Abstract
The present invention relates to a system as well as a method for extinguishing fire in an enclosed room (6) in which the enclosed room (6) is flooded with extinguishing gas at least until an extinguishing gas concentration capable of providing an extinguishing effect (a) is set in the flood zone. In order to achieve the realizing of a maximum extinguishing gas concentration (b) as quickly as possible without the flooding of the room (6) thereby posing a danger to people, it is inventively provided for the flooding of the enclosed room (6) to be divided into a pre-flooding phase and a main flooding phase subsequent thereto. The pre-flooding phase corresponds to an interval of time between the time (t.sub.1) the alarming starts to warn people of impending danger and a predefined time (t.sub.2). The main flooding phase corresponds to an interval of time between the predefined time (t.sub.2) and the time (t.sub.4) at which a maximum extinguishing gas concentration (b) is reached. The enclosed room (6) is flooded such that during the entire pre-flooding phase, the concentration of extinguishing gas in the enclosed room (6) does not exceed a predefined or predefinable value for the extinguishing gas employed which is below the critical NOAEL value.
Claims
1. A fire extinguishing system for extinguishing fire in an enclosed room by flooding the enclosed room with an extinguishing gas in a regulated manner, wherein the fire extinguishing system comprises: at least one extinguishing gas source for supplying the extinguishing gas; an extinguishing gas supply pipeline system configured to supply the extinguishing gas from the at least one extinguishing gas source to the enclosed room; and a control unit for setting an amount of extinguishing gas supplied to the enclosed room per unit of time, the control unit is configured to: adjust the amount of extinguishing gas supplied to the enclosed room per unit of time in an event of a fire or upon a manual actuation such that the enclosed room is flooded according to a predefined sequence of events, flood, during a pre-flooding phase lasting from an initial point in time up to a predefined point in time, the enclosed room with a concentration of the extinguishing gas that does not exceed a predefined or predefinable value for the extinguishing gas employed which is lower than the critical no-observed-adverse-effect level (NOAEL) value for the extinguishing gas employed, maintain, during a first sustained flooding phase subsequent to the pre-flooding phase, the concentration of the extinguishing gas in the enclosed room at the predefined or predefinable value based on a determination that the fire is not present in the enclosed room after the pre-flooding phase ends, flood, during a main flooding phase subsequent to the pre-flooding phase, the enclosed room with a maximum concentration of the extinguishing gas based on a determination that the fire in the enclosed room has not yet been extinguished or not completely extinguished.
2. The fire extinguishing system according to claim 1, further comprising a visual and/or acoustic alarm configured to provide a visual and/or acoustic warning for any persons within the enclosed room, wherein the control unit is configured to initiate the release of the extinguishing gas immediately upon the triggering of the visual and/or acoustic alarm.
3. The fire extinguishing system according to claim 1, further comprising at least one sensor configured to detect at least one fire characteristic in a spatial atmosphere of the enclosed room, wherein the control unit is further configured to initiate the pre-flooding phase when at least one fire characteristic is detected in the spatial atmosphere of the enclosed room.
4. The fire extinguishing system according to claim 1, further comprising: a first triggering component configured to connect a first extinguishing gas source to the enclosed room; and a second triggering component configured to connect a second extinguishing gas source to the enclosed room, wherein the control unit is further configured to trigger the first triggering component at a start of the the pre-flooding phase and to trigger the second triggering component at a start of the main flooding phase.
5. The fire extinguishing system according to claim 1, further comprising: a valve configured to connect the at least one extinguishing gas source to the enclosed room, and wherein the control unit is further configured to control the valve and partly open the valve during the pre-flooding phase and completely open the valve during the main flooding phase.
6. The fire extinguishing system according to claim 1, further comprising: a stop button connected to the control unit and configured to stop the pre-flooding phase when the stop button is actuated.
7. The fire extinguishing system according to claim 1, further comprising: at least one sensor configured to detect an oxygen content in ambient air of the enclosed room; and the control unit is further configured to set the amount of extinguishing gas supplied to the enclosed room per unit of time at least during the pre-flooding phase as a function of the detected oxygen content.
8. The fire extinguishing system according to claim 1, further comprising: an extinguishing gas generator connected to the enclosed room; and a valve configured to connect a further extinguishing gas source to the enclosed room, wherein the control unit is further configured to activate the extinguishing gas generator during the pre-flooding phase and actuate the valve, connected to the further extinguishing gas source, during the main flooding phase.
