prEN 12814-3

SLOVENSKI STANDARD
01-december-2026
Preskus zvarjenih spojev plastomernih polizdelkov - 3. del: Preskus lezenja pri
natezni obremenitvi
Testing of welded joints in thermoplastics semi-finished products - Part 3: Tensile creep
test
Prüfen von Schweißverbindungen aus thermoplastischen Kunststoffen - Teil 3:
Zeitstand-Zugversuch
Essais des assemblages soudés sur produits semi-finis en thermoplastiques - Partie 3:
Essai de fluage en traction
Ta slovenski standard je istoveten z: prEN 12814-3
ICS:
25.160.40 Varjeni spoji in vari Welded joints and welds
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
EUROPEAN STANDARD
NORME EUROPÉENNE
EUROPÄISCHE NORM
October 2026
ICS 25.160.40 Will supersede EN 12814-3:2014
English Version
Testing of welded joints in thermoplastics semi-finished
products - Part 3: Tensile creep test
Essais des assemblages soudés sur produits semi-finis Prüfen von Schweißverbindungen aus
en thermoplastiques - Partie 3: Essai de fluage en thermoplastischen Kunststoffen - Teil 3: Zeitstand-
traction Zugversuch
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 249.
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
© 2026 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 12814-3:2026 E
worldwide for CEN national Members.

Contents Page
Foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Symbols and designations . 5
5 Principle of the test . 6
6 Sampling procedures . 7
7 Dimensions of test specimens . 7
8 Cutting and preparation of test specimens . 9
9 Mechanical testing . 10
10 Test equipment . 10
11 Determination of the long-term welding factor . 11
12 Test report . 13
Annex A (informative) Resistance to slow crack growth . 14
Annex B (informative) Whole pipe tensile creep rupture test . 17
Annex C (informative) Minimum creep rupture time of the parent material (t ) for
tm
applicability of the long-term welding factor . 20
Annex D (informative) Testing of socket joints . 21
Bibliography . 24

Foreword
This document (prEN 12814-3:2026) has been prepared by Technical Committee CEN/TC 249 “Plastics”,
the secretariat of which is held by SIS.
This document is currently submitted to the CEN enquiry
This document will supersede EN 12814-3:2014.
In comparison with the previous edition, the following technical modifications have been made:
— the minimum test specimen lengths have been revised;
Introduction
The design of welded thermoplastics constructions under static load is based on the long-term creep
rupture with behaviour, specifically the resistance to slow crack growth of the thermoplastics material
and the welds.
For design purposes, the relevant characteristic values for the welded joints are the “long-term tensile
welding factors” to which this document provides the test method.
The long-term tensile welding factors are normally used in conjunction with the creep rupture curve of
the parent material, given for example in EN 1778, when designing welded semi-finished products under
static load.
The long-term tensile welding factor(s), the crack behaviour and the appearance of the fracture surface
provide information on the quality of the weld.
NOTE The behaviour of the failure obtained during the tensile creep test can be related to the notch sensitivity
of the parent material. An example of a test to provide information about the notch sensitivity of parent material is
given in Annex A.
1 Scope
This document specifies the dimensions, the method of sampling, the preparation of the test specimens
and the conditions for performing the tensile creep test perpendicular to the weld in order to determine
the long-term tensile welding factor.
A tensile creep test may be used in conjunction with other tests (e.g. bend test, tensile test, macrographic
examination, …) to assess the performance of welded assemblies made from thermoplastics materials.
The test is applicable to welded assemblies made from thermoplastics materials, filled or unfilled such as
tubes and fittings, sheets, plates and profiles, but not reinforced, irrespective of the welding process used.
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 ISO 291, Plastics — Standard atmospheres for conditioning and testing(ISO 291)
EN 13100-1, Non destructive testing of welded joints of thermoplastics semi-finished products — Part 1:
Visual examination
EN ISO 899-1, Plastics — Determination of creep behaviour — Part 1: Tensile creep (ISO 899-1)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
test temperature
temperature of the medium surrounding the test specimen during the test
3.2
test stress
test load divided by the minimum cross sectional area of the test specimen
3.3
creep rupture curve
regression curve through the geometric mean values of failure times
3.4
minimum failure time
t
tm
creep rupture time of the parent material to ensure that the test method is applicable
3.5
ductile fracture
large scale deformation of material from fracture surfaces
3.6
brittle fracture
little or no deformation of material from fracture surfaces
4 Symbols and designations
Symbols and designations are given in Table 1.
Table 1 — Symbols and designations
Symbols Designations Units
𝑎𝑎 Minimum measured thickness of test specimen within mm
calibrated and parallel length
𝑎𝑎 Nominal thickness of test piece mm
n
b Width of calibrated and parallel length of the test specimen mm
b Width of shoulder of the test specimen mm
c Depth of the notch mm
D Nominal outside diameter of the tube mm
n
𝑓𝑓 Long-term tensile welding factor
l
F Value of the force applied to the welded test specimen N
s
calculated from the chosen value of σ
s
F Value of the force applied to the unwelded test specimen N
t
calculated from the chosen value of σ
t
L Total length of the test specimen mm
L Minimum distance between the clamping jaws mm
j
L Calibrated and parallel length of the test specimen mm
a
Lw Maximum width of the weld bead of the test specimen mm
r Radius of shoulder of the test specimen mm
t Minimum failure time h
tm
σ Value of stress of the welded test specimens used in the N/mm
s
calculation of f
l
σ Reference stress. Value of stress of the unwelded test N/mm
t
specimens, used in the calculation of f
l
a
For extrusion and hot gas welds only.

