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

This document specifies requirements and test methods for factory made thermally insulated bonded fitting assemblies for hot water networks in accordance with prEN 13941-1, comprising a steel service fitting, rigid polyurethane foam insulation and a casing of polyethylene.
The fitting assembly may also include the following additional elements: measuring wires, spacers and diffusion barriers.
This document covers the following fitting assemblies: bend, tee, reducer, single use compensator and anchor.
This document applies to fitting assemblies with a minimum design pressure of 16 bar (overpressure).

Fernwärmerohre - Werkmäßig gedämmte Verbundmantelrohrsysteme für direkt erdverlegte Fernwärmenetze - Verbundformstücke, bestehend aus Stahl-Mediumrohr, Polyurethan-Wärmedämmung und Außenmantel aus Polyethylen

Dieses Dokument legt die Anforderungen und Prüfverfahren für werkmäßig gefertigte, wärmegedämmte Verbundformstücke für Fernwärmenetze in Übereinstimmung mit EN 13941-1 fest, die aus einer Stahlarmatur, einer Polyurethan-Hartschaumstoffwärmedämmung und einem Polyethylenmantel bestehen.
Das Verbundformstück könnte darüber hinaus die folgenden zusätzlichen Bauteile umfassen: Messdrähte, Abstandhalter und Diffusionsbarrieren.
Dieses Dokument behandelt folgende Verbundformstücke: Bogen, T-Stück, Reduzierstück, Einmalkompen-sator und Festpunktelement.
Dieses Dokument gilt für Verbundformstücke mit einem Mindestauslegungsdruck von 1,6 MPa (Überdruck).

Tuyaux de chauffage urbain - Systèmes bloqués monotubes 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

Le présent document spécifie les exigences et les méthodes d’essai applicables aux assemblages de raccords bloqués manufacturés isolés thermiquement pour les réseaux d'eau chaude, conformes au prEN 13941-1, comprenant un raccord de service en acier, une isolation en mousse rigide 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.
Le présent document couvre les assemblages de raccords suivants : coude, té, réducteur, compensateur à usage unique et pièce d’ancrage.
Le présent document s’applique aux assemblages de raccords de pression minimale de calcul de 16 bar (surpression).

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

Ta dokument določa zahteve in preskusne metode za tovarniško izdelane toplotno izolirane sestave fitingov za vročevodna omrežja v skladu s standardom prEN 13941-1, ki so sestavljeni iz jeklenih fitingov, trde poliuretanske izolacijske pene in polietilenskega plašča. Sestav fitingov lahko vključuje tudi naslednje dodatne elemente: merilne žice, distančnike in difuzijske pregrade. Ta dokument zajema naslednje sestave fitingov: kolena, T-komade, reducirne priključke, kompenzatorje za enkratno uporabo in sidra. Ta dokument se uporablja za sestave fitingov z minimalnim predvidenim tlakom 16 barov (nadtlak).

General Information

Status
Published
Public Enquiry End Date
31-Mar-2018
Publication Date
04-Nov-2019
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
24-Oct-2019
Due Date
29-Dec-2019
Completion Date
05-Nov-2019

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SLOVENSKI STANDARD
SIST EN 448:2020
01-januar-2020
Nadomešča:
SIST EN 448:2016
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 - Werkmäßig gedämmte Verbundmantelrohrsysteme für direkt
erdverlegte Fernwärmenetze - Verbundformstücke, bestehend aus Stahl-Mediumrohr,
Polyurethan-Wärmedämmung und Außenmantel aus Polyethylen
Tuyaux de chauffage urbain - Systèmes bloqués monotubes 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: EN 448:2019
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
SIST EN 448:2020 en,fr,de

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

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SIST EN 448:2020
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SIST EN 448:2020
EN 448
EUROPEAN STANDARD
NORME EUROPÉENNE
October 2019
EUROPÄISCHE NORM
ICS 23.040.07; 23.040.40 Supersedes EN 448:2015
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 - Verbund-Rohrsysteme mit einem

monotubes pour des réseaux d'eau chaude enterrés Mediumrohr für direkt erdverlegte Fernwärmenetze -

directement - Assemblages de raccords manufacturés Werkmäßig hergestellte Formstücke bestehend aus

pour tubes de service en acier, isolation thermique en Stahl-Mediumrohren, einer Wärmedämmung aus

polyuréthane et tube de protection en polyéthylène Polyurethan und einer Ummantelung aus Polyethylen

This European Standard was approved by CEN on 12 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 448:2019 E

worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
SIST EN 448:2020
EN 448:2019 (E)
Contents Page

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

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

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

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

3 Terms and definitions ................................................................................................................................... 7

