Cooling towers
COOLING TOWERS
Introduction
A cooling tower is a device used to
reduce the temperature of water. The
water is then recycled back into the many
processes and industries that use it.
Some industries use the water to control
the temperature (sensible heat), of a
process, like a car radiator. The HVAC
industry uses the water to condense the
refrigerant (latent heat).
In the past most of the processes requiring cooling use piped town water
through the equipment, cooling the equipment, and then drained the water to
the gutter (100% waste).
Because Australia is such a dry continent the water supply authorities
introduced the Water Conservation Act, which forced all the industries to install
cooling towers to recycle the water.
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Cooling towers
Terminology
Approach, is the difference between the temperature of the
water leaving the tower and the Wet Bulb temperature of the
air entering the tower.
Generally between 4 – 6K.
The smaller the approach the more efficient is the tower
Range, is the difference between the temperature of the
water entering and the water leaving the tower.
Generally between 8 – 10K.
Drift, is the evaporated water carried out of the tower with
the air. The amount of drift must be controlled because the
microorganisms can live in the drift and travel to and infect
humans. (Legionaries Disease)
Drift Eliminators, are to catch and condense the tower water as it is discharged as drift, causing it to fall
back into the tower basin as droplets.
Bleed Off, is the amount of tower water that is purposely drained away to waste in order to dilute the
circulating water with fresh town water.
This is needed as only the H2O evaporates leaving behind all the minerals that get into the tower water.
The H2O is constantly evaporating to reduce the temperature of the remaining water.
Fill, is the component of the tower that causes the circulating water to spread out over a large surface
area, which will increase the evaporation rate by offering the water to a greater volume of air.
Water Distribution System, is designed to evenly spray the circulating water over the Fill.
Make Up Water, is the fresh town water that is constantly being fed into the tower basin via a Ball Valve,
to replace the water that is lost to;
Drift (Evaporation)
Bleed Off
Louvers, are there to reduce sunlight on the water inside but allow air to be directed onto the fill. They
also retain the splash from the droplets falling from the fill.
Plume. Under certain atmospheric conditions the drift leaving the tower with condense as it hits the
surrounding air. It looks like fog but because it originates from a process it is referred to as Plume.
Dissolved Solids. The particles of dirt and minerals that circulate with the water rather than sink to the
bottom as mud.
Side Filtration. Some of the circulating water is pumped through a filter to remove the dissolved solids.
Inhibitor. Is a chemical added to the circulating water to prevent the dissolved solids in the water causing
rust and clogging the system’s tubing.
Microbial Growth. Or ‘bio-fouling’ is the Algae, Fungi and Bacteria that find the cooling tower environment
ideal for their growth.
Biocide. A chorine base chemical added to the circulating water to prevent microbial growth.
Ultra violet light. Is another method of killing bacteria where the circulating water is passed through clear
tubes that are exposed to ultra violet lights. The water must be kept very clean with filters for this method
to work (side filtration).
Ozone injection. Another means of killing bacteria.
Monitoring. Of the circulating water is needed to ensure the chemical additives are at the required
concentration.
Legionnaire’s Disease. Is caused by the bacteria Legionella Pneumophilia Bacillus, which grows in
the cooling tower water and infects humans as they breathe in the aerosols from the tower discharge.
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Cooling towers
Construction
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Cooling towers
Operation
The Basic Principle of Operation.
Evaporating some of the circulating water, cools the majority of the water in a
cooling tower.
How it Works
The evaporation process only takes place on the surface of a liquid and needs
latent heat of vaporization to happen (2256 kJ/kg). Sensible heat (4.19 kJ/kgK),
is drawn from the body of the water to the surface to supply the energy needed
for the latent heat. It can be seen that for a little evaporation a lot of sensible
heat will be needed therefore the main body of the circulating water is cooled
for very little lost of water.
Warm to hot water from the cooling process is
pumped to the top of the cooling tower and into
the sprays where the water is broken up into
droplets and distributed over the Fill.
The water droplet spreads out as it slides down
A cooling tower takes
the heat transfer law
‘the greater the
exposed surface area,
the greater will be the
rate of heat transfer
the Fill creating the surface area necessary for
evaporation.
The evaporation rate of the water is restricted by the amount of moisture
already in the air around it. To maintain evaporation the moistened air must be
replaced with dry air, usually by fans blowing air through the tower, (see types
of towers).
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Cooling towers
Types of Towers
Two basic types;
Natural Draft
Mechanical Draft
Natural Draft Towers, rely on
the heat of the water to generate
the air movement inside the
tower.
They are only used for very large
capacity
systems
such
as
Electricity Generation Plants,
where they are called Hyperbolic
Towers.
Cooling towers are not part of the refrigeration system, as no refrigerant flows
through them.
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Cooling towers
Mechanical Draft, are fitted with fans to improve the airflow through the tower
which increases the evaporation rate of the water which increases the capacity
of the tower. Mechanical Draft Towers are used just about everywhere
including the HVAC industry.
Generally a centrifugal fan is used to force the air into a tower, and tube axial
(propeller) fans are used to induce the air out the tower.
Mechanical towers are classified by the way the air flows through the water.
(remember, the water always falls).

