Inspection of pipes using Guided Waves:state of the art

A. Demma

Outline

•GW basics•Opportunities•Limitations•Latest developments•Conclusions

Principle

Transducer

Metal structure

Inspected Area

Transducer Ring

Inspected area Inspected area

UT

GWT

Reflection from a Feature(such as corrosion)

When the guided wave hits a change in cross section (or impedance), it reflects back toward the transducer

Transducer

Structure

Cross Section Change

The dark greySection represents theCross-sectional area

System Components

Wavemaker G3

TransducersRing

Lemo Cables

Position of Ring

Decay CurvesCorrosion is indicated

by large red component

Iconic representationof identified features

ForwardBackward

Series of Welds

-24d

B

0.0 5.0 10.00

90

180

270

360A

ngle

(de

g)

0.0

0.5

1.0

1.5

2.0

Am

p (L

inea

r)

+F5+F

4

+F3

+F2

+F1

-F1

-F2

Guided Waves (unrolled pipe view)

Why Guided Waves?

•100% volumetric coverage•Rapid screening•In Service inspection•Significantly reduced access costs

100% Volumetric coverage

Example:10” pipe, 12m length with 2 simple supports

Standard UT = 0.027% area coverageGuided Wave ~ 100% area coverage

UT check after GW inspection

Rapid screening

• Acts as filter: point out areas where more attention is needed

In-service inspection

• Temperature • Product• Pump noise, product flow

Reduced access costs

Think of costs for:

• Scaffolding

• Removing insulation

• Digging

• Operating underwater

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Standard pipe testing applications

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Pipe racks - 100% rapid screening

Pipe racks are generally straightforward to test. Very long ranges can be obtained

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Insulated pipes - Limit removal insulation

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Sleeved Road crossings-Test from accessible location

Only external access is required.

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Wall penetrations -Test from accessible location

Only external access is required.

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Overhead pipes - long range screening from accessible location

Only limited access needed, can reduce/remove the need for scaffolding

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Riser - Full splash zone screening

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Long range screening

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Earth wall

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River Crossing

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Corrosion under supports detected without direct access

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Buried pipes

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Limitation of guided waves in pipe testing applications

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Range

• 5-150 meters depending on local conditions

• Factors affecting range– geometry

– general pipe conditions

– material inside pipe

– embedding material

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Difficult geometry

• Only test through one bend in each direction

• Flanges and Ts represent the end of the test

• In general complex piping will be more difficult to inspect

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General condition of pipe

0.0 5.0 10.0 15.0 20.00.0

2.0

4.0

6.0

8.0

10.0

12.0

Distance (m)

Am

p (

mV

)

Clean PipeGenerally Corroded Pipe

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Effect of Pipe Contents

• Gases - no effect

• Liquids– Almost no effect on the torsional mode

• Sludge– Heavy viscous deposits in the pipe attenuate the signal and reduce the

test range

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Attenuative Wrappings

• Bitumen

• Polyethylene

• Factory applied insulation

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Case study

Sleeved Road crossing

Pipe inspected

•Sleeved Road crossing

•Pipe does not have any built-in support

Sleeved Road Crossing

Sleeved Road Crossing

WeldCall

Sleeved Road Crossing

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Latest advances

Wavemaker G4

New Monitoring gPIMS

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High temperature inspection

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Conclusion

• GW offers very good solution to many inspection problems

• Limitations of the method shall be taken into account

• G4 - new guided wave testing platform