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Maintenance and repair
10.4 Faults and troubleshooting
Faults
Page 78 of 96
CAUTION
A CHANGE IN OPERATING BEHAVIOUR MAY BE AN INDICATION OF PRE-
EXISTING DAMAGE TO THE CONTROL UNIT.
Do not put the Ex p system back into operation until the cause of the
fault has been eliminated.
It is assumed that the connection of all external electrical and mechanical
devices has been carried out correctly. Therefore, the proper setup and
connection of the electrical equipment should be checked first.
Error / Fault
Sporadic failure
Control unit out of order
The protected devices are
switched on without pre-
purge
During the pre-purging,
the purging gas valve
switches off briefly
The "Operate" LED does
not flash during the
purging time
01-37A2-7D0003_Operating instructions_MPC_20210923_0_en.docx
Possible cause
Cable break
Pressure drop / leakage
Mains voltage not
available
Device defective
Bypass activated
Wrong purging program
activated
Excessive amount of
purging gas is introduced
into the pressurised
enclosure
Purging gas is not
available
Purging gas valve does not
open or it opens only
partially
Purging gas does not flow
through the Ex p enclosure
in sufficient quantity
The target pressure of
pressure reducer is not
reached.
Ex p control unit
Motor Purge Controller
Remedy
Check connections
Check tightness and
leakage compensation
Check supply voltage
Return to manufacturer
Deactivate bypass
Check purging program
Reduce the size of the
purging gas nozzle
Check purging gas valve
for supply voltage
Check purging gas valve
for foreign particles in the
mechanical part
Increase inlet pressure to
setpoint
Check purging gas nozzle
for the correct value
Check setpoints "p3", and
"p1" of the control unit
Increase cross-section of
the purging gas supply line
The purging gas supply
line too small. Increase
cross-section of the
supply line
Remove closure or take
appropriate measures to
eliminate the reduction
Rev. 0
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