A routine harbor-assist operation close to Ingleside, Texas, turned hazardous when a tugboat collided with a big crude oil tanker on January 22, 2023. Whereas nobody was injured, each vessels sustained tens of millions in injury, highlighting the dangers posed by hydrodynamic forces in slender channels and prompting procedural adjustments for safer operations.
What Occurred
At round 3:30 p.m. native time, a tugboat was helping a tanker transiting inbound via the Corpus Christi Ship Channel. The tanker, in ballast situation with vital draft, was en path to load crude oil. As a part of the maneuver, the tugboat was assigned to the tanker’s starboard quarter.
To facilitate hawser connection, the tugboat’s mate carried out a 180-degree flip utilizing the vessel’s Z-drives, getting ready for a stern-first method. Throughout this repositioning, the tugboat fell again close to the tanker’s stern. The mate utilized most engine energy to regain place—however unknowingly entered a zone of low strain created by the tanker’s hull and propeller consumption.
This hydrodynamic suction, intensified by the vessel’s ballast draft and ahead velocity, overwhelmed the tugboat’s accessible thrust. Regardless of efforts to steer away, the tugboat was drawn in and struck by the tanker’s propeller.
The collision tore open the tugboat’s stern, flooding engine compartments and warping the hull. The tanker’s propeller additionally sustained injury to all 4 blades. To forestall the tug from sinking, its captain grounded the vessel close by. A minor hydraulic oil spill was rapidly contained. Harm estimates reached $3 million for the tugboat and $3.9 million for the tanker.
Possible Trigger
Investigators discovered that the tugboat was maneuvered close to the tanker’s starboard quarter—an space liable to sturdy hydrodynamic suction. The tug had inadequate reserve energy to counter these forces because of the vessels’ transit velocity. Consequently, the tugboat was drawn in and collided with the tanker’s propeller.
Classes Discovered
Hydrodynamic Forces Between Vessels in a Channel
When a big vessel strikes via a confined waterway, particularly in ballast situation, it generates low-pressure zones close to its hull—most importantly close to the consumption aspect of the propeller. These suction forces enhance exponentially with velocity and may pull in smaller vessels working close by.
Operators of smaller vessels, notably tugboats, should:
Keep a secure distance throughout close-proximity operations.
Guarantee they’ve sufficient reserve energy to counteract hydrodynamic suction.
If essential, delay method till the bigger vessel reduces velocity and the suction impact diminishes.
Pace Throughout Harbor-Help Maneuvers
Following the incident, the tugboat’s working firm instituted a coverage limiting stern-first maneuvers to speeds of seven knots or much less.
Harbor-assist operators utilizing Z-drive tugs are suggested to:
Set velocity thresholds for advanced maneuvers like stern-first landings.
Tailor these limits based mostly on the design and capabilities of the tugboat.
Talk these limits to ship pilots and masters upfront of the operation.
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Supply: NTSB
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