in the case of explosion hazard

The present invention relates to a system and a method for injecting an extinguishing agent in the form of an extinguishing powder or extinguishing liquid into a closed space when a risk of explosion occurs in the 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. hi order to be able to guarantee a good extinguishing action the extinguishing agent has to be well distributed, and in particular dispersed, in the closed space, m known systems this distribution is effected by mechanical dispersing means, such as a nozzle in the shape of a hemisphere in which a large number of openings are arranged. In such systems the extinguishing powder is thus compelled to move in different directions by the mechanical dispersing means. The powder flow encounters from these mechanical dispersing means a resistance which reduces the injection speed of the powder flow. The effectiveness and efficiency of the explosion suppression system is hereby considerably reduced.

Embodiments of the present invention have the object of obviating these drawbacks by providing a system and a method which can distribute an extinguishing agent flow in a more effective manner in a closed space which has to be protected against explosion risks.

Embodiments of the present invention are based inter alia on the insight of the inventors that in the existing systems the powder flow encounters resistance as a result of the mechanical dispersing means, whereby the injection speed of the powder flow is reduced, and that some of the energy present in the powder flow is not utilized optimally as a result of friction.

Embodiments of the invention provide a gas-based dispersion system for distributing the powder flow in the volume to be protected.

According to an aspect of the invention, a system is provided for injecting an extinguishing agent in the form of an extinguishing powder or extmguishing liquid into a closed space, comprising a storage vessel in which the extinguishing agent is stored, the storage vessel being provided with an outlet connectable to the closed space. The system further comprises a gas injector which can be activated upon detection of explosion hazard and which is provided with at least one nozzle which is configured, in the activated position of the gas injector, to inject gas into the extinguishing agent close to the outlet of the storage vessel in at least two non-parallel directions which are oriented toward the space to be protected. The injected gas flow exerts a force on the extinguishing agent around the nozzle and will entrain the extinguishing agent in the at least two non-parallel outflow directions. A gas and extinguishing agent flow can in this way propagate in different directions through the outlet of the storage vessel into the space to be protected, and provide for a good distribution.

The nozzle is preferably configured to cause the gas flow to diverge through the outlet of the storage vessel.

The gas injector preferably comprises an outlet to which a nozzle connects. This outlet is preferably an outlet with a relatively small diameter which is oriented parallel to the outflow direction through the outlet of the storage vessel such that the extinguishing agent flow encounters little obstruction as a result of this outlet. The nozzle is preferably arranged such that, in the activated position of the gas injector, it is located a short distance from the boundary between the outlet of the storage vessel and the space to be protected. This distance is typically less than 50 cm, preferably less than 20 cm, still more preferably less than 10 cm, and for instance less than 5 cm.

According to a possible embodiment, the nozzle is provided with an orienting part which, at least in the activated position of the gas injector, is located partially in front of the outlet of the gas injector. Such an orienting part forms an obstacle in the gas flow and thus creates a diverging flow. The orienting part is preferably arranged such that, in the activated position of the gas injector, it is located a short distance from the boundary between the outlet of the storage vessel and the space to be protected. This distance is typically less than 50 cm, preferably less than 20 cm, still more preferably less than 10 cm, and for instance less than 5 cm.

According to a possible embodiment, the gas injector is configured for the purpose, following activation thereof, of moving at least a part of the or each nozzle from a retracted position to an injection position. The nozzle can for instance be part of a sealing piece of the gas injector, and the gas injector can be configured for the purpose, after activation, of moving the sealing piece from a sealing position to an injection position. If the gas injector makes use of a gas under pressure, the force of this gas under pressure can likewise be used to cause the movement of the nozzle or of a part thereof from the retracted position to an injection position. According to a possible embodiment, the nozzle is provided with a plurality of outflow openings with different outflow directions. According to other variants, the nozzle has only one outflow opening, for instance an annular outflow opening.

The gas is preferably an extinguishing gas, still more preferably a cryogenic extinguishing gas, and for instance one of the following gases: carbon dioxide, nitrogen, argon, helium. The extinguishing agent is preferably a powder, for instance sodium bicarbonate, or a liquid, for instance water.

For the gas injector use can for instance be made of one or more relatively small containers.

Standard commercial containers used with liquid C0 ₂ in a quantity of 20 to 200 grams can for instance be suitable for use in embodiments of the invention.

According to a further developed embodiment, the system comprises detection means configured to detect explosions in the closed space and a control connected to the detection means and configured to activate the gas injector upon detection of explosion hazard by the detection means. According to another aspect of the invention, a method is provided for injecting an extinguishing agent in the form of an extinguishing powder or extinguishing liquid into a closed space. The method makes use of a storage vessel in which the extinguishing agent is stored. The storage vessel has an outlet which is connectable to the space to be protected. Upon detection of explosion hazard a gas is injected into the extinguishing agent, in or close to the outlet of the storage vessel, in at least two non-parallel directions which are such that a gas and exunguishing agent flow is generated through the outlet of the storage vessel in at least two non-parallel directions.

An orienting part is preferably arranged in or close to the outlet such that a substantially outward diverging gas flow is injected through the outlet of the storage vessel. A good distribution of the gas and extinguishing agent flow propelled outward through the outlet can in this way be obtained. The orienting part can for instance be arranged in a central part of the outlet.

According to a variant, one or more nozzles, each with one or more outflow openings, are used to orient the gas flow in the extinguishing agent in or close to the outlet of the storage vessel.