9. The fire extinguishing system according to claim 1, wherein the pre-flooding phase is at least 10 seconds.
Description
(1) Shown are:
(2) FIG. 1a: the temporal gradient of the extinguishing gas concentration in the enclosed room in a conventional fire extinguishing system in which a time-delayed flooding with advance warning period occurs;
(3) FIG. 1b: the temporal gradient of the oxygen concentration in the enclosed room during the flooding gradient shown in FIG. 1a;
(4) FIG. 2a: the temporal gradient of the extinguishing gas concentration in the enclosed room in an exemplary embodiment of the inventive fire extinguishing system in which no time-delayed flooding occurs;
(5) FIG. 2b: the temporal gradient of the oxygen concentration in the enclosed room during the flooding depicted in FIG. 2a;
(6) FIG. 3 a schematic view of one embodiment of the fire extinguishing system according to the invention;
(7) FIG. 4 a schematic view of a further embodiment of the fire extinguishing system according to the invention; and
(8) FIG. 5 a schematic view of a further embodiment of the fire extinguishing system according to the invention;
(9) FIG. 6 the temporal gradient of the extinguishing gas concentration in the enclosed room according to a further embodiment of the inventive fire extinguishing system with a first sustained flooding phase subsequent the pre-flooding phase;
(10) FIG. 7 the temporal gradient of the extinguishing gas concentration similar to the inventive fire extinguishing system depicted in FIG. 6 with a main flooding phase and subsequent second sustained flooding phase subsequent to the first sustained flooding phase;
(11) FIG. 8 the temporal gradient of the extinguishing gas concentration similar to the FIG. 2a depiction with a second sustained flooding phase subsequent the main flooding phase.
(12) FIG. 1a shows the flooding gradient of a conventional fire extinguishing system; i.e. the development of the extinguishing gas concentration in the enclosed room in which a time-delayed flooding with advance warning period occurs over time. In detail, FIG. 1a depicts the extinguishing gas concentration set in the enclosed room in relation to the time. An IT room serves as the enclosed room in the flooding gradient shown in FIG. 1a. FIG. 1b shows the development of the oxygen concentration in the enclosed room over time when, as shown in FIG. 1a, said room is flooded. CO.sub.2 serves as the extinguishing gas in the example shown in FIG. 1a.
(13) The t.sub.0 time indicates the point in time at which a fire detection device responds or respectively the point in time of a manual trigger being activated if same is provided. Due to equipment/system-related contingencies, the responding of an alarm mechanism to warn personnel within the extinguishing/hazard zone at time t.sub.1 normally follows with a slight delay compared to the responding of the fire detection device at time t.sub.0. Since fire extinguishing systems with which persons can be endangered by a flooding of the extinguishing zone must be equipped with delay mechanisms, a delayed flooding with advance warning period occurs in the flooding gradient shown in FIG. 1a. Specifically, the interval between time t.sub.1 (alarm mechanism response) and time t.sub.2 (gaseous extinguishing agent release) indicates the advance warning period to be provided for personnel safety reasons which needs to be calculated such that any given point within the extinguishing zone, the enclosed room respectively, can be exited without haste. According to the VdS 3518 Guidelines (July 2006) or the BGI 888 (January 2004), this advance warning period must be at least 10 seconds.
(14) Therefore, the accumulative flooding in the example known from the prior art shown in FIG. 1a does not start until time t.sub.2 since the gaseous extinguishing agent is not allowed to be released until this point in time. As can be noted from the FIG. 1a depiction, the extinguishing agent concentration increases relatively rapidly as of time t.sub.2 and reaches maximum extinguishing gas concentration b at time t.sub.4. An extinguishing gas concentration capable of providing an extinguishing effect a is already present at time t.sub.3. The t.sub.2-t.sub.3 interval is identified as the period for building up the extinguishing gas concentration capable of providing an extinguishing effect and the t.sub.2-t.sub.4 interval is identified as the accumulative flooding period. Maximum extinguishing gas concentration b is reached at time t.sub.4. This point in time thus marks the end of the accumulative flooding. Since no sustained flooding is provided for in the flooding gradient depicted in FIG. 1a, the extinguishing gas concentration continuously decreases as of time t.sub.4, which is attributable to leakages in spatial shell of the enclosed room. In consequence thereof, the extinguishing gas concentration capable of providing an extinguishing effect a is undershot at time t.sub.6. The interval between time t.sub.4 (end of accumulative flooding) and time t.sub.6 (falling below the extinguishing gas concentration capable of providing an extinguishing effect) should be long enough so that material within the enclosed room cools down sufficiently and reigniting can be prevented.
