SPECIFICATION

Field of Invention

This invention relates to a method for extinguishing fires. In particular, the invention relates to a method for extinguishing fires utilizing Halon-type agents with a liquid fluid.

Background of the Invention

Certain Halons, such as Halon 1301 (CF ₃ Br) and Halon 1211 (CF ₂ BrCl) , since at least the 1970's have been utilized as fire suppressants. As fire fighting agents, these chemicals exhibit certain qualities that render them particularly valuable. First, these Halons are clean and highly effective. They leave no residue and cause little, if any, secondary fire damage. For such reasons they are most compatible with electrical systems and other environments where residues and agent damage cannot be tolerated. Secondly, the Halons are three-dimensional fire fighting agents. They can inert flammable atmospheres to an extent not possible with foams, water, dry chemicals and other nongaseous agents. As further valuable qualities, the Halons 1301 and 1211 have relatively low toxicities as well as relatively low cost and exhibit stability and compatibility with other materials.

Because of superior fire fighting effectiveness, Halon 1301 has been primarily utilized commercially for "total flood" applications. Halon 1211, having a lower

vapor pressure, has been generally utilized for "streaming" fire fighting applications.

Unfortunately, the Halon 1301 and 1211 fire fighting agents, like the chlorofluorocarbons (CFCs) , have the potential to deplete stratospheric ozone layers and to accelerate global warming. These threats to the environment have been considered so serious that the Montreal Protocol in 1987 included production restrictions on the Halons as well as the CFCs. In anticipation of production decreases, development projects for Halon alternatives for fire fighting agents have been underway for several years. Substitute chemical agents are being investigated that can prove equally clean and effective and that have equally acceptable low toxicities. It is necessary that the chemicals be able to be used around electronic equipment, aircraft engines, computer facilities, and museum exhibits without damage from residue. Generally, there are five requirements to be met by these substitute Halon-type fire fighting agents: cleanliness, low ozone depletion potential, low global warming potential, low toxicity, and effectiveness. Cost is also a factor.

The industry generally expects today that substitute Halon-type fire fighting agents will continue to be segregated as to their effectiveness in "total-flood" applications and in "streaming" applications. Halon 1301 comprises the standard for the "total flood" substitute agent. Halon 1211 comprises the standard against which substitute

"streaming" agents will be measured. It is further generally expected in the industry that the usefulness of a substitute agent in streaming applications will be dependent upon the agent's "throw" characteristics as

measured by recognized standardized laboratory discharge testing.

The low ozone depletion potential and low global warming potential set by modern environmental concerns for chemical agents released into the atmosphere comprise stringent criteria. In developing acceptable substitute Halon-type fire extinguishing agents, it is anticipated that a "trade-off" will have to be accepted. That is, it is anticipated that industry will have to accept for Halon-type substitutes a

"trade-off" of fire fighting effectiveness for low ozone depletion potential, low global warming potential and acceptable toxicity levels. More importantly, it is expected that prominent among the fire fighting effectiveness factors that will have to be "traded-off" is "streamability" (as understood in the present art) . Environmentally friendly Halon-type substitute agents are predicted to predominantly comprise gases or such highly volatile fluids under atmospheric conditions that they traditionally are regarded as not "streamable".

Such discouraging predictions, at least for the near future, of the apparent inevitability of having to accept reduced fire fighting effectiveness for Halon- type substitutes in streaming applications, led to the present invention. The present invention discloses how even gaseous Halon-type fire fighting agents can be delivered effectively and efficiently to a fire, and with enhanced results, in "streaming" applications. In fact, the present invention should enhance the deliverability of the Halons themselves, a valuable application to the extent that Halons will continue to have limited usefulness.

The present invention teaches the delivery of Halon-type agents surrounded by an envelope of liquid

fluid. The term "liquid fluid" here is intended to refer to a fluid or fluid mixture that assumes or retains a liquid state under atmospheric conditions. Common liquid fluids may comprise water, foam, water and foam, water and foam concentrate, or other liquid fluid mixtures known to have beneficial fire fighting properties. "Fluid" is used herein to refer to a substance in its liquid or gaseous state.

