JP7526263B2 - CAFS system with improved air management system - Google Patents

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
This patent application claims priority to Italian Patent Application No. 102019000023679, filed December 11, 2019, the entire disclosure of which is incorporated herein by reference.

The present invention relates to a fire extinguishing system for a firefighting vehicle or apparatus, in particular a compressed air foam fire extinguishing system (CAFS) with an improved air management system.

A firefighting system, e.g. a firefighting vehicle or apparatus, includes a fire suppression system configured to deliver a fire-extinguishing compound that is directed at the flame to cause the flame to be extinguished.

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 contains a foaming agent additive dissolved in a large amount of water, i.e., 0.5 to 3% or up to 8% by volume of the additive. In the mixing chamber module, compressed air is mixed with such a solution.

Such an air-solution mixture is discharged at a pressure higher than atmospheric pressure by the outlet of a pipe directed towards the flame, which, when it expands, forms a foam with flame-extinguishing properties. In particular, the air content of the foam can be adjusted to a value in which the volume fraction of air relative to the liquid solution is between 3 and 20. As specified in the DIN EN standard 16327, such an air/solution ratio comprised between 3 and 10 is defined as a "wet foam", whereas an air/solution ratio comprised between 11 and 20 is defined as a "dry foam".

As a result of the above, the main challenge associated with a CAFS system is to continuously measure the air and water flows that are mixed together to provide the desired air/solution ratio. Therefore, measurement of these two flows is critical.

While measuring water flow is fairly straightforward, measuring air flow between 3000 and 6000 litres/min is not as straightforward.

The first approach to measuring air flow is to use a conventional air flow meter. However, air flow meters are very sensitive to air concentrations because water and other particles carried by the air flow can adhere to the sensor and disturb the current measurement signal, thereby slightly or completely altering the measured air flow.

A solution to the above problem has been found in that an air dryer can be placed upstream of the compressor intended to provide the compressed air flow in order to condense the moisture present in the air sucked in by the compressor. However, due to the above-mentioned air flow values required, such air dryers have dimensions that make them unusable in mobile firefighting devices/vehicles.

Another known solution to measure the air flow is to use mass air flow sensors, well known in the engine field. Indeed, for normal operating fields the air flow velocity is so low that the air does not condense at the sensor due to the small pressure drop.

However, the airflow may vary continuously as the air/solution mixture flow may be continuously altered by the operator depending on the flame conditions. Such variations in airflow values may result in fluctuations in the mass airflow sensor, thereby introducing vibrations and noise into the system.

Another alternative solution would be to provide a valve configured to have a working range of 40-4800 liters/minute. However, such valves are extremely expensive to manufacture and are not common in the market.

Due to the above, the problem of measuring and ensuring proper compressed air flow for CAFS systems remains.

Therefore, there is a need to provide a CAFS system that can quickly and precisely adjust the air/solution mixture according to the user's needs.

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.

In order that the invention may be better understood, preferred embodiments will now be described, by way of non-limiting example, with reference to the accompanying drawings, in which:
1 is a schematic representation of the innovative part of a compressed air foam extinguishing system according to the present invention. 1 is a schematic representation of possible combinations for providing the elements of a compressed air foam fire extinguishing system according to the present invention. 1 is a schematic representation of a compressed air foam fire extinguishing system according to the present invention.

FIG. 1 discloses a compressed air foam fire suppression system or CAFS1 essentially comprising a compressor means 2, an air conditioning system 3, and a mixing chamber module 4. In particular, the compressor means 2 is fluidly connected in series with the air conditioning system 3 which is fluidly connected in series with the mixing chamber module 4.

More specifically, the compressor means 2 is configured to increase the pressure of air, e.g. atmospheric air, obtained from a suitable source 5 by an air filter between the inlet 2a and outlet 2b of the compressor means 2. As is known, the compressor means 2 can be of any topology depending on the power requirements of the CAFS 1.

