2.1.1 The system should consist of a control panel
housing the gas analysis unit and sample extraction pump(s), connected
to gas sampling pipes, and one or more indicating units.
2.1.2 The system should be capable of continuously
measuring hydrocarbon gas concentrations, and may be arranged to operate
on a sequential scanning principle, provided that each sampling line
of each protected space is analysed at intervals not exceeding 30
min.
2.1.3 The system should be provided with a means
to monitor air flow acceptable to the Administration.
2.1.4 Means should be provided to prevent ballast
water from entering the system.
2.1.5 The system should have ingress protection
suitable for the installed location of each component. In any event,
the system should be designed such that dust may not enter in sufficient
quantity to interfere with the satisfactory operation of the equipment
and water splashing against the enclosure from any direction has no
harmful effect.
2.1.6 Enclosures containing electrical components
such as gas analysis units, extraction pumps, and alarm control devices
should be of gas-tight construction having doors fitted with gaskets.
Electrical components which would reasonably be expected to come into
contact with sample gases should be explosion-proof.
2.1.7 The system should be designed, constructed
and installed to prevent the leakage of hydrocarbon gases into any
accommodation and service spaces, control stations or machinery spaces.
2.1.8 The system should be designed to withstand
supply voltage variations and transients, ambient temperature changes,
vibration, humidity, shock, impact, and corrosion normally encountered
on ships, and to avoid the possibility of ignition of a flammable
gas mixture.
2.1.9 The switchover sequence should be designed
to keep changing the sampling line of each protected space according
to a planned sequence, even if flammable gas above the alarm level
is detected at a sampling point.