overview of ndt
TRANSCRIPT
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NON-DESTRUCTIVE TESTING
Examination of materials and components insuch a way that allows material to be examinated
without changing or destroying their usefulness
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Non-Destructive Testing
The four basic methods
Magnetic particle inspection (MT)
Dye penetrant inspection (PT)
Radiographic inspection (RT)
Ultrasonic inspection (UT)
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Dye penetrant inspection (PT)
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Dye Penetrant Inspection
Surface breaking defects only detected
Penetrant applied to the component and drawn intothe defects by capillary action
Applicable to all non- porous and non absorbing
materials.
Penetrants are available in many different types
Water washable contrast
Solvent removable contrast Water washable fluorescent
Solvent removable fluorescent
Post-emulsifiable fluorescent
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Dye Penetrant Inspection
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Dye Penetrant Inspection
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Dye Penetrant Inspection
Step 1. Pre-Cleaning
Cleaning preparation is very important on this method.
Usually solvent removal is been used
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Dye Penetrant Inspection
Step 2. Apply penetrant
After the application of the penetrant the penetrant is normally
left on the components surface for approximately 15 minutes
(dwell time). The penetrant enters any defects that may be
present by capillary action
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Dye Penetrant Inspection
Step 3. Clean off penetrant
After sufficient penetration time (dwell time) has been
given,excess removal penetrant stage take place. A damped
lint free tissue with solvent is used to clean the excess
penetrant.
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Dye Penetrant Inspection
Step 3. Apply developer
After the excess penetrant is been removed, a thin layer
of developer is applied.A penetrant drawn out by reversed
capillary action.
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Dye Penetrant Inspection
Step 4. Inspection / development time
Inspection should take place immediately after the developerhas been applied .Any defects present will show as a bleed
out during development time.
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Dye Penetrant Inspection
Step 5. Post-Cleaning
After the inspection has been performed post cleaning isrequired to prevent corrosion.
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Dye Penetrant Inspection
Colour contrast Penetrant
Fluorescent PenetrantBleed out viewed
under a UV-A lightsource
Bleed out viewed
under white light
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Dye Penetrant Inspection
Advantages
Simple to useInexpensive
Quick results
Can be used on anymaterial provided it
is not porous
More sensitive thanvisual inspection
Low operator skill
required
DisadvantagesSurface breaking defectonly
little indication of depths
Penetrant and developer
may contaminate
component
Surface preparation
criticalPost cleaning required
Not applicable on porous
material
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Magnetic particle inspection (MT)
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Magnetic Particle Inspection
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Magnetic Particle Inspection
Surface and slight sub-surface detection
Relies on magnetization of component being tested
Ferro-magnetic materials only can be tested
A magnetic field is introduced into a specimen being tested
Methods of applying a magnetic field, yoke, permanent
magnet, prods and flexible cables. Fine particles of iron powder are applied to the test area
Any defect which interrupts the magnetic field, will create aleakage field, which attracts the particles
Any defect will show up as either a dark indication or in thecase of fluorescent particles under UV-A light a green/yellowindication
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Collection of ink
particles due to
leakage field
Magnetic Particle Inspection
Prods
DC or
AC
Electro-
magnet
(yoke) DC or
AC
Crack
like
indicati
on
Cracklike
indicati
on
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Magnetic Particle Inspection
A crack likeindication
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Magnetic Particle Inspection
Alternatively to contrastinks, fluorescent inks
may be used for greater
sensitivity. These inks
require a UV-A light
source and a darkenedviewing area to inspect
the component
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Magnetic Particle InspectionTypical sequence of operations to inspect
a weldClean area to be tested
Apply contrast paint
Apply magnetisism to the component
Apply ferro-magnetic ink to the component
during magnetisingInterpret the test area
Post clean and de-magnatise if required
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Magnetic Particle Inspection
Advantages
Simple to use
Inexpensive
Rapid results
Little surface
preparation required
More sensitive thanvisual inspection
Disadvantages
Surface or slight sub-surface detection only
Magnetic materials
only
No indication of
defects depths
Detection is required
in two directions
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Radiographic inspection (RT)
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Radiographic InspectionThe principles of radiography
X or Gamma radiation is imposed upon a testobject
Radiation is transmitted to varying degrees
