Two-component positive pressure foaming device for foam extinguishing agent

Abstract

The invention relates to the technical field of fire safety, in particular to a foam extinguishing agent bi-component positive pressure foaming device which comprises a gas power module used for supplying gas, and the gas power module communicates with a gas-liquid control module used for controlling gas-liquid supply. The gas-liquid control module is communicated with a gas-liquid mixing and foaming module for mixing and foaming gas and liquid and a liquid power module for supplying liquid through a first three-way valve; the liquid power module comprises a first peristaltic pump and a second peristaltic pump, the first three-way valve is communicated with the first peristaltic pump and the second peristaltic pump through the second three-way valve, and the first peristaltic pump and the second peristaltic pump are electrically connected with the gas-liquid control module. The foaming agent not only can be used for foaming synergistic fire extinguishing foam liquid, but also can be used for foaming non-premixed gel foam; foam performance tests such as drainage time, stability, foaming times, fire extinguishing efficiency and burning resistance in a laboratory can be met; the fire extinguishing agent consumption is low, and the method can be used for small-scale testing in a laboratory.

Description

Technical Field

[0001] The invention relates to the technical field of fire safety, in particular to a two-component positive pressure foaming device for a foam fire extinguishing agent. Background Art

[0002] Foam is currently the main means of extinguishing oil fires. Foam can spread and cover the oil surface. On the one hand, it can cool the surface of the burning fuel. On the other hand, the covering effect on the fuel surface can block the fuel vapor to a certain extent and isolate the fuel from oxygen. With the ban of key components such as fluorocarbon surfactants in aqueous film-forming foam fire extinguishing agents due to environmental pollution, the research and development of new foam fire extinguishing agents has become an urgent need. The evaluation of foam performance plays an important role in the research and development of foam fire extinguishing agents. Therefore, convenient and stable foam generating devices are of great significance for the research and development of fire extinguishing agents. At present, most of the existing foam generating devices are large in scale and consume a large amount of raw materials (usually more than 20L), which is difficult to carry out in the laboratory; although the double syringe method consumes a small amount of foam liquid (usually 5-10ml), the amount of foam generated is also small (usually 20-50ml), and the gap between the test and the actual application scenario is large; in addition, the existing foam generating device can only mix a single foam liquid with air to foam, which is not applicable to the foam liquid or gel foam for two-component synergistic fire extinguishing.

[0003] Therefore, there is an urgent need for a two-component positive-pressure foaming device for foam fire extinguishing agents that can be used for the small-scale, precise, and automated preparation of multi-component fire-fighting foams and gel foams; and effectively improve the testing efficiency of fire-fighting foams and gel foams in the laboratory and the controllability of subsequent tests. Summary of the invention

[0004] The purpose of the present invention is to provide a foam fire extinguishing agent two-component positive pressure foaming device to solve the problems existing in the above-mentioned prior art.

[0005] To achieve the above-mentioned purpose, the present invention provides the following scheme: a two-component positive-pressure foaming device for a foam fire extinguishing agent, comprising a gas power module for supplying gas, the gas power module being connected to a gas-liquid control module for controlling the supply of gas and liquid, the gas-liquid control module being connected to a gas-liquid mixed foaming module for mixing and foaming gas and liquid and a liquid power module for liquid supply through a first three-way valve; the liquid power module comprising a first peristaltic pump and a second peristaltic pump, the first three-way valve being connected to the first peristaltic pump and the second peristaltic pump through a second three-way valve, and the first peristaltic pump and the second peristaltic pump being electrically connected to the gas-liquid control module.

[0006] Preferably, the gas power module comprises an air compressor, and the air outlet connecting pipe of the air compressor is provided with a first pipeline.

[0007] Preferably, the gas-liquid control module includes a pressure gauge, one end of the pressure gauge is connected to the first pipeline, the other end of the pressure gauge is connected to a gas mass flow meter, the end of the gas mass flow meter away from the pressure gauge is connected to an electromagnetic switch, and the end of the electromagnetic switch away from the gas mass flow meter is connected to the first three-way valve through a second pipeline.

