EP3010600B1

EP3010600B1 - System and method for limiting explosion hazard

Info

Publication number: EP3010600B1
Application number: EP14744270.1A
Authority: EP
Inventors: Paul Alfons Leon VAN GELDER; Peter Jozef Regina Maria MACKEN
Original assignee: Stuvex International NV
Current assignee: Stuvex International NV
Priority date: 2013-06-21
Filing date: 2014-06-17
Publication date: 2023-11-15
Anticipated expiration: 2034-06-17
Also published as: BE1021696B1; WO2014201527A1; EP3010600A1

Description

The present invention relates to a system and method for limiting, and in particular suppressing explosion hazard in a closed space.
Existing systems for suppressing explosion hazard are typically based on rapid injection of an extinguishing powder, typically sodium bicarbonate powder, into the closed space to be protected. According to known systems, extinguishing powder is stored together with a propellant, typically nitrogen gas, under high pressure (60 to 80 bar) in a storage vessel. Required for the purpose of storing propellants under a high pressure are pressurized containers which have to be regularly reinspected. According to another known system, a gas generator is used which generates the necessary high pressure at the moment of activation of the gas generator. Such a gas generator is however expensive and complex in manufacture.
US 1,241,664 discloses a fire extinguishing apparatus comprising a system of pipes provided with exposed automatic sprinkler heads, a tank containing liquid carbon dioxide, a water tank having a connection at its bottom part with said system of pipes, a conduit connecting said carbon dioxide tank with said water tank arranged to pass through and open above the water in said latter tank, a valve disposed in said conduit, and means for opening said valve on the opening of a sprinkler head.
US 2002/0027143 discloses an atomizing nozzle and fixed clean agent fire suppression system. The system stores gas fire suppressant in a liquefied state separate from propellant gas. Upon demand, the propellant charges the gas fire suppressant to provide a piston flow system that pushes the gas fire suppressant in the liquid state through a pipe network to the protected area of a building. DE 10 2006 032 503 discloses a similar fire extinguishing apparatus.
Embodiments of the present invention have the object of obviating these drawbacks by providing a system and a method which can limit or suppress an explosion hazard in more effective manner.
Embodiments of the present invention are based inter alia on the insight of the inventors that in the existing systems the extinguishing action is based substantially on the chemical and physical properties of the extinguishing powder and the interaction between the extinguishing powder and the explosion flame, and that a large part of the energy present in the propellant or generated gas is not utilized optimally.
An embodiment of a system according to the invention comprises a storage vessel in which an extinguishing agent is stored. The storage vessel is provided with an outlet intended to form a passage for fluid to the closed space upon detection of explosion hazard in the closed space. The system further comprises at least one container in which an at least partially liquid propellant is stored under pressure; and, for each container, an activator configured to create after activation thereof a fluid passage between the storage vessel and this container such that the propellant is propelled into the closed space together with the extinguishing agent following activation of the activator.
When the fluid passage is created between a container and the storage vessel in which a lower pressure prevails, typically roughly atmospheric pressure, the liquid propellant will flow out and expand over a certain period of time due to the use of a propellant which is present in partially liquid phase in the container. When the extinguishing powder begins to flow out to the closed space, the pressure in the container is further typically less high than in pressure vessels of prior art systems, and the pressure drops less quickly after activation than in prior art systems. This enables a good explosion suppression to be obtained with relatively small containers.
The propellant is preferably an extinguishing gas, still more preferably a cryogenic extinguishing gas, and for instance one of the following: carbon dioxide, nitrogen, argon, helium.
The extinguishing agent is a powder, for instance sodium bicarbonate.
The invention more particularly allows the use of one or more relatively small containers for which the legal requirements are less strict than for the pressure vessels used in known systems. Standard commercially used containers with liquid CO₂ of 20 to 200 grams can for instance be suitable for use in embodiments of the invention.
