The Ocean Guardian, a supply ship, was conducting a sea trial near Seattle on May 27, 2022, when a diesel engine suffered mechanical failure. A fire broke out in the engine room, causing about $1.1 million in damage, and the entire incident was traced to an improperly sized bearing.
This week, the NTSB released a report detailing the events that led to the fire.
In January and February of last year, maintenance was performed on the four Caterpillar model 3516B 16-cylinder diesel-driven main generators, each producing 2,669 horsepower. Maintenance was carried out by local factory-trained technicians: the fire happened in engine number 3. After the corrections, the ship carried out full operational tests in open water. But, during the sea trial, the crew heard a “big bang” and an engineer saw flames in the engine room that “appeared to engulf most of the engine”. The crew extinguished the fire with the carbon dioxide fixed fire extinguishing system on board before it could spread throughout the ship.
During maintenance, the number three main engine main bearings had been machined to a smaller diameter and undersized bearings were installed sometime before the 2022 maintenance.
Investigators also found that Caterpillar service technicians failed to identify the part number of the bearing on the service report and replaced it with a standard size one. Because it was the wrong size, the lube oil leaked out of the larger spaces. The decrease in lube oil supply pressure caused everything to heat up, and connecting rod bearings and various engine components came loose while the engine was running. The engine was damaged beyond repair.
According to the NTSB, the probable cause of the engine failure and subsequent fire was the replacement of a crankshaft main bearing with an incorrect size bearing during an engine overhaul.
After the fire, service company Caterpillar switched to a new tracking system that allows technicians to upload images and reports to their mobile phones to improve maintenance documentation.
The 261-foot-long, steel-hulled offshore supply vessel was built in 2003 and designed to carry cargo, supplies, personnel and equipment to support offshore energy operations.
