ISO/FDIS 11114-2

Gas cylinders -- Compatibility of cylinder and valve materials with gas contents

Bouteilles à gaz -- Compatibilité des matériaux des bouteilles et des robinets avec les contenus gazeux

General Information

• Status: Published
• ICS: 23.020.35 - Gas cylinders
• Technical Committee: ISO/TC 58 - Gas cylinders
• Drafting Committee: ISO/TC 58/WG 7 - Compatibility between gases and materials
• Current Stage: 5020 - FDIS ballot initiated: 2 months. Proof sent to secretariat
• Start Date: 29-Jul-2021
• Completion Date: 29-Jul-2021

RELATIONS

• Revised: ISO 11114-2:2013 - Gas cylinders -- Compatibility of cylinder and valve materials with gas contents
• Effective Date: 23-Apr-2020

Standards Content (sample)

FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 11114-2
ISO/TC 58
Gas cylinders — Compatibility of
Secretariat: BSI
cylinder and valve materials with gas
Voting begins on:
2021-07-29 contents —
Voting terminates on:
Part 2:
2021-09-23
Non-metallic materials
Bouteilles à gaz — Compatibilité des matériaux des bouteilles et des
robinets avec les contenus gazeux —
Partie 2: Matériaux non métalliques
ISO/CEN PARALLEL PROCESSING
RECIPIENTS OF THIS DRAFT ARE INVITED TO
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/FDIS 11114-2:2021(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN-
DARDS TO WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS. ISO 2021
---------------------- Page: 1 ----------------------
ISO/FDIS 11114-2:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/FDIS 11114-2:2021(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Materials ....................................................................................................................................................................................................................... 2

4.1 General ........................................................................................................................................................................................................... 2

4.2 Type of materials................................................................................................................................................................................... 2

5 General consideration .................................................................................................................................................................................... 3

6 Specific considerations .................................................................................................................................................................................. 4

6.1 General ........................................................................................................................................................................................................... 4

6.2 Non-compatibility risks ................................................................................................................................................................... 4

6.2.1 Violent reaction (oxidation/burning) (F)................................................................................................... 4

6.2.2 Mass loss (W) ...................................................................................................................................................................... 6

6.2.3 Swelling of material (S) .............................................................................................................................................. 6

6.2.4 Change in mechanical properties (M) ........................................................................................................... 6

6.2.5 Other compatibility considerations ................................................................................................................. 6

7 Compatibility data .............................................................................................................................................................................................. 7

7.1 Table of compatibility ....................................................................................................................................................................... 7

7.2 Symbols and abbreviated terms............................................................................................................................................... 8

7.2.1 Symbols for compatibility ........................................................................................................................................ 8

7.2.2 Abbreviated terms for materials ........................................................................................................................ 8

7.2.3 Symbols for compatibility risks .......................................................................................................................... 9

7.2.4 Examples ................................................................................................................................................................................. 9

7.2.5 Tables 1 and 2 ..................................................................................................................................................................10

Bibliography .............................................................................................................................................................................................................................19

© ISO 2021 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO/FDIS 11114-2:2021(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.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/

iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 58, Gas cylinders, in collaboration with

the European Committee for Standardization (CEN) Technical Committee CEN/TC 23, Transportable gas

cylinders, in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna

Agreement).

This third edition cancels and replaces the second edition (ISO 11114-2:2013), which has been

technically revised. The main changes compared with the previous edition are as follows:

— new materials were added in Table 1;
— Table 2, dedicated to the compatibility for liners, was added.
A list of all parts in the ISO 11114 series can be found on the ISO website.

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.
iv © ISO 2021 – All rights reserved
---------------------- Page: 4 ----------------------
ISO/FDIS 11114-2:2021(E)
Introduction

This document provides guidance on the compatibility of non-metallic materials used for gas cylinders

and gas cylinder valves with the gas contents of the cylinder. Compatibility of metallic materials is

covered in ISO 11114-1.

Non-metallic materials are very often used for the construction of gas cylinder valves as seals,

e.g. O-ring, gland packing, seats or as lubrication products to avoid friction. They are also commonly

used to ensure sealing of the valve/cylinder connection. For gas cylinders, they are sometimes used as

an internal coating or as a liner for composite materials.

