Kommandor Susan. A 24,000-hour service interval depended on genuine Caterpillar parts.
On 25 January 2025, Kommandor Susan was conducting sea trials in the Firth of Forth when diesel generator DG1 failed catastrophically. The failure caused an engine room fire and a complete blackout. The crew extinguished the fire and mustered safely.
Technical examination identified failure of a connecting rod bearing as the most likely root cause. Several bearings showed weak bonding of their copper layer.
DG1 had undergone a major overhaul in 2019. After the accident, investigators found CTP pistons, connecting rods and bearings in the engine. They found no evidence that these parts had been approved by a marine classification society.
Caterpillar had extended the engine’s major-overhaul interval to 24,000 hours on the basis that genuine Caterpillar components would be used in subsequent overhauls. DG1 failed after 13,466 running hours since the 2019 overhaul.
The former owner expected the contractor to use genuine parts but provided minimal oversight while other conversion work was in progress. Part authenticity was not verified, and the presence of substitute components was not communicated when the vessel was sold.
Four oil analysis reports showed no significant wear particles. The latest sample was taken 19 days and 127 running hours before the failure. Routine oil analysis did not identify the latent defect.
For critical machinery work, the control must cover the parts actually installed, not only the wording of the purchase order.
Before closing an overhaul, verify part identity, record the supporting certification and confirm that every extended service interval remains valid for the fitted components. The record must also remain available for the next owner or manager.
Check one recent critical overhaul on your vessel: can you trace the fitted bearings, pistons and connecting rods to their certificates and confirm that the approved service interval still applies?
#MarineAccidentInvestigation #MachineryFailure #Maintenance #FireSafety #LessonsLearned
