EN
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7. SELECTION CRITERIA OF THE HEAT EXCHANGERS ACCORDING TO THE PLACE OF INSTALLATION OF THE UNIT
N.B.: The purpose of this application guide is to provide gen-
eral information on the mechanisms of corrosion and corrosive
environments. The guide provides advice on the applications,
however, you cannot anticipate all the details concerning the
application in the actual destination place of our products in this
document. In addition, the requirements relating to the service
life of a potential product are not known. For these reasons, Aer-
mec prefers to work closely with the customers to fully understand
the requirements of the project and the operating environments.
Aermec assumes no liability for the completeness and correctness
of the information contained herein.
Potentially corrosive outdoor environments include areas near coasts,
industrial sites, densely populated urban areas, certain rural areas or a
combination of these environments. Other factors, including the pres-
ence of effluent gas, sewage vents or open sewage systems and the
exhaust of diesel engines can all be harmful for the microchannel coil.
•
Coastal/marine environments
: Coastal and marine environments
are distinguished by an abundance of sodium chloride (salt) transport-
ed by sea spray, vapour or mist. It is important to note that salt water
can be transported many miles by wind and tidal currents. It is not
uncommon for contamination due to salt water to occur 10 km away
from the coast. For this reason, equipment may have to be protected
from the electrolytes of marine origin.
•
Industrial Environments
: Industrial applications are associated with
several different conditions that can potentially produce a variety of at-
mospheric emissions. Contaminants from sulphur and nitrogen oxides
are most often linked to high-density urban environments. The com-
bustion of coal oils and fuel oils releases sulphur oxides (SO2, SO3) and
nitrogen oxides (NOx) into the atmosphere. These gases accumulate in
the atmosphere and return to the ground as acid rain or low pH dew.
Industrial emissions are not only potentially corrosive: many industrial
dust particles can be loaded with harmful components such as metal
oxides, chlorides, sulphates, sulfuric acid, carbon and carbon com-
pounds. In the presence of oxygen, water or high humidity environ-
ments, these particles can be extremely corrosive and in several forms,
including general and localised corrosion, such as pitting and anthill.
A combination of marine/industrial environments: Sea mist loaded
with salt, associated with the harmful emissions of an industrial
environment, poses a serious risk. The combined effects of the salt
loaded mist and industrial emissions accelerate corrosion. Within the
manufacturing plants, corrosive gas may result from the processing of
chemicals or by the typical industrial processes used in manufactur-
ing. Potential contributing factors that must be considered are open
sewers, vent openings, diesel exhaust, heavy traffic emissions, landfills,
exhaust from aircraft engines and ocean-going vessels, industrial pro-
duction, chemical treatment structures (cooling towers located nearby)
and fossil fuel electrical installations.
•
Urban Environments
: Densely populated areas generally have high
levels of emissions of motor vehicles and increases in duel use for heat-
ing buildings. Both conditions increase the concentration of sulphur
oxides (SOx) and nitrogen oxide (NOx). Inside a building, the gas can
be produced from cleaning agents, cigarette smoke, process opera-
tions and data centre printers. Corrosive atmospheres may even occur
in some closed areas, such as facilities with swimming pools and water
treatment systems.
The severity of corrosion in this environment is influenced by the levels
of pollution,
which in turn depend on several factors, including the population den-
sity of the area. Each piece of equipment installed in places immedi-
ately near exhaust of diesel engines, exhaust chimneys of incinerators,
chimneys of fuel-powered boilers or areas exposed to emissions from
fossil fuels, must be
considered an industrial application.
•
Rural Environments
: Rural environments may contain high levels of
pollution from ammonia and nitrogen products from animal excre-
ments, fertilizers and high concentration of diesel engine exhaust. The
approach to these environments must be entirely similar to that of
industrial environments.
Local weather conditions have a major role in the concentration or
dispersion of outdoor gaseous contaminants. Thermal inversions can
trap pollutants, thereby producing serious air pollution problems.
ADDITIONAL TIPS
Although each of the above corrosive environments can be detrimen-
tal to the life of the heat exchanger, several additional factors must
be considered before choosing the final design. The local climate sur-
rounding the site of application may be influenced by the presence of:
• Wind
• Dust
• Salty roads
• Swimming pools
• Diesel engine / traffic exhaust
• Localised mist
• Cleaning agents for domestic use
• Sewage system outlets
• Many other separate contaminants
Even within 3-5 km from these particular local climates a normal envi-
ronment with moderate characteristics can be classified as an environ-
ment that requires preventive corrosion measures. When these factors
are directly and immediately part of the environment, their influence is
further aggravating.
Application
Tip
• Urban Environments:
Coils O-R-S-V
Moderate environments
Standard coil ° (microchannel)
