SIST EN ISO 11118:2025

SLOVENSKI STANDARD
01-april-2025
Nadomešča:
SIST EN ISO 11118:2016
SIST EN ISO 11118:2016/A1:2020
Plinske jeklenke - Kovinske plinske jeklenke za enkratno polnitev - Specifikacija in
preskusne metode (ISO 11118:2025)
Gas cylinders - Non-refillable metallic gas cylinders - Specification and test methods
(ISO 11118:2025)
Gasflaschen - Metallische Einwegflaschen - Spezifikationen und Prüfverfahren (ISO
11118:2025)
Bouteilles à gaz - Bouteilles à gaz métalliques non rechargeables -Spécifications et
méthodes d'essai (ISO 11118:2025)
Ta slovenski standard je istoveten z: EN ISO 11118:2025
ICS:
23.020.35 Plinske jeklenke Gas cylinders
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 11118
EUROPEAN STANDARD
NORME EUROPÉENNE
January 2025
EUROPÄISCHE NORM
ICS 23.020.35 Supersedes EN ISO 11118:2015, EN ISO
11118:2015/A1:2020
English Version
Gas cylinders - Non-refillable metallic gas cylinders -
Specification and test methods (ISO 11118:2025)
Bouteilles à gaz - Bouteilles à gaz métalliques non Gasflaschen - Metallische Einwegflaschen -
rechargeables -Spécifications et méthodes d'essai (ISO Spezifikationen und Prüfverfahren (ISO 11118:2025)
11118:2025)
This European Standard was approved by CEN on 17 January 2025.

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
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 11118:2025 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 11118:2025) has been prepared by Technical Committee ISO/TC 58 "Gas
cylinders" in collaboration with Technical Committee CEN/TC 23 “Transportable gas cylinders” the
secretariat of which is held by BSI.
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 July 2025, and conflicting national standards shall be
withdrawn at the latest by July 2025.
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 ISO 11118:2015, EN ISO 11118:2015/A1:2020.
This document has been prepared under a standardization request addressed to CEN by the European
Commission. The Standing Committee of the EFTA States subsequently approves these requests for its
Member States.
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 11118:2025 has been approved by CEN as EN ISO 11118:2025 without any modification.

International
Standard
ISO 11118
Third edition
Gas cylinders — Non-refillable
2025-01
metallic gas cylinders —
Specification and test methods
Bouteilles à gaz — Bouteilles à gaz métalliques non
rechargeables — Spécifications et méthodes d’essai
Reference number
ISO 11118:2025(en) © ISO 2025
ISO 11118:2025(en)
© ISO 2025
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
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
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 11118:2025(en)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols . 3
5 Materials . 3
5.1 General requirements .3
5.2 Material types .4
5.2.1 Carbon and low-alloy steels . .4
5.2.2 Aluminium and aluminium alloy .4
5.2.3 Austenitic stainless steels .4
5.3 Chemical compositions .5
5.3.1 Carbon and low-alloy steels . .5
5.3.2 Aluminium and aluminium alloys.6
6 Inspection and testing . 6
7 Design . 6
7.1 General requirements .6
7.2 Calculation of pressure containing parts .6
7.3 Design drawings .7
8 Construction and workmanship . 7
8.1 Construction .7
8.1.1 Types of construction of cylinder shell .7
8.1.2 Cylinder non-refillability.11
8.1.3 Pressure relief devices .11
8.2 Workmanship .11
9 Type approval procedure .12
9.1 General requirements . 12
9.2 Prototype tests . . 12
9.2.1 General . 12
9.2.2 Material tests . 12
9.2.3 Tensile tests . 13
9.2.4 Burst tests .14
9.2.5 Drop tests .16
9.2.6 Dimension checks .17
9.2.7 Valve to cylinder interface test .18
9.3 Design type approval .18
10 Batch tests . .18
10.1 General requirements .18
10.2 Failure to meet test requirements .18
11 Tests on every cylinder . 19
11.1 Inspection .19
11.2 Proof pressure test .19
11.3 Leak testing .19
11.4 Rejection criteria .19
11.5 Repairs .19
12 Markings . 19
12.1 General .19
12.2 Manufacturing and operational markings .19
12.3 Other markings . 20

