IEC 61386-21:2021

IEC 61386-21 ®
Edition 2.0 2021-04
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Conduit systems for cable management –
Part 21: Particular requirements – Rigid conduit systems

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IEC 61386-21 ®
Edition 2.0 2021-04
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Conduit systems for cable management –

Part 21: Particular requirements – Rigid conduit systems

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.120.10 ISBN 978-2-8322-9704-9

– 2 – IEC 61386-21:2021 RLV © IEC 2021
CONTENTS
FOREWORD . 3
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 General requirements . 6
5 General conditions for tests . 6
6 Classification . 6
7 Marking and documentation . 7
8 Dimensions. 7
9 Construction . 9
10 Mechanical properties. 9
11 Electrical properties . 11
12 Thermal properties . 11
13 Fire hazard . 12
14 External influences . 12
15 Electromagnetic compatibility . 12
Annex A (normative) Classification coding for conduit systems . 18
Annex B (normative) Determination of material thickness . 18
Annex C (normative) Additional test requirements for conduit systems already
complying with IEC 61386-1:2008 . 18
Annex AA (informative) Calculation for minimum and maximum rate of increase of
force for 10.2.4 . 19

Figure 101 – Bending apparatus for metallic and composite conduits . 13
Figure 102 – Gauge for checking the minimum inside diameter of the conduit system
after impact, bending, collapse and resistance to heat tests . 14
Figure 103 – Bending apparatus for non-metallic and composite conduit . 15
Figure 104 – Arrangement for collapse test . 16
Figure AA.1 – Graph showing force against time for 750 N force. 19

Table 101 – Thread lengths . 8
Table 102 – Maximum entry diameter and minimum entry length details . 8
Table AA.1 – Minimum and maximum rate of increase of force for 10.2.4 . 20

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
CONDUIT SYSTEMS FOR CABLE MANAGEMENT –

Part 21: Particular requirements – Rigid conduit systems

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
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
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
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
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.
This redline version of the official IEC Standard allows the user to identify the changes made to
the previous edition IEC 61386-21:2002. A vertical bar appears in the margin wherever a change
has been made. Additions are in green text, deletions are in strikethrough red text.

– 4 – IEC 61386-21:2021 RLV © IEC 2021
International Standard IEC 61386-21 has been prepared by subcommittee 23A: Cable
management systems, of IEC technical committee 23: Electrical accessories:
This second edition cancels and replaces the first edition published in 2002. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) Subclause 7.1.103 has been added requiring the manufacturer to declare whether the
conduit is bendable;
b) Annex AA has been added to provide guidance on the application of a constantly
increasing force.
The text of this International Standard is based on the following documents:
FDIS Report on voting
23A/950/FDIS 23A/955/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all the parts in the IEC 61386 series, published under the general title Conduit
systems for cable management, can be found on the IEC website.
This document is to be used in conjunction with IEC 61386-1:2008 and
IEC 61386-1:2008/AMD1:2017.
This document supplements or modifies the corresponding clauses of IEC 61386-1:2008 and
IEC 61386-1:2008/AMD1:2017. Where a particular clause or subclause of IEC 61386-1:2008
and IEC 61386-1:2008/AMD1:2017 is not mentioned in this document, that clause or
subclause applies as far as is reasonable. Where this document states "addition",
"modification" or "replacement", the relevant text of IEC 61386-1:2008 and
IEC 61386-1:2008/AMD1:2017 is to be adapted accordingly.
Subclauses, tables and figures which are in addition to those in IEC 61386-1:2008 and
IEC 61386-1:2008/AMD1:2017 are numbered starting with 101. Annexes which are additional
to those in IEC 61386-1:2008 and IEC 61386-1:2008/AMD1:2017 are lettered AA, BB, etc.
In this document, the following print types are used:
– Requirements proper: in roman type.
– Test specifications: in italic type.
– Explanatory matter: in smaller roman type.

The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://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.

– 6 – IEC 61386-21:2021 RLV © IEC 2021
CONDUIT SYSTEMS FOR CABLE MANAGEMENT –

Part 21: Particular requirements – Rigid conduit systems

1 Scope
This clause of part 1 is applicable, except as follows:
Clause 1 of IEC 61386-1:2008 is applicable, except as follows:
Addition:
This part of IEC 61386 specifies the requirements for rigid conduit systems.
2 Normative references
This clause of part 1 is applicable.
Clause 2 of IEC 61386-1:2008 and of IEC 61386-1:2008/AMD1:2017 are applicable, except as
follows:
Addition:
IEC 61386-1:2008, Conduit systems for cable management – Part 1: General requirements
IEC 61386-1:2008/AMD1:2017
3 Terms and definitions
This clause of part 1 is applicable.
Clause 3 of IEC 61386-1:2008 and of IEC 61386-1:2008/AMD1:2017 are applicable.
4 General requirements
This clause of part 1 is applicable.
Clause 4 of IEC 61386-1:2008 is applicable.
5 General conditions for tests
This clause of part 1 is applicable.
Clause 5 of IEC 61386-1:2008 and of IEC 61386-1:2008/AMD1:2017 are applicable.
6 Classification
This clause of part 1 is applicable, except as follows:

Clause 6 of IEC 61386-1:2008 is applicable, except as follows:
Classifications 6.1.1, 1; 6.1.2, 1; 6.1.3, 2; 6.1.3, 3; 6.1.3, 4; 6.1.4, 1; and 6.1.5, 1 are not
applicable.
NOTE Rigid conduit systems according to 6.1.1, 2 and 6.1.2, 2 and classification 1X 1 from 6.2.1, Table 1 are not
allowed in France.
7 Marking and documentation
This clause of part 1 is applicable, except as follows:
Clause 7 of IEC 61386-1:2008 and of IEC 61386-1:2008/AMD1:2017 are applicable, except as
follows:
Addition:
7.1.101 The conduit shall be marked in accordance with 7.1 along its entire length at regular
intervals of preferably 1 m but not longer than 3 m and each length shall be marked at least
once.
Compliance is checked by inspection.
7.1.102 The manufacturer shall document, for the conduit system, the minimum inside
diameter and the classification in accordance with Clause 6.
Compliance is checked by inspection of the documentation.
7.1.103 The manufacturer shall declare whether the conduit is bendable and provide all
information, instructions and, if necessary, bending aids for proper and safe bending of the
conduit.
Compliance is checked by inspection and by the tests specified in 10.4 and 10.6.
8 Dimensions
Replacement:
8.1 Threads and outside diameters shall comply with IEC 60423.
Compliance is checked by means of the gauges specified in IEC 60423.
8.2 Threadable conduits and threadable conduit fittings, except terminating conduit fittings,
shall comply with Table 101. Non-threadable conduit fittings, except fittings which are part of
a conduit system declaring tensile strength, shall comply with Table 102. The minimum inside
diameter of the conduit system shall be as declared by the manufacturer.
Compliance is checked by measurement.

– 8 – IEC 61386-21:2021 RLV © IEC 2021
Table 101 – Thread lengths
Size External thread Internal thread
Minimum length Minimum length
mm mm mm
6 05,5 06,5
8 06,5 07,5
10 08,5 09,5
12 10,5 11,5
16 12,5 13,5
20 14,0 15,0
25 17,0 18,0
32 19,0 20,0
40 19,0 20,0
50 19,0 20,0
63 19,0 20,0
75 19,0 20,0
Table 102 – Maximum entry diameter and minimum entry length details
External thread Internal thread
Size Maximum entry diameter Minimum entry length
mm mm
6 06,5 06,0
8 08,5 08,0
10 10,5 10,0
12 12,5 12,0
16 16,5 16,0
20 20,5 20,0
25 25,5 25,0
32 32,6 30,0
40 40,7 32,0
50 50,8 42,0
63 63,9 50,0
75 75,9 50,0
Size Maximum entry Minimum entry
diameter length
mm mm mm
6 06,5 06,0
8 08,5 08,0
10 10,5 10,0
12 12,5 12,0
16 16,5 16,0
20 20,5 20,0
25 25,5 25,0
32 32,6 30,0
40 40,7 32,0
50 50,8 42,0
63 63,9 50,0
75 75,9 50,0
9 Construction
This clause of part 1 is applicable.
Clause 9 of IEC 61386-1:2008 is applicable.
10 Mechanical properties
This clause of part 1 is applicable, except as follows:
Clause 10 of IEC 61386-1:2008 and of IEC 61386-1:2008/AMD1:2017 are applicable, except
as follows:
10.2 Compression test
Subclause 10.2 is applicable with the following addition:
10.2.4 Add the following note at the end of Subclause 10.2.4:
NOTE In order to achieve a uniformly increasing compression force, the force indicated in Table 4 is divided by
time; this value is the required rate per second to fulfil the requirement.
Example: For a test force of 750 N an increase of the test force of 25 N/s is required (750 divided by 30 equals 25).
Informative Annex AA gives detailed calculations including tolerances for time and force.
10.4 Bending test
Replacement:
Conduits which are declared by the manufacturer as being bendable are tested in accordance
with 10.4.101, 10.4.102 or 10.4.103.
Addition:
– 10 – IEC 61386-21:2021 RLV © IEC 2021
10.4.101 Metallic conduits
10.4.101.1 Conduit sizes 16, 20 and 25 are subjected to a bending test by means of the
apparatus shown in Figure 101. Testing of other sizes is in accordance with the
manufacturer's instructions.
10.4.101.2 Samples having a length equal to 30 times the nominal diameter, are bent so that
when released, they have an angle of (90 ± 5)°, so that the inside radius of the bend is equal
to six times the nominal diameter.
10.4.101.3 For conduits with welded seams, six samples are tested, three with the seam on
the outside of the bend, three with the seam on the side.
10.4.101.4 After the test:
– the basic material of the conduits and the protective coating of the conduits shall show no
cracks visible to normal or corrected vision without magnification;
– seams, if any, shall not have opened;
– the section of the conduit shall not have distorted unduly.
The distortion of the section is checked as follows:
When the bent conduit is held in such a position that the straight portions are at an angle of
approximately 45° to the vertical, one end of the sample pointing upwards and the other
downwards, it shall be possible to pass the appropriate gauge as shown in Figure 102 through
the sample under its own weight and without any initial speed.
10.4.102 Non-metallic conduits
10.4.102.1 Conduit sizes 16, 20 and 25 are subjected to a bending test by means of the
apparatus shown in Figure 103. The length of the sample is approximately 500 mm ± 10 mm.
Testing of other sizes is in accordance with the manufacturer's instructions.
10.4.102.2 A bending aid, in the form of a coiled spring of square section metal wire, without
burrs and having an overall diameter between 0,7 mm and 1,0 mm less than the specified
minimum inside diameter of the conduit, or a bending aid recommended by the manufacturer,
is inserted into each sample before bending.
10.4.102.3 Before the test, The sample with the bending aid inserted is conditioned for at
least 2 h in a refrigerator within which the temperature is maintained at the declared
temperature as given in Table 1 with a tolerance of ±2 °C.
The bending apparatus is placed beside the refrigerator and The test is carried out within 10
12 s ± 2 s after the removal of the sample from the refrigerator.
10.4.102.4 Each sample is placed in position as shown in Figure 103, and held lightly in the
groove of the former by means of the clamp. The sample is bent round the former by moving
the bending rollers so that, when released, it has an angle of (90 ± 5)°. In this position, it shall
be possible to remove the bending aid without damage to the sample or the aid.
After the test, the sample shall show no cracks visible to normal or corrected vision without
magnification and it shall be possible to pass the appropriate gauge, as shown in Figure 102,
through the sample under its own weight and without any initial speed.
10.4.103 Composite conduits
Composite conduits which are declared by the manufacturer as being bendable are tested
both in accordance with 10.4.101 and 10.4.102, using new samples for each test.

