Abstract

This document specifies a procedure to qualify a preliminary welding procedure specification (pWPS) by welding procedure tests to produce a qualified welding procedure specification (WPS).
NOTE 1   The application of this document ensures that the qualification of the pWPS is carried out according to a uniform test procedure.
NOTE 2   The primary purpose of welding procedure qualification is to demonstrate that the joining process proposed for construction is capable of producing joints having the required mechanical properties for the intended application.
This document applies to the following thermoplastic welding processes:
—    hot gas welding: round nozzle, speed, wedge;
—    extrusion welding;
—   heated tool welding: butt, socket, wedge;
This document applies to the welding of the following products:
—   sheet
—   pipe (unreinforced, solid wall only);
—   fittings (unreinforced only);
—   lining membrane;
This document covers the welding of the following groups of materials:
a)   for sheets, pipes and fittings:
—   PVC (PVC-U, PVC-C);
—   PP (PP-B, PP-H, PP-R);
—   PE;
—   PVDF;
—   ECTFE, PFA and FEP;
b)   for lining membranes:
—   PVC-P;
—   PE;
—   ECB;
—   PP;
c) for pipes and fittings only:
—   PA-U (PA-U 11, PA-U 12).

Status
Not Published
Publication Date
17-Nov-2026
ICS
25.160.10 - Welding processes
Technical Committee
CEN/TC 249 - Plastics
Drafting Committee
CEN/TC 249/WG 16 - Welding of thermoplastics
Current Stage
5060 - Closure of Vote - Formal Approval
Start Date
10-Sep-2026
Due Date
12-Nov-2026
Completion Date
10-Sep-2026
Ref Project
kSIST FprEN 18205:2026 - Qualification of Welding Procedures for Plastic Materials

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EN 18205 is a CEN standard for qualifying welding procedures for plastic materials. It specifies how a preliminary welding procedure specification (pWPS) is tested to produce a qualified welding procedure specification (WPS) for thermoplastic welding of sheets, pipes, fittings and lining membranes. It is written for organizations that need to show that a proposed joining process can make joints with the required mechanical properties for the intended application.

What does EN 18205 specify?

EN 18205 specifies the procedure for qualifying a preliminary welding procedure specification (pWPS) by welding procedure tests. It covers how test pieces are made, examined, tested and recorded so that the result becomes a qualified WPS.

The scope is limited to specific thermoplastic welding processes and products. It applies to hot gas welding, extrusion welding, and heated tool welding, and to sheet, pipe, fittings and lining membrane products made from the listed thermoplastic material groups.

AnnexWhat it covers
Annex AInformative Welding procedure qualification record (WPQR) format for hot gas welding

The document is organized into scope, normative references, terms and definitions, the pWPS, the welding procedure test, test pieces, examination and testing, range of qualification, and an informative annex with a WPQR example. That structure matters in practice because it shows where to find the procedure, how to test it, and how far the resulting qualification can be extended.

What are the key requirements of EN 18205?

EN 18205 sets out a qualification route from pWPS to WPS, and it ties that route to defined test pieces, inspection, destructive testing and qualification limits. The main practical result is that a welding organization must prove its procedure on representative specimens before using it in production.

How is the procedure qualified?

Clause 4 requires the pWPS to be prepared in accordance with CEN/TS 16892. Clause 5 then requires the welding and testing of test pieces to follow Clauses 6 and 7.

In practice, this means the process settings, joint design and consumables are not chosen ad hoc. They have to be written down first, then verified by test.

What happens to the test pieces?

Clause 6 requires the test pieces to be prepared and welded in accordance with the pWPS, and their shape and dimensions are given in Figures 1 to 7. The figures cover butt welds on sheet and pipe, socket welds, and lap seams on lining membranes.

This matters because the qualification test must reflect the real joint form and product type. Cutting of specimens must avoid significant damage to the weld or heat affected zone, so sample preparation itself can affect validity.

How are the test pieces examined and tested?

