18V48/60B

Common issues

• Exhaust valve burning/seat wear from sustained high-load HFO operation, seen as a rising exhaust temperature on the affected cylinder
• Piston ring and liner wear or scuffing from lube oil feed rate mismatch or poor fuel quality
• Turbocharger fouling on compressor or turbine side, reducing boost pressure and raising exhaust temperatures
• Fuel injector wear or dribbling causing smoke and exhaust temperature deviation between cylinders
• Cylinder liner bore polishing/glazing from prolonged low-load running
• Crankcase bearing distress detected via oil mist detector or bearing temperature alarms
• Charge air cooler fouling, reducing charge air density and raising thermal load
• Cracking of exhaust manifold bellows/expansion joints from thermal cycling

Inspection checklist

• Check exhaust gas temperature spread between cylinders - more than roughly 50 C deviation typically points to an injector, valve or combustion issue
• Borescope inspection of cylinder liner, piston crown and exhaust valve seats at scheduled intervals
• Check turbocharger rotor for axial/radial play and inspect compressor/turbine blades for fouling or damage
• Verify fuel injector opening pressure and spray pattern on the test bench at overhaul
• Check main and crankpin bearing clearances via crankshaft deflection readings at scheduled intervals
• Inspect the crankcase for oil mist/blow-by via the relief valve and OMD readings
• Check charge air cooler differential pressure/temperature for fouling
• Verify governor/speed control and overspeed trip function
• Inspect turbocharger and exhaust manifold mounting/expansion joints for cracks

Service intervals

Typical intervals for this design class, not the manufacturer’s figures for your model. The manufacturer’s manual is binding.

Typical wear limits

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

Critical spares

• Exhaust valve complete with seat insert
• Fuel injector (complete unit)
• Cylinder liner
• Piston ring set (per cylinder)
• Main and crankpin bearing shells
• Turbocharger cartridge/rotor assembly

Safety

• Crankcase explosion risk after prolonged overheating or bearing failure - do not open crankcase doors immediately after a suspected hot spot, allow the mandated cooling time
• High-pressure fuel injection system - isolate and depressurise before opening injector or pump connections
• Turbocharger rotates at very high speed - never run with the casing open or guards removed
• Hot exhaust manifold and turbocharger surfaces - check lagging integrity to prevent burns and oil-leak fire risk
• Starting air system stores significant energy - isolate and vent before working on the starting air distributor or valves

Class survey

Main engines of this size are normally on Continuous Machinery Survey; class expects crankshaft deflection records, evidence of scheduled valve/injector/turbocharger overhauls per the maker's scheme, and a satisfactory crankcase explosion relief valve condition. Where a class-approved condition-based maintenance scheme is applied, oil analysis and vibration trend records can substitute for some fixed-interval openings.

Estimated lifetime: Medium-speed four-stroke trunk piston main engines of this class are typically designed for a major (bottom-end) overhaul interval in the order of 60,000-100,000 running hours with correct maintenance, and an overall service life well beyond that with periodic component renewal - confirm against MAN's maintenance schedule for the 48/60B.