HK1140443B - Inert gas fire extinguisher for reducing the risk of and extinguishing fires in a protected area - Google Patents

Description

The invention relates to an inert gas fire extinguishing system designed to reduce the risk of and extinguish fires in a confined space, whereby the inert gas fire extinguishing system has at least one high-pressure gas storage tank containing an oxygen-displacing gas at high pressure, whereby the high-pressure gas storage tank is connected to a collecting line by a quick-release valve, and whereby an extinguishing line is provided which is connected to the collecting line by a pressure reducing device on the one hand and to extinguishing pipes on the other.

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The basic principle of inert gas fire-extinguishing technology is based on the recognition that in closed spaces, which are only occasionally entered by humans or animals and whose facilities are sensitive to water, the fire risk can be reduced by reducing the oxygen concentration in the affected area to a value of, for example, about 12% vol. At such (reduced) oxygen concentration, most combustible materials can no longer ignite. The main application of inert gas fire-extinguishing technology is therefore also applicable to single-use EDV-based gases, electrical foam and gas-discharge heaters, enclosed facilities and warehouses with already high volumes of nitrogen. The result of this process is a reduction in the concentration of soluble oxygen in the atmosphere by about 78% vol. For example, if the volume of oxygen in the room is known to be less than 1%, then protection from nitrogen oxides and other nitrogen-dependent gases may be required.

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In particular, in the case of multi-stage inert gas fire-fighting systems currently known, it is not considered desirable to inert a single room in a stepwise manner, i.e. a gradual inerting of a given pressure drop level in accordance with different full-fledged events, with these steps being carried out at different levels of protection under particular conditions. In particular, in the case of a basic process such as inert gas fire-fighting, it is not known whether it is desirable to inert a single room in a stepwise manner, i.e. a gradual inerting of a single pressure drop level in accordance with different full-fledged events, with these steps being carried out at different levels of protection under particular conditions. In particular, in the case of a basic process such as inert gas fire-fighting, it is not known whether the inert gas is inerted in a certain way or not, and in the case of other processes, the inert gas inerting protection is made independent of the inert gas release level.

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The Commission has not yet adopted a proposal for a directive on the approximation of the laws of the Member States relating to the protection of workers from the risks related to exposure to ionizing radiation.

In particular, it does not take into account that, for example, in case of differently sized shelters, a maximum amount of inert gas introduced for inerting per unit of time should be adapted to the corresponding shelter. In particular, the available pressure relief and the compressive strength of the enclosure determine the maximum amount of inert gas allowed per unit of time introduced into the shelter. This maximum amount of inert gas introduced per unit of time into the shelter ultimately determines the event flow at the inerting of the shelter, i.e. the inerting rate applicable to the enclosure.

The problem therefore arises when an inert gas fire extinguisher is used as a multi-site system, i.e. when a preventive fire protection or fire suppression is provided for several fire rooms by the same inert gas fire extinguisher, that irrespective of which of the several fire rooms is to be flooded with an oxygen displacement gas, the inertisation of the fire room is carried out according to the same event cycle. Thus, in traditional multi-site fire extinguishers, the same amount of oxygen displacement pressure is supplied per unit of time to a fire room with a relatively small volume, to a fire room with a relatively large volume. This means that the amount of oxygen displacement pressure provided by the inert gas solution per unit of oxygen displacement gas would in fact depend considerably on the amount of protection measures available, in particular, on the amount of oxygen displacement that would be available in the fire room.

On the basis of this problem, the invention is based on the task of further training an inert gas fire extinguishing system, as is known from the publication DE 198 11 851 A1, in such a way that the inertisation of a protective chamber, i.e. the setting of a level of lowering in the atmosphere of the protective chamber, can be carried out according to different sequences of events.

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The advantages of the solutions of the present invention are obvious: the pressure reducing device, through which the pressure reducing line connected to the extinguishing nozzles is connected to the high-pressure collecting line (collecting tube), has several parallel branches, if necessary, capable of being connected to control the corresponding valves, each of which is equipped with a pressure reducing device with a known pressure reducing characteristic, and can be adjusted to the respective application by means of appropriate control of the valves located in the parallel branches, before the pressure reducing pressure is applied to the pressure reducing device. For example, it is conceivable that in the first two lines at least one pressure reducing device is used, for example, in the case of a second line, where the pressure reduction is provided for a reduction of the pressure of the gas supply, and the pressure reduction is significantly increased in the second line, if the pressure reduction is provided for a reduction of the pressure of the gas supply in the first line.

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It follows that the solution of the invention allows the provision of a multi-unit inert gas fire extinguisher, whereby the amount of oxygen-displacing gas supplied by the inert gas fire extinguisher to a shelter per unit of time can be adjusted to, for example, the pressure relief available for the space concerned.

In addition, the solution of the invention also allows the respective reduction levels, such as the basic or the full inerting level, to be adjusted according to different inerting curves in a multi-stage inerting process.

In a preferred development of the solution according to the invention, the inert gas fire extinguisher therefore also has a control device for automatically performing a multi-stage inerting process, whereby the oxygen content in the protective chamber is first reduced to a first lowering level (such as a basic inerting level) and then further reduced to one or more pre-set lowering levels if necessary, for example in the event of fire.

This training thus allows the inerting to be performed automatically in a multi-stage inerting process to adjust the respective attenuation levels according to different sequences of events adapted to the attenuation levels.

In the case of the latter training, it is preferable, if the control unit is trained to lower the oxygen content to a first level of reduction, to align the valves of the pressure relief device so that only one of the first parallel branches of at least two parallel branches is connected to the high pressure collecting line (collecting pipe) and the discharge line, and if the control unit is trained to further lower the oxygen content to a second level of reduction, to align the valves of the pressure relief device of the pressure relief type so that only one of the two parallel branches is connected to the high pressure collecting line and the discharge line, the discharge identifier being located in the opposite direction of the first parallel pressure relief device of the second parallel discharge line, the discharge identifier being located in the opposite direction of the first parallel pressure relief device.In this implementation of the solution, it is therefore conceivable that for the second parallel branch, through which the high-pressure line and the low-pressure line are connected, if the oxygen content in the protective chamber is further reduced from an already set first level of reduction to a predetermined second level of reduction, a pressure reduction line is chosen which has a relatively large steepness in relation to the steepness of the pressure reduction line of the pressure reduction unit used in the first parallel branch.

