Electrical apparatus for explosive gas atmospheres - Electrical resistance trace heating -- Part 1: General and testing requirements

Specifies general and testing requirements for electrical resistance trace heaters for application in explosive gas atmospheres. The standard covers trace heaters that may comprise either factory- or field- (work-site) assembled units, and which may be series heating cables, parallel heating cables or heating pads and heating panels that have been assembled and/or terminated in accordance with the manufacturer's instructions. This standard also includes requirements for termination assemblies and control methods used with trace heating. The hazardous areas referred to by this standard are those defined in EN 60079-10.

Elektrische Betriebsmittel für gasexplosionsgefährdete Bereiche - Elektrische Widerstands-Begleitheizungen -- Teil 1: Allgemeine Anforderungen und Prüfanforderungen

Matériel électrique pour atmosphères explosives gazeuses - Traçage par résistance électrique -- Partie 1: Règles générales et d'essais

Spécifie les règles générales et d'essais des résistances électriques de traçage en atmosphères explosives gazeuses. La norme s'applique aux résis-tances de traçage qui peuvent comprendre les unités assemblées sur site (site d'exploitation) ou en usine et qui peuvent être soit des câbles de traçage en série, soit des câbles de traçage en parallèle, soit des bandes ou des panneaux de traçage qui ont été assemblés et/ou équipés de terminaisons conformément aux instructions du constructeur. La présente norme comprend aussi des règles concernant les ensembles de terminaisons et les méthodes de contrôle appliquées au traçage par résistance. Les zones dangereuses auxquelles cette norme fait référence sont celles définies dans la EN 60079-10.

Električne naprave za eksplozivne plinske atmosfere - Električni uporovni grelni trakovi - 1. del: Splošno in zahteve za preskušanje (IEC 62086-1:2001 + popravek 2003)

General Information

Status
Published
Publication Date
30-Nov-2005
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
01-Dec-2005
Due Date
01-Dec-2005
Completion Date
01-Dec-2005

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EUROPEAN STANDARD EN 62086-1
NORME EUROPÉENNE
EUROPÄISCHE NORM October 2005
ICS 29.260.20
English version
Electrical apparatus for explosive gas atmospheres –
Electrical resistance trace heating
Part 1: General and testing requirements
(IEC 62086-1:2001 + corrigendum 2003)
Matériel électrique pour atmosphères Elektrische Betriebsmittel für
explosives gazeuses – gasexplosionsgefährdete Bereiche –
Traçage par résistance électrique Elektrische Widerstands-Begleitheizungen
Partie 1: Règles générales et d'essais Teil 1: Allgemeine Anforderungen und
(CEI 62086-1:2001 + corrigendum 2003) Prüfanforderungen
(IEC 62086-1:2001 + Corrigendum 2003)

This European Standard was approved by CENELEC on 2005-02-01. CENELEC members are bound to

comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European

Standard the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on

application to the Central Secretariat or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other

language made by translation under the responsibility of a CENELEC member into its own language and

notified to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Cyprus, Czech

Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,

Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden,

Switzerland and United Kingdom.
CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
Central Secretariat: rue de Stassart 35, B - 1050 Brussels

© 2005 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 62086-1:2005 E
---------------------- Page: 1 ----------------------
EN 62086-1:2005 - 2 -
Foreword

The text of the International Standard IEC 62086-1:2001 and its corrigendum February 2003, prepared

by IEC TC 31, Electrical apparatus for explosive atmospheres, was submitted to the CENELEC

Unique Acceptance Procedure and was approved by CENELEC as EN 62086-1 on 2005-02-01

without any modification.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2006-05-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2008-02-01
Annex ZA has been added by CENELEC.
__________
Endorsement notice

The text of the International Standard IEC 62086-1:2001 and its corrigendum February 2003 was

approved by CENELEC as a European Standard without any modification.
__________
---------------------- Page: 2 ----------------------
- 3 - EN 62086-1:2005
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

The following referenced documents are indispensable for the application of this document. For dated

references, only the edition cited applies. For undated references, the latest edition of the referenced

document (including any amendments) applies.

