Explosive atmospheres - Part 43: Equipment in adverse service conditions

IEC TS 60079-43:2017(E) which is a Technical Specification, provides guidance for equipment for use in explosive atmospheres in environments which may include ambient temperatures below -20 °С, and additional adverse conditions, including maritime applications. The purpose of this document is to provide recommendations to be considered for the design, manufacture and use of equipment. It is intended that this document be used for equipment operating within the environmental range specified on the certificate for the equipment. This document is intended to be used in conjunction with the IEC 60079 series and the ISO/IEC 80079 series.
Keywords: electrical equipment for use in explosive atmospheres

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Published
Publication Date
12-Nov-2017
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PPUB - Publication issued
Completion Date
13-Nov-2017
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IEC TS 60079-43
Edition 1.0 2017-11
TECHNICAL
SPECIFICATION
Explosive atmospheres –
Part 43: Equipment in adverse service conditions
IEC TS 60079-43:2017-11(en)
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IEC TS 60079-43
Edition 1.0 2017-11
TECHNICAL
SPECIFICATION
Explosive atmospheres –
Part 43: Equipment in adverse service conditions
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.260.20 ISBN 978-2-8322-5011-2

Warning! Make sure that you obtained this publication from an authorized distributor.

® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 3 ----------------------
– 2 – IEC TS 60079-43:2017 © IEC 2017
CONTENTS

FOREWORD ........................................................................................................................... 3

INTRODUCTION ..................................................................................................................... 5

1 Scope .............................................................................................................................. 6

2 Normative references ...................................................................................................... 6

3 Terms and definitions ...................................................................................................... 7

4 Environmental conditions affecting the equipment used in explosive atmospheres ........... 7

4.1 General ................................................................................................................... 7

4.2 Low temperature effects .......................................................................................... 7

4.3 Other environmental effects .................................................................................... 8

5 Recommendations for design of equipment ..................................................................... 8

5.1 General ................................................................................................................... 8

5.2 Atmospheres containing salt and chlorides ............................................................. 9

5.3 Snow conditions ...................................................................................................... 9

5.4 Solar Radiation ....................................................................................................... 9

5.5 Mechanical integrity ................................................................................................ 9

5.6 Icing and winterization .......................................................................................... 10

5.7 Impact of rapid cooling .......................................................................................... 10

6 Impact of low temperatures on types of protection ......................................................... 10

6.1 General ................................................................................................................. 10

6.2 Intrinsic safety "i" .................................................................................................. 10

6.3 Flameproof enclosure "d" ...................................................................................... 11

6.4 Pressurized enclosure "p" ..................................................................................... 11

6.5 Liquid immersion "o" ............................................................................................. 11

7 Selection, installation and use of equipment .................................................................. 11

7.1 Limited functionality .............................................................................................. 11

7.2 Cables and cable glands ....................................................................................... 11

7.3 Seals and sealing materials .................................................................................. 12

8 Maintenance of equipment ............................................................................................. 12

9 Hazardous area classification ........................................................................................ 12

Annex A (informative) Recommendations on materials ......................................................... 13

Annex B (informative) Solar radiation ................................................................................... 14

B.1 General ................................................................................................................. 14

B.2 Temperature gradients .......................................................................................... 14

B.3 Recommendations ................................................................................................ 14

B.3.1 Cables and glands ......................................................................................... 14

B.3.2 Equipment ..................................................................................................... 14

B.3.3 Protective measures ...................................................................................... 14

Annex C (informative) Electric motors in low temperatures ................................................... 15

C.1 General ................................................................................................................. 15

C.2 Explosion-protection ............................................................................................. 15

C.3 Factors that may affect design and performance ................................................... 15

Bibliography .......................................................................................................................... 17

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IEC TS 60079-43:2017 © IEC 2017 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
EXPLOSIVE ATMOSPHERES –
Part 43: Equipment in adverse service conditions
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

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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

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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

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4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications

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5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity

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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

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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.

The main task of IEC technical committees is to prepare International Standards. In

exceptional circumstances, a technical committee may propose the publication of a technical

specification when

• the required support cannot be obtained for the publication of an International Standard,

despite repeated efforts, or

• the subject is still under technical development or where, for any other reason, there is the

future but no immediate possibility of an agreement on an International Standard.

