SIST EN ISO 16809:2019
(Main)Non-destructive testing - Ultrasonic thickness measurement (ISO 16809:2017)
Non-destructive testing - Ultrasonic thickness measurement (ISO 16809:2017)
ISO 16809:2017 specifies the principles for ultrasonic thickness measurement of metallic and non-metallic materials by direct contact, based on measurement of time of flight of ultrasonic pulses only.
Zerstörungsfreie Prüfung - Dickenmessung mit Ultraschall (ISO 16809:2017)
Dieses Dokument legt die Grundlagen für die Messung der Dicke metallischer und nicht metallischer Werkstoffe mit Ultraschall durch unmittelbaren Kontakt mit dem Prüfgegenstand fest, ausschließlich basierend auf der Messung der Laufzeit von Ultraschallimpulsen.
Essais non destructifs - Mesurage de l'épaisseur par ultrasons (ISO 16809:2017)
Le présent document spécifie les principes pour le mesurage de l'épaisseur par ultrasons de matériaux métalliques et non métalliques par contact direct, exclusivement basés sur la mesure du temps de vol d'impulsions ultrasonores.
Neporušitvene preiskave - Ultrazvočno merjenje debeline (ISO 16809:2017)
Standard ISO 16809:2017 določa načela za ultrazvočno merjenje debeline kovinskih in nekovinskih materialov z neposrednim stikom, in sicer samo na podlagi merjenja časa preleta ultrazvočnih impulzov.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 16809:2019
01-november-2019
Nadomešča:
SIST EN 14127:2011
Neporušitvene preiskave - Ultrazvočno merjenje debeline (ISO 16809:2017)
Non-destructive testing - Ultrasonic thickness measurement (ISO 16809:2017)
Zerstörungsfreie Prüfung - Dickenmessung mit Ultraschall (ISO 16809:2017)
Essais non destructifs - Mesurage de l'épaisseur par ultrasons (ISO 16809:2017)
Ta slovenski standard je istoveten z: EN ISO 16809:2019
ICS:
19.100 Neporušitveno preskušanje Non-destructive testing
SIST EN ISO 16809:2019 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN ISO 16809:2019
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SIST EN ISO 16809:2019
EN ISO 16809
EUROPEAN STANDARD
NORME EUROPÉENNE
June 2019
EUROPÄISCHE NORM
ICS 19.100 Supersedes EN 14127:2011
English Version
Non-destructive testing - Ultrasonic thickness
measurement (ISO 16809:2017)
Essais non destructifs - Mesurage de l'épaisseur par Zerstörungsfreie Prüfung - Dickenmessung mit
ultrasons (ISO 16809:2017) Ultraschall (ISO 16809:2017)
This European Standard was approved by CEN on 8 April 2019.
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
© 2019 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 16809:2019 E
worldwide for CEN national Members.
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SIST EN ISO 16809:2019
EN ISO 16809:2019 (E)
Contents Page
European foreword . 3
2
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SIST EN ISO 16809:2019
EN ISO 16809:2019 (E)
European foreword
The text of ISO 16809:2017 has been prepared by Technical Committee ISO/TC 135 "Non-destructive
testing” of the International Organization for Standardization (ISO) and has been taken over as
EN ISO 16809:2019 by 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 December 2019, and conflicting national standards
shall be withdrawn at the latest by December 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 14127:2011.
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 16809:2017 has been approved by CEN as EN ISO 16809:2019 without any modification.
