IEC 60811-508:2012

IEC 60811-508 ®
Edition 1.0 2012-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electric and optical fibre cables – Test methods for non-metallic materials –
Part 508: Mechanical tests – Pressure test at high temperature for insulation
and sheaths
Câbles électriques et à fibres optiques – Méthodes d’essai pour les matériaux
non-métalliques –
Partie 508: Essais mécaniques – Essai de pression à température élevée pour
les enveloppes isolantes et les gaines

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IEC 60811-508 ®
Edition 1.0 2012-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electric and optical fibre cables – Test methods for non-metallic materials –

Part 508: Mechanical tests – Pressure test at high temperature for insulation

and sheaths
Câbles électriques et à fibres optiques – Méthodes d’essai pour les matériaux

non-métalliques –
Partie 508: Essais mécaniques – Essai de pression à température élevée pour

les enveloppes isolantes et les gaines

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX R
ICS 29.035.01; 29.060.20 ISBN 978-2-88912-984-3

– 2 – 60811-508  IEC:2012
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Test method . 6
4.1 General . 6
4.2 Apparatus . 6
4.2.1 Air oven . 6
4.2.2 Indentation device . 7
4.3 Insulation . 7
4.3.1 Sample and test piece preparation . 7
4.3.2 Procedure . 7
4.4 Sheath . 9
4.4.1 Sample and test piece preparation for sheaths . 9
4.4.2 Procedure . 10
5 Test report. 11
Annex A (normative) Calculation of the compressing force . 15
Annex B (informative) Recommended performance requirement . 17
Bibliography . 18

Figure 1 – Indentation device . 12
Figure 2 – Measurement of indentation . 12
Figure 3 – Measurement of indentation for small test pieces . 13
Figure 4 – Flat cable with a flat smaller side . 13
Figure 5 – Indentation device for flat cables with a flat smaller side . 14

Table A.1 – General value for k . 15

60811-508  IEC:2012 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTRIC AND OPTICAL FIBRE CABLES –
TEST METHODS FOR NON-METALLIC MATERIALS –

Part 508: Mechanical tests –
Pressure test at high temperature for insulation and sheaths

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
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2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
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6) All users should ensure that they have the latest edition of this publication.
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60811-508 has been prepared by IEC technical committee 20:
Electric cables.
This Part 508 of IEC 60811 cancels and replaces Clause 8 of IEC 60811-3-1:1985, which is
withdrawn. Full details of the replacements are shown in Annex A of IEC 60811-100:2012.
Significant technical changes with respect to the previous edition are as follows:
– re-statement of oven characteristics, especially relating to anti-vibration and to
temperature control;
– enhanced detail as to the preparations and testing of flat cables;
– enhanced detail as to thickness and dimensional measurements.
See also the Foreword to IEC 60811-100:2012.

– 4 – 60811-508  IEC:2012
The text of this standard is based on the following documents:
FDIS Report on voting
20/1304/FDIS 20/1353/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
This part of IEC 60811 shall be used in conjunction with IEC 60811-100.
A list of all the parts in the IEC 60811 series, published under the general title Electric and
optical fibre cables – Test methods for non-metallic materials, can be found on the IEC
website.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
60811-508  IEC:2012 – 5 –
INTRODUCTION
The IEC 60811 series specifies the test methods to be used for testing non-metallic materials
of all types of cables. These test methods are intended to be referenced in standards for
cable construction and for cable materials.
NOTE 1 Non-metallic materials are typically used for insulating, sheathing, bedding, filling or taping within cables.
NOTE 2 These test methods are accepted as basic and fundamental and have been developed and used over
many years principally for the materials in all energy cables. They have also been widely accepted and used for
other cables, in particular optical fibre cables, communication and control cables and cables for ships and offshore
applications.
– 6 – 60811-508  IEC:2012
ELECTRIC AND OPTICAL FIBRE CABLES –
TEST METHODS FOR NON-METALLIC MATERIALS –

Part 508: Mechanical tests –
Pressure test at high temperature for insulation and sheaths

1 Scope
This Part 508 of IEC 60811 gives the procedure for a pressure test at high temperature, which
typically applies to thermoplastic compounds used for insulating and sheathing materials.
NOTE 1 The method is principally intended for thermoplastic materials, but may be used for cross-linked
materials when specifically required by the relevant cable standard.
NOTE 2 The test method is not recommended for thicknesses below 0,7 mm.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60811-100:2012, Electric and optical fibre cables – Test methods for non-metallic
materials –Part 100: General
IEC 60811-201, Electric and optical fibre cables – Test methods for non-metallic materials –

Part 201: General tests – Measurement of insulation thickness
IEC 60811-202, Electric and optical fibre cables – Test methods for non-metallic materials –

Part 202: General tests – Measurement of thickness of non-metallic sheaths
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60811-100 apply.
4 Test method
4.1 General
This part of IEC 60811 shall be used in conjunction with IEC 60811-100.
This standard gives the method for the pressure test at high temperature which applies to
insulation and sheathing compounds.
All the tests shall be carried out not less than 16 h after the extrusion of the insulating or
sheathing compounds.
4.2 Apparatus
4.2.1 Air oven
The test shall be carried out in an oven. The oven shall use natural air circulation.

60811-508  IEC:2012 – 7 –
NOTE 1 Forced or continuous air circulation is not required. Ovens fitted with air stirring mechanisms are likely to
cause vibration.
The oven shall not incorporate any equipment likely to cause vibration, nor shall it include
exposed heating elements. The temperature of the air shall be maintained continuously at the
value specified in the relevant cable standard. The oven shall be capable of operating to
within ±2 K of the specified test temperature.
NOTE 2 The need for a temperature control to ±2 K is crucial. This is especially so if the material under test is a
thermoplastic with a sharp melting point (such as some ethylene polymers) as a small temperature rise above that
specified can result in a large increase in indentation.
In operation, the oven shall be located in a position free from vibration.
4.2.2 Indentation device
A device according to Figure 1 shall be used. It shall consist of a rectangular blade with an
edge (0,70 ±0,01) mm wide which can be pressed against the test piece under the influence
of an applied force.
4.3 Insulation
4.3.1 Sample and test piece preparation
For each core to be tested, three adjacent pieces shall be taken from a sample having a
length of 250 mm to 500 mm. The length of each piece shall be 50 mm to 100 mm.
From each core piece taken, any covering – including the semi-conducting layer, if any – shall
be removed mechanically. According to the type of cable, the test piece may have a circular,
flat or sector-shaped cross-section of length (45 ± 5) mm.
The cores of twin- and multiple-grouped-core flat cables without sheath shall not be separated
individually, except if the individual conductor cross-section is ≥ 10 mm . If so, a test piece
taken from the insulation of an individual core shall be tested.
The minimum thickness of insulation to be tested shall be 0,7 mm.
NOTE Insulation thickness down to 0,4 mm may be tested under certain circumstances, but it is not
recommended. If tests are made with samples having a thickness below 0,7 mm, it should be recorded as such in
the test report.
4.3.2 Procedure
4.3.2.1 Fixing of test pieces
The final test piece shall consist of a piece of the sample from 4.3.1.
Circular cores shall be mounted in the position shown in Figure 1 (3a).
A flat cable without sheath shall be laid on its flat/major axis side.
Sector-shaped cores shall be mounted on a support of an appropriate type as shown in
Figure 1 (3b and 3c).
All test pieces shall be fixed to the support in such a manner that they do not change position
during the test. Special care shall be taken with test pieces so that they do not curve under
the pressure of the blade.
– 8 – 60811-508  IEC:2012
4.3.2.2 Application of force
A force calculated according to Annex A shall be applied in a direction perpendicular to the
axis of the core.
The blade shall also be perpendicular to the relevant axis.
4.3.2.3 Protocol in air oven
The loaded blade shall be placed onto the fixed test piece at ambient temperature. The whole
assembly shall then be placed in the air oven which is at the specified test temperature.
The apparatus, with loaded test pieces, shall be placed in a position free from vibration (see
4.2.1).
The temperature of the air shall be maintained continuously at the value specified in the
relevant cable standard. In case of dispute, the temperature shall be checked by means of a
suitable temperature-measuring device, mounted at the same level as the test piece and as
close as possible to one of the test pieces and the temperature shall be continuously
monitored during the test.
NOTE 1 It is critical to ensure that the temperature does not, at any time, exceed the upper limit specified for
testing the particular material. Temperatures below the lower limit specified may be experienced briefly
immediately after starting the test. Such short periods may be ignored.
The assembly shall be kept in the test position for the time specified in the relevant cable
standard, or, if the time is not specified in the cable standard, for the following times:
– 4 h for test pieces having a value of D ≤ 15 mm
– 6 h for test pieces having a value of D > 15 mm.
NOTE 2 Details for the determination of D are found in Annex A.
4.3.2.4 Cooling
At the end of the specified duration, the test piece shall be rapidly cooled under load. This
operation may be carried out inside or outside the air oven by spraying the test piece with
cold water on the spot where the blade is pressing.
The test piece shall be removed from the apparatus when it has cooled to a temperature
where recovery of the insulation no longer occurs; the test piece shall then be cooled further
by immersion in cold water.
4.3.2.5 Measurement
Immediately after cooling, the test piece shall be prepared for determining the depth of
indentation.
The conductor shall be withdrawn, leaving the test piece in the form of a tube.
A narrow strip shall be cut from the test piece in the direction of the axis of the core,
perpendicular to the indentation as shown in Figure 2.
The strip shall be laid flat under a measuring microscope or a measuring projector and the
cross-wire shall be adjusted to the bottom of the indentation and the outside of the test piece
as shown in the same figure.
Small test pieces, up to about 6 mm external diameter, shall be cut transversely at and
adjacent to the indentation, as shown in Figure 3, and the depth of the indentation shall be

