BEKA BA314NG, Manual

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APPENDIX 1
ATEX Dust Certification
A1.0 ATEX dust certification
In addition to ATEX Ex nA certification permitting
installation in explosive gas atmospheres, which is
described in the main section of this instruction
manual, the BA314NG Tachometer has ATEX Ex tc
dust ignition protection by enclosure certification
permitting installation in combustible dust
atmospheres. The front panel push button switches
are non incendive and have been certified intrinsically
safe Ex ic without the need for Zener barriers or
galvanic isolators.
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 Tachometer’s Ex tc dust input and output safety
parameters are identical to the Ex nA gas parameters,
therefore all the electrical circuits shown in the main
section of this manual may also be used for Ex tc dust
applications.
A1.1 Zones, and Maximum Surface Temperature
The BA314NG has been ATEX dust certified
Group II, Category 3D
Ex ic tc IIIC T80ºC Dc
Ta = -40°C to 60°C
When connected to a suitable system the Tachometer
may be installed in:
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
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 +60°C
A1.2 Special conditions for safe use in dust
atmospheres.
Special conditions for safe use are specified by the
Ex ic tc certificate indicated by the certificate
number's 'X' suffix. These state that the BA314NG
Tachometer should be:
a. Supplied from a limited energy circuit with
output parameters in normal operation equal to,
or less than the instrument’s input parameters.
The certificate states that It is
not necessary to
power the instrument from an intrinsically safe
interface, such as a certified shunt diode safety
barrier or a galvanic isolator to comply with this
requirement.
b. Fitted with cable entry glands or conduit fittings
which maintain the impact and ingress
protection of the enclosure. Certified Ex e or
Ex n components satisfy these requirements.
The BA314NG is supplied fitted with one
certified M20 stopping plug and one temporary
hole plug which should be replaced with the
required gland or conduit fitting.
A1.3 Maintenance
The IEC guidance on maintenance procedures
EN 60079-17 permits live maintenance in Zone 22 if
a risk analysis demonstrates that this does not
introduce an unacceptable risk. The removal of
covers [opening of Ex tc enclosure] is permitted if
this can be done without contaminating the interior of
the enclosure and instrument with dust or moisture.
Some end-users may prefer not to permit live
maintenance to minimise risk.
ENSURE PLANT SAFETY BEFORE
STARTING MAINTENANCE
Live maintenance within the hazardous
area should only be performed when it is
permitted by risk analysis or when there is
no risk of a flammable atmosphere being
present.
The instrument assembly should only be removed
from the enclosure back-box when dust can not
enter the instrument enclosure. Before replacing the
instrument assembly the sealing gasket should be
inspected to ensure that it is undamaged and free
from foreign bodies.
Inspection of the Tachometers mechanical condition
and removal of accumulated dust from the front of
the instrument and the outside of the enclosure
should be regularly performed. The interval between
inspections depends upon environmental conditions.
Removal of flammable dust should be performed
with care to avoid creating a dust cloud.
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