ICS 93.025, 23.040.20, 23.040.45     DMS 374 -3:2021  
Second edition  
ISO 4427 -3:2019  
IDT 
 
 
 
DRAFT MALAWI STANDARD  
 
 
 
 
 
 
 
 
 
 
 
 
Plastics piping systems — 
Polyethylene (PE) pipes  and fittings for 
water supply —  
Part 3: Fittings  
 
 
 
 
 
 
 
 
 
 
 
 
NOTE: This is a Draft Malawi Standard and should not be regarded or used as a Malawi Standard  
__________________  
 Published by  
MALAWI STANDARDS BOARD   
 
  
 
 ICS 93.025, 23.040.20, 23.040.45     DMS 374 -3:2021  
Second edition  
ISO 4427 -3:2019  
IDT 
 
 
 
 
 
 
Plastics piping systems — Polyethylene 
(PE) pipes and fittings for water supply —  
Part 3: Fitting s 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Obtainable from the  
Malawi Bureau of Standards  
P O Box  946 
BLANTYRE  
 
Tel: +265 1 870 488  
Fax: +265 1 870 756  
E-mail: mbs@mbsmw.org   
Website: www.mbsmw.org   
Price based on 33 pages  
© Copyright reserved   
 
  
  
i 
 TABLE OF CONTENTS  
 
Contents  ................................ ................................ ................................ ................................ ...................  Page  
Foreword  ................................ ................................ ................................ ................................ ....................   i 
Introduction  ................................ ................................ ................................ ................................ ................   i 
Scope  ................................ ................................ ................................ ................................ .........................   1 
Normative references  ................................ ................................ ................................ ................................   1 
Terms and definitions  ................................ ................................ ................................ ................................   3 
Symbols and abbreviated terms  ................................ ................................ ................................ ................   4 
Material  ................................ ................................ ................................ ................................ ......................   4 
General characteristics  ................................ ................................ ................................ ..............................   5 
Geometrical characteristics  ................................ ................................ ................................ .......................   6 
Mechanical characteristics ................................ ................................ ................................ .........................   12 
Physical characteristics  ................................ ................................ ................................ .............................   15 
Chemical resistance of fittings in contact with chemicals  ................................ ................................ ..........   16 
Performance requirements  ................................ ................................ ................................ ........................   16 
Marking  ................................ ................................ ................................ ................................ ......................   16 
Packaging  ................................ ................................ ................................ ................................ ..................   17 
Annex A (normative) Socket fusion fittings  ................................ ................................ ................................   18 
Annex B (normative) Fabricated fittings  ................................ ................................ ................................ ....  20 
Annex C (informative) Examples of typical terminal connections for electrofusion fittings  .......................   27 
Annex D (normative) Short -term pressure test method  ................................ ................................ .............   29 
Annex E (normative) Tensile test for fitting/pipe assemblies  ................................ ................................ .....  31 
Bibliography  ................................ ................................ ................................ ................................ ...............   32 
 
 
FOREWORD  
 
 
This Draft Malawi Standard  is a r eview of MS 374 -3:1992, Black polyethylene pipes for the conveyance of 
liquids - Specification. Part 3: High density  black  polyethylene PE 80 pressure pipes . 
 
This Draft Malawi Standard  is an  identical adoption of the international standard, ISO 4427 -3: 2019 Plastics 
piping systems — Polyethylene (PE) pipes and fittings for water supply — Part 3: Fittings  
 
Acknowledgement is made for the use of the above standard.  
 
Introduction  
 
The DMS 374  series of standards are a set of system standards that specify the requirements for a piping 
system and its components when made from polyethylene (PE). The piping system is intended to be used in 
buried or above ground applications, for the conveyance of water for human consumption, raw water prior to 
treatment, drainage  and sewerage under pressure, vacuum sewer systems, and water for other purposes.  
 
In respect of potential adverse effects on the quality of water intended for human consumption caused by the 
products covered by the DMS 374  series, it does not provide info rmation on the restriction on the use of 
products.  
 
NOTE  - Guidance for assessment of conformity can be found in Reference  [2] in the Bibliography.  
 
 
TECHNICAL COMMITTEE  
 
This Draft Malawi Standard  was developed by the Technical Committee MBS/TC 2, Pipes and fittings , and 
the following companies and organisations  were represented : 
  
ii 
 Blantyre City Council;  
Blantyre Water Board;  
Flowtech Limited;  
Lilongwe Water Board;  
Malawi University of Business and Applied Sciences;  
Ministry of Forestry and Natural Resources;  
O.G. Plastics Limited;  
Ruo Consultants; and  
Southern Region Water Board  
 
 
NOTICE  
 
This Draft Malawi Standard  shall be revi ewed every five years, or earlier  when  it is necessary  in order to 
keep abreast of progress.  Comments are welcome and shall be  considered when the standard  is being  
reviewed .  
1 
 
 
 DMS 374-3:2021 
DRAFT MALAWI STANDARD  
Plastics piping systems — Polyethylene (PE) pipes and 
fittings for water supply —  
Part 2: Fitting s 
 
 
1 SCOPE  
 
This document specifies the fittings made from polyethylene (PE) for buried or above grou nd applications, 
intended for the conveyance of water for human consumption, raw water prior to treatment, drainage and 
sewerage under pressure, vacuum sewer systems, and water for other purposes.  
 
NOTE 1  - The intended uses include sea outfalls, laid in w ater and connection between pipes suspended below bridges.  
 
This document also specifies the test parameters for the test methods referred to in this document.  
 
In conjunction with the other parts of the DMS 374  series, this document is applicable to PE fi ttings, to joints 
with components of PE or other materials, intended to be used under the following conditions:  
 
a) a maximum allowable operating pressure (PFA) up to and including 25 bar1; 
 
b) an operating temperature of 20 °C as the reference temperature . 
 
NOTE 2  - For other operating temperatures, guidance is given in DMS 374 -1, Annex A.  
 
This document covers a range of maximum allowable operating pressures and gives requirements 
concerning colours.  
 
NOTE 3  - It is the responsibility of the purchaser or specifier to make the appropriate selections from these aspects, taking into account 
their particular requirements and installation practices or codes.  
 
This document is applicable to fittings of the following types:  
 
1. fusion fittings;  
 
a. electrofusion fittings;  
 
 b. spigot end fittings (for butt fusion using heated tools and electrofusion socket fusion);  
 
c. socket fusion fittings (see Annex A ); 
 
2. mechanical fittings;  
 
a. compression fittings;  
 
b. flanged fittings;  
 
3. fabricated fittings (see Annex B ). 
 
 
2 NORMATIVE REFERENCES  
 
The following standards contain provisions which, through reference in this text, constitute provisions of this 
Draft Malawi S tandard. All standards are subject to revision and, since any reference to a standard is 
deemed to b e a reference to the latest edition of that standard, parties to agreements based on this standard 
                                                 
1 1 bar = 0 .1 MPa = 105 Pa; 1 MPa = 1 N/mm2  
2 
 
 
 are encouraged to take steps to ensure the use of the most recent editions of the standards indicated below. 
Information on currently valid national and inte rnational standards can be obtained from  the Malawi Bureau 
of Standards . 
DMS 374 -1, Plastics piping systems for water supply, and for drainage and sewerage under pressure — 
Polyethylene (PE) — Part 1: General ; 
DMS 374 -2, Plastics piping systems for water s upply, and for drainage and sewerage under pressure — 
Polyethylene (PE) — Part 2: Pipes ; 
DMS 374 -5, Plastics piping systems for water supply, and for drainage and sewerage under pressure — 
Polyethylene (PE) — Part 5: Fitness for purpose of the system ; 
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 11 33-1, 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 -3, Thermoplastics pipes, fittings and assemblies for the conveyance of fluids — Determination of 
the resistance to internal pressure — Part 3: Preparation of components ; 
ISO 1167 -4, Thermop lastics 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 4433 -1, Thermoplastics pipes — Resistance to liquid chemicals — Classification — Part 1: Immersion 
test method ; 
ISO 4433 -2, Thermoplastics pipes — Resistance to liquid chemicals — Classification — Part 2: Polyolefin 
pipes ; 
ISO 9624, Thermoplastics pipes for flu ids under pressure — Mating dimensions of flange adapters and loose 
backing flanges Thermoplastics pipes for fluids under pressure — Mating dimensions of flange adapters and 
loose backing flanges ; 
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 -1, Plastics pipes and fittings — Equipment for fusion jointing polyethylene systems — Part 1: Butt 
fusion ; 
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 polyet hylene (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, Plastics piping systems — Mechanical fittings for pressure piping systems — Specifications ; and  
3 
 
 
 EN 681 -1:1996, Elastomeric seals — Materials requirements for pipe joint seals used in water and drainage 
applications — Part 1: Vulcanized rubber . 
 