In a two-stage inerting process, where the first lowering level corresponds, for example, to the basic inerting level and the second lowering level corresponds, for example, to the full inerting level, this preferred implementation of the inert gas fire extinguisher of the invention can ensure that, for example, in the event of a fire, the oxygen content is reduced from the basic inerting level to the full inerting level as quickly as possible.

As an alternative to the latter embodiment, it is of course conceivable that the control unit is trained to lower the oxygen content to the first lowering level, such as the basic inerting level, to direct the valves of the pressure relief device in such a way that only one first parallel branch of the at least two parallel branches of the pressure relief device is connected to the high pressure collection and low pressure relief lines, whereby the control unit is further trained to further lower the oxygen content to a second lowering level, such as the full inerting level, which is connected to the pressure relief device in such a way that two parallel lines are identical in the first and second parallel embodiments, and that it is conceivable to use at least two parallel and parallel solutions in the opposite direction of the first and second parallel reduction lines.

By connecting the first and second parallel branches of the pressure relief device to the extinguishing line in order to lower the oxygen content further to the second level of lowering, it is achieved that the reduction of the oxygen content to the second level of lowering can be achieved significantly more quickly than the reduction of the oxygen content to the first level of lowering. The further reduction to the second level of lowering is therefore carried out according to an inertization curve which runs steeper in the inertization curve of the pressure relief device, which is the measure of the maximum protection level for the second volume of oxygen, especially in the absence of the oxygen content to the first level of lowering. As with the previously described formulation, the protection of the second volume of oxygen is not guaranteed in relation to the maximum protection level for the exhaust gas, especially in the case of the maximum protection level for the exhaust gas, in relation to the maximum amount of protection per volume of the exhaust gas.

The solution of the invention is not limited to a pressure relief device having only two parallel branches. In particular, for applications where inerting of the chamber is to be carried out in more than two steps (deceleration levels), the pressure relief device should have a correspondingly higher number of parallel branches. For example, it is conceivable that the inert gas fire extinguisher will initially lower the oxygen content in the chamber to a basic inerting level, in the event of a fire (or in case of danger) the oxygen content in the chamber will be lowered from the inerting level to a lower inerting level and continuously lowered to this basic level for a given period of time, maintaining a complete inerting level,In order to ensure that, in such a (three-stage) inerting of the protective space, the individual reduction levels (basic, lower, full) for each event flow reduction to be performed and in particular the inerting curve can be individually adjusted, it is preferable that the pressure relief device of the inert gas fire extinguisher of the invention has at least three parallel branches with each one reducing device, each branch being connected via a control valve to the collecting and discharge manifold, and each pressure relief device, according to a known reduction design, is preferably located on a low pressure outlet, with a low pressure inlet of this device.If the control is trained to lower the oxygen content from the second lowering level to a third lowering level (such as the full inerting level), the valves of the pressure relief device shall be so directed that only one third of the three or more parallel branches is connected to the sump and extinguisher.

The solution according to the invention therefore enables the use of different pressure reduction measures for each inerting step (de-inerting level) in a multi-stage inerting process, in order to individually adjust the amount of oxygen-displacing gas supplied to the shelter per unit of time during the setting of the respective inerting level, so that the oxygen content can be reduced to the individual inerting levels according to different inerting curves. This is particularly necessary when different amounts of oxygen-displacing gas are required to set the individual inerting levels, i.e. when the spacing between the corresponding levels is different.

Currently, inert gas fire extinguishing technology commonly uses pressure reducing valves to reduce a relatively high inlet pressure (e.g. 300 bar) to an average outlet pressure of, for example, 60 bar. A pressure reducing device, which is made in the shape of a pressure reducing valve, has a pressure reducing characteristic where the outlet pressure is proportional to the exhaust pressure. When the quick release valve is opened in the inert gas fire extinguishing line, the high pressure oxygen gas displacement gas stored in at least one high pressure storage line is brought into the high pressure collection (solution) line, and then a high pressure reduction line is selected to help reduce the high pressure while the gas is being discharged in a low pressure collection line.

It should be borne in mind that during the inerting of the protective chamber the initial high pressure in the high pressure collecting line decreases relatively quickly if at least one of the high pressure gas storage tanks connected to the collecting line is emptied via an open quick-opening valve. If a pressure reducing device is used as a pressure switch, i.e. a throttle with a bore, the inerting curve has a high pressure peak at the beginning of the inerting process, which decreases relatively quickly in proportion to the pressure in the collecting line.

For example, a pressure relief device having a linear pressure relief feature is a pressure relief device which, despite the pressure on the inlet side (pressure relief) ensures that a given pressure is not exceeded on the outlet side, regardless of the input pressure applied over a given pressure range (working range). It is conceivable that a pressure relief device should be used as an output pressure relief device to achieve a maximum pressure difference, for example, when the pressure on the outlet side of a valve is fully applied (for example, when the valve is closed on a membrane) to achieve a maximum pressure difference.

The solution of the invention is not limited to an inert gas fire extinguisher that has only one high pressure gas storage. In a preferred embodiment, the inert gas fire extinguisher comprises at least two high pressure gas storage tanks connected to the collecting line by a quick-release valve, with each high pressure gas storage tank being connected to a parallel branch with a pressure reduction device. This is done by opening the quick-release valve from one of the high pressure storage tanks of at least two high pressure gas storage tanks, automatically reducing the valves of the pressure reduction device of the type, so that only the one branch assigned to the high pressure storage tank is connected to the collecting line and the gas is simultaneously discharged.

