1. NON DESTRUCTIVE TESTING(NDT)

2. Outline Introduction to NDT Overview of Six MostCommon NDT Methods Principle, Working & Application 3. INTRODUCTIONWhat is NDT ?The use of noninvasivetechniques to determinethe integrity of amaterial,component or structureorquantitatively measuresome characteristic ofan object.i.e. Inspect or measure without doing harm. 4. What are Some Usesof NDT Methods? Flaw Detection and Evaluation Leak Detection Location Determination Dimensional Measurements Structure and Microstructure Characterization Estimation of Mechanical and Physical Properties Stress (Strain) and Dynamic ResponseMeasurements Material Sorting and Chemical CompositionDetermination 5. When are NDT Methods Used?There are NDT application at almost any stagein the production or life cycle of a component. To assist in product development To monitor, improve or controlmanufacturing processes To verify proper processing such as heattreating Fatigue and Creep damage prediction To inspect fitness-for-service evaluation 6. Methods of NDTVisualMagnetic ParticleLiquid PenetrateReplicationEddy CurrentTap TestingRadiographyUltrasonicMicrowaveAcoustic EmissionThermographyLaser InterferometryFlux LeakageAcoustic MicroscopyMagnetic Measurements 7. Major types of NDT Detection of surface flaws Visual Magnetic Particle Inspection Fluorescent Dye Penetrant Inspection Detection of internal flaws Radiography Ultrasonic Testing Eddy current Testing 8. Visual InspectionMost basic and common inspectionmethod.Visual inspection refers to an NDTmethod which uses eyes, either aidedor non-aided to detect, locate andassess discontinuities or defects thatappear on the surface of material undertest.Tools include fiberscope's,borescopes, magnifying glasses andmirrors.Defects such as corrosion in boiler tube, which cannot be seenwith naked eyes can easily be detected and recorded by usingsuch equipment. 9. APPLICATIONSPortable videoinspection unit withzoom allowsinspection of largetanks and vessels,railroad tank cars,sewer lines.Remote visual inspection using arobotic crawler.Robotic crawlers permitobservation in hazardous ortight areas, such as air ducts,reactors, pipelines. 10. Advantages :- Cheapest NDT method Applicable at all stagesof construction ormanufacturing Do not require extensivetraining Capable of givinginstantaneous resultsLimitation :- Limited to onlysurface inspection Require goodlighting Require goodeyesight 11. Liquid Penetrate Inspection Liquid penetrate is an NDT method that utilizes the principleof capillary action in which liquid of suitable physicalproperties can penetrate deep into extremely fine cracks orpitting that are opened to the surface without being affected bythe gravitational force. 12. Advantages :- Simple to perform Inexpensive Applicable tomaterials withcomplex geometryLimitation :- Limited to detection ofsurface breakingdiscontinuity Not applicable to porousmaterial Require access for pre- andpost-cleaning Irregular surface may causethe presence of non-relevantindication 13. Magnetic Particle InspectionMagnetic particle testing (MT) is a NDTmethod that utilizes the principle ofMagnetization.Material to be inspected is firstmagnetized through one of many waysof magnetization.Once magnetized, a magnetic field isestablished within and in the vicinity ofthe material.Finely milled iron particles coated with a dye pigment are thenapplied to the specimen. These magnetic particles are attractedto magnetic flux leakage fields and will cluster to form anindication directly over the discontinuity.They provide a visual indication of the flaw. 14. Magnetic Particle InspectionThe presence of surface breakingand subsurface discontinuity on thematerial causes themagnetic field to leak and travelthrough the air.Such a field is called leakage field.When magnetic powder is sprayedon such a surface the leakage fieldwill attract the powder, forming apattern that resembles the shape ofthe discontinuity.This indication can be visuallydetected underproper lighting conditions 15. Examples of visible dry magnetic particle indicationsIndication of a crack in a saw blade Indication of cracks in a weldmentBefore and after inspection pictures ofcracks emanating from a holeIndication of cracks running betweenattachment holes in a hinge 16. Advantages :- Inexpensive Equipment are portable Equipment easy tooperate Provide instantaneousresults Sensitive to surface andsubsurfacediscontinuitiesLimitations :- Applicable only toferromagnetic materials Insensitive to internaldefects Require magnetizationand demagnetization ofmaterials to beinspected Require power supplyfor magnetization Material may be burnedduring magnetization 17. RadiographyThe radiation used in radiographytesting is a higher energy (shorterwavelength) version of theelectromagnetic waves that wesee as visible light. The radiation cancome from an X-ray generator or