IEC/IEEE 60079-30-2:2015

IEC/IEEE 60079-30-2 ®
Edition 1.0 2015-09
INTERNATIONAL
STANDARD
colour
inside
Explosive atmospheres –
Part 30-2: Electrical resistance trace heating – Application guide for design,
installation and maintenance
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IEC/IEEE 60079-30-2 ®
Edition 1.0 2015-09
INTERNATIONAL
STANDARD
colour
inside
Explosive atmospheres –
Part 30-2: Electrical resistance trace heating – Application guide for design,

installation and maintenance
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.260.20 ISBN 978-2-8322-2736-7

– 2 – IEC/IEEE 60079-30-2:2015
© IEC/IEEE 2015
CONTENTS
FOREWORD . 6
1 Scope . 10
2 Normative references . 10
3 Terms and definitions . 10
4 Application considerations . 10
4.1 General . 10
4.2 Corrosive areas . 11
4.3 Process temperature accuracy . 11
4.3.1 Type I . 11
4.3.2 Type II . 11
4.3.3 Type III . 11
4.4 Installation considerations . 11
5 Thermal insulation . 12
5.1 General . 12
5.2 Selection of insulating material . 12
5.3 Selection of weather barrier (cladding) . 13
5.4 Selection of economical thickness to provide optimum trace heating design. 13
5.5 Double insulation . 14
6 System design . 17
6.1 General . 17
6.2 Purpose of, and major requirement for, trace heating . 17
6.3 Training . 18
6.4 Selection of trace heater . 18
6.4.1 General . 18
6.4.2 Site-fabricated trace heaters . 18
6.4.3 Specific types of trace heating . 19
6.5 Maximum temperature determination . 19
6.5.1 General . 19
6.5.2 PTC characteristic . 19
6.5.3 Stabilized design . 20
6.5.4 Controlled design. 20
6.6 Heat up and cool down considerations . 20
6.7 Design information . 20
6.7.1 Design information documentation . 20
6.7.2 Isometric or trace heater configuration line lists and load charts . 21
6.8 Power system . 22
6.9 Earthing requirements . 22
6.10 Earth-fault protection of equipment . 23
6.11 Start-up at minimum ambient temperatures . 23
6.12 Long trace heater runs . 23
6.13 Flow pattern analysis . 23
6.14 Dead-leg control technique . 25
6.15 Chimney effect . 25
6.16 Safety shower and eyewash station design requirements . 26

© IEC/IEEE 2015
7 Control and monitoring . 26
7.1 General . 26
7.2 Mechanical controllers . 27
7.3 Electronic controllers . 27
7.4 Application suitability . 27
7.5 Location of controllers . 27
7.6 Location of sensors . 28
7.7 Alarm considerations . 28
7.7.1 General . 28
7.7.2 Trace heating circuit alarm . 28
7.7.3 Temperature alarms . 29
7.7.4 Other alarms . 29
7.7.5 Integrated control . 29
8 Recommendations for installation . 29
8.1 General . 29
8.2 Preparatory work . 30
8.2.1 General . 30
8.2.2 Scheduling and coordination . 30
8.2.3 Confirmation of equipment . 30
8.2.4 Receiving materials . 30
8.2.5 Warehousing and handling . 30
8.2.6 Personnel aspects . 30
8.3 Installation of trace heating circuits . 30
8.3.1 Coordination and equipment verification . 30
8.3.2 Pre-installation testing and design verification . 31
8.3.3 Visual examination . 31
8.3.4 Insulation resistance test . 31
8.3.5 Component substitution . 31
8.3.6 Location of power supply . 31
8.3.7 Installation of trace heaters . 32
8.3.8 Connections and terminations . 34
8.4 Installation of control and monitoring equipment . 36
8.4.1 General . 36
8.4.2 Verification of equipment suitability. 36
8.4.3 Temperature controller and monitoring devices . 36
8.4.4 Sensor considerations . 36
8.4.5 Controller operation, calibration, and access . 40
8.4.6 Necessary modifications . 40
8.5 Installation of thermal insulation system (see also Clause 5) . 40
8.5.1 General . 40
8.5.2 Preparatory work . 40
8.5.3 Installation of the thermal insulation materials . 40
8.5.4 Cladding . 41
8.5.5 Field (site work) circuit insulation resistance test . 41
8.5.6 Visual inspection . 41
8.5.7 Documentation . 42
8.6 Installation of distribution wiring and coordination with branch circuits . 42
8.6.1 General . 42
8.6.2 Earth-fault protective device . 42

