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- For differential pressure protection of positive displacement pumps
(FK/FL/FKL/FDS) and side channel pumps (FZ), a safety valve on
the outlet side with relief to the safe area or a circulation valve for
pressure relief from the outlet side to the inlet side must be
installed.
- Alternatively, a sensor-supported differential pressure monitoring
system can be installed.
Monitoring parameters: Differential pressure
- The circulation via a differential pressure valve leads to an increase
in the temperature of the pumping medium.
6.2 Safety instructions for the operation of pumps with shaft seals
Shaft seals are the main ignition sources. They do not normally take effect but must
be taken into account as a foreseeable fault because any possible failure of the fluid
supply can cause dry running. This means that the seal is not cooled. The non-
dissipated frictional heat leads (<1 s) to overheating and can become an effective
source of ignition.
Danger of explosion!
- Mechanical seals and rotary shaft seals must never run dry.
- Monitoring measures for the intended operation of seals must be
provided.
To ensure the safest possible continuous operation in Zones 1 and 2, the main
criterion "prevention of dry running" must be subject to continuous monitoring.
The following must be guaranteed for pumps with non-flammable pumping media
installed in Zone 2:
Monitoring of a pump with a single mechanical seal:
The product supply (inlet side) to the pump must be monitored in such
a way that
- the liquid flow is not lost
- the pumping medium is supplied as described under point 3.1.2
- the max. permissible pumping media temperature is maintained.
-
An explosive atmosphere never occurs inside the pump
Deviations from this require a separate manufacturer's approval
and can be found in the order-related documents!
