Subsea Cable Orientation Support via Rotary Sheave Segmentation
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Solution Overview
Problem
Existing methods for deploying and retrieving subsea cables with integrated accessories, such as sensor modules, often result in damage due to sharp bends when changing orientation from horizontal to vertical or vice versa, as conventional direction-changing mechanisms do not adequately manage the bend radius of these cables.
Innovation Solution
A support structure comprising at least four equidistantly and equiangularly spaced rotary sheaves, mounted on a rotary frame, allows the cable to extend in a straight line between sheaves, enabling a quarter-turn rotation to change the accessory's orientation without exposing it to damaging bends, with a tensioning unit and locking system to maintain desired tension and prevent unnecessary rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a conventional direction-changing wheel or sheave is used to change cable orientation from horizontal to vertical, then the cable deployment process is simple and acceptable for cables without stiff modules, but sharp bends or kinks occur where the cable enters the stiff unit, destroying the cable as it exceeds the minimum bend radius
Solution Approach 1:
The support structure is divided into multiple sheaves (at least four) arranged in a specific geometric configuration, with each sheave handling a specific segment of the cable path. This segmentation allows the cable to be supported at multiple points simultaneously, maintaining proper bend radius throughout the orientation change process while preventing sharp kinks at any single location.
Solution Approach 2:
The invention transitions from a single-plane direction change to a three-dimensional spatial arrangement of multiple sheaves. The sheaves are positioned at specific heights and horizontal distances, creating a spatial support configuration that guides the cable through a controlled three-dimensional path, thereby maintaining adequate bend radius during the horizontal-to-vertical transition.
2Reliability
If the diameter of the wheel is increased compared to the length of the stiff unit, then the bend radius problem is reduced to some extent, but the problem is not eliminated and the system complexity increases
Solution Approach 1:
Rather than using a single large-diameter wheel, the support structure segments the bending transition into multiple smaller sheaves. Each sheave has a manageable diameter, but their combined geometric arrangement creates the equivalent of a much larger effective bend radius, distributing the bending stress across multiple support points and eliminating the need for an excessively large single wheel.
Solution Approach 2:
The invention employs curved paths and rounded sheave surfaces to guide the cable through a smooth, continuous arc rather than a sharp angle. The geometric arrangement of sheaves creates a distributed curvature profile that maintains cable protection while using compact, practical sheave dimensions.
3Reliability
If bend restrictors are added at each end of the stiff module, then the sharp bend problem is mitigated to some extent, but the cable still risks damage during orientation change and the device complexity increases
Solution Approach 1:
The support structure introduces intermediary sheaves between the cable's horizontal and vertical paths. These sheaves act as mediators that guide the cable through a controlled transition, distributing the bending forces across multiple support points rather than concentrating stress at the ends of the stiff module, thereby providing superior protection compared to end-mounted restrictors alone.
4Productivity
If a linear traction unit with wheels or belts is used to control cable tension, then the cable can be deployed from storage, but fragile components such as sensor modules or connectors may be damaged due to squeezing forces on the cable
Solution Approach 1:
The sheaves in the support structure serve as intermediary support elements that bear the cable's weight and guide it through the orientation change without requiring excessive squeezing forces. By distributing the support function across multiple sheaves, the system reduces the tension and compression forces that would otherwise be concentrated on fragile components, enabling safer deployment of cables with sensitive integrated elements.
Data Source
Figure 1
Figure 2~3
Figure 4a~4d
AI summary
To eliminate the risk of damaging an elongate flexible element and/or an accessory integrated therein, such as a seismic cable having sensor modules distributed rather densely along the cable and forming therewith sections that risk being damaged, on passing from a generally horizontal/vertical orientation to a generally vertical/horizontal one during subsea laying or retrieving of the cable, a new direction changing support structure is provided. The support structure comprises at least two rotary sheaves and a rotary support frame for carrying the sheaves, and said at least two sheaves are spaced from each other a distance that is greater than a length of the accessory to permit the element with the integral accessory to extend in a straight line between the two sheaves. Each sheave has a rotational axis that is parallel to a rotational axis of the support frame, and the support frame is rotary at least between a position in which the accessory with associated ends of the element is located in a generally horizontal orientation and is supported by said sheaves and a position in which the accessory with associated ends of the element is located in a generally vertical orientation during continuous support by said sheaves.