EN 1555-3:2025

SLOVENSKI STANDARD
01-december-2025
Cevni sistemi iz polimernih materialov za oskrbo s plinastimi gorivi - Polietilen
(PE) - 3. del: Fitingi
Plastics piping systems for the supply of gaseous fuels - Polyethylene (PE) - Part 3:
Fittings
Kunststoff-Rohrleitungssysteme für die Gasversorgung - Polyethylen (PE) - Teil 3:
Formstücke
Systèmes de canalisations en plastique pour la distribution de combustibles gazeux -
Polyéthylène (PE) - Partie 3 : Raccords
Ta slovenski standard je istoveten z: EN 1555-3:2025
ICS:
83.140.30 Polimerne cevi in fitingi za Plastics pipes and fittings for
snovi, ki niso tekočine non fluid use
91.140.40 Sistemi za oskrbo s plinom Gas supply systems
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN 1555-3
EUROPEAN STANDARD
NORME EUROPÉENNE
October 2025
EUROPÄISCHE NORM
ICS 23.040.45 Supersedes EN 1555-3:2021
English Version
Plastics piping systems for the supply of gaseous fuels -
Polyethylene (PE) - Part 3: Fittings
Systèmes de canalisations en plastique pour la Kunststoff-Rohrleitungssysteme für die Gasversorgung
distribution de combustibles gazeux - Polyéthylène - Polyethylen (PE) - Teil 3: Formstücke
(PE) - Partie 3 : Raccords
This European Standard was approved by CEN on 11 August 2025.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 1555-3:2025 E
worldwide for CEN national Members.

Contents Page
European foreword . 4
Introduction . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 9
4 Symbols and abbreviated terms . 10
5 Material . 11
5.1 PE compound for fittings . 11
5.2 Material for non-polyethylene parts . 11
5.2.1 General . 11
5.2.2 Metal parts . 11
5.2.3 Sealing materials . 11
5.2.4 Greases and lubricants. 11
5.2.5 Other materials . 11
6 General characteristics . 12
6.1 Appearance . 12
6.2 Colour . 12
6.3 Design . 12
6.4 Appearance of factory-made joints . 12
6.5 Electrical characteristics for electrofusion fittings . 12
7 Geometrical characteristics . 13
7.1 Measurement of dimensions. 13
7.2 Dimensions of electrofusion socket fittings . 13
7.2.1 Diameters and lengths of electrofusion sockets . 13
7.2.2 Wall thicknesses . 15
7.2.3 Out-of-roundness of the bore of a fitting (at any point). 16
7.2.4 Spigots . 16
7.2.5 Other dimensions. 16
7.3 Dimensions of electrofusion saddle fittings . 16
7.4 Dimensions of spigot end fittings . 17
7.4.1 Diameters and lengths . 17
7.4.2 Wall thickness of the fusion end . 20
7.4.3 Wall thickness of the fitting body. 20
7.4.4 Other dimensions. 20
7.5 Design and dimensions of mechanical fittings . 20
7.5.1 General . 20
7.5.2 Mechanical fittings with polyethylene spigot ends . 21
7.5.3 Mechanical fittings with polyethylene electrofusion sockets . 21
7.5.4 Threads . 21
8 Mechanical characteristics . 21
8.1 General . 21
8.2 Requirements . 21
8.3 Performance requirements . 25
9 Physical characteristics . 26
9.1 Conditioning . 26
9.2 Requirements . 26
10 Performance requirements . 27
11 Technical information . 28
12 Marking . 28
12.1 General . 28
12.2 Minimum required marking of fittings . 29
12.3 Additional marking . 29
12.4 Fusion system recognition . 29
13 Delivery conditions . 30
Annex A (informative) Examples of typical terminal connections for electrofusion fittings . 31
Annex B (normative) Short-term pressure test method . 34
Annex C (normative) Tensile test for fitting/pipe assemblies . 36
Bibliography . 38

European foreword
This document (EN 1555-3:2025) has been prepared by Technical Committee CEN/TC 155 “Plastics
piping systems and ducting systems”, the secretariat of which is held by NEN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by April 2026, and conflicting national standards shall be
withdrawn at the latest by April 2026.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN 1555-3:2021.
