ISO 19078:2013
(Main)Gas cylinders — Inspection of the cylinder installation, and requalification of high pressure cylinders for the on-board storage of natural gas as a fuel for automotive vehicles
Gas cylinders — Inspection of the cylinder installation, and requalification of high pressure cylinders for the on-board storage of natural gas as a fuel for automotive vehicles
ISO 19078:2013 specifies the requirements for the inspection, installation and requalification of high pressure cylinders, designed and manufactured in accordance with the requirements of ISO 11439, for the on-board storage of natural gas as a fuel for automotive vehicles. It provides criteria, in the absence of guidance from the cylinder or vehicle manufacturer, for the acceptance (including any allowed rework) or rejection (including any allowed rework or destruction) of a cylinder and its installation.
Bouteilles à gaz — Inspection de l'installation des bouteilles, et requalification des bouteilles haute pression pour le stockage du gaz naturel, utilisé comme carburant, à bord des véhicules automobiles
General Information
Relations
Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 19078
Second edition
2013-01-15
Gas cylinders — Inspection of
the cylinder installation, and
requalification of high pressure
cylinders for the on-board storage of
natural gas as a fuel for automotive
vehicles
Bouteilles à gaz — Inspection de l’installation des bouteilles, et
requalification des bouteilles haute pression pour le stockage du gaz
naturel, utilisé comme carburant, à bord des véhicules automobiles
Reference number
©
ISO 2013
© ISO 2013
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any
means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the
address below or ISO’s member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2013 – All rights reserved
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Background information. 4
4.1 General . 4
4.2 Cylinder types and descriptions . 4
4.3 Required marking information . 5
5 Inspection body and inspectors . 5
6 Inspection equipment . 6
7 Cylinder, valve and pressure relief device inspection . 6
7.1 Inspection interval . 6
7.2 Conditions requiring immediate inspection . 6
7.3 Preparation for inspection . 7
7.4 Cylinder inspection . 8
7.5 Additional inspection of metal cylinders — CNG-1 and metallic areas of CNG-2, CNG-3 and
the metal bosses of CNG-4.13
7.6 Additional inspection requirements for composite cylinders (CNG-2, CNG-3 and CNG-4) 15
7.7 Valve and pressure relief device inspection .16
7.8 Cylinder marking.17
7.9 Cylinder inspection record/checklist .18
7.10 Cylinder final acceptance/rejection .18
7.11 Component final acceptance/rejection .19
8 Installation and mounting inspection .20
8.1 Installation and mounting of Natural Gas Vehicle fuel cylinders .20
8.2 Cylinder installation inspection .20
9 Condemned cylinders .22
9.1 General .22
9.2 Condemned cylinders .22
9.3 Destruction process .22
Annex A (informative) Depressurization and purging of CNG fuel cylinders .24
Annex B (informative) Conditions and usage that may warrant more frequent inspections .26
Annex C (informative) Inspection checklist example .27
Annex D (informative) Considerations for hydrostatic test and internal inspection .29
Bibliography .31
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International
Standards adopted by the technical committees are circulated to the member bodies for voting.
Publication as an International Standard requires approval by at least 75 % of the member bodies
casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 19078 was prepared by Technical Committee ISO/TC 58, Gas cylinders, Subcommittee SC 4,
Operational requirements for gas cylinders.
This second edition cancels and replaces the first edition (ISO 19078:2006), with the following main
technical revisions:
a) The scope clarifies the rework of some types of rejected cylinders;
b) The periodicity of inspection has been removed from this International Standard. The user is
referred to the requirements of ISO 11439 for this information;
c) Damage levels and criteria are more clearly defined and better align with ISO 11439;
d) Clause 7.11 was renamed to better clarify its intent;
e) Table 2 includes acceptance and rejection conditions for gas tight housing;
f) Reference to ISO 25760 for valve removal has been added; and
g) Annex A, Inspector qualifications (informative), and Annex F, Composite matrix (informative), were
removed.
iv © ISO 2013 – All rights reserved
Introduction
This International Standard sets out requirements regarding the periodic visual examination and
inspection of natural gas fuel cylinders installed in vehicles and the condition of their installation. These
cylinders are designed to store natural gas at high pressures.