It follows that the inert gas fire extinguisher according to the invention is designed to perform an inertisation process in which the oxygen content in the enclosure is first lowered to a certain first lowering level and maintained at that first lowering level, and in the event of a fire in the enclosure (or if necessary) the oxygen content in the enclosure is further lowered from the first lowering level to a certain second lowering level. The inert gas inertisation system according to the invention can be used to achieve that the oxygen pressure content in the enclosure is lowered to the first lowering level by means of a first inertisation followed by a pressure reduction line corresponding to the first lowering level of the enclosure and a second inertisation line corresponding to the second lowering level of the enclosure.

In order to achieve this inerting procedure, it is preferable to measure at least one fire-detector size in the enclosure, preferably continuously, with the help of a detector, to determine whether a fire is present in the enclosure or whether a fire that has already broken out in the enclosure has already been extinguished as a result of inerting. However, the measurement of the fire-detector size does not have to be continuous, but it is also conceivable that one of these measurements may be taken at specified times or depending on specified events.

A preferred embodiment of the solution of the present invention provides for the detection of a fire characteristic by means of an aspiration system, whereby representative air samples are taken from the room air of the protected space and fed to the fire characteristic detector.

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An aspirating fire detection device is a fire detection device which, for example, draws up, via a piping or duct system, at a number of points within the chamber, a representative fraction of the ambient air of the chamber to be monitored and then directs this fraction to a measuring chamber with a detector to detect a fire size. In particular, it would be conceivable for this detector, designed to detect a fire size of this type, to emit a signal which would also give a quantitative indication of the quantity of the fire gases present in the chamber air sucked in. This would make it possible to determine the time course of the fire or the time course of the different development of the fire, including the effectiveness of the fire suppression system, and in particular the amount of exhaust gas still needed to be supplied to the chamber.

The invention is not limited to the inert gas fire extinguishers described above, but also concerns an inertisation process, preferably with the inert gas fire extinguishing system of the invention, to reduce the risk and extinguish fires in a shelter. In this inertisation process, the oxygen content in the shelter is reduced to a certain initial lowering level in a first step of the process. This is done by preferably regulated introduction of an oxygen-pushing gas (inert gas) which is stored in at least one high-pressure storage tank or supplied by a nitrogen generator.In the case of a fire in the enclosure or if necessary, the oxygen content in the enclosure is then further reduced from the first level to a specified second level. The inerting process of the invention provides that the oxygen content in the enclosure is reduced to the first level according to a first inerting curve determined by a pressure relief line of a first pressure relief device located in a first parallel branch and that the oxygen content in the enclosure is further reduced to the second level according to a second inerting curve determined by a second pressure relief line located in a second parallel device.

It is also conceivable, of course, that if necessary the oxygen content in the shelter room may be further reduced from the second level of reduction to a certain third level of reduction.

The inertisation procedure according to the invention can be performed in particular by an inert gas fire extinguisher, which, as described above, has a pressure reducing device with at least two parallel branches, and in which the oxygen displacement gas is stored at high pressure, for example up to 300 bar, in high pressure gas storage tanks (such as steel containers). Before the oxygen displacement gas is introduced into the chamber, this initially high storage pressure is reduced to a maximum working pressure of 60 bar by a pressure reduction device placed in a first parallel branch of the pressure reduction device. The first parallel branching pressure reduction device in the software includes a suitable means of reducing the pressure, calculated by means of a pre-determined blur, for example by a blur calculation.

It is known that with the emptying of the high pressure gas storage tanks, the storage pressure in the containers of the extinguishing agent and thus the inlet pressure of the pressure reducing device located in the first parallel branch decreases.

The decreasing pressures in the high pressure gas storage tank or behind the aperture of the pressure relief device located in the first parallel branch also reduce the mass/volume flow of oxygen displacement gas introduced into the protective area. Therefore, in order to introduce a defined amount of oxygen displacement gas into the protective area at a predetermined time, care must be taken to ensure that there is a correspondingly high mass/volume flow at the start of the flow, with this high mass/volume flow at the start of the flow being prolonged by the decreasing/torque pressure at the exit of the high pressure gas storage tank. However, the problem is that the high mass/volume flow at the start of the flow transfers the corresponding pressure to the protective area through turbulence, overloads, etc.

The solution of the invention makes it possible to compare the mass/volume flow over the time available in a particularly easy to implement yet effective manner to prevent pressure and volume flow peaks at the beginning of the flood and thus to minimise the necessary protection measures in the protected area (e.g. pressure relief opening area).

For example, the solution of the invention allows the oxygen-displacing gas to be activated in one step, combined with a stepwise switching of parallel branches of the pressure-reducing device behind the extinguishing agent supply, and thus of pressure-reducing devices, for example in the form of flaps, to allow the oxygen-displacing gas to flow through a small flame cross section at the beginning of the flow at high stock pressure and through a gradually increased stock pressure at the beginning of the flow, thus reducing the current volumes at the beginning of the flow, which are also the case with conventional solution, which can result in safety measures.

The connection of the individual parallel branches of the pressure relief device, and thus the connection of the individual pressure relief devices, for example in the form of apertures, may be done additionally, at certain (pre-determined) times, adding another parallel branch to the extinguishing agent flow and adding the aperture cross-sections of the pressure relief devices used for pressure relief.

More generally, the invention therefore also concerns an inertisation process for reducing the risk of and extinguishing fires in a shelter, whereby an oxygen displacement gas stored under high pressure is first reduced to a working pressure and then introduced into the shelter to reduce the oxygen content in the shelter to a certain level of reduction, using a first pressure reduction device to reduce the pressure of the oxygen displacement gas stored under high pressure, which reduces the oxygen displacement gas already at the beginning of the reduction of the oxygen content, and using at least two additional pressure reduction devices to reduce the oxygen displacement gas at the beginning of the reduction of the oxygen content, which reduces the oxygen displacement gas after the start of the specified time.

The following illustrations give a detailed description of the inert gas fire extinguishing system of the invention.

