This invention relates generally to compositions useful for fighting fires and methods for making and using such compositions. More particularly, the invention relates to fire-fighting foams and to apparatuses for dispensing fire-fighting foams.
Fire-fighting foams are known for fighting fires, including coal mine fires. For example, U.S. Pat. No. 6,988,558 to Araki, et al., dated Jan. 24, 2006, discloses such foams and is incorporated herein by reference, in its entirety. Prior art fire-fighting foams are produced by adding an expansion gas to a liquid concentrate. The liquid concentrate typically comprises a nonflammable base liquid that often has a surfactant therein. A thickening agent is sometimes included in the liquid concentrate to increase the viscosity of the fire-fighting foam, thereby facilitating the retention of the fire-fighting foam when sprayed on burning fuel. Unfortunately, the expansion gas added to the liquid concentrate is air, which contains about 20% oxygen on a molar basis. Thus, the fire-fighting foam contains a component that feeds the fire it is intended to suppress or extinguish. In addition, some thickening agents contain available oxygen, which also supports fires. In the case of some coal mine fires, the available oxygen in the fire-fighting foam helps the fire continue for extended periods of time (e.g., years) before becoming extinguished.
Based on the foregoing, it is the general object of this invention to provide a fire-fighting foam that overcomes the drawbacks of prior art fire-fighting foams.
The present invention resides in one aspect in a method for making a fire-fighting foam. The method comprises cooling a liquid concentrate, combining the cooled liquid concentrate composition with an expansion gas, and allowing the combined liquid concentrate and expansion gas to expand.
The present invention resides in another aspect in a diffuser for dispensing a fire-extinguishing product, comprises a discharge line having an interior, a discharge line intake and a diffuser outlet; and a casing around a portion of the discharge line, the casing enclosing a space around said portion of the discharge line. The casing comprises a casing inlet and a casing outlet, and the discharge line comprises an aspirator inside the casing to permit fluid flow between the interior of the discharge line and the space enclosed by the casing.
The present invention resides in another aspect in an optional alternative method of making a fire-fighting foam. The alternative method comprises flowing a liquid concentrate through the diffuser via the diffuser intake, flowing an expansion gas into the inlet to combine the liquid concentrate with an expansion gas to produce a liquid-gas composition, and dispersing the liquid-gas composition via the diffuser outlet to yield a fire-fighting foam.
A method of delivering a fire-extinguishing product using the diffuser described herein comprises flowing a feed composition into the intake of the device and dispensing from the diffuser outlet a fire-extinguishing product that contains the feed composition.
A method of suppressing a fire, comprising making a fire-fighting foam by the method described herein and dispensing the foam onto the fire.
A fire-fighting foam is made from a liquid concentrate into which an expansion gas is mixed. In accordance with one aspect of this invention, the expansion gas is an inert gas that is substantially free of oxygen. The liquid concentrate comprises a nonflammable base liquid and, optionally, additives thereto such as a surfactant, thickener, etc. One suitable inert expansion gas is nitrogen; other suitable gases will be apparent to one of ordinary skill in the art. The liquid concentrate is cooled before the expansion gas is added thereto. Although in the specifically disclosed embodiments the nonflammable base liquid is water and the inert extractant gas is nitrogen, the foam is not so limited in this regard and other non-flammable liquids and inert gases are within the scope of the invention.
Preferably, the thickening agent (if any) present in the fire-fighting foam contains little or no available oxygen, so that the thickening agent does not contribute available oxygen to the fire-suppressing compositions.
The fire-fighting foam may be a high-expansion foam, i.e., a foam that is expandable to several times the volume of the initial starting material. A typical high-expansion foam is prepared from a concentrate that comprises a surfactant solubilized in a non-flammable solvent. One type of foam concentrate usable with the present invention is “High-expansion Concentrate, Type 2.0 AE35,” which is manufactured by the National Mine Service Company of North Indiana, Pa. Wetting agents may also be included in the concentrate to facilitate the penetration of the fuel. The foam may be proportioned (i.e., mixed with the fire-suppressing composition) in any ratio that results in a suitable mixture for fire-fighting purposes.
The fire-fighting foam may be applied directly onto a fire to extinguish the flames by smothering the fuel being oxidized and/or lowering the temperature of the fuel below its flash point. To smother the flames, the fire-fighting foam is used to isolate the fuel from contact with the ambient atmosphere, which contains oxygen. The fire-fighting foam may be dispersed to the burning fuel by using any suitable spray technique on the foam or on a fluid combination of the liquid concentrate and expansion gas that forms the foam, e.g., pressure spraying, sprinkling, or misting, e.g., by generating a fog that is directed over the fuel.
Referring now to
Referring now to
The diffuser 10 may be used in a variety of ways. In one embodiment, a fire-extinguishing product can be discharged via the diffuser 10, without adding anything to the feed composition via the diffuser 10.
Alternatively, the diffuser 10 can be used as a mixer to combine components of a fire-extinguishing product to be delivered from the diffuser outlet 18. Generally, a first component is provided via the intake 16 and a second component is provided via inlet 20. The first component and the second component intermix via the aspirator 24. In a specific embodiment, the diffuser 10 is used to prepare and disperse a fire-fighting foam. A liquid concentrate is provided as a feed composition via intake 16, and the expansion gas is added thereto as a second component, via inlet 20. The fluid combination of the liquid concentrate and expansion gas is then discharged via outlet 18 and is allowed to expand into a foam. Optionally, the liquid concentrate is cooled to a temperature below ambient temperature before it is provided to intake 16. The expansion gas (e.g., nitrogen) allows the mixture of the liquid concentrate and the expansion gas to expand into a foam as the mixture leaves the diffuser outlet 18. Excess liquid concentrate and nitrogen may be drained from the interior of the outer casing 12 through the drain outlet 22.
In other alternative embodiments, diffuser 10 can be used to add nitrogen gas (e.g., as a second component) to other types of fire-suppressing feed compositions for other fire-extinguishing products to be dispersed at outlet 18.
In yet another alternative embodiment, diffuser 10 can be used to proportion the liquid concentrate and expansion gas, or any other separate components of a fire-extinguishing product that are provided via the intake 16 and the inlet 20. Optionally, the proportioning may be effected by venturi-type devices or line-proportioning devices, both of which may also be applicable in portable equipment set-ups.
In a preferred embodiment, one method of extinguishing a fire (e.g., in a confined and/or poorly ventilated area, such as a mine) generally comprises the step of spraying or otherwise depositing the fire-extinguishing product onto the flaming fuel. In another embodiment, a method of extinguishing a fire comprises the steps of combining separate components of a fire-extinguishing product to create a flowing stream of the product, and spraying or otherwise depositing the product onto the flaming fuel.
The terms “first,” “second,” and the like, herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The terms “a” and “an” herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.
Although this invention has been shown and described with respect to the detailed embodiments thereof, it will be understood by those of skill in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed in the above detailed description, but that the invention will include all embodiments falling within the scope of the disclosure.
This application claims the benefit of U.S. provisional application No. 60/780,548, filed Mar. 8, 2006, which is hereby incorporated herein by reference, in its entirety.