Appendix 1
Dust certification
A1.0 ATEX dust certification
In addition to ATEX certification permitting installation
in explosive gas atmospheres which is described in
the main section of this instruction manual, the
BA307E-SS and the BA327E-SS indicators have
ATEX certification permitting installation in
combustible dust atmospheres.
This appendix describes ATEX installations in
explosive dust atmospheres conforming with
EN 60079-14
Electrical installations design, selection
and erection
. When designing systems for installation
outside the UK the local Code of Practice should be
consulted.
The indicator’s dust input and output safety
parameters are identical to gas parameters, therefore
all the electrical circuits shown in the main section of
this manual may also be used for dust applications.
Intrinsically safe systems in dust atmosheres only
have to comply with IIB requirements. Apparatus
certificates for intrinsically safe interfaces usually
specify Co and Lo for IIC gases, but for use with
apparatus in dust atmospheres these may be
increased to the IIB figures. For a IIC interface with a
Uo of 28V and an Io of 93mA, Co increases from
83nF to 650nF and Lo increases by a factor of 2.25
for IIB.
A1.1
Zones, and Maximum Surface
Temperature
The BA307E-SS and the BA327E-SS have been
ATEX certified as Group II, Category 1D Ex ia IIIC
T80ºC Da IP20 apparatus, Ta -40 to 70°C.
When connected to a suitable system the indicators
may be installed in:
Zone 20
explosive atmosphere in the form of a
cloud of combustible dust in air is
continuously present, or for long
periods or frequently.
Zone 21
explosive atmosphere in the form of a
cloud of combustible dust in air is likely
to occur occasionally in normal
operation.
Zone 22
explosive atmosphere in the form of a
cloud of combustible dust in air is not
likely to occur in normal operation, but if
it does occur, will only persist for a short
period.
Be used with dust in subdivisions:
IIIA
combustible flyings
IIIB
non-conductive dust
IIIC
conductive dust
(For use with IIIC conductive dusts
special conditions for safe use apply
– see section A1.4)
Having a Minimum Ignition Temperature of:
Dust cloud
120°C
Dust layer on indicator
155
°
C
up to 5mm thick
Dust layer on indicator
Refer to
over 5mm thick.
EN 60079-14
At an ambient temperature between -40 and +70°C
A1.3 Maintenance
ENSURE PLANT SAFETY BEFORE
STARTING MAINTENANCE
Live maintenance is permitted on
intrinsically safe equipment installed in a
hazardous area, but only certified test
equipment should be used.
Both models have IP66 front of panel protection
and a gasket is provided to seal the joint between
the instrument and the mounting panel thus
preventing dust ingress from the outside of the
mounting panel. The rear of the instruments is not
sealed, but ATEX dust certification is dependent on
the internal conformal coating of the instrument, so
dust ingress is acceptable except for use in IIIC
conductive dusts – see A1.4. However, the
amount of dust accumulating on the rear of the
indicator should always be minimised.
A1.4
Special conditions for use in IIIC dusts
The ATEX certificate for the loop powered
indicators has an ‘X’ suffix indicating that special
conditions for safe use are required for installion in
IIIC dust atmospheres, the certificate states:
‘For use in Group IIIC conductive gas
atmospheres, the indicator shall be
mounted such that the instrument
terminals have at least IP6X protection.’
This means that an indicator exposed to a IIIC
conductive dust atmospheres should be mounted
in an IP6X panel enclosure.
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