Impedance Probe for Prestressed Concrete Pipe Wire Break Detection
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Solution Overview
Problem
Conventional non-destructive testing methods, such as Eddy-current Testing, are impractical for detecting breaks in prestressed wires within prestressed concrete pipes due to limitations in depth penetration and accessibility, especially when a metal cylinder is embedded, and require complex coil setups which are time-consuming to set up and prone to spurious signals.
Innovation Solution
A method using a large impedance probe with multiple coils or a single solenoid to generate a strong magnetic field, allowing for the measurement of impedance along the pipe to detect anomalies indicative of prestressed wire breaks, avoiding the complications of separate transmit and receive coils and overcoming the limitations of conventional ECT probes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional Eddy-current Testing is used to detect breaks in prestressed wires, then the testing method is simple, but the depth penetration is insufficient and the metal cylinder blocks the signal
Solution Approach 1:
The patent introduces prestressed wires as an intermediary conductor between the exciter coil and detector coil. The magnetic field from the exciter coil induces currents in the prestressed wires, which then induce signals in the detector coil, allowing detection through the concrete pipe wall despite the metal cylinder blocking direct field penetration.
Solution Approach 2:
The patent replaces direct magnetic field penetration through the metal cylinder with an indirect electromagnetic induction path through the prestressed wires. Instead of attempting to penetrate the blocking metal cylinder directly, the system uses the wires as a conductive pathway to transmit the magnetic signal around the obstruction.
2Measurement precision
If Remote Field Testing with separate exciter and detector coils is used, then detection capability is improved, but the setup complexity increases and more time is required
Solution Approach 1:
The patent combines the exciter coil and detector coil into a single integrated probe assembly that can be inserted into the pipe. This merged design maintains the functional separation of excitation and detection while simplifying the overall setup procedure and reducing the time required for inspection operations.
3Reliability
If Remote Field Testing with wide coil spacing is used, then direct field effects are minimized, but the setup time increases and coupling must be carefully managed
Solution Approach 1:
The prestressed wires serve as an intermediary that transmits the magnetic signal from the exciter to the detector coil. This intermediary pathway allows the system to achieve reliable detection while maintaining appropriate coil spacing to minimize direct coupling, as the wires carry the signal rather than direct field penetration.
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 effective detection of breaks in prestressed wires by inducing significant currents in the wires despite large lift-off, providing clear impedance anomalies that indicate wire breaks, and can verify correct pipe section installation by analyzing impedance patterns.
Implementation Method 1
A magnetic field is generated by driving a time-varying current through the impedance probe
Implementation Method 2
The alternating current in the coil or coils generates a changing magnetic field which interacts with the conducting pipe and induces eddy currents within the metal cylinder embedded in the pipe wall
Implementation Method 3
the magnetic field travels outwards from the exciter coil, through the pipe wall, and along the pipe
Data Source
AI summary
A method is provided for inspecting a prestressed concrete pipe (PCP). An impedance probe is passed along the PCP. As the impedance probe travels along the PCP, a magnetic field within the impedance probe is generated and the impedance of the impedance probe is measured. The measured impedances are analyzed for anomalies, which may indicate broken prestressed wires. RFT probes, which are what are typically used for inspecting PCPs, require axial separation of two coils, one being an exciter coil and the other being a passive detector coil. However, there is only a single coil in an impedance probe and so the apparatus used to inspect the PCP is not as large axially. The apparatus used to inspect the PCP is simpler to set up than if an RFT probe is used, and coupling between a transmitter and a receiver is not a concern.