Clause 7 requires visual examination during all stages of welding and mechanical testing. The destructive testing depends on the joint type and product, with Table 1 linking each test piece to the relevant bend, tensile, peel or crush test standard and to the number of specimens.

The acceptance levels are also specific. Visual examination uses EN 13100-1, imperfection classification follows EN 14728, and acceptance levels for surface imperfections follow EN 16296. If the surface condition does not meet EN 16296, the test piece fails.

What is recorded in the WPQR?

Clause 7.2 requires a welding procedure qualification record (WPQR) that captures the assessed test piece, any re-tests, the relevant WPS items, and the visual and destructive test results. Annex A shows an example format for hot gas welding.

In practice, the WPQR is the paper trail that lets a buyer, auditor or engineer see exactly what was tested and what passed. It is also the document used to present the qualification in a uniform way.

How wide is the qualification range?

Clause 8 limits where the qualified procedure may be used. A standard welding procedure specification (sWPS) may be used in workshops or sites without further qualification, but any change outside the variable ranges of a WPS or sWPS requires a new welding procedure test.

The qualification is also tied to the organization responsible for welding, the parent material, thickness, welding process, welding position, joint type and quality level. In practice, that means a valid test on one material or joint form does not automatically cover a different one.

What changes trigger requalification?

Clause 8.9 gives process-specific triggers for requalification. Examples include changes in gas type, backing, welding speed, gas temperature, extrudate temperature, heater plate temperature, pressure settings, overlap length, and weld tool or nip roller type.

These limits matter because small parameter changes can alter joint quality. The standard therefore tells the welding organization which process variables must stay within the qualified range and which changes need a new test.

What terms does EN 18205 define?

The standard uses several key terms that matter for qualification and record keeping.

  • Preliminary welding procedure specification (pWPS) - the initial written welding instruction that is tested and qualified under this standard.
  • Welding procedure specification (WPS) - the qualified set of welding variables used for production welding.
  • Standard welding procedure specification (sWPS) - a WPS based on acceptable welding variables from standard industry practice and specified in standards or specifications.
  • Welding procedure qualification record (WPQR) - the record that collects the test results and assessment for each test piece.
  • Parent material - the base thermoplastic material being welded, which controls how far a qualification can be extended.
  • Quality level - the imperfection level used for acceptance; qualification applies to that level and any less stringent level.
  • Backing - the backing condition used during welding; changing between backing and no backing can require requalification.

Who uses EN 18205?

EN 18205 is used by welding organizations that qualify procedures for thermoplastic fabrication. It is relevant to makers of sheets, pipes, fittings and lining membranes, and to teams working with hot gas, extrusion and heated tool welding.

It is also used by quality managers, inspectors and buyers who need evidence that a procedure has been tested and recorded against a defined method. In practice, they use it to decide whether a WPS can be accepted for a given material, thickness, joint type and process window.

The document also matters to welding personnel and equipment suppliers. The standard requires written confirmation from the equipment manufacturer for welding positions intended to be used, so equipment capability is part of the qualification package.

Which standards are used with EN 18205?

EN 18205 relies on a set of named standards for test methods, inspection, vocabulary and related procedure control.

  • CEN/TS 16892 - gives the basis for preparing the pWPS.
  • EN 12814-1 - provides the bend test method used for several joint types.
  • EN 12814-2 - provides the tensile test method and short-term tensile welding factor reference.
  • EN 12814-4 - provides the peel test and crush test methods.
  • EN 12814-7 - provides the tensile test with waisted test specimens.
  • EN 12814-8 - gives the bend test acceptance requirements.
  • EN 13100-1 - gives the visual examination method for welded thermoplastic joints.
  • EN 14728 - classifies imperfections in thermoplastic welds.
  • EN 16296 - sets quality levels for surface imperfections.
  • EN 13067 - provides related terms and definitions for plastics welding personnel qualification.
  • EN ISO 23936-1 - supplies terms and definitions used for thermoplastics in oil and gas-related media.
  • ISO/TR 20118 - supplies terms and guidance linked to PVC fire characteristics.
  • ISO/TR 25901-1 - supplies general welding vocabulary.
  • ISO 13953 - supports the brittle rupture criterion for PE and PA-U pipe tensile testing.

