EP1911498B1 - Multi-stage inerting method for preventing and extinguishing fires is enclosed spaces - Google Patents

Abstract

The inertization process involves decreasing oxygen concentration in the protective room from a base inertization level to a first lowered level in the event of a fire in the protective room. The oxygen concentration in the protective room is maintained at the first lowered level for a preset time interval. The oxygen concentration is decreased to a full inertization level if the fire has not been extinguished by the time the preset time internal has elapsed.

Description

The present invention relates to an inerting method for reducing the risk and extinguishing fires in a shelter, wherein the oxygen content in the shelter is first lowered to a certain baseline inertial level, and then the oxygen content in the shelter is maintained continuously at the basic inertization level.

Such an inerting process is basically known from the prior art. For example, in the German patent DE 198 11 851 C2 an inerting method for reducing the risk and extinguishing indoor fires and a device for carrying out the method described. In this prior art it is envisaged to reduce the oxygen content in an enclosed space (hereinafter called "shelter") to a certain basic inerting level and, in the event of a fire, to further rapidly lower the oxygen content to a certain level of full inertization, thereby effectively extinguishing a fire To allow the lowest possible storage capacity for inert gas cylinders.

This inertization method is based on the knowledge that in enclosed spaces which are only occasionally entered by humans or animals and whose facilities react sensitively to the action of water, the risk of fire can be counteracted by the fact that the oxygen concentration in the affected area has a value of approximately 12% by volume is lowered. At this oxygen concentration, the most combustible materials stop burning. The main areas of application are EDP areas, electrical switch and distribution rooms, enclosed facilities as well as storage areas with high-quality assets. The extinguishing effect resulting from this process is based on the principle of oxygen displacement. The normal ambient air is known to be 21% by volume of oxygen, 78% by volume of nitrogen and 1% by volume of other gases. For the purpose of extinguishing, by introducing nitrogen, the nitrogen concentration in the relevant space is further increased, thereby reducing the oxygen content. It is known that a extinguishing effect begins when the oxygen content drops below 15% by volume. Depending on the flammable materials present in the shelter, a further lowering of the oxygen content to the mentioned 12 vol.% May be required.

The term "base inertization level" as used herein means a reduced oxygen level compared to the oxygen level of normal ambient air, but this reduced level of oxygen does not present any danger to persons or animals, so that they can easily enter the shelter. The basic inerting level corresponds, for example, to an oxygen content in the protected space of 15% by volume, 16% by volume or 17% by volume.

On the other hand, the term "full inertization level" is to be understood as meaning a further reduced oxygen content in comparison to the oxygen content of the basic inertization level, in which the flammability of most materials has already been reduced to such an extent that they can no longer be ignited. Depending on the fire load present in the affected shelter, the full inertization level is usually 11 vol.% Or 12 vol.% Oxygen concentration.

At the time of the DE 198 11 851 C2 known "inert gas extinguishing technology", as the flooding of a fire-prone or in fire room by oxygen-displacing gases, such as carbon dioxide, nitrogen, noble gases and mixtures thereof is called, the oxygen content in the shelter is first to a certain Grundinertisierungsniveau, for example, 16 vol. % lowered, and in case of a fire to a certain Vollinertisierungsniveau further lowered, for example, 12 vol .-% or below. By means of this two-stage inert gas process, in which the basic inerting level is initially set to reduce the risk of fires and in which, if necessary, further nitrogen is introduced by further introduction of inert gas to extinguish a fire, until the full inerting level is reached, the number the container needed for the oxygen displacing in case of fire Inert gases can be kept as small as possible. In particular, in this inertization process known from the prior art, there is no need to provide a relatively large storage capacity for inert gas cylinders in order to be able to set a full inerting level in the protective space in the event of fire.

However, in the practical application of this known method has proven to be problematic that in the inerting process in the event of a fire, that is, when in the atmosphere of the shelter a fire characteristic is detected, the oxygen content in the shelter lowered very quickly to the certain Vollinertisierungsniveau must become. This is done by the fact that in case of fire, the necessary gas volume is introduced into the shelter within a very short time in order to effectively contribute to the extinction of the fire can. Although in the known and described method, the problem of storage of inert gas bottles necessary for adjusting the Vollinertisierungsniveaus has been largely solved, but it has proved to be problematic that when setting the Vollinertisierungsniveaus within a very short time (albeit reduced) gas volume of the inert gas in the Shelter must be initiated, which is often not feasible in terms of the necessary pressure relief of the shelter. Even the inflow of the reduced gas volume to produce the Vollinertisierungsniveaus proves to be particularly problematic in shelters in which no structural relief is provided.

Furthermore, it is provided in the prior art described above, that in the event of a fire, the oxygen concentration in the shelter regardless of the size of the fire or the type of fire by releasing the total amount of extinguished extinguishing agent is lowered to the Vollinertisierungsniveau. In particular, no differentiation is provided in the prior art as to what stage the fire is already located. Thus, the setting of the Vollinertisierungsniveaus regardless of the question of whether, for example, a deep-seated conflagration or just a Schwellbrand is present, or which materials have caught fire in the shelter. For example, if only solids were ignited within the shelter, then full sanitation of the firefighting enclosure would be sufficient to contain about 14% by volume of oxygen to effectively prevent ignition of the solid, since the solids firing limit is about 15% by volume of oxygen lies. On the other hand, if flammable liquids in the shelter have caught fire, which is known to have an ignition limit below 15% by volume, then the full inertization must be carried out to combat the fire to said 12 vol .-% oxygen or less.

