IEC 60794-1-312:2024

Optical fibre cables - Part 1-312: Generic specification - Basic optical cable test procedures - Cable element test methods - Elongation test for buffer tubes at low temperature, Method G11B<br /> ,

IEC 60794-1-312: 2024 describes test procedures to be used in establishing uniform requirements of optical fibre cable elements for the mechanical property – tensile strength and elongation at low temperature. This document applies to optical fibre cables for use with telecommunication equipment and devices employing similar techniques, and to cables having a combination of both optical fibres and electrical conductors. Throughout the document, the wording "optical cable" can also include optical fibre units, microduct fibre units, etc.
This document partially cancels and replaces method G11B of IEC 60794-1-23:2019. This edition includes the following significant technical changes with respect to IEC 60794‑1‑23:2019:
a) alignment of the title with the content of the method.

Câbles à fibres optiques - Partie 1-312: Spécification générique - Procédures fondamentales d’essai des câbles optiques - Méthodes d’essais d'environnement - Essai d’allongement des tubes à basse température, Méthode G11B

IEC 60794-1-312: 2024 décrit les procédures d’essai à utiliser afin d'établir des exigences uniformes applicables aux caractéristiques mécaniques des éléments de câbles à fibres optiques – Résistance à la traction et allongement à basse température. Le présent document s’applique aux câbles à fibres optiques destinés à être utilisés dans les équipements de télécommunications et les dispositifs utilisant des techniques analogues, ainsi qu'aux câbles constitués à la fois de fibres optiques et de conducteurs électriques. Dans tout le document, l'expression "câble optique" peut également inclure des assemblages de fibres optiques, des assemblages de fibres pour microconduits, etc. Ce document annule et remplace partiellement la méthode G11B de l'IEC 60794-1-23:2019. Cette édition inclut les modifications techniques majeures suivantes par rapport à l’IEC 60794‑1‑23:2019:
a) alignement du titre sur le contenu de la méthode.

General Information

• Status: Published
• Publication Date: 30-Jan-2024
• ICS: 33.180.10 - Fibres and cables
• Technical Committee: SC 86A - Fibres and cables
• Current Stage: PPUB - Publication issued
• Start Date: 31-Jan-2024
• Completion Date: 02-Feb-2024

Relations

• Replaces: IEC 60794-1-23:2019 - Optical fibre cables - Part 1-23: Generic specification - Basic optical cable test procedures - Cable element test methods
• Effective Date: 05-Sep-2023

IEC 60794-1-312:2024 - Optical Fibre Cable Testing Standard

Overview

IEC 60794-1-312:2024 is an international standard developed by the International Electrotechnical Commission (IEC) that specifies the basic test procedures for optical fibre cable elements, focusing on the elongation test for buffer tubes at low temperatures (Method G11B). This standard is part of the broader IEC 60794 series, which covers the generic specifications and testing methods applicable to optical fibre cables used primarily in telecommunications and related electronic equipment.

This document updates and partially replaces the previous method G11B outlined in IEC 60794-1-23:2019, aligning the title with the actual content and refining the testing methodology. The standard addresses cables with various configurations, including those combining optical fibres and electrical conductors, and extends to optical fibre units and microduct fibre units.

Key Topics

• Elongation Test Method for Buffer Tubes at Low Temperature:
  This method determines the mechanical property of tensile strength and elongation of buffer tubes within optical fibre cables under low-temperature conditions. The focus on low temperature is critical for ensuring cable performance in harsh environments.

• Sample Preparation and Conditioning:
  Testing requires preparing representative buffer tube samples by removing coverings and any internal fill materials, then cutting open the tube for creating test pieces. Dumb-bell shaped test specimens are preferred for buffer tubes with external diameters exceeding 12.5 mm or sector-shaped cores. For smaller cores, tubular test pieces are used.

• Testing Procedures and Apparatus:
  The standard references complementary IEC test methods for materials and mechanical properties, including IEC 60811-401, IEC 60811-501, and IEC 60811-505, ensuring a robust and consistent testing framework. Elevated temperature conditioning of test specimens ensures reproducible results.

• General Requirements and Reporting:
  Guidelines for selecting samples, performing tests, documenting test results, and specifying test parameters ensure uniformity across manufacturers and testing labs, facilitating reliable product characterization and benchmarking.

Applications

This standard is essential for manufacturers, testing laboratories, and quality assurance teams working with optical fibre cables, especially those designed for use in outdoor environments and telecommunications networks exposed to varied climatic conditions including freezing temperatures. Its practical applications include:

• Telecommunication Network Infrastructure:
  Ensuring that cable elements maintain mechanical integrity and elongation performance under low-temperature stresses to avoid service disruption.

