prEN ISO 2553

• Abstract:

  This document defines the rules to be applied for symbolic representation of welded joints on technical drawings. This can include information about the geometry, manufacture, quality and testing of the welds. The principles of this document can also be applied to soldered and brazed joints.; It is recognized that there are two different approaches in the global market to designate the arrow side and other side on drawings. In this document:; — clauses, tables and figures which carry the suffix letter "A" are applicable only to the symbolic representation system based on a dual reference line;; — clauses, tables and figures which carry the suffix letter "B" are applicable only to the symbolic representation system based on a single reference line;; — clauses, tables and figures which do not have the suffix letter "A" or "B" are applicable to both systems.; The symbols shown in this document can be combined with other symbols used on technical drawings, for example to show surface finish requirements.; An alternative designation method is presented which can be used to represent welded joints on drawings by specifying essential design information such as weld dimensions, quality level, etc. The joint preparation and welding process(es) are then determined by the production unit in order to meet the specified requirements.; NOTE Examples given in this document, including dimensions, are illustrative only and are intended to demonstrate the proper application of principles.

• Status: Not Published
• Publication Date: 19-Dec-2027
• ICS: 01.100.20 - Mechanical engineering drawings
• Technical Committee: CEN/TC 121 - Welding
• Drafting Committee: CEN/TC 121 - Welding
• Current Stage: 4060 - Closure of enquiry - Enquiry
• Start Date: 19-Aug-2026
• Completion Date: 19-Aug-2026
• Ref Project: oSIST prEN ISO 2553:2026 - Welding and allied processes - Symbols for welding - Welded joints (ISO/DIS 2553:2026)

• Revises: EN ISO 2553:2019 - Welding and allied processes - Symbolic representation on drawings - Welded joints (ISO 2553:2019, Corrected version 2021-09)
• Effective Date: 13-Nov-2024

Overview

prEN ISO 2553:2026, developed by CEN, establishes international rules for the symbolic representation of welded joints in technical drawings. Applicable to both manual and computer-aided designs, this standard covers a variety of welding and allied processes, such as soldering and brazing. Its primary goal is to ensure clarity and consistency in communicating critical design, manufacturing, and quality information related to welded joints. The standard addresses the use of welding symbols, enabling effective documentation, specification, and verification of welds in mechanical engineering and construction projects.

Key Topics

• Welding Symbol Systems: The standard recognizes two principal approaches for indicating the arrow side and the other side on drawings:
  • System A: Based on a dual reference line format, typically used in accordance with ISO 2553:1992.
  • System B: Uses a single reference line, commonly adopted in Pacific Rim countries.
  • Content applicable to both systems is included without suffix, while system-specific guidance is clearly marked.
• Symbol Components: Clear definitions are provided for each element of a welding symbol, including the arrow, reference line, tail, elementary and supplementary symbols.
• Symbol Application: Standardized methods for combining welding symbols with other drawing symbols (such as surface finishes), and incorporating essential information like weld size, length, and quality level.
• Alternative Designation: The document offers alternative methods for specifying welded joints by representing key design information, leaving detailed joint preparation and welding process selection to the production team.
• Dimensions and Notations: Guidance is given on representing dimensions and tolerances for welds and joint preparations, ensuring unambiguous communication.

Applications

prEN ISO 2553 is valuable in various fields, supporting accurate specification, production, and inspection processes:

• Mechanical Engineering Drawings: Provides a common language for specifying welded joints, reducing misinterpretations and errors in manufacturing.
• Construction and Fabrication: Facilitates clear communication of weld requirements across diverse teams, including designers, engineers, and inspectors.
• Technical Product Documentation: Ensures consistency in product and project documentation, whether on paper or using CAD systems, with detailed weld geometry and testing requirements.
• Soldered and Brazed Joints: Though focused on welded joints, the principles are applicable to allied processes, supporting broader adoption in electronics, piping, and component assembly.
• Quality Assurance: By standardizing welding symbols, the document aids quality control procedures and compliance with regulatory or contractual requirements.

