STX-MAN 6L23/30H GenSet

Common issues

• Fuel valve fouling and carbon build-up, leading to poor atomization and increased exhaust temperatures.
• Exhaust valve seat wear and burning, especially when operating on HFO, causing loss of compression and blow-by.
• Turbocharger fouling on both turbine and compressor sides, reducing efficiency and increasing exhaust back pressure.
• Cylinder liner wear (scuffing or abrasive wear) due to poor lubrication, fuel quality, or cooling issues.
• Fuel injection pump element wear, leading to reduced injection pressure and uneven fuel distribution.
• Bearing wear (main and big end) due to lube oil contamination, insufficient pressure, or overloading.
• Cooling water system blockages or leaks, affecting engine temperature control and increasing thermal stress.
• Governor malfunction or instability, leading to frequency fluctuations or load hunting.

Inspection checklist

• Verify exhaust gas temperature spread (max. deviation +/- 30°C from average) and compare with logbook records.
• Check fuel oil system for leaks, proper viscosity control (viscometer reading), and filter differential pressures.
• Inspect cooling water system for leaks, proper pressure, and temperature, ensuring no abnormal vibrations in pumps.
• Monitor lubricating oil pressure, temperature, and level; visually inspect for leaks around seals and pipe connections.
• Listen for abnormal noises from engine internals, turbocharger (e.g., rubbing, whistling), and fuel pumps.
• Visually inspect turbocharger for signs of oil leakage, excessive carbon deposits, or foreign object damage on blades (if accessible).
• Check engine room for general cleanliness, absence of oil/fuel leaks, and proper functioning of bilge alarms.
• Verify governor response and stability during load changes; check linkage for free movement and wear.
• Inspect vibration dampener (if fitted) for signs of leakage or damage.
• Confirm proper functioning of all engine safety devices (overspeed trip, low lube oil pressure, high cooling water temperature).

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 units or nozzle tips and atomizers.
• Exhaust valve spindles and seats (or complete valve cages).
• Fuel injection pump elements and delivery valves.
• Full set of engine filters (fuel, lube oil, air).
• Gasket and O-ring sets for cylinder heads, fuel pumps, and common covers.
• Turbocharger bearing cartridge or repair kit.
• Engine safety sensors (e.g., overspeed, low lube oil pressure, high cooling water temperature).
• Piston rings (at least one set per cylinder).

Safety

• High-pressure fuel lines: Risk of spray fires from leaks, especially with HFO. Ensure proper shielding and regular inspection.
• Hot surfaces: Exhaust manifold, turbocharger, and other engine components operate at high temperatures. Ensure insulation is intact.
• Rotating machinery: Exposed rotating parts (flywheel, coupling, fan belts) pose entanglement hazards. Guards must be in place.
• Crankcase explosion: Risk from hot spots or bearing failures. Ensure crankcase relief valves are clear and functioning, and oil mist detector is operational.
• Noise levels: High noise levels in the vicinity of the running engine require hearing protection.

Class survey

Class surveyors will typically review engine logbooks for operational parameters, maintenance records (PMS adherence), and lube oil analysis reports. They will check the functionality of all safety devices (overspeed trip, low lube oil pressure, high cooling water temperature shutdowns). Crankshaft deflection readings are often requested. Visual inspection of the engine for leaks, general condition, and integrity of fuel and exhaust systems, including insulation. Generator insulation resistance and winding temperature alarms will also be checked. Any open-up inspections (e.g., cylinder head, piston, bearing) performed during the survey period will require documentation and surveyor attendance.