6H27/38

Common issues

• Common Rail Injector Fouling/Wear: Due to HFO operation and high injection pressures, nozzles can clog, wear, or leak, leading to poor combustion, increased exhaust temperatures, and potential liner damage. Regular fuel quality monitoring is crucial.
• Exhaust Valve Burning/Corrosion: High temperatures and corrosive elements (e.g., vanadium, sodium) in HFO combustion products can lead to rapid wear or burning of exhaust valve spindles and seats. Valve rotator functionality is critical.
• Turbocharger Fouling/Surging: Deposits from HFO combustion can build up on turbine blades and compressor wheels, reducing efficiency, increasing exhaust backpressure, and potentially causing surging, especially at lower loads. Frequent washing is often required.
• Cylinder Liner Scuffing/Wear: Inadequate lubrication, poor fuel combustion, abrasive particles, or cold corrosion can lead to excessive liner wear or scuffing, impacting compression, increasing lube oil consumption, and potentially causing piston seizure.
• High-Pressure Fuel Pump (HPFP) Issues: Wear in the HPFP elements, control valves, or pressure limiting valves can lead to unstable rail pressure, affecting engine performance, fuel efficiency, and potentially causing misfires.
• Bearing Wear (Main & Big End): Due to heavy loads, potential lube oil contamination (e.g., water, fuel dilution, soot), or degradation, accelerated wear of main and big end bearings can occur, leading to increased clearances and potential failure.
• Lube Oil Contamination/Degradation: HFO combustion byproducts (soot, acids, water, unburnt fuel) can rapidly contaminate and degrade lube oil, reducing its protective properties and requiring frequent oil changes or effective purification.
• Cooling System Blockages/Corrosion: Scale buildup or corrosion in cooling passages (especially charge air cooler and jacket water spaces) can reduce heat transfer efficiency, leading to localized overheating and reduced engine performance.

Inspection checklist

• Fuel System Integrity (Common Rail): Check for leaks from high-pressure lines, rail, and injectors. Inspect injector condition (external cleanliness, signs of leakage). Monitor rail pressure stability and fuel filter differential pressure.
• Exhaust Gas System: Check exhaust gas temperatures per cylinder (deviation > +/- 30°C is concerning). Inspect turbocharger for unusual noises, vibrations, or signs of oil leakage. Check exhaust manifold for leaks and insulation integrity.
• Cylinder Head & Valve Gear: Listen for abnormal noises (e.g., valve tappet clearance, injector knock). Check valve rotator operation (if fitted). Inspect for leaks around cylinder head covers and fuel lines. Verify proper cooling water flow from tell-tales.
• Lube Oil System: Check lube oil pressure, temperature, and level. Inspect for leaks from filters, coolers, and pipework. Take regular oil samples for analysis (viscosity, TBN, water, insolubles, wear metals).
• Cooling Water System: Check cooling water pressures and temperatures (jacket water, charge air cooler). Inspect for leaks and ensure proper treatment levels (nitrite/molybdate). Check expansion tank level.
• Engine Breathing & Crankcase: Check crankcase pressure (should be slightly negative). Inspect crankcase relief valves for signs of leakage or damage. Listen for abnormal sounds from inside the crankcase.
• Vibration & Noise: Monitor engine for abnormal vibrations or unusual noises that could indicate bearing issues, misfires, loose components, or turbocharger imbalance.
• Safety Devices: Verify proper operation of overspeed trip, low lube oil pressure shutdown, high cooling water temperature shutdown, and crankcase oil mist detector. Check alarm setpoints.
• Engine Mountings & Foundations: Inspect for signs of movement, corrosion, or damage to engine mounts and foundation bolts. Check chocking arrangements.
• Fuel Filters & Purifiers: Check differential pressure across fuel filters. Verify proper operation and cleanliness of HFO purifiers (bowl cleaning, discharge rates).

Service intervals

Typical wear limits

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

Critical spares

• Fuel Injector Assemblies (or Nozzle Tips): Essential for maintaining combustion quality and engine efficiency.
• Piston Rings (Complete Set for 1-2 Cylinders): For addressing liner/piston issues and maintaining compression.
• Exhaust Valve Spindles & Seats (1-2 Sets): Prone to wear and burning with HFO operation.
• Main & Big End Bearing Shells (1 Set each): For emergency replacement in case of bearing failure.
• Fuel Filters (Primary & Secondary): Frequent replacement items, crucial for protecting the common rail system.
• Lube Oil Filters: Essential for maintaining lube oil cleanliness and engine protection.
• Various Gaskets & O-rings: For cylinder head, fuel system, inspection covers, and general maintenance.
• Pressure/Temperature Sensors: Critical for monitoring, control, and safety systems. Often fail without warning.

Safety

• High-Pressure Fuel Leaks: Common Rail systems operate at extremely high pressures (up to 1800-2000 bar). A pinhole leak can create a jet that can penetrate skin, causing severe injury, or atomize fuel, creating an extreme fire hazard. Ensure proper shielding and leak detection.
• Hot Surfaces: Exhaust manifold, turbocharger, and other engine components operate at very high temperatures, posing severe burn risks. Ensure proper insulation and guarding are in place and maintained.
• Rotating Machinery: Exposed rotating parts (flywheel, coupling, shaft ends) present entanglement hazards. Always ensure all guards are securely in place before operation.
• Crankcase Explosions: Accumulation of oil mist in the crankcase, combined with a hot spot (e.g., failed bearing), can lead to a violent explosion. Ensure oil mist detector is functional, crankcase relief valves are clear, and proper ventilation is maintained.
• Pressurized Systems: Cooling water, lube oil, and starting air systems are under pressure. Improper handling during maintenance (e.g., opening systems without depressurizing) can lead to scalding, oil spray, or other injuries.

Class survey

Class surveyors will focus on verifying the engine's structural integrity, operational safety, and compliance with regulatory requirements. Key checks include: 1. **Documentation Review**: Engine logbooks, maintenance records, lube oil analysis reports, fuel oil bunkering and analysis reports, safety device test reports (overspeed, low LO pressure, high CW temp). 2. **Operational Test**: Verification of overspeed trip, remote/local control, emergency stop, and other safety shutdowns. Load tests may be required to confirm performance. 3. **Crankshaft Deflection Measurement**: Mandatory check at specific intervals (e.g., every 12,000-16,000 hours) to assess bearing and alignment condition. Readings must be within manufacturer's limits. 4. **Bearing Inspection (Main/Big End)**: Often required at specific running hours (e.g., 24,000-36,000h) or if deflection is out of limits. Visual inspection for wear, scoring, and measurement of clearances. 5. **Cylinder Head/Piston/Liner Inspection**: May require opening a representative number of units for visual inspection and measurement of wear (liners, rings, valve seats, piston crown condition). 6. **Fuel Injection System Integrity**: Visual inspection for leaks, proper shielding of high-pressure lines, and verification of fuel oil leak detection systems and alarms. Check for proper functioning of fuel oil supply and return systems. 7. **Turbocharger Inspection**: Visual check for integrity, signs of fouling, bearing play, and proper lubrication. May require opening for internal inspection at major intervals. 8. **Engine Foundations & Mountings**: Inspection for cracks, loose bolts, signs of excessive vibration or movement, and integrity of chocking arrangements. 9. **Safety Devices**: Physical inspection and functional testing of crankcase oil mist detector, relief valves, and other safety interlocks (e.g., jacket water high temperature, lube oil low pressure). 10. **General Condition**: Overall cleanliness, absence of leaks, proper insulation on hot surfaces, and integrity of piping, wiring, and instrumentation.