6L6N18(M)Y

Common issues

• Exhaust valve burning or corrosion due to HFO operation (vanadium/sulfur content).
• Fuel injector nozzle clogging, poor atomization, or carbon build-up, leading to poor combustion.
• Turbocharger fouling (both compressor and turbine sides) reducing efficiency and increasing exhaust temperatures.
• Piston ring wear or sticking, resulting in increased lube oil consumption and blow-by.
• Mechanical governor hunting, sluggish response, or wear in linkages affecting load stability.
• Main and connecting rod bearing wear, often exacerbated by lube oil contamination or insufficient pressure.
• High-pressure fuel pump element wear or sticking, causing uneven fuel delivery between cylinders.
• Fouling of jacket water and lube oil heat exchangers, leading to elevated operating temperatures.

Inspection checklist

• **Visual Leak Check**: Inspect for any leaks of fuel, lube oil, cooling water, or exhaust gas from pipes, flanges, and engine components.
• **Operational Parameters**: Verify all critical pressures (lube oil, jacket water, fuel) and temperatures (lube oil, jacket water, exhaust gas per cylinder) are within specified limits during operation and under load.
• **Exhaust Smoke Analysis**: Observe exhaust smoke color and density at various loads (idle, partial, full) for signs of poor combustion or excessive lube oil burning.
• **Crankcase Breather**: Check for excessive blow-by, indicating potential piston ring wear or cylinder liner issues.
• **Safety Devices Test**: Periodically test overspeed trip, low lube oil pressure shutdown, high jacket water temperature shutdown, and emergency stop functionality.
• **Fuel System Integrity**: Inspect high-pressure fuel lines (especially double-walled sections), fuel filters, and verify proper HFO/MGO changeover procedures and system cleanliness.
• **Foundation Bolts**: Check all engine foundation bolts for tightness and signs of movement or fretting.
• **Vibration and Noise**: Listen for abnormal knocking, grinding, or rattling noises, and check for excessive engine vibration at different RPMs and loads.
• **Maintenance Records Review**: Examine engine logbook, running hours, lube oil analysis reports, and recent maintenance activities to ensure compliance with manufacturer's schedule.

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 Nozzles (complete set or at least 50% of cylinders)
• Fuel Filter Elements (primary and secondary, full set)
• Lube Oil Filter Elements (full set)
• Exhaust Valves and Seats (at least 1-2 sets, critical for HFO operation)
• Piston Rings (at least 1 cylinder set)
• Connecting Rod Bearings (1 set)
• High-Pressure Fuel Pump Element (1 pc)
• Assorted O-rings and Gaskets (for common maintenance tasks like cylinder head or injector overhaul)

Safety

• **High-Temperature Surfaces**: Exhaust manifold, turbocharger casing, and HFO lines operate at high temperatures, posing severe burn hazards.
• **Crankcase Explosion Risk**: Accumulation of oil mist combined with hot spots (e.g., from bearing failure) can lead to a violent crankcase explosion. Ensure crankcase relief doors are functional.
• **High-Pressure Fuel Leaks**: Leaks from high-pressure fuel lines can atomize fuel, creating an invisible, highly flammable spray that can ignite upon contact with hot surfaces.
• **Moving Machinery**: Exposed rotating components (flywheel, shaft couplings, fan belts) present entanglement and crushing hazards. Ensure guards are in place.
• **Noise and Vibration**: Prolonged exposure to high noise levels requires hearing protection. Excessive vibration can indicate mechanical issues and lead to structural fatigue.

Class survey

Class surveyors typically focus on verifying the engine's operational integrity, safety systems, and adherence to maintenance schedules. Key checks include: 1. **Documentation Review**: Engine logbook, maintenance records, running hours, lube oil analysis reports, previous survey reports, and manufacturer's service bulletins. 2. **Operational Test**: Engine start-up, load response, governor stability, and verification of critical parameters (pressures, temperatures, RPM). 3. **Safety Device Functionality**: Testing of overspeed trip, low lube oil pressure shutdown, high jacket water temperature shutdown, and emergency stop. 4. **Crankcase Inspection**: At specified intervals (e.g., 12,000-24,000 hours), main and connecting rod bearings are inspected, and crankshaft deflection measurements are taken. 5. **Cylinder Head/Valve Gear Inspection**: At specified intervals, cylinder heads may be lifted for valve, seat, and spring inspection, especially critical for HFO operation. 6. **Fuel System Integrity**: Inspection of high-pressure fuel lines (double-walled where required), fuel filters, and HFO/MGO changeover procedures. 7. **Exhaust System**: Inspection for leaks, insulation integrity, and turbocharger condition. 8. **Foundation & Mounting**: Checking for secure mounting and absence of excessive vibration.