prEN ISO 20769-2

SLOVENSKI STANDARD
01-marec-2026
Neporušitvene preiskave - Radiografski pregled korozije in nanosov v ceveh z
rentgenskimi žarki in žarki gama - 2. del: Radiografski pregled dvojnih sten
(ISO/DIS 20769-2:2026)
Non-destructive testing - Radiographic inspection of corrosion and deposits in pipes by
X- and gamma rays - Part 2: Double wall radiographic inspection (ISO/DIS 20769-
2:2026)
Zerstörungsfreie Prüfung - Durchstrahlungsprüfung auf Korrosion und Ablagerungen in
Rohren mit Röntgen- und Gammastrahlen - Teil 2: Doppelwand-Durchstrahlungsprüfung
(ISO/DIS 20769-2:2026)
Essais non destructifs - Examen radiographique de la corrosion et des dépôts dans les
canalisations, par rayons X et rayons gamma - Partie 2: Examen radiographique double
paroi (ISO/DIS 20769-2:2026)
Ta slovenski standard je istoveten z: prEN ISO 20769-2
ICS:
19.100 Neporušitveno preskušanje Non-destructive testing
23.040.01 Deli cevovodov in cevovodi Pipeline components and
na splošno pipelines in general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
International
Standard
ISO/DIS 20769-2
ISO/TC 135/SC 5
Non-destructive testing —
Secretariat: DIN
Radiographic inspection of
Voting begins on:
corrosion and deposits in pipes by
2026-01-07
X- and gamma rays —
Voting terminates on:
2026-04-01
Part 2:
Double wall radiographic inspection
Essais non destructifs — Examen radiographique de la corrosion
et des dépôts dans les canalisations, par rayons X et rayons
gamma —
Partie 2: Examen radiographique double paroi
ICS: 19.100
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS.
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Reference number
ISO/DIS 20769-2:2026(en)
DRAFT
ISO/DIS 20769-2:2026(en)
International
Standard
ISO/DIS 20769-2
ISO/TC 135/SC 5
Non-destructive testing —
Secretariat: DIN
Radiographic inspection of
Voting begins on:
corrosion and deposits in pipes by
X- and gamma rays —
Voting terminates on:
Part 2:
Double wall radiographic inspection
Essais non destructifs — Examen radiographique de la corrosion et
des dépôts dans les canalisations, par rayons X et rayons gamma —
Partie 2: Examen radiographique double paroi
ICS: 19.100
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2026
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
BE CONSIDERED IN THE LIGHT OF THEIR
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
or ISO’s member body in the country of the requester.
NATIONAL REGULATIONS.
ISO copyright office
RECIPIENTS OF THIS DRAFT ARE INVITED
CP 401 • Ch. de Blandonnet 8
TO SUBMIT, WITH THEIR COMMENTS,
CH-1214 Vernier, Geneva
NOTIFICATION OF ANY RELEVANT PATENT
Phone: +41 22 749 01 11
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland Reference number
ISO/DIS 20769-2:2026(en)
ii
ISO/DIS 20769-2:2026(en)
Contents Page
Foreword .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Classification of radiographic techniques . 5
5 General . 6
5.1 Protection against ionizing radiation .6
5.2 Personnel qualification .6
5.3 Identification of radiographs .6
5.4 Marking .6
5.5 Overlap of films or digital images .6
5.6 Types and positions of image quality indicators (IQI) .7
5.6.1 Single wire IQI .7
5.6.2 Duplex wire IQI (digital radiographs).7
6 Recommended techniques for making radiographs . 7
6.1 Test arrangements .7
6.1.1 General .7
6.1.2 Double wall single image (DWSI) .7
6.1.3 Double wall double image (DWDI) .9
6.1.4 Alignment of beam and film/detector .11
6.2 Choice of radiation source .11
6.3 Film systems and screens . 12
6.4 Screens and shielding for imaging plates (computed radiography only) . 13
6.5 Reduction of scattered radiation . 15
6.5.1 Filters and collimators . 15
6.5.2 Interception of back scattered radiation . 15
6.6 Source-to-detector distance . 15
6.6.1 Double wall single image . 15
6.6.2 Double wall double image .16
6.7 Axial coverage and overlap.16
6.8 Circumference coverage .17
6.8.1 General .17
6.8.2 DWSI .17
6.8.3 DWDI .18
6.9 Selection of digital radiographic equipment .18
6.9.1 General .18
6.9.2 CR systems .18
6.9.3 DDA systems . .18
7 Radiograph/digital image sensitivity, quality and evaluation .18
7.1 Minimum image quality values.18
7.1.1 Wire image quality indicators .18
7.1.2 Duplex wire IQIs (digital radiographs) .19
7.1.3 Minimum normalized signal to noise ratio (digital radiographs) .19
7.2 Density of film radiographs .19
7.3 Film processing . 20
7.4 Film viewing conditions . 20
8 Measurement of differences in penetrated thickness .20
8.1 Principle of technique . 20
8.2 Measurement of attenuation coefficient . 20
8.3 Source and detector positioning . .21
8.4 Image grey level profiles .21
8.5 Validation .21

