prEN ISO 20769-1

SLOVENSKI STANDARD
01-marec-2026
Neporušitvene preiskave - Radiografski pregled korozije in nanosov v ceveh z
rentgenskimi žarki in žarki gama - 1. del: Tangencialni radiografski pregled
(ISO/DIS 20769-1:2026)
Non-destructive testing - Radiographic inspection of corrosion and deposits in pipes by
X- and gamma rays - Part 1: Tangential radiographic inspection (ISO/DIS 20769-1:2026)
Zerstörungsfreie Prüfung - Durchstrahlungsprüfung auf Korrosion und Ablagerungen in
Rohren mit Röntgen- und Gammastrahlen - Teil 1: Tangentiale Durchstrahlungsprüfung
(ISO/DIS 20769-1:2026)
Essais non destructifs - Examen radiographique de la corrosion et des dépôts dans les
canalisations, par rayons X et rayons gamma - Partie 1: Examen radiographique
tangentiel (ISO/DIS 20769-1:2026)
Ta slovenski standard je istoveten z: prEN ISO 20769-1
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 20769-1
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 1:
Tangential radiographic inspection
Essais non destructifs — Examen radiographique de la corrosion
et des dépôts dans les canalisations, par rayons X et rayons
gamma —
Partie 1: Examen radiographique tangentiel
ICS: ISO ics
THIS DOCUMENT IS A DRAFT CIRCULATED
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IS THEREFORE SUBJECT TO CHANGE
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Reference number
ISO/DIS 20769-1:2026(en)
DRAFT
ISO/DIS 20769-1:2026(en)
International
Standard
ISO/DIS 20769-1
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 1:
Tangential radiographic inspection
Essais non destructifs — Examen radiographique de la corrosion et
des dépôts dans les canalisations, par rayons X et rayons gamma —
Partie 1: Examen radiographique tangentiel
ICS: ISO ics
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
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Published in Switzerland Reference number
ISO/DIS 20769-1:2026(en)
ii
ISO/DIS 20769-1:2026(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 . 5
5.1 Protection against ionizing radiation .5
5.2 Personnel qualification .5
5.3 Identification of radiographs .5
5.4 Marking .6
5.5 Overlap of films or digital images .6
5.6 Types and positions of image quality indicators (IQI) .6
5.6.1 Single wire or step hole IQIs . .6
5.6.2 Duplex wire IQI (digital radiographs).6
6 Recommended techniques for making radiographs . 6
6.1 Test arrangements .6
6.1.1 General .6
6.1.2 Radiation source located on the pipe centre line .6
6.1.3 Radiation source located offset from the pipe centre line .8
6.1.4 Alignment of beam and film/detector .9
6.2 Choice of radiation source .9
6.3 Film systems and metal screens .10
6.4 Screens and shielding for imaging plates (computed radiography only) .11
6.5 Reduction of scattered radiation . 12
6.5.1 Filters and collimators . 12
6.5.2 Interception of back scattered radiation . 13
6.6 Source-to-detector distance . 13
6.7 Axial coverage and overlap. 13
6.8 Dimensional comparators .14
6.9 Image saturation and use of lead strips to avoid burn-off .16
6.10 Selection of digital radiographic equipment .16
6.10.1 General .16
6.10.2 CR systems .16
6.10.3 DDA systems . .16
7 Radiograph/digital image sensitivity, quality and evaluation .16
7.1 Evaluation of image quality .16
7.1.1 General .16
7.1.2 Maximum grey level in free beam (digital radiographs) .17
7.1.3 Minimum normalized signal-to-noise ratio (digital radiographs) .17
7.2 Density of film radiographs .17
7.3 Film processing .18
7.4 Film viewing conditions .18
7.5 Dimensional calibration of radiographs or digital images .18
7.5.1 General .18
7.5.2 Measurement of distances in radiographic setup . .19
7.5.3 Measurement of pipe outside diameter . 20
7.5.4 Dimensional comparator . 20
7.6 Wall thickness measurements for film radiographs . 20
7.7 Wall thickness measurements for digital radiographs . 20
7.7.1 Interactive on-screen measurements . 20
7.7.2 Grey-level profile analysis methods .21
7.8 Remaining thickness measurements for degradation . 22
7.8.1 Measurements for internal degradation . 22

