oSIST prEN ISO 23279:2026
(Main)Non-destructive testing of welds - Ultrasonic testing - Characterization of discontinuities in welds (ISO/DIS 23279:2026)
- 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
- Public Enquiry End Date
- 01-Nov-2026
- Technical Committee
- VAR - Welding
- Current Stage
- 4020 - Public enquire (PE) (Adopted Project)
- Start Date
- 10-Sep-2026
- Due Date
- 28-Jan-2027
oSIST prEN ISO 23279:2026 is the SIST publication of ISO/DIS 23279:2026 on non-destructive testing of welds by ultrasonic testing. It specifies how to characterize indications from weld discontinuities by classifying them as planar or non-planar, for inspectors, engineers, and quality personnel evaluating welded joints.
What does oSIST prEN ISO 23279:2026 specify?
oSIST prEN ISO 23279:2026 specifies a method for characterizing ultrasonic indications from discontinuities in welds. The method is also suitable for indications from discontinuities that break the surface after removal of the weld reinforcement.
The document is organized into five clauses and three annexes. Clauses 1 to 5 cover scope, references, terms, the classification principle, and the criteria for classification. Annex A gives the normative flowchart procedure, while Annexes B and C provide informative guidance on directional reflectivity and echo patterns.
| Annex | What it covers |
|---|---|
| Annex A | Normative flowchart procedure for classifying indications from internal discontinuities in welds |
| Annex B | Informative examples for directional reflectivity |
| Annex C | Informative basic dynamic echo patterns of reflectors |
What are the key requirements of oSIST prEN ISO 23279:2026?
oSIST prEN ISO 23279:2026 classifies indications by combining several ultrasonic observations rather than relying on one signal alone. In practice, the inspector has to look at signal height, how the indication responds to probe direction, and the shape of the A-scan and dynamic response.
How the classification principle works
Clause 4 says classification is based on welding technique, the geometrical position of the discontinuity, maximum echo amplitude, directional reflectivity, static echo pattern, and dynamic echo pattern. Figure A.1 should be used as a guided sequence, not as a standalone decision rule.
That matters because the same indication can look different from different beam angles. The standard expects the user to cross-check several signal features before deciding whether the discontinuity is planar or non-planar.
How echo amplitude is used
Clause 5 starts with a screening step based on maximum echo amplitude. An indication below the evaluation level in ISO 11666 is treated as not significant for characterization, unless a special application specifies a lower value.
An indication at least 6 dB above the reference level is associated with a planar discontinuity. In practice, strong reflections are treated as crack-like or lack-of-fusion-like until later stages confirm or correct that first decision.
When directional reflectivity is used
Stage 3 applies only to indications above a length limit tied to the weld thickness. For thicknesses up to 15 mm, the indication has to exceed the thickness; above 15 mm, it has to exceed the larger of half the thickness or 15 mm.
The comparison must be made on the same reflector, at the position of highest echo amplitude, and with probe setups that give comparable wavelengths when different wave types are used. The beam angles used for comparison must differ by at least 10°, and attenuation in weld material has to be considered when comparing a beam through the weld with one through base material only.
If the reflectivity difference meets the stated criteria, the indication is mainly treated as lack of fusion. For a user, this stage is the point where changing beam direction becomes a decision tool, not just a way to confirm detection.
How static and dynamic echo patterns are used
Stage 4 compares the static echo pattern, the A-scan, with the pattern from the reference reflector, a 3 mm diameter side-drilled hole. If the pattern is single and smooth in at least two testing directions, the indication is classified as non-planar, such as an inclusion.
If Stage 4 does not settle the case, Stage 5 uses the transverse dynamic echo pattern. This is the envelope of the echoes while the probe is moved perpendicular to the discontinuity in accordance with ISO 17640. Annex C explains the response patterns used for this step.
This matters in practice because smooth single responses point toward isolated non-planar features, while ragged, travelling, or clustered responses help separate planar defects from clusters of non-planar discontinuities.
What to do when the result is uncertain
Clause 5.6 allows complementary testing when there is doubt. The document names additional reflectivity directions, additional probes, movement of the probe parallel to the discontinuity, and other non-destructive testing methods such as radiography.
That means the classification is meant to support an evidence-based decision, not force a conclusion from one uncertain scan. Annex A also notes that a combination of inclusion and lack of fusion is treated as planar by the flowchart procedure.
