Introduction to Introduction to Non Destructive TestingNon Destructive Testing
NDTNDT
Ability to detect the condition of the object without destroying the functionality of the object
BASIC METHODS Visual Inspection - VT Penetrant Testing - PT Magnetic Particle Testing- MT Ultrasonic Testing - UT Radiographic Testing - RT
Visual InspectionVisual Inspection Inspection object surface visually is called
Visual Inspection May or may not use accessories Gauges for identifying the dimensions of
surface Magnifying glasses Borescope for internal inspection Thermal chalks, Thermocouple, for the
temperature measurement Etching for checking surface condition
EtchingEtching
for identification of gross metallurgical discontinuity such as in welds.
For detecting the surface opening – Fore runner to Penetrant Testing
Different Etchants available for different metals
Advantages & Disadvantages Advantages & Disadvantages
Advantages Simple Less training required Relatively less costly equipment
Disadvantages Slow Inspector Fatigue is more Surrounding environmental factors are important
Penetrant InspectionPenetrant Inspection
Is a method that reveals discontinuities open to surface by the seepage of a liquid penetrant medium into a surface open discontinuity which seeps out after removing the excess penetrant revealing the discontinuity
Stages of Penetrant TestingStages of Penetrant Testing Pre cleaning Application of penetrant Dwell Time Cleaning of Excess
penetrant Application of Developer Inspection Post Cleaning
DYE SYSTEMSDYE SYSTEMS
SOLVENT REMOVABLE DYE
DYE SYSTEMS DYE SYSTEMS
WATER WASHABLE DYE
POST EMULSIFICATION DYE
PT Indications PT Indications
Penetrant TestingPenetrant Testing
Advantages Simple methodEasy to train personnelCheapQuick
DisadvantagesOnly open defects can be detected
Magnetic Particle TestingMagnetic Particle Testing
When a ferromagnetic material is magnetised the flux lines flow inside the component
When there is a discontinuity in the material there is flux leakage
The leaking flux attracts a magnetic medium resulting in an indication.
Types of magnetisationTypes of magnetisation
Longitudinal MagnetisationCircular Magnetisation
AC MagnetisationDC MagnetisationHWDC magnetisation
Magnetic Particle TestingMagnetic Particle Testing
COIL METHOD YOKE METHOD.
HEAD SHOT METHOD
PROD METHOD CENTRAL CONDUCTOR
Types of Magnetisation - Types of Magnetisation - Circular MagnetisationCircular Magnetisation
Magnetic Particle TestingMagnetic Particle Testing
PROD METHOD
MAGNETIC MEDIUMMAGNETIC MEDIUM
DryWet
Fluorescent – Requires Ultra violet lamp in darkened area – More sensitive than
Non – Fluorescent
Magnetic Medium - Dry Magnetic Medium - Dry
Medium about 30 – 50 microns
Mixture of spherical and elongated powders
Spherical shape helps in mobility
Elongated shape helps in alignment to magnetic field
Dry Medium
MAGNETIC MEDIUM - WETMAGNETIC MEDIUM - WET
Oxides of iron used in suspension with water, kerosene, petroleum oil.
Size : 20- 30 microns More sensitive than dry
medium
DemagnetisationDemagnetisation Residual magnetism affects
further operation such as welding.
Demagnetisation is preferably done with AC
Object is moved slowly away from coil
After demagnetisation residual magnetism is checked with gauss meters
Magnetic Particle TestingMagnetic Particle Testing
Pre - CleaningMagnetisationApplying magnetic mediumInspectionPost cleaningDemagnetization
MagnetisationMagnetisation
Magnetisation to be applied in two mutually perpendicular direction
Magnetic medium to applied when the magnetisation is ‘ON’
Adequacy of field to be checked by field indicator ( Pie Gage )
Magnetic medium could be wet or dry / Fluorescent or non-fluorescent
Advantages & DisadvantagesAdvantages & Disadvantages
Advantages For detecting surface & sub-surface discontinuity Can be tested rapidly Not very costly Relatively less skill required for testingDisadvantages Only useful in ferro-magnetic materials Demagnetisation may be required for many of the
parts
Ultrasonic TestingUltrasonic Testing
A beam of high frequency wave is introduced into the test object which gets reflected from the surface of any discontinuity
Used to detect and locate the surface and internal discontinuities
Amplitude of a reflected sound pulse is nearly proportional to the size of the reflector
Ultrasonic TestingUltrasonic Testing
For Detecting internal flaws For almost all the materials –
metals, ceramic, rubber, composites etc..
Requires only one side access Portable equipment Non hazardous Can test up to about 10 m of
steel
Ultrasonic Testing Ultrasonic Testing
ULTRASONIC TESTING –ULTRASONIC TESTING –
PULSE ECHO TECHNIQUEPULSE ECHO TECHNIQUE Transducer acts as a pulser and receiver
Can detect the location and depth of defect
Only one side access is required
ULTRASONIC TESTING –ULTRASONIC TESTING –THROUGH TRANSMISSION TECHNIQUETHROUGH TRANSMISSION TECHNIQUE
• Separate transmitter Separate transmitter and receiverand receiver
• Accurate Alignement Accurate Alignement of transmitter and of transmitter and receiver requiredreceiver required
• Cannot locate the Cannot locate the depth of defectdepth of defect
PROBESPROBES
NORMAL BEAM PROBE DUAL CRYSTAL PROBE
Test ProcedureTest Procedure
Calculate scanning zones Calibrate unit Draw DAC Scan When indications
observed - check the height of signal, location
Calculate location and size of discontinuity
Scanning patterns
Location of defectsLocation of defects
IEDEFECT ECHO
BP
BP : Beam Path
Depth of defect :
D = BP Cos α
Position of defect
P = BP Sin α
Radiography TestingRadiography Testing
Employs x rays or gamma rays to penetrate an object, detect discontinuities by recording the difference on a recording device
For internal flawsPermanent recordRadiation Safety is a major concern
Basic PrincipleBasic Principle
X ray machines or Ir 192 or Co 60 main sources of radiation
Hole type or Wire type penetrameters used for checking sensitivity of radiograph
Source Radiation
Radiography Radiography
Uses Penetrameters for ensuring the quality of the radiography procedure
Penetrameters are hole type and wire type
Sufficient radiographic density is required for the radiograph for proper evaluation
TechniquesTechniques
Double wall Single imageSingle Wall Single Image Job WeldFilm Source Radiation
TechniquesTechniques
Job WeldFilm Source Radiation
Double Wall Double Image Panoramic Exposure
DOUBLE WALL DOUBLE IMAGE
SINGLE WALL SINGLE IMAGE
ASTM Hole Type Penetrameter
Tungsten Inclusion
Porosity
DIN Wire Type Penetrameter
Porosity
Tungsten Inclusion
Slag Inclusion Slag Inclusion
POROSITY POROSITY
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