A novel above-ground marking approach based on the girth weld impact sound for pipeline defect inspection

Above-ground marking systems, composed of instrumented pigs and above-ground markers (AGMs), have been widely used to locate defects in long-distance buried pipelines. However, the location error for most of the existing AGMs can be up to several tens of centimetres. In this paper, an innovative marking method based on the girth weld impact sound is proposed. An equally-spaced four-sensor linear array was employed to collect the impact sound between the pig and the girth weld in the pipeline. A time difference of arrival (TDOA) algorithm was applied to locate the weld. Experiments show that this method can clearly locate the position of a weld relative to the linear array in buried pipelines with an error of less than 0.1 m. It is envisioned that the method has great potential to monitor the safe operations of long-range buried pipelines.