60811-508  IEC:2012 – 9 –
determined as the difference between the microscope measurements on sectional views 1
and 2 as shown in the same figure.
All measurements shall be made in millimetres to two decimal places.
NOTE Care should be taken when making the measurement, as factors such as thermomechanical forces may
have distorted the upper surface of the sample, giving a false position for the top of indentation, and the true
indentation may differ from that measured directly at the point of indentation. It is therefore essential to use the
thickness value measured before applying the indenter as the baseline figure. If it is evident that distortion has
taken place, or in the case of any uncertainty about the result, a suitable correction to the value of indentation
should be made, thus:
– if the original thickness is δ, but after the test the apparent thickness has becomeδ1 , then for the purposes of
the calculation, the measured indentation (call it M) needs to be corrected by deducting an amount equal to
δ1 – δ ;
– the correct indentation percentage then becomes
M− (δ1−δ )
×100
δ
4.3.2.6 Expression of the results
The indentation values, measured on the three test pieces taken from each core or strip, shall
be calculated as a percentage of the insulation thickness (as measured in accordance with
Annex A). The median of the three values shall be recorded. If there are changes in thickness
due to the test, the formula in the NOTE in 4.3.2.5 should be used.
For flat cables, the median indentation value is the mean value of the indentation values from
all the cores of the same size in the sample.
NOTE In the absence of any requirement in the relevant cable standard, a recommendation is given in Annex B.
4.4 Sheath
4.4.1 Sample and test piece preparation for sheaths
For each sheath to be tested, three adjacent pieces shall be taken from a sample having a
length of 250 mm to 500 mm from which the covering (if any) and all the internal parts (cores,
fillers, inner covering, armour etc. if any) have been removed.
The length of each piece of sheathing shall be 50 mm to 100 mm.
From each piece of sheathing, a strip of width equal to about one-third of the perimeter, but
not more than 20 mm, shall be cut parallel to the direction of the axis of the cable if the
sheath does not have ridges.
If the sheath shows ridges caused by five or fewer cores, the strip shall be cut in the direction
of the ridges so that it contains at least one groove which lies approximately in the middle of
the strip throughout its length.
If the sheath has ridges caused by more than five cores, the strip shall be cut in the same
manner and these ridges shall be removed by grinding.
NOTE 1 A machine of the type specified in Annex A of IEC 60811-501:2012 has been found suitable for grinding
or cutting the ridges.
If the sheath is directly applied on a concentric conductor, an armour or on a metallic screen,
and therefore has ridges which cannot be ground or cut away (unless the diameter is large),
the sheath shall not be removed, and the whole cable piece shall be used as a test piece.

– 10 – 60811-508  IEC:2012
If the smaller sides of a flat cable are fully rounded in shape, this test shall be carried out on
one of the smaller sides. To calculate the compressing force (see Annex A), D is the minor
dimension of the cable and δ is the mean sheath thickness e as shown in Figure 4.
If the smaller sides are flat, or nearly flat, as depicted in Figure 4, a test piece shall be
prepared by cutting a strip from the wide side of the cable in the direction of the axis of the
cable. On the inner side, only the ridges shall be removed by grinding or cutting. The width of
the strip to be tested shall be at least 10 mm but not more than 20 mm. The thickness of the
strip shall be measured at the place where the compressing force, F, is applied.
NOTE 2 Insulation thickness down to 0,4 mm may be tested under certain circumstances, but it is not
recommended. If tests are made with samples having a thickness below 0,7 mm, it should be recorded as such in
the test report.
4.4.2 Procedure
4.4.2.1 Fixing of test pieces
The strips shall be supported by a metal mandrel, which may be halved in the direction of its
axis to make a more stable support.
NOTE A metal pin or a metal tube is suitable as a mandrel.
The radius of the mandrel shall be approximately equal to half the inner diameter of the test
piece.
The apparatus, the strip and the supporting mandrel shall be arranged so that the mandrel
supports the strip and the blade is pressed against the outer surface of the test piece.
Test pieces of flat cable sheaths shall be placed on a support as shown in Figure 5 when the
smaller sides of the cable are flat.
The force shall be applied in a direction perpendicular to the axis of the mandrel (or of the
cable when a whole cable piece is used) and the blade shall also be perpendicular to the axis
of the mandrel, or of the cable when a whole cable is used.
If the smaller sides of a flat cable are flat, or nearly flat, as depicted in Figure 4, the test piece
(strip) shall be bent around a mandrel having a diameter approximately equal to the diameter
of the core of the cable; the longitudinal axis of the strip shall be perpendicular to the axis of
the mandrel. Provision shall be made so that the inner surface of the strip shall be in contact
over at least 120° of the circumference of the mandrel (see Figure 5). The metal blade of the
test apparatus shall be placed on the middle of the test piece.
For flat cables where the smaller sides are flat, or nearly flat δ (in mm) is the thickness of the
strip at the place where the force is applied. D (in mm) is the diameter of the mandrel plus
twice the value of δ and as shown in Figure 5.
4.4.2.2 Application of force
A force calculated according to Annex A shall be applied in a direction perpendicular to the
axis of the mandrel (or of the cable when a whole cable piece is used).
The blade shall also be perpendicular to the relevant axis.
4.4.2.3 Protocol in air oven
See 4.3.2.3.
60811-508  IEC:2012 – 11 –
4.4.2.4 Cooling
See 4.3.2.4.
4.4.2.5 Measurement
The indentation shall be measured on a narrow strip cut from the test piece, as described in
4.3.2.5 and shown in Figure 2.
For flat cables where the smaller sides are flat, or nearly flat, the depth of indentation shall be
related to the original value, δ, as described in 4.4.2.1 and as shown in Figure 5.
NOTE Care should be taken when making the measurement, as factors such as thermomechanical forces may
have distorted the upper surface of the sample giving a false position for the top of indentation, and the true
indentation may differ from that measured directly at the point of indentation. It is therefore essential to use the
thickness value measured before applying the indenter as the baseline figure. If it is evident that distortion has
taken place, or in the case of any uncertainty about the result, a suitable correction to the value of indentation
should be made, thus:
– if the original thickness is δ, but after the test the apparent thickness has become δ1, then for the purposes of
the calculation, the measured indentation (call it M) needs to be corrected by deducting an amount equal to δ1
- δ;
– the correct indentation percentage then becomes:
M− (δ1−δ )
×100
δ
4.4.2.6 Expression of the results
See 4.3.2.6.
5 Test report
The test report shall be in accordance with that given in IEC 60811-100.

– 12 – 60811-508  IEC:2012
Dimensions in millimetres
IEC  273/12
Key
1 testing frame 3a, 3b, 3c supports
2 sample 4 load
Figure 1 – Indentation device
IEC  274/12
Key
1 indentation
2 thin slice to be cut out
3 sectional view of indent under microscope
4 cross-wire of the microscope
5 depth of Indentation
Figure 2 – Measurement of indentation

60811-508  IEC:2012 – 13 –
L
IEC  275/12
Key
1 indentation
2 section 1
3 section 2
4 sectional view 1 ("2") under measuring microscope
5 sectional view 2 ("3") under measuring microscope
L 3 mm to 5 mm
Figure 3 – Measurement of indentation for small test pieces

R
e e
1 1
e
e
IEC  276/12
Key
e distance between core groups
e sheath thickness
e mean sheath thickness
R radius approximately e
D minor dimension
NOTE Figure 4 shows where to take the samples from the sheath of a flat cable.
Figure 4 – Flat cable with a flat smaller side

e
e
D
– 14 – 60811-508  IEC:2012
F
IEC  277/12
Key
1 mandrel blade
2 mandrel
3 fixed test piece bent around mandrel
F force
Figure 5 – Indentation device for flat cables with a flat smaller side

60811-508  IEC:2012 – 15 –
Annex A
(normative)
Calculation of the compressing force

The force F, in newtons, which shall be exerted by the blade upon the test piece, shall be
given by the formula:
F= k 2 Dδ−δ
where
k is a coefficient which shall be specified in the standard for the type of cable;
δ  is the value of the thickness of the insulation or the sheath, as measured on the test
piece, and in accordance with IEC 60811-201 (insulation) or IEC 60811-202 (sheath);
D  is the mean value of the outer diameter of the test piece (insulation) or the mandrel
diameter plus twice the thickness (sheath).
If a value of k is not specified in the cable standard, it shall be taken from Table A.1.
Table A.1 – General value for k
k Insulation Sheath
0,6 Flexible cables and cores of flexible cables Flexible cables and cables
Cables for fixed installation having a value
Cores, with D ≤ 15 mm, for cables for fixed
installations D ≤15 mm
0,7 Cores, with D > 15 mm, and for sector-shaped Cables for fixed installation having a value
cores for cables for fixed installations D >15 mm

The force applied upon the piece of flat cable without sheath shall be twice the value given by
the above formula, where D is the mean value of the minor dimension of the test piece (see
Figure 4.)
In the case of insulation, the thickness shall be measured on a thin slice of the test piece as
close as possible to the intended point of indentation.
For flat cables without sheath, the outer diameter of the insulated cores is the mean diameter
of the individual cores of the same size, discounting any of smaller nominal conductor.
For sector-shaped cores, D is the mean value of the diameter of the “back” or circular part of
the sector, in millimetres, to one decimal place. This is determined from three measurements,
by means of a tape measure, of the circumference of the core assembly (the measurements
being made at three different places on the assembled cores).
In the case of the sheath of a flat cable, D is the minor outer dimension of the test piece.
If the smaller sides of a flat cable are fully rounded in shape, this test shall be carried out on
one of the smaller sides. To calculate the compressing force (see Annex A), D is the minor
δ is the mean sheath thickness e as shown in Figure 4.
dimension of the cable and
For flat cables where the smaller sides are flat, or nearly flat δ (in mm) is the thickness of the
strip at the place where the force is applied. D (in mm) is the diameter of the mandrel plus
twice the value of δ and as shown in Figure 5.

