WO2013151506A1

WO2013151506A1 - Apparatus and method for securing a first marine superstructure to a second marine superstructure

Info

Publication number: WO2013151506A1
Application number: PCT/SG2013/000129
Authority: WO
Inventors: Idar A. IVERSEN; Daljit Singh PANDHER
Original assignee: Primepoint Pte Ltd
Priority date: 2012-04-04
Filing date: 2013-04-03
Publication date: 2013-10-10

Abstract

Apparatus and methods for securing a first marine superstructure 1 to a second marine superstructure 2 are disclosed. The fully assembled apparatus, comprising one or more sliding fairlead apparatus 100, each comprising a moveable member 28 comprising a first face 28a and a second face 28b; a fairlead 29 mounted to the second face 28b of the moveable member 28 and configured to be attachable to a hawser line; and one or more support apparatus 200, each comprising a support member 24 having an upper portion and a lower portion mounted to the second marine superstructure 2 and a rail member 23 comprising a track that is connected to the support member 24, wherein each of the one or more sliding fairhead apparatus 100 is configured to be slidably attached to the track of the rail member 23 of a corresponding one of the one or more support apparatus 200, such that a connection between the first 1 and second marine superstructures 2 is formed upon attachment of a hawser line to the fairlead 29 mounted to the second face 28a of the moveable member 28 of the slidable fairlead apparatus 100.

Description

APPARATUS AND METHOD FOR SECURING A FIRST MARINE SUPERSTRUCTURE TO A SECOND MARINE SUPERSTRUCTURE

1. Field of Invention

This invention relates to an apparatus and method for securing a first marine superstructure to a second marine superstructure. More particularly, this invention relates to an apparatus and method for securing a first marine superstructure to a second marine superstructure (e.g. a tender assist semisubmersible (TAS) to a tension leg platform (TLP)) said apparatus and method using hawser lines to form a combined station keeping system that helps to reduce the effects of transverse and longitudinal motions on the drilling operation system.

2. Background of Invention

The listing or discussion of a prior-published document in this specification should not necessarily be taken as an acknowledgement that the document is part of the state of the art or is common general knowledge.

Tender assist drilling refers to the drilling activity which is supported by a Tender Assist Vessel (TAV) that has a main function to provide support for a drilling module operating on an offshore structure. By having a TAV, the loads which need to be placed on a TLP can be reduced as the vessel is able to provide storage, electricity and other required utilities necessary for the drilling rig to perform drilling operation. Typically, TAV can be categorized into three categories, which include: tender assist barge (TAB); tender assist semisubmersible (TAS); and also tender assist jack up (TAJU).

TAS is a type of TAV which is more suitable for deep water in comparison to TAB and TAJU. One of the main problems encountered during operating is that most TAS cannot be moored or kept alongside a TLP at an almost constant distance during extreme weather or operation conditions without collision with the TLP. Usually, independent mooring systems plus extra hawser lines are used to tie both vessels together for station keeping purposes and at the same time to maintain a spaced relationship between the vessels to avoid collision.

Hawser is a nautical term for a thick cable or rope used in mooring or towing a ship. The hawser concept is traditionally used for floating vessels in the marine and offshore industry. This concept was initially used for vessels which were berthing alongside another vessel or a fixed structure. The hawser concept was derived from the olden days when ships needed to be berthed along another structure while still in deeper waters, such as piers of ports, the reason for this is when the vessel is berthed at a deeper water depth, the vessel can set for its next voyage readily regardless of the tides. Tides become a concern mostly in shallow waters nearer to the shore line. However, this concept has evolved and it is now widely used in the marine and offshore industry. For example, hawsers are used in Catenary Anchor Leg Mooring (CALM) and Single Anchor Leg Mooring (SALM).

A Tender system with hawser lines is used to secure a semi-submersible tender to a TLP as shown in US patent no. 6,619,223 entitled "Tender with Hawser Line". In this patent, only two tensioned hawser lines are used to secure a semi-submersible tender to a TLP.

SUMMARY OF INVENTION

We now introduce, in this document, a method that is different to that shown in US patent No. 6,619,223. Instead of securing hawser lines to pad eyes or fixed fairleads on one end and a typical winch on the other end, the method uses custom-made sliding fairleads and hawser winches to control the hawser line tension and keep a first marine superstructure alongside a second marine super structure (e.g. a TAS alongside a TLP). A total of four hawser lines are used to provide sufficient redundancy and stiffness. However, more than four hawser lines may be used depending upon analysis of the site in question and the weight of the first and second marine superstructures (e.g. six or eight hawser lines). A TAS is expected to have higher heave in comparison to TLP under similar environmental conditions. In such a situation, sliding fairleads help to keep - constant distance between the TAS and the TLP regardless of the elevation difference and at the same time prevent vessel collisions. Furthermore, the gap between two vessels can be controlled and adjusted using the hawser winches. These features make man transfer, equipment and material handling between vessels easier and safer.

