ISO 14531-4:2006

INTERNATIONAL ISO
STANDARD 14531-4
First edition
2006-04-01


Plastics pipes and fittings — Crosslinked
polyethylene (PE-X) pipe systems for the
conveyance of gaseous fuels — Metric
series — Specifications —
Part 4:
System design and installation guidelines
Tubes et raccords en matières plastiques — Systèmes de tubes en
polyéthylène réticulé (PE-X) pour le transport de combustibles
gazeux — Série métrique — Spécifications —
Partie 4: Lignes directrices pour la conception et l'installation du
système




Reference number
ISO 14531-4:2006(E)
©
ISO 2006

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ISO 14531-4:2006(E)
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ISO 14531-4:2006(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope . 1
2 Normative references . 2
3 Terms and definitions. 2
4 Requirements . 5
4.1 Design . 5
4.1.1 General. 5
4.1.2 Materials . 5
4.1.3 Pressure ranges. 5
4.1.4 Minimum/maximum operating temperatures T /T . 6
min max
4.1.5 Pipes. 6
4.1.6 Pipeline components. 8
4.2 Construction. 10
4.2.1 Handling, transport and storage . 10
4.2.2 Jointing . 10
4.3 Laying . 12
4.3.1 General. 12
4.3.2 Open-trench installation . 12
4.3.3 Trenchless installation. 13
4.3.4 Stopping the gas flow. 13
5 Tests on site . 13
5.1 General. 13
5.2 Pressure test . 13
Annex A (informative) Assessment of lifetime using Miner's rule . 15
Bibliography . 16

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ISO 14531-4:2006(E)
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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 14531-4 was prepared by Technical Committee ISO/TC 138, Plastics pipes, fittings and valves for the
transport of fluids, Subcommittee SC 4, Plastic pipes and fittings for the supply of gaseous fuels.
ISO 14531 consists of the following parts, under the general title Plastics pipes and fittings — Crosslinked
polyethylene (PE-X) pipe systems for the conveyance of gaseous fuels — Metric series — Specifications:
⎯ Part 1: Pipes
⎯ Part 2: Fittings for heat-fusion jointing
⎯ Part 3: Fittings for mechanical jointing (including PE-X/metal transitions)
⎯ Part 4: System design and installation guidelines
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ISO 14531-4:2006(E)
Introduction
Further to the publication of International Standards for crosslinked polyethylene (PE-X) hot-water pipes, it has
become evident that the properties of PE-X, in particular its high fracture resistance and a recently established
socket and saddle fusion-jointing capability, render it suitable for use in high-performance gas-distribution
systems. The philosophy of ISO 14531 is to provide the basis for the introduction of PE-X gas pipe systems by
the specification of a performance envelope beyond that covered by existing PE standards in order to take its
application into regimes of higher operating pressures and extremes of operating temperature.
This part of ISO 14531 is therefore one part of a four-part system standard covering pipes, fittings for
heat-fusion jointing, fittings for mechanical jointing and design and installation guidelines. The content is
suitable for use by procurement authorities and distribution engineers responsible for the design, installation
and operation of pipeline systems.

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INTERNATIONAL STANDARD ISO 14531-4:2006(E)

Plastics pipes and fittings — Crosslinked polyethylene (PE-X)
pipe systems for the conveyance of gaseous fuels — Metric
series — Specifications —
Part 4:
System design and installation guidelines
1 Scope
This part of ISO 14531 provides guidance for the design, construction, installation and on-site testing of PE-X
pipeline systems. The standard deals with trenchless and open-trench installation methods.
This part of ISO 14531, when used in conjunction with the other parts of ISO 14531, provides the basis for the
design, manufacture and installation of PE-X piping systems (PE-X pipes, and PE-X and PE heat-fusion fittings
and mechanical fittings) for the supply of category D and category E hydrocarbon-based fuels (see
ISO 13623) at
1)
a) maximum operating pressures (MOPs) up to and including 16 bar and
b) a maximum operating temperature of +60 °C and
c) a minimum operating temperature of
1) −50 °C
2) −35 °C
3) −20 °C.
This part of ISO 14531 provides for the jointing and installation of PE-X and PE heat-fusion fittings and
mechanical fittings to PE-X pipes within the temperature range −5 °C to +40 °C. The jointing of pipes and
fittings outside the stated temperature range should be the subject of consultation between the pipeline
operator and the pipe, fitting and equipment manufacturers.
Users of this part of ISO 14531 should be aware that useful supplementary information is given in the
standards listed in the bibliography.

