ACOUSTIC EMISSION LEAK DETECTION OF LIQUID FILLED BURIED PIPELINE

Several limitations and difficulties exist in the inspection and maintenance of underground pipelines that cannot use pigs (pipeline inspection gauges). Leaking is unavoidable in such buried pipelines and poses serious problem to the environment as well as the pipeline owners. Pipeline leakages are usually apparent either when the pressure is dropping for no other obvious reason or when valuable product is lost. However, even in the best-case scenario, where the operators can isolate specific pipeline sections suspected to leak, it is often the case that the operators cannot reliably locate the exact position of the leak so as to take corrective measures. Acoustic emission (AE) is an excellent tool for detecting and locating leaks in buried pipelines. Access to the pipeline is required only locally for mounting AE sensors. Pipeline is pressurized and AE tested in 600-to-1000-m-long sections at a time. The AE sensors detect the turbulent flow at the leak orifice, and with the use of digital AE systems and specialized software, the position of the leak is provided. The present paper deals with the technical description and the physics of the AE leak detection technique, presents the advantages, limitations and requirements of the method, describes the necessary functions of AE equipment for performing such a task, and, finally, reports on several case-studies of successful leak detection and location of buried pipelines. The case studies cover both new and in-service buried pipelines of different sizes.