pre conference workshop on advanced digital imaging€¦ · interactive measurement of flaw...

1Digital Measurement of Dimensions

Uwe Zscherpel, [email protected] Federal Institute for Materials Research and Testing,

Division 8.3 “Radiological Methods”, Berlin, Germany

Pre Conference Workshop on AdvancedDigital imaging


Content:

1. Measurement principle: profile measurement in image data2. Length calibration and correct edge positions3. Wall thickness measurement in projection radiography4. Wall thickness measurement in penetration direction5. Measurement of flaw dimensions in weld inspection6. Conclusions

Software: Isee! available from http://dir.bam.de/ic


1. Measurement principle: profiles in image data

Three problems:

a) Images have pixels, must be calibrated in length(mm)

b) Radiographic images are unsharp, correct edgeposition?

c) Monitor displays only 256 gray values, but imagecould contain more (e.g. 16 bit = 65535 gray values)

Demo with Isee!


classical tangential set-up of TRT: film,imagingplate,orflatpanel

pipeline

radiation source, Ir 192

insulationtypical exposure:

profile line

3. Wall thickness measurement in projection radiography


Praktical application in the field: BASF

Projection Radiography

on-site exposure, Ir 192 radiograph

sourcefilm

Example : distribution station


visual evaluation of wall thickness

error sources:

- wrong density range - inaccurate edge detection (unsharpness)- wrong magnification factor

w

Projection Radiography


tangential wall thicknessalgorithm

wall thickness result

table with mea-surement regions

wall thickness deviation in mea-surement region

input exposure parameters

Projection Radiography PC based wall thickness measurement


synchronous display of positions in profile and image !


PC generated measurement protocolProjection Radiography


Demonstration with Isee! and stepped pipe

Ir 192 exposureCR image

pipe OD 148mm

steps with2 – 10 mm wall thickness


Limits of Tangential Radiography (TRT):

Energy: Lmax100 kV : 10 mm200 kV : 30 mm300 kV : 40 mm400 kV : 50 mmSe-75 : 60 mmIr-192 : 75 mmCo-60 : 120 mm

L max

W

Lmax = 2W sqrt(Da/W –1)

200 kV

300 kV


2006: Validation of wtScope, CR-Tower and Ir-192As measurement method according to ISO 17025

BAMBASFGE S&IT


2010: BAM certification of GE S&IT Rhythm WallThickness Modul versus wtScope:


See contributions of S. Burch at the WCNDT conference

2 Standard drafts available : prEN 16407: 2012-03


Second pipe inspection technique:

2. Corrosion assessment from local intensity (film density) changes (Double Wall Technique, DWT)

4. Wall thickness measurementin penetration direction


erosionw-w

intensity change, I

detector

pipesource

attenuation law: µeff - effective attenuation coefficientIw = I0 e -µeff w

local corrosion: wall thickness differences in penetration direction (DWT)

relative measurement: 2 step algorithm

1. Calibration:2. Measurement:

µeff = ln ( IREF / IIQI ) / wIQI

w = ln ( IREF / IMEAS ) / µeff


1. Calculation of effective attenuation coefficient µeff

signal atreference point

signal atmeasurement point

known pipe wall thicknessw at reference point

known hole depth

DWT for local corrosion measurement

Result: µeff = f(w)dep. on radiation energy andwall thickness differences

At first calibration


Demonstration with Isee! and stepped pipe

Ir 192 exposureCR image

pipe OD 148mm

steps with2 – 10 mm wall thickness

Penetrameterfunction


Comparison Film / CR

DWT with Ir 192:

reason: scatter sensitivity!

0

0,01

0,02

0,03

0,04

0,05

0,06

0 2 4 6 8 10 12 14

pipe wall thickness [mm]

effe

ctiv

e at

tenu

atio

n co

effic

ient

[1/m

m]

CR

Film

Result of wtScope validation for CR Tower byBAM / BASF / GE S&IT

µeff

Accuracy in practice: not better than 10 % of wall thickness !


5. Measurement of flaw dimensions in welds

Basis:ISO 10675 -1 SteelISO 10675-2 Al

(formerly EN 12517)

NDT of welds –acceptance levels for radiographic testing

Part 1: Steel, Ni, Ti & alloysPart 2: Al & alloys


Extension of Isee!“ for flaw measurement and evaluation

Modular: Visualization of indications, interactive verification and correction

Interactive measurementof pore diameters


8 mm steelClustered porosity: Evaluation of area 28mm² + 78 mm² / 1500 mm² = 7%Acceptance level 2, quality level C of EN ISO 5817


Interface to Isee! via ASCII file (*.ini format)

Open for external automatic flaw detection and evaluation!


PhD 2006 O. Alekseychuk, BAM : Automated crack detection, visualization by ISee! (rectangle and crack length)


• Automatic Defect Detection and Identification Processor (ADDIP), collection of special image processing algorithms for analysis of industrial radiographs

• ADDIP developed as programming environment for easy testing of algorithms for detection and classification of flaw indications in radiographic images

TU Szczecin,Poland exposure detection

Moduls for automatic flaw detection 2008


6. Conclusions

1. Measurement of dimensions only on raw data and not on the displayed monitor image (LUT clipping!)

2. Suitable calibration necessary (absolute dimension for TRT, µeff for DWT)

3. Corrosion measurement methods validated as RT measurment method acc. to ISO 17025 (measurement value AND measurement uncertainty)

4. Standards for corrosion inspection in preparation at CEN: prEN 16407 part 1 (TRT) and part 2 (DWT), will go to ISO?

5. Interactive measurement of flaw dimensions in ISee! possible, evaluation according to ISO 10675 supported

6. No general automatic flaw detection algorithms available, special algorithms (porosities, elongated cracks) developed and tested, simple interface to ISee!


The End

pre conference workshop on advanced digital imaging€¦ · interactive measurement of flaw...

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