Low Frequency Eddy Currents with magnetic Saturation for In-Line Detection and Sizing of Stress Corrosion Cracks

Under previous programs for the Pipeline Research Committee, Battelle has developed and field tested a low frequency eddy current instrument for characterizing stress corrosion cracks in pipelines. While a significant improvement over conventional magnetic particle inspections, the eddy current method as it was developed in these programs is limited to use for inspections of pipelines from the outside surface. This paper examines the possibility of using this low frequency eddy current equipment to detect and size stress corrosion cracks from the interior of the pipeline by magnetically saturating the pipeline to reduce its permeability and thereby increase penetration of the eddy currents into the pipe