iii
ISO 11118:2025(en)
13 Test reports and certificate of conformance .20
Annex A (normative) Non-refillable sealing devices — Specifications and prototype testing .21
Annex B (informative) Type approval certificate .27
Annex C (informative) Certificate of conformance .29
Annex D (informative) Yield point elongation (YPE) .31
Bibliography .34

iv
ISO 11118:2025(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 document 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 58, Gas cylinders, Subcommittee SC 3, Cylinder
design, in collaboration with the European Committee for Standardization (CEN) Technical Committee CEN/
TC 23, Transportable gas cylinders, in accordance with the Agreement on technical cooperation between ISO
and CEN (Vienna Agreement).
This third edition cancels and replaces the second edition (ISO 11118:2015), which has been technically
revised. It also incorporates the Amendment ISO 11118:2015/Amd 1:2019.
The main changes are as follows:
— the normative references have been updated;
— verification of minimum cylinder shell wall thickness has been added;
— the calculation of determination of minimum wall thickness has been simplified by fixing the “F” factor;
— welding qualification, including defining process and operator, has been modified;
— testing of nonrefillable valve sampling has been clarified;
— marking requirements based on UN Model Regulation requirements have been clarified.
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.

v
ISO 11118:2025(en)
Introduction
The purpose of this document is to facilitate agreement on the design and manufacture of non-refillable
metallic gas cylinders and their sealing devices in all countries. The requirements are based on knowledge
of, and experience with, materials, design requirements, manufacturing processes and controls in common
use for the manufacture of gas cylinders.
[10]
This document has been written so that it is suitable to be referenced in the UN Model Regulations .
In this document, the unit bar is used, due to its universal use in the field of technical gases. It should,
however, be noted that bar is not an SI unit, and that the corresponding SI unit for pressure is Pa (1 bar =
5 5 2
10 Pa = 10 N/m ).
Pressure values given in this document are given as gauge pressure (pressure exceeding atmospheric
pressure) unless noted otherwise.
Any tolerances given in this document include measurement uncertainties.

vi
International Standard ISO 11118:2025(en)
Gas cylinders — Non-refillable metallic gas cylinders —
Specification and test methods
1 Scope
This document specifies requirements for the material, design, inspections, construction and workmanship,
manufacturing processes, and tests at manufacture of non-refillable metallic gas cylinders of welded, brazed,
or seamless construction. This document also specifies the requirements for the non-refillable sealing
devices and their methods of testing. It is applicable to non-refillable metallic gas cylinders for compressed
and liquefied gases.
NOTE The specific gases permitted in cylinders constructed to this document can be limited by national or
international requirements.
This document is applicable to cylinders where:
1)
a) the test pressure does not exceed 250 bar (i.e. p ≤ 250 bar) for liquefied gases and 450 bar for
h
compressed gases; or
b) the product of the test pressure and the water capacity does not exceed 1 000 bar·litres (i.e.
p V ≤ 1 000 bar l); or
h
c) the test pressure exceeds 45 bar and the water capacity does not exceed 5 l (i.e. for p > 45 bar, then
h
V ≤ 5 l).
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 3651-2, Determination of resistance to intergranular corrosion of stainless steels — Part 2: Ferritic,austenitic
and ferritic-austenitic (duplex) stainless steels — Corrosion test in media containing sulfuric acid
ISO 4706:2023, Gas cylinders — Refillable welded steel cylinders — Test pressure 60 bar and below
ISO 6892-1, Metallic materials — Tensile testing — Part 1: Method of test at room temperature
ISO 7866:2012, Gas cylinders — Refillable seamless aluminium alloy gas cylinders — Design, construction and testing
ISO 9329-1, Seamless steel tubes for pressure purposes — Technical delivery conditions — Part 1: Unalloyed
steels with specified room temperature properties
ISO 9809-1:2019, Gas cylinders — Design, construction and testing of refillable seamless steel gas cylinders and
tubes — Part 1: Quenched and tempered steel cylinders and tubes with tensile strength less than 1 100 MPa
ISO 9809-4:2021, Gas cylinders — Design, construction and testing of refillable seamless steel gas cylinders and
tubes — Part 4: Stainless steel cylinders with an R value of less than 1 100 MPa
m
ISO 10156, Gas cylinders — Gases and gas mixtures — Determination of fire potential and oxidizing ability for
the selection of cylinder valve outlets
ISO 10286, Gas cylinders — Vocabulary
5 2
1) 1 bar = 0,1 MPa = 10 Pa; 1 MPa = 1 N/mm