iii
ISO/DIS 20769-2:2026(en)
8.6 Key points .21
9 Digital image recording, storage, processing and viewing .21
9.1 Scan and read out of image .21
9.2 Calibration of DDAs . 22
9.3 Bad pixel interpolation . 22
9.4 Image processing . 22
9.5 Digital image recording and storage . 22
9.6 Monitor viewing conditions . 22
10 Test report .23
Annex A (normative) Minimum image quality values .24
Annex B (normative) Penetrated thickness measurements from image grey levels .26
Bibliography .28

iv
ISO/DIS 20769-2:2026(en)
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.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 135, Non-destructive testing, Subcommittee SC
5, Radiographic testing.
This second edition cancels and replaces the first edition (ISO 20769-2:2018), which has been technically
revised.
The main changes are as follows:
— the normative references and bibliography have been updated;
— limitations on the inspection of complex geometry components are considered;
— editorial updated.
A list of all parts in the ISO 20769 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

v
DRAFT International Standard ISO/DIS 20769-2:2026(en)
Non-destructive testing — Radiographic inspection of
corrosion and deposits in pipes by X- and gamma rays —
Part 2:
Double wall radiographic inspection
1 Scope
This document specifies fundamental techniques of film and 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 document applies to the radiographic examination of pipes in metallic materials for service induced
flaws such as corrosion pitting, generalized corrosion and erosion. Besides its conventional meaning, “pipe”
as used in this document is understood to cover other cylindrical bodies such as tubes, penstocks, boiler
drums and pressure vessels. Complex geometry components such as bends and tees can present additional
challenges that may complicate their inspection by the techniques described in this Standard.
Weld inspection for typical welding process induced flaws is not covered, but weld inspection is included for
corrosion/erosion type flaws.
The pipes can be insulated or not, and can be assessed where loss of material due, for example, to corrosion
or erosion is suspected either internally or externally.
This document covers double wall inspection techniques for detection of wall loss, including double wall
single image (DWSI) and double wall double image (DWDI).
Note that the DWDI technique described in this document is often combined with the tangential technique
covered in ISO 20769-1.
This document applies to in-service double wall radiographic inspection using industrial radiographic film
techniques, computed digital radiography (CR) and digital detector arrays (DDA).
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements 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 16371-1:2011, Non-destructive testing — Industrial computed radiography with storage phosphor imaging
plates — Part 1: Classification of systems
ISO 16371-1, Non-destructive testing — Industrial computed radiography with storage phosphor imaging plates
— Part 1: Classification of systems
ISO 17636-2:2013, Non-destructive testing of welds — Radiographic testing — Part 2: X- and gamma-ray
techniques with digital detectors
ISO 19232-1:2013, Non-destructive testing — Image quality of radiographs — Part 1: Determination of the
image quality value using wire-type image quality indicators
ISO 11699-1, Non-destructive testing — Industrial radiographic film — Part 1: Classification of film systems for
industrial radiography
ISO/DIS 20769-2:2026(en)
ISO 11699-2, Non-destructive testing — Industrial radiographic films — Part 2: Control of film processing by
means of reference values
ISO 17636-2, Non-destructive testing of welds — Radiographic testing — Part 2: X- and gamma-ray techniques
with digital detectors