(15) It is to be kept in mind that according to the VdS Guidelines, the extinguishing gas concentration capable of providing an extinguishing effect a must be reached within 10, 60 or 120 seconds after the extinguishing agent has been released. Particularly in the case of rooms which enclose a large volume, such as for example high-bay storage facilities, etc. this requirement can only be met at relatively high expenditure. Conventional fire extinguishing systems must in particular be dimensioned such that they are able to introduce the necessary amount of extinguishing gas into the enclosed room so as to reach the concentration capable of providing an extinguishing effect a within delayed interval t.sub.2-t.sub.3.
(16) FIG. 1b depicts the temporal gradient of the oxygen concentration in the enclosed room (here: IT room) when, as shown in FIG. 1a, the enclosed room is flooded.
(17) According thereto, the oxygen concentration in the enclosed room is at a constant value (20.9 vol %) up until time t.sub.2, this value corresponding to the average ambient air oxygen content. Since accumulative flooding does not occur until time t.sub.2 according to the FIG. 1a representation, the oxygen concentration drops relatively rapidly in the FIG. 1b representation only as of this point in time and reaches a minimum value of 11.2 vol % at time t.sub.4. Since the flooding gradient depicted in FIG. 1a does not provide for any sustained flooding, the oxygen concentration continuously increases as of time t.sub.4 as ambient air infiltrates through leakages in the spatial shell of the enclosed room.
(18) The following will make reference to the representations provided in FIGS. 2a and 2b. FIG. 2a thereby shows the flooding gradient; i.e. the development of the extinguishing gas concentration in the spatial atmosphere of the enclosed room over time with a fire extinguishing system according to an exemplary embodiment of the inventive solution. FIG. 2b depicts the corresponding temporal development of the oxygen concentration in the spatial atmosphere of the enclosed room. The t.sub.0, t.sub.1, t.sub.2, t.sub.3, t.sub.4, t.sub.5 and t.sub.6 time points indicated on the time axis (x-axis) are accorded the same meaning as the corresponding time points in FIG. 1a. The y-axis, which in FIG. 2a illustrates the extinguishing gas concentration in the spatial atmosphere of the enclosed room, depicts the extinguishing gas concentration capable of providing an extinguishing effect as a and the maximum extinguishing gas concentration as b. As previously stated, the value of the extinguishing gas concentration capable of providing an extinguishing effect a depends on the fire load of the materials within the enclosed room. Such a characteristic extinguishing gas concentration capable of providing an extinguishing effect a for the enclosed room is called the design concentration in the fire technology field.
(19) In contrast to the flooding gradient depicted FIG. 1a, no time-delayed flooding occurs according to the teaching of the present invention. Instead, extinguishing gas is already being introduced into the enclosed room at time t.sub.1 (alarm mechanism response). The extinguishing gas concentration in the spatial atmosphere of the enclosed room insofar already starts rising at time t.sub.1. However, in order to be able to exclude risk to any people who may be in the enclosed room at the start of flooding (time t.sub.1), it is inventively provided for the extinguishing gas concentration of the extinguishing gas employed not to exceed a predefined or predefinable value a.sub.0 during an advance warning period which ends at time t.sub.2. This predefined or predefinable limit value a.sub.0 may not exceed the critical NOAEL value for the extinguishing gas employed and is preferably below said NOAEL value.
(20) The limit value a.sub.0 is in particularly dependent on the fire load of the enclosed room 6; i.e. is to be definable or predefined as a function of the fire load of the enclosed room. In order to minimize the time for building up the extinguishing gas concentration capable of providing an extinguishing effect a, is it advantageous according to the inventive method for the predefined or predefinable limit value a.sub.0 to be established no later than time t.sub.2, at which the advance warning period ends.
(21) As is also the case with conventional fire extinguishing systems, an acoustic and/or if needed visual alarm occurs in the inventive solution as of time t.sub.1 so as to warn any people there may be within the extinguishing zone. The advance warning period, which corresponds to the t.sub.1-t.sub.2 interval, is calculated such that the extinguishing zone; i.e. the enclosed room, can be exited from any given spot so as to ensure the evacuation of the enclosed room at time t.sub.2.
