ISO 11515:2022

INTERNATIONAL ISO
STANDARD 11515
Second edition
2022-08
Gas cylinders — Refillable composite
reinforced tubes of water capacity
between 450 l and 3000 l — Design,
construction and testing
Bouteilles à gaz — Tubes composites renforcés rechargeables d'une
capacité de 450 l à 3000 l — Conception, construction et essais
Reference number
© ISO 2022
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Published in Switzerland
ii
Contents Page
Foreword .v
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols . 5
5 Inspection and testing .6
6 Materials . 6
6.1 Liner materials . 6
6.2 Composite overwrap . 7
7 Design and manufacture . 7
7.1 General . 7
7.2 Design submission . 8
7.3 Manufacturing . 9
8 Type approval procedure .10
8.1 General . 10
8.2 Prototype tests . . 10
8.3 New design . 11
8.4 Design variants .12
8.5 Type approval test procedures and criteria . 17
8.5.1 General . 17
8.5.2 Hydraulic proof pressure test . 17
8.5.3 Hydraulic volumetric expansion test . 17
8.5.4 Liner burst test . 18
8.5.5 Tube burst test. 18
8.5.6 Ambient cycle test . 19
8.5.7 Environmental cycle test . 20
8.5.8 Flaw test . 21
8.5.9 Blunt impact test . 23
8.5.10 Fire resistance test . 24
8.5.11 Neck strength test . 26
8.5.12 Leak test . 27
8.5.13 Accelerated stress rupture test . . 27
8.5.14 Permeability test .28
8.5.15 Gas cycle test .28
8.5.16 Coatings test .29
8.5.17 Salt spray test . 30
8.5.18 Acid environment test .30
8.5.19 Vacuum test . 31
8.5.20 High velocity impact (gunfire) test . 31
8.5.21 Glass transition temperature test . 32
8.5.22 Resin shear strength test . 32
8.6 Failure of type approval tests . 32
9 Inspection and testing at time of manufacture .32
9.1 Liners for Type 2 and Type 3 tubes . 32
9.2 Failure of load-sharing liner batch tests . 33
9.3 Liners for Type 4 tubes. 33
9.4 Failure of non-load sharing liner batch tests .34
9.5 Overwrap materials .34
9.6 Composite tube. 35
9.7 Failure of batch tests . 35
iii
10 Tube marking .36
10.1 General .36
10.2 Additional marking.36
Annex A (informative) Example of a design approval certificate .37
Annex B (informative) Example of a test report.38
Annex C (normative) Ultrasonic inspection for seamless steel liners and metal tubing .40
Annex D (informative) Guidance for calculating permeation rates when using trace gases . 44
Bibliography .45
iv
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 ISO/TC 58, Gas cylinders, Subcommittee SC 3, Cylinder design.
This second edition cancels and replaces the first edition (ISO 11515:2013), which has been technically
revised. It also incorporates the Amendment, ISO 11515:2013/Amd.1:2018. The main changes are as
follows:
— the references have been updated;
— a resin shear strength test was added to the document and to Tables 2, 3 and 4,
— in 8.5.10, fire resistance test, the procedure has been changed to make the test more consistent;
— the criteria in 8.5.10.3 has been revised;
— in 8.5.15, gas cycle test, a new procedure has been added for the test to have a lower number of
cycles but with a significant hold time at pressure.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
v
Introduction
This document provides a specification for the design, manufacture, inspection and testing of composite
tubes for worldwide usage. The objective of this document 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 a lack of definitive International Standards and should not 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 .
Composite tubes can be used alone or in batteries to equip trailers or skids (ISO modules) or multiple
element gas containers (MEGCs) for the transportation and distribution of gases. This document does
not include consideration of any additional stresses that can occur during service or transport (e.g.
torsional/bending stresses). However, it is important that the stresses associated with mounting the
tube are considered by the assembly manufacturer and the tube manufacturer.
vi
INTERNATIONAL STANDARD ISO 11515:2022(E)
Gas cylinders — Refillable composite reinforced tubes
of water capacity between 450 l and 3000 l — Design,
construction and testing
1 Scope
This document specifies the minimum requirements for the materials, design, construction and
performance testing of
— Type 2 hoop-wrapped composite tubes,
— Type 3 fully-wrapped composite tubes, and
— Type 4 fully-wrapped composite tubes
with water capacities between 450 l and 3 000 l for storage and conveyance of compressed or liquefied
1)
gases with test pressures up to and including 1 600 bar and a design life of at least 15 years.
