EN ISO 17636-2:2013

SLOVENSKI STANDARD
01-september-2013
1DGRPHãþD
SIST EN 1435:1998
SIST EN 1435:1998/A1:2003
SIST EN 1435:1998/A2:2004
Neporušitvene preiskave zvarnih spojev - Radiografske preiskave - 2. del : X- in
gama žarki z uporabo digitalnih detektorjev (ISO 17636-2:2013)
Non-destructive testing of welds - Radiographic testing - Part 2: X- and gamma-ray
techniques with digital detectors (ISO 17636-2:2013)
Zerstörungsfreie Prüfung von Schweißverbindungen - Durchstrahlungsprüfung - Teil 2:
Röntgen­ und Gammastrahlungstechniken unter Anwendung digitaler Detektoren (ISO
17636-2:2013)
Contrôle non destructif des assemblages soudés - Contrôle par radiographie - Partie 2:
Techniques par rayons X ou gamma à l'aide de détecteurs numériquess (ISO 17636-
2:2013)
Ta slovenski standard je istoveten z: EN ISO 17636-2:2013
ICS:
25.160.40 Varjeni spoji in vari Welded joints
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 17636-2
NORME EUROPÉENNE
EUROPÄISCHE NORM
January 2013
ICS 25.160.40 Supersedes EN 1435:1997
English Version
Non-destructive testing of welds - Radiographic testing - Part 2:
X- and gamma-ray techniques with digital detectors (ISO 17636-
2:2013)
Contrôle non destructif des assemblages soudés - Contrôle Zerstörungsfreie Prüfung von Schweißverbindungen -
par radiographie - Partie 2: Techniques par rayons X ou Durchstrahlungsprüfung - Teil 2: Röntgen- und
gamma à l'aide de détecteurs numériquess (ISO 17636- Gammastrahlungstechniken mit digitalen Detektoren (ISO
2:2013) 17636-2:2013)
This European Standard was approved by CEN on 14 December 2012.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same
status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United
Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2013 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 17636-2:2013: E
worldwide for CEN national Members.

Contents Page
Foreword .3
Foreword
This document (EN ISO 17636-2:2013) has been prepared by Technical Committee CEN/TC 121 “Welding”
the secretariat of which is held by DIN, in collaboration with Technical Committee ISO/TC 44 "Welding and
allied processes".
This European Standard shall be given the status of a national standard, either by publication of an identical
text or by endorsement, at the latest by July 2013, and conflicting national standards shall be withdrawn at the
latest by July 2013.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN 1435:1997.
According to the CEN/CENELEC Internal Regulations, the national standards organisations of the following
countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech
Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece,
Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.
INTERNATIONAL ISO
STANDARD 17636-2
First edition
2013-01-15
Non-destructive testing of welds —
Radiographic testing —
Part 2:
X- and gamma-ray techniques with digital
detectors
Contrôle non destructif des assemblages soudés — Contrôle par
radiographie —
Partie 2: Techniques par rayons X ou gamma à l'aide de détecteurs
numériques
Reference number
ISO 17636-2:2013(E)
©
ISO 2013
ISO 17636-2:2013(E)
©  ISO 2013
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
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Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
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Published in Switzerland
ii © ISO 2013 – All rights reserved

ISO 17636-2:2013(E)
Contents Page
Foreword . iv
Introduction . v
1  Scope . 1
2  Normative references . 1
3  Terms and definitions . 2
4  Symbols and terms . 5
5  Classification of radiographic techniques . 6
6  General . 7
6.1  Protection against ionizing radiation . 7
6.2  Surface preparation and stage of manufacture . 7
6.3  Location of the weld in the radiograph . 8
6.4  Identification of radiographs . 8
6.5  Marking . 8
6.6  Overlap of digital images . 8
6.7  Types and positions of image quality indicators (IQI) . 8
6.8  Minimum image quality values . 9
6.9  Personnel qualification . 10
7  Recommended techniques for making digital radiographs . 10
7.1  Test arrangements . 10
7.2  Choice of tube voltage and radiation source . 16
7.3  Detector systems and metal screens . 18
7.4  Alignment of beam . 20
7.5  Reduction of scattered radiation . 20
7.6  Source-to-object distance . 22
7.7  Geometric magnification technique . 25
7.8  Maximum area for a single exposure . 26
7.9  Processing . 26
7.10  Monitor viewing conditions and storage of digital radiographs . 27
8  Examination report . 28
Annex A (normative) Recommended number of exposures which give an acceptable examination
of a circumferential butt weld . 30
Annex B (normative) Minimum image quality values . 35
Annex C (normative) Determination of basic spatial resolution . 41
Annex D (normative) Determination of minimum grey values for CR practice . 45
Annex E (informative) Grey values, general remarks . 50
Bibliography . 52

