ISO/TS 18226:2006

Plastics pipes and fittings — Reinforced thermoplastics pipe systems for the supply of gaseous fuels for pressures up to 4 MPa (40 bar)

ISO/TS 18226:2006 describes the use of reinforced thermoplastics pipe (RTP) systems for transmission of gaseous fuels at maximum operating pressures up to and including 40 bars, and service temperatures in the region - 50 °C to 120 °C, depending on the liner and cover materials. ISO/TS 18226:2006 relates to transmission systems in which wear and damage to the liner are restricted by limiting pigging operations to soft pigging only. The recommendations in ISO/TS 18226:2006 are confined to RTP and its associated in-line fittings and end-fittings. Where the other system components (elbows, tees, valves, etc.) are of conventional construction, they will be governed by existing standards and codes of practice. ISO/TS 18226:2006 specifies a qualification testing procedure for RTP systems. It also provides a procedure for reconfirmation of the design basis that may be used for product variants where changes have been made in design, materials or the manufacturing process.

Tubes et raccords en matières plastiques — Systèmes de canalisations en matière thermoplastique renforcée pour la distribution de combustibles gazeux à des pressions allant jusqu'à 4 MPa (40 bar)

General Information

• Status: Published
• Publication Date: 17-Sep-2006
• 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: 14-Nov-2020

Standards Content (Sample)

TECHNICAL ISO/TS
SPECIFICATION 18226
First edition
2006-10-01
Plastics pipes and fittings — Reinforced
thermoplastics pipe systems for the
supply of gaseous fuels for pressures up
to 4 MPa (40 bar)
Tubes et raccords en matières plastiques — Systèmes de canalisations
en matière thermoplastique renforcée pour la distribution de
combustibles gazeux à des pressions allant jusqu'à 4 MPa (40 bar)
Reference number
ISO/TS 18226:2006(E)
ISO 2006
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ISO/TS 18226:2006(E)
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ii © ISO 2006 – All rights reserved
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ISO/TS 18226:2006(E)
Contents Page

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

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

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

2 Normative references ........................................................................................................................... 1

3 Terms, definitions and abbreviations................................................................................................. 2

3.1 General terms and definitions ............................................................................................................. 2

3.2 Temperature- and pressure-related definitions................................................................................. 4

3.3 Abbreviations ........................................................................................................................................ 5

4 Performance requirements .................................................................................................................. 6

4.1 Materials ................................................................................................................................................ 6

4.2 Pipes and fittings.................................................................................................................................. 7

4.3 Re-qualification ..................................................................................................................................... 8

5 Process and quality control................................................................................................................. 8

6 Dimensions and marking ..................................................................................................................... 8

6.1 Dimensions............................................................................................................................................ 8

6.2 Marking .................................................................................................................................................. 8

7 Handling, storage and installation...................................................................................................... 8

Annex A (informative) Description of RTP Products ...................................................................................... 9

Annex B (informative) Liner material durability considerations ................................................................. 12

Annex C (informative) Rationale for the elevated temperature test............................................................ 14

Annex D (normative) Test procedures ........................................................................................................... 17

Annex E (normative) Qualification protocol.................................................................................................. 19

Annex F (informative) Process and quality control requirements .............................................................. 32

Bibliography ..................................................................................................................................................... 35

© ISO 2006 – All rights reserved iii
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ISO/TS 18226:2006(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.

In other circumstances, particularly when there is an urgent market requirement for such documents, a

technical committee may decide to publish other types of normative document:

⎯ an ISO Publicly Available Specification (ISO/PAS) represents an agreement between technical experts in

an ISO working group and is accepted for publication if it is approved by more than 50 % of the members

of the parent committee casting a vote;

⎯ an ISO Technical Specification (ISO/TS) represents an agreement between the members of a technical

committee and is accepted for publication if it is approved by 2/3 of the members of the committee casting

a vote.

An ISO/PAS or ISO/TS is reviewed after three years in order to decide whether it will be confirmed for a

further three years, revised to become an International Standard, or withdrawn. If the ISO/PAS or ISO/TS is

confirmed, it is reviewed again after a further three years, at which time it must either be transformed into an

International Standard or be withdrawn.