– 4 – IEC/IEEE 60079-30-2:2015
© IEC/IEEE 2015
8.6.3 Circuit protective device . 42
8.6.4 Tagging/Identification . 42
8.7 Commissioning . 42
8.7.1 Pre-commissioning check . 42
8.7.2 Functional check and final documentation. 43
9 Maintenance . 44
9.1 General . 44
9.2 Fault location . 44
9.3 Fault rectification . 44
10 Repairs . 45
10.1 General . 45
10.2 Practicability of repair to electric trace heaters . 45
10.2.1 Mechanical damage . 45
10.2.2 Damage due to corrosion . 45
10.2.3 Damage due to overheating . 45
10.3 Repair techniques for electrical trace heaters . 45
10.3.1 General . 45
10.3.2 In-line splice . 46
10.3.3 Connection via junction box . 46
10.4 Earthing . 46
10.5 Testing . 46
Annex A (informative) Example of design data record . 47
Annex B (informative) Checklist for installation requirements . 48
Annex C (informative) Example of trace heater commissioning record . 50
Annex D (informative) Example of maintenance schedule and log record . 52
Annex E (informative) Pipe heat loss considerations – Heat loss formula and example
calculations . 54
Annex F (informative) Vessel heat loss considerations . 60
F.1 General . 60
F.2 Insulation heat loss (Q ) . 60
ins
F.3 Slab surface areas (Q ) . 61
slab
F.4 Support heat loss (Q ) . 61
supt
F.5 Manhole heat loss (Q ) . 62
manhole
F.6 Convection coefficient formulae . 62
F.6.1 General . 62
F.6.2 Free convection, nonfluid surface, any orientation (h , h , h ) . 62
i co o
F.6.3 Forced convection, any orientation (h ) . 63
F.6.4 Radiation component, all coefficients (h , h , h , h ) . 63
f i co o
Annex G (informative) Heat up and cool down considerations . 65
G.1 Heat up . 65
G.2 Cool down . 66
Annex H (informative) Method to determine equivalent thicknesses of insulating
cements . 68
Bibliography . 69

Figure 1 – Thermal insulation – Weather-barrier installation . 15
Figure 2 – Typical temperature profile . 16

© IEC/IEEE 2015
Figure 3 – Flow pattern analysis example . 24
Figure 4 – Bypass example . 25
Figure 5 – Typical installation of control sensor and sensor for temperature limiting
control . 38
Figure 6 – Limiting device sensor on sheath of trace heater . 38
Figure 7 – Limiting device sensor as artificial hot spot . 39
Figure E.1 – Assumed temperature gradients . 55

Table 1 – Pre-installation checks . 32
Table A.1 – Example of design data record . 47
Table B.1 – Example of pre-commissioning check and trace heater installation record . 48
Table C.1 – Example of trace heater commissioning record . 50
Table D.1 – Example of maintenance schedule and log record. 52

