Explosion Venting Design for Thermal Runaway in Energy Storage Systems: Practical Challenges in FM-Standard Venting Calculations

FM energy storage system thermal runaway venting design: Practical challenges and feasible approaches for FM-standard vent area calculations

FM standard vent area calculation practical challenges and feasible approaches As lithium-ion battery energy storage systems (Battery Energy Storage Systems, BESS) continue to be deployed across industries, the risk of fires and explosions caused by system thermal runaway has become a critical safety issue that the industry must address. Internationally, whether under NFPA68 venting standard promoted by the U.S. National Fire Protection Association (NFPA) or the battery energy storage system data sheets developed by FM Global under FM5-33, the inevitability of thermal runaway in energy storage systems is acknowledged and venting measures are required in explosion protection designs to reduce the impact of internal gas deflagrations on the system and surrounding facilities.

However, because energy storage system manufacturers often cannot provide the relevant test data required as input for NFPA68 vent area calculations—primarily to save R&D and testing costs—and because current domestic regulations do not mandate thermal runaway venting design for energy storage systems, applications face many challenges in data acquisition and standard selection. This article will focus on the FM5-33 standard, examine its practical challenges and feasible approaches for vent area calculation, and propose corresponding solutions.

FM5-33 vent area calculation basis Energy storage system thermal runaway venting design: Unlike the NFPA68 method, which relies on extensive test data, FM Global’s FM5-33 standard emphasizes practicality and adopts the following strategies:

• Unified parameter method

When specific test data are lacking, propane can be used as a representative gas for vent area calculations, thereby providing a conservative design parameter with safety margin.

• Cost reduction

This approach can effectively reduce R&D and testing costs, while demonstrating high practical feasibility in vent panel selection and subsequent explosion protection design, offering energy storage system manufacturers a viable path that both reduces risk and meets standards.

Venting design considerations When performing venting design, the following aspects must be considered comprehensively:

• Vent opening placement

Vent openings should be located as far as possible from personnel activity areas and critical equipment to ensure that, in the event of a deflagration, released gases can be expelled smoothly and avoid secondary harm to the surrounding environment and equipment.

• Venting device performance

The performance of the venting device is critical; its response time, actuation/opening pressure, and other indicators must meet requirements for stability and reliability so it can act quickly and effectively in an emergency.

Conclusion Facing the risks of thermal runaway and gas deflagration in energy storage systems, manufacturers must seek the best balance among gas parameters, structural design, standards selection, and data availability. The loss-limiting (damage-limiting) structural design method and the propane parameter method provided by FM5-33 not only supply design bases with high safety margins but also provide an effective practical path for those who wish to reduce R&D costs and rapidly implement explosion protection designs.

Shanghai Tengxi Construction’s FM-standard vent area calculation services and ATEX-certified explosion vent panels are undoubtedly the best combined solution to address thermal runaway challenges, helping enterprises meet safety design requirements while effectively reducing deflagration risks and thereby improving the operational safety and overall compliance of energy storage systems.