It is an object of the current invention to provide an apparatus and method of securing a tender assist semisubmersible (TAS) to a tension leg platform (TLP) using the combination of hawser lines, sliding fairleads, hawser winches and quick release devices. Further, it is an object of the current invention whereby the sliding fairlead is mounted on a dolly, or moveable member/that can slide vertically in case of heave with the hawser tension adjustable using a hawser winch.

A first aspect of the invention relates to a sliding fairlead apparatus for use in connecting a first and a second marine superstructure together, comprising: a moveable member comprising a first face and a second face; and a fairlead mounted to the second face of the moveable member and configured to be attachable to a hawser line, wherein the first face of the moveable member is configured to be slidably attached to a track of a rail member, the rail member being attached to the second marine superstructure. Preferred features of this aspect are set out Claims 2 to 9.

A second aspect of the invention relates to a support apparatus for a second marine superstructure, the support apparatus comprising: a track for sliding arrangement with a moveable member of a sliding fairlead apparatus, the sliding fairlead apparatus being configured to be connected to a first marine superstructure; and a support member connected to the track and configured to be attached to the second marine superstructure. Preferred features of this aspect are set out in Claims 10 to 14.

Alternatively, the second aspect may be considered to be a support apparatus for use in connecting a first and a second marine superstructure together, comprising: a support member having an upper portion and a lower portion mounted to the second marine superstructure; and a rail member comprising a track that is connected to the support member, wherein the rail member is configured to be mounted by a sliding fairlead apparatus, as described in the first aspect of the invention, that is connected to the first marine superstructure and where the sliding fairlead apparatus is slidably attached to the track of the rail member. Preferred features of this aspect may be derived from Claims 10 to 14.

A third aspect of the invention relates to a hawser system constructed by connecting the fairlead apparatus of the first aspect of the invention together with the support apparatus of the second aspect of the invention, wherein the sliding fairlead apparatus of the first aspect is slidably attached to the support apparatus of the second aspect.

A fourth aspect of the invention relates to a system for connecting a first and a second marine superstructure together, comprising: one or more sliding fairlead apparatus, each comprising: a moveable member comprising a first face and a second face; a fairlead mounted to the second face of the moveable member and configured to be attachable to a hawser line; and one or more support apparatus, each comprising: a support member having an upper portion and a lower portion mounted to the second marine superstructure; and a rail member comprising a track that is connected to the support member, wherein each of the one or more sliding fairhead apparatus is configured to be slidably attached to the track of the rail member of a corresponding one of the one or more support apparatus, such that a connection between the first and second marine superstructures is formed upon attachment of a hawser line to the fairlead mounted to the second face of the moveable member of the slidable fairlead apparatus. Preferred features of this aspect are set out in Claims 17 to 34.

A fifth aspect of the invention relates to a method of coupling the fairlead apparatus to the support apparatus as described in any of the previous aspects of the invention, comprising the steps of:

(a) connecting the sliding fairlead apparatus to the support member;

(b) connecting the hawser line to the fairlead apparatus; and

(c) tensioning the hawser line to keep the first marine superstructure alongside the second marine superstructure; or comprising:

steps (a) to (c), where steps (a) and (b) are reversed.

For example, an embodiment of the invention relates to a hawser system for connecting a TLP to a TAS comprising; two double-drum hawser winches mounted on TLP; four sliding fairleads mounted on the end of TAS; four sets of quick acting release device mounted on TLP. Further embodiments of the invention relate to the method of using said system.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, together with the specification, illustrate some embodiments of the present invention, and, together with the description, serve to explain aspects and principles of the present invention.

FIG. 1 is a close-up top view of a sliding fairlead and rail member of the invention.

FIG. 2 is a side view of the sliding fairlead and rail member of FIG. 1, which also shows the relative positioning of the sliding fairlead and rail member on a TLP and a TAS.

FIG. 3 is an isometric perspective view of a TLP and TAS in operation using the devices of FIG.l and FIG. 2. FIG. 4 is a schematic top view of a TLP secured to a TAS showing the placement of the various lines needed to secure said marine superstructures in place, in particular, the use of four sliding fairleads between said vessels. FIG. 5 is a perspective view of the sliding fairleads and the hawser line arrangement of FIG. 4.

FIG. 6 is a close-up isometric view of some hawser lines attached to a hawser winch, a quick release device and horizontal sheave, as used in the arrangement of FIG. 4 and FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

Below, some embodiments of the present invention are shown and described, by way of illustration. However, the described embodiments may be modified in various different ways without departing from the scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive.

When an element is referred to as being "on" another element, it can be directly on the another element or may be indirectly on the another element with one or more intervening elements interposed therebetween. Also, when an element is referred to as being "connected to" another element, it can be directly connected to the another element or may be indirectly connected to the another element with one or more intervening elements interposed therebetween. Hereinafter, like reference numerals refer to like elements.

