ISO/FDIS 16611
(Main)Plastics piping systems for drainage and sewerage without pressure — Non-circular pipes and joints made of glass-reinforced thermosetting plastics (GRP) based on unsaturated polyester resins (UP) — Dimensions, requirements and tests
Plastics piping systems for drainage and sewerage without pressure — Non-circular pipes and joints made of glass-reinforced thermosetting plastics (GRP) based on unsaturated polyester resins (UP) — Dimensions, requirements and tests
ISO 16611:2017 specifies the required properties of the piping system and its components made from glass-reinforced thermosetting plastics (GRP) based on unsaturated polyester resin (UP) intended to be used for drainage or sewerage without pressure including culverts. It is the responsibility of the purchaser or specifier to make the appropriate selections taking into account their particular requirements and any relevant national regulations and installation practices or codes. ISO 16611:2017 is applicable to non-circular GRP-UP pipes, with flexible or rigid joints, primarily intended for use in buried installations but may also be used to reline existing non-circular pipe lines. NOTE 1 GRP-UP includes pipes with vinyl ester liners or made entirely from vinyl ester. NOTE 2 Piping systems conforming to ISO 16611:2017 can be used also for non-buried applications provided the influence of the environment, e.g. from UV-radiation, and the supports are considered in the design of the pipes, fittings and joints. ISO 16611:2017 is applicable to pipes, fittings and their joints of nominal sizes from DN 150 to DN 4000, which are intended to be used for the conveyance of surface water or sewage at temperatures up to 50 °C.
Systèmes de canalisation en plastiques pour réseaux d'assainissement sans pression — Tuyaux non-circulaires, assemblages de tuyaux et raccords en plastiques thermodurcissables renforcés de verre (PRV) à base de résines de polyester non saturé (UP) — Dimensions, exigences et essais
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Standards Content (Sample)
FINAL DRAFT
International
Standard
ISO/TC 138/SC 6
Plastics piping systems for
Secretariat: ASI
drainage and sewerage without
Voting begins on:
pressure — Non-circular pipes and
2025-10-28
joints made of glass-reinforced
Voting terminates on:
thermosetting plastics (GRP) based
2025-12-23
on unsaturated polyester resins
(UP) — Dimensions, requirements
and tests
Systèmes de canalisation en plastiques pour réseaux
d'assainissement sans pression — Tuyaux non-circulaires,
assemblages de tuyaux et raccords en plastiques
thermodurcissables renforcés de verre (PRV) à base de résines de
polyester non saturé (UP) — Dimensions, exigences et essais
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 SUPPOR TING DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
FINAL DRAFT
International
Standard
ISO/TC 138/SC 6
Plastics piping systems for
Secretariat: ASI
drainage and sewerage without
Voting begins on:
pressure — Non-circular pipes and
joints made of glass-reinforced
Voting terminates on:
thermosetting plastics (GRP) based
on unsaturated polyester resins
(UP) — Dimensions, requirements
and tests
Systèmes de canalisation en plastiques pour réseaux
d'assainissement sans pression — Tuyaux non-circulaires,
assemblages de tuyaux et raccords en plastiques
thermodurcissables renforcés de verre (PRV) à base de résines de
polyester non saturé (UP) — Dimensions, exigences et essais
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 SUPPOR TING DOCUMENTATION.
© ISO 2025
IN ADDITION TO THEIR EVALUATION AS
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ii
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 General requirements . 8
4.1 Classification .8
4.1.1 Categories .8
4.1.2 Nominal size .8
4.2 Materials .8
4.2.1 General .8
4.2.2 Reinforcement .9
4.2.3 Resin .9
4.2.4 Aggregates and fillers .9
4.2.5 Elastomers .9
4.2.6 Metals .9
4.3 Wall construction .9
4.3.1 Inner layer .9
4.3.2 Structural layer .10
4.3.3 Outer layer .10
4.3.4 Appearance .10
4.4 Reference conditions for testing .10
4.4.1 Temperature .10
4.4.2 Properties of water for testing .10
4.4.3 Loading conditions .10
4.4.4 Conditioning .10
4.4.5 Measurement of dimensions .10
4.4.6 Elapsed time for determination of long-term properties, (x) .11
4.5 Joints .11
4.5.1 General .11
4.5.2 Types of joint .11
4.5.3 Flexibility of the jointing system .11
4.5.4 Sealing ring . . .11
4.5.5 Adhesives .11
4.6 Assessment of conformity .11
5 Pipes .12
5.1 Geometrical characteristics . 12
5.1.1 Dimensions . 12
5.2 Mechanical characteristics . 13
5.2.1 General . 13
5.2.2 Short-term bending modulus . 13
5.2.3 Long-term creep bending modulus.14
5.2.4 Short-term bending resistance .14
5.2.5 Long-term bending strength . 15
5.2.6 Resistance to strain corrosion .17
5.2.7 Minimum initial longitudinal tensile strength .17
5.3 Marking .18
6 Fittings . 19
6.1 All types .19
6.1.1 General .19
6.1.2 Diameter series .19
6.1.3 Mechanical characteristics of fittings .19
6.1.4 Installed leak tightness of fittings .19
iii
6.1.5 Dimensions .19
6.2 Marking .19
7 Joint performance .20
7.1 General . 20
7.1.1 Requirements . 20
7.1.2 Test temperature . 20
7.1.3 Dimensions . 20
7.2 Flexible joints . 20
7.2.1 General . 20
7.2.2 Maximum allowable draw. 20
7.2.3 Maximum allowable angular deflection . 20
7.2.4 Maximum allowable misalignment. 20
7.2.5 Flexible non-end-load-bearing joints with elastomeric sealing rings .21
7.3 Rigid joints .21
7.3.1 General .21
7.3.2 Number of test pieces for type testing . 22
7.3.3 Test pieces . 22
Annex A (informative) Static calculation methods .23
Bibliography .24
iv
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 138, Plastics pipes, fittings and valves for the
transport of fluids, Subcommittee SC 6, Reinforced plastics pipes and fittings for all applications.
This second edition cancels and replaces the first edition (ISO 16611:2017), which has been technically
revised.