The test is carried out at the declared temperature as given in Table 1 with a tolerance of
±2 °C.
10.5 Flexing test
This subclause of part 1 is not applicable.
Subclause 10.5 of IEC 61386-1:2008 is not applicable.
10.6 Collapse test
Replacement:
10.6.101 Metallic conduits
Metallic conduits are not subjected to a collapse test.
10.6.102 Non-metallic and composite conduits
10.6.102.1 Conduits which are declared by the manufacturer as being bendable shall be
tested in accordance with 10.6.102.2. Before the test, conduits are bent in accordance with
10.4.102 with the exception of 10.4.102.3.
10.6.102.2 The samples are fixed to a rigid support by means of four straps, as shown in
Figure 104, after having removed the bending spring or any other bending aids recommended
by the manufacturer.
The support with the sample in position is kept for 24 h ± 15 min in a heating cabinet at the
declared temperature as given in Table 2 with a tolerance of ±2 °C.
After this period, with the support in such a position that the straight portions of the sample
are at an angle of approximately 45° to the vertical, one end of the sample pointing upwards
and the other downwards, it shall be possible to pass the appropriate gauge, as shown in
Figure 102, through the sample under its own weight and without any initial speed.
10.7 Tensile strength test
This subclause of part 1 is applicable, except as follows:
Subclause 10.7 of IEC 61386-1:2008 is applicable, except as follows:
10.7.3 Not applicable.
11 Electrical properties
This clause of part 1 is applicable.
Clause 11 of IEC 61386-1:2008 and of IEC 61386-1:2008/AMD1:2017 are applicable.
12 Thermal properties
This clause of part 1 is applicable, except as follows:
Clause 12 of IEC 61386-1:2008 is applicable, except as follows:
12.3 Replacement:
– 12 – IEC 61386-21:2021 RLV © IEC 2021
The load is then removed and immediately after its removal it shall be possible to pass the
appropriate gauge, as shown in Figure 102, through the conduit under its own weight and
without any initial speed, with the sample in the vertical position.
13 Fire hazard
This clause of part 1 is applicable.
Clause 13 of IEC 61386-1:2008 and of IEC 61386-1:2008/AMD1:2017 are applicable.
14 External influences
This clause of part 1 is applicable.
Clause 14 of IEC 61386-1:2008 and of IEC 61386-1:2008/AMD1:2017 are applicable.
15 Electromagnetic compatibility
This clause of part 1 is applicable.
Clause 15 of IEC 61386-1:2008 and of IEC 61386-1:2008/AMD1:2017 are applicable.
Addition:
Size Bending radius Radius of groove
Inside radius R Outside radius R r
mm mm mm mm
16 96 113 8,1
20 120 141 10,1
25 150 178 12,7
NOTE This drawing is not intended to govern design except as regards the dimensions shown.
Figure 101 – Bending apparatus for metallic and composite conduits

– 14 – IEC 61386-21:2021 RLV © IEC 2021

D 80 % of the manufacturer's declared minimum inside diameter of the conduit
system
Material Steel, hardened and polished, edges slightly rounded
+0,05
Manufacturing tolerance mm
Tolerance and axial dimension ±0,2 mm
Admissible wear 0,01 mm
NOTE The drawing is not intended to govern design except as regards the dimensions shown
Figure 102 – Gauge for checking the minimum inside diameter of the conduit system
after impact, bending, collapse and resistance to heat tests

Key
1 Bending roller
2 Clamp
3 Sample
4 Bending spring
5 Former
6 Section A – A
Size Radius to Radius of arc Radius of Diameter to
bottom of traced out by groove of bottom of
groove of centre of former and groove of
former bending bending bending
roller roller roller
R R r D
1 2
mm mm mm mm mm
16 48 84 8,1 24
20 60 105 10,1 30
25 75 131,25 12,6 37,5
NOTE This drawing is not intended to govern design except as regards the dimensions shown.
Figure 103 – Bending apparatus for non-metallic and composite conduit

– 16 – IEC 61386-21:2021 RLV © IEC 2021

Key
1 Sample
2 Rigid support
NOTE This drawing is not intended to govern design except as regards the dimensions shown.
Figure 104 – Arrangement for collapse test

Annex A
(normative)
This annex of part 1 is applicable

Annex B
(normative)
This annex of part 1 is applicable

– 18 – IEC 61386-21:2021 RLV © IEC 2021
Annex A
(normative)
Classification coding for conduit systems
Annex A of IEC 61386-1:2008 is applicable.

