4.1 The presentation of alerts and indicators should be
clear, distinctive, unambiguous and consistent.
4.2 All required alerts should be indicated by both audible
and visual means, except the emergency alarms of 3.2 which should be
indicated primarily by a signal. In machinery spaces with high ambient noise
levels, signals should be supplemented by indicators, presented in
accordance with 6.1. Signals and announcements may also be supplemented by
indicators in accommodation spaces.
4.3 Where audible alerts are interrupted by public
announcements the visual alert should not be affected.
4.4 A new alert condition should be clearly distinguishable
from those existing and acknowledged, e.g., existing and acknowledged alarms
and warnings are indicated by a constant light and new (unacknowledged)
alarms and warnings are indicated by a flashing light and an audible signal.
Audible signals should be stopped when silenced or acknowledged. At control
positions or other suitable positions as required, alert systems should
clearly distinguish between no alert (normal condition), alert, silenced and
acknowledged alert conditions.
4.5 Alerts should be maintained until they are acknowledged
and the visual indications of individual alerts should remain until the
fault has been corrected. If an alert has been acknowledged and a second
fault occurs before the first is rectified, the audible signal and visual
indication should be repeated.
4.6 Alerts and acknowledged alerts should be capable of
being reset only in case the abnormal condition is rectified.
4.7 The presentation and handling of alarms, warnings and
cautions indicated on the navigation bridge should comply with the
requirements of module C of resolution MSC.252(83) where applicable to ships
with Integrated Navigation Systems (INS) and, where fitted, with the
requirements of a bridge alert management system.
4.8 Required alert systems should be continuously powered
and should have an automatic change-over to a stand-by power supply in case
of loss of normal power supply. Emergency alarms and 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,
- the power-operated sliding watertight door closure alarm power sources
may be those used to close the doors;
- the fire-extinguishing pre-discharge alarm power source may be the
medium itself; and
- 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.
4.9 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 changeover to the
emergency source of electrical power in case of loss of normal power
4.10 Failure of power supply of required alert and alarm
systems should be indicated by an audible and visual alarm or warning.
4.11 Required alert and alarm systems should, as far as is
practicable, be designed on the fail-to-safety principle, e.g., a detection
circuit fault should cause an audible and visual alarm; see also FSS Code,
chapter 9, paragraph 184.108.40.206.
4.12 Provision should be made for functionally testing
required alerts and indicators. The Administration should ensure, e.g., by
training and drills, that the crew is familiar with all alerts.
4.13 Required alert, alarm and indicator systems should be
functionally independent of control systems and equipment, or should achieve
equivalent redundancy. Any additional requirements for particular alerts in
the IMO instruments applicable to the ship should be complied with.
4.14 Software and data for computerized alert and alarm
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 software and data.
4.15 Cables for fire and general emergency alarms and public
address systems and their power sources should be of a fire-resistant type
where they pass through high fire risk areas, and in addition for passenger
ships, main vertical fire zones, other than those which they serve. Systems
that are self monitoring, fail-safe or duplicated with cable runs as widely
separated as is practicable may be exempted provided that their
functionality can be maintained. 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.
4.16 To the extent considered practicable by the
Administration, general emergency alarm, fire alarm and fire-extinguishing
pre-discharge alarm should be arranged so that the audible signals can be
heard regardless of failure of any one circuit or component.
4.17 Means should be provided to prevent normal operating
conditions from causing false alerts, e.g., provision of time delays because
of normal transients.
4.18 The number of alerts and indicators which are not
required to be presented on the navigation bridge should be minimized.
4.19 The system should be designed so that alerts can be
acknowledged and silenced at the authorized control position. All alerts
presented on the navigation bridge should be capable of being acknowledged
and silenced as required in module C of resolution MSC.252(83) where
applicable to ships with Integrated Navigation Systems (INS) and, where
fitted, with the requirements of a bridge alert management system.
4.20 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).