Subsea Cable Joint Torsional Rigidity Restoration
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Solution Overview
Problem
The jointing of single armoured high voltage sea cables leads to a loss of natural torsional rigidity near the joint, causing torsional forces to be improperly absorbed and potentially transferring forces to the joined core members, resulting in functional impairment.
Innovation Solution
A joint design that includes a second armouring layer with elongated elements twisted in the opposite direction to the first armouring layer, positioned neighboring the outer mechanical casing, to restore torsional rigidity and redirect torsional forces away from the joint area, while being shorter than the first armouring layer to save costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a joint is created between two cable sections by opening the armouring layers and mechanically connecting core members, then the cable sections can be joined together, but the natural torsional rigidity of the cable is lost in the area close to the joint
Solution Approach 1:
The patent applies a second armouring layer specifically in the joint area neighboring the outer mechanical casing, while the first armouring layer extends along the entire cable length. This local differentiation restores torsional rigidity precisely where it is needed (at the joint) without requiring full-length double armouring, thus resolving the contradiction between ease of manufacture and stability of composition.
Solution Approach 2:
The patent creates a composite armouring structure by combining two different armouring layers: the first armouring layer (extending along the entire cable) and the second armouring layer (positioned at the joint area with opposite twist direction). This composite structure provides both mechanical connection capability and restored torsional rigidity, resolving the contradiction between jointing ease and torsional stability.
2Stability of the object's composition
If the first armouring layer is extended along the entire cable length to provide torsional support, then torsional rigidity is maintained, but the cost and weight of the cable increase
Solution Approach 1:
The second armouring layer is positioned only in the joint area neighboring the outer mechanical casing, extending for a limited length rather than along the entire cable. This localized application provides torsional support exactly where needed while minimizing additional weight, resolving the contradiction between maintaining torsional rigidity and reducing cable weight.
Solution Approach 2:
Instead of providing full-length double armouring (excessive action), the patent applies the second armouring layer partially only in the joint area where torsional rigidity restoration is critical. This partial action is sufficient to resolve the technical problem while avoiding unnecessary weight and cost.
3Stability of the object's composition
If the second armouring layer is extended along the entire cable length, then torsional rigidity is fully restored, but the manufacturing cost increases significantly
Solution Approach 1:
The second armouring layer is applied locally only in the joint area neighboring the outer mechanical casing, rather than along the entire cable length. This localized application restores torsional rigidity where most critical (at the joint) while significantly reducing material costs and manufacturing complexity compared to full-length application.
Solution Approach 2:
The patent uses partial action by applying the second armouring layer only where absolutely necessary (in the joint area) rather than throughout the entire cable. This partial application is sufficient to restore torsional rigidity at the critical joint location while minimizing manufacturing cost.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively restores torsional rigidity near the joint, ensuring that torsional forces are absorbed by unaffected sections of the cable, thereby preventing functional impairment and reducing the risk of force transfer to the joined core members.
Implementation Method 1
the second armouring layer includes a plurality of elongated armoring elements wound twisted in an opposite direction to the wires of the first armouring layer with respect to the longitudinal axis of the cable in order to increase the torsional rigidity of the area neighboring the casing
Data Source
Figure 1~3
Figure 4~6
AI summary
The present invention relates to a joint including two sections of an electric power cable, each cable section comprising at least one core member surrounded by a first armouring layer (10) for protecting the core member from tensile forces acting on the cable, the first armoring layer including a plurality of armoring wires arranged along the length of the cable and twisted in a first direction with respect to the longitudinal direction of the cable. The joint comprises at least one core joint between the core members of the cable sections, and an outer mechanical casing (13) surrounding the at least one core joint and mechanically connected to the first armoring layers of the cable sections, and a second armouring layer (11) positioned in an area neighboring the casing, surrounding at least one of the cable sections, and having one end mechanically connected to the casing and the other end terminated at a distance from the casing, and the second armouring layer includes a plurality of elongated armoring elements (11b) wound twisted in an opposite direction to the wires of the first armouring layer with respect to the longitudinal axis of the cable in order to increase the torsional rigidity of the area neighboring the casing. This invention also relates to a method for joining the two cable sections.