NOTE Where an international publication has been modified by common modifications, indicated by (mod), the relevant

EN/HD applies.
Publication Year Title EN/HD Year
IEC 60050-151 1978 International Electrotechnical Vocabulary - -
(IEV)
Part 151: Electrical and magnetic devices
IEC 60050-426 - Chapter 426: Electrical apparatus for - -
explosive atmospheres
IEC 60079-0 1998 Electrical apparatus for explosive gas - -
atmospheres
Part 0: General requirements
2) 4)
IEC 60364-3 - Electrical installations of buildings HD 384.3 S2 1995
(mod) Part 3: Assessment of general
characteristics
IEC 60050-151:1978 is superseded by IEC 60050-151:2001.
Undated reference.

IEC 60079-0:1998 is superseded by IEC 60079-0:2004, which is harmonized as EN 60079-0:2005 (mod).

Valid edition at date of issue.
---------------------- Page: 3 ----------------------
NORME CEI
INTERNATIONALE IEC
62086-1
INTERNATIONAL
Première édition
STANDARD
First edition
2001-01
Matériel électrique pour atmosphères
explosives gazeuses –
Traçage par résistance électrique –
Partie 1:
Règles générales et d'essais
Electrical apparatus for explosive
gas atmospheres –
Electrical resistance trace heating –
Part 1:
General and testing requirements
 IEC 2001 Droits de reproduction réservés  Copyright - all rights reserved

Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized in

utilisée sous quelque forme que ce soit et par aucun procédé, any form or by any means, electronic or mechanical,

électronique ou mécanique, y compris la photocopie et les including photocopying and microfilm, without permission in

microfilms, sans l'accord écrit de l'éditeur. writing from the publisher.
International Electrotechnical Commission 3, rue de Varembé Geneva, Switzerland
Telefax: +41 22 919 0300 e-mail: inmail@iec.ch IEC web site http://www.iec.ch
CODE PRIX
Commission Electrotechnique Internationale
PRICE CODE
International Electrotechnical Commission
Pour prix, voir catalogue en vigueur
For price, see current catalogue
---------------------- Page: 4 ----------------------
62086-1 © IEC:2001 – 3 –
CONTENTS
Page

FOREWORD .......................................................................................................................... 5

INTRODUCTION ....................................................................................................................7

Clause

1 Scope .............................................................................................................................. 9

2 Normative references....................................................................................................... 9

3 Definitions........................................................................................................................ 9

4 General requirements .................................................................................................... 19

5 Testing........................................................................................................................... 23

6 Marking.......................................................................................................................... 45

Bibliography ......................................................................................................................... 49

Figure 1 – Flammability test ................................................................................................. 25

Figure 2 – Impact test ..........................................................................................................29

Figure 3 – Cold bend test – Type test................................................................................... 31

Figure 4 – Moisture resistance test....................................................................................... 33

Figure 5 – Verification of rated output – Type test ................................................................ 37

Figure 6 – Verification of sheath temperature using system approach .................................. 41

Figure 7 – Maximum sheath temperature using the product classification approach ............. 43

Table 1 – Test voltages for the dielectric test ....................................................................... 23

---------------------- Page: 5 ----------------------
62086-1 © IEC:2001 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
–––––––––––
ELECTRICAL APPARATUS FOR EXPLOSIVE GAS ATMOSPHERES –
ELECTRICAL RESISTANCE TRACE HEATING –
Part 1: General and testing requirements
FOREWORD

1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising

all national electrotechnical committees (IEC National Committees). The object of the 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, the IEC publishes International Standards. 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. The 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 the 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 National Committees.

3) The documents produced have the form of recommendations for international use and are published in the form

of standards, technical specifications, technical reports or guides and they are accepted by the National

Committees in that sense.

4) In order to promote international unification, IEC National Committees undertake to apply IEC International

Standards transparently to the maximum extent possible in their national and regional standards. Any

divergence between the IEC Standard and the corresponding national or regional standard shall be clearly

indicated in the latter.

5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any

equipment declared to be in conformity with one of its standards.

6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject

of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.