– 16 – 60811-508  IEC:2012
In the case of a sheath, the thickness of the prepared test piece shall be measured as close
as possible to the intended point of indentation by any suitable method.
The values of δ and D are both expressed in millimetres, to two decimal places.

60811-508  IEC:2012 – 17 –
Annex B
(informative)
Recommended performance requirement

The performance requirements for a particular type or class of insulated conductor or cable
should preferably be given in the individual cable standard.
In the absence of any given requirement, it is recommended that the following value is
adopted for any cable tested against this standard:
– maximum indentation value (%): 50
NOTE The value of 50 % is inseparable from the underlying principle of the formula and is the same for all
materials. The severity of the test can be changed by variation of the factor k only, without altering the value of
50 %.
– 18 – 60811-508  IEC:2012
Bibliography
IEC 60811-3-1:1985, Common test methods for insulating and sheathing materials of electric
cables – Part 3: -Methods specific to PVC compounds – Section One – Pressure test at high
temperature – Tests for resistance to cracking
(withdrawn)
IEC 60811-203, Electric and optical fibre cables – Test methods for non-metallic materials –
Part 203: General tests – Measurement of overall dimensions
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 60811-501:2012, 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

___________
– 20 – 60811-508  CEI:2012
SOMMAIRE
AVANT-PROPOS . 21
INTRODUCTION . 23
1 Domaine d’application . 24
2 Références normatives . 24
3 Termes et définitions . 24
4 Méthode d’essai . 24
4.1 Généralités. 24
4.2 Appareillage . 25
4.2.1 Etuve à air . 25
4.2.2 Dispositif d’empreinte . 25
4.3 Enveloppe isolante . 25
4.3.1 Echantillonnage et préparation des éprouvettes . 25
4.3.2 Mode opératoire . 25
4.4 Gaine . 27
4.4.1 Echantillon et préparation des éprouvettes pour les gaines . 27
4.4.2 Mode opératoire . 28
5 Rapport d’essai . 29
Annexe A (normative) Calcul de la force de compression . 33
Annexe B (informative) Recommandations relatives aux exigences de fonctionnement . 35
Bibliographie . 36

Figure 1 – Dispositif d’empreinte . 30
Figure 2 – Mesure de l’empreinte . 30
Figure 3 – Mesure de l’empreinte pour les petites éprouvettes d’essai . 31
Figure 4 – Câble méplat avec un petit côté plat . 31
Figure 5 – Dispositif d’empreinte pour câbles méplats avec petit côté plat . 32

Tableau A.1 – Valeur générale pour k . 33

60811-508  CEI:2012 – 21 –
COMMISSION ÉLECTROTECHNIQUE INTERNATIONALE
____________
CÂBLES ÉLECTRIQUES ET À FIBRES OPTIQUES –
MÉTHODES D’ESSAI POUR LES MATÉRIAUX NON-MÉTALLIQUES –

Partie 508: Essais mécaniques –
Essai de pression à température élevée
pour les enveloppes isolantes et les gaines

AVANT-PROPOS
1) La Commission Electrotechnique Internationale (CEI) est une organisation mondiale de normalisation
composée de l'ensemble des comités électrotechniques nationaux (Comités nationaux de la CEI). La CEI a
pour objet de favoriser la coopération internationale pour toutes les questions de normalisation dans les
domaines de l'électricité et de l'électronique. A cet effet, la CEI – entre autres activités – publie des Normes
internationales, des Spécifications techniques, des Rapports techniques, des Spécifications accessibles au
public (PAS) et des Guides (ci-après dénommés "Publication(s) de la CEI"). Leur élaboration est confiée à des
comités d'études, aux travaux desquels tout Comité national intéressé par le sujet traité peut participer. Les
organisations internationales, gouvernementales et non gouvernementales, en liaison avec la CEI, participent
également aux travaux. La CEI collabore étroitement avec l'Organisation Internationale de Normalisation (ISO),
selon des conditions fixées par accord entre les deux organisations.
2) Les décisions ou accords officiels de la CEI concernant les questions techniques représentent, dans la mesure
du possible, un accord international sur les sujets étudiés, étant donné que les Comités nationaux de la CEI
intéressés sont représentés dans chaque comité d’études.
3) Les Publications de la CEI se présentent sous la forme de recommandations internationales et sont agréées
comme telles par les Comités nationaux de la CEI. Tous les efforts raisonnables sont entrepris afin que la CEI
s'assure de l'exactitude du contenu technique de ses publications; la CEI ne peut pas être tenue responsable
de l'éventuelle mauvaise utilisation ou interprétation qui en est faite par un quelconque utilisateur final.
4) Dans le but d'encourager l'uniformité internationale, les Comités nationaux de la CEI s'engagent, dans toute la
mesure possible, à appliquer de façon transparente les Publications de la CEI dans leurs publications
nationales et régionales. Toutes divergences entre toutes Publications de la CEI et toutes publications
nationales ou régionales correspondantes doivent être indiquées en termes clairs dans ces dernières.
5) La CEI elle-même ne fournit aucune attestation de conformité. Des organismes de certification indépendants
fournissent des services d'évaluation de conformité et, dans certains secteurs, accèdent aux marques de
conformité de la CEI. La CEI n'est responsable d'aucun des services effectués par les organismes de
certification indépendants.
6) Tous les utilisateurs doivent s'assurer qu'ils sont en possession de la dernière édition de cette publication.
7) Aucune responsabilité ne doit être imputée à la CEI, à ses administrateurs, employés, auxiliaires ou
mandataires, y compris ses experts particuliers et les membres de ses comités d'études et des Comités
nationaux de la CEI, pour tout préjudice causé en cas de dommages corporels et matériels, ou de tout autre
dommage de quelque nature que ce soit, directe ou indirecte, ou pour supporter les coûts (y compris les frais
de justice) et les dépenses découlant de la publication ou de l'utilisation de cette Publication de la CEI ou de
toute autre Publication de la CEI, ou au crédit qui lui est accordé.
8) L'attention est attirée sur les références normatives citées dans cette publication. L'utilisation de publications
référencées est obligatoire pour une application correcte de la présente publication.
9) L’attention est attirée sur le fait que certains des éléments de la présente Publication de la CEI peuvent faire
l’objet de droits de brevet. La CEI ne saurait être tenue pour responsable de ne pas avoir identifié de tels droits
de brevets et de ne pas avoir signalé leur existence.
La Norme internationale CEI 60811-508 a été établie par le comité d’études 20 de la CEI:
Câbles électriques.
La présente Partie 508 de la CEI 60811 annule et remplace l’Article 8 de la
CEI 60811-3-1:1985, qui est supprimée. L’ensemble des détails relatifs aux remplacements
figure dans l’Annexe A de la CEI 60811-100:2012.
Des modifications techniques importantes ont été effectuées par rapport à l’édition
précédente, comme suit:
– redéfinition des caractéristiques relatives à l’étuve, en particulier les caractéristiques
antivibratoires et le contrôle de la température;

– 22 – 60811-508  CEI:2012
– des détails supplémentaires relatifs aux préparations e
...

IEC 60811-508 ®
Edition 1.1 2017-07
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Electric and optical fibre cables – Test methods for non-metallic materials –
Part 508: Mechanical tests – Pressure test at high temperature for insulation
and sheaths
Câbles électriques et à fibres optiques – Méthodes d’essai pour les matériaux
non-métalliques –
Partie 508: Essais mécaniques – Essai de pression à température élevée pour
les enveloppes isolantes et les gaines

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IEC 60811-508 ®
Edition 1.1 2017-07
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Electric and optical fibre cables – Test methods for non-metallic materials –

Part 508: Mechanical tests – Pressure test at high temperature for insulation

and sheaths
Câbles électriques et à fibres optiques – Méthodes d’essai pour les matériaux

non-métalliques –
Partie 508: Essais mécaniques – Essai de pression à température élevée pour

les enveloppes isolantes et les gaines

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.035.01; 29.060.20 ISBN 978-2-8322-4654-2

IEC 60811-508 ®
Edition 1.1 2017-07
CONSOLIDATED VERSION
REDLINE VERSION
VERSION REDLINE
colour
inside
Electric and optical fibre cables – Test methods for non-metallic materials –
Part 508: Mechanical tests – Pressure test at high temperature for insulation
and sheaths
Câbles électriques et à fibres optiques – Méthodes d’essai pour les matériaux
non-métalliques –
Partie 508: Essais mécaniques – Essai de pression à température élevée pour
les enveloppes isolantes et les gaines

– 2 – IEC 60811-508:2012+AMD1:2017 CSV
 IEC 2017
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Test method . 6
4.1 General . 6
4.2 Apparatus . 6
4.2.1 Air oven . 6
4.2.2 Indentation device . 7
4.3 Insulation . 7
4.3.1 Sample and test piece preparation . 7
4.3.2 Procedure . 7
4.4 Sheath . 9
4.4.1 Sample and test piece preparation for sheaths . 9
4.4.2 Procedure . 10
5 Test report. 11
Annex A (normative) Calculation of the compressing force . 16
Annex B (informative) Recommended performance requirement . 18
Bibliography . 19

Figure 1 – Indentation device . 12
Figure 2 – Measurement of indentation . 12
Figure 3 – Measurement of indentation for small test pieces . 13
Figure 4 – Flat cable with a flat smaller side . 14
Figure 5 – Indentation device for flat cables with a flat smaller side . 15

Table A.1 – General value for k . 16

 IEC 2017
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTRIC AND OPTICAL FIBRE CABLES –
TEST METHODS FOR NON-METALLIC MATERIALS –
Part 508: Mechanical tests –
Pressure test at high temperature for insulation and sheaths
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
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in the subject dealt with may participate in this preparatory work. International, governmental and non-
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with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
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3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
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patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
This consolidated version of the official IEC Standard and its amendment has been prepared
for user convenience.
IEC 60811-508 edition 1.1 contains the first edition (2012-03) [documents 20/1304/FDIS and
20/1353/RVD] and its amendment 1 (2017-07) [documents 20/1735/FDIS and 20/1740/RVD].
In this Redline version, a vertical line in the margin shows where the technical content is
modified by amendment 1. Additions are in green text, deletions are in strikethrough red text. A
separate Final version with all changes accepted is available in this publication.

