- 1 LOADING SYSTEM [0001] The present invention relates to a loading system for transferring at least one medium between a first installation and a floating vessel, a retrieval system for use with such a loading system and a method for connecting the loading system to a vessel. [0002] A number of systems exist for transferring a medium between two units offshore, where one of the units is often a subsea installation, a floating storage unit or a platform and a transport vessel. [0003] Several of these systems have devices whereby, when the vessel is not in use, a transfer hose between the installation and the vessel is positioned partly located on the seabed. Having the hose located in such a position causes severe wear on some parts of the hose, resulting in the need to monitor the wear and carry out regular replacements of parts of the hose. These known loading systems are also often arranged so as to enable the loading vessel to rotate freely according to the weather when it is connected. In some systems this is accomplished by having a swivel system close to the point of attachment between the hose and the vessel, such as a swivel system round the attachment of the hose to the vessel or as a submerged buoy housed in a receiving station in the vessel where the actual buoy or the end of the hose that is attached to the vessel comprises swivel devices, described, for example, in US 6,688,348. In this case either the vessel must have a swivel system or alternatively a relatively heavy buoy/hose end will be required which has to be pulled up into the vessel by a swivel. The flexible hose, however, offers rather more limited flexibility. Another known system is the arrangement of a swivel system at the anchor point of the hose to the seabed. This provides greater flexibility since the axis of rotation is located at the seabed, but with such a solution all the dynamic elements are on the seabed with the problems this entails with regard to maintenance and repair. There are also systems which have anchored towers with swivel devices located above the surface of the water. However, these are exposed to wind and weather and represent an obstruction to traffic on the water.
-2 Summary of the Invention [0004] In accordance with the invention, there is provided a transfer system between a first installation and a vessel comprising a flexible transfer element and a retrieval arrangement for said flexible transfer element, which transfer element in an installed state and not in use, is arranged freely suspended from a first transfer element in a body of water with a substantially vertical orientation and with a free end comprising connecting devices for connection to the vessel at a distance from a seabed, wherein the transfer system comprises a guide element which is mounted slidably along the transfer element, a recovery line connected to the guide element and the transfer element at one end, and at least one marker buoy connected to the recovery line at a second end thereof. [0005] In one embodiment, the guide element comprises buoyancy devices, and the retrieval arrangement further comprises a guide line, where the recovery lines are secured to the free end of the transfer element, the guide line is secured to the transfer element near the free end, to the recovery line at a distance from an attachment point between the recovery line and the free end of the transfer element and where the guide element is further mounted slidably along the guide line between its two attachment points. [0006] In one embodiment, the guide element comprises weight elements and the recovery line is secured to the guide element, where the arrangement further comprises a releasable holding device for securing the guide element when the system is not in use, mounted at a distance from the free end of the transfer element. [0007] In another aspect, there is provided a method for connecting a transport system as described above with a loading system for transferring at least one medium between a first installation and a floating vessel, comprising an anchoring device which can be fixed relative to a seabed, at least one elongated first transfer element, normally vertically orientated in an installed state and connected to the anchoring device, comprising devices for connection to the first installation, a buoyancy system for ensuring that the first transfer element is under tension in an installed state, at least one flexible second transfer element arranged in the extension of the first transfer element, where a swivel arrangement is -3 mounted between the first and second transfer element, which swivel arrangement comprises a first swivel unit with an axis of rotation substantially parallel to a longitudinal axis of the elongated first transfer element, and a second swivel unit with a second axis of rotation oriented substantially perpendicularly relative to the first axis of rotation, where a free end of the second transfer element comprises devices for connection to the floating vessel and in an installed state when the system is not being used are located freely suspended in the body of water and has an orientation substantially parallel to the first transfer element; wherein the vessel arrives at the loading system location and picks up the marker buoy, whereupon the vessel reverses away from the loading system and begins to pull in the recovery line which is attached to the marker buoy, whereupon the free end of the flexible transfer element is pulled towards the vessel and connected thereto. Brief Description of the Drawings [0027] The invention will now be explained in greater detail with reference to the attached figures, in which: [0028] Figs. 1A-B illustrate the principles of an installed loading system according to the invention when in use and when not in use. [0029] Fig. 1C illustrates an alternative embodiment of an installed loading system when it is not in use. [0030] Fig. 2 illustrates a variant of a loading system in a little more detail. [0031] Fig. 3 illustrates a buoyancy system and the swivel arrangement. [0032] Fig. 4 illustrates a possible variant for connection of the swivel arrangement's parts to the first transfer element. [0033] Figs. 5A-B illustrate a connection of the second transfer element to the swivel -4 arrangement, viewed from the side and from above. [0034] Fig. 6 illustrates a first retrieval arrangement. [0035] Fig. 7 illustrates a second retrieval arrangement. [0036] Fig. 8 