ISO 11119-3:2020

Gas cylinders - Design, construction and testing of refillable composite gas cylinders and tubes - Part 3: Fully wrapped fibre reinforced composite gas cylinders and tubes up to 450 l with non-load-sharing metallic or non-metallic liners or without liners

This document specifies minimum requirements for the material, design, construction and workmanship, manufacturing processes, examination and testing at time of manufacture for: - type 4 composite fully wrapped cylinders or tubes with a non-load sharing liner and composite reinforcement on both the cylindrical portion and the dome ends; - type 5 fully wrapped cylinders or tubes without liners and with a test pressure of less than 60 bar and composite reinforcement on both the cylindrical portion and the dome ends; - water capacities up to 450 l; - for the storage and conveyance of compressed or liquefied gases; - cylinders and tubes with composite reinforcement of carbon fibre, aramid fibre or glass fibre (or a mixture thereof) within a matrix; - a minimum design life of 15 years. Cylinders and tubes manufactured and tested according to this document are not intended to contain toxic, oxidizing or corrosive gases. This document does not address the design, fitting and performance of removable protective sleeves. NOTE 1 References to cylinders in this document include composite tubes if appropriate. NOTE 2 ISO 11439 applies to cylinders intended for use as fuel containers on natural gas vehicles and ISO 11623 covers periodic inspection and re-testing of composite cylinders.

Bouteilles à gaz — Conception, construction et essais des tubes et bouteilles à gaz rechargeables en matériau composite — Partie 3: Tubes et bouteilles à gaz entièrement bobinés en matériau composite renforcés de fibres d'une contenance allant jusqu'à 450 l avec liners non métalliques ou métalliques non structuraux, ou sans liners

General Information

• Status: Published
• Publication Date: 22-Nov-2020
• ICS: 23.020.35 - Gas cylinders
• Technical Committee: ISO/TC 58/SC 3 - Cylinder design
• Drafting Committee: ISO/TC 58/SC 3/WG 27 - Composite cylinders
• Current Stage: 9092 - International Standard to be revised
• Start Date: 10-Jun-2025
• Completion Date: 13-Dec-2025

Relations

• Consolidated By: ISO/IEC 27006-1:2024 - Information security, cybersecurity and privacy protection - Requirements for bodies providing audit and certification of information security management systems - Part 1: General
• Effective Date: 06-Jun-2022
• Amended By: ISO 11119-3:2020/Amd 1:2023 - Gas cylinders - Design, construction and testing of refillable composite gas cylinders and tubes - Part 3: Fully wrapped fibre reinforced composite gas cylinders and tubes up to 450 l with non-load-sharing metallic or non-metallic liners or without liners - Amendment 1
• Effective Date: 30-Jul-2022
• Revises: ISO 11119-3:2013 - Gas cylinders - Refillable composite gas cylinders and tubes - Design, construction and testing - Part 3: Fully wrapped fibre reinforced composite gas cylinders and tubes up to 450L with non-load-sharing metallic or non-metallic liners
• Effective Date: 12-May-2018

Overview

ISO 11119-3:2020 - "Gas cylinders - Design, construction and testing of refillable composite gas cylinders and tubes - Part 3" defines minimum requirements for fully wrapped fibre‑reinforced composite gas cylinders and tubes (type 4 and type 5) with either non‑load‑sharing metallic/non‑metallic liners or without liners. It covers cylinders and tubes up to 450 L water capacity, intended for the storage and conveyance of compressed or liquefied gases, and specifies a minimum design life of 15 years. Cylinders manufactured to this standard are not intended for toxic, oxidizing or corrosive gases.

