Despite the importance of properly functioning cooling tower systems, operational control of cooling water treatment programs frequently is neglected, and thus is the single most common cause of program failure. The best possible combination of corrosion, scale and deposits control chemicals, with effective biocides, is completely worthless if not consistently and correctly applied to the cooling water.
Cooling water chemistry control begins with cooling water cycles, or the number of times that the dissolved salts in the fresh makeup water are concentrated by evaporation from the cooling system. This parameter commonly is obtained by measuring the conductivity of the cooling water and dividing it by the measured conductivity of the makeup water. Cycles also can be calculated using other parameters such as chlorides and dissolved solids. They are common to both the makeup and cooling water, and are not expected to be affected in any great degree by chemical additions or precipitations, or by makeup water and blowdown water volumes.
Control of cycles is critical in systems using non-softened makeup water. No chemical treatment program can cope with the excessive levels of hardness salts in cooling water resulting from very high cycles of concentration. Excessive levels of hardness salts in cooling water result in increased potential for scale formation. Cycles are controlled by discharging, or blowing down, concentrated water from the system and replacing it with fresh water. Blowdown, as this discharge is called, lowers the system concentration of dissolved solids.
One may ask: “Why use chemical treatments to operate at additional cycles when often no scale will form when operating at lower cycles?” The best answer is that operation at increased cycles substantially lowers both the makeup and blowdown requirements, cutting the cost of fresh water and sewage disposal. With corrosive waters, increasing the cycles so that the water is rendered less corrosive is an inexpensive means to improve corrosion control. Another point is that operation at increased cycles permits use of effective corrosion inhibitors that may be too costly to employ at the higher blowdown rates resulting from low-cycle operation.
Occasionally, the quality of the makeup water is so bad that a scale inhibitor must be employed just to use the water. In such cases, cycling reduces the cost of the scale inhibitor to an economic level.
If the chilled water system contains mild steel, copper alloys, aluminum or galvanized steel and uses makeup water that contains minerals and microbes water treatment is absolutely necessary if you want to protect your system for many years. Also, you need to constantly maintain the water treatment and monitor the results for corrosion, deposits and microbiological control to ensure that protection is continuing. Thermax range of water treatment products will provide solutions to all these problems.
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