ISO 19232-1, Non-destructive testing — Image quality of radiographs — Part 1: Determination of the image
quality value using wire-type image quality indicators
ISO 19232-5, Non-destructive testing — Image quality of radiographs — Part 5: Determination of the image
unsharpness and basic spatial resolution value using duplex wire-type image quality indicators
ISO 20769-1, Non-destructive testing — Radiographic inspection of corrosion and deposits in pipes by X- and
gamma rays — Part 1: Tangential radiographic inspection
ISO/TS 25107:2019, Non-destructive testing — NDT training syllabuses
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 20769-1 and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
axial coverage on the detector
L
d
total axial extent of the evaluated section of the pipe radiograph measured on the detector (3.6)
3.2
axial coverage on the pipe central axis
L
p
total axial extent of the evaluated section of the pipe radiograph measured along the central axis of the pipe
3.3
basic spatial resolution of a digital detector
detector
SR
b
half of the measured detector unsharpness in a digital image, which corresponds to the effective pixel size
and indicates the smallest geometrical detail, which can be resolved with a digital detector at a magnification
equal to one
Note 1 to entry: For this measurement, the duplex wire IQI is placed directly on the digital detector array (3.7) or
imaging plate.
[1] [2]
Note 2 to entry: The measurement of unsharpness is described in ISO 19232-5:2018 . See also ASTM E1000 and
[3]
ASTM E2736 .
[SOURCE: ISO 17636-2:2022, 3.8, modified reference for “digital detector array” adapted to this document]
3.4
basic spatial resolution of a digital image
image
SR
b
half of the measured image unsharpness in a digital image, which corresponds to the effective pixel size and
indicates the smallest geometrical detail, which can be resolved in a digital image
Note 1 to entry: For this measurement, the duplex wire IQI is placed directly on the object (source side).
[1] [2]
Note 2 to entry: The measurement of unsharpness is described in ISO 19232-5:2018 . See also ASTM E1000 and
[3]
ASTM E2736 .
ISO/DIS 20769-2:2026(en)
[SOURCE: ISO 17636-2:2022, 3.9]
3.5
computed radiography
CR
complete system comprising a storage phosphor imaging plate (IP) (3.22) and a corresponding read-out unit
(scanner or reader), which converts the information from the IP into a digital image and the control software
of the read-out unit
[SOURCE: ISO 17636-2:2022, 3.1, modified reference for “storage phosphor imaging plate” adapted to this
document and definition supplemented by “and the control software of the read-out unit“]
3.6
detector
D
detection device, consisting of a NDT film system or a digital radiography system using a CR (3.5) system or
a DDA (3.7) system
Note 1 to entry: Film systems and IPs can be used as flexible and curved detectors or in planar cassettes.
[4]
Note 2 to entry: For NDT film system, see ISO 11699-1:2008 .
3.7
digital detector array
DDA
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 and the control software
[SOURCE: ISO 17636-2:2022, 3.3]
3.8
double wall double image technique
DWDI
technique where the radiation source is located outside and away from the pipe, with the detector (3.6)
on the opposite side of the pipe and where the radiograph shows details from both the pipe walls on the
detector and source sides of the pipe
Note 1 to entry: See Figure 3.
3.9
double wall single image technique
DWSI
technique where the radiation source is located outside the pipe and close to the pipe wall, with the detector
(3.6) on the opposite side of the pipe and where the radiograph shows only detail from the pipe wall on the
detector side
Note 1 to entry: See Figure 1.
3.10
nominal wall thickness
t
thickness of the pipe wall as given by the manufacturer, neglecting the manufacturing tolerances

