Electrical apparatus for explosive gas atmospheres - Electrical resistance trace heating -- Part 2: Application guide for design, installation and maintenance

Pprovides guidance for the application of electrical resistance trace-heating systems in areas where explosive gas atmospheres may be present. It provides recommendations for the design, installation and maintenance of trace-heating equipment and associated control and monitoring equipment. This part supplements the requirements specified in EN 62086-1.

Elektrische Betriebsmittel für gasexplosionsgefährdete Bereiche - Elektrische Widerstands-Begleitheizungen -- Teil 2: Anwendungsleitfaden für Entwurf, Installation und Instandhaltung

Matériel électrique pour atmosphères explosives gazeuses - Traçage par résistance électrique -- Partie 2: Guide d'application pour la conception, l'installation et la maintenance

Fournit des lignes directrices quant à l'application des systèmes de traçage par résistance électrique dans les emplacements où l'on peut rencontrer des atmosphères explosives. Elle fournit des recommandations pour la conception, l'installation et la maintenance du matériel de traçage et du matériel associé de commande et de surveillance. La présente partie représente un complément des prescriptions spécifiées dans la EN 62086-1.

Električne naprave za eksplozivne plinske atmosfere - Električni uporovni grelni trakovi - 2. del: Vodila za zasnovo, vgraditev in vzdrževanje (IEC 62086-2:2001)

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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SLOVENSKI SIST EN 62086-2:2005
STANDARD
december 2005
Električne naprave za eksplozivne plinske atmosfere - Električni uporovni
grelni trakovi - 2. del: Vodila za zasnovo, vgraditev in vzdrževanje (IEC 62086-
2:2001)
Electrical apparatus for explosive gas atmospheres - Electrical resistance trace

heating - Part 2: Application guide for design, installation and maintenance (IEC

62086-2:2001)
ICS 29.260.20 Referenčna številka
SIST EN 62086-2:2005(en)

© Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno

---------------------- Page: 1 ----------------------
EUROPEAN STANDARD EN 62086-2
NORME EUROPÉENNE
EUROPÄISCHE NORM October 2005
ICS 29.260.20
English version
Electrical apparatus for explosive gas atmospheres –
Electrical resistance trace heating
Part 2: Application guide for design,
installation and maintenance
(IEC 62086-2:2001)
Matériel électrique pour atmosphères Elektrische Betriebsmittel für
explosives gazeuses – gasexplosionsgefährdete Bereiche –
Traçage par résistance électrique Elektrische Widerstands-Begleitheizungen
Partie 2: Guide d'application Teil 2: Anwendungsleitfaden
pour la conception, l'installation für Entwurf, Installation und
et la maintenance Instandhaltung
(CEI 62086-2:2001) (IEC 62086-2:2001)

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 62086-2:2005 E
---------------------- Page: 2 ----------------------
EN 62086-2:2005 - 2 -
Foreword

The text of the International Standard IEC 62086-2:2001, 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 62086-2 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 62086-2:2001 was approved by CENELEC as a European

Standard without any modification.
__________
---------------------- Page: 3 ----------------------
- 3 - EN 62086-2:2005
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 60079-0 1998 Electrical apparatus for explosive gas -
atmospheres
Part 0: General requirements
IEC 60079-10 Part 10: Classification of hazardous areas EN 60079-10 2)
1995 1996
IEC 60079-14 Part 14: Electrical installations in hazardous EN 60079-14 3)
1996 1997
areas (other than mines)
IEC 60079-17 Part 17: Inspection and maintenance of EN 60079-17 4)
1996 1997
electrical installations in hazardous areas
(other than mines)
IEC 62086-1 Electrical apparatus for explosive gas EN 62086-1 2005
2001
atmospheres - Electrical resistance trace
heating
Part 1: General and testing requirements

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

EN 60079-10:1996 is superseded by EN 60079-10:2003, which is based on IEC 60079-10:2002.

EN 60079-14:1997 is superseded by EN 60079-14:2003, which is based on IEC 60079-14:2002.

EN 60079-17:1997 is superseded by EN 60079-17:2003, which is based on IEC 60079-17:2002.