ISO 17636-2:2013(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 17636-2 was prepared by the European Committee for Standardization (CEN) in collaboration with ISO
Technical Committee TC 44, Welding and allied processes, Subcommittee SC 5, Testing and inspection of
welds in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
This first edition, together with ISO 17636-1, cancels and replaces ISO 17636:2003, of which it constitutes a
technical revision.
ISO 17636 consists of the following parts, under the general title Non-destructive testing of welds —
Radiographic testing:
 Part 1: X- and gamma-ray techniques with film
 Part 2: X- and gamma-ray techniques with digital detectors
The main changes are that:
 the normative references have been updated;
 the document has been divided into two parts — this part of ISO 17636 is applicable to radiographic
testing with digital detectors;
 X-ray devices up to 1 000 kV have been included;
 Annex C on determination of basic spatial resolution has been added;
 Annex D on determination of minimum grey values for CR practice has been introduced;
 Annex E with general remarks on grey values has been added;
 the text has been editorially revised.
Requests for official interpretations of any aspect of this part of ISO 17636 should be directed to the
Secretariat of ISO/TC 44/SC 5 via your national standards body. A complete listing of these bodies can be
found at www.iso.org.
iv © ISO 2013 – All rights reserved

ISO 17636-2:2013(E)
Introduction
This International Standard specifies fundamental techniques of radiography with the object of enabling
satisfactory and repeatable results to be obtained economically. The techniques are based on generally
recognized practice and fundamental theory of the subject, inspection of fusion welded joints with digital
radiographic detectors.
Digital detectors provide a digital grey value image which can be viewed and evaluated with a computer only.
The practice describes the recommended procedure for detector selection and radiographic practice.
Selection of computer, software, monitor, printer and viewing conditions are important but are not the main
focus of this part of ISO 17636.
The procedure specified in this part of ISO 17636 provides the minimum requirements and practice which
permits exposure and acquisition of digital radiographs with equivalent sensitivity for detection of
imperfections as film radiography, specified in ISO 17636-1.

INTERNATIONAL STANDARD ISO 17636-2:2013(E)

