The windlass/messenger winch type system is also suitable for application in any vessel that is moored with a pre-laid mooring system.

In its principal form the invention relates to an improved mooring windlass/messenger winch system that simplifies the handling and hook-up of the mooring lines.

Background of the invention Structures such as offshore oil production platforms (FPSO) are installed at various locations in the ocean where they may be exposed to heavy seas and ocean currents. It is necessary for such structures to be firmly anchored to avoid excessive lateral drift relative to the associated production risers from the wellhead on the ocean floor.

The anchoring structure commonly used has consisted of a substantial number of conventional anchors having flukes, which dig into the ocean bottom or permanent embedment type anchors that are permanently attached to the ocean bottom.

The mooring lines commonly consist of a first length of chain attached to the anchor, an intermediate length of synthetic rope or wire rope attached to the anchor chain and the other end attached to a second length of platform chain.

The mooring lines and anchors are transported and deployed from a large anchor handling work boat, with the free end of the platform chain attached to a buoy while the vessel or FPSO is brought to the location. The

vessel is then positioned in the center of the mooring line pattern, and the mooring lines are retrieved and attached to the vessel.

One type of conventional mooring arrangement for an FPSO has one mooring system located on the bow-consisting of ten or more lines-and one other mooring system located at the stem-consisting of eight or more lines, both systems on the main deck. A single vertical shaft windlass is used to handle the stern mooring lines and a single vertical shaft windlass is used for the bow mooring lines. The position of the windlass in relation to the deck level fairlead is limited by the minimum degree of chain wrap angle around the wildcat that is necessary in order for the wildcat to function properly.

A messenger line is attached to the free end of the buoyed off platform chain and passes through an underwater fairlead on the FPSO hull, up and over a deck level fairlead and around the vertical shaft windlass wildcat positioned on the centerline of the FPSO. The vertical shaft windlass wildcat is specially designed to pass the messenger line, connector and platform chain.

The anchor handling winch aboard the work boat hauls in on the messenger line and platform chain until the platform chain engages the wildcat and the end of the platform chain extends over the deck edge of the FPSO or alternately into one of several chain lockers on the FPSO.

Because of the potential relative movement between the work boat and the FPSO it is difficult and dangerous to maintain control of the messenger line and platform chain.

The windlass then hauls in on the platform chain and provides the proper tension. The platform chain is then stopped off at the deck edge fairlead and the excess chain cut off inboard of the deck edge fairlead. A large davit and/or crane and several tugged winches are required to man handle the excess chain off of the vertical windlass wildcat and over the side

of the FPSO. Because the chain is very heavy and difficult to handle on deck, the overall operation is time consuming and dangerous for the deck crew.

In the US 4,722, 293 issued on Feb. 2,1988 to Foster et al is described an integrated winch and windlass in that the chain wheel (wildcat) functions as part of an associated traction winch. The chain wheel is provided with a wire rope groove that is arranged to function essentially as a first groove of the traction winch, bearing much of the forces otherwise imposed on a conventional traction winch in mooring applications. Such an arrangement reduces the load requirements placed on the various components of the traction winch, including its breaking system.

In the US 5,984, 586 issued on Nov. 16, 1999 to Wudtke are provided a mooring unit and method to retrofitting such unit, in which the existing units are modified in order to be able to operating in deeper water where the operational parameters are more demanding than the original design parameters. Thus, there is a need for combination mooring unit having a winch with the capacity to raise the wire hope, chain, and anchor high enough to connect the chain directly to the windlass, and disconnect the chain from the wire rope, without exceeding the allowable design criteria, and without stalling. It is proposed to modify the existing mooring units in operation by providing left and right twin drum traction winch assemblies and additional winches. The existing wire rope drum are discharged, or reused with the additional winches, and the twin drum traction winch assemblies are vertically mounted within the support flanges where the removed wire rope drums were previously mounted.

In the US 6,089, 547 issued on Jul. 18, 2000 to Juelich et aI the problem of winch upgrading is also mentioned. The method described suggests replacing a drum winch with a traction winch module mounted on and supported by the existing mooring winch frame of the drum winch. The traction winch module includes a traction winch frame, a front traction drum

and a rear traction drum. The traction winch frame is affixed to the mooring winch frame. The drive shaft from the drum winch may be retained and linked to drive the traction winch The Foster, Wudtke, and Juelich patents are all used on MODU (mobile offshore drilling unit) type vessels. This type drilling vessel is designed for mobile operation and is moved from location to location In this type of system the anchors and mooring lines are carried aboard the vessel and require a separate winch/windlass for each and every mooring line. The mooring line is made up of an anchor, a length of chain attached to the anchor, and a very long length of wire rope (up to 15,000 ft. ) that is tensioned deployed, and retrieved by the traction winch and stored on a stowage reel aboard the vessel. Because the wire rope traction winch must react all of the mooring line loads including the breaking strength of the wire rope the unit is of heavy robust design.

