New possibilities for non-destructive testing of pipelines with intelligent pigs
Pipelines are considered to be the safest way for transportation of large amounts of liquid and gas over large distances. In the course of the lifetime of a pipeline, however, many effects can lead to damages affecting the integrity of the line, e.g. manufacturing-related anomalies, operationally induced anomalies or third-party damage. In order to avoid pipeline failures with potentially catastrophic consequences so-called intelligent pigs (or smart pigs) were developed during the last decades: These tools allow for the internal inspection (In-Line Inspection, ILI) of pipelines using non-destructive testing technologies for the early detection and sizing of defects. Most common are magnetic flux leakage (MFL) and ultrasonic techniques for corrosion inspection and the latter also for crack inspection. While the ultrasonic techniques offer superior sizing capabilities they are limited to the inspection of liquid pipelines where the medium itself provides the necessary coupling between the (piezoelectric) ultrasonic transducers and the pipe wall. However, this limitation can be overcome by recent developments using EMAT (Electro-Magnetic Acoustic Transducer) technology. By a special sensor design, the EMAT inspection is combined with eddy current (EC) inspection and MFL inspection at the same time. As a result, this new multi-technology approach offers improved sizing as well as enhanced feature identification for wall thickness inspection of gas pipelines.