RH/MAN-NA Series

Common issues

• Ball/roller bearing failure, often leading to rotor contact with casing, typically after 20,000-30,000 operating hours.
• Compressor wheel fouling from intake air contaminants, leading to imbalance, reduced efficiency, and potential blade damage.
• Oil seal leakage, resulting in oil carry-over to the compressor or turbine side, or external oil leaks from the bearing housing.
• Wastegate actuator malfunction or seizure (if fitted), causing incorrect boost pressure regulation.
• Turbine nozzle ring and/or blade fouling or erosion due to exhaust gas impurities and high temperatures.
• Abnormal noise (whining, grinding) or excessive vibration during operation, indicating bearing wear or rotor imbalance.
• Exhaust gas leaks from casing joints, exhaust piping, or turbine outlet, posing fire and CO hazards.

Inspection checklist

• External visual inspection for oil and exhaust gas leaks, casing cracks, loose fastenings, and integrity of insulation/lagging.
• Check rotor shaft axial and radial play (cold engine, if accessible) against OEM specified limits (e.g., max. 0.15-0.25mm axial, 0.08-0.12mm radial).
• Inspect compressor wheel for fouling, blade damage (chips, cracks, bending), and rubbing marks against the casing.
• Inspect turbine wheel and nozzle ring (requires opening exhaust side) for fouling, erosion, and blade damage.
• Verify wastegate actuator free movement and linkage condition (if fitted) to ensure proper boost control.
• Monitor operational parameters: boost pressure, exhaust gas temperatures (in/out), and listen for abnormal noise/vibration during engine operation.
• Check condition of lubricating oil supply/drain lines (for self-lubricated units) and verify oil level/pressure as applicable.

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

• Bearing cartridge/kit (including ball/roller bearings, spacers, locking nuts, circlips).
• Oil seal kit (for both compressor and turbine sides, including O-rings and sealing rings).
• Gasket and O-ring set for casing joints, exhaust inlet/outlet, and oil lines.
• Wastegate actuator (if fitted, especially if known for failures in the specific engine application).
• Compressor cleaning fluid/granules and associated injection equipment.

Safety

• High-speed rotating assembly: Risk of catastrophic uncontained failure (burst) if bearings fail, potentially causing severe injury or damage.
• Hot surfaces: Exhaust casing and piping operate at very high temperatures (400-600°C), posing a severe burn hazard. Ensure insulation is intact.
• Pressurized systems: Boost air (up to 4.0 pressure ratio) and exhaust gas are under pressure, risk of leaks or sudden release.
• Exhaust gas leaks: Risk of carbon monoxide (CO) poisoning in machinery spaces and potential fire hazard due to hot gas impingement on flammable materials.
• Oil mist leaks: From bearing housing or oil lines, creating a fire hazard, especially in hot machinery spaces.

Class survey

Class surveyors typically check for: verification of maintenance records (especially bearing replacements and major overhauls), external visual inspection for general condition, secure mounting, and absence of oil/exhaust gas leaks. They will also assess insulation/lagging integrity on hot surfaces, confirm operational parameters (boost pressure, exhaust temperatures) are within limits, and note any abnormal noise or vibration during engine operation. Safety devices, guards, and proper drainage arrangements are also inspected.

Estimated lifetime: 60,000 - 80,000 hours (with regular major overhauls and component replacements as per service intervals).