dependant upon the density of the material
through which it is travelling
Thinner areas and materials of a less density
show as darker areas on the radiograph
Thicker areas and materials of a greater
density show as lighter areas on a radiograph
Applicable to metals,non-metals and
composites
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Industrial Radiography
X - Rays
Electrically generated
Gamma Rays
Generated by the
decay of unstable
atoms
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Industrial Radiography
X - Rays
Electrically generated
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Industrial Radiography
Gamma Rays
Generated by the decay ofunstable atoms
R di hi I ti
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Source
Radiation beam Image quality indicator
Radiographic Inspection
Test specimenRadiographic film
R di hi I ti
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Source
Radiation beam Image quality indicator
Radiographic film with latent image after exposure
Radiographic Inspection
Test specimen
R di hi S iti it
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7FE12
Step / Hole type IQI Wire type IQI
Radiographic Sensitivity
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Wire Type IQI
Step/Hole Type IQI
Image Quality Indicators
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Radiographic Techniques
Single Wall Single Image (SWSI)- film inside, source outside
Single Wall Single Image (SWSI) panoramic
- film outside, source inside (internal exposure) Double Wall Single Image (DWSI)
- film outside, source outside (external exposure)
Double Wall Double Image (DWDI)- film outside, source outside (elliptical exposure)
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Single wall single image SWSI
IQIs should be placed source side
Film
Film
Single all single image SWSI
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Single wall single image SWSIpanoramic
IQIs are placed on the film side
Source inside film outside (single exposure)
Film
Double wall single image DWSI
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Film
Double wall single image DWSI
IQIs are placed on the film side
Source outside film outside (multiple exposure)
This technique is intended for pipe diameters
over 100mm
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Double wall single image DWSI
Radiograph
Identification
ID MR11
Unique identificationEN W10
IQI placing
A B Pitch marks
indicating readablefilm length
Double wall double image DWDI
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Film
Double wall double image DWDIelliptical exposure
IQIs are placed on the source or film side
Source outside film outside (multiple exposure)
A minimum of two exposures
This technique is intended for pipe diameters
less than 100mm
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Double wall double image DWDI
Shot A Radiograph
Identification
ID MR12
Unique identification EN W10
IQI placing
1 2 Pitch marks
indicating readablefilm length
4 3
Radiographic Inspection
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Radiographic Inspection
AdvantagesPermanent record
Little surface preparation
Defect identificationNo material type
limitation
Disadvantages
Expensive equipment
Bulky equipment ( x-ray )
Harmful radiation
Detection on defectdepending on orientation
Slow results
Required license to operate
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Ultrasonic inspection (UT)
Ultrasonic Inspection
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Ultrasonic Inspection Sub-surface detection
This detection method uses high frequency sound
waves, typically above 2MHz to pass through a material
A probe is used which contains a piezo electric crystal
to transmit and receive ultrasonic pulses and display the
signals on a cathode ray tube or digital display
The actual display relates to the time taken for the
ultrasonic pulses to travel the distance to the interface
and back
An interface could be the back of a plate material or adefect
For ultrasound to enter a material a couplant must be
introduced between the probe and specimen
Ult i I ti
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Ultrasonic Inspection
Ultrasonic testing is a good technique for the
detection of plate laminations and thickness surveys
Laminations detected using compression probes
Ult i I ti
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Ultrasonic Inspection
defect
0 10 20 30 40 50
defect
echoBack wall
echo
CRT DisplayCompression Probe
Material Thk
initial pulse
Ult i I ti
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Ultrasonic InspectionUT Set, DigitalPulse echo
signals
A scan Display
Compression probe Thickness checking the material
Ultrasonic Inspection
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Ultrasonic Inspection
Ultrasonic testing requires high operator for defect
identification
Most weld defects detected using angle probes
Ultrasonic Inspection
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Ultrasonic Inspection
Angle Probe
UT SetA Scan
Display
Ult i I ti
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Ultrasonic Inspection
0 10 20 30 40 50
initial pulse defect echo
CRT Display
sound path
Angle Probe
defect
Surface distance
Ultrasonic Inspection
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Ultrasonic Inspection
Advantages
Rapid resultsSub-surface detection
Safe
Can detect planar defectCapable of measuring the
depth of defects
May be battery poweredPortable
Disadvantages
Trained and skilledoperator required
Requires high operator
skill
Good surface finish
required
Difficulty on detecting
volumetric defectCouplant may
contaminate