Cylinder Liner Scuffing After a VLSFO Switch
A 12,000 TEU container ship is powered by a 9S90ME-C two-stroke engine, MCR 68,400 kW at 84 rpm. After switching from HSFO to a 0.50% S VLSFO with CCAI 850, viscosity 180 cSt at 50°C and water 0.35%, units 3 and 7 show exhaust-gas temperatures about 40°C above the other units, liner wear of 0.12 mm/1,000 h against a normal 0.05 mm/1,000 h, and drain-oil iron of 180 mg/kg. Cylinder oil feed is 1.05 g/kWh. Those two units have the oldest liners at 28,000 h; the others were relined 4,000 h ago. The fuel-treatment plant is reportedly normal. The technical manager wants to raise feed to 1.5 g/kWh, keep full sea speed and deal with the units at the next dry-dock in five months; the charter party has a tight schedule. The chief engineer is uneasy but has no clear instruction.
1. Diagnose the likely condition and decide whether the proposed full-speed operation should be accepted.
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The pattern points to adhesive wear/scuffing on units 3 and 7 rather than a fleet-wide fuel problem. Those units have the oldest liners and are at 28,000 h; the VLSFO has a high CCAI of 850, which means long ignition delay and afterburning, and the cylinder oil feed of 1.05 g/kWh is marginal at high load. The 40°C exhaust-temperature rise and drain-oil iron of 180 mg/kg are consistent with boundary lubrication and metal-to-metal contact. The fact that only the two oldest units are affected supports a liner-condition plus fuel-ignition interaction, not simply a bad fuel batch.
The proposal to raise feed to 1.5 g/kWh and keep full sea speed should not be accepted as written. A very high feed can create deposits and mask the underlying problem, and full load will continue the wear. The engine should be reduced to about 50–60% MCR while the affected units are inspected through the scavenge ports at the first safe opportunity. Increase cylinder oil feed on the affected units to the engine builder's high-wear or running-in rate, typically around 1.3–1.4 g/kWh, and monitor drain-oil iron and liner temperature. If liner temperature exceeds the alarm, iron rises above about 200 mg/kg, or scavenge inspection shows severe scoring, stop the engine and renew or hone the liners.
2. List the immediate fuel-system and lubrication checks and the medium-term corrective actions.
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Immediate checks: verify that every lubricator quill on units 3 and 7 is working and that the feed rate is actually being delivered; check fuel viscosity and temperature at the injection pumps; drain water from fuel tanks and check purifier operation and filters for cat fines; retain fuel and drain-oil samples. Analyse the fuel for ignition quality, water and catalyst fines. If the fuel is off specification, segregate it and notify the supplier through the owner's fuel-quality procedure.
Medium-term: improve ignition quality by blending or switching to a more suitable fuel; adjust injection timing in accordance with the engine builder's guidance for the fuel; replace or re-hone worn liners and renew piston rings as needed. Review cylinder oil BN and feed rate for a 0.50% S fuel and the actual liner condition. A higher-BN oil is not automatically correct; over-basing can cause deposits. Establish a cylinder condition monitoring programme with regular drain-oil analysis and scavenge inspections.
3. Explain the reporting and record-keeping obligations, including class, flag and MARPOL Annex VI.
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The chief engineer should report the degradation to the technical manager and, if the engine is derated or a classed machinery item is repaired, to class and flag. The master's overriding authority under ISM applies: a tight charter schedule is not a reason to run a damaged engine. The company should raise an ISM non-conformity covering the fuel-changeover procedure and the running-in instructions for the affected units.
Under MARPOL Annex VI, the fuel-changeover operation and the sulphur content of the fuel used must be recorded, and representative fuel samples must be retained. If the fuel is shown to be off specification, the supplier notification and sample records should be kept. If the engine power is reduced or a repair affects the vessel's certificates, class and flag must be informed before the ship resumes normal service.