APPARATUS AND METHOD FOR PRODUCING COMPRESSED AIR FOAM FOR FIRE FIGHTING AND FIRE FIGHTING APPARATUS

Abstract

The application relates to a method for producing compressed air foam for fire-fighting, wherein the method comprises the following steps: supplying a mixture of water and foaming agent via a supply line (12; 22) in a mixing chamber (11; 21) of a foaming line (10; 20), wherein a regulating device (14; 24) is disposed in the supply line (12; 22), by means of which a volume flow of the mixture can be regulated, suppling compressed air via a compressed air line (13; 23) in the mixing chamber (11; 21), wherein a further regulating device (15; 25) is disposed in the compressed air line (13; 23) by means of which a volume flow of the compressed air can be regulated, producing compressed air foam in the mixing chamber (11; 21) by foaming the mixture of water and foaming agent in the mixing chamber (11; 21) by means of the compressed air and discharging the compressed air foam from the foaming line (10; 20) via a mixing pressure regulator (17; 27) which regulates a mixing pressure in the mixing chamber (11; 21) into a delivery line (30; 40), wherein a pressure measuring device (31; 41) is disposed in the delivery line (30; 40), which records a pressure in the delivery line (30; 40) and which, like the regulating device (14; 24) and the further regulating device (15; 25), couples to the control device (26), and wherein the volume flow of the mixture of water and foaming agent and/or the volume flow of the compressed air is regulated by means of the control device (26) depending on the recorded pressure in the delivery line (30; 40). The application further relates to an apparatus for producing compressed air foam for fire-fighting.

Claims

1. A method for producing compressed air foam for fire-fighting, wherein the method comprises the following steps: supplying a mixture of water and foaming agent via a supply line in a mixing chamber of a foaming line, wherein a regulating device is disposed in the supply line, by means of which a volume flow of the mixture can be regulated, suppling compressed air via a compressed air line in the mixing chamber, wherein a further regulating device is disposed in the compressed air line by means of which a volume flow of the compressed air can be regulated, producing compressed air foam in the mixing chamber by foaming the mixture of water and foaming agent in the mixing chamber by means of the compressed air and discharging the compressed air foam from the foaming line via a mixing pressure regulator which regulates a mixing pressure in the mixing chamber into a delivery line, wherein a pressure measuring device is disposed in the delivery line, which records a pressure in the delivery line and which, like the regulating device and the further regulating device couples to the control device, and wherein the volume flow of the mixture of water and foaming agent and/or the volume flow of the compressed air is regulated by means of the control device depending on the recorded pressure in the delivery line.

2. The method according to claim 1, wherein the mixing pressure in the mixing chamber is regulated passively by means of the mixing pressure regulator.

3. The method according to claim 1, wherein the volume flow of the mixture of water and foaming agent is regulated discontinuously whereby graduated volume flows are set by means of the control device depending on the recorded pressure in the delivery line.

4. The method according to claim 1, wherein the volume flow of the compressed air is regulated discontinuously whereby graduated volume flows are set by means of the control device depending on the recorded pressure in the delivery line.

5. The method according to claim 1, wherein electronic data on various discontinuous regulating configurations for graduated volume flows of the mixture of water and foaming agent and/or compressed air are provided in the control device, wherein the various discontinuous regulating configurations are assigned to different configurations of the delivery line.

6. The method according to claim 1, wherein the mixing pressure regulator is designed with a pneumatically regulated mixing pressure regulator.

7. The method according to claim 6, wherein the compressed air regulated mixing pressure regulator is coupled to the compressed air line.

8. The method according to claim 1, wherein the pressure measuring device is disposed at an output of the mixing pressure regulator or adjacent thereto in the delivery line.

9. The method according to claim 1, wherein the control device, the pressure measuring device and the regulating devices in the supply line and the compressed air line are connected to a CAN bus system of a CAN network.

10. An apparatus for producing compressed air foam for fire-fighting comprising a foaming line which comprises a mixing chamber, wherein the mixing chamber is adapted to produce compressed air foam whereby a mixture of water and foaming agent is foamed in the mixing chamber by means of the compressed air, a supply line via which the mixture of water and foaming agent can be supplied to the mixing chamber, a compressed air line via which compressed air can be supplied to the mixing chamber, a regulating device which is disposed in the supply line and adapted to regulate a volume flow of the mixture, a further regulating device which is disposed in the compressed air line and adapted to regulate a volume flow of compressed air, a delivery line which adjoins a foaming line for discharging the compressed air foam via a mixing pressure regulator which can regulate a mixing pressure in the mixing chamber, a pressure measuring device which is disposed in the delivery line and is adapted to recorded a pressure in the delivery line and a control device which couples to the pressure measuring device and the regulating device and the further regulating device and is adapted to regulate the volume flow of the mixture of water and foaming agent and/or the volume flow of the compressed air depending on the recorded pressure in the delivery line.

11. A fire-fighting apparatus having an apparatus for producing compressed air foam according to claim 10, designed as a mobile or stationary fire-fighting apparatus.

Description

DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0024] Further exemplary embodiments are explained in detail hereinafter with reference to a FIGURE. The FIGURE shows a schematic view of an arrangement for an apparatus for producing compressed air foam for fire-fighting.

[0025] The design shown in the figure comprises two foaming lines 10, 20 which can be operated in parallel. Alternatively only one foaming line can be provided (not shown). A mixing chamber 11 is disposed in the foaming line 10. A further mixing chamber 21 is disposed in the further foaming line 20. A mixture containing water and at least one foaming agent is supplied to the mixing chambers 11, 21 via a supply line 12 and a further supply line 22. Compressed air is supplied in the mixing chamber 11 and the further mixing chamber 21 via a compressed air line 13 and a further compressed air line 23.

