SIST EN ISO 17636-2:2013
(Main)Non-destructive testing of welds - Radiographic testing - Part 2: X- and gamma-ray techniques with digital detectors (ISO 17636-2:2013)
Non-destructive testing of welds - Radiographic testing - Part 2: X- and gamma-ray techniques with digital detectors (ISO 17636-2:2013)
This part of ISO 17636 specifies fundamental techniques of digital radiography with the object of enabling satisfactory and repeatable results to be obtained economically. The techniques are based on generally recognized practice and fundamental theory of the subject. This part of ISO 17636 applies to the digital radiographic examination of fusion welded joints in metallic materials. It applies to the joints of plates and pipes. Besides its conventional meaning, “pipe”, as used in this International Standard, covers other cylindrical bodies such as tubes, penstocks, boiler drums, and pressure vessels. This part of ISO 17636 specifies the requirements for digital radiographic X- and gamma-ray testing by either computed radiography (CR) or radiography with digital detector arrays (DDA) of the welded joints of metallic plates and tubes for the detection of imperfections. Digital detectors provide a digital grey value (GV) image which can be viewed and evaluated using a computer. This part of ISO 17636 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 part of ISO 17636. The procedure specified in this part of ISO 17636 provides the minimum requirements for radiographic practice which permit exposure and acquisition of digital radiographs with equivalent sensitivity for detection of imperfections as film radiography, as specified in ISO 17636-1. This part of ISO 17636 does not specify acceptance levels for any of the indications found on the digital radiographs. If contracting parties apply lower test criteria, it is possible that the quality achieved is significantly lower than when this part of ISO 17636 is strictly applied.
Zerstörungsfreie Prüfung von Schweißverbindungen - Durchstrahlungsprüfung - Teil 2: Röntgen und Gammastrahlungstechniken unter Anwendung digitaler Detektoren (ISO 17636-2:2013)
Diese Europäische Norm legt grundlegende Techniken der digitalen Durchstrahlungsprüfung mit dem Ziel
fest, zufriedenstellende und wiederholbare Ergebnisse in wirtschaftlicher Weise zu erreichen. Die Techniken
beruhen auf allgemein anerkannten Vorgehensweisen und den grundlegenden Theorien zum Thema.
Die vorliegende Norm gilt für die digitale Durchstrahlungsprüfung von Schmelzschweißverbindungen in
metallischen Werkstoffen.
Sie gilt für Schweißverbindungen von Platten und Rohren. Neben der konventionellen Bedeutung sollten in
dieser Norm unter der Benennung „Rohr“ auch andere zylindrische Körper wie Druckleitungen, Kesseltrommeln
und Druckbehälter verstanden werden. Diese Norm steht im Einklang mit EN 14784-2.
Der vorliegende Teil der EN ISO 17636 legt die Anforderungen an die digitale Durchstrahlungsprüfung von
Schweißverbindungen an Metallrohren mit Röntgen- und Gammastrahlen unter Anwendung entweder der
Computer-Radiographie (CR) oder der Radiographie mit digitalen Matrixdetektoren (DDA, en: digital detector
arrays) fest, die dem Nachweis von Unregelmäßigkeiten dient.
Digitale Detektoren liefern ein digitales Grauwertbild, das nur mit einem Rechner betrachtet und ausgewertet
werden kann. Beschrieben wird das empfohlene Verfahren für die Auswahl des Detektors und die Durchstrahlungsprüfung.
Die Auswahl von Rechner, Software, Monitor, Drucker und Betrachtungsbedingungen ist
von Bedeutung, bildet jedoch nicht den Schwerpunkt dieser Norm. Das in dieser Norm festgelegte Verfahren
enthält die Mindestanforderungen an das Durchstrahlungsverfahren zur Gewinnung digitaler Durchstrahlungsbilder
mit einer Empfindlichkeit für den Nachweis von Unregelmäßigkeiten, die der in Teil 1 dieser Norm festgelegten
Radiographie mit Filmen gleichwertig ist.
Diese Norm legt keine Zulässigkeitsgrenzen für die Anzeigen fest.
Contrôle non destructif des assemblages soudés - Contrôle par radiographie - Partie 2: Techniques par rayons X ou gamma à l'aide de détecteurs numériquess (ISO 17636-2:2013)
L'ISO 17636-2:2013 spécifie les techniques fondamentales de radiographie numérique permettant d'obtenir des résultats satisfaisants et reproductibles de manière économique. Les techniques reposent sur une pratique généralement reconnue et sur la théorie fondamentale en la matière.
L'ISO 17636-2:2013 s'applique au contrôle par radiographie numérique des assemblages soudés par fusion de matériaux métalliques. Elle s'applique aux assemblages de plaques et de tubes. Outre sa signification conventionnelle, le terme «tube», tel qu'il est utilisé dans l'ISO 17636-2:2013, couvre d'autres corps cylindriques, tels que tuyaux, conduites forcées, réservoirs de chaudières et appareils à pression.
