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Digital radiography for the inspection of weld seams ofpipelines – better sensitivityEdson Vasques Moreira a , Heleno Ribeiro Simões a , José Maurício Barbosa Rabello b , JoséRubens de Camargo b & Marcelo dos Santos Pereira ca Tenaris Confab, Pindamonhangaba , São Paulo, Brazilb University of Taubaté – UNITAU , Taubaté, São Paulo, Brazilc Engineering faculty of Guaratinguetá, Paulista State University – UNESP , São Paulo, BrazilPublished online: 12 Feb 2010.

To cite this article: Edson Vasques Moreira , Heleno Ribeiro Simões , José Maurício Barbosa Rabello , José Rubens de Camargo& Marcelo dos Santos Pereira (2010) Digital radiography for the inspection of weld seams of pipelines – better sensitivity,Welding International, 24:4, 249-257, DOI: 10.1080/09507110902844022

To link to this article: http://dx.doi.org/10.1080/09507110902844022

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Digital radiography for the inspection of weld seams of pipelines – better sensitivity

Edson Vasques Moreiraa1, Heleno Ribeiro Simoesa, Jose Maurıcio Barbosa Rabellob, Jose Rubens de Camargob

and Marcelo dos Santos Pereirac

aTenaris Confab, Pindamonhangaba, Sao Paulo, Brazil; bUniversity of Taubate – UNITAU, Taubate, Sao Paulo, Brazil; cEngineeringfaculty of Guaratingueta, Paulista State University – UNESP, Sao Paulo, Brazil

(Received 1 August 2007; final version received 30 July 2008)

Conventional radiography, using industrial radiographic films, has its days numbered. Digital radiography, recently, hastaken its place in various segments of products and services, such as medicine, aerospace, security, automotive, etc. As wellas the technological trend, the digital technique has brought proven benefits in terms of productivity, sensitivity, theenvironment, tools for image treatment, cost reductions, etc. If the weld to be inspected is on a serried product, such as, forexample, a pipe, the best option for the use of digital radiography is the plane detector, since its use can reduce the length ofthe inspection cycle due to its high degree of automation. This work tested welded joints produced with the submerged arcprocess, which were specially prepared in such a way that it shows small artificial cracks, which served as the basis forcomparing the sensitivity levels of the techniques involved. After carrying out the various experiments, the digital methodshowed the highest sensitivity for the image quality indicator (IQI) of the wire and also in terms of detecting smalldiscontinuities, indicating that the use of digital radiography using the plane detector had advantages over the conventionaltechnique (Moreira et al. Digital radiography, the use of plane detectors for the inspection of welds in oil pipes and gas pipes.9th COTEQ and XXV National Testing Congress for Non Destructive Testing and Inspection; Salvador, Bahia, Brazil andBavendiek et al. New digital radiography procedure exceeds film sensitivity considerably in aerospace applications.ECNDT; 2006; Berlin). The works were carried out on the basis of the specifications for oil and gas pipelines, API 5L 2004edition (American Petroleum Institute. API 5L: specification for line pipe. 4th ed. p. 155; 2004) and ISO 3183 2007 edition(International Organization for Standardization, ISO 3183. Petroleum and gas industries – steel pipes for pipelinestransportation systems. p. 143; 2007).

Keywords: digital radiography; welding; industrial radiographic films; gas-lines; oil-lines

1. Introduction

The technique of conventional radiography, which uses

industrial radiographic films, has its days numbered. A

great movement, debates, evaluations, qualifications of

digital systems and their respective implementations have

occurred around the world in various segments. In the latest

Pan-American Conference on Non-Destructive Testing,

held in October 2007 in the city of Buenos Aires, it could be

noted that this theme is developing rapidly in various

companies and well-known institutions, which had the

chance to demonstrate the current state of play of digital

radiography through their works and presentations1 – 4. The

applicability of digital radiography in welded joints for

land and sea gas pipes and oil pipes was evaluated, along

with its use in medicine, aerospace, safety, automobile and

petrochemical segments.

Among the current options, the plane digital detector,

direct radiography is considered to be the best solution

for replacing the conventional technique in pipe

manufacturing lines, to add a technology that brings

various benefits, among which are an improvement in

radiographic sensitivity, not just in terms of image quality

indicators (IQI) but also in the detection of small

discontinuities; a major positive impact in environmental

terms, since it is more ecologically suitable due to its

elimination of the films, chemicals and rejects that occur

with the current technique; a more economical solutions,

with some cases seeing a cost reduction5 of around 60%;

a reduction in the inspection cycle time due to its high

degree of automation1 and a significant increase in test

productivity. Based on these strong attractions, each

industrial sector has tried to understand this technology

and look for the best way of applying it to the inspection

of its products.

