TWI-UT of Welds

Time base range. Maximum ultrasonic path length that can be displayed on a particular
time base.

Time corrected gain. Facility of flaw detectors to represent flaws of equal reflective
size with the same screen amplitude, irrespective of their depth in the material.

Time marker. See screen marker.

Toe-in-semi-angle. Half the angle between the normals to the crystal faces in a twin
crystal probe.

Total attenuation. Diminution of intensity of a particular mode, with travel range, of an
ultrasonic beam of any form arising from the combined effects of absorption, scatter and
geometric beam spread.

Total internal reflection. Reflection which occurs when the angle of incidence is
greater than the critical angle and the reflection coefficient is unity.

Transceiver. Probe used to generate and detect ultrasonic energy.

Transducer. Electroacoustical device for converting electrical energy into acoustical
energy and vice versa.

Transmission coefficient. Ratio of ultrasonic wave intensity transmitted across an
interface to the total wave energy incident upon the interface.

Transmission point. Point on the time base which corresponds to the instant at which
ultrasonic energy enters the material under examination.

Transmission technique. Technique in which the quality of a material is assessed by
the intensity of the ultrasonic radiation incident on the receiving probe after the waves
have travelled through the material.

Transverse wave. See shear wave.

Trigger/alarm condition. Condition where the equipment indicates that a piece of
material is suspect.

Trigger/alarm level. Level at which the ultrasonic equipment is required to
differentiate between acceptable and suspect material.

Triple bounce technique. See quadruple traverse technique.

Triple traverse technique. Technique in which a beam of ultrasonic waves is directed
into a region of a body under examination after having been reflected successively by
two surfaces of the body. Note: A synonymous term is double bounce technique.

Twin crystal probe. See double crystal probe.

Ultrasonic frequency. Any frequency of vibration greater than the range of audibility of
the human ear, generally taken as greater than 20kHz.

Ultrasonic mode changer. Device which causes vibrations of a particular mode (eg
compressional) in one body to produce vibrations of another mode (eg shear) in another
body.

Wavelength (λ). Perpendicular distance between two wave fronts with a phase
difference of one complete period.

NDT4-51015

Glossary 13 Copyright © TWI Ltd

Ultrasonic wave. Disturbance which travels through a material at ultrasonic frequency
by virtue of the elastic properties of that material.

Wedge (ultrasonic). Device placed between the probe and the test surface for the
purpose of causing ultrasonic waves to pass between the two at a particular angle.

Wetting Agent. Substance added to a coupling liquid to decrease its surface tension.

Young’s modulus of elasticity. In an elastic material, the ratio of tensile stress to
tensile strain.

NDT4-51015

Glossary 14 Copyright © TWI Ltd

Ultrasonic Inspection

Ultrasonic Testing (UT) - Welds

NDT4

Part 1 Principles of Sound

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NDT4-51015

Course Objectives History of Ultrasonic Testing

 Explain the theoretical background of the techniques.  From very early times castings were tested for
 Calibrate ultrasonic equipment. soundness by tapping with a hammer.
 Measure the thickness of steel plates and determine
 The piezo-electric effect was investigated by
levels of attenuation. Jacques and Pierre Curie in 1880/81.
 Locate and evaluate laminations.
 Select the correct type of probe to examine welded butt  Marine echo sounding for submarine and fish
detection developed from 1912.
joints in steel plate and aerospace
components/structures.  In 1929 Sokolov developed the first ultrasonic
 Report on the location and size of defects in typical test method for the detection of flaws in steel
welded butt joints. castings.
 Interpret code requirements.
 Meet the syllabus requirements for PCN/CSWIP Levels 1  Cathode ray tubes became available in the 1930s.
and 2.  Sproule designed and built the first pulse echo

Copyright © TWI Ltd flaw detector in 1942.

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What is Sound? What is Sound?

 A mechanical vibration. Sound waves are the vibration of particles in
 The vibrations create pressure waves. solids, liquids or gases.
 Sound travels faster in more elastic materials. Particles vibrate about a mean position.
 Number of pressure waves per second is the In order to vibrate they require mass and
elasticity.
frequency.
 Speed of travel is the sound velocity.

One cycle

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1

Properties of a Sound Wave

Velocity Frequency Wavelength Velocity

How quickly a sound How many vibrations V
wave travels. per second. f

Wavelength  

How far a sound wave advances
in completing one cycle.

