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.
-
-
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).
-
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: |