Where there is any conflict between this International Standard and any applicable regulation, the
regulation always takes precedence.
INTERNATIONAL STANDARD ISO 19078:2013(E)
Gas cylinders — Inspection of the cylinder installation, and
requalification of high pressure cylinders for the on-board
storage of natural gas as a fuel for automotive vehicles
1 Scope
This International Standard specifies the requirements for the inspection, installation and requalification
of high pressure cylinders, designed and manufactured in accordance with the requirements of
ISO 11439, for the on-board storage of natural gas as a fuel for automotive vehicles.
It provides criteria, in the absence of guidance from the cylinder or vehicle manufacturer, for the
acceptance (including any allowed rework) or rejection (including any allowed rework or destruction)
of a cylinder and its installation.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 11439, Gas cylinders — High pressure cylinders for the on-board storage of natural gas as a fuel for
automotive vehicles
ISO 15500-13, Road vehicles — Compressed natural gas (CNG) fuel system components — Part 13: Pressure
relief device (PRD)
ISO 15500-15, Road vehicles — Compressed natural gas (CNG) fuel system components — Part 15: Gas-tight
housing and ventilation hose
ISO 15501-1, Road vehicles — Compressed natural gas (CNG) fuel systems — Part 1: Safety requirements
ISO 15501-2, Road vehicles — Compressed natural gas (CNG) fuel systems — Part 2: Test methods
ISO 25760, Gas cylinders — Operational procedures for the safe removal of valves from gas cylinders
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
abrasion
damage to an area of the cylinder or its installation equipment caused by scraping, wearing, vibration or
rubbing away of the material by friction
Note 1 to entry: Abrasion can be the result of many cycles of something rubbing lightly on the surface of the
cylinder or its installation equipment, or due to a few cycles, perhaps only one, of heavy rubbing.
3.2
impact
blow to the surface of the cylinder that can significantly damage and/or indent the surface (e.g.
cutting, gouging)
Note 1 to entry: Impact can also induce such damage as delaminations, which are not readily apparent through
visual examination.
3.3
component
parts that are used directly in conjunction with the installation of the fuel container to include the
cylinder, valve, pressure relief device (PRD), vent and mounting
3.4
condemned
cylinder or piece of its installation equipment no longer fit for service and for which repair is not allowed
3.5
crazing
hairline cracking of the resin, giving it an opaque, frosty appearance
3.6
cut
damage caused by a sharp object coming into contact with the cylinder’s surface
3.7
delamination
form of composite damage, in which a separation develops between layers of the composite
3.8
destroyed
cylinder or piece of its installation equipment in a state that makes it physically unusable for its purpose
3.9
dome
curved end portion of the cylinder
3.10
external coating
surface treatment applied to the cylinder for environmental protection and/or improved appearance
3.11
gas tight housing
enclosure fitted at any potential leakage points (e.g. cylinder/valve connection or PRD) to collect and
vent any leaked gas to outside the vehicle
3.12
helical
winding in the longitudinal and circumferential direction on both the cylindrical and dome regions
of the cylinder
Note 1 to entry: The strands of reinforcing fibres are oriented at an angle to the longitudinal axis of the cylinder.
3.13
hoop direction
hoop pattern
winding along the cylindrical portion of the cylinder
Note 1 to entry: The strands of reinforcing fibres are oriented at an angle of nearly 90 degrees to the longitudinal
axis of the cylinder.
3.14
inspection body
organization that performs the visual inspection of compressed natural gas (CNG) cylinders used in
natural gas vehicles (NGVs)
3.15
inspector
individual who is authorized by an inspection body to perform the visual inspection
2 © ISO 2013 – All rights reserved
3.16
inspection mark
stamp, label or tag placed by an inspector on the cylinder indicating acceptance of the cylinder
3.17
Level 1 damage/condition
minor damage that can occur during normal use
Note 1 to entry: Such damage normally has no adverse effects on the safety of the cylinder and its continued use.
Scratched paint or nicks that have no appreciable depth in metal, or similar damage in the composite cylinder
paint or resin where there are no visible frayed fibres, are considered to be of this level of damage.
Note 2 to entry: See Table 1.