L'ISO 17636-2:2013 spécifie les exigences relatives au contrôle par radiographie numérique à rayons X et gamma des assemblages soudés de tubes métalliques pour la détection des imperfections, soit par radiographie numérique (CR) soit par radiographie avec des panneaux de détecteurs numériques (DDA).
Les détecteurs numériques produisent une image numérique en valeurs de gris (GV) qui ne peut être visualisée et évaluée qu'à l'aide d'un ordinateur. L'ISO 17636-2:2013 décrit le mode opératoire recommandé pour le choix des détecteurs et la pratique radiographique. Le choix de l'ordinateur, du logiciel, de l'écran, de l'imprimante et des conditions d'observation est important, mais ne constitue pas le centre d'intérêt de l'ISO 17636-2:2013. Le mode opératoire spécifié dans l'ISO 17636-2:2013 fournit les exigences minimales pour la pratique radiographique permettant l'exposition et l'acquisition des radiogrammes numériques avec une sensibilité de détection des imperfections équivalente à celle de la radiographie à l'aide de film, telle que spécifiée dans l'ISO 17636‑1.
L'ISO 17636-2:2013 ne spécifie pas les niveaux d'acceptation des indications trouvées sur les radiogrammes numériques.
Si les parties contractantes appliquent des critères d'essai moins rigoureux, il se peut que la qualité obtenue soit nettement inférieure à celle atteinte par l'application stricte de l'ISO 17636-2:2013.
Neporušitvene preiskave zvarnih spojev - Radiografske preiskave - 2. del : X- in gama žarki z uporabo digitalnih detektorjev (ISO 17636-2:2013)
Ta del ISO 17636 določa temeljne tehnike digitalne radiografije z namenom omogočanja zadovoljivih in ponovljivih rezultatov, ki so stroškovno ugodni. Tehnike so osnovane na splošno priznani praksi in temeljnem poznavanju subjekta. Ta del ISO 17636 velja za digitalne radiografske preiskave za talilno varjenje spojev kovinskih materialov. Velja za spoje plošč in cevi. Poleg svojega klasičnega pomena izraz „cev‟, uporabljen v tem mednarodnem standardu, zajema tudi druga cilindrična telesa, kot so dovodni kanali, bobni kotlov in tlačne posode. Ta del ISO 17636 določa zahteve za ugotavljanje napak vzdolžnih ali heličnih varov pri avtomatsko talilno obločno varjenih jeklenih ceveh z digitalno radiografsko rentgensko preiskavo z računalniško radiografijo (CR) ali radiografijo z digitalnimi detektorskimi nizi (DDA). Digitalni detektorji zagotavljajo digitalno sivinsko sliko (GV), ki jo je mogoče prikazati in oceniti prek računalnika. Ta del ISO 17636 določa priporočen postopek za izbiro detektorja in radiografsko prakso. Izbira računalnika, programske opreme, monitorja, tiskalnika in pogojev prikaza je pomembna, vendar ni ključni del tega dela ISO 17636. Postopek, določen v tem delu ISO 17636, zagotavlja minimalne zahteve za radiografsko prakso, ki omogočajo izpostavljenost in pridobivanje digitalnih rentgenskih slik z občutljivostjo zaznavanja napak, enako kot pri radiografskem filmu iz ISO 17636-1. Ta del ISO 17636 ne določa ravni sprejemljivosti za indikacije na rentgenskih slikah. Če pogodbene stranke uporabijo nizka preskusna merila, bo morda dosežena kakovost znatno nižja od kakovosti, dosežene s strogim upoštevanjem tega dela ISO 17636.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 17636-2:2013
01-september-2013
1DGRPHãþD
SIST EN 1435:1998
SIST EN 1435:1998/A1:2003
SIST EN 1435:1998/A2:2004
Neporušitvene preiskave zvarnih spojev - Radiografske preiskave - 2. del : X- in
gama žarki z uporabo digitalnih detektorjev (ISO 17636-2:2013)
Non-destructive testing of welds - Radiographic testing - Part 2: X- and gamma-ray
techniques with digital detectors (ISO 17636-2:2013)
Zerstörungsfreie Prüfung von Schweißverbindungen - Durchstrahlungsprüfung - Teil 2:
Röntgen und Gammastrahlungstechniken unter Anwendung digitaler Detektoren (ISO
17636-2:2013)
Contrôle non destructif des assemblages soudés - Contrôle par radiographie - Partie 2:
Techniques par rayons X ou gamma à l'aide de détecteurs numériquess (ISO 17636-
2:2013)
Ta slovenski standard je istoveten z: EN ISO 17636-2:2013
ICS:
25.160.40 Varjeni spoji in vari Welded joints
SIST EN ISO 17636-2:2013 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN ISO 17636-2:2013
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SIST EN ISO 17636-2:2013
EUROPEAN STANDARD
EN ISO 17636-2
NORME EUROPÉENNE
EUROPÄISCHE NORM
January 2013
ICS 25.160.40 Supersedes EN 1435:1997
English Version
Non-destructive testing of welds - Radiographic testing - Part 2:
X- and gamma-ray techniques with digital detectors (ISO 17636-
2:2013)
Contrôle non destructif des assemblages soudés - Contrôle Zerstörungsfreie Prüfung von Schweißverbindungen -
par radiographie - Partie 2: Techniques par rayons X ou Durchstrahlungsprüfung - Teil 2: Röntgen- und
gamma à l'aide de détecteurs numériquess (ISO 17636- Gammastrahlungstechniken mit digitalen Detektoren (ISO
2:2013) 17636-2:2013)
This European Standard was approved by CEN on 14 December 2012.