iii
ISO/DIS 20769-1:2026(en)
7.8.2 Measurements for external degradation . 23
8 Digital image recording, storage, processing and viewing .25
8.1 Scan and read out of image . 25
8.2 Multi radiograph technique . 25
8.3 Calibration of DDAs . 25
8.4 Bad pixel interpolation . 25
8.5 Image processing . 25
8.6 Digital image recording and storage . 25
8.7 Monitor viewing conditions . 26
9 Test report .26
Annex A (informative) Choice of radiation source for different pipes .28
Annex B (informative) Remaining thickness measurements for internal degradation .29
Annex C (informative) Remaining thickness measurements for external degradation .31
Bibliography .35

iv
ISO/DIS 20769-1:2026(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 20769-1:2018) 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;
— a penetrated thickness limit for high-energy X-rays is given in Table 1;
— the lower limits for filter thicknesses given in Table 4 and Table 5 have been reduced to zero,
— 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 20769-1:2026(en)
Non-destructive testing — Radiographic inspection of
corrosion and deposits in pipes by X- and gamma rays —
Part 1:
Tangential 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 steel pipes 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 can complicate their inspection by the techniques described in this document.
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 the tangential inspection technique for detection and through-wall sizing of wall loss,
including with the source:
a) on the pipe centre line; and
b) offset from pipe centre line by the pipe radius.
This document covers double wall radiography, and note that the double wall double image technique is
often combined with tangential radiography with the source on the pipe centre line.
This document applies to tangential radiographic inspection using industrial radiographic film techniques,
computed 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 9712, Non-destructive testing — Qualification and certification of NDT personnel
ISO 11699-1, Non-destructive testing — Industrial radiographic film — Part 1: Classification of film systems for
industrial radiography
ISO 11699-2, Non-destructive testing — Industrial radiographic films — Part 2: Control of film processing by
means of reference values
ISO 16371-1, Non-destructive testing — Industrial computed radiography with storage phosphor imaging plates
— Part 1: Classification of systems

ISO/DIS 20769-1:2026(en)
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 20769-2, Non-destructive testing — Radiographic inspection of corrosion and deposits in pipes by X- and
gamma rays — Part 2: Double wall radiographic inspection
ISO/TS 25107:2019, Non-destructive testing — NDT training syllabuses
3 Terms and definitions
For the purposes of this document, the following terms and definitions 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
actual wall thickness
t
act
real thickness of the pipe wall which can differ from the nominal thickness
3.2
measured wall thickness
t
meas
thickness of the pipe wall as measured on the radiograph or digital image
3.3
nominal wall thickness
t
thickness of the pipe wall as given by the manufacturer, neglecting the manufacturing tolerances
3.4
axial coverage on the detector
L
d
total axial extent of the evaluated section of the pipe radiograph measured on the detector (3.8)
3.5
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
3.6
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 (3.9) 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]

ISO/DIS 20769-1:2026(en)
3.7
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 .
[SOURCE: ISO 17636-2:2022, 3.9]
3.8
comparator
C
reference object of defined dimension c and material for dimensional calibration of a radiographic image
3.9
computed radiography
CR
complete system comprising a storage phosphor imaging plate (IP) (3.23) 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“]
3.10
detector
D
detection device, consisting of a NDT film system or a digital radiography system using a CR (3.9) system or
a DDA (3.11) 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 .
3.11
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]
3.12
imaged comparator dimension
c′
dimension of the comparator (3.6) measured on the detector (3.8)
3.13
imaged outside diameter
D ′
e
nominal outside diameter of the pipe measured on the detector
3.14
maximum penetrated thickness
w
max
maximum thickness of material for a pipe which occurs for a tangent to the inner pipe surface

