WO2007105162A1

WO2007105162A1 - Foam based fire extinguishing material

Info

Publication number: WO2007105162A1
Application number: PCT/IB2007/050802
Authority: WO
Inventors: Scott Allan Kuehl
Original assignee: Scott Allan Kuehl
Priority date: 2006-03-14
Filing date: 2007-03-12
Publication date: 2007-09-20

Abstract

The invention discloses a foam based fire extinguishing material having a foam based material expanded by means of an alkane emulsifiable gas.

Description

FOAM BASED FIRE EXTINGUISHING MATERIAL

FIELD OF INVENTION

The present invention relates to a foam based fire extinguishing material .

More particularly, the invention relates to a foam based fire extinguishing material having a liquid foam base.

BACKGROUND TO INVENTION

Known fire fighting materials reduce to and include the following five types of substances:

(a) Halon;

(b) DCP (dry chemical powder);

(C) CO2;

(d) Water; and

(e) Air blown water based foams.

The recommended substance type and the effectiveness thereof depends on various factors including :

(a) the nature of the fire;

(b) the location of the fire; and

(c) the speed of the fire.

The nature of the fire questions the fire source or fuel, namely is it petrochemical, electrical, chemical, etc.?

A general classification on the nature of a fire is as follows:

Class A fires: wood, plastic, other solids;

Class B fires: flammable liquids such as petrol or diesel; Class C fires: fires near electrical equipment (current can track through the extinguishing material back to the fireman);

Class D fires: metals such as steel powder, aluminium and magnesium

The location of the fire influences the determination of the type of medium to be used. Carbon dioxide would not be used in a confined space as there could be a risk of secondary suffocation. Water is not recommended for electrical fires due to increased risk of electrocution. DCP powder goes everywhere, blinds the operator and places him at risk in a policing operation and is only used in exceptional cases.

The speed of the fire is sometimes an important issue. Often it is desired to extinguish a fire before it has had time to spread thus causing financial and damage to property. If a fire can be put out immediately after it is detected and the fire extinguishing substance focused only on the area where the fire starts, then an advantage is achieved. The best way to accomplish speed is to automate the fire extinguishing system. Automatic and focused deployment can only be realised to the fullest potential when a rapid response fire extinguishing material is available and used with an extinguishing system. Extinguishing systems reduce to plumbing, valves and nozzles directing the material to the fire.

Traditional fire fighting foams are produced by mixing air into a liquid or water containing appropriate surfactants to obtain air blown foams. These are called film forming foams. Various ways of mixing the air are known to those trained in the state of the art. The most common way is through the use of a venturi nozzle. Those trained in the state of the art fully realise the potential of air blown foams and recognise their deficiencies as well. The limitations of these air blown foams are generally their deployment speed, degradation and drainage speed, mechanical stability and the bulky type of equipment used to deploy it. WO 99/52599 discloses the use of CO₂ or Freon gases at pressures where these gases liquefy and possibly emulsify in a water based foam precursor. A pre-pressurized self expanding foam is produced but the mechanical integrity and longevity of such types of foam are known to be inferior.

It is an object of the invention to suggest a foam based fire extinguishing material for overcoming the afore-mentioned problems.

SUMMARY OF INVENTION

According to the invention, a foam based fire extinguishing material includes a water-based foam obtained by

(a) mixing water, at least one dipolar molecular liquid and at least one surfactant to obtain a liquid-based mixture;

(b) pressuring the liquid-based mixture into a container with an alkane emulsifiable gas to form a foam precursor; and

(c) releasing the foam precursor from the container, the water based foam thus produced having a density of 20 - 200 kilograms per cubic metre.

Also according to the invention, a foam based fire extinguishing material includes a foam based material expanded by means of an alkane emulsifiable gas.

Yet further according to the invention, a fire extinguishing material includes a gel including

(a) water,

(b) at least one dipolar molecular liquid; and

(c) at least one surfactant.

Yet further according to the invention, a method of producing a foam based fire extinguishing material includes the steps (a) of mixing water, at least one dipolar molecular liquid and at least one surfactant to obtain a liquid-based mixture;

(b) of pressuring the liquid-based mixture into a container with an alkane emulsifiable gas to form a foam precursor; and

(c) releasing the foam precursor from the container to obtain a water based foam having a density of 20 - 200 kilograms per cubic metre.

Yet further according to the invention, a method of extinguishing fires, includes the step of covering a fire with a fire-extinguishing material as described in the specification.