Non-metallic materials not in contact with the gas are not covered by this document.

This document is based on current international experience and knowledge. Some data are derived

from experience involving a mixture of the gas concerned with a dilutant, where no data for single

component gases were available.
[7]

This document has been written so that it is suitable to be referenced in the UN Model Regulations .

© ISO 2021 – All rights reserved v
---------------------- Page: 5 ----------------------
FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 11114-2:2021(E)
Gas cylinders — Compatibility of cylinder and valve
materials with gas contents —
Part 2:
Non-metallic materials
1 Scope

This document gives guidance on the selection and evaluation of compatibility between non-metallic

materials for gas cylinders and valves and the gas contents. It is also applicable to tubes, pressure

drums and bundles of cylinders.

This document covers composite and laminated materials used for gas cylinders. It does not include

ceramics, glasses and adhesives.

This document considers the influence of the gas in changing the material and mechanical properties

(e.g. chemical reaction or change in physical state). The basic properties of the materials, such as

mechanical properties required for design purposes (normally available from the materials supplier),

are not considered. Other aspects, such as quality of delivered gas, are not considered.

The compatibility data given are related to single component gases but can be applicable to gas

mixtures.
This document does not apply to cryogenic fluids (this is covered in ISO 21010).
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 10286, Gas cylinders — Vocabulary
ISO 10297, Gas cylinders — Cylinder valves — Specification and type testing

ISO 11114-3, Gas cylinders — Compatibility of cylinder and valve materials with gas contents — Part 3:

Autogenous ignition test for non-metallic materials in oxygen atmosphere
ISO 15001, Anaesthetic and respiratory equipment — Compatibility with oxygen
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 terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
© ISO 2021 – All rights reserved 1
---------------------- Page: 6 ----------------------
ISO/FDIS 11114-2:2021(E)
3.1
competent person

person who has the necessary technical knowledge, qualification, experience and authority to assess

and approve materials for use with gases and to define any special conditions of use that are necessary

[SOURCE: ISO 11114-1:2020, 3.1, modified — "qualification" has been added to the definition.]

3.2
acceptable

satisfactory material/gas combination, under normal conditions of use, provided that any indicated

non-compatibility risks are taken into account
Note 1 to entry: Normal conditions of use are defined in Clause 5.
Note 2 to entry: Non-compatibility risks are provided in Table 1.
3.3
not acceptable
unsafe material/single gas combination, under normal conditions of use
Note 1 to entry: For gas mixtures, special conditions can apply.
Note 2 to entry: Normal conditions of use are defined in Clause 5.
3.4
dynamic sealing

non-metallic material used, in normal operation, to provide a pressure seal between two surfaces that

have relative motion to each other
4 Materials
4.1 General

Non-metallic materials shall be suitable for the intended service. They are suitable if their compatibility

is stated as acceptable in Table 1, and Table 2 for the cylinder liners, or the necessary properties have

been proved by tests or long and safe experience to the satisfaction of a competent person.

NOTE When plastic liner materials are used, it is necessary to use metallic bosses. For compatibility of

metallic bosses, see ISO 11114-1.

If coated materials are used, the suitability of the combination shall be assessed and approved if all

technical aspects have been considered and validated by a competent person. These technical aspects

include, but are not limited to, compatibility of the coating material with the intended gas, durability of

the coating during all its intended use and gas permeability through it.
4.2 Type of materials

The most commonly used non-metallic materials for gas cylinders and cylinder valves can be grouped

as follows:
— plastics;
— elastomers;
— fluid lubricants.
NOTE 1 Solid lubricants are sometimes used, e.g. MoS .
2 © ISO 2021 – All rights reserved
---------------------- Page: 7 ----------------------
ISO/FDIS 11114-2:2021(E)
Materials considered in this document are as follows:
a) plastics:
— polytetrafluoroethylene (PTFE);
— polychlorotrifluoroethylene (PCTFE);
— polyvinylidenefluoride (PVDF);
— polyamide (PA);
— polypropylene (PP);
— polyethylene (PE);