Induced draft cross flow

Induced draft counter flow

Forced draft cross flow

Forced draft counter flow
Forced draft cross flow
Induced draft counter flow
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Cooling towers
Evaporative Condensers.
An evaporative condenser (EC), is
considered
to
be
part
of
the
refrigeration system as it directly
condensers the refrigerant.
An EC doesn’t have fill it uses the
refrigerant piping to break up the
water drop as they spread around
the piping absorbing Latent Heat
directly from the refrigerant.
Evaporative Condenser
and Chillers Circuit
.
Capacity control for evaporative
condensers is limited to varying the
volume of air flowing in to the fan.
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Cooling towers
Water Circuits
Open Water Circuit.
These systems have the water that is doing the condensing or cooling being
passed through the air to reject the heat, e.g. a cooling tower is an Open Water
Circuit system.
Closed Water Circuits, (like a car
radiator)
The condensing water in this situation is
contained within a closed loop circuit (i.e.
the water being circulated between the
evaporative cooler and the shell and tube
condenser never comes in contact with
the outside atmosphere). The water is
pumped
through
evaporative
a
device
condenser
like
although
water in the tubes
only gives
sensible
the
heat
from
an
the
up
circulating
water. The cooled circulating water is
then fed to the remote water-cooled
condensers, (generally the shell and tube
type). This arrangement is common in
situations where a large number of
individual condensing units are used (e.g.
supermarkets).
Closed water circuits operate with a
high Td because the heat energy is
passed from the refrigerant to the closed
circuit water (in the shell and tube
condenser) and then from the closed
circuit
water
to
the
water
in
the
evaporative cooler, then to the air.
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Cooling towers
CAPACITY CONTROL
In order to maintain the required condensing
or process temperature against the changing
ambient WB temperature and varying load,
cooling towers need some form of capacity
control. The capacity of the tower depends
on the wet bulb temperature of the air
entering the cooling tower.
1. The simplest form of control is Fan
Cycling. It is inexpensive, but the fan should
not be cycled too often as it can lead to
motor burnout.
This system is used on
single and multi fan units, and units that do
not require critical temperature control.
The lower the WB temperature the greater the capacity
2. The next step is to have multi speed fan motors with cycling control combinations.
This method offers reduced operational costs and broader capacity control. Useful on
single fan towers. Both of the methods described above are used on tube axial fan
units.
Centrifugal fans normally use the following.
3. Modulating dampers are placed in the inlet of the centrifugal fan housing.
As the water temperature reduces the dampers are moved towards a closed
position.
If they close fully the modulating motor will trip a limit switch isolating
the fan motor. This method offers the best regulation if the fan type capacity control
is used.
4. If the ambient remains above freezing
a modulating valve can be used to recirculate the water back to the
condenser bypassing the cooling tower.
This method of capacity control is also
used when multiple condensers are
connected to the one cooling tower.
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Cooling towers
CALCULATING THE CAPACITY
Three factors need to be known:
The mass flow rate of the water flowing through the tower (kg/sec)
The specify heat capacity of the water (kJ/kg.K)
The change in temperature of the water (RANGE of the Tower).
Where:
Q =
M
=
c
=
Δť
=
THUS:
Quantity of energy in kJ/sec ( or kW)
Mass Flow Rate kg/sec (or L/s)
Specific heat in kJ/kg.K
(c of water = 4.19 kJ/kg.K)
Change in Temperature (K)
Q = M c Δť
EXAMPLE 1
A Cooling Tower has 6.7 litres (6.7kg/sec), of water passing
through it per second. The water is entering the tower at 34o
C and leaving the tower at 28 o C. Calculate the capacity.
6.7kg/sx4.19kJ/kg Kx6K
6. 7x 4. 19x 6
168.438 kJ/s or (kW)
APPROACH
The APPROACH is the difference of the WATER LEAVING the tower and the WB
TEMPERATURE of the AIR ENTERING the tower.
With a WB temp of 22 'C,
Approach = Water temp leaving - WB temp of air entering = 28°C-22°C = 6K
RANGE
The RANGE is the difference between the temperature of the WATER ENTERING
the tower and the WATER LEAVING the tower.
Range = 34°C - 28°C = 6 K
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Cooling towers
