Fresh water station “Regumaq X-25”
Advice regarding corrosion protection
Water quality requirements
Stainless steel heat exchanger soldered with:
SUBSTANCE
CONCENTRATION
(mg/l or ppm)
COPPER
NICKEL / STAIN
-
LESS STEEL
COPPER
with protective
layer
Chloride (Cl
-
) at 60 °C See
diagram on the reverse!
<100
100–150
>150
+
-
-
+
-
-
+
+
0
Hydrogen carbonate (HCO
3
-)
<70
70–300
>300
0
+
0
+
+
+
+
+
+
Sulphate (SO
4
2-
)
<70
>70
+
-
+
+
+
+
HCO
3
-
/ SO
4
2-
>1.0
<1.0
+
-
+
+
+
+
Electrical conductivity at 20 °C
<50 µS/cm
50–500 µS/cm
>500 µS/cm
0
+
0
+
+
+
+
+
+
pH
As a general rule, a lower pH value
(below 6) increases the risk of cor-
rosion, while a high pH value (over
7.5) reduces the risk of corrosion.
<6.0
6.0–7.5
7.5–9.0
9.0–9.5
>9.5
0
0
+
0
0
0
+
+
+
+
+
+
+
+
0
Free chlorine (Cl
2
)
<1
>1
+
-
+
-
+
0
Ammonium (NH
4
+
)
<2
2–20
>20
+
0
-
+
+
+
+
+
-
Hydrogen sulphide (H
2
S)
<0.05
>0.05
+
-
+
+
+
0
Free (aggressive) carbon dioxide
(CO
2
)
<5
5–20
>20
+
0
-
+
+
+
+
+
+
Nitrate (NO
3
-
)
<100
>100
+
0
+
+
+
+
NOTES:
+
Good durability under normal conditions
0
Corrosion may occur
-
Not recommended for use
The chemical composition of the potable water may be subjected to temporal fluctuations.
The materials used in the Oventrop fresh water and
dwelling stations are selected and processed in accor-
dance with strict quality specifications. The plate mate-
rial (stainless steel 1.4401) used in the heat exchanger
has proven its durability in potable water applications.
Despite this,
depending on the water quality, and in
particular in the case of high chloride concentrations
> 100 mg/l
, it is possible that
corrosion may cause
leakages
from the heat exchangers.
It is therefore very important for the plant engineer and/
or user to ensure that the fresh water and dwelling sta-
tions are only operated using
potable water
of a chem-
ical composition that is
non-corrosive
for the station
components.
If necessary, consult your local water supply company.
The following table contains thresholds for substances in
potable water when using heat exchangers with different
brazing materials
(copper, nickel or stainless steel).
It is important to note that
interactions
may occur
between certain substances in water that can cause
considerable damage to the materials used.
This includes the combination of hydrogen carbonate
with chloride and/or sulphate (see following page).
A suitable heat exchanger must therefore be selected
on the basis of the water characteristics and the sub-
stances it contains. Your local water supply company
will provide corresponding analyses on request.
