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6.4.2 Categories 2&3, Zones 1&2 (Ex-inside) monitoring parameters
The following monitoring parameters apply to pumps for which an occasional occurrence of
explosive gas atmospheres within the pump is permissible.
Monitoring
parameters
Measures
Dry running
inside the
pump
Double seal
Dry running inside the pump is
never
permitted for pumps with simple
mechanical seals or magnetic couplings. They are therefore also
never
approved for an internal explosive gas atmosphere!
Pumps with double mechanical seals can be operated for a short time
(depending on the pumping media temperature) without pumping
medium in the pump interior, provided that the seal supply system is
in operation and monitored (see flow and level monitoring of double
seals) and (forced) circulation/flushing is present.
Occasional occurrence of an explosive gas atmosphere within pumps
intended for this purpose is permissible (Zone 1 or Zone 2) if (forced)
circulation is present.
Permanent pumping of an explosive mixture is not permitted (Zone 0).
Dry running in
the sealing
chamber
Double seal
Seal supply
system
Flow monitoring of a flushed seal
If the flushing flow rate of a double seal reaches a critical value (high
temperature rise of the quench/sealing medium, rapid drop in the flow
rate or insufficient flow rate), the pump unit must be brought
automatically and immediately into a safe operating condition.
Switching off the pump unit.
The pump unit must not be put back into operation until the fault has
been rectified and the interlock reset.
A flow monitoring system must be installed in such
a way that the
sealing chamber is continuously filled with quench/sealing medium.
Fill level monitoring of a quenched/pressurized seal
If the filling level of the quench/sealing pressure system reaches a
critical value (container not sufficiently filled), the pump unit must be
brought automatically and immediately into a safe operating condition.
Switching off the pump unit.
The pump unit must not be put back into operation until the fault has
been rectified and the interlock reset.
Monitoring of the filling level of the quench/sealing pressure system
by automatically transferring it to a safe operating condition.
- Fill level switch in the sealing medium container switches when
the critical level of the sealing medium is reached.
If other or further values of these monitoring parameters must be
complied with, these are contained in the order-related
documentation, sectional drawing of the shaft seal or documentation
of the seal manufacturer.
Motor
protection
Temperature monitoring with thermistor temperature sensor (PTC ),
PT100 or thermoswitch in the winding (see operator's manual of the