[0008] Preferably, a check valve is installed on the second pipeline.

[0009] Preferably, the gas-liquid control module further includes a controller electrically connected to the electromagnetic switch, the pressure gauge, and the gas mass flow meter, and the controller is electrically connected to the first peristaltic pump and the second peristaltic pump.

[0010] Preferably, the gas-liquid mixed foaming module comprises a rectifying cavity, and the rectifying cavity is filled with a plurality of glass beads.

[0011] Preferably, the water inlet pipe of the rectification chamber is connected to the first three-way valve.

[0012] Preferably, the water outlet pipe of the first peristaltic pump is connected to the second three-way valve, and the water inlet pipe of the first peristaltic pump is connected to the first container.

[0013] Preferably, the water outlet pipe of the second peristaltic pump is connected to the second three-way valve, and the water inlet pipe of the second peristaltic pump is connected to the second container.

[0014] Preferably, a first damper is installed on the water outlet pipe of the first peristaltic pump, and a second damper is installed on the water outlet pipe of the second peristaltic pump.

[0015] The present invention discloses the following technical effects:

[0016] The present invention can be used not only for the foaming of synergistic fire-extinguishing foam liquid, but also for the foaming of non-premixed gel foam; it can make the foam liquid consumption less than 2L, and the foam production volume adjustable between 1-9L; it can meet the foam performance test requirements such as liquid analysis time, stability, foaming multiple, fire extinguishing efficiency and anti-burning performance in the laboratory; and it can accurately adjust the gas-liquid ratio through the gas-liquid control module to produce foams with different foaming multiples.

[0017] The foam fire extinguishing agent two-component positive pressure foaming device of the present invention is flexible and convenient, not only consumes less fire extinguishing agent, but can also be effectively used for small-scale tests in laboratories. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0020] Among them, 1. air compressor; 2. rectifier chamber; 3. glass beads; 4. first three-way valve; 5. check valve; 6. electromagnetic switch; 7. pressure gauge; 8. gas mass flow meter; 9. first damper; 10. first peristaltic pump; 11. first container; 12. second peristaltic pump; 13. second container; 14. second damper; 15. second three-way valve. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] Reference Figure 1 The present invention provides a two-component positive-pressure foaming device for a foam fire extinguishing agent, comprising a gas power module for supplying gas, the gas power module being connected to a gas-liquid control module for controlling the supply of gas and liquid, the gas-liquid control module being connected to a gas-liquid mixed foaming module for mixing and foaming gas and liquid and a liquid power module for supplying liquid through a first three-way valve 4; the liquid power module comprising a first peristaltic pump 10 and a second peristaltic pump 12, the first three-way valve 4 being connected to the first peristaltic pump 10 and the second peristaltic pump 12 through a second three-way valve 15, the first peristaltic pump 10 and the second peristaltic pump 12 being electrically connected to the gas-liquid control module.

[0024] The flow rates of the first peristaltic pump 10 and the second peristaltic pump 12 are between 0 and 2 L / min.

[0025] The present invention can be used not only for the foaming of synergistic fire-extinguishing foam liquid, but also for the foaming of non-premixed gel foam; it can make the foam liquid consumption less than 2L, and the foam production volume adjustable between 1-9L; it can meet the foam performance test requirements such as liquid analysis time, stability, foaming multiple, fire extinguishing efficiency and anti-burning performance in the laboratory; and it can accurately adjust the gas-liquid ratio through the gas-liquid control module to produce foams with different foaming multiples.

[0026] The foam fire extinguishing agent two-component positive pressure foaming device of the present invention is flexible and convenient, not only consumes less fire extinguishing agent, but can also be effectively used for small-scale tests in laboratories.

[0027] According to a further optimized solution, the gas power module includes an air compressor 1, and a first pipeline is connected to the air outlet of the air compressor 1. The compressed gas is sent into the first pipeline through the air compressor 1.

[0028] The air compressor 1 can also be replaced by a gas cylinder, which may contain compressed air, compressed nitrogen, carbon dioxide, etc.

