15
W W W . B A L T I M O R E A I R C O I L . C O M . A U
M A R 1 1 3 - 0
Water Treatment
Re-Circulated Water Quality
Guidelines
In cooling towers, cooling is accomplished by evaporation of a portion
of the process water as it flows through the tower. As this water
evaporates, the impurities originally present remain in the recirculating
water. The concentration of the dissolved solids increases rapidly and
can reach unacceptable levels. In addition, airborne impurities are
often introduced into the recirculating water, intensifying the problem.
If these impurities and contaminates are not effectively controlled, they
can cause scaling, corrosion, and sludge accumulations which reduce
heat transfer efficiency and increase system operating costs.
The degree to which dissolved solids and other impurities build up in
the recirculating water may be defined as the cycles of concentration.
Specifically, cycles of concentration is the ratio of dissolved solids
(for example: TDS, chlorides, sulfates) in the recirculating water to
dissolved solids in the make-up water.
For optimal heat transfer efficiency and maximum equipment life, the cycles
of concentration should be controlled such that the recirculating water is
maintained within the guidelines listed below:
Z600 Galv. Steel
SST or SST WTP
pH
7.0 to 9.0
6.5 to 8.5
Hardness as CaCO3
30 to 500 ppm
30 to 500 ppm max.
Alkalinity as CaCO3
500 ppm max.
500 ppm max.
Total Dissolved Solids
1000 ppm max.
1200 ppm max.
Chlorides
125 ppm max.
250 ppm max.
Sulfates
125 ppm max.
250 ppm max.
Re-Circulated Water Quality Guidelines