The main changes are as follows:
— the normative references have been updated;
— the definition of the initial ring stiffness has been aligned with that used in other GRP pipe standards,
see 3.3,
— the definition of the wet creep factor has been aligned with that used in other GRP pipe standards, see 3.5,
— the short-term flexural capacity was introduced as alternative parameter to measure the short-term
bending resistance, see 5.2.4,
— a new subclause on “Assessment of conformity” has been introduced (see 4.6),
— inconsistencies in Clause 7 "Joint performance” have been removed.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
v
Introduction
The purpose of this document is to standardize the requirements for non-circular glass-reinforced
thermosetting plastics pipes (GRP).
This document specifies the requirements for non-circular GRP pipe systems, designed to be used for the
renovation of existing channels or open cut installation.
This document specifies dimensions, requirements and tests of non-circular pipes, including short and long-
term properties. To establish long-term properties, it is recommended to use the circular pipes samples.
Annex A provides commonly used calculation methods for informational purposes. The calculation method
is selected by the designer.
This document does not include the recommended practice for installation.
vi
FINAL DRAFT International Standard ISO/FDIS 16611:2025(en)
Plastics piping systems for drainage and sewerage
without pressure — Non-circular pipes and joints made
of glass-reinforced thermosetting plastics (GRP) based
on unsaturated polyester resins (UP) — Dimensions,
requirements and tests
1 Scope
This document specifies the required properties of the piping system and its components made from glass-
reinforced thermosetting plastics (GRP), based on unsaturated polyester resin (UP) intended to be used for
drainage or sewerage without pressure including culverts.
It is the responsibility of the purchaser or specifier to make the appropriate selections taking into account
their particular requirements and any relevant national regulations and installation practices or codes.
This document is applicable to non-circular GRP-UP pipes, with flexible or rigid joints, primarily intended
for use in buried installations but may also be used to reline existing non-circular pipe lines.
NOTE 1 GRP-UP includes pipes with vinyl ester liners or made entirely from vinyl ester.
NOTE 2 Piping systems conforming to this document can be used also for non-buried applications provided the
influence of the environment, e.g. from UV-radiation, and the supports are considered in the design of the pipes,
fittings and joints.
This document is applicable to pipes, fittings and their joints of nominal sizes from DN 150 to DN 4000,
which are intended to be used for the conveyance of surface water or sewage at normal service conditions.
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.
ISO 75-2, Plastics — Determination of temperature of deflection under load — Part 2: Plastics and ebonite
ISO 178, Plastics — Determination of flexural properties
ISO 3126, Plastics piping systems — Plastics components — Determination of dimensions
ISO 4633, Rubber seals — Joint rings for water supply, drainage and sewerage pipelines — Specification for
materials
ISO 8513, Plastics piping systems — Glass-reinforced thermosetting plastics (GRP) pipes — Test methods for the
determination of the initial longitudinal tensile strength
ISO 8533, Glass-reinforced thermosetting plastics (GRP) pipes and fittings — Test methods to prove the design of
cemented or wrapped joints
ISO 8639, Glass-reinforced thermosetting plastics (GRP) pipes and fittings — Test methods for leaktightness and
proof of structural design of flexible joints
ISO 10468, Glass-reinforced thermosetting plastics (GRP) pipes — Determination of the ring creep properties
under wet or dry conditions
ISO 10928, Plastics piping systems — Glass-reinforced thermosetting plastics (GRP) pipes and fittings —
Methods for regression analysis and their use
ISO 10952, Glass-reinforced thermosetting plastics (GRP) pipes and fittings — Determination of the resistance
to chemical attack for the inside of a section in a deflected condition
EN 681-1, Elastomeric seals — Material requirements for pipe joint seals used in water and drainage applications
— Part 1: Vulcanized rubber
CEN/TS 14632, Plastics piping systems for drainage, sewerage and water supply, pressure and non-pressure —
Glass-reinforced thermosetting plastics (GRP) based on unsaturated polyester resin (UP) — Guidance for the
assessment of conformity
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
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
nominal size
BN × HN
alphanumerical designation of size, which is common to all components in a piping system, it is a convenient
pair of numbers for reference purposes that is related to the maximum internal breadth (B) and the
maximum internal height (H)
Note 1 to entry: The designation for reference or marking purposes consists of the letters BN(B) × HN(H) and the
numerical values for (B) and (H), when expressed in millimetres.
3.2
specific ring stiffness
S
physical characteristic of a circular pipe which is a measure of the resistance to ring deflection per metre
length under external load
Note 1 to entry: Specific ring stiffness is determined using the formula below and is expressed in Newtons per square
metre (N/m ):
EI⋅
S =
d
m
where
E is the apparent modulus of elasticity, which can be derived from the result of the ring stiffness
[1] 2
test, i.e. ISO 7685, expressed in Newtons per square metre (N/m );
d is the mean diameter of the pipe, in metres (m) (see 3.5);
m
I is the second moment of area in the longitudinal direction per metre length, in metres to the
fourth power per metre, (m /m):
e
I=
where e is the wall thickness of the pipe, in metres.
3.3
initial ring stiffness
S
[1]
value of ring stiffness S obtained when a circular pipe is tested in accordance with ISO 7685
Note 1 to entry: Initial ring stiffness is expressed in newtons per square metre (N/m ).
3.4
mean diameter
d
m
diameter of the circle corresponding to the middle of a circular pipe wall cross-section and given by either of
the following formulae:
dd=+e
mi
or
dd=−e
me
where
d is the internal diameter, in millimetres(mm);
i
d is the external diameter, in millimetres (mm);
e
e is the wall thickness of the pipe, in millimetres(mm).
Note 1 to entry: It is expressed in millimetres (mm).
3.5
wet creep factor
α
x,creep,wet
ratio of the long-term ring creep stiffness, S at x years to the ring stiffness S at position 1 at 0,1 hour
x,wet 0,1
Note 1 to entry: See 4.4.6 for value of x.
Note 2 to entry: Determined using circular test-pieces under sustained diametrical loading in wet conditions when
tested in accordance with ISO 10468
.
Note 3 to entry: Wet creep factor is a dimensionless number given by the formula:
S
x,wet
α =
x,creep,wet
S
01,
3.6
long-term ring stiffness
S
x,wet
determined value of ring stiffness S at x years for circular pipe
3.7
rerating factor
R
RF
multiplication factor that quantifies the relationship of a product’s mechanical, physical and chemical
properties under service conditions above 35 °C [design service temperature (3.17)] to those applicable at a
standard test temperature of 23 °C
3.8
short-term bending strength
σ
f
maximum flexural stress sustained by the test specimen during a bending test, when tested in accordance
with ISO 178
Note 1 to entry: Short-term bending strength is determined using the following formula and is expressed in
megapascals (MPa):
3FL
σ =
f
2bh
where
F is the load, in newtons (N);
L is the span, in millimetres (mm);
h is the thickness of the specimen, in millimetres (mm);
b is the width of the specimen, in millimetres (mm).
