COOLING WATER TREATMENT

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COOLING WATER TREATMENT
ABSTRACT Traditionally, chemical water treatment
has involved adding corrosion inhibitor and then
periodically testing for the residual. However
to be effective, these programs must also include
the control of scale and biological growth.
Controlling the 3 sides of the cooling water
triangle will drastically increase the
effectiveness of your water treatment program.
Failure to control any one component of the
triangle will lead to probable failure of your
water treatment program and repair or replacement
of your valuable capital equipment.
scale
corrosion
biological
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AVERAGE UTILITY BUDGET
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THE COST OF FAILURE
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TERMINOLOGY

• Conductivity- the measurement of how much
  electrical current water is carrying. Used to
  measure Cycles of Concentration (CoC)
• Cycles of Concentration- The number of times
  minerals have been concentrated in a system due
  to evaporation
• pH- measurement of free hydrogen in the water.
  Represents how acid or alkaline the water is.
• Blowdown- the removal of water from a cooling
  tower system to reduce or limit the Cycles of
  Concentration
• Corrosion Coupon Rack- piping assembly that is a
  slip stream from the main system used to hold
  corrosion coupons. Flow through the coupon rack
  should be regulated to 3-5 g.p.m.
• Pot Feeder- feeder used to introduce chemical
  into a closed system.
• Chemical Residual- the amount of chemical
  measured in a particular system
• White Rust- the formation of zinc hydroxide
  deposits in a galvanized cooling tower. Caused
  by inadequate cooling tower passivation at start
  up.
• Evaporation Credits- a program by-which a city
  will give you a credit on your water bill for the
  water evaporated from your cooling system.

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pH
pH can tell us whether the water has corrosive or
scaling tendencies. High pH tells us that the
water is more likely to cause scale or mineral
deposits. Low pH tells us that the water is more
likely to cause corrosion
8.5
9.3
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8.7
9.1

• CORROSION

SCALE
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CONDUCTIVITY

• Conductivity gives us an approximate idea of what
  the mineral content of the water is
• based on the water source used to supply the
  cooling tower. High conductivity is critical
• and can cause rapid scaling and mineral
  deposition on heat exchange surfaces (cooling
• tower fill and condenser tubes).
• In The Valley your cooling tower conductivity
  should run between 2500-3500 umhos.
• Conductivity above 3500 umhos an cause scaling
• Conductivity below 2500 indicates
  water/chemical waste

500
1700
1750
2100
3000
1900
SCALE
SCALE
Yellow caution
Red critical
Green good
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ASPECTS OF WATER TREATMET
Looking at a water treatment program for a
condenser water system it is easy to focus on the
traditional areas, such as

• Corrosion control
• Microbial control
• Deposition/scale control

While these are important, they do not take into
account the broader scope of what needs to be
done to ensure the maximum lifespan of these
systems. In designing a system consideration
needs to be given to each of the following
aspects SEE NEXT PAGE
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ASPECTS OF WATER TREATMENT-cont.

• Is it a new or existing system?
• If it is existing, are there corrosion products
  in it?
• Is there a risk of organic contamination?
• What level of monitoring can be expected (plant
  or supplier personnel)?
• How extensive is the fluid distribution piping?
• What are the typical blowdown rates?
• What is the metallurgy of the cooling tower?
• Does the system run constantly or intermittently?
• Are the tubes enhanced?

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ASPECTS OF WATER TREATMENT-cont.
The objective of a treatment program is to
minimize damage and allow the system to operate
as efficiently as possible. This means that

• The corrosion inhibitors need to be able to get
  to the metal surfaces
• Deposits are not present that can interfere with
  fluid circulation
• Microbes are not present that can compromise the
  corrosion protection

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CORROSION INHIBITORS
NOT ALL CHEMICALS ARE THE SAME!! In The Valley,
organic corrosion Inhibitors using polymers and
phosphonates are the most effective program

• Phosphates are used-good corrosion protection,
  can form mineral deposits in South Texas water.
• Zinc can be used, is not environmentally friendly
  and can CAUSE corrosion at pH over 8.5
• Molybdate is often used but is VERY expensive at
  useful levels
• New technology-organic base, safer to handle,
  lower liability, potentially improved performance.

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BIOCIDES
Approximately 70 of the cooling water chemical
programs that fail do so as a result of poor
biological control. The key to effective
biological control is applying the proper amount
of chemical with the proper frequency. A
vigorous biocide program will utilize
2-alternating products.

• Water with pH gt 8.0, chlorine is not acceptable
• Quaternary biocides neutralize most corrosion
  inhibitors
• Sulfur based biocides do not perform well in
  alkaline water
• Swimming pool floaties do not count as biocide

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SYSTEM MONITORING
Considering the liabilities of improperly
treating any system, monitoring is one of the
simplest ways of ensuring that performance
criteria are being met. The low cost combined
with the confirmation of due diligence makes
monitoring virtually mandatory.

• Corrosion coupons (mild steel lt 2.0/copper lt 0.2)
• Real time corrosion monitoring
• Mineral balance
• Regular evaluation of system water conditions
• DAILY testing and log sheets
• Electronic reporting from your controller

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CONTROL EQUIPMENT

• Water treatment control equipment has evolved
  significantly over the past 10 years.
  Controllers can do everything from notifying
  designated people of a problem, to emailing
  service reports and other information daily,
  weekly, or monthly.
• At a minimum, your cooling tower controller
  should control blowdown, chemical feed, 2
  biocides, and have an integrated flow switch.

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FILTRATION
The use of any means of filtration can help any
condenser water system. Filtration is
particularly important if your chiller has
enhanced tubes on either the condenser or the
evaporator side

• Filtration maintains low water turbidity allowing
  more economical and effective chemical treatment
• Filtration removes organic matter that can feed
  biological life in the cooling water
• Filtration removes environmental debris that can
  be a breading ground for Legionella Pnumophelia .

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CLEANING
Chemical water treatment is only an adjunct to
proper maintenance of a cooling water program.
C.T.I. (Cooling Tower Institute) recommends that
cooling towers be cleaned twice a year. Annual
inspection and brushing of condenser tubes is
also an important part of a good PM program.
Enhanced tube heat exchangers are especially
vulnerable to corrosion from even small amounts
of sludge, oxidation, or environmental debris.
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WATER TREATMENTS MYTHS

• Only theBig Companies can offer the latest
  technology-FALSE
• All chemicals are the same-FALSE
• If you have soft water you do not need chemical
  treatment-FALSE
• If the tubes are clean, the chemicals are
  working-FALSE, FALSE, FALSE,
• All chemicals are hazardous-FALSE
• Magnets-FALSE
• Panther Unit-FALSE
• Ozone-FALSE
• If it scales up we will clean it for free FALSE
  AND DECEPTIVE
• Concentrated products that are mixed on
  site-FALSE
• A little white rust can not be prevented-FALSE

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NOTES
For additional information contact Graham
Helburn, cell-512-694-6284, email-
ghelburn_at_aqualogicwc.com, Office-877-271-3625
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NOT ACCEPTABLE
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HAZARDOUS
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EXPECTATIONS
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EXPECTATIONS