Adaptive Noise Cancellation Schemes for Magnetic Flux Leakage Signals Obtained From Gas Pipeline Inspection

Nondestructiveevaluationofthegaspipelinesystemismost commonlyperformedusingmagneticfluxleakage(MFL) techniques.Amajorsegmentofthisnetworkemploysseamless pipes.ThedataobtainedfromMFLinspectionofseamlesspipesis contaminatedbyvarioussourcesofnoise;includingseamlesspipe noiseduetomaterialpropertiesofthepipe,lift-offvariationof MFLsensorduetomotionofthepipeandsystemnoiseduetoonboardelectronics. Thenoisecanconsiderablyreducethe detectabilityofdefectsignalsinMFLdata.Thispaperpresentsa newtechniqueforimprovingthesignal-to-noise-ratioinMFLdata obtainedfromseamlesspipes.Theapproachutilizesnormalized leastmeansquaresadaptivenoisefilteringcoupledwithwavelet shrinkagedenoisingtominimizetheeffectsofvarioussourcesof noise.Resultsfromapplicationoftheapproachtodatafromfield testsarepresented.Itisshownthattheproposedalgorithmis computationallyefficientanddataindependent. 1