In the known method, however - irrespective of the ignition limit of the material burning in the protected area - in principle a Vollinertisierung on, for example, said 11 vol .-% oxygen, so that under certain circumstances significantly more inert gas is supplied to the shelter than it to combat the fire would be necessary.

Based on this problem, the present invention is based on the object, which from the DE 198 11 851 C2 To further develop known and above-described inerting methods for reducing the risk and extinguishing fires in shelters so as to ensure that the use of the method in the shelter does not require any specially provided pressure relief at all, and at the same time to achieve that a fire can follow the amount of inert gas additionally introduced and used for fire fighting, depending on the extent of the fire, so as to be able to save inert gas and make the implementation of the inertization process more cost-effective.

This object is achieved in the inerting method mentioned above in that in the shelter at least or a predetermined times or depending on certain predetermined events at least one fire parameter is measured to determine whether or not in the shelter a fire is present, and that in In the event of a fire in the shelter, the oxygen content is further lowered from the base inertization level to a first lowering level, the oxygen content is continuously maintained for a first predetermined time at this first lowering level, and in a case when the fire is after the first predetermined time has elapsed is not yet extinguished, the oxygen content is lowered from the first subsidence level further to the Vollinertisierungsniveau.

The advantages of the method according to the invention are, in particular, that - in addition to the already known from the prior art advantage of lower storage capacity for inert gas - initially a smaller volume of gas is introduced into the shelter in case of fire, so that provided no structural pressure relief more in the shelter have to be. Thus, can be completely dispensed with pressure relief openings in the shelter. In other words, this means that with the solution according to the invention, the inerting method can be used for firefighting almost every room, especially without that special pressure relief openings must be provided in these premises.

The first descent level is selected to be between the base inerting level at which, to minimize the risk of fire in the shelter, the oxygen content in the shelter is already reduced compared to the oxygen level of the normal atmosphere and the full inertization level at which the flammability the existing materials in the shelter is reduced so much that they can no longer ignite.

It should be noted that the Grundinertisierungsniveau, which is set in advance in the shelter, that is, before the detection of a fire, can correspond to any, compared to the oxygen concentration of the normal atmosphere reduced oxygen concentration at which a free accessibility of the shelter still exists , This basic inerting level may of course also correspond to an oxygen concentration which is different from the 15% by volume described in the beginning. It would be conceivable, for example, to set an oxygen concentration in the protective space of 17% by volume as the basic inerting level, if this is necessary in individual cases.

Since, however, from a medical point of view in compliance with special instructions staying in areas with oxygen-reduced ambient atmosphere (at about 1 bar absolute ambient pressure) up to an oxygen concentration of 13 vol .-% harmless, it would of course also conceivable in the realization of the inerting process according to the invention to set a basic inerting level of, for example, 14% by volume or 13.5% by volume.

It is essential that in the inertization process according to the invention, after lowering the oxygen content to the specific basic inerting level, the oxygen content is also kept continuously at this basic inerting level. This is done, for example, by regularly or continuously measuring the oxygen content in the shelter and by controlled introduction of inert gas into the shelter to maintain the oxygen content at the basic inertization level. Of course, however, it is also conceivable that in addition to the controlled introduction of inert gas for maintaining the Grundinertisierungsniveaus fresh air is introduced into the shelter in a controlled manner, for example, to prevent the oxygen content due to introduction of an excessive amount of inert gas below the Grundinertisierungsniveau falls.

The person skilled in the art recognizes that the term "holding the oxygen content at a certain inertization level" as used herein means maintaining the oxygen content at the inertization level with a certain control range, the control range preferably being dependent on the type of protective space (for example, depending on from an air exchange rate applicable to the shelter or depending on the materials stored in the shelter) and / or depending on the type of inerting plant used, with which the method according to the invention is carried out. Typically, such a control range is 0.1 to 0.4% by volume. Of course, other control range sizes are also conceivable.

In addition to the abovementioned continuous or regular measurement of the oxygen content, however, it is also possible to maintain the oxygen content at the determined inertization level as a function of a previously performed calculation, in which calculation certain design parameters of the protective space are incorporated, such as, for example, the air exchange rate valid for the shelter , in particular the n50 value of the protection space, and / or the pressure difference between the protection space and the environment.

With respect to the full inertization level set in the inertization process of the present invention when the fire has not yet extinguished after the lapse of the first predetermined time, it should be noted that this full inertization level corresponds to an oxygen content at which fire in the shelter is effectively extinguished by oxygen displacement can be. The Vollinertisierungsniveau is chosen in advance depending on the fire load of the shelter and corresponds, for example, an oxygen content of 11 or 12 vol .-% or below. In particular, for shelters in which highly flammable liquid materials are stored, it may be necessary to select an even lower oxygen concentration for the protection chamber-specific full inertization level.

