FprEN 17151-1

• Abstract:

  This document specifies a test method for determining the long-term compression strength for a specified period on boxes made of thermoplastics materials for non-pressure underground conveyance and storage of surface water.; The test method is applicable for boxes that fail due to creep rupture when subjected to a constant applied stress and where the relationship of log(stress) vs. log(failure time) is linear and of constant gradient over the entire specified period with a coefficient of determination greater than 0,8.; The test method in this document allows extrapolation log(stress) vs. log(failure time) of up to two orders of magnitude in logarithmic time scale and also specifies a method of accelerated testing using time-temperature superposition of log(stress) vs. log(failure time) to enable a more rapid determination that a box obeys a constant gradient linear relationship of log(stress) vs. log(failure time) over the entire specified period.

• 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: 15-Sep-2027
• Completion Date: 15-Oct-2026
• Ref Project: oSIST prEN 17151-1:2026 - 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

• Revises: EN 17151:2019 - Plastics piping systems for non-pressure underground conveyance and storage of non-potable water - Test method for determination of long-term compression strength of boxes
• Effective Date: 08-Oct-2025

FprEN 17151-1 is a draft European Standard from CEN for testing thermoplastic boxes used in non-pressure underground conveyance and storage of surface water. It specifies how to determine long-term compression strength for a specified period, including an accelerated elevated-temperature method for products that show linear stress-time behaviour. It is aimed at manufacturers, test laboratories, and anyone specifying or verifying these box systems.

What does FprEN 17151-1 specify?

FprEN 17151-1 specifies a creep rupture test method for boxes made of thermoplastics materials. The method is intended for boxes that fail under constant compression stress and whose stress-time relationship stays linear over the specified period, with a coefficient of determination greater than 0,8.

The document also allows extrapolation over up to two decades on a logarithmic time scale. In practice, that means the measured test results are extended to estimate a 50-year long-term compression strength, rather than waiting for full-life testing.

The standard is organized into clauses for scope, references, terms, symbols, the test method, apparatus, test samples, procedures and analysis, and the test report. Annex A gives the fitting and lower confidence limit calculation used for the 50-year design-life result.

What are the key requirements of FprEN 17151-1?

The test is based on creep rupture under constant compression

FprEN 17151-1 measures how boxes behave when a constant load is applied until creep rupture occurs. Deflection is tracked against time, then the failure times are used to build a trend line and estimate future performance.

This matters because the standard is not a short-term strength check. It is a long-term prediction method, so the sample data and the regression quality drive the reported design value.

Two test routes are defined

FprEN 17151-1 gives Test method A with all creep rupture tests at (23 ± 2) °C, and Test method B with tests at 23 °C plus elevated temperatures. Method A needs at least 10 rupture tests, while Method B uses smaller data sets at the reference and elevated temperatures and then shifts the elevated-temperature data to create a mastercurve.

This matters when a manufacturer needs either a direct room-temperature program or a faster time-temperature superposition approach. Method B is the route for shortening test time while still checking that the material follows a consistent linear trend.

The data must be spread across the test period

For Method A, failure times are distributed across short, medium and long periods, with the longest test reaching at least 4 380 h unless otherwise specified. For Method B, the data set must span at least one decade of time, and the elevated-temperature sets must overlap in stress with the reference set.

This matters because a narrow cluster of failures cannot support a reliable extrapolation. The standard is designed to reduce uncertainty by forcing the test points across the time range that supports the 50-year estimate.

Regression quality is part of the pass/fail logic

FprEN 17151-1 requires a linear fit and checks the coefficient of determination, r, for the fitted curve. For the elevated-temperature route, each temperature-specific fit must meet the same quality threshold, and the gradients must be compatible enough to allow time-temperature shifting.

This matters because the result is only as strong as the fit. If the curve is not sufficiently linear, the 50-year result is not a valid basis for design or product comparison.

The apparatus and measurement system are tightly controlled

FprEN 17151-1 requires stiff compression plates, verified force measurement, and measuring devices for time, dimensions, displacement, weight, and temperature. If a force multiplication device or dead load is used, the applied load has to be validated with an EN ISO 7500-1:2018 calibrated load cell.

This matters because small measurement errors affect the extrapolated strength. The standard is therefore as much about controlled equipment as it is about loading the sample.

Test samples have defined preparation rules

FprEN 17151-1 requires the sample to represent the box and its integral components, which are the weakest part of the final construction. Samples must be at least 21 days old at the start of testing and conditioned in air at test temperature for at least 24 h immediately before testing.

This matters because curing, ageing and temperature history can change the result. The standard tries to make results comparable between products and laboratories.

