SIST EN 60079-30-2:2007

Explosive atmospheres -- Part 30-2: Electrical resistance trace heating - Application guide for design, installation and maintenance

This part of IEC 60079 provides guidance for the application of electrical resistance trace heating systems in areas where explosive gas atmospheres may be present, with the exception of those classified as zone 0. It provides recommendations for the design, installation, maintenance and repair of trace heating equipment and associated control and monitoring equipment. It does not cover devices that operate by induction heating, skin effect heating or direct pipeline heating, nor those intended for stress relieving. This part supplements the requirements specified in IEC 60079-30-1.

Explosionsfähige Atmosphäre -- Teil 30-2: Elektrische Widerstands-Begleitheizungen - Anwendungsleitfaden für Entwurf, Installation und Instandhaltung

Atmosphères explosives -- Partie 30-2: Traçage par résistance électrique - Guide d'application pour la conception, l'installation et la maintenance

La présente partie de la CEI 60079 fournit des lignes directrices pour l'application des systèmes de traçage par résistance électrique dans les emplacements où l'on peut rencontrer des atmosphères explosives, à l'exception de celles classées zone 0. 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. Elle ne couvre pas les dispositifs qui fonctionnent par chauffage par induction, chauffage à effet de peau ou chauffage par impédance, ni ceux destinés à la libération de contraintes.

Eksplozivne atmosfere - 30-2. del: Električni uporovni grelni trakovi - Vodilo za zasnovo, inštalacijo in vzdrževanje (IEC 60079-30-2:2007)

General Information

• Status: Published
• Publication Date: 04-Nov-2007
• Withdrawal Date: 30-Nov-2005
• ICS: 29.260.20 - Electrical apparatus for explosive atmospheres
• Technical Committee: EXP - Electrical apparatus for explosive atmospheres
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 05-Oct-2007
• Due Date: 10-Dec-2007
• Completion Date: 05-Nov-2007
• Ref Project: EN 60079-30-2:2007 - Explosive atmospheres - Part 30-2: Electrical resistance trace heating - Application guide for design, installation and maintenance

Relations

• Replaces: SIST EN 62086-2:2005 - Electrical apparatus for explosive gas atmospheres - Electrical resistance trace heating -- Part 2: Application guide for design, installation and maintenance
• Effective Date: 01-Mar-2010
• Replaced By: SIST EN 60079-30-2:2018 - Explosive atmospheres - Part 30-2: Electrical resistance trace heating - Application guide for design, installation and maintenance IEC/IEEE 60079-30-2:2015 (MOD)
• Effective Date: 11-Jul-2017

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN 60079-30-2:2007
01-december-2007
1DGRPHãþD
SIST EN 62086-2:2005
(NVSOR]LYQHDWPRVIHUHGHO(OHNWULþQLXSRURYQLJUHOQLWUDNRYL9RGLOR]D
]DVQRYRLQãWDODFLMRLQY]GUåHYDQMH,(&
Explosive atmospheres - Part 30-2: Electrical resistance trace heating - Application guide
for design, installation and maintenance
Explosionsfähige Atmosphäre - Teil 30-2: Elektrische Widerstands-Begleitheizungen -
Anwendungsleitfaden für Entwurf, Installation und Instandhaltung
Atmospheres explosives - Partie 30-2: Traçage par résistance électrique - Guide
d'application pour la conception, l'installation et la maintenance
Ta slovenski standard je istoveten z: EN 60079-30-2:2007
ICS:
29.260.20 (OHNWULþQLDSDUDWL]D Electrical apparatus for
HNVSOR]LYQDR]UDþMD explosive atmospheres
SIST EN 60079-30-2:2007 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------

EUROPEAN STANDARD
EN 60079-30-2

NORME EUROPÉENNE
April 2007
EUROPÄISCHE NORM

ICS 29.260.20 Supersedes EN 62086-2:2005


English version


Explosive atmospheres -
Part 30-2: Electrical resistance trace heating -
Application guide for design, installation and maintenance
(IEC 60079-30-2:2007)


