WO2005058424A1

WO2005058424A1 - Fire extinguishing system using foam

Info

Publication number: WO2005058424A1
Application number: PCT/CH2004/000725
Authority: WO
Inventors: Claude Ciocca
Original assignee: Claude Ciocca
Priority date: 2003-12-17
Filing date: 2004-12-09
Publication date: 2005-06-30
Also published as: EP1552860A1; SI1552860T1; ATE448837T1; EP1552860B1; ES2335982T3; DE60330170D1

Abstract

The invention concerns a fire extinguishing system using foam, comprising: a tube (10) designed to be arranged above a space to be protected and capable of being supplied by means of a pressurized water mixture and an emulsifier; and at least one extinguisher nozzle (12) consisting of at least one slot (24) provided in the wall of said tube and an expansion cage (26) configured to receive the liquid jet delivered by said slot and produce foam which is poured onto said space.

Description

FOAM FIRE EXTINGUISHING SYSTEM

The present invention relates to fire protection installations. It relates, more particularly, to an extinguishing system by sprinkling the fire using foam which is particularly well suited to fighting fires in large enclosed spaces, such as tunnels, parking lots or warehouses.

Such an installation must, first of all, be equipped with detectors: - with rapid response, that is to say reacting instantaneously to an abnormal rise in temperature, and - reliable, that is to say as little sensitive as possible to changes in temperature (frost, etc.) but also to dust or other soiling which may partially or completely "blind" them.

A fire-fighting installation in a large space must also be able to respond, in a targeted manner, to several fires separated from each other, which is frequent in a voluntary fire or when, in a tunnel, a first fire causes chain collisions and new fires. It is therefore vital that the installation intervenes at this location and is not prematurely in the process of extinction because it too quickly exhausted its resources on the first fire.

Due to the progress made in the field of foaming agents (generally liquid soaps), foam extinguishing systems have recently experienced a strong development. The attack on the fire by means of foam is not only more effective than that of a simple water installation, called "sprinkler", because it smothers the fire instead of bringing it oxygen, but, moreover, consumes much less water, which is a considerable advantage in tunnels. It will be noted, for example, that a medium expansion installation, well suited to this kind of space, requires only 1 liter of water to produce some 30 to 40 liters of foam. Document WO 03/041806 describes an installation for detecting and extinguishing fire in a tunnel, which meets the requirements set out above and attacks the fire using foam. This installation comprises a plurality of distinct assemblies each assigned to the protection of a sector of the tunnel and comprising, for each sector: - a plurality of thermal detectors each closing the end of a conduit supplied with compressed air and reacting to a abnormal rise in ambient temperature by opening said duct in the open air, - a foam extinguishing system taking place above the sector to be protected, and - control means which respond to a pressure drop resulting from venting at least one of said conduits by supplying said system with a mixture of pressurized water and foam concentrate allowing it to pour extinguishing foam onto this sector.

The main object of the present invention is to provide an improved version of a foam extinguishing system which can equip not only the above-mentioned installation, but also any existing installation, whether automatic or manual.

More specifically, the invention relates to a fire extinguisher system using foam, which comprises: - a tube intended to take place above the space to be protected and which can be supplied from the using a mixture of pressurized water and foam concentrate, and - at least one extinguishing nozzle comprising at least one slit made in the wall of said tube and a swelling cage arranged to receive the jet of liquid delivered through said slit and produce foam which is poured onto said space.

This extinguishing system also has the following main characteristics: - The slot is substantially parallel to the axis of the tube and to the axis of the cage. - The nozzle has several parallel slots. - The cage is made of mesh and has an upper wall with a triangle-shaped section, the edge of which faces the slot, parallel to it, and a curved lower wall substantially concentric with the tube. - The angle at the top of the triangle is substantially between 110 and 130 °. - The base of said triangle has substantially the same dimension as the diameter of the tube. - The base of the lower part of the cage has substantially the same dimension as that of the triangle. - The cage has an intermediate wall between its upper wall and its lower wall. - This intermediate wall is extended, beyond its junction with the upper wall, by a portion which ends substantially at the edge thereof. - The slot has a width between 0.3 and 1 mm and the edge of the top of the triangle of the cage is arranged about 1 mm from it. - The cage is secured to a collar taking place around the tube. - The system includes a plurality of nozzles arranged on the tube so as to distribute the watering throughout the space to be protected.