– 4 – IEC 60811-508:2012+AMD1:2017 CSV
 IEC 2017
International Standard IEC 60811-508 has been prepared by IEC technical committee 20:
Electric cables.
Significant technical changes with respect to the previous edition are as follows:
– re-statement of oven characteristics, especially relating to anti-vibration and to
temperature control;
– enhanced detail as to the preparations and testing of flat cables;
– enhanced detail as to thickness and dimensional measurements.
See also the Foreword to IEC 60811-100:2012.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
This part of IEC 60811 shall be used in conjunction with IEC 60811-100.
A list of all the parts in the IEC 60811 series, published under the general title Electric and
optical fibre cables – Test methods for non-metallic materials, can be found on the IEC
website.
The committee has decided that the contents of the base publication and its amendment will
remain unchanged until the stability date indicated on the IEC web site under
"http://webstore.iec.ch" in the data related to the specific publication. At this date, the
publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
 IEC 2017
INTRODUCTION
The IEC 60811 series specifies the test methods to be used for testing non-metallic materials
of all types of cables. These test methods are intended to be referenced in standards for
cable construction and for cable materials.
NOTE 1 Non-metallic materials are typically used for insulating, sheathing, bedding, filling or taping within cables.
NOTE 2 These test methods are accepted as basic and fundamental and have been developed and used over
many years principally for the materials in all energy cables. They have also been widely accepted and used for
other cables, in particular optical fibre cables, communication and control cables and cables for ships and offshore
applications.
– 6 – IEC 60811-508:2012+AMD1:2017 CSV
 IEC 2017
ELECTRIC AND OPTICAL FIBRE CABLES –
TEST METHODS FOR NON-METALLIC MATERIALS –

Part 508: Mechanical tests –
Pressure test at high temperature for insulation and sheaths

1 Scope
This Part 508 of IEC 60811 gives the procedure for a pressure test at high temperature, which
typically applies to thermoplastic compounds used for insulating and sheathing materials.
NOTE 1 The method is principally intended for thermoplastic materials, but may be used for cross-linked
materials when specifically required by the relevant cable standard.
NOTE 2 The test method is not recommended for thicknesses below 0,7 mm.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60811-100:2012, Electric and optical fibre cables – Test methods for non-metallic
materials –Part 100: General
IEC 60811-201, Electric and optical fibre cables – Test methods for non-metallic materials –

Part 201: General tests – Measurement of insulation thickness
IEC 60811-202, Electric and optical fibre cables – Test methods for non-metallic materials –

Part 202: General tests – Measurement of thickness of non-metallic sheaths
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60811-100 apply.
4 Test method
4.1 General
This part of IEC 60811 shall be used in conjunction with IEC 60811-100.
This standard gives the method for the pressure test at high temperature which applies to
insulation and sheathing compounds.
All the tests shall be carried out not less than 16 h after the extrusion of the insulating or
sheathing compounds.
4.2 Apparatus
4.2.1 Air oven
The test shall be carried out in an oven. The oven shall use natural air circulation.

 IEC 2017
NOTE 1 Forced or continuous air circulation is not required. Ovens fitted with air stirring mechanisms are likely to
cause vibration.
The oven shall not incorporate any equipment likely to cause vibration, nor shall it include
exposed heating elements. The temperature of the air shall be maintained continuously at the
value specified in the relevant cable standard. The oven shall be capable of operating to
within ±2 K of the specified test temperature.
NOTE 2 The need for a temperature control to ±2 K is crucial. This is especially so if the material under test is a
thermoplastic with a sharp melting point (such as some ethylene polymers) as a small temperature rise above that
specified can result in a large increase in indentation.
NOTE Thermoplastic materials with a sharp melting point (as some ethylene polymers) can experience a large
increase in indentation with a small temperature rise above the specified test temperature.
In operation, the oven shall be located in a position free from vibration.
4.2.2 Indentation device
A device according to Figure 1 shall be used. It shall consist of a rectangular blade with an a
flat edge (0,70 ±0,01) mm wide which can be pressed against the test piece under the
influence of an applied force.
4.3 Insulation
4.3.1 Sample and test piece preparation
For each core to be tested, three adjacent pieces shall be taken from a sample having a
length of 250 mm to 500 mm. The length of each piece shall be 50 mm to 100 mm.
From each core piece taken, any covering – including the semi-conducting layer, if any – shall
be removed mechanically. According to the type of cable, the test piece may have a circular,
flat or sector-shaped cross-section of length (45 ± 5) mm.
The cores of twin- and multiple-grouped-core flat cables without sheath shall not be separated
individually, except if the individual conductor cross-section is ≥ 10 mm . If so, a test piece
taken from the insulation of an individual core shall be tested.
The minimum thickness of insulation to be tested shall be 0,7 mm.
NOTE Insulation thickness down to 0,4 mm may be tested under certain circumstances, but it is not
recommended. If tests are made with samples having a thickness below 0,7 mm, it should be recorded as such in
the test report.
4.3.2 Procedure
4.3.2.1 Fixing of test pieces
The final test piece shall consist of a piece of the sample from 4.3.1.
Circular cores shall be mounted in the position shown in Figure 1 (3a).
A flat cable without sheath shall be laid on its flat/major axis side.
Sector-shaped cores shall be mounted on a support of an appropriate type as shown in
Figure 1 (3b and 3c).
All test pieces shall be fixed to the support in such a manner that they do not change position
during the test. Special care shall be taken with test pieces so that they do not curve under
the pressure of the blade.
– 8 – IEC 60811-508:2012+AMD1:2017 CSV
 IEC 2017
4.3.2.2 Application of force
A force calculated according to Annex A shall be applied in a direction perpendicular to the
axis of the core.
The blade shall also be perpendicular to the relevant axis.
4.3.2.3 Protocol in air oven
The loaded blade shall be placed onto the fixed test piece at ambient temperature. The whole
assembly shall then be placed in the air oven which is at the specified test temperature.
The apparatus, with loaded test pieces, shall be placed in a position free from vibration (see
4.2.1).
The temperature of the air shall be maintained continuously at the value specified in the
relevant cable standard. In case of dispute, the temperature shall be checked by means of a
suitable temperature-measuring device, mounted at the same level as the test piece and as
close as possible to one of the test pieces and the temperature shall be continuously
monitored during the test.
NOTE 1 It is critical to ensure that the temperature does not, at any time, exceed the upper limit specified for
testing the particular material. Temperatures below the lower limit specified may be experienced briefly
immediately after starting the test. Such short periods may be ignored.
The assembly shall be kept in the test position for the time specified in the relevant cable
standard, or, if the time is not specified in the cable standard, for the following times:
– 4 h for test pieces having a value of D ≤ 15 mm
– 6 h for test pieces having a value of D > 15 mm.
NOTE 2 Details for the determination of D are found in Annex A.
4.3.2.4 Cooling
At the end of the specified duration, the test piece shall be rapidly cooled under load. This
operation may be carried out inside or outside the air oven by spraying the test piece with
cold water on the spot where the blade is pressing.
The test piece shall be removed from the apparatus when it has cooled to a temperature
where recovery of the insulation no longer occurs; the test piece shall then be cooled further
by immersion in cold water.
4.3.2.5 Measurement
Immediately after cooling, the test piece shall be prepared for determining the depth of
indentation.
The conductor shall be withdrawn, leaving the test piece in the form of a tube.
A narrow strip shall be cut from the test piece in the direction of the axis of the core,
perpendicular to the indentation as shown in Figure 2.
The strip shall be laid flat under a measuring microscope or, a measuring projector and or an
optical digital image analyser of at least 10 × magnification. The cross-wire shall be adjusted
to the bottom of the indentation and the outside of the test piece as shown in the same figure.
In case of doubt, the measuring microscope shall be taken as the reference method.