3.18
Level 2 damage/condition
damage that is more severe than Level 1, but where after repair the cylinder is authorized to return to
service, or based upon the recommendations of the manufacturer may be classified as Level 1 or Level 3
Note 1 to entry: See 7.4.3 and Table 1.
3.19
Level 3 damage/condition
damage that requires a cylinder be condemned
Note 1 to entry: A Level 3 condition is such that the cylinder must be rendered unfit for continued service and
cannot be repaired.
Note 2 to entry: See Table 1.
3.20
liner
internal container of the cylinder, which sometimes carries pressure, that prevents leakage of gas
through the composite cylinder structure
3.21
manufacturer
cylinder maker, unless otherwise stated
3.22
marking
information permanently applied to an item (e.g. stamping and permanent labelling)
3.23
mounting brackets and/or straps
devices used to secure cylinders in a vehicle
3.24
overpressurization
pressurization of the cylinder, which at 15 °C results in a settled pressure that is higher than the working
pressure marked on the cylinder, or pressurization of a cylinder to a pressure that is above 26 MPa
independent of temperature conditions (for a 20 MPa working pressure cylinder)
3.25
pressure relief device
PRD
device that releases the contained gas in specific emergency conditions in accordance with ISO 15500-13
3.26
reinforcing fibres
continuous fibrous strands in the composite, such as carbon, aramid, glass or combinations thereof,
which withstand loads caused by pressurization
3.27
rejected cylinder or installation equipment
cylinder or its installation equipment that needs to be removed from service, i.e. disassembled from the
vehicle
Note 1 to entry: For Level 2 damage, the cylinder is evaluated further before repairing or condemning. For Level 3
damage, the cylinder or equipment is subsequently condemned.
3.28
repair
action, including rework, to return a cylinder to an acceptable Level 1 condition
3.29
resin
material that is used to bind and hold the fibres in place
3.30
working pressure
settled pressure, at a uniform temperature of 15 °C
3.31
stress corrosion cracking
SCC
phenomenon resulting in a split or rift in the materials, caused by a combination of load and
aggressive environment
Note 1 to entry: Such cracks in composite materials are typically sharply defined and can appear as a family of
cracks or as a single crack.
3.32
valve
device installed in one of the threaded openings of the cylinder used to allow gas flow into or from the cylinder
Note 1 to entry: A manual valve is turned on or off with a handle. A solenoid valve is turned on or off automatically.
Some solenoid valves can be operated manually with special tools.
3.33
vent line
high-pressure line used to conduct gas from a PRD to a location outside the vehicle, where gas can be
discharged safely
4 Background information
4.1 General
NGV cylinders inspected in accordance with this International Standard are designed and qualified
in accordance with ISO 11439. These cylinders have markings that identify the ISO 11439 type of
construction.
An inspection body shall perform all inspection work. Trained and qualified personnel shall perform
installations or other service required by this International Standard.
4.2 Cylinder types and descriptions
4.2.1 CNG-1 metal
CNG-1 cylinders are all metal and can be made of any alloy of steel or aluminium that meets the
qualification requirements outlined in ISO 11439.
4 © ISO 2013 – All rights reserved
4.2.2 CNG-2 metal liner partially reinforced with resin-impregnated continuous filament
(hoop-wrapped)
CNG-2 cylinders have a metallic liner with sufficient strength and thickness to carry the entire
longitudinal load at the required burst pressure, and to withstand the working pressure without
rupture. Metal liner materials are those identified under CNG-1 cylinders (see 4.2.1). These cylinders
are reinforced with fibres wound only in the hoop (circumferential) direction.
4.2.3 CNG-3 metal liner totally reinforced with resin-impregnated continuous filament
(fully wrapped)
CNG-3 cylinders have a metallic liner that is generally load carrying, but they do not have sufficient
strength and thickness to carry the longitudinal load at the burst pressure. They are reinforced with
fibres wound in both a helical and hoop pattern. Metal liner materials are those identified under CNG-1
cylinders (see 4.2.1).
4.2.4 CNG-4 non-metallic liner totally reinforced with resin-impregnated continuous filament
(all composite)
CNG-4 cylinders have a non-metallic liner that does not carry load. The liner is typically a thermoplastic
material. These cylinders are reinforced with fibres wound in both a helical pattern and hoop direction.
