prEN 12681-1

SLOVENSKI STANDARD
01-oktober-2025
Livarstvo - Radiografsko preskušanje - 1. del: Filmske tehnike
Founding - Radiographic testing - Part 1: Film techniques
Gießereiwesen - Durchstrahlungsprüfung - Teil 1: Filmtechniken
Fonderie - Contrôle par radiographie - Partie 1 : Techniques à l'aide de films
Ta slovenski standard je istoveten z: prEN 12681-1
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 12681-1:2017
English Version
Founding - Radiographic testing - Part 1: Film techniques
Fonderie - Contrôle par radiographie - Partie 1 : Gießereiwesen - Durchstrahlungsprüfung - Teil 1:
Techniques à l'aide de films Filmtechniken
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 12681-1:2025 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 . 8
5 Classification of radiographic techniques . 8
6 General preparations and requirements . 9
6.1 General preparations . 9
6.1.1 Protection against ionizing radiation . 9
6.1.2 Surface preparation and stage of manufacture . 9
6.2 Agreements . 9
6.3 Personnel qualification . 10
7 Test arrangements . 10
7.1 General. 10
7.2 Single wall penetration of plane areas . 10
7.3 Single wall penetration of curved areas . 10
7.4 Double wall penetration of plane and curved areas . 10
7.5 Choice of test arrangements for complex geometries . 10
7.6 Acceptable test area dimensions . 10
8 Choice of tube voltage and radiation source . 16
8.1 X-ray devices up to 1 000 kV . 16
8.2 Other radiation sources . 16
9 Film systems and metal screens . 17
10 Reduction of scattered radiation . 19
10.1 Metal filters and collimators . 19
10.2 Interception of backscattered radiation . 19
11 Source-to-object distance . 19
12 Optical density D of radiograph . 22
13 Film processing and viewing . 22
13.1 Processing. 22
13.2 Film viewing conditions . 23
14 Techniques for increasing the covered thickness range . 23
14.1 General. 23
14.2 Multiple film technique . 24
14.3 Contrast decreasing by higher radiation energy . 24
14.4 Contrast decreasing by beam hardening . 25
14.5 Contrast decreasing by thickness equalization . 25
15 Requirements on radiographs . 25
15.1 Identification of radiograph, test area, film position plan . 25
15.2 Marking of the test areas . 25
15.3 Overlap of films . 25
16 Verification of image quality . 25
17 Influence of crystalline structure . 26
18 Acceptance criteria . 26
18.1 General . 26
18.2 Severity levels . 26
18.3 Wall section zones . 26
19 Test report . 27
Annex A (normative) Minimum image quality values . 29
Annex B (normative) Severity levels for steel castings . 32
Annex C (normative) Severity levels for cast iron castings . 35
Annex D (normative) Severity levels for aluminium alloy and magnesium alloy castings . 38
Annex E (normative) Severity levels for copper alloy castings . 42
Annex F (normative) Severity levels for titanium and titanium alloy castings . 44
Annex G (informative) Significant technical changes between this document and the previous
edition . 46
Annex H (informative) Calculation of maximum X-ray tube voltages in Figure 13 . 47
Bibliography . 48

European foreword
This document (prEN 12681-1:2025) 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 12681-1:2017.
The significant technical changes with respect to EN 12681-1:2017 are given in Annex G.
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) film techniques. This part of the EN 12681 series
specifies the requirements for film radiographic testing of castings.
Films after exposure and processing become radiographs with different area of optical density.
Radiographs are viewed and evaluated using industrial radiographic illuminators.
This part of the EN 12681 series specifies the recommended procedure for the choice of operating
conditions and radiographic practice.
These procedures are applicable to castings produced by any casting process, especially for steel, cast
iron, aluminium, cobalt, copper, magnesium, nickel, titanium, zinc and any alloys of them.
NOTE This document considers EN ISO 5579.
This document does not apply to:
— radiographic testing of castings for aerospace applications (see EN 2002-21);
— radiographic testing of welded joints (see EN ISO 17636-1);
— radiography with digital detectors (see EN 12681-2);
— radioscopic testing (see the EN 13068 series).
