oSIST prEN 12814-3:2026
(Main)Testing of welded joints in thermoplastics semi-finished products - Part 3: Tensile creep test
- Abstract
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 longterm 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.
- Status
- Not Published
- Public Enquiry End Date
- 14-Dec-2026
- Technical Committee
- IPMA - Polimer materials and products
- Current Stage
- 4020 - Public enquire (PE) (Adopted Project)
- Start Date
- 26-Oct-2026
- Due Date
- 15-Mar-2027
oSIST prEN 12814-3:2026 is the Slovene publication of draft European Standard prEN 12814-3, issued by SIST/CEN. It specifies a tensile creep test perpendicular to welded joints in thermoplastics semi-finished products, so users can determine the long-term tensile welding factor for design and assessment. It is written for welded assemblies made from unreinforced thermoplastics such as tubes, fittings, sheets, plates and profiles, regardless of welding process.
What does oSIST prEN 12814-3:2026 specify?
oSIST prEN 12814-3:2026 specifies the dimensions of the specimens, how to take samples, how to prepare them, and how to run the tensile creep test perpendicular to the weld. The document is centered on measuring time to fracture under constant load so the long-term tensile welding factor can be derived.
The scope also places this test in context with other checks such as bend testing, tensile testing and macrographic examination. In practice, that means the tensile creep test is one part of a broader weld performance assessment, not a stand-alone judgement of joint quality.
The document is organized into 12 clauses and four informative annexes.
| Annex | What it covers |
|---|---|
| Annex A | Resistance to slow crack growth, including the Full Notch Creep Test (FNCT) and the Two Notch Creep Test (2NCT) |
| Annex B | Whole pipe tensile creep rupture test |
| Annex C | Minimum creep rupture time of the parent material for applicability of the long-term welding factor |
| Annex D | Testing of socket joints |
What are the key requirements of oSIST prEN 12814-3:2026?
The document’s key requirements are in Clauses 5 to 12. They cover how to prepare valid specimens, how to run the test under controlled conditions, and how to calculate the long-term tensile welding factor from the results.
Test principle and test conditions
Clause 5 states that a specimen is loaded at a constant force until it fractures, and the time to fracture is recorded. The test is run over a range of temperatures and loads, in a medium that must not swell or degrade the polymer, such as air or water-based media. For a user, this means the test medium must be selected carefully because it can affect the result.
Clause 5 also links the method to design use. The parent material must have a minimum creep rupture time before the long-term tensile welding factor can be applied for design purposes, and Annex C gives example values for some thermoplastics materials. If the parent material does not meet the required rupture time, the welding factor is not applicable for that design use.
Sampling and specimen preparation
Clause 6 requires welded and unwelded specimens to come from the same test piece. They are cut perpendicular to the welded joint at least eight hours after welding, and each specimen is marked so its original position can be identified. No heat treatment or mechanical straightening is allowed.
This matters because the welded and unwelded parts must be directly comparable. For sheets with different extrusion directions on either side of the weld, the unwelded specimen must come from the side with the lower creep rupture time.
Clause 8 requires cutting with parallel sides and minimum damage to the specimen. After cutting, the weld is visually examined according to EN 13100-1 and the result is recorded. That means the test report needs a traceable visual condition before mechanical loading begins.
Specimen dimensions and special cases
Clause 7 gives two specimen types, with dimensions shown in Figures 1 and 2 and Tables 2 and 3. The document also states how to handle profiles and small tubes. For tubes with a nominal outside diameter below 20 mm, the whole tube is tested.
The dimensions matter because they control the stress distribution during creep loading. The clause also says whether weld beads are left intact or removed depends on how the joint is used in service. That makes the specimen reflect the real welded product as closely as possible.
Mechanical testing and fracture criteria
Clause 9 requires conditioning to the test temperature before loading, following EN ISO 291, and the test temperature variation must stay within ± 1 °C. For each stress level and test temperature, at least six welded and six unwelded specimens are tested, using EN ISO 899-1.
The test conditions must be chosen so that at least 30 % of the fracture area shows brittle failure. In practice, this helps the test reveal the crack-growth behaviour the method is designed to assess. The clause also allows an aqueous surfactant solution to shorten test duration, if it is suitable for the material.
Determination of the long-term tensile welding factor
Clause 11 says the long-term tensile welding factor is determined from creep rupture curves for welded and unwelded specimens. Tests must cover at least two stress levels, and the curves are based on the geometric mean of the individual failure times.
