The Influence of Surface Eddy Current Probe Signal Smoothing on Assessing Stress-Corrosion Cracks Depth in Main Gas Pipeline

Abstract

The paper presents the results on the influence of signals smoothing of absolute and differential surface eddy current probes (ECP) above an individual crack and a group of stress-corrosion cracks on the accuracy of estimating the depths of stress-corrosion cracks during eddy current flaw detection of a main gas pipeline (MGP). Mathematical models demonstrate that the degree of signal smoothing of the surface ECP over an individual crack is higher than the degree of smoothing of the ECP signal over a group of stress-corrosion cracks in the MGP. Smoothing results in a decreased resolution of the surface ECP signal. The differential surface ECP is characterized by a higher resolution than the similar absolute surface ECP. The study demonstrates the reduction in amplitude difference between the actual signals of the absolute surface ECP over an individual crack and a group of stress-corrosion cracks, compared to the smoothed signal of the surface ECP. In the estimates of depths in the group of stress-corrosion cracks in MGP, obtained from the amplitude of the actual signal of the absolute surface ECP, where smoothing of the ECP signal is excluded, a significant reduction in the relative error is observed.