EP0693303A2

EP0693303A2 - Discharging fire and explosion suppressants

Info

Publication number: EP0693303A2
Application number: EP95303676A
Authority: EP
Inventors: Richard Francis Sears
Original assignee: Kidde Technologies Inc
Current assignee: Kidde Technologies Inc
Priority date: 1994-07-21
Filing date: 1995-05-30
Publication date: 1996-01-24
Also published as: CA2151420A1; EP0693303A3

Abstract

A nozzle unit for discharging and atomising a fire or explosion suppressant comprises a rigid-walled cylindrical container (4A) having a nozzle portion (20) at one end with radially directed discharge orifices (22). A rupturable barrier (16) normally blocks the nozzle portion (20) from the interior of the container (4). At the other end of the container (4), a piston (50) is positioned so as to be sealingly slidable along the container (4A) in response to pressure generated by a gas pressure generator (6). The moving piston (50) pressurises the suppressant agent within the hollow interior until the rupturable barrier (16) bursts. The suppressant agent is accelerated substantially instantaneously and discharged in atomised form through the discharge orifices (22). The arrangement is such that the pressurising gas does not come into contact with the suppressant agent. The piston may be replaced by a bellows containing the suppressant agent and closed off by an integral wall constituting the rupturable barrier. A plurality of the nozzle units may be connected together in a system to protect a specific area. The nozzle units may be connected individually by respective pipes to a common source of gas pressure instead of having their own individual gas generators.

Description

The invention relates to apparatus for discharging a fire or explosion suppressant, comprising discharge nozzle means, storing means for storing the suppressant juxtaposed with the nozzle means, and discharge means for applying gas pressure to the stored suppressant to discharge it through the nozzle means.
According to this aspect, the invention is characterised in that the discharge means applies the gas pressure to the suppressant without contact between the gas pressure and the suppressant.
The invention also relates to apparatus for discharging a fire or explosion suppression agent, comprising a rigid-walled container having a hollow interior, nozzle means providing a discharge orifice mounted on the container, means within the hollow interior of container defining an enclosure therein for receiving the suppressant agent, the means defining the enclosure including a rupturable barrier normally blocking the interior of the enclosure from the nozzle means, and gas producing means for generating high gas pressure to forcibly discharge the suppressant through the nozzle means.
According to this aspect, the invention is characterised in that the means defining the enclosure includes movable wall means within the hollow interior, in that the gas producing means generates the gas pressure within a region of the enclosure separated from the enclosure by the movable wall means whereby the movable wall means moves in response to the gas pressure to compress the suppressant agent within the enclosure until the rupturable barrier ruptures and the suppressant agent is forcibly discharged through the nozzle means.
Apparatus embodying the invention and for discharging fire and explosion suppressant materials will now be described, by way of example only, with reference to the accompanying diagrammatic drawings in which:

Figure 1 is a cross-section through one form of the apparatus;
Figure 2 is a cross-section through another form of the apparatus;
Figure 3 is a cross-section on the line III-III of Figure 2;
Figure 4 is a cross-section of part of the apparatus of Figures 2 and 3 to an enlarged scale;
Figure 5 is a cross-section through a modified form of the apparatus of Figures 2 and 3; and
Figures 6 and 7 are schematic views of two systems incorporating the apparatus of Figure 5.