3
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SIST EN ISO 16809:2019
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SIST EN ISO 16809:2019
INTERNATIONAL ISO
STANDARD 16809
Second edition
2017-11
Non-destructive testing — Ultrasonic
thickness measurement
Essais non destructifs — Mesurage de l'épaisseur par ultrasons
Reference number
ISO 16809:2017(E)
©
ISO 2017
---------------------- Page: 7 ----------------------
SIST EN ISO 16809:2019
ISO 16809:2017(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2017, Published in Switzerland
All rights reserved. Unless otherwise specified, 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
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2017 – All rights reserved
---------------------- Page: 8 ----------------------
SIST EN ISO 16809:2019
ISO 16809:2017(E)
Contents Page
Foreword .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Measurement modes . 1
5 General requirements . 3
5.1 Instruments . 3
5.2 Probes . 3
5.3 Couplant . 3
5.4 Reference blocks . 3
5.5 Test objects . 3
5.6 Qualification of personnel . 4
6 Application of the technique . 4
6.1 Surface conditions and surface preparation . 4
6.2 Technique . 4
6.2.1 General. 4
6.2.2 Measurement during manufacture . 5
6.2.3 In-service measurement of residual wall thickness . 5
6.3 Selection of probe . 6
6.4 Selection of instrument . 6
6.5 Materials different from the reference material . 6
6.6 Special measuring conditions . 7
6.6.1 General. 7
6.6.2 Measurements at temperatures below 0 °C . 7
6.6.3 Measurements at elevated temperatures . 7
6.6.4 Hazardous atmospheres . . 7
7 Instrument setting . 7
7.1 General . 7
7.2 Methods of setting . 8
7.2.1 General. 8
7.2.2 Digital thickness instruments . 8
7.2.3 A-scan instrument . 8
7.3 Checks of settings . 9
8 Influence on accuracy .10
8.1 Operational conditions.10
8.1.1 Surface conditions .10
8.1.2 Surface temperature .10
8.1.3 Metallic coating .11
8.1.4 Non-metallic coating .11
8.1.5 Geometry .12
8.2 Equipment .12
8.2.1 Resolution .12
8.2.2 Range .13
8.3 Evaluation of accuracy .13
8.3.1 General.13
8.3.2 Influencing parameters .14
8.3.3 Method of calculation .14
9 Influence of materials .14
9.1 General .14
9.2 Inhomogeneity .14
9.3 Anisotropy .14
© ISO 2017 – All rights reserved iii
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SIST EN ISO 16809:2019
ISO 16809:2017(E)
9.4 Attenuation .14
9.5 Surface conditions .14
9.5.1 General.14
9.5.2 Contact surface .15
9.5.3 Reflecting surface .15
9.5.4 Corrosion and erosion . .15
10 Test report .16
10.1 General .16
10.2 General information .16
10.3 Measurement data .17
Annex A (informative) Corrosion in vessels and piping .18
Annex B (informative) Instrument settings .23
Annex C (informative) Parameters influencing accuracy .26
Annex D (informative) Selection of measuring technique .32
Bibliography .37
iv © ISO 2017 – All rights reserved
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SIST EN ISO 16809:2019
ISO 16809:2017(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 Technical Committee ISO/TC 135, Non-destructive testing,
Subcommittee SC 3, Ultrasonic testing.
This second edition cancels and replaces the first edition (ISO 16809:2012), which has been technically
revised. The main changes compared to the previous edition are as follows:
— editorial improvements have been made;
— the terminology has been adapted to the latest edition of ISO 5577;
— Formulae (5) and (6) have been corrected.
© ISO 2017 – All rights reserved v
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SIST EN ISO 16809:2019
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SIST EN ISO 16809:2019
INTERNATIONAL STANDARD ISO 16809:2017(E)
Non-destructive testing — Ultrasonic thickness
measurement
1 Scope
This document specifies the principles for ultrasonic thickness measurement of metallic and non-
metallic materials by direct contact, based on measurement of time of flight of ultrasonic pulses only.
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 5577, Non-destructive testing — Ultrasonic testing — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 5577 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/
4 Measurement modes
The thickness of a part or structure is determined by accurately measuring the time required for a
short ultrasonic pulse generated by a transducer to travel through the thickness of the material once,
twice or several times.
The material thickness is calculated by multiplying the known sound velocity of the material with the
transit time and dividing by the number of times the pulse transits the material wall.
This principle can be accomplished by applying one of the following modes, see Figure 1.
