oSIST prEN 448:2023

SLOVENSKI STANDARD
oSIST prEN 448:2023
01-september-2023
Nadomešča:
SIST EN 448:2020
Cevi za daljinsko ogrevanje - Poviti enocevni sistemi za neposredno vkopana
vročevodna omrežja - Tovarniško izdelana armatura iz jeklenih delovnih cevi,
obdanih s poliuretansko toplotno izolacijo in zaščitnim plaščem iz polietilena
District heating pipes - Bonded single pipe systems for directly buried hot water networks
- Factory made fitting assemblies of steel service pipes, polyurethane thermal insulation
and a casing of polyethylene
Fernwärmerohre - Einrohr-Verbundsysteme für direkt erdverlegte Fernwärmenetze -
Werkmäßig gefertigte Formstückbaueinheiten, bestehend aus Stahl-Mediumrohren,
einer Wärmedämmung aus Polyurethan und einer Ummantelung aus Polyethylen
Tuyaux de chauffage urbain - Systèmes bloqués monotube pour les réseaux enterrés
d'eau chaude pour des réseaux d'eau chaude enterrés directement - Assemblages de
raccords manufacturés pour tubes de service en acier, isolation thermique en
polyuréthane et tube de protection en polyéthylène
Ta slovenski standard je istoveten z: prEN 448
ICS:
23.040.07 Cevovodi za daljinsko Pipeline and its parts for
ogrevanje in njihovi deli district heat
23.040.40 Kovinski fitingi Metal fittings
91.140.65 Oprema za ogrevanje vode Water heating equipment
oSIST prEN 448:2023 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN 448:2023

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oSIST prEN 448:2023


DRAFT
EUROPEAN STANDARD
prEN 448
NORME EUROPÉENNE

EUROPÄISCHE NORM

July 2023
ICS 23.040.07; 23.060.01 Will supersede EN 448:2019
English Version

District heating pipes - Bonded single pipe systems for
directly buried hot water networks - Factory made fitting
assemblies of steel service pipes, polyurethane thermal
insulation and a casing of polyethylene
Tuyaux de chauffage urbain - Systèmes bloqués Fernwärmerohre - Einrohr-Verbundsysteme für direkt
monotubes pour des réseaux d'eau chaude enterrés erdverlegte Fernwärmenetze - Werkmäßig gefertigte
directement - Assemblages de raccords manufacturés Formstückbaueinheiten, bestehend aus Stahl-
pour tubes de service en acier, isolation thermique en Mediumrohren, einer Wärmedämmung aus
polyuréthane et tube de protection en polyéthylène Polyurethan und einer Ummantelung aus Polyethylen
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 107.

If this draft becomes a European Standard, 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.

This draft European Standard was established by CEN 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.

Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.


EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2023 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 448:2023 E
worldwide for CEN national Members.

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oSIST prEN 448:2023
prEN 448:2023 (E)
Contents Page
European foreword . 4
Introduction . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 7
4 Requirements . 8
4.1 Steel parts . 8
4.1.1 Specification . 8
4.1.2 Wall thickness and diameter . 8
4.1.3 Bends . 8
4.1.4 T-pieces . 9
4.1.5 Reducers .10
4.1.6 Welding of steel parts .10
4.1.7 Surface condition .14
4.2 Casing .14
4.3 Polyurethane foam thermal insulation .14
4.4 Fitting assembly .14
4.4.1 General .14
4.4.2 Thermal insulation series .14
4.4.3 Fitting ends .14
4.4.4 Angle between casing segments of bend and minimum length .15