NOTE 2 PE covers grades such as HDPE (high density polyethylene), MDPE (medium density

polyethylene), LDPE (low density polyethylene), PEX (cross-linked), etc.
— polyethylene terephthalate (PET);
— polyetheretherketone (PEEK);
— polypropylene sulfide (PPS);
— polyvinyl chloride (PVC);
— polyimide (PI);
— polyoxymethylene (POM);
b) elastomers (rubber):
— butyl rubber (IIR);
— nitrile butadiene rubber (NBR);
— chloroprene rubber (CR);
— fluorocarbon rubber (FKM);
— methyl-vinyl-silicone rubber (VMQ);
— ethylene propylene diene rubber (EPDM);
— polyacrylate rubber (ACM);
— polyurethane rubber (PUR);
— epichlorohydrin rubber (ECO);
— methyl-fluoro-silicone rubber (FVMQ);
c) fluid lubricants:
— hydrocarbon (HC);
— fluorocarbon (FC).
5 General consideration

It is important to note that these materials are generic types. Within each material type there are

variations in the properties of the materials due to polymer differences and formulations used by

manufacturers to modify physical and chemical properties of the material. The user of the material

© ISO 2021 – All rights reserved 3
---------------------- Page: 8 ----------------------
ISO/FDIS 11114-2:2021(E)

should therefore consult the manufacturer and, if necessary, carry out tests before using the material

(e.g. for critical services such as oxygen and other oxidizing gases).

Lubricants are often used in valves to reduce friction and wear in the moving parts. For valves used for

oxidizing gases or for gases supporting combustion, if lubrication is required, it shall be ensured that

the lubricant is compatible for the intended application when the lubricated components are in contact

with the oxidizing gas or the gas supporting combustion.

Where the lubricant is listed as “not acceptable” in Table 1 for reasons other than violent reaction

(oxidation/burning) (F), it may be used safely and usually satisfactorily in applications which do not

involve contact in normal operation with the gas. An example of such an application is the lubrication of

the valve actuating mechanism not in contact with the gas.

Where the lubricant is listed as “not acceptable” for the reason of violent reaction (oxidation/burning)

(F), it should not be used in any part of the system that can be contacted by the gas, even under abnormal

conditions such as in the event of a failure of the gas sealing system. If there is a risk of violent reaction,

appropriate safety and suitability tests shall be carried out for the lubricant application before it is used

either on the lubricant itself, as specified in ISO 11114-3, or on the lubricated equipment in which it is

intended to be used, as specified in ISO 10297.

The properties of plastics and elastomers including compatibility are dependent on temperature. Low

temperature can cause hardening and the possibility of embrittlement, whereas high temperature

can cause softening and the possibility of material flow. Users of such materials shall check to ensure

their suitability over the entire operating temperature range specified by the cylinder and valve

manufacturing standards.

Some materials become brittle at low temperatures, especially at temperatures at the lower end of

the normal operating range (e.g. fluorocarbon rubber). Temperatures in the refrigerant or cryogenic

ranges affect many materials and caution shall be exercised at temperatures below −50 ° C. This risk

shall be considered in particular when transfilling by thermal siphoning at low temperature or similar

procedures, or for cylinders regularly filled at low temperatures (e.g. carbon dioxide).

6 Specific considerations
6.1 General

The compatibility of gases with non-metallic materials is affected by chemical reactions and physical

influences, which can be classified as defined in 6.2.
6.2 Non-compatibility risks
6.2.1 Violent reaction (oxidation/burning) (F)
6.2.1.1 Principle

Historically the majority of serious accidents from rapid oxidation or violent combustion have occurred

with oxidizing gas supporting combustion at high pressure. Thorough investigation of all materials and

factors should be conducted with great care and all data should be considered before designing or using

equipment to handle oxidizing gases or gases supporting combustion.

Compatibility depends mainly on the operating conditions (pressure, temperature, gas velocity,

particles, equipment design and application). The risk shall particularly be considered with gases such

as oxygen, fluorine, chlorine and nitrogen trifluoride. Most of the non-metallic materials can be ignited

relatively easily when in contact with oxidizing gases (see ISO 10156) and even when in contact with

gases not classified as oxidizing but still supporting combustion.

