Guided Wave UT

Guided Wave

Ultrasonic

Testing

New Tool Developments

• Rapid screening for In-service degradation

• Reduction in costs of gaining access

• Avoid removal of insulation or coating

• Ability to inspect inaccessible areas

– i.e clamps and cased or buried pipes

• 100% coverage

Guided Waves

Conventional UT versus LRUT

Weld

Metal loss

Metal loss

FlangeConventional

Transducer

Localised Inspection

Weld

Metal loss

Metal loss

FlangeGuided wave

transducersGuided Wave

100% Inspection

Features

Detection of internal or external metal loss

Sensitivity

• Metal loss down to 3% of pipe wall cross-section

• Reliable detection of 9% metal loss flaws

• Now able to discriminate clock position

Discrimination between flaws, pipe features, welds, casing supports, etc.

Longitudinal accuracy better than 1”

New Beam Focusing (Helps with Flaw Discrimination)

New C-SCAN Imaging (Visual Presentation of Circumferential Extent)

New Software System for Improved Analysis• Multiple Distance Decline Curves

• Select locations for multiple focusing

Long

range

Short

range

Surface condition Geometry Contents

Bare metal Straight lengths Gas

Smooth well bonded paint

Fusion bonded epoxy Attachments Liquid

Light pitting

Heavy pitting

Plastic, e.g. PVC Branches

Buried (earth or sand)

Bitumen coated Multiple

bends

High viscosity

Concrete coated Flanges

Performance Summary

Some Limitations of LRUT

Geometric features such as Elbows, Flanges, Tees, Welded

Supports, socked welds, etc will attenuate or totally absorb the

LRUT signal.

Additional LRUT locations are need before and after every

elbow to guaranty 100% coverage.

Focus only works in straight sections . It does not work after

elbows.

LRUT signal do not travel after flanges.

Some Limitations of LRUT

Big Tees or branches absorbs tremendous energy. Therefore

additional test locations are required before and after these

features.

It is not the right tool to detect isolated pin holes.

Signal to noise ratio decreases when testing buried pipes in

presence of heavy coatings or fluids. This reduces the

probability of detection of small indications.

LRUT does not provide a reading of the remaining wall / wall

thickness at the location of the indication.

General Description Sensitivity

9% Anomaly(not to scale)

Pipe cross section(100%)

3% Anomaly(not to scale)

Each quadrant = 25%Each Clock position ~ 8%

An approximation of the

cross section area Loss can

be given by:

The total CSL is then equal

to the sum of all the defect

present on the same cross

section (12% in this case)

pipepipe

defectdefect

ThicknessRadius

DepthLengthCSL

2

• Road and river crossings

• Power plant tubing

• Risers

• Offshore topsides pipework

• Jetty lines

• Jetty Supports

• Refinery pipework

• Chemical plant pipework

• Tank farm link lines

• Sphere legs

• Pipe bridges

• Spiral welded pipe

• Austenitic stainless steel

• Sprinkler systems

• Lamp-posts

Applications

Examples of Application

Road Crossings Buried Pipe

Sphere Support Leg Gas Pipelines

Teletest Focus Unit

Integrated Battery – 12 Hrs

Integrated Air Pump

Auto System Check

Rugged System

Easy to Transport

Features

Diameters – 1.5" to 48"

100% Coverage

Multi-Mode Modules

• Torsional & Longitudinal

• True Beam Focusing

Test Range

• Typical ±90 Ft.

• Ideal conditions ±350 Ft.

