12.8.1 Separation and duplication of electrical
supply should be provided for duplicated consumers of essential services.
During normal operation these consumers may be connected to the same
power-bus directly or via distribution boards or group starters, but
should be separated by removeable links or other approved means. Each
power-bus should be able to supply all equipment necessary to maintain
the control of propulsion, steering, stabilization, navigation, lighting
and ventilation, and allow starting of the largest essential electric
motor at any load. However, having regard to 12.1.2, partial reduction in the capability from normal operation
may be accepted. Non-duplicated consumers of essential services connected
to the emergency switchboard directly or via distribution boards may
be accepted. Automatic load-dependent disconnection of non-essential
consumers may be allowed.
12.8.2 Emergency source of electrical power
12.8.2.1 Where the main source of electrical power
is located in two or more compartments which are not contiguous, each
of which has its own self-contained systems, including power distribution
and control systems, completely independent of each other and such
that a fire or other casualty in any one of the spaces will not affect
the power distribution from the others, or to the services required
by 12.8.2.2, the requirements of 12.3.1, 12.3.2
and 12.3.4 may be considered satisfied without an additional
emergency source of electrical power, provided that:
-
.1 there is at least one generating set, meeting
the requirements of 12.3.12 and each
of sufficient capacity to meet the requirements of 12.8.2.2, in each
of at least two non-contiguous spaces;
-
.2 the arrangements required by .1 in each such
space are equivalent to those required by 12.3.6.1,
12.3.7 to 12.3.11 and 12.4 so
that a source of electrical power is available at all times to the
services required by 12.8.2: and
-
.3 the generator sets referred to in .1 and their
self-contained systems are installed in accordance with 12.3.2.
12.8.2.2 The electrical power available should
be sufficient to supply all those services that are essential for
safety in an emergency, due regard being paid to such services as
may have to be operated simultaneously. The emergency source of electrical
power should be capable, having regard to starting currents and the
transitory nature of certain loads, of supplying simultaneously at
least the following services for the periods specified hereinafter,
if they depend upon an electrical source for their operation:
-
.1 for a period of 12 h, emergency lighting:
-
.1.1 at the stowage positions of life-saving appliances;
-
.1.2 at all escape routes such as alleyways, stairways,
exits from accommodation and service spaces, embarkation points, etc.;
-
.1.3 in the public spaces, if any;
-
.1.4 in the machinery spaces and main emergency
generating spaces including their control positions;
-
.1.5 in control stations;
-
.1.6 at the stowage positions for fireman's outfits;
and
-
.1.7 at the steering gear;
-
.2 for a period of 12 h:
-
.2.1 the navigation lights and other lights required
by the International Regulations for Preventing Collisions at Sea
in force;
-
.2.2 electrical internal communication equipment
for announcements during evacuation;
-
.2.3 fire detection and general alarm system and
manual fire alarms; and
-
.2.4 remote control devices of fire-extinguishing
systems, if electrical;
-
.3 for a period of 4 h of intermittent operation:
-
.3.1 the daylight signalling lamps, if they have
no independent supply from their own accumulator battery; and
-
.3.2 the craft's whistle, if electrically driven;
-
.4 for a period of 12 h:
-
.4.1 the navigational equipment as required by chapter 13. Where such provision is unreasonable
or impracticable, the Administration may waive this requirement for
craft of less than 5,000 tons gross tonnage;
-
.4.2 essential electrically powered instruments
and controls for propulsion machinery, if alternate sources of power
are not available for such devices;
-
.4.3 one of the fire pumps required by 7.7.8.1;
-
.4.4 the sprinkler pump and drencher pump, if
fitted;
-
.4.5 the emergency bilge pump and all the equipment
essential for the operation of electrically powered remote controlled
bilge valves as required by chapter 10;
and
-
.4.6 craft radio facilities and other loads as
set out in 14.12.2;
-
.5 for a period of 10 min, power drives for directional
control devices including those required to direct thrust forward
and astern, unless there is a manual alternative acceptable to the
Administration as complying with 5.2.3.
12.8.2.3 Provision should be made for the periodic
testing of the complete emergency system including the emergency consumers
required by 12.8.2.2 and should include the testing of automatic starting
arrangements.
12.8.2.4 Where the emergency source of electrical
power is a generator, a transitional source of emergency electrical
power should be provided according to 12.8.3, unless the automatic
starting system and the characteristics of the prime mover are such
as to permit the emergency generator to carry its full rated load
as quickly as is safe and practicable, subject to a maximum of 45
s.
12.8.3 Transitional source of emergency electrical
power
The transitional source of emergency electrical power required
by paragraph 12.8.2.4 may consist of an accumulator battery suitably
located for use in an emergency which should operate without recharging
while maintaining the voltage of the battery throughout the discharge
period within 12% above or below its nominal voltage and be of sufficient
capacity and so arranged as to supply automatically, in the event
of failure of either the main or emergency source of electrical power,
at least the following services, if they depend upon an electrical
source for their operation:
-
.1 for a period of 30 min, the load specified
in 12.8.2.2.1, .2 and .3; and
-
.2 with respect to the watertight doors:
-
.2.1 power to operate the watertight doors, but
not necessarily simultaneously, unless an independent temporary source
of stored energy is provided. The power source should have sufficient
capacity to operate each door at least three times, i.e closed - open
- closed against an adverse list of 15°; and
-
.2.2 power to the control, indication and alarm
circuits for the watertight doors for half an hour.