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/TS 18226 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.

iv © ISO 2006 – All rights reserved
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ISO/TS 18226:2006(E)
Introduction

A reinforced thermoplastics pipe (RTP) comprises a thermoplastics liner with continuous reinforcement and a

thermoplastics outer cover. An RTP “system” comprises runs of RTP, along with the fittings required to

connect them to each other and to the other components of a conventional gas transmission system.

This Technical Specification is applicable for operating pressures up to 4 MPa (40 bar). However it may be

used for guidance in the development of RTP systems for higher operating pressures. It is intended to

accommodate the upgrading of the performance of RTPs and to provide a framework within which future

development can take place.

RTP can be used in both new pipe systems and in the replacement of corroded metallic pipes.

The principal load-bearing components of the RTP are high-strength reinforcing members in the form of fibres,

yarns, tapes or wire, which generally carry load only in tension. The reinforcing element may take the form of

helically-wound yarns or fibre-reinforced tapes, in which the matrix may be a thermoplastics resin.

In the most frequently employed configuration of reinforcement, dry (non-impregnated) aramid-fibre yarns are

encapsulated in a tape of polymer resin or adhesive. It is also possible to employ other classes of

reinforcement, such as glass, carbon or textile fibres, or metallic wire or strip.

The reinforcement may or may not be bonded to the liner or to the outer cover.

Several types of fitting design are possible, with joints made by mechanical means, electrofusion or other

methods of bonding or welding.
© ISO 2006 – All rights reserved v
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TECHNICAL SPECIFICATION ISO/TS 18226:2006(E)
Plastics pipes and fittings — Reinforced thermoplastics pipe
systems for the supply of gaseous fuels for pressures up to
4 MPa (40 bar)
1 Scope

This Technical Specification describes the use of reinforced thermoplastics pipe (RTP) systems for

transmission of gaseous fuels at maximum operating pressures up to and including 4 MPa (40 bar) , and

service temperatures in the region − 50 °C to 120 °C, depending on the liner and cover materials.

This Technical Specification relates to transmission systems in which wear and damage to the liner are

restricted by limiting pigging operations to soft pigging only.

The recommendations in this Technical Specification are confined to RTP and its associated in-line fittings

and end-fittings. Where the other system components (elbows, tees, valves, etc.) are of conventional

construction, they will be governed by existing standards and codes of practice.

This Technical Specification specifies a qualification testing procedure for RTP systems. It also provides a

procedure for reconfirmation of the design basis that may be used for product variants where changes have

been made in design, materials or the manufacturing process.

This Technical Specification provides informative annexes relating to quality assurance, product marking,

handling and storage.
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 4433-1:1997, Thermoplastics pipes — Resistance to liquid chemicals — Classification —

Part 1: Immersion test method

ISO 4433-2:1997, Thermoplastics pipes — Resistance to liquid chemicals — Classification —

Part 2: Polyolefin pipes

ISO 4433-3:1997, Thermoplastics pipes — Resistance to liquid chemicals — Classification —

Part 3: Unplasticized poly(vinyl chloride) (PVC-U), high-impact poly(vinyl chloride) (PVC-HI) and chlorinated

poly (vinyl chloride) (PVC-C) pipes

ISO 4433-4:1997, Thermoplastics pipes — Resistance to liquid chemicals — Classification — Part 4: Poly

(vinylidene fluoride) (PVDF) pipes

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

1) 1 bar = 0,1 MPa = 10 Pa.
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ISO/TS 18226:2006(E)

ISO 9080:2003, Plastics piping and ducting systems — Determination of the long-term hydrostatic strength of

thermoplastics materials in pipe form by extrapolation

ISO 12162:1995, Thermoplastics materials for pipes and fittings for pressure applications — Clarification and

designation — Overall service (design) coefficient

ISO 12176-1:1998, Plastics pipes and fittings — Equipment for fusion jointing polyethylene systems —

Part 1: Butt fusion

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

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)

ISO 14531-4, 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

ASTM D2992-01, Standard Practice for Obtaining Hydrostatic or Pressure Design Basis for “Fiberglass”

(Glass-Fiber-Reinforced Thermosetting-Resin) Pipe and Fittings
3 Terms, definitions and abbreviations

For the purpose of this document, the following terms, definitions and abbreviations apply.

