GB2340750A

GB2340750A - Extinguishing fires in building panels

Info

Publication number: GB2340750A
Application number: GB9818420A
Authority: GB
Inventors: Christopher John Hood
Original assignee: Wormald Ansul UK Ltd
Current assignee: Tyco Fire and Integrated Solutions UK Ltd
Priority date: 1998-08-25
Filing date: 1998-08-25
Publication date: 2000-03-01
Anticipated expiration: 2018-08-25
Also published as: GB2340750B; GB9818420D0

Abstract

Fires in composite building panels having a flammable core are extinguished using a fluid mist. The mist is generated by mist generators such as, for example, nozzles that are supplied with fire extinguishing fluid via a distribution manifold that has a heat sensor. When the heat sensor is actuated a valve in the manifold is opened to allow flow of fluid to the nozzles. The nozzles are disposed on one or both sides of the panels and are designed to generate a fluid mist of between 0 to 100 bar and having a droplet size of 60 to 900 microns. Panels typically comprise a pair of spaced metal panel members sandwiching a polystyrene filling.

Description

2340750 METHOD AND APPARATUS FOR EXTING111SHING A FIRE The present

invention relates to a method and apparatus for extinguishing a fire in a building or room that is fitted with composite panels of the type that comprise a pair of spaced panels members that sandwich an insulating core material such as polystyrene.

Composite sandwich panels of the type referred to above are commonly used as internal partitions or suspended ceilings in buildings such as factories for the food industry as they provide effective temperature insulation and can be cleaned easily. The sandwich panels are typically four to five inches thick. The panel members are generally constructed of metal and are therefore fire resistant but the insulating core material is often highly flammable particularly if it is polystyrene.

In recent years there have been several incidents in which a fire in a building has spread to the polystyrene core of composite sandwich panels resulting in the internal structure of the building collapsing. The unsafe nature of such structures in a fire has led to fire fighting personnel refusing to enter the building to deal with the fire.

It has been found that conventional fire extinguishing apparatus such as water sprinkler systems fitted in the building or hoses used by fire fighters to direct jets of water at the burning structure has not been sufficiently effective in extinguishing fires within sandwich panels. The water from such apparatus, which is generally directed at the panels, serves only to cool them and does not penetrate to the burning core material. This may have the effect of slowing the burning time of the core but does not extinguish the fire. When a significant amount of the core has been burnt the panels, which may form the wall or ceiling of the building interior, collapse. Moreover, since the core is hidden, it can often be difficult to detect the fact that a fire has spread to the panel core.

In practice, the sandwich panels are frequently rearranged to reconfigure the internal plan of a building and different types of panels having different cores may be mixed together. As a result, the fire hazard represented by sandwich panels can be difficult to identify or quantify.

2 It is an object of the present invention to obviate or mitigate the aforesaid disadvantages.

According to one aspect of the present invention there is provided a method for extinguishing a fire in a composite panel of a structure, the panel having an internal layer of flammable material comprising generating a fire extinguishing fluid mist to at least one side of the panel, the mist being generated at a pressure of 0 to 100 bar and having a droplet diameter of 60 to 900 microns.

Tests conducted by the applicant have indicated that a mist of this nature is extremely effective in extinguishing the fire in a core of a composite panel. The careful selection of the pressure and droplet size of the mist ensures that the fluid is drawn into the fire in the panel core, through a gap in the panel members, by convection. The selected droplet size increases the surface area of the fluid thereby giving it a greater capacity to cool.

Preferably the mist is not projected directly at the panel and is allowed to circulate and be drawn into the fire in an airborne state as well as collecting on the surface of the panel where its capacity to cool is beneficial. This is advantageous in comparison to prior designs in which the majority of water was directed only at the panels.

According to another aspect of the present invention there is provided fire extinguishing apparatus for extinguishing a fire in a composite panel of a building structure, the panel having an internal layer of flammable material, the apparatus comprising a source of fire extinguishing fluid connected to an inlet of a fluid distributor and a plurality of fluid mist generators connected to an outlet of the distributor, the distributor being actuated to open communication between the inlet and outlet by, a heat sensor at a predetermined temperature, wherein the fluid is supplied to the mist generators at a pressure of between 0 to 100 bar, the mist generators are designed to generate a fluid mist having a droplet diameter of between 60 to 900 microns and are disposed to at least one side of the panel.