A traction type winch is required for this type of system because of the inherent advantage of being able to handle ultra long lengths of wire rope as opposed to the limitations of a conventional drum type winch.

The traction type winch is not suitable for use on a production vessel mooring system that utilizes a messenger winch that in turn is not required to react the mooring loads and/or store and handle the full length mooring lines.

In case of FPSO type that is normally permanently anchored in very deep water in the unsheltered open sea, the mooring loads can be very high, so a large number of mooring lines arranged in a spread mooring pattern are required. Also, the FPSO cannot be detached from the mooring lines or the fluid carrying risers regardless of the environmental loads.

On the other hand, it is not practical from cost or weight consideration to provide a mooring windlass/winch for each mooring line that is capable

of storing the full scope of the mooring lines applied to a FPSO vessel that will have the mooring lines pre-Iaid on a permanent location.

To improve the system for handling the mooring lines for the FPSO the present invention presents a new conception of windlass/winch in that the vertical shaft type windlass is replaced with a horizontal shaft type windlass.

Accordingly, it is an objective of the present invention to provide a mooring winch system in that a horizontal shaft type mooring windlass/winch, which pivots horizontally about a single chain locker, enables a single windlass to service a plurality of mooring lines. The horizontal shaft windlass can be rotated in the horizontal plane and can be oriented to any horizontal angular position about a single chain locker located on the centerline of the vessel.

Another objective of the present invention is to provide a horizontal shaft type windlass that always maintains a uniform degree of chain wrap on the wildcat for any horizontal angular orientation of the windlass and thus allow more flexibility regarding the mooring deck machinery arrangement in the most advantageous location.

Another objective of the present invention is to improve the overall safety of the operation since the messenger line wire rope winch maintains control of the platform chain and messenger line at all times including removal of the excess platform chain over the side of the vessel.

An advantage of the present invention is that the messenger line wire rope winch mounted on the horizontal shaft windlass above and behind the wildcat inherently leads the platform chain to the front of the windlass wildcat where the wildcat tail chain is located. As consequence it is only necessary to disconnect the messenger line from the platform chain and connect the platform chain to the wildcat tail chain, no additional chain handling equipment, such as davits or tugged winches are required.

Another advantage is that the platform chain is connected outboard of the wildcat to the permanent wildcat tail chain. Thus, a conventional wildcat can be used because the wire rope messenger line and connector does not have to pass through the wildcat.

Summary of the Invention The present invention provides a horizontal shaft type windlass integral with a conventional wire rope type winch mounted above and behind the windlass wildcat. The combined windlass/winch is mounted on a circular foundation that permits the windlass to rotate in the horizontal plane about the centerline of the windlass chain locker.

The ability to orient the windlass and winch in the horizontal plane allows a single windlass to serve a number of mooring chains.

The horizontal shaft type windlass always maintains the same degree of chain wrap on the windlass head independent of the horizontal orientation of the windlass thus providing greater flexibility in the deck arrangement of the mooring equipment components.

The mooring chain and messenger line is connected to and disconnected from the permanent tail chain of the windlass outboard of the wildcat so the windlass does not need a special wildcat to handle the messenger line and the connector in addition to the chain. The integral wire rope winch serves as a messenger line winch to guide the mooring chain to the windlass wildcat.

The invention will be better understood with reference to drawings illustrating a preferred embodiment.

Brief description of the drawings In the drawings: FIG. 1 represents schematically a plan view of a FPSO main deck, showing the stern and bow mooring system.

FIG. 2 is a detailed side view of the windlass/winch of the invention.

FIG. 3 is a top view of the windlass/winch of the invention on a circular foundation.

FIG. 4 is a side sectional view of the windlass/winch of the invention.

FIG. 5 is a top sectional view illustrating the central bushing on the chain pipe.

FIG. 6 is a simplified sectional view of the vessel mooring system.

FIG. 6A to FIG. 6F is a side view of the windlass/winch of the invention, mounted on the deck of the vessel structure, performing different steps of the operation concerning the vessel mooring equipment.

FIG. 7 is a simplified sectional view of the vessel mooring system relative to auxiliary fairlead.

FIG. 7A to FIG. 7C is a side view of the windlass/winch of the invention, mounted on the deck of the vessel structure, performing different steps of the operation regarding the auxiliary fairlead vessel arrangement.

Description of preferred embodiment The invention can be applied to any type of vessel that has a pre-Iaid spread type mooring system. A FPSO is used as an example in order to make easier the comprehension, but it cannot be considered a limitation of the invention thought.

The anchors and mooring lines are preinstalled at the mooring location by using a conventional method well known by those skilled in the art. The FPSO is moved into position in the mooring pattern and the platform end of the mooring line chain is retrieved aboard the FPSO by the windlass/winch messenger line. The platform chain is stopped off at the deck edge fairlead.