Atmosphères explosives -  Explosionsfähige Atmosphäre -
Partie 30-2: Traçage Teil 30-2: Elektrische
par résistance électrique - Widerstands-Begleitheizungen -
Guide d'application pour la conception, Anwendungsleitfaden für Entwurf,
l'installation et la maintenance Installation und Instandhaltung
(CEI 60079-30-2:2007) (IEC 60079-30-2:2007)




This European Standard was approved by CENELEC on 2007-03-01. 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, Bulgaria, Cyprus, the
Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the 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


© 2007 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 60079-30-2:2007 E

---------------------- Page: 2 ----------------------

EN 60079-30-2:2007 - 2 -
Foreword
The text of document 31/662/FDIS, future edition 1 of IEC 60079-30-2, prepared by IEC TC 31,
Equipment for explosive atmospheres, was submitted to the IEC-CENELEC parallel vote and was
approved by CENELEC as EN 60079-30-2 on 2007-03-01.
This European Standard supersedes EN 62086-2:2005.
The general revisions and updating to produce EN 60079-30-2:2007 are a result of national comments
received.
The main technical differences apart from the general revision and updating of EN 62086-2:2005 are as
follows:
– corrections;
– extensive revision and additions for design and installation recommendations.
This standard is to be used in conjunction with EN 60079-30-1:2007, Explosive atmospheres – Part 30-1:
Electrical resistance trace heating – General and testing requirements.
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) 2007-12-01
– latest date by which the national standards conflicting
(dow) 2010-03-01
with the EN have to be withdrawn
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 60079-30-2:2007 was approved by CENELEC as a European
Standard without any modification.
__________

---------------------- Page: 3 ----------------------

- 3 - EN 60079-30-2:2007
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  When 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 (mod) 2004 Electrical apparatus for explosive gas EN 60079-0 2006
atmospheres -
Part 0: General requirements


IEC 60079-1 2003 Electrical apparatus for explosive gas EN 60079-1 2004
atmospheres - + corr. April 2006
Part 1: Flameproof enclosures "d"


1)
IEC 60079-7 2001 Electrical apparatus for explosive gas EN 60079-7 2003
atmospheres -
Part 7: Increased safety "e"


IEC 60079-10 2002 Electrical apparatus for explosive gas EN 60079-10 2003
atmospheres -
Part 10: Classification of hazardous areas


2)
IEC 60079-14 1996 Electrical apparatus for explosive gas EN 60079-14 1997
atmospheres -
Part 14: Electrical installations in hazardous
areas (other than mines)


3)
IEC 60079-17 1996 Electrical apparatus for explosive gas EN 60079-17 1997
atmospheres -
Part 17: Inspection and maintenance of
electrical installations in hazardous areas
(other than mines)


IEC 60079-30-1 2007 Explosive atmospheres - EN 60079-30-1 2007
Part 30-1: Electrical resistance trace heating -
General and testing requirements




1)
EN 60079-7 is superseded by EN 60079-7:2007, which is based on IEC 60079-7:2006.
2)
EN 60079-14 is superseded by EN 60079-14:2003, which is based on IEC 60079-14:2002.
3)
EN 60079-17 is superseded by EN 60079-17:2003, which is based on IEC 60079-17:2002.

---------------------- Page: 4 ----------------------

NORME CEI
INTERNATIONALE
IEC



60079-30-2
INTERNATIONAL


Première édition
STANDARD

First edition

2007-01


Atmosphères explosives –
Partie 30-2:
Traçage par résistance électrique –
Guide d’application pour la conception,
l’installation et la maintenance

Explosive atmospheres –
Part 30-2:
Electrical resistance trace heating –
Application guide for design, installation
and maintenance
© IEC 2007 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 any
utilisée sous quelque forme que ce soit et par aucun procédé, form or by any means, electronic or mechanical, including
électronique ou mécanique, y compris la photocopie et les photocopying and microfilm, without permission in writing from
microfilms, sans l'accord écrit de l'éditeur. the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: [phone] Telefax: [phone] E-mail: [e-mail] Web: www.iec.ch
CODE PRIX
XA
PRICE CODE
Commission Electrotechnique Internationale
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
Pour prix, voir catalogue en vigueur
For price, see current catalogue