Water used over the operational time of the tower
Water will be lost because of the evaporation of water and a percentage of water will
be bled off to reduce TDS.
Evaporation requires Latent Heat, LH = 2256 kJ/kg this is a constant.
Our example system has a capacity to remove 168.438 kJ/s of heat so if we divide the
capacity by the latent heat the answer will be the amount of water evaporated to carry
away the heat from the system.
Water = Q LH
168.438kJ/sec 2256 kJ/kg = 0.075kg/sec.
The amount of water bled off to waste is proportional to the amount of water evaporated,
which is proportional to the Range of the tower and the flow rate.
Therefore our example system has a towers range of 6K,
which equals 0.41% bleed off.
Convert % to decimal (0.41 / 100) that equates to 0.0041
Bleed off rate = Flow rate (kg /sec) x % of bleed off (as a
decimal).
6.7kg/sec x 0.0041 = 0.0275kg/sec.
Cooling Range K % of Bleed Off.
3.5
0.15
4.0
0.22
5.5
0.33
6.0
0.41
8.5
0.55
11.0
0.75
15.0
1.00
If our example tower operates for 12 hours (12 x 3600 sees)
each day then the volume of water used will be;
Operation time (in seconds) x Evaporation Rate + Bleed off rate (kg/sec)
Water used =12 hours x 3600 secs x (0.075 kg/sec + 0.0275kg/sec = 4426.7 litres
OTHER FACTORS (affecting the Tower Capacity)
The amount of surface area the water evaporates off and length of exposure
time;
The velocity of the air passing through the cooling tower (too fast results in
excessive 'drift');
The direction of airflow in relation to the water flow.
The lowest temperature to which the water can be cooled is the W.B.
temperature of the air entering, in which the water vapour in the leaving air will
be saturated, (any heat removed will cause the water to change back to a
liquid).
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Cooling towers
Review questions.
1. What type of heat is removed by the cooling tower water for the purpose of the
HVAC industry?
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2. Why did Australia introduce cooling towers?
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3. What is Bleed Off?
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4. Why can Dissolved Solids become a problem?
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5. List the two types of Biocides?
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6. How do humans catch Legionnaires Disease?
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7. How is cooling of the water achieved in a cooling tower?
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8. Why is the greater surface area heat transfer law applied to cooling towers?
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9. What will restrict the amount of heat transfer within a cooling tower?
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10. List the two basic types of cooling towers?
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11. Where are hyperbolic towers used?
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Cooling towers
12. List the four types of fan draft towers?
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13. What two types of fans are used on cooling towers?
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14. Is an evaporative condenser part of the refrigeration system?
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15. Do evaporative condensers have fill?
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16. List the two types of water circuits?
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17. What is the difference between them?
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18. Why is capacity control necessary on cooling towers?
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19. List the types of capacity control devices used on cooling towers?
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20. Explain why a modulating valve is needed on multiple condenser systems?
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Cooling towers
Legionnaires’ Disease
Legionnaires Disease is a form of pneumonia that can be fatal. It is caused by the
common bacteria Legionella Pneumophila Bacillus.
It is possible for anyone to catch the disease, provided the bacteria can get to the
deep parts of the lungs where the disease can grow, but certain groups within the
community are more prone to the illness that are others.
The groups most at risk generally include people with one or more of the following
characteristics:

Age over 50 years of age;

Are male;

Have a history of smoking;

Have a history of heavy alcohol intake;

