8H25/33

Common issues

• Fuel injection pump sticking and plunger immobilization, often caused by fuel sludge accumulation or low lubricity in low-sulphur fuels (specific to Common Rail).
• Exhaust valve burning, seat wear, or leakage, particularly when operating on HFO due to high thermal stress and corrosive elements.
• Cylinder liner scuffing or excessive wear, often linked to poor lubrication, fuel quality, or improper combustion.
• Turbocharger bearing failure, fouling of compressor/turbine blades, or surging, leading to reduced engine efficiency and power.
• Piston ring breakage, sticking, or excessive wear, resulting in increased blow-by, lube oil consumption, and reduced compression.
• High-pressure fuel pipe leaks within the Common Rail system, posing a significant fire and safety hazard due to atomized fuel.
• Main and connecting rod bearing wear or damage, typically caused by lube oil contamination, insufficient lubrication, or misalignment.
• Cooling water system fouling, corrosion, or pump issues, leading to inadequate heat dissipation and potential engine overheating.

Inspection checklist

• **Visual Inspection for Leaks**: Check all fuel, lube oil, and cooling water lines, flanges, pumps, and engine block for any signs of leakage. Pay close attention to high-pressure fuel lines and their shielding.
• **Exhaust Gas Temperature Monitoring**: Record and analyze cylinder-wise exhaust gas temperatures. Significant deviations indicate combustion issues, injector problems, or exhaust valve condition. Check overall average against load.
• **Crankcase Blow-by/Pressure**: Monitor crankcase pressure or measure blow-by. Excessive values indicate piston ring or liner wear. Ensure crankcase relief valves are clear.
• **Fuel Injector Performance**: Listen for abnormal knocking, observe exhaust smoke, and check for consistent cylinder power output. Consider opening injectors for spray pattern and atomization check if issues are suspected.
• **Turbocharger Condition**: Check for unusual noise, vibration, excessive axial or radial play in the rotor shaft, and proper boost pressure. Inspect air filter cleanliness and turbine/compressor blade condition.
• **Lube Oil Analysis Review**: Regularly review trends in wear metals, TBN, viscosity, water content, and fuel dilution. This provides early warning of internal component wear or contamination.
• **Safety Devices Functionality**: Test the overspeed trip, low lube oil pressure alarm/shutdown, high cooling water/exhaust temperature alarms, and emergency stop functions.
• **Engine Foundation Bolts**: Visually inspect all foundation bolts for tightness, signs of fretting, corrosion, or cracking in the chocking material.
• **Common Rail System Integrity**: Beyond leaks, check sensor readings for fuel pressure stability and control valve operation. Look for signs of external damage or tampering.
• **Cooling Water System**: Verify correct pressure, temperature, and inhibitor levels. Inspect heat exchangers for fouling and pumps for leaks or unusual noise.

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 Fuel Injector Unit (or nozzle/needle valve set for at least one cylinder)
• Exhaust Valve Spindle and Seat Ring (for at least one cylinder)
• Piston Rings (complete set for at least one cylinder)
• Connecting Rod Bearings (upper and lower halves for one cylinder)
• Fuel Filters (primary, secondary, and high-pressure Common Rail filters)
• Lube Oil Filters (main and fine filters)
• Turbocharger Bearing Cartridge (or complete rotor assembly)
• High-Pressure Fuel Pipe (for Common Rail system, prone to fatigue)
• Assorted Gaskets and O-rings (for common maintenance points like cylinder head, fuel pumps, inspection covers)

Safety

• **Crankcase Explosions**: Risk from ignition of oil mist due to hot spots (e.g., seized bearings, piston overheating) or excessive blow-by. Ensure crankcase relief valves are clear, correctly fitted, and regularly inspected.
• **High-Pressure Fuel Leaks (Common Rail)**: The Common Rail system operates at extremely high pressures (up to 2000 bar). Leaks can cause fuel to atomize, penetrate skin (leading to severe injury), or create a highly flammable spray, posing a significant fire hazard. Ensure all high-pressure lines are properly shielded and regularly inspected for integrity.
• **Hot Surfaces/Exhaust System**: Exposed exhaust manifolds, turbocharger, and other engine components operate at very high temperatures, posing a severe burn risk. Ensure insulation and guards are intact.
• **Rotating Machinery**: Entanglement risk from crankshaft, flywheel, and auxiliary drives. All rotating parts must have appropriate guards in place and these should be maintained.
• **Overspeed**: Malfunction of the governor or overspeed trip system can lead to catastrophic engine failure, potentially causing severe damage and injury. Regular testing of the overspeed trip is crucial.

Class survey

A class surveyor typically focuses on the engine's overall condition, safety systems, and compliance with statutory and class rules. Key checks include: 1. **Safety Devices**: Verification of overspeed trip, low lube oil pressure, high cooling water/exhaust temperature alarms, and emergency stops. Operational testing is often required. 2. **Crankcase Relief Valves**: Inspection for free movement, cleanliness, proper securing, and flame trap integrity. 3. **Fuel Oil System Integrity**: Thorough inspection for leaks, proper shielding of high-pressure lines (especially Common Rail), fire insulation, and functionality of quick-closing valves. 4. **Engine Foundation**: Visual inspection for cracks, loose bolts, signs of fretting, and integrity of chocking arrangements. 5. **Crankshaft Deflection**: Measurement to assess main bearing wear and alignment condition (often required at specific intervals, e.g., every 4-5 years). 6. **Cylinder Unit Inspection**: Opening of specific cylinders (as per survey schedule, typically 1-2 units) for piston, liner, and exhaust valve inspection. Wear measurements are taken. 7. **Bearing Inspections**: Opening of main and connecting rod bearings (as per survey schedule) for wear assessment and clearance checks. 8. **Documentation Review**: Examination of engine logbooks, maintenance records, lube oil analysis reports, previous survey reports, and class certificates to ensure compliance and track maintenance history. 9. **Operational Test**: Verification of engine performance, control systems, and alarm functions under various load conditions.