V Frequency
ƒ
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Copyright © TWI Ltd

High Frequency Sound Acoustic Spectrum

  V 5MHz compression Human Ultrasonic Range
f wave in steel 16Hz - 20kHz + 20kHz

  5,900,000 1.18mm 0 10 100 1K 10K 100K 1M 10M 100m
5,000,000 Testing

Copyright © TWI Ltd 0.5MHz - 50MHz

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Sound Travelling Through a Material Compression vs Shear

Velocity varies according to the material Frequency Compression Shear
 0.5MHz  11.8mm  6.5mm
Compression waves Shear waves  1 MHz  5.9mm  3.2mm
 2MHz  2.95mm  1.6mm
 Steel 5960m/sec  Steel 3245m/sec  4MHz  1.48mm  0.8mm
 Water 1490m/sec  Water NA  6MHZ  0.98mm  0.54mm
 Air 344m/sec  Air NA
 Copper 4700m/sec  Copper 2330m/sec The smaller the wavelength the better the sensitivity
Minimum detectable defect taken as half the wavelength

Less than half wavelength –
defect may not be detected

More than half wavelength –
defect should be detected

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2

Principal Waveforms Used in Compression Waves
UT Inspections
 Vibration and propagation in the same
 Compression - also known as Longitudinal. direction.
 Shear – also known as Transverse.
 Surface – also known as Rayleigh.  Travel in solids, liquids and gases.
 Lamb – also known as Plate.
Particle vibration Propagation
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Copyright © TWI Ltd

Compression Waves Shear Waves

Copyright © TWI Ltd  Vibration at right angles to direction of
propagation.

 Travel in solids only.
 Velocity  1/2 compression (in same material).

Particle vibration

Propagation

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Shear Waves Surface Waves

 Elliptical vibration.
 Velocity 8% less than shear.
 Penetrate up to one wavelength deep.

DIRECTION OF PROPAGATION

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3

Surface Waves Lamb Waves

 Propagate in thin plate materials where plate
thickness is equivalent to wavelength.

 Particle motion is a complex combination of
symmetrical and non-symmetrical elliptical
waves.

 Velocity varies with plate thickness and
wavelength.

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Long Range UT: Long Range UT:
Alaska 24" Road Crossing Alaska 24" Road Crossing

Copyright © TWI Ltd Weld

Reportable feature
Weld

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Long Range UT: Long Range UT:
Alaska 24" Road Crossing Wave Modes in Pipes

Copyright © TWI Ltd Longitudinal
Torsional
Flexural

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4

Sound Intensity Sound Intensity

Comparing the intensity of 2 signals I0 (V0)2
I1 (V1)2
I0 P0  Will lead to large ratios
I1 P1
 I0 (V0)2
I1 (V1)2
Therefore: Log..10  Log..10

Electrical power proportional to the square of I0 V0
the voltage produced I1 V1

P0 (V0)2 I0 (V0)2 Log..10  2Log..10 BELS
P1 (V1)2 I1 (V1)2
 Hence  I0 V0
I1 V1
Log..10  20Log..10 dB

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Take 2 Signals at 20% and 40% FSH Take 2 Signals at 10% and 100% FSH

What is the difference between them in dB? What is the difference between them in dB?

dB  20log10 H0 dB  20log10 H0
H1 H1

dB  20log10 40  20log10 2 dB  20log10 100  20log1010
20 10

dB  20 0.3010 dB  20 1
dB  6dB dB 20dB

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Amplitude Ratios in Decibels Sound Travelling Through a Material

 2:1 = 6bB = 50% Loses intensity due to
 4:1 = 12dB = 25%
 5:1 = 14dB = 20% Beam spread Attenuation
 10 : 1 = 20dB = 10%  Sound beam  Energy losses due
 100 : 1 = 40dB = 1%
comparable to a to material.
 Made up of
torch beam.
 Reduction differs absorption and

for small and large scatter.

reflectors.

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5

Scatter Scatter

 The bigger the grain  Scatter becomes Copyright © TWI Ltd
size the worse the significant as the average
problem. grain size exceeds about
1/10 of the wavelength.
 The higher the
frequency of the  If the average grain size
probe the worse the reaches 1/2 of the
problem. wavelength extremely
high attenuation will
occur.

 If the average grain size
exceeds the wavelength
ultrasonic testing will be
impossible.

Copyright © TWI Ltd

80% Beam Spread and Sound at an Interface
FSH Attenuation Combined
Sound will be either transmitted across or
40% Attenuation and beam reflected back.
FSH spread. 6dB+ reduction.
Reflected
80%
FSH

Interface How much is reflected and
transmitted depends upon the
36% relative acoustic impedance of
FSH the two materials.

No attenuation, only beam Transmitted
spread. 6dB reduction.

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Acoustic Impedance % Sound Reflected at an Interface

Definition Formula  Z1  Z2 2 100  % reflected
 Resistance to travel  Z1  Z2
 Z   V  
of sound waves 
within a material. Is the product of 

Measured in kg/m2 x sec density and velocity

 Steel 46.7 x 106 % sound reflected + % sound transmitted = 100%.

 Water 1.48 x 106

 Air 0.0041 x 106 Therefore:
% sound transmitted = 100% - % sound reflected.
 Perspex 3.2 x 106

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6

How Much Sound is Reflected at a Sound Generation
Steel to Water Interface?
 Hammers (Wheel tappers).
 Z1 (Steel) = 46.7 x 106  Magnetostrictive.
 Z2 (Water) =1.48 x 106  Lasers.
 Piezo-electric.
 46.7  1.48 2 100  % reflected
 46.7  1.48  Copyright © TWI Ltd

 45.22  2
 48.18 
100  % reflected

0.938562 =0.8809 x 100

=88.09%

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Piezo-Electric Effect Piezo-Electric Materials

 When exposed to an alternating current a Quartz Lithium sulphate
crystal expands and contracts.
 Resistant to wear.  Efficient receiver.
 Converting electrical energy into mechanical.  Insoluble in water.  Low electrical
 Resists ageing.
-+  Inefficient converter of impedance.
Alternating  Operates on low voltage.
AC current energy.  Water soluble.
 Needs a relatively high  Low mechanical strength.
+-  Useable only up to
voltage.
Copyright © TWI Ltd 130ºC.

