ISO 14531-3:2010

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)

ISO 14531-3:2010 specifies the physical properties and mechanical-performance requirements for full-end-load-resistant mechanical fittings for use in the connection of crosslinked polyethylene (PE‑X) pipes conforming to ISO 14531‑1 and in the construction of transition assemblies for joining PE‑X pipes to metal pipes having plain spigot, screw thread, compression socket and flange terminations. In addition, it lays down dimensional requirements and specifies some general material properties (including chemical resistance) together with a classification scheme for PE‑X fitting materials produced in the form of pipe. ISO 14531-3:2010, 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, PE‑X fusion fittings and mechanical fittings) for the supply of category D and category E hydrocarbon-based fuels.

Tubes et raccords en matières plastiques — Systèmes de tubes en polyéthylène réticulé (PE-X) pour le transport de combustibles gazeux — Série métrique — Spécifications — Partie 3: Raccords pour assemblage mécanique (y compris transitions PE-X/métal)

General Information

• Status: Published
• Publication Date: 21-Nov-2010
• ICS: 23.040.20 - Plastics pipes
• ICS: 23.040.45 - Plastics fittings
• ICS: 75.200 - Petroleum products and natural gas handling equipment
• Technical Committee: ISO/TC 138/SC 4 - Plastics pipes and fittings for the supply of gaseous fuels
• Drafting Committee: ISO/TC 138/SC 4 - Plastics pipes and fittings for the supply of gaseous fuels
• Current Stage: 9093 - International Standard confirmed
• Completion Date: 28-Oct-2021

Relations

• Revises: ISO 14531-3:2006 - 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)
• Effective Date: 17-Jul-2010

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 14531-3
Second edition
2010-12-01
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)
Tubes et raccords en matières plastiques — Systèmes de tubes
en polyéthylène réticulé (PE-X) pour le transport de combustibles
gazeux — Série métrique — Spécifications —
Partie 3: Raccords pour assemblage mécanique (y compris transitions
PE-X/métal)
Reference number
ISO 14531-3:2010(E)
ISO 2010
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ISO 14531-3:2010(E)
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ii © ISO 2010 – All rights reserved
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ISO 14531-3:2010(E)
Contents Page

Foreword ............................................................................................................................................................iv

Introduction.........................................................................................................................................................v

1 Scope......................................................................................................................................................1

2 Normative references............................................................................................................................2

3 Terms and definitions ...........................................................................................................................3

4 Materials .................................................................................................................................................3

4.1 General ...................................................................................................................................................3

4.2 Strength..................................................................................................................................................4

4.3 Chemical resistance..............................................................................................................................4

4.4 Lubricants ..............................................................................................................................................5

4.5 Reprocessable (re-work) material........................................................................................................5

5 Fittings....................................................................................................................................................5

5.1 Design.....................................................................................................................................................5

5.2 Appearance ............................................................................................................................................6

5.3 Dimensions ............................................................................................................................................7

5.4 Mechanical performance ......................................................................................................................7

5.5 Validation of fitting design and design pressure DP .......................................................................7

5.6 Performance requirements for fittings in conformity with ISO 10838 .............................................9

6 Elastomeric seals ..................................................................................................................................9

7 Marking...................................................................................................................................................9

7.1 Legibility.................................................................................................................................................9

7.2 Damage...................................................................................................................................................9

7.3 Minimum marking requirements........................................................................................................10

7.4 Labels ...................................................................................................................................................10

Annex A (normative) Resistance to gas constituents ..................................................................................11

Annex B (normative) Method of test of the integrity of a fitting after an external blow ............................12

Annex C (normative) Constant-strain thermal-cycling test..........................................................................14

Annex D (informative) Validation of fitting design pressure DP at 20 °C (plastic bodied fittings) .........16

Annex E (normative) Validation of fitting design pressure DP at 20 °C (metal bodied fittings) .............18

© ISO 2010 – All rights reserved iii
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ISO 14531-3:2010(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 14531-3 was prepared by Technical Committee ISO/TC 138, Plastic pipes, fittings and valves for the

transport of fluids, Subcommittee SC 4, Plastic pipes and fittings for the supply of gaseous fuels.