Have a medical condition or are undergoing a treatment that impairs the body’s
natural defence mechanisms.
Legionella is found in moist environments such as Lakes, Rivers, Creeks, Mud and
other water sources at temperatures ranging from approximately 5oC to 55oC.
However no cases of Legionnaires’ Disease has been proven to have been caused by
Legionella present in the natural environment.
All of the Legionnaires Disease outbreaks have been attributed to man made
environments.
The optimum conditions for the multiplication of Legionella Bacteria has been shown
to be between 35oC and 37oC with an acid balance between pH 6.5 and pH 6.9.
COOLING TOWERS and, EVAPORATIVE CONDENSERS provide this environment.
The primary concern with the cooling tower is its ability to spread the Legionella over a
vast area due to the Drift (aerosols) carrying the bacteria from the tower. The aerosols
are small enough to get into the lungs.
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Cooling towers
Operational and Servicing Checks of Cooling Towers
Before working on any cooling towers you must be aware and familiar with the
following
Legislation
The NSW Public Health Act 1991, Part 4, and the Regulation 2000 covers cooling
towers and lays out the laws controlling the maintenance and cleaning of cooling
towers, in the Public Health Act, a cooling tower is referred to as a Regulated
System.
Other states may have their own statuary requirements.
Standards
AS/NZS3666 parts 1,2,3.
Part 1 covers installation of Air Handling and Water Systems.
Part 2, covers Operation and Maintenance.
Part 3, covers control of Legionella through constant monitoring of water quality.
In New South Wales the AS/NZS 3666 has been incorporated into the Public Health
Act, so anything in AS/NZS 3666 is enforceable by the act.
Hand Book 32 (HB32), explains the Australian Standard 3666 and helps to show
how some procedures are to be done. The New Zealand standard uses another
publication.
Code of Practice. By the NSW Health Department.
Explains what the Health Department wants done to control microbial growth.
On page 29 of the code of Practice it states that only competent persons be
employed to carry out work on regulated systems. To be classed as competent, a
person needs to have completed some form of recognized training. Therefore it is
recommended that any person that is required to work on a cooling tower complete a
Health Department approved course,
As part of the licensing agreement with the NSW
Department of Fair Trading, the refrigeration trade course
must contain an element of microbial control and the Public
Health Act part 4, and the Regulations
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Cooling towers
Class Exercise.
Aim. To be able to use AS/NZS 3666 parts 1, 2, 3, the Public Health Act and
Regulations.
Purpose. Because of the requirement of the Department of Fair Trading
licensing, and because the standards are incorporated into the NSW Public
Health Act you must be able to reference information from them.
Task. Use the Australian standards, Acts and Regulation to locate the answers
for the following questions. Record where you found the answers.
a. What is the purpose of the Public Health Act part 4 or any other state
equivalent Act.
……………………………………………………………………………………
……………………………………………………………………………………
……………………………………………………………………………………
b. In order to comply with AS/NZS 3666.2 what manuals must be with the
regulated system?
……………………………………………………………………………………
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c. What is the required interval between cooling tower cleans?
……………………………………………………………………………………
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d. Can a cooling tower that does not have a working disinfection process
installed be turned on?
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e. From the NSW PH.act Regulation 2000, list the two maintenance
precautions?
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Cooling towers
f. Use AS/NZS 3666.2 to list the personal protective equipment needed to
clean a cooling tower?
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g. According to AS/NZS 3666.2 what must be done to an evaporative cooler
every three months?
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h. How often should a water sample be taken? Refer to AS/NZS 3666.3
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i. How long should the results from water sample be kept?
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j. List the requirements for the location of air intakes according to AS/NZS
3666.1?
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Cooling towers
Safety
Personal Safety.
Clothing should conform to Australian Standards AS/NZS 3666, part 2, which
incorporates other standards, AS 1715 and AS 1716.
AS 1715 specification of respirators and AS 1716, the wearing of the respirators
and masks.
The gloves and waterproof coveralls are used to protect your skin from the biocides in
the circulating water.
Only used to take
water sample
Full Face
Cartridge
Respirator
Wear gloves, waterproof shoes and water resistance coveralls and a half face
respirator with P2 grade twin filter
Public safety.
Always restrict public access when cleaning, and ensure that the cleaning spray is
contained within the operational area.
The safety and responsibilities can not be stressed
enough when microbial infection is involved
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Cooling Towers
Taking a Water Sample.
Safety.
If the sample has to be taken from an operational tower, then all the
appropriate safety clothing should be worn. Make sure the gloves are long
enough so that none of the circulating water will come into contact with the
skin.
Equipment.

