SIST EN ISO 16371-2:2018

SLOVENSKI STANDARD
01-marec-2018
Nadomešča:
SIST EN 14784-2:2005
Neporušitveno preskušanje - Industrijska računalniška radiografija s hranjenjem
na fosfornih ploščah - 2. del: Splošna načela za preskušanje kovinskih materialov
z uporabo rentgenskih žarkov in žarkov gama (ISO 16371-2:2017, popravljena
verzija 2018-05)
Non-destructive testing - Industrial computed radiography with storage phosphor imaging
plates - Part 2: General principles for testing of metallic materials using X-rays and
gamma rays (ISO 16371-2:2017, Corrected version 2018-05)
Zerstörungsfreie Prüfung - Industrielle Computer-Radiographie mit Phosphor-
Speicherfolien - Teil 2: Grundlagen für die Prüfung metallischer Werkstoffe mit Röntgen-
und Gammastrahlen (ISO 16371-2:2017)
Essais non destructifs - Radiographie industrielle numérisée avec plaques-images au
phosphore - Partie 2: Principes généraux de l'essai radiographique des matériaux
métalliques au moyen de rayons X et gamma (ISO 16371-2:2017)
Ta slovenski standard je istoveten z: EN ISO 16371-2:2017
ICS:
19.100 Neporušitveno preskušanje Non-destructive testing
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 16371-2
EUROPEAN STANDARD
NORME EUROPÉENNE
November 2017
EUROPÄISCHE NORM
ICS 19.100 Supersedes EN 14784-2:2005
English Version
Non-destructive testing - Industrial computed radiography
with storage phosphor imaging plates - Part 2: General
principles for testing of metallic materials using X-rays and
gamma rays (ISO 16371-2:2017, Corrected version 2018-
05)
Essais non destructifs - Radiographie industrielle Zerstörungsfreie Prüfung - Industrielle Computer-
numérisée avec écrans photostimulables à mémoire - Radiographie mit Phosphor-Speicherfolien - Teil 2:
Partie 2: Principes généraux de l'essai radiographique Grundlagen für die Prüfung von metallischen
des matériaux métalliques au moyen de rayons X et Werkstoffen mit Röntgen- und Gammastrahlen (ISO
gamma (ISO 16371-2:2017) 16371-2:2017)
This European Standard was approved by CEN on 5 September 2017.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

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

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2017 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 16371-2:2017 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
European foreword
This document (EN ISO 16371-2:2017) has been prepared by Technical Committee CEN/TC 138 “Non-
destructive testing” the secretariat of which is held by AFNOR, in collaboration with Technical
Committee ISO/TC 135 “Non-destructive testing”.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by May 2018, and conflicting national standards shall be
withdrawn at the latest by May 2018.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN 14784-2:2005.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,
Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.
Endorsement notice
The text of ISO 16371-2:2017, Corrected version 2018-05 has been approved by CEN as EN ISO 16371-
2:2017 without any modification.

INTERNATIONAL ISO
STANDARD 16371-2
First edition
2017-09
Corrected version
2018-05
Non-destructive testing — Industrial
computed radiography with storage
phosphor imaging plates —
Part 2:
General principles for testing of
metallic materials using X-rays and
gamma rays
Essais non destructifs — Radiographie industrielle numérisée avec
écrans photostimulables à mémoire —
Partie 2: Principes généraux de l'essai radiographique des matériaux
métalliques au moyen de rayons X et gamma
Reference number
ISO 16371-2:2017(E)
©
ISO 2017
ISO 16371-2:2017(E)
© ISO 2017
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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Published in Switzerland
ii © ISO 2017 – All rights reserved

