ISO 4437-3:2024

International
Standard
ISO 4437-3
Second edition
Plastics piping systems for
2024-02
the supply of gaseous fuels —
Polyethylene (PE) —
Part 3:
Fittings
Systèmes de canalisations en plastique pour la distribution de
combustibles gazeux — Polyéthylène (PE) —
Partie 3: Raccords
Reference number
© ISO 2024
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Published in Switzerland
ii
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 2
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 .5
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 .8
5 Material. 9
5.1 PE compound for fittings .9
5.2 Material for non-polyethylene parts .9
5.2.1 General .9
5.2.2 Metal parts .9
5.2.3 Sealing materials .9
5.2.4 Other materials .10
6 General characteristics . 10
6.1 Appearance .10
6.2 Colour .10
6.3 Design .10
6.4 Appearance of factory-made joints .10
6.5 Electrical characteristics for electrofusion fittings .10
7 Geometrical characteristics .11
7.1 Measurement of dimensions .11
7.2 Dimensions of electrofusion socket fittings .11
7.2.1 Diameters and lengths of electrofusion sockets .11
7.2.2 Wall thicknesses . 13
7.2.3 Out-of-roundness of the bore of a fitting (at any point) . 13
7.2.4 Spigots. 13
7.2.5 Other dimensions. 13
7.3 Dimensions of electrofusion saddle fittings . 13
7.4 Dimensions of spigot end fittings .14
7.4.1 Diameters and lengths .14
7.4.2 Wall thickness of the fusion end .16
7.4.3 Wall thickness of the fitting body .16
7.4.4 Other dimensions.16
7.5 Dimensions of socket fusion fittings .16
7.6 Design and dimensions of mechanical fittings .16
7.6.1 General .16
7.6.2 Mechanical fittings with polyethylene spigot ends .17
7.6.3 Mechanical fittings with polyethylene electrofusion sockets .17
7.6.4 Threads .17
8 Mechanical characteristics . 17
8.1 General .17
8.2 Requirements .17
8.3 Modifications of the fitting . 20
8.4 Performance requirements . 20

iii
9 Physical characteristics .21
9.1 Conditioning.21
9.2 Requirements .21
10 Performance requirements . .22
11 Technical information.22
12 Marking . .22
12.1 General . 22
12.2 Minimum required marking of fittings . 23
12.3 Additional marking. 23
12.4 Fusion system recognition . 23
13 Delivery conditions .24
Annex A (normative) Socket fusion fittings .25
Annex B (informative) Examples of typical terminal connections for electrofusion fittings .27
Annex C (normative) Short-term pressure test method .30
Annex D (normative) Tensile test for fitting/pipe assemblies .32
Annex E (informative) Formulae for calculating the equivalent dimensions of non-metric
electrofusion socket fitting series .34
Bibliography .35

iv
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 4437-3:2014), 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;
— the nominal diameter range of the electrofusion socket fittings and spigot end fittings has been increased
to 800 mm;
— the PE 80 20 °C/100 h control point has been changed to 10 MPa with a note to advise that 9 MPa is
applicable if the ISO 9080 data set for a material indicates that a lower value is applicable;
— 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.

v
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 fittings.
Requirements and test methods for materials and components, other than fittings, are specified in
ISO 4437-1, ISO 4437-2 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.

vi
International Standard ISO 4437-3:2024(en)
Plastics piping systems for the supply of gaseous fuels —
Polyethylene (PE) —
Part 3:
Fittings
1 Scope
This document specifies the characteristics of fusion fittings made from polyethylene (PE) as well as of
mechanical fittings for 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 4437-1, ISO 4437-2, 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 maximum operating pressures 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.
This document is applicable for fittings of the following types:
— electrofusion socket fittings;
— electrofusion saddle fittings;
— spigot end fittings (for butt fusion using heated tools and electrofusion socket fusion);
— socket fusion fittings;
— mechanical fittings.
NOTE 1 The fittings can be, for example, in the form of couplers, saddles, equal and reduced tees, reducers, elbows,
bends or end caps.
NOTE 2 Fabricated fittings are normally not used for gas applications except for larger dimensions or in the absence
of other solutions. Guidance can be found in ISO 4427-3:2019, Annex B.
5 2
1) 1 bar = 0,1 MPa = 10 Pa; 1 MPa = 1 N/mm .

