AU2010335657A1

AU2010335657A1 - A hang-off system and a hang-off structure

Info

Publication number: AU2010335657A1
Application number: AU2010335657A
Authority: AU
Inventors: Claus Dencker Christensen
Original assignee: National Oilwell Varco Denmark IS
Current assignee: National Oilwell Varco Denmark IS
Priority date: 2009-12-23
Filing date: 2010-11-26
Publication date: 2012-07-05
Anticipated expiration: 2030-11-26
Also published as: EP2516249B1; EP2516249A4; IN2012DN05240A; BR112012015463A2; CN102811902A; BR112012015463B1; CN102811902B; AU2010335657B2; EP2516249A1; WO2011076210A1; MY165258A

Abstract

The invention relates to a hang-off system for a offshore structure, e.g. for transporting hydrocarbons from a well at seabed (1) to a vessel (3) at sea surface. The hang-off system comprises a floating, moored weathervaning vessel (3) with a turret (11) wit a hang-off structure (8). The hang-off system (8) further comprises at least one flexible transporting unit (2) hanging from the hang-off structure (8). The turret (11) comprises a bearing and swivel system (5,9) connected to or integrated with the hang-off structure (11). The bearing and swivel system (5,9) comprises a centre axis (4), the flexible transporting unit (2) hangs-off from a hang-off connecting point (7) to a subsea connection point (1) in a structural relation such that a vector extending from the subsea connecting point (1) to the hang-off connection point (7) has a vertical and a horizontal component, and the horizontal component is perpendicular to a hang-off vertical plane extending through the centre axis of the bearing and swivel system. The hang-off vertical plane separates the hang-off structure (8) in a flexible transporting unit (2) heading part and an opposite part. The flexible transporting unit (2) heading part is horizontally closer to the subsea connection point (1) than the opposite part. The hang-off connecting point (7 is arranged in the opposite part of the hang-off structure (8). The hang-off system of the invention results in a reduced risk of subjecting the flexible transporting unit(s) (2) to high wear, to bending with damaging curvature and/or to over stretching of the flexible transporting unit (2).

Description

WO 2011/076210 PCT/DK2010/050324 A hang-off system and a hang-off structure TECHNICAL FIELD The present invention relates to hang-off system comprising a floating weathervaning vessel comprising a hang-off structure and one or more 5 flexible transporting units hanging from said hang-off structure. The invention also relates to a turret comprising a hang-off structure. BACKGROUND ART Hang-off systems comprising a floating weathervaning vessel with a hang-off structure and one or more flexible transporting units hanging from the hang 10 off structure are well know in the art and are generally used in the offshore transportation of fluids, electricity, electromagnetic waves and other media to or from a floating weathervaning vessel. A floating weathervaning vessel from which one or more flexible transporting units are leading to a subsea connection point usually comprises an external 15 turret system or an internal turret system. The internal turret system leads the flexible transporting units through the hull bottom whereas the external turret system leads the flexible transporting unit from a topside hang-off structure extending beyond the hull and the rail of the vessel. The weathervaning vessel is usually moored to the seabed such that it can 20 weathervane around the centre axis of its turret. The hang-off structure is usually mounted to the turret via a bearing and swivel system of the turret such that when the weathervaning vessel is weathervaning, the hang-off structure will be rotated with respect to the weathervaning vessel, but it will substantially not rotate with respect to the 25 flexible transporting units. In many situations only limited horizontal and/or vertical space is available for the weathervaning vessel and/or the flexible transporting units. In this text WO 2011/076210 PCT/DK2010/050324 2 "horizontal space" means horizontal space at the sea surface and/or at the seabed and/or any horizontal plane there between. "Vertical space" means depth of water from sea surface to seabed and/or from the keel of the weathervaning vessel to seabed. In such situations with limited space there is 5 a high risk that the flexible transporting unit is subjected to high wear and even to bending with damaging curvature and/or an over stretching of the flexible transporting unit. The object of the invention is to provide a hang-off system which results in a reduced risk of subjecting the flexible transporting unit(s) to high wear, to 10 bending with damaging curvature and/or to over stretching of the flexible transporting unit. DISCLOSURE OF INVENTION The object of the invention is solved by the hang-off system as defined in the 15 claims. Additional beneficial solutions which may have additional advantages are defined in the sub claims and are described in the following. The term 'seabed' is generally used to denote the subsea floor. In the prior art hang-off systems, the hang-of structure normally has been provided with an essential circular plate structure often integrated with a 20 mooring chaintable for mooring the weathervaning vessel by lines to the seabed. Circular openings in the circular plate structure arranged around the centre axis (normally also the centre axis for a bearing and swivel system) form hang-off connecting points for one or more flexible transporting units extending to a subsea connecting point. Generally, in prior art hang-off 25 systems one or more flexible transporting units were arranged to hang-off from a hang-off connecting point which was as close to the subsea connection point as possible.

WO 2011/076210 PCT/DK2010/050324 3 The inventor of the present invention has found that large and unpredictable benefits can be obtained by increasing the horizontal distance between the hang-off connecting point and the subsea connecting point and furthermore the inventor has provided a hang-off system which allows such an increase of 5 horizontal distance. Even though such an increase in horizontal distance requires the flexible transporting unit to be longer than in corresponding prior art systems, the benefits obtained with respect to reduced risk of subjecting the flexible transporting unit(s) to high wear, to bending with damaging curvature and/or to over stretching of the flexible transporting unit, far 10 exceed the drawbacks of using a slightly longer flexible transporting unit. The hang-off structure is in particular useful in highly shallow waters or areas with limited horizontal space for the weathervaning vessel, but it may also be beneficial in other offshore areas. The hang-off system of the invention is highly applicable in shallow waters with a depth of up to about 200 m, such 15 as preferably with a depth of up to about 100 m, such as with a depth of up to about 80 m. Further scope of applicability of the present invention will become apparent from the description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred 20 embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. The hang-off system of the invention comprises a floating, moored weathervaning vessel with a turret. 25 The weathervaning vessel may be any kind of weathervaning vessel with an external turret system or an internal turret system. Examples of weathervaning vessels include FPSO (Floating Production, Storage, and Offloading systems), FSO (Floating Storage and Offloading systems) and FSRU (Floating Storage and Regasification Unit systems).

