Patent Description:
<CIT> discloses a floating platform for recovery of oil and gas from offshore oil and gas fields that supports one or more decks above the water surface to accommodate equipment for drilling and processing oil, gas and water recovered from the oil and gas field. The platform includes a central column having a portion substantially below the water surface, and including a portion which extends above the water surface. The central column includes a base node and a plurality of pontoons extending outwardly therefrom and is anchored to the seabed by one or more tendons secured to the pontoons and to the seabed.

<CIT> discloses a tension-leg platform anchoring system is used to tether the columns of a floating platform to the seabed and restrict movement of the entire platform. The tension-leg platform anchoring system includes a topside and a plurality of anchored floating supports. The topside provides a deck for supporting workers and equipment. The anchored floating supports are used to keep the topside afloat and limit movement. The anchored floating support includes a column, at least one mooring assembly, and an anchor. The column is connected to the topside and is used to keep the tension-leg platform afloat.

The object is achieved by a yoke plate assembly for mooring a floating object in a body of water by means of a pair mooring lines, comprising an assembly plate for mechanically coupling to an anchor body, an elongated yoke plate with a centre thereof pivotally connected to the assembly plate by an articulation; a first lever arm having a first proximal end connected by a first coupler to a first end of the elongated yoke plate; a second lever arm having a second proximal end connected by a second coupler to a second end of the elongated yoke plate longitudinally opposite to the first end, wherein the first lever arm at a first distal end thereof is connectable by a first distal joint to one of the pair of mooring lines, and the second lever arm at a second distal end thereof is connectable by a second distal joint to the other of the pair of mooring lines,wherein the first coupler is arranged as a first uni-joint between the first end of the elongated yoke plate and the first lever arm, and the second coupler is arranged as a second uni-joint between the second end of the elongated yoke plate and the second lever arm.

Advantageously, the yoke plate assembly according to the invention, allows to achieve an improvement of load sharing between two mooring lines each connected at a respective end of the elongated yoke plate. The yoke plate assembly enables spreading equally tensile forces between the two mooring lines and hence divides extreme loads per a factor of two and divides the fatigue damage by a factor of eight. Additionally, the yoke plate assembly according to the invention, provides that line length differences between the two mooring lines, originating from either a difference in construction, or a difference due to the installation process, are compensated. When this is a fundamental requirement for the mooring system to perform adequately, the presence of the yoke plate assembly allows the use of conventional mooring components for the application, without going to expensive TLP tendons connectors for instance.

The application of the couplers as uni-joints advantageously allows the connection of each mooring line to articulate in two perpendicular planes, which, in case mooring chains are used, can significantly reduce out-of-plane bending fatigue.

In an embodiment, the yoke plate assembly as described above is arranged with articulation selected from a group comprising a one-axis joint, a two-axis joint, a gimbal joint, a rotary joint. Advantageously the articulation provides that the elongated yoke plate can incline due to different tensile force on each of mooring lines that can be attached to the elongated yoke plate and thus suppress large moments of force at the connections of the mooring lines on the elongated yoke plate.

In an embodiment, the invention provides a yoke plate assembly as described above, wherein the first lever arm at a first distal end thereof is connectable by a first distal joint to one of the pair of mooring lines, and the second lever arm at a second distal end thereof is connectable by a second distal joint to the other of the pair of mooring lines.

In an embodiment the invention provides a yoke plate assembly as described above, wherein the first and second coupler is a uni-joint with coplanar axes.

Advantageously, using uni-joint with coplanar axes avoids creating artificial moment loads by removing local lever arm between articulations.

In an embodiment, the invention provides a yoke plate assembly as described above, wherein the first and second lever arms each comprise a rod and a receptacle part for receiving the rod for forming a disconnectable coupling between them, in which each receptacle is connected to the respective coupler on the first end of the elongated yoke plate and the second end of the elongated yoke plate, respectively. Using a receptacle coupled to the yoke plate and a matching rod at the proximal end of the mooring line allows for a relatively simpler connection/disconnection scheme.

In an embodiment, the invention provides a yoke plate assembly as described above, wherein the joint between the first coupler and the first end of the elongated yoke plate and the first distal joint form a first elongated uni-joint, and the joint between the second coupler and the second end of the elongated yoke plate and the second distal joint form a second elongated uni-joint. The application of the couplers in combination with the lever arms as elongated uni-joints advantageously provides enhanced articulation in two planes for each mooring line to reduce out-of-plane bending fatigue.

