Guided Wave Testing and Monitoring Over Long and … and Long Range GWT.pdf · Guided Wave Testing...

David Alleyne, Tomasz Pialucha and Brian Pavlakovic

6 September 2017

Guided Wave Testing and Monitoring

Over Long and Short Ranges

BINDT Telford

2Guided Ultrasonics Ltd. - 06/09/2017

Outline

Background

Guided Wave Testing (GWT) Concepts

Wave Propagation

Tools for predicting and measuring guided waves

Interaction of GW in plates and pipes

Practical implementation

Pipe testing and Monitoring

Quantitative Short Range Scanning development

Conclusions

GWT Background

GWT research at Imperial College, London from

1980’s. Application to plates and pipes

Commercial application from late1990’s and

ongoing specialised development and

advancement in guided wave testing for

industrial inspection since.

On-going Research at Imperial College, other

Universities and research groups globally.

Mostly for long range screening.


Imperial College NDT Group, 1991?

Can Guided waves be useful for NDT?

Example Plants where guided waves…

Need to find corrosion…..

Pulse-echo test

Ultrasonic Testing (UT) Concept

GWT Screening Concept (LRUT)

• If the guided wave encounters a defect then part of the signal is reflected

• A single measurement inspects all the material in a long length of the structure

Transducer

Structure

Volts

Time, distance

Defect

End of structure

What happens if we just try......

Problems:

- Multiple modes

- Dispersion

- Sensitivity to defects varies with modes

"Dispersion curves" for a 1mm thick steel plate

Guided wave dispersion curves

L Rayleigh (1885); H Lamb (1917)

10

10Frequency (MHz)

a0

s0

a1

s1

s2

a2Phase

speed

(km/sec)

Development of the waveguide model

DISPERSE

Developments packaged in the modelling tool "DISPERSE"

SurfacesPlates

10

10Frequency (MHz)

a0

s0

a1

s1

s2

a2Phase

speed

(km/sec)

S0 at 100kHz (10mm Steel plate)


S0 100 kHz 6 cycles Gaussian

0 mm

100 mm

500 mm

1 meter

1.5 meters

-1.2

-0.8

-0.4

0.0

0.4

0.8

1.2

-25 25 75 125 175 225 275 325 375 425

-1.2

-0.8

-0.4

0.0

0.4

0.8

1.2

-25 25 75 125 175 225 275 325 375 425

-1.2

-0.8

-0.4

0.0

0.4

0.8

1.2

-25 25 75 125 175 225 275 325 375 425

-1.2

-0.8

-0.4

0.0

0.4

0.8

1.2

-25 25 75 125 175 225 275 325 375 425

-1.2

-0.8

-0.4

0.0

0.4

0.8

1.2

-25 25 75 125 175 225 275 325 375 425

S0 at 175kHz (10mm Steel plate)


S0 175 kHz 6 cycles Gaussian

0 mm

100 mm

500 mm

1 meter

1.5 meters

-1.2

-0.8

-0.4

0.0

0.4

0.8

1.2

-25 25 75 125 175 225 275 325 375 425

-1.2

-0.8

-0.4

0.0

0.4

0.8

1.2

-25 25 75 125 175 225 275 325 375 425

-1.2

-0.8

-0.4

0.0

0.4

0.8

1.2

-25 25 75 125 175 225 275 325 375 425

-1.2

-0.8

-0.4

0.0

0.4

0.8

1.2

-25 25 75 125 175 225 275 325 375 425

-1.2

-0.8

-0.4

0.0

0.4

0.8

1.2

-25 25 75 125 175 225 275 325 375 425

......and also:

BarsPipes

Composites

Embedded or

immersed

Multiple layers

Solids, fluids, anisotropic....

Solids

or

fluids

Development of Finite Element Modelling

Tools

Rajagopal, Lowe. J Acoust Soc Am, 122, 2007.

Rajagopal, Lowe. J Acoust Soc Am, 124, 2008.Drozdz, Moreau, Castaings, Lowe, Cawley. Rev Prog QNDE, 25, 2006.

Drozdz, Skelton, Craster, Lowe. Rev Prog QNDE, 26, 2007.

