Page 255 - Introduction to Marine Engineering

Chapter 13

Fire fighting and safety

Fire is a constant hazard at sea. It results in more total losses of ships than
any other form of casualty. Almost all fires are the result of negligence
or carelessness.
Combustion occurs when the gases or vapours given off by a substance
are ignited: it is the gas given off that burns, not the substance. The
temperature of the substance at which it gives off enough gas to
continue burning is known as the 'flash point'.
Fire is the result of a combination of three factors:

1. A substance that will burn.
2. An ignition source.
3. A supply of oxygen, usually from the air.

These three factors are often considered as the sides of the fire triangle.
Removing any one or more of these sides will break the triangle and
result in the fire being put out. The complete absence of one of the three
will ensure that a fire never starts.
Fires are classified according to the types of material which are acting
as fuel. These classifications are also used for extinguishers and it is
essential to use the correct classification of extinguisher for a fire, to
avoid spreading the fire or creating additional hazards. The classifica-
tions use the letters A, B, C, D and E.

Class A Fires burning wood, glass fibre, upholstery and furnishings.
Class B Fires burning liquids such as lubricating oil and fuels.
Class C Fires burning gas fuels such as liquefied petroleum gas.
Class D Fires burning combustible metals such as magnesium and
aluminium.
Class E Fires burning any of the above materials together with high
voltage electricity.

Many fire extinguishers will have multiple classifications such as A, B
and C.

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