As shown in Figure 1, the apparatus 4 comprises a cylindrical casing 5 made of suitable material to withstand the high pressures developed within it in use (as will be explained).
At one end of the chamber, a pressure generator 6 is mounted. The pressure generator may take any suitable form. Known forms of suitable pressure generator comprise pyrotechnic pressure generators of the azide type such as disclosed in United Kingdom Patent Specification No. 2174179. Alternatively, the pressure generator 6 could be of the explosive or cordite type. In either case, the pressure generator incorporates an igniter which, when electrically energised, causes the pressure generator to generate a high gas pressure very rapidly within the interior of the chamber 5.
As shown in Figure 1, the chamber 5 also incorporates a closed bellows arrangement 8 which is made of suitable flexible and resilient material so as to be a close fit within the interior of the chamber 5. The bellows arrangement 8 is closed using continuous welding techniques, thereby forming a hermetic suppressant container. At one of its ends, the bellows has an end face 10 which lies against an annular abutment 12 rigid with the interior wall of the chamber 5. A similar annular abutment 14 is fixed to the interior wall adjacent the other end face of the bellows which is constituted by a burst disc 16.
The interior space within the bellows 8 is charged with the extinguishant material. For example, this material may be an extinguishant sold by Great Lakes Chemical Corporation under the designation FM-200. However, any other suitable suppressant may be used, preferably one having zero ozone depletion potential (ODP) such as a suitable dry powder or water. The suppressant may be pumped into the interior of the bellows before the pressure generator 6 is placed in position, through a fill tube 7 connected to the interior of the bellows through an orifice in the end face 10 which is thereafter sealed. The pressure of the suppressant within the bellows 8 expands the bellows so that its end surfaces 10 and 16 are forced into contact with the abutments 12,14.
At the end of the chamber 5 opposite to the pressure generator 6, an end portion 20 of the cylindrical wall of the chamber 5 is provided and provides a discharge nozzle. The nozzle is formed by apertures 22 in the end portion 20 and the axial end face 25 of the chamber is closed off by a conical deflector plate 24. Mounted around the interior face of the apertured end portion 20 is a cylindrical filter assembly 26 of the sintered-type.
In use, the suppressant within the bellows 8 is discharged by activating the pressure generator 6. When activated, the pressure generator 6 produces a very rapid build-up of pressure within the volume 30. The bellows becomes compressed, the end face 10 moving away from the abutment 12 and towards the abutment 14. An annular PTFE seal or bore rider 32 prevents the gas pressure from entering the space between the wall of the chamber 5 and the bellows.
As the bellows becomes compressed, the pressure generated within the suppressant in the bellows increases very rapidly until the burst disc 16 of the bellows bursts. The extinguishant exits through the annular filter 26 and the apertures 22, being deflected radially outward by the conical deflector 24, the apertures 22 being provided around the complete circumferential surface of the end portion 20. Such radial discharge is free from discharge reaction forces.
The burst disc 16 of the bellows is arranged to be of suitable material so as to rupture at a predetermined pressure. The filter 26 acts as a screen causing the discharging suppressant to break up into droplets so as to enhance the atomization process. In addition, it acts as a debris screen to prevent discharge of fragments of the burst disc 16.
Effectively, the bellows acts as a piston, and substantially all of the suppressant will be expelled. The pressure generated by the pressure generator 6 may be arranged to rise very rapidly, at the order of 500 psi/mS (3.45MPa/mS).
The burst disc 16 may be arranged to burst at, say, 1,200 psi (8.27MPa). Substantially all of the extinguishant may be discharged within less than 70 milliseconds and effective atomisation is achieved.
As shown in Figure 4, which illustrates the end portion 20 but with the filter 26 removed, the holes 22 are shaped so as to direct the discharging suppressant not merely radially but also in directions inclined forwardly and rearwardly of the radial direction. In other words, the suppressant is discharged substantially omni-directionally. Again, the discharge reaction forces substantially cancel.
Figure 2 shows a modified design 4A in which items corresponding to those in Figure 1 are similarly referenced. In the design of Figure 2, the gas generator 6 forms one end of the enclosure. The gas generator is hermetic in design and is welded to the chamber 5 using a continuous welding technique in order to form a hermetic suppressant container.
There is no bellows 8 and the burst disc 16 is fixed by continuous welding to the annular abutment 14. The abutment 14 is fixed to the chamber 5 by continuous welding.
Instead of the bellows 8 of Figure 1, the apparatus 4A of Figure 2 incorporates a piston 50 advantageously made of moulded material and incorporating a sliding annular seal 52 and three projections 54 which act as bore riders.
The suppressant material is forced into the interior volume 56 through a fill tube 58 which is thereafter sealed. The pressure within the volume 56 forces the piston 50 into the position shown in Figure 2.
As before, ignition of the gas generator 6 generates a pressure which rises very rapidly within the volume 30 and moves the piston 50 to the right (as viewed in the Figure), thus compressing the suppressant within the volume 56 until the discharge disc 16 bursts. As the discharge approaches completion, the nose of the piston 50 passes through the abutment 14 causing the projections 54 to shear. The nose of the piston 50 enters the nozzle 24 such as to cause substantially complete expulsion of the suppressant.
The suppressant becomes atomised by the high pressure and exits through the discharge orifices 22.