1) Mode 1: Measure the transit time from an initial excitation pulse to a first returning echo, minus a
zero correction to account for the thickness of the probe's wear plate and the couplant layer (single-
echo mode).
2) Mode 2: Measure the transit time from the end of a delay line to the first back wall echo (single-
echo delay line mode).
3) Mode 3: Measure the transit time between back wall echoes (multiple-echo mode).
4) Mode 4: Measure the transit time for a pulse travelling from the transmitter to a receiver in contact
with the back wall (through-transmission mode).
© ISO 2017 – All rights reserved 1
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SIST EN ISO 16809:2019
ISO 16809:2017(E)
Mode 1 Mode 2
Mode 3 Mode 4
Key
A transmit/receive probe D transmission pulse indication
A1 transmit probe E1 to E3 back wall echoes
A2 receive probe F interface echo
A3 dual-element probe G delay path
B test object H received pulse
C sound path travel time
Figure 1 — Measurement modes
2 © ISO 2017 – All rights reserved
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SIST EN ISO 16809:2019
ISO 16809:2017(E)
5 General requirements
5.1 Instruments
The following types of instruments shall be used to achieve thickness measurement:
a) dedicated ultrasonic thickness measurement instruments with numerical display showing the
measured value;
b) dedicated ultrasonic thickness measurement instruments with numerical display showing the
measured value and A-scan presentation (waveform display);
c) instruments designed primarily for the detection of discontinuities with A-scan presentation of
signals. This type of instrument can also include numerical display of thickness values.
See 6.4.
5.2 Probes
The following types of probes shall be used; these are generally longitudinal wave probes:
— dual-element probes;
— single-element probes.
See 6.3.
5.3 Couplant
Acoustic contact between probe (probes) and material shall be provided, normally by application of a
fluid or gel.
The couplant shall not have any adverse effect on the test object, the equipment or represent a health
hazard to the operator.
For the use of the couplant in special measuring conditions, see 6.6.
The coupling medium should be chosen to suit the surface conditions and the irregularities of the
surface to ensure adequate coupling.
5.4 Reference blocks
The measuring system shall be calibrated on one or more samples or reference blocks representative of
the object to be measured, i.e. having comparable dimensions, material and structure. The thickness of
the blocks or the steps should cover the range of thickness to be measured. Either the thickness or the
sound velocity of the reference blocks shall be known.
5.5 Test objects
The object to be measured shall allow for ultrasonic wave propagation.
There shall be free access to each individual area to be measured.
The surface of the area to be measured shall be free of all dirt, grease, lint, scale, welding flux and
spatter, oil or other extraneous matter that could interfere with the testing.
If the surface is coated, the coating shall have good adhesion to the material. Otherwise it shall be
removed.
© ISO 2017 – All rights reserved 3
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SIST EN ISO 16809:2019
ISO 16809:2017(E)
When measuring through coating its thickness and sound velocity need to be known unless mode 3
is used.
For further details, see Clause 8.
5.6 Qualification of personnel
An operator performing ultrasonic thickness measurement according to this document shall have
a basic knowledge of the physics of ultrasound, and a detailed understanding and training related to
ultrasonic thickness measurements. In addition, the operator shall have knowledge of the product and
material to be tested.
It is assumed that ultrasonic thickness testing is performed by qualified and capable personnel. In order
to prove this qualification, it is recommended that personnel be qualified in accordance with ISO 9712
or equivalent.
NOTE For categories III and IV according to Pressure Equipment Directive 97/23/EC, Annex I, 3.1.3, there is
a requirement for personnel to be approved by a third-party organization recognized by a member state.
6 Application of the technique
6.1 Surface conditions and surface preparation
Using the pulse-echo method means that the ultrasonic pulse needs to pass the contact surface between
test object and the probe at least twice: when entering the object and when leaving it.
Therefore, a clean and even contact area with at least twice the probe's diameter is preferred. Poor
contact will result in loss of energy, distortion of signals and sound path.
To enable sound propagation all loose parts and non-adherent coatings shall be removed by brushing or
grinding.