Key topics and technical requirements

• Scope and applicability
  • Type 4: fully wrapped composite cylinders with a non‑load‑sharing liner.
  • Type 5: fully wrapped cylinders without liners (test pressure < 60 bar).
  • Fibre reinforcement: carbon fibre, aramid fibre, glass fibre, or mixtures within a matrix.
• Materials and construction
  • Requirements for liner materials (where used) and composite overwrap materials.
  • Matrix and fibre selection, workmanship and manufacturing process controls.
• Design submission and approval
  • Documentation and prototype testing requirements for type approval and new designs.
• Inspection, testing and batch control
  • Prototype and batch tests include: proof pressure, hydraulic elastic expansion, burst tests, ambient and environmental cycling, vacuum, flaw testing, drop/impact, high‑velocity impact (gunfire), fire resistance, permeability, leak tests, pneumatic cycle, liner burst, resin shear strength and glass transition temperature.
  • Marking, traceability and documentation requirements for manufacture and batch inspection.
• Limitations
  • Not covering removable protective sleeves, nor intended for corrosive/oxidizing/toxic gases.

Practical applications and users

• Manufacturers and design engineers of composite gas cylinders and pressure vessels use ISO 11119-3 for product design, material selection and production quality control.
• Test laboratories and certification bodies apply the standard for type approval, prototype testing and batch inspection.
• Transport and storage operators, industrial gas suppliers, and energy/utility companies rely on the standard to ensure safe cylinder use for compressed and liquefied gases.
• Regulators and procurement teams reference the standard for compliance with UN Model Regulations on the transport of dangerous goods and for harmonized international requirements.

Related standards

• ISO 11119 series (other parts covering design/testing variations)
• ISO 11439 - cylinders for natural gas vehicle fuel containers
• ISO 11623 - periodic inspection and re‑testing of composite cylinders
• References to ISO test methods for materials (e.g., tensile, hardness standards)

Keywords: ISO 11119-3:2020, composite gas cylinders, fully wrapped cylinders, type 4, type 5, carbon fibre, aramid fibre, glass fibre, cylinder testing, gas storage, compressed gases, liquefied gases.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 11119-3
Third edition
2020-11
Gas cylinders — Design, construction
and testing of refillable composite gas
cylinders and tubes —
Part 3:
Fully wrapped fibre reinforced
composite gas cylinders and tubes
up to 450 l with non-load-sharing
metallic or non-metallic liners or
without liners
Bouteilles à gaz — Conception, construction et essais des tubes et
bouteilles à gaz rechargeables en matériau composite —
Partie 3: Tubes et bouteilles à gaz entièrement bobinés en matériau
composite renforcés de fibres d'une contenance allant jusqu'à 450 l avec
liners non métalliques ou métalliques non structuraux, ou sans liners
Reference number
©
ISO 2020
© ISO 2020
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: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved

Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols . 4
5 Inspection and testing . 4
6 Materials . 4
6.1 Liner materials . 4
6.2 Composite materials . 5
7 Design and manufacture . 5
7.1 General . 5
7.2 Design submission . 6
7.3 Manufacturing . 8
8 Type approval procedure . 8
8.1 General requirements . 8
8.2 Prototype tests . 8
8.3 New design . 9
8.4 Design variants .10
8.5 Type approval test procedures and criteria .14
8.5.1 Proof pressure test .14
8.5.2 Hydraulic elastic expansion test .14
8.5.3 Cylinder burst test .15
8.5.4 Ambient cycle test .15
8.5.5 Vacuum test .17
8.5.6 Environmental cycle test.18
8.5.7 Environmentally assisted stress rupture test .19
8.5.8 Flaw test .19
8.5.9 Drop/impact test .21
8.5.10 High velocity impact (gunfire) test .24
8.5.11 Fire resistance test .25
8.5.12 Permeability test .27
8.5.13 Torque test on cylinder neck boss .28
8.5.14 Salt water immersion test .28
8.5.15 Leak test .29
8.5.16 Pneumatic cycle test .29
8.5.17 Liner burst test .30
8.5.18 Resin shear strength .31
8.5.19 Glass transition temperature .31
8.6 Failure of type approval tests .31
9 Batch inspection and testing .31
9.1 Liner .31
9.2 Failure of liner batch tests .32
9.3 Overwrap materials .32
9.4 Composite cylinder.32
9.5 Cylinder failure during type approval or batch testing .34
10 Cylinder marking .34
10.1 General .34
10.2 Additional marking .34
Annex A (informative) Examples of design approval certificate .36
Annex B (informative) Specimen test reports .37
Annex C (informative) Test report for equivalency .40
Annex D (informative) Standardized test requirements for thermally activated pressure
relief devices .42
Bibliography .47
iv © ISO 2020 – All rights reserved

