SIST EN ISO 7866:2012

SLOVENSKI STANDARD
01-december-2012
1DGRPHãþD
SIST EN 1975:1999
SIST EN 1975:1999/A1:2004
SIST EN 1975:1999/AC:2000
Plinske jeklenke - Ponovno polnljive plinske jeklenke iz celega iz aluminijevih zlitin
- Konstruiranje, izdelava in preskušanje (ISO 7866:2012)
Gas cylinders - Refillable seamless aluminium alloy gas cylinders - Design, construction
and testing (ISO 7866:2012)
Gasflaschen - Wiederbefüllbare nahtlose Gasflaschen aus Aluminiumlegierungen -
Auslegung, Bau und Prüfung (ISO 7866:2012)
Bouteilles à gaz - Bouteilles à gaz sans soudure en alliage d'aluminium destinées à être
rechargées - Conception, construction et essais (ISO 7866:2012)
Ta slovenski standard je istoveten z: EN ISO 7866:2012
ICS:
23.020.30 7ODþQHSRVRGHSOLQVNH Pressure vessels, gas
MHNOHQNH cylinders
77.150.10 Aluminijski izdelki Aluminium products
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 7866
NORME EUROPÉENNE
EUROPÄISCHE NORM
September 2012
ICS 23.020.30 Supersedes EN 1975:1999
English Version
Gas cylinders - Refillable seamless aluminium alloy gas
cylinders - Design, construction and testing (ISO 7866:2012)
Bouteilles à gaz - Bouteilles à gaz sans soudure en alliage Gasflaschen - Wiederbefüllbare nahtlose Gasflaschen aus
d'aluminium destinées à être rechargées - Conception, Aluminiumlegierungen - Auslegung, Bau und Prüfung (ISO
construction et essais (ISO 7866:2012) 7866:2012)
This European Standard was approved by CEN on 4 August 2012.

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, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United
Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2012 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 7866:2012: E
worldwide for CEN national Members.

Contents Page
Foreword .3
Foreword
This document (EN ISO 7866:2012) 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 March 2013, and conflicting national standards shall be withdrawn at
the latest by March 2013.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN 1975:1999.
According to the CEN/CENELEC Internal Regulations, the national standards organisations of the following
countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech
Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece,
Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.
Endorsement notice
The text of ISO 7866:2012 has been approved by CEN as a EN ISO 7866:2012 without any modification.

INTERNATIONAL ISO
STANDARD 7866
Second edition
2012-09-01
Gas cylinders — Refillable seamless
aluminium alloy gas cylinders — Design,
construction and testing
Bouteilles à gaz — Bouteilles à gaz sans soudure en alliage
d'aluminium destinées à être rechargées — Conception, construction et
essais
Reference number
ISO 7866:2012(E)
©
ISO 2012
ISO 7866:2012(E)
©  ISO 2012
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56  CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2012 – All rights reserved

ISO 7866:2012(E)
Contents Page
Foreword . v
Introduction . vi
1  Scope . 1
2  Normative references . 1
3  Terms and definitions . 1
4  Symbols . 2
5  Inspection and testing . 4
6  Materials . 4
6.1  General requirements . 4
6.2  Thermal treatments . 5
6.3  Test requirements . 6
6.4  Failure to meet test requirements . 6
7  Design . 7
7.1  General requirements . 7
7.2  Calculation of cylindrical shell thickness . 7
7.3  Design of ends (heads and bases) . 7
7.4  Neck design . 8
7.5  Foot rings . 11
7.6  Neck rings . 11
7.7  Design drawing . 11
7.8  High-strength and/or low-elongation gas cylinder designs . 11
8  Construction and workmanship . 11
8.1  General . 11
8.2  End forming . 11
8.3  Wall thickness . 12
8.4  Surface imperfections and defects . 12
8.5  Neck threads . 12
8.6  Out-of-roundness . 12
8.7  Exposure to heat . 13
8.8  Straightness . 13
8.9  Mean diameter . 13
9  Type approval procedure. 13
9.1  General requirements . 13
9.2  Prototype tests . 14
9.3  Type approval certificate . 15
10  Batch tests . 15
10.1  General requirements . 15
10.2  Tensile test . 17
10.3  Bend test and flattening test . 18
10.4  Hydraulic burst test . 19
10.5  Test requirements for high-strength and/or low-elongation gas cylinder designs . 21
11  Gas cylinder tests and examinations . 22
11.1  General . 22
11.2  Hydraulic test . 22
11.3  Hardness test . 23
11.4  Leakage testing . 23
ISO 7866:2012(E)
11.5  Examination for neck folds .23
11.6  Marking verification .23
11.7  Aluminium alloy gas cylinder surface features at time of manufacture .23
12  Certification .24
13  Marking .25
Annex A (normative) Corrosion tests .26
Annex B (normative) Test method to determine the sustained-load cracking resistance
of aluminium alloy gas cylinders .36
Annex C (informative) Typical type approval certificate .43
Annex D (informative) Acceptance certificate .44
Annex E (normative) Specific requirements for gas cylinders made of high-strength and/or low-
elongation aluminium alloy .46
Annex F (informative) Description and evaluation of manufacturing surface imperfections
and conditions for rejection of seamless aluminium alloy gas cylinders at time of product
acceptance .52
Annex G (normative) Batch size .59
Annex H (normative) Specific provisions for acetylene cylinder shells .60
Bibliography .61

