A compressed air foam system provided with an improved mixing system

Abstract

A compressed air foam system, CAFS (1), comprising a source (2) of water, an air management system (3) for providing a flow of compressed air, a solution dosing module (4) for providing an additive solution, and a mixing chamber module (5) configured to provide an air solution mixture to an output device (6), the mixing module (5) comprising an outlet conduit (8) fluidly connected to the output device (6) and an inlet conduit (7) fluidly connected to the source (2), the mixing module (5) comprising a plurality of bypass conduits (9a, 9b, 9c, 9d, 9e) between the inlet conduit (7) and the outlet conduit (8), the bypass conduits (9a, 9b, 9c, 9d, 9e) having different hydraulic diameters from each other and possibly valves (10) with associated different pressure openings.

Description

[0001] Cross-references to related applications

[0002] This patent application claims priority to Italian Patent Application No. 102021000010364, filed on April 23, 2021, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] This invention relates to fire extinguishing systems for fire trucks or equipment, and in particular to compressed air foam systems (CAFS) equipped with an improved mixing system. Background Technology

[0004] Fire suppression systems, such as fire trucks or equipment, are equipped with fire extinguishing systems that are configured to supply fire extinguishing compounds directed toward the fire in order to suppress the fire.

[0005] In particular, compressed air foam systems (CAFS) are well known in the art and involve the use of a mixture of compressed air and water / foaming agent solution in a predetermined percentage.

[0006] More specifically, the water / foaming agent solution comprises foaming agent additives dissolved in a large volume of water, i.e., 0.5% to 3% or 8% by volume of the additives. Compressed air is mixed with this solution in a mixing chamber module.

[0007] This air-solution mixture, under pressure higher than atmospheric pressure and ejected through an outlet in a pipe pointed towards the fire, expands to form foam with extinguishing properties. Specifically, the air volume of the foam can be adjusted to assume an air-to-liquid-solution ratio between 3 and 20 parts by volume. As defined in standard DIN EN 16327, such an air / solution ratio between 3 and 10 is defined as "wet foam," while an air / solution ratio between 11 and 20 is defined as "dry foam."

[0008] Based on the above, one issue related to the CAFS system is ensuring proper mixing between water and the water / foam solution to provide a suitable air / solution mixture.

[0009] However, air and water flows can vary continuously because operators can constantly adjust the flow or air / solution mixture depending on the fire situation. Such oscillations in the water flow can lead to unsatisfactory mixing of water, air, and foaming agent.

[0010] In fact, the water is usually regulated by a butterfly valve that is typically closed when the compressed air foam system is engaged. This butterfly valve does not provide a good enough water flow rate to ensure proper mixing between the water, foaming agent, and air. This drawback is particularly noticeable when the required water flow rate is low.

[0011] Therefore, there is a need to provide a CAFS system that can provide a good mixing between water, foam agent and air according to the needs of the user.

[0012] The object of the present application is to meet the above needs in a cost-effective and optimized manner. SUMMARY

[0013] The aforementioned object is achieved by a compressed air foam system as claimed in the appended claims. BRIEF DESCRIPTION OF DRAWINGS

[0014] For a better understanding of the present application, the preferred embodiments are described below, by way of non-limiting example, with reference to the accompanying drawings, in which: Figure 1 A schematic view of a compressed air foam system comprising a mixing module according to the present application is shown. DETAILED DESCRIPTION

[0015] Figure 1 A general schematic view of a compressed air foam system CAFS1 for a not shown fire fighting installation, for example a vehicle, is disclosed. The CAFS1 mainly comprises a source 2 of water, an air management system 3, a solution dosing system 4 and a mixing chamber 5. The mixing chamber 5 receives water from the source 2, a controlled and defined air flow from the air management system 3, an additive, for example a foam agent, from the solution dosing system 4 and is configured to mix these elements together to provide a suitable flow of fire fighting air / solution mixture at an outlet device 6 that can be connected to a pipe used by a fire fighter.

