ISO/TS 10839:2022
(Main)Polyethylene pipes and fittings for the supply of gaseous fuels — Code of practice for design, handling and installation
Polyethylene pipes and fittings for the supply of gaseous fuels — Code of practice for design, handling and installation
This document presents a code of practice dealing with polyethylene (PE) pipes and fittings for buried pipeline systems outside buildings, conforming to the ISO 4437 series, and designed to transport gaseous fuels [as defined in ISO 4437-1, e.g. methane, liquified petroleum gas (LPG), manufactured gas and hydrogen] within the temperature range –20 °C to +40 °C. This document also gives appropriate temperature-related requirements. The code of practice covers mains and service lines whose components are prepared for fusion or mechanical jointing. It also gives instructions for the design, storage, handling, transportation, laying conditions and fusion quality control of PE pipes and fittings as well as subsequent joint testing, backfilling, pipe system testing and commissioning. NOTE For the renovation code of practice, reference is made to the ISO 11299 series and to ISO 11295 for classification and to the ISO 21225 series for further information for trenchless replacement. The minimal requirements for the jointing methods are given in: — Annex A (butt fusion); — Annex B (electrofusion); and — Annex C (mechanical jointing). In some countries the use of heated-tools socket and saddle fusion is permitted; information on heated-tools fusion jointing techniques is given in Annex D. In the case of ground movement or shaking (e.g. earthquakes, etc.) it can be necessary to implement precautions mentioned in this document following guidelines provided by authorities (e.g. Eurocode 8,[7] EN 12007-1:2012, Annex A,[8] etc.), Workers' health and safety issues are outside the scope of this document.
Tubes et raccords en polyéthylène pour le transport de combustibles gazeux — Code de pratique pour la conception, la manutention et l'installation
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TECHNICAL ISO/TS
SPECIFICATION 10839
Second edition
2022-07
Polyethylene pipes and fittings for
the supply of gaseous fuels — Code
of practice for design, handling and
installation
Tubes et raccords en polyéthylène pour le transport de combustibles
gazeux — Code de pratique pour la conception, la manutention et
l'installation
Reference number
© ISO 2022
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Published in Switzerland
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and abbreviated terms . 2
3.1 Terms and definitions . 2
3.2 Symbols and abbreviated terms . 3
4 Design . 4
4.1 General . 4
4.2 Material, components and jointing equipment . 4
4.3 Maximum operating pressure . 5
4.4 Assembly techniques. 5
4.5 Squeeze-off properties . 5
5 Construction . 6
5.1 Competences . . . 6
5.2 Storage, handling and transport . . 6
5.2.1 General . 6
5.2.2 Storage . 6
5.2.3 Handling . 7
5.2.4 Transport . 7
5.3 Jointing. 8
5.4 Laying . 8
5.4.1 General . 8
5.4.2 Trench . 9
5.4.3 Drag forces . 9
5.4.4 Valves . 10
5.4.5 Connection to working systems . 10
5.4.6 Backfilling . 10
5.5 Pressure testing and commissioning . 10
6 Quality control .11
6.1 General . 11
6.2 Inspection prior to laying . 11
6.3 Inspection during laying . . 11
6.3.1 Laying . 11
6.3.2 Joint integrity .12
Annex A (normative) Butt fusion jointing procedure .20
Annex B (normative) Electrofusion jointing .25
Annex C (normative) Mechanical jointing.30
Annex D (informative) Socket fusion and saddle fusion fittings jointing procedures .31
Annex E (informative) Derating coefficient for various operating temperatures .32
Bibliography .33
iii
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).
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. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
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 4, Plastics pipes and fittings for the supply of gaseous fuels.
This second edition cancels and replaces the first edition (ISO/TS 10839:2000), which has been
technically revised.