[0029] To further optimize the solution, the gas-liquid control module includes a pressure gauge 7, one end of the pressure gauge 7 is connected to the first pipeline, the other end of the pressure gauge 7 is connected to a gas mass flow meter 8, the end of the gas mass flow meter 8 away from the pressure gauge 7 is connected to an electromagnetic switch 6, and the end of the electromagnetic switch 6 away from the gas mass flow meter 8 is connected to the first three-way valve 4 through a second pipeline.

[0030] To further optimize the solution, a check valve 5 is installed on the second pipeline to prevent the liquid from flowing back to the electromagnetic switch 6.

[0031] In a further optimized solution, the gas-liquid control module further includes a controller electrically connected to the electromagnetic switch 6, the pressure gauge 7, and the gas mass flow meter 8, and the controller is electrically connected to the first peristaltic pump 10 and the second peristaltic pump 12. The electromagnetic switch 6, the pressure gauge 7, the gas mass flow meter 8, the first peristaltic pump 10, and the second peristaltic pump 12 are controlled by the controller.

[0032] The gas mass flow meter 8 is an instrument for measuring gas flow, and its working principle is based on the principle of heat diffusion. The sensor consists of two reference-level thermal resistors (RTDs): one is the velocity sensor RH, and the other is the temperature sensor RMG that measures the temperature change of the gas. When these two RTDs are placed in the measured gas, the sensor RH is heated, and the other sensor RMG is used to sense the temperature of the measured gas. As the gas flow rate increases, the airflow takes away more heat, and the temperature of the sensor RH decreases.

[0033] The controller is a main command device that can change the wiring of the main circuit or control circuit and the resistance value in the circuit in a predetermined order to control the start, speed regulation, braking and reverse of the motor. It manages and regulates various equipment or processes in the system.

[0034] Classification of controllers:

[0035] Classification by control method:

[0036] Open-loop controller: There is no feedback link, and the output is controlled according to a pre-set program or instruction without considering the actual effect of the output. For example, a simple timed irrigation system opens and closes the irrigation valve according to the set time without considering the actual moisture content of the soil.

[0037] Closed-loop controller: There is a feedback loop and it can make adjustments based on the difference between the actual output and the set target. For example, a temperature control system can keep the temperature stable within the set range by continuously detecting the temperature and adjusting the heating or cooling equipment.

[0038] Classification by application field:

[0039] Industrial controller: widely used in the field of industrial automation. Programmable logic controller (PLC) is a typical industrial controller that can be programmed to control various equipment (such as motors, valves, conveyor belts, etc.) in the industrial production process. For example, in an automobile manufacturing production line, PLC can control the movement of robots, the start and stop of welding equipment, etc.

[0040] Process controller: used to control continuous processes, such as chemical and pharmaceutical industries. In chemical production, process controllers can accurately control the temperature, pressure, liquid level and other parameters of the reactor to ensure that the chemical reaction proceeds according to the predetermined conditions.

[0041] Motion controller: Mainly used to control mechanical motion, such as CNC machine tools, robots and other equipment. Motion controllers can accurately control the speed, torque and position of the motor to achieve complex motion trajectories. For example, on a CNC milling machine, the motion controller can control the motion path of the milling cutter according to the processing program to process high-precision parts.

[0042] According to a further optimized solution, the gas-liquid mixed foaming module comprises a rectifying cavity 2, and a plurality of glass beads 3 are filled in the rectifying cavity 2. The rectifying cavity is a cylindrical cavity with an inner diameter of 5-15 cm and a length of 8-15 cm; the diameter of the glass beads 3 is 2-10 mm.

[0043] In a further optimized solution, the water inlet pipe of the rectifying chamber 2 is connected to the first three-way valve 4. The distance between the check valve 5 and the first three-way valve 4 is less than 2 cm, which can effectively prevent the liquid in the rectifying chamber 2 from flowing back.

