prEN 12681-2

SLOVENSKI STANDARD
01-oktober-2025
Livarstvo - Radiografsko preskušanje - 2. del: Tehnike z digitalnimi detektorji
Founding - Radiographic testing - Part 2: Techniques with digital detectors
Gießereiwesen - Durchstrahlungsprüfung - Teil 2: Techniken mit digitalen Detektoren
Fonderie - Contrôle par radiographie - Partie 2 : Techniques à l’aide de détecteurs
numériques
Ta slovenski standard je istoveten z: prEN 12681-2
ICS:
77.040.20 Neporušitveno preskušanje Non-destructive testing of
kovin metals
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
EUROPEAN STANDARD
NORME EUROPÉENNE
EUROPÄISCHE NORM
July 2025
ICS 77.040.20 Will supersede EN 12681-2:2017
English Version
Founding - Radiographic testing - Part 2: Techniques with
digital detectors
Fonderie - Contrôle par radiographie - Partie 2 : Gießereiwesen - Durchstrahlungsprüfung - Teil 2:
Techniques à l'aide de détecteurs numériques Techniken mit digitalen Detektoren
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 190.
If this draft becomes a European Standard, 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.

This draft European Standard was established by CEN 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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
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.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 12681-2:2025 E
worldwide for CEN national Members.

Contents Page
European foreword . 4
Introduction . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 7
4 Symbols and abbreviated terms . 12
5 Classification of radiographic techniques and compensation principles . 13
5.1 Classification. 13
5.2 Compensation principles . 14
6 General preparations and requirements . 14
6.1 Protection against ionizing radiation . 14
6.2 Surface preparation and stage of manufacture . 15
6.3 Agreements . 15
6.4 Personnel qualification . 15
7 Test arrangements . 16
7.1 General. 16
7.2 Single wall penetration of plane areas . 16
7.3 Single wall penetration of curved areas . 16
7.4 Double wall penetration of plane and curved areas . 16
7.5 Choice of test arrangements for complex geometries . 17
7.6 Acceptable test area dimensions . 17
8 Choice of tube voltage and radiation source . 21
8.1 X-ray devices up to 1 000 kV . 21
8.2 Other radiation sources . 23
9 Metal screens for IPs and shielding . 24
10 Reduction of scattered radiation . 26
10.1 Metal filters and collimators . 26
10.2 Interception of backscattered radiation . 26
11 Source object and detector position . 27
11.1 General. 27
11.2 Source-to-object distance for magnification < 1,5 . 27
11.3 Conditions for magnification ≥ 1,5 . 30
11.4 Identification of image, test area, detector position plan . 31
12 Data processing . 31
12.1 Scan and read out of image . 31
12.2 Correction of DDAs . 31
12.3 Bad pixel interpolation . 32
12.4 Image processing . 32
13 Monitor viewing conditions and storage of digital images . 32
14 Techniques for increasing the covered thickness range . 33
14.1 General . 33
14.2 Contrast decreasing by higher radiation energy. 34
14.3 Beam hardening . 34
14.4 Thickness equalization . 34
15 Requirements on images . 35
15.1 Identification of images . 35
15.2 Marking of the test areas . 35
15.3 Overlap of digital images . 35
16 Image quality . 35
16.1 Types and positions of image quality indicators (IQI) . 35
16.2 Minimum image quality values. 36
16.3 Minimum normalized signal-to-noise ratio (SNR ) . 36
N
16.4 Compensation principle CP II . 37
16.5 Regular performance verification of digital radiography systems . 37
17 Influence of crystalline structure . 37
18 Acceptances criteria . 38
18.1 General . 38
18.2 Severity levels . 38
18.3 Wall section zones . 38
19 Test report . 39
Annex A (normative) Minimum image quality values . 41
Annex B (normative) Severity levels for steel castings . 45
Annex C (normative) Severity levels for cast iron castings . 48
Annex D (normative) Severity levels for aluminium and magnesium alloy castings . 50
Annex E (normative) Severity levels for titanium and titanium alloy castings. 53
Annex F (informative) Determination of basic spatial resolution . 55
Annex G (normative) Determination of minimum grey values for CR practice . 57
Annex H (informative) Grey values, general remarks (from EN ISO 17636-2:2022, Annex E) . 61
Annex I (informative) Calculation of maximum X-ray tube voltages in Figure 13 . 63
Annex J (informative) Significant technical changes between this document and the
previous edition . 64
Bibliography . 65

European foreword
This document (prEN 12681-2:2025) has been prepared by Technical Committee CEN/TC 190
“Foundry technology”, the secretariat of which is held by DIN.