(22) In order not to waste any time, the point in time at which the acoustic and/or if needed visual alerting is triggered corresponds to time t.sub.1 as of which the extinguishing gas is introduced into the enclosed room 6 in the course of the pre-flooding phase. The entire time interval t.sub.2-t.sub.1 or t.sub.2-t.sub.0 respectively is thereby available to order to able to ensure the evacuation of personnel from enclosed room 6.
(23) Comparing the flooding gradients of FIG. 1a and FIG. 2a shows that a specific extinguishing gas level is already set at time t.sub.2 in the inventive solution. This extinguishing gas level at time t.sub.2 corresponds to an extinguishing gas concentration a.sub.0 in the enclosed room below the critical NOAEL concentration for the extinguishing gas employed. Because a specific extinguishing gas level a.sub.0 has already been established in the enclosed room at time t.sub.2 (end of the advance warning period) in the flooding gradient according to FIG. 2a, the amount of extinguishing gas introduced into the enclosed room per unit of time needed to reach the maximum extinguishing gas concentration b at time t.sub.4 can be reduced in comparison to conventional solutions known from the prior art. This becomes apparent in the FIG. 2a representation by the fact of there being a lesser inclination to the flooding curve over the t.sub.2-t.sub.4 interval (flooding period of the accumulative flooding) compared to the gradient of the flooding curve depicted in FIG. 1a. The inventive solution thus enables a more temperate flooding of the enclosed room compared to the prior art, in consequence of which the pressure relief areas to be provided can be of smaller dimension.
(24) The t.sub.1-t.sub.2 interval; i.e. the time between the alarm mechanism response and the end of the advance warning period, is thus used according to the inventive solution to initially flood the extinguishing zone. The t.sub.1-t.sub.2 interval is also referred to herein as the pre-flooding phase. The so-called main flooding phase, corresponding to the t.sub.2-t.sub.4 interval, immediately follows the pre-flooding phase. In the flooding gradient shown in FIG. 1a, this interval corresponds to the total flooding time provided for the accumulative flooding.
(25) FIG. 2a depicts a flooding gradient which can be realized with an exemplary embodiment of the inventive fire extinguishing system. In the FIG. 2a flooding gradient, the amount of extinguishing gas introduced into the enclosed room per unit of time during the pre-flooding phase (t.sub.1-t.sub.2 interval) is just the same as the amount of extinguishing gas introduced into the enclosed room per unit of time during the main flooding phase (t.sub.2-t.sub.4 interval). This can then be realized when it is ensured that the extinguishing gas concentration capable of providing an extinguishing effect a is reached within the prescribed time interval after the fire extinguishing system being activated. Pursuant the VdS Guidelines, this interval is 60 or 120 seconds.
(26) In order to fundamentally ensure that the extinguishing gas concentration capable of providing an extinguishing effect a is reached within the predefined t.sub.0-t.sub.3 interval, it is necessary as applicable for the amount of extinguishing gas introduced into the enclosed room per unit of time during the main flooding phase (t.sub.2-t.sub.4 interval) to be greater than the amount of extinguishing gas introduced into the enclosed room per unit of time during the pre-flooding phase (t.sub.1-t.sub.2 interval).
(27) The following will reference the FIG. 3 representation in describing a feasible embodiment of the inventive fire extinguishing system 100. In the embodiment according to FIG. 3, the inventive fire extinguishing system 100 is used as a stationary area protection system and serves to protect all the contents of the room identified by reference numeral 6. Said room 6 is an enclosed room such as, for example, a high-bay storage facility, IT room or a switching/distribution cabinet.
(28) The fire extinguishing system 100 according to the schematic representation of FIG. 3 comprises an extinguishing gas source 8 for supplying an extinguishing gas. Used as the extinguishing gas source 8 in the embodiment depicted in FIG. 3 is a battery of compressed gas cylinders which keeps in store the amount of extinguishing gas required for both the pre-flooding phase as well as also the main flooding phase and, if applicable, also the sustained flooding phase.