3.9
long-term bending strength
σ
fx
calculated value of σ at x years for circular pipe
f
Note 1 to entry: Long-term bending strength is determined using methodology given in 5.2.5.3, using linear regression
analysis according to ISO 10928 on data of bending stress in hoop direction, and is expressed in megapascals (MPa):
d 1
m
6⋅⋅F ⋅
max
2 π
σα= ⋅
fx ki
l⋅e
with
35⋅⋅de+
i
α =
ki
33⋅⋅de+
i
where
F is the maximum force, in newtons (N);
max
d is the mean diameter, in millimetres (mm);
m
d is the inside diameter, in (mm);
i
e is the wall thickness, in millimetres (mm);
l is the length of specimen, in (mm);
α is the correction factor inner surface.
ki
3.10
short-term bending modulus
E
f
value of flexural modulus obtained when tested in accordance with ISO 178
Note 1 to entry: Short-term bending modulus is determined using the following formula and is expressed in
megapascals (MPa):
F
L
max
E = ⋅
f
s
4bh⋅ max
where
F is the maximum force, which corresponds to maximum deflection, in newtons (N);
max
s is the maximum deflection of specimen, in millimetres (mm);
max
b is the width of the specimen, in millimetres (mm);
h is the wall thickness of the specimen, in millimetres (mm);
L is the span of the specimen, in millimetres (mm).
3.11
long-term creep bending modulus
E
fx
calculated value of E at x years for circular pipe when tested in accordance with ISO 10468
f
Note 1 to entry: Long-term bending modulus is determined using the following formula and is expressed in
megapascals (MPa):
EE=⋅ α
f0xx ,creep,wet
where
E is the short-term bending modulus as a result of the creep test on circular profiles according to
ISO 10468, in megapascals (MPa);
α is the wet creep factor, see 3.6.
x,creep,wet
3.12
declared flexural capacity
M
B
maximum unitary bending moment declared by the manufacturer
Note 1 to entry: Declared flexural capacity is determined using the following formula and is expressed in N·mm/mm:
σ ⋅e
fd
M =
B
where
σ is the declared short-term bending strength, in megapascals (MPa);
fd
e is the wall thickness of the pipe, in millimetres (mm).
3.13
short-term flexural capacity
M
B,u
maximum unitary bending moment sustained by the test specimen during a bending test, when tested in
accordance with ISO 178
Note 1 to entry: flexural capacity is determined using the following formula and is expressed in N·mm/mm:
FL⋅
M =
B,u
4⋅b
where
F is the load corresponding to the maximum flexural stress σ as defined in ISO 178, in
fM
Newtons (N);
L is the span of the specimen, in millimetres (mm);
b is the width of the specimen, in millimetres (mm).
3.14
type test
test carried out to prove that a material, component, joint or assembly is capable of conforming to the
relevant requirement
3.15
laying length
total length of a pipe minus, where applicable, the manufacturer's recommended insertion depth of the
spigot(s) in the socket
Note 1 to entry: Laying length is expressed in metres (m).
3.16
normal service conditions
conveyance of surface water or sewage, in the temperature range 2 °C to 50 °C, with maximum water table
of 10 m, for 50 years
3.17
design service temperature
maximum sustained temperature at which the system is expected to operate
Note 1 to entry: Expressed in degrees Celsius (°C).
3.18
flexible joint
joint which allows relative movement between the pipes being joined
Note 1 to entry: Examples of this type of joint are: socket-and-spigot joint with an elastomeric sealing element
(including double socket designs)
3.19
rigid joint
joint which does not allow relative movement between the pipes being joined
Note 1 to entry: Examples of this type of joint are: flanged joint, including integral and loose flanges, wrapped or
cemented joint.
3.20
angular deflection
δ
angle between the axes of two adjacent pipes
Note 1 to entry: See Figure 1.
Note 2 to entry: Angular deflection is expressed in degrees (°).
3.21
draw
D
longitudinal movement of a joint
Note 1 to entry: See Figure 1.
Note 2 to entry: Draw is expressed in millimetres (mm).
3.22
total draw
T
sum of the draw, D, and the additional longitudinal movement, J, due to the presence of angular deflection
Note 1 to entry: See Figure 1.
Note 2 to entry: Total draw is expressed in millimetres (mm).
3.23
misalignment
M
distance by which the centrelines of adjacent pipes fail to coincide
Note 1 to entry: See Figure 1.
Note 2 to entry: Misalignment is expressed in millimetres (mm).
a)
b)
c)
d)
Key
D draw
J longitudinal movement arising from angular deflection of the joint
δ angular deflection of the joint
T total draw
M misalignment
Figure 1 — Joint movement
4 General requirements
4.1 Classification
4.1.1 Categories
Pipes conforming to this document shall be classified according to nominal size (BN × HN) (see 3.1), and
joint type, i.e. flexible or rigid (see 3.18 or 3.19).
4.1.2 Nominal size
The nominal size (BN × HN) (see 3.1) of pipes shall conform to the product declaration of the manufacturer.
4.2 Materials
4.2.1 General
The pipe shall be constructed using chopped and/or continuous glass filaments, strands or rovings, mats
or fabric synthetic veils, and polyester resin with or without fillers and if applicable additives necessary to
impart specific properties to the resin. The pipe or fitting may also incorporate aggregates, and if required
a thermoplastic liner.
4.2.2 Reinforcement
The glass used for the manufacture of the reinforcement shall be one of the following types:
a) type “E” glass, comprising primarily either oxides of silicon, aluminium and calcium (alumino–
calcosilicate glass) or oxides of silicon, aluminium and boron (alumino-borosilicate glass);
b) type “C” glass, comprising primarily oxides of silicon, sodium, potassium, calcium and boron (alkali
metal calcium glass with an increased boron trioxide content) which is intended for applications
requiring enhanced chemical resistance;
c) type “R” glass, comprising primarily oxides of silicon, aluminium, calcium and magnesium without
added boron;
d) type “E-CR” glass, comprising boron-free modified E-glass compositions for improved resistance to
corrosion by most acids.
In any of these types of glass small amounts of oxides of other metals will be present.