The effectiveness of the invention is attributed to possible multiple synergistic effects. These effects are believed to be experienced in the simultaneous delivery and application to a fire of a first fluid surrounded by a liquid fluid. First, in this simultaneous delivery process, the liquid fluid envelope enables and/or enhances the streaming of the enclosed first Halon-type fluid to the fire. The envelope may also enhance the retention of the first Halon-type fluid upon the fire, thereby increasing the available time in which the fluid can vaporize and exert its fire extinguishing effect as a gas. It is also believed that a volatile fluid delivered within a liquid fluid envelope may exchange heat with the liquid fluid envelope during transmission, which may enhance the first fluid's effective vaporization rate. Further, the liquid fluid envelope permits shaping and directing the placement of the first fluid over the fire, thereby allowing the maximization of the area of contact of the vapor with the fire. It is anticipated that a volatile first fluid or gas, or a portion thereof, may become entrained within the liquid fluid envelope, or a portion thereof, during the delivery process. This entrainment may enhance the delivery of the first fluid to the fire. The entrainment may also enhance the retention of the first fluid at the fire subsequent to delivery. On the other hand, a

vaporizing first fluid, by expansion, agitation and/or entrainment, may enhance the foaming of a liquid foam envelope during delivery. Assuming that the liquid foam envelope is capable of enhanced foaming, the enhanced foam should improve the liquid foam's fire fighting capability.

Summary of the Invention

The method of the present invention includes applying to a fire simultaneously a first Halon-type fluid surrounded by a second liquid fluid. First Halon-type fluids may comprise:

1. regarding Halon materials: Halon 1301 (i.e., CF ₃ Br) , 1211 (i.e., CF ₂ BrCl) and 2402 (i.e., C ₂ F,Br ₂ ) ; 2. regarding perfluorinated materials: CF _» ,

C ₂ F ₆ , C ₃ F _β , Perfluorohexane (i.e., C ₆ H ) , Perfluoroheptane (i.e., C ₇ H ₁₆ ) , Perfluorobutane (i.e., C _« F ₁₀ ) , Perfluoropentane (i.e., C ₅ F ₁₂ ) , and Perfluorooctane (i.e., C _β F _lβ ) ; 3. regarding HCFC materials:

HCFC-22 (i.e., CHC1F ₂ ) , available commercially from DuPont de Nemours & Co. ,

HCFC-122 (i.e., C ₂ HF ₂ C1 ₃ ) , available commercially from DuPont de Nemours & Co. , HCFC-123 (i.e., C ₂ F ₃ HC1 ₂ ) , available commercially from DuPont de Nemours & Co. ,

HCFC-124 (i.e., C ₂ F _» C1H) , available commercially from DuPont de Nemours & Co., as "FE 241", NAFS-3 (i.e., a proprietary blend of chlorofluorocarbons and a hydrocarbon that is sold by National American Fire Guardian as the "S-III" blend) ; 4. regarding HFC materials: HFC-125 (i.e. C ₂ F ₅ H) ,

HFC-227ea (i.e. C ₃ F ₇ H, available commercially by the Great Lakes Chemical Corporation as FM 200) ,

HFC-23 (i.e., CHF ₃ ) , available commercially from DuPont de Nemours & Co., as "FE 13";

5. regarding HBFC materials:

HBFC-22B1 (i.e., CHF ₂ Br) , available commercially from Great Lakes Chemical Corporation as "FM 100".

The materials above described are predominantly gases at 25°C and one atmospheric pressure. The following chart illustrates sample vapor pressures for the compounds.

Vapor Pressure

Compound rø 25 ^» C. 760 mmHt-M

Halon 1301 12,540

Halon 1211 2136 Halon 2402

HBFC-22B1 2999

HCFC-124 3153

NAFS-3 6169 (est.)

HFC-23 34,381 HFC-125 9823

HFC-227ea 3040

FC-3-1-10 2100

FC-5-1-14 232

FC-6-1-16 79 HCFC-22 7119

HCFC-123 672

The above compounds comprise straight or branched alkanes having between 1 to 8 carbon atoms. The compounds are fully saturated and are substituted with halogen (i.e., fluorine, chlorine or bromine) or hydrogen ada s.

It should be mentioned that some of the chemicals above, such as perfluoroheptane and perfluorooctane, are considered difficult to stream, not because of their vapor pressure but because they may not vaporize rapidly enough when they contact a fire.

It is difficult to define precisely a class of liquid materials that is difficult to stream because of their volatility. An ambient vapor pressure sufficiently high as to cause vaporization of the

material under nozzle conditions may be 34,381 mm Hg; however, even Halon 1301 with vapor pressure 12,540 mm Hg can be so volatile that it is not streamable. The vapor pressure of the compounds must be sufficiently high that they would at least readily vaporize upon contact with a fire.

