ISO 4437-1:2024

International
Standard
ISO 4437-1
Second edition
Plastics piping systems for
2024-02
the supply of gaseous fuels —
Polyethylene (PE) —
Part 1:
General
Systèmes de canalisations en plastique pour la distribution de
combustibles gazeux — Polyéthylène (PE) —
Partie 1: Généralités
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 . 3
3.1 Terms related to geometry .3
3.2 Terms related to material .4
3.3 Terms related to material characteristics .4
3.4 Terms related to service conditions .5
3.5 Terms related to joints .6
4 Symbols and abbreviated terms. 6
4.1 Symbols .6
4.2 Abbreviated terms .7
5 Material. 8
5.1 Material of the components .8
5.2 Compound .8
5.2.1 Additives and pigments .8
5.2.2 Colour .8
5.2.3 Characteristics .8
5.3 Fusion compatibility . 12
5.4 Classification and designation . . 13
5.5 Design coefficient and design stress . 13
5.6 Change of compound formulation . 13
Annex A (informative) Additional information related to the installation of PE 100-RC systems . 14
Annex B (informative) LPG and manufactured gas .16
Annex C (informative) Resistance to rapid crack propagation (RCP) . 17
Bibliography . 19

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,
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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 4437-1:2014), 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;
— Annex A has been added, discussing the performance of PE 100-RC type materials with enhanced
resistance to slow crack growth (SCG) and giving additional information for installation techniques;
— test methods have been updated and new test 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 materials and the general aspects of the plastics piping system.
Requirements and test methods for components of the piping system are specified in ISO 4437-2, ISO 4437-3
and ISO 4437-4.
Characteristics for fitness for purpose of the system are covered in ISO 4437-5.
Recommended practice for design, handling and installation is given in ISO/TS 10839.

v
International Standard ISO 4437-1:2024(en)
Plastics piping systems for the supply of gaseous fuels —
Polyethylene (PE) —
Part 1:
General
1 Scope
This document specifies materials and the general aspects of polyethylene (PE) piping systems in the field of
the supply of gaseous fuels.
It also specifies the test parameters for the test methods referred to in this document.
In conjunction with ISO 4437-2, ISO 4437-3, ISO 4437-4 and ISO 4437-5, 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 ISO 4437-5.
The ISO 4437 series covers a range of MOPs and gives requirements concerning colours.
It is the responsibility of the purchaser or specifier to make the appropriate selections from these aspects,
taking into account their particular requirements and any relevant national regulations and installation
practices or codes.
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 472, Plastics — Vocabulary
ISO 1043-1, Plastics — Symbols and abbreviated terms — Part 1: Basic polymers and their special characteristics
ISO 1133-1, Plastics — Determination of the melt mass-flow rate (MFR) and melt volume-flow rate (MVR) of
thermoplastics — Part 1: Standard method
ISO 1167-1, 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 1183-1, Plastics — Methods for determining the density of non-cellular plastics — Part 1: Immersion method,
liquid pycnometer method and titration method
5 2
1) 1 bar = 0,1 MPa = 10 Pa; 1 MPa = 1 N/mm .

ISO 1183-2, Plastics — Methods for determining the density of non-cellular plastics — Part 2: Density gradient
column method
ISO 4437-2:2024, Plastics piping systems for the supply of gaseous fuels — Polyethylene (PE) — Part 2: Pipes
ISO 4437-3:2024, 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 6259-1, Thermoplastics pipes — Determination of tensile properties — Part 1: General test method
ISO 6259-3, Thermoplastics pipes — Determination of tensile properties — Part 3: Polyolefin pipes
ISO 6964, Polyolefin pipes and fittings — Determination of carbon black content by calcination and pyrolysis —
Test method
ISO 9080, Plastics piping and ducting systems — Determination of the long-term hydrostatic strength of
thermoplastics materials in pipe form by extrapolation
ISO 11357-6, Plastics — Differential scanning calorimetry (DSC) — Part 6: Determination of oxidation induction
time (isothermal OIT) and oxidation induction temperature (dynamic OIT)
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 12162, Thermoplastics materials for pipes and fittings for pressure applications — Classification, designation
and design coefficient
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 13479:2022, Polyolefin pipes for the conveyance of fluids — Determination of resistance to crack propagation
— Test method for slow crack growth on notched pipes
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 15512, Plastics — Determination of water content
ISO 16770, Plastics — Determination of environmental stress cracking (ESC) of polyethylene — Full-notch creep
test (FNCT)
ISO 16871, Plastics piping and ducting systems — Plastics pipes and fittings — Method for exposure to direct
(natural) weathering
ISO 18488, Polyethylene (PE) materials for piping systems — Determination of Strain Hardening Modulus in
relation to slow crack growth — Test method
ISO 18489, Polyethylene (PE) materials for piping systems — Determination of resistance to slow crack growth
under cyclic loading — Cracked Round Bar test method
ISO 18553, Method for the assessment of the degree of pigment or carbon black dispersion in polyolefin pipes,
fittings and compounds
EN 12099, Plastics piping systems — Polyethylene piping materials and components — Determination of volatile
content
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 472, ISO 1043-1 and the following
apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1 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, that 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 the 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 of
the predicted hydrostatic strength (3.3.1)