Technical specifications are subject to review within three years of publication to decide

whether they can be transformed into International Standards.

IEC TS 60079-43, which is a technical specification, has been prepared by IEC Technical

committee 31: Equipment for explosive atmospheres.
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– 4 – IEC TS 60079-43:2017 © IEC 2017
The text of this technical specification is based on the following documents:
Enquiry draft Report on voting
31/1311/DTS 31/1328A/RVDTS

Full information on the voting for the approval of this technical specification can be found in

the report on voting indicated in the above table.

This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

A list of all parts in the IEC 60079 series, published under the general title Explosive

atmospheres, can be found on the IEC website.

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

stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to

the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.
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IEC TS 60079-43:2017 © IEC 2017 – 5 –
INTRODUCTION

IEC 60079-0 specifies the requirements for electrical equipment intended for use in explosive

atmospheres at standard atmospheric conditions:
• temperature –20 °C to +60 °C;
• pressure 80 kPa (0,8 bar) to 110 kPa (1,1 bar); and
• air with normal oxygen content, typically 21 % v/v.

In some cases, other parts of the IEC 60079 series also specify conditions outside the above

range, for example in IEC 60079-1.

IEC 60079-0 states the normal ambient temperature range as –20 °C to +40 °C and states

that electrical equipment designed for use in other than this normal ambient temperature

range is considered to be special and includes additional marking to communicate this to the

user.

IEC 60079-14 includes requirements for users to select and install equipment so that it is

suitable for the environmental conditions, but does not provide any specific guidance for

installations outside of the standard atmospheric conditions or for other adverse

environmental conditions.

Extreme climate conditions in Polar environments are challenging to explosion protection

technology and solutions. Conditions such as snow build-up, icing from spray and freezing of

precipitation can negatively affect the operation and safety of equipment. Extreme low

temperatures and weather conditions make it difficult to process hydrocarbons in open

outdoor process areas and it can also be challenging for equipment operation. Measures to

deal with these challenges are often called 'winterization'.

This document is a guide for equipment subject to adverse service conditions, for example

equipment considered as 'special' in IEC 60079-0. It is applicable to the design, manufacture,

installation, inspection and use of such equipment. Annex A gives recommendations on

materials and Annex C gives information on electric motors in low temperatures. It is possible

that some details in this technical specification will be relocated to relevant parts of the

IEC 60079 series at the next edition of each of those relevant parts as guidance material.

This technical specification does not at this time address other environmental conditions such

as high temperatures, which will be explored further at a later date.
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– 6 – IEC TS 60079-43:2017 © IEC 2017
EXPLOSIVE ATMOSPHERES –
Part 43: Equipment in adverse service conditions
1 Scope

This part of IEC 60079, which is a Technical Specification, provides guidance for equipment

for use in explosive atmospheres in environments which may include ambient temperatures

below –20 °С, and additional adverse conditions, including maritime applications.

The purpose of this document is to provide recommendations to be considered for the design,

manufacture and use of equipment. It is intended that this document be used for equipment

operating within the environmental range specified on the certificate for the equipment.

NOTE For detailed classification of climate conditions refer to IEC 60721 series and IEC 60068-1.

This document is intended to be used in conjunction with the IEC 60079 series and the

ISO/IEC 80079 series.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their

content constitutes requirements 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 60034-5, Rotating electrical machines - Part 5: Degrees of protection provided by the

integral design of rotating electrical machines (IP code) - Classification
IEC 60068 (all parts), Environmental testing
IEC 60079-0, Explosive atmospheres - Part 0: Equipment - General requirements

IEC 60079-11, Explosive atmospheres - Part 11: Equipment protection by intrinsic safety "i"

IEC 60079-14, Explosive atmospheres - Part 14: Electrical installations design, selection and

erection

IEC 60079-17, Explosive atmospheres - Part 17: Electrical installations inspection and

maintenance
IEC 60529, Degrees of protection provided by enclosures (IP Code)

IEC 60721-1, Classification of environmental conditions - Part 1: Environmental parameters

and their severities

IEC 60721-2-1, Classification of environmental conditions - Part 2-1: Environmental conditions

appearing in nature - Temperature and humidity
IEC TR 60721-4 (all parts), Classification of environmental conditions
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IEC TS 60079-43:2017 © IEC 2017 – 7 –
3 Terms and definitions

For the purposes of this document, the terms and definitions given in IEC 60079-0 apply.

