What is NFPA 652? Why do I need to know? Do I need to comply? Well those are good questions, especially if you are an industrial processor of powder materials. But first, let me address what or who is NFPA. The NFPA is an acronym that stands for National Fire Protection Association. According to the NFPA website, nfpa.org, the NFPA:
“The National Fire Protection Association (NFPA) is a global self-funded nonprofit organization, established in 1896, devoted to eliminating death, injury, property and economic loss due to fire, electrical and related hazards. NFPA delivers information and knowledge through more than 300 consensus codes and standards, research, training, education, outreach and advocacy; and by partnering with others who share an interest in furthering our mission. Our mission is to help save lives and reduce loss with information, knowledge and passion.”
The NFPA core operation is writing codes and standards designed to minimize the risk of fire and their impact. These codes and standards involve the establishment of criteria for production, operation, facility building and more. For more information please visit their website.
What is NFPA 652
NFPA 652 is a standard written and published by the NFPA. The title of NFPA 652 is “Standard on the Fundamental of Combustible Dust”. The scope of the document is to “provide the basic principles of and requirements for identifying and managing the fire and explosion hazards of combustible dusts and particulate solids”. One very important requirement of this standard, issued in 2016, is that it requires a “Dust Hazard Analysis” (DHA) be performed for all operations that generate, process, handle or store combustible dusts or particulate solids. This is a significant requirement, and before you can perform a DHA you must know whether the various dusts you “generate, process, hand or store” is combustible or not.
How to determine if a dust is combustible: The determination of combustibility is based on either one of two possible methodologies;
1. Historical data available from within your company and facility, or published data that are representative of
current materials and conditions, or
2. Analysis of material samples.
Can you deal with dusts in powder handling systems?
What do I need to do if my dust is combustible
Combustible dust are closely regulated by OSHA and the NFPA as a major work hazard. This exists in many industries, e.g. food, agriculture (includes feed manufacturing), metalworking, woodworking, plastics and more. Any company that has a workplace where combustible dusts exist must prepare a DHA or Dust Hazard Analysis to maintain NFPA 652 and OSHA compliance. This OSHA link provides some great additional information about combustible dust, explosions and some real world examples.
How to Complete a DHA
The Dust Hazard Analysis is a new form of the PHA (Process Hazard Analysis), which was specified and required by the NFPA beginning in the 1960s. However, as of September 2015 new installations, existing buildings, and any major changes are required to complete a DHA. This means that all facilities processing, handling or storing combustible dust are required to complete a DHA. The Dust Hazard Analysis is designed to help managers and owners ensure the safety of their facilities, workers, and equipment by identifying hazards and the steps that are to be taken to minimize risks associated with these hazards.
A While you can employ many consultants to assist you in preparing a DHA, the DHA preparation will typically include the following:
- Evaluation of fire, deflagration, and explosion hazards for each piece of your process, each building, and individual sections or rooms.
- Identification of ranges of safe operation for each piece of process equipment and the processes themselves included in your facilities that have combustible dusts, as well as precautions that you can take to ensure your process operates within the identified safe operating ranges.
- Data collection for your current system performance and the desired performance metrics.
- Recommendations for dust collection and management of combustible dusts.
- Documentation of the results of your Dust Hazard Analysis.
The Basics of a Dust Explosion
A dust explosion requires a few basic elements, including the combustible dust, space confinement, oxygen, a method of dispersion and an ignition source. If any one of these elements is missing, then the hazard or deflagration risk becomes much reduced.
The DHA should assess and divide your dusts into one of three groups:
– Not a hazard,
– Possibly a hazard
– Fire or Explosion Hazard
Next the DHA should address:
– Location of any potential dust hazards
– Is volume of dust adequate to allow fire or explosions
– The Kst value of the dusts (the deflagration index of a dust, a number that indicates a explosive power)
– The minimum concentration required for explosion of the dust
– Dust suspension potential that can occur during dust creation
– Will dust concentration exceed the minimum required for explosion
– Location of ignition sources and proximity to combustible dust
– Minimum air velocity for the minimum dust concentration to explode
– Minimum protective equipment required for employees
– Rate of dust being production
– Adequacy of the dust collection system
From there, a dust hazard management plan should be produced; including integrating a dust collection system to reduce levels combustible dusts; adding explosion and fire prevention standards in those areas with dust hazards; a housekeeping schedule that keeps the volume of dust under the minimum concentration required for explosion; closing off ignition sources or removing the dust hazard; documenting dust production, dust collection system volume and pressure, and the housekeeping required to keep dust below the minimum concentration for explosion; integrating safety or suppression features as reccomended.
The DHA is designed to help prevent combustible dust explosions in the workplace by recognizing hazards and taking steps to minimize or prevent risks well in advance of possible issues. Check the NFPA 652: Standards on the Fundamentals of Combustible Dust for more information.