Variable-Orientation Berth for Large Carriers

ABSTRACT Ship berthing and loading studies were carried out for a high-capacity offshore terminal designed to load coal into 250,000 DWT ships, near Newcastle, New South Wales, Australia. The resulting solution permits ships to berth at a varying angle in order to head into the waves to minimize wave-induced oscillation. Buoys and dolphins are used to rotate the moored ship and to pull it tight against the fenders to avoid bouncing and slamming, or to hold it off to prevent contact between ship and fenders. The local wave pattern was analyzed. Refraction and attenuation studies established that the direction of the waves reaching the berth is confined to a 45° sector. Laboratory tests and computer analysis of the behavior of the moored ships proved that motions can be reduced by varying the heading within the 45° sector. Operating experience at other offshore installations provided practical limits of acceptable motions. It was found that, with variable orientation, the berth availability will be at least 85%. The variation of the ship's heading was made possible by the use of a special ship loader, resembling a movable bridge, capable of reaching all hatches of the largest ship, regardless of orientation. INTRODUCTION A large, coal loading terminal is under construction at Kooragang Island in Newcastle, New South Wales, approximately 65 nautical miles (120 kms) north of Sidney Australia (Figure 1). At the completion of the first stage of construction this terminal will be able to ship out up to 15 million metric tons of coal per year. The terminal being located on the South Arm of the Hunter River, well inside the existing harbor of Newcastle, the size of ships that can be fully laden is limited to approximately 120,000 DWT. For the second stage of construction additional wharves might be built adjacent to the initial installations. It is, however, desirable to substantially increase the size of ships that can be fully laden at Newcastle. To achieve this two basic alternatives are available: deepening the harbor, or building a ship loading berth offshore, in the Tasman Sea. DESCRIPTION OF THE OFFSHORE ALTERNATIVE The most practical alternative is to construct a high-capacity loading berth offshore in naturally deep water. Similar berths have operated successfully elsewhere (e.g. Port Latta, Tasmania; Punta Colorado, Argentina; Huasco, Chile). Since the commissioning of Port Latta over 10 years ago, considerable development has taken place in the field of open sea technology, including refinements of mooring, fendering and ship loader design to enable operation to continue in more difficult wind and sea conditions than previously thought possible. A general location was selected offshore in the Newcastle Bight north of Stockton. The plans call for part overland and part tunnel conveyor to link the coal stockpiling and reclaiming system to the offshore ship loading berth.