US-20260128579-A1 - CONNECTIONS TO SUBSEA ELECTRICAL EQUIPMENT

Abstract

A pivoting cable connection for a subsea equipment unit comprises a tubular cable guide supported by the unit, extending along and around a pivot axis. A cable extending through the connection comprises an intermediate section extending along or beside the pivot axis within the cable guide and an outboard section, pivotable about the pivot axis, that extends away from the pivot axis in a direction transverse to the pivot axis. When installing or retrieving the unit onto or from the seabed, pivotal movement of the outboard section of the cable relative to the unit is accommodated by torsional deformation of the intermediate section of the cable. By allowing the cable to pivot above and below the pivot axis, the connection enables the unit to be lowered from a vessel that also pays out and lays the cable. Preliminarily, the cable can be coupled to the unit aboard the same vessel.

Inventors

• Øivind Stangeland
• Julien MANACH

Assignees

• SUBSEA 7 NORWAY AS

Dates

Publication Date

20260507

Application Date

20231020

Priority Date

20221021

Claims (20)

1. 1 .- 32 . (canceled)
2. 33 . A subsea equipment unit comprising a pivoting cable connection, the connection comprising: a cable guide supported by the unit for pivoting movement about a pivot axis, the cable guide extending along and around the pivot axis; and a cable extending on a cable path through the connection, wherein the cable comprises: an intermediate section at least partially within the cable guide, extending along or beside the pivot axis; and an outboard section, pivotable about the pivot axis, extending away from the pivot axis in a direction transverse to the pivot axis.
3. 34 . The subsea equipment unit of claim 33 , wherein the cable guide is tubular.
4. 35 . The subsea equipment unit of claim 33 , wherein the cable guide forms part of a yoke that is pivotable about the pivot axis and that supports the outboard section of the cable at a location offset laterally from the pivot axis.
5. 36 . The subsea equipment unit of claim 35 , further comprising an anchor formation that fixes the outboard section of the cable relative to the cable guide.
6. 37 . The subsea equipment unit of claim 35 , wherein the outboard section of the cable curves away from the pivot axis contained within a portion of the cable guide that correspondingly curves away from the pivot axis.
7. 38 . The subsea equipment unit of claim 35 , wherein the outboard section of the cable is supported by at least one arm extending from the cable guide.
8. 39 . The subsea equipment unit of claim 33 , wherein the outboard section of the cable curves away from the pivot axis onto an exit axis that is substantially orthogonal to the pivot axis.
9. 40 . The subsea equipment unit of claim 33 , wherein the outboard section of the cable curves away from the pivot axis in a plane containing the pivot axis.
10. 41 . The subsea equipment unit of claim 33 , wherein the outboard section of the cable is aligned with the subsea equipment unit.
11. 42 . The subsea equipment unit of claim 33 , wherein the pivot axis is substantially horizontal.
12. 43 . The subsea equipment unit of claim 33 , wherein the intermediate section of the cable is disposed between the outboard section of the cable and an inboard section of the cable that extends transversely relative to the pivot axis away from the pivot axis and toward equipment of the unit.
13. 44 . The subsea equipment unit of claim 43 , wherein the inboard section of the cable is in fixed relation to the unit.
14. 45 . The subsea equipment unit of claim 43 , wherein the inboard section of the cable is received in a duct that communicates with the cable guide.
15. 46 . The subsea equipment unit of claim 45 , wherein the duct and the inboard section of the cable together curve away from the pivot axis.
16. 47 . The subsea equipment unit of claim 45 , wherein a swivel acting between the duct and the cable guide permits pivotal movement of the cable guide relative to the duct about the pivot axis.
17. 48 . The subsea equipment unit of claim 47 , wherein the swivel surrounds an aperture in a support joining the connection to the subsea equipment unit and the duct communicates with the cable guide through the aperture.
18. 49 . The subsea equipment unit of claim 33 , wherein the intermediate section of the cable is arranged to deform in torsion as the outboard section pivots about the pivot axis.
19. 50 . The subsea equipment unit of claim 49 , wherein the intermediate section comprises two or more generally parallel strands arranged to bend along their length independently as the intermediate section deforms in torsion as a whole.
20. 51 . The subsea equipment unit of claim 33 , wherein a pair of supports spaced along the pivot axis join the connection to the subsea equipment unit.