ISO/DIS 20769-1:2026(en)
3.15
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, modified: reference for linearized grey values deleted]
3.16
normalized signal-to-noise ratio
SNR
N
image
ratio of signal-to-noise ratio (3.15) , normalized by the basic spatial resolution, SR as measured directly
b
in the 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, mm.
b
image detector
Note 1 to entry: SR can be substituted by SR (3.6) 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 (3.4) at magnification equal to 1.]
b b
3.17
outside diameter
D
e
nominal outer diameter of the pipe as given by the manufacturer, neglecting the manufacturing tolerances
3.18
pipe centre to detector distance
PDD
distance between the pipe centre and the detector (3.8)
3.19
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
v
[5]
[SOURCE: ISO/DIS 14096-1 , 3.3]
3.20
source size
d
size of the radiation source
[SOURCE: ISO 16371-2:2017, 3.15]
3.21
source-to-detector distance
SDD
distance between the source of radiation and the detector (3.8) measured in the direction of the beam
[SOURCE: ISO 17636-2:2022, 3.21, modified, references adapted to this document and Note 1 to entry
deleted]
ISO/DIS 20769-1:2026(en)
3.22
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
3.23
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]
4 Classification of radiographic techniques
The tangential radiographic techniques are divided into two classes:
— class TA, basic techniques;
— class TB, improved techniques.
The basic techniques, class TA, are intended for tangential radiography of generalized wall loss, such as that
due to erosion or large-scale corrosion.
The improved techniques, class TB, should be used for the more demanding tangential radiography of
localized corrosion pitting flaws, which require higher sensitivity for detection and sizing.
Further technique improvements beyond TB 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.

ISO/DIS 20769-1:2026(en)
5.4 Marking
Permanent markings should be made on the object to be examined 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 will appear on each film or detector. If the
radiographs are taken sequentially, the high-density marker shall be visible on each of the radiographs.
5.6 Types and positions of image quality indicators (IQI)
5.6.1 Single wire or step hole IQIs
For tangential radiography, single wire or step hole IQIs are not applicable.
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 7.1.3 and Annex A). The duplex wire IQI shall be placed adjacent
to 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. For both techniques, the
film or digital detector shall be placed as close to the pipe as possible.
6.1.2 Radiation source located on the pipe centre line
For this arrangement, the source is located in front of the pipe and with the film/detector at the opposite
side, as shown in Figure 1. The pipe can be non-insulated [Figure 1 a)] or insulated [Figure 1 b)].

ISO/DIS 20769-1:2026(en)
a) Non-insulated pipe
b) Insulated pipe
Key
1 detector, D
d source size
D imaged outside diameter
e
SDD source-to-detector distance
SPD source-to-pipe centre distance
PDD pipe centre to detector distance
Figure 1 — Test arrangement and distances for tangential radiography with the source on the pipe
centre line
Note that the wall loss can be located on either the inner diameter, outer diameter or both surfaces of the pipe.

