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7S70ME-C8.5

Main Engine 2-Stroke · Main Engines (2-Stroke)

Technical data from manufacturer or class sources · not yet verified by a person
21,700 kWPower
7Cylinders
700 mmBore
3,256 mmStroke
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The Hyundai 7S70ME-C8.5 is a low‑speed, electronically controlled two‑stroke marine diesel engine delivering roughly 8.5 MW of power, notable for its inline seven‑cylinder layout and multi‑fuel capability (HFO, VLSFO, MGO).

Specifications

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Configurationinline
Speed (rpm)91
Fuel TypeHFO/VLSFO/MGO
TechnologyME-C Electronically Controlled (MAN license)
Displacement l per cyl1253.1
Inspection

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Common issues

  • Fuel oil system issues: FIVA valve malfunctions, high-pressure fuel pump wear, injector nozzle clogging or burning due to poor fuel quality (HFO/VLSFO) or improper atomization.
  • Cylinder liner wear and scuffing: Accelerated wear, especially at top ring reversal point, due to cold corrosion (low load operation, VLSFO/MGO) or abrasive particles in fuel/lube oil.
  • Exhaust valve burning/seat wear: Due to high temperatures, poor sealing, or abrasive particles, leading to loss of compression and performance.
  • Turbocharger fouling/bearing wear: Reduced efficiency due to carbon deposits on compressor/turbine blades, or bearing damage from lubrication issues.
  • Scavenge space fires: Accumulation of unburnt fuel and lube oil deposits, particularly with older engines or poor combustion.
  • Electronic control system (ME-C) faults: Sensor failures, actuator issues, or software glitches affecting engine timing, fuel injection, and exhaust valve operation.
  • Piston ring breakage or sticking: Leading to blow-by, increased lube oil consumption, and reduced compression.
  • Crankshaft deflection and bearing wear: Indicative of alignment issues or prolonged heavy loading, leading to potential main bearing or crankpin bearing damage.

Inspection checklist

  • Visual inspection for leaks (fuel, lube oil, cooling water) around cylinder units, fuel pumps, and piping. Check for abnormal vibrations or unusual noises.
  • Review engine performance data: Scavenge air pressure/temperature, exhaust gas temperatures (individual cylinders and turbocharger), fuel consumption, cylinder oil feed rates. Compare with baseline and trend data.
  • Cylinder unit inspection (via indicator cocks/scavenge ports): Check for liner scuffing, piston crown condition, and exhaust valve condition. Look for signs of blow-by or abnormal deposits.
  • Fuel system integrity: Inspect high-pressure fuel lines for leaks, proper securing, and signs of fatigue. Check FIVA valve operation and fuel rail pressure stability.
  • Lubrication system checks: Verify lube oil levels, pressures (main, cylinder, turbocharger), and review recent lube oil analysis reports for wear metals and contamination.
  • Turbocharger inspection: Check bearing temperatures, air filter condition, and visually inspect compressor and turbine sides for fouling or damage (if accessible).
  • Scavenge space inspection: Check for accumulation of oil/carbon deposits, proper functioning of drain valves, and condition of fire dampers.
  • Safety device checks: Verify operation of overspeed trip, low lube oil pressure shutdown, high jacket water temperature shutdown, and emergency stops (review test logs).
  • Control system (ME-C) diagnostics: Review alarm history, fault codes, and operational parameters for any recurring issues or deviations.

Service intervals

Cylinder unit overhaul (piston, liner, exhaust valve):12,000 - 18,000 running hours (condition-based, depending on fuel and load)
Fuel injectors (inspection/overhaul):3,000 - 6,000 running hours
Exhaust valve overhaul (spindle & seat):6,000 - 12,000 running hours
Turbocharger minor overhaul (bearings, cleaning):8,000 - 16,000 running hours
Turbocharger major overhaul (rotor balancing, full inspection):24,000 - 48,000 running hours
Main bearings / Crankpin bearings (inspection):24,000 - 36,000 running hours
HP Fuel Pumps (common rail) / FIVA valves (inspection/overhaul):12,000 - 18,000 running hours
Alpha Lubricator pumps (inspection/overhaul):12,000 - 18,000 running hours

Typical wear limits

Cylinder liner wear (at top ring reversal point):Max 0.6-0.8% of bore diameter (e.g., 4.2-5.6 mm for 700mm bore) or absolute 6-8mm total wear.
Piston ring groove wear (axial clearance):Max 0.1-0.2 mm increase over new clearance, depending on ring position.
Exhaust valve seat recession/pitting:Max 1-2 mm recession or significant pitting/burning affecting sealing.
Main/Crankpin bearing clearances:Max 0.2-0.3 mm increase over new clearance, or exceeding manufacturer's specified maximum.
Piston rod gland packing leakage:Exceeding manufacturer's specified limits (e.g., >50-100 ml/hr per gland).
Turbocharger rotor radial/axial clearances:Exceeding manufacturer's specified limits (e.g., >0.15-0.2 mm radial).

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

Critical spares

  • Fuel injector nozzles (complete set for at least 2 cylinders)
  • Exhaust valve spindle & seat (complete unit, at least one)
  • Piston rings (complete set for at least one cylinder)
  • Cylinder liner (one spare, highly critical)
  • Main bearing shells (one complete set)
  • Crankpin bearing shells (one complete set)
  • FIVA valve assembly (one complete unit)
  • HP Fuel Pump (common rail type, one complete unit)
  • Turbocharger bearing cartridge (one complete unit)
  • Various O-rings, gaskets, and seals for common maintenance tasks

Safety

  • High-pressure fuel leaks: Risk of fire and serious injury (diesel spray penetration) from fuel lines, FIVA valves, or injectors.
  • Crankcase explosions: Potential for ignition of oil mist due to hot spots (e.g., bearing failure, piston overheating) or scavenge fires.
  • Scavenge fires: Accumulation of combustible deposits in the scavenge space, especially with poor combustion or high lube oil consumption.
  • Hot surfaces: Risk of burns from exhaust piping, turbocharger casing, and other engine components.
  • Rotating machinery: Danger from flywheel, turning gear, and shafting during operation or maintenance.
  • High voltage: ME-C control system components may involve high voltage, requiring strict adherence to electrical safety procedures.

Class survey

A class surveyor will typically focus on verifying the engine's structural integrity, operational safety, and compliance with classification rules. Key checks include: review of logbooks, maintenance records, lube oil analysis reports, and previous survey reports; verification of safety devices (overspeed, low LO pressure, high FW temp trips); visual inspection of crankcase internals (bearings, crankshaft, connecting rods) and scavenge spaces for cleanliness and abnormal wear; opening of one or two cylinder units (piston, liner, exhaust valve) for detailed inspection, especially if high running hours or performance issues are noted; inspection of fuel oil system for leaks and proper securing of high-pressure lines; examination of turbocharger and exhaust gas system; and verification of remote/local control and emergency stop systems. Emphasis is placed on condition monitoring data and the effectiveness of the vessel's Planned Maintenance System (PMS).

Estimated lifetime: 80,000 - 100,000 running hours before major overhaul (e.g., crankshaft inspection, full bearing renewal), with total engine life potentially exceeding 150,000-200,000 hours with continuous maintenance.

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