Twin-Fluid Hybrid Fire Suppression Explained
Today, there are a large variety of complex fire suppression systems available on the market. From traditional water-based sprinkler systems, the simplest and most widely used, to CO2, chemical and inert gas systems; each technology has unique advantages and disadvantages depending on hazard application.
After an in-depth analysis of existing fire suppression systems, there are a few overall challenges to fire suppression. Some systems require airtight room integrity with little or no ventilation in order to ensure effective fire suppression, but there are circumstances where this is not possible due to the design or nature of the space.
In the course of suppressing a fire, some systems can cause irreversible damage to expensive equipment, electronics, motors or controls because of wetting and chemicals. Many systems also require costly and time-consuming clean up after discharge due to the use of chemicals and/or high-volume wetting. Clean up of chemical systems may even be classified as hazardous, which can be expensive and inconvenient. This can also make system re-charge expensive and cause significant downtime in a facility.
Additionally, some systems that use chemicals are toxic to the environment and many systems can be extremely hazardous to occupants, requiring spaces to be evacuated before system discharge, whilst many systems can deplete oxygen levels to a threshold that is harmful to humans.
As a manufacturer of mechanical grooved piping systems well known for fire protection solutions, Victaulic set out to develop an alternative system that would address all these issues. The company researched other fields outside of fire protection that it hoped would lead to some solution paths to the goal of making even finer water particle sizes.
Atomising fluids has been long studied in other fields such as combustion science. Thinking outside the realm of traditional water mist methods that have been based on water being mechanically sheared by injecting it onto deflectors, Victaulic researched different hardware concepts for fluid atomization with parallel gas flow.
Research showed that combining cooling and oxygen dilution could be even more effective than either one alone. This combination was achieved with the Victaulic team’s use of nitrogen gas to atomize the water and act as a particle carrier to penetrate fire plumes.
The Victaulic team focused on a method of injecting the atomized droplets into a nitrogen “down-blast” to penetrate into fire plumes to get to the root of the fire for more efficient cooling using smaller than typical droplets, which collectively present a greater surface area. The larger the surface area, the faster that heat may be absorbed. A high rate of heat absorption reduces the risk of fire propagation by reducing convective and radiative heat transfers.
The result of these efforts is a unique category of fire suppression technology, recognized today by FM Approvals in FM 5580 “Hybrid Water & Inert Gas for Fire Extinguishing Systems”.
The Victaulic Vortex Fire Suppression System was the first to be approved in this FM category and because it uses a blend of inert clean agent gas and water mist, it is suitable for special hazard machinery spaces, turbine enclosures and flammable liquids.
The Victaulic Vortex system uses a supersonic jet stream of nitrogen to atomize a low-pressure stream of water into sub-10-micron water droplets. The droplets are as little as one 30th the size of water particles delivered by traditional water mist systems and provide as much as 50 percent more heat absorption and total extinguishing.
As the water droplets are atomized, they are evenly mixed with the nitrogen molecules and discharged into the hazard space in homogeneous suspension. Typically, in other twin-fluid technologies, nitrogen is a propellant of another suppressing agent like water mist, but the Victaulic Vortex system uses the water mist and nitrogen as complimentary extinguishing agents.
For smaller fires, the nitrogen is the primary extinguishing agent and reduces the oxygen to a level that is still breathable, but cannot sustain combustion. For larger fires, the ultra-fine water droplets cool the fire by absorbing the heat and reducing available oxygen.
In addition to providing highly effective fire suppression, this unique hybrid delivery results in a range of benefits. There is minimal wetting of protected areas, with the amount of water released per emitter as little as 3.79 liters/one gallon per minute. In comparison, traditional water sprinklers release more than 94,64 liters/25 gallons of water per minute per sprinkler while high-pressure water mist systems release 30,28 liters/eight gallons of water per nozzle per minute.
Vortex also permits a safe system discharge for environment and personnel. The system uses water and nitrogen, two readily available and naturally occurring elements, and no hazardous chemicals. During system discharge, oxygen saturation remains at safe levels for occupants as accepted by the US Environmental Protection Agency (EPA). Normal atmospheric condition is 79 percent nitrogen and 21 percent oxygen.
Water and nitrogen are readily available and, since there is minimal clean-up required, and minimal wetting, there is very little disruption to ongoing operations, so limited facility downtime and quick system recharge. In addition, due to the high-velocity swirling “vortex” discharge of the system, minimal room integrity is required and the system is effective in open spaces.