Related Standards

prEN ISO 2553 is closely linked to other international standards for technical drawings and welding:

• ISO 128-2: General principles for product documentation lines
• ISO 129-1: Presentation of dimensions and tolerances
• ISO 3098-2: Technical product documentation lettering
• ISO 4063: Nomenclature of welding, brazing, soldering, and cutting processes
• ISO 17659: Multilingual terms for welded joints with illustrations
• ISO/TR 25901 series: Vocabulary and terms for welding and allied processes
• ISO 14731: Responsibilities for welding coordination
• ISO 21920-1: Surface texture and finish

Adherence to prEN ISO 2553 promotes global best practices, consistency, and efficiency in documenting and interpreting welded joints, ultimately contributing to higher quality outcomes in engineering and manufacturing sectors.

SLOVENSKI STANDARD
01-julij-2026
Varjenje in sorodni postopki - Prikazovanje s simboli na risbah - Varjeni spoji
(ISO/DIS 2553:2026)
Welding and allied processes - Symbols for welding - Welded joints (ISO/DIS 2553:2026)
Schweißen und verwandte Prozesse - Symbolische Darstellung in Zeichnungen -
Schweißverbindungen (ISO/DIS 2553:2026)
Soudage et techniques connexes - Symboles pour le soudage - Assemblages soudés
(ISO/DIS 2553:2026)
Ta slovenski standard je istoveten z: prEN ISO 2553
ICS:
01.100.20 Konstrukcijske risbe Mechanical engineering
drawings
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 2553
ISO/TC 44/SC 7
Welding and allied processes —
Secretariat: BSI
Symbols for welding — Welded
Voting begins on:
joints
2026-05-27
ICS: 01.100.20; 25.160.40
Voting terminates on:
2026-08-19
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 is circulated as received from the committee 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 2553:2026(en)
DRAFT
ISO/DIS 2553:2026(en)
International
Standard
ISO/DIS 2553
ISO/TC 44/SC 7
Welding and allied processes —
Secretariat: BSI
Symbols for welding — Welded
Voting begins on:
joints
ICS: 01.100.20; 25.160.40
Voting terminates on:
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 is circulated as received from the committee 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: [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 2553:2026(en)
ii
ISO/DIS 2553:2026(en)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Welding symbol . 5
4.1 General .5
4.2 Basic welding symbol .5
4.3 Welding symbol systems .6
4.4 Elementary symbols .6
4.4.1 General .6
4.4.2 Combinations of elementary symbols .9
4.4.3 Double-sided butt welds .9
4.5 Supplementary symbols .10
4.5.1 General .10
4.5.2 Weld-all-around symbol . 15
4.5.3 Welds of the same type made from point to point . 15
4.5.4 Field welds .16
4.5.5 Root reinforcement — Butt welds made from one side .16
4.5.6 Welds on flanged butt and flanged corner joints .16
4.5.7 Multiple welds of the same type .16
4.6 Arrow line .19
4.6.1 General .19
4.6.2 Multiple arrow lines .19
4.6.3 Broken arrow line .19
4.7 Reference line and weld location . 20
4.7.1 Reference line - General . 20
4.7.2 Weld location . 20
4.7.3 Multiple reference lines .21
4.8 Tail . 22
5 Dimensioning of welds . .23
5.1 General . 23
5.2 Cross-sectional dimensions . 23
5.3 Length dimensions. 23
5.3.1 General . 23
5.3.2 Intermittent welds . 23
5.4 Butt welds .24
5.4.1 Fusion penetration .24
5.4.2 Double-sided welds .24
5.4.3 Flanged butt welds .24
5.4.4 Flare bevel and flare-V butt welds .24
5.5 Fillet welds .24
5.5.1 Weld size .24
5.5.2 Deep penetration fillet welds . 25
5.6 Plug welds in circular holes . 25
5.7 Plug welds in elongated holes (slots) . 25
5.8 Spot welds . 25
5.9 Seam welds . 25
5.10 Edge welds . 25
5.11 Stud welds . 26
5.12 Overlay welds. 26
5.13 Stake welds . 26
6 Dimensioning of joint preparations .38

iii
ISO/DIS 2553:2026(en)
6.1 General . 38
6.2 Root gap . 38
6.3 Included angle . 38
6.4 Root radius and depth of root faces — U and J butt joints. 39
6.5 Depth of joint preparation . 39
6.6 Countersink angle for plug welds . 40
7 Alternative butt weld symbol with required weld quality .40
7.1 General . 40
7.2 Example .41
Annex A (informative) Examples of the use of welding symbols .42
Annex B (informative) Tolerances and transition points for weld types .53
Annex C (informative) Alternative methods for designating intermittent butt and fillet welds .54
Annex D (normative) Symbols for non-destructive testing (NDT) .57
Bibliography .63