ISO 16371-2:2017(E)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols and abbreviated terms . 5
5 Personnel qualification . 6
6 Classification of computed radiographic techniques and compensation principles .6
6.1 Classification . 6
6.2 Compensation principles, CP I and CP II . 6
7 General . 7
7.1 Protection against ionizing radiation . 7
7.2 Surface preparation and stage of manufacture . 7
7.3 Identification of radiographs . 7
7.4 Marking . 7
7.5 Overlap of phosphor imaging plates . 7
7.6 Types and positions of image quality indicators and IQI values . . 8
8 Recommended techniques for making computed radiographs . 9
8.1 Test arrangements . 9
8.2 Choice of X-ray tube voltage and radiation source . 9
8.2.1 X-ray equipment . 9
8.2.2 Other radiation sources .10
8.3 CR systems and screens .11
8.3.1 Minimum normalized signal-to-noise ratio .11
8.3.2 Metal screens and shielding .11
8.4 Maximum unsharpness and basic spatial resolution for CR system selection .13
8.4.1 System selection .13
8.4.2 Compensation principle II .13
8.5 Alignment of beam .15
8.6 Reduction of scattered radiation .15
8.6.1 Metal filters and collimators .15
8.6.2 Interception of back scattered radiation .15
8.7 Source to object distance .15
8.7.1 General requirements .15
8.7.2 Testing of planar objects and curved objects with flexible IPs .15
8.7.3 Testing of curved objects with IPs in cassettes . .16
8.7.4 Exceptions for panoramic projection exposures with the source in the
centre of the pipe .16
8.8 Maximum area for a single exposure .18
8.9 Erasure of imaging plates .19
8.10 Data processing .19
8.10.1 Image processing .19
8.10.2 Monitor, viewing conditions and storage of digital radiographs .19
9 Test report .19
detector
Annex A (normative) Determination of basic spatial resolution, SR .
b
Annex B (normative) Determination of normalized SNR from SNR .26
N measured
Annex C (normative) Determination of minimum grey value .28
Bibliography .31
ISO 16371-2:2017(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
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).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on 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 the following
URL: www .iso .org/iso/foreword .html.
This document was prepared by the European Committee for Standardization (CEN) in collaboration
with ISO Technical Committee ISO/TC 135, Non-destructive testing, Subcommittee SC 5, Radiographic
testing, in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna
Agreement).
A list of all parts in the ISO 16371 series can be found on the ISO website.
This corrected version of ISO 16371-2:2017 incorporates the following correction:
— Figure A.1 b) has been corrected.
iv © ISO 2017 – All rights reserved

INTERNATIONAL STANDARD ISO 16371-2:2017(E)
Non-destructive testing — Industrial computed
radiography with storage phosphor imaging plates —
Part 2:
General principles for testing of metallic materials using
X-rays and gamma rays
1 Scope
This document specifies fundamental techniques of computed radiography with the aim of enabling
satisfactory and repeatable results to be obtained economically. The techniques are based on the
fundamental theory of the subject and tests measurements. This document specifies the general rules
for industrial computed X-rays and gamma radiography for flaw detection purposes, using storage
phosphor imaging plates (IP). It is based on the general principles for radiographic examination of
metallic materials on the basis of films, as specified in ISO 5579. The basic set-up of radiation source,
detector and the corresponding geometry are intended to be applied in accordance with ISO 5579 and
corresponding product standards such as ISO 17636 for welding and EN 12681 for foundry.
This document does not lay down acceptance criteria of the imperfections. Computed radiography (CR)
systems provide a digital grey value image which can be viewed and evaluated on basis of a computer
only. This practice describes the recommended procedure for detector selection and radiographic
practice. Selection of computer, software, monitor, printer and viewing conditions are important but
not the main focus of this document.
The procedure it specifies provides the minimum requirements and practice to permit the exposure
and acquisition of digital radiographs with a sensitivity of imperfection detection equivalent to film
radiography and as specified in ISO 5579. Some application standards, e.g. EN 16407, can require
different and less stringent practice conditions.
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 5579, Non-destructive testing — Radiographic testing of metallic materials using film and X- or gamma
rays — Basic rules
ISO 5580, Non-destructive testing — Industrial radiographic illuminators — Minimum requirements
ISO 9712, Non-destructive testing — Qualification and certification of NDT personnel
ISO 16371-1:2011, Non-destructive testing — Industrial computed radiography with storage phosphor
imaging plates — Part 1: Classification of systems
ISO 19232-1, Non-destructive testing — Image quality of radiographs — Part 1: Determination of the
image quality value using wire-type image quality indicators
ISO 19232-2, Non-destructive testing — Image quality of radiographs — Part 2: Determination of the
image quality value using step/hole-type image quality indicators
ISO 19232-3:2013, Non-destructive testing — Image quality of radiographs — Part 3: Image quality classes
ISO 16371-2:2017(E)
ISO 19232-5, Non-destructive testing — Image quality of radiographs — Part 5: Determination of image
unsharpness value using duplex wire-type image quality indicators
EN 12543 (all parts), Non-destructive testing — Characteristics of focal spots in industrial X-ray systems
for use in non-destructive testing
EN 12679, Non-destructive testing — Determination of the size of industrial radiographic sources —
Radiographic method
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at http: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
3.1
computed radiography system
CR system
complete system comprising a storage phosphor imaging plate (3.2) and a corresponding read-out unit
(scanner or reader) and system software, which converts the information from the IP into a digital image
3.2
storage phosphor imaging plate
imaging plate
IP
photostimulable luminescent material capable of storing a latent radiographic image of a material
being examined and upon stimulation by a source of red light of appropriate wavelength, generates
luminescence proportional to radiation absorbed
Note 1 to entry: When performing computed radiography (3.1), an IP is used in lieu of a film. When establishing
techniques related to source size or focal geometries, the IP is referred to as a detector, i.e. source-to-detector
distance (SDD).
3.3
structure noise of imaging plate
structure noise of IP
fixed pattern noise measured due to IP structure which is inherent from inhomogeneities in the
sensitive layer (graininess) and surface of a storage phosphor imaging plate (3.2)
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.
3.4
grey value
GV
numeric value of a pixel in a digital image
Note 1 to entry: This is equivalent to the term pixel value as defined in ASTM E 2033, E 2445, E 2446 and E 2007.
2 © ISO 2017 – All rights reserved