The main changes are as follows:
— the whole document has been redrafted in order to improve its readability;
— clauses referring to the jointing processes have been transformed into normative annexes (see
Annex A, Annex B and Annex C);
— the Scope has been updated to include hydrogen;
— Clause 2 and Clause 3 have been updated;
— various additional updates and corrections have been made throughout the document to reflect the
current state of the art;
— information on socket fusion jointing procedures has been deleted as this is the subject of other
published documents (see Annex D).
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.
iv
TECHNICAL SPECIFICATION ISO/TS 10839:2022(E)
Polyethylene pipes and fittings for the supply of gaseous
fuels — Code of practice for design, handling and
installation
1 Scope
This document presents a code of practice dealing with polyethylene (PE) pipes and fittings for buried
pipeline systems outside buildings, conforming to the ISO 4437 series, and designed to transport
gaseous fuels [as defined in ISO 4437-1, e.g. methane, liquified petroleum gas (LPG), manufactured gas
and hydrogen] within the temperature range –20 °C to +40 °C. This document also gives appropriate
temperature-related requirements.
The code of practice covers mains and service lines whose components are prepared for fusion or
mechanical jointing. It also gives instructions for the design, storage, handling, transportation, laying
conditions and fusion quality control of PE pipes and fittings as well as subsequent joint testing,
backfilling, pipe system testing and commissioning.
NOTE For the renovation code of practice, reference is made to the ISO 11299 series and to ISO 11295 for
classification and to the ISO 21225 series for further information for trenchless replacement.
The minimal requirements for the jointing methods are given in:
— Annex A (butt fusion);
— Annex B (electrofusion); and
— Annex C (mechanical jointing).
In some countries the use of heated-tools socket and saddle fusion is permitted; information on heated-
tools fusion jointing techniques is given in Annex D.
In the case of ground movement or shaking (e.g. earthquakes, etc.) it can be necessary to implement
precautions mentioned in this document following guidelines provided by authorities (e.g. Eurocode
[7] [8]
8, EN 12007-1:2012, Annex A, etc.),
Workers' health and safety issues are outside the scope of this document.
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 4437-1, Plastics piping systems for the supply of gaseous fuels — Polyethylene (PE) — Part 1: General
ISO 4437-2:2014, Plastics piping systems for the supply of gaseous fuels — Polyethylene (PE) — Part 2:
Pipes
ISO 4437-3, Plastics piping systems for the supply of gaseous fuels — Polyethylene (PE) — Part 3: Fittings
ISO 4437-4, Plastics piping systems for the supply of gaseous fuels — Polyethylene (PE) — Part 4: Valves
ISO 4437-5, Plastics piping systems for the supply of gaseous fuels — Polyethylene (PE) — Part 5: Fitness
for purpose of the system
ISO 12176-1, Plastics pipes and fittings — Equipment for fusion jointing polyethylene systems — Part 1:
Butt fusion
ISO 12176-2, Plastics pipes and fittings — Equipment for fusion jointing polyethylene systems — Part 2:
Electrofusion
ISO 12176-3, Plastics pipes and fittings — Equipment for fusion jointing polyethylene systems — Part 3:
Operator's badge
ISO 12176-4, Plastics pipes and fittings — Equipment for fusion jointing polyethylene systems — Part 4:
Traceability coding
ISO 12176-5, Plastics pipes and fittings — Equipment for fusion jointing polyethylene systems — Part 5:
Two-dimensional data coding of components and data exchange format for PE piping systems
ISO 13950, Plastics pipes and fittings — Automatic recognition systems for electrofusion joints
ISO 17885:2021, Plastics piping systems — Mechanical fittings for pressure piping systems — Specifications
EN 12327, Gas infrastructure — Pressure testing, commissioning and decommissioning procedures —
Functional requirements
3 Terms, definitions and abbreviated terms
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 Terms and definitions
3.1.1
butt fusion machine pressure
pressure indicated on the gauge or on a pressure display on a butt fusion machine, giving an indication
of the interface force applied to the pipe and/or fitting ends