This article sets out a study on this theme, in which test

pieces were tested from longitudinal joints along pipes

welded with the submerged arc process. The test pieces

were prepared in a way that produce artificial cracks in

them of varying sizes, to allow a comparison between the

sensitivities of the digital technique and the conventional

technique, which uses industrial films.

2. The pipe manufacturing process

For large welded pipes, which are manufactured in

accordance with specifications API 5L and ISO 3183, the

ISSN 0950-7116 print/ISSN 1754-2138 online

q 2010 Taylor & Francis

DOI: 10.1080/09507110902844022

http://www.informaworld.com

Welding International

Vol. 24, No. 4, April 2010, 249–257

Selected from Soldagem & Inspecao 2008 13(3) 227–236

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most important and productive process is the manufactur-

ing process known as UOE. This process has its name due

to the production line having a press that leaves the plate in

a ‘U’ shape, followed by a press that leaves it shaped like

an ‘O’. After the product is welded longitudinally, now it

is shaped like a pipe, it received the ‘E’ – expansion.

Figure 1 shows the Tenaris Confab manufacturing

process, located in Pindamonhangaba in the state of Sao

Paulo.

In summary, the process starts with the preparation of

the ends of the plates for welding, which is followed by

pressing and internal and external welding by the

submerged arc process with up to four wires. After this,

the pipe is subject to the expansion process, it is tested

hydrostatically, and the weld bead is inspected by

automated ultra sound and by radiography at its

extremes. Various other controls are carried out, and

the other steps of the process can be seen in the flow

chart shown.

Specifically, the radiographic test is carried out using

Class 1 or 2 industrial films6 using an X-ray source that

complies with the applicable specifications, with the

revealing process carried out by automatic processors,

in line with the manufacturer’s recommendations. The

quality of the radiographic technique is evaluated by

the IQIs7 for the wire, which are placed transversally over

the weld bead.

The plates of laminated carbon steel, which are used to

manufacture the pipes, are manufactured to meet the

requirements of the specifications referred to above or in

accordance with the client’s specifications, duly discussed

and evaluated by Tenaris Confab and its suppliers. For

high-resistance pipes, the workshops produce micro-alloy

steels with a high degree of control of fundamental

parameters throughout the whole manufacturing process8.

These make up a specific group of steels with a chemical

composition and other specific characteristics designed to

achieve high values of mechanical properties.

3. Digital radiography with a plane detector

After years of development to enable digital solutions to

offer excellent sensitivity with the safety of inviolability,

current digital radiography systems offer the possibility of

obtaining images that can detect small discontinuities with

much lower exposure demands than conventional systems.

Variations in part thicknesses or in the exposure time

normally cause darker or lighter radiographs, which are

easily improved with digital techniques. The advantages of

these digital radiography systems are as follows – image is

exhibited in real time; reducing the doses received;

method of acquiring, processing and improving the

image; partially or totally automated evaluations; and the

option of storing and retrieving the image9. By using

the plane detector, the whole operation is simplified from

eliminating handling the film in the radiation area and

obtaining the image to the time for integration, evaluation

and archiving of each image. The design of the digital

Figure 1. Flow chart of the ‘UOE’ process.

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radiography equipment using a plane detector for

evaluation of the samples prepared for this study can be

seen in Figure 2.

In Figure 3, the operating details of the plane digital

detector can be seen, which consist of millions of light-

sensitive pixels that are distributed in a matrix of diodes in

a rectangular frame.

4. Materials and techniques used

To carry out this work, test pieces were used that were

taken from manufactured pipes with thicknesses of 0.50000

(12.7 mm) and 1.00000 (25.4 mm) in line with the API 5L

2004 Edition X70 grade specification. Table 1 sets out the

values specified for this grade of material, when used as

the base metal. Table 2 gives the results found in chemical

analyses of the pipes, as base metal. These analyses were

carried out in accordance with the method indicated12 in

ASTM standard A751.

4.1 Preparation of the samples

Six samples, with dimensions of approximately

250 £ 250 mm, were taken from the region welded

longitudinally by submerged arc welding of tubes with

external diameters of 3200 (813 mm) and 4800 (1,219 mm)

and with nominal thickness of 0.500 (12.7 mm) and 1.000

(25.4 mm), respectively. After cutting, groups of cracks

were created in the samples. Next, these regions were

inspected by magnetic particles and then given a

radiographic scan with the conventional technique using

radiographic films as set out in Figure 4.

