19
Tower Cleaning, Water Treatment and Blowdown
Maintaining Water Quality:
The steel used in AV Series towers has been galvanized with a heavy zinc
coating averaging 2.0 mils in thickness. AV Series towers are also available
in stainless steel, which is even more corrosion resistant than galvanized
steel in certain environments. Other materials used (PVC fill, drift eliminators,
and louvers, aluminum fans, etc.) are selected to offer maximum service
life in a “normal” cooling tower environment, defined as follows:
Circulating water with a pH between 6.5 and 8; a chloride content (as NaCl)
below 500 ppm; a sulfate content (SO4) below 250 ppm; total alkalinity
(as CaCO
3
) below 500 ppm; calcium hardness (as CaCO
3
) above 50 ppm;
a maximum inlet water temperature not to exceed 125°F (51.7°C); no
significant contamination with unusual chemicals or foreign substances;
and adequate water treatment to minimize scaling.
• Startup Conditions: The water conditions during the initial tower opera-
tion are crucial in preventing premature corrosion of galvanized steel
(white rust). For at least the first eight weeks of operation, pH should
be controlled between 6.5 and 8.0 with hardness and alkalinity levels
between 100 and 300 ppm (expressed as CaCO
3
).
• Chlorine (if used) shall be added intermittently, with a free residual not
to exceed 1 ppm—maintained for short periods. Excessive chlorine
levels may deteriorate sealants and other materials of construction.
• An atmosphere surrounding the tower no worse than “moderate indus-
trial”, where rainfall and fog are no more than slightly acid, and they do
not contain significant chlorides or hydrogen sulfide (H
2
S).
• Many proprietary chemicals exist for control of scale, corrosion, and
biological growth and should be used prudently. Also, combinations
of chemicals may cause reactions which reduce treatment effective-
ness, and certain chemicals such as surfactants, biodispersants and
antifoams may increase drift rate.
Unless you purchased a stainless steel AV Series the structure of
your AV Series consists primarily of galvanized steel, therefore your
water treatment program must be compatible with zinc. In working
with your water treatment supplier, it is important that you recognize
the potential effects on zinc of the specific treatment program you
choose.
Warning
Operation
Summary of Contents for MARLEY AV 98-1514E
Page 1: ... Marley AV CoolingTower User Manual 98 1514E ...
Page 31: ......