iv © ISO 2012 – All rights reserved

ISO 7866:2012(E)
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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 7866 was prepared by Technical Committee ISO/TC 58, Gas cylinders, Subcommittee SC 3, and by
Technical Committee CEN/TC 23, Transportable gas cylinders in collaboration.
This second edition cancels and replaces the first edition (ISO 7866:1999), which has been technically
revised.
The following significant technical changes have been carried out:
 a new subclause (11.7) has been added to address unacceptable manufacturing defects and
unacceptable surface features at the time of manufacture and changes have been made to other
subclauses to compliment the new subclause;
 terms and definitions and the symbols have been revised;
 terminology changes included: “stress” changed to “strength”;
 various editorial errors were corrected;
 equipment calibration requirements were added;
 defining "defect" as a feature caused by the manufacturing/manufacturer; and
 defining "imperfection" as damage or feature not caused by manufacturing/manufacturer.

ISO 7866:2012(E)
Introduction
The purpose of this International Standard is to provide a specification for the design, manufacture, inspection
and testing of a seamless aluminium alloy gas cylinder for worldwide usage. The objective is to balance
design and economic efficiency against international acceptance and universal utility.
This International Standard aims to eliminate the concern about climate, duplicate inspections and restrictions
currently existing because of lack of definitive International Standards. This International Standard should not
be construed as reflecting on the suitability of the practice of any nation or region.
Following publication, this International Standard will be submitted for reference in the UN Recommendations
on the Transport of Dangerous Goods – Model Regulations.

vi © ISO 2012 – All rights reserved

INTERNATIONAL STANDARD ISO 7866:2012(E)

