An integral part of cooling tower care is treatment of the water recirculated within the system. Unfortunately, many cooling tower users usually fail to fulfil this important maintenance requirement because they are oblivious to its significance.
Let's discuss some key reasons as to why treatment of cooling tower water is so important.
It is a well-known fact that metal can reacts with corrosive ions and compounds dissolved in water. Corrosive water can readily react with the metal components of a cooling tower and cause corrosion/metal loss. This can, in turn, result in premature deterioration of key components, including the heat exchangers, the piping used to recirculate water, and the cold water basin.
In worst case scenarios, pitting, which is the formation of small holes in the metal due to corrosion, is only discovered after the equipment has failed. Failures of this kind can be disastrous, as they can result in complete plant shutdown and expensive repairs and/or parts replacement.
Corrosion also leads to a loss of operating efficiency as corrosion prevents effective heat transfer by insulating the metals. Treating cooling tower water with corrosion inhibitors is an effective way to solve problems associated with corrosive water.
Cooling tower water may contain calcium, magnesium and other dissolved minerals that can cause precipitation (deposit formation) within the equipment. This deposition is called scale and it usually interferes with heat transfer, accelerates the rate of corrosion, and leads to an overall decline of process efficiency.
In addition to its insulating properties, scale buildup progressively reduces the internal diameters of piping used to distribute water and roughens the internal walls of the pipes, thereby restricting proper water flow. To prevent rapid scale formation in cooling towers, the water should be treated with water softeners to get rid of any dissolved minerals.
Water is a life-giving solvent, but it can also be a breeding ground for algae, fungi, protozoa, and other forms of harmful bacterial organisms. If the biological growth is not properly controlled, it creates a natural adhesion surface that forms a bio-film within the cooling tower system. The bio-film encourages scale formation and increases corrosion rates, but also contributes to reduced thermal performance.
There is an extensive range of biocides that can be used to produce the best bacteria kill-rate. The choice of an appropriate biocides depends upon the specific type of biological element that has occurred in a cooling tower.