End-Fitting Insulating Coating for Flexible Pipe Corrosion Control
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Solution Overview
Problem
Unbonded flexible pipes used for offshore hydrocarbon transport face issues with stray currents causing galvanic corrosion due to electrical imbalances and wiring flaws, particularly in end-fittings with metallic components, which can lead to sparks and damage.
Innovation Solution
Applying a coating with high electrical resistivity, such as epoxy or polytetrafluoroethylene, to the metallic surfaces in the vicinity of the through-going opening in the end-fitting to prevent the transfer of stray currents and reduce the risk of galvanic corrosion, along with using insulating materials and gaskets to further isolate electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metallic components are used in end-fittings for electrical heating systems, then electrical conductivity is improved, but galvanic corrosion and stray currents increase
Solution Approach 1:
The patent introduces an intermediate insulating coating layer between metallic components in the end-fitting. This coating acts as a mediator that prevents direct electrical contact between dissimilar metals, thereby eliminating galvanic corrosion while still allowing thermal conduction for the heating system to function effectively.
Solution Approach 2:
The patent applies insulating coatings selectively to specific metallic surfaces within the end-fitting where galvanic corrosion is most likely to occur. This localized treatment maintains electrical conductivity where needed for the heating system while providing corrosion protection at critical interfaces between different metals.
2Object-affected harmful factors
If insulating coatings are applied to metallic surfaces in end-fittings, then galvanic corrosion is reduced, but electrical conductivity is decreased
Solution Approach 1:
The patent applies insulating coatings selectively to specific metallic surfaces within the end-fitting where galvanic corrosion is most likely to occur. This localized treatment maintains electrical conductivity where needed for the heating system while providing corrosion protection at critical interfaces between different metals.
Solution Approach 2:
The patent modifies the electrical conductivity parameter of metallic surfaces by applying coatings with controlled insulating properties. The coating thickness and material composition are optimized to provide sufficient corrosion protection while maintaining adequate electrical conductivity for the heating system's operational requirements.
3Loss of energy
If thermal insulation layers are applied to the pipe, then heat loss is reduced, but device complexity increases
Solution Approach 1:
The patent combines thermal insulation and electrical insulation functions into a single integrated coating system applied to the end-fitting and pipe surface. This merged solution provides both thermal energy conservation and electrical corrosion protection without requiring separate insulation layers, thereby reducing overall structural complexity.
Solution Approach 2:
The patent employs coating materials and structural designs that serve multiple functions simultaneously - providing both thermal insulation to reduce heat loss and electrical insulation to prevent galvanic corrosion. This multi-functional approach eliminates the need for separate specialized layers for each protection type.
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
Significantly reduces the occurrence of stray currents and associated galvanic corrosion in end-fittings, enhancing the reliability and longevity of the electrical heating systems in unbonded flexible pipes by preventing electrical contact and ensuring insulation against conductive films.
Implementation Method 1
the first surface of the first metallic part, at least in the vicinity of the through-going opening comprises a coating having a high electrically resistivity
Implementation Method 2
Due to the inherent electric resistance in the metallic armour layers a heating effect may be achieved
Data Source
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AI summary
An assembly comprising an end-fitting (10) and an unbonded flexible pipe (1) is disclosed, where the end-fitting (10) is adapted for connecting the unbonded flexible pipe (1) to a connector. The end-fitting (10) has a through-going opening (17) with a centreline (9) and a front end (11) and a rear end (12), and the end-fitting (10) further comprises means (24, 25) for establishing an electrical connection to a least one electrical heating system in said unbonded flexible pipe (1). Moreover, the end-fitting (10) comprises at least one first metallic part having a first surface contacting a second surface of at least one second part in the end-fitting (10) wherein the first surface of the first metallic part, at least in the vicinity of the through-going opening (17), comprises a coating (27, 29, 30) having a high electrically resistivity. The invention also discloses a method for providing an end-fitting (10) having good properties in respect of reducing galvanic corrosion.