12.3.1 In any craft there should be a self-contained
emergency source of electrical power located above the waterline in
the final condition of damage as referred to in Chapter
2. Automatic starting and switching devices should ensure an
emergency power supply as quickly as is practicable and in any case
within 20 seconds.
12.3.2 The location of the emergency source of
power should be such as to ensure, to the satisfaction of the Administration,
that a fire, or other serious failure in the space containing the
main source of electrical power or in the propelling machinery space
will not interfere with the supply or distribution of emergency power.
12.3.3 Provided that suitable measures are taken
for safeguarding independent circuits under all circumstances, the
emergency source of power may, in special cases, be used for short
periods, to supply non-emergency circuits.
12.3.4 The emergency source of power should be
capable of supplying simultaneously the following services:
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(a) for a period of 2 hours, emergency lighting:
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(i) at the stowage positions of life-saving appliances;
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(ii) at all escape routes, such as alleyways,
stairways, exits from accommodation and service spaces, embarkation
points, etc.;
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(iii) in the passenger compartments;
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(iv) in the machinery spaces and main emergency
generating spaces including their control positions;
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(v) in control stations;
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(vi) at the stowage positions for fireman's outfits;
and
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(vii) at the steering gear;
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(b) for a period of 2 hours:
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(i) main navigation lights, except for "not under
command" lights;
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(ii) electrical internal communication equipment
for announcements for passengers and crew required during evacuation;
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(iii) fire detection and general alarm system
and manual fire alarms; and
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(iv) remote control devices of fire extinguishing
systems, if electrical;
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(c) for a period of 4 hours of intermittent operation:
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(i) the daylight signalling lamps, if they have
no independent supply from their own accumulator battery; and
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(ii) the craft's whistle, if electrically driven;
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(d) for a period of 4 hours:
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(i) craft radio facilities required by the Administration
to be available in an emergency unless they are supplied by an independent
battery (see 13.3.2); and
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(ii) essential electrically powered instruments
and controls for propulsion machinery, if alternate sources of power
are not available for such devices; and
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(e) for a period of 12 hours: the "not under command"
lights.
12.3.5 The emergency lighting system should be
such that a fire or other occurrence in the spaces containing the
emergency source of electrical power will not render the main lighting
system inoperative.
12.3.6 The emergency source of electrical power
should either be an accumulator battery or a generator driven by a
suitable independent prime mover with supply of fuel from a separate
tank (see 7.1.1 (b) for flashpoint limit).
12.3.7 The accumulator battery should be capable
of carrying the emergency load without recharging whilst maintaining
the voltage throughout the discharge period within ±12 per
cent of its nominal voltage.
12.3.8 The emergency switchboard should be installed
as near as is practicable to the emergency source of power and should
be located in accordance with the requirements of 12.3.1 and 12.3.2. Where the emergency source of power is a
generator, the emergency switchboard should generally be located in
the same space.
12.3.9 Where the main and emergency sources are
of the same voltage and frequency, the emergency switchboard should
be supplied:
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(a) in normal operation from the main switchboard
by an interconnector feeder which is to be adequately protected at
the main switchboard against overload and short circuits; and
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(b) automatically from the emergency source of
power in the event of failure of the normal supply from the main switchboard.
Where the system is arranged for feed-back operation, the interconnector
feeder is also to be protected at the emergency switchboard at least
against short circuit.
12.3.10 An indicator should be mounted in the
craft's control position to indicate when the emergency accumulator
battery is being discharged, or when any emergency engine-driven generator
is in operation.
12.3.11 Arrangements should be made so that the
emergency system including the emergency source of power will function
satisfactorily, when the craft has a list or trim up to the maximum
angle anticipated, including any postulated damage cases considered
in Chapter 2.
12.3.12 Provision should be made for the periodic
testing of the complete emergency system, including the testing of
automatic arrangements.