ISO 4437-5:2024

International
Standard
ISO 4437-5
Second edition
Plastics piping systems for
2024-02
the supply of gaseous fuels —
Polyethylene (PE) —
Part 5:
Fitness for purpose of the system
Systèmes de canalisations en plastique pour la distribution de
combustibles gazeux — Polyéthylène (PE) —
Partie 5: Aptitude à l'emploi du système
Reference number
© ISO 2024
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Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
3.1 Terms related to geometry .2
3.2 Terms related to material .3
3.3 Terms related to material characteristics .3
3.4 Terms related to service conditions .4
3.5 Terms related to joints .4
4 Symbols and abbreviated terms. 5
4.1 Symbols .5
4.2 Abbreviated terms .6
5 Fitness for purpose of the system . 6
5.1 Method of preparation of assemblies for testing .6
5.1.1 General .6
5.1.2 Butt fusion joints .6
5.1.3 Electrofusion joints .7
5.1.4 Mechanical joints .7
5.1.5 Socket fusion joints .7
5.2 Requirements for fitness for purpose .7
5.2.1 General .7
5.2.2 Fitness for purpose of the system for butt fusion joints .7
5.2.3 Fitness for purpose of the system for electrofusion joints .8
5.2.4 Fitness for purpose of the system for mechanical joints .9
5.3 Conditioning.10
5.4 Requirements .10
5.5 Testing of pipe with coextruded layers .11
6 Design coefficient .11
Annex A (informative) Derating coefficients for operating temperatures .12
Annex B (normative) Rapid crack propagation resistance of pipe at operating temperature
less than 0 °C . .13
Bibliography . 14

iii
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
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 138, Plastics pipes, fittings and valves for the
transport of fluids, Subcommittee SC 4, Plastics pipes and fittings for the supply of gaseous fuels.
This second edition cancels and replaces the first edition (ISO 4437-5:2014), which has been technically
revised.
The main changes are as follows:
— PE 100-RC type materials with enhanced resistance to slow crack growth (SCG) have been added;
— test methods have been updated and new methods have been added for PE 100-RC materials.
A list of all parts in the ISO 4437 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
Introduction
The ISO 4437 series specifies the requirements for a piping system and its components made from
polyethylene (PE) compounds, which is intended to be used for the supply of gaseous fuels.
This document covers the characteristics of fitness for purpose of the system.
Requirements and test methods for materials and components of the piping system are specified in
ISO 4437-1, ISO 4437-2, ISO 4437-3 and ISO 4437-4.
Recommended practice for design, handling and installation is given in ISO/TS 10839.

v
International Standard ISO 4437-5:2024(en)
Plastics piping systems for the supply of gaseous fuels —
Polyethylene (PE) —
Part 5:
Fitness for purpose of the system
1 Scope
This document specifies the requirements of fitness for purpose of assembled polyethylene (PE) piping
systems in the field of the supply of gaseous fuels.
It specifies the requirements for electrofusion, socket fusion, butt fusion and mechanical joints.
It specifies the method of preparation of test piece joints and the tests to be carried out on these joints for
assessing the fitness for purpose of the system under normal and extreme conditions.
It specifies the test parameters for the test methods referred to in this document.
This document is intended to be used only by the product manufacturer and test laboratories to assess the
performance of components in accordance with ISO 4437-2, ISO 4437-3 and ISO 4437-4 when joined together
under normal and extreme conditions in accordance with this document. It is not intended for on-site testing
of pipe systems.
In conjunction with ISO 4437-1, ISO 4437-2, ISO 4437-3 and ISO 4437-4, this document is applicable to PE
pipes, fittings and valves, their joints, and joints with components of PE and other materials intended to be
used under the following conditions:
1)
a) a maximum operating pressure (MOP), up to and including 10 bar , at a reference temperature of 20 °C
for design purposes;
b) an operating temperature between −20 °C and 40 °C.
For operating temperatures between 20 °C and 40 °C, derating coefficients are defined in Annex A.
The ISO 4437 series covers a range of MOPs and gives requirements concerning colours.
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 1167-1:2006, Thermoplastics pipes, fittings and assemblies for the conveyance of fluids — Determination of
the resistance to internal pressure — Part 1: General method
ISO 1167-2, Thermoplastics pipes, fittings and assemblies for the conveyance of fluids — Determination of the
resistance to internal pressure — Part 2: Preparation of pipe test pieces
ISO 1167-4, Thermoplastics pipes, fittings and assemblies for the conveyance of fluids — Determination of the
resistance to internal pressure — Part 4: Preparation of assemblies
ISO 4437-2, Plastics piping systems for the supply of gaseous fuels — Polyethylene (PE) — Part 2: Pipes
5 2
1) 1 bar = 0,1 MPa = 10 Pa; 1 MPa = 1 N/mm .

