In today’s episode of the Dust Safety Science podcast, Chrissy Klocker, Applications Engineering Manager at Donaldson Company based in St. Paul, Minnesota, talks about five misconceptions surrounding the collection of combustible dust.
Chrissy did a presentation on common dust collection and combustible dust misconceptions at this year’s Dust Safety Conference. She speaks from a position of experience and authority: in her current position at Donaldson Company, she helps the field sales team and end-users mitigate the challenges that combustible dust presents in their processes and applications.
Misconception #1: Flame-Retardant (FR) Media Eliminates the Risk of an Event in a Dust Collector
FR media is filter media treated with a flame retardant, so that when it is exposed to an ignition source like a flame, it will self-extinguish. In dust collectors, the media is never completely free of caked-on dust, so when a spark or ember hits it, that dust will burn.
“When the dust is burning, the media can’t get rid of that ignition source, so it can’t self-extinguish,” Chrissy says. “The burning will continue… You would need additional fire protection measures both on the prevention side and the protection range.”
She pointed out that by the time the filters need changing, the dust collector fan is usually running at 100% capacity. The new, replacement filters don’t have the same level of resistance across the filter cake that the old ones did.
“One of the challenges with a lot of systems is if that fan is not dampened back to close off some of that airflow, you can end up pulling way more airflow than you expect. When you’re running a process that generates sparks, having a higher capture velocity can result in having more sparks being drawn into your system, and therefore more ignition sources.”
FR media is most effective before the dust cake starts to form. By dampening back the fan to ensure that the system is not pulling in as much air, the media can do its job without exposing the system to spark hazards.
Misconception #2: Fans Start Fires
In Chrissy’s experience, this misconception is due to the fact that the fan area suffers the most damage during dust collector fires. The reality is that damage is concentrated in this area because it moves the highest volume of air, making it the hottest point in the system.
“I think a lot of customers are missing the big picture of how the airflow is moving through the collector,” she says.
When the fan is sucking material through, it also sucks embers and sparks into the system, but doesn’t directly cause the fire. If a fan did actually create a spark, it would simply fly out of the outlet, where the bigger concern would be where the fan was exhausting.
Misconception #3: An Explosion Vent is All That’s Needed
Chrissy acknowledged that explosion vents are an important safety component, but they aren’t the only one needed to prevent or control combustible dust events.
“[If] you have an explosion event, do you have the proper mitigation strategies to stop that deflagration or hazard from extending to other pieces of process equipment? Do you have the isolation valve? Do you have fire protection?” she says.
There are different dust collection and mitigation strategies out there, and choosing the right one for a specific application is critical. In some cases, an explosion vent may not be the best choice, especially with pharmaceutical dust. You want to make sure you’re choosing a strategy that works for the dust, the process, the employees and the dust collector.
Misconception #4: There Are No Risks to Address With Dust Collectors Smaller Than Eight Cubic Feet
NFPA 652 states that if a dust collector is greater than eight cubic feet, it must be placed outside. Consequently, people assume that if they get a smaller machine, they won’t have to be concerned with the NFPA.
Although this seems like an easy way out, it can actually make things a little more complicated. An explosion in a smaller machine can still cause injuries, and when it’s not outside, people in the surrounding area can be injured. The machine doesn’t have the same mitigation strategies as its larger counterparts, so factors like housekeeping and worker practices in the vicinity become a lot more important.
Misconception #5: The Only Mitigation Choices Are the Prescriptive Actions Outlined in the NFPA Standards
“NFPA standards are written so that they can be adopted by a city or a state and then used as part of their code,” Chrissy explains. “But they aren’t actually code. And so when you read the standards, it often seems like this is the mandate, this is what you have to do.”
There are actually two compliance methods:
- Prescriptive: Using the methods outlined in the standards.
- Performance-based: Facility managers can devise their own mitigation strategy based on their risk assessment and dust hazard analysis.
With the performance-based method, one achieves the same goals as the prescriptive strategies by tailoring them to the facility’s application and process.
Conclusion
Mistakes and misconceptions happen in all industries, but in facilities handling combustible dust, they can lead to injury and death. Continuous learning and willingness to work with experts can reduce risk and help ensure everyone goes home safely at the end of the day.
If you would like to discuss further, leave your thoughts in the comments section below. You can also reach Chrissy Klocker directly:
Email: [email protected]
LinkedIn: https://www.linkedin.com/in/chrissy-klocker-5143666/
If you have questions about the contents of this or any other podcast episode, you can go to our ‘Questions from the Community’ page and submit a text message or video recording. We will then bring someone on to answer these questions in a future episode.
Resources mentioned
The resources mentioned in this episode are listed below.
Dust Safety Science
Combustible Dust Incident Database
Dust Safety Science Podcast
Questions from the Community
Dust Safety Academy
Dust Safety Professionals
Companies
Donaldson Company
Standards
NFPA 652
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DSS134: Five Misconceptions About Collecting Combustible Dust with Chrissy Klocker