4 Requirements ................................................................................................................................................... 7

5 Test methods ................................................................................................................................................. 17

6 Marking ............................................................................................................................................................ 21

Annex A (informative) Guidelines for inspection and testing ..................................................................... 23

Annex B (informative) Procedures for casing welding .................................................................................. 26

Annex C (informative) Waste treatment and recycling ................................................................................. 30

Bibliography ................................................................................................................................................................. 31

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SIST EN 448:2020
EN 448:2019 (E)
European foreword

This document (EN 448:2019) 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 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 448:2015.
In comparison with the previous edition, the main changes in EN 448:2019 are:

— editorial changes to the new structure of standards prepared by the Technical Committee

CEN/TC 107.

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 448:2020
EN 448:2019 (E)
Introduction
EN 448 has been aligned with EN 488 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;

— 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 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 15632 (all parts), District heating pipes — Pre-insulated flexible pipe 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 448:2020
EN 448:2019 (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 fitting, rigid

polyurethane foam thermal insulation and a casing of polyethylene.

The fitting assembly could also include the following additional elements: measuring wires, spacers and

diffusion barriers.

This document covers the following fitting assemblies: bend, tee, reducer, single use compensator and

anchor.

This document applies to fitting assemblies with a minimum design pressure of 1,6 MPa (overpressure).

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 — Preinsulated bonded pipe systems for directly buried hot water networks —

Surveillance systems

EN 14870-1, Petroleum and natural gas industries — Induction bends, fittings and flanges for pipeline

transportation systems — Part 1: Induction bends (ISO 15590-1)

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)

---------------------- Page: 7 ----------------------
SIST EN 448:2020
EN 448:2019 (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 9692-1:2013, Welding and allied processes — Types of joint preparation — Part 1: Manual metal arc

welding, gas-shielded metal arc welding, gas welding, TIG welding and beam welding of steels

(ISO 9692-1:2013)

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)

ISO 6761, Steel tubes — Preparation of ends of tubes and fittings for welding
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SIST EN 448:2020
EN 448:2019 (E)
3 Terms and definitions

For the purpose 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 Steel parts
4.1.1 General

The material of the fitting steel parts shall be certified in accordance with EN 10204. If traceability on

material is required by the end user it shall be specified at the time of ordering. Corresponding material

certificates shall be delivered to the end user if specified at the time of ordering.

4.1.2 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 fitting assemblies, this request shall be given whilst placing the order with the manufacturer of

the fitting assemblies.

Any later request for provision of such documentation can be too late and can possibly not be met by the

manufacturer, since the manufacturer shall organize the assignment of 3.1 certificates to pipes and part of

pipes before starting the production.
4.1.3 Wall thickness and diameter

According to the scope of this document, all components shall be designed for a minimum of 1,6 MPa.

If the fitting assemblies shall be used in situations with pressures higher than 1,6 MPa, extra calculations will

be necessary.

The minimum nominal wall thickness of all components shall prior to processing be at least the same as for

the service pipes regarding EN 253.

The nominal diameter, 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).
4.1.4 Bends
4.1.4.1 Butt welding bends

The dimensions shall be in accordance with EN 10253-2 with the exception that the bend radius shall

be ≥ 1,5 times the outer diameter.
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SIST EN 448:2020
EN 448:2019 (E)
4.1.4.2 Cold formed bends

Cold formed bends shall be produced from seamless pipe or longitudinal welded pipes. At cold formed bends

made of longitudinal welded pipes the weld bead shall be welded to factor V = 1 (calculation stress = 100 %).

After bending, the minimum wall thickness of the bent pipe shall be not less than 85 % of the wall thickness

of the straight pipe (see EN 253).
The maximum ovality in the bent area shall not exceed 6 %.
The formula for the calculation of the ovality is:
DD−
ss,max ,min
0 × 100 (1)
where
o is the ovality, in %;
is the maximum outside diameter;
s,max
is the minimum outside diameter in the same cross section in the bended
s,min
area;
is the specified outside diameter.

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.

4.1.4.3 Hot-formed bends

For hot-formed bends manufactured from straight pipes by means of inductive heating (induction bends), no

heat treatment is necessary as far as this method is applied with unalloyed or low-alloyed steel with

[Mo] < 0,65 %. Hot-formed bends shall be supplied in conformity with EN 14870-1.

If for the bending other heating methods are applied, heat treatment following the bending of the pipes is

required.

If a hot-formed bend shall be made from line pipe, this should be specified to the pipe manufacturer at the

time of ordering so that they can take this into account when selecting the (chemical) composition of the

pipe material and the welding filler material.

