Non-destructive testing - Radiographic inspection of corrosion and deposits in pipes by X - and gamma rays - Part 1: Tangential radiographic inspection (ISO 20769-1:2018)

This European Standard specifies fundamental techniques of film and digital radiography with the object of enabling satisfactory and repeatable results to be obtained economically. The techniques are based on generally recognized practice and fundamental theory of the subject.
This European Standard applies to the radiographic examination of pipes in metallic materials for service induced flaws such as corrosion pitting, generalized corrosion and erosion. 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.
Weld inspection for typical welding process induced flaws is not covered, but weld inspection is included for corrosion/erosion type flaws.
The pipes may be insulated or not, and can be assessed where loss of material due, for example, to corrosion or erosion is suspected either internally or externally.
This part of EN 16407 covers the tangential inspection technique for detection and through-wall sizing of wall loss, including:
a)   with the source on the pipe centre line, and
b)   with the source offset from it by the pipe radius.
Part 2 of EN 16407 covers double wall radiography, and note that the double wall double image technique is often combined with tangential radiography with the source on the pipe centre line.
This European Standard applies to tangential radiographic inspection using industrial radiographic film techniques, computed digital radiography (CR) and digital detector arrays (DDA).

Zerstörungsfreie Prüfung - Durchstrahlungsprüfung auf Korrosion und Ablagerungen in Rohren mit Röntgen- und Gammastrahlen - Teil 1: Tangentiale Durchstrahlungsprüfung (ISO 20769-1:2018)

Essais non destructifs - Examen radiographique de la corrosion et des dépôts dans les canalisations, par rayons X et rayons gamma - Partie 1: Examen radiographique tangentiel (ISO 20769-1:2018)

Le présent document spécifie les techniques fondamentales de radiographie film et de radiographie numérique permettant d'obtenir des résultats satisfaisants et reproductibles de façon économique. Ces techniques sont fondées sur les pratiques généralement reconnues et la théorie fondamentale sur ce sujet.
Le présent document s'applique à l'examen radiographique des canalisations en acier présentant des défauts induits par le service, tels que des piqûres de corrosion, une corrosion généralisée et l'érosion. Dans le présent document, il convient d'interpréter le terme « canalisation » au sens conventionnel ainsi que dans un sens plus large couvrant les autres corps cylindriques tels que les tubes, les conduites forcées, les corps de chaudière et les récipients sous pression.
La présente norme couvre uniquement l'examen des soudures visant à détecter l'éventuelle présence de défauts de type corrosion/érosion, et non les défauts classiques induits par les procédés de soudage.
Les canalisations peuvent être pourvues ou dépourvues d'isolation et faire l'objet d'une évaluation en cas de suspicion de perte de matière interne ou externe, par exemple due à la corrosion ou à l'érosion.
Le présent document traite de la technique d'examen radiographique tangentiel qui permet de détecter et de dimensionner la perte de matière dans le sens de l'épaisseur, notamment, avec la source:
a) alignée sur l'axe central de la canalisation; et
b) décalée de l'axe central de la canalisation d'une distance égale au rayon de la canalisation.
L'ISO 20769-2 couvre la radiographie double paroi et il faut noter que la technique double paroi/double image est souvent combinée avec l'examen radiographique tangentiel en plaçant la source sur l'axe central de la canalisation.
Le présent document s'applique aux examens radiographiques tangentiels qui utilisent des techniques de films radiographiques industriels, la radiographie numérique (CR) et les mosaïques de détecteurs numériques (DDA).

Neporušitvene preskave - Radiografski pregled korozije in nanosov v ceveh z rentgenskimi žarki in žarki gama - 1. del: Tangencialni radiografski pregled (ISO 20769-1:2018)

