Buried, high-impact poly(vinyl chloride) (PVC-HI) piping systems for the supply of gaseous fuels

ISO 6993-1:2006 specifies the requirements for pipes made of high-impact poly(vinyl chloride) (PVC-HI) intended to be used for the supply of gaseous fuels through buried pipelines having an operating temperature range of 0 degrees Celsius up to and including +30 degrees Celsius and a maximum operating pressure of 1 bar (100 kPa). It is applicable only to pipes manufactured from the high-impact PVC materials PVC-A, PVC-CPE and PVC-EPR. The pipes are suitable for those gases not containing potentially damaging components in such concentrations as to impair the properties of the pipe material.

Systèmes de canalisations enterrées en poly(chlorure de vinyle) à résistance au choc améliorée (PVC-HI) pour réseaux de combustibles gazeux

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Status
Published
Publication Date
13-Jun-2006
Current Stage
9060 - Close of review
Start Date
04-Jun-2020
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INTERNATIONAL ISO
STANDARD 6993-1
First edition
2006-06-01
Buried, high-impact poly(vinyl chloride)
(PVC-HI) piping systems for the supply of
gaseous fuels —
Part 1:
Pipes for a maximum operating pressure
of 1 bar (100 kPa)
Systèmes de canalisations enterrées en poly(chlorure de vinyle) à
résistance au choc améliorée (PVC-HI) pour réseaux de combustibles
gazeux —
Partie 1: Tubes pour une pression maximale de service de 1 bar
(100 kPa)
Reference number
ISO 6993-1:2006(E)
ISO 2006
---------------------- Page: 1 ----------------------
ISO 6993-1:2006(E)
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ii © ISO 2006 – All rights reserved
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ISO 6993-1:2006(E)
Contents Page

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

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

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

3 Terms and definitions........................................................................................................................... 2

4 Symbols and abbreviated terms ......................................................................................................... 4

5 Material .................................................................................................................................................. 5

6 General characteristics ........................................................................................................................ 6

7 Geometrical characteristics................................................................................................................. 6

8 Physical characteristics....................................................................................................................... 8

9 Mechanical characteristics .................................................................................................................. 8

10 General requirements for pipes .......................................................................................................... 9

11 Test methods....................................................................................................................................... 10

12 Marking ................................................................................................................................................ 11

Annex A (normative) Determination of resistance to gas constituents ..................................................... 12

Annex B (normative) Determination of resistance of pipes to external blows.......................................... 16

Bibliography ..................................................................................................................................................... 17

© ISO 2006 – All rights reserved iii
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ISO 6993-1:2006(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies

(ISO member bodies). The work of preparing International Standards is normally carried out through ISO

technical committees. Each member body interested in a subject for which a technical committee has been

established has the right to be represented on that committee. International organizations, governmental and

non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the

International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.

The main task of technical committees is to prepare International Standards. Draft International Standards

adopted by the technical committees are circulated to the member bodies for voting. Publication as an

International Standard requires approval by at least 75 % of the member bodies casting a vote.

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent

rights. ISO shall not be held responsible for identifying any or all such patent rights.

ISO 6993-1 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 first edition of ISO 6993-1, together with ISO 6993-2, ISO 6993-3 and ISO 6993-4, cancels and replaces

ISO 6993:2001, of which it constitutes a technical revision.

ISO 6993 consists of the following parts, under the general title Buried, high-impact poly(vinyl chloride)

(PVC-HI) piping systems for the supply of gaseous fuels:
⎯ Part 1: Pipes for a maximum operating pressure of 1 bar (100 kPa)
⎯ Part 2: Fittings for a maximum operating pressure of 200 mbar (20 kPa)

⎯ Part 3: Fittings and saddles for a maximum operating pressure of 1 bar (100 kPa)

⎯ Part 4: Code of practice for design, handling and installation
iv © ISO 2006 – All rights reserved
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INTERNATIONAL STANDARD ISO 6993-1:2006(E)
Buried, high-impact poly(vinyl chloride) (PVC-HI) piping
systems for the supply of gaseous fuels —
Part 1:
Pipes for a maximum operating pressure of 1 bar (100 kPa)
1 Scope

This part of ISO 6993 specifies the requirements for pipes made of high-impact poly(vinyl chloride) (PVC-HI)

intended to be used for the supply of gaseous fuels through buried pipelines having an operating temperature

1)

range of 0 °C up to and including +30 °C and a maximum operating pressure of 1 bar (100 kPa) .