 IEC 2017
A reading of 0,01 mm and an estimated reading to three decimal places shall be used when
measuring insulation with a specified thickness less than 0,7 mm.
NOTE 1 A test method using a dial micrometer is under consideration.
Small test pieces, up to about 6 mm external diameter, shall be cut transversely at and
adjacent to the indentation, as shown in Figure 3, and the depth of the indentation shall be
determined as the difference between the microscope measurements on sectional views 1
and 2 as shown in the same figure.
All measurements shall be made in millimetres to two decimal places.
NOTE 2 Care should be taken when making the measurement, as factors such as thermomechanical forces may
have distorted the upper surface of the sample, giving a false position for the top of indentation, and the true
indentation may differ from that measured directly at the point of indentation. It is therefore essential to use the
thickness value measured before applying the indenter as the baseline figure. If it is evident that distortion has
taken place, or in the case of any uncertainty about the result, a suitable correction to the value of indentation
should be made, thus:
– if the original thickness is δ, but after the test the apparent thickness has becomeδ1 , then for the purposes of
the calculation, the measured indentation (call it M) needs to be corrected by deducting an amount equal to
δ1 – δ ;
– the correct indentation percentage then becomes
M− (δ1−δ )
×100
δ
4.3.2.6 Expression of the results
The indentation values, measured on the three test pieces taken from each core or strip, shall
be calculated as a percentage of the insulation thickness (as measured in accordance with
Annex A). The median of the three values shall be recorded. If there are changes in thickness
due to the test, the formula in the NOTE in 4.3.2.5 should be used.
For flat cables, the median indentation value is the mean value of the indentation values from
all the cores of the same size in the sample.
NOTE In the absence of any requirement in the relevant cable standard, a recommendation is given in Annex B.
4.4 Sheath
4.4.1 Sample and test piece preparation for sheaths
For each sheath to be tested, three adjacent pieces shall be taken from a sample having a
length of 250 mm to 500 mm from which the covering (if any) and all the internal parts (cores,
fillers, inner covering, armour etc. if any) have been removed.
The length of each piece of sheathing shall be 50 mm to 100 mm.
From each piece of sheathing, a strip of width equal to about one-third of the perimeter, but
not more than 20 mm, shall be cut parallel to the direction of the axis of the cable if the
sheath does not have ridges.
If the sheath shows ridges caused by five or fewer cores, the strip shall be cut in the direction
of the ridges so that it contains at least one groove which lies approximately in the middle of
the strip throughout its length.
If the sheath has ridges caused by more than five cores, the strip shall be cut in the same
manner and these ridges shall be removed by grinding.

– 10 – IEC 60811-508:2012+AMD1:2017 CSV
 IEC 2017
NOTE 1 A machine of the type specified in Annex A of IEC 60811-501:2012 has been found suitable for grinding
or cutting the ridges.
If the sheath is directly applied on a concentric conductor, an armour or on a metallic screen,
and therefore has ridges which cannot be ground or cut away (unless the diameter is large),
the sheath shall not be removed, and the whole cable piece shall be used as a test piece.
If the smaller sides of a flat cable are fully rounded in shape, this test shall be carried out on
one of the smaller sides. To calculate the compressing force (see Annex A), D is the minor
dimension of the cable and δ is the mean sheath thickness e as shown in Figure 4.
If the smaller sides are flat, or nearly flat, as depicted in Figure 4, a test piece shall be
prepared by cutting a strip from the wide side of the cable in the direction of the axis of the
cable. On the inner side, only the ridges shall be removed by grinding or cutting. The width of
the strip to be tested shall be at least 10 mm but not more than 20 mm. The thickness of the
strip shall be measured at the place where the compressing force, F, is applied.
NOTE 2 Insulation Sheath thickness down to 0,4 mm may be tested under certain circumstances, but it is not
recommended. If tests are made with samples having a thickness below 0,7 mm, it should be recorded as such in
the test report.
4.4.2 Procedure
4.4.2.1 Fixing of test pieces
The strips shall be supported by a metal mandrel, which may be halved in the direction of its
axis to make a more stable support.
NOTE A metal pin or a metal tube is suitable as a mandrel.
The radius of the mandrel shall be approximately equal to half the inner diameter of the test
piece.
The apparatus, the strip and the supporting mandrel shall be arranged so that the mandrel
supports the strip and the blade is pressed against the outer surface of the test piece.
Test pieces of flat cable sheaths shall be placed on a support as shown in Figure 5 when the
smaller sides of the cable are flat.
The force shall be applied in a direction perpendicular to the axis of the mandrel (or of the
cable when a whole cable piece is used) and the blade shall also be perpendicular to the axis
of the mandrel, or of the cable when a whole cable is used.
If the smaller sides of a flat cable are flat, or nearly flat, as depicted in Figure 4, the test piece
(strip) shall be bent around a mandrel having a diameter approximately equal to the diameter
of the core of the cable; the longitudinal axis of the strip shall be perpendicular to the axis of
the mandrel. Provision shall be made so that the inner surface of the strip shall be in contact
over at least 120° of the circumference of the mandrel (see Figure 5). The metal blade of the
test apparatus shall be placed on the middle of the test piece.
For flat cables where the smaller sides are flat, or nearly flat δ (in mm) is the thickness of the
strip at the place where the force is applied. D (in mm) is the diameter of the mandrel plus
δ and as shown in Figure 5.
twice the value of
4.4.2.2 Application of force
A force calculated according to Annex A shall be applied in a direction perpendicular to the
axis of the mandrel (or of the cable when a whole cable piece is used).
The blade shall also be perpendicular to the relevant axis.

 IEC 2017
4.4.2.3 Protocol in air oven
See 4.3.2.3.
4.4.2.4 Cooling
See 4.3.2.4.
4.4.2.5 Measurement
The indentation shall be measured on a narrow strip cut from the test piece, as described in
4.3.2.5 and shown in Figure 2.
For flat cables where the smaller sides are flat, or nearly flat, the depth of indentation shall be
related to the original value, δ, as described in 4.4.2.1 and as shown in Figure 5.
NOTE Care should be taken when making the measurement, as factors such as thermomechanical forces may
have distorted the upper surface of the sample giving a false position for the top of indentation, and the true
indentation may differ from that measured directly at the point of indentation. It is therefore essential to use the
thickness value measured before applying the indenter as the baseline figure. If it is evident that distortion has
taken place, or in the case of any uncertainty about the result, a suitable correction to the value of indentation
should be made, thus:
– if the original thickness is δ, but after the test the apparent thickness has become δ1, then for the purposes of
the calculation, the measured indentation (call it M) needs to be corrected by deducting an amount equal to δ1
- δ;
– the correct indentation percentage then becomes:
M− (δ1−δ )
×100
δ
4.4.2.6 Expression of the results
See 4.3.2.6.
5 Test report
The test report shall be in accordance with that given in IEC 60811-100.

– 12 – IEC 60811-508:2012+AMD1:2017 CSV
 IEC 2017
Dimensions in millimetres
IEC  273/12
Key
1 testing frame 3a, 3b, 3c supports
2 sample 4 load
Figure 1 – Indentation device
IEC  274/12
Key
1 indentation
2 thin slice to be cut out
3 sectional view of indent under microscope
4 cross-wire of the microscope
5 depth of Indentation
Figure 2 – Measurement of indentation

 IEC 2017
L
IEC  275/12
Key
1 indentation
2 section 1
3 section 2
4 sectional view 1 ("2") under measuring microscope
5 sectional view 2 ("3") under measuring microscope
L 3 mm to 5 mm
Figure 3 – Measurement of indentation for small test pieces

– 14 – IEC 60811-508:2012+AMD1:2017 CSV
 IEC 2017
R
e e
1 1
e
e
IEC  276/12
Key
e distance between core groups
e sheath thickness
e mean sheath thickness
R radius approximately e
D minor dimension
NOTE Figure 4 shows where to take the samples from the sheath of a flat cable.
R
D
e e
3 3
IEC
Key
e mean sheath thickness
R radius of the corner
D minor dimension
Figure 4 – Flat cable with a flat smaller side

e
e
D
 IEC 2017
F
IEC  277/12
Key
1 mandrel blade
2 mandrel
3 fixed test piece bent around mandrel
F
force
Figure 5 – Indentation device for flat cables with a flat smaller side

– 16 – IEC 60811-508:2012+AMD1:2017 CSV
© IEC 2017
Annex A
(normative)
Calculation of the compressing force

The minimum force F, in N, which shall be exerted by the blade upon the test piece, shall be
given by the formula:
F = k 2 D δ − δ
where
k is a coefficient which shall be specified in the standard for the type of cable;
δ  is the value of the thickness of the insulation or the sheath, as measured on the test
piece, and in accordance with IEC 60811-201 (insulation) or IEC 60811-202 (sheath) in
millimetres;
D  is the mean value of the outer diameter of the test piece (insulation) or the mandrel
diameter plus twice the thickness (sheath), in millimetres.
If a value of k is not specified in the cable standard, it shall be taken from Table A.1.
Table A.1 – General value for k
k Insulation Sheath
0,6 Flexible cables and cores of flexible cables Flexible cables and cables
Cores, with D ≤ 15 mm, for cables for fixed Cables for fixed installation having a value
installations D ≤15 mm
0,7 Cables for fixed installation having a value
Cores, with D > 15 mm, and for sector-shaped
cores for cables for fixed installations D >15 mm

The force applied upon the piece of flat cable without sheath as described in 4.3.1 and with
conductor size < 10 mm shall be twice the value given by the above formula in a twin core
cable, where D is the mean value of the minor dimension of the test piece, or multiplied by the
number of cores if more than two cores (see Figure 4).
In the case of insulation, The thickness δ shall be measured on a thin slice of the test piece
as close as possible to the intended point of indentation.
For flat cables without sheath, the outer diameter of the insulated cores is the mean diameter
of the individual cores of the same size, discounting any of smaller nominal conductor D is
determined by calculating the mean diameter using the individual cores of the largest size.
For sector-shaped cores, D is the mean value of the diameter of the “back” or circular part of
the sector, in millimetres, to one decimal place. This is determined from three measurements,
by means of a tape measure, of the circumference of the core assembly (the measurements
being made at three different places on the assembled cores).
In the case of the sheath of a flat cable, D is the minor outer dimension of the test piece.
If the smaller sides of a flat cable are fully rounded in shape, this test shall be carried out on
one of the smaller sides. To calculate the compressing force (see Annex A), D is the minor
dimension of the cable and δ is the mean sheath thickness e as shown in Figure 4.
 IEC 2017
For flat cables where the smaller sides are flat, or nearly flat δ (in mm) is the thickness of the
strip at the place where the force is applied. D (in mm) is the diameter of the mandrel plus
δ and as shown in Figure 5.
twice the value of
In the case of a sheath, the thickness of the prepared test piece shall be measured as close
as possible to the intended point of indentation by any suitable method.
The values of δ and D are both expressed in millimetres, to two decimal places.

