Supplementary installation, operating and maintenance instructions English
Explosion-proof three-phase asynchronous motors with squirrel-cage rotor for high voltage
815001 Edition 09.2020
23
Annex 3
Pre-purge before start
Supplement to the operating instructions for explosion-protected electrical machines of ignition protection
types “ec” (only for atmospheres in Zone 2) with operating mode other than S1 or S2 and rated power over
100 kW and increased safety “eb”.
See also sections 3 and 5 “Ignition risk assessment”.
High-voltage electric machines in the W52R series have connections for pre-purging. A pre-purge must be
carried out according to section xx or xx.
Protective functions:
The “pre-purge” system ensures that there is no explosive gas inside the motor when the motor starts. If
there is explosive gas inside the motor , there is a risk of explosion during start-up.
The “pre-purge system” does not correspond to the ignition protection type “pressurised enclosure” Ex p II
according to IEC/EN 60079
–2, especially its pre-purging conditions.
System description
One flange in the motor for inert gas supply / one flange in the motor for gas discharge (for pre-purging).
The position of the flange is determined by the motor manufacturer.
Before putting the motor into operation, the free volume of the motor enclosure must be purged with inert
gas, if necessary after ignition risk assessment. After the purging phase, the input and output valves are
closed. There is no monitoring of the internal pressure.
One or two mechanical blow-off valves are fitted on the top of the motor.
Response pressure in the purging phase 3-20 mbar.
Inert gas supply e.g. via the following devices (input)/ball valve/controller with filter/pressure reducing
valve/safety valve/manometer
The devices for inert gas supply and gas outlet are not included in the scope of delivery.
They are only supplied by the motor manufacturer on special order.
Processed plant compressed air can also be used as inert gas.
When starting the motor, the interior of the motor must be filled with inert gas.
The purging time depends on the available inert gas volume (dm3/min) and the motor enclosure volume. The
required purging time must be determined before initial operation.
If the purging system contains electrical equipment, it must be tested and certified by an approved test centre
when used in potentially explosive atmospheres. The relevant installation regulations and national regula-
tions must be observed. Special attention must be paid to the operating instructions of the devices used!
