BEKA BA377NE, Manual

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Appendix 1 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, all BA377NE Timer or Clocks have ATEX
dust ignition protection by enclosure certification
Ex tc 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 Timer or Clock’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 dust applications.
A1.1 Zones, and Maximum Surface
Temperature
The BA377NE has been ATEX dust certified
Group II, Category 3D
Ex ic tc IIIC T80ºC Dc -40
≤ Ta ≤ 60°C
When connected to a suitable system the Timer or
Clock 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.
The BA377NE ATEX Type Examination Certificate
has an 'X' suffix to show that special conditions for
safe use are specified by the BA377NE Ex ic tc
certificate. These state that the BA377NE Timer or
Clock should be:
a. Mounted such that the instrument terminals
are protected by at least an IP54 enclosure
certified to IEC 60079-15 or IEC 60079-0 as
appropriate.
Note: An Ex t, Ex n, Ex e or Ex p certified
enclosure satisfies this requirement.
b. Instrument terminals must be supplied from
limited energy circuits.
Note: This means that the BA377NE should
only be connected to circuits with output
parameters in normal operation equal to, or
less than the instruments input parameters
which are the same as the Ex nA input
parameters specified in section 3 of this
manual.
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.
Before closing the Ex tc enclosure ensure
that the sealing gaskets are undamaged
and free from dirt and foreign bodies.
Inspection of t he Timer or Clocks 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.