Description

This invention relates to the challenges of connecting elongate flexible conductors or cables to subsea electrical equipment. Examples of such equipment include subsea transformers, pumps, compressors, variable-speed drives and switchgear, including any supporting or surrounding frames or structures. Subsea cables are used to convey electrical power to or from such equipment and may also be used for other purposes, for example to convey data signals. Some subsea cables are known in the art as umbilicals. Umbilicals typically comprise two or more conductors or other elongate elements such as fibre optics or fluid conduits, in addition to protective and reinforcing elements. Some subsea cables or smaller umbilicals are known in the art as flying leads. For simplicity, references in this specification to cables will encompass umbilicals and other flexible conductors such as flying leads. For connection to a preinstalled subsea structure, a cable may comprise a termination head or termination assembly including a connection hub to be coupled to a complementary destination hub of the subsea structure. Only one direction of connection is possible depending on the common axial orientation of the hubs, for example a horizontal or vertical direction. Sometimes, an articulated lifting yoke is mounted on a cable termination as exemplified by U.S. Pat. No. 9,206,652 and WO 2019/179986. The yoke is independent of and additional to the cable and is dedicated to installation. Consequently, the yoke constitutes a bulky piece of equipment that is, wastefully, useless after installation. Lifting yoke systems like those disclosed in U.S. Pat. No. 9,206,652 and WO 2019/179986 are not practical where the connection hub of a cable must itself be tilted relative to, or into axial alignment with, the destination hub. To the contrary, a lifting yoke is designed to compensate for tilting so that the connection hub will remain in a particular desired orientation, such as on a horizontal axis. It therefore remains a challenge to tilt a connection hub into a different orientation, such as onto a non-horizontal axis, while lifting the head. Indeed, heavy bend stiffeners are typically mounted on the cable to mitigate potential bending moments if this occurs. WO 2018/127552 introduces a mechanical pivot in a termination head for a flying lead cable. A connection hub of the termination head can be moved horizontally for connection to a destination hub while the remainder of the termination head is tilted at an angle to the horizontal due to constraints of lifting. For this purpose, a free section of flexible cable runs around the pivot between the connection hub and the remainder of the termination head, which is tilted. That free section of cable must bend sharply across the pivot, which risks damage to the cable through bending stresses and would be impractical for cables with large diameter or stiff construction and hence a large minimum bend radius. Prior art like WO 2018/127552 is unsuitable when a termination head is coupled to heavy electrical equipment, such as a subsea transformer, without an intermediate connection. Maintaining horizontality of the electrical equipment and the termination head is the most important constraint. In this respect, the challenges addressed by the invention are best understood by explaining conventional installation techniques used for subsea transformers as an example of subsea electrical equipment. A typical subsea transformer unit 10 is shown in FIG. 1, comprising transformer equipment 12 fixed within a supporting and surrounding frame 14. An umbilical cable 16 connects to the unit 10 and is fixed rigidly to an outrigger 18 at one end of the frame 12, either penetrating or extending through the outrigger 18 or being connected to a connector supported by the outrigger 18. The cable 16 is surrounded with a bend restrictor 20 extending outboard of the outrigger 18. Items of subsea equipment like the unit 10 shown in FIG. 1 are large and heavy loads that must be lifted horizontally and remain horizontal while being lowered from a surface vessel to the seabed or while being recovered from the seabed to the surface. A cable 16 connecting to the transformer equipment 12 via the frame 14 must therefore also be kept close to horizontal where it adjoins the frame 14. This complicates and prolongs conventional installation techniques as illustrated in FIGS. 2a to 4b, greatly increasing cost and requiring a lengthy weather window to be available. FIGS. 2a to 2c show a first installation technique that involves two operations to be performed by one or two vessels. Firstly, as shown in FIG. 2a, a first vessel 22 lays a power cable 16 on the seabed 24 with a connector 26 at its free end placed on or adjacent to a subsea foundation 28. Subsequently, as shown in FIG. 2b, the connector 26 at the free end of the cable 16 is retrieved to the surface 30 by a second vessel 32 that carries the unit 10. Via the connector 2