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see
www .iso .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 58, Gas cylinders, Subcommittee SC 3,
Cylinder design.
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.
This third edition cancels and replaces the second edition (ISO 11119-3:2013), which has been
technically revised. The main changes compared to the previous edition are as follows:
— References updated.
— 7.1.4 Minimum fibre stress ratios added.
— 8.5.9 Drop/impact test. Addition of new alternative test for cylinders up to and including 50 l water
capacity with dedicated compressed gas service. Addition of alternative impact test for tubes 150 l
and above.
— 8.5.11 Fire resistance test. Changes to the procedure to make the test more consistent. Adding a
criteria for tubes above 150 l to be tested for 5 min.
— 8.5.12 Torque test is now only required for taper threads.
— References updated
— 8.5.16 Pneumatic cycle test. New procedure for the test to have a lower number of cycles but, with a
significant hold time at pressure.
A list of all parts in the ISO 11119 series can be found on the ISO website.
Introduction
The purpose of this document is to provide a specification for the design, manufacture, inspection and
testing of cylinders for world-wide usage. The objective is to balance design and economic efficiency
against international acceptance and universal utility.
This document aims to eliminate the concern about climate, duplicate inspection and restrictions
currently existing because of lack of definitive International Standards and is not to be construed as
reflecting on the suitability of the practice of any nation or region.
[1]
This document has been written so that it is suitable to be referenced in the UN Model Regulations .
This document addresses the general requirements on design, construction and initial inspection and
testing of pressure receptacles of the Recommendations on the transport of dangerous goods: Model
[2]
regulations developed by the United Nations .
vi © ISO 2020 – All rights reserved

INTERNATIONAL STANDARD ISO 11119-3:2020(E)
Gas cylinders — Design, construction and testing of
refillable composite gas cylinders and tubes —
Part 3:
Fully wrapped fibre reinforced composite gas cylinders
and tubes up to 450 l with non-load-sharing metallic or
non-metallic liners or without liners
1 Scope
This document specifies minimum requirements for the material, design, construction and
workmanship, manufacturing processes, examination and testing at time of manufacture for:
— type 4 composite fully wrapped cylinders or tubes with a non-load sharing liner and composite
reinforcement on both the cylindrical portion and the dome ends;
— type 5 fully wrapped cylinders or tubes without liners and with a test pressure of less than 60 bar
and composite reinforcement on both the cylindrical portion and the dome ends;
— water capacities up to 450 l;
— for the storage and conveyance of compressed or liquefied gases;
— cylinders and tubes with composite reinforcement of carbon fibre, aramid fibre or glass fibre (or a
mixture thereof) within a matrix;
— a minimum design life of 15 years.
Cylinders and tubes manufactured and tested according to this document are not intended to contain
toxic, oxidizing or corrosive gases.
This document does not address the design, fitting and performance of removable protective sleeves.
NOTE 1 References to cylinders in this document include composite tubes if appropriate.
NOTE 2 ISO 11439 applies to cylinders intended for use as fuel containers on natural gas vehicles and
ISO 11623 covers periodic inspection and re-testing of composite cylinders.
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 527-1, Plastics — Determination of tensile properties — Part 1: General principles
ISO 527-2, Plastics — Determination of tensile properties — Part 2: Test conditions for moulding and
extrusion plastics
ISO 3341, Textile glass — Yarns — Determination of breaking force and breaking elongation
ISO 6506-1, Metallic materials — Brinell hardness test — Part 1: Test method
ISO 6508-1, Metallic materials — Rockwell hardness test — Part 1: Test method
ISO 6892-1, Metallic materials — Tensile testing — Part 1: Method of test at room temperature
ISO 7225, Gas cylinders — Precautionary labels
ISO 7866, Gas cylinders — Refillable seamless aluminium alloy gas cylinders — Design, construction
and testing
ISO 9809-1, 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 9809-2, Gas cylinders — Design, construction and testing of refillable seamless steel gas cylinders and
tubes — Part 2: Quenched and tempered steel cylinders and tubes with tensile strength greater than or
equal to 1 100 MPa
ISO 9809-3, Gas cylinders — Design, construction and testing of refillable seamless steel gas cylinders and
tubes — Part 3: Normalized steel cylinders and tubes
ISO 10618, Carbon fibre — Determination of tensile properties of resin-impregnated yarn
ISO 10286, Gas cylinders — Terminology
ISO 14130, Fibre-reinforced plastic composites — Determination of apparent interlaminar shear strength
by short-beam method
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 11114-4, Transportable gas cylinders — Compatibility of cylinder and valve materials with gas
contents — Part 4: Test methods for selecting steels resistant to hydrogen embrittlement
ISO 13769, Gas cylinders — Stamp marking
ASTM D7269, Standard Test Methods for Tensile Testing of Aramid Yarns
EN 12165, Copper and copper alloys. Wrought and unwrought forging stock
ASTM E1356–08, Standard Test Method for Assignment of the Glass Transition Temperatures by Differential
Scanning Calorimetry
3 Terms and definitions
For the purposes of this document, the terms and definitions 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 http:// www .electropedia .org/
3.1
aramid fibre
continuous filaments of aramid laid up in tow form
3.2
batch
set of homogeneous items or material
Note 1 to entry: The number of items in a batch can vary according to the context in which the term is used.
2 © ISO 2020 – All rights reserved