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 ISO 5579:2013, Non-destructive testing — Radiographic testing of metallic materials using film and X-
or gamma rays — Basic rules (ISO 5579:2013)
EN ISO 5580, Non-destructive testing — Industrial radiographic illuminators — Minimum requirements
(ISO 5580)
EN ISO 9712, Non-destructive testing — Qualification and certification of NDT personnel (ISO 9712)
EN ISO 11699-1, Non-destructive testing — Industrial radiographic film — Part 1: Classification of film
systems for industrial radiography (ISO 11699-1)
EN ISO 11699-2, Non-destructive testing — Industrial radiographic films — Part 2: Control of film
processing by means of reference values (ISO 11699-2)
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)
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, EN ISO 5579 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 5579:2013, definition 3.4]
3.5
object-to-film distance
b
largest (maximum) distance between the source side of the radiographed part of the test object and the
film surface measured along the central axis of the radiation beam
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 film,
measured along the central axis of the radiation beam
3.7
source-to-film distance
SFD
distance between the source of radiation and the film measured in the direction of the beam
Note 1 to entry: SFD = f + b
where
f source-to-object distance;
b object-to-film distance.
[SOURCE: EN ISO 5579:2013, definition 3.5, modified – description in words presented as formula]
4 Symbols and abbreviated terms
For the purposes of this document, the symbols and abbreviations apply:
b object-to-film distance
d source size
D optical density of film
f source-to-object distance
F film
IQI image quality indicator
S source of radiation
SFD source-to film-distance
t wall thickness
t nominal wall thickness
n
w penetrated thickness
5 Classification of radiographic techniques
The radiographic techniques are divided into two testing classes:
— Testing class A: basic techniques;
— Testing class B: improved techniques.
It is recommended to perform the testing according to testing class A, if not otherwise specified in the
order. Testing class B techniques are used when testing class A techniques are insufficiently sensitive.
If, for technical or industrial reasons, it is not possible to meet one of the conditions specified for testing
class B, such as the type of radiation source or the source-to-object distance f, it can be agreed by
contracting parties that the condition selected may be what is specified for testing class A. In film
radiography the loss of sensitivity shall be compensated by an increase of minimum optical density to 3,0
or by selection of a two class better film system. The other conditions for testing class B remain
unchanged, especially the image quality achieved. Because of the better sensitivity compared to testing
class A, the specimen may be regarded as being tested to testing class B. This does not apply if the special
SFD reductions as specified in Clause 11 for test arrangements Figure 3 and Figure 4 are used.
6 General preparations and requirements
6.1 General preparations
6.1.1 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.
6.1.2 Surface preparation and stage of manufacture
In general, surface preparation is not necessary, but where surface imperfections can cause difficulty in
detecting discontinuities, the surface shall be ground smooth.
Unless otherwise specified radiography shall be carried out after the final stage of manufacture, e.g. after
grinding or heat treatment.
NOTE For some aluminium and magnesium alloy castings, radiography can be carried out before heat
treatment.
6.2 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 film
position plan.
The following items shall be as agreed at the time of order:
a) manufacturing stage at which castings are to be tested;
b) extent of radiographic testing;
c) test areas;
d) surface condition;
e) testing class;
f) information about the film position plan;
g) marking of test areas on the casting;
h) image quality;
i) marking of the radiographs;
j) acceptance criteria;
k) any additional items;
l) any special requirements.
6.3 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.
7 Test arrangements
7.1 General
The test arrangements to be used shall be in accordance with:
Figure 1 to Figure 4: for single wall penetration;
Figure 5 to Figure 7: for double wall penetration;
Figure 8 to Figure 12: for test areas of complex section.
NOTE For an explanation of the symbols in the figures, see Clause 4.
If these arrangements are not applicable, other arrangements 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 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 Clause 11).
