Patent ID: 8292544

Claim:
A device for lowering or raising an undersea pipe between a vessel on the surface and the sea bottom, said pipe being constituted by unitary pipe elements assembled end to end, by welding, said lowering and raising device being installed on board a laying vessel and serving, at the end of assembling and laying the pipe from said vessel, to lower the top end of said pipe down to the sea bottom from the vessel, the other end of the pipe resting on the sea bottom and the remainder of the pipe being immersed in suspension, said lowering or raising device comprising: a structure mounted on board said vessel and forming a variable-inclination tower in an inclined position, suitable for receiving and supporting at least the terminal unitary pipe element comprising the top end of said pipe, the remainder of the pipe being immersed in suspension down to its other end lying on the sea bottom, the tower having a longitudinal axial direction, a bottom end and a to end; said tower being fitted with at least one guide element, suitable for guiding a movable gripper consisting in a carriage, in the longitudinal axial direction of the tower; and said movable gripper being suitable for being moved in translation along said guide element by means for actuating it in translation between a high position of said top end of said tower relative to a surface of the laying vessel and a low position of said top end of said tower relative to the surface of the laving vessel; wherein: said lowering or raising device comprises an abandonment chain having a free end, said chain fastened to the top end of said pipe, extending through said tower to said movable gripper, and passing around a first sheave secured to said carriage, so as to pass subsequently to a storage area where the free end of said chain is stowed, the portion of the abandonment chain between said first sheave and said storage area being subjected solely to the tension due to its own weight; said movable gripper being fitted with a first chain-locking device, suitable for locking said abandonment chain when it is in a closed position and for releasing said connection when said first locking device is in an open position; and a second chain-locking device being mounted proximate the bottom end of said tower below said low position of said gripper and suitable for locking said abandonment chain when said second locking device is in a closed position and for releasing said chain when said locking device is in an open position.