This document is currently submitted to the CEN Enquiry.
This document will supersede EN 12681-2:2017.
The significant technical changes with respect to EN 12681-2:2017 are given in Annex J.
Introduction
Radiography can be used to detect internal discontinuities in a casting. The discontinuities can be gas
holes, non-metallic inclusions, shrinkage, cracks, inserts or chills or inclusions that have lower or higher
densities than the parent metal. This document gives acceptance criteria through severity levels.
1 Scope
This document gives specific procedures for industrial X-ray and gamma radiography for discontinuity
detection purposes, using NDT (non-destructive testing) digital X-ray image detectors. This part of the
EN 12681 series specifies the requirements for digital radiographic testing by either computed
radiography (CR) or radiography with digital detector arrays (DDA) of castings.
Digital detectors provide a digital grey value image which can be viewed and evaluated using a
computer.
NOTE This part of the EN 12681 series complies with EN 14784-2 for CR. Some clauses and annexes are
taken from EN ISO 17636-2.
This part of the EN 12681 series 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 document. The procedure specified in this document
provides the minimum requirements for radiographic practice which permit exposure and acquisition
of digital images with equivalent sensitivity for detection of imperfections as film radiography, as
specified in EN 12681-1.
This document does not consider radiographic or radioscopic fitness for purpose testing as applied for
specific castings based on manufacturer’s internal requirements and procedures.
The requirements on image quality in testing class A and B testing of Annex A consider the good
workmanship quality for general casting applications as also required in EN 12681-1 for film
radiography.
The testing classes A and B reflect the quality requirements of current automated and semi-
A A
automated radiographic testing systems with DDAs and computer- or operator-based image evaluation,
and mini- or micro-focus tubes (spot size ≤ 1 mm) with reduced requirements to the unsharpness, but
unchanged requirements to contrast sensitivity as also required in EN 12681-1 for film radiography.
The specified procedures are applicable to castings produced by any casting process, especially for
steels, cast irons, aluminium, cobalt, copper, magnesium, nickel, titanium, zinc and any alloys of them.
This document does not apply to:
— the testing of welded joints (see EN ISO 17636-2);
— film radiography (see EN 12681-1);
— real time testing with radioscopy (see EN 13068-1; radioscopy with image intensifiers).
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.
EN 14784-1, Non-destructive testing — Industrial computed radiography with storage phosphor imaging
plates — Part 1: Classification of systems
EN ISO 9712, Non-destructive testing — Qualification and certification of NDT personnel (ISO 9712)
EN ISO 17636-2:2022, Non-destructive testing of welds — Radiographic testing — Part 2: X- and gamma-
ray techniques with digital detectors (ISO 17636-2:2022, Corrected version 2023-02)
EN 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 19232-1)
EN ISO 19232-2, Non-destructive testing — Image quality of radiographs — Part 2: Determination of the
image quality value using step/hole-type image quality indicators (ISO 19232-2)
EN ISO 19232-4, Non-destructive testing — Image quality of radiographs — Part 4: Experimental
evaluation of image quality values and image quality tables (ISO 19232-4)
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
19232-5)
ISO 5576, Non-destructive testing — Industrial X-ray and gamma-ray radiology — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 5576 and EN ISO 17636-2 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
wall thickness
t
thickness as measured on the casting
3.2
nominal wall thickness
t
n
thickness as specified on the drawing
3.3
penetrated thickness
w
thickness of material in the direction of the radiation beam calculated on the basis of the real
thicknesses of all penetrated walls
3.4
source size
d
size of the radiation source or focal spot size
[SOURCE: EN ISO 17636-2:2022, definition 3.20]
3.5
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
[SOURCE: EN ISO 17636-2:2022, definition 3.19]
3.6
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
[SOURCE: EN ISO 17636-2:2022, definition 3.22]
3.7
source-to-detector distance
SDD
distance between the source of radiation and the detector, measured in the direction of the beam
Note 1 to entry: SDD = f + b
where
f source-to-object distance
b object-to-detector distance
[SOURCE: EN ISO 17636-2:2022, definition 3.21]
3.8
geometric magnification
v
ratio of source-to-detector distance SDD to source-to-object distance f
[SOURCE: EN ISO 17636-2:2022, definition 3.24]
3.9
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
[SOURCE: EN ISO 17636-2:2022, definition 3.1]
3.10
storage phosphor imaging plate
IP
photostimulable luminescent material capable of storing a latent radiographic image of a material being
tested and, upon stimulation by a source of red light of appropriate wavelength, generates
luminescence proportional to radiation absorbed
Note 1 to entry: 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).
