WO1994023798A1

WO1994023798A1 - Fire suppressant foam generation apparatus

Info

Publication number: WO1994023798A1
Application number: PCT/US1994/004117
Authority: WO
Inventors: Dennis Edward Smagac
Original assignee: Dennis Edward Smagac
Priority date: 1993-04-16
Filing date: 1994-04-14
Publication date: 1994-10-27
Also published as: AU6704694A

Abstract

The fire suppressant foam generation and application apparatus produces a low moisture content fire suppressant foam mixture for use in fire fighting applications. The reduction in the water content of the fire suppressant foam is accomplished by the use of pressurized gas (101) in place of water to create the agitation and pressurized delivery capability. Furthermore, the use of the pressurized nitrogen eliminates the need for a large complex pumping apparatus to pump an incompressible fluid, such as water, that has been used in the past to agitate and supply the foam mixture to the spray nozzles. A pressurized gas operated pump (104) can be used to actively draw the water/foam mixture from a supply tank (103) and supply it under pressure to the outlet line (111) where it is mixed with and agitated by the pressurized nitrogen to create the resultant foam.

Description

FIRE SUPPRESSANT FOAM GENERATION APPARATUS

FIELD OF THE INVENTION

This invention relates to fire fighting apparatus and, in particular, to apparatus for generating and delivering a fire

suppressant foam for use in fire fighting purposes.

PROBLEM

It is a problem in the field of fire fighting to provide a sufficient volume of fire fighting material to suppress a fire. The traditional fire fighting material used for this purpose is water, which has the

undesirable side effect of causing significant amounts of water

damage to the real property in and around the area in which the fire

is engaged. In fact, in many situations the water damage to the real property is significantly in excess of the fire damage to the real

property. An alternative fire fighting material in use is fire suppressant foam. However, the difficulty with fire suppressant foam

is that the typical materials used for this purpose require complicated mixing and pumping apparatus and still produce a significant amount of water damage due to the relatively high water content of

the foam.

In a typical application, the availability of a significant water supply renders water as a fire fighting material the desired choice, since the fire suppressant foam itself requires a significant amount of water. In addition, fire suppressant foam requires complicated generation and delivery apparatus, thereby rendering it impractical for use except in certain selected applications, such as airport fire fighting applications where the use of water is ineffective in controlling the magnitude and extent of a fuel fire. There presently does not exist any apparatus that is effective in fire fighting applications that is simple in architecture and yet causes minimum ancillary damage to real property as a result of the fire suppression activity.

Rural homeowners face additional problems in protecting their property from the danger of wildfires. There is an increasing trend for people to build their homes in locations that are within what is called the wildland/urban interface. This is a term that describes the geographical areas where formerly urban structures, mainly residences, are built in close proximity to flammable fuels naturally found in wildland areas, including forests, prairies, hillsides and valleys. To the resident, the forest represents a beautiful environment but to a fire the forest represents a tremendous source of fuel. Areas that are popular wildland/urban interfaces are the

California coastal and mountain areas and the mountainous areas in Colorado (among others).

Residences built in these areas tend to be placed in locations that contain significant quantities of combustible vegetation and the structures themselves have combustible exterior walls and many have untreated wood roofs. Many of these houses are also built on sloping hillsides to obtain scenic views; however, slopes create natural wind flows that increase the spread of a wildfire. These

homes are also located a great distance away from fire protection equipment and typically have a limited water supply, such as a residential well with a minimal water flow in the range of one to three gallons per minute. Therefore, residences located in the wildland/urban interface do not have access to an adequate supply of the traditional fire suppressant material-water. Thus, traditional fire fighting technology has severe limitations in terms of its effectiveness and availability in many applications.

SOLUnON

The above described problems are solved and a technical

advance achieved in the field by the fire suppressant foam

generation and application apparatus of the present invention. This apparatus makes use of a commercially available low moisture content fire suppressant foam mixture in conjunction with novel foam generation and application apparatus to minimize the water damage to real property caused by the fire suppression activity. This apparatus is simple in structure and operation and makes use of a pressurized gas to create the water/foam mixture, propel it through the delivery apparatus and, in one embodiment, power an auxiliary pump to increase the delivery pressure of the fire suppressant materials. This apparatus is lightweight in construction, simple in architecture and can be implemented in a unit that is sufficiently compact to be installed on a lightweight utility vehicle, such as a four-wheel drive pick-up truck. This apparatus also does not require a large capacity source of water to create the fire suppressant materials that are applied to the fire.