Scattering of guided waves from a crack

Need to understand the

waves

Transducer

Pipe

Need to understand how they

reflect from defects

Need to do a lot of R&D, including:

...then develop transducers, instrumentation, controlling software, signal

processing, interpretation, operator training, formal procedures..... NDT inspector

training and qualification

Expertise, knowhow requirements...

Strategy for development of

Guided Wave Testing

• Select a guided wave mode that is sensitive to

defects of interest

• Select frequency and signal shape to control

dispersion

• Excite and receive specific mode(s)

• Control directionality

Dispersion Curves

T(0,1)

F(1,2)

F(2,3)

F(1,3)

L(0,2)

Guided waves for Sch 40 6” pipe

Alleyne, Lowe, Cawley. ASME J Appl Mech, 65, 1998.

Lowe, Alleyne, Cawley. ASME J Appl Mech, 65, 1998.

Reflection coefficient

of

torsional waves

Similar study done for extensional modes

0

10

20

30

40

50

0 10 20 30 40 50

Defect extent (% of circumference)

T(0,1)

F(1,2)

F(2,2)

Frequency 50 kHz

Reflection coefficient versus

circumferential length of defect

Alleyne, Pavlakovic, Lowe, Cawley. Insight, 43, 2001.

Reflection coefficient

of

torsional waves

Similar study done for extensional modes

0

20

40

60

80

100

0 20 40 60 80 100

Defect depth (% of thickness)

40

160

130

100

70

220Frequency (kHz)

190

6 inch pipe

Reflection coefficient versus

depth of defect

Early Research Transducers (early1990’s)

Wavemaker G4

Wavemaker G4mini

HD: High Definition

HT: High TemperatureLightweight Inflatable Ring

HT Solid RingInflatable Ring

Solid Ring

HT Inflatable Ring

HD Solid Ring HD Inflatable Ring

Low Profile Ring

Claw Transducers

Permanently Installed (gPIMS) Subsea Ring Rail Systems (G-Scan)

Extensive Product Range (2015)

Transducer RingsGuided Wave

Transduction Systems

Long range pipe screening

Why use Guided Waves

NPS 20” main gas gathering line

Rapid long range screeningFig 1: 200m coverage in < 5 minutes)

Screen inaccessible areasFig 2: Screening under sliding and clamped supports

Why use Guided Waves

NPS 6”Gas Line, North Africa

100% volumetric pipe coverageFig 1: C-scan provides precise circumferential

orientation of defects or features

Accurately locate defectsFig 2: Precise location of the defect allows easy follow

with more detailed NDT techniques (e.g. B-scan)

Internal Corrosion

detected 3.25m behind

test location at 6

o’clock orientation

OmniScan MX2 used to

carry out B-scan to confirm

dimensions.

6

3.25m

Testing offshore

Testing sub-sea

31

Guided Wave Testing Standards

• BSI – BS 9690-1:2011; BS 9690-2:2011

• ASTM – E2929-11

• ASME – Article 18

• NACE TG 410 – 2014

• IIW – Commission V – EN ISO (TC135/SC3)

• TUV certification: GUL GWT procedure certified

under EN standard 14748

Guided Ultrasonics Ltd. - 06/09/2017

32

Calibration critical for procedures

• Challenge is to develop GWT procedures and work

instructions using knowledge of the damage type that

is the major threat

– Equipment and certification requirements

– SNR and access restrictions

– Limitations

– Accuracy range and confidence

• Calibration is critical


33

Guided Waves Calibration

• Equipment calibration

– Manufacturer‘s calibration (electronic components)

– Automatic self-test functions

• User calibration

– Set-up of test parameters, e.g. ring size, transducer, test frequencies (mostly automated)

• Reference standard

test object = calibration test piece

– Distance calibration

– Comparison of the amplitude of indications with a reference


Summary

• Calibration methods until now sufficient for screening, but demanding applications require a more precise approach

• Direct measurement of outgoing amplitude possible with absolute calibration method (or of reflection coefficients with attenuation known)