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, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United
Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2013 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 17636-2:2013: E
worldwide for CEN national Members.
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SIST EN ISO 17636-2:2013
EN ISO 17636-2:2013 (E)
Contents Page
Foreword .3
2
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SIST EN ISO 17636-2:2013
EN ISO 17636-2:2013 (E)
Foreword
This document (EN ISO 17636-2:2013) has been prepared by Technical Committee CEN/TC 121 “Welding”
the secretariat of which is held by DIN, in collaboration with Technical Committee ISO/TC 44 "Welding and
allied processes".
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 July 2013, and conflicting national standards shall be withdrawn at the
latest by July 2013.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN 1435:1997.
According to the CEN/CENELEC Internal Regulations, the national standards organisations 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, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.
3
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SIST EN ISO 17636-2:2013
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SIST EN ISO 17636-2:2013
INTERNATIONAL ISO
STANDARD 17636-2
First edition
2013-01-15
Non-destructive testing of welds —
Radiographic testing —
Part 2:
X- and gamma-ray techniques with digital
detectors
Contrôle non destructif des assemblages soudés — Contrôle par
radiographie —
Partie 2: Techniques par rayons X ou gamma à l'aide de détecteurs
numériques
Reference number
ISO 17636-2:2013(E)
©
ISO 2013
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SIST EN ISO 17636-2:2013
ISO 17636-2:2013(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2013
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2013 – All rights reserved
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SIST EN ISO 17636-2:2013
ISO 17636-2:2013(E)
Contents Page
Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols and terms . 5
5 Classification of radiographic techniques . 6
6 General . 7
6.1 Protection against ionizing radiation . 7
6.2 Surface preparation and stage of manufacture . 7
6.3 Location of the weld in the radiograph . 8
6.4 Identification of radiographs . 8
6.5 Marking . 8
6.6 Overlap of digital images . 8
6.7 Types and positions of image quality indicators (IQI) . 8
6.8 Minimum image quality values . 9
6.9 Personnel qualification . 10
7 Recommended techniques for making digital radiographs . 10
7.1 Test arrangements . 10
7.2 Choice of tube voltage and radiation source . 16
7.3 Detector systems and metal screens . 18
7.4 Alignment of beam . 20
7.5 Reduction of scattered radiation . 20
7.6 Source-to-object distance . 22
7.7 Geometric magnification technique . 25
7.8 Maximum area for a single exposure . 26
7.9 Processing . 26
7.10 Monitor viewing conditions and storage of digital radiographs . 27
8 Examination report . 28
Annex A (normative) Recommended number of exposures which give an acceptable examination
of a circumferential butt weld . 30
Annex B (normative) Minimum image quality values . 35
Annex C (normative) Determination of basic spatial resolution . 41
Annex D (normative) Determination of minimum grey values for CR practice . 45
Annex E (informative) Grey values, general remarks . 50
Bibliography . 52
© ISO 2013 – All rights reserved iii
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SIST EN ISO 17636-2:2013
ISO 17636-2:2013(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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 17636-2 was prepared by the European Committee for Standardization (CEN) in collaboration with ISO
Technical Committee TC 44, Welding and allied processes, Subcommittee SC 5, Testing and inspection of
welds in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
This first edition, together with ISO 17636-1, cancels and replaces ISO 17636:2003, of which it constitutes a
technical revision.
ISO 17636 consists of the following parts, under the general title Non-destructive testing of welds —
Radiographic testing:
Part 1: X- and gamma-ray techniques with film
Part 2: X- and gamma-ray techniques with digital detectors
The main changes are that:
the normative references have been updated;
the document has been divided into two parts — this part of ISO 17636 is applicable to radiographic
testing with digital detectors;
X-ray devices up to 1 000 kV have been included;
Annex C on determination of basic spatial resolution has been added;
Annex D on determination of minimum grey values for CR practice has been introduced;
Annex E with general remarks on grey values has been added;
the text has been editorially revised.
Requests for official interpretations of any aspect of this part of ISO 17636 should be directed to the
Secretariat of ISO/TC 44/SC 5 via your national standards body. A complete listing of these bodies can be
found at www.iso.org.
iv © ISO 2013 – All rights reserved
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SIST EN ISO 17636-2:2013
ISO 17636-2:2013(E)
Introduction
This International Standard specifies fundamental techniques of radiography with the object of enabling
satisfactory and repeatable results to be obtained economically. The techniques are based on generally
recognized practice and fundamental theory of the subject, inspection of fusion welded joints with digital
radiographic detectors.