---------------------- Page: 4 ----------------------
NORME CEI
INTERNATIONALE IEC
62086-2
INTERNATIONAL
Première édition
STANDARD
First edition
2001-03
Matériel électrique pour atmosphères
explosives gazeuses –
Traçage par résistance électrique –
Partie 2:
Guide d'application pour la conception,
l'installation et la maintenance
Electrical apparatus for explosive
gas atmospheres –
Electrical resistance trace heating –
Part 2:
Application guide for design,
installation and maintenance
 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: 5 ----------------------
62086-2 © IEC:2001 – 3 –
CONTENTS
Page

FOREWORD...........................................................................................................................7

Clause

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

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

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

4 Application considerations ..............................................................................................11

4.1 General .................................................................................................................11

4.2 Corrosive areas .....................................................................................................11

4.3 Installation considerations......................................................................................11

4.4 Process temperature accuracy...............................................................................13

5 Thermal insulation ..........................................................................................................13

5.1 General .................................................................................................................13

5.2 Selection of insulating material ..............................................................................15

5.3 Selection of weather barrier (cladding) ...................................................................15

5.4 Selection of economical thickness..........................................................................19

5.5 Double insulation ...................................................................................................19

6 System design ................................................................................................................23

6.1 Introduction ...........................................................................................................23

6.2 Purpose of, and major requirement for, trace heating .............................................23

6.3 Heat loss calculations ............................................................................................23

6.4 Heat-up considerations ..........................................................................................25

6.5 Heat-loss design safety factor................................................................................29

6.6 Selection of trace heater........................................................................................29

6.7 Maximum temperature determination .....................................................................31

6.8 Design information.................................................................................................35

6.9 Power system ........................................................................................................37

6.10 Start-up at low ambient temperatures.....................................................................39

6.11 Long cable runs .....................................................................................................39

6.12 Flow pattern analysis .............................................................................................39

6.13 Dead-leg control technique ....................................................................................43

6.14 Chimney effect ......................................................................................................43

7 Control and monitoring equipment...................................................................................43

7.1 General .................................................................................................................43

7.2 Mechanical controllers ...........................................................................................43

7.3 Electronic controllers .............................................................................................45

7.4 Application suitability .............................................................................................45

7.5 Location of controllers ...........................................................................................45

7.6 Location of sensors ...............................................................................................45

7.7 Alarm considerations .............................................................................................47

---------------------- Page: 6 ----------------------
62086-2 © IEC:2001 – 5 –
Clause Page

8 Recommendations for installation, testing and maintenance ............................................49

8.1 Introduction ...........................................................................................................49

8.2 Application.............................................................................................................49

8.3 Preparatory work ...................................................................................................49

8.4 Installation of trace-heating systems ......................................................................55

8.5 Installation of trace heaters....................................................................................59

8.6 Installation of control and monitoring equipment.....................................................63

8.7 Installation of thermal insulation system (see also clause 5) ...................................65

8.8 Commissioning......................................................................................................67

8.9 Maintenance..........................................................................................................67

8.10 Repairs..................................................................................................................69

Figure 1 – Thermal insulation – Weather-barrier installation...................................................17

Figure 2 – Typical temperature profile ...................................................................................21

Figure 3 – Heated tank example............................................................................................41

Figure 4 – Bypass example ...................................................................................................41

Table 1 – Process types ........................................................................................................11

Table 2 – Pre-installation checks...........................................................................................53

Table 3 – Pre-commissioning checks and heater installation record .......................................73

Table 4 – Heater commissioning record.................................................................................75

Table 5 – Maintenance schedule and log record ....................................................................77

---------------------- Page: 7 ----------------------
62086-2 © IEC:2001 – 7 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTRICAL APPARATUS FOR EXPLOSIVE GAS ATMOSPHERES –
ELECTRICAL RESISTANCE TRACE HEATING –
Part 2: Application guide for design,
installation and maintenance
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 62086-2 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
31/347/FDIS 31/359/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.
---------------------- Page: 8 ----------------------
62086-2 © IEC:2001 – 9 –
ELECTRICAL APPARATUS FOR EXPLOSIVE GAS ATMOSPHERES –
ELECTRICAL RESISTANCE TRACE HEATING –
Part 2: Application guide for design,
installation and maintenance
1 Scope

This part of IEC 62086 provides guidance for the application of electrical resistance trace-

heating systems in areas where explosive gas atmospheres may be present.

It provides recommendations for the design, installation and maintenance of trace-heating

equipment and associated control and monitoring equipment.
This part supplements the requirements specified in IEC 62086-1.
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 60079-0:1998, Electrical apparatus for explosive gas atmospheres – Part 0: General

requirements
IEC 60079-10:1995, Electrical apparatus for explosive gas atmospheres – Part 10:
Classification of hazardous areas

IEC 60079-14:1996, Electrical apparatus for explosive gas atmospheres – Part 14: Electrical

installations in hazardous areas (other than mines)

IEC 60079-17:1996, Electrical apparatus for explosive gas atmospheres – Part 17: Inspection

and maintenance of electrical installations in hazardous areas (other than mines)

IEC 62086-1, Electrical apparatus for explosive gas atmospheres – Electrical resistance trace

heating – Part 1: General and testing requirements
3 Definitions

For the purposes of this part of IEC 62086, the definitions in IEC 62086-1 apply.