NOTE These descriptions for “C” glass and “E” glass are consistent with, but more specific than those given in
[2]
ISO 2078 .
The reinforcement shall be made from continuously drawn filaments of a glass conforming to type E, type
C or type R, and shall have a surface treatment compatible with the resin to be used. It may be used in any
form, e.g. as continuous or chopped filaments, strands or rovings, mat or fabric.
4.2.3 Resin
The resin used in the structural layer (see 4.3.2) shall have a temperature of deflection of at least 70 °C when
tested in accordance with ISO 75-2
NOTE Resins can be unsaturated polyesters or based on vinyl esters.
4.2.4 Aggregates and fillers
The size of particles in aggregates and fillers shall not exceed 1/5 of the total wall thickness of the pipe or
2,5 mm, whichever is the lesser.
4.2.5 Elastomers
Each elastomeric material(s) of the sealing component shall conform to the applicable requirements of
EN 681-1 or ISO 4633.
NOTE These standards are deemed to satisfy the 50 years design life of the pipe systems made in accordance
with this document. For design life exceeding 50 years see ISO 4633.
4.2.6 Metals
Where exposed metal components are used, there shall not be evidence of corrosion of the components after
the fitting has been immersed in an aqueous sodium chloride solution, 30 g/l, for 7 d at (23 ± 2) °C.
4.3 Wall construction
4.3.1 Inner layer
The inner layer shall comprise one of the following:
a) a thermosetting resin layer with or without aggregates or fillers and with or without reinforcement of
glass or synthetic filaments;
b) a thermoplastics liner.
The thermoplastic liner may require a bonding material compatible with all other materials used in the pipe
construction.
The resin used in this inner layer need not conform to the temperature of deflection requirements given in 4.2.3.
NOTE The construction of the liner influences the chemical and abrasion resistance of the pipe.
4.3.2 Structural layer
The structural layer shall consist of glass reinforcement and a thermosetting resin, with or without
aggregates or fillers.
4.3.3 Outer layer
The design of the outer layer of the pipe shall take into account the environment in which the pipe is to be
used. This layer shall be formed of a thermosetting resin with or without aggregates or fillers and with or
without a reinforcement of glass or synthetic filaments.
The use of special constructions is permitted when the pipe is expected to be exposed to extreme climatic,
environmental or ground conditions, for example, provision for the inclusion of pigments or inhibitors for
extreme climatic conditions or fire retardation.
The resin used in this outer layer need not conform to the temperature of deflection requirements in 4.2.3.
4.3.4 Appearance
Both internal and external surfaces shall be free from irregularities, which would impair the ability of the
component to conform to the requirements of this document.
4.4 Reference conditions for testing
4.4.1 Temperature
The mechanical, physical and chemical properties specified in all clauses of this document shall, unless
otherwise specified, be determined at (23 ± 5) °C.
For service temperatures over 35 °C, type tests (see 3.10) shall be carried out at least at the design service
temperature to establish rerating factors, R (see 3.8) for all long-term properties of relevance to be used in
RF
the design of pipes and fittings.
4.4.2 Properties of water for testing
The water used for the tests referred to in this document shall be tap water having a pH of 7 ± 2.
4.4.3 Loading conditions
Unless otherwise specified, the mechanical, physical and chemical properties specified in all clauses of this
document shall be determined using circumferential and longitudinal loading conditions, as applicable.
4.4.4 Conditioning
Unless otherwise specified, in case of dispute store the test piece(s) in air at the test temperature specified
in 4.4.1 for at least 24 h prior to testing.
4.4.5 Measurement of dimensions
In case of dispute, the dimensions of GRP-UP components shall be determined at the temperature specified
in 4.4.1. Measurements shall be made in accordance with ISO 3126 to determine conformity or otherwise
to the applicable limits. Routine measurements shall be determined at the prevailing temperature or at the
temperature specified in 4.4.1, according to the manufacturer’s preference.
4.4.6 Elapsed time for determination of long-term properties, (x)
The subscript x, in for example S (see 3.8), denotes the elapsed time for which the long-term property
x,wet
is to be determined. Unless otherwise specified, the long-term properties shall be determined at 50 years
(438 000 h).
4.5 Joints
4.5.1 General
The manufacturer shall declare the length and the maximum external dimension of the assembled joint.
4.5.2 Types of joint
A joint shall be classified as either flexible (see 3.18) or rigid (see 3.19) and in each case whether or not it is
capable of resisting end-loads.
4.5.3 Flexibility of the jointing system
4.5.3.1 Allowable maximum angular deflection
The manufacturer shall declare the allowable maximum angular deflection for which each joint is designed
and about which axis (B or H) the rotation occurs.
4.5.3.2 Maximum draw
The manufacturer shall declare the maximum draw (see 3.21) for which each joint is designed.
For flexible joints, the maximum draw, which includes the Poisson contraction and temperature effects, shall
not be less than 0,2 % of the laying length (see 3.15) of the longest pipe with which it is intended to be used.
4.5.4 Sealing ring
The sealing ring shall not have any detrimental effect on the properties of the components with which it is
used and shall not cause the test assembly to fail the functional requirements of Clause 6.
4.5.5 Adhesives
Adhesives, if required for jointing, shall be specified by the manufacturer of the joint. The joint manufacturer
shall ensure that the adhesives shall not have any detrimental effects on the components with which it is
used and shall not cause the test assembly to fail the functional requirements of Clause 6.
4.6 Assessment of conformity
Assessment of conformity of products specified in this document shall be made according to CEN/TS 14632.
NOTE CEN/TS 14632 details procedures and tests for product assessments such as type tests (TT), audit tests
(AT), BRT and process verification tests (PVT), as well as tests to assess the effects of changes in the design, process
and materials.
[3]
A testing laboratory for TT, AT and PVT should operate in accordance with ISO/IEC 17025 .
The scope of this document includes large diameters. Thus TT, AT and PVT may also include large sample sizes
or difficult structures where special testing equipment is needed. In case the accredited testing laboratory
is not equipped with these special testing facilities, the tests may be performed in the manufactures’
laboratories under the supervision of the testing or certification institute.
5 Pipes
5.1 Geometrical characteristics
5.1.1 Dimensions
Non-circular pipe profiles are available with various kinds of shapes (see Figure 2) and are designed
individually depending on their use, required hydraulic capacity and the static load they need to resist.
