Automated Storage and Retrieval Systems (ASRS) have revolutionized warehouse operations by enhancing efficiency and optimizing space utilization. However, these systems also introduce unique fire risks that require meticulous management to prevent catastrophic losses. This article explores the fire hazards associated with ASRS, focusing on robot design, early fire detection, and comprehensive fire protection strategies.
ASRS are intricate systems employing robots to manage high-density storage grids. Despite their operational benefits, these systems pose significant fire risks. A notable incident illustrating these risks is the Ocado fire on February 5, 2019. The fire originated from arcing at a robot charging station, which ignited the plastic top of a robot. Despite having an advanced air sampling fire detection system, the fire wasn't detected until it was visually observed on CCTV. By then, it had spread extensively, resulting in the complete destruction of a 240,000-square-foot automated storage facility.
One primary fire hazard in ASRS is the use of combustible materials in robot construction. The Ocado fire highlighted the dangers of plastic components near charging ports. To mitigate fire risks, robots should be designed with minimal combustible materials. Reducing or eliminating the use of plastics and other flammable substances can significantly decrease the likelihood of ignition.
Early fire detection is crucial in ASRS to ensure timely response and limit fire spread. Systems like the Very Early Smoke Detection Apparatus (VESDA), which sample air for smoke particles, can detect fires in their early stages, allowing for prompt intervention. The failure of the air sampling system in the Ocado fire underscores the need for robust and reliable detection mechanisms.
Effective fire protection in ASRS involves multiple strategies, including vertical barriers, sprinkler systems, and designated robot holding areas. Vertical barriers, made from minimum 20-gauge sheet metal, are installed from floor to the underside of storage grids, segregating areas into 1,000-square-foot sections to prevent fire spread. Maintaining a fire break next to these barriers by keeping one storage grid column empty is crucial to prevent heat transfer and ignition of materials on the other side.
In-rack sprinklers are essential to prevent vertical fire spread. For buildings with a height of 25 feet or less, minimum K14 pendant storage sprinklers can be used, eliminating the need for elevated mezzanines. These sprinklers provide comprehensive coverage and effective fire suppression. Additionally, designated holding areas free of combustibles are critical in the event of a fire. The Ocado fire demonstrated the risks associated with robots being the ignition source. By moving robots to safe holding areas away from flammable materials, the risk of fire spread can be minimized.
Access to the fire source is vital in ASRS. Removable wall panels and perimeter mezzanines can provide fire personnel with access points. Elevated mezzanines, installed 20 feet above the storage arrangement, allow firefighters to overlook the storage grid and access the fire, though they add to project costs. Alternatives such as monitor nozzles and vertical barriers can eliminate the need for elevated mezzanine.
Installing monitor nozzles at the ceiling with a maximum linear spacing of 100 feet, paired with infrared or visible flame detection cameras, allows for targeted fire suppression. These systems can be monitored and operated remotely from a control room, providing effective fire suppression without the need for elevated access points.
Minimizing fire risks in Automated Storage and Retrieval Systems requires a multifaceted approach that includes robust robot design, early fire detection, and comprehensive fire protection strategies. Addressing these key areas can significantly reduce the likelihood of fire incidents and ensure the safety of warehouse facilities. The lessons from incidents like the Ocado fire highlight the importance of proactive fire risk management in the evolving landscape of automated storage technology.
For any further inquiries regarding this topic, as well as for code consulting and fire engineering design support related to your project, please don’t hesitate to contact us via email at contact@engineeringfireprotection.com.
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