Page 20 - OHS, January/February 2021

COMBUSTIBLE DUST
effects of a dust fire or explosion. The second objective is “Mission Continuity,” where continued safe operations of the plant or facility are ensured if a dust fire or explosion were to occur. The third and final objective is “Mitigation of Fire Spread and Explosions,” which not only safeguards the facility against these affects, but prevents them from spreading to adjacent facilities and properties.
As mentioned above, NFPA 652 applies to all industries and to all facilities and operations manufacturing, processing, blending, conveying, repackaging, generating or handling combustible dust. It does not apply to commercial retail or commercially packaged warehousing facilities. So, the facility that makes breakfast cereal is covered, but the supermarket selling the cereal is not. It is the owner/operator of that breakfast cereal facility with the combus- tible dust who has to determine the combustible and explosible nature of the material handled at the facility.
Most materials that are not pure minerals or salts are combusti- ble or explosible. They are responsible for identifying and assessing any fire, flashfire or explosion hazards and managing those risks. They then should communicate these risks to both employees and contractors. The deadline to comply with these NFPA standards was September 7, 2020, with the exception of agricultural and food facilities, which had until January of 2022.
It is important to note that some of the requirements set forth in NFPA 652 and the other dust standards are not monitory, and parts of facilities or operations may be “grandfathered.” However, much of these standards do apply to existing operations and have to be adhered to for all new operations. A short list of the core parts of the standards that are not “grandfathered” are ignition source control requirements, facility housekeeping to remove hazardous dust level, personnel training, management systems to document hazards, process changes and conducting a Dust Hazards Analy- sis (DHA) to identify combustible and explosible dust hazards and recommend risk mitigation and engineering protocols.
Dust Hazards Analysis
The mandatory DHA requirement is a tool used to understand your specific materials and the hazards they pose, systematically evaluate your processes for risks, and then develop a roadmap to manage those risks by either administrative controls or engineer- ing controls. This whole process has to be documented, and those documents are retained for the life of your process or facility— whether it be 10 years or 100 years.
The DHA should be conducted in such a way as to classify a given facility location, process step or unit operation as a hazard, potential hazard or not a hazard at all. Then the DHA should rec- ommend process, operation, facility or material changes to miti- gate the identified hazard. Given the complex nature of this task and the nuanced nature of the identification/classification of the hazard, the DHA team should be led by a person qualified in the field of combustible and explosible dust hazards, with support from engineering staff, maintenance staff and plant floor operators.
NFPA 652 does not give specifics about the methodology to be used for a DHA, and thus they can be varied. If the facility falls under OSHA’s Process Safety Management requirements of con- ducting a Process Hazards Analysis (PHA), it may be already us- ing techniques such as a Hazard and Operability Study (HAZOP), a Failure Mode and Effects Analysis (FMEA), Fault Tree Analysis
Figure 1: Explosion pentagon.
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Figure 2: Dust testing schema.
(FTA) or a multitude of other methodologies. It may be appropri- ate for the facility to incorporate the DHA into the existing PSM program. The rigors of a formal PSM program are a little excessive for a DHA.
NFPA 654 had originally recommended that a PHA be per- formed on operations handling combustible dusts, but since that lead to confusion with the complex OSHA PSM program require- ments, the NFPA technical committee decided to re-term the haz- ards analysis to DHA and make it mandatory.
Methods of Analysis
Since a very elaborate methodology is not required by the NFPA standard, the approach selected for ease of implementation and ad- herence can be a simple Checklist Analysis combined with a “What If ” investigation. In this approach, the requirements of the NFPA 652 standard are converted into a checklist against which the facil- ity is audited for compliance. The gaps are then noted and plans can be made to add engineered or administrative solutions to fill the variances.
However, checklists and prescriptive mitigation schemes from the NFPA standards cannot deal with all possibilities. This is where supplementing the Checklist Analysis with a What If Analysis, car- ried out by an experienced team, can fill in the gaps. In short, the What If Analysis postulates various failure scenarios that can occur