​​Ocean Guardian pictured before the fire. (Source: Stabbert Maritime Group)​

Wrong Size Bearing Leads to Engine Failure and Fire on Supply Vessel


Editor’s note: An earlier version of this news release identified the service technicians being from Caterpillar; however, the technicians were from NC Power Systems. The news release has been updated.

​WASHINGTON (May 24, 2023) — An incorrectly sized bearing led to an engine failure and fire last year on board an offshore supply vessel near Seattle, the National Transportation Safety Board said Wednesday.

On May 27, 2022, the supply vessel Ocean Guardian was conducting a sea trial in Shilshole Bay when its no. 3 diesel generator engine suffered a mechanical failure, resulting in an engine room fire that caused $1.1 million in damages. No injuries or pollution were reported.

​After maintenance was completed on all four main diesel generator engines in January and February 2022, full-function tests of vessel systems were conducted in open waters. Du​ring the sea trial, the engineering crew heard a “large bang” and observed flames near the no. 3 main engine. The crew extinguished the fire using the vess​el’s carbon dioxide fixed fire-extinguishing system.

Investigators found that the no. 3 main engine’s main bearing journals had been machined down to a smaller diameter, and undersized bearings were installed at some point prior to the 2022 maintenance.

During the 2022 maintenance, service technicians from NC Power Systems (an independent company that contracted with Caterpillar to be a Caterpillar dealer and service Caterpillar products)​ did not identify the bearing’s part number on the service report and replaced it with a standard-sized one. The bearing’s incorrect size allowed lube oil to leak from the larger clearances of the bearing. The decreased lube oil supply pressure resulted in a rapid temperature increase of the connecting rod bearings and multiple engine components breaking free while the engine was running.

The NTSB determined the probable cause of the mechanical failure of the no. 3 main engine and resulting fire aboard the Ocean Guardian was the replacement of a crankshaft main bearing with an incorrectly sized bearing during an engine overhaul due to the engine service technicians not identifying the removed bearing’s part number, which resulted in the loss of lube oil pressure in adjacent connecting rod bearings.

“When maintenance is performed, correct replacement of machinery components is critical to ensuring safe and reliable vessel operation,” the report said. “Vessel crews and equipment manufacturer technicians should carefully identify and document part numbers of all components removed from shipboard equipment. Tracking systems are an effective form of record-keeping that can be used to ensure proper replacement part selection for reinstallation."

Following the engine failure and fire, the diesel engine service company switched to a new service tracking system that allows technicians to upload pictures and reports on their cell phones to improve documentation and information sharing between technicians.​

Marine Investigation Report 23-08​ is available online.​​​​​

To report an incident/accident or if you are a public safety agency, please call 1-844-373-9922 or 202-314-6290 to speak to a Watch Officer at the NTSB Response Operations Center (ROC) in Washington, DC (24/7).