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NFPA 770 Opens the Door to Hybrid Fire Extinguishing Systems in Industrial Settings

July 14, 2022
Booth #1802, Exhibit Floor
Knowledge Hub - Technology Horizons
Carbon dioxide (CO2) fire suppression systems are the most prevalent systems installed today to protect air-cooled hydroelectric generators. Widespread use, however, does not mean that they are the best option in terms of worker safety. In fact, the minimum concentration of CO2 required to extinguish a flame (34%) is lethal. The inherent safety of hybrid fire-extinguishing systems makes them a favorable option in areas where personnel are required, and with the recent publication of NFPA 770, “Standard on Hybrid (Water and Inert Gas) Fire-Extinguishing Systems,” these systems are gaining interest from plant owners. The standard was prepared for the use and guidance of those charged with purchasing, designing, installing, testing, inspecting, approving, listing, operating, or maintaining hybrid fire-extinguishing systems. This paper explains how NFPA 770 was developed, how it is being applied to installations in hydropower facilities, and why hybrid fire-extinguishing systems are being considered by plant owners as the only suitable alternative to replace aging CO2 systems. The introduction of the Victaulic Vortex™ system in 2003 marked an innovation milestone in the development of hybrid fire-extinguishing systems. The system uses supersonic distribution to create a homogeneous suspension of nitrogen and water molecules that are 10 microns in size attacking the oxygen and heat legs of the basic fire triangle to suppress and extinguish. The tiny droplets create a cloud that absorbs heat and reduces oxygen to a target level that safely extinguishes fire without compromising life-safety. A unique benefit to this system is that it eliminates the need for room integrity and allows system discharge as soon as smoke or fire is detected. There is almost no surface wetting, so very little cleanup is required after system discharge. Nitrogen is the primary extinguishing agent in smaller fires, reducing the oxygen level in the space within safe breathing tolerances, where combustion cannot be sustained. In larger fires, homogeneous mixtures are more effective, cooling the fire by absorbing the heat and reducing the available oxygen. The heat-absorbing water droplet surface area is 90 times greater than that of any standard sprinkler system. The discussion will provide a case study that explains how a Victaulic Vortex™ hybrid fire-extinguishing system was installed at Boundary Dam in Washington during a recent rewind. The project illustrates how a hybrid fire-extinguishing system has replaced a CO2 system in an aging hydropower facility to protect turbine generators and provides a compelling example of how new thinking and ingenuity are overcoming the challenges associated with traditional fire safety systems in the hydropower sector.

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