ISO 11118:2025(en)
ISO 10297, Gas cylinders — Cylinder valves — Specification and type testing
ISO 11114-1, Gas cylinders — Compatibility of cylinder and valve materials with gas contents — Part 1: Metallic
materials
ISO 11114-2, Gas cylinders — Compatibility of cylinder and valve materials with gas contents — Part 2: Non-
metallic materials
ISO 13769, Gas cylinders — Stamp marking
ISO 15614-1, Specification and qualification of welding procedures for metallic materials — Welding procedure
test — Part 1: Arc and gas welding of steels and arc welding of nickel and nickel alloys
ISO 15614-12, Specification and qualification of welding procedures for metallic materials — Welding procedure
test — Part 12: Spot, seam and projection welding
ISO 20703:2006, Gas cylinders — Refillable welded aluminium-alloy cylinders — Design, construction and testing
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 10286 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
batch
quantity of completed and pressure tested cylinders made
consecutively by the same manufacturer using the same manufacturing techniques to the same design, size,
and material specifications using the same type of welding machines (when applicable), welding procedures
(when applicable), and to the same heat treatment conditions (when applicable)
Note 1 to entry: See Clause 10 for details.
3.2
cylindrical shell
portion of the cylinder shell excluding the cylinder ends which is parallel to the centreline axis of the cylinder
3.3
cylinder shell
empty cylinder before affixing the non-refillable sealing device (3.12), but including all other permanent
attachments
3.4
material certificate
document issued by the material manufacturer which certifies the chemical analysis, mechanical properties,
heat treatment, processing techniques, or other properties/features if required
3.5
burst pressure
highest pressure reached in a cylinder during the burst test
3.6
test pressure
required pressure applied during the pressure test
3.7
working pressure
settled pressure of compressed gas at a uniform reference temperature of 15 °C (288 K) in a full gas cylinder

ISO 11118:2025(en)
3.8
minimum operating temperature
minimum temperature to which the cylinder contents can be exposed
Note 1 to entry: See 5.1.6.
3.9
non-refillable cylinder
cylinder including a non-refillable sealing device (3.12) that permits the cylinder to be filled only once
Note 1 to entry: Where there is no risk of ambiguity, the short abbreviated form “cylinder” is used in this document.
3.10
water capacity
volume of water required to completely fill an empty cylinder
3.11
processor
facility that anneals, rolls, slits, or otherwise, changes the material from the form received from the location
where the steel was melted
3.12
non-refillable sealing device
device permanently attached to the cylinder which, once activated, prevents the cylinder from being refilled
4 Symbols
a calculated minimum thickness, in millimetres, of the cylindrical shell
D nominal outside diameter of the cylinder, in millimetres
F design stress factor
P burst pressure of the cylinder, in bar
b
p test pressure, in bar above atmospheric pressure
h
p working pressure, in bar above atmospheric pressure
w
p non-refillable sealing device test pressure, in bar above atmospheric pressure
vt
R actual value of the yield strength, in megapascals, of the cylinder when tested
ea
R minimum guaranteed value of the yield strength, in megapascals, for the finished cylinder
eg
R actual value of the tensile strength, in megapascals, of the cylinder when tested
ma
R minimum guaranteed value of the tensile strength, in megapascals, for the finished cylinder
mg
V water capacity of the cylinder, in litres
5 Materials
5.1 General requirements
5.1.1 Cylinder shells shall be made of carbon or low alloy steels, austenitic stainless steel, aluminium, or
aluminium alloys. The materials used shall be specified by type (see 5.2) and chemical composition (see 5.3).
Materials shall not contain seams, cracks, laminations, or other injurious defects. For material requirements
of non-refillable sealing devices, see Annex A.