It shows: Figure 1a schematic view of a first exemplary embodiment of the inert gas fire extinguisher according to the invention;Figure 2a schematic view of another exemplary embodiment of the inert gas fire extinguisher according to the invention;Figure 3a time-evolution of the oxygen concentration in a shelter when using an inertisation process carried out by means of an embodiment of the inert gas fire extinguisher according to the invention;Figure 3b the time-evolution of a fire-risk measurement value of a smoke-risk measurement value in a high-volume room where the oxygen concentration is measured according to Figure 3a;Figure 4a time-evolution of the oxygen concentration in a shelter when using an inert gas fire extinguisher according to the invention;Figure 4b the time-evolution of a fire-risk measurement value of a smoke-risk measurement value in a high-volume room where the oxygen concentration is measured according to Figure 5a;Figure 4a short-range measurement of the oxygen concentration of a hydrogen-protective fuel is used to determine the amount of oxygen in the fire-risk gas in a shelter;Figure 4a short-rate measurement of oxygen concentration is used to determine the amount of oxygen in the fire-protective gas in a gas fire extinguisher according to the invention;Figure 4a short-evision is used to determine the amount of oxygen in the fire-risk measurement value of the gas in a gas fire extinguisher;Figure 4blast is used in a fire extinguisher;Figure 4blast is used to determine the amount of oxygen in the fire-risk measurement value of the fire exting gas in a gas fire extinguisher according to the process;Figure 5a fire extinguisher is used in the fire extinguisher;Figure 4blast is used in the fire extinguisher is used in a fire extinguisher is a fire extinguisher is a fire extinguisher;

Fig. 1 shows in a schematic view a first preferred embodiment of the inert gas fire extinguisher of the invention 100. The inert gas fire extinguisher 100 has a total of 5 high pressure gas storage tanks 1a, 1b, 1c, 2a, 2b, each of which is made, for example, as commercial 200 bar or 300 bar high pressure gas cylinders. It is also conceivable to replace high pressure gas cylinders with one or more high pressure storage tanks, for example in the form of high pressure gas storage tubes. In the high pressure gas storage tanks 1a, 1b, 1c, 2a, 2b, an acid-displaced or existing gas, such as nitrogen/dioxide, is stored under the table and high carbon dioxide.

In the inert gas fire extinguisher 100 depicted, the high pressure gas storage tanks 1a, 1b, 1c, 2a, 2b are divided into two groups consisting of the high pressure gas storage tanks 1a, 1b, 1c and 2a and 2b. The advantage of the classification of the high pressure gas storage tanks 1a, 1b, 1c and 2a, 2b into high pressure gas storage batteries is that, in a multi-inert gas fire extinguisher to set a certain level of abrasion in the atmosphere of a protective space 10, not all the high pressure gas storage tanks 1a, 1b, 1c, 1a, 2b can be used simultaneously, but only the high pressure gas storage tanks 1a, 1b, 1c, 1a, 2b and 2c.

Each high pressure gas storage tank 1a, 1b, 1c, 2a, 2b shall be connected to a high pressure collector tube 3 via a quick-release valve 11a, 11b, 11c, 12a, 12b. The respective quick-release valves 11a, 11b, 11c, 12a, 12b may be operated, if necessary, by means of appropriate control lines 13a, 13b from a control device 7 to connect the associated high pressure gas storage tank 1a, 1b, 1c, 2a, 2b to the high pressure collector line 3.

The high pressure collector line 3 is connected to a pressure relief device 6. The task of the pressure relief device 6 is to reduce, after opening at least one quick-opening valve 11a, 11b, 11c, 12a, 12b, the oxygen displacement gas flowing under high pressure into the high pressure collector line 3 to a predetermined operating pressure of, for example, 60 bar. Accordingly, a relatively high gas pressure is present at the input side of the pressure relief device 6 which is reduced to the low operating pressure by means of pressure relief devices 22, 32 and the pressure relief device 6 is connected to a low pressure displacement device 4L which is a low pressure displacement device 6L which is inserted into the pressure relief device 5 via a pressure relief device 6L on a pressure relief device 22 through a pressure relief device 10 through a pressure relief device 22 through a pressure relief device 32 through a pressure relief device 22 through a pressure relief device 10 in the pressure relief chamber.

According to the invention, the pressure relief device 6 has at least two, in the embodiment shown in Fig. 1, exactly two parallel branches 21, 31. In each parallel branch 21, 31 one of the pressure relief devices 22, 32 is located. Through corresponding valves 23, 33 controlled by the control device 7, the individual pressure relief devices 22, 32 of the respective parallel branches 21, 31 are connected to the high pressure assembly line 3 on the one hand and to the low pressure discharge line 4 on the other. Although in the representation shown in Fig. 1 the respective valves 23, 33 are located between the pressure relief device 3 and the corresponding pressure relief device 22, 32, it is conceivable that the valves 23, 33 are also located between the corresponding pressure relief devices 22, 32 and 4 of the pressure relief.

The control device 7 is connected via control lines 13a and 13b to the aforementioned high-pressure gas storage valves 11a, 11b, 11c, 12a, 12b of the high-pressure gas storage 1a, 1b, 1c, 2a, 2b, in order to connect, if necessary, the high-pressure gas storage 1a, 11a, 11b, 11c, 12a, 12b of the high-pressure gas storage valves 11a, 2b, 1c, 2a, 2b to the high-pressure gas storage 1a, 2b, 1c, 2b.

For example, it is conceivable that the pressure relief device 22 located in the first parallel 21 is designed as a pressure relief device 22 with a constant pressure relief indicator over a specified pressure range. If, then, the valve 23 is opened to flood the protective chamber 10 by means of the control device 7 and the valve 33 located in the second parallel 31 is closed, the pressure relief device 7 is opened at least once by means of the pressure relief device 11a, 11b, 11c, 12a, 12b, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10c, 10Since the pressure relief device 22 in the first parallel 21 has a constant pressure relief characteristic in the example design shown in Figure 1, a constant amount of oxygen displacement gas is supplied to the protective chamber 10 per unit time, provided that the valve 23 is opened and the valve 33 is closed. When inert gas is supplied through the first parallel 21 of the pressure relief device 6, the inertisation curve follows a straight line. The steepness of the (linear) inertisation curve is determined by the volume of the enclosed protective chamber 10 on the one hand and by the pressure relief device 22 (concentrated) operating in the direction of the pressure relief device on the other hand, depending on the direction of the pressure relief device 6 after each operation.at which pressure value the pressure relief device 22 designed, for example, as a pressure relief device 22 reduces the high pressure in the high pressure assembly line 3, the linear inertisation curve is more or less steep.