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 7-1, Pipe threads where pressure-tight joints are made on the threads — Part 1: Dimensions, tolerances and
designation
ISO 228-1, Pipe threads where pressure-tight joints are not made on the threads — Part 1: Dimensions, tolerances
and designation
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 1167-1:2006, Thermoplastics pipes, fittings and assemblies for the conveyance of fluids — Determination of
the resistance to internal pressure — Part 1: General method
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 3126, Plastics piping systems — Plastics components — Determination of dimensions
ISO 4437-1, Plastics piping systems for the supply of gaseous fuels — Polyethylene (PE) — Part 1: General
ISO 4437-2:2024, Plastics piping systems for the supply of gaseous fuels — Polyethylene (PE) — Part 2: Pipes
ISO 4437-5, Plastics piping systems for the supply of gaseous fuels — Polyethylene (PE) — Part 5: Fitness for
purpose of the system
ISO 11357-6, Plastics — Differential scanning calorimetry (DSC) — Part 6: Determination of oxidation induction
time (isothermal OIT) and oxidation induction temperature (dynamic OIT)
ISO 12176-5, Plastics pipes and fittings — Equipment for fusion jointing polyethylene systems — Part 5: Two-
dimensional data coding of components and data exchange format for PE piping systems
ISO 13950, Plastics pipes and fittings — Automatic recognition systems for electrofusion joints
ISO 13951, Plastics piping systems — Test method for the resistance of plastic pipe/pipe or pipe/fitting
assemblies to tensile loading
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 13957, Plastics pipes and fittings — Polyethylene (PE) tapping tees — Test method for impact resistance
ISO 16010, Elastomeric seals — Material requirements for seals used in pipes and fittings carrying gaseous fuels
and hydrocarbon fluids
ISO 17778, Plastics piping systems — Fittings, valves and ancillaries — Determination of gaseous flow rate/
pressure drop relationships
ISO 17885, Plastics piping systems — Mechanical fittings for pressure piping systems — Specifications
ISO 18488, Polyethylene (PE) materials for piping systems — Determination of Strain Hardening Modulus in
relation to slow crack growth — Test method

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.
3.1.3
mean outside diameter
d
em
value of the measurement of the outer circumference of the pipe or spigot end of a fitting in any cross-section
divided by π (= 3,142), rounded to the next greater 0,1 mm
3.1.4
minimum mean outside diameter
d
em,min
minimum value for the mean outside diameter (3.1.3) as specified for a given nominal size (3.1.1)
3.1.5
maximum mean outside diameter
d
em,max
maximum value for the mean outside diameter (3.1.3) as specified for a given nominal size (3.1.1)
3.1.6
out-of-roundness
ovality
difference between the maximum and the minimum outside diameters in the same cross-section of a pipe or
spigot
3.1.7
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 (3.1.9).
n
3.1.8
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 or valve at any point is E.
3.1.9
minimum wall thickness at any point
e
min
minimum value for the wall thickness at any point (3.1.8) around the circumference of a component
3.1.10
tolerance
permitted variation of the specified value of a quantity, expressed as the difference between the permitted
maximum and the permitted minimum value
3.1.11
standard dimension ratio
SDR
numerical designation of a pipe series (3.1.12), 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 (3.1.7)
3.1.12
pipe series
S
number for pipe designation
Note 1 to entry: The relationship between the pipe series, S, and the standard dimension ratio (SDR) (3.1.11) 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 (3.2.4) (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
virgin material
compound (3.2.1) in a form such as granules that has not been subjected to use or processing other than that
required for its manufacture and to which no reworked or recyclable materials have been added
3.2.3
reworked material
plastics materials from rejected unused products or trimmings that have been manufactured and retained
within plants owned and operated by the same legal entity
3.2.4
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
3.3.4
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 [13], [14] and [15].

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).
3.5 Terms related to joints
3.5.1
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
3.5.2
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
3.5.3
tapping tee
electrofusion saddle fitting (3.5.2) that contains a cutter to tap through the wall of the main pipe and remains
in the body of this fitting
3.5.4
branch saddle
electrofusion saddle fitting (3.5.2) that requires an ancillary cutting tool for drilling a hole in the adjoining
main pipe
3.5.5
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
3.5.6
socket fusion fitting
polyethylene (PE) fitting designed to accept the insertion of a pipe or spigot end to realize a fusion joint
between mating surfaces using the socket fusion process
3.5.7
mechanical fitting
fitting for assembling plastics pipes with each other or with a metal pipe or fitting, that includes one or more
compression zones to provide pressure integrity, leak tightness and resistance to end loads
[SOURCE: ISO 17885:2021, 3.1.1]
4 Symbols and abbreviated terms
4.1 Symbols
For the purposes of this document, the following symbols apply.

