AT AT-26

Common issues

• Bearing wear (journal and thrust bearings leading to increased axial/radial play and vibration)
• Turbine side fouling (carbon deposits reducing efficiency and causing imbalance)
• Compressor side fouling/erosion (dirt/oil deposits or foreign object damage reducing air delivery)
• Nozzle ring deformation or cracking (due to thermal stress or impact, affecting turbine efficiency)
• Oil leakage from bearing housing seals (labyrinth seals or piston rings, leading to oil consumption and fouling)
• Exhaust gas leakage from casing joints or cracks (reducing efficiency and creating hot spots)
• Rotor imbalance (due to fouling, erosion, or bearing wear, causing excessive vibration)
• Turbocharger surging (often an engine issue, but can manifest as TC instability)

Inspection checklist

• Check axial and radial play of the rotor shaft (using dial gauge, comparing to wear limits).
• Visually inspect turbine and compressor wheels for fouling, erosion, foreign object damage, and rubbing marks.
• Inspect nozzle ring and diffuser for fouling, cracks, deformation, and security.
• Check condition of bearing lubrication system: oil pressure, temperature, filter cleanliness, and signs of oil degradation.
• Inspect air filter (if fitted) and charge air cooler for cleanliness and damage.
• Verify security of all mounting bolts, pipe connections (exhaust gas, charge air, lube oil, drains).
• Check for any signs of oil or exhaust gas leakage from casing joints, seals, or drain lines.
• Monitor turbocharger performance parameters: boost pressure, exhaust gas temperatures (before/after turbine), RPM, and vibration levels.

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 assembly (journal and thrust bearings)
• Set of labyrinth seals (turbine and compressor side)
• Gasket and O-ring kit for overhaul
• Nozzle ring (especially if operating with heavy fuel oil)
• Oil filter elements (if integral to TC lube system)
• Mounting bolts and nuts (high-temperature resistant)

Safety

• High surface temperatures of exhaust casing (burn hazard).
• High rotational speeds of rotor (potential for catastrophic failure if bearings fail or foreign object ingress).
• High pressure in exhaust gas and charge air systems (potential for uncontrolled release).
• Hot pressurized lubricating oil (burn and spray hazard).
• Noise levels (hearing protection required in vicinity).

Class survey

Class surveyors typically review the turbocharger's maintenance records (logbook entries, overhaul reports, bearing clearances), check for signs of external leakage (oil, exhaust gas), verify security of mounting, and visually inspect the general condition of the casing and connections. They may also request to witness bearing play measurements if an overhaul is due or suspected. Performance parameters (boost pressure, exhaust temperatures) and safety devices (e.g., overspeed trip if fitted) are also of interest.

Estimated lifetime: 80,000 - 120,000 running hours for main casings and rotor assembly with proper maintenance and scheduled overhauls.