 
3 DEFINITIONS  
 
For the purposes of this document t he following definitions apply.  
 
For the purposes of this document, the terms and definitions given in DMS 374 -1 and the following apply.  
 
3.1 
electr ofusion socket fitting  
polyethylene (PE) fitting which contains one or more integral heating elements that are capable of 
transforming electrical energy into heat to realize a fusion joint with a spigot end or pipe  
 
3.2 
electrofusion saddle fitting  
polyeth ylene (PE) fitting which contains one or more integral 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 (top -loading or wraparound) which con tains an integral cutter used for cutting 
through the wall of the main pipe, which remains in the body of the tapping tee after installation  
 
3.2.2  
branch saddle  
electrofusion saddle fitting (top -loading or wraparound) which requires an ancillary cutting t ool for drilling the 
hole in the adjoining main pipe  
 
3.3 
spigot end fitting  
polyethylene (PE) fitting where the outside diameter of the spigot length is equal to the nominal outside 
diameter, dn, of the corresponding pipe  
 
3.4 
socket fusion fitting  
polyet hylene (PE) fitting where the socket mouth is designed to be fusion -jointed with a spigot end or a pipe 
using heated tools  
 
3.5 
fabricated fitting  
fitting produced from pipe conforming to DMS 374 -2 and/or from injection -moulded fittings in accordance 
with this document  
 
3.6 
mechanical fitting  
fitting, that generally includes a compression part to provide pressure integrity, leaktightness and resistance 
to end loads, for assembling polyethylene (PE) pipe to another PE pipe or any other element of the piping 
system  
Note 1 to entry : The fitting can create a radial compressive force (compression fitting) or an axial compressive force (flange 
connection).  
Note 2 to entry : A pipe -supporting sleeve providing a permanent support for a polyethylene (PE) pipe to preve nt creep in the pipe wall 
under radial compressive forces, can be applicable. In some cases, the supporting sleeve contributes to end load resistance.  
Note 3 to entry : The fitting can allow either a dismountable or permanently assembled joint.  
Note 4 to en try: The mechanical fitting can be supplied for field assembly or pre -assembled by the manufacturer.  
 
 
  
4 
 
 
 4 SYMBOLS AND ABBREVIATED TERMS  
 
For the purposes of this document, the symbols and abbreviated terms given in DMS 374 -1 apply.  
 
 
5 MATERIAL  
 
5.1 PE com pound  
 
The PE compound from which the fittings are made shall be in accordance with DMS 374 -1. 
 
The stress bearing PE parts of injection moulded fittings shall only be made from virgin material.  
 
Non-stress bearing PE parts shall be made from virgin materi al or own reprocessed material from a 
compound with the same MRS or a mixture of both materials.  
 
NOTE  - Since PE 40 is not commonly used for pressure applications, it is the intention of MBS/40  to withdraw all references to this 
compound at the next revis ion of the DMS 374  series (all parts).  
 
5.2 Material for non -polyethylene parts  
 
5.2.1  General  
 
The materials and constituent elements used in making the fitting (including elastomers and any metal parts) 
shall be as resistant to the external and internal environments as the other elements of the piping system 
and shall have a life expectancy under the following conditions at least equal to that of the PE pipe 
conforming to DMS 374 -2 with which they are intended to be used:  
 
a) during storage;  
 
b) under the  effect of the fluids being conveyed;  
 
c) with respect to the service environment and operating conditions.  
 
Other materials used in fittings and in contact with the PE pipe ( e.g., greases) shall not adversely affect the 
pipe performance or initiate stress  cracking.  
 
5.2.2  Metal parts  
 
All parts susceptible to corrosion shall be adequately protected, provided this is necessary for durability and 
function of the system.  
 
When dissimilar metallic parts are used which may be in contact with moisture, appropria te actions shall be 
taken to avoid galvanic corrosion.  
 
5.2.3  Elastomers  
 
Elastomeric materials used for the manufacture of seals shall conform to EN 681 -1. 
 
 
5.2.4  Other materials  
 
Greases or lubricants shall not exude on to the fusion areas and shall not  affect the long -term performance 
of the pipes and fittings nor have any adverse effect on the quality of the water.  
 
 
 
 
 
  
5 
 
 
 6 GENERAL CHARACTERISTICS  
 
6.1 Appearance  
 
When viewed without magnification, the internal and external surfaces of the fitting shall  be smooth, clean 
and free from scoring, cavities and other surface defects such as would prevent conformity of the fitting to 
this document.  
 
6.2 Design  
 
The design of the fitting shall be such that, when assembling the fitting onto the pipe or other comp onents in 
accordance with the manufacturer's recommendations, the electrical coils and/or seals are not displaced.  
 
6.3 Colour  
 
The PE part of fitting shall be either black or blue. For fabricated fittings, the colour characteristics of pipes 
shall be in a ccordance with DMS 374 -2. 
 
The blue colour is intended for the conveyance of water for human consumption only.  
For above -ground installations, all components other than black should be protected from direct UV light.  
 
6.4 Electrical characteristics for ele ctrofusion 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 e nergized 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  - The fitting during the fusion proc ess is part of an electrical system as defined in EN 60335 –1, HD 60364 –1, and IEC 60449  
(References [3], [4] and [ 5] in the Bibliography).  
 
The tolerance on the electrical resistance of the fitting at 23 °C shall be stated by the manufacturer. The 
resistan ce shall be between nominal res istance (−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 requireme nts. 
 
NOTE 3  - See Annex C  for the examples of typical electrofusion terminal connections.  
 
6.5 Appearance of factory -made joints  
 
The internal and external surfaces of the pipe and fitting after fusion jointing, examined visually without 
magnification, sh all 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 as a fusion marker.  
 
There shall be no wire movement leading to short circuiting when the electrofusion  fittings are jointed in 
accordance with the manufacturer’s instructions. There shall be no excessive creasing of the internal 
surfaces of the adjoining pipes or spigots.  
 
6.6 Effect on water quality  
 
For fittings to be used in contact with water intended for human consumption, see DMS 374 -1. 
 
 
 
 
  
6 
 
 
 
7 GEOMETRICAL CHARACTERISTICS  
 
7.1 Measurement of dimensions  
 
The dimensions of the fittings shall be measured in accordance with ISO 3126.  In case of dispute, the 
measurement of dimensions shall be made not less than 24 h after manufacture and after conditioning for at 
least 4 h at (23 ± 2) °C.  
 