Non-destructive testing of welds — Radiographic testing —
Part 2:
X- and gamma-ray techniques with digital detectors
1 Scope
This part of ISO 17636 specifies fundamental techniques of digital radiography with the object of enabling
satisfactory and repeatable results to be obtained economically. The techniques are based on generally
recognized practice and fundamental theory of the subject.
This part of ISO 17636 applies to the digital radiographic examination of fusion welded joints in metallic
materials. It applies to the joints of plates and pipes. Besides its conventional meaning, “pipe”, as used in this
International Standard, covers other cylindrical bodies such as tubes, penstocks, boiler drums, and pressure
vessels.
[6]
NOTE This part of ISO 17636 complies with EN 14784-2.
This part of ISO 17636 specifies the requirements for digital radiographic X- and gamma-ray testing by either
computed radiography (CR) or radiography with digital detector arrays (DDA) of the welded joints of metallic
plates and tubes for the detection of imperfections.
Digital detectors provide a digital grey value (GV) image which can be viewed and evaluated using a computer.
This part of ISO 17636 specifies the recommended procedure for detector selection and radiographic practice.
Selection of computer, software, monitor, printer and viewing conditions are important, but are not the main
focus of this part of ISO 17636. The procedure specified in this part of ISO 17636 provides the minimum
requirements for radiographic practice which permit exposure and acquisition of digital radiographs with
equivalent sensitivity for detection of imperfections as film radiography, as specified in ISO 17636-1.
This part of ISO 17636 does not specify acceptance levels for any of the indications found on the digital
radiographs.
If contracting parties apply lower test criteria, it is possible that the quality achieved is significantly lower than
when this part of ISO 17636 is strictly applied.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 5576, Non-destructive testing — Industrial X-ray and gamma-ray radiology — Vocabulary
ISO 9712, Non-destructive testing ------ Qualification and certification of NDT personnel
ISO 16371-1:2011, Non-destructive testing ------ Industrial computed radiography with storage phosphor
imaging plates ------ Part 1: Classification of systems
ISO 17636-2:2013(E)
ISO 19232–1, Non-destructive testing ------ Image quality of radiographs ------ Part 1: Image quality indicators
(wire type) — Determination of image quality value
ISO 19232–2, Non-destructive testing ------ Image quality of radiographs ------ Part 2: Image quality indicators
(step/hole type) — Determination of image quality value
ISO 19232–4, Non-destructive testing ------ Image quality of radiographs ------ Part 4: Experimental evaluation of
image quality values and image quality tables
ISO 19232–5, Non-destructive testing ------ Image quality of radiographs ------ Part 5: Image quality indicators
(duplex wire type) ------ Determination of image unsharpness value
EN 12543 (all parts), Non-destructive testing ------ Characteristics of focal spots in industrial X-ray systems for
use in non-destructive testing
EN 12679, Non-destructive testing ------ Determination of the size of industrial radiographic sources ------
Radiographic method
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 5576 and the following apply.
3.1
computed radiography
CR
storage phosphor imaging plate system
complete system comprising a storage phosphor imaging plate (IP) and a corresponding read-out unit
(scanner or reader), which converts the information from the IP into a digital image
3.2
storage phosphor imaging plate
IP
photostimulable luminescent material capable of storing a latent radiographic image of a material being
examined and, upon stimulation by a source of red light of appropriate wavelength, generates luminescence
proportional to radiation absorbed
NOTE When performing computed radiography, an IP is used in lieu of a film. When establishing techniques related
to source size or focal geometries, the IP is referred to as a detector, i.e. source-to-detector distance (SDD).
3.3
digital detector array system
DDA system
electronic device converting ionizing or penetrating radiation into a discrete array of analogue signals which
are subsequently digitized and transferred to a computer for display as a digital image corresponding to the
radiologic energy pattern imparted upon the input region of the device
3.4
structure noise of imaging plate
structure noise of IP
structure due to inhomogeneities in the sensitive layer (graininess) and surface of an imaging plate
NOTE 1 After scanning of the exposed imaging plate, the inhomogeneities appear as overlaid fixed pattern noise in the
digital image.
NOTE 2 This noise limits the maximum achievable image quality of digital CR images and can be compared with the
graininess in film images.
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ISO 17636-2:2013(E)
3.5
structure noise of digital detector array
structure noise of DDA
structure due to different properties of detector elements (pixels)
NOTE After read-out of the exposed uncalibrated DDA, the inhomogeneities of the DDA appear as overlaid fixed
pattern noise in the digital image. Therefore, all DDAs require, after read-out, a software based calibration (software and
guidelines are provided by the manufacturer). A suitable calibration procedure reduces the structure noise.
3.6
grey value
GV
numeric value of a pixel in a digital image
NOTE This is typically interchangeable with the terms pixel value, detector response, analogue-to-digital unit, and
detector signal.
3.7
linearized grey value
GV
lin
numeric value of a pixel which is directly proportional to the detector exposure dose, having a value of zero if
the detector was not exposed
NOTE This is typically interchangeable with the terms linearized pixel value, and linearized detector signal.
3.8
basic spatial resolution of a digital detector
detector
SR
b
corresponds to half of the measured detector unsharpness in a digital image and corresponds to the effective
pixel size and indicates the smallest geometrical detail, which can be resolved with a digital detector at
magnification equal to one
