Commissioning
Ex p control unit
Motor Purge Controller
Page 72 of 96
01-37A2-7D0003_Operating instructions_MPC_20210923_0_en.docx
Rev. 0
8.2
Commissioning
Preparation phase
The preparation phase begins with switching on the supply voltage for the Ex p
control unit and the purging gas supply.
After activation of the Ex p control unit and non-activated purging gas supply or
opened Ex p operating equipment, the following initial state is shown:
LED “Status” lights up
LED “p2” lights up
Procedure of the preparation phase:
The inflowing purging gas increases the internal pressure of the pressurised
purging gas.
The minimum pressure “p1” of the enclosure is exceeded.
LED “p1” lights up
LED “p2” goes out
The purging gas valve is opened via the control unit.
The next phase “Purging phase” is initiated.
Purging phase
The pressurised enclosure is purged with the purge gas in order to remove any
explosive gas-air mixture or to dilute it to a non-hazardous concentration before
the possible ignition sources in the pressurised enclosure are switched on.
This process prepares the pressurised enclosure for the operating phase. The
amount of purging required depends on the free volume of the pressurised
enclosure. The pre-purge process is constantly monitored by the sensors in the
sensor module and the pressure monitor.
In order to prevent the internal enclosure pressure from reaching an excessively
high value as a result of an impermissibly high flow resistance at the pressure
monitor of the Ex p control unit, the purging gas pressure is limited to the value
of “p5” during the pre-purge period.
Procedure of the purging phase:
Increase in the flow rate with purge gas.
The plate integrated in the pressure switch is raised.
Switching values of “p3” are exceeded.
LED “p3” lights up
The pre-purge time is counted down.
The “Operate” LED flashes
After the purging time has elapsed, the purging gas valve is closed.
The next phase “Operating phase” is initiated.
LED “p3” goes out
