GB2246294A

GB2246294A - Fire-extinguishing systems

Info

Publication number: GB2246294A
Application number: GB9114167A
Authority: GB
Inventors: Thomas David Cawley; Denis Shepherd
Original assignee: Hygood Ltd
Current assignee: Hygood Ltd
Priority date: 1990-06-29
Filing date: 1991-07-01
Publication date: 1992-01-29
Anticipated expiration: 2011-07-01
Also published as: GB2246294B; GB9114167D0; GB9014494D0

Abstract

A self-contained, trolley or skid-mounted fire-extinguishing system comprises a source 10 of high-pressure gas e.g. nitrogen which is utilised to power a motor 54 for driving a fan to cause a stream of air to flow through a foam generator 44. The gas is also used, at reduced pressure, to force water 32 through a venturi 36 where it entrains foam concentrate 38 to form a foam concentrate solution which is delivered to the generator 44 through a nozzle 53. <IMAGE>

Description

FIRE-EXTINGUISHING SYSTEMS This invention relates to fire-extinguishing systems, and particularly to such systems which operate by generating a fire-extinguishing foam.

It is an aim of the present invention to provide an efficient self-contained system for generating a fire-extinguishing foam.

According to a first aspect of the present invention there is provided a fire-extinguishing system comprising a generator arranged to generate a fire-extinguishing air foam and driven by pressurised gas.

According to a second aspect of the present invention there is provided a fire-extinguishing system comprising a source of gas under pressure, a supply of foamable solution, and a foam generator, the pressurised gas being arranged both to deliver a flow of foamable solution to the foam generator and to drive air supply means for causing a stream of air to flow through the foam generator.

Preferably the foamable solution is formed by utilising the pressure of, desirably, an inert gas to cause water to flow through a venturi where foam concentrate is inducted -nto the water stream from a separate supply.

Alternatively the foam concentrate can be added to the water supply to form a premix.

The air supply means may take the form of a fan driven by a motor powered by the pressurised gas, or of an air inductor which is similarly powered.

The system according to the present invention may take the form of a fixed installation but, as it is entirely self-contained, it may be made mobile by being mounted, for example, on a trolley or skids. Moreover, the system may be arranged to be actuated manually or actuated automatically by an electrical signal from a fire-detection system.

Although the invention may be carried out in a variety of different ways, one particular embodiment thereof will now be described, by way of example, with reference to the accompanying diagrammatic drawing.

As shown in the drawing a system for generating fire-extinguishing foam comprises a cylinder 10 containing nitrogen for supplying nitrogen to a high pressure manifold 12, the available pressure being monitored by a low pressure switch 14 and the down-stream pressure by a pressure regulator 16, downstream of which the lower pressure supply is branched to a fan motor manifold 18, and via a needle valve 20 and a pressure gauge 22, to a water pressure vessel 24. Upstream of the branch a solenoid valve 26 is fitted by-passed by a line 28 controlled by an emergency manual valve 30.

The water 32 in the water pressure vessel 24 is driven by pressure of the nitrogen into a water manifold 34 which is fitted with a venturi 36 by means of which high-expansion foam concentrate 38 contained in a tank 40 is introduced via a supply line 42 into the water stream.

Downstream of the venturi 36 the water manifold 34 leads to a foam generator 44 and is fitted with a pressure gauge 46 and a pressure switch 48.

The foam generator 44 has a foam-forming screen 50 through which an air stream generated by a fan 52 is driven after it has entrained foam concentrate solution delivered by the water manifold 34 through a nozzle 53. The fan 52 is powered by an air motor 54 supplied with nitrogen at reduced pressure through the fan motor manifold 18 which includes a needle valve 56, a pressure gauge 58 and a pressure switch 60.

For the purpose of testing the fan motor 54 a motor test line 62 including a fan motor test valve 64 bridges the solenoid valve 26, a non-return valve 66 being interposed in the fan motor manifold 18 immediately upstream of its junction with the line 62.

The foam produced by the above-described system is highly expanded, the ratio of foam to the foam concentrate solution being up to 1000:1 depending on the site conditions or hazard. The high-expansion foam generated by the system is an excellent fire-extinguishing medium for Class A, B and C risks; and it can also be used to reduce the evaporation rate of flammable or toxic fluids, or to displace flammable or toxic gases from an enclosure.

In alternative embodiments the source of compressed gas may be constituted by more than one cylinder of nitrogen, and another suitable compressed gas substituted for the nitrogen; and in the foam generator an air inductor may be substituted for the air motor-driven fan 52.

The arrangement of pressure gauges, pressure switches, pressure relief valves, stop valves and restrictor valves may of course be altered to meet the requirements of any particular installation.

Claims

1. A fire-extinguishing system comprising a generator arranged to generate a fire-extinguishing air foam and driven by pressurised gas.

2. A fire-extinguishing system comprising a source of gas under pressure, a supply of foamable solution, and a foam generator, the pressurised gas being arranged both to deliver a flow of foamable solution to the foam generator and to drive air supply means for causing a stream of air to flow through the foam generator.

3. A system as claimed in claim 2, in which the foamable solution is formed by utilising the pressurised gas to cause water to flow through a venturi where foam concentrate is inducted into a water stream from a separate water supply.

4. A system as claimed in claim 2, in which the foam concentrate is added to a water supply to form a pre-mix.

5. A system as claimed in claim 2, 3 or 4, in which the air supply means comprise a fan driven by a motor or an air inductor powered by the pressurised gas.

6. A system as claimed in any preceding claim, in which the pressurised gas is an inert gas.

7. A fire-extinguishing system substantially as hereinbefore described with reference to the accompanying drawing.

8. A system as claimed in any preceding claim and being a fixed installation.

9. A system as claimed in any one of claims 1 to 7, being a mobile installation.

10. A system as claimed in any preceding claim, being a manually-actuated system.

11. A system as claimed in any preceding claim, being a system arranged to be automatically actuated by an electrical signal from a fire-detection system.

12. The features as herein disclosed, or their equivalents, in any novel patentable selection.