Figure 2. Direct digital radiography. Source: Ref. 10.

Figure 3. Layout of the digital plane detector. Source: Ref. 11.

Table 1. Chemical composition specified for the API 5L pipe – base metal.

Material % C Mn P S Ti Nb þ V þ Ti CE

API 5L X70 Max 0.22 1.65 0.025 0.015 0.06 0.15 0.25

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4.2 Techniques used

In this work, two different radiographic techniques were

evaluated and compared. In the conventional technique, in

use at present, industrial radiographic films were used. In

the digital technique, a plane detector was used. The tests

were carried out using the simple wall – simple view

technique.

4.2.1 Conventional technique

For evaluation of the conventional technique, six samples

were subjected to a radiographic scan, using four types of

Class I films, in accordance with ASTM standards E 1185,

as shown in Table 3. All the works involved in running the

tests, processing the films and carrying out the evaluations

were held in the Tenaris Confab unit.

The films used, which were 1700 £ 3.500 (430 £ 89 mm)

were exposed in line with the manufacturers instructions

and with the aim of using the shortest exposure time,

noting that the values of the final optical density of the

scans, in the reinforced areas and in the glazed parts were

between 2.0 and 3.5 H and D, simulating the parameters

used in the production lines. The average exposure

parameters used for the current, voltage, time and focus-

film distance are set out in Table 4. To ensure suitable

evaluation of the radiographic scans, professional

technicians were used at every stage of the work, who

were experienced, qualified and certified under standards

ISO 9712 and EN 473.

The equipment and accessories described below were

used to carry out the conventional radiographic scans:

. YXLON International X-ray equipment, model MG

325, constant power output with Y.TU 320D03 vial

and focus with a dimension of 5.5 mm, in line13 with

EN 12543.. Lead screen, 0.027 mm thick.. Wire IQI in compliance with DIN 54 109.. Kodak X-OMAT B processor.. AGFA Gevaert D 102 densitometer.. BRASREMKO AT II negatoscope.

4.2.2 Digital technique

‘The equipment and accessories described below were

used to carry out the digital radiographic scans:

. YXLON International X-ray equipment, model MG

165, constant power output with Y.TU 160D05 vial

and focus with a dimension of 1.0 mm, in line with

EN 12543.. Plane detector Y. Panel XRD 0820.. Image System, 3500 FR – YXLON.. Wire IQI in compliance with DIN 54 109.. Double wire IQI in compliance14 with BS EN 462-5

– spatial resolution’.

Table 2. Chemical analysis of the pipes.

Material Dimensions % C Mn P S Ti Nb þ V þ Ti CE

API 5LX70 3200 £ 0.500 x 0.09 1.62 0.021 0.001 0.019 0.103 0.204800 £ 1.000 x 0.10 1.61 0.016 0.004 0.014 0.100 0.20

Figure 4. (a) Test piece – 100000 (25.4 mm). (b) Region of cracks detected by PM.

Table 3. Films used.

Brand Model CLASS ASTM E 1815–96 Speed Contrast Grade

Kodak Industrex T 200 I Average High Very fineKodak Industrex MX 125 I Low High Very fineAGFA D4 I Low Very high Extra fineAGFA D5 I Average High Very fine

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For the proposed experiments, a plane detector

manufactured by Perkin-Elmer was used; model XRD

0820 NA (Figure 5), 800 £ 800 (203 mm £ 203 mm), which

is based on amorphous silicon sensors, with more than one

million pixels, and a pixel size of 200mm.

The information is digitally process at 16-bit level

(giving 65,536 shades of grey) in order to obtain the

highest dynamic band and contrast, generating an image

with ultra-high sensitivity. The image integration time can

be varied between 133ms and 1 s, at 1ms intervals.

Table 5 sets out the parameters used to carry out the

digital radiographic test for the thicknesses involved.

For the 0.500 (12.7 mm) thickness, the integration was 200

screens and the integration time per screen was 0.2 s.

For the 1.000 (25.4 mm) thickness, the integration time per

screen was 1 s. The resulting processing times were 40 and

60 s, respectively.

As well as personnel specializing in digital radio-

graphic applications, to ensure suitable evaluation of the

images and standardization with the conventional

technique, professional staff were used at every stage of

the work, who were experienced, qualified and certified

under standards ISO 9712 and EN 473.

