2A-NDT-of-PE-KM

NDT of Fusion WeldsKen Murphy

Pipeline Innovation Research Club Seminar 2010

http://www.exova.com

• Destructive testing can be very disruptive & costly

• Even with destructive testing – no guarantee about welds

remaining

• Need test that tells us something about the actual weld

• Advances in technology making it possible:

• Digital Radiography – does not detect cold welds or dust

• Phased Array Ultrasound (PA-UT) – does not detect cold

welds or dust

• Microwave Imaging – shows great promise for all defects!

NDT OF FUSION JOINTS

Recap - Microwave (MW) imaging

• Material under inspection is bathed in microwave energy of an essentially constant frequency (≈25GHz)

• Energy is reflected from each interface of differing dielectric constants within specimen

• The reflected energy creates a resulting signal measured in volts

• The resulting voltage is sampled at discreet locations across sample to create an image

• Volumetric inspection technology: will view the entire thickness of the piece at once

Channel A & B are a ¼ wavelength apart

General Probe Configuration

Recap - Standard Acceptance Criteria for Butt Welds

• Acceptance Criteria for a Good Weld:

–Signal returns from the welds are crisp and unbroken lines of

(typically) blue/magenta colour.

–Weld signal returns are as broad & consistent as standard weld.

–Weld lines are singular in nature (i.e. – not dual lines).

–Reflections obtained from inner bead is close to the weld line,

uniformly spaced, and similar to standard weld.

–There are no extra rings / lines that indicate contamination species.

Recap - MW scan images: Standard Images

MW Scan Images: Standard images

Metal Tape under bead

SUMMARY: TESTING 250MM SDR11 BUTT WELDS

GoodPassPassBlind10

Problem indicatedFailPassBlind9

Problem indicatedFailFailBlind8

Poor - Weld is unacceptableFailFailFine (talc) Contamination (<1mm)7

OK with areas of interestPassPassGross (sand) Contamination (>1mm)

(contamination pushed into bead)

6

Some difference indicatedPassPassShorter Soak time (140 Seconds)5

Area of contamination

identified

FailFailGrease in selected region of joint area4

Some difference indicatedPassPass30 Seconds Dwell Time3

N/AN/AN/ANot completed2

Good - Weld acceptablePassPassBest Practice as per WIS 4-32-081

Microwave Scan

Assessment (NDT)

Tensile

Test

(WIS 4-32-08)

Bead Twist

Test (NDT)

Weld

Parameters

Joint #

Test Program – Joint # 1

Heat Affected ZoneTensile Test locations

Fusion Line

Metal tape

(Origin locater)

Stamp line

I.D.

O.D.

Test Program – Joint # 7 - Talc

Joint #7 <1mm Contamination (talc)

Tensile test locations

Test Program – Joint # 9 (Blind)

Tensile test Locations

Joint #9

Section of site joint - 1200mm SDR 21

Weld line not clearly evident in scan

Cross section of joint showing evidence of cold fusion

Tensile Test fracture surface showing brittle weld

Metal tape (Origin

locater)

PE100+ PROGRAMME 50MM THICK

Single pressure weld (50mm thick weld)

Weld line

Variation

in wall

thickness

Dual Pressure Weld (50mm thick weld)

Weld line

Poor weld (50mm thick weld)

Channel B Gray Scale Channel C

Assessment of EF field joints using MW Imaging

Exova

Code Description Year

New /

Rehab

Installed

6272-1

90mm SDR11, PE80 pipe &

coupler 1986 New

6272-2

90mm SDR17 PE80 pipe &

coupler + strap ferrule 1987 New

6272-3

90mm SDR17 / SDR11 PE80

pipe and coupler 2004 New

6272-4


coupler 1985 New

6272-5

90mm SDR17 , PE80 pipe &

coupler / PE100 stubb 1999 New

6272-690mm SDR17, PE100 pipe &


6272-7


coupler / PE100 stubb 2007 Rehab

6272-8


coupler 2002 New

6272-9



6272-10



6272-11125mm SDR11, PE80 pipe &

coupler 1989 New

6272-12

125mm SDR17, PE100 pipe /

PE80 coupler 1995 Rehab

Assessment of field joints using MW Imaging

Passed Joint: Exova Code 6272-5 (1999)

Cold Zones


Non-critical fail Exova Code:6272-3(2004)


Critical fail Exova code: 6727-11 (1989)

NDT inspection methods for EF joints

Phased array UT inspection of EF joint

MW imaging of EF joint (poor field joint)

Voiding

Wire movement

Well fused region of EF joint Voiding observed in EF joint

355mm EF joint – Brittle Failure

NDT field equipment

MW imaging On-site equipment

PA-UT equipment

Relevance of NDT?

• The integrity of PE butt welds is critical during the rehabilitation of pipelines using trenchless techniques

• Failure of a butt weld during installation will have significant cost, time and safety implications

• Questions concerning the integrity of EF joints is limiting the use of PE pipe materials in service critical applications

• Joint leakage could result in high repair costs and devastating environmental damage.

What guarantee is there that a joint is good?• Destructive testing can be very disruptive & costly

• Even with destructive testing – no guarantee about joints remaining

• Need test that tells us something about the actual joint• A reliable NDT method would help allay concerns over the integrity of PE

joints in the field.

• Significant research projects being conducted worldwide:– US DoE in conjunction with US-NRC– TESTPEP, a EU Framework 7 project

– Combined research by NYsearch and the EWI

Conclusions

• A considerable step forward in NDT inspection of PE piping systems has been made

• Poor quality joints can be detected using the MW imaging NDT technique in both butt fusion and electrofusion PE joints

• Mechanical testing has verified that MW imaging NDT can reliablyidentify poor quality joints

• Although MW imaging has shown significant potential in assessing EF joints, the use of other modern NDT techniques may help improve the interpretation of results

• MW imaging NDT used in conjunction with current site auditing practices could further improve the reliability and quality assurance of PE joints in the field

2A-NDT-of-PE-KM

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