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Level Indicators for a Cooling Tower

Cooling towers essentially lower water temperature by extracting heat from water flow through evaporation then expelling the heat into the atmosphere. Commercial air conditioning systems, manufacturing industries and power plants all utilize cooling towers. Certain substances can harm cooling towers, so their levels must be regulated. Level indicators monitor permissible and safe limits.

Copper/Zinc
- Copper and zinc are two common materials used in the construction of cooling towers. These materials enter the water of a tower as the result of corrosion. An example of a level indicator for copper is a concentration greater than 0.25 mg/l (milligrams per liter), according to industrial guidelines issued by the City and County of Honolulu, Hawaii. Although these guidelines are not enforceable and do not trigger any punitive action if exceeded, complying with them is part of Best Management Practices (BMPs). The level indicator for zinc is 0.5 mg/l. Rising levels of zinc or copper could indicate increased corrosion, corrected by either implementing corrosion protection or less reliance on these materials in the manufacturing process.
pH
- The pH scale measures whether a substance is an acid, base or neutral. The numbers run from 0 to 14, with 7 being neutral. A reading below 7 is an acid, and the lower the number, the more acidic the substance. Any measurement above 7 is a base. The level indicator for the pH level of water in a cooling tower is less than 7.
Water Velocity
- Another level indicator is the velocity of the water in the cooling tower pipes. Inadequate movement leads to copper erosion. The proper speed depends upon the water temperature. At 90 degrees Fahrenheit or below, the velocity needs to be greater than 8 feet per second. With the water temperature raised to 120 degrees, the velocity must exceed 5 feet per second. If the temperature of the water in the pipes reaches 150 degrees, then a velocity of greater than 3 feet per second is sufficient.
Legionnaires' Disease
- Legionnaires' Disease Bacteria (LDB) is a problem associated with cooling towers. The ideal temperature indicator for the bacteria to thrive is between 68 and 122 degrees Fahrenheit, according to the Occupational Safety &Health Administration. OSHA sets the level indicator for LDB at less than 10 CFU, or colony-forming unit, per milliliter. Cooling towers are a source of Legionnaires' Disease, and water sample testing is essential to monitor the growth of the bacteria.

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