3.3
batch of metallic liners
quantity of liners of the same nominal diameter, length, thickness and design, made successively from
the same batch of materials, subjected to the same manufacturing process and heat treated to the same
conditions of temperature and time
3.4
batch of non-metallic liners
quantity of liners of the same nominal diameter, length, thickness and design, made successively from
the same batch of materials and subjected to the same manufacturing process
3.5
batch of finished cylinders
production quantity of up to 200 finished cylinders successively produced by the same manufacturing
process, plus finished cylinders required for destructive testing, of the same nominal diameter, length,
thickness and design
3.6
burst pressure
highest pressure reached in a liner or cylinder during a burst test
3.7
carbon fibre
continuous filaments of carbon laid up in tow form
3.8
composite overwrap
combination of fibres and matrix
3.9
dedicated gas service
service in which a cylinder is to be used only with a specified gas or gases
3.10
equivalent fibre
fibre from the same material family and similar properties to a fibre in an approved cylinder design
3.11
equivalent liner
liner that are manufactured from the same nominal raw materials, using the same process of
manufacture and having the same physical structure and the same nominal physical properties as in an
approved cylinder design
3.12
equivalent matrix
resin matrix from the same chemical family and similar properties to the resin matrix used in a
previously prototype tested cylinder
3.14
glass fibre
continuous filaments of glass laid up in tow form
3.15
liner
inner portion of the composite cylinder, comprising a metallic or non-metallic vessel, whose purpose is
both to contain the gas and transmit the gas pressure to the fibres
3.16
matrix
material used to bind and hold the fibres in place
3.17
non-load-sharing liner
liner that has a burst pressure less than 5 % of the nominal burst pressure of the finished composite
cylinder
3.18
thermoplastic
plastics capable of being repeatedly softened by increase of temperature and hardened by decrease of
temperature
3.19
thermosetting
plastics that, when cured by the application of heat or chemical means, harden permanently into a
substantially infusible and insoluble product
3.20
nominal outside diameter
diameter of the cylinder specified by the manufacturer for the type approval including tolerances
(e.g. ±1 %)
3.21
working pressure
p
w
settled pressure of a compressed gas at a reference temperature of 15 °C in a full gas cylinder
3.22
glass transition temperature
Tg
the temperature where a polymer substrate changes from a rigid glassy material to a soft (not melted)
material, and is usually measured in terms of the stiffness, or modulus
4 Symbols
p burst pressure of liner bar
bl
p burst pressure of finished cylinder bar
b
p test pressure bar
h
p maximum developed pressure at 65 °C bar
max
5 Inspection and testing
To ensure that the cylinders conform to this document, they shall be subject to inspection and testing
in accordance with Clauses 6, 7, 8 and 9 by an inspection body (hereafter referred to as “the inspector”)
authorized to do so. Example forms of certificates that can be used are shown in Annexes A and B.
Equipment used for measurement, testing and examination during production shall be maintained and
calibrated within a documented quality management system.
6 Materials
6.1 Liner materials
6.1.1 The liner (including boss assembly) shall be manufactured from materials suitable for the gas
to be contained as specified in ISO 11114-1 and ISO 11114-2 where applicable. For compatibility with
4 © ISO 2020 – All rights reserved

