ISO 22621-6:2010

INTERNATIONAL ISO
STANDARD 22621-6
First edition
2010-04-15
Plastics piping systems for the supply
of gaseous fuels for maximum operating
pressures up to and including 2 MPa
(20 bar) — Polyamide (PA) —
Part 6:
Code of practice for design, handling
and installation
Systèmes de canalisations en matières plastiques pour la distribution
de combustibles gazeux pour des pressions maximales de service
inférieures ou égales à 2 MPa (20 bar) — Polyamide (PA) —
Partie 6: Code de pratique pour la conception, la manutention
et l'installation
Reference number
©
ISO 2010
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©  ISO 2010
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ii © ISO 2010 – All rights reserved

Contents Page
Foreword .iv
Introduction.v
1 Scope.1
2 Normative references.1
3 Terms and definitions .2
4 Symbols and abbreviated terms .3
5 Design.3
5.1 General .3
5.2 Materials, components and jointing equipment.3
5.3 Maximum operating pressure .4
5.4 Assembly techniques.4
5.5 Squeeze-off properties.4
6 Installation.4
6.1 Jointing procedure .4
6.2 Training.5
6.3 Heated-tool fusion jointing.5
6.4 Electrofusion jointing.11
6.5 Laying .14
7 Storage, handling and transport.16
7.1 General .16
7.2 Storage .16
7.3 Handling .18
7.4 Transport.18
8 Quality control .18
8.1 General .18
8.2 Inspection prior to laying.18
8.3 Inspection during laying.19
Annex A (informative) Derating coefficients for operating temperatures.21

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 22621-6 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.
ISO 22621 consists of the following parts, under the general title Plastics piping systems for the supply of
gaseous fuels for maximum operating pressures up to and including 2 MPa (20 bar) — Polyamide (PA):
⎯ Part 1: General
⎯ Part 2: Pipes
⎯ Part 3: Fittings
⎯ Part 5: Fitness for purpose of the system
⎯ Part 6: Code of practice for design, handling and installation
iv © ISO 2010 – All rights reserved

Introduction
This part of ISO 22621 addresses the common basic principles for gas supply systems. More detailed national
standards or codes of practice might exist in the ISO member countries. This part of ISO 22621 is intended to
be applied in association with those national standards or codes of practice related to the above-mentioned
basic principles.
INTERNATIONAL STANDARD ISO 22621-6:2010(E)

Plastics piping systems for the supply of gaseous fuels
for maximum operating pressures up to and including 2 MPa
(20 bar) — Polyamide (PA) —
Part 6:
Code of practice for design, handling and installation
1 Scope
This part of ISO 22621 specifies a code of practice dealing with polyamide (PA) piping systems, intended to
be buried outside buildings and used for the supply of gaseous fuels.
It is applicable to mains and service lines, the components of which are prepared for jointing by scraping
and/or machining, and gives instructions for the design, storage, handling, transportation, laying conditions
and fusion quality control of PA pipes and fittings up to and including 250 mm outside diameter, as well as
subsequent joint testing, backfilling, pipe system testing, commissioning and decommissioning.
The jointing methods covered by this part of ISO 22621 are butt fusion jointing and electrofusion jointing.
No special precautions are necessary for areas exposed to the influence of mining and earthquakes other
than those precautions mentioned in this part of ISO 22621.
It is the responsibility of users of this part of ISO 22621 to take existing and new national regulations into
account.
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 12162, Thermoplastics materials for pipes and fittings for pressure applications — Classification,
designation and design coefficient
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
EN 12327, Gas supply systems — Pressure testing, commissioning and decommissioning procedures —
Functional requirements
ISO 22621-1, Plastics piping systems for the supply of gaseous fuels for maximum operating pressures up to
and including 2 MPa (20 bar) — Polyamide (PA) — Part 1: General
ISO 22621-2, Plastics piping systems for the supply of gaseous fuels for maximum operating pressures up to
and including 2 MPa (20 bar) — Polyamide (PA) — Part 2: Pipes
ISO 22621-3, Plastics piping systems for the supply of gaseous fuels for maximum operating pressures up to
and including 2 MPa (20 bar) — Polyamide (PA) — Part 3: Fittings
ISO 22621-5, Plastics piping systems for the supply of gaseous fuels for maximum operating pressures up to
and including 2 MPa (20 bar) — Polyamide (PA) — Part 5: Fitness for purpose of the system
3 Terms and definitions
For the purposes of this document, the terms, definitions, symbols and abbreviated terms given in ISO 22621-1
and ISO 22621-5 and the following apply.
3.1
butt fusion machine pressure
pressure indicated on the manometer or on a pressure display on a butt fusion machine, giving an indication
of the interface force applied to the pipe or fitting ends
3.2
clearance
shortest distance between the outer limits of two objects
3.3
drag resistance
frictional resistance due to the weight of the length of pipe fixed in the movable clamp at the point at which
movement of the movable clamp is initiated (peak drag), or the friction occurring during movement (dynamic
drag)
3.4
electrofusion control box
unit 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
3.5
frictional losses in the butt fusion machine
force necessary to overcome friction in the whole mechanism of a butt fusion machine
3.6
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
3.7
operator
person authorized to build PA systems from pipes or fittings, based on a written procedure agreed on by the
pipeline operator
3.8
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
2 © ISO 2010 – All rights reserved

