EXPLOSION SUPPRESSION ARRANGEMENTS AND METHODS

Abstract: An explosion suppression arrangement is described for attachment to the outside wall of an area at risk from explosions which, on detection of an explosion in the area, discharges explosion suppressant material into the area to suppress the explosion. The arrangement comprises a container (14), with an outlet (16) closed by a frangible diaphragm (24), a source (20) of pressurized gas mounted within the container (14) for producing gas upon activation of the source (20), and a suppressant distribution device (22). When an explosion is detected, activating the source (20), the suppressant material (18) is pressurized by the pressurized gas exiting through the pipes (22) and the diaphragm (24) will break so discharging the suppressant material through the outlet (16).

Description: EXPLOSION SUPPRESSION ARRANGEMENTS AND METHODS The invention relates generally to explosion suppression arrangements and methods. More particularly, but not exclusively, the invention relates to arrangements and methods for suppressing explosions within protected areas where the conditions are such that explosions may occur. According to the invention, there is provided an explosion suppression arrangement for suppressing explosions within a protected area, comprising containing means for containing explosion suppressant material and having an outlet normally closed by frangible means, a source of pressure, pressure distribution means positioned within the containing means so as to be located within explosion suppressant material therein, the distribution means being pressurised by the source upon activation thereof so as to pressurise the suppressant material and break the frangible means to cause discharge of the suppressant material through the outlet According to the invention there is further provided an explosion suppression arrangement for suppressing explosions within a protected area, comprising containing means for containing explosion suppressant material and defining an outlet normally closed by frangible means, a source mounted within the containing means for producing pressurised gas upon activation of the source so as to pressurise the suppressant material and break the frangible means to cause discharge of the suppressant material through the outlet, the containing means, the frangible means and the source of pressurised gas being mountable as a unit adjacent the protected area. Explosion suppression arrangements embodying the invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings in which: Figure 1 is a schematic view showing one of the explosion suppression arrangements mounted on one wall of an area to be protected; Figure 2 is an enlarged schematic view of the explosion suppressant arrangement of Figure 1 ; and Figure 3 is a schematic view of another of the explosion suppressant arrangements. The explosion suppressant arrangement 1 of Figures 1 and 2 is mounted on one wall 10 of an area to be protected 12 such as a room or a large volume used in an industrial process, for example, a grain drying silo, vat or anywhere where the circumstances are such that an explosion might start and must be suppressed within a matter of milliseconds. As will be seen in Figure 1, the explosion suppressant arrangement comprises a container 14 which is attached to the outside of the wall 10 of the area 12 to be protected. A normally closed opening 16 is situated between the container 14 and the area to be protected 12. The container contains explosion suppressant material. In a manner to be explained in more detail, upon detection of an explosion in the area 12, the material is discharged into the area and suppresses the explosion. As can be more clearly seen in Figure 2, located within the container 14 are an explosion suppressant material 18 and a pressure source 20. In the embodiment to be described below, the explosion suppressant material is a powder such as mono-ammonium phosphate or sodium hydrogen carbonate. However, it will be appreciated that any suitable ABC explosion suppressant powder or any other suitable explosion suppressant material may be used. The pressure source 20 in this example is a pyrotechnic gas generator . The pyrotechnic gas generator 20 is provided with a system of outlet tubes 22 which extend from the pyrotechnic gas generator 20 into the body of the powder 18. The outlet 16 to the protected area 12 is closed by a frangible aluminium foil diaphragm 24. It will be appreciated that any other suitable form of frangible material may be used to close the outlet 16. A dispersing device 25 is mounted adjacent to the diaphragm 24, inside the container 14. A pressure detector 26 is positioned to be responsive to the pressure in the protected area 12 and is connected to an activating device 27 for the pyrotechnic gas generator 20 (e.g. by suitable electrical connector 28) . It will be appreciated that any suitable form