4.4.5 Polyethylene welding .15
4.4.6 Diameter and wall thickness of the casing .16
4.4.7 Minimum thickness of the thermal insulation in fitting assembly .17
4.4.8 Tolerances of the main fitting dimensions .17
4.4.9 Expected thermal life and long term temperature resistance .17
4.4.10 Thermal conductivity .17
4.4.11 Surface conditions at delivery .18
4.4.12 Measuring wires for surveillance system .18
5 Test methods .18
5.1 General .18
5.2 Test specimens .18
5.3 Steel parts .18
5.3.1 Leak-tightness test with water .18
5.3.2 Visual leak-tightness test by air with over pressure .19
5.3.3 Visual leak-tightness test by air with below atmospheric pressure.19
5.4 Casing .19
5.4.1 Visual testing of weld seams on casing .19
5.4.2 Bending test of weld seams on casing .22
5.5 Fitting assembly .23
5.5.1 Centre line deviation and angular deviation .23
5.5.2 Minimum thickness of the polyurethane foam thermal insulation .23
5.5.3 Thermal conductivity in unaged condition .23
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oSIST prEN 448:2023
prEN 448:2023 (E)
6 Marking . 24
6.1 General . 24
6.2 Steel service pipe . 24
6.3 Steel fittings . 24
6.4 Casing . 24
6.5 Fitting assembly . 24
Annex A (informative) Guidelines for inspection and testing . 26
A.1 General . 26
A.2 Manufacturer’s type test . 26
A.3 Manufacturer’s quality control . 26
A.4 Additional inspection . 26
A.5 Manufacturer’s responsibility . 26
Annex B (informative) Procedures for casing welding . 29
B.1 General . 29
B.2 Recommendations for site, machine and equipment . 29
B.3 Items . 29
B.4 Butt fusion welding . 30
B.4.1 Equipment . 30
B.4.2 Welding procedure . 31
B.5 Extrusion welding . 31
B.5.1 Equipment . 31
B.5.2 Welding procedure . 32
Annex C (informative) Waste treatment and recycling . 33
Bibliography . 34

