Contents OrganizationNon-Destructive Testing (NDT) Six most common NDT methods Process of each NDT Method Advantages and limitations of NDT methodsConclusion4www.sajetc.com
Company Profile www.sajetc.comSaj Engineering & Trading Company is established in 1998 to provide the Non-Destructive Testing (NDT) and Condition Monitoring (CM) solution in Bangladesh industrialMarket. Since then we are providing the NDT and CM solution in different types ofindustries like power generation, fertilizer, chemical, aviation shipbuilding, gas productionand distribution, cement, welding, paper, sugar, pharmaceuticals, research andeducational institutions. For the automobile and industrial market we are supplyinglubricants, filter, radiator and spark plug. For our products we represent the mostrenowned manufacturers in the world.As we have all sorts of latest NDT and CM products we have developed an industrialinspection service provider under the name of Saj Industrial & Inspection Company.And till now we have completed 35 Projects successfully and some projects is in our hand.Products:1.Non-Destructive Testing Products2.Condition Monitoring Products3.Sakura Automobile and Generator Filter4.Air Conditioner Energy Saver5.Maintenance Repair & Overhauling (MRO)Products6.PertaminaLubricants7.Scientific/Laboratory EquipmentsOur Services:1. Remote Visual Inspection/Endoscope2. Ultrasonic Testing3. Magnetic Particle Testing4. Radiography Testing5. PenetrantTesting6. Vibration Analysis7. Dynamic Balancing8. Transformer Leakage Repair9. Thermography Service10. Hardness Testing
Non-Destructive testing is theuse of noninvasive techniques todetermine the integrity of amaterial, component or structureor quantitatively measure somecharacteristics of an object. It isthe testing of materials, forsurface or internal flaws ormetallurgical condition, withoutinterfering in any way with theintegrity of the material or itssuitability for service.Non-Destructive Testing(NDT)6i.e. Inspect or measure without doing harm.www.sajetc.com
www.sajetc.com1. NDT increases the safety and reliability of the productduring operation.2. It decreases the cost of the product by reducing scrap andconserving materials, labor and energy.3. It enhances the reputation of the manufacturer as aproducer of quality goods. All of the above factors boostthe sales of the product which bring more economicalbenefits for the manufacturer.4. NDT is also used widely for routine or periodicdetermination of quality of the plants and structures duringservice.5. This not only increases the safety of operation but alsoeliminates any forced shut down of the plants.Importance of NDT7
www.sajetc.com9Six Most Common NDTMethods1. Visual Testing (VT)2. Dye Penetrant Testing (DPT)3. Magnetic Particle Testing (MPT)4. Ultrasonic Testing (UT)5. Eddy Current Testing (ECT)6. Radiography Testing (RT)
Visual TestingVisual testing is the most basic and common inspection methodinvolves in using of human eyes to look for defects. But now itis done by the use special tools such as video scopes,magnifying glasses, mirrors, or borescopes to gain access andmore closely inspect the subject area.10www.sajetc.comVisual Testing Equipments:•Mirrors (especially small, angled mirrors),•Magnifying glasses,•Microscopes (optical and electron),•Borescopes and fiber optic borescopes,•Closed circuit television (CCTV) systems,•Videoscope.
www.sajetc.comDye Penetrant TestingThis method is commonly used for detect the surface cracks ordefects. Dye penetrant Testing (DPT) is one of the most widelyused nondestructive Testing (NDT) methods. DPT can be usedto inspect almost any material provided that its surface is notextremely rough.12
13www.sajetc.comDye Penetrant Testing ProcessThree liquids areused in this method.1. Cleaner2. Penetrant3. Developer
Dye Penetrant Testing of a Boiler14At first the surface of the material that is to be tested is cleanedby a liquid. The liquid is called cleaner.www.sajetc.com
Dye Penetrant Testing of a Boiler15Then a liquid with high surface wetting characteristics is appliedto the surface of the part and allowed time to seep into surfacebreaking defects. This liquid is called penetrant. After five or tenminutes the excess penetrant is removed from the surface.www.sajetc.com
Then another liquid is applied to pull the trapped penetrant outthe defect and spread it on the surface where it can be seen. Thisliquid is called deveoper. 16www.sajetc.comDye Penetrant Testing of a Boiler
Findings17After Dye Penetrant Testingthere are two surface cracks areDetected.Two surface crackswww.sajetc.com
18Advantages of Dye PenetrantTesting This method has high sensitivity to small surfacediscontinuities. Large areas and large volumes of parts/materials can beinspected rapidly and at low cost. Indications are produced directly on the surface of the partand constitute a visual representation of the flaw. Aerosol spray can make penetrant materials very portable. Penetrant materials and associated equipments are relativelyinexpensive.www.sajetc.com
Limitations of Dye PenetrantTesting19www.sajetc.com Only surface breaking defects can be detected. Precleaning is critical since contaminants can mask defects. The inspector must have direct access to the surface beinginspected. Surface finish and roughness can affect inspection sensitivity. Post cleaning of acceptable parts or materials is required. Chemical handling and proper disposal is required.