Attached layers, like colour coating, plating, enamels, may stay on the object, but only a few thickness
meters are able to exclude these layers from being measured.
Very often, thickness measurements need to be done on corroded surfaces, e.g. storage tanks and
pipelines. To increase measuring accuracy the contact surface should be ground within an area at least
two times the probe's diameter. This area should be clean from corrosion products.
Care should be taken not to reduce the thickness below the minimum acceptable value.
6.2 Technique
6.2.1 General
The task of ultrasonic thickness measurements can be separated into two application areas:
— measurement during manufacture;
— in-service measurements of residual wall thickness.
Each area has its own special conditions which require special measuring techniques.
Using a knowledge of the material, geometry and thickness to be measured and the required accuracy,
the most suitable measuring equipment and mode shall be selected as follows (Annex D gives guidance):
a) depending on the thickness and the material, frequencies from 100 kHz with through-transmission
on highly attenuative materials up to 50 MHz on thin metal sheets shall be used;
b) if dual-element probes are used, then compensation for V-path error is required;
4 © ISO 2017 – All rights reserved
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SIST EN ISO 16809:2019
ISO 16809:2017(E)
c) on curved objects, the diameter of the probe contact area shall be significantly smaller than the
diameter of the test object.
The accuracy of the thickness measurement depends on how accurate the time of flight can be measured,
on the mode of time-measuring (zero crossing, flank-to-flank, peak-to-peak), on the mode chosen (with
multiple echoes, mode 3, the accuracy is higher than with modes 1 and 2), and on the frequencies which
can be used (higher frequencies provide higher accuracy than lower frequencies because of the more
accurate time measurement).
Ultrasonic thickness measurement is often required over an area of the component to be measured.
Where this is the case, consideration should be given to the spacing between each
...
SLOVENSKI STANDARD
oSIST prEN ISO 16809:2019
01-februar-2019
1HSRUXãLWYHQHSUHLVNDYH8OWUD]YRþQRPHUMHQMHGHEHOLQH ,62
Non-destructive testing - Ultrasonic thickness measurement (ISO 16809:2017)
Zerstörungsfreie Prüfung - Dickenmessung mit Ultraschall (ISO 16809:2017)
Essais non destructifs - Mesurage de l'épaisseur par ultrasons (ISO 16809:2017)
Ta slovenski standard je istoveten z: prEN ISO 16809
ICS:
19.100 Neporušitveno preskušanje Non-destructive testing
oSIST prEN ISO 16809:2019 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
---------------------- Page: 1 ----------------------
oSIST prEN ISO 16809:2019
---------------------- Page: 2 ----------------------
oSIST prEN ISO 16809:2019
INTERNATIONAL ISO
STANDARD 16809
Second edition
2017-11
Non-destructive testing — Ultrasonic
thickness measurement
Essais non destructifs — Mesurage de l'épaisseur par ultrasons
Reference number
ISO 16809:2017(E)
©
ISO 2017
---------------------- Page: 3 ----------------------
oSIST prEN ISO 16809:2019
ISO 16809:2017(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2017, Published in Switzerland
All rights reserved. Unless otherwise specified, 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
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2017 – All rights reserved
---------------------- Page: 4 ----------------------
oSIST prEN ISO 16809:2019
ISO 16809:2017(E)
Contents Page
Foreword .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Measurement modes . 1
5 General requirements . 3
5.1 Instruments . 3
5.2 Probes . 3
5.3 Couplant . 3
5.4 Reference blocks . 3
5.5 Test objects . 3
5.6 Qualification of personnel . 4
6 Application of the technique . 4
6.1 Surface conditions and surface preparation . 4
6.2 Technique . 4
6.2.1 General. 4
6.2.2 Measurement during manufacture . 5
6.2.3 In-service measurement of residual wall thickness . 5