NOTE 1 For this measurement, the duplex wire IQI is placed directly on the digital detector array or imaging plate.
[13]
NOTE 2 The measurement of unsharpness is described in ISO 19232-5, see also ASTM E2736 and
[8]
ASTM E1000.
3.9
basic spatial resolution of a digital image
image
SR
b
corresponds to half of the measured image unsharpness in a digital image and corresponds to the effective
pixel size and indicates the smallest geometrical detail, which can be resolved in a digital image
NOTE 1 For this measurement, the duplex wire IQI is placed directly on the object (source side).
[13]
NOTE 2 The measurement of unsharpness is described in ISO 19232-5, see also ASTM E2736, and
[8]
ASTM E1000.
3.10
signal-to-noise ratio
SNR
ratio of mean value of the linearized grey values to the standard deviation of the linearized grey values (noise)
in a given region of interest in a digital image
ISO 17636-2:2013(E)
3.11
normalized signal-to-noise ratio
SNR
N
signal-to-noise ratio, SNR, normalized by the basic spatial resolution, SR , as measured directly in the digital
b
image and/or calculated from the measured SNR, SNR , by
measured
88,6μm
SNR SNR
N measured
SR
b
3.12
contrast-to-noise ratio
CNR
ratio of the difference of the mean signal levels between two image areas to the averaged standard deviation
of the signal levels
NOTE The contrast-to-noise ratio describes a component of image quality and depends approximately on the product
of radiographic attenuation coefficient and SNR. In addition to adequate CNR, it is also necessary for a digital radiograph
to possess adequate unsharpness or basic spatial resolution to resolve desired features of interest.
3.13
normalized contrast-to-noise ratio
CNR
N
contrast-to-noise ratio, CNR, normalized by the basic spatial resolution, SR , as measured directly in the
b
digital image and/or calculated from the measured CNR, i.e.
88,6μm
CNR CNR
N
SR
b
3.14
aliasing
artefacts that appear in an image when the spatial frequency of the input is higher than the output is capable
of reproducing
NOTE Aliasing often appears as jagged or stepped sections in a line or as moiré patterns.
3.15
cluster kernel pixel
CKP
bad pixel which does not have five or more good neighbourhood pixels
[11]
NOTE See ASTM E2597 for details on bad pixels and CKP.
3.16
nominal thickness
t
thickness of the parent material only where manufacturing tolerances do not have to be taken into account
3.17
penetration thickness change
t
change of penetrated thickness relative to the nominal thickness due to beam angle
3.18
penetrated thickness
w
thickness of material in the direction of the radiation beam calculated on the basis of the nominal thicknesses
of all penetrated walls
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ISO 17636-2:2013(E)
3.19
object-to-detector distance
b
largest (maximum) distance between the radiation side of the radiographed part of the test object and the
sensitive layer of the detector along the central axis of the radiation beam
3.20
source size
d
size of the radiation source or focal spot size
NOTE See EN 12679 or EN 12543.
3.21
source-to-detector distance
SDD
distance between the source of radiation and the detector, measured in the direction of the beam
NOTE SDD = f  b
where
f source-to-object distance
b object-to-detector distance
3.22
source-to-object distance
f
distance between the source of radiation and the source side of the test object, most distant from the detector,
measured along the central axis of the radiation beam
3.23
external diameter
D
e
nominal external diameter of the pipe
3.24
geometric magnification
v
ratio of source-to-detector distance SDD to source-to-object distance, f
4 Symbols and abbreviated terms
For the purposes of this standard, the symbols given in Table 1 apply.
Table 1 — Symbols and abbreviated terms
Symbol Term
b object-to-detector distance
b’ object-to-detector distance perpendicular to test object
d source size, focal spot size
D external diameter
e
f source-to-object distance
f ′ source-to-object distance perpendicular to test object
SNR signal-to-noise ratio
ISO 17636-2:2013(E)
SNR normalized signal-to-noise ratio
N
t nominal thickness
t penetration thickness change
u geometric unsharpness
G
u inherent unsharpness of the detector system, excluding any geometric unsharpness, measured from
i
the digital image with a duplex wire IQI adjacent to the detector
u required image unsharpness measured in the digital image at the object plane with a duplex wire IQI
im
u total image unsharpness, including geometric unsharpness, measured in the digital image at the
T
detector plane with a duplex wire IQI at the object plane
v geometric magnification
w penetrated thickness
CKP cluster kernel pixel
CNR contrast-to-noise ratio
CNR normalized contrast-to-noise ratio
N
CR computed radiography
D detector
DDA digital detector array
IP storage phosphor imaging plate
IQI image quality indicator
S radiation source
SDD source-to detector-distance
SR basic spatial resolution as determined with a duplex wire IQI adjacent to the detector
b
detector
SR basic spatial resolution of a digital detector
b
image
SR basic spatial resolution as determined with a duplex wire IQI on the source side of the object
b
5 Classification of radiographic techniques and compensation principles
5.1 Classification
The radiographic techniques are divided into two classes:
 Class A: basic techniques;
 Class B: improved techniques.
Class B techniques are used when class A might be insufficiently sensitive.
Better techniques compared to class B are possible and may be agreed between the contracting parties by
specification of all appropriate test parameters.
The choice of digital radiographic technique shall be agreed between the contracting parties.
Nevertheless, the visibility of flaws using film radiography or digital radiography is equivalent when using class
A and class B techniques, respectively. The visibility shall be proven by the use of IQIs according to
ISO 19232-1 or ISO 19232-2 and ISO 19232-5.
If, for technical reasons, it is not possible to meet one of the conditions specified for class B, such as the type
of radiation source or the source-to-object distance, f, it may be agreed between the contracting parties that
6 © ISO 2013 – All rights reserved

