Introduction to
Introduction to
Non Destructive Testing
NDT
NDT
Ability to detect the condition of Ability to detect the condition of the objectthe object
without destroying the functionality of the object
without destroying the functionality of the object
BASIC METHODS
BASIC METHODS
VVisual isual InspecInspection tion -- VTVT
PenPenetretrant Tant Testesting -ing - PTPT
MagneMagnetic Patic Particle rticle TTestinesting-g- MTMT
UltraUltrasonic sonic TTestinesting -g - UTUT
Visual Inspection
Visual Inspection
Inspection object surface visually is calledInspection object surface visually is called
Visual Inspection
Visual Inspection
May May or or may may not not use use accessoriesaccessories
Gauges Gauges for for identifying identifying the the dimensions dimensions ofof
surface
surface
Magnifying glassesMagnifying glasses
Borescope for internal inspectionBorescope for internal inspection
Thermal chalks, Thermocouple, for theThermal chalks, Thermocouple, for the
temperature measurement
temperature measurement
Etching
Etching
for identification of grossfor identification of gross
metallurg
metallurgical ical discontinuitydiscontinuity
such as in welds.
such as in welds.
For detecting the surfaceFor detecting the surface
opening
opening – – Fore runner toFore runner to
Penetran
Penetrant Tt Testingesting
Different EtchantsDifferent Etchants
available for different
available for different
metals
Advantages & Disadvantages
Advantages Simple
Less training required
Relatively less costly equipment
Disadvantages
Slow
Inspector Fatigue is more
Penetrant 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 Testing
Pre cleaning Application of penetrant Dwell Time Cleaning of Excess penetrant Application of Developer Inspection Post CleaningDYE SYSTEMS
DYE SYSTEMS
WATER WASHABLE DYE
POST EMULSIFICATION DYE
Penetrant Testing
Advantages
Simple method
Easy to train personnel
Cheap
Quick
Disadvantages
Magnetic 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 magnetisation
Longitudinal Magnetisation
Circular Magnetisation
AC Magnetisation
DC Magnetisation
HWDC magnetisation
Magnetic Particle Testing
HEAD SHOT METHOD
PROD METHOD CENTRAL CONDUCTOR
Types of Magnetisation
-Circular Magnetisation
Magnetic Particle Testing
MAGNETIC MEDIUM
Dry
Wet
Fluorescent
– Requires Ultra violet lamp in darkened area – More sensitive than
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
MAGNETIC MEDIUM - WET
Oxides of iron used in
suspension with water, kerosene, petroleum oil.
Size : 20- 30 microns More sensitive than dry
Demagnetisation
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
Magnetic Particle Testing
Pre - Cleaning
Magnetisation
Applying magnetic medium
Inspection
Post cleaning
Magnetisation
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 & Disadvantages
Advantages For detecting surface & sub-surface discontinuity Can be tested rapidly
Not very costly
Relatively less skill required for testing
Disadvantages
Only useful in ferro-magnetic materials
Demagnetisation may be required for many of the
Ultrasonic 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
Ultrasonic 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
Ultrasonic Testing
ULTRASONIC TESTING
–PULSE ECHO TECHNIQUE
Transducer acts as a pulser and receiver Can detect the location and depth of
defect
ULTRASONIC TESTING
–THROUGH TRANSMISSION TECHNIQUE
•
Separate
transmitter
and receiver
•
Accurate Alignement of
transmitter
and
receiver required
•
Cannot
locate
the
PROBES
Test Procedure
Calculate scanning zones Calibrate unit
Draw DAC Scan
When indications
observed - check the
height of signal, location
Calculate location and
size of discontinuity
Location of defects
IE DEFECTECHO BP BP : Beam Path Depth of defect : D = BP Cos α Position of defect P = BP Sin αRadiography Testing
Employs x rays or gamma rays to penetrate
an object, detect discontinuities by
recording the difference on a recording
device
For internal flaws
Permanent record
Basic 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
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
Techniques
Double wall Single image Single Wall Single Image
Techniques
Job Film Weld Source Radiation
DOUBLE WALL DOUBLE IMAGE
SINGLE WALL SINGLE IMAGE
ASTM Hole Type Penetrameter
Tungsten Inclusion
Porosity DIN Wire Type
Penetrameter
Porosity Tungsten Inclusion