Metallic bosses are used to accept accessories such as valves and PRDs. Boss materials are typically
aluminium alloy or stainless steel.
4.3 Required marking information
The marking requirements of ISO 11439 shall be reviewed to verify the exact wording, lettering size and
required content as follows:
a) “CNG ONLY”;
b) “DO NOT USE AFTER MM/YYYY” (providing the month and year of expiry);
c) the manufacturer’s identification;
d) the cylinder identification (a unique serial number for each cylinder);
e) the working pressure;
f) the ISO standard, along with cylinder type and certification registration number (if applicable);
g) the words “Use only a manufacturer-approved PRD”;
h) the date of manufacture (month and year);
i) any additional markings, as required by the regulations of the country (or countries) of use.
When labels are used, all cylinders shall have a unique identification number and the manufacturer’s
identification stamped on an exposed metallic surface, to permit tracing in the event of the label
being destroyed.
5 Inspection body and inspectors
The inspection body shall be recognized in accordance with the regulations in the country of use.
In order to ensure that the cylinders are fit for continued safe use, the inspection shall be carried out
exclusively by persons competent to do so. The inspector shall have available and within easy access
during the inspection the equipment described in Clause 6 and the documentation referenced in 7.3.2.
The vehicle to be inspected shall be positioned in such a way that the inspector has unimpeded access to
the surface of the cylinder, or else in accordance with the vehicle manufacturer’s recommendations (see
7.3.5). If the inspector finds areas, such as those described in Clause 7, that require additional inspection or
testing, the cylinder shall be depressurized in accordance with the recommendations in Annex A and with
the manufacturer’s instructions, and then removed from the vehicle. If the inspector determines that the
cylinder needs to be permanently removed from service, this shall be done in accordance with Clause 9.
6 Inspection equipment
6.1 Adequate light, sufficient to illuminate all surfaces clearly, in order to examine properly the external
surfaces of cylinders, mounting brackets, valves, vent lines, etc.
CAUTION — To avoid combustion or fire, either use explosion-proof lights or ensure that the area
is well ventilated.
6.2 Angled inspection mirrors, or other suitable devices, to aid in the examination of cylinder surfaces
that are partially concealed by the installation.
6.3 Various hand tools, to remove covers, shields or other installed equipment, such that the external
cylinder surfaces, brackets, valves, PRDs and other components can be viewed.
6.4 Torque wrench, to verify that the mounting bracket bolts are properly tightened.
6.5 Depth gauge, to determine the depth of cuts, pits and abrasions. A commercial-type pit or depth
gauge should be used for this purpose; alternatively, the use of other equipment to estimate imperfection
depths is acceptable.
6.6 Rule and straightedge, in combination, to evaluate indentations and bulges.
6.7 Rule or tape measure, to determine the length of noted cuts and the general area of abrasion.
6.8 Commercial-type leak test fluid, which does NOT contain ammonia, harsh corrosives or chemicals
incompatible with the system materials (the fluid is usually a mild soap solution that meets these criteria).
A methane gas detector may also be used to test for leakage. Additional information is provided in 7.6.4.
6.9 Ultrasonic thickness gauge, to determine the remaining wall thickness on cylinders with exposed
metal regions (excluding boss).
7 Cylinder, valve and pressure relief device inspection
7.1 Inspection interval
CAUTION — Failure to perform diligent and accurate inspections on a regular basis, or promptly
(in the case of a potentially damaging incident or unusual behaviour), can result in a serious
accident causing severe damage or injury, or both.
NGV fuel storage systems shall be visually inspected by a recognized inspector (see Clause 5), at intervals
as stated in ISO 11439. Annex B specifies typical conditions and usage that may warrant more frequent
inspections, while Annex D outlines specific considerations relating to internal inspections.
7.2 Conditions requiring immediate inspection
Inspections usually are carried out as stated in 7.1 on pressurized cylinders; however, due to the high
risk presented by cylinders described in this clause, it is essential to depressurize the cylinder and
consider the following list prior to the normal inspection procedure in 7.4.
