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WATER TREATMENT
The thermal system water must comply with the Laws in force, therefore it is good practise to use treatment units when the line
water is particularly rich in calcium carbonate, which causes scale build-ups and corrosion.
The table includes some indicative values:
Characteristics
pH*
Hardness (CaCo2)
Iron (Fe)**
Copper (Cu)**
Oxygen (O
)
2
Appearance
* 8 is the maximum acceptable pH value in case of radiators in aluminium or light alloys.
** Higher values indicate on-going corrosion phenomena.
*** In case of agents which form oxygen film and/or surplus, do not observe this value with intermittent operation or operation
without deaerator, but use the additive.
LIMESTONE BUILD-UPS
Limestone build-ups reduce the heat exchange between the combustion gases and water, leading to an abnormal increase of
temperature of the parts exposed to the flame and thus to a significant reduction of the Boiler service life.
Limestone gathers in the points where the wall temperature is higher and the best defence against it, at the construction level,
is to eliminate the superheating areas.
Scale build-ups form an insulating layer which decreases the heat exchange of the boiler, penalising its efficiency. This means that
a significant part of the heat obtained from the combustion is not fully transferred to the system water, but is lost through the
chimney.
LIMESTONE DIAGRAM
Lost heat
%
30
20
10
0
CORROSION ON WATER SIDE
The corrosion of the Boiler metal surfaces on the water side is due to the iron transit into solution through its ions (Fe+). In this
process, the presence of dissolved gases, in particular oxygen and carbon dioxide, is very important. Corrosion phenomena often
occur with softened and/or demineralised water, which by nature is more aggressive against iron (acid water with Ph < 7); in these
cases, even when scale build-ups are prevented, corrosions can occur and it is necessary to treat the water with corrosive process
inhibitors.
20
Cooke Industries - Phone: +64 9 579 2185
Scale
°Fr
mg/kg
mg/kg
mg/l
5
10
limestone mm
Email: sales@cookeindustries.co.nz
Filling water
-
< 15
-
-
< 0.05***
Clear
15
20
Web: www.cookeindustries.co.nz
Circuit water
7-8
-
< 0.5
< 0.1
-
Possibly clear
30
Installation
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