STORM
™
- SETTLING RATE MONITOR
INSTALLATION, OPERATION & MAINTENANCE MANUAL
ESTDS-STORM-IOM - REV K
Page 8 of 31
5
PRINCIPLE OF OPERATION
5.1
Description of Operation
The
STORM™ Settling Rate Monitor is a stand‐alone
Flocculant and Coagulant dosing control
system for use in Thickener applications. The device measures the settling time of Thickener
feed samples withdrawn from the Thickener centre-well.
A sample is drawn from the Thickener centre-well into the Settling Cylinder. When the Settling
Cylinder is full, the flocculated particles will start to settle, passing the optical sensor.
5.2
Settling Rate
–
Flocculant Dose Control
Turbidity monitoring is used to determine the settlement rate. The settling rate is used to
control Flocculant addition. When the flocculated material is draw into the Settling Cylinder it
will begin to settle, with an interface between the flocculated solids and the clear supernatant.
When this interface passes the optical sensor, the time is recorded. Should the sample settle
too quickly, the Flocculant dose rate will be reduced. If the sample settles too slowly, the
Flocculant dose rate will be increased.
5.3
Supernatant Turbidity
–
Coagulant Dose Control
The final supernatant turbidity can be used to control Coagulant addition. When all the
particles have settled, the supernatant turbidity is measured. This reading controls the
Coagulant dose rate. If the residual turbidity is too high, the Coagulant dose rate will be
increased. If the residual turbidity is low, the Coagulant dose rate will be decreased.
5.4
Sampling Sequence
Step
Description
Line purge
Air is blown into Settling Cylinder to purge sample tube
Vacuum
Air pressure is directed to a venturi vacuum generator to draw the
centre-well sample into the Settling Cylinder. Conductivity level sensors
in the Settling Cylinder stop the sample when the cylinder is full.
Settle Time
Settle timer begins counting when the cylinder is full. Settle time will be
recorded when the turbidity measurement instrument identifies the
solids/liquid interface.
Supernatant
Turbidity
After a further pre-set time, the supernatant (clear liquid) turbidity will
be recorded.
Vacuum Release
After the supernatant turbidity is recorded, the vacuum is released and
the sample is returned to the centre-well with the assistance of air
pressure line purging.
Cylinder Spray
Water is sprayed into the cylinder through a spray nozzle system to
clean the Settling Cylinder and the turbidity instrument.
