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TOFDisaNonDestructiveTestingwhichisreliableweldinginspectiontechniquewithhighdetectionrate.
Time of Flight Diffraction is based on the Principle of
Diffractionincontrasttore�lectionofultrasoundasusedin
conventional UT. Diffraction takes place at its extremities
whenultrasoundisincidentatlineardiscontinuitysuchas
crack.Thedepthofcracktipscanbecalculatedautomatically
bytrigonometryapplicationbyusingthemeasuredtimeof
�lightofthepulse.TOFDisverysensitiveindetectingallthe
typesofdefect,irrespectiveofitsorientation.
ToFDisanadvancedinspectiontechniqueusesthe
diffractedsound initiating fromthe �lawtips.And
whichdoesnotrelyonthere�lectivityofthe�law.Itis
abletodetect�lawsirrespectiveoftheirorientation
ortype.
Acoupleofprobessitontheoppositesidesofaweld.
Oneoftheprobesemitsanultrasonicpulsewhichis
pickedupbytheprobeontheotherside.
Inanundamagedpipe,thesignalspickedupbythe
receiver probe are from two waves: one which
travelsalongthesurfaceandtheotherre�lectsoff
the far wall.When a crack is present, there is a
diffractionoftheultrasonicwavefromthetip(s)of
thecrack.Byusingthemeasuredtimeof�lightof
the pulse, the depth of a crack tip is calculated
trigonometrically.
AdvantagesofTOFD
This unique ultrasonic technique has greatadvantageindetectionof�laws,speedanditisthemostaccuratedefectsizingtechnique.
TOFD is proven to be a technique, whichcombineshighdetectionratewithaveryhighreliability in pre-service and in-serviceinspections.
Absenceofradiationisoneofitsmostimportantadvantagesforweldinspection
Nearly independent of fluctuation in surface conditions.
Defect position and size can be exactly determined.
ApplicationAreasofTOFD
Pre-serviceinspection
Ø Weldinspectionofvessels,pipelinesandplates
In-serviceinspection
Ø Weldinspectionofvessels,pipelinesandplates
Ø Detectingcorrosionunderneathreinforcement
ringsofnozzles
Ø Detectingcorrosionunderneath
Ø Reinforcementringsofnozzles
Ø Claddingthicknessmeasurement
Ø Determiningdepthofcracks
No evacuation of areas during operationbecausenoradiationisused.
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