• Cable Design and Development:
  Providing engineers with standardized test methods to validate new cable designs and buffer tube materials against low-temperature elongation requirements.

• Quality Control and Compliance:
  Supporting manufacturers and operators in certifying their optical fibre cables meet international performance criteria, aiding in market access and regulatory compliance.

Related Standards

IEC 60794-1-312:2024 is part of a broader set of standards in the IEC 60794 series governing optical fibre cables. Key related documents include:

• IEC 60794-1-2: Generic specification and general guidance for basic optical cable test procedures.
• IEC 60794-1-23:2019: The previous comprehensive test methods for optical cable elements, now partially replaced by IEC 60794-1-312.
• IEC 60811 Series: Test methods for non-metallic materials used in cable insulation and sheaths, referenced for material aging, mechanical testing, and elongation at low temperatures.

Experts and stakeholders should consider these standards collectively to achieve comprehensive cable testing and quality assurance consistent with international best practices.

---

By adhering to the IEC 60794-1-312:2024 standard, optical fibre cable manufacturers and testers can ensure accurate measurement of buffer tube elongation at low temperature, fostering durable, high-performance cables needed for reliable telecommunication networks worldwide.

Standards Content (Sample)

IEC 60794-1-312 ®
Edition 1.0 2024-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Optical fibre cables –
Part 1-312: Generic specification – Basic optical cable test procedures – Cable
element test methods – Elongation test for buffer tubes at low temperature,
Method G11B,
Câbles à fibres optiques –
Partie 1-312: Spécification générique – Procédures fondamentales d’essai des
câbles optiques – Méthodes d’essais d'environnement – Essai d’allongement
des tubes à basse température, Méthode G11B
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IEC 60794-1-312 ®
Edition 1.0 2024-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Optical fibre cables –
Part 1-312: Generic specification – Basic optical cable test procedures – Cable

element test methods – Elongation test for buffer tubes at low temperature,

Method G11B,
Câbles à fibres optiques –
Partie 1-312: Spécification générique – Procédures fondamentales d’essai des

câbles optiques – Méthodes d’essais d'environnement – Essai d’allongement

des tubes à basse température, Méthode G11B

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.180.10  ISBN 978-2-8322-8133-8

– 2 – IEC 60794-1-312:2024 © IEC 2024
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 General requirements . 7
5 Method G11B: Elongation of buffer tubes at low temperature . 7
5.1 Object . 7
5.2 Sample . 7
5.2.1 General . 7
5.2.2 Preparation and conditioning of test pieces . 7
5.2.3 Determination of cross-sectional area . 11
5.3 Apparatus . 12
5.4 Procedure . 12
5.5 Requirements . 13
5.6 Details to be specified . 13
5.7 Details to be reported . 13
Bibliography . 14

Figure 1 – Dumb-bell test piece . 8
Figure 2 – Small dumb-bell test piece . 9
Figure 3 – Punch end showing groove . 9
Figure 4 – Test pieces cut by grooved punch . 9
Figure 5 – Machine for preparing test pieces . 10

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
OPTICAL FIBRE CABLES –
Part 1-312: Generic specification –
Basic optical cable test procedures – Cable element test methods –
Elongation test for buffer tubes at low temperature, method G11B

FOREWORD
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shall not be held responsible for identifying any or all such patent rights.
IEC 60794-1-312 has been prepared by subcommittee 86A: Fibres and cables, of IEC technical
committee 86: Fibre optics. It is an International Standard.
This document partially cancels and replaces method G11B of IEC 60794-1-23:2019.
This edition includes the following significant technical changes with respect to
IEC 60794-1-23:2019:
• alignment of the title with the content of the method.

– 4 – IEC 60794-1-312:2024 © IEC 2024
The text of this International Standard is based on the following documents:
Draft Report on voting
86A/2395/FDIS 86A/2414/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
A list of all parts in the IEC 60794 series, published under the general title Optical fibre cables,
can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn, or
• revised.
INTRODUCTION
This document contains method G11B of IEC 60794-1-23:2019, which will be withdrawn. The
title of the test method G11B and the content were not in line with each other. In the title micro
tubes are mentioned, but the text stated that the test is intended for buffer tubes circular cross-
section having an external diameter greater than 12,5 mm and for sector-shaped cores large
enough to prepare dumb-bells. In the new title, micro tubes are skipped with respect to
IEC 60794-1-23:2019.
The system for optical fibre test methods have been restructured and renumbered. The optical
cable element test methods contained in IEC 60794-1-23:2019 will now be individually
numbered in the IEC 60794-1-3xx series. Each test method is now considered to be an
individual document rather than part of a multi-test method compendium. Full cross-reference
details are given in IEC 60794-1-2.

