Compositions – Fire-extinguishing – Gas generative – chemically
Reexamination Certificate
2000-02-15
2001-04-17
Anthony, Joseph D. (Department: 1714)
Compositions
Fire-extinguishing
Gas generative, chemically
C252S002000, C252S004000, C252S007000, C149S017000, C149S047000, C149S062000, C149S077000, C149S078000
Reexamination Certificate
active
06217788
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to fire suppression compositions and devices, and more particularly to a fire suppression composition and device that utilizes iron-containing species and/or non-halide potassium salts as environmentally innocuous, chemically acting fire suppression additives.
2. Brief Description of the Related Art
The majority of fire extinguishing systems used today, in applications such as commercial and military aircraft, ground vehicles (autos, trucks, buses), and surface ships, rely on the chemical agents generally known as Halons. Halons are materials generally composed of brominated or chlorinated fluorocarbon compounds. Examples of common Halons include Halon-1301 (CF
3
Br) and Halon-1211 (CF
2
ClBr). Halons have been shown to depend upon a combination of (1) chemical effectiveness (e.g., quenching of reactive chemical radical intermediates associated with the combustion process), and (2) physical effectiveness (e.g., cooling the combustion flame and dilution of the combustion ingredients). This effective combination of fire suppressive characteristics have led to a wide use of Halons as a firefighting composition.
Recently, international cooperation has resulted in an agreement (the Montreal Protocol, 1987) to discontinue both production and use of all Halons due to evidence that Halons contribute to the depletion of stratospheric ozone. This development has led to a search for alternative, environmentally innocuous agents that act in a similar manner to Halons for the suppression and extinction of fire, but without the ozone-depleting effects.
The search for alternatives to Halon-1301 has focused in large part on agents that closely mimic the chemical, physical, and fluid mechanical properties of CF
3
Br, particularly other halocarbon systems. Concerns about the effects of bromine on ozone depletion potential (ODP) narrowed this search to fluorocarbons or hydrogenated fluorocarbons, e.g. HFC-227 and HFC-125. However, these compounds were observed to be much less effective per unit mass or volume with respect to Halon 1301. There has been some recent attention directed towards the use of CF
3
I as an alternative agent. However, its efficacy is hampered by concerns regarding high altitude emissions. Comparisons of pure inert gas (e.g., bottled nitrogen or carbon dioxide) are also quite unfavorable with respect to Halon-1301, due in particular to the large volumes required for agent storage of these compressed gases.
A class of “superagents” has long been known, which exhibit fire suppression effectiveness much greater than Halon-1301. The foremost example of these agents is iron pentacarbonyl, Fe(CO)
5
, but other examples include chromyl chloride, CrO
2
Cl
2
, and tetraethyl lead, Pb(C
2
H
5
)
4
, as well as powdered materials such as K
3
Fe(CN)
6
. However, while effective at suppressing fires, these superagents are toxic, and are therefore less useful in general suppression applications.
An alternative approach to fire suppression has been based upon technology similar to that used in automobile airbag devices. In this approach, the fire suppression agent is a mixture of inert gases which are stored in the form of solid propellants. Upon combustion in a solid propellant gas generator (SPGG), these solids produce large quantities of nitrogen, carbon dioxide, and water vapor. The compact nature of the SPGG device makes it an efficient means for storing gas-generating agents in a solid form. For a solid propellant formulation which yields 50% gas, volumes required for agent storage approach that of Halon-1301; high-efficiency propellant formulations meet both mass and volume envelopes of Halon systems.
Functioning of a SPGG fire suppression device is quite similar to that of more conventional bottle blowdown systems in that both begin with electronic squib initiation. In the case of SPGG's, a squib initiates the combustion of solid propellant grain or grains, which may be present in granular form (e.g. the size of sand particles), the form of pills similar in size to aspirin tablets, or larger tablets (e.g., sized like a salami). The propellant formulation, containing an intimate mixture of fuel and oxidizer plus additives, rapidly combusts to generate large amounts of inert gas and water vapor. The inert gas blend is then exhausted into the fire zone to effect suppression. In practice, this type of fire extinguishing composition generates large amounts of inert gases CO
2
, N
2
, and H
2
O, which together act to quench flames through a combination of cooling, dilution and flame strain.