5 Principle of the test
The test involves subjecting a test specimen to a constant load until fracture occurs. The time to fracture
is measured and recorded.
NOTE An alternative test using a whole pipe welded sample rather that a test specimen cut form the weld is
given in Annex B.
The tests are carried out over a range of temperatures and loads, and in a test medium. Only such media
shall be used which cause no swelling or degradation of the polymer. Examples of available test media
are air, water or solutions of demineralized water with detergents.
Care should be taken to ensure that the condition of the test medium does not influence the results of the
test.
The applicability of the long-term tensile welding factor for design purposes requires a minimum creep
rupture time for the parent material (t ). Before determining the long-term welding factor for the
tm
materials mentioned in Annex C, a tensile creep test should be carried out on the parent material at one
of the test conditions given in Table C.1. The values of creep rupture time should be at least that quoted
in Table C.1.
Application standards may prescribe higher values for these rupture times depending upon the semi-
finished product and material.
6 Sampling procedures
Welded and unwelded test specimens shall be taken from the same test piece.
NOTE In the case of socket joints, see Annex D.
The test specimens (welded and unwelded) shall be cut perpendicular to the welded joint at least eight
hours after welding. For sheets where the extrusion direction is different on either side of the weld, the
unwelded test specimens shall be taken from the side of the test piece which has the lowest creep rupture
time.
Each test specimen shall be marked in order to identify its original position within the test piece.
No heat treatment or mechanical straightening operations shall be carried out on the test specimen.
7 Dimensions of test specimens
The dimensions of test specimens according to Figure 1 are given in Table 2 and those according to
Figure 2 are given in Table 3.
Profiles can be tested if test specimens are in accordance with the dimensions given in Table 2 or Table 3.
For tubes having nominal outside diameter less than 20 mm, the whole tube shall be tested. In this case,
the minimum distance between the clamps shall be 200 mm.
Key
Lj  = L0 + (2xb)
Figure 1 — Type 1 test specimen for flat and tubular assemblies

Figure 2 — Type 2 test specimen for flat and tubular assemblies

Table 2 — Dimensions of type 1 test specimens
Dimensions in millimetres
D or 𝑎𝑎 b L L
n n 0
D
n
20 ≤ D < 50 a + 80 ≥ 120
n
n
D
n
50 ≤ D < 100 120 ≥ 170
n a +
n
D ≥ 100 or
n
flat assemblies:
𝑎𝑎 ≤ 10 15 120 ≥ 170
n
10 < a ≤ 20 30 120 ≥ 170
n
𝑎𝑎 > 20 1,5 x a 3 x 𝑎𝑎 + L ≥ L + 80
n n n w 0
with 120 min
Table 3 — Dimensions of type 2 test specimens
Dimensions in millimetres
D or 𝑎𝑎 b min. b L L r
n n 1 0
D
n
20 ≤ Dn < 50 a + b + 10 Lw + 60 ≥ 160 60
n
D
n
50 ≤ D < 100 b + 10 L + 60 ≥ 170 60
n a + w
n
Dn ≥ 100 or
flat assemblies:
𝑎𝑎 ≤ 10 10 20 115 ≥ 210 60
n
10 < 𝑎𝑎 ≤ 20 30 40 115 ≥ 240 60
n
𝑎𝑎 > 20 1,5 x 𝑎𝑎 2,5 x 𝑎𝑎 3 x 𝑎𝑎 + L ≥ 2,5 x L 60
n n n n w 0
with 120 min
Where the beads are left intact in service, they shall be left intact for the test. Where the beads are
removed in service, they shall be removed prior to testing.
The minimum value for b shall be 6 mm. The tolerance for b shall be ± 1 mm. The tolerance for L shall
be ± 2 mm.
The variation of b over the length L shall not exceed ± 2 % of the average value of b.
8 Cutting and preparation of test specimens
The tensile creep test specimens shall be cut with parallel sides as shown in Figures 1 and 2. During
cutting, heating of the test specimen shall be minimized.
The cutting operation shall not cause any damage to the test specimen.
After cutting, a visual examination of the weld according to EN 13100-1 shall be carried out and recorded.
9 Mechanical testing
The stress is applied to the test specimen at constant temperature, static tensile load and constant
ambient conditions.
Test specimens shall be conditioned to the test temperature before loading for a time according to
EN ISO 291. The variation of the test temperature shall not exceed ± 1 °C.
For every stress level and every test temperature, a minimum number of six welded test specimens and
six unwelded test specimens shall be tested. The test shall be carried out according to EN ISO 899-1.
The test conditions shall be chosen in such a way that at least 30 % of the fracture area has undergone
brittle failure, as described in Figure 3.
To shorten the duration of the test, it is possible to use an appropriate aqueous surfactant solution as the
contact medium for both welded and unwelded test specimens.
The test specimens shall be progressively subjected to the test load. The
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