IEC 61779-6:1999

Electrical apparatus for the detection and measurement of flammable gases - Part 6: Guide for the selection, installation, use and maintenance of apparatus for the detection and measurement of flammable gases

Gives guidance on the selection, installation, use and maintenance of electrically operated group II apparatus for the detection and measurement of flammable gases complying with the requirements of IEC 61779-1 to IEC 61779-5. For the purpose of this standard, flammable gases shall include flammable vapours. This standard applies only to group II apparatus intended for use in industrial and commercial safety applications, involving areas classified in accordance with IEC 60079-10.

General Information

• Status: Replaced
• Publication Date: 29-Jun-1999
• ICS: 17.060 - Measurement of volume, mass, density, viscosity
• ICS: 29.260.20 - Electrical apparatus for explosive atmospheres
• Technical Committee: TC 31 - Equipment for explosive atmospheres
• Drafting Committee: MT 60079-29 - TC 31/MT 60079-29
• Current Stage: DELPUB - Deleted Publication
• Completion Date: 16-Aug-2007

Relations

• Replaced By: IEC 60079-29-2:2007 - Explosive atmospheres - Part 29-2: Gas detectors - Selection, installation, use and maintenance of detectors for flammable gases and oxygen
• Effective Date: 05-Sep-2023

Standards Content (Sample)

INTERNATIONAL IEC
STANDARD
61779-6
First edition
1999-06
Electrical apparatus for the detection
and measurement of flammable gases –
Part 6:
Guide for the selection, installation, use and
maintenance of apparatus for the detection
and measurement of flammable gases
Appareils électriques de détection et de mesure
des gaz combustibles –
Partie 6:
Directives pour le choix, l'installation, l'utilisation
et l'entretien des appareils électriques de détection
et de mesure de gaz inflammables

Reference number
Numbering
As from 1 January 1997 all IEC publications are issued with a designation in the
60000 series.
Consolidated publications
Consolidated versions of some IEC publications including amendments are

available. For example, edition numbers 1.0, 1.1 and 1.2 refer, respectively, to the
base publication, the base publication incorporating amendment 1 and the base

publication incorporating amendments 1 and 2.

Validity of this publication
The technical content of IEC publications is kept under constant review by the IEC,
thus ensuring that the content reflects current technology.
Information relating to the date of the reconfirmation of the publication is available
in the IEC catalogue.
Information on the subjects under consideration and work in progress undertaken
by the technical committee which has prepared this publication, as well as the list
of publications issued, is to be found at the following IEC sources:
• IEC web site*
•
Catalogue of IEC publications
Published yearly with regular updates
(On-line catalogue)*
• IEC Bulletin
Available both at the IEC web site* and as a printed periodical
Terminology, graphical and letter symbols
For general terminology, readers are referred to IEC 60050: International
Electrotechnical Vocabulary (IEV).
For graphical symbols, and letter symbols and signs approved by the IEC for
general use, readers are referred to publications IEC 60027: Letter symbols to be
used in electrical technology, IEC 60417: Graphical symbols for use on equipment.
Index, survey and compilation of the single sheets and IEC 60617: Graphical symbols
for diagrams.
* See web site address on title page.

INTERNATIONAL IEC
STANDARD
61779-6
First edition
1999-06
Electrical apparatus for the detection
and measurement of flammable gases –
Part 6:
Guide for the selection, installation, use and
maintenance of apparatus for the detection
and measurement of flammable gases
Appareils électriques de détection et de mesure
des gaz combustibles –
Partie 6:
Directives pour le choix, l'installation, l'utilisation
et l'entretien des appareils électriques de détection
et de mesure de gaz inflammables

 IEC 1999  Copyright - all rights reserved
No part of this publication may be reproduced or utilized in any form or by any means, electronic or
mechanical, including photocopying and microfilm, without permission in writing from the publisher.
International Electrotechnical Commission 3, rue de Varembé Geneva, Switzerland
Telefax: [phone] e-mail: [e-mail] IEC web site http://www.iec.ch
Commission Electrotechnique Internationale
PRICE CODE
XA
International Electrotechnical Commission
For price, see current catalogue