ISO 16371-2:2017(E)
3.5
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 equivalent to the term linearized pixel value as defined in ASTM E 2033, E 2445, E 2446
and E 2007.
3.6
basic spatial resolution of CR system
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 CR
system at magnification equal to one
Note 1 to entry: For this measurement, the duplex wire IQI is placed directly on the CR imaging plate.
Note 2 to entry: The measurement of unsharpness is described in ISO 19232-5; see also ASTM E 2002.
3.7
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 in the image 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 ISO 19232-5; see also ASTM E 2002.
Note 3 to entry: The effective pixel size of the image (basic spatial resolution of the digital image) depends on
pixel pitch, geometrical unsharpness, detector unsharpness and magnification.
3.8
signal-to-noise ratio
SNR
quotient of mean value of the linearized grey values (3.5), which is the signal intensity 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 SNR depends on the radiation dose and the CR system properties.
3.9
normalized signal-to-noise ratio
SNR
N
image
signal-to-noise ratio (3.8), normalized by the basic spatial resolution, SR , which may be SR or
b
b
detector
SR , as measured directly in the digital image and/or calculated from the measured SNR,
b
SNR , by
measured
88,6μm
SNRS=⋅NR
Nmeasured
SR
b
ISO 16371-2:2017(E)
3.10
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.
3.11
normalized contrast-to-noise ratio
CNR
N
contrast-to-noise ratio (3.10), normalized by the basic spatial resolution, SR , as measured directly in
b
the digital image and/or calculated from the measured CNR, by
88,6μm
CNRC=⋅NR
N
SR
b
3.12
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.
3.13
nominal thickness
t
thickness of the material in the region under examination
Note 1 to entry: Manufacturing tolerances do not have to be taken into account.
3.14
penetrated thickness
w
thickness of material in the direction of the radiation beam calculated on basis of the nominal thickness
(3.13) of all penetrated walls
Note 1 to entry: For multiple wall techniques, the penetrated thickness is calculated from the nominal thickness
of all penetrated walls.
3.15
source size
d
size of the radiation source or focal spot size
Note 1 to entry: See EN 12543 (X-ray-sources) or EN 12679 (gamma ray sources). Manufacturer's values may be
used if they conform to these standards.
3.16
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
4 © ISO 2017 – All rights reserved