The perfluorinated materials comprise a preferred subclass of materials. More particularly, C,F ₁₀ and/or a blend of C ₄ F ₁₀ and C ₆ F ₁₂ comprise preferred agents for the first fluid. A blend of a fluid that tends at least to vaporize in transit with a fluid that tends to vaporize upon application to the fire may have usefulness in reaching enclosed fires, such as within aircraft engines. In these applications a fluid that reaches the fire predominantly in liquid form may drain into the enclosed burning compartments prior to vaporizing and exerting its fire extinguishing effect as a gas. Such may comprise an important technique in selected fire fighting scenarios. Preferably, the first and second fluids are delivered to the fire from a distance of at least 50 feet. The second fluid is a liquid as discharged and preferably includes a foam or foaming agent. A film- forming foam is suitable in many applications. The method of this invention can be practiced by discharging a Halon-type first chemical fluid from a first conduit via a first conduit orifice while a second liquid fluid is discharged from a second conduit via a second conduit orifice, the two conduits being coupled together in a nozzle. The first and second orifices are relatively sized and relatively positioned with respect to a fire fighting nozzle such that the discharged first fluid chemical is surrounded by the discharged second liquid fluid. The discharged first

fluid travels within the envelope defined by the second fluid.

Many useful means for supplying a second fluid, such as water, water/foam and/or water and foam concentrate to the second conduit of a nozzle, are known in the art. Any of the known means for supplying such fluids to the conduit should suffice.

Many useful means for supplying a first chemical fluid to a first conduit are also known in the art, including means for supplying gaseous fluids and volatile fluids. Such means could comprise, for instance, a line attached to a bottle with fittings to attach the end of the line to the first conduit. The first fluid could enter the conduit and be discharged in liquid or gaseous form. A source of pressure controls the entry of the fluid.

The flow path of the second liquid fluid as it is discharged from the second orifice preferably comprises a cone. (The term cone, as used herein, would encompass a cylinder as a special case.) In preferred embodiments, the cone is hollow. The first chemical fluid is discharged from the first conduit orifice such that its flow path is contained within the cone envelope. As the two fluids travel to the fire, the first fluid may comprise a gas or a vapor or may vaporize. A gas or vapor tends to fill the envelope defined by the cone of the liquid fluid trajectory. It is believed that a portion of the first fluid, liquid or vapor, may penetrate and become entrained within the second liquid fluid envelope.

One method of use of the invention may include initially applying to a fire the liquid fluid, preferably a water/foam composition, without the first chemical fluid. If the liquid fluid can be applied in a spray broad enough to encompass a fire, the fluid is

so applied and then the breadth of the second liquid spray is narrowed as the volume of the fire diminishes. Alternately, when the expanse of the fire is too great to be encompassed by an initial liquid foam spray, the fire is initially attacked from one side with the second liquid foam. The area of extinguished fire is gradually enlarged with further application of the liquid foam. When flaming elements are encountered, such as elements of a three-dimensional fire, and such flame is not extinguished by the liquid foam, then the first chemical fluid may be delivered to the spot simultaneously with, surrounded by and sculpted and controlled by, the second liquid fluid envelope. The particular chemicals used in the first fluid may depend upon the type of fire and the strategy adopted for maximizing the effectiveness of the vaporization of the first chemical.

Brief Description of the Drawings Figures 1 through 5 offer cross-sectional views of five embodiments of a dual fluid nozzle and apparatus suitable to practice the present invention.

Figures 6 through 10 illustrate one preferred method of this invention as applied to a three dimensional fire.

Figure 11 illustrates a flow pattern for the delivery of dual fluid streams.

Figures 12a through 12e and Figures 13a and b illustrate other preferred methods of this invention.

Description of the Preferred Embodiment

Figs. 1-5 illustrate five embodiments of a nozzle and apparatus for the simultaneous application of dual fluids to a fire, suitable to be utilized to practice the present invention. The nozzle is comprised of

second conduit or barrel B, made up in the preferred embodiment of two portions referred to as Bl and B2. Bl telescopicly slides over B2 from its leftmost open position, shown, to its rightmost and most closed position, where stop 62 abuts shoulder 64. With Bl in its leftmost position, liquid fluid LF is discharged in the broadest pattern. With the barrel in its rightmost position, liquid fluid LF if discharged in its narrowest pattern. The pattern of discharge of the second fluid, or liquid fluid LF, from the nozzle of Figs. 1-5 tends to assume the shape of a hollow cone, discussed further below. The breadth of the cone is affected by the relative position of Bl. The conical shape tends to be hollow because of the obstruction to flow provided by elements 0 and 00 and mixing chamber M of Figs. 1-5, also more fully discussed below.