Digital detectors provide a digital grey value image which can be viewed and evaluated with a computer only.
The practice describes 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 part of ISO 17636.
The procedure specified in this part of ISO 17636 provides the minimum requirements and practice which
permits exposure and acquisition of digital radiographs with equivalent sensitivity for detection of
imperfections as film radiography, specified in ISO 17636-1.
© ISO 2013 – All rights reserved v
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SIST EN ISO 17636-2:2013
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SIST EN ISO 17636-2:2013
INTERNATIONAL STANDARD ISO 17636-2:2013(E)
Non-destructive testing of welds — Radiographic testing —
Part 2:
X- and gamma-ray techniques with digital detectors
1 Scope
This part of ISO 17636 specifies fundamental techniques of digital radiography with the object of enabling
satisfactory and repeatable results to be obtained economically. The techniques are based on generally
recognized practice and fundamental theory of the subject.
This part of ISO 17636 applies to the digital radiographic examination of fusion welded joints in metallic
materials. It applies to the joints of plates and pipes. Besides its conventional meaning, “pipe”, as used in this
International Standard, covers other cylindrical bodies such as tubes, penstocks, boiler drums, and pressure
vessels.
[6]
NOTE This part of ISO 17636 complies with EN 14784-2.
This part of ISO 17636 specifies the requirements for digital radiographic X- and gamma-ray testing by either
computed radiography (CR) or radiography with digital detector arrays (DDA) of the welded joints of metallic
plates and tubes for the detection of imperfections.
Digital detectors provide a digital grey value (GV) image which can be viewed and evaluated using a computer.
This part of ISO 17636 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 part of ISO 17636. The procedure specified in this part of ISO 17636 provides the minimum
requirements for radiographic practice which permit exposure and acquisition of digital radiographs with
equivalent sensitivity for detection of imperfections as film radiography, as specified in ISO 17636-1.
This part of ISO 17636 does not specify acceptance levels for any of the indications found on the digital
radiographs.
If contracting parties apply lower test criteria, it is possible that the quality achieved is significantly lower than
when this part of ISO 17636 is strictly applied.
2 Normative references
The following referenced documents are indispensable for the application 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 5576, Non-destructive testing — Industrial X-ray and gamma-ray radiology — Vocabulary
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 2013 – All rights reserved 1
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SIST EN ISO 17636-2:2013
ISO 17636-2:2013(E)
ISO 19232–1, Non-destructive testing ------ Image quality of radiographs ------ Part 1: Image quality indicators
(wire type) — Determination of image quality value
ISO 19232–2, Non-destructive testing ------ Image quality of radiographs ------ Part 2: Image quality indicators
(step/hole type) — Determination of image quality value
ISO 19232–4, Non-destructive testing ------ Image quality of radiographs ------ Part 4: Experimental evaluation of
image quality values and image quality tables
ISO 19232–5, Non-destructive testing ------ Image quality of radiographs ------ Part 5: Image quality indicators
(duplex wire type) ------ Determination of image unsharpness value
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 terms and definitions given in ISO 5576 and the following apply.
3.1
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
3.2
storage phosphor 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 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).
3.3
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
3.4
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 After scanning of the exposed imaging plate, the inhomogeneities appear as overlaid fixed pattern noise in the
digital image.
NOTE 2 This noise limits the maximum achievable image quality of digital CR images and can be compared with the
graininess in film images.
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SIST EN ISO 17636-2:2013
ISO 17636-2:2013(E)
3.5
structure noise of digital detector array
structure noise of DDA
structure due to different properties of detector elements (pixels)
NOTE After read-out of the exposed uncalibrated 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 calibration (software and
guidelines are provided by the manufacturer). A suitable calibration procedure reduces the structure noise.
3.6
grey value
GV
numeric value of a pixel in a digital image
NOTE This is typically interchangeable with the terms pixel value, detector response, analogue-to-digital unit, and
detector signal.
3.7
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 This is typically interchangeable with the terms linearized pixel value, and linearized detector signal.
3.8
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 For this measurement, the duplex wire IQI is placed directly on the digital detector array or imaging plate.
[13]
NOTE 2 The measurement of unsharpness is described in ISO 19232-5, see also ASTM E2736 and
[8]
ASTM E1000.
3.9
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 For this measurement, the duplex wire IQI is placed directly on the object (source side).
[13]
NOTE 2 The measurement of unsharpness is described in ISO 19232-5, see also ASTM E2736, and
[8]
ASTM E1000.
3.10
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
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SIST EN ISO 17636-2:2013
ISO 17636-2:2013(E)
3.11
normalized signal-to-noise ratio
SNR
N
signal-to-noise ratio, SNR, normalized by the basic spatial resolution, SR , as measured directly in the digital
b
image and/or calculated from the measured SNR, SNR , by
measured
88,6μm
SNR SNR
N measured
SR
b
3.12
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 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.
3.13
normalized contrast-to-noise ratio
CNR
N
contrast-to-noise ratio, CNR, normalized by the basic spatial resolution, SR , as measured directly in the
b
digital image and/or calculated from the measured CNR, i.e.
