Side view of the Lan Jiang with its 3,800-ton Amclyde derrick crane.
China's state oil company CNOOC recently took delivery of its first derrick/laybarge from the Yantai Raffles Shipyard in Shandong, The $109 million Lan Jiang, which is also the first pipelay barge built in China, will be able to lay concrete-coated pipes in diameters ranging from 4 in. to 48 in. in up to 150 meters water depth. The vessel was built to a basic design provided by IHC Gusto Engineering in Schiedam. SAS in Gouda supplied the pipe handling system.
Gusto's was first approached by CNOOC for the planned new vessel early in 1998. The work scope was completed in December 1999. Friede Goldman Halter in Louisiana was appointed main contractor for the ensuing barge construction program, performed by Yantai Raffles. The latter also undertook detailed engineering of the barge in cooperation with CNOOC. Much of the vessel's key equipment was fabricated in the US, but not the 3,800-ton Amclyde derrick crane, which was assembled in Shandong. Prior to the final sea trials of the vessel, the crane successfully performed a 4,220 metric ton lift.
Vessel dimensions
The vessel has an overall length of 157.5 meters, a molded breadth of 48 meters, a depth at side of 12.5 meters, and a maximum loaded draft of 8 meters. Displacement when fully laden will be 54,000 metric tons. The vessel was designed for unrestricted ocean service, and has been classified as such by ABS. It features a box-shaped hull, with the cross-section designed with a large bilge. Added stability is attained through a relatively high center of buoyancy and a large water line area, while the steel weight has been minimized.
The vessel has been designed without camber and sheer. The forecastle comprises two decks. Up to 280 workers and marine staff can be accommodated in the living quarters.
Power generation is provided by three diesel sets generating 9.6 MW in total. For primary users, power is distributed at 6.6 kV AC, 50 Hz. The propulsion system comprises two underwater mountable azimuthing thrusters, both fixed pitch and frequency controlled. These are located at the stern, not protruding below the keel plane. The thrusters are purely for in-field movements. Pipelay operations are enacted by means of the vessel's mooring system.
Pipehandling equipment
The vessel is equipped with a firing line and stinger at the starboard. The latter is designed to be easily detached during survival conditions. Initially and primarily, it will lay single-joint pipes, although provision has been made to accommodate a double-jointing version in the future.
In general, the firing line will be enclosed. Maximum weights that can be handled are 30 tons for a single joint, and 60 tons for a double joint. Minimum water depth for laying operations is 6 meters. For concrete coated pipes up to 48-in. OD, the maximum operable water depth is 100 meters. That limit drops to 150 meters for installation of 36-in. pipes. Maximum anticipated laying speed is 1,750 meters per day.
Friede Goldman Halter commissioned SAS to design, manufacture, and supply the pipe handling system. Among other items, this comprises longitudinal rollers, a transverse conveyor system, line-up units, deck support rollers, and pipe track supports.
SAS delivered this equipment as scheduled in November 2000, complete with a skid-mounted hydraulic power unit. Onboard the vessel, there are three pipe storage bays that can accommodate 62 joints of 48-in. pipe. The main deck's storage load capacity is 10 tons/sq meter.
According to Gusto, the barge could be adapted at some point to also lay reeled flexible lines, following deck modifications. The vessel could theoretically be adapted for deeper operations, if required by CNOOC, partly through an upgrade of the mooring system.
Currently, the vessel is designed for survival in 50-year storm conditions (with a significant wave height of 12 meters). In pipelay mode, the vessel can work in waves up to 2.5 meters high, with a 4 knot current.
The vessel's first pipelay job will be in the Wengchang fields offshore Hainan Island. It will work mainly in Chinese waters, but could also be made available for other pipelay projects in the Far East.
