Common issues
- Compressor fouling (reduces efficiency, increases surge risk)
- Turbine-end deposits (reduces efficiency, increases exhaust back pressure, potential imbalance)
- Bearing wear (increased vibration, oil leakage, potential rotor damage, reduced performance)
- Charge-air pressure loss (indicates fouling, leaks in system, or bearing issues)
- Rotor imbalance (leads to excessive vibration, accelerated bearing wear, and potential catastrophic failure)
- Oil leakage (from bearing housing seals, connections, or casing cracks)
- Exhaust gas leakage (from casing joints, expansion bellows, or cracks, leading to energy loss and safety hazard)
- Casing cracks (due to thermal stress, vibration, or material fatigue)
Inspection checklist
- Visual inspection of compressor and turbine blades for fouling, erosion, foreign object damage (FOD), or cracks.
- Check rotor axial and radial play (bearing clearance) against manufacturer's specified limits using a dial gauge.
- Inspect oil supply and drain lines for leaks, proper flow, and oil quality (discoloration, contamination).
- Verify charge air cooler condition (if applicable) and air filter cleanliness; check for air leaks in the charge air system.
- Examine exhaust gas casing, nozzle ring, and insulation for cracks, hot spots, deformation, or leaks.
- Monitor turbocharger RPM, boost pressure, and exhaust gas temperatures (before/after turbine) for deviations from normal operating parameters and trends.
- Check all mounting bolts, chocks, and anti-vibration mounts for tightness and signs of movement or corrosion.
- Inspect overspeed trip mechanism functionality (if testable without engine shutdown) and verify alarm settings.
- Listen for unusual noises or vibrations during operation; check for excessive casing vibration.
- Verify proper functioning of compressor and turbine wash systems, including nozzle integrity and drainage.
Service intervals
| Minor Inspection/Cleaning (compressor wash, visual checks, performance monitoring) | 2,000 - 4,000 running hours |
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| Intermediate Inspection (bearing check/replacement, turbine wash, seal inspection) | 8,000 - 12,000 running hours |
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| Major Overhaul (full dismantling, bearing replacement, rotor balancing, casing inspection, NDT) | 16,000 - 24,000 running hours |
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| Workshop Overhaul (rotor reconditioning/replacement, extensive NDT, full component renewal) | 36,000 - 48,000 running hours |
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| Annual Class Survey | As per Class requirements (typically yearly) |
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Typical wear limits
| Radial Bearing Clearance (Journal Bearings) | Max. 0.15 - 0.25 mm (new: 0.08 - 0.12 mm). Exceeding this indicates significant wear and requires replacement. |
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| Axial Bearing Clearance (Rotor Float) | Max. 0.15 - 0.25 mm (new: 0.05 - 0.10 mm). Critical for preventing blade contact with casings; exceeding this requires thrust bearing replacement. |
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| Compressor/Turbine Blade Tip Clearance | Max. increase of 0.5 mm from new value. Excessive clearance reduces efficiency; contact indicates severe bearing wear or rotor damage. |
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| Oil Pressure (Inlet to Bearings) | Min. 1.5 - 2.0 bar (at operating temperature). Below this indicates lubrication issues, risking bearing damage. |
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Ranges are typical for this design class. Always confirm against the manufacturer documentation for your serial number.
Critical spares
- Complete set of journal and thrust bearings (including sleeves and washers)
- Oil sealing rings and O-rings for bearing housing and critical connections
- Gasket sets for casing joints, exhaust gas inlet/outlet, and oil connections
- High-temperature bolts and nuts for critical casing connections
- Oil filter elements (if integral to TC lubrication system)
- Compressor wash nozzles and associated spray system components
Safety
- High surface temperatures (exhaust casing, turbine housing) posing severe burn hazards. Always use appropriate PPE and allow for cooling.
- Potential for rotor burst due to overspeed, severe imbalance, or material fatigue, leading to high-velocity projectile hazards. Ensure overspeed trip is functional.
- High-pressure charge air lines and exhaust gas lines, risk of sudden release of hot gas or air during inspection or maintenance.
- Hot oil and oil mist hazards during inspection or maintenance, risk of fire or burns. Ensure proper ventilation and fire precautions.
- Noise levels requiring hearing protection during operation and inspection. Prolonged exposure can cause permanent hearing damage.
Class survey
During annual or special surveys, the Class Surveyor will typically review maintenance records, running hours, and performance logs (boost pressure, exhaust temperatures, RPM trends). A thorough visual inspection will be conducted for external leaks (oil, exhaust gas, air), casing integrity, mounting security, and proper functioning of safety devices like the overspeed trip. The condition of insulation, drainage arrangements, and general cleanliness are also noted. Verification of critical spare parts availability as per manufacturer's recommendations and the vessel's Planned Maintenance System (PMS) is often part of the check. Any signs of abnormal operation or excessive wear must be documented and addressed.
Estimated lifetime: 48,000 to 72,000 hours before major workshop overhaul of the rotor assembly and extensive casing inspection, assuming strict adherence to maintenance schedules and intermediate bearing changes.