Corrosion Monitoring Using Galvanic Cable Conductor Design
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Solution Overview
Problem
Existing corrosion monitoring systems for metal pipelines fail to detect corrosion caused by water ingress into insulation systems in a timely manner, as the corrosion rates of the monitoring cables and pipelines are often similar, making it difficult to identify potential pipeline defects before significant damage occurs.
Innovation Solution
A corrosion monitoring system using an electric cable with a smaller, less corrosion-resistant first conductor and a larger, more corrosion-resistant second conductor, where a DC galvanic connection is maintained during non-measurement periods to enhance the difference in corrosion rates, and a coaxial cable with a water-permeable insulator to facilitate faster corrosion detection on the first conductor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cable with similar corrosion resistance to the pipeline is used for monitoring, then the cable provides reliable long-term monitoring, but the corrosion detection is delayed because the cable corrodes at the same rate as the pipeline
Solution Approach 1:
The patent applies local quality by creating a localized zone of accelerated corrosion at the cable-pipeline interface through galvanic coupling. The monitoring cable is designed with specific local properties (galvanic connection to pipeline, controlled corrosion rate) that differ from the rest of the cable system, allowing it to corrode faster than the pipeline in that specific location while maintaining overall monitoring reliability
Solution Approach 2:
The patent changes the corrosion rate parameter of the monitoring cable by establishing a galvanic connection with the pipeline. This electrical connection alters the electrochemical environment, increasing the corrosion rate of the cable relative to the pipeline, thereby enabling earlier detection of water ingress and corrosion risks without sacrificing monitoring reliability
2Loss of time
If the first conductor is made of less corrosion resistant material to accelerate corrosion detection, then corrosion risk is detected earlier, but the cable structure becomes less stable
Solution Approach 1:
The patent uses composite materials by combining two different conductor materials with distinct corrosion properties within a single cable structure. The first conductor uses less corrosion-resistant material for accelerated detection, while the second conductor uses more corrosion-resistant material to maintain structural stability. This composite approach allows the cable to simultaneously achieve early corrosion detection and long-term structural integrity
Solution Approach 2:
The patent introduces an intermediary element (the galvanic connection between conductors) that mediates between the conflicting requirements of early detection and structural stability. The electrical and galvanic coupling between the two conductors creates a controlled corrosion environment that accelerates detection without compromising the overall cable structure, as the more corrosion-resistant second conductor provides structural support
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
Enables earlier detection of corrosion risks by accelerating the corrosion rate of the first conductor, allowing for timely intervention before pipeline damage occurs, while minimizing additional corrosion on the pipeline.
Implementation Method 1
a DC galvanic connection between the first and second electrical conductor is present in the system at least during long periods wherein no measurements are performed
Data Source
Figure 1~2
Figure 3a~3b
Figure 4~5
AI summary
The risk of corrosion due to ingress of water into a mantle around a metal pipe or other metal object is monitored. An electric cable is used in the mantle, with a first conductor and a larger, second conductor, such as a core conductor and an outer conductor of a coaxial cable. The material of the first conductor is chosen to be less corrosion resistant in the system than the material of the second conductor. The outer surface of the metal object is the same material as the first conductor or a more corrosion resistant material. Thus, relatively fast corrosion of the first conductor can be used to monitor the risk of corrosion. Preferably, the system contains a galvanic connection between the first and second conductor at least during normal use in the system, which speeds of corrosion of the first conductor in the presence of water. The corrosion may be detected for example by means of time domain reflectometry of signals transmitted along the cable. In the case of the coaxial cable, the outer conductor and the electrical isolation are water permeable, e.g. braided.