3.1 General terms and definitions
3.1.1
aramid
class of high-strength organic fibre “aromatic amide”
2) 2)
EXAMPLES Twaron , Kevlar .
3.1.2
application-related service factor(s)

multiplication factor(s) applied to the manufacturer's nominal pressure rating, to allow for effects such as

cyclicity
3.1.3
ballooning

inflation of the cover of an RTP, by pressurised gas, that has accumulated in the reinforcing layer

3.1.4
blistering

damage in polymer materials caused by the release of absorbed gas on sudden decompression

3.1.5
carbon fibre
class of high-strength graphite-based reinforcing fibre

2) Twaron and Kevlar are examples of suitable products available commercially. This information is given for the

convenience of users of this document and does not constitute an endorsement by ISO of these products.

2 © ISO 2006 – All rights reserved
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ISO/TS 18226:2006(E)
3.1.6
cyclic
fatigue
service conditions where the internal pressure fluctuates
3.1.7
dynamic
service condition involving external time-dependent loads
3.1.8
elevated temperature test

constant-pressure survival test aimed at verifying that no undesirable failure mode can occur between the end

of the qualification test period and the end of the design life
3.1.9
end-fitting

joint that occurs at either end of a run of RTP, where it is connected to other parts of the system

3.1.10
fitting
coupler
pipe joint
3.1.11
glass fibre
high-strength inorganic reinforcement based on E-glass or S-glass
3.1.12
in-line fitting
pipe joint between adjacent lengths of RTP
3.1.13
lower prediction limit
97,5 % lower prediction limit of the mean regression curve
3.1.14
minimum required strength

lower prediction limit at 20°C in a thermoplastics pipe at 50 years in accordance with ISO 9080:2003, rounded

down in accordance with ISO 12162:1995
3.1.15
Principal
party that initiates and pays for a project, or his agent

NOTE The Principal will generally specify the technical requirements of a project.

3.1.16
principal mode
only failure mode that shall be permitted in the pressure testing of RTP
3.1.17
product family
group of RTP products having certain similarity characteristics
3.1.18
product-family representative
member of a product family, chosen for full qualification
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ISO/TS 18226:2006(E)
3.1.19
product variability factor

factor, allowing for product variability, applied to the Lower Prediction Limit (LPL) pressure, to give the

Manufacturer's Nominal Pressure Rating (MNPR)
3.1.20
product variant

member of the same product family, to which certain permissible changes have been made

3.1.21
rapid crack propagation

undesirable fracture mode, in which a crack propagates along a pipeline at very high speed

3.1.22
regression analysis

statistical procedure to establish a design rating from pressure test results carried out over a period of 104 h

(or a number of pressure cycles)
3.1.23
safety class
classification associated with a particular probability of failure
3.1.24
stress rupture
static fatigue
failure, as a result of a period under steady stress or pressure
3.1.25
survival test

constant-pressure test, to demonstrate that a product performs at least as well as the qualified product

3.2 Temperature- and pressure-related definitions
3.2.1
design temperature
maximum operating temperature of the RTP system
3.2.2
FAT pressure
Factory Acceptance Test pressure
3.2.3
LPL pressure
pressure obtained by extrapolating the LPL to the design life
3.2.4
long-term hydrostatic pressure
pressure obtained by extrapolating the mean regression curve to the design life
3.2.5
manufacturer's nominal pressure rating

pressure obtained by multiplying the LPL pressure by the product variability factor

3.2.6
maximum service pressure

pressure obtained by multiplying the manufacturer's nominal pressure rating by application-related service

factors
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ISO/TS 18226:2006(E)
3.2.7
maximum operating temperature

maximum temperature to which the piping is expected to be exposed during normal operational activities,

including start-up and shut-down operations, but excluding abnormal situations such as a fire

3.2.8
minimum operating temperature

minimum temperature to which the piping is expected to be exposed during normal operational activities,

including start-up and shut-down operations and controlled blow-out, but excluding abnormal situations such

as piping rupture
3.2.9
qualification test temperature

temperature at which pressure tests are carried out to establish the lower prediction limit

NOTE The design temperature shall not exceed this temperature.
3.2.10
short-term hydrostatic pressure
pressure corresponding to the LPL pressure at a prescribed time of 100 h or less
3.2.11
short-term burst pressure

burst pressure measured in a short-term test, where pressure is increased at a prescribed rate at