illustrates five sequences for use of the retrieval arrangement illustrated in fig. 7. [0037] Fig. 9 illustrates an alternative guide element and [0038] Fig. 10 illustrates a third retrieval arrangement. [0039] In figs. 1A and B a loading system according to the invention is illustrated during use and when not in use. The loading system comprises an anchoring device 5 located on a seabed 1 under a body of water with a surface 2. To the anchoring device 5 is connected a first elongated transfer element 6 which is arranged substantially vertically in the body of water. At the top of the first transfer element 6 is mounted a buoyancy system 10 with the result that the first transfer element 6 is always under tension. At the top of the first transfer element 6 there is also mounted a swivel arrangement 15. A second transfer element 7 is connected via the swivel arrangement 15 with the first transfer element 6. When in a connected state, the second transfer element which is flexible will be connected to a vessel 3 at the surface as indicated in fig. 1A and when it 7 is not connected it will be freely suspended in the body of water substantially parallel to the first transfer element 6. The first transfer element 6 also comprises shock-protection devices 8 in the area of the first transfer element 6 which is located near a free end of the second transfer element 7 in a disconnected state. [0040] In fig. 1C an alternative loading system is illustrated when it is not in use. The loading system is anchored to the seabed 1 via an anchoring device 5. To the anchoring device 5 is secured a first transfer element 6, which at the end facing away from the seabed -5 1 is joined to the flexible second transfer element 7 via a swivel arrangement 15, mounted in connection with a buoyancy system 10. The first transfer element 6 also comprises shock-protection devices 8, thus preventing a free end of the second transfer element 7 comprising devices 14 for connection to a vessel during use from knocking against the first transfer element 6. A retrieval arrangement 19 for recovering the free end of the second transfer element 7 is also indicated in the figure. In this case the first installation 4 comprises a floating vessel 400, which may be a drilling vessel, production vessel, interim storage vessel or other vessel floating on the surface 2. From this vessel 400 extends a line 401 floating in the body of water for transferring media, which line 401 is also equipped with buoyancy elements 402 which keep it floating in a stable manner in the body of water without being exposed to more stress than necessary. This line 401 is connected with the loading system and the first transfer element 6 by connecting devices 13. The connecting devices 13 are mounted at a good distance from the seabed 1, thereby avoiding the need for the line 401 to be pulled right down to a seabed in cases where the depth of the water, for example, is over 1000 metres. The connecting devices 13, however, are mounted vertically below a position for the free end of the flexible second transfer element 7, thereby preventing them from getting in each other's way. In a variant the first transfer element 6 may also be terminated at the connecting devices 13 and secured to the anchoring device 5 close to this point, as an alternative to passing it all the way down to the seabed. A transfer element may also be envisaged with several connecting devices which may be mounted at the seabed or at a distance therefrom or a combination thereof. [0041] Fig. 2 illustrates a system corresponding to that in fig. 1 but in rather more detail. The first transfer element 6 is connected to a first installation 4 via a connecting device 13 in connection with the anchoring device 5. The first transfer element 6 further comprises a flexible coupling 9 which permits a longitudinal axis of the first transfer element 6 to form an angle of around 15 degrees with a vertical axis. In this embodiment the shock-protection devices comprise both a mat structure 8' and a distance element 8" in order to prevent contact between the first transfer element 6 and a free end of the second transfer element 7. The buoyancy system 10 comprises a buoyancy element 11 mounted at the top of the first transfer element 6. The top of this buoyancy element forms a base 12 for the swivel -6 arrangement 15. The swivel arrangement 15 comprises a first swivel unit 16 with an axis of rotation substantially parallel to the longitudinal axis of the first transfer element 6, and a second swivel unit 17 with an axis of rotation substantially perpendicular relative to the axis of rotation of the first swivel unit 16. The second transfer element 7 is connected to the outlet of the second swivel unit 17 and via its flexibility is either connected to a vessel 3 with devices 14 for connection to equipment aboard the vessel or suspended substantially parallel to the first transfer element 6 when it is not in use, both variants being indicated in the figure. Furthermore, a coupling 27 is provided between the second swivel unit 17 and the second transfer element 7. Couplings 27 are also provided between the first transfer element 6 and the first swivel unit 16 and between the swivel units 16, 17. This provides the possibility of disconnecting these parts and taking the parts requiring repair up to the surface. The system also comprises sensors 41 for detection of, for example, relative position. Flexural stiffeners 40 may also be mounted in connection with the coupling 27 at the point of attachment of the flexible second transfer element 7 to a fixed part which in this case is represented by the second swivel unit 17. The flexural stiffener 40 extends from the coupling 27 for some length beyond the second transfer element 7. [0042] In fig. 3 the buoyancy system 10 and the swivel arrangement 15 are depicted in a more schematic way. Here it can be clearly seen that the axis of rotation for the first swivel unit 16 is perpendicular relative to the axis of rotation of the second swivel unit 17. A rigid pipe piece is also mounted between the outlet of one swivel unit and the inlet of the second swivel unit, since the outlet and the inlet have different orientation. [0043] Fig. 4 illustrates a variant where the swivel arrangement 15 is connected to an upper end of the first transfer element 6. The left side of the figure shows it being connected and the right side shows it in a connected condition. In this case