ISO 16371-2:2017(E)
3.17
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 is the source-to-object distance (3.18) and b is the object-to-detector
distance (3.16).
3.18
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 beam
3.19
geometric magnification
v
ratio of source-to-detector distance (3.17) to source-to-object distance (3.18)
4 Symbols and abbreviated terms
For the purposes of this document, the symbols and abbreviated terms given in Table 1 apply.
Table 1 — Symbols and abbreviated terms
Symbol Term
b object-to-detector distance
CNR contrast-to-noise ratio
CNR normalized contrast-to-noise ratio
N
CR computed radiography
d source size, focal spot size
D detector (imaging plate)
f d source-to-object distance
GV grey value
GV linearized grey value
lin
IP storage phosphor imaging plate
IQI image quality indicator
S radiation source
SDD source-to detector-distance
SNR signal-to-noise ratio
SNR normalized signal-to-noise ratio
N
image
detector
SR
b basic spatial resolution, which may be SR or SR depending on the context
b
b
detector
basic spatial resolution as determined with a duplex wire IQI adjacent to the detector
SR
b
basic spatial resolution as determined with a duplex wire IQI on the source side of the object
image
SR
b
t nominal thickness
u t geometric unsharpness
G
u inherent unsharpness of the detector system, excluding any geometric unsharpness, measured
i
from the digital image with a duplex wire IQI adjacent to the detector
u total image unsharpness, including geometric unsharpness, measured in the digital image at the
T
detector plane with a duplex wire IQI at the object plane
ISO 16371-2:2017(E)
Table 1 (continued)
Symbol Term
u image unsharpness, including geometric unsharpness, measured in the digital image with a duplex
Im
wire IQI at the object plane normalized to magnification
v geometric magnification
w penetrated thickness
5 Personnel qualification
Personnel performing non-destructive examination in accordance with this document shall be qualified
in accordance with ISO 9712 or equivalent to an appropriate level in the relevant industrial sector. The
personnel shall prove additional training and qualification in digital industrial radiology.
[10]
NOTE Training content for digital industrial radiology can be found in TCS-60 document of IAEA .
6 Classification of computed radiographic techniques and compensation
principles
6.1 Classification
Computed radiographic techniques are subdivided into two classes:
— Class A: basic technique;
— Class B: improved technique.
Class B technique is used when class A may be insufficiently sensitive.
Better techniques, compared with class B, 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 parties concerned.
Nevertheless, the perception of flaws using film radiography or computed radiography is comparable
by using class A and class B techniques, respectively. The perceptibility shall be proven by the use of
IQIs according to ISO 19232-1, ISO 19232-2 and ISO 19232-5.
If, for technical reasons, it is not possible to meet one of the conditions specified for class B, such as the
type of radiation source or the source-to-object distance, f, it may be agreed between the contracting
parties that the condition selected may be that specified for class A. The loss of sensitivity shall be
compensated by an increase of minimum grey value and SNR (recommended increase of SNR by a
N N
factor > 1,4). Because of the resulting improved sensitivity compared to class A, the test object may be
regarded as examined within class B if the correct IQI sensitivity is achieved.
6.2 Compensation principles, CP I and CP II
6.2.1 General. Two rules (see 6.2.2 and 6.2.3) are applied in this document for radiography with CR to
achieve a sufficient contrast sensitivity.
Application of these rules requires the achievement of a minimum contrast-to-noise ratio, CNR ,
N
normalized to the detector basic spatial resolution per detectable material thickness difference, Δw. If
the required normalized contrast-to-noise ratio (CNR per Δw) cannot be achieved due to an insufficient
N
value of one of the following parameters, this can be compensated by an increase in the SNR.
6.2.2 CP I. Compensation for reduced contrast (e.g. by increased tube voltage) by increased SNR (e.g.
by increased tube current or exposure time).
6 © ISO 2017 – All rights reserved