– 18 – IEC 60811-508:2012+AMD1:2017 CSV
 IEC 2017
Annex B
(informative)
Recommended performance requirement

The performance requirements for a particular type or class of insulated conductor or cable
should preferably be given in the individual cable standard.
In the absence of any given requirement, it is recommended that the following value is
adopted for any cable tested against this standard:
– maximum indentation value (%): 50
NOTE The value of 50 % is inseparable from the underlying principle of the formula and is the same for all
materials. The severity of the test can be changed by variation of the factor k only, without altering the value of
50 %.
 IEC 2017
Bibliography
IEC 60811-3-1:1985, Common test methods for insulating and sheathing materials of electric
cables – Part 3: -Methods specific to PVC compounds – Section One – Pressure test at high
temperature – Tests for resistance to cracking
(withdrawn)
IEC 60811-203, Electric and optical fibre cables – Test methods for non-metallic materials –
Part 203: General tests – Measurement of overall dimensions
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 60811-501:2012, 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

___________
– 20 – IEC 60811-508:2012+AMD1:2017 CSV
 IEC 2017
SOMMAIRE
AVANT-PROPOS . 21
INTRODUCTION . 23
1 Domaine d’application . 24
2 Références normatives . 24
3 Termes et définitions . 24
4 Méthode d’essai . 24
4.1 Généralités. 24
4.2 Appareillage . 25
4.2.1 Etuve à air . 25
4.2.2 Dispositif d’empreinte . 25
4.3 Enveloppe isolante . 25
4.3.1 Echantillonnage et préparation des éprouvettes . 25
4.3.2 Mode opératoire . 25
4.4 Gaine . 27
4.4.1 Echantillon et préparation des éprouvettes pour les gaines . 27
4.4.2 Mode opératoire . 28
5 Rapport d’essai . 29
Annexe A (normative) Calcul de la force de compression . 34
Annexe B (informative) Recommandations relatives aux exigences de fonctionnement . 36
Bibliographie . 37

Figure 1 – Dispositif d’empreinte . 30
Figure 2 – Mesure de l’empreinte . 30
Figure 3 – Mesure de l’empreinte pour les petites éprouvettes d’essai . 31
Figure 4 – Câble méplat avec un petit côté plat . 32
Figure 5 – Dispositif d’empreinte pour câbles méplats avec petit côté plat . 33

Tableau A.1 – Valeur générale pour k . 34

 IEC 2017
COMMISSION ÉLECTROTECHNIQUE INTERNATIONALE
____________
CÂBLES ÉLECTRIQUES ET À FIBRES OPTIQUES –
MÉTHODES D’ESSAI POUR LES MATÉRIAUX NON-MÉTALLIQUES –
Partie 508: Essais mécaniques –
Essai de pression à température élevée
pour les enveloppes isolantes et les gaines
AVANT-PROPOS
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IEC 60811-508 ®
Edition 1.2 2023-11
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Electric and optical fibre cables – Test methods for non-metallic materials –
Part 508: Mechanical tests – Pressure test at high temperature for insulation and
sheaths
Câbles électriques et à fibres optiques – Méthodes d'essai pour les matériaux
non-métalliques –
Partie 508: Essais mécaniques – Essai de pression à température élevée pour
les enveloppes isolantes et les gaines

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IEC 60811-508 ®
Edition 1.2 2023-11
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Electric and optical fibre cables – Test methods for non-metallic materials –
Part 508: Mechanical tests – Pressure test at high temperature for insulation and
sheaths
Câbles électriques et à fibres optiques – Méthodes d'essai pour les matériaux
non-métalliques –
Partie 508: Essais mécaniques – Essai de pression à température élevée pour
les enveloppes isolantes et les gaines
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.035.01, 29.060.20 ISBN 978-2-8322-7792-8

IEC 60811-508 ®
Edition 1.2 2023-11
CONSOLIDATED VERSION
REDLINE VERSION
VERSION REDLINE
colour
inside
Electric and optical fibre cables – Test methods for non-metallic materials –
Part 508: Mechanical tests – Pressure test at high temperature for insulation and
sheaths
Câbles électriques et à fibres optiques – Méthodes d'essai pour les matériaux
non-métalliques –
Partie 508: Essais mécaniques – Essai de pression à température élevée pour
les enveloppes isolantes et les gaines

– 2 – IEC 60811-508:2012+AMD1:2017
+AMD2:2023 CSV  IEC 2023
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Test method . 6
4.1 General . 6
4.2 Apparatus . 7
4.2.1 Air oven . 7
4.2.2 Indentation device . 7
4.3 Insulation . 7
4.3.1 Sample and test piece preparation . 7
4.3.2 Procedure . 7
4.4 Sheath . 9
4.4.1 Sample and test piece preparation for sheaths . 9
4.4.2 Procedure . 10
5 Test report. 11
Annex A (normative) Calculation of the compressing force . 16
Annex B (informative) Recommended performance requirement . 18
Bibliography . 19

Figure 1 – Indentation device . 12
Figure 2 – Measurement of indentation . 12
Figure 3 – Measurement of indentation for small test pieces . 13
Figure 4 – Flat cable with a flat smaller side . 14
Figure 5 – Indentation device for flat cables with a flat smaller side . 15

Table A.1 – General value for k . 16

+AMD2:2023 CSV  IEC 2023
INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
ELECTRIC AND OPTICAL FIBRE CABLES –
TEST METHODS FOR NON-METALLIC MATERIALS –

Part 508: Mechanical tests –
Pressure test at high temperature for insulation and sheaths

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
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9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
This consolidated version of the official IEC Standard and its amendments has been
prepared for user convenience.
IEC 60811-508 edition 1.2 contains the first edition (2012-03) [documents 20/1304/FDIS
and 20/1353/RVD], its amendment 1 (2017-07) [documents 20/1735/FDIS and
20/1740/RVD] and its amendment 2 (2023-11) [documents 20/1735/FDIS and
20/1740/RVD].
In this Redline version, a vertical line in the margin shows where the technical content
is modified by amendments 1 and 2. Additions are in green text, deletions are in
strikethrough red text. A separate Final version with all changes accepted is available
in this publication.
– 4 – IEC 60811-508:2012+AMD1:2017
+AMD2:2023 CSV  IEC 2023
International Standard IEC 60811-508 has been prepared by IEC technical committee 20:
Electric cables.
Significant technical changes with respect to the previous edition are as follows:
– re-statement of oven characteristics, especially relating to anti-vibration and to
temperature control;
– enhanced detail as to the preparations and testing of flat cables;
– enhanced detail as to thickness and dimensional measurements.
See also the Foreword to IEC 60811-100:2012.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
This part of IEC 60811 shall be used in conjunction with IEC 60811-100.
A list of all the parts in the IEC 60811 series, published under the general title Electric and
optical fibre cables – Test methods for non-metallic materials, can be found on the IEC
website.
The committee has decided that the contents of this document and its amendments 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,
• replaced by a revised edition, or
• amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
+AMD2:2023 CSV  IEC 2023
INTRODUCTION
The IEC 60811 series specifies the test methods to be used for testing non-metallic materials
of all types of cables. These test methods are intended to be referenced in standards for
cable construction and for cable materials.
NOTE 1 Non-metallic materials are typically used for insulating, sheathing, bedding, filling or taping within cables.
NOTE 2 These test methods are accepted as basic and fundamental and have been developed and used over
many years principally for the materials in all energy cables. They have also been widely accepted and used for
other cables, in particular optical fibre cables, communication and control cables and cables for ships and offshore
applications.
– 6 – IEC 60811-508:2012+AMD1:2017
+AMD2:2023 CSV  IEC 2023
ELECTRIC AND OPTICAL FIBRE CABLES –
TEST METHODS FOR NON-METALLIC MATERIALS –

Part 508: Mechanical tests –
Pressure test at high temperature for insulation and sheaths

1 Scope
This Part 508 of IEC 60811 gives the procedure for a pressure test at high temperature, which
typically applies to thermoplastic compounds used for insulating and sheathing materials.
NOTE 1 The method is principally intended for thermoplastic materials, but may be used for cross-linked
materials when specifically required by the relevant cable standard.
NOTE 2 The test method is not recommended for thicknesses below 0,7 mm.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60811-100:2012, Electric and optical fibre cables – Test methods for non-metallic
materials –Part 100: General
IEC 60811-201, Electric and optical fibre cables – Test methods for non-metallic materials –

Part 201: General tests – Measurement of insulation thickness
IEC 60811-202, Electric and optical fibre cables – Test methods for non-metallic materials –