Annex B
(normative)
Determination of material thickness
Annex B of IEC 61386-1:2008 is applicable.

Annex C
(normative)
Additional test requirements for conduit systems
already complying with IEC 61386-1:2008
Annex C of IEC 61386-1:2008 and of IEC 61386-1:2008/AMD1:2017 are applicable.

Addition:
Annex AA
(informative)
Calculation for minimum and maximum rate of increase of force for 10.2.4
The following information is provided to assist test engineers calculate the required rate of
increase of force vs time for compression test machines which have tolerances on the rate of
load application.
Calculations for minimum and maximum rate of increase of force for 10.2.4:
– minimum rate equals minimum force (Table 4) divided by maximum time (33 s);
– nominal rate equals nominal force (Table 4) divided by nominal time (30 s);
– maximum rate equals maximum force (Table 4 +4 %) divided by minimum time (27 s).
For 750 N force, this can be shown by Figure AA.1 as force (N) against time (s).

Key
Line 1. is maximum rate
Line 2. is minimum rate
Figure AA.1 – Graph showing force against time for 750 N force

– 20 – IEC 61386-21:2021 RLV © IEC 2021
For all force levels, the calculations are as given in Table AA.1.
Table AA.1 – Minimum and maximum rate of increase of force for 10.2.4
Compression force Rate (N/s)
(N) Minimum Nominal Maximum
125 3,8 4,2 4,8
320 9,7 10,7 12,3
750 22,7 25,0 28,9
1 250 37,9 41,7 48,1
4 000 121,2 133,3 154,1
___________
IEC 61386-21 ®
Edition 2.0 2021-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Conduit systems for cable management –
Part 21: Particular requirements – Rigid conduit systems

Systèmes de conduits pour la gestion du câblage –
Partie 21: Exigences particulières – Systèmes de conduits rigides

– 2 – IEC 61386-21:2021 © IEC 2021
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 General requirements . 5
5 General conditions for tests . 5
6 Classification . 5
7 Marking and documentation . 5
8 Dimensions. 6
9 Construction . 7
10 Mechanical properties. 7
11 Electrical properties . 9
12 Thermal properties . 9
13 Fire hazard . 9
14 External influences . 9
15 Electromagnetic compatibility . 10
Annex A (normative) Classification coding for conduit systems . 14
Annex B (normative) Determination of material thickness . 14
Annex C (normative) Additional test requirements for conduit systems already
complying with IEC 61386-1:2008 . 14
Annex AA (informative) Calculation for minimum and maximum rate of increase of
force for 10.2.4 . 15

Figure 101 – Bending apparatus for metallic and composite conduits . 10
Figure 102 – Gauge for checking the minimum inside diameter of the conduit system
after impact, bending, collapse and resistance to heat tests . 11
Figure 103 – Bending apparatus for non-metallic and composite conduit . 12
Figure 104 – Arrangement for collapse test . 13
Figure AA.1 – Graph showing force against time for 750 N force. 15

Table 101 – Thread lengths . 6
Table 102 – Maximum entry diameter and minimum entry length details . 7
Table AA.1 – Minimum and maximum rate of increase of force for 10.2.4 . 16

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
CONDUIT SYSTEMS FOR CABLE MANAGEMENT –

Part 21: Particular requirements – Rigid conduit systems

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
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
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
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
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 61386-21 has been prepared by subcommittee 23A: Cable
management systems, of IEC technical committee 23: Electrical accessories:
This second edition cancels and replaces the first edition published in 2002. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) Subclause 7.1.103 has been added requiring the manufacturer to declare whether the
conduit is bendable;
b) Annex AA has been added to provide guidance on the application of a constantly
increasing force.
– 4 – IEC 61386-21:2021 © IEC 2021
The text of this International Standard is based on the following documents:
FDIS Report on voting
23A/950/FDIS 23A/955/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all the parts in the IEC 61386 series, published under the general title Conduit
systems for cable management, can be found on the IEC website.
This document is to be used in conjunction with IEC 61386-1:2008 and
IEC 61386-1:2008/AMD1:2017.
This document supplements or modifies the corresponding clauses of IEC 61386-1:2008 and
IEC 61386-1:2008/AMD1:2017. Where a particular clause or subclause of IEC 61386-1:2008
and IEC 61386-1:2008/AMD1:2017 is not mentioned in this document, that clause or
subclause applies as far as is reasonable. Where this document states "addition",
"modification" or "replacement", the relevant text of IEC 61386-1:2008 and
IEC 61386-1:2008/AMD1:2017 is to be adapted accordingly.
Subclauses, tables and figures which are in addition to those in IEC 61386-1:2008 and
IEC 61386-1:2008/AMD1:2017 are numbered starting with 101. Annexes which are additional
to those in IEC 61386-1:2008 and IEC 61386-1:2008/AMD1:2017 are lettered AA, BB, etc.
In this document, the following print types are used:
– Requirements proper: in roman type.
– Test specifications: in italic type.
– Explanatory matter: in smaller roman type.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://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.
CONDUIT SYSTEMS FOR CABLE MANAGEMENT –

