BEKA BA377E-SS, Руководство пользователя

Страница: 50 / 65

50
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
BA377E-SS Timer or Clock has 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 Timer or Clock's dust input and output safety
parameters are identical to its 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
atmospheres 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 4 for IIB.
A1.1 Zones, and Maximum Surface
Temperature.
The BA377E-SS has been ATEX dust certified as
Group II, Category 1D
Ex ia IIIC T80ºC Da -40 ≤ Ta ≤ 60°C
When connected to a suitable system the BA377E-
SS 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 +60°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.
The BA377E-SS has 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. The rear of
the instrument has IP20 protection therefore when
used in any dust application the panel enclosure in
which the instrument is mounted should provide at
least IP54 ingress protection. For applications in IIIC
conductive dusts, IP6X protection is required.
A1.4 Special conditions for safe use
The ATEX certificate has an ‘X’ suffix indicating that
special conditions for safe use are required for
installation dust atmospheres, the certificate states:
•
For use in group III explosive dust
atmospheres the BA377E-SS shall be
mounted such that the rear of the instrument
has at least IP54 protection.
• For use in group IIIC conductive explosive
dust atmospheres the BA377E-SS shall be
mounted such that the rear terminals have
at least IP6X protection.