| Buried metal pipeline transportation is an important energy transport mode,and its corrosion detection has become an important component of the safe operation of the pipeline.There are many methods for detecting the corrosion of buried pipelines,among which laser detection,magnetic flux leakage detection,ultrasonic detection and far-field Eddy current detection are mainly used in the detection of buried pipelines,for long-distance buried pipelines,there are some limitations,and the "NOPIG" method is a new method,which can not be used in practice.Based on the transient electromagnetic method,this paper develops a rapid corrosion detection system for buried pipeline from four aspects:Theoretical analysis,software development,instrument optimization and experimental verification.Firstly,the secondary response voltage curves of the pipeline with different residual wall thickness are obtained by ANSYS electromagnetic modeling,and the relationship between the transient electromagnetic early response and the wall thickness is analyzed,and the apparent depth-apparent resistivity curve is calculated.By analyzing the relationship between the apparent resistivity at the apparent depth of lm and the wall thickness of the buried pipeline,the estimation formula of the wall thickness of the buried pipeline is obtained.Furthermore,the effects of soil resistivity,pipe depth,pipe inner diameter and pipe cover thickness on the formula are analyzed.When the soil resistivity changes in the range of 10?·m?400?·m,the error of the wall thickness formula is smaller,the maximum error is only 1.95%,and the maximum error is 30.53%when the pipe cover thickness changes in the range of 0 mm?200 mm.The buried depth and inner diameter of pipeline have great influence on the calculation of wall thickness.In order to reduce the calculation error of the wall thickness caused by different pipe buried depth and pipe inner diameter,the wall thickness estimation formula is optimized,and a corrected wall thickness estimation formula with pipe buried depth and inner diameter is proposed.Then,the module of software and equipment communication,data stack and noise reduction,data window display and pipe wall thickness calculation are designed,and the software of acquisition and post-processing is developed.In view of the low efficiency of the traditional transient electromagnetic point measurement mode,the transient electromagnetic continuous measurement mode combined with the GPS real-time positioning system is proposed,and the traditional transient electromagnetic hardware and software systems are optimized,the transient electromagnetic continuous dynamic detection based on the corrosion of buried pipeline is realized.Finally,a corrosion detection model of buried pipeline is built,and the transient electromagnetic point detection model and the continuous detection model developed in this paper are used to detect the model.The advantages and disadvantages of the two inspection modes are compared from the inspection effect and the construction efficiency respectively.The starting point of the corrosion percentage curve measured in the point inspection mode is more but the position is accurate,the corrosion percentage curves measured in the continuous mode are smooth but have some distance deviation.The detection efficiency of point detection mode is low,and that of continuous detection mode is high.Using the transient electromagnetic continuous measurement and detection system for buried pipelines developed in this paper,it is possible to achieve rapid detection of corrosion of long buried pipelines,which is suitable for pipeline corrosion detection survey... |
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