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  
 
When measured in accordance with 7.1, the diameters and lengths of electrofusion sockets (see Figure 1 ) 
shall be in accordance with Table 1  
 
 
 
Key 
 
D1 “mean inside diameter in the fusion zon e” measured in a plane parallel to the plane of the mouth at a distance of L3 + 0.5 L2 
 
D2 bore, which is the minimum diameter of the flow channel through the body of the fitting where  
D2 ≥ (dn – 2emin) 
 
L1 “design penetration depth” of the pipe or male en d of a spigot fitting (in case of a coupling without stop, it is not greater than half the 
total length of the fitting)  
 
L2 heated length within a socket as declared by the manufacturer to be the nominal length of the fusion zone  
 
L3 distance between the m outh 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 where L3 shall be ≥ 5 mm  
 
Figure 1 — Dimensions of electrofusion sockets  
 
Table 1 — Electrofusion socket dimensions  
 
Dimensions in millimetres  
1 2 3 4 
Nominal diameter of 
the fitting  
dn Depth of penetration  Fusion zone  
 
L2,min L1,min L1,max  
20 25 41 10 
25 25 41 10  
7 
 
 
 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 63 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 
 
The mean inside diameter of the fitting in the middle of the fusion zone (see D1 in Figure 1 ) shall be not less 
than dn. 
 
The manufacturer shall decl are the actual minimum and maximum values of D1 and determine their 
suitability for joint assembly and check the fitness for purpose of the fitting by testing in accordance with 
DMS 374 -5. 
 
In the case of a fitting having sockets of differing nominal diame ters, each one shall conform to the 
requirements for the nominal diameter of the corresponding component.  
 
7.2.2  Wall thickness  
 
In order to prevent stress concentrations, any changes in wall thickness of the fitting body shall be gradual.  
a) The wall thic kness of the body of the fitting at any point, E, shall be greater than or equal to emin for the 
corresponding pipe at any part of the fitting located at a distance beyond a maximum of 2L1/3 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 relationship between the wall thickness of the fitting, E, and the pipe, emin, shall  be in accordance 
with Table 2 . 
 
 
  
8 
 
 
  
Table 2 — Relationship between pipe and fitting wall thickness  
 
1 2 3 
Material  Relationship between fitting wall thickness, E, 
and pipe wall thickness , emin Pipe  Fitting  
PE 80  PE 100  E ≥ 0.8emin 
PE 100  PE 80  E ≥ 1.25emin 
 
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 8.5. 
 
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 dn. 
 
7.2.4  Spigots  
 
For fittings that contain spigot outlets ( e.g., electrofusion equal tee with spigotted branch), the di mensions of 
the spigot shall be according to 7.4. 
 
NOTE  - For technical and design reasons, the shape of the minimum bore cross -section area can be different from the one of spigot 
fittings as given in 7.4. 
 
7.2.5  Other dimensions  
 
The dimensional characte ristics 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 sh all 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 electrofusion 
sockets in accordance with 7.2. 
 
The manufa cturer shall specify the overall dimensions of the fitting in the technical file. These dimensions 
shall include the maximum height of the saddle, H, and for tapping tees the height of the service pipe, H1 or 
H2 (see Figure 2 ). 
 
NOTE  - For technical and de sign reasons, the minimum bore diameter D2 can be different from the one of spigot fittings as given in 7.4. 
 
 
 
9 
 
 
 Key 
 
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  
 
H1 height of service pipe, which comprises the distance from the axis of the main pipe to the axis of the service pipe  
 
H2 height of service pipe, which comprises the distance from the top of the main pipe to the axis of the service pipe  
 
L width of the tapping tee, which comprises the distance between the axis of the pipe and the plane of the mouth of the service te e 
 
Figure 2 — Dimensions of electrofusion saddle fittings  
 
7.4 Dimensions of spigot end fittings  
 
7.4.1  Diameter and length  
 
When m easured according to 7.1, the dimensions of spigot end fittings (see Figure 3 ) shall conform to the 
values given in Table 3 . 
 
 
Key 
D1 mean outside diameter of fusion end piece  
D2 bore comprising minimum diameter of flow channel through body of fitting  
E body wall thickness of fitting  
E1 fusion face wall thickness  
L1 cut-back length of fusion end piece  
L2 tubular length of fusion end piece  
a D1 is measured in any plane parallel to the plane of the entrance face at a distance not g reater than L2 (tubular length) from the 
plane of the entrance face.  
b The measurement of this diameter does not include the fusion bead, if any.  
c It comprises the thickness measured at any point of the wall of the fitting.  
d It is measured at any point a t a maximum distance of L1 (cut back length) 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 DMS 374 -2, Table 2. E1 for small dimensions is at 
least 3 mm.  
e It com prises the initial depth of the spigot end necessary for butt fusion or reweld and may be obtained by joining a length of pip e to 
the spigot end of the fitting provided the wall thickness of the pipe is equal to E1 for its entire length.  
f It 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; assembly with a socket fusion fitting; the use of a mecha nical 
scrape r. 
Figure 3 — Dimensions of spigot fittings  
 
 
 
 
 
 
 
 
 
 
10 
 
 
 Table 3 — Spigot dimensions  
 
Dimensions in millimetres  
1 2 3 4 5 6 7 8 9 10 11 12 
Nominal 
outside 
diameter 
of spigot  Mean 
outside 
diameter of 
fusion end a Min. 
bore
b Electrofusion c Socke
t 
fusion  Butt 
fusion 
 Out- 
of- 
round - 
ness  Cut- 
back 
length  Tubular 
length d Tubular 
length  Out- 
of- 
round - 
ness  Cut- 
back 
length  Tubular 
length  
dn D1 D2 L1 L2 L2 L1 L2 
 min Max.  min Max.  min min min Max.  min Normal e Special f 
20 20.0 20.3 13 0.3 25 41 11 — — — — 
25 25.0 25.3 18 0.4 25 41 12,5 — — — — 
32 32.0 32.3 25 0.5 25 44 14,6 — — — — 
40 40.0 40.4 31 0.6 25 49 17 — — — — 
50 50.0 50.4 39 0.8 25 55 20 — — — — 
63 63.0 63.4 49 0.9 25 63 24 1.5 5 16 5 
75 75.0 75.5 59 1.2 25 70 25 1.6 6 19 6 
90 90.0 90.6 71 1.4 28 79 28 1.8 6 22 6 
110 110.0 110.7 87 1.7 32 82 32 2.2 8 28 8 
125 125.0 125.8 99 1.9 35 87 35 2.5 8 32 8 
140 140.0 140.9 111  2.1 38 92 — 2.8 8 35 8 
160 160.0 161.0 127 2.4 42 98 — 3.2 8 40 8 
180 180.0 181.1 143 2.7 46 105 — 3.6 8 45 8 
200 200.0 201.2 159 3.0 50 112 — 4.0 8 50 8 
225 225.0 226.4 179 3.4 55 120 — 4.5 10 55 10 
250 250.0 251.5 199 3.8 60 129 — 5.0 10 60 10 
280 280.0 281.7 223 4.2 75 139 — 9.8 10 70 10 
315 315.0 316.9 251 4.8 75 150 — 11.1 10 80 10 
355 355.0 357.2 283 5.4 75 164 — 12.5 10 90 12 
400 400.0 402.4 319 6.0 75 179 — 14.0 10 95 12 
450 450.0 452.7 359 6.8 100 195 — 15.6 15 60 15 
500 500.0 503.0 399 7.5 100 212 — 17.5 20 60 15 
560 560.0 563.4 447 8.4 100 235 — 19.6 20 60 15 
630 630.0 633.8 503 9.5 100 255 — 22.1 20 60 20 
710 710.0 714.9 567 10.6 125 280 — 24.8 20 60 20 
800 800.0 805.0 639 12.0 125 300 — 28.0 20 60 20 
a Tolerance  are in accordance  with ISO 11922 -1, grade  B (see Reference  [6] in the Bibliography).  
b The requirement  on D2 are only applicable  for SDR  11 or higher.  
c Spigot  fittings  designed  for electrofusion  are also suitable  for butt fusion.  
d The values  of L2 (electrofusion)  are based  on the following  equations:  
— for dn ≤ 90, L2 = 0,6 dn + 25 mm;  
— for dn ≥ 110 to dn ≤ 710, L2 = dn/3 + 45 mm.  
e Used by  preference.  
f Used for fittings  fabricated in the factory.  
  