---------------------- Page: 5 ----------------------

60079-30-2 © IEC:2007 – 3 –
CONTENTS
FOREWORD.7

1 Scope.11
2 Normative references .11
3 Terms and definitions .13
4 Application considerations.13
4.1 General .13
4.2 Corrosive areas.13
4.3 Process temperature accuracy .15
4.4 Installation considerations .15
5 Thermal insulation .17
5.1 General .17
5.2 Selection of insulating material.17
5.3 Selection of weather barrier (cladding) .19
5.4 Selection of economical thickness .21
5.5 Double insulation.23
6 System design.27
6.1 Introduction .27
6.2 Purpose of, and major requirement for, trace heating .27
6.3 Heat loss calculations.27
6.4 Heat-up considerations.31
6.5 Heat-loss design safety factor .33
6.6 Selection of trace heater .33
6.7 Maximum temperature determination.41
6.8 Design information .47
6.9 Power system.49
6.10 Start-up at low ambient temperatures .51
6.11 Long trace heater runs .51
6.12 Flow pattern analysis.51
6.13 Dead-leg control technique.55
6.14 Chimney effect .55
7 Control and monitoring .55
7.1 General .55
7.2 Mechanical controllers.55
7.3 Electronic controllers.57
7.4 Application suitability.57
7.5 Location of controllers .57
7.6 Location of sensors .57
7.7 Alarm considerations.59
8 Recommendations for installation .63
8.1 Introduction .63
8.2 Preparatory work.63
8.3 Installation of trace heating circuits .65

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60079-30-2 © IEC:2007 – 5 –
8.4 Installation of control and monitoring equipment.77
8.5 Installation of thermal insulation system (see also Clause 5) .87
8.6 Installation of distribution wiring and coordination with branch circuits.91
8.7 Commissioning.93
9 Maintenance.95
9.1 General .95
9.2 Fault location .95
9.3 Fault rectification.97
10 Repairs .97
10.1 General .97
10.2 Practicability of repair to electric trace heaters .97
10.3 Repair techniques for electrical trace heaters.99
10.4 Earthing .99
10.5 Testing .99

Figure 1 – Thermal insulation – Weather-barrier installation.21
Figure 2 – Typical temperature profile.25
Figure 3 – Equilibrium conditions for workpiece maintenance.37
Figure 4 – Equilibrium conditions for upper limit evaluation.39
Figure 5 – Heated tank example .53
Figure 6 – Bypass example.53
Figure 7 – Typical installation of control sensor and sensor for temperature limiting
control .81
Figure 8 – Limiting device sensor on surface of trace heater.83
Figure 9 – Limiting device sensor as artificial hot spot .85

Table 1 – Process types .15
Table 2 – Pre-installation checks .67
Table 3 – Example of pre-commissioning check and trace heater installation record.101
Table 4 – Example of trace heater commissioning record.103
Table 5 – Example of maintenance schedule and log record .105

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60079-30-2 © IEC:2007 – 7 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

EXPLOSIVE ATMOSPHERES –

Part 30-2: Electrical resistance trace heating –
Application guide for design, installation and maintenance


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 provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
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 60079-30-2 has been prepared by IEC technical committee 31:
Equipment for explosive atmospheres.
This edition cancels and replaces the first edition of IEC 62086-2 published in 2001 and
constitutes a technical revision.
The general revisions and updating to produce the first edition of IEC 60079-30-2 are as a
result of National comments received.
The main technical differences apart from the general revision and updating a former edition
of IEC 62086-2, are as follows:
a) corrections;

---------------------- Page: 8 ----------------------

60079-30-2 © IEC:2007 – 9 –
b) extensive revision and additions for design and installation recommendations.
This Part 30-2 is to be used in conjunction with the first edition of IEC 60079-30-1:2006,
Explosive atmospheres – Part 30-1: Electrical resistance trace heating – General and testing
requirements.
The text of this standard is based on the following documents:
FDIS Report on voting
31/662/FDIS 31/672/RVD

Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
The list of all parts of IEC 60079 series, under the general title Explosive atmospheres, can
be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in
the data related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.