ISO/DIS 20769-2:2026(en)
3.11
normalized signal-to-noise ratio
SNR
N
image
ratio of signal-to-noise, normalized by the basic spatial resolution, SR , (3.4) as measured directly in the
b
digital image and/or calculated from the measured SNR, by:
where
c is a constant (0,088 6 mm);
image
SR is the basic spatial image resolution, in mm.
b
SR image SR detector
Note 1 to entry: can be substituted by (3.3) at magnification equal to 1.
b b
[SOURCE: ISO 17636-2:2022, 3.11, modified: “(3.5) as measured directly in the digital image and/or” is
added and “Note 1 to entry: If the duplex wire IQI is positioned directly on the detector without a test object,
image detector image
SR is equal to the measured SR , which can be used instead of SR .” is changed to “Note 1 to
b b b
image detector
entry: SR can be substituted by SR (3.3) at magnification equal to 1.”]
b b
3.12
object-to-detector distance
b
distance between the radiation side of the test object and the detector surface measured along the central
axis of the radiation beam
3.13
outside diameter
D
e
nominal outer diameter of the pipe as given by the manufacturer, neglecting the manufacturing tolerances
3.14
penetrated thickness
w
thickness of material in the direction of the radiation beam calculated on the basis of the nominal thickness
Note 1 to entry: For double wall radiographic inspection of a pipe, the minimum value for w is twice the pipe wall
thickness. For multiple wall techniques (pipes in pipe or liners), the penetrated thickness is calculated from the
nominal wall thicknesses t.
3.15
pipe centre to detector distance
PDD
distance between the pipe centre and the detector (3.6)
3.16
pixel size
P
geometrical centre-to-centre distance between adjacent pixels in a row (horizontal pitch P ) or column
h
(vertical pitch P ) of the scanned image, the larger of both determines the pixel size P
v
D
Note 1 to entry: The pixel size is the limiting value of the basic spatial resolution SR of the digitization system.
b
[SOURCE: ISO 14096-1:2025, 3.3]
3.17
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
[SOURCE: ISO 17636-2:2022, 3.10]

ISO/DIS 20769-2:2026(en)
3.18
source size
d
size of the radiation source
[SOURCE: ISO 16371-2:2017, 3.15]
3.19
source-to-detector distance
SDD
distance between the source of radiation and the detector (3.6) measured in the direction of the beam
[SOURCE: ISO 17636-2:2022, 3.21, deleted: Note 1 to entry]
3.20
source-to-object distance
f
distance between the source of radiation and the source side of the test object measured along the central
axis of the radiation beam
[SOURCE: ISO 17636-2:2022, 3.22, deleted: Note 1 to entry]
3.21
source-to-pipe centre distance
SPD
distance between the source of radiation and the pipe centre (pipe axis) measured in the direction of the beam
3.22
storage phosphor imaging plate
IP
photostimulable luminescent material capable of storing a latent radiographic image of a material being
examined and which, upon stimulation by a source of red light of appropriate wavelength, generates
luminescence proportional to radiation absorbed
[SOURCE: ISO 17636-2:2022, 3.2, modified “examined” instead of “tested” and deleted Note 1 to entry]
3.23
total effective penetrated thickness
w
tot
total equivalent thickness of metallic material in the direction of the radiation beam calculated on the
basis of the nominal thickness, with allowance for any liquid or other material present in the pipe and any
insulation
4 Classification of radiographic techniques
The double wall radiographic techniques are divided into two classes:
— basic techniques DWA;
— improved techniques DWB.
The basic techniques are intended for double wall radiography of generalized and localized wall loss.
For the basic techniques, DWA, when using Ir 192 sources for pipes with penetrated thicknesses between 15
mm and 35 mm, the sensitivity for detection is high for imperfections, provided their diameters are greater
than or equal to 2 mm and the material loss is typically greater than or equal to 5 % of the pipe penetrated
thickness, in the absence of liquid or other products in the pipe. When using Se 75, the corresponding
detection sensitivity is high for 2 mm diameter or larger imperfections with material loss greater than or
equal to 4 % of the pipe penetrated thickness. The detection sensitivity is improved for flaws with larger
diameters, whereas the presence of liquid or other products, and external insulation, can reduce the