ISO 11118:2025(en)
5.1.2 The cylinder manufacturer shall specify the chemical and mechanical requirements to the material
supplier.
5.1.3 The cylinder manufacturer shall obtain a material certificate from the manufacturer/processor of
the material certifying the chemical analysis of the cast. The certificate shall be issued by the manufacturer
of the material and shall confirm compliance to the material specification.
5.1.4 The cylinder manufacturer shall verify that the materials are in accordance with the cylinder
manufacturer specifications.
5.1.5 All materials used in the construction of the pressure containing parts of the cylinder shall be
traceable.
5.1.6 All materials shall be suitable for use at the minimum operating temperature or at –20 °C, whichever
is the lower.
5.1.7 The materials used for manufacture of the cylinder shell shall be compatible with the intended gas
service as specified in ISO 11114-1 or ISO 11114-2.
5.1.8 Contact between dissimilar metals resulting in damage by galvanic corrosion shall be avoided.
5.2 Material types
5.2.1 Carbon and low-alloy steels
5.2.1.1 The steel used for the fabrication of gas cylinder shells shall be made in an electric furnace or,
by the basic oxygen process, shall have non-ageing properties and shall be fully killed (de-oxidized) by
aluminium and/or silicon.
5.2.1.2 Carbon steel for cold deep drawn seamless, welded, or brazed cylinder shells shall have non-ageing
properties, processed free of stretcher strain, and shall be fully killed with aluminium and/or silicon. The
chemical composition shall meet the requirements of 5.3.1.1.
5.2.1.3 Carbon steel for other welded cylinder shells shall have a chemical composition which meets the
requirements of 5.3.1.2. The maximum tensile strength shall not exceed 700 MPa.
5.2.1.4 Carbon steel for cylinder shells made from seamless steel tubing with integrally formed ends, hot
drawn, and finished shall have a chemical composition which meets the requirements of 5.3.1.3.
5.2.1.5 Low alloy steels shall conform to ISO 4706:2023, 5.2.1 or ISO 9809-1:2019, 6.1, 6.2, and 6.3.
5.2.2 Aluminium and aluminium alloy
5.2.2.1 Aluminium alloys with a tensile strength greater than 500 MPa shall not be used.
5.2.2.2 Aluminium alloys used for cylinders shall conform to the material requirements of ISO 7866:2012,
6.1 and 6.2 or ISO 20703:2006, 4.1 and 4.2, as appropriate.
5.2.2.3 Pure aluminium is permitted and shall have a minimum aluminium content of 99,0 %.
5.2.3 Austenitic stainless steels
5.2.3.1 For austenitic stainless steels, the maximum tensile strength shall not exceed 800 MPa.

ISO 11118:2025(en)
5.2.3.2 The cylinder manufacturer shall take into consideration the loss of material strength within the
heat affected zone of any weld.
5.2.3.3 Austenitic stainless steels for all types of cylinder shells shall conform to ISO 9809-4:2021, 6.1 and 6.2.
5.2.3.4 Due to the risk of sensitization to inter-granular corrosion resulting from hot working/welding for
each material specification and heat-treatment method, a corrosion test shall be carried out in accordance
with ISO 3651-2 on a specimen taken from a finished cylinder.
Some grades of stainless steels can be susceptible to environmental stress corrosion cracking. Special
precautions should be taken in such cases.
5.3 Chemical compositions
5.3.1 Carbon and low-alloy steels
5.3.1.1 Carbon steels having non-aging properties for cold deep drawn welded or brazed cylinder shells
shall have the following chemical composition limits in % mass fraction given in Table 1.
Table 1 — Cylinder shell and ends non-aging properties for cold deep drawn chemistry allowable limits
Element Maximum content
% (mass fraction)
Carbon ≤ 0,12
Manganese ≤ 0,50
Phosphorus ≤ 0,025
Sulfur ≤ 0,025
5.3.1.2 Carbon steels for welded cylinder shells other than cold deep drawn shall have the following
chemical composition limits in % mass fraction given in Table 2.
Table 2 — Cylinder shell and ends other than cold deep drawn chemistry allowable limits
Element Maximum content
% (mass fraction)
Carbon ≤ 0,25
Manganese ≤ 0,50
Phosphorus ≤ 0,025
Sulfur ≤ 0,025
5.3.1.3 Carbon steels for cylinder shells made of seamless steel with integrally formed ends, hot drawn,
and finished shall have the following chemical composition limits in % mass fraction given in Table 3.
Table 3 — Seamless steel with integrally formed ends, hot drawn cylinder shell chemistry
allowable limits
Element Maximum content
% (mass fraction)
Carbon ≤ 0,55
Manganese ≤ 1,70
Phosphorus ≤ 0,025
Sulfur ≤ 0,025
ISO 11118:2025(en)
5.3.2 Aluminium and aluminium alloys
Aluminium and aluminium alloys shall have a maximum lead and bismuth contents not exceeding 0,003 % each.
6 Inspection and testing
To ensure that the cylinders conform to this document, they shall be subject to inspection and testing
in accordance with Clauses 9 to 11 and Annex A by an inspection body (hereinafter referred to as “the
inspector”).
Tests and examinations performed to demonstrate compliance with this document shall be conducted using
instruments calibrated before being put into service and thereafter according to an established program.
7 Design
7.1 General requirements
7.1.1 The calculation of the cylindrical wall thickness of the pressure containing parts shall be related to
the guaranteed minimum yield strength of the finished cylinder (R ).
eg
7.1.2 The design of the cylinder shell shall be such that the pressure containing parts, when subjected to
the test pressure (p ), shall not show any permanent visible deformation.
h
7.1.3 Welded aluminium and welded aluminium alloy cylinders are limited to a maximum of 60 bar test
pressure.
7.2 Calculation of pressure containing parts
The minimum thickness of the cylindrical shell of the pressure containing parts shall not be less than any of
the three values determined in 7.2 a), b), and c).
a) The minimum thickness of the cylindrical shell shall be not less than that necessary for the minimum
burst pressure to be greater than 1,6 times the test pressure (p ) and such that the requirements of
h
9.2.4.5 and Clause 11 are met.
b) The minimum thickness of the cylindrical shell shall not be less than that calculated by the Lamé - von
Mises formula as given in Formula (1).
 
