The Use of Reflection Mode Ultrasonic Transceiver Sensor in Pipeline Inspection Guage to Monitor Pipeline Internal Corrosion

Aging gas transmission pipelines are prone to internal corrosion due to the presence of carbon dioxide and hydrogen sulphide in the natural gas constituents. Commonly, the in-line inspection tool known as Pipeline Inspection Gauge (PIG) is applied to perform the corrosion inspection of the pipeline. This paper describes an ultrasonic instrumentation system for PIG to monitor internal corrosion of pipeline. The system consists of ultrasonic transceiver sensor, ultrasonic driving circuitry and data acquisition system. The hardware is equipped with a sensor carrier which is propelled along the test pipeline. The time of flight (TOF) of the ultrasonic wave is measured and was used to evaluate the internal corrosion of pipeline. An initial experimental instrument was set up to perform the distance measurement test at a frequency of 390 kHz, to simulate the changes of pipe wall thickness due to corrosion effect. Surface anomalies were created at different positions to simulate the changes of pipe wall thickness due to the corrosion effect. Variation in measured distances implied the existence of the surface anomalies. The results of the simulated surface anomalies showed that the percentage error was less than + 5%. The large value of average DC voltage gave indication of distance increment due to the depth of the surface anomalies. The developed ultrasonic instrumentation system is capable to monitor the internal corrosion of pipeline.