hydrogen see ISO 11114-4. Materials used to manufacture the components of boss assemblies attached
to non-metallic liners shall fulfil the material performance requirements of this document.
6.1.2 The metallic liner or metallic boss component materials shall conform to the following material
performance tests in the appropriate standard:
a) seamless steel liners or bosses: the material tests in ISO 9809-1, ISO 9809-2 or ISO 9809-3;
b) seamless stainless steel liners or bosses: the material tests in ISO 9809-4;
c) seamless aluminium alloy liners or boss components: Sustained load cracking test and stress
corrosion cracking test (if size permits sample extraction) in line with ISO 7866;
d) brass boss components: material composition as defined in EN 12165.
Testing carried out on material sample coupons is acceptable for metallic boss components; where
coupons are to be used, the coupons shall be produced from a representative sample of raw material.
(i.e. if a component is manufactured from bar stock, the coupon shall be manufactured from bar stock).
6.1.3 The materials used shall be of uniform and consistent quality. The composite cylinder
manufacturer shall verify that each new batch of materials has the correct properties and is of satisfactory
quality, and maintain records from which the batch of materials used for the manufacture of each cylinder
can be identified.
6.1.4 When a neck ring is provided, it shall be of a material compatible with that of the cylinder, and
shall be securely attached by a method appropriate to the liner material.
6.2 Composite materials
6.2.1 The overwrap materials shall be carbon fibre or aramid fibre or glass fibre, or any mixture
thereof.
6.2.2 The matrix shall be a polymer suited to the application, local environmental conditions and to
the intended life of the product.
6.2.3 The suppliers of the filament material and the matrix component materials shall provide
sufficient documentation for the composite cylinder manufacturer to be able to identify fully the batch of
materials used in the manufacture of each cylinder.
6.2.4 The materials used shall be of uniform and consistent quality. The composite cylinder
manufacturer shall verify that each new batch of materials has the correct properties and is of satisfactory
quality, and maintain records from which the batch of materials used for the manufacture of each cylinder
can be identified. A certificate of conformance from the material manufacturer is considered acceptable
for the purposes of verification.
6.2.5 Batches of materials shall be identified and documented to the satisfaction of the inspector.
7 Design and manufacture
7.1 General
7.1.1 A type 4 fully-wrapped composite gas cylinder with non-load-sharing metallic or non-metallic
liner shall comprise:
a) an internal metal or non-metallic liner which carries no significant load;
b) metallic boss(es) for thread connections, where these are part of the design;
c) a composite overwrap formed by layers of continuous fibres in a matrix; and
d) an optional external protection system.
Where necessary, care shall be taken to ensure that there is no adverse reaction between the liner and
the reinforcing fibre by the application of a suitable protective coating to the liner prior to the wrapping
process.
7.1.2 A type 5 fully-wrapped cylinder without liner with a test pressure of less than 60 bar shall
comprise:
a) metallic boss(es) for thread connections, where these are part of the design;
b) a composite overwrap formed by layers of continuous fibres in a matrix and
c) an optional external protection system.
Type 5 cylinders and tubes made from two or more parts joined together are not permitted under this
document.
7.1.3 Cylinders shall be designed with one or two openings along the central axis only. Threads shall
extend completely through the neck or have sufficient threads to allow full engagement of the valve.
7.1.4 The cylinders shall be designed for high reliability under sustained load and cyclic loading.
Therefore, it is necessary to take account of the properties of the individual composite fibres and to
establish their respective minimum fibre stress ratios.
The fibre stress ratio is defined as the fibre stress at design minimum burst pressure divided by the
fibre stress at 2/3 test pressure.
The minimum fibre stress ratios shall be as follows:
— for glass: 3,6;
— for aramid: 3,1;
— for carbon: 2,4;
The fibre stress ratio for type 4 and type 5 cylinders can be confirmed by burst testing. The strength
of the individual types of fibres used in hybrid construction may be verified by testing of containers
reinforced with a single type of fibre. In a hybrid construction, the applicable stress ratio requirements
shall be met in one of the two following ways:
a) if load sharing between the various fibre reinforcing materials is considered a fundamental part of
the design, each fibre shall meet the stated stress ratio requirements;
b) if load sharing between fibres is not considered as a fundamental part of the design, then one of the
reinforcing fibres shall be capable of meeting the stress ratio requirements even if all other fibre
reinforcing materials are removed.
7.1.5 Examples of certificates are shown in Annexes A and B.
7.2 Design submission
7.2.1 The design submission for each new design of cylinder shall include a detailed drawing, along
with documentation of the design including manufacturing and inspection particulars, as detailed in
7.2.2, 7.2.3 and 7.2.4.
6 © ISO 2020 – All rights reserved

