Top loading cable plough

Abstract

A plough for burying a cable has a base frame, an upper frame member and a ploughshare support; a topside of the ploughshare support features a cable trough; and a cable guiding path extends from a front end to a rear end of the plough. The cable guiding path is arranged between the base frame and the upper frame member and along the cable trough. The upper frame member is movably connected relative to the base frame, such that the upper frame member may move between a first position. The upper frame member is arranged above the cable guiding path, and a second position wherein the upper frame member is displaced away from the cable guiding path. The whole extent of the cable guiding path is accessible from above when the upper frame member is in the second position, such that a cable may be lowered onto the cable guiding path.

Claims

1. A top loading plough for burying a cable, the plough comprises: a base frame, an upper frame member; a ploughshare support; a topside of the ploughshare support features a cable trough; and a cable guiding path extends from a front end to a rear end of the plough, the cable guiding path is arranged between the base frame and the upper frame member and along the cable trough; and the upper frame member is movably connected relative to the base frame, such that the upper frame member may move between a first position, wherein the upper frame member is arranged above the cable guiding path, and a second position wherein the upper frame member is displaced away from the cable guiding path; wherein the whole extent of the cable guiding path is accessible from above when the upper frame member is in the second position, such that a cable may be lowered onto the cable guiding path, said top loading plough further comprising a cable depressor that may be positioned above the cable trough to hold a cable in place during use, the cable depressor is movably connected relative to the cable trough, such that the cable depressor may move between a first position, wherein the cable depressor is arranged above the cable trough and the cable guiding path, and a second position, wherein the cable depressor is displaced away from the cable guiding path, wherein the cable depressor is pivotably connected relative to the cable trough by a double-axis pivot connection, the double-axis pivot connection arranged to move the cable depressor away from the cable trough in an upwards direction and in a lateral direction relative to the cable trough.

2. The plough according to claim 1, comprising a bellmouth arranged at the front end, the bellmouth comprises an upper section and a lower section, the upper section is movably connected relative to the lower section, such that the upper section may move between a first position, wherein the bellmouth surrounds the cable guiding path, and a second position wherein the upper section is displaced away from the cable guiding path.

3. The plough according to claim 2, wherein the upper frame member comprises the upper section of the bellmouth.

4. The plough according to claim 1, wherein the upper frame member comprises a lifting and docking system, including stab-in guides.

5. The plough according to claim 1, wherein the upper frame member is pivotably connected relative to the base frame, such that the upper frame member may move between the first position and the second position.

6. The plough according to claim 1, wherein the upper frame member is pivotably connected relative to the base frame by at least one pivot coupling.

7. The plough according to claim 6, wherein the upper section is pivotably connected relative to the lower section by the at least one pivot coupling.

8. The plough according to claim 6, wherein the at least one pivot coupling interconnects the upper frame member and the base frame.

9. The plough according to claim 1, wherein the movement of any of the upper section, the upper frame member and the cable depressor between their respective first and second positions is remote controlled.

10. A method of loading a cable into a cable plough, the cable plough comprising a base frame, an upper frame member and a ploughshare support a topside of the ploughshare support features a cable trough, a cable guiding path extends from a front end to a rear end of the plough, the cable guiding path arranged between the base frame and the upper frame member and along the cable trough; the upper frame member is movably connected relative to the base frame; said top loading plough further comprising a cable depressor that may be positioned above the cable trough to hold a cable in place during use, the cable depressor is movably connected relative to the cable trough, such that the cable depressor may move between a first position, wherein the cable depressor is arranged above the cable trough and the cable guiding path, and a second position, wherein the cable depressor is displaced away from the cable guiding path, wherein the cable depressor is pivotably connected relative to the cable trough by a double-axis pivot connection, the double-axis pivot connection arranged to move the cable depressor away from the cable trough in an upwards direction and in a lateral direction relative to the cable trough wherein the method comprises the steps of: arranging the plough on a seabed; moving the upper frame member from a first position, wherein the upper frame member is arranged above the cable guiding path, to a second position wherein the upper frame member is displaced away from the cable guiding path; lowering a cable onto the cable guiding pat when the upper frame member is in the second position.

11. The method according to claim 10, wherein the plough comprises a bellmouth arranged at the front end, the bellmouth comprises an upper section and a lower section, the upper section being movably connected relative to the lower section, and the step of lowering the cable onto the cable guiding path is preceded by a step of: moving the upper section from a first position, wherein the bellmouth surrounds the cable guiding path, to a second position wherein the upper section is displaced away from the cable guiding path.