This document is applicable to expected service temperatures between −40 °C and +65 °C.
NOTE Type 4 tubes manufactured and tested to this document are not intended to contain toxic, oxidizing or
corrosive gases.
This document is applicable to tubes with composite reinforcement of carbon fibre or aramid fibre or
glass fibre (or a mixture thereof) in a matrix.
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 306, Plastics — Thermoplastic materials — Determination of Vicat softening temperature (VST)
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 4624:2016, Paints and varnishes — Pull-off test for adhesion
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 7225, Gas cylinders — Precautionary labels
ISO 7866, Gas cylinders — Refillable seamless aluminium alloy gas cylinders — Design, construction and
testing
ISO 9227:2017, Corrosion tests in artificial atmospheres — Salt spray tests
ISO 9712, Non-destructive testing — Qualification and certification of NDT personnel
5 2
1) 1 bar = 0,1 MPa = 10 Pa; 1 MPa = 1 N/mm .
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 10286, Gas cylinders — Vocabulary
ISO 10618, Carbon fibre — Determination of tensile properties of resin-impregnated yarn
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 11120, Gas cylinders — Refillable seamless steel tubes of water capacity between 150 l and 3000 l —
Design, construction and testing
ISO 13341, Gas cylinders — Fitting of valves to gas cylinders
ISO 13769, Gas cylinders — Stamp marking
ISO 14130, Fibre-reinforced plastic composites — Determination of apparent interlaminar shear strength
by short-beam method
ASTM D522, Standard Test Methods for Mandrel Bend Test of Attached Organic Coatings
ASTM D1308, Standard Test Method for Effect of Household Chemicals on Clear and Pigmented Organic
Finishes
ASTM D2344, Standard Test Method for Short-Beam Strength of Polymer Matrix Composite Materials and
Their Laminates
ASTM D2794, Standard Test Method for Resistance of Organic Coatings to the Effects of Rapid Deformation
(Impact)
ASTM D3170, Standard Test Method for Chipping Resistance of Coatings
ASTM D7269, Standard Test Methods for Tensile Testing of Aramid Yarns
ASTM E1356, Standard Test Method for Assignment of the Glass Transition Temperatures by Differential
Scanning Calorimetry
ASTM G154, Standard Practice for Operating Fluorescent Ultraviolet (UV) Lamp Apparatus for Exposure of
Non-metallic Materials
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 10286 and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
aramid fibre
continuous filaments of aramid laid up in tow form, used for reinforcement
3.2
autofrettage
pressure application procedure which strains the metal liner (3.18) past its yield point sufficient to
cause permanent plastic deformation, and results in the liner having compressive stresses and the
fibres having tensile stresses when at zero internal gauge pressure
3.3
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.
3.4
batch of load-sharing liners
quantity of liners (3.18) of the same nominal diameter, length, thickness and design, made successively
from the same material cast (heat) and processed in the same heat treatment equipment (i.e. a
continuous furnace process or a single furnace charge) using the same heat treatment parameters
3.5
batch of non-load sharing liners
quantity of non-load sharing liners of the same nominal diameter, length, thickness and design, made
successively and subjected to the same continuous manufacturing process
3.6
batch of metal bosses
quantity of metal bosses of the same nominal diameter, length, thickness and design, made successively
from the same material cast (heat) and processed in the same heat treatment equipment using the same
heat treatment parameters
3.7
batch of composite tubes
quantity of up to 200 finished tubes (3.24) successively produced (plus finished tubes required for
destructive testing), of the same nominal diameter, length, thickness and design
Note 1 to entry: The batch (3.3) of finished tubes can contain different batches of liners, fibres and matrix (3.21)
materials.
