EN ISO 11439:2000

SLOVENSKI STANDARD
01-maj-2002
3OLQVNHMHNOHQNH9LVRNRWODþQHMHNOHQNH]D]HPHOMVNLSOLQ]DSRJRQPRWRUQLKYR]LO
YJUDMHQHQDYR]LOR,62
Gas cylinders - High pressure cylinders for the on-board storage of natural gas as a fuel
for automotive vehicles (ISO 11439:2000)
Gasflaschen - Gasflaschen zur Mitführung von verdichtetem Erdgas als Treibstoff für
Kraftfahrzeuge (ISO 11439:2000)
Bouteilles a gaz - Bouteilles haute pression pour le stockage de gaz naturel utilisé
comme carburant a bord des véhicules automobiles (ISO 11439:2000)
Ta slovenski standard je istoveten z: EN ISO 11439:2000
ICS:
23.020.30 7ODþQHSRVRGHSOLQVNH Pressure vessels, gas
MHNOHQNH cylinders
43.060.40 Sistemi za gorivo Fuel systems
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 11439
NORME EUROPÉENNE
EUROPÄISCHE NORM
September 2000
ICS 43.060.40
English version
Gas cylinders - High pressure cylinders for the on-board storage
of natural gas as a fuel for automotive vehicles (ISO
11439:2000)
Bouteilles à gaz - Bouteilles haute pression pour le Gasflaschen - Gasflaschen zur Mitführung von
stockage de gaz naturel utilisé comme carburant à bord verdichtetem Erdgas als Treibstoff für Kraftfahrzeuge (ISO
des véhicules automobiles (ISO 11439:2000) 11439:2000)
This European Standard was approved by CEN on 15 September 2000.
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 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 Management Centre has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,
Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2000 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 11439:2000 E
worldwide for CEN national Members.

Page 2
Foreword
Corrected 2001-03-28
The text of the International Standard ISO 11439:2000 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 2001, and conflicting national
standards shall be withdrawn at the latest by March 2001.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of
the following countries are bound to implement this European Standard: Austria, Belgium,
Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy,
Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United
Kingdom.
Endorsement notice
The text of the International Standard ISO 11439:2000 was approved by CEN as a European
Standard without any modification.
NOTE: Normative references to International Standards are listed in annex ZA (normative).

Page 3
Annex ZA (normative)
Normative references to international publications
with their relevant European publications
This European Standard incorporates by dated or undated reference, provisions from other
publications. These normative references are cited at the appropriate places in the text and the
publications are listed hereafter. For dated references, subsequent amendments to or revisions
of any of these publications apply to this European Standard only when incorporated in it by
amendment or revision. For undated references the latest edition of the publication referred to
applies (including amendments).
NOTE Where an International Publication has been modified by common modifications,
indicated by (mod.), the relevant EN/HD applies.
Publication Year Title EN Year
ISO 306 1994 Plastics - Thermoplastic materials - EN ISO 306 1996
Determination of Vicat softening
temperature (VST)
ISO 527-2 1993 Plastics - Determination of tensile EN ISO 527-2 1996
properties - Part 2: Test conditions for
moulding and extrusion plastics
(including Corr 1:1994)
ISO 2808 1997 Paints and varnishes - Determination of EN ISO 2808 1999
film thickness
ISO 4624 1978 Paints and varnishes - Pull-off test EN 24624 1992
ISO 6506-1 1999 Metallic materials - Brinell hardness test - EN ISO 6506-1 1999
Part 1: Test method
ISO 6506-2 1999 Metallic materials - Brinell hardness test - EN ISO 6506-2 1999
Part 2: Verification and calibration of
testing machines
ISO 6506-3 1999 Metallic materials - Brinell hardness test - EN ISO 6506-3 1999
Part 3: Calibration of reference blocks
ISO 14130 1997 Fibre-reinforced plastic composites - EN ISO 14130 1997
Determination of apparent interlaminar
shear strength by short-beam method

INTERNATIONAL ISO
STANDARD 11439
First edition
2000-09-15
Gas cylinders — High pressure cylinders
for the on-board storage of natural gas as a
fuel for automotive vehicles
Bouteilles à gaz — Bouteilles haute pression pour le stockage de gaz