[SOURCE: EN ISO 17636-2:2022, definition 3.2]
3.11
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
[SOURCE: EN ISO 17636-2:2022, definition 3.3]
3.12
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 to entry: After scanning of the exposed imaging plate the inhomogeneities appear as overlaid fixed pattern
noise in the digital image.
Note 2 to entry: This noise limits the maximum achievable image quality of digital CR images and can be
compared with the graininess in film images.
[SOURCE: EN ISO 17636-2:2022, definition 3.4]
3.13
structure noise of digital detector array
structure noise of DDA
structure due to different properties of detector elements (pixels)
Note 1 to entry: After read out of the exposed uncorrected 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
correction procedure (software and guidelines are provided by the manufacturer). A suitable correction
procedure reduces the structure noise.
[SOURCE: EN ISO 17636-2:2022, definition 3.5]
3.14
grey value
GV
numeric value of a pixel in a digital image
Note 1 to entry: This is typically interchangeable with the terms pixel value, detector response, analogue-to-digital
unit, and detector signal.
[SOURCE: EN ISO 17636-2:2022, definition 3.6]
3.15
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 1 to entry: This is typically interchangeable with the terms linearized pixel value, and linearized detector
signal.
[SOURCE: EN ISO 17636-2:2022, definition 3.7]
3.16
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 to entry: For this measurement, the duplex wire IQI according EN ISO 19232-5 is placed directly on the
digital detector array or imaging plate. The measurement of unsharpness is described in EN ISO 19232-5, see also
ASTM E 2736 and ASTM E 1000.
[SOURCE: EN ISO 17636-2:2022, definition 3.8]
3.17
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 to entry: For this measurement, the duplex wire IQI is placed directly on the object (source side).
Note 2 to entry: The measurement of unsharpness is described in EN ISO 19232-5, see also ASTM E 2736, and
ASTM E 1000.
[SOURCE: EN ISO 17636-2:2022, definition 3.9]
3.18
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
Note 1 to entry: The region of interest shall contain at least 1 100 pixels.
3.19
normalised signal-to-noise ratio
SNR
N
image
SNR, normalised by the basic spatial resolution SR as measured directly in the digital image and/or
b
calculated from measured SNR
image
Note 1 to entry: SNRN = SNR ∙ c / SRb ; c = 0,088 6 mm.
image
Note 2 to entry: SRb is used for images with magnification.
3.20
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 1 to entry: 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.
[SOURCE: EN ISO 17636-2:2022, definition 3.12]
3.21
normalised contrast-to-noise ratio
CNR
N
image
CNR, normalised by the basic spatial resolution SR as measured directly in the digital image and/or
b
calculated from measured CNR
image
Note 1 to entry: CNR = CNR ∙ c / SR ; c = 0,088 6 mm.
N b
3.22
aliasing
artefacts that appear in an image when the spatial frequency of the input is higher than the output is
capable of reproducing
Note 1 to entry: Aliasing often appears as jagged or stepped sections in a line or as moiré patterns.
[SOURCE: EN ISO 17636-2:2022, definition 3.14]
3.23
cluster kernel pixels
CKP
bad pixels which do not have five or more good neighbourhood pixels
Note 1 to entry: See ASTM E 2597/E 2597M for details on bad pixels and CKP.