Copyright © TWI Ltd

Polarised Crystals Probe Design

 Powders heated to high Examples: Compression wave Electrical
temperatures.  Barium titanate Housing connectors
Damping
 Pressed into shape. (Ba Ti O3). Transducer
 Cooled in very strong  Lead metaniobate
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electrical fields. (Pb Nb2 O6).
 Lead zirconate titanate

(Pb Ti O3 or Pb Zr O3).

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7

Probe Design Probe Design

Shear wave Transducer Twin crystal Advantages:
Damping Perspex wedge  Can be focused.
Transmitter Receiver  Measure thin plate.
Copyright © TWI Ltd Damping  Near surface

Insulator Focusing resolution.
lens
Disadvantages:
 Difficult to use on

curved surfaces.
 Sizing small defects.
 Signal

amplitude/focal spot
length.

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Ultrasonic Test Methods

 Pulse Echo.
 Through Transmission.
 Transmission with Reflection.

Ultrasonic Testing
Part 2

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Pulse Echo Testing Defect Position

 Single probe sends and receives sound. B B
 Gives an indication of defect depth and A

dimensions. No indication from defect A (wrong orientation)
 Not fail safe.
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Copyright © TWI Ltd

8

Through Transmission Testing Through Transmission Testing
T
 Transmitting and receiving probes on opposite
sides of the specimen. Transmission
signal
 Presence of defect indicated by reduction in
transmission signal. R

 No indication of defect location. Copyright © TWI Ltd
 Fail safe method.

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Minor Defect Through Transmission Testing
TT
Advantages: Disadvantages:
R Transmission R  Less attenuation.  Defect not located.
 No probe ringing.  Defect can’t be
 No dead zone.
 Orientation does not identified.
 Vertical defects don’t
matter.
show.
signal reduced Transmission  Must be automated.
 Need access to both
signal
surfaces.
disappears

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Transmission with Reflection Transmission with Reflection
TR TR

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9

Pulse Length Pulse Length

 A short pulse of electricity is applied to a  The longer the pulse, the more penetrating
piezo-electric crystal. the sound.

 The crystal begins to vibrate, increases to  The shorter the pulse, the better the
maximum amplitude and then decays. sensitivity and resolution.
Maximum
Short pulse, 1 Long pulse, 12 cycles
10% of or 2 cycles
Maximum Copyright © TWI Ltd

Pulse length

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Ideal Pulse Length The Sound Beam

 Dead zone.
 Near zone or Fresnel.
 Far zone or Fraunhofer.

5 cycles for weld testing Copyright © TWI Ltd

Copyright © TWI Ltd

The Sound Beam Sound Beam

Near zone: Far zone:
 Thickness  Thickness

measurement. measurement.
 Detection of defects.  Detection of defects.
 Sizing of large  Sizing of all defects.

defects only.

Near zone length as small as possible.

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10

Near Zone Near Zone

Near Zone D2  What is the near zone length of a 5MHz
 4 compression probe with a crystal diameter of

D2 f 10mm in steel?
 4V
  V Near Zone D2 f
f  4V

Near Zone  10 2  5,000 ,000
4  5,920 ,000

 21 .1mm

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Near Zone Beam Spread

 The bigger the diameter the bigger the near In the far zone sound pulses spread out as they
move away from the crystal.
zone.
 (/2)
 The higher the frequency the bigger the near

zone.

 The lower the velocity the bigger the near

zone.

Near Zone D2 D2 f K KV
 4  4V D Df
sin(2 )  or
Should large diameter crystal probes have a
high or low frequency?

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Beam Spread Beam Spread

sin(2 )  K or KV sin(2 )  K or KV
D Df D Df

Edge, K=1.22  The bigger the diameter the smaller the beam
20dB, K=1.08 spread.
6dB, K=0.56
 The higher the frequency the smaller the
Beam axis beam spread.

Which has the larger beam spread, a compression
or a shear wave probe?

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11

Beam Spread Testing Close to Side Walls

What is the half beam spread of a 10mm, 5MHz Remember!
The ultrasonic pulse is a
compression wave probe in steel to the 20dB pressure wave which can
be diverted from its
point? original path by other
waves exerting pressure
sin (  )  KV from the side.
2 Df
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 1 .08  5920
5000  10 Testing Close to Side Walls

 0 .1278  7 .35 o

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Testing Close to Side Walls

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Sound at an Interface Inclined Incidence (not at 90°)

Sound will be either transmitted across or Angle of incidence = angle of reflection
reflected back.
60o 60o
Reflected
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Interface

Transmitted

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12

Inclined Incidence (not at 90°) Ghost Echoes

Comp Comp  Pulse repeat frequency (PRF) is typically of
the order of 1,000Hz.
Shear
 In 1/1,000 of a second a compression wave in
60° 60° steel travels about 5.96m.