Part 202: General tests – Measurement of thickness of non-metallic sheaths
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60811-100 apply.
4 Test method
4.1 General
This part of IEC 60811 shall be used in conjunction with IEC 60811-100.
This standard gives the method for the pressure test at high temperature which applies to
insulation and sheathing compounds.
All the tests shall be carried out not less than 16 h after the extrusion of the insulating or
sheathing compounds.
+AMD2:2023 CSV  IEC 2023
4.2 Apparatus
4.2.1 Air oven
The test shall be carried out in an oven. The oven shall use natural air circulation. Either an
oven with natural air circulation or one with fan-assisted circulation may be used. If vibrations
from a fan-assisted oven causes inconsistent results, an oven with natural air circulation shall
be used instead.
NOTE 1 Forced or continuous air circulation is not required. Ovens fitted with air stirring mechanisms are likely to
cause vibration.
The oven shall not incorporate any equipment likely to cause vibration, nor shall it include
exposed heating elements. The temperature of the air shall be maintained continuously at the
value specified in the relevant cable standard. The oven shall be capable of operating to
within ±2 K of the specified test temperature.
NOTE 2 The need for a temperature control to ±2 K is crucial. This is especially so if the material under test is a
thermoplastic with a sharp melting point (such as some ethylene polymers) as a small temperature rise above that
specified can result in a large increase in indentation.
NOTE Thermoplastic materials with a sharp melting point (as some ethylene polymers) can experience a large
increase in indentation with a small temperature rise above the specified test temperature.
In operation, the oven shall be located in a position free from vibration.
4.2.2 Indentation device
A device according to Figure 1 shall be used. It shall consist of a rectangular blade with an a
flat edge (0,70 ±0,01) mm wide which can be pressed against the test piece under the
influence of an applied force.
4.3 Insulation
4.3.1 Sample and test piece preparation
For each core to be tested, three adjacent pieces shall be taken from a sample having a
length of 250 mm to 500 mm. The length of each piece shall be 50 mm to 100 mm.
From each core piece taken, any covering – including the semi-conducting layer, if any – shall
be removed mechanically. According to the type of cable, the test piece may have a circular,
flat or sector-shaped cross-section of length (45 ± 5) mm.
The cores of twin- and multiple-grouped-core flat cables without sheath shall not be separated
individually, except if the individual conductor cross-section is ≥ 10 mm . If so, a test piece
taken from the insulation of an individual core shall be tested.
The minimum thickness of insulation to be tested shall be 0,7 mm.
NOTE Insulation thickness down to 0,4 mm may be tested under certain circumstances, but it is not
recommended. If tests are made with samples having a thickness below 0,7 mm, it should be recorded as such in
the test report.
4.3.2 Procedure
4.3.2.1 Fixing of test pieces
The final test piece shall consist of a piece of the sample from 4.3.1.
Circular cores shall be mounted in the position shown in Figure 1 (3a).
A flat cable without sheath shall be laid on its flat/major axis side.

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Sector-shaped cores shall be mounted on a support of an appropriate type as shown in
Figure 1 (3b and 3c).
All test pieces shall be fixed to the support in such a manner that they do not change position
during the test. Special care shall be taken with test pieces so that they do not curve under
the pressure of the blade.
4.3.2.2 Application of force
A force calculated according to Annex A shall be applied in a direction perpendicular to the
axis of the core.
The blade shall also be perpendicular to the relevant axis.
4.3.2.3 Protocol in air oven
The loaded blade shall be placed onto the fixed test piece at ambient temperature. The whole
assembly shall then be placed in the air oven which is at the specified test temperature.
The apparatus, with loaded test pieces, shall be placed in a position free from vibration (see
4.2.1).
The temperature of the air shall be maintained continuously at the value specified in the
relevant cable standard. In case of dispute, the temperature shall be checked by means of a
suitable temperature-measuring device, mounted at the same level as the test piece and as
close as possible to one of the test pieces and the temperature shall be continuously
monitored during the test.
NOTE 1 It is critical to ensure that the temperature does not, at any time, exceed the upper limit specified for
testing the particular material. Temperatures below the lower limit specified may be experienced briefly
immediately after starting the test. Such short periods may be ignored.
The assembly shall be kept in the test position for the time specified in the relevant cable
standard, or, if the time is not specified in the cable standard, for the following times:
– 4 h for test pieces having a value of D ≤ 15 mm
– 6 h for test pieces having a value of D > 15 mm.
NOTE 2 Details for the determination of D are found in Annex A.
4.3.2.4 Cooling
At the end of the specified duration, the test piece shall be rapidly cooled under load. This
operation may be carried out inside or outside the air oven by spraying the test piece with
cold water on the spot where the blade is pressing.
The test piece shall be removed from the apparatus when it has cooled to a temperature
where recovery of the insulation no longer occurs; the test piece shall then be cooled further
by immersion in cold water.
4.3.2.5 Measurement
Immediately after cooling, the test piece shall be prepared for determining the depth of
indentation.
The conductor shall be withdrawn, leaving the test piece in the form of a tube.
A narrow strip shall be cut from the test piece in the direction of the axis of the core,
perpendicular to the indentation as shown in Figure 2.

+AMD2:2023 CSV  IEC 2023
The strip shall be laid flat under a measuring microscope or, a measuring projector and or an
optical digital image analyser of at least 10 × magnification. The cross-wire shall be adjusted
to the bottom of the indentation and the outside of the test piece as shown in the same figure.
In case of doubt, the measuring microscope shall be taken as the reference method.
A reading of 0,01 mm and an estimated reading to three decimal places shall be used when
measuring insulation with a specified thickness less than 0,7 mm.
NOTE 1 A test method using a dial micrometer is under consideration.
Small test pieces, up to about 6 mm external diameter, shall be cut transversely at and
adjacent to the indentation, as shown in Figure 3, and the depth of the indentation shall be
determined as the difference between the microscope measurements on sectional views 1
and 2 as shown in the same figure.
All measurements shall be made in millimetres to two decimal places.
NOTE 2 Care should be taken when making the measurement, as factors such as thermomechanical forces may
have distorted the upper surface of the sample, giving a false position for the top of indentation, and the true
indentation may differ from that measured directly at the point of indentation. It is therefore essential to use the
thickness value measured before applying the indenter as the baseline figure. If it is evident that distortion has
taken place, or in the case of any uncertainty about the result, a suitable correction to the value of indentation
should be made, thus:
– if the original thickness is δ, but after the test the apparent thickness has becomeδ1 , then for the purposes of
the calculation, the measured indentation (call it M) needs to be corrected by deducting an amount equal to
δ1 – δ ;
– the correct indentation percentage then becomes
M− (δ1−δ )
×100
δ
4.3.2.6 Expression of the results
The indentation values, measured on the three test pieces taken from each core or strip, shall
be calculated as a percentage of the insulation thickness (as measured in accordance with
Annex A). The median of the three values shall be recorded. If there are changes in thickness
due to the test, the formula in the NOTE in 4.3.2.5 should be used.
For flat cables, the median indentation value is the mean value of the indentation values from
all the cores of the same size in the sample.
NOTE In the absence of any requirement in the relevant cable standard, a recommendation is given in Annex B.
4.4 Sheath
4.4.1 Sample and test piece preparation for sheaths
For each sheath to be tested, three adjacent pieces shall be taken from a sample having a
length of 250 mm to 500 mm from which the covering (if any) and all the internal parts (cores,
fillers, inner covering, armour etc. if any) have been removed.
The length of each piece of sheathing shall be 50 mm to 100 mm.
From each piece of sheathing, a strip of width equal to about one-third of the perimeter, but
not more than 20 mm, shall be cut parallel to the direction of the axis of the cable if the
sheath does not have ridges.
If the sheath shows ridges caused by five or fewer cores, the strip shall be cut in the direction
of the ridges so that it contains at least one groove which lies approximately in the middle of
the strip throughout its length.

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If the sheath has ridges caused by more than five cores, the strip shall be cut in the same
manner and these ridges shall be removed by grinding.
NOTE 1 A machine of the type specified in Annex A of IEC 60811-501:2012 has been found suitable for grinding
or cutting the ridges.
If the sheath is directly applied on a concentric conductor, an armour or on a metallic screen,
and therefore has ridges which cannot be ground or cut away (unless the diameter is large),
the sheath shall not be removed, and the whole cable piece shall be used as a test piece.
If the smaller sides of a flat cable are fully rounded in shape, this test shall be carried out on
one of the smaller sides. To calculate the compressing force (see Annex A), D is the minor
dimension of the cable and δ is the mean sheath thickness e3 as shown in Figure 4.
If the smaller sides are flat, or nearly flat, as depicted in Figure 4, a test piece shall be
prepared by cutting a strip from the wide side of the cable in the direction of the axis of the
cable. On the inner side, only the ridges shall be removed by grinding or cutting. The width of
the strip to be tested shall be at least 10 mm but not more than 20 mm. The thickness of the
strip shall be measured at the place where the compressing force, F, is applied.
If the oversheath is solidly bonded to a metal sheath, then the oversheath shall not be
removed from the metal sheath.
NOTE 2 Insulation Sheath thickness down to 0,4 mm may be tested under certain circumstances, but it is not
recommended. If tests are made with samples having a thickness below 0,7 mm, it should be recorded as such in
the test report.
4.4.2 Procedure
4.4.2.1 Fixing of test pieces
The strips shall be supported by a metal mandrel, which may be halved in the direction of its
axis to make a more stable support.
NOTE A metal pin or a metal tube is suitable as a mandrel.
The radius diameter of the mandrel shall be approximately equal to half the inner diameter of
the test piece.
The apparatus, the strip and the supporting mandrel shall be arranged so that the mandrel
supports the strip and the blade is pressed against the outer surface of the test piece.
Test pieces of flat cable sheaths shall be placed on a support as shown in Figure 5 when the
smaller sides of the cable are flat.
The force shall be applied in a direction perpendicular to the axis of the mandrel (or of the
cable when a whole cable piece is used) and the blade shall also be perpendicular to the axis
of the mandrel, or of the cable when a whole cable is used.
If the smaller sides of a flat cable are flat, or nearly flat, as depicted in Figure 4, the test piece
(strip) shall be bent around a mandrel having a diameter approximately equal to the diameter
of the core of the cable; the longitudinal axis of the strip shall be perpendicular to the axis of
the mandrel. Provision shall be made so that the inner surface of the strip shall be in contact
over at least 120° of the circumference of the mandrel (see Figure 5). The metal blade of the
test apparatus shall be placed on the middle of the test piece.
For flat cables where the smaller sides are flat, or nearly flat δ (in mm) is the thickness of the
strip at the place where the force is applied. D (in mm) is the diameter of the mandrel plus
twice the value of δ and as shown in Figure 5.