What does the EN 18205 document contain?

EN 18205 contains worked-out guidance in the form of test-piece figures, a test matrix, qualification-range rules and a record template. Figures 1 to 7 show the test-piece layouts for butt welds on sheet and pipe, socket welds, and lining membrane lap seams.

Table 1 links each test piece to the applicable test standard and the required number of specimens. Table 2 sets the thickness qualification ranges for certain welding processes, which is what a welding engineer uses to decide how far one tested thickness can be extended.

The document also describes how to carry out visual examination, how to handle re-testing, and how to judge failure and pass conditions for bend, peel and tensile tests. Annex A gives a practical WPQR format for hot gas welding, which is useful for procedure approval files, internal audits and traceable production records.

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Frequently Asked Questions

EN 18205:2026 is a draft published by the European Committee for Standardization (CEN). Its full title is "Qualification of Welding Procedures for Plastic Materials". This standard covers: This document specifies a procedure to qualify a preliminary welding procedure specification (pWPS) by welding procedure tests to produce a qualified welding procedure specification (WPS). NOTE 1 The application of this document ensures that the qualification of the pWPS is carried out according to a uniform test procedure. NOTE 2 The primary purpose of welding procedure qualification is to demonstrate that the joining process proposed for construction is capable of producing joints having the required mechanical properties for the intended application. This document applies to the following thermoplastic welding processes: — hot gas welding: round nozzle, speed, wedge; — extrusion welding; — heated tool welding: butt, socket, wedge; This document applies to the welding of the following products: — sheet — pipe (unreinforced, solid wall only); — fittings (unreinforced only); — lining membrane; This document covers the welding of the following groups of materials: a) for sheets, pipes and fittings: — PVC (PVC-U, PVC-C); — PP (PP-B, PP-H, PP-R); — PE; — PVDF; — ECTFE, PFA and FEP; b) for lining membranes: — PVC-P; — PE; — ECB; — PP; c) for pipes and fittings only: — PA-U (PA-U 11, PA-U 12).

This document specifies a procedure to qualify a preliminary welding procedure specification (pWPS) by welding procedure tests to produce a qualified welding procedure specification (WPS). NOTE 1 The application of this document ensures that the qualification of the pWPS is carried out according to a uniform test procedure. NOTE 2 The primary purpose of welding procedure qualification is to demonstrate that the joining process proposed for construction is capable of producing joints having the required mechanical properties for the intended application. This document applies to the following thermoplastic welding processes: — hot gas welding: round nozzle, speed, wedge; — extrusion welding; — heated tool welding: butt, socket, wedge; This document applies to the welding of the following products: — sheet — pipe (unreinforced, solid wall only); — fittings (unreinforced only); — lining membrane; This document covers the welding of the following groups of materials: a) for sheets, pipes and fittings: — PVC (PVC-U, PVC-C); — PP (PP-B, PP-H, PP-R); — PE; — PVDF; — ECTFE, PFA and FEP; b) for lining membranes: — PVC-P; — PE; — ECB; — PP; c) for pipes and fittings only: — PA-U (PA-U 11, PA-U 12).

EN 18205:2026 is classified under the following ICS (International Classification for Standards) categories: 25.160.10 - Welding processes. The ICS classification helps identify the subject area and facilitates finding related standards.