(29) The individual compressed gas cylinders of extinguishing gas source 8 can be connected by means of valves 11 to a pipeline system 1a, 1b which is in turn connected to nozzles 2 appropriately distributed within the enclosed room 6. In the event of a fire, the compressed gas cylinder tank valves 11 are opened so that the extinguishing gas provided in the compressed gas cylinders can be fed into the enclosed room 6 via the pipeline system 1a, 1b and nozzles 2.
(30) The individual compressed gas cylinder tank valves 11 can preferably be triggered automatically by means of a control unit 10. The (selectively) automatic triggering can ensue by means of mechanical, pneumatic or electrical systems and/or a combination of the aforementioned possibilities.
(31) The flooding of the enclosed room 6 with extinguishing gas is initiated by the control unit 10 at time t.sub.1 as soon as a fire sensor 4 provided in the enclosed room 6 signals the control unit 10 of the presence of at least one fire characteristic in the ambient air of enclosed room 6.
(32) So that the extinguishing gas concentration in the enclosed room 6 will not exceed the predefined or predefinable value a.sub.0 for the extinguishing gas employed during the pre-flooding phase, the embodiment depicted in FIG. 3 makes use of a regulating valve 3 able to be controlled by the control unit 10. Specifically, this regulating valve 3 divides the pipeline system 1a, 1b by means of which the extinguishing gas source 8 is connected to the nozzles 2 into a first section 1a and a second section 1b. These two pipeline sections 1a, 1b are connectable via the regulating valve 3.
(33) The control unit 10 in the embodiment of the inventive fire extinguishing system 100 depicted in FIG. 3 is designed so as to control the valve mechanism 3 such that it is only partly open during the pre-flooding phase and completely open during the main flooding phase. Specifically, the control unit 10 controls the valve mechanism 3 during the pre-flooding phase such that the concentration of extinguishing gas in the enclosed room 6 does not exceed the predefined critical concentration value a.sub.0 during the pre-flooding phase.
(34) As can be further seen from the FIG. 3 representation, the inventive fire extinguishing system 100 preferably comprises a visual and/or acoustic alarm mechanism 5. This alarm mechanism 5 serves to warn any people who may be inside the enclosed room 6. To this end, the alarm mechanism 5 is connected to the control unit 10, whereby the control unit 10 immediately activates the alarm mechanism 5 as soon as the fire sensor 4 notifies the control unit 10 of the presence of at least one fire characteristic in the ambient air of enclosed room 6. Alternatively or additionally hereto, it is also conceivable for the control unit 10 to trigger the alarm mechanism 5 when the fire extinguishing system 100 has been manually triggered, for example by the actuating of a manual trigger.
(35) At least one sensor 12 is further provided for detecting the oxygen content in the spatial atmosphere of the enclosed room 6. The control unit 10 receives the values detected by the oxygen sensor 12 continuously or at predetermined times or upon predetermined events and regulates the amount of extinguishing gas supplied to the enclosed room 6 per unit of time as a function of the detected oxygen content, at least during the pre-flooding phase.
(36) As can be further noted from the FIG. 3 representation, a pressure relief flap 7 is provided in the spatial shell of the enclosed room 6. This pressure relief flap 7 serves to prevent damage to the room 6 due to high excess pressure when the enclosed room 6 is flooded in response to a fire.
(37) The following will reference the FIG. 4 representation in describing a further embodiment of the inventive fire extinguishing system 100. The fire extinguishing system 100 depicted in FIG. 4 substantially corresponds to the system described above with reference to the FIG. 3 representation, whereby however an alternative solution is used to keep ready the amount of extinguishing gas necessary for flooding the enclosed room 6.
(38) In detail, the embodiment of the inventive fire extinguishing system 100 schematically depicted in FIG. 4 provides for a first extinguishing gas source 8a in which the amount of extinguishing gas needed for the pre-flooding phase is held and a second extinguishing gas source 8b in which the amount of extinguishing gas needed for the main flooding phase is held. Since the amount of extinguishing gas needed for the pre-flooding phase is usually less than the amount of extinguishing gas needed for the main flooding phase, the first extinguishing gas source 8a can beas FIG. 4 indicatesof smaller dimensions than the second extinguishing gas source 8b. In the embodiment of the inventive fire extinguishing system 100 depicted in FIG. 4, respective batteries of compressed gas cylinders are used for the first and second extinguishing gas sources 8a, 8b.
