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Case Application Note

Weld Inspection of 8 mm – 75 mm thickness with

Gamma Ir192 Radiation Isotope &

Digital Computed Radiography Technology This Case Application report describes the CR – Computed Radiographic Image Quality that meets the requirements of ASME Section VIII Division 1 (UW - 51 & UW – 52), Division 2 (Al-510 & AI-511), ASME Section 1 (PW - 51), ASME B31.1 (136.4.5), EN444 and EN1435 standards. This computed radiographic image quality is achieved by using an Ir192 radiation isotope. The radiographic image quality is assessed by measuring the contrast sensitivity and the radiographic resolution measured with the geometric unsharpness. The results measured are comparable to those achieved with conventional radiography.

Selection of radiographic technique and the radiation source depends on various factors such as: • The types of the material that you are inspecting • Thickness of the material • Types of defects, flaws • Radiographic sensitivity required by the referencing code, standards or specifications • The cost of radiography

Ir192 is one of the most important sources of energy for use in industrial γ-Radiography for Non Destructive Testing of metals. Due to its high-energy spectra, it is widely used for thick wall inspection (with CR one can inspect up to 100mms of material thickness). With Computed Radiography it has eliminated the requirement for Co60 radiation sources.

The Ir192 gamma source characteristics coupled with the source activity controls the overall quality of the radiographic image. Technical details of the source are as follows:

Ir192 Isotope Details

19277 Ir 115

Half life 73.831 d 8 Jπ 4 (+) Sπ(keV) 6198.08.20 Sp(keV) 5729.4.12

Prod. Mode Fast neutron activation Thermal neutron activation

ENSDF Citation NDS 84, 717 (1998) Literature cut-off date 1-Aug-1998 Author(s) C. M. Baglin References since cut-off 192Ir decay from 1998-98 (NSR)

Decay Properties Mode Branching (%) Q-value (keV) References β 95.24 4 1459.7 19 88Li06 E 4.76 4 1046.2 23 88Li06

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Ir192 – Technical Data

Conventional Radiography

Computed Radiography

Gamma-radiation source, isotope Se-75, Ir-192 Se-75, Ir-192 T1/2 Se-75 T1/2 Ir-192

≈120 day ≈74 day

≈480 day ≈296 day

E, MeV (activity, to Ci) Se-75 Ir-192

≈0,215(120) ≈0,400 (120)

≈0,215(120) ≈0,400 (120)

Active core size, mm Se-75 Ir-192

To Ø 3x3 To Ø 4x4

To Ø 3x3 To Ø 4x4

Thickness of material exposure (Fe), mm. Se-75 Ir-192

5-30 10-60

5-70

10-120 Transportation and recharging Container (4 channels) Container (4 channels) Overall dimensions of the exposure head (mm)

300x130x270

300x130x270

Mass of exposure head (kg) ≈20 ≈20 Ir192 – Characteristics Radiographic Technique Setup

Thulium Tm-170

YtterbiumYb-169

SeleniumSe-75

Iridium Ir-192

Cobalt Co-60

Gamma energy (keV) 52-84 63-308 66-401 206-612 1173-1333

Half life (days) 128 32 120 74 1925

Gamma constant* 0.025 0.125 0.203 0.48 1.30 Source Output (radiation nominal dose at 1 meter) 160 µS/H

34 µS/H

130 µS/H

350 µS/H

ODD

Ir192 Radiation Isotope Device

SFD1000 mm

SOD975 mm

Weld Plate25 mm

Imaging Plate

Lead




Test Samples for Ir192 Trials

No. Item Description Image

1 CR Phantom

2 14 mm Steel Plate

3 25 mm Steel Plate

4 38 mm Steel Plate

5 52 mm Steel Plate




Ir192 Results and Radiographic Image Mentioned below are the Results (with Radiographic Image and Exposure Parameters) of the Ir192 trials that have been carried out on different thickness of Steel Plate - Weld Samples and the CR Phantom. Note: The Radiographic Images displayed here are only for illustration purpose. The actual images are of high quality and contain more details. CR Phantom - Exposure Parameters & Radiograph Image

10mm Steel Plate - Exposure Parameters & Radiograph Image

Source Curie Strength

Exposure Time

SFD (Source to Film Distance)

Scanner Gain Filter Result - IQI

Ir192 15.8 45 1000 mm 600 125μm Pb 10th Line Pair


Exposure Time



Ir192 15.8 10M 10S 1000 mm 600 125μm Pb 10th wire on 10FE – 0.40 Diameter




Note: The Radiographic Images displayed here are only for illustration purpose. The actual images are of high quality and contain more details. 14mm Steel Plate - Exposure Parameters & Radiograph Image



Exposure Time



Ir192 15.8 10M 00S 1000 mm 600 125μm Pb 6th line pair on Duplex 7th wire on 6FE – 0.80

diameter


Exposure Time



Ir192 15.8 20M 48S 1000 mm 600 125μm Pb 6th line pair on Duplex 9th wire on 6FE – 0.50

diameter




Note: The Radiographic Images displayed here are only for illustration purpose. The actual images are of high quality and contain more details. 38mm Steel Plate - Exposure Parameters & Radiograph Image



Exposure Time



Ir192 15.7 15M 20S 600 mm 600 125μm Pb 9th wire on 6FE – 0.50 diameter

9th wire on 1B11 – 0.51 Diameter


Exposure Time

SFD (Source to Film

Distance)


Ir192 15.7 32M 54S 600 mm 600 125μm Pb 6th wire on 1FE – 1.00 diameter




Note: The Radiographic Images displayed here are only for illustration purpose. The actual images are of high quality and contain more details


Conclusions

From the above results it can be seen that, for the range of plate thicknesses tested, acceptable results are achieved by taking 35% of the calculated D4 exposure time as an exposure, achieving required sensitivity and an equivalent radiographic density of 2.0 to 2.9 in the weld. It is provisionally assumed that this relationship will hold for exposures up to and including 75mm (to inspect greater thickness of material – radiographic techniques need to be developed).


Exposure Time

SFD (Source to Film

Distance)


Ir192 15.7 65M 00S 450 mm 600 125μm Pb

Documents

Computerised Supplier of the World’s Most Advanced ... Application - CR with IR 192 (72... · Supplier of the World’s Most Advanced Imaging, Digital ... requirements of ASME Section