naturel utilisé comme carburant à bord des véhicules automobiles
Reference number
ISO 11439:2000(E)
©
ISO 2000
ISO 11439:2000(E)
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ii © ISO 2000 – All rights reserved

ISO 11439:2000(E)
Contents Page
Foreword.iv
Introduction.v
1 Scope .1
2 Normative references .1
3 Terms and definitions .2
4 Service conditions.5
5 Approval and certification .7
6 Requirements for type CNG-1 metal cylinders.10
7 Requirements for type CNG-2 hoop-wrapped cylinders.17
8 Requirements for type CNG-3 fully-wrapped cylinders.27
9 Requirements for type CNG-4 all-composite cylinders .37
10 Marking .46
11 Preparation for dispatch .47
Annex A (normative) Test methods and criteria .48
Annex B (normative) Ultrasonic inspection .56
Annex C (informative) Approval and certification procedures.60
Annex D (informative) NDE defect size by flawed cylinder cycling .62
Annex E (informative) Report forms.63
Annex F (informative) Environmental test .66
Annex G (informative) Verification of stress ratios using strain gauges .71
Annex H (informative) Manufacturer’s instructions for handling, use and inspection of cylinders .72
ISO 11439:2000(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 3.
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 International Standard may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 11439 was prepared by Technical Committee ISO/TC 58, Gas cylinders, Subcommittee
SC 3, Cylinder design.
Annexes A and B form a normative part of this International Standard. Annexes C to H are for information only.
iv © ISO 2000 – All rights reserved

ISO 11439:2000(E)
Introduction
Cylinders for the on-board storage of fuel for natural gas vehicle service are required to be light-weight, at the same
time maintaining or improving on the level of safety currently existing for other pressure vessels. These
requirements are achieved by:
a) specifying service conditions precisely and comprehensively as a firm basis for both cylinder design and use;
b) using an appropriate method to assess cyclic pressure fatigue life and to establish allowable defect sizes in
metal cylinders or liners;
c) requiring design qualification tests;
d) requiring non-destructive testing and inspection of all production cylinders;
e) requiring destructive tests on cylinders and cylinder material taken from each batch of cylinders produced;
f) requiring manufacturers to have a comprehensive quality system documented and implemented;
g) requiring periodic re-inspection and, if necessary, retesting in accordance with the manufacturer’s instructions;
h) requiring manufacturers to specify as part of their design, the safe service life of their cylinders.
Cylinder designs that meet the requirements of this International Standard:
a) will have a fatigue life which exceeds the specified service life;
b) when pressure cycled to failure, will leak but not rupture;
c) when subject to hydrostatic burst tests, will have factors of “stress at burst pressure” over “stress at working
pressure” that exceed the values specified for the type of design and the materials used.
Owners or users of cylinders designed to this International Standard should note that the cylinders are designed to
operate safely if used in accordance with specified service conditions for a specified finite service life only. The
expiry date is marked on each cylinder and it is the responsibility of owners and users to ensure that cylinders are
not used after that date, and that they are inspected in accordance with the manufacturer’s instructions.
INTERNATIONAL STANDARD ISO 11439:2000(E)
Gas cylinders — High pressure cylinders for the on-board storage
of natural gas as a fuel for automotive vehicles
1 Scope
This International Standard specifies minimum requirements for serially produced light-weight refillable gas
cylinders intended only for the on-board storage of high pressure compressed natural gas as a fuel for automotive
vehicles to which the cylinders are to be fixed. The service conditions do not cover external loadings which may
arise from vehicle collisions, etc.
This International Standard covers cylinders of any steel, aluminium or non-metallic material construction, using
any design or method of manufacture suitable for the specified service conditions. This International Standard does
not cover cylinders of stainless steel or of welded construction.
