PRODUCT INFORMATION
INDEX
DATE
Dep. 2
IO-C-M-20-001e D
February 2016
COOLING WATER QUALITY AND TREATMENT
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1. GENERAL INFORMATION
When installing the engine, one point to bear in mind is the quality of the cooling water that will be used, in order
to prevent heat transfer problems.
Any water treatment programme mainly aims at protecting the cooling system from corrosion, deposit or scale
which might impair the continuous flow of the coolant.
The most common problems with an engine cooling system are as a result of corrosion, cavitation,
microbiological growth, deposits and scale.
Corrosion
This is a metal degrading process arising from oxygen-triggered chemical or electrochemical reactions. As for
cooling systems, the reactive medium is water that attacks the metallic materials of piping and heat exchangers.
Corrosion is dependent upon the effect of temperature, high salinity (especially of chlorides), high water speed,
alkalinity or acidity, dissolved solids, dissolved gas traces, microbial growth and pollution by manufacturing
process waste. The major negative effect of corrosion is a decrease in the engine components’ fatigue strength.
The following are the most frequently occurring types of corrosion:
Electrochemical:
Bonding of metals of varying electrochemical properties.
Chemical:
pH and salinity
Physical:
Abrasion and cavitation
Differential aeration:
Low deposits
Bacterial:
Sulphate-reducing bacteria, ferrobacteria, nitrifying bacteria, denitrifying bacteria.
Cavitation
Cavitation is the creation of bubbles within a liquid when it passes through a high pressure area at high speed
and increases when the pressure is low in the cooling system and/or when there are leaks. In addition, as the
vibration increases, so the number of bubbles in the coolant also increases. These bubbles cause erosive
corrosion of the cylinder wall and frequently lead to pitting of cylinder walls.
To solve cavitation problems, purge the cooling circuit thoroughly and, for applications requiring high
temperature, keep the circuit under pressure. Also add coolant additives that will cover the metal surfaces and
limit cavitation-induced erosion and pinholes.
Scale
This is the crystallisation and deposition in their solid form of different combined ions present in water, due to
oversaturation of the solution at a given temperature. It usually appears as compact, hard and adhering deposits
of predominantly inorganic matters, but may occasionally take soft, non-adhesive forms and be a mixture of
organic and inorganic components.
The major compositions of scale include, but are not limited to: calcium carbonate, calcium sulphate, calcium
phosphate, magnesian salts, silica, and iron and manganese compounds. Scale forming depends on multiple
factors such as temperature, salt concentration, pH and alkalinity, dissolved solids content, fluid-dynamic and
thermostatic conditions of the system, etc.
4.1.5
O&M_2.002211.810_A_10_2016
