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

This document specifies requirements and test methods for straight lengths of factory made thermally insulated bonded single pipe assemblies for hot water networks in accordance with EN 13941-1, comprising a steel service pipe, polyurethane foam thermal insulation and a casing of polyethylene.
The pipe assembly can also include the following additional elements: measuring wires, spacers and diffusion barriers.

Fernwärmerohre - Einzelrohr-Verbundsysteme für direkt erdverlegte Fernwärmenetze - Werkmäßig gefertigte Verbundrohrsysteme, bestehend aus Stahl-Mediumrohr, einer Wärmedämmung aus Polyurethan und einer Ummantelung aus Polyethylen

Dieses Dokument legt die Anforderungen und Prüfverfahren fest für gerade Abschnitte von werkmäßig gedämmten Einzelrohrsystemen für Fernwärmenetzwerke in Übereinstimmung mit EN 13941-1, die aus einem Stahl-Mediumrohr, einer Polyurethan-Hartschaumstoffwärmedämmung und einem Polyethylenmantel bestehen.
Das Verbund-Rohrsystem kann darüber hinaus die folgenden zusätzlichen Bauteile umfassen: Messdrähte, Abstandhalter und Diffusionsbarrieren.

Tuyaux de chauffage urbain - Systèmes bloqués de tuyaux pour les réseaux d'eau chaude enterrées directement - Assemblages de tubes de service en acier manufacturés, isolation thermique en polyuréthane et tube de protection en polyéthylène

Le présent document spécifie les exigences et les méthodes d’essai applicables aux longueurs droites des assemblages de tubes bloqués manufacturés isolés thermiquement pour les réseaux d'eau chaude conformes à l’EN 13941-1, comprenant un tube de service en acier, une isolation thermique en mousse de polyuréthane et un tube de protection en polyéthylène.
L’assemblage de raccord peut également comprendre les éléments supplémentaires suivants : câbles de mesure, entretoises et barrières anti-diffusion.

Cevi za daljinsko ogrevanje - Poviti enocevni sistemi za neposredno vkopana vročevodna omrežja - Tovarniško izdelan cevni sestav iz jeklene delovne cevi, obdane s poliuretansko toplotno izolacijo in zaščitnim plaščem iz polietilena

Ta evropski standard določa zahteve in preskusne metode za ravne odseke tovarniško izdelanih toplotno izoliranih enocevnih sestavov za vročevodna omrežja v skladu s standardom prEN 13941-1:2016, ki so sestavljeni iz jeklenih cevi, trde poliuretanske izolacijske pene in polietilenskega plašča. Cevni sestav lahko vključuje tudi naslednje dodatne elemente: merilne žice, distančnike in difuzijske pregrade.

General Information

Status
Published
Publication Date
15-Oct-2019
Current Stage
6060 - Definitive text made available (DAV) - Publishing
Due Date
16-Oct-2019
Completion Date
16-Oct-2019

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SLOVENSKI STANDARD
SIST EN 253:2020
01-januar-2020
Nadomešča:
SIST EN 253:2009+A2:2015
Cevi za daljinsko ogrevanje - Poviti enocevni sistemi za neposredno vkopana
vročevodna omrežja - Tovarniško izdelan cevni sestav iz jeklene delovne cevi,
obdane s poliuretansko toplotno izolacijo in zaščitnim plaščem iz polietilena

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
Fernwärmerohre - Werkmäßig gedämmte Verbundmantelrohrsysteme für direkt
erdverlegte Fernwärmenetze - Verbund-Rohrsystem bestehend aus Stahl-Mediumrohr,
Polyurethan-Wärmedämmung und Außenmantel aus Polyethylen
Tuyaux de chauffage urbain - Systèmes bloqués de tuyaux pour les réseaux d'eau
chaude enterrées directement - Assemblages de tubes de service en acier

manufacturés, isolation thermique en polyuréthane et tube de protection en polyéthylène