7.2.2 Documentation for the liner and metal boss(es) shall include (but not be limited to):
a) material(s), including limits of chemical analysis;
b) dimensions, minimum thickness, straightness and out-of-roundness with tolerances;
c) process and specification of manufacture;
d) heat-treatment, temperatures, duration and tolerances;
e) inspection procedures (minimum requirements);
f) material properties;
g) dimensional details of valve threads and any other permanent features;
h) method of sealing boss to liner for bonded bosses.
7.2.3 Documentation for composite overwrap shall include (but not be limited to):
a) fibre material, specification and mechanical properties requirements;
b) minimum composite thickness;
c) thermosetting matrix: specifications (including resin, curing agent and accelerator), and resin bath
temperature where applicable;
d) thermoplastic matrix system: main component materials, specifications and process temperatures;
e) overwrap construction including the number of strands used, number of layers and layer orientation
and tensioning of the fibre at wrapping (where applicable);
f) curing process, temperatures, duration and tolerances;
g) adhesive system, main components, curing agent, accelerator, materials and specifications where
applicable.
7.2.4 Documentation for the composite cylinder shall include (but not be limited to):
a) nominal water capacity in litres at ambient conditions;
b) list of intended contents if intended for dedicated gas service;
c) working pressure, p (if applicable), that shall not exceed 2/3 times test pressure;
w
d) test pressure, p ;
h
e) maximum developed pressure at 65 °C for specific dedicated gas(es), p ;
max
f) minimum design burst pressure;
g) design life in years; cylinders with a test pressure of less than 60 bar shall have a non-limited
design life;
h) nominal weight of the finished composite cylinder, including tolerances;
i) for cylinders without liners, the method of sealing the boss to cylinder (if applicable);
j) details of components which are permanently attached and form part of the qualified design (e.g.
neck rings, protective boots, etc).
7.3 Manufacturing
7.3.1 The liner and metal bosses, where incorporated, shall be manufactured in accordance with the
manufacturer's design (see 7.2.2).
7.3.2 The composite cylinder shall be fabricated from a non-load-sharing liner, or fabricated on a
disposable mandrel, fully over-wrapped with layers of continuous fibres in a matrix applied under
controlled tension to develop the design composite thickness as specified in 7.2.3.
Liners can be stripped and re-wound provided that the overwrap has not been cured. The liner shall
not be overwrapped if it has been damaged or scored by the stripping process.
7.3.3 After wrapping is completed the composite shall be cured (if appropriate) using a controlled
temperature profile as specified in the documentation in 7.2.3. The maximum temperature shall be such
that the mechanical properties of the liner material, if fitted, and composite overwrap are not adversely
affected.
NOTE If cylinders are subjected to fibre tensioning during wrapping, the tensioning is recorded or
monitored.
8 Type approval procedure
8.1 General requirements
Each new cylinder design shall be submitted by the manufacturer to the inspector. The type approval
tests detailed in 8.2 shall be performed, under the supervision of the inspector, on each new cylinder
design or design variant.
8.2 Prototype tests
8.2.1 A minimum of 30 cylinders of the new design shall be made available for prototype testing.
Upon successful completion of all prototype tests, the remaining untested cylinders from the prototype
qualification batch can be used for service.
8.2.2 If, for special applications, the total number of cylinders required is less than 30, enough cylinders
shall be made to complete the prototype tests required, in addition to the production quantity. Then the
approval validity shall be limited to this batch only.
For a limited design change (design variant), in accordance with Table 1, a reduced number of cylinders
shall be selected by the inspector.
8.2.3 The batch of liners, prior to being wrapped, shall conform to the design requirements and shall
be inspected and tested in accordance with 9.1.
8.2.4 The composite material(s), prior to the cylinders being wrapped, shall conform to the design
requirements and shall be tested in accordance with 9.3.
8.2.5 Tests for a new cylinder design shall be supervised by an inspector and shall consist of:
a) hydraulic proof pressure test, in accordance with 8.5.1, or hydraulic elastic expansion test, in
accordance with 8.5.2;
b) cylinder burst test in accordance with 8.5.3;
c) ambient temperature cycle test, in accordance with 8.5.4;
8 © ISO 2020 – All rights reserved

