Study On Weak Signal Processing Technology Applied To Pulsed Eddy Current Testing System

Recognized as the lifeline in ocean oil and gas engineering,submarine pipeline is perceived to be the safest and the most convenient way to transport offshore oil and gas.Although high-quality steel is selected to ensure the texture of pipeline,the decrease of wall thickness caused by corrosion results in pipeline's failure due to the transportation of corrosive liquid with high temperature and pressure.In recent years,pipeline leakage accident happens frequently around the world because of long in-service time and laggard inspection technology.Pulsed Eddy Current Testing(PECT)is one of the emerging nondestructive testing technology,which is based on electromagnetic performance changes of the object.This technique can implement rapid measurement of residual wall thickness without affecting the working state and destroying protective layer of pipelines.Consequently,the research of Pulsed Eddy Current Testing technology applied in the measurement of submarine pipeline's wall thickness is of great significance to ensure safe and stable operation of submarine pipeline.However,PECT output signal is extremely weak.In the light of this,how to measure weak signal of magnetic variation,acquire denoised detection signal and extract useful information from feature signal are vital problems in this field.In this paper,the development trend and existing problems of PECT technique are discussed based on previous researches.Firstly,basic theory of Pulsed Eddy Current Testing is researched in the perspective of electromagnetic principle,and the equivalent circuit model is used to analyze the characteristics of output signal in detection system.Secondly,numerical simulation model is built to calculate the quantitative results of the output signal and select proper figures for wall thickness measurement by analyzing signal.Thirdly,the testing system focuses on how to improve system's anti-jamming ability and difficulty of signal extraction.Useful signal is extracted with the help of signal processing program.In the process of system construction,the emphasis is placed on the design of hardware system and data handling program.PECT testing device is accomplished for measuring steel plate's thickness.Finally,performance testing of PECT system is conducted.The result shows that relative error is less than 10% for the steel plate's thickness ranging from 9.5 mm to 27.6 mm.This paper conducts intensive research in weak signal processing technology applied to pulsed eddy current testing system.PECT testing system used to measure steel plate's thickness is accomplished,which has broad prospects of engineering application.