WO 2011/076210 PCT/DK2010/050324 4 Weathervaning vessels with turrets are well known in the art, e.g. as described above. The turret may be as the prior art turret with the modification(s) specified in the claims and described below. The turret system of the hang-off system of the invention comprises a hang 5 off structure and at least one flexible transporting unit hanging from the hang-off structure. A hang-off structure is a structure to which the flexible transporting unit or units are connected and hang-off from. The hang-off structure is the part of the turret from where the flexible transporting unit exits the weathervaning 10 vessel and passes on to connection with another structure, in the present hang-off system a subsea structure. The flexible transporting unit may be any kind of flexible transporting units which are usable in such a hang-off system. The flexible transporting unit may for example be a flexible riser or an umbilical. Preferably the hang-off 15 system comprises a plurality of flexible transporting units e.g. comprising a plurality of risers, such as a plurality of risers and optionally at least one umbilical. Flexible transporting units - sometimes also called jumpers - such as risers and umbilicals are well known in the art. Risers are usually applied for transportation of petrochemical products from the seabed to a sea surface 20 installation such as a weathervaning vessel. Umbilicals are often used for transporting fluids, electricity, signals and other to and/or from installations at or beyond the seabed. The turret comprises a bearing and swivel system connected to or integrated with the hang-off structure. 25 The term "connected to" indicates that the parts connected to each other are two parts with distinguished functions. The term "integrated with" indicates that the integrated parts at least have some common structures or common functional part(s).

WO 2011/076210 PCT/DK2010/050324 5 Bearing and swivel systems of weathervaning vessels are well known in the art and may for example be as described in US 5,517,937. The bearing and swivel system of the turret is the part of the turret that ensures that the weathervaning vessel can weathervane around the turret, usually around a 5 centre axis of the bearing and swivel system. In one embodiment the bearing and swivel system comprises two parts which are rotatably connected to each other. A first part of the bearing and swivel system is connected in a substantially stiff connection to a hull of the weathervaning vessel and a second part connected to the hang-of structure 10 and preferably a mooring system such as a mooring chaintable through which the weathervaning vessel is moored by lines. In the hang-off system of the invention, the bearing and swivel system comprises a centre axis, which herein is defined as an axis of rotation of the bearing and swivel system. The flexible transporting unit hangs-off from a 15 hang-off connecting point to a subsea connection point. The hang-off connecting point is defined as the point closer to the centre axis provided by the bearing and swivel system of the hang-off structure from where the flexible transporting unit hangs-off (the in length direction last point of connection). Normally the flexible transporting unit will hang-off from 20 a hang-off aperture provided in the hang-off structure and the final area of connection is the periphery of this hang-off aperture. Accordingly, the hang off connecting point is the point along the periphery of the hang-off aperture which is closer to the centre axis provided by the bearing and swivel system. The subsea connection point is the connection point between the flexible 25 transporting unit and a subsea structure, which in length direction of the pipe is closer to the hang-off connecting point. If several points are equally close, the subsea connection point is the midpoint of the two more distinct of such several equally close points.