Ta evropski standard določa temeljne tehnike filmske in 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 evropski standard velja za radiografski pregled cevi in kovinskih materialov za poškodbe, ki so posledica uporabe, kot na primer jamičasta korozija, splošna korozija in erozija. Poleg svojega klasičnega pomena izraz »cev«, kot je uporabljen v tem standardu, zajema tudi druga cilindrična telesa, kot so dovodni kanali, bobni kotlov in tlačne posode.
Standard ne zajema pregleda zvarov za običajne napake, ki so posledica varilnega postopka, vključuje pa pregled zvarov za napake, ki so posledica korozije/erozije.
Cevi so lahko izolirane ali ne in jih je mogoče pregledati, če se sumi na notranjo ali zunanjo poškodbo materiala, ki je posledica korozije ali erozije.
Ta del standarda EN 16407 zajema tehniko tangencialnega pregleda za odkrivanje in ugotavljanje obsega poškodbe sten, ki se izvede skozi steno, vključno z:
a) virom na središčnici cevi in
b) virom, odmaknjenim od središčnice za polmer cevi.
2. del standarda EN 16407 zajema radiografijo prek dveh sten. Dvoslikovna tehnika prek dveh sten se pogosto uporablja skupaj s tangencialno radiografijo z virom na središčnici cevi.
Ta evropski standard velja za tangencialni radiografski pregled, ki uporablja tehnike industrijskega radiografskega filma, računalniško digitalno radiografijo (CR) ali radiografijo z digitalnimi detektorskimi nizi (DDA).

General Information

Status
Published
Publication Date
06-Feb-2019
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
15-Nov-2018
Due Date
20-Jan-2019
Completion Date
07-Feb-2019

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SLOVENSKI STANDARD
SIST EN ISO 20769-1:2019
01-marec-2019
1DGRPHãþD
SIST EN 16407-1:2014
Neporušitvene preskave - Radiografski pregled korozije in nanosov v ceveh z

rentgenskimi žarki in žarki gama - 1. del: Tangencialni radiografski pregled (ISO

20769-1:2018)

Non-destructive testing - Radiographic inspection of corrosion and deposits in pipes by X

- and gamma rays - Part 1: Tangential radiographic inspection (ISO 20769-1:2018)

Zerstörungsfreie Prüfung - Durchstrahlungsprüfung auf Korrosion und Ablagerungen in

Rohren mit Röntgen- und Gammastrahlen - Teil 1: Tangentiale Durchstrahlungsprüfung

(ISO 20769-1:2018)

Essais non destructifs - Examen radiographique de la corrosion et des dépôts dans les

canalisations, par rayons X et rayons gamma - Partie 1: Examen radiographique
tangentiel (ISO 20769-1:2018)
Ta slovenski standard je istoveten z: EN ISO 20769-1:2018
ICS:
19.100 Neporušitveno preskušanje Non-destructive testing
23.040.01 Deli cevovodov in cevovodi Pipeline components and
na splošno pipelines in general
SIST EN ISO 20769-1:2019 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST EN ISO 20769-1:2019
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SIST EN ISO 20769-1:2019
EN ISO 20769-1
EUROPEAN STANDARD
NORME EUROPÉENNE
October 2018
EUROPÄISCHE NORM
ICS 19.100 Supersedes EN 16407-1:2014
English Version
Non-destructive testing - Radiographic inspection of
corrosion and deposits in pipes by X - and gamma rays -
Part 1: Tangential radiographic inspection (ISO 20769-
1:2018)

Essais non destructifs - Examen radiographique de la Zerstörungsfreie Prüfung - Durchstrahlungsprüfung

corrosion et des dépôts dans les canalisations, par auf Korrosion und Ablagerungen in Rohren mit

rayons X et rayons gamma - Partie 1: Examen Röntgen- und Gammastrahlen - Teil 1: Tangentiale

radiographique tangentiel (ISO 20769-1:2018) Durchstrahlungsprüfung (ISO 20769-1:2018)

This European Standard was approved by CEN on 5 August 2018.

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

© 2018 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 20769-1:2018 E

worldwide for CEN national Members.
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SIST EN ISO 20769-1:2019
EN ISO 20769-1:2018 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

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SIST EN ISO 20769-1:2019
EN ISO 20769-1:2018 (E)
European foreword

This document (EN ISO 20769-1:2018) has been prepared by Technical Committee ISO/TC 135 "Non-

destructive testing" in collaboration with Technical Committee CEN/TC 138 “Non-destructive testing”

the secretariat of which is held by AFNOR.

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 April 2019, and conflicting national standards shall be

withdrawn at the latest by April 2019.

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 16407-1:2014.