+AMD2:2023 CSV  IEC 2023
If the oversheath is bonded to a metal sheath it shall be tested as if the metal sheath were the
mandrel. In this case the metal sheath shall be supported so that it is not deformed during the
test.
It is advised to use a mandrel with a diameter between 1 to 1,1 times the inner diameter of the
test piece.
4.4.2.2 Application of force
A force calculated according to Annex A shall be applied in a direction perpendicular to the
axis of the mandrel (or of the cable when a whole cable piece is used).
The blade shall also be perpendicular to the relevant axis.
4.4.2.3 Protocol in air oven
See 4.3.2.3.
4.4.2.4 Cooling
See 4.3.2.4.
4.4.2.5 Measurement
The indentation shall be measured on a narrow strip cut from the test piece, as described in
4.3.2.5 and shown in Figure 2.
For flat cables where the smaller sides are flat, or nearly flat, the depth of indentation shall be
related to the original value, δ, as described in 4.4.2.1 and as shown in Figure 5.
NOTE Care should be taken when making the measurement, as factors such as thermomechanical forces may
have distorted the upper surface of the sample giving a false position for the top of indentation, and the true
indentation may differ from that measured directly at the point of indentation. It is therefore essential to use the
thickness value measured before applying the indenter as the baseline figure. If it is evident that distortion has
taken place, or in the case of any uncertainty about the result, a suitable correction to the value of indentation
should be made, thus:
– if the original thickness is δ, but after the test the apparent thickness has become δ1, then for the purposes of
the calculation, the measured indentation (call it M) needs to be corrected by deducting an amount equal to δ1
- δ;
– the correct indentation percentage then becomes:
M− (δ1−δ )
×100
δ
4.4.2.6 Expression of the results
See 4.3.2.6.
5 Test report
The test report shall be in accordance with that given in IEC 60811-100.

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+AMD2:2023 CSV  IEC 2023
Dimensions in millimetres
IEC  273/12
Key
1 testing frame 3a, 3b, 3c supports
2 sample 4 load
Figure 1 – Indentation device
IEC  274/12
Key
1 indentation
2 thin slice to be cut out
3 sectional view of indent under microscope
4 cross-wire of the microscope
5 depth of Indentation
Figure 2 – Measurement of indentation

+AMD2:2023 CSV  IEC 2023
L
IEC  275/12
Key
1 indentation
2 section 1
3 section 2
4 sectional view 1 ("2") under measuring microscope
5 sectional view 2 ("3") under measuring microscope
L 3 mm to 5 mm
Figure 3 – Measurement of indentation for small test pieces

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+AMD2:2023 CSV  IEC 2023
R
e e
1 1
e
e
IEC  276/12
Key
e distance between core groups
e sheath thickness
e mean sheath thickness
R radius approximately e
D minor dimension
NOTE Figure 4 shows where to take the samples from the sheath of a flat cable.
R
D
e e
3 3
IEC
Key
e mean sheath thickness
R radius of the corner
D minor dimension
Figure 4 – Flat cable with a flat smaller side

e
e
D
+AMD2:2023 CSV  IEC 2023
F
IEC  277/12
Key
1 mandrel blade
2 mandrel
3 fixed test piece bent around mandrel
F force
Figure 5 – Indentation device for flat cables with a flat smaller side

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+AMD2:2023 CSV  IEC 2023
Annex A
(normative)
Calculation of the compressing force

The minimum force F, in N, which shall be exerted by the blade upon the test piece, shall be
given by the formula:
F= k 2 Dδ−δ
where
k is a coefficient which shall be specified in the standard for the type of cable;
δ  is the value of the thickness of the insulation or the sheath, as measured on the test
piece, and in accordance with IEC 60811-201 (insulation) or IEC 60811-202 (sheath) in
millimetres;
D  is the mean value of the outer diameter of the test piece (insulation) or the mandrel
diameter plus twice the thickness (sheath), in millimetres.
If a value of k is not specified in the cable standard, it shall be taken from Table A.1.
Table A.1 – General value for k
k Insulation Sheath
0,6 Flexible cables and cores of flexible cables Flexible cables and cables
Cores, with D ≤ 15 mm, for cables for fixed Cables for fixed installation having a value
installations D ≤15 mm
0,7 Cores, with D > 15 mm, and for sector-shaped Cables for fixed installation having a value
cores for cables for fixed installations D >15 mm

The force applied upon the piece of flat cable without sheath as described in 4.3.1 and with
conductor size < 10 mm shall be twice the value given by the above formula in a twin core
cable, where D is the mean value of the minor dimension of the test piece, or multiplied by the
number of cores if more than two cores (see Figure 4).
In the case of insulation, The thickness δ shall be measured on a thin slice of the test piece
as close as possible to the intended point of indentation.
For flat cables without sheath, the outer diameter of the insulated cores is the mean diameter
of the individual cores of the same size, discounting any of smaller nominal conductor D is
determined by calculating the mean diameter using the individual cores of the largest size.
For sector-shaped cores, D is the mean value of the diameter of the “back” or circular part of
the sector, in millimetres, to one decimal place. This is determined from three measurements,
by means of a tape measure, of the circumference of the core assembly (the measurements
being made at three different places on the assembled cores).
In the case of the sheath of a flat cable, D is the minor outer dimension of the test piece.
If the smaller sides of a flat cable are fully rounded in shape, this test shall be carried out on
one of the smaller sides. To calculate the compressing force (see Annex A), D is the minor
dimension of the cable and δ is the mean sheath thickness e3 as shown in Figure 4.

+AMD2:2023 CSV  IEC 2023
For flat cables where the smaller sides are flat, or nearly flat δ (in mm) is the thickness of the
strip at the place where the force is applied. D (in mm) is the diameter of the mandrel plus
δ and as shown in Figure 5.
twice the value of
In the case of a sheath, the thickness of the prepared test piece shall be measured as close
as possible to the intended point of indentation by any suitable method.
The values of δ and D are both expressed in millimetres, to two decimal places.

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Annex B
(informative)
Recommended performance requirement

The performance requirements for a particular type or class of insulated conductor or cable
should preferably be given in the individual cable standard.
In the absence of any given requirement, it is recommended that the following value is
adopted for any cable tested against this standard:
– maximum indentation value (%): 50
NOTE The value of 50 % is inseparable from the underlying principle of the formula and is the same for all
materials. The severity of the test can be changed by variation of the factor k only, without altering the value of
50 %.
+AMD2:2023 CSV  IEC 2023
Bibliography
IEC 60811-3-1:1985, Common test methods for insulating and sheathing materials of electric
cables – Part 3: -Methods specific to PVC compounds – Section One – Pressure test at high
temperature – Tests for resistance to cracking
(withdrawn)
IEC 60811-203, Electric and optical fibre cables – Test methods for non-metallic materials –
Part 203: General tests – Measurement of overall dimensions
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 60811-501:2012, 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

___________
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+AMD2:2023 CSV  IEC 2023
SOMMAIRE
AVANT-PROPOS . 21
INTRODUCTION . 23
1 Domaine d’application . 24
2 Références normatives . 24
3 Termes et définitions . 24
4 Méthode d’essai . 24
4.1 Généralités. 24
4.2 Appareillage . 25
4.2.1 Etuve à air . 25
4.2.2 Dispositif d’empreinte . 25
4.3 Enveloppe isolante . 25
4.3.1 Echantillonnage et préparation des éprouvettes . 25
4.3.2 Mode opératoire . 26
4.4 Gaine . 28
4.4.1 Echantillon et préparation des éprouvettes pour les gaines . 28
4.4.2 Mode opératoire . 28
5 Rapport d’essai . 30
Annexe A (normative) Calcul de la force de compression . 35
Annexe B (informative) Recommandations relatives aux exigences de fonctionnement . 37
Bibliographie . 38

Figure 1 – Dispositif d’empreinte . 31
Figure 2 – Mesure de l’empreinte . 31
Figure 3 – Mesure de l’empreinte pour les petites éprouvettes d’essai . 32
Figure 4 – Câble méplat avec un petit côté plat . 33
Figure 5 – Dispositif d’empreinte pour câbles méplats avec petit côté plat . 34

Tableau A.1 – Valeur générale pour k . 35

+AMD2:2023 CSV  IEC 2023
COMMISSION ÉLECTROTECHNIQUE INTERNATIONALE

____________
CÂBLES ÉLECTRIQUES ET À FIBRES OPTIQUES –
MÉTHODES D’ESSAI POUR LES MATÉRIAUX NON-MÉTALLIQUES –

Partie 508: Essais mécaniques –
Essai de pression à température élevée
pour les enveloppes isolantes et les gaines

AVANT-PROPOS
1) La Commission Electrotechnique Internationale (IEC) est une organisation mondiale de normalisation
composée de l'ensemble des comités électrotechniques nationaux (Comités nationaux de l’IEC). L’IEC a pour
objet de favoriser la coopération internationale pour toutes les questions de normalisation dans les domaines
de l'électricité et de l'électronique. A cet effet, l’IEC – entre autres activités – publie des Normes
internationales, des Spécifications techniques, des Rapports techniques, des Spécifications accessibles au
public (PAS) et des Guides (ci-après dénommés "Publication(s) de
...