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.
Two
basically different types of equipment are available on board ship for the
control of fires. These are small portable extinguishers and large fixed
installations. The small portable extinguishers are for small fires which, by
prompt on-the-spot action, can be rapidly extinguished. The fixed installation
is used when the fire cannot be fought or restrained by portable equipment or
there is perhaps a greater danger if associated areas were to be set on fire.
The use of
fixed installations requires evacuation of the area containing the fire which,
if it is the machinery space, means the loss of effective control of the ship.
Various types of both portable and fixed firefighting equipment are available.
Fire
protection on ships is provided by detection and fire-fighting equipment
together with structural features which are intended to contain an outbreak of
fire and the employment when required of non-combustible materials to prevent
its spread.
Fire is the
result of a combination of three factors: a substance that will burn, an ignition source,
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 classifications 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. Fire
fighting at sea may be considered in three distinct stages, detection — locating
the fire; alarm — informing the rest of the ship; and control — bringing to
bear the means of extinguishing the fire.
There are
four principal types of portable extinguisher usually found on board ship.
These are the soda-acid, foam, dry powder and carbon dioxide extinguishers.
A variety of
different fixed fire-fighting installations exist, some of which are specifically
designed for certain types of ship. A selection of the more general
installations will now be outlined.
Machinery
spaces are protected by fixed fire extinguishing installations, the fire main
and extinguishers. Any statutory fixed installation must be operable from a
position outside of the space. Any emergency stops for machinery and vent fans,
means of securing openings and fuel tank valve shut-off devices, must also be
located external to the space.
Engine room
fires have been started by neglected oil leaks with the combustible material,
in the form of fuel or lubricating oil dripping on to and being ignited by hot
exhaust manifolds. There are a number of examples of combustible materials and
potential ignition sources in machinery spaces.
A fire when it starts is usually small enough to be dealt with by a vigilant watchkeeper using a portable fire extinguisher. A fire which develops undetected in an unmanned machinery space (or one where the watchkeeper is in a control room) could require complete shutdown, evacuation and employment of the inert gas system. With unmanned spaces, an efficient alarm system for early detection is vital.
A fire when it starts is usually small enough to be dealt with by a vigilant watchkeeper using a portable fire extinguisher. A fire which develops undetected in an unmanned machinery space (or one where the watchkeeper is in a control room) could require complete shutdown, evacuation and employment of the inert gas system. With unmanned spaces, an efficient alarm system for early detection is vital.
I. Answer the questions.
1. What is the
most frequent reason for a fire?
2. What types of
fire-fighting equipment are used on board ships?
3. What does the
use of fixed installation require?
4. How is fire
prevention provided on board ships?
5. What are the
three factors which result in a fire?
6. What can
ensure that a fire never starts?
7. How are fires
classified?
8. What are the
three stages of fire fighting at sea?
9. What are the
types of portable extinguishers?
10. How are
fixed fire-fighting installations operated?
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