6 © ISO 2013 – All rights reserved
An inspection shall be performed immediately on a depressurized CNG cylinder, prior to filling or
returning it to service, if for example
a) the cylinder or vehicle in which it is installed is involved in a fire,
b) the cylinder is exposed to excessive heat,
c) the cylinder is dropped during installation or subjected to impact,
d) the NGV has been involved in a collision,
e) the cylinder is suspected to have been damaged,
f) any odour is detected (e.g. a compound added to natural gas to enable it to be detected),
g) there is unusual behaviour including, but not limited to:
1) unexpected loss of gas pressure;
2) rattling or other indications of looseness;
3) unusual snapping or hissing sounds,
NOTE Some minor noise is not unusual for composite materials when cylinders are being pressurized or
depressurized.
h) the cylinder is reinstalled after removal from the vehicle,
i) the cylinder installation is changed significantly,
j) the cylinder is transferred to another vehicle, or
k) the cylinder has been overpressurized, not in accordance with the limits of its design.
7.3 Preparation for inspection
7.3.1 Background vehicle information
CAUTION — A cylinder shall not be pressurized with air or an oxidizing gas mixture prior to use
or inspection. This can create a reactive mixture with the gas that the cylinder was previously
filled with and can be very dangerous.
The cylinder owner/vehicle operator should be questioned regarding any known conditions or incidents
that could have caused damage to the cylinder. The inspector shall review service and previous cylinder
inspection records (if available) prior to the inspection. Knowledge of the service history and interviews
of the cylinder owner/vehicle operator concerning known repairs and accidents can provide insight,
which can aid in the inspection process.
Known conditions or incidents that could have caused damage to the cylinder include, but are not limited to
a) overpressurization,
b) dropping of the cylinder (during installation),
c) impacts to the cylinder,
d) exposure to excessive heat or fire,
e) vehicle accidents, and
f) exposure to harsh chemicals.
7.3.2 Background information
Before starting the inspection, pertinent information shall be reviewed from the following sources:
— the cylinder manufacturer;
— the vehicle manufacturer (when the CNG fuel system is factory-installed);
— the after-market installers (when the CNG fuel system is installed after the vehicle is manufactured,
and installed by someone other than the vehicle manufacturer).
As a minimum, this shall include a survey of ISO 11439, including inspection criteria for the specific
cylinder and vehicle model. This review should include a study of the maintenance manual and
recommendations and guidance documents for the cylinder and its installation.
7.3.3 Cylinder external surface
The external surface of the cylinder shall be clean and free from dirt or other debris that impedes the
ability to clearly determine the condition of the external surface of the cylinder (see 7.3.5). Shields or
covers that inhibit the inspection shall be removed or opened, to gain access to the cylinder surface area
for inspection.
If a sleeve, which can conceal damage, is fitted to a cylinder, it should be removed to enable a thorough
inspection to be performed.
7.3.4 Cylinder depressurization
Cylinders do not require depressurizing prior to inspection.
Cylinders that require immediate inspection (see 7.2) shall be depressurized prior to examination.
Cylinders with known or suspected Level 2 damage shall be depressurized prior to inspection. Cylinders
with Level 3 damage and cylinders to be condemned shall be depressurized (see 9.2). Compliance with
all authorities having jurisdiction in the depressurization process and release of CNG to the atmosphere
is mandatory. Depressurization guidelines are given in Annex A.
7.3.5 Cylinder access
Resin, paint or coatings of installed cylinders shall not be removed for the visual inspection. The cylinder
shall not be disassembled from the vehicle for inspection unless visual damage or deterioration is noted
on the exposed cylinder surface, or if damage is believed to have occurred on an unexposed surface.
If the cylinder surface is not accessible, the cylinder shall be disassembled from the vehicle for visual
inspection or tested by a method appropriate for its installation.
7.4 Cylinder inspection
7.4.1 Cylinder acceptance and rejection criteria
In the absence of any recommendation from the cylinder manufacturer, Table 1 shall be used for the
acceptance and rejection criteria for cylinders. Table 1 shall not be used without a thorough understanding
and knowledge of Clause 7, as well as of the manufacturer’s instructions.
7.4.2 Damage evidence
Visual inspection of the cylinder external surface is the primary means of detecting cylinder damage.
Evidence of potential damage includes
— corrosion,
— cuts,
8 © ISO 2013 – All rights reserved
— scratches,
— gouges,
— cracks,
— exposed fibres,
— dents,
— bulges,
— fractures,
— material loss/removal,
— discolouration of the cylinder surface (soot, charring, chemical attack, etc.),
— evidence of heat exposure,
— impact or accidents, and
— deterioration of surface materials.