The method according to the invention is characterized in that, in the event of a fire, the oxygen content in the protection space is lowered from the preset initial inerting level to the first lowering level. The lowering to the first lowering level occurs, for example, as a function of a corresponding signal from a fire detection device for detecting a fire parameter in the room air of the protective room.

The term "fire characteristic" is understood to mean physical quantities which undergo measurable changes in the ambient air of an incipient fire, e.g. the ambient temperature, the solid or liquid or gas content in the ambient air (formation of smoke in the form of particles or aerosols or vapor) or the ambient radiation. For example, in the inerting process according to the invention, in particular after the oxygen content has been reduced to the basic inertization level, constantly representative air samples can be taken from the room air in the protected area to be monitored and added to a detector for fire parameters which in case of fire sends a corresponding signal to the inertization process controlling controller for setting the first lowering level outputs. This is a procedural implementation of the connection of a known aspirative fire detection device with the inert gas extinguishing technique, which is based on the inertization process according to the invention.

An aspirative fire detection device is to be understood as a fire detection device which sucks, for example via a pipeline or duct system at a plurality of locations within the shelter, a representative subset of the room air of the protected space to be monitored and this subset then a measuring chamber with the detector for detecting a fire characteristic feeds. In particular, it would be conceivable that this detector for detecting a fire parameter is designed in such a way to output a signal which also makes possible a quantitative statement with regard to the fire parameters present in the sucked subset of the ambient air. Thus, it would be possible to record the time course of the fire or the time course of the development of the fire, so as to determine the effectiveness of setting and holding the different inerting in the shelter. In particular, it would be possible to obtain a statement about which required amount of inert gas still needs to be supplied to the shelter for fire extinguishment.

After lowering the oxygen content from the base inerting level to the first subsidence level, the oxygen content at this first subsidence level is maintained continuously for a first predetermined time. This first predetermined time is advantageously chosen as a function of the shelter, depending on the fire load stored in the shelter and / or depending on other parameters, and is for example 10 minutes. In particular, the first predetermined time should be a time interval which is long enough to be sufficient Accuracy to make a statement as to whether the lowering of the oxygen content of the Grundinertisierungsniveaus to the first subsidence level has led to complete fire extinction in the shelter. On the other hand, the first predetermined time should be a time interval which is sufficiently short to prevent more damage being caused by the delayed setting of the full inertization level in the shelter due to the fire which has broken out there.

Whether or not the fire has extinguished after the expiration of the first predetermined time in the shelter can be determined, for example, by a preferably quantitative measurement of at least one fire parameter in an actively drawn-in representative subset of the room air. Of course, other methods are also conceivable with which it can be determined whether the fire has already extinguished after the first predetermined time in the shelter.

Advantageous developments of the method according to the invention are specified in the subclaims.

Thus, in a particularly preferred realization of the inerting method according to the invention, it is provided that the oxygen content in the shelter is further lowered from the first subsidence level to a second subsidence level other than the full inertization level and maintained continuously at that second subsidence level for a second predetermined time when the second subsidence level Fire after the first predetermined time is not extinguished, and then, if the fire is still not extinguished after the second predetermined time, the oxygen content is lowered from the second lowering level further to the Vollinertisierungsniveau.

The second lowering level of this preferred further development of the inerting method according to the invention is advantageously between the first lowering level and the full inerting level and, like the first lowering level, is selected as a function of the shelter and depending on the fire load stored in the shelter. Of course, however, it is also conceivable to select the first and / or the second lowering level as a function of the technical realization of an inerting system provided for carrying out the inerting process according to the invention.

The advantage of this preferred further development is obvious: by introducing a further lowering level between the first lowering level and the full inerting level, it is possible to adapt the inerting method even more precisely to the protected space to be monitored. In particular, therefore, in a fire, the lowering of the Grundinertisierungsniveau to the Vollinertisierungsniveau about two intermediate lowering levels, whereby the problem described above in terms of the necessary pressure relief in the shelter is further mitigated.

Also, since the oxygen content in the shelter is maintained at the second subsidence level for a second predetermined time, the amount of gas necessary to finally and effectively extinguish the fire can be more accurately adjusted. Thus, it is conceivable, for example, that the fire has not been completely extinguished after the first predetermined time has expired, since materials have caught fire in the protective space whose critical ignition limit is still below the oxygen content which corresponds to the first subsidence level. Since the oxygen content corresponding to the second subsidence level is below the oxygen content of the first subsidence level, setting and maintaining the oxygen content at the second subsidence level for the second predetermined time may also extinguish a fire of materials whose critical ignition limit is below the first subsidence level Lowering levels but above the second lowering level is. In other words, in such a case, effective fire extinguishment is already achievable without having to lower the oxygen content in the shelter to the full inertization level. It can be seen here that in the choice of the first and second lowering levels, the fire load present in the protected space to be monitored can play an important role.

With respect to the second predetermined time during which the oxygen content in the shelter is maintained at the second subsidence level, what has been said above in relation to the first predetermined time is substantially the same.