12. The method according to claim 10, wherein the step of lowering the cable onto the cable guiding path is preceded by a step of: moving the cable depressor from a first position, wherein the cable depressor is arranged above the cable trough and the cable guiding path, to a second position, wherein the cable depressor is moved away from the cable guiding path.

13. The method according to claim 10, wherein the step of lowering the cable onto the cable guiding path is followed by the steps of: moving the upper frame member, and optionally any of the upper section and the cable depressor, into their respective first positions, such that the cable is held in place along the cable guiding path.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Embodiments of the invention is described in detail by reference to the following drawings:

[0067] FIG. 1 is a perspective view of an exemplary plough according to the invention.

[0068] FIG. 2 is a perspective view of the plough in FIG. 1 during initial lowering of a cable onto a cable guiding path of the plough.

[0069] FIG. 3 is a front side view of the plough in FIG. 2.

[0070] FIG. 4 is a side view of the plough in FIG. 2.

[0071] FIG. 5 is a detailed view of the plough in FIG. 2.

[0072] FIG. 6 is a topside view of the plough in FIG. 2.

[0073] FIG. 7 is a perspective view of the plough in FIG. 1 featuring a cable arranged along the cable guiding path of the plough.

[0074] FIG. 8 is a perspective view of the plough in FIG. 1 featuring a cable arranged along and accommodated in the cable guiding path of the plough.

DETAILED DESCRIPTION OF THE INVENTION

[0075] In the following, an exemplary plough according to the invention will be discussed in more detail with reference to the appended drawings.

[0076] In an initial step of a cable burying operation using the plough according to the invention, the plough is arranged on a seabed, see FIG. 1. After being landed on the seabed, the plough 1 is prepared for loading of a cable 2 by pivoting an upper frame member 9 away from a base frame 8, see FIG. 2. By opening an upper section of the plough, the cable 2 may be loaded onto the plough from above.

[0077] The upper frame member 9 is pivotably connected to the base frame 8 by two pivot couplings 14, see FIG. 5. In the present embodiment, the upper frame member comprises a lifting and docking interface, including stab-in guides 10. The

[0078] A bellmouth 3 is arranged at a front end 15 of the plough 1, and a ploughshare support 4 is arranged at a rear end 16.

[0079] A topside of the ploughshare support 4 features a cable trough 6. A cable depressor 5 may be positioned above the cable trough 6 to hold a cable 2 in place during the cable laying operation. The ploughshare support 4 features a ploughshare 13 arranged at an edge of the ploughshare support 4 facing the front end 15.

[0080] A cable guiding path 7, see FIGS. 3 and 6, extends from the front end 15 to the rear end 16. The cable guiding path 7 passes through the bellmouth 3, bellow the upper frame member 9 and within the cable trough 6.

[0081] The upper frame member 9 may move between a first position, wherein the upper frame member 9 is arranged above the cable guiding path 7, and a second position wherein the upper frame member 9 is displaced away from the cable guiding path 7. The upper frame member 9 may be locked in the first position by a locking assembly 20. In the present embodiment, the locking assembly features a cooperating pin 20a and hole 20b mechanism.

[0082] The cable depressor 5 is pivotably connected relative to the cable trough 6 via a double-axis pivot connection 17, see FIG. 5. The pivot connection 17 allows the cable depressor 5 to pivot between a first position, wherein the cable depressor 5 is arranged above the cable trough 6, see FIG. 1, and a second position, wherein the cable depressor 5 is displaced upwards and away from the cable trough 6 in a lateral direction, see FIG. 2.

[0083] The bellmouth 3 features an upper section 3a and a lower section 3b. The upper section 3a is pivotably connected relative to the lower section 3b, such that the upper section 3a may pivot between a first position, wherein the bellmouth 3 surrounds the cable guiding path 7, and a second position wherein the upper section 3a is pivoted away from the cable guiding path 7. The lower section 3b may be fixed to, or constitute an integral part of, the base frame 8. In the second position, the upper section 3a is displaced in a lateral direction relative to the longitudinal direction of the cable guiding path 7.

[0084] The bellmouth 3 has a tapered inner periphery suitable for avoiding small bend radii being forced upon a cable 2 entering the plough 1 at the front end 15.

