IEC 60079-27:2008

IEC 60079-27
Edition 2.0 2008-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Explosive atmospheres –
Part 27: Fieldbus intrinsically safe concept (FISCO)

Atmosphères explosives –
Partie 27: Concept de réseau de terrain de sécurité intrinsèque (FISCO)

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IEC 60079-27
Edition 2.0 2008-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Explosive atmospheres –
Part 27: Fieldbus intrinsically safe concept (FISCO)

Atmosphères explosives –
Partie 27: Concept de réseau de terrain de sécurité intrinsèque (FISCO)

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
M
CODE PRIX
ICS 29.260.20 ISBN 2-8318-9539-1

– 2 – 60079-27 © IEC:2008
CONTENTS
FOREWORD.3

1 Scope.5
2 Normative references .5
3 Terms, definitions and abbreviations .6
3.1 Terms and definitions .6
3.2 Abbreviations .6
4 Apparatus requirements .6
4.1 General .6
4.2 FISCO power supplies.6
4.2.1 General .6
4.2.2 Additional requirements of “ia” and “ib” FISCO power supplies .6
4.2.3 Additional requirements of “ic” FISCO power supplies .7
4.3 FISCO field devices.7
4.3.1 General .7
4.3.2 Additional requirements of “ia” and “ib” FISCO field devices .8
4.3.3 Additional requirement of “ic” FISCO field devices .8
4.4 Terminator.8
4.5 Simple apparatus .8
4.6 Marking .9
4.7 Examples of marking .9
5 System requirements.10
5.1 General .10
5.2 Additional requirements of “ic” FISCO systems.11

Annex A (informative) Typical system .12

Bibliography.13

Figure A.1 – Typical system.12

Table 1 – Assessment of maximum output current for use with “ia” and “ib” FISCO
rectangular supplies.7
Table 2 – Assessment of maximum output current for use with “ic” FISCO rectangular
supplies .7

60079-27 © IEC:2008 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
EXPLOSIVE ATMOSPHERES –
Part 27: Fieldbus intrinsically safe concept (FISCO)

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60079-27 has been prepared by subcommittee 31G: Intrinsically-
safe apparatus, of IEC technical committee 31: Equipment for explosive atmospheres.
This second edition cancels and replaces the first edition issued in 2005. It constitutes a
technical revision.
The significant change with respect to the first edition is that this standard replaces the
FNICO requirements with the requirements of an “ic” FISCO system.
The text of this standard is based on the following documents:
CDV Report on voting
31G/169/CDV 31G/176A/RVC
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.

– 4 – 60079-27 © IEC:2008
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts of the IEC 60079 series, under the general title: Explosives 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.
60079-27 © IEC:2008 – 5 –
EXPLOSIVE ATMOSPHERES –
Part 27: Fieldbus intrinsically safe concept (FISCO)

1 Scope
This part of IEC 60079 contains the details of apparatus, systems and installation practice for
use with the Fieldbus Intrinsically Safe Concept (FISCO). It is based on the concepts of
Manchester encoded, bus powered systems designed in accordance with IEC 61158-2 which
is the physical layer standard for Fieldbus installations.
The constructional and installation requirements of FISCO apparatus and systems are
determined by IEC 60079-11, IEC 60079-14, and IEC 60079-25, except as modified by this
standard. Part of a Fieldbus device may be protected by any of the methods of explosion
protection listed in IEC 60079-0, appropriate to the zone of intended use. In these
circumstances, the requirements of this standard apply only to that part of the apparatus
directly connected to the intrinsically safe trunk or spurs.
NOTE 1 Certification to the FISCO requirements does not prevent apparatus also being certified and marked to
IEC 60079-11 in the conventional manner so that they may be used in other systems. Some apparatus certified
befo
...