Certain embodiments of the present invention are described herein with reference to the accompanying drawings. However, the present invention may be implemented in various different forms within the scope of the claims, and the embodiments described herein are to be regarded as illustrative, rather than restrictive.

In the description below, some detailed description of functions or configurations may be omitted where such would be known to those of ordinary skill in the art, such that unnecessary description may not make unclear the technical principles of the present invention. In the drawings, where the same components are shown in several drawings, the same reference numerals may be repeated. Further, sizes or thicknesses shown in the drawings may be exaggerated and not to scale for convenience or purposes of illustration, and the actual sizes or thicknesses may be different.

In all aspects and embodiments of the invention, the terms "comprising" or "comprises" and equivalent words may be replaced by "consists of" and equivalent wordings or "consists essentially of" and equivalent wordings and vice versa.

This invention relates to an apparatus and method for securing a first marine superstructure to a second marine superstructure. In particular, this invention relates to a method of securing a TLP 1 to a TAS 2 using hawser lines and sliding fairleads.

Embodiments of this invention relate to the arrangement, use and design of a sliding fairlead. A typical sliding fairlead, as shown in FIG. 1 and FIG. 2, comprises: a support structure 24 that is connected to the adjacent superstructure 25; a rail 23 mounted on the support structure 24; a fairlead 29; a dolly (or moveable member) 28 on which a fairlead 29 is mounted. As depicted in FIG. 3, and described in more detail below, four sets of hawser lines 9, 10, 11 & 12, each comprising the components described above are used to secure the first and second marine superstructures together.

Figs. 1 and 2 relate to a sliding fairlead apparatus 100 for use in connecting a first and a second marine superstructure (e.g. TLP 1 and TAS 2) together, comprising: a moveable member 28 comprising a first face 28a and a second face 28b; and a fairlead 29 mounted to the second face 28b of the moveable member 28 and configured to be attachable to a hawser line (e.g. 31 in FIG. 2), wherein the first face 28a of the moveable member 28 is configured to be slidably attached to a track of a rail member 23, the rail member 23 being arranged to be attached to the second marine superstructure (e.g. 25 in FIG. 2). As shown in Fig. 2, a hawser line 31 is fed through the fairlead 29 and is secured at one end to a hawser winch 30 and at the other end to a quick release mechanism 32. This arrangement secures the hawser line 31 and the sliding fairlead apparatus to a first marine superstructure (e.g. TLP 1). It is intended that the hawser tension be adjustable by the hawser winch 30.

In yet further embodiments of the invention, the first face 28a of the moveable member 28 comprises a hollowed section 28c corresponding to an isoceles trapezium in cross-section, wherein the longer base and legs of the isosceles trapezium form part of the first face 28a of the movement member and the shorter base is open to receive the track of the rail member 23, as shown in FIG. 1. A fairlead 29 is mounted to the movement member by welding, also as shown in Fig. 1. In embodiments of the invention, the moveable member of the sliding fairlead apparatus 100 is a dolly 28. When used herein, the terms "dolly" and "moveable member" relate to a device capable of smooth, reversible movement along a track or rail.

Figs. 1 and 2 also relate to a support apparatus 200 for use in connecting a first and a second marine superstructure together (e.g. TLP 1 and TAS 2), comprising: a support member 24 having an upper portion and a lower portion mounted to the second marine superstructure (e.g. TAS 2); and a rail member 23 comprising a track that is connected to the support member 24, wherein the rail member 23 is configured to be mounted by a sliding fairlead apparatus as shown in Figs. 2 and 3 that is connected to the first marine superstructure (e.g. TAS 1) and where the sliding fairlead apparatus is slidably attached to the track of the rail member 24.

In further embodiments of the invention, the support apparatus 200 may alternatively be described as a support apparatus 200 for a second marine superstructure 2, the support apparatus 200 comprising: a track 23 for sliding arrangement with a moveable member 28 of a sliding fairlead apparatus 100, the sliding fairlead apparatus being configured to be connected to a first marine superstructure 1; and a support member 24 connected to the track 23 and configured to be attached to the second marine superstructure.

In embodiments of the invention, the support member 24 is a rectangular steel box structure welded to the main deck at the bottom of the deck box and it acts as a vertical support for the platform. In yet further embodiments of the invention, a trapezium steel box structure 23 is welded to the upper segment of the support member 24. The trapezium steel box structure 23 acts like a rail/track that enables a dolly or movement member 28 to move vertically. In other words, a rail member/track 23 in the form of a box structure is welded to the upper portion of the support member, 24 and wherein the box structure has an isosceles trapezium shape in cross-section, such that the isosceles trapezium shape acts as the track 23 for the moveable member 28 of the sliding fairlead apparatus 100.

For all of the steel box structures mentioned herein (e.g. 23, 24), lightening holes 201, 202 are provided to reduce the structural weight and allow appropriate reinforcement to be added under the deck for strengthening purposes in embodiments of the invention. Such lightening holes 201, 202 are holes cut through a central portion of the box structures 23, 24 to form hollowed tubes throughout the length of said box structures 23, 24 and function to reduce the overall weight of said box structures 23, 24.