88,6μm
CNR CNR
N
SR
b
3.14
aliasing
artefacts that appear in an image when the spatial frequency of the input is higher than the output is capable
of reproducing
NOTE Aliasing often appears as jagged or stepped sections in a line or as moiré patterns.
3.15
cluster kernel pixel
CKP
bad pixel which does not have five or more good neighbourhood pixels
[11]
NOTE See ASTM E2597 for details on bad pixels and CKP.
3.16
nominal thickness
t
thickness of the parent material only where manufacturing tolerances do not have to be taken into account
3.17
penetration thickness change
t
change of penetrated thickness relative to the nominal thickness due to beam angle
3.18
penetrated thickness
w
thickness of material in the direction of the radiation beam calculated on the basis of the nominal thicknesses
of all penetrated walls
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SIST EN ISO 17636-2:2013
ISO 17636-2:2013(E)
3.19
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
3.20
source size
d
size of the radiation source or focal spot size
NOTE See EN 12679 or EN 12543.
3.21
source-to-detector distance
SDD
distance between the source of radiation and the detector, measured in the direction of the beam
NOTE SDD = f b
where
f source-to-object distance
b object-to-detector distance
3.22
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
3.23
external diameter
D
e
nominal external diameter of the pipe
3.24
geometric magnification
v
ratio of source-to-detector distance SDD to source-to-object distance, f
4 Symbols and abbreviated terms
For the purposes of this standard, the symbols given in Table 1 apply.
Table 1 — Symbols and abbreviated terms
Symbol Term
b object-to-detector distance
b’ object-to-detector distance perpendicular to test object
d source size, focal spot size
D external diameter
e
f source-to-object distance
f ′ source-to-object distance perpendicular to test object
SNR signal-to-noise ratio
© ISO 2013 – All rights reserved 5
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SIST EN ISO 17636-2:2013
ISO 17636-2:2013(E)
SNR normalized signal-to-noise ratio
N
t nominal thickness
t penetration thickness change
u geometric unsharpness
G
u inherent unsharpness of the detector system, excluding any geometric unsharpness, measured from
i
the digital image with a duplex wire IQI adjacent to the detector
u required image unsharpness measured in the digital image at the object plane with a duplex wire IQI
im
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
v geometric magnification
w penetrated thickness
CKP cluster kernel pixel
CNR contrast-to-noise ratio
CNR normalized contrast-to-noise ratio
N
CR computed radiography
D detector
DDA digital detector array
IP storage phosphor imaging plate
IQI image quality indicator
S radiation source
SDD source-to detector-distance
SR basic spatial resolution as determined with a duplex wire IQI adjacent to the detector
b
detector
SR basic spatial resolution of a digital detector
b
image
SR basic spatial resolution as determined with a duplex wire IQI on the source side of the object
b
5 Classification of radiographic techniques and compensation principles
5.1 Classification
The radiographic techniques are divided into two classes:
Class A: basic techniques;
Class B: improved techniques.
Class B techniques are used when class A might be insufficiently sensitive.
Better techniques compared to class B are possible and may be agreed between the contracting parties by
specification of all appropriate test parameters.
The choice of digital radiographic technique shall be agreed between the contracting parties.
Nevertheless, the visibility of flaws using film radiography or digital radiography is equivalent when using class
A and class B techniques, respectively. The visibility shall be proven by the use of IQIs according to
ISO 19232-1 or 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
6 © ISO 2013 – All rights reserved
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SIST EN ISO 17636-2:2013
ISO 17636-2:2013(E)
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 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 class A, the test specimen may be
N
regarded as being examined to class B, if the correct IQI sensitivity is achieved. This does not apply if the
spec
...
SLOVENSKI STANDARD
oSIST prEN ISO 17636-2:2011
01-april-2011
Neporušitvene preiskave zvarnih spojev - Radiografske preiskave - 2. del : X- in
gama žarki z uporabo digitalnih detektorjev (ISO/DIS 17636-2:2010)
Non-destructive testing of welds - Radiographic testing - Part 2: X- and gamma-ray
techniques with digital detectors (ISO/DIS 17636-2:2010)
Zerstörungsfreie Prüfung von Schweißverbindungen - Durchstrahlungsprüfung - Teil 2:
Röntgen und Gammastrahlungstechniken unter Anwendung digitaler Detektoren
(ISO/DIS 17636-2:2010)
Contrôle non destructif des assemblages soudés - Contrôle par radiographie - Partie 2:
Techniques par rayons X ou gamma à l'aide de détecteurs numériquess (ISO/DIS 17636
-2:2010)
Ta slovenski standard je istoveten z: prEN ISO 17636-2
ICS:
25.160.40 Varjeni spoji in vari Welded joints
oSIST prEN ISO 17636-2:2011 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
---------------------- Page: 1 ----------------------
oSIST prEN ISO 17636-2:2011
---------------------- Page: 2 ----------------------
oSIST prEN ISO 17636-2:2011
EUROPEAN STANDARD
DRAFT
prEN ISO 17636-2
NORME EUROPÉENNE
EUROPÄISCHE NORM
November 2010
ICS 25.160.40 Will supersede EN 1435:1997
English Version
Non-destructive testing of welds - Radiographic testing - Part 2:
X- and gamma-ray techniques with digital detectors (ISO/DIS
17636-2:2010)
Contrôle non destructif des assemblages soudés - Contrôle Zerstörungsfreie Prüfung von Schweißverbindungen -
par radiographie - Partie 2: Techniques par rayons X ou Durchstrahlungsprüfung - Teil 2: Röntgen- und
gamma à l'aide de détecteurs numériquess (ISO/DIS Gammastrahlungstechniken unter Anwendung digitaler
17636-2:2010) Detektoren (ISO/DIS 17636-2:2010)
This draft European Standard is submitted to CEN members for parallel enquiry. It has been drawn up by the Technical Committee
CEN/TC 121.
