ut of pressure vessel construction welds

8/10/2019 UT of Pressure Vessel Construction Welds

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Second level

Third level

Fourth level

Fifth level

1

Ultrasonic inspection of pressurevessel construction welds using

phased arrays


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Talk Outline

Weld inspections

Codes, including ASME Code Case 2235

Some dos and donts of phased arrays

AUT inspection instruments

Mechanics: some suggestionsSummary


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Weld inspections


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Linear Scanning Philosophy

Select arrays to give adequate coverage; need toensure HAZ and weld zone covered

Scan weld in parallel linear motion, or move weld past

stationary arrays -> much faster.

Left: raster scans Right: linear scans


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Electronic and Linear Scanning Typical weld inspection using combined

electronic and linear scanning. ASME-type 45oand 60oshear wave & TOFD

inspections; ~10x faster than raster scanning.

Need to cover weld, HAZ, any position errors

=> significant amount of coverage.

Works well for wide gap welds.


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Sample ResultsTop, side, end View

This image

shows weld

profile

superimposedon top, side,

end and

waveform

view.


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UT Zone Discrimination Weld is divided into many

Zones, each covering 2-3mm of weld wall

UT beams are focused to

~2 mm, and angled for

Lack of Fusion UT transducers are

designed and positioned

to inspect each zone

Scanner travels linearlyround pipe at high speed

Both sides of the weld

center line are inspected

independently


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Codes

ASME Code Case 2235 permits automatedultrasonic inspection of welds


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Advantages of AUT vs. RT

AUT does not disrupt production No safety hazard from AUT; no radiation

Immediate feedback on the weld quality

AUT can measure the defect height forFitness-For-Purpose analysis, => shouldreduce repairs and costs.

AUT inspections can be tailored to the weldprofile, vessel geometry and inspectionrequirements

Can maximize Probability of Detection

All data is stored, unlike manual UT

High production rates.


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Some Dos and Donts


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Dos and donts - calibration

DO

Calibrate array entire array for reproducible

and code-acceptable results

Best approach is to scan over calibrationreflectorthen compensate electronically

using software


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Dos and donts Weld overlays

DO

Add weld

overlay if

possible Helps locate

defects relative

to weld profile

and surface


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Dos and donts 3D images

MAYBE

Can do 3Dimaging withTomoView

Good pictures,

BUT needmaximum height,length etc.

ASME box more

useful for analysis Developmentdone with ZetecQuebec. Image courtesy of Zetec


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Dos and donts S-scans

DONT: perform single S-Scans on thick sections

Can calibrate S-scans at any angle on SDHS-scan does not necessarily give best angles for weld

inspections


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Inspection Systems

Instrumentation


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OmniScanPortable Phased Array

UnitBattery-powered/AC16/128 unit

Performs electronic

and sectorial scansPulse-echo, TOFD

etc.

Can operate withencoders or full

scanners

User-friendly software

With array and

encoder, OmniScan is a

complete system


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PV-100 System

Conventional multiprobe system with encodedhandscanner or automated scanner

Uses TOFD for weld midwall, and pulse-echo for

root and cap to give 100% coverage.


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PV-200

Uses full phased array units (Tomo III or FOCUS

LT) with automated scanners

Performs many different inspections, incl. TOFD

and top, side, end views

General purpose inspections.


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FOCUS LT

New instrumentreplaces FOCUS

As capable as

FOCUS, but

smaller, lighter,cheaper

Runs TomoView

Performs multiplescans

simultaneously

Good data

analysis


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PV-300Special ECA-Fitness

For Purposeapplications

200% NDE coverage

Multiple NDE

techniques

o Pulse-echo

o Tandem

o TOFD

o Eddy current


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Mechanics

From semi-automated to fully

automated


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Encoded ArraySimplest and

cheapest solutionWorks with

OmniScan

Can give top,side, end views

and TOFD

Limited byposition accuracy

and single

functionscans


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Handscanners

Low cost and easy to useCan use conventional or

phased arrays

Uses TOFD and pulse-echo

Good approach for very

thick wallsNeed allowance for

operator error


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Welding Bands

Good forpipes up to

~1.5 m

Quick, easy

and accurate

Routinely

used on

pipelineconstruction.


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Rotate the VesselGood for

fabricators, whorotate to weld

Simplest

mechanical solutionCan accommodate

position errors with

phased arrays

No safety hazard,

no delays


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Magnetic wheel scannersVariety of scanners

available from R/DTech and externally

Follows magnetic

strip, so can scan

nozzles, unusualgeometrys etc.

Can also use

joysticks, pre-

programming etc. forcontrol


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Robotics

Expensive, but very flexible solution

Robot can manipulate large probe pan with

many NDE devices.


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Advantages of Phased Arrays

Speed: scanning with phased arrays is much faster than single probeconventional mechanical systems, with better coverage;

Flexibility: set-ups can be changed in a few minutes, and typically alot more component dimensional flexibility is available;

Inspection angles: a wide variety of inspection angles can be used,depending on the requirements and the array;

Small footprint: small matrix arrays can give significantly moreflexibility for inspecting restricted areas than conventional probes

Imaging: showing a true depth image of defects is much easier tointerpret than a waveform. The data can be saved, analyzed and re-displayed as required.


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Conclusions

Many different PA & AUT systems can be used to

fulfill ASME 2235 and other weld inspection codes: portable phased arrays (OmniScan),

TOFD-based (PV-100)

more powerful phased arrays (PV-200 and FOCUS LT).

Many possibilities for delivery systems: handscanners,

welding bands,

magnetic wheel scanners,

rotate the vessel,

robotics. Choice is controlled by codes, component

requirements, budget and knowledge.

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