The loading and rupture criteria are strictly documented

FprEN 17151-1 requires one constant load per sample, with the load held within ± 2 % for the duration of the test. A pre-load is applied first, the full load is then reached quickly, and rupture is defined consistently for all data points.

This matters because the rupture time must mean the same thing in every test. Without that consistency, the regression and the lower confidence limit would not be comparable.

The report must support traceability and analysis

FprEN 17151-1 requires the test report to identify the sample, test temperature, fixtures, plate type, loads, rupture curves, failure criteria, fitting results, shift factors where relevant, the final long-term compression strength, and factors that may have affected the result.

This matters because the standard is intended for technical decision-making. The report has to show not only the final value, but also how it was obtained.

What terms does FprEN 17151-1 define?

• Box - a thermoplastic cuboid-shaped element, with or without sidewalls, used to create a modular storage system.
• Integral component - a load-bearing part that contributes to the overall strength of the box.
• Long-term compression strength (σ) - the 95 % lower confidence limit of the applied stress for which the sample would survive 50 years without creep rupture.
• Linear behaviour - a condition where stress vs. log(time) or log(stress) vs. log(failure time) stays linear across the recorded and extrapolated lifetime.
• Test duration periods (TDP1, TDP2, TDP3, TDP4) - the time bands used to distribute creep rupture failures across the test program.
• Lower confidence limit (LCL) - the conservative stress value calculated in Annex A for the 50-year design life.
• Mastercurve - the combined curve built from reference-temperature and shifted elevated-temperature results in Method B.

Who uses FprEN 17151-1?

FprEN 17151-1 is used by manufacturers of thermoplastic boxes for surface water management, test laboratories, and product developers. Quality managers and certification or conformity assessment teams use it to set test programs, review creep rupture data, and document long-term compression strength.

Buyers and specifiers may also use it when they need a test method that can compare products on a common basis. The standard is especially relevant where boxes are used in modular underground storage systems and the user needs a defensible 50-year strength value.

What changed in FprEN 17151-1 from the previous edition?

FprEN 17151-1 supersedes EN 17151:2019. The foreword lists these changes relative to the previous edition:

• the 23 °C test procedure was improved;
• an elevated-temperature test method was added;
• the linear fit data set was defined more clearly, including the r requirement;
• Annex A of EN 17151:2019 was deleted;
• the document number was changed in Part 1.

Which standards are used with FprEN 17151-1?

• EN ISO 7500-1:2018 - gives the calibration and verification basis for the force-measuring system in the compression testing machine.
• ISO 9080 - is cited as the methodological basis for the extrapolation approach used in this standard.
• Part 2 of prEN 17151 - is the companion part in the same series and covers creep behaviour of boxes.
• ISO/TS 28037:2010 - is cited in Annex A for statistical background on straight-line calibration and covariance.

What does the FprEN 17151-1 document contain?

FprEN 17151-1 contains the full test workflow from sample preparation to final reporting. The core technical material is in Clause 8, which sets out the two test methods, the creep rupture procedure, the data plotting rules, and the mastercurve approach for elevated temperatures.

The document also includes Table 1 to Table 4 for distributing failure times, Figure 1 for test-direction identification, and Figure 2 for the mastercurve concept. Annex A provides the regression method, the confidence-limit calculation, and the formulas used to derive the 50-year long-term compression strength.

SLOVENSKI STANDARD
01-marec-2026
Cevni sistemi iz polimernih materialov, ki delujejo po težnostnem principu in so
položeni v zemljo, za transport in shranjevanje nepitne vode - 1 del: Preskusna
metoda za ugotavljanje dolgotrajne tlačne odpornosti zabojev
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
Kunststoff-Rohrleitungssysteme für die drucklose unterirdische Entwässerung für Nicht-
Trinkwasser – Teil 1: Prüfverfahren zur Bestimmung der Langzeitdruckfestigkeit von
Versickerungsblöcken
Systèmes de canalisations en plastique pour le transport et le stockage souterrains sans
pression des eaux de surface - Partie 1 : Méthode d’essai pour la détermination de la
résistance à la compression à long terme des structures alvéolaires ultra-légères
Ta slovenski standard je istoveten z: prEN 17151-1
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 17151-1
NORME EUROPÉENNE
EUROPÄISCHE NORM
December 2025
ICS 23.040.01 Will supersede EN 17151:2019
English Version
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
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 1 : Méthode d'essai pour la Teil 1: Prüfverfahren zur Bestimmung der
détermination de la résistance à la compression à long Langzeitdruckfestigkeit von Versickerungsblöcken
terme des 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 17151-1:2025 E
worldwide for CEN national Members.