Cylinders covered by this International Standard are designated as follows:
CNG-1 Metal
CNG-2 Metal liner reinforced with resin impregnated continuous filament (hoop wrapped)
CNG-3 Metal liner reinforced with resin impregnated continuous filament (fully wrapped)
CNG-4 Resin impregnated continuous filament with a non-metallic liner (all composite)
NOTE Cylinders designed in accordance with ISO 9809-1, ISO 9809-2, ISO 9809-3 and ISO 7866 can be used for this
service provided these designs meet additional requirements as specified in this International Standard.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this International Standard. For dated references, subsequent amendments to, or revisions of, any of these
publications do not apply. However, parties to agreements based on this International Standard are encouraged to
investigate the possibility of applying the most recent editions of the normative documents indicated below. For
undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC
maintain registers of currently valid International Standards.
ISO 148:1983, Steel — Charpy impact test (V-notch).
ISO 306:1994, Plastics — Thermoplastic materials — Determination of Vicat softening temperature (VST).
ISO 527-2:1993, Plastics — Determination of tensile properties — Part 2: Test conditions for moulding and
extrusion plastics (incorporating Technical Corrigendum 1:1994).
ISO 2808:1997, Paints and varnishes — Determination of film thickness.
ISO 11439:2000(E)
1)
ISO 4624:— , Paints and varnishes — Pull-off test for adhesion.
ISO 6506-1:1999, Metallic materials — Brinell hardness test — Part 1: Test method.
ISO 6892:1998, Metallic materials — Tensile testing at ambient temperature.
ISO 7225, Gas cylinders — Precautionary labels.
ISO 7866:1999, Gas cylinders — Refillable seamless aluminium alloy gas cylinders — Design, construction and
testing.
ISO 9227:1990, Corrosion tests in artificial atmospheres — Salt spray tests.
ISO 9712:1999, Non-destructive testing — Qualification and certification of personnel.
ISO 9809-1:1999, Gas cylinders — Refillable seamless steel gas cylinders — Design, construction and testing —
Part 1: Quenched and tempered steel cylinders with tensile strength less than 1 100 MPa.
ISO 9809-2:2000, Gas cylinders — Refillable seamless steel gas cylinders — Design, construction and testing —
Part 2: Quenched and tempered steel cylinders with tensile strength greater than or equal to 1 100 MPa.
2)
ISO 9809-3:— , Gas cylinders — Refillable seamless steel gas cylinders — Design, construction and testing —
Part 3: Normalized steel cylinders.
ISO 14130:1997, Fibre-reinforced plastic composites — Determination of apparent interlaminar shear strength by
short-beam method.
ASTM D522-93a, Standard Test Methods for Mandrel Bend Test of Attached Organic Coatings.
ASTM D1308-87(1998), Standard Test Method for Effect of Household Chemicals on Clear and Pigmented Organic
Finishes.
ASTM D2794-93(1999)e1, Standard Test Method for Resistance of Organic Coatings to the Effects of Rapid
Deformation (Impact).
ASTM D3170-87(1996)e1, Standard Test Method for Chipping Resistance of Coatings.
ASTM D3418-99, Standard Test Method for Transition Temperatures of Polymers by Differential Scanning
Calorimetry.
3)
ASTM G53-93 , Standard Practice for Operating Light and Water-Exposure Apparatus (Fluorescent UV-
Condensation Type) for Exposure of Nonmetallic Materials.
4)
NACE TM0177-96 , Laboratory Testing of Metals for Resistance to Sulfide Stress Cracking and Stress Corrosion
Cracking in H S Environments.
3 Terms and definitions
For the purposes of this International Standard the following terms and definitions shall apply:
1) To be published. (Revision of ISO 4624:1978)
2) To be published
3) To be discontinued in 2000 and replaced by G154.
4) NACE standards are available from NACE International, PO Box 218340, Houston, Texas 77218-8340, U.S.A.
2 © ISO 2000 – All rights reserved

ISO 11439:2000(E)
3.1
authorized inspection authority
competent inspection authority, approved or recognized by the regulatory authority of the user country, for the
supervision of construction and testing of cylinders
3.2
auto-frettage
pressure application procedure used in manufacturing composite cylinders with metal liners, which strains the liner
past its yield point sufficient to cause permanent plastic deformation
NOTE This results in the liner having compressive stresses and the fibres having tensile stresses at zero internal pressure.