• Removes most problems of current calibration methods

• Works also with other features (not just welds), even if defective

• Ultimately this leads to improved false-call rate and therefore reliability

34

Guided Waves Calibration

© by Guided Ultrasonics Ltd 2013 – DO NOT RE-DISTRIBUTE

35Guided Ultrasonics Ltd. - Screening and Monitoring Oct 2011

CUI and road crossing pipes

• Road crossings and

insulated pipe

inspected for CUI

• Inspections while

pipes operational

36Guided Ultrasonics Ltd. - Screening and Monitoring Oct 2011

CUI

• Insulated steam

pipe-work at

340°C

• Pipes tested while

operational

37

Corrosion Under Supports (CUPS)

Touch point corrosion detected using GWT. The CSC range can be

less than a few per cent, therefore control of the GWT critical for

success. More later


38

GWT strategy – Touch Point corrosion

➢Torsional mode axial propagation

– Select correct equipment options and set-up

– Screen many from on accessible position (cost efficiency)

– P/E test configuration with SNR limits (corrosion type)

– Accurate calibration for DAC setting

– Limitations, range and confidence

– Prove up (no matter how limited) where possible

– Compare results for improved accuracy and confidence

– Prove-up with QSR1

➢Circumferential or axial propagation QSR1…


39

Example – corrosion patch


-16dB

-20 0 20 40 6012

9

6

3

12

Clo

ck

-20 0 20 40 600.0

0.2

0.4

0.6

0.8

1.0

1.2

Distance (ft)

Am

p (

Lin

ear)

F

weld

ed p

late

Weld

Weld

Cat 1

Corr

osi

on

Support

Weld

Cat 3

Support-F1

40

Example – pitting corrosion

Guided Ultrasonics Ltd. - 06/09/2017-1

8dB

-100 -50 0 5012

9

6

3

12

Clo

ck

-100 -50 0 500.0

0.5

1.0

1.5

Distance (ft)

Am

p (

Lin

ear) W

eld

ed s

upport-F2

Conta

ct s

upport

Conta

ct s

upport

Weld

ed s

upport

weld

weld

ed s

upport

Corr

osi

on p

it

Weld

Hig

h c

onta

ct lo

adin

g

Elb

ow

41

Example – wear to pipe


-18dB

-10.0 0.0 10.0 20.012

9

6

3

12

Clo

ck

-10.0 0.0 10.0 20.00.0

0.5

1.0

1.5

Distance (ft)

Am

p (

Lin

ear)

-F1

+F1

+F2

Corrosion monitoring using guided

waves

▪ GWT needs access to the pipe – often this accounts for a large fraction ofthe inspection cost

▪ Safety implications of accessing the site, for example excavations,working at height, hazardous areas

➢ Recurrent testing for monitoring pipe condition can therefore be costly andcarry risks

Permanently installed sensors

gPIMS®

▪ Simplifies recurrent inspections

▪ Access to test point only required once, then reduces or eliminates

access costs

▪ Increased coverage and sensitivity

▪ Simplifies comparison of data by subtraction from baseline result

▪ Enables tracking and trending

Permanently installed sensors

gPIMS®

▪ Easy-to-install array sensor bonded to the pipe

▪ Connection box with cable leading to sensor

▪ Data collection via any 4th generation Wavemaker instrument

Corrosion Monitoring with gPIMS®

▪ Looking for differences between repeat tests

▪ Thousands of results each year

Data interpretation – what is the

difference?

Before After

Subtraction of two data sets

-

=

Residual

Before After

Advanced subtraction required

Compensation algorithm

▪ Baseline at a certain temperature

▪ Decide on some reference features such as welds

▪ Stretch current result trace so amplitude and position

of reference features aligned

▪ Then subtract

Managing changes in result traces

▪ Features now suppressed, leaving a small residual

-40dB (or 1% CSC)

-40 -20 0 20

65

2.5

1

0.5

0.25

0.1

0.05

0.025

Delt

a (

50dB

)

Refe

rence

: 2011-1

0-0

5 (

-627 d

ays

)

-40 -20 0 20

65

2.5

1

0.5

0.25

0.1

0.05

0.025

Distance (m)

gC

-244#1106 (

50dB

)

Test

ed: 2013-0

6-2

3

169+56,0

44'0

0" A1

W2

169+56,0

44'0

0" A1

Efficiency of baseline subtraction

▪ In order to achieve a residual of about -40dB or 1%, the

current result should not be more than 5 - 10°C different

from the baseline

➢ This generally necessitates more than one baseline

▪ Therefore the recommendation is to collect as many baseline

results within the first year of operation as possible

▪ Specially developed monitoring software can automatically

choose the optimum baseline to use for best subtraction

efficiency.

