Cooling Towers are a main part of the HVAC system in many buildings and just like any other mechanical piece; towers should be properly maintained to assure optimum performance and efficiency. A major part of ensuring you get the proper life and operation out of your towers is to keep up with the water treatment in the tower. Here are a few reasons why keeping up with the tower’s water conditioning can increase the life of your tower:
Corrosion:
Corrosion is an inevitable part of having a cooling tower and it cannot be completely eliminated. Corrosion needs to be controlled to the proper pH levels to help pacify the waters natural corrosives. South Florida waters require that the conductivity be maintained above 1500 to 2000 parts per million, elevating the pH to above 8.6 in order to properly control the corrosion in the system. Unnecessary corrosion can cause higher costs, due to premature failure and it will also lower your towers efficiency.
Determining Acceptable Corrosion Rates:
Corrosion rates should be balanced in conjunction with the projected life of the equipment to determine if they are acceptable. Corrosion rates should be monitored to verify the corrosion control in the system. Mild steel corrosion rates should be maintained at less than 1.5 mils per year. Copper corrosion rates should be maintained at less than .2 mils per year.
Conductivity:
Conductivity is the measurement of total dissolved solids. Tower water is cycled to reduce water usage in the tower. The cooling tower removes the heat from the water, through evaporation. Minerals and solids increase and cycle up over time as the tower continues to evaporate water. There are two variations of conductivity and they are low and high conductivity.
High conductivity (above 2200 parts per million) could cause scale deposits to form in the condenser tubes, tower and condenser piping system. High conductivity will be a sign of excessive scale in the tower, which will transfer through the piping into the strainers; this will decrease the water flow into the condenser and will cause a loss of heat transfer in the heat exchangers. Immediate action must be taken to lower the conductivity below 2200 parts per million.
Low conductivity is quite different than high conductivity, low conductivity occurs when water is lost from the cooling tower. There are two main reasons for low conductivity in the tower and they are: the tower overflowing due to excessive water and improper make-up float operation. The solenoid bleed line should also be checked in order to ensure that excessive water loss does not occur. Loss of water in the tower will cause the system to pump more city water in than necessary, which will in turn raise your water costs and lower your efficiency.
Biological Fouling:
Biological fouling is the accumulation of microorganisms, plants and algae on submerged structures. The cooling tower fans draw these contaminants into the tower with the air and they are introduced to the water. Sunlight increases the development of algae and other biological matter, increasing the growth rate of these contaminants. Algaecides are used to control these growths and to ensure that they do not reach unacceptable levels. To keep the biological fouling at proper levels, dual algaecide systems should be used. The system should consist of a liquid algaecide and an oxidizing algaecide. If algae and slime already exist in the tower, the tower should be shocked and pressure cleaned to remove the biological fouling. Algae and slime in the system can be hazardous to the occupant’s health. It can also plug the hot basin distributors, this would cause the hot water overflow basin to overflow and this would reduce the GPM and decrease your efficiency. Scale and algae in the system will also decrease the cubic feet per minute, which will cause the fan to run harder, causing unnecessary stress on the system and decreasing efficiency.
Keeping your cooling towers water at an optimal balance can save your building money in the long and short run, by running the system as efficiently as possible. It can also save you money by decreasing your operating and maintenance costs.