WO 2011/076210 PCT/DK2010/050324 6 In the hang-off system of the invention the hang-off structure and the flexible transporting unit are arranged such that risk of damaging the flexible transporting unit is reduced. A vector extending from the subsea connecting point to the hang-off connection point has a vertical and a horizontal 5 component, the horizontal component is perpendicular to a hang-off vertical plane extending through the centre axis of the bearing and swivel system, the hang-off vertical plane separates the hang-off structure in a flexible transporting unit heading part and an opposite part. The flexible transporting unit heading part is horizontally closer to the subsea connection point than 10 the opposite part. In the present invention the hang-off connecting point is arranged in the opposite part of the hang-off structure, thereby reducing the risk of damaging the flexible transporting unit. As mentioned above the hang-off system of the invention may comprise any kind of turret system providing one or more hang-off connecting points as 15 described herein. In one embodiment the weathervaning vessel has a hull and comprises an external turret system where the hang-off structure is a topside hang-off structure fixed at a position beyond the hull of the weathervaning vessel. External turret systems as such are well known in the art, and are often used 20 in vessels which have temporarily or permanently been rebuilt to become a weathervaning vessel. External turret systems are often relatively small compared with internal turret systems and are in particular used in shallow water applications, but they may also be used at deeper water. In one embodiment the weathervaning vessel has a hull and comprises an 25 internal turret arranged inside and/or below the hull of the weathervaning vessel. Such internal turret can in principle have any size. The weathervaning is preferably moored by lines to the seabed and/or to one or more fixed structures such that it can rotate fully or partly around the centre axis of the bearing and swivel system. Generally it is preferred to moor WO 2011/076210 PCT/DK2010/050324 7 the weathervaning vessel directly by lines to the seabed for providing a safe mooring. The moored weathervaning vessel generally has a large freedom to move to adapt to the forces applied to the weathervaning vessel e.g. by wind, water 5 current and waves, and even though the weathervaning vessel is moored the movements of the weathervaning vessel may become quite considerable. The weathervaning vessel may for example be able to rotate such that it can have an optimal position with respect to wind, water current and/or waves to be as stable on the water as possible. In one embodiment the weathervaning 10 vessel and the mooring thereof is arranged such that the weathervaning vessel is always facing the wind. In one embodiment the turret system comprises a mooring chaintable, the weathervaning vessel is moored by lines connected to the mooring chaintable such that it can rotate fully or partly around the centre axis of the bearing and 15 swivel system, the mooring chaintable preferably is connected to or integrated with the bearing and swivel system, such that the weathervaning vessel in moored condition can weathervane around the centre axis of the bearing and swivel system while keeping the mooring chaintable substantially non-rotating with respect to the mooring to the seabed and/or subsea 20 structure(s). In one embodiment the mooring chaintable and the hang-off structure are connected to each other. Both the mooring chaintable and the hang-off structure are substantially non-rotating with respect to the mooring to the seabed and/or subsea structure(s), while the weathervaning vessel may or 25 may not weathervane. The connection between the mooring chaintable and the hang-off structure may be any kind of connection e.g. mechanical, chemical and/or physical, preferably a relatively stiff connection. The connection between the mooring chaintable and the hang-off structure may WO 2011/076210 PCT/DK2010/050324 8 be a direct connection or a connection via another element such as an axis shaft of the turret. In one embodiment the mooring chaintable and the hang-off structure are integrated with each other and comprise for example a totally or partly 5 common structure comprising one or more apertures for the flexible transporting unit to provide hang-off connecting points and totally or partly carrying the chaintable for mooring the weathervaning vessel. In one embodiment the bearing and the swivel system, the mooring chaintable and the hang-off structure are integrated with each other and 10 comprise for example a bearing and swivel system comprising a first and a second part rotatable with respect to each other and a totally or partly common structure comprising at least a part of the second part of the bearing and swivel system and comprising one or more apertures for the flexible transporting unit to provide hang-off connecting points and totally or partly 15 carrying the chaintable for mooring the weathervaning vessel. In one embodiment where the hang-off structure is at least partly integrated with the mooring chaintable, the hang-off structure comprises a first part and a second part where the first part is at least partly provided by the mooring chaintable - i.e. the first part is totally or partly provided by a common 20 structure. The second part of the hang-off structure is an extension of the first part and/or a part connected to the first part in a stiff connection. The second part thereby preferably provides a major part of the opposite part of the hang-off structure. In a preferred embodiment the second part extends in a direction away from 25 the hang-off vertical plane. Thereby the at least one hang-off connecting point is arranged in the second part of the hang-off structure and an even further reduction of the risk of damaging the one or more flexible transporting units will be obtained. By providing the second part to extend in a direction away from the hang-off vertical plane large freedom in designing the hang-off WO 2011/076210 PCT/DK2010/050324 9 system is obtained, and any limitation with respect to available horizontal and/or vertical space provides much less difficulties and further the risk that the flexible transporting unit will be subjected to high wear, damaging curvature and/or an over stretching is highly reduced. 5 In one embodiment the hang-off structure has a larger opposite part than the flexible transporting unit heading part. The flexible transporting unit heading part has a heading part length from the hang-off vertical plane and the opposite part has an opposite part length from the hang-off vertical plane. In one embodiment the opposite part length is 10 substantially longer than the heading part length, more preferably the opposite part length is at least about 10 % longer, such as at least about 20 % longer, such as at least about 30 % longer, such as at least about 50 % longer, such as at least about 75 % longer, such as at least about 100 % longer, such as at least about 125 % longer, such as at least about 150 % 15 longer, such as at least about 200 % longer, such as up to about least about 1000 % longer than the heading part length. All lengths from the hang-off vertical plane are measured as lengths perpendicular to the hang-off vertical plane. In one embodiment the opposite part length is at least about 0.5 m longer, 20 such as at least about 1 m longer, such as at least about 2 m longer, such as at least about 4 m longer, such as at least about 6 m longer, such as at least about 8 m longer, such as at least about 10 m longer, such as at least about 12 m longer, such as at least about 14 m longer, such as at least about 16 m longer, such as up to about least about 18 m longer than the heading part 25 length. The at least one hang-off connecting point has a hang-off distance to the hang-off vertical plane. In one embodiment the hang-off distance is at least about 1 m, such as at least about 2 m, such as at least about 4 m, such as at least about 6 m, such as at least about 8 m, such as at least about 10 m, WO 2011/076210 PCT/DK2010/050324 10 such as at least about 12 m, such as at least about 14 m, such as at least about 16 m, such as at least about 18 m, such as at least about 20 m, such as at least about 22 m, such as at least about 24 m, such as at least about 26 m, such as at least about 28 m, such as at least about 30 m. 5 All distances from the hang-off vertical plane are measured as distances perpendicular to the hang-off vertical plane. The subsea connection point may in principle be any kind of connection point to any kind of subsea structure e.g. a connection point connecting the flexible transporting unit to a subsea structure or directly to the seabed. The subsea 10 connection point may be a fixed connection or a non-fixed connection. Generally it is desired that the subsea structure has a mechanical influence on the flexible transporting unit, i.e. it provides some forces to the flexible transporting unit e.g. by providing the flexible transporting unit with a curvature. 15 In one embodiment the subsea connection point is a connection to a subsea structure in the form of a fixed structure, preferably fixed directly to the seabed, such as a riser tower and a subsea anchoring device for anchoring the one or more flexible transporting units. Examples of such fixed subsea structures are for example described in US 4,182,584 and US 7,040,841. 20 In one embodiment the subsea connection point is a connection to a subsea structure in the form of a subsea structure moored to a fixed structure, the subsea structure preferably comprises a buoyancy system, more preferably the subsea structure is a moored mid water arch. Such mid water arch is well known in the art. 25 In one embodiment the subsea connection point is a connection to a subsea structure held in position by the one or more flexible transporting units. The subsea structure may preferably comprise a buoyancy system, more preferably the subsea structure is a moored mid water arch or a mid water jacket.

