Reinforced Cable Joint Water Barrier for Subsea Bending Reliability
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Solution Overview
Problem
Joining power cables with welded metal-based water barriers poses challenges in maintaining mechanical and electrical properties, particularly when combining static and dynamic cables, as the adhesion between lead-based sealing and polymeric sheathing is critical to prevent buckling or rupturing of the underlying metal or lead-based water barriers at the joint.
Innovation Solution
A reinforced water barrier system is implemented, featuring a lead-based intermediate water barrier with a polyethylene-based adhesive and thermoplastic layer, thermally set, radially extending across the joint and attached to both metal water barriers, with additional reinforcement layers if necessary, to enhance adhesion and prevent buckling or rupturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a lead-based sealing is used to join power cables with welded metal-based water barriers, then adhesion between the sealing and polymeric sheathing is improved, but buckling or rupturing of the underlying metal water barrier occurs at the joint
Solution Approach 1:
The patent applies composite materials by combining lead-based sealing with a polyethylene-based adhesive layer and a thermoplastic reinforcement layer. This composite structure provides both adhesion to the polymeric sheathing and mechanical reinforcement to prevent buckling or rupturing of the underlying metal water barrier, resolving the contradiction between improving adhesion and maintaining structural strength.
Solution Approach 2:
The patent implements beforehand cushioning by placing a thermoplastic reinforcement layer over the lead-based sealing before the polymeric sheathing is applied. This reinforcement layer acts as a protective cushion that prevents buckling or rupturing of the metal water barrier at the joint, anticipating and preventing mechanical failures before they occur during cable installation or operation.
2Ease of manufacture
If conventional joining methods are used for power cables with welded metal-based water barriers, then manufacturing simplicity is maintained, but the joint becomes a weak link with reduced mechanical and electrical properties
Solution Approach 1:
The patent introduces an intermediary structure consisting of a lead-based sealing with polyethylene adhesive and thermoplastic reinforcement layers between the metal water barriers and the outer polymeric sheathing. This intermediary structure facilitates reliable joining while maintaining both mechanical strength and electrical properties, preventing the joint from becoming a weak link despite the increased manufacturing complexity.
3Adaptability or versatility
If static cables with lead water barriers are joined to dynamic cables with welded metal water barriers, then cable compatibility is achieved, but the joint lacks fatigue resistance required for dynamic conditions
Solution Approach 1:
The patent uses composite materials with a thermoplastic reinforcement layer that provides fatigue resistance, enabling the joint to withstand dynamic bending conditions. This composite structure allows compatible joining of static cables with lead water barriers and dynamic cables with welded metal water barriers while maintaining the reliability required for dynamic applications.
Solution Approach 2:
The patent applies local quality by providing enhanced reinforcement specifically at the joint area where fatigue resistance is most critical. The thermoplastic reinforcement layer and polyethylene adhesive are concentrated at the joint between static and dynamic cables, providing localized fatigue resistance without requiring reinforcement throughout the entire cable length, thus achieving adaptability while maintaining reliability.
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 maintains the integrity of the joint under bending tests, ensuring watertight sealing and mechanical stability by enhancing adhesion between the lead-based sealing and underlying metal water barriers, preventing failures observed in prior methods.
Implementation Method 1
a reinforcing element is located radially around and attached to a part of the intermediate water barrier adjacent to the attachment at the second end of the intermediate water barrier, the attachment at the second end of the intermediate water barrier and further to a part of the second outer sheathing of the second power cable section, wherein the reinforcing element comprises a first layer of a polyethylene based adhesive and a second thermoplastic layer that are thermally set
Data Source
AI summary
A reinforced water barrier over a joint between power cables is suited for subsea cables having different water barrier/sheathing designs. The reinforced water barrier has an intermediate water barrier made of lead or a lead alloy which stretches over the joint and is attached to the underlaying water barriers of the joined cables, and which is reinforced by being coated with a layer of polyethylene based adhesive followed by a layer of polymeric outer sheathing. The adhesive layer and the layer of polymeric outer sheathing are thermally set by a heat treatment.