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NDT Systems & Services

Copyright 2009, NDT Systems & Services. 10/2009

Ultrasound Inspection Tools –

Technology and Experience

NDT Systems & Services AG


10/2009Copyright 2009, NDT Systems & Services.

Contents

• Functioning Principle – UT Wall Thickness Measurement

• Requirements for Baseline Inspection

• Examples of Features detected in Baseline Surveys

• Corrosion Growth Monitoring using UT

• Outlook on new Technologies




Wall Thickness Measurement




Ultrasonic Tool for WT Measurement




Comparison UT – MFL Tools

Ultrasonic MFLMeasurement quantitative (mm) qualitative (%wt)

- direction independent circ.-overestimatedlong.-underestimated

- shape independent smooth trans.-underest. sharp edges-overest.

Product liquid (gas requires batch) liquid, gasWT-capability up to 50 mm depends on tool




Influence of Pipe and Feature Type

Ultrasonic MFLSeamless Pipe wt measurement

not affectedflux leakage affected by wt-change

Pipe-in-Pipe / Casings wt measurement not affected

casing may affect magnetic field

Stainless Steel Pipe yes noMid-wall defects yes noChanneling Corrosion yes axial MFL – no

circ. MFL – yes




Requirements for Baseline Inspection

• Ensure no critical manufacturing / construction

defects are present

• Verify pipe manufacturing tolerances

• Create reference for future inspections




Typical Construction and Man. Features

• Ovalities / dents

• Wall thickness variations

• Inclusions / laminations

• Surface inhomogenities

• Grinding

• Pipe Misalignment

• Weld Defects

ML Inspection Tools




Requirements for Baseline Inspection

The technical delivery conditions of steel pipes for pipelines for combustible fluids (requirement class B) are specified in EN 10208-2.

Wall thickness tolerances of EN 10208-2Seamless pipe:

4 mm < wt < 25 mm - 12.5 %wt > 25 mm - 3.0 mm or - 10 %

Welded pipe:wt < 10 mm - 0.5 mm10 mm < wt < 20 mm - 5 %wt > 25 mm - 1.0 mm




Detection Thresholds @ 15mm wt

0

10

20

30

40

50

0 0,5 1 1,5 2 2,5 3 3,5 4 4,5 5defect width [WT]

defe

ct d

epth

[% o

f WT]

Man. tolerances acc. to EN 10208-2

XHR internal

UT Standard Resolution

UT Pitting Resolution

10/20 MFL

pinhole pitting general corrosion




Corrosion Growth – Single Feature

Accuracyfor Depth

Sizing

Accuracy@ 15mm wt

Repeated inspections -increase in

depth to confirm

corrosion growth

Min. re-inspection interval @ assumed corr. growth rate of 0.4mm / year

UT - UT ± 0.4mm @conf. > 90%

± 0.4mm 0.7 mm 1.75 years

MFL - MFL ± 10% of wt @ conf. 90%

± 1.5mm 2.5 mm 6.25 years

MFL XHR -MFL XHR

± 5% of wt @ conf. 90%

± 0.75mm 1.3 mm 3.25 years

UT - MFL 1.9 mm 4.75 years




Example of Baseline Inspection

Length of inspected pipeline section

approx. 30 km

Pipeline diameter 12"

Wall thickness range 34.5 mm – 38.7 mm, predominant: 34.5 mm

Prevalent weld type seamless

Steel grade API 5L X65




Internal Surface Roughness




Internal ML – 4.2mm deep




Internal ML – 3.8mm deep




Internal Indentations – 3.4mm deep




External ML – Grinding, 6.2mm deep




WT Variation at GW – 6.0mm deep




Deposit at bottom of Pipe



Feature Monitoring – Growth 1.2mm (1)



New Technologies – LineExplorer 3TM

Tool Characteristics

• Tool based on 3 different inspection technologies including EMAT

• Does not require liquid couplant

• Defect specification comparable to UT tools



New Technologies – LineExplorer 3TM




Conclusions

• Quantitative inspection techniques should be preferred for baseline surveys

• Re-inspection intervals depend on the inspection technology to be used and the expected corrosion growth rate

• UT wall thickness measurement tools are an efficient means for corrosion monitoring




Thank you for your attention!

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