Page 98 - Occupational Health & Safety, July 2017

COMBUSTIBLE DUST
agement controls, such as prohibiting hot work or other actions that could provide an ignition source.
With so many factors to consider with- in your building and operations, it can be overwhelming to even know where to start. Wisely, that is why the standard also re- quires a dust hazard evaluation.
However, you don’t have to wait for a formal dust hazard evaluation to identify problems and begin to make changes. In many cases, facilities may know they have issues they need to address and they’d pre- fer to tackle the low-hanging fruit before having an evaluation. In that case, a quali- fied consultant can do a walkthrough of your facility and your manufacturing pro- cesses and help you identify hazards. These walkthroughs are fact-finding expeditions in which the risks are identified and priori- tized to give the facility management team a punch list of needed improvements that will likely come up on an evaluation.
A consultant can also help you identify steps within your processes that may create a hazard. For instance, in any process that handles combustible dust or other poten- tially combustible materials, the form and composition of the materials may change throughout the process. What may not have been combustible in steps one to 101 may become combustible in the next man- ufacturing step due to changes in material composition or the introduction of a new element. You must understand exactly what is happening at each stage of your process to understand where the real issues are.
Dust Sampling and
Laboratory Testing
A consultant will help develop a compre- hensive sampling plan to take dust samples at numerous locations around your facil- ity, as well as at each potentially hazard- ous process step identified during the walkthrough. These samples will then be laboratory tested to determine their level of combustibility. Lab testing will determine whether your dust can be ignited under a wide variety of circumstances and will give you the data you need to either prevent it or mitigate it.
Facilities working without an experi- enced consultant also can implement test- ing if they develop a sampling plan that covers the basics and they have a person on staff who is familiar with the characteris-
tics of combustibility of dust and how the steps of their manufacturing process impact those characteristics. Facilities doing testing themselves can usually locate contract labo- ratories that will test their samples and give them a report to document the findings.
The initial laboratory testing is a ba- sic “go/no go” style test that determines whether the dust will combust under a variety of conditions. These tests typically run around $1,000 to complete, and results are usually relatively quick. If your dust is noncombustible, you are good to go. If it does combust under testing, then a battery of additional testing is needed to determine at what minimum concentration can be ignited, what is the minimum amount of ignition energy required to create an explo- sion, and other parameters. These tests can run about $5,000 to complete.
Conducting a Dust Hazard Analysis
The dust hazard evaluation is the step that helps things come together for most facili- ties. It helps management teams to answer key questions and understand the size and scope of their potential dust hazard, as well as the circumstances that contribute to the danger level, in order to develop the man- agement systems needed to mitigate risks and prevent continued problems.
A dust hazard analysis usually includes a table exercise with the key personnel there who know the building equipment and processes involved. This may include an outside consultant as a facilitator but also may include production managers, plant engineers, maintenance engineers, quality control inspectors, and even mate- rial handlers. Depending upon your facili- ties’ products and processes, you may have specialized staff such as a plant chemist who should be a part of the analysis.
Once the team is assembled, the group will go through the entire manufacturing process step by step and identify all of the aspects of that step that could contribute to a hazardous condition. For instance, if 50-pound bags of material are poured into a machine hopper, what happens if too much or too little material is added? If the temperature control on that machine fails, could an ignition source be created? What if some other control system fails? Could a ventilation system be added to collect and remove dust associated with dump- ing these bags? Or could the materials be
loaded in different increments, or via a dif- ferent method, to eliminate the dust? The team collectively brainstorms the potential problems that could pop up at each step, to be able to plan for contingencies to mitigate potential disaster.
When no problems are found, the team moves to the next step. If a potential prob- lem is uncovered, the team brainstorms how to fix that problem to prevent its oc- currence. When possible, engineering so- lutions are created to eliminate potential problems and prevent human error. When engineering solutions are not feasible, management solutions are implemented to control human behavior.
Once the team has gone through the full process and has identified the risk points, as well as the degree of risk, it can then prioritize the response and begin to implement mitigation options.
Revisiting Dust Hazard
Analysis Over Time
No process is stagnant for its lifetime. There will be times when you choose to upgrade equipment, modify your manufacturing process, or expand your operations. Each significant change is another opportunity to evaluate and stop to ask yourself, “Okay, what’s the impact of doing this? Are we causing more hazards? If so, how are we going to deal with those?”
Eliminating dust hazards comes down to vigilant awareness of your facility and your practices and an understanding of what creates an unsafe condition.
Consultants are available to help you through the process of getting ready for, and conducting, a dust hazard analysis. Whether you choose to use a consultant or go it on your own, keep in mind the basics of good dust handling practices, be thor- ough in your planning and prep work, and follow through on mitigating any risks that are identified. As past industrial disasters have shown us, the cost of doing nothing is far too high to ignore.
Tim Colliton, PE (MN), CIH, is a project engineer for Wenck (www.wenck.com), an employee-owned consulting enterprise with a united team of engineers, scientists, haz- ardous materials specialists, construction, and business professionals. Ordering infor- mation for copies of NFPA 652 can be found at www.nfpa.org.
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