[SOURCE: EN ISO 17636-2:2022, definition 3.15]
3.24
inherent unsharpness
u
i
unsharpness of the detector system, excluding any geometric unsharpness, measured from the digital
image with a duplex wire IQI adjacent to the detector
detector
Note 1 to entry: ui = 2 ∙ SRb
3.25
image unsharpness
u
im
unsharpness measured in the digital image at the object plane with a duplex wire IQI at this plane too
3.26
total image unsharpness
u
T
including geometric and inherent unsharpness, measured in the digital image at the detector plane with
a duplex wire IQI at the object plane
Note 1 to entry: u is calculated by the following formula:
T
u uu+
T Gi
3.27
geometric unsharpness
u
G
unsharpness measured in the digital image at the detector plane with a duplex wire IQI at the object
plane with a high resolution detector excluding the inherent detector unsharpness
Note 1 to entry: uG is calculated by the following formula:
b
ud×
G
f
4 Symbols and abbreviated terms
For the purposes of this document, the following symbols and abbreviations apply:
w penetrated thickness
t wall thickness
t nominal wall thickness
n
b object-to-detector distance
d source size
f source-to-object distance
f minimum source-to-object distance
min
S source of radiation
D radiographic detector
SDD source-to-detector distance
=
=
v geometric magnification
CR computed radiography
IP storage phosphor imaging plate
DDA digital detector array system
D diagonal size of the detector area
d
GV grey value
GV linearized grey value
lin
IQI image quality indicator
detector
SR basic spatial resolution of a digital detector
b
image
SR basic spatial resolution of a digital image
b
SNR signal-to-noise ratio
SNR normalized signal-to-noise ratio
N
CNR contrast-to-noise ratio
CNR normalized contrast-to-noise ratio
N
u geometric unsharpness
G
CKP cluster kernel pixel
u inherent detector unsharpness.
d
u image unsharpness
im
u total image unsharpness
T
5 Classification of radiographic techniques and compensation principles
5.1 Classification
The radiographic techniques for film replacement are divided into two testing classes:
— Testing class A: basic techniques;
— Testing class B: improved techniques.
The techniques for automated DDA based testing are divided into two testing classes:
— Testing class A : basic automated techniques;
A
— Testing class B : improved automated technique.
A
NOTE Automated DDA based techniques are used in industry for fast testing of castings mainly in serial
production. These automated techniques are not considered as film replacement technique.
It is recommended to perform the testing according to testing class A or A , if not otherwise specified in
A
the order, testing class B or B techniques are used when testing class A or A are insufficiently
A A
sensitive. This document does not cover fitness for purpose testing with IQI requirements different
from Table A.1 to Table A.3.
Automated testing in the testing classes A and B , shall fulfil the contrast sensitivity requirements
A A
(Table A.1 and Table A.2) of testing class A or B, but reduced unsharpness requirements as specified in
Annex A, Table A.4.
If, for technical or industrial reasons, it is not possible to meet one of the conditions specified for testing
class B, such as the energy of radiation source or the source to object distance f, the condition selected
may be what is specified for testing 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 testing class A, the casting may be
N
regarded as being tested to testing class B, if the correct IQI sensitivity is achieved. This does not apply
if the special SDD reduction as specified in Clause 11 for test arrangements Figure 3 and Figure 4 are
used.
5.2 Compensation principles
Three rules to be applied in this document for radiography with digital detectors to achieve sufficient
contrast sensitivity.
This requires achieving a minimum contrast-to-noise ratio, normalized to the detector basic spatial
resolution (CNR ) per detectable material thickness difference Δw. If the required normalized contrast-
N
to-noise ratio (CNR per Δw) cannot be achieved due to an insufficient value of one of the following
N
parameters, this can be compensated by an increase in the signal to noise ratio (SNR):
CP I: Compensation for reduced contrast (e.g. by increased tube voltage) by increased SNR (e.g. by
increased tube current or exposure time).
image
CP II: Compensation for insufficient detector sharpness (the value of SR higher than specified)
b
by increased SNR (increase in the single IQI wire or step hole value for each missing duplex
wire pair value).
CP III: Compensation for increased local interpolation unsharpness, due to bad pixel correction for
DDAs, by increased SNR.
These compensation principles are based on the following approximation for small discontinuity sizes
(Δw < < w), see Formula (1):
CNR µ × SNR
N eff
const× (1)
image
∆w
SR
b
where
μ effective attenuation coefficient, which is equivalent to the specific material contrast;
eff
CNR 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 safety requirements
shall be applied.
NOTE Local, national or international safety precautions are especially important to apply when using
ionizing radiation.
=
6.2 Surface preparation and stage of manufacture
In general, surface preparation is not necessary, but where surface imperfections can cause difficulties
in detecting discontinuities, the surface shall be ground smooth.
NOTE Surface roughness and internal granularity of test objects appear in digital images similar to image
noise. This can hide small discontinuities and reduce the IQI sensitivity.