Dimensions in millimetres
a) b)
c) d)
Key
R radius of the semi-circular portion
B maximum internal breadth
H maximum internal height
Figure 2 — Typical pipe profile shapes
The external dimensions of pipe profiles, as well as their overall length shall be agreed between the
manufacturer and the client. Any measured wall thicknesses shall be equal to or exceed the minimum
required wall thickness previously agreed between the manufacturer and client.
The laying length (see 3.14) shall comply with the agreed laying length subject to a tolerance of +20 mm
and −10 mm.
5.2 Mechanical characteristics
5.2.1 General
When determining the mechanical properties of the structural layer, e.g. the calculation of E-modulus,
tensile strength, etc., the thickness of outside and inside layers
...
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ISO /TC 138/SC 06/WG 03 6
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Secretariat: ASI
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Section start: New page, Header distance from edge:
Date: 2025-08-0510-14 1.27 cm, Footer distance from edge: 1.27 cm
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...
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Plastics piping systems for drainage and sewerage without
pressure — Non-circular pipes and joints made of glass-reinforced
thermosetting plastics (GRP) based on unsaturated polyester resins
(UP) — Dimensions, requirements and tests
Systèmes de canalisation en plastiques pour réseaux d'assainissement sans pression — Tuyaux non-circulaires,
assemblages de tuyaux et raccords en plastiques thermodurcissables renforcés de verre (PRV) à base de résines
de polyester non saturé (UP) — Dimensions, exigences et essais
FDIS stage
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ISO DIS/FDIS 16611:2024 (E2025(en)
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All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication
may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, Formatted: Indent: Left: 0 cm, Right: 0 cm, Space
or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO Before: 0 pt, No page break before, Adjust space
at the address below or ISO’s member body in the country of the requester. between Latin and Asian text, Adjust space between
Asian text and numbers
ISO copyright office
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CP 401 • Ch. de Blandonnet 8
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CH-1214 Vernier, Geneva
Phone: + 41 22 749 01 11
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EmailE-mail: copyright@iso.org
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Website: www.iso.orgwww.iso.org
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Published in Switzerland
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ii © ISO 2023 2025 – All rights reserved
ii
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Contents
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Foreword . v
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 General requirements . 11
5 Pipes . 15
6 Fittings . 24
7 Joint performance . 25
Annex A (informative) Static calculation methods . 29
Bibliography . 30
Foreword . v
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 General requirements . 8
4.1 Classification . 8
4.1.1 Categories . 8
4.1.2 Nominal size . 8
4.2 Materials. 8
4.2.1 General . 8
4.2.2 Reinforcement . 8
4.2.3 Resin . 8
4.2.4 Aggregates and fillers . 8
4.2.5 Elastomers . 9
4.2.6 Metals . 9
4.3 Wall construction . 9
4.3.1 Inner layer . 9
4.3.2 Structural layer . 9
4.3.3 Outer layer . 9
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4.3.4 Appearance . 9
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4.4.1 Temperature . 9
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4.4.3 Loading conditions . 10
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4.4.4 Conditioning . 10
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iii
ISO DIS/FDIS 16611:2024 (E2025(en)
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4.4.6 Elapsed time for determination of long-term properties, (x) . 10
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4.5 Joints . 10
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4.5.1 General . 10
4.5.2 Types of joint . 10
4.5.3 Flexibility of the jointing system . 10
4.5.4 Sealing ring . 10
4.5.5 Adhesives . 11
4.6 Assessment of conformity . 11
5 Pipes . 11
5.1 Geometrical characteristics . 11
5.1.1 Dimensions . 11
5.2 Mechanical characteristics . 12
5.2.1 General . 12
5.2.2 Short-term bending modulus . 13
5.2.3 Long-term creep bending modulus . 13
5.2.4 Short-term bending strength . 14
5.2.5 Long-term bending strength . 15
5.2.6 Resistance to strain corrosion . 16
5.2.7 Minimum initial longitudinal tensile strength . 16
5.3 Marking . 18
6 Fittings . 18
6.1 All types . 18
6.1.1 General . 18
6.1.2 Diameter series . 18
6.1.3 Mechanical characteristics of fittings . 18
6.1.4 Installed leak tightness of fittings . 18
6.1.5 Dimensions . 18
6.2 Marking . 19
7 Joint performance . 19
7.1 General . 19
7.1.1 Requirements . 19
7.1.2 Test temperature . 19
7.1.3 Dimensions . 19
7.2 Flexible joints . 19
7.2.1 General . 19
7.2.2 Maximum allowable draw . 19
7.2.3 Maximum allowable angular deflection . 20
7.2.4 Maximum allowable misalignment . 20
7.2.5 Flexible non-end-load-bearing joints with elastomeric sealing rings . 20
7.3 Rigid joints . 21
7.3.1 Wrapped or cemented . 21
Annex A (informative) Examples for static calculation . 22
Bibliography . 23
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iv © ISO 2023 2025 – All rights reserved
iv
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Foreword
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ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of
ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
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ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights
in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s)
which may be required to implement this document. However, implementers are cautioned that this may not
represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents.www.iso.org/patents. ISO shall not be held responsible for identifying any or all such
patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
Field Code Changed
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This document was prepared by Technical Committee ISO/TC 138, Plastics pipes, fittings and valves for the
transport of fluids, Subcommittee SC 6, Reinforced plastics pipes and fittings for all applications.
This second edition cancels and replaces the first edition (ISO 16611:2017), which has been technically
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revised.
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The main changes are as follows:
— — the normative references have been updated;
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— — the definition of the initial ring stiffness has been aligned with that used in other GRP pipe standards,
stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
see 3.3,Error! Reference source not found., 3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
— — the definition of the wet creep factor has been aligned with that used in other GRP pipe standards, see
3.5,Error! Reference source not found.,
— — the short-term flexural capacity was introduced as alternative parameter to measure the short-term Formatted: Adjust space between Latin and Asian text,
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bending resistance, see 5.2.4, 5.2.4,
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— — a new subclause on “Assessment of conformity” has been introduced (see 4.6),4.6),
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— — inconsistencies in clause 77 "Joint performance” have been removed.
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Any feedback or questions on this document should be directed to the user’s national standards body. A
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complete listing of these bodies can be found at www.iso.org/members.htmlwww.iso.org/members.html.
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v
ISO DIS/FDIS 16611:2024 (E2025(en)
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Introduction
spacing: single
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The purpose of this document is to standardize the requirements for non-circular glass-reinforced
thermosetting plastics pipes (GRP).