[0016] The air management system 3 can be implemented in different ways, for example according to the system described in the international patent application PCT IB2020061830 and therefore it is not further described herein for the sake of brevity.

[0017] The solution dosing system 4 can also be implemented in different known ways. Both the solution dosing system 4 and the air management system 3 are configured to provide respective pressurized fluid flows into the mixing chamber 5 of the foam solution and compressed air, respectively.

[0018] The source 2 of water can be of different types as known in the art, such as a water pump, a hydrant.

[0019] Preferably, the mixing chamber 5 defines a first inlet 5a in fluid connection with the source 2, a second inlet 5b in fluid connection with an output 4a of the dosing system 4, a third inlet 5c in fluid connection with an output 3a of the air management system 3 and an outlet 5d in fluid connection with the outlet device 6.

[0020] According to the described embodiment, the mixing chamber 5 comprises an inlet conduit 7, an outlet conduit 8 and a plurality of bypass conduits 9a, 9b, 9c, 9d fluidically interposed between the inlet conduit 7 and the outlet conduit 8.

[0021] In the following, the terms "upstream" and "downstream" are used to refer to the water path from the source 2 to the outlet device 6.

[0022] The inlet conduit 7 is fluidically connected from one side to the source 2 and to the bypass conduits 9a, 9b, 9c, 9d, 9e downstream of the source 2, while the outlet conduit 8 is fluidically connected from one side to the outlet device 8 and to the bypass conduits 9a, 9b, 9c, 9d, 9e upstream of the outlet device 6.

[0023] In detail, the first bypass conduit 9a is upstream of the second bypass conduit 9b, the second bypass conduit 9b is upstream of the third bypass conduit 9c, the third bypass conduit 9c is upstream of the fourth bypass conduit 9d, the fourth bypass conduit 9d is upstream of the fifth bypass conduit, the fifth bypass conduit being only downstream of the source 2. In other words, from the point of view of the outlet device 6, the first bypass conduit 9a is upstream of the second bypass conduit 9b, the second bypass conduit 9b is upstream of the third bypass conduit 9c, the third bypass conduit 9c is upstream of the fourth bypass conduit 9d, the fourth bypass conduit 9d is upstream of the fifth bypass conduit, the fifth bypass conduit being only upstream of the outlet device 6.

[0024] In particular, the output 4a of the dosing system 4 and the output 3a of the air management system 3 are both fluidically connected only to the first bypass conduit 9a, i.e. the most downstream bypass with respect to the source 2. More preferably, the output 3a of the air management system 3 is fluidically connected to the first bypass conduit 9a upstream of the outlet conduit 8 and downstream of the output 4a of the dosing module 4. The dosing module output 4a is fluidically connected to the first bypass conduit 9a downstream of the inlet conduit 7.

[0025] Advantageously, the number of bypass conduits 9a, 9b, 9c, 9d, 9e is N and the hydraulic diameter of the (M)th bypass conduit 9a, 9b, 9c, 9d, 9e is smaller with respect to the (M+1)th bypass conduit 9a, 9b, 9c, 9d, 9e, where N and M are integers and M is smaller than N.

[0026] According to the described embodiment, the hydraulic diameter of the first conduit 9a is smaller with respect to the second conduit 9b, the hydraulic diameter of the second conduit 9b is smaller with respect to the third conduit 9c, the hydraulic diameter of the third conduit 9c is smaller with respect to the fourth conduit 9d, the hydraulic diameter of the fourth conduit 9d is smaller with respect to the fifth conduit 9e. Preferably, the inlet and outlet conduits 7 have a hydraulic diameter substantially the same or greater than the fifth conduit 9e.

[0027] More preferably, the outlet duct 8 has a variable diameter between the duct 9a and the duct 9e. In particular, the section of the outlet duct 8 between the (M)th duct and the (M+l)th duct has substantially the same diameter as the (M)th duct.

