Study On Ultrasonic Testing Technology Of Not Paint Removal Pipings

The on-line inspection of painted pipes is a necessary means for the safety inspection of in-service pipelines.At present,the ultrasonic testing technology with painted pipes is mainly based on paint removal detection and fixed-point inspection,and it is difficult to realize the paint detection of in-service pipelines and long distance scanning detection.Therefore,by studying the influence of the paint layer on the ultrasonic test results and studying the influence of the ultrasonic transducer and the detection device on the ultrasonic signal,the difficulty of the ultrasonic detection signal and the difficulty in scanning detection of the painted pipe is solved to some extent.Firstly,in the two cases of unpainted layer and lacquered layer,the acoustic pressure and the transmittance of the sound intensity and the reflectivity of the ultrasonic layer are calculated and analyzed,and the thickness of the paint layer itself and the frequency of the ultrasonic transducer are painted.The key factors affecting the propagation of the ultrasonic waves,and the lacquer layer reduces the sound intensity of the ultrasonic waves during ultrasonic propagation,resulting in energy loss of the ultrasonic waves.Secondly,the lacquer layer will attenuate the ultrasonic wave,and the medium attenuation is the most important.The degree of attenuation depends on the nature,thickness,density,composition and proportion of the lacquer layer.However,the attenuation of paint layer to ultrasonic wave is limited.In the fixed-point test of different thickness plate test pieces with different thickness paint layers,it can be determined that the error of the ultrasonic test result of the epoxy resin paint layer below 200 mm is within the range of±0.15 mm.In the case of scanning detection with painted pipes,the choice of transducer and parameter design determine the quality of the detection signal and the detection results.By comparing and analyzing the sound field characteristics of circular planar transducers and circular focusing transducers.The sound field characteristics,because of the concentrated energy of the focus transducer,are more suitable for detecting thin thickness,coarser and coated workpieces,so it is more appropriate to use a focus transducer to scan the painted tube.Finally,the frequency of the processed transducer was determined to be 2.5MHz,5MHz and8 MHz.The piezoelectric wafer material was selected as lead zirconate titanate piezoelectric ceramic,the wafer diameter was 10 mm,the backing material was tungsten powder-epoxy resin,protective film and The acoustic lens material is made of plexiglass,wherein the acoustic lens is a concave planar acoustic lens with a radius of curvature of 65 mm.After calculation and selection,Finally,by designing three sets of different structure detection coupling devices and two sets of different walking mechanisms,and by analyzing the internal flow field of the coupling device,flow field stability,eddy current interference and air bubbles Excluding other aspects as the theoretical basis for judging the coupling effect,and using the design model as a blueprint to process a complete set of testing devices for actual testing experiments,the test results meet the basic requirements for scanning and testing of painted pipes,and the detection error Within 0.2mm.During the test,it was found that the water flow at the water outlet had a backflow impact due to the high nozzle height,which caused interference to the detection signal.The height of the nozzle and the velocity of the outlet determine the degree of disturbance of the water flow.By simulating the flow field at the outlet,theoretically the nozzle flow rate should be less than 8mm/s,and the nozzle height should be adjusted within 1mm-2mm.At this time,the flow disturbance will be weakened.