In order to achieve that the inertisation process according to the invention can effectively extinguish a fire that has broken out in the protection space, even if the reduction of the oxygen content from the base inerting level to the full inertisation level takes place over a plurality of subsidence levels, it is provided in a preferred development that the protection space remains so long the full inertization level is maintained continuously until the fire is completely extinguished. The event of complete extinguishment of the fire in the shelter is detected in a preferred manner again by means of a corresponding detector for detecting fire characteristics. Again, there is again an aspirative fire detection device, as already described above. Of course, with regard to maintaining the oxygen content at the Vollinertisierungsniveau also conceivable that the oxygen content in the shelter may temporarily be well below the critical for Vollinertisierungsniveau oxygen concentration. The lower limit of the control range within which the oxygen content is to be controlled while maintaining the full inertization level may be any value downwards. Of course, to detect the event of complete extinguishment of the fire in the shelter, another method, such as an optical method, is applicable. It would also be conceivable that the Vollinertisierungsniveau is held in the shelter until a manual release, for example, from already arrived emergency services, takes place.

In a further preferred further development of the inerting method according to the invention, it is provided that, after the first and / or the second predetermined time has elapsed, the oxygen content in the protective space is raised again to the basic inerting level if, after the first or the second predetermined time has elapsed, the fire in the protective space has gone out. This is a procedural development, with the result that in the shelter only the amount of gas required for extinguishing fire is supplied, in particular the inerting is gradually reduced until the fire is extinguished, and wherein after the extinguishment of the fire another Reduction of the oxygen content, for example, to the second subsidence level or on the Vollinertisierungsniveau no longer occurs. As a result, in particular inert gas can be saved.

Particularly preferably, in the last-mentioned further development of the inerting process, it is provided that the raising of the oxygen content in the protective space to the basic inerting level occurs after the first or the second predetermined time has elapsed as a function of a further, preferably manual, release. Since this further release can be carried out, in particular, independently of the inerting system which carries out the inertization process according to the invention, in this preferred embodiment there is an increased safety with regard to system faults or errors. Of course, the further release can also be done automatically on the basis of an independent device for detecting a fire parameter in the shelter.

Particularly preferably, in the inertization process according to the invention and in its developments mentioned, it is provided that the first reduction level, which corresponds to a further reduced oxygen content compared to the oxygen content of the base inertization level, is selected as a function of an oxygen content corresponding to the ignition limit value of the fire loads present in the protection space. It should be noted at this point that the ignition limit of a given material may be slightly higher than its extinction limit.

In this case, the inflammatory limit of a substance is preferably determined with a test method of VdS loss prevention as close to reality and reproducibly as possible in the experiment, if this value is unknown for materials or articles. In such an experiment, the solids to be tested are ignited at 20.9 vol .-% oxygen content with an ignition source. The time required for this is measured. In the following, the oxygen content is then lowered in the course of several experiments at defined ambient conditions until the ignition source is allowed to act on the material for a doubled period of time without igniting it. In particular, the following quantities are recorded or adjusted: oxygen content of the test atmosphere; Temperature during the test; Wind speed in the test room; Duration of inflammation; Flame temperature; and humidity in the test room. When determining a corresponding value for a liquid, it is particularly important to additionally record and take into account the air pressure as well as the temperature of the liquid and the environment. To determine the extinction limit while the material is ignited in normal air with 20.9 vol .-% oxygen content. Then the oxygen concentration is slowly reduced until the fire goes out.

For electrical risks, for example, the ignition limit is 15.9 vol.% Oxygen content, while the extinguishing limit corresponds to an oxygen content of 15.5 vol.%. Of course, in addition or as an alternative thereto, the consideration of other parameters is also conceivable in determining the oxygen content corresponding to the first reduction level.

With regard to the second subsidence level, which is further reduced in comparison to the oxygen content of the first subsidence level, provision is advantageously made for it to be selected as a function of an oxygen content corresponding to the extinguishment threshold of the fire loads present in the shelter. It is conceivable in this case in particular that the second lowering level below the oxygen content is equal to the extinguishing limit of existing in the shelter fire loads. Of course, the second level of reduction can also be determined in advance, taking into account other aspects.

For the technical realization of the inertization process according to the invention as well as the preferred further developments described above, it is provided that at least one fire parameter is measured in the shelter, preferably continuously, to determine whether there is a fire in the shelter or if the fire is already extinguished in the shelter , However, the measurement of the fire parameter does not have to be continuous, but it is also conceivable that at predetermined times or depending on certain predetermined events, such a measurement takes place. The measurement of the fire parameter is preferably carried out by means of a detector of the detection of fire parameters, which emits a corresponding signal for further inerting in case of fire. By way of example, representative air samples are taken from the room air in the protected space to be monitored and fed to the fire characteristic detector.

On the other hand, it would also be conceivable that several different fire characteristics are measured in the shelter, preferably continuously, in order to determine the burning material burning in the protection space. This exploits the knowledge that every burning material releases characteristic fire parameters during combustion. These characteristic fire characteristics can thus be used to make statements about the nature of the burning fire, which provides essential advantages in a fire for effective fire fighting and possibly foreseen precautions, especially with regard to a fast, effective and environmentally friendly fire fighting.