d) environmental cycle test, in accordance with 8.5.6;
e) flaw test, in accordance with 8.5.8;
f) drop/impact test, in accordance with 8.5.9;
g) high velocity impact (gunfire) test, in accordance with 8.5.10;
h) torque test on cylinder neck boss in accordance with 8.5.13;
i) leak test in accordance with 8.5.15;
j) pneumatic cycle test in accordance with 8.5.16;
k) resin shear strength in accordance with 8.5.18.
l) glass transition test in accordance with 8.5.14;
8.2.6 Tests that are optional depending upon the design and intended use of the cylinder are:
a) vacuum test in accordance with 8.5.5 (mandatory if a cylinder is to be exposed to a vacuum in
service);
b) environmentally assisted stress rupture test in accordance with 8.5.7 (mandatory for cylinders
with load sharing glass or aramid fibre);
c) permeability test in accordance with 8.5.12 if cylinders are manufactured with non-metallic liners
or without liners;
d) fire resistance test in accordance with 8.5.11;
e) salt water immersion test in accordance with 8.5.14 (mandatory for cylinders used in underwater
applications).
8.2.7 For approval of a design variant as specified in 8.4, it is only necessary to carry out the tests as
prescribed in Table 1. Under supervision of the inspector. A cylinder, approval by a reduced series of
tests shall not be used as a basis for a second design variant approval with a reduced set of tests (i.e.
multiple changes from an approved design are not permitted) although individual test results can be
used as applicable (see 8.4.2).
8.2.8 Tests can be combined such that one cylinder can be used for more than one test. For example,
the cylinder burst test in 8.5.9 Drop/impact test can be used to satisfy the requirement of 8.5.3 Burst test.
8.2.9 If the results of the above prototype tests are satisfactory, the inspector shall issue a design
approval certificate a typical example of which is given in Annex A.
8.2.10 After completion of the tests the cylinders shall be destroyed or made incapable of holding
pressure.
8.3 New design
8.3.1 This clause specifies when a composite cylinder is a new design for the purposes of this
document. Subclause 8.4 specifies when a composite cylinder is a design variant.
8.3.2 A new cylinder design requires full type approval testing. A 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. A relocation of a factory does not require a new cylinder
design approval provided all equipment and procedures remain the same as for the original design
approval;
b) it is manufactured by a process that is significantly different from the process used in the design type
approval. A significant change is regarded as a change that would give rise to a measurable change
in the performance of the liner and/or finished cylinder. The inspector determines when a change in
process or design or manufacture is significantly different from the original qualified design;
c) the nominal outside diameter has changed more than 50 % from the qualified design;
d) a fibre of the same specification classification and mechanical properties but with a different linear
density shall not be considered a new fibre type. Minor changes in the wrapping pattern shall not
be considered to be a new design;
e) the cylinder is manufactured with a new fibre type. A fibre shall be considered to be of a new fibre
type when:
1) the fibre is of a different classification (e.g. glass, aramid or carbon);
2) the fibre is produced from a different precursor [e.g. Polyacrylonitrile (PAN) or pitch for
carbon];
3) the fibre is not equivalent [see 8.4.1 i)] to the fibre in the original design;
f) the matrix materials (i.e. resin, curing agent, accelerator) are different and not chemically
equivalent to the original design (e.g. a change from an epoxy to a polyester);
g) the test pressure has increased more than 60 % from the qualified design.
8.3.3 A cylinder shall also be considered to be of a new design compared with an existing approved
design if the method of liner manufacture or liner design has changed and when:
a) it is manufactured from a material of different composition or composition limits from that used in
the original type tests;
