Imaging of pipeline irregularities using a PIG system based on reflection mode ultrasonic sensors

Abstract

Natural gas transmission pipelines age after a certain duration and are prone to internal anomalies due to the presence of carbon dioxide and hydrogen sulphide in the natural gas constituents. An intelligent pipeline inspection gauge (PIG) is one method that is used to evaluate pipeline integrity, particularly damage resulting from corrosion threats. In this paper, an ultrasonic prototype PIG was developed that incorporates reflection mode ultrasonic sensors to measure anomalies on the internal surfaces of pipelines. The system consists of ultrasonic sensors, conditioning circuits and a data acquisition system (DAS). Sixty ultrasonic sensors were used mode at a frequency of 390 kHz. Surface anomalies were simulated at different locations on the internal surface of the pipeline to simulate changes in the pipe wall thickness. Variation in the measured distances implied the existence of surface anomalies. The results showed that the percentage error was less than ±0.50%.