Ta slovenski standard je istoveten z: EN 253:2019
ICS:
23.040.07 Cevovodi za daljinsko Pipeline and its parts for
ogrevanje in njihovi deli district heat
23.040.10 Železne in jeklene cevi Iron and steel pipes
91.140.65 Oprema za ogrevanje vode Water heating equipment
SIST EN 253:2020 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 253:2020
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SIST EN 253:2020
EN 253
EUROPEAN STANDARD
NORME EUROPÉENNE
October 2019
EUROPÄISCHE NORM
ICS 23.040.07; 23.040.10 Supersedes EN 253:2009+A2:2015
English Version
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

Tuyaux de chauffage urbain - Systèmes bloqués de Fernwärmerohre - Werkmäßig gedämmte

tuyaux pour les réseaux d'eau chaude enterrées Verbundmantelrohrsysteme für direkt erdverlegte

directement - Assemblages de tubes de service en acier Fernwärmenetze - Verbund-Rohrsystem bestehend

manufacturés, isolation thermique en polyuréthane et aus Stahl-Mediumrohr, Polyurethan-Wärmedämmung

tube de protection en polyéthylène und Außenmantel aus Polyethylen
This European Standard was approved by CEN on 26 August 2019.

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, Turkey 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

© 2019 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 253:2019 E

worldwide for CEN national Members.
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SIST EN 253:2020
EN 253:2019 (E)
Contents Page

European foreword ................................................................................................................................................................ 3

Introduction ............................................................................................................................................................................. 4

1 Scope ............................................................................................................................................................................. 5

2 Normative references ............................................................................................................................................. 5

3 Terms and definitions ............................................................................................................................................ 6

4 Requirements ............................................................................................................................................................ 6

5 Test methods .......................................................................................................................................................... 16

6 Marking ..................................................................................................................................................................... 26

Annex A (informative) Relation between actual continuous operating conditions and

accelerated ageing test conditions.................................................................................................................. 28

Annex B (informative) Guidelines for inspection and testing .............................................................................. 32

Annex C (normative) Thermal conductivity of factory made pipe assemblies — Test procedure ........ 36

Annex D (informative) Waste treatment and recycling ......................................................................................... 41

Bibliography .......................................................................................................................................................................... 42

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SIST EN 253:2020
EN 253:2019 (E)
European foreword

This document (EN 253:2019) has been prepared by Technical Committee CEN/TC 107 “Prefabricated

district heating and district cooling pipe systems”, the secretariat of which is held by DS.

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 2020, and conflicting national standards shall be withdrawn at

the latest by April 2020.

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 253:2009+A2:2015.

In comparison with the previous edition, the main changes in this new edition of EN 253 are:

— editorial changes to the new structure of standards prepared by the Technical Committee CEN/TC 107;

— specification of steel grade moved into EN 13941-1;
— added thermal insulation series;
— added linear water tightness: requirements and test method;

— revised description of expected thermal life and long term temperature resistance in balance with

EN 13941-1;
— revised description on shear strength: requirements and test method;
— removed Tangential shear strength and long-term creep resistance and modulus;

— revised Annex A, “Relation between actual continuous operating condition and accelerated ageing test

conditions”;
— removed Annex C, “Calculated Continuous Operating Temperature (CCOT)”.

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, Turkey and the United Kingdom.

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SIST EN 253:2020
EN 253:2019 (E)
Introduction

This specification is part of the standards for bonded pipe systems for district heating using polyurethane

(PUR) foam thermal insulation applied to bond to a steel service pipe and a polyethylene (PE) casing.

The other standards from CEN/TC 107 covering this subject are:

— EN 448, 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;

— EN 488, District heating pipes – Bonded single pipe systems for directly buried hot water networks –

Factory made steel valve assembly for steel service pipes, polyurethane thermal insulation and a casing of

polyethylene;

— EN 489-1, District heating pipes – Bonded single and twin pipe systems for directly 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 directly buried hot water

networks – Surveillance systems;

— EN 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;

— EN 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.

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SIST EN 253:2020
EN 253:2019 (E)
1 Scope

This document specifies requirements and test methods for straight lengths of factory made thermally

insulated bonded single pipe assemblies for hot water networks in accordance with EN 13941-1, comprising

a steel service pipe, polyurethane foam thermal insulation and a casing of polyethylene.

