Page 118 - International safety guide for oil tankers and terminals

INTERNATIONAL SAFETY GUIDE FOR OIL TANKERS AND TERMINALS

5.3.3 Flame Inhibiting Agents
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Flame inhibitors are materials that interfere chemically with the combustion
process and thereby extinguish the flames. However, cooling and removal of
fuel is also necessary if re-ignition is to be prevented.
electrical fires. It must be directed into the flames.พาณิชย์นาวี
5.3.3.1 Dry Chemical
Dry chemical, as a flame inhibitor, is a material that extinguishes the
flames of a fire by interfering chemically with the combustion process. Dry
chemicals have a negligible cooling effect and, if re-ignition due to the
presence of hot metal surfaces is to be prevented, the fuel must be
removed or cooled using water.

Certain types of dry chemical can cause the breakdown of a foam
blanket and only those labelled as being foam compatible should be used
in conjunction with foam.

Dry chemical may be discharged from an extinguisher, a hose reel nozzle,
a fire truck monitor, or a fixed system of nozzles as a free flowing cloud. It
is most effective in dealing with a fire resulting from an oil spill by
providing rapid fire knock-down, and can also be used in confined spaces
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where protection against the inhalation of powder may be necessary. It is
especially useful on burning liquids escaping from leaking pipelines and
joints. It is a non-conductor and is suitable therefore for dealing with
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Dry chemical clogs and becomes unusable if it is allowed to become
damp when stored or when extinguishers are being filled.

Dry chemical is prone to settlement and compaction caused by vibration.
Maintenance procedures should include a schedule for inverting or rolling
the extinguishers to keep the dry chemical powder in a free flowing state.

5.3.3.2 Vaporising Liquids (Halons)
Halon gases are known to have significant ozone depleting properties
and, under the terms of the Montreal Protocol, production of halon was
phased out in 2000. New halon fire-fighting installations have been
prohibited on ships since July 1992. However, many installations will
remain in service for the foreseeable future and, if correctly operated, will
continue to provide adequate fire protection.

Vaporising liquids, in the same way as dry chemical powder, have a flame
inhibiting effect and also have a slight smothering effect. There are a
number of different liquids available, all halogenated hydrocarbons, often
identified by a system of halon numbers.

The halons are most effective in enclosed spaces such as computer
centres, storage rooms, engine rooms or pump rooms, generator
enclosures and similar locations.

All halons are toxic to some degree because contact with hot surfaces
and flames causes them to break down, yielding toxic substances. All
personnel should therefore evacuate the area where halons are to be
used, although it is possible to start the discharge of halons before the
evacuation is complete because the normal concentrations encountered
in extinguishing fires are tolerable for brief periods. After the fire has been
extinguished, the area should be thoroughly ventilated. If it is necessary
to enter the area before ventilation, suitable breathing apparatus should
be used.

84 © ICS/OCIMF/IAPH 2006