11 
 
 
 7.4.2  Wall thickness of the fusion end  
 
The wall thickness of the fusion end,  E1, shall be at least equal to the minimum wall thickness of the pipe, 
with a minimum valu e of 3 mm.  
 
A thickness reduction, for example 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 de + 1 mm).  
 
The permissible tolerance of the wall thickness, E1, at any point shall conform to the tolerance given in              
DMS 374 -2, Table 2  for the same wall thicknesses.  
 
7.4.3  Wall thickness of the fitting body  
 
The wall thickness, E, of the fitting body measured at any point, shall be at least equal to the  nominal wall 
thickness, en, of the pipe.  
 
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, s uch as overall dimensions or clamping 
requirements, shall be stated in a technical file.  
 
7.5 Dimensions of socket fusion fittings  
 
Where the description and dimensions of fittings of this type is required, Annex A  applies.  
 
7.6 Dimensions of fabricated fi ttings  
 
Where the description and dimensions of fittings of this type is required, Annex B  applies.  
 
7.7 Design and dimensions of mechanical fittings  
 
7.7.1  General  
 
Mechanical fittings shall conform to ISO 17885.  
 
Mechanical fittings shall allow installat ion with pipes according to DMS 374 -2. 
 
If mechanical fittings are intended for jointing with spigot ends of fittings, spigot length ( L2) and cut back 
length ( L1) should be considered (see Table 3 ). 
 
The fittings shall be designed and manufactured in such a way that they can be used buried or above 
ground. Pre -assembled mechanical fittings shall not be capable of being dismantled.  
 
The fittings shall be designed to avoid twisting of the PE pipe during assembly.  
 
The fittings shall not be assembled by thread  cutting the PE pipe.  
 
7.7.2  Mechanical fittings with polyethylene spigot ends  
 
Polyethylene spigot ends shall conform to 7.4. 
 
7.7.3  Mechanical fittings with polyethylene electrofusion sockets  
 
Electrofusion sockets shall conform to 7.2. 
 
7.7.4  Threads  
 
Threads on metal ends shall conform to ISO 7 -1 or ISO 228 -1, as applicable.   
12 
 
 
  
7.8 Dimensions of loose backing flanges and flange adapters  
 
Dimensions of loose backing flanges and flange adapters shall be in accordance with  ISO 9624.  
 
 
8 MECHANICAL CHARACTERI STICS  
 
8.1 General  
 
Fittings shall be tested assembled with pipes conforming to DMS 374 -2 and/or fittings conforming to this 
document.  
 
Jointed pipe and fitting test pieces shall be assembled in accordance with the technical instructions of the 
manufacture r, taking into account the manufacturing and assembly tolerances and the extreme conditions of 
utilization described in DMS 374 -5. 
 
8.2 Conditioning  
 
Unless otherwise specified in the applicable test method, the test pieces shall be conditioned at (23 ± 2)  °C 
prior to testing.  
 
8.3 Requirements  
 
When tested in accordance with the test methods as specified in Table 4 using the indicated parameters, the 
fittings shall have mechanical characteristics conforming to the requirements given in Table 4 , as applicab le 
to the following types of fitting:  
 
— (A) electrofusion socket fitting and socket fusion fitting;  
 
— (B) electrofusion saddle fitting;  
 
— (C) spigot end fitting.  
 
For mechanical fittings, the require ments of ISO 17885  shall apply.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  
13 
 
 
 Table 4 — Mechanical characteristics  
 
1 2 3 4 5 
Characteristic  Requirements  Test parameters  Test method  Parameter  Value  
Hydrostatic  
strength  
(20 °C, 100 h)  No failure 
during test 
period of any 
test piece  End caps  Type  A of ISO 1167 -
1:2006  ISO 1167 -
1:2006  
and ISO 1167 -4 Orientation  Free 
Conditioning time  Shall conform to 
ISO 1167 -1:2006  
  Number of test pieces a 3  
  Type of test b Water -in-water   
  Circumferential 
(hoop) stress in 
pipec for: PE 80  10.0 MPa   
PE 100  12.0 MPa  
  Test per iod 100 h   
  Test temperature  20 °C   
Hydrostatic  
strength  
(80 °C, 165 h)  No failure 
during test 
period of any 
test piece d End caps  Type  A of ISO 1167 -
1:2006  ISO 1167 -
1:2006  
and ISO 1167 -4 Orientation  Free 
Conditioning time  Shall conform to 
ISO 116 7-1:2006  
  Number of test pieces a 3  
  Type of test b Water -in-water   
  Circumferential 
(hoop) stress in 
pipec for: PE 80  4.5 MPa   
PE 100  5.4 MPa  
  Test period  165 h   
  Test temperature  80 °C   
NOTE  Each  assembly  shall  be prepared  from components  (pipes  and fittings)  of the same  pressure  class.  
a     The number of test pieces given indicates the number required to establish a value for the characteristic described in Table 4 . 
The number of test pieces required for factory production control and process control should be listed in the manufacturer’s  quality  
plan.  Guidance  on assessment  of conformity  can be found  in CEN/TS  12201–7. (See  Reference  [2] in the Bibliography).  
b Alternatively, for dn > 450 mm, the test can also be performed in air. In case of dispute, water -in-water test shall be used.  For 
fitting  type (B) dn > 450 mm, alternative  testing  is allowed  (e.g., pressurization  through  saddle  outlet).  
c The test pressure  shall  be calcu lated  using  the design  standard  dimension  ratio (SDR)  of the fitting.  
d Only brittle  failures  shall  be taken  into account.  If a ductile  failure  occurs  before  165 h, the test can be repeated  
according to 8.4. 
e Longest  length  of brittle  failure  in any of the test samples.  
f Test sample  can be mechanically  reduced  in wall thickness  for testing  purpose  of large  diameter  fittings  by keeping  a 
minimum of 15 mm wall thickness of each component.  
g Alternatively,  for fittings  type (B) dn > 450 mm, this characteristic  can be checked  by the strip-bend  test according  to ISO 21751.  
(See Reference [7] in the Bibliography)  
h Applicable to dn 90 mm and  above.  
 
 
 
 
 
 
  
14 
 
 
 Table 4 (continued)  
 
1 2 3 4 5 
Characteristi c Requirements  Test parameters  Test method  Parameter  Value  
Hydrostatic  
strength  
(80 °C, 1 000 h)  No failure 
during test pe - 
riod of any test 
piece  End caps  Type  A of ISO 1167 -
1:2006  ISO 1167 -
1:2006  
and ISO 1167 -4 Orientation  Free 
Conditioning t ime Shall conform to 
ISO 1167 -1:2006  
Number of test pieces a 3 
Type of test b Water -in-water  
Circumferential 
(hoop) stress in 
pipec for: PE 80  4,0 MPa  
PE 100  5,0 MPa  
Test period  1 000 h  
Test temperature  80 °C  
Decohesive 
resistance  
(A) Length of 
initiation rupture 
≤ L2/3 in brittle 
failure e Test temperature 
Number of test 
pieces a,f 23 °C  
Shall conform to  
ISO 13954 and ISO 
13955  ISO 13954  
ISO 13955  
Evaluation of 
ductility of 
fusion joint 
interface  
(B)g Surface of 
rupture  
Ld ≤ 50 % an d 
Ad ≤ 25 %,  
brittle failure  Test temperature 
Number of test 
pieces a,f 23 °C  
Shall conform to 
ISO 13956  ISO 13956  
Tensile strength 
for butt fusion  
(C)h Test to failure: 
ductile – pass 
brittle – fail Test temperature 
Number of test 
pieces a,f 23°C  
Shall con form to 
ISO 13953  ISO 13953  
Impact 
resistance  
(B: Tapping  
tees only)  No failure, no  
leakage  Test temperature 
Falling height 
Mass of the striker  
Number of test pieces a 0 °C 
2 m 
2.5 kg 
1 ISO 13957  
NOTE  Each  assembly  shall  be prepared  from components  (pipes  and fittings)  of the same  pressure  class.  
a     The number of test pieces given indicates the number required to establish a value for the characteristic described in Table 4 . 
The number of test pieces required for factory production control and process control should be listed in the manufacturer’s  quality  
plan.  Guidance  on assessment  of conformity  can be found  in CEN/TS  12201–7. (See  Reference  [2] in the Bibliography).  
b Alternatively, for dn > 450 mm, the test can also be performed in air. In case of dispute, water -in-water test shall be used.  For 
fitting  type (B) dn > 450 mm, alternative  testing  is allowed  (e.g. pressurization  through  saddle  outlet).  
c The test pressure  shall  be calculated  using the design  standard  dimension  ratio (SDR)  of the fitting.  
d Only brittle  failures  shall  be taken  into account.  If a ductile  failure  occurs  before  165 h, the test can be repeated  
according to 8.4. 
e Longest  length  of brittle failure  in any of the test samples.  
f Test sample  can be mechanically  reduced  in wall thickness  for testing  purpose  of large  diameter  fittings  by keeping  a 
minimum of 15 mm wall thickness of each component.  
g Alternatively,  for fittings  type (B) dn > 450 mm, this characteristic  can be checked  by the strip-bend  test according  to ISO 21751.  
(See Reference [7] in the Bibliography)  
h Applicable to dn 90 mm and  above.  
  
