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5.2 Intrinsically Safe Requirements
These requirements relate to the interconnecting wiring made to
and from Model 6540 203 and 6548 000 Katharometer Analyzer
Panels in the hazardous area and those for remote ancillary
items connected to the system.
5.2.1 Cable Requirements
The interconnecting cables between the various units of the gas
analysis system are subject to stringent limitations because of
the requirements of the intrinsic safety certification. These are
listed below and detailed in Fig. 5.1.
All cables entering the hazardous area must be kept separate
from cables in the safe area. Cables entering the hazardous
area must not be run with other cables and terminations must
have an earthed screen to separate them from connections for
other circuits. The detailed requirements are as follows:
1) Connections between Model 006540 203 or 006548
000 Katharometer Analyzer Panels and the 4234 PSU
All cables from the Katharometer in the hazardous area
must have an inductance/resistance ratio not exceeding
20µH/ (for Gr oup IIC gases). Also the maximum loop
resistance of this interconnecting cable is limited to 1.5 ;
this may place a limitation on the length of the total cable
run.
Twist single sheathed conducting cables together to
reduce their mutual inductance and route them
separately from cabling for non-intrinsically safe circuits
in the safe area.
2) Connections between Model 006540 203 or 006548
000 Katharometer Analyzer Panels and Model 6553
Display Unit
Katharometer to display unit cables, carrying the output
signals through zener barrier units inside the display unit,
are subject to of a maximum inductance/resistance ratio
of 20µH/ (for gr oup IIC gases). These wires are
indicated by a
in Fig. 5.3.
5 ELECTRICAL INSTALLATION
5.2.2 Recommended Cables
The choice of wiring cable is restricted by the limitations
imposed by the certification parameters. Care must be taken to
ensure that the specification of the cable required for
interconnection lengths is such that the certification parameter
limits are not exceeded – see Notes 2a, b and c in Fig. 5.1.
Cables manufactured to DEF STAN 61-12 Part 5 should comply,
but care must be taken over the number or cores included in the
cable; there is a significant difference between the 2-core and
6-core cables. The diameter over the screen in the 6-core cable
is greater than that of the 2-core and this diameter affects both
the inductance and capacitance values.
The values of a typical DEF STAN 61-12 Part 5 cable are:
Inductance (µH/metre)
Capacitance (pF/metre)
L/R (µH/ )
Test voltage
Rated voltage
Typical cables may be obtained at the following addresses:
www.permanoid.co.uk
www.Belden.com
Note. Interconnection lengths and number of cores will dictate
which cable is required e.g. Belden 9512 cable.
5.2.3 Installing Remote Ancillary Items
Any indicator/controllers, or other electrical equipment,
connected to TB1 of the Model 6553 Display Unit must not be
supplied from, nor contain, a voltage source greater than 250V
DC or 250V RMS with respect to earth.
5.2.4 Full Intrinsically Safe Requirements
For systems to be modified or used with other gases the full
ATEX requirements must be complied with as follows:
1) The total Capacitance and Inductance or Inductance to
Resistance ratio (L/R) of the cables connecting the
katharometer unit to the hazardous area terminals of the
display unit (TB2) and power supply unit terminals (TB1)
must not exceed the values in Fig. 5.1.
2) Any junction boxes used in the hazardous or safe areas
must conform to ATEX Directive 9/94/EC, specifically
clauses 6.1 and 6.3.1 of EN50020:1994.
When the AK100 gas analyzer system has been correctly
installed in accordance with the requirements for intrinsic
safety in Section 5.2 – refer to Section 6 for system set up.
2-core
6-core
0.325
0.467
190
143
8.6
11.4
2kV AC for one minute
440V RMS
19
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