Eddy current testing is a widely used NDT inspection technique for both ferrous and non-ferrous materials. This may explain why it was one of the very early techniques implemented on an inline inspection tool (ILI) back in the 1970s, following the first implementation of Magnetic Flux Leakage (MFL) tools. Eddy current testing is primarily developed to accurately detect and size surface breaking defects. The technology is now mature and has been deployed in various applications, most notably for pipeline in-ditch inspection.

The most common use of eddy current technology in ILI tools is a simple configuration for lift-off measurement. This offers a way to discriminate between internal and external corrosion on a volumetric tool (MFL) or enhance caliper-based geometry measurements. The most advanced applications of eddy current testing are targeting measurement of electromagnetic properties of the pipe wall to either measure material properties (pipe grade) or pipe stress due to external loading.

This paper will present the latest effort in developing eddy current testing for strain measurement in pipelines. The fundamental physical principles will be reviewed, and some key parameters considered during the design. Internal validation steps and results will be highlighted. 

The technology developed by NDT Global under the name of ETEC-GEO (Eddy current Technology - Geohazard) is specifically targeting threats related to Geohazard. Working with IMU (Inertial Measurement Unit) and Geometry module, the combination of measurements, so-called Geohazard tool, is believed to offer the best dataset to detect and characterize Geohazards in pipelines.

With collaboration and support of pipeline operators, the Geohazard tool is undergoing a validation campaign with the first results presented for a known and managed reference geohazard event. Correlation to known events is key to validating new technology, and the site presented has extensive data available to fully understand and validate the Geohazard tool measurement.