the buoyancy system 10 comprises buoyancy elements 11' mounted on the upper end of the first transfer element 6, forming a part of a base 12 for the swivel arrangement 15. The system is provided with a rigid pipe element 28 between the swivel units 16, 17, where the first swivel unit has a substantially vertical axis of rotation and the second swivel unit 17 has a substantially horizontal axis of rotation, the swivel units 16, 17 being locked against -7 rotation during the installation. At the outlet of the second swivel unit 17 the swivel arrangement comprises an additional pipe element 28' which is terminated against a coupling 27 against the flexible second transfer element 7. It can also be seen that the flexible second transfer element 7 is provided with a flexural stiffener 40 in the area of connection with the coupling 27. The system also comprises lifting lugs 29 for attaching lifting wires 30, and guide elements 31, in the form of pins and funnels, and guide wires 32 for correct insertion of the elements in the coupling 27 between the swivel arrangement 15 and the top of the first transfer element 6. [0044] Where it is only a case of repairing the second flexible transfer element 7, the first and second swivel units 16, 17 can be locked by means of locking devices 18, thus preventing them from rotating freely, as indicated in figs. 5A and B. In this case too guide wires 32 may be employed for correct insertion of the parts of the coupling 27 between the second transfer element 7 and the swivel arrangement 15. [0045] Fig. 6 illustrates a first variant of a retrieval arrangement 19. A guide element 20 is arranged slidably along the flexible second transfer element 7. In this embodiment the guide element 20 comprises weight elements 26 and is connected to a recovery line 21. The recovery line 21 is connected at its other end to one or more marker buoys 22 when the system is not in use. The vessel 3 will pick up the marker buoy 22. A releasable holding device 24 at the attachment of the flexible transfer element 7 to the swivel arrangement 15 will release guide element 20 which on account of its weight will fall down over the second transfer element 7 to the free end thereof, whereupon, by winching in the recovery line 21, the vessel can pick up the free end with the connecting devices 14 and connect the free end to the vessel 3. When the vessel is released, the process is reversed. [0046] An alternative retrieval arrangement is illustrated in fig. 7 and the five sequences in fig. 8. The guide element 20 is mounted slidably on the flexible transfer element 7. In this case the recovery line 21 is secured directly to the free end of the flexible transfer element 7. Furthermore, a guide line 23 is secured to the end of the flexible transfer -8 element 7 and a point on the recovery line 21 at a distance therefrom. The guide element 20 is connected slidably to the guide line 23. When a vessel has picked up the marker buoy 22 and begins to winch in the recovery line while reversing away from the loading system, the guide line 23 and the guide element 20 with their built-in buoyancy will guide the lifting point between the recovery line 21 and the flexible transfer element 7 to the end of the flexible transfer element 7, as illustrated in the sequences 1 to 5. [0047] Fig. 9 illustrates a possible design of a guide element for use in the retrieval arrangement depicted in figs. 7 and 8. The flexible transfer element 7 will normally be composed of several elements and the junction of these elements will usually have a slightly smaller diameter than the rest of the transfer element 7. In order to prevent the guide element 20 becoming jammed when sliding over these portions of the transfer element 7, it is preferably provided with a length that permits an end of the guide element 20 to abut against the transfer element 7 on a side of the portion with smaller diameter, before the opposite end of the guide element 20 comes to the portion with smaller diameter. For a guide element with built-in buoyancy, this can be accomplished by providing the guide element 20 with a plurality of buoyancy devices 25 in the form of balls provided rotatingly relative to a frame 250. This also helps to provide good sliding conditions between the guide element 20 and the transfer element 7. As illustrated, the guide element 20 may also include a caster 251 to facilitate the running of the guide line 23. [0048] The retrieval arrangement according to the invention with a guide element running along the flexible transfer element will also have the effect of cleaning fouling off the flexible transfer element. [0049] An alternative retrieval arrangement is illustrated in fig. 10, where the flexible second transfer element 7 is shown connected to a swivel arrangement 15, with the rest of the loading system not illustrated. A recovery line 21 is connected to the free end of the second transfer element 7. The recovery lines 21 extend from the free end down to a portion 25 of the recovery lines 21 close to or located on the seabed 1, whereupon it -9 extends up to a marker buoy 22 at the surface 2, thus enabling the recovery line to be picked up by a vessel which is to be connected to the loading system. The portion 25 of the recovery lines is a weighted portion of the lines with greater deadweight than the rest of the line. The weight may be included in the lines, be provided by an external weight element, be woven into the lines or arranged on the lines in another way. By means of such a device the line can be handled by winches on board a vessel without having to stop the recovery/deployment process in order to disconnect an anchor, for example, from the recovery line. This is an advantageous solution. [0050] The invention has now been explained with reference to special embodiments illustrated in the attached figures. A person skilled in the art will appreciate that changes and modifications may be made to these embodiments which fall within the scope of the invention as defined in the attached claims. The loading system will also be equipped with the necessary shut-off valves, corrosion protection, etc. which will be understood by a skilled person. [0051] The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as, an acknowledgement or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates. [0052] Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" or 'comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.