In one embodiment, a source of pressurized nitrogen is used to supply the propellant. The nitrogen is applied via a pressure regulator to a supply line that joins with an outlet line from the water/foam mixture supply tank. The configuration of the fixture that interconnects these two lines creates a Venturi effect, wherein the pressurized nitrogen draws the water/foam mixture from its supply tank through a check valve. The pressurized nitrogen supplies a foaming action as the water/foam mixture is driven down the pipe and also forces the resultant foam through the delivery apparatus, such as a conventional fire hose. An alternative embodiment makes use of a pressurized gas operated pump that can be driven by an auxiliary supply of pressurized gas, such as an air compressor, to supply the water/foam mixture to thereby conserve the pressurized nitrogen for use in the creation of the fire suppressant foam.

The water/foam mixture uses commercially available foaming agents that are expanded by the application of the pressurized gas to create the fire suppressant foam without the need for pressurized water as a propellant. This has multiple benefits, including the reduction in the moisture content of the fire suppressant foam and avoiding the need for complex water pumping apparatus to create the stream of pressurized water. The elimination of water as a delivery agent thereby renders this apparatus independent of a large supply of water that is typically needed for fire fighting purposes. In addition, since water is an incompressible medium, its storage and delivery cannot be improved by pressurization, whereas the use of an inert gas such as nitrogen provides great opportunity for storage efficiency since the gas can be pressurized to extremely high levels, thereby efficiently storing a vast quantity of propellant in a small physical space. Similarly, the use of a pressurized gas powered pumping system to increase the pressure of the delivered water/foam mixture does not unduly complicate the apparatus since pumps of low weight and size are available for this purpose. The

resultant apparatus is therefore extremely lightweight, compact in

dimensions and inexpensive to implement. Control of the flow of the pressurized gas and water/foam mixture is accomplished by way of simple check valves and pressure regulators, thereby eliminating the complex apparatus presently in use. Use of a water/foam mixture as a fire fighting material is beneficial, since a small quantity of the mixture expands to produce a tremendous volume of fire fighting material. Therefore, a significant volume of fire fighting materials can be created using a small quantity of water/foam mixture and a compact source of pressurized gas. This novel apparatus can therefore be implemented inexpensively in a compact implementation unknown in the prior art.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 illustrates in block diagram form the overall architecture of the fire suppressant foam generation apparatus of the present invention; Figure 2 illustrates an alternative embodiment of the apparatus of the present invention;

Figure 3 illustrates a cross-sectional view of a typical pump that can be used in the implementation of this system;

Figure 4 illustrates one embodiment of a delivery apparatus; and

Figure 5 illustrates a cross-sectional view of a foam mixing fixture that can be used in this apparatus.

DETAILED DESCRIPTION

There is an increased incidence of home building in the area defined as the wildland/urban interface. This area is where

residences are built in close proximity to the flammable fuels

naturally found in wildland areas, including forests, prairies, hillsides and valleys. These areas typically represent the confluence of a plurality of factors that render fire fighting difficult, if not impossible. The primary factor is combustible vegetation which is found in abundance in these areas. An approaching fire ignites the surrounding vegetation in a step by step attack on a home and may reach intensities that render conventional fire fighting methods ineffectual. In particular, when the fire reaches an intensity of 500 btu per foot of fire line front per second of burning, the fire is considered to be beyond control by use of organized means. Beyond 1000 btu per foot per second a fire can be expected to feature dangerous spotting, fire whirls, crowning and major runs with high rates of spread and violent fire behavior, such a tornado-like winds. Spotting is particularly difficult to deal with since it occurs as wind borne burning embers are carried far ahead of the main fire front. These embers land in receptive fuels and can fall on the roof of a home or a woodpile and start new fires far in advance of the fire line front. In addition, many of the structures built in these rural areas are constructed of materials that are of highly susceptible to fires. Primary among these are untreated wood roofs such as untreated wood shingles or wood shake roofing. Furthermore, these structures have combustible exterior walls or affiliated wood