In the case of the last-mentioned embodiment, it is particularly preferred that the first and / or the second lowering level be selected depending on the ignition and / or extinguishing limit value of the determined firing material. Accordingly, it is possible to adapt the used inert gas extinguishing technique in an optimal manner to the individual case and in particular to the burning material, which makes it possible that in case of fire, the amount of additional to be introduced into the shelter and used for firefighting inert gas very can be adapted exactly to the extent and type of fire.

As already indicated, the detector is preferably designed in such a way as to provide a quantitative statement with regard to the detected fire parameters, in order thus to monitor the time course of the fire in the protected space to be monitored and to initiate appropriate measures for setting the different oxygen levels. It would be conceivable that the entire inertization process together with the detector for determining the fire characteristic and including a controller for evaluating the output from the detector signals fully automatically or at least partially automatically, so as independent as possible and in some way intelligent inertization to reduce the risk and to clear fires in the shelter.

In a particularly preferred embodiment of the last-mentioned embodiment, in which at least one fire parameter is measured in the protected room to determine whether there is a fire in the shelter, it is provided that this determination as to whether there is a fire in the shelter is dependent on a plurality of measured values of the fire parameter and / or in dependence on a multiplicity of different threshold values of the fire parameters measured in the protected room. This ensures the reliability of the system. In particular, it would be conceivable that the system only notifies a fire when fire characteristics are detected with several different sensors. Furthermore, it is conceivable that the at least one fire parameter is quantitatively measured, whereby the lowering of the oxygen content to the first and / or the second reduction level is effected as a function of the quantitative measured value of the fire parameter. Of course, the same applies to the lowering of the oxygen content to the Vollinertisierungsniveau.

In this context, it is particularly preferably provided that the at least one fire parameter is measured quantitatively, and that the duration of holding the oxygen content at the first and / or second lowering level in dependence on the measured value or the measured values of the fire characteristic (s). Thus, the used inert gas extinguishing technology can be adapted very precisely to the individual case. In particular, it is thus made possible that, in the event of a fire, the amount of inert gas additionally to be introduced into the shelter and to be used for firefighting can be adapted very precisely to the extent and type of fire.

In order to be able to maintain the oxygen content at the initial inertization level, the first reduction level, the second reduction level and / or the full inertization level in the inertization method according to the invention, is preferably provided that in the shelter, preferably continuously, the oxygen content is measured, being introduced controlled depending on the measured oxygen content inert gas in the shelter. In addition to this, or as an alternative to the controlled introduction of inert gas, it would also be conceivable for oxygen, for example in the form of fresh air, to be introduced depending on the measured oxygen content, in order to maintain the inerting level.

Of course, however, it is also conceivable here that the oxygen content is not measured in the protective space in order to make it possible to maintain the set inerting level, but that the concentration of the inert gas contained therein, such as, for example, nitrogen or carbon dioxide, is detected in the protective space with a corresponding detector. It would also be conceivable, in addition to the measurement of the oxygen value or the inert gas value, to determine the required amount of inert gas, which must be introduced into the protective space for holding the set inerting level, by means of an arithmetic calculation. Such a calculation should preferably take place in consideration of protection space-specific parameters, such as the air exchange rate, etc.

In the following, a preferred embodiment of the method according to the invention is explained in more detail with reference to FIGS.

Fig. 1A

der zeitliche Verlauf der Sauerstoffkonzentration in einem Schutzraum bei Anwendung einer bevorzugten Ausführungsform des erfindungsgemäßen Inertisierungsverfahrens;

Fig. 1B

der zeitliche Verlauf eines quantitativen Messwertes der Brandkenngröße bzw. des Rauchpegels im Schutzraum, in welchem die Sauerstoffkonzentration gemäß dem in Fig. 1A gezeigten Kurvenverlauf mit Hilfe der bevorzugten Ausführungsform des erfindungsgemäßen Inertisierungsverfahrens abgesenkt wird;

Fig. 2A

der zeitliche Verlauf der Sauerstoffkonzentration in einem Schutzraum bei der Durchführung einer bevorzugten Ausführungsform des erfindungsgemäßen Inertisierungsverfahrens, wobei nach Ablauf der ersten vorgegebenen Zeit der Brand erloschen ist;

Fig. 2B

der zeitliche Verlauf des quantitativen Messwertes der Brandkenngröße bzw. des Rauchpegels in dem Schutzraum gemäß Fig. 2A.

Fig. 3A

der zeitliche Verlauf der Sauerstoffkonzentration in einem Schutzraum bei der Durchführung einer bevorzugten Ausführungsform des erfindungsgemäßen Inertisierungsverfahrens, wobei nach Ablauf der ersten vorgegebenen Zeit der Brand nicht vollständig erloschen ist; und

Fig. 3B

der zeitliche Verlauf des quantitativen Messwertes der Brandkenngröße bzw. des Rauchpegels in dem Schutzraum gemäß Fig. 3A.