Productivity

• Typical 1,000 Ft. per day

Service Temperature up to +260°F

Advantages

Easy to use unit and tool design for

quick data collection

Multimode – Longitudinal and torsional

wavemodes on one tool

Focusing – Defect distribution around

circumference “one-click” away

User friendly interface with report

manager generator

Minitest

Advantages:

1.5-4” Diameter Pipes

1.5” Thick Collar

3-ring Torsional

Light Weight Design

Modularize (1/2” Changes)

Limitation:

No Beam Focusing or Multi-

Mode Functionality

Collar design

Robust composite construction

Integrated clamp and bladder

Collars link for >24”

Multimode

Lightweight

Cost efficient

Easily Transported

New Software

Automated set-up

Fast and reliable defect detection

Simultaneous Multimode Shots

Simplified Analysis

Multiple DAC Curves

On-site MS Word report generator

<15 min data collection

Defect only detected using Longitudinal

waves

Torsional: No defects detected using T mode

• Longitudinal: both the pipe end and the defect

could be identified

FOCUS

-0.5

0

0.5

1

0

15

30

45

60

75

90

105

120

135

150

165

180

195

210

225

240

255

270

285

300

315

330

345

Applying the appropriate

correction factors allows a

concentration of energy

(focus) at a specific angle

for a given distance from

the transducer.

Benefits of focusing

Focusing allows the energy to be

concentrated where the defect is,

increasing sensitivity and giving

position and size information

Focal Spot – Actual measured shape

0

0.25

0.5

0.75

1

0

15

30

45

60

75

90

105

120

135

150

165

180

195

210

225

240

255

270

285

300

315

330

345

Specified target shape function Numerically predicted shape Actual Measured Shape

Small

sidelobes

predicted

Similar

sidelobes

Main lobes all at

correct angle and

shape

Focus – Benefits

Improved Sensitivity to smaller defects

Better call/no call information

Improved prioritisation of calls

Ability to find angular position of defects

Improved presentation possibilities for results

Directionality data from focusing

DefectWindowed time

domain of interest

Windowed time

domain of

interest

180o

0

6

0.5

2.0

1.0

2.5

1.5

3.5

4.0

3.0

0

0.26

0.33

0.25

0.75

0.75

0.7

0.63

3.13

0o

45o

90o

135o

225o

270o

315o

Focused at z= 32.8 ft.

