Application of Guided Wave Technology to Buried Piping · PDF fileIAEA/EPRI Technical Meeting...

IAEA/EPRI Technical Meeting on the Aging Management of Buried and

Underground Piping and Tanks

Application of Guided Wave Technology to Buried Piping

Mike Quarry

Project Manager EPRI Charlotte, NC

October 15, 2014

© 2009 Electric Power Research Institute, Inc. All rights reserved.

Objective

• The objective of this session is to introduce the use of guided wave to the inspection of buried pipe, and identify some of its key uses and limitations.

• EPRI “Buried Pipe Guided Wave Examination Reference Document” – 1019115 is an excellent reference and should read prior to any guided wave testing at your site.

• A Guided Wave Seminar is also conducted yearly in Charlotte for a more detailed discussion.


Animation of Guided Wave Crack Detection


• Probes or sensors are installed on the component and pulsed with the GW system.

• Probes “listen” for reflected energy and convert to an electrical signal that is recorded for subsequent data analysis. Exact values are not displayed. Peaks in reflection of degradation are evaluated

Generation of Guided Waves

Piezoelectric Probe Magnetostrictive Sensor


Electronics and Setup of Equipment


Mode Shape of T(0,1) torsional mode (twisting)


Guided Wave Concept

A guided wave is generated by a ring of piezoelectric transducers. The guided wave propagates down the pipe and changes in the cross-section of the pipe or material properties create reflections. These include welds, flaws, corrosion, flanges, valves, wall thickness changes, etc. The reflections propagate back to the ring where they are received. The received signal is plotted as a function of distance from the ring. Typically welds are used as reference markers and calibration for the test. Prior to the setup, UT thickness measurements should be taken to verify pipe thickness.

Transducer Ring

Flaw Weld

Amplitude

Guided

Wave

Reflection Reflection

Distance


Where Guided Waves Are Being Used

• Oil and gas industry

– Road Crossings Cased Piping

– “Non-piggable” lines

• Chemical processing

– Corrosion under insulation

– Wall penetrations

• Aerospace industry – Structural Health Monitoring

Guided waves are still a relatively new technology and most applications

have only begun using GW in the last 10 years. Buried applications have

been studied in the last 3 to 4 yrs.


Benefits of Guided Waves

• Efficient 100% volume inspection of a large section

• Can potentially propagate long lengths, although flanges and large valves act as obstructions

• Inaccessible locations including wall penetrations, buried, coated, or obstructed areas

• Limited cleaning and excavation (required at locations where transducer ring is applied), but does require removal of coating

• Does not require access to inside of pipe or cleaning of inside pipe walls

• May inspect while system is operating

• No risk of getting anything stuck or lossed inside of pipe

• No risk of contaminating inspection equipment

• Potential for periodic monitoring via permanently mounting sensors

• Technology available from 2” to 96” diameter


Challenges of Guided Waves

• Thick viscous coatings attenuate signal, thus reducing effective inspection lengths and sensitivity to flaws

• Flanges are barriers for guided wave propagation – inspection beyond a flange is not possible

• Elbows distort the guided wave signal and reduce signal-to-noise making inspection beyond them difficult

• Distinguishing flaws from other nonaxisymmetric reflectors such as welded attachments

• Quantifying size of damage is often not highly accurate

Work needs to be done in these areas to study and improve GW capabilities.


Current Guided Wave Capabilities/Limitations

Guided Waves CAN

Guided Waves CANNOT

Provide a rapid method of screening relatively long runs of pipe

Provide actual remaining wall thickness

Detect inside and outside surface wall loss as well as circumferential cracks

Differentiate between inside and outside wall loss

Examine an inaccessible area of a component from a remote location

Inspect past a flange or detect isolated small pits or “pin-holes” reliably over long distances

Be used to examine a pipe containing a product

Accurately size damage


24” Pipe mockup with an elbow and several flaws – elliptical dishes and flat-bottom holes

Flaws

EPRI Report 3002000466, “Nondestructive Evaluation: Guided Wave Analysis Tools”


Flaws in 24” Pipe Mockup

Flaw #1 – 3” x 1” (50% thru-wall) Flaw #2 – 2” x 1” (50% thru-wall)

Flaw #3 – 1” dia. flat-bottom holes

(50% thru-wall) set of 3 – 1 ft. apart Flaw #4 – 6” x 1” (50% thru-wall)


GW data with MsS sensor at right end of pipe

270o 90o

TOP – 0o

180o

7’

5’

8’ 6’

270o 315o

90o

0o

#1 #3 #2

#4

Flaw #1

Weld

Flaw #3 Flaw #4 Flaw #2

Bend

Weld

Bend Weld

MsS sensor

Reverberation

End of Pipe

MsS Strip


Sources of attenuation for Guided Waves which reduce propagation distances

• Coatings

• Concrete

• Soil

• Surface Roughness

• Pipe Product (sludge)

• Material Attenuation – cast iron is usually highly attenuative


GW Data from Pritec coated Pipe 1 with native clay backfill shows a reflection from a flange at about 40’

20 40 60

0.0

0.2

0.4

0.6

0.8

1.0

Distance (ft)

Am

p

(L

in

ea

r)

+F1


GW Data from Pritec coated Pipe 3 with pea gravel backfill shows a reflection from a flange at about 80’

0 20 40 60 800.0

0.2

0.4

0.6

Distance (ft)

Am

p

(L

in

ea

r)

+F1 +F2


Surface Roughness

• Scattering can take place at the surfaces of the pipe as the guided wave bounces back and forth during propagation

• As roughness increases so will scattering and attenuation

• As pipes age surface roughness can increase

• Attenuation due to surface roughness becomes significant when it reaches 10%-20% or greater of the wall thickness along most of the pipe

• Some pipes with heavy pitting throughout the pipe may not be inspectable


Elbows and Bends

• Elbows reflect and distort guided wave energy making inspection beyond them more difficult

• 45’s are generally worse than 90’s

• Distortion worsens as the radius of curvature tightens

• Pipe that pulled-bends cause much less distortion provided their radius of curvature is greater than 3.


Obtaining Credit for Guided Wave as a Direct Examination

• EPRI Report 3002000468, “Nondestructive Evaluation: Guidelines for Obtaining Credit for Guided Wave as a Buried Pipe Direct Examination

• EPRI has done research providing a technical justification for obtaining credit for guided wave as a direct exam

• Created a framework with performance indicators based on experimental data to show the essentials criteria for determining if an exam should count as a direct exam


Periodic Monitoring via permanently installed OD Guided Wave Sensors

• Collars can be installed on a pipe system permanently with leads to come later and test without digging again for access.

• Has the benefit of having baseline data, so signal processing techniques can be used to look for changes.

• EPRI Report 1025213, “Buried Pipe Structural Health Monitoring”

Application of Guided Wave Technology to Buried Piping · PDF fileIAEA/EPRI Technical Meeting...

Documents

Transcript of Application of Guided Wave Technology to Buried Piping · PDF fileIAEA/EPRI Technical Meeting...