Clearing The Fog Around Water Mist
Perhaps a good starting
point is to explain how high-pressure water mist suppression systems in
general, and the new Tyco MicroDrop® in particular, work.
Tyco's MicroDrop®
system is water that, at a pressure of 100bar,
converts on discharge to a fine atomised mist.
This fine mist evaporates very quickly and is converted into steam that
smothers the fire and prevents further oxygen from reaching it. At the same
time, the evaporation of the water creates a significant cooling effect. So the
fire is extinguished by oxygen displacement and cooling.
This combines the fire suppression
characteristics of both conventional water-based suppression systems - deluge
or sprinkler systems- and gaseous fire suppression systems.
Obviously, water mist is extremely popular from an environmental standpoint, as it contains nothing but pure, potable water and so is completely safe for people and harmless to the environment. Also, when compared with conventional water sprinkler systems, the MicroDrop® system uses only ten percent of water for a given area. This has the benefit of minimising the potential for water damage on discharge or in the unlikely event of an unwanted system release. Smaller pipework dimensions result in a considerable reduction in weight, and enable the system to be installed in confined spaces.
OFFICE & ARCHIVE PROTECTION
Water-based systems in general have not been overly popular in offices, archives and museums for wholly understandable reasons. With the unprecedented growth of electronic IT and communications technology in the past few decades, businesses have become entirely dependent upon it for their very survival. And, as every schoolchild is taught: water and electricity do not mix! Water also has the potential to irreparably damage documents and destroy age-old manuscripts and historic artefacts and treasures.
These concerns are very real indeed when considering conventional sprinkler systems and water deluge systems due to the massive volumes of water with which they attack a fire. In reality, the water can do as much collateral damage as the fire itself. However, the high-pressure water mist option overcomes these challenges.
The 90 percent reduction in the volume of water when compared with a typical sprinkler system means that the risk of water damage is considerably reduced. Additionally, the fine mist traps embers and smoke particles, washing them out of the contaminated air, so minimising damage to equipment, the interior of the building and its contents. Bonuses of the MicroDrop® system are that installations demand much less space, either very little or no water is required from the public water supply, and the solution severely limits the damage caused by heat. Systems can be installed with dry piping that ensures that there is neither pressure nor water in the protected area, so avoiding the risk of water damage in the unlikely event of leaking pipes.
PAINT SPRAY BOOTH FIRE SAFETY
The MicroDrop® system is also extremely useful for protecting industrial areas that traditionally have been protected by carbon dioxide (CO2) suppression system installations that have often necessitated the inconvenient closing-off of the area to contain the gas.
Paint spray boots and paint drying ovens are typical examples that also include the challenge of installing an extinguishing system that will safely suppress flammable liquid fires. Water deluge systems have been used, but have proven to be less than ideal due to the volume of water that is discharged and the inevitable ensuing damage that is done to electronic equipment and the surrounding areas. There are also question marks about deluge systems' suitability to extinguish certain types of hazardous liquid fires.
For these applications, the MicroDrop® system uses traditional nozzles to cover the hazardous area itself, while a row of micro-nozzles mounted on a pipe is used to create a curtain of water mist in front of any large openings to the booth. This curtain helps to minimise the amount of oxygen that would otherwise be sucked into the fire; it also reduces the amount of toxic smoke and gases that would escape into the surrounding production environment.
INDUSTRIAL DEEP FAT FRYER PROTECTION
Conventional thinking has it that using water to attempt to extinguish a fat fire that, in all probability involves hot or burning cooking oil, is not merely unwise - it is extremely dangerous. The reasoning again is sound; the water, if applied from a conventional water sprinkler system, a portable extinguisher or a hose will merely expand rapidly in the burning oil exploding into an uncontrollable inferno.
However, high-pressure water mist has proven that water itself is not the issue; it is the way in which it is applied to the fire that is the critical consideration. Indeed, the very fine droplets produced by the Tyco MicroDrop® system are ideal for extinguishing of industrial deep fat fryers, and fires in associated ducts. The water mist system also lowers the temperature of the hot oil, reducing the possibility of re-ignition and importantly in a commercial environment enables the facility to be placed back into production with the minimum of production downtime
A typical MicroDrop® system comprises separate cylinders filled with nitrogen and water; alternatively the water can be pump-driven to provide a continuous supply of water mist. When the system activates, the ventilation system and heat sources for the frying equipment are switched off, and the system can be operated manually or automatically when linked to a fire detection system.
