JP7703684B2 - Compressed air foam fire extinguishing system with improved mixing system - Google Patents

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
This patent application claims priority to Italian Patent Application No. 102021000010364, filed April 23, 2021, the entire disclosure of which is incorporated herein by reference.

(Technical field of the invention)
The present invention relates to a fire suppression system for a fire engine or apparatus, and in particular to a compressed air foam fire suppression system (CAFS) with an improved mixing system.

A firefighting system, such as a firefighting vehicle or apparatus, includes a fire extinguishing system configured to deliver a fire extinguishing compound that is directed at the fire to suppress the fire.

In particular, compressed air foam fire suppression systems (CAFS) are widely known in the art and involve the use of a mixture of compressed air and a water/foam solution in preset proportions.

More specifically, the water/foaming agent solution includes a foaming agent additive dissolved in a large volume of water, i.e., 0.5% to 3% or 0.5% to 8% by volume of the additive. Compressed air is mixed with such solution in a mixing chamber module.

Such an air-solution mixture is at a pressure higher than atmospheric pressure and is released by the outlet of the tube directed towards the fire, which, when expanding, forms a foam having fire-extinguishing properties. In particular, the air content of the foam can be adjusted to a value consisting of 3 to 20 parts by volume of air relative to the liquid solution. As specified in the standard DIN EN 16327, an air/solution ratio consisting of between 3 and 10 is defined as a "wet foam", while an air/solution ratio consisting of between 11 and 20 is defined as a "dry foam".

In accordance with the above, one problem associated with CAFS systems is ensuring accurate mixing between the water and the water/foam solution to provide a proper air/solution mixture.

However, the air and water flows or the air/solution mixture may be continuously altered by the operator in response to fire conditions, resulting in continuous changes in air and water flows. Such variations in water flow may lead to insufficient mixing between the water, air and foaming agent.

In practice, the water is generally regulated by a butterfly valve that is usually closed when the compressed air foam system is activated, which does not provide a water flow with a good velocity to ensure a proper mix between the water, foam and air. This drawback is especially evident when low water flows are required.

Therefore, a need is felt to provide a CAFS system that can provide good mixing between water, foaming agent and air as per the needs of the user.

The object of the present invention is to meet the above-mentioned needs in a cost-effective and optimal manner.

The above objectives are achieved by the compressed air foam fire extinguishing system described in the accompanying set of claims.

For a better understanding of the invention, preferred embodiments are described below, by way of non-limiting example, with reference to the accompanying drawings, in which:
FIG. 1 shows a schematic representation of a compressed air foam fire extinguishing system with a mixing module according to the present invention.

Figure 1 discloses a general schematic representation of a compressed air foam fire extinguishing system CAFS1 for a fire fighting installation, e.g. a vehicle, not shown. CAFS1 essentially comprises a water source 2, an air management system 3, a solution metering system 4 and a mixing chamber 5. The mixing chamber 5 is configured to receive water from the source 2, a defined controlled air flow from the air management system 3 and an additive, e.g. a foaming agent, from the solution metering system 4, mix these elements together and provide a suitable flow of air/solution mixture for fire fighting to an outlet device 6 which may be connected to a pipe for use by a firefighter.

The air management system 3 may be embodied in a variety of ways, for example by the system described in International Patent Application No. PCT/IB2020/061830, and therefore, for the sake of brevity, will not be described further herein.

The solution metering system 4 may also be embodied in a variety of known manners. Both the solution metering system 4 and the air management system 3 are configured to provide pressurized fluid flows of foam solution and compressed air, respectively, to the mixing chamber 5.

The water source 2 can take a variety of forms, such as a water pump or a fire hydrant, as are well known in the art.

Preferably, the mixing chamber 5 defines a first inlet 5a fluidly connected to the source 2, a second inlet 5b fluidly connected to the output 4a of the metering system 4, a third inlet 5c fluidly connected to the output 3a of the air management system 3, and an outlet 5d fluidly connected to the outlet device 6.

According to the described embodiment, the mixing chamber 5 comprises an inlet conduit 7, an outlet conduit 8, and a number of bypass conduits 9a, 9b, 9c, 9d arranged in parallel fluid between the inlet conduit 7 and the outlet conduit 8.

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

The inlet conduit 7 is fluidly connected on 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 fluidly connected on one side to the outlet device 8 and to the bypass conduits 9a, 9b, 9c, 9d, 9e upstream of the outlet device 6.

