Fire Protection Solutions for Canopy and High Bay Structures

High bay and canopy structures pose unique challenges when it comes to fire protection. These expansive spaces, often found in industrial settings, warehouses and outdoor canopies, require specialized fire suppression systems that can quickly and effectively detect and combat fires. Traditional methods, such as sprinklers and beam detectors, face limitations in these environments, making it crucial to explore alternative solutions to properly protect these spaces. Recognizing this, we developed the patented Fire Rover Automatic Water Cannon (AWC), a fire protection technology designed to provide rapid detection, visual verification and targeted suppression, thereby reducing nuisance alarms and ensuring enhanced safety measures.

High bay and canopy structures are characterized by their towering ceilings, which can significantly delay the activation of conventional fire detection and suppression systems. Sprinklers, for instance, rely on heat detection to trigger water release. Still, the height of these ceilings often means the fire has significantly progressed by the time the sprinklers activate. This delay can result in extensive damage and increased risk to personnel safety. Figure 1 shows a typical time to activation of a fire sprinkler in a high bay versus the time to activation for an optical flame detector (OFD). OFDs use line-of-site detection methods and are tested to FM Global standards, typically at 100 feet (about 30 meters) with a small pan fire. The fire size at detection for the OFDs is between 100 and 250 kilowatts (kW), while the fire size at detection for the overhead sprinkler in a high bay require the fire to grow to be over 40 times larger. Picture a small campfire compared to a very large bonfire!

Figure 1 – Graph of time to detection for a sprinkler in a high bay versus optical flame detection.

Moreover, in open-air environments like tall canopies, weather conditions such as wind can pose additional complications. The buoyant plume generated by a fire can be easily dispersed by wind, thus challenging the effectiveness of traditional sprinkler systems. Even moderate wind speeds can push the plume entirely out of the structure, something which could result in activation of the wrong sprinkler heads or failing to fight the fire altogether.

For a recent project, modeling of the sprinkler activation of a high bay open structure was conducted using the National Institute of Standards and Technology’s Fire Dynamics Simulator (FDS), an open-source computational fluid dynamics package. FDS utilizes Large Eddy Simulation (LES) numerical solution approaches to model the dispersion of gases, and specifically low-speed, thermally driven flows like those typically found in fire scenarios. A Cartesian grid system is applied over which the solutions for thermal plume concentration with time can be solved.

Eight scenarios were modeled using varying fire sizes and structure openings. A simple mockup of the building was simulated to evaluate the effects of wind on a smoke plume with the open-walled building. Four scenarios were run using two heat release rates (1 MW and 5 MW) and two rollup door configurations (one door and four doors). The fire source was place in the middle of the processing pit area, as shown in Figure 5. The wind was prescribed at 14.5 mph (about 6.5 m/s) entering the open side of the building and exiting through the rollup door(s). This represents the average wind speed in the area, according to the National Oceanic and Atmospheric Administration, and the prevailing wind direction. The simulations used a coarse grid with cell size of approximately 1.6 feet (about 50 cm) for a computational domain of 1,416,960 total grid cells. Simulations were run for a minimum 20-minute duration. The domain also included an array of sprinklers located above the fire with a 10-foot (30.5 cm) spacing. The sprinklers had an activation temperature of 135 degrees Fahrenheit (57 degrees Celsius) and a relative thermal index of 130.

The simulations changed the fire size, door configuration and wind speed. In all the simulations without a wind condition (0 mph), sprinkler activation was achieved. However, sprinkler activation was achieved in only one of the four simulations with wind. The modeling was limited to steady state fires, one wind speed and direction. Despite these limitations, the modeling clearly demonstrates sprinkler activation can be compromised under average wind conditions. Figures 2 and 3 are slice images taken from the model runs. Figure 2 used a 5 MW steady state fire with four open doors and no wind. The fire modeled a steady state fire instantaneously producing 5 MW to capture an extreme thermal condition. This results in extremely fast sprinkler activation times. Figure 3 models the same door and fire scenario but incorporates an average wind condition. Despite the extreme thermal condition, the wind can deflect the plume. This effect would be even greater if a fire growth rate was incorporated into the model rather than the large steady state fire.

Figures 4 and 5 are images from of scenario S2W-5MW, demonstrating the wind flow and smoke condition, respectively. In this scenario, four doors were open, the fire was 5 MW and a 14 mph (about 6 m/s) wind condition was imposed on the structure. It can be seen from the figures that the wind is directed through the building, and thereby deflecting the plume and carrying a very significant amount of the heat out of the structure.