WO 2011/076210 PCT/DK2010/050324 11 As indicated above buoyancy systems are well know in the art and include in practice any systems that can hold a part of the flexible transporting unit at a position above the seabed by means of having a lower density than the sea water. Buoyancy systems usually employ one or more elements comprising 5 low density materials or elements with enveloped air. In one embodiment the at least one flexible transporting unit comprises or is supported by a buoyancy system arranging the at least one flexible transporting unit in a wave configuration. In one embodiment the at least one flexible transporting unit is supported by 10 a buoyancy system in hog bend. In one embodiment the hang-off system comprises a moored buoy; the weathervaning vessel is arranged to weathervane around the moored buoy. In one embodiment the at least one flexible transporting unit comprises one or more of a flexible riser and an umbilical. The hang-off system may 15 preferably comprise a plurality of flexible transporting units, such as a plurality of risers and optionally at least one umbilical. In principle there is no upper limit to the number of flexible transporting units provided that the hang-off system can carry the weight and is designed sufficiently large to the number of flexible transporting units. 20 In one embodiment the hang-off system comprises at least 2, such as at least 3, such as at least 4, such as at least 5, such as at least 6, such as at least 7, such as at least 8, such as at least 9, such as at least 10, such as at least 15 flexible transporting units. Not all of the flexible transporting units need to have hang-off connecting points arranged in the opposite part of the hang-off 25 structure. In one embodiment it is desired that at least about half, such as at least about 60 %, such as at least about 70 %, such as at least about 80 %, such as about 90 %, such as preferably all of the flexible transporting units, each hangs-off from a hang-off connecting point to a subsea connection point, WO 2011/076210 PCT/DK2010/050324 12 providing a hang-off vertical plane extending through the centre axis of the bearing and swivel system, and the hang-off connecting point(s) is/are arranged in the opposite part of the hang-off structure. All percentages of flexible transporting units are rounded up to whole flexible 5 transporting units. Some flexible transporting units are more sensible to being damaged when subjected to high wear, bending with low curvature and/or stretching, whereas other flexible transporting units have a higher resistance. In general risers are more sensitive to high wear, bending with low curvature and/or 10 stretching than umbilicals, and large flexible transporting units are more sensitive to high wear, bending with low curvature and/or stretching than small flexible transporting units (large/small relates to the inner diameter of the flexible transporting units). In one embodiment the hang-off system comprises a plurality of flexible 15 transporting units in the form of risers or in the form of risers and umbilicals, at least about half, such as at least about 60 %, such as at least about 70 %, such as at least about 80 %, such as about 90 %, such at preferably all of the flexible transporting units in the form of risers, each hangs-off from a hang off connecting point to a subsea connection point, providing a hang-off 20 vertical plane extending through the centre axis of the bearing and swivel system, and the hang-off connecting point is arranged in the opposite part of the hang-off structure. In one embodiment the hang-off system comprises a plurality of flexible transporting units in the form of risers or in the form of risers and umbilicals, 25 at least about half, such as at least about 60 %, such as at least about 70 %, such as at least about 80 %, such as about 90 %, such at preferably all of the flexible transporting units in the form of risers having an inner diameter of at least about 3", such as at least about 4", such as at least about 5", such as at least about 6", such as at least about 8", such as at least about 10", such as WO 2011/076210 PCT/DK2010/050324 13 at least about 12", such as at least about 14", such as at least about 16", such as at least about 18", such as at least about 20", such as at least about 22", such as at least about 24", such as at least about 26", such as at least about 28", such as at least about 30", each hang-off from a hang-off 5 connecting point to a subsea connection point, providing a hang-off vertical plane extending through the centre axis of the bearing and swivel system, and the hang-off connecting point is arranged in the opposite part of the hang-off structure. In one embodiment the hang-off system comprises at most 1 flexible 10 transporting unit hanging-off from the flexible transporting unit heading part, preferably the hang-off system comprises at most 2, such as at most 3, such as at most 4, such as at most 5, such as at most 6, such as at most 7, such as at most 8 flexible transporting units hanging-off from the flexible transporting unit heading part. Any flexible transporting unit(s) hanging-off 15 from the flexible transporting unit heading part is preferably less sensitive to being damaged when subjected to high wear, bending with low curvature and/or stretching, than a flexible transporting unit hanging-off from the opposite part of the hang-off structure. In one embodiment the hang-off system comprises at most 1 flexible 20 transporting unit hanging-off from the flexible transporting unit heading part, preferably the hang-off system comprises at most 2, such as at most 3, such as at most 4, such as at most 5, such as at most 6, such as at most 7, such as at most 8 of the flexible transporting units hanging-off from the flexible transporting unit heading part, preferably the one or more flexible 25 transporting units hanging-off from the flexible transporting unit heading part comprise at least one umbilical and/or at least the flexible transporting units with a small inner diameter. In one embodiment where the hang-off system comprises a plurality of flexible transporting units each hanging-off from a hang-off connecting point 30 to a subsea connection point, providing a hang-off vertical plane extending WO 2011/076210 PCT/DK2010/050324 14 through the centre axis of the bearing and swivel system, the hang-off connecting point is arranged in the opposite part of the hang-off structure, it is desired that the hang-off vertical planes for the respective flexible transporting units differ from each other. Thereby the flexible transporting 5 units will not have an entirely uniform curvature, but they may for example be closer to each other at some length sections than in other length sections. It may also be possible to provide relatively sensitive flexible transporting units with additional length for an extra protection. In one embodiment where the hang-off system comprises a plurality of 10 flexible transporting units each hanging-off from a hang-off connecting point to a subsea connection point, providing a hang-off vertical plane extending through the centre axis of the bearing and swivel system, the hang-off connecting point is arranged in the opposite part of the hang-of structure, it is desired that the hang-off vertical planes for at least 2 or more of the flexible 15 transporting units are substantially identical. In one embodiment the hang-off vertical planes for all of the flexible transporting units are substantially identical. In this embodiment the flexible transporting units may be arranged in a substantially parallel structure and have a substantially identical curvature. 20 Alternatively the flexible transporting units may be arranged to be closer to each other at some length sections than in other length sections. It may also be possible to provide relatively sensitive flexible transporting units with additional length for an extra protection. In one embodiment at least 2, preferably all of the hang-off connecting points 25 are arranged in the opposite part of the hang-off structure. The turret system may be provided at any position inside or external to the weathervaning vessel. Depending on the application and the available space as well as the number and size of the flexible transporting units some positions of the turret system may be more preferable than other positions.

WO 2011/076210 PCT/DK2010/050324 15 In one embodiment the turret system is an external turret system, the bearing and swivel system is positioned forward of the weathervaning vessel, the bearing and swivel system preferably being positioned substantially in a vertical plane of a straight forward sailing direction of the weathervaning 5 vessel. In one embodiment the weathervaning vessel has a hull with a keel and the turret system is an external turret system, the bearing and swivel system positioned backward of the weathervaning vessel, the bearing and swivel system preferably being positioned substantially in a vertical plane comprising 10 the keel. The keel is the spine of the vessel, which runs along the bottom thereof and usually constitutes the lowermost part of the weathervaning vessel. In one embodiment the weathervaning vessel comprises a hull, a bow and a stern, and a length of the hull determined as the maximal length in a plane 15 perpendicular to the water line, the turret system is an internal turret system, positioned at a distance from the stern of up to about 95 %, such as at a distance from the stern up to about 5 % of the hull length, such as from about 5 % to about 10 % of the hull length, such as from about 10 % to about 15 % of the hull length, such as from about 15 % to about 20 % of the 20 hull length, such as from about 20 % to about 25 % of the hull length, such as from about 25 % to about 30 % of the hull length, such as from about 30 % to about 35 % of the hull length, such as from about 35 % to about 40 % of the hull length, such as from about 40 % to about 45 % of the hull length, such as from about 45 % to about 50 % of the hull length, such as 25 from about 50 % to about 55 % of the hull length, such as from about 55 % to about 60 % of the hull length, such as from about 60 % to about 65 % of the hull length, such as from about 65 % to about 70 % of the hull length, such as from about 70 % to about 75 % of the hull length, such as from about 75 % to about 80 % of the hull length, such as from about 80 % to 30 about 85 % of the hull length, such as from about 85 % to about 90 % of the WO 2011/076210 PCT/DK2010/050324 16 hull length, such as from about 90 % to about 95 % of the hull length from the stern. When determining the length of the hull bowsprit and other fittings should be excluded. 5 In one embodiment the turret system is an internal turret system, positioned at a distance from the stern of up to about 550 m, such as up to about 525 m, such as up to about 500 m, such as up to about 475 m, such as up to about 450 m, such as up to about 425 m, such as up to about 400 m, such as up to about 375 m, such as up to about 350 m, such as up to about 325 m, such as 10 up to about 300 m, such as up to about 275 m, such as up to about 250 m, such as up to about 225 m, such as up to about 200 m, such as up to about 175 m, such as up to about 150 m, such as up to about 125 m, such as up to about 100 m, such as up to about 75 m, such as up to about 50 m, such as up to about 25 m from the stern. 15 In one embodiment the turret system is applied in the aft of the vessel. The difference of aft and stern is that the aft is the inside (onboard) rearmost part of the vessel, while the stern refers to outside (off board) rearmost part of the vessel. In situations where the hang-off system comprises at least 2 flexible 20 transporting units with the hang-off connecting points arranged in opposite parts of the hang-off structure, the hang-off connecting points may be arranged in any pattern and with any mechanically possible distance. Generally it is desired that such 2 or more hang-off connecting points are arranged with a distance which is at least the average outer diameter of the 25 flexible transporting units. In one embodiment the hang-off connecting points are arranged in a pattern such that the hang-off vertical planes for the flexible transporting units are substantially identical. In one embodiment the hang-off connecting points are arranged in a side by side relation with a substantially equal distance to the substantially identical hang-off vertical planes. In one WO 2011/076210 PCT/DK2010/050324 17 embodiment the substantially identical distance to the substantially identical hang-off vertical planes is preferably at least about 2 m, such as at least about 4 m, such as at least about 6 m, such as at least about 8 m, such as at least about 10 m, such as at least about 12 m, such as at least about 14 m, 5 such as at least about 16 m, such as at least about 18 m, such as at least about 20 m, such as at least about 22 m, such as at least about 24 m, such as at least about 26 m, such as at least about 28 m, such as at least about 30 m. The invention also relates to a turret for a floating, moored weathervaning 10 vessel. The turret comprises a hang-off structure and a bearing and swivel system connected to or integrated with the hang-off structure. The bearing and swivel system comprises a centre axis. The hang-off structure of the turret has a hang-off body with a hang-off extent in a plane perpendicular to the centre axis, and an outer periphery of 15 the hang-off body comprising an asymmetrical shape. The hang-off body may preferably comprise a first and a second part, the periphery of the first part comprises a distance to the centre axis which is substantially uniform and the periphery of the second part comprises one or more distances to the centre axis which are longer than the substantially 20 uniform distance to the centre axis of the periphery of the first part. In one embodiment the turret comprises a mooring chaintable connected to or integrated with the bearing and swivel system. In one embodiment of the turret, the mooring chaintable and the hang-off structure are connected to each other. The connection between the mooring 25 chaintable and the hang-off structure may be any kind of connection e.g. mechanical, chemical and/or physical, preferably a relatively stiff connection. The connection between the mooring chaintable and the hang-off structure may be a direct connection or a connection via another element such as an axis shaft of the turret.