Part 21: Particular requirements – Rigid conduit systems

1 Scope
Clause 1 of IEC 61386-1:2008 is applicable, except as follows:
Addition:
This part of IEC 61386 specifies the requirements for rigid conduit systems.
2 Normative references
Clause 2 of IEC 61386-1:2008 and of IEC 61386-1:2008/AMD1:2017 are applicable, except as
follows:
Addition:
IEC 61386-1:2008, Conduit systems for cable management – Part 1: General requirements
IEC 61386-1:2008/AMD1:2017
3 Terms and definitions
Clause 3 of IEC 61386-1:2008 and of IEC 61386-1:2008/AMD1:2017 are applicable.
4 General requirements
Clause 4 of IEC 61386-1:2008 is applicable.
5 General conditions for tests
Clause 5 of IEC 61386-1:2008 and of IEC 61386-1:2008/AMD1:2017 are applicable.
6 Classification
Clause 6 of IEC 61386-1:2008 is applicable, except as follows:
Classifications 6.1.1, 1; 6.1.2, 1; 6.1.3, 2; 6.1.3, 3; 6.1.3, 4; 6.1.4, 1; and 6.1.5, 1 are not
applicable.
NOTE Rigid conduit systems according to 6.1.1, 2 and 6.1.2, 2 and classification 1 from 6.2.1, Table 1 are not
allowed in France.
7 Marking and documentation
Clause 7 of IEC 61386-1:2008 and of IEC 61386-1:2008/AMD1:2017 are applicable, except as
follows:
– 6 – IEC 61386-21:2021 © IEC 2021
Addition:
7.1.101 The conduit shall be marked in accordance with 7.1 along its entire length at regular
intervals of preferably 1 m but not longer than 3 m and each length shall be marked at least
once.
Compliance is checked by inspection.
7.1.102 The manufacturer shall document, for the conduit system, the minimum inside
diameter and the classification in accordance with Clause 6.
Compliance is checked by inspection of the documentation.
7.1.103 The manufacturer shall declare whether the conduit is bendable and provide all
information, instructions and, if necessary, bending aids for proper and safe bending of the
conduit.
Compliance is checked by inspection and by the tests specified in 10.4 and 10.6.
8 Dimensions
Replacement:
8.1 Threads and outside diameters shall comply with IEC 60423.
Compliance is checked by means of the gauges specified in IEC 60423.
8.2 Threadable conduits and threadable conduit fittings, except terminating conduit fittings,
shall comply with Table 101. Non-threadable conduit fittings, except fittings which are part of
a conduit system declaring tensile strength, shall comply with Table 102. The minimum inside
diameter of the conduit system shall be as declared by the manufacturer.
Compliance is checked by measurement.
Table 101 – Thread lengths
Size External thread Internal thread
Minimum length Minimum length
mm mm mm
6 05,5 06,5
8 06,5 07,5
10 08,5 09,5
12 10,5 11,5
16 12,5 13,5
20 14,0 15,0
25 17,0 18,0
32 19,0 20,0
40 19,0 20,0
50 19,0 20,0
63 19,0 20,0
75 19,0 20,0
Table 102 – Maximum entry diameter and minimum entry length details
Size Maximum entry Minimum entry
diameter length
mm mm mm
6 06,5 06,0
8 08,5 08,0
10 10,5 10,0
12 12,5 12,0
16 16,5 16,0
20 20,5 20,0
25 25,5 25,0
32 32,6 30,0
40 40,7 32,0
50 50,8 42,0
63 63,9 50,0
75 75,9 50,0
9 Construction
Clause 9 of IEC 61386-1:2008 is applicable.
10 Mechanical properties
Clause 10 of IEC 61386-1:2008 and of IEC 61386-1:2008/AMD1:2017 are applicable, except
as follows:
10.2 Compression test
Subclause 10.2 is applicable with the following addition:
10.2.4 Add the following note at the end of Subclause 10.2.4:
NOTE In order to achieve a uniformly increasing compression force, the force indicated in Table 4 is divided by
time; this value is the required rate per second to fulfil the requirement.
Example: For a test force of 750 N an increase of the test force of 25 N/s is required (750 divided by 30 equals 25).
Informative Annex AA gives detailed calculations including tolerances for time and force.
10.4 Bending test
Replacement:
Conduits which are declared by the manufacturer as being bendable are tested in accordance
with 10.4.101, 10.4.102 or 10.4.103.
Addition:
10.4.101 Metallic conduits
10.4.101.1 Conduit sizes 16, 20 and 25 are subjected to a bending test by means of the
apparatus shown in Figure 101. Testing of other sizes is in accordance with the
manufacturer's instructions.
– 8 – IEC 61386-21:2021 © IEC 2021
10.4.101.2 Samples having a length equal to 30 times the nominal diameter, are bent so that
when released, they have an angle of (90 ± 5)°, so that the inside radius of the bend is equal
to six times the nominal diameter.
10.4.101.3 For conduits with welded seams, six samples are tested, three with the seam on
the outside of the bend, three with the seam on the side.
10.4.101.4 After the test:
– the basic material of the conduits and the protective coating of the conduits shall show no
cracks visible to normal or corrected vision without magnification;
– seams, if any, shall not have opened;
– the section of the conduit shall not have distorted unduly.
The distortion of the section is checked as follows:
When the bent conduit is held in such a position that the straight portions are at an angle of
approximately 45° to the vertical, one end of the sample pointing upwards and the other
downwards, it shall be possible to pass the appropriate gauge as shown in Figure 102 through
the sample under its own weight and without any initial speed.
10.4.102 Non-metallic conduits
10.4.102.1 Conduit sizes 16, 20 and 25 are subjected to a bending test by means of the
apparatus sho
...