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, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland 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
Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2010 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN ISO 17636-2:2010: E
worldwide for CEN national Members.
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oSIST prEN ISO 17636-2:2011
prEN ISO 17636-2:2010 (E)
Contents Page
Foreword .3
2
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oSIST prEN ISO 17636-2:2011
prEN ISO 17636-2:2010 (E)
Foreword
This document (prEN ISO 17636-2:2010) has been prepared by Technical Committee CEN/TC 121 “Welding”,
the secretariat of which is held by DIN, in collaboration with Technical Committee ISO/TC 44 "Welding and
allied processes".
This document is currently submitted to the parallel Enquiry.
This document will supersede EN 1435:1997.
3
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oSIST prEN ISO 17636-2:2011
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oSIST prEN ISO 17636-2:2011
DRAFT INTERNATIONAL STANDARD ISO/DIS 17636-2
ISO/TC 44/SC 5 Secretariat: ANSI
Voting begins on: Voting terminates on:
2010-11-04 2011-04-04
INTERNATIONAL ORGANIZATION FOR STANDARDIZATION • МЕЖДУНАРОДНАЯ ОРГАНИЗАЦИЯ ПО СТАНДАРТИЗАЦИИ • ORGANISATION INTERNATIONALE DE NORMALISATION
Non-destructive testing of welds — Radiographic testing —
Part 2:
X- and gamma-ray techniques with digital detectors
Contrôle non destructif des assemblages soudés — Contrôle par radiographie —
Partie 2: Techniques par rayons X ou gamma à l'aide de détecteurs numériques
ICS 25.160.40
ISO/CEN PARALLEL PROCESSING
This draft has been developed within the European Committee for Standardization (CEN), and processed
under the CEN-lead mode of collaboration as defined in the Vienna Agreement.
This draft is hereby submitted to the ISO member bodies and to the CEN member bodies for a parallel
five-month enquiry.
Should this draft be accepted, a final draft, established on the basis of comments received, will be
submitted to a parallel two-month approval vote in ISO and formal vote in CEN.
To expedite distribution, this document is circulated as received from the committee secretariat.
ISO Central Secretariat work of editing and text composition will be undertaken at publication
stage.
Pour accélérer la distribution, le présent document est distribué tel qu'il est parvenu du
secrétariat du comité. Le travail de rédaction et de composition de texte sera effectué au
Secrétariat central de l'ISO au stade de publication.
THIS DOCUMENT IS A DRAFT CIRCULATED FOR COMMENT AND APPROVAL. IT IS THEREFORE SUBJECT TO CHANGE AND MAY NOT BE
REFERRED TO AS AN INTERNATIONAL STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS BEING ACCEPTABLE FOR INDUSTRIAL, TECHNOLOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN NATIONAL REGULATIONS.
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT, WITH THEIR COMMENTS, NOTIFICATION OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPORTING DOCUMENTATION.
