Which of the following maintenance criteria would be the basis of planned maintenance?

Correct Answer: Option D — Equipment running hours

Planned maintenance is fundamentally based on time-based or usage-based intervals. Equipment running hours provide a quantifiable metric to schedule routine inspections, lubrication, and component replacements, ensuring machinery reliability before failure occurs. This proactive approach is the cornerstone of a vessel's Planned Maintenance System (PMS) as required by safety management standards.