The ATSB has found that the tanker, Dampier Spirit, did not have sufficient speed to safely evade a cyclone that was approaching the coast of Western Australia after its mooring hawser failed on 6 April 2006.
Dampier Spirit is a floating storage and offloading tanker for the Stag oil platform near Dampier, Western Australia, that is usually attached to a mooring buoy one nautical mile from the platform. At the time of the incident, the 106 668 tonne tanker had a partial load of about 12 100 tonnes of crude oil on board.
At 0958 on 6 April 2006, the ship was forced to put to sea as Cyclone Hubert approached when the mooring hawser attaching the ship to the buoy failed under load. The ship's master had delayed making the decision to disconnect from the buoy when the cyclone was declared, a delay which effectively reduced the time available to navigate the ship safely out of the cyclone's path.
Once disconnected from the buoy, the ship had difficulty making sufficient headway in the strong winds and heavy seas produced by the cyclone because its speed was limited by 'slow steaming' fuel injector nozzles that had been fitted in the main engine and by the build-up of marine growth on the hull.
Dampier Spirit was tracking towards Tryal Rocks for over three hours until the wind eased at 0305 on 7 April, allowing the tanker to sail into safer water. If it had grounded on Tryal Rocks, its cargo of crude oil may have spilled into the sea, resulting in significant damage to the environmentally sensitive mangroves and turtle nesting grounds in the area.
The report also concludes that the company guidelines for disconnection from the CALM buoy did not provide unambiguous advice to the master, the mooring hawser had been weakened by its service conditions and the master did not adequately consider the time needed to safely avoid the cyclone when making the decision to disconnect and depart from the buoy.
The ATSB has made two safety recommendations with the aim of preventing further incidents of this type.
Copies of the report can be downloaded from the ATSB's internet site at www.atsb.gov.au,