Operating Instructions
SILAS
Controller for Zones 2 and 22
Version 2.00
Page 8 of 28
SILAS_E_110806.doc Operating Instructions for the SILAS Controller
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Technical data are subject to change
5.
Description of the System
The
SILAS
Controller
can be used in combination with the pressure control device and the digital purge valve for all
normal applications (control panels, control enclosures, printers, operator terminals etc.) in Ex zone 2 and Ex zone 22.
5.1
Use in Ex Zone 2
The user decides on his own responsibility about the use of a purging cycle. However he must be absolutely certain before
switching on the overpressure-monitored control panelthat there are no more potentially explosive gas mixtures inside the
control panel or that the gas concentration is less than 25% of the lower explosion limit of gases. This can be ensured either
by manually measuring the gas concentration using suitable measuring apparatus or by means of a
SILAS
Controller
monitored purging cycle for the automatically monitored dilution of the gas mixtures
.
After assembling the
SILAS
Controller
, the pressure control device and the purge valve on the enclosure and after
connecting the mains voltage and purge gas, the system starts automatically. The system then regulates and monitors the
purge gas flow rate and the enclosure’s internal pressure during the purging cycle and the enclosure’s internal pressure
during the operating phase.
If the minimum pressure “P 1” in the panel is exceeded during the purging cycle, the
SILAS
Controller
connects the
purging-air nozzle in the input valve. If the pressure and accordingly the flow at the pressure control device module
(switching value of “P 3”) is sufficient, the preset remaining purging time counts down to zero. At the end of the pre-purging
time the purging-air nozzle closes and the leakage losses of the overpressure-monitored control panel are compensated by
means of the needle valve inside the purge valve.
The following functions are assigned to the various pressure switch values:
P1: “MIN” disconnection threshold: when the pressure falls below this value, an alarm is activated.
P2: Pre-alarm: when the pressure falls short of this pressure value, a pre-alarm is activated.
P3: Purging pressure: when the pressure exceeds this pressure value, a purging time is activated.
P4: “MAX” disconnection threshold: when this pressure value is exceeded, the alarm is activated.
When the purge pressure falls below the value of "P 3", the purge time circle stopped after the time setting of "Delay" and
the purge time counter will be set to the complete purge time.
To
prevent
the internal pressure reaching an excessively high value as a result of an impermissibly
high flow resistance
at the pressure control device for the internal pressure, the purging pressure can be limited during the pre-purging time to
the “P 4” value (PRG Y3 programming, see chapter on Settings). When a digital valve is used, the purging-air nozzle will
switch off for a short time on reaching “P4” (overpressure control).