ISO 4437-3, Plastics piping systems for the supply of gaseous fuels — Polyethylene (PE) — Part 3: Fittings
ISO 4437-4, Plastics piping systems for the supply of gaseous fuels — Polyethylene (PE) — Part 4: Valves
ISO 11413:2019, Plastics pipes and fittings — Preparation of test piece assemblies between a polyethylene (PE)
pipe and an electrofusion fitting
ISO 11414:2009, Plastics pipes and fittings — Preparation of polyethylene (PE) pipe/pipe or pipe/fitting test
piece assemblies by butt fusion
ISO 13477, Thermoplastics pipes for the conveyance of fluids — Determination of resistance to rapid crack
propagation (RCP) — Small-scale steady-state test (S4 test)
ISO 13478, Thermoplastics pipes for the conveyance of fluids — Determination of resistance to rapid crack
propagation (RCP) — Full-scale test (FST)
ISO 13953, Polyethylene (PE) pipes and fittings — Determination of the tensile strength and failure mode of test
pieces from a butt-fused joint
ISO 13954, Plastics pipes and fittings — Peel decohesion test for polyethylene (PE) electrofusion assemblies of
nominal outside diameter greater than or equal to 90 mm
ISO 13955, Plastics pipes and fittings — Crushing decohesion test for polyethylene (PE) electrofusion assemblies
ISO 13956, Plastics pipes and fittings — Decohesion test of polyethylene (PE) saddle fusion joints — Evaluation
of ductility of fusion joint interface by tear test
ISO 17885, Plastics piping systems — Mechanical fittings for pressure piping systems — Specifications
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1 Terms related to geometry
3.1.1
nominal size
DN/OD
numerical designation of the size of a component related to the outside diameter
Note 1 to entry: It is a convenient round number approximately equal to the manufacturing dimension in millimetres
(mm). It is not applicable to components designated by thread size.
3.1.2
nominal outside diameter
d
n
specified outside diameter assigned to a nominal size (3.1.1)
Note 1 to entry: Nominal outside diameter is expressed in millimetres (mm).

3.1.3
nominal wall thickness
e
n
numerical designation of the wall thickness of a component, which is a convenient round number,
approximately equal to the manufacturing dimension in millimetres (mm)
Note 1 to entry: For thermoplastics components conforming to the ISO 4437 series, the value of the nominal wall
thickness, e , is identical to the specified minimum wall thickness at any point (3.1.5).
n
3.1.4
wall thickness at any point
e
wall thickness at any point around the circumference of a component rounded to the next greater 0,1 mm
Note 1 to entry: The symbol for the wall thickness of a fitting and valve body at any point is E.
3.1.5
minimum wall thickness at any point
e
min
minimum value for the wall thickness at any point (3.1.4) around the circumference of a component
3.1.6
standard dimension ratio
SDR
numerical designation of a pipe series (3.1.7), which is a convenient round number, approximately equal to
the dimension ratio of the nominal outside diameter (3.1.2) and the nominal wall thickness (3.1.3)
3.1.7
pipe series
S
number for pipe designation
Note 1 to entry: The relationship between the pipe series, S, and the standard dimension ratio (SDR) (3.1.6) is given by
the following formula, as specified in ISO 4065.
SDR−1
S =
3.2 Terms related to material
3.2.1
compound
homogenous extruded mixture of base polymer (3.2.2) (polyethylene) and additives (i.e. anti-oxidants,
pigments, carbon black, UV-stabilizers and others) at a dosage level necessary for the processing and use of
components
3.2.2
base polymer
polymer produced by the material supplier for the manufacture of the compound (3.2.1)
3.3 Terms related to material characteristics
3.3.1
lower confidence limit of the predicted hydrostatic strength
σ
LPL
quantity, with the dimensions of stress, which represents the 97,5 % lower confidence limit of the predicted
hydrostatic strength at temperature θ and time t
Note 1 to entry: It is expressed in megapascals (MPa).

3.3.2
minimum required strength
MRS
value of the lower confidence limit of the predicted hydrostatic strength (3.3.1) at 20 °C and 50 years, rounded
down to the next smaller value of the R10 series or R20 series
Note 1 to entry: Only compounds (3.2.1) with an MRS of 8 MPa or 10 MPa are specified in this document.
Note 2 to entry: The R10 series and the R20 series conform to ISO 3.
Note 3 to entry: It is expressed in megapascals (MPa).
[SOURCE: ISO 12162:2009, 3.3, modified — Note 1 to entry has been removed and replaced with new Notes
1 to 3 to entry.]
3.3.3
design coefficient
C
coefficient with a value greater than 1 which takes into consideration service conditions as well as properties
of the components of a piping system other than those represented in the lower confidence limit
3.4 Terms related to service conditions
3.4.1
gaseous fuel
fuel which is in gaseous state at a temperature of 15 °C at atmospheric pressure
Note 1 to entry: There are proposals to inject gases from renewable sources in natural gas networks, e.g. hydrogen
(H ). This is the subject of ongoing research.
3.4.2
maximum operating pressure
MOP
maximum effective pressure of the fluid in the piping system which is allowed in continuous use
Note 1 to entry: It is expressed in bar. It takes into account the physical and the mechanical characteristics of the
components of a piping system. It is calculated using the following formula:
20×MRS
MOP =
C ×()SDR − 1
Note 2 to entry: Research on long-term performance prediction of polyethylene gas distribution systems shows a
possible service life of at least 100 years; see References [7], [8] and [9].
3.4.3
reference temperature
temperature for which the piping system is designed
Note 1 to entry: It is used as the base for further calculation when designing a piping system or parts of a piping
system for operating temp
...