3 The heat sensor is preferably disposed below a panel which forms a ceiling of the building and at least one heat sensor is disposed to each side of the panel no more than 3 metres from the panel.

The heat sensor is conveniently in the form of a frangible container of fluid that expands with heat such that at a predetermined temperature the container is broken to release a valve in the distributor so that fluid is distributed from the source to the nozzles. This is advantageous since the sensor is not dependent on a supply of power, such as electricity, to operate. The sensor may alternatively be a frangible metallic element that breaks at a predetermined temperature.

A specific embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is a schematic plan view of fire extinguishing apparatus used in the present invention and installed on a test rig; Figure 2 is a schematic sectioned view along line A-A of figure 1; Figure 3 is a schematic sectioned view along line B-B of figure 2; Figure 4 is a sectioned side view of a fluid distributor of the apparatus of figure 1; Figure 5 is a side view of a mist nozzle of the apparatus of figure 1; Figure 6 is a sectioned view along line C-C of the nozzle of figure 5; and Figure 7 is a plan view of a diffuser of the nozzle of figures 5 and 6.

Referring now to the drawings, the fire extinguishing apparatus of the present invention is shown, in figures 1 to 3, installed in a building constructed for test purposes. The building comprises an outer structure 1 of tin that is furnished internally with a plurality of composite sandwich panels 2 that form an internal compartment comprising vertical end and partition walls 3, 4 and a suspended ceiling 5. The internal compartment is divided into two parts by the partition wall 4 which extends between two side walls 6 and runs parallel to the two end walls 3) (one only shown).

There is a significant clearance 7 between a roof 8 of the building and the suspended ceiling panels 5.

4 Each composite panel comprises two metal sheets spaced apart by a small distance which is filled by a core material of polystyrene to form a sandwich construction. Panels of this type are commonly used particularly in the food industry as they provide for efficient insulation and can be cleaned easily by wiping down the surface of each metal sheet.

The fire extinguishing apparatus comprises a plurality of mist generating nozzles 10 that are supplied, via pipework, with water from a mains standpipe 11 outside the building. The pipework in the building is disposed in the clearance 7 above the ceiling 5 above the partition wall 4 and comprises a main inlet conduit 12 that extends parallel to the partition wall 4 which is connected to three pairs of transverse branch conduits 13. The end of each branch conduit 13 is connected to an inlet 14 of a respective manifold 15 disposed to one side of the partition wall 4. An outlet 16 of each manifold 14 is connected to at least one of the nozzles 10 via a nozzle supply conduit 16 that extends above the ceiling 5. As will be seen from figures I to 3, in the test three manifolds 15 were disposed at regular intervals on each side of the partition wall 4 below the ceiling 5. On one side of the partition wall 4 the manifold outlets 16 are connected to two nozzles 10 in series and on the other side only one nozzle 10. The nozzle supply conduit 16 has a vertical branch 17 that is connected to further nozzles 1 Oa located in the clearance 7 above the ceiling 5.

It will be seen from the arrangement described that nozzles 10, 10a are disposed on both sides of the partition wall 4 and on both sides of the ceiling 5.

The manifold 15, shown in detail in figure 4, is of known configuration and comprises an inlet conduit 14 and a perpendicular outlet conduit 16 separated therefrom by a valve 18. An opposing inlet is not used and is sealed closed in use. Actuation of the valve 18 is controlled by a heat sensor 19 that comprises a frangible glass bulb 20 filled with a liquid. An end of the bulb 20 is connected to the valve 18 which is held by the bulb 20 against a biasing force (provided by, for example, a compression spring and/or hydraulically) in a configuration that closes communication between the inlet 14 and outlet 16 of the manifold 15. In use, as the temperature of the surroundings increases in the liquid in the bulb 20 expands so as to shatter the bulb 20 thereby releasing the biasing force so as to allow the valve 18 to open the manifold 15. Each manifold 15 is disposed within 3 metres of the partition wall 4 so as to ensure that the heat sensor 19 responds rapidly to a fire in the vicinity of the wall.

