GB2345849A

GB2345849A - Fire Extinguishant

Info

Publication number: GB2345849A
Application number: GB9900637A
Authority: GB
Inventors: Frank Fitch; Devang Patel
Original assignee: Chubb Fire Ltd
Current assignee: Chubb Fire Ltd
Priority date: 1999-01-12
Filing date: 1999-01-12
Publication date: 2000-07-26
Anticipated expiration: 2019-01-12
Also published as: EP1064055A1; WO2000041770A1; GB2345849B; AU1056300A

Abstract

A fire extinguishant solution consisting of a modified aqueous fire fighting foam and a salt selected from a group containing potassium lactate, a glycollic acid salt, a lactic acid salt, a hydroxybutyric acid salt, a tartaric acid salt, potassium glycollate, potassium hydroxybutyrate and potassium tartrate, wherein the aqueous fire fighting foam is modified by the removal of a foam boosting component such as butyl diglycol.

Description

2345849 FIRE EXTINGUISHANT The present invention relates to a fire

extinguishant solution.

According to the present invention there is provided a fire extinguishant solution consisting of a modified aqueous fire fighting foam and a salt selected from a group containing potassium lactate, a glycollic acid salt, a lactic acid salt, a hydroxybutyric acid salt, a tartaric acid salt, potassium glycollate, potassium hydroxybutyrate and potassium tartrate, wherein the aqueous fire fighting foam is modified by the removal of a foam boosting component such as butyl diglycol.

According to the invention, there is also provided a fire extinguishant solution consisting of a salt selected from a group containing potassium lactate, a glycolIic acid salt, a lactic acid salt, a hydroxybutyric acid salt, a tartaric acid salt, potassium glycollate, potassium hydroxybutyrate and potassium tartrate in a proportion from 5 weight % to 60 weight %, a fluorosurfactant in a proportion from 0.02 weight % to 1 weight %, a hydrocarbon surfactant in a proportion from 0.05 weight % to 0.5 weight %, and a trace of biocide, the remainder being water.

Fire extinguishant solutions in accordance with the invention will now be described by way of example.

2 It is desirable to combine the benefits of foam extinguishants with the fast fire knockdown effect of fire extinguishing powders. However, an extinguishant combining a salt such as potassium lactate or citrate with a fluorosurfactant has been found to be unstable and unsatisfactory.

An alternative approach is to combine an aqueous foam fire fighting compound (AFFF) with a salt such a potassium lactate. This is also unsatisfactory since the resulting solution is unclear and unstable and has an increased viscosity.

It has been found, however, in accordance with the invention that an AFFF which has been modified by the removal of the foam booster (typically butyl diglycol) provides a highly effective fire extinguishant when combined with a salt such as potassium lactate. Furthermore, the resulting water-based compound has a low freeze temperature (being usable at temperatures less than -30' Q and provides a cost-effective method of producing small particles of extinguishant within a fire for more effective fire-fighting. Furthermore, the fire extinguishant has an approximately neutral PH, is non-toxic, and it improves on powder base extinguishants in that it is easier to distribute through pipework without clogging and is easier to clean up after discharge. It also provides a more effective fire extinguishant than water or a foam/water mix.

Although potassium lactate is the preferred salt, salts of glycollic acid, lactic acid, 3 hydroxybutyric acid and tartaric acid may be used. Also potassium glycollate, potassium hydroxybutyrate or potassium tartrate salts may be used.

The preferred composition is 5 weight % to 60 weight % potassium lactate, 0.02 weight % to I weight % fluorosurfactant, 0.05 weight % to 0.5 weight % hydrocarbon surfactant, and a trace of biocide, the remainder being water.

Comparative tests using this composition have been conducted on a 1 m' test rig with all sides covered apart from the front. An obstruction in the form of a car engine was placed in the centre of the rig and the extinguishant agents were discharged via horizontal jets or overhead sprays. Five litres of diesel with 1 litre of petrol floating on a water base was used as the fuel. The fire was allowed to bum for 30 seconds to allow for full fire involvement of the diesel before extinguishant actuation.

The following results were obtained:

AGENT EXTINCTION TIME DISCHARGE TIME COMMENTS (Seconds) (Seconds) PREFERRED COMPOSITION 250 ml(210gms) 1.6 Fire almost extinguished Preferred Composition 500 ml(420gms) - - Fire extinguished Preferred Composition I Litre (0.83kg) 2.89 8.17 Fire extinguished Preferred Composition I Litre (0.83kg) 0.51 3.58 Fire extinguished easily Preferred Composition 4 COMPARATIVE TESTS 9 It (9kg) AFFF premix 45 106 Fire extinguished 0.25 kg Halon 1211 1.63 4.17 Fire extinguished 0.5 kg Halon 1211 1.38 2.89 Fire extinguished 0.5 kg FM200 2.90 5.46 Fire just extinguished 0.5 kg FE36 5.63 Fire was not extinguished These tests show that the preferred composition has a better performance than AFFF premix, FM200 and FE36. The performance approaches that of Halon 1211.

The preferred extinguishant may be used for fixed systems and portable appliances. Potassium lactate is non-toxic and generally harmless.

In operation, the various components of the extinguishant contribute to the extinguishing action. Thus, the water cools the flammable liquid to below its ignition temperature and the fire goes out. The limiting factor is the droplet size; hence the success of mist and fog systems as compared to jets of water. The smaller the droplet size the greater the surface area, and the more effective the spray. The water droplets absorb heat as they boil and turn to water vapour. This water vapour also takes up significantly more volume, thus diluting the local oxygen level. The addition of the modified AFFF reduces the surface tension of the water to below 20mN/m, and the water forms smaller droplets. The greater surface area of the smaller droplets increases the speed of operation of the extinguishant. Finally, the potassium lactate is broken down by the fire. Heat is absorbed as the compound breaks down and potassium ions are liberated which break the 'fire chain'. Potassium lactate absorbs more energy as it breaks down than potassium bicarbonate which has been used as an extinguishant. The solution droplets entering the combustion zone and impinging on the hot surfaces will release the potassium lactate from the solution.

Claims

6 CLAIMS

1. A fire extinguishant solution consisting of a modified aqueous fire fighting foam and a salt selected from a group containing potassium lactate, a glycollic acid salt, a lactic acid salt, a hydroxybutyric acid salt, a tartaric acid salt, potassium glycollate, potassium hydroxybutyrate and potassium tartrate, wherein the aqueous fire fighting foam is modified by the removal of a foam boosting component such as butyl diglycol.

2. A fire extinguishant solution according to claim 1, wherein the salt is present in a proportion of from 5 weight % to 60 weight %.

3. A fire extinguishant solution according to claim 1 or claim 2, wherein the fluorosurfactant is present in a proportion of from 0.02 weight % to 1 weight %.

4. A f ire extinguishant solution according to any preceding claim, wherein the hydrocarbon surfactant is present in a proportion from 0.05 weight % to 0.5 weight %.

5. A fire extinguishant solution consisting of a salt selected from a group containing potassium lactate, a glycollic acid salt, a lactic acid salt, a hydroxy butyric acid salt, a tartaric acid salt, potassium glycollate, potassium hydroxybutyrate and potassium tartrate in a proportion from 5 weight % to 60 weight %, a fluorosurfactant in a proportion from 7 0.02 weight % to I weight %, a hydrocarbon surfactant in a proportion from 0.05 weight % to 0.5 weight %, and a trace of biocide, the remainder being water.

6. A fire extinguishant solution including a modified AFFF as described herein.