3.1.2
clearance
shortest distance between the outer limits of two objects
3.1.3
drag resistance
frictional resistance due to the weight of the length of pipe fixed in the moveable clamp at the point
at which movement of the moveable clamp is initiated (peak drag), or the friction occurring during
movement (dynamic drag)
3.1.4
electrofusion control unit
equipment implementing the output fusion parameters of voltage or current and time or energy to
execute the fusion cycle as specified by the electrofusion fitting manufacturer
3.1.5
frictional losses in the butt fusion machine
force necessary to overcome friction in the whole mechanism of a butt fusion machine
3.1.6
fusion operator
person trained to carry out fusion jointing between polyethylene (PE) pipes and/or fittings
Note 1 to entry: Fusion jointing is based on a written procedure agreed by the pipeline operator
Note 2 to entry: The fusion operator is trained for one or more fusion–jointing procedures
3.1.7
interface force
force between the fusion surfaces of the pipe(s) and/or fitting(s) during the fusion cycle, as specified in
the fusion diagram
3.1.8
operator
person authorized to build polyethylene (PE) systems from pipes and/or fittings, based on a written
procedure agreed by the pipeline operator
3.1.9
overall service (design) coefficient
C
overall coefficient, with a value greater than 1, which takes into consideration service conditions as
well as properties of the components of a piping system
3.1.10
pipeline operator
private or public organization authorized to design, construct and/or operate and maintain a gas supply
system
3.1.11
soil cover
vertical distance between the top of a buried pipe and the normal surface after finishing work
EXAMPLE Including pavement.
3.2 Symbols and abbreviated terms
A depth
a correct bead root
B bead width
B average bead width
m
b rejected bead root
C overall service (design) coefficient
D temperature derating coefficient
F
d external diameter of pipe or spigot fitting
e
EF electrofusion
e pipe or fitting nominal wall thickness
n
F maximum drag force (N)
L insertion depth
MOP maximum operating pressure
MPa megapascal
MRS minimum required strength
N Newton
p pressure
p critical rapid crack propagation pressure
RCP
RCP rapid crack propagation
SDR standard dimension ratio
SF safety factor
t time
UV ultraviolet
V misalignment
WPS welding procedure specification
σ maximum tensile stress (MPa)
σ tensile stress at yield (MPa)
y
4 Design
4.1 General
A written laying procedure, authorized by the pipeline operator, shall be made available prior to the
construction of a pipeline. The laying procedure shall include specification of the jointing procedure
(butt fusion, or electrofusion, or mechanical), the pipe and fitting materials to be used, the trenching
and backfilling requirements, the pressure testing and commissioning requirements, and the data to be
collected for the traceability system.
The selection of materials, standard dimension ration (SDR) series, dimensions and assembling
techniques shall be the responsibility of the pipeline operator.
There are two SDR series in common use for gas supply systems: SDR 17 and SDR 11. Other SDR series
can also be used, such as SDR 26 for renovation.
The training and the level of skill of the operator(s) shall be in accordance with the requirements of the
jointing procedures.
General guidelines for supervision and quality control are given in Clause 6.
NOTE Information on the suitability of pipes made from PE100-RC for trenchless technologies is given in
[9]
ISO 4437-1 and EN 1555-1.
4.2 Material, components and jointing equipment
The PE materials and components used shall conform to ISO 4437-1, ISO 4437-2, ISO 4437-3, ISO 4437-4,
ISO 4437-5 and ISO 17885. Other components not covered by the above-mentioned International
Standards shall conform to the relevant national standards or in the absence of such documents,
the components shall meet the performance requirements of the system as demonstrated by the
manufacturer.
The fusion equipment used for the construction of the pipeline shall conform to the requirements of
ISO 12176-1 or ISO 12176-2. If the operation of the fusion equipment requires an operator's badge,
the badge shall conform to ISO 12176-3. Traceability of PE materials shall refer to ISO 12176-4 and/or
ISO 12176-5.