Show it:

Fig. 1A

the time course of the oxygen concentration in a shelter using a preferred embodiment of the inertization process according to the invention;

Fig. 1B

the time course of a quantitative measurement of the fire parameter or the smoke level in the shelter, in which the oxygen concentration according to the in Fig. 1A shown curve is lowered by means of the preferred embodiment of the inertization process according to the invention;

Fig. 2A

the time course of the oxygen concentration in a shelter in carrying out a preferred embodiment of the inertization process according to the invention, wherein after the first predetermined time the fire is extinguished;

Fig. 2B

the time course of the quantitative measurement of the fire characteristic or the smoke level in the shelter according to Fig. 2A ,

Fig. 3A

the time course of the oxygen concentration in a shelter in carrying out a preferred embodiment of the inertization process according to the invention, wherein after the first predetermined time the fire is not completely extinguished; and

Fig. 3B

the time course of the quantitative measurement of the fire characteristic or the smoke level in the shelter according to Fig. 3A ,

Fig. 1A and Fig. 1B show in each case the oxygen concentration and the quantitative measured value of the fire parameter or the smoke level in a protective space to which a preferred embodiment of the inerting method according to the invention is applied. It is shown that the oxygen concentration is lowered to a Grundinertisierungsniveau and kept continuously until the time t0 in the shelter. The Grundinertisierungsniveau corresponds in this preferred example, a concentration of 17.0 vol .-% oxygen in the indoor air of the monitored shelter.

The continuous maintenance of the oxygen content in the shelter at the basic inertization level up to the time t0 is preferably carried out by continuously measuring the oxygen concentration in the shelter and by a controlled introduction of inert gas or fresh air into the shelter. As already mentioned, the term "maintaining the oxygen concentration at a certain inertization level" herein means maintaining the oxygen concentration within a certain control range, that is, within a range defined by upper and lower thresholds. The maximum amplitude of the oxygen concentration in this control range is adjustable in advance and is for example 0.1 to 0.4 vol .-%.

In the concentration curves shown in the figures, the corresponding inertization level always represents the lower threshold value of the control range. Of course, this does not necessarily have to be the case in principle. For example, it is also conceivable that the corresponding inertization level the upper threshold range or the middle range, that is the value between the upper and the lower threshold range, determines.

In the in Fig. 1A In the scenario represented, a fire alarm is emitted by a fire characteristic detector (not shown) to a controller at time t0, which controls the performance of the inertization process according to the invention on an inert gas system. In particular, at this point in time t0, the smoke level or the quantitative measured value of the fire parameter, which is detected continuously or at predetermined times by the fire characteristic detector, has exceeded a first threshold value (alarm threshold 1), as in FIG Fig. 1B can be seen. In response to this fire alarm, the oxygen content in the shelter is further lowered from the baseline inert level to the first descent level. The first lowering level (lowering level 1) in the illustrated curve corresponds to an oxygen concentration of 15.9% by volume. As the timing of the Fig. 1A can be seen, the lowering of the oxygen content to the first lowering level takes place within a shortest possible time. This is made possible by a rapid introduction of a predetermined amount of inert gas. Thus, shortly after alarming the fire alarm, the oxygen concentration in the shelter is lowered to the lowering level 1.

Subsequently, the oxygen concentration is maintained at this first lowering level for a first predetermined time ΔT1. At the same time, the quantitative limit value of the at least one fire parameter in the room air of the protective room is determined continuously with the fire characteristic quantity detector. In the illustrated scenario, the quantitative value of the fire parameter increases steadily in the room air of the shelter, despite the reduction of the oxygen content to the first subsidence level. This is an indication that despite the further reduced oxygen content of the fire in the shelter is not extinguished.

If, what in the in the Figures 1A and 1B As shown in the scenario shown, after the first predetermined time .DELTA.T1 the quantitative measured value of the fire parameter exceeds a second predetermined alarm threshold, it is assumed that the fire has not yet extinguished, so that the fire alarm emitted at the time t0 is confirmed again. Confirmation of the fire alarm at time t1 causes the oxygen concentration in the shelter to be rapidly lowered from the first setback level (for example, 15.9 vol% oxygen) to the second setback level. This is done again by quickly introducing a certain amount of inert gas, so that immediately after the confirmation of the fire alarm at the time t1 the oxygen concentration has reached the second reduction level in the amount of, for example, 13.8 vol .-% oxygen.

At this second descent level, the oxygen content in the shelter is maintained for a second predetermined time ΔT2. This is again done by controlled tracking of inert gas or by controlled introduction of fresh air.

The curve of the Fig. 1B However, it can be seen that the reintroduction of inert gas for adjusting the second lowering level has not led to a complete containment of the broken fire in the shelter. Although the quantitative measured value of the fire parameter initially shows a stagnation in this time window ΔT2, which means that the spread of the fire in the shelter could at least be suppressed, the smoke level or the quantitative measured value of the fire parameter increases again after a certain time and exceeds even the alarm threshold 3, at which a main alarm is triggered. The exceeding of the alarm threshold 3 takes place at the in Fig. 1B illustrated scenario ready before time t2.

After expiration of the second predetermined time .DELTA.T2, that is, at time t2, it is determined in the inertization method according to the invention whether the current quantitative measured value of the fire parameter is above the third alarm threshold (alarm threshold 3). If this is the case for example in the scenario Fig. 1B If this is the case, the fire alarm is confirmed, which means that the fire that has broken out in the shelter has not yet extinguished despite the reduction of the oxygen concentration to the second subsidence level.