iv
ISO/DIS 2553:2026(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 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 7, Representation and terms.
Any feedback, question or request for official interpretation related to any aspect of this document should be
directed to the Secretariat of ISO/TC 44/SC 7 via your national standards body. A complete listing of these
bodies can be found at www.iso.org/members.html. Official interpretations, where they exist, are available
from this page: https://committee.iso.org/sites/tc44/home/interpretation.html.
This sixth edition cancels and replaces the fifth edition (ISO 2553:2019), which has been technically revised.
The main changes compared to the previous edition are as follows:
— The changes from the 2019 edition will be added after the DIS ballot.

v
ISO/DIS 2553:2026(en)
Introduction
The symbols given in this document can be used in technical product documentation (TPD) for welded
components. For the purposes of this document, TPD can be on paper or generated using electronic means
e.g. CAD systems.
Design-related specifications, such as type, thickness, and length of weld, weld quality, surface treatment,
filler material and testing specifications, can be indicated directly at the weld by means of the symbols. The
principals of this document can be applied to brazed and soldered joints.
Clarity can be improved by references to collective information in the TPD or references to additional
design-related documents.
Preparation for production can require detailed welding-related planning. The type of representation
described in this document can be used for this purpose and complemented by additional production-related
information (e.g. welding position, welding process, WPS, joint preparation, preheating). This information is
often given in production-related documents, such as work schedules or welding procedure specifications
(WPS).
TPDs are intended to clearly and understandably illustrate design-related specifications. Welding-related
TPDs are prepared and checked by specially trained personnel (see ISO 14731).
This document recognizes that there are two different approaches in the global market to designate the
arrow side and other side on TPDs, and allows for either to be used in isolation, to suit a particular market
need. Application of either approach identifies a welding symbol in accordance with this document. The
approach in accordance with system A is based on ISO 2553:1992 . The approach in accordance with system
B is based upon standards used by Pacific Rim countries.

vi
DRAFT International Standard ISO/DIS 2553:2026(en)
Welding and allied processes — Symbols for welding —
Welded joints
1 Scope
This document defines the rules to be applied for symbolic representation of welded joints. This can include
information about the geometry, manufacture, quality and testing of the welds.
The symbols are intended to enable standardized representation of the welds to be made,
For the purposes of this document, drawings can be on paper or generated using electronic means e.g. CAD
systems.
It is recognized that there are two different approaches in the global market to designate the arrow side and
other side. In this document:
— clauses, tables and figures which carry the suffix "system A" are applicable only to the symbolic
representation system based on a dual reference line;
— clauses, tables and figures which carry the suffix "system B" are applicable only to the symbolic
representation system based on a single reference line;
— clauses, tables and figures which do not have the suffix "system A" or "system B" are applicable to both
systems.
The symbols shown in this document can be combined with other symbols, for example to show surface
finish requirements.
An alternative designation method is presented which can be used to represent welded joints by specifying
essential design information such as weld dimensions, quality level, etc. The joint preparation and welding
process(es) are then determined by the production unit in order to meet the specified requirements.
The principles of this document can also be applied to soldered and brazed joints.
NOTE Examples given in this document, including dimensions, are illustrative only and are intended to
demonstrate the proper application of principles.
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 128-2, Technical product documentation (TPD) — General principles of representation — Part 2: Basic
conventions for lines
ISO 129-1, Technical product documentation (TPD) — Presentation of dimensions and tolerances — Part 1:
General principles
ISO 3098-2, Technical product documentation — Lettering — Part 2: Latin alphabet, numerals and marks
ISO 4063, Welding, brazing, soldering and cutting — Nomenclature of processes and reference numbers
ISO 17659:2002, Welding — Multilingual terms for welded joints with illustrations
ISO/TR 25901-1, Welding and allied processes — Vocabulary — Part 1: General terms

