Research On On-line Broken Wire Detection System Of PCCP Pipeline Based On Remote Field Eddy Current Technology

Prestressed steel cylinder concrete pipe(PCCP)is a kind of multi-layer mixed pipe.It has the tensile strength of steel wire,the compressive property of concrete and the anti-leakage property of steel plate.It is a kind of high-performance water delivery method.PCCP is widely used in national water conservancy,municipal engineering pipeline,and drainage of the city.Due to its special layered structure and the underground environment,the detection of external broken wires of the pipeline is a challenge.In addition,the period of PCCP pipelines used in China is relatively short,and its defect detection is still a blank area in China.Therefore,the research on PCCP pipeline detection technology makes a great value.In this paper,the far field eddy current technology is used to detect the defects of the PCCP wires.In addition,a model is built to simulate the electromagnetic eddy current test of PCCP pipeline,and the eddy current test experimental verification of the same scale model of PCCP pipeline is carried out to explore a new method for online defect detection of PCCP pipeline.In this paper,the theoretical analysis of the far-field eddy current detection system is carried out,and it is proved that the broken wire defect is mainly manifested in the variation of the induced voltage amplitude and phase.Then through the Comsol electromagnetic simulation,the non-broken wire pipeline,the number of broken wires and the frequency of the excitation signal are simulated,and the amplitude and phase of the voltage on the detection coil are obtained,which lays a foundation for the subsequent experiments.In the detection system design of this paper,the DDS module is responsible for generating the sinusoidal excitation signal,and the excitation coil is input to generate the far-field eddy current signal after being excited by the power amplifier.The data acquisition card is used to pick up the signal on the detection coil and send it to the upper computer for data processing.In the data processing system,the detection signal is first filtered by a band pass filter,and then the detection signal is processed by a quadrature lock-in amplifier to obtain the amplitude and phase changes.Finally,the defect of the PCCP pipeline to be tested is obtained by analyzing the variation of the amplitude and phase of the detected signal.In the experimental part of this paper,the PCCP model with different number of broken wires and different broken wire defects is tested,and experimental results and the simulation results are good agreement.The actual signals under different broken conditions of PCCP pipeline are obtained,and the pattern recognition of the signals is finally realized.