NA NA70

Common issues

• Bearing wear (journal and thrust bearings) leading to excessive axial/radial play and vibration.
• Compressor fouling due to dirty intake air or oil carry-over, reducing efficiency and leading to surging.
• Turbine fouling/erosion/damage from poor fuel combustion, exhaust gas impurities, or foreign object damage (FOD).
• Oil leakage from bearing housings, seals (especially labyrinth seals), or oil supply/drain lines.
• Cracks in turbine casing, exhaust gas manifold, or nozzle ring due to thermal cycling and stress.
• Rotor imbalance causing excessive vibration, accelerated bearing wear, and potential contact with casings.
• Exhaust gas leakage from casing joints, particularly between turbine casing and gas outlet casing.
• Surging, often indicative of compressor fouling, air filter blockage, or engine operational issues.

Inspection checklist

• Check for oil leaks around bearing housings, oil lines, and casing joints. Note any discoloration or accumulation.
• Inspect compressor wheel for cleanliness, erosion, foreign object damage, and tip rub marks. Check air filter condition.
• Inspect turbine wheel (if accessible) for cleanliness, erosion, cracks, and foreign object damage. Check nozzle ring condition.
• Measure axial and radial play of the rotor shaft. Compare with manufacturer's limits.
• Check security of all mounting bolts, especially those securing the turbocharger to the engine and casings.
• Verify integrity of cooling water lines (if applicable) and oil supply/drain lines for leaks or damage.
• Listen for unusual noises (whining, grinding, rubbing) during operation. Monitor vibration levels.
• Inspect exhaust gas casings and manifold for cracks, hot spots, or signs of gas leakage.
• Check functionality of the overspeed trip device (if fitted) and associated alarms.
• Verify lubricating oil pressure and temperature are within specified operating ranges.

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 cartridge set (journal and thrust bearings)
• Oil seals (labyrinth seals, piston rings)
• Gasket and O-ring kit for casing joints and oil lines
• Air filter elements
• Nozzle ring segments (if applicable, or complete nozzle ring)
• Overspeed trip bolt/sensor (if mechanical trip is fitted)
• Balancing weights (for minor re-balancing during overhaul)
• Lubricating oil pump (if integral and critical for operation)

Safety

• High rotational speeds (up to 20,000-30,000 RPM for this size) pose a risk of rotor burst if overspeed or severe imbalance occurs.
• Extremely high temperatures (up to 600°C) in the turbine casing and exhaust gas piping, causing severe burns.
• Pressurized hot oil and exhaust gases can cause injury or fire if leaks develop.
• High noise levels during operation require hearing protection in the vicinity.
• Potential for foreign object ejection during rotor failure or casing rupture.

Class survey

Class surveyors typically focus on the overall integrity and safe operation. Key checks include: absence of oil/gas leakages; satisfactory bearing clearances (axial and radial play measurements); evidence of proper maintenance (logbook entries, overhaul reports); satisfactory condition of air intake filter; integrity of exhaust gas casings (no cracks or deformation); proper functioning of safety devices (e.g., overspeed trip, alarms); and general cleanliness and absence of excessive vibration during operation. They will also verify that the turbocharger is suitable for the engine's current rating and that any repairs or major overhauls have been conducted by approved workshops using genuine parts.

Estimated lifetime: 60,000 - 100,000 hours (with regular maintenance and major overhauls)