In an embodiment, the invention provides a yoke plate assembly as described above, that further comprises a stopper mechanism for limiting an inclination angle of the elongated yoke plate relative to a surface plane of the assembly plate up to a predetermined maximum angle value.

The stopper mechanism advantageously protects the yoke plate assembly against mechanical damage in case one of the mooring lines in the pair would disconnect and the full tension would transfer to the connection of the yoke plate with other mooring line.

In addition, the invention relates to a mooring arrangement for mooring a floating object in a body of water by means of at least a pair of mooring lines attached to the floating object, in accordance with claim <NUM>, to a floating object floating in a body of water, moored to the bed of the body of water by a mooring arrangement in accordance with claim <NUM> and to a method of manufacturing a yoke plate assembly in accordance with claim <NUM>.

The invention will be explained in more detail below with reference to drawings in which illustrative embodiments thereof are shown.

The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto.

<FIG> shows a view in cross-section of the yoke plate assembly according to an embodiment of the invention.

As shown here, the yoke plate assembly <NUM> is arranged on an anchor body <NUM> that is located on a seabed <NUM>. Further, the yoke plate assembly <NUM> is coupled to a pair of mooring lines or mooring chains 5a, 5b that are attached to a floating object (not shown).

The yoke plate assembly <NUM> comprises an assembly plate <NUM>, a yoke plate <NUM>, an articulation <NUM>, first and second lever arms 25a, 25b, first and second couplers 30a, 30b and first and second links 35a, 35b.

The yoke plate <NUM> consists of an elongated beam with a central articulation <NUM> coupled to the assembly plate <NUM>. The central articulation <NUM> comprises a central axis <NUM> about which the yoke plate <NUM> can rotate for balancing the forces exerted on each of the mooring lines.

Each beam end <NUM> is arranged with a cylindrical opening. The cylindrical openings are configured to hold an axis of rotation <NUM> parallel to the central axis <NUM>. Each axis of rotation <NUM> is configured to provide a pivoted coupling to a proximal end of one of the first and second lever arms 25a, 25b respectively.

Finally, each of the first and second lever arms 25a, 25b is mechanically coupled to one of the mooring lines 5a, 5b.

Advantageously, the yoke plate assembly <NUM> provides an enhanced load sharing between the pair of mooring lines 5a, 5b. Differences in tensile force between the mooring lines can be accommodated by a rotation about the central axis <NUM>. Also, differences in the length of the mooring lines 5a, 5b can be compensated by a rotation of the yoke plate.

According to an embodiment, the coupling between a distal end of the lever arm and the associated mooring line is by means of a first pivoting axis <NUM>. The coupling at the proximal end of the lever arm comprises a second pivoting axis <NUM>. By configuring in each lever arm that the second pivoting axis <NUM> is perpendicular to the axis of rotation <NUM>, an extended uni-joint 36a, 36b is formed. Advantageously, using a set-up with extended uni-joints provides a suppression of out-of-plane bending of the mooring chains during mooring by allowing perpendicular rotations around the first pivoting axis <NUM> and the associated axis of rotation <NUM>.

<FIG> shows a perspective view of a yoke plate assembly according to an embodiment of the invention. Within the yoke plate assembly, the yoke plate <NUM> is arranged in parallel between two guiding plates <NUM> that extend upward from the surface plane of the assembly plate <NUM>.

The assembly plate <NUM> is mounted on top of the anchor body <NUM>. According to the invention, the anchor body can be any seabed anchor type as will be appreciated by the person skilled in the art. Such anchor type includes, but is not limited to, as a gravity anchor, a suction pile, a driven pile and a hybrid anchor (i.e. a mixed structure of gravity anchor and suction pile).

According to an embodiment, the plane of the yoke plate is under an inclination angle α relative to the vertical towards the floating object so that it is aligned with the inclination of the mooring line. In this manner moments of force at equilibrium position are being reduced, as depicted in <FIG>.

<FIG> show side views of a yoke plate <NUM> and associated articulation <NUM> in accordance with embodiments of the invention. According to the invention, the articulation <NUM> is configured to provide at least a rotation of the yoke plate relative to the surface plane <NUM> of the assembly plate along a central axis <NUM> that is parallel to the axis of rotation <NUM> of the couplings at the beam ends <NUM> of the yoke plate.