Unless otherwise specified digital radiography shall be carried out after the final stage of manufacture,
e.g. after grinding or heat treatment.
For some aluminium and magnesium alloy castings, radiography may be carried out before heat
treatment.
6.3 Agreements
Castings with a complex geometry can include areas which cannot be tested by radiography or can only
be partly tested. Such areas shall be identified before starting the radiographic testing. Areas which
cannot be tested by radiography shall be noted by all contracting parties and be marked on the
exposure plan.
The following items shall be as agreed at the time of order:
a) manufacturing stage;
b) extent of radiographic testing;
c) test areas;
d) surface condition;
e) testing class;
f) information about the detector position plan;
g) marking of test areas on the casting;
image detector
h) image quality requirements (IQI wire or step hole, SR , SR , SNR );
b b N
i) marking of the radiographs;
j) acceptance criteria;
k) any additional items;
l) any special requirements, e.g. minimum dimensions of discontinuities to detect.
6.4 Personnel qualification
Unless otherwise agreed, testing shall be performed by personnel, qualified in accordance with
EN 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
radiography.
7 Test arrangements
7.1 General
For CR systems, the test arrangements to be used shall be in accordance with:
— Figure 1 to Figure 4 for test areas of single wall penetration
— Figure 5 to Figure 7 for double wall penetration;
— Figure 8 to Figure 12 for test areas of complex section.
If these arrangements are not applicable, other arrangements may be used.
For DDA systems, the test arrangements to be used shall be in accordance with:
— Figure 1, Figure 2 b), Figure 3 b) for single wall penetration;
— Figure 5 to Figure 7 for double wall penetration;
— Figure 8 to Figure 12 for test areas of complex section.
If these arrangements are not applicable, other arrangements may be used.
With DDA systems, often a geometric magnification technique is employed. Figure 4 for central
panoramic projection is not applicable for DDAs. Alternatively a scanning line detector array or a
scanning multi line DDA may be used.
7.2 Single wall penetration of plane areas
The test arrangement for single wall penetration of plane areas shall be in accordance with Figure 1.
7.3 Single wall penetration of curved areas
The test arrangement for single wall penetration of curved areas shall be in accordance with either
Figure 2, Figure 3 or Figure 4.
NOTE Rigid detectors or IPs in cassettes can be used if the corresponding increase of b is considered for the
calculation of the distance f between the source and source side of the test object (see 11.1).
7.4 Double wall penetration of plane and curved areas
The test arrangement for double wall penetration of plane and curved areas shall be in accordance with
either Figure 5, Figure 6 or Figure 7.
In the case of test arrangements according to Figure 5, the distance of the source from the surface of the
test area shall be minimized provided that the requirements of IQI and unsharpness are met.
In the case of test arrangements according to Figure 6 and Figure 7, the discontinuities shall be
classified with reference to the single wall thickness. In the case of different wall thicknesses the
reference shall be the smaller one.
Double wall penetration shall be used, as an overview technique according to Figure 7, if the
geometrical conditions make other test arrangements difficult to apply or if there is a better sensitivity
for detecting discontinuities by using this technique. It shall be ensured that unacceptable
discontinuities are detected with sufficient certainty. The required image quality shall be met.
7.5 Choice of test arrangements for complex geometries
Unless otherwise agreed, the test arrangements for complex geometry areas shall be in accordance with
Figure 8 to Figure 12 (as appropriate).
7.6 Acceptable test area dimensions
The test area to be captured with one radiographic image should be limited in a way that the required
minimum SNR values (see Table 3 and Table 4) or minimum grey values (CR only, see Annex G) is met
N
in the region of interest.
In addition to the requirements above, the angle of incident radiation in the entire region of interest
shall not exceed 30°.
NOTE This value can be larger, if special orientations of discontinuities can be detected in this way or if it is
the only way to test areas otherwise impossible to test.