of explosion detector may be used in place of the pressure detector 26. When an explosion is detected by the pressure detector 26, a signal is produced on line 28 which actuates the pyrotechnic gas generator 20. Gas is thereupon rapidly generated which is discharged through the outlet tubes 22 into the body of the powder 18. This discharge of gas pressurizes the powder 18 within the container 14 and the diaphragm 24 breaks. The powder 18 is discharged by gas pressure through the outlet 16 into the protected area to suppress the explosion. The dispersing device 27 ensure that the discharging powder is dispersed widely within the area 12. Because the outlet 16 is relatively wide, the dispersing device 27 can be mounted within the container 14. Because of this, and also because the gas generator 20 is mounted inside the container 14, the whole apparatus is self-contained and can be simply secured in any suitable way to an opening formed in the wall of the protected area. In explosion suppression arrangements in which the outlet is relatively small, the dispersing device must be mounted outside the outlet and inside the protected area. In these cases, some sort of mounting bracket or connection means has to be used, making assembly of the arrangement much more difficult. As the gas generator 20 is located within the body of the powder 18, the powder 18 is fluidized when the pyrotechnic gases are generated, thus avoiding compaction, and also cooling the gases. In this way, the powder is ejected through the outlet 16 in the form of sprayed particles accompanied by the cooled gas. As the gas is cooled by being injected into the body of the powder 18, its pressure is rapidly reduced, thus avoiding any significant increase of the pressure within the protected area 12. However, the pressure is still sufficient to break the diaphragm 24 and to eject the powder into the protected area 12. The arrangement is thus advantageous over arrangements in which the pyrotechnically generated gas is applied from outside the container to the powder which can cause the powder to be ejected into the protected area in the form of a "plug" of compacted powder, followed by a quantity of hot gas. The plug of powder will not suppress the explosion so well as sprayed particles. As the container 14 is completely packed with suitable powder 18, it will be appreciated that this arrangement can be used in any orientation and can simply be refilled after use. Furthermore, there is no above-atmospheric pressure within the container until an explosion is detected. It is therefore not necessary to use a container conforming to pressure vessel regulations. It is desirable to monitor the integrity of the diaphragm 24. If the diaphragm should corrode or otherwise fail, some of the powder 18 may enter the area 12 and may contaminate its contents. Secondly, of course, the powder will not be available when it is needed for explosion suppression. In order to monitor the integrity of the diaphragm, the interior of the container 14 is slightly pressurized (e.g. to 0.2 bar above-atmospheric pressure) by means of a suitable pressure source 29. A pressure detector 30 monitors the pressure within the container 14 and produces a warning signal if the presure within the container falls as a result of failure of the diaphragm 24 (or for any other reason) . Because the pressure within the container is only very slightly above-atmospheric, the container is still not subject to pressure vessel regulations. A partial vacuum could be used within the container for the same purpose. In Figure 3 , parts corresponding to those in other Figures are similarly referenced. In a different form of the invention shown in Figure 3, the pyrotechnic gas generator is replaced by an external source 31 of stored pressurized gas, which is connected by a valve 32 to the network of outlet pipes 22 located within the body of the powder 18 inside the container 14. The pressure detector 26 is connected to the valve 32. When an explosion is detected by the pressure detector 26, a signal 28 is sent to open the valve 32. Once the valve 32 is open, the pressurized gas within the external source 31 is released into the network of outlet pipes and hence into the body of the powder 18 in the container 14. The gas acts to fluidize the powder 18 and to increase the pressure within the container 14 as previously described. Once the pressure has reached a predetermined level, the diaphragm 24 will break and the powder will be dispersed into the protected area 12 by the dispersing device 25. The arrangement of Figure 3 may be provided with means for monitoring the integrity of the diaqphragm 24 similar to that provided for the embodiment of Figure 2. It will be appreciated that the explosion suppressant material need not be a powder but may be a liquid such as water, a halocarbon extinguishant, a fluorinated hydrocarbon, or any other suitable form of liquid extinguishant.