It is recommended to determine per batch, diameter, wall thickness and bend radius, through mechanical

testing, that the bends comply with the applicable material specifications. It is customary that a

representative bend or an (additional) section of a bend of adequate length be manufactured during the

production process and that 10 % of the bends be tested.
4.1.4.4 Tolerances of bending angles

The deviation from the nominal bending angle shall not exceed the tolerances given in Table 1.

Table 1 — Deviations from nominal bending angle
Deviation
Nominal diameter of
service pipe
≤ DN 200 ±2,0°
> DN 200 ±1,0°
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SIST EN 448:2020
EN 448:2019 (E)
4.1.5 T-pieces
4.1.5.1 Forged T-pieces

The wall thickness t and t see EN 10253-2, shall be at least the same as those for the straight pipes, see

EN 253. All other dimensions shall be in accordance with EN 10253-2.
4.1.5.2 Welded T-pieces

Welded T-pieces shall be manufactured by drawing a collar on which the branch pipe is welded or by

welding the branch pipe directly to the main pipe. 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. When using branch pipe directly welded to the main pipe, compensating (reinforcement) plates can be

used according to EN 13941-1 requirements.
4.1.5.3 Tolerances of angles between branch pipes and main pipes

The branch pipes shall be perpendicular to the main pipes within a tolerance of ± 2,0°.

4.1.6 Reducers

Reducers shall be in accordance with EN 10253-2, except for the wall thicknesses T and T see EN 10253-2

which shall be at least the same as for the straight pipes (see EN 253) to be welded to the fittings.

4.1.7 Anchors

The anchors shall be marked with the information concerning maximum loads for which the construction

was designed and calculated. The lifetime of the system shall not be influenced by the anchors construction.

4.1.8 Single use compensators
A single use compensator shall comply with the requirements of EN 13941-1.
4.1.9 Caps

Caps (dished ends) shall be in accordance with EN 10253-2 and comply with the requirements of

EN 13941-1.
4.1.10 Fusion welding of steel fittings
4.1.10.1 Filler material

Filler material shall after welding have mechanical characteristics comparable with the parent metal.

4.1.10.2 Welding process

All types of fusion welding are acceptable but arc welding with covered electrodes and gas-shielded metal-

arc welding are preferred. The welding process shall be specified and approved in accordance with

EN ISO 15607.
The method of approval may be chosen by the manufacturer.
Fittings of wall thickness ≥ 5,6 mm shall be welded in more than one pass.
4.1.10.3 Preparation for welding

Pipe ends shall be prepared in accordance with the welding procedure used. When using covered electrodes

or gas-shielded metal-arc welding, pipe ends and fittings with equal wall thickness shall be prepared in

accordance with EN ISO 9692-1.

Table 2 of this document is derived from EN ISO 9692-1:2013, Table 1 and gives the relation between wall

thickness and reference number.
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SIST EN 448:2020
EN 448:2019 (E)

Table 2 — Preparation of ends of pipes and fittings for weldings according to EN ISO 9692-1:2013

Symbol Type of preparation Wall thickness t of steel service Reference to
pipe fittings or fitting end EN ISO 9692-1:2013, Table 1
II Square preparation t < 3 mm 1.2.1
V Single V preparation 3 mm ≤ t ≤ 10 mm 1.3
Y Single Y preparation with t > 10 mm 1.5
broad root face
NOTE Symbols are in accordance with EN ISO 2553.

Pipe ends and fittings with different wall thicknesses shall be prepared and adapted for misalignment in

accordance with Table 3 and Figure 1 of this document.
Table 3 — Adaptation of misalignment and difference in wall thickness
Adaptation Required action
Misalignment
Misalignment h ≤ 0,3 t, max. 1 mm Figure 1 detail A
Misalignment 1 mm < h ≤ 10 mm Adaptation of pipe ends
Misalignment h > 10 mm Extra fitting Extra prepared steel fitting minimum
length.
The seam spacing shall be such that the
heat-affected zones do not overlap or
interact. A spacing of 100 mm or more is
recommended. The minimum spacing is
50 mm.
Difference in wall thickness

Differences in wall thickness: t' ≤ 1,5 tn Figure 1 detail B Adaptation of thicker wall t'

Differences in wall thickness: t' > 1,5 t Figure 1 detail C Adaptation of both sides

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SIST EN 448:2020
EN 448:2019 (E)
Key
h misalignment
tn smallest wall thickness
t’ largest wall thickness

