DRAWING NO. 13 — DOSAGE EXPLANATION
The dosage adjustment is used to set (or change) the ratio of
chemical gas flow rate with respect to the process variable
(Water Flow Rate) and the water quality (Demand). When
using a flow proportional system, 100% dosage is achieved
when the chemical feeder is operating at 100% of its feed rate
based on an incoming flow meter signal representing 100% of
water flow rate. As long as this ratio is maintained, the dosage
is 100%.
EXAMPLE (See above graph):
A 500 PPD maximum feed chlorinator must operate at 500 PPD
to treat a maximum water flow rate of 10 MGD. If the water
flow rate decreases to 5 MGD (50%), the SMARTVALVE™ will
automatically decrease the chlorinator gas feed rate to 250 PPD
(50%) which is still 100% dosage.
In actual plant and system operation, however, the actual “required”
dosage is rarely 100%. Because of this, the SMARTVALVE™
is designed to provide a wide range of dosage adjustment
(10% - 400%) and is easily set by the system operator via the
keypad.
1. At dosage settings greater than 100%, proportionality is lost
at some water flow rate less than the designed maximum rate.
If the dosage setting is increased to 200% for example,
proportional control is only maintained up to 50% of water flow
rate because at these conditions, the feeder is already at its
maximum and cannot further respond to water flow rate
requirements above 50%.
2. At dosage settings less than 100%, a portion of the operating
range of the feeder is sacrificed. If the dosage setting is
decreased to 50% for example, the upper 50% of the feeder’s
metering tube cannot be used.
Reasonable dosage adjustments of a properly sized flow
proportional system are normal. Excessive and extreme
adjustments could be the result of an under- or oversized
system requiring a change in overall system capacity. At a
minimum, this usually requires changing the SMARTVALVE’s
valve plug and the metering tube in the gas feeder unit.
ADDITIONAL COMPONENTS MAY ALSO BE NEEDED.
CHLORINE
FEED RATE
WATER FLOW RATE
0 MGD
0%
2.5 MGD
25%
5 MGD
50%
7.5 MGD
75%
10 MGD
100%
500 PPD
450 PPD
400 PPD
350 PPD
300 PPD
250 PPD
200 PPD
150 PPD
100 PPD
50 PPD
0 PPD
(100%)
(90%)
(80%)
(70%)
(60%)
(50%)
(40%)
(30%)
(20%)
(10%)
(0%)
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