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
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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 19078:2013(E)
©
ISO 2013
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ISO 19078:2013(E)
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ISO 19078:2013(E)
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
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ISO 19078:2013(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International
Standards adopted by the technical committees are circulated to the member bodies for voting.
Publication as an International Standard requires approval by at least 75 % of the member bodies
casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 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.
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ISO 19078:2013(E)
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.
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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.
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ISO 19078:2013(E)
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
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ISO 19078:2013(E)
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
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ISO 19078:2013(E)
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.
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ISO 19078:2013(E)
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
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ISO 19078:2013(E)
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.
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ISO 19078:2013(E)
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.
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ISO 19078:2013(E)
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
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