structures such as decks and woodpiles located under decks or placed too close to the structure. Many of the structures are located on a slope which creates a natural wind flow that increases the speed of a wildfire by creating a chimney effect. The remote location of these structures impedes the ability of fire fighting equipment to reach the site of a fire. Finally, there is typically a

significant lack of water available for fire fighting purposes. There

are no hydrants or ponds and a fire tanker truck must respond to the site of the fire in order to provide a source of water for fire fighting purposes. These structures typically have a domestic water supply that consists of a well of limited volumetric capacity. Therefore, the confluence of many or all of these factors make fire

fighting in this environment difficult at best.

Traditional fire fighting may be somewhat ineffectual in the wildland/urban interface but is successful in other residential applications. However, a problem with the use of water as a fire

suppressant material is that it causes significant ancillary damage to a residence and its contents as a result of fire fighting activity.

Therefore, it is desirable to find an alternative fire suppressant

material. Theory of Operation

Figure 1 illustrates in block diagram form the overall

architecture of the fire suppressant foam generation and application apparatus of the present invention. Fire suppressant foam is a combination of a fluid/foam mixture and a propellant which functions to both agitate the fluid/foam mixture to create the expanded foam and to deliver it through the application apparatus to the fire. The fire retardant foam generation and application apparatus produces a dry fire suppressant foam mixture for use in fire fighting applications. The reduction in the fluid content of the fire suppressant foam is accomplished by the use of pressurized gas in place of a fluid to create the agitation and pressurized delivery capability. Furthermore, the use of the pressurized gas eliminates the need for a large complex pumping apparatus to pump an incompressible fluid, such as water, that has been used in the past to agitate and supply the foam mixture to the spray nozzles. A hydraulic or pressurized gas operated pump can be used to actively draw the water/foam mixture from a supply tank and supply it under pressure to the outlet line where it is mixed with and agitated by the pressurized gas to create the resultant foam. In a typical application, a 210 tank of water/foam mixture can produce 4000 gallons of water-based biodegradable foam without the need of complex pumping apparatus. In this option, the use of the nitrogen gas has multiple benefits since the nitrogen gas is an inert element and does not support fire. A gallon of foaming concentrate is used for 320 gallons of water and, when mixed with high pressure air or nitrogen gas, a tremendous expansion of the foaming material takes place to create the fire suppressant foam. This fire suppressant foam functions to extinguish the fire by means of a number of different characteristics.

The small amount of detergent in the foaming agent enables the water to overcome the surface tension created by oils and dust normally found on interior and exterior surfaces. This allows the foam to penetrate and wet the flammable materials that comprise the structure much more quickly than the application of water alone. Also, because the foam is able to soak into the wood and vegetation instantly, evaporation is much less of a problem than the use of water that tends to pool on surfaces. The foam bubbles at the bottom of the foam wet and cool the surface that is to be protected. Furthermore, the top layer of the foam bubbles to provide a lingering cooling cover of oxygen-free insulation and heat reflection. The nitrogen gas that permeates the fire suppressant foam starves the fire of oxygen, therefore retarding the spread of the fire to the materials on which the foam has been applied. The foam therefore penetrates, cools and smothers the fire while the water would simply run off or evaporate in a similar, application. System Architecture

This apparatus is a completely passive system that does not

require the use of electricity or gasoline powered pumps for

operation. Therefore, in a wildfire environment, when the power lines are typically down and there is a limited supply of water available for fire fighting purposes, this apparatus provides a unique combination of capabilities that make it ideal for application in this environment. In the embodiment illustrated in Figure 1, the water/foam mixture (fire suppressant foam fluid) is stored in a storage tank 103 in premixed form in proportions dictated by the manufacturer of the foam concentrate. A typical foaming material is sold by Chemonics Industries, Inc. under the trade name of "FIRE- TROL^® FIREFOAM^® 103". This foaming agent (foam concentrate) is a proprietary mixture of foaming and wetting agents in a non- flammable solvent. The concentrate is diluted with a fluid, such as water, to produce the water/foam mixture which expands into the resultant fire suppressant product when agitated by a propellant and delivered through an appropriate system of pipes or hoses, which further enhances the agitation. In the fire suppressant foam generation apparatus, the propellant consists of the inert gas nitrogen that is stored in a highly pressurized condition in one or more nitrogen bottles 101 which are interconnected via a manifold 102. The output of the nitrogen manifold 102 is applied through a pressure regulator 105 of conventional design to a supply line 106. The supply line 106 can supply one or more foam mixing systems via junction 107 which can lead to a plurality of the apparatus illustrated in Figure 1. For the purpose of simplicity of illutration, this additional apparatus is not replicated in Figure 1. The pressurized nitrogen applied through supply line 106 can be used to power the pressurized gas driven pump 104 or an additional source of pressurized gas, such as air compressor 115, can be used to supply pressurized gas via line 110 to operate the

