TCT 12

Common issues

• Bearing wear (journal and thrust) due to contaminated lubricating oil, insufficient oil pressure, or high operational loads.
• Compressor fouling (air side) from dirty intake air, leading to reduced efficiency, increased scavenge air temperature, and potential surging.
• Turbine fouling (gas side) from exhaust gas deposits, causing reduced turbine efficiency, increased exhaust back pressure, and higher exhaust temperatures.
• Rotor imbalance and excessive vibration caused by uneven fouling, blade damage (erosion, corrosion, FOD), or bearing wear.
• Surging, particularly during rapid load changes, low-load operation, or due to compressor/turbine fouling, which can damage blades and bearings.
• Oil leakage from bearing housing seals (labyrinth seals) due to wear, carbon buildup, or incorrect clearances.
• Cracks in turbine casing or exhaust gas manifold connections due to thermal stress cycling or excessive vibration.
• Failure of turbocharger speed sensor or bearing temperature sensors, leading to loss of monitoring and protection.

Inspection checklist

• Operational Data Review: Log and compare current turbocharger RPM, exhaust gas temperatures (in/out), scavenge air pressure/temperature, lubricating oil pressure/temperature (in/out), and bearing temperatures against baseline and alarm limits.
• Noise and Vibration Check: Listen for unusual noises (whining, grinding, rubbing) and perform vibration measurements on bearing housings. Compare with acceptable limits (e.g., ISO 10816-3 for machinery vibration).
• External Visual Inspection: Check for oil leaks from bearing housing, oil supply/drain lines, and connections. Inspect insulation integrity on hot parts (turbine casing, exhaust pipes) and look for signs of overheating or cracks on the casing.
• Air Filter/Silencer Condition: Inspect the air filter elements for cleanliness and damage. Ensure the silencer is free from obstructions.
• Compressor Side Inspection (when accessible): Visually inspect compressor wheel for fouling, erosion, foreign object damage (FOD), or signs of rubbing. Check diffuser and volute for deposits or damage.
• Turbine Side Inspection (when accessible): Visually inspect turbine wheel for fouling, erosion, cracks, or FOD. Check nozzle ring for deposits, damage, or excessive clearances.
• Bearing Condition (during overhaul): Inspect journal and thrust bearings for wear, scoring, discoloration, or signs of overheating. Measure clearances and compare to wear limits.
• Rotor Shaft Inspection (during overhaul): Check rotor shaft for run-out, signs of rubbing, or damage to journals and labyrinth seal areas.

Service intervals

Typical wear limits

Ranges are typical for this design class. Always confirm against the manufacturer documentation for your serial number.

Critical spares

• Journal bearings (complete set for one side)
• Thrust bearing (complete set)
• Sealing rings (labyrinth seals, oil seals for both compressor and turbine sides)
• Gasket and O-ring kit for complete overhaul
• Lubricating oil filter elements (if applicable to TC system)
• Nozzle ring (especially for engines operating with heavy fuel oil or high thermal loads)
• Turbocharger speed sensor
• Bearing temperature sensors

Safety

• High Rotational Speeds: The rotor operates at extremely high RPMs. Potential for uncontained failure of rotor components (e.g., blades, shaft) leading to shrapnel. Always ensure safety covers are in place and never operate with damaged components.
• High Temperatures: Turbine casing, exhaust gas piping, and associated components reach very high temperatures. Risk of severe burns. Ensure proper insulation is maintained and use appropriate PPE during inspection or maintenance.
• High Pressure: Scavenge air pressure can be significant. Ensure proper depressurization of the air side before opening any components. Exhaust gas pressure can also be hazardous.
• Heavy Lifting: The rotor assembly, casings, and other components can be very heavy. Use certified lifting gear and follow safe lifting procedures to prevent injury.
• Confined Space Entry: If working inside exhaust ducts or air manifolds connected to the turbocharger, follow strict confined space entry procedures, including gas testing, ventilation, and standby personnel.

Class survey

A class surveyor will typically check the following: 1. Documentation: Verification of maintenance records, service reports, spare parts inventory, and class-approved overhaul procedures. Review of logbook entries for operational parameters and reported defects. 2. Operational Performance: Review of historical and current operational data (RPM, temperatures, pressures) to ensure the turbocharger is operating within design parameters and without chronic issues (e.g., surging, high vibration). 3. Safety Devices: Functionality check of overspeed trip, low lubricating oil pressure alarm, and high bearing temperature alarms. Verification of emergency shutdown procedures. 4. Physical Condition: External visual inspection for oil leaks, cracks, corrosion, proper insulation, and secure mounting. Assessment of general cleanliness and housekeeping around the unit. 5. Vibration Levels: May request recent vibration readings or witness a vibration check to ensure levels are within acceptable limits. 6. Compliance: Ensure compliance with SOLAS, MARPOL, and relevant classification society rules regarding machinery installation, maintenance, and safety.

Estimated lifetime: 24,000 - 36,000 hours (before major overhaul with component replacement; the unit itself can last the lifetime of the engine with proper maintenance and component renewal)