3.9
pipeline operator
private or public organization authorized to design, construct or operate and maintain a gas supply system
3.10
soil cover
vertical distance between the top of a buried pipe and the normal surface after finishing work
4 Symbols and abbreviated terms
d outside diameter of pipe at any point
e
MOP maximum operating pressure
MRS minimum required strength
RCP rapid crack propagation
SDR standard dimension ratio
5 Design
5.1 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, 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, 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 shall be in accordance with the requirements of the jointing
procedures.
General guidelines for supervision and quality control are given in Clause 8.
5.2 Materials, components and jointing equipment
The PA materials and components used shall conform to ISO 22621-1, ISO 22621-2 and ISO 22621-3, as
relevant.
Other components not covered by the above-mentioned parts of ISO 22621 shall conform to the relevant
national standards.
If pipes and fittings are to be stored outside, requirements on maximum storage time shall be given in the
laying procedure. PA materials shall be stabilized to give protection against a UV radiation level of 3,5 GJ/m .
It is desirable that national bodies give recommendations for allowed storage times in their countries.
The fusion equipment used for the construction of the pipeline shall comply with 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.
5.3 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 PA system depends
on the type of resin used (the MRS), the pipe SDR series and the service conditions, and is limited by the
overall service (design) coefficient, C, and the RCP criteria.
The overall service (design) coefficient, C, for thermoplastics materials is 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 PA pipeline
systems for natural gas.
20 ×MRS
MOP = (1)
CD×−SDR 1×
()
F
NOTE The derating factor, D , is a coefficient used in the calculation of the MOP which takes into account the
F
influence of the operating temperature. Derating factors for various operating temperatures are given in Annex A.
The ratio of the critical RCP pressure to the MOP shall be W 1,5 at the minimum operating temperature. The
critical RCP pressure is dependent on temperature, pipe size and type of PA material used. It is defined in this
subclause in accordance with ISO 22621-1, based on the full-scale test method in accordance with
ISO 22621-1:2007, Annex C, which specifies a test temperature of 0 °C.
Where the pipe temperature decreases below 0 °C, the p /MOP ratio shall be recalculated using a p (critical
c c
pressure) value determined from the minimum expected operating temperature of the pipe. If necessary, the
value of the MOP shall be reduced so as to maintain the p /MOP ratio at a value W 1,5.
c
5.4 Assembly techniques
Jointing procedures may vary depending on the pipe size used.
Fusion is the preferred jointing method. Preference shall be given to butt fusion and electrofusion.
Components made from PA 11 shall be heat fusion jointed only to components made from PA 11.
Components made from PA 12 shall be heat fusion jointed only to components made from PA 12.
Components made from polyamide are not fusion compatible with components made from other polymers.
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 operator, and the quality control methods to
be used.
5.5 Squeeze-off properties
When squeeze-off techniques are considered, the suitability of the pipe for squeeze-off shall be established in
accordance with the manufacturer's recommendations.
6 Installation
6.1 Jointing procedure
The jointing operation shall be performed in accordance with the pipeline operator's written procedure and
shall take into account the procedures outlined in ISO 22621-5:2010, Annex A, for butt fusion jointing and
ISO 22621-5:2010, Annex B, for electrofusion jointing.
4 © ISO 2010 – All rights reserved

