The Centre, Birchwood Park, WarringtonWednesday 17th April 2013

David Ludlow, AMECBINDT & ICORR Symposium on Inspection and Monitoring Techniques to Manage the Corrosion of Valuable Assets

Stress Corrosion Cracking Test Pieces for Inspection Qualification and NDT Development

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Overview

What do we doStress corrosion cracking (SCC)InspectionNDT test piecesMISTIQ SCC test piecesNDT developmentsCase studyFuture developmentsConclusions

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AMEC NDT Inspection Capability

Concept Development

Plant Implementation

Design

Problem Understanding

Inspection Techniques

Rigs and Test Pieces

Deployment

Training

Inspection Specification

Reliability Testing

Qualification Strategy

Procedure Development Data Analysis

Inspection AuditHuman Factors

Human Factors

Research

Modelling and Simulation

Training Audit

Monitoring & Inspection DesignInspection ValidationCentre

Independent Qualification Body

Qualification Consultancy

Technical Justifications

Site Support

Technology Transfer

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Why Inspect?

Plant Failures:Flixborough explosion – SCC of chemical reactor, UK 1974Bhopal accident, India 1984Swiss swimming pool collapse caused by SCC, 1985Carlsbad pipeline explosion, New Mexico, 2000 El Al Boeing 747 crash caused by SCC, Amsterdam 1992

SCC is major degradation mechanism & difficult to

detect

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Stress Corrosion Cracking

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SCC Initiation & Growth

Schematic diagram showing SCC initiation and growth(Ref. R. Staehle, “Predicting the SCC of Reactor Components from First Principles”, EUROCORR, 2009, Nice, France, Acropolis Palais de Congress, 6-10 September, 2009)

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SCC 2-D Morphology

TGSCCChloride SCC in 304L ASS

Ref. Colorado Metallurgical Services

IGSCCLeft Ref. NACE (Inconel heat exchanger)

Right Ref. Okamura, Japan NPP

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SCC 2-D Morphology

SKI Report 2006:24 Crack Characterisation for In-service Inspection Planning

Nearly 100 SCC defects characterised from plant, 77% IGSCC

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SCC 3-D Morphology

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Inspection

Asset ManagementPeriodic NDT during outageRisk based approach (RBI)NDT needs careful design

TechniqueEquipmentPersonnel

Design needs validationFormal Qualification

Holy Grail

Universal Technique

No Operational Interference

Early Warning

Future

Structural Health Monitoring

Now?

Targeted Online Monitoring

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NDT Techniques

SCC SurfaceVisual Liquid dye penetrant (LPI)Magnetic particle (MPI)Eddy current (ECT)Electro-magnetic

VolumetricUltrasonicsRadiographyAcoustic emission

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NDT Test Piece Development

Representative test pieces

–Material, geometry, defectsCrack defects

–EDM notches, fatigue cracks (smooth defects)

E.g. UT response weaker for SCC compared to fatigue cracks leading to SCC defects being missed / unreported during plant inspections

Requirement for realistic SCC defects

(rough defects)

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AMEC MISTIQ SCC Process

Need for IGSCC in Inconel alloysControl over crack length & depthAccelerated processStainless steels & DM weldsStandard plate specimensBespoke specimensDedicated rigsFE analysis support

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SCC Images

Plant SCC AMEC MISTIQ SCC

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NDT Developments using SCC Test Pieces

Online data collectionGates & alarmsSignal processingEnhanced visual displayData analysisPhased array

– Total focussing method (TFM)

– Full matrix capture (FMC)

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UT Online Monitoring

Pulse echo– SCC initiation – First stages of

growth

Time of flight diffraction (TOFD)

– SCC crack depth

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Online Data Collection

Pre SCC TOFD A-scan

SCC

TOFD A-scanB-scan showing SCC initiation &

growth

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Online Data Analysis: Gates & Alarms

Automated Recognition

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Enhanced Visual Display

A-scan from Marker

3-D View Control

Rotatable

3-D View

Slider to Move

A-scan Marker

Prototype UT software with enhanced visualisation

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UT Phased Array

Phased array TFM image superimposed on

MISTIQ SCC

(grade 304 plate)

FMC is data collection for every transmit-

receive combination.

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Case Study

Objective– To deliver large DM weld

SCC specimen to Japan for round robin trials

Challenges–Largest SCC bespoke

specimen –DM weld composition–Rig design & loading

conditions–NDT–Delivery schedule–SCC target: 20mm wide &

20mm deep

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Case Study

Weld metal trialsLoading conditions: FE analysisNDT

–UT specialised probes–DPI

Destructive Examination

Ref. E.Journal of Advanced Manufacturing, Vol.3 No.3 NT40 & Vol.2 No.2 NT24

162116232232729271

Depth mm

Lengthmm

Depth mm

Lengthmm

Specimen

Destructive Examination

NDT

weld

carbon steelstainless steel (304)

cladding

weld

carbon steelstainless steel (304)

cladding

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Future Developments

SCC in ferritic steels & Al alloysTGSCC NDT specimensComplicated geometries e.g. full pipe sectionsDegradation mechanisms – pitting, general corrosionThermal fatigue & H cracking specimens

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Conclusions

There is a real need for realistic SCC specimens to improve inspection systems for SCC detection & sizing

AMEC MISTIQ SCC test pieces offer a step improvement over conventional test pieces for SCC inspections

–Widely used in qualified inspections for NPP

Targeted NDT techniques can be adapted for online condition monitoring

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Questions?

AcknowledgementsBINDT & ICORR

AMEC – Nick Smart, Bernard McGrath & MID Team

Contact:David LudlowT: 01925 254914E: david.ludlow@amec.com

AMEC Clean Energy- EuropeWalton House, Birchwood,Warrington, Cheshire, WA3 6GA