Air Contamination - EVAPCO ATC-E Maintenance Instruction

If a chemical water treatment program is used, all chemicals
selected must be compatible with the unit's materials of
construction as well as other equipment and piping used
in the system. Chemicals should be fed through automatic
feed equipment to a point which ensures proper control and
mixing prior to reaching the evaporative cooling equipment.
Chemicals should never be batch fed directly into the basin of
the evaporative cooling equipment.
Evapco does not recommend the routine use of acid due to
the destructive consequences of improper feeding; however,
if acid is used as part of the site specific treatment protocol,
it should be pre-diluted prior to introduction into the cooling
water and fed by automated equipment to an area of the
system which ensures adequate mixing. The location of the
pH probe and acid feed line should be designed in conjunction
with the automated feedback control to ensure that proper
pH levels are consistently maintained throughout the cooling
system. The automated system should be capable of storing
and reporting operational data including pH reading and
chemical feed pump activity. Automated pH control systems
require frequent calibration to ensure proper operation and to
protect the unit from increased corrosion potential.
The use of acids for cleaning should also be avoided. If acid
cleaning is required, extreme caution must be exercised and
only inhibited acids recommended for use with the unit's
materials of construction should be used. Any cleaning
protocol, which includes the use of an acid, shall include a
written procedure for neutralizing and flushing the evaporative
cooling system at the completion of the cleaning.
Flume/equalizer DO NOT ensure proper controlled mixing of
water in multiple cells. Operate multiple cells individually.
Control of Biological Contamination
Evaporative cooling equipment should be inspected regularly
to ensure good microbiological control. Inspections should
include both monitoring of microbial populations via culturing
techniques and visual inspections for evidence of biofouling.
Poor microbiological control can result in loss of heat transfer
efficiency, increase corrosion potential, and increase the
risk of pathogens such as those that cause Legionnaires'
disease. The site specific water treatment protocol should
include procedures for routine operation, startup after a shut-
down period, and system lay-up, if applicable. If excessive
microbiological contamination is detected, a more aggressive
mechanical cleaning and/or water treatment program should
be undertaken.
It is important that all internal surfaces, particularly the basin,
be kept clean of accumulated dirt and sludge. Additionally,
drift eliminators should be inspected and maintained in good
operating condition.
Gray Water and Reclaimed Water
The use of water reclaimed from another process as a
source of makeup water for evaporative cooling equipment
can be considered as long as the resultant recirculating
water chemistry conforms to the parameters noted in
Table 3. It should be noted that using water reclaimed from
other processes may increase the potential of corrosion,
microbiological fouling, or scale formation. Gray water or
reclaimed water should be avoided unless all of the associated
risks are understood and documented as part of the site
specific treatment plan.
12
Operation and Maintenance Instructions

Air Contamination

Evaporative cooling equipment draws in air as part of normal
operation and can scrub particulates out of the air. Do not
locate the unit next to smokestacks, discharge ducts, vents,
flue gas exhausts, etc. because the unit will draw in these
fumes which may lead to accelerated corrosion or deposition
potential within the unit. Additionally, it is important to locate
the unit away from the building's fresh air intakes to prevent
any drift, biological activity, or other unit discharge from
entering the building's air system.
Cold Weather Operation & Ice Management
EVAPCO counterflow evaporative cooling equipment is well
suited to operate in cold weather conditions. The counterflow
design encases the heat transfer media (fill and/or coils)
completely, and protects it from the outside elements such as
wind which can cause freezing in the unit.
When the evaporative cooling unit is going to be used during
cold weather conditions, several items need to be considered
including unit layout, recirculating water, unit recirculating
piping, unit heat transfer coils, unit accessories and capacity
control of the units.
More information can be found in Bulletin 116-E, pages 21-26.
Freeze Protection of Recirculating Water
The simplest and most effective way of keeping the
recirculated water from freezing is to use a remote sump.
With a remote sump, the recirculating water pump is
mounted remotely at the sump and whenever the pump
is shut off, all recirculating water drains back to the sump.
Recommendations for sizing the remote sump tank and
recirculating water pumps for coil products are presented
for Evaporative Condensers and Closed Circuit Coolers in
their respective catalog. The pressure drop through the water
distribution system measured at the water inlet is as follows in
Table 4 (See next page).
If a remote sump cannot be used, basin heaters are available
to keep the recirculating water from freezing when the pump
is turned off. Electric heaters may be used to heat the basin
water when the unit is shut down. The make-up water supply,
overflow and drain lines, as well as the pump and pump piping
up to the overflow level must be heat traced and insulated
to protect them from damage. Any other connections or
accessories at or below the water level, such as electronic
water level controllers, must also be heat traced and insulated.
Note: Using basin heaters will not prevent the fluid in the
coils, nor the residual water in the pump or pump piping
from freezing.
A condenser or cooler cannot be operated dry (fans on, pump
off) unless the water is completely drained from the pan. The
pan heaters are sized to prevent pan water from freezing only
when the unit is completely shut down.