3.8
burst pressure
highest pressure reached in a tube (3.24) or liner (3.18) during a burst test
3.9
carbon fibre
continuous filaments of carbon laid up in tow form, used for reinforcement
3.10
composite overwrap
combination of fibres and matrix (3.21) used to reinforce the tube (3.24), including any barrier or
protective layers that are a permanent part of the design
3.11
dedicated gas service
service in which a tube (3.24) is used only with specified gas or gases
3.12
equivalent fibre
fibre from the same material family and similar properties to a fibre used in a previously prototype
tested tube (3.24)
3.13
equivalent liner
liner (3.18) 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 (within ±5 %) of the
approved liner design
3.14
equivalent matrix
resin matrix (3.21) from the same chemical family and similar properties to the resin matrix used in a
previously prototype tested tube (3.24)
3.15
exterior coating
layers of material applied to the tube (3.24) as protection or for cosmetic purposes
Note 1 to entry: The coating can be transparent or opaque.
3.16
glass fibre
continuous filaments of glass laid up in tow form, used for reinforcement
3.17
leak
−3
escape of gas at a rate greater than 5 × 10 mbar·l/s through a defect rather than permeation
3.18
liner
inner portion of the composite tube (3.24), whose purpose is both to contain the gas and transmit the
gas pressure to the fibres
3.19
load-sharing liner
liner (3.18) that has a burst pressure (3.8) greater than or equal to 5 % of the nominal burst pressure of
the finished composite tube (3.24)
3.20
non-load-sharing liner
liner (3.18) that provides no load sharing for the finished composite tube (3.24)
3.21
matrix
material that is used to bind and hold the fibres in place
3.22
minimum design burst pressure
minimum burst pressure (3.8) specified by the manufacturer
3.23
representative composite tube
shorter tube (3.24) with the same nominal diameter, and manufactured using the same materials and
manufacturing technique, and using a representative wrapping pattern (same number of strands and
same number of layers) so as to represent an equivalent stress compared to a full-scale prototype
3.24
tube
transportable pressure receptacle with a water capacity exceeding 150 l
3.25
tubing
hollow cylindrical body of metal or other material, used for conveying or containing liquids or gases
3.26
Type 2 tube
hoop-wrapped tube (3.24) with a load-sharing liner (3.19) and composite reinforcement on the
cylindrical portion only
3.27
Type 3 tube
fully wrapped tube (3.24) with a load-sharing liner (3.19) and composite reinforcement on both
cylindrical portion and dome ends
3.28
Type 4 tube
fully wrapped tube (3.24) with a non-load-sharing liner (3.20) and composite reinforcement on both
cylindrical portion and dome ends
3.29
glass transition temperature
T
g
temperature where a polymer substrate changes from a rigid glassy material to a soft (not melted)
material, usually measured in terms of the stiffness, or modulus
4 Symbols
p burst pressure of the finished tube bar
b
p test pressure bar
h
p maximum developed pressure at 65 °C bar
max
p working pressure bar
w
E notch length mm
T notch depth mm
S tube nominal wall thickness mm
W notch width mm
T glass transition temperature °C
g
N pressurization cycles to test pressure —
N pressurization cycles to maximum developed pressure —
d
y number of years of design life —
t nominal composite thickness —
L length of tube m
n viscosity of gas 1 μ centipoise
n viscosity of gas 2 μ centipoise
Q flow rate of gas 1 ACM/h
(actual cubic meters/
hour)
Q flow rate of gas 2 ACM/h
5 Inspection and testing
To ensure that the tubes conform to this document, they shall be subject to inspection and testing in
accordance with Clauses 6, 7, 8 and 9.
Tests and examinations performed to demonstrate conformity to this document shall be conducted
using instruments calibrated before being put into service and thereafter according to an established
programme.
NOTE Other requirements can apply in relevant national or regional regulations of the country (countries)
where the tubes are intended to be used.
6 Materials
6.1 Liner materials
6.1.1 Load-sharing liner materials shall conform in all relevant respects to the appropriate
International Standards:
a) seamless steel liners: ISO 9809-1, ISO 9809-2, ISO 9809-3 or ISO 11120, as appropriate;
b) seamless aluminium alloy liners: ISO 7866.