ISO/DIS 2553:2026(en)
ISO/TR 25901-3, Welding and allied processes — Vocabulary — Part 3: Welding processes
ISO/TR 25901-4, Welding and allied processes — Vocabulary — Part 4: Arc welding
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 17659, ISO/TR 25901-1,
ISO/TR 25901-3, ISO/TR 25901-4, and the following 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 https:// www .electropedia .org/
3.1
welding symbol
symbol consisting of an arrow line (3.3) and a reference line (3.4) and which can also include elementary
symbols (3.8) and supplementary symbols (3.9), dimensions and/or tail (3.5)
Note 1 to entry: See Clause 4.
3.2
basic welding symbol
symbol consisting of an arrow line (3.3), reference line (3.4) and tail (3.5) used when the joint is not specified
and only to indicate that a welded joint is to be made
Note 1 to entry: See 4.2.
3.3
arrow line
leader line used to indicate that the joint is to be welded generally drawn at 135° to the reference line (3.4)
Note 1 to entry: See 4.6.
3.4
reference line
part of the welding symbol (3.1) on which the elementary symbol (3.8) is located, generally drawn parallel to
the bottom edge of the drawing
Note 1 to entry: See 4.7.
3.5
tail
V-shaped element added to the end of the continuous reference line (3.4) away from the arrow line (3.3)
Note 1 to entry: See 4.8.
3.6
arrow side
side of the joint to which the arrow line (3.3) is pointing
Note 1 to entry: See 4.7.2.1.
3.7
other side
opposite side of the joint to the arrow side (3.6)
Note 1 to entry: See 4.7.2.1.
ISO/DIS 2553:2026(en)
3.8
elementary symbol
symbol forming part of the welding symbol (3.1) attached to the reference line (3.4) to indicate the type of
weld and joint preparation
Note 1 to entry: See 4.4.
3.9
supplementary symbol
symbol used in conjunction with elementary symbols (3.8) to convey additional information about the joint
Note 1 to entry: See 4.5.
3.10
complementary information
non-symbolic information, relevant to the welds being made, which may be included in the tail (3.5) of the
welding symbol (3.1)
Note 1 to entry: See 4.8.
3.11
intermittent weld
series of weld elements made at intervals along a joint
[SOURCE: ISO/TR 25901-1:2016, 2.1.6.15]
Note 1 to entry: See 5.3.2.
3.11.1
chain intermittent weld
intermittent weld (3.11) on each side of a joint arranged so that the weld elements lie opposite one another
along the joint
Note 1 to entry: These are usually fillet welds in T-joints and lap joints.
Note 2 to entry: See 5.3.2.2.
[SOURCE: ISO/TR 25901-1:2016, 2.1.6.17, modified — Note 2 to entry has been adapted.]
3.11.2
staggered intermittent weld
intermittent weld (3.11) on each side of a joint arranged so that the weld elements on one side lie opposite the
spaces on the other side (3.7) along the joint
Note 1 to entry: These are usually fillet welds in T-joints and lap joints.
Note 2 to entry: See 5.3.2.3.
[SOURCE: ISO/TR 25901-1:2016, 2.1.6.16, modified — Note 2 to entry has been adapted.]
3.12
offset
distance between the start of welding on one side of a staggeredintermittent weld (3.11.2) and the start of
welding on the other side (3.7)
Note 1 to entry: See 5.3.2.3, C.2.3, Table C.1, No. 3, C.3.3 and Table C.2, No. 3.
3.13
back run
DEPRECATED: sealing run
final run deposited on the root side of a fusion weld
[SOURCE: ISO/TR 25901-1:2016, 2.1.8.21]

ISO/DIS 2553:2026(en)
3.14
backing weld
backing in the form of a weld
3.15
nominal weld length
design length of a weld
Note 1 to entry: Nominal weld length is the length where the weld has its full size.
3.15.1
nominal length of weld element
nominal length of each element of the weld
Note 1 to entry: Nominal weld length is the length where the weld has its full size.
3.16
nominal throat thickness
a
design value of the height of the largest isosceles triangle that can be inscribed in the section of a fillet weld
Note 1 to entry: If other dimensions are specified, e.g. fillet welds with unequal leg lengths (see Table 6, No. 2.2) , they
need to be clearly specified.
[SOURCE: ISO/TR 25901-1:2016, 2.1.7.8, modified — The symbol a has been added. Note 1 to entry has been
changed.]
3.17
leg length
z
distance from the actual or projected intersection of the fusion faces and the toe of a fillet weld, measured
across the fusion face
[SOURCE: ISO/TR 25901-1:2016, 2.1.7.5, modified — The symbol z has been added.]
3.18
fusion penetration
joint penetration
s
DEPRECATED: weld metal thickness
depth of the weld metal at the joint interface, excluding the reinforcement or for overlay welding, the
thickness of the weld metal (see Table 6, No. 9.1)
3.19
deep penetration throat thickness
a
d
nominal throat thickness (3.16) to which a certain amount of fusion penetration is added
Note 1 to entry: previous editions of ISO 2553 used s instead of a
d
[SOURCE: ISO/TR 25901-1:2016, 2.1.7.9, modified — The symbol a has been added. Note 1 to entry has been
d
deleted.]
3.20
flare-bevel weld
butt weld between a joint member with a curved surface and another with a planar surface
Note 1 to entry: See Table 6, No. 1.7 .
[SOURCE: ISO/TR 25901-1:2016, 2.1.6.18]

