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18
Water Treatment and Blowdown
Maintaining Water Quality:
ThesteelusedinMCFluidCooler'shasbeengalvanizedwithaheavy
zinccoatingaveraging2.0milsinthickness.Othermaterialsused(PVC
drift eliminators, bearing, belts) 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signicantcontaminationwithunusualchemicalsorforeign
substances; and adequate water treatment to minimize scaling.
• StartupConditions:Thewaterconditionsduringinitialuid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 (H2S).
• 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.
Operation
Note