Relevant sections are those covering materials, thermal treatments, neck design, construction and
workmanship and mechanical tests. Design requirements are excluded since these are specified by the
manufacturer for the design of the composite tube (see 7.2.2).
6.1.2 The composite tube manufacturer shall verify that each new batch of materials has the
specified properties and qualities and shall maintain records so that the cast of material and the heat
treatment batch where applicable, used for the manufacture of each tube can be identified. A certificate
of conformance, from the liner material manufacturer is considered acceptable for the purposes of
verification.
6.1.3 The liner shall be manufactured from a metal or alloy suitable for the gas to be contained in
accordance with ISO 11114-1, if applicable.
6.1.4 When a neck ring is provided, it shall be of a material compatible with that of the tube and shall
be securely attached by a method appropriate to the liner material.
6.1.5 Non-load-sharing liner materials shall conform in all relevant respects to the appropriate
standards, as follows:
a) The liner (including metal boss) shall be manufactured from a material suitable for the gas to be
contained in accordance with ISO 11114-1 and ISO 11114-2 or demonstrated and documented by
suitable testing.
b) Metal bosses that are attached to a non-load sharing liner shall fulfil the type approval testing
requirements of this document.
c) The tensile yield strength and ultimate elongation of plastic liner material shall be determined at
−50 °C in accordance with ISO 527-2. The test results shall demonstrate the ductile properties of
the plastic liner material at temperatures of −50 °C or lower by meeting the values specified by the
manufacturer.
d) Polymeric materials from finished liners shall be tested in accordance with a method described in
ISO 306. The softening temperature shall be at least 100 °C.
6.2 Composite overwrap
6.2.1 The overwrap filament materials shall be carbon fibre or aramid fibre or glass fibre (or any
mixture thereof).
NOTE Glass fibre reinforced composite tubes can be susceptible to chemical attack and degradation after
being in contact with aggressive acids (e.g. battery acid).
6.2.2 The resin matrix shall be a thermosetting or thermoplastic polymer suited to the application,
environment and intended life of the product, for example, epoxy or modified epoxy with an amine or
anhydride curing agent, vinyl esters and polyesters.
6.2.3 The supplier of the filament material and the resin matrix system component materials shall
provide documentation for the composite tube manufacturer to be able to identify fully the batch of
materials used in the manufacture of each tube.
6.2.4 The composite tube manufacturer shall verify that each new batch of materials has the correct
properties and is of satisfactory quality, and shall maintain records from which the batch of materials
used for the manufacture of each tube can be identified. A certificate of conformance from the material
manufacturer is considered acceptable for the purposes of verification.
6.2.5 The batches of materials shall be identified, documented and supplied to the inspector.
6.2.6 The manufacturer shall ensure that there is no adverse reaction between the liner and the
reinforcing fibre, for example, by the application of a suitable protective coating to the liner prior to the
wrapping process (if necessary).
7 Design and manufacture
7.1 General
7.1.1 A Type 2 composite tube shall comprise:
a) an internal metal liner with one or two openings along the central axis only, which carries all the
longitudinal load and part of the circumferential load;
b) the liner designed to withstand a burst pressure greater than 0,85 of the test pressure of the
finished tube.
c) a composite overwrap formed by layers of continuous fibres in a matrix along the parallel portions
of the tube sidewall;
d) an optional exterior coating to provide external protection; when this is an integral part of the
design it shall be permanent.
7.1.2 A Type 3 composite tube shall comprise:
a) an internal metal liner with one or two openings along the central axis only, which carries part of
the longitudinal and circumferential load;
b) a composite overwrap formed by layers of continuous fibres in a matrix;
c) an optional exterior coating to provide external protection. When this is an integral part of the
design it shall be permanent.
7.1.3 A Type 4 composite tube shall comprise:
a) an internal non-load-sharing liner with one or two openings along the central axis only;
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;
d) an optional exterior coating to provide external protection; when this is an integral part of the
design it shall be permanent.
7.2 Design submission
7.2.1 The design submission for each new design of tube 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.
The design submission can cover a design family of composite tubes of the same diameter and pressure
with different cylindrical lengths from 2× the diameter and up to 5× the length of the representative
composite tube and with a water capacity between 450 l and 3 000 l.
