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Module 10 - 1

Module 10

Visual
Inspection and
Other
NDE Methods
and
Symbols
A
W
S
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Module 10 - 2

Visual Inspection
Very cost effective
 Limited to surface only
 Requires

– Training
– Experience
– Welding knowledge
– Proper tools

Must be continuous, ongoing

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Module 10 - 3

Application of VT
Before welding
 During welding
 After welding

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Module 10 - 4

VT Before Welding
Review documents
 Check welding procedures
 Qualify/Certify welders, or check
certifications
 Establish hold points
 Develop inspection plan
 Develop system for reject identification
 Develop defect repair system

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VT Immediately Before
Welding

Module 10 - 5

Check
 Check
 Check
 Check
 Check
 Check

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base and filler metals
welding equipment
weld preparations
joint fitup
weld joint cleanliness
preheat, if required

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Module 10 - 6

VT During Welding
Note welder skills
 Check welding variables/procedure
compliance
 Examine tacks and roots
 Check backgouged surfaces
 Check preheat temperatures
 Check interpass temperatures
 Check interpass cleaning

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Module 10 - 7

VT After Welding
Examine weld appearance
 Check weld size and length
 Check part dimensions
 Monitor other NDE methods
 Monitor postweld heat treating
 Prepare inspection reports

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Module 10 - 8

Visual Inspection Tools

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Module 10 - 9

Prebending
and
Presetting
Pieces to
Allow for
Distortion
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Temperature
Measurements

Module 10 - 10

Required for:
– Preheat
– Interpass temperature limits
– Post weld heat treatments

Typically achieved by:
– Temperature sensitive crayons
– Digital pyrometers

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Temperature-sensitive
Crayons

Module 10 - 11

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Module 10 - 12

Digital
Contact
Pyrometer

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Module 10 - 13

Fillet Weld Size
Convex or concave ??
 Use correct template gage
 Estimate between gage sizes
 Measure to nearest 1/32” or 1/16”
 Measure smallest region

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Module 10 - 14

Measuring Fillet Size

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Module 10 - 15

Nondestructive Testing
“Method of testing to evaluate
quality and not effect end-use
serviceability”

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Elements of all NDE
Methods

Module 10 - 16

Source of probing energy
 Discontinuities alter probing
energy
 Detection of energy alteration
 Indication of energy alteration
 Recording and evaluating
indications

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Module 10 - 17

Common NDE Methods
Penetrant  Magnetic Particle  Radiographic  Ultrasonic  Eddy Current 

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PT
MT
RT
UT
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Module 10 - 18

Penetrant Testing
Surface discontinuities only
 Relies on penetrant ‘bleedout’
 Magnifies discontinuity size
 Several methods

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Module 10 - 19

PT Types
Visible dye
 Fluorescent dye

Three removal systems:
 Solvent
 Water
 Emulsifiable

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Module 10 - 20

Clean the Surface

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Module 10 - 21

Apply Penetrant

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Module 10 - 22

Dwell Time
Varies with the nature of the job,
typically in the range of 2 to 20
minutes, or longer in special cases

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Module 10 - 23

Remove Excess Penetrant

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Remove Excess Penetrant

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Remove Excess Penetrant

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Module 10 - 26

Remove Excess Penetrant

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Module 10 - 27

Apply Developer
In
this
example,
spray can is too
close to the weld
surface, which can
lead to excessive
developer
on
surface. A distance
of 10-12 inches is
better.

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Module 10 - 28

Excessive Developer
Note ‘runs’ caused
by excess
developer; this can
mask
discontinuities

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Module 10 - 29

Evaluate PT
Note porosity and
crack indications

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Module 10 - 30

Clean Part
Post inspection removal of developer
residues
may
be
required,
particularly if work piece is to be
weld repaired or painted.

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Module 10 - 31

PT Advantages
Relatively simple
 All types of metals
 Quite sensitive
 Quite portable

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Module 10 - 32

PT Limitations
Somewhat slow
 Limited to surface
 Smooth surfaces required

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Module 10 - 33

PT Results
Sketches
 Photographs
 Lift off tapes

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Module 10 - 34

Magnetic Particle Testing
Parts are magnetized
 Iron particle accumulation at flaw
 Magnifies flaw size
 Relatively quick process

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Module 10 - 35

Aspects of a Magnet
Magnetic flux (field)
 North and south poles
 Like sign poles repel
 Opposite signs attract
 Flux lines are parallel to each
other; do not cross

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Module 10 - 36

Magnetic Fields
Produced by two methods:
 Permanent magnets
 Electro magnets
– Direct current
– Alternating current
– Half wave rectified AC

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Module 10 - 37

Permanent Magnet

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Module 10 - 38

Electromagnets
“A current-carrying conductor
creates a magnetic flux around the
conductor and perpendicular to the
current flow.”

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Module 10 - 39

Magnetic Field Around
Conductor

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Module 10 - 40

MT Principles
“A flaw oriented transverse to
magnetic flux creates poles of
opposite signs at edges of flaw.
Very attractive to iron particles”

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Module 10 - 41

Magnetic Particles
Iron based
 Dry or wet
 Types

– Color dyed
– Fluorescent

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Module 10 - 42

Longitudinal Magnetism

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Module 10 - 43

Circular Magnetism

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MT Steps
Magnetize part
 Apply iron particles
 Evaluate accumulation
 Clean part
 Demagnetize part

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Module 10 - 45

MT Equipment
AC
 AC
 AC
 AC
 AC

/ DC bench units
yokes
/ DC yokes
/ DC prods
/ DC coils

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Module 10 - 46

Central Conductor Method

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Module 10 - 47

MT Method
--Yoke

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Module 10 - 48

MT Method
--Prods

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Module 10 - 49

MT Advantages
Rapid
 Very sensitive
 Low cost
 Portable

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Module 10 - 50

MT Limitations
Magnetic materials only
 Poor with thick coatings
 Limited to surface, or near-surface
 Demagnetization may be required

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Module 10 - 51

MT Results
Sketches
 Photographs
 Lift off tapes

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Module 10 - 52

Radiographic Testing

“Based on the principle of
preferential radiation transmission
or absorption.”