15 
 
 
 8.4 Retest conditions  
 
A fracture in a brittle mode in less  than 165 h shall constitute a failure; however, if a sample in the 165 h test 
fails in a ductile mode in less than 165 h, a retest shall be performed at a selected lower stress in  order to 
achieve the minimum required time for the selected stress obtained  from the line through the stress/time 
points in accordance with Table 5 . 
 
Table 5 — Circumferential (hoop) stress at 80 °C and associated minimum test period  
 
1 2 3 4 
PE 80  PE 100  
Stress  
MPa Minimum test 
period  
h Stress  
MPa Minimum test 
period  
h 
4.5 165 5.4 165 
4.4 233 5.3 256 
4.3 331 5.2 399 
4.2 474 5.1 629 
4.1 685 5.0 1 000  
4.0 1 000  — — 
 
8.5 Performance requirements  
 
Where 7.2.2 b applies, electrofusion socket fittings shall, additionally, be in accordance with Table 6 . 
 
Table 6 — Performance r equirements  
 
1 2 3 4 5 
Characteristic  Requirement  Test parameters  Test method  Parameter  Value  
 
 
 
 
 
Short -term internal 
pressure resistance   
 
Failure pressure 
shall be greater than 
pressure equivalent 
of 2 × MRS  
calculated for 
thickest -walled pipe 
for which fitting has 
been designed  End caps  Type A of  
ISO 1167 -
1:2006   
 
 
 
 
Annex D  Orientation  free 
Conditioning time  12 h 
Type of test  Water -in-water  
Minimum pressure:   
PE 80 pipe, SDR 11 32 bar  
PE 100 p ipe, SDR 11  40 bar  
Pressure increase rate  5 bar/min  
Test temperature  20 °C  
Resistance to 
tensile load  Minimum elongation 
shall be 25 % 
before pipe yields   
Test temperature   
23 °C   
Annex E  
1 bar = 0,1 MPa = 105 Pa; 1 MPa = 1 N/mm2. 
 
 
9 PHYSICAL CHARACTERISTICS  
 
9.1 Conditioning  
 
Unless otherwise specified in the applicable test method, the test pieces shall be conditioned at (23 ± 2) °C 
prior to testing.   
16 
 
 
 9.2 Requirements  
 
When tested in accordance with the test meth ods as specified in Table 7 using the indicated parameters, the 
fittings shall have physical characteristics conforming to the requirements given in Table 7 . 
 
For mechanical fittings, the requirements of ISO 17885  shall apply.  
 
Table 7 — Physical character istics  
 
1 2 3 4 5 
Characteristic  Requirements  Test parameters  Test method  
Parameter  Value   
Oxidation 
induction time 
(Thermal stability)  ≥20 min  Test temperature  200 °Cb ISO 11357 -6 
Number of test piecesa 3 
Test environment  Oxygen  
Melt mass -flow 
rate (MFR)  After processing 
maximum deviation 
of ±20 % of the value  
measured on the 
batch used to 
manufacture the fitting  Loading mass  5 kg ISO 1133 -1 
Test temperature  190 °C  
Time  10 min  
Number of test piecesa Shall conform to 
ISO 1133 -1 
a  The number of test pieces given indicates the number required to establish a value for the characteristic described   in Table 7. The 
number of test pieces required for factory production control and process control should be listed in the manufacturer’s  quality  plan.  
Guidance  on assessment  of conformity  can be found  in CEN/TS  12201–7 (Reference  [2] in the Bibliography).  
b Test can be carried out at 210 °C or 220 °C provided that there is a clear correlation to the results at 200 °C; in case of d ispute, the 
reference temperature shall be 200 °C.  
 
 
10 CHEMICAL RESISTANCE OF FITTINGS IN CONTACT WITH CHEMICALS  
 
If, for a particular application, it is necessary to evaluate the chemical resistance of the fitting, then the fitting 
shall be classified in accordance with I SO 4433 -1 and ISO 4433 -2. 
 
NOTE  - Guidance for the resistance of polye thylene products to chemicals is given in ISO/TR 10358  (Reference [ 8] in the Bibliography). 
This guidance only addresses chemical resistance of products not submitted to any stress, and can need to be completed to add itional 
testing.  
 
 
11 PERFORMANCE REQUI REMENTS  
 
When fittings conforming to this document are assembled to each other or to components conforming to 
other parts of the DMS 374  series, the joints shall be in accordance with DMS 374 -5. 
 
 
12 MARKING  
 
12.1 General  
 
All fittings shall be marked acco rding to 12.2. 
 
The marking on the product shall be permanent, legible and shall not initiate cracks or other types of failure.  
 
If printing is used, the colour of the printed information shall differ from the basic colour of the product.  
 
The marking shal l be such that it is legible without magnification.  
  
17 
 
 
 NOTE  - The manufacturer is not responsible for marking that is illegible owing to actions caused during installation and use such as  
painting, scratching, covering of components or using detergents, etc.  on the components unless agreed or specified by the 
manufacturer.  
 
There shall be no marking over the minimum spigot length of the fitting.  
 
12.2 Minimum required marking  
 
The minimum required marking shall be in accordance with Table 8 . 
 
For fabricated f ittings, marking shall at least mention manufacturer's identification (by name or code) on the 
product or on a label. Further elements may be agreed between the manufacturer and purchaser.  
 
Table 8 — Minimum required marking  
 
1 2 
Aspect  Marking  
Reference  to this document  ISO 4427 -3a 
Manufacturer's identification  Name or code  
Manufacturer's information  b 
Nominal diameter of pipe, dn e.g. 110  
Material and designation  e.g. PE 100  
Nominal pressure  e.g. PN 16a  
Design application series  e.g. SDR 11 or S5  
Applicable  SDR  fusion  range  of pipe (only  for electrofu - 
sion fittings)  e.g. SDR 11 –SDR 26 a 
a This information may be printed on a label, with one label attached to the fitting or to the individual bag. The label shall  be of 
sufficient  quality  as to be intact  and legible  at the time of installation.  
b In clear figures or in code providing traceability to the production period within year and month and, if the manufacturer  is 
producing  at different  sites,  the production  site. 
 
12.3 Fusion system recogniti on 
 
Fusion fittings should have a system, either numerical, electromechanical or self -regulatory as described in 
ISO 13950,  for recognizing the fusion parameters and facilitating the fusion process.  
 