pressurized gas driven pump 104. Alternatively, a hydraulicly or mechanically driven pump can be used in lieu of the presurized gas driven pump 104, especially if this apparatus is mounted on a vehicle. If pressurized nitrogen is used to operate pump 104, a tap line 116 draws pressurized nitrogen from supply line 106 and applies it through pressure regulator 107 to the pressurized gas supply intake of pump 104. In either case, whether pressurized air is used from air compressor 115 or pressurized nitrogen from supply line 106, the pressurized gas functions to operate pump 104 to actively draw the water/foam mixture from holding tank 103 via line 109 and output it through check valve 102 at a significantly increased pressure to water/foam mixture volume valve 113. The water/foam mixture volume valve 113 controls the flow of the water/foam mixture to thereby controllably regulate the water/foam and pressurized gas mixture that is provided to create the agitated foam mixture. A propellant supply line 108 is provided to draw the pressurized nitrogen from supply line 106 and apply it via fixture 118 to the water/foam mixture output by the water/foam mixture volume valve

113. The pressurized water/foam mixture enters outlet line 111 and is propelled down the length of outlet line 111 by the action of the pressurized nitrogen gas being added thereto via fixture 118. The action of the pressurized nitrogen gas mixing with the water/foam mixture causes this material to expand significantly in volume and move rapidly down the outlet pipe 111 to the spray nozzle 114 that is used by a fire fighter to apply the fire suppressant foam to the object engulfed in flames. The outlet 114 can also be a plurality of sprinkler heads located on the interior or exterior of a structure to provide a passive application of the foam to the object to be protected.

Pressurized Gas Operated Pump Figure 3 illustrates a cross-sectional view of a pressurized gas driven pump 104 that is presently available from Wilden Pump and Engineering Company and which is sold under various trade names. One model of Wilden pumps is sold under the trade name CHAMP™ which is an air operated double diaphragm non-metallic seal-less positive displacement pump. This pump is manufactured from polypropylene, polyvinylidine fluoride and Teflon^® materials to provide chemical resistance, excellent mechanical properties and flex fatigue resistance in a lightweight inexpensive package. This pump can pump from 1/10 to 155 gallons/minute. These pumps are self- priming and variable capacity.

In operation, compressed gas is applied directly to the liquid column and is separated therefrom by a pair of elastomer diaphragms 301, 302. The diaphragms 301, 302 operate in opposition to provide a balanced load and create a steady pumping output. The product to be pumped, also called "slurry", is input at an inlet 311 located in the bottom of the pump 104 and drawn up into the liquid chamber by the operation of the diaphragms 301 , 302.

The two diaphragms 301, 302 are mechanically connected by arm

303 and operated by means of the air pressure supplied by a set of air valves (not shown). When a pressurized diaphragm 302 reaches the full limit of its stroke, forcing the slurry out to the outlet pipe 312 located at the top of the pump 104, an air valve is activated to shift the air supply pressure to the inner side of the opposite diaphragm

301. Meanwhile, when the pressurized diaphragm 302 is going through its active stroke, the other diaphragm 301 is being drawn inward, creating a suction to draw slurry into the liquid chamber 321 through the pump inlet 311. Check valves located in the pump inlet 311 and outlet 316 prevent a back flow between the diaphragms

301 , 302 caused by the sequential operation of the two diaphragms 301, 302. Thus, the two diaphragms 301, 302 are cooperatively operative to create a suction in one fluid chamber 321 while pressurizing the second fluid chamber 322 to output a flow of the slurry. Simple air valves shift the pressurized gas to one or the other diaphragms 301, 302 dependent on the position of the

diaphragms 301 , 302 in their range of motion. The pump 104 can

be operated by means of the pressurized nitrogen or by an auxiliary source of pressurized gas, such as a portable air compressor 115.