The pipe assembly can also include the following additional elements: measuring wires, spacers and

diffusion barriers.
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 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 10220, Seamless and welded steel tubes — Dimensions and masses per unit length

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 14419, District heating pipes — Preinsulated bonded pipe systems for directly buried hot water networks —

Surveillance systems

EN 17248, District heating and district cooling pipe systems — Terms and definitions

EN ISO 845, Cellular plastics and rubbers — Determination of apparent density (ISO 845)

EN ISO 1133 (all parts), Plastics — Determination of the melt mass-flow rate (MFR) and melt volume-flow rate

(MVR) of thermoplastic (ISO 1133 series)

EN ISO 2505, Thermoplastics pipes — Longitudinal reversion — Test method and parameters (ISO 2505)

EN ISO 3126, Plastics piping systems — Plastics components — Determination of dimensions (ISO 3126)

EN ISO 4590, Rigid cellular plastics — Determination of the volume percentage of open cells and of closed cells

(ISO 4590)

EN ISO 6259-1, Thermoplastics pipes — Determination of tensile properties — Part 1: General test method (ISO

6259-1)

EN ISO 8497:1996, Thermal insulation — Determination of steady-state thermal transmission properties of

thermal insulation for circular pipes (ISO 8497:1994)
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SIST EN 253:2020
EN 253:2019 (E)

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 3127:2017, Thermoplastics pipes — Determination of resistance to external blows — Round-the-clock

method (ISO 3127:1994)

EN ISO 9080, Plastics piping and ducting systems — Determination of the long-term hydrostatic strength of

thermoplastics materials in pipe form by extrapolation (ISO 9080)

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 12162, Thermoplastics materials for pipes and fittings for pressure applications — Classification,

designation and design coefficient (ISO 12162)
EN ISO 844, Rigid cellular plastics — Determination of compression properties
ISO 6761, Steel tubes — Preparation of ends of tubes and fittings for welding

ISO 6964, Polyolefin pipes and fittings — Determination of carbon black content by calcination and pyrolysis —

Test method

ISO 11414:2009, Plastics pipes and fittings — Preparation of polyethylene (PE) pipe/pipe or pipe/fitting test

piece assemblies by butt fusion

ISO 13953, Polyethylene (PE) pipes and fittings — Determination of the tensile strength and failure mode of

test pieces from a butt-fused joint

ISO 16770, Plastics — Determination of environmental stress cracking (ESC) of polyethylene — Full notch

creep test (FNCT)

ISO 18553, Method for the assessment of the degree of pigment or carbon black dispersion in polyolefin pipes,

fittings and compounds
3 Terms and definitions

For the purposes of this document, the terms and definitions given in EN 17248 apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
4 Requirements
4.1 General

Unless otherwise specified, the requirements shall be valid for each single measurement.

For information on suitable guidelines for inspection, see Annex B.
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EN 253:2019 (E)
4.2 Steel service pipe
4.2.1 Specification
Steel grades are specified in EN 13941-1.

All steel pipes and components used for manufacturing of pipe 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 pipe assemblies, this request shall be given whilst placing the order with the manufacturer of the

pipe assemblies.

NOTE Any later request for provision of such documentation could be too late and possibly can't be met by the

manufacturer, since the manufacturer has to organize the assignment of 3.1 certificates to the steel service pipes before

starting the production.
A length of pipe shall not include a circular weld.
4.2.2 Diameter
The diameter shall be in accordance with Table 1 which is derived from EN 10220.

The tolerances on the outside diameter, d , of the steel service pipe at the pipe ends, shall be in accordance

with EN 10216-2, EN 10217-2 or EN 10217-5. Diameter measurements shall be made using a

circumferential tape. The diameter shall be calculated as the actual circumference divided by π. Outside

diameter, d , 168,3 and smaller may be measured using a slide calliper.

The out-of-roundness shall be determined in accordance with EN 10216-2, EN 10217-2 or EN 10217-5.