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oSIST prEN 448:2023
prEN 448:2023 (E)
European foreword
This document (prEN 448:2023) has been prepared by Technical Committee CEN/TC 107 “Prefabricated
district heating and district cooling pipe system”, the secretariat of which is held by DS.
This document is currently submitted to the CEN Enquiry.
This document will supersede EN 448:2019.
The main changes compared to the previous edition are listed below:
— two more ultrasonic testing methods for testing of welds are added to Table 4;
— alignment with the structure of EN 253;
— according to 4.1.3.3, the requirements for hot-formed bends are to be agreed between purchaser and
supplier;
— according to 4.1.3.3, the requirements for hot-formed bends are to be agreed between purchaser and
supplier;
— anchors are no longer included;
— single use compensators and caps are no longer included, they are covered by EN 13941-1;
— for steel welding, requirements for the welding contractor and welding consumables are specified in
4.1.6.1 and 4.1.6.3;
— requirements for steel weld preparation are omitted;
— requirements for distance between parallel weld seams are specified in 4.1.6.5.2;
— preparation of set-on branch with steel plate for reinforcement has been added in 4.1.6.5.3;
— requirement for imperfections of weld seams in 4.1.6.6.1 has been adapted to EN 13941-2;
— non-destructive testing (NDT) of weld seams in 4.1.6.6.2 is adapted to EN 13941-2;
— test methods for leak testing of steel weld seams have been clarified in 5.3;
— requirements for visual inspection of PE weld seams in 5.4.1 have been revised and explanatory
figures have been added;
— requirements for marking of fitting assemblies have been added in 6.5;
— recommendations for qualifications of PE welders have been added to B.1.
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oSIST prEN 448:2023
prEN 448:2023 (E)
Introduction
prEN 448 has been aligned with prEN 488-1 and other relevant European Standards.
Other standards from CEN/TC 107 are:
— EN 253, District heating pipes - Bonded single pipe systems for directly buried hot water networks -
Factory made pipe assembly of steel service pipe, polyurethane thermal insulation and a casing of
polyethylene
— prEN 488-1, District heating pipes — Bonded single pipe systems for directly buried hot water networks
— Part 1: Factory made steel valve assembly for steel service pipes, polyurethane thermal insulation
and a casing of polyethylene;
— prEN 488-2, District heating and district cooling pipes - Bonded pipe systems for directly buried hot and
cold water networks - Part 2: Factory made steel valve assembly for draining and venting, polyurethane
thermal insulation and a casing of polyethylene
— EN 489-1, District heating pipes - Bonded single and twin pipe systems for buried hot water networks -
Part 1: Joint casing assemblies and thermal insulation for hot water networks in accordance with
EN 13941-1
— EN 13941-1, District heating pipes - Design and installation of thermal insulated bonded single and
twin pipe systems for directly buried hot water networks - Part 1: Design
— EN 13941-2, District heating pipes - Design and installation of thermal insulated bonded single and
twin pipe systems for directly buried hot water networks - Part 2: Installation
— EN 14419, District heating pipes - Bonded single and twin pipe systems for buried hot water networks
- Surveillance systems
— EN 15632 (all parts), District heating pipes - Factory made flexible pipe systems
— prEN 15698-1, District heating pipes - Bonded twin pipe systems for directly buried hot water networks
- Part 1: Factory made twin pipe assembly of steel service pipes, polyurethane thermal insulation and
one casing of polyethylene
— prEN 15698-2, District heating pipes - Bonded twin pipe systems for directly buried hot water networks
- Part 2: Factory made fitting and valve assemblies of steel service pipes, polyurethane thermal
insulation and one casing of polyethylene
— EN 17248, District heating and district cooling pipe systems - Terms and definitions
— EN 17414 (all parts), District cooling pipes - Factory made flexible pipe systems
— EN 17415 (all parts), District cooling pipes - Bonded single pipe systems for directly buried cold water
networks
— EN 17878 (all parts), District heating pipes - Factory made flexible pipe systems with a lower
temperature profile
Waste management and recycling of materials is dealt with in Annex C.
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oSIST prEN 448:2023
prEN 448:2023 (E)
1 Scope
This document specifies requirements and test methods for factory made thermally insulated bonded
fitting assemblies for hot water networks in accordance with EN 13941-1, comprising a steel service pipe,
in most cases a steel fitting, polyurethane (PUR) foam thermal insulation and a casing of polyethylene.
The fitting assembly can also include the following additional elements: measuring wires, spacers and
diffusion barriers.
This document covers the following fitting assemblies: bend, tee and reducer.
This document applies to fitting assemblies with a minimum design pressure of 1,6 MPa.
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 253, District heating pipes - Bonded single pipe systems for directly buried hot water networks - Factory
made pipe assembly of steel service pipe, polyurethane thermal insulation and a casing of polyethylene
EN 10204, Metallic products - Types of inspection documents
EN 10216-2, Seamless steel tubes for pressure purposes - Technical delivery conditions - Part 2: Non-alloy
and alloy steel tubes with specified elevated temperature properties
EN 10217-2, Welded steel tubes for pressure purposes - Technical delivery conditions - Part 2: Electric
welded non-alloy and alloy steel tubes with specified elevated temperature properties
EN 10217-5, Welded steel tubes for pressure purposes - Technical delivery conditions - Part 5: Submerged
arc welded non-alloy and alloy steel tubes with specified elevated temperature properties
EN 10253-2, Butt-welding pipe fittings - Part 2: Non alloy and ferritic alloy steels with specific inspection
requirements
EN 12814-1, Testing of welded joints of thermoplastics semi-finished products - Part 1: Bend test
EN 13018, Non-destructive testing - Visual testing - General principles