– 2 – 61779-6 © IEC:1999(E)
CONTENTS
Page
FOREWORD . 4

INTRODUCTION .5

Clause
1 General.6

1.1 Scope . 6
1.2 Normative references. 6
2 Definitions.7
3 Measuring principles.11
3.1 Catalytic sensor.11
3.2 Thermal conductivity sensor. 12
3.3 Electromagnetic radiation absorption sensor – usually infrared . 13
3.4 Semi-conductor sensor.14
3.5 Electrochemical sensors.14
3.6 Flame ionization detectors (FID). 15
4 Selection of apparatus . 15
4.1 General.16
4.2 Selection criteria.16
4.3 Miscellaneous factors affecting selection of apparatus. 18
5 Behaviour of gas releases. 19
5.1 Nature of a release . 19
5.2 Outdoor sites and open structures. 21
5.3 Buildings and enclosures . 21
5.4 Environmental considerations.22
6 Installation of fixed gas detection apparatus . 22
6.1 Basic considerations for the installation of fixed systems . 22

6.2 Location of sensors. 23
6.3 Installation of sensors . 24
6.4 Timing of installation during construction operations. 25
6.5 Safety in fixed systems . 25
6.6 Environmental conditions.26
6.7 Sample lines.27
6.8 Access for calibration and maintenance . 27
6.9 Commissioning.27
6.10 Operating instructions, plans and records. 28

61779-6 © IEC:1999(E) – 3 –
Clause Page
7 Use of portable and transportable flammable gas detection apparatus. 28

7.1 General. 28

7.2 Initial and periodic check procedures for portable and transportable instrumentation. 29

7.3 Guidance on the use of portable and transportable apparatus. 29

8 Special precautions for fixed and portable apparatus. 30

9 Maintenance, routine procedures and general administrative control . 31

9.1 General.31

9.2 Operational checks.31
9.3 Maintenance.32
9.4 Sensors.34
9.5 Flow systems.34
9.6 Readout devices.34
9.7 Alarms.3 5
9.8 Workshop calibration test. 35
9.9 Routine tests and re-calibration procedures. 36
9.10 General administrative control . 36
10 Training.36
Annex A (informative) Flammability limits (LFL and UFL) of certain flammable gases
and vapours. 37
Annex B (informative) Environmental and application check-list for flammable gas
detectors (typical) . 55
Annex C (informative) Instrument maintenance record for flammable gas detectors
(typical). 57
Annex D (informative) Minimum environmental demands for IEC 61779-4
(group II 100 % LFL) and IEC 61779-5 (group II 100 % (v/v) gas) . 58

– 4 – 61779-6 © IEC:1999(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION

___________
ELECTRICAL APPARATUS FOR THE DETECTION

AND MEASUREMENT OF FLAMMABLE GASES -–

Part 6: Guide for the selection, installation, use and maintenance

of apparatus for the detection and measurement of flammable gases

FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of the IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, the IEC publishes International Standards. Their preparation is
entrusted to technical committees; any IEC National Committee interested in the subject dealt with may
participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. The IEC collaborates closely with the International Organization
for Standardization (ISO) in accordance with conditions determined by agreement between the two
organizations.
2) The formal decisions or agreements of the IEC on technical matters express, as nearly as possible, an
international consensus of opinion on the relevant subjects since each technical committee has representation
from all interested National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical reports or guides and they are accepted by the National Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject
of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61779-6 has been prepared by subcommittee 31L: Electrical
apparatus for the detection of flammable gases, of IEC technical committee 31: Electrical
apparatus for explosive atmospheres.
The text of this standard is based on the following documents:
FDIS Report on voting
31L/60/FDIS 31L/61/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 3.
Annexes A, B, C and D are for information only.
A bilingual version of this standard may be issued at a later date.

61779-6 © IEC:1999(E) – 5 –
INTRODUCTION
Flammable gas detection apparatus may be used whenever there is the possibility of a hazard

to life or property caused by the accumulation of a flammable gas-air mixture. Such apparatus

can provide a means of reducing the hazard by detecting the presence of the flammable
gas and issuing suitable audible or visual warnings. Gas detectors may also be used to initiate
specific precautions (for example plant shutdown, evacuation, operation of fire extinguishing

procedures).
Apparatus may be used to monitor a gas atmosphere below the lower flammable limit in

circumstances where accumulation of gas may result in a concentration of the gas/air mixture

to potentially explosive levels.

– 6 – 61779-6 © IEC:1999(E)
ELECTRICAL APPARATUS FOR THE DETECTION

AND MEASUREMENT OF FLAMMABLE GASES –

Part 6: Guide for the selection, installation, use and maintenance

of apparatus for the detection and measurement of flammable gases

1 General
1.1 Scope
1.1.1 This part of IEC 61779 gives guidance on the selection, installation, use and
maintenance of electrically operated group II apparatus for the detection and measurement of
flammable gases complying with the requirements of IEC 61779-1 to IEC 61779-5. It is a
compilat
...