Other characteristics of the present invention will emerge from the description which follows, given with reference to the appended drawing, in which: - Figure 1 is a schematic representation of an installation according to the invention; - Figures 2 and 3 are views in longitudinal and cross section of a foam nozzle fitted to this installation; and - Figure 4 illustrates how to fix the cages of the extinguishing nozzles to the tube. FIG. 1 very schematically represents, seen from the ground, a portion of the roof of a road tunnel equipped with an installation using a foam extinguishing system according to the invention.

The installation proposed by way of nonlimiting example is divided into sectors of approximately twenty to thirty meters, each comprising a sprinkler tube 10 disposed under the roof of the tunnel, parallel to the axis AA of the sector concerned, and provided with foam extinguisher nozzles 12 arranged, approximately every three meters. These nozzles are directed towards the ground and, in the example shown, aligned along the axis AA.

The installation also includes a mixer 14, the inlet E1 of which is connected to a single pressurized water pipe 16 passing through the tunnel and the inlet of which E2 is connected to a foam concentrate tank 18 via a regulating valve 20. The outlet S of the mixer 14 is connected to the sprinkler tube 10 via a control valve 22.

Reference will now be made to FIGS. 2 and 3 which show, more precisely, the sprinkler tube 10 and the foam extinguishing nozzles 12 according to the invention.

The tube 10 is of circular section. Its diameter is typically between 25 and 150 mm and its length is that of the sector, that is to say from twenty to thirty meters in the example described.

The nozzles 12 each consist of a slot 24 formed in the wall of the tube 10 vertical to its axis AA and parallel to it and of a device 26, called a foam expansion cage, disposed in front of the slot. Typically, the length thereof is between 60 and 100 mm and its width is approximately 0.2 to 1 mm depending on the water supply and the flow rate of foam necessary for extinction.

The expansion cage 26 is formed by an upper wall 28, a lower wall 30 and an intermediate wall 32, produced by means of a mesh of stainless steel or synthetic material whose mesh is between 1 and 3 mm. The upper wall 28 has a triangle-shaped section, the edge of which faces the slot 24 parallel to it and is arranged about 1 mm from it. The angle at the top of the triangle is between 110 and 130 °, while its base has substantially the same dimension as the diameter of the tube 10.

The lower wall 30 is curved, with a center substantially coincident with that of the tube 10. Its base has the same dimension as that of the upper wall 28.

The intermediate wall 32, planar, provides the connection between the upper wall 28 and the lower wall 30. It will be noted that it extends, beyond its junction with the upper wall 28, by a portion 34 which ends at the level of the edge thereof. The distance between the edge and the point furthest from the bottom wall 30 is typically between 30 and 50 mm.

The walls of the cage 26 are advantageously joined by welding or by stapling.

As shown in FIG. 4, the edge of the upper wall 28 is extended, at its two ends, by a tongue 36 which is welded to a collar 38 taking place around the tube and hanging on it using a loop 40 and a hook 42.

In operation, when a fire is detected by any means, the control valve 22 is opened manually or automatically. A mixture of water and foam concentrate, the content of which, typically from 2 to 5%, has been previously adjusted by the regulating valve 20, is sent to the sprinkler tube 10.

The slot 24 creates a powerful jet directed on the edge of the upper wall 28. This jet penetrates into the cage 26 and invades it while generating a suction current which brings in air mixing intimately with the particles of liquid.

The mixture then passes through the intermediate wall 32 and the bottom wall 30 with a pressure still sufficient to confine the emulsion and produce a dense foam heavy enough to cover the floor of the tunnel without being dragged by drafts.

It will be noted that the projected jet of water and foam concentrate is sufficiently deflected so that foam is also produced above the cage 26 and passes through the upper portion 34 of the intermediate wall 32, thus adding to the foam. ejected from the cage.

Very interestingly and surprisingly, experience shows that the cage 26 also has the effect of diverting the jet of foam by 90 °. It is likely that this deviation is due to Coriolis forces. Thus, the foam forms a screen whose plane is substantially perpendicular to the longitudinal axis of the tunnel and which folds down and absorbs the smoke from the fire.

