ST6

Common issues

• Compressor Fouling: Accumulation of dirt, oil mist, and combustion residues on compressor impeller blades and diffuser. Leads to reduced air mass flow, lower boost pressure, increased exhaust gas temperature, and potential surging.
• Turbine Fouling: Deposits of unburnt fuel, carbon, and ash on turbine blades and nozzle ring. Causes reduced turbine efficiency, higher exhaust back pressure, increased exhaust gas temperature, and loss of engine power.
• Bearing Wear (Journal & Thrust): Deterioration of plain bearings due to insufficient lubrication, contamination, or excessive load. Manifests as increased rotor play (axial and radial), vibration, noise, and potential oil leaks. Critical for rotor stability.
• Oil Seal Wear: Degradation of labyrinth or piston ring seals. Results in oil carry-over into the compressor (leading to fouling) or turbine (leading to carbon deposits and smoke from exhaust), and increased oil consumption.
• Rotor Imbalance: Can be caused by uneven fouling, blade damage, or bearing wear. Leads to excessive vibration, accelerated bearing wear, and potential damage to the casing or shaft.
• Exhaust Gas Leaks: From turbine casing joints, exhaust manifold connections, or gland seals. Reduces turbine efficiency, increases engine room temperature, and poses a safety hazard.

Inspection checklist

• Visual Inspection for Leaks: Check all casing joints, oil supply/drain lines, and exhaust connections for oil, water, or exhaust gas leaks. Pay attention to discoloration or residue.
• Rotor Free Rotation & Axial/Radial Play: With the engine stopped and cool, manually rotate the rotor to check for smooth, unrestricted movement. Gently push/pull the shaft to check for excessive axial and radial play (bearing wear indicator).
• Compressor & Turbine Blade Condition: Inspect blades for fouling, erosion, corrosion, cracks, or foreign object damage (FOD). Check for rubbing marks on casings.
• Oil System Integrity: Verify oil supply pressure (if gauge available), check oil filter condition (if accessible), and inspect oil drain for obstructions. Ensure oil level in engine sump is correct.
• Mounting & Securing: Check all mounting bolts, brackets, and supports for tightness and signs of cracking or corrosion. Ensure vibration dampers (if fitted) are in good condition.
• Operational Parameters (During Running): Monitor boost pressure, exhaust gas temperatures (before/after turbine), turbocharger RPM, and oil inlet/outlet temperatures. Look for deviations from normal operating ranges.
• Vibration Monitoring: Listen for unusual noises or use a vibration meter to check casing vibration levels. High vibration indicates imbalance or bearing issues.
• Air Filter Condition: Inspect the turbocharger air intake filter for cleanliness and integrity. A clogged filter restricts airflow and causes compressor surging.

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 Set (Journal and Thrust bearings)
• Oil Seal Rings / Labyrinth Seals (Compressor and Turbine sides)
• Gasket & O-Ring Kit (for all casing joints and oil lines)
• Nozzle Ring Segments (if applicable to ST6 design)
• Compressor Cleaning Fluid/Granules
• Mounting Bolts/Studs (especially for exhaust side connections)
• Oil Filter Element (if dedicated turbocharger oil filter)

Safety

• Hot Surfaces: Turbocharger casings and exhaust pipes operate at extremely high temperatures (300-600°C). Risk of severe burns. Ensure proper insulation and warning signs.
• High-Speed Rotating Parts: The rotor operates at tens of thousands of RPM. Never attempt to open casings or work near the turbocharger while the engine is running. Risk of entanglement and severe injury.
• High Pressure Exhaust Gas/Air: Potential for sudden release of hot, high-pressure gases or air during maintenance if not properly depressurized.
• Oil Mist & Fire Hazard: Leaking oil can atomize and ignite on hot surfaces, leading to engine room fires. Regular inspection for oil leaks is crucial.
• Heavy Component Handling: During overhaul, components like the turbine casing or rotor assembly can be heavy and require proper lifting gear and procedures to prevent injury.

Class survey

Surveyor will verify maintenance records (PMS), review operational performance logs, visually inspect external condition for leaks/damage, check securing arrangements, and confirm functionality of safety devices (e.g., overspeed trip, alarms). If opened for overhaul, bearing clearance measurements and NDT reports will be reviewed. All significant repairs or replacements must be documented with relevant certificates.