4.3 Maximum operating pressure
The maximum operating pressure (MOP) of the system shall be selected by the pipeline operator on
the basis of the gas supply system operating requirements and the materials used. The MOP of a PE
system depends on the type of resin used (the minimum required strength, MRS), the pipe SDR series
and the service conditions, and is limited by the overall service (design) coefficient, C, and the rapid
crack propagation (RCP) criteria.
The overall service (design) coefficient C for thermoplastics materials should be as specified in
ISO 12162. This coefficient is used to calculate the MOP of the pipeline. C shall be greater than or equal to
2 for PE pipeline systems for natural gas. For other gases, a higher C value according to ISO 4437-1:2012,
Annex A, can be defined.
The MOP shall be calculated using Formula (1):
20 × MRS
MOP = (1)
CS ×−DR 1 × D
()
F
NOTE The temperature derating coefficient, D , is used in the calculation of the MOP which takes into
F
account the influence of the operating temperature.
The temperature derating coefficient, D , for various operating temperatures is given in Annex E.
F
The ratio of the critical RCP pressure, p , to the MOP shall be ≥ 1,5 at the minimum operating
RCP
temperature. The critical RCP pressure, p , is dependent upon temperature, pipe size, SDR and type
RCP
of PE material used. It is defined in accordance with ISO 4437-1 and ISO 4437-2, which specify a test
temperature of 0 °C.
Where the pipe operating temperature decreases below 0 °C, the p /MOP ratio shall be recalculated
RCP
using a p value determined from the minimum expected operating temperature of the pipe. If
RCP
necessary, the value of the MOP shall be reduced so as to maintain the p /MOP ratio at a value ≥ 1,5.
RCP
4.4 Assembly techniques
Jointing procedures may vary depending upon the type of PE material and the pipe size used. Butt
fusion and electrofusion are the preferred jointing methods. For the butt fusion jointing procedure, a
reference to ISO 21307 is useful.
For electrofusion and heated-tools socket fusion processes including the operation of fusion control
units, refer to the manufacturers of these components including the control units.
For fusion joints, evidence of the fusion compatibility between the jointing materials should be given.
A written jointing procedure, authorized by the pipeline operator, shall be available prior to the
construction of a pipeline. The jointing procedure shall include specification of the jointing method, the
fusion parameters, the fusion equipment, the jointing conditions, the level of skill of the fusion operator,
and the quality control methods to be used.
4.5 Squeeze-off properties
When squeeze-off techniques are considered, the suitability of the pipe for squeeze-off shall be
confirmed in accordance with ISO 4437-2:2014, Annex C.
5 Construction
5.1 Competences
Operators shall be competent in the field of the assigned job. Operators shall possess the necessary
skills and required knowledge and the ability to operate with awareness.
NOTE 1 Specific courses provide training for the competencies that can be certified by a third party
organization operating, for example, in accordance with ISO/IEC 17020.
NOTE 2 An example of a specific training course for fusion operators can be found in ISO/TR 19480.
5.2 Storage, handling and transport
5.2.1 General
PE pipes are available in coils, drums or straight lengths. Fittings are normally individually packed.
Mishandling of the pipes and fittings shall be avoided to protect them against gouges, scratches, cuts,
holes, kinks or flattening.
5.2.2 Storage
PE pipes can be stored outside and under UV radiation provided that requirements for the resin as
stated in ISO 4437-1 are met. Coloured pipes (e.g. yellow or orange) can be subject to degradation
if solar UV radiation exceeds values as given in ISO 4437-1:2014, Table 2. The user of this document
should consider information of the pipe manufacturer for allowable UV radiation dose with determined
regional UV radiation level during storage.
NOTE 1 Information on regional levels of UV radiation may be found on web pages of national authorities e.g.
meteorological institutes.