EN 13941-1, District heating pipes - Design and installation of thermal insulated bonded single and twin
pipe systems for directly buried hot water networks - Part 1: Design
EN 13941-2, District heating pipes - Design and installation of thermal insulated bonded single and twin
pipe systems for directly buried hot water networks - Part 2: Installation
EN 14419, District heating pipes - Bonded single and twin pipe systems for buried hot water networks -
Surveillance systems
EN 17248, District heating and district cooling pipe systems - Terms and definitions
EN ISO 3452-1, Non-destructive testing - Penetrant testing - Part 1: General principles (ISO 3452-1)
EN ISO 3834-3, Quality requirements for fusion welding of metallic materials - Part 3: Standard quality
requirements (ISO 3834-3)
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oSIST prEN 448:2023
prEN 448:2023 (E)
EN ISO 5579, Non-destructive testing - Radiographic testing of metallic materials using film and X- or
gamma rays - Basic rules (ISO 5579)
EN ISO 5817, Welding - Fusion-welded joints in steel, nickel, titanium and their alloys (beam welding
excluded) - Quality levels for imperfections (ISO 5817)
EN ISO 8501-1, Preparation of steel substrates before application of paints and related products - Visual
assessment of surface cleanliness - Part 1: Rust grades and preparation grades of uncoated steel substrates
and of steel substrates after overall removal of previous coatings (ISO 8501-1)
EN ISO 9606-1, Qualification testing of welders - Fusion welding - Part 1: Steels (ISO 9606-1)
EN ISO 9934-1, Non-destructive testing - Magnetic particle testing - Part 1: General principles (ISO 9934-1)
EN ISO 10675-1, Non-destructive testing of welds - Acceptance levels for radiographic testing - Part 1: Steel,
nickel, titanium and their alloys (ISO 10675-1)
EN ISO 11666, Non-destructive testing of welds - Ultrasonic testing - Acceptance levels (ISO 11666)
EN ISO 14732, Welding personnel - Qualification testing of welding operators and weld setters for
mechanized and automatic welding of metallic materials (ISO 14732)
EN ISO 15607, Specification and qualification of welding procedures for metallic materials - General rules
(ISO 15607)
EN ISO 16810, Non-destructive testing - Ultrasonic testing - General principles (ISO 16810)
EN ISO 17636-1, Non-destructive testing of welds - Radiographic testing - Part 1: X- and gamma-ray
techniques with film (ISO 17636-1)
EN ISO 17636-2, Non-destructive testing of welds - Radiographic testing - Part 2: X- and gamma-ray
techniques with digital detectors (ISO 17636-2)
EN ISO 17637, Non-destructive testing of welds - Visual testing of fusion-welded joints (ISO 17637)
EN ISO 17638, Non-destructive testing of welds - Magnetic particle testing (ISO 17638)
EN ISO 17640, Non-destructive testing of welds - Ultrasonic testing - Techniques, testing levels, and
assessment (ISO 17640)
EN ISO 23277, Non-destructive testing of welds - Penetrant testing - Acceptance levels (ISO 23277)
EN ISO 23278, Non-destructive testing of welds - Magnetic particle testing - Acceptance levels (ISO 23278)
3 Terms and definitions
For the purpose of this document, the terms and definitions given in EN 17248 apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— IEC Electropedia: available at https://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp
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oSIST prEN 448:2023
prEN 448:2023 (E)
4 Requirements
4.1 Steel parts
4.1.1 Specification
Steel grades are specified in EN 13941-1.
All steel service pipes and steel fittings used for manufacturing of fitting assemblies under the scope of
this document shall as a minimum be delivered to the manufacturer with an inspection certificate 3.1
according to EN 10204. The inspection certificate shall on request be passed on to the customer.
In case a material related inspection certificate 3.1 according to EN 10204 is required by the client who
orders the fitting assemblies, this request shall be given whilst placing the order with the manufacturer
of the fitting assemblies.
NOTE 1 Any later request for provision of such documentation could be too late and possibly can’t be met by the
manufacturer, since the start of the production is depending on organizing the assignment of 3.1 certificates to the
steel valves and parts of the steel service pipes beforehand.
NOTE 2 For cold-formed bends, the material according to EN 10204 apply to the values of the chemical
composition, but not to the values of the mechanical properties.
4.1.2 Wall thickness and diameter
According to the scope of this document, all steel components shall be designed for a minimum of 1,6 MPa.
If the fitting assemblies are used in situations with design pressures higher than 1,6 MPa, extra
calculations will be necessary.
The nominal diameter and the minimum nominal wall thickness of all steel components shall prior to
processing be at least the same as for the service pipes regarding EN 253.
At the end of the fitting assembly, the outside diameter, the tolerances on the diameter of the pipe ends
and the wall thickness shall be the same as for the service pipes in accordance with EN 253.
Subject to design considerations other wall thicknesses than those given in EN 253 may be used, but in
no case shall these be less than the minima indicated in EN 253.
All components shall be designed in accordance with EN 13941-1, for the actions and stresses that
normally occur during the service life of the fitting assembly (or of the component).
4.1.3 Bends
4.1.3.1 Butt welding bends
The manufacturing process and dimensions shall be in accordance with EN 10253-2 with the exception
that the bend radius shall be ≥ 1,5 times the outer diameter.
4.1.3.2 Cold formed bends
Cold formed bends shall be produced from seamless pipe or longitudinal welded pipes.
After bending, the minimum wall thickness of the bent pipe shall be not less than 85 % of the wall
thickness of the straight service pipe, see EN 253.
The maximum ovality in the bent area shall not exceed 6 %.
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oSIST prEN 448:2023
prEN 448:2023 (E)
The formula for the calculation of the ovality is:
DD−
s,,max s min
O ⋅ 100 (1)
D
s
where
O is the ovality, in %;
is the maximum outside diameter;

