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What type of water treatment do you recommend
for a closed-loop cooling system?
What type of water treatment do you recommend
for an open-loop cooling system?
Do I need to treat the water in my closed-loop
cooling system?
How do I purge the air from the overhead pipes?
Why does my pump growl?
How do I troubleshoot pumps using a pump curve
and pressure gauge?
What pipe size do you recommend for my system?
How do I determine the volume of glycol required
for my cooling system?
What suppliers do you recommend for ethylene
glycol or propylene glycol?
What is the difference between ethylene glycol
and propylene glycol?
What is the difference between freeze protection
and burst protection?
What percentage of glycol/water do I need for
my cooling system?
What type of filtration do you recommend for
cooling tower water?
Who would you recommend for water treatment?
What type of water treatment
do you recommend for a closed-loop cooling system?
Most closed-loop water systems use a sodium nitrite based inhibitor and
a biocide to prevent biological contamination. These inhibitors will protect
both the ferrous and non-ferrous materials in your piping system. Vendors
can supply the inhibitor with a colorant, which allows the treatment to
be visually monitored.
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What type of water treatment do you recommend
for an open-loop cooling system?
Because evaporative towers
scrub the air that passes through them, they are prone to collecting debris
from the air. This debris can accumulate and cause flow restrictions; as
well as aggravate corrosion. Also, after the water evaporates, dissolved
minerals are left behind and accumulate rapidly. For these reasons, a properly
engineered and administered water treatment program must be employed continuously
with the cooling tower.
In an open tower cooling system, the water quality must be regularly monitored
and treated to control the following conditions:
1) Lime scale and other water mineral deposits
2) Corrosion of all types
3) Micro-biological growth, such as algae, bacteria, fungus and molds
4) Suspended solids accumulations, such as airborne dirt and debris that
is washed into the cooling tower water.
Dry Coolers recommends consulting a local water treatment supplier (Calgon,
Nalco, Culligan, etc.) that is familiar with your local water quality to
monitor your treatment program.
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Do I need to treat the water
in my closed-loop cooling system?
Closed-loop systems are less susceptible to corrosive agents than Open
Tower systems. For this reason they are often left untreated. However,
closed-loop systems must have corrosion protection. An untreated closed-loop
water system can cause serious corrosion in your equipment.
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How do I purge
the air from the overhead pipes?
While the system is running,
vent the high points in the process discharge piping to remove air from
the pipe. Most problems with the initial start-up are associated with filling
the system and releasing air out of the process piping.
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Why does my pump
growl?
If it sounds like there are marbles in your pump, it is more then likely
caused by cavitation, or air getting into the pump. Both of these problems
will severely shorten the life of the pump impeller, and should be corrected
immediately.
We will be posting an article on troubleshooting these problems shortly.
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How do I troubleshoot pumps
using a pump curve and pressure gauge?
ITT Industries’ Techtalk has a fantastic article that describes troubleshooting
using a pump curve here.
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What pipe size do you recommend
for my system?
Typically, the piping should be sized large enough so that frictional
pressure drop within the piping system make up less than 10% of the operating
pressure of the system. For example, a system operating at 100 psi should
have less than 10 psi of frictional pressure losses in the piping system.
Pressure
losses in a piping system can be readily determined using the "equivalent
length" method that is found in most piping handbooks. Since most
piping systems are not complex, we have provided a simple table to use
as a rule of thumb for sizing the piping. Use this table for systems requiring
less than 200’ length of pipe (less than 30’ for gravity drain)
and that have a minimum number of valves and bends. Larger and more complex
systems may need special consideration. Consult Dry Coolers for recommendations.