3.3
auto-frettage pressure
pressure within the over-wrapped cylinder at which the required distribution of stresses between the liner and the
over-wrap is established
3.4
batch
�composite cylinders� group of not more than 200 cylinders plus cylinders for destructive testing, or if greater, one
shift of successive production of cylinders, successively produced from qualified liners having the same size,
design, specified materials of construction and process of manufacture
3.5
batch
�of metal cylinders/liners� group of not more than 200 cylinders/liners plus cylinders/liners for destructive testing, or
if greater, one shift of successive production of metal cylinders/liners, successively produced having the same
nominal diameter, wall thickness, design, specified material of construction, process of manufacture, equipment for
manufacture and heat treatment, and conditions of time, temperature and atmosphere during heat treatment
3.6
batch
�of non-metallic liners� group of not more than 200 liners plus liners for destructive testing, or if greater, one shift of
successive production of non-metallic liners, successively produced having the same nominal diameter, wall
thickness, design, specified material of construction and process of manufacture
3.7
burst pressure
highest pressure reached in a cylinder during a burst test
3.8
composite cylinder
cylinder made of resin-impregnated continuous filament wound over a metallic or non-metallic liner
NOTE Composite cylinders using non-metallic liners are referred to as all-composite cylinders.
3.9
controlled tension winding
process used in manufacturing hoop-wrapped composite cylinders with metal liners by which compressive stresses
in the liner and tensile stresses in the over-wrap at zero internal pressure are obtained by winding the reinforcing
filaments under significant high tension
3.10
filling pressure
pressure to which a cylinder is filled
ISO 11439:2000(E)
3.11
finished cylinders
completed cylinders which are ready for use, typical of normal production, complete with identification marks and
external coating including integral insulation specified by the manufacturer, but free from non-integral insulation or
protection
3.12
fully-wrapped cylinder
cylinder with an over-wrap having a filament-wound reinforcement both in the circumferential and axial direction of
the cylinder
3.13
gas temperature
temperature of gas in a cylinder
3.14
hoop-wrapped cylinder
cylinder with an over-wrap having a filament-wound reinforcement in a substantially circumferential pattern over the
cylindrical portion of the liner so that the filament does not carry any significant load in a direction parallel to the
cylinder longitudinal axis
3.15
liner
container that is used as a gas-tight, inner shell, on which reinforcing fibres are filament-wound to reach the
necessary strength
NOTE Two types of liner are described in this International Standard – metallic liners that are designed to share the load
with the reinforcement, and non-metallic liners that do not carry any part of the load.
3.16
manufacturer
person or organization responsible for the design, fabrication and testing of the cylinders
3.18
over-wrap
reinforcement system of filament and resin applied over the liner
3.19
prestress
process of applying auto-frettage or controlled tension winding
3.20
service life
life, in years, during which the cylinders may safely be used in accordance with the standard service conditions
3.21
settled pressure
gas pressure when a given settled temperature is reached
3.22
settled temperature
uniform gas temperature after the dissipation of any change in temperature caused by filling
3.23
test pressure
required pressure applied during a pressure test
3.24
working pressure
settled pressure of 200 bar at a uniform temperature of 15 °C
4 © ISO 2000 – All rights reserved

ISO 11439:2000(E)
4 Service conditions
4.1 General
4.1.1 Standard service conditions
The standard service conditions specified in this clause are provided as the basis for the design, manufacture,
inspection, testing and approval of cylinders that are to be mounted permanently on vehicles and used to store
natural gas at ambient temperatures for use as a fuel on the vehicles.
4.1.2 Use of cylinders
The service conditions specified are also intended to provide information on how cylinders manufactured in
accordance with this International Standard may safely be used; this information is intended for
a) manufacturers of cylinders;
b) owners of cylinders;
c) designers or contractors responsible for the installation of cylinders;
d) designers or owners of equipment used to refuel vehicle cylinders;
e) suppliers of natural gas;
f) regulatory authorities who have jurisdiction over cylinder use.
4.1.3 Service life
The service life for which cylinders are safe shall be specified by the cylinder manufacturer on the basis of use
under service conditions specified herein. The maximum service life shall be 20 years.
