AS/NZS 60079.11:2000

1 - AS/NZS 60079.11:2000 ELECTRICAL APPARATUS FOR EXPLOSIVE GAS ATMOSPHERES - INTRINSIC SAFETY `I'
4 - PREFACE
5 - CONTENTS
7 - 1 Scope
8 - 2 Normative references
9 - 3 Definitions
9 - 3.1 intrinsically safe circuit
9 - 3.2 electrical apparatus
9 - 3.3 intrinsically safe apparatus
9 - 3.4 associated apparatus
10 - 3.5 normal operation
10 - 3.6 fault
10 - 3.7 countable fault
10 - 3.8 non-countable fault
10 - 3.9 infallible component or infallible assembly of components
10 - 3.10 infallible separation or insulation
10 - 3.11 simple apparatus
10 - 3.12 internal wiring
10 - 3.13 minimum igniting current (MIC)
10 - 3.14 minimum igniting voltage
11 - 3.15 maximum r.m.s. a.c. or d.c. voltage (Um)
11 - 3.16 maximum input voltage (Ui)
11 - 3.17 maximum output voltage (Uo)
11 - 3.18 maximum input current (Ii)
11 - 3.19 maximum output current (Io)
11 - 3.20 maximum input power (Pi)
11 - 3.21 maximum output power (Po)
11 - 3.22 maximum external capacitance (Co)
11 - 3.23 maximum internal capacitance (Ci)
11 - 3.24 maximum external inductance (Lo)
12 - 3.25 maximum internal inductance (Li)
12 - 3.26 maximum external inductance to resistance ratio (Lo/Ro)
12 - 3.27 maximum internal inductance to resistance ratio (Li/Ri)
12 - 3.28 clearance
12 - 3.29 distance through casting compound
12 - 3.30 distance through solid insulation
12 - 3.31 creepage distance in air
12 - 3.32 creepage distance under coating
12 - 3.33 fuse rating (In)
12 - 3.34 sealed gas tight cell or battery
12 - 3.35 sealed valve-regulated cell or battery
13 - 3.36 diode safety barrier
13 - 4 Grouping and classification of intrinsically safe apparatus and associated apparatus
13 - 5 Categories of electrical apparatus
13 - 5.1 General
13 - 5.2 Category ‘ia’
14 - 5.3 Category ‘ib’
14 - 5.4 Simple apparatus
15 - 6 Apparatus construction
15 - 6.1 Enclosures
15 - 6.2 Wiring and small component temperatures
15 - 6.2.1 Dust layers on Group I equipment
15 - 6.2.2 Wiring within apparatus
16 - 6.2.3 Printed circuit wiring
17 - 6.2.4 Small components
18 - 6.3 Facilities for connection of external circuits
18 - 6.3.1 Terminals
19 - 6.3.2 Plugs and sockets
20 - 6.3.3 Determination of maximum external inductance to resistance ratio (Lo/Ro) for resistance limited power source
21 - 6.3.4 Permanently connected cable
21 - 6.4 Separation distances
21 - 6.4.1 Separation of conductive parts
22 - 6.4.2 Voltage between conductive parts
23 - 6.4.3 Clearance
23 - 6.4.4 Separation distances through and requirements of casting compound
24 - 6.4.5 Separation distances through solid insulation
24 - 6.4.6 Composite separations
25 - 6.4.7 Creepage distance in air
25 - 6.4.8 Creepage distance under coating
29 - 6.4.9 Requirements for assembled printed circuit boards
29 - 6.4.10 Separation by earth screens
29 - 6.4.11 Internal wiring
29 - 6.4.12 Electric strength tests
30 - 6.4.13 Relays
30 - 6.5 Protection against polarity reversal
30 - 6.6 Earth conductors, connections and terminals
31 - 6.7 Encapsulation used for the exclusion of a potentially explosive atmosphere
31 - 7 Components on which intrinsic safety depends
31 - 7.1 Rating of components
32 - 7.2 Connectors for internal connections, plug-in cards and components
32 - 7.3 Fuses
33 - 7.4 Primary and secondary cells and batteries
33 - 7.4.1 General
33 - 7.4.2 Electrolyte leakage
33 - 7.4.3 Cell and battery voltages
34 - 7.4.4 Internal resistance of battery and cell
34 - 7.4.5 Current-limiting devices for batteries in associated apparatus
34 - 7.4.6 Current-limiting devices for batteries to be used and replaced in explosive atmospheres
34 - 7.4.7 Current-limiting devices for batteries to be used but not replaced in explosive atmospheres
34 - 7.4.8 External contacts for charging batteries
35 - 7.4.9 Battery construction
35 - 7.5 Semiconductors
35 - 7.5.1 Transient effects
35 - 7.5.2 Shunt voltage limiters
36 - 7.5.3 Series current limiters
36 - 7.6 Failure of components and connections
37 - 7.7 Piezo-electric devices
37 - 8 Infallible components, infallible assemblies of components and infallible connections
37 - 8.1 Mains transformers
37 - 8.1.1 Winding faults
37 - 8.1.2 Protective measures
37 - 8.1.3 Transformer construction
38 - 8.1.4 Transformer type tests
39 - 8.1.5 Routine test of mains transformers
39 - 8.2 Transformers other than mains transformers
39 - 8.3 Damping windings
39 - 8.4 Current-limiting resistors
40 - 8.5 Blocking capacitors
40 - 8.6 Shunt safety assemblies
40 - 8.6.1 General
41 - 8.6.2 Safety shunts
41 - 8.6.3 Shunt voltage limiters
42 - 8.7 Wiring and connections
42 - 8.8 Galvanically separating components
43 - 9 Diode safety barriers
43 - 9.1 General
43 - 9.2 Construction
43 - 9.2.1 Mounting
43 - 9.2.2 Facilities for connection to earth
43 - 9.2.3 Protection of components
44 - 10 Type verifications and type tests
44 - 10.1 Spark ignition test
44 - 10.1.1 General
44 - 10.1.2 Spark test apparatus
45 - 10.2 Explosive test mixtures
45 - 10.3 Calibration of the spark test apparatus
45 - 10.4 Tests with the spark test apparatus
45 - 10.4.1 Circuit test
46 - 10.4.2 Safety factors
47 - 10.4.3 Testing considerations
47 - 10.4.4 Results of spark tests
47 - 10.5 Temperature tests
48 - 10.6 Voltage tests
48 - 10.7 Small component ignition test
49 - 10.8 Determination of parameters of loosely specified components
49 - 10.9 Tests for cells and batteries
49 - 10.9.1 General
49 - 10.9.2 Electrolyte leakage test for cells and batteries
50 - 10.9.3 Spark ignition and surface temperature of cells and batteries
50 - 10.10 Mechanical tests
50 - 10.10.1 Casting compound
51 - 10.10.2 Partitions
51 - 10.11 Tests for apparatus containing piezoelectric devices
51 - 10.12 Type tests for diode safety barriers and safety shunts
52 - 10.13 Cable pull test
52 - 11 Routine verifications and tests
52 - 11.1 Routine tests for diode safety barriers
52 - 11.1.1 Completed barriers
52 - 11.1.2 Diodes for 2-diode ‘ia’ barriers
52 - 11. 2 Routine tests for mains transformers
53 - 12 Marking
53 - 12.1 General
53 - 12.2 Marking of connection facilities
55 - 13 Documentation
56 - Annex A - Assessment of intrinsically safe circuits
56 - A.1 Basic criteria
56 - A.2 Assessment using reference curves and tables
57 - A.3 Examples of simple circuits
77 - Annex B - Spark test apparatus for intrinsically safe circuits
77 - B.1 Test methods for spark ignition
86 - Annex C - Measurement of creepage distances, clearances and separation distances through casting compound and through solid
86 - C.1 Clearances and separation distances through casting compound and through solid insulation
87 - C.2 Creepage distances
89 - Annex D - Encapsulation
89 - D.1 Adherence
89 - D.2 Temperature