ISO/DIS 20769-2:2026(en)
sensitivity for material loss depending on their properties. Different detection sensitivities may apply for
penetrated thicknesses less than 15 mm and greater than 35 mm.
The presence of external corrosion product can reduce the techniques sensitivity to corrosion due to the
increased radiation attenuation in the product, which can even exceed the reduced attenuation caused by
the loss of steel. Build-up of internal solid material (e.g. scale) in pipes can similarly reduce sensitivity to
internal degradation.
These techniques can also be used for detection of deposits inside the pipe.
The improved techniques should be used where higher sensitivity is required such as for radiography of
fine, localized corrosion pitting.
Further improvements, beyond the improved techniques described herein, are possible and may be agreed
between the contracting parties by specification of all appropriate test parameters.
The choice of radiographic technique shall be agreed between the concerned parties.
5 General
5.1 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 measures shall
be taken to ensure the safety and health of personnel.
5.2 Personnel qualification
Personnel performing non-destructive examination in accordance with this document shall be certified in
radiographic testing in accordance with ISO 9712 or an equivalent internationally or nationally accepted
certification scheme to an appropriate level in the relevant industrial sector. The personnel shall be able
to prove that they have undergone additional training in digital industrial radiology (see Syllabuses in
ISO/TS 25107:2019) if digital detectors are used.
5.3 Identification of radiographs
Symbols shall be affixed to each section of the object being radiographed. The images of these symbols
shall appear in the radiograph outside the region of interest where possible and shall ensure unambiguous
identification of the section.
5.4 Marking
Permanent markings on the object to be examined should be made in order to accurately locate the position
of each radiograph.
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.
5.5 Overlap of films or digital images
When radiographing an area with two or more films or separate detectors, the films or detectors shall
overlap sufficiently to ensure that the complete region of interest is radiographed. This shall be verified by a
high-density marker on the surface of the object which appears on each film or detector. If the radiographs
is taken sequentially, the high-density marker shall be visible on each of the radiographs.

ISO/DIS 20769-2:2026(en)
5.6 Types and positions of image quality indicators (IQI)
5.6.1 Single wire IQI
The quality of image shall be verified by use of IQIs in accordance with ISO 19232-1:2013 .
For DWDI, the single wire IQI used shall be placed preferably on the source side of the test object at the
centre of the area of interest. The IQI shall be in close contact with the surface of the object. If the IQIs cannot
be placed in accordance with the above conditions (insulated pipes), they shall be placed on the detector
side. The image quality shall be determined at least once from a comparison exposure with one IQI placed at
the source side and one at the detector side under the same conditions.
For DWSI, the single wire IQI used shall be placed on the detector side of the test object at the centre of the
area of interest. If possible, the IQI shall be in close contact with the surface of the object. However, if this is
not possible due for example to the presence of insulation, the IQI shall be in contact with the film/detector.
For both DWDI and DWSI, the wire IQIs shall be aligned across the pipe, with their long axis angled at a
few degrees (2° to 5°) to the orthogonal to the pipe axis. The IQI location should be in a section of uniform
thickness, near to the pipe centre line.
For DWDI, where the IQIs are placed at the detector side, the letter “F” shall be placed near the IQI and it
shall be noted in the test report.
The extent of image quality verification for repeat exposures of closely similar objects under identical
conditions shall be subject to agreement between the contracting parties.
5.6.2 Duplex wire IQI (digital radiographs)
IQIs in accordance with ISO 19232-5 should be used for measurement of the basic spatial resolution of the
CR/DDA system in a reference radiograph (see 7.1.2 and ISO 19232-5). The duplex wire IQI shall be placed
on the source side of the imaging plate or detector array and positioned a few degrees tilted (2° to 5°) to the
digital rows or columns of the digital image.
6 Recommended techniques for making radiographs
6.1 Test arrangements
6.1.1 General
Normally, radiographic techniques in accordance with 6.1.2 and 6.1.3 shall be used.
The technique presented in 6.1.2 is normally used for larger diameter pipes. The technique presented in
6.1.3 is generally used for smaller diameter pipes (less than typically about 150 mm outside diameter).
For both techniques, the film or digital detector shall be placed as close to the pipe as possible.
6.1.2 Double wall single image (DWSI)
For this arrangement with curved detectors or film, the source is located near to the pipe and with the film/
detector on the opposite side, as shown in Figure 1 a) (without insulation) and Figure 1 b) (with insulation).
The relevant distances for determination of source to detector distance, SDD (see 6.6), are also shown.

ISO/DIS 20769-2:2026(en)
a) Non-insulated pipe
b) Insulated pipe
Key
1 detector
Figure 1 — Test arrangement for double wall single image radiography (DWSI) using a curved
detector
Note that the wall loss can be located on either the inner diameter, outer diameter or both surfaces of the
pipe wall adjacent to the detector. Wall loss on the source side of the pipe is not imaged.
For rigid planar detectors, DWSI can also be applied as shown in Figure 2 a) and Figure 2 b). Although, with
this arrangement, a smaller fraction of the pipe circumference can be inspected at each position.

