ECH EVAPORATIVE CONDENSERS
OPERATION
140.910-IOM (DEC 13)
Page 11
CORROSION PROTECTION
Frick products are constructed of corrosion-resistant materi-
als. The fill (if applicable) is made of a polyvinyl chloride (PVC),
which requires no protection against rot, decay, rust or biologi-
cal attack.
Other materials listed below are used in the equipment con-
struction:
Galvanized Steel Components
: Inspect the galvanized steel
components for blemishes or corrosion. Wire brush and recoat
the affected areas with a cold galvanizing compound such as
zinc rich compound (ZRC).
Thermosetting Hybrid Polymer Components
: Galvanized steel
components protected with the Thermosetting Hybrid Polymer
may develop scratches, scrapes or blemishes. Touch up these
with a repair kit. In the unlikely event that the damage is more
extensive than simple scratches or minor blemishes, contact
your local Frick Representative.
Stainless Steel Components
: Inspect stainless steel components
for signs of blemishes or corrosion. Clean with stainless steel
wool as necessary. If more extensive corrosion is prevalent,
contact your local Frick Representative.
Fiberglass Reinforced Polyester (FRP) Components
: Dual air
inlet ECH-D products are provided with FRP casing panels as
standard. Inspect the casing panels for accumulation of dirt and
clean them with soap and water as necessary.
Corrosion and Treatments
•
Corrosion – Red rust on steel components and “white rust”
on galvanized surfaces will affect the longevity of the unit.
•
Scale Formation – Scale not only reduces heat transfer
and system efficiency, but also may lead to under deposit
corrosion.
•
Biological Fouling – Slime and algae formations may
reduce heat transfer, promote corrosion, and harbor
pathogens such as Legionella.
Since the quality of the ambient air and makeup water varies
significantly from job site to job site, Frick strongly recom-
mends obtaining the services of a competent water treatment
specialist prior to the initial start-up of the evaporative cooling
equipment. Additionally, to protect against the risk of Legionella
contamination, never operate the cooling equipment without
adequate biological control.
Corrosion and Scale Control
•
To control corrosion and scale, maintain the water
chemistry of the recirculating water within certain
parameters. The specific measures required vary from
system to system and are dependent on the chemistry of
the makeup water, the metallurgy of the piping and heat
transfer devices exposed to the recirculating water, and
the temperatures at which the system will be operating.
•
Bleed/blowdown, the continuous flow of a small portion
of the recirculating water to a drain, is used to control
the concentration of dissolved solids. On rare occasions,
this may be adequate to control scale and corrosion. More
often, however, chemical scale and corrosion inhibitors
are necessary, which raise the allowable level of dissolved
solids without the risk of scale and corrosion.
•
Keep the chemically treated water within the guidelines
given in Table 2. In cases where bleed/blowdown alone is
being employed for corrosion and scale control, without
chemical treatment, your water treatment specialist may
recommend more conservative limits than those shown in
Table 2.
Table 2: Quality Guidelines for Chemically Treated
Circulating Water
Property of Water
Recommended Level
pH
6.5 to 9.0
(1)
Hardness as CaCO3
30 to 750 ppm
(2)
Alkalinity as CaCO3
500 ppm maximum
(2)
Total Dissolved Solids (TDS) 1500 ppm maximum
Conductivity
2400 micromhos
(3)
Chlorides
250 ppm maximum Cl (410 ppm
maximum as NaCl)
Sulfates
250 ppm maximum
Silica
150 ppm maximum
NOTES:
1. Galvanized steel units require passivation in order to
prevent white rust (refer to passivation below).
2. Hardness and alkalinity limits may be exceeded under
certain circumstances. Consult your water treatment
specialist for recommendations.
3. The conversion factor used to determine conductivity is
0.625 (TDS = 0.625 x Conductivity).
Chemical Treatment Requirements
Chemical treatment programs must meet the following require-
ments:
•
The chemicals must be compatible with the unit materials
of construction as well as other materials used in the
system (pipe, heat exchanger, etc.).
•
Chemical scale and corrosion inhibitors, particularly acid
(if used), should be introduced into the circulating water
through automatic feeders. This should be done at a point
in the system where total mixing and dilution occur, before
reaching the evaporative cooling equipment. The preferred
injection point for chemical scale and corrosion inhibitors
is on the discharge side of the system circulating pump(s).
These chemicals should not be batch fed directly into the
unit’s cold water basin or water distribution system, as this
can severely damage areas directly contacted.
•
When chlorine is added to the system, free residual
chlorine should not exceed 1 ppm, except as noted in
start-up and shutdown section. Exceeding this limit may
accelerate corrosion.
Passivation
•
Passivation is the formation of a protective, passive,
carbonate layer on galvanized steel surfaces.
•
On the newly installed units, to provide maximum
protection from corrosion, take special measures to
passivate galvanized steel surfaces.
•
To ensure proper passivation of the galvanized steel, keep
the pH of the circulating water between 7.0 to 8.2 for four
to eight weeks after start-up, or until new zinc surfaces
turn dull gray in color.