7.4.3 Damage levels
The extent of the damage is categorized as Level 1, Level 2 or Level 3.
The cylinder damage levels identified in this International Standard are given as general guidelines.
The inspection body shall accept manufacturer-specified acceptance criteria where noted in Table 1, if
such criteria are based upon cylinder test results. Where not noted, or where the manufacturer does not
provide acceptance criteria based upon testing, the inspection body shall apply the acceptance criteria
in this International Standard. In the absence of acceptance criteria based upon testing, all Level 2
conditions shall be identified as Level 3 conditions. The surface of the cylinder shall be inspected for
evidence of damage. Damage observed shall be evaluated in accordance with Table 1.
Whenever cylinder damage is discovered, the likely cause of the damage shall be investigated. When
cylinder damage is caused by installation, severity or conditions of service (see Annex B), or by improper
cylinder use, the inspector shall advise the cylinder owner of the need to take corrective action to
prevent or reduce further cylinder damage, or to prevent damage to a replacement cylinder. The original
cylinder installer shall develop such actions and if necessary will involve the cylinder manufacturer.
7.4.3.1 Level 1
Cylinders with no external visual damage or minor damage are categorized as Level 1 damage and are
acceptable; hence, no repair is required.
7.4.3.2 Level 2
Cylinders with damage that requires repair, testing or condemnation as advised by the cylinder
manufacturer are categorized as Level 2 damage. Level 2 damage is also reserved for conditions specified
by the manufacturer, which can differ from Level 1 or Level 3 damage outlined in Table 1. Level 2
conditions are either shown to be acceptable (Level 1) by the manufacturer’s test and investigation
results, or else evaluated to be Level 3.
7.4.3.3 Level 3
Cylinders with damage that is sufficiently severe that it shall not be repaired, but shall be rejected and
subsequently condemned are categorized as Level 3 damage.
7.4.4 Cuts, scratches, gouges and abrasion
The rejection criteria for these types of damage may be provided by the manufacturer (e.g. abrasion
in accordance with 7.5.5). Full details of acceptance and rejection conditions can be found in Table 1.
Damage between Level 1 and Level 3 is determined to be acceptable or rejectable by the cylinder
manufacturer’s guidance, based upon the manufacturer’s test data (see 7.4.3).
Repair instructions shall be obtained from the manufacturer.
Table 1 — Acceptance and rejection conditions for cylinders
Decision
Type of
Description Remarks
damage
Level 1 accept Level 2 Level 3 reject
All cylinder types
Marking Stamping, Required infor- Some required information Required infor- Manufacturer may
labelling and mation is present is not legible; manufacturer mation is not leg- supply new labelling
attached infor- and legible may supply information for ible or any trace- if serial number is
mation repair ability; repair not legible.
allowed
If this information is
unavailable this becomes
Level 3.
Cuts/ A sharp impres- When depth Greater than Level 1 damage For CNG-1 when Composite cylinders
scratches/ sion where is less than that is accepted and can be depth is ≥ 0,5 mm may be repaired if
gouges material has 0,25 mm and (for repaired in accordance with or the remaining fibres are not cut or
been removed composites only) the manufacturer’s specifi- wall thickness separated.
or redistrib- no fibres were cations (composite cylinders is less than the
uted. Also exposed, cut or only). minimum design
includes line separated wall thickness.
corrosion pit-
For CNG-2, −3, −4
ting where dis-
For types CNG-2, −3 and −4,
type cylinders,
tance between
a depth included between
when the depth
the pits is less
0,25 mm and 1,25 mm when
is greater than
than one pit
other parameters are critical
1,25 mm.
width
(length, width, number), in
accordance with the manu-
facturer’s recommendations.
For type CNG-1 cylinders
when depth is ≥ 0,25 mm and
< 0,5 mm, repair (e.g. grind-
ing for steel) in accordance
with the manufacturer’s
recommendations provided
the minimum design wall
thickness is maintained.