5 2
1) 1 bar = 10 N/m = 100 kPa.
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ISO 14531-4:2006(E)
2 Normative references
The following referenced documents are indispensable for the application 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 4065, Thermoplastic pipes — Universal wall thickness table
ISO 8085-3, Polyethylene fittings for use with polyethylene pipes for the supply of gaseous fuels — Metric
series — Specifications — Part 3: Electrofusion fittings
ISO 9080, Plastics piping and ducting systems — Determination of the long-term hydrostatic strength of
thermoplastics materials in pipe form by extrapolation
ISO 10838 (all parts), Mechanical fittings for polyethylene piping systems for the supply of gaseous fuels
ISO/TS 10839:2000, Polyethylene pipes and fittings for the supply of gaseous fuels — Code of practice for
design, handling and installation
ISO 12162, Thermoplastics materials for pipes and fittings for pressure applications — Classification and
designation — Overall service (design) coefficient
ISO 12176-2, Plastics pipes and fittings — Equipment for fusion jointing polyethylene systems — Part 2:
Electrofusion
ISO 13623, Petroleum and natural gas industries — Pipeline transportation systems
ISO 13760, Plastics pipes for the conveyance of fluids under pressure — Miner's rule — Calculation method
for cumulative damage
ISO 14531-1:2002, Plastics pipes and fittings — Crosslinked polyethylene (PE-X) pipe systems for the
conveyance of gaseous fuels — Metric series — Specifications — Part 1: Pipes
ISO 14531-2, Plastics pipes and fittings — Crosslinked polyethylene (PE-X) pipe systems for the conveyance
of gaseous fuels — Metric series — Specifications — Part 2: Fittings for heat-fusion jointing
ISO 14531-3, Plastics pipes and fittings — Crosslinked polyethylene (PE-X) pipe systems for the conveyance
of gaseous fuels — Metric series — Specifications — Part 3: Fittings for mechanical jointing (including
PE-X/metal transitions)
EN 12007-1, Gas supply systems — Pipelines for maximum operating pressure up to and including 16 bar —
Part 1: General functional recommendations
EN 12007-2, Gas supply systems — Pipelines for maximum operating pressure up to and including 16 bar —
Part 2: Specific functional recommendations for polyethylene (MOP up to and including 10 bar)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
nominal outside diameter
d
n
numerical designation of size which is common to all components in a thermoplastics piping system other than
flanges and components designated by thread size
NOTE 1 It is a convenient round number for reference purposes.
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ISO 14531-4:2006(E)
NOTE 2 The nominal outside diameter expressed in millimetres is the minimum mean outside diameter d of pipe
e,min
produced in accordance with ISO 14531-1.
3.2
nominal wall thickness
e
n
nominal designation of wall thickness of a pipe in millimetres in accordance with ISO 4065
3.3
standard dimension ratio
SDR
ratio of the nominal outside diameter of a pipe to its nominal wall thickness
d
n
SDR =
e
n
NOTE The value of the SDR is selected from Table 5 in ISO 14531-1:2002.
3.4
gaseous fuel
fuel which is in a gaseous state at a temperature of +15 °C and a pressure of 1 bar
3.5
category D gaseous fuel
natural gas
NOTE Categories of gaseous and liquid fuels are defined in detail in ISO 13623.
3.6
category E gaseous fuel
LPG vapour or natural gas conveyed in association with liquid condensate
NOTE Categories of gaseous and liquid fuels are defined in detail in ISO 13623.
3.7
design pressure
DP
pressure on which design calculations are based
NOTE The design pressure for pipes is designated DP and for fittings DP .
P F
3.8
design stress
σ
S
pipe wall circumferential stress calculated from the design pressure DP and pipe SDR with a maximum
P
limiting value determined by the quotient of MRS and the overall service (design) coefficient C
θ, t
3.9
maximum operating pressure
MOP
highest effective pressure, in bars, of the gas in the piping system which is allowed in continuous use
NOTE The MOP takes into account the physical and the mechanical characteristics of the components of a piping
system.
3.10
temporary operating pressure
TOP
maximum pressure that can be generated on a temporary basis under the control of the regulating devices
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ISO 14531-4:2006(E)
3.11
maximum incidental pressure
MIP
maximum pressure generated for example by surges or failure of pressure control equipment and limited by
the activation of overpressure protection devices
3.12
pipeline operator
private or public organization authorized to design, construct and/or operate and maintain the gas supply
system
3.13
minimum required strength
MRS
θ, t
value of σ for the pipe material, in megapascals, calculated using ISO 9080 for a specific design
lpl
temperature θ and lifetime t and then categorized in accordance with Table 3
NOTE At 20 °C and 50 years, MRS = MRS.
θ, t
3.14
overall service (design) coefficient
C
overall coefficient, with a value greater than 1,0, which takes into consideration service conditions as well as
properties of the components of a piping system other than those represented in the lower prediction limit
(3.15)
3.15
lower prediction limit
σ
lpl
quantity, expressed in megapascals, which can be considered as a property of the material and which
represents the 97,5 % lower prediction limit of the long-term hydrostatic strength at a temperature of 20 °C
and a time of 50 years in water
3.16
heat-fusion fitting
fitting designed to connect PE-X pipes to form an assembly for subsequent jointing by heat fusion and the
creation of an integral pipe-to-fitting connection
3.17
operating-temperature range
assumed range of temperatures experienced by a PE-X pipeline at the intended service location, for use in
the process of designing the pipeline for operation at MOP
3.18
minimum operating temperature
T
min
minimum operating temperature (above and/or below ground) expected during the service life of the pipeline
3.19
maximum operating temperature
T
max
maximum operating temperature (above and/or below ground) expected during the service life of the pipeline
3.20
design temperature
θ
temperature used to determine MRS
θ, t
NOTE See 4.1.5.3.
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ISO 14531-4:2006(E)
4 Requirements
4.1 Design
4.1.1 General
The design pressure (DP) of any PE-X pipeline component shall not be less than the intended maximum
operating pressure (MOP) of the pipeline. The DP shall be at least 2,0 bar. The MOP shall be selected from a
range of pressures up to a maximum of 16 bar in accordance with the requirements of the pipeline operator.
NOTE Requirements for MOP in the gas industry are not standardized on the basis of PN pressure ratings. An
alternative classification system has been adopted in CEN (EN 12007) and is incorporated in Table 1.
Operating pressures during transient conditions in excess of MOP are permitted provided they are of limited
frequency and duration. Guidance regarding acceptable levels of transient operating pressure conditions is
given in 4.1.3.
The normal permissible operating-temperature ranges for PE-X pipelines extend from −50 °C to a maximum of
+60 °C and are applicable up to the maximum pressure (MOP) of 16 bar. Limiting temperatures are
dependent upon the materials used in the manufacture of pipes and fittings (see 4.1.4). Operating
temperatures up to 70 °C are not excluded by this part of ISO 14531 provided local regulations permit.
4.1.2 Materials
The materials and components used in PE-X pipelines shall conform to ISO 14531-1, ISO 14531-2 or
ISO 14531-3, as appropriate.
Other materials, components and equipment used shall conform to a relevant ISO standard or appropriate
national standard that ensures a product fit for the purpose intended.
4.1.3 Pressure ranges
Internal pressures generated in PE-X pipelines under transient operating conditions should not exceed the
values given in Table 1.
Table 1 — Transient pressure limits
Pressures in bars
Maximum operating pressure Temporary operating pressure Maximum incidental pressure
a b
(MOP) (TOP) (MIP)
5 < MOP u 16
1,20 × MOP 1,30 × MOP
2 < MOP u 5
1,30 × MOP 1,40 × MOP
0,1 < MOP u 2
1,50 × MOP 1,75 × MOP
MOP u 0,1
1,50 × MOP 2,50 × MOP
a
TOP is the maximum pressure that can be generated on a temporary basis under the control of the regulating devices.
b
MIP is, for example, the maximum pressure generated by surges or failure of pressure control equipment and is limited by the activation
of overpressure protection devices.