4.2.3 Wall thickness

The wall thicknesses, t, and masses shall be in accordance with EN 10220 with a minimum as indicated in

Table 1. The tolerances on the wall thickness of the steel service pipe, shall be in accordance with

EN 10216-2, EN 10217-2 or EN 10217-5.
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SIST EN 253:2020
EN 253:2019 (E)
Table 1 — Steel service pipe dimensions
Nominal diameter Outside diameter Wall thickness
DN d t
mm
15 21,3 2,0
20 26,9 2,0
25 33,7 2,3
32 42,4 2,6
40 48,3 2,6
50 60,3 2,9
65 76,1 2,9
80 88,9 3,2
100 114,3 3,6
125 139,7 3,6
150 168,3 4,0
200 219,1 4,5
250 273,0 5,0
300 323,9 5,6
350 355,6 5,6
400 406,4 6,3
450 457,0 6,3
500 508,0 6,3
600 610,0 7,1
700 711,0 8,0
800 813,0 8,8
900 914,0 10,0
1 000 1 016,0 11,0
1 200 1 219,0 12,5
4.2.4 Surface condition

In order to ensure proper bonding between the steel service pipe and the thermal insulation, the following

procedure shall be followed:

Prior to thermal insulation, the outer surface of the pipe shall be cleaned so that it is free from rust, mill

scale, oil, grease, dust, paint, moisture and other contaminants.

Before cleaning the steel service pipe, the outer surface shall comply with rust grade A, B or C according to

EN ISO 8501-1, without pitting.
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SIST EN 253:2020
EN 253:2019 (E)
4.3 Casing
4.3.1 Material properties
4.3.1.1 Material composition

The casing material shall be black coloured PE virgin or rework material containing only those anti-oxidants,

UV-stabilizers and carbon black necessary for the manufacture and use of pipe assemblies to this

specification. The black coloured PE material to be extruded shall be tested in accordance with EN ISO 9080

and classified at least a PE 80 material in accordance with EN ISO 12162.

The casing may be a separately manufactured pipe or be applied directly onto the PUR thermal insulation by

extrusion.

The carbon black content shall, when tested in accordance with ISO 6964, be (2,5 ± 0,5) % by mass.

The carbon black shall be finely dispersed in the material. When tested in accordance with 5.2.3, the

following requirements shall be met:
— Carbon black agglomerates and particles shall be grade ≤ 3.
— Dispersion rating shall be A1, A2 or A3 according to ISO 18553.

NOTE The required carbon black content ensures UV stability for the service life.

4.3.1.2 Melt mass-flow rate

The melt mass-flow rate (MFR), in g/10 min, of black PE materials used for the manufacturing of casings

shall lie within 0,2 < MFR ≤ 1,0 g/10 min determined in accordance with EN ISO 1133 (all parts), condition

5 kg, 190 °C.

Black coloured PE materials conforming to 4.3.1.1, which do not differ more than 0,5 g/10 min in MFR shall

be considered fusible to each other.

Casings made of PE materials outside this MFR range of 0,5 g/10 min may be fusion welded provided that

the manufacturer of the pipe assembly has demonstrated fusion compatibility by preparing a butt fusion

joint using the parameters as specified in Annex A of ISO 11414:2009. The requirement of fusion

compatibility is a ductile failure mode of the joint when tested at 23 °C in accordance with ISO 13953.

4.3.1.3 Thermal stability

The thermal stability is determined by oxygen induction time (OIT) of the black coloured PE material and

shall be at least 20 min when tested at 210 °C according to EN ISO 11357-6.
4.3.1.4 Use of rework material

Only clean, not degraded, rework material, generated from the manufacturer's own production, shall be

used.
4.3.2 Casing properties
4.3.2.1 Nominal outside diameter
The nominal outside diameter of the casing should be selected from Table 2.
The actual outside diameter shall be measured in accordance with EN ISO 3126.
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SIST EN 253:2020
EN 253:2019 (E)
4.3.2.2 Wall thickness