---------------------- Page: 9 ----------------------

60079-30-2 © IEC:2007 – 11 –
EXPLOSIVE ATMOSPHERES –

Part 30-2: Electrical resistance trace heating –
Application guide for design, installation and maintenance



1 Scope
This part of IEC 60079 provides guidance for the application of electrical resistance trace
heating systems in areas where explosive gas atmospheres may be present, with the
exception of those classified as zone 0.
It provides recommendations for the design, installation, maintenance and repair of trace
heating equipment and associated control and monitoring equipment. It does not cover
devices that operate by induction heating, skin effect heating or direct pipeline heating, nor
those intended for stress relieving.
This part supplements the requirements specified in IEC 60079-30-1.
2 Normative references
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.
IEC 60079-0:2004, Electrical apparatus for explosive gas atmospheres – Part 0: General
requirements
IEC 60079-1:2003, Electrical apparatus for explosive gas atmospheres – Part 1:Flameproof
enclosures “d”
IEC 60079-7:2001, Electrical apparatus for explosive gas atmospheres – Part 7: Increased
safety ‘e’
IEC 60079-10:2002, 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 60079-30-1:2006, Explosive atmospheres – Part 1: Electrical resistance trace heating –

General and testing requirements

---------------------- Page: 10 ----------------------

60079-30-2 © IEC:2007 – 13 –
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60079-0,
IEC 60079-1 and IEC 60079-7 apply.
1
NOTE Additional terms and definitions applicable to explosive atmospheres can be found in IEC 60050 (426) .
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) shall be specified. The specification shall
state the zone (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 conditions
may be especially onerous, these conditions shall 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 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, those parts should be
suitable for the environment.
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 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 lined or coated 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 established
at the time of installation may become degraded due to corrosion during the operation of the
plant.
—————————
1
IEC 60050-426, International Electrotechnical Vocabulary (IEV) – Part 426: Electrical apparatus for explosive
atmospheres

---------------------- Page: 11 ----------------------

60079-30-2 © IEC:2007 – 15 –
4.3 Process temperature accuracy
4.3.1 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).
4.3.2 Type II
A Type II process is one for which the temperature should be maintained within a moderate
band. Control by pipeline sensing mechanical thermostats is typical.
4.3.3 Type III
A Type III process is one for which the temperature should be controlled within a narrow
band. Electronic 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 preheat an empty pipe or raise the fluid temperature, or both, within a specified
range and time interval. Type III systems require strict adherence to flow patterns and thermal
insulation systems.
4.4 Installation considerations
If failure of any part of the trace heating system can result in a safety or process problem,
then the trace heating system may be considered to be a critical component of the total
process. The temperature control and circuit monitoring requirements of an application may
be defined according to the temperature control types described in 4.3, together with the
circuit monitoring criticality as described in Table 1.
Table 1 – Process types
Desired accuracy of process temperature control
Is trace heating a critical
component of the
Above a minimum point Within a moderate band Within a narrow band
process?
Type I Type II Type III
Yes = Critical (C-) C – I C – II C – III
No = Non-critical (NC-) NC – I NC – II NC – III

When trace heating is critical to the process, circuit monitoring for correct operation,
malfunction alarms, and back-up (redundant) trace heaters should be considered. Spare or
back-up controllers can be specified to be automatically activated in the event of a fault being
indicated by the monitoring/alarm system. This is sometimes known as "redundancy". Back-up
trace heaters may allow maintenance or repairs to be performed without a process shutdown
and may be used to enhance reliability.

