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CSWIP 3.1 Welding Inspection
TWI Training & ExaminationTWI Training & ExaminationServicesServices
NonNon--Destructive TestingDestructive Testing
Course Reference WIS 5Course Reference WIS 5
Course notes section reference 15Course notes section reference 15
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Non-Destructive Testing
A welding inspector should have a working knowledge of NDTmethods and their applications, advantages and disadvantages.
Four basic NDT methodsFour basic NDT methods Magnetic particle inspection (MT)
Dye penetrant inspection (PT)
Radiographic inspection (RT)
Ultrasonic inspection (UT)
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Non-Destructive Testing
Surface Crack DetectionSurface Crack Detection
Liquid Penetrant (PT or Dye-Penetrant)
Magnetic Particle Inspection (MT or MPI)
Volumetric InspectionVolumetric Inspection
Ultrasonics (UT)
Radiography (RT)
Each technique has advantages & disadvantages with respectEach technique has advantages & disadvantages with respect
to:to:
Technical Capability and CostTechnical Capability and Cost
Note:Note: The choice of NDT techniques is based on consideration ofThe choice of NDT techniques is based on consideration of
these advantages and disadvantagesthese advantages and disadvantages
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Penetrant Testing (PT)Penetrant Testing (PT)
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Penetrant Testing
Main features:Main features:
Detection of surface breaking defects only.
This test method uses the forces of capillary action
Applicable on any material type, as long they are non porous.
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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Step 1. PreStep 1. Pre--CleaningCleaning
Ensure surface is very Clean normally with the use of a solvent
Penetrant Testing
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Step 2. ApplyStep 2. Apply penetrantpenetrant
After the application, the penetrant is normally left on the
components surface for approximately 15-20 minutes (dwell time).The penetrant enters any defects that may be present by capillaryaction.
Penetrant Testing
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Step 3. Clean offStep 3. Clean off penetrantpenetrant
the penetrant is removed after sufficient penetration time (dwell
time).Care must be taken not to wash any penetrant out off any defectspresent
Penetrant Testing
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Step 3. Apply developerStep 3. Apply developer
After the penetrant has be cleaned sufficiently, a thin layer of
developer is applied.The developer acts as a contrast against the penetrant and allowsfor reverse capillary action to take place.
Penetrant Testing
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Step 4. Inspection / development timeStep 4. Inspection / development time
Inspection should take place immediately after the developer has
been applied.any defects present will show as a bleed out during developmenttime.After full inspection has been carried out post cleaning is generallyrequired.
Penetrant Testing
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ColourColour contrastcontrast PenetrantPenetrant
FluorescentFluorescent PenetrantPenetrant Bleed out viewedBleed out viewedunder a UVunder a UV--A lightA light
sourcesource
Bleed out viewedBleed out viewedunder white lightunder white light
Penetrant Testing
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Penetrant Testing
AdvantagesAdvantages
Simple to use
Inexpensive
Quick results
Can be used on any non-
porous material Portability
Low operator skill required
DisadvantagesDisadvantages
Surface breaking defect only
little indication of depths
Penetrant may contaminatecomponent
Surface preparation critical
Post cleaning required Potentially hazardous
chemicals
Can not test unlimited times
Temperature dependant
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Penetrant Testing
Comparison with Magnetic Particle InspectionComparison with Magnetic Particle Inspection
ADVANTAGESADVANTAGES
easy to interpret results
no power requirements
relatively little training required
can use on all materials
DISADVANTAGESDISADVANTAGES
good surface finish needed
relatively slow
chemicals - health & safety issue
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Any QuestionsAny Questions
Penetrant Testing
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Magnetic Particle testing (MT)Magnetic Particle testing (MT)
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Magnetic Particle Testing
Main features:Main features:
Surface and slight sub-surface detection
Relies on magnetization of component being tested
Only Ferro-magnetic materials 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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A crack likeA crack like
indicationindication
Magnetic Particle Testing
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Alternatively to contrast inks, fluorescent inks may be used forAlternatively to contrast inks, fluorescent inks may be used for
greater sensitivity. These inks require a UVgreater sensitivity. These inks require a UV--A light source and aA light source and a
darkened viewing area to inspect the componentdarkened viewing area to inspect the component
Magnetic Particle Testing
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Typical sequence of operations to inspect a weldTypical sequence of operations to inspect a weld
Clean area to be tested
Apply contrast paint
Apply magnetisism to the component
Apply ferro-magnetic ink to the component during magnatising
Iterpret the test area
Post clean and de-magnatise if required
Magnetic Particle Testing
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AdvantagesAdvantages
Simple to use
Inexpensive
Rapid results