b) the material properties are outside the original design limits;
c) it is manufactured by a different process.
8.4 Design variants
8.4.1 For cylinders that are variants of another design, a reduced type approval testing programme
is required as specified in Table 1. A cylinder shall be considered to be a design variant if changes are
limited to the following.
a) The nominal length of the cylinder has changed by more than 5 %.
b) The nominal outside diameter has changed by 50 % or less.
c) There is a change in the design test pressure up to and including 60 %. Where a cylinder is to be
used and marked for a lower test pressure than that for which design approval has been given, it is
not deemed to be of a new design or design variant.
d) There have been changes to the composite thickness outside the tolerances provided in the design
submission or a change in the wrap pattern other than those necessary to accommodate the
changes of diameter and/or length.
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e) When equivalent matrix materials are used: epoxy, vinyl ester, and polyester systems are not
chemically equivalent to each other, but two epoxy-based systems would be considered chemically
equivalent as long as the minimum requirements of interlaminar shear testing are achieved and
has a glass transition temperature (Tg) equal to or higher than the system being replaced.
f) The minimum wall thickness of the liner has changed by more than 10 %.
g) The design or method of joining the neck boss to the liner has changed.
h) When equivalent overwrapping fibres are used:
1) equivalent fibres are manufactured from the same nominal raw materials, using the same
process of manufacture and having the same physical structure and the same nominal physical
properties, and where the average tensile strength and modulus is within ±5 % of the fibre
properties in an approved cylinder design. Carbon fibres made from the same precursor can be
equivalent, Aramid, carbon and glass fibres are not equivalent;
2) where a new equivalent fibre has been prototype tested for an existing design, then all the
manufacturer's existing prototype tested designs are regarded as prototype tested with the
new fibre without the need for any additional prototype testing.
i) When an equivalent liner is used:
1) equivalent liners are manufactured from the same nominal raw materials, using the same
process of manufacture and having the same physical structure and the same nominal physical
properties as in an approved cylinder design;
2) the equivalent liner material shall be subjected to the material tests specified in 9.1.2 for metal
liners and 9.1.3 for polymer liners and the liner burst test specified in 8.5.18 and shall meet the
minimum requirements specified in 7.2.2 and the criteria of 8.5.18;
3) where a new equivalent liner has been prototype tested for an existing design, all the
manufacturer's existing prototype tested designs are regarded as prototype tested with the
new liner without the need for any additional prototype testing.
j) When the cylinder thread has changed: when a cylinder design has only a different thread compared
to an approved design only the torque test, in accordance with 8.5.13, shall be performed.
8.4.2 A cylinder approval by a reduced series of tests (a "design variant") shall not be used as a basis
for a second design variant approval with a reduced set of tests (i.e. multiple changes from an approved
design are not permitted). If a test has been conducted on a design variant (A) that falls within the testing
requirements for a second variant (B), then the result for (A) can be applied to the new design variant
(B) test programme. However, design variant (A) shall not be used as the reference for determining the
testing required for any new design variant.
8.4.3 Where a design variant involves more than one parameter change, all the tests required by those
parameter changes shall be performed once only.
8.4.4 The inspector shall determine the level of reduced testing if not defined in Table 1, but a fully
approved design shall always be used as a reference for the new design va
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