It is applicable only to pipes manufactured from the high-impact PVC materials PVC-A, PVC-CPE and

PVC-EPR. The pipes are suitable for those gases not containing potentially damaging components in such

concentrations as to impair the properties of the pipe material.
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 1167-1:2006, Thermoplastics pipes, fittings and assemblies for the conveyance of fluids — Determination

of the resistance to internal pressure — Part 1: General method

ISO 2505:2005, Thermoplastics pipes — Longitudinal reversion — Test method and parameters

ISO 2507-1, Thermoplastics pipes and fittings — Vicat softening temperature — Part 1: General test method

ISO 2507-2, Thermoplastics pipes and fittings — Vicat softening temperature — Part 2: Test conditions for

unplasticized poly(vinyl chloride) (PVC-U) or chlorinated poly(vinyl chloride) (PVC-C) pipes and fittings and for

high impact resistance poly(vinyl chloride) (PVC-HI) pipes

ISO 3126, Plastics piping systems — Plastics components — Determination of dimensions

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

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

thermoplastics materials in pipe form by extrapolation

ISO 9852, Unplasticized poly(vinyl chloride) (PVC-U) pipes — Dichloromethane resistance at specified

temperature (DCMT) — Test method
ISO 9969, Thermoplastics pipes — Determination of ring stiffness
5 2
1) 1 bar = 0,1 MPa = 10 Pa; 1 MPa = 1 N/mm
© ISO 2006 – All rights reserved 1
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ISO 6993-1:2006(E)

ISO 16871, Plastics piping and ducting systems — Plastics pipes and fittings — Method for exposure to direct

(natural) weathering

EN 922:1994, Plastics piping and ducting systems — Pipes and fittings of unplasticized poly(vinyl chloride)

(PVC-U) — Specimen preparation for determination of the viscosity number and calculation of the K-value

3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1 Geometrical definitions
3.1.1
nominal outside diameter

numerical designation of size which is common to all components in a thermoplastics piping system other than

flanges and components designated by thread size
NOTE 1 It is a convenient round number for reference purposes.

NOTE 2 For metric pipes conforming to ISO 161-1, the nominal outside diameter, expressed in millimetres, is the

minimum mean outside diameter d .
em, min
3.1.2
mean outside diameter

measured length of the outer circumference of the pipe divided by π, rounded up to the nearest 0,1 mm

NOTE The value for π is taken to be 3,142.
3.1.3
minimum outside diameter
e,min
minimum value of the mean outside diameter
NOTE It is equal to the nominal outside diameter d , expressed in millimetres.
3.1.4
maximum outside diameter
e,max
maximum value of the mean outside diameter
3.1.5
outside diameter at any point

measured outside diameter through the cross-section at any point of the pipe, rounded up to the nearest

0,1 mm
3.1.6
out-of-roundness

difference between the measured maximum outside diameter and the measured minimum outside diameter in

the same cross-sectional plane of the pipe
3.1.7
nominal wall thickness

wall thickness, in millimetres, tabulated in ISO 4065, corresponding to the minimum wall thickness, e , at

min
any point
2 © ISO 2006 – All rights reserved
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ISO 6993-1:2006(E)
3.1.8
mean wall thickness

arithmetic mean of at least four measurements regularly spaced around the same cross-sectional plane of the

pipe, including the measured minimum and maximum values obtained, rounded up to the nearest 0,1 mm

3.1.9
wall thickness at any point

measured wall thickness at any point around the circumference of the pipe, rounded up to the nearest 0,1 mm.

