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Selection of Equipment &
Type of Ex Protection for
Dust locations. Aug. 2010
Mike Scott : EXB Electric (Pty) Ltd.
www.exbelectric.co.za
Tel. + 27 11 887 8941
Fax. + 27 11 887 8945
EXB Electric (Pty) Ltd.
Thank You
Peter Turnherr, CEO of thuba and a
member of numerous working groups and
committees (IEC) associated with Explosion
Protection.
Peter has made available a lot of information and
material used in this presentation.
The thuba group of companies are mainly
concerned with various aspects of Explosion
Protection.
EXB Electric (Pty) Ltd.
Disclaimer
All information in this presentation is given in good
faith and does NOT replace standards, codes of
practice and any other requirements of industry or
other.
EXB Electric (Pty) Ltd and / or the writer / presenter
will / are NOT responsible for any errors / miss-
understandings.
EXB Electric (Pty) Ltd.
IEC 60079-14
International Standards
IEC 60079-17 IEC 60079-19
EXB Electric (Pty) Ltd.
Qualifications of personnel
The design of the installation, the selection of
equipment and the erection covered by this
standard shall be carried out only by persons
whose training has included instruction on the
various types of protection and installation
practices, relevant rules and regulations and
on the general principles of area classification.
The competency of the person shall be relevant to
the type of work to be undertaken.
EXB Electric (Pty) Ltd.
Information required
• Classification of the hazardous area including
the equipment protection level requirements
where applicable
• Where applicable, dust classification in relation
to the subgroup of the electrical equipment
• Surface temperature of the dust involved
EXB Electric (Pty) Ltd.
Information required
• Minimum ignition temperature of the
combustible dust cloud, minimum ignition
temperature of the combustible dust layer
and minimum ignition energy of the
combustible dust cloud
• External influences and ambient temperature
EXB Electric (Pty) Ltd.
General requirements
Hazardous areas are classified into Zones 20, 21
and 22 for combustible dusts according to
IEC 60079-10-2 in order to facilitate the selection
of appropriate electrical equipment and the design
of suitable electrical installations.
EXB Electric (Pty) Ltd.
General requirements
Electrical installations in hazardous areas shall
also comply with the appropriate requirements
for installations in non-hazardous areas.SANS 10142 in RSA
However the requirements for non-hazardous
areas are insufficient for installations in
hazardous areas.
SANS 10086 in RSA
EXB Electric (Pty) Ltd.
General requirements
Equipment shall be installed in accordance with
its documentation.
EXB Electric (Pty) Ltd.
General requirements
Installations should be designed and equipment
and materials installed with a view to providing
ease of access for inspection and maintenance
(IEC 60079-17).
EXB Electric (Pty) Ltd.
Selection of repaired, second hand
or existing equipment
When it is intended that existing, second hand or
repaired equipment is to be installed in a new
installation, it shall only be reused if:
a) it can be verified that the equipment is
unmodified and is in a condition that meets the
content of the original certificate (including any
repair or overhaul)
b) any changes to equipment standards relevant to
the item considered do not require additional
safety precautions.
EXB Electric (Pty) Ltd.
Use of equipment that is not certified
simple electrical apparatus used within an
intrinsically safe circuit. (The I S loop needs
certification)
EXB Electric (Pty) Ltd.
Equipment Protection Level (EPL)
20
Equipment Protection Level (EPL)Zone
22
21
Dc, Db and Da
Db and Da
Da
EXB Electric (Pty) Ltd.
Comparison of Dust Zones and Gas Zones.
Dust (Zone 20) ~ Gas (Zone 0)
Dust (Zone 21) ~ Gas (Zone 1)
Dust (Zone 22) ~ Gas (Zone 2)
(NB: approximately)
EXB Electric (Pty) Ltd.
Type of protection and EPL
Type of protection
Da
General requirements
Protection by enclosure
EPL
IEC 60079-31
IEC 60079-0
Standard
iaD
ta
Code
IEC 61241-11Protection by intrinsic safety
Protection by encapsulation ma IEC 60079-18
EXB Electric (Pty) Ltd.