Claims: CT.A TMS 1. An explosion suppression arrangement for suppressing explosions within a protected area, comprising containing means (14) for containing explosion suppressant material (18) and having an outlet (16) normally closed by frangible means (24), characterised by a source of pressure (20,31), and pressure distribution means (22) positioned within the containing means (14) so as to be located within explosion suppressant material (18) therein, the distribution means (22) being pressurised by the source (20,32) upon activation thereof so as to pressurise the suppressant material (18) and break the frangible means (24) to cause discharge of the suppressant material (18) through the outlet (16) . 2. An arrangement according to claim 1, characterised in that the source (20,31) is mounted within the containing means (14) . 3. An arrangement according to claim 2, characterised in that the source is a pyrotechnic gas generator (20) . 4. An arrangement according to claim 2 or 3 , characterised in that the distribution means comprises pipe means (22) extending outwardly from the source (20) within the containing means (14) . 5 An arrangement according to claim 1, characterised in that the source (31) is mounted externally of the containing means (14) and connected to the distribution means (22) by pipe means. 6. An arrangement according to any preceding claim, characterised by dispersing means (25) for directing the suppressant material (18) as it is discharged through the outlet (16) 7. An arrangement according to claim 6, characterised in that the dispersing means (25) is mounted within the containing means (14) 8. An arrangement according to any preceding claim, characterised in that the cross-sectional area of the outlet (16) is not substantially less than the cross-sectional area of the containing means (14) immediately adjacent to the outlet (16) 9. An explosion suppression arrangement for suppressing explosions within a protected area, comprising containing means (14) for containing explosion suppressant material (18) and defining an outlet (16) normally closed by frangible means (24) , characterised by a source (20) mounted within the containing means (14) for producing pressurised gas upon activation of the source (20) so as to pressurise the suppressant material (18) and break the frangible means (24) to cause discharge of the suppressant material (18) through the outlet (16) , the containing means (14), the frangible means (24) and the source (20) of pressurised gas being mountable as a unit adjacent the protected area . 10. An arrangement according to claim 9, characterised by dispersing means (25) mounted inside the containing means (14) adjacent the frangible means (24) and as part of the unit, the dispersing means (25) directing the suppressant material (18) as it is discharged through the outlet (16) . 11. An arrangement according to claim 9 or 10, characterised by gas distribution means (22) positioned within the containing means (14) as part of the unit for distributing the pressurised gas within the suppressant material (18) . 12. An arrangement according to any preceding claim, characterised by sensing means (29,30) for sensing leakage of the suppressant material from the containing means (14). 13. An arrangement according to claim 12, characterised in that the sensing means comprises means (29) for normally maintaining the interior of the containing means (14) at a pressure slightly different from atmospheric pressure, and monitoring means (30) for monitoring the pressure within the containing means (14) and indicating leakage of the suppressant material (18) from the containing means (14) in response to change of the pressure within the containing means (14) towards atmospheric pressure. 14. An arrangement according to any preceding claim, characterised in that the explosion suppressant is a powder (18) . 15. An arrangement according to claim 14, characterised in that the powder is any suitable ABC explosion suppressant powder. 16. An arrangement according to claim 15, characterised in that the powder is mono-ammonium phosphate. 17 An arrangement according to claim 15, characterised in that the powder is sodium hydrogen carbonate. 18. An arrangement according to any one of claims 1 to 13, characterised in that the explosion suppressant is a liquid. 19. An arrangement according to claim 18, characterised in that the liquid is water. 20. An arrangement according to claim 18, characterised in that the liquid is a fluorocarbon extinguishant. 21. An arrangement according to claim 18, characterised in that the extinguishant is Du Pont FE36, or similar fluorinated hydrocarbon. 22. An arrangement according to any preceding claim, characterised in that the frangible means is a diaphragm (24). 23. An arrangement according to claim 22, characterised in that the diaphragm (24) is formed from aluminium.

Inventors: MOORE PETER, MOORE, PETER
Applicants: KIDDE FIRE PROTECTION LTD, MOORE PETER, KIDDE FIRE PROTECTION LIMITED, MOORE, PETER
Application year: 1998
Main classification: A62C35
IPC codes: A62C13, A62C35