This second edition cancels and replaces the first edition (ISO 14531-3:2006), of which it constitutes a minor

revision.

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
iv © ISO 2010 – All rights reserved
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ISO 14531-3:2010(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.

This part of ISO 14531 is structured to ensure the supply of mechanical fittings with an end-load resistance

greater than that exhibited by the pipe(s) to which the fittings are connected.
© ISO 2010 – All rights reserved v
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INTERNATIONAL STANDARD ISO 14531-3:2010(E)
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)
1 Scope

This part of ISO 14531 specifies the physical properties and mechanical-performance requirements for full-

end-load-resistant mechanical fittings for use in the connection of crosslinked polyethylene (PE-X) pipes

conforming to ISO 14531-1 and in the construction of transition assemblies for joining PE-X pipes to metal

pipes having plain spigot, screw thread, compression socket and flange terminations. In addition, it lays down

dimensional requirements and specifies some general material properties (including chemical resistance)

together with a classification scheme for PE-X fitting materials produced in the form of pipe.

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, PE-X fusion fittings and mechanical

fittings) for the supply of category D and category E hydrocarbon-based fuels (see ISO 13623) at

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.

Conformity to this part of ISO 14531-3 of mechanical fittings produced in accordance with ISO 10838-1,

ISO 10838-2 or ISO 10838-3 may be claimed subject to the satisfactory conclusion of the tests listed in 5.6

and an end-use restriction on operating temperatures to the temperature range −20 °C to +40 °C.

NOTE It is recognized that mechanical fittings conforming to ISO 10838-1, ISO 10838-2 or ISO 10838-3 are limited to

a maximum operating temperature of 40 °C. Provision is made in ISO 14531-4 for the use on a restricted-temperature

basis of ISO 10838 fittings conforming to 5.6 in conjunction with PE-X pipes conforming to ISO 14531-1. The fitting

manufacturer's technical file should also be consulted for relevant supporting information.

For installation purposes, this part of ISO 14531 provides for the jointing of mechanical fittings to PE-X pipes

within the temperature range −5 °C to +40 °C.
5 2
1) 1 bar = 10 N/m = 100 kPa.
© ISO 2010 – All rights reserved 1
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ISO 14531-3:2010(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 7-1, Pipe threads where pressure-tight joints are made on the threads — Part 1: Dimensions, tolerances

and designation

ISO 1167-1, Thermoplastics pipes, fittings and assemblies for the conveyance of fluids — Determination of

the resistance to internal pressure — Part 1: General method

ISO 1167-2, Thermoplastics pipes, fittings and assemblies for the conveyance of fluids — Determination of

the resistance to internal pressure — Part 2: Preparation of pipe test pieces

ISO 1167-3, Thermoplastics pipes, fittings and assemblies for the conveyance of fluids — Determination of

the resistance to internal pressure — Part 3: Preparation of components

ISO 16010, Elastomeric seals — Material requirements for seals used in pipes and fittings carrying gaseous

fuels and hydrocarbon fluids

ISO 3127, Thermoplastics pipes — Determination of resistance to external blows — Round-the-clock method

ISO 3458, Assembled joints between fittings and polyethylene (PE) pressure pipes — Test of leakproofness

under internal pressure

ISO 4437, Buried polyethylene (PE) pipes for the supply of gaseous fuels — Metric series — Specifications

ISO 8085-3:2001, 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 10838-1:2000, Mechanical fittings for polyethylene piping systems for the supply of gaseous fuels —

Part 1: Metal fittings for pipes of nominal outside diameter less than or equal to 63 mm

ISO 10838-2:2000, Mechanical fittings for polyethylene piping systems for the supply of gaseous fuels —

Part 2: Metal fittings for pipes of nominal outside diameter greater than 63 mm

ISO 10838-3:2001, Mechanical fittings for polyethylene piping systems for the supply of gaseous fuels —

Part 3: Thermoplastics fittings for pipes of nominal outside diameter less than or equal to 63 mm

