Research On Inspection Technology Of Pipeline Anticorrosion Layer Based On Ultrasonic Guided Waves

The oil and gas pipeline is often protected by external anticorrosive layer.Anticorrosive layer in the soil is susceptible to corrosion,damage caused by a variety of reasons,and lose the protection effect.Thus resulting in pipeline fracture,or even explosion and other hazards.It causes waste of energy,economic loss,and endangers the safety of people and property.At present,the international use of outer detection methods for the detection of defects in the coating.These methods are to add incentives to the pipeline,artificial in the pipe along the top of the test.This requires a lot of manpower,time,and by terrain and weather and other natural conditions.The ultrasonic guided wave is used to detect the defects of the anticorrosion layer in the pipeline,which avoids the limitation of the natural environment on the detection and saves manpower and material resources.According to the inner detection of anticorrosion layer defects in the pipeline,the propagation mode,path and echo signal energy,wave packet independence of the ultrasonic wave guided by the single-layer steel plate and the double layer board with the intact coating are studied in this paper.The energy attenuation,critical angle and waveform transformation of ultrasonic guided waves propagating in a solid medium are analyzed and studied.Based on the displacement field and stress field of ultrasonic guided waves propagating in a solid medium,the reflection and refraction coefficients of ultrasonic guided waves at the interface between layers are deduced based on the convergence condition at the interface between the two layers of solid dielectric.Nine groups of piezoelectric ultrasonic inclined probes with three different center frequencies and three different K values were used to detect the anticorrosion layer completely stripped of single-layer and double layer plate structure with good anticorrosion layer of the detection.The peak to peak,the packet independence,the energy mean and the peak scale coefficient of the echo signal are analyzed,A method of selecting piezoelectric ultrasonic oblique probe for detecting the anticorrosion layer in pipeline is proposed.Based on the probe selection method,select the 5MHz,K1 piezoelectric ultrasonic oblique probe with anticorrosion layer of steel plate to detect.The maximum critical value defect identification method is used to quantify and locate the peeling of the coating.The experimental results show that the energy of the ultrasonic guided wave echo signal decreases with the increase of probe center frequency and increases with the decrease of probe K value.The energy of the echo signal received when the ultrasonic guided wave propagates in a single plate with a completely stripped anticorrosion layer,is greater than the energy of echo signal detected during it propagates in the double layer of the anticorrosive layer.According to this experiment detected objects 5MHz,K1 piezoelectric ultrasonic diagonal probe is used for detection,the echo signal is not only good in the wave packet,but also has the largest peak scale factor.It is the best way to judge whether the coating has stripping defects with the detection conditions.The maximum critical value method is adopted to quantify and locate the coating peeling,and the accuracy increases with the increase of the peeling length of the coating.The results provide a basis for the engineering realization of the detection of the stripping defects in the pipeline by ultrasonic guided wave.