In <FIG>, a yoke plate assembly <NUM> is shown in which the articulation <NUM> is configured with the central axis <NUM> perpendicular to the length of the yoke plate and parallel to the surface plane <NUM> of the assembly plate, and with couplings at the beam ends <NUM> of the yoke plate that have axis of rotation <NUM> parallel to the central axis.

In <FIG>, a yoke plate assembly <NUM> is shown in which the articulation <NUM> comprises the central axis <NUM> as described above with reference to <FIG>, and a second central axis 16a that extends substantially perpendicular to the central axis and is parallel to the surface plane <NUM> of the assembly plate. In this embodiment, the articulation <NUM> allows that the yoke plate can incline by rotation about the second central axis 16a. As a result, the yoke plate assembly is capable of suppressing large moments at mooring line connections at the beam ends <NUM> of the yoke plate <NUM>.

In <FIG>, a yoke plate assembly <NUM> is shown in which the articulation <NUM> comprises an arrangement of a gimbal to allow the yoke plate <NUM> to change its orientation relative to the surface plane <NUM> and to align with a (change of) direction of the mooring lines or chains 5a, 5b.

In <FIG>, a yoke plate assembly <NUM> is shown in which the articulation <NUM> comprises a rotary joint to allow the yoke plate <NUM> to change its orientation relative to the surface plane <NUM> and to align with a (change of) direction of the mooring lines.

<FIG> shows a side view of a yoke plate assembly according to an embodiment of the invention.

In this embodiment, the yoke plate assembly comprises first and second couplers 30a, 30b that are each embodied as an uni-joint with coplanar axes 16c, i.e., a pair of axes perpendicular to each other and rotating within the same plane (i.e., a gimbal). In such a uni-joint two coplanar articulations are integrated in a respective beam end <NUM> of the yoke plate <NUM> and are connected to the lever arms 25a; 25b. During service life this uni-joint arrangement can protect a mooring chain attached to the lever arm against damage by out-of-plane-bending.

<FIG> shows a side view of a yoke plate assembly according to an embodiment of the invention. In this embodiment, the yoke plate assembly <NUM> comprises first and second couplers 30a, 30b that are each embodied as an uni-joint with coplanar axes 16c as explained above with reference to <FIG>. Additionally, the lever arm 25a; 25b consists of a rod <NUM> and a receptacle <NUM>. The rod <NUM> is configured to be at the proximal end <NUM> of the mooring line. The receptacle <NUM> is coupled to the uni-joint 30a; 30b and is capable of receiving a head <NUM> of the rod <NUM>: For example the receptacle <NUM> comprises a reversed ratchet system <NUM> to ensure securing the head <NUM> of the rod head into the receptacle <NUM>. Thus a connectable coupling between the head <NUM> of the rod <NUM> and the receptacle <NUM> is formed. In each of the uni-joints, the receptacle <NUM> is connected to the respective coupler 30a; 30b on the corresponding beam end <NUM> of the elongated yoke plate <NUM>. The connectable coupling simplifies operations of subsea connecting of mooring lines with/from the yoke plate assembly.

<FIG> shows a perspective view of a yoke plate assembly <NUM> according to a further embodiment of the invention. In this embodiment, the yoke plate assembly <NUM> as described in relation to the preceding figures, comprises a stopper mechanism <NUM> that limits the maximal inclination of the yoke plate in case of a large difference in tensile force between the mooring lines.

As shown in <FIG>, the stopper mechanism <NUM> consists of two elongated slots <NUM> and two associated round slider pins <NUM>. Each elongated slot <NUM> is arranged in at least one of the parallel guiding plates <NUM> at a position corresponding to a position where one of the associated slider pins <NUM> is attached on the yoke plate <NUM>. Each of the slider pins <NUM> extends from the yoke plate <NUM> perpendicular to the guiding plate <NUM> and is inserted into the associated elongated slot <NUM>. A rotation of the yoke plate <NUM> around the central axis <NUM> becomes limited by a length 42b of the elongated slots along which the slider pins can move.

An alternative stopper mechanism (not shown here) could be formed by a pair of stopper chains or lines that are coupled between the assembly plate <NUM> and a respective beam end <NUM> of the yoke plate. The length of each stopper chain or line restricts the maximal angle of rotation the yoke plate <NUM> can reach.