From the opposite side of the air conditioning system 3, the mixing chamber module 4 generally and essentially comprises a first inlet 4a fluidly connected to the air conditioning system 3, a second inlet 4b of known topology fluidly connected to a source 6 of foam solution, and an output 4c fluidly connected to a fire extinguishing system 7 configured to allow the discharge of the foam mixed in the mixing chamber module 4. It is clear that such a fire extinguishing system 7 can be of any topology, for example a pipe with a dedicated nozzle at the end.

It is advantageous for the CAFS1 to be provided with a safety means 8 that is fluidly interposed between the compressor means 2 and the air conditioning system 3 and is configured to allow the discharge of compressed air when the pressure of the compressed air fed by the compressor means 2 to the air conditioning system 3 reaches a predetermined value.

Preferably, such safety means 8 comprises a pressure relief valve 9 fluidly connected downstream of the output 2b and upstream of the air conditioning system 3 and configured to open and allow the air conditioning system 3 to discharge when the pressure in the air conditioning system 3 reaches a threshold value, for example about 11 or 12 bar, the pressure of the compressed air being typically 10 bar.

The safety means also allows the pressure value provided by the compressor means 2 to the air conditioning system 3 to be maintained stable to avoid pressure peaks.

According to the present invention, the air conditioning system 3 comprises a plurality of dispensing modules 10 interposed in fluid parallel between the output 2b of the compression means 2 and the mixing chamber module 4, each dispensing module being configured to be controlled to allow the passage of air from the compression means 2 to the mixing chamber module 4, and each dispensing module being configured to allow the passage of a predetermined flow different from at least another dispensing module 10.

In the exemplary embodiment, seven different dispensing modules 10 are fluidly interposed in parallel between the compression means 2 and the mixing chamber module 4.

Each dispensing module 10 comprises a valve means 11 and a nozzle 12 in fluid series with each other, with the valve means 11 upstream of each nozzle 12 to allow or deny the passage of air from the compressor means 2 to the nozzle 12. Each nozzle 12 is in direct fluid connection to a mixing chamber module 4.

According to a further aspect of the invention, the first dispensing module 10 has a first base flow value and the other dispensing modules have various flow values that are at least N times the first base flow value, where N is preferably an integer. Preferably, the other dispensing modules each have a flow value that is twice that of the preceding module.

Thus, in the disclosed embodiment, the seven dispense modules 10 allow for flow rate adjustment with ²⁷ or 128 possible values for governing the flow rate at the input to the mixing chamber module 4 .

Preferably, the first dispensing module is sized to allow a flow rate of 50 liters/minute, the second 100 liters/minute, the third 200 liters/minute, the fourth 400 liters/minute, the fifth 800 liters/minute, the sixth 1600 liters/minute, and the seventh 3200 liters/minute, as described above.

Furthermore, according to DIN EN 16327 the solution flow should be comprised between 200 and 1600 liters/min, while the air flow should be at least three times higher, i.e. 600 to 4800. According to the proposed embodiment, the theoretical maximum is 6350 liters/min, so that the air range of 600-4800 liters/min can be easily provided.

The pressure relief valve 9 also maintains a constant pressure at the output of the compressor means 2, so that the flows of each dispensing module 10 join together to form the mixing chamber module 10, thereby providing the desired air flow rate, with accuracy set by the dispensing module with the lowest flow rate.

In fact, by opening more valve means 11 at the same time, the flows passing through the different nozzles 12 merge. According to the values given above, by adjusting the opening of the valve means 11, flows from 50, 100, 150 [. . . ] to 6250, 6300, 6350 [. . . ] can be provided.

In accordance with a further aspect of the invention, each nozzle 12 may be implemented by coupling together a certain number of low flow nozzles. Indeed, as shown in FIG. 2, where possible nozzle bore configurations are depicted, a 100 L/min nozzle may consist of two 50 L/min bores, and a 3200 L/min nozzle may consist of eight 400 L/min bores. Thus, the full range of possible flow rates may be easily achieved with as few as two bores, as shown diagrammatically.

The CAFS 1 further comprises a control unit 13 connected to the mixing chamber module extinguishing installation 7, to the water flow sensor and to each valve means 11. Such control unit 13 is configured to control the opening or closing of each valve means 11 according to signals emanating from the extinguishing installation 7 and/or the mixing chamber module 4.