The liquid-based mixture may be additionally be over pressurised with an inert gas such as nitrogen in order to build up the head pressure in the container.

The foam precursor may be adapted to self-expand once released from the container to form the water-based foam.

The density of the water based foam may be determined by the amount of emulsifiable gas used to pressurise the liquid-based mixture.

The dipolar molecular liquid may be at least one compound selected from the group comprising water, an alcohol, glycol and methanol.

The type of dipolar molecular liquid may be determined by environmental standards and/or the low and high end use temperature limits in ambient conditions.

The amount of dipolar molecular liquid may be determined by environmental standards and/or the low and high end use temperature limits in ambient conditions.

At least one surfactant may be ionic and/or non-ionic.

The liquid-based mixture may include a base agent neutralising the ionic surfactants at least partially. The liquid-based mixture may include a soluble polymer.

The mixture may include in situ cross-linkable monomers of any molecular weight.

The alkane emulsifiable gas may include at least one compound selected from the group comprising short-chained alkanes, ethane, butane, propane, pentane and/or mixtures thereof.

The liquid-based mixture may includes at least one humectant.

The foam precursor may be adapted to expand only on a hot substrate and/or when exposed to elevated temperatures.

The method to fight fires may be automated and/or robotic and/or computer controlled and/or manually controlled.

The water-based foam may have a density of 20 - 200 kilograms per cubic meter.

The water based foam may include emulsified pepper and/or CS (tear gas) chemicals and/or other noxious but otherwise harmless additives.

The water based foam may include at least one dye adapted to stain for prolonged periods of time.

The dye may be adapted to stain skin.

The dye may be adapted to be illuminated in UV and flourescent light.

The dye may be coloured in the visual part of the spectrum.

The material may be deployed by means of deployment equipment.

The deployment may be triggered by flames, heat, automatically and/or manually.

The material may be adapted to act as a crime barrier. The material may be adapted to smother flames and/or fires by preventing oxygen from coming into contact with the flames and/or fires.

The material may include at least one identification inks.

The deployment may be automated and/or robotic and/or computer controlled and/or manually controlled

DETAILED DESCRIPTION OF INVENTION & EXAMPLES

The invention will now be described by way of example.

(c) releasing the foam precursor from the container, the water based foam having a density of 20 - 200 kilograms per cubic metre.

The fire extinguishing medium includes water which is mixed with surfactants and the subsequent mixture is then pressurised with an emulsifiable gas in a pressurised container to obtain a foam precursor. The emulsifiable gas is selected from the group of short chained alkanes. Releasing the foam precursor from the pressurised container results in a self-rising water-based foam of mechanical integrity and controllable density.

The mechanical integrity of a water based foam is highly dependent on the bubble size: the finer the bubbles, the better. Unlike air blown foams, the foam in accordance with the invention, namely a LPG (liquid petroleum gas) blown foam, produces the finest bubbles possible without the need for mixing equipment. This stability leads to stable foams at very low density. Because of this and because the foam precursor is self-rising. Relatively small volumes can be conveniently carried to remote areas (on an object or geographically) with a small sacrifice in equipment size. Furthermore, if automated, men need not be involved in the initial fire suppression cycle.

The water-based foam in accordance with the invention will put out fires but also that it has other attributes that make it superior to other fire extinguishing materials especially in specific circumstances.

The water-based foam is expanded with flammable hydrocarbon. Thus inviting questions of flammability.

The foam precursor (water, glycols and surfactants) is charged with about 5-8 weight % butane, propane or mixtures thereof as this serves as the expansion agent. While under pressure, the liquefied gas becomes a stable emulsion within the foam precursor. There does exist a head pressure of pure gas above the liquid, this being diluted in proportion to the difference between the vapour pressure of the gas and any additional propellant gas (nitrogen) placed on top of this to aid in the expulsion cycle.

Once deployed, the liquefied gas vaporises once the applied pressure reaches the vapour pressure of the particular liquefied gas being used. Thus the water- based foam is a self-expanding foam. The foam does not have to be created by mechanical mixing with air. As it existed within the water-based foam as a micro-particle emulsion, a fine liquefied droplet becomes a gas bubble formed within cells of water. Other components in the water-based foam, the surfactant bouquet, stabilize these bubbles against collapse. Within the foam there is little to no oxygen. Hydrocarbon gas is flammable between approximately 3 to 9% in air. If mixed with too little air, combustion cannot take place and if there is too much hydrocarbon, combustion cannot take place. Thus the flammability question then reduces to, if the water-based foam is deployed, does a partial pressure of hydrocarbon gas between 3 and 9% exist anywhere in or most importantly, around the external boundaries of the foam? Moreover, where there is such a place, is there sufficient hydrocarbon gas to sustain combustion?

