WO2022050935A1

WO2022050935A1 - Systems and methods for adjusting the length of tension leg platform tethers

Info

Publication number: WO2022050935A1
Application number: PCT/US2020/048934
Authority: WO
Inventors: Qi Xu; Ken TURNER; Myoung Choi; Zaqie REZA; Andrew Kyriakides
Original assignee: Modec, Inc.
Priority date: 2020-09-01
Filing date: 2020-09-01
Publication date: 2022-03-10
Also published as: JP2023090703A; JP7307092B2; EP4208387A1; WO2022050935A8; JP2023501836A

Abstract

A link plate system for a connecting a tether to a TLP via a first pin and a second pin. The link plate system may include a plurality of link plates. Each link plate may include a first hole sized to receive the first pin that connects the link plate to the TLP and a second hole sized to receive the second pin that connects the link plate to the tether. The length of each link plates may he sized and the holes of each link plate may be positioned and sized such that a distance between the first pin and the second pin is different for each link plate so as to allow adjustment of the connection length between the TLP and the tether.

Description

Systems and Methods for Adjusting the Length of Tension Leg Platform Tethers BACKGROUND [0001] This section is intended to provide relevant background information to facilitate a better understanding of the various aspects of the described embodiments. Accordingly, it should be understood that these statements are to be read in this light and not as admissions of prior art. [0002] A tension leg platform (TLP) is a floating platform anchored to a foundation on the seabed by mooring elements, often called tension legs, tethers, or tendons. The tendons are maintained in tension at all times by ensuring net positive TLP buoyancy under all environmental conditions. The tendons stiffly restrain the TLP against vertical offset, essentially preventing heave, pitch and roll, yet they compliantly restrain the TLP against lateral offset, allowing limited surge, sway and yaw. Each tether requires a length adjustment so that all the tethers can be equally tensioned under various uncertainties, such as variation in pile top elevation and tether length. [0003] The ability to adjust the length of a tether is crucial for tether system integrity. In the traditional TLP tether design, the length adjustment mechanism is achieved by a length adjustment joint (LAJ) and a segmented grip with matching grooves, which can lock the grooved joint at any position. Without the LAJ, tethers will be under the risk of over tension, which may lead to tether break, or under tension, which may lead to tether buckling and/or snatching load depending on type of tether main body. The conventional length adjustment mechanism involves a large forged cylindrical structure and hydraulically actuated segmented receptacle. However, the LAJ is a relatively expensive component, making it unsuitable for some TLP projects. BRIEF DESCRIPTION OF THE DRAWINGS [0004] Embodiments of the systems for adjusting the length of tension leg platform tethers are described with reference to the following figures. The same numbers are used throughout the figures to reference like features and components. The features depicted in the figures are not necessarily shown to scale. Certain features of the embodiments may be shown exaggerated in scale or in somewhat schematic form, and some details of elements may not be shown in the interest of clarity and conciseness. [0005] FIG. 1 is an isometric view of a tension leg platform (TLP), according to one or more embodiments; [0006] FIG. 2 is a diagram of a TLP tether assembly, according to one or more embodiments; [0007] FIG. 3 is a 3D perspective view of the top connector assembly of FIG. 2; and [0008] FIG.4 is a plan view of a link plate system for use with the top connector assembly of FIG.3. DETAILED DESCRIPTION [0009] The present disclosure describes a system for adjusting the length of tension leg platform (TLP) tethers. The system provide an alternative to costly length adjustment joints typically used to adjust the length of tethers. Additionally, the system provides fine adjustment of each tether to ensure that the load due to maintaining the position of the TLP is spread evenly between all tethers. [0010] FIG.1 is an isometric view of a tension leg platform (TLP) 100, according to one or more embodiments. The TLP 100 includes a base 102 made up of columns 104 connected via ring pontoons 106. The columns 104 are coupled to tethers 108 that are anchored to piles (not shown) driven into the seafloor 110, as described in more detail below. The tethers 108 prevent vertical motion of the TLP 100, such as heave, pitch, and roll, while allowing limited horizontal motion, such as surge, sway, and yaw. The lengths of the tethers 108 are sized such that the load due to restraining the TLP is spread equally between the tethers 108. [0011] In the illustrated embodiment, the base 102 supports a wind turbine 112 used to generate electrical power. However, the base 102 may also support a platform, such as an oil and gas production platform or other types of offshore platforms, suitable for