An Experimental Study on Pressure Fluctuation and Its Influence on Inspection Signals during an Ultrasonic Tool Passing Through Circumferential Weld Seam

In oil and gas pipeline inspections, the performance of the inline ultrasonic internal detector depends on the transmission and reception of ultrasonic echo signals by its transducer. Wave propagation is affected by environmental noise, particularly from high-pressure background noise and pressure wave transmission. The detector’s passage through girth weld seams induces significant pressure fluctuations, which are essential for locating the detector. Considering these factors is crucial for signal analysis. To address this, experiments with a frequency modulation control system were conducted on an experimental platform. Nine simulation experiments focused on the detector’s operation through circumferential weld seams, collecting high-frequency pressure and ultrasonic echo signal data. The analysis targeted the impact of pressure changes on wall thickness measurement accuracy. Notable pressure fluctuations occurred when the detector passed girth weld seams, with a maximum change of 1.36 MPa in Experiment 7# at the 4th weld seam. Experiment 9# showed the highest noise amplitude of  0.00013 and 0.00302 when passing the 1st girth weld seam, and the highest average speed, 0.13 m/s, was recorded in Experiment 5#. Despite these variations, they minimally affected the inspection tool’s accuracy, confirming its reliability under environmental influences.