FprEN 17151-2

• Abstract:

  This document specifies a test method for determining the creep behaviour under compression of boxes made of thermoplastic materials intended for use in a modular system for non-pressure underground conveyance and storage of surface water.

• Status: Not Published
• Publication Date: 03-Feb-2027
• ICS: 23.040.01 - Pipeline components and pipelines in general
• Technical Committee: CEN/TC 155 - Plastics piping systems and ducting systems
• Drafting Committee: CEN/TC 155/WG 26 - Storm Water Management
• Current Stage: 5020 - Submission to Vote - Formal Approval
• Start Date: 15-Oct-2026
• Due Date: 20-Nov-2026
• Completion Date: 15-Oct-2026
• Ref Project: oSIST prEN 17151-2:2026 - Plastics piping systems for non-pressure underground conveyance and storage of surface water - Part 2: Test method for determination of creep behaviour of boxes

FprEN 17151-2 is a CEN draft European Standard for a laboratory test method on thermoplastic boxes used in modular systems for non-pressure underground conveyance and storage of surface water. It specifies how to load the boxes in compression, measure deformation over time, and calculate creep behaviour and creep factor for product evaluation, design data and type testing.

What does FprEN 17151-2 specify?

FprEN 17151-2 specifies a test method for determining the compressive creep behaviour of boxes made of thermoplastic materials intended for use in a modular system for non-pressure underground conveyance and storage of surface water.

The document is organized into clauses on scope, normative references, terms and definitions, symbols and units, apparatus, test sample, test procedure, analysis and test report. It also includes one normative annex for regression analysis.

Annex	What it covers
Annex A	Regression analysis with time as the independent variable, including data suitability and straight-line fitting

The foreword places FprEN 17151-2 in the prEN 17151 series alongside Part 1, which deals with long-term compression strength of boxes.

What are the key requirements of FprEN 17151-2?

FprEN 17151-2 is built around controlled compression loading, time-based deformation measurement and regression-based extrapolation. In practice, the method only works if the test setup, sample preparation and data recording are consistent.

• Clause 5 requires a compression testing apparatus that applies a constant load through stiff plates at 90° ± 1° to the bottom plate. Plate flexure must be low, and the force system must be validated to EN ISO 7500-1:2018 class 2. This matters because bending or poor force calibration can distort creep results.
• Clause 6 says the test sample shall be a box with integral components that represents the weakest entity of the final construction. Homogeneous extruded boxes are cut to make a representative sample, and testing is normally in the vertical installation direction. This ties the test to the real installed orientation.
• Clauses 6.2 and 6.3 require one sample per test load unless otherwise specified, a minimum age of 21 days, and at least 24 h conditioning in air at the test temperature. This gives the material time to stabilize before loading.
• Clause 7.1 calls for at least three load levels, chosen so failure does not occur during the test. The text gives 15 %, 12 % and 9 % of short-term compression strength measured according to EN 17150 as examples. That means the test is meant to measure creep, not rupture.
• Clauses 7.2 and 7.3 set the default test temperature at (23 ± 2) °C and require one constant load per sample, with load variation limited to ±2 %. The procedure uses a pre-load of 5 kPa to 10 kPa, then the full load, with continuous displacement recording and dense early-time readings. This is what makes the strain-time curve usable.
• Clause 7.4 links test duration to the extrapolation target and says extrapolation should generally not exceed two decades of log time. The example shows that prediction to 50 years needs at least 4 380 h of test data.
• Clause 8 defines strain from deflection and the height after pre-load, then uses regression on strain versus log time to obtain extrapolated strain and creep factor. Annex A gives the least-squares method and rejects data if the squared correlation coefficient r is below 0.9.
• Clause 9 requires the test report to identify the sample, test conditions, applied stress, plots, extrapolated strain, creep factors, regression details and any incidents that could affect the result. This is the record buyers, labs and specifiers use to compare data.

What terms does FprEN 17151-2 define?

• Creep - increase in strain with time when a constant force is applied.
• Creep factor - strain ratio for a given applied stress and time.
• Strain - the measured deflection expressed relative to the height after pre-load.
• Compressive stress - the applied force divided by the loaded area of the box.
• Pre-load - the initial low compressive load used before the full test load is applied.
• Isochronous plot - a plot of extrapolated strain versus stress at a fixed time, used to read intermediate values.
• r value - the squared coefficient of correlation used in Annex A to check whether the regression data are suitable.

Who uses FprEN 17151-2?

FprEN 17151-2 is used by manufacturers of thermoplastic box systems, testing laboratories, product developers and quality teams working on underground surface-water storage and conveyance products. It is also relevant to certification bodies and purchasers who need a defined compression creep test when checking technical data or acceptance criteria.

Which standards are used with FprEN 17151-2?

• EN 17150 - provides the short-term compression strength of boxes used as a basis for selecting creep test loads.
• prEN 17151-1 - the companion Part 1 in the same series, covering long-term compression strength of boxes.
• EN ISO 7500-1:2018 - provides calibration and verification requirements for the force-measuring system of the compression testing machine.
• EN ISO 899-1:2017 - is cited as the source for the definition of creep.

What does the FprEN 17151-2 document contain?

FprEN 17151-2 contains the apparatus requirements, sample conditioning rules, load selection guidance, test procedure, analysis steps and reporting items for a compression creep test. It also includes symbols and units, a figure showing the test direction, a strain-versus-log-time plot, and an isochronous plot used for extrapolation. Annex A gives the regression approach used to fit the strain-time data and to check whether the data are suitable for analysis.