A sterile 250ml re-sealable container, containing Sodium Thiosulphate to
neutalize the chlorine. Usually supplied by the analysing company.

A means of keeping the sample between 2 and 6oC, while transporting it
for analysing.

A means of recording sample location and time of sample taking.
Procedure.

Only open the container once it is in the water to be sampled.

Do not open it and leave it sitting, as other contamination can enter giving
false readings.

Take the sample from circulating water, not some place where the water is
still.

Place the container in an insulated transport vessel.

Do not leave in direct sunlight.

Record the sample taken for Authorities records.
Water Analysis.
Only use a National Analytical Test Authority (NATA) accredited laboratory to
analyze a sample. The laboratory must notify you if they find a sample that
has a high legionella count.
The results of the test must be recorded and stored safely for seven years.
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Cooling Towers
Water Sample Collection Practical.
Aim: To be able to collect a water sample from an operating
cooling tower in accordance with AS/NZS 3666 part 3, while
meeting the OH&S requirements.
Task.
1. Read AS/NZS 3666 part 3 section 2 ( risk assessment)
2. Read AS/NZS 3666 part 3 section 2 (technique for sample
collection).
3. Complete the risk assessment and hand it in to the teacher
for approval.
4. Complete the water sample collection while the teacher is
present.
Review.
Complete the worksheet on water sample collection from the
package or hand out.
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Cooling Towers
Decontamination
If a tower has a high Legionella reading confirmed by the analysing
laboratory, then the system will have to be shut down and decontaminated.
Recommended procedure;
1. Circulate a dispersant throughout the system.
2. Drain and refill.
3. Dose with Sodium hypochlorite to maintain a free chlorine residual of 25 to
50 mg/l at a pH of 7 to 7.6 for 30 minutes.
4. Drain and refill.
5. Dose with Sodium Hypochlorite to maintain a Chlorine residual of 5 mg/l at
a pH of 7 to 7.6 for 12 hours.
6. Drain the system and clean cooling tower wetted surfaces.
7. Dose with Sodium Hypochlorite to maintain a free Chlorine residual of
5mg/l at a pH of 7 to 7.6 for one hour.
8. Drain and refill.
9. Start full water treatment and put system back into service.
10. Wait at least 72 hours before taking another water sample.
Draining of the system should be to the sewer or in accordance with Local
Authority or other relevant authority. Some authorities require the water to be
pumped into a container for disposal.
Safety with Chemicals
The chemicals used to clean and disinfect a cooling tower are harmful and
extreme care must be observed when using them. There must be Material
Safety Data Sheets for all the chemicals where they are stored and used.
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Cooling Towers
Cleaning Cooling Towers & Evaporative Condensers
The most effective way of avoiding all the problems encountered with a
cooling tower is a regular and thorough manual washout every six months.
(see AS/NZS 3666 Part 2) The process is particularly important before a
tower is commissioned or restarted after a shutdown period of one week or
more. Wash out is compulsory under the Public Health Act, which carry heavy
fines if it is not done.
Before cleaning a tower the operator must check the service and
maintenance records to see if there has been any changes made to the
system or if anything needs to be done before shut down.
Also the tower should be inspected for any possible faults that may affect the
cleaning process.
During the cleaning process the public must be kept out of the operational
area, and the sprays must be confined to the operational area.
The tower must be fully dismantled and the interior and components scrubbed
with a high pressure water cleaner
Local councils have been given the job of monitoring the installation
maintenance and cleaning of cooling towers, as set out in the Public Health
Act 1991.
They are required by the Public Health Act 1991, to set up a register of all the
“regulated systems” (cooling towers),in their area and to routinely go and
check that the systems complies with the Act.
The council officer has the right under the Act to inspect any Regulated
System and view all associated maintenance records, when ever the council
thinks it is necessary.
The council will also require written notification of any changes that are made
to a Regulated System.
Any maintenance must be recorded (Public Health Act
1991), giving the details of the work and the record must
be signed by the person doing the work and the owner
or owner appointed representative.
Complied by Bruce Davison.
Local Councils have an
obligation to the public
to conduct inspections
and to police accurate
records of maintenance,
cleaning and microbial
control.
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Cooling Towers
Practical.
Cleaning a Cooling Tower
Aim: to learn the skills necessary to clean a cooling tower.
Task: Clean a cooling tower as required by AS/NZS3666 and the Public
Health Act.
Equipment:
a. Safety clothing as required by AS/NZS3666.
b. Cooling tower.
c. Operation manual.
d. Cleaning equipment.
Procedure:
a. Complete a Risk Assessment for the task.
b. Wear all required PPE.
c. Follow operation manual and shut down the tower.
d. Dismantle tower.
e. High pressure clean all internal components as instructed.
f. Reassemble tower.
g. Fill the tower with water to the required depth.
h. Follow the operations manual and start the tower.
i. Check operation.
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Cooling Towers
Maintenance
Expensive breakdowns, Legionella, inefficiencies and increased running costs
can mostly be attributed to poor maintenance.
Preventative maintenance should provide the owner/user with the following;