Little surface preparation
required
Possible to inspect throughthin coatings
DisadvantagesDisadvantages
Surface or slight sub-surfacedetection only
Magnetic materials only
No indication of defects depths
Only suitable for linear defects Detection is required in two
directions
Magnetic Particle Testing
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Magnetic Particle Testing
Comparison with Penetrant TestingComparison with Penetrant Testing
ADVANTAGESADVANTAGES
much quicker than PT instant results
can detect near-surface imperfections (by current flow technique)
less surface preparation needed
DISADVANTAGESDISADVANTAGES
only suitable for ferromagnetic materials
electrical power for most techniques
may need to de-magnetise (machine components)
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Any QuestionsAny Questions
Magnetic Particle Testing
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Ultrasonic Testing (UT)Ultrasonic Testing (UT)
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Main Features:Main Features:
Surface and subSurface and sub--surface detectionsurface detection
This detection method uses high frequency sound waves,This detection method uses high frequency sound waves,typically above 2MHz to pass through a materialtypically above 2MHz to pass through a material
A probe is used which contains aA probe is used which contains a piezopiezo electric crystal toelectric crystal to
transmit and receive ultrasonic pulses and display thetransmit and receive ultrasonic pulses and display the
signals on a cathode ray tube or digital displaysignals on a cathode ray tube or digital display The actual display relates to the time taken for theThe actual display relates to the time taken for the
ultrasonic pulses to travel the distance to the interface andultrasonic pulses to travel the distance to the interface and
backback
An interface could be the back of a plate material or a defectAn interface could be the back of a plate material or a defect
For ultrasound to enter a material a couplant must beFor ultrasound to enter a material a couplant must be
introduced between the probe and specimenintroduced between the probe and specimen
Ultrasonic Testing
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DigitalDigital
UT Set,UT Set,Pulse echoPulse echo
signalssignals
A scanA scanDisplayDisplay
Compression probeCompression probe checking the materialchecking the material ThicknessThickness
Ultrasonic Testing
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defectdefect
00 1010 2020 3030 4040 5050
defectdefect
echoechoBack wallBack wall
echoecho
CRT DisplayCRT DisplayCompression ProbeCompression Probe
MaterialMaterial ThkThk
initial pulseinitial pulse
Ultrasonic Testing
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Angle ProbeAngle Probe
UT SetUT SetA ScanA Scan
DisplayDisplay
Ultrasonic Testing
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initial pulse
defect echo
defectdefect
defect
0 10 20 30 40 50
CRT Display
0 10 20 30 40 50
initial pulse
defect echo
CRT Display
Skip
Full Skip
Ultrasonic Testing
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AdvantagesAdvantages
Rapid results
Both surface and
sub-surface detection
Safe
Capable of measuring thedepth of defects
May be battery powered
Portable
DisadvantagesDisadvantages
Trained and skilled operatorrequired
Requires high operator skill
Good surface finish required
Defect identification
Couplant may contaminate
No permanent record
Calibration Required
Ferritic Material (Mostly)
Ultrasonic Testing
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Ultrasonic Testing
Comparison with RadiographyComparison with Radiography
ADVANTAGESADVANTAGES
good for planar defects
good for thick sections
instant results
can use on complex joints
can automate
very portable
no safety problems (parallel working is possible)
low capital & running costs
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Ultrasonic Testing
Comparison with Radiography
DISADVANTAGESDISADVANTAGES
no permanent record (with standard equipment) not suitable for very thin joints
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Any QuestionsAny Questions
Ultrasonic Testing
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Radiographic Testing (RT)Radiographic Testing (RT)
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The principles of radiographyThe principles of radiography
X or Gamma radiation is imposed upon a test object
Radiation is transmitted to varying degrees dependant upon thedensity of the material through which it is travelling
Thinner areas and materials of a less density show as darkerareas on the radiograph
Thicker areas and materials of a greater density show as lighterareas on a radiograph
Applicable to metals,non-metals and composites
Radiographic Testing
R di hi T i
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X Rays
Electrically generated
Gamma Rays
Generated by the decay ofunstable atoms
Radiographic Testing
R di hi T ti
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SourceSource
Radiation beamRadiation beam Image quality indicatorImage quality indicator
10fe16
10fe16
Test specimenTest specimenRadiographic filmRadiographic film
Radiographic Testing
R di hi T ti
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SourceSource
Radiation beamRadiation beam Image quality indicatorImage quality indicator
Radiographic film with latent image after exposureRadiographic film with latent image after exposure
10fe16
10fe16
Test specimenTest specimen
10fe16
10fe16
Radiographic Testing
R di hi T ti
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Radiographic Testing
DensityDensity -- relates to the degree of darknessrelates to the degree of darkness
ContrastContrast -- relates to the degree of differencerelates to the degree of difference
DefinitionDefinition -- relates to the degree of sharpnessrelates to the degree of sharpness
