Under previous programs for the Pipeline Research Committee, field tested a low frequency eddy current instrument for detecting and characterizing stress corrosion cracks in pipelines was developed. While a significant improvement over conventional magnetic particle inspections in some respects, the eddy current method as it was developed in these programs can only be used with surface breaking defects. Thus, it is limited to use for inspections of pipelines from the outside surface. In this program, we examined the use of a saturating magnetic field to allow increased penetration of the eddy...
Under previous programs for the Pipeline Research Committee, field tested a low frequency eddy current instrument for detecting and characterizing stress corrosion cracks in pipelines was developed. While a significant improvement over conventional magnetic particle inspections in some respects, the eddy current method as it was developed in these programs can only be used with surface breaking defects. Thus, it is limited to use for inspections of pipelines from the outside surface. In this program, we examined the use of a saturating magnetic field to allow increased penetration of the eddy current field into the pipe material, providing the ability to detect and characterize stress corrosion cracks from the interior of the pipeline. Until recently, eddy current inspections of steel were the exception not the norm, primarily because low frequency eddy current instruments were not available. In eddy current testing, the eddy current field grows smaller as it penetrates into the material being tested.