The use of pipes at TOP shall be the responsibility of the pipeline operator. Acceptability for use at TOP can
be assessed using Miner’s rule in a supplementary design calculation undertaken in accordance with the
guidelines given in Annex A and in conjunction with the pipe manufacturer.
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ISO 14531-4:2006(E)
4.1.4 Minimum/maximum operating temperatures T /T
min max
The minimum operating temperature T for PE-X pipelines shall not be lower than the critical RCP
min
temperature for the PE-X pipe to be used. Critical rapid crack propagation (RCP) temperatures specified for
PE-X pipe are given in ISO 14531-1 and listed in Table 2. The marking of the PE-X pipe should be examined
for confirmation regarding the limiting critical temperature.
The maximum operating temperature T for PE-X pipelines shall not exceed the design temperature θ
max
selected for the pipeline (see 4.1.5.3) with a limiting value of +60 °C. In exceptional circumstances a maximum
operating temperature of 70 °C may be considered if permitted by local regulations and the design constraints
detailed in this standard.
PE-X pipelines incorporating PE fusion fittings and mechanical fittings conforming to ISO 8085-3 and
ISO 10838 respectively shall be restricted to a minimum operating temperature T of −20 °C and a
min
maximum operating temperature T of +40 °C (see ISO 14531-2, ISO 14531-3 and the fitting
max
manufacturer's technical file).
Table 2 — Critical RCP temperature limits for PE-X pipes
a
Critical RCP temperature
PE-X pipe
°C
Class 1 −50
Class 2
−35
Class 3
−20
a
Corresponding stress levels are given in Part 1 of this International Standard.

