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the Netherlands |
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Azimuth thrusters for pipe-laying vessel
The 140-m X 40-m pipe-laying vessel Jascon 5 was completed and commissioned in Singapore for Offshore Contractors Ltd., in Sembawang’s Singapore Shipyard, in April 2004, and was deployed in the Middle East by Sea Trucks Group, Offshore Contractors’ owner. For this ship, HRP Thrusters b.v. supplied eight azimuth propulsion units, each rated at 1,566 kW, and direct diesel driven by CAT 3516B engines, at 1,800-rpm maximum speed.
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Jascon 5 during sea trials in the South China Sea.
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All eight Azimuth thrusters installed were HRP 7000 series. The three aft as well as the three forward ones are well-mounted – the two amidships are retractable. For maximum bollard pull, each thruster is equipped with a 19A type nozzle around the propeller. Each thruster produces a bollard pull thrust of about 25 mt, creating a total thrust of 200 mt. Thrusters were built and delivered under full ABS classification.
The six well-mounted thrusters are all top mounted, which means they can be withdrawn without dry docking the vessel. The two retractable thrusters are installed for increasing the vessel’s DP capabilities and extra force for tensioning during pipe-lay work.
In the upper position (storage), the thrusters are disconnected from the diesel engines. To deploy them, the thrusters lower hydraulically to their lower position until the propellers are fully protruded. Once a thruster is lowered and the input shaft is in line with the diesel engine, a pin coupling, activated by hydraulic cylinders, connects the thruster to the engine. A built-on type clutch on the input shaft engages or disengages the thruster from its prime mover.
During lifting and lowering, the thruster is guided by four vertical rods installed on the top side and underwater, at the bottom side of the top plate. The upper guide bars align the thruster in front of the pin coupling. The lower bars are guiding the propeller during its vertical travel and counteract thrust forces during azimuth operation. When the thruster is fully retracted, a set of latches prevent the thruster from uncontrolled lowering.
For the wheelhouse, HRP delivered the panels for the forward and aft bridges. Although Jascon 5 is equipped with a DP 3 system, for which the interfaces are integrated in the HRP control system, manual control is also possible from both forward and aft panels. On the aft panel, it is possible to control each thruster individually or have the three forward and three aft thrusters combined under two joysticks.
The shipyard also installed a Huisman – Itrec heavy lift crane, which can revolve with a full load of 800 mt, and 25-mt and 35-mt pedestal cranes which enable the vessel to handle all pipe loading and general duties. The vessel contains an accommodation deckhouse for a complement of up to 350 persons. HRP’s branch office in Singapore, HRP Asia Pte. Ltd., performed the majority of work related to supervision during installation and commissioning. 
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