Figs. 1 and 2 further relate to a system for connecting a first 1 and a second 2 marine superstructure together by the connection of the sliding fairlead apparatus 100 described to the support apparatus 200, each as described above, this connection is achieved by connecting the moveable member 28 to the track 23 that is attached to the support member 24 which is in turn mounted to the second marine superstructure (e.g. TAS 2), such that a hawser line 31 connects the fairlead 29 to the first marine superstructure (e.g. the TLP 1) and hence connects the first 1 and second 2 marine superstructures together. In embodiments of the invention, the tension of the hawser line 31 is controlled by a hawser winch 30, as depicted in Fig. 2.

In yet further embodiments of the invention, when the movement member 28 and the rail member/track 23 slidably attached together, between the movement member 28 and the rail member/track 23, there is a small gap of about 10mm, such as between 5 mm and 15 mm. The contact surfaces between the movement member 28 and the rail member/track 23 are lubricated to minimize fiction and wear. There are stoppers 26 &

27 on both ends of the rail member/track 23 to prevent the movement member 28 from moving out of the rail member/track 23 and absorb the impact of a collision in case the movement member 28 moves to the end of the rail member/track 23. In case of damage, the whole movement member 28 can be replaced by a new one by removing one of the stoppers 26, 27. This allows the moveable member 28 to be disengaged and for a new dolly/moveable member 28 to be attached, followed by replacement of the stopper 26, 27.

For example, an inverted "C" shape plate is used as a dolly, or movement member, 28 in Fig. 1. Said "C" shape in the plate forms an open-ended isosceles in cross-section that is capable of being coupled to the track of the rail member/track 23. A typical fairlead 29 is mounted on the dolly by welding, as shown in FIG. 1. Between the dolly 28 and the rail/track 23, there is a small gap of about 10mm. The contact surfaces between the dolly

28 and the rail/track 23 are lubricated to minimize fiction and wear. There are stoppers 26 & 27 on both ends of rail/track 23 to prevent the dolly 28 from moving out of the rail 23 and absorb the impact of a collision in case the dolly 28 moves to the end of the rail 23. In case of damage, the whole dolly 28 can be replaced by ^'a new one by removing one of the stoppers 26, 27.

In embodiments of the invention, as shown in FIG. 2, the hawser line 31 is connected from a hawser winch 30 mounted on TLP 1, goes through fairlead 29 mounted on the dolly 28 onboard TAS 2 before it is terminated at quick release device 32 mounted on TLP 1. When used in any embodiment of the invention, the quick release device 32 is used to release the hawser line 31 within a short period of time in case of emergency.

In embodiments of the invention as shown in Fig. 2, the fairlead 29 is able to slide vertically along the track of the rail member/track 23 mounted to the support structure 24 by means of a movement member 28 whenever the hawser line 31 moves up and down due to heave. The rail member 23 and movement member 28 are designed in such a way that they are able to work in the worst environmental conditions that the first and second marine superstructures are allowed to operate in. The length of the rail member 23 is based on the maximum vertical displacement between the first and second marine superstructures. The fairlead 29 is designed so that it is able to rotate in an orthogonal direction with respect to the sliding direction of the movement member 28 whenever the hawser line 31 is moving from side to side because of a swinging motion. The maximum orthogonal rotation angle of the fairlead 29 is based on the result of mooring analysis, taking into consideration the worst environmental conditions. When a plurality of sliding fairleads are coupled to a plurality of hawser lines (e.g. as shown Figs. 3, 4 and 5 and described in more detail below) the first and second marine superstructures are able to move together as a single body in spite of dynamic loading.

In specific embodiments of the invention where the rail is attached to the TAS 2, the fairlead 29 is able to slide vertically along the rail mounted 23 on support structure 24 by means of a dolly (or movement member) 28 whenever the hawser line 31 moves up and down due to heave.

FIG. 3 depicts an embodiment of the invention, wherein a TLP 1 and a TAS 2 have been connected together using the system 400 of the current invention. FIGs. 4 and 5 further depict this apparatus 400 in schematic (FIG. 4) and expanded (FIG. 5) forms.