---------------------- Page: 12 ----------------------

60079-30-2 © IEC:2007 – 17 –
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.
Prior to any heat loss analysis for an electrical
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31/662/FDIS
FINAL DRAFT INTERNATIONAL STANDARD
PROJET FINAL DE NORME INTERNATIONALE
Project number IEC 60079-30-2 Ed. 1.0
Numéro de projet
IEC/TC or SC CEI/CE ou SC Secretariat / Secrétariat
TC 31 United Kingdom

Submitted for parallel voting in CENELEC
Distributed on / Diffusé le Voting terminates on / Vote clos le
Soumis au vote parallèle au CENELEC
2006-09-29 2006-12-01
Also of interest to the following committees Supersedes document
Intéresse également les comités suivants Remplace le document
TC 18 31/585/CDV and 31/625/RVC
Functions concerned
Fonctions concernées
Safety EMC Environment Quality assurance
Sécurité CEM Environnement Assurance de la qualité
INTERNATIONAL ELECTROTECHNICAL COMMISSION COMMISSION ÉLECTROTECHNIQUE INTERNATIONALE
THIS DOCUMENT IS A DRAFT DISTRIBUTED FOR APPROVAL. IT MAY NOT BE REFERRED TO AS AN INTERNATIONAL STANDARD UNTIL PUBLISHED
AS SUCH.
IN ADDITION TO THEIR EVALUATION AS BEING ACCEPTABLE FOR INDUSTRIAL, TECHNOLOGICAL, COMMERCIAL AND USER PURPOSES, FINAL
DRAFT INTERNATIONAL STANDARDS MAY ON OCCASION HAVE TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL TO BECOME STANDARDS
TO WHICH REFERENCE MAY BE MADE IN NATIONAL REGULATIONS.

CE DOCUMENT EST UN PROJET DIFFUSÉ POUR APPROBATION. IL NE PEUT ÊTRE CITÉ COMME NORME INTERNATIONALE AVANT SA PUBLICATION
EN TANT QUE TELLE.
OUTRE LE FAIT D'ÊTRE EXAMINÉS POUR ÉTABLIR S'ILS SONT ACCEPTABLES À DES FINS INDUSTRIELLES, TECHNOLOGIQUES ET COMMERCIALES,
AINSI QUE DU POINT DE VUE DES UTILISATEURS, LES PROJETS FINAUX DE NORMES INTERNATIONALES DOIVENT PARFOIS ÊTRE EXAMINÉS EN
VUE DE LEUR POSSIBILITÉ DE DEVENIR DES NORMES POUVANT SERVIR DE RÉFÉRENCE DANS LES RÈGLEMENTATIONS NATIONALES.

Title
IEC 60079-30-2 Ed. 1.0: Explosive atmospheres - Part 30-2: Electrical resistance
trace heating - Application guide for design, installation and maintenance

Titre
CEI 60079-30-2 Ed. 1.0: Atmosphères explosives - Partie 30-2: Traçage par
résistance électrique - Guide d'application pour la conception, l'installation et la
maintenance



ATTENTION ATTENTION
VOTE PARALLÈLE IEC – CENELEC
CEI – CENELEC PARALLEL VOTING
L’attention des Comités nationaux de la CEI, membres du The attention of IEC National Committees, members of
CENELEC, est attirée sur le fait que ce projet final de CENELEC, is drawn to the fact that this final Draft
Norme internationale est soumis au vote parallèle. Un International Standard (DIS) is submitted for parallel
bulletin de vote séparé pour le vote CENELEC leur sera voting. A separate form for CENELEC voting will be sent to
envoyé par le Secrétariat Central du CENELEC. them by the CENELEC Central Secretariat.

Copyright © 2006 International Electrotechnical Commission, IEC. All rights reserved. It is
permitted to download this electronic file, to make a copy and to print out the content for the sole
purpose of preparing National Committee positions. You may not copy or "mirror" the file or
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writing from IEC.
FORM FDIS (IEC)/FORMULAIRE FDIS (CEI) 2002-08-08

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60079-30-2/FDIS © IEC – 2 –
CONTENTS
FOREWORD.4