The answer is no, the water-based foam acts like an inert blanket. The fire fighting/extinguishing mechanism is one of smothering the fire depriving it of oxygen. It is however important to realise that the deployed water-based foam could be thought of as a sponge filled with flammable gas. The water-based foam is, however, a closed cell foam and the surfactant stabilised water skins that contain the flammable gas have to be designed to be stable enough to prevent a chain reaction whereby one cell explodes and releases its contents into the air allowing mixing to concentrations between 3 to 9% in the presence of an ignition source. The heat generated by the combustion on the external surface of the water-based foam would have to be strong enough to destroy adjacent bubble walls that in turn would release their flammable contents and thus continue to support combustion at the expense of consuming the water-based foam from the outside in.

Experiments have shown that the kinetics of this potential chain reaction is negligibly slow compared to the rate at which it can put out the ignition source in the first place. Water-based foam compositions and deployed densities determine how stable and robust the cell walls are. A water-based foam with a too low density can allow flame propagation but the mechanical properties of water-based foam's at these unstable densities are poor so as to preclude their use in any case. The cell walls are intrinsically impervious to hydrocarbon gas diffusion but kinetic diffusion is a function of cell wall thickness. The density is the parameter that sets the lower end of the range on useable water-based foam densities. The higher limit of useable water-based foam densities is mainly set by ergonomic criteria. Fewer deployments at higher densities are obtained, the water-based foam does not work any better at higher densities and in fact denser foams sag and slide off of vertical surfaces more quickly and otherwise are influenced more by gravity.

One representative example of a water-based foam includes water and other small molecules in the class of glycols. A foaming agent is defined as the material causing the medium to expand after release from a pressurised container. This allows the foaming agent to undergo a phase transformation from an emulsifiable liquid into a gas. Suitable foaming agents are typified by butane and propane or mixtures thereof. The surfactant stabilises the water/gas mixture so that gravity and surface tension forces are minimised enabling the foam to retain its structure for prolonged periods of time without collapse. Humectants also serve to prolong the lifetime of a water based foam in that they reduce evaporation and lower the melting point or increase the boiling point of the foam precursor. The structure of the foam consists of a continuous liquid phase termed the ^λfoam concentrate' and a discontinuous gas phase called the ^λgas phase'.

In addressing the mechanical integrity issue, it has been demonstrated that foam concentrate mixtures containing soluble polymers provide for a foam stable for over 12 hours without degradation of the effective density, this depending upon the ambient temperature and humidity. In a more advanced formulation, it has been demonstrated that a polyvinyl alcohol based foam concentrate can be blown simultaneously, as a binary charge with a sodium borate solution. The borate crosslinks the polyvinyl alcohol almost instantly creating a stiff expanded foam with excellent mechanical strength and longevity. In another formulation, it has been demonstrated that a polyacrylic acid based foam concentrate can be neutralised with ammonium hydroxide up to a critical point where the concentrate is on the verge of gelling. After blowing the foam, the excess ammonia is free to evaporate into the butane gas filled cells of the foam or out of the foam altogether. The depletion of ammonia from the liquid phase precipitates the acrylic acid polymer producing a stiff expanded gel of exceptional mechanical integrity.

Typically, a surfactant stabilised foam would not only contain water as the main constituent, but soluble polymers in addition to the surfactant. These soluble polymers thicken the foam increasing its longevity against drainage and its ability to stick well to any substrate. Such polymers could be polyacrylic acid, polyvinyl alcohol, guar gum and many others. Inorganic material like bentone clay, a thixotropic agent may also be used.

Trials failed to produce stable Freon blown foams having sufficient mechanical integrity and longevity. CO₂ blown foams also have poor characteristics because the gas is soluble in the water phase and this leads to rapid bubble agglomeration and drainage.

