Patent EA-000822-B1 (EA)
Title: Method and apparatus for connecting an underwater flexible riser to a structure on the surface
Inventor: TEIXEIRA MARCELO JOSE BARBOSA
IPC: F16L37/127
Filed: 1997-11-04
Abstract: 1. Apparatus for connecting an underwater flexible riser to a structure on the surface, said underwater flexible riser (14) having a terminal connection (15) fastened to its connection end and a traction head (16) connected to said terminal connection (15) comprising: a coupling device (8) fastened to the end of the underwater flexible riser (14) and a guide device (1; 51) which has guiding means (2B) and locking means (27; 27A) for locking the coupling device (8) when the coupling device is raised from the sea bed by at least one cable (19) so that, when the coupling device (8) is locked on the guide device (1; 51), the connection end of the underwater flexible riser (14) can continue to be raised by the cable (19) up to any point on the structure, which is located on the surface, where connection of the underwater flexible riser (14) will take place, characterized by actuating means (6, 24; 39) for unlocking said locking means (27; 27A) to release the coupling device (8) from the guide device (1; 5). 2. Apparatus according to claim 1, characterized in that the coupling device (8) has a guide (11) whose upper part (11 A) has the shape of a cylinder and whose lower part (11B) has the shape of a frustum of a cone. 3. Apparatus for connecting an underwater flexible riser to a structure on the surface, said underwater flexible riser (14) having a terminal connection (15) fastened to its connection end and a traction head (16) connected to said terminal connection (15) comprising : a coupling device (8) fastened to the end of the underwater flexible riser (14); and a guide device (1; 51) which has guiding means (2B) and locking means (27; 27A) for locking the coupling device (6) when the coupling device is raised from the sea bed by at least one cable (19) so that, when the coupling device (8) is locked on the guide device (1; 51), the connection end of the underwater flexible riser (14) can continue to be raised by the cable (19) up to any point on the structure, which is located on the surface, where connection of the underwater flexible riser (14) will take place, characterized in that the coupling device (8) has a guide (11) whose upper part (11A) has the shape of a cylinder and whose lower part (11B) has the shape of a frustum of a cone and in that the locking mechanism (27; 27A) comprises locking panels pivotally mounted on the guide device (1; 51) and shaped to engage the frustoconical lower part (11 B) of the guide (11). 4. Apparatus according to claim 3, characterized in that in that the lower part of each locking pawl (3) has the shape of a claw (21) and can pass inside a slot in the lower part (2B) of a body (2) of the guide device (1; 51) to engage the frustoconical lower part (11 B) of the guide (11). 5. Apparatus according to claim 3 or 4, characterized in that the locking means (27) of the guide device (1) for locking the coupling device (8) comprise a lacking mechanism which comprises a locking ring (5), an unlocking collar (6), a guide element (7), supports (20), and elastic elements (4) for the locking pawls (3); in that the guide element (7) and the supports (20) are fastened securely to the body (2); in that the pivots for the locking pawls (3) are spindles (18) securely fastened to the supports (20); in that inside the supports (20) there are elastic elements (4) whose function is to hold the locking paw) (3) in the locking position; and in that the locking ring (5) is intended to hold the respective locking pawl (3) in the locked position, after the coupling device (8) has been coupled to the guide device (1), with the aim of preventing, after completion of the coupling operation, any vibrations or movements causing unlocking of the coupling device (8). 6. Apparatus according to claim 3 or 4, characterized in that the locking means of the guide device (51) for locking the coupling device (8) comprises a locking mechanism (27A) which comprises supports (31) for the locking pawls (30), elastic elements (32), spindles (33) and movement-limiting means (35); in that the locking pawls (30) are fastened on the supports (31) by means of the spindles (33); in that the movement-limiting means (35) are mounted on the upper part of the locking pawls (30), and the locking pawls (30) are mounted on the supports (31), in such a manner that they can be pivoted about the axes of the spindles (33) and be moved transversely in an oblique direction with respect to the axis of symmetry of the body (2); in that the elastic elements (32) are mounted on the inner part of the supports (31) and their function is to hold the respective locking pawl (30) in the locking position after the coupling device (8) has been coupled to the guide device (51), with the aim of preventing, after completion of the coupling operation, any vibrations or movements giving rise to unlocking of the coupling device (8). 