Where bar codes are used for the numerical recognition, the bar -code label shall be stuck to the fitting and 
shall be protected against deterioration.  
 
NOTE  - ISO 12176 -5 (Reference [ 9] in the Bibliography), defines a 2D code which will also enable the recognition of the fusion 
parameters.  
 
 
13 PACKAGING  
 
The f itting shall be packaged in bulk or individually protected where necessary in order to prevent 
deterioration and contamination.  
 
The packaging shall have at least one label with the manufacturer’s name, type and dimensions of the part, 
number of units and any special storage conditions.    
18 
 
 
 Annex A  
(normative)  
 
Socket fusion fittings  
 
As applicable, the dimensions of socket fusion fittings shall be in accordance with Tables A.1 and A.2. The 
diameter at the root shall not be greater than the diameter at the mo uth. See Figure A.1.  
 
Table A.1 — Socket dimensions — Nominal sizes 16 to 63 inclusive  
 
Dimensions in millimetres  
1 2 3 4 5 6 7 8 9 10 11 12 13 
 
Nom. 
size 
DN/ 
OD Nom. 
inside 
diam. 
of 
socket  Mean inside diameter of 
socket   
Out-of- 
round - 
ness   
Min. 
bore  Socket 
refer - 
ence 
length  Heated socket 
length  Penetration of 
pipe into 
socket  
Mouth  Root  (L – 2.5) (L) (L – 3.5) (L − 1) 
dn D1,min  D1,max  D2,min  D2,max  max.  D3 Lmin L2,min  L2,max  L3,min  L3,max  
16 16 15.2 15.5 15.1 15.4 0.4 9 13.3 10.8 13.3 9.8 12.3 
20 20 19.2 19.5 19.0 19.3 0.4 13 14.5 12.0 14.5 11.0 13.5 
25 25 24.1 24.5 23.9 24.3 0.4 18 16.0 13.5 16.0 12.5 15.0 
32 32 31.1 31.5 30.9 31.3 0.5 25 18.1 15.6 18.1 14.6 17.1 
40 40 39.0 39.4 38.8 39.2 0.5 31 20.5 18.0 20.5 17.0 19.5 
50 50 48.9 49.4 48.7 49.2 0.6 39 23.5 21.0 23.5 20.0 22.5 
63 63 62.0a 62.4 a 61.6 62.1 0.6 49 27.4 24.9 27.4 23.9 26.4 
Maximum  L2 = L mm; minimum  L2 calculated  from (L – 2.5) mm. 
Maximum  L3 = (L − 1) mm; minimum  L3 = (L – 3.5) mm. 
a Where rerounding clamps are used, the maximum diameter of 62 .4 mm may be increased by 0.1 mm to 62 .5 mm. Conversely,  
where  a peeling  technique  is used,  the minimum  diameter  of 62.0 mm may be reduced  by 0.1 mm to 61.9 mm. 
 
Table A.2 — Socket dimensions — Nominal sizes 75 to 125 inclusive  
Dimensions in millimetres  
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 
 
Nom. 
size 
DN/OD   
Mean 
outside 
diameter of 
pipe  Nom. 
inside 
diam. 
of 
socke
t Mean inside 
diameter of 
socket  Out- 
of- 
round - 
ness   
Min. 
bore   
Socket 
ref. 
length  Heate
d 
socket 
length  Penetration 
of pipe into 
socket  
Mouth  Root  (L − 4) (L) (L − 5) (L − 1) 
dem min  dem max  dn D1,min  D1,max  D2,min  D2,max  max. D3 Lmin L2,min  L2,max  L3,min  L3,max  
75 75,0 75,5 75 74,3 74,8 73,0 73,5 0,7 59 30 26 30 25 29 
90 90,0 90,6 90 89,3 89,9 87,9 88,5 1,0 71 33 29 33 28 32 
110 110,0  110,6  110 109,4 110,0  107,7  108,3  1,0 87 37 33 37 32 36 
125 125,0  125,6  125 124,4  125,0  122,6  123,2  1,0 99 40 36 40 35 39 
Maximum L2 = L mm; minimum L2 calculated from ( L − 4) mm.  
Maximum L3 = (L − 1) mm; minimum L3 = (L − 5) mm.  
 
 
  
19 
 
 
 
 
Key 
 
D1 mean inside diameter o f socketa 
D2 mean inside root diameterb 
D3 minimum borec 
De outside diameter  
L reference socket lengthd 
L1 actual length of socket from mouth to shoulder (if present)  
L2 heated length of fittinge 
L3 insertion depthf 
L4 heated length of pipeg 
a It is the me an diameter of the circle at the intersection of the extension of the socket with the plane of the socket mouth.  
b It is the mean diameter of the circle in a plane parallel to the plane of the mouth and separated from it by distance L, whic h is the 
referen ce length of the socket.  
c It is the minimum diameter of the flow channel through the body of the fitting.  
d It is the theoretical minimum socket length used for the purpose of calculation.  
e It is the length of penetration of the heated tool into the sock et. 
f It is the depth of the heated pipe end into the socket.  
g It is the depth of penetration of the pipe end into the heated tool.  
 
Figure A.1 — Socket and pipe dimensions   
20 
 
 
 Annex B  
(normative)  
 
Fabricated fittings  
 
B.1 General  
 
The fabricated fittings sh all be in accordance with Tables B.1 and B.2, as applicable.  
 
For dimensions above and including DN630, the requirements on hydrostatic strength at 20°C and 80°C in 
Table B.1 may be assessed by indirect testing. The indirect test method used and the correl ation or safe 
relationship of the indirect testing to the specification of Table B.1 shall be documented in the manufacturer’s 
quality plan. The indirect test method shall be agreed between the manufacturer and the end user.  
 
The pipes used for manufacturi ng these fittings shall be in accordance with DMS 374 -2 and the butt fusion 
machine shall be in accordance with ISO 12176 -1. 
 
This annex applies only to fabricated fittings obtained by the butt fusion process. If other fusion techniques 
are used (e.g. extr usion welding), additional derating factors will have to be taken into account.  
 
The PN rating of fabricated fittings shall be derived from the PN of the used pipes and the geometry derating 
factors given in B.3 and B.5. 
 
The manufacturer shall be responsi ble for the design and the pressure rating of the fittings. It is his 
responsibility to demonstrate conformity to the declared PN. The pressure rating as well as the applicable 
derating factor, f, shall be recorded in the manufacturer's technical file. The  minimum testing to demonstrate 
the performance of the fitting design is given in Table B.1.  
 
In some cases, fabricated fittings are made out of injection moulded fittings or pipes of the next lower SDR 
series where the wall thickness is internally machine d back to the next higher SDR. For such fittings, the 
derating factors may differ from those given in this annex.  
 
Special requirements concerning the appearance of fabricated fittings, e.g. bead removal, shall be agreed 
between the manufacturer and purcha ser. 
 