Examples A water-based foam in accordance with the invention includes the following composition :

(a) long chain alcohol : 2.66 weight%

(b) non-ionic surfactant: 3.44 weight%

(c) ionic surfactant: 3.73 weight%

(d) base to pH 6.5: 0.196 weight%

(e) humectant: 9.56 weight%

(f) water: 80.4 weight%

(g) CB 48: 5.75 weight % of total of (a) to (f)

In order to demonstrate the flexibility in the above composition, it has been shown that the water in the above formula can be replaced by sea water without seriously effecting optimal properties.

Another composition in accordance with the invention, applicable to sub-zero temperatures (down to -15), is as follows:

(a) long chain alcohol : 2.66 weight%

(b) non-ionic surfactant: 3.44 weight%

(c) ionic surfactant: 3.73 weight%

(d) base to pH 6.5: 0.196 weight%

(e) humectant: 29.68 weight%

(f) water: 60.27 weight%

(g) propane 5.75 weight % of the total of (a) to (f)

One of the main advantages of the water-based foam based on LPG is the fact that a self contained rapid delivery system can be built around the water- based foam. The emulsified gas not only serves as the expansion agent, it also produces a head pressure on the container equal to the vapour pressure of the gas used at the ambient temperature. Additional head pressure can be achieved by adding nitrogen gas to the storage vessel. Due to the enhanced mechanical stability and low drainage characteristics achievable through the low density water-based foam in accordance with the invention, a multitude of deployments can expected from a small reservoir.

As long as the pressurized liquid is kept at a pressure above the vapour pressure of the emulsifiable gas, the liquid containing the emulsified gas will flow like a liquid. This allows for a deployment system that can exhaust large amounts of extinguishing material through pipes and finally through valves without the need for pumps. Extra nitrogen pressure can increase the flow rate and the deployment speed of the foam precursor. The self-expanding nature of the foam precursor has the advantage that no air mixing equipment is required. Because the water-based foam expands only once it reaches the vapour pressure of the emulsifiable gas, valve and spray nozzle configurations can be developed using parts designed for water. The water-based foam emerges from the deployment nozzle at high velocity and the water-based foam expands between the nozzle and the substrate to be covered by water- based foam. The water-based foam deployment system throws an inert blanket over the combustible material instantly. The water-based foam thickness, density and number of repeated deployments are other extrinsic parameters that can be controlled to suit the fire fighting application.

The water-based foam may or may not put out fires as well as other extinguishing media on a per kilo comparative basis, though this depends on the type of application and subjective application judgements related to any situation. The advantages are the instantaneous nature of the deployment and the use of a minimal amount of highly stable material. As such the deployment can be automated, the valves triggered by sensors, e.g. thermocouples. Volume flooding nozzles have been made as well as self- propelled rotary sprayers able to cover surfaces quickly.

Because the water based foam is so stable, it can put out fires on vertical and open surfaces with a minimum of material. Re-ignition is also minimized on vertical and horizontal open surfaces because the foam can continue to cover a hot combustable for long periods of time.

Experiments

Repeated multiple deployments of water-based foams in accordance with the invention were applied instantly to a fire created by single or repeated Molotov Cocktail (petrol bomb) attacks on the outside of an armoured vehicle for example. This has been demonstrated on a 1 square meter plate whereby repeated 750 ml petrol bomb attacks were defeated with 1 kg lots of water- based foam deployed in 1 second using only a pulse from a 24 volt power supply, a 1/2 inch solenoid valve, a fixed pipe and 1 pop-up rotary nozzle. The density of the water-based foam was 45 kg/m³ in this case. 20 kg of material would allow for 15 to 20 instantaneous deployment cycles.

Tire and other surface based fires are put out by this material as deployed through the same dispensing device used in PCT/I BO 1/02293. In a patent application by Kidde (US 20060278412 ) the advantages of putting out fires before they become ^λdeep seated' is put forth elegantly. This material, in accordance with the invention put forth here, and dispensing device provides a real material that can achieve this goal.

Engine bay fires can be put out by flooding the engine compartment with water-based foam within 2 seconds.

In the crime barrier application, the barrier foam can be deployed monolithically to a disabled vehicle by manual means or buy automated means, activated by a combination of mechanical vibration and/or sonic sensor and subsequent signal processing activation. Criminal intent can be weakened by the shock effect of the deployment, the increased work effort in determining the proper course to continue the assault and, in the near-in situation, the irritation the pepper additive or other additives might create in the eyes or skin of any instigator could further reduce criminal intent. Furthermore, regardless of the success of the assault, instigators would be stained with colorants, some of which could be to some degree invisible to visual radiation but visible in the ultraviolet part of the spectrum (Coates Brothers Inks SPJ4282 or SPJ2012 for example). This marking effect could enable crime fighters to identify perpetrators at a road block for example.

