What Happened
What Happened
On April 22, 2021, about 1330 local time, the no. 3 main engine aboard the passenger and car ferry Wenatchee suffered a mechanical failure during a sea trial in Puget Sound near Bainbridge Island, Washington. The failure led to the ejection of components from the engine and resulted in a fire in the no. 2 engine room. The crew isolated the space, and the fire self-extinguished before it could spread throughout the vessel. There were 13 crewmembers aboard and no passengers. No injuries or pollution were reported. Damage to the Wenatchee was estimated at $3,790,000.
What We Found
What We Found
We determined that the probable cause of the mechanical failure of the no. 3 main engine aboard the passenger vessel Wenatchee was a connecting rod assembly that came loose and separated from the crankshaft due to insufficient tightening (torqueing) of a lower basket bolt during the recent engine overhaul.
What We Recommended
Tightening of Fasteners
The NTSB has investigated several recent casualties that likely were caused by a failure to tighten fasteners on marine engines to the manufacturer’s recommended torque settings. Undertorqueing a fastener may cause excess vibration or allow the fastener to come loose, while overtorqueing may lead to failure of the fastener or the machinery component being secured. When installing fasteners, personnel should use a calibrated torque wrench, follow the manufacturer’s recommended tightening guide and torque values, and verify that all required torque requirements have been completed.
Containing Engine Room Fires
Engine rooms contain multiple fuel sources as well as mechanical ventilation, making the spaces especially vulnerable to rapidly spreading fires. The crew of the Wenatchee effectively contained the spread of a fire by removing fuel and oxygen sources. Vessel crews should familiarize themselves and train frequently on machinery, fuel oil, lube oil, and ventilation shutoff systems to quickly act to contain and suppress engine room fires before they can spread to other spaces and/or cause a loss of propulsion and electrical power.