Abrasion Damage to When the depth Greater than Level 1 damage For CNG-1 when Composite cylinders
an area of the is less than that is accepted and can be depth is ≥ 0, 5 mm may be repaired
cylinder or its 0,25 mm and (for repaired in accordance with or the remaining if fibres are not
installation composites only) the manufacturer’s specifi- wall thickness exposed, cut or sepa-
equipment no fibres were cations (composite cylinders is less than the rated.
caused by exposed, cut or only). minimum design
scraping, wear- separated wall thickness.
ing, vibration
For CNG-2, −3, −4
and rubbing of
For type CNG-1 cylinders
type cylinders,
the material
when depth is ≥ 0,25 mm and
when the depth
away by fric-
< 0,5 mm, repair (e.g. grind-
is greater than
tion (see 3.1)
ing for steel) in accordance
1,25 mm.
with the manufacturer’s
recommendations provided
the minimum design wall
thickness is maintained.
10 © ISO 2013 – All rights reserved
Table 1 (continued)
Decision
Type of
Description Remarks
damage
Level 1 accept Level 2 Level 3 reject
All cylinder types
Charring/ Blackening or None or washes Follow the manufacturer’s Permanent char-
soot browning of an off test guidelines for Level 2 ring; discoloura-
area damage (see 7.4.5) tion
Gas leakage Loss of contents None detected If the cylinder leaks it shall Leak detected
through a not be repaired.
defect (not
intended to
include loss by
If through composite
permeation)
material (if permeation sus-
pected), see 7.6.4 and seek
the manufacturer’s advice.
Chemical Cylinder is Cleans off; no Chemical unknown; effects Permanent Manufacturer shall
attack subjected to a residue or effect, on cylinder materials discolouration, provide guidance
chemical that and chemical is unknown; moves to Level 3 loss/disruption of on exposure to
corrodes, dis- known not to if these cannot be resolved material, chemi- chemicals; (see under
solves or has affect cylinder cal is known to “Stress corrosion
any adverse materials affect cylinder cracking”).
effect on the materials; can-
material not determine if
materials have
been affected
Weathering Effects of the Minor gloss loss Only coating or non-struc- Structural mate- Repainting with the
sun’s ultraviolet or chalking tural material is affected; rials affected manufacturer’s guid-
radiation may be repainted (see 7.4.7) ance might change
Level 2 to Level 1.
Cylinder types CNG-2, −3 and −4
Impact, e.g. Cylinder Damaged area is Damage is uncertain, requir- Permanent defor- Contact manufacturer
caused by material was less than 1 cm ing the manufacturer’s mation of cylinder if additional advice is
collision or struck or hit. and no other dam- advice or liner, or needed.
accident The resin may age is apparent frosted/damaged
have a frosted area is greater
or smashed than 1 cm (does
appearance not pass the
“coin-tap” test;
see 7.6.3)
Stress Fibres may Materials in Possibility that cracking Identified stress Contact manufacturer
corrosion crack or split contact with or splitting has occurred, corrosion crack- if questionable condi-
cracking as a result of a chemical(s) (not because cylinder was known ing tion exists.
chemical attack, prone to cause to have had chemical contact
favoured by stress corrosion
stresses in the cracking but
material nothing visible is
detected)
Table 1 (continued)
Decision
Type of
Description Remarks
damage
Level 1 accept Level 2 Level 3 reject
Cylinder types CNG-1 and metal portions of other designs
Bulge Visible swelling None Could be bow shape rather Visible or detect-
of cylinder than bulge (see 7.5.3) able bulge
Corrosion, An isolated hole When depth is Repair (e.g. grinding for When depth is If Level 1 corrosion is
pits caused by a less than 0,25 mm steel) in accordance with the ≥ 0,25 mm and found, the manufac-
chemical, oxida- manufacturer’s recommen- the remaining turer’s recommended
tion or rusting dations provided the mini- wall thickness procedure to prevent
of material mum design wall thickness is less than the further corrosion
is maintained minimum design should be followed.
wall thickness.
