Defect detection in pipes using guided waves

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1、Ultrasonics36(1998)147-154DefectdetectioninpipesusingguidedwavesM.J.S.Lowe*,D.N.Alleyne,P.CawleyAbstractThedetectionofcorrosionininsulatedpipesisofmajorimportancetotheoilandchemicalindustries.Currentmethodsinvolvingpoint-by-pointinspectionareexpensivebec

2、auseoftheneedtoremovetheinsulation.AnalternativemethodwhichisbeingdevelopedatImperialCollegeistopropagateguidedwavesinthewallsofthepipes,andtolookforreflectionsfromdefects.Thetestconfigurationisessentiallypulse-echo;theinsulationisremovedatjustonelocatio

3、nonapipeandthesignalsarethentransmittedandreceivedusingasingletransducerunit.Thetechniqueiscurrentlyundergoingfieldtrials.Thispaperpresentsareviewofthestudiesofthepropagationofthewavesandtheirsensitivitytodefectswhichhavebeenconductedinordertoprovideasou

4、ndscientificbasisforthemethod.Issuesofimportanceweretheselectionoftheoptimumguidedwavemodesandtheestablishmentofrelationshipsbetweenthedefectsizeandthestrengthofwavereflection.Analyticalandnumericalstudieswereconductedinparallelwithanextensiveexperimenta

5、lprogramme.01998ElsevierScienceB.V.Kqwords:Guidedwaves:Lambwaves;NDE;Pipeinspection1.Introductiontoothersizes.Thetestingschemeemploysapulse-echoarrangementfromasinglelocationonapipe,usingTheoil,gas,chemicalandpetro-chemicalindustrieswaveswhichareguidedal

6、ongthepipewall,illustratedoperatehundredsofkilometresofpipelines,oftentrans-inFig.1.Thewavesareexcitedandreceivedusingaportingcorrosivesubstances.Ahighproportionoftheseringtransducermadeupofmechanicallyindependentindustrialpipelinesareinsulated,sothateve

7、nexternaldry-coupledpiezo-electricelementsdistributedaroundcorrosioncannotreadilybedetectedwithouttheremovalthecircumference.Byexcitingalloftheelementsequallyoftheinsulation.whichinmostcasesisprohibitivelyandconcurrently,anaxiallysymmetricmodeisexpensive

8、.Thereisthereforeanurgentneedforthelaunched.Thepresenceandaxiallocationofdefectsindevelopmentofaquick,reliablemethodforthedetec-thepipewallaredeterminedbyanyreflectionsandtheirtionofcorrosionunderinsulation(CUI).arrivaltim