The main changes are as follows:
— reference to information related to the suitability of PE pipe systems for 100 % hydrogen and its
admixtures with natural gas has been made;
— terms and definitions have been distributed over EN 1555-1, EN 1555-2 and EN 1555-3;
— symbols and their definitions for geometrical characteristics on electrofusion socket fittings, spigot
end fittings and tapping tees have been harmonized with other standards in ISO;
— Clause 5 has been restructured;
— the minimum bore for electrofusion socket fittings have been harmonized with the minimum bore
for spigot end fittings;
— test speeds have been added for testing the decohesive resistance;
— the performance requirements for joints have been mentioned more explicitly by adding Table 8;
— the technical file has been changed to technical information and fully revised.
System Standards are based on the results of the work being undertaken in ISO/TC 138 “Plastics pipes,
fittings and valves for the transport of fluids”, which is a Technical Committee of the International
Organization for Standardization (ISO).
They are supported by separate standards on test methods to which references are made throughout the
System Standard.
The System Standards are consistent with general standards on functional requirements and on
recommended practice for installation.
EN 1555 consists of the following parts:
— EN 1555-1, Plastics piping systems for the supply of gaseous fuels — Polyethylene (PE) — Part 1:
General;
— EN 1555-2, Plastics piping systems for the supply of gaseous fuels — Polyethylene (PE) — Part 2: Pipes;
— EN 1555-3, Plastics piping systems for the supply of gaseous fuels — Polyethylene (PE) — Part 3:
Fittings (this document);
— EN 1555-4, Plastics piping systems for the supply of gaseous fuels — Polyethylene (PE) — Part 4: Valves;
— EN 1555-5, Plastics piping systems for the supply of gaseous fuels — Polyethylene (PE) — Part 5: Fitness
for purpose of the system.
In addition, the following document provides guidance on the assessment of conformity:
— CEN/TS 1555-7, Plastics piping systems for the supply of gaseous fuels — Polyethylene (PE) — Part 7:
Guidance for assessment of conformity.
NOTE EN 12007-2 prepared by CEN/TC 234 “Gas infrastructure”, deals with the recommended practice for
installation of plastics pipes system in accordance with EN 1555 (all parts).
Any feedback and questions on this document should be directed to the users’ national standards body.
A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organisations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia,
Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland,
Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of North
Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the United
Kingdom.
Introduction
The EN 1555 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
EN 1555-1, EN 1555-2 and EN 1555-4.
Characteristics for fitness for purpose of the system are covered in EN 1555-5. CEN/TS 1555-7 gives
guidance for assessment of conformity.
Recommended practice for design, handling and installation is given in EN 12007-2.

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.
NOTE 1 Additional information related to the installation of PE 100-RC systems is given in EN 1555-1:2025,
Annex A.
NOTE 2 Additional information about the suitability of PE pipe systems for hydrogen and its admixtures is given
in EN 1555-1:2025, Annex B.
It also specifies the test parameters for the test methods referred to in this document.
In conjunction with EN 1555-1, EN 1555-2, EN 1555-4 and EN 1555-5, 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:
a) a maximum operating pressure, MOP, up to and including 10 bar , at a design reference temperature
of 20 °C;
b) an operating temperature between −20 °C and 40 °C.
For operating temperatures between 20 °C and 40 °C, derating coefficients are specified in EN 1555-5.
The EN 1555 series covers a range of MOPs and gives requirements concerning colours.
This document is applicable for fittings of the following types:
a) electrofusion socket fittings;
b) electrofusion saddle fittings;
c) spigot end fittings (for butt fusion using heated tools and electrofusion);
d) mechanical fittings.
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 guidance or regulations and
installation practices or codes.
