Corroded wire rope leads to expensive bulk carrier crane failure

The National Transportation Safety Board has released its report on a July 23, 2023 incident when a hoisting wire rope on one of the cranes on the cargo ship Thorco Basilisk failed as it was offloading a wind turbine component at the Greensport Terminal on the Houston Ship Channel. The failure caused the component, a 69-tonne wind turbine nacelle, to drop onto the vessel’s cargo hold tweendeck.

No injuries were reported. Damages to the ship and cargo were estimated between $3 million and $5 million.

An examination of the hoisting wire rope showed significant external corrosion and wear; however, the visible signs of external corrosion could not be fully seen until the grease on the rope was removed. While annual surveys were performed on the ropes, the surveys primarily involved visual inspections to look for wear and would not have identified the underlying corrosion below the grease.

While the hoisting rope had been in use for 9 years, still within the standard 10-year period of use, a postcasualty examination found “the wire rope was near the end of its service life and probably should have been discarded.”

The operating company has since updated its planned maintenance system to require crane wire rope replacement every 5 years.

“Saltwater and humid ocean air cause corrosion of metals, presenting challenges for the maintenance of high-strength steel wire ropes on vessels,” the report said. “A deteriorated wire rope directly affects a crane’s ability to safely and reliably handle loads up to its rated capacity (safe working load). Therefore, diligent inspection, maintenance, and management of wire ropes are essential. Working wires should be changed at recommended intervals, or more frequently, depending on operating conditions and use.”

• Download the full report HERE