The selection of a material for use with oxygen or an oxygen enriched atmosphere, or both, is primarily

a matter of understanding the circumstances that cause the material to react with oxygen. Most

4 © ISO 2021 – All rights reserved
---------------------- Page: 9 ----------------------
ISO/FDIS 11114-2:2021(E)

materials in contact with oxygen will not ignite without a source of ignition energy (friction, heat of

compression, particle impacts, etc.). When an energy input rate, as converted to heat, is greater than

the rate of heat dissipation, and the resulting heat increase is continued for sufficient time, ignition and

combustion will occur.
Thus, two general factors shall be considered:

a) the materials compatibility properties (ease of ignition and energy of combustion);

b) the different energy sources that will produce a sufficient increase in the temperature of the

material.

These general factors should be viewed in the context of the entire system design so that the following

specific factors will assume the proper relative significance:

— the properties of the materials, which include the factors affecting ease of ignition and the conditions

affecting potential resulting damage (heat of reaction);

— the operating conditions [e.g. pressure, temperature, oxygen or oxidizing gas concentrations in a

gas mixture, or both, influence of dilutant (e.g. helium), surface contamination];

— the potential sources of ignition (e.g. friction, heat of compression, heat from mass impact, heat from

particle impact, static electricity, electrical arc, resonance, internal flexing);

— the possible consequence (e.g. effects on the surroundings such as propagation of fire);

— the additional factors (e.g. performance requirements, prior experience, availability).

In conclusion, the evaluation of compatibility of non-metallic materials is more critical than that of

metallic materials, which generally perform well when in contact with oxygen.
6.2.1.2 Specifications for oxidizing gases

In accordance with 6.2.1.1, it is not possible to make a simple statement concerning the compatibility

of non-metallic materials with oxidizing gases such as oxygen, chlorine, nitric oxide, nitrous oxide,

nitrogen dioxide, nitrogen trifluoride, etc. (see ISO 10156).

For fluorine, which is the most oxidizing gas, all non-metallic materials would historically fall into the

classification “not acceptable”.

For fluorine mixtures, the gases industry now has evidence of successful testing and safe history of use

of PTFE and PCTFE under controlled conditions (e.g. low concentration and low pressure). Therefore,

following an assessment and authorization by a competent person, these materials are acceptable in

similar conditions. Oxygen and other oxidizing gases can react violently when tested with all non-

metallic materials listed in 4.2 a), 4.2 b) and 4.2 c). Some materials such as PTFE and FKM are more

resistant to ignition than other plastics and elastomers. HC lubricants are normally not acceptable. Under

certain conditions other plastics and elastomers listed can be safely used in oxidizing service without

presenting some of the disadvantages of PTFE, i.e. poor mechanical properties and risk of release of

toxic products for breathing gas applications (see ISO 15001), or FKM, i.e. swelling, poor mechanical

properties at low temperature, risk of release of toxic products in breathing gas applications, etc.

Consequently, non-metallic materials may only be used if it has been proven by tests (or long and safe

service experience), taking into account all the operating conditions and especially the design of the

equipment, that their use is safe. ISO 11114-3 and ISO 21010 give test methods for polymeric materials

and fluid lubricants that result in conservative value. Some non-metallic materials can be safely used

at higher pressure if they are satisfactorily tested in the final design configuration, e.g. in gas cylinder

valves and regulators. Cylinder valves intended to be used for oxidizing gas service shall be tested in

accordance with ISO 10297.
© ISO 2021 – All rights reserved 5
---------------------- Page: 10 ----------------------
ISO/FDIS 11114-2:2021(E)
6.2.2 Mass loss (W)
6.2.2.1 Extraction

Solvent extraction of plasticizers from elastomers can cause shrinkage, especially in highly plasticized

products.

