20
Water Treatment and Blowdown
Maintaining Water Quality:
The steel used in MH Fluid Cooler's has been galvanized with a heavy
zinc coating averaging 2.0 mils in thickness. Other materials used (PVC
fill, drift eliminators, and louvers, aluminum fans, cast iron Geareducer,
etc.) are selected to offer maximum service life in a “normal” fluid cooler
environment, defined as follows:
Recirculating 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 al-
kalinity (as CaCO
3
) below 500 ppm; calcium hardness (as CaCO
3
) above
50 ppm; no significant contamination with unusual chemicals or foreign
substances; and adequate water treatment to minimize scaling.
• Startup Conditions: The water conditions during initial fluid cooler op-
eration 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.
The structure and coil of your fluid cooler 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.
Note
Operation