It is advantageous if such control unit 13 is an electronic control unit and therefore the valve means 11 is an electrically operated valve and the aforementioned signals are signals provided by sensors configured to provide an estimate of a related quantity from the mixing chamber module 4 (i.e. the mixing chamber module, the water/solution flow provided in the mixing chamber module 4) and the extinguishing installation 7, e.g. the flow rate of the air-foam solution selected by the operator.

In practice, the control unit 13 is arranged so that the operator selects the desired air bubble solution, for example by pressing a button or by making a selection on a specific display, and considers the combination of valve means 11 that must be kept open or closed to achieve such value. In order to select the correct open/closed combination of valve means 11, it is therefore necessary that the control unit 13 stores or has access to a memory in which the values of the flow rate of each specific dispensing module of the air conditioning system 3 are stored. Preferably, each value of the desired air flow rate at the mixing chamber module 4 can be stored together with the associated open/closed combination of the valve means 11 concerned.

Figure 3 shows a more complete scheme of possible implementations of all the elements of CAFS1.

In particular, the compressor means 2 may comprise another compressor means 2' in parallel, configured to provide another compressed air flow, for example when such compressor means 2, 2' are small in size. It is clear that each compressor means 2, 2' may comprise a respective check valve 20, 20'.

The air conditioning system 3, in the illustrated case, comprises eight dispensing modules 10, each with a valve 11 and nozzle 12 as described in detail above. As noted above, the air conditioning system is configured to provide an air flow rate of 50 to 3000 (and optionally up to 6000 or more).

The air conditioning system 3 is then fluidly connected to the mixing chamber module 4 with an associated check valve 21 and connected to the safety means 8 as described above, and may further comprise a pressure sensor means 26.

In particular, the water supply to the mixing chamber module 4 is provided from a vehicle water supply line 22 fed by an associated pump 23 configured to increase the pressure of water taken from a source, for example a tank carried on the vehicle.

In the conduit fluidly connecting the water supply line 22 and the mixing chamber module 4, the CAFS 1 may further comprise an optional suppression stage 24, known per se and therefore not described in detail, configured to suppress the supply of water to the mixing chamber module 4 when such water is required for other priority operable uses by the vehicle.

Furthermore, at all times in the conduit fluidly connecting the water supply line 22 and the mixing chamber module 4, the CAFS 1 comprises a water flow meter means 25 configured to measure the water flow rate to the mixing chamber module 4. In particular, the water flow meter means 25 can measure a water flow rate between, for example, 0 and 3000 liters/min.

Optionally, upstream and downstream of the suppression stage 3, the CAFS 1 may also include pressure sensor means 26 configured to detect water pressure from the mixing chamber module 24.

The CAFS 1 further comprises an additive dispensing module 27 configured to provide a measured amount of additive to the mixing chamber module 4. In particular, and by way of example, the additive dispensing module 27 comprises an additive container 28 into which the additive is pumped by a pump 29 to the mixing chamber module 4. In a conduit fluidly connecting the pump 29 to the mixing chamber module 4, the additive dispensing module 27 comprises a safety means 8, preferably comprising a relief valve 9, for maintaining the pressure below a preset threshold, e.g. 16 bar.

The additive dispensing module 27 is further provided in a conduit fluidly connecting the pump 29 and the mixing chamber module 4, and the CAFS 1 includes an additive flow meter means 30 configured to measure the flow rate of the additive from the mixing chamber module 4. In particular, the additive flow meter means 25 is capable of measuring water flow rates between 0 and 30-60 liters/min.

Thus, in the proposed embodiment, the mixing chamber module 4 is configured to mix the water, additive and airflow together to provide an air/solution mixture to the fire extinguishing device 7.

The mixing chamber module 4 therefore comprises a first mixer 31 configured to mix together a water flow and an additive flow, and a second mixer 32 downstream of the first mixer 31 configured to mix together a water-additive solution and an air flow to generate a solution-air mixture that is discharged by the fire suppression device 7. The water flow meter 25, the additive flow meter 25, and a pressure sensor 26, if present, are all electrically connected to the electronic control unit so that the proper air flow is seen in the mixing chamber 4.