ISO 16371-2:2017(E)
detector
6.2.3 CP II. Compensation for insufficient detector sharpness (the value of SR higher than
b
specified) by increased SNR (increase in the single IQI wire or step hole value for each missing duplex
wire pair value).
6.2.4 Theoretical background. These compensation principles are based on the following
approximation for small flaw sizes (Δw < < w) as shown in Formula (1):
CNR μ ⋅SNR
N eff
=⋅c (1)
image
Δw
SR
b
where
c is a constant;
µ is the effective attenuation coefficient, which is equivalent to the specific material contrast.
eff
7 General
7.1 Protection against ionizing radiation
WARNING — Exposure of any part of the human body to X-rays or gamma rays can be highly
injurious to health. Wherever X-ray equipment or radioactive sources are in use, appropriate
legal requirements must be applied.
Local or national or international safety precautions when using ionizing radiation shall be strictly
applied.
7.2 Surface preparation and stage of manufacture
In general, surface preparation is not necessary, but where surface imperfections or coatings might
cause difficulty in detecting defects, the surface shall be ground smooth or the coatings shall be
removed.
Unless otherwise specified, computed radiography shall be carried out after the final stage of
manufacture, e.g. after grinding or heat treatment.
7.3 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.
7.4 Marking
Permanent markings on the object to be examined shall be made in order to accurately locate the
position of each radiograph.
Where the natures of the material and/or its service conditions do not permit permanent marking, the
location may be recorded by means of accurate sketches or photographs.
7.5 Overlap of phosphor imaging plates
When radiographing an area with two or more separate phosphor imaging plates (IP), the IPs 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 that will appear on each image. If the radiographs
will be taken sequentially, the high density marker shall be visible on each of the radiographs.
ISO 16371-2:2017(E)
7.6 Types and positions of image quality indicators and IQI values
The quality of images shall be verified by use of image quality indicators (IQIs) in accordance with
ISO 19232-5 and ISO 19232-1 or ISO 19232-2. If not otherwise specified by the contracting parties, the
required IQI values of ISO 19232-3 shall be achieved. The IQIs shall be placed on the source side of the
object. If this is not possible, the IQIs shall be placed on the detector side of the object with an additional
letter F.
NOTE Positioning of IQIs on the detector side would apply, for example, for double wall single image in-
service inspection.
Following the procedure outlined in Annex A, a reference image is required for the verification of the
basic spatial resolution of the CR system. The basic spatial resolution or duplex wire value shall be
determined to verify whether the system hardware meets the requirements specified as a function
of the penetrated material thickness in Table 5. In this case, the duplex wire IQI shall be positioned
directly on the imaging plate or imaging plate cassette.
The use of a duplex wire IQI (ISO 19232-5) for production radiographs is not compulsory. The
requirement for using a duplex wire IQI additionally to a single wire IQI for production radiographs
may be part of the agreement between the contracting parties. If used on production radiographs, the
duplex wire IQI shall be positioned on the object. The measured basic spatial resolution of the digital
image
image (SR ) (see Annex A), shall not exceed the maximum values specified as a function of the
b
penetrated material thickness (Table 5). For single image inspection, the single wall thickness is taken
as the penetrated material thickness. For double wall double image inspection (ISO 19232-3), with the
duplex wire on the source side of the object, the penetrated material thickness is taken as the outer
image
object dimension for determination of the required basic spatial resolution (SR ) from Table 5. The
b
detector
basic spatial resolution of the detector (SR ) for double wall double image inspection shall
b
correspond to the values of Table 5 chosen on the basis of twice the nominal single wall thickness as the
penetrated material thickness.
If the geometric magnification technique is applied with v > 1,2, then the duplex wire IQI (ISO 19232-5)
shall be used on all production radiographs.
The duplex wire IQI shall be positioned tilted by a few degrees (2° to 5°) to the digitally achieved rows
or columns of the digital image. If the IQI is positioned at 45° to the digital lines or rows, the obtained
IQI number shall be reduced by one.
The contrast sensitivity of digital images shall be verified by use of IQIs, in accordance with the specific
application as given in ISO 19232-3.
The single wire or step hole IQIs used shall be placed preferably on the source side of the test object
at the centre of the area of interest. The IQI shall be in close contact with the surface of the object. Its
location shall be in a section of uniform thickness characterized by a uniform grey value (mean) in the
digital image.
According to the IQI type used, cases a) and b) shall be considered.
a) When using a single wire IQI, the wires shall be on a location of constant thickness, which shall
ensure that at least 10 mm of the wire length shows in a section of uniform grey value or SNR .
N
b) When using a step hole IQI, it shall be placed in such a way that the hole number required is placed
close to the region of interest.
For double wall double image exposures, the IQI type used can be placed either on the source or on the
detector side. If the IQIs cannot be placed in accordance with the above conditions, the IQIs are placed
on the detector side and the image quality shall be determined at least once from comparison exposure
with one IQI placed at the source side and one at the detector side under the same conditions. If filters
are used in front of the detector, the IQI shall be placed in front of the filter.
8 © ISO 2017 – All rights reserved