Mode conversion  Using a PRF of 1,000Hz a steel slab up to
5.96/2 = 2.98m thick can be tested.
Copyright © TWI Ltd
 If the slab exceeds 2.98m thick sound will
arrive back at the probe after a second pulse
of sound has been emitted.

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Ghost Echoes Ghost Echoes

 Thus the flaw detector will display an echo at  Ghost echoes can be eliminated by reducing
a range equal to the actual range minus the PRF, on flaw detectors which provide the
2.98m. facility to do this.

 Such an echo is called a ghost echo.  On many older portable flaw detectors it is not
 In the A-scan display the position of such possible to adjust PRF.

echoes tends to oscillate slightly, even when Copyright © TWI Ltd
the probe itself remains stationary.
 Ghost echoes can cause problems when
testing bulky components that have low
ultrasonic attenuation.

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Inclined Incidence(not at 90°) Snell’s Law

Incident I
Material 1
Transmitted
The sound is refracted due to differences in sound Material 2 R
velocity in the 2 materials.
sin I  V in Material 1
Copyright © TWI Ltd sin R V in Material 2

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13

Snell’s Law Snell’s Law

C sin I  V in Material1 C sin I  V in Material1
20 sin R V in Material 2 15 sin R V in Material 2

Perspex sin (20) 2730 Perspex sin (15)  2730
sin (48.3) 5960 sin R 5960


Steel 0 .4580  0 .4580 Steel sin R  sin( 15 5960 )
48.3 34.4 2730

C C sin R  0 .565

R  34 .4

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Snell’s Law 1st Critical Angle

C C Compression wave refracted
20 27.4 at 90 degrees

Perspex

Steel 48.3 C
C
S 33
24 S

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2nd Critical Angle 1st Critical Angle Calculation

C C C 27.2 sin I 2730
57 sin 90 5960


Perspex sin (90 )  1

S (Surface Wave) C 2730
90 5960
Steel sin I 
Shear wave refracted at 90 degrees.
Shear wave becomes a surface wave. sin I  0.458

Copyright © TWI Ltd S I  27 .26

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14

2nd Critical Angle Calculation Summary

C C sin I  2730  Standard angle probes between 1st and 2nd
57.4 sin (90) 3240 critical angles (45,60,70).
Perspex
Steel S sin (90 )  1  Stated angle is refracted angle in steel.
 1st critical angle: compression refracted at 90
sin I  2730
3240 degrees.
 2nd critical angle: shear refracted at 90.
sin I  0.8425  2nd critical angle produces surface waves.

I  57 .4 Copyright © TWI Ltd

Copyright © TWI Ltd

Snell’s Law Automated Inspections

 Calculate the 1st critical angle for a  Pulse echo.
perspex/copper interface.  Through transmission.
 Transmission with reflection.
 V Comp perspex: 2730m/sec.  Contact scanning.
 V Comp copper: 4700m/sec.  Gap scanning.
 Immersion testing.
sin I  2730  0 .5808  35 .5
4700

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Gap Scanning Bubblers and Squirters

 Probe held a fixed distance above the surface Copyright © TWI Ltd
(1 or 2mm).
15
 Couplant is fed into the gap.

Couplant

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Bubblers and Squirters Immersion Testing

 Component is placed in a water filled tank.
 Item is scanned with a probe at a fixed

distance above the surface.

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Immersion Testing Immersion Testing Angulation

Water path Compression
distance Shear

Front surface Back surface Copyright © TWI Ltd

Water path distance

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Ultrasonic Displays Ultrasonic Displays

C scan A scan
 Time or distance along X axis.
Plan view  Returned echo amplitude Y axis.

D scan B scan B scan

Side view End view End view

Copyright © TWI Ltd C scan

Plan view

D scan

Side view

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16

Time of Flight Diffraction Time of Flight Diffraction

The probes are designed to flood the entire cross Copyright © TWI Ltd
section with a wide range of compression and shear
wave angles. The diffracted signals from the tips of
non-planar defects permit extremely accurate sizing.

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Other Special Techniques Other Special Techniques

Copyright © TWI Ltd Self-tandem, ferritic steel,

100mm thick

Shear wave Inspection depth

angle (D, mm)

62 95

66 67

70 46

74 29

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Ultrasonic Inspection

 Sensitivity.
 Scanning procedure.
 Defect sizing.

Ultrasonic Testing
Part 3

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17

Sensitivity Methods of Setting Sensitivity

The ability of an ultrasonic system to find the  Smallest defect at maximum test range.
smallest specified defect at the maximum testing  Back wall echo.
range.  Disc equivalent.
 Grass levels.
Depends upon  Side-drilled holes, DAC curves.
 Probe and flaw detector combination.
 Material properties. Copyright © TWI Ltd
 Probe frequency.
 Signal-to-noise ratio.

