WO2000041770A1

WO2000041770A1 - Fire extinguishant

Info

Publication number: WO2000041770A1
Application number: PCT/GB1999/003620
Authority: WO
Inventors: Frank Fitch; Devang Patel
Original assignee: Chubb Fire Limited
Priority date: 1999-01-12
Filing date: 1999-11-02
Publication date: 2000-07-20
Also published as: GB2345849A; GB2345849B; EP1064055A1; AU1056300A

Abstract

A fire extinguishant solution comprising 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 an anionic hydrocarbon surfactant such as sodium octyl sulphate.

Description

FIRE EXTINGUISHANT

The present invention relates to a fire extinguishant solution-

According to the present invention there is provided a fire extinguishant solution

comprising 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 exclusion of an anionic

hydrocarbon surfactant such as sodium octyl sulphate.

According to the invention, there is also provided a fire extinguishant solution consisting

of 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 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 %, a foam booster such as

diethylene glycol monobutyl ether in a proportion from 0.1 weight % to 2.0 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. It is desirable to combine the benefits of foam extinguishants with the fast fire knock¬

down 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 or alteration of a hydrocarbon surfactant (typically an

anionic surfactant) 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 -40° C) 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,

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 % (most preferably 45 weight %

to 55 weight %) potassium lactate, 0.02 weight % to 1 weight % (most preferably 0.08

weight % to 1.0 weight % fluorosurfactant (Atochem Forarfac 1157N), 0.05 weight % to

0.5 weight % (most preferably 0.2 weight % to 0.3 weight %) hydrocarbon surfactant

(Henkel APG 325N), 0.1 weight % to 2.0 weight % (most preferably 0.4 weight % to 0.6

weight %) foam booster (Diethylene glycol monobutyl ether [butyl carbiton/butyl

diglycol]) and a trace of biocide (Nippon Bactrachem W15), the remainder being water.

The foam booster is optional but its inclusion improves the performance of the

extinguishant.

Comparative tests have been conducted on a lm³ 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 burn for 30 seconds to allow for full fire involvement of the diesel before

extinguishant actuation. The following results were obtained:

Tests have also been conducted to compare the effect of the preferred composition and

AFFF on polar-solvent fires.

Tests were conducted on a fire tray as described in MoD Defence standard 42-41 /Issue

1, 0.25m² fire tray. Comparative tests were conducted with a 3 ltr. portable fire

extinguisher filled with AFFF and the preferred composition respectively.

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

CLAΪMS

1. A fire extinguishant solution comprising a modified aqueous fire fighting foam and

a salt selected from a group containing potassium lactate, a glycollic acid salt, a lactic

hydroxybutyrate and potassium tartrate, wherein the aqueous fire fighting foam is

modified by the exclusion of an anionic hydrocarbon surfactant such as sodium octyl

sulphate.

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 aqueous

fire fighting foam includes a fluorosurfactant present in a proportion of from 0.02 weight

% to 1 weight %.

4. A fire extinguishant solution according to any preceding claim, wherein the

aqueous fire fighting foam includes a hydrocarbon surfactant present in a proportion from

0.05 weight % to 0.5 weight %.

5. A fire extinguishant solution according to any preceding claim, wherein the

aqueous fire fighting foam includes a foam booster present in a proportion from 0.1 weight % to 2.0 weight %.

6. 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

0.02 weight % to 1 weight %, a hydrocarbon surfactant in a proportion from 0.05 weight

% to 0.5 weight %, a foam booster such as diethylene glycol monobutyl ether in a

proportion from 0.1 weight % to 2.0 weight % and a trace of biocide, the remainder being

water.

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