AT20

Common issues

• Bearing wear (axial and radial play exceeding limits)
• Compressor fouling/deposits (reducing efficiency, potential for surge)
• Turbine fouling/deposits (reducing efficiency, increasing exhaust back pressure)
• Rotor imbalance (due to deposits, damage, or bearing wear, leading to vibration)
• Oil leakage from bearing housing (internal or external)
• Exhaust gas leakage from turbine casing, flanges, or expansion bellows
• Foreign Object Damage (FOD) to compressor or turbine blades
• Cracks in turbine casing due to thermal stress

Inspection checklist

• Visual inspection of compressor and turbine blades for damage (chips, cracks, bending), erosion, and fouling.
• Measure rotor axial and radial play using a dial gauge to assess bearing condition.
• Inspect for oil leakage around bearing housing, oil inlet/outlet lines, and drain.
• Check for exhaust gas leakage from turbine casing joints, exhaust manifold connections, and expansion bellows.
• Verify the condition and cleanliness of the air filter element.
• Inspect the lubricating oil system for correct pressure, temperature, and oil quality (if accessible).
• Check security of all mounting bolts and supports for the turbocharger and associated piping.
• Ensure condensate drains from the compressor casing are clear and functional.
• During operation, monitor boost pressure, exhaust gas temperatures (before/after turbine), and listen for abnormal noises or vibrations.

Service intervals

Typical wear limits

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

Critical spares

• Bearing set (thrust and journal bearings)
• Oil seals (labyrinth seals, O-rings for bearing housing)
• Gasket set (for casings, oil lines, exhaust connections)
• Air filter elements
• Lubricating oil filter elements (if separate from engine system)
• Specialized tools for disassembly/assembly (e.g., rotor locking tools)

Safety

• Hot surfaces: Turbocharger casings and exhaust piping operate at very high temperatures, posing severe burn risks.
• High-speed rotating parts: The rotor operates at extremely high RPM; never attempt to inspect or touch while running.
• Pressurized systems: Air and exhaust gas lines are under pressure; ensure depressurization before opening.
• Noise hazard: High noise levels during operation require hearing protection.
• Oil mist/fire risk: Oil leaks onto hot surfaces can ignite, leading to engine room fires.

Class survey

Class surveyors typically review maintenance records (running hours, previous inspections, repairs), verify turbocharger performance parameters (boost pressure, exhaust gas temperatures), conduct an external visual inspection for leaks (oil, exhaust gas), check the security of mounting, and confirm the functionality of safety devices (e.g., overspeed trip, alarm functions). If the turbocharger has been opened for maintenance, they will verify bearing clearances and component condition against manufacturer specifications. Availability of critical spare parts as per class requirements is also checked.