Each Victaulic Vortex emitter can protect up to 70,79 cubic meters/2,500 cubic feet of space, and the system is scalable to cover as much space as required. Zones can be centrally controlled and independently activated for fire suppression where it is needed.
The Victaulic Vortex system also features a low operating discharge pressure of approximately 1,72 bar/25 psig at the system emitter. Most high-pressure water mist systems operate at 103 bar/1500 to 172 bar/2500 PSIG, and inert gas systems operate at 172bar/2,500 psig.
The low discharge pressure of the Victaulic Vortex system is especially beneficial in corrosive environments because it allows for the use of plastic pipe, and emitters can be specially designed from PTFE/PVDF. This is not possible with CO2 or high-pressure water mist systems. Nitrogen at 1,72bar/25 psig enters the emitter while water at less than 0,35bar/5 psig enters the water jacket external to the nitrogen flow.
As nitrogen exits the emitter, shock discs are created as the flow changes speeds from sonic to subsonic. Additional shock discs are created when the nitrogen encounters the foil. When the water is introduced into these shock discs from the ring of concentric holes at the base of Victaulic’s patented emitter, it is atomized to ultra-fine droplets, which are blended into the nitrogen flow at high velocity.
After the water is atomized, it is carried in the nitrogen flow at equal partial pressures. Since the water is suspended in the nitrogen, it maintains its momentum and is capable of being projected for relatively large distances and, in the process, becoming entrained in fire plumes.
FM Approvals has approved the Victaulic Vortex system for special-hazard machinery spaces and turbine enclosures, in applications such as internal combustion engines or other equipment using fuel and/or lubrication fluids with volatilities less than or equal to heptanes, and incidental use or storage of limited quantities of flammable liquid of not more than two drums of 208 L (55 gallons).
In turbine enclosures, uniform cooling of the casing is critical to successful fire suppression. Uneven cooling can cause the equipment to shrink unevenly, allowing the blade to interfere with the casing at the risk of ruining the turbine.
Suppressing fires within turbines and machine spaces also requires a system that can uniformly penetrate vented or shielded areas, without requiring room integrity. The Victaulic Vortex system has been tested and proven to be highly effective in these spaces in part because of its high-velocity hybrid distribution and heat absorption.
With its FM 5580 approval, Vortex is suitable for a wide range of additional industrial applications. These include machinery space applications such as oil pumps, oil tanks, fuel filters, generators, transformer vaults, gear boxes, drive shafts, lubrication skids, diesel engine driven generators and other similar machinery using fuel and/or lubrication fluids with volatilities less than or equal to light diesel.
Vortex systems can already be found protecting key industry across the globe, including at the state-of-the-art “AP4” production line in Kentucky, USA, which is owned by North American Stainless (NAS), part of the Acerinox Group.
The new facility is one of the largest of its kind on the planet and Vortex met the challenges it presented, including protection of sensitive equipment without using large quanities of water, effectiveness in corrosive environments, open space effectiveness without requiring room integrity, minimum downtime following discharge, and design flexibility for expansion and maintenance.
The Victaulic Vortex system has also been recognized by the EPA with a Significant New Alternative Policy (SNAP) approval, listing the system as a hybrid inert gas, water-based system and an acceptable replacement for Halon 1301 in total flooding applications.
Furthermore, in recent testing carried out by Victaulic involving a Vortex system discharge in an environment designed to simulate an information technology setting, data was not lost nor were any hard drives damaged due to the simulated fire suppression.
There are already numerous installs in information technology areas, minimizing the amount of water around computer equipment. These include the Golden Ears Bridge Data Center in Canada, which benefitted from flexible and green Vortex technology, and the Zappos Data Center in the US, where the Victaulic system fulfilled a specific need to suppress fires out in the open.
The Vortex approach is an innovation that takes the best of all systems and moves these technologies forward.
The system’s ability to create a homogeneous suspension of sub 10-micron water droplets in nitrogen while maintaining a high momentum and low operating pressures has demonstrated fire suppression capabilities surpassing previously known water or inert gas systems.
The system is also scalable, providing robust fire suppression to machinery spaces and other hazardous environments with minimal water damage and a fast return to operations after a system discharge.
For more information, go to www.victaulic.com