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 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 film should be limited in a way that the required
optical density according to Clause 12, Table 4 is met 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 cassette b) with rigid cassette
Figure 2 — Test arrangement for single wall penetration of curved areas with the source on the
convex side and the film on the concave side of the test area
a) with flexible cassette b) with rigid cassette
Figure 3 — Test arrangement for single wall penetration of curved areas with eccentric
positioning of the source on the concave side and the film 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 film on the convex side of the test area

Figure 5 — Test arrangement for double wall penetration of plane or curved test areas; source
and film outside the test area, only the film side wall imaged for evaluation
Figure 6 — Test arrangement for double wall penetration of plane or curved test areas; several
exposures; source and film 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 film 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 cross like 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. The maximum
values of X-ray tube voltage versus thickness are given in Figure 13.
NOTE The calculations for the curves in Figure 13 are described in Annex H.

Key
1 copper/nickel and alloys 4 aluminium and alloys
2 steel and cast irons w penetrated thickness in mm
3 titanium and alloys U X-ray voltage in kV
Figure 13 — Maximum X-ray voltage U for X-ray devices up to 1 000 kV as a function of
penetrated thickness w and material
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 1 for steels, cast irons, cobalt, copper and nickel based alloys.
For aluminium, magnesium, titanium and zinc testing using Se 75, the penetrated material 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 radiographs having as good detection
sensitivity as X-rays used with appropriate technique parameters. However because of the advantages of
gamma ray sources in handling and accessibility, Table 1 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 16
is achieved. It is recommended that better film system classes are used for testing of penetrated
thicknesses below 10 mm with Se 75 than required in Tables 2 and 3.
For certain applications wider material thickness ranges may be permitted, if sufficient image quality can
be achieved.
For gamma rays, the total travel-time to and from the source position shall not exceed 10 % of the total
exposure time.
Table 1 — Penetrated thickness range for gamma ray sources and X-ray equipment with X-ray
potential above 1 MV for steels, cast irons, cobalt, copper and nickel base alloys
Penetrated thickness
a
w
Radiation source
mm
Testing class A Testing class B
Se 75 10 ≤ w ≤ 40 14 ≤ w ≤ 40
Ir 192 10 ≤ w ≤ 100 20 ≤ w ≤ 90
Co 60 40 ≤ w ≤ 200 60 ≤ w ≤ 150
X-ray potentials from 1 MV up to 4 MV 30 ≤ w ≤ 300 50 ≤ w ≤ 180
b b
X-ray potentials from 4 MV up to 12 MV w ≥ 50 w ≥ 70
b b
X-ray potentials above 12 MV w ≥ 80 w ≥ 100
a
If there are different thicknesses imaged with one exposure, an averaged value of these thicknesses can be
used.
b
The minimum penetrated wall thickness may be reduced by 10 mm in testing class A and by 20 mm in testing
class B, if film system class C1 according to EN ISO 11699-1 is used, provided the IQI requirements are met.
9 Film systems and metal screens
For radiographic testing, film system classes shall be used in accordance with EN ISO 11699-1.
For different radiation sources, the minimum film system classes are given in Table 2 and Table 3.
When using metal screens good contact between films and screens are required. This may be achieved
either by using vacuum-packed films or by applying pressure.
Other screen thicknesses may be also used provided the required image quality is achieved.