ISO/DIS 2553:2026(en)
3.21
flare-V weld
butt weld between two members with curved surfaces
Note 1 to entry: See Table 6, No. 1.6 .
[SOURCE: ISO/TR 25901-1:2016, 2.1.6.19]
3.22
field weld
weld made outside workshops usually at the place of final installation
[SOURCE: ISO/TR 25901-1:2016, 2.1.8.40]
3.23
stake weld
narrow profile seam or spot weld, made in a lap joint or T-joint
Note 1 to entry: Stake welds have either deeper or narrower profiles or both (see Table 1, No 23 and 24) compared to
fusion seam or fusion spot welds and are typically used for electron beam welding or laser beam welding.
4 Welding symbol
4.1 General
A reference line and arrow line are required elements. Additional elements may be included to convey
specific information.
It is preferable to show the welding symbol on the same side of the joint that the weld is to be made, i.e. the
arrow side (see 4.7).
The thickness of the arrow lines, reference line, elementary symbols and lettering shall be in accordance
with ISO 128-2 and ISO 3098-2.
In order not to overburden drawings, reference should either be made to notes on the drawing or to other
documents.
If the required weld cannot be designated using the symbols in this document, reference shall be made to
other documents and/or figures.
4.2 Basic welding symbol
If joint details are not specified and the only requirement is to indicate that a joint is to be welded, the basic
symbol shown in Figure 1 may be used. In this case, a dual reference line is not required for system A (see
4.7.1 A) as no details concerning the weld are being conveyed.
The basic welding symbol shall comprise an arrow line, reference line and a tail.

ISO/DIS 2553:2026(en)
Key
1 arrow line
2 reference line
3 tail
NOTE This symbol is often used to indicate the location of tack welds.
Figure 1 — Basic welding symbol (joint details and type not specified)
4.3 Welding symbol systems
This document recognizes two different systems, A and B, to designate the arrow side and other side.
The symbolic representation in system A is based on a dual reference line consisting of a continuous line and
a dashed line (see 4.7).
The symbolic representation in system B is based on a single reference line (see 4.7).
Clauses, Tables and Figures which carry the suffix "system A" or "system B" are applicable only to system A
or system B respectively.
Clauses, tables and figures which do not have a suffix are applicable to both systems.
System A and system B shall not be mixed. The system used shall be clearly indicated including units of
measurement in accordance with ISO 129-1.
Examples of comprehensive welding symbols showing the location of elements are given in Figure A.1.
4.4 Elementary symbols
4.4.1 General
Elementary symbols, in accordance with Table 1, may be added to the reference line in both systems A and B
to indicate the type of weld to be made.
Elementary symbols form part of the welding symbol and shall be drawn attached to the reference line
generally at the mid-point.
Elementary symbols may be complemented by:
— supplementary symbols (see 4.5 and Table 3);
— dimensions (see Clause 5);
— complementary information.
The orientation of the elementary symbols shall not be changed to that shown in Tables 1 to 3.
Annex B gives guidance on tolerances and transition points for butt welds, edge welds and fillet welds.