International Standard IEC 62086-1 has been prepared by IEC technical committee 31:

Electrical apparatus for explosive atmospheres.
The text of this standard is based on the following documents:
FDIS Report on voting
31/343/FDIS 31/348/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 3.

The committee has decided that the contents of this publication will remain unchanged

until 2003. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.

The contents of the corrigendum of February 2003 have been included in this copy.

---------------------- Page: 6 ----------------------
62086-1 © IEC:2001 – 7 –
INTRODUCTION

This part of IEC 62086 is intended to provide a comprehensive overview of the essential

requirements and testing appropriate to electric surface heating equipment used in explosive

gas atmospheres. The requirements of this standard are considered to be the minimum

requirements for zone 1 or zone 2. While some of this work already exists in national

standards or international standards, this standard has collated much of this existing work and

added considerably to it. This standard should be read in conjunction with IEC 62086-2:

Electrical apparatus for explosive gas atmospheres – Electrical resistance trace heating –

Part 2: Application guide for design, installation and maintenance .
___________
To be published.
---------------------- Page: 7 ----------------------
62086-1 © IEC:2001 – 9 –
ELECTRICAL APPARATUS FOR EXPLOSIVE GAS ATMOSPHERES –
ELECTRICAL RESISTANCE TRACE HEATING –
Part 1: General and testing requirements
1 Scope

This part of IEC 62086 specifies general and testing requirements for electrical resistance

trace heaters for application in explosive gas atmospheres. The standard covers trace heaters

that may comprise either factory- or field- (work-site) assembled units, and which may be

series heating cables, parallel heating cables or heating pads and heating panels that have

been assembled and/or terminated in accordance with the manufacturer’s instructions.

This standard also includes requirements for termination assemblies and control methods

used with trace heating. The hazardous areas referred to by this standard are those defined in

IEC 60079-10.
2 Normative references

The following normative documents contain provisions which, through reference in this text,

constitute provisions of this part of IEC 62086. For dated references, subsequent

amendments to, or revisions of, any of these publications do not apply. However, parties to

agreements based on this part of IEC 62086 are encouraged to investigate the possibility of

applying the most recent editions of the normative documents indicated below. For undated

references, the latest edition of the normative document referred to applies. Members of IEC

and ISO maintain registers of currently valid International Standards.

IEC 60050(151):1978, International Electrotechnical Vocabulary (IEV) – Chapter 151:

Electrical and magnetic devices

IEC 60050(426), International Electrotechnical Vocabulary (IEV) – Chapter 426: Electrical

apparatus for explosive atmospheres

IEC 60079-0:1998, Electrical apparatus for explosive gas atmospheres – Part 0: General

requirements

IEC 60364-3, Electrical installations of buildings – Part 3: Assessment of general characteristics

3 Definitions

For the purpose of this part of IEC 62086, the following definitions as well as the definitions

given in IEC 60050(426) and IEC 60079-0 apply.
3.1
ambient temperature

temperature surrounding the object under consideration. Where electrical trace heaters are

enclosed in thermal insulation, the ambient temperature is the temperature exterior to such

thermal insulation
---------------------- Page: 8 ----------------------
62086-1 © IEC:2001 – 11 –
3.2
branch circuit

that portion of the wiring installation between the overcurrent device protecting the circuit and

the trace heater unit(s)
3.3
connections
(terminations)
3.3.1
cold lead

electrically insulated conductor or conductors used to connect a trace heater to the branch

circuit and designed so that it does not produce significant heat
3.3.2
end termination

termination, which may be heat producing, applied to a trace heater at the end opposite that

where the power is supplied
3.3.3
power termination
termination applied to the end of a trace heater at which the power is supplied
3.4
tee

electrical connection of trace heaters, in series or in parallel, to accommodate a tee or branch

3.5
dead leg

segment of process piping segregated from the normal flow pattern for the purpose of

providing a heat-loss reference
3.6
design loading

minimum power that will meet the design requirements, in the worst conditions, after voltage

and resistance tolerances and appropriate safety factors have been considered
3.7
factory fabricated

trace heating cable, tape or device, including the necessary terminations and connections,

assembled into units or sets
3.8
field-assembled

trace heaters supplied in bulk with terminating components to be assembled at the work site

