3.1 The presentation of alarms and indicators
should be clear, unambiguous, and consistent.
3.2 All required alarms should be indicated by
both audible and visual means, except the emergency alarms of 2.2 which should be indicated primarily by audible
alarms. In machinery spaces with high ambient noise levels, audible
alarms should be supplemented by visual alarms in accordance with 5.1. Audible alarms may also be supplemented by
visual alarms in accommodation spaces.
3.3 A new alarm condition should be clearly distinguishable
from those existing and accepted, e.g., existing and accepted alarms
are indicated by a constant light and new alarms are indicated by
a flashing light. At control positions or other suitable positions
as required, alarm systems should clearly distinguish between normal,
alarm, and accepted alarm conditions.
3.4 Alarms should be maintained until they are
accepted and the visual indications of individual alarms should remain
until the fault has been corrected, when the alarm system should automatically
reset to the normal operating condition. If an alarm has been accepted
and a second fault occurs before the first is rectified, the audible
and visual alarms are to operate again.
3.5 Alarms should only be capable of being cancelled
if the condition causing them has been dealt with successfully.
3.6 Required alarm systems should be continuously
powered and should have automatic change-over to a stand-by power
supply in case of loss of normal power supply. Emergency alarms and
primary alarms should be powered from the main source of electrical
power and from the emergency sources of electrical power defined by
SOLAS regulations II-1/42 or II-1/43 unless other arrangements
are permitted by those regulations, as applicable, except that:
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.1 the power-operated sliding watertight door
closure alarm power sources may be those used to close the doors;
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.2 the fire-extinguishing medium alarm power source
may be the medium itself; and
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.3 continuously charged, dedicated accumulator
batteries of an arrangement, location and endurance equivalent to
that of the emergency source of electrical power may be used instead
of the emergency source.
3.7 Required rudder angle indicators and power-operated
sliding watertight door position indicators should be powered from
the main source of electrical power and should have an automatic change-over
to the emergency source of electrical power in case of loss of normal
power supply.
3.8 Failure of the normal power supply of required
alarm systems should be indicated by an audible and visual alarm.
3.9 Required alarm systems should, as far as is
practicable, be designed on the fail-to-safety principle, e.g., an
open detection circuit should cause an audible and visual alarm; see
also SOLAS regulations II-2/13.1.2 and II-1/51.1.4.
3.10 Provision should be made for functionally
testing required alarms and indicators. The Administration should
ensure, e.g., by training and drills, that the crew is familiar with
all emergency and primary alarms.
3.11 Required alarms and indicator systems should
be functionally independent of control systems and equipment, or should
achieve equivalent redundancy. Any additional requirements for particular
alarms in the IMO instruments applicable to the ship should be complied
with.
3.12 Computer programs for computerized alarm
and indicator systems should not be permanently lost or altered as
a result of power supply loss or fluctuation. Provision should be
made to prevent unintentional or unauthorized alteration of computer
programs.
3.13 Cables for emergency alarms and their power
sources should be of a fire-resistant type and be run as directly
as is considered practicable by the Administration. Equipment and
cables for emergency alarms and indicators (e.g. watertight doors'
position indicators) should be arranged to minimize risk of total
loss of service due to localized fire, collision, flooding or similar
damage.
3.14 To the extent considered practicable by the
Administration, emergency alarms should be arranged so that the audible
alarm signal can be heard regardless of failure of any one circuit
or component.
3.15 Means should be provided to prevent normal
operating conditions from causing false alarms, e.g., provision of
time delays because of normal transients.
3.16 Alarms and indicators on the navigating bridge
are to be minimized. Alarms and indicators which are not required
alarms and indicators for the navigating bridge should not be placed
on the navigating bridge, unless permitted by the Administration.
3.17 The system should be arranged so that all
alarm signals can be accepted or cancelled at the appropriate control
position only.
3.18 In order to facilitate maintenance and reduce
risk of fire or harm to personnel, consideration should be given to
providing means of isolation of sensors fitted to tanks and piping
systems for flammable fluids or fluids at high temperature or pressure
(e.g. valves, cocks, pockets for temperature sensors).