Figure 1 — Misalignment, difference in wall thickness and steel service pipe end preparation, in

accordance with EN 13941-2

When manufacturing T-pieces with the branch pipe welded directly to the main pipe, preparations shall

comply with Figure 2.
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SIST EN 448:2020
EN 448:2019 (E)
Key

a section X at crotch of right angle branch c section Y at flank of unequal branch. Ratios of

diameters > 2/3
b section Y at flank of unequal branch. Ratios of
diameters ≤ 2/3 d section W at flank of equal branch
Figure 2 — Preparation of set-on branches
4.1.10.4 Inspection of welds
4.1.10.4.1 Detail a – Visual surface examination

When visual surface examination is carried out, it shall be in accordance with 5.3.1. The examinations

include a check of surface, internal, joint geometry and multiple imperfections. The welding shall comply

with “quality level B” of EN ISO 5817.
4.1.10.4.2 Detail b – Leak tightness test

When a leak-tightness test is carried out in accordance with 5.3.2 or 5.3.3, the welds shall fulfil the

conditions stated there.
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SIST EN 448:2020
EN 448:2019 (E)
4.1.10.4.3 Detail c – Non-destructive examination of welds

When non-destructive is carried out, it shall be in accordance with 5.3.4. The weld shall comply with

“quality level B” of EN ISO 5817.
4.1.10.5 Competence of the welder

The welder shall have a valid certificate according to EN ISO 9606-1 for the techniques, material groups,

dimension ranges and welding position concerned. Welding personnel operating mechanized welding

equipment shall be qualified in accordance with EN ISO 14732.
4.1.11 Surface condition

In order to ensure proper bonding between the steel service pipe and the Polyurethan (PUR) foam thermal

insulation, the following procedure shall be followed:

a) prior to PUR foam, 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;

b) before cleaning the pipe, the outer surface of the pipe shall comply with rust grade A, B or C according to

EN ISO 8501-1, without pitting.
4.2 Casing
The casings shall meet the requirements of EN 253.
The casing shall be tested in accordance with 5.4 of this document.
4.3 Polyurethane (PUR) foam thermal insulation

The PUR foam thermal insulation for fitting assemblies shall meet the requirements of EN 253 and shall be

tested in accordance with 5.5 of this document. Test specimens from fitting assemblies to establish foam

properties shall be taken in accordance with 5.2 of this document.
4.4 Fitting assemblies
4.4.1 Fitting ends
4.4.1.1 Service pipe

The ends of the steel service pipes shall be free from thermal insulation according to EN 253 and shall be

prepared for welding in accordance with ISO 6761.
4.4.1.2 Centre line deviation

When tested in accordance with 5.6.1 the distance between centre lines of the steel service pipe and the

casing at fitting ends shall not exceed the limits given in EN 253.
4.4.1.3 Angular deviation between steel service pipe and casing

When tested in accordance with 5.6.1, the angular deviation between centre lines of the not insulated end of

the service pipe, and the casing at a length of 100 mm from the end, shall not exceed 2°.

4.4.2 Angle between casing segments of bend and minimum length

The maximum angle, α, between two adjacent segments of the casing of a bend shall not exceed 45°, see

Figure 4.

The length, L, see Figure 3, of the casing at the ends of the fittings shall not be less than 200 mm.

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SIST EN 448:2020
EN 448:2019 (E)
Key
a α ≤ 45° with minimum 2 segments
b α > 45° with minimum 3 segments
Figure 3 — Segmental casing pipe bends
4.4.3 Requirements of polyethylene welding
4.4.3.1 General
The quality of a PE weld cannot easily be tested with non-destructive methods.

The observation of proper working procedures shall ensure that the welds are leak-tight.

The welding process should, therefore, be performed according to a documented procedure in accordance

with Annex B or its equivalent.
For PE welding the following precautions shall be taken and documented:
a) only casing materials fulfilling the requirements of EN 253 shall be used;

NOTE For the casing of fittings normally PE-pipes are used as semi-finished products.

b) weld fillers of PE shall fulfil the requirements of EN 253;
c) proven welding processes using suited and maintained tools shall be used;

d) the personnel shall be trained and possess a valid evidence of their qualifications;

e) a 100 % visual examination according to 4.4.3.3 shall be carried out.
4.4.3.2 Melt flow rate

The melt flow rate of the casings to be welded shall not differ more than 0,5 g/10 min when determined in

accordance with EN 253.
4.4.3.3 Visual appearance

All welds shall be examined in accordance with 5.6.2. The following requirements shall be fulfilled:

a) Butt fusion welding:
1) the valley between the weld beads shall not go beneath the pipe surface;

2) the permitted butt misalignment shall not exceed 20 % of the wall thickness on the entire seam

length. On particular fittings, such as extruded tees, a butt misalignment of up to 30 % and the

resulting imperfection can be tolerated. The permitted butt misalignment applies internally as well

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