Interleaved Electrode Arrays for Subsea Control Module Leak Detection
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Solution Overview
Problem
Existing subsea control module (SCM) leak detection systems cannot effectively detect hydraulic fluid ingress and suffer from corrosion due to current flow through electrodes, while being insensitive to glycol-based hydraulic fluid contamination.
Innovation Solution
The system employs interleaved electrode arrays on an insulating mat with gold-plated flexible printed wiring boards, connected to conditioning and detection circuitry, using resistance, capacitance, and pressure measurements to detect both sea water and hydraulic fluid ingress, reducing corrosion through controlled current flow and multiple measurement methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If metal electrode pairs are used for leak detection, then sea water ingress can be detected, but the electrodes suffer from corrosion due to current flow
Solution Approach 1:
The patent replaces the traditional metal electrode system with a capacitive sensing system using printed circuit board traces. This substitution eliminates direct current flow through metal electrodes, preventing corrosion while maintaining detection capability through electrical field interaction with the fluid medium.
Solution Approach 2:
The invention changes the detection parameter from direct electrical conductivity measurement through metal electrodes to capacitive coupling measurement. By using insulated traces and measuring changes in electrical field distribution, the system detects fluid ingress without the harmful side effect of electrode corrosion.
2Device complexity
If traditional electrode pairs are used, then detection circuitry is simple, but hydraulic fluid ingress cannot be detected
Solution Approach 1:
The capacitive sensing system using printed circuit board traces serves multiple detection functions: it detects both sea water ingress and hydraulic fluid ingress, provides location information through trace positioning, and maintains compatibility with existing operational amplifier circuits. This multi-functionality resolves the limitation of traditional electrode pairs.
Solution Approach 2:
The insulating panel and printed circuit board traces act as intermediaries between the detection circuitry and the fluid environment. This intermediary structure enables detection of various fluid types through capacitive coupling without requiring direct electrical contact, thus expanding detection versatility while keeping circuitry relatively simple.
3Measurement precision
If electrode pairs are mounted on insulating panels, then sea water detection is enabled, but the system cannot distinguish between different fluid types
Solution Approach 1:
Different regions of the printed circuit board are assigned different trace patterns and positions to detect specific fluid types. By localizing detection capabilities to specific trace configurations, the system can distinguish between sea water and hydraulic fluid ingress based on which traces are affected.
Solution Approach 2:
The detection system is segmented into multiple independent trace pairs or groups, each potentially optimized for detecting specific fluid types. This segmentation allows the system to identify which fluid is present by analyzing which segments show changes in capacitive properties.
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 accurate detection of hydraulic fluid and sea water ingress with reduced electrode corrosion, providing a zoned measure of fluid displacement and supporting the well operator with reliable monitoring and corrective actions.
Implementation Method 1
the conductivity of the contaminate in the oil is much less than that due to sea water and thus the existing contamination detection technique described before was not sensitive enough to be able to detect the ingress of trans-aqua fluids
Implementation Method 2
ingress of these contaminants displaces the transformer oil from the base of the SCM upwards
Implementation Method 3
using resistance, capacitance, and pressure measurements to detect both sea water and hydraulic fluid ingress
Data Source
Figure 1~2
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AI summary
A subsea control module has a casing (1) inside which there is at least one pair of electrodes, there being electronic means (26-33) connected with the electrodes of the or each pair for monitoring at least one electrical characteristic between the electrodes as a result of a fluid to which the electrodes are exposed, the or each pair of electrodes comprising an array (19) in which each electrode of the pair has finger portions interleaved with finger portions of the other electrode.