EcoWater CHC Series Service And Troubleshooting Manual page 98

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Chloride (Cl ): Like Sodium (Na), most chloride salts are very soluble in water. They can cause
corrosion at high levels. Chloride is used to calculated cycles of concentration because it is stable in
cooling water systems.
Total Dissolved Solid (TDS): TDS is the total concentration of dissolved components, such as salts
and sugar. Salts, like NaCl, dissociate into ions; while some organic matters, like sugar, do not break
up into ions when dissolved in water. There are different approaches to determine TDS, but it is
commonly estimated from conductivity.
Conductivity: Conductivity is defined as the ability of an aqueous solution to carry an electric current
and can be easily measured by a conductivity meter. It is used to estimate Total Dissolved Solids
(TDS).
Cooling water problems
Scale - Minerals such as calcium and magnesium are relatively insoluble in water and can form scale
deposits when exposed to conditions commonly found in cooling water systems. A layer of scale as
thin as 1/64 inch can reduce heat exchanger efficiency by 15%. Scale formation can be controlled by
scale inhibitors such as threshold inhibition chemicals and scale conditioners. Chemical treatments
include acids, polymers and polyphosphates which prevent scale formation by keeping the scale-
forming minerals in solution to prevent deposits from forming.
Corrosion - Most metals used in cooling water systems are very susceptible to corrosion. Keeping
surfaces clean is the most important aspect of preventing corrosion, since under-deposit corrosion can
take place and result in serious damage. Corrosion can be uniformly distributed throughout the system
or it can be localized, causing severe pitting and rapid equipment failure. There are various corrosion
inhibitors used in chemical treatment.
Microbiological deposits - More cooling water treatment programs fail due to lack of microbiological
control than any of the other two problems mentioned above. Scale, corrosion, and fouling often are
symptoms of an unsuccessful program, but the root cause is inadequate microbiological control.
Makeup water and wind can carry microorganisms into a cooling water system. Uncontrolled
microbiological fouling can lead to problems at every point in the cooling water system. Corrosion
occurs under the bacterial slime layer. Inorganic foulants are trapped in this slime layer, compounding
the problem. Microbiological chemicals often used include chlorine, chlorine alternatives, and
appropriate biocides
Rarely do corrosion, scale and fouling occur independently of one another. Usually two or all three
develop together to cause loss of heat transfer and premature metal loss. For example, microbial
fouling can cause scaling and corrosion to occur; corrosion can contribute to iron fouling and
encourage more corrosion to occur. To break this cycle, proper problem identification is important for
selecting and applying a practical, economical solution to any deposit problem.
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