Gas cylinders — Refillable seamless aluminium alloy gas
cylinders — Design, construction and testing
1 Scope
This International Standard specifies minimum requirements for the material, design, construction and
workmanship, manufacturing processes and tests at time of manufacture of refillable seamless aluminium
alloy gas cylinders of water capacities up to and including 150 litres for compressed, liquefied and dissolved
gases for worldwide use (normally up to 65 °C).
2 Normative references
The following referenced documents are indispensable for the application 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 6506-1, Metallic materials — Brinell hardness test — Part 1: Test method
ISO 6508-1, Metallic materials — Rockwell hardness test — Part 1: Test method (scales A, B, C, D, E, F, G,
H, K, N, T)
ISO 6892-1, Metallic materials — Tensile testing — Part 1: Method of test at room temperature
ISO 7438, Metallic materials — Bend test
ISO 7539-6:2011, Corrosion of metals and alloys — Stress corrosion testing — Part 6: Preparation and use of
pre-cracked specimens for tests under constant load or constant displacement
ISO 10461, Gas cylinders — Seamless aluminium-alloy gas cylinders — Periodic inspection and testing
ISO 11117, Gas cylinders — Valve protection caps and valve guards — Design, construction and tests
ISO 13341, Gas cylinders — Fitting of valves to gas cylinders
ISO 13769, Gas cylinders — Stamp marking
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
artificial ageing
heat treatment process in which the solute phase is precipitated to give an increased yield strength and tensile
strength
3.2
bar·litres
product of the test pressure (in bars) and the water capacity (in litres)
ISO 7866:2012(E)
3.3
batch
quantity of gas cylinders, plus gas cylinders for destructive testing, of the same nominal diameter, wall
thickness, length and design, made successively from the same cast of aluminium alloy and subjected to the
same heat treatment on the same equipment for the same duration of time
NOTE See Table G.1 for batch size requirements.
3.4
design stress factor (variable)
F
ratio of equivalent wall stress at test pressure, p , to the guaranteed minimum yield strength, R
h eg
3.5
IAA
registration record of international alloy designations and chemical composition limits for wrought aluminium
1)
and wrought aluminium alloys as published by the Aluminum Association
NOTE Such aluminium alloys are designated by the prefix “AA”.
3.6
mass of a gas cylinder
combined mass of the gas cylinder and all permanently attached parts (e.g. foot ring, neck ring), but without
the valve
NOTE Mass is expressed in kilograms.
3.7
quenching
controlled rapid cooling in a suitable medium to retain the solute phase in solid solution
3.8
solution heat treatment
thermal treatment which consists of heating products to a suitable temperature and holding them at that
temperature long enough to allow constituents to enter into solid solution
3.9
stabilizing heat treatment
non-ageing heat treatment applied to 5 000-series aluminium alloys in order to minimize changes in
mechanical properties and structure under service conditions
3.10
yield strength
value corresponding to the 0,2 % proof strength (0,2% non-proportional elongation), R , for aluminium
p0,2
alloys
4 Symbols
a calculated minimum wall thickness, in millimetres, of the cylindrical shell (see Figure 1)
a′ guaranteed minimum wall thickness, in millimetres, of the cylindrical shell
A percentage elongation after fracture
b guaranteed minimum thickness, in millimetres, at the centre of a convex base (see Figure 1)

1) Aluminum Association Inc., 900, 19th Street N.W., Washington D.C., 20006-2168, USA.
2 © ISO 2012 – All rights reserved

ISO 7866:2012(E)
d’ positive circular development of fracture
d’’ negative circular development of fracture
D nominal outside diameter, in millimetres, of the cylinder (see Figure 1 and Figure 2)
D nominal outside diameter, in millimeters, of the cylinder neck (see Figure 2)”.
D diameter, in millimetres, of the bend test former (see Figure 5)
f
E modulus of elasticity
F design stress factor (variable) (see 3.4)
H outside height, in millimetres, of the domed part (convex head or base end) (see Figure 1)
L′ length of short branch of fracture, in millimeters
L′′ length of long branch of fracture, in millimeters
L original gauge length, in millimetres, as defined in ISO 6892-1 (see Figure 4)
o
n ratio of the diameter of the bend test former to the actual thickness of the test specimen, t
p actual burst pressure, in bars above atmospheric pressure
b
p failure pressure, in bars
f
p hydraulic test pressure, in bars above atmospheric pressure
h
p upper cycling pressure, in bars
u
p observed pressure when gas cylinder starts yielding during hydraulic bursting test, in bars above
y
atmospheric pressure
r inside knuckle radius, in millimetres (see Figure 1)
r tip radius, in millimeters
c
r inside crown radius, in millimetres (see Figure 1)
i
R maximum stress value, in MPa
R actual value of the yield strength, in megapascals, as determined by the tensile test specified in 10.2
ea
for the finished gas cylinder
R minimum guaranteed value of the yield strength (see 3.10), in megapascals, for the finished gas
eg
cylinder
R actual value of the tensile strength, in megapascals, as determined by the tensile test specified in
ma
10.2 for the finished gas cylinder
R minimum guaranteed value of the tensile strength, in megapascals, for the finished gas cylinder
mg
R 0,2 % proof strength (0,2% non-proportional elongation), for aluminium alloys
p0,2
S original cross-sectional area, in square millimetres, of the tensile test specimen in accordance with
o
ISO 6892-1
t actual wall thickness, in millimetres, of the test specimen
ISO 7866:2012(E)
t average cylinder wall thickness, in millimetres, in the position of testing during the flattening test
m
T titre of hydrogen peroxide in g per litre
u ratio of distance between knife edges at the end of test to the average cylinder wall thickness
w width, in millimetres, of the narrow, parallel-sided section of a tensile test specimen (see Figure 4)
z correction factor
5 Inspection and testing
NOTE Evaluation of conformity can be performed in accordance with the regulations recognized by the country(ies)
where the gas cylinders are intended to be used.
To ensure that the gas cylinders conform to this International Standard, they shall be subjected to inspection
and testing in accordance with Clauses 9, 10 and 11 by an inspection body, hereafter referred to as the
“Inspection Body”, authorized to do so.
Equipment used for measurement, testing and examination during production shall be maintained and
calibrated within a documented quality managment system.
6 Materials
6.1 General requirements
6.1.1 Aluminium alloys and their chemical composition limits shall be as specified in Table 1. Other
aluminium alloys may be used to produce gas cylinders provided they satisfy all the requirements of this
International Standard and are approved by the relevant authority for cylinder use.
6.1.2 The gas cylinder manufacturer shall identify the gas cylinders with the particular casts of the alloy
from which they are made, and shall obtain and provide certificates of the analysis of the casts used. If check
analysis is required, they shall be carried out either on test specimens taken from material in the form supplied
by the producer of the aluminium alloy or from finished gas cylinders.
6.1.3 Some aluminium alloys are not compatible with certain gases and gas mixtures, e.g. corrosive gases
(see ISO 11114-1). The manufacturer shall use materials compatible with the intended gas service when the
purchaser indicates the intended gas.
4 © ISO 2012 – All rights reserved