The nozzles are carefully oriented and positioned at a selected distance from the partition wall 4 and ceiling 5. The selected distance obviously depends on the dimensions of the building and the panels 4, 5 but is designed to prevent mist being projected directly at the panels.

The design of each nozzle 10 is of typical known configuration and is shown in figure 5 to 7. It comprises a main body 21 having a conduit defining an inlet and an outlet 23. The inlet 22 has a filter 24 to prevent particles entering the nozzle 10. Water egresses from the nozzle outlet 23 and hits a diffuser disc 25 thereby breaking up the incident water into a mist. In the present invention the nozzles 10 are designed to generate a mist droplet diameter of 60 to 900 microns and the water is supplied to the nozzles 10 at a pressure of 0 to 100 bar.

In operation, when there is a fire in a building one or more heat sensors 19 associated with the manifolds 15 operate to open the manifold valves 18 (as described earlier) so that water is supplied to the open nozzles 10 and mist is generated above and below the ceiling 5 and to each side of the partition wall 4. Should the fire penetrate to the core of the panels 4, 5, the mist is designed to extinguish the burning core.

In tests performed by the applicant the core of the partition wall 4 or the ceiling panel 5 was set on fire. It was established that by generating mist at the relatively low pressure and droplet size referred to above and directing it so that it is not directly incident on the panels, the airborne mist droplets are drawn into an exposed fire in the core of a panel by heat convection from the fire rather as well as settling on the panel surfaces. This means that the water is able to extinguish the fire rapidly and efficiently. The relatively small mist droplet size also ensures that the cumulative surface area of the water is large so providing more cooling capacity.

6 The present invention provides for rapid and efficient extinction of fires in composite panels of the kind defined above so permitting fire fighting personnel to enter the building without the risk of the structure collapsing on them. It also uses heat sensors that are not reliant on an electrical (or other) supply of power that may be severed in the fire.

It is to be understood that the figures shown relate to a test rig only and minor modifications may be made to the design without departing from the scope of the invention as defined in the appended claims. In particular, any convenient source of fluid extinguishing water may be provided to supply the nozzles. In addition, the water source may be at atmospheric pressure and pumped to the requisite pressure of between 0 to 100 bar. Moreover, the frangible glass bulb may be replaced by any other suitable heat sensor such as, for example, a frangible metallic element that breaks at a predetermined temperature.

7

Claims

1 A method for extinguishing a fire in a composite panel of a structure, the panel having an internal layer of flammable material, comprising generating a fluid mist to at least one side of the panel, the mist being generated at a pressure of 0 to 100 bar and having a droplet diameter of 60 to 900 microns.

2. A method according to claim 1, wherein the mist is not projected directly at the panel.

3. Fire extinguishing apparatus for extinguishing a fire in a composite panel in a structure having at least one composite panel that has an internal layer of flammable material, the apparatus comprising a source of fire extinguishing fluid connected to an inlet of a fluid distributor and a plurality of fluid mist generators connected to an outlet of the distributor, the distributor being activated by a heat sensor to open communication between the inlet and outlet at a predetermined temperature, wherein the fluid is supplied to the mist generators at a pressure of between 0 to 100 bar, the mist generators are designed to generate a fluid mist having a droplet diameter of between 60 to 900 microns and are disposed such that at least one mist generator is to at least one side of the panel.

4. Fire extinguishing apparatus according to claim 3, wherein the mist generator is designed such that it is not projected directly at the panel.

5. Fire extinguishing apparatus according to claim 4, wherein the heat sensor is disposed below a panel which forms a ceiling of the building and at least one detector is disposed to each side of the panel no more than -3 3 metres from the panel.

6. Fire extinguishing apparatus according to claim 4 or 5, wherein the heat sensor is in the form of a frangible container of fluid that expands with heat such that at a 8 predetermined temperature the container is broken to open a valve in the distributor so that fluid is distributed from the source to the mist generators via the distributor.

7. Fire extinguishing apparatus according to claim 4 or 5, wherein the heat sensor is a frangible metallic element that breaks at a predetermined temperature so as to open a valve in the distributor so that fluid is distributed from the source to the mist generators via the distributor

8. Fire extinguishing apparatus substantially as hereinbefore described with reference to the accompanying drawings.

9. A method for extinguishing a fire substantially as hereinbefore described with reference to the accompanying drawings.