NOTE 3 The fittings can be, for example, in the form of couplers, saddles, equal and reduced tees, reducers,
elbows, bends or end caps.
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.
EN 682, Elastomeric Seals — Materials requirements for seals used in pipes and fittings carrying gas and
hydrocarbon fluids
EN 1555-1:2025, Plastics piping systems for the supply of gaseous fuels — Polyethylene (PE) — Part 1:
General
EN 1555-2:2025, Plastics piping systems for the supply of gaseous fuels — Polyethylene (PE) — Part 2: Pipes

1 5 2
1 bar = 0,1 MPa = 10 Pa; 1 MPa = 1 N/mm .
EN 1555-5, Plastics piping systems for the supply of gaseous fuels — Polyethylene (PE) — Part 5: Fitness for
purpose of the system
EN 10226-1, Pipe threads where pressure tight joints are made on the threads — Part 1: Taper external
threads and parallel internal threads — Dimensions, tolerances and designation
EN 10226-2, Pipe threads where pressure tight joints are made on the threads — Part 2: Taper external
threads and taper internal threads — Dimensions, tolerances and designation
EN ISO 228-1, Pipe threads where pressure-tight joints are not made on the threads — Part 1: Dimensions,
tolerances and designation (ISO 228-1)
EN 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 1133-1)
EN 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 1167-1:2006)
EN 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 1167-4)
EN ISO 3126, Plastics piping systems — Plastics components — Determination of dimensions (ISO 3126)
EN ISO 11357-6, Plastics — Differential scanning calorimetry (DSC) — Part 6: Determination of oxidation
induction time (isothermal OIT) and oxidation induction temperature (dynamic OIT) (ISO 11357-6)
EN ISO 17778, Plastics piping systems — Fittings, valves and ancillaries — Determination of gaseous flow
rate/pressure drop relationships (ISO 17778)
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 17885:2021, 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 terms and definitions given in EN 1555-1, EN 1555-2 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
electrofusion socket fitting
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
3.2
electrofusion saddle fitting
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
3.2.1
tapping tee
electrofusion saddle fitting (3.2) (top loading or wrap round) that contains a cutter to tap through the wall
of the main pipe and remains in the body of this fitting
3.2.2
branch saddle
electrofusion saddle fitting (3.2) (top loading or wrap round) that requires an ancillary cutting tool for
drilling a hole in the adjoining main pipe
3.3
spigot end fitting
fitting where the outside diameter of the spigot end is equal to the nominal outside diameter, d , of the
n
corresponding pipe
3.4
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
For the purposes of this document the symbols and abbreviated terms given in EN 1555-1, EN 1555-2
and the following apply.
A percentage of decohesion (area)
d
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 of the fusion end piece
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 plastic body of the
fitting
E fusion face wall thickness
E wall thickness (at any point) of the fitting body
h internal depth of the terminal shroud
H height of the saddle, i.e. the distance from the top of the main pipe to the top of the
tapping tee or saddle
h distance between the upper part of the terminal shroud and the contact area
H height of the service pipe, i.e. the distance from the top of the main pipe to the axis of
the service pipe
H height of the contact area
L depth of penetration of the pipe or spigot end fitting
L heated length within the socket, i.e. the nominal length of the fusion zone as declared
by the manufacturer
L distance between the mouth of the fitting and the start of the fusion zone, i.e. the
nominal unheated entrance length of the fitting as declared by the manufacturer
L cut-back length of the fusion end piece
L tubular length of the fusion end piece
L percentage of decohesion (length)
d
W width of the tapping tee, i.e. the distance between the axis of the main pipe and the
plane of the mouth of the service tee

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 EN 1555-1. The stress-
bearing PE parts of fittings made from pipe shall be made from pipe conforming to EN 1555-2, except for
the geometrical characteristics.
