Cooling Towers

Maintaining Water Quality
Air quality at any particular site can be the cause of serious adverse effects on both cooling tower longevity and its ability to function thermally, complicated by an undesirable and unpredictable change in water quality. Cooling towers are extremely effective air washers and the technological advances which are intended to improve their thermal performance also serve to increase their air washing efficiency. Consequently the quality of the water being circulated over a tower quickly reflects the quality of the air with which it is in intimate contact. The air exits a cooling tower much cleaner than it enters. This constant washing of the incoming air plus the base characteristics of the make-up water supply are the parameters which establish the ultimate quality of the continuously re-circulated water stream complicated by the fact that the process of evaporation has the ability to cause incoming contaminant levels to concentrate tremendously. ln order to establish a basis for the utilization of standard construction materials the following "normal" water conditions have become arbitrarily defined:

• A circulating water with a pH between 6 and 8; a chloride content (as NaCl) below 750 ppm; a sulphate content (SO4) below 1200 ppm; a sodium bicarbonate (NaHCO3) content below 200 ppm; a maximum temperature of 120 F; no significant contamination with unusual chemicals or foreign substances: and adequate water treatment to minimize corrosion and scaling.
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• Chlorine, if used, added intermittently with a free residual not to exceed 1 ppm maintained for short periods. An atmosphere surrounding the tower no worse than moderate Industrial where rainfall and fog are only slightly acid and do not contain significant chlorides or hydrogen sulfide (H2S).
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Water conditions falling outside these limits would warrant an investigation of the combined effect of all the constituents on each component material. In many cases it will be found that very few components require a change in materials. Wood and plastic components for example are very tolerant of chemical excursions far beyond these limits. Conversely carbon steel items are relatively unforgiving of all but the most limited variations.

 
Some of the most glaring effects of EcoBeam XL are: