RU120

Common issues

• Compressor wheel fouling leading to reduced air flow and efficiency, often indicated by increased exhaust gas temperature and reduced boost pressure.
• Turbine-side fouling (carbon deposits) causing reduced turbine efficiency, increased back pressure, and potential imbalance, leading to higher exhaust temperatures before turbine.
• Bearing wear (journal and thrust bearings) resulting in excessive axial and radial play, leading to rotor contact with casings, vibration, and potential catastrophic failure.
• Oil seal leakage, manifesting as oil in the charge air cooler (compressor side) or oil in the exhaust gas (turbine side), indicating worn seals or excessive bearing play.
• Rotor imbalance due to uneven fouling, blade damage, or bearing wear, causing excessive vibration and accelerated component wear.
• Foreign Object Damage (FOD) to compressor or turbine blades from ingested debris, leading to imbalance, reduced efficiency, and potential blade fracture.
• Cracks in the turbine casing or exhaust gas manifold due to thermal stress cycling, leading to exhaust gas leakage and reduced performance.
• Reduced turbocharger speed or surge due to air filter blockage, charge air cooler fouling, or engine combustion issues.

Inspection checklist

• Check axial and radial play of the rotor shaft. Typical new limits: Axial 0.10-0.25mm, Radial 0.05-0.15mm. Max allowable: Axial up to 0.40-0.50mm, Radial up to 0.25-0.35mm. Refer to specific IHI manual for exact values.
• Visually inspect compressor and turbine wheels for fouling, erosion, cracks, or foreign object damage (FOD). Ensure blades are clean and intact.
• Inspect turbocharger casing (compressor, bearing, turbine) for cracks, oil leaks, exhaust gas leaks, or signs of rubbing/contact.
• Check condition of air filter elements and charge air cooler for cleanliness and integrity. Blockages here directly impact turbocharger performance.
• Verify oil supply and drain lines for proper flow, leaks, and signs of carbonization or sludge buildup, especially in the drain line.
• Monitor turbocharger speed, boost pressure, and exhaust gas temperatures (before and after turbine) against engine load and manufacturer's specifications. Look for deviations.
• Listen for unusual noises (whining, grinding, rubbing) and check for excessive vibration during operation. Use a vibration meter if available.
• Inspect mounting bolts and supports for tightness and integrity. Ensure no signs of movement or stress on the connections.
• Check condition of labyrinth seals and ensure no excessive blow-by or oil carry-over.

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 kit (journal bearings, thrust bearing, thrust collar, 'O' rings, seals, locking rings).
• Oil seal rings (both compressor and turbine side).
• Gasket set for casing joints, oil inlet/outlet, and exhaust connections.
• Air filter elements (if external filter is used).
• Specific high-tensile bolts and nuts for casing assembly and mounting.
• Cleaning agents/kits for compressor and turbine washing (if applicable).
• Spare rotor shaft assembly (for critical applications or remote voyages, though less common as a standard spare).

Safety

• High temperatures: Turbocharger casings and exhaust pipes operate at extremely high temperatures (up to 600°C+). Risk of severe burns. Ensure proper insulation and warning signs.
• High-speed rotating machinery: The rotor operates at speeds up to 100,000+ RPM. Never attempt to open or work on the turbocharger while the engine is running or recently shut down.
• Pressurized components: Charge air and exhaust gas are under pressure. Ensure all connections are secure and relief valves (if fitted) are operational.
• Oil mist and fire hazard: Oil leaks, especially from the bearing casing, can create oil mist which is a fire hazard if it comes into contact with hot surfaces.
• Noise: Turbochargers generate significant noise. Hearing protection is mandatory when working in the vicinity of an operating turbocharger.
• Lockout/Tagout: Always ensure the main engine is properly shut down, isolated, and tagged out before commencing any maintenance work on the turbocharger.

Class survey

The Class Surveyor will typically focus on the overall condition, safety, and operational integrity of the turbocharger. Key checks include: visual inspection for leaks (oil, exhaust gas), cracks, and secure mounting; verification of maintenance records and logbook entries (performance parameters, cleaning, bearing replacements); confirmation of safety devices (e.g., overspeed trip if fitted, alarms); assessment of bearing play if the turbocharger is opened for maintenance during the survey; and ensuring compliance with manufacturer's service recommendations and classification society rules. They will also verify that critical spare parts are onboard as per Class requirements.

Estimated lifetime: With proper maintenance, regular bearing replacements, and scheduled overhauls (typically every 8,000-12,000 hours), an IHI RU120 turbocharger can achieve a total operational lifetime of 50,000 to 100,000+ hours before requiring major component replacement (e.g., new rotor shaft or complete casing sections).