NA NA90

Common issues

• Bearing wear (journal and thrust bearings) leading to increased rotor play and vibration.
• Compressor wheel fouling or erosion, reducing efficiency and airflow, often due to dirty intake air or oil carry-over.
• Turbine wheel and nozzle ring fouling or erosion, impacting engine performance and increasing exhaust back pressure, typically from poor fuel combustion or exhaust gas quality.
• Oil leakage from bearing housing seals (labyrinth or piston ring type), leading to oil consumption and potential contamination of compressor/turbine sides.
• Rotor imbalance or shaft bending due to impact damage, uneven fouling, or bearing failure, causing excessive vibration.
• Surging, often indicated by a 'barking' sound, caused by engine load changes, severe fouling, or incorrect turbocharger matching.
• Cracks in exhaust gas casing or turbine inlet/outlet ducts due to thermal stress or vibration.

Inspection checklist

• Check for any visible oil or water leaks around the turbocharger casing, oil lines, and cooling water connections.
• Measure rotor axial and radial play using a dial gauge. Compare readings to manufacturer's specified limits (e.g., axial new: 0.15-0.25mm, max: 0.40-0.50mm; radial new: 0.20-0.35mm, max: 0.50-0.65mm).
• Inspect compressor wheel for fouling, erosion, damage (e.g., foreign object impact), and signs of rubbing against the casing.
• Inspect turbine wheel and nozzle ring (if accessible without major disassembly) for fouling, erosion, cracks, and foreign object damage.
• Check bearing housing temperatures using an IR thermometer; look for abnormal hot spots or significant differences between bearings.
• Verify the condition of the air filter elements and ensure the intake ducting is clean and free of obstructions.
• Inspect exhaust gas bellows and insulation for integrity, signs of leaks, or damage.
• Confirm proper lubricating oil pressure and flow to the turbocharger, and check oil drain lines for clear passage.
• Listen for abnormal noises (e.g., whistling, grinding, surging) during operation and assess vibration levels (manual check or with a vibration meter).

Service intervals

Typical intervals for this design class, not the manufacturer’s figures for your model. The manufacturer’s manual is binding.

Typical wear limits

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

Critical spares

• Complete bearing assembly (journal and thrust bearings) with associated O-rings/gaskets.
• Oil sealing rings (labyrinth or piston ring type) for both compressor and turbine ends.
• Full set of casing gaskets and O-rings for routine maintenance and overhauls.
• Air filter elements (if applicable to the specific intake system).
• Nozzle ring segments or complete nozzle ring (depending on design and wear condition).
• Diffuser (can be susceptible to erosion/damage).
• Special tools for rotor locking, lifting, and bearing removal/installation.

Safety

• High temperatures: Exhaust gas casing and turbine components operate at extremely high temperatures (up to 600°C+). Always allow for cooling before inspection/maintenance.
• High rotational speeds: The rotor operates at tens of thousands of RPM. Uncontained failure due to imbalance or material fatigue can be catastrophic.
• Pressurized systems: Compressor discharge air and exhaust gas are under pressure. Ensure systems are depressurized before opening.
• Hot lubricating oil: The oil system operates at elevated temperatures. Exercise caution during oil sampling or draining.
• Noise hazard: Turbochargers generate significant noise levels. Hearing protection is mandatory in their vicinity.

Class survey

Class surveyors typically focus on: reviewing maintenance records, running hours, and previous survey reports; checking external condition for leaks, insulation integrity, and secure mounting; verifying operational parameters (boost pressure, exhaust temperatures, RPM) against acceptable ranges; assessing vibration levels; inspecting safety devices (e.g., overspeed trip functionality); and, at major overhaul intervals (typically 12,000-16,000 hours or 5-year special survey), requiring opening for internal inspection of bearings, rotor, and gas passages. Lubricating oil analysis reports are also often reviewed.

Estimated lifetime: 12,000 - 16,000 running hours before major overhaul requiring bearing replacement, rotor balancing, and significant component inspection/replacement. Total design life of main casings and rotor shaft can exceed 60,000 hours with proper maintenance and component replacement.