Type of protection and EPL
Type of protection
Db
Protection by enclosure
Type of protection „pD“
Protection by encapsulation
EPL
IEC 61241-11
IEC 60079-31
Standard
pD
mb
ibD
Code
tb
IEC 61241-4
IEC 60079-18
Protection by intrinsic safety
EXB Electric (Pty) Ltd.
Type of protection and EPL
Type of protection
Dc
Protection by enclosure
EPL
IEC 60079-31
IEC 61241-4
Standard
mc
tc
Code
pD
IEC 60079-18Protection by encapsulation
Type of protection „pD“
EXB Electric (Pty) Ltd.
Suitability of apparatus for less hazardous
locations.
DUST Hazardous Locations
EPL level Da : Suitable for Zones 20 & 21 & 22
EPL level Db : Suitable for Zones 21 & 22
EPL level Dc : Suitable for Zone 22 ONLY
GAS Hazardous Locations
EPL level Ga : Suitable for Zones 0 & 1 & 2
EPL level Gb : Suitable for Zones 1 & 2
EPL level Gc : Suitable for Zone 2 ONLY
EXB Electric (Pty) Ltd.
Group III (Dust)
IIIA
Equipment groups (dust)
IIIC
IIIB
Conductive dust
Non-conductive dust
Fibres
EXB Electric (Pty) Ltd.
Comparison of Equipment Groups.
Group I : Fiery Mines, (Firedamp (Methane / Coal Dust))
Group II : Industries other than mines. (surface industries)
Group II A : Propane for Example
Group II B : Ethylene for Example
Group II C : Hydrogen gas for Example
Group III : Dusts.
Group III A : Fibres. Polyester / cotton for example
Group III B : Non Conductive dust. Grain for example
Group III C : Conductive dust. Aluminum for example
EXB Electric (Pty) Ltd.
Dust clouds
Temperature limitations because of the presence
of dust clouds
The maximum surface temperature of the
apparatus shall not exceed two-thirds of the
minimum ignition temperature in degrees Celsius
(C) of the dust/air mixture concerned:
Tmax ≤ ⅔ TCL
where TCL is the minimum ignition temperature of the cloud of
dust
EXB Electric (Pty) Ltd.
Dust layers
• Temperature limitation because of the presence
of dust layers
– up to 5 mm thickness
– above 5 mm up to 50 mm
– dust layers above 50 mm
EXB Electric (Pty) Ltd.
EXB Electric (Pty) Ltd.
Dust layers
EXB Electric (Pty) Ltd.
Plugs and socket outlets for dust
• Socket outlets shall be installed so that dust will
not enter the socket outlet with or without a plug
in place.
• To minimize the ingress of dust in the event of a
dust cap being accidentally left off, socket outlets
shall be positioned at an angle, which is not more
than 60 degrees to the vertical, and the opening
facing downwards.
EXB Electric (Pty) Ltd.
Plugs and socket outlets for dust
≤ 60°
EXB Electric (Pty) Ltd.
External factors
• Thermal effects
• Chemical effects
• Mechanical effects
• Varying pressure conditions
• Effects of movement and vibration
• Electrical effects
• Moisture
• Ingress of process liquids
• Corrosion
• Small animals, rodents and insects
EXB Electric (Pty) Ltd.
Equipment shall normally be designed
for use in an ambient temperature range
between –20 ºC and 40 ºC; in this case,
no additional ambient temperature
marking
is required.
Example of extended ambient temperature
range Tamb
Tamb –30C to 65C.
Ambient temperature
EXB Electric (Pty) Ltd.
Ambient temperature
EXB Electric (Pty) Ltd.
Ambient temperature
EXB Electric (Pty) Ltd.
