In today’s episode of the Dust Safety Science podcast, Chrissy Klocker, Technical Services Manager at Donaldson Company, presents recommended options for collecting combustible metal dusts. We’ve gotten a number of questions recently on metal dust: what the requirements are, the applications that handle it, and options for collecting it, and Chrissy is here to lend her professional insights.
What Applications and Processes Generate Metal Dust?
Chrissy explained that the metal fabrication industry is vast and encompasses a wide range of activities. Traditional processes such as welding and grinding are common, along with advanced technologies like laser and plasma cutting, and thermal spray techniques. All these activities fall under the umbrella of metal fabrication.
Within these shops, various processes are performed, often with dedicated equipment for each. Sometimes, a single collector handles multiple processes. The workflow includes receiving sheet steel, punching it out, grinding edges, laser cutting, and welding the pieces together. It’s a comprehensive mix of methods, all contributing to the overall metal fabrication process.
About Battery Applications
Battery technology is evolving rapidly. The volume of plants being constructed for battery production has increased quickly. As battery shapes and sizes change, so do the shapes and sizes of the vehicles they fit into. This has led to many production lines being modified and updated, each with its own processes.
Battery production is a broad topic, but it’s also new and introduces new contaminants, processes, and hazards. Many people are still unsure about these hazards and how to mitigate them. Learning and evolving are ongoing processes, and as customers hear from other industries and companies, they too are adapting their strategies and tactics to handle these changes.
Much of the technology is related to system design. Understanding the entire system and its impact on hazards within the process is crucial. This includes everything from the hood and dust collection system to the dust collector, the fan, secondary filters, and all the controls. When designed, installed, and maintained properly, these components work together to reduce the risk of an event. However, when there are upset conditions or improper design, the risk of hazards increases.
Currently, there are many design changes and new strategies emerging. Observing these developments and understanding how they interact will shape the future of the battery industry.
What Are the Different Types of Equipment Involved?
Chrissy explained that in metal fabrication applications, cartridge collectors are commonly used due to the fine and uniform dust contaminants produced. Traditional baghouse technology, which uses felt media to filter out particulates, is often not efficient enough for these fine particles. Therefore, cartridge technology is more prevalent.
Cartridge technology can be configured in various ways. Traditional cartridge dust collectors have a hood ducted to a dust collector that can be located either indoors or outdoors. Downdraft benches are another option, providing a work surface where air is pulled downward away from the worker, filtered, and recirculated back into the plant. This setup is particularly convenient for tasks like grinding, where larger particles are directed downward toward the filter media by the airflow.
Many customers are seeking alternative strategies for air collection, such as using canopy hoods to pull air from above or ambient style collection systems to filter floating contaminants from the air. Each strategy has its advantages. For instance, ambient collection can help clear any haze in the room, but depending on the system’s goals—whether it’s to collect the product or avoid workplace hazards like exposure to certain materials—different approaches may be necessary.
An ambient solution is not effective for protecting the worker’s breathing zone. Therefore, a combination of different strategies is often used in a facility. Collectors can come in various styles, such as ducted to a wet collector or a downdraft bench style wet collector. These systems are often employed to comply with NFPA 44 or specific application requirements.
How is an Overall Dust Control Strategy Developed?
The first thing to consider is the material being worked with. Many job shops handle various materials, such as carbon steel one day, aluminum another day, and stainless steel on another. The NFPA strongly recommends against mixing metals to avoid the risk of a thermite reaction.
It’s also important to determine if it makes sense to use one dust collector or have separate collectors for different materials. This decision also depends on the available space for the equipment, whether it needs to be placed indoors or outdoors, and the hours of operation.
For dry dust collectors, protecting equipment indoors versus outdoors, returning air back into the building, and the type of material being worked with are all factors in choosing the right mitigation solution. If a facility only works with carbon steel and iron, and the dust collector is located outside, the selection process becomes more straightforward. The next step is to decide on the protection method for the collector, such as explosion vents, flameless vents, or chemical suppression.
Additional questions include whether there is test data to support a KST value and if the materials are combustible. Traditional questions in combustible dust applications apply, but metal dust mitigation is more challenging. Most manufacturers perform tests to confirm if their devices can be used with metal applications, so it’s crucial to ensure the appropriate device is selected. For example, if using a passive isolation valve, it must be tested and confirmed suitable for the metal dust in question. Getting confirmation from vendors that their products are appropriate for the specific dust is a critical step in the process.
Testing Metal Dust
Testing metal dust could be an entire podcast topic on its own due to its complexity. There are numerous factors to consider. For instance, with laser or plasma cutting, one might assume that 100% of the dust is oxidized and therefore not combustible. However, incidents of fires occurring shortly after can prove this assumption wrong.