Copyright © TWI Ltd

Scanning Procedure Scanning Procedure

 Parent material. Parent material
 Root inspection. 0 degree both sides
 Side wall inspection.
 Weld body.  To maximum range for angle probes.
 Transverse scan.  Full skip distance for 60° or 70° probes.

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Parent Plate Inspection Using Scanning Procedure
00 Compression Probe
 Weld root.
 Half skip from both sides.

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18

Fixed Root Scan Scanning Procedure

Weld fusion faces
Half to full skip from both sides.

Copyright © TWI Ltd A probe which strikes fusion faces at 90 degrees.
Probe angle = 90 - (1/2 root angle).

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Scanning Procedure Scanning Procedure

Weld body Fusion face and weld body inspection
Half skip to full skip from both sides
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Full skip 1/2 Skip

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Scanning Procedure Scanning Procedure

Transverse
70 degree

Transverse scan

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19

Nozzle Welds Tee Butt Welds

Scanning procedure

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Defect Identification Echodynamics

 Echodynamics. Crack:
 Defect characterisation. Type 3A defect
Crack at 900 to beam
Lack of fusion, Gas pore Type 3B defect
Pattern 1 type defect Crack oblique to beam

Copyright © TWI Ltd Porosity
Type 4 defect

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Defect Characterisation

Signal amplitude Probe manipulation dB  20log10 H0 sin I  V in Material1
Lateral Depth H1 sin R V in Material 2

 Z1  Z2  2 V
 Z1  Z2  t=
  100  % reflected
2f

Orbital Swivel sin(  ) K or KV V
2 D Df f
  

Near Zone D2 D2 f
 4  4V

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20

Ultrasonic Equipment

Y Plates

Ultrasonic Testing
Part 4

Cathode Ray Tube X Plates
Tungsten Filament
Focusing Rings
Electron Stream

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Ultrasonic Equipment Ultrasonic Equipment

Attenuator Attenuator

Probe Time Base Probe Time Base

Pulse Pulse
Transmitter Transmitter

Pulse Generator Pulse Generator
(Timer) (Timer)

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Calibration Calibration

Using A4 block (also known as V2 or kidney block) 25mm -- excites crystal on return - signal at 25% screen.
+ 50mm -- does not excite crystal - no signal
+25mm -- excites crystal on return - signal at
(25mm +50mm + 25mm) =100% screen

12.5 or 20mm

35 40 45 50 60

25mm radius 70 50mm radius 25mm radius 0 10 20 30 40 50 60 70 80 90 100
75
1.5 or 5mm hole 50mm radius

Copyright © TWI Ltd Remember! Although the sound makes a return journey,
we only show a single journey on the CRT.

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21

Calibration Calibration

25mm -- excites crystal on return - signal at 25% screen. 50mm - excites crystal - signal at 50% screen
+ 50mm -- does not excite crystal - no signal +25mm - does not excite crystal - no signal
+25mm -- excites crystal on return - signal at
(25mm +50mm + 25mm) =100% screen

25mm radius 0 10 20 30 40 50 60 70 80 90 100 25mm radius 0 10 20 30 40 50 60 70 80 90 100

50mm radius 50mm radius

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Calibration Written Instruction

50mm - excites crystal - signal at 50% screen U ltra s o n ic F law D e te ctio n W ritte n In s tru c tio n
+25mm - does not excite crystal - no signal
+50mm - excites crystal - signal at 125% screen R efe ren c e N u m b er: A BC 01 Is s ue N u m b e r 0 0 1
C om p o ne n t:
C o m p o n e n t I.D .: D o u b le V w e ld , C a rb o n S te e l P la te , 2 5 m m , M M A
P re p a re d B y:
A p p ro v e d B y: T ag No. 13XX
C om pan y:
A im o f In s p e c tio n : U .T . T es te r S ig n : D ate :

A re a o f T e st: Q .A . M a nn S ig n : D ate :
S ta g e o f M a n u fa c tu re :
S u rfa c e C o n d itio n : Y a h o o T e c h n ica l In te rn a tio n a l
C o u p lan t:
F law D e tec to r: 1 0 0 % e x a m in a tio n to fin d d e fe c ts in w e ld a n d H A Z , c a rrie d
P ro b e s:
C alib ratio n B lo ck s o u t in a c c o rd a n c e w ith B S E N 1 7 1 4 :1 9 9 8 L e v e l D a n d P C N
S ca n n in g :
U T 001 Rev 0
T im eb a se C a lib ratio n : 1 0 0 % o f w e ld b o d y , H A Z a n d 1 0 m m p a re n t p la te e ith e r s id e
S e n s itiv ity S e ttin g s :
E v a lu a tio n o f In d ic a tio n s : o f w e ld

