The Four Basic Problems
There are four basic problems associated with all heating and cooling water systems:
Scale: How Does Scale Get Into My System?
While all four are very important, scale is of particular concern to Chardon. When water is evaporated from the cooling tower water, the dissolved and suspended solids remain behind. Make-up water to compensate for the water lost through evaporation is automatically added by the level control valve incorporated in the system. The make-up water adds more dissolved solids to the cooling tower water. The solids left behind by evaporation plus the solids brought in by the make-up water causes solids in the cooling tower water to increase in concentration, a phenomenon called cycles of concentration. Because water can only maintain a specific quantity of dissolved solids in solution, a point is reached where solids will precipitate out of solution and deposit as scale. Scale deposits reduce heat transfer by insulating heat transfer surfaces. Prevention of deposits in the cooling system is one of the prime objectives of a sound water treatment program. The amount of solids that can be safely carried before precipitation occurs depends on several factors and should be established by a reputable water treatment company. Maintaining the maximum safe concentration of dissolved solids has direct implications on the overall cost of operating a cooling system.
Learn more about scale prevention chemicals here.
Corrosion: Are There Different Types?
Corrosion in a cooling water system can be divided into two categories. General corrosion involves a uniform and lightly distributed attack over the entire area of the metal. Pitting exists when a large part of the area is protected and only small localized areas are attacked. Pitting is considered more harmful since a large corrosive force is concentrated in a very small area. Rapid penetration of the surface and failure may result. Conditions which foster corrosion include high levels of dissolved oxygen, high temperature, and high velocity of liquid across metal surfaces, low pH, high concentrations of sulfate and chloride ions and galvanic action. The prevention of corrosion usually requires treatment of the water to make it less aggressive in terms of metal solubility. Chemicals may also be added to develop protective coating or film on metal surfaces.
Airborne Contaminants: Am I Getting Airborne Contaminants in My System?
Airborne contaminants removed from the air as it passes through the tower can accumulate in heat exchangers, condensers, piping and tower packing. While air in most metropolitan areas contains only a few micrograms of airborne material per cubic meter, cooling towers can pass billions of cubic meters of air every month resulting in the accumulation of a significant amount of particulates in the system. The situation is made worse by nearby highways, agricultural operations and high smog levels which radically increase the amount of particulate in the air. Deposits resulting from the accumulation of airborne contaminants can restrict heat transfer, restrict water flow, promote corrosion and facilitate microbiologically influenced corrosion. Airborne contaminants do not typically cause problems in closed loop or boiler systems because the contact time between the air and water is minimal. Still, material deposited in piping systems before system start-up can become suspended and re-deposit on heat exchange surfaces.
Microbiological Growth: Is Algae in My Water System?
The final major problem classification is microbiological fouling, or the living portion of airborne contaminants. Common soil bacteria and algal spores are omnipresent and can be brought into the cooling system by the air moving through the tower. With adequate sunlight and proper food supply they can multiply and form an insulating layer on heat transfer surfaces, restrict water flow, reduce tower cooling efficiency and increase the rate of corrosion. Microbiological fouling is most common in the cooling tower environment. High temperatures in boiler applications eliminate most bacteria entrained in condensate return and feedwater systems. The closed nature of most loops prevents the inoculation of microorganisms into the water. Legionella also resides in the microbiological family.
To learn more about Legionella and how we can help you control it, visit our page here.