WO 2011/076210 PCT/DK2010/050324 18 In one embodiment of the turret the mooring chaintable and the hang-off structure are integrated with each other and comprise for example a totally or partly common structure comprising one or more apertures for the flexible transporting unit to provide hang-off connecting points and totally or partly 5 carrying the chaintable for mooring the weathervaning vessel. In one embodiment of the turret the bearing and the swivel system, the mooring chaintable and the hang-off structure are integrated with each other and comprise for example a bearing and swivel system comprising a first and a second part rotatable with respect to each other [where] and a totally or 10 partly common structure comprising at least a part of the second part of the bearing and swivel system and comprising one or more apertures for the flexible transporting unit to provide hang-off connecting points and totally or partly carrying the chaintable for mooring the weathervaning vessel. In one embodiment of the turret where the hang-off structure is at least 15 partly integrated with the mooring chaintable, the hang-off structure comprises a first part and a second part where the first part is at least partly provided by the mooring chaintable - i.e. the first part is totally or partly provided by a common structure. The second part of the hang-off structure is an extension of the first part and/or a part connected to the first part in a stiff 20 connection. The second part thereby provides the opposite part of the hang of structure. In a preferred embodiment of the turret the second part extends in a direction away from the hang-off vertical plane. Thereby the at least one hang-off connecting point is arranged in the second part of the hang-off 25 structure In one embodiment of the turret the hang-off body comprises a first and a second part, the periphery of the first part comprises a first short distance to the centre axis and the periphery of the second part comprises a second long distance to the centre axis which is longer than the first short distance to the WO 2011/076210 PCT/DK2010/050324 19 centre axis of the periphery of the first part, preferably the second long distance is at least about 0.5 m longer, such as at least about 1 m longer, such as at least about 2 m longer, such as at least about 4 m longer, such as at least about 6 m longer, such as at least about 8 m longer, such as at least 5 about 10 m longer, such as at least about 12 m longer, such as at least about 14 m longer, such as at least about 16 m longer, such as up to about least about 18 m longer than the first short distance to the centre axis of the periphery of the first part. In one embodiment of the turret the hang-off structure comprises at least one 10 hang-off point for hanging off a flexible transporting unit, the at least one hang-off point is arranged in the second part of the hang-off body, preferably in a distance from the centre axis of at least about 2 m, such as at least about 4 m, such as at least about 6 m, such as at least about 8 m, such as at least about 10 m, such as at least about 12 m, such as at least about 14 m, such 15 as at least about 16 m, such as at least about 18 m, such as at least about 20 m, such as at least about 22 m, such as at least about 24 m, such as at least about 26 m, such as at least about 28 m, such as at least about 30 m. BRIEF DESCRIPTION OF DRAWINGS 20 The invention will be explained more fully below in connection with a preferred embodiment and with reference to the drawings in which: FIG. 1 shows a schematical side view of a hang-off system of the invention. FIG. 2 shows the hang-off system of FIG. 1 in a schematic, partly transparent, 25 perspective view. FIG. 3 shows the hang-off system of FIG. 1 in a slightly perspective view.

