Watertight integrity, bilge, ballast, and stability instrumentation
What the exam tests
This domain tests watertight integrity indications, bilge alarms, ballast monitoring, and the loading or stability instrument. The exam wants evidence that the bridge knows the actual door, tank and bilge condition, not the intended condition.
Core rules
Watertight door position must be indicated on a panel on the navigation bridge, with audible and visual alarms when a door closes remotely or is opened. Doors must not be held open in a way that defeats the subdivision. Bilge level alarms are required in periodically unattended machinery spaces and other unmanned spaces where flooding could go undetected. Ballast tank contents and draught readings feed the loading computer, which must be approved for the ship and used within its limitations. A stability instrument must be type-approved and checked against the approved stability booklet. Sensors need calibration and fault indication.
Worked example
The bridge indicator shows a lower-deck watertight door as open while the ship is at sea. The watchkeeper must not assume the sensor is wrong. The door is treated as an integrity breach until a crew member confirms the local position and closes it. The event, alarm and restoration are recorded. If the indicator later shows closed but the local door is open, the sensor is defective and the door is still a breach.
Traps
Do not rely on a green light without checking the local door after maintenance. Do not use a loading computer outside its approved trim or tank configuration. Do not ignore a bilge alarm because it is recurrent; recurrent alarms can indicate a real leak. Do not confuse ballast sequence control with stability approval.