Flexible Pipe End-Fitting Insulation for Stray Current Suppression
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Solution Overview
Problem
Unbonded flexible pipes used for offshore hydrocarbon transport face issues with fluid viscosity and blockage due to cooling by sea water, which is addressed by electric heating, but leads to leak currents causing local heating, sparks, and system failure due to unintended electricity flow.
Innovation Solution
An end-fitting assembly with coaxially arranged armour layers, electrically insulated from each other, and a local volume filled with an electrically insulating fluid, moisture absorbing fluid, or transformer oil to prevent leak currents, ensuring a fluid-tight connection and reducing the risk of galvanic corrosion and spark formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electric heating is applied to the unbonded flexible pipe to prevent fluid solidification, then the fluid transport reliability is improved, but leak currents cause local heating, sparks, and system failure
Solution Approach 1:
The patent introduces an electrically insulating layer as an intermediary between the first and second armour layers. This insulating layer prevents direct electrical contact between the conductive armour layers, thereby blocking leak current paths while allowing the electric heating system to function safely for fluid transport
Solution Approach 2:
The patent uses an electrically insulating fluid filling the cavity within the end-fitting to prevent leak currents. The fluid acts as an electrical insulator, blocking unintended current paths between armour layers and electrical connections, thus preventing local heating and sparks while maintaining the heating system's effectiveness
2Use of energy by moving object
If electric heating system is implemented using armour layers as conductors, then the heating efficiency is improved, but unintended electricity flow paths are created
Solution Approach 1:
The electrically insulating layer positioned between the first and second armour layers acts as a mediator that allows the armour layers to function as heating conductors while preventing unintended current leakage. The insulator enables controlled current flow for heating while blocking stray current paths
Solution Approach 2:
The patent employs thin film or layer insulation (electrically insulating layer) between the conductive armour layers. This thin insulating barrier maintains the flexibility of the pipe while effectively blocking electrical leakage paths, allowing the armour layers to serve dual purposes as both structural reinforcement and heating elements
3Device complexity
If metallic armour layers are used as electrical conductors for heating, then the device complexity is reduced, but galvanic corrosion and spark formation risks increase
Solution Approach 1:
The electrically insulating layer and insulating fluid act as intermediaries that protect the metallic armour layers from galvanic corrosion by preventing direct electrical contact between dissimilar metals. This extends system lifespan while maintaining the simple structure of using armour layers as conductors
Solution Approach 2:
The patent converts the potentially harmful effect of having conductive armour layers (risk of galvanic corrosion and sparks) into a benefit by introducing insulating measures that allow the armour layers to function as heating elements without suffering from their conductive nature. The insulation transforms the risk into a controlled, beneficial heating system
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 suppresses leak currents, preventing local heating and spark formation, thereby maintaining the electrical insulation properties and extending the system's lifespan by ensuring a reliable electrical connection and insulation within the end-fitting.
Implementation Method 1
a local volume in the end-fitting adjacent to the electrically insulating layer comprises a functional fluid selected from an electrically insulating fluid, a moisture absorbing fluid and a transformer oil
Implementation Method 2
a local volume in the end-fitting adjacent to the electrically insulating layer comprises a functional fluid selected from an electrically insulating fluid, a moisture absorbing fluid and a transformer oil
Implementation Method 3
it has been found that one or more of the metallic armour layers of the pipe may be used as conductors enabling heating, by passing a current through the armour layer
Data Source
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AI summary
The present invention relates to an assembly comprising an end-fitting (10) for terminating an unbonded flexible pipe (1) and an unbonded flexible pipe (1). The unbonded flexible pipe (1) comprises a first (2) and a second (4) armour layer co-axially arranged, and an electric heating system The end-fitting (10) comprises means (22) for mechanically anchoring the first armour layer (2) to the end-fitting (10) and comprises electrical connections for connecting the first armour layer (2) to a power-source. The end-fitting (10) also comprises means (24a, 24b) for mechanically anchoring the second armour layer (4) to the end-fitting (10). The first (2) and second (4) armour layers are electrically insulated from each other by at least one electrically insulating layer (3) in the end-fitting (10) and the end-fitting (10) comprises a local volume (35) in the end-fitting (10) adjacent to the electrically insulating layer (3) adapted for injection of a functional fluid.