ISO 17636-2:2013(E)
the condition selected may be that specified for class A. The loss of sensitivity shall be compensated by an
increase of minimum grey value and SNR for CR or SNR for the DDA-technique (recommended increase of
N N
SNR by a factor >1,4). Because of the better sensitivity compared to class A, the test specimen may be
N
regarded as being examined to class B, if the correct IQI sensitivity is achieved. This does not apply if the
special SDD reduction as described in 7.6 for test arrangements 7.1.4 and 7.1.5 are used.
5.2 Compensation principles, CP I, CP II or CP III
5.2.1 General. Three rules (see 5.2.2 to 5.2.4) are applied in this part of ISO 17636 for radiography with
digital detectors to achieve a sufficient contrast sensitivity.
Application of these rules requires the achievement of a minimum contrast-to-noise ratio, CNR , normalized to
N
the detector basic spatial resolution per detectable material thickness difference w. If the required normalized
contrast-to-noise ratio (CNR per w) cannot be achieved due to an insufficient value of one of the following
N
parameters, this can be compensated by an increase in the SNR.
5.2.2 CP I. Compensation for reduced contrast (e.g. by increased tube voltage) by increased SNR (e.g. by
increased tube current or exposure time).
5.2.3 CP II. Compensation for insufficient detector sharpness (the value of SR higher than specified) by
b
increased SNR (increase in the single IQI wire or step hole value for each missing duplex wire pair value).
5.2.4 CP III. Compensation for increased local interpolation unsharpness, due to bad pixel correction for
DDAs, by increased SNR.
5.2.5 Theoretical background. These compensation principles are based on the following approximation
for small flaw sizes (w << w):
µ SNR
CNR
N eff
 c
w SR
b
where
c is a constant;
µ is the effective attenuation coefficient, which is equivalent to the specific material contrast;
eff
CNR is the normalized CNR, as measured in the digital image.
N
6 General preparations and requirements
6.1 Protection against ionizing radiation
WARNING — Exposure of any part of the human body to X-rays or gamma-rays can be highly
injurious to health. Wherever X-ray equipment or radioactive sources are in use, appropriate legal
requirements shall be applied.
Local or national or international safety precautions when using ionizing radiation shall be strictly applied.
6.2 Surface preparation and stage of manufacture
In general, surface preparation is not necessary, but where surface imperfections or coatings can cause
difficulty in detecting defects, the surface shall be ground smooth or the coatings shall be removed.
Unless otherwise specified, digital radiography shall be carried out after the final stage of manufacture, e.g.
after grinding or heat treatment.
ISO 17636-2:2013(E)
6.3 Location of the weld in the radiograph
Where the digital radiograph does not show the weld, high density markers shall be placed on either side of
the weld.
6.4 Identification of radiographs
Symbols shall be affixed to each section of the object being digitally radiographed. The images of these
symbols shall appear in the digital radiograph outside the region of interest where possible and shall ensure
unambiguous identification of the section.
6.5 Marking
Permanent markings on the object to be examined shall be made in order to accurately locate the position of
each digital radiograph (e.g. zero point, direction, identification, measure).
Where the nature of the material and/or its service conditions do not permit permanent marking, the location
may be recorded by means of accurate sketches or photographs.
6.6 Overlap of digital images
When digitally radiographing an area with two or more separate detectors (imaging plates), they shall overlap
sufficiently to ensure that the complete region of interest is digitally radiographed. This shall be verified by a
high density marker on the surface of the object which is to appear on each digital image. If the radiographs
are taken sequentially, the high density marker shall be visible on each of the radiographs.
6.7 Types and positions of image quality indicators
The quality of image shall be verified by use of image quality indicators (IQIs) in accordance with ISO 19232-5
and ISO 19232-1 or ISO 19232-2.
Following the procedure outlined in Annex C, a reference image is required for the verification of the basic
spatial resolution of the digital detector system. The basic spatial resolution or duplex wire value shall be
determined to verify whether the system hardware meets the requirements specified as a function of the
penetrated material thickness in Tables B.13 and B.14. In this case, the duplex wire IQI shall be positioned
directly on the digital detector. The use of a duplex wire IQI (ISO 19232-5) for production radiographs is not
compulsory. The requirement for using a duplex wire IQI additionally to a single wire IQI for production
radiographs may be part of the agreement between the contracting parties. For use on production radiographs,
the duplex wire IQI shall be positioned on the object. The measured basic spatial resolution of the digital
image
image ( SR ) (see Annex C), shall not exceed the maximum values specified as a function of the
b
penetrated material thickness (Tables B.13 or B.14). For single image inspection, the single wall thickness is
taken as the penetrated material thickness. For double wall double image inspection (Figures 11 or 12), with
the duplex wire on the source side of the pipe, the penetrated material thickness is taken as the pipe diameter
image
for determination of the required basic spatial resolution ( SR ) from Tables B.13 and B.14. The basic
b
detector
spatial resolution of the detector ( SR ) for double wall double image inspection shall correspond to the
b
values of Tables B.13 and B.14 chosen on the basis of twice the nominal single wall thickness as the
penetrated material thickness.
If the geometric magnification technique (see 7.7) is applied with v  1,2, then the duplex wire IQI (ISO 19232-
5) shall be used on all production radiographs.
The duplex wire IQI shall be positioned tilted by a few degrees (2° to 5°) to the digital rows or columns of the
digital image. If the IQI is positioned at 45° to the digital lines or rows the obtained IQI number shall be