ISO 12162, Thermoplastics materials for pipes and fittings for pressure applications — Classification,

designation and design coefficient

ISO 13623, Petroleum and natural gas industries — Pipeline transportation systems

ISO 13951, Plastics piping systems — Test method for the resistance of polyolefin pipe/pipe or pipe/fitting

assemblies to tensile loading

ISO 13957, Plastics pipes and fittings — Polyethylene (PE) tapping tees — Test method for impact resistance

ISO 14531-1, 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

2 © ISO 2010 – All rights reserved
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ISO 14531-3:2010(E)

ISO 14531-4:2006, 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

ISO 16010, Elastomeric seals — Material requirements for seals used in pipes and fittings carrying gaseous

fuels and hydrocarbon fluids

ISO 19899, Plastics piping systems — Polyolefin pipes and mechanical fitting assemblies — Test method for

the resistance to end load (AREL test)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
mechanical fitting

fitting within a pipeline system that relies, fully or in part, upon the mechanical loading of component parts to

effect a pipeline seal that provides pressure integrity, leaktightness and resistance to end loads

3.2
end-load resistance

resistance to end load transmitted via the connecting pipe and generated by internal pressure, pipeline

external interference and thermally induced pipe stresses in any combination

NOTE Full-end-load resistance is the condition in which the joint is stronger than the connecting pipe when exposed

to all applied end loads.
3.3
design temperature
temperature used to determine the minimum required strength MRS
θ, t
NOTE See ISO 14531-4.
3.4
design pressure
pressure upon which design calculations are based
NOTE 1 See ISO 14531-4.

NOTE 2 For fittings, the design pressure is designated DP , whereas for pipes it is designated DP .

F P
4 Materials
4.1 General

The materials from which the fitting components are manufactured shall have properties consistent with the

production of a mechanical fitting with a pressure and end-load resistance equal to or better than that of the

connecting PE-X pipes over the intended design life.

Materials (e.g. plastics, rubbers and metals) utilized in the manufacture of fittings conforming to this

International Standard shall be supplied in accordance with a relevant ISO standard. For rubber ring seals, the

applicable standard shall be ISO 16010; for PE and PE-X materials the standard shall be ISO 14531-2.

Alternative standards may be utilized in cases where suitable ISO standards do not exist. In such cases,

fitness for purpose shall be established.
© ISO 2010 – All rights reserved 3
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ISO 14531-3:2010(E)

All metal parts susceptible to corrosion shall be adequately protected. When dissimilar metallic materials are

used which may be in contact with moisture, steps shall be taken to avoid the possibility of galvanic corrosion.

The manufacturer of the fittings shall maintain the availability of a technical file (generally confidential) with all

relevant data to prove the conformity of fittings to this part of ISO 14531. Any change in the materials used

that is likely to affect product quality and performance shall require a re-assessment of material performance

against the requirements of this part of ISO 14531.
4.2 Strength

The susceptibility of materials to crack failure in locations of high stress concentration, e.g. at threads, shall be

examined. Materials shown to be vulnerable to brittle fracture throughout the specified operating temperature

range(s) as given in Clause 1 shall be discarded as failing to conform to this part of ISO 14531.

Thermoplastic materials (reinforced and un-reinforced) incorporated in fitting components subjected to

long-term, time-dependent tensile stresses shall be evaluated in the form of pipe in accordance with ISO 9080,

and the MRS determined for classification in accordance with ISO 12162. Materials that are shown by the test

to be likely to exhibit premature failure at the intended maximum operating temperature within the fitting

design life shall be rejected as unsuitable for use.

Unclassified materials may be introduced provided fitting assemblies containing such unclassified material

elements are subjected to long-term hydrostatic-strength tests to demonstrate that the MRS of the connecting

PE-X pipe(s) is not impaired in such cases.
4.3 Chemical resistance

The selection of component materials shall take into account the effect of gas stream chemicals associated

with the transport of category D and category E gaseous fuels, as classified by ISO 13623, on the material

properties of components contained within the fitting assembly.