MARITIME STORAGE & ACCOMMODATION
The Tyco MicroDrop® system is particularly suitable for protecting accommodation and service areas on both cargo and passenger-carrying ships, is approved to the International Maritime Organisation [IMO] Resolution A 800, and by all of the major international classification societies.
The MicroDrop® system creates a high pressure only during the extinguishing process. This high pressure ensures that areas around any hot surfaces are cooled but, as the water mist evaporates before it reaches the hot metal, there is no risk of shock cooling and so changes in the metal structure are avoided.
The water mist nozzles in accommodation areas are usually the closed type that incorporates a glass bulb that fractures at a pre-determined temperature, releasing the high-pressure water mist. However, a more sophisticated system is available that allows remote temperature reading and remote activation of the nozzles. This enables the officer in charge to instigate proactive firefighting measures by creating a water mist barrier around the affected area.
ENGINE PROTECTION ? TOTAL FLOODING & LOCAL APPLICATION
A major advantage of high-pressure water mist suppression for the total flooding protection of ships' engine rooms is that the small quantity of water needed to extinguish a fire is harmless to equipment.
Tyco MicroDrop® can therefore be used to replace Halon systems and is a much safer first attack option to supplement the traditional carbon dioxide (CO2) suppression systems that are unsuitable for applications where people are likely to be exposed to the gas, as they represent a serious toxic hazard and risk to life. The system is approved by all of the major international classification societies to IMO 668 [Alternative Arrangements for Halon Firefighting Extinguishing Systems in Machinery Spaces and Pump Rooms] for engine rooms up to 3,000 cubic metres.
The MicroDrop® system for local application in ships' engine rooms complies with IMO 913 [Guidelines for the Approval of Fixed Water-based Local Application Firefighting Systems]. The standard system is cost effective and easy to install, and includes an addressable detection and activation mechanism for unattended engine rooms. This particular system operates at a minimum of 80bar. It comprises: a pump unit skid with an electrical panel that is ready for connection to the ship?s power and water supply; section valves that are remotely operated for each piece of equipment that is protected; nozzles, pipes, fittings, main lines, detection heads and alarm units for each section.
A similar system, again complying with the requirements of IMO 913, is available to provide local protection for machinery spaces. It is a dry-pipe system for automatic or manual activation that meets the new requirements of Regulation 7 of SOLAS [International Convention for the Safety of Life at Sea] Chapter 11-2 [Revised Guidelines for the Approval of Sprinkler Systems].
WIND TURBINE SOLUTION
With the fast-expanding use of wind turbines for power generation and their high capital cost, fire protection has become a major concern. Due to the very nature of their design and construction, they do not easily lend themselves to gaseous suppression systems. They also present wind farm operators with the added challenges that they are often in remote and difficult to access locations, and that the fire is most likely to occur many metres up in the Turbine's nacelle or housing.
These obstacles are overcome using a MicroDrop® system to protect the entire turbine. This is made possible by the very low water consumption that is required, the small and lightweight pipe diameters, and the compact pump - all of which can be fully contained within the nacelle. The water tank on the pump contains a heating element to make the unit frost-proof, plus there is battery back-up in case of power failure.
WHERE TO NEXT?
According to a report prepared in the UK in 2005 by the Building Research Establishment, there are: 'still a number of myths, misunderstandings and lack of knowledge about water mist systems.' Much of this undoubtedly relates to a lack of understanding regarding how water mist systems work, and a misunderstanding of the very appreciable difference between water mist systems and sprinkler systems. What is undeniable though is that water mist technology is an emerging and credible fire protection technology that has properties that make it an attractive choice for selected applications, particularly where low water availability, consumption or discharge by the fire protection system is a major consideration.
With the growing concern for the environment and a strengthening desire to adopt sustainable solutions, it is a firefighting technology that can also rightly take its place alongside the other leading solutions that are safe for people, safe for property and safe for the environment. Indeed, there is every reason to believe that we will see an increasingly fast take-off of MicroDrop® in such industries as food manufacturing and for such applications as engine and emission test cells, generator and engine compartments and flammable liquid stores.
Further details are available by telephone on +44 (0) 1493 417600, by fax on +44 (0) 1493 417700, or via email at ashiner@tycoint.com.
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