Table 2 — Film system classes and metal screens for the radiography of steels, cast irons, cobalt,
copper and nickel base alloys
Film system
Penetrated thickness Type and thickness of metal screens
a
class
Radiation source
Testing Testing
w Testing class A Testing class B
class A class B
none or up to 0,03 mm front and back
X-ray potentials ≤ 100 kV
screens of lead
C 3
X-ray potentials > 100 kV up to 0,15 mm front and back screens of
all w C 5
to 150 kV lead
X-ray potentials > 150 kV 0,02 mm to 0,15 mm front and back
C 4
to 250 kV screens of lead
0,02 mm to 0,2 mm front and back screens
w ≤ 50 mm C 4
of lead
X-ray potentials > 250 kV
C 5
b
to 500 kV
0,1 mm to 0,2 mm front screens of lead
w > 50 mm C 5
0,02 mm to 0,2 mm back screens of lead
w ≤ 75 mm C 5 C 4
X-ray potentials > 500 kV 0,25 mm to 0,7 mm front and back screens
c
to 1 000 kV of steel or copper
w > 75 mm C 5 C 5
0,02 mm to 0,2 mm front and back screens
Se 75 all w C 5 C 4
of lead
0,1 mm to 0,2 mm
0,02 mm to 0,2 mm
front screens of
front screens of lead
Ir 192 all w C 5 C 4 b
lead
0,02 mm to 0,2 mm back screens of lead
w ≤ 100 mm C 4
0,25 mm to 0,7 mm front and back screens
Co 60 C 5
c
of steel or copper
w > 100 mm C 5
w ≤ 100 mm C 3
X-ray potentials from 0,25 mm to 0,7 mm front and back screens
C 5
c
1 MV up to 4 MV of steel or copper
w > 100 mm C 5
up to 1 mm front screen of copper, steel or
w ≤ 100 mm C 4 C 4
d
tantalum
X-ray potentials from
100 mm < w ≤ 300 mm C 4
4 MV up to 12 MV
back screen of copper or steel up to 1 mm
C 5
d
w > 300 mm C 5
or tantalum up to 0,5 mm
e
w ≤ 100 mm C 4 C 1
up to 1 mm front screen of tantalum
No back screen
X-ray potentials above 100 mm < w ≤ 300 mm C 4
12 MeV
C 5
e
up to 1 mm front screen of tantalum up to
w > 300 mm C 5
0,5 mm back screen of tantalum
a
Better film system classes may also be used, see EN ISO 11699-1.
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 test object and the film.
c
In testing class A also 0,5 mm to 2,0 mm screens of lead may be used.
d
In testing class A lead screens 0,5 mm to 1 mm may be used by agreement between the contracting parties.
e
Tungsten screens may be used by agreement.
Table 3 — X-ray potentials, film system classes and metal screens for aluminium, magnesium,
titanium and zinc
a
Film system class
Type and thickness of intensifying
Radiation source
Testing Testing
screens
class A class B
none or up to 0,03 mm front and up to
X-ray potentials ≤ 150 kV
0,15 mm back screens of lead
0,02 mm to 0,15 mm front and back
X-ray potentials > 150 kV to 250 kV C 3
screens of lead
C 5
0,1 mm to 0,2 mm front and back screens
X-ray potentials > 250 kV to 500 kV
of lead
b
not 0,2 mm front and 0,1 mm to 0,2 mm back
Se 75
applicable screens of lead
a
Better film system classes may also be used, see EN ISO 11699-1.
b
Instead of one 0,2 mm lead screen, two 0,1 mm lead screens may be used.
10 Reduction of scattered radiation
10.1 Metal filters and collimators
In order to reduce the effect of scattered radiation, direct radiation shall be collimated as much as possible
to the section under examination.
With Se 75, Ir 192 and Co 60 radiation sources or in case of edge scatter a sheet of lead can be used as a
filter of low energy scattered radiation between the test object and the film. The thickness of this sheet is
0,5 mm to 2 mm in accordance with the penetrated thickness.
10.2 Interception of backscattered radiation
It shall be ensured that the effect of backscattered radiation is minimized.
The presence of backscattered radiation should be checked for each new test arrangement by a lead
letter B (with a minimum height of 10 mm and a minimum thickness of 1,5 mm) placed immediately
behind the cassette. If the image of this symbol records as a lighter image on the radiograph, it shall be
rejected. If the symbol is darker or invisible the radiograph is acceptable and demonstrates good
protection against backscattered radiation.
If necessary, the film shall be shielded from backscattered radiation by an adequate thickness of lead at
least 1 mm, or of tin at least 1,5 mm, placed behind the film-screen combination (or the cassette).
11 Source-to-object distance
The minimum source-to-object distance f depends on the source size or focal spot size d and on the
min
object-to-film distance b. The source size or focal spot size d shall be in accordance with manufacturer’s
values. Values in accordance with the EN 12543 series (for X-ray tubes), EN 12679 (for isotopes) or
EN IEC 62976 (for LINACs) may also be used
When the source size or focal spot size is specified by two dimensions, the larger shall be used.