– 6 – IEC/IEEE 60079-30-2:2015
© IEC/IEEE 2015
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
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IEC collaborates closely with IEEE in accordance with conditions determined by agreement between the two
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terms of that agreement.
2) The formal decisions of IEC on technical matters express, as nearly as possible, an international consensus of
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3) IEC/IEEE Publications have the form of recommendations for international use and are accepted by IEC
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© IEC/IEEE 2015
International Standard IEC/IEEE 60079-30-2 has been prepared by IEC technical committee
31: Equipment for explosive atmospheres, in cooperation with the Petroleum & Chemical
Industry Committee of the IEEE Industrial Applications Society under the IEC/IEEE Dual Logo
Agreement.
NOTE A list of IEEE participants can be found at the following URL:
http://standards.ieee.org/downloads/60079/60079-30-2-2015/60079-30-2-2015_wg-participants.pdf.
This first edition of IEC/IEEE 60079-30-2 cancels and replaces the first edition of IEC 60079-
30-2 published in 2007 and constitutes a technical revision.
This edition includes the following significant changes, apart from a general review and
updating of the first edition of IEC 60079-30-2, harmonization with IEEE Std 515, with respect
to the previous edition:
• the relocation of trace heater product design methodology and requirements to IEC/IEEE
60079-30-1;
• the relocation and/or duplication of information on installation, maintenance, and repair to
the MTs under SC31J for their addition into IEC 60079-14, IEC 60079-17, and IEC 60079-
19;
• the inclusion of more detailed information on safety showers and eyewash units;
• the introduction of Annexes from IEEE Std 515.
The significance of changes between IEC 60079-30-2, Edition 1.0 (2007) and IEC/IEEE
60079-30-2, Edition 1.0 (2014) is as listed below:
Type
Changes Clause Minor and Extension Major
editorial technical
changes changes
Addition of clarification for the exclusion of areas
1 X
coverage classifications of EPLs Ga and Da
Addition of requirements for the Division method of
1  C1
area classification that may be applied by some users
Relocation of heat loss design requirements to
6.3 X
IEC/IEEE 60079-30-1
Addition of safety shower and eyewash station design
6.16  C2
requirements
Addition of Annex for an example of a design data
Annex A X
record
Addition of Annex for a checklist of installation
Annex B X
requirements
Addition of Annex for an example of a trace heater
Annex C X
commissioning record
Addition of Annex for an example of a maintenance
Annex D X
schedule and log record
Addition of Annex for pipe heat loss considerations Annex E X
Addition of Annex for vessel heat loss considerations Annex F X
Addition of Annex for heat up and cool down
Annex G X
considerations
Addition of Annex for a method to determine the
Annex H X
equivalent thickness of insulating cements
NOTE The technical changes referred to include the significance of technical changes in the revised IEC
Standard, but they do not form an exhaustive list of all modifications from the previous version.