[0028] Therefore, the section of the outlet duct 8 between the duct 9a and the duct 9b has substantially the same diameter as the duct 9a, the section of the outlet duct 8 between the duct 9b and the duct 9c has substantially the same diameter as the duct 9b, the section of the outlet duct 8 between the duct 9c and the duct 9d has substantially the same diameter as the duct 9c, the section of the outlet duct 8 between the duct 9d and the duct 9e has substantially the same diameter as the duct 9d, and then the last section has the same diameter as the duct 9e, i.e. the diameter of the input duct 7.

[0029] Advantageously, at least some of the bypass ducts 9a, 9b, 9c, 9d, 9e are provided with valve means 10 configured to allow the passage of fluid from the inlet duct 7 towards the outlet duct 8 only through the respective bypass duct. In particular, such valve means comprise different pressure control openings, thus allowing the water to flow on the respective bypass duct according to the pressure of the water in the inlet duct 7.

[0030] In particular, in the example disclosed, the first bypass duct 9a, i.e. the one directly fluidically connected to the air management system 3 and to the dosing module 4, is free, i.e. always allows the passage of fluid from the inlet duct 7 towards the outlet duct 8. In other words, the first bypass duct 9a is not provided with the above-mentioned valve means.

[0031] Advantageously, the other bypass ducts 9b, 9c, 9d provided with the check valves 10 have different opening pressures, i.e. the respective check valves 10 are sized to thereby allow the passage of fluid at different pressure levels.

[0032] In detail, the opening pressure level of the check valve 10a on the second bypass duct 9b is lower with respect to the check valve 10b on the third bypass duct 9c, which in turn has a lower opening pressure level with respect to the check valve 10c on the fourth bypass duct 9d.

[0033] Advantageously, one of the bypass ducts 9a, 9b, 9c, 9d, 9e is provided with valve means 11 configured to be actively controlled to allow the passage of fluid from said inlet duct 7 to said outlet duct 8.

[0034] In particular, the fifth bypass duct 9e is provided with an electrically actuated valve 11, such as an on-off valve, configured to allow or refuse the passage of fluid from the inlet duct 7 towards the outlet duct 8.

[0035] The operation of the CAFS1 according to the present application and as described above is as follows.

[0036] In general, the water provided by the source 2 flows towards the inlet conduit 7 and to the first bypass conduit 9a. In this conduit having a minimum hydraulic diameter, the speed of the water is increased, the water is first mixed with the foaming agent coming from the opening 4a and then with the compressed air coming from the opening 3a. Then, the water passes to the outlet conduit which has a greater diameter and allows a good mixing of the water at high speed and pre-mixed with the foaming agent with the compressed air. The mixed solution then flows towards the outlet device 6.

[0037] If the water pressure increases, the check valve 10a of the second bypass spring opens and allows the water to pass directly into the outlet conduit 8 downstream of the second bypass conduit 9b. In this way, the solution is further mixed before passing into the outlet device 6. The same happens if the water pressure increases further, allowing the check valves 10b, 10c of the third bypass conduit 9c and of the fourth bypass conduit 9d to open.

[0038] If the user only needs water and not the foaming solution and the air, the valve 11 can be controlled to open, allowing the water flow to pass directly to the output device 6 mainly in the fifth bypass conduit 9e. In fact, only a small amount of water flows through the conduits 7, 9a and 8 to be mixed again into the output conduit 8; however, due to the difference in diameter, the main part of the water passes directly through the conduit 9e.

[0039] In view of the foregoing, the advantages of the compressed air foam system CAFS1 according to the present application are evident.

[0040] Thanks to the proposed mixing module, it is possible to mix water with foaming solution and air in a very effective way, avoiding poor quality foaming solution at the outlet device.

[0041] Moreover, the mixing module is particularly compact and cost-effective.

[0042] Furthermore, the mixing module operates in a very wide range of water pressures and produces a foam mixture of the same quality.

