NA NA98

Common issues

• Bearing wear (journal and thrust bearings) leading to increased clearances, vibration, and potential rotor damage.
• Fouling and erosion of turbine blades and nozzle ring due to poor fuel combustion or exhaust gas impurities, reducing efficiency and increasing exhaust back pressure.
• Fouling and erosion of compressor impeller and diffuser due to dirty intake air or water ingress, leading to reduced boost pressure and surging.
• Oil leakage from bearing housings or casing joints, indicating seal failure or excessive bearing wear.
• Vibration due to rotor imbalance (fouling, damage) or bearing deterioration, potentially causing structural fatigue.
• Exhaust gas leakage from turbine casing joints, expansion bellows, or manifold connections, reducing efficiency and posing safety risks.
• Turbocharger surging, often caused by engine operating conditions, compressor fouling, or damaged components.
• Failure or malfunction of the water washing system (if fitted), leading to rapid turbine side fouling.

Inspection checklist

• Visual inspection for any signs of oil, exhaust gas, or water leaks around the turbocharger casing, oil lines, and expansion bellows.
• Check rotor axial (end float) and radial clearances. Listen for unusual noises during run-down after engine shutdown.
• Inspect compressor and turbine wheels for fouling, erosion, foreign object damage (FOD), or blade cracks (requires opening air filter and exhaust gas sides).
• Examine the condition of the air filter elements and ensure the intake ducting is clear and secure.
• Verify the integrity of all mounting bolts, anti-vibration elements, and support structures.
• Check the condition of the lubricating oil system: oil pressure, temperature, and filter cleanliness. Ensure oil supply and drain lines are unobstructed.
• Inspect the nozzle ring and diffuser for fouling, erosion, or damage (requires opening turbine casing).
• Assess the functionality and condition of the water washing system, including nozzles and drain lines (if fitted).
• Check the insulation on hot parts of the turbine casing and exhaust gas piping for damage or degradation.
• Verify the operation of overspeed trip mechanisms and associated alarms (if applicable).

Service intervals

Typical wear limits

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

Critical spares

• Complete bearing cartridge assembly (journal and thrust bearings)
• Oil seals (labyrinth rings, piston rings, O-rings)
• Gasket sets for casing joints, oil lines, and exhaust connections
• Air filter elements
• Nozzle ring segments (if modular design) or complete nozzle ring
• Expansion bellows for exhaust gas inlet/outlet
• Lubricating oil pump (if external and critical for specific applications)
• Set of mounting bolts and anti-vibration elements

Safety

• High surface temperatures (up to 500-600°C) on the turbine casing and exhaust gas piping, posing severe burn hazards. Ensure insulation is intact.
• High-speed rotating machinery (up to 20,000-30,000 RPM for this size), presenting a risk of disintegration or entanglement if covers are removed during operation.
• Pressurized exhaust gas and charge air. Leaks can cause severe burns, hearing damage, or create an oxygen-rich environment (fire risk).
• Hot lubricating oil under pressure, posing burn and fire hazards in case of leakage.
• High noise levels requiring hearing protection in the vicinity of the operating turbocharger.

Class survey

Class surveyors typically focus on the overall condition, cleanliness, and absence of leaks (oil, gas, water). They will check the security of mounting, connections, and insulation. Documentation of routine maintenance, bearing renewals, and major overhauls (including rotor balancing certificates) is critical. If opened for inspection, bearing clearances (axial and radial) will be verified against manufacturer's limits. The functionality of safety devices (e.g., overspeed trip, alarms) and general performance (e.g., boost pressure, exhaust temperatures) will be considered. Any signs of excessive vibration or unusual noise will warrant further investigation.

Estimated lifetime: 80,000 - 100,000 hours (for main casings and rotor shaft, assuming regular maintenance and component renewals)