ISO/DIS 20769-1:2026(en)
6.1.3 Radiation source located offset from the pipe centre line
For this arrangement, the radiation source is located in front of the pipe and with the film/detector at the
opposite side, as shown in Figure 2 a) (non-insulated pipe) and Figure 2 b) (insulated pipe).
a) Non-insulated pipe
b) Insulated pipe
Key
1 detector, D
d source size
D inaged outside diameter
e
SDD source-to-detector distance
SPD source-to-pipe centre distance
PDD pipe centre to detector distance
Figure 2 — Test arrangement and distances for tangential radiography with the source offset from
the pipe centre line
ISO/DIS 20769-1:2026(en)
In this test arrangement, the source is offset from the pipe centre line, and is aligned with the centre of the
pipe wall, as shown in Figure 2. Note that the wall loss can be located on either the inner diameter, outer
diameter or both surfaces of the pipe.
6.1.4 Alignment of beam and film/detector
The beam of radiation shall be directed at the centre of the area being examined.
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 in6.1.2 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
For tangential radiography, the choice of radiation source should be determined by the maximum penetrated
thickness of the pipe, w , which occurs for the path forming a tangent to the pipe inner diameter, as shown
max
in Figure 3.
Key
1 detector, D
d source size
w maximum penetrated thickness
max
Figure 3 — Maximum penetrated thickness, w , for the tangential technique
max
The maximum penetrated thickness, w , is given by Formula (1):
max
(1)
where
t is the nominal thickness of the pipe;
D is the outside diameter of the pipe.
e
Table 1 gives recommended limits on the maximum penetrated thickness for different radiation sources.
Some forms of insulation (e.g. highly absorbing) can lead to a reduction in the limits on maximum penetrated
thickness, w , given in Table 1.
max
By agreement between the contracting parties, these values may vary provided the position of the inner
diameter edge can be measured with acceptable accuracy on the resulting radiograph/digital image using
the methods described in 7.6 or 7.7.

ISO/DIS 20769-1:2026(en)
Table 1 — Maximum penetrated thickness range for different radiation sources for steel
Radiation source Limits on maximum penetrated thickness,w
max
mm
Basic (for generalized wall loss) Improved (for pitting flaws)
X-ray (100 kV) ≤10 ≤7
X-ray (200 kV) ≤30 ≤20
X-ray (300 kV) ≤40 ≤30
X-ray (400 kV) ≤50 ≤35
X-ray equipment with 6 MeV energy ≤200 -
Se 75 ≤55 ≤40
Ir 192 ≤80 ≤60
Co 60 ≤120 ≤85
For digital radiographs, somewhat higher values for the limits on maximum penetrated thickness than those
given in Table 1 may be used.
To determine the appropriate source(s) for a particular pipe, the maximum penetrated thickness, w ,
max
should be determined using Formula (1) and compared with the values given in Table 1. A graphical
illustration of this procedure is given in Annex B.
To avoid motion unsharpness, in cases where radiographs are produced using gamma rays, the total travel
time of the source to the exposure position and rewind shall not exceed 10 % of the total exposure time.
6.3 Film systems and metal screens
For radiographic examination, film system classes shall be used in accordance with ISO 11699-1.
The radiographic film system class and metal screens to use with films for different radiation sources are
given in Table 2 and Table 3. See also ISO 17636-1:2022, Table 3 and Table 4.
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 20769-1:2026(en)
Table 2 — Film system classes and metal screens for tangential radiography of steel, copper and
nickel based alloy pipes
a
Film system class
Radiation source Type and thickness of metal screens
Class TA Class TB
X-ray potentials
C 5 C 4 0,02 mm to 0,15 mm front and back screens of lead
≤250 kV
b
X-ray potentials 0,1 mm to 0,2 mm front screens of lead
C 5 C 4
>250 kV to 500 kV 0,02 mm to 0,2 mm back screens of lead
X-ray potentials
0,25 mm to 0,7 mm front and back
C 5 C 4
c
screens of steel or copper
>500 kV to 1 000 kV
Se 75
d
C 6 C 5 0,02 mm to 0,2 mm front and back screens of lead
Ir 192
0,25 mm to 0,7 mm front and back screens
Co 60 C 6 C 5
c
of steel or copper
X-ray equipment with ener- 0,25 mm to 0,7 mm front and back screens
C 6 C 5
c
gy from 1 MeV to 4 MeV of steel or copper
d
Up to 1 mm front screen of copper, steel or tantalum
X-ray equipment with ener-
C 6 C 5
Back screen of copper or steel up to 1 mm and
gy above 4 MeV
d
tantalum up to 0,5 mm
a
Better film system classes may also be used.
b
Ready-packed films with a front screen up to 0,03 mm may be used if an additional lead screen of 0,1 mm is placed between
the object and the film.
c
In class TA, 0,5 mm to 2,0 mm screens of lead may also be used.
d
In class TA, lead screens 0,5 mm to 1 mm may be used by agreement between the contracting parties.
Table 3 — Film system classes and metal screens for tangential radiography of aluminium and
titanium pipes
a
Film system class
Radiation source Type and thickness of metal screens
Class TA Class TB
X-ray potentials
None or up to 0,03 mm front and up to 0,15 mm back screens
of lead
≤150 kV
X-ray potentials
b
C 6 C 5 0,02 mm to 0,2 mm front and back screens of lead
>150 kV to 500 kV
Se 75
b
0,02 mm to 0,2 mm front and back screens of lead
Ir 192
a
Better film system classes may also be used.
b
Instead of one 0,2 mm lead screen, two 0,1 mm lead screens may be used.
Different film systems may be used by agreement of the contracting parties, provided the required optical
densities defined in 7.2 are achieved.
6.4 Screens and shielding for imaging plates (computed radiography only)
When using metal front screens, good contact between the sensitive detector layer and screens is required.
This can be achieved either by using vacuum-packed IPs or by applying pressure. Lead screens not in
intimate contact with the IPs can contribute to image unsharpness. The intensification obtained by use of
lead screens in contact with IPs is significantly smaller than in film radiography.
Many IPs are very sensitive to low energy backscatter and X-ray fluorescence of back-shielding from lead.
This effect contributes significantly to edge unsharpness and reduced SNR, and should be minimized. It is
recommended that steel or copper shielding be used directly behind the IPs. Also, a steel or copper shielding
between a backscatter lead plate and the IP can improve the image quality. Modern cassette and detector