ISO 7866:2012(E)
Table 1 — Chemical composition of materials
Chemical composition (% by mass) Others
Type of alloy
(IAA registered AA
Si Fe Cu Mn Mg Cr Ni Zn Ti Zr Pb Al
designation)
min. 0,7 — — 0,40 0,40 — — — — — — — —
6351A Remainder
max. 1,3 0,50 0,10 0,8 0,8 — — 0,20 0,20 — 0,003 0 0,05 0,15
min. 0,7 — — 0,40 0,60 — — — — — — — —
1 6082A Remainder
max. 1,3 0,50 0,10 1,0 1,2 0,25 — 0,20 0,10 — 0,003 0 0,05 0,15
min. 0,40 — 0,15 — 0,8 0,04 — — — — — — —
6061A Remainder
max. 0,8 0,7 0,40 0,15 1,2 0,35 — 0,25 0,15 — 0,003 0 0,05 0,15
min. — — — 0,50 4,5 — — — — — — — —
2 5283A Remainder
max. 0,30 0,30 0,03 1,0 5,1 0,05 0,03 0,10 0,03 0,05 0,003 0 0,05 0,15
min. — — 1,8 — 1,3 0,15 — 6,1 — — — — —
7060 Remainder
max. 0,15 0,20 2,6 0,20 2,1 0,25 — 7,5 0,05 0,05 0,003 0 0,05 0,15
min. — — 1,7 — 1,5 0,15 — 5,5 — — — — —
7032 Remainder
max. 0,10 0,12 2,3 0,05 2,5 0,25 0,05 6,5 0,1 0,05 0,003 0 0,05 0,15
min. — — 5,2 0,15 0,20 — — — — — — — —
4 2001 Remainder
max. 0,20 0,20 6,0 0,50 0,45 0,10 0,05 0,10 0,20 0,05 0,003 0 0,05 0,15
The bismuth content shall not exceed 0,0030 % (by mass).
NOTE The above materials are used extensively throughout the world in preference to the alloy compositions quoted in ISO 209. They are
included in this International Standard quoting the IAA registered designations, but making reference to ISO 209 where it is considered applicable.

