The invention relates to a vessel, such as an Anchor Handling Supply Vessel (AHSV), comprising, a hull having a longitudinal midplane defining a starboard and a port side of the hull, a cable for picking up tensile forces, a winch connected to the hull for taking up the first cable and driving means for driving the winch in rotation. The invention also relates to a method for raising a load under water using such a vessel.
Floating platforms at sea, such as Floating Production, Storage and Offloading (FPSO) platforms for processing and storage of oil and gas, are positioned nearby drilling platforms and anchored to the sea bottom by multiple anchor lines. Water depths at such locations can be as high as 1.500 meter. Pullout forces for lifting the anchors used for positioning FPSO’s are unpredictable and can exceed 1.000 metric ton. For lifting such anchors and anchor lines use is made of Anchor Handling Supply Vessels of the above mentioned type. Thereto a cable is connected to the anchor line and/or to the anchor. By driving the winch in rotation a pullout force will be exerted on the anchor. However, during operation at sea there is a risk of significant heeling which even may lead to capsizing of the vessel due to the forces and the moment exerted by the cable on the vessel. This even more holds in case of rough sea conditions, wherein wind and waves increase the risk of heeling of the vessel.
The invention has for its object to provide a vessel, which at least partially obviates the above stated drawbacks. Patent pending.
According to the invention a vessel, such as an Anchor Handling Supply Vessel, is provided for this purpose, which comprises a hull having a longitudinal midplane defining a starboard and a port side of the hull, a first cable for picking up tensile forces, a first winch connected to the hull for taking up the first cable, driving means for driving the first winch in rotation, wherein the hull is provided with a passage for passing the first cable, wherein a first end of the passage extends through the hull substantially at the midplane of the hull and below the water line of the hull. A given force exerted by the cable on the vessel results in a decreased moment, due to the decreased distance between the force line exerted on the vessel and the midplane of the vessel. The force exerted by the cable on the vessel is a stabilizing force, which tends to prevent heeling of the vessel and substantially exerts a downward force. As a result, there is a decreased risk of significant heeling or capsizing of the vessel. Also, higher pullout forces can be applied or lighter vessels can be used. In this context by cable is also meant rope, wire, chain etc. The vessel may also be a pontoon, ship or boat. The midplane can be a plane of symmetry of the hull, depending on the design of the hull.