prEN ISO 23279

• Abstract:

  ISO 23279:2017 specifies how to characterize indications from discontinuities by classifying them as originating from planar or non-planar embedded discontinuities.; This procedure is also suitable for indications from discontinuities that break the surface after removal of the weld reinforcement.

• Status: Not Published
• Publication Date: 02-Mar-2028
• ICS: 25.160.40 - Welded joints and welds
• Technical Committee: CEN/TC 121 - Welding
• Drafting Committee: CEN/TC 121/WG 21 - Testing of welds
• Current Stage: 4020 - Submission to enquiry - Enquiry
• Start Date: 10-Sep-2026
• Completion Date: 10-Sep-2026
• Ref Project: oSIST prEN ISO 23279:2026 - Non-destructive testing of welds - Ultrasonic testing - Characterization of discontinuities in welds (ISO/DIS 23279:2026)

• Revises: EN ISO 23279:2017 - Non-destructive testing of welds - Ultrasonic testing - Characterization of discontinuities in welds (ISO 23279:2017)
• Effective Date: 27-Nov-2024

prEN ISO 23279 is a CEN draft of ISO/DIS 23279:2026 for non-destructive testing of welds by ultrasonic testing. It specifies how to characterize indications from discontinuities in welds by classifying them as originating from planar or non-planar embedded discontinuities, and the same procedure is also suitable for indications that break the surface after removal of weld reinforcement. The document is used by ultrasonic testing personnel, welding inspectors, and anyone who has to decide whether a weld indication is likely to be a lack of fusion, crack, inclusion, porosity, or another type of reflector.

What does prEN ISO 23279 specify?

prEN ISO 23279 specifies a classification method for ultrasonic indications in welds. The method turns raw echo observations into a practical decision about whether an indication is more likely to come from a planar or non-planar discontinuity.

The document is organized into a short scope, references and terms section, then the principle of classification and the detailed criteria. Its normative Annex A gives the flowchart used for classification, while Annexes B and C provide supporting information for directional reflectivity and echo-pattern interpretation.

Annex	What it covers
Annex A	Normative flowchart procedure for classifying indications from internal discontinuities in welds
Annex B	Informative guidance on directional reflectivity
Annex C	Informative basic dynamic echo patterns of reflectors

What are the key requirements of prEN ISO 23279?

prEN ISO 23279 classifies indications by combining several ultrasonic observations, not by relying on one measurement alone. In practice, the operator has to compare amplitude, directionality, and echo patterns in a defined order so that the result is repeatable and traceable.

How the classification starts

Clause 4 says the classification is based on welding technique, the geometrical position of the discontinuity, maximum echo amplitude, directional reflectivity, static echo pattern, and dynamic echo pattern. That matters because the same reflector can look different depending on probe angle, weld geometry, and scan direction.

Clause 5.1 says the same probes should preferably be used for detection and classification, and the flowchart in Annex A standardizes the decision path. Thresholds are set by comparison with the distance-amplitude curve (DAC), the reference level when Time-Corrected Gain (TCG) is used, or the amplitudes seen from different directions.

How the stages work

• Stage 1 filters out weak indications below the evaluation level in ISO 11666. In practice, this prevents insignificant low-level echoes from being over-interpreted.
• Stage 2 treats indications at or above the reference level plus 6 dB as associated with a planar discontinuity. This is the first strong sign that the reflector may be a lack of fusion or a crack-like feature.
• Stage 3 uses directional reflectivity, but only for indications long enough to qualify under the thickness-dependent length criterion. The method compares the same reflector from different directions, with beam angles separated by at least 10°, and expects a strong amplitude imbalance before classifying the indication as planar.
• Stage 4 compares the static echo pattern, or A-scan, with the pattern from a 3 mm diameter side-drilled hole. If the response is single and smooth in at least two directions, the indication is treated as non-planar, such as an inclusion.
• Stage 5 examines the transverse dynamic echo pattern, which is the echo envelope seen while moving the probe perpendicular to the discontinuity. Annex C defines the patterns used here; some patterns support planar classification, while a clustered pattern points to multiple non-planar reflectors.

What the stage results mean in practice

Clause 5.3 says indications that satisfy the directional reflectivity criteria are mainly due to lacks of fusion. That is important for acceptance decisions because lack of fusion is typically treated differently from rounded inclusions or porosity.