– 6 – IEC 60794-1-312:2024 © IEC 2024
OPTICAL FIBRE CABLES –
Part 1-312: Generic specification –
Basic optical cable test procedures – Cable element test methods –
Elongation test for buffer tubes at low temperature, method G11B

1 Scope
This part of IEC 60794 describes test procedures to be used in establishing uniform
requirements of optical fibre cable elements for the mechanical property – tensile strength and
elongation at low temperature.
This document applies to optical fibre cables for use with telecommunication equipment and
devices employing similar techniques, and to cables having a combination of both optical fibres
and electrical conductors.
Throughout the document, the wording "optical cable" can also include optical fibre units,
microduct fibre units, etc.
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.
IEC 60794-1-2, Optical fibre cables – Part 1-2: Generic specification – Basic optical cable test
procedures – General guidance
IEC 60811-401, Electric and optical fibre cables – Test methods for non-metallic materials –
Part 401: Miscellaneous tests – Thermal ageing methods – Ageing in an air oven
IEC 60811-501, Electric and optical fibre cables – Test methods for non-metallic materials –
Part 501: Mechanical tests – Tests for determining the mechanical properties of insulating and
sheathing compounds
IEC 60811-505, Electric and optical fibre cables – Test methods for non-metallic materials –
Part 505: Mechanical tests – Elongation at low temperature for insulations and sheaths
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp

4 General requirements
IEC 60794-1-2 is the reference guide to test methods of all types. It shall be considered for
general requirements and definitions.
5 Method G11B: Elongation of buffer tubes at low temperature
5.1 Object
This test is to determine the elongation of the buffer tubes at low temperature. For this test, the
test method IEC 60811-501, IEC 60811-505 and IEC 60811-401 shall apply.
5.2 Sample
5.2.1 General
Each buffer tube to be tested shall be represented by two samples of suitable length.
5.2.2 Preparation and conditioning of test pieces
After all covering has been removed, the buffer tube shall be cut open in the direction of the
axis, after which the fibre and any filling compound, if any, shall be removed.
Dumb-bell test pieces are intended for buffer tubes circular cross-section having an external
diameter greater than 12,5 mm and for sector-shaped cores large enough to prepare dumb-
bells. Where it is not possible to prepare dumb-bells, the tubular test pieces as described below
are suitable for testing the performance of cores of smaller diameter.
a) Conditioning of test pieces
1) Elevated temperature conditioning
NOTE 1 Elevated temperature conditioning is not an ageing treatment. It is used as a means of ensuring
stable and consistent test pieces when required. It is used a) when called for in the relevant cable standard,
or b) if there is a doubt or disagreement about a result and the test needs to be repeated. In either case,
the conditioning applies only to the test piece as taken from the cable before any subsequent treatment
(ageing, compatibility test, oil immersion, etc.).
Where conditioning at elevated temperature is used, such conditioning shall be carried
out as follows:
– for dumb-bells:
i) after the removal of the buffer tube from the cable but before the cutting of strips;
ii) after grinding (or cutting) to obtain parallel surfaces. Where grinding (or cutting)
is not needed, the conditioning shall be performed at the point in the test protocol
according to i);
– for tubular test pieces: after removal of the fibre, and any filling compound, but before
applying the reference marks, if any, for measurement of the extension.
Where the relevant cable standard calls for conditioning at elevated temperature, it shall
be for the time and temperature given in that standard. Where, in case of doubt, the test
has to be repeated, the conditioning shall be 24 h at 70 °C ± 2 °C, or a lower temperature
corresponding to the maximum operating temperature of the cable.
2) Room temperature conditioning
Before determination of the cross-sectional area, all test pieces shall be protected from
direct sunlight and maintained for at least 3 h at a temperature of 23 °C ± 5 °C.