For exposure geometries, except for those in Figure 2 b) and Figure 3 b), the distance f shall be chosen so
that the ratio of this distance to the source size d, i.e. f/d, is not below the values given by Formula (1) and
Formula (2):
For testing class A use Formula (1):
2/3
f /,d ≥×75 b (1)
For testing class B use Formula (2):
2/3
f / d ≥×15 b (2)
where
b, f, d is given in millimetres (mm).
If the distance b < 1,5 t the dimension b in Formula (1) and Formula (2) and Figure 14 shall be replaced
by the wall thickness t.
For determination of the source-to-object distance f the nomogram in Figure 14 may be used. The
min
nomogram is based on Formula (1) and Formula (2).
For exposure geometries set on the basis of Figure 2 b) and Figure 3 b), the distance f shall be chosen so
that the ratio of this distance to the source size, d, i.e. f/d, is not below the values given by Formula (3)
and Formula (4):
For testing class A use Formula (3):
f b
≥×75, (3)
d
t
For testing class B use Formula (4):
f b
≥×15 (4)
d
t
where
t is the wall thickness to test, in millimetres (mm);
b is the object-to-film distance, in millimetres (mm).

Key
b object-to-film distance, in mm A testing class A
d source size in mm B testing class B
f minimum source-to-object distance, in mm
min
NOTE This nomogram does not apply for exposure geometries as shown in Figure 2 b) and Figure 3 b).
Figure 14 — Nomogram for the determination of minimum source-to-object distance (f ) in
min
relation to object-to-film distance (b) and the source size (d)
The opening angle 2β of the X-ray tube window and the film size d (diagonal) limit the applicable SFD.
f
Therefore, according to Formula (5), SFD should be:
d
f
(5)
SFD ≥ 0,5 ×
tan β
( )
The typical opening angle of the X-ray tube window for NDT is 2β = 40° (±20°). Formula (5) is simplified
for these tubes to Formula (6):
SFD ≥ 1, 4 × d (6)
f
If the radiation source could be placed inside the test object to be radiographed (techniques shown in
Figure 3 and Figure 4) to achieve a more suitable direction of exposition and when a double wall
technique (see Figure 5 to Figure 7) is avoided this method should be preferred. The reduction in
minimum source-to-object distance should not be greater than 40 %.
When the source is located centrally inside the test object and film outside (technique shown in Figure 4)
and provided that the IQI requirements are met, this percentage may be increased. However, the
reduction in minimum source-to-object distance shall not be greater than 50 %.
12 Optical density D of radiograph
Exposure conditions should be such that the minimum optical density of the radiograph in the area
evaluated is greater than or equal to those given in Table 4.
Table 4 — Optical density of the radiographs
a,b
Testing class Optical density (D)
A ≥ 2,0
B ≥ 2,3
a
A measuring tolerance of ± 0,1 is permitted.
b
For test areas with different wall thicknesses an optical density > 1,5 for class A and > 2,0 for class B is
sufficient, if the image quality requirements given in Table A.1 to Table A.3 are met.
High optical densities can be used with advantage where the viewing light is sufficiently bright in
accordance with 13.2. The maximum readable optical density of the film depends on the film viewer used
and its maximum luminance (see EN ISO 5580). The maximum readable optical density shall be posted
on the viewer.
In order to avoid unduly high fog densities arising from film ageing, development or temperature, the fog
density shall be checked periodically on a non-exposed sample taken from the films being used, and
handled and processed under the same conditions as the actual radiograph. The fog density shall not
exceed 0,3. Fog density here is specified as the total optical density (emulsion and base) of a processed,
unexposed film.
If double film viewing is requested the optical density of one single film shall not be lower than 1,3.