6.2 Thermal treatments
6.2.1 Heat-treatable alloys (see Table 1, groups 1, 3 and 4)
The manufacturer shall specify, in the type approval documentation, the solution heat treatment and artificial-
ageing temperatures and the minimum times for which the gas cylinders have been held at those
temperatures. The medium used for quenching after solution heat treatment shall be identified.
6.2.2 Non-heat-treatable alloys (see Table 1, group 2)
The manufacturer shall specify, in the type approval documentation, the type of metal-forming operation
carried out (extrusion, drawing, ironing, head forming, etc.).
Unless the alloy is subjected to a temperature in excess of 400 °C during the forming process, a stabilizing
heat treatment shall be carried out at a temperature above 220 °C, and the temperature and time at that
temperature shall be identified by the manufacturer.
6.2.3 Control of specified heat treatment
During the heat treatment, the manufacturer shall comply with the following tolerances:
a) temperatures:
 solution temperature 10 °C,
 artificial ageing temperature 5 °C,
 stabilizing temperature 10 °C;
Group
Each
Total
ISO 7866:2012(E)
b) time gas cylinders actually spend at this temperature during treatment:
 solution treatment 30 %,
 ageing treatment 20 %,
 stabilizing treatment 10 %.
6.3 Test requirements
The material of the finished gas cylinders shall conform to Clauses 9, 10 and 11.
6.4 Failure to meet test requirements
6.4.1 In the event of failure to meet test requirements, retesting or reheat treatment and retesting shall be
carried out as follows:
a) If there is evidence of a fault in carrying out a test, or an error of measurement, a second test shall be
performed, on the same gas cylinder if possible. If the result of this test is satisfactory, the first test shall
be ignored.
b) If the test has been carried out in a satisfactory manner and the failure is in a test representing the
prototype or batch gas cylinders, the procedure detailed in either 6.4.2 or 6.4.3 shall be followed.
c) If the test has been carried out in a satisfactory manner and the failure is in a test applied to every gas
cylinder, then only those gas cylinders which failed the test require retesting or reheat treatment and
retesting, provided the cause of the failure is well identified. If the failure is due to the heat treatment
applied, the failed gas cylinders shall be subjected to the procedure in 6.4.3. If the failure is due to a
cause other than the heat treatment applied, all defective gas cylinders shall be rejected.
6.4.2 Two further gas cylinders selected at random from the same batch shall be subjected to the tests
specified in 10.1.3 a) and 10.1.3 b). If both gas cylinders meet the specified requirements, the batch shall be
accepted. Should either gas cylinder fail to meet the specified requirements, the batch shall
a) be rejected,
or
b) be treated in accordance with 6.4.3.
6.4.3 The batch of gas cylinders shall be reheat-treated and two further gas cylinders shall be tested in
accordance with 10.1.3 a) and 10.1.3 b). If both gas cylinders meet the specified requirements, the batch shall
be accepted. Should either gas cylinder fail to meet the specified requirements, the batch shall be rejected.
6.4.4 For heat-treatable alloys, where it can be established that the heat treatment was at fault for failure of
a test, the batch of gas cylinders may additionally (more than once) be re-solution heat-treated and/or aged.
However, the batch may only be submitted to the Inspection Body one more time for testing after the initial
submission. If the batch presented to the Inspection Body for the second test or tests fails one or more tests,
the batch shall be condemned.
6 © ISO 2012 – All rights reserved

ISO 7866:2012(E)
7 Design
7.1 General requirements
7.1.1 The calculation of the wall thickness of the pressure-containing parts shall be related to the yield
strength, R , of the material.
eg
7.1.2 For calculation purposes, the value of the yield strength, R , is limited to a maximum of 0,90R for
eg mg
seamless aluminium alloy gas cylinders.
7.1.3 The internal pressure upon which the calculation of wall thickness is based shall be the hydraulic test
pressure, p .
h
7.1.4 Wherever any exposure to heat is necessary (e.g. for gas cylinders for dissolved acetylene, where the
process by which the porous material is manufactured can modify the characteristics of the aluminium alloy
used; see Annex H), this shall be considered when designing the shell.
7.2 Calculation of cylindrical shell thickness
The guaranteed minimum thickness of the cylindrical shell, a′, shall not be less than the thickness calculated
using relationships (1) and (2), and additionally condition (3) shall be satisfied:

10FRp 3
D eg h

a1 (1)