[0026] The volume flow of the mixture containing water and foaming agent can be regulated with the aid of a respective regulating device 14, 24 in the supply line 12, 22, for example by means of a regulating valve. For example, a volume regulating flow is provided. The volume flow of the compressed air can be regulated with the aid of a respective further regulating device 15, 25 in the compressed air line 13, 23. In each case one volume flow regulating valve can be provided.

[0027] The regulating device 14, 24 and the further regulating device 15, 25 each couple to a control device 26. The control device 26 in a respective delivery line 30, 40 which adjoins the foaming line 10, 20 via a respective mixing pressure regulator 17, 27 is connected to a respective pressure measuring device 31, 41. The pressure measuring device 31, 41 is adapted to record a pressure in the delivery line 30, 40 in each case. Depending on the measured pressure signals, the volume flows for the mixture comprising water and foaming agent and the compressed air are regulated with the aid of the control device 26. For this purpose corresponding control signals are applied to the regulating device 14, 24 and the further regulating device 15, 25.

[0028] The mixing pressure regulators 17, 27 which can be designed as mixing pressure valves, couple to the compressed air line 13, 23 via a respective pressure reducer 18, 28. Alternatively a mixing pressure regulator 17, 27, optionally incorporating pressure reducers, can be coupled to a compressed air braking system of a fire-fighting vehicle if the apparatus is disposed on such a vehicle.

[0029] The mixing pressure regulators 17, 27 can thus be set to a desired value by means of pneumatic regulation. If this desired value is exceeded so that a pressure higher than the desired value exists in the foaming line 10, 20, in particular in the mixing chamber 11, 21, the compressed air foam produced in the mixing chamber 11, 21 passes from the foaming line 10, 20 into the delivery line 30, 40. A desired mixing pressure in the respective mixing chamber 11, 21 is maintained with the aid of the mixing pressure regulator 17, 27.

[0030] The foam is produced in the mixing chamber 11, 21, for example at a mixing pressure, which is sometimes also designated as foam pressure, of 6 bar. At this pressure the introduced compressed air is still compressed. Nozzles at the delivery line 30, 40 can be dimensioned, for example, so that an input pressure of about 1.5 bar always prevails at the input of the nozzle. This pressure loss from 6 to 1.5 bar is not based exclusively on friction for the compressed air foam during transport in the delivery line 30, 40 but in particular on decompression.

[0031] For a usual hose line to a nozzle, the fire brigade can usually use hoses having a diameter of 42 mm in the delivery line 30, 40. This then results in a flow of 170 l/min (water fraction in the foam). For a single hose line to a foam generator this is completely unproblematical. However, if the extinguishing attack is made, for example in accordance with FwDv 3 (fire brigade service regulationthree units in extinguishing deployment), initially a hose having a diameter of 75 mm and then a distributor of 342 mm is used so that at the end of the delivery line 30, 40, optionally three nozzles must be serviced simultaneously. The 75 mm hose would be sufficient to transport the hose volume of 510 l/min (3170) so that the delivery could be adjusted to this flow. However it would only function as long as all three connected nozzles are open. If one of the three nozzles is closed, the flow of the two media, mixture and compressed air does not decrease uniformly but results in a pressure rise which in turn hinders the air injection so that the foam becomes very wet and no longer possesses the necessary extinguishing properties. If two of the three pipes are closed, the line pressure is so high that no more air can be injected. Here the proposed regulation of the volume flows enables reasonable operation.

[0032] The mixing pressure regulator 17, 27 ensures that the foam in the mixing chamber 11, 21 is always produced at the same pressure, for example 6 bar. This is important since one of the media is a compressed gas, namely compressed air, which has different volumes at different pressures. However, if the compressed foam flows through the mixing pressure regulator 17, 27 into the initially empty pipeline in the delivery line 30, 40, it decompresses abruptly since general ambient pressure prevails in the pipe. A slight increase in pressure only occurs here with time and depending on the conveying length and conveying height located therebehind, so that an initial pressure of 2.5 to 4.5 bar is established as long as the output opening (on the nozzle) has a sufficiently large cross-section in order to deliver the foam volume produced. If this is not the case, a pressure rise occurs at this point which lies above half the tolerance limits. This pressure is notified to the control device 26 by means of the pressure measuring devices 31, 41. The control device 26 actuates the regulating device 14, 24 and the further regulating device 15, 25. The regulation can be accomplished for example in steps of 170 l/min so that the flow of 510 l water would be initially reduced to 340 l. If the initial pressure again drops to the desired value, the setting remains but if it drops too far, the original value would be reproduced again since it can be assumed that the one nozzle was only closed briefly.

[0033] The features disclosed in the preceding description, the claims and the figure can therefore be important both individually and in any combination for implementing various aspects in their different embodiments.

REFERENCE LIST

[0034] 10 Foaming line

[0035] 11 Mixing chamber

[0036] 12 Supply line

[0037] 13 Compressed air line

[0038] 14, 24 Regulating device

[0039] 15, 25 Further regulating device

[0040] 17, 27 Mixing pressure regulator

[0041] 18, 28 Pressure reducer

[0042] 20 Further foaming line

[0043] 21 Further mixing chamber

[0044] 22 Further supply line

[0045] 23 Further compressed air line

[0046] 26 Control device

[0047] 30, 40 Delivery line

[0048] 31, 41 Pressure measuring device