4.1.5 Pipes
4.1.5.1 General
PE-X pipes used to construct PE-X pipelines shall conform to ISO 14531-1 and shall be designed in
conformity with 4.1.5.2 to 4.1.5.4.
4.1.5.2 Selection of nominal wall thickness e
n
The nominal wall thickness of the pipe e shall be calculated using the following equation:
n
d
n
e =
n
SDR
in which the value of the SDR is pre-determined by the following relationship:
20 ×MRS
θ,t
SDR=+1
DP××CC
PM A
where
MRS is the σ of the pipe material, in megapascals, calculated using ISO 9080 for a specific design
θ, t lpl
temperature θ and lifetime t and then categorized in accordance with Table 3;
DP is the pipe design pressure, which is equal to or greater than the MOP;
P
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ISO 14531-4:2006(E)
C is a design coefficient equal to 1,25 that reflects the effect on long-term hydrostatic strength
M
σ (see 4.2.2 in ISO 14531-1:2002) of the material/process-related properties of the pipe
LTHS
other than those represented in σ ;
lpl
C is an applications-based design coefficient introduced by the pipeline operator that takes into
A
account the pipeline MOP and the pipeline's operating environment [e.g. the type of gas being
conveyed and the pipe location (remote areas or urban sites)] and any relevant national
regulations.
When the calculated value of SDR is not a recognized value defined in ISO 4065, the next lower value shall
be selected.
NOTE The product of C and C is nominally equal to C, the overall service (design) coefficient as defined in
m A
ISO 12162. Rounding of the SDR value may lead to a value of C > C × C .
m A
4.1.5.3 Design temperature θ
The design temperature θ is the anticipated maximum operating temperature of the pipe at the intended pipe
position. The selected design temperature shall not be less than 0 °C nor greater than 60 °C.
NOTE A design based upon the maximum operating temperature is regarded as conservative, and an advantage
may be gained from a precise analysis that incorporates Miner's rule (see ISO 13760), utilizing safety factors agreed to by
the pipeline operator.
4.1.5.4 Overall service (design) coefficient C
Using the selected SDR value determined in accordance with 4.1.5.2, calculate the design stress σ from
S
DP
P
σ=−(SDR 1)
S
20
and then the overall service (design) coefficient C from
MRS
θ,t
C =
σ
S
The selection and/or acceptance of the coefficient C shall be the responsibility of the pipeline operator who is
defined in 3.12.
NOTE Currently for gas applications a minimum value of C equal to 2,0 is incorporated in ISO 4437 for PE pipes. If
not otherwise defined by the pipeline operator, this value should also be used for PE-X.
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ISO 14531-4:2006(E)
Table 3 — Categorized values for CRS
θ, t
a
Range of σ at θ and t CRS
lpl θ, t
MPa MPa
5,00 u σ u 5,59 5,00
lpl
5,60 u σ u 6,29 5,60
lpl
6,30 u σ u 7,19 6,30
lpl
7,20 u σ u 7,99 7,20
lpl
8,00 u σ u 8,99 8,00
lpl
9,00 u σ u 9,99 9,00
lpl
10,00 u σ u 11,19 10,00
lpl
11,20 u σ u 12,49 11,20
lpl
12,50 u σ u 13,99 12,50
lpl
a
This list of categorized values is subject to review dependent upon the outcome of the revision of ISO 12162.

