System for handling conventional and synthetic moorings lines, cables and the like aboard a vessel

Abstract

A large capacity, rotating horizontal carousel for deployment and storage of synthetic rope located below the main deck of an anchor handling vessel or other vessel. The system includes a transfer system of rollers and sheaves for transferring the lines to deployment winches. According to one aspect, the system is mounted on a dedicated anchor handling vessel, but can also be adapted to mount on other vessels such as barges, cargo vessels, etc.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 USC §119(e) to U.S. Provisional Application 61/435806, filed 25 Jan. 2011.

FIELD OF THE INVENTION

The invention relates to systems for handling anchor cables and mooring lines, more specifically to a system arranged for the handling of conventional and synthetic anchor cables and mooring lines aboard a vessel.

BACKGROUND

Many marine applications, such as for example offshore oil platforms and other petroleum-related activities require very long lengths of anchoring chains or cables. Specially designed vessels are utilized to transport and handle these large amounts of chain/cable.

Increasingly, synthetic rope mooring lines are being utilized for offshore installations. Such synthetic lines are often used in place of traditional chain mooring lines in deeper offshore locations. Synthetic rope is more buoyant, and is almost neutral with respect to weight in the sea, but has a considerable dry weight and volume (typically in permanent moorings ˜25 kg/m).

Synthetic rope is also used increasingly for anchoring in areas with a large amounts of infrastructure and equipment installed on the seabed. Synthetic rope, together with underwater buoys, can more safely cross over pipelines, cables and other installations on the seabed with less risk of damage to the seabed installations and equipment.

Synthetic rope requires greater care in handling, and presents unique challenges compared to traditional mooring lines however. Synthetic rope is susceptible to damage by contact with steel wire, sharp edges and the like. Synthetic rope also requires significantly more volumetric capacity as the diameter is significantly larger than, for example steel wire or chain moorings.

Storage of synthetic ropes on board anchor handling ships is currently performed using conventional drums located on the main deck of the ship and the deck above the main deck. Since synthetic rope requires much greater storage volume, the current solution is to simply equip the vessel with additional drums. Often vessels are equipped with additional drums under or over the main deck to increase the total capacity.

The current method of handling and storage of synthetic ropes aboard anchoring vessels has the following problems associated with them:

Since each drum has its own line, with a different entrance path for its line, there will be many different lines crossing in different directions. This increases the risk of damage to the line, as well as presenting a security risk for the crew.

Use of several drums and associated line guidance is a not cost efficient.

Using several drums positioned at various locations on the ship increases the complexity with respect to maintaining the vessel's stability as the weight of the various drums changes during deployment or retrieval of the line.

The drums take up valuable space on the main and upper deck that could be better used for other purposes.

SUMMARY OF THE INVENTION

The present invention solves the aforementioned problems with know systems and methods for handling synthetic mooring lines aboard anchoring vessels.

The system of the invention comprises a large capacity, rotating horizontal carousel for deployment and storage of synthetic rope located below the main deck of an anchor handling vessel or other vessel. The system further comprises a transfer system comprising rollers and sheaves for transferring the lines to the deployment winches. According to one aspect, the system is mounted on a dedicated anchor handling vessel, but can also be adapted to mount on other vessels such as barges, cargo vessels, etc.

The carousel is preferably located on the tank top below the main deck. Rotation of the device is carried out by one or more drive units located around its periphery, or by other appropriate motorized means. The carousel preferably has a removable structure for dividing the carousel into sections. The device according to one aspect is modular, to facilitate assembly through a removable hatch in the deck.

Deployment and recovery of synthetic rope in the device is done using a support arm equipped with rollers and wheels to prevent contact with sharp objects.

The use of a rotating horizontal carousel achieves a significant increase of the vessel's storage volumes in a cost effective manner that does not impair the ship's stability.

The vessel optionally has winches for handling traditional mooring lines in addition to the carousel for handling the synthetic lines.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a partial side cross-section of an anchor handling vessel

FIG. 2 shows a carousel according to the invention arranged on the tank top under the main deck

DETAILED DESCRIPTION

FIG. 1 shows an anchor handling vessel 10 with a main deck 11, on which is mounted a conventional winch 12 for handling traditional anchoring lines. Under the conventional winch is located one or more chain lockers 13 for storage of traditional chain mooring lines and the like.

A rotating horizontal carousel 14 for storage and handling of synthetic rope is arranged below the main deck on the tank top. Alternative locations for the carousel can of course be employed, but this area of the ship will normally be preferred due to, for example, issues of stability and space considerations.