6.3 Selection of probe . 6
6.4 Selection of instrument . 6
6.5 Materials different from the reference material . 6
6.6 Special measuring conditions . 7
6.6.1 General. 7
6.6.2 Measurements at temperatures below 0 °C . 7
6.6.3 Measurements at elevated temperatures . 7
6.6.4 Hazardous atmospheres . . 7
7 Instrument setting . 7
7.1 General . 7
7.2 Methods of setting . 8
7.2.1 General. 8
7.2.2 Digital thickness instruments . 8
7.2.3 A-scan instrument . 8
7.3 Checks of settings . 9
8 Influence on accuracy .10
8.1 Operational conditions.10
8.1.1 Surface conditions .10
8.1.2 Surface temperature .10
8.1.3 Metallic coating .11
8.1.4 Non-metallic coating .11
8.1.5 Geometry .12
8.2 Equipment .12
8.2.1 Resolution .12
8.2.2 Range .13
8.3 Evaluation of accuracy .13
8.3.1 General.13
8.3.2 Influencing parameters .14
8.3.3 Method of calculation .14
9 Influence of materials .14
9.1 General .14
9.2 Inhomogeneity .14
9.3 Anisotropy .14
© ISO 2017 – All rights reserved iii
---------------------- Page: 5 ----------------------
oSIST prEN ISO 16809:2019
ISO 16809:2017(E)
9.4 Attenuation .14
9.5 Surface conditions .14
9.5.1 General.14
9.5.2 Contact surface .15
9.5.3 Reflecting surface .15
9.5.4 Corrosion and erosion . .15
10 Test report .16
10.1 General .16
10.2 General information .16
10.3 Measurement data .17
Annex A (informative) Corrosion in vessels and piping .18
Annex B (informative) Instrument settings .23
Annex C (informative) Parameters influencing accuracy .26
Annex D (informative) Selection of measuring technique .32
Bibliography .37
iv © ISO 2017 – All rights reserved
---------------------- Page: 6 ----------------------
oSIST prEN ISO 16809:2019
ISO 16809:2017(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 Technical Committee ISO/TC 135, Non-destructive testing,
Subcommittee SC 3, Ultrasonic testing.
This second edition cancels and replaces the first edition (ISO 16809:2012), which has been technically
revised. The main changes compared to the previous edition are as follows:
— editorial improvements have been made;
— the terminology has been adapted to the latest edition of ISO 5577;
— Formulae (5) and (6) have been corrected.
© ISO 2017 – All rights reserved v
---------------------- Page: 7 ----------------------
oSIST prEN ISO 16809:2019
---------------------- Page: 8 ----------------------
oSIST prEN ISO 16809:2019
INTERNATIONAL STANDARD ISO 16809:2017(E)
Non-destructive testing — Ultrasonic thickness
measurement
1 Scope
This document specifies the principles for ultrasonic thickness measurement of metallic and non-
metallic materials by direct contact, based on measurement of time of flight of ultrasonic pulses only.
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 5577, Non-destructive testing — Ultrasonic testing — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 5577 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/
4 Measurement modes
The thickness of a part or structure is determined by accurately measuring the time required for a
short ultrasonic pulse generated by a transducer to travel through the thickness of the material once,
twice or several times.
The material thickness is calculated by multiplying the known sound velocity of the material with the
transit time and dividing by the number of times the pulse transits the material wall.
This principle can be accomplished by applying one of the following modes, see Figure 1.
1) Mode 1: Measure the transit time from an initial excitation pulse to a first returning echo, minus a
zero correction to account for the thickness of the probe's wear plate and the couplant layer (single-
echo mode).
2) Mode 2: Measure the transit time from the end of a delay line to the first back wall echo (single-
echo delay line mode).
3) Mode 3: Measure the transit time between back wall echoes (multiple-echo mode).
4) Mode 4: Measure the transit time for a pulse travelling from the transmitter to a receiver in contact
with the back wall (through-transmission mode).