WO 2011/076210 PCT/DK2010/050324 20 FIG. 4 shows a turret of a hang-off system seen in a schematic view from below. The figures are schematic and may be simplified for clarity. Throughout, the same reference numerals are used for identical or corresponding parts. 5 The hang-off system of FIG 1 comprises a floating, moored weathervaning vessel 3 comprising a turret 11. The turret comprises a bearing and swivel system 5, 9, a mooring chaintable 9 and a hang-off structure 9, 8. The bearing and swivel system 5, 9, a mooring chaintable 9 and a hang-off structure 9, 8 are integrated with each other in that they have the mooring 10 chaintable 9 as a common structure. The bearing and swivel system comprises a centre axis 4 which in FIG. 1 also provides a side view of a hang off vertical plane as explained in the following. The hang-off structure 9, 8 comprises a first part 9 in common with the swivel system 5, 9, and the mooring chaintable 9, and further the hang-off structure 9, 8 comprises a 15 second part 8 applied as an extension of the first part 9 but the second part 8 could as well have been connected to the first part. The second part 8 of the hang-off structure 9, 8 extends in a direction away from the hang-off vertical plane 4. The weathervaning vessel 3 is moored by lines 6 from the mooring chaintable 20 9 to the seabed. The hang-off system comprises 2 flexible transporting units 2. As explained above the hang-off system could comprise only one or it could comprise more than two. The flexible transporting units 2 hang from the second part of the hang-off structure 8. Each of the flexible transporting units 2 hang-off from a hang-off connecting point 7 to a subsea connection point 25 12 of a sub sea structure 1. A hang-off vertical plane 4 is defined for each flexible transporting unit 2, and in the example of FIG. 1 the hang-off vertical planes 4 for the two flexible transporting units are substantially identical and therefore only one can be seen. The hang-off vertical plane for a flexible transporting unit is found as follows: A vector extending from the subsea WO 2011/076210 PCT/DK2010/050324 21 connecting point 12 to the hang-off connection 7 point has a vertical and a horizontal component, the horizontal component is perpendicular to a hang off vertical plane extending through the centre axis of the bearing and swivel system. 5 The hang-off vertical plane 4 separates the hang-off structure 9, 8 in a flexible transporting unit heading part on the side of the hang-off vertical plane 4 horizontally closer to the subsea connecting point 12 (left side of the hang-off vertical plane 4) and an opposite part horizontally closer to the hang-off connecting point 7 (right side of the hang-off vertical plane 4). 10 The hang-off connecting point 7 is arranged in the second part of the hang off structure which constitutes the major part of the opposite part of hang-off structure. FIG. 2 shows the same hang-off system as FIG. 1 but in a schematic, partly transparent, perspective view. The turret system is an external turret system 15 with the external turret 11 connected near the bow 10 of the weathervaning vessel 3. FIG. 3 shows the same hang-off system as FIG. 1 but in a slightly perspective view. The shape of the subsea structure 1 is more visible and it can be seen that the flexible transporting units 2 follow a substantially parallel pattern. 20 FIG. 4 shows a turret of a hang-off system seen in a schematic view from below. The turret shown in FIG. 4 could be similar to the turret 11 of FIG. 1. The turret comprises a bearing and swivel where only an axis shaft 5 of the bearing and swivel system is visible, a mooring chaintable 9 and a hang-off structure 9, 8 integrated with the mooring chaintable 9 in that they have the 25 mooring chaintable 9 as a common structure. The hang-off structure 9, 8 comprises a first part 9 in common with the mooring chaintable 9, and further the hang-off structure 9, 8 comprises a second part 8 connected to the first part 9 or applied as an extension to the first part 9.

WO 2011/076210 PCT/DK2010/050324 22 In non-mounted condition apertures for mounting of the flexible transporting units are applied in the second part 8 of the hang-off structure 9, 8. In mounted condition, i.e. as applied in a hang-off system as it is shown in FIG. 4, the turret is moored by mooring lines 6 and two flexible transporting 5 units 2 are arranged to hang-off from hang-off connecting points 7 which are points along the periphery of the apertures closest to the centre axis 4 of the bearing and swivel system. In the example shown in FIG. 4 the flexible transporting units have identical hang-off vertical planes 4 and the flexible transporting units pass with a right angle through the hang-off vertical planes 10 4 as indicated with reference 10. Some preferred embodiments have been shown in the foregoing, but it should be stressed that the invention is not limited to these, but may be embodied in other ways within the subject-matter defined in the following claims.

Claims

1. A hang-off system comprising a floating, moored weathervaning vessel comprising a turret with a hang-off structure and at least one flexible 5 transporting unit hanging from the hang-off structure, the turret comprises a bearing and swivel system connected to or integrated with the hang-off structure, the bearing and swivel system comprises a centre axis, the flexible transporting unit hangs-off from a hang-off connecting point to a subsea connection point, a vector extending from the subsea connecting point to the 10 hang-off connection point has a vertical and a horizontal component, the horizontal component is perpendicular to a hang-off vertical plane extending through the centre axis of the bearing and swivel system, the hang-off vertical plane separates the hang-off structure in a flexible transporting unit heading part and an opposite part, the flexible transporting unit heading part 15 is horizontally closer to the subsea connection point than the opposite part, the hang-off connecting point is arranged in the opposite part of the hang-off structure.

2. A hang-off system as claimed in claim 1, wherein the weathervaning vessel has a hull and comprises an external turret system where the hang-off 20 structure is a topside hang-off structure fixed at a position beyond the hull of the weathervaning vessel.

3. A hang-off system as claimed in claim 1, wherein the weathervaning vessel has a hull and comprises an internal turret arranged inside and/or below the hull of the weathervaning vessel. 25

4. A hang-off system as claimed in any one of claims 1-3, wherein the weathervaning is moored by lines to the seabed and/or to one or more fixed structures such that it can rotate fully or partly around the centre axis of the bearing and swivel system. WO 2011/076210 PCT/DK2010/050324 24

5. A hang-off system as claimed in any one of claims 1 to 4, wherein the weathervaning comprises a mooring chaintable, the weathervaning vessel is moored by lines connected to the mooring chaintable such that it can rotate fully or partly around the centre axis of the bearing and swivel system, the 5 mooring chaintable preferably is connected to or integrated with the bearing and swivel system.

6. A hang-off system as claimed in claim 5, wherein the bearing and swivel system, the mooring chaintable and the hang-off structure are connected to each other, preferably the bearing and the swivel system, the mooring 10 chaintable and the hang-off structure are integrated with each other.

7. A hang-off system as claimed in claim 6, wherein the hang-off structure is at least partly integrated with the mooring chaintable, the hang-off structure preferably comprises a first part and a second part, the first part being at least partly provided by the mooring chaintable, the second part being an 15 extension of the first part and/or a part connected to the first part in a stiff connection, preferably the second part extends in a direction away from the hang-off vertical plane.

8. A hang-off system as claimed in claim 7, wherein the at least one hang-off connecting point is arranged in the second part of the hang-off structure. 20

9. A hang-off system as claimed in any one of claims 1 to 8, wherein the hang-off structure has a larger opposite part than the flexible transporting unit heading part, preferably the flexible transporting unit heading part has a heading part length from the hang-off vertical plane and the opposite part has an opposite part length from the hang-off vertical plane, the opposite part 25 length is substantially longer than the heading part length, more preferably the opposite part length is at least about 10 % longer, such as at least about 20 % longer, such as at least about 30 % longer, such as at least about 50 % longer, such as at least about 75 % longer, such as at least about 100 % longer, such as at least about 125 % longer, such as at least about 150 % WO 2011/076210 PCT/DK2010/050324 25 longer, such as at least about 200 % longer, such as up to about least about 1000 % longer than the heading part length.