At least the pressure rating PN of the fitting shall be marked on the fitting, on a label or the packaging.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  
21 
 
 
 Table B.1 — Performance requirements — Fabricated fittings  
 
1 2 3 4 5 
Characteristic  Requirement  Test parameters  Test method  
Parameter  Value  
Hydrostatic 
strength at 20 °C  No failure  of any 
test piece  during 
test period  End caps  Type A a ISO 1167 -1 
ISO 1167 -3 Conditioning period  According to 
ISO 1167 -1 
Number of test pieces b 3 
Type of test c Water -in-water  
Test temperature  20 °C  
Test period  100 h  
Circumferential (hoop) stress 
ford:  
PE 40  7 MPa × f 
PE 80  10 MPa × f 
PE 100  12 MPa × f 
Hydrostatic 
strength at 80 °C  No failure  of any 
test piece  during 
test period  End caps  Type A a ISO 1167-1 
ISO 1167 -3 Conditioning period  According to 
ISO 1167 -1 
Number of test pieces b 3 
Type of test  Water -in-water c 
Test temperature  80 °C  
Test period  1 000 h  
Circumferential (hoop) stress 
ford:  
PE 40  2 MPa × f 
PE 80  4 MPa × f 
PE 100  5 MPa × f 
Tensile strength 
for fabricated 
fittings e Test to failure: 
Ductile — 
Pass Brittle — 
Fail Test temperature  23 °C  ISO 13953  
Number of test pieces b According to 
ISO 13953  
NOTE  f is the declared  derating  factor  related  to the fitting to be tested.  
a Type  B end caps  may be used  for batch  release  tests  for diameters  ≥500  mm. 
b    The number of test pieces given indicates the quantity required to establish a value for the characteristic described in this table.  
The number  of test pieces required  for factory  production  control  and process  control  should  be listed  in the manufacturer’s quality  plan.  
c Alternatively,  for dn > 450 mm, the test can also be performed  in air. In case  of dispute,  water -in-water  test shall  be used.  
d The stress  shall  be calculated  using  the nominal  dimensions  of the pipe used  in the test assembly.  
e Samples  are to be taken  from joints  between  longitudinal  aligned  segments  to produce  a flat specimen  geometry.  
 
B.2 Dimensions  
 
See Table B.2 . 
 
Larger nominal outsi de diameters are permitted and dimensions shall be agreed between the manufacturer 
and the end -user.  
 
  
22 
 
 
 Table B.2 — Fabricated fitting dimensions  
Dimensions in millimetres  
1 2 3 4 5 
Nominal outside 
diameter  
dn Minimum tubular 
length of fitting  
le Nominal bend 
radius  
r Nominal 
branch length  
z Nominal angle of 
fitting  
α 
90 150  
 
 
 
 
 
 
 
 
 
 
Declared by the 
fitting manufacturer  
e.g. 1 .5 × d 
2 × d 
2.5 × d 
3 × d  
 
 
 
 
 
 
 
 
 
 
 
 
Declared by the 
fitting manufacturer   
 
 
 
 
 
 
 
 
 
Declared by the 
fitting manufacturer  
With a tolerance  
of ±2°  
The maximum 
tolerance for  pipe 
bends shall  be 
±5° 110 150 
125 150 
140 150 
160 150 
180 150 
200 150 
225 150 
250 250 
280 250 
315 300 
355 300 
400 300 
450 300 
500 350 
560 350 
630 350 
710 350 
800 350 
900 400 
1 000  400 
1 200  400 
1 400  550 
1 600  550 
 
B.3 Segmented bends  
 
Examples of typical fabricated bends made out of pipe segments are shown in Figures B.1 and B.2. Only 
indicated dimensions shall be considered. A full set of dimensions shall be provided by the technical  
documentation of the fitting manufacturer.  
  
23 
 
 
 
 
Key 
dn, le and r and α shall be in accordance with Table B.2  
dn nominal outside diameter  
le tubular length of fusion end piecea 
r nominal bend radius of fitting  
z nominal length of fitting branch to axis  
α nominal angle of fitting  
a The length shall allow the following (in any combination): the use of clamps required in the case of butt fusion; assembly wi th an 
electrofusion fitting; assembly with a socket fusion fitting; the use of a mechanical scraper.  
 
Figur e B.1 — Segmented bends  
 
For bends fabricated out of pipe segments, the following derating rules for the calculation of the PN shall 
apply:  
 
PN = fB × PN pipe 
where  
 
fB is the derating factor related to the bend segment design (see Table B.3 ); 
 
PNpipe  is the nominal pressure of the pipe.  
 
Practice has shown that these factors are applicable. Results of testing according to Table B.1  will 
determine the applicable factor fB. 
 
  
24 
 
 
  
 
Key 
β  cut angle (shall not be greater than 15°)  
dn nominal outside diameter  
 
Figure B.2 — Segment design  
 
Table B.3 — Derating factors for segmented bends  
 
1 2 
Cut angle  
β Derating factor  
fB 
≤7.5° 1.0 
7.5° < β ≤ 15°  0.8a 
a In accordance with B.1, the test results of the man ufacturer may 
demonstrate  that a derating  factor  of 1,0 or another  factor  is applicable  
 
 
B.4 Swept bends  
 
Fabricated pipe bends are not required to accord with the drawings given in Figure B.3 . Only indicated 
dimensions shall be considered. A full set of  dimensions shall be provided by the fitting manufacturer in his 
technical literature.  
 
The minimum wall thickness of the pipe bend after bending shall be in accordance with DMS 374 -2. 
Destructive techniques may be used to demonstrate consistency of the ma nufacturing process.  
 
For bends  fabricated out  of pipes, usually no derating factor applies. Results of testing according to                      
Table B.1  shall demonstrate this.  
 
 
25 
 
 
 
 
 
Key 
dn, le and r and α shall be in accordance with Table B.2  
dn nominal outside diameter  
le tubular length of fusion end piecea 
r  nominal bend radius of fitting  
z  nominal length of fitting branch to axis  
α  nominal angle of fittingb 
a The length shall allow the following (in any combination): the use of clamps required in th e case of butt fusion; assembly with an 
electrofusion fitting; assembly with a socket fusion fitting; the use of a mechanical scraper.  
b Special measures may be taken to keep the pipe -bend angle in place during storage and handling of the fitting.  
 
Figure B.3 — Swept bends  
 
B.5 Segmented tees  
 
Fabricated tees made out of pipe segments are not required to accord with the drawings given in Figure B.4 . 
Only indicated dimensions shall be considered. A full set of dimensions shall be provided by the technical 
documentation of the fitting manufacturer.  
  
26 
 
 
 
 
 
Key 
dn, le and r and α shall be in accordance with Table B.2  
dn nominal outside diameter  
le tubular length of fusion end piecea 
z1, z2, z3 nominal lengths of fitting branch to axis  
α nominal angle of fitting (±2 °) 
a The length shall allow the following (in any combination): the use of clamps required in the case of butt fusion; assembly wi th 
an electrofusion fitting; assembly with a socket fusion fitting; the use of a mechanical scraper. 
 
Figure B.4 — Segmented t ees 
 
For tees fabricated out of pipe segments, the following derating rules for the calculation of the PN shall 
apply:  
 
PN = fT × PN pipe 
where  
 
fT is the derating factor for these tees, having a value of 0 .5; 
 
PN pipe is the nominal pressure of the pipe.  
 
Practice has shown that these factors are applicable. Results of testing according to Table B.1  will 
determine the applicable factor fT. 
  
27 
 
 
 Annex C  
(informative)  
 
Examples of typical terminal connections for electrofusion fittings  
 
Figures C.1 and C.2 illus trate examples of te rminal connections suitable for use with voltages ≤48 V (types A 
and B).  
 
Dimensions in millimetres  
 
 
Key 
A active part   
C1 outside diameter of the terminal shroud  C1 ≥ 11,8  
C2 diameter of the active part of the terminal  C2 = 4,00 ± 0,1  
C3 internal dia meter of the terminal shroud  C3 = 9,5 ± 1,0  
C4 maximum overall diameter of the base of the active part  C4 ≤ 6,0  
H internal depth of the terminal  H ≥ 12,0  
H1 distance between the upper part of the terminal shroud 
and the active part  H1 = 3,2 ± 0,5  
a The height of the active part, H2, is such that 7 ≤ H2 ≤ H − H1  
 
Figure C.1 — Typical type A connection  
 
 
 
  
28 
 
 
 
 
Key 
A active part   
C1 outside diameter of the terminal shroud  C1 = 13,00 ± 0,5  
C2 diameter of the active part of the terminal  C2 = 4,70 ± 0,1  
C3 internal diameter of the terminal shroud  C3 = 10,0 − 0,1/+0,5  
H internal depth of the terminal shroud  H ≥ 15,5  
H1 distance between the upper part of the terminal shroud and the active part  
 
Figure C.3 illustrates an example of a typical electrofusion te rminal connection suitable for use with voltages 
up to 250 V (type C).  
 