FIG. 4 schematically displays the lines required to moor the first 1 (e.g. a TLP) and second 2 (e.g. TAS) marine superstructures and also the lines required to secure the structures together, as according to the current invention. In the specific embodiment of FIG. 4, there is shown the spread mooring system of the TAS 2 consists of eight mooring lines 15, 16, 17, 18, 19, 20, 21 & 22 with two lines on each corner of the vessel. In addition to their respective mooring systems, both TLP 1 and TAS 2 are tied together using hawser lines 9, 10, 11 & 12. In Fig. 4, the support apparatus 3, 4, 5 and 6, each comprising a support member 24 and a rail member/track 23, are mounted to the TAS 2, while each sliding fairlead apparatus 100 mounted to said support apparatus 200 is secured to the TLP 1 via the hawser lines 9, 10, 11 & 12 and hawser winches 7, 8. The TLP 1 has two extra mooring lines 138i 14 on one end and, as previously described, the TLP 1 is connected to the TAS 2 through four hawser lines 9, 10, 11 & 12 on the other end. Unless otherwise stated, the hawser line connections depicted in Fig. 4 can be reversed such that the support apparatus is mounted to the TLP 1, while the sliding fairlead apparatus and hawser lines are secured to the TAS 2. Further, unless otherwise stated, in all embodiments of the invention, the TAS 2 can be any tender support vessel, such as a: tender assist barge (TAB); tender assist semisubmersible (TAS); and also tender assist jack up (TAJU).

In embodiments of the invention, the eight mooring lines of TAS 15, 16, 17, 18, 19, 20, 21 & 22 and extra two mooring lines 13 & 14 for TLP are of the steel catenary type. Chain is used as the lower segment of every mooring line while wire rope is used as the upper segment. During anchor deployment for the mooring systems, assistance from anchor tug boat(s) is necessary.

The hawser lines 9, 10, 11 & 12 used in the hawser system have adequate strength, elasticity and stiffness to accommodate the wave frequency and at the same time enable the first and second marine structures (e.g. TLP 1 and TAS 2) to move together as a single body.

In an embodiment of the invention, as depicted in Figs. 4 and 5, all four support apparatus 3, 4, 5 & 6 are located at bow ship and on a similar transverse frame of the TAS. The support apparatus 3 & 6 are seated directly on the vessel's side shells, that is the side shells of the TAS 2, whereas the support apparatus 4 & 5 are seated somewhere near the center longitudinal bulkhead, that is near the center longitudinal bulkhead of the TAS. The locations of both support apparatus 4 & 5 are affected by the predetermined hawser line arrangement 9, 10, 11 & 12 (see FIG. 5) and location of hawser winches 7 on the TLP 1. However, the distance between support apparatus 3 & 4 must always be similar to the distance between support apparatus 5 & 6 to ensure the hawser line arrangement is symmetric (as shown in FIGs. 4 and 5).

In embodiments of the invention, hawser lines 9 & 10 share a double-drum mooring winch 7 and the same applies to hawser lines 11 & 12 (e.g. see FIG. 5).

From top view as shown in FIG. 4 & 5, the hawser lines 9 & 12 are parallel to the longitudinal centerline of the vessel (i.e. TAS 2) whereas the hawser lines 10 & 11 are with certain angle from the longitudinal centerline of the vessel (i.e. TAS 2). Hawser line 10 crosses over hawser line 11 at a point between the TAS 2 and TLP 1. The hawser line 10 is set at approximately 45 degree (clockwise) from the vessel's longitudinal centerline while the hawser line 11 is approximately 45 degree (anticlockwise) from the vessel's longitudinal centerline. These angles may be varied if the sliding fairleads and hawser line arrangement are different to that shown in FIG. 1 & 5. Both the hawser lines 10 & 11 are directed to hawser winches using horizontal sheaves (e.g. 35, as shown in FIG. 6). It will be appreciated that angles other than 45 degrees can be used in the invention, depending upon a full site analysis and the number of hawser lines and sliding fairleads are necessary.

That is, Figs. 4 and 5 disclose, as an aspect of the current invention, a system for connecting a first (e.g. TLP 1) and a second marine superstructure together, comprising:

one or more sliding fairlead apparatus 100, each comprising: a moveable member 28 comprising a first face 28a and a second face 28b; and a fairlead 29 mounted to the second face 28b of the moveable member 28 and configured to be attachable to a hawser line 9, 10, 11, 12; and

one or more support apparatus 200, each comprising: a support member 24 having an upper portion and a lower portion mounted to the second marine superstructure (e.g. TAS 2); and a rail member 23 comprising a track that is connected to the support member 24, wherein each of the one or more sliding fairhead apparatus 100 is paired to a corresponding support apparatus 200 from the one or more support apparatus 200 to form a connection between the first and second marine superstructures (e.g. TLP 1 and TAS 2) and the first face 28a of the moveable member 28 of the sliding fairlead apparatus 100 is configured to be slidably attached to the track of the rail member 23 of the support apparatus 200. As will be appreciated, a hawser line 9, 10, 11, 12 having a first end and a second end is required to connect the fairlead 29 to the first marine superstructure (e.g. TLP 1) when the system is in operation. It will be appreciated that the sliding fairlead apparatus 100 and the support apparatus 200 may be connected together on the second marine superstructure (e.g. TAS 2) in the first instance and then a hawser line 9, 10, 11, 12 is threaded through the fairlead apparatus 100 (i.e. fairlead 29) to provide the desired connection to the first marine superstructure (e.g. TLP 1). Alternatively, the hawser line 9, 10, 11, 12 may be attached to the sliding fairlead apparatus 100 first, which is then slidably attached to the support apparatus 200. In embodiments of the invention, the system comprises at least four sliding fairlead apparatus and a corresponding number of support apparatus (for clarity these are depicted together as 3, 4, 5 and 6 in FIGs. 4 and 5), forming at least four connections between the first 1 and second 2 marine superstructures, as shown in Figs. 4 and 5. In yet further embodiments, there may be four, six or eight fairlead apparatus and corresponding support apparatus. The exact number to be used is determined by the skilled person upon considering the weight of the two marine superstructures to be connected and following a full site analysis.

