Engine damage digest: catalytic fines and fuel contamination

Anonymized synthesis of common findings on abrasive engine wear caused by catalytic fines in residual and VLSFO bunkers, with the practical defences that prevent an unplanned overhaul.

Catalytic fines — aluminium and silicon oxides carried over from refinery processing ("cat fines") — are among the most damaging contaminants in residual and VLSFO bunkers. Under high injection pressure they embed in liner, piston-ring and fuel-injection surfaces, causing rapid abrasive wear and, in severe cases, scuffing and power loss.

ISO 8217 permits aluminium plus silicon up to 60 mg/kg as bunkered, but engine makers typically require the fuel entering the engine to be conditioned down to roughly 10–15 mg/kg. Effective settling, correct purifier throughput and temperature, and regular draining and cleaning of settling and service tanks are the primary defences.

Field practice: draw representative samples at bunkering and downstream of the purifiers, monitor differential pressure across filters, and avoid overloading purifiers by pushing throughput. A single high-cat-fine bunker acted on early is a maintenance event; ignored, it becomes an unplanned overhaul.

This digest is an anonymized synthesis of common findings, provided for training and prevention. It does not reference any specific vessel, operator or incident.