The factor is calculated as the ratio of the stress value for the weld to the stress value for the parent material at identical failure times. If the curves are parallel, the factor is constant across the time range. If they are not parallel, the factor is calculated at a reference stress agreed between the contracting parties.
Clause 11 also defines how invalid failures are handled. Failures in the clamps are disregarded, and failures close to the clamps are treated as clamp failures under the distances stated for the specimen type. If type 1 specimens keep failing in the clamps, type 2 specimens are used instead.
Test report
Clause 12 lists the required report content. The report needs enough detail to identify the test piece, the specimen geometry, the weld type, the test temperature and medium, the applied force or stress, the fracture appearance, the rupture time, and the calculated long-term tensile welding factor. For users, this is the evidence trail needed for design work, audits, or technical comparison.
What terms does oSIST prEN 12814-3:2026 define?
- Test temperature - the temperature of the medium surrounding the specimen during the test.
- Test stress - the test load divided by the minimum cross-sectional area of the specimen.
- Creep rupture curve - the regression curve through the geometric mean values of failure times.
- Minimum failure time - the creep rupture time of the parent material used to confirm that the method is applicable.
- Ductile fracture - fracture showing large-scale deformation of the material.
- Brittle fracture - fracture showing little or no deformation.
- Full Notch Creep Test (FNCT) - an annex method used to assess the resistance to slow crack growth of the parent material.
- Two Notch Creep Test (2NCT) - an annex method for parent materials with wall thickness below 10 mm.
Who uses oSIST prEN 12814-3:2026?
oSIST prEN 12814-3:2026 is used by laboratories, plastics processors, pipe and fitting manufacturers, and engineers responsible for welded thermoplastic constructions. It is also relevant to quality managers who need a repeatable way to compare welded and unwelded material performance.
The document supports design and product qualification work for tubes, fittings, sheets, plates, profiles, and socket joints. It is also used when checking whether a welding process needs adjustment, because the annex methods can be used for comparative purposes and process optimization.
What changed in oSIST prEN 12814-3:2026 from the previous edition?
This draft will supersede EN 12814-3:2014. The foreword states one technical modification: the minimum test specimen lengths have been revised.
Which standards are used with oSIST prEN 12814-3:2026?
- EN ISO 291 - gives the standard atmospheres used for conditioning and testing before loading.
- EN 13100-1 - provides the visual examination method for welded joints before the mechanical test.
- EN ISO 899-1 - supplies the tensile creep test method that Clause 9 uses for the mechanical testing procedure.
- EN 1778 - is cited in the introduction as an example of the design context where the parent-material creep rupture curve is used to calculate allowable values.
What does the oSIST prEN 12814-3:2026 document contain?
The document contains the test principle, specimen sampling rules, specimen dimensions, cutting and preparation instructions, mechanical testing conditions, equipment guidance, the calculation method for the long-term tensile welding factor, and the test report content. Figures 1 and 2 show the two main specimen geometries, and Figures 3 to 5 explain fracture appearance, test equipment, and the creep-rupture curve method.
It also includes informative annexes with related methods and special cases. Annex A gives FNCT and 2NCT procedures for assessing slow crack growth, Annex B describes a whole-pipe tensile creep rupture test for comparative use, Annex C gives example minimum creep rupture times for some thermoplastics materials, and Annex D gives a specific procedure for socket joints.
Relations
- Effective Date
- 06-May-2026
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Frequently Asked Questions
oSIST prEN 12814-3:2026 is a draft published by the Slovenian Institute for Standardization (SIST). Its full title is "Testing of welded joints in thermoplastics semi-finished products - Part 3: Tensile creep test". This standard covers: 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 longterm 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.
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 longterm 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.
oSIST prEN 12814-3:2026 is classified under the following ICS (International Classification for Standards) categories: 25.160.40 - Welded joints and welds. The ICS classification helps identify the subject area and facilitates finding related standards.
oSIST prEN 12814-3:2026 has the following relationships with other standards: It is inter standard links to SIST EN 12814-3:2014. Understanding these relationships helps ensure you are using the most current and applicable version of the standard.
oSIST prEN 12814-3:2026 is available in PDF format for immediate download after purchase. The document can be added to your cart and obtained through the secure checkout process. Digital delivery ensures instant access to the complete standard document.
Standards Content (Sample)
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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