For metal and metal-lined cylinders, the service life shall be based upon the rate of fatigue crack growth. The
ultrasonic inspection, or equivalent, of each cylinder or liner shall ensure the absence of flaws which exceed the
maximum allowable size. This approach permits the optimized design and manufacture of light weight cylinders for
natural gas vehicle service.
For all-composite cylinders with non-metallic non-load bearing liners the service life shall be demonstrated by
appropriate design methods, design qualification testing and manufacturing controls.
4.2 Maximum pressures
This International Standard is based upon a working pressure of 200 bar settled at 15 °C for natural gas as a fuel
with a maximum filling pressure of 260 bar. Other working pressures may be accommodated by adjusting the
pressure by the appropriate factor (ratio); e.g., a 250 bar working pressure system will require pressures to be
multiplied by 1,25.
Except where pressures have been adjusted in this way, the cylinder shall be designed to be suitable for the
following pressure limits:
a) a pressure that would settle to 200 bar at a settled temperature of 15 °C;
b) the maximum shall not exceed 260 bar, regardless of filling conditions or temperature.
ISO 11439:2000(E)
4.3 Design number of filling cycles
Cylinders shall be designed to be filled up to a settled pressure of 200 bar at a settled gas temperature of 15 °Cfor
up to 1 000 times per year of service.
4.4 Temperature range
4.4.1 Gas temperature
Cylinders shall be designed to be suitable for the following gas temperature limits:
a) the settled temperature of gas in cylinders, which may vary from a low of � 40 °C to a high of � 65 °C.
b) the developed gas temperatures during filling and discharge, which may vary beyond these limits.
4.4.2 Cylinder temperatures
Cylinders shall be designed to be suitable for the following material temperature limits:
a) the temperature of the cylinder materials may vary from – 40 °Cto� 82 °C.
b) temperatures over � 65 °C shall be sufficiently local, or of short enough duration, that the temperature of gas in
the cylinder never exceeds � 65 °C, except under the conditions of 4.4.1 b).
4.5 Gas composition
4.5.1 General
Cylinders shall be designed to tolerate being filled with natural gas meeting the specification either of dry gas or wet
gas as follows. Methanol and/or glycol shall not be deliberately added to the natural gas.
4.5.2 Dry gas
Water vapour shall be limited to less than 32 mg/m (i.e. a pressure dewpoint of � 9 °C at 200 bar).
Constituent maximum limits shall be:
Hydrogen sulfide and other soluble sulfides
23 mg/m
Oxygen 1 % (volume fraction)
Hydrogen, when cylinders are manufactured from 2 % (volume fraction)
a steel with an ultimate tensile strength exceeding
950 MPa
4.5.3 Wet gas
This is gas that has a higher water content than that of dry gas.
Constituent maximum limits shall be:
Hydrogen sulfide and other soluble sulfides
23 mg/m
Oxygen 1 % (volume fraction)
6 © ISO 2000 – All rights reserved

ISO 11439:2000(E)
Carbon dioxide 4 % (volume fraction)
Hydrogen 0,1 % (volume fraction)
4.6 External surfaces
It is not necessary for cylinders to be designed for continuous exposure to mechanical or chemical attack, e.g.
leakage from cargo that may be carried on vehicles or severe abrasion damage from road conditions. However,
cylinder external surfaces shall be designed to withstand inadvertent exposure to the following, consistent with
installation being carried out in accordance with the instructions to be provided with the cylinder:
a) water, either by intermittent immersion or road spray;
b) salt, due to the operation of the vehicle near the ocean or where ice-melting salt is used;
c) ultra-violet radiation from sunlight;
d) impact of gravel;
e) solvents, acids and alkalis, fertilizers;
f) automotive fluids, including petrol, hydraulic fluids, battery acid, glycol and oils;
g) exhaust gases.
5 Approval and certification
5.1 Inspection and testing
Evaluation of conformity is required to be performed in accordance with the relevant regulations of the country(ies)
where the cylinders are used.