Clause 5.4 and 5.5 separate single smooth reflectors from rough, travelling, or clustered responses. In practice, this helps the examiner distinguish between a simple isolated reflector and a discontinuity that behaves like a crack or a group of defects.

Clause 5.6 allows complementary testing when the result is uncertain. The document explicitly allows more reflectivity directions, additional probes, probe movement parallel to the discontinuity, or another NDT method such as radiography.

What terms does prEN ISO 23279 define?

prEN ISO 23279 uses the terms and definitions from ISO 5577. The following terms are central to reading the standard:

• A-scan - The static ultrasonic display used to judge whether the echo is single, smooth, ragged, or clustered.
• Distance-amplitude curve (DAC) - A reference curve used to compare echo amplitudes at different sound paths.
• Time-Corrected Gain (TCG) - A gain method that replaces direct DAC comparison when setting the reference level.
• Directional reflectivity - The change in echo amplitude when the same reflector is tested from different directions.
• Planar discontinuity - A discontinuity that tends to show strong directionality and crack-like behavior, such as lack of fusion.
• Non-planar discontinuity - A discontinuity that tends to give a smoother, less directional ultrasonic response, such as inclusion or porosity.
• Transverse dynamic echo pattern - The echo envelope observed while moving the probe perpendicular to the discontinuity.
• Reference reflector - The standard 3 mm diameter side-drilled hole used in Stage 4 comparisons.

Who uses prEN ISO 23279?

prEN ISO 23279 is used by ultrasonic testing personnel who inspect welds and decide how to classify indications. It also supports welding quality managers, NDT procedure writers, and buyers or contractors who need a clear technical basis for weld acceptance, reporting, or dispute resolution.

The standard is relevant wherever welded joints are examined by ultrasonic testing and the type of discontinuity has to be identified consistently.

What changed in prEN ISO 23279 from the previous edition?

prEN ISO 23279 is the fourth edition and cancels and replaces ISO 23279:2017. The foreword says this edition has been technically revised.

Which standards are used with prEN ISO 23279?

prEN ISO 23279 cites two normative references:

• ISO 5577 - provides the vocabulary used for the terms and definitions in the document.
• ISO 17640 - provides ultrasonic testing techniques, testing levels, and assessment, and is also the basis for the probe movement and testing approach used in the dynamic pattern clauses.

What does the prEN ISO 23279 document contain?

The document contains a classification flowchart in Annex A, supporting examples for directional reflectivity in Annex B, and detailed descriptions of five basic dynamic echo patterns in Annex C. These annexes are used to help the examiner move from an ultrasonic indication to a classification that can be documented and defended.

It also includes the key thresholds and comparison rules used in the flowchart, plus the conditions for applying each stage. For a reader setting up a weld inspection procedure, the most useful parts are the staged decision process, the A-scan and envelope pattern descriptions, and the examples that show how planar and non-planar responses differ in practice.