1 Scope.6
2 Normative references .6
3 Terms and definitions .7
4 Application considerations.7
4.1 General .7
4.2 Corrosive areas.7
4.3 Process temperature accuracy .8
4.4 Installation considerations .8
5 Thermal insulation .9
5.1 General .9
5.2 Selection of insulating material.9
5.3 Selection of weather barrier (cladding) .10
5.4 Selection of economical thickness .11
5.5 Double insulation.12
6 System design.14
6.1 Introduction .14
6.2 Purpose of, and major requirement for, trace heating .14
6.3 Heat loss calculations.14
6.4 Heat-up considerations.16
6.5 Heat-loss design safety factor .17
6.6 Selection of trace heater .17
6.7 Maximum temperature determination.21
6.8 Design information .24
6.9 Power system.25
6.10 Start-up at low ambient temperatures .26
6.11 Long trace heater runs .26
6.12 Flow pattern analysis.26
6.13 Dead-leg control technique.28
6.14 Chimney effect .28
7 Control and monitoring .28
7.1 General .28
7.2 Mechanical controllers.28
7.3 Electronic controllers.29
7.4 Application suitability.29
7.5 Location of controllers .29
7.6 Location of sensors .29
7.7 Alarm considerations.30
8 Recommendations for installation .32
8.1 Introduction .32
8.2 Preparatory work.32
8.3 Installation of trace heating circuits .33

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60079-30-2/FDIS © IEC – 3 –
8.4 Installation of control and monitoring equipment.39
8.5 Installation of thermal insulation system (see also Clause 5) .44
8.6 Installation of distribution wiring and coordination with branch circuits.46
8.7 Commissioning.47
9 Maintenance.48
9.1 General .48
9.2 Fault location .48
9.3 Fault rectification.49
10 Repairs .49
10.1 General .49
10.2 Practicability of repair to electric trace heaters .49
10.3 Repair techniques for electrical trace heaters.50
10.4 Earthing .50
10.5 Testing .50

Figure 1 – Thermal insulation – Weather-barrier installation.11
Figure 2 – Typical temperature profile.13
Figure 3 – Equilibrium conditions for workpiece maintenance.19
Figure 4 – Equilibrium conditions for upper limit evaluation.20
Figure 5 – Heated tank example .27
Figure 6 – Bypass example.27
Figure 7 – Typical installation of control sensor and sensor for temperature limiting
control .41
Figure 8 – Limiting device sensor on surface of trace heater.42
Figure 9 – Limiting device sensor as artificial hot spot .43

Table 1 – Process types .8
Table 2 – Pre-installation checks .34
Table 3 – Example of pre-commissioning check and trace heater installation record.51
Table 4 – Example of trace heater commissioning record.52
Table 5 – Example of maintenance schedule and log record .53

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INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

EXPLOSIVE ATMOSPHERES –

Part 30-2: Electrical resistance trace heating –
Application guide for design, installation and maintenance


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 provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
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 60079-30-2 has been prepared by IEC technical committee 31:
Equipment for explosive atmospheres.
This edition cancels and replaces the first edition of IEC 62086-2 published in 2001 and
constitutes a technical revision.
The general revisions and updating to produce the first edition of IEC 60079-30-2 are as a
result of National comments received.
The main technical differences apart from the general revision and updating a former edition
of IEC 62086-2, are as follows:
a) corrections;

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60079-30-2/FDIS © IEC – 5 –
b) extensive revision and additions for design and installation recommendations.
This Part 30-2 is to be used in conjunction with the first edition of IEC 60079-30-1:2006,
Explosive atmospheres – Part 30-1: Electrical resistance trace heating – General and testing
requirements.
The text of this standard is based on the following documents:
FDIS Report on voting
XX/XX/FDIS XX/XX/RVD

Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
The list of all parts of IEC 60079 series, under the general title Explosive atmospheres, can
be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
1
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in
the data related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
—————————
)
1
The National Committees are requested to note that for this publication the maintenance result date is 2011.