The flow rate Q of the foam produced is given by the formula: Q = κ P * f in which K is an experimental shape coefficient, characteristic of the nozzle, P is the pressure of the mixture in the tube 10 and f is the coefficient of expansion defined as the ratio between the volume of foam produced and the volume of liquid.

Take for example: - a tunnel 24 m long and 9 m wide; - an installation with nozzles having a slot 80 mm long and 0.6 mm wide, which have a coefficient K of 26.2 and an expansion f of 30; and - a mixture of water and foam concentrate circulating at a pressure of 3 bars.

The objective of this installation is to produce a thickness of 15 cm of foam per minute and per square meter, distributed uniformly over the roadway of the tunnel. This thickness is sufficient to extinguish most fires.

The tunnel pavement having a surface of 9 x 24 = 216 m ² , the desired foam flow rate is 216 x 0.15 = 32.4 m ³ / min. A single nozzle, dimensioned as described above, produces: 26.2 x 3 ^1/2 x 30 = 1.351 m ³ / min of foam.

Thus, the installation must include 32.4 / 1, 351 = 24 nozzles.

The flow rate of the mixture circulating in the sprinkler tube will be 26.2 * 3 ^1/2 * 24 = 1089 L / min. For a mixture comprising 5% foam concentrate, the water flow rate must therefore be 1034 L / min.

It will be noted that the example of calculation given above does not take account of the pressure losses caused by the piping. For a finer calculation, it is possible to calculate the pressure differences between two adjacent nozzles caused by the pressure drops and therefore to differentiate the flow of foam produced by each nozzle.

The present description has been made with reference to a tube 10, the slots 24 of which are all aligned vertically with its axis AA. It goes without saying that, depending on the size of the tunnel, it may be advantageous, for a better distribution of the foam, to stagger the slots in staggered rows, for example, at 45 ° relative to the vertical diameter of the tube. Of course, the cages are always centered on the slots.

It goes without saying, also, that, for a very wide tunnel, the installation can comprise two or three parallel tubes distributed under the roof.

Furthermore, to increase the flow rate of foam produced, each nozzle may include a plurality of slots centered on the edge of the top of the triangle of the cage, for example, three 0.2 mm slots separated by 2 mm.

Thus is proposed an inexpensive foam extinguishing system, easy to install, compact and particularly effective.

Claims

1. Fire extinguishing system using foam, characterized in that it comprises: - a tube (10) intended to take place above a space to be protected and which can be supplied with using a mixture of pressurized water and foam concentrate, and - at least one extinguishing nozzle (12) consisting of at least one slot (24) formed in the wall of said tube and an overflow cage (26) arranged to receive the jet of liquid delivered by said slot and produce foam which is poured onto said space.

2. System according to claim 1, characterized in that said slot (24) is substantially parallel to the axis of the tube (10) and to the axis of the cage (26).

3. System according to one of claims 1 and 2, characterized in that said nozzle comprises a plurality of parallel slots (24).

4. System according to one of claims 1 to 3, characterized in that said cage (26) is made of mesh and comprises: - an upper wall of triangle-shaped section (28) whose edge faces said slot (24), parallel to it, and - a curved lower wall (30) substantially concentric with the tube (10).

5. System according to claim 4, characterized in that the angle at the top of said triangle is substantially between 110 and 130 °.

6. System according to one of claims 4 and 5, characterized in that the base of said triangle has substantially the same dimension as the diameter of the tube (10).

7. System according to claim 6, characterized in that the base of said lower part (30) has substantially the same dimension as that of said triangle.

8. System according to claim 7, characterized in that said cage (26) has an intermediate wall (32) between the upper wall (28) and the lower wall (30).

9. System according to claim 8, characterized in that said intermediate wall (32) is extended, beyond its junction with the upper wall (28), by a portion (34) which ends substantially at the fish bone.

10. System according to one of claims 1 to 9, characterized in that said slot (24) has a width between 0.2 and 1 mm and in that said edge is arranged about 1 mm from it.

11. System according to one of claims 1 to 10, characterized in that said cage (26) is integral with a fixing collar (38) taking place around the tube (10).

12. System according to one of claims 1 to 11, characterized in that it comprises a plurality of nozzles (12) arranged on said tube (10) so as to distribute the watering in the space to be protected.