The apparatus shown in Figure 2 does not have the filter 26 of Figure 1 but this may be provided if required.
Atomisation of the discharged suppressant agent is achieved, in both forms of the apparatus described, by the kinetic effects of the very high velocity with which the suppressant is discharged. This high velocity is obtained by the use of a high discharge superpressure. Because of the presence of the piston in both forms of the apparatus described, which causes the suppressant agent to be rapidly pressurised until the burst disc ruptures, the discharged suppressant accelerates extremely rapidly, almost instantaneously, to its discharge velocity, thus optimising atomisation. If the developing gas pressure were to be applied directly to the suppressant agent, acceleration of the suppressant would be much slower. Atomisation is also assisted by the fact that the suppressant is stored immediately adjacent to the discharge orifices. The apparatus described may be used to discharge the extinguishants disclosed in, and to implement the procedures disclosed in, co-pending published European patent specification No. 0562756.
In both forms of the apparatus, there is no contact between the suppressant and the high pressure gas. This is advantageous when certain types of pressure generator are used which can produce toxic or potentially corrosive substances within the gas. This is particularly so with cordite-type gas generators. This makes the apparatus described especially suitable for applications, such as aircraft applications, where the presence of such toxic or potentially corrosive substances within the discharged suppressant is unacceptable.
Because the suppressant is pushed out by a piston or similar means, the discharge of the suppressant is independent of attitude (except to the marginal extent where acceleration forces on the piston will have an effect).
The whole apparatus 4 or 4A can effectively be regarded as a nozzle "unit" which contains the suppressant. Thus, multiple units 4,4A could be deployed in a large or cluttered environment, each such unit being independent in the sense that it contains its own gas generator. Such multiple units could be connected to a central control unit by individual electrical connections (for activating the individual gas generators) to form a system. However, in very high temperature environments such as aircraft engine nacelles, a pyrotechnic gas generator may not have adequate thermal stability and this may lead to degradation of its operating characteristics. In order to overcome this problem, a modified form of the nozzle unit of Figures 2 and 3 may be used as shown in Figure 5. In the nozzle unit 4B of Figure 5, items corresponding to items in Figures 2 and 3 are similarly referenced. As shown in Figure 5, the nozzle unit 4B does not use a gas generator. Instead, it has a gas coupling 60 for hermetic connection to a pipeline connecting it to a separate gas source. The separate gas source may be a gas generator or a source of stored gas. A seal disc 61 seals off the inner end of the pipe coupling 60. The interior 56 is, as before, filled with the suppressant. In use, the pressurised gas breaks the seal disc 61 and propels the piston 50 to the right to discharge the suppressant in the manner previously described. As shown in Figure 6, a plurality of nozzle units 4B are mounted in an area to be protected and are connected, via their couplings 60 and pipelines 62, to a solenoid or cartridge activated valve 64 and thence to a gas storage bottle 66. When suppression is to take place, the valve 64 is opened (automatically, for example) and the gas stored under pressure in the bottle 66 is fed via the pipelines 62 to all the nozzle units 4B and operates them in the manner described.
Figure 7 shows a system again employing nozzle units 4B but in which the pipelines 62 are connected to the output 68 of a gas generator 70. When suppression is to take place, the gas generator 70 is activated (automatically, for example) to generate gas pyrotechnically and the gas is again fed via the pipelines 62 to all the nozzle units 4B and activates them as described.
The arrangements shown in Figures 6 and 7 do not involve pipeline suppressant loss which occurs in known systems in which a plurality of extinguishant discharge heads are fed under pressure from a centralised supply of suppressant. In the nozzle units 4B, the suppressant is stored in respective sealed quantities in the units themselves.
A nozzle unit 4B of the form shown in Figure 5 can if desired be used singly, and connected to a supply of stored pressurized gas or to a gas generator.
In all the embodiments described, there is none of the high pressure gas within the discharged suppressant agent. Therefore, the density of the discharging stream of suppressant agent is not reduced by the presence of any gas other than the vapour of the suppressant agent itself. This allows the diameters of the discharge orifices to be smaller for a given mass flow rate, which enhances the atomisation effectiveness.
The use of a gas generator is advantageous, as compared with the use of a stored supply of gas under pressure, in that the superpressure produced by the gas generator is substantially unaffected by temperature; with gas stored under pressure, this is not the case. In addition, the chamber 5 of the apparatus described does not have to meet the pressure fatigue requirements of a normal high pressure storage vessel (which must withstand repeated variations in pressure due to thermal cycles). The chamber 5 of the apparatus described simply has to be able to withstand the superpressure produced by the gas when suppression is to take place, and clearly this only has to be withstood for a relatively short time; the vapour pressure of the suppressant agent itself is very much lower than this superpressure. Therefore, very high levels of superpressure can be used, without the penalty of increasing container weight. Leakage of stored high pressure gas from the nozzle unit is also avoided.
Because the suppressant agent is stored on its own and without any pressurising gas, the status of the suppressant can be determined by a simple weight check.