D
s,max
is the minimum outside diameter in the same cross section in the bended area;

D
s,min
is the specified outside diameter.
D
s
There shall be no folding in the bent area. Waves can be accepted, when the maximum height between
trough and crest of the wave does not exceed 25 % of the nominal wall thickness of the bent pipe.
4.1.3.3 Hot-formed bends
Hot-formed bends shall be delivered by agreement between purchaser and supplier. If nothing else is
agreed, the same requirements apply as in 4.1.3.2.
4.1.3.4 Tolerances of bending angles for cold- and hot-formed bends
The deviation from the nominal bending angle for cold- and hot-formed bends shall not exceed the
tolerances given in Table 1.
Table 1 — Deviations from nominal bending angle for cold- and hot-formed bends
Nominal diameter of Deviation
service pipe
≤ DN 200 ±2,0°
> DN 200 ±1,0°
4.1.4 T-pieces
4.1.4.1 T-pieces produced by hot deformation process
T-pieces shall be produced by hot deformation processes according to EN 10253-2.
The wall thickness t and t , see EN 10253-2, shall be at least the same as those for the straight pipes, see
1
EN 253. All other dimensions shall be in accordance with EN 10253-2.
4.1.4.2 T-piece as set-on branch
T-pieces as set-on branch shall be manufactured by welding the branch pipe directly to the main pipe,
without or with compensating (reinforcement) plates according to EN 13941-1 requirements, see
Figure 2 and Figure 3. The branch pipes shall be perpendicular to the main pipes within a tolerance
of ± 2,0°.
4.1.4.3 T-piece by drawing a collar
T-pieces by drawing a collar shall be manufactured by hot drawing a collar on which the branch pipe is
welded. The wall thickness of the collar shall be at least the same as that for the branch pipe, see EN 253.
The collar shall be drawn opposite the welding seam in the main pipe.
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oSIST prEN 448:2023
prEN 448:2023 (E)
T-pieces manufactured by drawing a collar shall be free from external and internal surface defects that
can be detected by visual testing.
The internal and external surface finish of the fittings shall be typical of the manufacturing process and,
where applicable, the heat treatment employed. Normally the finish and surface
...