IEC 61779-2:1998

INTERNATIONAL
IEC
STANDARD
61779-2
First edition
1998-04
Electrical apparatus for the detection
and measurement of flammable gases –
Part 2:
Performance requirements for group I apparatus
indicating a volume fraction up to 5 %
methane in air
Appareils électriques de détection et de mesure
des gaz combustibles –
Partie 2:
Règles de performances des appareils du groupe I pouvant
indiquer une fraction volumique jusqu'à 5 %
de méthane dans l’air
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 Graphical symbols for use on equipment.
, IEC 60417:
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
61779-2
First edition
1998-04
Electrical apparatus for the detection
and measurement of flammable gases –
Part 2:
Performance requirements for group I apparatus
indicating a volume fraction up to 5 %
methane in air
Appareils électriques de détection et de mesure
des gaz combustibles –
Partie 2:
Règles de performances des appareils du groupe I pouvant
indiquer une fraction volumique jusqu'à 5 %
de méthane dans l’air
 IEC 1998  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.
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Commission Electrotechnique Internationale
PRICE CODE
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International Electrotechnical Commission
Pour prix, voir catalogue en vigueur
For price, see current catalogue

– 2 – 61779-2 © IEC:1998(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION

___________
ELECTRICAL APPARATUS FOR THE DETECTION

AND MEASUREMENT OF FLAMMABLE GASES –

Part 2: Performance requirements for group 1 apparatus

indicating a volume fraction up to 5 % methane in air

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 61779-2 has been prepared by subcommittee 31L: Electrical
apparatus for the detection of flammable gases, of IEC technical committee 31: Electrical
apparatus for explosive atmospheres.
This standard should be read in conjunction with IEC 61779-1.

The text of this standard is based on the following documents:
FDIS Report on voting
31L/48/FDIS 31L/53/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.
A bilingual version of this standard may be issued at a later date.

61779-2 © IEC:1998(E) – 3 –
ELECTRICAL APPARATUS FOR THE DETECTION

AND MEASUREMENT OF FLAMMABLE GASES –

Part 2: Performance requirements for group 1 apparatus

indicating a volume fraction up to 5 % methane in air

1 Scope
1.1 This part of IEC 61779 specifies requirements for group I (as defined in part 1) portable,
transportable and fixed apparatus for the detection and measurement of methane
concentrations in mine air. The apparatus, or parts thereof, are intended for use in mines
susceptible to firedamp. The requirements and test methods applicable to the apparatus
covered by this standard are specified in part 1.
NOTE  The use of group I apparatus may not be permitted without the additional and prior approval of the
relevant authority in mines under its jurisdiction, see note 1 of 1.1.1 of part 1.
1.2 This standard is restricted to apparatus intended for the detection and measurement of
volume ratios of methane in air from a volume fraction of 0 % up to, but not exceeding, a
volume fraction of 5 %.
2 Definitions
For the purpose of this part of IEC 61779, the definitions given in part 1 apply.
3 General requirements
The apparatus shall comply with the general requirements specified in part 1 and with the
performance requirements specified in clause 4 of this standard.
Compliance shall be determined in accordance with the appropriate test requirements and
methods, including initial calibration, specified in part 1.
It shall be verified that the contents of the manufacturer's instruction manual are in accordance
with the requirements specified in part 1.
4 Performance requirements
4.1 General
The normal conditions for tests are specified in 4.3 of part 1. Compliance shall be determined
in accordance with the test methods specified in 4.4 of part 1.
4.2 Unpowered storage
After being submitted to the conditions specified in 4.4.2 of part 1, the apparatus shall meet the
requirements specified in 4.3 to clause 5 of this standard.
4.3 Calibration curve (not applicable to alarm-only apparatus)
After initial adjustment with the standard test gas, each individual indication in the three sets of
indications (after correction using the manufacturer's calibration curve, if necessary) obtained
for each of the four gas volume ratios distributed over the measuring range shall not differ
from these volume ratios by more than a volume fraction of ±0,1 % methane or ±5 % of the
indication, whichever is the greater.

– 4 – 61779-2 © IEC:1998(E)
4.4 Stability (continuous duty apparatus)

Continuous duty apparatus shall comply with the following requirements:

a) short-term stability
The short-term variation shall not exceed a volume fraction of ±0,1 % methane or ±5 % of

the indication, whichever is the greater.

b) long-term stability (fixed and transportable apparatus)

The long-term variation shall not exceed a volume fraction of ±0,1 % methane or ±5 % of

the indication, whichever is the greater.

c) long-term stability (portable apparatus)
The long-term variation shall not exceed a volume fraction of ±0,1 % methane or ±5 % of
the indication, whichever is the greater.
4.5 Stability (spot-reading apparatus)
The variation shall not exceed a volume fraction of ±0,1 % methane or ±5 % of the indication,
whichever is the greater.
4.6 Alarm
The alarm(s) shall operate during the test. If a latching alarm is provided, the manual reset
action shall be checked.
4.7 Temperature
The variation of the indication from that at 20 °C, over the temperature range –10 °C to +40 °C,
o o o
(temperatures for test: –10 C, 20 C, 40 C), shall not exceed a volume fraction of ±0,2 %
methane or ±10 % of the indication, whichever is the greater.
4.8 Pressure
The variation of the indications at 80 kPa and 120 kPa from the indication at 100 kPa shall not
exceed a volume fraction of ±0,2 % methane or ±30 % of the indication, whichever is the
greater, in air and in the standard test gas.
4.9 Humidity
The variation of the indications at 20 % RH and 90 % RH from the indication at 50 % RH, at
+40 °C, shall not exceed a volume fraction of ±0,2 % methane or ±10 % of the indication,
whichever is the greater.
4.10 Air velocity
The variation of the indication shall not exceed a volume fraction of ±0,1 % methane or ±5 % of
the indication, whichever is the greater.
4.11 Flow rate
The variation of the indication shall not exceed a volume fraction of ±0,1 % methane or ±5 % of
the indication, whichever is the greater.
4.12 Orientation
The variation of the indication shall not exceed a volume fraction of ±
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