 
 
Key 
A active part   
C1 outside diameter of the terminal shroud  C1 ≥ C3 + 2.0  
C2 diameter of the active part of the terminal  C2 ≥ 2.0 ± 0.1  
C3 internal diameter of the terminal shr oud C3 ≥ C2 + 4.0  
H1 distance between the upper part of the terminal shroud 
and H1: sufficient to ensure a degree of the active part 
protection of IP 2 X as defined in IEC 60529  
a The height of the active part, H2, is such that 7.0 ≤ H2.  (See Reference [ 10] in the Bibliography)  
 
Figure C.3 — Typical type C connection  
  
29 
 
 
 Annex D  
(normative)  
 
Short -term pressure test method  
 
D.1 Principle  
 
A test piece, consisting of an electrofusion fitting assembled with one or more PE pipes having reduced free 
length suf ficient to suppress pipe failure and create preferential failure in the fitting or in the connecting pipe -
to-fitting joint, is placed in a controlled -temperature environment and subjected to an essentially continually 
increasing internal hydraulic pressure  until failure occurs. The method is designed to establish the short -term 
failure pressure of the fitting/pipe assembly.  
 
D.2 Apparatus  
 
D.2.1  Constant -temperature water bath , in accordance with ISO 1167 -1, capable of being maintained at 
(20 ± 2) °C.  
 
D.2.2 Pressure test equipment , in accordance with ISO 1167 -1, capable of applying a continuously 
increasing internal hydraulic pressure at a rate of (5 ± 1) bar/min2 until the test piece fails.  
 
D.2.3  Pressure gauge , having an accuracy of not less than 1 % of full-scale deflection and with a hand 
which indicates the maximum pressure reached.  
 
A gauge shall be used that will indicate the failure pressure at approximately mid -scale. The gauge should 
preferably be equipped with a surge protection device.  
 
The gaug e shall be located in a position within the pressure system such that it will indicate the internal 
pressure of the test piece without being affected by pressure transients within the pressure supply lines, etc.  
 
D.3 Test piece  
 
The test piece shall be an assembly of one or more electrofusion fittings connected to PE pipes, with a 
minimum free pipe length between fittings of any type not exceeding dn. 
 
The pipes used shall be the thickest -walled pipe for which the fitting has been designed.  
 
The test piece shall be closed with type A end caps in accordance with ISO 1167 -1. 
 
D.4 Procedure  
 
Attach the end caps to the test piece and fill it with water at ambient temperature.  
 
Connect the test piece to the pressure source, ensuring that no air is trapped in the test assembly.  
 
Immerse the test piece in the constant -temperature bath and condition it at (20 ± 2) °C for at least as long as 
the period defined in ISO 1167 -1 for the appropriate pipe wall thickness.  
 
Increase the pressure uniformIy at a rate of (5 ± 1) bar/min until failure of the test piece occurs.  
 
Record the pressure at failure.  
 
After testing, inspect the test piece and record the location and mode of failure.  
 
D.5 Test report  
 
The test report shall include the following information:  
 
                                                 
2 1 bar = 0,1 MPa = 105 Pa; 1 MPa = 1 N/mm2  
30 
 
 
 a) a reference to this document, i.e. DMS 374 -3; 
 
b) all details necessary for complete identification of the pipes and socket fusion fittings used, including 
manufacturer, type of material and size of fitting and pipe;  
 
c) the details of the fusion -jointing procedure us ed to assemble the test piece;  
 
d) the pressure at failure;  
 
e) the time to failure;  
 
f) the failure location;  
 
g) the mode of failure, e.g. ductile in fitting, brittle along fusion interface;  
 
h) any factor that could have affected the results, such as an  incident or operating detail not specified in 
Annex D;  
 
i) the date of test.  
 
  
31 
 
 
 Annex E  
(normative)  
 
Tensile test for fitting/pipe assemblies  
 
E.1 Principle  
 
A test piece consisting of an electrofusion fitting and two connecting PE pipes is subjected to a n increasing 
tensile load at a constant pulling rate until ductile pipe failure occurs. The test is conducted at a constant 
temperature and is intended to simulate the creation of longitudinal tensile loading along a pipeline as a 
consequence of external m echanical interference. Rupture of the fitting or the connecting fusion joints is not 
an acceptable failure mode.  
 
E.2 Apparatus  
 
This shall be in accordance with ISO 13951,  with the additional requirement that the tensile -testing machine 
shall be capable of accommodating a test piece elongation of 25 % and of sustaining a constant test speed 
of (5 ± 1 .25) mm/min.  
 
E.3 Test piece  
 
The test piece shall be in accordance with ISO 13951.  
 
In cases where dn ≥ 180 mm and where the conduct of tensile tests on fitting/pipe assemblies is beyond the 
limits of the available test equipment, the testing of joint segments can be appropriate. Testing of segment 
test pieces shall not be undertaken, however, unless a cor relation with testing of complete pipe/joint 
assemblies has been established.  
 
NOTE  - When testing segmented test pieces, leak tightness is not checked.  
 
E.4 Procedure  
 
This shall be in accordance with ISO 13951,  but without the requirement for the load to  be constant. The 
pulling rate shall be 5 mm/min ± 25 %, sustained until a test piece elongation of 25 % is reached.  
 
E.5 Test report  
 
The test report shall include the following information:  
 
a) a reference to this document, i.e. DMS 374 -3; 
 
b) all detail s necessary for complete identification of the pipes and electrofusion fittings used, including the 
manufacturer, type of material, and size of fitting and pipe;  
 
c) the details of the fusion -jointing procedure used to assemble the test piece;  
 
d) the test  temperature;  
 
e) the leak tightness and integrity of the fitting and fusion joint after 25 % elongation of the test piece;  
 
f) any factor that could have affected the results, such as an incident or operating detail not specified in 
Annex E;   
 
g) the date  of test.  
  
32 
 
 
 Bibliography  
 
[1] ISO 4437 -3, Plastics piping systems for the supply of gaseous fuels — Polyethylene (PE) — Part 3: 
Fittings  
 
[2] CEN/TS 12201 -7, Plastics piping systems for water supply — Polyethylene (PE) — Part 7: Guidance 
for the assessment  of conformity  
 
[3]  EN 60335 -1, Household and similar electrical appliances — Safety — Part 1: General requirements 
(IEC 60335 -1:2001, modified)  
 
[4]  HD 60364 -1, Low-voltage electrical installations — Part 1: Fundamental principles, assessment of 
general  characteristics, definitions (IEC 60364 -1:2005, modified)  
 
[5] IEC 60449, Voltage bands for electrical installations of buildings  
 
[6]  ISO 11922 -1:2018, Thermoplastics pipes for the conveyance of fluids — Dimensions and tolerances 
— Part 1: Metric series  
 
[7]  ISO 21751, Plastics pipes and fittings — Decohesion test of electrofusion assemblies — Strip-bend 
test 
 
[8]  ISO/TR 10358, Plastics pipes and fittings — Combined chemical -resistance classification table  
 
[9] ISO 12176 -5:—3), Plastics pipes and fitti ngs — Equipment for fusion jointing polyethylene systems 
— Part 5: Two -dimensional data coding of components and data exchange format for PE piping 
systems  
 
[10] IEC 60529:1989, Degrees of protection provided by enclosures (IP Code)  
 
[11] ISO 13950, Plasti cs pipes and fittings — Automatic recognition systems for electrofusion joints  
  
 
 
 
  
  
 
 
ICS 93.025, 23.040.20, 23.040.45     DMS 374 -3:2021  
Second edition  
ISO 4427 -3:2019  
IDT 
 
 
 
 
 
 
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