(39) In the event of fire, or when the fire extinguishing system 100 is activated respectively, the control unit 10 actuates a first triggering mechanism 3a at time t.sub.1. This first triggering mechanism 3a serves to mechanically, pneumatically or electrically open the respective tank valves 11 of the individual compressed gas cylinders of the first extinguishing gas source 8a so that the amount of extinguishing gas kept in store in the first extinguishing gas source 8a can be fed into the enclosed room 6 via the pipeline system 1 and nozzles 2. At time t.sub.2; i.e. after the advance warning period has ended, or at the end of the pre-flood phase respectively, the control unit 10 actuates a second triggering mechanism 3b which opens the respective tank valves 11 of the individual compressed gas cylinders of the second extinguishing gas source 8b so that the amount of extinguishing gas kept in store by the second extinguishing gas source 8b can be fed into the enclosed room 6 via the pipeline system 1 and nozzles 2. The control unit 10 is thereby designed such that the time t.sub.2, at which the second triggering mechanism 3b is activated and the second extinguishing gas source 8b triggered, can be predefined.
(40) The following will reference the FIG. 5 representation in describing a further embodiment of the inventive fire extinguishing system 100. This embodiment differs from the systems schematically depicted above with reference to the FIGS. 4 and 5 representations by an alternative realization of the extinguishing gas sources which supply the extinguishing gas needed to flood the enclosed room 6.
(41) In detail, an inert gas generator is provided in the embodiment of the inventive fire extinguishing system 100 depicted in FIG. 5. Same comprises a compressor 9a and a downstream filtering device 9b, particularly a membrane filter device. The compressor 9a compresses ambient air which is thereafter fed to the filtering device 9b. A gas separation occurs in the filtering device 9b such that nitrogen-enriched air is yielded at one outlet 12 of the filtering device 9b of the inert gas generator and oxygen-enriched air is yielded at another outlet 13 of the filtering device 9b of the inert gas generator. In the embodiment depicted in FIG. 5, the nitrogen-enriched air serves as the extinguishing gas supplied to the enclosed room 6 during the pre-flooding phase. For this purpose, the corresponding outlet 12 of the filtering device 9b of the inert gas generator is connected to the enclosed room 6 by means of a pipeline system 1 and nozzles 2.
(42) In the event of fire, or when the fire extinguishing system 100 is actuated respectively, the control unit 10 activates the inert gas generator, and particularly compressor 9a, at time t.sub.1. In consequence thereof, the inert gas generator provides nitrogen-enriched air which is supplied to the enclosed room 6 by a pipeline system 1 allocated to the inert gas generator or by pipeline system 1 if applicable. The amount of nitrogen-enriched air supplied per unit of time during the pre-flooding phase can be regulated by control unit 10, for example by accordingly varying the output of compressor 9a.
(43) On the other hand, the extinguishing gas needed for the main flooding phase is provided by a further extinguishing gas source 8c. This further extinguishing gas source 8c is again realized as a battery of compressed gas cylinders in the embodiment of the inventive fire extinguishing system 100 depicted in FIG. 5. Moreover provided is a triggering mechanism 3c allocated to the further extinguishing gas source 8c. The control unit 10 can open the respective tank valves 11 of the individual compressed gas cylinders of the further extinguishing gas source 8c by means of this triggering mechanism 3c, this occurring at time t.sub.2; i.e. subsequent to the pre-flooding phase and at the end of the advance warning period. The extinguishing gas kept in store by the further extinguishing gas source 8c during the main flooding phase then flows through the pipeline system 1 to the nozzles 2 and from there into the enclosed room 6.
(44) FIG. 6 yields a further flooding gradient which is similar to the FIG. 2a flooding gradient up until the predefined time (t.sub.2) constituting the end of the pre-flooding phase. In the FIG. 6 embodiment, a first sustained flooding phase (interval t.sub.2-t.sub.2a) follows the pre-flooding phase (interval t.sub.1-t.sub.2) during which the concentration of extinguishing gas in the enclosed room 6 is kept at predefined or predefinable value a.sub.0. Thus, potential flare-ups due to the oxygen concentration increasing again in the enclosed room 6 in the absence of the first sustained flooding phase is effectively prevented or such a risk of re-ignition is considerably reduced during this first sustained flooding phase from time t.sub.2 to time t.sub.2 to time t.sub.2a, particularly in the case of fire being present prior to the first sustained flooding phase; i.e. during the pre-flooding phase.