The gas is preferably an extmguishing gas, and still more preferably CO ₂ , Ar, N, He, or a combination thereof. The extinguishing agent is preferably a powder or a liquid.

The invention further relates to a device comprising a closed space, for instance 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. Advantageous embodiments of the system and the method are described in the claims. In addition, the method is preferably applied using an embodiment of a system as described above.

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 device according to the invention; Figure 2 shows a schematic section of an embodiment of a gas injector for use in a system according to the invention;

Figure 3 shows a schematic section of an embodiment of a system according to the invention; and Figure 4 shows a schematic section of an embodiment of a nozzle for use in the system of the invention.

Figure 1 illustrates a first embodiment of an explosion suppression device according to the invention. The device comprises a storage vessel 10 in which an extinguishing agent B, typically an extinguishing powder, is stored. Storage vessel 10 can be under roughly atmospheric pressure, but can also be a pressure vessel which is under a high pressure. Storage vessel 10 is provided with an outlet 1 1 which, following activation of the system, can communicate with an inlet of a closed volume 50, for instance a silo which is typically under roughly atmospheric pressure. The system further comprises a gas injector 20. The gas injector comprises a container 21 in which a gas is stored under pressure, which gas can be partially liquid, for instance liquid C0 ₂ under a pressure of

10 to 20 bar. The gas injector further comprises an activator 22 configured to create after activation thereof a passage for fluid between storage vessel 10 and container 21. This activator 22 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 21 such that, following activation of activator 22, the gas D moves under pressure through an outlet 23 to storage vessel Gas injector 20 can be activated upon detection of explosion hazard and is configured in the activated position to inject gas into the extinguishing agent B close to outlet 1 1 and in the direction of volume SO. Gas injector 20 further comprises a nozzle, formed here by an outlet 23 and an orienting part 24, for the purpose of bringing about a gas and extinguishing agent flow in several non-parallel directions PI, P2. Orienting part 24 is located partially in front of outlet 23 of gas injector 20 and thus deflects the gas flow in different directions PI, P2. Nozzle 23, 24 thus has an outflow opening which lies all the way around orienting part 24 and brings about a flared gas flow. The gas flow entrains extinguishing powder to the space to be protected and provides for a good distribution thereof in the volume SO to be protected. The distance (D) between orienting part 24 and volume SO, the distance between outlet 23 and orienting part 24, the pressure in container 21, the shape and dimensions of outlet 23 and orienting part 24 and so on can be further optimized for the purpose of obtaining the best possible distribution in volume SO. Container 21 of gas injector 20 can for instance be a small C0 ₂ container with a volume smaller than 0.S litre, preferably smaller than 0.2 litre, in which liquid C(¾ is stored, for instance under a pressure of 10 to 20 bar, typically under a pressure of about IS bar at room temperature.

For the purpose of generating the powder flow the system further comprises powder flow generating means 40 in the form of a gas generator or of a container with a gas under high pressure (for instance 60 to 80 bar). The powder flow generating means 40 is preferably arranged such that, following activation of an associated activator 4 1 , the gas provides for a loosening of the extingrishing powder B which is typically stored in a compacted state in storage vessel 10. According to yet another variant, a separate powder flow generating means 40 is not provided and storage vessel 10 is a pressure vessel under a determined pressure which ensures that an extinguishing agent flow is initiated when a passage is created from storage vessel 10 to silo SO.

Although figure 1 shows only one powder flow generating means 40, a plurality of powder flow generating means 40 and associated activators 41 can also be provided which, after activation, introduce gas under pressure into storage vessel 10.

In the illustrated embodiment one explosion suppression system is provided in a side wall of silo SO. The skilled person will appreciate that a plurality of such systems, which communicate with different openings in the wall of silo SO, 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 activators 22, 1 upon detection of a risk of explosion. It is further possible to provide between storage vessel 10 and silo SO 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 gas.

Figure 2 illustrates another suitable nozzle 123, 124 for a gas injector for use in a system according to the invention. The nozzle comprises an outlet 123 which is movable in the direction of arrow F between an injection position (position of figure 2) and a closing position; and which is mounted on a gas container 21. Outlet 123 is provided along its periphery with a number of outflow openings 12S and is provided at its outer end with an orienting part 124 for generating a diverging gas flow, inter alia along arrows P , P2. Nozzle 123, 124 can therefore likewise function here as part of a closing mechanism of the gas injector.

Figure 3 illustrates another embodiment of a system according to the invention. The system comprises a storage vessel 10 for an extinguishing agent B and a gas injector 20 with a container 21 and an outlet 223 connected to a head 224 with outflow openings 225 which are arranged in a side wall of head 224 for the purpose of creating gas flows P1-P4 in the extinguishing agent in the direction of the volume 250 to be protected. In this embodiment the container 21 with gas under pressure, preferably a gas which is partially in the liquid phase, is likewise used to generate a powder flow in the direction of outlet 1 1 of the storage vessel, see outlets 227, 228. Additional pressure vessels or gas generators 40 can optionally be provided, as in the embodiment of figure 1.

Figure 4 illustrates yet another embodiment of a nozzle 324 with a number of outlets 326 for creating several outflow openings 325 connected at an angle relative to each other to a central pipe 323 for the purpose of creating respective gas flows P1-P3 in an extinguishing agent B. 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.