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The Automatic Water Cannon (AWC) is developed specifically for addressing the challenges posed by high bay and canopy structures. This state-of-the-art system integrates advanced technology to address the limitations of traditional fire protection methods, providing efficiency and effectiveness.

The AWC utilizes thermal detection and flame detection to swiftly identify fire incidents within high bay and canopy environments. This rapid detection ensures firefighting measures are initiated at the earliest possible stage, minimizing the spread of flames and reducing the potential for extensive damage.

Once a fire is detected, the AWC deploys targeted suppression via a remotely controlled monitor, delivering water, foam or listed water additive agents directly to the source of the fire. This targeted approach ensures maximum effectiveness in extinguishing flames while minimizing water usage and collateral damage. A FM Global report from April 2020 entitled “Reducing Water Demands with Innovative Fire Protection Solutions” showed that AWCs like Fire Rover reduced the water demand by up to 92% when compared to traditional sprinkler systems.

One of the key advantages of the AWC is its ability to provide visual verification of fire incidents, significantly reducing the occurrence of nuisance alarms. Traditional fire detection systems often rely solely on sensor data, leading to false alarms triggered by factors such as dust, steam or electrical interference.

By integrating visual verification capabilities, the AWC distinguishes between actual fire events and false alarms, allowing for prompt and accurate response by firefighting personnel. Not only does this enhance the overall safety, but it also reduces operational disruptions and maintenance costs associated with false-alarm incidents. This is done utilizing certified UL Central Stations for monitoring, alarm verification, targeting and suppression activation (Figure 6). 

Summary

High bay and canopy structures present unique challenges for fire protection, necessitating specialized solutions that can overcome the limitations of traditional methods. The AWC represents the latest innovation in this regard, offering rapid detection, targeted suppression and visual verification capabilities specifically tailored for these environments.

With its ability to overcome the delays inherent in traditional fire protection systems and mitigate the impact of external factors such as wind, the AWC ensures enhanced safety and peace of mind for personnel operating within high bay and canopy structures. By investing in advanced technologies like the AWC, organizations can effectively safeguard their assets, personnel and operations against the threat of fire, ensuring uninterrupted productivity and business continuity.

About the Authors

Ryan Fogelman, JD/MBA, is vice president of strategic partnerships for Fire Rover. He is focused on bringing innovative safety solutions to market, and two of his solutions have won the distinguished Edison Innovation Award for Industrial Safety and Consumer Products. He has been compiling and publishing the “Reported Waste & Recycling Facility Fires In The US/CAN” since February 2016 and the “Waste & Recycling Facility Fires Annual Report.” Fogelman regularly speaks on the topic of the scope of fire problems facing the waste and recycling industries, early detection solutions, proper fire planning and early-stage fire risk mitigation. Additionally, Fogelman is on the National Fire Protection Association’s Technical Committee for Hazard Materials. (Connect with Ryan on LinkedIn at https://www.linkedin.com/in/ryanjayfogelman or email at [email protected])

James “Andy” Lynch, MSc, is CEO of Fire Solutions Group (FSG). For more than 25 years, Lynch has amassed extensive experience in fire protection engineering, code consulting, fire research and product development. Lynch has extensive fire testing experience, having conducted numerous test series for litigation purposes, the military and commercial products. Lynch has a B.S. in Mechanical Engineering and a M.E. in Fire Protection Engineering from Worcester Polytechnic Institute. He is a member of the Salamander Honorary Fire Protection Engineering Society, National Fire Protection Association (NFPA), Society of Fire Protection Engineers, National Fire Sprinkler Association and International Association for Fire Safety Science. Lynch also serves as a member of NFPA’s Fire Testing Committee and on the New NFPA 715 Standard for the Installation of Fuel Gases Detection and Warning Equipment. (Connect with Andy on LinkedIn at https://www.linkedin.com/in/jamesalynch or email at [email protected])

Fire Rover is one of the financial supporters of the Burning Matters Newsletter.

P.S. I enjoyed working with Andy 20 some years ago when we were both at Combustion Science and Engineering. Here is a paper we published together - I think I will write a newsletter about it at some point: https://link.springer.com/article/10.1023/A:1025374032640