In more detail, the fifth bypass conduit is downstream of the supply source 2 only, the fourth bypass conduit 9d is upstream of the fifth bypass conduit, the third bypass conduit 9c is upstream of the fourth bypass conduit 9d, the second bypass conduit 9b is upstream of the third bypass conduit 9c, and the first bypass conduit 9a is upstream of the second bypass conduit 9b. In other words, from the perspective of the outflow device 6, the fifth bypass conduit is upstream of the outflow device 6 only, the fourth bypass conduit 9d is upstream of the fifth bypass conduit, the third bypass conduit 9c is upstream of the fourth bypass conduit 9d, the second bypass conduit 9b is upstream of the third bypass conduit 9c, and the first bypass conduit 9a is upstream of the second bypass conduit 9b.

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

It is advantageous if 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 less than the hydraulic diameter of the (M+1)th bypass conduit (9a, 9b, 9c, 9d, 9e), where N and M are integers and M is less than N.

According to this embodiment, the fifth conduit 9e has a smaller hydraulic diameter than the fourth conduit 9d, the third conduit 9c has a smaller hydraulic diameter than the fourth conduit 9d, the second conduit 9b has a smaller hydraulic diameter than the third conduit 9c, and the first conduit 9a has a smaller hydraulic diameter than the second conduit 9b. Preferably, the inflow and outflow conduits 7 have a hydraulic diameter substantially the same as or larger than the fifth conduit 9e.

More preferably, the outflow conduit 8 has a variable diameter between conduits 9a and 9e. In particular, the section of the outflow conduit 8 between the (M)th conduit and the (M+1)th conduit has substantially the same diameter as the (M)th conduit.

Thus, the section of the outflow conduit 8 between conduits 9a and 9b has substantially the same diameter as conduit 9a. The section of the outflow conduit 8 between conduits 9b and 9c has substantially the same diameter as conduit 9b. The section of the outflow conduit 8 between conduits 9c and 9d has substantially the same diameter as conduit 9c. The section of the outflow conduit 8 between conduits 9d and 9e has substantially the same diameter as conduit 9d. And the final section of the outflow conduit 8 has the same diameter as conduit 9e, i.e. the same diameter as the input conduit 7.

Advantageously, at least some of the bypass conduits 9a, 9b, 9c, 9d, 9e are provided with valve means 10 arranged to allow the passage of fluid only in the respective bypass conduit from the inlet conduit 7 to the outlet conduit 8. In particular, such valve means are provided with various pressure controlled openings to allow the flow of water into the respective bypass conduit depending on the water pressure in the inlet conduit 7.

In particular, in the disclosed example, the first bypass conduit 9a, i.e. the bypass conduit that is directly fluidly connected to the air management system 3 and the metering module 4, is free. "Free" means that it always allows the passage of fluid from the inlet conduit 7 to the outlet conduit 8. In other words, the first bypass conduit 9a is not provided with the valve means mentioned above.

The other bypass conduits 9b, 9c, 9d with check valves 10 are advantageously provided with various opening pressures, i.e., each check valve 10 has dimensions that allow fluid passage at various pressure levels.

In particular, the check valve 10b in the third bypass conduit 9c has a lower opening pressure level than the check valve 10c in the fourth bypass conduit 9d, and the check valve 10a in the second bypass conduit 9b has a lower opening pressure level than the check valve 10b in the third bypass conduit 9c.

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

In particular, the fifth bypass conduit 9e includes an electrically actuated valve 11, such as an on-off valve, configured to permit or deny passage of fluid from the inlet conduit 7 to the outlet conduit 8.

The operation of CAFS1 according to the present invention as described above is as follows.

Generally, water provided by the source 2 flows into the inlet conduit 7 and then into the first bypass conduit 9a. Such conduit, which has the smallest hydraulic diameter, increases the velocity of the water that is mixed first with the foaming agent coming from the opening 4a and then with the compressed air coming from the opening 3a. It then proceeds to the outlet conduit, which has a larger diameter and allows good mixing of the high-velocity water premixed with the foaming agent and the compressed air. The mixed solution then flows to the outlet device 6.

If the water pressure increases, the check valve 10a of the second bypass spring opens, allowing the water to pass directly to the outlet conduit 8 downstream of the second bypass conduit 9b, thus further mixing the solution before proceeding to the outlet device 6. The same happens if a further increase in water pressure allows the check valves 10b, 10c of the third and fourth bypass conduits 9c, 9d to open.