7. Apparatus according to any one of claims 1 to 4, characterized in that the connection end of the underwater flexible riser is enclosed in a bending stiffener (9). 8. Apparatus according to any one of claims 1 to 4, characterized in that the underwater flexible riser (14) is fastened to the coupling device (8) by means of shearing pins (12). 9. Apparatus according to any one of claims 1 to 4, characterized in that the guiding means of the guide device (1; 51) for guiding the coupling device (8) comprises a body (2) whose upper part (2A) has the shape of a cylinder and whose lower part (28) has the shape of a frustum of a cone and the lower part (2B) operates as a buffer for the lower part (11 B) of the body (11) of the coupling device (8). 10. Method for the use of the apparatus according to claim 5, for connecting a underwater flexible riser to a structure on the surface, characterized in that it comprises the following steps: - initially with the application of a rotational movement to a locking ring (5) of a locking mechanism (27) so that projections (23) on the locking ring (5) no longer impede the turning movement of locking pawls (3) about the axes of the spindles (16) fastened to supports (20) which are connected to a body (2) of a guide device (1); - traction is then applied to a cable (19) which is connected to a traction head (16) which, in turn, is connected to a terminal connection (15) which is connected to an underwater flexible riser (14) coming from the sea bed and which has its connection end fastened to a coupling device (8); - continuing the raising movement, the lower part (2B) of the body (2) of the guide device (1) acts as a guide for perfect coupling of a guide (11) of the coupling device (8) inside the body (2) of the guide device (1) untill the lower part (11 B) of the guide (11) touches the claws (21) of the locking pawls (3) of the locking mechanism (27), at which point the claws (21) are pushed outside the body (2); - as soon as the lower part (11 B) of the guide (11) projects beyond the claws (21), the elastic elements (4) force the locking pawls (3) to pivot in the opposite direction, forcing the claws (21) to lock the assembly formed by the coupling device (8) and the guide device (1); - the cable (19) continues applying traction to the assembly, which breaks shearing pins (12) fastening the coupling device (8) to the assembly formed by the underwater flexible riser (14), the terminal connection (15) and the traction head (15), which assembly is conveyed to its connection point at any location on the structure; - when it is necessary to disconnect the coupling device (3) for withdrawal of the underwater flexible riser (14) the locking ring (5) must initially be turned so that its projections (23) no longer prevent the locking pawls (3) from pivoting about the spindles (18); - next, an unlocking collar (6) which slides on a guide element (7) connected to the body (2) moves axially downwards; and - on entering into contact with the heads (24) of the locking pawls (3), the unlocking collar (6) forces the locking pawls to pivot about the axes of the spindles (18), which means that the claws (21) no longer lock the coupling device (8), allowing the coupling device to emerge from inside the guide device (1) and consequently releasing the underwater flexible riser (14). 11. Method for the use of the apparatus according to claim 6 for fastening an underwater flexible riser to a structure on the surface, characterized in that it comprises the following steps: - initially traction is applied to a cable (19) which is connected to a traction head (16) which, in turn, is connected to a terminal connection (15) which is connected to an underwater flexible riser (14) coming from the sea bed and which has its connection end fastened to a coupling device (8); - continuing the raising movement, the lower part (2B) of the body (2) of a guide device (51) acts as a guide for perfect coupling of the guide (11) of the coupling device (6} with the body (2) of a guide (11) of the guide device (51) until the lower part (11 B) of the guide (11) touches the claws (34) of locking pawls (30) of a locking mechanism (27A), at which point the claws (34) are pushed outside the body (2) until the movement-limiting means (35) touch the tabs (42) of supports (31); - from this point, continuing the raising movement, the locking pawls (30) are moved in an oblique direction with respect to the axis of symmetry of the body (2), allowing the claws (34) to project beyond the lower part (11 B) of the guide (11); - as soon as the lower part (11 B) of the guide (11) projects beyond the claws (34), elastic elements (32) force the locking pawls (30) to pivot in the opposite direction, forcing the claws (34) to lock the assembly formed by the coupling device (8) and the guide device (51); - the cable (19) continues applying traction to the assembly, which breaks shearing pins (12) holding the coupling device (8) to the assembly formed by the underwater flexible riser (14), terminal connection (15) and traction head (16), which assembly is