If the casing includes a diffusion barrier the wall thickness of one single PE layer of the casing shall be in

accordance with Table 2.
The actual wall thickness shall be measured in accordance with EN ISO 3126.
Table 2 — Casing dimensions
Nominal outside Minimum wall
diameter thickness
D e
c min
mm mm
90 3,0
110 3,0
125 3,0
140 3,0
160 3,0
180 3,0
200 3,2
225 3,4
250 3,6
280 3,9
315 4,1
355 4,5
400 4,8
450 5,2
500 5,6
560 6,0
630 6,6
710 7,2
800 7,9
900 8,7
1 000 9,4
1 100 10,2
1 200 11,0
1 400 12,5
4.3.2.3 Appearance, surface finish, casing ends

The internal and external surfaces of the casing shall be clean and free from such grooving or other defects

that might impair its functional properties (see 5.2.1).
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SIST EN 253:2020
EN 253:2019 (E)

The casing ends shall be cleanly cut and shall be square within 2,5° with the axis of the pipe.

Surface treatment to improve the shear strength between the PUR foam and casing is permissible provided

that the treated pipe assembly still complies with the specification.
4.3.2.4 Elongation at break

The elongation at break determined in accordance with 5.2.2 shall not be less than 350 %.

4.3.2.5 Heat reversion

When tested in accordance with EN ISO 2505, the longitudinal length at any position on the casing shall not

change by more than 3 %. On inspection after testing, the casing shall not show any faults, cracks, cavities or

blisters.
4.3.2.6 Stress crack resistance

When tested in accordance with 5.2.4, the time to failure shall not be less than 300 h.

4.4 Polyurethane (PUR) foam thermal insulation
4.4.1 Composition

The manufacturer of the pipe assembly shall be responsible for the choice of raw materials, composition and

manufacturing conditions.

The manufacturer shall keep records, documenting the raw materials used, the prescribed mixing ratio and

the tests performed.

The records shall demonstrate that the PUR foam from production of pipe assemblies is of the same

composition as the foam sample used for the ageing test in 5.4.2 and meets the requirements of 4.4.

4.4.2 Cell structure
4.4.2.1 General appearance
The PUR foam shall have a uniform cell structure free from smears.
4.4.2.2 Cell size

The average cell size of the cells in a radial direction shall be less than 0,5 mm, determined in accordance

with 5.3.2.1.
4.4.2.3 Closed cell content

The closed cell content determined in accordance with 5.3.2.2 shall be not less than 88 %.

4.4.2.4 Voids and bubbles

The average area of voids and bubbles determined on the five cross sections in accordance with 5.3.2.3 shall

not constitute more than 5 % of the cross sectional area of the PUR foam. No single void shall be larger than

2/3 of the insulation thickness between the steel service pipe and the casing at the position of the void.

4.4.3 Compressive strength

The compressive strength or the compressive stress at 10 % relative deformation as defined in EN ISO 844

shall be not less than 0,3 MPa in a radial direction when tested in accordance with 5.3.3.

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SIST EN 253:2020
EN 253:2019 (E)
4.4.4 Foam density

The density of the foam at any position shall comply with the criteria below when calculated in accordance

with 5.3.4.

At both pipe ends, all three specimens shall each have a density of minimum 55 kg/m .

4.4.5 Water absorption at elevated temperature

When tested in accordance with 5.3.5, the water absorption after 90 min of immersion in boiling water shall

not exceed 10 % of the original volume. The volume of each specimen after the test shall not be less than

75 % of the original volume.
4.5 Pipe assembly
4.5.1 General
All requirements are valid including the diffusion barrier, if any.
4.5.2 Thermal insulation series

For thermal insulation series, Table 3 gives the allocation of the nominal diameter of service pipes and

casing diameters.
Table 3 — Thermal insulation series
Nominal diameter of Casing diameter, Casing diameter, Casing diameter,
service pipes thermal insulation thermal insulation thermal insulation
series 1 series 2 series 3
a b b b
DN D D D
C C C
mm mm mm
20 90 110 125
25 90 110 125
32 110 125 140
40 110 125 140
50 125 140 160
65 140 160 180
80 160 180 200
100 200 225 250
125 225 250 280
150 250 280 315
200 315 355 400
250 400 450 500
300 450 500 560
350 500 560 630
400 560 630 710
450 630 710 800
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SIST EN 253:2020
EN 253:2019 (E)
Nominal diameter of Casing diameter, Casing diameter, Casing diameter,
service pipes thermal insulation thermal insulation thermal insulation
series 1 series 2 series 3
a b b b
DN D D D
C C C
mm mm mm
500 710 800 900
600 800 900 1 000
700 900 1 000 1 100
800 1 000 1 100 1 200
900 1 100 1 200
1 000 1 200
1 200 1 400
Dimensions, see Table 1
Dimensions, see Table 2
4.5.3 Pipe ends without thermal insulation