A percentage of decohesion (area)
d
C design coefficient
c outside diameter of the terminal shroud
c diameter of the contact area of the terminal
c internal diameter of the terminal shroud
c maximum overall diameter of the base of the contact area
d mean outside diameter
em
d maximum mean outside diameter
em,max
d minimum mean outside diameter
em,min
d nominal outside diameter
n
d mean inside diameter in the fusion zone
d bore, i.e. the minimum diameter of the flow channel through the body of the fitting
d mean outside diameter of fusion end piece
d mean inside mouth diameter of the socket
d mean inside root diameter of the socket
E wall thickness (at any point) of a fitting or valve body
E fusion face wall thickness
e wall thickness at any point
e minimum wall thickness at any point
min
e nominal wall thickness
n
strain hardening modulus
p
H height of the saddle, which comprises the distance from the top of the main pipe to the top of the
tapping tee or saddle
H height of service pipe, which comprises the distance from the axis of the main pipe to the axis of the
service pipe
H height of service pipe, which comprises the distance from the top of the main pipe to the axis of the
service pipe
h internal depth of the terminal shroud
h distance between the upper part of the terminal shroud and the contact area
h height of the contact area
L percentage of decohesion (length)
d
L depth of penetration of the pipe or male end of a spigot fitting
L heated length within a socket as declared by the manufacturer to be the nominal length of the fusion
zone
L distance between the mouth of the fitting and the start of the fusion zone as declared by the manu-
facturer to be the nominal unheated entrance length of the fitting
L cut-back length of fusion end piece
L tubular length of fusion end piece
L heated length of the fitting, i.e. the length of penetration of the heated tool into the socket
L insertion depth, i.e. the depth of the heated pipe end into the socket
L heated length of pipe, i.e. the depth of penetration of the pipe end into the heated tool
L reference socket length, i.e. the theoretical minimum socket length used for the purpose of calculation
L actual length of the socket, i.e. the length from mouth to shoulder, if any
S pipe series
t time
W width of the tapping tee, which comprises the distance between the axis of the main pipe and the
plane of the mouth of the service tee
θ temperature
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.
DN/OD nominal size, outside diameter-related
LPL lower predicted limit
MFR melt mass-flow rate
MOP maximum operating pressure
MRS minimum required strength
PE polyethylene
RC raised crack resistance
RCP rapid crack propagation
SDR standard dimension ratio
SHT strain hardening test
5 Material
5.1 PE compound for fittings
The stress-bearing PE parts of injection moulded fittings or compression moulded plates, for example the
main body of the fitting, shall only be made from virgin material conforming to ISO 4437-1. The stress-
bearing PE parts of fittings made from pipe shall conform to ISO 4437-2.
Other materials may be used for non-stress-bearing parts, e.g. clamps for electrofusion saddle fittings that
only maintain a function during installation.
A fitting can only be designated as a PE 100-RC fitting if:
— it is produced from PE 100-RC materials which fulfil the requirements of ISO 4437-1:2024, Tables 1 and
2, and are declared as PE 100-RC by the raw material producer; and
— it fulfils the requirements of Table 4 of this document for PE 100-RC.
5.2 Material for non-polyethylene parts
5.2.1 General
All components shall conform to the relevant International Standards. Alternative standards may be applied
in cases where International Standards do not exist. In all cases, fitness for purpose of the system of the
components shall be demonstrated.
The materials and the constituent elements used in making the fitting (including elastomers and any metal
parts used) shall be as resistant to the external and internal environments as the other elements of the
piping system. They shall have an expected lifetime at least equal to that of the PE pipes conforming to
ISO 4437-2 with which they are intended to be used under the following conditions:
a) during storage;
b) under the effect of the gas conveyed therein;
c) with respect to the service environment and operating conditions.
The requirements for the level of material performance of non-polyethylene parts shall be at least as
stringent as that of the PE compound for the piping system. Reworked materials shall not be used for stress-
bearing parts.
Non-stress-bearing fitting parts may be made from other materials, e.g. clamps for electrofusion saddle
fittings that only maintain a function during installation.
Other materials used in fittings in contact with the PE pipe shall not adversely affect pipe performance or
initiate stress cracking.
5.2.2 Metal parts
All metal parts susceptible to corrosion shall be adequately protected, providing this is necessary for the
durability and function of the system.
When dissimilar metallic materials are used, steps shall be taken to avoid the possibility of galvanic
corrosion.
5.2.3 Sealing materials
Elastomeric seals shall conform to ISO 16010.
Other sealing materials are permitted if proven suitable for gas supply systems.