Specifies the construction and testing of intrinsically safe apparatus, intended for use in potentially explosive atmospheres and for associated apparatus, which is intended for connection to intrinsically safe circuits which enter such atmospheres. It also contains details of the test apparatus previously published as IEC 60079-3.

1.1 This part of AS/NZS 60079 specifiesthe construction and testing of intrinsically safeapparatus, intended for use in potentially explosive atmospheres and for associatedapparatus, which is intended for connection to intrinsically safe circuits which entersuchatmospheres. It also contains details of the test apparatus previously published as IEC 60079-3.1.2 This standard supplements IEC 60079-0:1998, the requirements of which applyto intrinsically safe apparatus and to associated apparatus except as indicated in the following list.If associated apparatus is protected by a type of protection listed in IEC 60079-0 then therequirements of that method of protection together with the relevant parts of IEC60079-0 also apply to the associated apparatus. The list of exclusions which follows is directly applicable to associated apparatus intended for use in situations where there is no potentially explosive atmosphere and in other circumstances shouldbe used in combination with the requirements ofthe other methods of protection.1.3 This standard is applicable to electrical apparatus in which the electrical circuitsthemselves are incapable of causing an explosion in the surrounding explosive atmospheres.1.4 This standard is also applicable to electrical apparatus orparts of electrical apparatus located outside the potentially explosive atmosphere orprotected by another type of protection listed in IEC 60079-0, where the intrinsic safety of theelectrical circuits in thepotentially explosive atmosphere may depend upon the design and construction of such electrical apparatus or parts of such electrical apparatus. The electrical circuits exposed to the potentially explosive atmosphere are evaluated for use in such an atmosphere by applying this standard.

First published as AS/NZS 60079.11:2000.