ADVANCED ULTRASONIC IN-LINE INSPECTION FOR THE ASSESSMENT OF PIPELINES AFFECTED BY PITTING AND PINHOLE CORROSION

The network of pipelines worldwide is growing and aging which leads to an ever increasing focus towards integrity management of these pipelines. One major challenge faced by today's operators is the realization and management of corrosion of pipelines. Unless detected, sized and documented correctly corrosion does pose as a major time-dependent threat to the aging pipeline network which eventually, if undetected and uncontrolled, can lead to catastrophic failures. Inline inspection (ILI) by means of intelligent pigs is widely used to ensure a safe operation of pipelines. Ultrasonic technology (UT) is currently the most accurate and reliable inline inspection technology available in the market. Highly specialized UT ILI tools can detect and size pipeline threats related to corrosion or cracking. High resolution tools as available today allow for the reliable inspection of tiny corrosion defects such as pittings or even pinholes. These small but often deep anomalies are severe forms of corrosion known to have caused pipeline failures in the past. The economic environment for oil companies has changed significantly in the last few years where reduced prices and margins for oil transportation and production challenge pipeline operators globally. At these tight margins, operators must scrutinize closely the indirect costs of performing inspections. Any constraints imposed by required inspections have the potential to negatively affect margin, including the reduction of pipeline flow rates to accommodate optimum inline inspection conditions. The latest generation of UT tools offer higher inspection speeds which overcome the need for flow reduction, therefore reducing transportation losses due to the reduction of throughput. In addition, there is also a need for enhanced axial and circumferential resolution to enable reliable detection and sizing of e.g. pinhole corrosion defects. Without the necessary measuring resolution these defects otherwise might go undetected and un-accounted for. In this contribution, the latest improvements of ultrasonic ILI are described and illustrated by inspection results.