The propellant is preferably such that the propellant expands upon activation of the activator and herein absorbs ambient heat. The extinguishing agent will cool due to expansion of liquefied gas in the container. A cooling effect is in this way brought about which can further contribute toward suppressing of the explosion in the closed space.
According to a further developed embodiment, the system comprises detection means which are configured to detect explosions in the closed space, and a control connected to the detection means and configured to activate the activator upon detection of explosion hazard by the detection means.
According to a possible embodiment, the system further comprises a gas generator and an additional activator configured to activate the gas generator for the purpose of injecting generated gas into the storage vessel such that the extinguishing agent and the gas generated by the gas generator are propelled into the closed space. The control is then preferably configured to also activate the additional activator upon detection of explosion hazard by the detection means. The gas generator is preferably configured for the purpose, following activation of the additional activator, of generating a first pressure which is higher during a first time period than in a second subsequent time period, and the container with propellant is preferably configured to generate after activation a second pressure which is lower than the first pressure during the first time period and higher than the first pressure during the second time period. It is noted that the gas generator used in systems of the invention can typically be much smaller than the gas generator used in prior art systems.
The invention further relates to a device comprising a closed space in the form of a silo, in which roughly atmospheric pressure typically prevails, with a first inlet to which an embodiment of the above described system is connected. The closed space can further be provided with an outlet which is connected to a conduit in which a shut-off valve is accommodated. The shut-off valve is movable from an open to a closed position when a risk of explosion is detected. Such a shut-off valve is configured to close the conduit very quickly, whereby the consequences of explosion propagation in conduits are limited or avoided. The control can for this purpose be further configured to control the shut-off valve in order to move it to the closed position upon detection of explosion hazard by the detection means. The shut-off valve can be a mechanical or chemical shut-off valve, or a shut-off valve as described in the Belgium patent application with filing number BE 2012/0559 or BE 2012/0742 in the name of applicant.
The invention further relates to a method for limiting explosion risks in a closed space, comprising of storing an extinguishing agent in a storage vessel with an outlet connected to the closed space; providing at least one container in which an at least partially liquid propellant is stored under pressure; and, upon detection of explosion hazard, creating for each container a fluid passage between the storage vessel and this container such that the propellant is propelled into the closed space together with the extinguishing agent, the extinguishing agent being a powder.
The propellant is preferably an extinguishing gas, and still more preferably CO₂, Ar, N, He, or a combination thereof. The extinguishing agent is a powder. The container with the at least partially liquid extinguishing gas can be chosen as described above in respect of the system.
According to a further embodiment, a gas generator can likewise be activated for the purpose of injecting generated gas into the storage vessel such that the extinguishing agent and the gas generated by the gas generator are propelled into the closed space. A first pressure is preferably generated by the gas generator which is higher during a first period than during a second subsequent period, and a second pressure is generated with the container with propellant which is lower than the first pressure during the first period and higher than the first pressure during the second period. As noted above, the gas generator necessary here can typically be much smaller than the gas generator used in prior art systems.
Advantageous embodiments of the system and the method are described in the claims.
The invention will be further elucidated on the basis of a number of by no means limitative exemplary embodiments of the system and the method according to the invention with reference to the accompanying drawings, in which:

