GB2233226A

GB2233226A - Fire extinguishing substance.

Info

Publication number: GB2233226A
Application number: GB9013856A
Authority: GB
Inventors: David Nicholas Ball; David John Spring; Simon John Davies
Original assignee: Kidde Graviner Ltd
Current assignee: Kidde Graviner Ltd
Priority date: 1989-06-23
Filing date: 1990-06-21
Publication date: 1991-01-09
Also published as: AU5832090A; GB9013856D0; WO1991000122A1; EP0478625A1; GB8914458D0

Abstract

A fire extinguisher comprises a container (10) containing water (16) which is pressurised by relatively high pressure carbon dioxide within a space (18). Because of its solubility in water, a substantial amount of carbon dioxide is held in the water in solution. When a valve arrangement (14) opens, the gas pressure within the container ejects the water through an outlet (15), initially in the form of relatively large droplets which, because of their size, are optimally projected towards the seat of the fire. However, as the droplets are projected towards the fire, the carbon dioxide dissolved in each droplet comes out of solution and breaks the droplets up into smaller droplets, thus very significantly increasing the fire extinguishant capability of the water. The water may include phosphates and/or citrates for increasing the solubility of the carbon dioxide in the water and may also include an anti-freeze agent and a surfactant.

Description

METHODS, APPARATUS AND SUBSTANCES FOR EXTINGUISHING FIRES The invention relates to methods, apparatus and substances for extinguishing fires.

According to the invention, there is provided a fire extinguishing substance, comprising water containing dissolved gas which is held in solution by applied pressure.

According to the invention, there is further provided fire extinguishing apparatus, comprising a container having a normally closed outlet and partially filled with water and containing carbon dioxide part of which is dissolved within the water and the remainder of which is not dissolved in the water and pressurises the water within the container such that opening of the outlet causes the water to be ejected in droplet form and the droplets to break up thereafter under the influence of the carbon dioxide dissolved in them.

According to the invention, there is yet further provided a method of extinguishing fires, comprising the steps of dissolving a gas within water, and projecting the water towards the fire in relatively large droplet form initially such that the dissolved gas thereafter escapes from the droplets thereby breaking them up into smaller droplets.

Methods, apparatus and substances according to the invention for extinguishing fires will now be described, by way of example only, with reference to the accompanying drawing which is a partial cross-section through a fire extinguisher.

The fire extinguisher comprises a generally cylindrical metal casing 10 built to withstand relatively high internal pressure and having an outlet arrangement 12.

The outlet arrangement 12 incorporates a valve arrangement 14 which will not be described in detail but may take any convenient form. When actuated, by means not shown, the valve arrangement opens and extinguishant (to be described below) passes under high pressure into the outlet arrangement 12 and thence through an outlet 15. One suitable form of valve arrangement comprises a valve member which normally blocks the interior of the container 10 from the outlet arrangement 12 but which may be released rapidly by electrical energisation of a detonator which explosively opens the valve member.

The container 10 contains an extinguishant in the form of water 16 partially filling the container but leaving a space 18. The space 18 is pressurised with a gas, the pressure of this gas causing the extinguishant water 16 to be ejected at high velocity through the outlet 15 when the valve arrangement 14 opens.

The gas 18 (which may be a mixture of gases) is so chosen that it or one of its component gases is significantly soluble in water. The quantity of gas placed in the container during initial filling is such that, taking into account the following factors, namely (a) the quantity of water 16, (b) the amount of the gas which is dissolved in the water 16, the pressure of the gas in the space 18 is sufficient to cause the water to be ejected satisfactorily through the outlet 15 when the valve arrangement is opened and throughout the temperature range over which operation is required.

The pressure of the gas in the space 18 is such that, when the extinguisher is operated, the water emerging from the outlet 15 will be in droplet form. However, and as already explained, the water contains a significant amount of dissolved gas and each such droplet will therefore contain dissolved gas. As the droplets emerge from the outlet into the ambient atmosphere and are propelled towards the fire, the gas pressure within each droplet, no longer restrained by the pressure of the gas in the space 18, will cause it to break up producing significantly smaller droplets.

Such significantly smaller droplets have greater fire extinguishant capability than the initial relatively large droplets.

The relatively large initial size of the droplets is advantageous because it has the effect that they are propelled further by the gas pressure than would small droplets. However, because they break up into much smaller droplets as they are propelled towards the seat of the fire, they give the extinguishant a greater fire extinguishant capability than it would otherwise have.

Advantageously, the gas 18 is carbon dioxide. Carbon dioxide has a very significant solubility in water, amounting to around 60 grams per litre of water at 200C and at a carbon dioxide pressure of 5.lMPa.

Another suitable gas is nitrous oxide, N2O.

Advantageously, a suitable agent is added to the water 16 to increase the solubility of the gas in it. Where the gas is carbon dioxide, suitable solubility increasing agents are phosphates, such as dipotassium hydrogen phosphate, K2HPO4; carbonates, such as potassium carbonate K2C03, or sodium carbonate, Na CO ; borate salts, such as disodium tetraborate, Na2B4 0 amino compounds, such as ethanolamine, diethanolamine, triethanolamine, 6-amino-n-hexanoic acid, tri(hydroxymethyl)methylamine, glycine, lysine, phenyl alanine, aspartic acid, or proline; and citrates, such as sodium citrate, Na3C6H5 07.