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 20769-1:2018 has been approved by CEN as EN ISO 20769-1:2018 without any

modification.
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SIST EN ISO 20769-1:2019
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SIST EN ISO 20769-1:2019
INTERNATIONAL ISO
STANDARD 20769-1
First edition
2018-09
Non-destructive testing —
Radiographic inspection of corrosion
and deposits in pipes by X- and
gamma rays —
Part 1:
Tangential radiographic inspection
Essais non destructifs — Examen radiographique de la corrosion et
des dépôts dans les canalisations, par rayons X et rayons gamma —
Partie 1: Examen radiographique tangentiel
Reference number
ISO 20769-1:2018(E)
ISO 2018
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SIST EN ISO 20769-1:2019
ISO 20769-1:2018(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2018

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2018 – All rights reserved
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SIST EN ISO 20769-1:2019
ISO 20769-1:2018(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 2

4 Classification of radiographic techniques .................................................................................................................................. 4

5 General ............................................................................................................................................................................................................................ 5

5.1 Protection against ionizing radiation .................................................................................................................................. 5

5.2 Personnel qualification .................................................................................................................................................................... 5

5.3 Identification of radiographs ...................................................................................................................................................... 5

5.4 Marking ......................................................................................................................................................................................................... 5

5.5 Overlap of films or digital images ........................................................................................................................................... 5

5.6 Types and positions of image quality indicators (IQI) ......................................................................................... 5

5.6.1 Single wire or step hole IQIs .................................................................................................................................. 5

5.6.2 Duplex wire IQI (digital radiographs) ........................................................................................................... 5

6 Recommended techniques for making radiographs ....................................................................................................... 6

6.1 Test arrangements ............................................................................................................................................................................... 6

6.1.1 General...................................................................................................................................................................................... 6

6.1.2 Radiation source located on the pipe centre line ................................................................................ 6

6.1.3 Radiation source located offset from the pipe centre line ........................................................... 7

6.1.4 Alignment of beam and film/detector ........................................................................................................... 9

6.2 Choice of radiation source ......... .................................................................................................................................................... 9

6.3 Film systems and metal screens ...........................................................................................................................................10

6.4 Screens and shielding for imaging plates (computed radiography only)..........................................11

6.5 Reduction of scattered radiation ..........................................................................................................................................12

6.5.1 Filters and collimators .............................................................................................................................................12

6.5.2 Interception of back scattered radiation ..................................................................................................13

6.6 Source-to-detector distance .....................................................................................................................................................13

6.7 Axial coverage and overlap ........................................................................................................................................................14

6.8 Dimensional comparators ..........................................................................................................................................................15

6.9 Image saturation and use of lead strips to avoid burn-off .............................................................................16

6.10 Selection of digital radiographic equipment ..............................................................................................................16

6.10.1 General...................................................................................................................................................................................16

6.10.2 CR systems .........................................................................................................................................................................17

6.10.3 DDA systems .....................................................................................................................................................................17

7 Radiograph/digital image sensitivity, quality and evaluation...........................................................................17

7.1 Evaluation of image quality .......................................................................................................................................................17

7.1.1 General...................................................................................................................................................................................17

7.1.2 Maximum grey level in free beam (digital radiographs) ............................................................17

7.1.3 Minimum normalized signal-to-noise ratio (digital radiographs) .....................................17

7.2 Density of film radiographs ......... ..............................................................................................................................................18

7.3 Film processing....................................................................................................................................................................................18

7.4 Film viewing conditions ...............................................................................................................................................................18

7.5 Dimensional calibration of radiographs or digital images .............................................................................19

7.5.1 General...................................................................................................................................................................................19

7.5.2 Measurement of distances in radiographic setup ............................................................................19

7.5.3 Measurement of pipe outside diameter ....................................................................................................20

7.5.4 Dimensional comparator .......................................................................................................................................20

7.6 Wall thickness measurements for film radiographs ............................................................................................20

7.7 Wall thickness measurements for digital radiographs ......................................................................................21

7.7.1 Interactive on-screen measurements .........................................................................................................21

7.7.2 Grey-level profile analysis methods .............................................................................................................21

7.8 Remaining thickness measurements for degradation .......................................................................................22

© ISO 2018 – All rights reserved iii
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SIST EN ISO 20769-1:2019
ISO 20769-1:2018(E)