NOTE 2 ISO 4437-1 resistance to weathering is based on a cumulative exposure of 3,5 GJ/m UV radiation level
Coloured pipes which have been stored outdoor uncovered for longer than recommended by the
manufacturer shall only be used if tested in accordance with Table 1.
Table 1 — Minimum tests for evaluating coloured pipes when over-exposed to UV radiation
Test Source and method
Elongation at break (all wall thicknesses) ISO 4437-2:2014, Table 4
Hydrostatic strength (80 °C, 1 000 h) ISO 4437-2:2014, Table 4
Decohesive resistance ISO 4437-5:2014, Table 5
PE fittings and valves can be stored following the manufacturer's recommendation.
Straight pipes shall be stacked on a suitable surface, preferably flat and free from stones or other
projections or sharp objects likely to deform or damage the pipes. Pipes and fittings shall be stored in
such a way as to minimize the possibility of the material being damaged by crushing or piercing.
The distances “x” (Figure 1) between support frames holding packs of pipes together shall be equal in
order to allow the frames to be stacked.
The support frame shall not be nailed together and should be constructed in such a way that the load is
directly supported by the frame and not by the pipes.
Key
x distance between supports
1 support frame
Figure 1 — Support frame
The exact height to which straight pipes can be stacked depends on many factors such as material,
size, wall thickness and ambient temperature. Stacking shall avoid distortion of pipes over the limits as
given by the manufacturer during the storage. The manufacturer's stacking recommendations shall be
followed.
PE pipes may be coiled or wound on drums. Coils of large-diameter pipes with d ≥ 110 mm shall be
e
stored vertically in purpose-built racks or cradles. Where loose straight pipes are stacked in pyramidal
fashion, this shall not exceed a height of 1 m. Fittings shall be stored in their original packaging until
being prepared for use. Contact with aggressive reagents or solvents shall be avoided.
The pipes with the earliest extrusion date should be used first for installation. The fittings with
the earliest manufacturing date should be used first for installation. Guidance from the product
manufacturer should be considered.
5.2.3 Handling
Initial handling of straight pipes shall be made with the pipes as delivered by the manufacturer (e.g.
in their own packaging), thus minimizing damage during this phase. When loading, unloading or
handling, it is preferable to use mechanical equipment to move or stack the packages. The pipes shall
not be dragged or thrown along the ground. If handling equipment is not used, choose techniques which
are not likely to damage the pipes and/or fittings.
Coils of pipe stacked on pallets are easily handled using a forklift truck. Individual coils shall not be
rolled off the edge of a vehicle load platform. Coils shall be slung individually when off-loading with a
crane. Before laying a pipe, ensure that the drum is positioned correctly and that its axle will remain
stable during the unrolling operation. While unrolling, ensure that the pipe is not damaged.
Fittings and valves shall be handled in accordance with manufacturer instructions and left in original
packaging until use.
5.2.4 Transport
When transporting straight pipes, flatbed vehicles shall be used. The bed shall be free from nails and
other protuberances. The pipes shall rest uniformly on the vehicle over their whole length, and shall be
securely held in place during transport.
Coiled pipes shall be transported stacked on a pallet or as individual coils, and be firmly secured to the
vehicle. The height of the top of a drum when loaded on a vehicle shall take into consideration the local
regulations on the maximum height and any limitations expected on the route. Drums shall be firmly
secured to the vehicle.
Fittings and valves shall be transported in accordance with manufacturer instructions.
5.3 Jointing
The jointing operation, either mechanical or fusion, shall be performed in accordance with the pipeline
operator’s written procedure. The minimal jointing requirements, given in Annex A, Annex B and
Annex C, shall be respected.
The fusion procedure specification shall take into account the relevant fusion standards, if existing,
and any recommendation from the pipe, fitting and accessory manufacturers.
NOTE 1 The relevant International Standard for butt-fusion jointing procedure is ISO 21307.