ISO/DIS 20769-1:2026(en)
designs can consider this effect and can be constructed in a way such that additional steel or copper shielding
outside the cassette is not required.
NOTE Due to the protection layer between the lead and the sensitive layer of an IP, the effect of intensification by
electrons is considerably reduced and appears at higher energies. Depending on the radiation energy and protection
layer design, the effect of intensification amounts to between 20 % and 100 % only (compared to no screen).
The small intensification effect generated by a lead screen in contact with an IP can be compensated for by
increased exposure time or milliampere. minutes, if no lead screens are used. Since lead screens in contact
with IPs can generate scratches on IPs, if not carefully separated for the scan process, lead screens should be
used for intermediate filtering of scattered radiation outside of cassettes.
Table 4 and Table 5 show the recommended screen materials and thicknesses for different radiation sources.
Other screen thicknesses may be also agreed between the contracting parties. The usage of metal screens is
recommended in front of IPs, and they can also reduce the influence of scattered radiation when used with DDAs.
Table 4 — Metal front screens for CR for tangential radiography of steels, copper and nickel based alloys
Radiation source Type and thickness of metal front screens
mm
a
X-ray potentials ≤250 kV 0 to 0,1 (lead)
a
X-ray potentials >250 kV to 1 000 kV 0 to 0,3 (lead)
Class TA: 0 to 0,3 (lead)
a
Ir 192, Se 75
Class TB: 0 to 0,8 (steel or copper)
b
Co 60 0,3 to 0,8 (steel or copper) + 0,6 to 2,0 (lead)
b
X-ray potentials >1 MV 0,3 to 0,8 (steel or copper) + 0,6 to 2,0 (lead)
a
Pb screens may be replaced completely or partially by Fe or Cu screens. The equivalent thickness for Fe or Cu is three times
the Pb thickness.
b
In the case of multiple screens (steel + lead), the steel screen shall be located between the IP and the lead screen. Instead of
steel or steel and lead screens, those composed of copper, tantalum or tungsten may be used if the image quality can be proven.
Table 5 — Metal front screens for CR for the digital tangential radiography of aluminium and
titanium
Radiation source Type and thickness of metal front screen
...