5. Results

Specifications API 5L and ISO 3183 were analysed in

terms of their acceptability for use in digital radiography

as a replacement for the conventional technique, which

currently use radiographic film. These specifications

accept another image mode, under which the sensitivity

achieved would be equivalent to that obtained with the

use of radiographic films. In the next part, we set out the

results obtained form the experiments carried out,

comparing the digital technique with the conventional

technique.

5.1 Experiment 1 – thickness of 1.00000 (25.4mm)

5.1.1 Conventional technique

Figure 6 shows the correctly scanned radiography from an

AGFA D4 film, relating to the test piece with a thickness

of 1.00000 (25.4 mm). At the moment the radiograph is

evaluated in the negatoscope, note that the sensitivity

obtained by the conventional technique, measured by

means of the wire IQI, was wire 12 (W12). In the region

within the rectangle, a group of cracks can also be seen.

Figure 7 shows an enlargement of the region

containing the spreading cracks, contained within the

rectangle drawn in Figure 6.

5.1.2 Digital technique

Figure 8 is a radiographic image of the 1.00000 (25.4 mm)

test piece, obtained using the digital technique. It was seen,

during evaluation of this digital image, that the sensitivity

obtained, also measured by means of the wire IQI, was

wire 13 (W13). In the region within the rectangle, a group

of branched cracks can be seen.

Table 4. Average parameters used for the exposures.

Test piece(in.)

Current(mA)

Voltage(kV)

Time(s)

Film focus distance(mm)

0.500 13 201 12 7001.000 13 218 60 700

Figure 5. Plane detector, XRD 0820 NA.

Table 5. Parameters used in the digital technique.

Sample 1.000 (in.) 0.500 (in.)

Detector focus distance (DFD), mm 550 550Object focus distance (OFD), mm 400 400Focal length (EN 12543), mm 1.0 1.0Amplification 1.4 1.4Voltage (kV) 160 160Current (mA) 6.25 6.25Integration time (s) 100 200Integration time per screen (s) 1.0 0.2

Figure 6. Radiographic image obtained with the conventionalradiographic technique, indicating the region containing a groupof cracks and the IQI image, showing radiographic sensitivitylevel of W12.

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In Figure 9, the results can be seen of the use of a high-

pass 17 £ 17p filter, with more detail of the area with the

branching cracks, and the IQIs for the single and double

wire.

Figure 10 shows an enlargement of the region delimited

by the rectangle in Figure 8, containing the spreading

cracks. On the basis of the scale used, it is possible to

estimate the size and layout of the cracks detected.

In Figure 11, it is possible to see the same region as

shown in Figure 10. Based on the scale used, and by suing

the high-pass 17 £ 17p filter, it is possible to estimate with

a greater degree of detail the size of the cracks found.

In terms of the radiographic sensitivity determined by

the IQI for the wires used, a comparison of the results

obtained in the conventional technique with the images

from the digital technique shows that the sensitivity

achieved in the digital technique (W13) was higher

than that obtained by the conventional technique (W12).

Figure 7. Radiographic image enlarging the region containingcracks, as indicated in Figure 6.

Figure 8. Radiographic image obtained with the digitalradiographic technique, indicating the region containing agroup of cracks and the IQI image, showing a radiographicsensitivity level of W13.

Figure 9. Radiographic image as shown in Figure 8, using the17 £ 17p high-pass filter.

Figure 11. Radiographic image as shown in Figure 10, usingthe 17 £ 17p high-pass filter. The radiographic sensitivityobtained was W 13.

Figure 10. Radiographic image enlarging the region containingspreading cracks, as indicated in Figure 8, obtained by the digitaltechnique.

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The sensitivity achieved by the digital technique when the

17 £ 17p high-pass filter was used was also greater than

that achieved with the conventional technique. In terms of

the sensitivity to detect small defects, when the radio-

graphic scans obtained from the conventional technique

are compared with those obtained in the digital technique,

shown in Figures 7, 10 and 11, it can be concluded that the

capacity to define small cracks is higher in the digital

technique than in the conventional technique. In Figure 10,

regions can be seen with cracks that are smaller in size

than those seen in Figure 7. When studying Figure 11, note

that, with the use of the 17 £ 170 high-pass filter, the

sensitivity to detect small cracks is considerably enhanced.

