SOLVING
Cooling Tower Water Problems
Cooling towers do just one job: they cool the
heated water that goes through the chiller to remove the heat from the refrigerant that is
cooling the building.
- 60% of the problem is scaling
- 20% of the problem is bacteria
- 10% of the problem is corrosion
- 10% of the problem is filtration
A CHEMICAL-FREE solution to these problems
is achieved by using a combination of deploying electronically generated copper alloy ions
into the water, oxidation and polarization of the minerals in the water, and a filtration
system specifically designed to remove the biological residues and dissolved solids from
the water.
SOLUTIONS.
The incoming water condition and amount of evaporation are defining factors in the amount
of particulate concentration which occurs in cooling towers. A reading of 30ppm (parts per
million) of chlorides is common in many commercial areas, and that reading will rise and
fall as the environment changes so readings are taken continuously to determine the ppm
level and to control the ion levels required to maintain a system free of algae, bacteria,
virus, corrosion and scale.
When treating a cooling tower. we must treat the entire water circulation system, i.e.,
the water inlet to the tower, the pump, piping and fittings, and the chiller condenser.
In water treatment terminology, one often encounters the term "cycles of
concentration". This refers to the number of times the dissolved solids in the
circulating water have increased as a result of evaporation. For example, if the make-up
water has 100 parts per million (ppm) of Total Dissolved Solids (TDS), and the condenser
water contains 300ppm, 3 cycles of concentration has been reached.
As each cycle of concentration takes place, a large amount of water is lost because
cooling towers utilize an open-air evaporation process to cool the water. After an average
of 3 to 6 cycles, depending upon the hardness factor of the incoming water, a lot of water
has been lost due to evaporation, leaving the minerals and bacteria in the remaining
water. Currently, your system responds when a conductivity sensor, which monitors the
electrical state of the water, sends a signal to a bleed off valve to purge a specific
amount of water, known as the "blowdown". At the same time the system refills
itself with fresh water, known as make-up water. This purging process and make-up water
induction reduces the TDS so scaling can be controlled and does not clog up the tube
bundle in the condenser or the tower itself.
It is also important to note that scale control chemicals are automatically injected
into the water to help control scaling. After installation of the Ion Generation System,
which kills the algae, bacteria, viruses and eliminates the scaling, the existing chemical
injection system and blowdown process just described will both be totally eliminated,
creating an annual savings in both water and chemical treatment, and will eliminate the
cost of brushing the tube bundles and acid treating the tower, condenser, and piping each
year.
During the initial ionization and oxidation period, the particulate levels in the water
will buildup at a fast rate due to the removal of existing scale and biofim throughout the
system and equipment. The only effect of this buildup will be to activate the automatic
backwash cycle more frequently. After a few short weeks, the frequency will normalize and
the system will remain clear of algae, bacteria, viruses and scale.
Filtration, Conductivity, pH Control and Backwash
FILTRATION in heat transfer/cooling systems is needed for
three reasons:
1. The removal of any airborne particulates which
are caught by the system, for example, dust, dirt, etc., being caught by the cooling tower
and then re-circulated throughout the system. Such dust, dirt, etc., could readily plug
heat exchanger tubes and flow channels.
2. The removal of existing scale in a system as the
oxidation and polarization of the water softens and renders the existing hard scale on
heat transfer surfaces clean.
3. The prevention of scale buildup on heat transfer
surfaces, when a system is clean so that the normal precipitation and nucleation of solids
which occurs from solution can be removed.
The make-up water that replaces water lost in the backwash process contains minerals
and sometimes chemicals, bacteria and viruses that add to the problem, which is then held
in solution and removed by the specially designed filtration system in order to maintain
the system free of scale and biofilm.
CONDUCTIVITY in heat transfer/cooling systems must be
carefully controlled.
When the water conductivity reaches a set-point level, the system's electronic control
system sends a signal to the ion generation electrode adjusting its ion output to increase
the level of oxidation being induced into the water stream. The conductivity measurement
is based on the level of TDS in the water which varies the electrical conductivity of the
water and is used as the control parameter for the level of oxidation needed to clear the
water. In a typical cooling tower application the control of conductivity ranging from
between 1,000 to 1,200 microhms/cm will usually produce 3 to 4 cycles of concentration and
control the cooling tower water adequately.
pH CONTROL is important in minimizing the rate of
corrosion in a heat transfer/cooling system.
The measure of the concentration of hydrogen ions present in a solution is critical. A
pH= 7 reading means the solution is essentially neutral. To avoid corrosion problems,
controlling the pH in an alkaline range of between 8 and 9 is important, however, when the
pH is alkaline, there is a greater tendency towards scaling from dissolved solids. The ION
Generation System also handles that problem in that it can effectively operate in higher
pH while still inhibiting scale deposits.
The Ion Generation System electronically monitors both the pH and conductivity levels
within their control range providing continuous cleansing of the water resulting in a
scale-free operation. Scale acts as a host substance upon and inside which algae and
bacteria can grow and hide. Elimination of the scale removes the host substance and
eliminates the possibility that biologicals in the water will cling to any surface on
contact. The copper IONs generated by the System will kill the bacteria and algae and keep
the residue in solution until it is trapped and removed by the filtration system.
CORROSION
The presence and growth of micro-organisms in heat transfer/cooling systems
cause plugged water passages and severe deterioration of metal surfaces by under-deposit
corrosion. Iron deposition and corrosion is caused by the metabolism of "iron
bacteria", which can remove water soluble ferrous salts and deposit them as insoluble
ferric oxides. These oxides tend to grow rapidly and can reach sizes large enough to
restrict water flow. The ION Generation System kills the micro-organisms.
Another group of bacteria produce acids and waste which attack metal surfaces directly.
These organisms can convert water-soluble sulfur compounds into hydrogen sulfide. One of
the most common sulfate–reducing bacteria is desulfovibria. This bacterium uses
organic nutrients from the decomposition of other bacteria or algae as food. This process
often takes place under existing biofilm or scale deposits. The corrosive action of
desulfovibrio can produce condenser tube penetration in as little as six weeks.
A third group of corrosive bacteria common to cooling towers are know as nitrifying
bacteria. The bacteria react with dissolved ammonia to produce nitric acid. This acid
lowers pH and causes localized attack on both copper and steel. Lastly, algae, a major
source of trouble in cooling tower water systems, adheres to metal surfaces and
accelerates pitting by the release of oxygen during the metabolic process. Large algae
growths also impede the effectiveness of biocidal treatments by absorbing them.
Again, the ION GENERATION SYSTEM is the chemical free SOLUTION
to Cooling Tower Water Problems.