prEN 17151-1:2025 (E)
Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Symbols and units . 6
5 Test method . 7
6 Apparatus . 7
6.1 Compression testing apparatus . 7
6.2 Measuring devices . 8
7 Test sample . 8
7.1 General . 8
7.2 Number . 9
7.3 Age . 9
7.4 Conditioning . 9
8 Test methods, procedures and analyses . 9
8.1 Test method A, with all creep rupture tests at (23 ± 2) °C . 9
8.1.1 Procedure. 9
8.1.2 Analysis . 9
8.2 Test method B, including creep rupture tests at elevated temperatures . 10
8.2.1 Procedure. 10
8.2.2 Analysis . 11
8.3 Creep rupture test procedure . 13
9 Test report . 14
Annex A (normative) Procedure for fitting creep rupture data and determining the LCL
strength for a design life of 50 year . 16
A.1 Requirements . 16
A.2 Principles of the analysis . 16
A.3 Analysis method . 17
prEN 17151-1:2025 (E)
European foreword
This document (prEN 17151-1:2025) 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.
This document will supersede EN 17151:2019.
This document includes the following significant changes with respect to EN 17151:2019:
— test procedure 23 °C improved (8.1);
— test method including creep rupture tests at elevated temperatures (8.2);
— linear fit data set better defined with requirement r ;
— Annex A of EN 17151:2019 deleted;
— the number of the document is changed in part 1.
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

prEN 17151-1:2025 (E)
Introduction
This document is intended to reflect the current state of knowledge of determining and predicting the
long-term lifetime of products mentioned in the scope while maintaining reasonable testing times for
producers and developers of these systems.
The products covered by this document are part of surface water management systems.
CEN/TC 155 is aware that these products are used in modular systems and that the long-term
compression strength determined by this document applies to a single box and might not reflect the
maximum allowable loads on an installed system.
The test method follows the principles of ISO 9080 [1] and applies them to the testing of boxes.
Linearity is assumed to extrapolate the stress vs. log(time) or log(stress) vs. log(time) curve from the
results of the creep rupture tests.

