ABS Provides, Operating Instructions Manual, Page: 19 / 32

EN
19
10. Maintenance and controls by the user
MAINTENANCE AND CONTROLS BY THE USER
Use, when necessary, inhibited brine antifreeze solutions and verify them periodically, avoiding their contact
with air. Always verify the toxicity/danger of antifreeze solutions before handling. Water-glycol mixture with
the passing of time decays and gives rise to acid products that can start corrosion processes. The degradation
of products in the water-glycol mixture may allow biological proliferation also and thus bacteria formation
can give rise to corrosion. For these reason glycol has to be used with suitable corrosion inhibitors. These have
a life span of 1-2 years so it is important to periodically verify the percentage in the water-glycol mixture.
Attention: glycol and inhibitors may be insufficient due to “top ups” of water in the circuit, then it is important
to integrat the right glycol and inhibitors percentage. The parameters to be checked regularly are the
antifreeze concentration and the pH of water-glycol mixture.
For marine heat exchangers, it is necessary to equip the plant with special anodes which must be checked or
replaced regularly.
To determinate the water quality, refer to the following table.
The above mentioned list indicates only some parameters that principally determine the quality of water. The
elements briefly described can be present together and lead to more serious effects.
For all these reasons we recommend to:
DO NOT REMOVE REFRIGERANT FROM PRIMARY CIRCUIT WITHOUT HAVING A
FLOW IN THE SECONDARY CIRCUIT - IF THIS IS NOT POSSIBLE MAKE SURE THAT THE
SECONDARY CIRCUIT IS COMPLETELY EMPTY TO AVOID FREEZING.
DO NOT OPEN THE HEAT EXCHANGER UNDER PRESSURE
10.1 Water quality
Water quality, as regard
s
chemical composition (salinity, pH), is very important for the performance and the
life of the heat exchanger.
Excess
ive
of hardness of water may cause the formation of a layer of deposits on the internal surface of the
tubes that may reduce the performances and the life of the internal parts of the heat exchanger.
Below
are
some of the main factors that influence the water quality:
Salinity: an increase of salinity causes an increase of electric conductibility and therefore a higher risk of
galvanic corrosion. Be advise
d
that, if you use sea water, salinity’s values change depending on the sea.
pH: pH is normal on values around alkalinity (6.8 – 8.4). For a correct work such values have to be maintained.
Dissolved oxygen: an increase of the dissolved oxygen content in water may cause an increase of corrosion.
Bio-fouling: it includes microbiological fouling. Bio-fouling can create anaerobic conditions and make
the attack of sulphate-reducing bacteria possible as well as aeration conditions with the consequence of
localized corrosion.
Suspended solids: may form deposits which decrease performances and may cause corrosion and/or
erosion.