Small Diameter Remote Field Eddy Current Inspection for Unpiggable Pipelines

In-line inspection tools cannot inspect most of the natural gas transmission pipelines and distribution mains due to restrictions in the pipelines that will not allow a tool equipped with current inspection technologies to pass. Remote field eddy current (RFEC) inspection is an excellent candidate for inspecting a pipeline with multiple diameters, valve and bore restrictions and tight or miter bends. The results of this paper show that the RFEC technique can inspect pipeline materials, and that all of the components needed for RFEC inspection can be made much smaller that the pipe diameter. RFEC inspection is commercially available for inspecting small diameter piping without restrictions, several hundred feet at a time. The prototype design described in this paper shows this technology will work in a free-swimming tool that can inspect miles of pipeline at time and bypass restrictions.