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60079-30-2/FDIS © IEC – 6 –
EXPLOSIVE ATMOSPHERES –

Part 30-2: Electrical resistance trace heating –
Application guide for design, installation and maintenance



1 Scope
This part of IEC 60079 provides guidance for the application of electrical resistance trace
heating systems in areas where explosive gas atmospheres may be present, with the
exception of those classified as zone 0.
It provides recommendations for the design, installation, maintenance and repair of trace
heating equipment and associated control and monitoring equipment. It does not cover
devices that operate by induction heating, skin effect heating or direct pipeline heating, nor
those intended for stress relieving.
This part supplements the requirements specified in IEC 60079-30-1.
2 Normative references
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.
IEC 60079-0:2004, Electrical apparatus for explosive gas atmospheres – Part 0: General
requirements
IEC 60079-1:2003, Electrical apparatus for explosive gas atmospheres – Part 1:Flameproof
enclosures “d”
IEC 60079-7:2001, Electrical apparatus for explosive gas atmospheres – Part 7: Increased
safety ‘e’
IEC 60079-10:2002, 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 60079-30-1:2006, Explosive atmospheres – Part 1: Electrical resistance trace heating –

General and testing requirements

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3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60079-0,
IEC 60079-1 and IEC 60079-7 apply.
2
NOTE Additional terms and definitions applicable to explosive atmospheres can be found in IEC 60050 (426) .
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) shall be specified. The specification shall
state the zone (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 conditions
may be especially onerous, these conditions shall 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 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, those parts should be
suitable for the environment.
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 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 lined or coated 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 established
at the time of installation may become degraded due to corrosion during the operation of the
plant.
—————————
2
IEC 60050-426, International Electrotechnical Vocabulary (IEV) – Part 426: Electrical apparatus for explosive
atmospheres

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4.3 Process temperature accuracy
4.3.1 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).
4.3.2 Type II
A Type II process is one for which the temperature should be maintained within a moderate
band. Control by pipeline sensing mechanical thermostats is typical.
4.3.3 Type III
A Type III process is one for which the temperature should be controlled within a narrow
band. Electronic 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 preheat an empty pipe or raise the fluid temperature, or both, within a specified
range and time interval. Type III systems require strict adherence to flow patterns and thermal
insulation systems.
4.4 Installation considerations
If failure of any part of the trace heating system can result in a safety or process problem,
then the trace heating system may be considered to be a critical component of the total
process. The temperature control and circuit monitoring requirements of an application may
be defined according to the temperature control types described in 4.3, together with the
circuit monitoring criticality as described in Table 1.
Table 1 – Process types
Desired accuracy of process temperature control
Is trace heating a critical
component of the
Above a minimum point Within a moderate band Within a narrow band
process?
Type I Type II Type III
Yes = Critical (C-) C – I C – II C – III
No = Non-critical (NC-) NC – I NC – II NC – III

When trace heating is critical to the process, circuit monitoring for correct operation,
malfunction alarms, and back-up (redundant) trace heaters should be considered. Spare or
back-up controllers can be specified to be automatically activated in the event of a fault being
indicated by the monitoring/alarm system. This is sometimes known as "redundancy". Back-up
trace heaters may allow maintenance or repairs to be performed without a process shutdown
and may be used to enhance reliability.

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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.
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.
These factors should be considered and the selection optimised according to the operator’s
criteria:
– temperature rating;
– thermal conductivity, λ, of the insulation;
– mechanical properties;
– chemical compatibility and corrosion resistance;
– moisture resistance;
– health risks during installation;
– fire resistance;
– toxicological properties when exposed to fire;
– costs.
Insulation materials commonly available include:
– expanded silica;
– mineral fibre;
– cellular glass;
– urethane;
– fibreglass;
– calcium silicate;
– polyisocyanurate;
– perlite silicate.

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For soft insulants (mineral fibre, fibreglass, etc.), actual pipe size insulation may be used in
many cases by banding the insulation tightly. Care should be taken to prevent the trace
heater from being buried within the insulation, which may cause damage to the trace 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.
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).
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.

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60079-30-2/FDIS © IEC – 11 –
1
B A-A
B
2
3
5
6
4
A
8
A
2
7


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

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60079-30-2/FDIS © IEC – 12 –
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
...