[0044] In a further optimized solution, the outlet pipe of the first peristaltic pump 10 is connected to the second three-way valve 15 , and the inlet pipe of the first peristaltic pump 10 is connected to the first container 11 , so that the liquid in the first container 11 is transported by the first peristaltic pump 10 .

[0045] In a further optimized solution, the outlet pipe of the second peristaltic pump 12 is connected to the second three-way valve 15 , and the inlet pipe of the second peristaltic pump 12 is connected to the second container 13 , so that the liquid in the second container 13 is transported by the second peristaltic pump 12 .

[0046] According to a further optimization scheme, a first damper 9 is installed on the water outlet pipe of the first peristaltic pump 10 , and a second damper 14 is installed on the water outlet pipe of the second peristaltic pump 12 .

[0047] Damper A device used to reduce or eliminate vibration and noise in a piping system; usually installed on a fluid pipe.

[0048] Type of damper:

[0049] Water pipe damper: This damper uses the principle of capillary pressure to reduce, delay and damp the water hammer or air hammer generated instantly when the water pump or air pump is started, cut off its peak value, and turn it into a small fluctuation that is harmless to instruments and pressure or temperature transmitters.

[0050] Tuned mass damper (TMD): This type of damper broadens the range of its action frequency band by increasing the mass ratio or number, thereby achieving a good vibration reduction effect at the target frequency. Pipeline dynamic pressure damper: This type of damper mainly includes multiple damping plates, gaskets and clamping devices. There are several small holes distributed on the damping plates. The positions of the small holes of each two adjacent damping plates are staggered, and a gasket is placed between the two. The entire string of damping plates and gaskets is clamped by a clamping device.

[0051] Damper for pipeline vibration reduction: This type of damper connects the piston rod to the piston, and a balance chamber is set at the rear end of the piston. The balance chamber and the cylinder are on the same axial direction. There are metal rubber and a balance piston in the balance chamber, and metal rubber is set under the balance piston. When the volume in the hydraulic oil chamber changes, the balance piston can move freely with the piston rod due to the good compressibility and recovery of the metal rubber, and the pressure of the hydraulic oil chamber is balanced by changing the volume in the balance chamber.

[0052] Viscous damper: This type of damper is made based on the principle that fluid movement, especially when the fluid passes through the throttling hole, will produce throttling resistance. It is a damper related to the speed of piston movement. It is widely used in high-rise buildings, bridges, seismic reconstruction of building structures, seismic resistance of industrial pipeline equipment, military industry and other fields.

[0053] The first damper 9 and the second damper 14 absorb or dissipate energy to reduce vibration and impact in the pipeline system, thereby extending the service life of the equipment.

[0054] Directions:

[0055] The gas outlet of the gas power module is connected to the pressure gauge 7 through a first pipeline, and the gas mass flow meter 8 is connected to the first three-way valve through a second pipeline.

[0056] Two different liquids are poured into the first container 11 or the second container 13 respectively.

[0057] Confirm that the gas-liquid control module is powered on, the first peristaltic pump 10 and the second peristaltic pump 12 are connected to the power supply, and the first peristaltic pump 10 and the second peristaltic pump 12 are electrically connected to the controller through the data control line, and the main power switch of the gas-liquid control module and the power switches of the first peristaltic pump 10 and the second peristaltic pump 12 are turned on in turn; the two different liquids are transported to the rectifier chamber 2 through the first peristaltic pump 10 and the second peristaltic pump 12 for mixing and foaming.

[0058] After the foaming is completed, the first peristaltic pump 10 and the second peristaltic pump 12 are turned off, water is poured into the first container 11 or the second container 13, and the first container 11 or the second container 13 is started. When there is no foam at the outlet of the rectifying cavity 2, it means that it is clean.

[0059] The following is an experimental comparison:

[0060] Experiment 1

[0061] The foam liquid is used: 0.12wt% alkyl polyglycoside (APG810), 0.1wt% silicone surfactant Silok®8022, 0.12wt% sodium dodecylbenzene sulfonate as a composite surfactant, 0.03wt% xanthan gum and 0.1wt% polyethylene glycol as a foam stabilizer. The foam liquid is placed in the second container 13 for standby use; the synergistic fire extinguishing component 2-bromo-3,3,3-trifluoropropene (2-BTP for short) is placed in the first container 11 for standby use.

