Study On Key Techniques In Acoustic Above Ground Marker

With the rapid development of pipeline transmission sector, pipeline accidents occur frequently, and cause enormous economic loss and environmental pollution. The pipeline inspection gauge(Smart PIG) can inspect pipeline defects, such as corrosion, deformation and crack, and identify the potential threat, also prevent the pipeline accidents. Smart PIG locate the pipeline defects by the odometer, and the odometer will bring great errors of the defects'location. As the ancillary equipment of the Smart PIG, the above ground marker(AGM), which is designed to eliminate the errors of the odometer and precisely locate the pipeline defects with the error of less than 1m, record the time when the Smart PIG is passing through the known location.In order to satisfy the new requirement of more depth and thicker pipeline wall, a new acoustic AGM was proposed in this paper, by comparing the advantages and disadvantages of the existing AGM and basing on the development trends of AGM.Besides, four key technologies of the acoustic AGM has been studied. Aiming at the shortcoming of unstable signal acquisition of the existing acoustic AGM, a acoustic AGM experimental system was established, which was successfully applied in the field experiments, and the stability of the system was improved.Considering the low accuracy and poor anti-jamming ability of the existing acoustic AGM, a acoustic method of AGM with single acoustic sensor, based on the function fitting envelope, was put forward. Experients showed that, the accuracy of the method in this paper is much higher than the traditional envelope method, and the anti-jamming ability is improved.according to the problem of the small inspected depth of AGM with single acoustic sensor, a method of acoustic AGM based on acoustic sensor array signals enhancement is presented, which collected data by a linear array vertical to the pipe, and enhanced the crash sound of the Smart Pig by using of delayed-add beam-forming algorithm, as a result, the SNR of the crash sound was gained by 20 db, and the inspected depth was increased to 8 m.Because of the short propagation distance and unobvious features of the crash sound, this paper put forward a method of AGM based on the weld impact sound. The weld was located based on the time difference of arrival (TDOA) algorithm, by using a linear array along the pipe to collect data. Experients showed that, The error of the TDOA weld location method is less than 0.4m.