First conduit C of Fig. 1 contains an inlet 66 having a fitting 67 and outlet orifice 68. First fluid, designated VF, is illustrated as supplied in this embodiment from bottle 71 through line 69. Alternately, first fluid VF is supplied from bottle 75 through lines 73 and 69 as shown by dashed lines in Figs. 1-5. If the first fluid VF comprises a gas, standing the bottle on end, as shown by dashed lines, may suffice to supply gaseous fluid while laying the bottle on its side may suffice to supply liquid fluid. Regulator 77 may be installed in the line between a bottle and the nozzle. Fitting 67 aids in attaching the bottle line to the nozzle. Many means for supplying a fluid, including a liquid or a gas, to a nozzle are known in the art and most should suffice for the purposes of this invention. The means shown in the drawing are for illustrative purposes.

The first fluid VF supplied to the nozzle through inlet 66 is discharged from outlet 68 of first conduit C. A major portion of first conduit C is approximately aligned with the axis of the second conduit or barrel B. In the preferred embodiment the first fluid may be supplied to the nozzle as a gas or a liquid under pressure. Second fluid L enters the second conduit or barrel of the nozzle from the left and proceeds generally through the barrel from left to right around structural obstructions. A portion of the liquid LI in the embodiment of Fig. 1 flows through inlet 71 of eductor system E. Eductor system E is located within the center of the axial bore surrounding first conduit C. Liquid LI that flows through eductor E enters chamber 70. In chamber 70, eduction pressure pulls foam concentrate F from an external source through conduit 72 and into the eductor chamber. The liquid LI and foam concentrate F mix and flow through channel 74 surrounding a portion of the first conduit. The fluid LI plus the foam F enter mixing chamber M defined between obstructions O and 00. Additional liquid L2 may enter mixing chamber M through ducts D in obstruction 0. The liquid and foam exit mixing chamber M at annular outlet 80. This liquid and foam mixture mixes with the remainder of the liquid flowing through the outer portion of the axial bore of the second conduit or barrel. The total liquid and foam mixture is discharged from the annular second conduit orifice OA of the barrel. The direction of discharge is toward the right in the drawing. Obstructions 0 and 00 associated with mixing chamber M are located in the approximate center of the second conduit or barrel and in the outlet area of the barrel. Obstructions 0 and 00, together with mixing chamber M in the preferred embodiment of Fig. 1, cooperate with the second conduit

or barrel such that the liquid foam stream LF discharged from the barrel is discharged in the configuration of a hollow cone.

Figure 2 comprises an alternate embodiment of a dual fluid nozzle. Figure 2 differs from Figure 1 predominantly in that the first conduit C is attached by means 92 to the outside of second conduit or barrel B. In particular, first conduit C is attached to portion Bl of barrel B. Dash lines 94 indicate in Figure 2 that foam need not be educted by the eductor through only one eductor conduit. Indeed, foam concentrate F can be educted through multiple conduits. Figure 2A illustrates the preferred design of a portion of first conduit C that intersects the discharging second liquid foam mixture LF. Figure 2A illustrates that, preferably, first conduit C at this portion would have an aerodynamic design such that the liquid foam stream would flow around the conduit in a path of least resistance and least turbulence. Figure 3 illustrates an embodiment of the invention wherein the second fluid comprising the liquid and foam concentrate have already been combined before they enter the second conduit or barrel at inlet 73 on the left of B2. The liquid and foam combination may continue to flow in an inner path through the axial bore of second conduit or barrel B to mixing chamber M wherein a portion of the liquid and foam mixture is further aerated before joining a portion of the liquid and foam mixture that passes through the outer area of the axial bore. In Figure 3, as in Figure 1, the first fluid is supplied to first conduit C which contains a portion substantially aligned with the center of the axial bore of the barrel.

The embodiment of Figure 4 is like the embodiment of Figure 3 in that the second liquid L and foam

concentrate F is supplied to the nozzle already mixed. The embodiment of Figure 4 is like the embodiment of Figure 2 in that the first fluid conduit C is affixed to the exterior of forward barrel Bl. Again, since first conduit C itself intersects the liquid and foam spray emerging from the outlet orifice OA of second conduit or barrel B, preferably first conduit C embodies an aerodynamic design for a portion of its length in which the conduit intersects the path of the liquid fluid being discharged.

The embodiment of the nozzle illustrated in Figure 5 is like the embodiment of Figure 3. That is, the liquid L and foam concentrate F are supplied already mixed to the inlet area 73 to the left on barrel portion B2 in the embodiment of Figure 5. The liquid and foam comprising the second fluid, however, do not pass through a central portion surrounding the first fluid conduit C in the axial bore.