10. A hang-off system as claimed in any one of claims 1 to 9, wherein the flexible transporting unit heading part has a heading part length from the 5 hang-off vertical plane and the opposite part has an opposite part length from the hang-off vertical plane, the opposite part length is at least about 0.5 m longer, such as at least about 1 m longer, such as at least about 2 m longer, such as at least about 4 m longer, such as at least about 6 m longer, such as at least about 8 m longer, such as at least about 10 m longer, such as at least 10 about 12 m longer, such as at least about 14 m longer, such as at least about 16 m longer, such as up to about least about 18 m longer than the heading part length.

11. A hang-off system as claimed in any one of claims 1 to 10, wherein the at least one hang-off connecting point has a hang-off distance to the hang-off 15 vertical plane, the hang-off distance is at least about 1 m, such as at least about 2 m, such as at least about 4 m, such as at least about 6 m, such as at least about 8 m, such as at least about 10 m, such as at least about 12 m, such as at least about 14 m, such as at least about 16 m, such as at least about 18 m, such as at least about 20 m, such as at least about 22 m, such 20 as at least about 24 m, such as at least about 26 m, such as at least about 28 m, such as at least about 30 m.

12. A hang-off system as claimed in any one of claims 1 to 11, wherein the subsea connection point is connecting the flexible transporting unit to a subsea structure or directly to the seabed, the subsea connection point may 25 be a fixed connection or a non-fixed connection.

13. A hang-off system as claimed in any one of claims 1 to 12, wherein the subsea connection point is a connection to a subsea structure in the form of a fixed structure, preferably fixed directly to the seabed, such as a riser tower, WO 2011/076210 PCT/DK2010/050324 26 a mid water arch, e.g. a mid water jacket and a subsea anchoring device for anchoring the one or more flexible transporting units.

14. A hang-off system as claimed in any one of claims 1 to 13, wherein the subsea connection point is a connection to a subsea structure moored to a 5 fixed structure, the subsea structure preferably comprises a buoyancy system, more preferably the subsea structure is a moored mid water arch.

15. A hang-off system as claimed in any one of claims 1 to 14, wherein the subsea connection point is connected to a subsea structure held in position by the at least one flexible transporting unit, the subsea structure preferably 10 comprises a buoyancy system, more preferably the subsea structure is a moored mid water arch or a mid water jacket.

16. A hang-off system as claimed in any one of claims 1 to 15, wherein the at least one flexible transporting unit comprises or is supported by a buoyancy system arranging the at least one flexible transporting unit in a wave 15 configuration.

17. A hang-off system as claimed in any one of claims 1 to 16, wherein the at least one flexible transporting unit is supported by buoyancy system in hog bend.

18. A hang-off system as claimed in any one of claims 1 to 17, wherein the 20 hang-off system comprises a moored buoy, the weathervaning vessel is arranged to weathervane around the moored buoy.

19. A hang-off system as claimed in any one of claims 1 to 18, wherein the at least one flexible transporting unit comprises one or more of a flexible riser, an umbilical, preferably the hang-off system comprises a plurality of flexible 25 transporting units, such as a plurality of risers and optionally at least one umbilical.

20. A hang-off system as claimed in any one of claims 1 to 19, wherein the hang-off system comprises at least 2, such as at least 3, such as at least 4, WO 2011/076210 PCT/DK2010/050324 27 such as at least 5, such as at least 6, such as at least 7, such as at least 8, such as at least 9, such as at least 10, such as at least 15 flexible transporting units, at least about half, such as at least about 60 %, such as at least about 70 %, such as at least about 80 %, such as about 90 %, such as preferably 5 all of the flexible transporting units, each hangs-off from a hang-off connecting point to a subsea connection point, providing a hang-off vertical plane extending through the centre axis of the bearing and swivel system, the hang-off connecting point is arranged in the opposite part of the hang-of structure. 10

21. A hang-off system as claimed in any one of claims 1 to 20, wherein the hang-off system comprises a plurality of flexible transporting units in the form of risers or in the form of risers and umbilicals, at least about half, such as at least about 60 %, such as at least about 70 %, such as at least about 80 %, such as about 90 %, such as preferably all of the flexible transporting units in 15 the form of risers, each hangs-off from a hang-off connecting point to a subsea connection point, providing a hang-off vertical plane extending through the centre axis of the bearing and swivel system, the hang-off connecting point is arranged in the part of the hang-of structure.

22. A hang-off system as claimed in any one of claims 1 to 21, wherein the 20 hang-off system comprises a plurality of flexible transporting units in the form of risers or in the form of risers and umbilicals, at least about half, such as at least about 60 %, such as at least about 70 %, such as at least about 80 %, such as about 90 %, such as preferably all of the flexible transporting units in the form of risers having an inner diameter of at least about 3", such as at 25 least about 4", such as at least about 5", such as at least about 6", such as at least about 8", such as at least about 10", such as at least about 12", such as at least about 14", such as at least about 16", such as at least about 18", such as at least about 20", such as at least about 22", such as at least about 24", such as at least about 26", such as at least about 28", such as at least 30 about 30", hang-off from a hang-off connecting point to a subsea WO 2011/076210 PCT/DK2010/050324 28 connection point, providing a hang-off vertical plane extending through the centre axis of the bearing and swivel system, the hang-off connecting point is arranged in the opposite part of the hang-of structure.

23. A hang-off system as claimed in any one of claims 1 to 22, wherein the 5 hang-off system comprises at most 1 flexible transporting unit hanging-off from the flexible transporting unit heading part, preferably the hang-off system comprises at most 2, such as at most 3, such as at most 4, such as at most 5, such as at most 6, such as at most 7, such as at most 8 flexible transporting units hanging-off from the flexible transporting unit heading part. 10

24. A hang-off system as claimed in any one of claims 1 to 23, wherein the hang-off system comprises at most 1 flexible transporting unit hanging-off from the flexible transporting unit heading part, preferably the hang-off system comprises at most 2, such as at most 3, such as at most 4, such as at most 5, such as at most 6, such as at most 7, such as at most 8 of the 15 flexible transporting units hanging-off from the flexible transporting unit heading part, preferably the one or more flexible transporting units hanging off from the flexible transporting unit heading part comprise at least one umbilical and/or at least the flexible transporting units with small inner diameter. 20

25. A hang-off system as claimed in any one of claims 1 to 24, wherein the hang-off system comprises a plurality of flexible transporting units, each hanging-off from a hang-off connecting point to a subsea connection point, providing a hang-off vertical plane extending through the centre axis of the bearing and swivel system, the hang-off connecting point is arranged in the 25 opposite part of the hang-of structure, and the hang-off vertical planes for the respective flexible transporting units differ from each other.