In order to ensure that the cylinders are in compliance with this International Standard they shall be subject to
design approval in accordance with 5.2, and inspection and testing in accordance with either clause 6, 7, 8 or 9 as
appropriate to the construction. This shall be carried out by an authorized inspection authority (hereafter referred to
as “the Inspector”) recognized in the countries of use. The Inspector shall be competent for inspection of cylinders.
Test procedures are detailed in annex A and annex B. An example of acceptable approval and certification
procedures is included in annex C.
5.2 Type approval procedure
5.2.1 General
Type approval consists of 2 parts:
a) design approval, comprising submission of information by the manufacturer to the Inspector, as detailed in
5.2.2.
b) prototype testing, comprising testing carried out under the supervision of the Inspector. The cylinder material,
design, manufacture and examination shall be proved to be adequate for their intended service by meeting the
requirements of the prototype tests specified in 6.5, 7.5, 8.5 or 9.5, as appropriate for the particular cylinder
design.
The test data shall also document the dimensions, wall thicknesses and weights of each of the test cylinders.
ISO 11439:2000(E)
5.2.2 Design approval
Cylinder designs shall be approved by the Inspector. The following information shall be submitted by the
manufacturer with a request to the Inspector for approval:
a) statement of service, in accordance with 5.2.3;
b) design data, in accordance with 5.2.4;
c) manufacturing data, in accordance with 5.2.5;
d) quality system, in accordance with 5.2.6;
e) fracture performance and NDE defect size, in accordance with 5.2.7;
f) specification sheet, in accordance with 5.2.8;
g) additional supporting data, in accordance with 5.2.9.
5.2.3 Statement of service
The purpose of this statement of service is to guide users and installers of cylinders as well as to inform the
Inspector. The statement of service shall include:
a) a statement that the cylinder design is suitable for use in the service conditions defined in clause 4 for the
service life of the cylinder;
b) a statement of the service life;
c) a specification for the minimum in-service test and/or inspection requirements;
d) a specification for the pressure relief devices, and insulation if provided;
e) a specification for the support methods, protective coatings and any other items required but not provided;
f) a description of the cylinder design;
g) any other information and instructions necessary to ensure the safe use and inspection of the cylinder.
5.2.4 Design data
5.2.4.1 Drawings
Drawings shall show at least the following:
a) title, reference number, date of issue, and revision numbers with dates of issue if applicable;
b) reference to this International Standard and the cylinder type;
c) all dimensions complete with tolerances, including details of end closure shapes with minimum thicknesses
and of openings;
d) mass, complete with tolerance, of cylinders;
e) material specifications, complete with minimum mechanical and chemical properties or tolerance ranges and,
for metal cylinders or metal liners, the specified hardness range;
8 © ISO 2000 – All rights reserved

ISO 11439:2000(E)
f) other data such as, autofrettage pressure range, minimum test pressure, details of the fire protection system
and of any exterior protective coating.
5.2.4.2 Stress analysis report
A finite element stress analysis or other stress analysis shall be carried out.
A table summarizing the calculated stresses shall be provided.
5.2.4.3 Material property data
A detailed description of the materials and tolerances of the material properties used in the design shall be
provided. Test data shall also be presented characterizing the mechanical properties and the suitability of the
materials for service under the conditions specified in clause 4.
5.2.4.4 Fire protection
The arrangement of pressure relief devices, and insulation if provided, that will protect the cylinder from sudden
rupture when exposed to the fire conditions in A.15 shall be specified. Test data shall substantiate the effectiveness
of the specified fire protection system.
5.2.5 Manufacturing data
Details of all fabrication processes, non-destructive examinations, production tests and batch tests shall be
provided.
The tolerances for all production processes such as heat treatment, end forming, resin-mix ratio, filament tension
and speed for controlled tension winding, curing times and temperatures, and auto-frettage procedures shall be
specified.
Surface finish, thread details, acceptance criteria for ultrasonic scanning (or equivalent), and maximum lot sizes for
batch tests shall also be specified.
5.2.6 Quality control programmme
The manufacturer shall specify methods and procedures in accordance with a quality assurance system acceptable
to the Inspector and that will comply with any relevant regulations of the country(ies) where the cylinders are to be
used.
