4
Although the BA304C indicator does not itself
comply with the requirements for simple apparatus,
the EC-Type Examination Certificate specifies that
under fault conditions the voltage, current and
power at the 4/20mA input terminals 1 and 3 will
not exceed those specified for simple apparatus.
This allows the BA304C to be connected into any
intrinsically safe circuit protected by a Zener barrier
or galvanic isolator providing the output
parameters of the circuit do not exceed:
Uo
=
30V dc
Io
=
200mA
Po
=
0.85W
The BA304C EC-Type Examination Certificate
specifies that the maximum equivalent capacitance
and inductance between the two 4/20mA input
terminals 1 and 3 is:
Ci
=
20nF
Li
=
10µH
To determine the maximum permitted cable
parameters, these figures should be subtracted
from the maximum cable capacitance and
inductance permitted by the certificate for the loop
into which the indicator is being installed.
3.3 Zones, gas groups and T rating
The BA304C has been certified Group II, Category
1G, EEx ia IIC T5, Tamb -40 to 60oC. When
connected to a suitable system the indicator may
be installed in:
Zone
0
explosive gas air mixture
continuously present.
Zone 1
explosive gas air mixture likely to
occur in normal operation.
Zone 2
explosive gas air mixture not likely
to occur, and if it does will only
exist for a short time.
Be used with gases in groups:
Group
A
propane
Group
B
ethylene
Group
C
hydrogen
Having a temperature classification of:
T1
450°C
T2
300°C
T3
200°C
T4
135°C
T5
100°C
This allows BA304C indicators to be installed in all
Zones and to be used with most common industrial
gases.
WARNING installation in Zone 0
When installed in a Zone 0 potentially
explosive atmosphere requiring apparatus
of Category 1G, the indicator shall be
installed such that even in the event of rare
incidents, an ignition source due to impact
or friction between the aluminium enclosure
and iron/steel is excluded.
3.4 Certification Label Information
The certification label is fitted on the top outer
surface of the enclosure. It shows the ATEX
certification information plus BEKA associates
name and location. Non European certification
information may also be included.
The instrument serial number and date of
manufacture are shown on a separate label within
the instrument enclosure.
4. SYSTEM DESIGN FOR HAZARDOUS AREAS
4.1 Transmitter loops
A BA304C indicator may be connected in series
with almost any intrinsically safe 4/20mA current
loop and calibrated to display the measured
variable or control signal in engineering units.
There are two basic design requirements:
1.
The intrinsic safety output parameters of
the 4/20mA loop, which are defined by the
Zener barrier or galvanic isolator, must be
less than:
Uo
=
30V dc
Io
=
200mA
Po
=
0.85W
2.
The loop must be able to tolerate the
additional 1.1V required to operate the
indicator.