What it is
Condition-based maintenance replaces calendar-driven overhaul with intervention triggered by measured machine condition. Onboard, its commercial value has a specific name: survey credit. With a programme approved by the classification society, continuous monitoring substitutes for opening machinery up for inspection.
How it works
Requirements are broadly consistent across societies. The owner submits a programme listing the machinery in scope, measurement points, directions and intervals. Instruments must be calibrated and personnel certified, with ISO 18436-2 category II as a practical floor. A baseline is recorded on entry to the programme, records must run unbroken, and a surveyor confirms the programme annually.
Why continuity is the hard part
Diagnostics are the easy half. A gap in the record costs the credit and sends the machine back to open-up survey, so the binding constraint is reporting discipline across crew changes, connectivity outages and changes of technical management. Programmes fail on missing months far more often than on missed defects — and the cost of that failure is a drydock line item, not a maintenance one.