210FR
eg

where
0,65
the value of F is the lesser of and 0,85;
RR/
eg mg
R /R shall not exceed 0,90.
eg mg
The wall thickness shall also satisfy the relationship:
D
a  + 1mm (2)
with an absolute minimum of 1,5 mm.
The burst ratio shall be satisfied by test. The following condition shall be met:
p /p  1,6 (3)
b h
When choosing the minimum guaranteed value of the thickness of the cylindrical shell, a′, the manufacturer
shall ensure that the thickness is sufficient to satisfy both the calculations and the required verification testing.
NOTE It is generally assumed that p  1,5  the service pressure for compressed gases for gas cylinders designed
h
and manufactured to this International Standard.
7.3 Design of ends (heads and bases)
7.3.1 The thickness and shape of the base and head of the gas cylinders shall be such as to meet the
requirements of the tests specified in 10.4 (hydraulic burst test) and 9.2.3 (pressure-cycling test).
To achieve satisfactory stress distribution, the gas cylinder wall thickness shall increase progressively in the
transition zone between the cylindrical shell and the ends, particularly the base. Examples of typical shapes of
convex heads and base ends are shown in Figure 1.
ISO 7866:2012(E)
7.3.2 The thickness at any part of a convex end shall be not less than the minimum wall thickness of the
cylindrical part.
7.3.3 The inside crown radius, r, shall be not greater than 1,2  the inside diameter of the shell, and the
i
knuckle radius, r, shall be not less than 10 % of the inside diameter of the shell.
7.3.4 Where the conditions of 7.3.3 are not fulfilled, the gas cylinder manufacturer shall prove by the
prototype tests as required in 9.2 that the design is satisfactory.
7.4 Neck design
7.4.1 The external diameter and thickness of the formed neck end of the gas cylinder shall be adequate for
the stresses resulting from the fitting of the valve to the gas cylinder. The stresses can vary according to the
thread diameter, its form and the sealant used in fitting the valve. The requirements specified in ISO 13341 (or
as recommended by the manufacturer where that International Standard does not apply) shall be applied,
since permanent damage to the gas cylinder could otherwise result.
7.4.2 In establishing the minimum thickness, consideration shall be given to obtaining a thickness of the
wall in the gas cylinder neck which will prevent permanent expansion of the neck during the initial and
subsequent fittings of the valve into the gas cylinder.
In specific cases (e.g. very thin walled cylinders), where the stresses resulting from the initial and subsequent
fittings of the valve to the gas cylinder cannot be supported by the neck itself, the neck may be designed to
require reinforcement, such as a neck ring or shrunk-on collar, provided the reinforcement material and
dimensions are clearly specified by the manufacturer and this configuration is part of the type approval
procedure.
7.4.3 Gas cylinders may be designed with one or two openings but both shall be along the central gas
cylinder axis.
8 © ISO 2012 – All rights reserved

ISO 7866:2012(E)
Figure 1 — Typical ends
ISO 7866:2012(E)
Figure 1 — Typical ends (continued)
10 © ISO 2012 – All rights reserved