SLOVENSKI STANDARD
01-marec-2026
Cevni sistemi iz polimernih materialov, ki delujejo po težnostnem principu in so
položeni v zemljo, za transport in shranjevanje površinske vode - 2. del:
Preskusna metoda za ugotavljanje leznih lastnosti zabojev
Plastics piping systems for non-pressure underground conveyance and storage of
surface water - Part 2: Test method for determination of creep behaviour of boxes
Kunststoff-Rohrleitungssysteme für die drucklose unterirdische Entwässerung für Nicht-
Trinkwasser - Teil 2: Prüfverfahren zur Bestimmung des Kriechverhaltens von
Versickerungsblöcken
Systèmes de canalisations en plastique pour le transport et le stockage souterrains sans
pression des eaux de surface - Partie 2 : Méthode d’essai pour la détermination du
comportement au fluage des structures alvéolaires ultra-légères
Ta slovenski standard je istoveten z: prEN 17151-2
ICS:
23.040.03 Cevovodi za zunanje sisteme Pipeline and its parts for
transporta vode in njihovi deli external water conveyance
systems
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
EUROPEAN STANDARD
prEN 17151-2
NORME EUROPÉENNE
EUROPÄISCHE NORM
December 2025
ICS 23.040.01
English Version
Plastics piping systems for non-pressure underground
conveyance and storage of surface water - Part 2: Test
method for determination of creep behaviour of boxes
Systèmes de canalisations en plastique pour le Kunststoff-Rohrleitungssysteme für die drucklose
transport et le stockage souterrains sans pression des unterirdische Entwässerung für Nicht-Trinkwasser -
eaux de surface - Partie 2 : Méthode d'essai pour la Teil 2: Prüfverfahren zur Bestimmung des
détermination du comportement au fluage des Kriechverhaltens von Versickerungsblöcken
structures alvéolaires ultra-légères
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 155.
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 17151-2:2025 E
worldwide for CEN national Members.

prEN 17151-2:2025 (E)
Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Symbols and units . 5
5 Apparatus . 6
5.1 Compression testing apparatus . 6
5.2 Measuring devices . 6
6 Test sample . 7
6.1 General. 7
6.2 Number . 7
6.3 Age and conditioning . 7
7 Test procedure . 8
7.1 Loads . 8
7.2 Test temperature . 8
7.3 Test procedure . 8
7.4 Test duration . 8
8 Analysis . 8
8.1 Plot strain vs time . 8
8.2 Creep factor . 10
8.2.1 Creep factor at test stress . 10
8.2.2 Strain at specific stress . 10
9 Test report . 10
Annex A (normative) Regression analysis with time as the independent variable . 12
A.1 Principle . 12
A.2 Regression with time as the independent variable . 12
A.2.1 General. 12
A.2.2 Suitability of data . 13
A.2.3 Functional relationships . 13
Bibliography . 14

prEN 17151-2:2025 (E)
European foreword
This document (prEN 17151-2:2025) has been prepared by Technical Committee CEN/TC 155 “Plastics
piping systems and ducting systems”, the secretariat of which is held by NEN.
This document is currently submitted to the CEN Enquiry.
prEN 17151 consists of the following parts under the general title Plastics piping systems for non-pressure
underground conveyance and storage of surface water:
— Part 1: Test method for determination of long-term compression strength of boxes
— Part 2: Test method for determination of creep behaviour of boxes (this document)

prEN 17151-2:2025 (E)
Introduction
The test described in this document determines the extent to which thermoplastic units will deform
permanently under the influence of constant compressive stress. Creep occurs as a function of time through
extended exposure to levels of stress that are below the yield strength of the material.
Creep tests are performed in compression at different load levels and the deflection over time is measured.
The load levels are selected to ensure that failure does not occur within the time frame of the test.
The creep tests are carried out by testing a series of samples placed between two stiff plates with different
constant compression loads applied. Deflection is recorded against time. The linear portion of the creep
strain plot can be extrapolated to predict the strain at a given time longer than the test period, normally
dictated by the application design. From these extrapolated curves a creep factor can be obtained.

prEN 17151-2:2025 (E)
1 Scope
This document specifies a test method for determining the compressive creep behaviour of boxes made of
thermoplastic materials intended for use in a modular system for non-pressure underground conveyance
and storage of surface water.
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 17150, Plastics piping systems for non-pressure underground conveyance and storage of non-potable
water — Test method for determination of short-term compression strength of boxes
prEN 17151-1, Plastics piping systems for non-pressure underground conveyance and storage of surface
water — Part 1: Test method for determination of long-term compression strength of boxes
EN ISO 7500-1:2018, Metallic materials — Calibration and verification of static uniaxial testing machines —
Part 1: Tension/compression testing machines — Calibration and verification of the force-measuring system
(ISO 7500-1:2018)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply in addition to the terms and
definitions in prEN 17151-1.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp/
— IEC Electropedia: available at https://www.electropedia.org/
3.1
creep
increase in strain with time when a constant force is applied
[SOURCE: EN ISO 899-1:2017] [1]
3.2
creep factor
strain ratio for a given applied stress and time
4 Symbols and units
For the purposes of this document, the following symbols and units apply.
b initial width of box mm
i
d deflection at time t mm
e e
F force applied kN
h initial height of box mm
i
h height of box after pre-load mm
l initial length of box mm
i
prEN 17151-2:2025 (E)
t time to which test results are extrapolated h
e
γ creep factor for stress level i at extrapolated time -
te,i
ε extrapolated strain at t %
e e
ε strain at extrapolated time for stress level i %
te,i
ε strain at 3 min (0,05 h) for stress level i %
t0,05,i
σ compressive s
...