Claims

PATENT CLAIMS

1. A foam based fire extinguishing material includes a foam based material expanded by means of an alkane emulsifiable gas.

2. A material as claimed in claim 1, in which the foam based material is a water-based foam obtained by

3. A material as claimed in claim 2, in which the liquid-based mixture is additionally over pressurised with an inert gas such as nitrogen in order to build up the head pressure in the container.

4. A material as claimed in claim 2 or claim 3, in which the foam precursor is adapted to self-expand once released from the container to form the water-based foam.

5. A material as claimed in any one of claims 2 to 4, in which the density of the water based foam is determined by the amount of emulsifiable gas used to pressurise the liquid-based mixture.

6. A material as claimed in any one of claims 2 to 5, in which the dipolar molecular liquid is at least one compound selected from the group consisting of water, an alcohol, glycol and methanol.

7. A material as claimed in any one of claims 2 to 6, in which the type of dipolar molecular liquid is determined by environmental standards and/or the low and high end use temperature limits in ambient conditions.

8. A material as claimed in any one of claims 2 to 7, in which the amount of dipolar molecular liquid is determined by environmental standards and/or the low and high end use temperature limits in ambient conditions.

9. A material as claimed in any one of claims 2 to 8, in which at least one surfactant is ionic and/or non-ionic.

10. A material as claimed in any one of claims 2 to 9, in which the liquid- based mixture includes a base agent neutralising the ionic surfactants at least partially.

11. A material as claimed in any one of claims 2 to 10, in which the liquid- based mixture includes a soluble polymer.

12. A material as claimed in any one of claims 2 to 11, in which the liquid- based mixture includes in situ cross-linkable monomers of any molecular weight.

13. A material as claimed in any one of the preceding claims, in which the alkane emulsifiable gas includes at least one compound selected from the group consisting of short-chained alkanes, ethane, butane, propane, pentane and/or mixtures thereof.

14. A material as claimed in any one of claims 2 to 13, in which the liquid- based mixture includes at least one humectant.

15. A material as claimed in any one of claims 2 to 14, in which the foam precursor is adapted to expand only on a hot substrate and/or when exposed to elevated temperatures.

16. A material as claimed in any one of claims 2 to 15, in which the water- based foam has a density of 20 - 200 kilograms per cubic meter.

17. A material as claimed in any one of claims 2 to 16, in which the water based foam includes emulsified pepper and/or CS (tear gas) chemicals and/or other noxious but otherwise harmless additives.

18. A material as claimed in any one of the preceding claims, in which the water based foam includes at least one dye adapted to stain human skin for prolonged periods of time.

19. A material as claimed in claim 18, in which the dye is adapted to stain skin.

20. A material as claimed in claim 18 or claim 19, in which the dye is adapted to be illuminated in UV and flourescent light.

21. A material as claimed in any one of claims 18 to 20, in which the dye is coloured in the visual part of the spectrum.

22. A material as claimed in any one of the preceding claims, which is deployed by means of deployment equipment.

23. A material as claimed in claim 22, in which the deployment is triggered by flames, heat, automatically and/or manually.

24. A material as claimed in any one of the preceding claims, which is adapted to act as a crime barrier and/or in combination with a fire suppression role.

25. A material as claimed in any one of the preceding claims, in which is adapted to smother flames and/or fires by preventing oxygen from coming into contact with the flames and/or fires.

26. A material as claimed in any one of the preceding claims, which includes at least one identification inks.

27. A fire extinguishing material, which includes a gel including

(a) water,

(b) at least one dipolar molecular liquid; and

(c) at least one surfactant.

28. A method of producing a foam based fire extinguishing material includes the steps

(a) of mixing water, at least one dipolar molecular liquid and at least one surfactant to obtain a liquid-based mixture;

29. A method as claimed in claim 28, which is automated and/or robotic and/or computer controlled and/or manually controlled.

30. A method of extinguishing fires, includes the step of covering a fire with a fire-extinguishing material as claimed in any one of claims 1 to 27.

31. A foam based fire extinguishing material substantially as hereinbefore described with reference to the examples.

32. A method of producing a foam based fire extinguishing material substantially as hereinbefore described with reference to the examples.

33. A method of extinguishing fires substantially as hereinbefore described with reference to the examples.