©
International Organization for Standardization, 2010
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oSIST prEN ISO 17636-2:2011
ISO/DIS 17636-2
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ii ISO 2010 – All rights reserved
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oSIST prEN ISO 17636-2:2011
prEN ISO 17636-2:2010 (E)
Contents Page
Foreword .v
Introduction.vi
1 Scope.1
2 Normative references.1
3 Terms and definitions .2
4 Symbols and terms .5
5 Classification of radiographic techniques.6
6 General.6
6.1 Protection against ionizing radiation .6
6.2 Surface preparation and stage of manufacture .6
6.3 Location of the weld in the radiograph .6
6.4 Identification of radiographs.6
6.5 Marking.7
6.6 Overlap of digital images.7
6.7 Types and positions of image quality indicators (IQI).7
6.8 Minimum image quality values .8
6.9 Personnel qualification.8
7 Recommended techniques for making digital radiographs.8
7.1 Test arrangements .8
7.1.1 General .8
7.1.2 Radiation source located in front of the object and with the detector at the opposite side
(see Figure 1) .9
7.1.3 Radiation source located outside the object and detector inside (see Figures 2 to 4) .9
7.1.4 Radiation source centrally located inside the object and with the detector outside (see
Figures 5 to 7) .10
7.1.5 Radiation source located off-centre inside the object and detector outside (see figures 8
to 10) .11
7.1.6 Elliptic technique (see Figure 11) .12
7.1.7 Perpendicular technique (see Figure 12).12
7.1.8 Radiation source located outside the object and detector on the other side (see
Figures 13 to 18).13
7.1.9 Technique for different material thicknesses (see Figure 19) .15
7.2 Choice of tube voltage and radiation source .15
7.2.1 X-ray devices up to 1000 kV .15
7.2.2 Other radiation sources.16
7.3 Detector systems and metal screens.17
7.3.1 Minimum normalized Signal-to-Noise-Ratio (SNR ) .17
N
7.3.2 Compensation principle (II) .18
7.3.3 Screens for IPs and shielding .18
7.4 Alignment of beam .20
7.5 Reduction of scattered radiation .20
7.5.1 Metal filters and collimators.20
7.5.2 Interception of backscattered radiation.20
7.6 Source-to-object distance .21
7.7 Magnification technique .23
7.8 Maximum area for a single exposure .24
7.9 Processing .24
7.9.1 Scan and read out of image .24
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prEN ISO 17636-2:2010 (E)
7.9.2 Calibration of DDAs. 25
7.9.3 Bad pixel interpolation . 25
7.9.4 Image processing . 25
7.10 Monitor viewing conditions and storage of digital radiographs. 26
8 Examination report . 26
Annex A (normative) Recommended number of exposures which give an acceptable examination
of a circumferential butt weld. 28
Annex B (normative) Minimum image quality values. 33
Annex C (normative) Determination of basic spatial resolution . 41
Annex D (normative) Determination of minimum grey values for CR practice . 43
D.1 Determination of normalized SNR from SNR . 43
N measured
D.2 Determination of minimum grey values . 44
Annex E (informative) Grey values, general remarks . 48
Bibliography. 50
iv © ISO 2009 – All rights reserved
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oSIST prEN ISO 17636-2:2011
prEN ISO 17636-2:2010 (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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 17636-1 was prepared by Technical Committee CEN/TC 121, Welding and by Technical Committee
ISO/TC 44, Welding and allied processes, Subcommittee SC 5 in collaboration.
This second edition cancels and replaces the first edition ISO 17636: 2003 which has been technically
revised.
The main changes are :
⎯ normative references were updated;
⎯ document was divided into two parts where the present part is applicable for radiographic testing with
digital detectors;
⎯ X-ray devices up to 1 000 kV were included;
⎯ normative Annex C on determination of basic spatial resolution was added;
⎯ normative Annex D on determination of minimum grey values for CR practice was introduced;
⎯ informative Annex E with general remarks on grey values was added;
⎯ document was editorially revised.
ISO 17636 consists of the following parts, under the general title Non-destructive testing of welds —
Radiographic testing:
⎯ Part 1: X- and gamma ray techniques with film
⎯ Part 2: X- and gamma ray techniques with digital detectors
© ISO 2009 – All rights reserved v
DRAFT 2010
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oSIST prEN ISO 17636-2:2011
prEN ISO 17636-2:2010 (E)
Introduction
This standard specifies fundamental techniques of radiography with the object of enabling satisfactory and
repeatable results to be obtained economically. The techniques are based on generally recognized practice
and fundamental theory of the subject, inspection of fusion welded joints with digital radiographic detectors.
Digital detectors provide a digital grey value image which can be viewed and evaluated with a computer only.
The practice describes the recommended procedure for detector selection and radiographic practice.
Selection of computer, software, monitor, printer and viewing conditions are important but not in the main
focus of this standard.
The procedure specified in this standard, provides the minimum requirements and practice which permits to
expose and acquire digital radiographs with equivalent sensitivity for detection of imperfections as film
radiography, specified in part 1 of this standard.
vi © ISO 2009 – All rights reserved
DRAFT 2010
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oSIST prEN ISO 17636-2:2011
DRAFT INTERNATIONAL STANDARD ISO/DIS 17636-2
Non-destructive testing of welds — Radiographic testing —
Part 2:
X- and gamma-ray techniques with digital detectors
1 Scope
This European Standard specifies fundamental techniques of digital radiography with the object of enabling
satisfactory and repeatable results to be obtained economically. The techniques are based on generally
recognized practice and fundamental theory of the subject.
This standard applies to the digital radiographic examination of fusion welded joints in metallic materials.
It applies to the joints of plates or pipes. Besides its conventional meaning, "pipe" as used in this standard
should be understood to cover other cylindrical bodies such as tubes, penstocks, boiler drums and pressure
vessels. This standard complies with EN 14784-2.
This Part of ISO 17636 specifies the requirements for digital radiographic X- and gamma ray testing by either
computed radiography (CR) or radiography with digital detector arrays (DDA), of the welded joints of metallic
tubes for the detection of imperfections.
Digital detectors 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 in the
main focus of this standard. The procedure specified in this standard, provides the minimum requirements and
practice which permits to expose and acquire digital radiographs with equivalent sensitivity for detection of
imperfections as film radiography and as specified in Part 1 of this standard.