© ISO 2017 – All rights reserved 1
---------------------- Page: 9 ----------------------
oSIST prEN ISO 16809:2019
ISO 16809:2017(E)
Mode 1 Mode 2
Mode 3 Mode 4
Key
A transmit/receive probe D transmission pulse indication
A1 transmit probe E1 to E3 back wall echoes
A2 receive probe F interface echo
A3 dual-element probe G delay path
B test object H received pulse
C sound path travel time
Figure 1 — Measurement modes
2 © ISO 2017 – All rights reserved
---------------------- Page: 10 ----------------------
oSIST prEN ISO 16809:2019
ISO 16809:2017(E)
5 General requirements
5.1 Instruments
The following types of instruments shall be used to achieve thickness measurement:
a) dedicated ultrasonic thickness measurement instruments with numerical display showing the
measured value;
b) dedicated ultrasonic thickness measurement instruments with numerical display showing the
measured value and A-scan presentation (waveform display);
c) instruments designed primarily for the detection of discontinuities with A-scan presentation of
signals. This type of instrument can also include numerical display of thickness values.
See 6.4.
5.2 Probes
The following types of probes shall be used; these are generally longitudinal wave probes:
— dual-element probes;
— single-element probes.
See 6.3.
5.3 Couplant
Acoustic contact between probe (probes) and material shall be provided, normally by application of a
fluid or gel.
The couplant shall not have any adverse effect on the test object, the equipment or represent a health
hazard to the operator.
For the use of the couplant in special measuring conditions, see 6.6.
The coupling medium should be chosen to suit the surface conditions and the irregularities of the
surface to ensure adequate coupling.
5.4 Reference blocks
The measuring system shall be calibrated on one or more samples or reference blocks representative of
the object to be measured, i.e. having comparable dimensions, material and structure. The thickness of
the blocks or the steps should cover the range of thickness to be measured. Either the thickness or the
sound velocity of the reference blocks shall be known.
5.5 Test objects
The object to be measured shall allow for ultrasonic wave propagation.
There shall be free access to each individual area to be measured.
The surface of the area to be measured shall be free of all dirt, grease, lint, scale, welding flux and
spatter, oil or other extraneous matter that could interfere with the testing.
If the surface is coated, the coating shall have good adhesion to the material. Otherwise it shall be
removed.
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When measuring through coating its thickness and sound velocity need to be known unless mode 3
is used.
For further details, see Clause 8.
5.6 Qualification of personnel
An operator performing ultrasonic thickness measurement according to this document shall have
a basic knowledge of the physics of ultrasound, and a detailed understanding and training related to
ultrasonic thickness measurements. In addition, the operator shall have knowledge of the product and
material to be tested.
It is assumed that ultrasonic thickness testing is performed by qualified and capable personnel. In order
to prove this qualification, it is recommended that personnel be qualified in accordance with ISO 9712
or equivalent.
NOTE For categories III and IV according to Pressure Equipment Directive 97/23/EC, Annex I, 3.1.3, there is
a requirement for personnel to be approved by a third-party organization recognized by a member state.
6 Application of the technique
6.1 Surface conditions and surface preparation
Using the pulse-echo method means that the ultrasonic pulse needs to pass the contact surface between
test object and the probe at least twice: when entering the object and when leaving it.
Therefore, a clean and even contact area with at least twice the probe's diameter is preferred. Poor
contact will result in loss of energy, distortion of signals and sound path.
To enable sound propagation all loose parts and non-adherent coatings shall be removed by brushing or
grinding.
Attached layers, like colour coating, plating, enamels, may stay on the object, but only a few thickness
meters are able to exclude these layers from being measured.
Very often, thickness measurements need to be done on corroded surfaces, e.g. storage tanks and
pipelines. To increase measuring accuracy the contact surface should be ground within an area at least
two times the probe's diameter. This area should be clean from corrosion products.
Care should be taken not to reduce the thickness below the minimum acceptable value.
6.2 Technique
6.2.1 General
The task of ultrasonic thickness measurements can be separated into two application areas:
— measurement during manufacture;
— in-service measurements of residual wall thickness.
Each area has its own special conditions which require special measuring techniques.