[0043] Moreover, by varying the number of bypass conduits, it is possible to vary the range of water pressures. Therefore, the proposed mixing module is universal and allows an economy of scale production.

[0044] In particular, the universality of the proposed mixing system is evident. In fact, the mixing system can be used to provide the output device with a foaming solution without air, an air foaming solution or simply water. Therefore, with respect to the known systems, the mixing system provides all the functions via a single module.

[0045] It is clear that modifications can be made to the compressed air foam system CAFS 1 described, which do not go beyond the scope of protection defined by the claims.

[0046] By way of example, the number of by-pass conduits can vary. Similarly, the valve devices 10, 11 can be replaced by different types of valves having the same opening characteristics.

Claims

1. A compressed air foam system (1) comprising: a source (2) of water; an air management system (3) for providing a flow of compressed air; a solution dosing module (4) for providing an additive solution; and a mixing chamber module (5) configured to provide an air solution mixture to an output device (6), the mixing chamber module (5) comprises an outlet conduit (8) fluidically connected to the output device (6) and an inlet conduit (7) fluidically connected to the source (2), the mixing chamber module (5) comprises a plurality of bypass conduits (9a, 9b, 9c, 9d, 9e) between the inlet conduit (7) and the outlet conduit (8), each of the bypass conduits (9a, 9b, 9c, 9d, 9e) having a hydraulic diameter different from one another, the air management system (3) and the dosing module (4) are fluidically connected to at least one of the bypass conduits (9a, 9b, 9c, 9d, 9e), the air solution mixture is obtainable in the outlet conduit (8) from the compressed air, the water and the additive solution.

2. The compressed air foam system of claim 1, wherein, the number of the bypass conduits (9a, 9b, 9c, 9d, 9e) is N and the hydraulic diameter of the Mth bypass conduit (9a, 9b, 9c, 9d, 9e) is greater than the hydraulic diameter of the M-1th bypass conduit (9a, 9b, 9c, 9d, 9e), where M is lower than or equal to N.

3. The compressed air foam system of claim 1, wherein, one bypass conduit (9e) has a hydraulic diameter equal to or greater than the diameter of the inlet conduit (7).

4. The compressed air foam system of claim 1, wherein, the outlet conduit (8) has a variable diameter between the bypass conduits (9a, 9b, 9c, 9d, 9e), wherein the diameter of the section of the outlet conduit (8) between the Mth conduit (9a, 9b, 9c, 9d, 9e) and the M-1th conduit (9a, 9b, 9c, 9d, 9e) is equal to the diameter of the M-1th conduit (9a, 9b, 9c, 9d, 9e), where N is the number of bypass conduits (9a, 9b, 9c, 9d, 9e) and M is a number lower than or equal to N.

5. The compressed air foam system of claim 1, wherein, the air management system (3) and the dosing module (4) are both fluidically connected to the same bypass conduit (9a).

6. The compressed air foam system of claim 1, wherein, the air management system (3) is fluidically connected downstream of the dosing module (4) according to the direction of the water flow.

7. The compressed air foam system of claim 1, wherein, at least one of the bypass conduits (9a, 9b, 9c, 9d, 9e) comprises valve means (10, 11) configured to regulate the passage of water towards the outlet conduit (8).

8. The compressed air foam system of claim 7, wherein, the valve means comprise check valves (10a, 10b, 10c) configured to allow the passage of fluid only from the inlet conduit (7) to the outlet conduit (8) only when the pressure of the water in the inlet conduit (7) exceeds a predetermined value.

9. The compressed air foam system of claim 8, wherein, the opening pressure of the check valves (10a, 10b, 10c) provided in the bypass conduits (9b, 9c, 9d) is different from one another.

10. The compressed air foam system of claim 7, wherein, The valve arrangement comprises a valve (11) configured to be actively controlled to allow or deny passage of fluid through one of the bypass conduits (9e).

11. A fire fighting vehicle comprising a compressed air foam system according to any one of claims 1 to 10.

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