The demonstration of adequate chemical resistance shall be made by subjecting a joint assembly to the test

listed in Table 1 and by the provision for consideration by the pipeline operator of relevant environmental

stress cracking failure data from tests using chemical compounds encountered in, or external to, gas piping

systems.

NOTE Materials should have a demonstrated resistance to environmental stress cracking when exposed, under stress,

to chemical compounds encountered in, or external to, gas piping systems since liquids such as antifreeze agents,

odorants and hydrocarbons are known to have a deleterious effect on some plastics, particularly under service conditions.

Table 1 — Chemical resistance
Characteristic Units Requirement Test parameters Test method
Resistance to gas h No failure when tested to Temperature: 80 °C ISO 1167-1
constituents 1 000 h
Pipe hoop stress: 2 MPa Test piece in
accordance with
ISO 1167-2
Type A end caps
Annex A
4 © ISO 2010 – All rights reserved
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ISO 14531-3:2010(E)
4.4 Lubricants

Lubricants and/or greases may be used to assist in joint assembly or for corrosion protection subject to the

following measures being taken:

a) The fitting manufacturer shall provide evidence that the lubricant and/or grease does not have a

deleterious effect on the performance of the component parts of the fitting likely to be in contact with the

connecting PE-X pipe.

b) The fitting assemblies used for testing conformity with the requirements of this part of ISO 14531 shall

have the lubrication in place.
c) Surfaces intended for fusion jointing shall be free of lubrication.
4.5 Reprocessable (re-work) material

PE-X shall not be reprocessed and used in the manufacture of fittings intended to conform to this part of

ISO 14531.

Non-crosslinked base material for PE-X components, produced in the course of manufacturing fittings

conforming to this part of ISO 14531, may be reprocessed if derived from the same non-crosslinked material

grade already employed in the relevant production. Products containing reprocessed material shall conform to

the requirements of this part of ISO 14531.

The extent of any use of reprocessable PE 80 and PE 100 material shall be in accordance with ISO 4437 and

ISO 8085 (see e.g. ISO 8085-3:2001, Subclause 5.3).

The manufacture of components from other thermoplastic materials shall utilize virgin material compounds

unless an acceptable manufacturing history is available that demonstrates a capability of manufacturing

components produced from reprocessable materials.
For metallic materials, refer to relevant ISO standards.
5 Fittings
5.1 Design

Mechanical fittings, including any integral heat-fusion joints, shall be designed for the connection of PE-X

pipes conforming to ISO 14531-1 to create full-end-load, pressure-resistant pipe/fitting assemblies conforming

to the requirements of this part of ISO 14531. Transition assemblies connecting PE-X pipes to metal pipes

(e.g. steel or iron) shall also meet the requirements of this part of ISO 14531.

Terminating and integral heat-fusion joints made of PE or PE-X materials shall conform to ISO 14531-2.

The effect of pipe outside diameter and wall thickness tolerances specified in ISO 14531-1 shall be taken into

account.

The provision of end-load resistance shall not rely on the influence of internal pressure.

The fitting design pressure DP at a design temperature θ of 20 °C shall be declared by the fitting

manufacturer in accordance with Table 2 and recorded in the manufacturer's technical file. The declaration of

design pressure shall take into account stress concentration effects generated by the fitting and joint assembly

geometries and shall be supported by the provision of appropriate experimental data (see 5.5) or design

calculations. The effect on the design pressure at 20 °C of variations in operating temperature from 0 °C to

+60 °C shall be established and recorded in the technical file.
NOTE The pipeline operator is required by ISO 14531-4 to ensure that MOP u DP .
© ISO 2010 – All rights reserved 5
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ISO 14531-3:2010(E)
Table 2 — Fitting design pressure DP (θ = 20 °C)
Fitting type
bar
Type 1 2,0
Type 2 5,0
Type 3 10,0
Type 4 16,0

The fitting shall be designed to be leaktight throughout the pressure range extending from 25 mbar up to

1,5DP (see Table 3) and the temperature range(s) defined in Clause 1, in any combination.

