Study Of Apparent Resistivity Imaging Technology For Pipelines Corrosion Detection

Due to the changing of working environment and inner parameter, buried pipelinewill cause the danger such as corrosion perforation, this not only pollutes theenvironment, but also brings great losses to the national economy. Therefore, in-servicedetection of buried pipeline corrosion degrees is of greatest importance to the safeoperation of pipelines. At present, methods of detecting pipeline corrosion includemagnetic flux leakage testing、ultrasonic testing、eddy current testing technology and soon, but all these methods can not be used in in-service detection. The paper will applythe transient electromagnetic method to in-service detection of buried pipeline corrosion,and explain transient electromagnetic data using the apparent resistivity parameter.This paper according to the electromagnetic field theory in homogenous half space,equivalent calculates the transient electromagnetic field of pipeline, and deducestransient electromagnetic response model of layered media; According to the models toanalyze the transient electromagnetic signal, point out the influence relationship ofcut-off time and data processing. Through the comparison of three cut-off timecorrection methods, put forward the correction method of trapezoid estimate; Designtwo kinds of central loop sensors as the need of testing, by the analyzed of responsecurve and the optimization matching of experimental parameters, select the sensor thatthe transmitting coil is1.0m*1.0m(turns of10) and the receiving coil is0.5m*0.5m(turns of20), the optimum transmitting frequency f=4Hz when detectingpipeline is in a depth of1meter, the preamplifier gain is8and main gain is16; In thetransient electromagnetic data processing use the apparent resistivity imaging forqualitative and quantitative interpretation. To the solution of apparent resistivity, use thecorrection factor α to amend the normalized induction emf, thus the traditional solutionof apparent resistivity are improved, then the calculation results shows that apparentresistivity has unique solution; Put forward the calculation of inversion depth based onsmoke theory and achieved time depth conversion, so develop the imaging software forburied pipeline corrosion detection. Finally, the dual-channel transient electromagneticinspection system is used for the actual in-service detection of field buried pipelines.The actual test indicates that buried pipelines apparent resistivity imaging results canintuitionistic display pipelines abnormalities. This subject will provide security for thenormal operation of the buried pipeline.