Riser methods and apparatuses

1. A method of repairing a shaft, wherein the shaft is a subsea riser for use in the oil industry, the method comprising:

cutting through the shaft at a pre-determined location, resulting in a first shaft section and a second shaft section;

attaching a gripper unit apparatus onto the first shaft section;

landing an alignment and installation apparatus onto said gripper unit apparatus, the alignment and installation apparatus carrying a component to be installed on the cut end of the first shaft section, wherein the component is a connector for connecting the first shaft section to a flexible pipe;

pitching and rotating the alignment and installation apparatus to align an axis of the connector with the axis of the first shaft section;

contracting the alignment and installation apparatus, thereby translating the connector substantially along the axis of the first shaft section until the cut end of the first shaft section is positioned on or within the connector; and

activating the connector to secure it onto the first shaft section, thereby enabling the communication of fluids between the flexible pipe and the first shaft section, wherein the gripper unit apparatus comprises teeth that are arranged to protrude slightly into the surface of a shaft and are arranged to attach the gripper unit apparatus to any position along part of a section of a shaft such that the gripper unit apparatus is not restricted to only attaching to an external flange or fixed connector on part of a section of a shaft.

2. The method according to claim 1 , wherein said step of landing the alignment and installation apparatus comprises:

suspending the alignment and installation apparatus from a topside vessel, such that a portion of the apparatus designed to mate with the gripper unit apparatus is positioned substantially above the gripper unit apparatus;

maneuvering the alignment and installation apparatus substantially along the axial direction of the first shaft section until said portion of the alignment and installation apparatus comes into contact with the gripper unit apparatus; and

releasing the alignment and installation apparatus from the topside vessel such that the alignment and installation apparatus becomes supported on the first shaft section by the gripper unit apparatus.

3. The method according to claim 2 , further comprising using a remotely operated vehicle to guide the alignment and installation apparatus whilst it is suspended from the topside vessel.

4. The method according to claim 2 , wherein the alignment and installation apparatus is configured such that it transmits substantially only axial loads to the first shaft section via the gripper unit apparatus when it is released from the topside vessel onto the gripper unit apparatus.

5. The method according to claim 1 , wherein the gripper unit apparatus comprises:

a body comprising two half-shells having internal surfaces of semi-circular cross section;

a plurality of segments arranged inside the two half-shells and comprising teeth for gripping onto the riser; and

a cap provided on the body and shaped so as to interface with a docking device;

wherein an installation tool operable by a ROV is arranged to cause the two half-shells to close around the riser, thereby securing the gripper unit apparatus to the riser; and wherein the alignment and installation apparatus comprises:

a frame;

an interface element for supporting said component, the interface element being removably attached to the frame;

the docking device, wherein the docking device is configured to mate with the gripper unit apparatus provided on the riser, the docking device being movably attached to the frame; and

one or more actuators for controlling the position of the frame relative to the riser when in use.