EN 60079 – 0 : 2009 - 08 General Requirements
IEC 61241-2-1
Methods for determining the minimum
ignition temperatures of dust
IEC 61241-2-2
Method for determining the electrical
resistivity of dust in layers
IEC 61241-20-3
Method for determining minimum ignition
energy of dust/air mixtures
EN 60079-31:2008
Protection by Enclosure «t»
EN 61241- 4:2006
Protection by Pressurization «pD»
EN 61241-11:2006
Intrinsic Safety «iD»
EN 60079-18:2008
Protection by Encapsulation «m»
EN 60079-10-2:2009
Area classification
EN 60079-14:2009
Electrical installation design,
selection and erection
EN 60079-17:2007
Inspection and maintenance
EN 60079-19:2007
Repair and Overhaul
Standards for dust
Protection by Enclosure «t»
EXB Electric (Pty) Ltd.
Group III
IIIA
Equipment groups (dust)
IIIC
IIIB
conductive dust
non-conductive dust
fibres
EXB Electric (Pty) Ltd. 36
2.Aging resistance testing
(thermal endurance)
Hot and cold
storage tests
3.Testing for mechanical
strengthImpact test
4.Testing for dust
protectionIngress test in
dust test chamber
5. ElectrostaticsTake appropriate
measures
1.Limiting surface
temperatureThermal
tests
Protection by enclosure «t»
EXB Electric (Pty) Ltd.
Protection by enclosure «t»
Sequence of tests
Testing for aging resistance
Testing for mechanical strength
Testing for dust protection
Evaluation of dust protection taking into
consideration aging and mechanical
influences
EXB Electric (Pty) Ltd.
Protection by enclosure «t»
Dust ingress protection IP 6X
Equipment for Zones 20 and 21
Equipment for Zone 22 with conductive dust
Dust ingress protection IP 5X
Equipment for Zone 22 with non-conductive
dust
EXB Electric (Pty) Ltd.
Protection by enclosure «t»
Intrinsic Safety «iD»
EXB Electric (Pty) Ltd.
Intrinsic safety «iD»
• Energy limitation (current and voltage)
• Equipotential bonding
• Isolation of non-intrinsically-safe circuits
• Marking
• Verification of the safety of the interconnection
(equipment parameters, including conductor
length)
EXB Electric (Pty) Ltd.
Marking
• Text inscription «Intrinsically safe circuit»
• If coloured marking, only light blue such as
RAL 5012
EXB Electric (Pty) Ltd.
Simple apparatus
• No internal cells or batteries
(exception: thermocouples, photocells, etc.,)
limited to 1.5 V, 100 mA and 25 mW
• Connection to a single source only
• No internal voltage/current transformation
EXB Electric (Pty) Ltd.
Simple apparatus
• If these conditions are met, the protection
against spark ignition is afforded primarily by
the source – the «associated apparatus».
• This associated apparatus must be tested and
certified.
EXB Electric (Pty) Ltd.
Marking simple apparatus
No ATEX mark may be applied to the apparatus!
Simple Apparatus
EXB Electric (Pty) Ltd.
Associated apparatus
• apparatus must not be installed in the Ex area
• apparatus has an intrinsically safe output
(observe the interconnection parameters!)
• designation [Ex iD] IIIC
EXB Electric (Pty) Ltd.
[Ex iD] IIIC
Associated apparatus
NOTE the square brackets used in the marking.
EXB Electric (Pty) Ltd.
Associated apparatus
EXB Electric (Pty) Ltd.
Hazardous area
Switching contacte.g. pressure switch, thermostat
Mains
Non-hazardous area
Output
Associated apparatus
Pressurized enclosure «p»
EXB Electric (Pty) Ltd.
EXB Electric (Pty) Ltd.
Pressurized enclosure «pD»
• Enclosure containing components that are not
Explosion Protected. (Standard Ignition Capable
components)
• Continuous monitoring for minimum pressure
Minimum requirement 0.5 mbar (power switched off at
≤ 0.8 mbar if a leak occurs)
• Switching off means isolating from power supply
(max. rating 1.5 V, 100 mA, 25 mW)
• Prepurging not permitted
EXB Electric (Pty) Ltd.
EXB Electric (Pty) Ltd.
thuba
Blue [is]
Ex tD [ibD] [pD] A21 IP65 T70°C
Ex e mb [ib] [px] IIC T4
EXB Electric (Pty) Ltd.
Thank you for your attentiveness.
Thank you to SAFA for this
opportunity.
Questions?