Fire extinguishers – Processes – Of extinguishing fire
Reexamination Certificate
1999-11-16
2001-01-16
Kashnikow, Andres (Department: 3752)
Fire extinguishers
Processes
Of extinguishing fire
C169S065000
Reexamination Certificate
active
06173791
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to suppression of accidental fires involving cooking oil or fat, and more particularly concerns employment of pure water mist in such suppression, as well as extinction of such fires.
In recent years, the development of high-efficiency cooking equipment with high energy input rates and the widespread use of vegetable oils with high burning temperature have increased potential risks to life and property loss. Almost 50% of all accidental fires in hotels, restaurants and fast food outlets start in kitchens and the majority of these involve liquid cooking oil or fat fires. These fires are the hardest to extinguish and are easily re-ignited. Suppressing cooking oil fires has been identified as the primary fire challenge in restaurant cooking areas. Recently cooking oil fires, due to their different behavior from other types of liquid fuel fires, were re-classified into a new class of fire, Class K, by the National Fire Protection Association (NFPA); a similar classification is also being considered by the Loss Prevention Council and other agencies around the world.
Previous studies showed that foam, powder and carbon dioxide are not as effective in suppressing cooking oil fires as they are for other types of liquid fuel fires. Currently, wet chemical agents, as defined by NFPA-17A, are the primary means used to extinguish grease fires in cooking areas. They are effective in extinguishing these fires, but may cause irritation to the skin and eyes as well as clean-up problems after fire extinguishment. Furthermore, the system cost of wet chemical agents is relatively high. As a result, there is a significant need for improving fire safety and reducing the cost of protecting restaurant cooking areas through the introduction of a new effective extinguishing system.
SUMMARY OF THE INVENTION
It is a major object of the invention to provide method and apparatus to efficiently and effectively suppress such fires, through use of water mist. Such mists are non-toxic, and do not contribute to environmental problems.
Basically, the invention provides a method of extinguishing a fire characterized by production of flames openly rising above an upwardly presented liquid fat or grease zone, the fat or grease being combustible to produce the fire. The steps of the method include
a) locating a mist forming nozzle to direct mist toward the rising flames,
b) delivering essentially pure water under pressure to the nozzle so that the nozzle forms a jet stream of water mist delivered from the nozzle as a rapid expanding flow of concentrated mist,
c) and directing the mist stream into the flames to substantially encompass the flames, and to flow toward the fat or grease zone, and for a sufficient time to extinguish the flames and to lower the temperature of the surface of the fat or grease zone to a level below combustion temperature.
It is another object of the invention to carry out the above step c) to effect rapid conversion of such mist to steam, which expands outwardly about the fat or grease zone, and rapidly blankets or hovers closely about that zone, blocking air or oxygen access to the fat or grease zone.
Another object is to locate the mist forming nozzle directly above said zone and at a spacing such that the downward stream of mist expands in flowing downwardly, to quickly encompass cool, and extinguish the flames.
Rapid mist stream formation and travel into the flames is effected by supply of pure water to the nozzle at a pressure level between 220 and 450 psi, and preferably above 245 psi. Also, the length of time needed for mist stream delivery toward the fat or grease zone is typically less than about 10 seconds, for effecting flame extinction. The use of mist instead of water droplets assures such rapid flame extinction, since mist provides maximum water surface area exposed to the flame, with wide area distribution.
Another object is to eliminate electrical or gas heating of the fat or grease in conjunction with flow of mist into the flames. For that purpose, the method may include detecting the presence of flames, and then effecting delivery of the water under pressure to the nozzle, to form the mist.
A yet further object includes provision of a portable carrier, and storing water under pressure on the carrier, and in a position to be delivered to the nozzle. A water storage vessel may be provided on the carrier, the vessel having an outlet for water to be delivered to the nozzle, and providing a conduit connecting such outlet to nozzle. The portable carrier is then easily located near a fat fryer installation to be protected as in a restaurant, in accordance with the invention.
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Haefliger William W.
Kashnikow Andres
Nguyen Dinh Q.
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