5.2.7 Fracture performance and non-destructive examination (NDE) defect size
The manufacturer shall specify the maximum defect size for non-destructive examination which will ensure leak
before break (LBB) fracture performance and will prevent failure of the cylinder during its service life due to fatigue,
or failure of the cylinder by rupture.
The maximum defect size shall be established by a method suitable to the design, an example of a suitable method
is given in annex D.
5.2.8 Specification sheet
A summary of the documents providing the information required in 5.2.2 shall be listed on a specification sheet for
each cylinder design. The title, reference number, revision numbers and dates of original issue and version issues
of each document shall be given. All documents shall be signed or initialled by the issuer.
ISO 11439:2000(E)
5.2.9 Additional supporting data
Additional data which would support the application, such as the service history of material proposed for use, or the
use of a particular cylinder design in other service conditions, shall be provided where applicable.
5.3 Type approval certificate
If the results of the design approval according to 5.2 and the prototype testing according to 6.5, 7.5, 8.5 or 9.5, as
appropriate to the particular cylinder design, are satisfactory, the Inspector shall issue a test type approval
certificate. An example of a type approval certificate is given in the annex E.
6 Requirements for type CNG-1 metal cylinders
6.1 General
This International Standard does not provide design formulae nor list permissible stresses or strains, but requires
the adequacy of the design to be established by appropriate calculations and demonstrated by testing to show that
cylinders are capable of consistently passing the materials, design qualification, production and batch tests
specified in this International Standard.
The design shall ensure a “leakage-before-break” failure mode under feasible degradation of pressure parts during
normal service. If leakage of the metal cylinder occurs, it shall be only by the growth of a fatigue crack.
6.2 Materials
6.2.1 General requirements
Materials used shall be suitable for the service conditions specified in clause 4. The design shall not have
incompatible materials in contact.
6.2.2 Controls on chemical composition
6.2.2.1 Steel
Steels shall be aluminium- and/or silicon-killed and produced to predominantly fine grain practice.
The chemical composition of all steels shall be declared and defined at least by:
a) the carbon, manganese, aluminium and silicon contents in all cases;
b) the chromium, nickel, molybdenum, boron and vanadium contents, and that of any other alloying elements
intentionally added.
The sulfur and phosphorus content in the cast analysis shall not exceed the values shown in Table 1.
Table 1 — Maximum sulfur and phosphorus limits
Tensile strength
< 950 MPa W 950 MPa
sulfur 0,020 % 0,010 %
phosphorus
0,020 % 0,020 %
Level of
sulfur +
0,030 % 0,025 %
phosphorus
10 © ISO 2000 – All rights reserved

ISO 11439:2000(E)
6.2.2.2 Aluminium
Aluminium alloys may be used to produce cylinders provided that they meet all requirements of this International
Standard and have maximum lead and bismuth contents not exceeding 0,003 %.
5)
NOTE A list of registered alloys is maintained by the Aluminum Association Inc entitled Registration Record of
International Alloy Designations and Chemical Composition Limits for Wrought Aluminum and Wrought Aluminum Alloys.
6.3 Design Requirements
6.3.1 Test pressure
The minimum test pressure used in manufacture shall be 300 bar (1,5 times working pressure).
6.3.2 Burst pressure
The minimum actual burst pressure shall be not less than 450 bar.
6.3.3 Stress analysis
The stresses in the cylinder shall be calculated for 200 bar, test pressure and design burst pressure. The
calculations shall use suitable analysis to establish stress distributions to justify the minimum design wall
thicknesses.
6.3.4 Maximum defect size
The maximum defect size at any location in the metal cylinder such that the cylinder shall meet pressure cycling
and LBB requirements shall be specified.
The allowable defect size for NDE shall be determined by an appropriate method, e.g. as described in annex D.
6.3.5 Openings
Openings are permitted in heads only. The centre line of openings shall coincide with the longitudinal axis of the
cylinder.
6.3.6 Fire protection
The cylinder design shall be protected with pressure relief devices. The cylinder, its materials, pressure relief
devices (PRD) and any added insulation or protective material shall be designed collectively to ensure adequate
safety during fire conditions in the test specified in A.15. A manufacturer may specify alternative PRD locations for
specific vehicle installations ini order to optimize safety considerations.
