Mooring System

• US 20140038479A1
• Filed: 09/17/2013
• Published: 02/06/2014
• Est. Priority Date: 03/17/2011
• Status: Active Grant

• Current Assignee: Nautricity Ltd.
• Original Assignee: Nautricity Ltd.
• Inventors: Johnstone, Cameron, Pratt, Dave
• Granted Patent: US 9,828,069 B2
• Time in Patent Office: Days
• US Class Current: 441/22
• CPC Class Codes: B63B 21/20 Adaptations of chains, ropes, hawsers, or the like, or of parts thereof
• CPC Class Codes: B63B 21/50 Anchoring arrangements or methods for special vessels, e.g. for floating drilling platforms or dredgers
• CPC Class Codes: B63B 22/04 Fixations or other anchoring arrangements
• CPC Class Codes: B63B 22/18 having means to control attitude or position, e.g. reaction surfaces or tether
• CPC Class Codes: F03B 17/061 with rotation axis substantially in flow direction
• CPC Class Codes: F05B 2240/97 on a submerged structure
• CPC Class Codes: Y02E 10/20 Hydro energy
• CPC Class Codes: Y02E 10/30 Energy from the sea, e.g. using wave energy or salinity gradient

Abstract

A mooring system (10) for use in mooring a marine device (24) within a fluid (12) subject to flow comprises a mooring line (16) to be secured to an anchor (18) and defining a tether point for a marine device (24), and a loading assembly (20) secured to the mooring line (16) and configured to generate hydrodynamic lift when exposed to flow to apply tension to the mooring line (16).

In embodiments of the invention the loading assembly (20) is configured to also generate a buoyancy force, such that tension is applied to the mooring line (16) by a combination of the hydrodynamic lift force and the buoyancy force.

Claims

1. A mooring system for use in mooring a marine device within a fluid subject to flow, comprising:

a mooring line to be secured to an anchor and defining a tether point for a marine device; and

a loading assembly secured to the mooring line and configured to generate hydrodynamic lift when exposed to flow to apply tension to the mooring line.

2. The system according to claim 1, wherein the loading assembly is configured to also generate a static force to apply tension to the mooring line, such that tension is applied to the mooring line by a combination of the hydrodynamic lift force and the static force.

3. The system according to claim 2, wherein the static force is substantially independent of flow velocity.

4. The system according to claim 2, wherein the static force is configured to establish a minimum desired tension within the mooring line.

5. The system according to claim 2, wherein the loading assembly comprises a common structure configured to generate both the hydrodynamic lift force and the static force.

6. The system according to claim 1, wherein the loading assembly comprises at least one buoyant structure configured to generate a buoyancy force to apply tension to the mooring line.

7. The system according to claim 6, wherein the at least one buoyant structure is configured to generate a buoyancy force for applying a minimum desired tension within the mooring line.

8. The system according to claim 6, wherein at least one buoyant structure defines a profile configured to generate hydrodynamic lift when exposed to flow.

9. The system according to claim 1, wherein the loading assembly comprises at least one hydrofoil section configured to generate hydrodynamic lift.

10. The system according to claim 9, wherein at least one hydrofoil section defines a buoyant structure, such that said hydrofoil section is configured to generate both a hydrodynamic lift force and a buoyancy force to apply tension to the mooring line.

11. The system according to claim 9, wherein the loading assembly comprises a single hydrofoil section.

12. The system according to claim 9, wherein the loading assembly comprises a plurality of hydrofoil sections.

13. The system according to claim 12, wherein multiple hydrofoil sections are secured to a common structure.

14. The system according to claim 13, wherein the common structure defines a buoyant structure.

15. The system according to claim 9, wherein the loading assembly comprises a hydrofoil section having at least one end cap arrangement configured to reduce or minimise hydrodynamic drag.

16. The system according to claim 9, wherein the angle of attack of the hydrofoil section is selected to maintain a centre of buoyancy of the hydrofoil section between leading and trailing edges thereof

17. The system according to claim 9, wherein the angle of attack of the hydrofoil section relative to the flow is adjustable.

18. The system according to claim 9, comprising a swivel arrangement for use in permitting at least one of selecting and adjusting of the angle of attack of the hydrofoil section.

19. The system according to claim 18, wherein the swivel arrangement comprises a yoke to which the hydrofoil section is mounted, wherein the yoke defines a pivot point about which the hydrofoil section is rotated to adjust the angle of attack.

20. The system according to claim 19, wherein the hydrofoil section is secured to the yoke via one or more elongate components.

21. The system according to claim 20, wherein the elongate components are sized to permit the hydrofoil section to adopt a desired angle of attack.

22. The system according to claim 20, wherein at least one elongate component is secured to a leading edge of the hydrofoil section, and at least one elongate component is secured to a trailing edge of the hydrofoil section.

23. The system according to claim 1, comprising a thrust arrangement configured to apply an active thrust within or on the loading assembly.

24. The system according to claim 23, wherein the thrust arrangement comprises one or more thrusters.

25. The system according to claim 23, wherein the thrust arrangement is configured to be selectively activated.

26. The system according to claim 23, wherein the thrust arrangement is configured to provide a thrust within the loading arrangement to effectively apply tension within the mooring line.

27. The system according to claim 23, wherein the thrust arrangement is configured to provide a thrust which assists in controlling the angle of attack of the loading assembly.

28. The system according to claim 23, wherein the thrust arrangement is configured to be powered by at least one of an on-board power supply and power generated by a tethered marine device.

29. The system according to claim 1, comprising an anchor to which the mooring line is secured.

30. The system according to claim 29, wherein the anchor comprises a subsea anchor, such as a seabed anchor.

31. The system according to claim 29, wherein the anchor comprises a surface or topside anchor.

32. A method of mooring a marine device within a fluid subject to flow, the method comprising:

securing a mooring line to an anchor;

securing a loading assembly to the mooring line;

securing a marine device relative to the mooring line; and

using the loading assembly to generate hydrodynamic lift to apply tension to the mooring line.

33. A mooring system for use in a fluid subject to flow, comprising:

a mooring line to be secured to an anchor; and

a buoy assembly secured to the mooring line and defining a profile configured to generate hydrodynamic lift when exposed to flow, wherein the buoy applies tension to the mooring line by a combination of buoyancy and the generated hydrodynamic lift forces.

34. A loading assembly for applying tension to a mooring line within a fluid subject to flow, comprising a structure to be coupled to a mooring line and being configured to generate hydrodynamic lift when exposed to flow to apply tension to the mooring line.

35. A loading assembly for applying tension to a mooring line within a fluid subject to flow, comprising a buoyant structure to be coupled to a mooring line and defining a profile configured to generate hydrodynamic lift when exposed to flow, wherein the structure applies tension to the mooring line by a combination of buoyancy and the generated hydrodynamic lift forces.