Both ends of the service pipe shall be free from thermal insulation. The manufacturer shall declare a value

for the length of this free ends between 150 mm and 250 mm. The tolerance on the declared value within

this range shall be ± 10 mm.
Service pipe ends shall be prepared for welding in accordance with ISO 6761.
4.5.4 Diameter and wall thickness of the casing

The outside diameter of the casing shall at any point be between the minimum diameter D and the

min

maximum diameter D as given in Table 4. The minimum wall thickness of the casing, e , shall at any

max min

point be in accordance with Table 4. The measured values for the outside diameter and wall thickness shall

be rounded off to the next higher 0,1 mm.
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EN 253:2019 (E)
Table 4 — Casing dimensions of the pipe assembly
Nominal Minimum Maximum Minimum wall
outside outside outside thickness
diameter diameter diameter
min
D D D
c min max
mm mm mm
90 90 95 3,0
110 110 116 3,0
125 125 132 3,0
140 140 147 3,0
160 160 168 3,0
180 180 189 3,0
200 200 206 3,2
225 225 232 3,4
250 250 258 3,6
280 280 289 3,9
315 315 325 4,1
355 355 366 4,5
400 400 412 4,8
450 450 464 5,2
500 500 515 5,6
560 560 577 6,0
630 630 649 6,6
710 710 732 7,2
800 800 824 7,9
900 900 927 8,7
1 000 1 000 1 030 9,4
1 100 1 100 1 133 10,2
1 200 1 200 1 236 11,0
1 400 1 400 1 442 12,5
4.5.5 Centre line deviation

The distance between the centre lines of the steel service pipe and the casing at any point shall not exceed

the limits given in Table 5.
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EN 253:2019 (E)
Table 5 — Centre line deviation related to the nominal diameters
Nominal outside diameter of casings Maximum centre line deviation
mm mm
90 to 160 3,0
180 to 400 5,0
450 to 630 8,0
710 to 800 10,0
900 to 1 400 14,0
4.5.6 Expected thermal life and long term temperature resistance
4.5.6.1 General remarks

The decline in shear strength over time is a combination of thermal stresses and oxidative processes.

Annex A describes the state of the art knowledge on this subject.

According to EN 13941-1, pipe systems for district heating shall be designed for a service life of minimum

30 years for continuous operation with hot water at various temperatures up to 120 °C and at individual

time intervals with a peak temperature up to 140 °C. The sum of these individual time intervals shall, in

average, not exceed 300 h a year.

The estimation of service life at continuous operating temperatures lower than 120 °C requires assumptions

about the Arrhenius activation energy (E ), see Annex A. A service life of at least 50 years is generally

obtained at a continuous operating temperature lower than 115°C.

The estimation of service life at continuous operating temperatures higher than 120 °C is outside the scope

of EN 253.
4.5.6.2 Shear strength

The shear strength shall fulfil the minimum requirements of Table 6 in both unaged and aged condition.

The shear strength shall be tested in axial direction in unaged condition shall be tested in axial direction in

accordance with 5.4.1. The shear strength in aged condition shall be tested in accordance with 5.4.2.

Table 6 — Shear strength
Test temperature Test clause τ
min.
MPa
unaged aged
45 % of
(real) initial
23 ± 2 5.4.1.4 0,12
value and
0,12
140 ± 2 5.4.1.5 0,08 0,08

At the test temperature of (23 ± 2) °C, the shear strength in aged condition shall be minimum 45 % of the

shear strength in unaged condition. The shear strength shall be reported together with the foam density.

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