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

The operator of the fire extinguishing device 7 selects a particular value for the air bubble flow rate. Accordingly, a particular signal (calculated by the electronic control unit as described above) is provided to the control unit 13 which considers/selects the appropriate opening/closing combination of the valve means 11.

For example, based on the exemplary values above, if an operator requires an air flow of 1350 to the mixing chamber module, the valve means of the first, second, fourth and fifth dispensing modules 10 will allow fluid to pass to provide the proper air flow value.

The control of the water and additive flows is known per se and therefore will not be described in detail. Again, the electronic control unit 13 controls the resulting flow of water and solution to the mixing chamber module 4, after the operator has confirmed the required air-solution mixture flow and its properties.

In accordance with the above, the present invention further comprises:
Obtaining data relating to the airflow required by the mixing chamber module 4 of the CAFS 1;
- selecting a specific combination of valve means 11 opening at least one dispense module 10 that matches the required air flow rate in the mixing chamber module 4;
- actuating the valve means 11 of at least one of said dispensing modules 10 selected in the preceding paragraph;
The present invention relates to a method for providing a predetermined air flow rate to a mixing chamber module 4 of a CAFS system, comprising:

Advantageously, the above-mentioned method is stored and executed by the review means of the electronic control unit 13 described above.

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

The proposed control is stable, robust, precise and can be implemented in an economical manner. Indeed, the pressure difference is maintained constant at the nozzle 12 opening, so its flow rate is easily determined and is not affected by dirty particles and water condensation. Furthermore, the nozzle does not have the vibration/noise problems of prior art systems and can be stored in a very small space. As an example, a 400 liter/min nozzle has a diameter of only 2-3 mm.

Furthermore, the wear of such nozzles can be checked with cost-effective means such as feeler gauges and therefore their accuracy can be checked in time. Furthermore, because simple mechanical elements are used, the CAFS1 is particularly robust and can be used in a wide variety of atmospheric conditions.

The system is very easy to use, i.e. no complex electronic controls are required, so even untrained personnel can use the proposed CAFS1 fire extinguishing equipment base.

In particular, the use of a 2x2 nozzle system with a substantially binary system can be controlled by very simple software, for example by a stored table that defines the binary sums between the nozzles.

Furthermore, the proposed CAFS1 is instantaneous, thus overcoming the delays of slow-speed control systems (to avoid vibrations).

The pressure relief valve 9 provides a specified inlet pressure upstream of the nozzle 11 in a simple and robust manner.

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

Firstly, the possible combinations of injection modules 10 described above are particularly advantageous due to their economical manufacture. However, it is clear that a possible number of different injection modules 10 can be provided, covering different minimum flow values and different flow distributions therebetween. Indeed, such properties can be customized according to the specific use of the fire extinguishing installation 7.

As already mentioned, the valve means 11, compressor means 2 and extinguishing equipment 7 may vary depending on the topology of the fire fighting apparatus/vehicle.

Furthermore, it is possible, even if less economical, to provide hydraulic or pneumatic control of the valve means 11 according to the claimed invention.

1. Compressed Air Foam Fire Extinguishing System (CAFS)
2, 2' Compressor means 2a Input 2b Output 3 Air conditioning system 4 Mixing chamber module 4a First inlet 4b Second inlet 4c Outlet 5 Supply source 6 Supply source 7 Fire extinguishing system 8, 8' Safety means 9 Pressure relief valve 10 Dispensing module 11 Valve means 12 Nozzle arrangement 13 Control unit 20, 20', 21 Check valve 22 Vehicle water supply line 23 Pump 24 Suppression stage 25 Water flow meter means 26 Pressure sensor means 27 Additive dispensing module 28 Additive container 29 Pump 30 Additive flow meter means 31 First mixer 32 Second mixer

Claims (13)