use with a TLP. [0012] Turning now to FIG.2, FIG.2 is a diagram of a TLP tether assembly 200, according to one or more embodiments. The TLP tether assembly 200 includes a tether 202 that couples the hull 204 of the TLP to a pile 206 or other foundation structure on the sea floor 208 via an upper connector assembly 210 and a bottom connector assembly 212. The length of the tether 202 is based on the estimated distance between the pile 206 and the hull 204. In at least one embodiment, the tether 202 is made of a synthetic material. In other embodiments, the tether 202 may be made out of composite material, steel, or other suitable materials known to those skilled in the art. [0013] As shown in FIG.3, the top connector assembly 210 includes a mounting bracket 300, a dual axis joint 302, a pull head 304, a link plate 306, and an H-link 308. Certain tethers may also optionally include a coupler 310. Further, H-link 308 may alternatively be a Y-link for certain tethers. The mounting bracket 300 is coupled to both the hull 204 and the dual axis joint 302 to couple the upper connector assembly 210 to the hull 204 via an upper connector pin 312. The dual axis joint 302, in turn, is further coupled to the link plate 306 via an upper link plate pin 314. The dual axis joint allows the upper connector assembly 210 and, therefore, the tether 202 to rotate about the upper connector pin 312 and the upper link plate pin 314, while preventing vertical movement of the upper connector assembly 210. [0014] The link plate 306 is further coupled to the H-link 308 via a lower link plate pin 316 and the H-link 308 is further coupled to the thimble 310 via an H-link pin 318. The thimble 310 is further coupled to the tether 202 (not shown in FIG.3). The H-link 308 allows for additional rotation about both the lower link plate pin 316 and the H-link pin 318. However, some embodiments may omit the H-link 308 and the thimble 310 may be coupled to the link plate 306 via the lower link plate pin 316. [0015] The link plate 306 is used to vary the connection length between the hull 204 and the tether 202, as discussed in more detail below with reference to FIG. 4. This allows compensation for the difference between the length of the tether 202, which is based on the estimated distance between the pile 206 and the upper connector location on the hull 204, and the actual distance between the pile 206 and the upper connector location on the hull 204. [0016] Although FIG. 3 shows an upper connector assembly 210, the bottom connector assembly 212 may include the same components and function as described above with reference to FIG.3; however, the mounting bracket 300 of the bottom connector assembly 212 is coupled to the pile 206. [0017] Referring now to FIG.4, FIG.4 shows link plate assemblies 400, 402, 404 for use with the upper connector assembly 210 of FIG.3. Each link plate 406, 408, 410 of the link plate assemblies 400, 402, 404 has an upper hole 412 that the upper link plate pin 314 extends through to connect the link plate 406, 408, 410 to the dual axis joint 302. The link plates 406, 408, 410 also have a lower hole 414 that the lower link plate pin 316 extends through to connect the link plate to the H-link 308 shown in FIG.3 or Y-link. [0018] The holes 412, 414 of each link plate are positioned and sized such that the distance 416 between the upper link plate pin 314 and the lower link plate pin 316 is different for each link plate 406, 408, 410. The distance 416 between the upper link plate pin 314 and the lower link plate pin 316 may be varied via the holes 412, 414 to allow for adjustment of the distance between the upper link plate pin 314 and the lower link plate pin 316 and thus the connection length of the tether 202. [0019] Additionally, the lower hole 414 may be slotted and a pin sleeve 418 may be disposed within the lower hole 414 and surrounding the lower link plate pin 316, as shown in FIG. 4 and described below. The distance 420 between the lower link plate pin 316 and the lower end 422 of the lower hole 414 may be varied via the pin sleeve 418 to allow for adjustment. Accordingly, the link plates shown in FIG. 4 may be used to vary the connection length between the tether 202 and the pile 206. [0020] The pin sleeve 418 may be asymmetric and the hole 424 through the sleeve offset, as shown in FIG. 4, so as to allow different connection lengths with the same link plate 406, 408, 410. The offset hole 424 in the pin sleeve 418 allows the pin sleeve 418 to be rotated 180° between two positions to change the distance 420 between the lower link plate pin 316 and the lower end 422 of the lower hole 414, providing for further adjustment of the distance 416 between the upper link plate pin 314 and the lower link plate pin 316. [0021] While FIG.4 depicts three link plates 406, 408, 410, the upper connector assembly 210 only utilizes a single link plate 406, 408, 410, as shown in FIG. 3, at a time depending on the desired connection length. In order to determine the correct link plate 406, 408, 410, the as-built connection length is determined and the link plate 406, 408, 410 is selected for the connection