S afe ty: A s w e ld e d

C h e c k s a n d C a lib ra tio n s : U n d re s s e d , s c a n n in g s u rfa c e s to p e rm it fu ll a n d u n if o rm
V is u a l In s p e c tio n :
R e p o rtin g A c tio n s : c o u p lin g , R a < 1 2 .5  m
R e p o rtin g :
U C A 1 , U ltra g e l o r e q u iv a le n t
S ke tch :
K ra u tk ra m e r U S M 2 o r e q u iv a le n t
N o n -c o m p lian c e: T w in C rys ta l c o m p re s s io n p ro b e 1 0 m m 5 M H z 0 0
M in im u m O p e ra to r L e v e l: S in g le c rys ta l s h e a r w a v e p ro b e 1 0 m m 4 M H z 4 5 0 ,6 0 0, 7 0 0
P o s t E x a m in a tio n :
P re s e rv atio n : A2, A4, A5 and A7

S c a n 1 – c o m p re s s io n s c a n o f a ll p la te to b e s c a n n e d w ith

a n g le p ro b e s .
S c a n 2 – F ix e d ro o t s c a n 7 0 0
S c a n 3 – 4 5 0,6 0 0,7 0 0 s c a n o f fu s io n fa c e a n d w e ld b o d y
S c a n 4 – 4 5 0 s c an fo r tra ns v e rs e d e fe c ts

M a x im u m s c a n n in g s p e e d 5 0 m m /s e c . W ith o v e rla p o f 1 0 %

p ro b e d ia m e te r.

Scan 1 – 0 - 50m m S c a n 2 ,3 ,4 0 – 10 0m m

D A C fro m 3 m m s id e d rille d h o le s .

T ra n sfe r c o rre c tio n to B S E N 5 8 3 -2

A ll in d ic a tio n s e q u a l o r e x c e e d in g D A C + c o rre c tio n fa c to r

a n d in e x c e s s o f 5 m m in a n y d im e n s io n to b e e v a lu a te d

u s in g a b e a m g e o m e try te c h n iq u e to e s ta b lis h m a x im u m

e c h o a m p litu d e , le n g t h , th ro u g h w a ll d im e n s io n s a n d d e f e c t
c h a ra c te ris a tio n . C o rre c tio n fa c to rs to b e :- 0 0 D A C + 8 d B

S h e ar w a ve D A C + 1 4d B T ran sve rse sca n +1 4 d B .
L a m in a tio n s c a n a t F u ll S c re e n H e ig h t 2 nd B a c k W a ll E c h o

C a re to b e ta k e n w h e n liftin g s p e c im e n s , C o m p a n y a n d

S ta tu to ry N a tio n a l H e a lth a n d S a fe ty p ro c e d u re s to b e

a d he re d to. C orre c t P P E to b e w o rn .
A ll e q u ip m e n t to b e te s te d in a c c o rd a n c e w ith B S 4 3 3 1 p a rts

1 & 2 . R e c o rd s o f a ll te s ts a n d c a lib ra tio n s to b e k e p t.

C a rry o u t v is u a l in s p e c tio n o f s u rfa c e , re p o rt a n y

irre g u la rit ie s o r n o n -c o n fo rm a n c e s to S u p e rv is o r

0 10 20 30 40 50 60 70 80 90 100 110 120 130 A ll in s p e ctio n s to b e re c o rd e d o n a p p ro ve d re p o rt fo rm a t

25mm radius 50mm radius Id e n tific a tio n o f w e ld a n d fo llo w in g in fo rm a tio n to b e re c o rd e d

Copyright © TWI Ltd f o r e a c h in d ic a t io n e x c e e d in g D A C + c o rre c tio n fa c to rs a n d

5 m m le n g th :- L e n g th , d e p th , th ro u g h w a ll d im e n s io n , p o s itio n

w ith re s p e c t to d a tu m , m a x im u m e c h o a m p litu d e a n d d e f e c t

c h a ra c te ris a tio n .

S k e tc h e s to b e p ro d u c e d fo r e a c h in d ic a tio n e v a lu a te d

g iv in g :- th ro u g h w a ll, le n g th , d e p th a n d d is ta n c e fro m

c e n tre lin e . A n o ve ra ll p la n vie w sh a ll b e p ro d u c e d g ivin g a ll

in d ic a tio n p o s itio n s in re s p e c t to d a tu m .

A n y n o n -c o n fo rm a n c e in re la tio n t o th is in s tru c tio n s h a ll b e

b ro u g h t to th e S u p e rv is o r’s a tte n tio n im m e d ia te ly .

P C N le v e l 1 , U ltra s o n ic te s tin g , w ith a ll in d ic a tio n s c h e c k e d

b y S u p e rv is o r, o r n o m in a te d L e v e l 2 o p e ra to r

A ll tra c e s o f c o u p la n t to b e re m o v e d

P la te to b e f re e fro m a ll c o u p la n t, c h in a g ra p h o r p e n c il

m a rk s , w a te r a n d o th e r c o n ta m in a n ts a re to b e re m o v e d fro m

th e s u rfa c e a n d a lig h t c o v e r in g o f o il a p p lie d p rio r to s to ra g e .