In embodiments of the invention, as depicted in Figs. 4 and 5, the second marine superstructure comprises a first 3a and a second 6a side shell and a longitudinal bulkhead 7, wherein: one of the support apparatus 3 is mounted to the first side shell 3a; one of the support apparatus 6 is mounted to the second side shell 6a; and two of the support apparatus 4, 5 are mounted near to and either side of the centre of the longitudinal bulkhead 7. For example the support apparatus 3 mounted to the first side shell 3a and the support apparatus 4 mounted adjacent to it form a first pairing; and the support apparatus 6 mounted to the second side shell 6a and the support apparatus 5 mounted adjacent to it form a second pairing, wherein the distance between the support apparatus of the first pairing is similar to the distance between the support apparatus of the second pairing. For example the distance between the support members/apparatus of the first pairing and the distance between the support members/apparatus of the second pairing is approximately identical.

In embodiments of the invention, as depicted in Figs. 4 and 5, the hawser lines 9, 12 of two of the sliding fairlead apparatus 3, 6 are arranged parallel to the longitudinal centreline of the second marine superstructure (e.g. TAS 2); and the hawser lines 10, 11 of two of the sliding fairlead apparatus 4, 5 are arranged at an angle to the longitudinal centreline of the second marine superstructure. For example, one of the two hawser lines 10 arranged at an angle to the longitudinal centreline of the vessel crosses over the other 11 at a point between the first and second marine superstructures (e.g. TLP 1, TAS 2). In yet further embodiments of the invention, hawser line 10 has an angle of approximately 45° clockwise to the longitudinal centreline of the superstructure (e.g. TAS 2), while the other hawser line 11 has an angle of approximately 45° anti-clockwise to the longitudinal centreline of said superstructure.

In yet further embodiments of the invention, as depicted in Fig. 6, each of the two hawser lines 10, 11 arranged at an angle to the longitudinal centreline of the second marine superstructure is in contact with a horizontal sheave 35 mounted to the first marine superstructure 1.

In yet further embodiments of the invention, e.g. as depicted in Figs. 4 and 5, the respective hawser lines 9, 12 of the two sliding fairlead apparatus arranged parallel to the longitudinal centreline of the second marine superstructure 2 are connected, via the respective fairlead and moveable member, to the support members 3, 6 mounted on the first side shell 3a and the second side shell 3b, respectively. For hawser lines 10 & 11, the lines are terminated at quick release devices located right below horizontal sheaves. As shown in FIG. 6, hawser line 11 is terminated at the quick release device 36 located directly below the horizontal sheave 35. For hawser lines 9 and 12, the lines are terminated at quick release devices located close to the hawser winch. As shown in Fig. 6, hawser line 12 is terminated at the quick release device 32 located adjacent to hawser winch 8. The quick release devices need to be small and compact with minimum height. The hawser winches 8 mentioned above are preferably ones with compact size, AC driven motor and with disk break.

When a plurality of sliding fairleads are coupled to a plurality of hawser lines (e.g. as shown Figs. 3, 4 and 5) the first and second marine superstructures are able to move together as a single body in spite of dynamic loading.

In specific embodiments of the invention where the rail is attached to the TAS 2, the fairlead 29 is able to slide vertically along the rail mounted on support structure by means of a dolly (or movement member) 28 whenever the hawser line 31 is moving up and down due to heave. The rail 23 and dolly 28 are designed in such a way that they are able to work in the worst environmental conditions the TAS 2 is allowed to operate. The length of the rail 23 is sized based on the maximum vertical displacement between TAS 2 and TLP 1.

The TAS 2 mentioned herein is without any dynamic positioning system, therefore tug boats are needed for ocean transit to field. Once the TAS 2 is towed to the desired field, anchors are deployed as part of its station keeping system. After TAS's anchor deployment, the setup of the hawser line system between TAS 2 and TLP 1 is carried out together with the deployment of two TLP mooring lines 13 & 14. All of these operations must be carried out in calm weather.

