The Pulsed Eddy Current Testing Method And Research Of Pipeline Inwall Corrosion

Because of its unique advantages, ferromagnetic pipeline has become to one of the main transport means, which was widely used in petroleum, chemical and power field, etc. During tube' long-running process often resulting in corrosion and thinning in the internal pipeline with a cladding layer, due to the corrosive properties of its transmission medium and working environment, etc. threaten the operation' reliability and safety seriously. Therefore, the periodic non-destructive testing(NDT)on pipeline corrosion condition is essential. Pulsed eddy current testing(PECT) as the rapidly developed novel electromagnetic NDT methods, with the merits of abundant spectral information, high signal penetrating has become an indispensable part of modern NDT field. The application prospect is very promising.Based on lots of literatures, this article taken the ferromagnetic pipe with cladding layer pipe as the subject, investigated the related issues of pipe wall detection which need to stop running, remove the cladding layer.Finite element software was used to simulation analysis on the PECT of ferromagnetic pipe wall' corrosion flaw, observed the eddy current density distribution of pipeline, and characterized on the response signal from detection coil, the variation between corrosion defect depth and induced voltage signal was obtained. Furthermore, many factors which affect PECT were investigated by simulation software, such as the influence of variety of the cladding layer thickness, the signal parameters of pulse excitation(voltage amplitude, frequency and duty cycle) and the parameters of excitation coil(diameter, height and turns) on detect results. Provide a theoretical basis for the design of the detection system.According to the theoretical model and simulation results, designed the overall design framework of PECT system, and completed the design elements of each module part, including signal generation module, power amplifier module, sensor module and data acquisition module, build the test platform of PECT system on ferromagnetic pipe wall corrosion defects successfully.The established experimental testing platform was used to detect large area uniform corrosion and small area corrosion pits defects of the inner wall of the pipe specimens. Based on the detection signal' filtered and de-noising, extracted the eigen values of time domain and frequency domain analysis. Compared the variation between corrosion defects and response signal of Pulsed Eddy current, the effectiveness of detection system was verified. Meanwhile, the detection results of testing systems under different cladding layer thickness was investigated by this study. The reliability of PECT system was verified, which demonstrated the feasibility of project design. Provide a reference for the design of the detection system.