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Ultrasonic Flaw Detection Ultrasonic Flaw Detection
Written Instruction Written Instruction

Reference Number: ABC01 Issue Number 001 Evaluation of Indications: All indications equal or exceeding DAC + correction factor and in excess of 5mm in
Component: any dimension to be evaluated using a beam geometry technique to establish
Component I.D.: Double V weld, Carbon Steel Plate, 25mm, MMA maximum echo amplitude, length, through wall dimensions and defect characterisation.
Prepared By: Correction factors to be :- 00 DAC + 8dB Shear wave DAC + 14dB.
Approved By: Tag No. 13XX Transverse scan +14dB.
Company: Lamination scan at Full Screen Height 2nd Back Wall Echo
Aim of Inspection: U.T. Tester Sign: Date:
Date:
Area of Test: Q.A. Mann Sign:
Stage of Manufacture:
Surface Condition: Yahoo Technical International
Couplant:
Flaw Detector: 100% examination to find defects in weld and HAZ, carried out in accordance with Safety: Care to be taken when lifting specimens, Company and Statutory National Health
Probes: BSEN 1714:1998 Level D and PCN UT 001 Rev 0 and Safety procedures to be adhered to. Correct PPE to be worn.
100% of weld body, HAZ and 10mm parent plate either side of weld
Calibration Blocks As welded Checks and Calibrations: All equipment to be tested in accordance with BS EN 12668 parts 3 Records of all tests
Scanning: Undressed, scanning surfaces to permit full and uniform coupling, Ra < 12.5m and calibrations to be kept.

Timebase Calibration: UCA 1, Ultragel or equivalent Visual Inspection: Carry out visual inspection of surface, report any irregularities or non-
Sensitivity Settings: Krautkramer USM2 or equivalent Reporting Actions: conformances to Supervisor.
Twin Crystal compression probe 10mm 5MHz 00 Reporting:
Single crystal shear wave probe 10mm 4MHz 450 ,600, 700 All inspections to be recorded on approved report format.
A2, A4, A5 and A7 Sketch:
Identification of weld and following information to be recorded for each
Scan 1 – compression scan of all plate to be scanned with angle probes. indication exceeding DAC + correction factors and 5mm length:-
Length, depth, through wall dimension, position with respect to datum,
Scan 2 – Fixed root scan 700 maximum echo amplitude and defect characterisation.

Scan 3 – 450,600,700 scan of fusion face and weld body Sketches to be produced for each indication evaluated giving:- through wall, length,
depth and distance from centreline. An overall plan view shall be produced giving all
Scan 4 – 450 scan for transverse defects indication positions in respect to datum.

Maximum scanning speed 50mm/sec. With overlap of 10% probe diameter.

Scan 1 – 0 - 50mm Scan 2,3,4 0 – 100mm

DAC from 3mm side drilled holes.

Transfer correction to BS EN 583-2

Copyright © TWI Ltd Copyright © TWI Ltd

22

Ultrasonic Flaw Detection 00 on all plate to be scanned with angle probes
Written Instruction Fixed root scan with suitable angle to hit root
450, 600, 700 Fusion face and weld body scan
Non-compliance: Any non-conformance in relation to this Transverse scan
instruction shall be brought to the Supervisor’s attention
immediately. Copyright © TWI Ltd

Minimum Operator Level: PCN level 1, Ultrasonic testing, with all indications
checked by Supervisor or nominated Level 2 operator.

Post Examination: All traces of couplant to be removed.

Preservation: Plate to be free from all couplant, chinagraph or
pencil marks, water and other contaminants are to be
removed from the surface and a light covering of oil
applied prior to storage.

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Equipment Checks: Bs En 12668-3 Maintenance Checks

 BS EN 12668-3 : 2000 Characterisation and In line with BS EN 12668 Part 3
Verification of Ultrasonic Examination Combined equipment.
Equipment Part 3: Combined Equipment.
 Linearity of flaw detector timebase.  Weekly.
 Prior to using an ultrasonic flaw detector and  Linearity of equipment gain.  Weekly.
search unit combination it is important to  Index point of each angle probe.  At least Daily.
ensure that this is performing adequately.  Angle of probes.  At least Daily.
 Physical state.  Daily.
 BS EN 12668-3 describes the tests that should  Pulse duration.  Weekly.
be used to ensure that ultrasonic flaw  Sensitivity/signal to noise ratio.  Weekly.
detectors and probes are in good working
order. Calibration of timebase - every time the probe is changed

Copyright © TWI Ltd Copyright © TWI Ltd

Maintenance Checks Maintenance Checks

Linearity of flaw detector timebase Linearity of flaw detector timebase
Place a compression probe on the side of a V1 or V2 Bring each successive backwall echo up to 80%
(A2, A4) block and adjust range and delay until you screen height and check that the leading edge lines
have 10 backwall echoes on the screen, making sure up with the appropriate graticule mark. Deviation
that the first and last echoes coincide with the correct should not be over 2% of full screen width.
scale marks.

Copyright © TWI Ltd Copyright © TWI Ltd

23

Maintenance Checks Maintenance Checks

Linearity of equipment gain Linearity of equipment gain
Obtain a signal from the 1.5 mm hole in V1 or V2 and Increase the signal height using the gain control by
set to exactly 80% FSH. 2dB and check the height increases to 100% FSH.