NOTE Additional definitions applicable to explosive atmospheres can be found in IEC 60050-426, International

Electrotechnical Vocabulary – Part 426: Equipment for explosive atmospheres.

ISO and IEC maintain terminological databases for use in standardization at the following

addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
4 Environmental conditions affecting the equipment used in explosive
atmospheres
4.1 General

For the purposes of this document, the environmental conditions and specific operating

parameters are considered to the extent that they can cause failure of the equipment or its

parts related to explosion protection properties.

Useful information on climate classifications can be found in the IEC 60721 series. These

documents provide for five classifications of Tropical, Arid, Temperate, Cold and Polar. If a

manufacturer wishes to reference equipment as conforming to one of those classifications, it

is recommended the temperatures shown in the specific part of IEC 60721 be used, for

example in establishing the temperatures to be applied for the thermal endurance to heat and

cold tests in IEC 60079-0.

The main environmental factors which may affect the equipment addressed by this document

individually or in combination, include:
– low temperature;
– humidity;
– corrosive media;
– powder snow;
– precipitation;
– spray from waves;
– high winds;
– solar radiation; and
– mechanical effects.

The effect of these factors can be significant, particularly if they arise jointly. Information on

these effects is provided below.
4.2 Low temperature effects
For low temperatures, the following may be relevant and should be considered:
– electrochemical capacitors may freeze and fail;
– battery units may discharge;
– wax and protective compounds may become solid and crack;
– rubber materials may lose elasticity and fail;
– greases may freeze affecting parts such as hinges and shafts;
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– 8 – IEC TS 60079-43:2017 © IEC 2017
– relays may malfunction;
– amplifying properties of transistors may decrease;
– loss of ductility or embrittlement of materials or welded joints may occur;

– differential expansion or contraction of materials may have an impact on correct fitting of

components;

– oil viscosity increases, and flow may be restricted or cease, which may cause loss of

protection, or failure of mechanical systems;

– oil as dielectric insulation in aged electrical equipment may contain higher water content

which may reduce its dielectric strength or even cause dielectric failure.
4.3 Other environmental effects

High humidity can occur due to changes in temperature, for example, in maritime conditions.

In these cases, the following may be relevant and should be considered:
– dielectric permeability of insulation materials may increase;
– surface resistance of insulation materials may decrease;
– permittivity of air gaps may decrease;

– auxiliary physical-chemical processes in dielectrics and metals may occur, for example

corrosion or biological changes.

These conditions may cause undesirable changes in the capacitance of capacitors, decrease

in insulation resistance, swelling and peeling of dielectrics, metal corrosion, or formation of

mould inside the equipment.

Salt or other contaminants may exacerbate many of the problems that humidity creates, such

as reduced insulating properties and increased corrosion.
5 Recommendations for design of equipment
5.1 General

IEC 60079-0 requires equipment to be constructed in accordance with the applicable safety

requirements of relevant industrial standards. Such standards can include the IEC 60068

series of standards on environmental testing which include some tests relevant to adverse

service conditions. The IEC TR 60721-4 series includes references to relevant tests in the

IEC 60068 series.

Where equipment can be subject to adverse service conditions while in operation, the

manufacturer should supply additional information necessary for the selection, installation,

operation and maintenance of the equipment under those conditions. The upper and lower

values of temperature and humidity should be specified. The recommended values for the

climate classifications are given in IEC 60721-1 and IEC 60721-2-1. Where relevant, the rate

of temperature change for which the equipment is intended should also be specified in the

instructions for the equipment.

NOTE For the same type of equipment, different ranges of temperature are often specified depending on the

specific application.

When storage and transportation conditions before installation exceed the temperature range

covered by the certificate, the potential impact of these temperatures on the Type of

Protection of the equipment should be addressed in the instructions supplied by the

manufacturer. Where such information is not provided in the instructions, it is recommended

that the storage temperatures are not outside the range covered by the certificate.

Types of Protection should remain effective while such equipment is exposed to adverse

service conditions. This will need to be considered during selection and installation, and also

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IEC TS 60079-43:2017 © IEC 2017 – 9 –

considered during inspection and maintenance. Guidance on these aspects is included in

Clauses 7 and 8.