aradioactive source.High Electrical PotentialElectrons+ -X-ray Generatoror RadioactiveSource CreatesRadiationRadiationPenetratethe SampleExposure Recording DeviceRadiography is an NDT method,which uses penetrating radiation.In this inspection the source ofradiation can be from radioactivesources, typically Irridium-192,Cobalt-60, Caesium-137, which emitgamma rays or from a speciallybuilt machine that can emit X rays. 18. Film RadiographyThe part is placed between theradiation source and a piece of film.The part will stop some of theradiation. Thicker and more densearea will stop more of the radiation.X-ray filmTop view of developed filmThe film darkness(density) will vary withthe amount of radiationreaching the filmthrough the test object.= less exposure= more exposure 19. Radiographic Images 20. Advantages :- Applicable to almost allmaterials Produce permanentimages that are readilyretrievable for futurereference Capable of detectingsurface, subsurface andinternal discontinuities Capable of exposingfabrication errors atdifferent stages offabrication Many equipment areportableLimitations :- Radiation used ishazardous to workersand members of public Expensive method Incapable of detectinglaminar discontinuities Results are notinstantaneous. Itrequires film processing,interpretation andevaluation Require highly trainedpersonnel in the subjectof radiography as wellas radiation safety. 21. ConductivematerialEddy Current TestingCoilCoil'smagnetic fieldEddycurrentsEddy current'smagnetic field 22. Eddy Current TestingEddy current testing is particularly well suited for detectingsurface cracks but can also be used to make electrical conductivityand coating thickness measurements. Here a small surface probeis scanned over the part surface in an attempt to detect a crack. 23. Advantages :- The results can be obtainedinstantaneously The inspection system caneasily be automated Equipment are portable andsuitable for field application Some equipment are madededicated for specificmeasurement (e.g.,conductivity, crack, depth,etc)Limitations :- Applicable only toconducting materials Require highly skillful andexperienced operator Applicable only for thedetection of surface andsubsurface discontinuity. 24. Ultrasonic Inspection (Pulse-Echo)High frequency sound waves are introduced into amaterial and they are reflected back from surfaces orflaws.Reflected sound energy is displayed versus time, andinspector can visualize a cross section of the specimenshowing the depth of features that reflect sound. fplatecrackinitialpulsecrackechoback surfaceecho0 2 4 6 8 10Oscilloscope, or flawdetector screen 25. Advantages :- Limitations :- Requires only one sideaccessibility Capable of detectinginternal defect Not hazardous Applicable for thicknessmeasurement, detectionof discontinuity, anddetermination of materialproperties Can provide the size ofdiscontinuity detected Very sensitive to planartype discontinuity Suitable for automation Equipment are mostlyportable and suitable forfield inspection Not capable of detectingdefect whose plane isparallel to the direction ofsound beam Require the use of couplantto enhance soundtransmission Require calibration blocksand reference standards Require highly skillful andexperience operator Not so reliable for surfaceand subsurfacediscontinuity due tointerference between initialpulse and signal due todiscontinuity. 26. Inspection of Raw Products Forgings, Castings, Extrusions, 27. Inspection FollowingSecondary Processing Machining Welding Grinding Heat treating Plating etc. 28. Power Plant InspectionPeriodically, power plants areshutdown for inspection.Inspectors feed eddy currentprobes as well as UT probesinto heat exchanger tubes tocheck for corrosion damage.ProbePipe with damage 29. Rail InspectionSpecial cars are used toinspect thousands of milesof rail to find cracks thatcould lead to a derailment. 30. Storage Tank InspectionRobotic crawlersuse ultrasound toinspect the walls oflarge above groundtanks for signs ofthinning due tocorrosion.Cameras onlongarticulatingarms are usedto inspectundergroundstorage tanksfor damage. 31. Pressure Vessel InspectionThe failure of a pressure vesselcan result in the rapid release ofa large amount of energy. Toprotect against this dangerousevent, the tanks are inspectedusing radiography andultrasonic testing. 32. Pipeline InspectionNDT is used to inspect pipelinesto prevent leaks that coulddamage the environment. Visualinspection, radiography andelectromagnetic testing are someof the NDT methods used.Radiography of weld joints.Magnetic flux leakage inspection.This device, known as a pig, isplaced in the pipeline and collectsdata on the condition of the pipe as itis pushed along by whatever is beingtransported. 33. Crash of United Flight 232Sioux City, Iowa, July 19, 1989A defect that wentundetected in anengine disk wasresponsible forthe crash ofUnited Flight 232.