www.sajetc.comMagnetic Particle TestingThis method is suitable for the detectionof surface and near surfacediscontinuities in magnetic material,mainly ferrite steel and iron. Magneticparticle Testing (MPT) is anondestructive testing method used fordefect detection. MPT is fast andrelatively easy to apply, and materialsurface preparation is not as critical as itis for some other NDT methods.20
www.sajetc.comIn the first figure the magnetized metal has no crack and there only twopoles that is north pole and south pole. And in second figure themagnetized metal has a crack and at the crack point there createsanother north and south pole for the magnetic flux leakage.SNS NN SMagnetic Flux LineFig.1: Magnetized Metal with no crack Fig.2: Magnetized Metal with crackCrackMagnetic Flux LeakageBasic Principle of MPT
22Magnetic Particle TestingProcess22www.sajetc.comThe first step in a magneticparticle testing is to magnetize thetest component by a MPTequipment. If there any defects onthe surface or near to the surfaceare present, the defects will createa leakage field.Then finely milled iron particles coated with a dye pigment areapplied to the specimen. These particles are attracted to magneticflux leakage fields and will cluster to form an indication directlyover the defects. This indication can be visually detected underproper lighting conditions.
www.sajetc.comMagnetic Particle Testing in SuperheaterPipe Welding23First the welding joint is magnetized by MPT equipment. Then finelymilled iron particles are applied to the magnetized weld joint.
Magnetic Particle Testing in GasPipe Welding24www.sajetc.comIron particles make acluster at the weldingjoint for magneticflux leakage becauseof welding defects.Cluster
It does not need very stringent pre-cleaning operation. It is the best method for the detection of surface and near tothe surface cracks in ferromagnetic materials. Fast and relatively simple NDT method. Generally inexpensive. Will work through thin coating. Highly portable NDT method. It is quicker.25Advantages Magnetic ParticleTestingwww.sajetc.com
Limitations of Magnetic ParticleTesting Material must be ferromagnetic. Orientation and strength of magnetic field is critical. Detects surface and near-to-surface discontinuities only. Large currents sometimes require..26www.sajetc.com
www.sajetc.comUltrasonic TestingThis technique is used for the detectionof internal surface (particularly distantsurface) defects in sound conductingmaterials. In this method highfrequency sound waves are introducedinto a material and they are reflectedback from surface and flaws. Reflectedsound energy is displayed versus time,and inspector can visualize a crosssection of the specimen showing thedepth of features.27
www.sajetc.comA typical UT system consists of several functional units, such asthe pulser/receiver, piezoelectric transducer, and display devices. Apulser/receiver is an electronic device that can produce highvoltage electrical pulses. Driven by the pulser, the transducergenerates high frequency ultrasonic energy. The sound energy isintroduced and propagates through the materials in the form ofwaves. When there is a discontinuity (such as a crack) in the wavepath, part of the energy will be reflected back from the flawsurface. The reflected wave signal is transformed into an electricalsignal by the piezoelectrical transducer and is displayed on ascreen.Basic Principle of UltrasonicTesting28
Basic Principle of UltrasonicTestingIn the figure below, the reflected signal strength is displayedversus the time from signal generation, when a echo wasreceived. Signal travel time can be directly related to thedistance. From the signal, information about the reflectorlocation, size, orientation and other features can sometimesbe gained.29www.sajetc.com0 2 4 6 8 10crackechoback surfaceechoinitialpulseOscilloscope, or flawdetector screenplatecrackPiezoelectricTransducer
Piezoelectric TransducerA transducer is a device that converts energy from one form toanother. Presently, piezoelectric material is commonly used as abasic component of transducers. A piezoelectric element is acrystal which delivers a voltage when mechanical force isapplied between its faces, and it deforms mechanically whenvoltage is applied between its faces. Because of thesecharacteristics piezoelectric element is capable of acting as botha sensing and a transmitting element. Piezoelectric transducershave been conventionally used to convert electric signals intosound wave, or to convert sound wave into electric signals.www.sajetc.com30
32www.sajetc.comTest Techniques:Normal and Angle Beam• In normal beam testing, the sound beamis introduced into the test article at 90degree to the surface.• In angle beam testing, the sound beam isintroduced into the test article at someangles other than 90.• The choice between normal and anglebeam inspection usually depends on twoconsiderations:- The orientation of the feature ofinterest – the sound should bedirected to produce the largestreflection from the feature.- Obstructions on the surface of thepart that must be worked around.