The advantages of SPGG units for fire suppression are many. In a SPGG, the fire suppression agent is stored at atmospheric pressure in hermetically sealed units, both contributing to long service lifetimes. Upon combustion, the gases can be produced in timeframes ranging from about 50 ms to several seconds, and the devices are operable over a wide range of temperatures. In addition, the generated gaseous agents (N
2
, CO
2
, H
2
O) are chemically benign and pose no threat to atmospheric ozone. However, despite its effectiveness, the use of this fire extinguishing composition is limited in several scenarios, e.g., aircraft drybays, where undesirable bay overpressures arise from the large volumes of gas at elevated temperatures, and is not weight competitive in other cases where, e.g., the higher thermal loads arising from propellant combustion must be offset by sufficient thermal mass.
Additional fire extinguishing approaches are described in the following U.S. Patents.
U.S. Pat. No. 4,601,344, “Pyrotechnic Fire Extinguishing Compounds” by Reed, Jr. et al. issued Jul. 22, 1986.
U.S. Pat. No. 5,113,947, “Fire Extinguishing Methods and Compositions Utilizing 2-chloro-1,1,1,2-tetrafluoroethane” by Robin issued May 19, 1992.
U.S. Pat. No. 5,117,917, “Fire Extinguishing Methods Utilizing Perfluorocarbons” by Robin et al. issued Jun. 2, 1992.
U.S. Pat. No. 5,124,053, “Fire Extinguishing Methods and Blends Utilizing Hydrofluorocarbons” by Iikubo et al. issued Jun. 23, 1992.
U.S. Pat. No. 5,423,384, “Apparatus for Suppressing a Fire” by Galbraith et al. issued Jun. 13, 1995.
U.S. Pat. No. 5,465,795, “Fire Suppression Apparatus for Generating Steam from a Water-Ice Mixture” by Galbraith et al. issued Nov. 14, 1995.
U.S. Pat. No. 5,609,210, “An Apparatus and Method for Suppressing a Fire” by Galbraith et al. issued Mar. 11, 1997.
U.S. Pat. No. 5,613,562, “An Apparatus for Suppressing a Fire” by Galbraith et al. issued Mar. 25, 1997.
U.S. Pat. No. 5,756,006, “Flame Extinguishing Pyrotechnic and Explosive Composition” by Reed et al. issued May 26, 1998.
Additionally, workers at the National Institute of Standards and Technology (Babushok, V.; Tsang, W.; Linteris, G. T.; Reinelt, D. Comb. Flame 1998, Vol. 115, 551-560) have explored the chemical limits to flame inhibition, comparing the chemical kinetics of hydrocarbon flames in the presence of Halon-1301 and various superagents, and examined the reaction rates in light of measured extinction concentration data.
In view of the above, there exists a need for alternatives to Halons, particularly alternatives that are environmentally innocuous and which meet the mass/weight requirements and size restrictions for confined spaces. The present invention is believed to be an answer to that need.
SUMMARY OF THE INVENTION
In one aspect, the present invention is directed to a fire suppression composition, comprising a propellant comprising a fuel and an oxidizer, the propellant capable of generating inert gas; and a fire suppression additive selected from the group consisting of iron-containing compounds, non-halide potassium salts, and combinations thereof.
In another aspect, the present invention is directed to a fire suppression composition, comprising a propellant comprising from about 5 to about 50% by weight of a fuel and from about 20 to about 90% by weight of an oxidizer, the propellant capable of generating inert gas; and from about 1 to about 25% by weight of a fire suppre
Holland Gary F.
Wucherer Edward J.
Anthony Joseph D.
Garabedian Todd E.
Primex Aerospace Company
Wiggin & Dana
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