How to do Guided Wave Testing of Pipelines

Guided wave testing (GWT) is one of NDT methods using low-frequency ultrasonic waves that propagate along the length of a pipeline. The procedure of GWT consists of cleaning pipe surface, install probe, turn on equipment, acquire data, record pipe information, analyze data, and report findings. It is fundamentally the same as the conventional ultrasonic testing including testing procedure and analyzing data except using bigger size of ultrasonic probe, using low frequencies of 10 to 250 kHz, and inspecting a long distance of pipeline with a single test location. Therefore, the guided wave testing is also known as Long-Range Ultrasonic Testing (LRUT) and Guided Wave Ultrasonic Testing (GWUT). Although guided wave testing is similar to conventional ultrasonic testing in testing procedure, it requires lots of training and experience for inspectors to do the data analysis and reporting properly. The difficulties of GWT are coming from the long inspection range and the various conditions of pipelines such as coating, buried and aboveground, viscosity of pipe content, many geometric features that are welded or attached on pipeline, different sizes of pipe, and pipe surface condition. However, the upgrades in guided wave probes, data analysis software, and procedure make the field testing easier and thus allow finding many different sizes of defects in pipelines using multiple center frequencies.