Standard Laboratory Temperature (SLT)
3.2.12
standard laboratory temperature
temperature of 23 °C ± 2 °C
3.2.13
survival test pressure
pressure for a 1 000 h survival test
NOTE This is the pressure of the LPL line at 1 000 h.
3.3 Abbreviations
ASTM American Society for Testing and Materials
API American Petroleum Institute
BS British Standard
CEN Comité Européen de Normalisation
COV Coefficient of Variation
DVS German Standard
EN European Standard
ESC Environment-Sensitive Cracking
FAT Factory Acceptance Test
F Regression relationship constant
G Regression line gradient
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ISO/TS 18226:2006(E)
IGE Institution of Gas Engineers
ISO International Standard Organization
LPL Lower Prediction Limit
LTHP Long-Term Hydrostatic Pressure
MNPR Manufacturer's Nominal Pressure Rating
MRS Minimum Required Strength
MSP Maximum Service Pressure
PA11 Polyamide 11 (Trade name Rilsan )
PE Polyethylene
PE-X Cross-linked polyethylene (also referred to as XLPE)
PM Principal Mode of failure
PVDF Polyvinylidene fluoride
PVF Product Variability Factor
QA Quality Assurance
RCP Rapid Crack Propagation
RTP Reinforced Thermoplastic Pipe
SLT Standard Laboratory Temperature
STBP Short-Term Burst Pressure
STHP Short-Term Hydrostatic Pressure
UV Ultraviolet
WIS Water Industry Specification
4 Performance requirements
4.1 Materials
4.1.1 Liner materials

Liner materials shall conform to an appropriate Standard for gas applications (i.e. ISO 4437 and EN 1555 in

the case of polyethylene, and ISO 14531 for PE-X). For polyethylene and PE-X liners, the MRS shall be at

least 8 MPa.

3) Rilsan is an example of a suitable product available commercially. This information is given for the convenience of

users of this document and does not constitute an endorsement by ISO of this product.

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ISO/TS 18226:2006(E)

Other thermoplastics materials (for example, PVDF and PA11) may be used, provided they conform to the

material requirement of a relevant ISO pipe standard and that fitness for the purpose has been established. In

all cases, materials shall be evaluated and classified in accordance with ISO 12162:1995 (see Annex E, E.2).

The liner shall possess RCP resistance at a stress equal to a minimum of 1,5 times the stress induced at the

MSP and minimum operating temperature (see E.3.2).

The liner material shall have adequate resistance to blistering. A suitable procedure is described in

API Spec 17J, Section 6.2.3.2.
4.1.2 Cover materials

Cover materials shall conform to the material requirements of a relevant ISO pipe standard, for example

ISO 4437 or ISO 14531, and fitness for the purpose shall be established.

In the case of pipes that may be exposed to sunlight during storage or service the manufacturer shall

demonstrate that the cover possesses adequate resistance to UV and to UV-transmissions when the

reinforcement is susceptible to UV-damage.
4.1.3 Reinforcements

The manufacturer shall provide the data required to demonstrate the short-term and long-term load-bearing

capability of the reinforcement, as described in Annex A.

The manufacturer shall ensure that the tape supplier operates an effective quality plan relating to all aspects

of tape manufacture. The following characteristics shall be considered in the quality plan: reproducible

strength, dimensional consistency, evenness and reproducibility of cord spacing.
4.2 Pipes and fittings

Each type of RTP pipe body shall be qualified by means of the regression procedure described in Annex E.

The fittings used for these tests may be fittings as used in the field or re-usable test end-fittings. At least one

regression point shall be measured in excess of 10 000 h, with field end-fittings attached to both ends of the

pipe body.

The regression test results shall be used to determine the regression-line gradient, the LTHP and the LPL for

the RTP system, using the statistical procedure described in ISO 9080:2003.

In addition to the regression tests, every field fitting/pipe body combination shall pass an elevated temperature

test, as described in Annex C, to verify the integrity of the fitting/pipe body connection.

The manufacturer shall inform the Principal of any substantial change to the fittings and/or pipe body.

The manufacturer shall prove and guarantee that any change to the field fittings or to the re-usable test

end-fittings does not invalidate the results of qualification tests.

RTP products shall be divided into product families, as described in Annex E. Each product family shall have a

representative named the product-family representative. Other products within the family are termed “product

variants”.

The qualification test temperature shall be greater than or equal to the design temperature.