5.2 Experiment 2 – thickness of 0.50000 (12.7mm)

5.2.1 Conventional technique

Figure 12 shows a digitally processed copy of the AGFA

D4 film in regard to the test piece with a thickness of

0.50000 (12.7 mm). During evaluation of this radiographic

scan in the negatoscope, it was confirmed that the

sensitivity achieved by measuring the IQI of the wire, for

the conventional technique, was wire 13 (W13). In the

region defined by the rectangle, the existence of a group of

cracks can be seen.

Figure 13 shows an enlargement of the region

containing the branched cracks, within the rectangle

drawn in Figure 12.

5.2.2 Digital technique

Figure 14 shows the radiographic image of the test piece,

0.50000 (12.7 mm) thick, obtained by using the digital

technique. It was seen during the evaluation of the digital

image that the sensitivity obtained, measured by means of

the wire IQI was wire 15 (W15). In the region defined by

the rectangle, the cracks spreading out within the weld

bead can be seen.

Figure 15 gives the result of using the 17 £ 17p high-

pass filter, which shows more details of the spreading

cracks, and the wire IQIs for single and double wire.

During evaluation of the digital image, the sensitivity

obtained, measured by means of the wire IQI was wire 16

(W16).

In Figure 16, an enlargement of the region defined by

the rectangle can be seen, containing the spreading cracks

within the weld bead. On the basis of the scale used, it is

Figure 12. Radiographic image obtained with the conventionalradiograph technique, indicating the region defined by therectangle, containing a group of cracks and the IQI image,showing a radiographic sensitivity level of W13.

Figure 13. Radiographic image enlarging the region containingspreading cracks, as indicated in Figure 12.

Figure 14. Radiographic image obtained with the digitalradiograph technique, indicating the region defined by therectangle, containing a group of cracks and the IQI image,showing a radiographic sensitivity level of W15.

Figure 15. Radiographic image as shown in Figure 14, usingthe high-pass 17 £ 17p filter. The radiographic sensitivityobtained was W 16.

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possible to estimate the size and layout of the cracks

detected.

Figure 17 shows the same region displayed in Figure 10

after using the 17 £ 17p high-pass filter, enlarging the

cracks in the weld bead, which is indicated by the

rectangle drawn in Figure 15. On the basis of the scale

used and with the use of the 17 £ 17p high-pass filter, it is

possible to estimate mote details and sizes for the cracks

detected.

In terms of radiographic sensitivity determined by the

IQI for the wires used, comparing the results obtained

with the conventional technique with the images from

the digital technique, it can be seen that the sensitivity

achieved in the digital technique (W15) is greater than that

obtained with the conventional technique (W13). The

sensitivity obtained using the digital technique with the

use of the 17 £ 17p high-pass filter (W16) was also higher

than that obtained by the conventional technique (W13). In

terms of sensitivity in detecting small defects, when a

comparison is made of the radiographs obtained from

using the conventional technique and the images obtained

from the digital technique, as shown in Figures 13, 16, and

17, it can be concluded that the capacity to detect small

cracks is greater when using the digital technique than

with the conventional technique. In Figure 16, regions can

be seen with cracks that are smaller in size than those seen

in Figure 13. A study of Figure 17 shows that, with the

application of the 17 £ 17p high-pass filter, sensitivity in

detecting small cracks is increased considerably.

5.3 Evaluation of sensitivity – IQI of the wire

The radiographic sensitivity, determined by the use of the

wire IQIs, corresponds to the wire with the smallest

diameter that can be seen as a radiographic image in a

scan. In the case of the wire IQIs used in this study,

specified in accordance with standard DIN 54109, the

higher the number used to designate a given wire in the

indicator, the smaller its diameter.

Table 6 sets out the results obtained in the experiments

carried out. Column 1 gives the thicknesses of the test

pieces used in the experiments. Column 2 gives the

specifications of the wires in the IQIs used in the

experiments that must be visualized in the radiographic

image for each one of the thicknesses examined, as

demanded by specifications API 5L 2004 Edition and ISO

3183, 2007 Edition. Column 3 sets out the results obtained

for radiographic sensitivity using conventional radiogra-

phy. Columns 4 and 5 show the results obtained for

radiographic sensitivity using digital radiography with

the normal image and then with the application of the

17 £ 17p filter.

The results obtained with the use of the digital

technique, in terms of sensitivity, are better overall than

those obtained by using the conventional technique. It can

also be seen that the most expressive improvement, in

terms of the smallest wire visualized, was obtained with a

thickness of 0.50000 (12.7 mm) with the use of the 17 £ 17p

high-pass filter.

