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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