Other qualification issues are examined in Annex E.
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ISO/TS 18226:2006(E)
4.3 Re-qualification

Re-qualification may be required when any change to the RTP system is made by the manufacturer. The

manufacturer shall inform the Principal if any changes to the previous qualified RTP product family have

occurred.

Depending on the level of change, the following re-qualification options are defined:

⎯ unimportant – previous qualification remains valid;

⎯ minor – (partial) re-qualification will be required in accordance with Annex E;

⎯ major – (full) re-qualification will be required in accordance with Annex E.
The manufacturer and Principal shall agree on the classification of each change.
NOTE Currently, major or minor changes cannot be defined with greater precision.
5 Process and quality control

The manufacturer shall produce a quality plan relating to all aspects of the manufacturing process. The quality

assurance procedure for RTP is described in Annex F. It requires that either batch tests or a hydrotest be

carried out on the product or, where required by the application, both types of test.

6 Dimensions and marking
6.1 Dimensions

The nominal size of the pipe shall be the internal diameter of the liner expressed in millimetres (mm). The

preferred nominal size shall be a multiple of 25 mm, enabling an approximate correspondence to be

maintained with inch sizes.
6.2 Marking

The required information shall be permanently marked on the pipe body, in a colour that contrasts that of the

pipe, the height of the characters being at least 5 mm (10 mm on pipes larger than 150 mm in diameter).

The required markings should be repeated at reasonable intervals to be agreed with the Principal.

The following information shall be given on the RTP pipe body:
⎯ Manufacturer's name or trademark.
⎯ The word, “GAS” or “GAZ”.
⎯ ISO/TS 18226.
⎯ Nominal pipe size in mm.
⎯ Product identification code.
Markings shall be durable and non-damaging.
The Principal may request additional markings if necessary.
7 Handling, storage and installation

The manufacturer shall provide the Principal with written instructions on the handling, storage and installation

requirements of the RTP system.
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ISO/TS 18226:2006(E)
Annex A
(informative)
Description of RTP Products
A.1 General

An RTP ‘system' comprises runs of RTP, along with the fittings required to connect them to each other and to

the other components of a conventional gas transmission system. The essential components of such a system

are

⎯ a thermoplastics liner, the main function of which is to contain the fluid being transmitted,

⎯ an even number of balanced helical windings of continuous reinforcement, to resist the applied pressure

and other loads; these can be applied using a number of possible processes, including helical tape-

wrapping, filament winding and braiding,
⎯ an outer protective thermoplastics cover, and

⎯ a system of fittings to enable runs of RTP to be connected to one another and to other components.

A.2 Liner

The thermoplastics liner may be manufactured in-line with the RTP production process or supplied as a

separate component. It may, on occasion, be necessary to join lengths of liner by butt fusion. When this is

done, it should be carried out according to a recognised standard, for example EN 1555-1, EN 1555-2,

EN 1555-3, EN 1555-4 or EN 1555-5, using butt fusion equipment meeting ISO 12176-1. The procedure

should be documented and a QA system should be in place to ensure that the properties of the joint are equal

to those of the parent pipe.

To fulfil its function of containing the transported fluid, the liner material should have adequate resistance to

degradation from all the components of the fluid. Resistance to degradation includes

⎯ resistance to physical interaction, which may cause leaching, excessive swelling, plasticisation and

consequent loss of properties,
⎯ resistance to chemical attack, and
⎯ resistance to wear and abrasion by suspended solids.

The liner should also possess sufficient ductility to enable it to withstand the strains imposed upon it during

RTP manufacture, storage and deployment (which may involve reeling or axial loads). It should also be able to

resist long-term loads imposed upon it by joints and fittings without excessive creep. Furthermore, it should be

capable of withstanding the strains imposed during pressurisation and, where appropriate, cyclic

pressurisation.

The liner acts as a barrier to limit the diffusion of gas or vapour. The accumulation of gas at the interface

between the liner and the reinforcing layer must not lead to blistering of the cover, or to collapse of the liner, if

the RTP is suddenly depressurised. Certain corrosive gaseous species may also have an undesirable effect

on the reinforcement. In situations where significant diffusion takes place through the liner, the RTP system

may be equipped with a means of venting the gas, for instance at the fitting.
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ISO/TS 18226:2006(E)

The liner does not normally contribute to the strength of an RTP except under rare loading conditions; for

instance, if the RTP is subjected to external pressure.
...