This document specifies the requirements for non-circular GRP pipe systems, designed to be used for the
renovation of existing channels or open cut installation.
This document specifies dimensions, requirements and tests of non-circular pipes, including short and long-
term properties. To establish long-term properties, it is recommended to use the circular pipes samples.
Annex AAnnex A provides commonly used calculation methods for informational purposes. The calculation
method is selected by the designer.
This document does not include the recommended practice for installation.
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vi © ISO 2023 2025 – All rights reserved
vi
DRAFT International Standard ISO/FDIS 16611:2025(en)
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Plastics piping systems for drainage and sewerage without
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pressure — Non-circular pipes and joints made of glass-reinforced
between Asian text and numbers
thermosetting plastics (GRP) based on unsaturated polyester resins
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(UP) — Dimensions, requirements and tests
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1 Scope Formatted: Adjust space between Latin and Asian text,
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This document specifies the required properties of the piping system and its components made from glass- stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
reinforced thermosetting plastics (GRP)), based on unsaturated polyester resin (UP) intended to be used for
drainage or sewerage without pressure including culverts.
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It is the responsibility of the purchaser or specifier to make the appropriate selections taking into account
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their particular requirements and any relevant national regulations and installation practices or codes.
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This document is applicable to non-circular GRP-UP pipes, with flexible or rigid joints, primarily intended for
stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
use in buried installations but may also be used to reline existing non-circular pipe lines.
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
NOTE 1 GRP-UP includes pipes with vinyl ester liners or made entirely from vinyl ester.
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NOTE 2 Piping systems conforming to this document can be used also for non-buried applications provided the
influence of the environment, e.g. from UV-radiation, and the supports are considered in the design of the pipes, fittings
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and joints.
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This document is applicable to pipes, fittings and their joints of nominal sizes from DN 150 to DN 4000, which Formatted: Default Paragraph Font
are intended to be used for the conveyance of surface water or sewage at normal service conditions.
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2 Normative references
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The following documents are referred to in the text in such a way that some or all of their content constitutes
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requirements of this document. For dated references, only the edition cited applies. For undated references,
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the latest edition of the referenced document (including any amendments) applies.
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ISO 75--2, Plastics — Determination of temperature of deflection under load — Part 2: Plastics and ebonite
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ISO 178, Plastics — Determination of flexural properties
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ISO 3126, Plastics piping systems — Plastics components — Determination of dimensions
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ISO 4633, Rubber seals — Joint rings for water supply, drainage and sewerage pipelines — Specification for
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materials
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ISO 8513, Plastics piping systems — Glass-reinforced thermosetting plastics (GRP) pipes — Test methods for the
determination of the initial longitudinal tensile strength
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ISO 8533, Glass-reinforced thermosetting plastics (GRP) pipes and fittings — Test methods to prove the design of
cemented or wrapped joints Formatted: Default Paragraph Font, Font: Italic
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ISO 8639, Glass-reinforced thermosetting plastics (GRP) pipes and fittings — Test methods for leaktightness and
spacing: single, Tab stops: Not at 17.2 cm
proof of structural design of flexible joints
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ISO 10468, Glass-reinforced thermosetting plastics (GRP) pipes — Determination of the ring creep properties
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under wet or dry conditions
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ISO 10928, Plastics piping systems — Glass-reinforced thermosetting plastics (GRP) pipes and fittings — Methods
for regression analysis and their use
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ISO 10952, Glass-reinforced thermosetting plastics (GRP) pipes and fittings — Determination of the resistance
to chemical attack for the inside of a section in a deflected condition Formatted: Default Paragraph Font, Font: Italic
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ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories
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EN 681-1, Elastomeric seals — Material requirements for pipe joint seals used in water and drainage
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applications — Part 1: Vulcanized rubber
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CEN/TS 14632, Plastics piping systems for drainage, sewerage and water supply, pressure and non-pressure —
Glass-reinforced thermosetting plastics (GRP) based on unsaturated polyester resin (UP) — Guidance for the
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assessment of conformity
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3 Terms and definitions
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For the purposes of this document, the following terms and definitions apply.
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ISO and IEC maintain terminology databases for use in standardization at the following addresses:
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— — ISO Online browsing platform: available at https://www.iso.org/obphttps://www.iso.org/obp
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— — IEC Electropedia: available at https://www.electropedia.org/https://www.electropedia.org/
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3.1 3.1
nominal size
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BN × HN
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alphanumerical designation of size, which is common to all components in a piping system, it is a convenient
Formatted
...
pair of numbers for reference purposes that is related to the maximum internal breadth (B) and the maximum
internal height (H)
Formatted
...
Formatted
...
Note 1 to entry: The designation for reference or marking purposes consists of the letters BN(B) × HN(H) and the
numerical values for (B) and (H), when expressed in millimetres. Formatted: Regular Italic, Font: Bold, Not Italic
Formatted: Regular, Font: Bold
3.2 3.2
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specific ring stiffness
S
Formatted
...
physical characteristic of a circular pipe which is a measure of the resistance to ring deflection per metre
Formatted
...
length under external load
Formatted: Regular Italic, Font: Bold, Not Italic
Note 1 to entry: Specific ring stiffness is determined using the formula below and is expressed in Newtons per square
Formatted
...
metre (N/m ):
EI
S
d
m
where
Formatted: Font: 10 pt
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E is the apparent modulus of elasticity, which can be derived from the result of the ring stiffness
test, i.e. ISO 7685 [1], expressed in Newtons per square metre (N/m );
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...
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2 © ISO #### 2025 – All rights reserved
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d is the mean diameter of the pipe, in metres (m) (see 3.5);
m Formatted: Font: 11 pt
I is the second moment of area in the longitudinal direction per metre length, in metres to the
fourth power per metre, (m /m):
e
I
where e is the wall thickness of the pipe, in metres.
𝐸⋅𝐼
3.3𝑆 =
𝑑
m
where
E is the apparent modulus of elasticity, which can be derived from the result of the ring stiffness test, i.e.
[ ] 2
ISO 7685, Error! Reference source not found. expressed in Newtons per square metre (N/m );
d is the mean diameter of the pipe, in metres (m) (see Error! Reference source not found.);
m
I is the second moment of area in the longitudinal direction per metre length, in metres to the fourth power per metre,
(m /m):
𝑒
𝐼 =
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where e is the wall thickness of the pipe, in metres.
and Asian text, Adjust space between Asian text and
numbers
3.3
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initial ring stiffness
S
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[
value of ring stiffness S obtained when a circular pipe is tested in accordance with ISO 7685 [1] Error!
