Ut P4

NDT Training & Certification

Ultrasonic Testing Part 4

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Ultrasonic Testing  Sensitivity  Defect

sizing  Scanning procedures

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Sensitivity  The

ability of an ultrasonic system to find the smallest specified defect at the maximum testing range

Depends upon  Probe and flaw detector combination  Material properties  Probe frequency  Signal to noise ratio mmz 2003

Methods of Setting Sensitivity  Smallest

defect at maximum test

range  Back wall echo  Disc equivalent  Grass levels  Notches  Side Drilled Holes, DAC Curves mmz 2003

Artificial / actual defect

Example: The defect echo is set to FSH (Full Screen Height)

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Sizing Methods 6 dB Drop  For sizing large planar reflectors only  Signal / echo reduced to half the height  Example: 100% to 50% 80% to 40% 70% to 35% 20% to 10%

Centre of probe marked representing the edge of defect.

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6 dB Drop Defect

BWE

The back wall echo reduced as some part of the beam now striking the defect

Plan View

The echo of the defect has NOT yet maximise as the whole beam Not yet striking the defect mmz 2003

6 dB Drop Defect

Now the whole beam is on the defect Back wall echo is now may be reduced or disappeared

Plan View mmz 2003

6 dB Drop Defect

BWE

The probe is moved back until the echo is reduced by half of it’s original height At this point the probe centre beam is directly on the edge of the defect Plan View

The probe is then removed and the centre is marked, and repeat to size the whole mmz 2003 defect

Sizing Method  Maximum

Amplitude Technique For sizing multifaceted defect – eg. crack Not very accurate Small probe movement

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Maximum Amplitude

Multifaceted defect : crack

The whole probe beam is on the on the defect At this point, multipoint of the defect reflect the sound to the probe The echo (signal) show as a few peaks mmz 2003

Maximum Amplitude

Multifaceted defect : crack The probe is moved out of the defect, the signal disappeared If the edge of the beam strike the edge of the defect, a very small echo appears

If the probe is moved into the defect, the signals height increase One of the peak maximised At this point the MAIN BEAM is directly at the edge of the defect

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Maximum Amplitude

Remember: The peak which maximised does not have to be the tallest or the first one

Length

The probe is to be moved to the other end of the defect The signals will flactuate as the beam hits the different faces of the defects

Mark the point under the centre of the probe which indicates the edge of the defect

The probe is moved back into the defect and to observe a peak of the signal maximises mmz 2003

The length of the defect is measured

Equalization Technique The equalization technique can ONLY be used Defect BWE if the defect is halfway the thickness

At this point the whole beam is on the back wall At this point the whole beam is on the defect At the edge of the defect, half of the beam is on the defect, and another half is on the back wall

The BWE is at it maximum The Defect echo is at it maximum The defect echo is at equal height as the back wall The point is marked as the edge of defect mmz 2003

20 dB Drop Defect

20 dB Beam profile

BWE

10%

When the main beam is on the defect the defect signal is at it maximum If the probe is moved and the signal is observed until it is reduced to 10% (20dB Drop), the edge of the beam is on the edge of the defect Repeat the above at the other side of the defect Using the pre-constructed Beam profile and a plotting card, the defect maybe sized mmz 2003

Scanning procedure  Parent

material  Root inspection  Side wall inspection  Weld body  Transverse scan

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Scanning Procedure  Parent

Material

0 degree both sides

 To

maximum range for angle probes  Full skip distance for 60 or 70 mmz 2003

Scanning Procedure  Weld

Root

Half skip from both sides

For PCN exams :  70 degree probe at half skip from both mmz 2003 sides

Scanning Procedure Weld Fusion Faces  Half to full skip from both sides

A probe which strikes fusion faces at 90 degrees Probe angle = 90 - (1/2 Root angle) mmz 2003

Scanning Procedure  Weld

Body

Half skip to full skip from both sides Full Skip

1/2 Skip

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Scanning Procedure  Transverse

70 degree

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Nozzle Welds  Scanning

procedure

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Tee butt welds

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Defect Identification  Echodynamics  Defect

characterisation

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Echodynamics Crack Lack of fusion,Gas pore

Porosity Slag inclusion mmz 2003

Defect characterisation  Signal



Lateral



Orbital

amplitude

 Probe



manipulation Depth



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Swivel

dB  20 Log..10

H0 H1

Sine I Vel in Material 1  Sine R Vel in Material 2

2

 Z1  Z 2     100  % reflected  Z1  Z 2 

V  f

 K KV Sine  or 2 D Df 2

D Near Zone  4 mmz 2003

2

D f  4V

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Weld inspection sd = s sinß

F

s

sd' = a - x d' = s cosß

0

2

40

T

4

30

6

20

8

10

10

d = 2T - t'

sd sd'

ß

= probe angle

s

= sound path

sd

= surface distance

sd‘ = reduced surface distance d

= actual depth

T

= material thickness

s d

ß

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WELDING DEFECTS Root

Toe

Lack of Penetration Lack of Fusion Root Crack

Toe Crack

Weld Fusion zone

Weld Volume

Lack of side wall fusion Side wall crack

Slag Porosity Lack of inter-run fusion Centre line crack

1

T

2

T

R

3

T

R

R

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0

2

4

6

8

10

0

2

4

6

8

10

0

2

4

6

8

10