What terms does oSIST prEN ISO 23279:2026 define?
oSIST prEN ISO 23279:2026 relies on the vocabulary of ISO 5577, and these are the key terms used in the document.
- Indication - the ultrasonic signal or response being evaluated for its origin.
- Planar discontinuity - a discontinuity that behaves like a flat or crack-like reflector and tends to show strong directional reflectivity.
- Non-planar discontinuity - a discontinuity that gives a smoother, less directional ultrasonic response, such as an inclusion or porosity.
- A-scan - the static ultrasonic display used in Stage 4 to judge whether the echo pattern is single and smooth.
- Directional reflectivity - the change in echo amplitude when the same reflector is tested from different beam directions.
- Distance-amplitude curve (DAC) - the reference curve used as one basis for comparing echo amplitudes in the flowchart procedure.
- Time-Corrected Gain (TCG) - a gain correction method used as another basis for amplitude comparison.
- Dynamic echo pattern - the moving envelope of echoes seen while the probe is scanned across the indication.
Who uses oSIST prEN ISO 23279:2026?
oSIST prEN ISO 23279:2026 is used by people who perform, review, or specify ultrasonic inspection of welded joints. That includes NDT technicians, welding inspectors, quality managers, and engineers in fabrication, inspection, and acceptance work.
It is especially useful where a team has to decide whether an indication is more consistent with a planar flaw or a non-planar one. Buyers and contract writers can also use it to define the inspection method expected on welded components.
What changed in oSIST prEN ISO 23279:2026 from the previous edition?
oSIST prEN ISO 23279:2026 is the fourth edition. It cancels and replaces ISO 23279:2017, and the foreword says it has been technically revised.
Which standards are used with oSIST prEN ISO 23279:2026?
oSIST prEN ISO 23279:2026 refers to these standards in its text:
- ISO 5577 - provides the vocabulary used for ultrasonic testing terms and definitions.
- ISO 17640 - provides ultrasonic testing techniques, testing levels, and assessment, and is used for the probe movement described in the dynamic echo pattern stage.
- ISO 11666 - provides the evaluation level used in the first amplitude screening step.
What does the oSIST prEN ISO 23279:2026 document contain?
oSIST prEN ISO 23279:2026 contains a classification method, a flowchart procedure, and supporting examples for interpreting ultrasonic responses from weld discontinuities. The main text explains the sequence from amplitude screening through directional reflectivity and echo-pattern analysis.
Annex A provides the decision flowchart and threshold structure used to sort indications into planar or non-planar categories. Annex B shows examples of testing directions for directional reflectivity. Annex C shows five basic dynamic echo patterns, including single, extended, rough, travelling, and multiple-reflector responses.
The document also uses a reference reflector in the pattern comparison step and gives examples of how probe movement changes the displayed response. That makes it useful not only for classification, but also for training, procedure writing, and review of inspection records.
Relations
- Effective Date
- 01-Oct-2026
Get Certified
Connect with accredited certification bodies for this standard
DVS-ZERT GmbH
German welding certification society.
CARES (UK Certification Authority for Reinforcing Steels)
UK certification for reinforcing steels and construction.
EWF/IIW (European/International Welding Federation)
International welding personnel certification.
Sponsored listings
Frequently Asked Questions
oSIST prEN ISO 23279:2026 is a draft published by the Slovenian Institute for Standardization (SIST). Its full title is "Non-destructive testing of welds - Ultrasonic testing - Characterization of discontinuities in welds (ISO/DIS 23279:2026)". This standard covers: 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.
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.
oSIST prEN ISO 23279:2026 is classified under the following ICS (International Classification for Standards) categories: 25.160.40 - Welded joints and welds. The ICS classification helps identify the subject area and facilitates finding related standards.
oSIST prEN ISO 23279:2026 has the following relationships with other standards: It is inter standard links to SIST EN ISO 23279:2018. Understanding these relationships helps ensure you are using the most current and applicable version of the standard.
oSIST prEN ISO 23279:2026 is available in PDF format for immediate download after purchase. The document can be added to your cart and obtained through the secure checkout process. Digital delivery ensures instant access to the complete standard document.
Standards Content (Sample)
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
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
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: +41 22 749 01 11
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Email: copyright@iso.org
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
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 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.
...