IEC 61386-21 ®
Edition 2.0 2021-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Conduit systems for cable management –
Part 21: Particular requirements – Rigid conduit systems

Systèmes de conduits pour la gestion du câblage –
Partie 21: Exigences particulières – Systèmes de conduits rigides

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IEC 61386-21 ®
Edition 2.0 2021-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Conduit systems for cable management –

Part 21: Particular requirements – Rigid conduit systems

Systèmes de conduits pour la gestion du câblage –

Partie 21: Exigences particulières – Systèmes de conduits rigides

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.120.10 ISBN 978-2-8322-1053-1

– 2 – IEC 61386-21:2021 © IEC 2021
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 General requirements . 5
5 General conditions for tests . 5
6 Classification . 5
7 Marking and documentation . 5
8 Dimensions. 6
9 Construction . 7
10 Mechanical properties. 7
11 Electrical properties . 9
12 Thermal properties . 9
13 Fire hazard . 9
14 External influences . 9
15 Electromagnetic compatibility . 10
Annex A (normative) Classification coding for conduit systems . 14
Annex B (normative) Determination of material thickness . 14
Annex C (normative) Additional test requirements for conduit systems already
complying with IEC 61386-1:2008 . 14
Annex AA (informative) Calculation for minimum and maximum rate of increase of
force for 10.2.4 . 15

Figure 101 – Bending apparatus for metallic and composite conduits . 10
Figure 102 – Gauge for checking the minimum inside diameter of the conduit system
after impact, bending, collapse and resistance to heat tests . 11
Figure 103 – Bending apparatus for non-metallic and composite conduit . 12
Figure 104 – Arrangement for collapse test . 13
Figure AA.1 – Graph showing force against time for 750 N force. 15

Table 101 – Thread lengths . 6
Table 102 – Maximum entry diameter and minimum entry length details . 7
Table AA.1 – Minimum and maximum rate of increase of force for 10.2.4 . 16

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
CONDUIT SYSTEMS FOR CABLE MANAGEMENT –

Part 21: Particular requirements – Rigid conduit systems

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
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
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
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
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 61386-21 has been prepared by subcommittee 23A: Cable
management systems, of IEC technical committee 23: Electrical accessories:
This second edition cancels and replaces the first edition published in 2002. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) Subclause 7.1.103 has been added requiring the manufacturer to declare whether the
conduit is bendable;
b) Annex AA has been added to provide guidance on the application of a constantly
increasing force.
– 4 – IEC 61386-21:2021 © IEC 2021
The text of this International Standard is based on the following documents:
FDIS Report on voting
23A/950/FDIS 23A/955/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all the parts in the IEC 61386 series, published under the general title Conduit
systems for cable management, can be found on the IEC website.
This document is to be used in conjunction with IEC 61386-1:2008 and
IEC 61386-1:2008/AMD1:2017.
This document supplements or modifies the corresponding clauses of IEC 61386-1:2008 and
IEC 61386-1:2008/AMD1:2017. Where a particular clause or subclause of IEC 61386-1:2008
and IEC 61386-1:2008/AMD1:2017 is not mentioned in this document, that clause or
subclause applies as far as is reasonable. Where this document states "addition",
"modification" or "replacement", the relevant text of IEC 61386-1:2008 and
IEC 61386-1:2008/AMD1:2017 is to be adapted accordingly.
Subclauses, tables and figures which are in addition to those in IEC 61386-1:2008 and
IEC 61386-1:2008/AMD1:2017 are numbered starting with 101. Annexes which are additional
to those in IEC 61386-1:2008 and IEC 61386-1:2008/AMD1:2017 are lettered AA, BB, etc.
In this document, the following print types are used:
– Requirements proper: in roman type.
– Test specifications: in italic type.
– Explanatory matter: in smaller roman type.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://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.
CONDUIT SYSTEMS FOR CABLE MANAGEMENT –