NOTE 2 In some countries “fusion procedure specification” is also defined as “welding procedure specification
(WPS)”
PE pipes, fittings and accessories may be jointed either by heated-tool fusion jointing, electrofusion
jointing or mechanical jointing. The jointing and quality control methods used for the construction of
the gas supply system shall be appropriate to the design of the network.
Fusion operators shall possess the necessary skill and knowledge and ability to produce joints of
consistently high quality. To this end, they shall receive formal training under the supervision of a
qualified instructor.
The gas company can require evidence of training or qualification for fusion.
NOTE 3 An example of formal training and assessment can be found in ISO/TR 19480.
The same level of skill, knowledge and ability is required for mechanical jointing. The gas company can
require evidence of training or qualification. When tightening or untightening a mechanical joint, it is
essential that torsional stress is not transmitted to the pipe.
5.4 Laying
5.4.1 General
Care shall be taken to prevent damage to the pipes and fittings during the whole of the laying process.
Changes in direction of a PE pipeline when laying can be made using pre-formed bends or elbow fittings
or by making use, within limits, of the natural flexibility of the pipe. Natural flexibility may be used for
bend radii ≥ 25 × d , and also for smaller radii for certain SDR values and materials, provided that this is
e
consistent with operational experience and good engineering practice.
NOTE 1 In general, the flexibility is a factor of SDR, environmental temperature and material. The pipe
manufacturer can be consulted for additional guidance or instructions.
NOTE 2 Information on the bend radii for mechanical joints are given in Annex C.
The flexibility of PE pipes is reduced in cold weather. If the temperature falls below –15 °C for straight
pipes and for fittings, or below 0 °C for coiled pipes, special handling instructions, issued by the
manufacturers, shall be followed.
Machine-bending of pipes or bending after the application of heat in the fields shall not be used.
Where PE pipes, fittings and valves are allowed to be installed above ground they shall be protected
against mechanical damage and, in case of non-black pipes, UV degradation.
If the gas pipeline isn’t protected by the surrounding soil, special consideration should be taken to
reduce any kind of risk, e.g. ignition sources, high temperatures, etc.
The minimum clearance between the pipe and obstacles (e.g. utilities, structures or immovable rocks)
shall be 200 mm from the pipe surface. If this minimum clearance cannot be observed, a protection
barrier shall be installed. Special precautions shall be taken if the gas pipeline crosses or is laid
alongside other buried services, e.g. a hot water or steam pipeline, a petrol-carrying pipe, a petrol
station or a high-voltage cable, etc.
Stresses caused by differences in temperature between laying and operation shall be taken into
consideration. The position of the pipeline shall be recorded before backfilling.
To minimize the possibility of damage to the pipeline by external influences, at least one of the following
measures shall be considered:
a) place a warning device, for example a protection tile hazard tape, etc. along the top of the pipe;
b) place a tracer wire to enable the pipe to be located again in future;
c) install permanently visible above-ground markings, especially at road, railway and water crossings,
at blow-off devices, on private land, at boundaries between plots of land, and at points where the
pipeline changes direction.
5.4.2 Trench
Excavating and backfilling of the trench shall be in accordance with the written procedure authorized
by the pipeline operator. The width of the trench bottom shall be large enough to allow correct
installation and backfilling.
If it should be necessary to perform any fusion jointing in the trench, the width of the trench can need
to be larger, depending on the type of fusion jointing and the type of equipment used.
Pipes may be laid in the trench without preparation of the bottom, if this consists of relatively soft,
fine-grained soils free of large and sharp-edged stones and other hard objects, and where the bottom of
the trench can readily be brought to an even finish providing uniform support for the pipes over their
whole length.
5.4.3 Drag forces
Pipes shall not be overstressed by tensile forces during laying. If the pipe is laid by drag, care shall be
taken that the drag force is not greater than the values given by Formula (2) and Formula (3):
σ××π d
e
F = (2)
SF×SDR
σ
y
σ = (3)
12, 5
where:
F is the maximum drag force, in N;
SDR is the standard dimension ratio;
d is the outside diameter of the pipe, in mm;
e
σ is the maximum tensile stress, in MPa;
SF is the safety factor;
σ is the tensile stress at yield, in MPa.
y
NOTE 1 A value of 2,0 is normally used for SF.
