ISGOTT Chapter 5 Fire Fighting

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This Chapter describes the types of fire that may be encountered, together with the
means of extinguishing fires. Descriptions of fire-fighting equipment to be found on
tankers and in terminals are provided in Chapters 8 and 19 respectively.
5.1 THEORY OF FIRE-FIGHTING
Fire requires a combination of fuel, oxygen, a source of ignition, and a continuous
chemical reaction, commonly referred to as combustion.
Fires are extinguished by the removal of heat, fuel or air, or by interrupting the chemical
reaction of combustion. The main objective of fire fighting is to either reduce the
temperature, remove the fuel, exclude the supply of air, or interfere chemically with the
combustion process with the greatest possible speed.
5.2 TYPES OF FIRE AND APPROPRIATE EXTINGUISHING AGENTS
The classification of fires given below is that historically provided in ISGOTT and
conforms to the classifications used within the European Union (EU). Alternative
classifications may be used outside the EU.
5.2.1 CLASS A - ORDINARY (SOLID) COMBUSTIBLE MATERIAL FIRES
Class A fires are those involving solid cellulosic materials such as wood, rags, cloth,
paper, cardboard, clothing, bedding, rope and other materials such as plastic, etc.
Cooling by large quantities of water, or the use of extinguishing agents containing a large
proportion of water, is of primary importance when fighting fires involving ordinary
combustible material. Class A materials can support deep-seated and smouldering fires
long after visible flames are extinguished. Therefore, cooling the source and surrounding
area should continue long enough to ensure that no re- ignition of deep-seated fires is
possible.

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5.2.2 CLASS B - FIRES INVOLVING FLAMMABLE AND COMBUSTIBLE
HYDROCARBON LIQUIDS
Class B fires are those that occur in the vapour-air mixture over the surface of flammable
and combustible liquids such as crude oil, gasoline, petrochemicals, fuel and lubricating
oils, and other hydrocarbon liquids. Fires involving flammable gases are generally
included in this classification.
These fires are extinguished by isolating the source of fuel (stopping flow of fuel),
inhibiting the release of combustible vapours or by interrupting the chemical reaction of
the combustion process. Since most Class B materials burn with greater intensity and reignite
more readily than Class A materials, more effective extinguishing agents are
generally required.
Class B liquids are generally divided into the two broad categories of non-volatile
(combustible) and volatile (flammable) materials. This division is generally sufficient to
ensure that proper precautions and measures can be specified for handling Class Bliquids. In short, ‘non-volatile’ materials have a flash point of 60°C (140°F) or above, as
determined by the closed cup method of testing. ‘Volatile’ materials have a flash point
below 60°C (140°F), as determined by the same method. Flammable gases are volatile
materials that typically exhibit flash points at temperatures at or below the ambient range
and have relatively high vapour pressures, compared to flammable (volatile) liquids, when
in the liquid state. A liquefied gas, as referred to in the following text, is a flammable gas
that has undergone a phase change to the liquid state by refrigeration or pressurisation.
Low expansion foam, defined and discussed in Section 5.3.2.1, is an effective agent for
extinguishing most hydrocarbon liquid fires. It should be applied so as to flow evenly and
progressively over the burning surface, avoiding undue agitation and submergence. This
can best be achieved by directing the foam discharge against any vertical surface
adjacent to the fire, both in order to break the force of discharge and to build up an
unbroken smothering blanket. If there is no vertical surface, the discharge should be
advanced in oscillating sweeps in the direction of the wind when possible, taking care to
avoid foam plunging into the liquid. Foam spray streams, while limited in range, are also
effective.
Flammable liquid fires of limited size can be rapidly extinguished with dry chemical
agents, but are subject to re-ignition when hot surfaces are in contact with flammable
vapours.
Combustible liquid fires which have not been burning for an extended period, can be
extinguished by water fog or water spray if the whole burning surface is accessible. The
surface of the burning oil transfers its heat rapidly to water droplets which present a very
large cooling surface area. The flame can be extinguished with advancing and oscillating
sweeps of fog or spray across the complete width of the fire. Any oil fire which has been
burning for some time is more difficult to extinguish with water, since the oil will have been
heated to a progressively greater depth and cannot readily be cooled to a point where it
ceases to give off gas.
Water should only be applied to oil fires as a spray or fog. The use of a water jet may
spread the burning oil by splashing or overflow.
An aspect that must be borne in mind with liquid petroleum is the risk of re-ignition, so that
a continuing watch and preparedness should be maintained.

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5.2.3 CLASS C - ELECTRICAL EQUIPMENT FIRES
Class C fires involve energised electrical equipment. These fires may be caused by a
short circuit, overheating of circuits or equipment, lightning, or fire spread from other
areas. The immediate action should be to de-energise electrical equipment. Once deenergised,
a non-conductive agent such as carbon dioxide should be used. Dry chemical
is an effective non-conductive extinguishing agent, but is difficult to clean up after use. If
the equipment cannot be de-energised, it is vital that a non-conductive agent be used.

eagle1208

嘿嘿，就是看不懂，要是能看懂就好了……不过，还是非常感谢！！