Guided Waves in NDT – Basics, Applications and Recent … · 2009-06-05 · Guided Ultrasonics...

T. VogtD. Alleyne

Guided Waves in NDT – Basics,Applications and Recent Developments

Guided Ultrasonics Ltd.

2Guided Ultrasonics Ltd. -

Outline

• Guided waves basics• Recent advances in GWUT:

– Unrolled pipe display– Focusing– Frequency sweeping

• GUL Training and Certification Scheme• Example Applications• Summary


• Developer and manufacturer of the Wavemaker pipe screening system

• NOT a service provider• Resource for support, training, and consultancy• Company formed in 1999 uniting individuals

experienced in developing guided wave inspection techniques

About Guided Ultrasonics Ltd.


• Currently over 120 Wavemaker systems have been sold worldwide and over 1200 transducer rings

• Over 80 clients worldwide from over 30 countries including, USA, China, South Korea, Russia, UK, Australia, Mexico, France, Denmark, Norway, Saudi Arabia and South Africa.

World map with countries shaded

Current clients


Guided Ultrasonics Ltd.

• Application of guided waves in NDT started only 20-30 years ago

• Development at Imperial College London started in 1987 Alleyne & Cawley

• First generation system of actual technology licensed to TWI in 1997-1998

• GUL started in 1999 by the patent holders of the GW technology

• Second generation system 1999 (Wavemaker SE16)• Third generation system 2005 (Wavemaker G3)


Guided Waves in Pipes

• Guided waves exist in structures with boundaries• There are different modes of propagation, determined by the

geometry of the structure

Guided wavePipe

Transducer array


Guided Waves

Practical implementation – Wavemaker G3TM



Dispersion curves

0 20 40 60 80 1000.0

2.0

4.0

6.0

Frequency (kHz)

Torsional T(0,1)

Gro

up V

eloc

ity (m

/ms)



Symmetric (torsional) Non-symmetric (flexural)

Guided wave modes



Symmetric reflection carries information about the cross-section change

Incoming wave(symmetric)

Reflected wave(symmetric)

PipeTransmitted wave(symmetric)



Mode converted signal carries information about the circumferential orientation/size

Incoming wave(symmetric)

Reflected waves(symmetric and non-symmetric)

PipeTransmitted waves(symmetric and non-symmetric)



The percentage cross-section change is given by the reflection amplitude, but it could be…

… concentrated in a narrow portion of the pipe (e.g. a critical deep defect)

… equally distributed around the circumference (e.g. a shallow wall loss)


Guided Waves (A-Scan)

Typical A-scan type result showing a symmetric mode only (longitudinal or torsional)

0.0 5.0 10.00.0

0.5

1.0

1.5

2.0

Distance (m)

Amp

(Lin

ear)

+F5

+F4

+F3

+F2

+F1

-F1

-F2

Weld DAC

Call DAC


Guided Waves (A-Scan)

Typical A-scan type result showing torsional and flexural response (note defect in weld)

0.0 5.0 10.00.0

0.5

1.0

1.5

2.0

Distance (m)

Amp

(Lin

ear)

+F5

+F4

+F3

+F2

+F1

-F1

-F2


Unrolled pipe view

Guided Waves (C-Scan)

-24d

B

0.0 5.0 10.00

90

180

270

360

Angl

e (d

eg)

0 0

0.5

1.0

1.5

2.0

Amp

(Lin

ear)

+F5

+F4

+F3

+F2

+F1

-F1

-F2


Example focusing at -2m and 90deg

Guided Waves (Focusing)


Dynamic frequency sweeping

• Allows the inspector to sweep through the frequencyand bandwidth after collection

• The entire applicable frequency range is collected in one single test

• The inspector can then change the frequency and the bandwidth seamlessly (sub-kHz) of the displayed A-and C-Scan


Frequency sweeping

Advantages– Time saving when collecting data– Takes away responsibility from the inspector to choose best

frequencies on site– More information available which was not visible before

when collecting single frequencies– Extremely important in applications where the feature

response is frequency dependent– Helps distinguishing different features (e.g. defects from

supports)


Training and Certification

GUL Training and Qualification Scheme since 2002:Largely EN473 compliant (where applicable)

– Initial 5 day training course leading to temporary GUL Level 1 certification mandatory when purchasing equipment

– On-site support (typically minimum of 5 days) after the initial training course to gain full Level 1 certification

– Examination requirements, revalidation, etc. in line with EN473

– Advanced training courses for special applications (buried, road-crossings, tube testing etc.)



Active promotion of the GUL training scheme through uniquehardware and software features:– Inspector has to log-on to the instrument with his personal

operator key– Key keeps information about his certification and additional

qualifications, as well as usage information– Enables monitoring and validating operator experience



Wavemaker G3 features numerous elements to ensure data quality and remove responsibility from the inspector:

– Reduced number of options for the operator when collecting data (e.g. selection of frequencies)

– Automatic checks to ensure equipment is in good order– Easy on-board fault finding when problems occur– Monitoring of correct use of the equipment (e.g. coupling)– Software blocks analysis if quality of data poor or equipment

faulty (dependent on operator qualification).– Self calibration and sensitivity determination


Example Applications

Applications developed by and commercially available from Guided Ultrasonics Ltd:

– Sub-sea and top-side off-shore pipe-work– Tubes (heat exchanger, boiler, etc.)– Permanent monitoring system (PIMS)– Lamppost– Low-profile probes (e.g. for external boiler tube testing)– Rails

More developments in the pipeline!


Sub-sea inspection


Tube inspection (T-Scan)


Rail inspection (G-Scan)


Permanent Monitoring (PIMS)


Summary

Recent advances include– Unrolled pipe view– Focusing– Frequency sweeping

Training and certification scheme– Largely compliant with EN473 where applicable– Active promotion through hard- and software features

Specialised areas for guided wave testing include tube, rail, sub-sea testing, as well as permanent monitoring of pipe.

Guided Waves in NDT – Basics, Applications and Recent … · 2009-06-05 · Guided Ultrasonics...

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