26. A hang-off system as claimed in any one of claims 1 to 24, wherein the hang-off system comprises a plurality of flexible transporting units, each hanging-off from a hang-off connecting point to a subsea connection point, WO 2011/076210 PCT/DK2010/050324 29 providing a hang-off vertical plane extending through the centre axis of the bearing and swivel system, the hang-off connecting point is arranged in the opposite part of the hang-of structure, and the hang-off vertical planes for at least 2 of the flexible transporting units are substantially identical, preferably 5 the hang-off vertical planes for all of the flexible transporting units are substantially identical.

27. A hang-off system as claimed in any one of claims 19 to 26, wherein at least 2, preferably all of the hang-off connecting points are arranged in the opposite part of the hang-off structure. 10

28. A hang-off system as claimed in any one of claims 1 to 27, wherein the turret system is an external turret system, the bearing and swivel system is positioned forward of the weathervaning vessel, the bearing and swivel system preferably being positioned substantially in a vertical plane of a straight forward sailing direction of the weathervaning vessel. 15

29. A hang-off system as claimed in any one of claims 1 to 27, wherein the weathervaning vessel comprises a hull with a keel and the turret system is an external turret system, the bearing and swivel system positioned backward of the weathervaning vessel, the bearing and swivel system preferably being positioned substantially in a vertical plane comprising the keel. 20

30. A hang-off system as claimed in any one of claims 1 to 27, wherein the weathervaning vessel comprises a hull, a bow and a stern, and a length of the hull determined as the maximal length in a plane perpendicular to the water line, the turret system is an internal turret system positioned at a distance from the stern of up to about 95 %, such as at a distance from the stern up 25 to about 5 % of the hull length, such as from about 5 % to about 10 % of the hull length, such as from about 10 % to about 15 % of the hull length, such as from about 15 % to about 20 % of the hull length, such as from about 20 % to about 25 % of the hull length, such as from about 25 % to about 30 % of the hull length, such as from about 30 % to about 35 % of the hull WO 2011/076210 PCT/DK2010/050324 30 length, such as from about 35 % to about 40 % of the hull length, such as from about 40 % to about 45 % of the hull length, such as from about 45 % to about 50 % of the hull length, such as from about 50 % to about 55 % of the hull length, such as from about 55 % to about 60 % of the hull length, 5 such as from about 60 % to about 65 % of the hull length, such as from about 65 % to about 70 % of the hull length, such as from about 70 % to about 75 % of the hull length, such as from about 75 % to about 80 % of the hull length, such as from about 80 % to about 85 % of the hull length, such as from about 85 % to about 90 % of the hull length, such as from about 10 90 % to about 95 % of the hull length from the stern.

31. A hang-off system as claimed in any one of claims 1 to 27, wherein the weathervaning vessel comprises a stern, the turret system is an internal turret system positioned at a distance from the stern of up to about 550 m, such as up to about 525 m, such as up to about 500 m, such as up to about 475 m, 15 such as up to about 450 m, such as up to about 425 m, such as up to about 400 m, such as up to about 375 m, such as up to about 350 m, such as up to about 325 m, such as up to about 300 m, such as up to about 275 m, such as up to about 250 m, such as up to about 225 m, such as up to about 200 m, such as up to about 175 m, such as up to about 150 m, such as up to about 20 125 m, such as up to about 100 m, such as up to about 75 m, such as up to about 50 m, such as up to about 25 m from the stern.

32. A hang-off system as claimed in any one of claims 1 to 31, wherein the hang-off system comprises at least 2 flexible transporting units, the hang-off connecting points of the bearing and swivel system being arranged in a 25 pattern such that the hang-off vertical planes for the flexible transporting units are substantially identical, the hang-off connecting points preferably being arranged in a side by side relation with a substantially equal distance to the substantially identical hang-off vertical planes, the substantially identical distance to the substantially identical hang-off vertical planes preferably being 30 at least about 2 m, such as at least about 4 m, such as at least about 6 m, WO 2011/076210 PCT/DK2010/050324 31 such as at least about 8 m, such as at least about 10 m, such as at least about 12 m, such as at least about 14 m, such as at least about 16 m, such as at least about 18 m, such as at least about 20 m, such as at least about 22 m, such as at least about 24 m, such as at least about 26 m, such as at least 5 about 28 m, such as at least about 30 m.

33. A turret for a floating, moored weathervaning vessel, the turret comprising a hang-off and a bearing and swivel system connected to or integrated with the hang-off structure, the bearing and swivel system comprises a centre axis, the hang-off structure has a hang-off body with a 10 hang-off extent in a plane perpendicular to the centre axis, and an outer periphery of the hang-off body comprising an asymmetrical shape.

34. A turret as claimed in claim 33, wherein the hang-off body comprises a first and a second part, the periphery of the first part comprises a distance to the centre axis which is substantially uniform and the periphery of the second 15 part comprises one or more distances to the centre axis which is longer than the substantially uniform distance to the centre axis of the periphery of the first part.

35. A turret as claimed in any one of claims 32 and 33, wherein the hang-off body comprises a first and a second part, the periphery of the first part 20 comprises a first short distance to the centre axis and the periphery of the second part comprises a second long distance to the centre axis which is longer than the first short distance to the centre axis of the periphery of the first part, preferably the second long distance is at least about 0.5 m longer, such as at least about 1 m longer, such as at least about 2 m longer, such as 25 at least about 4 m longer, such as at least about 6 m longer, such as at least about 8 m longer, such as at least about 10 m longer, such as at least about 12 m longer, such as at least about 14 m longer, such as at least about 16 m longer, such as up to about least about 18 m longer than the first short distance to the centre axis of the periphery of the first part. WO 2011/076210 PCT/DK2010/050324 32

36. A turret as claimed in any one of claims 34 and 35 wherein the, wherein the hang-off structure comprises at least one the hang-off point for hanging off a flexible transporting unit, the at least one hang-off point is arranged in the second part of the hang-off body, preferably in a distance from the centre 5 axis of at least about 2 m, such as at least about 4 m, such as at least about 6 m, such as at least about 8 m, such as at least about 10 m, such as at least about 12 m, such as at least about 14 m, such as at least about 16 m, such as at least about 18 m, such as at least about 20 m, such as at least about 22 m, such as at least about 24 m, such as at least about 26 m, such as at least 10 about 28 m, such as at least about 30 m.