User manual Pomac PLP Lobe pump
26 CE/PLP (1406) EN-12
5.4. In operation
! Never operate a pump with a shut-off discharge valve or a blocked discharge line, if no
pressure relief valve is fitted!
! If a pressure relief valve is fitted, do not allow the pump vent through it for long! A
pressure relief valve is a safety device and not a flow control!
! Avoid extreme temperature fluctuations of the pumped liquid. These may cause damage
to the pump because of expanding/shrinking of pump parts.
! The maximum values given for pressure, speed or temperature may never be exceeded!
5.5. Operating principle of the safety valve
In case a safety valve is mounted:
If the pump operated with a closed pressure valve, the pumped liquid is by-passed via the
opened safety valve. A relatively small quantity of liquid will circulate constantly and the heat,
generated by the internal liquid friction, is no longer evacuated to outside. The liquid
temperature will increase strongly and the maximally permitted liquid temperature may be
exceeded.
! If a safety valve is mounted, do not let the pump circulate for too long! A safety valve is a
safety device and may never be used as control valve!
Under normal system conditions the valve must remain closed. When the safety valve has been
put into operation, a deviation of the normal conditions has occurred.
Always find the cause of this and take proper measures!
5.6. Shutting down
! Ensure that the pump does not run dry when emptying it! Dry running is only permitted if
the pump is equipped with a flushed shaft seal!
1. Shut down the pump by shutting down the power supply to the drive.
2. In case the system remains pressurized, keep stop valves in flush lines OPEN.
3. If the pump is equipped with heating jackets, keep stop valves in the heating system OPEN
in case the pump conveys a liquid that may congeal at lower temperatures.
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