Couplant33A couplant is a material (usually liquid)that facilitates the transmission of ultrasonicenergy from the transducer into the testspecimen. Couplant is generally necessarybecause the acoustic impedance mismatchbetween air and solids (i.e. such as the testspecimen) is large. The couplant displacesthe air and makes it possible to get moresound energy into the test specimen so thata usable ultrasonic signal can be obtained.In contact ultrasonic testing a thin film ofoil, glycerin or water is generally usedbetween the transducer and the test surfacewww.sajetc.com
Calibration Standards34www.sajetc.comCalibration is a operation of configuring the ultrasonic testequipment to known values. This provides the inspector witha means of comparing test signals to known measurements.Calibration standards come in a wide variety of materialtypes, and configurations due to the diversity of inspectionapplications.The following slides provide examples of specific types ofstandards.
35www.sajetc.comCalibration StandardsThickness calibration standardsmay be flat or curved for pipe andtubing applications, consisting ofsimple variations in materialthickness.Distance/Area Amplitude standardsutilize flat bottom holes or sidedrilled holes to establish knownreflector size with changes insound path form the entry surface.ASTM Distance/Area AmplitudeIIWThis calibration standards for usein angle beam inspections whenflaws are not parallel to entrysurface.
Advantages of Ultrasonic Testing Thickness and lengths up to 30 ft can be tested. Position, size and type of defect can be determined. Instant test results. Portable. Capable of being fully automated. Access to only one side necessary.36www.sajetc.com
Limitations of Ultrasonic Testing The operator can decide whether the test piece is defective ornot while the test is in progress. Considerable degree of skill necessary to obtain the fullestinformation from the test. Very thin sections can prove difficult.37www.sajetc.com
Eddy Current Testing38www.sajetc.comThis method is widely used to detectsurface flaws, to measure thin walls fromone surface only, to measure thin coatingsand in some applications to measuredepth. This method is applicable toelectrically conductive materials only. Inthis method eddy currents are produced inthe product by bringing it close to analternating current carrying coil. The mainapplications of the eddy current techniqueare for the detection of surface orsubsurface flaws, conductivitymeasurement and coating thicknessmeasurement.
39www.sajetc.comApplication of ECTCrack DetectionCorrosion MonitoringMaterial Thickness MeasurementsCoating Thickness MeasurementsConductivity Measurements
40www.sajetc.comElectromagnetic Induction•Eddy currents are created through a process calledelectromagnetic induction.•When alternating current is applied to the conductor, such ascopper wire, a magnetic field develops in and around theconductor.•This magnetic field expands as the alternating current rises tomaximum and collapses as the current is reduced to zero.