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:
— the stress bearing part is produced from PE 100-RC materials which fulfil the requirements of
EN 1555-1:2025, Tables 1 and 2, and are declared as PE 100-RC by the raw material producer;
— 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 European standard(s). Alternative standards may be
applied in cases where suitable European Standards do not exist.
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.
Other materials used in fittings in contact with the PE pipe shall not adversely affect pipe performance or
initiate stress cracking.
In all cases, fitness for purpose of the system of the components shall be demonstrated.
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, galvanic corrosion shall be avoided.
5.2.3 Sealing materials
Elastomeric seals shall conform to EN 682.
Other sealing materials are permitted if proven suitable for gas supply systems.
5.2.4 Greases and lubricants
Greases or lubricants shall not exude onto fusion areas, and shall not affect the long-term performance of
fitting materials.
5.2.5 Other materials
Other materials as stress bearing part of the fitting shall have an expected lifetime at least equal to that
of the PE pipes conforming to EN 1555-2 with which they are intended to be used under the following
conditions:
a) during storage;
b) under the effect of gaseous fuels conveyed therein (see EN 1555-1);
c) with respect to the service environment, e.g. for corrosion, mechanical resistance and material
degradation;
d) during operation.
Non-stress-bearing fitting parts, e.g. clamps for electrofusion saddle fittings that only maintain a function
during installation, may be made from other 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
EN 1555-1.
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 tapping cutter, or other means of
indicating the cutter 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.
There shall be no excessive creasing of the internal surfaces of the adjoining components.
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 A 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 EN 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
condition: L ≥ 5 mm.
The value of L is not greater than half the total length of the fitting in case of coupling without stop.
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 plastic body of the fitting
L depth of penetration of the pipe or spigot end fitting
L heated length within the socket, i.e. the nominal length of the fusion zone as declared by the manufacturer
L distance between the mouth of the fitting and the start of the fusion zone, i.e. the nominal unheated
entrance length of the fitting as declared by the manufacturer
Figure 1 — Dimensions of electrofusion socket fittings
Table 1 — Dimensions of electrofusion socket fittings (see Figure 1)
Dimensions in millimetres
Nominal b Depth of penetration Fusion zone
Bore
diameter
d D L L
n 2 1 2
a
min. min. min.
max.
16 9 25 41 10
20 13 25 41 10
25 18 25 41 10
32 25 25 44 10
40 31 25 49 10
50 39 28 55 10
63 49 31 63 11
75 59 35 70 12
90 71 40 79 13
110 87 53 82 15
125 99 58 87 16
140 111 62 92 18
160 127 68 98 20
180 143 74 105 21
200 159 80 112 23
225 179 88 120 26
250 199 95 129 33
280 223 104 139 35
315 251 115 150 39
355 283 127 164 42
400 319 140 179 47
450 359 155 195 51
500 399 170 212 56
560 447 188 235 61
630 503 209 255 67
Nominal b Depth of penetration Fusion zone
Bore
diameter
d D L L
n 2 1 2
a
min. min. min.
max.
710 567 220 280 74
800 639 230 300 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 minimum tubular length of spigots L according to
Table 3.
b
The requirement on D is only applicable for SDR 11 or higher.
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.
7.2.2 Wall thicknesses
In order to prevent stress concentrations, any changes in wall thickness of the fitting body shall be
gradual.
a) The wall thickness at any point of the fitting body, E , shall be greater than or equal to e for the
1 min
corresponding pipe at any part of the fitting located at a distance beyond a maximum of 2/3 L from
all entrance faces if the fitting and the corresponding pipe are made from a polyethylene having the
same MRS.
If the fitting is produced from a polyethylene having an MRS that is different from that of the
corresponding pipe, the relation between the wall thickness of the fitting, E , and the pipe, e , shall
1 min
be in accordance with Table 2.
b) In the case of a wall thickness design different from that according to a), fittings and associated fusion
joints shall additionally meet the performance requirements given in 8.3.
