Real Life Accident: Flood Tide Breaks Mooring Lines, Vessel Strikes Bridge

A small products tanker docked at terminal to load a cargo of tallow. The pilot had given the Master the local pilot information card that warned of three to five knot tidal currents in the river waterway. The card also warned of the importance of skilled line tending when moored in the river, stating: “equal tension or equal weight on all ropes at all times; mooring winch brakes shall have a holding near the strength of the line”.

The next day after loading, and in order to refuel, the vessel was shifted about three miles downriver during slack water. This was accomplished by the same pilot from the previous day and the transit was uneventful. At the new berth, ten mooring lines were used as illustrated.  Because of draught considerations, the vessel was docked such that the ship’s bow extended 30 feet beyond the east end of the wharf.

Credits: nautisnt.org
Credits: nautisnt.org

After docking, a crew member conducting a patrol noticed dust and smoke coming from the brakes of the mooring line drums on the bow. The alert was given and the bridge team tried using the ship’s bow thrusters to push the vessel toward the dock but to no avail.

As the vessel’s bow was pushed into the river, the three mooring lines that were on bitts parted (both forward springs and one aft spring). The remaining mooring lines were on winches; the winch brakes began slipping and the lines quickly ran free off the drums and fell into the water. Within about 10 minutes of the initial warning, the ship was adrift in the river. Anchors were dropped but they only slowed the drift. A few minutes later the vessel struck a bridge, which sustained approximately $2.5 million in damage, while damages to the vessel were estimated at $1 million.

Lessons learned

  • All mooring lines should be equally tensioned so as to share the load.
  • Never underestimate the force a current can exert on the vessel and carefully evaluate the vessel’s mooring situation with respect to possible current interactions.
  • Mooring winch brakes should always be in top condition and properly adjusted.
  • Given the vessel’s bow was exposed to the flood tide current, several bow lines should have been on bitts as opposed to on mooring winches.

Reference: nautinst.org

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3 Comments

  1. Unsafe berth for the size of the ship.

    Bow protruding from end of wharf is inviting disaster to happen. Even with equally tensioned lines this is no match to the force of a five knot current.

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