<FIG> shows a schematic view of a mooring arrangement comprising a floating object <NUM> and a yoke plate assembly <NUM> according to an embodiment of the invention.

The mooring arrangement involves a floating object <NUM> on which a pair of mooring points <NUM> is arranged. Each of the mooring points <NUM> is configured to connect to a mooring line <NUM>, <NUM> in which one mooring point connects to a proximal end <NUM> of a first mooring line <NUM> and the other mooring point connects to a proximal end <NUM> of a second mooring line <NUM>. The first and second mooring lines <NUM>, <NUM> form a pair of mooring lines that at their respective distal end <NUM>, <NUM> connect to a respective beam end <NUM> of the yoke plate <NUM>. Thus, the first and second mooring lines run in parallel between the floating object <NUM> and the yoke plate assembly <NUM>. In this manner a tension leg comprising two parallel mooring lines <NUM>, <NUM> can be formed.

According to a further embodiment, each of the first and second mooring lines <NUM>, <NUM> comprises a proximal chain portion <NUM>, a steel wire rope portion <NUM>, and a distal chain portion <NUM>, in which one end of the proximal chain portion <NUM> is coupled to one end of the steel wire rope portion <NUM> and the other end of the steel wire rope portion <NUM> is coupled to one end of the distal chain portion <NUM>. The other end of the proximal chain portion <NUM> is coupled to the mooring point on the crossbar by means of a chain connector <NUM>.

The other end of the distal chain portion <NUM> is coupled to the distal end of the lever arm 25a; 25b of the corresponding beam end <NUM> of the yoke plate beam <NUM> at the yoke plate assembly <NUM>.

<FIG> shows a schematic view of a floating object <NUM>; <NUM> moored by a mooring arrangement <NUM> comprising a yoke plate assembly <NUM> according to an embodiment of the invention.

A floating object <NUM>; <NUM> floating on a sea <NUM>, is coupled at each of its mooring points <NUM> to an associated yoke plate assembly <NUM>. At each mooring point <NUM> the floating object <NUM>; <NUM> is coupled to a corresponding beam end <NUM> of the yoke plate <NUM> of the yoke plate assembly <NUM> by a pair of mooring lines or mooring chains 5a, 5b. The mooring line may be constructed in a same manner as described above with reference to <FIG>.

Each yoke plate assembly is attached by its assembly plate <NUM> to a corresponding anchor body <NUM> that is placed at the seabed <NUM>.

The floating object <NUM>; <NUM> can be arranged as tension leg platform (TLP), or have a TLP configuration, by tensioning the mooring chains 5a, 5b between the mooring points <NUM> and the anchor body <NUM>. The yoke plate assembly according to the invention allows that conventional mooring components such as mooring chains can be used. Advantageously, the mooring arrangement according to the invention can significantly reduce costs in comparison with traditional TLP that require custom-made and expensive tendon connectors to balance loads between tendons.

In an embodiment, the floating object <NUM>; <NUM> comprises a construction having a wind turbine mounted on a floating frame equipped with buoyancy tanks provided with mooring points.

Claim 1:
A yoke plate assembly (<NUM>) configured for mooring a floating object (<NUM>, <NUM>) in a body of water by means of a pair mooring lines (<NUM>, <NUM>) between the yoke plate assembly and the floating object, comprising
an assembly plate (<NUM>) configured for mechanically coupling to an anchor body (<NUM>), an elongated yoke plate (<NUM>) with a centre thereof pivotally connected to the assembly plate by an articulation (<NUM>);
a first lever arm (25a) having a first proximal end (<NUM>) connected by a first coupler (30a) to a first end (<NUM>) of the elongated yoke plate;
a second lever arm (25b) having a second proximal end (<NUM>) connected by a second coupler (30b) to a second end (<NUM>) of the elongated yoke plate longitudinally opposite to the first end, wherein the first lever arm at a first distal end (<NUM>) thereof is connectable by a first distal joint to one of the pair of mooring lines,
and the second lever arm at a second distal end (<NUM>) thereof is connectable by a second distal joint to the other of the pair of mooring lines,
wherein the first coupler is arranged as a first uni-joint between the first end of the elongated yoke plate and the first lever arm,
and the second coupler is arranged as a second uni-joint between the second end of the elongated yoke plate and the second lever arm.