From this point on the improved windlass/winch of the present invention is relevant in the process.

The windlass/winch of the present invention includes: a) a pair of spaced apart pedestals and frame;

b) a wildcat shaft journeled in the pedestals: c) a wildcat mounted on the wildcat shaft; d) a wire rope messenger winch mounted on said pedestals, that works in conjunction with the wildcat to lead the mooring chain to the windlass; e) a special circular foundation that is centered over the windlass chain locker which bearing pads support the windlass/winch on the top of said circular foundation and allows the mooring windlass/winch to pivot horizontally about the vertical center of the chain locker chain pipe ; f) a central bushing on the chain pipe ; g) a number of gearboxes with drive pinions power associated to the wildcat drive gear.

Referring to the drawings, wherein like numerals denote identical elements throughout different views, there is schematically represented in FIG. 1 the deck arrangement of the vessel mooring system 1. A windlass/winch 2 of the invention is positioned in the center of the stern mooring system 3 and of the bow mooring system 4, respectively ; auxiliary fairlead 5 and deck level fairlead 6 are also shown. Each single windlass/winch can be rotated in the horizontal plane to handle and tension a plurality of mooring lines.

FIG. 2-FIG. 5 show different views of the windlass/winch 2 of the invention, mounted on the deck of the vessel structure 1.

A pair of spaced apart pedestals 7 and frame 8 is mounted on a special circular foundation 9, which is centered on the chain pipe 10. This special circular foundation 9 can be seen in detail in FIG. 5.

A wildcat mounted on wildcat shaft 11 containing a portion of mooring chain 12, and a wire rope messenger 13, are equally mounted on

said pedestals 7. The wire rope messenger winch 13 works in conjunction with the wildcat 11 to lead the mooring chain 12 to a windlass.

The windlass/winch 2 is supported on the top of the circular foundation 9 by means of bearing pads 14a, 14b, 14c, which by its turn is centered on the chain pipe 10 by means of bushings 15, as shown in detail in FIG. 3-FIG. 5.

The wildcat 11 can be driven by means of gearboxes 16a, 16b, 16c with drive pinions 17a, 17b, 17c that connect the wildcat drive gear 18.

The mooring principal operations are well known of that familiar with offshore oil production. However, by using the windlass/winch of the invention the operation can be conducted in a simplified manner.

FIG. 6 illustrates an elevation view of the vessel mooring equipment arrangement. The windlass/winch 2 is placed on the chain pipe 10 and chain locker 19, and the deck fairlead 6 and the underwater fairlead 22 are showed.

FIG. 6A-FIG. 6F illustrate the operation steps following. The wire rope messenger line 20 is deployed outboard from the wire rope messenger winch 13, passing through the deck fairlead 6, which chain stopper 21 remains disengaged, and following through the underwater fairlead 22 to receive a platform chain 23 pending from the buoy (not shown). The end of the platform chain 23 is attached to the connector 24 at the end of the messenger line 20 by mean of a detachable link 25 and retrieved to the deck of the vessel. The chain stopper 21 is engaged when a short length of the platform chain 23 is onboard; the platform chain is detached from the messenger line and attached to the windlass tail chain 12. The windlass 11 tensions the platform chain 23 and the chain stopper 21 is disengaged. Then, the platform chain is retrieved and locked off at the deck level chain stopper 21 and deck fairlead 6, and the chain is cut off at a predetermined length (approximately 100 meters).

The chain windlass is only required to develop the minimum tension required to preload the mooring line loads and not the breaking strength of the chain. The full breaking strength of the mooring line is reacted by a chain stopper independent of the windlass/winch.

The messenger wire line is disconnected outboard of the wildcat and does not pass through the wildcat. The wire line messenger winch is only required to handle and store enough scope of wire rope to retrieve the end of the preinstalled mooring line (up to 400 meters).

FIG. 7 is an elevation view of the windlass/winch and the auxiliary fairlead vessel arrangement. The windlass/winch 2, centered on the top of the chain locker 19, is repositioned to line up with the auxiliary fairlead 5.

FIG. 7A-FIG. 7C illustrate the operation steps following.

A messenger line 26 from the workboat winch (not shown in figures) is passed through the auxiliary fairlead 5 and attached to the excess platform chain 23 in the chain locker 19. The windlass 11 pays out the platform chain 23, under tension, until the platform chain is outboard of the windlass wildcat. Meanwhile the workboat winch retrieves the end of the platform chain. The auxiliary fairlead chain stopper 27 is engaged and the outboard chain detached. The windlass/winch messenger wire rope line 20 is attached to the outboard chain by means of a detachable link 25. The messenger winch takes the chain load and the chain stopper 27 is disengaged. As the workboat retrieves the excess platform chain the messenger line winch 20 maintains control of the vessel end of the chain.

As illustrated the improved mooring windlass/winch system of the invention enhance with advantage the handling and hook-up of the mooring lines simplifying the operational procedure.