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Phased Array and Time of Flight Diffraction (TOFD) Codes and Specifications

Michael MolesNAVSEA 271st meeting, May 2011

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Outline on AUT Codes

ASME – AUT and Phased Array codesASME - Code requirementsTOFD Codes – incl. ASMEOther code activities – API, ASTM, AWS,

EN, ISO etc.Summary

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ASME Codes

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ASME AUT Codes TodayAUT dominated for years by ASME Code

Case 2235 (from Sections I, VIII and XII)

Now replaced by three Mandatory Appendices (publ. July 2010) in Section V

No commitment to specific technologies: wide variety of options - technique, equipment, mechanics, data displays etc.

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ASME Mandatory Appendices VI-VIII

Based on Performance Demonstration (Procedure Qualification)

Requires detection of three defects (ID, OD, sub-surface)

Requires full data collection and encoder

(Modified versions of CC 2235 in API 620 App U, B31.3 CC 181 etc.)

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ASME Mandatory Appendices VI-VIII

MUCH easier to read and use than CC 2235Written in plain English For example, Performance Qualification

allows + 25% on wall thickness and 0.9-1.5 on diameter.

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The Portable Approach

One person operation:• OmniScan• twin phased arrays,• TOFD • handscanner• couplant and pump• linear scanning.

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Phased Array Codes and Code CasesThree AUT Mandatory Appendices (VI-VIII):

– Workmanship

– Fracture Mechanics-based

– Procedure Qualification (Performance Demo)

Two PA Mandatory Appendices (IV-V):– Manual PA (E-scans and S-scans)

– Encoded linear scanning using linear arrays (E-and S-scans)

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ASME Phased Array Mandatory Appendix Requirements

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Phased Array Mand. App. RequirementsCalibrate all beams (OK for OmniScan)Use same Focal Law for cal as for scanningFor encoded scanning:Develop Scan Plan to show coverage and

appropriate anglesUse two (or more) S-scans if requiredScan parallel to weld with encoder/full data

collection at fixed distance from centerline

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Phased Array Mand. App. RequirementsRequires “appropriate angles” for bevel

incidence angles (undefined)Usual ‘Essential Variable’ recording

requirementsRequires 50% beam overlap Requires <5% data drop-out for encoded

scanningExtensive reporting requirements.

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Calibrating wedge delayThe operator sets a time

gate with enough width to encompass all the reflections at all angles and positions.

Operator then “calibrates” the wedge delay using the automatic calibration process.

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Sensitivity calibration Need to correct for

angle effects (ACG) and time effects (TCG)

OmniScan has ACG correction, but easiest to use Auto-TCG function.

Auto-TCG does both ACG and TCG operations in a single step.

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Sample Auto-TCG results

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Scan Plans

Ray tracing using ESBeamTool with sample Bevel Incidence Angles (arrowed) calculated on 25 mm wall double-V weld.Can check if angles “not appropriate”

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ASME B31.3 Code Case 181 (-2)Recently re-written - againCurrently out for ballotEssentially converts CC 181-2 to

“workmanship” Overall, should be a major step forward for

pipes In addition, ASME Section V Code Case

2638 allows much greater flexibility in cal blocks.

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TOFD Codes, especially ASME

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TOFD SignalsTransmitter Receiver

Lateral wave

LW

Upper tip Lower tip

Back-wall reflection

BW

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Typical TOFD Display•Gray scale and rf for phase info.

•OD and ID visible

•Defects detectable in middle

•L-wave display only (usually)

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TOFD Advantages and DisadvantagesExcellent PoD for mid-wall defectsGood detection of mis-oriented defectsRapid (and relatively low cost) inspections

Dead zone of ~3mm at outer surfacePotential dead zone at inner surfaceCan be difficult to interpret.

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TOFD CodesWell “codified”, primarily from Europe “Invented” and developed thereSome pluses and minuses of various TOFD

codes, e.g. how to calibrate etcWell-used and well-developed techniqueBUT, does require skilled and trained

operators.

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TOFD CodesBS7706 essentially a “guideline” EN583_6 good, but not well known in North

AmericaReplaced by EN14751ASTM E-2373-04 publishedASME TOFD Code (Section V Article 4

Mandatory Appendix III) published in 2006 ASME TOFD Interpretation Manual

(Nonmandatory App. N) published.

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ASME TOFD CodeGood code; requires calibrating on ASME

side-drilled holesCurrent calibration alternatives from Europe:

– known defects– grain noise– lateral wave

ASME requires conventional UT for ID and OD to cover off dead zones (unlike most other TOFD Codes).

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ASME TOFD Code Calibration

TT/4

3T/4

Weld Thicknessin. (mm)

Hole Diameterin. (mm)

Up to 1 (25) 3/32 (2.4)

Over 1 (25) thru 2 (50)

1/8 (3.2)

Over 2 (50) thru 4 (100)

3/16 (4.8)

Over 4 (100) 1/4 (6)

Calibration using standard ASME notches

Defined in Mandatory Appendix III.

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Other Code Activities –API, AWS, ASTM, EN/ISO etc.

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Code activities - API

API similar in approach to ASME; two organizations typically work together

Approval using PA for API UT 1 and UT 2 procedures with no changes

Essentially scan known samples using new technology/techniques

Phased arrays now widely used for API, e.g. API RP2X and API 1104.

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Code activities - AWSA “prescriptive” code, different from ASME

With 2006 version => new technology and technique approvals are codified

Major problem: each case requires the “Engineers” approval

Working on mandatory Annex for AUT

AWS responding - slowly.

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Code activities – ASTM (1)ASTM E-2491-06 Recommended

Practice for phased array set-up

Requires full “angle corrected gain” (ACG) and “time corrected gain (TCG) over SDH calibration range

Limits to angular range based on recommendations and calibration.

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Code activities – ASTM (2)Recent E-2700 RP for PA of weldsEssentially allows contact testing for ferritic

steel weldsNo great surprises here.

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EN/ISO

Still working on PA code development

Third version more realistic, but still needs a little work

Very bureaucratic organization

But expect EN/ISO phased array code in a couple of years.

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Code Summary

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Code activities – ASME summaryPhased arrays, TOFD and AUT inherently

accepted by ASME (and other codes)May need to get techniques and procedures

approved e.g. by Performance Demonstration approaches

Complete ASME Phased Array and TOFD (Time-Of-Flight Diffraction) Codes now available.

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Code activities – other summaryASTM RP for PA set-up published (E-2491)ASTM RP for PA of welds published (E-

2700)API generally accepts PAAWS D1.1 still requires Engineer’s approvalEuropeans “still behind” on PA and AUT

codes.

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Thank you

Any more questions?