7.8.1 Measurements for internal degradation ..................................................................................................22

7.8.2 Measurements for external degradation ..................................................................................................24

8 Digital image recording, storage, processing and viewing ....................................................................................26

8.1 Scan and read out of image .......................................................................................................................................................26

8.2 Multi radiograph technique ......................................................................................................................................................26

8.3 Calibration of DDAs ..........................................................................................................................................................................26

8.4 Bad pixel interpolation .................................................................................................................................................................26

8.5 Image processing ...............................................................................................................................................................................26

8.6 Digital image recording and storage .................................................................................................................................26

8.7 Monitor viewing conditions ......................................................................................................................................................27

9 Test report ................................................................................................................................................................................................................27

Annex A (informative) Choice of radiation source for different pipes ...........................................................................29

Annex B (informative) Remaining thickness measurements for internal degradation ...............................30

Annex C (informative) Remaining thickness measurements for external degradation ..............................33

Bibliography .............................................................................................................................................................................................................................37

iv © ISO 2018 – All rights reserved
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SIST EN ISO 20769-1:2019
ISO 20769-1:2018(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 of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www .iso

.org/iso/foreword .html.

This document was prepared by Technical Committee ISO/TC 135 Non-destructive testing, Subcommittee

SC 5 Radiographic testing.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/members .html.
A list of all parts in the ISO 20769 series can be found on the ISO website.
© ISO 2018 – All rights reserved v
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SIST EN ISO 20769-1:2019
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SIST EN ISO 20769-1:2019
INTERNATIONAL STANDARD ISO 20769-1:2018(E)
Non-destructive testing — Radiographic inspection of
corrosion and deposits in pipes by X- and gamma rays —
Part 1:
Tangential radiographic inspection
1 Scope

This document specifies fundamental techniques of film and digital radiography with the object of

enabling satisfactory and repeatable results to be obtained economically. The techniques are based on

generally recognized practice and fundamental theory of the subject.

This document applies to the radiographic examination of steel pipes for service induced flaws such as

corrosion pitting, generalized corrosion and erosion. Besides its conventional meaning, “pipe” as used

in this document is understood to cover other cylindrical bodies such as tubes, penstocks, boiler drums

and pressure vessels.

Weld inspection for typical welding process induced flaws is not covered, but weld inspection is

included for corrosion/erosion type flaws.

The pipes can be insulated or not, and can be assessed where loss of material due, for example, to

corrosion or erosion is suspected either internally or externally.

This document covers the tangential inspection technique for detection and through-wall sizing of wall

loss, including with the source:
a) on the pipe centre line; and
b) offset from pipe centre line by the pipe radius.

ISO 20769-2 covers double wall radiography, and note that the double wall double image technique is

often combined with tangential radiography with the source on the pipe centre line.

This document applies to tangential radiographic inspection using industrial radiographic film

techniques, computed radiography (CR) and digital detector arrays (DDA).
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 9712, Non-destructive testing — Qualification and certification of NDT personnel

ISO 11699-1, Non-destructive testing — Industrial radiographic film — Part 1: Classification of film

systems for industrial radiography

ISO 11699-2, Non-destructive testing — Industrial radiographic films — Part 2: Control of film processing

by means of reference values

ISO 16371-1, Non-destructive testing — Industrial computed radiography with storage phosphor imaging

plates — Part 1: Classification of systems

ISO 19232-5, Non-destructive testing — Image quality of radiographs — Part 5: Determination of the

image unsharpness value using duplex wire-type image quality indicators
© ISO 2018 – All rights reserved 1
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SIST EN ISO 20769-1:2019
ISO 20769-1:2018(E)
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 https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
3.1
actual wall thickness
act
real thickness of the pipe wall which can differ from the nominal thickness
3.2
axial coverage

total axial extent of the evaluated section of the pipe radiograph measured on the

detector (3.8)
3.3
axial coverage

total axial extent of the evaluated section of the pipe radiograph measured

along the central axis of the pipe
3.4
basic spatial resolution
detector

smallest geometrical detail, which can be resolved in a digital image at a magnification

equal to 1; corresponds to half of the measured image unsharpness in a digital image; corresponds to

the effective pixel size (3.19) of the magnified image; and is determined from the smallest number of the

duplex wire pair, which is not separable by visual inspection or from the smallest number of the duplex

wire pair with less than 20 % modulation depth in a linearized profile

Note 1 to entry: For this measurement, the duplex wire IQI is placed directly on the digital detector (3.8) array or

imaging plate.
detector

Note 2 to entry: The measurements of SR and unsharpness are described in ISO 19232-5. and