reduced by one.
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ISO 17636-2:2013(E)
The contrast sensitivity of digital images shall be verified by use of IQIs, in accordance with the specific
application as given in Tables B.1 to B.12 (see also ISO 19232-1 or ISO 19232-2).
The single wire or step hole IQIs used shall be placed preferably on the source side of the test object at the
centre of the area of interest on the parent metal beside the weld. The IQI shall be in close contact with the
surface of the object. Its location shall be in a section of uniform thickness characterized by a uniform grey
value (mean) in the digital image.
According to the IQI type used, cases a) and b) shall be considered.
a) When using a single wire IQI, the wires shall be directed perpendicular to the weld and its location shall
ensure that at least 10 mm of the wire length shows in a section of uniform grey value or SNR , which is
N
normally in the parent metal adjacent to the weld. For exposures in accordance with 7.1.6 and 7.1.7, the
IQI can be placed with the wires across the pipe axis and they should not be projected into the image of
the weld.
b) When using a step hole IQI, it shall be placed in such a way that the hole number required is placed close
to the weld.
For exposures in accordance with 7.1.6 and 7.1.7, the IQI type used can be placed either on the source or on
the detector side. If the IQIs cannot be placed in accordance with the above conditions, the IQIs are placed on
the detector side and the image quality shall be determined at least once from comparison exposure with one
IQI placed at the source side and one at the detector side under the same conditions. If filters are used in front
of the detector, the IQI shall be placed in front of the filter.
For double wall exposures, when the IQI is placed on the detector side, the above test is not necessary. In this
case, refer to the correspondence tables (Tables B.9 to B.14).
Where the IQIs are placed on the detector side, the letter F shall be placed near the IQI and it shall be stated
in the test report.
The identification numbers and, when used, the lead letter F, shall not be in the area of interest, except when
geometric configuration makes it impractical.
If steps have been taken to guarantee that digital radiographs of similar test objects and regions are produced
with identical exposure and processing techniques, and no differences in the image quality value are likely,
the image quality need not be verified for every digital radiograph. The extent of image quality verification
should be subject to agreement between the contracting parties.
For exposures of pipes with diameter 200 mm and above with the source centrally located at least three IQIs
should be placed equally spaced at the circumference. The IQI images are then considered representative for
the whole circumference.
6.8 Minimum image quality values
Tables B.1 to B.14 show the minimum quality values for metallic materials. For other materials these
requirements or corresponding requirements may be agreed upon by contracting parties. The requirements
shall be determined in accordance with ISO 19232-4.
In the case where Ir 192 or Se 75 sources are used, IQI values worse than the ones listed in Tables B.1 to
B.12 may be accepted by agreement of contracting parties as follows:
Double wall, double image techniques, both class A and B (w  2t):
 10 mm  w  25 mm 1 wire or step hole value less for Ir 192;
 5 mm  w  12 mm 1 wire or step hole value less for Se 75.
ISO 17636-2:2013(E)
Single wall single image and double wall single image techniques, class A:
 10 mm  w  24 mm 2 wire or step hole values less for Ir 192;
 24 mm  w  30 mm 1 wire or step hole value less for Ir 192;
 5 mm  w  24 mm 1 wire or step hole value less for Se 75.
Single wall single image and double wall single image techniques, class B:
 10 mm  w  40 mm 1 wire or step hole value less for Ir 192;
 5 mm  w  20 mm 1 wire or step hole value less for Se 75.
6.9 Personnel qualification
Personnel performing non-destructive examination in accordance with this part of ISO 17636 shall be qualified
in accordance with ISO 9712 or equivalent to an appropriate level in the relevant industrial sector. The
personnel shall be able to prove they have undergone additional training and qualification in digital industrial
radiology.
7 Recommended techniques for making digital radiographs
NOTE Unless otherwise explained, definitions of the symbols used in Figures 1 to 21 can be found in Clause 4.
7.1 Test arrangements
7.1.1 General
Normally digital radiographic techniques in accordance with 7.1.2 to 7.1.9 shall be used.
The elliptical technique (double wall and double image) in accordance with Figure 11 should not be used for
external diameter D > 100 mm or wall thickness t > 8 mm or weld width >D / 4. Two 90° displaced images
e e
are sufficient if t / D < 0,12, otherwise three images are needed. The distance between the two projected
e
weld images shall be about one weld width.
When it is difficult to carry out an elliptical examination for D  100 mm, the perpendicular technique in
e
accordance with 7.1.7 may be used (see Figure 12). In this case, three exposures 120 ° or 60 ° apart are
required.
For test arrangements in accordance with Figures 11, 13, and 14, the inclination of the beam shall be kept as
small as possible and be such as to prevent superimposition of the two images. The source-to-object distance,
f, shall be kept as small as possible for the technique shown in Figure 13, in accordance with 7.6. The IQI
shall be placed close to the detector with a lead letter F.
Other digital radiographic techniques may be agreed by the contracting parties when it is useful, e.g. for
reasons such as the geometry of the piece or differences in material thickness. In 7.1.9, an example of such a
case is presented. Additionally, thickness compensation with the same material may be applied.
NOTE In Annex A the minimum number of digital radiographs necessary is given in order to obtain an acceptable
radiographic coverage of the total circumference of a butt weld in pipe.
If the geometric magnification technique is not used, the detector shall be placed as close to the object as
possible.
10 © ISO 2013 – All rights reserved