7.2.2 Documentation for either the liner or metal boss(es), or both, shall include:
a) material details, 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, where applicable;
e) inspection procedures (minimum requirements);
f) material properties (including hardness for Type 2 and Type 3 tubes);
g) minimum design burst pressure (for Type 2 and Type 3 tube liners);
h) dimensional details of valve threads;
i) method of sealing boss to liner for Type 4 tubes.
7.2.3 Documentation for the composite overwrap shall include:
a) fibre material, specification and mechanical properties requirements;
b) minimum composite thickness;
c) resin system – main components and resin bath temperature where applicable;
d) thermoplastic matrix system – main component materials, specifications and process temperatures;
e) thermosetting matrix – specifications (including resin, curing agent and accelerator), and resin
bath temperature where applicable;
f) overwrap construction including the number of strands used, number of layers, and layer
orientation;
g) curing process, temperatures, duration and tolerances.
7.2.4 Documentation for the composite tube shall include:
a) water capacity in litres;
b) dimensions, minimum thickness, straightness and out of roundness with tolerances;
c) list of intended contents if intended for dedicated gas service;
d) working pressure, p , which shall not exceed 2/3 of the test pressure;
w
e) test pressure, p ;
h
f) allowable range of elastic expansions and permanent expansions, if appropriate, for the design
when volumetric expansion test is used (see 9.5.4);
g) maximum developed pressure at 65 °C for specific dedicated gas(es), p ;
max
h) minimum design burst pressure;
i) design life in years (15 years or more);
j) autofrettage pressure and approximate duration, where applicable;
k) tensioning of the fibre at winding, where applicable;
l) mass and manufacturing tolerance;
m) details of components which are permanently attached and form part of the qualified design (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 tube shall be fabricated from a load-sharing or non-load-sharing liner, over-
wrapped with layers of continuous fibres in a matrix, applied under controlled conditions to develop
the design composite thickness.
Liners can be stripped and re-wound provided that the overwrap has not been cured. The liner shall
not be over-wrapped if it has been damaged or scored by the stripping process.
7.3.3 After winding is completed the composite shall be cured (if appropriate) using a controlled
temperature profile as specified in 7.2.3. The maximum temperature shall be such that the mechanical
properties of the liner material are not adversely affected.
7.3.4 If tubes are subjected to an autofrettage operation, the autofrettage pressure and duration
shall be as specified in 7.2.4. The manufacturer shall demonstrate the effectiveness of the autofrettage
by appropriate measurement technique(s) acceptable to the inspector.
7.3.5 If tubes are subjected to a pre-stressing or fibre tensioning during winding to actively change
the final stresses in the finished tube, the level of stress shall be as specified in 7.2.4 and levels of stress
of tensioning shall be recorded or monitored.
8 Type approval procedure
8.1 General
The design submission of each new design of composite tube shall be submitted by the manufacturer to
the inspector. The type approval tests detailed in 8.2 shall be carried out on each new design or design
variant under the supervision of the inspector.
8.2 Prototype tests
8.2.1 A sufficient number of tubes shall be made available from a single batch to complete the
prototype testing or testing of the design variant.
NOTE Additional tubes from the same prototype batch can be made available in case of test equipment
failure.
8.2.2 The inspector shall verify that the batch of liners, prior to being wrapped, conforms to the
design requirements and are inspected and tested in accordance with 9.1 or 9.3, as appropriate.
8.2.3 The inspector shall verify that the composite material(s), prior to the tubes being wrapped,
conform to the design requirements and are tested in accordance with 9.4.
8.2.4 The inspector shall verify that all tubes in the batch produced for new design approval conform
to the design submission and are tested in accordance with 9.5. Except for the cases identified in 8.2.5,
the inspector shall supervise the tests shown in Table 1. An “A” in the relevant column of Table 1 shows
that the test is required for the appropriate tube category. An “O” in the relevant column of Table 1
shows that the test is required for particular designs, materials and uses. The relevant clause for each
test describes when the test is required.