EN 18205:2026 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
oSIST prEN 18205:2025
01-september-2025
Kvalifikacija postopkov varjenja za polimerne materiale
Qualification of Welding Procedures for Plastic Materials
Qualifizierung von Schweißverfahren für Kunststoffe
Qualification des modes opératoires de soudage des matières plastiques
Ta slovenski standard je istoveten z: prEN 18205
ICS:
25.160.10 Varilni postopki in varjenje Welding processes
83.080.01 Polimerni materiali na Plastics in general
splošno
oSIST prEN 18205:2025 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

oSIST prEN 18205:2025
oSIST prEN 18205:2025
DRAFT
EUROPEAN STANDARD
prEN 18205
NORME EUROPÉENNE
EUROPÄISCHE NORM
June 2025
ICS 25.160.10
English Version
Qualification of Welding Procedures for Plastic Materials
Qualification des modes opératoires de soudage des Qualifizierung von Schweißverfahren für Kunststoffe
matières plastiques
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
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 18205:2025 E
worldwide for CEN national Members.

oSIST prEN 18205:2025
prEN 18205:2025(E)
Contents Page
European Foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 6
3 Terms and definitions . 7
4 Preliminary welding procedure specification . 7
5 Welding procedure test . 7
6 Test piece . 7
6.1 Welding of test pieces . 7
6.2 Shape and dimensions of test pieces and test specimens . 7
7 Examination and testing . 12
7.1 Type and extent of testing . 12
7.1.1 Visual examination . 12
7.1.2 Destructive testing. 12
7.2 Welding procedure qualification record (WPQR) . 12
7.3 Acceptance levels . 13
7.3.1 Visual examination . 13
7.3.2 Destructive testing. 13
7.3.3 Re-testing . 14
8 Range of qualification . 14
8.1 General . 14
8.2 Related to the organization responsible for welding . 14
8.3 Related to the parent material . 14
8.4 Related to material thickness. 15
8.5 Related to welding process . 15
8.6 Related to welding position . 15
8.7 Related to type of joint . 16
8.8 Related to the quality level . 16
8.9 Specific to process . 16
8.9.1 Hot gas welding . 16
8.9.2 Extrusion welding . 16
8.9.3 Heated tool butt welding . 17
8.9.4 Heated tool socket welding . 18
8.9.5 Heated tool wedge welding . 18
8.9.6 Hot gas wedge welding . 19
Annex A (informative) Welding procedure qualification record (WPQR) - Hot gas welding . 20
oSIST prEN 18205:2025
prEN 18205:2025 (E)
European Foreword
This document (prEN 18205:2025) 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.
oSIST prEN 18205:2025
prEN 18205:2025(E)
Introduction
This document covers the principles to be observed in the qualification testing of welding procedures for
thermoplastic materials.
oSIST prEN 18205:2025
prEN 18205:2025 (E)
1 Scope
This document specifies a procedure to qualify a preliminary welding procedure specification (pWPS) by
welding procedure tests to produce a qualified welding procedure specification (WPS).
NOTE 1 The application of this document ensures that the qualification of the pWPS is carried out according to
a uniform test procedure.
NOTE 2 The primary purpose of welding procedure qualification is to demonstrate that the joining process
proposed for construction is capable of producing joints having the required mechanical properties for the intended
application.
This document applies to the following thermoplastic welding processes:
— hot gas welding: round nozzle, speed, wedge;
— extrusion welding;
— heated tool welding: butt, socket, wedge;
This document applies to the welding of the following products:
— sheet
— pipe (unreinforced, solid wall only);
— fittings (unreinforced only);
— lining membrane;
This document covers the welding of the following groups of materials:
a) for sheets, pipes and fittings:
— PVC (including all kinds of PVC-U, PVC-C) and ABS;
— PP;
— PE;
— PVDF;
— ECTFE, PFA and FEP;
b) for lining membranes:
— PVC-P;
— PE;
— ECB;
— PP;
c) for pipes and fittings only:
— PA-U 11 and PA-U 12.
oSIST prEN 18205:2025
prEN 18205:2025(E)
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 12814-1, Testing of welded joints of thermoplastics semi-finished products - Part 1: Bend test
EN 12814-2, Testing of welded joints of thermoplastics semi-finished products - Part 2: Tensile test
EN 12814-4, Testing of welded joints of thermoplastics semi-finished products - Part 4: Peel test
EN 12814-7, Testing of welded joints of thermoplastics semi-finished products - Part 7: Tensile test with
waisted test specimens
EN 12814-8, Testing of welded joints of thermoplastics semi-finished products - Part 8: Requirements
EN 13100-1, Non destructive testing of welded joints of thermoplastics semi-finished products - Part 1:
Visual examination
EN 14728, Imperfections in thermoplastic welds - Classification
EN 16296, Imperfections in thermoplastics welded joints - Quality levels
EN 13067, Plastics welding personnel - Qualification of welders - Thermoplastics welded assemblies
CEN/TS 16892, Plastics - Welding of thermoplastics - Specification of welding procedures
EN ISO 23936-1, Oil and gas industries including lower carbon energy - Non-metallic materials in contact
with media related to oil and gas production - Part 1: Thermoplastics (ISO 23936-1)
ISO/TR 20118, Plastics – Guidance on fire characteristics and fire performance of PVC materials used in
building applications
ISO/TR 25901-1, Welding and allied processes — Vocabulary — Part 1: General terms
ISO 13953, Polyethylene (PE) pipes and fittings — Determination of the tensile strength and failure mode
of test pieces from a butt-fused joint
oSIST prEN 18205:2025
prEN 18205:2025 (E)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 13067, ISO 23936-1,
ISO/TR 20118, ISO/TR 25901-1 and the following apply.
ISO and IEC maintain terminoloy databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at http://www.iso.org/obp
— IEC Electropedia: available at http://www.electropedia.org/
3.1
standard welding procedure specification
sWPS
welding procedure specification that contains acceptable welding variables based on standard industry
practice and is specified in national or international standards or specifications
4 Preliminary welding procedure specification
The preliminary welding procedure specification shall be prepared in accordance with CEN/TS 16892.
5 Welding procedure test
The welding and testing of test pieces shall be in accordance with Clauses 6 and 7.
6 Test piece
6.1 Welding of test pieces
Preparation and welding of the test pieces shall be carried out in accordance with the pWPS.
6.2 Shape and dimensions of test pieces and test specimens
The dimensions of the test piece and the number of test specimens to be cut from the test piece are
specified in Figures 1 to 7.
The shapes, dimensions and conditioning of the test specimens are specified in the relevant test
standards.
Cutting the test specimens shall be carried out without significant damage to the welds and their heat
affected zones.
oSIST prEN 18205:2025
prEN 18205:2025(E)
Minimum dimensions in millimetres