Example:
A 150 gpm Vacuum Furnace Cooling System with a plate & frame heat
exchanger and a cooling tower. This type of loop has closed-loop process
piping and open loop cooling tower piping. Assume 150 gpm for both loops:
| Section
of Pipe |
Minimum
Pipe Diameter |
| Process
supply piping to the furnace |
3" |
| Process
return piping (from the furnace to the tank) |
4" |
| Cooling
tower supply pipe |
3" |
| Cooling
tower gravity drain to remote sump tank |
5" |
RECOMMENDED
MAXIMUM FLOW
| Pipe Diameter (in) |
Max. Supply Piping Flow Rate |
Max. Return Piping Flow Rate for Furnaces (1) |
Max. Gravity Return Flow for Remote Towers (2) |
| 1 |
10 |
6 |
2 |
| 1.5 |
35 |
20 |
9 |
| 2 |
75 |
40 |
22 |
| 2.5 |
120 |
70 |
40 |
| 3 |
200 |
120 |
63 |
| 4 |
350 |
250 |
135 |
| 5 |
550 |
450 |
247 |
| 6 |
800 |
750 |
400 |
| 8 |
1500 |
1500 |
865 |
| 10 |
2500 |
2500 |
1570 |
| 12 |
4000 |
4000 |
2540 |
(1) Typically, the back
pressure on a furnace must be minimized. The return water piping for a furnace
is usually one size larger than the supply pipe. For example, if a furnace
requires a 3" supply, then a 4" return is used.
(2) The gravity drain flow returning from a cooling tower is based on a
minimum pipe slope of 1/2" / ft with the pipe 3/4 full of water. Based
on Manning Formula, n = 0.015. The length of the gravity drain pipe should
be kept to a minimum to prevent overflowing the indoor tank and prevent
water from backing up in the tower basin.
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How do I determine the volume
of glycol required for my cooling system?
It is often necessary to determine the volume of water held in a cooling
system so that appropriate concentrations of corrosion inhibitor and/or
glycol can be added.
The volume of water in your system is determined by adding the volume
of water in your pipes, tanks, cooling equipment, and your process equipment.
At your request, Dry Coolers can provide the cooling equipment volumes.
The following table may be used as a guide for determining the volume
within pipes.
| PIPE
SIZE (in) |
GALLONS/100
FT OF PIPE |
| 1" |
4.5 |
| 1.5" |
10.6 |
| 2" |
17 |
| 2.5" |
25 |
| 3" |
38 |
| 4" |
66 |
| 5" |
104 |
| 6" |
147 |
| 8" |
260 |
| 10" |
410 |
| 12" |
587 |
| SYSTEM
VOLUME CALCULATIONS |
| Volume
in Piping |
|
| Volume
in Tanks |
|
| Volume
in Equip. |
|
| TOTAL
VOLUME (GAL) |
|
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What suppliers do you recommend for ethylene glycol or propylene glycol?
Sources
of Ethylene and Propylene Glycol Based Anti-Freeze as of 11/21/01.
| Supplier |
Phone |
Propylene Glycol |
Ethylene Glycol |
| Dow Chemical |
800-447-4369 |
DowFrost |
Dowtherm |
| Houghton Chemical Co. |
617-254-1010 |
Safe-T-Therm |
Wintrex |
| Interstate Chemical Co. |
800-422-2436 |
Intercool NFP |
Intercool NFE |
| Huntsman Petrochemical |
713-235-6000 |
Jeffcool P155 |
Jeffcool E105 |
| Noble Company |
800-678-6625 |
NoBurst-100 |
None |
| DOW/Union Carbide |
800-331-6451 |
Ucar Protherm |
UcarTherm |
| |
|
Norkool |
TriTherm |
Tell
your supplier to include corrosion inhibitors to protect copper and iron.
Also, make sure they add a colorant to the glycol so that any leakage/spillage
can be detected.
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What is the difference
between ethylene glycol and propylene glycol?
ETHYLENE GLYCOL
Many of the present uses for ethylene glycol are based on its properties
as a freezing point depressant, but this compound is also valuable in
numerous applications which depend upon one or more additional properties.
The ease with which it reacts with other chemical intermediates plus its
solvent, lubricant, plasticizing, and hygroscopic properties-all are likewise
responsible for its popularity as an industrial raw material.
