Eagle Security Systems Ltd

Galtee House 1 Heanor Road

ILKESTON

Derbyshire

DE7 8DY

admin@eaglesecurity.org.uk

0115 944 1234

Fire Extinguishers

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Eagle Security Systems Limited

1 Heanor Road

Ilkeston

Derbyshire

DE7 8DY

0115 944 1234

Email admin@eaglesecurity.org.uk

Alarms, Burglar Alarms, Intruder Alarms, Fire Alarms, CCTV, Access Control, Electric Security Fencing, Safes, Door  Telephones


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Which Extinguisher Carbon Dioxide Water Mist Foam Water Fire Extinguisher Wet Chemical Dry Powder Ancillaries

Powder

These are useful multi-purpose extinguishers which are suitable for dealing with fires in electrical equipment and flammable liquids, as well as Class A risks, such as wood, solids and paper.


Advantages

The advantages of powder are as follows:

• suitable for Class A, B and C fires;

• safe to use on electrical equipment;

• fast flame knock-down;

• non-toxic;

• effective against running fuel fires; and

• mass-for-mass, the most efficient firefighting medium.


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Powder may not readily penetrate the spaces inside electrical equipment and, since it does not have the cooling properties of water, re-ignition is common. The use of a powder also results in the medium being spread widely and, even after a small fire, a considerable period may be necessary to clear it up, particularly where it gets inside machinery.

Powder is generally the most suitable extinguishant for fires involving flammable liquids. Powder acts more rapidly than foam and is particularly suitable for dealing with fires which may spread to surrounding materials before a complete foam blanket can form over the burning liquid. It should be noted, however, that if both extinguishing agents are to be used in firefighting operations, the powder should be used first and the area then sealed with foam after the flames have been extinguished. This is because powder acts faster, then foam cools and discourages re-ignition. It is also vital that the powder and foam are compatible.

Powder extinguishers deal more effectively with larger areas of burning liquid than other extinguishers of comparable size. They are effective too on fires in freeflowing liquids, especially where the liquid spills over a fairly large area.

Class B and C fires are extinguished by reactivity of powder within the flame. Fire is a chain reaction whereby free radicals are generated. When finely divided particles of BC powders are introduced into the flame, the recombination of radicals is inhibited

and the chain reaction is interrupted. Providing sufficient powder is available, the combustible air/vapour fuel mixture is diluted and available heat dissipated. Subsequently, the chain reaction is terminated and burning stops.

Class A fires are initially extinguished by a BC-type flame knock down. However, fires of thistype frequently contain glowing embers which, if left, tend to re-ignite and regenerate the burning process.

Powders containing phosphate/sulphate mixtures have melting points of 150°C to 180°C. In contact with hot smouldering materials, the powder grains fuse to give a sticky, oxygen impermeable, barrier. The pores in the material (from which flammable gases may be liberated) are blocked by the sticky residues and re-ignition prevented. Therefore Class A fires

require ABC powder.

Class D fires are based on burning metals and particularly the alkali metals including sodium, potassium, caesium and lithium. The problem with metal fires, generally,

is that they react violently with other firefighting media. Water and any of the foam

materials evolve an explosive gas-hydrogen. Carbon dioxide also gives a violent

chemical reaction.

Conventional powder extinguishers are of little use on metal fires because the velocity of application scatters the burning material – both BC and ABC type powders react with the burning metal. Only Class D powders should be used on

this type of fire.

Application of Class D powders is most effectively achieved by a gently pouring action to prevent scattering of the burning material. This may be from an extinguisher fitted with a special lance or, in the case of small isolated risks, shovel application may be appropriate. In this way, complete coverage of the burning material is possible without spreading the hazard. The high temperatures inherent in fires of this nature are sufficient to stimulate formulation of a semi-fluid crust, which binds together the powder particles. Air is excluded by the rugged crust and the fire is extinguished.

Rapid dissipation of excess heat through the crust assists in cooling, thereby increasing the resistance to re-ignition.

Thus, there are four types of powder extinguisher: ABC powders: these are commonly referred to as general purpose, multi-purpose, or all purpose powders. They are also very effective against running fuel fires. The powder is a mono-ammonium phosphate, treated with flow and moisture repellent additives. ABC powders are suitable for use in stored pressure or gas cartridge

type extinguishers. They are non-toxic, and mass for mass offer the most effective

firefighting medium.

• BC powders: these are commonly referred to as standard powder. They contain sodium or potassium bicarbonate treated with flow and moisture repellent additives. They offer fast knock down and can be used in environments over a wide temperature range of -20°C to 60 °C (EN 3 models). As the name suggests, these powders are recommended for use on Class B and C fires. They are particularly

effective against fire involving alcohols, ketones and esters.

• D powders: these are suitable for fires involving metals. Once the type of metal has been established, specialist advice should be sought to identify the most suitable type of powder to be used. Generally speaking for metal fires not involving lithium, a sodium chloride-based powder is appropriate, for example, Croda M28 F; and for metal fires involving lithium, graphite-based powder is more suitable, for example, Chubb L2, Ansul Lith-X. Powder should be applied gently to the burning metal through a low velocity applicator. This is to allow a thick blanket to be built up over the burning metal with the minimum of disturbance.

High performance powders: these are for special applications. An example is

Monnex (potassium bicarbonate urea base), which is a type of BC powder. It is

recommended for large Class B and C fires and is effective against fires containing

alcohols, ketones and esters

4


Advantages

The advantages of powder are as follows:

• suitable for Class A, B and C fires;

• safe to use on electrical equipment;

• fast flame knock-down;

• non-toxic;

• effective against running fuel fires; and

• mass-for-mass, the most efficient firefighting medium.


Limitations

It is important that the mixing or cross-contamination of different powders be avoided. Some mixtures react, sometimes after a long delay, producing water and carbon dioxide with consequent caking of the powder. In closed containers, this can result in a pressure rise, which could cause the extinguisher to explode.

The disadvantages of powder extinguishers are that they are messy and can

contaminate over a wide area. For instance they may contaminate food or expensive equipment. They may reduce visibility when discharged in confined areas, which could jeopardize rescue and escape. They do not prevent re-ignition of flammable liquids and are ineffective against obstructed Class B fires. They cannot partially extinguish Class B fires. Powders can also be corrosive. Only compatible powders can be used with foams.


4kg powder

£ 24.95

Item:

Price:

6kg powder

£ 25.95

Item:

Price:

9kg powder

£ 31.95

Item:

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6kg Stainless Steel  powder

£ 66.95

Item:

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9kg Stainless Steel  Powder

£ 74.95

Item:

Price:

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Typical Applications

Firetrace stops fires where they start.

Typical Applications

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