Digital Radiographic Inspection replacing traditional RT and 3D RT Development

Iploca Novel Construction Meeting 27&28 March 2014 Geneva

By Jan van der Ent

Technical Authority International

Contents

Introduction of Digital Radiography

Advantages of digital radiography

Digital Radiography inspection methodology

RTD RAYSCAN system

Digital detector and Image processing principle

Time delayed integration

Image Quality indicator

Software features

Practical benefits of RTD RAYSCAN

Future development, 3D tomography

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Introduction of Digital Radiography

Radiographic image = x-ray image (photography)

RTR = Real Time Radiography = direct x-ray image

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Digital RTR vs. Conventional RT

Advantages of digital vs. conventional RT:

Shorter exposure times (due to high sensitivity)

Reduced angle of radiation beam

Improved radiation safety (lower keV)

Direct on-line weld image display

No residual products lower costs

• No use of chemicals

• No film

Large dynamic range (multiple film classes covered)

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Geometric unsharpness comparison

Image 1 : Poor geometric un-sharpness, high radiation risk!

Image 2 : Multiple exposures, high radiation risk!

Image 3 : RAYSCAN system methodology

– Eliminates geometrical un-sharpness

– Eliminates multiple images

– Reduces the radiation risk

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Panoramic film

Crawler

Directional film

Detector

External source

RAYSCAN METHODOLOGY

IMAGE 1 IMAGE 2 IMAGE 3

Movie Rayscan system

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Digitial RT system development

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2” 12” 16” 20” 24”

Shielded

Unshielded

The heart of the Rayscan: Digital Sensor

Rayscan uses a digital sensor (like a digital photocamera... but for Xrays)

The Xray-photographs are 6mm wide and up to 220mm long

300 photographs (or frames) a second are being made!

Software re-constructs all photographs to a complete weld-image

High efficiency of sensor makes it possible to inspect large wall thicknesses with relative low radiation.

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Active

area

Digital X-ray detector principle

Direct detection of x rays with:

Biased semiconductor

Collection array

X-ray photons hit the semiconductor

X-ray photons generate charges in semiconductor

Field separates charges

Charges are processed by collection array

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Incident

x-ray

photons

Field

electrode Dielectric

layer

Semi-

conductor

Collection array –

(signal to computer)

RTR inspection methodology

DWSI technique used in the RTR system

Tube and detector rotate around the pipe and the data is processed.

After full rotation the whole weld is captured and processed by the software.

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Detector

Tube

Pipe

Time Delayed Integration (TDI)

The detector has to read at least one image when it moves by the width of a pixel.

The (e.g.) seven pixel rows of the detector acquire different parts of the weld (color).

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Detector

Tube

Pipe

1 2 3 4 5 6 7 1 2 3 4 5 6 7

1. frame

Time Delayed Integration (TDI)

The detector moves. For the second acquisition the seven pixel rows cover a new area of the weld, i.e., additionally “mid blue” but not “dark red” anymore)

The pixel rows are shifted by one row.

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Detector

Tube

Pipe

1 2 3 4 5 6 7

1 2 3 4 5 6 7

2. frame

1. frame

Time Delayed Integration (TDI)

After another acquisition the pixel rows are shifted by two with “dark blue” as an additional weld area.

And so forth for all acquisitions!

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Detector

Tube

Pipe

1 2 3 4 5 6 7 1 2 3 4 5 6 7

1 2 3 4 5 6 7

1 2 3 4 5 6 7

3. frame

2. frame

1. frame

Image Reconstruction

The software has to resort the acquired data by taking into account the shift in rows.

The 1. frame gives the image data for the first seven pixels.

The 2. frame is shifted by one pixels and is added to the image data shifted by one.

The 3. frame is shifted by two pixels and added accordingly.

The image builds up from the frames by integration (summing up). The number of frames depends on the pixel rows of the detector.

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1 2 3 4 5 6 7

1 2 3 4 5 6 7

1 2 3 4 5 6 7

3. frame

2. frame

1. frame

image data

pixel position

RTD RayScan system performance

Minimal motion un-sharpness

No film un-sharpness

Image quality equal or better than film or other digital RT

High performance (using constant potential X-ray ) with lower radiation, see example below;

Conventional directional X ray 300 keV x-ray radiation

Digital CP RT 160 keV x-ray radiation

Noise reduction improved image quality

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Image Quality Indicators (IQI)

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Single wire IQI Double wire IQI (Rayleigh criterion >20%)

According to EN 1435, soon to be accepted ISO 17636 part 1 and 2 (DR)

IQI’s are used to measure sensitivity and spatial resolution

Single : Sensitivity

Double : Spatial resolution

Image Enhancement with RTD RayScan

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Wall Thickness 16mm, 8” CS - 175kV, 4mA

Brightness

Contrast

Digital Zoom with RTD RayScan

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Wall Thickness 16mm, 8” CS - 175kV, 4mA

Cluster porosity Source side IQI –13th wire visible Scattered porosity

Defect Evaluation and Marking

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Practical Benefits of RTD RayScan

Typical benefits of RTD RAYSCAN

No films or consumables, no storage cabinets required

No darkroom, no processors or chemicals (chemical waste)

No waiting time for film development

Less personnel (scanner tech + operator)

Digital enhancement tools

Lower radiation

Wide range of pipe sizes and wall thickness

However also the Digital radiographic inspection technique, despite the mentioned benefits, is limited to the use of standard workmanship acceptance criteria as no defect height can be measured.

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3D Development: Applus RTD TomoCAR for Accurate Defect Sizing and Characterization

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Why 3D Radiographic Inspection?

Defect orientation

Defects can be missed due to orientation

Position of Source relative to film

Defects can be missed due to orientation

Operator subjective interpretation

Influence of human judgment

Probability of Detection

Is negative influence by above factors

Standard Radiographic

Doesn’t offer defect height sizing

Main objectives are :

• To improve the Probability of Detection

• To introduce ECA based acceptance criteria into the RT

inspection

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Inspection principle

3D testing of objects

100-1000 projections

High measurement time

Scanning in X direction through weld

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X -scan direction

X

Defect height visible in cross section

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Defect height System Data analysis

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What is more

in the pipeline?

Thank you!

Jan van der Ent

ApplusRTD

Technical Authority Pipeline Department