SIST EN ISO 18491:2026

SLOVENSKI STANDARD
01-september-2026
Varjenje in sorodni postopki - Merjenje energije obloka (ISO 18491:2026)
Welding and allied processes - Measurement of arc energies (ISO 18491:2026)
Schweißen und verwandte Verfahren - Messen der Schweißenergie (ISO 18491:2026)
Soudage et techniques connexes - Mesure des énergies de l'arc (ISO 18491:2026)
Ta slovenski standard je istoveten z: EN ISO 18491:2026
ICS:
25.160.01 Varjenje, trdo in mehko Welding, brazing and
spajkanje na splošno soldering in general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 18491
EUROPEAN STANDARD
NORME EUROPÉENNE
July 2026
EUROPÄISCHE NORM
ICS 25.160.01
English Version
Welding and allied processes - Measurement of arc
energies (ISO 18491:2026)
Soudage et techniques connexes - Mesure des énergies Schweißen und verwandte Verfahren - Messen der
de l'arc (ISO 18491:2026) Schweißenergie (ISO 18491:2026)
This European Standard was approved by CEN on 16 June 2026.

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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye 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
© 2026 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 18491:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 18491:2026) has been prepared by Technical Committee ISO/TC 44 "Welding
and allied processes" in collaboration with Technical Committee CEN/TC 121 “Welding and allied
processes” 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 January 2027, and conflicting national standards shall
be withdrawn at the latest by January 2027.
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.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
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, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO 18491:2026 has been approved by CEN as EN ISO 18491:2026 without any modification.

International
Standard
ISO 18491
First edition
Welding and allied processes —
2026-06
Measurement of arc energies
Soudage et techniques connexes — Mesure des énergies de l'arc
Reference number
ISO 18491:2026(en) © ISO 2026
ISO 18491:2026(en)
© ISO 2026
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
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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
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
ISO 18491:2026(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 General . 2
5 Welding equipment and measuring devices . 3
6 Determination of arc energy . 3
7 Measurement parameters . 4
7.1 General .4
7.2 Arc voltage . .4
7.3 Welding current .4
7.4 Total instantaneous energy or average instantaneous power .4
7.5 Welding speed and length of the run .5
8 Calibration and validation of measuring instruments . 5
Annex A (informative) Range of power source types and measurement methods . 6
Annex B (informative) Conversion factors . 8
Bibliography . 9

iii
ISO 18491:2026(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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
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 44, Welding and allied processes, Subcommittee
SC 10, Quality management in the field of welding, in collaboration with the European Committee for
Standardization (CEN) Technical Committee CEN/TC 121, Welding and allied processes, in accordance with
the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
This first edition of ISO 18491 cancels and replaces ISO/TR 18491:2015, which has been technically revised.
The main changes are as follows:
— update of normative references in Clause 2;
— update of terms used throughout this document;
— addition of precisions regarding the guidelines for voltage measurement in 7.2;
— addition of a new Annex B "Conversion factors";
— update of the Bibliography.
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. Official interpretations of ISO/TC 44 documents, where they exist, are
available from this page: https://committee.iso.org/sites/tc44/home/interpretation.html.

iv
ISO 18491:2026(en)
Introduction
Welding “arc energy” or “heat input” are fundamental values used to manage the consistency of weld metal
and heat-affected zone properties. The ISO 15614 series requires the measurement of the welding energies
implemented during a welding procedure qualification, but it does not give details about the methods to be
used. Likewise, during the construction of a welded assembly, inspectors should make sure that the welding
energies conform with the Welding Procedure Specification (WPS); however, the details of the methods
to be used are again not specified. Therefore, there can be a lack of consistency between the methods
used to measure the welding energies during welding of the test piece and the methods used during the
manufacturing process. This is a potential source of error which could have implications on the safety or
quality of a welded component or structure.
Moreover, modern technology in microprocessors and electrical power manipulation have yielded
welding power sources and control systems that are capable of generating complex waveforms. However,
these control systems and waveforms increase the difficulties related to voltage and current intensity
measurements, as their values are manipulated at frequencies which can reach thousands of Hertz. The
measuring instruments generally used by inspectors, such as TRMS clamp meters, can no longer be relied on
to correctly measure the welding energy since differences exceeding 30 % with respect to the true energy
can sometimes be found.
This document provides guidance on how to accurately measure welding energy, both in the case of
traditional welding systems and those that employ complex waveforms.

v
International Standard ISO 18491:2026(en)
Welding and allied processes — Measurement of arc energies
1 Scope
This document specifies methods for measuring the parameters needed to calculate arc energies for arc
welding processes.
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 17662, Welding — Calibration, verification and validation of equipment used for welding, including ancillary
activities
ISO/TR 17671 (all parts), Welding — Recommendations for welding of metallic materia
...