In either case, the water/foam mixture is actively drawn from the supply tank 103 and output through a check valve 112 in a

pressurized condition by the operation of pump 104.

Alternative Embodiment Figure 2 illustrates an alternative simplified embodiment of the apparatus of Figure 1. The pump 104 is replaced by a Venturi creating fixture 118 for application when the water/foam mixture does not have to be actively drawn from supply tank 103. In

operation, the nitrogen bottles 101 supply pressurized nitrogen through manifold 102 and regulator 105 to supply line 106 as

disclosed above. The optional additional supply lines can be provided through fixture 117. Propellant supply line 108 applies the

pressurized nitrogen through nitrogen volume valve 113 to fixture

118 to provide the pressurized nitrogen to outlet line 111 for delivery of the pressurized foam to spray nozzle 114. A check valve 112 is

provided in the line 109 that interconnects the supply tank 103 with

fixture 118. The fixture 118 consists of a Y connector that injects the pressurized nitrogen at an acute angle into the supply line 109 that interconnects the water/foam supply tank 103 with the outlet pipe

111. The action of the pressurized nitrogen entering fixture 118 causes the water/foam mixture to be drawn forward into the outlet pipe 111 and causes the agitation and expansion of the foam as it is delivered down the outlet pipe 111 to the spray nozzle 114.

Figure 5 illustrates, in cross-sectional view, one embodiment

of a Venturi-creating fixture 118 that can be used for the purposes described above. The Venturi-creating fixture 118 consists of a body

500 that interconnects at a first end with the line that is connected

via check valve 112 to water/foam mixture tank 103 and at a second

end with outlet pipe 111. Located witin the body 500 of Venturi- creating fixture 118 are one or more injection pipes 501-50n. The injection pipes 501 -50n are aligned substantially along the length of body 500 and can be slightly angled from the centerline thereof to

create a spiral flow of the nitrogen gas received from mixture control valve 113, to which the injection pipes 501 -50n are connected through the walls of body 500. This spiral flow on the inected nitrogen gas enhances the foaming action created by the admixture

of the nitrogen gas to the water/foam mixture. The number, location and dimenions of the injection pipes 501 -50n are selected in

conjunction with the range of nitrogen gas-water/foam fluid mixtures that are desired as well as the degree of foaming that is to be

created in Venturi-creating fixture 118. As noted above, the injection

of the nitrogen gas creates a suction effect to draw the water/foam mixture from water/foam mixture tank 103 into Venturi-creating fixture 118.

Permanently Installed Delivery Systems

In addition to use with a manual delivery system as described above, the fire suppressant foam generation apparatus can be used with a permanently installed delivery system similar to conventional

sprinkler systems used in residential and commercial buildings. An

example of a typical residential sprinkler system is shown in Figure 4 wherein a two-story residential structure has seven sprinkler heads 401-407 installed in the 717 square foot first floor of the structure and four additional sprinkler heads 408-411 installed in the 574 square foot second floor of the structure. Using standard design

criteria for fire sprinkler systems, a flow rate of approximately 65

gallons of water per minute is required for effective fire fighting in such a system. It is obvious that this installation would be

impractical in a wildland/urban interface environment since this volume of water is typically unavailable. In operation, this flow of

water also causes a significant amount of water damage to the contents of the structure and also some damage to the structure

itself if left in operation for a significant amount of time.

The water/foam mixture volume valve 113 in the fire

suppressant foam generating apparatus is used to regulate the moisture content of the resultant fire retardant foam that is produced. The water damage that results from dispensing fire retardant foam from the residential sprinkler system is thereby significantly reduced. The reduction of water damage is especially important in a business environment where numerous paper records are maintained. Therefore, the inlet 400 of the sprinkler system illustrated in Figure 4 can be connected to outlet pipe 111 of the fire suppressant foam generation apparatus to obtain the benefits of the use of a low moisture content fire suppressant foam in a

conventional residential fixed installation sprinkler system.

