IEC 61779-6:1999 pdf download – 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

IEC 61779-6:1999 pdf download – 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.
1.1.1 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 PEG 61779-5. It is a compilation of practical knowledge to assist the user, and applies to apparatus, instruments and systems that indicate the presence of a flammable or potentially explosive mixture of gas or vapour with air by using an electrical signal from a gas sensor to produce a meter reading. to activate a visual or audible pre-set alarm or other device, or any combination of these
NOTE — When in classitied areas. tire apparatus should be so inStalled and used that is not capable 01 itSeti igniting a combustible gas-air miatur, It should th,rqlor, comply with th, requirements ol IEC 60079-tO
For the purpose of this standard, flammable gases shall include flammable vapours.
1.1.2 This standard applies only to group II apparatus intended for use in industrial and commercial safety applications, involving areas classified in accordance wiIh IEC 60079-10.
For the purpose of this standard, apparatus includes
a) fixed apparatus:
b) transportable apparatus: and
C) portable apparatus.
1.1.3 This standard is not intended to cover the following:
a) apparatus intended Only for the detection of non-flammable toxic gases;
b) apparatus of laboratory or scientific type intended only for analysis or measurement purposes;
c) apparatus intended for underground mining applications:
d) apparatus intended for applications In explosives processing and manufacture:
e) apparatus intended only for process control applications:
I) apparatus intended for the detection of a potentially flammable atmosphere resulting from dust or mist in air.
1.2 Normative references
The following normative documents contain provisions which, through reference In this text. constitute provisions of this part of PEC 61779. For dated references, subsequent amendments to. or revisions of, any of these publications do not apply. However, parties to agreements based on this part of PEG 61779 are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below- For undated references, the latest edition of the normative document referred to applies. Members of IEC and ISO maintain registers of currently valid International Standards.
2.4
continuous duty apparatus
combustible gas detecting apparatus that is powered for long periods of time, but may have either continuous or intermittent sensing
2.5
continuous sensing
mode of operation En which power is applied continuously to the sensing element and readings are taken continuously
2.6
diffusion apparatus
apparatus in which the transfer of gas from the atmosphere to the gas sensing element takes place by diffusion, i.e. there is no aspirated flow
2.7
electrochemlcal sensor
sensor, the operatIon of which depends upon changes of the electrical parameters of electrodes placed in an electrolyte due to redox reactions of the gas on the suriace of the electrodes
2.8
electromagnetic radiation absorption sensor
sensor, the operation of which depends upon the absorption of electromagnetic radiation by the gas being tetected
2.9
explosion protected apparatus
apparatus incorporating a type of protection covered by the IEC 60079 series of standards
2.10
explosive gas atmosphere
mixture with air, under normal atmospheric conditions, of flammable material in the form of gas or vapour, in which, after ignition, combustion spreads throughout the unconsumed mixture
NOTE 1 — This definilice apecitically excludes dulls and fibres m suspension air. Mists ate not covered by tiles siandard,
NOTE 2 — Althouqh a mixture mat has a concentration above the upper explosive limit ieee 2.1.9) is not an explosive atmosphere, in crtan cases tgr area clesaifical,on purposes, ifs advisable to consider ii as in xplosiv gas atmosphere
NOTE 3 — Normal atmospheric conditions include vanahons abov, and bofow r&•rence bv.ls of 101,3 kPa and 20 C prov.ded the variations have a negIçle affect on the explosive properties ot the flammable materials.
explosive range
range of gas or vapour mixtures with air between the explosive (flammable) limits
2.12
fixed apparatus
apparatus which is intended to have all its parts permanently installed.