(45) The flooding gradient pursuant to FIG. 6 hereby represents the case of no fire being determined within the enclosed room when the status of enclosed room 6 is checked. It is particularly conceivable here for a manual resetting to occur at t.sub.2a; i.e. that the end of the first sustained flooding phase occurs at time t.sub.2a by the manual actuating of a corresponding apparatus, for example a button. Subsequent to t.sub.2a, which marks the end of the first sustained flooding phase, the supply of extinguishing gas therefore stops such that the concentration of extinguishing gas decreases again as time continues.
(46) In contrast thereto, it is evident from the FIG. 7 flooding gradient that a main flooding phase (interval t.sub.2a-t.sub.4) follows the first sustained flooding phase also provided here. Similar to that as previously stated in conjunction with the FIG. 2a flooding gradient, an effective extinguishing gas concentration a is reached at time t.sub.3 during the main flooding phase. After time t.sub.3, extinguishing gas continues to be supplied during the main flooding phase until maximum extinguishing gas concentration b is reached. In contrast to the embodiment depicted in FIG. 2a, however, a second sustained flooding phase now follows at time t.sub.4, during which extinguishing gas is further fed into the enclosed room 6 in regulated manner such that the extinguishing gas concentration capable of providing an extinguishing effect in dependence on the fire load of the enclosed room 6 is not exceeded over the course of the entire second sustained flooding phase (interval t.sub.4-t.sub.6). The t.sub.4-t.sub.6 interval which denotes the second sustained flooding phase is hereby selected for example such that the materials within the enclosed room will cool down and thus renewed combustion (reigniting) during this period be effectively prevented. In this context, compared to the embodiment from FIG. 2a, the fact that unknown possibly large leakages from enclosed room 6 will not contribute to reducing the interval of time between the end of the accumulative flooding and the time at which the extinguishing gas concentration capable of providing an extinguishing effect is undershot after the main flooding phase to the extent of not being able to effectively prevent such re-ignition is hereby particularly advantageous.
(47) Lastly, FIG. 8 shows an exemplary flooding gradient in which a second sustained flooding phase (interval t.sub.4-t.sub.6) is likewise provided subsequent to the main flooding phase. In contrast to the embodiment according to FIG. 7, however, no first sustained flooding phase is provided here. In other words, the main flooding phase directly follows the pre-flooding phase in the flooding gradient according to the FIG. 8 embodiment. The main flooding phase is in turn directly followed by the second sustained flooding phase, during which the extinguishing gas concentration in the enclosed room is always kept above the extinguishing gas concentration capable of providing an extinguishing effect by the regulated post-feeding of extinguishing gas. This embodiment thus corresponds to a situation in which the checking of the enclosed room's status yields the fact that a fire which broke out in the enclosed room 6 has not been suppressed or not sufficiently suppressed following the end of the pre-flooding phase and thus a main flooding phase is to proceed immediately after the pre-flooding phase so as to reach the extinguishing gas concentration capable of providing an extinguishing effect a as quickly as possible. It is hereby in turn conceivable for time t.sub.6, which marks the end of the second sustained flooding phase, to be either predefined or manually defined at a later point in time. A manual defining at a later point in time thus corresponds to a manual reset which can occur upon determining, for example by manual verification, that a fire which broke out in the enclosed room 6 has not been suppressed or not sufficiently suppressed following the end of the pre-flooding phase.
(48) The solution according to the invention is not limited to the embodiments of the fire extinguishing system 100 depicted as examples in the figures. It is particularly conceivable for the control unit 10 to regulate the entire flooding gradient such that the enclosed room 6 is flooded according to a predefined sequence of events.
LIST OF REFERENCE NUMERALS
(49) 1 pipeline system 1 pipeline system (nitrogen generator) 1a, 1b first/second pipeline section 2 nozzles 3 regulating valve 3a first triggering mechanism for first extinguishing gas source 8a 3b second triggering mechanism for second extinguishing gas source 8a 3c triggering mechanism for further extinguishing gas source 8c 4 fire sensor 5 alarm mechanism 6 enclosed room/flood zone 7 pressure relief flap 8 common extinguishing gas source 8a first extinguishing gas source 8b second extinguishing gas source 8c further extinguishing gas source 9a nitrogen generator compressor 9b nitrogen generator filtering device 10 control unit 11 tank valve 12 oxygen sensor 100 fire extinguishing system
