The turbocharger employs a self-contained lubrication system utilizing ball and roller bearings. The bearings are housed within a casing, the bottom of which acts as an oil sump. A gear pump, driven directly by the turbine shaft, draws oil from this sump and delivers a pressurized jet of oil directly to the bearings. Both the turbine and blower sides utilize this identical system. A sight glass allows for oil level monitoring, while drain and fill plugs facilitate maintenance. This design is typically found in axial flow turbochargers.

The blower side employs a double-row ball bearing to accommodate axial thrust loads and axially locate the turbocharger rotor assembly. The turbine side utilizes a single-row ball bearing, allowing for thermal expansion of the rotor shaft. Leaf springs are incorporated between the outer race of the bearings and the housing to dampen vibrations and reduce bearing chatter, extending bearing life.

Advantages of the Lubrication System

• The gear pump-driven system ensures better lubrication at increased speeds.
• The initial cost of the system is low, as it does not require external components like coolers or filters.
• The pump's location at the aft end of the shaft makes inspection and maintenance straightforward.
• The system operates independently of the main engine lubrication system, reducing complexity and risk of cross-contamination.
• Turbine oil, with superior thermal and lubricating properties, enhances performance and reliability.

Disadvantages of the Lubrication System

• The system provides poor lubrication at low speeds due to the gear pump's dependence on turbine shaft rotation.
• Oil in the sump must be renewed periodically to maintain performance.
• If the attached gear pump fails, it can lead to insufficient lubrication, causing damage to the turbocharger bearings.
• The use of turbine oil, while beneficial, adds to operational costs due to its premium quality and price.

The Incident

On April 01, 2025, during a voyage from Singapore to Sydney, the main engine's #2 turbocharger suffered a sudden and unexpected failure. At 10:05 PM, crew members noticed abnormal noise and severe vibrations from the unit. The main engine was promptly stopped, and the turbocharger was isolated and allowed to cool down.

Upon inspection, it was discovered that the turbine blades were heavily fouled with deposits. This fouling caused an imbalance in the rotor, leading to intense vibrations that ultimately damaged the turbocharger's bearings.

Proposed Action

The immediate action taken was to replace the damaged bearings with spares available on board. The turbine and compressor sides were thoroughly cleaned to remove the fouling. After reassembling the turbocharger, it was tested and found to be operating successfully, allowing the vessel to resume its voyage.

To address the root cause and prevent a recurrence, the following actions were proposed:

• Implement a Strict Washing Schedule: The main cause of the failure was the lack of regular turbine cleaning (water and dry washing). To avoid future incidents, a periodic washing schedule for turbocharger #2 has been implemented in accordance with the manufacturer's recommendations.
• Proactive Maintenance on Other Units: The second engineer has also recommended a proactive overhaul of turbocharger #1 at the next available opportunity. The washing schedule for this unit had also been neglected since its last overhaul, and a similar failure could occur. This preventative measure, requiring permission from the Chief Engineer and Master, will ensure the reliability of both turbochargers.