Carousel 14 is comprised of segments with sufficient internal structure to carry expected load. Segments are inserted into the vessel through a hatch in the deck and joined together inside the vessel. The number of segments will depend on the size of the hatch and available space inside the vessel. The carousel is fitted with a bearing means, such as for example rotating wheels and wheel pairs 15 transferring the horizontal and vertical forces to the ship's structure.

The capacity and sectioning of carousel 14 may be altered by using removable poles dividers 16. In one embodiment, poles are fitted into slots in the bottom structure to allow dividers to be installed in the carousel. Poles enabling circular sectioning will be linked together at the top.

The center area 17 of the carousel can be used for different purposes, for example as a space for fuel storage and other purposes.

The carousel is rotated by motorized drive means, for example by drive units 18, here shown as four friction wheels that rest against the side walls of the carousel. Other appropriate drive means may also be employed, such as a gear and sprocket drive, a belt drive or the like.

To lead the synthetic rope to and from the carousel, a moveable chute 19 is employed. According to one embodiment, the guide chute will be arranged with rollers to turn sheaves and a transition funnel through the decks. The transition funnel may be closed by a hatch when not in use avoiding humidity entering into the vessel.

EXAMPLE

An example of a possible arrangement of the system of the invention aboard a vessel for handling synthetic rope is described below, in comparison to a typical traditional anchor handling vessel. One skilled in the art will appreciate that various modifications may be made with the scope of the invention.

Prior Art Systems

A typical anchor handling vessel of the type with largest present day capacity (these have generally been built within the last five years):

The ship's length: 85-110 meters

The ship's breadth: 22-27 meters

Typical winch set-up for handling and installation of mooring systems:

• • Main winch
    • Special Handling drum
    • Core diameter 3500 mm×drum length 5400 mm×outer dia. 6500 mm
    • Tow/Working drum
    • Core diameter 1500 mm×drum length 3750 mm×outer dia. 2150 mm
    • Tow/Working drum
    • Core diameter 1500 mm×drum length 3750 mm×outer dia. 3500 mm
      • Total drum capacity of 3100 meters dia 203 mm Polyester rope

Secondary winch

• • • 2×Secondary winch drums
    • Core diameter 1500 mm×drum length 4500 mm×outer dia. 4500 mm
      • Drum capacity 2×1600 meters (dia 203 mm) Polyester rope

Storage Winches

• • • 2×storage winch drums
    • Core diameter 1500 mm×drum length 4500 mm×outer dia. 4500 mm
      • Drum capacity 2×1600 meters (dia 203 mm) Polyester rope

Total capacity of known systems: 9 500 m (dia 203 mm) Polyester rope

Example of a Vessel Equipped with the System According to the Present Invention

The ship's length: 85-90 meters

The ship's breadth: 20-25 meters

Typical winch set-up for handling and installation of mooring systems:

Main winch

• • • Anchor Handling Drum
    • Core diameter 2400 mm×drum length 7000 mm×outer dia. 5050 mm
    • Anchor Handling Drum
    • Core diameter 2400 mm×drum length 7000 mm×outer dia. 5050 mm
    • Total drum capacity of 5400 meters dia 203 mm Polyester rope

Secondary

• • • 2×Secondary winch drums
    • Core diameter 1500 mm×drum length 5200 mm×outer dia. 4900 mm
    • Drum capacity 2×2400 meters dia 203 mm Polyester rope

Horizontal, below-deck carousel

• • • Anchor Handling carousel
    • Core diameter 6150 mm×drum height 5000 mm×outer dia. 17800 mm
      • Carousel capacity 28,600 m (dia 203 mm) Polyester rope

Total capacity: 38 800 m dia 203 mm Polyester rope

Claims

1. A system for storage, deployment and retrieval of elongated flexible members such as mooring lines, anchor lines, cables and the like aboard a vessel, the system comprising:

a. A horizontally rotatable carousel adapted to be mounted on a lower deck area of a vessel, said carousel arranged to receive, store and deploy an elongated flexible member,

b. Motorized drive mechanism for rotating the carousel,

c. Bearing means arranged between the carousel and the vessel's structure,

d. A chute for leading the elongated flexible member from the outside environment to the below deck area.

2. The system according to claim 1, wherein the carousel comprises removable dividers for selectively altering the storage capacity of the carousel.

3. The system according to claim 1 or 2, wherein the carousel is adapted to be retrofitted in an existing vessel having a hatch leading to the below deck area, wherein the carousel is a modular construction, the components of which are of a size small enough to be transferred through the hatch.

4. The system according to claim 1 or 2, wherein the guide chute is movable.

5. The system according to claim 4, wherein guide chute is arranged with rollers to turn sheaves and a transition funnel through the decks, said transition funnel having a closeable hatch.

6. The system according to claim 1, wherein the carousel has a capacity of up to 28,600 m of 203 mm diameter polyester rope.