AT AT-17

Common issues

• Bearing wear (journal and thrust bearings), leading to increased clearances and potential rotor contact.
• Fouling of turbine blades and nozzle ring due to combustion byproducts, reducing efficiency and increasing exhaust back pressure.
• Fouling or damage to compressor wheel (e.g., foreign object ingestion, erosion), leading to reduced boost pressure and efficiency.
• Oil leakage from bearing housing seals (labyrinth or piston ring type), often visible as oil stains on casing or in exhaust gas.
• Excessive vibration due to rotor imbalance (fouling, damage) or bearing wear, potentially causing structural damage.
• Exhaust gas leakage from turbine casing joints or exhaust manifold connections, reducing efficiency and posing safety risks.
• Turbocharger surging, indicated by unstable engine operation, fluctuating boost pressure, and characteristic 'whooshing' sound.

Inspection checklist

• Check for any signs of oil or exhaust gas leakage around casing joints, bearing housing, and connections.
• Measure radial and axial bearing clearances (if accessible without full disassembly) to assess bearing wear.
• Inspect compressor wheel for fouling, erosion, foreign object damage, and rubbing marks against the casing.
• Inspect turbine blades and nozzle ring (if accessible) for fouling, erosion, cracks, and signs of rubbing.
• Verify security of all mounting bolts, pipe connections (oil, air, exhaust), and insulation covers.
• Check condition of air filter elements and ensure charge air cooler is clean and free of leaks.
• Monitor turbocharger lubricating oil pressure and temperature (if separate system) and inspect oil for contamination.
• Listen for unusual noises (e.g., grinding, whistling, surging) and observe vibration levels during operation.
• Ensure drain lines from the bearing housing are clear and free-flowing.

Service intervals

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 bearings, thrust bearing, thrust collar)
• Oil sealing rings / Labyrinth seals (for both compressor and turbine sides)
• Full gasket set for casing joints, exhaust gas inlet/outlet, and oil lines
• Nozzle ring (especially if operating on heavy fuel oil or with high exhaust temperatures)
• Compressor wheel (if operating environment poses high risk of foreign object damage)
• Balancing shims and locking washers
• O-rings and sealing washers for oil connections

Safety

• High surface temperatures of the turbine casing and exhaust gas piping, posing severe burn hazards. Ensure insulation is intact.
• High rotational speeds (up to 40,000-60,000 RPM for this size), creating a risk of disintegration if severely unbalanced or damaged. Maintain proper clearances and balancing.
• Pressurized exhaust gas and charge air lines, requiring caution during inspection for leaks and ensuring secure connections.
• Hot lubricating oil (if separate system) and hot engine components during maintenance, requiring appropriate PPE.
• High noise levels during operation, necessitating hearing protection in the vicinity.

Class survey

The class surveyor will typically check the overall external condition for cleanliness, signs of oil or exhaust gas leakage, and security of mounting. They will observe the turbocharger's performance during engine trials, noting boost pressure, exhaust temperatures, and any unusual noises or vibrations. Maintenance records, particularly for bearing changes, major overhauls, and cleaning cycles, will be reviewed. The integrity of safety devices such as casing insulation and guarding will also be verified. Any evidence of excessive vibration, overheating, or poor performance will trigger a request for internal inspection or further investigation.

Estimated lifetime: 16,000 - 24,000 running hours (before major overhaul, assuming regular maintenance and cleaning)