What indicates an overheated bearing in the main propulsion unit?

The indication of an overheated bearing in the main propulsion unit is primarily linked to the high temperature of the lube oil leaving the bearing. When a bearing overheats, it can significantly increase the temperature of the lubricating oil as it flows out. Monitoring the temperature of the lube oil is crucial because it helps identify abnormalities in the bearing's operating condition.

High temperatures can lead to deterioration of the oil and further damage to the bearing itself. In a properly functioning system, the lube oil temperature should remain within acceptable operating limits; hence, an increase typically signifies potential overheating and subsequent failure if not addressed promptly.

While increased vibration, low oil pressure, and oil discoloration can also hint at issues within the propulsion unit, they may not be as direct or specific indicators of bearing overheating. For instance, increased vibration can result from various mechanical issues, not solely overheating. Low oil pressure can indicate other problems such as leaks or pump failure, while oil discoloration is typically a sign of oil degradation over time rather than a real-time indication of overheating. Therefore, monitoring the temperature of the lube oil is key to diagnosing overheating in bearings effectively.