Mariners should conduct regular water chemistry testing, Nenita report finds

After the grounding of bulk carrier Nenita On November 19th 2016, a National Transportation Safety Board (NTSB) investigation has noted that maintaining proper water chemistry in engine cooling water systems reduced corrosion, scale, and the formation of deposits, which ensured effective cooling  to satisfy system operating requirements. “Mariners should conduct testing per the manufacturer’s recommended schedule, ensure levels of treatment are correct, and maintain water quality within specified limits. Insufficient cooling water maintenance may result in increased corrosion, clogging of cooling water passages, or, ultimately, the failure of equipment,” the NTSB said.

NTSB also noted that over the past two years it had investigated three separate accidents that might have been caused by a failure to tighten fasteners on marine engines to the manufacturer’s recommended torque settings. It said that under-torqueing a fastener might cause excess vibration or allow a fastener to come loose, while over-torqueing might lead to failure of the fastener or the machinery component being secured. “When installing fasteners, mariners should use a calibrated torque wrench and follow the manufacturer’s recommended tightening guide and torque values”, the NTSB said.

Fully-laden Marshall Islands-registered bulk carrier Nenita was outbound on the Columbia River when the vessel suffered an engine failure impacting its ability to manoeuvre. The vessel subsequently ran aground at Three Tree Point on the Washington State side of the river, damaging its bulbous bow and hull. After the grounding, the Nenita was towed to Longview, Washington, for temporary repairs. There were no injuries or reported pollution as a result of the accident.

The NTSB said that contributing to the accident was the lack of information relayed from shipboard personnel to the pilot about the status of the main engine, which prevented him from taking effective corrective action following the engine.