[17]
ASTM E2002 .
3.5
basic spatial resolution
image

smallest geometrical detail, which can be resolved in a digital image at a magnification

>1; corresponds to half of the measured image unsharpness in a digital image; corresponds to the

effective pixel size (3.19) of the magnified image; and is determined from the smallest number of the

duplex wire pair, which is not separable by visual inspection or from the smallest number of the duplex

wire pair with less than 20 % modulation depth in a linearized profile
image

Note 1 to entry: The measurements of SR and unsharpness are described in ISO 19232-5. and

[17]
ASTM E2002 .
3.6
comparator

reference object of defined dimension c and material for dimensional calibration of a radiographic image

2 © ISO 2018 – All rights reserved
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SIST EN ISO 20769-1:2019
ISO 20769-1:2018(E)
3.7
computed radiography

complete system comprising a storage phosphor imaging plate (IP) (3.23) and a corresponding read-

out unit (scanner or reader), which converts the information from the IP into a digital image and the

control software of the read-out unit
3.8
detector

detection device, consisting of a NDT film system (see ISO 11699-1) or a digital radiography system

using a CR system or a DDA system

Note 1 to entry: Film systems and IPs can be used as flexible and curved detectors or in planar cassettes.

3.9
digital detector array
DDA

electronic device converting ionizing or penetrating radiation into a discrete array of analogue

signals which are subsequently digitized and transferred to a computer for display as a digital image

corresponding to the radiologic energy pattern imparted upon the input region of the device and the

control software
3.10
imaged comparator dimension
dimension of the comparator (3.6) measured on the detector (3.8)
3.11
imaged outside diameter
D ′
nominal outside diameter of the pipe measured on the detector
3.12
maximum penetrated thickness
max

maximum thickness of material for a pipe which occurs for a tangent to the inner pipe surface

3.13
measured wall thickness
meas
thickness of the pipe wall as measured on the radiograph or digital image
3.14
nominal wall thickness

thickness of the pipe wall as given by the manufacturer, neglecting the manufacturing tolerances

3.15
normalized signal-to-noise ratio
SNR
image

ratio of signal-to-noise, normalized by the basic spatial resolution, SR , (3.5) as measured directly

in the digital image and/or calculated from the measured SNR , by:
measured
88,6 μm
SNRS= NR
Nmeasured
SR image SR detector
Note 1 to entry: can be substituted by (3.4) at magnification equal to 1.
b b
© ISO 2018 – All rights reserved 3
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SIST EN ISO 20769-1:2019
ISO 20769-1:2018(E)
3.16
outside diameter

nominal outer diameter of the pipe as given by the manufacturer, neglecting the manufacturing

tolerances
3.17
pipe centre to detector distance
PDD
distance between the pipe centre and the detector (3.8)
3.18
pixel size

geometrical centre-to-centre distance between adjacent pixels in a row (horizontal pitch) or column

(vertical pitch) of the scanned image
[SOURCE: ISO 14096-2:2005, 3.2]
3.19
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
3.20
source size
size of the radiation source
[SOURCE: ISO 16371-2:2017, 3.15]
3.21
source-to-detector distance
SDD

distance between the source of radiation and the detector (3.8) measured in the direction of the beam

3.22
source-to-pipe centre distance
SPD

distance between the source of radiation and the pipe centre (pipe axis) measured in the direction of

the beam
3.23
storage phosphor imaging plate

photostimulable luminescent material capable of storing a latent radiographic image of a material being

examined and which, upon stimulation by a source of red light of appropriate wavelength, generates

luminescence proportional to radiation absorbed
4 Classification of radiographic techniques
The tangential radiographic techniques are divided into two classes:
— class TA, basic techniques;
— class TB, improved techniques.
The basic techniques, class TA, are intended for tangential radiography of
...

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