SensitivitySensitivity -- relates to the overall quality of the radiographrelates to the overall quality of the radiograph
Densitometer
Radiographic Sensitivity
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7FE127FE12
Step / Hole type IQIStep / Hole type IQI Wire type IQIWire type IQI
Radiographic Sensitivity
Radiographic Sensitivity
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Wire Type IQIWire Type IQI
Step/Hole Type IQIStep/Hole Type IQI
Radiographic Sensitivity
Radiographic Techniques
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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)
Radiographic Techniques
Single Wall Single Image (SWSI)
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IQIIQIss should be placed source sideshould be placed source side
FilmFilm
FilmFilm
Single Wall Single Image (SWSI)
Single Wall Single Image Panoramic
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IQIIQIss are placed on the film sideare placed on the film side
Source inside film outside (single exposure)Source inside film outside (single exposure)
FilmFilm
Single Wall Single Image Panoramic
Double Wall Single Image (DWSI)
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IQIIQIss are placed on the film sideare placed on the film side
Source outside film outside (multiple exposure)Source outside film outside (multiple exposure)
This technique is intended for pipe diameters over 100mmThis technique is intended for pipe diameters over 100mm
FilmFilm
Double Wall Single Image (DWSI)
Double Wall Single Image (DWSI)
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RadiographRadiograph
IdentificationIdentification
IDIDMR11MR11
Unique identificationUnique identificationEN W10EN W10
IQI placingIQI placing
AA BB Pitch marks indicatingPitch marks indicatingreadable film lengthreadable film length
Double Wall Single Image (DWSI)
Double Wall Single Image (DWSI)
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RadiographRadiograph
Double Wall Single Image (DWSI)
Double Wall Double Image (DWDI)
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FilmFilm IQIIQIss are placed on the source or film sideare placed on the source or film side
Source outside film outside (multiple exposure)Source outside film outside (multiple exposure)
A minimum of two exposuresA minimum of two exposures
This technique is intended for pipe diameters less than 100mmThis technique is intended for pipe diameters less than 100mm
Double Wall Double Image (DWDI)
Double Wall Double Image (DWDI)
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Shot A RadiographShot A Radiograph
IdentificationIdentification
IDMR12
Unique identificationUnique identification EN W10
IQI placingIQI placing
1 2 Pitch marks indicatingPitch marks indicating
readable film lengthreadable film length
4 3
Double Wall Double Image (DWDI)
Double Wall Double Image (DWDI)
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Elliptical RadiographElliptical Radiograph
11 22
44 33
Double Wall Double Image (DWDI)
Radiography
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Radiography
PENETRATING POWERPENETRATING POWER
Question:Question:
What determines the penetrating power of an XWhat determines the penetrating power of an X--ray ?ray ?
the kilothe kilo--voltage appliedvoltage applied (between anode & cathode)(between anode & cathode)
Question:Question:
What determines the penetrating power ofWhat determines the penetrating power of a gamma ray ?a gamma ray ?
the type of isotopethe type of isotope (the wavelength of the gamma rays)(the wavelength of the gamma rays)
Radiography
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Radiography
GAMMA SOURCESGAMMA SOURCES
IsotopeIsotope Typical Thickness RangeTypical Thickness Range
Iridium 192Iridium 192 10 to 50 mm10 to 50 mm (mostly used)(mostly used)
Cobalt 60Cobalt 60 > 50 mm> 50 mm
YtterbiumYtterbium < 10 mm< 10 mm
ThuliumThulium < 10 mm< 10 mm
CaesiumCaesium < 10 mm< 10 mm
Radiographic Testing
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AdvantagesAdvantages
Permanent record
Little surface preparation
Defect identification
No material type limitation
Not so reliant upon operatorskill
Thin materials
DisadvantagesDisadvantages
Expensive consumables
Bulky equipment
Harmful radiation
Defect require significant
depth in relation to theradiation beam (not good forplanar defects)
Slow results
Very little indication of depths
Access to both sides required
g p g
Radiographic Testing
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Radiographic Testing
Comparison with Ultrasonic ExaminationComparison with Ultrasonic Examination
ADVANTAGESADVANTAGES
good for non-planar defects
good for thin sections
gives permanent record
easier for 2nd party interpretation
can use on all material types
high productivity
direct image of imperfections
Radiographic Testing
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g p g
Comparison with Ultrasonic Examination
DISADVANTAGESDISADVANTAGES
health & safety hazard
not good for thick sections
high capital and relatively high running costs
not good for planar defects
X-ray sets not very portable
requires access to both sides of weld
frequent replacement of gamma source needed (half life)
Radiographic Testing
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Any QuestionsAny Questions
Questions
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QU 1.QU 1. Name four NDT methods
QU 2.QU 2. State the two radiation types used in industrial radiographyand state advantages of each.
QU 3.QU 3. Give the advantages and disadvantages of radiography andconventional ultrasonic inspection.
QU 5QU 5 State the main limitations of dye penetrant inspection.
QU 4.QU 4. Give the main disadvantages of magnetic particleinspection and give at least three methods to magnetise acomponent.
NonNon--Destructive TestingDestructive Testing