The use of digital radiography enables a significant

increase in radiographic sensitivity, as determined by the

use of wire IQIs, in the radiographic scans obtained from

the test pieces examined. This effect can be verified by an

analysis of the graph shown in Figure 18, in which

radiographic sensitivity, determined by the smallest

diameter wire that can be seen in the scans carried out is

set out for each one of the techniques used and for each one

of the thicknesses of the test pieces used in the

experiments.

Since the smaller the diameter of wire that is visible,

the greater the radiographic sensitivity obtained it can be

Figure 16. Detail of the region shown in Figure 14 (cracks).

Figure 17. Radiographic image as shown in Figure 16, usingthe high-pass 17 £ 17p filter.

Table 6. Requirements and results obtained by using theconventional method and the digital method.

Thicknessof the testpiece (in.)

IQI of the wire

Requirement Film

Digitalradiography

(normal)Radiography

(high pass filter)

1.000 W 10 W 12 W 13 W 130.500 W 12 W 13 W 15 W 16

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seen that for the 1.00000 (25.4 mm) thickness an

improvement in radiographic sensitivity was obtained

with the use of the digital technique, demonstrated by the

visualization in the radiographic scan of wire with a

diameter of 250mm when the conventional technique was

used, and wire with a diameter of 200mm when the digital

technique was used. For the 0.50000 (12.7 mm) thickness,

these values were 200mm for the conventional technique

and 100mm for the digital technique.

6. Conclusions

Based on the results set out, it can be concluded that the

technique of direct digital radiography was more sensitive

than the conventional technique, both in terms of the

smallest wire visible in the IQIs and in the detection of

actual small defects within the welds. As a result, and as

set out in specifications API 5L 2004 Edition and ISO

3183, 2007 Edition, the use of digital radiography utilizing

a plane detector can be employed directly on production

lines for pipes in the oil and gas sector, with advantages

over the conventional technique. Therefore, the use of the

digital technique represented an advance in quality over

the radiographic test process that is currently in use, as

well as high degree of automation, which will improve

productivity, safety, image storage and factors related to

the environment.

Acknowledgements

The authors would like to thank the company Yxlon Internationalfor carrying out the tests, as well as those in charge of the Mastersprogramme of the University of Taubate and the Paulista State

University – UNESP, of the Engineering faculty of Guaratingueta.Finally, their thanks go to Tenaris Confab for their support interms of technical and financial resources to ensure that thiswork could take place.

Note

1. Email: emoreira@confab.com.br

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3. Ewert U, Zscherpel U, Bavendiek K. Strategies for filmreplacement in radiography – a comparative study. IV Pan-American Conference on Non Destructive Testing; BuenosAires, October 2007.

4. Mango S. How to evaluate the radiographic performance andlong-term stability of a computed radiography system. IVPan-American Conference on Non Destructive Testing;Buenos Aires, October 2007.

5. Diamond A. Stationary & portable use of a-Si Flat panels inNDT industries. http://www.ndt.net the NDT Database &Journal, ISSN: 1435-4934, ECNDT November 2006.

6. American Society for Testing and Materials, ASTM and1815. Classification of film systems for industrial Radiogra-phy, 2006. p. 6.

7. Deutsche Institute for Normalization, DIN 54109. Non-Destructive testing – Image quality of radiographs. Imagequality classes for iron material; 1989. p. 8.

8. Roza J. Development of high resistance pipes with athickness of 19.05 mm. 61st Annual Congress of the ABM;Rio de Janeiro, July 2006.

9. Rocha J. Micro detectors for silicon based on scintillators fordigital radiography. University of the Minho, Guimaraes,Portugal, 2003.

10. Andreucci R. Industrial radiology. 6th Edition; 2003.11. Bavendiek K. Flat panel detector – calibration for a high

SNR, BAM Berlin, 2005.12. American Society for Testing and Materials, ASTM A-751.

Standard test methods, practices, and terminology forchemical analysis of steel products, 2001. p. 5.

13. European Standard, EN 12543. Non destructive testing –characteristics of focal spots in industrial X-ray systems foruse in non destructive testing – Part 1 Scanning method1999. p. 12.

14. British Standard, BS EN-462-5. Non-destructive testing –Image quality of radiographs Part 5 Image quality indicators(duplex wire type), determination of image and sharpnessvalue, 1996. p. 10.

Figure 18. Radiographic sensitivity shown by the differentradiographic techniques studied.

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