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X-Ray Machine (aimed
down)

Module 10 - 53

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Module 10 - 54

Radiation Absorption
“Thicker, or higher density materials
absorb more radiation, resulting in
less transmission to the film.”

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Module 10 - 55

Absorption vs Thickness

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Metal Densities

Module 10 - 56

Grams/cubic centimeter
Aluminum

2.70

Steel

7.87

Copper

8.96

Lead

11.34

Tungsten

19.30

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Module 10 - 57

Absorption vs Density

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Module 10 - 58

Radiation Types

Gamma radiation sources
– Iridium 192
– Cobalt 60
– Cesium 137

X-Ray
– Machine

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Module 10 - 59

RT Steps
Position radiation source
 Position film behind object
 Expose radiation
 Develop film
 Evaluate

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Module 10 - 60

Film Density Vs Flaws
Darker film zones:
 Cracks, slag, porosity
 Incomplete joint penetration
Lighter film zones:
 Tungsten inclusions
 Melt through, reinforcement

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Hole Type Image Quality
Indicators

Module 10 - 61

2T
hole
1T
hole
4T
hole

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Wire Type Image Quality
Indicators

Module 10 - 62

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Module 10 - 63

RT Equipment
Radiation source

Densitometer /
– X-ray machine
film density
– Gamma radiation
strips
source
 Film processor
 Radiation monitor

Film holders
 IQI’s

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Film viewers

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Module 10 - 64

Orientation of Source,
Plate, & Film

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Module 10 - 65

RT Advantages
Detects subsurface flaws
 Used for all materials
 Film is permanent record

– If stored properly

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Module 10 - 66

RT Limitations
Radiation hazard
 Requires access to both sides
 Flaw orientation
 Flaw types
 Film interpretation

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Module 10 - 67

RT Results
Film
 Video tape
 Sketches

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Module 10 - 68

Ultrasonic Testing
“Based on the propagation of sound
waves through materials, and the
reflected echo from density changes.”

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Module 10 - 69

Piezoelectric Effect
“Refers to materials which can convert
electrical energy to mechanical energy
and vice versa.”

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Module 10 - 70

Principles of Sound
Sound travels within a given material at a
constant velocity, based in part, on material
density. Sound will not travel in a vacuum.
There are several types of sound waves:
Longitudinal (straight beam)
 Shear (angle beam)
 Others not pertinent to weld inspection

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Module 10 - 71

UT Equipment & Operation
Electronic base unit
 Piezoelectric transducer
 Calibration blocks

Couple probe to part with couplant
 Carry out testing
 Evaluate signals

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Module 10 - 72

UT Process

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Module 10 - 73

Longitudinal
Calibration

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UT Process - 1 of 2

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Module 10 - 75

UT Process - 2 of 2

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Module 10 - 76

Angle Beam
Testing of
Weld

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Module 10 - 77

Weld Testing - 1 of 2

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Module 10 - 78

Weld Testing - 2 of 2

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Module 10 - 79

UT Advantages
A true volumetric test
 One side access
 Very accurate
 Deep penetration - 200”
 Critical flaws found
 Equipment fully portable

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Module 10 - 80

UT Limitations
Highly skilled operator
 Smooth surfaces
 Groove welds > 1/4” thick

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Module 10 - 81

Eddy Current Testing
“Based on the principle of eddy currents
being formed in conductive materials in
the presence of an AC coil and changes in
those eddy currents by material
changes.”

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Module 10 - 82

Test
Coil

Induced Eddy
Currents

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Module 10 - 83

ET Uses
Flaw detection
 Metal thickness
 Coating thickness
 Metal hardness
 Heat treatment

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Module 10 - 84

ET CRT
Displays

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Module 10 - 85

ET Equipment
Base unit, CRT or meter
 AC probe (coil)
 Calibration standards

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Module 10 - 86

ET Advantages
No contact required with part
 No couplant required
 Readily Automated
 Applicable to all metals

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Module 10 - 87

ET Limitations
Highly skilled operator
 “Too sensitive”
 Shallow penetration - 3/16”
 Calibration standards required
 Requires surface cleanliness
 Magnetic materials more difficult

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Module 10 - 88

NDE Symbols
Similar to weld symbols
 Shorthand notation
 Very useful
 Combine with weld symbols

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Module 10 - 89

Standard Location of
Elements for NDE Symbols

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NDE Test Methods Abbreviations
1 of 2
Acoustic Emission

AET

Eddy Current

ET

Leak

LT

Magnetic Particle

MT

Neutron Radiography

NRT

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NDE Test Methods Abbreviations
2 of 2
Penetrant

PT

Proof

PRT

Radiography

RT

Ultrasonic

UT

Visual

VT

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Module 10 - 92

WIT Summary
Have covered much material in 3 days
 Workbook and Sample Fundamentals
Exam are good guides to your grasp of
each Module, and may point towards
areas needing more study in Manual
 Urge all to study these subjects in greater
depth as part of continuing education

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