Projection Radiography. application on stream

Transcription

1 Projection Radiography application on stream common research project BASF and BAM, later with AGFA/GE IT, IT, IAEA: computer based radiographic wall wall thickness measurement contents: --basic principles --software for forevaluation and and documentation --corrosion depth evaluation --validation of of methods 1

2 Projection Radiography Examples on Corrosion and Erosion Corrosion and Seads Corrosion Erosion 2

3 History: radiographic wall thickness evaluation applied since ca nearly no literature until 1980 growing importance in chemical industry caused by onstream application since 1996 projects BASF und BAM for physical studies standardization open (IAEA Draft) BASF drawing from

4 classical set-up: typical exposure: radiation source, Ir 192 insulation pipe line film, imaging plate, or flat panel profile line 4

5 Projection Radiography Example : distribution station film source on-site exposure, Ir 192 radiograph 5

6 Projection Radiography visual evaluation of wall thickness error sources: w - wrong density range - inaccurate edge detection (unsharpness) - wrong magnification factor 6

7 Principle of projection radiography tangential penetration of pipe wall f - film focus distance r - outer pipe radius R - outer radius of insulation w - wall thickness projection on detector plane pipe insulation w` measured on film 7

8 Projection Radiography PC based wall thickness measurement overview of measurement equipment (BASF at 2000, before CR): RT exposure scanner PC protocol screen/film : film digitisation RCF + F8 (16 bit, 300 dpi) (7% of exposure time of Pb+D7) software for measurement (algorithms) and documentation data base 8

9 Projection Radiography PC based wall thickness measurement film digitisation imaging plate flat panel single program for evalution of all digital images, no size limitation support for all detectors by external 16 bit LUT tables for linearisation (gray value proportional to radiation intensity) 9

10 16 bit software platform wtscope.exe image processing know-how on on Windows PC: (ISee!, see --fully fully16 16 bit bitdata datadepth for forevaluation and and display --unlimited image sizes, limited only onlyby bymain mainmemory (>1 (>1 GByte) --all all detectors (digitized film, film, imaging plates, flat flatpanel detectors) via via external bit bitlookup Tables (LUT) linearizable, ASCII text text -fast - fast rekursive moving average filtering for forarbitrary sizes sizesof of high high and and low lowpass filters, convolution with withvariable kernels (ASCII text) text) --sub-sampling for forimage display with withtrue trueaveraging --error errorestimation for formeasured values and and geometric correction --quick documentation of of measurements by byprotocol generation and and transfer to to Word --protection of of application by byindividual encrypted license keys keys 10

11 Projection Radiography PC based wall thickness measurement input exposure parameters wall thickness result table with measurement regions tangential wall thickness algorithm wall thickness deviation in measurement region 11

12 synchronous display of positions in profile and image! position correction by hand, if algorithm fails! 12

13 Projection Radiography PC generated measurement protocol 13

14 Projection Radiography Algorithms : PC based wall thickness measurement problem: correct detection of wall positions characteristic points, curve fitting, CT reconstr. inner wall of pipe max. outer wall of pipe projected wall thickness w 14

15 Limits of of Tangential Radiography (TRT): L max W L max = 2W sqrt(d a /W 1) 300 kv 200 kv Energy: L max 100 kv : 10 mm 200 kv : 30 mm 300 kv : 40 mm 400 kv : 50 mm Se-75 : 60 mm Ir-192 : 75 mm Co-60 : 120 mm 15

16 Radiographic Evaluation of Corrosion and Deposits in Pipelines: Results of an IAEA Co-ordinated Research Programme Steel pipes up up to to 20 with NDT film and X-ray, Ir-192, Co Algeria Hungary Romania Iran Pakistan Germany Uruguay Syria India Turkey Malaysia Canada 16

17 Fabricated Reference Blocks with Steps and Holes: Iran Idea: explore inspection methods with known wall thicknesses 17

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19 algorithm detects edges, visual not seeable in image : extension of application range in comparison to visual evaluation Ir 192, DN200: 6 11 mm Co 60, DN300: mm 19

20 2005: Validation of of wtscope, CR-Tower and Ir-192 BAM BASF GE IT 20

21 Validation as as measurement method according to to ISO 17025: Steel pipes mm dia, empty, water filled, w/o insulation 21

22 Radiographic Corrosion Inspection Two inspection techniques possible : 2. Corrosion assessment from local film density changes (Double Wall Technique, DWT) 22

23 local corrosion : wall thickness differences in penetration direction (DWT) source pipe erosion w-δw intensity change, ΔI attenuation law: detector I w = I 0 e -µ eff w µ eff - effective attenuation coefficient relative measurement: 1. Calibration: 2. Measurement: 2 step algorithm µ eff = ln ( D REF / D IQI ) / Δw IQI Δw = ln ( D REF / D MEAS ) / µ eff 23

24 DWT for local corrosion 1. Calculation of effective attenuation coefficient µ eff known hole depth signal at measurement point signal at reference point known pipe wall thickness w at reference point Result: µ eff eff = f(w) dep. on on radiation energy and wall thickness differences 24

25 IAEA CRP, film Calculated attenuation coefficient (1/mm) 0,50 0,45 0,40 0,35 0,30 0,25 0,20 0,15 0,10 0,05 0,00 Double wall technique 6" and 8", 100 kv, with and without insulation y = 0,6689x -0,3385 R 2 = 0,7316 y = 0,5039x -0,3927 R 2 = 0, Penetrated steel wall thickness (mm) Iran, Uruguay insulation decreasing µ eff eff with penetrated wall and insulation 25

26 IAEA CRP, film 0,10 0,09 Double wall technique, Ir 192 Ir-192 Calculated attenuation coefficient (1/mm) 0,08 0,07 0,06 0,05 0,04 0,03 0,02 0,01 0,00 Uruguay Iran Uruguay with Insulation Iran with Insulation Penetrated steel wall thickness (mm) % of of all all measurements: µ eff eff = /- +/ mm

27 IAEA CRP, film 0,045 Double wall technique Co-60 Calculated attenuation coefficient [1/mm] 0,040 0,035 0,030 0,025 0,020 0,015 0,010 0,005 0,000 12" pipe 8" pipe mean µeff Penetrated steel wall thickenss [mm] % of of all all measurements: µ eff eff = /- +/ mm

28 Computer based evaluation with withwtscope/isee! software: accuracy mm, mm, µ eff =0.028/mm eff 28

29 Comparison Film // CR DWT with Ir-192: Result of wtscope validation for CR Tower by BAM / BASF / GE IT effective attenuation coefficient [1/mm] 0,06 0,05 0,04 0,03 0,02 0,01 µ eff CR Film reason: scatter sensitivity! pipe wall thickness [mm] 29

30 Projection Radiography Summary program for PC based routine measurements on images from all radiographic detectors, tangential wall thickness measurement and local corrosion, simple documentation wall thickness range enlarged compared with visual evaluation in projection radiography measurement of corrosion depth (in centre of pipe) validation as measurement methods acc. to ISO programs transfered to GE IT for worldwide marketing (Rhythm Version 2 all methods implemented) differences in sensitivity to scattered radiation between film and imaging plates inspection technique not standardised, written practice necessary! standard development has to be started soon 30

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