3.9
heat loss
energy flow from a pipe, vessel or equipment to its surroundings
---------------------- Page: 9 ----------------------
62086-1 © IEC:2001 – 13 –
3.10
heat sink
part that conducts and dissipates heat away from a workpiece

NOTE Typical heat sinks are pipe shoes, pipe supports and items of large mass such as valve actuators or pump

bodies.
3.11
heat-transfer aids

thermally conductive materials, such as metallic foils or heat-transfer compounds used to

increase the heat-transfer efficiency from trace heaters to the workpiece
3.12
heating pad

trace heater comprising series- or parallel-connected elements having sufficient flexibility to

conform to the shape of the surface to be heated
3.13
heating panel

non-flexible trace heater comprising series- or parallel-connected elements fabricated to

conform to the general shape of the surface to be heated
3.14
high-limit temperature

maximum allowable temperature of the system, including piping, fluid and heating system

3.15
maximum ambient temperature

highest ambient temperature at which the trace heating is operable and should perform

according to specified requirements
3.16
maximum withstand temperature

maximum operating or exposure temperature that will not adversely effect the thermal stability

of the heater and its component parts
3.17
metallic covering

metal sheath or braid used to provide physical protection for a trace heater, and/or an

electrical earth path
3.18
minimum ambient temperature

lowest ambient temperature specified at which trace heating is operable and performs

according to specified requirements (and on which heat-loss calculations are based)

3.19
operating voltage
actual voltage applied to the trace heater when in service
3.20
overjacket

continuous layer of insulating material applied outside the metallic sheath, screen or

armouring to protect against corrosion
---------------------- Page: 10 ----------------------
62086-1 © IEC:2001 – 15 –
3.21
power density

power output in watts per linear metre for trace heater cables and cable units, and in watts

per square metre for trace heater pads and panels and trace heater pad and panel units

3.22
rated output

total power or power per unit length of heating cable or trace heater, at rated voltage,

temperature and length, which is normally expressed in watts per metre or watts per square

metre
3.23
rated voltage

voltage to which operating and performance characteristics of trace heaters are referred

3.24
routine test

test to which each individual device is subjected during or after manufacture to ascertain

whether it complies with certain criteria
[IEV 151-04-16]
3.25
series trace heater(s)

heating elements electrically connected in series with a single current path and with a specific

resistance at a given temperature for a given length
3.26
sheath

uniform and continuous metallic or non-metallic outer covering enclosing the heating tape or

cable used to provide protection for the cable against influence from the surroundings

(corrosion, moisture etc.). See overjacket, 3.20
3.27
sheath temperature

temperature of the outermost continuous covering that may be exposed to the surrounding

atmosphere
3.28
stabilized design

concept where the temperature of the trace heater will, by design and use, stabilize below the

limiting temperature, under the most unfavourable conditions, without the need for a

protective system to limit the temperature
3.29
start-up current
current of a trace heater immediately upon energizing
3.30
system documentation

information provided by the supplier to allow satisfactory understanding, installation and safe

use of the trace heating system
---------------------- Page: 11 ----------------------
62086-1 © IEC:2001 – 17 –
3.31
temperature controller

device or combination of devices incorporating a means of sensing temperature and of

controlling the power to the trace heater
3.32
temperature sensor
(sensing element)

device which is designed to respond to temperature providing an electrical signal or

mechanical operation
3.33
thermal insulation

material having air- or gas-filled pockets, void spaces, or heat-reflecting surfaces that, when

properly applied, retards the transfer of heat
3.34
trace heater

device designed for the purpose of producing heat on the principle of electrical resistance and

typically composed of one or more metallic conductors or an electrically conductive material,

suitably electrically insulated and protected
3.35
trace heater unit
(trace heater set)

series trace heater cable, parallel trace heater cable, heater pad or heater panel suitably

terminated in conformity with the manufacturer’s instructions
3.36
trace heating

utilization of electric trace heater cables, pads, panels and support components, externally

applied and used to raise or maintain the temperature of contents in piping, tanks and