Figure 1 shows a schematic section of a first embodiment of a system according to the invention;
Figure 2 shows a schematic section of a second embodiment of a system according to the invention; and
Figure 3 illustrates a schematic graph of the pressure as a function of time for the second embodiment.

Figure 1 illustrates a first embodiment of an explosion suppression system according to the invention. The system comprises a storage vessel 10 in which an extinguishing agent B, an extinguishing powder, is stored. Storage vessel 10 is typically under roughly atmospheric pressure. Storage vessel 10 is provided with an outlet 11 which, following activation of the system, can communicate with an inlet of the closed volume, here a silo 50 which is typically also under roughly atmospheric pressure. The system further comprises a container 20 in which an at least partially liquid propellant D is stored under pressure, for instance liquid CO₂ under a pressure of 10 to 20 bar, and an activator 21 which is configured to create after activation thereof a passage for fluid between storage vessel 10 and container 20. This activator 21 is represented schematically and can be embodied in many different ways, and can for instance be a pin which makes an opening in a wall or closing cover of container 20 such that, following activation of the activator, the propellant D passes from the liquid state to the gaseous state, moves to storage vessel 10 and propagates together with the extinguishing agent B into silo 50. The propellant flowing out of container 20 can be partially in the liquid phase and partially in the gaseous phase.
Container 20 is preferably arranged such that, following activation of the activator, the propellant also provides for a loosening of the extinguishing powder B which is typically stored in compacted state in storage vessel 10. In the illustrated variant the container is arranged outside storage vessel 10, although container 20 could also be arranged in storage vessel 10.
Although figure 1 shows only one container 20, a plurality of containers 20 and associated activators 21 can also be provided, these introducing propellant into storage vessel 10 after activation. These activators 21 can optionally be activated simultaneously. These one or more containers 20 can for instance be small CO₂ bottles with a volume of less than 0.5 litre, preferably less than 0.2 litre, in which liquid CO₂ is stored, for instance under a pressure of 10 to 20 bar, typically under a pressure of about 15 bar at room temperature.
In the illustrated embodiment one explosion suppression system is provided in a side wall of silo 50. The skilled person will appreciate that a plurality of such systems, which communicate with different openings in the wall of silo 50, can be provided.
A gas or substance explosion consists of a rapid combustion of a gas or substance and air mixture and can be detected at a very early stage by detection means 30 which are known to the skilled person and which transmit a detection signal to a control 40. Control 40 is configured to activate the activator 21 for the purpose of creating the fluid passage between container 20 and storage vessel 10. It is further possible to provide between storage vessel 10 and silo 50 a barrier, for instance a rupture plate, which is eliminated following activation of the system, for instance by the rupture plate being broken as a result of the increased pressure in storage vessel 10, for the purpose of creating a passage for extinguishing agent and propellant.
The effectiveness and efficiency of the explosion suppression can be considerably improved in that the propellant itself can have an extinguishing action and in that the propellant expands during the transition from the liquid to the gaseous phase and absorbs heat and so brings about a cooling effect which further enhances the explosion suppression. Both the extinguishing agent and the propellant are then at a relatively low temperature, which enhances the explosion suppression. It is also possible to make use of relatively small, commercially available propellant containers 20 in which propellant is stored in at least partially liquid form, whereby the weight and the cost price of embodiments of systems according to the invention can be considerably lower than the known systems in which heavy pressure vessels are used.
Figure 2 illustrates a second embodiment of an explosion suppression system according to the invention. The system is similar to the system of figure 1, with the difference that a gas generator 60 with additional activator 61 is further provided. The additional activator 61 is configured to activate gas generator 60 and to inject generated gas under high pressure into storage vessel 10 such that the extinguishing agent B and the gas generated by the gas generator are propelled into the closed space 50. Control 40 is then further configured to activate the additional activator 61 upon detection of explosion hazard by detection means 30.
Figure 3 illustrates schematically a possible variation in the pressure as a function of time for a gas generator 60 and a container 20 according to an embodiment of the invention. Gas generator 60 is typically configured for the purpose, following activation of the additional activator 61, of generating a first pressure P1 as a function of time which is higher during a first time period T1 than during a second subsequent time period T2, and container 20 with propellant is typically configured to generate after activation a second pressure P2 as a function of time which is lower than the first pressure P1 during the first time period T1 and higher than the first pressure during the second time period T2. It is further noted that activators 21, 60 of container 20 and gas generator 60 can optionally be activated simultaneously. The graph of figure 3 shows an example in which activator 21 of container 20 is activated a period ΔT after activator 61 of gas generator 60. A shorter response time of the system will hereby be possible. According to a variant (not illustrated), activator 61 of gas generator 60 can be activated a period ΔT after activator 21 of container 20 in order to increase the extinguishing agent injection time.
The use of the gas generator in combination with a container makes it possible to make the system even quicker or to extend injection time. The gas generator 60 which is added in the variant of figure 2 can typically be much smaller than the gas generators of known explosion suppression systems, since gas generator 60 is only used here to give the system a faster start or to extend the extinguishing agent injection time, and the major part of the explosion suppression takes place by making efficient use of the propellant D stored in at least partially liquid form.
The invention is not limited to the above described exemplary embodiments and the skilled person will appreciate that many modifications and variants can be envisaged within the scope of the invention, which is defined solely by the following claims.