Corrosion monitoring example

▪ Simple subtraction – difficult to detect change

-100 0 100

1.4

1

0.5

0.25

0.1

0.05

0.025

Delt

a (

40dB

)

-100 0 100

1.4

1

0.5

0.25

0.1

0.05

0.025

Distance (ft)

G3-5

1#1583 (

40dB

)

1 1 1 1 111 1 1 1

209+60 209+00 208+40Ring +F1207+80 207+20

111 111 1 1 11

208+40E1W4W3209+00W2W1 E2 W5 207+80W6 207+20W7 W8209+60

▪ Basic subtraction

Corrosion monitoring example

▪ Advanced subtraction subtraction – much simpler change detection

-150 -100 -50 0 50 1000.00

0.10

0.20

0.30

0.40

0.50

Delt

a (

Lin

ear)

-150 -100 -50 0 50 1000.00

0.10

0.20

0.30

0.40

0.50

Distance (ft)

G3-5

1#1583 (

Scale

d L

inear)

1 1 1 1 1 11 1 1 1

209+60 209+00 208+40Ring +F1207+80 207+20

111 1 11 1 1 11

208+40E1W4W3209+00W2W1 E2 W5 207+80W6 207+20W7 W8209+60

53

Corrosion Under Pipe Supports

(CUPS)

Quantitative Measurement of

Corrosion Under Support

Different Concepts…

Aim of Short Range Testing

Tomography approach

Produce map or profile of depths of corrosion

Critical parameter is maximum depth

Tomography Attempt - 2015

Tomography approach

Produce map or profile of depths of corrosion

Critical parameter is maximum depth

Top Path

Bottom Path

ReceiverTransmitter

QSR1 measurement parameters

Circumferential Guided Waves used to Measure Wall Thickness.

Multiple families of modes

Dispersive modes

At each location scanned the QSR1 system automatically measures:

The pipe diameter

Distance between Transmitter and Receiver

Top Path wall thickness

Bottom Path wall thickness

Bottom Path Minimal Wall Thickness.

QSR1 - Short Range Scanning

Adapts to different pipe wall thickness.

Quantitative measure remaining minimum

wall1.

Quantitative measure of average wall

thickness.

Estimates where the wall loss location is.

Notes:1 : Down to about half of the nominal wall thickness (and report any areas with less

than half nominal wall

Quantitative Short Range - QSR1

Guided Ultrasonics are currently working on an innovative testing system QSR1 to quantitatively measure corrosion at supports.

QSR1 automatically measures the size of corrosion to the depths of up to half of the pipe wall thickness.

QSR1 also automatically measures pipe diameter and pipe wall thickness around the pipe circumference from a single location in a fraction of a second.


Ex-service 12 inch pipe with the hidden Corrosion Under Pipe Support (CUPS) type defect was scanned by QSR1 in order to obtain the profile of the area.


The scanned defect was then visually examined and the QSR1 scan was compared with the reference laser scan of the area.


0

1

2

3

4

5

6

7

8

9

10

-200 -150 -100 -50 0 50 100 150 200

Rem

ainin

g W

all

Thic

knes

s (m

m)

Axial Position Along the Pipe (mm)

QSR1 measurement

Laser measurement

QSR1 top path measurement

Very good agreement was achieved between the laser scan of the defected area

(red line) and the QSR1 measurements (blue line).

Over the last 20 years pipe screening for corrosion has

become a powerful method in different industries.

Screening long lengths from a single location and in a

single test generates big savings when inspecting or

monitoring.

Continuous innovation and developing new devices to

improve sensitivity and coverage has been critical to

success.

The new Quantitative short range screening technology

together with cloud computing and artificial intelligence

will facilitate new levels of industrial adoption.

Conclusions

Guided Wave Testing and Monitoring Over Long and … and Long Range GWT.pdf · Guided Wave Testing...

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Transcript of Guided Wave Testing and Monitoring Over Long and … and Long Range GWT.pdf · Guided Wave Testing...