Part 21: Particular requirements – Rigid conduit systems

1 Scope
Clause 1 of IEC 61386-1:2008 is applicable, except as follows:
Addition:
This part of IEC 61386 specifies the requirements for rigid conduit systems.
2 Normative references
Clause 2 of IEC 61386-1:2008 and of IEC 61386-1:2008/AMD1:2017 are applicable, except as
follows:
Addition:
IEC 61386-1:2008, Conduit systems for cable management – Part 1: General requirements
IEC 61386-1:2008/AMD1:2017
3 Terms and definitions
Clause 3 of IEC 61386-1:2008 and of IEC 61386-1:2008/AMD1:2017 are applicable.
4 General requirements
Clause 4 of IEC 61386-1:2008 is applicable.
5 General conditions for tests
Clause 5 of IEC 61386-1:2008 and of IEC 61386-1:2008/AMD1:2017 are applicable.
6 Classification
Clause 6 of IEC 61386-1:2008 is applicable, except as follows:
Classifications 6.1.1, 1; 6.1.2, 1; 6.1.3, 2; 6.1.3, 3; 6.1.3, 4; 6.1.4, 1; and 6.1.5, 1 are not
applicable.
NOTE Rigid conduit systems according to 6.1.1, 2 and 6.1.2, 2 and classification 1 from 6.2.1, Table 1 are not
allowed in France.
7 Marking and documentation
Clause 7 of IEC 61386-1:2008 and of IEC 61386-1:2008/AMD1:2017 are applicable, except as
follows:
– 6 – IEC 61386-21:2021 © IEC 2021
Addition:
7.1.101 The conduit shall be marked in accordance with 7.1 along its entire length at regular
intervals of preferably 1 m but not longer than 3 m and each length shall be marked at least
once.
Compliance is checked by inspection.
7.1.102 The manufacturer shall document, for the conduit system, the minimum inside
diameter and the classification in accordance with Clause 6.
Compliance is checked by inspection of the documentation.
7.1.103 The manufacturer shall declare whether the conduit is bendable and provide all
information, instructions and, if necessary, bending aids for proper and safe bending of the
conduit.
Compliance is checked by inspection and by the tests specified in 10.4 and 10.6.
8 Dimensions
Replacement:
8.1 Threads and outside diameters shall comply with IEC 60423.
Compliance is checked by means of the gauges specified in IEC 60423.
8.2 Threadable conduits and threadable conduit fittings, except terminating conduit fittings,
shall comply with Table 101. Non-threadable conduit fittings, except fittings which are part of
a conduit system declaring tensile strength, shall comply with Table 102. The minimum inside
diameter of the conduit system shall be as declared by the manufacturer.
Compliance is checked by measurement.
Table 101 – Thread lengths
Size External thread Internal thread
Minimum length Minimum length
mm mm mm
6 05,5 06,5
8 06,5 07,5
10 08,5 09,5
12 10,5 11,5
16 12,5 13,5
20 14,0 15,0
25 17,0 18,0
32 19,0 20,0
40 19,0 20,0
50 19,0 20,0
63 19,0 20,0
75 19,0 20,0
Table 102 – Maximum entry diameter and minimum entry length details
Size Maximum entry Minimum entry
diameter length
mm mm mm
6 06,5 06,0
8 08,5 08,0
10 10,5 10,0
12 12,5 12,0
16 16,5 16,0
20 20,5 20,0
25 25,5 25,0
32 32,6 30,0
40 40,7 32,0
50 50,8 42,0
63 63,9 50,0
75 75,9 50,0
9 Construction
Clause 9 of IEC 61386-1:2008 is applicable.
10 Mechanical properties
Clause 10 of IEC 61386-1:2008 and of IEC 61386-1:2008/AMD1:2017 are applicable, except
as follows:
10.2 Compression test
Subclause 10.2 is applicable with the following addition:
10.2.4 Add the following note at the end of Subclause 10.2.4:
NOTE In order to achieve a uniformly increasing compression force, the force indicated in Table 4 is divided by
time; this value is the required rate per second to fulfil the requirement.
Example: For a test force of 750 N an increase of the test force of 25 N/s is required (750 divided by 30 equals 25).
Informative Annex AA gives detailed calculations including tolerances for time and force.
10.4 Bending test
Replacement:
Conduits which are declared by the manufacturer as being bendable are tested in accordance
with 10.4.101, 10.4.102 or 10.4.103.
Addition:
10.4.101 Metallic conduits
10.4.101.1 Conduit sizes 16, 20 and 25 are subjected to a bending test by means of the
apparatus shown in Figure 101. Testing of other sizes is in accordance with the
manufacturer's instructions.
– 8 – IEC 61386-21:2021 © IEC 2021
10.4.101.2 Samples having a length equal to 30 times the nominal diameter, are bent so that
when released, they have an angle of (90 ± 5)°, so that the inside radius of the bend is equal
to six times the nominal diameter.
10.4.101.3 For conduits with welded seams, six samples are tested, three with the seam on
the outside of the bend, three with the seam on the side.
10.4.101.4 After the test:
– the basic material of the conduits and the protective coating of the conduits shall show no
cracks visible to normal or corrected vision without magnification;
– seams, if any, shall not have opened;
– the section of the conduit shall not have distorted unduly.
The distortion of the section is checked as follows:
When the bent conduit is held in such a position that the straight portions are at an angle of
approximately 45° to the vertical, one end of the sample pointing upwards and the other
downwards, it shall be possible to pass the appropriate gauge as shown in Figure 102 through
the sample under its own weight and without any initial speed.
10.4.102 Non-metallic conduits
10.4.102.1 Conduit sizes 16, 20 and 25 are subjected to a bending test by means of the
apparatus shown in Figure 103. The length of the sample is 500 mm ± 10 mm. Testing of
other sizes is in accordance with the manufacturer's instructions.
10.4.102.2 A bending aid, in the form of a coiled spring of square section metal wire, without
burrs and having an overall diameter between 0,7 mm and 1,0 mm less than the specified
minimum inside diameter of the conduit, or a bending aid recommended by the manufacturer,
is inserted into each sample before bending.
10.4.102.3 The sample with the bending aid inserted is conditioned for at least 2 h in a
refrigerator within which the temperature is maintained at the declared temperature as given
in Table 1 with a tolerance of ±2 °C.
The test is carried out within 12 s ± 2 s after the removal of the sample from the refrigerator.
10.4.102.4 Each sample is placed in position as shown in Figure 103, and held lightly in the
groove of the former by means of the clamp. The sample is bent round the former by moving
the bending rollers so that, when released, it has an angle of (90 ± 5)°. In this position, it shall
be possible to remove the bending aid without damage to the sample or the aid.
After the test, the sample shall show no cracks visible to normal or corrected vision without
magnification and it shall be possible to pass the appropriate gauge, as shown in Figure 102,
through the sample under its own weight and without any initial speed.
10.4.103 Composite conduits
Composite conduits which are declared by the manufacturer as being bendable are tested
both in accordance with 10.4.101 and 10.4.102, using new samples for each test.
The test is carried out at the declared temperature as given in Table 1 with a tolerance of
±2 °C.
10.5 Flexing test
Subclause 10.5 of IEC 61386-1:2008 is not applicable.