NOTE 2 The tensile stress at yield, σ is as provided by the pipe manufacturer.
y,
The drag force, F, obtained by Formula (2), relates to an environmental temperature of 20 °C and can
be applied to the pipe for a relatively short time. For higher temperatures, derating factors should be
applied to Formula (2).
5.4.4 Valves
Valves shall be installed so that they do not expose the PE pipe to unnecessary stress during opening or
closing. PE valves shall conform to ISO 4437-4.
Valves are available with either a steel/iron or a plastics body. With steel/iron-body valves, special
precautions shall be taken against corrosion and to avoid stresses induced on the PE pipes by their
weight.
5.4.5 Connection to working systems
Where there can be a release of gas in the working area, static-charge accumulation shall be avoided.
In order to avoid static charges, the pipeline system shall be connected to earth during manipulations,
for example by draping water-soaked cloths, made of natural fibre, over all pipes and fittings likely to
be handled so that the cloths touch both the pipe and the ground.
5.4.6 Backfilling
Unless otherwise specified, buried pipelines and casings shall have a minimum soil cover of 0,6 m
(0,6 m cover can potentially not be necessary for small diameter PE service pipes). Exceptions may
be made for pipes entering metering or regulating boxes, but such pipes shall be protected against
external interference. Greater soil cover shall be provided in areas of deep ploughing, drainage, roads
with heavy traffic, and railway or waterway crossings.
Excavated materials may be used as backfill provided that they are free from stones and sharp objects
likely to damage the pipe and free of wooden materials. If this is not the case, qualified backfill material
shall be used.
NOTE Backfill materials can be subject to national or local regulations.
Pipes made of PE100-RC show a higher resistance against slow crack growth, so may be installed
without sand embedding and/or with the re-use of the excavated soil.
The pipe shall be uniformly supported; material around the pipe shall be compacted so as to avoid
excessive pipe ovality. This shall be done layer by layer.
5.5 Pressure testing and commissioning
Pressure testing and commissioning shall be in accordance with EN 12327.
NOTE Pipeline pressures can be subject to national or local regulations.
Consideration shall be given to the need for any special precautions to be taken to protect persons and
property if air or inert gas is used as the test medium.
For test temperatures below 0 °C, the possibility of a reduction in critical RCP pressure, p , shall be
RCP
taken into account in the pipeline preparation and test procedure adopted.
Pressurized PE pipelines at ambient temperature are subject to expansion by creep that can potentially
affect the results of pressure testing. At higher test pressures, this effect can be significant. Appropriate
allowance shall be made for pressure losses due to creep when interpreting pressure test results.
If air is used, oil from the compressor shall be prevented from entering the pipeline and the air
temperature shall not exceed 40 °C, to prevent damage to the pipes and/or fittings.
After the finalization of the piping installation, including the positive result of pressure testing, the
piping system is prepared for commissioning.
6 Quality control
6.1 General
The pipes, fittings and associated equipment shall be inspected to confirm the conformity with the
laying procedure.
The inspection may be carried out by the personnel engaged in jointing. Additional inspections shall
be carried out by a competent person at a frequency depending on the conditions of use. The results of
each inspection shall be recorded.
[14][15]
Destructive and/or non-destructive testing on joints made in the field may also be carried out to
ensure that the quality conforms to the jointing procedure.
6.2 Inspection prior to laying
Pipes, fittings and associated equipment shall be inspected prior to laying to confirm conformity with
the required ISO standard, pipe and fitting diameters, SDR and MRS as given by the pipe and fitting
marking information.
