Subsea Pipeline Direct Electrical Heating System
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Solution Overview
Problem
Existing subsea pipeline heating systems face issues with high current requirements leading to overheating of cables, AC corrosion, and safety concerns due to magnetic fields and stray currents, particularly in deep-water fields where chemical hydrate removal methods pose environmental risks.
Innovation Solution
The system employs multiple conductor cables with varying phase angles to reduce current in supply cables, uses a short-circuit connection between pipelines, and incorporates a subsea capacitor bank to minimize current transfer through anodes and seawater, optimizing pipe impedance through surface treatments and finite element simulations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If large conductor cross sections are used to supply high currents for DEH system, then power supply capability is improved, but cable cost and installation complexity increase
Solution Approach 1:
The patent combines multiple single-core cables into a multi-core cable assembly, where multiple conductors are bundled together to provide the required high current capacity. This merging approach allows the system to achieve the necessary power supply capability while maintaining manageable cable handling and installation characteristics, as the multi-core cable is pre-assembled and treated as a single installable unit.
Solution Approach 2:
The patent segments the high current requirement into multiple parallel conductors within the cable assembly. Instead of using a single large cross-section conductor, the system divides the current path across multiple smaller conductors (e.g., multiple 500 mm² conductors instead of one larger conductor), which reduces the skin effect and improves current distribution while maintaining the total current-carrying capacity.
2Temperature
If traditional single-phase DEH system is used, then heating function is achieved, but cable overheating and AC corrosion problems occur
Solution Approach 1:
The patent transitions from a single-phase symmetric DEH system to a three-phase asymmetric system. By introducing three phases with 120-degree phase differences, the system creates an asymmetric current distribution that eliminates the neutral point potential fluctuations characteristic of single-phase systems. This asymmetry in phase arrangement prevents the cyclic heating and cooling of cables that leads to overheating and reduces AC corrosion by stabilizing the electromagnetic field.
Solution Approach 2:
The patent changes the electrical parameters of the DEH system by introducing three-phase power with different phase angles (120-degree separation). This parameter change transforms the current waveform and frequency characteristics, resulting in more uniform heat generation along the pipeline and reduced peak currents in individual cables, thereby preventing cable overheating and minimizing AC corrosion effects.
3Reliability
If multiple anodes are distributed over 50m length to limit current transfer density, then corrosion protection is improved, but system complexity and installation cost increase
Solution Approach 1:
The patent applies local quality by concentrating corrosion protection measures at specific locations rather than distributing anodes uniformly along the pipeline. The three-phase connection arrangement creates natural current distribution patterns that provide effective cathodic protection at critical zones (connection points and current transfer zones) without requiring extensive anode distribution along the entire pipeline length, thereby reducing system complexity 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
This configuration reduces power losses in cables, minimizes AC corrosion, and decreases the risk of overheating and magnetic field exposure, enhancing the efficiency and safety of subsea pipeline heating while reducing investment costs and environmental impact.
Implementation Method 1
conductor cables, W, supplies electrical power from at least one top side power supply to M of the parallel subsea pipelines N
Implementation Method 2
The amount of current induced is sufficient in relation to the inherent resistivity of the conductive sections to cause the generation of heat within the pipeline sections
Implementation Method 3
By conductive and convective heat transfer, the heat induced into the pipeline structure is transferred to a fluid flow within the pipeline
Implementation Method 4
By conductive and convective heat transfer, the heat induced into the pipeline structure is transferred to a fluid flow within the pipeline
Implementation Method 5
The current is preferably an alternating current of frequency which causes a majority of the current to travel at or near the outer surfaces of the pipeline sections which increases the effective resistivity of the sections and heat generation therein
Data Source
Figure 1A~2A
Figure 2B~3c
Figure 4~6
AI summary
Means for high efficiency induction heating or direct electrical heating, DEH, of a number, M, M [1, N] of a group of parallel subsea pipelines N, where N? [2,8), and where a number of conductor cables, W, supplies electrical power from at least one top side power supply (207, G1, G2) to M of the parallel subsea pipelines N. The numbers of electric conductors, W, from the at least one top side (207, G1, G2) power supply connected to the M pipelines is defined to be in the group W? [N, N + 1], where N, W and M are natural numbers. It is furthermore disclosed a system for induction heating or DEH of subsea pipelines.