10.6 Collapse test
Replacement:
10.6.101 Metallic conduits
Metallic conduits are not subjected to a collapse test.
10.6.102 Non-metallic and composite conduits
10.6.102.1 Conduits which are declared by the manufacturer as being bendable shall be
tested in accordance with 10.6.102.2. Before the test, conduits are bent in accordance with
10.4.102 with the exception of 10.4.102.3.
10.6.102.2 The samples are fixed to a rigid support by means of four straps, as shown in
Figure 104, after having removed the bending spring or any other bending aids recommended
by the manufacturer.
The support with the sample in position is kept for 24 h ± 15 min in a heating cabinet at the
declared temperature as given in Table 2 with a tolerance of ±2 °C.
After this period, with the support in such a position that the straight portions of the sample
are at an angle of approximately 45° to the vertical, one end of the sample pointing upwards
and the other downwards, it shall be possible to pass the appropriate gauge, as shown in
Figure 102, through the sample under its own weight and without any initial speed.
10.7 Tensile test
Subclause 10.7 of IEC 61386-1:2008 is applicable, except as follows:
10.7.3 Not applicable.
11 Electrical properties
Clause 11 of IEC 61386-1:2008 and of IEC 61386-1:2008/AMD1:2017 are applicable.
12 Thermal properties
Clause 12 of IEC 61386-1:2008 is applicable, except as follows:
12.3 Replacement:
The load is then removed and immediately after its removal it shall be possible to pass the
appropriate gauge, as shown in Figure 102, through the conduit under its own weight and
without any initial speed, with the sample in the vertical position.
13 Fire hazard
Clause 13 of IEC 61386-1:2008 and of IEC 61386-1:2008/AMD1:2017 are applicable.
14 External influences
Clause 14 of IEC 61386-1:2008 and of IEC 61386-1:2008/AMD1:2017 are applicable.

– 10 – IEC 61386-21:2021 © IEC 2021
15 Electromagnetic compatibility
Clause 15 of IEC 61386-1:2008 and of IEC 61386-1:2008/AMD1:2017 are applicable.
Addition:
Size Bending radius Radius of groove
Inside radius R Outside radius R r
mm mm mm mm
16 96 113 8,1
20 120 141 10,1
25 150 178 12,7
NOTE This drawing is not intended to govern design except as regards the dimensions shown.
Figure 101 – Bending apparatus for metallic and composite conduits

D 80 % of the manufacturer's declared minimum inside diameter of the conduit
system
Material Steel, hardened and polished, edges slightly rounded
+0,05
Manufacturing tolerance mm
Tolerance and axial dimension ±0,2 mm
Admissible wear 0,01 mm
NOTE The drawing is not intended to govern design except as regards the dimensions shown
Figure 102 – Gauge for checking the minimum inside diameter of the conduit system
after impact, bending, collapse and resistance to heat tests

– 12 – IEC 61386-21:2021 © IEC 2021

Key
1 Bending roller
2 Clamp
3 Sample
4 Bending spring
5 Former
6 Section A – A
Size Radius to Radius of arc Radius of Diameter to
bottom of traced out by groove of bottom of
groove of centre of former and groove of
former bending bending bending
roller roller roller
R R r D
1 2
mm mm mm mm mm
16 48 84 8,1 24
20 60 105 10,1 30
25 75 131,25 12,6 37,5
NOTE This drawing is not intended to govern design except as regards the dimensions shown.
Figure 103 – Bending apparatus for non-metallic and composite conduit

Key
1 Sample
2 Rigid support
NOTE This drawing is not intended to govern design except as regards the dimensions shown.
Figure 104 – Arrangement for collapse test
...