Pipes and fittings showing obvious defects, e.g. excessive scoring, shall be clearly marked as unsuitable
and discarded. Limitations on outside storage of pipes or fittings shall not have been exceeded.
The equipment used shall be in accordance with the relevant standards e.g. in case of equipment for
fusion jointing ISO 12176-1 and ISO 12176-2. When standards do not exist, the equipment shall be as
defined in industry specification and its use shall be in accordance with the manufacturer's instruction
of use and maintenance.
Prior to use, the equipment shall be visually inspected to ensure that the device is free of damage, e.g.
broken cables, and it shall be verified that calibration and maintenance frequencies, as specified by the
manufacturer, are fulfilled.
A written jointing procedure shall be available.
6.3 Inspection during laying
6.3.1 Laying
Soil and trench conditions shall conform to the written installation procedure authorized by the
pipeline operator.
If surface defects with a depth of more than 10 % of the nominal pipe wall thickness are found, the
section concerned shall be cut out.
Inspection during the laying of pipelines and the construction of associated installations shall include
the following:
a) inspection of the pipes for serious surface defects, deformation or pipe end toe-in, immediately
prior to and during laying;
b) inspection of the trench to ensure that it is the correct depth and width and that it provides the
minimum clearance with respect to other buried structures;
c) inspection of the bottom of the trench immediately prior to lowering the pipeline into place and
during backfilling of the trench to ensure that the pipeline is not damaged by sharp objects, such as
stones or pieces of metal;
d) inspection during the lowering of the pipeline into the trench to ensure that this takes place
correctly, that no damage occurs and that the pipeline is placed in the correct position.
The installation of new PE materials (e.g. PE100-RC) can present a reason for pipeline operators to
reconsider some of the above inspections (e.g. backfilling material requirements, etc).
6.3.2 Joint integrity
6.3.2.1 General
The quality of the joint depends on strict adherence to the written jointing procedure, the use of well-
maintained/calibrated equipment conforming to the relevant standard and the competence of the
operators.
Quality control shall be performed on-site by the persons involved in the work concerned. Further,
supervision and inspection may be carried out by a supervisor who shall guarantee the quality of the
work performed and in addition provide a quality control report.
6.3.2.2 Visual inspection criteria
6.3.2.2.1 Butt fusion joints
The following inspections shall be executed:
a) Bead symmetry
Joints shall have a smooth symmetrical bead around the entire pipe circumference as shown in
Figure 2. The depth, A, of the bead depression shall not extend below the pipe surface.
An asymmetrical bead profile between the same components shall initially be considered as
indicative of poor joint quality subject to a confirmation assessment by an authorized person.
Where the pipes and/or fittings have different MFRs, the bead may be asymmetrical but still
satisfactory. In assessing the results of the joint tests under standard conditions, acceptable levels
of asymmetry shall be determined.
Key
A depth
Figure 2 — Bead symmetry
b) Alignment
Pipes, fittings and valves shall be as closely aligned as possible.
The misalignment V shall not exceed 0,1 e . Where this leads to values of less than 1 mm, testing of
n
joints shall be undertaken to identify the maximum allowable misalignment (Figure 3).
This value shall not be exceeded anywhere around the circumference of the two parts adjacent to
the fusion bead.
Key
V misalignment
B bead width
Figure 3 — Alignment
One method of determining an acceptable bead width value, B, is by experimentally using pipes and
a butt fusion machine operating at the specified conditions. The mean value, B , is determined from
m
several joints made under the conditions defined in the jointing procedure. It is recommended, for
quality control purposes on-site, that the measured bead width B does not exceed ±20 % of B .
m
The use of GO/NO-GO gauges, manufactured according to these recommended limits, can
potentially facilitate checking (Figure 5).
c) Bead removal
Removal of the external fusion bead, using appropriate tools, is possible without damage to the
pipe (Figure 4). The removed bead is then available for inspection.
Figure 4 — Bead removal
Bead gauges may be used to assess the bead width
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