Table 2 — Relation between fitting wall thickness, E , and pipe wall thickness, e
1 min
Pipe and fitting material
Relationship
Pipe Fitting
PE 80 PE 100 or PE 100-RC E ≥ 0,8 e
1 min
PE 100 or PE 100-RC PE 80 E ≥ 1,25 e
1 min
7.2.3 Out-of-roundness of the bore of a fitting (at any point)
When a fitting leaves the site of the manufacturer, the out-of-roundness of the bore of a fitting at any
point shall not exceed 0,015 d .
n
7.2.4 Spigots
For fittings that contain spigot outlets (e.g. electrofusion equal tee with a spigot branch), the dimensions
of the spigot shall conform to 7.4.
For technical and design reasons, the shape of the minimum bore cross-section area can be different from
that of spigot fittings as given in 7.4.
7.2.5 Other dimensions
The dimensional characteristics appropriate to each manufacturer, such as the overall dimensions or
mounting dimensions shall be specified in a technical file.
In the case of a coupling without an internal stop or with a removable centre register, the geometry of the
fitting shall allow the penetration of the pipe through the fitting.
7.3 Dimensions of electrofusion saddle fittings
Outlets from tapping tees and branch saddles shall have spigots in accordance with 7.4 or an electrofusion
socket in accordance with 7.2. The manufacturer shall specify the overall dimensions of the fitting in a
technical file. These dimensions shall include the main pipe and outlet dimensions, maximum height of
the saddle, H, and for tapping tees the height of the service pipe, H (see Figure 2).
For technical and design reasons, the minimum bore diameter, D , may be different from that of spigot
fittings as given in 7.4.
Key
H height of the saddle, i.e. the distance from the top of the main pipe to the top of the tapping tee or saddle
H height of service pipe, i.e. the distance from the top of the main pipe to the axis of the service pipe
W width of the tapping tee, i.e. the distance between the axis of the main pipe and the plane of the mouth of
the service tee
Figure 2 — Dimensions of tapping tees (electrofusion saddle fittings)
7.4 Dimensions of spigot end fittings
7.4.1 Diameters and lengths
The dimensions of spigot end fittings (see Figure 3) shall conform to the values given in Table 3.
The mean outside diameter of the fusion end piece (D) is measured in any plane parallel to the plane of
the mouth and at a distance not greater than the tubular length of the fusion end piece (L ) from that
plane.
The measurement of the bore (D ) does not include the fusion bead B (if present).
The fusion face wall thickness (E) is measured at any point at a maximum distance of L (cut-back length
of the fusion end piece) from the entrance face and shall be equal to the pipe wall thickness and tolerance
to which it is intended to be butt-fused, as specified in EN 1555-2. E is at least 3 mm.
The cut-back length of the fusion end piece (L ) comprises the initial depth of the spigot end necessary
for butt fusion or reweld and can be obtained by joining a length of pipe to the spigot end of the fitting,
provided that the wall thickness of the pipe is equal to E for its entire length.
The tubular length of the fusion end piece (L ) comprises the initial length of the fusion end piece and
shall allow the following (in any combination): the use of clamps required in the case of butt fusion,
assembly with an electrofusion fitting, the use of a mechanical scraper.
Key
D mean outside diameter of the fusion end piece
D bore, i.e. the minimum diameter of the flow channel through the plastic body of the fitting
E fusion face wall thickness
E wall thickness (at any point) of the fitting body
L cut-back length of the fusion end piece
L tubular length of the fusion end piece
Figure 3 — Dimensions of spigot end fittings
Table 3 — Diameters and lengths of spigot end fittings
Dimensions in millimetres
Nominal Mean outside diameter of b Out-of- Cut-back Tubular
Bore
diameter the fusion end piece roundness length c
length
d D D L L
n 1 2 4 5
a
min. min. max. min. min.
max.