When the user requires only water, and not foam solution and air, valve 11 is controlled to open, thereby allowing the water flow mainly in fifth bypass conduit 9e to pass directly to output device 6. In fact, only a small amount of water flows through conduits 7, 9a, 8 to be mixed again in output conduit 8. However, due to the diameter difference, the main part of the water passes directly through conduit 9e.

Considering the above, the advantages of the compressed air foam fire extinguishing system CAFS1 according to the present invention are clear.

Thanks to the proposed mixing module it is possible to mix water with foam solution and air in a very effective manner, avoiding a poor quality foam solution in the outflow device.

What's more, the mixed module is particularly compact and cost-effective.

Furthermore, the mixing module operates over a very wide range of water pressures to produce the same quality foam mix.

In addition, by varying the number of bypass conduits, it is possible to vary the hydraulic range. Thus, the proposed mixing module is versatile and offers economies of scale in production.

In particular, the versatility of the proposed mixing system is evident. In fact, the mixing system can be used to provide an air-free foam solution, an air-foam solution or simply water to the output device. Thus, in comparison with known systems, the mixing system provides all functions via a single module.

It is clear that modifications may be made to the compressed air foam fire extinguishing system CAFS1 described in this application that do not go beyond the scope of protection defined in the claims.

By way of example, the number of bypass conduits may vary. Similarly, the valve means 10, 11 may be replaced by valves of various configurations having the same opening characteristics.

1. Compressed Air Foam Fire Extinguishing System (CAFS)
2 Supply source 3 Air management system 3a Output 4 Solution metering system 4a Output 5 Mixing chamber 5a First inlet 5b Second inlet 5c Third inlet 5d Outlet 6 Outlet device 7 Inlet conduit 8 Outlet conduit 9a, 9b, 9c, 9d, 9e Bypass conduit 10a, 10b, 10c Check valve 11 Valve means

Claims (8)

1. A compressed air foam fire extinguishing system (CAFS) (1) comprising a source of water (2), an air management system (3) providing a compressed air flow, a solution metering module (4) 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) 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 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 the others;
said air management system (3) and said solution metering module (4) are fluidly connected to at least one of said bypass conduits (9a, 9b, 9c, 9d, 9e);
said air-solution mixture being obtained by said compressed air stream , said water and said additive solution in said outlet conduit (8) ;
at least one of said bypass conduits (9a, 9b, 9c, 9d, 9e) is provided with a valve means (10, 11) configured to regulate the passage of said water to said outlet conduit (8);
said valve means comprising check valves (10a, 10b, 10c) configured to only allow passage of fluid from said inlet conduit (7) to said outlet conduit (8) only when the water pressure in said inlet conduit (7) exceeds a predetermined value;
Among the check valves (10a, 10b, 10c) provided in the bypass conduit (9b, 9c, 9d), an opening pressure of one of the check valves (10a) is lower than an opening pressure of the other check valves (10b, 10c);
Compressed air foam fire extinguishing system. The compressed air foam fire extinguishing system of claim 1, wherein the number of bypass conduits (9a, 9b, 9c, 9d, 9e) is N, the hydraulic diameter of the (M)th bypass conduit (9a, 9b, 9c, 9d, 9e) is greater than the hydraulic diameter of the (M-1)th bypass conduit (9a, 9b, 9c, 9d, 9e), and M is less than or equal to N. The compressed air foam extinguishing 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). The compressed air foam fire extinguishing system of claim 1, wherein the outlet conduit (8) has a variable diameter between the bypass conduits (9a, 9b, 9c, 9d, 9e), and the diameter of the section of the outlet conduit (8) between the (M)th bypass conduit (9a, 9b, 9c, 9d, 9e) and the (M-1)th bypass conduit (9a, 9b, 9c, 9d, 9e) is equal to the diameter of the (M-1)th bypass conduit (9a, 9b, 9c, 9d, 9e), where N is the number of bypass conduits (9a, 9b, 9c, 9d, 9e) and M is less than or equal to N. 2. The compressed air foam fire extinguishing system of claim 1, wherein both the air management system (3) and the solution metering module (4) are fluidly connected to the same bypass conduit (9a). 2. The compressed air foam extinguishing system of claim 1, wherein the air management system (3) is fluidly connected downstream of the solution metering module (4) in the water flow direction. 7. A compressed air foam fire extinguishing system as claimed in any one of claims 1 to 6 , wherein the valve means comprises a valve (11) configured to be actively controlled to allow or deny the passage of fluid in one of the bypass conduits (9e). A fire vehicle comprising the compressed air foam fire extinguishing system according to any one of claims 1 to 7 .

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