Fitting design shall take into account the expectation on site of a minimum pipe/fitting component temperature

of −5 °C and a maximum of +40 °C prior to joint construction. Preheating of components which are

at temperatures less than −5 °C is permissible and, if applicable, both the equipment for this, and guidance on

its use, shall be supplied by the fitting manufacturer.

Internal stiffeners incorporated in the design of the fitting shall comply with the following:

a) They shall be rigid with a continuous circular geometry in the in situ state and shall provide support over

the entire area of pipe compression.

NOTE Stiffeners with convolutions should be assessed for pipe support on the basis of projected area.

b) They shall contain a means of readily indicating their location at their design position within the pipe and

shall not be susceptible to longitudinal displacement after assembly.

c) Only one type of stiffener shall be used for each pipe diameter and pipe standard dimension ratio (SDR).

NOTE This is necessary to prevent several stiffeners being supplied for each pipe size in order to accommodate

variations in connecting-pipe tolerances. In this way, the possibility of selecting an incorrect stiffener is avoided.

The fitting shall be capable of field assembly. Special mechanical assembly tools, if required, shall be supplied

by the manufacturer. Assembly tooling shall be designed to avoid causing any visible deformation or

weakening of the components being joined which could have an adverse effect on the performance of the joint

assembly.

Transition fittings intended for connection to steel pipe by welding shall be designed to facilitate the conduct of

the welding operation without detriment to the overall performance of the jointed assembly.

The design of fittings shall take into account the possible use above ground as well as below ground. Factors

to consider shall include the effect of natural weathering and external corrosion.

Bore geometry arrangements shall ensure that the pressure drop across the fitting is kept to a minimum and

that provision is made in the design of straight couplings greater than 125 mm diameter for the unrestricted

passage of pipe pigging tools.

Joint assembly forces shall not induce twisting deformation of the connecting PE-X pipe(s).

Threading on metal terminations shall conform to ISO 7-1.
5.2 Appearance

When viewed without magnification, fitting components shall not show any signs of surface defects or

inclusions that would prevent conformity of the fitting with this part of ISO 14531.

6 © ISO 2010 – All rights reserved
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ISO 14531-3:2010(E)
5.3 Dimensions

Fitting components shall be manufactured with dimensions and tolerances selected to ensure that the

performance of the mechanical-fitting assembly incorporating PE-X pipes to ISO 14531-1 conforms to this part

of ISO 14531, including leak-free operation at the design pressure throughout the pipeline service life.

The minimum internal bore diameter d shall be stated by the manufacturer in his technical file.

5.4 Mechanical performance

Mechanical fittings shall be assembled with PE-X pipes in accordance with the fitting manufacturer's

instructions.

Test piece arrangements shall also reflect the possible connection of fittings to PE-X pipes produced by

different process methods e.g. PE-Xa, PE-Xb (see ISO 14531-1).

When evaluated in accordance with the test methods specified in Table 3, using the parameters indicated, the

jointed pipe/fitting test piece shall conform to the requirements given in Table 3.

Jointed pipe/fitting test pieces shall be based upon the thinnest-walled and thickest-walled pipe for which the

fitting was designed (largest and smallest SDR).

A declaration regarding the suitability of use with PE-X pipes, and any limiting conditions associated with such

use, shall be included in the fitting manufacturer's technical file.

Test pieces subjected to hydrostatic-strength testing shall be tested using an internal pressure determined by

the following equation:
20σ
e,min
y,min
where
p is the internal test pressure, in bars;

σ is the value of the hydrostatic stress, in megapascals, corresponding to the test duration and test

temperature conditions given in Table 3;

d is the minimum value of the mean outside diameter specified for a given nominal diameter d of

e,min n
the adjoining pipe(s) (see ISO 14531-1);

e is the minimum permissible value of the wall thickness e at any point around the circumference of

y,min y
the adjoining pipe(s) (see ISO 14531-1).

NOTE The control points for hydrostatic strength specified in Table 3 were derived using experimental data

supplemented by theoretical calculations. As experience is gained in the implementation of this part of ISO 14531, the

specification levels may be reviewed.
5.5 Validation of fitting design an
...