The Study of Possibility of Stress-Corrosion Cracks Group Resolution by Eddy-Current Flaw Detector

The question on the possibilities of spatial resolution for a group of stress-corrosion cracks in the body of a steel pipe under eddy current control was considered. Using a VD-12NFP eddy current flaw detector, stress-corrosion cracks on specimens with artificial defects were investigated. Specimens were made according to the results of statistical studies of linear dimensions and the location of stress-corrosion cracks of operational origin in a section of the main gas pipeline. In the course of the research, it was revealed that it is possible to achieve sufficient spatial resolution for a group of stress-corrosion cracks in the pipe body using signals from a detachable eddy current probe (ECT) of the transformer type, which is part of the eddy current flaw detector. For this, the diameter of the probe core should not exceed the interval between adjacent defects in the group of cracks. The signal half width of the detachable eddy current probe installed above the defect is an informative parameter for the eddy current probe signals. It depends on the number of defects in the stress-corrosion crack group.