prEN 17151-1:2025 (E)
1 Scope
This document specifies a test method for determining the long-term compression strength for a
specified period on boxes made of thermoplastics materials for non-pressure underground conveyance
and storage of surface water.
The test method is applicable for boxes that fail due to creep rupture when subjected to a constant applied
stress and where the relationship of stress or log(stress) vs. log (failure time) is linear and of constant
gradient over the entire specified period with a coefficient of determination greater than 0,8.
The test method in this document allows extrapolation of stress or log(stress) vs. log(failure time) of up
to two decades in time and also specifies a method of accelerated testing using time-temperature
superposition of stress or log(stress) vs. log(failure time) to enable a more rapid determination that a
box obeys a constant gradient linear relationship of stress or log(stress) vs. log(failure time) over the
entire specified period.
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 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.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at https://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp
3.1
box
thermoplastic cuboid shaped element, with or without sidewalls, used to create a modular storage system
3.2
integral component
load bearing component contributing to the overall strength of the box
3.3
initial height, length, width
h , l , b
i i i
respectively height (test direction), length and width of the sample before testing, in mm
3.4
initial height after pre-load
h
height of the sample after applying a pre-load, but before the load is further increased and recorded, in
mm
prEN 17151-1:2025 (E)
3.5
long-term compression strength
σ
r
95 % lower confidence limit of the applied stress for which the sample would survive 50 years without
creep rupture, in kN/m
3.6
linear behaviour
products that exhibit linear behaviour are defined as those that exhibit a linear relationship of stress vs.
log(time) or log(stress) vs. log (failure time) throughout the recorded and extrapolated lifetime
3.7
test duration periods (TDP1, TDP2, TDP3, TDP4)
specifies the duration of a series of creep rupture tests failing in a specific period of time
4 Symbols and units
For the purposes of this document, the following symbols and units apply.
Units
h initial height mm
i
l initial length mm
i
b initial width mm
i
h initial height after pre-load mm
σ failure stress, long-term kN/m
fl
σ failure stress, short-term kN/m
fs
σmax short-term compression strength kN/m
σ long-term compression strength kN/m
r
t time when the test load is applied h
t failure time, short-term h
fl
t failure time, long-term h
fs
a, b constants for fitting a straight line -
y, x variables for fitting a straight line -
t time h
σ applied stress kN/m
T reference temperature °C
T1, …, Ti elevated test temperatures °C
log α , …, log α shift factors -
1 i
σ , …, σ average stresses kN/m
1 average i average
prEN 17151-1:2025 (E)
a , a , …, a y-intercepts -
0 1 i
b , b , …, b gradients -
0 1 i
s , s , …, s standard errors -
b0 b1 bi
2 2 2 2
r , r , r , …, r coefficients of determination -
1 2 i
y , x data pair for fitting a straight line number i -
i i
t , σ data pair of time and stress number i -
i i
N number of data pairs -
u(a), u(b) the standard uncertainties in the fit -
intercept, u(a), the fit gradient, u(b)
5 Test method
Creep rupture tests are performed at different load levels, either at 23 °C (method A – see 8.1) or at 23 °C
and elevated temperatures (method B – see 8.2).
The load levels and for method B the temperatures are selected to distribute the failures evenly over log-
(time).
The creep rupture tests are carried out by testing a series of samples placed between two stiff plates with
different constant compression loads applied at a constant temperature. Deflection is recorded against
time. The different times taken for creep rupture to occur are used to plot a trend line which, when
extrapolated, can be used to predict the stress at which creep rupture will occur at a specific time in the
future. The uncertainty of the extrapolated value is determined to enable the definition of a lower limit
at a specified confidence level.
NOTE Creep rupture tests give information on a change of strain at failure with failure time.
6 Apparatus
6.1 Compression testing apparatus
The testing apparatus shall be capable of applying a constant load via stiff plates. The load may be applied
either directly or indirectly, e.g. by use of a lever arm arrangement. The load shall be applied
perpendicular (90° ± 1°) to the bottom plate.
Where the compression load can be applied to the test sample, the plates shall be flat, smooth and clean
and shall not deform during the test to an extent that would affect the results. The out of plane
deformation of the plates shall be less than 1,0 mm for the loads applied. The upper plate shall be fixed
(plate type 1) or shall have the capability to rotate around one or both horizontal axes (plate type 2). If a
test sample has integral protrusions, it is allowed to use an additional loose flat plate with recesses as a
load distribution layer to secure acceptable contact between the surface of the test sample and the plate
of the testing machine or remove the integral protrusions.
The length and the width of each plate shall be greater than the length and width of the test sample.
If the force is applied by a force multiplication device, the resultant load applied to the sample shall be
validated using an appropriate load cell that has been calibrated according to EN ISO 7500-1:2018, class
2.
prEN 17151-1:2025 (E)
6.2 Measuring devices
Timing devices shall be capable of continuously measuring the testing time with an accuracy of 1 min or
less.
Dimensional measuring devices shall be capable of determining the test piece dimensions with an
accuracy of 1 mm or less.
Displacement measuring devices shall be capable of continuously measuring and recording the distance
between the two plates of the compression machine with an accuracy of 0,1 mm or less.
Weighing devices shall be capable of measuring the weight of the test sample, with an accuracy better
than 0,1 % of the sample weight. They shall be capable of measuring the weight of the plate(s) and the
dead load, if applicable, with an accuracy better than 0,5 % of the weight of the plates or dead load.
Load measuring device shall be capable of continuously measuring and recording the magnitude of the
compression load being applied onto the sample with an accuracy according to EN ISO 7500-1:2018 class
2 or better.
Where dead loads are used that do not change their weight throughout the period of the test, no
continuous measuring and recording of the compression load being applied is required. However, the
resultant load applied to the sample using a dead load shall be validated before and after the test using
an appropriate load cell that has been calibrated according to EN ISO 7500-1:2018 to be class 2 or better.
If the difference is greater than the allowed variation, in 8.3, the data shall be discarded.
NOTE Porous/ hygroscopic dead weights, e.g. concrete, can change weight due to age and environmental
conditions, especially humidity.
Temperature measuring devices, capable of continuously measuring and recording the temperature of
the environment around the sample with an accuracy of 0,1 °C.
7 Test sample
7.1 General
The test sample shall consist of a box with integral components which represent the weakest entity of the
final construction.
Figure 1 — Identification of the test direction of the box
In Figure 1, the Z-direction is the preferred vertical direction of installation.
Those which are homogeneous extruded boxes shall be cut to obtain a test sample representative of the
structure of the box and shall furthermore be cut with a minimum length of 0,5 m in the Z-direction. The
ratio between the X-direction and Z-direction, and Y-direction and the Z-direction shall be less than 1,0.
Identification of the test direction can be found in Figure 1.
prEN 17151-1:2025 (E)
7.2 Number
The number of test samples shall be one per test, if not otherwise specified in the referring standard.
7.3 Age
At the start of testing in accordance with Clause 8, the age of the test samples shall be at least 21 days.
7.4 Conditioning
The test samples shall be conditioned in air at test temperature for at least 24 h immediately prior to
testing in accordance with Clause 8.
8 Test methods, procedures and analyses
8.1 Test method A, with all creep rupture tests at (23 ± 2) °C
8.1.1 Procedure
Unless otherwise specified in the referring standard, carry out the following procedure at a test
temperatu
...