length. The pile end of the tether 202 is first connected to the pile 206 via the bottom connector assembly 212. The upper end of the tether is then pulled towards the TLP and the upper connector assembly 210 is assembled to connect the tether to the TLP. If needed, a pin sleeve 418 may also be selected for a connection length and installed within the link plate 406, 408, 410 to allow for further adjustment of the connection length. [0022] Alternatively, this process may be reversed and the upper end of the tether may first be connected to the hull 204 via the upper connector assembly 210. The pile end of the tether 202 is then connected to the pile 206 with the bottom connector assembly 212 as described with the upper connector assembly 210. [0023] Further examples include: [0024] Example 1 is link plate system for a connecting a tether to a TLP via a first pin and a second pin. The link plate system includes a plurality of link plates. Each link plate includes a first hole sized to receive the first pin that connects the link plate to the TLP and a second hole sized to receive the second pin that connects the link plate to the tether. The length of each link plates is sized and the holes of each link plate are positioned and sized such that a distance between the first pin and the second pin is different for each link plate so as to allow adjustment of the connection length between the TLP and the tether. [0025] In Example 2, the embodiments of any preceding paragraph or combination thereof further include wherein the second holes are further sized to receive any one of a plurality of pin sleeves sized to receive the second pin, each pin sleeve of the plurality of pin sleeves allowing for a different distance between the second pin positioned within the pin sleeve and a lower end of the second hole. [0026] In Example 3, the embodiments of any preceding paragraph or combination thereof further include wherein at least one the plurality of pin sleeves is asymmetric and positionable so as to allow different two different connection lengths with the same pin sleeve. [0027] Example 4 is a top connector assembly for connecting a TLP to a tether. The top connector assembly includes a dual axis joint configured to couple to the TLP, a link plate including a first hole and a second hole, a first pin extending through the first hole to couple the dual axis joint to the link plate, and a second pin extending through the second hole to couple the link plate to the tether. A distance between the first pin and the second pin is based on a connection length between the TLP and the tether. [0028] In Example 5, the embodiments of any preceding paragraph or combination thereof further include a pin sleeve disposed within the second hole and sized to receive the second pin. The distance between the second pin positioned within the pin sleeve and a lower end of the second hole is based on the connection length. [0029] In Example 6, the embodiments of any preceding paragraph or combination thereof further include wherein at the pin sleeve is asymmetric and positionable so as to allow two different connection lengths with the same pin sleeve. [0030] Example 7 is tether assembly for connecting a TLP to a pile. The tether assembly includes a tether having an upper end and a pile end and a connector. The connector includes a dual axis joint configured to couple to one of either the TLP or the pile, a link plate including a first hole and a second hole, a first pin extending through the first hole to couple the dual axis joint to the link plate, and a second pin to couple the link plate to the tether, the second pin extending through the second hole. A distance between the first pin and the second pin is based on a connection length between either one of the tether and the TLP or the tether and the pile. [0031] In Example 8, the embodiments of any preceding paragraph or combination thereof further include wherein the connector further includes a pin sleeve disposed within the second hole that receives the second pin. The distance between the second pin positioned within the pin sleeve and a lower end of the second hole is based on the connection length. [0032] In Example 9, the embodiments of any preceding paragraph or combination thereof further include wherein at the pin sleeve is asymmetric and positionable so as to allow two different connection lengths with the same pin sleeve. [0033] In Example 10, the embodiments of any preceding paragraph or combination thereof further include wherein the connector is a top connector configured to couple the TLP to the tether. [0034] In Example 11, the embodiments of any preceding paragraph or combination thereof further include wherein the connector is a bottom connector configured to couple the pile to the tether. [0035] In Example 12, the embodiments of any preceding paragraph or combination thereof further include wherein the tether includes polyester. [0036] Example 13 is a TLP. The TLP includes a hull, a pile, a tether having an upper end and a pile end, a top connector coupling the upper end of the tether to the hull at a top connector location on the hull, and a