SLOVENSKI STANDARD
01-oktober-2026
Neporušitveno preskušanje zvarnih spojev - Ultrazvočno preskušanje -
Karakterizacija nehomogenosti v zvarnih spojih (ISO/DIS 23279:2026)
Non-destructive testing of welds - Ultrasonic testing - Characterization of discontinuities
in welds (ISO/DIS 23279:2026)
Zerstörungsfreie Prüfung von Schweißverbindungen - Ultraschallprüfung -
Charakterisierung von Inhomogenitäten in Schweißnähten (ISO/DIS 23279:2026)
Essais non destructifs des assemblages soudés - Contrôle par ultrasons -
Caractérisation des discontinuités dans les assemblages soudés (ISO/DIS 23279:2026)
Ta slovenski standard je istoveten z: prEN ISO 23279
ICS:
25.160.40 Varjeni spoji in vari Welded joints and welds
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
International
Standard
ISO/DIS 23279
ISO/TC 44/SC 5
Non-destructive testing of
Secretariat: AFNOR
welds — Ultrasonic testing —
Voting begins on:
Characterization of discontinuities
2026-09-07
in welds
Voting terminates on:
2026-11-30
Essais non destructifs des assemblages soudés — Contrôle
par ultrasons — Caractérisation des discontinuités dans les
assemblages soudés
ICS: 25.160.40
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document has not been edited by the ISO Central Secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
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.
Reference number
ISO/DIS 23279:2026(en)
DRAFT
ISO/DIS 23279:2026(en)
International
Standard
ISO/DIS 23279
ISO/TC 44/SC 5
Non-destructive testing of
Secretariat: AFNOR
welds — Ultrasonic testing —
Voting begins on:
Characterization of discontinuities
in welds
Voting terminates on:
Essais non destructifs des assemblages soudés — Contrôle
par ultrasons — Caractérisation des discontinuités dans les
assemblages soudés
ICS: 25.160.40
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document has not been edited by the ISO Central Secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2026
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
BE CONSIDERED IN THE LIGHT OF THEIR
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POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
or ISO’s member body in the country of the requester.
NATIONAL REGULATIONS.
ISO copyright office
RECIPIENTS OF THIS DRAFT ARE INVITED
CP 401 • Ch. de Blandonnet 8
TO SUBMIT, WITH THEIR COMMENTS,
CH-1214 Vernier, Geneva
NOTIFICATION OF ANY RELEVANT PATENT
Phone: [phone]
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ISO/DIS 23279:2026(en)
ii
ISO/DIS 23279:2026(en)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle of classification . 1
5 Criteria for classification . 2
5.1 General .2
5.2 Maximum echo amplitude (stages 1 and 2) .3
5.2.1 Low amplitudes (stage 1) .3
5.2.2 High amplitudes (stage 2) .3
5.3 Directional reflectivity (stage 3) .3
5.3.1 Applicability based on length .3
5.3.2 Application conditions .3
5.3.3 Directional reflectivity criteria .3
5.3.4 Result .4
5.4 Static echo pattern (stage 4) .4
5.5 Transverse dynamic echo pattern (stage 5) .4
5.6 Complementary testing .4
Annex A (normative) Classification of indications from internal discontinuities in welds —
Flowchart procedure . 5
Annex B (informative) Directional reflectivity . 9
Annex C (informative) Basic dynamic echo patterns of reflectors .11

iii
ISO/DIS 23279:2026(en)
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
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www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 44, Welding and allied processes, Subcommittee
SC 5, Testing and inspection of welds.
This fourth edition cancels and replaces the third edition (ISO 23279:2017), which has been technically
revised.
Requests for official interpretations of any aspect of this document 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
DRAFT International Standard ISO/DIS 23279:2026(en)
Non-destructive testing of welds — Ultrasonic testing —
Characterization of discontinuities in welds
1 Scope
This document specifies how to characterize indications from discontinuities by classifying them as
originating from planar or non-planar embedded discontinuities.
This procedure is also suitable for indications from discontinuities that break the surface after removal of
the weld reinforcement.
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
ISO 17640, Non-destructive testing of welds — Ultrasonic testing — Techniques, testing levels, and assessment
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:
— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
4 Principle of classification
Classification of discontinuities as planar or non-planar is based on several parameters:
a) welding techniques;
b) geometrical position of the discontinuity;
c) maximum echo amplitude;
d) directional reflectivity;
e) static echo pattern (i.e. A-scan);
f) dynamic echo pattern (envelope).
The process of classification involves examining each of the parameters against all the others in order to
arrive at an accurate conclusion.
For guidance, Figure A.1 gives the classification of indications from internal weld discontinuities suitable for
general applications.
ISO/DIS 23279:2026(en)
Figure A.1 shall be applied in conjunction with the two parameters a) and b) listed above and not taken in
isolation.
The classification procedure specified in this document is also suitable for indications that come from
surface breaking discontinuities after removal of the weld reinforcement (see Figure 1).
Dimensions in millimetres
Key
A ground weld
Figure 1 — Origin of indications from a weld
5 Criteria for classification
5.1 General
The classification is carried out by the successive application of several discriminatory criteria to:
a) maximum echo amplitude;
b) directional reflectivity;
c) static echo pattern (A-scan);
d) dynamic echo pattern (envelope).
These criteria shall be applied using the flowchart procedure according to Annex A and as described in
Clause 5.
It is recommended that the same probes be used for detection and for classification of discontinuities. The
flowchart procedure standardizes a system of classification.
...