AERMEC NRV 0550, Technical Manual

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The guide provides advice for applications. Although recommendations are
given, all the details about the real world application of our products cannot
be fully covered in this document.
For these reasons, this section contains the basic warnings and precautions
to be taken into account in general, it being understood that:
— The final choice of the type of exchanger according to the place of in -
stallation is left to the client (or to the professional appointed by him).
— In any case, it is recommended to wash the coils with adequate fre -
quency (a maximum time interval of three months is recommended,
shorter in conditions of particularly dirty and aggressive atmospheres)
to preserve their condition and ensure the proper functioning of the
unit.
Potentially corrosive outdoor environments include areas near coasts, indu -
strial sites, densely populated urban areas, certain rural areas or a combi -
nation of these environments. Other factors, including the presence of ef -
fluent gas, sewage vents or open sewage systems and the exhaust of diesel
engines can all be harmful for the microchannel coil.
The purpose of this application guide is to provide general information on
the mechanisms of corrosion and corrosive environments.
SEA COAST ENVIRONMENTS
Coastal or marine environments are characterized by the abundance of
sodium chloride (salt) which is carried by sea spray, mist, or fog. Most im -
portantly, this salt water can be carried more than several miles by ocean
breezes and tidal currents. It's not uncommon to experience salt-water con -
tamination as far as 10km from the coast.
For this reason, it may be necessary to protect the exchangers from elec -
trolytes of marine origin through the appropriate choice of materials and /
or appropriate protective treatment.
INDUSTRIAL ENVIRONMENTS
Industrial applications are associated with several different conditions that
can potentially produce a variety of atmospheric emissions.
Contaminants from sulphur and nitrogen oxides are most often linked to
high-density urban environments. The combustion of coal oils and fuel
oils releases sulphur oxides (SO
2
, SO
3
) and nitrogen oxides (NO
x
) 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, ch -
lorides, sulphates, sulfuric acid, carbon and carbon compounds.
In the presence of oxygen, water or high humidity environments, these par -
ticles can be extremely corrosive and in several forms, including general and
localised corrosion, such as pitting and anthill.
MIX OF SEASIDE AND INDUSTRIAL ENVIRONMENTS
Sea mist loaded with salt, associated with the harmful emissions of an indu -
strial environment, poses a serious risk.
The combined effects of the salt loaded mist and in-dustrial emissions ac -
celerate corrosion.
Within the manufacturing plants, corrosive gas may result from the proces -
sing of chemicals or by the typical industrial processes used in manufactu -
ring.
Potential sources of risk to be considered are open sewage systems, exhaust
vents, diesel engine exhaust, emissions from heavy traffic, landfills, aircraft
and ocean-going ship engine exhaust, industrial production, chemical tre -
atment facilities (cooling towers in the vicinity) and fossil fuel power plants.
URBAN ENVIRONMENTS
Densely populated areas generally have high levels of emissions of motor
vehicles and increases in duel use for heating buildings.
Both conditions elevate sulfur oxide (SO
x
) and nitrogen oxide (NO
x
) concen -
trations.
Corrosive atmospheres may even occur in some closed areas, such as facili -
ties with swimming pools and water treatment systems.
It is advisable to pay particular attention to the positioning of the units if it
occurs in the immediate vicinity of these places, and to avoid that they are
installed in the vicinity of outlets for the expulsion of air coming from them,
or in any case exposed to such atmospheres.
Corrosion severity in this environment is a function of the pollution levels,
which in turn depend on several factors including population density in the
area.
Any equipment installed in locations immediately adjacent to diesel engine
exhausts, incinerator flues, fuel-fired boiler flues, or areas exposed to fossil
fuel emissions shall be considered subject to the same measures as an in -
dustrial application.
RURAL ENVIRONMENTS
Rural environments may contain high levels of pollution from ammonia and
nitrogen products from animal excrements, fertilizers and high concentra -
tion 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 disper-
sion of outdoor gaseous contaminants.
Thermal inversions can trap pollutants, thereby producing serious air pol -
lution problems.
ADDITIONAL TIPS
Although each of the above corrosive environments can be detrimental to
the life of the heat exchanger, several additional factors must be considered
before choosing the final design.
The local climate surrounding the site of application may be influenced by
the presence of:
— wind
— dust
— road salts
— swimming pools
— diesel engines discharge / traffic
— 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 environment
that requires preventive corrosion measures. When these factors are di -
rectly and immediately part of the environment, their influence is further
aggravating.
Only in the absence of potentially risky situations such as those indicated
above can an environment be considered moderate.
Application Tip
Severe environments Coils with suitable protection
Moderate environments Standard coil °
-
SELECTION CRITERIA OF THE HEAT EXCHANGERS ACCORDING TO THE PLACE OF INSTALLATION OF THE UNIT