3.1.10
standard dimension ratio
SDR

numerical designation of a pipe series, which is approximately equal to the ratio of the nominal outside

diameter d to the nominal wall thickness e :
n n
SDR=
NOTE It is a convenient round number for reference purposes.
3.2 Material definitions
3.2.1
high-impact poly(vinyl chloride)
PVC-HI
mixture of unplasticized PVC and an impact-resistance modifier
3.2.2
lower confidence limit of the predicted hydrostatic strength
LPL

quantity with the dimensions of stress, which represents the 97,5 % lower confidence limit of the predicted

hydrostatic strength for a single value at a temperature T and a time t
NOTE It is denoted as σ = σ .
LPL (T, t, 0,975)
3.2.3
minimum required strength
MRS

value of σ , at a temperature of 20 °C and a time 50 years, σ , rounded down to the next

LPL (20, 50 years, 0,975)

smaller value of the R 10 series or of the R 20 series conforming to ISO 3 and ISO 497, depending on the

value of σ
LPL
3.2.4
overall service [design] coefficient

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 other than those represented in the σ

LPL
3.3 Definitions related to service conditions
3.3.1
natural gas

gaseous fuel containing a mixture of hydrocarbons, primarily methane, but generally also including ethane,

propane and higher hydrocarbons in much smaller amounts, as well as some inert gases such as nitrogen

and carbon dioxide, plus minor amounts of trace constituents

NOTE Natural gas remains in the gaseous state under the temperature and pressure conditions normally found in

service.
© ISO 2006 – All rights reserved 3
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ISO 6993-1:2006(E)
3.3.2
pressure
overpressure relative to atmospheric pressure
3.3.3
maximum operating pressure
MOP

maximum effective pressure of the gas in a piping system, expressed in bars, which is allowed in continuous

use

NOTE 1 It takes into account the physical and the mechanical characteristics of the components of the piping system.

NOTE 2 MOP is given by the equation:
20× MRS
MOP=
C×−(SDR 1)
4 Symbols and abbreviated terms
4.1 Symbols
C overall service (design) coefficient
d outside diameter at any point
d maximum outside diameter
e,max
d mean outside diameter
d minimum outside diameter
e,min
d nominal outside diameter
e nominal wall thickness
e wall thickness at any point
e maximum wall thickness
max
e mean wall thickness
e minimum wall thickness
min
σ hoop stress
σ lower confidence limit
LPL
4 © ISO 2006 – All rights reserved
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ISO 6993-1:2006(E)
4.2 Abbreviated terms
PVC-A acrylate modified PVC
PVC-CPE chlorinated polyethylene modified PVC
PVC-EPR ethylene propylene rubber modified PVC
MOP maximum operating pressure
MRS minimum required strength
PVC-HI high-impact PVC
PVC-U unplasticized PVC
SDR standard dimension ratio
STIS specific tangential initial stiffness
THT tetrahydrothiophene
5 Material
5.1 Composition

The pipes shall be made of high-impact PVC, to which only such additives are added that are necessary to

facilitate conformity of the components to this part of ISO 6993.
The impact-resistant modified PVC shall be one of the following compositions:
a) a mixture based on PVC;
b) a blend based on PVC;
c) a copolymer based on PVC;
d) a combination of these types.

The proportion of the impact modifier in the composition shall be at least 7 % by mass.

5.2 Long-term strength

The MRS value of the extrusion material shall be at least 18 MPa. Conformity to this requirement shall be

proven using a long-term evaluation in accordance with ISO 9080. Testing shall be carried out at 20 °C, 40 °C

and 60 °C, for periods up to 9 000 h. At 60 °C no knee shall occur before 5 000 h.

This test shall be carried out on test pieces in the form of a solid wall extruded pipe made from the relevant

extrusion material.

NOTE The MRS evaluation is used for a material qualification and is not intended to be used for a pressure rating.

5.3 Vicat softening temperature

The Vicat softening temperature of the extrusion material shall be not less than 76 °C when determined in

accordance with ISO 2507-1 and ISO 2507-2.
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ISO 6993-1:2006(E)
5.4 K-value

The K-value of the unplasticized polyvinyl chloride (PVC-U) resin in the extrusion material shall exceed 65,

when measured in accordance with EN 922.
5.5 UV stability

Test samples of the extrusion material in the form of a pipe of d 63 shall be exposed to weathering in

accordance with 11.1 and 11.3. After exposure, the impact resistance of the weathered side shall be

determined in accordance with Annex B, using a falling weight of (750
...

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