ISO 17636-2:2013(E)
If flexible detectors are not applicable and rigid cassettes or planar digital detector arrays are used as shown
in Figures 2 b), 8 b), 13 b), and 14 b), the source-to-detector distance SDD shall be calculated from the wall
thickness t and the largest distance of the detector to the source side surface of the object b and the focal spot
size or source size d, as specified in 7.6, Formulae (3) and (4).
7.1.2 Radiation source located in front of the object and with the detector at the opposite side
(see Figure 1)
Figure 1 — Test arrangement for plane welds and single wall penetration
7.1.3 Radiation source located outside the object and detector inside (see Figures 2 to 4)

a) with curved detectors b) with planar detectors
Figure 2 — Test arrangement for single wall penetration of curved objects

Figure 3 —Test arrangement for single-wall penetration of curved objects (set-in weld)
ISO 17636-2:2013(E)
Figure 4 —Test arrangement for single wall penetration of curved objects (set-on weld)
7.1.4 Radiation source centrally located inside the object and with the detector outside
(see Figures 5 to 7)
Figure 5 —Test arrangement for single wall penetration of curved objects, planar detectors not
applicable
Figure 6 —Test arrangement for single wall penetration of curved objects (set-in weld)

Figure 7 — Test arrangement for single wall penetration of curved objects (set-on weld)
12 © ISO 2013 – All rights reserved

ISO 17636-2:2013(E)
7.1.5 Radiation source located off-centre inside the object and detector outside (see Figures 8 to 10)

a) with curved detectors b) with planar detectors
Figure 8 — Test arrangement for single wall penetration of curved objects

Figure 9 —Test arrangement for single wall penetration of curved object (set-in weld)

Figure 10 —Test arrangement for single wall penetration of curved objects (set-on weld)
SIST EN
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