Claims

Apparatus for discharging a fire or explosion suppressant, comprising discharge nozzle means (22), storing means (4;4A;4B) for storing the suppressant juxtaposed with the nozzle means (22), and discharge means (6) for applying gas pressure to the stored suppressant to discharge it through the nozzle means (22), characterised in that the discharge means (6) applies the gas pressure to the suppressant without contact between the gas pressure and the suppressant.
Apparatus according to claim 1, characterised by a rupturable barrier (16) for blocking the suppressant from the nozzle means (22), the rupturable barrier (16) being arranged to rupture when subjected to at least a predetermined pressure.
Apparatus according to claim 1 or 2, characterised in that the storing means comprises an enclosure (8;56) for receiving the suppressant, the enclosure being partly defined by movable wall means (10;50) and including means (16) for connecting the interior of the enclosure (8;56) to the nozzle means (22), and means (6) applying the gas pressure to the movable wall means (10;50) from outside the enclosure (8;56) to move the movable wall means (10;50) in a direction to force the suppressant through the nozzle means (22).
Apparatus according to claim 3, characterised in that the movable wall means (10;50) is forced to move through a predetermined extent of travel sufficient to discharge substantially all of the suppressant from the enclosure (8;56).
Apparatus according to claim 3 or 4, characterised in that the means for connecting the interior of the enclosure (8) to the nozzle means (22) comprises a barrier (16) arranged to rupture when subjected to at least a predetermined pressure.
Apparatus according to claim 3, characterised in that the storing means comprises a rigid-walled container (4) having a hollow interior, and in that the said enclosure is defined by a closed flexible bellows (8) mounted in the interior of the container (4), a portion of the outside of the bellows constituting the movable wall means (10), the discharge means comprising means (6) applying gas pressure to the said portion (10) of the outside of the bellows (8) and within the hollow interior so as to compress the bellows (8), the bellows (8) incorporating a wall portion (16) which constitutes the means for connecting the interior of the enclosure (8) to the nozzle means (22) and is arranged to rupture under the pressure developed in the bellows (8) to allow the suppressant to discharge through the nozzle means (22).
Apparatus according to claim 3, characterised in that the storing means comprises a rigid-walled container (4A;4B) having a hollow interior (56) and piston means (50) which is sealingly slidable within the hollow interior (56) and which forms the movable wall means, the said enclosure being defined between one face of the piston means (50) and a rupturable barrier (16) which is positioned within the container (4A;4B) and which constitutes the means for connecting the interior of the enclosure (56) to the nozzle means (22), the discharge means (6) applying the gas pressure to the other face of the piston means (50) so that the piston means (50) moves to compress the suppressant agent within the enclosue (56) until the rupturable barrier (16) ruptures whereby the suppressant agent is discharged through the nozzle means (22).
Apparatus according to any one of claims 5 to 7, characterised by screening means (26) for the discharge of fragments of the rupturable barrier (16).
Apparatus according to any preceding claim, characterised in that the discharge means comprises gas generating means (6) mounted on the storing means (4;4A;4B).
Apparatus according to any one of claims 1 to 5, characterised in that the discharge means comprises a source of the gas pressure connected to the storing means (4B) by a pipe.
Apparatus according to claim 10, characterised in that the source of the gas pressure is gas generating means (70).
Apparatus according to claim 10, characterised in that the source of the gas pressure is a container (66) containing gas under pressure.
A plurality of separate apparatuses each according to any one of claims 10 to 12, characterised in that the said source is connected to the storing means of each of them by a respective said pipe (62).
Apparatus for discharging a fire or explosion suppression agent, comprising a rigid-walled container (4;4A;4B) having a hollow interior, nozzle means (22) providing a discharge orifice mounted on the container (4;4A;4B), means within the hollow interior of container (4;4A;4B) defining an enclosure (8;56) therein for receiving the suppressant agent, the means defining the enclosure including a rupturable barrier (16) normally blocking the interior (8;56) of the enclosure from the nozzle means (22), and gas producing means for generating high gas pressure to forcibly discharge the suppressant through the nozzle means (22), characterised in that the means defining the enclosure includes movable wall means within the hollow interior (10;50), in that the gas producing means (6) generates the gas pressure within a region of the enclosure (8;56) separated from the enclosure (8;56) by the movable wall means (10;50) whereby the movable wall means (10;56) moves in response to the gas pressure to compress the suppressant agent within the enclosure (8;56) until the rupturable barrier (16) ruptures and the suppressant agent is forcibly discharged through the nozzle means (22).
Apparatus according to claim 14, characterised in that the enclosure is defined by a flexible bellows (8) having a hollow interior, part of the bellows comprising the rupturable barrier (16) and another part thereof comprising the movable wall means (10).
Apparatus according to claim 14, characterised in that the container (4A;4B) has at least a portion of constant cross-section, and in that the rupturable barrier comprises a rupturable wall (16) across the constant-cross section portion and the movable wall means comprises a piston (50) slidable in response to the gas pressure towards the rupturable wall (16) and along the portion of constant cross-section.