5.2.4 Other materials
Greases or lubricants shall not exude onto fusion areas and shall not affect the long-term performance of
fitting materials.
6 General characteristics
6.1 Appearance
When viewed without magnification, the internal and external surfaces of fittings shall be clean, and
shall have no scoring, cavities or other surface defects to an extent that would prevent conformity to this
document.
No component of the fitting shall show any signs of damage, scratches, pitting, bubbles, blisters, inclusions
or cracks to an extent that would prevent conformity of the fittings to the requirements of this document.
6.2 Colour
The colour of the PE parts of the fitting shall be either black, yellow or orange in accordance with ISO 4437-1.
6.3 Design
The design of the fitting shall be such that, when assembling the fitting onto the pipe or other component,
electrical coils and/or seals are not displaced.
Tapping tees may be provided with upper and lower end stops for the drill, or other means of indicating the
drill position according to the manufacturer’s instructions.
Tapping tees may be provided with a means to prevent uncontrolled gas release during tapping.
6.4 Appearance of factory-made joints
The internal and external surfaces of the pipe and fitting after fusion jointing, examined visually without
magnification, shall be free from melt exudation outside the confines of the fitting, apart from that which
may be declared acceptable by the fitting manufacturer or used deliberately as a fusion marker.
Any melt exudation shall not cause wire movement in electrofusion fittings such that it leads to short-
circuiting when jointed in accordance with the manufacturer’s instructions. There shall be no excessive
creasing of the internal surfaces of the adjoining pipes.
6.5 Electrical characteristics for electrofusion fittings
The electrical protection that shall be provided by the fusion process depends on the voltage and the current
used and on the characteristics of the electricity power source.
For voltages greater than 25 V, direct human contact with energized parts shall not be possible when the
fitting is in the fusion cycle during assembly in accordance with the instructions of the manufacturers of the
fittings and of the assembly equipment, as applicable.
NOTE 1 Electrofusion fittings are part of an electrical circuit when connected to the control units. Definitions of
electrical circuits and applicable protections are found in the relevant IEC standards.
The tolerance on the electrical resistance of the fitting at 23 °C shall be stated by the manufacturer. The
resistance shall be between nominal resistance (−10 %) and nominal resistance [(+10 %) + 0,1 Ω].
NOTE 2 0,1 Ω is the assumed value of the contact resistance.

The surface finish of the terminal pins shall allow a minimum contact resistance in order to satisfy the
resistance tolerance requirements.
NOTE 3 See Annex B for examples of typical electrofusion terminal connections.
7 Geometrical characteristics
7.1 Measurement of dimensions
The dimensions of the fitting shall be measured in accordance with ISO 3126 and rounded to the next
0,1 mm. In case of dispute, the measurement shall be made at least 24 h after manufacture and after being
conditioned for at least 4 h at (23 ± 2) °C.
Additionally, for spigot end fittings provided with temporary supports, dimensional measurement shall be
performed at least 1 h after removal of the supports.
Indirect measurement at the stage of production is allowed at shorter time periods, provided that evidence
is shown of correlation.
7.2 Dimensions of electrofusion socket fittings
7.2.1 Diameters and lengths of electrofusion sockets
For electrofusion sockets (see Figure 1) having a nominal diameter as given in Table 1, the socket diameter
and lengths shall be given by the manufacturer and shall conform to Table 1 with the following conditions:
a) L ≥ 5 mm;
b) d ≥ d − 2e
2 n min
Key
d mean inside diameter in the fusion zone measured in a plane parallel to the plane of the mouth at a distance of
L + 0,5L from that face
3 2
d bore, i.e. the minimum diameter of the flow channel through the body of the fitting
L depth of penetration of the pipe or male end of a spigot fitting; in case of a coupling without stop, it is not greater
than half the total length of the fitting
L heated length within a socket as declared by the manufacturer to be the nominal length of the fusion zone
L distance between the mouth of the fitting and the start of the fusion zone as declared by the manufacturer to be the
nominal unheated entrance length of the fitting
Figure 1 — Dimensions of electrofusion socket fittings

Table 1 — Dimensions of electrofusion socket fittings (see Figure 1)
Dimensions in millimetres
Nominal Depth of penetration Fusion zone
diameter
a
d L L L
n 1,min 1,max 2,min
16 25 41 10
20 25 41 10
25 25 41 10
32 25 44 10
40 25 49 10
50 28 55 10
63 31 63 11
75 35 70 12
90 40 79 13
110 53 82 15
125 58 87 16
140 62 92 18
160 68 98 20
180 74 105 21
200 80 112 23
225 88 120 26
250 95 129 33
280 104 139 35
315 115 150 39
355 127 164 42
400 140 179 47
450 155 195 51
500 170 212 56
560 188 235 61
630 209 255 67
710 220 280 74
800 230 300 82
a
An extended L value may be agreed between the end user and the manufacturer. In this case,
compatibility of such fittings is not given with components with a tubular length of spigots L
2,min
according to Table 3.
The mean inside diameter of the fitting in the middle of the fusion zone (see d in Figure 1) shall not be less
than d .
n
In the case of a fitting having sockets of differing nominal diameters, each one shall conform to the
requirements for the nominal diameter of the corresponding component.
Information for non-metric series is given in Annex E.

7.2.2 Wall thicknesses
In order to prevent stress concentrations, any changes in wall thickness of the fitting body shall be gradual.
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