___________
To be published.
---------------------- Page: 9 ----------------------
62086-2 © IEC:2001 – 11 –
4 Application considerations
4.1 General
This standard supplements the requirements of IEC 60079-14 and IEC 60079-17.

Where trace-heating systems are to be installed in explosive gas atmospheres, full details of

the hazardous area classification(s) (IEC 60079-10) should be specified. The specification

should state the zone of risk (1 or 2), gas group (IIA, IIB or IIC) and temperature classification

in accordance with IEC 60079-0. Where special considerations apply or where site condi-

tions may be especially onerous, these conditions should be detailed in the trace-heating

specification.

Where trace-heating systems are to be installed on mobile equipment or interchangeable skid

units, the specification for these trace-heating systems should be designed to accommodate

the worst conditions in which the trace-heating system may be used.

Where any parts of the trace-heating system are likely to be exposed to ultraviolet radiation,

those parts should be suitable for use in such conditions.
4.2 Corrosive areas

All components of electric trace-heating systems should be examined to verify that they are

compatible with any corrosive materials that may be encountered during the lifetime of the

system. Trace-heating systems operating in corrosive environments may have a higher

potential for failure than in non-corrosive environments. Deterioration of the thermal insulation

system is made worse by corrosion of the weather barrier and the possibility of pipeline and

vessel leaks soaking the thermal insulation. Particular attention should be given to the

materials of piping systems, as well as the electric trace-heating systems, as related to the

effective earth-leakage/ground-fault return path. The use of non-metallic or hybrid piping

systems may further complicate the earth-leakage/ground-fault return path and special

consideration should be given to these piping systems. Earth-leakage/ground-fault return paths

that are established at the time of installation may become degraded due to corrosion during

the operation of the plant.
4.3 Installation considerations

For convenience, various process types, according to the degree of application criticality and

process temperature accuracy required, may be specified (see table 1). However, it should be

recognized that each specific application may involve a combination of considerations.

Table 1 – Process types
Process temperature accuracy required
Within a Within a narrow
Above a
Application criticality
minimum point moderate band band type III
type I type II
Critical (C-) C – I C – II C – III
Non-critical (NC-) NC – I NC – II NC – III
Critical applications
Non-critical applications
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62086-2 © IEC:2001 – 13 –

When the trace heating is critical to the process, consideration should be given to circuit

monitoring (heating circuits should be monitored for correct operation and alarms provided to

indicate damage or fault) and to back up (redundant) heating systems. Spare or back-up trace

heating controls may be specified to be automatically activated in the event of a fault being

indicated by the monitoring/alarm system. This is sometimes known as “redundance”. Back-up

trace heating allows maintenance and repairs to be performed without a process shutdown.

4.4 Process temperature accuracy
4.4.1 Type I

A type I process is one for which the temperature should be maintained above a minimum

point. Ambient sensing control may be acceptable. Large blocks of power may be controlled by

means of a single control device and an electrical distribution panel board. Heat input may be

provided unnecessarily at times and wide temperature excursions should be tolerable. Energy

efficiency may be improved through the use of dead-leg control techniques (see 6.13).

4.4.2 Type II

A type II process is one for which the temperature should be maintained within a moderate

band. Pipeline sensing mechanical thermostats may be typical.
4.4.3 Type III

A type III process is one for which the temperature should be controlled within a narrow band.

Pipe-sensing controllers using thermocouple or resistance-temperature detector (RTD) units

facilitate field (work site) calibration and provide maximum flexibility in the selection of

temperature alarm and monitoring functions. Heat input capability may be provided to heat up

or raise the fluid temperature, or both, within a specified range and time interval. Type III

considerations require strict adherence to flow patterns and thermal insulation systems.

5 Thermal insulation
5.1 General

The selection, installation and maintenance of thermal insulation should be considered a key

component in the performance of an electrical trace-heating system. The thermal insulation

system is normally designed to prevent the majority of heat loss with the trace-heating system

compensating for the remainder. Therefore, problems with thermal insulation will have a direct

impact on the overall system performance.