Copyright © TWI Ltd Copyright © TWI Ltd

Maintenance Checks Maintenance Checks

Linearity of equipment gain Linearity of equipment gain
Reduce by 2 dB and check it goes back to 80% FSH. Reduce by a further 6 dB and check it goes down to
40% FSH.

Copyright © TWI Ltd Copyright © TWI Ltd

Maintenance Checks Maintenance Checks

Linearity of equipment gain Linearity of equipment gain
Reduce by a further 6 dB and check it goes down to Reduce as before by another 6 dB and check it goes
20% FSH. down to 10% FSH.

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Maintenance Checks Maintenance Checks

Linearity of equipment gain Linearity of equipment gain
Finally reduce by another 6 dB and the signal should
fall to 5% FSH. Decibels Screen height Deviation

Copyright © TWI Ltd 0dB 80% 0
+2dB 100% At least 95%
-2dB
-6dB 80% 0
-12dB 40% 37 to 43%
-18dB 20% 17 to 23%
-24dB 10%
8 to 12%
5% visible, below 8%

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Maintenance Checks Maintenance Checks

Probe index Beam Angle
This check is for angle probes only.
Position probe on either a V1 or V2 block facing the Quick method
quadrant.  Place probe on calibration block.
Move probe backwards and forwards to maximise signal.  When signal is maximised, the beam angle can be read from
When signal is at maximum the index point will correspond
with the engraved line on the block. the engraved scale.
Tolerance should be within 1mm.  Accuracy should be approximately within 1.5° Tolerance

within 2°.
This method is not accurate enough when weld testing – use
1.5mm holes in IOW block.

30 35 40 45 50 55 60

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Maintenance Checks Maintenance Checks

Beam angle Pulse duration
 Obtain a signal from the 1.5 mm hole in a V1 or V2 block.
More accurate method, (also able to check index point at  Maximise the signal to 100% FSH.
 Measure the width of the signal at 10% screen height.
same time).  The typical pulse width for a 5 MHz compression probe is
 Place probe on reference block (A5).
 Using at least 3, preferably 4 side drilled holes, maximise 2 mm whilst for a 4 MHz shear wave probe the typical
value is about 1.3 mm.
and measure depth and stand-off to front of the probe
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to plot hole location.

 On a scale drawing draw a straight line through the

points. a1 a2 a3

t1 X = probe index
t2 θ = beam angle
t3 t3

t2

t1
θ

x a1 a2 a3

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25

Maintenance Checks Maintenance Checks

Physical state and external aspects Sensitivity and signal to noise ratio
Visually inspect the outside of the ultrasonic unit,  Obtain a signal from the 1.5 mm hole in a V1
probes, cables and calibration blocks for
physical damage or wear which could influence or V2 block.
the reliability of the test .  Maximise the signal to 20% FSH.

Note the dB setting.

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Maintenance Checks Maintenance Checks

Sensitivity and signal to noise ratio Squint (Not required by BS EN 12668)
 Remove probe from block and remove couplant  Place the probe on the V1 block on the

from face. 100mm radius and maximise the signal.
 Place probe on its side.  Check if the probe edge is parallel to the edge
 Increase signal height on the gain until the grass
of the block.
at the same range is up to 20% FSH.  If the probe is not square then it will have

The difference in dB is the signal to noise ratio squint.
 Note that the probe will give a return signal
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from not only the centre of the radius but
also from the edges.

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Maintenance Checks Maintenance Checks

Squint (To BS 4331) Squint: Measurement of squint angle - Method 1
 Place probe on side of V1 and obtain signal
Probe placed on 100mm radius
from the edge of the block at half or full skip.
Probe getting return signal from corner of radius  Maximise the signal by swivelling the probe.
 Lay a ruler along the side of the probe - the
Probe with squint
ruler should meet the edge of the block at 90°
Copyright © TWI Ltd when measured with a protractor.

900

Angle of squint

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26

Maintenance Checks Maintenance Checks

Squint: Measurement of squint angle - Method 2 Resolving power (Resolution)
 Place probe on side of V1 and obtain signal Using the A7 block, place the probe on the flat face
of the block, at the centre of the radius.
from the 1.5mm hole at half or full skip.
 Maximise the signal by swivelling the probe. 6dB 6dB
 Lay a ruler along the side of the probe - the
Full resolution Part resolution
ruler should stay a constant distance from the
edge of the probe in relation to the hole . R60 R74

Angle of squint 5mm R62 R69
4mm R65
Copyright © TWI Ltd 3mm
2mm

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Maintenance Checks

Resolving power (resolution)
 Good resolution is usually defined as distinguishing two

echoes which are less than 2 to 2.5 wavelengths apart.
 Determine which are the appropriate steps on the A7

block, place the probe at the centre of the radii, on the
flat surface with the beam giving echoes of equal height
from either side of the step.
 The screen trace must show the two signals distinctly
split to more than half their height ie >6dB.

6dB 6dB

Full Part resolution
resolution

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27