[0085] The plough features a height-adjustable skid assembly connected to the base frame 8. The skid assembly is arranged to lower and raise the base frame 8 relative to the seabed and comprises a pair of skids 11 and a pair of stabilizer legs 12 arranged on opposite sides of the base frame 8. During a cable laying operation, the skids 11 and stabilizer legs 12 are retracted towards the base frame 8 to lower the ploughshare 13 into the seabed.

[0086] The plough is in communication with the topside while being arranged on the seabed, for instance via an umbilical 18. Thus, the movement of any of the upper section 3a, the upper frame member 9 and the cable depressor 5 between their respective first and second positions is remote controlled. In this manner, the plough may initially be lowered to the seabed having the upper section 3a, the upper frame member 9 and the cable depressor 5 in their respective first positions, i.e. covering at least parts of the cable guiding path 7, as shown in FIG. 1.

[0087] After being arranged on the seabed, the upper section 3a, the upper frame member 9 and the cable depressor 5 are moved to their respective second positions providing free access to the whole extent of the cable guiding path 7 from above. The cable may subsequently be lowered towards the cable guiding path of the plough, see FIGS. 2-5, and arranged along said path, see FIGS. 6 and 7. Finally, the upper section 3a, the upper frame member 9 and the cable depressor 5 are moved to their respective first positions to secure the cable along the cable guiding path 7, see FIG. 8.

[0088] When the cable 2 is secured, the ploughshare 13 is lowered towards towards/into the seabed (not shown) and the ploughing/cable laying operation may start. During the ploughing operation, the plough is towed via the wire 19 by a suitable towing vessel.

[0089] The method made possible by use of the plough according to the invention minimizes the bend radii forced onto the cable during loading and installation at the seabed. The avoidance of small bend radii allows for the use of the plough with cables of different types and designs than what is commonly possible with the prior art ploughs.

[0090] In the specific embodiment of the invention illustrated in FIGS. 1-8, the upper frame member 9 is pivotably connected to the base frame 8. However, in further embodiments it is envisioned that the upper frame member 9 may be movably connected to the base frame 8 by any suitable connection allowing the upper frame member to move between the first position and the second position. Such connections may for instance include slide connectors allowing the upper frame member 9 to move linearly relative to the base frame 8. The linear movement may be in a lateral direction relative to the longitudinal direction of the cable guiding path 7. Various combinations of slide and pivot connections may also be used to move the upper frame member 9 between the first and second positions.

[0091] In the specific embodiment of the invention illustrated in FIGS. 1-8, the upper section of the bellmouth 3 is pivotably connected to the base frame 8. However, in further embodiments it is envisioned that the upper section 3a may be movably connected relative to the base frame 8 by any suitable connection allowing the upper section 3a to move between the first position and the second position. Such connections may for instance include slide connectors allowing the upper section 3a to move linearly relative to the base frame 8. The linear movement may be in a lateral direction relative to the longitudinal direction of the cable guiding path 7. Various combinations of slide and pivot connections may also be used to move the upper section 3a between the first and second positions.

[0092] In the specific embodiment of the invention illustrated in FIGS. 1-8, the cable depressor 5 is pivotably connected relative to the cable trough 6 via a double-axis pivot connection 17. However, in further embodiments it is envisioned that the cable depressor 5 may be movably connected relative to cable trough 6 by any suitable connection allowing the cable depressor 5 to move between the first position and the second position. The cable depressor 5 may for instance be connected relative to the cable trough 6 via a pivot coupling for moving the cable depressor 5 in a vertical direction and a slide connector for moving the cable depressor in a lateral direction relative to the longitudinal direction of the cable guiding path 7 or cable trough 6

[0093] In the specific embodiment of the invention illustrated in FIGS. 1-8, the upper section of the bellmouth 3 is an integral part of the upper frame member 9, while the cable depressor 5 may be moved as a separate element independent of the upper frame member. However, in other embodiments of the invention, the movements required to provide access to the cable guiding path 7 from above may be obtained by other structural combinations of the upper section 3a, the upper frame member and the cable depressor. Such structural combinations may comprise having the upper section of the bellmouth pivotably connected to the base frame independent of the upper frame member. Other combinations may comprise having the cable depressor pivotably connected to the upper frame member.

[0094] It is also envisioned that any of the upper section 3a and the upper frame member 9 may be comprised by a plurality of elements, wherein each element may be moved between a first and second position relative to the cable guiding path. The upper frame member may for instance comprise two halves, wherein each half may be moved to a second position on opposite sides of the cable guiding path.