Flowserve URB 2 - Manual (Page 44)

44
Glossary
– continued –
Cell constant (conductivity control):
The cell constant is a geometric quantity characteristic of the level electrode and is taken into account
when calculating the conductivity. However, in the course of time this constant may chance, e. g. due
to dirt deposits accumulated on the measuring electrode.
If a reference measurement yields a result that differs from the indicated conductivity value check the
temperature compensation first. Only if the temperature coefficient setting is no longer sufficient for a
correct compensation should you modify the cell constant. In this case change the cell constant until
the reading and the indicated conductivity agree.
24hour purging pulse (conductivity control):
To prevent blocking of the continuous blowdown valve a purging pulse is triggered when the mains
voltage is switched on. The continuous blowdown valve is actuated and opens for 2 minutes. After this
period the valve is motored into the CLOSED position where it remains for 2 minutes. Then the valve is
motored into the OPERATING position or into the required control position.
This process is repeated every 24 hours. During stand-by operation the time interval continues without
triggering off the purging pulse. Note that during the purging process the MIN limit is not active.
The 24 hour purging pulse can be switched ON or OFF.