Key
1 discard
2 6 bend test specimens cut from within this area
Figure 1 — Test piece for a butt weld on sheet (for bend test specimens)
oSIST prEN 18205:2025
prEN 18205:2025 (E)
Key
1 4 test specimens, 1 in each location (x1, x2, y1, y2)
l ≥ 350 or 2 dn, whichever is longer
Figure 2 — Test piece for a butt weld on pipe (for bend or tensile test specimens)
Minimum dimensions in millimetres

Key
1 discard
2 5 tensile test specimens cut from within this area
3 tensile test specimens (for reference)
Figure 3 —Test piece for a butt weld on sheet (for tensile test specimens)
oSIST prEN 18205:2025
prEN 18205:2025(E)
Key
1 socket
2 pipe
l ≥ 5 dn
Figure 4 — Test piece for a socket weld
Minimum dimensions in millimetres

a) Test piece for lining membranes b) Lap seam without testing channel
Key
1 discard
2 5 peel test specimens cut from within this area
3 welding zone
Figure 5 — Test piece for lining membranes - Lap seam without testing channel
oSIST prEN 18205:2025
prEN 18205:2025 (E)
Minimum dimensions in millimetres

a) Test piece for lining membranes b) Lap seam with testing channel
Key
1 discard
2 5 peel test specimens cut from within this area
3 welding
...