 
10FR − 3 p
D
eg h
 
a=−1   (1)
 
 
2 10FR
eg
 
 
with F = 0,85
c) The minimum thickness of the cylindrical shell shall not be less than that calculated by using Formula (2)
or Formula (3) as appropriate.
Formula (2) (for steel):
a=+D/650 04, (2)
Formula (3) (for aluminium alloys):
a=+D/300 05, (3)
NOTE It is generally assumed that p is equal to 1,5 times working pressure for compressed gases.
h
ISO 11118:2025(en)
7.3 Design drawings
Fully dimensioned drawing(s) of the non-refillable cylinder shall be supplied which includes the following as
a minimum:
a) material specifications for cylinder shells including, but not limited to R and R (MPa). In addition,
eg mg
the material specifications for the non-refillable sealing device shall be noted;
b) test pressure (bar);
c) minimum burst pressure (bar);
d) minimum thickness of the cylindrical shell (mm);
e) minimum water capacity (litre) (for cylinders ≤ 2 l, the water capacity may be reported in ml);
f) nominal cylinder outside diameter (mm);
g) dimensions of the cylinder ends (mm);
h) overall length of the cylinder (mm);
i) heat treatment (if any);
j) method of construction;
k) welding/brazing procedure designation (if any);
l) specifications for valve outlet connection or cylinder threaded connection for use (if applicable);
m) cylinder design identification;
n) design standard (i.e. ISO 11118:2025);
o) date and revision identity of drawing;
p) manufacturer’s identity;
q) content and position of markings;
r) description of non-refillable sealing device that guarantees non-refillability and, if applicable, piercing
force and energy required to pierce membranes.
8 Construction and workmanship
8.1 Construction
8.1.1 Types of construction of cylinder shell
The cylinder shells shall be of seamless, welded, or brazed construction. The minimum wall thickness of
the cylindrical shell shall be verified during the production process. The frequency and method used to
determine the minimum cylindrical shell wall thickness shall be agreed with the inspector.
8.1.1.1 Seamless construction
8.1.1.1.1 Seamless cylinder shells shall be produced by
a) forging or drop forging from a solid ingot or billet,
b) manufacturing from seamless tube, or
c) pressing from a flat plate (cold deep drawn).