Table 1 — Prototype testing for new designs
Design tests with subclause number Type 2 Type 3 Type 4
8.5.2 Hydraulic proof pressure test, or
A A A
8.5.3 Hydraulic volumetric expansion test
8.5.4 Liner burst test A A —
8.5.5 Tube burst test A A A
8.5.6 Ambient temperature cycling test A A A
8.5.7 Environmental cycling test A A A
8.5.8 Flaw test — A A
8.5.9 Blunt impact test A A A
8.5.10 Fire resistance test A A A
8.5.11 Neck strength test — — A
8.5.12 Leak test — — A
8.5.13 Accelerated stress rupture test O O O
8.5.14 Permeability test — — O
8.5.15 Gas cycling test — — A
Key
A : all tube designs tested
O : only required for particular designs, materials and uses
a
Tubes being used for other tests may be used.
b
Coating tests can be carried out on sections/domes of tubes as appropriate.
Table 1 (continued)
Design tests with subclause number Type 2 Type 3 Type 4
a b
8.5.16 Coatings test (where applicable) O O O
8.5.17 Salt spray test O O O
8.5.18 Acid environment test O O O
8.5.19 Vacuum test — — O
8.5.20 High velocity impact (gunfire) test O A A
8.5.21 Glass transition temperature test A A A
8.5.22 Resin shear strength test A A A
Key
A : all tube designs tested
O : only required for particular designs, materials and uses
a
Tubes being used for other tests may be used.
b
Coating tests can be carried out on sections/domes of tubes as appropriate.
8.2.5 For variations in design from the new design tube as specified in 8.4, it is only necessary to
carry out the tests as prescribed in Tables 2 to 4 as appropriate. A tube approval obtained 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).
8.2.6 If the results of the verifications and tests according to 8.2.2, 8.2.3 and 8.2.4 as modified by
8.2.5 are satisfactory, the inspector shall issue a type approval certificate. A typical example of such an
approval certificate is given in Annex A.
8.2.7 After completion of the tests the tubes shall be destroyed or made incapable of holding pressure.
8.3 New design
8.3.1 This subclause specifies when a composite tube is a new design for the purposes of this
document. Subclause 8.4 specifies when a composite tube is a design variant.
8.3.2 A new tube design requires full type approval testing. A tube shall be considered to be of a new
design compared to an existing approved design if the following applies.
a) It is manufactured in a different factory. A relocation of a factory does not require a new tube design
approval provided all materials, 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 have a measurable change
in the performance of either the liner or the finished tube, or both. The inspector shall determine
when a change in process or design or manufacture is significantly different from the original
qualified design.
c) The nominal outside diameter has changed by more than 50 % from the qualified design.
d) The composite overwrap materials are significantly different from the qualified design, for
example, different resin system or fibre type.
e) The test pressure has increased by more than 60 % from the qualified design.
8.3.3 A tube shall also be considered to be of a new design compared to an existing approved design if
the following applies.
a) The liner manufactured from a material of different composition or composition limits from that
used in the original type tests.
b) The liner material properties are outside the original design limits.
8.4 Design variants
8.4.1 For tubes similar to an approved design, a reduced type approval testing programme is allowed.
A tube shall be considered to be a design variant if the following applies.
a) The outside diameter has changed by 50 % or less.
b) The autofrettage pressure has changed by more than 5 %.
c) Either the base profile or the base thickness of the liner, or both, has changed relative to the tube
diameter and minimum wall thickness.
d) There is a change in the design test pressure up to and including 60 %. Where a tube will be used
and marked for a lower test pressure than that for which the design approval has been given, it is
not deemed to be of a new design or design variant.
e) When changes in diameter or pressure are made, the structural wall elements shall operate at the
same, or lower nominal stress levels as the original design (e.g. if pressure or diameter increase,
the wall thickness has to increase proportionally).
f) The minimum composite thickness has changed by more than 5 % for reasons other than a change
in test pressure or diameter.
g) The minimum wall thickness of the liner has changed by more than 5 %.
h) When equivalent matrix materials are used:
1) New matrix materials are equivalent if they are from the same chemical family (epoxy, vinyl
ester or polyester) and the minimum requirements of interlaminar shear testing are achieved
and the new matrix material has a T equal to or higher than the system being replaced.
g
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