For example, the pressure relief device 32 located in the second parallel branch 31 may also be designed as a pressure relief device 32 which, therefore, delivers a constant pressure output over a given working area independently of the input pressure. It is preferable to provide that the pressure relief line of the pressure relief device 32 located in the second parallel branch 31 is different from the pressure relief line of the pressure relief device 22 located in the first parallel branch 21. For example, it is conceivable that the pressure relief device 32 located in the second parallel branch 32 is designed to provide a constant pressure output greater than the pressure relief line of the first parallel branch 21 located in the first parallel branch. In this way, it is possible to reduce the maximum permissible pressure protection volume of the gas chamber with the maximum permissible flow of 10 volumes of the gas. In the case of the present device, it is necessary to adapt the protection to the maximum permissible flow of 10 volumes of the gas chamber.

As shown in Figure 1, the inert gas fire extinguisher 100 of the invention is also equipped with a fire detection system, which has at least one fire size sensor 9. This fire size sensor 9 is connected to the control unit 7 by a control line in the embodiment shown. The fire detection system is used to continuously or at specified times or events check whether a fire has broken out in the ambient air of the enclosed room.

The inertisation process which can be achieved by means of the control device 7 is described below in the context of Figures 3a, 3b and 4a, 4b.

It is further shown in Figure 1 that the inert gas fire extinguisher 100 is also equipped, in the exemplary embodiment, with a sensor 8 for detecting the oxygen concentration in the room atmosphere of the chamber 10. The measurements taken by the sensor 8 continuously or at specified times or events are fed to the control unit 7 via a corresponding data line. In this way, it is possible that the control unit 7 can be used to keep the oxygen concentration in the chamber 10 at a specified lowering level by means of any necessary tracking of oxygen displacement gas within a certain control range.

In Fig. 2 a further embodiment of the inert gas fire extinguisher 100 of the invention is shown. The inert gas fire extinguisher 100 shown in Fig. 2 is essentially the same as the one described above with reference to Fig. 1 except that in the embodiment shown in Fig. 2 the pressure relief device 6 has a total of three parallel branches 21, 31 and 41 with a pressure relief device 22, 32, 42 each. Each parallel branch 31, 21, 41 of the pressure relief device is connected via a valve 23, 33, 43 controlled by the control device 7 to the high pressure collector 3 and the low pressure discharge device 4.

Preferably in the embodiment shown in Figure 2, the individual pressure relief devices 22, 32, 42 have different pressure relief characteristics. By a corresponding actuation of valves 23, 33, 43 and by connecting either one of the three parallel branches 21, 31, 41, or two of the three parallel branches 21, 31, 41, or all three parallel branches 21, 31, 41 simultaneously to the high pressure collecting line 3 on the one hand and the low pressure discharge line 4 on the other, the inerting of the protective space 10 can be achieved according to a total of six different inerting curves.

The pressure relief devices 21, 31, 41 shown in Figures 1 and 2 may be designed as pressure relief devices, which have a constant, straight line pressure relief characteristic over at least a given range of input pressure, so that, regardless of the input pressure (pressure in the high pressure manifold 3) a constant output pressure source is provided.

On the other hand, it is obvious but also conceivable that at least some of the pressure reducing devices used in the pressure reducing device 6 22, 32, 42 are designed as pressure gauges, whereby the pressure is reduced by a change in cross-section by means of a throttle disc with a bore of a certain diameter. The size of the bore is designed to suit the inert gas fire extinguisher according to its intended use. A pressure reducing device where the pressure reduction is achieved by means of a pressure gauge has a curved pressure reduction line which depends on the flow of the input pressure (pressure in the high pressure cell and hence pressure drop 3) and, in particular, immediately after opening the inert gas fire extinguisher, 11a, 12c, 11c, 12c.

If the inerting of the protection area 10 is done by means of a pressure relief device which has a pressure relief bar, the inerting curve assumes an arc-like flow.

Although the embodiments of the inert gas fire extinguishing system 100 of the invention shown in Figures 1 and 2 are shown as single-sphere fire extinguishing systems, it is of course conceivable to use it as a multi-sphere fire extinguishing system.

A method of inertisation to be performed with the inert gas fire extinguisher 100 of the invention is described below with reference to Figures 3a, b and 4a, b.

Figures 3a and 3b show the oxygen concentration and the quantity of a fire-sample 9 measured by the fire-sample sensor, respectively, and the smoke level in the chamber 10, using a multi-stage inerting process using an inert gas fire extinguisher 100 according to the present invention.

At time t0 the inerting of the protective space 10 begins by continuously supplying an oxygen-displacing gas to the atmosphere of the enclosed space 10 until time t1. The figure in Fig. 3a shows that the inerting curve runs in a straight line and relatively flat over the time interval t0 - t1. This curve shape of the inerting curve is possible, for example, by connecting the first of at least two parallel branches 31, 21, 41 of the pressure relief device 6 to the high pressure collector 3 and the low pressure discharge line 4, in which case a pressure relief device 22 is provided in this first parallel branch 21 as a printer.

Err1:Expecting ',' delimiter: line 1 column 554 (char 553)

In the scenario shown in Fig. 3a, at time t0 a fire alarm is given by the fire size detector 9 shown in Fig. 1 and 2 to the control unit 7 which controls the inerting process, i.e. the reduction of the oxygen level to the first level of reduction. In particular, at this time t0 the smoke level or the quantity measured of the fire size, recorded by the fire size detector 9 continuously or at specified times, has exceeded a first active threshold (alarm threshold 1) as shown in Fig. 3b. In response to this fire alarm level, the oxygen concentration in the protective volume is reduced by approximately 15% during the initial reduction. The oxygen concentration in the initial reduction is reduced by approximately 21%. This corresponds to a decrease in the oxygen concentration at the first level of reduction (Fig. 3a) during the initial reduction (approximately 3.9%) of the fire level.