This standard does not specify acceptance levels of the indications.
If contracting parties apply lower test criteria, the quality achieved may be significantly lower than when this
standard is strictly applied.
2 Normative references
The following referenced documents are indispensable for the application 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 462-1, Non-destructive testing. Image quality of radiogaphs. Part 1 : Image quality indicators (wire type),
determination of image quality value.
EN 462-2, Non-destructive testing. Image quality of radiographs. Part 2 : Image quality indicators (step/hole
type). Determination of image quality value.
EN 462-5, Non-destructive testing. Image quality of radiographs. Part 5 : Image quality indicators (duplex wire
type), determination of image unsharpness value.
EN 473, Non-destructive testing — Qualification and certification of NDT personnel — General principles
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oSIST prEN ISO 17636-2:2011
prEN ISO 17636-2:2010 (E)
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
EN 14784-1:2005, Non-destructive testing — Industrial computed radiography with storage phosphor imaging
plates — Part 1: Classification of systems
ISO 5576, Non-destructive testing — Industrial X-ray and gamma-ray radiology — Vocabulary
ISO 9712, Non-destructive testing — Qualification and certification of personnel
ISO 19232–1, Non-destructive testing — Image quality of radiographs — Part 1: Image quality indicators (wire
type) - Determination of image quality value
ISO 19232–2, Non-destructive testing — Image quality of radiographs — Part 2: Image quality indicators
(step/hole type) - Determination of image quality value
ISO 19232–3, Non-destructive testing — Image quality of radiographs — Part 3: Image quality classes for
ferrous metals
ISO 19232–4, Non-destructive testing — Image quality of radiographs — Part 4: Experimental evaluation of
image quality values and image quality tables
ISO 19232–5, Non-destructive testing — Image quality of radiographs — Part 5: Image quality indicators
(duplex wire type) - Determination of image unsharpness value
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 5576:1997 and the following apply.
3.1
computed radiography
storage phosphor imaging plate system
complete system of a storage phosphor imaging plate (IP) and a corresponding read out unit (scanner or
reader), which converts the information of the IP into a digital image
3.2
storage phosphor imaging plate
IP
photostimulable luminescent material that is capable of storing a latent radiographic image of a material being
examined and, upon stimulation by a source of red spectrum light of appropriate wavelength, will generate
luminescence proportional to radiation absorbed
NOTE When performing computed radiography, an IP is used in lieu of a film. When establishing techniques related
to source focal geometries, the IP is referred to as a detector (i.e. source-to detector-distance or SDD).
3.3
digital detector array system
DDA system
electronic device that converts ionizing or penetrating radiation into a discrete array of analog signals which
are subsequently digitised 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
3.4
structure noise of IP
structure due to inhomogeneties in the sensitive layer (graininess) and surface of an IP
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oSIST prEN ISO 17636-2:2011
prEN ISO 17636-2:2010 (E)
NOTE 1 After scanning of the exposed imaging plate the inhomogeneties appear as overlaid fixed pattern noise in the
digital image.
NOTE 2 This noise limits the maximum achievable image quality of digital IP images and can be compared with the
graininess in film images.
3.5
structure noise of DDA
structure due to different properties of detector elements (pixels)
NOTE After read out of the exposed uncalibrated DDA. The inhomogeneties appear as overlaid fixed pattern noise in
the digital image. All DDAs are typically applied after a software based calibration (software and guideline is provided by
the manufacturer). A suitable calibration procedure reduces the structure noise.
3.6
grey value
numeric value of a pixel in a digital image
NOTE This is typically interchangeable with the term pixel value, detector response, analog-to-digital unit, and
detector signal.
3.7
linearised grey value
numeric value of a pixel which is directly linearised proportional to the detector exposure dose and has the
value zero if the detector was not exposed
NOTE This is typically interchangeable with the term linearised pixel value, and linearised detector signal.
3.8
signal-to-noise ratio
SNR
quotient of mean value of the linearised grey values and standard deviation of the linearised grey values
(noise) in a given region of interest in a digital image
3.9
basic spatial resolution
SR
b
corresponds to ½ 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 The measurement of unsharpness is described in ISO 19232-5, see also ASTM E 1000.
3.10
normalized signal-to-noise ratio
SNR
N
SNR, normalized by the basic spatial resolution SR as measured directly in the digital image and/or
b
calculated from measured SNR by
measured
SNR = SNR ×()88,6µm / SR
N measured b
3.11
contrast-to-noise ratio
CNR
quotient of the difference of the mean signal levels between two image areas and the averaged standard
deviation of the signal levels
NOTE It describes a component of image quality and depends approximately on the product of radiographic
attenuation coefficient and SNR. In addition to adequate CNR, a digital radiograph must also possess adequate
unsharpness or basic spatial resolution to resolve desired features of interest.
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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 This will often appear as jagged or stepped sections in a line or as moiré patterns.
3.13
cluster kernel pixels
CKP
pixels which do n
...
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