The reaffirmation of the fire alarm at time t2 causes the oxygen content in the shelter to be further lowered from the second descent level to the full inertization level, again by rapidly introducing a corresponding amount of inert gas. This corresponding amount of inert gas can be determined in advance depending on the room parameters of the shelter, such as the fire load and the size of the room and the tightness and the air exchange rate of the room. The curve of the Fig. 1A it can be seen that immediately after the time t2, that is immediately after the re-confirmation of the fire alarm, the oxygen concentration has reached the predetermined Vollinertisierungsniveau.

The Vollinertisierungsniveau is designed so that it corresponds to an oxygen concentration that is below the ignition limit of existing materials in the shelter (fire load). By setting the Vollinertisierungsniveaus in the shelter so the fire is completely extinguished by deoxygenation, while effectively preventing reignition of the materials in the shelter.

The curve of the Fig. 1B It can be seen that after setting the Vollinertisierungsniveaus (at time t2), the quantitative measurement of the fire characteristic decreases continuously, which means that the fire is extinguished or extinguished. The full inertization level should be maintained at least until the temperature in the shelter has dropped below the critical limit of ignition of the material. However, it would also be conceivable that the Vollinertisierungsniveau is held until emergency services have arrived and taken by means of a manual release, for example, the inert gas extinguishing system, which operates according to the inerting process according to the invention, from its automatic fire extinguishing mode.

In carrying out the inertization process according to the invention, as exemplified by the Figures 1A and 1B is shown, the Vollinertisierungsniveau is thus set via two intermediate stages, namely the first and the second lowering level. In other words, this means that in the inventive method required for effective fire extinguishing inert gas is released only in subsets, so that in the shelter on pressure relief openings can be dispensed with entirely, or that only much smaller dimensioned pressure relief openings must be provided in the shelter.

In the FIGS. 2A and 2B shows another scenario in which after the first predetermined time .DELTA.T1 the fire in the shelter has already extinguished. The curve of the Fig. 2B In particular, it can be seen that after triggering the fire alarm at the time t0, the quantitative measured value of the fire parameter first stagnates and then continuously decreases, which is an indication that the fire in the shelter has gone out.

At time t1, that is to say after the first predetermined time ΔT1 has elapsed, the quantitative measured value of the fire parameter (cf. Fig. 2B ) below the first alarm threshold, so that at time t1 the fire alarm is not confirmed. By having the fire alarm unconfirmed at time t1, the oxygen concentration in the shelter can be raised again to the basic inertization level the fire in the shelter is extinguished. This can be done for example by controlled introduction of fresh air.

In the inertization process according to the present invention, it is provided that the increase in the oxygen concentration in the shelter to the basic inertization level upon unconfirmed fire alarm is either initiated automatically, for example by the inerting plant, with which the inertization process according to the invention is carried out. Alternatively, however, it would also be conceivable that the increase in the oxygen concentration to the basic inerting level, even with an unconfirmed fire alarm, may only take place with an additional (independent) release. This independent additional release may be, for example, a manual release of emergency services. It would also be conceivable, however, to use a parallel system which is completely self-sufficient for the inerting system in order to determine whether the fire detected in the shelter at time t0 has actually disappeared and whether a re-ignition of the fire may be ruled out.

In the FIGS. 3A and 3B Another scenario is shown in which, after lowering the oxygen concentration in the shelter to the first descent level at time t0 and after maintaining the oxygen concentration at the first descent level for the first predetermined time ΔT1, the fire that has broken out in the shelter is not completely extinguished, which This is noticeable by the fact that the quantitative measured value of the fire parameter in the time window ΔT1 does not decrease continuously, but stagnates or even increases slightly in part. In contrast to the scenarios described above, however, this is a fire that has only been partially extinguished or passed into a swell fire. However, the fire is not large enough that at time t1, ie after the first predetermined time ΔT1, the quantitative measured value of the fire parameter exceeds the second alarm threshold which serves to confirm the fire alarm.

In this case, it is provided in the preferred embodiment of the inertization process according to the invention that the first lowering level is held again for a first predetermined time .DELTA.T1, in order subsequently to be able to make a statement about the fire condition of the protective space, that is to say at time t2. If, at the time t2, that is, after the second expiry of the first predetermined time, the quantitative measured value of the fire parameter is still above the first alarm threshold, it is provided in this illustrated embodiment that the oxygen concentration is further lowered from the first subsidence level to the second subsidence level as the Fig. 3A can be seen.

However, it would also be conceivable that the first lowering level is again held for a further first predetermined time ΔT1, and that subsequently a decision is made with regard to the further course of action.

As already described above, the first and the second predetermined time ΔT1 and ΔT2 are selected application-specific. Furthermore, it should be noted that the oxygen concentrations, which correspond to the respective inerting levels in the illustrated embodiments, are of course only exemplary. It should also be noted that the decision criteria and scenarios described above with regard to the first subsidence level are, of course, also applicable analogously with regard to the second subsidence level.

It should be noted at this point that, for example, in the German patent DE 198 11 851 C2 described inerting can be used to carry out the inertization process according to the invention.

