Rigid Sea Joint Insulation for Lighter Submarine Cable Corrosion Protection
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Solution Overview
Problem
Rigid sea joints for submarine power cables face corrosion issues due to seawater exposure, which can be exacerbated by the use of metal bend restrictors, leading to increased material requirements and weight, limiting vessel choice and weather windows for offshore operations.
Innovation Solution
The system employs electrically insulating elements between the metal bend restrictors and the outer mechanical casing, allowing sacrificial anodes to protect only the casing, while the bend restrictors are allowed to corrode freely, thus reducing the overall weight and material requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metal bend restrictors are connected to the outer metal casing, then the cables are protected from overbending, but the uncoated metal surface area increases and the protection time provided by sacrificial anodes is shortened
Solution Approach 1:
The patent introduces an electrically insulating element as an intermediary between the metal bend restrictor and the outer metal casing. This insulating element allows the bend restrictor to perform its mechanical function of preventing cable overbending while simultaneously blocking the electrical connection that would otherwise create a galvanic cell and accelerate corrosion of the protected casing.
2Duration of action of stationary object
If the amount of sacrificial anode material is increased to protect the outer metal casing, then the protection time is extended, but the mass of the rigid sea joint increases significantly making it heavier and more expensive
Solution Approach 1:
The patent extracts the bend restrictor from the galvanic protection system by introducing an electrically insulating element. This separation removes the bend restrictor from the list of components that require galvanic protection, allowing the sacrificial anodes to be sized solely based on the protected surface area of the outer metal casing, thereby reducing the total mass of anode material required.
3Reliability
If the mass of sacrificial anode material is increased to prolong protection time, then the outer metal casing is better protected, but the rigid sea joint becomes heavier and the choice of laying vessel and weather window becomes more limited
Solution Approach 1:
The electrically insulating element acts as a mediator that decouples the bend restrictor from the corrosion protection system. This allows the system to maintain reliable corrosion protection with minimal anode material while keeping the overall weight low, thereby preserving flexibility in vessel selection and operational weather windows.
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
This design maintains the integrity of the outer mechanical casing while minimizing the need for additional sacrificial anode material, keeping the system lightweight and cost-effective, thereby expanding vessel options and improving operational flexibility.
Implementation Method 1
a first electrically insulating element arranged between the first metal adapter flange and the outer mechanical metal casing, electrically insulating the outer mechanical metal casing from the first metal bend restrictor
Implementation Method 2
rigid sea joints may be provided with sacrificial anodes designed to provide a galvanic protection to the outer metal casing
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A rigid sea joint system (7) for jointing submarine power cables, the rigid sea joint system (7) comprising: an outer mechanical metal casing (7a) arranged to accommodate an electrical joint between a first submarine power cable and a second submarine power cable, the outer mechanical metal casing (7a) having a first end provided with a first opening configured to receive a portion of the first submarine power cable into an interior of the outer mechanical metal casing (7a), and a second end provided with a second opening configured to receive a portion of the second submarine power cable into the interior of the outer mechanical metal casing (7a), a first metal adapter flange (27a) attached to the first end, around the first opening, a second metal adapter flange (27b) attached to the second end, around the second opening, a first metal bend restrictor (7b) attached to the first metal adapter flange (27a), a second metal bend restrictor (7c) attached to the second metal adapter flange (27b), a first electrically insulating element (8d) arranged between the first metal adapter flange (27a) and the outer mechanical metal casing (7a), electrically insulating the outer mechanical metal casing (7a) from the first metal bend restrictor (27a), and a second electrically insulating element (8g) arranged between the second metal adapter flange (27b) and the outer mechanical metal casing (7a), electrically insulating the outer mechanical metal casing (7a) from the second metal bend restrictor (7c).