Continuous monitoring of the fire development in compartment 10 during the reduction of oxygen to the first reduction level will allow the fire to be fully extinguished during the reduction.

In the scenario shown in Figures 3a and 3b, the fire could not be completely extinguished by time t2 as shown by the evolution of the fire parameters in Figures 3b. Rather, in the scenario shown, the quantitative value of the fire parameters in the room air of the shelter 10 is increasing steadily despite the reduction of the oxygen content to the first reduction level, which is an indication that despite the reduced oxygen content the fire in the shelter 10 has not been extinguished.

If, as in the scenarios shown in Figures 3a and 3b, after a first specified time ΔT1, i.e. at time t2, the quantity measured for the fire size exceeds a second specified alarm threshold, the fire is assumed to be still not extinguished, so that the fire alarm issued at time t0 is confirmed again. Confirmation of the fire alarm at time t2 causes the oxygen concentration in the enclosure 10 to decrease further from the first reduction level (e.g. 15,9% vol. oxygen) to a second reduction level. This is achieved by accelerating the amount of oxygen (e.g. 13,8% vol. oxygen) released at time t0 to a certain level (e.g. t1 and t2) so that the relative decrease in oxygen concentration between the second reduction level and the second reduction level is also significantly greater in comparison with the time t0 - t2 - t3 - t3 - t3 - t2 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t3 - t

The slope of the inerting curve is increased in the illustrated embodiment, for example, by connecting in the pressure relief device 6 a second parallel branch 31 in addition to the first parallel branch 21 in which a pressure relief device 32 is arranged in the shape of a pressure relief device 6.

The corresponding curve in Fig. 3b shows that the re-injecting of inert gas to adjust the second level of descent did not lead to a complete containment of the fire that broke out in the shelter. Although the quantitative measurement of the fire signal initially shows a stagnation in a time window ΔT2, which means that the spread of the fire in the shelter could be at least suppressed, after a certain time the smoke measurement or the quantitative measurement of the fire signal again rises and even exceeds the threshold of 3, at which a main alarm is triggered. The exceeding of the alarm wave 3 occurs at the time shown in Fig. 3b at the time of the scenario t4.

The re-confirmation of the fire alarm at time t4 will cause the oxygen content in the chamber to be further reduced from the second lowering level to the full inerting level, this time by introducing as quickly as possible an appropriate amount of oxygen-displacing gas into the atmosphere of the chamber. In particular, at least two parallel branches 21 and 31 will be opened simultaneously in the pressure relief device 6 to allow the greatest possible inert gas flow through the pressure relief device 6.

The level of inerting is preferably set to an oxygen concentration below the flammable limit of the materials present in the enclosure (fire load), so that the fire is completely extinguished by oxygen release while effectively preventing the materials in the enclosure from igniting again.

The curve shown in Figure 3b shows that after setting the level of full inertisation (at time t5), the quantity of the measured fire size decreases continuously, which means that the fire is extinguished. The level of full inertisation should be maintained at least until the temperature in the shelter has fallen below the critical ignition limit of the material. However, it would also be conceivable to maintain the level of full inertisation until emergency services arrive and the inert gas extinguisher is taken out of its automatic fire-extinguishing mode, for example by a long-term manual release.

In the inerting process, as illustrated in Figures 3a and 3b, the total inerting level is adjusted over two intermediate steps, the first and second lowering levels, with a different pressure reduction measure applied for each intermediate step, which is ultimately reflected in the curve of the inerting curve.

Figures 4a and 4b show another scenario in which the oxygen content is reduced from the original 21% vol. to the first level of reduction (e.g. 15.9% vol.) according to a straight inerting curve which deliberately has a slope so low that the oxygen content in the shelter is reduced to the first level of reduction only after a relatively long period of time.

In the scenario shown in Figure 4, the curve of Figure 4b shows that after the fire alarm is dissolved at time t0, the quantity of the fire signal initially stagnates and then decreases continuously, indicating that the fire has been extinguished in the protective compartment. At time t1, the quantity of the fire signal is below the first alarm threshold, so that the initiation of oxygen displacement can be adjusted to set the first level of displacement. The solution according to the invention therefore allows the gas used to extinguish the gas to be adjusted according to the needs.

In Fig. 5 a schematic view is shown of another exemplary embodiment of the inert gas fire extinguisher 100 of the invention, this time the inert gas fire extinguisher 100 is constructed as a multi-field system providing preventive fire protection or fire suppression for a total of two shelters 10-1 and 10-2 from one and the same inert gas fire extinguisher 100.

As already mentioned, the problem with conventional multi-site fire extinguishers is that, regardless of which of the enclosures is to be flooded with an oxygen displacement gas, the inertisation of the enclosure is carried out according to the same event sequence. Thus, in conventional multi-site fire extinguishers, an enclosure with a relatively small volume of space is supplied with the same amount of oxygen displacement gas per unit of time as an enclosure with a relatively large volume of space. Since the amount of inert gas solution available per unit of time from the inert gas installation depends in particular on the pressure relief measures of the respective enclosures, this means that in the case of an enclosure with a relatively small volume of space, the inertisation process is much slower than would be possible if this were actually the case.

The solution of the invention, shown in an exemplary embodiment in Fig. 5, is achieved in a particularly easy to implement yet effective way, by providing preventive fire protection or fire suppression for several compartments 10-1, 10-2 with one and the same inert gas fire extinguisher 100, whereby in case of fire or if necessary in relation to one of several compartments 10-1, 10-2 inertisation can be initiated to adapt to the compartment concerned. In particular, it is considered that, for example, in compartments of different dimensions, inertisation may be achieved by applying a maximum pressure of inert gas per unit time to the corresponding compartment. This is demonstrated by the fact that, as already indicated, in particular, the pressure of inert gas per unit time is fixed, in particular the pressure of inert gas per unit of the compartment. In particular, the maximum pressure of inert gas per unit of time is fixed, and the maximum pressure of inert gas per unit of inert gas is fixed.