Polyamide pipes, fittings and accessories may be jointed by heated-tool fusion jointing or electrofusion 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 and take into account the requirements of ISO 22621-5.
6.2 Training
The operator shall be competent in the appropriate laying and jointing methods. He or she shall possess the
necessary skill and knowledge to produce joints of consistently high quality.
Operators shall receive formal training under the supervision of a qualified instructor. The gas company may
require a certificate indicating that the operator has reached an adequate standard in accordance with national
or local regulations.
6.3 Heated-tool fusion jointing
6.3.1 General
Heated-tool fusion joints shall be made under defined conditions of pressure, time and temperature, using a
written procedure (see 6.1). Mating surfaces should be heated to their fusion temperature and then brought
into contact with one another.
6.3.2 Fusion temperature
The production of a strong fusion bond depends, among other things, on the fusion temperature of the
polyamide material: overheating can degrade the material, and insufficient heating does not soften it
adequately.
The temperature range over which any particular polyamide material may be satisfactorily jointed shall be
considered. The jointing procedure shall specify the heating cycle and the temperature levels for the
polyamide material selected.
Cold weather and wind can adversely affect the fusion temperature. Under these circumstances, special
precautions, such as shielding, end caps and longer heating times shall be considered.
6.3.3 Fusion equipment
The butt fusion equipment used shall conform to ISO 12176-1.
As high-quality fusion joints cannot be made with fusion equipment in poor condition, maintenance of the
fusion equipment is very important and shall be carried out on a regular basis. The cleanliness and integrity of
the heating surfaces, the ability of the heating tools to produce the correct temperature and the correct
alignment and operation of the equipment when used are of paramount importance.
The heating tools are designed to maintain uniform temperatures within the fusion temperature range of the
particular polyamide material and shall have calibrated means of measuring and indicating the temperature. A
precise temperature measurement device, such as a pyrometer or a digital thermometer with a surface
temperature sensor, may be used to check the surface temperature of the heating tools, although additional
care is necessary to avoid inconsistency of readings when such a device is used.
All heating tools used shall be electrically heated.
6.3.4 Butt fusion
6.3.4.1 Principle
The butt fusion technique consists of heating the planed ends with the mating surfaces by holding them
against a flat heating plate until molten, removing the heating plate, pushing the two softened ends against
one another, holding under pressure for a prescribed time and allowing the joint to cool (see Figure 1).

a) Heating b) Fusion
Key
1 heating plate
a
Pressure during heating.
b
Pressure during fusion.
Figure 1 — Butt fusion
Pipes or fittings with fusion ends of different SDR values shall not be jointed by butt fusion.
6.3.4.2 Butt fusion cycle
The butt fusion cycle can be represented by a pressure/time diagram for a defined fusion temperature.
Different butt fusion cycles are available, depending on the pipe diameter and the working conditions. The butt
fusion cycle used shall be specified in the written procedure.
Figure 2 is an example of a butt fusion diagram.
6 © ISO 2010 – All rights reserved

Key
t time
a
Phase 1.
b
Phase 2.
c
Phase 3.
d
Phase 4.
e
Phase 5.
f
Phase 6.
Figure 2 — Butt fusion cycle
Table 1 — Butt fusion cycle and parameters
Parameter Value Unit
Heater-plate temperature, T 240 ± 20 °C
a b
Phase 1 Pressure, p 0,3 ± 0,1 MPa
Time, t Measured as the time until B is reached s
Bead width, B d u 110: 0,5 < B u 1,5 mm
1 n 1
110 < d u 180: 2 < B u 4 mm
n 1
a
Phase 2 Pressure, p 0,03 ± 0,02 MPa
Time, t (30 + 0,5d ) ± 20 s
2 n
Phase 3 Time, t Maximum value: 3 s
Phase 4 Time, t Maximum value: 3 s
a
Phase 5 Pressure, p 0,3 ± 0,1 MPa
Time, t 12 ± 3 min
Phase 6 Time, t Minimum value: 1,5e min
6 n
Maximum value: 20 min
a
This pressure is the interface pressure and is related to d , e and the butt fusion equipment used.
n n
b 2
1 MPa = 1 N/mm .
The pressures shall be chosen such that the required force is produced at the interface, irrespective of
frictional and pressure losses in the butt fusion machine and drag resistance from the pipe system.
In the case of machines with hydraulic power rams, the force is normally indicated in terms of the applied
cylinder pressure. For such machines, a specific calibration table is provided which gives the relationship
between the real interface pressure and the pressure indicated by the manometer (pressure gauge).
6.3.4.3 Butt fusion temperature
The butt fusion temperature is normally situated between 220 °C and 260 °C and is given in the jointing
procedure.
6.3.4.4 Butt fusion jointing
This subclause gives an overview of the minimum operations necessary to produce a butt fusion joint with a
specified butt fusion cycle and temperature.
a) Reduce the drag resistance as much as possible, for example by using pipe rollers.
b) Clamp the spigot ends of the pipe(s) or fitting(s) in the butt fusion machine.
c) Clean the spigot ends.
d) Check that the butt fusion machine is compatible with the pipe diameter and the prescribed butt fusion
cycle.
e) Plane the pipes parallel by moving the movable clamp against the planing tool (see Figure 3). The closing
pressure shall be sufficient to produce a steady flow of PA slivers on both sides of the planing tool.
Planing is complete when the pipe face(s) or fitting face(s) are plane and parallel to each other.
8 © ISO 2010 – All rights reserved
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