Flexible Pipe Cover Layer to Prevent Sheath Partial Discharge
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Solution Overview
Problem
Unbonded flexible pipes equipped with electric heating systems experience rapid degradation due to voltage-induced partial discharges across the internal pressure sheath, which is detrimental to the material over time.
Innovation Solution
The implementation of a conforming cover layer made from an electrically conductive material with bulk resistance greater than the carcass, applied to the internal pressure sheath, to absorb charges and prevent the formation of local electric domains, thereby minimizing partial discharges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If electric heating systems are implemented in unbonded flexible pipes using the carcass as a heating element, then the pipe can provide heating functionality for fluid transport, but voltage-induced partial discharges occur across the internal pressure sheath causing rapid material degradation
Solution Approach 1:
A conforming cover layer made from electrically conductive material is introduced as an intermediary between the internal pressure sheath and the external environment. This cover layer absorbs charges and prevents the formation of local electric domains, thereby eliminating partial discharges while allowing the electric heating system to continue functioning. The cover layer has bulk resistance greater than the carcass to ensure proper charge absorption characteristics.
2Use of energy by moving object
If the internal pressure sheath is used as an electrical insulator between conductive layers, then electric current can be conducted through the carcass for heating, but voltage drop across the pressure sheath creates charged domains leading to partial discharges
Solution Approach 1:
The conforming cover layer acts as a charge-absorbing intermediary on the outer surface of the internal pressure sheath. It provides a path for charge dissipation that prevents the accumulation of charged domains that would otherwise lead to partial discharges through the insulating pressure sheath material.
Solution Approach 2:
The electrical properties of the system are modified by adding the conforming cover layer with specific bulk resistance characteristics. This changes the charge distribution and dissipation parameters, preventing the voltage-induced partial discharge phenomenon while maintaining the necessary electrical insulation function of the pressure sheath.
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 reduces the risk of partial discharges, enhancing the longevity and reliability of the electric heating system in unbonded flexible pipes by preventing charge accumulation on the pressure sheath surface.
Implementation Method 1
a carcass made from an electrically conductive material, the carcass being adapted for connection to an electric power source for conducting an electric current
Implementation Method 2
the internal pressure sheath is partly or fully covered with a conforming cover layer made from a material which is electrically conductive and having a bulk resistance larger than the specific resistance of the electrically conductive material of the carcass
Implementation Method 3
The internal pressure sheath will function as an electrical insulator between the electrically conductive layers
Data Source
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AI summary
An unbonded flexible pipe (1) having a length and a longitudinal axis and comprising, from the inside and out, a carcass (2) made from an electrically conductive material, an internal pressure sheath (3) made from an extruded polymer, at least one external armour layer (4) and an outer sheath (5), in which the carcass (2) is adapted for connection to an electric power source for conducting an electric current. Moreover, at least a part of the external armour layer (4) is electrically conductive, the carcass (2) and the external armour layer (4) allowing a difference in electric potential to be established partly or fully over the internal pressure sheath (3), wherein the internal pressure sheath (3) is partly or fully covered by a conforming cover layer made from a material which is electrically conductive and has a bulk resistance larger than the specific resistance of the electrically conductive material of the carcass (2).