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Dr. Basab Bhattacharya

Exova (Singapore) Pte Ltd.

Engineering Critical Analysis (ECA)& Fracture Toughness of Pipelines

Outline

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Outline

Factors controlling cost of Pipeline construction

Engineering Critical analyses of pipeline -introduction and importance

Acceptance criteria obtained from an Engineering

Critical Analysis

Evaluation of Fracture Toughness data

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Cost Reduction Options for pipeline installation

New pipeline design and construction plan

High productivity welding and advanced NDT

methods to increase production rate Reduction in welding repair rates

Recommendations

Use of proper welding process (Auto welding)

Replace Traditional workmanship criteria with ECA to

produce safe Acceptance Criteria for welding

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Engineering Critical Assessment

ECA enables the significance of flaws to be assessed in

terms of structural integrity during installation andoperational phases of the pipeline.

Used for calculating the defect acceptance criteria for fabrication.

Replaces arbitrary 'workmanship' standards normally used asacceptance criteria for NDT of welds.

Essential when replacing volumetric based NDT methods byAutomated Ultrasonic Testing (AUT) which require defect height as

part of an acceptance criteria.

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ECA for Pipeline

Analysis must consider defect tolerance under stresses (staticor dynamic) at different phases of the pipeline

Installation stage

Peak installation stress or strain

Installation fatigue

Hydro test pressure

Operation phase

fatigue loading due temperature or pressure variation,

VIV etc

Worst case loading during operation

Corrosion effect

Effect of Sour service conditions

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Computational analysis - key processes

Construction of the FADCalculation of Nominal Stresses (crack driving forces)Calculation of Kmat ValuesCalculation of reference stressLr cut of limit

Calculation of Kapplied

Determination of acceptable defect sizes

Unsafe

Critical

Safe

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Tolerable Defect Sizes for Installation and Operational conditions

Mainline welds42OD x 14.1 mm WT Pipe

Height (mm) Length (mm)

1.5 527

2.0 281

2.5 154

3.0 89

3.5 59

Tolerable Defect Sizes for Installation and Operational conditionsMainline welds including AUT uncertainty of measurementH=1 mm, length = 3mm

42OD x 14.1mm WT Pipe

Height (mm) Length (mm)

0.5 5241.0 278

1.5 151

2.0 86

2.5 56

Final Acceptance Criteria (example)

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Types of Weld Defects

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Advantages of using AUT with ECA

AUT inspection applied with ECA-based tolerabledefect acceptance criteria offers several advantagesover conventional radiographic inspection

Superior detection and sizing of planar flaws

Accurate assessment of the significance of weld flaws

Reduce Repair Rates as well as cost and installationtime of pipeline

Potential increased productivity

Avoidance of radiation hazards Increased confidence in engineering design limits

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Importance of Fracture Toughness testing and ECA

Fracture toughness test results on project material arevital input parameters of an ECA.

It is essential to measure the Fracture Toughness

properties of a structure properly in order to perform ECAof a pipeline.

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FRACTURE TOUGHNESS -Geometry and Terms

Fracture Toughness express in terms of -KIC, CTOD, JIC, CTOD-R Curves, J-R Curves

Specimen configurations include -Single-Edge Notched Bend (SENB)

Single-Edge Notched Tension (SENT)

Test conditions replicate serviceElevated and cryogenic temperaturesDynamic fracture toughness

Strain and agedSour service environment

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For more information contact

Basab Bhattacharya

Technical ManagerExova Singapore LaboratoryTel - +65 6372 5610E-mail basab.b@exova.com