基于交流场指纹法的金属管道缝隙腐蚀监测方法

Monitoring method for crevice corrosion of metal pipeline based on alternating current field signature method

场指纹法(FSM)是一种基于电位阵列的金属管道在线腐蚀监测方法。传统的直流FSM(DCFSM)是在管道中通直流电流激励,通过监测电极间的电压变化推算出管道内部腐蚀。DCFSM在缝隙腐蚀监测方面,侧重于监测缝隙的起始及扩展方向。而在深度检测方面,由于DCFSM每个电极对间仅有一个电压值用于求解腐蚀,因而只能使用经验公式,检测精度低。交流场指纹法(ACFSM)核心是将现有的DCFSM的电流激励换为交流,通过变频获得电极对间多个频率点的电压值;利用多个电压值求解缝隙腐蚀深度,提高缝隙腐蚀深度检测精度。ACFSM依据交流电流在管道内分布满足趋肤效应,不同频率的电流在金属中的渗透深度不同,测量电极间的电压也不同。本文在介绍ACFSM原理基础上,创新地提出了一种依据多频电压值求解FC值随频率的变化曲线,利用曲线导数值来计算管道内缝隙腐蚀深度的方法。理论分析和实验表明,本文提出的方法可以精确地检测缝隙腐蚀的深度,弥补了DCFSM在缝隙腐蚀监测精度上的不足。

Field signature method（ FSM） is a kind of online metal pipe corrosion monitoring based on the potential drop-array.The traditional direct current FSM（ DCFSM） is based on the excited direct current（ DC）,and the pipeline internal corrosion is calculated by monitoring the voltage variation between electrodes.Initiation and orientation of crevice corrosion is emphasized in crevice corrosion monitoring with the DCFSM.Due to only a voltage value exsiting between every pair electrodes for solving corrosion in DCFSM,some experiential formulas should be used,and the accuracy is low.The core of alternating current FSM（ ACFSM） is based on replacingt the AC excitation source by the DC excitation source,and several voltage values are achieved by changing the frequency t.Using multi-frequency voltages to solve the depth of crevice corrosion,the accuracy is improved.ACFSM is based on AC distribution meeting with the skin effect in metal pipe,ACs with different frequencies penetrates different depths,and different voltage value between electrodes are gained.The basic principle is of ACFSM is presented,and an innovative method is proposed by solving FC curve according to multi-frequency voltage primarily by using the derivative of FC curve to compute depth of crevice corrosion.Theoretical analysis and experiment results show that the proposed method can detect crevice corrosion accurately,and it makes up DCFSM in the crevice corrosion depth detection.