ISO 16371-2:2017(E)
For double wall exposures, when the IQI is placed on the detector side, the above test is not necessary.
In this case, refer to the corresponding tables of ISO 19232-3.
Where the IQIs are placed on the detector side, the letter F shall be placed near the IQI and it shall be
stated in the test report.
The identification numbers and, when used, the lead letter F, shall not be in the area of interest, except
when geometric configuration makes it impractical.
If steps have been taken to guarantee that digital radiographs of similar test objects and regions are
produced with identical exposure and processing techniques and no differences in the image quality
value are likely, the image quality need not be verified for every digital radiograph. The extent of image
quality verification should be subject to agreement between the contracting parties.
For exposures of pipes with diameter 200 mm and above with the source centrally located, at least
three IQIs should be placed equally spaced at the circumference. The IQI images are then considered
representative for the whole circumference.
If the IQI cannot be placed inside a hollow object or a pipe for inspection (e.g. with source centrally
located), it can be located outside. The required IQI values shall be determined by a reference exposure
with IQIs on the source and the detector sides of the pipe or a hollow object.
8 Recommended techniques for making computed radiographs
8.1 Test arrangements
Test arrangements shall be determined from the specific application standards, e.g. ISO 17636-2 and
EN 12681.
8.2 Choice of X-ray tube voltage and radiation source
8.2.1 X-ray equipment
To maintain good flaw sensitivity, the X-ray tube voltage should be as low as possible and the SNR in
N
the digital image should be as high as possible. Recommended maximum values of tube voltage versus
thickness are given in Figure 1. These maximum values are best practice values for film radiography.
Imaging plates with high structure noise of the sensitive IP layer (coarse grained) should be applied
with about 20 % less X-ray voltage as indicated in Figure 1 for class B testing. High definition imaging
plates, which are exposed similar to X-ray films and having low structure noise (fine grained) should be
exposed with X-ray voltages of Figure 1 or higher if the SNR is sufficiently increased (see Note below).
N
ISO 16371-2:2017(E)
Key
1 copper/nickel and alloys
2 steel
3 titanium and alloys
4 aluminium and alloys
w penetrated material thickness in mm
U X-ray voltage in kV
Figure 1 — X-ray voltage for X-ray devices up to 1 MV as function of penetrated material
thickness and material
NOTE An improvement in contrast sensitivity can be achieved by an increase in contrast at constant SNR
N
[by reduction of tube voltage and compensation by higher exposure (e.g. milliampère ⋅ minutes)]; or improvement
in contrast sensitivity by an increase in SNR [by higher exposure (e.g. milliampère ⋅ minutes)] at constant
N
contrast (constant kilovolt level); increased tube voltage [at a constant exposure (e.g. milliampère ⋅ minutes)]
reduces the contrast and increases the SNR . The contrast sensitivity improves if the increase in SNR is higher
N N
than the contrast reduction due to the higher energy.
8.2.2 Other radiation sources
The permitted penetrated thickness ranges for gamma ray sources and X-ray equipment above 1 MeV
are given in Table 2.
By agreement of the contracting parties, the value for Ir-192 may be reduced furthermore to 10 mm and
for Se-75 to 5 mm penetrated wall thickness, provided the required image quality of ISO 19232-3 is met.
On thin specimens, gamma rays from Ir-192 and Co-60 will not produce computed radiographs having
as good defect detection sensitivity as X-rays used with appropriate technique parameters. However,
because of the advantages of gamma ray sources in handling and accessibility, Table 2 gives a range of
thickness for which each of these gamma ray sources may be used when the use of X-rays is difficult.
For certain applications, wider wall thickness ranges may be permitted, if sufficient image quality can
be achieved.
10 © ISO 2017 – All rights reserved

ISO 16371-2:2017(E)
In cases where radiographs are produced using gamma rays, the travel time to and from the source
position shall not exceed 10 % of the total exposure time.
Table 2 — Penetrated material thickness range for gamma ray sources and X-ray equipment
with energy from 1 MeV and above for steel, copper and nickel-based alloys
Penetrated material thickness, w
Radiation source
mm
Class A Class B
Tm-170 w ≤ 5 w ≤ 5
a
Yb-169 1 ≤ w ≤ 15 2 ≤ w ≤ 12
b
Se-75 10 ≤ w ≤ 40 14 ≤ w ≤ 40
Ir-192 20 ≤ w ≤ 100 20 ≤ w ≤ 90
Co-60 40 ≤ w ≤ 200 60 ≤ w ≤ 150
X-ray equipment with energy 1 to 4 MeV 30 ≤ w ≤ 200 50 ≤ w ≤ 180
X-ray equipment with energy 4 to12 MeV 50 ≤ w 80 ≤ w
X-ray equipment with energy > 12 MeV 80 ≤ w 100 ≤ w
a
For aluminium and titanium, the penetrated material thickness is 10 ≤ w ≤ 70 for class A and 25 ≤ w ≤ 55 for class B.
b
For aluminium and titanium, the penetrated material thickness is 35 ≤ w ≤ 120 for class A.
The maximum penetrated thicknesses as given in Table 2 may be e
...