ISO/DIS 20769-2:2026(en)
a) Non-insulated pipe
b) Insulated pipe
Key
1 detector
Figure 2 — Test arrangement for double wall single image radiography (DWSI) using a planar
detector
6.1.3 Double wall double image (DWDI)
For this arrangement, the radiation source is located in front of the pipe and with the planar film/detector at
the opposite side, as shown in Figure 3 a) (non-insulated pipe) and Figure 3 b) (insulated pipe).

ISO/DIS 20769-2:2026(en)
a) Non-insulated pipe
b) Insulated pipe
Key
1 detector
Figure 3 — Test arrangement for double wall double image radiography (DWDI)
With DWDI, the wall loss can be located on either the inner diameter, outer diameter or both surfaces of the
pipe, and on either the source or detector side of the pipe.

ISO/DIS 20769-2:2026(en)
If DWDI and tangential radiographic techniques are combined, the requirements of ISO 20769-1 shall
also be met.
6.1.4 Alignment of beam and film/detector
The beam of radiation shall be directed at the centre of the area being examined and should be perpendicular
to the pipe axis.
For DWDI, the film or detector should be aligned to be orthogonal to the centre of the radiation beam.
Modifications to these alignments and the test arrangements given in 6.1.2 and 6.1.3 can be needed in
special cases, due for example to the presence of obstructions.
Other ways of radiographing may be agreed between contracting parties.
6.2 Choice of radiation source
Penetrated thickness ranges for X-ray and gamma ray sources are given in Table 1 and Figure 4. By agreement
between contracting parties, these ranges can be extended.
The maximum X-ray voltages shown in Figure 4 are best practice values for film radiography of welds. If
DDAs with accurate calibration are used, sufficient image quality can still be obtained using higher X-ray
voltages than those shown in Figure 4. For CR applications reduced X-ray voltages by at least 20 % are
recommended in comparison to Figure 4.
In cases where radiographs are produced using gamma rays, the total travel time to position and rewind the
source shall not exceed 10 % of the total exposure time.
By agreement between the contracting parties, the penetrated thickness minimum value for Ir 192 and Se
75 may be reduced to 5 mm of steel.
Table 1 — Total effective penetrated thickness ranges for gamma-ray and high energy X-ray
sources for steel pipes
Total effective penetrated thickness, w
tot
Radiation source mm
basic technique, DWA improved technique, DWB
Yb 169 1 ≤ w ≤ 15
tot
a
Se 75 5 ≤ w ≤ 55 10 ≤ w ≤ 40
tot tot
Ir 192 10 ≤ w ≤ 100 20 ≤ w ≤ 90
tot tot
Co 60 40 ≤ w ≤ 200
tot
X-ray equipment with energy from
30 ≤ w ≤ 200
tot
1 MeV to 4 MeV
X-ray equipment with energy from
w ≥ 50
tot
4 MeV to 12 MeV
X-ray equipment with energy above
w ≥ 80
tot
12 MeV
a
For aluminium and titanium, the penetrated material thickness is 35 mm ≤ w ≤ 120 mm for class DWA and DWB testing.
tot
ISO/DIS 20769-2:2026(en)
Key
1 copper/nickel and alloys
2 steel
3 titanium and alloys
4 aluminium and alloys
w penetrated thickness in mm
U X-ray voltage in kV
Figure 4 — Maximum X-ray voltage for X-ray devices up to 1 000 kV as a function of penetrated
thickness and material
For product filled pipes, the additional radiation attenuation caused by the product shall be allowed for in
the selection of sources. For a water-filled pipe, the penetrated thickness, w, for steel tested with Ir 192 shall
be increased by approximately one-ninth of the path length in the water to calculate w . For an oil-filled
tot
pipe, w shall be increased by approximately one-eleventh of the path length in the oil to calculate w .
tot
For insulated pipes, the additional radiation attenuation caused by the insulation shall be allowed for in the
selection of sources.
6.3 Film systems and screens
For radiographic examination, film system classes shall be used in accordance with ISO 11699-1 .
The radiographic film system class and metal screens for different radiation sources are given in Table 2.
When using metal screens, good contact between films and screens is required. This can be achieved either
by using vacuum-packed films or by applying pressure.

ISO/DIS 20769-2:2026(en)
Table 2 — Film system classes and metal screens for double wall radiography of steel, copper and
nickel based alloy pipes
a
Film system class
Radiation so
...