MB 90MB

Common issues

• Bearing wear (journal and thrust) leading to increased clearances and vibration, often due to lubrication issues or contamination.
• Compressor and/or turbine fouling, resulting in reduced efficiency, surging, and increased exhaust gas temperatures.
• Oil leaks from bearing housings, often due to worn seals, carbonization, or incorrect oil pressure.
• Vibration due to rotor imbalance, bearing wear, or foreign object damage (FOD) to blades.
• Exhaust gas leaks from casing joints, expansion bellows, or manifold connections, reducing efficiency and posing safety risks.
• Casing cracks, particularly in the turbine section, caused by thermal stress or excessive vibration.
• Surging, indicated by fluctuating boost pressure and engine instability, often due to fouling, incorrect engine load, or damaged components.
• Overspeed trip malfunction or incorrect setting, posing a severe safety hazard.

Inspection checklist

• Visual inspection for oil leaks (bearing housing, drain lines), exhaust gas leaks (casing joints, bellows), and signs of casing cracks or damage.
• Check turbocharger speed, boost pressure, exhaust gas temperatures (in/out), and charge air temperature/pressure against normal operating parameters.
• Listen for unusual noises (whining, grinding, rubbing) indicating bearing wear or blade contact.
• Inspect compressor and turbine blades for fouling, erosion, foreign object damage (FOD), and tip rub marks (requires opening inspection covers).
• Check axial and radial clearances of the rotor (if accessible during maintenance) to assess bearing wear.
• Verify the condition of the air filter elements and charge air cooler for cleanliness and integrity.
• Inspect the condition of insulation and lagging around the turbine casing and exhaust piping.
• Confirm proper functioning of the overspeed trip mechanism and its last test date.
• Review turbocharger maintenance log for recent service, cleaning, and reported issues.

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 set of bearing cartridges (journal and thrust bearings)
• Oil seals and O-rings for bearing housings and casing joints
• Gasket sets for turbine and compressor casings, and exhaust gas connections
• Lubricating oil filter elements
• Overspeed trip sensor and/or actuator
• Air filter elements (if applicable to the specific intake arrangement)
• Nozzle ring segments (if prone to wear in specific applications)

Safety

• High surface temperatures of the turbine casing and exhaust gas piping, requiring proper insulation and warning signs.
• High-speed rotating machinery (rotor operates at tens of thousands of RPM), posing a risk of uncontained failure if bearings or blades fail.
• High pressure in charge air and exhaust gas systems, requiring secure connections and pressure relief devices.
• Potential for hot oil spray from leaks under pressure, creating fire hazards.
• Significant noise levels during operation, necessitating hearing protection in the vicinity.

Class survey

Class surveyors will typically focus on verifying the overall operational integrity and safety of the turbocharger. This includes reviewing maintenance records (bearing changes, cleaning logs, overspeed trip tests, running hours), checking for external oil and exhaust gas leaks, assessing the condition of insulation and lagging, and confirming the proper functioning of safety devices. They will also observe operational parameters (boost pressure, temperatures, speed) and may request access to inspect the compressor and turbine sections if there are concerns. Availability of critical spare parts and a valid overspeed trip certificate are also key points.

Estimated lifetime: 36000 hours (before first major overhaul, with proper intermediate maintenance)