[0062] The gas flow rate is 7 L / min, the foam liquid flow rate of the second peristaltic pump 12 is set to 0.7 L / min, and the cooperative fire extinguishing component liquid flow rate of the first peristaltic pump 10 is set to 0.02 L / min, to obtain a two-component cooperative fire extinguishing foam.

[0063] Experiment 2

[0064] The foam liquid is used: 0.12wt% alkyl polyglycoside (APG810), 0.1wt% silicone surfactant Silok®8022, 0.12wt% sodium dodecylbenzene sulfonate as a composite surfactant, 0.03wt% xanthan gum and 0.1wt% polyethylene glycol as a foam stabilizer. The foam liquid is placed in the second container 13 for standby use; the synergistic fire extinguishing component 2-bromo-3,3,3-trifluoropropene (2-BTP for short) is placed in the first container 11 for standby use.

[0065] The gas flow rate is 5 L / min, the foam liquid flow rate of the second peristaltic pump 12 is set to 0.7 L / min, and the coordinated fire extinguishing component liquid flow rate of the first peristaltic pump 10 is set to 0.02 L / min, to obtain a two-component coordinated fire extinguishing foam.

[0066] Experiment 3

[0067] The foam liquid used: 0.21wt% alkyl polyglycoside (APG810), 0.175wt% silicone surfactant Silok®8022, 0.21wt% sodium dodecylbenzene sulfonate as a composite surfactant, 0.175wt% sodium alginate as a foam stabilizer and cross-linking agent A, the mixed solution of the above substances is placed in the second container 13 for standby use; 0.23wt% calcium chloride solution is placed in the first container 11 as cross-linking agent B for standby use.

[0068] The gas flow rate is 4 L / min, the liquid flow rate of the second peristaltic pump 12 is set to 0.4 L / min, and the liquid flow rate of the first peristaltic pump 10 is set to 0.3 L / min, to obtain a two-component gel foam.

[0069] Experiment 4

[0070] The foam liquid used: 0.21wt% alkyl polyglycoside (APG810), 0.175wt% silicone surfactant Silok®8022, 0.21wt% sodium dodecylbenzene sulfonate as a composite surfactant, 0.175wt% sodium alginate as a foam stabilizer and cross-linking agent A, the mixed solution of the above substances is placed in the second container 13 for standby use; 0.23wt% calcium chloride solution is placed in the first container 11 as cross-linking agent B for standby use.

[0071] The gas flow rate is 6 L / min, the liquid flow rate of the second peristaltic pump 12 is set to 0.4 L / min, and the liquid flow rate of the first peristaltic pump 10 is set to 0.3 L / min, to obtain a two-component gel foam.

[0072] Experiment 5

[0073] The foam liquid used: 0.21wt% alkyl polyglycoside (APG810), 0.175wt% silicone surfactant Silok®8022, 0.21wt% sodium dodecylbenzene sulfonate as a composite surfactant, 0.175wt% sodium alginate as a foam stabilizer and cross-linking agent A, the mixed solution of the above substances is placed in the second container 13 for standby use; 0.23wt% calcium chloride solution is placed in the first container 11 as cross-linking agent B for standby use.

[0074] The gas flow rate is 10 L / min, the liquid flow rate of the second peristaltic pump 12 is set to 0.4 L / min, and the liquid flow rate of the first peristaltic pump 10 is set to 0.3 L / min, to obtain a two-component gel foam.