– 8 – IEC/IEEE 60079-30-2:2015
© IEC/IEEE 2015
Explanations:
A) Definitions
Minor and editorial changes
clarification
decrease of technical requirements
minor technical change
editorial corrections
These are changes which modify requirements in an editorial or a minor technical way. They
include changes of the wording to clarify technical requirements without any technical change,
or a reduction in level of existing requirement.
Extension   addition of technical options
These are changes which add new or modify existing technical requirements, in a way that
new options are given, but without increasing requirements for equipment that was fully
compliant with the previous standard. Therefore, these will not have to be considered for
products in conformity with the preceding edition.
Major technical changes  addition of technical requirements
increase of technical requirements
These are changes to technical requirements (addition, increase of the level or removal)
made in a way that a product in conformity with the preceding edition will not always be able
to fulfil the requirements given in the later edition. These changes have to be considered for
products in conformity with the preceding edition. For these changes additional information is
provided in clause B) below.
NOTE These changes represent current technological knowledge. However, these changes should not normally
have an influence on equipment already placed on the market.
B) Information about the background of ‘Major Technical Changes’
C1 – The requirements for the Division method of area classification are applicable only for
users of this standard intending qualification for these areas.
C2 – The design requirements for safety showers and eyewash units have been included for
harmonization and for added safety.
The text of this standard is based on the following IEC documents:
FDIS Report on voting
31/1190/FDIS 31/1199/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.
International standards are drafted in accordance with the ISO/IEC Directives, Part 2.
This standard is intended to be used in conjunction with IEC/IEEE 60079-30-1:2014,
Explosive atmospheres – Part 30-1: Electrical resistance trace heating – General and testing
requirements.
A list of all parts of IEC 60079 series, under the general title Explosive atmospheres, can be
found on the IEC website.
© IEC/IEEE 2015
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
– 10 – IEC/IEEE 60079-30-2:2015
© IEC/IEEE 2015
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 atmospheres may be present, with the exclusion of
those classified as requiring EPL Ga/Da (traditional relationship to Zone 0 and Zone 20
respectively). This standard also provides guidance for explosive atmospheres incorporating
the Division method of area classification that may be applied by some users of this standard.
NOTE Information on the Division method is given in NFPA 70 and CSA C22.1.
It provides recommendations for the design, installation, maintenance and repair of trace
heating systems including 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.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60050-426, International Electrotechnical Vocabulary – Part 426: Equipment for explosive
atmospheres
IEC 60079-0, Explosive atmospheres – Part 0: Equipment – General requirements
IEC 60079-15, Explosive atmospheres – Part 15: Equipment protection by type of protection
“n”
IEC/IEEE 60079-30-1, Explosive atmospheres – Part 30-1: Electrical resistance trace heating
– General and testing requirements
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-426,
IEC 60079-0 and IEC/IEEE 60079-30-1 apply.
4 Application considerations
4.1 General
This part of IEC 60079 supplements the requirements specified in IEC 60079-14, IEC 60079-
17 and IEC/IEEE 60079-30-1.
Where trace heating systems are to be installed in explosive atmospheres, full details of the
area classifications shall be specified. The specification shall state, as applicable, the

© IEC/IEEE 2015
required equipment protection levels Gb, Gc, Db, and Dc (traditional relationship to Zone 1,
Zone 2, Zone 21, and Zone 22 respectively), and/or the Division 1 and Division 2 explosive
atmospheres, the gas or dust groups, and temperature classification. Where special
considerations apply or where site conditions may be especially onerous, these conditions
shall be detailed in the trace heating specification.
The specification for heating systems to be installed on mobile equipment or skid units (e.g.
re-locatable structures) should accommodate the adverse 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 moisture leaks
soaking the thermal insulation.
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 or ambient
proportional control techniques (see 6.14).
4.3.2 Type II
A Type II process is one for which the temperature should be maintained within a moderate
band. Control by 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 controllers using thermocouple or resistance-temperature detector (RTD)
process temperature sensors 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.
When trace heating is critical to the process, circuit monitoring for correct operation,
malfunction alarms, and back-up 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. Back-up trace heaters may allow maintenance or
repairs to be performed without a process shutdown and may be used to enhance reliability.

– 12 – IEC/IEEE 60079-30-2:2015
© IEC/IEEE 2015
5 Thermal insulation
5.1 General
The selection, installation and maintenance of thermal insulation is a key component in the
performance of an electrical trace heating system. The thermal insulation system is normally
designed to limit heat loss with the trace heating system compensating for the remainder.
Therefore, problems with thermal insulation 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 with consideration for optimum trace heater
design;
– selection of the proper insulation size.
Information about the equivalent thickness of insulating cements is given in Annex H.
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;
© IEC/IEEE 2015
– polyisocyanurate;
– perlite silicate.
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.
Insulation for valves, flanges, pumps, instruments, and other irregularly shaped equipment
may be constructed for the particular configuration. This can be fabricated from block,
insulation segments or flexible removable covers.
Non-insulated or partially insulated pipe supports or equipment require additional heat input to
compensate for the higher heat loss. Insulating cements or fibrous materials should be used
to fill cracks and joints. Where insulating cements are used for total insulation of an irregular
surface, a proportionally thicker layer of insulating cement may be applied to achieve the
desired insulating capability.
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 rainsto
...