Figure 1 — Test arrangement for single wall penetration of plane areas

a) with flexible detectors b) with rigid detectors
Figure 2 — Test arrangement for single wall penetration of curved areas with the source on the
convex side and the detector on the concave side of the test area
a) with flexible detectors b) with rigid detectors
Figure 3 — Test arrangement for single wall penetration of curved areas with eccentric
positioning of the source on the concave side and the detector on the convex side of the test area

Figure 4 — Test arrangement for single wall penetration of curved areas with central
positioning of the source on the concave side and the detector on the convex side of the test area,
not for rigid detectors
Figure 5 — Test arrangement for double wall penetration of plane or curved test areas; source
and detector outside the test area, only the detector side wall imaged for evaluation
Figure 6 — Test arrangement for double wall penetration of plane or curved test areas; several
exposures; source and detector outside of the test area; both walls imaged for evaluation

Figure 7 — Test arrangement for double wall penetration of plane or curved test areas;
overview exposure; source and detector outside of the test area; both walls imaged for
evaluation
a) standard arrangement b) alternative arrangement
b) should only be used if a) is not possible.
Figure 8 — Examples for edges and flanges
a) standard arrangement b) alternative arrangement
b) should only be used if a) is not possible.
Figure 9 — Examples for ribs
Figure 10 — Example for crosslike geometries
Figure 11 — Example for wedge geometries

a) for supports b) for ribs
Figure 12 — Example for ribs and supports
8 Choice of tube voltage and radiation source
8.1 X-ray devices up to 1 000 kV
To maintain good detection sensitivity, the X-ray tube voltage should be as low as possible and the SNR
N
in the digital image should be as high as possible. Recommended maximum values of X-ray tube voltage
versus penetrated thickness are given in Figure 13. These maximum values are best practice values for
film radiography.
After accurate correction, DDAs can provide sufficient image quality at significantly higher voltages
than those shown in Figure 13.
Imaging plates with high structure noise in the sensitive IP layer (coarse grained) should be applied
with about 20 % less X-ray voltage than indicated in Figure 13 for testing class B testing. High definition
imaging plates, which are exposed similarly to X-ray films and having low structure noise (fine grained)
can be exposed with the X-ray voltages of Figure 13 or significantly higher if the SNR is sufficiently
N
increased.
NOTE Compensation principle I (CP I).
An improvement in contrast sensitivity can be achieved by:
—   an increase in contrast at constant SNR [by reduction of tube voltage and compensation by higher exposure
N
(e.g. mA⋅min)];
—   an increase in SNRN [by higher exposure (e.g. mA⋅min)] at constant contrast (constant tube voltage).
Increased tube voltage [at a constant exposure (e.g. mA⋅min)] reduces the contrast and increases the
SNR . The contrast sensitivity improves if the increase in SNR is higher than the contrast reduction due
N N
to the higher energy.
Key
1 copper/nickel and alloys 4 aluminium and alloys
2 steels and cast irons w penetrated thickness in mm
3 titanium and alloys U X-ray voltage (potential) in kV
Figure 13 — Recommended X-ray voltage U for X-ray devices up to 1 000 kV as a function of
penetrated thickness w and material
NOTE The calculations for the curves in Figure 13 are described in Annex I.
For some casting applications where the thickness changes across the area of test object being
radiographed, a modification of technique with a higher voltage may be used, but it should be noted that
an excessively high tube voltage will lead to a loss of detection sensitivity. If there are different
thicknesses imaged with one exposure, an averaged value of these thicknesses can be used.
8.2 Other radiation sources
The penetrated thickness ranges for gamma ray sources and X-ray potentials higher than 1 MV are
given in Table 2 for steels, cast irons, cobalt, copper and nickel-based alloys.
For testing of aluminium, magnesium, titanium, zinc and their alloys using Se 75, the penetrated
thickness is 35 mm ≤ w ≤ 120 mm for testing class A.
Gamma rays from Se 75, Ir 192 and Co 60 sources will not produce digital images having as good
detection sensitivity as X-rays used with appropriate technique parameters. Because their dose rate of
radiation is lower, the contrast-to-noise ratio is worse with gamma ray sources. However because of the
advantages of gamma ray sources in handling and accessibility, Table 2 gives a range of thicknesses for
which each of these gamma ray sources may be used when the use of X-ray tubes is difficult.
By agreement between the contracting parties, the penetrated material thickness for Ir 192 may be
further reduced to 10 mm.
By agreement between the contracting parties, the penetrated material thickness for Se 75 may be
further reduced for testing class A or testing class B, provided the required image quality as stated in
Clause 16 is achieved.
For certain applications wider material thickness ranges may be permitted, if sufficient image quality
can be achieved.
In cases where digital images are produced by CR using gamma rays, the total travel time to and from
...