The primary function of thermal insulation is to reduce the rate of heat transfer from a surface

that is operating at a temperature other than ambient. This reduction of energy loss may

– reduce operating expenses;
– improve system performance;
– increase system output capability.
---------------------- Page: 11 ----------------------
62086-2 © IEC:2001 – 15 –

Prior to any heat loss analysis for an electrically traced pipeline, vessel or other mechanical

equipment, a review of the selection of the insulation system is recommended. The principal

areas for consideration are as follows:
– selection of an insulation material;
– selection of a weather barrier (cladding);
– selection of the economic insulation thickness;
– selection of the proper insulation size.
5.2 Selection of insulating material

The following are important aspects to be considered when selecting an insulation material:

– thermal characteristics;
– mechanical properties;
– chemical compatibility;
– moisture resistance;
– personnel safety characteristics;
– fire resistance;
– smoke, toxicity;
–cost.
Insulation materials commonly available include:
– expanded silica;
– mineral fibre;
– cellular glass;
– urethane;
– fibreglass;
– calcium silicate;
– isocyanurate;
– perlite silicate.

For soft insulants (mineral fibre, fibre-glass, etc.), actual pipe size insulation may be used in

many cases by banding the insulation tightly. Care should be taken to prevent the heater from

being buried within the insulation, which may cause damage to the heater or may restrict

proper heat transfer. As an alternative, the next largest pipe size insulation that can easily

enclose pipe and electric trace heater is also acceptable. Rigid insulation (calcium silicate,

expanded silica, cellular glass, etc.), may be pipe-size insulation if board sections are cut to fit

the longitudinal joint. This type of installation technique is commonly referred to as an extended

leg installation. Alternatively, the next largest insulation size may be selected to accommodate

the trace heater. In all cases, the insulation size and thickness should be clearly specified.

5.3 Selection of weather barrier (cladding)

Proper operation of an electrically trace heated system depends upon the insulation being dry.

Electric tracing normally has insufficient heat output to dry wet thermal insulation. Some

insulation materials, even though removed from the piping and force dried, never regain their

initial characteristics after once being wet.
---------------------- Page: 12 ----------------------
62086-2 © IEC:2001 – 17 –

Straight piping may be weather-protected with metal jacketing, polymeric, or a mastic system.

When metal jacketing is used, it should be smooth with formed, modified “S” longitudinal joints.

The circumferential end joints should be sealed with closure bands and supplied with sealant

on the outer edge or where they overlap (see figure 1).
IEC 156/01
Key
1 – Metal jacket 5 – Closure band
2 – Insulation 6 – Insulated strap
3 – Metal jacket insulated pipe 7 – Movement
4 – Mastic sealer 8 – Pipe
Figure 1 – Thermal insulation – Weather-barrier installation
---------------------- Page: 13 ----------------------
62086-2 © IEC:2001 – 19 –

Jacketing that is overlapped or otherwise closed without sealant is not effective as a barrier to

moisture. A single, unsealed joint can allow a considerable amount of water to leak into the

insulation during a rainstorm.

The type of weather barrier used should, as a minimum, be based on a consideration of the

following:
– effectiveness in excluding moisture;
– corrosive nature of chemicals in the area;
– fire protection requirements;
– durability to mechanical abuse;
–cost.
5.4 Selection of economical thickness

At a minimum, an economic consideration of the insulation will weigh the initial costs of the

materials and installation against the energy saved over the life of the insulation. It should be

noted that the actual insulation thicknesses do not always correspond exactly to the nominal

insulation thickness. When choosing the insulation size, considerations should be made as to

whether or not the actual pipe-size insulation is suitable for accommodating both pipe and trace

heater.
5.5 Double insulation

The double insulation technique may be employed when the pipe temperature exceeds the

maximum allowable temperature of the trace heater. Prevention of the freezing of condensate

in high-temperature steam lines when these lines are not in use is a typical application. It

consists of locating the trace heater between two layers of insulation surrounding the pipe. The

essence of the double-insulation technique is to determine the correct combination of inner and

outer insulation type and thickness that will result in an acceptable interface temperature for

the trace heater. This relationship is illustrated in figure 2. Note that maximum ambient

temperature conditions should be considered in this determination.
---------------------- Page: 14 ----------------------
62086-2 © IEC:2001 – 21 –
IEC 157/01
Key
1 – Pipe 6 – Maximum temperature pipe
2 – Inner insulation layer 7 – Interface temperature
3 – Heat tracer 8 – Outer insulation surface temperature
4 – Outer insulation layer 9 – Ambient temperature
5 – Metal foil (aluminium) 10 – Radius
Figure 2 – Typical temperature profile
---------------------- Page: 15 ----------------------
62086-2 © IEC:2001 – 23 –
6 System design
6.1 Introduction

When designing trace-heating systems for use in explosive gas atmospheres, additional

constraints are imposed due to the requirements and classification of the area under

consideration. The design of any trace-heating system shoul
...

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