[0075] Referring to Table 1, the data on the foaming multiples of Experiments 1, 2, 3, 4 and 5 show that under the same foam fire extinguishing agent formula, the use of the fire extinguishing agent two-component positive pressure foaming device of the present invention can effectively control the foaming multiple by adjusting the gas-liquid ratio; at the same time, compared with the negative pressure foaming device and the compressed air foaming system, the present invention can achieve the foaming of the fire extinguishing agent for two-component coordinated fire extinguishing, as well as the foaming of the gel foam that cannot be pre-mixed. The foam produced by the present invention is poured into a 100ml measuring cylinder through a hose, and the foam height change is observed to evaluate the foam stability. The consumption of the foam liquid by this test method is less than 600ml, which is much less than the consumption of the foam liquid (5L) when the negative pressure foaming device and the compressed air foaming system are tested. During the liquid separation stability test, the foam produced by the present invention is poured into a 2L foam collection container, and the change of the liquid precipitation mass over time is recorded. The foam liquid consumption in this process is less than 1L, which is much less than the consumption of the foam liquid (5L) when the negative pressure foaming device and the compressed air foaming system are tested.

[0076] Table 1

[0077]

[0078] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0079] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A two-component positive pressure foaming device for foam fire extinguishing agent, characterized in that: It comprises a gas power module for supplying gas, the gas power module is connected to a gas-liquid control module for controlling the supply of gas and liquid, the gas-liquid control module is connected to a gas-liquid mixing and foaming module for mixing and foaming gas and liquid and a liquid power module for supplying liquid through a first three-way valve (4); The liquid power module comprises a first peristaltic pump (10) and a second peristaltic pump (12); the first three-way valve (4) is connected to the first peristaltic pump (10) and the second peristaltic pump (12) via a second three-way valve (15); the first peristaltic pump (10) and the second peristaltic pump (12) are electrically connected to the gas-liquid control module.

2. The foam fire extinguishing agent two-component positive pressure foaming device according to claim 1, characterized in that: The gas power module comprises an air compressor (1), and an air outlet communicating pipe of the air compressor (1) is provided with a first pipeline.

3. The foam fire extinguishing agent two-component positive pressure foaming device according to claim 2, characterized in that: The gas-liquid control module comprises a pressure gauge (7), one end of the pressure gauge (7) is connected to the first pipeline, the other end of the pressure gauge (7) is connected to a gas mass flow meter (8), the end of the gas mass flow meter (8) away from the pressure gauge (7) is connected to an electromagnetic switch (6), and the end of the electromagnetic switch (6) away from the gas mass flow meter (8) is connected to the first three-way valve (4) through a second pipeline.

4. The foam fire extinguishing agent two-component positive pressure foaming device according to claim 3, characterized in that: A check valve (5) is installed on the second pipeline.

5. The foam fire extinguishing agent two-component positive pressure foaming device according to claim 3, characterized in that: The gas-liquid control module further comprises a controller electrically connected to the electromagnetic switch (6), the pressure gauge (7), and the gas mass flow meter (8), and the controller is electrically connected to the first peristaltic pump (10) and the second peristaltic pump (12).

6. The foam fire extinguishing agent two-component positive pressure foaming device according to claim 1, characterized in that: The gas-liquid mixed foaming module comprises a rectifying cavity (2), wherein a plurality of glass beads (3) are filled in the rectifying cavity (2).

7. The foam fire extinguishing agent two-component positive pressure foaming device according to claim 6, characterized in that: The water inlet pipe of the rectifying chamber (2) is connected to the first three-way valve (4).

8. The foam fire extinguishing agent two-component positive pressure foaming device according to claim 1, characterized in that: The water outlet pipe of the first peristaltic pump (10) is connected to the second three-way valve (15), and the water inlet pipe of the first peristaltic pump (10) is connected to the first container (11).

9. The foam fire extinguishing agent two-component positive pressure foaming device according to claim 8, characterized in that: The water outlet pipe of the second peristaltic pump (12) is connected to the second three-way valve (15), and the water inlet pipe of the second peristaltic pump (12) is connected to the second container (13).

10. The foam fire extinguishing agent two-component positive pressure foaming device according to claim 9, characterized in that: A first damper (9) is installed on the water outlet pipe of the first peristaltic pump (10), and a second damper (14) is installed on the water outlet pipe of the second peristaltic pump (12).

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