ISO/DIS 2553:2026(en)
If clear illustration by means of symbols is not possible, cross-sections of the welds may be shown and
dimensioned.
Table 1 — Elementary symbols
Illustration of weld type
Designation
a
No. (dashed lines show joint preparation Symbol
(weld type)
prior to welding)
b
1 Square butt
b
2 Single-V butt
Single-V butt with
b
broad root face
b
4 Single-bevel butt
Single-bevel butt with
b
broad root face
b
6 Single-U butt
b
7 Single-J butt
8 Flare V
9 Flare bevel
10 Fillet
11 Plug
ISO/DIS 2553:2026(en)
TTabablele 1 1 ((ccoonnttiinnueuedd))
Illustration of weld type
Designation
a
No. (dashed lines show joint preparation Symbol
(weld type)
prior to welding)
c
12.1 Resistance spot
12.2 Projection
13 Fusion spot
c
14 Resistance seam
15 Fusion seam
16 Stud
Steep-flanked
b
single-V butt
Steep-flanked
b
single-bevel butt
c
19 Edge
ISO/DIS 2553:2026(en)
TTabablele 1 1 ((ccoonnttiinnueuedd))
Illustration of weld type
Designation
a
No. (dashed lines show joint preparation Symbol
(weld type)
prior to welding)
Flanged butt
20.1
(see also Table 4)
20.2 Flanged corner
21 Overlay
c
22 Stake spot
c
23 Stake seam
a
The grey line is not part of the symbol. It indicates the position of the reference line.
b
Butt welds are full penetration unless otherwise indicated by dimensions on the welding symbol or by reference to
other information, for example the WPS.
c
Symbol can also be used for joints with more than 2 members.
4.4.2 Combinations of elementary symbols
Elementary symbols may be combined as required to represent particular weld configurations.
4.4.3 Double-sided butt welds
The elementary symbols shall be arranged opposite each other on the reference line, including all required
information, when used to represent double-sided butt welds.
In the case of symmetrical double-sided welds with identical symbols and dimensions, the dashed reference
line should be deleted for system A (see Table 2).
An example of an asymmetrical double-sided weld is shown in Table A.3.

ISO/DIS 2553:2026(en)
Table 2 — Combined elementary symbols to represent symmetrical double-sided welds
a b
No. Weld type Illustration of weld Symbol
1 Double-V butt
2 Double bevel butt
3 Double-U butt
Double bevel butt
4 (with broad root face)
and fillet welds
a
Welds may be partial or full penetration which is to be indicated by dimensions on the welding symbol (see Table 6, No. 1.1
and No. 1.2) or by reference to other information, for example the WPS.
b
The grey line is not part of the symbol. It indicates the position of the reference line.
4.5 Supplementary symbols
4.5.1 General
Additional information concerning the required joint may be provided by the use of supplementary symbols
in accordance with Table 3. Supplementary symbols can, for example, provide information about the shape
of the weld or how the welded joint shall be made.

ISO/DIS 2553:2026(en)
Table 3 — Supplementary symbols
a a
No. Designation Symbol Application example Illustration of weld
b
Flush
(flat-finished)
b
2 Convex
b
3 Concave
Toes blended smooth-
4 No example
c
ly
d
a)  Back run
(made after the sin-
gle-V butt weld)
d
b)  Backing weld
(made before the sin-
gle-V butt weld)
Specified root rein-
6 forcement (butt welds)
e
7a Backing (unspecified)
f
7b Permanent backing
Removable/
7c
f
temporary backing
a
The grey line is not part of the symbol and is included to show the position of symbol on reference line and/or the arrow line
only.
b
Welds that require approximately flush, convex or concave faces without post-weld finishing are specified by use of the flush,
convex or concave contour symbol.
Welds to be finished flush, convex or concave by post-weld finishing or that require a flat but not flush surface require additional
information, e.g. addition of a note in the tail of the welding symbol.
Other symbols in accordance with ISO 21920-1may be used to specify surface finish.
c
The toes shall be blended smoothly by welding or finishing. Processing details may be specified in the work instructions or
WPS.
d
The weld run sequence may be indicated e.g. by use of multiple reference lines, a note in the tail or by reference to a weld
procedure specification.
e
In system B, also used to designate flanged butt/corner welds (see 4.5.6).
f
M, material to be part of the final welded joint, MR, material to be removed after welding. Further information on the material
can be included in the tail or elsewhere.
g
The material and the dimensions of the consumable insert or spacer can be specified in the tail of the welding symbol or on
the drawing.
h
Explanations of a, z, n, l and (e) are given in Clause 5.
i
An alternative can be to add complementary information “TYPICAL” (usually abbreviated “TYP”) in the tail of the welding
symbol to avoid repeating identical welding symbols on the same drawing. Either methods can be used, but only when the joints
represented are identical in all details. All applicable joints shall be identified, e.g., “TYP at six lifting lugs.”