Claims

System for limiting explosion hazard in a closed space (50), comprising a storage vessel (10) in which an extinguishing agent (B) is stored, the storage vessel (10) being provided with an outlet (11) connectable to the closed space, the system further compriseing:
- at least one container (20) in which an at least partially liquid propellant (D) is stored under pressure; and

- for each container, an activator (21) configured to create after activation thereof a passage for fluid between the storage vessel (10) and this container such that, following activation of the activator (21), the propellant propagates into the closed space (50) together with the extinguishing agent (B);
characterized in that the extinguishing agent (B) is a powder.
System as claimed in claim 1, characterized in that the propellant is an extinguishing gas, preferably a cryogenic extinguishing gas.
System as claimed in any of the foregoing claims, characterized in that the propellant is one of the following: carbon dioxide, nitrogen, argon, helium.
System as claimed in any of the foregoing claims, characterized in that the pressure and temperature in the storage vessel (10) are such that the propellant expands upon activation of the activator (21).
System as claimed in any of the foregoing claims, characterized in that the propellant is such that the propellant expands upon activation of the activator (21) and herein absorbs ambient heat when the pressure in the storage vessel (10) and in the closed space (50) is about 1 atm and the temperature lies between -20 and 60°C.
System as claimed in any of the foregoing claims, characterized in that the system further comprises: detection means (30) which are configured to detect explosion hazard in the closed space; and a control (40) connected to the detection means (30) and configured to activate the activator (21) upon detection of explosion hazard by the detection means (30).
System as claimed in any of the foregoing claims, characterized in that the system further comprises a gas generator (60) and an additional activator (61) configured to activate the gas generator (60) for the purpose of injecting generated gas into the storage vessel (10) such that the extinguishing agent (B) and the gas generated by the gas generator (60) are propelled into the closed space.
System as claimed in claims 6 and 7, characterized in that the control (40) is further configured to activate the additional activator (61) upon detection of explosion hazard by the detection means (30).
System as claimed in claim 7 or 8, characterized in that the gas generator (60) is configured for the purpose, following activation of the additional activator (61), of generating a first pressure which is higher during a first time period than in a second subsequent time period, and that the container with propellant is configured to generate after activation a second pressure which is lower than the first pressure during the first time period and higher than the first pressure during the second time period.
Device comprising a closed space (50) in the form of a silo (50) with a first inlet to which a system as claimed in any of the claims 6-9 is connected.
Device as claimed in claim 10, characterized in that the silo (50) has an outlet (11) which is connected to a conduit in which a shut-off valve is accommodated, which shut-off valve is movable from an open to a closed position, wherein the control (40) is further configured to control (40) the shut-off valve in order to move it to the closed position upon detection of explosion hazard by the detection means (30).
Method for limiting explosion risks in a closed space, comprising of storing an extinguishing agent (B) in a storage vessel (10) connected to the closed space, the method further comprising :
- providing at least one container (20) in which an at least partially liquid propellant (D) is stored under pressure; and

- upon detection of explosion hazard, creating for each container a passage between the storage vessel (10) and this container such that the propellant is propelled into the closed space (50) together with the extinguishing agent (B);
characterized in that the extinguishing agent (B) is a powder.
Method as claimed in claim 12, characterized in that the propellant is an extinguishing gas, and preferably one of the following: carbon dioxide, nitrogen, argon, helium.
Method as claimed in claim 12 or 13, further comprising of activating a gas generator (60) and injecting generated gas into the storage vessel (10) such that the extinguishing agent (B) and the gas generated by the gas generator (60) are propelled into the closed space; wherein preferably a first pressure is generated with the gas generator (60) which is higher during a first time period than during a second subsequent time period, and wherein a second pressure is generated with the container with propellant which is lower than the first pressure during the first period and higher than the first pressure during the second period.