Geoscience Reference
In-Depth Information
This can be expressed as gpd flow:
0.0000653 MGD = 65.3 gpd flow
24.10.8 C hemiCal F eed p ump : p erCent s troKe s etting
Chemical feed pumps are generally positive displacement pumps (also called piston pumps ). This
type of pump displaces, or pushes out, a volume of chemical equal to the volume of the piston. The
length of the piston, called the stroke , can be lengthened or shortened to increase or decrease the
amount of chemical delivered by the pump. As mentioned, each stroke of a piston pump displaces
or pushes out chemical. When calculating the percent stroke setting, use the following equation:
Requiredfeed (gpd)
Maxim
Stroke setting (%)
=
(24.102)
um feed (gpd)
EXAMPLE 24.74
Problem: The required chemical pumping rate has been calculated as 8 gpm. If the maximum
pumping rate is 90 gpm, what should the percent stroke setting be?
Solution: The percent stroke setting is based on the ratio of the gpm required to the total possible
gpm:
Requiredfeed (gpd)
Maxim
8 gpm
90 gpm
Stroke setting (%)
=
=
×
100
=
8.9%
um feed (gpd)
24.10.9 C hemiCal s olution F eeder s etting ( m l/ min )
Some chemical solution feeders dispense chemical as milliliters per minute (mL/min). To calculate
the mL/min solution required, use the following equation:
gpd 3785 mL/gal
1440 min/d
×
Solution (mL/min)
=
(24.103)
ay
EXAMPLE 24.75
Problem: The desired solution feed rate was calculated to be 7 gpd. What is this feed rate expressed
as m L/m in?
Solution: Because the gpd flow has already been determined, the mL/min flow rate can be calcu-
lated directly:
gpd 3785 mL/gal
1440 min/day
×
7 gpd
× 3785 mL/gal
1440 min/day
Solution
=
=
=
18 mL/min
24.10.10 C hemiCal F eed r ate C alibration
Routinely, to ensure accuracy, we need to compare the actual chemical feed rate with the feed rate
indicated by the instrumentation. To accomplish this, we use calibration calculations. To calculate
the actual chemical feed rate for a dry chemical feed, place a container under the feeder, weigh the
container when empty, and then weigh the container again after a specified length of time, such as
30 min. Then actual chemical feed rate can then be determined as
 
Search WWH ::




Custom Search