In today’s episode of the Dust Safety Science podcast, we are discussing how to avoid the chimney effect when fighting grain dryer fires.
We have been reviewing a large number of helpdesk tickets since the launch of Dust Safety Science. Our aim is to organize and categorize these queries to create a useful database for our community. During this process, we discovered an interesting ticket from September 2018 regarding chimney effects in grain dryer fires.
This piece of information was provided by Claudio Rocha from Argentina. We’d like to express our gratitude to Claudio for his contribution- he has been a dedicated supporter and follower of our work for over five years, dating back to when he first sent this information in 2018. Over time, he has shared numerous insightful observations, including thoughts on the chimney effect in grain dryer fires.
What is the Chimney Effect?
The discussion begins with understanding what the chimney effect is. Claudio’s insights came in response to a comment about a dryer fire video, where he noticed that the grain dryer had fans on top and queried why these fans were spinning during firefighting efforts, even with the power shut off.
Initially uncertain of the answer, Claudio provided a detailed document explaining the phenomenon. He described that the chimney effect occurs when a grain dryer, or similar storage equipment like a silo, has fans on top. In the event of a fire or smoldering combustion inside the dryer, fresh air is pulled in through these fans towards the fire, while gases are expelled from the top. This process is analogous to the function of a flue in a residential chimney.
The closing of a flue dampens a fire, while opening it can cause the fire to become more aggressive and spread quickly. This effect is particularly pronounced when fans are positioned at the top of a dryer. Claudio pointed out in his response that this situation can significantly complicate efforts to extinguish fires in grain dryers, leading to increased damage. This issue, often overlooked, poses a substantial challenge in his field of firefighting.
How Can the Chimney Effect Be Mitigated?
Claudio suggested a straightforward solution: placing flaps over the fans to close them in case of a fire or smoldering in the dryer. This would prevent air from being drawn in, which fuels the fire through oxygenation. He also offered several cautionary notes based on his experience with dryer fires and firefighting.
Implement Flaps Over the Fans
The first thing to consider is the implementation of flaps over the fans. He said he doesn’t see very often, but it would be a great way to dampen and reduce the impact of these fires and these smaller combustion silos that the flaps should be activated from the ground, either with a metal cord, wire or some other type of mechanism. You don’t really want to have to have teammates or firefighters climb the silo to get access to close these flaps.
Careful Firefighting Efforts
The second point emphasizes that firefighting efforts in cases of silo fires should be slow and methodical. Rather than pouring water onto the silo, which proves ineffective, firefighters are advised to introduce water into the silo. This approach is critical for successfully managing such fires.
In preparation for such scenarios, it’s advisable for firefighting teams to visit potential sites in advance, particularly in rural areas where access to advanced technology and equipment might be limited. The key aspect of these pre-visit assessments is to ensure that their hoses can access the hatches of silos or grain dryers. This is to verify that their equipment is capable of reaching the necessary points for effectively introducing water into the system. These preparatory measures are essential for efficient and effective firefighting in such situations.
Silos Can Expand
It’s important to remember that the contents of silos can expand, potentially causing structural issues. Excessive water introduction into a silo can exacerbate these problems, possibly leading to its collapse, which poses significant safety risks. Therefore, careful consideration must be given to the amount of water used.
Station Resources Carefully
Personnel, trucks, and firefighting equipment must also be strategically positioned. When combating fires in grain silos and dryers, it’s essential to station these resources in locations that minimize the risk of harm from structural damage or explosions, such as dust or smoke explosions. Ensuring a safe working area that allows both access to the silo and the safety of personnel is vital.
Avoid Climbing Silos
The final point to note is the high risk associated with firefighters climbing silos to extinguish fires. This practice has been linked to numerous accidents, including cases where firefighters are thrown from silos due to explosions. Tragically, these incidents have led to firefighter fatalities in numerous instances, both in the United States and globally. Avoiding the need for firefighters to climb silos is an important safety consideration in these situations.
Conclusion
This episode not only underscores the importance of addressing specific challenges in industrial fire safety but also stresses the broader responsibility of maintaining vigilance and adhering to safety protocols in industrial operations. The knowledge shared here aims to aid firefighting professionals and industrial workers in better preparing for and responding to fire incidents in grain silos and dryers, ultimately contributing to safer work environments and the prevention of tragic incidents.
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
Thanks for Listening!
To share your thoughts:
- Leave a note in the comment section below
- Ask a question to be answered on the show
- Share this episode on LinkedIn, Twitter or Facebook
To help out the show:
- Subscribe to the podcast on iTunes
- Leave a review and rate our show in iTunes to help the podcast reach more people
Download the Episode
DSS254: Avoiding the Chimney Effect when Fighting Grain Dryer Fires