bottom connector coupling the pile end of the tether to the pile at a bottom connector location on the pile. At least one of the top connector and the bottom connector includes a dual axis joint configured to couple to one of either the TLP or the pile, a link plate including a first hole and a second hole, a first pin extending through the first hole to couple the dual axis joint to the link plate, and a second pin extending through the second hole to couple the link plate to one of either the upper end of the tether or the pile end of the tether. A distance between the first pin and the second pin is based on a connection length between either one of the tether and the TLP or the tether and the pile. [0037] In Example 14, the embodiments of any preceding paragraph or combination thereof further include wherein the top connector includes the dual axis joint coupled to the TLP at the top connector location, the link plate, the first pin extending through the first hole to couple the dual axis joint to the link plate, the second pin extending through the second hole to couple the link plate to the upper end of the tether. The distance between the first pin and the second pin is based on a connection length between the tether and the TLP. [0038] In Example 15, the embodiments of any preceding paragraph or combination thereof further include wherein the bottom connector includes the dual axis joint coupled to the pile at the bottom connector location, the link plate, the first pin extending through the first hole to couple the dual axis joint to the link plate, and the second pin extending through the second hole to couple the link plate to the pile end of the tether. The distance between the first pin and the second pin is based on a connection length between the tether and the pile. [0039] In Example 16, the embodiments of any preceding paragraph or combination thereof further include wherein the at least one of the top connector and the bottom connector further includes a pin sleeve disposed within the second hole that receives the second pin. The distance between the second pin positioned within the pin sleeve and a lower end of the second hole is based on the connection length. [0040] In Example 17, the embodiments of any preceding paragraph or combination thereof further include wherein at the pin sleeve is asymmetric and positionable so as to allow two different connection lengths with the same pin sleeve. [0041] In Example 18, the embodiments of any preceding paragraph or combination thereof further include wherein the tether includes polyester. [0042] Example 19 is a method for installing a TLP. The method includes coupling a pile end of a tether to a pile. The method also includes measuring a connection length between an upper end of the tether and a top connector location on a hull of the TLP. The method further includes installing a link plate in a top connector, the link plate including a first hole and a second hole, wherein a distance between a first pin of the top connector extending through the first hole and a second pin of the top connector extending through the second hole is based on the connection length. The method also includes coupling the upper end of the tether to the hull via the top connector. [0043] In Example 20, the embodiments of any preceding paragraph or combination thereof further include wherein installing the link plate includes installing a pin sleeve in the second hole of the link plate that receives the second pin. The distance between the second pin positioned within the pin sleeve and a lower end of the second hole is based on the connection length. [0044] In Example 21, the embodiments of any preceding paragraph or combination thereof further include wherein at the pin sleeve is asymmetric and positionable so as to allow two different connection lengths with the same pin sleeve. [0045] Certain terms are used throughout the description and claims to refer to particular features or components. As one skilled in the art will appreciate, different persons may refer to the same feature or component by different names. This document does not intend to distinguish between components or features that differ in name but not function. [0046] Reference throughout this specification to “one embodiment,” “an embodiment,” “an embodiment,” “embodiments,” “some embodiments,” “certain embodiments,” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the present disclosure. Thus, these phrases or similar language throughout this specification may, but do not necessarily, all refer to the same embodiment. [0047] The embodiments disclosed should not be interpreted, or otherwise used, as limiting the scope of the disclosure, including the claims. It is to be fully recognized that the different teachings of the embodiments discussed may be employed separately or in any suitable combination to produce desired results. In addition, one skilled in the art will understand that the description has broad application, and the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to suggest that the scope of the disclosure, including the claims, is limited to that embodiment.

