          
Furrow Pump, Inc.
P.O.
Box 1849
8525 SW
St. Helens Dr.
Wilsonville,
OR 97070
Phone:
(800) 937-3666
FAX:
(800) 377-9960
www.furrowpump.com
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| Example
1: Short Form |
| Q: |
A customer has a
wastewater pH that varies between 3 and 11, and a discharge window of 5 to 10. His
flow ranges from zero to 500 gallons per minute, with an existing flowmeter that has a 4
to 20 mA output. How can this treatment system be set up for both pH and flow
proportional treatment? |
|
|
| A: |
Connect the flowmeter
signal directly to a chemical pump, setting it for 4 mA at zero flow and 20 mA at 500
gpm. Any flow above the minimum measurable amount will start the pump, whose output
will increase until it reaches its maximum at 500 gpm. Next, using an on/off pH
controller, put its low and high set points at 6 and 9, and plug the pump power into the
output relay. This works for either and acid or caustic pump, or even both
simultaneously. The result of this arrangement is chemical pumping that increases in
proportional to flow, but only if the measured pH is either below 6 or above 9, since the
pump has no power to operate within the 6 to 9 pH window. That makes this treatment
system both pH and flow proportional. |
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