NA-LV NA70-LV

Common issues

• Bearing wear (journal and thrust) due to lubrication issues, contamination, or high loads, leading to increased rotor play and vibration.
• Compressor fouling (dirt, oil carry-over) reducing air flow and efficiency, indicated by increased pressure drop across compressor and reduced boost pressure.
• Turbine fouling (soot, unburnt fuel) reducing exhaust gas flow and efficiency, leading to higher exhaust gas temperatures before turbine and reduced power.
• Nozzle ring and/or turbine blade damage (erosion, cracks, foreign object damage - FOD) affecting gas flow dynamics and rotor balance.
• Oil leakage from bearing housing seals, leading to oil consumption, potential fire hazard, and contamination of compressor/turbine sides.
• Casing cracks or deformation due to thermal stress, vibration, or improper mounting, compromising structural integrity and gas tightness.
• Excessive vibration due to rotor imbalance (fouling, damage), bearing wear, or misalignment, potentially leading to catastrophic failure.
• Malfunction of auxiliary systems like water wash nozzles (if fitted) or air filter differential pressure sensors.

Inspection checklist

• Visually inspect turbocharger casing for cracks, signs of oil leakage, corrosion, and integrity of insulation blankets.
• Check rotor free rotation by hand (engine stopped and locked) for smooth movement, listening for any rubbing or grinding noises.
• Measure rotor axial and radial play using a dial gauge to compare against specified wear limits.
• Inspect compressor wheel for cleanliness, blade damage (nicks, bends), and signs of rubbing against the casing.
• Inspect turbine wheel and nozzle ring (if accessible without major dismantling) for cleanliness, erosion, cracks, and blade damage.
• Verify integrity and tightness of all oil supply and drain lines, air intake, and exhaust gas connections.
• Check condition of air filter elements; ensure they are clean and undamaged, and differential pressure is within limits.
• Monitor turbocharger oil pressure and temperature (if separate system or dedicated sensors) and compare with engine parameters.
• Review vibration monitoring data and trends for any anomalies or increases over time.
• Confirm tightness of mounting bolts and check for any signs of movement or fretting at the mounting feet.

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 set (journal and thrust bearings)
• Oil seals and O-ring kits for bearing housing
• Gasket set for casing and connections
• Air filter elements
• Nozzle ring segments (if modular design)
• Special tools for dismantling and assembly (e.g., rotor locking tool, lifting gear)
• Vibration sensor (if integrated and prone to failure)

Safety

• High surface temperatures: Exhaust gas casing and turbine outlet can reach 400-600°C, posing severe burn risks. Ensure insulation is intact.
• High rotational speeds: Rotor operates at up to 15,000-20,000 RPM. Never attempt to inspect or touch rotating parts. Ensure engine is stopped and locked out before any work.
• Pressurized systems: Air intake and exhaust gas systems are under pressure. Depressurize before opening any connections.
• Hot oil and oil mist: Potential for hot oil spray from leaks or during maintenance, creating slip hazards and fire risks.
• Noise levels: Turbochargers generate significant noise (100-120 dB). Hearing protection is mandatory in the vicinity.

Class survey

Class surveyors will typically verify the following: 1. Review of maintenance records, including routine inspections, bearing replacements, and major overhauls, ensuring compliance with manufacturer's recommendations. 2. Examination of engine logbook data for turbocharger performance parameters (boost pressure, exhaust gas temperatures before/after turbine, turbocharger RPM, oil pressures/temperatures) to identify any deviations or trends. 3. External visual inspection for structural integrity of the casing, mounting arrangements, insulation, and absence of oil or gas leaks. 4. Verification of turbocharger vibration levels, either from onboard monitoring systems or by portable vibration analysis. 5. Check for proper functioning of safety devices and alarms related to the turbocharger (e.g., high exhaust gas temperature, low oil pressure, overspeed trip if fitted). 6. Confirmation of air filter condition and cleanliness. 7. For Tier III applications, any associated exhaust gas treatment or recirculation systems interacting with the turbocharger will also be scrutinized for proper operation and integration.