Using a knowledge of the material, geometry and thickness to be measured and the required accuracy,
the most suitable measuring equipment and mode shall be selected as follows (Annex D gives guidance):
a) depending on the thickness and the material, frequencies from 100 kHz with through-transmission
on highly attenuative materials up to 50 MHz on thin metal sheets shall be used;
b) if dual-element probes are used, then compensation for V-path error is required;
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c) on curved objects, the diameter of the probe contact area shall be significantly smaller than the
diameter of the test object.
The accuracy of the thickness measurement depends on how accurate the time of flight can be measured,
on the mode of time-measuring (zero crossing, flank-to-flank, peak-to-peak), on the mode chosen (with
multiple echoes, mode 3, the accuracy is higher than with modes 1 and 2), and on the frequencies which
can be used (higher frequencies provide higher accuracy than lower frequencies because of the more
accurate time measurement).
Ultrasonic thickness measurement is often required over an area of the component to be measured.
Where this is the case, consideration should be given to the spacing between each measurement. Such
spacing should be even and the use of a grid is recommended. The grid size should be selected to give a
balance between the confidence in the results and the work content involved.
Measuring the thickness ultrasonically means measuring the time of flight and then calculating the
thickness assuming a constant sound velocity (see Clause 7). If the velocity is not constant within the
path the ultrasonic pulse has travelled, the accuracy of the measurement will be severely affected.
6.2.2 Measurement during manufacture
6.2.2.1 Modes 1, 2 and 3
Where the pulse-echo mode is used, the flow charts in Figures D.1 and D.2 give guidance on the selection
of the best technique and equipment.
Thickness measurement on clean parallel surfaces may be carried out with simple numerical display
thickness instruments.
On composite materials which generate echoes in addition to the back wall echo, it is recommended
that thickness instruments with A-scan displays [type 5.1 b) or 5.1 c)] be used to select the correct echo
of the thickness measurement.
6.2.2.2 Mode 4
If the material is highly attenuative and large thicknesses need to be measured, no echo technique can
be used, i.e. only through-transmission (mode 4) is applicable.
Two probes on opposite sides of the test object shall then be used. The instrument therefore shall allow
for operation with separate transmitter and receiver (TR mode). In most cases, the frequency shall be
lower than 1 MHz. Special low-frequency instruments from group c) in 5.1 with low-frequency probes
shall be used.
6.2.3 In-service measurement of residual wall thickness
During in-service testing, measurements need to be taken on materials that are subject to corrosion or
erosion. The surfaces can be rough and contain pitting or other defects (see Annex A) which are areas
of low reflectivity.
For these applications, the use of dual-element probes is recommended. The sensitivity shall be set
manually to detect the bad reflecting areas.
Where it is necessary to take a lot of measurements, the readings shall be values with the information
on the location of the measuring point. Special testing programs are available to achieve this (data
logging).
With in-service testing, the environmental conditions are very important. Equipment can be needed
which can withstand high temperatures and harsh environments, or has special electrical shielding.
The flowcharts in Figures D.3 and D.4 give guidance on in-service thickness measurements.
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6.3 Selection of probe
Having chosen a suitable measurement procedure according to 6.2, i.e. a general decision for a probe
type (single- or dual-element) has been made, there are other parameters that need to be considered
when matching the probe to the measuring conditions.
Wide-band probes offer a shorter pulse than narrow-band probes, thus giving a suited flank or peak to
start and stop the time-of-flight measurement, giving a better resolution when measuring thin sheets
or coatings.
Additionally, a wide frequency band always gives a stable echo even when attenuating materials need
to be measured.
Probe size and frequency shall be chosen to cover the measurement range by a narrow sound beam to
get an echo from a well-defined area.
For dual-element probes the focal range shall cover the expected thickness range.
When measuring small thicknesses, a delay path shall be used. The measurement shall be done with
the interface echo (delay path/test object) and the first back wall echo from the test object (mode 2) or
to make the measurement using mode 3. The material of the delay path shall be chosen to generate a
suitable interface echo. Using the same material as the test object does not generate an interface echo.
When the materi
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