Early detection of problems that may lead to a breakdown.

Maintain the systems efficiency.

Determine that the system is complete and operating correctly.

Remove the need to do corrective repairs.

Maintain Bacteria to safe levels.
The maintenance management should contain the following;
Inspection reports, each individual system, regardless if they are side by
side and the same brand, need to have an inspection report developed for it.
Maintenance and Operating Manuals, need to be clear and comprehensive,
there should be no doubt as what needs to be done.
The object of the manuals is to apply AS 3666, to the system and to ensure
that the maximum performance and operating life are gained with effective
use of labour.
All manuals should have the following generic information;
1. Define the system that the manual applies to.
2. List the function and performance of the system.
3. Provide normal operating instructions.
4. Detail shut down and corrective procedures.
5. Provide details of any repairs, modifications or breakdowns.
Records and log book, of any work on the system must be kept on-site, and
copies should be given to the owner/user.
Water treatment information should include a Material Safety Data Sheet for
all chemicals stored on-site. There also should be an authorisation to use the
chemicals for the type of system on-site.
All maintenance and maintenance records are to be completed to the AS
3666 minimum standard. Failure to comply with these Standards can result in
Supreme Court action under the Public Health Act 1991.
It is imperative that service personnel, owners and users of cooling towers are
committed to ongoing preventative maintenance
Complied by Bruce Davison.
24
Cooling Towers
Operational Check List.
Cooling Tower Casing.
•
•
•
•
•
•
rattles and vibrations.
water and air leaks while in operation.
amount of drift discharge.
signs of rusting.
condition of louvres and screens.
paint or coating for damage.
Cooling Tower Internal Components.
• fill for alignment, seal, distortion, damage, slime, algae and
poor water coverage.
• sprays or decks for operation and uniformity of distribution
over the fill.
• drift eliminators for location, damage, seal, scale, algae, slime
or blockage.
• Ball float operation.
Fan.
•
•
•
•
•
noise, vibration and free running.
where fitted, the fan drive for adjustment and alignment.
guards and screens for rust and fixing.
motor full load amps.
condition of impeller, housing scroll, shaft, bearings and
supports.
Pump and Pipe work.
• leaks.
• corrosion.
• vibration.
• Drains are clear.
• pumps smooth running.
• pump's gland.
• motor amps.
Chemical Dosing System, (normally a separator contractor).
 Pumps operation.
 Chemical levels and types, safety data sheets.
 Bleed off rate.
Complied by Bruce Davison.
25
Cooling Towers
Sample of a maintenance report of a Water Cooling System.
Date of Service.
Type of service
Maintenance................
Water sample..............
Name of Owner or User...............................................................................................
Address of Premises....................................................................................................
Location of Tower.........................................................................................................
Tower: Site Number.......................................................................................................
Type..................................................................................................................
Make and Model...............................................................................................
Treatment Type..............................................................................................................
Brand and chemicals used.............................................................................................
Water Sample;
Total Plate Count....................................................................................
Legionella report required
yes.
no.
Report forwarded to Local Authority
yes
no
Physical Condition of tower..........................................................................................