Claims

CLAIMS What is claimed is: 1. A link plate system for a connecting a tether to a tension leg platform (TLP) via a first pin and a second pin, the link plate system comprising: a plurality of link plates, each link plate comprising a first hole sized to receive the first pin that connects the link plate to the TLP and a second hole sized to receive the second pin that connects the link plate to the tether; and wherein the length of each link plates is sized and the holes of each link plate are positioned and sized such that a distance between the first pin and the second pin is different for each link plate so as to allow adjustment of the connection length between the TLP and the tether.

2. The system of claim 1, wherein the second holes are further sized to receive any one of a plurality of pin sleeves sized to receive the second pin, each pin sleeve of the plurality of pin sleeves allowing for a different distance between the second pin positioned within the pin sleeve and a lower end of the second hole.

3. The system of claim 2, wherein at least one the plurality of pin sleeves is asymmetric and positionable so as to allow different two different connection lengths with the same pin sleeve.

4. A top connector assembly for connecting a TLP to a tether, the top connector assembly comprising: a dual axis joint configured to couple to the TLP; a link plate comprising a first hole and a second hole; a first pin extending through the first hole to couple the dual axis joint to the link plate; a second pin extending through the second hole to couple the link plate to the tether; and wherein a distance between the first pin and the second pin is based on a connection length between the TLP and the tether.

5. The assembly of claim 4, further comprising a pin sleeve disposed within the second hole and sized to receive the second pin, the distance between the second pin positioned within the pin sleeve and a lower end of the second hole being based on the connection length.

6. The assembly of claim 5, wherein at the pin sleeve is asymmetric and positionable so as to allow two different connection lengths with the same pin sleeve.

7. A tether assembly for connecting a TLP to a pile, the tether assembly comprising: a tether having an upper end and a pile end; and a connector comprising: a dual axis joint configured to couple to one of either the TLP or the pile; a link plate comprising a first hole and a second hole; a first pin extending through the first hole to couple the dual axis joint to the link plate; a second pin to couple the link plate to the tether, the second pin extending through the second hole; and wherein a distance between the first pin and the second pin is based on a connection length between either one of the tether and the TLP or the tether and the pile.

8. The assembly of claim 7, wherein the connector further comprises a pin sleeve disposed within the second hole that receives the second pin, the distance between the second pin positioned within the pin sleeve and a lower end of the second hole based on the connection length.

9. The assembly of claim 8, wherein at the pin sleeve is asymmetric and positionable so as to allow two different connection lengths with the same pin sleeve.

10. The assembly of claim 7, wherein the connector is a top connector configured to couple the TLP to the tether.

11. The assembly of claim 7, wherein the connector is a bottom connector configured to couple the pile to the tether.

12. The assembly of claim 7, wherein the tether comprises polyester.

13. A TLP comprising: a hull; a pile; a tether having an upper end and a pile end; a top connector coupling the upper end of the tether to the hull at a top connector location on the hull; a bottom connector coupling the pile end of the tether to the pile at a bottom connector location on the pile; and wherein at least one of the top connector and the bottom connector comprises: a dual axis joint configured to couple to one of either the TLP or the pile; a link plate comprising a first hole and a second hole; a first pin extending through the first hole to couple the dual axis joint to the link plate; a second pin extending through the second hole to couple the link plate to one of either the upper end of the tether or the pile end of the tether; and wherein a distance between the first pin and the second pin is based on a connection length between either one of the tether and the TLP or the tether and the pile.

14. The TLP of claim 13, wherein the top connector comprises: the dual axis joint coupled to the TLP at the top connector location; the link plate; the first pin extending through the first hole to couple the dual axis joint to the link plate; the second pin extending through the second hole to couple the link plate to the upper end of the tether; and wherein the distance between the first pin and the second pin is based on a connection length between the tether and the TLP.

15. The TLP of claim 13, wherein the bottom connector comprises: the dual axis joint coupled to the pile at the bottom connector location; the link plate; the first pin extending through the first hole to couple the dual axis joint to the link plate; the second pin extending through the second hole to couple the link plate to the pile end of the tether; and wherein the distance between the first pin and the second pin is based on a connection length between the tether and the pile.

16. The TLP of claim 13, wherein the at least one of the top connector and the bottom connector further comprises a pin sleeve disposed within the second hole that receives the second pin, the distance between the second pin positioned within the pin sleeve and a lower end of the second hole based on the connection length.

17. The TLP of claim 16, wherein at the pin sleeve is asymmetric and positionable so as to allow two different connection lengths with the same pin sleeve.

18. The TLP of claim 13, wherein the tether comprises polyester.

19. A method for installing a TLP, the method comprising: coupling a pile end of a tether to a pile; then measuring a connection length between an upper end of the tether and a top connector location on a hull of the TLP; then installing a link plate in a top connector, the link plate comprising a first hole and a second hole, wherein a distance between a first pin of the top connector extending through the first hole and a second pin of the top connector extending through the second hole is based on the connection length; and then coupling the upper end of the tether to the hull via the top connector.

20. The method of claim 19, wherein installing the link plate comprises installing a pin sleeve in the second hole of the link plate that receives the second pin, wherein the distance between the second pin positioned within the pin sleeve and a lower end of the second hole based on the connection length.

21. The method of claim 20, wherein at the pin sleeve is asymmetric and positionable so as to allow two different connection lengths with the same pin sleeve.