Non Directional response from a weld

180o

0

6

0.5

2.0

1.0

2.5

1.5

3.5

4.0

3.0

0

2.80

3.75

2.8

2.50

2.25

3.4

2.50

2.70

0o

45o

90o

135o

225o

270o

315o

Unfocused - 3% notch in 16” pipeUnfocused result

0

50

100

150

200

250

0.0

1

0.2

3

0.4

6

0.6

8

0.9

1

1.1

3

1.3

6

1.5

8

1.8

1

2.0

3

2.2

6

2.4

8

2.7

1

2.9

3

3.1

6

3.3

8

3.6

1

3.8

3

4.0

6

4.2

8

4.5

1

4.7

3

4.9

6

5.1

8

5.4

1

5.6

3

5.8

5

6.0

8

6.3

6.5

3

6.7

5

6.9

8

7.2

7.4

3

7.6

5

7.8

8

8.1

8.3

3

8.5

5

m

sig

nal

am

pli

tud

e

Notch position

Pipe endInitial pulse

Focused at NotchFocused result

0

50

100

150

200

250

0.0

1

0.2

3

0.4

6

0.6

8

0.9

1

1.1

3

1.3

6

1.5

8

1.8

1

2.0

3

2.2

6

2.4

8

2.7

1

2.9

3

3.1

6

3.3

8

3.6

1

3.8

3

4.0

6

4.2

8

4.5

1

4.7

3

4.9

6

5.1

8

5.4

1

5.6

3

5.8

5

6.0

8

6.3

6.5

3

6.7

5

6.9

8

7.2

7.4

3

7.6

5

7.8

8

8.1

8.3

3

8.5

5

m

sig

nal

am

pli

tud

e

Initial pulse

Notch signal

Pipe end

Focused in Line and at 90° to Notch

0

50

100

150

200

250

0.0

1

0.2

3

0.4

6

0.6

8

0.9

1

1.1

3

1.3

6

1.5

8

1.8

1

2.0

3

2.2

6

2.4

8

2.7

1

2.9

3

3.1

6

3.3

8

3.6

1

3.8

3

4.0

6

4.2

8

4.5

1

4.7

3

4.9

6

5.1

8

5.4

1

5.6

3

5.8

5

6.0

8

6.3

6.5

3

6.7

5

6.9

8

7.2

7.4

3

7.6

5

7.8

8

8.1

8.3

3

8.5

5

m

sig

nal

am

pli

tud

e

in line with notch 90 deg to notch

Pipe end

Notch

Initial pulse

Practical Implementation

Energy Focused in-line with Defect

Energy Focused 180° from Defect

Focal Response with constant area

Defect

Shape with

constant

area loss

Axi

Symmetric

response

showing

amplitude

Focus

response

showing

angular

distribution

0

45

90

135

180

225

270

315

0

45

90

135

180

225

270

315

0

45

90

135

180

225

270

315

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25 30

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25 30

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25 30

Deep

5% Area

Medium Depth

5% Area

Shallow

5% Area

Focal Response – Constant Angle

Defect

Shape with

constant

area loss

Axi

Symmetric

response

showing

amplitude

Focus

response

showing

angular

distribution

0

45

90

135

180

225

270

315

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25 30

0

45

90

135

180

225

270

315

0

45

90

135

180

225

270

315

Deep

10% Area

Shallow

2% Area

Medium Depth

5% Area

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25 30

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25 30

Improved Focusing

Sound energy concentrated in one region

Rotation 8 times around pipe

4 times greater sensitivity than cross sectional volume

Multi defect focus capability

Defect / Feature discrimination

Circumferential information is obtained.

Data can be displayed in a more easily interpreted manner.

The operator needs to distinguish between:

• Areas of concern that need immediate attention

• Areas to earmark for inspection in the future

• Areas of no significant problems

This method provides semi-quantitative results

It is an efficient classifier of defects

Enhanced high resolution plots

Classification Scheme

Combine axisymmetric amplitude with distribution of the angular response from focusing, to get a follow-up priority

Defect Category C, where• Amplitude is less than -18dB from weld signal, C = 1

• Amplitude is between -18dB and -12dB from weld , C = 2

• Amplitude is greater than -12dB from weld, C = 3

Directionality Distribution D, where• Angular distribution is less than 45°, D = 3

• Angular distribution is between 45° and 90°, D = 2

• Angular distribution is between 90° and 315°, D = 1

• Angular distribution is 360°, D = 0

A-scan Threshold Levels

Noise

-14dB

Girth welds

100% Reflector

Flange

-20dB

-26dB

-32dB

A-Scan Threshold Levels

Category 1

Category 2

Category 3

Directionality Category 3 Defect

Directionality Category 2

Directionality Category 1

Directionality Category 0

Evaluation Matrix

Product of C and D gives Follow up priority

Low priority Moderate priority High priority

If C x D = 0, the response is a weld

Follow up

priority

Defect Category, C

1 2 3

Directionalit

y

Distribution

, D

0 0 0 0

1 1 2 3

2 2 4 6

3 3 6 9

Usefulness of Focusing

Information about the circumferential extents

GWT- Cased vs. Buried

CUI (Corrosion Under Insulation)

GWT indications confirmed with AUT

Underground Test

Results of Underground Test Loop

Bridge Crossing

Results of Bridge Crossing Test

Certification

TWI Certification Ltd issued the Examination and Syllabus for the

Certification of Personnel Engaged in Guided Wave Ultrasonic Inspection for

the Detection of Corrosion in Pipe – outlined in the LRU Written Practice ISS

2.2 rev 0 Dated May 2007.

• The certifying scheme is the CSWIP-ES-12-04 1st Edition Feb 2004 (Requirements for

Employer Specific Certification of Personnel Engaged in NDT).

• The certification as a minimum complies with ISO 9712 and EN 473.

• Techcorr has eight (8) Level 2 and six (6) Level I Technicians certified under this scheme.

• Most of our Technicians are metallurgical or mechanical engineers whom have gone

through a three (3) year training process internally via our operations in Latin America.