be combustible or explosible.
This is a retroactive requirement. Existing facilities are allowed three years from the effective date of the standard (Sept. 7, 2015) to complete a DHA. Reasonable progress toward completing a DHA shall be made during this time.
The standard allows for two options for determining the combustibility or explosibility of dust or particulate material. First, historical facility data or published data that are accurate representations of current materials and process conditions. Second, analysis of representative samples according to defined test methods in the standard. There are several labs that can perform the required testing and analysis according to the methods required.
Specific to the milling and grain industry, NFPA 61: Standard for the Prevention of Fires and Dust Explosions in Agricultural and Food Processing Facilities, 2017 Edition was also recently updated. This standard addresses the requirements for facility construction, ventilation and venting, heat transfer operations, dust control measures, equipment design and installation, explosion prevention and protection, pneumatic conveying, and building fire prevention.
This standard was reorganized from 13 chapters into 9 chapters that align with NFPA 652. It now also includes the requirements for performing and documenting a DHA.
It is important to understand the characteristics of the material being handled and the process conditions. These NFPA standards provide guidelines for addressing hazardous material.
However, there is not a single solution for all applications. Defining these requirements begins during the design phase or project improvement phase of a facility, and continues through the operation and maintenance of the plant. The best solutions are a function of evaluating the risk conditions (DHA), understanding owner/operator requirements, and the options available:
Risk conditions (DHA)
- Determine hazards of materials (Kst, Pmax, MIE, MEC, AIT, MIT etc.)
- Identify and assess operating hazards and zone requirements
- Rating required for the protected equipment (i.e. Pred for material air separator)
- Control of possible ignition sources (spark detection, prevention, spark resistant, static)
Additional owner/operator requirements
- Equipment protection (venting, flameless venting, suppression, isolation)
- Equipment location
- Authority Having Jurisdiction (AHJ) or specific insurer requirements
- Operating costs and maintenance
- Manage and communicate hazards
An important element of your strategy
It is essential to understand how the dust collection system integrates into the overall risk assessment and operation of your facility. A well-designed system that is compliant can assist greatly in managing any dispersed dust. It can also provide important energy and maintenance savings for your facility, giving you a reduced cost of operation as opposed to a unit with a lower initial price.
Expectations of a good dust collection system:
- Reduce fugitive dust inside facility and on equipment
- Protect the assets (people, equipment and facilities)
- Reduce the "tracking of dust" everywhere
- Increase storage capacity
- Reduce potential for explosions
- Better product flow ability
The proper identification of hazards and the design and implementation of equipment and processes to the appropriate NFPA standards will reduce the risk of handling combustible dust.
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