Subscript
]
Reference source not found.
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Note 1 to entry: Initial ring stiffness is expressed in newtons per square metre (N/m ).
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3.4 3.4
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mean diameter
stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
d
m
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
diameter of the circle corresponding to the middle of a circular pipe wall cross-section and given by either of
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the following formulae:
and Asian text, Adjust space between Asian text and
numbers
d d e
mi
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𝑑 = 𝑑 + 𝑒 Formatted: Regular Sub, Font: Bold, Not Superscript/
m i
Subscript
or
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d d e
me
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between Latin and Asian text, Adjust space between
𝑑 = 𝑑 − 𝑒
m e
Asian text and numbers, Tab stops: Not at 0.7 cm +
where 1.4 cm + 2.1 cm + 2.8 cm + 3.5 cm + 4.2 cm + 4.9
cm + 5.6 cm + 6.3 cm + 7 cm
di is the internal diameter, in millimetres(mm);
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d is the external diameter, in millimetres (mm)
e
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e is the wall thickness of the pipe, in millimetres(mm).
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di is the internal diameter, in millimetres(mm);
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Formatted: Font: Bold
Formatted: HeaderCentered
de is the external diameter, in millimetres (mm);
e is the wall thickness of the pipe, in millimetres(mm).
Note 1 to entry: It is expressed in millimetres (mm).
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3.5 3.5
stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
wet creep factor
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
αx,creep,wet
Formatted: TermNum2, Adjust space between Latin
ratio of the long-term ring creep stiffness, S at x years to the ring stiffness S at position 1 at 0,1 hour
x,wet 0.,1
and Asian text, Adjust space between Asian text and
numbers
Note 1 to entry: See 4.4.64.4.6 for value of x.
Formatted: Regular Italic, Font: Bold, Not Italic
Note 2 to entry: Determined using circular test-pieces under sustained diametrical loading in wet conditions when
Formatted: Regular Italic Sub, Font: Bold, Not Italic,
tested in accordance with ISO 10468
.
Not Superscript/ Subscript
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Note 3 to entry: Wet creep factor is a dimensionless number given by the formula:
Subscript
S
Formatted: Adjust space between Latin and Asian text,
x ,wet
x ,creep,wet
Adjust space between Asian text and numbers, Tab
S
0,1
stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
3.6
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𝑆
𝑥,wet
𝛼 =
𝑥,creep,wet
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𝑆
0,1
3.6
long-term ring stiffness
Formatted: Adjust space between Latin and Asian text,
Sx,wet Adjust space between Asian text and numbers
determined value of ring stiffness S at x years for circular pipe
Formatted: Regular Italic, Font: Bold, Not Italic
Formatted: Regular Italic Sub, Font: Bold, Not Italic,
3.7 3.7
Not Superscript/ Subscript
rerating factor
RRF
Formatted: Regular Sub, Font: Bold, Not Superscript/
multiplication factor that quantifies the relationship of a product’s mechanical, physical and chemical
Subscript
properties under service conditions above 35 °C [design service temperature (3.17)](Error! Reference source
Formatted: Regular Italic, Font: Bold, Not Italic
not found.)] to those applicable at a standard test temperature of 23 °C
Formatted: Regular Sub, Font: Bold, Not Superscript/
Subscript
3.8 3.8
short-term bending strength
σ
f Formatted: Regular Italic, Font: Bold, Not Italic
maximum flexural stress sustained by the test specimen during a bending test, when tested in accordance with
Formatted: Regular Sub, Font: Bold, Not Superscript/
ISO 178
Subscript
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Note 1 to entry: Short-term bending strength is determined using the following formula and is expressed in
megapascals (MPa):
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3FL
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f
stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
2bh
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
3𝐹𝐿
𝜎 =
f
2𝑏ℎ
Formatted
...
where Formatted: Font: 10 pt
F is the load, in newtons (N);
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...
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4 © ISO #### 2025 – All rights reserved
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Formatted: HeaderCentered, Left, Space After: 0 pt,
Line spacing: single, Tab stops: Not at 0.71 cm
L is the span, in millimetres (mm);
Formatted: Font: 11 pt
h is the thickness of the specimen, in millimetres (mm);
b is the width of the specimen, in millimetres (mm).
3.9
F is the load, in newtons (N);
L is the span, in millimetres (mm);
h is the thickness of the specimen, in millimetres (mm);
b is the width of the specimen, in millimetres (mm).
3.9
long-term bending strength
Formatted: Left, Adjust space between Latin and Asian
σ x
f text, Adjust space between Asian text and numbers
calculated value of σ at x years for circular pipe
f
Formatted: Regular Italic, Font: Bold, Not Italic
Formatted: Adjust space between Latin and Asian text,
Note 1 to entry: Long‐term bending strength is determined using methodology given in 5.2.5.3,5.2.5.3, using linear
Adjust space between Asian text and numbers
regression analysis according to ISO 10928 on data of bending stress in hoop direction, and is expressed in megapascals
(MPa):
Formatted: Regular Sub, Font: Bold, Not Superscript/
Subscript
d 1
m
6F Formatted: Regular Italic Sub, Font: Bold, Not Italic,
max
2 π
Not Superscript/ Subscript
fx ki
le
Formatted: Not Raised by / Lowered by
𝑑 1 Formatted: Adjust space between Latin and Asian text,
m
6 ⋅ 𝐹 ⋅ ⋅
𝑚𝑎𝑥
2 𝜋 Adjust space between Asian text and numbers, Tab
𝜎 = ⋅ 𝛼
𝑓𝑥 ki
𝑙 ⋅ 𝑒 stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
with
Formatted: Default Paragraph Font
Formatted: Default Paragraph Font
35de
i
ki
33de
i Formatted: Note, Adjust space between Latin and
Asian text, Adjust space between Asian text and
3 ⋅ 𝑑 + 5 ⋅ 𝑒
𝑖 numbers, Tab stops: Not at 0.7 cm + 1.4 cm + 2.1 cm
𝛼 =
𝑘𝑖
+ 2.8 cm + 3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3
3 ⋅ 𝑑 + 3 ⋅ 𝑒
𝑖
where
Formatted: Equation Legend_Title, Adjust space
Fmax is the maximum force, in newtons (N); between Latin and Asian text, Adjust space between
Asian text and numbers, Tab stops: Not at 0.7 cm +
d is the mean diameter, in millimetres (mm); 1.4 cm + 2.1 cm + 2.8 cm + 3.5 cm + 4.2 cm + 4.9
m
cm + 5.6 cm + 6.3 cm + 7 cm
d is the inside diameter, in (mm);
i
e is the wall thickness, in millimetres (mm);
l is the length of specimen, in (mm);
α is the correction factor inner surface.