Figures 6-10 illustrate one preferred embodiment of the method of the present invention. Combustible fluid 34 is illustrated as spewing through outlet 42 under pressure from a remote source, creating a three- dimensional fire. The fire or combustion 38 of the fluid rises in the air, generating smoke 40. Pool 30 of the fluid forms on ground 52 and is encompassed by flames 32. In Figure 7 nozzle 44 is brought to the three dimensional fire. A broad spray 46 of a liquid fluid, preferably liquid with a film forming foam composite, is applied to the fire in a breadth sufficient to encapsulate the fire, when possible. The liquid fluid spray is shown applied, in this embodiment, as a hollow cone. Figure 7 indicates the hollow area of the cone. Upon the application of the liquid fluid spray the static fire 32 of pool 30 diminishes. Figure 8 illustrates that the spray of

liquid foam fluid has extinguished static fire 32 in pool 30 and has diminished the size of the three dimensional fire with combustion area 38. Figure 8 also illustrates that the breadth of the liquid fluid spray 46 has been reduced as the extent of the three dimensional fire has been reduced. In Figure 8 liquid fluid spray 46 is still being thrown in a configuration having a hollow center 48. Figure 9 illustrates the application of a first chemical Halon-type fluid 50, discharging from nozzle 44 and being delivered to the fire as a gas or vapor, predominantly through the hollow center of the envelope comprising the cone of liquid fluid spray 46. The static fire from pool 30 remains extinguished. The gas or vapor or vaporizing of the first fluid is directed to the diminished combustion portion 38 of the three dimensional fire. Figure 10 illustrates ground area 52 with the fire extinguished. Liquid fluid spray 46 may continue to be applied to pool 30 and surging fluid 34, that now adds to pool 30. However, there is no more combustion or fire. The gas or vapor or vaporizing fluid, delivered to and retained upon combustion portion 38 of the fire by the hollow cone envelope of liquid fluid 46, completed the fire extinction process. If the pool 30 of flames 32 is too large to be encompassed by a broad spray 46 of a liquid fluid from nozzle 44, as described above, an alternate fire fighting technique is illustrated in Figures 12a through 12e. The fire fighter begins at one edge of the flaming pool, illustrated as tank T, and applies the liquid fluid LF, preferably a liquid with a film forming foam composite. An edge of the fire F is extinguished thereby and this extinguished portion is gradually widened to include more of the pool, as illustrated in Figures 12b and 12c. If a three-

dimensional fire 3DF or segment of the fire F containing a burning area whose fuel is replenished from a remote source, is encountered within the pool, such as for instance might be offered by a dripping fuel line, then that element can be encompassed by an appropriately broad spray of the liquid fluid LF while simultaneously a first Halon-type fluid VF is discharged from the nozzle and applied, as in Figure 12d. Without the simultaneous application of a suitable first fluid encompassed within the second liquid fluid, the 3DF fire from the replenishing source may not be extinguishable. It might create a hole in the foam being applied to the pool, preventing the gradual systematic extinction of the fire in the full tank.

The disclosed method has further application in crash rescue fire fighting involving airplane crash fires, illustrated in Figures 13a and 13b. First, the engines may burn, offering a further example of a three-dimensional element, that is a spot of fire fed by a remote fuel source, in which the present invention can be utilized. Crash rescues also offer another possibility for the use of the dual fluid nozzle, apparatus and method. Frequently in such crashes it is desired to tunnel or cut a path through a thin film fire comprised of flammable liquid on the ground to reach the fuselage or cockpit of the plane. Suitable application of liquid foam can create a tunnel, as illustrated in Figure 13a. In the fuselage or cockpit itself, it is desirable to quickly inert the atmosphere. This maneuver suggests the use of a first Halon-type fluid delivered within an envelope of a liquid foam fluid, to inert the area, as illustrated in Figure 13b.

Figure ll illustrates a flow path of a first chemical fluid 50 and a second fluid 46 wherein the first fluid is delivered within the envelope of the second fluid. In Figure 11 the flow path of the second fluid is illustrated as that of a hollow cone. The flow path of the first fluid within the hollow cone envelope is illustrated as filling the interior space of the cone and partially becoming entrained within the second fluid envelope. The foregoing disclosure and description of the invention are illustrative and explanatory thereof. Various changes in the size, shape and materials as well as the details of the illustrated construction may be made without departing from the spirit of the invention.