– 8 – IEC 60794-1-312:2024 © IEC 2024
b) Dumb-bell test pieces
Dumb-bell test pieces shall be used whenever possible. They shall be prepared from
samples of buffer tube, cut open in the direction of the axis.
Each sample of buffer tube shall be cut into strips of an appropriate length. The strips shall
be marked to identify the sample from which they are cut and their positions relative to each
other in the original sample.
The strips of buffer tube shall be ground or cut, so as to obtain two parallel smooth surfaces
between the reference marks mentioned below, care being taken to avoid undue heating.
An example of a cutting machine is given in 5.3. For polyethylene (PE) and polypropylene
(PP) buffer tube, cutting only, not grinding, shall be employed. After cutting or grinding,
including any removal of burrs, the thickness of the strips shall not be less than 0,8 mm and
not more than 2,0 mm. If it is not possible to prepare dumb-bell test pieces that comply with
the minimum thickness of 0,8 mm, then tubular test pieces shall be used. If tubular test
pieces cannot be prepared, then dumb-bells thinner than 0,8 mm may be used, but the rate
of separation shall be 25 mm/min.
The test report should also include the fact that non-compliant dumb-bells were used and
that the result is indicative.
A dumb-bell test piece, in accordance with Figure 1 or Figure 2, shall then be punched from
each prepared strip of buffer tube, or if possible, two dumb-bell test pieces shall be punched
side by side.
Dimension in millimeters
Key
1 reference marks
Figure 1 – Dumb-bell test piece
In order to improve the reliability of the results, the following is recommended:
– the punch should be very sharp to minimize imperfections in the test piece;
– a cardboard or other suitable support should be placed between the strip and the base
plate; this support shall be marked during punching, but not completely cut through by
the punch;
– burrs on the sides of the test piece should be avoided.
For materials where punching results in burrs, the following method may be used:
1) each end of the punch shall have a groove approximately 2,5 mm wide and 2,5 mm high
(see Figure 3);
2) the cut dumb-bell test pieces shall remain attached at both ends with the strip previously
prepared according to the requirements of 5.2.2 b) (see Figure 4);
3) with the machine given in 5.3, an additional 0,10 mm to 0,15 mm thickness can be cut
away to remove possible burrs resulting from the dumb-bell punch; when this operation
is completed, the dumb-bell test pieces shall be cut through at their ends in order to
remove them from the strip.
When the diameter of the core is too small to allow the dumb-bell to be cut in accordance
with Figure 1, then a smaller dumb bell test piece in accordance with Figure 2 shall be
punched from each prepared strip.

Dimension in millimeters
Key
1 reference marks
Figure 2 – Small dumb-bell test piece
Dimension in millimeters
Figure 3 – Punch end showing groove

Figure 4 – Test pieces cut by grooved punch
The central 20 mm for the larger dumb-bells or 10 mm for the smaller dumb-bells shall be
marked on each test piece, immediately before the tensile test.
NOTE 2 Where a contact extensometer is used, the pre set grips at the required spacing are deemed to
constitute a mark.
Dumb-bell test pieces with incomplete ends are permitted, provided that the breaking point
occurs between the reference marks.
An example of a cutting machine is given in Figure 5.

– 10 – IEC 60794-1-312:2024 © IEC 2024

Key
1 steel roll, partly grooved 4 blade, fixed or moving
2 steel roll, rubber-tyred 5 part of strip used for test piece
3 strip 6 rejected part of strip

Figure 5 – Machine for preparing test pieces
Two rolls, one made of steel and partly grooved (1), and the other, in rubber-tyred steel (2),
drive the strip (3) against a highly sharpened fixed, or moving blade (4) (surgical scalpel
quality).
The strip is longitudinally cut into two parts: part (5) from which the test piece is cut, and part
(6), which is rejected.
The thickness of part (6) can be limited to 0,1 mm if necessary. For this purpose, consideration
should be given to the behaviour of the material prepared and the preservation of the blade
sharpness.
When the strip (3) has marks of tearing or scratching, which may induce a premature break, it
is recommended that part (6) be cut and rejected from both sides.
c) Tubular test pieces
Tubular test pieces shall be used only when the dimensions of the buffer tube are such that
it is not possible to prepare dumb-bell test pieces.
The samples of buffer tube shall be cut into pieces approximately 100 mm long and the fibre
and any filling compound removed, ensuring the buffer tube is not damaged. The tubes shall
be marked to identify the sample from which they were prepared and their relative positions
in the sample.
The central 20 mm shall be marked immediately before the tensile test.
NOTE 3 Where a contact extensometer is used, the pre set grips at the required spacing are deemed to
constitute a mark.
d) Sequence of determination of cross-sectional area and ageing