associated equipment
3.37
type test

test of one or more devices made to a certain design to show that the design meets certain

specifications
[IEV 151-04-15]
3.38
weather barrier

material that, when installed on the outer surface of thermal insulation, protects the thermal

insulation from water or other liquids, from physical damage caused by sleet, wind or

mechanical abuse; and from deterioration caused by solar radiation or atmospheric

contamination
3.39
workpiece
object to which a trace heater is applied

NOTE Examples include process equipment such as piping, vessels, tanks, valves, instruments and similar

equipment.
---------------------- Page: 12 ----------------------
62086-1 © IEC:2001 – 19 –
4 General requirements
4.1 General

Electrical resistance trace heating within the scope of this standard shall be designed and

constructed so as to ensure electrical, thermal and mechanical durability and reliable

performance so that, in normal use, it poses no danger to the user or the surroundings.

Electrical resistance trace heater and terminations shall comply with one or more of the types

of protection listed in IEC 60079-0 and additionally with the requirements of this standard.

The manufacturer shall declare the maximum operating temperature in degrees Celsius. The

materials used in the trace heater shall withstand a temperature of no less than the maximum

operating temperature +20 K, when tested in accordance with 5.1.10.
In this standard
– resistance trace heaters are not considered to be windings;

– clause 7 of IEC 60079-0 does not apply to electrical insulating materials of trace heaters.

4.2 Trace heaters

Trace heaters shall be provided with a metallic braid or metallic sheath which shall cover at

least 70 % of the surface. They shall be capable of withstanding an impact load of 7 J or 4 J

when tested in accordance with 5.1.5. For the 4 J impact load, the heater shall be marked

with the symbol "X".
4.3 Terminations and connections

Terminations and connections may be identified as an integral part of a trace heater, or may

be identified separately, in which case they are regarded as Ex components in accordance

with clause 13 of IEC 60079-0. Terminations and connections are tested as part of a

representative trace heater unit; see 5.1.1.
4.4 Circuit protection requirements for branch circuits

The minimum requirements for trace heating systems for use in hazardous areas are as

follows:
a) a means of isolating all line conductors from the supply;
b) over-current protection provided for each branch circuit;

c) a means of protecting against earth faults which depend on the type of system earthing

(see IEC 60364-3 for definitions).
For TT and TN systems:

d) a residual-current protective device for each branch circuit having a rated residual

operating current not greater than 300 mA. The device shall have a break time not

exceeding 150 ms at five times the rated residual operating current. Values of 30 mA and

30 ms are preferred unless there is evidence that this will result in a marked increase in

nuisance tripping.

NOTE 1 The function of this protection, which is additional to the over-current protection, is to limit the heating

effect due to abnormal earth fault and earth leakage currents.
NOTE 2 The requirements of a), b), c) and d) may be performed by one device.
---------------------- Page: 13 ----------------------
62086-1 © IEC:2001 – 21 –
For IT systems:

e) an electrical insulation monitoring device shall be installed to disconnect the supply

whenever the electrical resistance is not greater than 50 Ω/V of rated voltage.
4.5 Control and temperature requirements
4.5.1 General

A trace heating system shall be designed so that under all conditions that may reasonably be

foreseen the surface temperature of the trace heaters is limited to the temperature

classification or ignition temperature, less 5 K for temperatures less than or equal to 200 °C

or less 10 K for temperatures greater than 200 °C. This shall be achieved either by a

stabilized design in accordance with 4.5.2, or by the use of temperature control devices in

accordance with 4.5.3 to limit the maximum equipment temperature.

When multiple trace heaters (especially on pipes with different flow conditions) are grouped

together under a single surface-sensing temperature control device, each one shall be

analysed as a stabilized pipe design.
4.5.2 Stabilized design for zone 1 and zone 2 applications

Stabilized design applications, in which the maximum surface temperature of the trace heater

is determined without thermostatic control, shall employ either the systems approach

specified in 5.1.11.2 or the product classification approach specified in 5.1.11.3.