The water advantageously also includes an anti-freeze agent (which may be the same substance as the solubility increasing agent, such as dipotassium hydrogen phosphate, or potassium carbonate).

In the foregoing ways, the fire extinguishant capabilities of water can be significantly increased and this enables water to be used as an extinguishant in applications where, hitherto, bromofluorocarbon substances (Halons) would have been used.

A surfactant may also be added with advantage, particularly if the surfactant is of the anionic type, e.g. sodium lauryl sulphate, or sodium dodecylbenzene sulphonate and the like, or of the cationic type, e.g.

lauryl trimethylammonium chloride and the like.

Suitable arrangements, not shown, are incorporated for enabling the container 10 to be re-filled and re-pressurised after use.

The gas 18 may be a single component. However, as stated, it need not be wholly composed of the same gas as is dissolved in the water 16. Mixtures of gases which have differing solubilities in water 16 may be used. Advantageously, a relatively soluble gas (such as carbon dioxide) may be used in combination with a relatively insoluble gas, such as nitrogen, argon or helium. This permits the total pressure in the container to be raised above that achievable by the soluble gas alone.

Advantageously, a small amount of a nucleating agent can be added to the water to improve the evolution rate of the gas from solution when the pressure is released. Such nucleating agents have to be essentially insoluble in the water. Examples of suitable nucleating agents are silica, talc, or feldspar.

Claims

1. A fire extinguishing substance, comprising water containing dissolved gas which is held in solution by applied pressure.

2. A substance according to claim 1, in which the applied pressure is gas pressure applied to and externally of the water wholly by the same gas as is dissolved in the water.

3. A substance according to claim 1, in which the applied pressure is pressure applied to and externally of the water by a mixture of gases1 one of which is the same gas as is dissolved in the liquid.

4. A substance according to claim 3, in which the mixture contains one or more other gases which is or are relatively insoluble in the water.

5. A substance according to claim 4, in which the or one of the other gases is selected from nitrogen, argon and helium.

6. A substance according to any preceding claim, including one or more additives in the water for increasing the solubility therein of the dissolved gas.

7. A substance according to any one of claims 1 to 5, in which the dissolved gas is carbon dioxide.

8. A substance according to claim 7, including one or more additives in the water for increasing the solubility therein of the carbon dioxide.

9. Fire extinguishing apparatus, comprising a container having a normally closed outlet and partially filled with water and containing carbon dioxide part of which is dissolved within the water and the remainder of which is not dissolved in the water and pressurises the water within the container such that opening of the outlet causes the water to be ejected in droplet form and the droplets to break up thereafter under the influence of the carbon dioxide dissolved in them.

10. Apparatus according to claim 9, including at least one further gas which is relatively insoluble in water and is not dissolved in the water and assists the undissolved carbon dioxide is pressurizing the water within the container.

11. A substance or apparatus according to any one of claims 8 to 10, in which one said additive is a phosphate.

12. A substance or apparatus according to claim 11, in which the phosphate is dipotassium hydrogen phosphate.

13. A substance or apparatus according to any one of claims 8 to 10, in which one said additive is a carbonate.

14. A substance or apparatus according to claim 13, in which the carbonate is potassium carbonate or sodium carbonate.

15. A substance or apparatus according to any one of claims 8 to 10, in which one said additive is an amino compound.

16. A substance or apparatus according to claim 15, in which the amino compound is selected from ethanolamine, diethanolamine, triethanolamine, 6-amino-n-hexanoic acid, tri(hydroxylmethyl)methylamine, glycine, lysine, phenyl alanine, aspartic acid, and proline.

17. A substance or apparatus according to any one of claims 8 to 10, in which one said additive is a citrate.

18. A substance or apparatus according to claim 17, in which the citrate is sodium citrate.

19. A substance according to any one of claims 1 to 5, in which the dissolved gas is nitrous oxide.

20. A substance or apparatus according to any preceding claim, including an anti-freeze agent within the water.

21. A substance or apparatus according to any preceding claim, including a surfactant within the water.

22. Fire extinguishing apparatus, comprising a container containing a substance according to any one of claims to 1 to 8 and 19 and having a releasable outlet for ejection of the water by the said applied pressure.

23. A method of extinguishing fires, comprising the steps of dissolving a gas within water, and projecting the water towards the fire in relatively large droplet form initially such that the dissolved gas thereafter escapes from the droplets thereby breaking them up into smaller droplets.

24. A method according to claim 23, in which the droplets are projected by force applied externally to the water by gas pressure which also maintains the dissolved gas dissolved in the water.

25. A method according to claim 24, in which the pressure-applying gas is or includes the same gas as is dissolved in the water.

26. A method according to any one of claims 23 to 25, in which the dissolved gas is carbon dioxide.

27. A method according to any one of claims 23 to 25, in which the dissolved gas is nitrous oxide.

28. A fire extinguishing substance, substantially as described herein.

29. Fire extinguishing apparatus, substantially as described with reference to the accompanying drawing.

30. A method of extinguishing fires, substantially as described herein.