The buffer tube need not be ground or cut if the inner and outer surfaces are smooth, and its
mean specified thickness does not exceed 2,0 mm. Samples having a thickness exceeding this
limit, or samples having imprints or ridges on the inner side, shall be ground or cut to obtain
two parallel and smooth surfaces, and a thickness which does not exceed 2,0 mm. The minimum
thickness after grinding or cutting shall be 0,8 mm but if the original thickness of the buffer tube
does not allow it, then 0,6 mm shall be permitted as the minimum thickness. Grinding and
cutting shall be carefully carried out to avoid undue heating and mechanical stresses in the
buffer tube.
All strips shall be conditioned at 23 °C ± 5 °C for at least 3 h.
After this preparation, two dumb-bells from each sample in accordance with Figure 1, or if
necessary Figure 2, shall be punched in the direction of the axis of each sample; if possible,
two dumb-bells shall be punched side by side.
If an apparatus is used which allows the direct measurement of the distance between the marker
lines during the test, the dumb-bells shall be marked in accordance with 5.2.2.
5.2.3 Determination of cross-sectional area
a) Dumb-bell test piece
The cross-sectional area of each test piece is the product of the common width and the
measured individual minimum thickness which shall be determined as follows.
For the width:
– the common width is the minimum width of three, randomly selected test pieces;
– if there is doubt about the uniformity of the width, this shall be measured at three positions
on the top and the bottom side of the three test pieces. The mean of the top and bottom
side measurements shall be calculated for each position. The common width shall be the
minimum of the nine mean values determined on the test pieces;
– in the case of further doubt, the width is measured on each individual test piece.
For the thickness, the thickness of each test piece is the minimum of three thickness
measurements carried out in the area to be stretched.
The measurements shall be carried out by an optical instrument or by a dial gauge giving a
contact pressure not exceeding 0,07 N/mm .
The instrument shall be capable of measuring the thickness with an error of not more than
0,01 mm and the width with an error of not more than 0,04 mm.
In case of doubt, where technically possible, an optical instrument shall be used.
Alternatively, a dial gauge with a maximum contact pressure of 0,02 N/mm may be used.
An appropriate curved foot of the dial gauge should be used if the central part of the dumb-
bell is still curved.
b) Tubular test piece
In the middle of the sample being used to prepare the test pieces, a piece shall be taken to
determine the cross-sectional area, A, in square millimetres, of the test piece, using one of
the following methods. In case of doubt, the methods 2) and 3) shall be used.
1) From the dimensions, using the formula:
A π()D−δδ
(1)
where
δ is the mean value of the thickness of the buffer tube, in millimetres, rounded off to two
decimal places;
D is the mean value of the outer diameter of the test piece, in millimetres, rounded off
to two decimal places.
=
– 12 – IEC 60794-1-312:2024 © IEC 2024
2) From the density, the mass and the length, using the formula:
1000× m
A=
(2)
dl×
where
m is the mass of the test piece, in grams, to three decimal places;
d is the density, in grams per cubic centimetre, to three decimal places;
l is the length, in millimetres, to one decimal place.
3) From the volume and the length, the volume being determined by means of immersion
in, for example ethyl alcohol, using the formula:
V
A= (3)
l
where
V is the volume, in cubic millimetres, to two decimal places;
l is the length, in millimetres, to one decimal place.
Ensure there are no air bubbles in or on the surface of the test piece during immersion.
5.3 Apparatus
The test may be carried out on a machine provided with a cooling device or on a machine
installed in a cooling chamber.
Using a liquid as the refrigerant, the conditioning time shall be not less than 10 min at the
specified test temperature.
When cooling in air, the conditioning time for cooling the apparatus and test piece together shall
be at least 4 h. If the apparatus has been pre-cooled, this period may be reduced to 2 h, and if
the apparatus and test piece have been pre-cooled, the conditioning time after the test piece
has been fixed in the apparatus shall be not less than 1 h.
If a liquid mixture is used for cooling, it shall not impair the buffer tube.
5.4 Procedure
The grips of the tensile apparatus shall be of a non-self-tightening type. In both pre-cooled
grips, the dumb-bell shall be clamped over the same length.
The free length between the grips shall be about 30 mm for both types of dumb-bells if the
direct measurement of the distance between the marker lines is to be made during the test.
If the displacement of the grips is to be measured, the free length between the grips shall be
30 mm ± 0,5 mm for the dumb-bell in accordance with Figure 1, and 22 mm ± 0,5 mm for the
dumb-bell in accordance with Figure 2.
The speed of separation of the grips of the tensile machine shall be 25 mm/min ± 5 mm/min.
The test temperature shall be as specified in the relevant specification.

The elongation shall be determined by measuring the distance between the marker lines, if
possible, or between the grips at the moment of the rupture.
For calculating the elongation, the increase of the distance between the marker lines shall be
related to the initial distance of 20 mm (or 10 mm if the dumb-bell in accordance with Figure 2
is used), and expressed as a percentage of this distance.
If the alternative method of measuring the distance between the grips is used, the increase of
this distance shall be related to the original distance, being 30 mm for the dumb-bell in
accordance with Figure 1, and 22 mm for the dumb-bell in accordance with Figure
...