A compressed air foam fire extinguishing system or CAFS (1) comprising compressor means (2) for increasing air pressure between an input (2a) and an output (2b), a source (6) of water-additive solution , and a mixing chamber module (4) configured to provide an air-solution mixture comprising pressurized air and said water-additive solution,
the mixing chamber is further fluidly connectable to a fire extinguishing system (7), and further comprising an air conditioning system (3) fluidly interposed in series between the output (2b) of the compressor means (2) and the mixing chamber module (4), the air conditioning system (3) comprising a plurality of dispensing modules (10) fluidly interposed in parallel with one another between the output (2b) of the compressor means (2) and the mixing chamber module (4), each dispensing module (10) configured to selectively allow passage of a predetermined compressed air flow to the mixing chamber module, the plurality of dispensing modules (10) being dimensioned such that the predetermined flow of one dispensing module (10) is different from the predetermined flow of the other dispensing modules (10) ;
each dispensing module (10) comprises a valve means (11) and a nozzle arrangement (12), said valve means (11) being arranged in series upstream of said nozzle arrangement (12) and configured to allow or deny the passage of fluid from said compressor means (2) to said nozzle arrangement (12), said nozzle arrangement (12) being dimensioned to allow the passage of a preset air flow at a predefined pressure;
a control unit (13) configured to be connected to the fire extinguishing system (7) and to each valve means (11), the control unit (13) being configured to control the opening or closing of each valve means (11) in response to a signal issued from the fire extinguishing system (7) and/or from the mixing chamber module (4).
Compressed air foam fire extinguishing system. 2. The system of claim 1 , wherein the predetermined flow of the other dispense module (10) is N times the flow of the one dispense module (10). The system of claim 1, wherein the number of dispensing modules is N, the predetermined flow of the (N)th dispensing module (10) is twice the predetermined flow of one (N-1)th dispensing module (10), and N is an integer. The system of claim 1, further comprising a safety means (8) fluidly interposed between the output (2b) of the compressor means (2) and the air conditioning system (3), the safety means (8) being configured to discharge compressed air when a pressure between the output (2b) and the air conditioning system (3) reaches a predetermined value. 5. A system as claimed in claim 4 , wherein said safety means (8) comprises a pressure relief valve (9). 2. The system of claim 1 , wherein said control unit (13) is an electronic control unit and said valve means (11) is an electrically operated valve means. 2. The system of claim 1 , wherein the nozzle arrangement (12) is embodied by a single nozzle having a predefined flow size or by a plurality of said nozzles having predefined flow sizes coupled together in parallel. The system according to claim 1, wherein the dispensing modules (10) are seven modules: a first dispensing module selectively allowing an air flow of 50 liters/minute to pass, a second dispensing module selectively allowing an air flow of 100 liters/minute to pass, a third dispensing module selectively allowing an air flow of 200 liters/minute to pass, a fourth dispensing module selectively allowing an air flow of 400 liters/minute to pass, a fifth dispensing module selectively allowing an air flow of 800 liters/minute to pass, a sixth dispensing module selectively allowing an air flow of 1600 liters/minute to pass, and a seventh dispensing module selectively allowing an air flow of 3200 liters/minute to pass. The system of claim 1, wherein the mixing chamber module (4) comprises a first mixer (31) for providing a mixture of the pressurized air and the water-additive solution, and a second mixer (32) downstream of the first mixer (31) for mixing the mixture with the compressed air flow. The system of claim 1, wherein the compressor means (2) comprises a plurality of compressors (2) in parallel with each other. A firefighting system comprising a system according to any one of claims 1 to 10 . A fire engine comprising a system according to any one of claims 1 to 11 . 7. A method for providing a predetermined air flow rate to a mixing chamber module (4) of a compressed air foam fire extinguishing system or CAFS system according to claim 6 , comprising the steps of:
- obtaining data relating to the air flow rate required in the mixing chamber module (4) of the system (1);
- selecting a specific combination of valve means (11) for opening at least one dispensing module (10) that matches the required air flow rate in said mixing chamber module (4);
- actuating the valve means 11 of at least one relevant dispensing module (10) selected in the preceding paragraph;
The method includes:

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