Some solvents, e.g. acetone or DMF (dimethylformamide) used for dissolved gases such as acetylene,

can damage non-metallic materials.
Liquefied gases can act as solvents.
6.2.2.2 Chemical attack

Some non-metallic materials can be chemically attacked by gases, e.g. the chemical attack of silicone

elastomers by ammonia.
NOTE This attack can sometimes lead to the complete destruction of the material.
6.2.3 Swelling of material (S)

Elastomers and plastics can be subject to swelling due to gas (or liquid) absorption. This can lead to an

unacceptable increase of dimensions (especially for O-rings) or the cracking due to sudden out-gassing

when the partial pressure is decreased, e.g. carbon dioxide with fluorocarbon.

Initial swelling can be masked by subsequent extraction of plasticizers and fillers while in service. Other

important effects such as changes in mechanical strength and hardness should also be considered.

Differences in the compounding, formulation and curing of a given elastomer can cause significant

differences in the swelling of the material in service.

Regardless of the above compatibility evaluation, the design configuration (e.g. static or dynamic

sealing) shall be taken into account before deciding to use elastomers or plastics. In this document, a

swelling of more than approximately 15 % in normal service conditions is marked N (in particular not

acceptable for dynamic sealing); a swelling less than this is marked A (acceptable) provided other risks

are also acceptable.

NOTE There is also a risk of cross bonding between sulfur vulcanised rubbers and copper alloys.

6.2.4 Change in mechanical properties (M)

Gases can lead to an unacceptable change of mechanical properties in some non-metallic materials.

This can result, for example, in an increase in hardness or a decrease in elasticity (i.e. an increase in

compression set). ISO 1817 gives testing methods to check the influence of the gas on the mechanical

properties.
6.2.5 Other compatibility considerations
6.2.5.1 Impurities in the gas (I)

Some gases contain typical impurities which it is possible will not be compatible with the intended

materials (e.g. acetone in acetylene, hydrogen sulfide in methane).
6.2.5.2 Contamination of the material (C)

Some materials become contaminated in toxic gas use by the toxic gas and become hazardous

themselves (e.g. during maintenance of equipment).
6 © ISO 2021 – All rights reserved
---------------------- Page: 11 ----------------------
ISO/FDIS 11114-2:2021(E)
6.2.5.3 Release of dangerous products (D)

Many materials when subjected to extreme conditions (such as elevated temperature) can release

dangerous products (e.g. toxic products). This risk shall be considered in particular for breathing gases

as specified in ISO 15001.
6.2.5.4 Ageing (G)

Ageing is a gradual change in the mechanical and physical properties of the material due to the

environment in which it is used or stored (e.g. exposure to UV light). Many elastomer and plastic

materials are particularly subject to ageing; some gases like oxygen and in general exposure to high

temperatures can accelerate the ageing process, leading to degradation such as cracking, brittleness, etc.

6.2.5.5 Permeation (P)
Permeation is a slow process by which gas passes through materials.

The permeation of some gases (e.g. helium, hydrogen, carbon dioxide) through non-metallic materials

can be significant. For a given material, the permeation rate mainly depends on the temperature,

pressure, thickness and surface area of the material in contact with the gas. The molecular radius

of the gas and the specific formulation of plasticizers and other additives can cause a wide range of

permeation rates for a particular type of plastic or elastomer.

This risk shall be considered for effects to the surroundings (e.g. toxicity, fire potential).

Permeation through the liner can lead to gas pressure between the liner and the composite, thus

potentially causing liner collapse and/or blistering.
7 Compatibility data
7.1 Table of compatibility

Table 1 lists the gases in alphabetic order with their UN number. The compatibility data are given using

the symbols and abbreviated terms defined in 7.2.1 and 7.2.2. When a gas/material combination is not

acceptable, the main reason is given, using the appropriate abbreviation for the non-compatibility risk

(see 6.2). The abbreviated terms are also sometimes used for acceptable combinations to show a limited

risk.

If no UN number is listed in Table 1 for a gas (or a liquid), this means that this gas has no official UN

number but it can be transported using a generic NOS (not otherwise specified) number (e.g. compressed

gas, flammable, NOS, UN 1954).
Compatibility evaluations are based on the following documents:
— literature data;
— operational experiences;
— laboratory tests.

The material resistance to gases can be estimated by simple immersion tests in the respective gas with

approximately the sam
...