The inventive method requires the regular or continuous monitoring of the oxygen content and the fire characteristics content in the target area. For this purpose, the oxygen concentration or the inert gas concentration and the quantitative value of the fire parameter or the concentration of the smoke level in the target area is regularly and permanently determined by appropriate sensors and fed to a controller of an inert gas fire extinguishing system, in response to the extinguishing agent supply or the fresh air supply to the target area controls.

Although the method according to the invention has been described above with two intermediate stages (first and second subsidence level), it is of course also possible for the method according to the invention to have more than two intermediate stages in order to allow an even better adaptation of the method to the protective space.

Claims (17)

1. Inertization method for reducing the risk of fires and for extinguishing fires in a protected room, with the following method steps:

   a) the oxygen content in the protected room is lowered to a specified basic inertization level;

   b) the oxygen content in the protected room is continuously held at the basic inertization level;
   characterized by
   the following further method steps:

   c) at least one fire characteristic is measured in the protected room continuously, or at predetermined times, or in dependence upon specified predetermined occurrences, in order to determine whether or not there is a fire in the protected room;

   d) in the event of a fire in the protected room, the oxygen content in the protected room is further lowered from the basic inertization level to a first lowered level;

   e) the oxygen content in the protected room is continuously held for a first predetermined time at the first lowered level; and

   f) the oxygen content in the protected room is further lowered from the first lowered level to a full inertization level if the fire has still not gone out after expiry of the first predetermined time.
2. Inertization method according to Claim 1, wherein the oxygen content in the protected room is further lowered from the first lowered level first to a second lowered level, which is different from the full inertization level, and continuously held at the second lowered level for a second predetermined time if the fire has still not gone out after expiry of the first predetermined time, and wherein the oxygen content in the protected room is then further lowered from the second lowered level to the full inertization level if the fire has still not gone out even after expiry of the second predetermined time.
3. Inertization method according to Claim 1 or 2, wherein in the protected room the full inertization level is continuously held at least until the fire in the protected room has gone out.
4. Inertization method according to one of the preceding claims, wherein, after expiry of the first or of the second predetermined time, the oxygen content in the protected room is raised again to the basic inertization level if the fire in the protected room has gone out after expiry of the first or of the second predetermined time.
5. Inertization method according to Claim 4, wherein the raising of the oxygen content in the protected room to the basic inertization level after expiry of the first or of the second predetermined time is carried out in dependence upon a further, preferably manual, release.
6. Inertization method according to one of the preceding claims, wherein:

   - the basic inertization level corresponds to an oxygen content which is reduced in comparison to the oxygen content of the ambient air;

   - the first lowered level corresponds to an oxygen content which is further reduced in comparison to the oxygen content of the basic inertization level;

   - the second lowered level corresponds to an oxygen content which is further reduced in comparison to the oxygen content of the first lowered level; and

   - the full inertization level corresponds to an oxygen content which is further reduced in comparison to the oxygen content of the second lowered level.
7. Inertization method according to one of the preceding claims, wherein the first lowered level is selected in dependence upon an oxygen content which corresponds to the ignition limiting value of the fire loads which are present in the protected room.
8. Inertization method according to Claim 7, wherein the first lowered level is identical to the oxygen content which corresponds to the ignition limiting value of the fire loads which are present in the protected room.
9. Inertization method according to one of the preceding claims, wherein the second lowered level is selected in dependence upon an oxygen content which corresponds to the extinguishing limiting value of the fire loads which are present in the protected room.
10. Inertization method according to Claim 9, wherein the second lowered level lies below the oxygen content which corresponds to the extinguishing limiting value of the fire loads which are present in the protected room.
11. Inertization method according to one of the preceding claims, wherein in the protected room at least one fire characteristic is measured, preferably continuously, in order to determine whether there is a fire in the protected room.
12. Inertization method according to one of the preceding claims, wherein in the protected room a plurality of fire characteristics are measured, preferably continuously, in order to determine the flammable material which is burning in the protected room.
13. Inertization method according to Claim 12, wherein the first and/or the second lowered level is, or are, selected in dependence upon the ignition limiting value and/or extinguishing limiting value of the determined flammable material.
14. Inertization method according to Claim 12 or 13, wherein the determining of whether there is a fire in the protected room is carried out in dependence upon a multiplicity of measured values of the fire characteristic and/or in dependence upon a multiplicity of different threshold values of the fire characteristics which are measured in the protected room.
15. Inertization method according to one of Claims 12 to 14, wherein the at least one fire characteristic is quantitatively measured, and wherein the lowering of the oxygen content in the protected room to the first lowered level, to the second lowered level and/or to the full inertization level is carried out in dependence upon the quantitative measured value of the fire characteristic.
16. Inertization method according to one of Claims 12 to 15, wherein the at least one fire characteristic is quantitatively measured, and wherein the duration of the holding of the oxygen content at the first and/or at the second lowered level is carried out in dependence upon the quantitative measured value of the fire characteristic.
17. Inertization method according to one of the preceding claims, wherein in the protected room the oxygen content is measured, preferably continuously, and wherein the holding of the oxygen content at the basic inertization level, at the first lowered level, at the second lowered level and/or at the full inertization level, is carried out by a controlled feed of inert gas and/or by a controlled feed of oxygen, for example in the form of fresh air.

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