13 Film processing and viewing
13.1 Processing
Films are processed in accordance with the conditions recommended by the film and chemical
manufacturer to obtain the selected film system class. Particular attention shall be paid to temperature,
developing time and washing time. The film processing shall be controlled regularly in accordance with
EN ISO 11699-2. The radiographs should be free from defects due to processing or other causes which
would interfere with evaluation.
13.2 Film viewing conditions
The radiographs shall be evaluated in a darkened room on an area of the viewing screen with an
adjustable luminance in accordance with EN ISO 5580. The viewing screen shall be masked to the area of
interest.
14 Techniques for increasing the covered thickness range
14.1 General
In many applications it is useful to image a larger thickness range within one film exposure. Figure 15
provides information on the expected thickness range (difference between maximum penetrated
thickness and minimum penetrated thickness) for steels and cast irons depending on the optical density
ratio in the radiograph. This can be done by one of the following techniques:
— multiple film technique;
— contrast decreasing by higher radiation energy;
— contrast decreasing by beam hardening;
— contrast decreasing by thickness equalization.

Key
X Thickness range in millimetres (mm)
Y Quotient of optical density D /D for films
max min
Figure 15 — Estimation of possible covered thickness range for different radiation energy levels
for steels and cast irons
14.2 Multiple film technique
For multiple film technique two or more films with different sensitivities are exposed at the same time
(see Figure 16) and viewed singly or together.

Key
D optical density of film
a film system with a higher film system class (higher ISO speed, see EN ISO 11699-1)
b film system with a lower film system class (lower ISO speed, see EN ISO 11699-1)
c lateral dimension
Figure 16 — Arrangement for multiple film technique
There shall be at least one screen between each of the films. When paper backed lead screens are used
for film radiography two screens shall be inserted with the metal layer to the film side. Films and front
and back screens shall be chosen in accordance with Table 2 and Table 3.
Areas on the radiograph with high light intensities shall be masked to avoid dazzle while viewing.
Viewing identification marks (at least 2) shall be imaged to ensure the exact positioning of multiple films
on top of each other. The geometrical features of the casting and of their images on the radiographs shall
correspond.
If double film viewing is used the optical density of a single film (see Clause 12) shall not be less than 1,3.
14.3 Contrast decreasing by higher radiation energy
For X-ray sources up to 800 kV, the maximum permissible tube voltage according to Figure 13 may be
exceeded by max. 30 %. For increasing the covered thickness range, X-ray sources may be replaced by
gamma ray sources or linear accelerators.
The image quality requirement(s) given in Annex A, Table A.1 to Table A.3, shall be met.
14.4 Contrast decreasing by beam hardening
Beam hardening for contrast decreasing is permissible, if the image quality requirement(s) given in
Table A.1 to Table A.3 are met.
14.5 Contrast decreasing by thickness equalization
In radiography imaging different wall thicknesses with one exposure on one radiograph is possible by
covering the area of thinner wall thickness – which is imaged on the radiograph with higher optical
density of the film – with material equalizing the differences in wall thickness, so that the requirements
of optical density of the film according to Clause 12 are met for the whole thickness range.
The equalizing material shall be free from discontinuities and from coarse structure and shall not cause
image disturbance that could harm a good analysis of the test area.
15 Requirements on radiographs
15.1 Identification of radiograph, test area, film position plan
There shall be a clear identification of the test area and of the corresponding radiograph.
For castings which require a large number of radiographs a film position plan or photo documentation
shall be prepared. The position of each film and the corresponding test areas shall have a clearly specified
co-ordination.
In cases where the test arrangement figure according to this document does not specify the position of
the radiation source, either a special plan of the radiation sources shall be prepared or the radiation
source shall be noted in the film position plan or a photo documentation.
15.2 Marking of the test areas
Permanent markings on the object to be tested shall be made in order to accurately locate the position of
each radiograph (e.g. zero point, direction, identification, measure).
Where the nature of the material and/or its service conditions does not permit permanent marking, the
location may be recorded by means of accurate sketches or photographs.
15.3 Overlap of films
When radiographing an area with two or more separate films, the films shall overlap sufficiently to ensure
that all the test area is radiographed. This shall be verified by high densit
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