ISO 7866:2012(E)
7.5 Foot rings
When a foot ring is provided, it shall be sufficiently strong and made of material compatible with that of the gas
cylinder. The shape should preferably be cylindrical and shall give the gas cylinder sufficient stability. The foot
ring shall be secured to the gas cylinder by a method other than welding, brazing or soldering. To prevent
ingress of water, any gaps which could form water traps shall be sealed by a method other than welding,
brazing or soldering.
7.6 Neck rings
When a neck ring is provided, it shall be sufficiently strong and made of material compatible with that of the
gas cylinder, and shall be securely attached by a method other than welding, brazing or soldering.
The manufacturer shall ensure that the axial load necessary to remove the neck ring is greater than 10  the
mass of the empty gas cylinder, but not less than 1 000 N, and that the minimum torque necessary to rotate
the neck ring is 100 Nm.
Where the gas cylinder manufacturer fits valve protection, it shall be in accordance with the requirements
specified in ISO 11117.
7.7 Design drawing
A fully dimensioned drawing, including tolerances, shall be prepared which includes the specification of the
material and makes reference to this International Standard.
7.8 High-strength and/or low-elongation gas cylinder designs
Requirements for these designs are given in Annex E.
8 Construction and workmanship
8.1 General
The gas cylinder shall be produced by
a) cold or hot extrusion from cast or extruded or rolled billet,
b) cold or hot extrusion from cast or extruded or rolled billet, followed by cold drawing,
c) cupping, flow forming, spinning and cold drawing sheet or plate,
d) open necking at both ends of an extruded or cold-drawn tube (see Figure 2), and
e) non-welding techniques.
Manufacturing defects shall not be corrected by plugging.
8.2 End forming
The neck shall be formed by an appropriate method, e.g. forging, swaging or spinning. Where heat has to be
applied to form the gas cylinder′s neck/shoulder, it shall be ensured that an appropriately controlled heat
distribution is achieved prior to the forming operation, e.g. by means of induction heating. This approach shall
be used irrespective of the method employed for the manufacture of the shell.
The end-forming operation chosen shall result in a visibly smooth surface, especially in the neck/shoulder
areas, which has no feature or defect [e.g. unacceptable folds (see 11.5) or cracks] which will adversely affect
the performance or integrity of the gas cylinder.
ISO 7866:2012(E)
Figure 2 — Necked ends of tube
8.3 Wall thickness
Each gas cylinder shall be examined, at the time of production, for thickness. The wall thickness at any point
shall be not less than the minimum thickness specified.
8.4 Surface imperfections and defects
Each gas cylinder shall be examined, at the time of production, for internal and external surface imperfections
and defects.
The internal and external surfaces of the finished gas cylinder shall be free from defects that would adversely
affect the safe working of the gas cylinder.
Such defects shall be removed by local dressing (where permitted) or the cylinder shall be condemned.
The wall thickness of any dressed areas shall not be less than the minimum thickness specified in the design.
Imperfections are subject to the requirements of 11.7.
8.5 Neck threads
The neck threads shall conform to the design specification to permit the use of a corresponding valve, thus
minimizing neck stresses following the valve-fitting operation.
Neck threads shall be checked using gauges corresponding to the agreed neck thread, or by an alternative
method agreed between the parties, e.g. where the internal neck thread is specified to be in accordance with
ISO 11363-1 the corresponding gauges are specified in ISO 11363-2.
8.6 Out-of-roundness
The out-of-roundness of the cylindrical shell, i.e. the difference between the maximum and minimum outside
diameters in the same cross-section, shall not exceed 2 % of the mean of these diameters.
12 © ISO 2012 – All rights reserved

ISO 7866:2012(E)
8.7 Exposure to heat
Any exposure to heat after the heat treatment or stabilization treatment shall not modify the characteristics of
the aluminium alloy used to the extent that the mechanical properties fall below the minimum guaranteed
values. When exposure to heat is necessary (see 7.1.4), extensive trials shall be performed to verify that the
minimum design criteria are always met.
8.8 Straightness
The maximum deviation of the cylindrical part of the shell from a straight line shall not exceed 3 mm per metre
length.
8.9 Mean diameter
The mean external diameter shall not deviate from the nominal design diameter by more than 1 % or 1 mm,
whichever is the larger.
9 Type approval procedure
9.1 General requirements
A technical specification for each new design of gas cylinder [or gas cylinder family in the case of item f)
below], including a design drawing, design calculations, alloy details and details of heat treatment, shall be
submitted by the manufacturer to the Inspection Body. The type approval tests detailed in 9.2 shall be carried
out on each new design under the supervision of the Inspection Body.
A gas cylinder shall be considered to be of a new design compared with an existing approved design when
a) it is manufactured in a different factory; or
b) it is manufactured by a different process (see 8.1) [this includes the case when major process changes
(e.g. a change in the neck-forming method) are made during the production period]; or
c) it is manufactured from an alloy of different composition limits from that used in the original prototype
tests; or
d) it is given a different heat treatment that is outside the temperature and time ranges specified in 6.2.3; or
e) the base profile and the base thickness have changed relative to the gas cylinder diameter and calculated
minimum wall thickness; or
f) the overall length of the gas cylinder has increased by more than 50 % (gas cylinders with a
length/diameter ratio less than 3 shall not be used as reference gas cylinders for any new design with this
ratio greater than 3); or
g) the nominal outside diameter has changed; or
h) the design wall thickness has changed; or
i) the hydraulic test pressure has been increased (where a gas cylinder is to be used for lower-pressure
duty than that for which design approval has been given, it shall not be deemed to be a new design); or
j) the guaranteed minimum yie
...