The multi-sector fire extinguisher 100 shown in Fig. 5 is essentially the same as the one-sector fire extinguisher 100 shown in Fig. 1 and described above. In particular, the multi-sector fire extinguisher 100 shown in Fig. 5 has several high-pressure gas storage tanks 1a, 1b, 1c, 2a, 2b, each of which may be operated, for example, as a commercial 200-bar or 300-bar high-pressure gas cylinder, and in which an oxygen-displacing gas or a gas-mixed gas is stored under high pressure. Each of the pressure gas storage tanks 1a, 21b, 21c, 21c, 21c, 2b, 21b, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c, 21c 21c, 21c, 21c 21c, 21c 21c, 21c 21c, 21c 21c 21c, 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c 21c

Unlike the single-section fire-extinguisher schematically shown in Figure 1, the multi-section fire-extinguisher 100 shown in Figure 5 divides the low-pressure fire-extinguisher 4 connected to the output side of the pressure relief device 6 into two parallel branches 4-1 and 4-2, each parallel branch 4-1, 4-2 in one of the two protective compartments 10-1, 10-2 each through a variety of extinguishing nozzles 5. Each parallel branch 4-1, 4-2 of the low-pressure fire-extinguisher 4 is connected to the low-pressure fire-extinguisher 4 via a valve 41, 42 attached to the control device 7 by the low-pressure relief device 4 and thus to the output of the pressure relief device 6.

In the case of the multi-area fire extinguisher 100 as shown in Figure 5, the pressure relief devices 22, 32 in the two parallel branches 21, 31 of the pressure relief device 6 each have a pressure relief line adapted to one of the two protection spaces 10-1, 10-2. For example, it is conceivable that the pressure relief device 22 in the first parallel branch 21 may have a pressure relief line adapted to the maximum permissible load of the first protection space 10-1. If then the pressure relief valve 23 is opened to the flow of the first protection space 10-1 by means of the control device 7 and the pressure relief valve 23 is closed by means of the pressure relief valve 31 in the second parallel, then the pressure relief device 33 is opened by means of the second parallel valve 33 - if the pressure relief device 11 is opened by means of a double-stroke flowing valve 4 - if the pressure relief device 11 is opened by means of a double-stroke flowing valve 4 - if the pressure relief device 11 is opened by means of a double-stroke flowing valve 4 - if the pressure relief device 11 is opened by means of a double-stroke flowing valve 4 - if the pressure relief valve 4 is opened by means of a double-stroke flowing valve 4 - if the pressure relief valve 4 is opened by means of a double-stroke flowing valve 4 - if the pressure relief valve 4 is opened by means of a double-stroke flowing valve 4 - if the pressure relief valve 4 is opened by means of a double-stroke flowing valve 4 - if the pressure relief valve 4 is opened by means of a double-stroke valve 4 - if the pressure relief valve 4 is opened by means of a double-stroke valve 4 - if the pressure relief valve 4 is opened by means of the first protection space 10 - if the first protection space 10 is closed by means of the first protection space 10 - if the pressure relief valve 6 is opened by means of the first protection space 10 - if the first protection space 10 is closed by means of the first protection space 10 - if the pressure relief valve is closed by means of the first pressure relief valve 6 - if the first pressure relief valve 6 is closed by means of the first pressure relief valve 6 - if the first pressure relief valve 6 - if

Since the pressure relief device 22 located in the first parallel branch 21 has a pressure relief line adapted to the maximum allowable load of the first protection chamber 10-1, the inerting of the first protection chamber 10-1 shall be carried out according to a sequence of events specifically adapted to the first protection chamber 10-1.

Since the pressure relief device 32 located in the second parallel branch 31 of the pressure relief device 6 may have a pressure relief line corresponding to the maximum allowable load on the second protection space 10-2, inerting of the second protection space 10-2 may also be carried out, if necessary, according to a sequence of events specifically adapted to the second protection space 10-2.

Claims (14)