4.1.6 Pipeline components
4.1.6.1 Heat-fusion fittings
4.1.6.1.1 Selection criteria
Heat-fusion fittings selected for use shall have at the pipeline design temperature θ a design pressure DP , as
F
declared by the fitting manufacturer in his technical file (see ISO 14531-2), equal to or greater than the design
pressure of the pipe DP .
P
Heat-fusion fittings selected for use with PE-X pipes to form a PE-X pipeline system shall conform to
ISO 14531-2 (alternatively, fittings conforming to ISO 8085-3 may be used provided that the additional tests
specified in ISO 14531-2 for ISO 8085-3 fittings have been completed satisfactorily).
Fittings manufactured to ISO 14531-2 can be expected to have an operating-temperature range up to the
minimum/maximum defined by the temperature limits of −50 °C and +60 °C. The fitting manufacturer's
technical file shall be inspected to establish the permissible operating-temperature range of the fitting. The
minimum permissible operating temperature of the fitting shall be equal to or higher than the applicable
temperature listed in Table 2. The maximum permissible operating temperature of the fitting shall be equal to
or lower than the design temperature θ. The acceptable operating-temperature range for fittings conforming to
ISO 8085-3 is −20 °C to +40 °C.
Heat-fusion fittings selected for connection to PE-X pipes shall have an SDR application range that includes
the SDR of the pipe to which connection is intended.
4.1.6.1.2 Fusion compatibility
Fusion compatibility of heat-fusion fittings with PE-X pipes shall be a primary consideration at the pipeline
design stage.
PE-X fittings manufactured to conform to ISO 14531-2 may not be compatible with all PE-X pipes produced to
ISO 14531-1. Information regarding specific fusion compatibility relationships (fitting/pipe) shall be sought from
the technical file of the fitting manufacturer.
NOTE Consultation with the fitting manufacturer should be undertaken in conjunction with reference to the guidance
given in ISO 14531-2.
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ISO 14531-4:2006(E)
Fittings in conformity with ISO 14531-2 may be manufactured from PE 80 and PE 100 materials. PE fittings of
this type shall only be used if they are individually marked with ISO 8085 as the standard reference number
supported by evidence given in the manufacturer's technical file regarding use and suitability for fusion jointing
to PE-X pipe.
4.1.6.2 Mechanical fittings — selection criteria
Mechanical fittings selected for use shall have at the pipeline design temperature θ, a design pressure DP
F(θ)
as declared by the fitting manufacturer in his technical file (see ISO 14531-3), equal to or greater than the
design pressure for the pipe, DP .
P
Mechanical fittings (metal and plastic bodied) selected for use with PE-X pipes to form a PE-X pipeline system
shall conform to ISO 14531-3. Alternatively, fittings conforming to ISO 10838-1, ISO 10838-2 or ISO 10838-3
may be used provided that the additional tests specified in ISO 14531-3 for ISO 10838 fittings have been
completed satisfactorily.
Fittings manufactured to ISO 14531-3 can be expected to have an operating temperature range up to a
maximum defined by temperature limits of −50 °C and +60 °C. The technical file of the fitting manufacturer
shall be inspected to establish the permissible operating-temperature range of the fitting. The minimum
permissible operating temperature of the fitting shall be equal to or higher than the applicable temperature
listed in Table 2. The maximum permissible operating temperature of the fitting shall be equal to or lower than
the design temperature θ. The acceptable operating-temperature range for fittings conforming to ISO 10838-1,
ISO 10838-2 or ISO 10838-3 is −20 °C to +40 °C.
Mechanical fittings conforming to ISO 14531-3 or ISO 10838, selected for use with PE-X pipes to form a PE-X
pipeline system, should be regarded as full-end-load-resistant with a resistance to longitudinal tensile force at
least as good as pipe.
The use of anti-shear sleeves should be considered in cases where substantial relative movement is
anticipated between the fitting and PE-X pipe of d u 40 mm.
e
NOTE Manufacturer’s advice should be sought regarding allowable limits in such circumstances.
Consideration shall be given to the need for the on-site corrosion protection of metallic parts not claimed to be
corrosion-resistant by the fitting manufacturer.
4.1.6.3 Protection systems
4.1.6.3.1 External interference
For above- and below-ground pipe systems, the
...