PROPYLENE GLYCOL
Propylene glycol is unique among the glycols in that its very low toxicity
permits it to be taken internally. Because of this fact there are grades
intended for industrial use and those intended for applications that may
involve absorption into the human body. In common with the other glycols,
propylene glycol is odorless and colorless and has a wide range of solvency
for organic materials, plus being completely water soluble.
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What is the difference
between freeze protection and burst protection?
Freeze Protection requires a glycol concentration level sufficient to
prevent the formation of ice crystals at the lowest temperature experienced
by the fluid. Freeze protection is imperative when the system requires
pumping.
Burst Protection only requires a glycol concentration high enough to prevent
bursting and other mechanical damage from freezing, but not necessarily
high enough to keep the fluid pumpable. Burst protection requires less
glycol than freeze protection and is suitable for chilled water systems
that are dormant in the winter.
As
the temperature drops below the freezing point of the fluid in a system
with burst protection, ice crystals begin to form and the solution becomes
a slush. The fluid expands as ice is formed. This mixture may or may not
be pumpable, but it is fluid enough so that the excess volume flows into
an expansion tank without damage to the system. As the temperature drops
further and all the water freezes, the glycol will begin to freeze and
contract.
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What percentage
of glycol/water do I need for my cooling system?
For freeze protection, the required concentration of inhibited glycol
fluid in a system depends on the operating conditions of the system and
the lowest expected ambient temperature. For corrosion protection, it’s
also important to consider the materials of construction, the age of the
system and other variables. Your local glycol supplier representative
can help you analyze the specific requirements for your system.
The table below shows the protection from freeze damage provided by various
concentrations of DOWFROST glycol inhibited fluids. To determine the concentration
required, select the lowest expected ambient temperature and decide whether
the cooling system requires freeze protection to keep it pumpable, or
burst protection to simply prevent damage from fluid expansion.
As a further measure of protection against dilution error, or unexpected
cold temperatures, select a temperature that is at least 5°F colder
than the lowest expected ambient temperature. If, for example, the lowest
expected temperature is -15°F, select the line in the table below
for -20°F. The table shows that at this temperature, a solution of
45% DOWFROST is required for freeze protection. A concentration of 30%
to provide burst protection at this temperature.
PERCENT VOLUME GLYCOL CONCENTRATION REQUIRED
| |
Freeze Protection |
Burst Protection |
| Temperature °F |
DOWFROST |
DOWFROST |
| 20 |
17% |
11% |
| 10 |
26% |
18% |
| 0 |
34% |
23% |
| -10 |
41% |
28% |
| -20 |
45% |
30% |
| -30 |
49% |
33% |
| -40 |
51% |
35% |
| -50 |
53% |
35% |
| -60 |
55% |
35% |
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What
type of filtration do you recommend for cooling tower water?
The fan on a cooling tower draws in thousands of cubic feet per minute of
outside air that contains sand, dust, insects, and fibers from vegetation.
These airborne contaminants mix with the process cooling water and eventually
these suspended particles find their way into heat transfer surfaces. After
a period of time these surfaces become fouled and insulated causing equipment
to run hotter and replacement or repair is necessary.
By removing 98% of these suspended solids mechanically, fouling is greatly
reduced and chemical water treatment and bleed from the system can be reduced
significantly.
Full stream filtration protects the system from dirt deposits such as winds
blowing over newly plowed fields, chunks of scale eroding from steel pipe
or foreign deposits encountered by adding new piping to an existing system.
By utilizing an optional purge receptacle, expensive treated process water
is not wasted in the purge cycle. A small continuous flow of dirt laden
process water removed by the separator is filtered and contained in the
receptacle while the clean water is returned to the cooling system. The
receptacle can then be isolated for easy contaminant removal without interrupting
the process water flow and zero discharge to the sewer.
The key to good filtration is to provide a system where the dirt laden water
can enter the suction of the pump that discharges into the CyClean separator
for maximum filtration of the system. If the solids can be kept in suspension,
they will eventually enter the suction of the pump and then be filtered
by the separator before they foul your equipment.
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Who would you recommend for
water treatment?
Consult with the supplier relative to your specific needs.
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