1. An inert gas fire extinguisher (100) for reducing the risk of and extinguishing fires in a protected room (10, 10-1, 10-2), wherein the inert gas fire extinguisher (100) comprises at least one high-pressure gas tank (1a, 1b, 1c; 2a, 2b) in which an oxygen-displacing gas is stored under high pressure, wherein the high-pressure gas tank (1a, 1b, 1c; 2a, 2b) is connectable to a collecting line (3) via a quick-release valve (11a, 11b, 11c; 12a, 12b), and wherein an extin-guishing line (4, 4-1, 4-2) is further provided which is connected on one side to the collecting line (3) via a pressure-reducing device (6) and on the other side to extinguishing nozzles (5), characterized in that the pressure-reducing device (6) comprises at least two parallel branches (21, 31, 41), each having a pressure-reducing unit (22, 32, 42), wherein each parallel branch (21, 31, 41) is connectable to the collecting line (3) and the extinguishing line (4, 4-1, 4-2) via a controllable valve (23, 33, 43), and wherein each pressure-reducing unit (22, 32, 42) is designed to reduce a high input pressure to a low output pressure according to a preset pressure-reducing characteristic.
2. The inert gas fire extinguisher (100) according to claim 1, wherein a control device (7) is further provided to automatically effect a multistage inerting process in which the oxygen content in the protected room (10, 10-1, 10-2) is first lowered to a first reduced level and then further lowered as needed to another preset reduced level or successively to multiple preset reduced levels, wherein the control device (7) is designed to control the valves (23, 33, 43) of the pressure-reducing device (6) to set the reduced level such that the oxygen content in the protected room (10, 10-1, 10-2) reduces in accordance with a preset inerting curve.
3. The inert gas fire extinguisher (100) according to claim 2, wherein the control device (7) is designed to control the valves (23, 33, 43) of the pressure-reducing device (6) to lower the oxygen content to the first reduced level such that only one first parallel branch (21; 31) of the at least two parallel branches (21, 31, 41) is connected to the collecting line (3) and the extinguishing line (4, 4-1, 4-2), and wherein the control device (7) is further designed to control the valves (23, 33, 43) of the pressure-reducing device (6) to further lower the oxygen content to a second reduced level such that only one second parallel branch (31; 21) of the at least two parallel branches (21, 31, 41) is connected to the collecting line (3) and the extinguishing line (4, 4-1, 4-2), wherein the pressure-reducing characteristic of the pressure-reducing unit (22) arranged in the first parallel branch (21) differs from the pressure-reducing characteristic of the pressure-reducing unit (32) arranged in the second parallel branch (31).
4. The inert gas fire extinguisher (100) according to claim 2, wherein the control device (7) is designed to control the valves (23, 33, 43) of the pressure-reducing device (6) to lower the oxygen content to the first reduced level such that only one first parallel branch (21) of the at least two parallel branches (21, 31, 41) is connected to the collecting line (3) and the extinguishing line (4, 4-1, 4-2), and wherein the control device (7) is further designed to control the valves (23, 33, 43) of the pressure-reducing device (6) to further lower the oxygen content to a second reduced level such that the first parallel branch (21) and a second parallel branch (31) of the at least two parallel branches (21, 31, 41) are connected to the collecting line (3) and the extinguishing line (4, 4-1, 4-2).
5. The inert gas fire extinguisher (100) according to any one of claims 2 to 4, wherein the pressure-reducing device (6) comprises at least three parallel branches (21, 31, 41) each having a pressure-reducing unit (22, 32, 42), wherein each parallel branch (21, 31, 41) is connectable to the collecting line (3) and the extinguishing line (4, 4-1, 4-2) via a controllable valve (23, 33, 43), and wherein each pressure-reducing unit (22, 32, 42) is designed to reduce a high input pressure to a low output pressure according to a preset pressure-reducing characteristic, and wherein the control device (7) is designed to control the valves (23, 33, 43) of the pressure-reducing device (6) to lower the oxygen content from the second reduced level to a third reduced level such that only one third parallel branch (41) of the at least three parallel branches (21, 31, 41) is connected to the collecting line (3) and the extinguishing line (4, 4-1, 4-2).
6. The inert gas fire extinguisher (100) according to any one of the preceding claims, wherein at least some of the pressure-reducing units (22, 32, 42) exhibit a pressure-reducing characteristic with which, irrespective of a set input pressure, the output pressure does not exceed a predefined pressure value.
7. The inert gas fire extinguisher (100) according to any one of the preceding claims, wherein at least some of the pressure-reducing units (22, 32, 42) exhibit a pressure-reducing characteristic with which the output pressure is proportionally dependent on the input pressure.
8. The inert gas fire extinguisher (100) according to any one of the preceding claims, wherein at least some of the pressure-reducing units (22, 32, 42) exhibit a pressure-reducing characteristic with which, irrespective of a set input pressure, the output pressure assumes a predefinable constant pressure value over at least a specific range of pressure.
9. The inert gas fire extinguisher (100) according to any one of the preceding claims which comprises at least two high-pressure gas tanks (1a, 1b, 1c; 2a, 2b) which are connectable to a collecting line (3) via a quick-release valve (11a, 11b, 11c; 12a, 12b), wherein a parallel branch having a pressure-reducing unit (22, 32, 42) is allocated to each high-pressure gas tank (1a, 1b, 1c; 2a, 2b) such that when the quick-release valve (11a, 11b, 11c; 12a, 12b) of one high-pressure gas tank (1a, 1b, 1c; 2a, 2b) of the at least two high-pressure gas tanks (1a, 1b, 1c; 2a, 2b) opens, the valves (23, 33, 43) automatically control the pressure-reducing device (6) such that only the parallel branch (21, 31, 41) allocated to the one high-pressure gas tank (1a, 1b, 1c; 2a, 2b) is connected to the extinguishing line (4, 4-1, 4-2) and the collecting line (3).
10. An inerting method for reducing the risk of and extinguishing fires in a protected room (10, 10-1, 10-2) in which an oxygen-displacing gas stored under high pressure is first reduced to a working pressure and subsequently introduced into the protected room (10, 10-1, 10-2) so as to lower the oxygen content in the protected room (10, 10-1, 10-2) to a specific reduced level, characterized in that a first pressure-reducing unit (22; 32) arranged in a first parallel branch (21; 31) is used to reduce the pressure of the oxygen-displacing gas stored under high pressure, and through which the oxygen-displacing gas flows as soon as the oxygen content begins to be lowered; and that at least one second pressure-reducing unit (32; 22) arranged in a second parallel branch (31; 21) is further used to reduce the pressure of the oxygen-displacing gas stored under high pressure, and through which the oxygen-displacing gas only flows after a predefined period of time has passed since the oxygen content began to be lowered.
11. The inerting method according to claim 10, wherein the first pressure-reducing unit (22; 32) is a pressure aperture exhibiting a first aperture cross-section, and wherein the second pressure-reducing unit (22; 32) is a pressure aperture exhibiting a larger aperture cross-section than the first aperture cross-section.
12. The inerting method according to claim 10 or 11, wherein after the predefined time set for reducing the pressure has passed, the oxygen-displacing gas flows through both the first pressure-reducing unit (22; 32) as well as through the at least one second pressure-reducing unit (32; 22).
13. The inerting method according to any one of claims 10 to 12, wherein the inerting method comprises the following steps:

    a) lowering the oxygen content in the protected room (10) to a specific first reduced level;

    b) maintaining the oxygen content in the protected room (10) at or below the first reduced level; and

    c) in the event of a fire in the protected room (10) or if otherwise needed, the oxygen content in the protected room (10) is further lowered from the first reduced level to a specific second reduced level,

    wherein the lowering of the oxygen content in the protected room (10) to the first reduced level ensues in accordance with a first inerting curve which is predetermined by a pressure-reducing characteristic of the first pressure-reducing unit (22; 32), and wherein the further lowering of the oxygen content in the protected room (10) to the second reduced level ensues in accordance with a second inerting curve which is predetermined by a pressure-reducing characteristic of the second pressure-reducing unit (32; 22).
14. The inerting method according to claim 13, wherein at least one fire parameter is measured in the protected room (10, 10-1, 10-2), preferably continuously, in order to determine the presence of fire in said protected room (10, 10-1, 10-2).