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14. WATER QUALITY AND MARINE VERSIONS
Water quality, understood in terms of chemical composition (salinity, pH), quantity of suspended solids,
dissolved oxygen and bioburden (bacteria, algae and microorganisms), is very important for the
operation and life of the heat exchanger.
The substances dissolved and/or suspended in water can build up on the external surface of the
EXCHANGER tubes. The possible fouling layer prevents thermal exchange causing a drop in performance
of the heat exchanger.
The quality of the water can affect both the thermal performance and life of the heat exchanger.
Below follow some of the main parameters which determine water quality:
Salinity: Increasing water salinity increases electrical conductivity and therefore galvanic
interactions that can give rise to corrosion. Please note that, if you are using sea water, the
salinity values vary from sea to sea (e.g., salinity values of the Mediterranean Sea 25 g/L, Persian
Gulf 44g/L, Baltic Sea 7.8 g/L).
pH: The pH of sea water is normally at values tending to alkalinity (7.4 ÷ 8.4). For correct
operation, these values should be met.
Dissolved oxygen: An increase in the amount of dissolved oxygen also accentuates corrosion.
Bioburden: It consists of animal and plant microorganisms; they can create anaerobic conditions
and favour the attack of sulphate-reducing bacteria or differentiated aeration conditions, hence
giving rise to localized corrosion and/or degradation phenomena affecting protective coatings.
Suspended solids: The suspended solids can give rise to deposits and sediments and result in
lower performance and erosion and corrosion phenomena.
It is recommended to extend the life of the machine:
Always install filters on the water intake circuit to reduce to a minimum the entry of solid
particles which are a possible cause of erosion and fouling.
Carry out a periodic cleaning of the heat exchanger to eliminate any deposits using
compressed air and appropriate brushes.
In any case do not clean with inappropriate mechanical systems, such as drills or jets at too
high a pressure.
Do not clean with aggressive chemical detergents. Before the use of a chemical detergent,
check compatibility with the construction materials of the EXCHANGER.
GB
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