Pressure relief devices shall be approved to a standard acceptable to the Inspector in the country of use.
6.3.7 Attachments
When a neck ring, foot ring or an attachment for support is provided, it shall be of material compatible with that of
the cylinder and shall be securely attached by a method other than welding, brazing or soldering.
th
5) Aluminum Association Inc., 900 19 Street N.W., Washington D.C., 20006-2168, U.S.A.
ISO 11439:2000(E)
6.4 Construction and workmanship
6.4.1 End closure
Each cylinder shall be examined for thickness and surface finish before end forming operations are carried out.
The base ends of aluminium cylinders shall not be sealed by a forming process.
The base ends of steel cylinders which have been closed by forming shall be NDE inspected or equivalent.
Metal shall not be added in the process of closure at the ends.
6.4.2 Heat treatment
After end forming the cylinders shall be heat treated to the hardness range specified for the design. Localized heat
treatment is not permitted.
6.4.3 Neck threads
Threads shall be clean cut, even, without surface discontinuities, to gauge and comply with International Standards
acceptable to the Inspector.
6.4.4 Exterior environmental protection
The exterior of cylinders shall meet the requirements of the acid environment test of A.14. Exterior protection may
be provided by using any of the following:
a) a surface finish giving adequate protection (e.g. metal sprayed on to aluminium, anodizing); or
b) a protective coating (e.g. organic coating, paint); if exterior coating is part of the design, the requirements of
A.9 shall be met.
c) a covering impervious to the chemicals listed in A.14.
Any coatings applied to cylinders shall be such that the application process does not adversely affect the
mechanical properties of the cylinder. The coating shall be designed to facilitate subsequent in-service inspection
and the manufacturer shall provide guidance on coating treatment during such inspection in order to ensure the
continued integrity of the cylinder.
Manufacturers are advised that an environmental performance test that evaluates the suitability of coating systems
is provided in annex F.
6.5 Prototype testing procedure
6.5.1 General requirements
Prototype testing shall be conducted on each new design, on finished cylinders which are representative of normal
production and complete with identification marks. The test cylinders shall be selected and the prototype tests
detailed in 6.5.2 witnessed by the Inspector. If more cylinders are subjected to the tests than are required by this
International Standard, all results shall be documented.
6.5.2 Prototype tests
6.5.2.1 Tests required
In the course of the type approval, the Inspector shall select the necessary cylinders for testing and witness the
following tests:
12 © ISO 2000 – All rights reserved

ISO 11439:2000(E)
� the tests specified in 6.5.2.2 or 6.5.2.3 (material tests) on 1 cylinder;
� the test specified in 6.5.2.4 (hydrostatic pressure burst test) on 3 cylinders;
� the test specified in 6.5.2.5 (ambient temperature pressure cycling test) on 2 cylinders;
� the test specified in 6.5.2.6 (LBB test) on 3 cylinders;
� the test specified in 6.5.2.7 (bonfire test) on 1 or 2 cylinders as appropriate;
� the test specified in 6.5.2.8 (penetration test) on 1 cylinder.
6.5.2.2 Material tests for steel cylinders
Material tests shall be carried out on steel cylinders as follows:
a) Tensile test
The material properties of the steel in the finished cylinder shall be determined in accordance with A.1 and shall
meet the requirements listed therein.
b) Impact test
The impact properties of the steel in the finished cylinder shall be determined in accordance with A.2 and shall
meet the requirement listed therein.
c) Sulfide stress cracking resistance test
If the upper limit of the specified tensile strength for the steel exceeds 950 MPa, the steel from a finished cylinder
shall be subjected to a sulfide stress cracking resistance test in accordance with A.3 and meet the requirements
listed therein.
6.5.2.3 Material tests for aluminium alloy cylinders
Material tests shall be carried out on aluminium alloy cylinders as follows:
a) Tensile test
The material properties of the aluminium alloy in the finished cylinder shall be determined in accordance with A.1
and shall meet
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