ISO/DIS 2553:2026(en)
TTabablele 3 3 ((ccoonnttiinnueuedd))
a a
No. Designation Symbol Application example Illustration of weld
g
8 Spacer
a)  Joint showing insert in
place
g
9 Consumable insert
b)  Welded joint showing
root bead (insert incorporat-
ed into root). Single V butt
weld not shown
a
The grey line is not part of the symbol and is included to show the position of symbol on reference line and/or the arrow line
only.
b
Welds that require approximately flush, convex or concave faces without post-weld finishing are specified by use of the flush,
convex or concave contour symbol.
Welds to be finished flush, convex or concave by post-weld finishing or that require a flat but not flush surface require additional
information, e.g. addition of a note in the tail of the welding symbol.
Other symbols in accordance with ISO 21920-1may be used to specify surface finish.
c
The toes shall be blended smoothly by welding or finishing. Processing details may be specified in the work instructions or
WPS.
d
The weld run sequence may be indicated e.g. by use of multiple reference lines, a note in the tail or by reference to a weld
procedure specification.
e
In system B, also used to designate flanged butt/corner welds (see 4.5.6).
f
M, material to be part of the final welded joint, MR, material to be removed after welding. Further information on the material
can be included in the tail or elsewhere.
g
The material and the dimensions of the consumable insert or spacer can be specified in the tail of the welding symbol or on
the drawing.
h
Explanations of a, z, n, l and (e) are given in Clause 5.
i
An alternative can be to add complementary information “TYPICAL” (usually abbreviated “TYP”) in the tail of the welding
symbol to avoid repeating identical welding symbols on the same drawing. Either methods can be used, but only when the joints
represented are identical in all details. All applicable joints shall be identified, e.g., “TYP at six lifting lugs.”

ISO/DIS 2553:2026(en)
TTabablele 3 3 ((ccoonnttiinnueuedd))
a a
No. Designation Symbol Application example Illustration of weld
10 Weld-all-around
a
The grey line is not part of the symbol and is included to show the position of symbol on reference line and/or the arrow line
only.
b
Welds that require approximately flush, convex or concave faces without post-weld finishing are specified by use of the flush,
convex or concave contour symbol.
Welds to be finished flush, convex or concave by post-weld finishing or that require a flat but not flush surface require additional
information, e.g. addition of a note in the tail of the welding symbol.
Other symbols in accordance with ISO 21920-1may be used to specify surface finish.
c
The toes shall be blended smoothly by welding or finishing. Processing details may be specified in the work instructions or
WPS.
d
The weld run sequence may be indicated e.g. by use of multiple reference lines, a note in the tail or by reference to a weld
procedure specification.
e
In system B, also used to designate flanged butt/corner welds (see 4.5.6).
f
M, material to be part of the final welded joint, MR, material to be removed after welding. Further information on the material
can be included in the tail or elsewhere.
g
The material and the dimensions of the consumable insert or spacer can be specified in the tail of the welding symbol or on
the drawing.
h
Explanations of a, z, n, l and (e) are given in Clause 5.
i
An alternative can be to add complementary information “TYPICAL” (usually abbreviated “TYP”) in the tail of the welding
symbol to avoid repeating identical welding symbols on the same drawing. Either methods can be used, but only when the joints
represented are identical in all details. All applicable joints shall be identified, e.g., “TYP at six lifting lugs.”

ISO/DIS 2553:2026(en)
TTabablele 3 3 ((ccoonnttiinnueuedd))
a a
No. Designation Symbol Application example Illustration of weld
Weld between two
points (see 4.5.3)
12 Field weld No example
Staggered intermit-
h
tent welds
Multiple welds (of the
i
same type)
a
The grey line is not part of the symbol and is included to show the position of symbol on reference line and/or the arrow line
only.
b
Welds that require approximately flush, convex or concave faces without post-weld finishing are specified by use of the flush,
convex or concave contour symbol.
Welds to be finished flush, convex or concave by post-weld finishing or that require a flat but not flush surface require additional
information, e.g. addition of a note in the ta
...