ki
Formatted: Font: 10 pt
3.10 F is the maximum force, in newtons (N);
max Formatted: FooterCentered, Left, Space Before: 0 pt,
d is the mean diameter, in millimetres (mm); Line spacing: single, Tab stops: Not at 17.2 cm
m
di is the inside diameter, in (mm);
Formatted: Font: 10 pt
e is the wall thickness, in millimetres (mm);
Formatted: Font: 11 pt
Formatted: Font: Bold
Formatted: HeaderCentered
l is the length of specimen, in (mm);
αki is the correction factor inner surface.
3.10
Formatted: TermNum2, Adjust space between Latin
short-term bending modulus
and Asian text, Adjust space between Asian text and
E
f numbers
value of flexural modulus obtained when tested in accordance with ISO 178
Formatted: Regular Italic, Font: Bold, Not Italic
Formatted: Regular Sub, Font: Bold, Not Superscript/
Note 1 to entry: Short-term bending modulus is determined using the following formula and is expressed in
Subscript
megapascals (MPa):
Formatted: Left, Adjust space between Latin and Asian
F text, Adjust space between Asian text and numbers
L
max
E
f
s Formatted: Default Paragraph Font
4bh
max
Formatted: Adjust space between Latin and Asian text,
𝐿 𝐹
𝑚𝑎𝑥 Adjust space between Asian text and numbers
𝐸 = ⋅
f
4𝑏 ⋅ ℎ 𝑠
max
Formatted: Default Paragraph Font
Formatted: Adjust space between Latin and Asian text,
where
Adjust space between Asian text and numbers, Tab
F is the maximum force, which corresponds to maximum deflection, in newtons (N);
max
stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
s is the maximum deflection of specimen, in millimetres (mm);
max
Formatted: Equation Legend_Title, Adjust space
between Latin and Asian text, Adjust space between
b is the width of the specimen, in millimetres (mm);
Asian text and numbers, Tab stops: Not at 0.7 cm +
1.4 cm + 2.1 cm + 2.8 cm + 3.5 cm + 4.2 cm + 4.9
h is the wall thickness of the specimen, in millimetres (mm);
cm + 5.6 cm + 6.3 cm + 7 cm
L is the span of the specimen, in millimetres (mm).
Formatted: TermNum2, Adjust space between Latin
and Asian text, Adjust space between Asian text and
3.11 F is the maximum force, which corresponds to maximum deflection, in newtons (N);
max
numbers
s is the maximum deflection of specimen, in millimetres (mm);
max
Formatted: Left, Adjust space between Latin and Asian
b is the width of the specimen, in millimetres (mm);
text, Adjust space between Asian text and numbers
h is the wall thickness of the specimen, in millimetres (mm);
L is the span of the specimen, in millimetres (mm). Formatted: Regular Italic, Font: Bold, Not Italic
Formatted: Regular Sub, Font: Bold, Not Superscript/
Subscript
3.11
Formatted: Regular Italic Sub, Font: Bold, Not Italic,
long-term creep bending modulus
Not Superscript/ Subscript
Efx
Formatted: Adjust space between Latin and Asian text,
calculated value of E at x years for circular pipe when tested in accordance with ISO 10468
f
Adjust space between Asian text and numbers
Note 1 to entry: Long-term bending modulus is determined using the following formula and is expressed in
Formatted: Default Paragraph Font
megapascals (MPa):
Formatted: Default Paragraph Font
Formatted: Adjust space between Latin and Asian text,
EE
fxx0 ,creep,wet
Adjust space between Asian text and numbers, Tab
stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
𝐸 = 𝐸 ⋅ 𝛼
f𝑥 0 𝑥,creep,wet
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
Formatted
where .
E is the short-term bending modulus as a result of the creep test on circular profiles Formatted: Font: 10 pt
according to ISO 10468, in megapascals (MPa);
Formatted: Font: 10 pt
Formatted
...
α is the wet creep factor, see 3.6.
x,creep,wet
Formatted: Font: 11 pt
6 © ISO #### 2025 – All rights reserved
Formatted: Font: 11 pt
Formatted: Font: 11 pt
Formatted: HeaderCentered, Left, Space After: 0 pt,
Line spacing: single, Tab stops: Not at 0.71 cm
3.12
E0 is the short-term bending modulus as a result of the creep test on circular profiles according to ISO 10468, in
megapascals (MPa);
αx,creep,wet is the wet creep factor, see Error! Reference source not found.
3.12
declared flexural capacity
Formatted: Left, Adjust space between Latin and Asian
MB text, Adjust space between Asian text and numbers
maximum unitary bending moment declared by the manufacturer
Formatted: Regular Italic, Font: Bold, Not Italic
Formatted: Regular Sub, Font: Bold, Not Superscript/
Note 1 to entry: Declared flexural capacity is determined using the following formula and is expressed in N·mm/mm:
Subscript
e
Formatted: Font: Bold, Not Italic
fd
M
B
Formatted: Adjust space between Latin and Asian text,
Adjust space between Asian text and numbers
𝜎 ⋅ 𝑒
fd
𝑀 =
Formatted: Note
𝐵
where
Formatted: Equation Legend_Title, Adjust space
is the declared short-term bending strength, in megapascals (MPa);
between Latin and Asian text, Adjust space between
fd
Asian text and numbers, Tab stops: Not at 0.7 cm +
1.4 cm + 2.1 cm + 2.8 cm + 3.5 cm + 4.2 cm + 4.9
e is the wall thickness of the pipe, in millimeters (mm).
cm + 5.6 cm + 6.3 cm + 7 cm
3.13 σ is the declared short-term bending strength, in megapascals (MPa);
fd
e is the wall thickness of the pipe, in millimetres (mm).
Formatted: TermNum2, Adjust space between Latin
3.13
and Asian text, Adjust space between Asian text a
...
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