The method of connecting the first and second marine superstructures together can be achieved in two ways. The first method requires that the sliding fairlead apparatus 100 and support apparatus 200 are connected together. This is easily achieved by removing one of the stops 26, 27, mating the sliding fairlead apparatus 100 and support apparatus 200 together in a slidable arrangement and then replacing the stop 26, 27 that was removed. Subsequently, the fairlead 31, which is attached to the hawser winch 30 is threaded through the fairlead 29 mounted to the second face 28a of the moveable member 28 and is then attached to the quick release mechanism 32. This is repeated for each of the sliding fairleads 100, support members 200 and hawser lines 31 of the system in question. For example, the hawser lines 9, 10, 11, 12 may connect the TLP 1 to the TAS 2 by way of the sliding fairlead/support apparatus combinations 3, 4, 5, 6. As will be apparent to the skilled person, the second method of connecting the first and second marine superstructures together involves connecting the hawser line 31 to the fairlead 29 mounted to the second face 28a of the moveable member 28 first before connecting the sliding fairlead apparatus 100 to the support apparatus 200, the connection of the hawser line 31 to the quick release device 32 is generally accomplished before the insertion of the sliding fairlead apparatus 100 into the support apparatus 200.

Claims

1. A sliding fairlead apparatus for use in connecting a first and a second marine superstructure together, comprising:

a moveable member comprising a first face and a second face; and

a fairlead mounted to the second face of the moveable member and configured to be attachable to a hawser line, wherein

the first face of the moveable member is configured to be slidably attached to a track of a rail member, the rail member being arranged to be attached to the second marine superstructure.

2. The sliding fairlead apparatus of Claim 1, further comprising a hawser line for attaching the fairlead to the first marine superstructure.

3. The sliding fairlead apparatus of Claim 2, further comprising a hawser winch and a quick release mechanism for securing the hawser line to the first marine superstructure.

4. The sliding fairlead apparatus of Claim 3, wherein the hawser winch is a double drum mooring winch capable of securing two hawser lines from two sliding fairlead apparatus.

5. The sliding fairlead apparatus of Claim 4, wherein each hawser line is secured by a separate quick release mechanism.

6. The sliding fairlead apparatus of any one of Claims 3 to 5, wherein a tension applied to the hawser line is regulated by the^' hawser winch.

7. The sliding fairlead apparatus of any one of Claims 2 to 6, wherein the fairlead is further configured to rotate in an orthogonal direction with respect to the sliding direction of the movement member in response to a movement from the hawser line.

8. The sliding fairlead apparatus of any preceding claim, wherein the first face of the moveable member comprises a hollowed section corresponding to an isoceles trapezium in cross-section, wherein the longer base and legs of the isosceles trapezium form part of the first face of the movement member and the shorter base is open to receive the track of the rail member.

9. A support apparatus for a second marine superstructure, the support apparatus comprising:

a track for sliding arrangement with a moveable member of a sliding fairlead apparatus, the sliding fairlead apparatus being configured to be connected to a first marine superstructure; and a support member connected to the track and configured to be attached to the second marine superstructure.

10. The support apparatus of Claim 9, wherein the support member has a rectangular box structure welded to the main deck of the second marine superstructure and acts as a vertical support for the marine superstructure.

11. The support apparatus of Claim 9 or Claim 10, wherein:

(a) the support member is made of steel; and/or

(b) the support member further comprises a hole through its core to reduce the weight of said support member.

12. The support apparatus of any one of Claims 9 to 11, wherein the support member further comprises and upper portion and a lower portion, wherein the track is a box structure welded to the upper portion of the support member and wherein the box structure has an isosceles trapezium shape in cross-section, such that the isosceles trapezium shape acts as the track for the moveable member of the sliding fairlead apparatus.

13. The support apparatus of Claim 12, wherein:

(a) the track is made of steel; and/or

(b) the track further comprises a hole through its core to reduce the weight of said support member.

14. The support apparatus of any one of Claims 9 to 13, wherein the track further comprises:

an upper terminus and a lower terminus;

a stopper attached to the upper terminus; and

a stopper attached to the lower terminus, wherein

the stoppers are adapted for removal and replacement to enable coupling of the sliding fairlead apparatus to the rail member and, when coupled, prevent the sliding fairlead apparatus from decoupling from the rail member.

15. A hawser system comprising the sliding fairlead apparatus of any one of Claims 1 to 8 and the support apparatus of any one of Claims 9 to 14, wherein the sliding fairlead apparatus is slidably attached to the support apparatus.

16. A system for connecting a first and a second marine superstructure together, comprising:

one or more sliding fairlead apparatus, each comprising:

a moveable member comprising a first face and a second face; a fairlead mounted to the second face of the moveable member and configured to be attachable to a hawser line; and

one or more support apparatus, each comprising:

a support member having an upper portion and a lower portion mounted to the second marine superstructure; and

a rail member comprising a track that is connected to the support member, wherein

each of the one or more sliding fairhead apparatus is configured to be slidably attached to the track of the rail member of a corresponding one of the one or more support apparatus, such that a connection between the first and second marine superstructures is formed upon attachment of a hawser line to the fairlead mounted to the second face of the moveable member of the slidable fairlead apparatus.