4.5.3 Controlled design

Controlled design applications, which require the use of a temperature control device to limit

the maximum pipe temperature, shall comply with a) for zone 1 and either a) or b) for zone 2:

a) for zone 1 or zone 2 applications: controlled design applications, which require the use of

a temperature control device to limit the maximum surface temperature, shall utilize a

protective device that will de-energize the system after exceeding the maximum operating

temperature, and a reset shall only be possible by hand after the previously defined

process conditions have returned. In case of an error by, or damage to the sensor, the

heating system shall be de-energized before replacing the defective equipment. The

adjustment of the protective device shall be secured and sealed to avoid manipulation.

The protective device shall operate independently from the temperature monitoring

system;

b) for zone 2 applications: a single temperature controller with failure annunciation may be

used. If so, provision of adequate monitoring of such annunciation, such as 24 h
surveillance, shall be made.

NOTE If the control devices are not being provided by the manufacturer, sufficient instructions for selection and

installation should be provided.
---------------------- Page: 14 ----------------------
62086-1 © IEC:2001 – 23 –
5 Testing
5.1 Type tests
5.1.1 General

The provisions of 23.4.1 of IEC 60079-0 apply with the following additions. Samples of trace

heaters at least 3 m in length, unless otherwise specified, shall be selected for testing. Tests

shall be conducted at a temperature between 10 °C and 40 °C unless otherwise stated herein.

Terminations and connections that are to be installed as an integral part of the trace heater,

whether intended to be factory-fabricated or field-assembled, shall be subjected to the same

tests as the trace heater, except where otherwise noted. These connections shall include end

terminations, tees, in-line splices and power terminations, as well as glands, fittings and seals

where a heating cable enters a termination enclosure.
5.1.2 Dielectric test

The dielectric test shall be performed on trace heaters in accordance with table 1.

Table 1 – Test voltages for the dielectric test
Rated voltage Test voltage
V a.c. r.m.s.
< 30 V r.m.s 500
< 60 V d.c. 500
≥ 30 V r.m.s. 2 E + 1 000
≥ 60 V d.c.
2 E + 1 000

The test voltage, where E is the rated voltage, shall be applied between the conductors and

the metallic braid or sheath at a rate of rise of neither less than 100 V/s nor more than

200 V/s and maintained for 1 min without dielectric breakdown. The test voltage waveform

shall be essentially sinusoidal, with a frequency of 45 Hz to 65 Hz.
5.1.3 Electrical insulation resistance test

The electrical insulation resistance shall be measured on the test sample(s) prepared in

accordance with 5.1.1 after the dielectric test specified in 5.1.2. The resistance of the

electrical insulation shall be measured between conductors and the metallic outer covering, or

a specially applied conductive metal tape or braid, by means of a d.c. voltage of 1 000 V for

mineral insulated heaters and 2 500 V for polymer insulated heaters. The measured value

shall be not less than 50 MΩ.
5.1.4 Flammability test

A flammability test shall be performed on trace heaters. The test shall be made in a room free

from draughts. The sample trace heater at least 450 mm in length shall be supported in a

vertical position. For pads, panels and other trace heaters, the sample width shall be 80 mm.

---------------------- Page: 15 ----------------------
62086-1 © IEC:2001 – 25 –

A gummed unbleached paper indicator shall be wrapped once around the sample so that it

projects 20 mm from the sample. The paper indicator shall be positioned 250 mm above the

point at which the inner blue cone of the flame contacts the sample. A layer of dry, pure

surgical cotton not more than 6 mm in depth shall be placed underneath the sample so that

the distance from the cotton to the point of the flame application is 250 mm.

The height of the natural gas flame of the burner shall be adjusted to 130 mm with an inner

blue cone 40 mm high, as shown in figure 1a. The burner shall be tilted to an angle of 20°

from the vertical and the flame applied to the cable so that the tip of the inner blue cone of the

flame touches the specimen at the point approximately 150 mm above its lower end. The

flame shall be brought up to the trace heater in such a manner that the vertical plane

containing the major axis of the burner tube is at right angles to the plane of the cable being

tested as shown in figure 1b. The flame shall be applied for 15 s, then removed for 15 s, until

five such
...

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