ISO 11118:2025(en)
8.1.1.1.2 Welding and brazing are only permitted to attach the non-refillable sealing device.
a) Welding shall be carried out only on cylinders made of weldable materials.
b) Brazing shall be carried out only on cylinders made of materials not degraded by this procedure.
8.1.1.2 Welded construction
8.1.1.2.1 General requirements
The welding of longitudinal and circumferential seams shall be by a semi-automatic or automatic process.
The longitudinal seam weld, if any, shall be of the butt type weld joint as illustrated in Figure 1 a).
The circumferential seam(s), if any, shall be as illustrated in Figure 1 a), b), c) or d).
Welded joints shall have strength greater than the tensile strength of the finished cylindrical wall.
The welding procedure and operator qualifications shall include, as a minimum, welds representative of
those made in production representing the variables in the materials and the process. Requalifying of the
procedures and operators shall be required if there is a change in any of the essential variables as specified
in 8.1.1.2.2.7.
a) Butt weld joint c) Butt weld joint with backing ring
b) Offset weld d) Joggle weld
Figure 1 — Weld joints
8.1.1.2.2 Welding qualifications
8.1.1.2.2.1 General
a) All welding equipment, welding operators and welding procedures may be approved by meeting the
requirements of 8.1.1.2.2 to 8.1.1.2.2.9 or those given in ISO 5817 (level B), ISO 9606-1, ISO 10042 (level
C), ISO 14732, ISO 15613, ISO 15614-1 and ISO 15614-12, as appropriate.
b) Records of welders and welding operator qualifications and welding procedure qualifications shall be
kept on file by the manufacturer.
c) Welding procedure specification approval tests shall be carried out such that the welds shall be
representative of those made in production.
d) Welders, welding operators and welding procedures shall pass the approval tests for the specific type of
work and procedure specification concerned.
8.1.1.2.2.2 Materials for pressure and non-pressure containing parts
The materials used for qualification shall be the same as those specified in the procedure specification and
those used for the production.

ISO 11118:2025(en)
8.1.1.2.2.3 Positions of welds
For welder qualification, the position of the part for welding shall be the same as that in the actual
manufacturing.
8.1.1.2.2.4 Welding consumables
The weld consumables shall be the same as those specified in the procedure specification, those tested from
the welders, and those used for the production.
8.1.1.2.2.5 Retesting
Where a welder or welding operator fails to meet the requirements of this document
a) an immediate retest shall be carried out of two test welds of the type failed, both of which shall meet all
the requirements of the standard, or
b) a retest shall be carried out provided there is evidence that the operator has had further training and
practice to the design and procedure specification.
8.1.1.2.2.6 Period of validity
A welder and welding operator shall be requalified on the design if the design has not been produced by the
welder for a period of six months or more. Records of effectiveness shall be retained by the manufacturer.
8.1.1.2.2.7 Essential variables of the welding process
The welding procedure specification and welder qualification shall be tested and approved when any of the
following changes are made, if not already covered:
a) a change to the base materials;
b) a change to the welding material;
c) a change to the weld process;
d) a change to the weld position;
e) a decrease of 30 °C or more in the minimum specified preheating temperature;
f) the omission or addition of a backing ring in single pass welds;
g) a change from multiple pass to single pass per side;
h) a change to the shielding gas or to the composition (if greater than a 15 % change in the mixture);
i) a change from a single arc to multi arc or vice versa.
8.1.1.2.2.8 Welder and weld operator qualification tests
a) For longitudinal welds:
1) bend test, root of weld;
2) weld tensile test.
b) For circumferential welds:
1) macro test;
2) weld tensile test.
c) For threaded connections to cylinder ends: macro tests, 180° apart.

ISO 11118:2025(en)
d) For welded attachments, foot rings, collars, rupture disc, or lugs: macro test.
e) For fillet welds: macro tests, 180° apart.
8.1.1.2.2.9 Acceptance
a) For bend tests:
Upon completion of the test, the test piece (weld metal and base material) shall remain uncracked.
b) For tensile tests:
The tensile strength value obtained, R , shall not be less than that guaranteed by the cylinder
ma
manufacturer regardless of the fracture location.
c) For macro tests:
The etched specimen shall be prepared to a resolution where visually, examination can occur to
determine adequate root penetration into both members as to the established design (e.g. ISO 17639).
8.1.1.3 Brazed construction
Butt weld brazed joints shall not be used.
Three-piece cylinder designs with brazed seams shall not be permitted.
Brazing shall not be used for aluminium or aluminium alloy cylinders.
Brazing materials shall be compatible with the intended gas being placed in the cylinder.
The brazing m
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