NORIMOS 4 1000pt

Common issues

• Sensor or transmitter drift/failure causing false alarms
• Wiring or connector corrosion in engine-room junction boxes leading to intermittent signal loss
• I/O card or process station module failure
• HMI/operator panel slow response or lock-ups after long uptime
• Loss of communication on a Modbus/serial field bus segment
• Backup battery/UPS degradation affecting alarm system availability during a power loss
• Configuration mismatch after a partial firmware/software update

Inspection checklist

• Functional test of a representative sample of alarm points (class-required annual test)
• Verify group and individual alarm/shutdown functions on selected inputs
• Check battery backup autonomy and charging condition
• Inspect field wiring and junction boxes for corrosion and moisture ingress
• Confirm event logger/printer is recording and time-synchronised
• Check redundancy/failover of process stations if fitted
• Verify HMI alarm acknowledgement and screen response
• Confirm installed firmware/software revision matches the approved configuration record

Service intervals

Critical spares

• I/O module, analog and digital (matching card type)
• Power supply unit
• HMI/operator panel unit
• Backup battery pack
• Field wiring terminal blocks/connectors

Safety

• Never silence a repeated alarm without first confirming the root cause - false-alarm fatigue can mask a real fault
• Backup power failure can leave the engine room without alarm coverage - autonomy must be tested, not assumed
• Isolate power before replacing a live I/O card

Class survey

For ships with an unattended machinery space (UMS/AUT) notation, the alarm and monitoring system is surveyed under the periodical UMS survey, which typically includes a sample functional test of alarms, shutdowns and the dead-man/watchcall arrangement; keep the approved alarm point list on board for reference.