Cleanliness of Tower....................................................................................................
Nature of any work preformed .....................................................................................
.......................................................................................................................................
.......................................................................................................................................
Date of next maintenance ............................................................................................
Nature of any repairs to be made during the next maintenance
.......................................
.......................................................................................................................................
.......................................................................................................................................
Signature of service person ………………………………………………………………..
Signature of Owner/user ..............................................................................................
To Be Completed by the Local Authority (if required
Report checked by ..................................................................................................
Signature .................................................................................................................
Date .........................................................................................................................
Any action to be taken:
No
Yes, .........................................................................................................................
..................................................................................................................................
Complied by Bruce Davison.
26
Cooling Towers
Shut Down.
This process should be followed if the tower is to be off line for a while.
•
Drain the system to prevent stagnant water, or circulate the
chemicals if the water is to be left in the system.
•
Repair any rust or damaged paint.
•
Clean the tower.
•
Co-ordinate a condenser clean for this time period.
Emergency Shut Off.
A procedures manual should be written for each individual C.T. and site, but
generally;
1. Notify the owner and users of the cooling tower.
2. Shut off condensers and all other equipment supplied by the
Cooling Tower.
3. Stop the fan.
4. Stop the pump.
Complied by Bruce Davison.
27
Cooling Towers
Review Questions
1. List four groupings of components that need to be checked during a
service?
2. List three items that need to be checked on the Dosing system?
3. List the four steps for an emergency shut down?
4. How long must the results from a water sample be kept?
5. What must be done to the sump water from a cooling tower during
cleaning?
6. Why are towers cleaned?
7. How often are they cleaned?
8. List the two pre-cautions that must be followed during a tower clean?
Complied by Bruce Davison.
28
Cooling Towers
9. Where does Legionnaires disease manifests? (C of P)
10. Why are cooling towers such a concern regarding Legionnaire
disease?
11. Beside Legionnaire disease what other things are harmful in cooling
towers?
12. What are the optimum conditions for the growth of Legionella?
13. What is the purpose of preventative maintenance?
14. Why are new cooling tower installations washed out before use?
15. What must be added to the circulating water after the clean?
Complied by Bruce Davison.
29
Cooling Towers
Assignment.
Aim.
To gain an understanding of the pipe work and components of an
operational cooling tower.
Task.
Draw a schematic diagram of the twin cooling towers installation at
TAFE NSW Sydney Institute.
Procedure.
 Locate and record all the components attached to the systems pipe
work.
 Draw a sketch of the pipe work and component placement.
 Convert your sketch to a schematic using the correct symbols or
labelling the component on the drawing.
 Hand in the drawing for marking.
Cooling tower Pipe work
Complied by Bruce Davison.
30
Cooling Towers
OH&S HAZARD IDENTIFICATION AND RISK ASSESSMENT OF WORKING PROCEDURES IN TAFE
Examples of Potential hazards may include but are not limited to:
Electrical

