Fire Sprinklers and Battery Rack Storage
The world is driven by batteries whether it be a AA battery for the tv remote or a 150-pound battery that’s used to back up server power in a city high-rise. Batteries are used by the thousands every single day for multiple applications. The fire protection industry, specifically the fire sprinkler industry, is trying to address new challenges that batteries and rack storage poses. Rack storage is a combination of vertical, horizontal, and diagonal members that support stored materials. Racks can be fixed or portable. (NFPA13 Section 188.8.131.52). Living in the current Covid climate, warehouses have been popping up like mushrooms to accommodate the rapid expansion of online shopping. Big box stores have dominated the market by mass producing distribution warehouses all over the country.
Batteries by nature are a self-contained environment that produce their own energy which in turn can serve as the fuel load of a fire. There are many types of batteries on the market that are being tested and studied on how they interact with fire sprinklers, such as lithium-ion phosphate, lithium nickel oxide, and lithium manganese oxide batteries. The biggest threat that needs to be controlled by fire sprinklers when protecting batteries is thermal runaway.
Thermal runaway is a chain reaction within a battery cell that can be very difficult to stop once it has started. It occurs when the temperature inside a battery reaches the point that causes a chemical reaction to occur inside the battery. The energy stored in that battery is released very suddenly and the process is repeated battery to battery. Imagine rack storage that is holding batteries that is 25 feet tall and 50 feet long. This is a recipe that could potentially create a fire load that cannot be stopped by conventional measures.
Li-ion batteries are specifically listed in NFPA 13 as a commodity that is outside of the scope of that standard. NFPA has created NFPA 855, The Standard for the installation of Stationary Energy Storage Systems (ESS), which provides protection criteria for li-ion batteries but only when they are used in an energy storage system, which is not the same as battery storage. NFPA’s Fire Protection Research Foundation has provided research in conjunction with FM Global to provide guidance for batteries in a storage application. This research consisted of 3 phases each phase produced reports that can be found at this link: https://www.nfpa.org/News-and-Research/Data-research-and-tools/Hazardous-Materials/Lithium-ion-batteries-hazard-and-use-assessment
While the intent of this research was to assist the NFPA 13 committee to determine adequate protection criteria for battery storage, such criteria has not yet been adopted. Additionally, while the reports conclude with an acceptable protection arrangement, it stops short of a full criteria. For example, while the report references findings for the protection specific storage array up to 15 ft with 40 ft ceilings, providing K-22.4 sprinklers spaced 10 ft by 10 ft and operating at 35 psi, they do not provide an indication as to what the size of the design area should be.
FM Global data sheet 8-1 does provide guidance for Li-ion batteries which mirrors the findings reflected in the Fire Protection Research Foundation’s report. The FM Data sheet provides a minimum number of sprinklers flowing at a total of 12 sprinklers. This study can be found here: https://www.nfpa.org/News-and-Research/Data-research-and-tools/Suppression/Sprinkler-Protection-Guidance-for-Lithium-Ion-Based-Energy-Storage-Systems –Jeffrey Dunkel, Fire Protection Engineer National Fire Sprinkler Association (NFSA)
The NFPA 13 standard detailing fire sprinkler installation in commercial structures breaks down what we would envision a fire sprinkler system would look like. Piping on the ceilings with either an upright or pendent sprinkler head spaced every few feet apart and maybe sidewall sprinkler heads in strategic locations. With the uptick of big warehouse and distribution centers being built that house thousands of square feet of rack storage, a traditional fire sprinkler system may face challenges when presented with such a unique fuel load. The NFPA 13 2019 edition documents a secondary option, in-rack fire sprinklers, that work independently from overhead fire sprinklers and add more fire protection to rack storage.
Several modern in-rack sprinkler systems are now available that use a “virtual floor” concept. These in-rack sprinkler systems are designed to protect commodity stored in racks in conjunction with the ceiling sprinkler system. This allows the ceiling sprinkler system to be designed independently of the in-rack sprinkler system by considering the highest level of in-rack sprinklers as a “virtual floor”. Consider the top level of in-rack sprinklers as a floor when selecting the ceiling sprinkler system design criteria. See the specific criteria in NFPA 13, 2019 edition, Section 25.8 and FM Data Sheet 8-9 Section 2.3.6 for complete details and limitations.
Fire sprinkler protection and battery rack storage is still new territory and is evolving every day. As the data from research becomes available the NFPA will continue to keep the pulse of the industry and distribute new and tested best practices for the fire protection environment. In the meantime, if you are working on a project that encompasses fire sprinklers and rack storage or battery rack storage, feel free to visit www.nfsa.org and leverage the resources available to all NFSA members.
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