The selection of equipment, design of installations and maintenance should consider the

environmental factors and performance as required by IEC 60079-14 and IEC 60079-17. This

technical specification can also be used to provide additional guidance for these aspects.

5.2 Atmospheres containing salt and chlorides

When equipment is intended for use in areas where it can be exposed to salt mist,

requirements for corrosion resistance due to salt mist should be applied.

NOTE Useful information on classification of chemically active substances and the effect of these substances on

equipment can be found in the IEC 60721-3 series, IEC 60654-4 and ISO 9223.
5.3 Snow conditions

Under powder snow conditions equipment with an ingress protection rating of IP6X,

according to IEC 60529 or IEC 60034-5, is recommended to prevent powder snow entering an

enclosure in a similar way to dust ingress.

Heat dissipating equipment, particularly those with rotating parts, should be protected against

the effect of fallen snow that can melt when the equipment is switched on and re-freeze when

it is switched off. Such equipment should be installed so it is protected against snow or

heated to prevent freezing.
5.4 Solar Radiation

The requirements for the resistance to solar radiation may only need to be applied to parts

which are exposed to solar radiation in working conditions rather than to the whole equipment.

Annex B contains additional information and recommendations regarding solar radiation.

NOTE For equipment with other than white or silver-white surfaces that are subject to solar radiation, the surface

temperatures could rise at least 5K. See Annex B for details.
5.5 Mechanical integrity

At low temperatures, increased requirements for mechanical integrity should be considered.

For equipment, this is addressed during the preparation of a certificate as required by

IEC 60079-0. For installations, this may mean additional requirements, for example mounting

requirements.

NOTE Some grades of steel and cast iron become more brittle at temperatures below -20 °C.

For equipment intended for use in the open air or in rooms (spaces), where the air

temperature and humidity variations do not significantly differ from those in the open air, at a

temperature below -20 °С, the following should be considered:

• In threaded joints, where dissimilar materials with different temperature expansion

coefficients mate, consideration should be given to avoid damage to materials and to

ensure the required tightness when the dimensions of parts change due to the wide range

of temperatures that may be encountered;

• Parts subject to wear, for example as a result of friction, should not wear at a faster rate at

low temperatures compared with wear in temperate climates;

• For parts that may have low impact resilience at low temperature, additional measures

may be necessary to ensure their integrity.
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– 10 – IEC TS 60079-43:2017 © IEC 2017
5.6 Icing and winterization

If operating conditions of equipment and their design parameters do not exclude ice deposits

(icing) that affect the Type of Protection, then appropriate measures should be applied, for

example by 'winterization'.

Winterization can be achieved by placing the equipment in temperature controlled areas or

other anti-icing actions that prevent ice formation on surfaces, structures or equipment. Action

against icing includes heating of the air or the equipment.
5.7 Impact of rapid cooling

Snow, rain, spray or failure of winterization systems can lead to rapid cooling of equipment,

resulting in falling pressure and condensation inside equipment. Enclosures can deform and

lose their ingress protection after exposure to heat and humidity followed by rapid cooling.

Pressure differentials caused by variations in temperatures can cause water to migrate from

one enclosure to another via interconnecting cables.

The use of a suitable breathing device for pressure relief may be a solution for the above

problems.
6 Impact of low temperatures on types of protection
6.1 General

Atmospheric temperatures below -20 °C can compromise the Type of Protection of the

equipment and this should be addressed in the assessment and testing of the equipment.

Where these low temperatures are not specifically addressed in the Type of Protection

standard, consideration should be given to critical aspects that can arise, with examples given

in the clauses below.
6.2 Intrinsic safety "i"

The performance characteristics of components used in intrinsically safe apparatus such as

barriers and power supplies with limited spark duration with dynamic intrinsically safe

elements change at low temperatures. Such changes should be considered by selection of

appropriate components and should be assessed in accordance with IEC 60079-11 using the

manufacturer's specified operating temperature. This rating should consider changes in the

operation of semiconductor components that impact the ability of intrinsically safe apparatus

to provide the required intrinsically safe function.

Efficiency of intrinsic safety of the power supplies with dynamic intrinsically safe elements

applied in such systems depends on ambient temperature where they are used. Under low

temperatures, the sensitivity of dynamic semiconductor elements of intrinsically safe power

supplies degrades and the switching time increases. IEC 60079-11 specifies that spark

ignition tests shall be carried out
...

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