28
In order to achieve water quality which is acceptable to the cooling tower
(as well as the remainder of your circulating water system), the selected
water treatment company must work from a relatively constant level of
concentrations. This stabilization of contaminant concentrations is usually
accomplished by
blowdown, which is the constant discharge of a portion
of the circulating water to waste. As a rule, acceptable levels on which to
base a treatment schedule will be in the range of 2-4 concentrations. The
following table shows the minimum amount of blowdown (percent of flow)
required to maintain different concentrations with various cooling ranges*:
Maintenance
*
Range = Difference between hot water temperature coming to tower and cold water
temperature leaving tower.
EXAMPLE:
700 GPM (44.2 L/s) circulating rate, 18
°
F (10
°
C) cooling
range. To maintain 4 concentrations, the required blowdown is 0.458% or
.00458 times 700 GPM (44.2 L/s), which is 3.2 GPM (0.2 L/s).
If tower is operated at 4 concentrations, circulating water will contain four
times as much dissolved solid as the makeup water, assuming none of the
solids form scale or are otherwise removed from the system.
When water treatment chemicals are added, they should not be
introduced into the circulating water system via the cold water basin
of the cooling tower. Water velocities are lowest at that point, which
results in inadequate mixing.
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Note
Summary of Contents for Primus P11
Page 1: ...Manual 04 131 User Manual Models P11 through P15 ...
Page 39: ...39 ...