41Current FlowElectromagnetic InductionIf another electrical conductor is brought into the proximity ofthis changing magnetic field, the reverse effect will occur.Magnetic field cutting through the second conductor will causean “induced” current to flow in this second conductor. Eddycurrents are a form of induced currents!www.sajetc.com
42www.sajetc.comCrack DetectionCrack detection is one of the primary uses of eddy currentinspection. Cracks cause a disruption in the circular flow patternsof the eddy currents and weaken their strength. This change instrength at the crack location can be detected.Magnetic FieldFrom Test CoilMagnetic FieldFromEddy CurrentsEddy CurrentsCrack
43www.sajetc.comEddy Current TestingEquipments
Probes - Mode of OperationEddy current probes are available in a large variety of shapesand sizes. In fact, one of the major advantages of eddy currentinspection is that probes can be custom designed for a widevariety of applications. Eddy current probes are classified by theconfiguration and mode of operation of the test coils.44www.sajetc.com
45www.sajetc.comDifferent Types of ProbesAbsolute Probes Surface Probes Bobbin Probes
46www.sajetc.com46Advantages of Eddy CurrentTestingSensitive to small cracks and other defectsDetect surface and near surface defectsInspection gives immediate resultsEquipment is very portableMethod can be used for much more than flaw detectionInspects complex shapes and sizes of conductive materials
47www.sajetc.comLimitations of Eddy CurrentTestingOnly conductive materials can be inspected.Surface must be accessible to the probe.Skill and training required is more extensive than othertechniques.Surface finish and roughness may interfere.Depth of penetration is limited.
Radiography Testing48www.sajetc.comRadiography Testing (RT), or industrialradiography is a nondestructive testing (NDT)method of inspecting materials for hidden flawsby using the ability of short wavelengthelectromagnetic radiation (high energy photons)to penetrate various materials.Radiographic Testing Method is nothing but totake the shadow picture of an object onto a filmby the passage of X-ray or Gamma ray throughit. It is the same as the medical radiography (X-ray). Only difference in their wave length.
Radiography Testing ProcessThe principles are the same for both X and Gamma radiography.In X-radiography the penetrating power is determined by thenumber of volts applied to the X-Ray tube - in steelapproximately 1000 volts per inch thickness is necessary. Toproduce an X or Gamma radiograph, the film package is placedclose to the surface of the subject. The source of radiation ispositioned on the other side of the subject some distance away,so that the radiation passes through the subject and on to thefilm.49www.sajetc.com
Radiography Testing ProcessAfter the exposure period the film is removed, processed, dried,and then viewed by transmitted light on a special viewer.Various radiographic and photographic accessories arenecessary, including such items as radiation monitors, filmmarkers, image quality indicators, darkroom equipment, etc.Where the last is concerned there are many degrees ofsophistication, including fully automatic processing units.These accessories are the same for both X and Gammaradiography systems. Also required are such consumable itemsas radiographic film and processing chemicals50www.sajetc.com
51www.sajetc.comX-ray filmTop view of developed filmElectrons-+RadiationPenetratethe SampleRadiography Testing ProcessX-ray Generator orRadioactive SourceCreates RadiationRadioactive Source
52www.sajetc.comEssential Elements for RadiographyTesting1. A source of penetrating radiation, such as an X-ray machine.2. The object to be radiographed, such as a weldment.3. A recording or viewing device, usually photographic (X-ray)film enclosed in a light tight holder.4. A qualified radiographer trained to produce a satisfactoryexposure.5. A person skilled in the interpretation of radiographs.
Radiation SafetyIonizing radiation is an extremely important NDT tool but itcan pose a hazard to human health. For this reason, specialprecautions must be observed when using and working aroundionizing radiation. Complicating matters further is the fact thatGamma and X-ray radiation are not detectable by the humanbody. However, the risks can be minimized when the radiationis handled and managed properly.54www.sajetc.com
Information is presented pictorially. A permanent record is provided which may be viewed at atime and place distant from the test.Useful for thin sections.Sensitivity declared on each film suitable for any material.55www.sajetc.comAdvantages of RadiographyTesting
56www.sajetc.comPossible health hazard. Need to direct the beam accurately for two-dimensionaldefects. Film processing and viewing facilities are necessary Not suitable for automation. Not suitable for surface defects.Limitations of RadiographyTesting
57www.sajetc.comIn Bangladesh NDT is a new technology and system forindustrial inspection and testing. Many developed countries areused this technology because of its huge benefits.Modern NDT methods will become just as an important tool forrisk based inspection approaches and maintenance planning. Forthis purpose every industry should have a NDT division withNDT personnel.Conclusion