16 16,0 16,3 9 0,3 25 41
20 20,0 20,3 13 0,3 25 41
25 25,0 25,3 18 0,4 25 41
32 32,0 32,3 25 0,5 25 44
40 40,0 40,4 31 0,6 25 49
50 50,0 50,4 39 0,8 25 55
63 63,0 63,4 49 0,9 25 63
75 75,0 75,5 59 1,2 25 70
90 90,0 90,6 71 1,4 28 79
110 110,0 110,7 87 1,7 32 82
125 125,0 125,8 99 1,9 35 87
140 140,0 140,9 111 2,1 38 92
160 160,0 161,0 127 2,4 42 98
180 180,0 181,1 143 2,7 46 105
200 200,0 201,2 159 3,0 50 112

225 225,0 226,4 179 3,4 55 120
250 250,0 251,5 199 3,8 60 129
280 280,0 281,7 223 4,2 75 139
315 315,0 316,9 251 4,8 75 150
355 355,0 357,2 283 5,4 75 164

400 400,0 402,4 319 6,0 75 179
450 450,0 452,7 359 6,8 100 195
500 500,0 503,0 399 7,5 100 212
560 560,0 563,4 447 8,4 100 235
630 630,0 633,8 503 9,5 100 255
710 710,0 714,3 567 10,6 125 280
800 800,0 804,8 639 12,0 125 280
Nominal Mean outside diameter of b Out-of- Cut-back Tubular
Bore
diameter the fusion end piece roundness length c
length
d D D L L
n 1 2 4 5
a
min. min. max. min. min.
max.
a
The tolerance grades conform to ISO 11922-1:2018 [5], Grade B.
b
Minimum bore is for SDR 11. Other minimum bores have to be agreed between manufacturer and
end user.
c
Spigot end fittings may have a shorter tubular length L for factory assemblies or in association with
appropriate electrofusion fittings.

7.4.2 Wall thickness of the fusion end
The fusion face wall thickness of the fusion end, E, shall be at least equal to the minimum wall thickness
of the pipe with a minimum value of 3 mm.
A thickness reduction (e.g. a chamfered edge) is permitted between the plane of the entrance face and a
plane parallel to it, located at a distance not greater than (0,01 d + 1 mm).
n
The permissible tolerance of the wall thickness value, E, at any point shall conform to the tolerance given
in EN 1555-2:2025, Table 2, for the same wall thickness.
7.4.3 Wall thickness of the fitting body
The wall thickness of the fitting body measured at any point, E , shall be at least equal to the nominal
wall thickness, e , of the pipe.
n
Any changes in wall thickness inside the body of the fitting shall be gradual in order to prevent stress
concentrations.
7.4.4 Other dimensions
The dimensional characteristics appropriate to each manufacturer, such as overall dimensions or
clamping requirements, shall be stated in a technical file.
7.5 Design and dimensions of mechanical fittings
7.5.1 General
Mechanical fittings shall conform to ISO 17885 for application in gas supply systems. They shall be
capable of assembly onto a PE pipe conforming to EN 1555-2, using instructions provided by the
manufacturer.
If the insertion depth of the mechanical fitting does not allow for assembly with a spigot end according to
this document, this shall be mentioned in the manufacturer’s instructions.
The fittings shall not be assembled by thread cutting the PE pipe.
The fitting and tools should be designed to avoid any damage that can affect the performance of the
assembly.
A stiffener can be used if required to provide a permanent support for a PE pipe to prevent creep in the
pipe wall under radial compressive forces (see ISO 17885:2021, Annex B).
The fitting can allow either a dismountable or permanently assembled joint.
7.5.2 Mechanical fittings with polyethylene spigot ends
Polyethylene spigot ends shall conform to 7.4.
7.5.3 Mechanical fittings with polyethylene electrofusion sockets
Electrofusion sockets shall conform to 7.2.
7.5.4 Threads
Threads on metal ends shall conform to EN 10226-1, EN 10226-2 or EN ISO 228-1, as applicable.
8 Mechanical characteristics
8.1 General
Fittings shall be tested using pipes, which conform to EN 1555-2.
Jointed pipe and fitting test pieces shall be
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