Corrosion, Corrosion pits When depth is Repair (e.g. grinding for When depth is
line in a narrow less than 0,25 mm steel) in accordance with the ≥ 0,25 mm and
band, such that and the length is manufacturer’s recommen- the length is
the distance less than 50 mm dations provided the mini- greater than
between pits mum design wall thickness 100 mm. The
is greater than is maintained remaining wall
one pit width. If thickness is less
pits are closer, than the mini-
see under mum design wall
“Cuts/ thickness.
scratches/
gouges”
General cor- An area of Area corrosion Repair (e.g. grinding for Corrosion depth
rosion material loss is less than 25 % steel) in accordance with the is below mini-
due to chemical of the outside manufacturer’s recommen- mum wall thick-
oxidation or surface area, dations provided the mini- ness or the area
rusting provided that the mum design wall thickness is 25 % or more
remaining thick- is maintained of the outside
ness is at least surface area.
minimum design
wall thickness
Dents A depression Dents less than N/A cylinder cannot be Dents 1,6 mm or A large shallow dent is
in the cylinder 1,6 mm deep and repaired. more deep and less of a concern than
that has neither which are larger the largest diam- a small shallow dent.
penetrated nor than 50 mm eter or length is A dent with sharp
removed mate- in diameter or less than 50 mm angles creates mate-
rial length rial stresses, which
reduce cylinder safety.
Corrosion Metal corrosion None visible Corrosion deposits or stains Corrosion at the Corrosion deposits
of metals as evidenced on originating from unknown edge of the com- or stains originating
under com- the composite chemical, beneath or at posite, which has from corroded vehicle
posite surface or on the edge of the composite. Level 3 charac- components other
the liner sur- Cylinder shall be referred to teristics of line than the cylinder are
face adjacent manufacturer. If effects on corrosion not to be confused
to the edge of cylinder materials unknown; with this phenom-
the composite moves to Level 3 and these enon.
material cannot be resolved.
7.4.5 Fire and excessive heat damage
Excessive heating (e.g. resulting from the cylinder not being properly located in relation to a vehicle
exhaust system or being involved in a fire) can cause significant damage to the cylinder.
Cylinders showing evidence of fire or excessive heat exposure (not necessarily sooting) are defined as
having Level 3 damage and are to be rejected, condemned and destroyed.
Fire damage can be evident on exposed cylinder surfaces (e.g. burning, discolouration, darkening,
charring or sooting of the surface, melted or deformed attachments or materials). Sooting might only
be dirt or settled debris in which case it shall be wiped off the cylinder and be considered as Level 1.
12 © ISO 2013 – All rights reserved
For composite cylinders, severe exposure can result in resin removal and loose fibres. Other indications
of heat or fire exposure include burning; charring; discolouration of the coating, label or cylinder; and
evidence of connection distortion, such as melted or deformed attachments or installation materials.
7.4.6 Chemical attack
The cylinder shall be examined for evidence of chemical attack. Chemical damage can appear in the
form of an alteration to the cylinder surface (e.g. corrosion, discolouration, etching, pitting, blistering
and swelling). For composites, chemical damage can also include softening, stress corrosion cracks and
resin loss. In extreme cases, the composite can exhibit fractures and broken or loose fibres.
Minor discolouration and no material loss are defined as Level 1 damage and are considered acceptable,
provided that
a) the chemical to which the cylinder has been exposed is known,
b) the chemical has been totally removed from the cylinder surface,
c) the cylinder surface has been cleaned, and
d) the cylinder manufacturer’s recommendations have been followed.
Any evidence of blistering, swelling, softening, resin removal and broken or loose fibres in the composite
attributable to chemical attack is defined as Level 3 damage.
CNG-1 cylinders and the metallic areas of other cylinder types exhibiting signs of chemical attack (e.g.
pitting, corrosion and/or oxidation) shall be evaluated in accordance with the requirements of Table 1.
The materials used in the cylinder are resistant to chemical agents encountered in the normal fuel
cylinder environment. The cylinder, however, shall be maintained in a clean state and shall not be allowed
to have prolonged exposure to moisture, automotive fluids, cargo chemicals or corrosive agents.
7.4.7 Weathering
The cylinder can exhibit degradation of the external surface/coating after prolonged exposure to
sunlight and weather. This can result in discolouration and/or potential deterioration of the coating
on exposed surfaces. This condition is defined as Level 1 damage or Level 2 damage, provided that
there is no evidence of surface metal corrosion or loose or broken fibres. After completion of the
inspection process, the affected surface with Level 2 damage should be repaired by application
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.
Loading comments...