Contact with
live wires or
terminals causing
Shock
Flash to eyes
Burns
Falls

Discharge of
capacitor causing
Shock
Flash to eyes
Burns
Falls
Mechanical
Pressure

Caught by
operating
machinery

Struck by
moving machinery
or objects

Caught by
movement of
mechanical parts

Crushed by
objects moving or
falling

Entrapment

Excessive
vibration
Chemical
Injury from releases
of stored energy in
Refrigerants
Nitrogen
Oxy –
Acetylene.
Propane.
Ammonia.

Fire or
Explosion from
Build up of
flammable gases
Ignition of
existing flammable
products

Contaminants/
Toxins causing
Suffocation
Burns
Poisoning from
products
Gravity / Noise
Gas Welding

Falls from or
into vessels

Falls from
structures

Impact injuries
from falling
objects

Engulfment by
product
Sound levels
>85dBA causing
hearing damage
from
Operating
machinery

Using
equipment

Injury due to
- burns
-high temperature
- naked flames
- releases from
stored pressure
vessels.
- fire hazard.
- risk of explosions
- lack of ventilation.
-
Determine the Risk Ranking
1-2 = High (Immediate action required) 3-5 = Medium Risk
Radiation

Extremes of
temperature

Burns

UV from
welding flashes

UV from
exposure to sun

X-Ray
exposure

Eye damage
from laser
Provide PPE
How severely could it 2. How likely is it to be that bad – what is the probability of It happening
hurt someone
VERY LIKELY LIKELEY
UNLIKELEY
VERY UNLIKELEY
Or
Could happen at
How Ill could it make
Could happen Could happen very Probably never will
any time
rarely
happen
someone?
occasionally
KILL OR PERMANENTLY
1
1
2
3
DISABLED
LONG TERM ILLNESS OR
1
2
3
4
SERIOUS INJURY
LOST TIME INJURY
2
3
4
5
3
4
5

Strains and
sprains lifting
objects

Strains and
sprains moving
objects

Slips and trips
from
Spillage/slippe
ry surfaces
Uneven/unstab
le surfaces
Poor lighting

Crush injury
Biological

Disease or
illness from fungal
spores eg.
Legionnaires

Disease from
blood products eg.
Hepatitis,
brucellosis
6 = Low
1.
FIRST AID
Biomechanical
Appropriate PPE for the task
training in how to use
Safe work procedures Correct work procedures
Job rotation
Relieve stress/boredom
Training
Know the dangers. How to do work
correctly
Design
Design out or modify
Eliminate
Remove or substitute
Adopt a safer process
Can it be done any other way
Enclose or isolate
Use guards, close off
Ventilation
Provide adequate ventilation
6
Complied by Bruce Davison.
31
Cooling Towers
OHS Risk Assessment and Control (Educational) – By activity)
College: Sydney Institute/Ultimo
Activity
Potential Hazards
Section/ Refrigeration
Risk
Rating
Topic: Cooling Towers.
Control Measures
Responsibility
Implementation
Date
Revised
Risk
Rating
Student’s Name: _______________________ Position: __________________ Signature: _________________
Complied by Bruce Davison.
32
Cooling Towers
Answers to review questions.
Section1
1. Latent heat.
2. Because of the Water Conservation Act.
3. Controlled draining of the circulating water to reduce TDS.
4. Reduce chemical effectiveness, clog system pipe work.
5. Oxidizing and Non-oxidizing.
6. Breathing in Legionella enriched aerosols.
7. By evaporating some the circulating water.
8. To increase the evaporation rate.
9. High RH% and air flow
10. Natural and Forced draft.
11. Very large industrial process.
12.
a.
b.
c.
d.
Induced draft counter flow.
Induced draft cross flow.
Forced draft counter flow.
Forced draft cross flow.
13. Propeller and centrifugal.
14. Yes.
15. No.
16. Open and closed.
17. Closed, the circulating water doesn’t come into contact with the
atmosphere, an open does.
18. To compensate for load charges.
19. Fan speed and water by-pass.
20. Individual condenser’s regulating valves will reduce the amount of water
flowing in them therefore the cooling tower will need to regulate the volume of
water flowing from it to them.
Complied by Bruce Davison.
33
Cooling Towers
Answers to Law Questions.
a. NSW Public Health Act Part 4 clause 43.
b. AS/NZS 3666.2 2.6.1
c. AS/NZS 3666.2 2.5.1
d. AS/NZS 3666.1 4.1.4 also in the Regulation 2000 part 3 clause 9 (2)
e. Regulation 2000 part 4 clause 10.
f. AS/NZS 3666.2
table A1.
g. AS/NZS 3666.2
2.3.4.
h. Refer to AS/NZS 3666.3 foreword and 3.3.1.
i.
AS/NZS 3666.3
3.7.
j. AS/NZS 3666.1 2.3.2
Complied by Bruce Davison.
34
Cooling Towers
Section 2.
21.
1.
2.
3.
4.
5.
Cooling tower casing.
Internal components.
Fan.
Pump and pipe work.
Dosing system.
22.
1. pump
2. chemical levels
3. bleed off rate.
23.
1.
2.
3.
4.
Notify the owner.
Stop any equipment connected to the cooling tower.
Stop the fan.
Stop the pump.
24. Seven years.
25. Drained to sewer or contained by trade waste company.
26. It is the LAW.
27. Every six months.
28. Kept the public away and contain the spray from cleaning.
29. In human lungs.
30. They have the ability to spread the disease.
31. Chemicals.
32. 35 to 37oC.
33. Reduce running costs.
34. To remove construction waste.
35. Corrosion inhibitor.
Complied by Bruce Davison.
35