Summary

In summary, the fire suppressant foam generation and application apparatus produces a low moisture content fire suppressant foam mixture for use in fire fighting applications. The reduction in the water content of the fire suppressant foam is accomplished by the use of pressurized gas in place of water to

create the agitation and pressurized delivery capability.

Furthermore, the use of the pressurized nitrogen eliminates the need

for a large complex pumping apparatus to pump an incompressible fluid, such as water, that has been used in the past to agitate and

supply the foam mixture to the spray nozzles. A pressurized gas operated pump can be used to actively draw the water/foam mixture from a supply tank and supply it under pressure to the outlet line where it is mixed with and agitated by the pressurized nitrogen to create the resultant foam.

Claims

I CLAIM:

1. Apparatus for generating fire suppressant foam comprising: a source of pressurized gas; a source of fire suppressant foam fluid; means for delivering a stream of fire suppressant foam; means for producing a flow of said fire suppressant foam fluid from said source of fire suppressant foam fluid to said delivering means; and means for injecting a controllable amount of said pressurized gas into said flow of fire suppressant foam fluid to expand said fire suppressant foam fluid into fire suppressant foam.

2. The apparatus of claim 1 wherein said source of pressurized gas comprises at least one container of pressurized inert gas.

3. The apparatus of claim 1 wherein said pressurized gas comprises nitrogen.

4. The apparatus of claim 1 wherein said producing means comprises: means for drawing a controllable flow of said fire suppressant foam fluid from said source of fire suppressant foam fluid.

5. The apparatus of claim 4 wherein said drawing means comprises a pressurized gas operated pump.

6. The apparatus of claim 4 wherein said producing means further comprises: valve means for regulating an output flow of said fire suppressant foam fluid from said drawing means.

7. The apparatus of claim 6 wherein said injecting means comprises: means for regulating said controllable amount of said pressurized gas injected into said flow of fire suppressant foam fluid following said fire suppressant foam fluid passing through said valve means.

8. The apparatus of claim 1 wherein said producing means comprises: means, responsive to a flow of said pressurized gas, for drawing a controllable flow of said fire suppressant foam fluid into said flow of pressurized gas.

9. The apparatus of claim 8 wherein said injecting means comprises: valve means for supplying a controllable flow of said pressurized gas.

10. The apparatus of claim 1 wherein said source of fire suppressant foam fluid comprises a holding tank containing a mixture of fire suppressant foam concentrate and a fluid.

11. The apparatus of claim 1 wherein said delivery system comprises a combination of pipes and foam delivery heads attached to said pipes, permanently installed inside a structure.

12. A method of generating fire suppressant foam for a foam delivery system using a source of pressurized gas and a source of fire suppressant foam fluid, comprising the steps of: producing a flow of said fire suppressant foam fluid from said source of fire suppressant foam fluid to said delivery system; nd injecting a controllable amount of said pressurized gas into said flow of fire suppressant foam fluid to expand said fire suppressant foam fluid into fire suppressant foam for said foam delivery system.

13. The method of claim 12 wherein said source of pressurized gas comprises at least one container of pressurized inert gas.

14. The method of claim 13 wherein said pressurized gas comprises nitrogen.

15. The method of claim 12 wherein said step of producing comprises: drawing, via a pump, a controllable flow of said fire suppressant foam fluid from said source of fire suppressant foam fluid.

16. The method of claim 15 wherein said step of producing further comprises: regulating an output flow of said fire suppressant foam fluid from said pump using a valve.

17. The method of claim 16 wherein said step of injecting comprises: regulating said controllable amount of said pressurized gas injected into said flow of fire suppressant foam fluid following said fire suppressant foam fluid passing through said valve.

18. The method of claim 12 wherein said step of producing comprises: drawing, in response to a flow of said pressurized gas, a controllable flow of said fire suppressant foam fluid into said flow of pressurized gas.

19. The method of claim 18 wherein said step of injecting comprises: supplying a controllable flow of said pressurized gas using a valve.

20. The method of claim 12 wherein said source of fire suppressant foam fluid comprises a holding tank containing a mixture of fire suppressant foam concentrate and a fluid.