Thermal applications present the challenge of identifying the actual properties and characteristics of the dust in the dust collector. If a collector is located close to a process without spark mitigation and has short duct runs, partially oxidized particulates can mix with fully oxidized dust that has been sitting overnight, creating a potential hazard.
In welding, the presence of pickling oil on sheet steel can complicate matters. The oily contaminant produced during welding can result in different KST values for the weld fume. Clean material might have one KST value, while material with oil residue might have another. Understanding the material being worked with is crucial.
For aluminum and legacy metals, the NFPA recommends testing in a larger chamber to obtain a more accurate KST value, as the dust can burn hotter and faster in larger volumes. If tested in a 20-liter chamber, the KST value should be doubled. For example, if a dust test results in a KST of 150, the design should account for a KST of 300 for mitigation equipment.
Identifying the actual characteristics of the dust is challenging due to its dynamic nature in different applications and processes. Accurate dust testing is essential to ensure proper mitigation strategies.
What Applications Use Wet Dust Collection?
Wet collectors are often preferred in buffing and polishing applications. While baghouse collectors can handle buffing and polishing, they may not be suitable for lower volume operations. In these cases, wet collectors are a better option. Polishing materials often involve using a rouge, which can be grease or oil-based. This process generates a sticky, oily, and greasy product similar to lint. Traditional cartridge collectors are not suitable for these applications as the oils tend to clog the cartridges, leading to premature failure.
Wet collectors are ideal for handling the sticky mix of metal shavings, cotton, lint, and oil produced during buffing and polishing. These collectors are more effective in managing such materials, which could otherwise pose a significant fire hazard.
Although primarily selling dry collectors, it is acknowledged that wet collectors are favored by many customers because the NFPA allows their use in metal applications without additional protection. However, waste management is a growing concern. The waste stream from wet collectors must be properly managed and disposed of, considering environmental regulations.
When choosing a collection system, it’s important to consider the entire process, ensuring it works effectively from start to finish for the specific needs of the facility.
What Are Common Mistakes?
Many thermally generated processes produce off-gases like ozone or solvents, which should not be recirculated back into the building. Effective fire and explosion mitigation involves recognizing not only the dust and contaminants being collected but also any solvents or vapors from the process. These vapors often have lower minimum ignition energies compared to dust, making practices like bonding and grounding, or using conductive media, crucial in a dust collection system.
Bonding and grounding should be applied to the entire system, including ducting, hoods, and ancillary equipment, to ensure everything is electrically classified. This is a hazard that many people overlook until after their process starts, and they notice these byproducts.
For metal applications, it is also important to have a thermal detector in the dust collection system to identify any temperature rises, indicating a potential smoldering fire or other issues, especially during off-hours. This early detection, added to NFPA 44 a few years ago, provides an alarm before a sprinkler system activates, allowing for timely responses such as evacuating employees, shutting down the process, and following emergency protocols.
Ignition mitigation is vital, and temperature monitoring or alarms can significantly decrease the severity of an event by providing early warning signs. If full protection or prevention measures are not chosen, having an alert system is essential to mitigate the overall risk.
Yeah, I guess just really make sure that you are picking components and strategies that work for the dust. So if it’s, you know, from a fire standpoint, not everything can be put out with water. So if it’s CO2 or argon or another, you know, Inerting agent, something like that, but just really making sure you’ve got good documentation from the vendors that you’re working with that the components that you have are compatible for your material that you’re working with. And then, you know, in the case that you do have an event, learn from it, right? Figure out what went wrong, what can you do better and make those changes and keep learning from what you’ve got going on at your facility.
Conclusion
The safe and efficient collection of combustible metal dust is a multifaceted approach. Understanding the specific processes and materials, selecting appropriate equipment, implementing effective mitigation strategies, and continuously learning from each experience are all crucial elements. Chrissy Klocker’s insights highlight the importance of adapting to the evolving landscape of metal fabrication and battery production, emphasizing the need for thorough documentation, proper system design, and proactive hazard identification. By integrating these practices, facilities can better manage risks, enhance safety, and improve overall operational efficiency.
If you would like to discuss further, leave your thoughts in the comments section below. You can also reach Chrissy Klocker directly:
Website: https://www.donaldson.com/en-us/
LinkedIn: https://www.linkedin.com/in/chrissy-klocker-5143666/
Email: [email protected]
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
Companies
Donaldson Company
Organizations
Institute of Hazardous Materials Management
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DSS273: Understanding Your Options For Collecting Combustible Metal Dusts with Chrissy Klocker