17. The system of Claim 16, wherein each of the one or more sliding fairlead apparatus further comprises a hawser line having a first end and a second end that connects the fairlead mounted to the second face of the moveable member to the first marine superstructure.

18. The system of Claim 17, wherein the hawser line of the one or more sliding fairlead apparatus is secured to the first marine superstructure by a hawser winch at the first end and a quick release mechanism to the second end.

19. The system of Claim 17 or Claim 18, wherein a tension applied to the hawser line is regulated by the hawser winch.

20. The system of any one of Claims 17 to Claim 19, wherein the hawser winch is a double drum mooring winch capable of securing two hawser lines from two fairlead apparatus.

21. The system of any one of Claims 17 to 20, wherein the fairlead mounted to the second face of the moveable member of the at least one fairlead apparatus is further configured to rotate in an orthogonal direction with respect to the sliding direction of the movement member in response to a movement from the hawser line.

22. The system of any one of Claims 17 to 21, wherein the first face of the moveable member comprises a hollowed section corresponding to an isoceles trapezium in cross-section, wherein the longer base and legs of the isosceles trapezium form part of the first face and the shorter base is open to receive the track of the rail member.

23. The system of any one of Claims 17 to 22, wherein the rail member of the one or more support apparatus is a box structure welded to the upper portion of the support member and wherein the box structure has an isosceles trapezium shape in cross-section, such that the isosceles trapezium shape acts as the track for the sliding fairlead apparatus.

24. The system of any one of Claims 17 to 23, wherein the rail member of the one or more support apparatus, further comprises:

an upper terminus and a lower terminus;

a stopper attached to the upper terminus; and

a stopper attached to the lower terminus, wherein

the stoppers are adapted for removal to enable coupling of the sliding fairlead apparatus to the rail member and, when coupled, prevent the sliding fairlead apparatus from decoupling from the rail member.

25. The system of any one of Claims 17 to 24, wherein the system comprises at least four sliding fairlead apparatus and four corresponding support apparatus, forming four connections between the first and second marine superstructures.

26. The system of Claim 25, wherein the system comprises six or eight fairlead apparatus and corresponding support apparatus.

27. The system of Claim 25, wherein the second marine superstructure comprises a first and a second side shell and a longitudinal bulkhead, wherein:

one of the support apparatus is mounted to the first side shell;

one of the support apparatus is mounted to the second side shell; and

two of the support apparatus are mounted near to and either side of the centre of the longitudinal bulkhead.

28. The system of Claim 27, wherein:

the support apparatus mounted to the first side shell and the support apparatus mounted adjacent to it form a first pairing; and

the support apparatus mounted to the second side shell and the support apparatus mounted adjacent to it form a second pairing, wherein

the distance between the support apparatus of the first pairing is similar to the distance between the support apparatus of the second pairing.

29. The system of Claim 28, wherein the distance between the support apparatus of the first pairing and the distance between the support apparatus of the second pairing is approximately identical.

30. The system of any one of Claims 25 and 27 to 29, wherein: the hawser lines of two of the sliding fairlead apparatus are arranged parallel to the longitudinal centreline of the second marine superstructure; and

the hawser lines of two of the sliding fairlead apparatus are arranged at an angle to the longitudinal centreline of the second marine superstructure.

31. The system of Claim 30, wherein one of the two hawser lines arranged at an angle to the longitudinal centreline of the vessel crosses over the other at a point between the first and second marine superstructures.

32. The system of Claim 31, wherein one of the two hawser lines arranged at an angle to the longitudinal centreline of the second marine superstructure has an angle of approximately 45° clockwise to the longitudinal centreline of said superstructure, while the other hawser line has an angle of approximately 45° anti-clockwise to the longitudinal centreline of said superstructure.

33. The system of any one of Claims 30 to 32, wherein each of the two hawser lines arranged at an angle to the longitudinal centreline of the second marine superstructure is in contact with a separate horizontal sheave mounted to the first marine superstructure.

34. The system of any one of Claims 30 to 33, as dependent upon Claims 25, 27 and 28, wherein the respective hawser lines of the two sliding fairlead apparatus arranged parallel to the longitudinal centreline of the second marine superstructure are connected, via the respective fairlead and moveable member, to the support apparatus mounted on the first side shell and the second side shell, respectively.

35. The fairlead apparatus of any one of Claims 1 to 8, the support apparatus of any one of Claims 9 to 14, the system of Claim 15 and the system of any one of Claims 16 to 34, wherein the first and second marine superstructures are selected from a tension leg platform and a tender assist semisubmersible, where the first and second marine superstructures are not identical.

36. A method of coupling the fairlead apparatus of any one of Claims 2 to 8 and 15 to 34 to the support apparatus of any one of Claims 9 to 34, comprising the steps of:

(a) connecting the sliding fairlead apparatus to the support member;

(b) connecting the hawser line to the fairlead apparatus; and

steps (a) to (c), where steps (a) and (b) are reversed.