Wrong Sized Bearing Caused Engine Failure and Fire on Offshore Supply Vessel

The National Transportation Safety Board (NTSB) has determined an improperly sized bearing resulting in an engine failure and subsequent fire on board an offshore supply vessel near Seattle last year.

The incident took place on May 27, 2022, when the supply vessel Ocean Guardian was undergoing a sea trial in Shilshole Bay. The vessel’s no. 3 diesel generator engine experienced a mechanical failure, resulting in a fire in the engine room.

Fortunately, there were no injuries or pollution reported, but the damages amounted to $1.1 million.

Prior to the incident, maintenance had been carried out on all four main diesel generator engines between January and February 2022. Following the maintenance, full-function tests of the vessel systems were conducted in open waters. However, during sea trial, the engineering crew heard a loud noise and noticed flames near the no. 3 main engine. They promptly used the vessel’s carbon dioxide fixed fire-extinguishing system to extinguish the fire.

Investigations revealed that the main bearing journals of the no. 3 main engine had been machined to a smaller diameter, and undersized bearings had been installed sometime before the 2022 maintenance. When the maintenance took place, the Caterpillar service technicians failed to identify the part number of the bearing on the service report and replaced it with a standard-sized bearing.

The incorrect size of the bearing caused lube oil to leak from the larger clearances, resulting in a decrease in lube oil supply pressure. Consequently, the connecting rod bearings experienced a rapid temperature increase, leading to the failure of multiple engine components while the engine was in operation.

The NTSB determined that the primary cause of the engine failure and subsequent fire on the Ocean Guardian was the replacement of a crankshaft main bearing with an incorrectly sized one during the engine overhaul. This error occurred because the engine service technicians failed to identify the part number of the removed bearing, resulting in a loss of lube oil pressure in the adjacent connecting rod bearings.

The report highlighted the importance of correctly replacing machinery components during maintenance to ensure safe and reliable vessel operation. It emphasized the need for vessel crews and equipment manufacturer technicians to carefully identify and document part numbers of all components removed from shipboard equipment. The use of tracking systems was also recommended as an effective method of record-keeping to ensure the proper selection of replacement parts during reinstallation.

As a result of the engine failure and fire incident, the local Caterpillar service company has implemented a new service tracking system that allows technicians to upload pictures and reports using their cell phones to improve documentation and information sharing between technicians.

Read the report: Marine Investigation Report 23-08

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