3.3.4
design stress
σ
s
allowable stress for a given application at 20 °C that is derived from the minimum required strength, MRS
(3.3.2), by dividing it by the design coefficient, C (3.3.3)
Note 1 to entry: This is demonstrated in the following formula:
MRS
σ =
s
C
Note 2 to entry: It is expressed in megapascals (MPa).
3.3.5
melt mass-flow rate
MFR
value relating to the viscosity of the molten material at a specified temperature and load
Note 1 to entry: It is expressed in grams per 10 minutes (g/10 min).
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 [14], [15] and [16].
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 temperatures different from the reference temperature (see ISO 4437-5).
3.4.4
manufactured gas
synthetic gas
gas which has been treated and can contain components that are not typical of natural gas
Note 1 to entry: Manufactured (synthetic) gases can contain substantial amounts of chemical species that are not
typical of natural gases or common species found in atypical proportions as in the case of wet and sour gases.
Note 2 to entry: Manufactured gases fall into two distinct categories, as follows:
a) those that are intended as synthetic or substitute natural gases, and that closely match true natural gases in both
composition and properties;
b) those that, whether or not intended to replace or enhance natural gas in service, do not closely match natural
gases in composition.
Case b) includes gases such as town gas, coke oven gas (undiluted), and LPG/air mixtures. None of which is
compositionally similar to a true natural gas (even though, in the latter case, it can be operationally interchangeable
with natural gas).
[SOURCE: ISO 14532:2014, 2.1.1.4]
3.5 Terms related to joints
3.5.1
butt fusion joint
joint made by heating the planed ends of pipes or spigot end fittings (3.5.6), the surfaces of which are
fused together by holding them against a flat heating plate until the polyethylene material reaches fusion
temperature, removing the heating plate quickly and pushing the two softened ends against one another
3.5.2
fusion compatibility
ability of two similar or dissimilar polyethylene compounds (3.2.1) to be fused together to form a joint
3.5.3
electrofusion joint
joint between a polyethylene electrofusion socket fitting (3.5.4) or electrofusion saddle fitting (3.5.5) and a
pipe or spigot end fitting (3.5.6), made by heating the electrofusion fitting by the Joule effect of the heating
element incorporated at their jointing surfaces, causing the material adjacent to them to melt, and the pipe
and fitting surfaces to fuse
3.5.4
electrofusion socket fitting
polyethylene (PE) fitting which contains one or more integrated heating elements that are capable of
transforming electrical energy into heat to realize a fusion joint with a spigot end or a pipe
3.5.5
electrofusion saddle fitting
polyethylene (PE) fitting which contains one or more integrated heating elements that are capable of
transforming electrical energy into heat to realize a fusion joint onto a pipe
3.5.6
spigot end fitting
polyethylene (PE) fitting where the outside diameter of the spigot end is equal to the nominal outside
diameter (3.1.2) of the corresponding pipe
4 Symbols and abbreviated terms
4.1 Symbols
For the purposes of this document, the following symbols apply.
C design coefficient
d nominal outside diameter
n
E wall thickness (at any point) of a fitting and valve body
e wall thickness (at any point) around the circumference of a component
e minimum wall thickness (at any point)
min
e nominal wall thickness
n
strain hardening modulus
p
p critical pressure
c
p critical pressure obtained in full-scale test
c,full-scale
p critical pressure obtained in S4-test
c,s4
S pipe series
t time
θ temperature
Δσ stress range
σ design stress
s
σ lower confidence limit of the predicted hydrostatic strength
LPL
4.2 Abbreviated terms
For the purposes of this document, the following abbreviated terms apply.
AFNCT accelerated full notch creep test
ANPT accelerated notched pipe test
CRB cracked round bar (test)
DN/OD nominal size
FNCT full notch creep test
LPL lower predicted limit
LPG liquefied petroleum gas
MFR melt mass-flow rate
MOP maximum operating pressure
MRS minimum required strength
NPT notched pipe test
OIT oxidation induction time
PE polyethylene
PLT point load test
RC raised crack resistance
RCP rapid crack propagation
SCG slow crack growth
SDR standard dimension ratio
SHT strain hardening test
5 Material
5.1 Material of the components
The pipes, fittings and valves shall be made of a PE compound conforming to this document.
This document includes materials classified PE 80 and PE 100.
Another type of PE 100, designated PE 100-RC with enhanced resistance to SCG, is also included in this
document; see Annex A for additional information.
The material described in this document is a compound, which shall be supplied in the form of granules,
suitable for the production of pipes conforming to ISO 4437-2, fittings conforming to ISO 4437-3 or valves
conforming to ISO 4437-4.
5.2 Compound
5.2.1 Additives and pigments
The compound shall be made by adding to the PE base polymer only those additives and pigments (e.g. carbon
black) necessary for the manufacture of pipes, fittings and valves conforming to ISO 4437-2, ISO 4437-3 and
ISO 4437-4, as applicable, and for their fusibility, storage and use.
The carbon black used in the production of black compound shall have an average (primary) particle size of
10 nm to 25 nm.
All additives and pigments shall be uniformly dispersed.
5.2.2 Colour
The colour of the compound shall be yellow (PE 80), orange (PE 100 and PE 100-RC) or black (PE 80, PE 100
and PE 100-RC).
5.2.3 Characteristics
5.2.3.1 Characteristics of the compound in the form of granules
The compound in the form of granules used for the manufacture of pipes, fittings and valves shall have
characteristics conforming to the requirements given in Table 1.

Table 1 — Characteristics of the compound in the form of granules
Test parameters
a
Characteristic Requirement Test method
Parameter Value
Compound density ≥ 930 kg/m Test temperature 23 °C ISO 1183-1 or
c
ISO 1183-2
b
Number of test pieces Shall conform
to ISO 1183-1 or
c
ISO 1183-2
d
Oxidation induction time ≥ 20 min Test temperature 210 °C ISO 11357-6
(OIT) (thermal stability)
Test atmosphere Oxygen
Sample mass (15 ± 2) mg
b
Number of test pieces 3
Melt mass-flow rat
...